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

Urea Manufacturing Plant

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

Urea Manufacturing Plant

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…………………………………………………

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

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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…………………………………………………………

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

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

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

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

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

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

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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…………………………………………………

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

30

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

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

32

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

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

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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…………………………………………

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

35

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

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

36

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

36

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

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

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

38

Chapter 3

Comprehensive design project V

Urea Manufacturing Plant

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 ……………………………………………………………………

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

43

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

44

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

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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

5.1.3 Carbamate Condenser………………………………………………

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…………………………………………

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

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

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

76

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

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

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

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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

7.1.4 Carbamate Condenser………………………………………………

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

Urea Manufacturing Plant

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………………….

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

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

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

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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

Urea Manufacturing Plant

Chapter 01

CHAPTER 1 LITERATURE SURVEY

Comprehensive design project 1

Urea Manufacturing Plant

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

Urea Manufacturing Plant

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.

Comprehensive design project 3

Urea Manufacturing Plant

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