Urea Final Report

UREA MANUFACTURING PLANT CH 4200 – Comprehensive Design Project

Project Coordinator: Dr. Maneesha Gunasekara Group Members: G.A.M.C. Ariyathilaka

050029P

A.N. Buddhika

050050V

K.R.M.G. Kahatapitiya

050192G

K.D.N. Karunarathna

050206G

D.D.D.P.Sandasiri

050404L

Comprehensive design project

Urea Manufacturing Plant

ACKNOWLEDGEMENT First of all we would like to grant our heartiest gratitude to our project coordinator, Dr. Maneesha Gunasekara (lecturer- Chemical & Process Engineering department, University of Moratuwa) for all the guidance and support that she has given us to complete this design project in a successful manner. Dear Madam, please expect our sincere thanks for your kind hearted support and genuine friendly attitude shown towards our work. Thank you very much for spending your precious time to share your knowledge & experience with us. Then again, we must not forget all the staff members of Chemical & Process Engineering department, including the head of the department Dr. Jagath Premachandra , for all the assistance and support given us for accomplish the project. Without your support we may have not come this far, so please accept our sincere thanks .Also we thank the level-4, semester-1 coordinator, Dr. Suren Wijekoon, lecturer- Chemical & Process Engineering Department, University of Moratuwa. And finally, a special thank should be given to the staff of Sri Lanka Custom Office who provide us data related to urea imports.

Thank you, G.A.M.C. Ariyathilaka A.N. Buddhika. K.R.M.G. Kahatapitiya K.D.N. Karunarathna D.D.D.P.Sandasiri

Comprehensive design project I


PREFACE The final year project is task, where we apply our knowledge & experience, gained throughout the four year degree course, in a practical scenario. Here we have done it in our best capacity. It is a step which finally determines the capability to perform as chemical engineers. The ultimate goal of the final year design project on urea manufacturing plant is to find out the feasibility of setting up such a plant in Sri Lanka. In Sri Lanka urea is being used as a fertilizer in the agriculture sector. Other than as a fertilizer, urea is hardly used in any industry or any other sector even though urea has number of industrial and commercial uses. Sri Lanka imports urea from other countries such as Saudi Arabia, India, and China. The total import volume of urea is around 330,000 MT per annum. Sri Lankan government gives urea fertilizer in subsidized price for farmers. From the budget 2008, Sri Lanka allocated 15 billion rupees for fertilizer subsidies. However in the past with the establishment of The Urea Plant at Sapugaskanda, Sri Lanka became self sufficient in fertilizer requirements of the country. In 1982, the annual production of urea at Sapugaskanda factory was 310,000 tons. Then the country's annual demand was only 290,000 tons. The excessive production of 20,000 tons of urea was exported earning foreign exchange around Rs. 200 million. In 1982 the annual savings of State Fertilizer Corporation stood at Rs.750 million. In addition it had provided direct employment opportunities to 1,250 workers. Sapugaskanda Urea plant was closed in January 1987. In the world point of view urea is produced on a scale of some 100,000,000 tons per year worldwide. Urea is produced from synthetic ammonia and carbon dioxide. Urea can be produced as prills, granules, flakes, pellets, crystals, and solutions. More than 90% of world production is destined for use as a fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use (46.7%).Urea is highly soluble in water and is, therefore, also very suitable for use in fertilizer solutions. Solid urea is marketed as prills or granules. The advantage of prills is that, in general, they can be produced more cheaply than granules, which, because of their narrower particle size distribution, have an advantage over prills if applied mechanically to the soil. In Sri Lanka establishing urea manufacturing plant has many advantages. It will have greater effect on country‟s economy, development in agriculture sector, providing employment and other tangible and intangible benefits. But without having an ammonia Comprehensive design project II

Urea Manufacturing Plant production process from which in most cases raw materials for urea manufacturing (ammonia and carbon dioxide) is derived, it is rather difficult and unfeasible to establish a urea plant along considering the availability of raw materials. Considering the project it is presumed that ammonia and some instance carbon dioxide is imported. According to the current demand of Sri Lanka, the urea demand of the country with in next five years will be around 350,000 MT per annum. So we decided to design a Urea manufacturing plant to fulfill that requirement. Our plant is operated for 328 days per year. And rest of the year can be allocated for maintenance of the plant. Constructing of this kind of manufacturing plant will enhance the country‟s development since the ultimate product urea is directly related with country‟s economy and growth in agriculture sector and a utility for many other industries. On the other hand the global demand for urea is increasing rapidly; specially in Asian countries. Under those circumstances we present the final year comprehensive design project which would be beneficial for country‟s development. The design project is combined in to this report, consist of 8 chapters. Chapters include Literature survey, Process selection and Economic aspects, Process description and Flow sheet, Site selection, Mass balance calculation, Material flow sheet, Heat balance calculation, Tabulated heat balance.

Comprehensive design project III


CONTENTS

Page No

Chapter 01 1.0 Literature Survey.………………………………………………………………..

02

1.1 Urea ……………………………………………………………………………..

02

1.1.1 Synthetic urea ……………………………………………………….

02

1.1.2 Commercial production of urea ……………………………………..

02

1.1.3 Chemical characteristics of urea ……………………………………

03

1.1.4 Physical characteristics of urea ……………………………………..

04

1.1.5 Raw materials of urea manufacturing ………………………………

04

1.1.5.1 Ammonia ………………………………………………….

04

1.1.5.1.1 Ammonia Production …………………………

05

1.1.5.1.2 Ammonia storage …………………………….

06

1.1.5.2 Carbon Dioxide ……………………………………….......

06

1.1.6 Applications of urea……………………….………………………..

06

1.1.6.1 Agricultural use ……………………………………………

06

1.1.6.1.1 Advantages of Fertilizer Urea………………..

07

1.1.6.1.2 Soil Application and Placement of Urea……..

07

1.1.6.1.3 Spreading of Urea……………………………

08

1.1.6.2 Industrial use………………………………………………

08

1.1.6.3 Further commercial uses…………………………………..

08

1.1.6.4 Laboratory use…………………………………………….

10

1.1.6.5 Medical use……………………………………………….

10

1.1.6.5.1 Drug use ……………………………………..

10

1.1.6.5.2 Diagnostic use ………………………………

10

1.1.6.6 Textile use…………………………………………………

10

1.2 Global production and consumption of Urea…………………………………..

11

1.2.1 Range of global uses of urea………………………………………..

14

1.3 Urea Prices……………………………………………………………………..

15

1.4 Urea Production and Consumption in Sri Lanka………………………………

15

Chapter 2 2.0 Process Selection & Economic Aspects………………………………………..

18

2.1 Feasibility Study………………………………………………………………..

18

Comprehensive design project IV

Urea Manufacturing Plant 2.1.1 Introduction…………………………………………………………

18

2.1.2 Technical & Economic Feasibility…………………………………

19

2.1.2.1 Plant Capacity…………………………………………….

19

2.1.3 Social & Environmental Feasibility…………………………………

20

2.1.4 Plant Components…………………………………………………..

20

2.2 Process Selection……………………………………………………………….

21

2.2.1 Conventional Processes…………………………………………….

21

2.2.1.1 Once through Process……………………………………..

21

2.2.1.2 Conventional Recycle Process ……………………………

21

2.2.2 Stamicarbon CO2 – stripping process………………………………

24

2.2.3 Snamprogetti Ammonia and self stripping processes………………

27

2.2.4 Isobaric double recycle process ……………………………………

28

2.2.5 ACES process………………………………………………………

29

2.2.6 Process comparison…………………………………………………

29

2.2.6.1 Advantages of ACES Process…………………………….

30

3.0 Process Description and flow sheet……………………………………………

32

3.1 Process Description – ACES Process………………………………………….

32

3.1.1 ACES Urea plants available in the world…………………………..

34

3.2 Main component of the process……………………………………………….

34

3.2.1 Reactor……………………………………………………………..

34

3.2.2 Stripper……………………………………………………………..

34

3.2.3 Carbamate Condenser………………………………………………

35

3.2.4 Scrubber……………………………………………………………

35

3.2.5 Medium Pressure Decomposer……………………………………..

35

3.2.6 Low Pressure Decomposer…………………………………………

35

3.2.7 Medium Pressure Absorber………………………………………...

35

3.2.8 Low Pressure Absorber…………………………….………………

36

3.2.9 Flash Separator……………………………………………………..

36

3.2.10 Lower Separator…………………………………………………..

36

3.2.11 Upper Separator…………………………………………………..

36

3.2.12 Granulation Plant………………………………………………….

37

3.3 Typical product quality………………………………………………………...

38

Chapter 3

Comprehensive design project V


Chapter 4 4.0 Site Selection & Plant Layout……………………………………………….…

40

4.1 Site Selection……………………………………………………………………

40

4.1.1 Availability of raw materials……………………………………..…

40

4.1.2 Infrastructure facilities………………………………………………

41

4.1.3 Legal obligations enforced by relevant authority or the government

42

4.1.4 Environment and Climate Conditions………………………………

42

4.1.5 Labour Force availability……………………………………………

42

4.1.6 Social considerations……………………………………………….

42

4.1.7 Waste Management……………………………………………...…

43

4.2 Plant Layout ……………………………………………………………………

43

4.2.1 Importance …………………………………………………..……..

43

4.3 Environmental Impact Assessment…………………………………………….

44

4.3.1 Objectives of EIA Assessment……………………………………..

44

4.3.2 Impact of the Urea Plant on the environment ………………………

45

4.3.3 Emissions to Air……………………………………………………

46

4.3.4 Emissions to Water…………………………………………………

46

4.3.5 Emissions to Land…………………………………………………..

46

4.3.6 Elimination Methods……………………………………………….

47

4.4 Safety Of the Urea Plant………………………………………………………..

49

4.4.1 Safety factors relevant to urea ……………………………………..

50

4.4.2 Safety Factors Relevant to Ammonia………………………………

53

4.4.3 Safety Factors Relevant to Ammonium Carbamate ………………

57

4.4.4 Safety Factors Relevant to Biurete (byproduct)……………………

60

Chapter 5 5.0 Mass Balance Calculation……………………………………………………..

64

5.1 Material Balance………………………………………………………………

64

5.1.1 Reactor……………………………………………………………..

66

5.1.2 Stripper……………………………………………………………..

67


68

5.1.4 Scrubber……………………………………………………………

69

5.1.5 High Pressure Decomposer………………………………...………

70

5.1.6 Low Pressure Decomposer …………………………………………

71

Comprehensive design project VI

Urea Manufacturing Plant 5.1.7 Low Pressure Absorber…………………………………………….

72

5.1.8 Medium Pressure Absorber…………………………………………

73

5.1.9 Flash Separator……………………………………………………..

74

5.1.10 Lower Separator…………………………………………………..

75

5.1.11 Upper Separator…………………………………………………...

76

5.1.12 Waste Water Treatment Unit………………………………….…..

77

5.1.13 Granulator…………………………………………………………

78

5.1.14 Screen……………………………………………………………...

79

5.1.15 Product Cooler…………………………………………………….

80

5.1.16 Bag Filter………………………………………………………….

81

Chapter 6 Material Flow Sheet………………………………………………………………

83

Chapter 7 7.0 Heat Balance Calculation………………………………………………………

85

7.1 Main Process Energy Balance…………………………………………………

85

7.1.1 Reactor……………………………………………………………..

88

7.1.2 Stripper……………………………………………………………..

90

7.1.3 Scrubber…………………………………………….………………

91


93

7.1.5 High pressure decomposer…………………………………………

95

7.1.6 Low pressure decomposer…………………………………………

96

7.1.7 Low pressure absorber……………………………………………..

98

7.1.8 High pressure absorber……………………………………………..

99

7.1.9 Flash separator……………………………………………………..

101

7.1.10 Lower separator…………………………………………………..

102

7.1.11 Upper separator…………………………………………………...

103

7.1.12 Process wastewater treatment unit………………………………..

104

7.2 Granulation Plant………………………………………………………………

105

7.2.1 Granulator………………………………………………………….

105

7.2.2 Product cooler……………………………………………………...

105

Chapter 8 8.0 Tabulated Heat Balance………………………………………………………..

107

Comprehensive design project VII


References ………………………………………………………...

List of Figures

109

Page No

Figure 1.1 Chemical structures of urea molecules…………………………………

03

Figure 1.2 (a) The change in world consumption………………………………….

11

Figure 1.3: Global distribution of the consumption of urea fertilizer……………..

13

Figure 1.4 Urea import data……………………………………………………..…

16

Figure 2.1 Conventional process flow diagram……………………………………

23

Figure 2.2 CO2 stripping process flow diagram……………………………………

26

Figure 3.2 Functional block diagram of the ACES…………………………………

32

Figure 3.1 Process Flow Sheet……………………………………………………..

32

Figure 3.3 Pipe and Instrumentation diagram………………………………………

33

Figure 3.4 Granulation plant ………………………………………………………

37

Figure 3.5 Spout-Fluid Bed Granulator…………………………………………….

37

Figure 3.6 Power Consumption of Spout-Fluid Bed Granulation………………….

38

Figure 3.7 Various sizes of granules ………………………………………………

38

Figure 4.1 Plant layout……………………………………………………….…….

43

Figure 6.1 Material Flow Sheet…………………………………………………….

83

List of Tables

Page No

Table1.1 chemical characteristics of urea…….……………………………………

04

Table 1.2 Physical Characteristics of Urea…………………………………………

04

Table 1.3 Urea Prices………………………………………………………………

15

Table 3.1 ACES Urea plants available in the world Process……………………….

34

Table 4.1 Ammonia releases from urea plants……………………………………..

45

Table 4.2 Typical consumption figures for a granulation plant……………………

45

Table 4.3 Emissions from Urea manufacturing process…………………………..

45

Table 5.1 Compound in urea manufacturing……………………………………….

65

Table 8.1 Tabulated Heat Balance…………………………………………………

107

Comprehensive design project VIII


Chapter 01

CHAPTER 1 LITERATURE SURVEY

Comprehensive design project 1


Chapter 01

1.0 Literature Survey 1.1 Urea Urea is an oraganic compound with the chemical formula (NH2)2CO. Urea is also known by the International Nonproprietary Name (INN) carbamide, as established by the World Health Organization. Other names include carbamide resin, isourea, carbonyl diamide, and carbonyldiamine.

1.1.1 Synthetic urea It was the first organic compound to be artificially synthesized from inorganic starting materials, in 1828 by Friedrich Wöhler, who prepared it by the reaction of potassium cyanate with ammonium sulfate. Although Wöhler was attempting to prepare ammonium cyanate, by forming urea, he inadvertently discredited vitalism, the theory that the chemicals of living organisms are fundamentally different from inanimate matter, thus starting the discipline of organic chemistry. This artificial urea synthesis was mainly relevant to human health because of urea cycle in human beings. Urea was discovered; synthesis in human liver in order to expel excess nitrogen from the body. So in past urea was not considered as a chemical for agricultural and industrial use. Within the 20th century it was found to be a by far the best nitrogenic fertilizer for the plants and became widely used as a fertilizer. Urea was the leading nitrogen fertilizer worldwide in the 1990s.Apart from that urea is being utilized in many other industries. Urea is produced on a scale of some 100,000,000 tons per year worldwide. For use in industry, urea is produced from synthetic ammonia and carbon dioxide. Urea can be produced as prills, granules, flakes, pellets, crystals, and solutions.More than 90% of world production is destined for use as a fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use (46.7%). Therefore, it has the lowest transportation costs per unit of nitrogen nutrient. Urea is highly soluble in water and is, therefore, also very suitable for use in fertilizer solutions (in combination with ammonium nitrate).

1.1.2 Commercial production of urea Urea is commercially produced from two raw materials, ammonia, and carbon dioxide. Large quantities of carbon dioxide are produced during the manufacture of ammonia from coal or from hydrocarbons such as natural gas and petroleum-derived raw materials. This allows direct synthesis of urea from these raw materials. The production of urea from ammonia and carbon dioxide takes place in an equilibrium reaction, with incomplete conversion of the Comprehensive design project 2


Chapter 01

reactants. The various urea processes are characterized by the conditions under which urea formation takes place and the way in which unconverted reactants are further processed. Unconverted reactants can be used for the manufacture of other products, for example ammonium nitrate or sulfate, or they can be recycled for complete conversion to urea in a totalrecycle process. Two principal reactions take place in the formation of urea from ammonia and carbon dioxide. The first reaction is exothermic: 2 NH3 + CO2 ↔ H2N-COONH4 (ammonium carbamate) Whereas the second reaction is endothermic: H2N-COONH4 ↔ (NH2)2CO + H2O Both reactions combined are exothermic.

1.1.3 Chemical characteristics of urea

Figure 1.1 Chemical structures 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 (and energetically favorable) hydrogen bond network is probably established at the cost of efficient molecular packing: The structure is quite open, the ribbons forming tunnels with square cross-section. Urea is stable under normal conditions.



Chapter 01

IUPAC name

Diaminomethanal

Chemical formula

(NH2)2CO

Molecular mass

60.07 g/mol (approximate)

Dipole moment pH

4.56 p/D (100g.L-1 in water, 20ºC) ~9

Table1.1 chemical characteristics of urea

1.1.4 Physical characteristics of urea Urea is a white odourless solid. Due to extensive hydrogen bonding with water (up to six hydrogen bonds may form - two from the oxygen atom and one from each hydrogen) urea is very soluble.

Density

1.33·10³ kg/m³, solid

Melting point

132.7 °C (406 K) decomposes

Boiling point

NA 108 g/100 ml (20 °C) 167 g/100 ml (40 °C)

Solubility in water

251 g/100 ml (60 °C) 400 g/100 ml (80 °C) 733 g/100 ml (100 °C)

Vapour pressure

<0.1 hPa

Bulk density

0.8 kg.m-3

Table 1.2 Physical Characteristics of Urea

1.1.5 Raw materials of urea manufacturing 1.1.5.1 Ammonia Ammonia, NH3, is a comparatively stable, colourless gas at ordinary temperatures, with a boiling point of –33 C. Ammonia gas is lighter than air, with a density of approximately 0.6 times that of air at the same temperature. The characteristic pungent odors of ammonia can be detected as low as 1-5ppm. Ammonia can be highly toxic to a wide range of organisms. In humans, the greatest risk is from inhalation of ammonia vapour, with effects including irritation and corrosive damage to skin, eyes and respiratory tracts. At very high levels, inhalation of Comprehensive design project 4


Chapter 01

ammonia vapour can be fatal. When dissolved in water, elevated levels of ammonia are also toxic to a wide range of aquatic organisms. Ammonia is highly soluble in water, although solubility decreases rapidly with increased temperature. Ammonia reacts with water in a reversible reaction to produce ammonium (NH 4)+ and hydroxide (OH) - ions, as shown in equation. Ammonia is a weak base, and at room temperature only about 1 in 200 molecules are present in the ammonium form (NH4)+. The formation of hydroxide ions in this reaction increases the pH of the water, forming an alkaline solution. If the hydroxide or ammonium ions react further with other compounds in the water, more ammonia with react to reestablish the equilibrium. NH3 + H2O

+

-

(NH4) + OH

While ammonia-air mixtures are flammable when the ammonia content is 16-25% by volume, these mixtures are quite difficult to ignite. About 85% of the ammonia produced worldwide is used for nitrogen fertilizers. The remainder is used in various industrial products including fibers, animal feed, and explosives.

1.1.5.1.1 Ammonia Production Essentially all the processes employed for ammonia synthesis are variations of the Haber-Bosch process, developed in Germany from 1904-1913. This process involves the reaction of hydrogen and nitrogen under high temperatures and pressures with an iron based catalyst. This process also requires large energy consumption. Ammonia is generally produced at a few large plants with stream capacities of 1000 tonnes/day or greater. The formation of ammonia from hydrogen and nitrogen is a reversible reaction, as shown in equation [2]. The fraction of ammonia in the final gas mixture is dependent on the conditions employed. Unreacted hydrogen and nitrogen gases separated from the ammonia and are usually recycled. In almost all modern plants, the ammonia produced is recovered by condensation to give liquid ammonia. H2 + 3N2

2NH3

The source of nitrogen is always air. Hydrogen can be derived from a number of raw materials including water, hydrocarbons from crude oil refining, coal, and most commonly natural gas. Hydrogen rich reformer off-gases from oil refineries have also been used as a source of hydrogen. Steam reforming is generally employed for the production of hydrogen from these raw materials. This process also generates carbon dioxide, which can then be used as a raw material in the production of urea. Comprehensive design project 5


Chapter 01

Trace impurities in the feed gases, such as sulphur compounds and chlorides, can have a detrimental effect on the production of ammonia by poisoning the catalysts employed. The feed gases, therefore, need to be purified prior to use.

1.1.5.1.2 Ammonia storage Anhydrous ammonia is usually stored as a liquid in refrigerated tanks at –33.3 C and atmospheric pressure, often in doubled-walled tanks with the capacity for hundreds or thousands of tonnes. The low temperature is usually maintained by the venting of ammonia gas. The vented gas is reliquefied for recycling, or absorbed in water to make aqueous ammonia. Relatively small quantities of anhydrous ammonia are sometimes stored under pressure in spherical vessel at ambient temperature. Ammonia is corrosive to alloys of copper and zinc and these materials must never be used in ammonia service. Iron and steel are usually the only metals used in ammonia storage tanks, piping and fittings.

1.1.5.2 Carbon Dioxide CO2 is a odourless and colourless gas which contain 0.03% in the atmosphere. It is emitted as a pollutant from number of industries. CO2 can be obtained from ammonia production process as a by product.

1.1.6 Applications of urea 1.1.6.1 Agricultural use More than 90% of world production is destined for use as a fertilizer. Urea is used as a nitrogen-release fertilizer, as it hydrolyses back to ammonia and carbon dioxide, but its most common impurity, biuret, must be present at less than 2%, as it impairs plant growth. Urea has the highest nitrogen content of all solid nitrogeneous fertilizers in common use (46.4%N.) It therefore has the lowest transportation costs per unit of nitrogen nutrient. In the past decade urea has surpassed and nearly replaced ammonium nitrate as a fertilizer In the soil, urea is converted into the ammonium ion form of nitrogen. For most floras, the ammonium form of nitrogen is just as effective as the nitrate form. The ammonium form is better retained in the soil by the clay materials than the nitrate form and is therefore less subject to leaching. Urea is highly soluble in water and is therefore also very suitable for use in fertilizer solutions, e.g. in “foliar feed‟ fertilizers. Commercially, fertilizer urea can be purchased as prills or as a granulated material. In the past, it was usually produced by dropping liquid urea from a "prilling tower" while drying Comprehensive design project 6


Chapter 01

the product. The prills formed a smaller and softer substance than other materials commonly used in fertilizer blends. Today, though, considerable urea is manufactured as granules. Granules are larger, harder, and more resistant to moisture. As a result, granulated urea has become a more suitable material for fertilizer blends. 1.1.6.1.1 Advantages of Fertilizer Urea Urea can be applied to soil as a solid or solution or to certain crops as a foliar spray. Urea usage involves little or no fire or explosion hazard. Urea's high analysis, 46% N, helps reduce handling, storage and transportation costs over other dry N forms. Urea manufacture releases few pollutants to the environment. Urea, when properly applied, results in crop yield increases equal to other forms of nitrogen. Nitrogen from urea can be lost to the atmosphere if fertilizer urea remains on the soil surface for extended periods of time during warm weather. The key to the most efficient use of urea is to incorporate it into the soil during a tillage operation. It may also be blended into the soil with irrigation water. A rainfall of as little as 0.25 inches is sufficient to blend urea into the soil to a depth at which ammonia losses will not occur. Urea breakdown begins as soon as it is applied to the soil. If the soil is totally dry, no reaction happens. But with the enzyme urease, plus any small amount of soil moisture, urea normally hydrolizes and converts to ammonium and carbon dioxide. This can occur in 2 to 4 days and happens quicker on high pH soils. Unless it rains, urea must be incorporated during this time to avoid ammonia loss. Losses might be quite low if the soil temperature is cold. The chemical reaction is as follows: CO(NH2)2 + H2O + urease

2NH3 +CO2

1.1.6.1.2 Soil Application and Placement of Urea The volatility of urea depends to a great extent on soil temperature and soil pH. If properly applied, urea and fertilizers containing urea are excellent sources of nitrogen for crop production. After application to the soil, urea undergoes chemical changes and ammonium (NH 4 +) ions form. Soil moisture determines how rapidly this conversion takes place. When a urea particle dissolves, the area around it becomes a zone of high pH and ammonia concentration. This zone can be quite toxic for a few hours. Seed and seedling roots Comprehensive design project 7


Chapter 01

within this zone can be killed by the free ammonia that has formed. Fortunately, this toxic zone becomes neutralized in most soils as the ammonia converts to ammonium. Usually it's just a few days before plants can effectively use the nitrogen. Although urea imparts an alkaline reaction when first applied to the soil, the net effect is to produce an acid reaction. Urea or materials containing urea should, in general, be broadcast and immediately incorporated into the soil. Urea-based fertilizer applied in a band should be separated from the seed by at least two inches of soil. 1.1.6.1.3 Spreading of Urea Urea can be bulk-spread, either alone or blended with most other fertilizers. Urea often has a lower density than other fertilizers with which it is blended. This lack of "weight" produces a shorter "distance-of-throw" when the fertilizer is applied with spinner-type equipment. In extreme cases this will result in uneven crop growth and "wavy" or "streaky" fields. Urea and fertilizers containing urea can be blended quite readily with monoammonium phosphate (11-52-0) or diammonium phosphate (18-46-0). Urea should not be blended with superphosphates unless applied shortly after mixing. Urea will react with superphosphates, releasing water molecules and resulting in a damp material which is difficult to store and apply. Urea fertilizer can be coated with certain materials, such as sulfur, to reduce the rate at which the nitrogen becomes available to plants. Under certain conditions these slow-release materials result in more efficient use by growing plants. Urea in a slow-release form is popular for use on golf courses, parks, and other special lawn situations. 1.1.6.2 Industrial use Urea has the ability to form 'loose compounds', called clathrates, with many organic compounds. The organic compounds are held in channels formed by interpenetrating helices comprising of hydrogen-bonded urea molecules. This behaviour can be used to separate mixtures, and has been used in the production of aviation fuel and lubricating oils. As the helices are interconnected, all helices in a crystal must have the same 'handedness'. This is determined when the crystal is nucleated and can thus be forced by seeding. This property has been used to separate racemic mixtures. 1.1.6.3 Further commercial uses  A stabilizer in nitrocellulose explosives Comprehensive design project 8


Chapter 01

 A reactant in the NOx-reducing SNCR and SCR reactions in exhaust gases from combustion, for example, from power plants and diesel engines  A component of fertilizer and animal feed, providing a relatively cheap source of nitrogen to promote growth  A raw material for the manufacture of plastics, to be specific, urea-formaldehyde resin  A raw material for the manufacture of various glues (urea-formaldehyde or ureamelamine-formaldehyde); the latter is waterproof and is used for marine plywood  An alternative to rock salt in the de-icing of roadways and runways; it does not promote metal corrosion to the extent that salt does  An additive ingredient in cigarettes, designed to enhance flavour  A browning agent in factory-produced pretzels  An ingredient in some hair conditioners, facial cleansers, bath oils, and lotions  A reactant in some ready-to-use cold compresses for first-aid use, due to the endothermic reaction it creates when mixed with water  A cloud seeding agent, along with salts, to expedite the condensation of water in clouds, producing precipitation  An ingredient used in the past to separate paraffins, due to the ability of urea to form clathrates (also called host-guest complexes, inclusion compounds, and adducts)  A flame-proofing agent (commonly used in dry chemical fire extinguishers as Ureapotassium bicarbonate)  An ingredient in many tooth whitening products  A cream to soften the skin, especially cracked skin on the bottom of one's feet  An ingredient in dish soap.  To make potassium cyanate  A melt agent used in re-surfacing snowboarding halfpipes and terrain park features  A raw material for melamine production More than 95% of all melamine production is based on urea. Stamicarbon‟s parent company DSM is the largest melamine producer in the world.  A supplementary substitute protein source in feedstuffs for cattle and other ruminants. Because of the activity of micro-organisms in their cud, ruminants are able to metabolize certain nitrogen containing compounds, including urea, as protein substitutes. In the USA this capability is exploited on a large scale. Western Europe, in contrast, uses little urea in cattle feed.



Chapter 01

 Feed for hydrolyzation into ammonia which in turn is used to reduce emissions from power plants and combustion engines.  Other, miscellaneous products such as de-icing material for airport runways. Although on a smaller scale than as a fertilizer or as raw material for synthetic resins, urea is also used as a raw material or auxiliary material in the pharmaceutical industry, the fermenting and rewing industries and in the petroleum industry. 1.1.6.4 Laboratory use Urea is a powerful protein denaturant. This property can be exploited to increase the solubility of some proteins. For this application, it is used in concentrations up to 10 M. Urea is used to effectively disrupt the noncovalent bonds in proteins. Urea is an ingredient in the synthesis of urea nitrate. Urea nitrate is also a high explosive very similar to ammonium nitrate, however it may even be more powerful because of its complexity. 1.1.6.5 Medical use 1.1.6.5.1 Drug use Urea is used in topical dermatological products to promote rehydration of the skin. If covered by an occlusive dressing, 40% urea preparations may also be used for nonsurgical debridement of nails. This drug is also used as an earwax removal aid. Like saline, urea injection is used to perform abortions. It is also the main component of an alternative medicinal treatment referred to as urine therapy. 1.1.6.5.2 Diagnostic use Isotopically-labeled urea (carbon-14 - radioactive, or carbon-13 - stable isotope) is used in the urea breath test, which is used to detect the presence of the bacteria Helicobacter pylori (H. pylori) in the stomach and duodenum of humans. The test detects the characteristic enzyme urease, produced by H. pylori, by a reaction that produces ammonia from urea. This increases the pH (reduces acidity) of the stomach environment around the bacteria. Similar bacteria species to H. pylori can be identified by the same test in animals such as apes, dogs, and cats . 1.1.6.6 Textile use Urea is a raw material for urea-formaldehyde resins production in the adhesives and textile industries. A significant portion of urea production is used in the preparation of ureaComprehensive design project 10


Chapter 01

formaldehyde resins. These synthetic resins are used in the manufacture of adhesives, moulding powders, varnishes and foams. They are also used for impregnating paper, textiles and leather. In textile laboratories they are frequently used both in dyeing and printing as an important auxiliary, which provides solubility to the bath and retains some moisture required for the dyeing or printing process.

1.2 Global production and consumption of Urea Commercial urea production began in the 1920s with the development of the Haber-Bosch process.

Figure 1.2 (a) The change in world consumption (million metric tons of N) of total synthetic nitrogen fertilizers (solid line) and urea consumption (solid bars) since 1960. Data for 2005– 2020 (shown as the shaded region) are calculated assuming an annual increase of 3% in total consumption and 5% in the fraction that is urea. (b) Same data as in panel (a) with the fraction that is urea displayed as a percentage of the total nitrogen fertilizer. Urea is processed into granules or other forms. Urea production is energy intensive. Most commonly, it is produced using natural gas, so the major producing regions are those where natural gas is abundant. Several leading manufacturing countries for urea are Russia, Canada, and Saudi Arabia, but other Middle East producers, including Iran and Iraq are (or were before the Gulf Wars) significant. In the US, urea production facilities are located mainly in the Gulf of Mexico states. Comprehensive design project 11


Chapter 01

Production of urea has at least doubled every decade since 1980 in the Middle East, increasing from 2 million metric tons per year in 1980 to 10 million metric tons year per in 2000. Further expansion of production is anticipated in the coming years in Kuwait, Qatar, Egypt, Oman and Iran. From the mid-1970s to the early 1990s, Russia (USSR) erected at least 40 new ammonia and urea production facilities. Production of urea in China tripled from 1989 to 1999. Dramatic increases in global production have also occurred in many countries since 2000, with several Latin American countries increasing production by more than 25%. As late as the 1960s, urea represented only about 5% of world nitrogen fertilizer use. However, urea usage escalated in the 1980s, such that it represented about 40% of global nitrogen fertilizer by the early 1990s, and soon thereafter urea surpassed ammonium nitrate as the most common nitrogen fertilizer. It is now estimated that urea represents >50% of world nitrogen fertilizer (Figure 1b). Assuming urea consumption continues at 5% per year, as projected for many parts of the world, urea consumption may reach 70% of total nitrogen use by the end of the next decade (Figure 1b): this is a dramatic global change in the composition of nitrogen applied to land throughout the globe. Such projections depend on global commodity markets, construction of new plants, and other factors that are difficult to project, but most of this increase is expected to occur in developing countries, particularly in Asia and Latin America. China and India together account for about half of the global consumption, and have at least doubled their consumption of urea in the past decade. In India, Bangladesh and Pakistan, urea fertilizer has been heavily subsidized (as much as 50% of the cost of production) leading to its widespread use and overapplication. The US and Canada now represent about 20% of the global urea market, with urea constituting about 30% of US synthetic nitrogen fertilizer usage. Consumption is increasing even in regions where land applications of nitrogen have heretofore been low. The rural Canadian provinces of Manitoba, Saskatchewan and Alberta, for example, are now the regions where over 70% of Canada‟s urea is consumed. Urea is the only form of fertilizer used in British Columbia forests. In Latin America, consumption of urea has fluctuated more than in Asia during the past decade due to various economic crises and unstable political environments, leading to fluctuating incentives and subsidies. This global trend in increased urea consumption represents both a net increase in total nitrogen applied, as well as a shift from the use of nitrate or anhydrous ammonium to urea. These increases parallel the increases in the production of both cereal and meat (associated with increasing human population) that have occurred globally in the past several decades. Urea is used in the production of virtually all crops from corn to Christmas trees, sugar cane to sweet Comprehensive design project 12


Chapter 01

potatoes, and vegetables to vineyards. Urea is preferable to nitrate for growing rice in flooded soils, and thus the Far East and the Mid-East are major consumers of urea. In coated form, urea becomes a slow-release fertilizer and this is one of the most popular forms for applications to lawns, golf courses, and parks, as well as many crops. The global shift toward the use of urea fertilizer stems from several advantages it has over other fertilizer forms. It is less explosive than ammonium and nitrate when stored, it can be applied as a liquid or solid, and it is more stable and cost effective to transport than other forms of reactive nitrogen. The increasing production of „granular‟ urea has contributed to its widespread use, as this is safe and easy to transport. Urea also contains twice the nitrogen of ammonium sulfate, making application rates per unit of fertilizer less costly for individual farmers. With the growth of large, industrial farms, the economics and safety of urea transport and storage are thus major factors in the shift away from ammonium nitrate.

Figure 1.3: Global distribution of the consumption of urea fertilizer, in metric tons per year by country, in 1960 (upper panel) and in 1999 (lower panel), based on data from the Global Fertilizer Industry data base (FAO 2001),These estimates of urea consumption do not include uses other than fertilizer.



Chapter 01

1.2.1 Range of global uses of urea While more than 75% of manufactured urea is consumed as nitrogen fertilizer, there are other significant uses of urea, which also are increasing globally. One such use is as a feed additive for ruminants, used to stimulate gut microbial flora. This application represents about 10% of non-fertilizer usage. Urea can be added directly to feed, such as in urea-treated wheat or rice straw, or mixed with molasses („urea–molasses licks‟ or „urea multi-nutrient blocks‟) for sheep, cattle, water buffalo, and horses. Urea may also be used as a fertilizer of the grasslands on which cattle or sheep may graze. Another direct application of urea to land is as urea-based herbicides or pesticides (sulfonyl urea pesticides). In this case, urea is chemically synthesized with a poison or inhibitor. Sulfonyl urea is one of the preferred herbicides for broadleaf and grassy weeds. It is also commonly used in non-agricultural situations, such as to control weeds in railroad and electric utility rights of way. Urea-based herbicides potentially have a large impact by both increasing urea inputs and reducing the potential for local uptake. Urea has long been used as a de-icer. Commercial airports and airfields are the largest consumers of these de-icing materials, although recommendations are now in place to reduce its usage in the US and elsewhere because of its recognized contribution to water pollution. Even with such reductions, it is still the de-icer of choice under some weather conditions. It is also used fairly extensively for domestic ice-melting applications (e.g. roads and sidewalks). Urea may also be spread on agricultural crops to prevent frost when temperatures drop to a level that may cause crop damage, and commercial formulations of urea are available for this purpose. Urea is also used in some direct applications to seawater. It is used in the growing world aquaculture industry. In intensive shrimp culture, for example, ponds may be fertilized with urea and superphosphate to initiate an algal bloom that eventually serves as food for the commercial resource. A significant proportion of such nutrients are subsequently discharged to local waters with pond effluent, as only a small fraction of added nutrients ultimately winds up in marketable product. Urea may also be spread on coastal oil spills, to stimulate the growth of natural bacteria populations which break down the oil; it was widely used, for example, during the Exxon Valdez spill, and has been used in numerous other spills since. For the Exxon Valdez spill, fertilizer applications continued for years following the initial crisis, and this approach was estimated to have enhanced the degradation of the oil by 2–5-fold.



Chapter 01

In addition to the direct applications of urea to land and sea, urea is used in many other applications, including manufacture of a wide range of common materials such as urea formaldehyde and plastics. This use represents about 50% of the non-fertilizer urea. Urea is also an additive in fire retardant paints, tobacco products, and in some wines. In the cosmetics industry, urea is an ingredient in moisturizing creams. There are numerous uses of urea in holistic medicine therapies. One application currently being considered which would greatly expand the global use of urea is as a reductant in catalytic and non-catalytic reduction of combustion products in vehicles.

1.3 Urea Prices The world price for urea has trended downwards in real terms since 1975, although it can be volatile. In real terms (1990s), the price per ton was $438 in 1975; $309 in 1980; $199 in 1985, and $131 in 1990. These prices are on a bulk FOB basis, and freight and bagging charges of about $20 to $25 per ton must be added to arrive at bagged import costs. From 1991 to 2000, the prices of urea ($/ton) are shown in the table below: year

1991

1992

1993

1994

1995

1996

1997

1998 1999 2000 Mean

Urea

$151

$123

$ 94

$131

$194

$187

$128

$103 $ 78

$112 $130

($/ton) Source: IMF, International Financial Statistics, Yearbook and July, 2001 issues.

Table 2.3 Urea Prices

1.4 Urea Production and Consumption in Sri Lanka In Sri Lanka urea is being used as a fertilizer in the agriculture sector. Other than as a fertilizer, urea is hardly used in any industry or any other sector even though urea has number of industrial and commercial uses. Sri Lanka imports urea from other countries such as Saudi Arabia, India, and China. . The total import volume of urea is around 330,000 MT per annum. Sri Lankan government gives urea fertilizer in subsidized price for farmers. From the budget 2008, Sri Lanka allocated 15 billion rupees for fertilizer subsidies. However in the past with the Urea Plant at Sapugaskanda, Sri Lanka was able to became self sufficient in fertilizer requirements of the country. In 1982, the annual production of urea at Sapugaskanda factory was 310,000 tons. Then the country's annual demand was only 290,000 tons. The excessive production of 20,000 tons of urea was exported earning foreign



Chapter 01

exchange around Rs. 200 million. In 1982 the annual savings of State Fertilizer Corporation stood at Rs.750 million. Urea plant was closed in January 1987. According to the Sri Lanka Custom data records, following graphs shows total urea imports to the country within past 10 years and relative costs involved. TOTAL UREA IMPORTS 350000

Quantity (MT)

300000 250000 200000 150000 100000 50000 0 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Year

Total Cost in Rs Millions

UREA IMPORTS 14000 12000 10000 8000 6000 4000 2000 0 1997

1999

2000

2001

2002

2004

2005

2006

2007

Year Figure 1.4 Urea import data With the development in agriculture sector under present government policies and considering global food crisis, urea demand will further increase in spite there is a concern to use organic fertilizers such as compost instead of urea. Urea is being used as the main fertilizer for paddy as well as for other crops. Excessive applying of urea without considering the requirement has damage water bodies in some part of Sri Lanka. Comprehensive design project 16


Chapter 02

CHAPTER 2 PROCESS SELECTION AND ECONOMIC ASPECTS



Chapter 02

2.0 Process Selection & Economic Aspects 2.1 Feasibility Study 2.1.1 Introduction Urea white crystalline solid containing 46% nitrogen is widely used in the agriculture industry as an animal feed additive and fertilizer. Agriculture forms the major sector in the national economy of the majority of the countries in the Southeast Asian region. As these countries try to expand the sector, through diversification of agriculture and extensive multiple cropping programs, the demand for agriculture chemicals growing day by day. Large population countries like China, India, Pakistan, and Bangladesh are largely manufacturing the Urea for Domestic consumption. Due to high cost of the production facility Government incentives are common in 3rd world countries. In Middle East Saudi Arabia developed the large production facility of Urea production as an allied industry of the petroleum product. The surplus amount is being exported to neighboring countries. Sri Lanka imports urea from other countries such as Saudi Arabia, India, and China. . The total import volume of urea is around 310,000 MT per annum. Sri Lankan government gives urea fertilizer in subsidized price for farmers. From the budget 2008, Sri Lanka allocated 15 billion rupees for fertilizer subsidies. The Urea Plant at Sapugaskanda, Sri Lanka was established in 1980s to fulfil fertilizer requirement of the country. In 1982, the annual production of urea at Sapugaskanda factory was 310,000 tons. Then the country's annual demand was only 290,000 tons. The excessive production of 20,000 tons of urea was exported earning foreign exchange around Rs. 200 million. In 1982 the annual savings of State Fertilizer Corporation stood at Rs.750 million. In addition it had provided direct employment opportunities to 1,250 workers. So the previous plant is Sapugaskanda had been able to gain profits while making Sri Lanka self sufficient in urea. In the present urea fertilizer prices in global markets are increasing and most countries establishing urea manufacturing plants to support growing agriculture sector while saving cost of urea fertilizer imports. It is necessary to establish urea manufacturing plant in Sri Lanka in order to meet growing demand for urea fertilizer and to save fertilizer subsidies given by the government. Apart from those benefits it can earn foreign exchange by exporting excess production and provide employment for local community.



Chapter 02

2.1.2 Technical & Economic Feasibility When considering economic feasibility, raw material cost could be higher than usual since all most all urea manufacturing plants is being operated along with ammonia plants in order to produce raw materials (Ammonia and carbon dioxide: The carbon is produced as a byeproduct from the ammonia plant) for urea manufacturing process. To establish a urea plant without ammonia plant, raw materials has to be imported. It is not a better option, but under the circumstances Ammonia has to be imported from abroad. Considering the carbon dioxide, it is emitted by number of industries as a waste from which it has to be derived and purify. If it is not viable it is too has to be imported. Transportation cost will quite high (shipping costs, import taxes etc) so imported raw materials will be higher than when produced in ammonia plant. Plant technology is considered as high. Japan, China and North European countries are licensing the technology. Government incentives can be obtained for construction and operation since high costs are involved. The plant can be ordered directly from the manufacturers which basically sell the license of technology. Local fabrication can be carried out. Where as more critical equipments can be imported. Latest technology for confirming the quality and purity of the finished good is very important to complete the existing units. Companies involve in urea manufacturing technology and have license for technology. 1. Toyo Engineering corporation ( Japan ) 2. Mitsubishi Heavy industries ( Japan ) 2.1.2.1 Plant Capacity Urea plant capacity is on the rise since its establishment in 1940. In 1969 1800 MT/day plant was the largest. In Nineties 2000 tons urea plants become standardized. Now up to 3500 tons/day plants are under construction and planning. In this project we are planning to establish 1070 Mt/day plant having overall annual production of 350,000 MT. Plant is expected to operate 328 days per annum. Current Sri Lankan annual demand for urea is around 310,000 and it is not expected to fluctuate very much according to the statistical data obtained for past ten years. So Plant capacity is sufficient for meeting the current demand as well as growing demand in the future.



Chapter 02

2.1.3 Social & Environmental Feasibility Environmental feasibility is discussed under environmental impact assessment (EIA) and in site selection. Social issues are considered under site selection.

2.1.4 Plant Components The components of a urea plant can be divided in to two categories 1. Static Equipment 2. Rotating equipment

Static Equipment Reactor: Reactor is the largest and heaviest key equipment in the urea plant. This is the place where Ammonia and Carbon di-oxide react together. The performance of the reactor influences the performance of the whole urea plant. The size of the shell depends upon the size of plant. For a plant of 2000 tons capacity the height of the shell will be around 30 Meters and Dia around 3 meters.

Stripper Stripper is also a key component where the excess ammonia is separated.

Carbamate Condensers They are relatively smaller in size

HP Rotating Machines CO2 Compressors This is the largest and most critical rotating equipment. Very large compressors are used of approximate capacities of around 30,000 N cubic meter/hour capacity

HP Ammonia pumps and Carbomate pumps piping Stainless steel 316 L pipes are utilized

HP Control Valves Various control valves are required. The most critical is the solution feed control valve from the reactor to stripper. The material is stainless steel Comprehensive design project 20


Chapter 02

2.2 Process Selection Several processes are used to urea manufacturing. Some of them are used conventional technologies and others use modern technologies to achieve high efficiency. These processes have several comparable advantages and disadvantages based on capital cost, maintenance cost, energy cost, efficiency and product quality. Some of the widely used urea production processes are 1. Conventional processes 2. Stamicarbon CO2 – stripping process 3. Snamprogetti Ammonia and self stripping processes 4. Isobaric double recycle process 5. ACES process

2.2.1 Conventional Processes 2.2.1.1 Once through Process In this process non converted ammonia was neutralized with acid such as nitric acid to produce ammonium salt such as ammonium nitrate as co products of urea production. In this way, a relatively simple urea process scheme was realized. The main disadvantages of this process are the large quantity of ammonia salt formed as co product and the limited amount of overall carbon dioxide conversion that can be achieved.

2.2.1.2 Conventional Recycle Process Here all of the non converted ammonia and carbon dioxide were recycled to the urea reactor. In first generation of this process the recirculation of non converted NH 3 and CO2 was performed in two stage. The first recirculation was operated at medium pressure (18-25 bar); the second at low pressure (2-5 bar). The first recirculation comprises at least a decomposition heater, in which carbamate decompose into gaseous NH3 and CO2, and while excess NH3 evaporate simultaneously. The off gas from this first decomposition step was subjected to rectification, from which relatively pure ammonia at the top and a bottom product consisting of an aqueous ammonium carbamate solution were obtained. Both products are recycled separately to the urea reactor. In these processes, all non converted CO 2 was recycled as associated water recycle. Because of the detrimental effect of water on reaction conversion, achieving a minimum CO2 recycle so achieve maximum CO2 conversion was more important than achieving a low NH3 recycle. All conventional processes therefore typically operate at high NH 3:CO2 ratios (4-5 Comprehensive design project 21


Chapter 02

mol/mol) to maximize CO2 conversion per pass. Although some of these conventional processes partly equipped with ingenious heat exchanging net works have survived until now. Their importance decreased rapidly as the so-called stripping process was developed.



Chapter 02

Comprehensive design project Figure 2.1 Conventional process flow diagram

23


Chapter 02

2.2.2 Stamicarbon CO2 – stripping process In this process to achieve maximum urea yield per pass through the reactor at the stipulated optimum pressure of 140 bar, an NH3:CO2 molar ratio of 3:1 is applied. The greater part of the unconverted carbamate is decomposed in the stripper, where ammonia and carbon dioxide are stripped off. This stripping action is effected by countercurrent contact between the urea solution and fresh carbon dioxide at synthesis pressure. Low ammonia and carbon dioxide concentration in the stripped urea solution are obtained. Such that the recycle from the low pressure recirculation stage is minimized. These low concentration of both ammonia and carbon dioxide in the stripper effluent can be obtained at relatively low temperatures of the urea solution because carbon dioxide is only sparingly soluble under such conditions. Condensation of ammonia and carbon dioxide gases, leaving the stripper, occurs in the high pressure carbamate condenser as synthesis pressure. As a result, the heat liberated from ammonium carbamate formation is at a high temperature. This heat is used for the production of 4.5bar steam for use in the urea plant itself. The condensation in the high pressure carbamate condenser is not effected completely. Remaining gases are condensed in the reactor and provide the heat required for the dehydration of carbamate, as well as for heating the mixture to its equilibrium temperature. In recent improvement to this process, the condensation of off gas from the stripper is carried out in a pre reactor, where sufficient residence time for the liquid phase is provided. As a result of urea and water formation in condensing zone, the condensation temperature is increased, thus enabling the production of steam at higher pressure level. The feed carbon dioxide, invariably originating from an associated ammonia plant, always contains hydrogen. To avoid the formation of explosive hydrogen-oxygen mixture in the tail gas of the plant, hydrogen is catalytically removed from the CO 2 feed. Apart from the air required for this purpose, additional air is supplied to the fresh CO 2 input stream. This extra potion of oxygen is needed to maintain a corrosion-resistance layer on the stainless steel in the synthesis section. Before the inert gases, mainly oxygen and nitrogen, are purged from the synthesis section, they are washed with carbamate solution from the low pressure recirculation stage in the high pressure scrubber to obtain a low ammonia concentration in the subsequently purged gas. Further washing of the off gas is performed in a low pressure absorber to obtain a purge gas that is practically ammonia free. Only one low pressure recirculation stage is required due to the low ammonia and carbon dioxide in the stripped urea solution. Because of the ideal ratio between ammonia and carbon dioxide in the recovered gases in this section, water dilution of the resultant ammonium carbamate is at a minimum despite the low pressure (about 4 bar). As a result of efficiency of the stripper, the quantities of ammonium carbamate for recycle to the Comprehensive design project 24


Chapter 02

synthesis section are also minimized, and no separate ammonia recycle is required. The urea solution coming from the recirculation stage contains about 75 wt% urea. This solution is concentrated in the evaporation section. If the process is combined with a prilling tower for final product shaping, the final moisture content of urea from the evaporation section is 0.25 wt%. If the process is combined with a granular unit, the final moisture content may wary from 1 to 5 wt%, depending on granulation requirements. Higher moisture content can be realized in a single stage evaporator; where as low moisture content are economically achieved in a two stage evaporation section. When urea with an extremely low biuret content is required ( at maximum of 0.3 wt%) pure urea crystals are produced in a crystallization section. These crystals are separated from the mother liquor by combination of sieve bends and centrifuges and are melted prior to final shaping in a prilling tower or granulation unit. The process condensate emanating from water evaporation from the evaporation or crystallization sections contains ammonia and urea. Before this process condensate is purged, urea is hydrolyzed into ammonia and carbon dioxide, which are stripped off with steam and return to urea synthesis via the recirculation section. This process condensate treatment section can produce water with high purity, thus transforming this “waste water” treatment into the production unit of a valuable process condensate, suitable for, e.g., cooling tower or boiler feed water makeup. Since the introduction of the Stamicarbon CO2 stripping process, some 125 units have been built according to this process all over the world.



Chapter 02

Comprehensive design project Figure 2.2 CO2 stripping process flow diagram

26


Chapter 02

2.2.3 Snamprogetti Ammonia and self stripping processes In the first generation of NH3 and self strip ping processes, ammonia was used as stripping agent. Because of the extreme solubility of ammonia in the urea containing synthesis fluid, the stripper effluent contained rather large amount s of dissolved ammonia, causing ammonia overload in down stream section of the plant. Later versions of the process abandoned the idea of using ammonia as stripping agent; stripping was achieved only by supply of heat. Even without using ammonia as a stripping agent, the NH 3:CO2 ratio in the stripper effluent is relatively high. So the recirculation section of the plant requires an ammonia-carbomate separation section The process uses a vertical layout in the synthesis section. Recycle within the synthesis section, from the stripper via the high pressure carbamate condenser, through the carbamate separator back to the reactor, is maintained by using an ammonia-driven liquid-liquid ejector. In the reactor, which is operated at 150 bars, NH3:CO2 molar feed ratio of 3.5 is applied. The stripper is of the falling film type. Since stripping is achieved thermally, relatively high temperatures (200-210 0C) are required to obtain a reasonable stripping efficiency. Because of this high temperature, stainless steel is not suitable as a construction material for the stripper from a corrosion point of view; titanium and bimetallic zircornium – stainless steel tubes have been used Off gas from the stripper is condensed in a kettle type boiler. At the tube side of this condenser the off gas is absorbed in recycled liquid carbamate from the medium pressure recovery section. The heat of absorption is removed through the tubes, which are cooled by the production of low pressure steam at the shell side. The steam produced is used effectively in the back end of the process. In the medium pressure decomposition and recirculation section , typically operated at 18 bar, the urea solution from the high pressure stripper is subjected to the decomposition of carbamate and evaporation of ammonia. The off gas from this medium pressure decomposer is rectified. Liquid ammonia reflux is applied to the top of this rectifier; in this way a top product consisting of pure gaseous ammonia and a bottom product of liquid ammonium carbamate are obtained. The pure ammonia off gas is condensed and recycled to the synthesis section. To prevent solidification of ammonium carbamate in the rectifier, some water is added to the bottom section of the column to dilute the ammonium carbamate below its crystallization point. The liquid ammonium carbamate-water mixture obtained in this way is also recycled to the synthesis section. The purge gas of the ammonia condenser is treated in a scrubber prior to being purged to the atmosphere. Comprehensive design project 27


Chapter 02

The urea solution from the medium pressure decomposer is subjected to a second low pressure decomposition step. Here further decomposition of ammonium carbamate is achieved, so that a substantially carbamate –free aqueous urea solution is obtained. Off gas from this low pressure decomposer is condensed and recycled as an aqueous ammonium carbamate solution to the synthesis section via the medium pressure recovery section. Concentrating the urea water mixture obtained from the low pressure decomposer is preformed in a single or double evaporator depending on the requirement of the finishing section. Typically, if prilling is chosen as the final shaping procedure, a two stage evaporator is required, whereas in the case of a fluidized bed granulator a single evaporation step is sufficient to achieve the required final moisture content of the urea melt. In some versions of the process, heat exchange is applied between the off gas from the medium pressure decomposer and the aqueous urea solution to the evaporation section. In this way, the consumption of low pressure steam by the process is reduced. The process condensate obtained from the evaporation section is subjected to a desorption hydrolysis operation to recover the urea and ammonia contained in the process condensate.

2.2.4 Isobaric double recycle process This process is developed by Montedison, is characterized by recycle of most of the un reacted ammonia and ammonium carbamate in two decomposer in series, both operating at the synthesis pressure. A high molar NH3:CO2 ratio (4:1 to 5:1) in the reactor is applied. As a result of this choice ratio, the reactor effluent contains a relatively high amount of non converted ammonia. In the first, steam heated, high pressure decomposer, this large quantity of free ammonia is mainly removed from the urea solution. Most of the residual solution, as well as some ammonium carbamate, is removed in the second high pressure decomposer where steam heating and CO2 stripping are applied. The high pressure synthesis section is followed by two low pressure decomposing stages of traditional design, where heat exchange between the condensing off gas of the medium pressure decomposition stage and the aqueous urea solution to the final concentration section improves the overall energy consumption of the process. Probably because of the complexity of this process, it has not achieved great popularity so far. This process or parts of the process are used in four revamps of older conventional plant.



Chapter 02

2.2.5 ACES process ACSE (Advanced Process for Cost and Energy Saving) process has been developed by Toyo Engineering Corporation. Its synthesis section consist of the reactor, stripper, two parallel carbamate condensers and a scrubber all operated at 175 bar. The reactor is operated at 1900C and an NH3:CO2 molar feed ratio of 4:1. Liquid ammonia is fed directly to the reactor, whereas gaseous carbon dioxide after compression is introduced into the bottom of the stripper as a stripping aid. The synthesis mixture from the reactor, consisting of urea, unconverted ammonium carbamate, excess ammonia, and water, is fed to the top of the stripper.

2.2.6 Process comparison Process Conventional Processes -

.

Advantages

Disadvantages

Simple process

Once through process

Large quantity of ammonia salt is formed as co product Overall carbon dioxide conversion is low. High production cost High energy cost High environment pollution

Conventional Processes

High CO2 conversion

High production cost

– High energy cost

Conventional recycle process

High environment pollution

Stamicarbon CO2 –

Has high urea yield per

stripping process

pass

High production cost High energy cost

High purity



Chapter 02

Snamprogetti Ammonia

Low consumption of low

and self stripping

pressure steam

High production cost High energy cost

processes Isobaric double recycle

Complex process

process ACES process

Low production cost

High capital cost

High energy recovery Low environment pollution High efficiency

Among above urea manufacturing processes, ACES process is selected because of it has following advantages compared to other processes

2.2.6.1 Advantages of ACES Process Less HP piping and construction materials owing to lower elevation layout, fewer HP vessels and simplified synthesis loop Easier erection using commonly available construction equipment and techniques owing to low elevation layout and fewer and smaller HP vessels Easier operation supported by forced circulation by HP ejector, low elevation layout and fewer HP equipment Easier maintenance owing to low elevation layout and fewer HP equipment Less energy consumption owing to optimized synthesis conditions and proprietarily designed reactor and stripper Even though initial capital investment is higher than the other processes, it will overcome by lower production cost per metric ton of urea



Chapter 03

CHAPTER 3 PROCESS DESCRIPTION AND FLOW SHEET



Chapter 03

3.0 Process Description and flow sheet 3.1 Process Description – ACES Process Advanced Process for Cost and Energy process consists of the reactor, stripper, two parallel carbamate condensers and a scrubber. All above equipments are operated at 175 bar.

Figure 3.1 Functional block diagram of the ACES Process



Chapter 03

The reactor is operated at 1900C and an NH3:CO2 molar feed ratio of 4:1. Liquid ammonia is fed directly to the reactor, whereas gaseous carbon dioxide after compression is introduced into the bottom of the stripper as a stripping aid. The synthesis mixture from the reactor, consisting of urea, unconverted ammonium carbamate, excess ammonia, and water, is fed to the top of the stripper. The stripper has two functions. Its upper part is equipped with trays where excess ammonia is partly separated from the stripper feed by direct countercurrent contact of the feed solution with the gas coming from the lower part of the stripper. This pre stripping in the top is said to be required to achieve effective CO 2 stripping in the lower part. In the lower part of the stripper (a falling film heater), ammonium carbamate is decomposed and the resulting CO2 and NH3 as well as the excess NH3 are evaporated by CO2 stripping and steam heating. The overhead gaseous mixture from the top of the stripper is introduced into the carbamate condenser. Here the gaseous mixture is condensed and absorbed by the carbamate solution coming from the medium pressure recovery stage. Heat liberated in the high pressure carbamate condenser is used to generate low pressure steam. The gas and liquid from the carbamate condensers are recycled to the reactor by gravity flow. The urea solution from the stripper, with a typical NH3 content of 15 wt%, is purified further in the subsequent medium and low pressure decomposers, operating at 17.5 and 2.5 bars, respectively. Ammonia and carbon dioxide separated from the urea solution here are recovered through stepwise absorption in the low and medium pressure absorbers. Condensation heat in the medium pressure absorber is transferred directly to the aqueous urea solution feed in the final concentration section; the purified urea solution is concentrated further either by two stage evaporation up to 99.7 % for urea prill production or by a single evaporation 98.5 % for urea granule production. Water vapour formed in the final concentrating section is condensed in surface condensers to form process condensate. Part of this condensate is used as an absorbent in the recovery sections, where as remainder is purified in the process condensate treatment section by hydrolysis and steam stripping, before being discharge from the urea plant. The highly concentrated urea solution is finally processed either through the prilling tower or via the urea granulator. Instead of concentration via evaporation, the ACES process can also be combined with a crystallization section to produce urea with low biuret content.



Chapter 03

3.1.1ACES Urea plants available in the world

Table 3.1 ACES Urea plants available in the world Process

3.2 Main component of the process 3.2.1 Reactor The reactor is operated at 190 °C and 175 bar. NH3:CO2 molar feed ratio to the reactor is 4:1. One pass conversion rate of CO2 to urea is about 68%. NH3 is directly fed to the reactor. Following reaction occurs inside the reactor. NH2COONH4 + heat ↔ NH2CONH2 + H2O

∆H = +23 kJ/mol

2NH3 + CO2 ↔ NH2COONH4 + heat

∆H = -84 kJ/mol

3.2.2 Stripper Carbon dioxide is introduced into the bottom of the stripper as a stripping aid. The synthesis mixture from the reactor, consisting of urea, unconverted ammonium carbamate, excess ammonia, and water, is fed to the top of the stripper. Medium pressure steam is supplied to the stripper. The stripper has two functions. Its upper part is equipped with trays where excess ammonia is partly separated from the stripper feed by direct countercurrent contact of the feed solution with the gas coming from the lower part of the stripper. This pre stripping in the top is said to be required to achieve effective CO2 stripping in the lower part. In the lower part of the stripper (a falling film heater), ammonium carbamate is decomposed and the resulting CO 2 and NH3 as well as the excess NH3 are evaporated by CO2 stripping and steam heating. The overhead gaseous mixture from the top of the stripper is introduced into the carbamate condenser. Following reaction occurs inside the stripper. Comprehensive design project 34


Chapter 03

NH2COONH4 + heat ↔ 2NH3 + CO2 NH3(l)

→

∆H = +84 kJ/mol

NH3(g)

3.2.3 Carbamate Condenser Carbamate condenser is fed with overhead gaseous mixture from the top of the stripper, In this unit the gaseous mixture is condensed and absorbed by the carbamate solution coming from the medium pressure recovery stage. Heat liberated in the high pressure carbamate condenser is used to generate low pressure steam. The gas and liquid from the carbamate condensers are recycled to the reactor by gravity flow. 2NH3 + CO2 ↔ NH2COONH4 + heat NH3(g)

→

∆H = -84 kJ/mol

NH3(l)

3.2.4 Scrubber In the scrubber Ammonia and Carbon Dioxide coming from the reactor are absorbed to ammonia and ammonium carbamate solution which is going to Carbamate Condenser.

3.2.5 Medium Pressure Decomposer The urea solution from the stripper, with a typical NH3 content of 15 wt%, is purified further in the medium pressure decomposer operating at 17.5 bars. No external heat supply. NH2COONH4 + heat ↔ 2NH3 + CO2 NH3(l)

→

∆H = +84 kJ/mol

NH3(g)

3.2.6 Low Pressure Decomposer After the medium pressure decomposer, further purification of urea solution occurs inside the low pressure decomposer which is operating at 2.5 bar. External heat supply is available. all ammonia and ammonium carbamate are removed by the Low Pressure Decomposer. NH2COONH4 + heat ↔ 2NH3 + CO2 NH3(l)

→

∆H = +84 kJ/mol

NH3(g)

3.2.7 Medium Pressure Absorber In medium pressure absorber ammonia and carbon dioxide separated from the urea solution in medium pressure decomposer are recovered. Condensation heat in the medium pressure absorber is transferred directly to the aqueous urea solution feed in the final concentration section. Comprehensive design project 35


Chapter 03

2NH3 + CO2 ↔ NH2COONH4 + heat

∆H = -84 kJ/mol

3.2.8 Low Pressure Absorber In low pressure absorber ammonia and carbon dioxide separated from the urea solution in low pressure decomposer are recovered. Heat release from that reaction is used to produce steam at 2 bar. This steam is used for evaporation process of lower and upper separator. 2NH3 + CO2 ↔ NH2COONH4 + heat

∆H = -84 kJ/mol

3.2.9 Flash Separator This unit is operated at 1.0 bar and 110 °C. Here by reducing the pressure, let water to evaporate and concentrate the urea solution. H2O(l) →

H2O(g)

3.2.10 Lower Separator This is a calendria type evaporator. This is operated at 0.55 bar vacuum pressure and at 110 °C Here the purified urea solution is further concentrated and required heat is taken from 2 bar pressure steam produced in low pressure absorber.

3.2.11 Upper Separator This is evaporative type separator. This is operated at 0.55 bar vacuum pressure and at 112 °C Urea solution coming from the lower separator is further concentrated. Output from that unit has 99.2% pure urea. After that urea solution is sent to granulation section.



Chapter 03

3.2.12 Granulation Plant The Urea Granulation process consists of following three sections. • granulation section • recycle and product cooling section • dust removal and recovery section Aqueous urea solution from urea plant is fed to the granulator to enlarge recycle particles in the granulator. In the granulator, the granules are dried and cooled simultaneously. The granulator is operated at 110-115oC and at slightly negative pressure. Enlarged urea particles are cooled to about 90ºC in the after-cooler inside the granulator to be transported to the recycle section. Figure 3.4 Granulation plant

The discharged granules are separated into three sizes, product, small and large size by the screen. Product size granules are further cooled below 60ºC in the product cooler to be sent to the urea storage or bagging facility. Large size granules are crushed by the crusher. The rushed particles and smaller size particles from the screen are recycled to the granulator as seed.Urea dust contained in the exhaust air from the granulator and the product cooler is scrubbed in the dust scrubber by contacting counter currently with aqueous urea solution. The urea dust content in the exit air of the bag filter is 30 mg/m3 or less. Urea recovered in the bag filter, approximately 2.5-3.5 % of production rate, is recycled to the urea granulator.

Figure 3.5 Spout-Fluid Bed Granulator Comprehensive design project 37


Chapter 03

Figure 3.6 Power Consumption of Spout-Fluid Bed Granulation

3.3 Typical product quality Total Nitrogen

46.3wt%

Biuret

0.7wt%

Moisture

0.25wt%

Formaldehyde

0.45wt%

Size (2-4mm)

95wt%

Hardness

3.5kg at 3mm

Various sizes of granules

Figure 3.7 Various sizes of granules



Chapter 04

CHAPTER 4 SITE SELECTION



Chapter 04

4.0 Site Selection & Plant Layout 4.1 Site Selection Site selection is the making the ultimate choice of site where business or manufacturing plant is going to be established. It is an important task to be done in a business case. By selecting the suitable site for the manufacturing plant it would be able to reduce the transportation cost of raw materials and energy, make easy access to infrastructure facilities, availability of labour force and many other benefits. Selection should be done by considering cost and benefits of available alternative sites. It is a strategic decision to be made, where improper decision may cause considerable loss. So it may requied to select ideal or optimum location for the business.

Following Facts should be concern regarding site selection Availability of raw material Infrastructure facilities Legal obligations enforced by relevant authority or the government Environment and climate conditions Labour force availability Social considerations Waste management

4.1.1 Availability of raw materials Main raw materials for urea manufacturing are ammonia and carbon dioxide. Currently ammonia plant is not there in Sri Lanka. Ammonia has to be imported from abroad. Considering the carbon dioxide, it is emitted by number of industries as a waste from which it has to be derived and purify. Otherwise any alternative option such as importing should be concerned. In case of ammonia it is cost effective to locate the site near a harbor or sea where it is directly taken in to the storage tanks. The previous urea plant was there in Sapugaskanda along with ammonia plant and petroleum refinery. It is not viable to consider that site since ammonia plant is not there and considering transportation cost. Considering available sites in costal areas in Sri Lanka we select two sites Hambantota and Trincomalee for assessment. Hambantota has many advantages regarding a large chemical plat like urea.



Chapter 04

Hambanthota is developing area under “Mahinda Chinthana” concept. Many developing projects are underway. An international sea port is going to be established in hambantota which can handle large ships which are unable to access in the Colombo port. Also infrastructure facilities will be developed along with these projects. Vast amount of land is available for low cost in order to establish the plant closed to Hambantota port. Even if there are no enough qualified employees in Hambantota area, due to rapid development along with good infrastructure facilities it would be easy to attract employees from outside areas. Government welcomes projects related to hambantota area and many benefits can be gain such as reduction in tax, grace periods for loans etc. The government is planning to establish a petroleum refinery in Hambanthota. In Trincomalee much of above mentioned benefits are there, but considering the establishment of petroleum refinery and massive port compared to Trincomalee, Hambantota becomes the more suitable option. It is not economical to import ammonia and carbon dioxide from abroad because of high transportation cost and additional amount of money have to be spend on buying those materials. Those raw materials can be produced at low cost in Sri Lanka. So it is better to have an ammonia plant. Under the government‟s plan to establish a petroleum refinery in Hambanthota, hydrogen can be gained as a byproduct from petroleum refinery and it can be use as a raw material for ammonia production. So it would be better to have ammonia plant in future to aid urea production.

4.1.2 Infrastructure facilities Hambanthota is a one of main cities in southern part of Sri Lanka which is situated 237 km away from Colombo. Since it is a coastal area we have to consider climate as well as infrastructure facilities such as water, electricity and roads. Direct Infrastructure facilities for urea plant such as transportation, electricity, telecommunication and indirect infrastructures for the employees such as education, health, food, accommodations etc. are being recently developed in Hambantota. On the other hand in Hambanthota there is scarcity of sufficient water reservoirs for the various purpose of the urea plant due to dry zone. But we can fulfill some amount of our water requirement like cooling water using sea water and other requirements using water distribution project which is being develop along with other development projects. Highways are being constructed connecting hambantota port and other developing sites such as air port. So Transportation of other required materials would be more convenient. Other private and public sector facilities including telecommunication, government authorities will also be developed. Comprehensive design project 41


Chapter 04

4.1.3 Legal obligations enforced by relevant authority or the government Yala Sanctuary Park is situated in Hambanthota area. So government obligation may arise for such a urea manufacturing plant construction. Some families may have to resettle to clear the construction area of urea manufacturing plant. Legal obligations may arise from people. Compensation and resettlement should be done in order to avoid such difficulties. Since chemicals are used in the manufacturing it would be necessary to comply with government regulations regarding handling and storing of such chemicals. Emissions from the urea plant should be under permissible conditions. Since site is in costal area air emissions may not have much impact. Sound regulations may not have to be considered extensively since area is remote. Tax and other financial considerations may vary with related to selected site.

4.1.4 Environment and Climate Conditions Hambantota is located in semi-arid zone in Sri Lanka. Climate is much dryer, but in the coastal side it is much humid so it can lead to corrosion in metallic component in the plant. Law rain fall is an advantage for urea production. Because of coastal wind emissions from the plant may dilute easily and air emission problems may not arise. Only difficulty is the lack of water resources. Sea water should be utilized in order to fulfill water requirement for some extent. But water is needed to be transported from available area nearby. Accommodation for labours and other staff should be constructed considering dry weather.

4.1.5 Labour Force availability Many people in rural areas like Hambantota are not permanently employed. People from villages may move in to cities nearby or even to Colombo to find employment. So establishing a plant in such area will produce around 1200 direct jobs and many other indirect job opportunities. It will solve unemployment problem to considerable extent. So labour availability is not an issue, but difficulties may arise in finding qualified people.

4.1.6 Social considerations Obstacles may arise from residential people and from environmentalists. Peoples will resist construction work and may take legal actions. Proper mechanism to resettle residential people who may lose their homes should be established collaboration with government. Environmental concerns should be considered including air emissions, waste disposal, sound levels and necessary steps should be take to control or maintain under permissible levels. Also site should cause minimum environment damage during construction and operation. Comprehensive design project 42


Chapter 04

4.1.7 Waste Management Waste management restrictions are being enforced by the regulations. Plant site should accommodate disposal of waste in to the sea or to the land. Chemical wastes are there from the plants which are considered hazardous. Selected site should have facilities for both waste processing and for storage until waste is properly disposed. Social considerations are important in waste management. Locating plant in a remote location is an advantage.

4.2 Plant Layout The efficiency of production depends on how well the various machines; production facilities and employee‟s amenities are located in a plant. Only the properly laid out plant can ensure the smooth and rapid movement of material, from the raw material stage to the end product stage. Plant layout refers to the arrangement of physical facilities such as machinery, equipment, storages, departments etc. with in the factory building in such a manner so as to have quickest flow of material at the lowest cost and with the least cost in processing the product from the raw material to the finished product.

4.2.1 Importance Plant layout is an important decision as it represents long-term commitment. An ideal plant layout should provide the optimum relationship among output, floor area and manufacturing process. It facilitates the production process, minimizes material handling, time and cost, and allows flexibility of operations, easy production flow, makes economic use of the building, promotes effective utilization of manpower, and provides for employee‟s convenience, safety, comfort at work, maximum exposure to natural light and ventilation. It is also important because it affects the flow of material and processes, labour efficiency, supervision and control, use of space and expansion possibilities etc.

An efficient plant layout is one that can be instrumental in achieving the Following objectives: a) Proper and efficient utilization of available floor space b) To ensure that work proceeds from one point to another point without any delay c) Provide enough production capacity. d) Reduce material handling costs e) Reduce hazards to personnel f) Utilize labour efficiently Comprehensive design project 43


Chapter 04

g) Increase employee morale h) Reduce accidents i) Provide for volume and product flexibility j) Provide ease of supervision and control k) Provide for employee safety and health l) Allow ease of maintenance m) Allow high machine or equipment utilization n) Improve productivity

4.3 Environmental Impact Assessment An Environment Impact Assessment is an assessment of the possible positive impact or negative impact which the project may have on the natural environment. The purpose of the assessment is to ensure that decision makers consider environmental impacts used to decide whether to proceed with the project. The International Association for Impact Assessment (IAIA) defines an environmental impact assessment as "the process of identifying, predicting, evaluating and mitigating the biophysical, social, and other relevant effects of development proposals prior to major decisions being taken and commitments made.

4.3.1 Objectives of EIA Assessment To ensure that proponents take primary responsibility for protection of the environment influenced by their proposals To ensure that best practicable measures are taken to minimize adverse impacts on the environment, and that proposals meet relevant environmental objectives and standards to protect the environment, and implement the principles of sustainability To provide opportunities for local community and public participation, as appropriate, during the assessment of proposals To encourage proponents to implement continuous improvement in environmental performance and the application of best practice environmental management in implementing their proposal To ensure that independent, reliable advice is provided to the Government before decisions are made



Chapter 04

4.3.2 Impact of the Urea Plant on the environment In the early part of previous decade ammonia consumption per ton of final product of 575 kg or even higher used to be acceptable. This figure implies however a loss of some 8 kg per tonne of final product produced (Table 1), which for a 2000 mtd plant would result in a loss of 16 mtpd ammonia either in the form of urea or straight ammonia. Presently ammonia consumptions of some 567 kg per tonne are released in the large single stream plants. Since this figure is very close to the theoretical consumption figure, the conclusion is that losses in steady operation are approaching the zero targets.

Ammonia releases from urea plants Early nineteen eighties 8 kg NH3/mt final product Presently

0.7 kg NH3/mt final product

Table 4.1 Ammonia releases from urea plants Not only ammonia, carbon dioxide and urea releases from process plants have a negative influence on the environment but also the unnecessary use of energy is negative from an environmental point of view and from the economic point of view as well. Following table shows the present typical energy consumption for urea production

Typical consumption figures for a granulation plant Steam (22 bar, 330oC)

805 kg/mt urea

Steam (4 bar saturated) (production)

-415 kg/mt urea

Electricity (including granulation section)

50 kWh/mt urea

Cooling water (including granulation section) 58 mt/mt urea Table 4.2 Typical consumption figures for a granulation plant Emissions from Urea manufacturing process are listed below. Emission Media Substance Ammonia Formaldehyde Methanol Total Nitrogen Particulate Matter (PM10) Volatile Organic Compounds(VOCs)

To Atmosphere   

To Water

Via Solid Waste

   

  

 

Table 4.3 Emissions from Urea manufacturing process Comprehensive design project 45


Chapter 04

4.3.3 Emissions to Air Air emissions may be categorised as either fugitive or point source emissions. Fugitive Emissions These are emissions that are 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, and leaks from valves and flanges are also examples of fugitive emissions. Point Source Emissions These emissions are exhausted into a vent or stack and emitted through a single point source into the atmosphere. Above table highlights common air emissions from urea manufacturing processes.

4.3.4 Emissions to Water Emissions of substances to water can be categorised as discharges to: Surface waters (eg. lakes, rivers, dams, and estuaries); Coastal or marine waters Storm water Because of the significant environmental hazards posed by emitting toxic substances to water, most facilities emitting above listed substances to waterways are required by the relevant environment authority to closely monitor and measure these emissions. The existing sampling data can be used to calculate annual emissions. If no wastewater monitoring data exists, emissions to process water can be calculated based on a mass balance or using emission factors.

4.3.5 Emissions to Land 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 categorised as: surface impoundments of liquids and slurries; and unintentional leaks and spills.



Chapter 04

In general, there are four types of emission estimation techniques (EETs) that may be used to estimate emissions from the facility. The four types are: Sampling or direct measurement; Mass balance; Fuel analysis or other engineering calculations; and Emission factors

4.3.6 Elimination Methods Presently plants are equipped with the following features to keep the effluent and emission at extremely low levels: N/C ratio meter Waste water treatment section Absorbers Special operational facilities

N/C ratio meter in the Synthesis section Instead of using a gaschromatograph or a mass spectrometer in the gas phase of the synthesis section, Nitrogen/Carbon (N/C) ratio meters are installed in the liquid phase (reactor liquid outlet) of the urea synthesis section The principle of this N/C meter is based on the linear relationship between liquid density and the N/C ratio. The density is measured continuously with a solartron meter, being an instrument in which vibrations are measured in an extremely accurate way whereby the vibrations are a measure of the density of the reactor liquid. This N/C ratio meter allows the process at all times to be operated at the optimum ratio to achieve highest reactor efficiency combined with higher energy efficiency. Special procedures are used to eliminate emissions during start-up.

Urea plant waste water treatment section The process water in urea plants contains ammonia, carbon dioxide and urea. The concentrations of these components vary within a range depending on the operating conditions, On average, the concentrations in the process water are about 6 wt.% ammonia, 4 wt.% carbon dioxide and 1 wt.% urea.



Chapter 04

Sources of the ammonia and urea are Condensate from the evaporators. Off-gases from the recirculation section, which are absorbed in the process water. Off-gases from the synthesis section, which are absorbed in the process water. Flush and purge water for pumps. Liquid drains. The purpose of the process water treatment is to remove ammonia, carbon dioxide and urea from the process condensate. For every tonne of urea produced, approximately 0.3 tonnes of water are formed. This water is usually discharged from the urea concentration and evaporation section of the plant. Removal of ammonia and urea from wastewaters can be a problem as it is difficult to remove one in the presence of the other. One method used to overcome this problem is the hydrolysis of urea to ammonium carbamate, which is decomposed to ammonia and carbon dioxide. These gases can then be stripped from the wastewaters. Urea plants are in operation that produces wastewaters with ammonia and urea levels below 1ppm. This water can then be used for a variety of purposes depending on the required quality such as cooling water or Boiling Feed Water make-up. The recovered ammonia and carbon dioxide are returned to the process to be subsequently converted into urea.

Absorbers Absorbers are used in urea plant to eliminate emissions to the atmosphere, can be classified as follows: (1) The vent from the synthesis section of the plant The purge from the urea synthesis section contains inerts, ammonia and carbon dioxide. To avoid ammonia emissions from this purge a low pressure absorber is installed in purge stream. First the ammonia is washed out with a large flow of low concentrated and cooled process water and secondly the remaining ammonia is absorbed in cooled condensate or clean waste water. (2) The vent from the low pressure section of the plant The ammonia and carbon dioxide present in the off gases of the recirculation section, the Process Water Treatment System and the evaporation section are washed out in an atmospheric absorber where large amounts of cooled low concentrated process water are used to absorb all the ammonia present in said off gases.



Chapter 04

Special start-up, shut-down and draining facilities Because of the present low releases during steady state operation in urea manufacturing the consideration regarding environmental issues has changed towards further reducing of effluents and emissions from non-continuous sources during non-steady state conditions such as start-up and shut-down situations. A change in the start-up procedure of the urea synthesis section has reduced the impact on the environment considerably. Presently the ability to measure the feed flows (NH3 and CO2) very accurate in combination with the ability to measure the N/C ratio have enabled us to feed the synthesis section from the very beginning of the start-up with the correct NH3/CO2 ratio, thus eliminating the need, during the initial stage of start-up, to vent excess CO2 accompanied by some NH3 into the atmosphere. Special shut-down and draining facilities assure that non converted NH 3 and CO2 are recovered by the process after a shut-down. To achieve this facility to feed clean water to dilute the carbamate formed from non converted NH3 and CO2 from the synthesis section has been introduced. The dilution should be to the extent that no ammonia will escape from the liquid under atmospheric pressure. The water is in principle introduced in the low pressure carbamate condenser and subsequently cooled to increase absorption capacity, and drained in the ammonia water tank. After restart of the plant the NH3 and CO2 in this tank are recovered via the waste water treatment section. The clean water used for the dilution may be an amount of clean waste water stored for such purpose. In case sufficient condensate is available in the complex no such additional storage of clean waste water is required and condensate may be used as well.

4.4 Safety Of the Urea Plant It is must to consider occupational safety and health when designing a manufacturing plant. Safety is the major factor in any industrial process to safeguard employees, environment, surrounding living peoples etc. Also there are legal obligations which are imposed by government for chemical processing factories to operate and maintain. When considering the safety, it is mainly due to the risk of urea which is the main product of plant and ammonia; one of the main raw materials for production and risk caused by other intermediate product.



Chapter 04

4.4.1 Safety factors relevant to urea Stability and Reactivity Produce biuret when expose to heat Urea has high solubility. So it should store under dry conditions. It has high stability and low reactivity with normal conditions

Flammability Urea is non-flammable material

Flash point: Not applicable Flammability limits: Not applicable Auto-ignition temperature: Not applicable The substance decomposes on heating above melting point, producing toxic gases, and reacts violently with strong oxidants, nitrites, inorganic chlorides, chlorites and perchlorates, causing fire and explosion hazard

Hazard identification Classified as hazardous chemical according to criteria in the HS (Minimum Degrees of Hazard) Regulations 2001 Route of entry and health hazards Harmful if swallowed. - It may cause irritation Harmful if inhaled. Causes serious eye irritation. Harmful to terrestrial vertebrates.

Inhalation: Slight irritant. Elevated exposure may result in mucous membrane irritation (nose & throat). may cause nausea, vomiting, diarrhea and GI irritation. Skin: Irritant. Prolonged contact may result in irritation, itching and possible skin rash. Eyes: Irritant. May cause lachrymation, irritation, pain & redness Ingestion: Has diuretic effect. Ingestion of large quantities may lead to nausea and vomiting.

No adverse health effects expected under normal conditions. Urea can be irritating to skin and eyes.Too high concentrations in the blood can cause damage to organs of the body. Low concentrations of urea such as in urine are not dangerous. It has been found that urea can cause Comprehensive design project 50


Chapter 04

algal blooms to produce toxins, and urea in runoff from fertilizers may play a role in the increase of toxic blooms.

First aid (Emergency procedure) In the event of an emergency, remove the victim from further exposure, send for medical assistance, and initiate the following emergency procedures: Skin Wash exposed area with soap and water. If irritation persists, get medical attention as soon as possible. Eyes Wash eyes with plenty of water for at least 15 minutes, lifting lids occasionally. Seek Medical Aid. Inhalation Remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen Ingestion If swallowed, induce vomiting immediately after giving two glasses of water. Never give anything by mouth to an unconscious person. Fire Extinguisher Any means suitable for extinguishing surrounding fire. Fire extinguisher should available in any risky places in the plant. Extinguishing media: CO2, foam, dry powder, water

Handling & Storage Precautionary Statements Keep out of reach of children. Avoid breathing vapors, or dusts. Wash hands thoroughly after handling. Do not eat drink or smoke when using this product. Avoid unintended release to the environment. Use with adequate ventilation. Avoid contact with eyes, skin, and clothes.



Chapter 04

Safe Handling Avoid generating dusts. Use only outdoors or in a well-ventilated area. Storage Store in sealed containers in cool, dry, well ventilated place away from incompatible materials. Wash thoroughly after handling. Keep container closed. Transportation No special transport requirements necessary Environmental Exposure Limit (EEL): Not assigned Avoid washing excessive amounts into streams and waterways.

Exposure Controls & Personal Protection Exposure Standards Workplace Exposure Standards (WES): Particulates not otherwise classified Inspirable dust 10mg/m3 Respirable dust 3mg/m3 Personal Protective Equipment Respiratory: If dusts particles are present wear suitable dust mask. Eyes/Face: Safety glasses. If dusts present wear goggles. Skin: use Overalls and gloves.

Eye wash facilities should be available. Wash hands after working with substance. Collect and place in clean sealable containers. Avoid generating dusts.

Engineering Controls Ventilation: Use in well ventilated area. If dusts are generated use local extraction to control

Disposal Considerations Observe local authority restrictions that may apply. Collection into sealable containers and dispose of in an approved land fill. If practicable apply excess fertilizer at recommended rates to appropriate land. Rinse containers thoroughly prior to re-use. Otherwise render unusable, and dispose of as waste. Comprehensive design project 52


Chapter 04

4.4.2 Safety Factors Relevant to Ammonia Stability and reactivity Ammonia has very low stability because it converts to ammonium hydroxide or other ammonium salt by combining with water or other salts. But it has no reactivity under normal conditions. Incompatible materials Ammonia reacts vigorously with fluorine, chlorine, HCl, HBr, nitrosyl chloride, chlorine monoxide, aldehydes, boron, boron halides, calcium, amides, chromyl chloride, nitrogen dioxide, trioxygen difluoride, and nitrogen trichloride , halogens, heavy metals and many other materials. Hazardous decomposition products form with hydrogen at very high temperature. Hazardous polymerization will not occur. Flammability Ammonia is slightly flammable material. Flash point: Not applicable Flammability limits: Not applicable Auto-ignition temperature: 1274oF

Hazard identification Irritating or corrosive to exposed tissues. Inhalation of vapors may result in pulmonary edema and chemical pneumonitis

Route of entry and health hazards Harmful if contact with eye Harmful if inhaled. Irritant if contact with skin and eye

Eye effects Mild concentrations of product will cause conjunctivitis. Contact with higher concentrations of product will cause swelling of the eyes and lesions with a possible loss of vision.



Chapter 04

Exposure to 50 ppm or less for 5 minutes was not considered irritating by volunteers, while exposure to 72 ppm was irritating to a few individuals and 134 ppm was irritating and caused tearing. At 700 ppm, the gas is immediately and severely irritating. Direct contact with the liquefied gas can cause frostbite and corrosive injury to eye. Permanent eye damage or blindness could result. Severe, permanent eye injury, including an almost complete loss of vision, has been reported following direct contact with liquefied ammonia gas. Skin effects Mild concentrations of product will cause dermatitis or conjunctivitis. Contact with higher concentrations of product will cause caustic-like dermal burns and inflammation. Toxic level exposure may cause skin lesions resulting in early necrosis and scarring. High levels of airborne ammonia gas dissolve in moisture on the skin, forming corrosive ammonium hydroxide. At 10000 ppm, ammonia is mildly irritating to moist skin. At 20000 ppm, the effects are more pronounced and 30000 ppm may produce chemical burns with blistering. These same exposure levels would be almost certainly fatal due to inhalation health effects. Direct contact with liquefied gas can cause frostbite and corrosive burns. Symptoms of mild frostbite include numbness, prickling and itching in the affected area. Symptoms of more severe frostbite include a burning sensation and stiffness of the affected area. The skin may become waxy white or yellow. Blistering, tissue death and gangrene may also develop in severe cases. Corrosive burns of the skin have resulted from direct contact with a jet of liquefied ammonia. Permanent scarring of the skin may result. Ingestion effects Since product is a gas at room temperature, ingestion is unlikely.

Inhalation effects Corrosive and irritating to the upper respiratory system and all mucous type tissue. Depending on the concentration inhaled, it may cause burning sensations, coughing, wheezing, shortness of breath, headache, nausea, with eventual collapse. Toxic effects to the respiratory system, senses, liver, kidneys and bladder observed in mammalian species from prolonged inhalation exposures at above 100 ppm Inhalation of excessive amounts affects the upper airway (larynx and bronchi) by causing caustic-like burning Comprehensive design project 54


Chapter 04

resulting in edema and chemical pneumonitis. If it enters the deep lung, pulmonary edema will result. Pulmonary edema and chemical pneumonitis are potentially fatal conditions.

Long term health effects of exposure to Ammonia gas No significant differences in lung function were observed in workers exposed to 9.2 ppm ammonia for an average of 12.2 years compared to controls with very low exposure (less than 1 ppm). No conclusions can be drawn from one case report which described lung injury following long-term exposure to ammonia because the person was a long-term smoker. People with repeated exposure to ammonia may develop a tolerance (or acclimatization) to the irritating effects after a few weeks.

First aid (Emergency procedure) Eyes Flush contaminated eye(s) with copious quantities of water. Part eyelids to assure complete flushing. Continue for a minimum of 15 minutes. Persons with potential exposure to ammonia should not wear contact lenses. Skin Remove contaminated clothing as rapidly as possible. Flush affected area with copious quantities of water. In cases of frostbite or cryogenic "burns" flush area with lukewarm water. Do not use hot water. A physician should see the patient promptly if the cryogenic "burn" has resulted in blistering of the dermal surface or deep tissue freezing. Ingestion Not specified. Seek immediate medical attention. Inhalation Prompt medical attention is mandatory in all cases of overexposure. Rescue personnel should be equipped with self-contained breating apparatus. Conscious persons should be assisted to an uncontaminated area and inhale fresh air. Quick removal from the contaminated area is most important. Unconscious persons should be moved to an uncontaminated area, given mouth-to-mouth resuscitation and supplemental oxygen. Keep victim warm and quiet. Assure that mucus or vomited material does not obstruct the airway by positional drainage.



Chapter 04

Fire Extinguisher Extinguisher media Water fog, foam. Use media suitable for surrounding fire. Fire extinguished instruction If possible, stop the flow of gas. Since ammonia is soluble in water, it is the best extinguishing media not only in extinguishing the fire, but also absorbing the escaped ammonia gas. Use water spray to cool surrounding containers.

Handling & Storage Earth-ground and bond all lines and equipment associated with the ammonia system. Electrical equipment should be non-sparking or explosion proof. Gaseous or liquid anhydrous ammonia corrodes certain metals at ambient temperatures. The presence of oxygen enhances the corrosion of ordinary or semialloy steels. The addition of water inhibits this enhancement. Keep anhydrous ammonia systems scrupulously dry. Use only in well-ventilated areas. Valve protection caps must remain in place unless container is secured with valve outlet piped to use point. Do not drag, slide or roll cylinders. Use a suitable hand truck for cylinder movement. Use a pressure regulator when connecting cylinder to lower pressure (<500 psig) piping or systems. Do not heat cylinder by any means to increase the discharge rate of product from the cylinder. Use a check valve to trap in the discharge line to prevent hazardous back flow into the cylinder. Protect cylinders from physical damage. Store in cool, dry, well-ventilated area away from heavily trafficked areas and emergency exits. Do not allow the temperature where cylinders are stored to exceed 125oF (52oC). Cylinders should be stored upright and firmly secured to prevent falling or being knocked over. Full and empty cylinders should be segregated. Use a "first in-first out" inventory system to prevent full cylinders from being stored for excessive periods of time. Never carry a compressed gas cylinder or a container of a gas in cryogenic liquid form in an enclosed space such as a car trunk, van or station wagon. A leak can result in a fire, explosion, asphyxiation or a toxic exposure.



Chapter 04

Engineering controls Use local exhaust ventilation to reduce concentrations to within current exposure limits. A laboratory type hood is suitable for handling small or limited quantities.

Personal protection Eye/face protection Gas tight chemical goggles or full-face piece respirator. Skin protection Protective gloves made of any suitable material. Respiration protection Respiratory protection with full face piece or self-contained breathing apparatus should be available for emergency use. Air purifying respirators must be equipped with suitable cartridges. Do not exceed maximum use concentrations. Do not use air purifying respirators in oxygen deficient/immediately dangerous to life and health (IDLH) atmosphere. Consult manufacturer‟s instructions before use. Other general protections Safety shoes, safety shower, eyewash "fountain".

Disposal Considerations Do not attempt to dispose of residual waste or unused quantities. Return in the shipping container properly labeled, with any valve outlet plugs or caps secured and valve protection cap in place to BOC Gases or authorized distributor for proper disposal.

4.4.3 Safety Factors Relevant to Ammonium Carbamate Stability and reactivity Ammonium carbamate is stable compound, but may be moisture sensitive. Incompatible with strong oxidizing agents, strong acids, strong bases Hazardous polymerization will not occur Decompose to ammonia and carbon dioxide when heated up to 140 oF

Incompatible materials Strong acids. Ammonium carbamate reacts with chlorine, bromine, mercury, silver and hypochlorite to form explosive compounds.



Chapter 04

Flammability Ammonium carbamate is not a flammable material Ammonia vapors in the range of 16% to 25% by volume in air can explode on contact with an ignition source. The use of welding or flame cutting equipment on process lines is not recommended unless all ammonium carbamate has been removed. Avoid welding in confined space. Flash point: Not applicable Flammability limits: Not applicable Auto-ignition temperature: not applicable

Hazard identification Ammonium carbamate has a potential for acute health effects Eyes and Skins Eyes: Noticeable irritation to the eyes will occur at ammonia concentrations of 100 PPM. Severe irritation to the eyes will occur at concentrations of 400 PPM. Skin: Contact with ammonium carbamate can result in first, second and third degree burns. Inhalation Severe irritation of nose and throat occurs at ammonia concentrations of 400 PPM. Serious coughing and bronchial spasms occur at ammonia concentrations of 1,700 PPM. Less than a thirty minute exposure to ammonia concentrations of 1,700 PPM may be fatal. IDLH at 300 PPM. Ingestion Ingestion may be fatal. May result in first, second or third degree burns.

First aid (Emergency procedure) Eyes Immediately flood with large amounts of water for at least 15 minutes. Seek medical attention. Skin Remove contaminated clothing immediately. Flush the skin with large amounts of water until all material is removed (at least 15 minutes). Wash all contaminated clothing before re-use.



Chapter 04

Ingestion Do not induce vomiting. Encourage the victim to drink large amounts of water, substituting as available, diluted vinegar, lemon juice or orange juice. Inhalation Use respiratory protection as necessary and remove to fresh air at once. If breathing stops, administer artificial respiration

Fire Extinguisher Extinguisher media: Water Avoid direct streams of water application which may result in chemical exposure due to splashing Fire extinguishing agents to avoid CO2 may react violently. Use water spray to control ammonia vapors. Adding water to ammonium carbamate will generate heat and increase the ammonia vapors generated. Wear full protective clothing with an approved self contained breathing apparatus.

Storage and Handling Provide ventilation sufficient to maintain exposure to ammonia vapors below the permissible exposure limit. Avoid all contact with the body. Minimize gas contact. Employ good maintenance practices to prevent leaks. Keep away from heat and open flames. Use good process control measures to prevent releases. Preferably stored outside. Otherwise in cool, dry well-ventilated non-combustible location away from all ignition sources and oxidizers.

Exposure Controls/Personal Protection Engineering Controls Vessel and drum labels are required on all containers. Personnel training should include adequate inspection techniques on equipment such as pumps, hoses, and valves. Eye Protection Face shield and tight fitting gas tight splash goggles Protective Clothing Chemical resistant suit with rubber or vinyl gloves and rubber boots



Chapter 04

Respiratory Protection Use a NIOSH/MSHA approved full-face negative pressure respirator fitted with ammonia cartridges for exposures at or below 300 PPM. For concentrations above 300 PPM, use a full-face positive pressure self-contained breathing apparatus Other Protective Clothing or Equipment Provide an eyewash station and safety shower at sites handling or storing Ammonium Carbamate.

Disposal Considerations Product Disposal Disposal of ammonium carbamate may be subject to federal, state and local regulations.

General Comments Handlers of this product should review their operations in terms of applicable laws and regulations, and then consult with appropriate regulatory agencies before discharging or disposing of any waste material.

4.4.4 Safety Factors Relevant to Biurete (byproduct) Stability and reactivity Product is very stable under normal conditions Stability is not change with temperature Stability is not change with varies conditions Not available incompatibility substances Non-corrosive in presence of glass. Polymerization will not occur.

Flammability Not flammable under normal conditions and may be combustible at high temperature. Auto-Ignition Temperature: Not available. Flash Points: Not available. Flammable Limits: Not available After the combustion products are carbon oxides (CO, CO2), nitrogen oxides (NO, NO2...).



Chapter 04

Hazard identification Potential Acute Health Effects: Hazardous in case of skin contact (irritant), of ingestion, of inhalation. Slightly hazardous in case of skin contact (permeator), of eye contact (irritant). Potential Chronic Health Effects: Hazardous in case of skin contact (irritant), of ingestion, of inhalation. Slightly hazardous in case of skin contact ( permeator ), of eye contact (irritant). No carcinogenic effects No mutagenic effects No teratogenic effects

First aid (Emergency procedure) Eye Check for and remove any contact lenses. In case of contact, immediately flush eyes with plenty of water for at least 15 minutes. Cold water may be used. Get medical attention if irritation occurs. Skin In case of contact, immediately flush skin with plenty of water. Cover the irritated skin with an emollient. Remove contaminated clothing and shoes. Cold water may be used. Wash clothing before reuse. Thoroughly clean shoes before reuse. Get medical attention. Serious Skin Contact Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek medical attention. Inhalation If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention. Ingestion Do not induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. If large quantities of this material are swallowed, call a physician immediately. Loosen tight clothing such as a collar, tie, belt or waistband.

If the contamination is series it should call a doctor immediately Comprehensive design project 61


Chapter 04

Fire Extinguisher Small fire: Use dry chemical powder. Large fire: Use water spray, fog or foam. Do not use water jet.

Handling and storage Keep away from heat. Keep away from sources of ignition. Empty containers pose a fire risk; evaporate the residue under a fume hood. Ground all equipment containing material. Do not breathe dust. Avoid contact with skin. Wear suitable protective clothing. In case of insufficient ventilation, wear suitable respiratory equipment. If you feel unwell, seek medical attention and show the label when possible. Keep container tightly closed. Keep container in a cool, wellventilated area.

Exposure Controls & Personal Protection Engineering Controls Use process enclosures, local exhaust ventilation, or other engineering controls to keep airborne levels below recommended exposure limits. If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminants below the exposure limit.

Personal Protection Ware safety glasses, Lab coat, Dust respirator. Be sure to use an approved/certified respirator or equivalent, Gloves. In large Spill use Splash goggles, Full suit, Dust respirator, Boots, Gloves. A self contained breathing apparatus should be used to avoid inhalation of the product. Suggested protective clothing might not be sufficient; consult a specialist before handling this product.



Chapter 05

CHAPTER 5 MASS BALANCE CALCULATION



Chapter 05

5.0 Mass Balance Calculation 5.1 Material Balance Urea production per day

=

1060.0 MT

CO2 conversion

=

68.00%

CO2 requirement per day

=

777.3 MT

NH3 requirement per day

=

600.7 MT

Compound

Chemical Formula

Molecular Weight (kg/kmol)

Ammonia

NH3

17

Carbon dioxide

CO2

44

Ammonium Carbamate

NH2COONH4

78

Water

H2O

18

Urea

NH2CONH2

60

Table 5.1 Compound in urea manufacturing Input ratio to reactor

NH3 : CO2

Molar ratio

4 : 1

Weight ratio

68 : 44

Reactions involved in the process 2NH3 + CO2 ↔ NH2COONH4 + heat Sch

2

1

1

Mass

34

44

78

Wt%

0.4359

0.5641

1.0000

NH2COONH4 + heat ↔ NH2CONH2 + H2O Sch:

1

1

1

Mass

78

60

18

Wt%

1.0000

0.7692

0.2308



Chapter 05

2NH3 + CO2 ↔ NH2CONH2 + H2O Sch:

2

1

1

1

Mass

34

44

60

18

0.7692

0.2308

Wt%

0.4359 0.5641



Chapter 05

5.1.1 Reactor Weight MT/day

Component NH3

4.8 12.79%

CO2 Flow rate Temperature Pressure

32.4 37.2 190 175

Component CO2 Flow rate Temperature Pressure

Component NH3 A. Carbamate Flow rate Temperature Pressure

Component Urea Carbamate Component NH3 Flow rate Temperature Pressure

Weight MT/day 600.7 600.7 170 175

Wt % 100.00% MT/day °C bar

Wt %

NH3 H2O Flow rate Temperature Pressure

87.21% MT °C bar Weight MT/day 263.3 263.3 170 175 Weight MT/day 486.1


Wt % 23.76%

1559.7 76.24% 2045.9 MT/day 170 °C 175 bar Weight MT/day Wt % 1060.0 36.90% 591.0 20.57% 903.6

31.46%

318.0 11.07% 2872.6 MT/day 190 °C 175 bar



Chapter 05

5.1.2 Stripper

Component Component Urea Carbamate NH3 H2O Flow rate Temperature Pressure

Weight MT/day Wt % 1060.0 36.90% 591.0 20.57% 903.6

31.46%

NH3 CO2 Flow rate Temperature Pressure

Weight MT/day

Wt %

612.4 44.89% 751.8 55.11% 1364.3 MT/day 190 °C 175 bar

318.0 11.07% 2872.6 MT/day 190 °C 175 bar

MP STEAM COND.


Weight MT/day 700.0 700.0 110 175

Component Urea Carbamate Wt %

NH3

100.00% MT °C bar

H2O Flow rate Temperature Pressure

Weight MT/day Wt % 1060.0 48.00% 499.1 22.60% 331.3

15.00%

318.0 14.40% 2208.3 MT/day 178 °C 175 bar



Chapter 05

5.1.3 Carbamate Condenser

Component Component NH3 CO2 Carbamate Flow rate Temperature Pressure

Weight MT/day

Wt %

56.4

26.89%

22.7 10.82% 130.7 62.29% 209.8 MT/day 153 °C 175 bar

NH3 CO2 Flow rate Temperature Pressure

Weight MT/day

Wt %

612.4 44.89% 751.8 55.11% 1364.3 MT/day 190 °C 175 bar

STM

Component NH3 Carbamate Flow rate Temperature Pressure

SC


Weight MT/day 263.3 263.3 170 175

Wt % 100.00% MT °C bar

Weight MT/day

Component CO2 Carbamate Flow rate Temperature Pressure

Weight MT/day

Wt %

212.3 28.89% 522.7 71.11% 735.1 MT/day 150 °C 175 bar

Wt %

263.3 14.44% 1559.7 85.56% 1823.0 MT/day 170 °C 175 bar



Chapter 05

5.1.4 Scrubber

Component NH3 CO2 Flow rate Temperature Pressure

Weight MT/day Wt % 1.4

12.79%

9.7 87.21% 11.2 MT/day 189 °C 175 bar


Component Component NH3 CO2 Flow rate Temperature Pressure

Weight MT/day

NH3 Wt %

4.8 12.79% 32.4 37.2 190 175

87.21% MT °C bar

CO2 Carbamate Flow rate Temperature Pressure

Weight MT/day 53.1 130.7 183.8 150 175

Wt % 28.89% 71.11% MT/day °C bar

Weight MT/day Wt % 56.4

26.89%

22.7 10.82% 130.7 62.29% 209.8 MT/day 153 °C 175 bar



Chapter 05

5.1.5 High Pressure Decomposer

Component

Component Urea Carbamate NH3 H2O Flow rate Temperature Pressure

Weight MT/day Wt %

NH3

327.3

79.49%


84.5 20.51% 411.7 MT/day 157 °C 17.5 bar

Weight MT/day Wt % 1060.0 48.00% 499.1 22.60% 331.3

15.00%

318.0 14.40% 2208.3 MT/day 178 °C 175 bar


Weight MT/day Wt % 1060 59.00% 349.4 19.45% 69.3

3.85%

318.0 17.70% 1796.6 MT/day 157 °C 17.5 bar



Chapter 05

5.1.6 Low Pressure Decomposer


Weight MT/day Wt % 1060 59.00% 349.4 19.45% 69.3

3.85%

318.0 17.70% 1796.6 MT/day 157 °C 17.5 bar

Weight MT/day Wt %

Component NH3

221.5

44.67%


274.4 55.33% 495.9 MT/day 129 °C 2.5 bar

Component H2O Urea NH3 Flow rate Temperature Pressure


Weight MT/day 77.3 77.3 80 20

Component Urea Wt %

H2O

100.00% MT °C bar

NH3 Flow rate Temperature Pressure

Weight MT/day Wt % 20 0.6

94.79% 2.84%

0.5 2.37% 21.1 MT/day 129 °C 2.6 bar

Weight MT/day Wt % 1060.6 75.81% 338.0

24.16%

0.5 0.04% 1399.1 MT/day 129 °C 2.5 bar



Chapter 05

5.1.7 Low Pressure Absorber

Component

Weight MT/day Wt %

NH3

221.5

44.67%


274.4 55.33% 495.9 MT/day 129 °C 2.5 bar

CW


Weight MT/day Wt % 9.5 1.91% 486.4 98.09% 495.9 MT/day 129 °C 1.5 bar



Chapter 05

5.1.8 Medium Pressure Absorber

Weight MT/day

Component

Wt %

NH3

328.7

77.73%


94.2 22.27% 422.9 MT/day 151 °C 17.5 bar


Component

Weight MT/day Wt % 9.5 1.91% 486.4 98.09% 495.9 MT/day 129 °C 17.5 bar

Weight MT/day Wt %

NH3

265.4

28.89%

CO2 Carbamate Flow rate Temperature Pressure

0.0 0.00% 653.4 71.11% 918.8 MT/day 150 °C 12 bar



Chapter 05

5.1.9 Flash Separator

Component

Component Urea H2O NH3 Flow rate Temperature Pressure

Weight MT/day Wt %

H2O Urea

105.6 0.3

99.53% 0.28%


0.2 0.19% 106.1 MT/day 190 °C 0.55 bar

Weight MT/day Wt % 1060.6 75.81% 338.0

24.16%

0.5 0.04% 1399.1 MT/day 178 °C 2.5 bar


Weight MT/day Wt % 1060.3 82.00% 232.4

17.98%

0.3 0.02% 1293.0 MT/day 110 °C 0.7 bar



Chapter 05

5.1.10 Lower Separator

Component


Weight MT/day Wt %

H2O Urea

152.8 0.2

99.74% 0.13%


0.2 0.13% 153.2 MT/day 110 °C 0.55 bar

Weight MT/day Wt % 1060.3 82.00% 232.4

17.98%

0.3 0.02% 1293.0 MT/day 110 °C 2 bar


Weight MT/day Wt % 1060.1 93.00% 79.7

6.99%

0.1 0.01% 1139.9 MT/day 110 °C 0.7 bar



Chapter 05

5.1.11 Upper Separator

Component


Weight MT/day Wt %

H2O Urea

71.1 0.1

99.72% 0.14%


0.1 0.14% 71.3 MT/day 112 °C 0.55 bar

Weight MT/day Wt % 1060.1 93.00% 79.7

6.99%

0.1 0.01% 1139.9 MT/day 110 °C 2 bar

Component Urea

Weight MT/day Wt % 1060.0 99.20%


8.5 0.80% 1068.5 MT/day 112 °C 0.8 bar



Chapter 05

5.1.12 Waste Water Treatment Unit

Weight MT/day Wt %

Component Component

Weight MT/day Wt %

H2O Urea

105.6 0.3

99.53% 0.28%


0.2 0.19% 106.1 MT/day 110 °C 1 bar

H2O Urea

223.9 0.3

99.73% 0.13%


0.3 0.13% 224.5 MT/day 110 °C 1 bar

Waste Water Treatment Unit

Component Component

Weight MT/day Wt %

H2O Urea

20.0 0.6

94.79% 2.84%


0.5 2.37% 21.1 MT/day 129 °C 2.6 bar

Weight MT/day Wt %

H2O Urea

309.5 100.00% 0.0 0.00%


0.0 0.00% 309.5 MT/day 40 °C 1 bar



Chapter 05

5.1.13 Granulator Weight MT/day Wt % 720.8 99.20%

Component Urea H2O Flow rate Temperature Pressure Component Urea H2O Flow rate Temperature Pressure


5.8 0.80% 726.6 MT/day 89 °C 1 bar

Component Urea

0.3 0.80% 32.1 MT/day 52 °C 1.5 bar


H2O

0.1

Air Flow rate Temperature Pressure

0.00%

2356.9 99.55% 2367.6 MT/day 55 °C 6 bar

GRANULATION SECTION

Component Urea


Component Urea



8.5 0.80% 1068.5 MT/day 112 °C 2 bar


14.5 0.80% 1816.5 MT/day 90 °C 1 bar

Component Air Flow rate Temperature Pressure

Weight MT/day 2356.89 2356.89 35 6




Chapter 05

5.1.14 Screen

Component Urea



14.5 0.80% 1816.5 MT/day 89.5 °C 1 bar

Component Urea H2O Flow rate Temperature Pressure

Weight MT/day Wt % 243.8 99.20% 2.0 0.80% 245.8 MT/day 89.5 °C 1 bar


Weight MT/day Wt % 477.0 99.20% 3.8 0.80% 480.8 MT/day 89.5 °C 1 bar

Component Urea



8.7 0.80% 1089.9 MT/day 89.5 °C 1 bar



Chapter 05

5.1.15 Product Cooler

Component Urea


Component Urea


8.7 0.80% 1089.9 MT/day 89 °C 1 bar



Weight MT/day 6213.62 6213.62 35 6

H2O


Weight MT/day Wt % 21.2 0.34% 0.2

0.00%

6213.6 99.66% 6235.0 MT/day 45 °C 6 bar

Component Urea



8.5 0.80% 1068.5 MT/day 60 °C 1 bar



Chapter 05

5.1.16 Bag Filter


Weight MT/day Wt % 8570.5 8570.5 52 1

100.00% MT/day °C bar

Component Urea H2O




Weight MT/day Wt % 31.8 0.37% 0.3

0.00%

8570.5 99.63% 8602.6 MT/day 52 °C 6 bar

0.3 0.93% 32.1 MT/day 52 °C 1 bar



Chapter 06

CHAPTER 6 MATERIAL FLOW SHEET



Chapter 06

Material Flow Sheet

Comprehensive design project Figure 6.1 Material Flow Sheet

83


Chapter 07

CHAPTER 7 HEAT BALANCE CALCULATION



Chapter 07

7.0 Heat Balance Calculation 7.1 Main Process Energy Balance 2 NH3 + CO2

NH2COONH4 + HEAT

NH2COONH4 + HEAT

2NH3 + CO2

-84 KJ/mol

NH2CONH2 + H2O

+23 KJ/mol

NH2CONH2 + H2O

-60 KJ/mol

Ammonia Liquid T (ºC)

60

80

112

Cp (KJ/KgK)

5.6

5.87

8.6

Ammonia Vapour T (ºC)

87

127

167

207

Cp (KJ/KgK)

2.2

2.3

2.37

2.44

CO2(g) T (ºC)

27

127

227

Cp (KJ/KgK)

0.84

0.94

1.01

T (0C)

80

120

200

Cp (KJ/KgK)

1.26

1.36

1.56

T (0C)

80

120

200

Cp (KJ/KgK)

1.4

1.6

2.1

Urea Vapour

Urea Liquid



Chapter 07

Urea Solid T (0C)

27

77

127

Cp (KJ/KgK)

1.56

1.8

2.04

T (0C)

27

127

177

Cp (KJ/KgK)

4.18

4.26

4.39

Water Liquid

Cp of the Carbamate

=

2.3 KJ/KgK

For NH3 liquid Cp = a + bT + cT2 5.6 = a + 333b + 3332c

(1)

5.87 = a + 353b + 3532c

(2)

2

8.6 = a + 385b + 385 c

(3)

From (1), (2) & (3) a = 163.44

b = - 0.9338

c = 1.38*10-3

For NH3 gas Cp = a + bT + cT2 2.2 = a + 360b + 3602c

(4)

2.3 = a + 400b + 4002c

(5)

2.44 = a + 480b + 4802c

(6)

From (4), (5) & (6) a = 0.4

b = 7.25*10-3

c = -6.25*10-6

For CO2 gas Cp = a + bT + cT2 0.84 = a + 300b + 3002c

(7)

0.94 = a + 400b + 4002c

(8)

2

1.01 = a + 500b + 500 c

(9)

From (7), (8) & (9) Comprehensive design project 86

Urea Manufacturing Plant a = 0.36

Chapter 07

b = 2.05*10-3

c = -1.5*10-6

For Urea Cp = a + bT + cT2 1.4 = a + 353b + 3532c

(10)

1.6 = a + 393b + 3932c

(11)

2.1 = a + 473b + 4732c

(12)

From (10), (11) & (12) a = 1.08

b = -2.77*10-3

c = 1.04*10-5



Chapter 07

7.1.1 Reactor 190 ºC

170 ºC

MPS 198.3°C COND. 198.3°C

170 ºC

170 ºC MPS

Q2

130 ºC

LPS

Q1 34 ºC

190 ºC

Low pressure steam load at 5 bar pressure and 151.8 ºC for ammonia heating

/day

Medium pressure steam load at 13 bar and 191.6 ºC for ammonia heating Comprehensive design project 88


Chapter 07

Urea formation heat by decomposing Ammonium Carbamate

Ammonium Carbamate production in the reactor

Ammonium Carbamate formation heat

Heat required for increasing raw materials to 190 ºC

Energy required to reactor

Medium pressure steam load at 15 bar and 198.3ºC for reactor heating



Chapter 07

7.1.2 Stripper 190 °C

190°C MP STEAM COND.

198.3 °C 198.3 °C

178°C

110 °C

Decomposition energy of Ammonium Carbamate

Heat released from Urea

Heat released from Ammonium Carbamate

Heat released from Water



Chapter 07

Heat absorbed by Carbon Dioxide

Heat absorbed for Ammonia vaporization

Energy required for stripper

Medium pressure steam load at 13bar and 191.6 ºC for heating

7.1.3 Scrubber

189 °C

150 °C

190 °C

153 °C



Chapter 07

Heat released from up flow

Heat released from down flow

Heat absorbed by Ammonia and Ammonium Carbamate

Energy loss



Chapter 07

7.1.4 Carbamate Condenser 150 °C 153 °C

STM 151.8 °C

190 °C

145 °C SC

170 °C 170 °C

Formation energy of Ammonium Carbamate at 170 C

Heat absorbed by Ammonium Carbamate




Chapter 07

Heat absorbed by Ammonia

Condensation heat and sensible heat released by Ammonia

Heat released by Carbon Dioxide

Heat released from Carbamate condenser

Production of steam load at 5bar Assume Cp of water at 145 C-150 C = 4.27 kJ/kg



Chapter 07

7.1.5 High pressure decomposer 157 °C

178 °C

157 °C



Heat released from Ammonium Carbamate




Chapter 07

Heat released by Ammonia


Energy loss

7.1.6 Low pressure decomposer 129 °C

157 °C

LPS 151.8 °C

129 °C

COND. 151.8 °C

129 °C 80°C



Chapter 07





Condensation heat released by water vapour from WWTU


Heat released by Ammonia



Chapter 07

Heat released by Carbon Dioxide

Energy required to reactor

Medium pressure steam load at 13 bar and 191.8 ºC for heating

Low pressure steam load at 5 bar and 151.8 ºC for heating

7.1.7 Low pressure absorber

129 °C

CW

129 °C Formation energy of Ammonium Carbamate at 129 C



Chapter 07

Condensation heat released by Ammonia

Heat released from LP Absorber

Cooling water requirement

7.1.8 High pressure absorber

157 °C

129 °C

150 °C

Operating temperature calculation



Chapter 07

Formation energy of Ammonium Carbamate at 151 C

Condensation heat released by Ammonia

Energy loss due to reduce temperature

Energy released from HP Absorber

Heat released to heat output from LPD

Heat released to cooling water

Cooling water requirement



Chapter 07

7.1.9 Flash separator 110 °C 191.8 °C MPS

150 °C Urea slurry 129°C

140°C 178 °C 150 °C

COND. 191.8 °C

110 °C


Heat released from water

Heat absorbed by water vaporization

Heat loss

Heat required for slurry heat to 178 C



Chapter 07

Heat recovered from MP Absorber

Additional heat required by 13bar MP steam

MP steam load

7.1.10 Lower separator 110°C

110 °C LPS 151.8 °C 151.8 °C COND.

110 °C


Energy loss



Chapter 07

Total energy requirement

5bar LP steam load

7.1.11 Upper separator

112 °C

110 °C LPS 151.8 °C 151.8 °C COND.

112 °C


Heat absorbed by urea and water



Chapter 07

Energy loss

Total energy requirement

5bar LP steam load

7.1.12 Process wastewater treatment unit Heat requirement of WWTU

Low pressure steam load at 5 bar and 151.8 ºC for heating

Cooling heat of process wastewater from flash separator

Cooling water load

Cooling heat of process wastewater from lower and upper separator

Cooling water load



Chapter 07

7.2 Granulation Plant 7.2.1 Granulator Heat removed from granulator

6 bar cooling Air load

7.2.2 Product cooler Heat removed from Product cooler

6 bar cooling Air load



Chapter 08

CHAPTER 8 TABULATED HEAT BALANCE



Chapter 08

8.0 Tabulated heat balance 8.1 Tabulated Heat Balance Input Energy

MJ/day

Heating of Ammonia due to low pressure steam

471962.08

Heating of Ammonia due to high pressure steam

300428.45

Heat supplied to Reactor

899260.67

Heat supplied to Stripper

123475.64

Heat supplied to LPD by low pressure steam

104259.64

Heat supplied to LPD by high pressure steam

97492.80

Heat supplied to Flash Separator

172190.9

Heat supplied to Lower Separator

416783.04

Heat supplied to Upper separator

199581.49

Heat supplied to Wastewater Treatment Plant Total input energy

63000.50 2848435.21

Output Energy Heat out from Scrubber Heat out from Carbamate condenser Heat out from HPD

MJ/day 124.70 1255586.69 6596.25

Heat out from LP Absorber

570330.38

Heat out from HP Absorber

251197.87

Heat out from Wastewater cooling 1

255948.00

Heat out from Wastewater cooling 2

512283.2

Heat out from Granulator

47434.75

Heat out from Product Cooler

62527.63

Total output energy

2962029.47

Table 8.1 Tabulated Heat Balance Comprehensive design project 107


Chapter 08

Difference between input and output energy

=

113594.26 MJ/day

Total heat output greater than the total heat input. So this difference is due to heat generated in the reaction. But the amount of theoretical heat generated in the reaction is much higher than this value. That difference between actual and theoretical value happens because of the heat losses occurred during the process.



REFERENCES Book References Urea manufacturing processes in Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Volume A27 Perry's Chemical Engineers' Handbook - Perry, R.H. and Green, D.W. (Editors) MARTYN S. RAY; DAVID W. JOHNSTON - Chemical Engineering Design Project: A Case Study Approach World Wide Web references Ammonia and Urea Production http://www.nzic.org.nz/ChemProcesses/production/1A.pdf Urea - http://www.stamicarbon.com/urea/_en/index.htm Urea - www.epa.gov/ttn/chief/ap42/ch08/final/c08s02.pdf Urea Production and Manufacturing process www.icis.com/v2/chemicals/9076560/urea/process.html Urea – Wikipedia, the free encyclopedia - en.wikipedia.org/wiki/Urea Fertilizer Urea - www.extension.umn.edu/distribution/cropsystems/DC0636.html UREA - www.jtbaker.com/msds/englishhtml/u4725.htm Urea - www.3rd1000.com/urea/urea.htm MSDS safety data sheets for ammonium carbamate, urea, and ammonium from http://msds.chem.ox.ac.uk/ MSDS urea - http://www.sciencestuff.com/msds/C2950.html - Science Stuff Inc.,1104 Newport Ave, Austin, TX, USA MSDS urea - http://www.pusri.co.id/data/MSDS-urea.PDF E-book References The Environmental Impact of a Stamicarbon 2000 mtpd Urea Plant - Authors: Will Lemmen (Licensing Manager) and Hans van Baal (Licensing Manager) Latest Urea Technology for Improving Performance and Product Quality by EIJI SAKATA (Senior Process Engineer),TAKAHIRO YANAGAWA (PROCESS ENGINEER) --TOYO ENGINEERING CORPORATION , TOKYO JAPAN Escalating worldwide use of urea – a global change contributing to coastal eutrophication by PATRICIA M. GLIBERT, JOHN HARRISON, CYNTHIA HEIL and SYBIL SEITZINGER


Stamicarbon CO2 - Stripping Urea Process

l e

CW Steam

m

g i

h ff

TCW

j

Water

TCW Cond.

NH3

c

Steam

a) CO2 compressor b) Hydrogen removal reactor c) Urea reactor d) High-pressure stripper e) High-pressure carbamate condenser f) High-pressure scrubber g) Low-pressure absorber h) Low-pressure decomposer and rectifier i) Pre-evaporator j) Low-pressure carbamate condenser k) Evaporator l) Vacuum condensation section m) Process condensate treatment CW - Cooling water TCW - Tempered cooling water

k Steam

Cond.

b

CO2

Cond. d Urea melt to granulation a

Convectional Urea Plant j

NH3

i e c d f Water

g CO2

h

a b

Air

Urea

a) CO2 compressor; b) High pressure ammonia pump; c) Urea reactor; d) Medium-pressure decomposer; e) Ammonia carbamate separation column; f) Low-pressure decomposer; g) Evaporator; h) Prilling; i) Desorber (waste water stripper); j) Vacuum condensation section

pond

Fuel tanks Ammonia storage tank Process area

Garden

Waste water treatment plant

Guard room

CO2 Storage tank Cooling tower

Water tank

Guard room

Urea store house Administration section

Granualization area

Cooling tower

FLASH SEPARATOR

Clean gas out

STM

SCRUBBER SC

BAG FILTER

CARBAMATE CONDENSER

LOWER SEPARATOR

UPPER SEPARATOR

LPD

STM HPD

SC

REACTOR HP ABSORBER STRIPPER

MP STEAM MP steam

COND.

LP steam

COMPRESSOR

NH3

CO2

LP ABSORBER

CW

GRANULATION SECTION SURFACE CONDENCER

PC STRIPPER

CW

UREA GRANULES

AIR

CW CW

UPC

AIR HYDROLYSER

Urea flow lines other process lines Steam line Condensed water line Cooling water line

Clean gas out BAG FILTER T FLASH SEPARATOR

T

T LOWER SEPARATOR

UPPER SEPARATOR

T P

STM

T

GRANULATION SECTION

SC

CO2

SURFACE CONDENCER

T

HP ABSORBER

STRIPPER MP STEAM MP steam

LP ABSORBER T

UREA GRANULES PC STRIPPER

CW

T

CW

T HYDROLYSER

CW

T

Waste water

COND.

T

AIR

CW T LP steam

FIRE TUBE BOILER COMPRESSOR

NH3

CO2

CONDENSED WATER TANKS

COOLING TOWER

POND WATER

Feed Water

Component Urea

g ComponenMT/day NH3

1.4

CO2

SCRUBBE R

11.2 MT/day 189 °C

Pressure

175 bar

Component CO2

Weight

Flow rate Temperature Pressure

Flow rate Component

87.21%

Flow rate Temperatu

Component

ComponenWeight Wt % NH3 53.1 28.89% Carbamate 130.7 71.11%

Wt %

263.3

100.00%

Flow rate

263.3 MT/day 170 °C

Pressure

NH3 CO2

12.79%

9.7

Flow rate Temperature

Component Weight

H2O

Wt %

12.79% 87.21%

37.2 MT 190 °C 175 bar


Component NH3

REACTOR

327.3


84.5 20.51% 411.7 MT/day 157 °C 17.5 bar

79.49%

150 °C 175 bar

Weight

Flow rate Temperatu Pressure


2045.9 MT/day 170 °C

0.5

0.04%


76.24%

Component Urea

735.1 MT/day 150 °C

Carbamate NH3 H2O

175 bar


ComponenWeight Wt % NH3 612.4 44.89% CO2 751.8 55.11% Flow rate

175 bar

Temperatu Pressure

Urea H2O

1060.3 232.4

82.00% 17.98%

NH3

0.3

0.02%

Flow rate

1399.1 MT/day 129 °C 2.5 bar

Component NH3

190 °C 175 bar

499.1 331.3

22.60% 15.00%

318 14.40% 2208.3 MT/day 178 °C 175 bar

Weight

Wt %

9.5

Carbamate Flow rate

1364.3 MT/day

MT/day Wt % 1060 48.00%

Temperature Pressure

1.91%

486.4 98.09% 495.9 MT/day 129 °C 1.5 bar

H2O Flow rate

1060 349.4 69.3

Component Weight Wt % NH3 600.7 100.00% Flow rate

600.7 MT/day

Component Urea Carbamate NH3 H2O

Temperature

170 °C

Flow rate

Pressure

175 bar


318

STRIPPER

HP ABSORB ER

59.00% 19.45% 3.85%

190 °C 175 bar



Pressure

175 bar

H2O

338

79.7 0.1

Flow rate Temperature Pressure CO2 COMPRESSOR

H2O Flow rate

5.8 0.80% 726.6 MT/day

SCREEN

6.99% 0.01%

Urea NH3 Flow rate Temperature Pressure

0.3 0.28% 0.2 0.19% 106.1 MT/day 110 °C 1 bar

WWTP UNIT

Air

0.3 8570.5

0.00% 99.63%

Flow rate

8602.6 MT/day 52 °C 6 bar

PRODUC T COOLER

89 °C 1 bar

Component Urea

Weight MT/day Wt % 10.6 0.45% 0.1 0.00% 2356.9 99.55% 2367.6 MT/day 55 °C 6 bar

Component Urea H2O Air Flow rate Temperature Pressure

Weight MT/day Wt % 21.2 0.34% 0.2 0.00% 6213.6 99.66% 6235 MT/day 45 °C 6 bar

Weight Component MT/day Wt % 1081.2 99.20% Urea H2O 8.7 0.80%

Weight MT/day Wt % 20 94.79% 0.6

2.84%

0.5 2.37% 21.1 MT/day 129 °C 2.6 bar

Weight MT/day Wt %

Component

Weight MT/day Wt %

H2O

Urea

0.3

0.13%

Urea

0

0.00%

NH3

0.3

0.13%

NH3

0

0.00%

110 °C 1 bar


89 °C C 1 bar


99.73%

224.5 MT/day

1089.9 MT/day

Component Urea H2O

223.9


H2O

99.20%

H2O Air Flow rate Temperature Pressure

H2O

Flow rate

0.37%

Wt %

720.8

1139.9 MT/day 110 °C 0.7 bar


99.53%

31.8

MT/day Wt % 1060.1 93.00%

Component H2O

105.6

Urea

Pressure

Urea


H2O

1.5 bar

Component Weight

Flow rate

Weight MT/day Wt %

BAG FILTER

GRANULATOR

24.16%

129 °C 2.5 bar

Component

Temperature

0.5 0.04% 1399.1 MT/day


32.1 MT/day 52 °C

Pressure

UPPER SEPARATO R

MT/day Wt % 1060.6 75.81%

Component

Component CO2


1 bar

112 °C 2 bar


263.3 100.00%

ht MT/d Wt % 77.3 100.00% 77.3 MT 80 °C 20 bar

0.80%

1068.5 MT/day

H2O NH3

Weight MT/day Wt %

170 °C

0.3

Wt % 1060 99.20% 8.5 0.80%

Component Urea

LP ABSORBER

263.3 MT/day

H2O

Pressure

Component Component CO2

90 °C

LPD

11.07%

2872.6 MT/day

99.20%

Weight MT/day Wt %

Weight

Urea

Weight MT/day Wt % 1060 36.90% 591 20.57% 903.6 31.46%

31.8

Temperature

157 °C 17.5 bar


NH3 Flow rate

Urea

Weight MT/day Wt %

318 17.70% 1796.6 MT/day

Component Urea

Pressure

Component

0.80%

1816.5 MT/day

110 °C 0.7 bar Component Urea H2O

Urea Carbamate NH3

Temperature

14.5

g MT/day Wt %

1293 MT/day


HPD

CARBAMATE CONDENSER

MT/day Wt % 486.1 23.76% 1559.7

NH3

Component

Wt %

263.3 100.00% 263.3 MT/day 170 °C 175 bar

75.81% 24.16%

LOWER SEPARATOR

175 bar

A. Carbamate

Pressure

NH3

1060.6 338

Component

Weight MT/day Wt %

Flow rate

Weight ComponenMT/day Wt % NH3 212.3 28.89% Carbamate 522.7 71.11%

Component CO2

Wt %

Urea H2O

FLASH SEPARATOR

183.8 MT/day

Temperatu Pressure

Wt %

4.8 32.4

Weight MT/day

Weight MT/day Wt %

MT/day Wt % 1802 99.20%

309.5 100.00%

309.5 MT/day 40 °C 1 bar

Weight MT/day 1060

Wt % 99.20%

8.5

0.80%

1068.5 60 1

MT/day °C bar

Urea Final Report

Recommend Documents