Dalhousie University Department of Chemical Engineering
Liquid Phase Alkylation of Benzene with Ethylene
Jeffrey MacDonald Richard Roda Michael Beresford CHEE 4842 Plant Design Date Submitted: April 22th, 2005
Table of Contents List of Figures............................................................................................................................... iv List of Tables ................................................................................................................................ iv 1
Introduction ....................................................................................................................... 1
1.1 Ethyl Benzene Reaction System .................................................................................... 1 1.2 Methods of Producing Ethyl Benzene............................................................................ 2 1.2.1 Gas-phase Production Using Zeolite Catalysts (Mobil/Badger) ................................ 2 1.2.2 Liquid Phase Production with AlCl3: Friedel-Crafts/Alcar Process.......................... 4 1.2.3 Liquid Phase Reaction Using Zeolite Catalyst in a Fixed Bed (Lummus/UOP EBOneTM)................................................................................................................................ 7 1.2.4 Process Selection ...................................................................................................... 11 2 Process Simulation .......................................................................................................... 12 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3
HYSYS Simulation Fluid Property Package ............................................................... 12 Reaction Kinetics ......................................................................................................... 12 HYSYS Process Flow Diagram .................................................................................... 14 Section 1: Feed Preparation......................................................................................... 16 Section 2: Alkylation Reaction and Effluent Cooling .................................................. 19 Section 3: Benzene and Ethyl Benzene Separation .................................................... 22 Section 4: Transalkylation ........................................................................................... 25 Section 5: Cooling Water System................................................................................. 27 Energy Requirement Summary ................................................................................... 28 Market Survey ................................................................................................................. 29
3.1 UOP Process................................................................................................................. 29 3.2 Styrenics Industry (Nova Chemicals).......................................................................... 29 3.3 Plant Location .............................................................................................................. 30 3.4 Raw Material Availability ........................................................................................... 31 3.4.1 Ethylene20 ................................................................................................................. 32 3.4.2 Benzene .................................................................................................................... 33 3.4.3 Operating Results, 2003 versus 200220 .................................................................... 34 3.5 Demand ........................................................................................................................ 35 3.6 Outlook ......................................................................................................................... 36 4 Costs ................................................................................................................................. 37 4.1 4.2 4.3 4.4 5
Equipment Costs.......................................................................................................... 37 Capital Costs ................................................................................................................ 39 Direct Operating Costs ................................................................................................ 40 Profitability .................................................................................................................. 41 Environmental Considerations........................................................................................ 43
5.1 Plant Design Considerations ....................................................................................... 43 5.1.1 Greenhouse Gas Emissions...................................................................................... 43 5.1.2 Vapour Flaring ......................................................................................................... 44 5.1.3 Process and Waste Water Treatment: Oily Water Sewer ....................................... 45 5.2 Environmental Regulation: Plant Operation Considerations..................................... 45 5.2.1 Canadian Environmental Protection Act ................................................................ 46 5.2.2 National Pollutant Release Inventory ..................................................................... 47 5.3 ISO Certification .......................................................................................................... 48 5.4 Material Concerns........................................................................................................ 50 5.5 Case Study: Texas Nova Chemical Plant Explosion and Release............................... 51 6 Safety ............................................................................................................................... 52 6.1
Chemical Properties..................................................................................................... 52
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6.1.1 Ethylene ................................................................................................................... 53 6.1.2 Benzene .................................................................................................................... 54 6.1.3 Ethyl Benzene .......................................................................................................... 56 6.1.4 Di-ethyl Benzene and Tri-ethyl Benzene................................................................. 58 6.1.5 Toluene ..................................................................................................................... 58 Y-zeolite Catalyst ................................................................................................................. 59 6.1.6 Chemical Property Summary: Explosion Characteristics....................................... 60 6.2 Material Storage .......................................................................................................... 61 6.2.1 Compressed Gas Storage ......................................................................................... 61 6.2.2 Liquid Storage .......................................................................................................... 64 6.2.3 Catalyst Solids Storage ............................................................................................ 65 6.2.4 Storage related hazards ........................................................................................... 65 6.2.5 Inherently Safer Material Storage .......................................................................... 66 6.3 Material Transportation .............................................................................................. 67 6.4 Hazard Analysis........................................................................................................... 69 6.4.1 Dow Fire & Explosion Index .................................................................................... 69 6.4.2 Chemical Exposure Index ........................................................................................ 70 6.4.3 Hazard Analysis: What-if......................................................................................... 72 6.5 Case Studies................................................................................................................. 73 6.5.1 Benzene and Ethylene Explosions........................................................................... 73 6.5.2 Short Term Ethyl Benzene Exposure ...................................................................... 75 6.5.3 Long Term Benzene Exposure ................................................................................. 75 6.5.4 Lessons to be learned ............................................................................................... 76 7 Conclusions ...................................................................................................................... 78 8
Recommendations ............................................................................................................ 80
8.1 Process Recommendations ........................................................................................... 80 8.2 Safety and Environmental Recommendations ............................................................ 80 8.3 Economical Recommendations..................................................................................... 81 References.................................................................................................................................... 82 References.................................................................................................................................... 82 A.
Economics Spreadsheet ................................................................................................... 86
B.
Sample Equipment Cost Calculations............................................................................. 88
C.
Glossary............................................................................................................................ 90
D.
What-if? Analysis............................................................................................................. 91
E.
F&EI Sample Calculations .............................................................................................. 94
F.
CEI Sample Calculations............................................................................................... 102
G.
HYSYS Workbook Output ............................................................................................. 105
iii
List of Figures Figure 1-1: Friedel-Crafts alkylation of Benzene to form EB. ..................................................... 4 Figure 1-5: EBOne process.3........................................................................................................ 10 Figure 2-2: Section 1 feed preparation........................................................................................ 17 Figure 2-3: Section 2 alkylation reactor assembly...................................................................... 19 Figure 2-4: Section 3 benzene and ethyl-benzene separation. ................................................... 22 Figure 2-5: Section 4 transalkylation. ........................................................................................ 25 Figure 2-6: Section 5 transalkylation of DEB............................................................................. 27 Figure 3-1: Styrene/EB plant location (Sarnia, Ont.)................................................................. 31 Figure 3-2: Alberta ethylene cost advantage (¢/lb).70 ................................................................. 32 Figure 3-3: Selling prices for ethylene, benzene, and styrene for 2003-2004.23 ......................... 34 Figure 3-4: Demand for ethyl benzene since 1998 (in millions of kg). ....................................... 36 Figure 4-1: Rate of return as a function of selling price............................................................. 41 Figure 4-2: Relationship of total capital cost and total operating cost as a function of EB production. ........................................................................................................................... 42 Figure 4-3: Relationship of ROR as a function of EB production for various selling prices of EB (current = $US 1.12/kg). ...................................................................................................... 42 Figure 6-1: Typical ethylene storage tank. ................................................................................. 63 Figure 2: CEI hazard distance map ............................................................................................ 71
List of Tables Table 2-1: Operation-section key ................................................................................................ 14 Table 2-2: Plant section description. ........................................................................................... 16 Table 2-3: Section 1 conditions.................................................................................................... 17 Table 2-4: Section 2 reactor conditions. ...................................................................................... 20 Table 2-5: Recycle 2 and E2 Inlet stream data. .......................................................................... 20 Table 2-6: Section 4 conditions.................................................................................................... 26 Table 2-7: Energy requirements summary. ................................................................................ 28 Table 3-1: Yearly North American production of EB.25 .............................................................. 36 Table 4-1: Equipment costs (all equipment is carbon steel)....................................................... 38 Table 4-2: Capital costs (EB = 156,000 tonne/yr). ...................................................................... 39 Table 4-3: Direct operating costs (EB = 156,000 tonne/yr)......................................................... 40 Table 4-4: Indirect operating costs (EB = 156,000 tonne/yr)...................................................... 41 Table 5-1: CEPA 200 regulatory limits.32 ................................................................................... 47 Table 6-1: NFPA codes for chemicals used in the production of EB. ......................................... 53 Table 6-2: Ethylene exposure limits.40 ........................................................................................ 53 Table 6-3: Benzene exposure limits data.45................................................................................. 55 Table 6-4: Ethyl benzene recommended exposure limits.49 ........................................................ 57 Table 6-5: PPE material and break through time.49 ................................................................... 58 Table 6-6: Important explosion chemical properties for design considerations......................... 61 Table 6-7: Dow F&EI for the EB plant. ...................................................................................... 69 Table 6-8: CEI calculated values................................................................................................. 71
iv
Executive Summary An ethyl benzene plant has been designed using a liquid phase alkylation of benzene with ethylene. The process is to be implemented at the Nova Chemical styrene plant in Sarnia, Ontario. Several EB synthesis processes were evaluated: the Mobil/Badger gas-phase process, the Alcar/AlCl3 liquid phase process, and the Lummus/UOP EBOneTM liquid phase process. The EBOneTM process was selected as a basis because it uses a safe and less expensive fixed bed catalyst, moderate operating conditions, and low benzene-to- ethylene feed ratio.
A benzene-ethylene feed is introduced into an alkylation reactor assembly forming EB and undesired di-ethyl benzene. A distillation separation system composed of two columns is used to separate benzene and EB from the main process stream. Benzene is recycled to the alkylation feed and transalkylation section. The transalkylation reactor is then used in conjunction with a recycled benzene feed to convert separated DEB to additional EB. This stream is recycled to the entrance of the separations system. The HYSYS 3.2 simulation software package was used to model the necessary unit operations and processes in the EB synthesis process.
Based on the current simulation and a plant capacity of 18,000 kg/h (156,000 tonne/a) of EB, the plant has a positive net present value of US$ 7.2 million, based on a MARR of 20% with an IRR of 27%. The plant capital investment is estimated at US$ 23 million, with total operating costs at approximately US$ 160 million. Product revenue is estimated at US$ 175 million in EB sales, at a current selling price of US$ 1.12/kg. The vast majority of un-reacted benzene is recycled, and a negligible amount is purged to tankage. Plant life is estimated at 20 years. v
The selling price of EB to turn a profit at a MARR of 20% is US$ 1.09/kg. This was determined by calculating the effect of EB selling price on rate of return. The effect of EB production with respect to equipment cost and operational costs was also determined. The value-added increase in EB selling price is marginal compared to the benzene cost of US$ 1.05/kg. It is difficult to predict benzene cost as the value has oscillated in the past 8 months.
Plant capacity is currently at 156,000 tonne/a, comparable to that of the Nova Chemical plant of 150,000 tonne/a. The benzene-ethylene ratio of 5:1 fed into the alkylation assembly is too large. An excess of benzene is left un-reacted to cycle through the recycle streams of the plant. Complications with the HYSYS 3.2 software makes this change difficult, and other designs may be required to lower this ratio. This benzene increases reboiler duty costs, column costs, and large amounts of circulated benzene.
Dow F&EI and CEI analysis indicated the areas of highest risk in the plant. The most notable area is the alkylation assembly feed, which had a CEI of 1120 and Dow F&EI of 165. The design must be modified to minimize the amount of hazardous material in this section of the plant. Decreasing the benzene-ethylene ratio should reduce the amount of recycled benzene and decrease the overall flow rate into the reactor assembly.
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1 Introduction The reaction of benzene with ethylene produces ethyl benzene and by-product di-ethyl benzene. Ethyl benzene is an intermediate in the production of styrene. Nova Chemical Corporation has contracted to update their existing ethyl benzene synthesis process at their styrene plant in Sarnia, Ontario. A declining trend of profitability resulting from subsequent yearly losses prompted Nova Chemical to evaluate new technology in the synthesis of ethyl benzene.
There are multiple technologies in current practice in the styrene industry. The fundamental differences are related to the reaction phase and vessel system. In the following sections, several methods of ethyl benzene production are explored to determine which technologies offer the best combination of profitability and inherent safety.
1.1 Ethyl Benzene Reaction System The proposed plant design involves creating ethyl benzene from the raw components of benzene and ethylene. The chemical reaction to create ethyl benzene is: C6 H 6 + C 2 H 4 → C6 H 5 C 2 H 5
(1.1)
Eq.(1.1) for the reaction of benzene and ethylene to form EB is accompanied by five side reactions. Three of them are shown in Eq. (1.2), (1.3), and (1.4). C6 H 6 + 2C 2 H 4 → C6 H 4 (C 2 H 5 )2
(1.2)
C6 H 5C 2 H 5 + C 2 H 4 → C6 H 4 (C 2 H 5 )2
(1.3)
C6 H 6 + C6 H 4 ( C 2 H 5 ) 2
1
2C6 H 5C 2 H 5
(1.4)
The reaction illustrated in Eq. (1.2) and (1.3) produces an undesired product, DEB. Proper use of LeChatelier’s Principle can force the equilibrium reaction described by Eq. (1.4) to yield as much desired product (EB) as possible. Eq. (1.5) and (1.6) show two further side reactions, but are negligible for simulation purposes.
C6 H 5C 2 H 5 + C2 H 4 → CH 3C6 H 4C3H 7
(1.5)
C6 H 5C 2 H 5 + C2 H 4 → (CH 3 )2 C6 H 3C 2 H 5
(1.6)
The kinetics for these two reactions were not found to be documented in literature. However it has been shown that the reaction extents for both reactions are negligible when simulating the process.1 As such, Eq. (1.1)-(1.4) shall be used for design in HYSYS. Several process designs can be implemented to favour the production of EB. Several methods for creating ethyl benzene are discussed in the proceeding section.
1.2 Methods of Producing Ethyl Benzene Most production methods of creating ethyl benzene have approximately 95 mol% conversion.1 The three methods discussed in this report include the creation of ethyl benzene in the gas-phase reaction (Mobil/Badger), in the liquid phase using an AlCl3 acid catalyst, and a liquid phase reaction in fixed bed reactors using a zeolite catalyst.
1.2.1 Gas-phase Production Using Zeolite Catalysts (Mobil/Badger) The gas-phase reaction to create ethyl benzene using a zeolite catalyst is referred to as the Mobil/Badger process. The mechanism for creating EB differs from the AlCl3 and Alcar process (see Section 1.2.2), since the zeolite catalyst produces a carbonium ion which activates the ethylene to create an adsorbed electrophilic species which is quickly attacked by benzene. This in turn causes a faster reaction; however, more by-
2
products are produced as well which have to be recycled and converted back to useful product using a transalkylator.
Approximate operating conditions are 675-725 K and 200-400 psig. The operating conditions are significantly higher than those for the liquid phase process, resulting in higher risk and cost of operation. In addition, the benzene/ethylene ratio is approximately 8-16 by mole fraction for the gas-phase reaction. Such a large ratio is needed since the catalyst used is highly deactivated by the presence of ethylene as more carbonaceous species are created.
Catalyst life using a gas-phase reaction is a major downfall of the gas-phase process. The catalyst requires regeneration every two to four weeks. To maintain steady state operation, it is typical to run two reactors in parallel. Because of this, the costs associated with this process are high as shutdown costs, catalyst costs, and deactivated catalyst disposal are high. In addition, because the B/E ratio is high, the costs of operation are higher in order to retrieve and recycle the excess benzene.
The gas-phase reaction does have some positive aspects. The zeolite catalyst is safer environmentally and disposal costs are not as high. Also, the catalyst is non-corrosive and therefore special materials, which are required for the AlCl3 and Alcar process, are not required. However, the catalyst life problem is a major issue with this process. The AlCl3, Alcar, and liquid process using zeolite catalysts resolve this issue. Figure 1.1 illustrates the operation of a Mobil/Badger process.2
3
1.2.2 Liquid Phase Production with AlCl3: Friedel-Crafts/Alcar Process One method of creating EB is through a Friedel-Crafts reaction of ethylene in the presence of an aluminum chloride acid catalyst (AlCl3). This reaction occurs in the liquid phase and is illustrated in Figure 1-1.
R X
R
AlCl3 (cat) -HX
Figure 1-1: Friedel-Crafts alkylation of Benzene to form EB. Where R = Ethylene group X = Chlorine atom With this process, the AlCl3 is injected as fine particles into the alkylator reactor where the ethyl benzene is formed. The AlCl3 is quite often promoted with HCl or ethylene chloride to reduce the amount of AlCl3 required for the reaction. Once through the reactor, the AlCl3 is filtered out of the product by water washing and then sent for disposal or regeneration. To recover the unwanted di-ethyl benzene and other unwanted products, a transalkylator is commonly used. Here, the unwanted products are reconverted to EB, hence increasing feed conversion.2
The liquid phase process has several advantages over the gas-phase process because temperatures and pressures are reduced which lead to saving in operating costs. In addition, the operation is safer since operating conditions are not as severe. Typical running conditions for temperature and pressure are between 420-470 K and 70-150 psig
for
the
alkylation
and
transalkylation
processes.
In
addition,
the
benzene/ethylene (B/E) ratio is lower at approximately 1.5-2.5 by mole ratio.
4
5 Figure 1-2: Mobil/Badger Process.2
Having a lower B/E ratio reduces the operation costs associated with removing the unreacted benzene and provides a more economical plant operation.2 Another positive aspect of the liquid phase reaction is that the catalyst is not subjected to high deactivation rates. However, this type of catalyst does have some downfalls.
The catalyst used in the AlCl3 process is an acid, which tends to corrode the operating equipment unless the internals of the equipment are lined with special materials (such as brick or glass). The use of such materials increase construction costs and may be expensive to maintain as some are quite fragile. In addition, the catalyst is injected and removed from the process on a continuous basis, leading to higher operation costs in water and filtration when the catalyst is separated from the process stream. Finally, the AlCl3 catalyst is hazardous to the environment and there are relatively high costs involved in assuring that it is stored and disposed of properly.
Further process designs, such as the Alcar Process from Universal Oil Products (UOP) resolved some of the downfalls of the AlCl3 process. It used a fixed bed of BF3 catalyst which had reduced corrosion concerns and eliminated the need for continuous catalyst removal. However, the Alcar process did require much higher operating pressures of approximately 500 psig and therefore increasing operating costs. Also, the problem of the AlCl3 catalyst disposal was also present when using the BF3 catalyst. The AlCl3 and Alcar processes are shown in Figures 1-3 and 1-4, respectively.
Research continues for the use of a zeolite catalyst in a fixed bed for a liquid phase reaction of ethylene and benzene to create ethyl benzene.2
6
1.2.3 Liquid Phase Reaction Using Zeolite Catalyst in a Fixed Bed (Lummus/UOP EBOneTM) Similiar to the Mobil/Badger process, the liquid phase reaction uses a zeolite catalyst which does not require special material for reactor internals, piping, or in other parts of the process. In addition, the zeolite catalyst is not as harmful to the environment which saves in disposal costs. There are several patents for this type of reaction, however, the Lummus/UOP EBOne is the most recent and provides the most benefits.3
This process, like the preceding AlCl3 and Alcar process, requires an alkylator and a transalkylator. In addition, the operating temperature and pressures are similar to that of the AlCl3 process. The B/E alkylator feed ratios range from 1.5-2.0 on a molar basis. Since temperatures and pressures are not extreme and B/E ratios are relatively low, there are large savings available in operational costs when compared to the Mobil/Badger process. Further, since the catalyst is contained in fixed beds there are reduced operational costs when compared to the AlCl3 and Alcar process because the catalyst does not have to be continuously removed from the process using a filter and washing.
7
8 Figure 1-3: Production of EB using AlCl3 process.2
9 Figure 1-4: Production of EB using the Alcar process.2
The most positive aspect of the EBOne process is that catalyst life is claimed to be at least five years for the alkylator and the transalkylator when using the EBZ-500™ and EBZ-100™ as the fixed bed catalyst, respectively. Also, these catalysts may be regenerated for at least three cycles. Therefore, they constitute a more economical alternative to conventional catalyst. Further savings are realized since shutdowns are less frequent to change out the catalyst in the fixed beds of the reactors. A diagram of the EBOne process is shown below in Figure 1-5.
Figure 1-5: EBOne process.3 As Figure 1-5 shows, the main reaction takes place in the “Alkylation Section” in the presence of the EBZ-500™ catalyst in fixed beds. The ethylene and benzene react to form the product ethyl benzene and other unwanted products. The top product of this reactor flows to the “Benzene Column” where the excess benzene is removed from the product stream and then sent back as recycle with “Fresh Benzene”. The remaining gas is then sent to a “Lights Removal Column” where any un-reacted ethylene is sent 10
to a flaring system. Any un-separated benzene is also combined with the recycled benzene stream.
The bottoms of the “Benzene Column” are sent to the midsection of the “Ethyl Benzene Column”. The ethyl benzene product is separated from the other unwanted products as distillate and then sent to storage. The bottoms of the “Ethyl Benzene Column” are sent to the mid section of the “Poly-ethyl Benzene Column”. The distillate of this column is condensed and combined with some recycle benzene and then sent to the “Transalkylation Section”.
In the “Transalkylation Section” the side reaction (DEB and TEB) products are reacted in the presence of the EBZ-100™ catalyst in fixed beds to form more ethyl benzene. The top product of “Transalkylation Section” is then combined with the top product of the “Alkylation Section”, where it repeats the process loop. The bottom product of the “Poly-ethyl Benzene Column” is mostly a viscous tar material which is disposed of as a waste material.
1.2.4 Process Selection The EBOne process offers the best economical benefits, operating conditions, safety, and environmental considerations. The EBOne process has been successfully used in 15 fully operational plants with capacities ranging from 65,000 tonne/yr to 200,000 tonne/yr. Five more plants are in the construction phase licensing the EBOne process. The first plant has being operating at full capacity for 12 years.3 Low operating conditions, liquid phase reactions, and the environmentally friendly zeolite catalyst were the primary determinants in selecting this process for a design basis.
11
2 Process Simulation 2.1 HYSYS Simulation Fluid Property Package The Peng-Robinson property fluid package was used for this simulation. It utilizes the Peng-Robinson (PR) equation of state model which can be seen in the HYSYS help manual. It was chosen because the PR model gives good results for non-polar systems, and has a wide range of materials that can be used for accurate results. All the components used in the production of EB are either non-polar or contain very weak dipole moments. It was also noted that HYSYS contained all the necessary interaction parameters for the PR EOS model, which sharply improves accuracy.
2.2 Reaction Kinetics Kinetics for the “Alkylation Section” are taken from Qi and Zhang (2004)1. The kinetics takes into account the use of zeolite catalyst. The reaction of benzene with ethylene to produce the product ethyl benzene is as follows:
C6 H6 + C2H4 → C6 H5C2 H5
r1 =8.4×10-5exp( -45.8
RT
)C E1.0 C B 0.32
(2.7)
The reaction of benzene with two moles of ethylene to produce di-ethyl benzene is as follows: C6 H6 + 2C2H4 → C6 H4 (C2 H5 )2
r2 =6.03×10-4 exp( -61.6
RT
)CE1.3CB 0.33
(2.8)
The reaction of ethyl benzene with ethylene to produce di-ethyl benzene is as follows: C6 H5C2H5 + C2H4 → C6 H4 (C2 H5 )2
r3 =8.5×10-7 exp( -86.4
RT
)CE1.77 CEB 0.35
(2.9)
The three kinetic equations above have the units of kgmole/m3s. The activation energies given in Qi and Zhang (2004) did not contain information on units. A second source indicated that the units were kcal/mol.7 The results of a conversion of the activation values into kJ/kgmol are shown above in Eq. (2.7)-(2.9). The equilibrium 12
reaction of benzene with di-ethyl benzene to form two moles of ethyl benzene is as follows:
C6 H 6 + C 6 H 4 ( C 2 H 5 ) 2
ln ( K EQ ) =
2C6 H 5 C2 H 5
276.6 -0.3599 T
(2.10)
The reactions for the “Transalkylator Section” were modeled using the equilibrium expression in Eq. (2.10). These were derived using thermodynamic assumptions described in literature.8 The equilibrium constant can be related to temperature using the following expression:
Ho 1 1 ln K ′ =K R T T′
(
)
(2.11)
Where K K′ H° T T′
= = = = =
Equilibrium constant at temperature T Reference Equilibrium constant at temperature T’ Standard enthalpy change of reaction Arbitrary temperature Reference temperature at value of Equilibrium constant K
The reference temperature and equilibrium constant were given in Qi and Zhang (2004). These values had a K value of 0.883 and a T value of 571 K.1 The standard reaction enthalpy was determined using HYSYS as -2.4x103 J/mol. Manipulation of Eq. (2.11) and substituting the appropriate values in for variables yields Eq. (2.10).
In the following section, a detailed description of the simulation in HYSYS will be presented discussing each major unit operation with its function, parameters such as height, diameter, required work/duty, etc.
13
2.3 HYSYS Process Flow Diagram Figure 2-1 shows the HYSYS process flow diagram in its entirety. There are 14 main process operations contained in five sections of the plant. Table 2-1 summarizes the PFD labels of these operations with descriptions of the equipment and the section of the plant in which they are contained. Table 2-2 shows a summary of each of the five sections of the plant.
Table 2-1: Operation-section key PFD Label P-1 E-1 P-2 R-1-1A/R-1-2A R-2-1A/R-2-2A R-1-1B/R-1-2B R-2-1B/R-2-2B VLV-100 E-2 C-1 C-2 C-3 E-3 R-3-1A R-3-1B
Operation Description Fresh benzene feed pump to Alkylator Alkylation Feed Cooling Water Heat Exchanger C-1 Recycle Pump Train One Alkylation Section Train Two Alkylation Section Train One Equilibrium Reactor Train Two Equilibrium Reactor Alkylation Effluent Pressure Reducer R-1 Assembly Effluent Cooling Water Heat Exchanger Benzene Separation Column EB Separation Column Flash Drum C-2 Bottoms Cooling Water Heat Exchanger Transalkylation Alkylator Transalkylation Equilibrium Reactor
14
Plant Section Section 1 Section 1 Section 1 Section 2 Section 2 Section 2 Section 2 Section 2 Section 3 Section 3 Section 3 Section 3 Section 4 Section 4 Section 4
15 Figure 2-1: HYSYS simulation PFD.
Table 2-2: Plant section description. Section Number Section 1 Section 2
Section 3 Section 4 Section 5
Brief Description Feed preparation section of the plant. Its purpose is to prepare the feed components for the reactions in Section 2. Alkylation section of the plant which is divided into two trains of reactors. The purpose of this section is to form ethyl benzene from ethylene and benzene raw components. It contains four real reactors, a reducing valve and an effluent cooling water heat exchanger. Benzene and ethyl benzene separation section of the plant. It contains two distillation columns and a flash drum. Transalkylation section of the plant. Converts some of the diethyl benzene to ethyl benzene using C-1 benzene recycle Cooling water section of the plant. It provides the plant with the required cooling water needed in the distillation columns, reactor cooling jackets, and the three cooling water heat exchangers.
A detailed description of each section is discussed in the following sections. Operating conditions, performance, design specifications are discussed in further detail.
2.4 Section 1: Feed Preparation The purpose of this section of the ethyl benzene plant is to prepare the feed components for processing in Section 2 of the plant where the alkylation reaction occurs. This section handles a large recycle benzene stream which is combined with the raw feed components.
Section 1 of the EB plant includes the fresh feed streams of benzene and ethylene, the benzene feed pump (P-1), the benzene recycle pump (P-2), and
16
the R-1/R-2 assembly feed heat exchanger (E-1). The raw ethylene arrives on site from a pipeline which operates at approximately 4 MPa and is reduced to 1.8 MPa before entering the main plant. The feed and recycle are mixed then cooled using a cooling water shell and tube heat exchanger (E-1). The tube side of the exchanger contains the cooled product which then proceeds to Section 2 for alkylation. A HYSYS schematic of this section is shown in Figure 2-2.
Figure 2-2: Section 1 feed preparation.
Table 2-3 summarizes the composition, operating conditions, and flow rates for the important streams. Table 2-3: Section 1 conditions.
Temperature [°C] Pressure [kPa] Mass Flow Rate [kg/h] Benzene Mole Frac. Ethylene Mole Frac.
Fresh Benzene 25 101 14,500
Ethylene Raw Feed 268 1800 4769
0.99 0.00
0.0 1.0
17
90 1800 78,530
TrainFeed 40 1780 78.530
Recycle Feed 83 1800 59,260
0.83 0.17
0.83 0.17
0.98 0.02
E-1-Inlet
To pump the fresh benzene to the reactor conditions of 1.8 MPa, the pump requires 10.5 kW of power when running at 75% efficiency. In order to prevent catalyst deactivation, the feed ratios of the benzene/ethylene (B/E ratio) are adjusted using a spreadsheet (Feed Ratios and Reactor Calculations) to a value of 5.5 on a molar basis. This ratio may be reduced further to approximately 1.4 by the addition of more ethylene. However the HYSYS simulation became unstable for any attempts to decrease the ratio. If this ratio is decreased any further than 1.4, the deactivation of the zeolite catalysts in the R-1 assembly becomes a major issue requiring the shutdown of the R-1 reactor for catalyst re-activation or worse, replacement.1 It should be noted that increasing this ratio in HYSYS drastically improved the benzene conversion, however HYSYS does not take catalyst deactivation into account, and as such, the simulation is bound to this constraint.9 The desired B/E ratio from the reactor inlet steam (Train Feed) is controlled in the HYSYS simulation through a spreadsheet (“Feed Ratios and Reactor Calculations”).
The E-1 heat exchanger is simulated with a complex shell and tube heat exchanger. The process stream flows on the tube side of the exchanger and the cooling water passes through the shell side. Heat integration was not possible however, since no heating is required in the simulation other then the re-boilers in the distillation columns (where heat integration is not used).
18
2.5 Section 2: Alkylation Reaction and Effluent Cooling Section 2 of the ethyl benzene plant consists of a benzene/ethylene alkylation reactor assembly which forms the product compound of ethyl benzene and other by-products such as diethyl benzene. The assembly is divided into two trains, Train 1 and Train 2. Each train consists of two CSTR reactors and two equilibrium reactor models to simulate the non-reversible and equilibrium reactions, respectively, represented in Eq. (2.7)-(2.10). The overall purpose of this section of the plant is to facilitate a reaction to produce ethyl benzene at the highest yield and level of safety as possible. A schematic of this section of the plant is illustrated in Figure 2-3.
Figure 2-3: Section 2 alkylation reactor assembly.
The two trains are identical to each other in terms of mass flow rate, pressure, temperature, and composition. Table 2-4 summarizes the process
19
details for each reactor while the conditions for the Recycle 2 and E2 Inlet stream can be seen in Table 2-5.
Table 2-4: Section 2 reactor conditions.
Temperature (°C) Pressure (kPa) Mass Flow Rate (kg/h) Benzene Mole Frac. Ethylene Mole Frac. EB Mole Frac DEB Mole Frac.
R-1-1-A/ R-2-1 125 1700 39,210
R-1-1B-Liq/ R-2-1B 125 1700 39,210
0.870 0.073 0.00 0.056
0.822 0.073 0.096 0.0081
R-1-2A/ R-1-2B R-2-2A R-2-2B 138 138 1700 1700 39,210 39,210 0.837 0.021 0.107 0.034
0.821 0.021 0.14 0.017
Table 2-5: Recycle 2 and E2 Inlet stream data.
Temperature (°C) Pressure (kPa) Mass Flow Rate (kg/h) Benzene Mole Frac. Ethylene Mole Frac. EB Mole Frac DEB Mole Frac.
Recycle 2 20 500 22,540 0.846 0.007 0.135 0.012
E2 In 115 500 100,000 0.826 0.018 0.016 0.016
The volume of each CSTR model is approximately 35m3 , which are ordered in series for both trains as illustrated in Figure 2-3. Realistically, a reactor reaches its size limit around 250 m3. The reactor volume had a negligible effect on the benzene conversion. HYSYS encountered some difficulties in performing accurate case studies to optimize the reactor volumes. However,
20
35m3 was the smallest volume to which HYSYS would converge without giving inappropriate results.
At steady state, the R-1 assembly runs at 125°C and 1700 kPa in which there is a 13°C exotherm in the second R-1 of each train. These process conditions are based on U.S. Patent 6,504,071 and most conditions fall within the proposed ranges.10 To improve heat efficiency of the plant, the reactors were allowed to provide more exotherm instead of using large amounts of energy to cool the reactant contents. The reactor outlets are cooled just enough to maintain them in the liquid phase. As a result, the reactant outlets do not require heating to become a saturated liquid before entering C-1. Since cooling water is cheaper then steam this more economical.
E-2 was simulated using a complex shell and tube heat exchanger. The process stream flows in the tube side of the exchanger and is cooled by water passing through the shell side of the exchanger. Again heat integration was not possible as there are no process streams that require heating other than the re-boilers of the distillation columns.
In order to obtain a respectable life of the EBZ-500TM catalyst, the B/E ratio must be maintained as high as possible in order to keep ethylene as a limiting reagent, and therefore limiting its interaction with the catalyst and
21
causing deactivation. As previously stated, the deactivation of the catalyst increases operational costs in the forms of increased shutdowns and catalyst replacement and regeneration. However, this ratio must also be kept as low as possible to prevent high separation cost of benzene in C-1.
2.6 Section 3: Benzene and Ethyl Benzene Separation Section 3 of the ethyl benzene plant consists of two distillation columns (C-1 and C-2) and a flash drum (C-3). This section of the plant is used to separate benzene and ethyl benzene from the main process stream. A schematic of this section of the plan is shown in Figure 2-4.
Figure 2-4: Section 3 benzene and ethyl-benzene separation.
22
The benzene separation occurs in C-1 in which the distillate stream is 99.7% benzene (m.f.). A portion of the distillate proceeds to C-3 for flaring and to provide benzene to the transalkylation section. This is accomplished by invoking a 40 kPa pressure drop allowing some of the process stream to flash off. The remainder is recycled back to the feed section of the plant for further reaction in the R-1 assembly. The bottoms of the column proceed to C-2 for further separation. Process details of C-1 inlets and outlets are detailed in Table 2-6 and the process details of C-3 can be seen in Table 2-7. Table 2-6: Section 3 C-1 process data.
Temperature [°C] Pressure [kPa] Mass Flow Rate [kg/h] Benzene Mole Frac. Ethylene Mole Frac. EB Mole Frac. DEB Mole Frac.
C-1-Feed 107 470 101,000 0.083 0.018 0.139 0.016
C-1-Distillate 83 400 79,470 0.976 0.022 0.002 0.0
C-1-Liquid 194 400 21,470 0.051 0.001 0.848 0.100
Table 2-7: Section 3 C-3 process data. Out-4 Temperature [°C] Pressure [kPa] Mass Flow Rate [kg/h] Benzene Mole Frac. Ethylene Mole Frac. EB Mole Frac. DEB Mole Frac.
83 400 19,820 0.977 0.022 0.002 0.00
23
Benzene to Tankage 82 360 47 0.311 0.689 0.00 0.00
Benzene to Transalk 82 360 19,770 0.991 0.007 0.002 0.00
C-1 is approximately 16.3 m high, has a diameter of approximately 3.4 m, and contains 27 actual trays (assuming a tray efficiency of 60%). The feed stage is on tray number 19, where the column is numbered from top to bottom. C-1 removes 99.5% of the benzene from the process stream. The reflux ratio is 15.8 and the column has a pressure drop of 70 kPa.
The bottoms of C-1 are sent to C-2 where ethyl benzene is separated from diethyl benzene. C-2 is approximately 20.3 m high, has a diameter of 2.3 m, and contains 33 trays assuming 60% tray efficiency. C-2 removes 99.9% of the ethyl benzene from the process stream. Table 2-8 illustrates the process details of C-2. The distillate stream of C-2 is the product stream of ethyl benzene while the bottoms of the column are mainly diethyl benzene which is transalkylated to produce more diethyl benzene product. Table 2-8: Section 3 C-2 process data.
Temperature [°C] Pressure [kPa] Mass Flow Rate [kg/h] Benzene Mole Frac. Ethylene Mole Frac. EB Mole Frac. DEB Mole Frac.
C-2-Distillate 185 360 18,770 0.042 0.0 0.978 0.0
C-2-Liq 240 360 2700 0.0 0.0 0.007 0.993
Table 2-8 shows a summary of the design specifications of C-1 and C-2.
24
Table 2-8: Section 3 C1 and C2 design summary.
Height (m) Width (m) Number of Actual Trays (60% Efficiency) Reflux Ratio Re-boiler Duty (kW) Condenser Duty (kW) Feed Stage
C-1 16.3 3.4 27
C-2 20.3 2.3 33
0.7 16 16 11
2.1 5 5 19
2.7 Section 4: Transalkylation Section 4 of the EB plant design is the transalkylation reaction section. A diagram of this section is shown in Figure 2-5.
Figure 2-5: Section 4 transalkylation. Approximately 23,000 kg/h enters the transalkylator. A breakdown of the stream components are shown in Table 2-6.
25
Table 2-6: Section 4 conditions. Component Benzene Ethylene EB DEB Toluene
E-3-Out (mol %) 90.7 1.7 0.2 7.2 <0.0001
R-3-1B-Liq (mol %) 80.4 0.3 17.4 1.9 <0.0001
The Transalkylator (R-3-1A & R-3-1B) makes use of the equilibrium and CSTR
models.
Equilibrium
kinetics
were
described
in
Eq.
(2.11).
Approximately an 83% conversion of EB to DEB was obtained. Conditions for the
transalkylation
section
were
not
described
in
the
supporting
documentation for EB production. However, a paper documenting the transalkylation reaction of EB to form benzene and DEB operates their transalkylator at high temperatures (400-600 K).11 Since the reverse is required for this plant design, it is logical that lower temperatures are required for the reaction to produce EB. This is supported by inspection of Eq. (2.10). The transalkylation process is independent of pressure, and as such there is no reason to lower the pressure when it will need to be increased again for the recycle loop.12
The reactor has been sized at 30 m3. The simulation did not converge at lower volumes, and the conversion achieved at higher volumes was negligible. The bottoms of C-2 is mixed with the benzene recycle and cooled to 25°C and maintained at 360 kPa. A larger proportion of DEB is desired to increase the
26
amount of EB formed, however this is related to the high benzene-ethylene ratio entering the R-1/R-2 assembly. There is too much unreacted benzene circulating the recycle streams, and not enough ethylene is present to increase the amount of EB and DEB formed.
2.8 Section 5: Cooling Water System Section 5 of the EB plant consists of the upper and lower cooling water headers for the plant. Figure 2-6 shows the upper header inlet and lower header.
Figure 2-6: Section 5 transalkylation of DEB.
Cooling water at 22°C and 100 psig enters the upper header and exits the plant at 55°C and 100 psig. Approximately 633,000 kg/h of cooling water is required. The outlet temperature was determined to be below 60-70°C to avoid scaling issues. An inlet temperature of 22°C was selected based on an average seasonal temperature.
27
2.9 Energy Requirement Summary The energy requirements for the plant are summarized in Table 2-7. It is readily apparent that the largest utility costs are the condenser and re-boiler of the columns C-1 and C-2. Steam is used for the re-boiler requirements as the temperatures are not unrealistically large. Relatively low pressures are used in the plant resulting in low pump costs.
Table 2-7: Energy requirements summary. Energy Stream P-1-D P-2-D E-1 R-1-1A-D R-1-1B-D R-1-2A-D R-1-2B-D R-2-1A-D R-2-1B-D R-2-2A-D R-2-2B-D E-2 C-1-CD C-1-RD C-2-CD C-2-RB E-3 R-3-1A-D R-3-1B-D P-3-D
Unit P-1 P-2 E-1 R-1-1A R-1-1B R-1-2A R-1-2B R-2-1A R-2-1B R2-2A R-2-2B E-2 C-1 C-1 C-2 C-2 E-3 R-3-1A R-3-1B P-3
28
Power Req. [kW] 10 40 -2,150 -110 -34 490 -10.5 -110 -34 490 -10.5
-415 16,000 16,000 5,000 5,000 853 -128 -25 1.5
3 Market Survey Over 99.9% of the ethyl benzene produced in the world is used in the manufacture of styrene. Therefore, the demand for ethyl benzene is determined primarily by styrene production.16 EB is also used in the manufacturing of industrial solvents and, on occasion, in the production of diethyl benzene, acetophenone and ethyl anthrax-quinone.
3.1 UOP Process In 1996, UOP and Lummus successfully commercialized a new zeolitic EBZ500 catalyst for the alkylation of benzene with ethylene to produce EB.19 The first commercial plant to use the liquid-phase process began production in 1990 by the Nippon Styrene Monomer Corporation (Japan). The plant used the UOC-4120 zeolite catalyst manufactured by UOP for both the alkylation and transalkylation reactors. Two subsequent plants were constructed in Japan in 1994, this time, using the newly developed EBZ-100 transalkylation catalyst. By 1997, full-scale plants were using EBZ-500 (the catalyst proposed for the current project) in South-East Asia, Japan, and Germany.
3.2 Styrenics Industry (Nova Chemicals) Styrene is produced from ethyl benzene, which in turn, is made from benzene and ethylene. All of the ethylene and a significant portion of the benzene requirements for the styrene facility in Sarnia are supplied from the
29
Corunna, Ontario olefins facility. The remaining benzene feedstock is purchased from nearby petroleum refineries.20
Nova’s global styrenic polymer feedstock requirements are presently met through internal styrene monomer production and long-term supply arrangements. For locations in Europe requiring styrene, Nova uses a series of trans-Atlantic arrangements with other producers (at local-producer economics). Three separate acquisitions of styrenics assets from ARCO Chemical Company, Huntsman Corporation and Shell Petroleum Company Limited in 1996, 1998 and 2000, respectively, resulted in Nova being net sellers of styrene monomer.20
Current styrene monomer production capacity, together with long-term supply contracts, exceeds Nova’s annual requirements for styrenic polymer production by 500 million kg. In a tight market, this allows for maximum styrenic polymer sales. It also allows for the sale of scarce monomer at high prices in the spot market. However, when demand for styrene and polystyrene diminish, excess styrene monomer must be sold at low spot prices, straining profit margins.
3.3 Plant Location The geographical location of a plant can play a pivotal role in the design of a plant. When considering a location, many variables must be considered before
30
a conclusion can be drawn on the best site. Although, there can be major environmental aspects to be concerned with, the major factor is for the most economical location such as the availability of raw materials and ambient temperatures. 13
The Nova Chemicals styrene plant is located in Sarnia-Lambton's Chemical Valley, about 230 km west of Toronto, Ontario. Figure 3-1 depicts a map of the location with respect to several of the Great Lakes and Detroit, Michigan. The Sarnia site supplies styrene to Nova Chemicals' Montreal, Quebec and Springfield,
Massachusetts
polystyrene
operations
as
well
as
other
commercial operations in North America and Europe.21
Figure 3-1: Styrene/EB plant location (Sarnia, Ont.).
3.4 Raw Material Availability As discussed in Section 3.2, all ethylene feedstock is obtained from Corunna, as does the majority benzene feed. Both arrive on-site via pipeline. The balance benzene is purchased from local plants.
31
3.4.1 Ethylene20 Nova Chemical owns two ethylene facilities in Canada. The major plant is located in Joffre, Alberta and accounts for 75% of their total ethylene production. The remaining 25% is manufactured at the Corunna, Ontario olefins plant in a flexi-cracker. All ethylene plants at Joffre use ethane as their primary feedstock. Natural gas is purchased to replace the energy loss due to the extracted ethane from the gas stream.
The Joffre site is the largest ethylene complex in the world and runs more economically than its similar counterparts in the US. In 2003 and 2002, this advantage was approximately $0.09/kg, down from about $0.11/kg in 2001, and down from a 14-year historical average of $0.13/kg (Figure 3-2). In 2002 and for most of 2003, excess supply reduced the price for ethane relative to natural gas on the U.S. Gulf Coast (USGC) and caused the cost advantage to decline. In the second half of 2004, demand for ethane began to improve on the USGC and for 2004, the average ethylene advantage increased to $0.15/kg. This results in a feedstock cost of $0.48/kg.
Figure 3-2: Alberta ethylene cost advantage (¢/lb).70 32
The ethylene plant in Corunna has the flexibility to switch part of its feedstock slate between natural gas liquids and crude oil derivatives, depending on market conditions. Feedstock decisions are made by using a model that calculates the most profitable mix of end products that can be produced from the optimal feedstock slate.
3.4.2 Benzene A worldwide shortage of benzene, combined with strong demand for the key raw material has sent prices skyrocketing in 2004. Prices have more than doubled to record highs of $4.25 per US gallon for spot product and $3.95 per US gallon for contract benzene earlier this year. Current benzene price is approximately $3.50 per US gallon ($1.05/kg).
Rapidly increasing benzene pricing (see Figure 3-3) could hurt the US styrene market, however, exports have been strong enough to maintain production. Export pricing on styrene monomer does support these higher benzene levels, especially since ethylene and natural gas prices have moderated. Currently, US styrene demand has been unremarkable.22
33
Ethylene (US contracts; cts/lb) 45 40 35 30 25 20 15 10 5 0 Oct-03 Nov-03 Jan-04 Mar-04 Apr-04 Jun-04 Aug-04 Sep-04 Nov-04 Dec-04
Benzene (US spot; $/gal) 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Oct-03 Nov-03 Jan-04 Mar-04 Apr-04 Jun-04 Aug-04 Sep-04 Nov-04 Dec-04
Methanol (US spot;cts/gal)
Styrene (US spot; cts/lb) 70 60 50 40 30 20 10 0 Oct-03 Nov-03 Jan-04 Mar-04 Apr-04 Jun-04 Aug-04 Sep-04 Nov-04 Dec-04
100 90 80 70 60 50 40 30 20 10 0 Oct-03 Nov-03 Jan-04 Mar-04 Apr-04 Jun-04 Aug-04 Sep-04 Nov-04 Dec-04
Figure 3-3: Selling prices for ethylene, benzene, and styrene for 20032004.23
3.4.3 Operating Results, 2003 versus 200220 Nova’s styrenics business results declined in 2003, bringing their net loss to $130 million from a $102 million loss in 2002. Price increases implemented throughout 2003 kept pace with rapidly rising feedstock costs but were more than offset by higher natural gas-based utilities and distribution costs, as well as the negative impact of the outage on the Bayport, Texas styrene monomer facility. As feedstock costs increased in the fourth quarter of 2003, and continued to rise in early 2004, styrene prices continue to increase. These price increases were announced for styrene monomer and the full slate of styrenic polymers in both North America and Europe. The price increased by $0.07-$0.13/kg between December 2003 and March 2004. Implementation of announced price increases depends on many factors, including market conditions, the supply/demand balance for each particular product and feedstock costs. Price increases have varying degrees of success. They are 34
typically phased in and can differ by product or market. Benchmark price indices sometimes lag behind price increase announcements due to the timing of publication. Revenues increased $274 million, or 21%, from $1,305 million in 2002 to $1,579 million in 2003 due to pricing improvement and strong styrene monomer sales.
3.5 Demand The current global market is stable for styrene, but is poised to tighten considerably, owing to a significant number of turnarounds planned for the first two quarters of 2004. A possible roadblock to any run-up in styrene is its main feedstock benzene, which has seen its price rise because of higher energy costs (as discussed in Section 3.4.2).24
North American demand for ethyl benzene is shown in Figure 3-4. The market is still recuperating from the substantial decrease in demand in 2001, but is expected to increase to six billion kg by 2007.15 Current North American production is shown in Table 3-1, and speculates that there is presently more ethyl benzene being produced than the market can support.
35
6500 $6,119
Demand (millions of kg)
6000
$6,128
$5,858
$5,434
5500
5000
$5,554
$4,819
4500
4000 1998
1999
2000
2001
2002
2003
Figure 3-4: Demand for ethyl benzene since 1998 (in millions of kg). Table 3-1: Yearly North American production of EB.25 Capacity [millions of kg/yr]
Producer BP Chemicals, Texas City, TX
500
Chevron, St. James, LA
800
Cos-Mar, Carville, LA
1,000
Dow, Freeport, TX
850
Huntsman, Odessa, TX
150
Lyondell Chemical, Channelview, TX
1,350
Nova, Bayport, TX
650
Sterling, Texas City, TX
900
Westlake, Lake Charles, LA
150
Nova Chemicals, Sarnia, Ont.
430 Total
6,780
3.6 Outlook Ethyl benzene’s market growth depends highly on the demand for styrene. At current rates, the demand for styrene is growing globally at about 5% annually.15 However, growth in North America is only expected to increase by 36
2% in the long term. Accordingly, ethyl benzene is only expected to increase by 2%.
World demand for ethyl benzene in 2001 was about 23 million metric tons. Overall ethyl benzene demand will increase at an average annual rate of 4.6% from 2001 to 2006 (or 3.4% from 2000 to 2006), resulting in global ethyl benzene demand of about 29 million metric tons in 2006. Consumption is expected to grow the fastest in the Middle East and South America.16
4 Costs The current NPV of the plant is US$ 7 million. This value is based on the assumed 20-year life of the plant and a MARR of 20%. A new process technology is considered a medium level of risk, which corresponds to an MARR between 16-24%.14 The discounted rate of return (ROR) was determined to be 27%.
4.1 Equipment Costs Equipment costs have been calculated for the current plant design based on available data from Peters and Timmerhaus.14 Estimated purchasing and installation costs are shown in Table 4-1. For economical reasons, carbon steel was selected for equipment construction. Carbon steel has suitable corrosion resistance for the chemicals used in the production of EB.14
37
Total purchasing costs in 2004 amount to US$ 3.6 million and total installation costs are US$ 2.3 million. The two distillation columns (C-1 and C-2) account for the largest portion (60%) of the equipment costs. Table 4-1: Equipment costs (all equipment is carbon steel). EB = 156,000 tonne/yr Purchase Cost, US $ 121,800
Install Cost, US $ 54,800
2,600
1,200
35 m3; CS jacketed; 300 psia 35 m3
121,800
54,800
2,600
1,200
35 m3; CS jacketed; 300 psia 35 m3
121,800
54,800
2,600
1,200
16 m3/h
5,600
2,400
10 kW 68 m3/h
1,300 9,300
600 4,000
Pump (P-3)
39 kW 26 m3/h
2,600 6,600
1,100 2,800
Pump Motor (P-3)
2 kW
500
200
33,400
15,000
Equipment CSTR (R-1)
CSTR Motor (R-1) CSTR (R-1)
CSTR Motor (R-1) CSTR (R-1)
CSTR Motor (R-1) Pump (P-1) Pump Motor (P-1)
Pump (P-2) Pump Motor (P-2)
Description 35 m3; CS jacketed; 300 psia 35 m3
p. 628
P = 0.08(V) 3 380(P)0.53 21,000(V)0.529
p. 520
P = 0.08(V) 3 380(P)0.53 21,000(V)0.529
p. 520
P = 0.08(V) 3 380(P)0.53 2,048(v) 0.36 380(P)0.53 2,048(v) 0.36 380(P)0.53 2,048(v) 0.36 380(P)0.53
p. 520
3.3
Heat Exchanger (E-1)
26.9 m2
8,279
3,312
1,290(A)0.565
Heat Exchanger (E-2)
35.4 m2
9,684
3,873
1,290(A)0.565
Heat Exchanger (E-3) Dist Col (C-1)
34.6 m2 3.4 m diameter; 27 trays; 16.3 m height, = 0.6 59E6 kJ/h; 212 m2 59E6 kJ/h; 713 m2
9,546
3,818
1,051,200
788,400
1,290(A)0.565 1,230(D)1.39 × Ntray 4,050(D)1.39 × H
104,800
78,600
245,100
110,300
Reboiler (C-1)
38
Ref (P&T)
21,000(V)0.529
Separator
Condenser (C-1)
m3
Cost Formula
15,000(V)
0.67
A = Q/(1500 × TL ) 7,400(A)0.70 A = Q/(4000 × T) 7,400(A)0.70
p. 628
p. 628
p. 519 p. 520 p. 519 p. 520 p. 519 p. 520 p. 864
p. 682 p. 682 p. 682 p. 794
p. 682 p. 682
Dist Col (C-2)
Condenser (C-2) Reboiler (C-2)
2.3 m diameter; 33 trays; 20.3 m height, = 0.6 18E6 kJ/h; 242 m2 18E6 kJ/h; 368 m2
Totals (2002) Totals (3Q 2004)
977,300
733,000
1,230(D)1.39 × Ntray 4,050(D)1.39 × H
p. 794
115,100
86,300
A = Q/(1500 × TL )
p. 682
2,470(A)0.70 A = Q/(4000 × T)
154,100 3,345,000 3,576,000
2,470(A)0.70
69,400 2,178,000 2,328,000
M&S = 1117 M&S = 1194
4.2 Capital Costs The capital costs for the preliminary plant design are shown in Table 4-2. The capital cost includes equipment, materials, labour, indirect construction costs, engineering, and contingencies. The total capital investment was estimated at US$ 23.7 million or $US 150/tonne-yr. Table 4-2: Capital costs (EB = 156,000 tonne/yr). Item Factor Equipment Installation Instrumentation 0.36 (E) Piping 0.68 (E) Electrical 0.11 (E) Building 0.18 (E) Yard 0.10 (E) Service facilities 0.70 (E) (Land) 0.06 (E) Total Direct Plant Cost (excl. _land) Engineering 0.33 (E) Construction 0.41 (E) Legal Expenses 0.04 (E) Contractors Fees 0.22 (E) Contingency 0.44 (E) Total Indirect Plant Cost Fixed-Capital Investment Start-Up Expense 0.10 (FCI) Working Capital 0.89 (E) Total Capital Investment
39
Cost, US $ 3,576,100 2,328,100 1,287,400 2,431,700 393,400 643,700 357,600 2,503,200 214,600 13,521,100
Reference P&T, p. 244 P&T, p. 251 P&T, p. 251 P&T, p. 251 P&T, p. 251 P&T, p. 251 P&T, p. 248 P&T, p. 176 -
1,180,100 1,466,200 143,000 786,700 1,573,500 5,149,500 18,670,700 1,867,100 3,182,700 23,720,000 ($150/tonne-yr)
P&T, p. 251 P&T, p. 251 P&T, p. 251 P&T, p. 251 P&T, p. 251 P&T, p. 340 P&T, p. 251 -
p. 682
4.3 Direct Operating Costs The projected direct operating costs are summarized in Table 4-3. Since catalyst is purchased once every five years, an annual equivalent rate was calculated. Approximately 96% of the annual cost is associated with the raw material; 83% of which is benzene.
The indirect operating costs, or fixed costs, are represented in Table 4-4. The projected total operating costs (direct and indirect) for the EB plant is estimated at US$ 160.2 million, or US$ 1,030/tonne.
Table 4-3: Direct operating costs (EB = 156,000 tonne/yr). Item
Benzene Ethylene Catalyst Power Water Steam Labour Supervision Maint. & repair Oper. Supplies Labour supplies
Rate
Basis
14,200 kg/yr 4,770 kg/yr 43,500 kg/5yr 50 kW 633,000kg/yr 4,160 kg/yr 0.15 (L)
1.05 0.484 0.05 $0.055/kwh $8E-6/kg (20°C) $7.70E-3/kg (P=100psia) $25/h -
0.07 (FCI) 0.15 (M&R)
-
0.15 (L)
40
Cost , US $/yr 129,717,000 20,081,900 12,400 24,000 44,100
Ref 23 Ref 23 Ref 26 Ref 27 P&T, p. 266
2,769,000 2,175,000 326,300
P&T, p. 266 P&T, p. 265 P&T, p. 270
1,306,900 196,000
P&T, p. 266 P&T, p. 268
326,300
P&T, p. 204
Reference
Table 4-4: Indirect operating costs (EB = 156,000 tonne/yr). Item Basis Taxes 0.015 (FCI) Insurance 0.01 (FCI) Overhead 0.60 (L+S+M) Administration 0.20 (L) Indirect Operating Costs Total Operating Costs
Cost, US $/yr 280,100 186,700 2,284,900 435,000 3,186,700 160,165,700 ($1,030/tonne)
Reference P&T, p. 269 P&T, p. 269 P&T, p. 270 P&T, p. 270 -
4.4 Profitability The current plant design is economically viable. Figure 4-1 shows the expected rate of return as a function of the selling price of ethyl benzene at the current EB selling price of $1.12/kg.71 Note that all other variables (e.g. purchasing price of raw material) are held constant in the calculation. Figure 4-1 indicates that EB can be sold for $1.02/kg to break even and $1.09/kg to
Rate of Return (%)
meet the MARR of 20% based on the current production. 100 90 80 70 60 50 40 30 20 10 0
ROR = 27% Current = $1.12/kg
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
Selling Price of EB ($)
Figure 4-1: Rate of return as a function of selling price. Figure 4-2 shows the relationship of total capital cost (TCI) in $/tonne-year and total operating cost (TOC) in $/tonne as a function of EB production. At 41
the current production rate of 156,000 tonne/yr, the TCI and TOC are approximately $US 150/tonne-year and $US 1,030/tonne, respectively.
Total Capital Investment
Total Operating Cost 1,200.0
210.0 1,000.0
Total Operating Cost
170.0
800.0
150.0
Total Capital Investment
130.0
600.0
110.0
400.0
$ TOC/tonne
$ TCI/tonne-year
190.0
90.0 200.0 70.0 50.0
0.0
110,000
120,000
130,000
140,000
150,000
160,000
170,000
180,000
EB Production (tonne/yr)
Figure 4-2: Relationship of total capital cost and total operating cost as a function of EB production. Figure 4-3 shows the relationship between ROR and ethyl benzene production for various selling prices of EB. 50 45 $1.20/kg
40 35 $1.15/kg
ROR (%)
30 $1.12/kg (Current Price)
25 $1.10/kg
20 15 10
$1.05/kg
5 Current Rate = 156,000 tonne/yr 0 50,000
70,000
90,000
110,000
130,000 150,000 170,000 EB Production (tonne/yr)
190,000
210,000
230,000
250,000
Figure 4-3: Relationship of ROR as a function of EB production for various selling prices of EB (current = $US 1.12/kg). 42
5 Environmental Considerations The following sections discuss general environmental considerations that should be made during the design phase of the EB process.
5.1 Plant Design Considerations There are two main concerns that should be taken into consideration for the plant design and costing: green house gas emissions and waste water treatment.
5.1.1 Greenhouse Gas Emissions
It is expected that steam shall be generated from the combustion of natural gas. This natural gas shall be bought within Nova Chemical’s pipeline near Sarnia. Combustion of the natural gas will produce greenhouse gas emissions that will have to be treated or separated if emissions do not meet the regulation guidelines. Two possibilities for managing CO2 emissions are CO2 sequestration versus CO2 capture and storage.
Carbon dioxide sequestration is the natural act of CO2 storage in nature in a sink. A sink, defined by the United Nations Framework on Climate Change, is a process, activity, or mechanism which removes a greenhouse gas from the atmosphere. There are three main sinks: biospheres (oceans and forests),
43
geological formations (coal beds and active or depleted oil and gas reservoirs), and material sinks (wood products, chemicals, and plastics).
Carbon dioxide capture and storage is an industrial process to capture CO2 from a waste stream and either direct it to a natural sink or store it for industrial use. Modern industry dictates that the safest and most reliable sink is to store CO2 in natural gas and oil reservoir. Based on the current steam requirements for the plant, it is possible that a significant amount of natural gas will be needed to supply the energy requires for the process.28 The greenhouse gasses released from combustion must be either captured or sequestered.
5.1.2 Vapour Flaring The vent gas from column C-1 that cannot be recovered will have to be vented. An alternative is to flare the gas. Flaring the gas will burn the released ethylene and benzene, producing CO2. While this may increase the amount of CO2 exiting the plant, a high efficiency flare can reduce or eliminate the release of benzene and ethylene through the stack.
It is important to ensure that the flare gas does not contain liquid droplets, as they will not necessarily combust upon exit from the plant. The release of benzene is of most concern, as it may exit as liquid droplets in the vent gas. It must be ensured that a high efficiency flare system is designed, along with
44
other preventative measures such as a scrubbing section to eliminate other vent gas impurities. A centralized vent system could be designed around the plant equipment such that vent gases exit a common flare system. This could work barring any unforeseen chemical issues, such as unwanted reactions in the vent system or explosion concerns.29
5.1.3 Process and Waste Water Treatment: Oily Water Sewer Design of a waste treatment facility integrated into the plant design is extremely important for both environmental and safety reasons. Rainwater run off, waste water, process water, and sewage from the plant must all be specially treated. Dumping this into a municipal sewer without treatment is illegal. Process water used for heating and cooling must be treated before release into the environment. This includes temperatures and concentrations.
One hazard associated with oily water sewers is H2S release. Hot process water containing dissolved H2S enters the sewer system, and as the temperature drops, H2S gas is released as a result of a decrease in solubility. This can poison plant employees and release into the environment. Design must take this into consideration.30
5.2 Environmental Regulation: Plant Operation Considerations Environmental regulations govern many aspects of a plant design. Regulations put restrictions on effluent concentrations of hazardous
45
substances, enforce penalties for environmental misconduct, and enforce equipment design constraints. Environmental regulation is a hot topic in Canada. The ultimate governing body for Canadian environmental issues is Environment Canada.
5.2.1 Canadian Environmental Protection Act CEPA is a legal document describing the environmental regulations enforced by Environment Canada.31 It covers a wide range of topics from emission guidelines
to
hazardous
chemical
inventories
to
procedural
safety
requirements. While analysis of the document in its entirety is not required at this time, the most notable guideline from the act is outlined in CEPA 200.
CEPA 200 is a regulation that requires companies to report to Environment Canada concerning the chemicals outlined in the act that break concentration and storage threshold limits proposed by CEPA 200.32 For the purposes of this plant design, it will be necessary to establish this relationship with Environment Canada. Regulation thresholds are detailed in Table 5-1 for the chemicals present in the production of EB.
It is interesting to note that DEB was not present in the regulatory list. This may be because it is generally considered an undesirable byproduct. It is expected that the threshold limits will be breached and as such, detailed reporting will be required as prescribed by CEPA 200.
46
Table 5-1: CEPA 200 regulatory limits.32
Benzene Ethylene EB Toluene
CAS #
UN #
Molar Conc. [%]
71-43-2 100-41-4 74-85-1 108-85-3
1114 1175 1038 & 1962 1294
1.0 1.0 1.0 1.0
Threshold Storage Quantity [tonnes] 10 7000 4.5 2500
5.2.2 National Pollutant Release Inventory The National Pollutant Release Inventory (NPRI) is a standardized method of facilitating the documentation and reporting of pollutant release. It is a legal requirement for companies to follow the NPRI reporting system subject to a specific detailed list of criteria33:
•
Facility size, capacity
•
Employee hours, conditions (over 20,000 h per year threshold)
•
Substance criteria subject to NPRI chemical listings o Part 1A Substances – Core substance list since inception o Part 1B Substances – Includes mercury, arsenic, cadmium, lead etc. (Toxic metals concentrated by human interaction with the environment) o Part 2 Substances – 17 Polycyclic aromatic hydrocarbons (PAH’s) o Part 3 Substances – Dioxins/ furans and hexachlorobenzene (HCB)
47
o Part 4 Substances – Criteria air contaiminants (CAC’s) o Part 5 Substances – Special volatile organic compounds VOC’s
If any one of the criteria is met, then an NPRI report is required. The NPRI also provides a standard for reporting substance releases. The legal basis for the NPRI reporting is covered under Section 46(1) of the Canadian Environmental Protection Act (CEPA).31 Further CEPA requirements involve the creation of emergency action and prevention plans, procedural safety plans, and occupational health and safety committees / systems. An example of such a program standard is the NFPA 1600 Standard form emergency disaster management.34
All main process chemicals used in this plant fall under Part 1A. The threshold limits outlined in CEPA 200 determine whether reporting is required. It is expected that NPRI reporting will be required for this plant once in operation.
5.3 ISO Certification Nova Chemical is an ISO 9001:2000 company. Most ISO (International Standards Organization) standards are designed for specific engineering applications. The ISO 9000 and 14000 standards families are generic management
system
standards.
They
deal
with
customer
quality
requirements, complying with regulations, and environmental objectives.
48
The ISO 9000 standard family is a standard centered on quality management, and provides a standard definition for product quality. It removes the subjective nature of company policy and quality control by creating a set of standards and definitions. It also describes in detail a general quality management system that can be incorporated into any process.35 This management system, already in place at Nova Chemical Corporation, is an important model for ethyl benzene quality control and plant condition quality. It will be the basis for the quality control team stationed at the Sarnia styrene plant.
The ISO 14000 environmental management standards family is designed to minimize the harmful effects of a plant or company on the environment. It encompasses standards based on the fundamental principles of Plan, Do, Check, Act. These are:36
•
Prioritizing environmental aspects (Plan)
•
Integration of environmental aspects in design and development (Plan, Do)
•
Communicating environmental performance (Do)
•
Monitoring environmental performance (Check)
•
Monitoring system performance (Check)
49
•
Program improvement (Act)
Both ISO 9000 and 14000 are designed around the principles of Plan, Do, Check, and Act. These methods are generic to all business practices and are not specific to any one process. Since Nova Chemical is an ISO 9001:2000 certified company, business practices and quality control should already be a company standard, and as such, focus should be directed to the implementation of ISO 14000. It is recommended that these standards should be used to design plant environmental management systems in conjunction with NPRI reporting and company procedural safety techniques.
The health and explosion hazards presented by the aromatic compounds and ethylene warrant the formulation of a strict environmental control policy, which will include procedural safety measures for materials reception, storage, and handling; emergency response protocol, employee training and educational programs; and environmental testing protocol. These represent a fraction of the necessary programs required to satisfy the ISO 14000 standards family criteria.
5.4 Material Concerns As mentioned in the Plant Safety section, the chemicals used in this process present significant human health hazards. Benzene, EB, DEB, and toluene are also toxic to plants and animals. Furthermore, benzene can contaminate
50
ground water and soil. EB and DEB degrade over a span of three days; however benzene takes a much longer time to degrade in soil. Through implementation of ISO 9000 and 14000, programs shall be created for material control and environmental protocol regarding material safety and environmental policy.
5.5 Case Study: Texas Nova Chemical Plant Explosion and Release On June 11th 2003, a fire broke out at the Nova Chemical plant in Bayport, Texas. The heat from the fire ruptured pipes carrying EB. The EB ignited, causing an explosion that sent EB soaring into the air and damaged surrounding equipment.
The limited knowledge available concerning the effects of EB on the human body made remediation difficult. Several workers were exposed to high levels of EB, causing skin irritation, redness, and swelling. The surrounding area, close to several residential complexes, was contaminated with low levels of EB.
Late testing done by Nova Chemical indicated that there was no EB soil contamination. Independent testing indicated that not only were there levels of 34 ppb above the regulation soil contamination limit, but the soil also
51
contained significantly higher levels of benzene, which is much more dangerous. Nova Chemical failed to comment on these findings.37,38
The Nova Chemical explosion illustrates the need for proper substance reporting and appropriate environmental management. Failure to provide information on soil sampling in the allotted time cost Nova Chemical $25,000 per day until they were released. Legal costs and losses in production contribute to losses in revenue. Proper reporting and hazardous inventory accounting could have prevented the release of benzene into the surrounding community. An environmental management system, such as that proposed by the ISO 14000 standard, could be useful in conjunction with NRPI reporting to act as management related loss prevention and mitigation.
6 Safety The following sections address health and safety concerns associated with the inherent properties of all process chemicals, chemical storage hazards, and chemical transportation.
6.1 Chemical Properties The chemicals involved in the production of EB carry safety and health concerns intrinsic to their properties. Descriptions of each chemical and their role in the process are outlined in the following section.
52
6.1.1 Ethylene Ethylene is a colorless gas with a sweet odor at standard temperature and pressure, and a chemical formula of C2H4. Ethylene is extremely flammable, with lower and upper explosion limits of 3.1% to 32.0%, lower and upper flammability limits of 2.7% and 36.0%39, and is considered a simple asphyxiant. Its boiling point is -103.0°C. Table 6-1 shows NFPA hazard codes for the chemicals used in the plant.
Table 6-1: NFPA codes for chemicals used in the production of EB. NFPA Hazard Category
Ethylene40
Benzene42
EB47
DEB51
Toluene53
Rating Key
Health
0
2
2
2
2
Flammability
4
3
3
2
3
Reactivity
0
0
0
0
0
0 = No Hazard 1 = Slight 2 = Moderate 3 = Serious 4 = Severe
Hazard Codes
A summary of exposure limits from various organizations are outlined in Table 6-2.
Table 6-2: Ethylene exposure limits.40 Exposure Limit OSHA-PEL ACGIH-TLV-TWA (8h) Carcinogen? LD50/LC50
Value / Description Simple Asphyxiant Simple Asphyxiant No No Effect
Ethylene is not toxic nor is it carcinogenic. There are no minimum concentrations to report other than to ensure that an oxygen concentration of
53
19.5% is maintained to prevent asphyxiation. There are three main safety concerns with ethylene: •
Flammability
•
Gas compression
•
Asphyxiation
This raises issues of fire prevention and suppression, explosion protection, compressed gas storage, and health concerns in the event that there is an ethylene leak. Ethylene gas leaks could cut off oxygen to plant workers, causing severe injury or death. Compressed gas requires specific storage and handling procedures, while fire fighting systems must be installed that can effectively deal with an ethylene explosion or fire.40 Water spray and fog techniques supported by alcohol resistant foam, dry chemical, and CO2 are acceptable as fire suppression media.
6.1.2 Benzene Benzene is a clear liquid at standard temperature and pressure, and produces an aromatic signature odor.41 It has an aromatic ring structure with a chemical formula of C6H6. Benzene vapours are flammable and will ignite at lower and upper explosion limits of 1.0% to 6.7%, and a flammability range of 1.3% to 7.1%. It has a boiling point of 80.9°C, so vapourization can occur if the temperature becomes too high. The NFPA hazard codes for benzene are displayed in Table 6-1.
54
Benzene poses extreme health hazards to plant workers if not properly contained. It is carcinogenic and attacks the central nervous system.43 Moderate periods of exposure can cause cancer (leukemia). It can enter the body through inhalation, ingestion, and skin absorption. Benzene has a very high absorption rate through the skin.44 Table 6-3 outlines the exposure limits and classifications for various occupational health and safety organizations.
Table 6-3: Benzene exposure limits data.45 Exposure Limit OSHA-TLV-TWA (8h) OSHA-STEL LDLo LD50 LC50 LD50 Dose: Dose: ACGIH IARC NTP IRIS OSHA
Value/ Description 1.6 mg/m3 (0.5 ppm) A1-Skin 8 mg/m3 (2.5 ppm) 50 mg/kg (oral/man) 930 mg/kg (oral/rat) 10,000 ppm / 7 hour (inhalation/ rat) 2,890 µg/m3 (intraperitoneal / rat) 20 mg/ 24h/ Skin/ Rabbit – moderate irritation 2 mg/ 24h/ Eye/ Rabbit – Severe Irritation Group A1 Carcinogen Group 1 Carcinogen Group 1 Carcinogen EPA Class A Carcinogen Group X Carcinogen
It should be noted that the odor threshold for benzene is 12 ppm, much higher than the recommended exposure limits. 46 An employee could work in an environment above the recommended exposure limit without knowing that hazardous quantities of benzene were in the atmosphere. Benzene raises two major safety concerns: •
Flammability
•
Worker exposure / health risks 55
Fire prevention and suppression techniques will be important as flames can travel along the vapour trail above liquid benzene to the source, such as a storage tank. Dry chemical, alcohol resistant foam and CO2 extinguishing media should be used. Water is only effective for cooling the source. The severe impact of benzene on the human body means that strict procedures, proper PPE, and minimizing exposure will be extremely important when handling the chemical.42
6.1.3 Ethyl Benzene Ethyl benzene is a clear colorless liquid at standard temperature and pressure, and produces an aromatic smell, similar to benzene. Its chemical formula is C6H5C2H5. Apart from a higher boiling point of 136°C, it has very similar properties to benzene. It is insoluble in water and has similar flammability limits of 1.0% to 6.7%. EB, like benzene, is stable and nonreactive. The NFPA hazard codes for EB are displayed in Table 6-1.
EB is extremely hazardous to human health from prolonged exposure. It is carcinogenic, attacking the central nervous system.48 Aspiration may cause pulmonary edema and hemorrhage. Skin absorption rate is high, causing skin irritation, reddening, blistering, and dermatitis. EB can also cause sister chromatid exchange. Table 6-4 outlines some occupational health and safety exposure limits. It is important to note that the odor threshold is well below
56
the recommended exposure limits. The level at which one can detect the odor is much less than the recommended threshold limit, so employees can detect leaks before they reach harmful levels. Table 6-4: Ethyl benzene recommended exposure limits.49 Exposure Limit ACGIH-TLV-TWA (8h) ACGIH-STEL (15min) NIOSH OSHA-PEL-TWA (8h) Air Odor Threshold
Value/ Description 100 ppm (434 mg/m3) 125 ppm (543 mg/m3) REL (10 h TWA): 100 ppm STEL (15 min): 125 ppm 100 ppm 2.3 ppm
EB poses similar identifiable hazards to benzene: •
Flammability
•
Worker exposure / health risks
Fire suppression techniques should be installed in the event of an EB fire. EB fire suppression requires CO2, alcohol-resistant foam, or dry chemical extinguishers. Water may be used to cool the area near the source of the fire. Larger fires may also be controlled using water spray or fog techniques. Proper PPE must be worn. Specific materials must be used for PPE, as degradation can occur rapidly. The table below shows various materials and approximate time for degradation of PPE material. EB should be kept away from heavy oxidizers to prevent violent reaction. EB shall be handled in a similar fashion to benzene within the plant.
57
Table 6-5: PPE material and break through time.49 Material Barricade Viton Teflon Butyl Rubber Natural Rubber Neoprene Nitrile Rubber Polyethylene Polyvinyl Alcohol Polyvinyl Chloride Saranex
6.1.4
Breakthrough Time [h] >8 >8 >4 <1 <1 <1 <1 <1 <1 <1 <1
Di-ethyl Benzene and Tri-ethyl Benzene
DEB and TEB chemical properties are similar to EB. Both are flammable and can cause serious health problems to humans.50 Their boiling points marginally increase as more ethyl groups are added to the benzene ring.
Fire hazards and health risks shall be handled in a similar fashion to EB and benzene. The hazards of adding more ethyl groups to the benzene ring to create EB, DEB, and TEB seem to decrease slightly, while boiling points increase.
6.1.5
Toluene
Toluene is an aromatic compound with similar characteristics to benzene. It has similar LFL-UFL limits (1.0%-7.0%) and a wider LEL-UEL range (3.3%19.0%). Due to the added functional group attached to the benzene ring, it
58
has a higher boiling and flash point (111°C and 7°C).52 The NFPA hazard codes for toluene are displayed in Table 6-1.
The most notable risks associated with toluene are the same as benzene: •
Flammability
•
Worker exposure / health risks
Mitigation of toluene fires requires similar strategies to benzene fires. Carbon dioxide, alcohol-resistant foam, and dry chemical extinguishers are all required for smaller fires. Water will not be useful for direct fire extinguishing, however it can be used to cool the fire source to augment suppression techniques. A water mist or fog can be used for larger fires to suppress vapours.54
Toluene presents the same health risks as benzene. The IARC warns that toluene has cancer causing properties. The carcinogenic properties of toluene attack the central nervous system of the body, with multiple points of entry.43 Toluene is present in minimal amounts within the plant, as it is considered an impurity in an almost pure benzene mixture. As such, it does not pose a large hazard relative to benzene in the mixture.
Y-zeolite Catalyst The Y-zeolite catalyst used for the alkylator and transalkylator are the EBZ500 and EBZ-100 catalysts, respectively. The nominal diameter of the
59
spherical catalyst particles is 2.2 mm. It has a density of 740 kg/m3 and does not contain any precious metals. The catalyst does not pose any safety hazard. It is inert in storage and the dust explosion risk is minimal. The catalyst is stored in 210 L steel drums in a cool dry area. Substances such as water, oxygenates, olefins, chlorides, and sulfur poison the catalyst. The catalyst has a long cycle length of 3 to 5 years per regeneration, and can last for three regeneration cycles.55 The y-zeolite catalysts from UOP are safe and environmentally friendly, thus the risk associated with storage and use is minimal.
6.1.6
Chemical Property Summary: Explosion Characteristics
Certain chemical properties have a direct impact on process planning and design. Table 6-6 shows a summary of explosion-related properties of the major chemicals present in ethyl benzene production. Table 6-6 is useful for identifying chemicals that may require significant safety allowances due to the likelihood of an explosion or fire. For all practical purposes in the production of EB, ethylene is a gas. In conjunction with a wide explosion limit range, ethylene has the greatest explosion risk.
60
Table 6-6: Important explosion chemical properties for design considerations.
Substance Ethylene Benzene Ethyl benzene Di-ethyl benzene Toluene57
Boiling Point [°C]
Flash Point [°C]
LFL-UFL [%]
LEL-UEL [%]
-103.7 80.1 136.2 180.0
-11.0 18.056 58.0
2.7-36.0 1.3-7.1 1.0-6.7 0.8-6.0
3.1-32.0 1.0-6.7 1.0-6.7 0.8-6.0
Vapour Pressure [mmHG] @ 20°C -a 166.5 7.1 1.1b
111.0
7.0
1.0-7.0
3.3-19.0
22.0
a…above critical pressure b…value determined at 25°C
Storage will also be an issue, as there are requirements for compressed gas storage, which has its own set of problems, as outlined in Section 6.2. The properties in Table 6-6 and the health risks associated with each substance shall be used to design material storage and transportation schemes.
6.2 Material Storage Substance storage is divided into three major groups: compressed gas storage, liquid storage, and catalyst solids storage.
6.2.1
Compressed Gas Storage
Ethylene is non-corrosive, so most building materials are acceptable for storage tanks, provided they are non-combustible in the event of an explosion or fire. The construction should be designed such that not only could the tank store ethylene under high pressure, but could reduce risk in the event of explosion though an inherently safer and stronger design. The electrical
61
system should be non-sparking and explosion proof. All lines associated with the ethylene system should be earth grounded and bonded to minimize the risk or leaks or pipeline ruptures leading to explosion. Check valves or traps should be installed in the discharge line to prevent backflow of unwanted materials.40 This may eliminate the possibility of oxygen entering the tank, increasing the possibility of ignition or fire.
Ethylene should be stored in a well ventilated, cool, dry area. Storage in excess of 54°C is not recommended, and a pressure regulator should be used when connecting to systems or piping below 2000 psig.40 Smaller gas cylinders should be stored in areas of low traffic, and appropriately chained to a fixed structural element in the event of yoke or valve rupture. Cylinder valves should be designed to break at an opening of no more than 0.75 cm. This limits gas leak velocity and reduces the likelihood a gas cylinder will become airborne.58
Based on material properties, ethylene is stored as a compressed gas or in cryogenic storage. An industrial storage tank designed by Universal Industrial Gases, Inc., is seen below in Figure 6-1.
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Figure 6-1: Typical ethylene storage tank.
This vessel can store between 6,000 to 80,000 gallons, and stores ethylene between 75 and 175 psig59. Industrial ethylene is cryogenically stored as a liquid60. It should be noted that at 175 psig, ethylene must be kept below 43.0°C to be stored as a liquid.
Cryogenic ethylene storage systems designed by Larsen & Toubro Limited store ethylene at atmospheric pressure and -104°C (saturation temperature) using R-22 as a refrigerant. Tanks are insulated and double walled using concrete and other non-combustible materials. A water-foam fire fighting system can be installed for fire suppression. A flare can be installed for the proper incineration of escaping vapours. A DCS (Distributive Control System) is generally implemented for control over tank operations such as tank loading, discharge, and conditions such as temperature and pressure. An
63
explosion barrier was installed as an engineered safety device to help protect surroundings against explosion.61
For this project, an ethylene system would be designed or subcontracted to companies such as Larsen & Toubro Limited or Universal Industrial Gases Limited. Tank construction cost, inert gas material costs, and energy costs for the cryogenic refrigeration system would have to be taken into account.
6.2.2
Liquid Storage
Benzene and ethyl benzene are both liquids at room temperature. While specific information on industrial storage of benzene could not be obtained, general considerations for designing a benzene storage system shall be discussed.
Benzene and ethyl benzene must be stored in a cool, dry area. It is important that the area is well ventilated to decrease the likelihood that vapours could accumulate. It is extremely easy for benzene vapours to accumulate into an explosion air mixture. Inerting a storage tank with nitrogen can be used to decrease oxygen concentrations in the tank and reduce the likelihood of explosion or fire.62
Another common problem with benzene is accumulation of static charge. Agitated benzene and EB mixtures can accumulate static charge. This
64
charge, if allowed to increase, can ignite benzene vapours and cause an explosion. Lower temperatures or chemical additives to increase conductivity can be used to dissipate charge. Minimal agitation also helps to prevent charge build up. Reducing the flow rate in transfer operations as well as incorporating longer residence times in piping can make the process inherently safer by reducing static charge build up.63
6.2.3
Catalyst Solids Storage
Data on catalyst properties and storage was difficult to obtain as most of the information is highly proprietary. It is known however that the Y-zeolite catalyst used in this process is generally obtained in drums of dry catalyst. Based on this information, it is assumed that they should be kept in a dry cool place. The consumption of catalyst is minimal compared to that of the raw materials benzene and ethylene, and as such storage will be on a much smaller scale.
6.2.4
Storage related hazards
The following points are hazards that arise from the storage of the raw materials for the process. They shall only be mentioned here, and expanded if they become significant in economic analysis.
•
Cryogenic expansion leading to explosion
65
•
Extreme cold from cryogenic gas
•
Evaporated cryogenic gas can cause asphyxiation (denser than air)
•
R-22 refrigeration system hazards, storage of R-22
Cryogenic expansion of a liquefied gas is when a gas evaporates so quickly that the pressure relief systems cannot handle the overpressure from expansion. This is generally due to an increase in storage temperature.
6.2.5
Inherently Safer Material Storage
A storage area could be made safer through use of the principles of inherent safety. They can be applied to several areas of material storage.
Ethylene poses the greatest explosion risk. It may be prudent to design the storage system to use several smaller storage tanks. This will minimize the amount of ethylene available for combustion in the event of a fire. This can be extended to the storage of benzene and the product, ethyl benzene.
R-22 is used as a refrigerant for the cryogenic storage of ethylene. It may be wise to limit the amount of R-22 stored at the facility. There is no sense in storing enough R-22 to last several years when it would be safer to store enough for a few months of operation. R-22 is generally recycled, so optimization of the R-22 refrigeration system could reduce the amount of new R-22 required for storage. If a safer refrigerant is available, the alternatives
66
could be studied to measure profitability whether the increase in safety is justified in the cost. This is an example of material substitution.
Benzene and EB must be stored in well ventilated areas. Design of the ventilation systems should be such that natural heat convection and plant layout maximizes plant ventilation characteristics while minimizing cost. Heat from reactors and boilers creates a natural convection air current, which could be utilized to aid in ventilation of the plant. Since much of the equipment is outside, ventilation is not as great a problem. Design of the plant should be such that confined spaces and areas where vapours could be trapped is at a minimum.
Storage conditions are such that it is not practical to move storage conditions closer to standard conditions. Moderating temperatures and pressures for the storage of ethylene is not practical. Cryogenic storage is safe such that the risk justifies its use. Furthermore, it is much more economical to store ethylene as a liquid, increasing density and storing more ethylene in the same space than a gas.
6.3 Material Transportation Ethylene can be transported in large shipping tankers overseas. However, Nova Chemical has an ethylene plant in Joffre, Alberta, and another plant in Corunna, Ontario, that also produces ethylene. The Sarnia plant receives
67
both benzene and ethylene feed stocks from the Corunna plant directly via pipeline.64
Pipelines are covered under many regulatory bodies, such as the Office of Pipeline Safety for the Department of Transport in the U.S. The TPSSC (Technical Pipeline Safety Standards Committee) and THLPSSC (Technical Hazardous Liquids Pipeline Safety Committee) outline standards for pipeline safety for the U.S. Such standards include codes for areas of high residential growth and environmental regulations.65 No information on pipeline regulation could be found on the Environment Canada website, however further research is required.
Basic considerations for pipeline design include: •
Length
•
Material fluid
•
Throughput
•
Geography and climate
•
Construction material
Temperatures in the pipeline can affect fluid flow and pipeline integrity. The length of the pipeline can in part reflect the energy requirements for pumping. Fluid properties affect what type of pipeline construction material is needed, and pumping requirements. The size of the pipeline depends on the flow rate that is desired as well as the velocity of the fluid through the pipe.
68
Higher velocities can put unnecessary forces on the pipeline. The pipeline must be designed to minimize leaks, climate effects, and environment hazards.
6.4 Hazard Analysis 6.4.1
Dow Fire & Explosion Index
The Dow Fire and Explosion indices were used to identify the areas of highest fire and explosion potential in the plant design. An index was created for the major unit operations: each R-1/R-2 assembly reactor, R-3, C-1, and C-2. A summary of the calculated Dow F&EI values is shown in Table 6-7.
Table 6-7: Dow F&EI for the EB plant. Unit
Dow F&EI
R-1/R-2 R-3 C-1 C-2
165 102 60 69
It is clear that the feed into the main alkylation section R-1/R-2 has the most potential for explosion and fire. The main contributing factor to the high value calculated for each reactor in the R-1/R-2 assembly is the large volume of benzene flowing, mainly from the C-1 recycle. The R-1/R-2 assembly also contains the largest amount of ethylene, which requires the use of a higher material safety factor than R-3, which contains very little ethylene.
69
The columns have a low index. This is partly due to the fact that the columns are outside, designed with proper drainage control systems, and do not contain any reactions. These traits minimize the general process hazard penalty. The large volume of material holdup in the columns, primarily benzene, contributes a significant penalty; however it is to be expected given the operation and the size of the columns. The moderate pressures contribute a minor penalty in comparison.
It should be noted that although C-1 and C-2 have the lowest indices, business interruption costs the plant $US 10 million as opposed to $US 2.9 million from the R-1/R-2 assembly. C-1 and C-2 contain more product. Fires and explosions from C-1 or C-2 would result in loss of product and a much more expensive unit operation.
It can be concluded from the Dow F&EI that the R-1/R-2 assembly will require further hazard analysis. Detail of the Dow F&EI can be seen in Appendix E.
6.4.2
Chemical Exposure Index
A Chemical Exposure Index was calculated for each of the major units and flow intersections. A summary of the results is shown in Table 6-8.
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Table 6-8: CEI calculated values. Hazard Distances (ft) CEI Min Mid Max 940 21,000 30,000 39,000 1090 25,000 35,000 46,000
Benzene Feed Recycle Benzene into C-1 Benzene out of R-1/R-2 Assembly 960 22,000 31,000 Benzene into R-1/R-2 1120 25,000 36,000 Assembly Benzene into R-3 540 12,000 17,000 Benzene Flash Drum Inlet 540 12,000 17,000
40,000 47,000 22,000 23,000
The CEI values calculated were extremely high. This can be partially attributed to the large volumes of benzene, the chemically hazardous component, in the system. The majority of process units handle benzene as a liquid, but at a temperature above its boiling point. Any loss in pressure would cause the benzene to vaporize. A worst case scenario of benzene exposure is shown in Figure 2.
Figure 2: CEI hazard distance map 71
The concentric circles represent increasing hazard distances for the R-1/R-2 assembly feed in the event of a worst cast exposure. The prevailing wind for the area and direction of flow of the nearby St. Clair River is also shown72. Benzene exposure concentrations of 1.5 ppm, 2.5 ppm, and 5 ppm correspond to the maximum, middle, and minimum exposure distances, respectively. The amount benzene in each unit is directly related to the CEI, where a higher amount of benzene yields a large CEI. It was determined that the R-1/R-2 assembly will require further hazard analysis.
6.4.3
Hazard Analysis: What-if
A what-if analysis was used to identify potential hazards and appropriate actions required for a variety of scenarios that can take place around the R-1/ R-2 assembly. The what-if analysis can be seen in Appendix D. The following cases were considered: • • • • • • •
Liquid benzene spill Benzene human exposure Fire near R-1/R-2 assembly R-1/R-2 assembly explosion Reactor pressure loss Reactor temperature increase Feed system malfunction
It was determined that all forms of fire prevention and mitigation equipment/systems
are
required,
such
as
CO2/dry
chemical/water
extinguishers, water curtains, alarms, and valve shut-off system. Proper ventilation systems, spill protection systems such as absorbents, chemical
72
sewers, and chemical level sensor systems should be implemented. Fire barricades, reactor materials of construction, and explosion venting should be sufficient for a worst case scenario. Procedural safety measures such as training and emergency action plans should be properly implemented and practiced. Lastly, PPE should be available at appropriate locations for the hazards involved, such as a benzene spill.
It is recommended that a what-if analysis should be conducted for other areas of the plant, as well as a HAZOP once chemical data and design becomes finalized.
6.5 Case Studies The following case studies demonstrate the hazards associated with handling the chemicals in the EB plant, and illustrate instances where proper industrial safety and loss management principles could have been used to prevent or mitigate consequences.
6.5.1
Benzene and Ethylene Explosions
On November 24th, 2001, a Louisiana polymer plant exploded. The source was from a failed safety valve. A controlled release of ethylene and propylene caused the safety valve to rupture, causing the leak. The vapours found an ignition source and exploded. Action was quickly taken to stop further vapour leak, and the fires burnt out once the leak was stopped.66
73
On November 4th, 1985 at Petroleum Stripping Inc., two employees were stripping a benzene barge that was not bonded to prevent static sparking. A spark ignited the vapours, causing an explosion. Both employees were killed as a result of burning and trauma.67
These case studies point out the severity of a leak leading to an explosion for both ethylene and benzene. The ethylene explosion was deemed an accident. The safety valve may not have been properly sized for the operation. It is important to finalize a design and to ensure that it is not changed during construction. Changes can cause a butterfly effect of problems around the plant. The benzene explosion was due to employee negligence, and it is a possibility that they were not informed of the hazards of a flammable vapour and static charge.
To prevent problems such as these from happening, ensuring a consistent design and construction phase of the plant will avoid incorrect equipment sizing. Incorporating employee training programs and procedures for handling chemicals such as benzene will go a long way to improving employee and plant safety.
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6.5.2
Short Term Ethyl Benzene Exposure
On March 18th 1993 at Automotive Switch Co., a contractor was using concrete sealant containing significant quantities of EB to apply to a floor space. A plastic enclosure was used to control dust in the work area. Employees of the plant began to complain about smells and respiratory difficulty. The contractor workers and plant employees began to evacuate the building as more and more people began to suffer the effects of exposure to the leaking sealant. A strong negative pressure within the plant forced sealant vapours through holes in the plastic enclosure and into the plant stock room, which circulated vapours throughout the plant. No MSDS sheet was provided to properly treat the illnesses on site.68
Such an accident is difficult to predict. Better measures to control sealant vapours and provide MSDS sheets should have been considered. This is an example of a deficiency in a loss prevention program and procedural safety. A procedure for controlling vapours should have been implemented. This hazard would have been identified using any of the appropriate hazard identification techniques, such as a What-If analysis or Checklist.
6.5.3
Long Term Benzene Exposure
On April 11th 1988, an employee of C.F. Hoekel Company died of cancer as a result of long term exposure to benzene. The employee was a pen-ruler for the print shop. He used different dyes and inks for custom orders such as county
75
ledgers. The pen-ruling machines were old, dating back to the early 1900’s. He used a mist sprayer apply to benzene, alcohol, and other solvents to clean the ink pens. He did not make use of proper PPE. There was no local exhaust system, nor was he trained in the proper use and handling of benzene. A drum of benzene had be left near the work area for years. No labeling or monitoring was done to ensure employee exposure or safety. The employee was diagnosed with a plastic anemia in early 1988, and died April 11th 1988 as a result of the cancer.69
This is a prime example of the effect of long term benzene exposure. The worker was unaware that benzene posed a significant hazard to his health. The company was either unaware or negligent in providing the proper training and procedures for handing benzene and properly cleaning equipment. It would have been inherently safer to use a cleaning product that was less hazardous. This is a principle of inherent safety known as substitution.
6.5.4
Lessons to be learned
These cast studies document accidents that could have been avoided. They place emphasis on the importance of implementing the following loss management principles:
76
•
It is important to incorporate as many effective inherently safer designs and engineered safety devices as possible in the design stage process. An update in a design may impact a section that had already been completed. Proper sizing considerations may not be taken into account, and as such valves, piping, and other equipment may not be large or strong enough.
•
Hazard identification techniques should be used as early as possible to determine the hazards associated with all plant systems, from loading to processing to transport of products. What-if analyses, checklists, HAZOP, DOW F&EI and Chemical Exposure Indices can be used to find hazards and perform risk assessment.
•
Implement proper procedures for all aspects of a plant, in areas such as receiving raw materials, material storage and local transport, processing, maintenance, emergency procedures, to name a few. This also includes workplace inspections.
•
Provide training for plant employees to ensure they understand the scope of the operation and the hazards associated with their job.
These are a handful of all the considerations that must be looked at to properly design an industrial safety and loss management program in the EB plant. Many of these shall be considered in the design stage of the EB plant.
77
7 Conclusions Ethyl benzene is primarily a reaction intermediate in the production of styrene and styrene derived products. The Lummus/UOP EBOneTM process is one such method to synthesize EB from the reaction of benzene with ethylene. It has been successfully implemented globally at various styrene production plants.
Ethyl benzene plants are generally uneconomical; however gains are made in the production of ethyl benzene derivatives, such as styrene and polystyrene. Given the small relative price difference between benzene and EB, large quantities of EB must be produced to turn a profit. The proposed production (based on Nova Chemicals’ current yearly rate), is approximately 156,000 tonne/yr.
The current NPV of the plant is US$ 7 million, based on the assumed 20-year life of the plant and a MARR of 20%. An MARR of 20% was selected since a new process technology is considered a medium level of risk, which corresponds to an MARR between 16-24%.14 The discounted rate of return (ROR) was determined to be 27%.
The R-1/R-2 reactor assembly contains two trains of reactors, each consisting of two alkylation reactors. Running the reactors in this fashion reduces the
78
volumetric flow rate through each reactor, allowing for reasonably sized reactors of 35 m3. Operating temperatures and pressures range between 120°C-135°C and 1800 kPa.
The largest operational cost in the plant is the amount of raw benzene being used in the process. A recycle system has been implemented in the simulation in order to reduce the amount of purged benzene from 24,000 kg/h to 26 kg/h. In addition, this approach provides the transalkylation section with the benzene it requires for its transalkylation reaction thus eliminating the requirement of raw benzene to the R-2 reactor assembly.
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8 Recommendations The following sections outline recommendations made to improve the plant design.
8.1 Process Recommendations •
The underlying problem affecting many areas of the plant is the high benzene-ethylene feed ratio entering the R-1/R-2 assembly. Insufficient ethylene is introduced into the system. As a result, excess benzene is circulating through the recycle loops. It is desired that more benzene be reacted with ethylene by decreasing this ratio to as low as 1.4:1 to limit the amount of benzene in the large recycle streams.
8.2 Safety and Environmental Recommendations The following recommendations outline what should be considered for the plant design: •
Further hazard analysis should be conducted on other areas of the plant, including a full HAZOP and What-if/Checklist.
•
The R-1/R-2 assembly feed should be reworked to minimize the amount of material present in a given unit or pipe. Currently, the recycle and feed streams are mixed before being cooled to the appropriate reaction temperature. It is desired that the mixing be redesigned such that no pipe or unit contains the entire flow into the assembly.
80
•
Plant layout should be considered using supporting data from Dow F&EI, CEI, and unit sizing.
8.3 Economical Recommendations Current economic values are based on estimated values from literature. However, to determine a more accurate representation of the actual cost, contractors must be consulted for equipment pricing. Detailed drawings for each piece of equipment will also be necessary for a full economic analysis.
81
References 1. Qi, Zhiwen and Zhang, Reishang. Alyklation of benzene with ethylene in a packed reactive distillation column, Ind. Eng. Chem. Res. v.43 (15), 4105-4111, 2004. 2. Encyclopedia of Chemical Processing Design, v.20, 77-78, 1984. 3. UOP: Petrochemical. Lummus/UOP EBOneTM Process, http://www.uop.com/objects/EBOne 20Process.pdf 4. Qi, Zhiwen and Zhang, Reishang. Alyklation of benzene with ethylene in a packed reactive distillation column, Ind. Eng. Chem. Res. v.43 (15), 4105-4111, 2004. 5. Encyclopedia of Chemical Processing Design, v.20, 77-78, 1984. 6. UOP: Petrochemical. Lummus/UOP EBOneTM Process. http://www.uop.com/objects/EBOne%20Process.pdf 7. Tokmakov, I.V. and Lin, M.C., J. Phys. Chem. A 2004, 108, 9697-9714 8. Smith, J.M. et al., Introduction to Chemical Engineering Thermodynamics. New York, McGraw-Hill Higher Education, 2001. 9. Sardina, H.H et al., Manufacture of Alkylbenzenes, 1991, U.S. Patent 5,003,119 10. Zhang, J et al., Process and apparatus for preparation of ethyl benzene by alkylation of benzene with dilute ethylene contained in dry gas by catalytic distillation, 2000, U.S. Patent 6,504,071 11. Standard Reaction for acidity Characterization Ethyl Benzene Disproportionation, IZA Catalysis Comission, 2002. http://www.izacatalysis.org/EB_Disprop.html 12. Catalysis and Reaction Engineering, http://thor.tech.chemie.tumuenchen.de/~tc2/eng/teaching/industr_chem_process2/5.3_alkylation_ etbenzene.pdf 13. Peters, M.S. and Timmerhaus, K.D., Plant Design and Economics for Chemical Engineers, McGraw-Hill, 4th Ed., 1991 14. Peters, M.S. and Timmerhaus, K.D., Plant Design and Economics for Chemical Engineers, McGraw-Hill, 5th Ed., 2002 15. Chemical Market Reporter; Jun 14, 2004; 265, 24; ABI/INFORM Global pg. 27 16. http://ceh.sric.sri.com/Public/Reports/645.3000/ 17. Manufacturing Sites, http://www.novachem.com/03_locations/03_m_sarnia.html 18. http://www.apme.org/media/public_documents/20010821_120531/58.pd f 19. Narsolis, F., et al., High Performance Catalyst for Liquid Phase EB Technology, Petrochemicals And Gas, 2001 20. http://www.novachem.com/AnnualReport03/pdfs/MgmtDiscussion.pdf 21. http://www.novachem.com/03_locations/03_m_sarnia.html 22. articles.findarticles.com/ p/articles/mi_m0FVP/is_6_264/ai_107254269
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23. CW price report, Chemical Week; Nov 17, 2004; 166, 38; ABI/INFORM Global, pg. 27 24. Brown. R., Styrene Poised for Tight First Half of 2004, Chemical Market Reporter; Dec 1, 2003; 264, 19; ABI/INFORM Global, pg. 1 25. http://www.the-innovation-group.com/ChemProfiles/Ethyl benzene.htm 26. http://www.ars.usda.gov/research/publications/Publications.htm?seq_n o_115=137352 27. Green Power Suppliers, http://www.electricitychoices.org/greenpower.html 28. Environment Canada: Greenhouse Gas Emissions: http://www.ec.gc.ca/energ/oilgas/co2/co2_general_e.htm 29. Environment Canada: Vapour Flaring: http://www.ec.gc.ca/energ/oilgas/flaring/flaring_general_e.htm 30. Local Hazardous Waste Management in King County: Oily Water: http://www.govlink.org/hazwaste/business/wastedirectory/wastedetails. cfm?wasteid=142 31. Department of Justice, Canada: Canadian Environmental Protection Act: http://laws.justice.gc.ca/en/C-15.31/ 32. Environment Canada: CEPA 200 Substance Reporting: http://www.ec.gc.ca/CEPARegistry/guidelines/impl_guid/x4.cfm 33. Environment Canada: National Pollutant Release Inventory: http://www.ec.gc.ca/pdb/npri/2003Guidance/Guide2003/NPRI_Guide_2 003.pdf#page=104 34. NFPA 1600 Standard: Disaster Emergency Planning & Business Continuity Standard: http://www.cheminst.ca/divisions/psm/CEPA200/MacKay%20CEPA%2 0200%20Preparedness%20%20Response%20Feb.%2004.ppt#262,12,NF PA%201600 35. ISO (International Standards Organization) http://www.iso.org 36. ISO 14000 Environmental Management System: http://www.iso.org/iso/en/prods-services/otherpubs/iso14000/model.pdf 37. Nova Chemical Explosion Bayport, Texas: http://www.texasbucketbrigade.org/newsletter/june%20newsletter.html 38. Nova Chemical Explosion Bayport, Texas: Release Information: http://kpft.igc.org/news/070203story5.html 39. Engineering Tool Box - http://www.engineeringtoolbox.com/9_423.html 40. BOC Gases – MSDS – Ethylene – http://www.vngas.com/pdf/g33.pdf 41. Physical and Theoretical Chemistry Laboratory http://physchem.ox.ac.uk/MSDS/BE/benzene.html 42. MSDS - Benzene http://www.ril.com/cmshtml/msdsben.pdf?page_id=516 43. International Agency for Research on Cancer - http://wwwcie.iarc.fr/monoeval/crthall.html
83
44. MSDS – Ethyl benzene http://www.osha.gov/SLTC/healthguidelines/ethyl benzene/recognition.html 45. Petro Canada – Benzene MSDS Sheet 46. MSDS Benzene http://www.ejnet.org/plastics/polystyrene/benzene.html 47. CHEMREST – Comprehensive guide to Chemical Resistant Best Gloves http://www.chemrest.com/Toxicity%20and%20Risk%20Codes/Ethyl%20 Benzene.htm 48. International Agency for Research on Cancer - http://www.iarc.fr/ 49. MSDS - Ethyl benzene http://www.osha.gov/SLTC/healthguidelines/ethyl benzene/recognition.html 50. MSDS – DEB - https://fscimage.fishersci.com/msds/38247.htm 51. CPChemTM MSDS – Chevron Phillips Chemical Company LP 52. Mallinckrodt Chemicals http://www.jtbaker.com/msds/englishhtml/t3913.htm 53. ScienceStuff.com - http://www.sciencestuff.com/msds/C2881.html 54. Mallinckrodt Chemicals http://www.jtbaker.com/msds/englishhtml/t3913.htm 55. UOP – http://www.uop.com 56. International Training Organization http://www.itcilo.it/actrav/actrav-english/telearn/osh/ic/100414.htm 57. Mallinckrodt Chemicals http://www.jtbaker.com/msds/englishhtml/t3913. 58. Canadian Center for Occupational Health & Safety http://www.ccohs.ca/oshanswers/chemicals/compressed/compress.html 59. Universal Industrial Gases Inc. http://www.uigi.com/lng_eth_tanks.html 60. Larsen & Toubro Limited http://www.lntenc.com/lntenc/services/industries/chemical/cryogenic.htm 61. Larsen & Toubro Limited http://www.lntenc.com/projects/chemical/cryogenicprojects.htm 62. Petro Canada – Benzene MSDS Sheet 63. Canadian Center for Occupational Health and Safety http://www.ccohs.com/oshanswers/chemicals/chem_profiles/benzene/wo rking_ben.html 64. Nova Chemical, http://www.novachem.com/03_locations/03_manufacturing_f.html 65. USDOT – Office of Pipeline Safety - http://ops.dot.gov/ 66. Louisiana polymer plant explosion: http://www.acusafe.com
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67. Petroleum Stripping Inc. benzene explosion: http://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=144984 63 68. Automotive Switch Co.: EB employee exposure: http://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=675231 69. C.F. Hoekel Company: Long term benzene exposure: http://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=145060 59 70. Nova Chemicals 2004 Annual Report, http://www.novachem.com/AnnualReport04/nova.htm 71. Viswanathan, P., ACN: Asian Chemical News, Mar 14-Mar 20, 2005. Vol.11, Iss. 482; pg. 25 72. Sarnia Prevailing Winds, http://www.theweathernetwork.com
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Appendices A. Economics Spreadsheet ITEM Labour (4 operators)
VALUE $25/h
Plant life Hours/year Feed water
20 a 8700 $0.008/kg
ITEM Project Start Plant Start-up Income Tax
VALUE Sept 2006 Sept 2007 60.0%
$/kg Ethylene ($/lb) Benzene ($/gal) Styrene ($/lb) Ethylbenzene ($/lb)
0.22 3.5 0.64 0.5104
0.484 1.05 1.12288
Equipment Costs (M&S Index = 1117) EQUIPMENT CSTR (R-1-1A) CSTR Motor (R-1-1A) CSTR (R-1-2A) CSTR Motor (R-1-2A) CSTR (R-2-1A) CSTR Motor (R-2-1A) CSTR (R-2-2A) CSTR Motor (R-2-2A) CSTR (R-3-1A) CSTR Motor (R-3-1A)
TYPE Reactor R_Motor Reactor R_Motor Reactor R_Motor Reactor R_Motor Reactor R_Motor
SIZE Volume Volume Volume Volume Volume Volume Volume Volume Volume Volume
Pump (P-1) Pump Motor (P-1) Pump (P-3) Pump Motor (P-3) Pump (P-2) Pump Motor (P-2) DIST COL (C-1)
Pump P_Motor Pump P_Motor Pump P_Motor
Vol. Flow Rate Power (Duty) Vol. Flow Rate Power (Duty) Vol. Flow Rate Power (Duty) Diameter Ntray Height Q TLout TLin Delta TL Area Q TLout TLin Delta TL Area Diameter Ntray Height Q TLout TLin Delta TL Area Q TLout TLin Delta TL Area
DC_Trays DC_H Condenser (C-1)
Cond Reboiler (C-1)
Reb DIST COL (C-2) DC_Trays DC_H Condenser (C-2)
Cond Reboiler (C-2)
Reb
Separator (V-100)
Sep
HX1 HX2 HX2
HX HX HX
IMPORTED SPECS
UNITS 35.0 35.0 35.0 35.0 35.0 35.0 35.0 35.0 30.0 30.0
PURCHASE COST, $000INSTAL (%) 122 $ 45.00 3 45.00 122 45.00 3 45.00 122 45.00 3 45.00 122 45.00 3 45.00 111 45.00 2 45.00
16.1 10.2 25.6 1.5 67.8 38.5 3.4 26.7 16.3 5.89E+07 82.6 132.1 49.5 211.7 5.92E+07 193.8 214.6 20.7 713.4 2.3 33.3 20.3 1.80E+07 184.7 188.5 3.9 242.3 1.79E+07 241.2 253.4 12.2 367.6
Volume 0 Area Area Area
Total cost (2002) M&S cost index for 2002 335 M&S cost index for 3Q 2004 Total cost (2004)
152.0538
86
42.50 42.50 42.50 42.50 42.50 42.50
2 1 3 0 4 1
397 654
75.00 75.00
298 491
105
75.00
79
245
45.00
110
369 608
75.00 75.00
277 456
154
3.3
15.4
6 1 7 0 9 3
115
33,399 $
26.9 35.4 34.6
8,279 9,684 9,546 $
$
INSTALL COST, $000 55 1 55 1 55 1 55 1 50 1
3,345,443 $ 1117 1194 3,576,060 $
7.50E+01
86
45.00
69
45.00
15,029
40.00 40.00 40.00
3,312 3,873 3,818
2,177,942 1117 1194 2,328,077
87
1.12
$
2
-$23,720,434.22
PV
$7,202,033
$0.00
-$23,720,434.22
NPV
$0.00
-$23,720,434.22
152777.7778
$5,511,469.00
3
0
$4,592,890.83
$18,440,987.91 $933,533.66 $17,507,454 $10,504,472.55 $7,936,515
$156,979,035.63 $175,420,024
Products EB (kg/hr)
NPV for the first 7 years
$0.00
$0.00
-$23,720,434.22
Gross Revenue Depreciation Gross Profit Tax Net Profit $18,440,987.91 $933,533.66 $17,507,454 $10,504,472.55 $7,936,515
1
$156,979,035.63 $175,420,023.54
$3,182,693.71 $20,537,740.51
0
20% P&T (p. 322) Medium Level of Risk 60% 20 8700
23,720,434.22 $18,670,673
$
Operating Costs Product sales
Working capital Capital (excl. Working cap)
Year
Interest Rate (%) Tax Rate (%) Economic life (# Years) Hours/year
Total Plant Cost FCI Products EB ($/kg) Total Working Capital
4
0 1 2
Interest Charge
5
8 8 8
6
7
Payment Balance 36652.54988 7,116,130.27 36652.54988 7,648,768.14 36652.54988 8,224,017.04
0
$3,827,409.03
$18,440,988 $933,533.66 $17,507,454 $10,504,472.55 $7,936,515
0
$3,189,507.52
$18,440,988 $933,533.66 $17,507,454 $10,504,472.55 $7,936,515
0
$2,657,922.94
$18,440,988 $933,533.66 $17,507,454 $10,504,472.55 $7,936,515
61397.96239
$2,214,935.78
$18,440,988 $933,533.66 $17,507,454 $10,504,472.55 $7,936,515
$10,504,472.55
$156,979,035.63 $156,979,035.63 $156,979,035.63 $156,979,035.63 $156,979,035.63 $175,420,024 $175,420,024 $175,420,024 $175,420,024
Year
17,956.70
B. Sample Equipment Cost Calculations The cost equation is in the form of: C = Co (size)n
(B.1)
Where: C = cost of equipment Co = a constant n = cost exponent Co and n are found knowing two values of cost and size. Taking the natural log (ln) of Eq. (B.1.): ln(C) = n ln(size) + ln(Co )
(B.2)
And with two values, one gets:
ln
(size)2 C2 = n ln (size)1 C1
(B.3)
Cost of stirred reactor Description: Carbon steel, 300 psia (2070 kPa) {current process is at 260 psia} From Fig 13-15, p. 628 (P&T, 2002) 6.0 m3 = $40,000 0.2 m3 = $5,000 So,
ln
40,000 6 = n ln 5,0001 0 .2
Solve for n: n = 0.611 then from Eq. B.2, Co = 13,880 ∴ cost = 13,880(Volume)0.611
88
(B4)
Cost of Heat Exchanger Description: Fixed-tube-sheet heat exchanger; Material adjustment factor: 1.0 (Carbon steel) From Fig 14-18, p. 682 (P&T, 2002) 5 m2 = $3,000 400 m2 = $30,000 So,
ln
30,000 400 = n ln 3,0001 5
Solve for n: n = 0.525 then from Eq. B.2, Co = 12,900 ∴ cost = 12,900(Area)0.525
89
(B.6)
C. Glossary ACGIHTLV DEB EB IARC IRIS IRR LD50/LC50 LDLo/LCLo LEL-UEL LFL-UFL NFPA NIOSHREL NTP OSHA-PEL ROR STEL TEB TWA
American Conference of Governmental Industrial Hygienists Threshhold Limit Value Di-ethyl benzene Ethyl benzene International Agency for the Research on Cancer Integrated Risk Information System Internal rate of return Lethal Dose/ Concentration Kill 50% Lowest published lethal dose Lower and upper explosive limits Lower and upper flammability limits National Fire Prevention Association National Institute for Occupational Health and Safety Recommended Exposure Limit National Toxicology Program Occupational Health and Safety Association Permissible Exposure Limit Rate of return Short Term Exposure Limit (15 min) Tri-ethyl benzene Time weighted average
90
D. What-if? Analysis
WHAT-IF
CONSEQUENCE(S)
1) What if there is a Benzene spill from a surge drum in the R1 assembly?
• Flammable vapors within 1.3 vol% or below or 8 vol% high may ignite off the surge drum pumps or other ignition source. Causing Harm or loss to process, personnel and/or environment. • Human exposure to a carcinogenic chemical
2) What if there is human exposure to benzene near the R-1 assembly?
• Exposure to a carcinogenic substance which may result in burns to the eyes and face and increase potential of cancer.
3) What if there is a fire near the R-1 assembly? (includes: benzene, ethylbenzene, and ethylene)
• Possible loss to property, process, people and environment.
EXISTING SAFEGUARDS • Safety shower, fire blankets, and CO2/Dry Chemical extinguishers are present near the surge drum and every 20 meters thereafter. • Level controls present on the surge drum with operator alarms and control options via a remote source. • Chemical sewers and proper treatment of sewage.
• See existing safeguards for surge drum spill. • PPE such as safety glasses, coveralls and safety gloves. • Safety procedures for cleanup and evacuation. • Fire codes enforced, and practiced by fire hall or department. • Safety awareness by management to employees regarding fire hazards of chemicals used on plants. • Fire alarms on site • Fire retardant construction and materials.
91
RECOMMENDATIONS • Ensure that safety devices such as safety showers, extinguishers, and remote control are operational and maintained. • Safety courses (WHMIS) to ensure employees are aware of the hazards. • Inspection of process to minimize benzene or other chemical spill from unit operations. • Ensure the process controller is functioning properly or calibrated correctly on a regular basis. • Investigate and control the amount of raw benzene contained in the plant site. • Ensure that PPE is in good working condition. • Ensure that procedures for evacuation and cleanup are up to date and in practices.
• Ensure codes are in practice • Ensure MSDS’s of flammable components are on site (for hazard awareness) • Quarterly fire drill improvement plans by fire hall and management
4) What if a reactor in the R-1 assembly explodes?
• Property Damage • Injury/death • Halted production • Fire can spread to other parts of the plant
5) What if the reactor section looses pressure (pressure decrease)?
• Ethylene/ benzene flash • Possible leak of gas into plant / atmosphere • Vapors enter downstream operations / pumps • Heat exchanger efficiency will decrease as a result of vapors in tubes (poor contact, heat transfer properties of vapor)) • Distillation column operating conditions will be affected • Reactor pressure causes explosion • Temperature runway degrades tubes • Temperature and pressure damages reactor internals • Temperature causes coking (fine particles degrades catalyst) • Possible loss to People • Loss to process during shutdown. • Possible loss to environment due to
6) What-if reactor pressure/ temperature increases well above desired operational values? (exothermic reaction)
• Explosion barricades • Proper plant layout where reactors are outside minimum range for explosion (Dow F&EI) • Sprinkler/ CO2/ Chemical Extinguishers • Water curtain • Emergency shut-off valve system • High strength materials construction for the reactors • None currently present in simulation • Water curtain to contain any large vapor release
• Pressure Safety Release/ Valve • temperature controlled jacket around reactor • appropriate unit operations upstream to control reactor feed • appropriate process control in place to control reactor conditions
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• Proper emergency procedural training practices regularly • Ensure adequate PPE is readily accessible in the event of an explosion (for Benzene exposure, smoke etc.) • Install Properly functioning explosion venting to direct explosive force
• Redundant compressors and pumps • Vapor collection and recycle systems
• Ensure engineered safety items are incorporated into process, and ensure all are in proper working condition • Update or create more rigorous safety inspections and protocols for reactor maintenance • Inspect process control to ensure it is properly tuned. • Follow proper maintenance schedule and equipment strategies
7) What if there is an Ethylene feed system complication? (explosion, fire, etc.)
reactor spillage or vapors released into air. • process shut down • non-sparking or ignition components installed (unit operations) • Storage tanks ignite and exploding, causing damage to the property and halting process. People and environment may also be harmed.
• Properly labeled storage area and tanks • NO SMOKING signs appropriately placed • Explosion barricades protecting existing equipment • Chemical monitoring and alarm systems both portable and fixed. • Fire retardant construction and materials.
93
• investigate whether nonsparking or ignition unit operations are used • Incorporate a maintenance schedule to ensure tight seals on fittings and assess degradation of storage area. • Reduce the amount of Ethylene stored in one place. • Install proper ventilation system to avoid gas buildup. • Possible redundant feed system design
E. F&EI Sample Calculations R-1/R-2 Assembly 1
Material Factor: Ethylene Penalty Factor Range
General Process Hazards Base Factor
24.00 Penalty Factor Used
1.00
1.00
A.
Exothermic Chemical Reactions
0.30 - 1.25
0.50
B.
Endothermic Processes
0.20 - 0.40
0.00
C.
Material Handling and Transfer
0.25 - 1.05
0.00
D.
Enclosed or Indoor Process Units
0.25 - 0.90
0.45
E.
Access
0.25 - 0.35
0.00
F.
Drainage and Spill Control
0.25 - 0.50
0.00
(gallons)
305,000
General Process Hazards Factor (F1) 2
1.95
Special Process Hazards Base Factor
A.
Toxic Material(s)
B.
Sub-Atmospheric Pressure (<500 mmHG)
C.
Operation in or near flammable range Tank farms storage flammable 1 liquids Process upset of 2 purge failure Always in flammable 3 range
D.
Dust explosion (See Table 3)
E.
Pressure (See Figure 2) (psig)
F.
Low Temperature
G.
Quantity of Flammable/Unstable Material
1 2 3
1.00
1.00
0.20 - 0.80
0.40
0.50
0.00 0.00
0.50
0.00
0.30
0.30
0.80
0.00
0.25 -2.00
0.00
Operating Pressure
244
0.48
Relief Setting
300
0.53
0.52
0.20 - 0.30
0.00
Quantity (lb) Hc (BTU/lb) Liquids or Gasses in Process (Fig. 3) Liquids or Gasses in Storage (Fig. 4) Combustible Solids in Storage, Dust in Process (Fig. 5)
43000 18,000 1.32 0.00
0.00
H.
Corrosion and Erosion
0.10 - 0.75
0.00
I.
Leakage 0 Joints and Packing
0.10 - 1.50
0.00
J.
Use of Fired Equipment (Fig. 6)
K.
Hot Oil Heat Exchange System
L.
Rotating Equipment
0.00 0.15 - 1.15
0.00
0.50
0.00
Special Process Factor (F2)
3.53
Process Unit Hazards Factir (F1 x F2) = F3
6.89
Fire and Explosion Index (F3 x MF = F&EI)
165.25
94
1. Process Control Credit Factors (C1)
Feature
Credit Factor Used
Credit Factor Used
Feature
a. Emergency Power
0.98
f. Inert Gas
1.00
b. Cooling
0.97
g. Operating Instructions/Procedures
0.91
c. Explosion Control
0.84
h. Reactive Chemical Review
0.91
d. Emergency Shutdown
0.98
i. Other Process Hazard Analysis
0.94
e. Computer Control
0.93 C1 Value
0.57
2. Material Isolation Credit Factor (C2)
Feature
Credit Factor Used
Credit Factor Used
Feature
a. Remote Control Valves
0.96
c. Drainage
0.91
b. Dump/Blowdown
0.98
d. Interlock
0.98 C2 Value
0.84
3. Fire Protection Credit Factor (C3)
Feature
Credit Factor Used
Credit Factor Used
Feature
a. Leak Detection
0.94
f. Water Curtains
0.97
b. Structural Steel
0.98
g. Foam
0.94
c. Fire Water Supply
0.94
h. Hand Extinguishers/Monitors
0.98
d. Special Systems
0.91
i. Cable Protection
0.94
e. Sprinkler Systems
0.81 C3 Value Loss Control Credit Factor = C1 x C2 x C3
0.54 0.25
1. Fire & Explosion Index (F&EI)…………………………………… (See Front)
165.25
2. Radius of Exposure (ft)……………………………………………….… (Figure 7)
138.81
3. Area of Exposure (ft2)…………………………………………………………………
60535.58
4. Value of Area of Exposure……………………………………………………….….
$112,088.00
5. Damage Factor………………………………………………………….. (Figure 8)
6.50
6. Base Maximum Probable Property Damage……………………………. (4x5)
$728,572.00
7. Loss Control Credit Factor………………………………………... (See Above)
0.25
8. Actual Maximum Probable Property Damage…………………………. (6x7)
$185,650.33
9. Maximum Probable Days Outage………………………………….. (Figure 9)
8.00
10. Business Interruption…………………………………………………………….
$2,908,888.89
95
R-3 1
Material Factor: Benzene
General Process Hazards Base Factor
Penalty Factor Range
16.00 Penalty Factor Used
1.00
1.00
A.
Exothermic Chemical Reactions
0.30 - 1.25
0.50
B.
Endothermic Processes
0.20 - 0.40
0.00
C.
Material Handling and Transfer
0.25 - 1.05
0.00
D.
Enclosed or Indoor Process Units
0.25 - 0.90
0.45
E.
Access
0.25 - 0.35
0.00
F.
Drainage and Spill Control General Process Hazards Factor (F1) Special Process Hazards
0.25 - 0.50
0.00
2
(gallons)
305,000
1.95
Base Factor A. B. C.
Toxic Material(s) Sub-Atmospheric Pressure (<500 mmHG) Operation in or near flammable range
D. E.
2 3
Always in flammable range
Dust explosion (See Table 3) Pressure (See Figure 2) (psig)
F.
Low Temperature
G.
Quantity of Flammable/Unstable Material
1.00
0.20 - 0.80
0.40
0.50
0.00 0.00
Tank farms storage flammable liquids Process upset of purge failure
1
1.00
0.50
0.00
0.30
0.30
0.80
0.00
0.25 -2.00
0.00
Operating Pressure
52
0.24
Relief Setting
75
0.27
0.25
0.20 - 0.30
0.00
Quantity (lb)
44000
Hc (BTU/lb)
18,000
1
Liquids or Gasses in Process (Fig. 3)
1.33
2
Liquids or Gasses in Storage (Fig. 4) Combustible Solids in Storage,
0.00
Dust in Process (Fig. 5)
0.00
3
H.
Corrosion and Erosion
0.10 - 0.75
0.00
I.
Leakage 0 Joints and Packing
0.10 - 1.50
0.00
J.
Use of Fired Equipment (Fig. 6)
K.
Hot Oil Heat Exchange System
L.
Rotating Equipment
0.00
Special Process Factor (F2) Process Unit Hazards Factir (F1 x F2) = F3
0.15 - 1.15
0.00
0.50
0.00 3.29 6.41
Fire and Explosion Index (F3 x MF = F&EI)
102.52
96
1. Process Control Credit Factors (C1) Credit Factor Used
Feature
Credit Factor Used
Feature
a. Emergency Power
0.98
f. Inert Gas
1.00
b. Cooling
0.97
g. Operating Instructions/Procedures
0.91
c. Explosion Control
0.84
h. Reactive Chemical Review
0.91
d. Emergency Shutdown
0.98
i. Other Process Hazard Analysis
0.94
e. Computer Control
0.93 C1 Value
0.57
2. Material Isolation Credit Factor (C2) Credit Factor Used
Feature
Credit Factor Used
Feature
a. Remote Control Valves
0.96
c. Drainage
0.91
b. Dump/Blowdown
0.98
d. Interlock
0.98 C2 Value
0.84
3. Fire Protection Credit Factor (C3) Credit Factor Used
Feature
Credit Factor Used
Feature
a. Leak Detection
0.94
f. Water Curtains
0.97
b. Structural Steel
0.98
g. Foam
0.94
c. Fire Water Supply
0.94
h. Hand Extinguishers/Monitors
0.98
d. Special Systems
0.91
i. Cable Protection
0.94
e. Sprinkler Systems
0.81 C3 Value Loss Control Credit Factor = C1 x C2 x C3
1. Fire & Explosion Index (F&EI)…………………………………… (See Front)
0.54 0.25
102.52
2. Radius of Exposure (ft)……………………………………………….… (Figure 7)
86.11
(ft2)…………………………………………………………………
23297.04
4. Value of Area of Exposure……………………………………………………….….
$97,981.00
5. Damage Factor………………………………………………………….. (Figure 8)
5.50
6. Base Maximum Probable Property Damage……………………………. (4x5)
$538,895.50
7. Loss Control Credit Factor………………………………………... (See Above)
0.25
8. Actual Maximum Probable Property Damage…………………………. (6x7)
$137,318.11
9. Maximum Probable Days Outage………………………………….. (Figure 9)
7.00
10. Business Interruption…………………………………………………………….
$2,545,277.78
3. Area of Exposure
97
Material Factor: Benzene
C-1
1
Penalty Factor Range
General Process Hazards Base Factor
16.00 Penalty Factor Used
1.00
1.00
A.
Exothermic Chemical Reactions
0.30 - 1.25
0.00
B.
Endothermic Processes
0.20 - 0.40
0.00
C.
Material Handling and Transfer
0.25 - 1.05
0.00
D.
Enclosed or Indoor Process Units
0.25 - 0.90
0.00
E.
Access
0.25 - 0.35
0.00
F.
Drainage and Spill Control
0.25 - 0.50
0.00
(gallons)
305,000
General Process Hazards Factor (F1) 2
1.00
Special Process Hazards Base Factor
A. B. C.
Toxic Material(s) Sub-Atmospheric Pressure (<500 mmHG) Operation in or near flammable range Tank farms storage flammable 1 liquids Process upset 2 of purge failure Always in flammable range 3
D.
Dust explosion (See Table 3)
E.
Pressure (See Figure 2) (psig)
Operating Pressure Relief Setting
F. G.
Hc (BTU/lb)
1.00
0.20 - 0.80
0.40
0.50
0.00 0.00
0.50
0.00
0.30
0.30
0.80
0.00
0.25 -2.00
0.00
78
0.28
117
0.33
0.28
0.20 - 0.30
0.00
Low Temperature Quantity of Flammable/Unstable Material Quantity (lb)
1.00
80,0 00 20,0 00
1
Liquids or Gasses in Process (Fig. 3)
1.76
2
Liquids or Gasses in Storage (Fig. 4)
0.00
3
Combustible Solids in Storage Dust in Process (Fig. 5)
0.00
H.
Corrosion and Erosion
0.10 - 0.75
0.00
I.
Leakage 0 Joints and Packing
0.10 - 1.50
0.00
J.
Use of Fired Equipment (Fig. 6)
K.
Hot Oil Heat Exchange System
L.
Rotating Equipment Special Process Factor (F2) Process Unit Hazards Factir (F1 x F2) = F3
0.00 0.15 - 1.15 0.50
Fire and Explosion Index (F3 x MF = F&EI)
0.00 0.00 3.74 3.74 59.86
98
1. Process Control Credit Factors (C1)
Feature
Credit Factor Used
Credit Factor Used
Feature
a. Emergency Power
0.98
f. Inert Gas
1.00
b. Cooling
0.97
g. Operating Instructions/Procedures
0.91
c. Explosion Control
0.84
h. Reactive Chemical Review
0.91
d. Emergency Shutdown
0.98
i. Other Process Hazard Analysis
0.94
e. Computer Control
0.93 C1 Value
0.57
2. Material Isolation Credit Factor (C2)
Feature
Credit Factor Used
Credit Factor Used
Feature
a. Remote Control Valves
0.96
c. Drainage
0.91
b. Dump/Blowdown
0.98
d. Interlock
0.98 C2 Value
0.84
3. Fire Protection Credit Factor (C3)
Feature
Credit Factor Used
Credit Factor Used
Feature
a. Leak Detection
0.94
f. Water Curtains
0.97
b. Structural Steel
0.98
g. Foam
0.94
c. Fire Water Supply
0.94
h. Hand Extinguishers/Monitors
0.98
d. Special Systems
0.91
i. Cable Protection
0.94
e. Sprinkler Systems
0.81 C3 Value Loss Control Credit Factor = C1 x C2 x C3
0.54 0.25
1. Fire & Explosion Index (F&EI)…………………………………… (See Front)
59.86
2. Radius of Exposure (ft)……………………………………………….… (Figure 7)
50.28
3. Area of Exposure (ft2)…………………………………………………………………
7941.87
4. Value of Area of Exposure……………………………………………………….….
$919,725.00
5. Damage Factor………………………………………………………….. (Figure 8)
5.50
6. Base Maximum Probable Property Damage……………………………. (4x5)
$5,058,487.50
7. Loss Control Credit Factor………………………………………... (See Above)
0.25
8. Actual Maximum Probable Property Damage…………………………. (6x7)
$1,288,973.32
9. Maximum Probable Days Outage………………………………….. (Figure 9)
20.00
10. Business Interruption…………………………………………………………….
$7,272,222.22
99
C-2 1
Material Factor: Benzene Penalty Factor Range
General Process Hazards Base Factor
16.00 Penalty Factor Used
1.00
1.00
A.
Exothermic Chemical Reactions
0.30 - 1.25
0.00
B.
Endothermic Processes
0.20 - 0.40
0.00
C.
Material Handling and Transfer
0.25 - 1.05
0.00
D.
Enclosed or Indoor Process Units
0.25 - 0.90
0.00
E.
Access
0.25 - 0.35
0.00
F.
Drainage and Spill Control
0.25 - 0.50
0.00
(gallons)
305,000
General Process Hazards Factor (F1) 2 A.
Special Process Hazards Base Factor
B.
Toxic Material(s) Sub-Atmospheric Pressure (<500 mmHG)
C.
Operation in or near flammable range
D. E.
1.00 1.00
1.00
0.20 - 0.80
0.40
0.50
0.00 0.00
1
Tank farms storage flammable liquids
0.50
0.00
2
Process upset of purge failure
0.30
0.30
3
Always in flammable range
0.80
0.00
0.25 -2.00
0.00
Dust explosion (See Table 3) Operating Pressure Relief Setting
Pressure (See Figure 2) (psig)
F.
Low Temperature
G.
Quantity of Flammable/Unstable Material Quantity (lb) Hc (BTU/lb)
78
0.28
117
0.33
0.28
0.20 - 0.30
0.00
400,000 20,000
1
Liquids or Gasses in Process (Fig. 3)
2.33
2
Liquids or Gasses in Storage (Fig. 4)
0.00
3
Combustible Solids in Storage, Dust in Process (Fig. 5)
0.00
H.
Corrosion and Erosion
0.10 - 0.75
0.00
I.
Leakage 0 Joints and Packing
0.10 - 1.50
0.00
J.
Use of Fired Equipment (Fig. 6)
K.
Hot Oil Heat Exchange System
L.
Rotating Equipment
0.00
Special Process Factor (F2)
0.15 - 1.15
0.00
0.50
0.00 4.31
Process Unit Hazards Factir (F1 x F2) = F3
4.31
Fire and Explosion Index (F3 x MF = F&EI)
68.93
100
1. Process Control Credit Factors (C1)
Feature
Credit Factor Used
Credit Factor Used
Feature
a. Emergency Power
0.98
f. Inert Gas
1.00
b. Cooling
0.97
g. Operating Instructions/Procedures
0.91
c. Explosion Control
0.84
h. Reactive Chemical Review
0.91
d. Emergency Shutdown
0.98
i. Other Process Hazard Analysis
0.94
e. Computer Control
0.93 C1 Value
0.57
2. Material Isolation Credit Factor (C2)
Feature
Credit Factor Used
Credit Factor Used
Feature
a. Remote Control Valves
0.96
c. Drainage
0.91
b. Dump/Blowdown
0.98
d. Interlock
0.98 C2 Value
0.84
3. Fire Protection Credit Factor (C3)
Feature
Credit Factor Used
Credit Factor Used
Feature
a. Leak Detection
0.94
f. Water Curtains
0.97
b. Structural Steel
0.98
g. Foam
0.94
c. Fire Water Supply
0.94
h. Hand Extinguishers/Monitors
0.98
d. Special Systems
0.91
i. Cable Protection
0.94
e. Sprinkler Systems
0.81 C3 Value Loss Control Credit Factor = C1 x C2 x C3
0.54 0.25
1. Fire & Explosion Index (F&EI)…………………………………… (See Front)
68.93
2. Radius of Exposure (ft)……………………………………………….… (Figure 7)
57.90
3. Area of Exposure (ft2)…………………………………………………………………
10531.79
4. Value of Area of Exposure……………………………………………………….….
$1,345,347.00
5. Damage Factor………………………………………………………….. (Figure 8)
5.50
6. Base Maximum Probable Property Damage……………………………. (4x5)
$7,399,408.50
7. Loss Control Credit Factor………………………………………... (See Above)
0.25
8. Actual Maximum Probable Property Damage…………………………. (6x7)
$1,885,472.71
9. Maximum Probable Days Outage………………………………….. (Figure 9)
30.00
10. Business Interruption…………………………………………………………….
$10,908,333.33
101
F. CEI Sample Calculations A sample calculation for the CEI is shown below, using the feed to the R-1/R2 assembly. The Chemical Exposure Index (CEI) was calculated using the procedure on page 3 of the “Chemical Exposure Index Guide, September 1993, 2nd edition. Step One:
Define the chemical being investigated and the conditions at which the scenario is taking place. In our case this is not a scenario, it is a real event.
The chemical properties are as follows. Chemical Name: Temperature: Pressure: Rate of Release:
Benzene (Gas): Assume that all the liquid vaporized 83°C 400 kPa at C-1 assembly 60,000 kg/hr × 1 hr/60 min=1,000 kg/min=2,200 lb/min
Step Two: Find the ERPG-2/EEPG-2 data from Table 1 on page 6. addition find the Molecular Weight from this table as well.
In
The data is as follows: ERPG-1 (ppm) = 1.5 ERPG-2 (ppm) = 2.5 ERPG-3 (ppm) = 5 Molecular Weight = 78.1 g/mol
Step Three: Determine the Airborne Quantity (AQ) using a gas relationship and US/BRIT Units. The equation for calculating AQ is as follows: (AQ)=3.751D 2 Pa MW/(T+459) Where: AQ is the Airborne Quantity D is the diameter of the hole (inches) Pa is the absolute pressure (Pg +14.7) Pg is the gauge pressure (PSIG)
102
(1)
The result of the AQ calculation is as follows: (AQ)=3.751(1 in.) 2 (190 psia) 70.9/(180.5o F+459)=2,140
Step Three (Alternate): AQ(Alternate)=130,000 lb/hr/1 hr × 1 hr/60 min=2,170 lb/min Step Four: Calculate the CEI using the following formula: CEI=281.8 AQ/(ERPG-2×MW)
(2)
Where: CEI is the Chemical Exposure Index ERPG-2 is the Emergency Exposure Planning Guideline (ppm)
The result of the CEI calculation is as follows:
CEI=281.8 2,200/(2.5)(78.1) =936 The value of this CEI is quite high. The guide states on page i, a CEI greater then 200 for a facilities will require further risk analysis. The calculation of the Hazard Distance (HD) using US/Brits units is done using the following expression.
HD=9,243 AQ/ERPG(MW) Where: HD is the Hazard Distance (ft) AQ is the Airborne Quantity (ppm) ERPG is the Emergency Exposure Planning Guideline MW is the molecular weight
The result for the HD expression for ERPG-1 is as follows:
HD=9,243 2,167/1.5(78.1) =39,800 ft
103
The result for the HD expression for ERPG-2 is as follows:
HD=9,243 2,167/2.5(78.1) =30,800 ft
The result for the HD expression for ERPG-3 is as follows:
HD=9,243 2,167/5(78.1) =21,800 ft
104
G. HYSYS Workbook Output
105
