Table of Contents 1.0
INTRODUCTION INTRODUCTION................................ ................................................. .................................. ................................. ................................. ....................... ...... 2
2.0
PROCESS PROCESS SELECTION SELECTION............................... ................................................ .................................. ................................. ............................ ............ 9
3.0
MATERIAL MATERIAL BALANCE BALANCE ................................ ................................................ ................................. ................................. ............................. ............. 21
4.0
ENERGY ENERGY BALANCE............. BALANCE............................. ................................. ................................. ................................. ................................. .................. .. 31
5.0
MECHANICAL MECHANICAL DESIGN ............................... ................................................ .................................. ................................. .......................... .......... 48
6.0
SITE SELECTION SELECTION ................................ ................................................. ................................. ................................. .................................. ................... 52
7.0
ECONOMIC ECONOMIC ANALYSIS ANALYSIS ............................... ................................................ .................................. ................................. .......................... .......... 62
8.0
PINCH ANALYSIS ANALYSIS................................ ................................................. ................................. ................................. .................................. ................... 85
9.0
ENVIRONMENTAL CONSIDERATION .................. ......... .................. ................... ................... ................... ................... ............ ... 90
10.0
PLANT LAYOUT LAYOUT .................................. ................................................... ................................. ................................. .................................. ................... 96
11.0
SUMMARY AND CONCLUSION ................... ......... ................... .................. ................... ................... .................. ................... ............. ... 99
12.0
REFERENCES REFERENCES............................... ................................................ .................................. ................................. .................................. ...................... .... 101
UREA FROM AMMONIA AND CARBON DIOXIDE
1.0 INTRODUCTION
1.0 INTRODUCTION 1.1. LITERATURE LITERATURE SURVEY -
Urea (NH2CONH2) is an organic compound and it is also known as carbamide. Ammonia is usually used in agriculture ag riculture sector especially to make fertilizers. Urea is made from ammonia (NH3) and carbon dioxide (CO2). The production of ammonia and urea are being done separately.
1.2. HISTORY OF UREA -
Urea is being discovered discovered in the urine by H.M Rouelle in 1773. It was synthesized in 1828 by Friedrich Wohler and urea is the first organic compound that has being synthesized from inorganic starting materials. It was found when Wohler attempt to synthesis ammonia cyanate. When he react silver cyanate with ammonium chloride, the reaction produce white crystalline materials which is quite identical with the urea in the urine. In the year 1870, urea had being produced by heating in ammonium carbonate in a sealed vessel.
1.3. COMMERCIAL PRODUCTION -
-
-
-
Urea is a nitrogen-containing chemical product which is produced in in excess of 140,000,000 tonnes per year worldwide, of which more than 90% of world production is destined for used as fertilizer. Ammonia is being produce from the reaction of ammonia and carbon dioxide and it is also being produced commercially. Urea can be produced as prills, granules, flakes, pellets, crystals and also solutions. In the urea containing containing the highest nitrogen in all solids nitrogenous fertilizers fertilizers in common used (46.4%N). It also containing the highest concentration dries nitrogen fertilizer available. So it has the lowest transportation costs per unit of nitrogen nutrient. Urea also suitable for liquid liquid fertilizer because it is soluble in the water. The solid ureas are being market as prills or granules. Prills Prills are cheaper compare to granules since prills has the narrower size particles. Narrow size of particles has the advantage if it is applied mechanically to soil.
1.4. CHEMICAL AND PHYSICAL PROPERTIES OF UREA
1.4.1. CHEMICAL PROPERTIES
UREA is an organic compound and it is also known as Carbamide. IUPAC name
Diaminomethanal
Chemical formula
(NH2)2CO.
Molecular mass
60.07 g/mol
Dipole moment
4.56 p/D
Melting point
132 oF
Solubility
Highly water soluble
FIGURE 1: CHEMICAL STRUCTURE OF UREA MOLECULES
The urea molecule is planar and retains its full molecular point symmetry due to conjugation of one of each nitrogen’s P orbital to the carbonyl double bond. Each carbonyl oxygen atom accepts four N-H-O hydrogen bonds, a very unusual feature for such a bond type. This dense hydrogen bond network is probably established at the cost of efficient molecular packing. Urea is stable under normal conditions.
1.4.2. PHYSICAL PROPERTIES Solid urea will melt at 135oC. Due to extensive hydrogen bonding with water urea is very soluble. 1.33 1.33 x 10 kg/m kg/m , sol solid id Density 132.7oC decomposes Melting point Colorless Color odorless Odor Solubility in water
108 g/100 ml (20oC) 167 g/100 ml (40oC) 251 g/100 ml (60oC) 400 g/100 ml (80oC) 733 g/100 ml (100oC)
Vapour pressure
< 10 Pa
Bulk density
0.8 kg.mg -3
FIGURE 2: CRYSTALINE UREA
1.5.
RAW MATERIALS
1.5.1. PRODUCTION OF AMMONIA AMMONIA AND CARBON DIOXIDE Ammonia is synthesis from hydrogen, H2 from natural gas and nitrogen, N2 from the air by Haber-Bosch process. This process involves the reaction of hydrogen and nitrogen under high pressure and temperature. However, natural gas contains some sulfurous compounds which damage the catalysts used u sed in this process. These are removed by reacting them with zinc oxide, e.g. ZnO + H2S
ZnS + H2O
The methane from the natural gas is then reacted with water to form hydrogen and carbon monoxide. Later it also reacted with water to form carbon dioxide. CH4 + H2O CH4 + 2H2O
3H2 + CO 4H2 + CO2
Then the reaction of carbon monoxide with water is converted to hydrogen and carbon dioxide, and carbon dioxide is removed: CO + H2O
H2 + CO2
The nitrogen and hydrogen are then reacted at high pressure and temperature using an iron catalyst to form ammonia: N2 + 3H2 2NH3
Figure 3 : BLOCK FLOW DIAGRAM OF AMMONIA PRODUCTION
1.5.2. SYNTHESIS GAS PRODUCTION The raw materials for preparing ammonia in nitrogen and hydrogen ratio 1:3 are water, nitrogen (from the air), carbon-containing and hydrogen (from natural gas). Water and methane from natural gas is injected in the primary steam reforming. After mixed it, the mixing is the flowed through the secondary steam reforming. 1.5.3. METHANATION Methanation is a physical-chemical process to generate methane from a mixture of various gases out of biomass fermentation. Methane is the reverse reaction of steam methane reforming which converts methane into synthesis gas. The main components are carbon monoxide and hydrogen. CO + 3H2
CH4 + H2O
1.5.4. FEEDSTOCK PRE-TREATMENT AND RAW GAS PRODUCTION: The chemical reaction go through gasification process where water, oxygen, air are combined. It yields a gas mixture made from CO and H2in various proportions along with carbon dioxide and nitrogen from air is used.
Any carbon containing feedstock will undergo a reaction: CH4 + H2O
3H2 + CO
∆H= 88563.678 BTU/Ibmole
Natural gas consists predominantly of methane and is therefore the most hydrogen-rich and energetically the best raw material for the steam-reforming route. The reforming ammonia reaction is split into two sections. The first section, the primary reformer proceed the process in indirectly heated tubes filled with nickel-containing reforming catalyst and is controlled to achieve a partial conversion only. The second section, the secondary reformer proceed the process where the gas is mixed with a controlled amount of air introduced through a nozzle. By combustion of a quantity of the gas the temperature is raised sufficiently at higher temperature to about 1200oC that the endothermic reforming reaction is completed with the gas adiabatically passing the catalyst layer. Carbon Monoxide Shift Conversion: Carbon oxide must be removed from the raw synthesis gas of the gasification process in order to synthesis ammonia. In the water gas shift reaction, carbon monoxide serves as reducing agent for water to yield hydrogen and carbon dioxide and additional hydrogen: CO + H2O
H2 + CO2
1.6.
APPLICATION OF UREA 1.6.1
In Agriculture: Agriculture: Urea is being used as fertilizers and animals feed. As known urea is -
-
1.6.2
containing nitrogen and the nitrogen in it can help to promote growth for both animals and plants. Ureas are also used in much multicomponent solid fertilizer formulation. There are some advantages by using urea as fertilizers which are urea are more safer to ship and handle, it also not corrosive to equipment compare if using nitrogen fertilizers, urea is high solubility in water so it is easy to move in the soils and the last one is by using urea as fertilizers it can be applied in many ways such as using equipment or by spreading it by using hand.
In Industrial: -
-
-
With the mixed with many organics compounds urea has the ability to form a loose compound. The organic compounds are held in channels formed by interpenetrating helices comprising of hydrogen bonded area molecules. This kind of behavior has been used to separate mixture. This has been apply in production of lubricating oils. Ureas are also use as raw materials for manufactured plastics (example urea-formaldehyde rasins) and glue (example ureamelamine-formaldehyde). It also used as additive ingredient in cigarette, some ingredients for making facial cleanser and also as a reactant in some ready to use cold compresses for first aid used.
1.6.3. In Medicals: -
-
In medicals urea has been used to produce barbituric acids. Urea is reacting with the malonic acids to form barbituric acids. Barbituric acids are the parents of barbiturate drugs. Barbiturate drug is act as central nervous system depressant. Urea also has been used to produce acylureas and urethanes for use as sedatives and hypnotic. It is being made as sleeping pills. It is used in the treatment of insomnia and in surgical anesthesia.
UREA FROM AMMONIA AND CARBON DIOXIDE
2.0 PROCESS SELECTION
2.0
PROCESS SELECTION
2.1 Chronology of process process Focusing into two processes (Partial recycle process and Total recycle process) 2.1.1
Partial Recycle Process
This process is one of the simplest methods and also the least expensive (both capital investment and operating cost). This method is divided into three main type of process. Before partial recycle process being discovered, as shown in figure 1(typical unit involving synthesis section only) liquid ammonia and gaseous carbon dioxide dioxide are pumped into urea reactor at about 200 atm. The reactor temperature is maintain at about 185 Celsius by regulating the amount of excess ammonia about 100% excess NH3 is required, and about 35% of the total NH3 is converted to urea (75% of carbon dioxide is converted). The reactor effluent solution contains about 80% urea after carbamate stripping. The unconverted NH3 and CO2 are driven off at moderate pressure by stream heating the effluent solution to carbamate strippers. Even though this process is the simplest of a urea process, there are some limitations regarding ammonia gas. It is the least flexible and cannot be operate unless some provision is made to utilize the large amount of off gas ammonia. Thus it must be used in conjunction with the coproduction of some other material. For example ammonium phosphate (used ammonia). One case in which the system can be used is the production of urea ammonium nitrate solution; the converted NH3 is used to make ammonium nitrate solution. This solution than be mixed with the urea solution. Even in this case, most new plant uses a TOTAL RECYCLE PROCESS. Regarding partial recycle process all part of the off-gas ammonia and carbon dioxide from the carbonate strippers is recycle to the urea reactor. Recycling is accomplished by absorbing the stripper urea effluent, in the process steam condense or in mother liquor from the crystallization finishing process. In this manner the amount of NH3 in off-gas is reduced. Any proportion of the unreacted ammonia can be recycled. Typically the amount of ammonia that must use in some other process is reduced to about 15% of that from a comparable once-through unit. Mitsui Toatsu has made changes to the process and it be rename as Mitsui Toatsu partial-recycle process as shown in figure 2. Liquid NH3 and gaseous CO2 are pumped to the urea reactor at 200 atm. The temperature of the reactor is maintained at about 185 Celsius by proper balance of excess NH3 and carbonate solution feed. About 100%-110% excess NH3 is used, about 70% of the NH3 and 87% of the CO2 are converted to urea. The remaining 30% of the NH3 must be used in some other process. The reactor effluent contains about 80% urea.
Figure 1: Typical once through urea process
Figure 2: Mitsui Toatsu partial-recycle process
Unreacted NH3 and CO2 are separated from the urea solution in the high pressure separator and in two three steam-heated carbonate stripper at successively lower pressure. The off-gas from the separator and the first stage stripper is absorbed in the high pressure absorber by a side stream of partially stripper reactor effluent from the high pressure separator. Heat involved in the absorber reaction is removed (to increase absorption capacity) by the addition and expansion of part of liquid ammonia from the top of the absorber is also recycled to the urea reactor after being condensed, Since the amount of ammonia carbarnate that can be absorbed in the absorber solution describe above is limited by its solubility in the system H 2O-urea-NH3, part of the ammonia and carbon dioxide cannot be recycled and must be used in the production of a co-product nitrogen material. As in the once through process, the operation of the urea plant still must coincide with that of the co-product plant. Other partial recycle process different in detail but accomplish similar results. Although the investment cost is somewhat lower than for total recycle, the advantages apparently does not compensate for the inflexibility arising from the necessity of operating a co-product plant with mutual interdependency problems. However the partial recycle process continue to find application, particularly, where UAN solution is a co-product. 2.1.2.
Total Recycle process
In this process, all the unconverted ammonia-carbon dioxide mixture recycled to the urea reactor (conversion 99%) and no nitrogen co-product is necessary. This is the most flexible of the urea process because it depends upon the CO2 and NH3 supply from its supporting ammonia plant for operation. However it also the most expensive in investment and operating cost. Therefore, if the production of other material requiring ammonia is planned, an integrated once-through or partial-recycle unit would have lower investment and perhaps lower operating costs. The disadvantages are decreased reliability arising from mutual dependence of two plants, inflexibility in proportions of co-products, and difficulties in synchronizing the operation of two plants. Because of these difficulties, most manufactures prefer a total recycle process, even when a second nitrogen product is desired.
The urea reactor effluent contains urea and water resulting from the synthesis reaction; it also contains unconverted carbanate and excess ammonia. These ingredients must separate to give a urea solution reasonably free from the other material and to recycle the CO2 and NH3 to the synthesis reactor. In order to separate carbamate from urea, it must be decomposed according to the equation.
NH2CO2NH4 (reversible) CO2 + 2NH3
This reaction is the reverse of the first step of the synthesis process and is strongly endothermic (37.7 kcal/g-mole). The decomposition is accomplished by various combinations of supplying heat, lowering pressure of one or more ingredients. The NH3 and CO2 are removed from the urea solution as gases accompanied by some of the water in vapor form. Naturally the CO2 and NH3 will recombine (released heat) when the temperature is decreased or the pressure increased. Hence condensing by cooling and/or compressing a gaseous mixture of CO2, NH3 and H2O produces a carbamate solution. This process can be classified in five groups according to the recycle principle.
1. 2. 3. 4. 5.
Hot gas mixture recycle Separated gas recycle Slurry recycle Carbamate solution recycle Stripping.
The separate gas recycle method was developed overcome the difficulties of the mixed hot gas recycle process. The CO2 and NH3 can be compressed separately without difficulties caused by carbamate formation. Process of this type were developed by inverta (Switzerland) and CPI-Allied (United States). The principle of the process is that CO2 in the gas mixture from the decomposers is absorbed selectivity in a solvent such as monoethanolamine (MEA). The NH3remaining after CO2 removed is compressed and recycle to the synthesis reactor. The CO2 is desorbed from the MEA solvent by heating and it is recycled separately. The process has the advantage that conversion is not reduced by recycling water to the reactor and that the problem of recycling corrosive solution to the reactor is avoided. Offsetting this is the difficulty in recovering heat and cost of MEA makeup. The number of plants using the method is relatively small and it is not known to be in use in any of the large plants (1000 tpd and up ) built in recent years. The principle of the slurry recycle process is that the CO2-NH3-H2O gas mixture goes to a reactor to which light paraffin oil is added. Carbamate, formed in the reactor as an oil suspension, which contains 35%-40% solids, is pumped into the urea synthesis unit wish fresh CO2 and NH3.the mixture then goes through the carbarmate decomposers and the oil is separated from the urea solution by decantation for reuse.
CONDENSE CO2-IN RECY-OUT
RECY-IN
COMP
MIXER
REACTOR
CO2-OUT FEED
TOP-LPS HPS HPS-IN DRYER NH3-OUT
GRANULE
LPS VALVE H PS PS- OU OU T
LPS- IN
BOT-LPS
PUMP NH3-IN
PRODUCT D-OUT
The process inlet involves 2 streams that is inlet for NH 3 and CO2 respectively, labeled as NH3 in and CO2 in. For NH3 pump in used while in inlet for CO2 compressor is used. Both stream then being channeled to the main reactor In the main reactor, with temperature of 125 Celsius and 125 bars, the reaction occurs and will produce Urea, NH3, CO2, carbamate, h2O, and biuret as product. All product. All this substances known as HPS in and be transfer into High Pressure Separator (HPS) at condition 125 atm. From HPS there are two outlets. I outlet is for recycle stream and another is product stream. For recycle stream, the components is carbamate is being recycle back, and be channeled back into feed stream that goes into the main reactor (Total recycle process). For outlet stream from HPS main have urea, NH3, CO2, H2O and biuret. With a help from valve the pressure is reduce from 125 atm to 5 atm and goes into the Lower Pressure Separator (LPS). At LPS there also have two product streams as in HPS, ones is Biuret as top LHS and other components as BOTTOM LPS. Other components are urea, NH3, CO2 and H2O. BOTTOM LPS next will be channeled to the dryer, to remove the moisture contents. After that’s process it will pass t hrough granule. granule. At granule, it will undergo process to make a fine powder for the urea.
2.1.3. Other process Once-through urea process The unconverted carbamate is decomposed to NH3 & CO2 gas by heating the urea synthesis reactor effluent mixture at low pressure. The NH3 & CO2 gas is separated from the urea solution and utilized to produce ammonium salts by absorbing NH3, either in sulfuric or nitric acid. In this process liquid NH3 is pumped through a high pressure plunger pump and gaseous CO2 is compressed through a compressor up to the urea synthesis reactor pressure at an NH3 to CO2 feed mole ratio of 2/1 or 3/1. The reactor usually operates in a temperature range from 175 to 190 Celsius. The reactor effluent is let down in pressure to about 2 atm and the carbamate decomposed and stripped from the urea-product solution in a steam heated shell & tube heat exchanger. The moist gas, separated from the 85-90 % urea product solution, & containing about 0.6 tons of gaseous NH3 per ton of urea produced is usually sent to an adjacent ammonium nitrate or ammonium sulfate producing plant for recovery. An average conversion of carbamate to urea of about 60 % is attained. Excess heat is removed from the reactor by means of a low-pressure steamproducing coil in an amount of about 280,000 cal/Kg urea produced.
Once-through urea process
2.1.4. Comparison between types of reactor
Criteria
Plug flow reactor
Continuous stirred tank reactor
Batch reactor
Semi-batch reactor
Phase suitability
Primarily gas phase but liquid phase also applicable
Primarily gas phase but liquid phase also applicable
Gas phase, liquid phase & liquid-solid phase
Gas phase, liquid phase & liquid-solid phase
Usage
Large scale, Fast reaction, Homogenous Reaction, Continuous Production, High temperature, Available with tube or without tube
When agitation is required,
Small scale production,
Hydrolysis,
Series configuration for different concentration stream
Intermediate or once short production,
High conversion per unit volume,
Continuous operation,
Low operation cost,
Good operation control,
Continuous operation,
Easily adapt to two phase run,
Good heat transfer.
Simplicity for construction,
Advantages
Chlorination, Reactive distillation.
Pharmaceutical, Fermentation.
Low operating(labour) cost
High conversion per unit volume( per pass ), Flexibility of process operation (one reactor for multiple process),
Excellent control of raw material(limit unwanted side reaction)
Easy to clean.
Easy to clean.
Disadvantag es
Shout down and cleaning may be expensive,
Lowest conversion per unit volume,
High operating cost,
By-passing and
Product quality
Not common for industrial application.
Poor temperature control.
channelling possible with poor agitation
may varies compared to continuous process.
The reason that Plug flow reactor is chosen because this reaction involves between two reactant in gaseous state (ammonia and carbon dioxide). Theoretically plug flow reactor more familiar with reaction between gaseous states. Other reactor also can be consider, but in order to achieve production of 300000 kg day of urea, plug flow reactor is more suitable in large scale. The production of urea also is continuous production. For temperature of 185 Celsius can be consider last high temperature reaction, thus PFR are the best choice. CSTR, batch, and semi-batch are more focusing one batch production, that not very suitable for production of urea. Although in this production, the temperature is between 20-185 Celsius. That is more easy control by using batch reactor, temperature still in the range of PFR temperature. In economy aspect, low operation cost, is one of the aspects that have the main role, although it may be costly when reach time to shout down and cleaning the reactor, it being cover by the profit generate by the production of urea.
2.2. Selection of process
2.1.2.
Total recycle processes
One of the reasons that total recycle process is chosen is the conversion of urea. In this process the conversion of urea is about 99% (satisfied with the aim to achieve conversion of urea between (40%-70%). This is because all unconverted ammonia-carbon dioxide mixture is recycle and no nitrogen co-product is necessary (reducing the cost)
2.1.3.
Scoring and screening of two process
Factor Conversion of urea
Partial recycle process
Total recycle process
80%
99%
Both processes give out high rate of conversion of urea, but to achieve the aim, the process with the highest conversion is selected. This is to make sure that when the process is undergoing, the possibility to get lower conversion of urea will be reduced. Pressure (average)
200 atm
125 atm
At constant temperature, conversion increases with pressure up to the critical point which is the point which is the point at which the vapour phase is substantially eliminated and the reactant are in the liquid state. The critical temperature is a complex function of the temperature and composition of the reactor content. For example at 150 Celsius a pressure about 100 atm might be near optimum for a stoichiometric NH3; CO 2 ratio, but at this temperature the rate of reaction is unacceptably slow. At the preferred temperature of 180-210 Celsius, pressure of 140-250 atm is commonly. thus the lower the pressure are better. Temperature (average)
185 Celsius
185 Celsius
Conversion of ammonia carbamate to urea in the absence of excess ammonia increase with the temperature to the maximum of about 50% at 170-190 Celsius when the pressure is high to keep the reactant in the liquid state. The rate of reaction increase with the temperature; it is slow at 150 Celsius and below (with stoichiometric NH3:CO2 ratio) and quite rapid at 210 Celsius. A satisfactory approach to equilibrium can be obtained in the temperature range of 180200 Celsius in 0.3-1.0 hours or at lower temperature with the excess ammonia. Corrosion difficulties increase with the temperature and the range of 180-210 Celsius Celsius is generally accepted as optimum for most processes
Equipment
Generally this process using More equipment than partial less equipment that total recycle process recycle process The more complex the reaction involving the more complex equipment that will be used up. The equipment equipment involves involves include heater, cooler
Cost
Less cost
High cost
Partial recycle process
Total recycle process
Conversion of urea
-1
1
Pressure
-1
1
Temperature
0
0
Equipment
1
-1
Cost
1
-1
High investment payback
0
1
Total
0
1
Factor
Chosen
×
2.3. Process Description
First, the raw material, ammonia (NH3) at 20oC, 9 bar and considered pure is pumped into mixer thus increase the pressure to 125 bar. For the carbon dioxide (CO2), raw material available is at 20oC and 1 bar, also considered pure. The CO2 then is feed to the mixer through a compressor which increased the pressure to 125 bar. The mixer mix three streams before been feed to the reactor which is the NH3 and CO2 raw and also the ammonium carbamate recycle stream. At the reactor, re actor, the feed at temperature 86.92 8 6.920C is allowed to react thus produce urea and water. Small amount of biuret is also produce as a side product. NH3 and CO2 is first react to produce ammonium carbamate. 95% of equilibrium is achieved at this rate. The limiting reaction for this process is the conversion of ammonium carbamate to urea and water where the result fluctuates to 40 – 70 % conversion. For the calculation, 40% conversion of urea is taken. Then, all the remaining reactant and product that formed in the reactor enter the stripper. Carbamate is removed in the top stream of stripper and remaining compound is leaves the stripper at the bottom. Carbamate leaves the stripper in form of vapor. Since carbamate required in feed stream is in liquid phase, a condenser is put in the recycle stream. By using steam at 40 bar with 200C of superheat, the temperature of the stream is reduced from 185 to 170 0C and the phase of carbamate is change from vapor to liquid phase. Carbamate leaves the condenser at temperature 1700C and pressure of 125 bar and will fed into the mixer. Before entering the medium pressure separator, MPS and low pressure stripper, the pressure of components leave the stripper is reduce from 125 bars to 18 bars and 18 bars to 5 bars respectively by using valves. Half of composition of NH3 and CO2 is removed in the top stream of MPS and the remaining NH3 and CO2 is removed in the LPS. All the NH 3 and CO2 are transferred to storage tank to be reuse back as feed. Remaining component of urea, water and Biuret is leave the MPS and then LPS at the bottom stream with pressure 18 bars, temperature 140 0C and pressure 5 bars and temperature 800C respectively. Next step is to reduce composition of water in product stream to 0.5% only. Vacuum evaporator and prilling tower equipment is used for this process. The pressure of the product stream leave the evaporator at 0 bar pressure since it operates in vacuum condition. The temperature also reduces from 800C to 27.250C. Then, component that leaves the evaporator at temperature 27.250C and pressure 0bar is entering the prilling tower. Air at temperature at 250C is used to remove the remaining water in the product stream. At the end of the process, the products components leave at the bottom of tower at pressure 1 bar and temperature 250C, meanwhile air leave at temperature 260C. There are no waste and wastewater treatment is needed since there no waste are produced and the water leave the temperature in pure composition and at low temperature in this plant.
UREA FROM AMMONIA AND CARBON DIOXIDE
3.0 MATERIAL BALANCE
3.0
MATERIAL BALANCE
Selected capacity = 9.9 × 107 kg/year No of working days = 330 day Daily production = 300,000 kg/day Production rate of urea: 300,000
x = 12,500
Composition final product 98.5 % urea = 0.985 (12500) = 12312.5 1 % biuret = 0.01 (12500) = 125
0.5 % water = 0.005 (12500) = 62.5
Reaction: 2NH3 +
CO2
(34)
(44)
NH2COONH4 (100% completion)
= ∆H =
(78)
NH2COONH4
CO (NH2)2 + H2O (40% completion) ∆H = -21
(78)
(60)
(18)
Side reaction: 2NH2CONH2
NH2CONHCONH2 + NH3
(120) (120)
(103) (103)
17
Overall reaction 2NH3 + CO2 (34)
From reaction
130
CO (NH2)2 + H2O (Overall conversion 95%)
(44)
(60)
(18)
:
125 of biured produced by =
x 125
= 145.631 of urea
Therefore, urea produced by reaction: 12 312.5 From reaction
+ 145.631 = 12 458.131
:
x 12458.131 = 7059.608 CO2 feed = x 12456.131 = 9135.963 NH3 feed =
Overall conversion = 0.95
= 7431.166 = 9616.803 CO2 required = NH3 required =
It 100% completion of urea in reaction
:
x 9616.803 = 13113.822 of urea produced For 95% conversion: 0.95 x 13113.822 = 12458.131 Urea is converting to biuret in reaction 12458.131
:
- 12312.5 = 145.6309 of urea
Water produced:
x 12458.131 = 3737.439 For 40% completion of urea: Flow rate of steam, ṁin = CO2
+
2NH3
NH3 react =
= 30781.25
NH2CONH2
+
H2O
x 12458.131 = 7059.608
CO2 react =
x 12458.131 = 9135.963
2NH2CONH2
+
2NH3
NH2CONHCONH2
+
NH3
x 145.631 = 20.631
NH3 produced =
For unreacted NH3: 7431.166 – 7059.608 +20.631 = 392.189
For unreacted CO2:
9616.803 - 9135.963 = 480.84 Carbamate: ṁin,total = ṁout,total
30781.25 = 392.189 + 480.84 + 12312.5 + 3737.439 +125 + ṁcarbamate Hence, ṁcarbamate = 13733.282
3.1.
Reactor
o
o
T = 86.92 C
T = 180 C
Reactor: P= 125 bar
NH3 = 7431.166 kg/h
o
T=180 C
NH3= 392.189 kg/h
CO2= 9616.803 kg/h
CO2=480.84 kg/h
Carbamate=13733.282 kg/h
Carbamate= 13733.282 kg/h Urea= 12312.5 kg/h Water= 3737.439 kg/h Biure Biuret= t=125 125 k /h
Input
Output
Material
Flow rate(kg/h)
Mass fraction
Flow rate(kg/h)
Mass fraction
NH3
7431.166
0.24
NH3
392.189
0.013
CO2
9616.803
0.31
CO2
480.84
0.016
Carbamate
13733.282
0.45
Carbamate
13733.282
0.446
Total
30781.251
100
Urea
12312.5
0.400
Water
3737.439
0.121
Biuret
125
0.004
Total
30781.25
1
Material
3.2.
Stripper
Carbamate= 13733.282 kg/h
Stripper: o
T=40 C
P=125 bar o
T=180 C o
T=185 C NH3=392.189 kg/h CO2=480.84 kg/h
NH3=392.189 kg/h
Carbamate=13733.282 kg/h
CO2= 480.84 kg/h
Urea = 12312.5 kg/h
Urea=12312.5 kg/h
Water=3737.437 kg/h
Water= 3737.439 kg/h
=
Material NH3
CO2
Carbamate
Biuret =125 kg/h
Input
Output
Flow rate(kg/h)
Mass fraction
Flow rate(kg/h)
Mass fraction
392.189
0.0127 13733.282
1
NH3
392.189
0.023
480.84
0.0156
Material Top product: Carbamate Bottom Product:
13733.282
0.4462
CO2
480.84
0.0282
Urea
12312.5
0.4000
Urea
12312.5
0.7222
Water
3737.437
0.1120
Water
3737.439
0.219
Biuret
125
0.00406
Biuret
125
0.00733
Total
30781.25
1
Total
17047.968
1
3.3.
Medium Pressure Separator (MPS) o
T=185 C
NH3=196.095 kg/h CO2= 240.42 kg/h
o
T=140 C o
T=185 C
MPS: P=18 bar
NH3=392.189 kg/h
CO2= 240.42 kg/h
CO2=480.84 kg/h
Urea=12312.5 kg/h
Urea = 12312.5 kg/h
Water= 3737.439 kg/h
Water=3737.437 kg/h
Biu Biuret ret =12 =125 5k h
Biuret = 125 kg/h
Material
NH3=196.095 kg/h
Input
Output
Flow rate(kg/h)
Flow rate(kg/h)
Mass fraction
NH3
196.095
0.449
CO2 Bottom Product: NH3
240.42
0.551
196.095
0.00485
Mass fraction
Material Top Product:
NH3
CO2
392.189
0.023
480.84
0.0282
12312.5
0.7222
Urea Water
3737.439
0.219
CO2
240.42
0.00595
Biuret
125
0.00733
Urea
12312.5
0.305
Total
17047.968
1
Water
3737.439
0.0925
Biuret
125
0.00309
Total
40413.034
1
3.4.
Lower Pressure Separator (LPS) NH3=196.095 kg/h CO2= 240.42 kg/h o
T=140 C LPS: o
T=80 C P=5 bar NH3=196.095 kg/h CO2=240.42 kg/h Urea = 12312.5 kg/h
Urea=12312.5 kg/h
Water=3737.437 kg/h
Water= 3737.439 kg/h
Biuret = 125 kg/h
Biuret =125 kg/h
Input Material
Flow rate(kg/h)
Output Mass fraction
Material
Flow rate(kg/h)
Mass fraction
Bottom Product: NH3
Top Product: 196.095
0.00485
NH3
196.095
0.449
CO2
240.42
0.00595
240.42
0.551
Urea
12312.5
0.305
CO2 Bottom Product: Urea
12312.5
0.761
Water
3737.439
0.0925
Water
3737.439
0.231
Biuret
125
0.00309
Biuret
125
0.00773
Total
40413.034
1
Total
16174.930
1
3.5.
Vacuum Evaporator
o
T=80 C Water= 3611.159 kg/h
o
T=27.25 C o
T=80 C Vacuum Evaporator: Urea = 12312.5 kg/h
P=0 bar
Urea=12312.5 kg/h (98%) Water= 126.28 kg/h
Water=3737.437 kg/h Biuret =125 kg/h Biuret = 125 kg/h
Total mass balance: Mass in = Mass out F=E+P Mass balance of urea: 12312.5 = (0.98P) P = 12563.78 Input
Output
Flow rate(kg/h)
Mass fraction
Flow rate(kg/h)
Mass fraction
Urea
12312.5
0.761
3611.159
1
Water
3737.439
0.231
12312.5
0.9800
Material
Material Top Product: Water Bottom Product: Urea
Biuret
125
0.00773
Water
126.28
0.01
Total
16174.930
1
Biuret
125
0.01
Total
12563.78
1
3.6.
Prilling Tower Water = 63.74 kg/h
Air o
T=26 C
o
T=27 C
Prilling Tower: P=1 bar o
T=25 C F Urea = 12312.5 kg/h Air Water=126.28 kg/h Biuret = 125 kg/h
E Urea=12312.5 kg/h (98.5%) Water= 62.5 kg/h Biuret =125 kh/h
E = 12500kg/h (production rate) Input
Output
Flow rate(kg/h)
Mass fraction
Flow rate(kg/h)
Mass fraction
Urea
12312.5
0.9800
63.74
1
Water
126.28
0.01
12312.5
0.985
Material
Material Top Product: Water Bottom Product: Urea
Biuret
125
0.01
Water
62.5
0.005
Total
12563.78
1
Biuret
125
0.01
Total
12500
1
UREA FROM AMMONIA AND CARBON DIOXIDE
4.0 ENERGY BALANCE
4.0
4.1
ENERGY BALANCE
Method of calculation
Energy balance are necessary in order to determine energy that needed in a process such as for heating and cooling, as well as power that needed in process design. In manual calculation calculati on done in design project, calculation was done by using equation from previous lesson such as in Elementary Principle of Chemical Processes. First law of thermodynamics also applied which states that energy cannot be created or destroyed. In forming manual energy balance calculations, some assumptions are made as below: i. ii. iii.
Pure reactant are used Values calculated up to 3 decimal place Energy out = Energy in + Generation – Generation – Consumption – Consumption – Accumulation Accumulation
There are some other assumptions regarding to the equipment itself which are: i. ii. iii. iv.
The potential and kinetic energy of streams are neglected, there are only enthalpy changes are considered For standard enthalpy, the standard reference used are; ΔH = 0, P0 = 1atm, T0 = 298 K Equipment is assumed working in ideal condition Equipment is assumed perfectly insulated
4.2 Equations Used in Energy Balance Equation used in calculation shown in table below: Table 4.1:
List of formula used
Denotation
Formula
Heat Capacity, Cp (kJ/mol.˚C)
a + bT + cT2 + dT3
Heat Load (kJ/hr)
Q = m.λ
Error Percentage, %
% error =
(Chemical Properties Handbook, Handbook, Mc Graw Hills )
Compounds
Table 4.2: Heat capacities of compounds Cp = a + bT + cT2 + dT3 + eT4 (J/mol.K)
Ammonia Carbon Dioxide Ammonium Carbamate
0.03515+0.00002954T 0.03515+0.0000295 4T+(4.42x10 +(4.42x10-9)T2+(-6.69 x10-12) T3 23.5061+0.038066T+(7.40x10-5)T2+(-2.23x10-7)T3+ (-2.34x10-10)T4
Urea Water
35.19258+0.079627T+(0.000473)T2+(-1.21x10-6)T3+ (1.26-9)T4
1 + 0.439932T
92.053+(-0.04)T+(-0.000211)T2+(5.35x10-7)T3 (KNOVEL Database)
λ = ∆H vap = A(1-T/Tc)n (kJ/mol)
Ammonium Carbamate Ammonia Urea Carbon Dioxide Water
Table 4.3: Enthalphy of vaporization A Tc (K)
38.049 31.523 87.864 18.26 52.053
Table 4.4:
Compund
Ammonia Carbon Dioxide Ammonium Carbamate Urea Water Biuret
n
539.82 0.38 405.65 0.364 705 0.38 304.19 0.24 647.13 0.321 (Chemical Properties Handbook, Mc Graw Hills)
Heat of Formation of Compounds Heat of Formation, ∆Hf at Tref = 298.15 K
-67.20 kJ/kmol -393.509 kJ/kmol -154.17 kJ/kmol -235.5 kJ/kmol -285.8 kJ/kmol -565.8 kJ/kmol (Chemical Properties Handbook, Handbook, Mc Graw Hills )
4.3
Energy Balance Calculation
Assumption: Datum temperature = 0˚C Compounds that involve in this energy balance are ammonia (NH 3), Carbon dioxide (CO 2), Ammonium carbamate (N2H6CO2), Urea (CH4 N2O), water (H2O) and biuret (C 2H5 N3O2). 4.3.1. Reactor
T = 180˚C T = 86.92˚C 86.92 ˚C NH3 = 7431.166 kg/hr CO2 = 9616.803 kg.hr N2H6CO2 = 13733.282 kg/hr Total= 30781.251 kg/hr
Reactor 180˚C
NH3 = kg/hr CO2 = 37970.466 kg.hr N2H6CO2 = 75662.576 kg/hr CH4 N2O = 48611.11 kg/hr H2O = 14756.70365 kg/hr C2H5 N3O2 = 496.031746 kg/hr Total= 30781.25 kg/hr
Figure 6.1: Energy Flow across a Reactor Calculation for Inlet Stream: At 86.92˚C: CpNH3 : 0.03515+0.00002954T+(4.42x10 0.03515+0.00002954T +(4.42x10-9)T2+(-6.69 x10-12) T3 = 0.002 kJ/kg.˚C CpCO2 : 41.2067 + (-0.1071T) + (4.4902 x10-4 T2) + (-6.5056 x10-7 T3) + (4.9123 x10-10 T4) = 0.723 kJ/kg.˚C CpN2H6CO2 : 1 + 0.439932T = 0.503 kJ/kg.˚C Cp of mixture = ∑ xiCpi = = 0.473 kJ/kg.˚C Heat from inlet stream = mCp∆T = 30781.25 x 0.473 x 86.92 = 1265514.456 kJ/hr ∆H0reaction = ∆H0r,R-1 + ∆H0r,R-2 = ∆H0f,products + ∆H0f,reactants = (-130) + 21 = -109 kJ/kmol (Exothermic reaction)
Amount of urea formed during reaction = 205.208 205.20 8 kmol/hr Thus, heat of reaction = 205.208 kmol/hr = -22367.672 kJ/hr
-109 kJ/kmol
Calculation for Outlet Stream: At 180˚C: CpNH3 : 0.03515+0.00002954T+(4.42x10 0.03515+0.00002954T +(4.42x10-9)T2+(-6.69 x10-12) T3 = 0.002 kJ/kg.˚C CpCO2 : 41.2067 + (-0.1071T) + (4.4902 x10-4 T2) + (-6.5056 x10-7 T3) + (4.9123 x10-10 T4) = 0.753 kJ/kg.˚C CpN2H6CO2 : 1 + 0.439932T = 1.028 kJ/kg.˚C CpCH4N2O : 35.19258+0.079627T+(0.000473)T2+(-1.21x10-6)T3+ (1.26-9)T4 = 0.986 kJ/kg.˚C CpH2O : 92.053+(-0.04)T+(-0.000211)T2+(5.35x10-7)T3 = 4.508 kJ/kg.˚C CpC2H5N3O2 : 1.784 kJ/kg.˚C Cp of mixture = ∑ xiCpi = (0.002 x 0.013) + (0.753 x 0.016) + (1.028 x 0.446) + (0.986 x 0.400) + (4.508 x 0.121) + (1.784 x 0.004 ) = 1.418 kJ/kg.˚C 75.338 90.925 Heat from outlet stream = mCp∆T = 30781.25 x 1.418 x 180 = 7856606.25 kJ/hr
Heat input + Heat of reaction – Heat Output = Rate of Accumulation 1265514.456 + (-22367.672) – 7856606.25 = Rate of Accumulation Rate of Accumulation = -6613459.466 kJ/hr = -1837.072 kW = -1.837 MW Therefore, heat supply needed to sustain the reactor temperature at 180 oC is approximately 2 MW.
4.3.2. Stripper
Heat output from reactor outlet stream is heat input to stripper = 7856606.25 kJ/hr
T = 185˚C 185˚C N2H6CO2 = 13733.282 kmol/hr T = 180˚C 180˚C NH3 = 392.189 kg/hr CO2 = 480.84 kg.hr N2H6CO2 = 13733.282 kg/hr CH4 N2O = 12312.5 kg/hr H2O = 3737.439 kg/hr C2H5 N3O2 = 125 kg/hr
T = 185˚C 185˚C
STRIPPER 185˚C
NH3 = 392.189 kmol/hr CO2 = 480.84 kmol/hr CH4 N2O = 12312.5 kmol/hr H2O = 3737.439 kmol/hr C2H5 N3O2 = 125 kmol/hr
Figure 6.2: Energy Flow Across A Stripper Calculation for Outlet Stream: For liquid at 185˚C: CpNH3 : 0.03515+0.00002954T 0.03515+0.00002954T+(4.42x10 +(4.42x10-9)T2+(-6.69 x10-12) T3 = 0.002 kJ/kg.˚C CpCO2 : 41.2067 + (-0.1071T) + (4.4902 x10-4 T2) + (-6.5056 x10-7 T3) + (4.9123 x10-10 T4) = 0.755 kJ/kg.˚C CpCH4N2O : 35.19258+0.079627T+(0.000473)T2+(-1.21x10-6)T3+ (1.26-9)T4 = 0.999 kJ/kg.˚C CpH2O : 92.053+(-0.04)T+(-0.000211)T2+(5.35x10-7)T3 = 4.490 kJ/kg.˚C CpC2H5N3O2 : 1.784 kJ/kmol.˚C Cp of mixture = ∑ xiCpi = (0.023 x 0.002) + (0.028 x 0.755) + (0.722 x 0.999) + (0.219 x 4.490) + (0.007 x 1.784) = 5.464 kJ/kg.˚C Heat from outlet stream stream = mCpΔT = (17047.968 x 5.464 x 185) = 17232767.97 kJ/hr = 4786.88 kW = 4.787 MW
For gas at 185˚C: CpN2H6CO2 : 1 + 0.439932T = 1.056 kJ/kg.˚C Thus, heat carried by ammonium carbamate = mCpΔT+mλ , where λcarbamate λcarbamat e = 0.118 kJ/kg = (13733.282 kg/hr x 1.056 kJ/kg.˚C x 185) + (13733.282 kg/hr x 0.118 kJ/kg) = 2684554.499 kJ/hr = 745.71 kW = 0.746 MW
Heat input – Heat Output = Rate of Accumulation 2.182 MW – (0.746 MW + 4.787 MW) = Rate of Accumulation Rate of Accumulation = -3.351 MW Therefore, heat supply needed is about 3.5 MW to the stripping process.
4.3.3. Carbamate Condenser
H2O T = 20 oC P = 40 bar
T = 185 oC
N2H6CO2 =13733.282 kg/hr (Vapour)
CARBAMATE CONDENSER
T = 170 oC N2H6CO2 = 13733.282 kg/hr (Liquid) Figure 6.3: Energy Flow Across Carbamate Condenser Heat transfer, Q = Heat in – Heat out
Heat in = 13733.282 kg/hr 1.056 kJ/kg.oC 185 oC = 2.683 MJ/hr
Heat out = 13733.282 kg/hr 0.972 kJ/kg.oC 170 oC = 2.269 MJ/hr Q = 2.683 MJ/hr – 2.269 MJ/hr = 0.414 MJ/hr = 414 kJ/hr Water properties: Pressure 40 bar with Tsat 250.3 oC Cp= 4.289 kJ/kg.oC
Q = mCp T Take basis of calculation for mass transfer is 1000 kg of water per hour
414 kJ/hr = (1000 kg/hr 4.289 kJ/kg.oC) T
T = 0.1
o
C
Therefore, temperature out for water is = 20 oC + 0.1 oC = 20.1 oC
4.3.4. Medium Pressure Separator
Heat input to equipment = 17232767.97 17232767.97 kJ/hr
T = 185oC
T = 185˚C 185˚C
M P
NH3 = 392.189 kg/hr CO2 = 480.84 kg/hr CH4 N2O = 12312.5 kg/hr H2O = 3737.439 kg/hr C2H5 N3O2 = 125 kg/hr
S
NH3 = 196.094 kg/hr CO2 = 240.42 kg/hr
T = 140˚C 140 ˚C
NH3 = 196.095 kg/hr CO2 = 240.42 kg/hr CH4 N2O = 12312.5 kg/hr H2O = 3737.439 kg/hr C2H5 N3O2 = 125 kg/hr
Figure 6.4: Energy Crossflow Across Medium Pressure Separator
Calculation for Outlet Stream: For liquid at 140˚C: CpNH3 : 0.03515+0.00002954T+(4.42x10 0.03515+0.00002954T +(4.42x10-9)T2+(-6.69 x10-12) T3 = 0.002 kJ/kg.˚C CpCO2 : 41.2067 + (-0.1071T) + (4.4902 x10-4 T2) + (-6.5056 x10-7 T3) + (4.9123 x10-10 T4) = 0.759 kJ/kg.˚C CpCH4N2O : 35.19258+0.079627T+(0.000473)T2+(-1.21x10-6)T3+ (1.26-9)T4 = 0.880 kJ/kg.˚C CpH2O : 92.053+(-0.04)T+(-0.000211)T2+(5.35x10-7)T3 = 4.655 kJ/kg.˚C CpC2H5N3O2 = 1.784 kJ/kmol.˚C Cp of mixture = ∑ xiCpi = (0.012 x 0.002) + (0.014 x 0.759) + (0.741 x 0.880) + (0.225 x 4.655) + (0.008 x 1.784) = 1.724 kJ/kg.˚C Heat from outlet stream stream = mCpΔT = (16611.454 kg/hr x 1.724 kJ/kg.˚C x 140˚C) = 4009340.537 kJ/hr
For gas at 185˚C: For ammonia: λ = 31.523 31.523 x (1-
)0.364
= 1.792 kJ/kg x = 0.449 CpNH3 : 0.03515+0.00002954T+(4.42x10 0.03515+0.00002954T +(4.42x10-9)T2+(-6.69 x10-12) T3 = 0.002 kJ/kmol.˚C For carbon dioxide: λ = 18.26 18.26 x (1-
)0.24
= 0.390 kJ/kg x = 0.551 CpCO2 : 41.2067 + (-0.1071T) + (4.4902 x10-4 T2) + (-6.5056 x10-7 T3) + (4.9123 x10-10 T4) = 0.755 kJ/kg.˚C λ of mixture = ∑ xiλi = (0.449 x 1.792) + (0.551 x 0.449) = 1.020 kJ/kg Cp of mixture = ∑ xiCp = (0.449 x 0.002) + (0.551 x 0.755) = 0.417 kJ/kg.˚C Heat out for steam = mCpΔT+mλ = (436.514 kg/hr x 0.417 kJ/kg.˚C x 140) + ( 436.514 kg/hr x 1.020 kJ/kg )
= 25928.932 kJ/hr Assumption: Cooling Cooling water at 25˚C 25˚C enter and leaves leaves the equipment equipment at 50˚C Heat cooling water gained = Heat in - Heat out So, Q cooling water = 2.92 x 107 – (1.42 x 107 + 1.54 x 105) = 1.49 x 107kJ/hr Q = mCpΔT Thus, m = Q/Cp∆T
= (1.49 x 107kJ/hr) / ( 5.05 kJ/kg.˚C x 25˚C) = 1.18 x 105 kg/hr Heat input – Heat Output = Rate of Accumulation 17232767.97 kJ/hr – (4009340.537 kJ/hr + 25928.932 kJ/hr) = Rate of Accumulation Rate of Accumulation = 13197498.5 kJ/hr = 3665.972 kW = 3.666 MW Therefore, to avoid heat accumulation, water is used as coolant thus produces steam for reactor and stripper process.
4.3.5.
Low Pressure Separator
Heat input to equipment = 4009340.537kJ/hr 4009340.537 kJ/hr
NH3 = 196.095 kg/hr CO2 = 240.42 kg/hr
T = 140˚C 140 ˚C
T = 80˚C 80˚C L
NH3 = 196.095 kg/hr CO2 = 240.42 kg/hr CH4 N2O = 12312.5 kg/hr H2O = 3737.439 kg/hr C2H5 N3O2 = 125 kg/hr
P S
CH4 N2O = 12312.5 kg/hr H2O = 3737.439 kg/hr C2H5 N3O2 = 125 kg/hr
Figure 6.5: Energy Flow Across Low Pressure Separator
Calculation for Outlet Stream: For liquid at 80˚C: CpCH4N2O : 35.19258+0.079627T+(0.000473)T2+(-1.21x10-6)T3+ (1.26-9)T4 = 0.734 kJ/kg.˚C
CpH2O : 92.053+(-0.04)T+(-0.000211)T2+(5.35x10-7)T3 = 4.876 kJ/kg.˚C CpC2H5N3O2 = 1.784 kJ/kg.˚C Cp of mixture = ∑ xiCpi = (0.761 x 0.734) + (0.231 x 4.876) + (0.008 x 1.784) = 1.699 kJ/kg.˚C
Heat from liquid outlet stream = mCpΔT = (16174.939 kg/hr x 1.699 kJ/kg.˚C x 80˚C)
= 2198497.709 kJ/hr
For gas at 140˚C: For ammonia: λ = 31.523 31.523 x (1-
)0.364
= 1.792 kJ/kg x = 0.449 CpNH3 : 0.03515+0.00002954T+(4.42x10 0.03515+0.00002954T +(4.42x10-9)T2+(-6.69 x10-12) T3 = 0.002 kJ/kg.˚C
For carbon dioxide: λ = 18.26 18.26 x (1-
)0.24
= 0.390 kJ/kg x = 0.551 CpCO2 : 41.2067 + (-0.1071T) + (4.4902 x10-4 T2) + (-6.5056 x10-7 T3) + (4.9123 x10-10 T4) = 0.759 kJ/kmol.˚C
λ of mixture = ∑ xiλi = (0.449 x 1.792) + (0.551 x 0.449) = 1.020 kJ/kg Cp of mixture = ∑ xiCp = (0.449 x 0.002) + (0.551 x 0.759) = 0.419 kJ/kg.oC Heat that escape = mCpΔT+mλ = (16174.939 kg/hr x 0.419 kJ/kg.oC x 140oC) + (16174.939 kg/hr x1.020kJ/kg)
= 965320.36 kJ/hr
Heat input – Heat Output = Rate of Accumulation 4009340.537 kJ/hr – (2198497.709 kJ/hr + 965320.36 kJ/hr) = Rate of Accumulation Rate of Accumulation = 845522.468 kJ/hr = 234.867 kW = 0.235 MW Therefore, to avoid heat accumulation, water is used as coolant thus produces steam for reactor and stripper process.
4.3.6. Evaporator
Heat Input = 2198497.709 kJ/hr H2O= 3611.159 kg/hr T = 85˚C 85˚C T = 85˚C 85˚C CH4 N2O = 12312.5 kg/hr H2O = 3737.439 kg/hr C2H5 N3O2 = 125 kg/hr
T = 27˚C 27˚C
EVAPORATOR CH4 N2O = 12312.5 kg/hr H2O = 126.28 kg/hr C2H5 N3O2 = 125 kg/hr
Figure 6.2: Energy Flow Across A Evaporator
For liquid at 27oC: CpCH4N2O : 35.19258+0.079627T+(0.000473)T2+(-1.21x10-6)T3+ (1.26-9)T4 = 0.628 kJ/kg.˚C CpH2O : 92.053+(-0.04)T+(-0.000211)T2+(5.35x10-7)T3 = 5.046 kJ/kg.˚C CpC2H5N3O2 = 1.784 kJ/kg.˚C Cp of mixture = ∑ xiCp = (0.980 x 0.628) + (0.010 x 5.046) + (0.010 x 1.784) = 0.684 kJ/kg.˚C So, mCp∆T = 12563.78 kg/hr x 0.684 kJ/kmol.˚C x 27˚C = 232027.889 kJ/hr
Assumption: λ steam steam at 85˚C is 2651.5 2651.5 kJ/kg and heat of of evaporation is 2295.5 2295.5 kJ/kg
Heat input + Heat input by stream = Heat carried by water vapour + Energy of bottom product Heat input + S1 λS1 = E1 HE1 + Energy of bottom product 2198497.709 kJ/hr + (S1 x 2651.5 kJ/kg) = (3611.159 kg/hr x 2295.5 kJ/kg) + 232027.889 kJ/hr S1 = 2384.667 kg/hr
4.3.7. Prilling Tower
Air T = 26˚C 26˚C
63.78 kg/hr water vapour
T = 27˚C 27˚C
CH4 N2O = 12312.5 kg/hr H2O = 126.28 kg/hr C2H5 N3O2 = 125 kg/hr
Air T = 25˚C 25˚C
T = 25oC
CH4 N2O = 12312.5 kg/hr H2O = 62.5 kg/hr C2H5 N3O2 = 125 kg/hr
Figure 6.6: Energy Balance Across Prilling Tower
Heat input to unit operation = 232027.889 kJ/hr At 25oC: CpCH4N2O : 35.19258+0.079627T+(0.000473)T2+(-1.21x10-6)T3+ (1.26-9)T4 = 0.624 kJ/kg.˚C
CpH2O : 92.053+(-0.04)T+(-0.000211)T2+(5.35x10-7)T3 = 5.052 kJ/kg.˚C
CpC2H5N3O2 = 1.784 kJ/kg.˚C Cp of mixture = ∑ xiCp g = (0.985 x 0.624) + (0.005 x 5.052) + (0.010 x 1.784) = 0.658 kJ/k.˚C
So, heat output mCp∆T = 12500 kg/hr
x
0.658 kJ/kg.˚C kJ/kg.˚C x 25˚C 25˚C
= 205625 kJ/hr Assumption: Humidity of air at 25˚C is 0.01 with Cp equal to 1.009 kJ/kg.˚C kJ/kg .˚C Heat carried by air = Heat Hea t input- Heat output Q dry air = 232027.889 kJ/hr - 205625 kJ/hr = 26402.889 kJ/hr Thus,mass flow rate of air: = 26402.889 kJ/hr = 26167.383 kg/hr
kJ/kg.˚C x 1˚C) (1.009 kJ/kg.˚C
4.4. Process flow diagram (by aspen 8.0)
45
4.5.
Stream table Material Balance Table
Stream ID
HP-NH3
HP-CO2
FEED
STRIP-IN
RECY-IN
RECYOUT
STRIPOUT
From
P-1
C-1
M-1
R-1
S-1
CONDEN
S-1
To
M-1
M-1
R-1
S-1
CONDEN
M-1
V-1
Phase
Liquid
Liquid
Liquid
Liquid
Vapor
Liquid
Liquid
AMMONIA
7431.166
0
7431.166
392.189
0
0
392.189
CARBO-01
0
9616.803
9616.803
480.84
0
0
480.84
Substream: MIXED Mole flow
Kg/hr
4.5.
Stream table Material Balance Table
Stream ID
HP-NH3
HP-CO2
FEED
STRIP-IN
RECY-IN
RECYOUT
STRIPOUT
From
P-1
C-1
M-1
R-1
S-1
CONDEN
S-1
To
M-1
M-1
R-1
S-1
CONDEN
M-1
V-1
Phase
Liquid
Liquid
Liquid
Liquid
Vapor
Liquid
Liquid
AMMONIA
7431.166
0
7431.166
392.189
0
0
392.189
CARBO-01
0
9616.803
9616.803
480.84
0
0
480.84
AMMON-01
0
0
UREA
0
0
0
12312.5
0
0
12312.5
WATER
0
0
0
3737.439
0
0
3737.439
BIURET
0
0
0
125
0
0
125
Substream: MIXED Mole flow
Kg/hr
Total Pressure Temperature
13733.282 13733.282 13733.282 13733.282
7431.166 9616.803 30781.251 bar 0
C
30781.25
0
13733.282 13733.282 17047.968
125
125
125
125
125
125
125
20
20
86.92
180
185
170
185
46
UREA FROM AMMONIA AND CARBON DIOXIDE
5.0 MECHANICAL DESIGN
47
5.0
MECHANICAL DESIGN
5.1. Reactor
Where;
= residence time
F
= Volumetric flow rate into the reactor in
V
= Volume of the reactor in
Density of liquid Density of gas at 185
= 618kg/
Density of carbamate = 1600 ⁄ ⁄ ⁄ ⁄ ⁄ ⁄ ⁄ ⁄ ⁄ ⁄ ⁄
48
5.2. Stripping Column x 0 0.02 0.08 0.14 0.24 0.46 0.6 0.8 1.0
y 0 0.1 0.26 0.4 0.56 0.8 0.9 1 1.6
Rectification Operating Line (ROL) Yn+1 = Thus
Xn + XD :
slope
Intercept =
=
XD
XB = 0 XF = 0.5 XD= 1 Stripping Operating Line (SOL) Y=
X -XB
From the graph, number of stages is equal to 5.
49
STRIPPER
50
UREA FROM AMMONIA AND CARBON DIOXIDE
6.0 SITE SELECTION
51
6.0
SITE SELECTION
6.1. INTRODUCTION
A preliminary site study will be conducted before proceeding with plant construction. The location of the chemical plant is the key player as it can influence the plant operation and its feasibility. The site of the plant is a vital aspect that must be taken into consideration in order to obtain maximum profitability of the project as well as for the future expansion of the plant. The plant should be located specifically where the minimum cost of production and distribution can be obtained. 6.2. SITE SELECTION CRITERIA
There are some factors that should be considered in selecting the suitable site. The characteristics of a site location chosen will have huge market effect on the success or otherwise of a commercial venture. The choice of the final site should be based on a complete survey of the advantage of various geographical areas, in addition to the advantage and disadvantages of available industrial estates. The basic site selection process takes into account the economic and geography of the area in which the plant site will be placed. The principal factors that need to be considering for the site location are: Location with respect to the marketing area Raw material supply Transport facilities Availability of labor Availability of utilities: I. Water II. Fuel III. Power Availability of suitable land Environment impact, including effluent disposal Local community considerations Climate Political and strategic consideration
6.3. Marketing Area
Materials that had been produced in the bulk quantities it usually the cost of the product per metric ton is relatively low and the cost of transportation is a significant fraction of the sales price so the plant should be located close to the primary market . This consideration is much less important for the low volume production and high priced products. 52
6.4.
Raw Materials
Availability and price of suitable raw materials will often determine the site location. Plant that produce bulk chemicals are best being located close to the source of the major raw material. The source of raw materials can be far from the plant but as long as the cost of the shipping product is less than the cost of shipping feed it will be fine. 6.5.
Transport
The transportation of materials and products to and from the plant can be an overriding consideration in site location. A site should be selected that is at least close to the major forms of transport such as road, rail, waterway (canal or river) or sea port. Road transport is increasingly used and it is suitable for local distribution from a central warehouse. Rail transport is usually cheaper for a long distance transport of bulk chemical compare to other type of transport. The air transport is convenient and efficient for the movement of personnel and essential equipment and supplies, and the proximity of the site to a major airport should be considered. 6.6.
Availability of Labor
Labor is needed for construction of the plant and its operation. Skilled construction construction workers are often brought in the outside the site area but there should be an adequate pool of unskilled labor available locally and labor suitable for training to operate to operate the plant. Skilled craft workers such as electricians, welders and pipe fitters will be needed for plant maintenance. Local labor laws, trade union customs and restrictive practices must be considered when assessing the availability and suitability of the local labor for recruitment and training. 6.7.
Utilities(services)
Chemical processes invariably required large quantities of water for cooling and general process use, and the plant must be located near a source of water of suitable quality. Process water may be drawn from a river, from wells, or purchased from a local authority. At some sites, the cooling water required can be taken from a river or lake, or from the sea. At other locations cooling towers will be needed. Electrical power is needed all the sites. Electrochemical processes require large quantities of power and must be located close to a cheap source of power. A competitively priced fuel must must be available on site for steam steam and power generation.
53
6.8.
Environmental Impact and Effluent Disposal
All industrial processes produce waste products, and full consideration must be given to the difficulties and cost of their disposal. The disposal of toxic and harmful effluents will be covered by local regulations, and the appropriate authorities must be consulted during the initial site survey to determine the standards that must be met. An environmental impact assessment should be made for each new project or major modification or addition to an existing process. 6.9.
Local Community Consideration
The proposal plant must be fit in with and be acceptable to the local community. Full consideration must be given to the safe location of the plant so that it does not impose a signification additional risk to the local population. Plants should generally be sited so as not to be upwind of residential areas under the prevailing wind. On the new site, the local community must be able to provide adequate facilities for the plant personnel such as school, bank, and housing. The local community must also be consulted about plant water consumption and discharge and the effect of the plant on local traffic. Some communities welcome new plant construction as a source of new jobs and economic prosperity. More effluent communities generally do less to encourage the building of new manufacturing plants, and in some cases may actively discourage chemical plant construction. 6.10.
Land
Sufficient suitable land must be available for the proposed plant and for future expansion. The land should ideally be flat, well drained and have suitable load-bearing characteristics. A full site evaluation should be made to determine the need for piling or other special foundations. Particular care must be taken when building plants on reclaimed land near the ocean in earthquake zones because of poor seismic character of such land. 6.11.
Climate
Adverse climatic conditions at a site will increase costs. Abnormally low temperatures require the provision of additional insulation and special heating for equipment and pipe runs. Stronger structures are needed at locations subject to high wind or earthquakes. 6.12.
Political and Strategic Considerations
Capital grants, tax concessions, and other inducement are often given by governments to direct new investment to preferred locations, such as areas of high unemployment. The availability of such grant can be the overriding consideration in site selection. In the globalized economy, there may be an advantage to be grained by locating the plant within an area with preferential tariff agreements.
54
6.13.
Site Selection Comparisons
Below table is the comparison site selection for plant of production of urea in Gurun, Bintulu and Prai.
Gurun Industrial Park
Kidurong Light Industrial Estate
Prai Industrial Complex
Gurun, Kedah
Bintulu, Sarawak
Prai, Pulau Pinang
Location
Raw Materials
Nafas NPK Fertilizer Gurun
Jaya Chemical Supplier
PKSJ Commodities Sdn. Bhd.
Transport Facilities
Land
East Coast Expressways Expressways Butterworth Railway Station
MISC Berhad (malaysia international shipping corporation)
Water
Air
Penang International Airport
Pan-Borneo Highways
Bintulu Port
Bintulu Airport
Lebuh Raya Utara – Selatan Butterworth Railway Station Prai Port
Penang International Airport
55
Gurun Industrial Park
Kidurong Light Industrial Estate
Prai Industrial Complex
Utilities
Water
Power
Syarikat Air Darul Aman Nur Generation Plants Sdn. Bhd.
Approve
Local community
Climate
climate is in the range of 35oC – 40oC
Cardno International Pty. Ltd. Sarawak Power Generation Plant
Prai Power Station (Prai Power Sdn. Bhd.)
Sarawak Electricity Supply Corporation (SESCO) Approve
Perbadanan Bekalan Air Pulau Pinang
climate is in the range of 35oC – 40oC
Approve
climate is in the range of 35oC – 40oC
Gurun Industrial Park
Kidurong Light Industrial Estate
Prai Industrial Complex
Utilities
Water
Power
Syarikat Air Darul Aman
Nur Generation Plants Sdn. Bhd.
Approve
Local community
Climate
Cardno International Pty. Ltd.
Sarawak Power Generation Plant
Prai Power Station (Prai Power Sdn. Bhd.)
Sarawak Electricity Supply Corporation (SESCO) Approve
climate is in the range of 35oC – 40oC
Perbadanan Bekalan Air Pulau Pinang
Approve
climate is in the range of 35oC – 40oC
climate is in the range of 35oC – 40oC
Area Available
150.5 hectares
97.3 hectares
211.8 hectares
Land price (per square feet)
RM 12.00
RM 20.00
RM 19.00
Gurun Industrial Park
Kidurong Light Industrial Estate
Prai Industrial Complex
56
Environmental Effect
Availability of Labor
Supported by steam generation and distribution system, demineralization water system, cooling water system, instrument air system, nitrogen production unit and waste water treatment.
Use SIL 3 certified system for the protection of environment where the requirement is met by highly available H51q controller.
The noise generated from compressor operation will not impose adverse impacts to the residents (1.5 km)
NAZA Automotive Manufacturing Sdn. Bhd. Perwaja Steel Sdn. Bhd. Langkasuka institution centre
Local Exhaust Ventilations have been set up in all the formulation plants for the control of air pollution.
Implemented its waste water management to minimize effects to the surrounding environment.
designated a storage facility to manage all scheduled wastes generated from manufacturing activities to ensure proper monitoring before dispatching them for treatment
University Putra Malaysia (Bintulu Campus)
Bintulu GIATMARA
Kolej Damai Institution
PERDA institution (PERDATECH) Silicon Technology Institution Yayasan Bumiputra Pulau
Environmental Effect
Availability of Labor
Supported by steam generation and distribution system, demineralization water system, cooling water system, instrument air system, nitrogen production unit and waste water treatment.
Use SIL 3 certified system for the protection of environment where the requirement is met by highly available H51q controller.
The noise generated from compressor operation will not impose adverse impacts to the residents (1.5 km)
Local Exhaust Ventilations have been set up in all the formulation plants for the control of air pollution.
Implemented its waste water management to minimize effects to the surrounding environment.
designated a storage facility to manage all scheduled wastes generated from manufacturing activities to ensure proper monitoring before dispatching them for treatment
NAZA Automotive Manufacturing Sdn. Bhd.
Perwaja Steel Sdn. Bhd. Langkasuka institution centre
University Putra Malaysia (Bintulu Campus)
Bintulu GIATMARA
Kolej Damai Institution
PERDA institution (PERDATECH) Silicon Technology Institution Yayasan Bumiputra Pulau Pinang
IKM Gurun
UiTM Permatang Pauh
Universiti Sains Malaysia
57
Weight
Gurun, Kedah
Bintulu, Sarawak
Prai, Pulau Pinang
5
4
3
3
Ammonia
5
4
3
4
Carbon dioxide
5
5
5
4
5
5
2
2
5
5
4
5
Characteristics Locations
Raw materials
Land price (per square feet) Land
Weight
Gurun, Kedah
Bintulu, Sarawak
Prai, Pulau Pinang
5
4
3
3
Ammonia
5
4
3
4
Carbon dioxide
5
5
5
4
5
5
2
2
Land
5
5
4
5
Water
5
3
5
4
Air
5
5
5
5
Availability of labor
5
3
4
5
Availability of utilities (overall)
5
3
4
3
Site consideration (area availability)
5
4
4
4
Climate
5
4
4
4
Local community consideration
5
5
5
5
65
50
48
48
1
2
2
Characteristics Locations
Raw materials
Land price (per square feet)
Transportation
Total Ranking
Guidelines: 1= Too Bad ; 2 = Bad; 3 = Average ; 4 = Fairly Good ; 5 = Good Ranking: 1 = selected location
6.14.
Selected Site Location
In ordered to make the site selection, there are some criteria that need to be considered before the site is being selected. For examples criteria that need to be consider are transportation, climate, availability of labor, utilities, the most importance thing are the supplier of the raw materials and many more. After some consideration of the criteria after scoring and also screening process site location of Gurun Industrial Area has been selected as the plant of urea production. There are some reasons below that why Gurun is being chosen. 6.14.1. Industry Type and Location
Suitability of Gurun Industrial Park in Kedah to build our plant is good since this area is an established industrial park that most of the industries here have related each other. This area also is located far away from the residential area so it is safe from the communities that live in Gurun area. 6.14.2. Reasonable Land Price
In Gurun Industrial Park, the land per square feet is only RM12.00. The price is cheaper compare to the other industrial area. There is about 150.5 hectares of land that is available in this area. Since to build a plant needed around 10 acres this means that the land available is more than enough to build our plant. 10 acre of land in Gurun is about RM5, 227,200. The land in Gurun is more reasonable and cheaper compare to the other two industrial area which are RM8, 712,000 in Bintulu and RM 8, 276,400 in Prai. It also has many facilities in this area such as waste disposal, storage and workforce. 6.14.3.Raw Materials Supply
Comparing the three locations, Gurun Industrial Park is the most suitable location since it is the nearest location to the suppliers of the raw materials and this is the most important things in the industry. This is because the raw material is the main things that needed to make the product. As example without reactant, reaction cannot be occurring and product cannot be produce. The nearest supplier of the raw materials of ammonia and carbon dioxide to the plant is Nafas NPK Fertilizer Gurun. The raw material is can easily be transport through land since there is North-South a highway and also it can easily be transported by train since Gurun railway station is just a stone throw from the plant location. By choosing Gurun, cost for transportation can be reduced and possibility of shortage of raw material supply is low. 6.14.4. Availability of Labor
The growth of chemical and urea industry in Gurun has also increased demand for workers. In Gurun Industrial Park, the nearest training centers such as ‘ Institusi Kemahiran MARA’(IKM) Gurun. Skill labors are also not a problem and easy to get. Malaysia has many well trained chemical engineering students. Some famous Institutes which have students of chemical engineering that not really situated in Gurun but near to the Gurun such as Universiti Sains Malaysia, University Technology Mara Malaysia (Kedah) and University Technology PETRONAS. Jobs of high skilled labor can be filled by them.
6.14.5. Utilities
Gurun Industrial Park has water supply from Syarikat Air Darul Aman. Syarikat Air Darul Aman is supply water not only in for the Gurun Industrial Park but supply to whole Kedah. Electricity supply is from Nur Generation Plants Sdn. Bhd. Every water supply and also the electricity supply to the plant are being paid monthly and there is also contract for them to supply water and electricity to the plant for a few years. By having this facilities, there will be no problem regarding to the required utilities and can focus more on the business of urea (fertilizers). 6.14.6. Climate
Malaysia is safe country and there is no four seasons occur in Malaysia. The weather is nearly same all over the Malaysia. Thus, climate is not too important factor to be considered since Malaysia is free of major natural disasters such as hurricane, volcanoes eruption, earthquake and tornado. Malaysia is also breezed by light winds, bringing a gentle cooling effect on the climate. 6.14.7. Political and Strategic Location
In Malaysia, politic is relatively stable. Any site whether led by the opposition or governing party did not effect the industries since industries will bring income to the country. Using MIBC for the shipping make it more easily to import and export the fertilizers. 6.14.8. Transportation Facilities
There are many good roads to access Gurun from all directions in Malaysia. Gurun is near to to East Coast Expressway and it is about 350km long from other parts of the peninsular Malaysia. Plant that located in Gurun usually air transportation will be at Penang International Airport ( Bayan Lepas) because it is more nearer compare to Langkawi International Airport. Broad transportation networks allow for fast transportation of goods throughout the state.
UREA FROM AMMONIA AND CARBON DIOXIDE
7.0 ECONOMIC ANALYSIS
7.0
ECONOMIC ANALYSIS
7.1.
CAPITAL COST
Capital costs is associated of the cost of construction of a new plant , the reconstruction or modification from existing chemical plant. Table 7.1 : Summary of Capital Estimating Classifications CLASS OF ESTIMATE
DESCRIPTION DATA : Typically relies on cost information
Order-of-Magnitude Estimate ( Ratio or Feasibility )
Study Estimate ( Major Equipment or Factored)
for a complete process taken from previously built plants are then adjusted using appropriate scalling factors, for capacity, and for inflation to provide the estimated capital cost. DIAGRAMS : Block flow diagram DATA : It utilizes a list of the major equipment found in the process and is roughly sized and the approximate cost determined. The total cost of equipment is then factored to give the estimated capital cost. DIAGRAMS : Based on Process flow diagram
Preliminary Design Estimate ( Scope )
Definitive Estimate ( Project Control )
Detailed Estimate ( Firm or Contractor’s )
and costs from generalized charts DATA : Requires more accurate sizing of equipment. Approximate layout of equipment is made along with estimates of piping, instrumentation and electrical requirements. DIAGRAM : Process Flow Diagram,includes vessel sketches for equipment , preliminary ploy plan and elevation diagram DATA : Requires preliminary specifications for all the equipment, utilities, instrumentation, electrical and off-sites DIAGRAMS : Final PFD ,vessel sketches, plot plan and elevation diagrams , utility balances and P&ID DATA : Requires complete engineering of the process and all related off-sites and utilities and at the end of this detailed estimate, the plant is ready to go to the construction stage. DIAGRAMS : All diagrams are required to
complete the construction of the plant
( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.1.1.
LANG FACTOR TECHNIQUE
Lang Factor method is the simple technique use to estimate the capital cost of chemical plant. The cost determined from this method represent the cost to build a major expansion to an existing chemical plant. The greater the Lang Factor, the less the purchased costs contribute to the plant costs.The values for Lang Factor , FLang are shown in the table 7.7 below. Capital Cost = Lang Factor x Sum of purchased Costs oa All Major Equipment Type of Chemical Plant
Lang Factor = FL a n g
Fluid processing plant
4.74
Solid-fluid processing plant
3.63
Solid processing plant
3.10
The capital cost calculation is determined using equation below CTM = FLang
∑
Where, CTM = the capital cost (total module) of the plant
= the purchased cost for the major equipment units n = the total number of individual units FLang = the Lang Factor ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.1.2.
MODULE COSTING TECHNIQUE
This method is the common technique to estimate the cost of a new chemical chemical plant as the best for making preliminary cost estimates. This costing technique relates all costs back to the purchased cost of equipment evaluated for some base conditions. These base conditions are handled by using multiplying factors that depends on the following : a. The specific equipment type b. The specific system pressure c. The specific materials of construction Equation below is to calculate the bare module cost for each piece of equipment. Bare module is the sum of the direct and indirect costs. CBM = Cop FBM
Where CBM = bare module equipment cost : direct and indirect costs for each unit FBM = bare module cost factor multiplication factor to account for the items plus the specific materials of construction and operating pressure. Cop = purchased cost for base conditions : equipment made of the most common material , usually carbon steel and operating at near ambient pressures. ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.1.3.
PRESSURE FACTORS FOR THE PROCESS VESSELS
For tvessel > 0.0063 m If FP,vessel is less than 1,then FP,vessel = 1. For pressures less than -0.5barg, FP,vessel =1.25.It should be noted that equation above is strictly true for the case when the thickness of the vessel wall is less than 1/4D ; for vessel in the range D= 0.3 to 4.0 m. ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.1.4.
PRESSURE FACTORS FOR OTHER PROCESS EQUIPMENT
The pressure factor , Fp ,for the remaining process equipment are given by the following general form: log10 Fp = C1 + C2 log10 P + C3 (log10)2 The value of C1 , C2 and C3 can be find at table A.2 at appendix A in reference book Analysis, Synthesis, and Design of Chemical Processes ,Third Edtion , Richard Turton . ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.2.
MANUFACTURING COST
Is the sum of all resources consumed in the process of making the products. Factors affecting the cost of manufacturing a chemical product: a. Direct manufacturing costs :- Represent operating expenses that vary vary with the production of the product demand drops, production rate is reduced to less than the design capacity and at this lower rate , we would expect a reduction in the factors making up the direct manufacturing costs. b. Fixed manufacturing costs :- These costs are independent pf changes in production rate. c. General expenses :- Represent an overhead burden that is necessary to carry out business functions include management , sales, financing and research functions. Cost of manufacturing,COM are Fixed capital investment (FCI) : (CTM or CGR), cost of operating labor (COL), cost of utilities (C UT), cost of waste treatment (CWT) and cost of raw materials (CRM). The cost of manufacture with depreciation ,COM is COM = 0.28FCI + 2.73 COL + 1.23 (CUT + CWT + CRM ) The cost of manufacture without depreciation, COMd is COMd = 0.180FCI + 2.73 COL + 1.23 (CUT + CWT + CRM ) ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.2.1.
STREAM FACTOR (SF)
The fraction of time of time that the plant is operating in a year must be known so that the yearly cost of raw materials or utilities can be calculated. It is also represents the fraction of time that the process unit is on-lined and operating at design capacity. Stream Factor (SF) =
The typical value of stream factor are in the range of 0.96 to 0.90. ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.2.2.
COST OF OPERATING LABOR ( COL )
This technique used to estimate operating labor requirement is based on dataaa obtained from five chemical companies and correlated by Alkayat and Gerrard and the equation as below: NOL = (6.29 + 31.7P2 + 0.23NNP )
0.5
Where , NOL = number of operators per shift P : number of processing steps involving NNP = Number of nonparticulate processing steps ( compressors, towers, reactors, heaters, exchangers) The cost of labor can be calculated as follows : Operating labor cost , COL = FOL x Labor Salary ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.2.3.
UTILITY COST ( CUT )
The costs of utilities are directly influenced by the cost of fuel. It includes but not limited to fuel gas , oil.coal , electric power steam (all pressures ), cooling water , process water, boiler feed water , instrument air, inert gas and refrigeration costs.Specific difficulties concern when estimating the cost of fuel, which directly impact the price of utilities such as electricity , steam and thermal fluids. ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.2.4.
RAW MATERIAL COST (CRM)
Raw material are often the natural resources such as oil , iron and wood before they are processes to form a product. Raw material are important to the production process of a country that has abundant natural resources and has an opportunity to export the materials to other countries. Raw material cost is a cost of material or substance used in the primary production or manufacturing a product.Raw materials are often referred to as commodities, which are brought and sold on commodities exchanges around the world and can be estimated by using the current price listed in such publications as the Chemical Market (CMR) . Reporter (CMR) When doing economic evaluations for new , existing, or future plants, need to establish the true selling or purchase price for all raw materials and products because the largest
operating is nearly always the cost of raw materials.The raw materials cost can be calculated by multiplying the amount produce per year with the cost per unit weight. ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.2.5.
WASTE TREATMENT COST ( CWT)
The costs of waste treatment is the cost related to treat the waste and by-product being produced from the process. As environmental regulations continue to tighten , the problems and costs associated with the treatment of waste chemical streams will increase. In recent years there has been a trend to try to reduce or eliminate the volume of these streams through waste minimization strategies. Such strategies involve utilizing alternative process technology or using additional recovery steps in order to reduce or eliminate waste streams. Although waste minimization will become increasingly important in the future, the need to treat waste streams will continue.From our process our waste produce only a pure water and the rest of the waste actually can be recycle and are stored in a storage tank. ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.3.
BREAK-EVEN ANALYSIS
Break-even analysis is the analysis of income, cost and profit structures with particular reference to the break-even point, to show the effect on break-even point of changed in income and cost. This required an estimation of fixed costs (FC) ,variable cost (VC) and total revenues (TR). (Chemical Engineering Engineering Design, Fourth Edition by R.K. Sinnott)
7.3.1.
FIXED COST (FC)
Fixed cost (FC) is the costs that do not vary with the production rate. This type of cost is actually all the bills that need to be throughout the entire plant operation. Such examples are : 1. 2. 3. 4. 5. 6. 7. 8. 9.
Maintenance Operating Labor Supervision Laboratory cost Plant overheads Capital changes Rates Insurance License fees & royalty payments
Fixed cost (FC) can be calculated by this formula :
Where , QT = Total plant operating per year F = Fixed cost per tonne ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.3.2.
VARIABLE COST (VC)
Variable cost (VC) is the costs that are dependent on the amount of product produced. Example of variable cost are: 1. 2. 3. 4.
Raw materials cost Miscellaneous operating materials costs Utilities cost Shipping and packaging
Variable cost (VC) can be calculated as below :
Where, V = Variable cost per tonne Q = Production capacity per year Hence,
is mainly to determine, the quantity at which the product at an assumed price, will generate enough revenue to start earning profit during the plant starts its operation. Break- even point is to estimate the volume or capacity for the company to reach the total cost equal to the total revenue and no profit was earned yet. So, it can be defined as: Break even = ( fixed cost / contribution ) x Selling price Contribution = Selling price – Variable cost This calculation will determines how many products needed to be selling to break even. Once reached this point, all the cost associated with the production of urea is recovered and beyond this point, it shows the plant start earning profits. ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace B. Whiting/joseph A. Shaeiwitz )
7.4.
CALCULATION
7.4.1. CAPITAL COST i.
Reactor
Volume = 65.40 m3 Temperature = 180 oC = 453 K Pressure = 125 bar = Purchased Equipment Cost, Cpo TABLE A.1 Equipment Cost Data (From Appendix A) Equipment Type Reactors
Equipment Description Jacketed nonagitated
K1
K2
K3
3.3496
-0.2765
0.0025
Capacity, Units Volume, m3
Min Size 5
Max Size 45
To calculate Cpo Log10 Cpo = K1 + K2 log10 A + K3 (log10 A)2 = 3.3496 + [-0.2765 log10 64.80] + 0.0025 (log10 64.80)2 Cpo = $ 719.29 x 3.4 = RM 2445.59x Bare Module Cost ,CBM Equipment Type Reactor
TABLE A.7 Equipment Description Jacketed nonagitated
Bare Module Factor , FBM 4.0
To calculate CBM, CBM = Cpo FBM = RM 2463 x 4.0 = RM9852 ii.
Separator High Pressure
Volume = 21.80 m3 Purchased Equipment Cost, Cpo TABLE A.1 Equipment Cost Data (From Appendix A) ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace C.Bailie/Wallace B. Whiting/joseph Whiting/ joseph A. Shaeiwitz ) Equipment Type Process vessel
Equipment Description Vertical
K1
K2
K3
3.4974
0.4485
0.1074
Capacity, Units Volume, m3
Min Size 0.3
Max Size 520
To calculate Cpo Log10 Cpo = K1 + K2 log10 21.8 + K3 (log10 21.8)2 = [ 3.4974 + (0.4485 x 1.34 ) + 0.1074 (1.34)2 ] = RM 66483.88 Bare Module Cost ,CBM TABLE A.2 from ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard Turton,Richard C.Bailie/Wallace C.Bailie/Wallace B. Whiting/joseph Whiting/joseph A. Shaeiwitz ) Identification Equipment Type Equipment Material of Number Description Construction 20 Process vessel Horizontal vertical Stainless Steel From Figure A.18 Material Factor, FM = 3.1 To calculate CBM, TABLE A.2 : Constant for Bare Module Factor Equipment Type Process Vessel
Equipment Description Vertical
B1 2.25
B2 1.82
CBM = Cpo FBM = Cpo ( B1 + B2 FMFP) log10 FP = C1 + C2 log10 + C3(log10 P)2 C1 = C2 = C3 =0 so FP =1 Thus, CBM = RM 66483.88[ 2.25 + (1.82x 3.1 x 1)] = RM 424690.78 iii.
Separator Low Pressure
Volume : 24.56 m3 Purchased Equipment Cost, Cpo TABLE A.1 : Equipment Cost Data (From Appendix A) ( Sources : Analysis, Synthesis Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace C.Bailie/Wallace B. Whiting/joseph Whiting/ joseph A. Shaeiwitz )
Equipment Type Process vessel
Equipment Description Vertical
K1
K2
K3
3.4974
0.4485
0.1074
Capacity, Units Volume, m3
Min Size 0.3
Max Size 520
To calculate Cpo Log10 Cpo = K1 + K2 log10 A + K3 (log10 A)2 = [ 3.4974 + (0.4485 log10 24.56 ) + 0.1074 (1.39)2 ] = RM 72844.42 Bare Module Cost ,CBM TABLE A.2 Identification Number
Equipment Type
Equipment Description
Material of Construction
20
Process vessel
Horizontal vertical
Stainless Steel
From Figure A.18 Material Factor, FM = 3.1 To calculate CBM, TABLE A.2 : Constant for Bare Module Factor . ( Sources : Analysis, Synthesis and Design of Chemical Processes ,Third Edition, Richard Turton,Richard C.Bailie/Wallace C.Bailie/Wallace B. Whiting/joseph Whiting/joseph A. Shaeiwitz Shaeiwitz )
Equipment Type
Equipment Description
B1
B2
Process Vessel
Vertical
2.25
1.82
CBM = Cpo FBM = Cpo ( B1 + B2 FMFP) log10 FP = C1 + C2 log10 P + C3(log10 P)2 C1 = C2 = C3 =0 so FP =1 Thus, CBM = RM 72844.42 [ 2.25 + (1.82x 3.1 x 1)] = RM 574888.16
TABLE 2 :Summary fixed capital cost estimation Equipment
Unit
Total Price (RM)
Separator
2
999,578.94
Reactor
1
9852.00
Condenser
1
3,772,929.07
Compressor
1
826,829.95
Pump
1
66,184.68
mixer
1
149,60.00
Evaporator
1
1,212,780.00
Prilling Tower
1
340,340.00
Stripper
1
377,400.00
Storage tank
4
151,536.00
Valve
1
124,780.00
TOTAL
7,897,170.64
FLang = 4.74: taken from Table 7.7 for fluid processing plant
= Flang[ CBM,reactor + CBM,condenser + CBM,separator, + CBM,compressor + CBM,pump + CBM,mixer +CBM,evaporator + CBM,prillingtower + CBM,stripper ] = 4.74[9852 + 3,772,929.07+ 999,578.94 + 826,829.95 + 66,184.68 + 149,40 + 1,212,780 + 340,340 + 377,400] = RM 7,897,170.64
7.4.2. MANUFACTURING MANUFACTURING COST 7.4.2.1. STREAM FACTOR (SF)
= 0.9041 7.4.2.2.
COST OF OPERATING LABOR Equipment Types
Number of Equipment
Compressor Mixer Reactor Separator Condenser Valve Dryer Prilling Tower Pump mixer stripper Total
1 1 1 2 1 2 1 1 3 2 1 10
1 0 1 2 1 0 1 0 0 2 1 9
Where;
= number of operators per shift
P
= number of processing steps involving the handling of particulate solids. P=0
= number of of nonparticulate processing processing steps handling steps steps and includes compression, heating and cooling, mixing, and reaction.
( ) Number of operator per shift = 2.89
Assumptions : Working day for 1 operator Plant operates Plant running Operation hour 1 year 1 Year Plant shutdown (maintenance) Shift needed for plant Operator needed in a plant Total Operating Labor Cost
RM 212,800.00
A single worker
Plant operate
s
Hence, operating labor;
Operation hour;
Salary per month: Position Operator Manager Assistant manager Engineer Total
7.4.2.3.
Salary (RM) 1,800.00 5,000.00 3,500.00 3,000.00 13,300.00
UTILITY COST (CUT)
The cost of utilities, CUT to produce 3.3 x 106 kg urea per day is estimated: Electricity at 440 V three-phase 50 Hz Price = RM 0.20 /kWh The cost of electricity =
= RM 660,000.00/yr
Cooling water at 24°C Price = RM 45.15/ 1000m3 The cost of cooling water =
= RM 3,575,880.00/ yr
Dry saturated steam at 140°C Price = RM 84.51/ 1000kg
The cost of dry saturated steam =
= RM 4,685,234.40 / yr
Cost of utilities, CUT = RM 660,000.00/yr + RM 3,575,880.00/ yr + RM 4,685,234.40 / yr = RM 8,921,114.40 / yr
7.4.2.4.
RAW MATERIAL COST (CWM)
Mass flow rate of NH3 = 7059.624 kg/hr Mass flow rate of CO2 = 9134.984 kg/hr Convert to kg/hr NH3 = 6.1842 × 107 kg/yr CO2 = 8.0022 × 107 kg/yr Chemical NH3 CO2
Cost RM/kg 2 1.2
Ammonia : CRM = NH3 = 6.1842 × 107 kg/yr × RM 2/kg × 0.94 0.94 = RM 116 Million/yr Million/yr Carbon dioxide : CRM = CO2 = 8.0022 × 107 kg/yr × RM 1.2/kg × 0.94 = RM 90 Million/yr
With depreciation
Without depreciation
7.4.3. BREAK EVEN ANALYSIS ANALYSIS
Product Urea
Production (kg per day) 3.3 x 10
Total sales Selling price (RM per kg) 6.10
R (RM per year) 2.013,000.00
Break even = ( fixed cost / contribution ) x Selling price
Contribution
= Selling price – Variable cost = RM 2,013,000.00 / yr - RM 11.2 million/yr = RM 9.15 million
Breakeven Point = ( RM 7897170 / RM 9.15 million) = 0.00537 x RM 2,013,000.00 = RM 173,177.40 / yr
7.4.4. PROFITIBILITY ANALYSIS Profitability Criteria for Project Evaluation
The profitability is evaluated based on: i. Time ii. Cash iii. Interest Rate Each of those bases, the discounted and non-discounted rate might considered. For nondiscounted technique, the value of time and money is not considered and it is not recommended for evaluating new, large projects. However, it is still and has been used to evaluate smaller projects such as process improvement schemes. Non-discounted Profitability Criteria
There are four criterion of non-discounted profitability which are time criterion, cash criterion and interest rate criterion. The term used in time criterion is the payback period (PBP), also known as the payout period, payoff period and cash recovery period. From the book of Engineering Analysis of Chemical Processes by Richard Turton/Richard C.Bailie/Wallace B.Whiting/Joseph A.Shaeiwitz, the definition of payback period is defined as follows: PBP = time required, after start-up, to recover the fixed capital investment, FCI , for the project
As for the cash criterion, there are two types of it which is cumulative cash position (CCP) and cumulative cash ratio (CCR). CCP is the value of the project at the end of its life.
Finally for the interest rate criterion, the term used is rate of return on investment (ROROI).
Discounted Profitability Criteria
The difference between non-discounted profitability and the discounted profitability is that for the latter we discount the yearly cash flows back to time zero. Then, the resulting is used to evaluate profitability. For time criterion the discounted payback period (DPBP) is defined in similar manner to the non-discounted profitability. DPBP = time required, after start-up, to recover the fixed capital investment, FCIL, for the project
The project with the shortest discounted payback period is the most wanted. As for the cash criterion, the discounted cumulative cash position or most commonly known as net present value (NPV) or net present worth value (NPW) is defined as
A present value ratio of unity for a project represents a break -even situation. Values that are greater than unity shows that the projects is profitable, whereas those that are less than unity represents the unprofitable projects. Non-discounted cash flow
Cost of land, CL
= RM 5 million
Fixed capital investment, FCIL
= RM 2,897,170.64
Fixed capital investment, FCIL year 1
= RM 1,448,585.32
Fixed capital investment, FCIL year 2
= RM 1,448,585.32
Plant start-up at end of year 2 Working capital
= 15% x FCIL = 0.15 × RM 2,897,170.64 = RM 434,575.60
The sales revenue and costs of manufacturing are given below Yearly sales revenue (after start-up), R = Selling price x production = RM 270,000,000 Cost of manufacturing excluding depreciation allowance (after start-up), COMd = RM 266,391,714.30/yr Depreciation, D = 10% × FCI = 0.10 × RM 7,897,170.64 = RM 789,717.06 Taxation rate, t = 45% Assume a project life of 10 years. Salvage value of plant, S = FCIL – D = RM 2,897,170.64 – RM 789,717.06 = RM 2,107,453.58
NONDISCOUNTED CASH FLOW End of year (k)
Investment
dk
FCIL-∑dk
R
(R-COMd-
COMd
Cumulative
Cash Flow
dk)×(1-t)+dk
Cash Flow
0
-5000000.00
2897170.64
-5000000.00
-5000000.00
1
-1448585.32
2897170.64
-1448585.32
-6448585.32
2
-1883160.92
2897170.64
-1883160.92
-8331746.24
3
579434.13
7317736.51
270000000
266391714.3
2245302.49
2245302.49
-6086443.75
4
1463547.30
6433623.34
270000000
266391714.3
2643153.42
2643153.42
-3443290.33
5
1286724.668
6610445.97
270000000
266391714.3
2563583.24
2563583.24
-879707.09
6
1322089.194
6575081.45
270000000
266391714.3
2579497.27
2579497.27
1699790.18
7
1315016.289
6582154.35
270000000
266391714.3
2576314.47
2576314.47
4276104.65
8
1316430.87
6580739.77
270000000
266391714.3
2576951.03
2576951.03
6853055.67
9
1316147.954
6581022.69
270000000
266391714.3
2576823.71
2576823.71
9429879.39
10
1316204.537
6580966.10
270000000
266391714.3
2576849.18
2576849.18
12006728.56
11
1316193.221
6580977.42
270000000
266391714.3
2576844.08
2576844.08
14583572.65
1316195.484
6580975.16 6580975.16
272107453.6
266391714.3
3735944.58
5843398.16
20426970.81
12
6184575.60
Land + Working Capital
5000000 + 434575.60
5434575.6
Payback period (PBP)
(-3443290.33-5434575.6)/(5434575.6+879707.09)=(4-x)/(x-5)
x=2.4081
Cumulative Cash Position (CCP)
20426970.81
Cumulative Cash Ratio (CCR)
-3.451703427
ROROI
0.779898615
77.99%
80
Cumulative Cash Flow Diagram for Nondiscounted 30000000.00
20000000.00
w o l F h s a 10000000.00 C e v i t a l u m u C
0.00 0
-10000000.00
1
2
3
4
5
6
7
Time after project Start (years)
8
9
10
11
12
13
Cumulative Cash Flow Diagram for Nondiscounted 30000000.00
20000000.00
w o l F h s a 10000000.00 C e v i t a l u m u C
0.00 0
1
2
3
4
5
-10000000.00
6
7
8
9
10
11
12
13
Time after project Start (years)
81
DISCOUNTED CASH FLOW End of year (k)
Nondiscounted Cash Flow
Discounted Cash Flow
Cumulative Discounted
Discounted Cash Flow
Cumulative Discounted
(i=0.1)
Cash Flow (i=0.1)
(i=0.15)
Cash Flow (i=0.15)
0
-5000000.00
-5000000.00
-5000000.00
-5000000.00
-5000000.00
1
-1448585.32
-1316895.75
-6316895.75
-1259639.41
-6259639.41
2
-1883160.92
-1556331.34
-7873227.08
-1423940.20
-7683579.61
3
2245302.49
1686928.99
-6186298.09
1476322.83
-6207256.78
4
2643153.42
1805309.35
-4380988.74
1511231.55
-4696025.23
5
2563583.24
1591783.50
-2789205.24
1274553.95
-3421471.29
6
2579497.27
1456058.96
-1333146.28
1115187.85
-2306283.43
7
2576314.47
1322056.69
-11089.60
968532.04
-1337751.40
8
2576951.03
1202166.67
1191077.08
842409.86
-495341.53
9
2576823.71
1092824.80
2283901.88
732494.12
237152.59
10
2576849.18
993486.91
3277388.79
636957.71
874110.30
11
2576844.08
903168.13
4180556.91
553875.17
1427985.47
12
5843398.16
1861886.73
6042443.65
1092172.90
2520158.36
Discounted land + working capital
5000000+434575.60/1.1^2 = 5359153.39
Discounted Payback period (DPBP)
(3.65-2)=1.65 yr
NPV
6042443.65
PVR
-1.767467213
DISCOUNTED CASH FLOW End of year (k)
Nondiscounted Cash Flow
Discounted Cash Flow
Cumulative Discounted
Discounted Cash Flow
Cumulative Discounted
(i=0.1)
Cash Flow (i=0.1)
(i=0.15)
Cash Flow (i=0.15)
0
-5000000.00
-5000000.00
-5000000.00
-5000000.00
-5000000.00
1
-1448585.32
-1316895.75
-6316895.75
-1259639.41
-6259639.41
2
-1883160.92
-1556331.34
-7873227.08
-1423940.20
-7683579.61
3
2245302.49
1686928.99
-6186298.09
1476322.83
-6207256.78
4
2643153.42
1805309.35
-4380988.74
1511231.55
-4696025.23
5
2563583.24
1591783.50
-2789205.24
1274553.95
-3421471.29
6
2579497.27
1456058.96
-1333146.28
1115187.85
-2306283.43
7
2576314.47
1322056.69
-11089.60
968532.04
-1337751.40
8
2576951.03
1202166.67
1191077.08
842409.86
-495341.53
9
2576823.71
1092824.80
2283901.88
732494.12
237152.59
10
2576849.18
993486.91
3277388.79
636957.71
874110.30
11
2576844.08
903168.13
4180556.91
553875.17
1427985.47
12
5843398.16
1861886.73
6042443.65
1092172.90
2520158.36
Discounted land + working capital
5000000+434575.60/1.1^2 = 5359153.39
Discounted Payback period (DPBP)
(3.65-2)=1.65 yr
NPV
6042443.65
PVR
-1.767467213
82
Interest or Discount Rate
NPV
0%
20426970.81
10%
6042443.65
15%
2520158.36
Interest or Discount Rate
NPV
0%
20426970.81
10%
6042443.65
15%
2520158.36
83
UREA FROM AMMONIA AND CARBON DIOXIDE
UREA FROM AMMONIA AND CARBON DIOXIDE
8.0 PINCH ANALYSIS
8.0
PINCH ANALYSIS
STREAM 1 2 3
CONDITION Cold Cold Hot
Tin (oC) 86.92 180 185
Tout (oC) 180 185 170
ṁCp (kW/ oC) 4.042 9.671 2.878
Q (kW) -376.23 -48.355 43.170
Step 1 : Temperature interval ,ΔTm = 5 oC
Step 2 : Temperature interval diagram Stream ṁCp
3
1
2.878
4.042
190 oC
2
∑ ṁCpΔT
9.671 185 oC -48.355
A
185 oC
180 oC B
170 oC
-17.461 165 oC
C
91.92 oC
-315.599 86.92 oC -381.415
85
Step 3 : Cascade Diagram C H O
A
O
Q = -381.415 -48.355
L
T
D B
U
-17.461
U
T
T
I L
C
I
-315.599
L
I
I
T
T Y
Step 4 : Minimum Number of Heat Exchanger ABOVE PINCH
HU 48.355
2 -48.355
Minimum number of heat exchanger = 1
86
BELOW PINCH 3
HU
43.170
333.059
1 -376.229
Minimum number of heat exchanger = 2
Step 5 : Design the th e Heat Exchanger Network ABOVE PINCH
ṁCp hot < ṁCp cold
3
Stream ṁCp
2.878
1
2
4.042
9.671
190 oC
185 oC
185 oC
180 oC
o
1
185 C Q1= 48.355 180 oC
1
87
BELOW PINCH
3
Stream ṁCp
1
2.878
2
4.042
185 oC
9.671
180 oC
170 oC
165 oC
91.92 oC
86.92 oC 180 oC 3
Q3= 333.059
185 oC 2 170 oC
Q2= 43.170
2
86.92 oC
Step 6: Minimum utility and minimum number of exchanger MUMNE
185 oC 3
180 oC 1
2
o
185 C
180 oC
3
2
1
86.92 oC
170 oC
88
UREA FROM AMMONIA AND CARBON DIOXIDE
9.0 ENVIRONMENTAL CONSIDERATION
89
9.0
ENVIRONMENTAL CONSIDERATION
Emission to land, air and water
Environmental friendliness of the product
Waste management
Environmental Consideratios
Visual impact
Smells
Noise
9.1.
EMISSION IN LAND
Under the National Pollutant Inventory (NPI), three ways can be accomplish to emit the product to the land:
Discharges of substances to sewer or tailings dam. Deposit of substances to landfill. Removal of substances from a facility for destruction, destruction, treatment, recycling, reprocessing, recovery, or purification.
Emissions of substances to land on-site include solid wastes, slurries, and sediments. Emissions arising from spills, leaks, and storage and distribution of materials containing listed substances may also occur to land. These emission sources can be broadly categorized as:
surface impoundments of liquids and slurries 90
Unintentional leaks and spills. 9.2. EMISSION IN AIR
There are two categories of air emission which is either fugitive or point source emissions. The fugitive type of emission do not released through a vent or stack. Examples of fugitive emissions include dust from stockpiles, volatilization of vapour from vats, open vessels, or spills and materials handling. Emissions emanating from ridgeline roof-vents, louvres, and open doors of a building as well as equipment leaks, leaks from valves and flanges is one of fugitive emission. While for point source emission is emissions that exhausted into a vent or stack and emitted through a single point source into the atmosphere. In production of urea, when ammonia is mixed with oxygen, it burns with a pale yellowish-green flame. Ammonia is decomposed into its constituent element at high pressure and with the presence of catalyst. The process where chlorine is passed into ammonia, forming nitrogen and hydrogen chloride caused the ignition to occur. The highly explosive nitrogen trichloride (NCl 3) is formed if there is excess chlorine present. In the absence of a catalyst (such as platinum gauze), the combustion of ammonia is quite difficult as the temperature of the flame is usually lower than the ignition temperature of the ammonia-air mixture. The flammable range of ammonia in air is 16 –25%.
9.3.
EMISSION IN WATER
Ammonia is miscible with water. water. In a basic aqueous solution of ammonia, ammonia, it can be expelled by boiling. The maximum concentration of ammonia in saturated water solution has a density of 0.880 g/cm3 and is often known as '.880 ammonia'. Ammonia does not burn readily or sustain combustion except under narrow fuel-to-air mixtures of 15 –25% air. Emissions of substances to water can be categorized as discharges to: Surface waters such as lakes, rivers, dams, and estuaries Coastal or marine waters Stormwater.
9.4.
WASTE MANAGEMENT
Waste management is the process of collection, transport, processing or disposal, managing and monitoring of waste materials. It is usually relates to materials produced by human activity, and the process is generally undertaken to reduce their effect on health, environment or aesthetics. Waste management is a distinct practice from resource recovery which focuses on delaying the rate of consumption of natural natural resources. The resources. The waste materials whether solid, liquid, gaseous or radioactive are fall within the remit of waste management. The practices of waste management can be differed for develop and developing nations, for urban and rural areas and for residential residential and industrial and industrial producers. Management of nonhazardous waste residential and institutional waste in metropolitan areas is usually the responsibility of local local government authorities, while management for non-hazardous non -hazardous commercial
91
and industrial and industrial waste is usually the responsibility of the generator subject to local, national or international authorities.
9.5.
SMELL
Ammonia is a colourless gas colourless gas with a characteristic pungent characteristic pungent smell. smell.
9.6.
NOISE
Noise pollution is the disturbing or excessive noise excessive noise that may harm the activity or balance of human or animal life. There are two types in describing noise which is indoor and outdoor noise. The source of most outdoor noise worldwide is mainly caused by machines by machines and transportation and transportation systems, motor vehicles, aircraft, vehicles, aircraft, and trains. and trains. While for Indoor noise is caused by machines, building activities, music performances, and especially in some workplaces. In our designed plant, the noise pollution involve comes from pump, heater, cooler, liquid-liquid extraction, absorber, separator, conversion reactor and distillation column. Increases in plant size and the advent of a single stream plant have inevitably led to equipment size being increased and this, together with the use of higher fluid velocities aimed at minimizing capital cost, has produced noise problems of a scale not seen on older plant designed to more conservative criteria. Therefore, much more attention has had to pay to noise control in recent years both in remedying plant problems and avoiding them by good design. The impacts of noise are permanent hearing loss, a rise in blood pressure, and increases in stress and also can cause death to human and also to animal.
9.7.
VISUAL IMPACT
There are three step that play the main role in this aspe ct that’s are Reduction Remediation Compensation
It is to demonstrate how significant environmental effects have been avoided, reduced or remediated. That means landscape must be an integral part of the project design process, with the plant extent, form and design emerging from locality of that plant development area.
9.7.1. Matching the local landscape Restoration design should also be considered at the earliest stage. There are an enormous variety of options which can be considered as part of a restoration scheme, which will be agreed between the operator, the mineral product association (MPA) and the local communities and interest groups. It will need to fit in with other development plans as part of the overall Spatial Plan. For example there may be a need for residential housing or an industrial estate. Restoration to include some aspect of public amenity is possible, and most schemes now contain elements of habitat conservation or creation, to enable Local Authorities to fulfill some of 92
the objectives in their Biodiversity Action Plans. In rural setting the most successful restoration schemes are those that look to be part of the local landscape
9.7.2. Mitigation Strategies Landscape measures that may be used under a number of different strategies are outlined below
9.7.3. Screening The area that being develop, is a new area, it will be estimate that the residence area will increase, especially in the radius of plant area. This is because of the job opportunities offered. Beside that their might other plant will be develop.
9.8.
THE ENVIRONMENTAL FRIENDLINESS OF THE PRODUCT
Refer to the air pollution Index (API) scale between 0-50 is good. 51-100 is moderate. 101-200 in scale is unhealthy meaning that human being should be prevented from going outside if not an emergency case. Scale 201-300 is very unhealthy. This situation should be prevented by staying at home and drinks a lot of water. Scale 301 and above hazardous. If this situation happens, emergency degree should be applied throughout the country because this could fatal to human being. The production of urea will not affect the air quality, due to less waste product dispose to the air. There are some waste water dispose but the quantity is small, and the effect on environmental can be neglect. The effect on environmental friendly is reduced because of the recycle system is practiced. If there are equipment leak during the reaction, NH 3 and CO2 is not harmful to environment. Ammonia contributes significantly to the nutritional the nutritional needs of terrestrial organisms by serving as a precursor to food to food and fertilizers. and fertilizers. Ammonia, Ammonia, either directly or indirectly, is also a building-block for the synthesis of many pharmaceuticals. many pharmaceuticals. Ammonia Ammonia also used in many commercial cleaning products. Although in wide use, ammonia is both caustic both caustic and hazardous. and hazardous. The various control technologies available to control ammonia emissions include both add-on control devices and pollution prevention techniques. There are pollution prevention techniques that are recommended:
Use natural gas as feedstock for the ammonia plant to minimize minimize air emission emission if possible. To reducing the need for natural gas, use hot process gas from the secondary reformer to heat to heat the primary reformer tubes. Direct hydrogen hydrogen cyanide (HCN) gas in a fuel oil gasification gasification plant to a combustion unit to prevent its release. Use carbon dioxide dioxide removal processes that do not release toxics toxics to the environment. environment.
93
94
UREA FROM AMMONIA AND CARBON DIOXIDE
10.0 PLANT LAYOUT
95
10.0 PLANT LAYOUT 10.1.
Plant facilities layout
A facility is regarded as a building or a precinct. A layout of a building is the map that shows the location of the building around the urea plant such as car park, cafe, mosque and more others. The most important place workers need to know is fire assembles point .A model facilities layout should be able to provide an ideal relationship between raw materials, equipment, manpower and final product at minimal cost under safe and comfortable environment. An efficient and effective facilities layout can cover the following objectives: I. II. III.
To provide optimum space to organize equipment and facilitate movements of goods To operate safe and comfortable work environment To promote safety plant as well as its worker
Figure (1): Plant Facility Layout of Urea Plant
96
Guidelines:
Power Station Car Park Cafe
Storage tank for Raw Materials and Product
Main Entrance Guard House
Cooling Tower
Control Room Fire Assemble Point
Mosque
Treatment Plant Fire station
Roads
Main Office Urea Plant
In the figure (1) shows the location of building around the urea plant, there is power station which will be supply power to the whole plant so that there will be enough power to generate the plant. If not enough power is being supply, the plant company will be loss in many aspect. There are also facilities for workers such as car park, café and also mosque for prayer. The most important place in this plant is control room since the function of control room is a room serving as a central space where a large physical facility or physically dispersed service can be monitored and controlled. Main office is for the management of the plant. Besides that, there is also treatment plant which functions as to treat the waste from the production of urea. Moreover, there are also storage tank for raw materials and product and cooling tower to transfer process waste heat to the atmosphere. Most important things for safety of the workers fire station and also fire assemble point should have. The fire assemble point is the place for the workers to assemble when there is emergency case such as if there is fire f ire in the plant.
97
UREA FROM AMMONIA AND CARBON DIOXIDE
11.0 SUMMARY AND CONCLUSION
98
11.0 SUMMARY AND CONCLUSION 11.1.
SUMMARY
The process of production of urea from ammonia and carbon dioxide plant is to be designed for the production of 300,000 kg/day of urea at elevated temperature and pressure, using a total-recycle process in which the mixture leaving the reactor is stripped by the carbon dioxide feed. The feed pure liquid ammonia is at 20 oC and 9 bar and pure gaseous carbon dioxide also 20 oC and atmospheric pressure. This reaction takes place in two stages,in the first, ammonium carbamate is formed in exothermic and the second the carbamate is dehydrated in endothermic .Both reaction are reversible and goes to 40 to 70% completion. The waste produce are water, ammonia and carbon dioxide but ammonia and carbon dioxide are directly stored into the storage tank to be used as raw material. Only water flows out. The removal of water is formed to produce granule of urea. The overall equipment used are reactor, separator, condenser, compressor, dryer, stripper, prilling tower, compressor and storage tank. These flow processes will produce 0.985 of purity. 11.2.
CONCLUSION
For the production of urea at 300 000 kg/day, the raw material need is at least 178347.984 kg/day of ammonia and 230803.272 kg/day of carbon dioxide. This considered the worst operating condition with only 40% conversion where in real production, the conversion varies up to 70% where in result higher production can be obtain with given raw material. Because of this, the ammonia and carbon dioxide removed is stored and will be reuse in batch process. The fertilizer granules contain 98.5% urea, 0.5% water and 1.0% biuret. The economic analysis including Capital & manufacturing cost, break even point, cash flow and profitability analysis has been calculated. Project evaluation criteria are divided into two types; Nondiscounted Profitability Criteria and Discounted Profitability Criteria together with plotting of graph for both criteria of Cumulative Cash Flow versus Time after Project Start. For Nondiscounted Cash Flow, Cumulative Cash Position (CCP) and Cumulative Cash Ratio (CCR) are 20426970.81 and -3.451703427 respectively with the percent of ROROI of 77.99%. While for Discounted Cash Flow, the Payback Period (PBP) is 1.65 years. Net Present Value (NPV) and Present Value Ratio (PVR) are 6042443.65 and -1.767467213 respectively. The site selection for plant of production of 3 area in Gurun, Bintulu and Prai have been compared. There are Gurun Industrial Park, Kidurong Light Industrial Estate and Prai Industrial Complex. The Gurun Industrial Park in Kedah has been selected for plant production of urea been through with process of selection. Environmental consideration in manufacturing urea is being considered as stated above. The consideration criteria include emission to land, air and water, waste management, smells, noise, visual impact and the environmental friendliness of the product. The strategic Plant layout of this urea production is being organized according regulation and safety in order to make plant run smoothly without accident and a nd injured occurred.
99
UREA FROM AMMONIA AND CARBON DIOXIDE
12.0 REFERENCES
100
12.0 REFERENCES
Fertilizer Manual, United National Industrial Development Organization (UNIDO), Kluwer Academic Publishers, ISBN 0-7923-5032-4
H. Scott Fogler, Elements of Chemical Reaction Engineering, Fourth Edition.
Elementary Principle Of Chemical Process, Richard M. Felder, Wiley Publisher, Third Edition, 2005
R.G. Compton, C.H. Bamford, C.F.H. Tippert. Kinetics and Chemical
Technology. Volume 23. Elsevier Science Publishers B.V.
Chemical and Biochemical Reactor and Process Control, Control, John Metcalfe Coulson, John Francis Richardson, !994, Page 102
Ammonia Plant Safety ( And Related Facilities) – Volume 39 – Page 42
101
