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A PLANT DESIGN PROJECT REPORT on PRODUCTION of 1500 MTPD of DI-AMMONIUM PHOSPHATE

Zuneeb Nazir

DDP-FA12-BEC-101

Muhammad Faisal Sultan

DDP-FA12-BEC-049

Umar Farooq

DDP-FA12-BEC-091

Muhammad Aziz ul Haq

DDP-FA12-BEC-047

A report submitted in partial fulfillment of the Requirements for the award of the degree of Bachelor of Science (Chemical Engineering)

Department of Chemical Engineering COMSATS Institute of Information Technology MAY, 2016

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Muhammad Faisal Sultan, Zuneeb Nazir, Muhammad Umer Farooq, Muhammad Aziz ul Haq

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A plant design project report on production of 1500 MTPD Of Di-Ammonium Phosphate (DAP).

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Fa12 – Spring 2016

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A PLANT DESIGN PROJECT REPORT on PRODUCTION of 1500 MTPD of DI-AMMONIUM PHOSPHATE (DAP)

Zuneeb Nazir

DDP-FA12-BEC-101

Muhammad Faisal Sultan

DDP-FA12-BEC-049

Umar Farooq

DDP-FA12-BEC-091

Muhammad Aziz ul Haq

DDP-FA12-BEC-047

A report submitted in partial fulfillment of the Requirements for the award of the degree of Bachelor of Science (Chemical Engineering)

Department of Chemical Engineering COMSATS Institute of Information Technology June, 2016

v

We declare that this thesis entitled “Production of 1500 MTPD of Di-Ammonium Phosphate ” is the result of our own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree.

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ACKNOWLEDGEMENT

In preparing this thesis, we were in contact with many people and teachers. They have contributed towards our understanding and thoughts. But in particular, we like to express our sincere appreciation to our supervisor, Engr. Muhammad Sarfraz Akram, for giving us initiative of this study. His Inspiring guidance, remarkable suggestions, keen interest and friendly discussions enabled us to complete this thesis. Without his support and interest this thesis would not have been the same as presented here.

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ABSTRACT Until about the beginning of nineteenth century, world agriculture depends upon on empirically developed agricultural practices. About that time, however the growth in understanding of plant physiology, and thus of plant growth needs and fertilization possibilities, began to parallel the rapid advance of general chemical knowledge and scientific study of the plant needs become possible. To determine the feasibility of or need for fertilization requires knowing (1) which of the required elements if any are deficient in soil; (2) what chemical forms of the deficient elements are assailable by the plant s thus suitable as fertilizers; (3) what quantity of fertilizer material is required to meet the needs of the crop; and (4) whether the crop yield increase resulting from fertilizer application would warrant the cost of fertilizer production and application. Phosphorus plays major role in photosynthesis and some other vital processes. It stimulates early growth and root formation, promotes seed formation and contributes to the general hardness of the plants. Without phosphorus seeds would be sterile. Diammonium phosphate (DAP), was introduced as a commercially viable fertilizer in the early 1950s. Although the ammonium phosphate are mixed fertilizer containing both nitrogen and phosphorus, it is appropriate to consider these materials as primarily phosphate suppliers. The TVA process has been in operation since 1960s and since greater profitability and economy have been the driving factors for industrial research and development, the journey to obtain a better process to produce Diammonium phosphate did not end here but it further evolved towards a different approach in producing DAP by using a pre neutralizer before pipe cross reactor

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Table of Contents CHAPTER 1 .............................................................................................................................. 1 Introduction and History ............................................................................................................ 1 1.1

Plants, Soil and Fertilizers: ......................................................................................... 1

1.1.1 1.2

Categories of Plant Nutrients: .............................................................................. 3

Classification of Fertilizers ......................................................................................... 5

1.2.1

Direct fertilizers ................................................................................................... 5

1.2.2

Indirect fertilizers ................................................................................................. 5

1.2.3

Complete fertilizers .............................................................................................. 5

1.2.4

Incomplete fertilizers ........................................................................................... 5

1.2.5

Mixed Fertilizers .................................................................................................. 6

1.2.6

Natural fertilizers ................................................................................................. 6

1.3

Nature of Chemical Fertilizers .................................................................................... 6

1.3.1 1.4

Chemical Content: ............................................................................................... 6

Phosphate Fertilizers ................................................................................................... 8

1.4.1

Requirement of Phosphorous ............................................................................... 8

1.4.2

Historic Sources: .................................................................................................. 8

1.4.3

Phosphate Fertilizers from mineral phosphates: .................................................. 9

1.4.4

Diammonium Phosphate ...................................................................................... 9

1.5

Economic survey of Fertilizer sector of Pakistan...................................................... 10

CHAPTER 2 ............................................................................................................................ 11

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Process Selection ..................................................................................................................... 11 2.1

Ammonia: .................................................................................................................. 11

2.1.1 2.2

Process Steps of Ammonia Production: ............................................................. 11

Ammonia Synthesis Processes: ................................................................................. 12

2.2.1

Kellog Low-Energy Ammonia Process: ............................................................ 12

2.3

Selection of the Process............................................................................................. 12

2.4

Diammonium Phosphate (DAP) (NH4)2HPO4 ........................................................ 14

2.5

Raw Materials: .......................................................................................................... 14

2.6

Importance Of DAP: ................................................................................................. 14

2.7

Manufacturing Of DAP: ............................................................................................ 15

2.7.1

(TVA) Atmospheric Saturator Process: ............................................................. 15

2.7.2

(TVA) Vacuum Crystallizer Process: ................................................................ 16

2.7.3

DAP As By-Product of Coke-Oven Plants: ....................................................... 16

2.7.4

(TVA) Processes for Production of Granular DAP: .......................................... 17

2.7.5

Selection of Process: .......................................................................................... 18

2.8

Raw Materials: .......................................................................................................... 18

2.9

Sources of raw materials: .......................................................................................... 19

2.10

Preparation of raw material: .................................................................................. 19

2.10.1 Phosphoric Acid: ................................................................................................ 19 CHAPTER 3 ............................................................................................................................ 22 Description of Process Flow Diagram: .................................................................................... 22

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3.1

Process Details: ......................................................................................................... 22

3.1.1

Ammonia: .......................................................................................................... 22

3.1.2

Phosphoric Acid: ................................................................................................ 22

3.1.3

Pre Neutralizer: .................................................................................................. 23

3.1.4

Pipe Cross Reactor: ............................................................................................ 24

3.1.5

Ammoniator Granulator: .................................................................................... 24

CHAPTER 4 ............................................................................................................................ 28 Material Balance: ..................................................................................................................... 28 4.1

Material Balance across Screen 2.............................................................................. 28

4.2

Material Balance across Screen 1: ............................................................................ 30

4.3

Material Balance across Dryers: ............................................................................... 30

4.4

Material Balance across Granulator: ......................................................................... 31

4.5

Material Balance across Pre Neutralizer: .................................................................. 33

4.6

Material Balance across Pipe Cross Reactor: ............................................................ 34

CHAPTER 5 ............................................................................................................................ 37 Energy Balance ........................................................................................................................ 37 5.1

Energy Balance across Pre Neutralizer: .................................................................... 37

5.2

Energy Balance across Pipe Cross Reactor: .............................................................. 38

5.3

Energy Balance across Granulator: ........................................................................... 39

5.4

Energy Balance across Dryer: ................................................................................... 41

CHAPTER 6 ............................................................................................................................ 43

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Designing ................................................................................................................................. 43 6.1

Centrifugal Pump Design .......................................................................................... 43

6.2

Pre Neutralizer Design: ............................................................................................. 48

6.2.1

Agitator Design: ................................................................................................. 49

6.3

Pipe Cross Reactor Designing: .................................................................................. 52

6.4

Dryer Design ............................................................................................................. 56

6.4.1

Higher Efficiency Design: ................................................................................. 61

6.5

Design of H3PO4 Storage tank: ................................................................................. 67

6.6

Sulphuric acid storage tank: ...................................................................................... 70

CHAPTER 7 ............................................................................................................................ 72 Process Control Instrumentation .............................................................................................. 72 7.1

Introduction of Process Control Instrumentation: ..................................................... 72

7.1.1

Elements of control system: ............................................................................... 73

7.2

Controller: ................................................................................................................. 75

7.3

Control Loops:........................................................................................................... 77

7.4

Flow control on NH3 stream: .................................................................................... 80

7.5

Flow control on H3PO4 stream:................................................................................ 81

7.6

Flow control on pipe reactor: .................................................................................... 82

7.7

Flow control on granulator: ....................................................................................... 83

7.8

Instrumentation on pipe reactor: ............................................................................... 84

7.9

Temperature control on granulator:........................................................................... 85

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CHAPTER 8 ............................................................................................................................ 87 Cost Estimation ........................................................................................................................ 87 8.1

Cost Estimation: ........................................................................................................ 87

8.1.1

Process Engineering Cost Index ........................................................................ 87

8.1.2

Total Physical Plant Cost (PPC): ....................................................................... 88

8.1.3

Fixed Capital Cost (FCC): ................................................................................. 88

8.1.4

Working Capital Cost (WCC):........................................................................... 89

8.2

Total Operating Cost Estimation: .............................................................................. 89

8.3

Dap Cost: ................................................................................................................... 91

CHAPTER 9 ............................................................................................................................ 92 PLANT LOCATION & SAFETY ........................................................................................... 92 9.1

PLANT LOCATION: ............................................................................................... 92

9.1.1

Societal considerations: ..................................................................................... 92

9.1.2

Availability of raw material: .............................................................................. 93

9.1.3

Property cost: ..................................................................................................... 93

9.1.4

Taxation: ............................................................................................................ 93

9.1.5

Labor availability: .............................................................................................. 93

9.1.6

Energy availability and cost: .............................................................................. 93

9.1.7

Transportation accessibility: .............................................................................. 95

9.1.8

Environmental permit: ....................................................................................... 95

9.1.9

Living conditions: .............................................................................................. 95

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9.1.10

Environmental considerations:........................................................................... 95

Effluent from the DAP unit: ................................................................................................ 96 9.1.11 Fluoride emission: .............................................................................................. 96 9.1.12 Ammonia: .......................................................................................................... 97 9.1.13 DAP dust: ........................................................................................................... 97 9.1.14 Water discharge: ................................................................................................ 97 CHAPTER 10 .......................................................................................................................... 98 HAZOP ANALYSIS ............................................................................................................... 98 10.1

Introduction: .......................................................................................................... 98

10.1.1 Safety Points: ..................................................................................................... 98 10.1.2 Building and Process Equipment Safety: ........................................................... 99 10.2

TVA granular process:......................................................................................... 100

10.2.1 Special Hazards and Precautions: .................................................................... 100 10.3

HAZOP Analysis for Pre-Neutralizer: ................................................................ 103

10.4

HAZOP study for Scrubber: ................................................................................ 106

10.5

HAZOP study for Storage Vessel:....................................................................... 107

10.6

HAZOP study for Granulator: ............................................................................. 108

References: ............................................................................................................................. 110

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CHAPTER 1

Introduction and History

1.1 Plants, Soil and Fertilizers: Fertilizer is a material that contains one or more chemical elements necessary for proper development and growth of plants. The important fertilizer are fertilizer animal, manures and plant residue, these are also called Natural or Mineral Fertilizer. A synthetic fertilizer is a material produced by industrial process with a specific purpose of being used as a fertilizer. A fertilizer is essential in today’s agricultural system to replace the elements extracted from the soil by the plants in the form of food [1]. Pakistan is an agriculture based country. Fertilizer sector contributes 25% to the GDP. Cropped area of Pakistan has 54% of food grain crop. 87% of the fertilizer is used to enhance crop production. 92% of the consumed fertilizer contains nitrogen. Nitrogenous fertilizers are classified to organic and In-organic compounds as shown in figure 1. Amide fertilizers being organic in nature are further classified to urea and calcium cyanimide. The fertilizer industry in Pakistan has an oligopolistic structure. The product is differentiated and there are almost nine firms in the industry. The current situation in the industry is one of the excess demand. Currently domestic supply capacity is 5.8 mntpa (millions tons per annum) and demand is 6.8 mntpa [2]. Fauji Fertilizers Bin Qasim is the only domestic producer of Diammonium Phosphate (DAP) a fertilizer which is required in the planting of new crop. Currently FFBL’s share of DAP market is 30% with 70% of the market being supplied with imports[1].

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1.1.1 Categories of Plant Nutrients: Plants nutrients are usually categorized as being structural elements, primary nutrients, secondary nutrients and micronutrients. A typical analysis for the dry matter from a healthy plant in terms of these nutrients is shown in Table 1.1.

Elements

Amounts in Whole plant % ( Dry Weight)

Structural Elements Oxygen

45

Carbon

44

Hydrogen

6

Primary Nutrients Nitrogen

2

Phosphorous

0.5

Potassium

1.0

Secondary Nutrients Calcium

0.6

Magnesium

0.3

Sulfur

0.4

Micronutrients Boron

0.005

Chlorine

0.015

Copper

0.0001

Iron

0.020

Manganese

0.050

Molybdenum

0.0001

Zinc

0.0100

Total

99.9011

Table 0.1: Relative amount of different elements in plant

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A detailed overview of plant need and demand of these three types of nutrients along with their sources and importance is given below.

1.1.1.1 Primary Nutrients: The elements nitrogen, phosphorus, and potassium are primary nutrients not only because healthy plant growth requires them in relative abundance, but also because these are the primary elements that most often must be furnished by fertilizers. None of these elements is a principal component of the usual soil minerals. Elemental nitrogen is the primary component of the atmosphere (79% by volume). To most plant however. This form of nitrogen is totally inaccessible. Agricultural crop growth causes relatively rapid depletion of the primary nutrients in the soil. Thus replenishment by fertilization becomes essential. The principal task of the chemical fertilizer industry worldwide is to furnish agriculture with chemical forms of nitrogen (N), phosphorus (P), and potassium (K) that when applied to the soil, can be readily assimilated by crop plants. Ability to include secondary nutrients and micronutrients in the fertilizers when needed is also a responsibility of the industry, but volume wise it is the production of N, P and K fertilizers that defines the industry.

1.1.1.2 Secondary Nutrients These secondary nutrients, calcium, magnesium and sulfur are also very important. These are known as secondary because of the need of furnished through fertilizer application, because these elements also are abundant components of soil minerals at most locations. These elements also are incidental components of many fertilizers. Moreover the widespread agricultural practice of liming by application of pulverized limestone or dolomite to the soil intended chiefly for control of soil pH, incidentally adds calcium and magnesium. Many soils contain sulfur pawing to atmospheric emissions from the industrial burning of coal and from volcanic eruptions. Thus intentional fertilizations to furnish the secondary elements in majority cases omitted. However there are expectations like there are large area in Continent Australia and the South-eastern United States that are naturally deficient in sulfur and can be made more fertile by this application of Sulphur containing fertilizers.

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1.1.1.3 Micronutrients: Most micronutrient elements are sufficiently present in native soils or impurities in nonmicronutrients fertilizers applied to soil. Thus fertilization to provide these micronutrients elements specifically can often be omitted. Important exceptions arise in cases from repeated cropping. In these special cases significant benefits are obtained by the application of small amounts of micronutrient sources and on the Volumatic basis this is only a small part of the world of fertilizer industry.

1.2 Classification of Fertilizers We can classify the fertilizers into following: 1.2.1 Direct fertilizers Such fertilizers which are assimilated directly by the plants are known as direct fertilizers.

1.2.2 Indirect fertilizers Such substances which are introduced into the soil just to increase their mechanical, chemical and biological properties are known as indirect fertilizers.

1.2.3 Complete fertilizers Such fertilizers contains all the important ingredients for the growth of plants in the combine form so that extra fertilizers are not needed.

1.2.4 Incomplete fertilizers Fertilizers which contain only few elements such as ammonium phosphate or potassium nitrate are called incomplete fertilizers.

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1.2.5 Mixed Fertilizers Such fertilizers which contains many ingredients and which are get by mechanical mixing of various fertilizers are known as mixed fertilizers.

1.2.6 Natural fertilizers Natural fertilizers can be classified into two sub groups.

1.2.6.1 Organic fertilizers Naturally present organic fertilizers include manure, worm casting, peat moss, seaweed and sewage.

1.2.6.2 Inorganic fertilizers Naturally occurring inorganic fertilizers include Chilean sodium nitrate, mined rock phosphate, and limestone (which is a calcium source).

1.3 Nature of Chemical Fertilizers

1.3.1 Chemical Content: Numerous chemical compounds have been shown to be suitable as sources of primary nutrients in fertilizers. A partial listing is given in Table 1.2. Because the route of these nutrients into the plant is through root absorption from the soil solution, solubility of the compounds in the soil solution is of prime importance. All of the Di-calcium Phosphate. Di-Calcium phosphate nevertheless is suitably soluble in most soil solutions and is recognized as a highly acceptable fertilizer component. Agronomic response to phosphorus in fertilizers can be suitably predicated by laboratory measurement of solubility in certain neutral or alkaline citrate solution reagents. Solubility in pure water therefore is not a necessity although a certain degree of water solubility is recommended by most agronomists.

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Compound

Primary Nutrient Content, % N

P2O5

K2O

Nitrogen Sources Ammonia

82.2

Ammonium Sulfate

21.2

Ammonium Nitrate

35.0

Sodium Nitrate

16.5

Calcium Nitrate

17.0

Urea

46.6

Calcium Cynide

34.9

Mono ammonium phosphate

12.1

61.7

Diammonium Phosphate

21.2

53.7

Potassium nitrate

13.8

46.6

Phosphorus Sources Mono Calcium Phosphate

60.6

Di Calcium Phosphate

52.1

Mono Ammonium Phosphate

12.1

61.7

Diammonium phosphate

21.2

53.7

Potassium Phosphate

33.4

66.5

Potassium Phosphate Potassium Chloride

63.1

Potassium Sulfate

54.0

Potassium Magnesium Sulfate

22.7

Potassium Nitrate

13.8

46.6

Potassium phosphate

33.4

66.5

Table 0.2: Amount of Nutrients in different fertilizers

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1.4

Phosphate Fertilizers

1.4.1 Requirement of Phosphorous Phosphorous plays an important role in photosynthesis and some other vital processes. It stimulates early growth and root formation promotes seed formation and contributes to the general hardness of the plants. Without phosphorous seeds would be sterile. The required concentration of phosphorous in the soil solution depends primarily on the crop species being grown and the level of production desired. Australian researchers indicates that concentration of 0.2 – 0.3 ppm is adequate for a verity of crops. Mr. Fox of the University of Hawaii refers to the phosphorous in soil solution needed by the crops concentration of phosphorous as the external phosphorous requirement of several crops. Maximum crops grain yields may be obtained when solution concentration are as low as 0.01ppm if the yield potential is low but yield potential is associated with a level of about 0.025ppm. The requirement of wheat is on average slightly greater than for corn. Sorghum is believed to have a requirement similar to that of corn, soybean has much higher requirement then corn. Two types of phosphorous in soil are used: Organic soil phosphorous and inorganic soil phosphorous. The main requirement is only concerned with inorganic phosphorous.

1.4.2 Historic Sources: The phosphorous content of most virgin soil is very low. Furthermore the phosphorous content of soil is in forms unavailable to plants. Also there are practically no natural routes of phosphorous replenishment operating other than the natural recycling of plant material and animal wastes. The growth of legumes in a crop rotation pattern, although effective for supplying nitrogen, does nothing towards supplying phosphorous. Organic manures do furnish some phosphorous but are much less effective than in supplying nitrogen, for these reasons repeated cropping of land without fertilization can soon deplete the supply of phosphorous and the land becomes barren. One fertilization practice initiated in the early nineteenth century that was effective in furnishing phosphorous was the application of ground bones to soil. Raw bones normally contain 8-10 % phosphorous (20-25% P2O5) and are thus rich phosphorous sources.

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Decomposition of raw bones in soil is quite slow however limiting effectiveness. Also the supply of bones is insignificant in regard to world need for phosphate fertilizer. In about 1830, in England sulfuric acid pretreatment of bones was began as an effective method of increasing the availability of the phosphorous to growing plants. About 10 years later, similar sulfuric acid treatment of mineral phosphate ore was begun to produce the effective fertilizer product now known as ordinary (or normal) super phosphate.

1.4.3 Phosphate Fertilizers from mineral phosphates: Essentially all fertilizer phosphate is derived from mineral phosphate. Deposits of mineral phosphate are abundant and widely dispersed throughout the world. Nearly all of the mineable deposits are minerals of the apatite group represented by the general formula Ca5 (F, Cl, OH, 0.5CO3) (PO4)3 as mined essentially the ores require beneficiation to reduce the content of clay silica or other extraneous material. Beneficiation methods commonly used are washing and floatation using various flotation agents. Beneficiated ores as supplied to fertilizers producers rang in P2O5 content has been 32% but is decreasing as high grade ores become exhausted. The phosphorous content of ores and concentrates is in the trade usually expressed as bone phosphate of lime (% BPL) which is tricalcium phosphate Ca3 (PO4)3. Concentrate of 32% P2O5 content has a grade of 69.9% BPL.

1.4.4 Diammonium Phosphate Diammonium phosphate (DAP), (NH4)2HPO4 was introduced as a commercially viable fertilizer in the early 1950s. Since that time its acceptance has been phenomenal. For the year ended June 30, 1990, about 3.2 x 106 t of diammonium phosphate (1.5x106t P2O5) was produced in the United States and used by U.S farmers. This consumption represented about 38% of total U.s fertilizer P2O5 usage. Additional quantities were produced for export. Worldwide ammonium phosphate fertilizer consumption (diammonium and monoammonium) for the same period amounted to 11.1x10C t of P2O5, which was about 31% of total fertilizer P2O5 utilization. Although the ammonium phosphate are strictly speaking mixed fertilizers, containing both nitrogen and phosphorous it is appropriate to consider these materials as primarily phosphate suppliers.

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1.5 Economic survey of Fertilizer sector of Pakistan Realizing the importance of fertilizers for an agricultural country, the development of this industry in Pakistan is considered. Until 1950 the use of chemical fertilizer in Pakistan was unknown. The first imports were made in 1952, as a consequence of an acute food shortage. The use of fertilizers increased slowly in enhancing the yield of crops. The government of Pakistan has taken several significant steps to boost agricultural production over the last five years. The domestic production of fertilizer during the first nine months (JulyMarch, 2010-11) of the current fiscal year was up by 4.5 percent. The import of fertilizer increased by 133 percent; hence the total availability of fertilizer also increased by 25.3 percent. Total off take of fertilizer surged by 23.8% due to a subsidy of Rs.500 per bag of Sulfate of Potash (SOP)/ Marinate of potash

(MOP) has been announced. Nitrogen off-take increased

by 15.4% while that of phosphate by 66.2%. Main reasons for increased off-take of fertilizers were affordable price of DAP and higher support price of wheat. Average retail sale prices of nitrogenous fertilizers increased while that of phosphate decreased considerably.

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CHAPTER 2

Process Selection

2.1 Ammonia: Ammonia is a chemical compound with the formula NH3. At 20oC and 1atm pressure ammonia is a gas with a characteristic pungent smell. Its main use are in the production of fertilizers, explosives and polymers. Ammonia can also be used directly as a fertilizers by forming a solution with irrigation water, without additional chemical processing. This later use allows the continuous growing nitrogen dependent crops such as maize without crop rotation. Ammonia is well suited as a refrigeration units. Ammonia is also the basic raw material for most of the military explosives, ash, nitric acid, Nylon, Plastic, Dyes, Rubbers and refrigeration and many others [1].

2.1.1 Process Steps of Ammonia Production: Today the term Ammonia synthesis is increasingly used when referring to the total ammonia production process. Synthesis conditions are no longer viewed in isolation. They are important consideration in the total process but can be determined properly only in relation to the total plant integration. The complete process of industrial ammonia production can be subdivided into the following sections: [1] A) Synthesis Gas Production 1) Feedstock pretreatment and gas generation 2) Carbon monoxide conversion 3) Gas purification B) Compression C) Synthesis.

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2.2 Ammonia Synthesis Processes: Following are the process which can be used for the ammonia synthesis. 1. Kellogg Low-Energy Ammonia Process 2. Haldor Topsee Process 3. Krupp-Uhde Process [2].

2.2.1 Kellog Low-Energy Ammonia Process: The Kellogg process is along traditional lines, operating with steam/carbon ratio of about 3.3 and stoichiometric amount of process air and low methane slip from the secondary reformer. The synthesis pressure depends on plant size and is between 140 and 180 bar. Temperatures of the mixed feed entering the primary reformer and of the process air entering the secondary reformer are raised to the maximum extent possible with today’s metallurgy. This allows reformer firing to be reduced and, conversely, the reforming pressure to be increased to some extent to save compression costs. An important contribution comes from Kellogg’s proprietary cross-flow horizontal converter, which operates with catalyst of small particle size, low inlet ammonia concentration, and high conversion. Low-energy carbon removal systems contribute to the energy optimization. When possibilities to expert steam or power are limited, part of secondary reformer waste heat is used, in addition to steam generation, for steam superheating, a feature in common with other modern concepts. Proprietary items in addition to them horizontal converter are the traditional Kellogg’s reformer, transfer lines and secondary reformer arrangement, waste-heat boiler, and chiller in the refrigeration section [4].

2.3 Selection of the Process There are various process use for ammonia production from decades but Kellogg’s process has its own benefits which are discussed below. Kellogg’s process big advantage is that it can be implemented in one of three ways: ➢ As an expansion to an already existing plant. ➢ As a retrofit design to an already existing plant ➢ As a grassroots design when building a brand new plant.

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Kellogg’s Process potential increases capacity and to provides a suitable retrofit design. Synthesis loop that had separate feed streams for hydrogen and nitrogen allowed the Kellogg’s process reactor to be run under a variety of stream rations. Kellogg’s process reactor was a three bed radial flow converter with a unique proprietary sealing system which avoided hotspots within the catalyst bed. The Kellogg’s process catalyst was loaded in its oxidized state just as most catalyst are although it is only active in the reduced state. Therefore fresh synthesis gas, which heated the catalyst bed to 637 K was used to for the reduction process. The synthesis loop operated at the original design pressure of 2000 psia. A continuous purge is required in this retrofit because the expanded plant contains more inert than in the original synthesis loop. This is more efficient and highly flexible system has been very easy to operate and has paved the way for grassroots facilities. Grassroots designs are different from retrofit and expansion designs in that they use 3 and 4 bed intercooled reactors. The reaction for this is so that the iron catalyst can take advantage of high ammonia reaction rates at low ammonia concentrations. As the reaction progresses, however, the ammonia concentrations increase and the iron catalyst loses its effectiveness. The Kellogg’s process catalyst is then used to produce high exit ammonia concentrations at low pressures, since it can be used at high ammonia concentrations. In Kellogg’s process the lower pressure synthesis loop, which leads to significant capital savings, results from the use of a single case gas compressor with thinner walled and lighter vessels, fittings and piping. This synthesis loop is also advantageous in that it uses energy more efficiently by recovering heat at a much higher temperature, yielding a 40% decrease in energy conversion relative to conventional designs. Since the synthesis loop is less complex than in other plants, operator attention is expected to be less as well. In addition all of these benefits bring with them an expectation of greater reliability. Kellogg’s process implemented as either a retrofit, expansion, or grassroots design, has proven to have significant benefits such as reduced capital costs and energy savings. Kellogg’s ammonia synthesis configuration leads to an economically advantageous and flexible ammonia plants [3].

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2.4 Diammonium Phosphate (DAP) (NH4)2HPO4 Diammonium Phosphate (DAP) is a very important fertilizer that fulfills the need of phosphate requirement in the soil. Following are the properties of DAP [5]. •

Fertilizer grade: 18-46-0.

•

Dry fertilizer product.

•

Acid-forming fertilizer.

•

Initial soil reaction can produce free NH3, which can cause seeding injury if too much fertilizer is placed near the seed.

Diammonium phosphate (DAP) has become one of the most extensively used fertilizer materials in comparison with other fertilizer salts.

2.5 Raw Materials: Ammonia (NH3) and Phosphoric acid (H3PO4) are the main raw materials: both are taken from different sources ammonia is produced from natural gas while phosphoric acid is produced from treatment of phosphate rock [4].

2.6 Importance Of DAP: It provides high concentration of plant food with favorable agro manic and physical properties and it can be used for direct application. DAP is nonpoisonous, non-explosive and noninflammable. It is a prominent base material for dry mixing or blending to produce other grades. It not only provides high concentration of plant food but it also compatible with mist mix fertilizer material such as ammonium nitrate, ammonium sulfate, urea, potassium chloride and maintains good physical properties. It provides economical method for fixing ammonia in solid form (twice as much as monoammonium phosphate) and it provides increased water solubility of products by contributing a high content of soluble P2O5. When used in producing wet mix N-P-K grades can provide the following additional factors [7]: ➢ Decrease amount of reactants otherwise requires in ammoniators. ➢ Lower moisture contents in formulation: which decrease drying requirement. ➢ May contributes to higher production rates.

15

➢ Improve physical stability. ➢ Lessens tendency of product caking in storage.

2.7 Manufacturing Of DAP: These are the following process which are available for the manufacturing of DAP. 1. Tennessee Valley Authority (TVA) atmospheric saturator process. 2. Tennessee Valley Authority (TVA) vacuum crystallizer process. 3. Tennessee Valley Authority (TVA) process for the production of granular DAP. 4. DAP as by-product of coke-oven plants. 5. Fisans fertilizer DAP process [7].

2.7.1 (TVA) Atmospheric Saturator Process: Diammonium phosphate (DAP) was produced from anyhow ammonia and electric furnace phosphoric acid in a pilot plant using an atmospheric saturator process in the late 1940’s. This process consists of aggregates of thin tubular crystals bounded by a film of fine crystal. The product contained 5% of mono ammonium phosphate, but free of impurities. The DAP was produced in a continuous single stage atmospheric saturator by continuously feeding gaseous ammonia and strong electric furnace phosphoric acid (75-85% H3PO4), at an ammonia-phosphate ratio 2:1 into a saturated solution of ammonium phosphate at about 60 to 70oC. DAP crystallized out of the solution and was recovered by settling, centrifuging, washing and drying. The ammonia and phosphoric acid mole ration in the solution was maintained as low as practical without precipitating mono ammonium phosphate. This mole ratio was about 1.6, which corresponded to a pH of 5.8 to 6.0. The DAP crystals precipitate from this solution were wet with a film of relatively more acidic mother liquor, a portion of which was displaced by water during washing and the reminder crystallized in the surface of the DAP crystal. The pilot plant produced about 40 pound of DAP per hour per square foot saturator cross section. When it is compared with other fertilizer salts the Diammonium phosphate (DAP) product was comparatively stable resisted compatible physical characteristics and on exposure to 30oC and relative humidity up to 80%, moisture absorption and ammonia loss were negligible [7].

16

Drawbacks: Attempt to use wet process phosphoric acid for production of DAP by the atmosphere saturator process were unsatisfactory because of the formation of precipitates that retarded filtration.

2.7.2 (TVA) Vacuum Crystallizer Process: This process was started in the early 1950s when Tennessee Valley Authority (TVA) produced Diammonium phosphate (DAP) on demonstration scale in a vacuum crystallizer. The process which was earlier developed in pilot plant consisted of feeding gaseous ammonia and furnace grade phosphoric acid into the vacuum crystallizer. This product was a coarse crystalline material containing 21% nitrogen and 53% phosphorous pentoxide [8]. Drawbacks: Attempt to use wet process phosphoric acid for production of DAP by the atmosphere saturator process were unsatisfactory because of the formation of precipitates that retreated filtration. Same results reported in vacuum crystallizer.

2.7.3

DAP As By-Product of Coke-Oven Plants:

The coke-oven by-product manufactures began producing Diammonium phosphate (DAP) in the plants that originally designed for ammonium sulfate production. Modification were made in ammonium sulfate and Diammonium phosphate (DAP) to meet the market demand. The Colorado Fuel & Iron Company used a single stage saturated system. In 1956, Ford Motor Company, steel division, at Dearborn, Michigan began operation of a plant having two stages absorption for by-product of Diammonium phosphate (DAP) [8]. Gas driven off in the pyrolytic distillation of coal, called “coking” contain approximately 1% by volume of ammonia. Therefore an absorption type scrubber was used to strip the ammonia from the effluent gas before releasing the gas to atmosphere. Two type of the ammonia saturator or scrubber were most commonly used the absorption pf the ammonia. In the Koppers or single stage tube type saturator, the gas was dispersed into the acid liquid phase by means of a submerged sparger ring or cracker pipes. Secondary cleanup of ammonia from the gas was accomplished by sprays in the vessel above the tube [7].

17

In the second type of the saturator, designed by the Otto construction Company, the liquid level was below the reaction zone of the vessel. The gas flowed upwards through the vertical cylindrical vessel, counter-current to acid liquor sprays from a main bank of nozzles and from auxiliaries nozzle located near the inlet and outlet [8]. Drawback: The crystal formation and separation process were essentially the same for diammonium phosphate (DAP) as for ammonium sulfate. However because of complication in settling resulting from a difference in specific gravity between diammonium phosphate crystal and the liquor at the operating pH and temperature, approximately twice as much settling tank area and a non-turbulent feed were necessary for successful settling of DAP product crystal.

2.7.4 (TVA) Processes for Production of Granular DAP: In the early 1960s TVA developed what is perhaps today the most widely accepted process for production of granular diammonium phosphate. Although a number of the Dorr-Oliver blunger type plants are still in operation, most recent new plants have been the (TVA) type having a pre neutralizer for partial ammoniation of the phosphoric acid and completion of ammoniation in a TVA patented rotary ammoniator granulator instead of a bulger. Granulation is controlled by recycling product fines to the drum. Numerous refinements and variations have been made in the process in subsequent plants, especially in the areas of dust control, ammonia recovery, energy conversion, metering, controls, etc. [6, 7, 8]. The basic process involves partial pre neutralization of the acid in a pre-neutralizer (reaction tank) followed by completion of ammoniation to diammonium phosphate in the rotary ammoniators-granulator. Excess ammonia, which must be fed to ammoniator-granulator to produce diammonium phosphate, is recovered by scrubbing the off gases with the acid to be used in the process. The granular product is normally dried and in most plants cooled, and screened, having the undersized and crushed oversized recycle to the granulator to control granulation [7]. Two important features of this process of this process are as follows: 1) The heat of reaction of ammonia and phosphoric acid is used to evaporate water in the neutralizer.

18

2) Advantage are taken of the maximum solubility of the ammonia/phosphoric acid mole ratio of about 1.45 therefore, the pre neutralizer is operated at as near this point as is practical to obtain the most concentrated slurry having satisfactory fluidity. This slurry can either flow by gravity into a saw tooth weir pipe for distribution in the ammoniatorgranulator, or be pumped into a spared spray system located over the moving bed of dry recycle inside the ammoniator-granulator. The latter procedure has proved most satisfactory. It provides more consistent control and better slurry distribution. Ammoniation of the slurry in the ammoniator granulator drum to a mole ratio of 2.0 lowers the solubility and cause crystallization of the diammonium phosphate. This decreases the amount of the liquid phase present, thereby lowering the recycle requirement [8]. Because it is possible to crystallizer pure ammonium phosphate from solutions containing a different ratio of ammonia-to-phosphoric acid to that of pure compound, commercial production of diammonium phosphate become practical. When the two salts, MAP and DAP, are mixed in approximately the percentages by C, the solubility of the combined salts is much greater than for either of the compounds at the same temperature. The relationships are similar for the other temperatures [6]. Some of the plants originally equipped with blungers have been modified to use TVA-type rotary ammoniator instead of blunger. Plants built in the United States in the recent years use the TVA-type rotary ammoniator-granulator [6].

2.7.5 Selection of Process: The best process for DAP production is the TVA granulation process. The advantages of the process with individual equipment are described below [7]:

2.8 Raw Materials: There are two main raw material needed for the production of Diammonium Phosphate. 1. Phosphoric Acid (H3PO4) 2. Anhydrous Ammonia (NH3)

19

2.9 Sources of raw materials: The sources of raw materials are as follows: 1. Phosphoric Acid is obtained from phosphate rock. 2. Ammonia required is obtained from natural gas.

2.10 Preparation of raw material: This section gives a brief account of the preparation of the raw materials required for the production of Diammonium phosphate from their naturally occurring sources.

2.10.1 Phosphoric Acid: The formation of phosphoric acid from phosphate rock is described below.

2.10.1.1 Phosphate rock and its mining: Phosphate rock is a non-detrital sedimentary rock which contains high amounts of phosphate bearing minerals. The phosphate content of Phosporite is at least 15-20%. Which is a large enrichment over the typical sedimentary rock content of less than 0.2%. The phosphate is present as fluorapatite Ca3 (PO4)3F (CFA) typically in cryptocrystalline masses (grain sizes < 1µm) referred to as cellophane. It is also present as hydroxyapatite Ca5 (PO4)3OH, which is often dissolved from vertebrate bones and teeth, whereas fluorapatite can originate from hydrothermal veins. Other sources also include chemically dissolved phosphate minerals from igneous and metamorphic rock. Phosphorite deposits often occur in extensive layers, which cumulatively cover tons of thousands of square kilometers of the Earth’s crust. Phosphate rock is typically found an average of 25 feet beneath the ground’s surface. The phosphate matrix is a mixture of pebbles, sand and clay. The sandy layer of soil covering this matrix is removed by electrically operated draglines. A dragline is powerful machine that digs phosphate rock around the clock. The draglines equipped with large buckets then dig the matrix and deposit the materials into a shallow containment area called a well. Here high pressure water guns controlled by operators in a portable pit car, liquefy the materials into a watery mixture called slurry. The material is then transported through pipeline to a beneficiation plant.

20

The washer is the first step in separating phosphate from the clay and sand. Here large clay balls are mechanically disintegrated in equipment called log washers. The materials then moves through a series of vibrating screens (+16 meshes) where it is cleansed of clay and the pebble sized phosphate is recovered as a finished product. The pebble is moved to dewatering tanks and the inventory pile by conveyors. The sand and the fine particles of phosphate called concentrate are retained for flotation processing. The clay that has been separated from the matrix is pumped through pipelines to storage ponds (clay setting ponds), where the clay slowly settles to the bottom. At the flotation plant reagents are mixed with the concentrate. This process separates the two components. The sand is transported by pipelines to the mine for use in land reclamation. The phosphate concentrate is sent to dewatering tanks and then to the inventory pile.

2.10.1.2 Phosphoric acid synthesis: Phosphoric acid can be made by two processes.

Electric Furnace Process: This process involves the electric furnaces melting of the ore using coke and silica to produce elemental phosphorous, which is then converted to phosphoric acid by first oxidizing (burning) to it to produce P2O5 and then absorbing P2O5 in water. This process results in a food grade acid of high purity that has been proven to be too expensive for general fertilizer use. The following reactions are considered to take place. Ca.F2.3Ca (PO4)2 + 9SiO2 + 15C 4P + 5O2

2P2O5

P2O5 + 3H2O

2H3PO4

CaF2 + 6P + 15CO

21

Wet Process for Phosphoric acid: This process involves an initial step in which the ore is solubilized in sulfuric acid, because of this requirement for this acid it is obvious that sulfur is a raw material of considerable importance to the fertilizer industry. The acid rock reaction results in formation of phosphoric acid and precipitates of calcium sulfate. The second principle step in the wet process is filtration to separate the phosphoric acid from the precipitated calcium sulfate. Wet process phosphoric acid is much less pure than electric furnace acid, but for most fertilization production the impurities such as iron aluminum and magnesium are not objectionable and actually contribute to improve physical condition of the finished fertilizer. Impurities also furnish some micronutrient fertilizer elements. The chemistry of phosphoric acid manufacture and purification is highly complex, largely because of the presence of impurities in the rock. The main chemical reactions in the acidulation of phosphate rock using sulfuric acid to produce acid.

22

CHAPTER 3

Description of Process Flow Diagram:

3.1 Process Details: A flow diagram of the process Tennessee Valley Authority (TVA) process for the production of granular DAP being used in this plant is displayed in process diagram. Any referrals made to the flow sheet in the following passages of process description would refer to this diagram. The following passages give a detailed description of the flow sheet. The manufacture of DAP starts with the provision of raw materials of the desired grade. For a quality product of the raw materials should be free from any impurities which in reality is not 100% possible. Details of the grade of raw materials being used for DAP production are given below.

3.1.1 Ammonia: Ammonia being used is anhydrous, 99.5% pure and having a nitrogen content 82.4%.

3.1.2 Phosphoric Acid: Phosphoric acid being used is merchant grade having 52% P2O5 content and containing 1217% impurities. The exact composition of phosphoric acid in the feed is: H3PO4 =

71.77%

H2O

=

13.187%

Inert

=

15.043%

(P2O5 = 52%)

23

3.1.3 Pre Neutralizer: With a single reaction tank, the anhydrous ammonia is normally feed at from 2-4 location around the circumference in the lower portion of the tank. Either liquid or vaporized ammonia is used in as much as heat and additional equipment is normally required to vaporize the ammonia. The phosphoric acid is normally fed from source as 54% P2O5 content. This varies in this range depending on the source of rock used in making the wet process phosphoric acid, which in turn varies the impurities entering with the acid. The mole ratio of ammonia to phosphoric acid is normally held between 1.4 and 1.45. This will normally give the maximum solubility for the slurry. The temperature of the slurry is normally maintained at about 115.5 oC. For operating control the mole ratio is determined by periodically checking the pH of slurry samples. At a mole ratio of 1.45 some free ammonia is lost in the steam from the pre neutralizer. Therefore, the exhaust from the pre neutralizer is scrubbed with acid. One scrubber is generally used for the pre neutralizer and ammoniator-granulator. The slurry containing between 16 and 20% water is normally pumped to a spray header in the ammoniator-granulator. In the early systems the pre neutralizer tank was located above the ammoniator-granulator, which permitted gravity flow of the slurry to the ammoniatorgranulator [8].

24

3.1.4 Pipe Cross Reactor: In a pipe cross reactor process, chemical heat of reaction between ammonia and phosphoric acid results in the production of a hot mixture of low moisture melt and steam. This melt is used to cause granulation, having an emission temperature between 115.5 to 137.7oC, instead of steam and water as used in the conventional process. The pipe cross reactor is a reaction tube mounted so that the acids, ammonia and water are added in a section just outside the feed of the rotary ammoniator-granulator and having the reaction tube extending into the ammoniator-granulator for discharge onto a moving bed of dry material [7]. Ammonia and water are mixed before entering through a smaller tube at the feed end of the reactor. This tube extends beyond the section where the acids are added and mixed before reacting with the ammonia. Phosphoric acids is introduced through lines installed perpendicular to the reactor tube. The water introduces a smoother reaction between the ammonia and acid. By the reacting these materials inside a confined area, much of the chemical heat of reaction is retained to vaporize most of the water entering with the ammonia and acid, this water is removed in the exhaust gases from the granulator. The temperature of the melt is well above its normal melting point when it is discharged. Pressure from the reaction provides good distribution of the near anhydrous melt as it leaves discharge section of the pipe reactor. The basic advantage of the pipe cross is that a higher percentage of the heat of reaction of ammonia with acid can be used to evaporate water entering with raw material and still provide a proper fluid state to build product size granules when the material is discharged on to a bed of moving fine recycling material without problem in distributing and transferring the low moisture melt from the reactor [8].

3.1.5 Ammoniator Granulator: The advantages reported for the ammoniator granulator [7]. 1. Power requirements are generally lower to blunger. 2. Maintenance costs, especially in replacement of paddles or blades are lower as compared to the blunger. 3. It is easy to provide effective fume removal. 4. Even distribution of liquids under the bed is easier than blunger.

25

Less recycle is required rather than the blunger type this reduces the requirements for subsequent operations such as drying, cooling, sizing and recycles handling with considerable increases in the cost of energy in recent years this becomes an important consideration [6]. The partially reacted product mono ammonium phosphate from the pipe reactor is directly sprayed into the ammoniator granulator through the slotted discharge of the pipe reactor. As the pipe reactor is placed inside the ammoniator granulator thus no pumping equipment is required. The ammoniator granulator is an inclined rotating drum in which the slurry from the reactor is sprayed on a bed of ammonium phosphate solids and recycled under-sized Dap granules from the screens. The partially reacted reactor product is produced to completion by further ammoniation to diammonium phosphate in the ammoniator granulator by using additional anhydrous ammonia which is sparged from beneath the bed by using a sparger. Overall NH3:H3PO4 mole ratio is brought to 2. This granulator drastically decreases ammonium phosphate solubility and this promotes solidification and releases further heat of reaction which volatilizes additional moisture. Beside the formation of granules from the reactor slurry the undersized granules from the screens are coated by the slurry which also contributes to granule formation and growth. The recycle rate of undersized product to the granulator in process is 1.5 kg per kg of product. Variation of this recycle rate is principle control over granulation efficiency in the drum. Some quality of sulfuric acid is also added to the granulator to adjust the grade of the DAP of the DAP by reacting more readily with ammonia than phosphoric acid thus reducing the percentage of P2O5 in the final product. The motion of the granulator causes the rolling slurry and solids to turn into granules and the angle of the granulator and its angular speed is critical to product flow rate and most importantly in maintaining the size range of the granules. The Diammonium phosphate granules from the ammoniator granulator are at a temperature of 98oC and contain a moisture content of about 3.5%. The product from the granulator needs drying which is sent to dryer. In both the pipe cross reactor and rotary ammoniator granulator the absorption of feed ammonia is incomplete thus acid scrubbing of the effluent vapors from these units is an important feature of the process. The effluent vapors from the granulator also contain water vapors evaporated in the reactor and the granulator. The ammonia vapors are absorbed and neutralized in the scrubber by diluted phosphoric acid having a P2O5 concentration of 35% which is achieved by diluting feed phosphoric acid having P2O5 concentration of 52% through water as seen in the flow sheet. The partially ammoniated phosphoric acid is then recycled back to the pipe cross

26

reactor and thus becomes one of the two phosphoric acid streams as mentioned earlier and also visible from the flow sheet. The water vapors are expelled as off gases. The granular diammonium phosphate from the granulator is sent to the rotary cooler where they are cooled by contacting them counter currently with ambient air at a temperature of 35oC. Through this cooling operation some moisture is also lost rendering the cooled product to have a moisture content of 2%. The Diammonium phosphate granules are then sent to the screens where they are screened for size. The undersized granules are recycled back to the granulator where they are coated with the reactor slurry to increase their size. While the oversized granules are sent to the crusher where they are crushed and again sent back for screening. The desired sized granular ammonium phosphate is sent to the packaging and storage section.

27

28

CHAPTER 4

Material Balance:

Material Balance for the Production of 1500 Tons per Day of Diammonium Phosphate Capacity = 1500 TPD = 62500 Kg/hr

Composition

%

Amount (Kg/hr)

(NH4)2SO4

12%

7500

Moisture

1%

625

Inert

5%

3125

DAP

82%

51250

Total

100%

62500

4.1 Material Balance across Screen 2

Screen 2 PRODUCT Assuming 30% of the total input is going out as fines Total Input =

Output/0.7 = 62500/0.7 =

89285.71 Kg/hr

Undersize =

In – Out =89285.71-62500 = 26785.71 Kg/hr

29

30

4.2 Material Balance across Screen 1:

Assuming 25% Over Size and 20% Undersize Total (Oversized + Undersized) =

45%

Total Input = Output/0.55 =

89285.71/0.55 =

Oversized =

162337.65 x 0.25 =

27056.28 Kg/hr

Undersized = 162337.65 x 0.20 =

21645.02 Kg/hr

162337.65 kg/hr

4.3 Material Balance across Dryers:

Outputs of Dryers to Screens =

162337.65 Kg/hr

1.5% of the output going to the Dryer Cyclone Total Output from Dryer =

162337.65/0.985 =

164809.79 Kg/hr.

Input of Dryer Cyclone =

164809.79 - 162337.67 =

2472.14 Kg/hr.

31

Assume That 1% Moisture is Present in Product Amount of Moisture in Output =

0.01 x 164809.79 =

1648.09 Kg/hr.

Dry Output with Out moisture =

164809.79-1648.09 =

163161.7 Kg/hr

Input of Dryer with 4% Moisture = 163161.7/0.96 =

169960.10 Kg/hr

Moisture Removed =

5150.3 Kg/hr

169960.10-164809.79 =

Product (NH4)2SO4 = 164809.79 x 0.12 =

19777.17 Kg/h

Inert =

164809.79 x 0.05 =

8240.48 Kg/h

Moisture =

164809.79 x 0.01 =

1648.09 Kg/hr

DAP =

164809.79 x 0.82 =

135144.02 Kg/hr

4.4 Material Balance across Granulator:

For Recycle Stream: Recycle Stream

=

Output of Dryer-Product

DAP

= 135144.02 – 51250

= 83894 Kg/hr

Moisture

= 1648.09 – 625

= 1023.09 Kg/hr

Inert

= 8240.48 – 3125

= 5115.4 Kg/hr

(NH4)2SO2

= 19777.17-7500

= 12277.1 Kg/hr

Total =

102309.06 Kg/hr

32

Output of the Granulator =

169960.10 Kg/hr

DAP =

135144.02 Kg/hr

Moisture =

6798.4 Kg/hr

Inert =

8240.48 Kg/hr

(NH4)2SO4 =

19777.17 Kg/hr

Amount of DAP produced in the Granulator: Output – Recycle =

51250 Kg/hr

Amount of (NH4)2SO4 Produced in Granulator: Output - Recycle =

51250 Kg/h

(NH4)2S04 produced in granulator

7500 Kg/hr

Molecular mass of DAP =

132.07 Kg/Kmol

Moles of DAP produces =

51250/132.07 =

388.05kmol/hr

Reaction: (NH4)H2PO4 + NH3

(NH4)2HPO4

MAP

DAP

+ Ammonia

From the Equation of the Phosphoric Acid and Ammonia Required: Moles of H3PO4 and NH3 consumed =

388.05 Kmol/hr

Phosphoric Acid Consumption =

388.05 x 98 =

38028.9 Kg/hr

Ammonia Consumption =

388.05 x 17.03 =

6608.8 Kg/h

33

4.5 Material Balance across Pre Neutralizer:

H3PO4 + NH3

NH4H2PO4

From Previous Calculations 388.05 Kmol/hr of Phosphoric Acid produced 388.05 Kmol/hr of MAP According to stoichiometry The mole ratio in Pre Neutralizer in the ratio NH3

:

H3PO4

1.45

:

1

Moles of Ammonia in the Pre Neutralizer = 388.05 x 1.45 =

562.67 Kmol/hr

At this ratio the 90% of the phosphoric acid is consumed in the Pre neutralizer

Phosphoric Acid Consumed =

349.245 Kmol/hr

Hence Moles of MAP Produced =

349.245 Kmol/hr

Moles of NH3 Consumed=

349.245 Kmol/hr

Molar mass of MAP =

115.02 Kg/Kmol

34

Amount of MAP =

349.245 x 115.02 =

40170 Kg/hr

Amount of NH3 Consumed =

349.245 x 17.031=

5947.99 Kg/hr

Moles of NH3 leave the Pre Neutralizer =

562.67 - 349.245 =

213.425 Kmol/hr

Amount NH3 leave the Pre Neutralizer =

213.425 x 17.031 =

3634.84 Kg/hr

Moles of H3Po4 leaves Pre neutralizer =

388.09 - 349.245 =

38.805 Kmol/hr

Amount of Phosphoric Acid =

38.805 x 98 =

3802.89 Kg/hr

Amount of H2O Required in Pre Neutralizer =40170 x 100/275 =

14607.270Kg/hr

Assumption 100 Kg H20/1000 Kg of MAP Production Required Amount of water Evaporated =

4017 Kg/hr

Water going to PCR =

14607.27 - 4017 =

Amount of Inert enter in Pre Neutralizer =

3125 Kg/hr

10590.2 Kg/hr

4.6 Material Balance across Pipe Cross Reactor:

Remaining phosphoric acid of 95% reaction of MAP Production Complete in PCR

Ammonia is excess to H3PO4: Moles of MAP Produced =

38.805 x .95

=

Amount of MAP =

36.8647 x 115.02 =

Moles of NH3 Consumed =

36.8647 Kmol/hr

Amount of NH3 =

36.8647 x 17.031 =

36.8647 Kmol/hr 4240.18 Kg/hr

627.8427 Kg/hr

35

Total MAP =

4240.18.33 + 40170 =

44410.18 Kg/hr

Ammonia leaves the Pipe cross reactor =

3634.84 - 627.8427 =

3011.99 Kg/hr

Make up water adding PCR =

4240.18.35 x 100/275 =

1541.88 Kg/hr

Water Evaporated From Pipe Cross Reactor: Water evaporated from PCR =

424.018 Kg/hr

Water output from PCR =

10590.27+1541.88-424.018 =

11708.132 Kg/hr

Manipulation Across Granular: To maintain ratio NH3: H3PO4 (2:1) Amount of NH3 Required =

776.04 Kmol/hr =

13216.73 Kg/hr

Reaction: NH4H2PO4 + NH3

(NH4)2HPO4

H2SO4

(NH4)2SO4

+ NH3

Molecular Mass of (NH4)2SO4 =

132.154 Kg/Kmol

Moles of (NH4)2SO4 Produced =

7500/132.154 =

Moles of H2SO4 Consumed =

56.75 Kmol/hr

Amount of H2SO4 consumed =

56.75x98 =

Moles of NH3 Consumed =

56.75 Kmol/hr

Amount of NH3 Consumed =

56.75x17.031=

Amount of NH3 from PCR =

3011.99 Kg/hr

Amount of NH3Coming from the Storage = 13216.73 – 3011.99 =

56.75 Kmol/hr

5561.5 Kg/hr

966.51 Kg/hr

10242.6Kg/hr

36

Amount of ammonia consumed in granulator=6608.8 + 966.51 =

7575.31 Kg/hr

Amount of NH3 goes to the Scrubber =

13216.73 - 7575.31 =

5641.42 Kg/hr

Total Water Input =

1170.81 + 10590.23+1023.9 =12784.94 Kg/hr

Water output =

6798.4 Kg/hr

Water evaporated =

5992.425 Kg/hr

Amount of H2O added in scrubber in NH3 = 2422.215 Kg/hr

Manipulation across Pipe Cross Reactor: Total Amount of NH3 required in Pre neutralizer = 562.67 x 17.031=

9582.83 Kg/hr

NH3 coming from Storage =

9582.83 - 5641.42 = 3941.41 Kg/hr

Total Water Required in Pre Neutralizer=

14607.27 Kg/hr

H20 Coming from Source =

14607.27 - 2422.21= 12185.055 Kg/hr

37

CHAPTER 5

Energy Balance

Reference Temperature =

25˚C =

298.15 K

5.1 Energy Balance across Pre Neutralizer:

Heat In: Heat in by NH3 from Storage =

3941.41x4.96 (238.65 - 298.15) =

Heat in by H3PO4 from storage=

38030.80x2.7709 (333.15-298.15) = 3688284.03 KJ/hr

Heat in by H2O from storage =

12185.055x 4.18(333.15-298.15) = 1782673.54 KJ/hr

Heat in by inert Gypsum with H3PO4 from storage = =

-1163188 KJ/hr

3125x1.09 (333.15-298.15) 119218.75 KJ/hr

Heat In by NH3 from Scrubber =

5641.42x2.17 (343.15-298.15) =

550884.66 KJ/hr

Heat in H2O from Scrubber =

2422.15x4.60 (343.15-298.15)

501385.05KJ/hr

Heat generated by Production of MAP =

4070x1339.78 =

53818962.6 KJ/hr

38

Heat Out Heat out with NH3 to PCR =

3634.84x2.17 (413.15-298.15) =

Heat Consumed to take NH3 from 238.65 to 306.45 K = =

907074.32 KJ/hr

3941.41x2.09 (238.65-306.45) 558505.67 KJ/hr

Heat Consumed to Vaporize ammonia =3941.41 x 753.624 =

2970341.17 KJ/hr

Heat out by Inert =

3125x1.09 (413.15-298.15) =

391718.75 KJ/hr

Heat out with H3PO4

3802.96 x 2.6221(413.15-298.15) = 1146729.15 KJ/hr

Heat out with MAP =

40170x1.21 (413.15-298.15)

5178515.5 KJ/hr

Heat out H2O evaporated=

4017x1.9 (413.15-298.15) =

877714.5 KJ/hr

Heat out H2O goes to PCR =

10590.27x3.97 (413.15-298.15) =

4834987.7 KJ/hr

Heat Required for Phase change of H2O =4017x1737.5=

6979537.5KJ/hr

5.2 Energy Balance across Pipe Cross Reactor:

Heat in from the neutralizer =

22967709.76 KJ/hr

Heat in by heat at 298.15 from storage =1541.88 x 4.17(298.15-298.15)

= 0 KJ/hr

Heat generated to produce MAP =

4240.18.35x1339.78

=5681846.20 KJ/hr

Heat Out with NH3 =

3011.99x 2.09(393.15-298.15)

=598030.61 KJ/hr

Heat out by Inert =

3125x 1.09(393.15-298.15)

=323593.75 KJ/hr

Heat out with MAP =

44410.18x 1.12(393.15 - 298.15)

=4725243.15KJ/hr

39

Heat out with H2O evaporated =

424.08 x 1.9 (393.15-298.15 )

Heat out H2O goes to granulator =

11708.132x 4.17(393.15-298.15)

5.3

=76546.44 KJ/hr =4638176.49 KJ/hr

Energy Balance across Granulator:

Heat In Heat In From PCR to Granulation Excluding Heat of Content with H2O Evaporated= 10324553.07 KJ/hr Heat In by NH3 from Storage=

10242.6 x 7.11(238.65- 298.11) =

4333080.7 KJ/hr

Heat In by H2SO4 from storage=

5561.5x1.42 x (313.5-298.15) =

276406KJ/hr

Heat in by DAP of Recycle Stream =83894x1.88x (343.15-298.15) =

7097432.4 KJ/hr

Heat In by (NH4)2SO4 of Recycle Stream = 12277.13x 1.64x (343.15-298.15) = 906055.14 KJ/hr Heat in by Inert of recycle stream = 5115.48x 1.09x (343.15 - 298.15) = 250914.29KJ/hr Heat in by moisture of recycle stream = 1023.09x 3.98(343.15 - 298.15) = 183235.4KJ/hr Heat generated by DAP production

= 51250x544.28

= 27894350KJ/hr

Heat out Heat out with NH3 to scrubber =

5641.42x2.09 (363.15 - 298.15) =

766386.9KJ/hr

Heat consume to vaporize moisture = 10242.6x753.624 =

7719069.1KJ/hr

Heat out by Inert =

583838KJ/hr

8240.48x1.09 (363.15 - 298.15) =

40

Heat consumed to take NH3 from 238.65 to 298.15K

= 10242.62x2.302 (298.15 - 238.65) = 1402918.6KJ/hr

Heat out with DAP

=135144.02 x 1.121 x (363.15 - 298.15) = 10629077.17KJ/hr

Heat out with moisture goes to Dryer =6798.4x4.17 (363.15 - 298.15) =

1842706.32KJ/hr

Heat out with (NH4)2SO4 =

19777.17x1.632 (363.15 - 298.15) = 2097962.194KJ/hr

Heat out with H2O evaporated=

5992.425x4.17 (413.15 - 298.15) = 2873667.4KJ/hr

Heat required for phase change of H2O = 5992.425 x 1737=

10408842.2KJ/hr

Heat consumed to vaporize water = 5992.425 x 753.6=

4515891.4KJ/hr

41

5.4 Energy Balance across Dryer:

Heat In from granulator =

39966691.8 KJ/hr

Heat in by Air =

1000x1.04 (433.15-29185) =

Total Heat in =

40107091.8 Kg/hr

140400 KJ/hr

Hot Out Heat consumed by water by

5150.31x4.18 (413.15-363.15) =

1076414.7 KJ/hr

Heat Consumed to vaporize =

5150.31x1737=

5977342 KJ/hr

Heat out By DAP=

135144x1.12 (393.15-298.15) =

1437932.6 KJ/hr

Heat out by (NH4)2SO4 =

19777.17 x 1.63 (393.15-298.15) = 3062494.7 KJ/hr

Heat out by inert=

8240.48x1.09 (393.15-298.15) =

853301.7KJ/hr

Heat out by Air =

1000x1.04 (365.15-298.19) =

69680 KJ/hr

Heat out by Moisture =

1648.09x4.18 (393.15-298.11) =

654456.5KJ/hr

Total Heat Out =

13131622.2 KJ/h

42

43

CHAPTER 6

Designing

6.1 Centrifugal Pump Design Phosphoric acid pump form storage to reactor: For phosphoric acid: Mass flow rate

=

m

=

43670 kg/hr

m

=

12.15 kg/sec

=

⍴

=

1579 kg/m3

Volumetric flow rate =

u

=

0.00769 m3/sec

μ

=

9.4 cSt

=

9.4 × 10-6 × 1579

=

0.014796 Ns/m2

Density

Kinetic Viscosity (at 25 oC)

=

Dynamic Viscosity

=

Optimum pipe diameter: Dia opt

Area

=

=

293 m0.53 (density)-0.37

=

293 (12.15)0.53 (1579)-0.37

=

72.15 mm

=

π/4 D2 =

π/4 (0.07215)2

=

4.086 × 10-3 m2

0.07215 m

44

Static and Dynamic Head Calculation: Dynamic Head: Using the equation given below:

𝑙 ⍴𝑣 2 ∆𝑃𝑓 = 8𝑓( )( ) 𝑑 2 Velocity

=

u

Reynolds’s Number =

=

flow rate / area

=

0.014796 / 4.086×10-3

=

3.62 m/s

Re

=

(Density × Dia × velocity) / viscosity =

(1579×0.07215×3.62) / 0.00769

=

53629

=

5 × 104

Relative Roughness: For commercial steel pipe Absolute roughness

=

0.046 mm

Relative roughness

=

A.roughness / Dia

=

0.046 / 72.15

=

6.37 × 10-4

=

f

0.0025

From graph in Coulson & Richardson Vol 6. Pipe friction factor

=

=

6.37 × 10-4

45

Table 6.1: Miscellaneous Losses Fitting Valve

Number of

No of Equivalent Pipe Diameters

Sharp Reduction

1

25 × 1

25

1

50 × 1

50

45o standard elbow

3

15 × 3

45

Gate valve ½ open

1

200 × 1

200

NRV

1

18 × 1

18

(Tank Out) Sharp Expansion (Tank In)

Total: = Effective length

=

338 × dia

Assume Pipe Length Total Length

=

338 × 0.07215

=

24.385 m

=

25 m

=

E.lenght + A.length

=

25 + 24.385

=

49.385m

=

338

49.5 m

Now, putting all values in equation (A), So, we get Dynamic Head

=

ΔPf

= 8f × (L/D) × Density × (velocity2 / 2) = 8(0.0025)×(49.5/0.07215)×1579×(3.622/2) = 141960 N/m2

or Pa

46

Static Head: Δz

Suppose: Static Head

=

ΔP

=

10 m

=

(P2 – P1) =

217680 N/m2

Energy Balance Equation:

𝑔∆𝑧 +

∆𝑃 ∆𝑃𝑓 − −𝑊 =0 ⍴ ⍴

(9.8 × 10) + (217680 / 1579) ̶ (141960 / 157\9 )

=

W

So, Work

=

W

=

145.9 J/kg

Efficiency of pump

=

57 %

Power

=

(W × m) / efficiency

Power

=

(145.9 × 12.15) / 0.57

Power

=

3109.5 watt

≈

3.1 Kwatt

Pump Efficiency: From Graph:

Pump Power:

Pump Head: Head

=

(ΔPf / (9.81 × density)) + (ΔP / (9.81 × density)) + Δ z

Head

=

9.16

=

33.2 m

+

14.06 +

10

47

Pump RPM: From Graph: Single Stage Pump with 3500 rpm. Net Positive Suction Head (Available): 𝑁𝑃𝑆𝐻(𝑎) =

𝑃𝑓 𝑃 𝑃𝑣 +𝐻− − ⍴∗𝑔 ⍴∗𝑔 ⍴∗𝑔

Where

NPSHa

P

=

Atmospheric Pressure

Pf

=

Dynamic Head

Pv

=

Vapor Pressure

=

(101325/9.81*1579)+10-(141960/9.81*1579)-(933.26/9.81*1579)

=

6.56+10 ̶ 9.164 ̶

=

7.336 m

0.060

48

6.2 Pre Neutralizer Design:

Reactants

Mass Flow Rate

Density

Volumetric Flow Rate

( kg/hr)

(kg/m3)

(m3/hr)

NH3

9565.39

610

15.68096

H3PO4

38028.9

1579

24.084167

Water

14607.27

997

14.65122

Inert

3125

2320

1.346982

Total

55.763329

Reaction Involved: NH3+ H3PO4

NH4H2PO4

Reaction Kinetics: Temperature in Reaction

= 394.11 K

Pressure in Reactor

= 40 psig

Rate of Reaction

= 1.169 Kmol/m3sec

= 2.72 atm

Order of Reaction

=

2nd Order Reaction

Limiting Reactant

=

Phosphoric Acid H3PO4

Calculation Based upon Phosphoric Acid: (Limiting Reactant) Moles of H3PO4 = n= 388.9 Kmol/hr Volumetric flow rate of H3PO4 = Vo

= 24.084167 m3/hr

Initial Concentration of H3PO4 = CAo

= 16.1122 Kmol/m3

Final Concentration of H3PO4 = CA

= 0.83 Kmol/m3

49

Volume of Reactor: Now by using Residence Time Equation: Residence Time = t=

V= V=

𝑉 𝑉𝑜

=

CAo.𝑋A

[16]

−𝑟A

VoCAo.𝑋A −𝑟A 0.15489×16.1122×0.9 1.169

Volume of Reactor =V = 1.86 m3

Length and Diameter of Reactor: The typical length to diameter ratio L/D is: 1.6 L/D=1.6

(Range: 0-5 for low Pressure)

L=1.6 D Volume of reactor = V = 1.86 =

𝜋𝐷²𝐿 4

𝜋𝐷²1.6𝐷 4

Diameter of Reactor =

D =1.15 m

Length of Reactor =

L = 1.85 m

Residence time = 𝜏 =

𝑉 𝑉𝑜

=

𝑉 0.15489

6.2.1 Agitator Design: Impeller to tank Diameter ratio= 0.4

= 12.5 sec

50

Di = 0.4D Di = Impeller Diameter D = Diameter ofTank Di = 0.4×1.15 Di = 0.46 m Power Number = Np = KReFr =

Reynold Number = Re =

Froude Number = Fr =

𝑃 𝐷⁵𝑁ᵌ𝜌

𝐷𝑖²𝑁𝜌 𝜇𝑧

𝐷𝑖𝑁² 𝑔

P = Power of Shaft, W, K= a constant depends on agitator type, size, and tank geometry ρ = Fluid Density, kg/m3 μ = Fluid Viscosity Ns/m2 N = Agitator Speed s-1 (Revolutions Per Second)(rps) Di = agitator Diameter, m, g = gravitational constant, 9.81 m/s2 ƿ = Blade Pitch ƿ

𝐷𝑖

=1

Ƿ = 0.46m Np = 0.19 (From Power Correlation Graph Coulson Vol.6 Figure: 10.85) 0.46²×16.666×1178.75

Re =

Re = 845

4.9215

51

Fr =

0.46×16.666² 9.81

Fr = 13 So power required = P = Np×N3×Di5×ρ P = 0.19×16.663×0.465×1178.75 P = 21348.4 W

52

6.3 Pipe Cross Reactor Designing:

Reactants

Mass Flow Rate

Density

Volumetric Flow Rate

( kg/hr)

(kg/m3)

(m3/hr)

NH3

3634.84

610

5.8626

H3PO4

38028.9

1579

2.4084

Water

14607.27

997

12.2497

Inert

3125

2320

3.551

MAP

40170

1800

22.3167

Total

46.3884

Total volumetric flow rate of reactants

= Vo

= 46.3884 m3/hr

Temperature in reactor

=150oC

= 423 K

Pressure in reactor

= 60 psig

= 4.08 atm

REACTION: NH3 + H3PO4

NH4H2PO4

Reaction takes place in reactor with ratio NH3

:

H3PO4

1.45

:

1

[12]

Limiting Reactant

= H3PO4 (phosphoric acid)

Order of reaction

= 1st order reaction

53

Phosphoric acid is our limiting reactant.so calculation based on the phosphoric acid. Moles of phosphoric acid

= 380.89/97

Volumetric flow rate of H3PO4

= 2.4084 m3/hr

Initial concentration = Co

= 39.205/2.4084

Final concentration

= Co (1 - X H3PO4)

= C H3PO4

= 39.205 Kmol/hr

= 16.28 Kmol/m3

Assume change in concentration is negligible. Final concentration

= C H3PO4

C H3PO4

= 16.11 (.001)

= Co (1 – X H3PO4)

= .01611 Kmol/m3 From the Arrhenius equation. 𝐾 = 𝐴𝑒𝐸𝑎/𝑅𝑇 Rearrange the Arrhenius equation. 𝑙𝑛𝐾 =

𝐸𝑎 + 𝑙𝑛𝐴 𝑅𝑇

Assume the granulation of MAP fertilizer has the same factors for the pipe cross reactor.[18] Ea=44.2 kJ/mol A = 1.08 x 10-5 sec-1 Arrhenius equation. 𝑙𝑛𝐾 =

lnK = 0.86 K = 2.41 sec-1

𝐸𝑎 + 𝑙𝑛𝐴 𝑅𝑇

54

We developed rate equation.[16] Rate of reaction

= K Ca

Rate of reaction

=K Co (1 – X H3PO4)

Rate of reaction

=3.88 x10-2 Kmol/m3sec

C NH3

= Moles of NH3 /Volumetric flow rate

Moles of NH3

= 3634.8=/17.031

= 213.8 Kmol/hr

Volumetric flowrate

= 5.8626

= 36.4701 Kmol/m3

Simpson 1/3 rule.

𝑉=

ℎ 𝐹𝑎𝑜 4𝐹𝑎𝑜 𝐹𝑎𝑜 [ + + ] 3 −𝑟𝑎 𝑥 = 0 −𝑟𝑎 𝑥 = .045 −𝑟𝑎 𝑥 = .09

V=0.492 m3 V= 492000cm3

Residence time: t

= V/Vo

t

= (0.492) / .01289

t

= 38 sec

From the manual of designing L/D ratio:[13] L/D

= 36

L

= 36D

(taken from design parameters for pipe cross reactors)

55

Volume of Reactor: Volume of Reactor

= π/4 (D2 x 36D) = 3.14/4(36D3)

0.492 = 3.14/4 x 36 D3

Further calculation: D

= 0.2591 m

= 25 cm

L

= 9.32 m

= 932 cm

Area of the sparger [19] Area=length x Diameter Length = .5 D Length = 12.5cm Diameter= .25D Diameter= 6.25 cm Area of the sparger. Area = 78 cm2

Material of construction of pipe cross reactor is 316 L stainless steel.

56

6.4 Dryer Design

Design Steps: •

Dryer Heat Duty

•

Air Needed

•

Dryer Diameter

•

Dryer Length

•

Dryer Speed

Dryer Heat Duty: Given Feed Conditions: Mass flow rate of feed

= 169960.1 Kg/hr

Mass Flow Rate of solid Granules (ms)

= 163161.69 Kg/hr

Initial Moisture Contents: (XA)

= 4%

Final Moisture Contents: (XB)

= 1%

Temperature of Granules before Drying Tsa = 95°C Temperature of Granules after Drying Tsb

= 110°C

Air Properties: Ambient air conditions: Dry bulb temperature = 30°C Wet bulb temperature = 22°C Relative Humidity of Entering Air Hb = 0.015 Kg of moisture/Kg of dry air Dry bulb Temperature Entering Air Thb = 160°C Wet bulb temperature of entering air Twb = 75°C

Temperature of air at exit = Tha

NTU= ln (Thb – Twb) / (Tha – Twb)

57

NTU range is 1.5 to 2.5 NTU = 1.8 By putting the values Tha = 90°C Latent heat of vaporization = 998.2 BTU/lb

Rate of heat transfer: mv= ms (Xa – Xb) mv = 163161.69 ( 0.04 – 0.01) mv = 5098.8 Kg/hr

Heat Duty for the dryer:

Cp for solid granules = 1.21 KJ/Kg.K Cp for vapours

= 1.89 KJ/Kg.K

Cp for water

= 4.28 KJ/Kg.K

By putting all of the values in the heat duity equation Heat duity, Qt = 448589.87 KJ/hr

Mass flow rate of air:

mg(1+Hb) = qt/Csb(Thb – Tha) where, Csb

= Humid heat of gas at inlet

58

mg

= 448589.87/ [ 1.068 * 1.015 * (70)]

mg

= 499.8ton/day

Diameter of Dryer: Diameter of Dryer = D= (4*S /π)0.5 Mass Velocity of Air in a direct contact rotary dryer is 400-5000 lb/square feet So we take G

= 4500 lb/ft2.hr

So this cross sectional area of dryer at this mass velocity S = 40ft2

Volumetric Heat Transter co-efficient: Ua = 0.5G.67 / D Ua = 13.8Btu/hr.ft3.°F

Length of rotary dryer: Length of Rotary dryer = L = qt /(0.125πDG0.67 ΔT) ΔT

= (Thb –Twb) – ( Tha - Twb) / ln [ (Thb –Twb) / ( Tha - Twb)]

ΔT

= 40.4°C

Length of rotary dryer = qt /(0.125πDG0.67 ΔT) L

= 31ft

59

L/D ratio check: The L/D ratio for the dryer should be between 3 – 10 Therefore our L/D ratio is greater than 3 and lower than 10, so our calculations are true. So dimensions are expectable.

RPM: Assume the peripheral speed of rotation to be 30 ft/min RPM = 30/7.3 = 4.1 The revolution of a drier varies between 2 – 5

No. of flights in dryer: Flights N = 3*D

= 3*7 = 21 flights

60

Designing of Cyclone Separator: Reference Temperature

20˚C

Actual temperature

90 ˚C

Feed Contents

Density

Mass Flow Rate

Volumetric Flow Rate

(Kg/m3)

Total Feed input x Content %

Mass flow rate/Density

Kg/hr

m3/hr

DAP

(82%)

1620

2472.14 x 0.82 = 2027.1542

15.68096

Moisture

(01%)

995.1

2472.14 x 0.01 = 24.7214

24.084167

Inert

(05%)

2320

2472.14 x 0.05 = 123.607

14.65122

(NH4)2SO4

(12%)

1770

2472.14 x 0.12 = 296.6568

1.346982

Total

6705.1

1.49703

Particle Size (µm)

Percentage by Weight less than

70

85

60

70

40

65

25

60

10

35

7

20

4

10

Anticipated particle size distribution Mass Flow rate of air

= 500 tpd

61

Density of Air at 90 oC

= 0.9721 Kg/m3

Volumetric Flow rate

= 500/0.9721 = 21431.2656 m3/hr = 5.95 m3/sec

Design Equation of Cyclone Separator Q=Axv A=Q/v Q= Volumetric Flow rate of Feed A = Area V = Velocity of entering Feed The area of entering feed of higher efficiency Design is: A = 0.5Dc x 0.2Dc A = 0.1 Dc2

…………… (1)

Dc = Diameter of Cyclone Body 0.1 Dc2 = Q/v Particle size: Not less than 90% of the material shall pass through 4 mm IS sieve and be retained on 1 mm IS sieve. Not more than 5% shall be below 1 mm size. As we have to deal with tiny particles and these are expensive and we can't waste this product as it could also be a cause of pollution so we will chose the Design below:

6.4.1 Higher Efficiency Design: Where: d1 = mean diameter of particle separated at the standard conditions at the chosen separating efficiency. d2 = mean diameter of the particle separated in the proposed design at the same separating efficiency. Dc1 = diameter of the standard cyclone = 8 inch (203 mm)

62

Dc2 = diameter of proposed cyclone mm Q1 = Standard flow rate for high efficiency design = 223m3/hr Δρ1 = solid - density difference in standard conditions = 2000 kg/m3 Δρ2 = density difference, proposed design μ1 = test fluid viscosity (air at 1 atm, 20˚C) = 0.018 mNs/m2 μ2 = viscosity proposed fluid

Putting this in eq (1) Standard Velocity

= (223m3/hr) / (0.1x0.04121m2) = 54113.07935 m/hr = 54113.07935/3600 m/sec = 15m/sec

63

Let’s Assume Velocity 15m/sec Diameter of Cyclone Body =

Dc2

= (5.95/1.5)1/2 = 1.999 m

As the Cyclone is for higher efficiency Design: De Width of Gas feed Chamber:

= 0.995 m

= 0.2 x Dc2 = 0.2 x 0.995 = 0.199 m

Height of Gas feed chamber

= 0.5 x Dc2 = 0.5 x 0.995 = 0.4975 m

Length of Cone

= 2.5 x Dc2 = 2.5 x 0.995 = 2.4875 m

Length of separating chamber

= 1.5 x Dc2 = 1.5 x 0.995 = 1.4925 m

Diameter of Gas exit pipe

= 0.5 x Dc2 = 0.5 x 0.995 = 0.4975 m

64

Length of gas exit pipe in the separating chamber

= 0.5 x Dc2 = 0.5 x 0.9990 = 0.4995m

Diameter of solid exit pipe

= 0.375 x Dc2 = 0.975 x 0.995 = 0.373 m

Cyclone Required

= 1.99 / 0.203 = 10

Flow rate per Cyclone = Q2

= 21431.26 / 10 = 2143.126 m3/hr

Δρ2

= solid density - fluid density (Air) = 6705.1 - 0.9721 = 6704.1279 kg/m3

Scaling Factor: d2/d1 = { (Dc2/Dc1)3 x Q1/Q2 x Δρ1/Δρ2 x μ2/μ1} 1/2 Δρ1

= 2000 Kg/m3

μ1

= 0.018 mNs/m2

μ2

= 2.1658

= 1.8 x 10-5 N.s/m2

x 10-5 N.s/m2

d2/d1 = { (Dc2/Dc1)3 x Q1/Q2 x Δρ1/Δρ2 x μ2/μ1} 1/2

65

= {(0.995/0.203)3 x (223/2143.126) x (2000/6704.1279) x (2.1658 x 10-5/1.8 x 10-5)} ½ = 2.095 A2

= Area of exit pipe

= 3.14/4 (0.5 Dc) 2 = 3.14/4 (0.5 x 0.995) = 0.194 m2

As

= Area of Cyclone

= 3.14 Dc x (1.5 Dc + 2.5Dc) = 3.14 (0.995) (1.5 (0.995) + 2.5(0.995)) = 12.43 m2

A1

= Area

of inlet Duct

= 0.2 Dc x 0.5Dc = 0.2 (0.995) x 0.5(0.95) = 0.099 m2

Pressure Drop: Φ

= fc.As / A1

Fc

= 0.005 for Gases

Φ

= fc.As / A1 = (0.005 x 12.43) / 0.099

Φ

= 0.63

𝑟𝑡

𝐷𝑐− 2 = 0.5𝐷𝑐

𝑟𝑒

2.0𝐷𝑐

= 1.8 u1

= (2143.126/3600) x (1/0.99)

66

= 6 m/s u2

= (2143.126/3600) x (1/0.194) = 3.06 m/s

ΔP

= ρf/203 {u12 [1 + 2ϕ2 (2rt/re - 1)] + 2u22} = 0.9721/203 {(6)2 [1 + 2(0.9)2 (2(1.8) - 1)] + 2(3.06)2} = 0.004788 [187.632 + 18.8] = 0.988 milibar [5].

67

6.5 Design of H3PO4 Storage tank: Flow rate

= 38028.9 + 5641.6 = 43670.3Kg/hr

Volumetric flow rate of H3PO4

= 43670.3 / 1579 = 27.66 m3/ hr

Volumetric flow rate

= 27.66 + 3.45 = 31.11 m3/ hr

Assuming: L/D ratio

=2

L

= 2D

Volume

= Area x Length 31.11 = (πD2/6) x 2D

D

= 3.10 m

L

= 6.2 m

Thickness

= Pi x Di/ (2f - Pi)

……………........... (1)

Where, Di

= Internal diameter

Pi

= Internal pressure

f

= Design stress

Now Internal pressure: Internal pressure = Pi = ρgh = 1579 Kg/m3 x 9.8 m/sec2 x 6.19 m = 95785.2 N/m2

68

= 0.9386 atm = 0.0952 N/mm2

For stainless steel: f = 150 N/mm2

Thickness

= Pi x Di/2f - Pi = 0.095 x 3100/ (2 x 150 – 0.095) = 1 mm

Corrosion allowance = 2 mm So Thickness (l)

= 3 mm

Domed Head: We use a standard dished head Crown radius

= RC = Di = 3.10 m

Knuckle radius

= RK = 6% of RC = 0.186 m

Assuming no joints

J= 1

Stress Concentration: Cs

= 1/4[3 + (Rc / Rk )1/2] = 0.25x [3 + 4.08] = 1.77

69

Now Thickness (I)

= Pi x RC x CS/ [2fJ + Pi(CS – 0.2)] = 0.095 x 3100 x 1.77 / [300 + 0.095(1.77 – 0.2)] = 1.8 mm = 2 mm

For standard ellipsoidal head, Thickness

= Pi x Di/ (2f – 0.2Pi)

By putting values, Thickness

= 1 mm

So an ellipsoidal head is most economical, hence we will take thickness as wall 3mm [5].

70

6.6 Sulphuric acid storage tank: Flow rate

= 5561.5 Kg/hr

Mass

= 133476 Kg

Density at 25°C

= 1840 Kg/m3

Volume of H2SO4

= 133476/1840 = 72.54 m3

Design volume will be 12.5% above from the operated volume. Total volume required

= (0.125 x 72.54) + 72.54 = 81.6 m3

Assume;

L/D

=2

L

= 2D

Volume

Height of fluid

= Area x Length 81.6

= πD2/6 x 2D

D

= 4.25 m

L

= 8.5 m = 1840 Kg/m3 x 9.8 m/sec2 x 8.35 m = 150567.2 Kg/m.sec2 = 150.567 KN/m2 = 1.485 atm = 0.15 N/mm2

Thickness, (l)

= Pi x Di / (2f - Pi)

For Stainless steel, f

= 16 N/ mm2

Thickness, (l)

= 0.15 x 4170 / (2 x 165 – 0.15) = 2 mm

71

Corrosion allowance

= 2 mm

Thickness

= 4 mm

Domed head: Crown radius

= RC

= 4.17 m

Knuckle radius

=RK

= 0.25m

Assuming no joints,

J=1

Stress concentration: CS

= 1/4[3 + (RC/RK)1/2] = 0.25[3 + (4.17/0.25)1/2] = 1.77

Thickness

= Pi x RC x CS / [2f x Pi (CS – 0.2)] = 0.15 x 4250 x 1.77 / [330 x 0.15(1.77 – 0.2)] = 14.2 mm = 14 mm

For a standard ellipsoidal head, Thickness

= Pi x Di / (2fJ – 0.2Pi) = 0.15 x 4250 / [330 – 0.2(0.15)] = 2 mm

Ellipsoidal head is economical than head with 4mm wall of the tank.

72

CHAPTER 7

Process Control Instrumentation

7.1 Introduction of Process Control Instrumentation: As the field of process control has matured over the last 30 years, it has become one of the core areas in chemical engineering. One of the important themes that we emphasize here is the need to understand the process-its operation, constrains, design, and objectives. The way the plant is design has a large impact on how it should be controlled and what level of control performance can be obtained. (1) Thus the operating pressures, temperatures, concentration of chemical, and so on, should always be within allowable limits process may be controlled more precisely to give more uniform and higher quality products by the application of automatic control, often leading to higher profits. Additionally, processes which respond too rapidly to be controlled by human operators can be controlled automatically. Automatic control is beneficial in certain remote, hazardous, or routine operations. As it is very obvious that process profit is usually the most important advantage to be obtained by applying automatic control, the quality of control and its cost should be compared with the economic return expected and the process technical objectives. The economic return includes reduced operating costs, maintenance cost, product cost and overall cost. Objectives The main objective of instrumentation and process control are: Safety: •

To keep process variables within defined safe operating limits.

•

To detect dangerous situations as they develop and to provide alarms and automatic shutdown system.

•

To interlocks and alarms and thus prevent accidents [14].

73

Smooth production To achieve the desire output of the product

Quality: To maintain the product composition within he specified quality standards. Economics: To operate at the lowest production cost, in a typical chemical processing plant these objectives are achieved by a combination of automatic control, manual monitoring and laboratory analysis. 7.1.1 Elements of control system: In almost every control configuration, we can distinguish the following hardware elements. 1. The chemical process 2. Measuring element or sensor 3. Transducers 4. Transmission lines 5. Controllers 6. The final control element The chemical process It represents the material equipment together with physical or chemical operation that occurs. In this discussion, the process is fermentation. The measuring instrument or the sensors Such instruments are used to measure the disturbance, the controlled output variables, or the necessary secondary output variables and are the main sources of information about what is going on in the process. The measuring means depend upon the types of variable, which is to be measured, and these variables must be recorded also. Following are some typical sensors, which are used for different variables measurements [14]. •

Pressure sensors

74

•

Temperature sensors

•

Flow rate sensors

•

Level sensors

Characteristics example of these types of sensors is as follows. Thermocouples or resistance thermometers: For measuring the temperature, also used for severe purpose some radiation detectors may also be used.

Venturi meters also flow nozzles for flow measurements.

Gas chromatograph: It is used for measuring the composition of the steam. A good device for the measurement depends upon the environment in which it is to be used. Like a thermometer, it is not a good measuring device, as its signal is not rapidly transmitted. So signal transmission is very important in selecting the measuring device. So the measuring device must be rugged and reliable for an industrial environment.

Transducers Many measurements cannot be used for control until they are converted to physical quantities such as electric voltage and current a pneumatic signal. For example, stream gauges are metallic conductors whose resistance changes when mechanical strain is imposed on it. Thus they can be used to convert a mechanical signal to electric one.

Transmission lines These are used to carry measurements signal from measuring device to the controller. In the past, mostly transmission lines were pneumatic nature that they are using the compressed air or liquid to transmit the signal but with the automation of industry and advent of electronic controllers, electric lines have over-ruled the pneumatic operations,

75

many times the measurements coming from a device are very weak and these must be amplified to get the things right. So it is very often to find amplifies in the transmission lines to the controller. For example the output of a thermocouple is only a few milli-volts so they must be amplified to few volts to get the controller.

7.2 Controller: This is hardware element that has “intelligence”. It receives the information from the measuring device and decides what action must be carried out. The older controllers were controller limited intelligence, could perform very limited and simple operations and could implement very simple control laws. The use of digital computers in this field has increased the use of complication control laws. The final control element: this is the hardware element that implements the decision taken by the controller. For example, if the controller decides that flow rate of the outlets stream should be increased or decreased in order to keep the level of the liquid in a tank then the final control element which is a control value in this case implements the decision by slightly opening or closing the value. Modes of control There are various modes in which the process can be controlled. The different Modes depend upon the types of controllers and the action it takes to control any process variable. Actually the controller action is dependent on the output signal of the transmitter (sensor with transducer) used to control the process. Different controllers react in different manner to control this off-set between the controlled variable and the set point. On the prescribed basis, following are the different types of control actions. •

On-off control

•

Proportional control

•

Integral control

•

Rate or derivative control

•

Composite control

Also there are combined control actions of different types of controllers. Actually in different operations, it is very rare that only one of the above control actions is found but a

76

composite control action is the more often practice. Following are typical composite control modes, which are usually used. Proportional-Integral controller (PI-Controllers) Proportional-Derivative controller (PD-controller) Proportional-Integral-Derivative controller (PID-controller) Characteristics of controller •

Pneumatic controllers

•

Electronic controllers

•

Hydraulic controllers

While dealing with the gases, the controller and the final control element may be pneumatically operated due to the following reasons, 1. The pneumatic controller is very rugged and almost free of maintenance. The pneumatic equipment is simple. 2. Pneumatic controller appears to be safer in a potentially explosive atmosphere which is often present in the industry. 3. Transmissions distances are short pneumatic and electronic transmissions system are generally equal up to about 200 to 300 feet. Above this distance electronic system beings to offer savings. Actually in industry, only P, PI, and PID control modes are the usual practice. The selection of most appropriate type of controller for any particular environment is a very systematic procedure. There are many ways and means that how a particular type of system may be controlled through which type of controller. Usually type of controller is selected using only quantitative considerations stemming from the analysis of the system and ending at the properties of that particular controller and the control objective. Proportional, integral and derivative control modes also affect the response of the system. Following is the summarized criterion to select the appropriate controller for any process depending upon the detailed study of the controller and control variable along with process severity.

77

1. If possible, use a simple proportional controller: Simple P-controller can be used if we can achieve acceptable off-set with not too high values of gain. So for gas pressure and liquid level control, usually a simple proportional controller may be used. 2. If a simple P-controller is not acceptable, use PI-controller: A steady-state error always remains for proportional controller so in systems where this off-set is to be minimizes, a PI-controller is incorporated. So in flow control applications, usually PIcontroller is found. 3. Used a PID-controller to increase the speed of the closed loop response and retain robustness: The anticipatory characteristic of the derivative control enables to use somewhat higher values of proportional gains so that off-set is minimized with lesser deviations and good response of the system. Also it adds the stability to the system. So this type of control is used for sluggish multiline short best controller is selected on following basis; I.

Severity of process

II.

Accuracy required

III.

Cost

7.3 Control Loops: For instrumentation and control of different sections and equipment’s of plants, following control loop are most often used. 1. Feed backward control loop 2. Feed forward control loop 3. Ratio control loop 4. Auctioneering control loop 5. Split range control loop 6. Cascade control loop

78

Feedback control loop: A method of control in which a measured value of a process variable is compared with the desired value of the process variable and any necessary action is taken. Feedback Control is considered as the basic control loop system. Its disadvantage lies in its operational procedure, for example if a certain quantity is entering in a process, then a monitor will be there at the process to note its value. Any changes from the set point will be sent to the final control element through the controller so that to adjust the incoming quantity according to desired value (set point). But in fact change has already occurred and only corrective action can be taken while using feedback-control system. 1. Feed forward control loop This is a control method designed to prevent errors from occurring in a process variable. This control system is better than feedback control because it anticipates the change in the process variable before it enters the process takes the preventive action. While in feedback enter system action is taken after the change has occurred. 2. Ration control A control loop in which, the controlling element maintains a predetermined ratio of one variable to another. Usually this control loop is attached to such as system where two different streams. Enter a vessel for reaction that may be of any kind. To maintain the stoichiometric quantities of different streams this loop is used so that to ensure proper process going on in the process vessel. 3. Auctioneering control loop This type of control loop is normally used for a huge vessel where, reading of a single variable may be different at different locations. This type of control loop ensures safe operation because it employs all the readings of different locations simultaneously, and compares them with the set point, if any of those readings is deviating from the set point then the controller sends appropriate signal to final control elements.

79

4. Split range loops In this loop controller is per set with different values corresponding to different action to be taken at different conditions. The advantage of this loop is to maintain the proper conditions and avoid abnormalities at very differential level.

5. Cascade control loop. This is a control in which two or more control loops are arranges so that the output of, one controlling element adjust the set point of another controlling element. This control loop is used where proper and quick controls difficult by simple feed forward or feed backward control. Normally first loop is a feedback control loop. We have selected a cascade control loop for our heat exchanger in order to get quick on proper control [14].

80

7.4 Flow control on NH3 stream: As the ratio of ammonia fed to the pipe reactor to that fed to granulator is 1.9 : 1, so ratio controller will be applied on the NH3 stream coming from storage.

81

7.5 Flow control on H3PO4 stream: As the ratio of H3PO4 fed to the reactor and to that of scrubber is 1.7 : 1, so ratio controller will also do the job here, as follows. [14].

82

7.6 Flow control on pipe reactor: The flow of liquid NH3 and H3PO4 to the pipe reactor is controlled by a ratio controller. The pipelines for these materials are also equipped with flow indicator. The flow valve is controlled by a controller which maintains the desired ratio of 1.45 : 1 (NH3 : H3PO4) to provide the conditions of maximum solubility. [14].

83

7.7 Flow control on granulator: The ratio controller is applied to maintain the ratio of 1:1 of slurry:NH3 sparges. [14].

84

7.8 Instrumentation on pipe reactor: The pipe reactor is equipped with a temperature transmitter and pressure transmitter mounted on the panel. The cold slurry coming from the scrubber controls the temperature in pipe reactor i.e. 150°C. A flow valve controls the flows of scrubber slurry from tank. The pressure indicator is used to record any significant change in pressure in the pipe reactor. As an increase in temperature will give rise to an increase in pressure. Thus pressure will in turn reduce the flow of NH3 and H3PO4 which reduce the temperature and pressure.

85

7.9 Temperature control on granulator: The temperature in the granulator is maintained at 95°C in the granulator by the following instrumentation [14].

86

87

CHAPTER 8

Cost Estimation

8.1 Cost Estimation: Purchased equipment cost = Ce = C x Sn Where: Ce = Purchased equipment cost S = Characteristic size parameter n = index for that type of equipment [5,10] 8.1.1 Process Engineering Cost Index Year

Cost Index

2004

444.2

2014

576.1

2015

562.1

The following table was made by using the above equation: Equipment

Cost ($) Year 2004

2015

Ammonia Tank

21067

26658

Sulfuric acid Tank

51678

65394

Granulator

187180

236861

Pipe Cross Reactor

232277

293928

Pre-Neutralizer

50823

64313

Phosphoric Acid Tank

18874

23883

Crusher

23227

61360

88

Other Cost (40%)

-

308961

Dryer, Scrubber, Screen

-

-

Total Cost

1081364$

Exchange rate for December 2015: 1 $ = 104.83 PKR 8.1.2 Total Physical Plant Cost (PPC): f1

Equipment Erection

0.45

f2

Piping

0.45

f3

Instrumentation

0.15

f4

Electrical

0.10

f5

Building, Process

0.10

f6

Utilities

0.45

f7

Storage

0.20

f8

Site Development

0.05

f9

Ancillary Building

0.20

Total Physical Plant Cost, PPC

= PCE (1 + f1 + f2 +... +f 9) = 1081364 (3.15) = 3406296 $

8.1.3 Fixed Capital Cost (FCC): f10

Contractors Fee

0.05

f11

Contingency Reserve

0.10

f12

Design of Engineering

0.25

Fixed Capital Cost, FCC

= PCC (1 + f10 + f11 + f12) = 3406296 (1.40)

[5]

89

= 4768815$ 8.1.4 Working Capital Cost (WCC): Working capital cost

= 5% of Fixed Cost = 238440 $

Total Capital Cost

= Fixed cost + Working cost = 238440 + 4768815 = 5007255 $

8.2 Total Operating Cost Estimation: Fixed Cost: •

Maintenance Cost

= 5% of Fixed Capital = 0.05 x 4768815 = 238440 $ per year

•

Capital Charges

= 10% of Fixed Capital = 0.10 x 4768815 = 476881 $ per year

•

Insurance

= 1% of Fixed Capital = 0.01 x 4768815 = 47688 $ per year

•

Local Rates

= 2% of Fixed Capital = 95376 $ per year

•

Royalties

= 1% of Fixed Capital = 47688 $ per year

90

Fixed Cost

= Maintenance Cost + Capital Charges + Local taxes + Insurance +

Royalties Fixed Cost

= 238440 + 476881 + 47688 + 95376 + 47688 = 906073 $ per Year

Variable Cost: Plant Attainment

= 95%

Operating time for plant attainment = 0.95 x 365 = 347 days per year Miscellaneous Materials

= 10% of the Maintenance Cost = 0.10 x 238440 = 23844 $ per year

Raw Material: 1. Ammonia (NH3) Cost

= Flow Rate x Operating time x Cost per ton = 475 x 347 x 545 = 89829625 $ per year

2. Phosphoric Acid Cost

= Flow Rate x Operating time x Cost per ton = 914 x 347 x 850 = 269584300 $ per year

Utilities Cost: 1. Total Electricity Cost

= 0.037 $ per KWh

91

Total Variable Cost: Total Variable Cost:

= Miscellaneous Material + Raw Material Cost + Utilities = 359437769 $ per year

Total Operating Cost

= Fixed Cost +Total Variable Cost = 359437769 + 906073 = 360343842 $ per year

8.3 Dap Cost: Cost of Diammonium Phosphate

= Total Operating Cost / Production per Year = 360343842 / 520500 = 0.692 $ per Kg

Exchange rate for December 2015: 1$ Cost of a 50 Kg DAP Sack

= 104.83 PKR = 0.692 x 104.83 x 40 = PKR 2900

92

CHAPTER 9

PLANT LOCATION & SAFETY

9.1 PLANT LOCATION: Selecting an appropriate site for the plant is a critical factor in determining its profitability and success. Several factors must be taken into account when selecting a site for the plant. These factors are as follows: •

Societal consideration

•

Raw material availability

•

Property cost

•

Taxation

•

Labor availability

•

Energy availability and cost

•

Transportation accessibility

•

Environmental permit

•

Living conditions

9.1.1 Societal considerations: The most primary factor in determining the suitability of a region for the eraction of plant is the social and cultural trends of the area. Many societies do not easily accept industrial development. They might consider it a threat to their peaceful environment some societies resist the presence of people from other regions because they feel that their Cultural norms might be endangered due to the presence of people from other cultures. In some areas where agriculture is the main source of livelihood, people might not be easily convinced to sell their lands.

93

9.1.2 Availability of raw material: The raw material must be easily available. The plant must be locational near the industries that produced ammonia and phosphoric acid. If the phosphoric acid and ammonia is also produced with in the same industry, then it should be located where phosphate rock and natural gas is present at a lower cost of extraction or purchase.

9.1.3 Property cost: The cost of land is important in determining the overall investment for the plant. Plant must generally be located away from residential areas because the land price is generally high there. Industrial areas or remote areas near the raw materials are preferable locations.

9.1.4 Taxation: The tax rates vary from region to region. Different tad patterns must be studied before taking the final step of deciding the region because it is a lifelong commitment with the authorities. Unstable political conditions may also be a discourage factor as new government might revise the tax rates. Industrial zones and tax free zones are more preferable areas to set up any industry.

9.1.5 Labor availability: Labor force is considered to be the “wheels” of an industry. It is important for the plant to be located in such an area where the availability of both skilled and unskilled labor of the industry. It is preferable to set up the industry in the vicinity of another similar industry it adds to the ease of finding skilled labor and also might cut down the extra expense that might be incurred in training the unskilled.

9.1.6 Energy availability and cost: The electricity and gas facilities should be available and at a reasonable cost. These facilities are generally available at discounted rate in the industrial zones. If the plant must be located in

94

some place where electricity is not available then alternative power production options must be carefully looked upon before taking the final decision.

95

9.1.7 Transportation accessibility: For a competent product price, the industry must be located near highways or ports as it is easier to get raw-materials and products transported in and out of the industry. The location must also be close to the market in order to save transportation expenses and time.

9.1.8 Environmental permit: An environmental based line is usually required to establish how the plant would affect the surroundings. Air quality issues can be the deciding factor in sitting. As air permits often take the most time to obtain. Water pollution also needs to be addressed. Federal, state and regional regulations are often in conflict with each other. Hiring a consultant to steer a way through this compels myrid of regulations can be useful. What the environmental discharges are and how best to mitigate their effects by providing a plant that this design to minimize the impact are key issues.

9.1.9 Living conditions: The facilities and environment that could be offered in the industry might be a factor to attract skilled personnel and members of higher management to come to remote locations. So while selecting the location it is important to take into considerations the ability of the region to support such environment and facilities, like schools, clubs, etc. these things are a vital for the growth of the industry.

9.1.10 Environmental considerations: The environmental problems that different countries have to face vary with their stage of development, the structure of their economies and their environmental plies. The standards imposed by industrial economies may set reasonable along term goals but developing countries like Pakistan rarely have the means to adopt them immediately. Instead each country must determine its own priorities. However the main body of this chapter deals with the regulatory control established by the environmental laws.

96

Effluent from the DAP unit: Major Effluent from the pant using phosphoric acid and ammonia as a raw material from the production of DAP may include. •

Fluoride

•

Ammonia

•

DAP dust

•

Water

A brief description of each is given below. 9.1.11 Fluoride emission: Fluoride emission is a major concern of both the Industry and the environmental protection agencies use to the nature of the chemistry involved in the preparation of phosphoric acid and the DAP fertilizer. Although not classified as endangering public health, fluoride emissions have been designed as well as fare related pollutant. The evolution of fluoride from the manufacture of mono ammonium phosphate (MAO) and Diammonium phosphate (DAP) is dependent upon the fluoride of phosphoric acid. In the case of MAP and DAP operation the major sources of fluoride and ammonia emission are the reactors and the granulators. Since fluoride emissions are considered to be welfare rather than health related. Environmental laws allow applying less stringent requirements for the existing regulated facility. Considerable flexibility resists in weighing factors such as economic conditions, physical constraints, technical feasibility and environmental impact on the surrounding community. Flexibility allowed for granular DAP plant is 0.060 lbs of fluoride/ton of P2O5. Since 1979 there have been no significant improvements in fluoride removal efficiencies by scrubbing or the demonstration of emerging technologies for fluoride control. In order to determine the type of equipment most suitable for fluoride control, the nature of emissions must be first examined.

97

9.1.12 Ammonia: Ammonia is a colorless, alkaline gas, is lighter than air and possesses a unique pungent order. The flue gasses from the reactor and granulator contain unreacted ammonia. This is recovered from the flue vapors in the scrubber by absorbing in phosphoric acid. Despite these protective measures some of it escapes into the environment. Ammonia can also leak through pipes and equipment and could be hazardous to the health of the workers, as it is rapidly carried to long distances by air. Any detectable release of ammonia can be absorbed by spraying water over the leakage site in order to prevent an accident while the problem is being worked on.

9.1.13 DAP dust:

In the DAP plant the DAP dust procedure from the cooler and screening and crushing equipment can be of serious concern. These particles can cause respiratory and other health related problem. The control of particulate sources from screening crushing can be handled by bad houses, while those from cooler can be handled by cyclone separators.

9.1.14 Water discharge: Environmental control in the phosphatic fertilizer industry is more complex than just scrubbing air and gaseous emissions. The scrubber water, used to efficiently clean the air being discharge via the stacks, must now meet the standards of discharge promulgated under the clean water act.

98

CHAPTER 10

HAZOP ANALYSIS

10.1 Introduction: The objective of HAZOP study is to provide safety, health and care to all the man power working in the plant and to provide maintenance and safety to the plant by reducing risk of the accident. 10.1.1 Safety Points: General Safety Rules 1. Face shield and gloves should be worn because every time there is a danger of coming in contact with a corrosive liquid. 2. Be prepared for any condition that would prove hazardous to personnel or equipment should be kept. 3. High-pressure leaks should be reported immediately. 4. If any chemical spill occurs, clean the area of any source of ignition and wash down the area slowly with water to minimize vaporization. 5. Operators should be aware of location of emergency and safety equipment. 6. Operators should be aware of all the toxic, corrosive and flammable materials used in the process. 7. Firefighting equipment should not be tampered with. 8. Access to ladders, escapes, safety showers, eyewash stations and air mask stations must be kept clear. Waste material and refuses must be kept in proper locations where they will not cause fire. 9. If any safety equipment is not working properly, it should be reported and set right. 10. No smoking is allowed in the plant or its vicinity.

99

10.1.2 Building and Process Equipment Safety: Any acceptable design must contain the minimization of building and equipment hazards such as corrosion, fire explosion and hazards caused due to fumes and poisonous materials. Special care should be given to the disposal of waste material. Elimination of process leakage and spillage hazards due to corrosion and other factors should be paid extra attention.

Lights: Proper light arrangements should be made to facilitate the movement and working of personnel and minimizing the risk of tripping over pipes.

Electrical and Mechanical Hazards: Electrical and mechanical hazards should be minimized. Every machine should be equipped with proper safety guards. Poor and faulty wiring, overloaded circuits and improperly loaded circuits should not be used.

Chemical Hazards: Special care should be given to avoid any exposure to sulfuric acid and phosphoric acid. Most reliable manuals for safety are chemical safety data sheet compiled by manufacturing chemist’s association. These manuals discuss the safe handling of most hazardous chemicals while also providing drawing, data tables and graphs.

Personnel Safety: Special equipment such as safety goggles, gloves and ear muffs should be provided to the personnel so they can enhance their performance in a safe and healthy environment.

100

10.2 TVA granular process: In TVA granular process it is acid base reaction. So safety should be kept in mind. High pressure and temperature streams are major concern for the safety purposes. Special procedures are used to avoid contact with sulfuric acid and phosphoric acid.

10.2.1 Special Hazards and Precautions: ➢ Sulfuric acid cause rapid damage to human beings which cause serious consequences. Fumes of sulfuric acid cause serious damage to the respiratory system. ➢ Liquid or spray mist may produce tissue damage particularly on mucous membranes of eyes. Skin contact may produce burns. Severe over exposure causes death .Inflammation of eyes is characterized by redness. ➢ Phosphoric acid in case of skin contact or eye contact is very hazardous. Liquid or spray mist may produce tissue damage particularly on mucous membranes of eye. Mouth and respiratory tract. Severe over exposure can result in death. ➢ In case of eye contact immediately flush eyes with the plenty of water for at least for 15 minutes.in case of skin contact flush skin with plenty of water for at least 15 minutes. Wash with soap or antibacterial cream. ➢ Ammonia is a flammable gas. If it is heated it May explode.it is very toxic if it is inhaled and also very toxic for aquatic life. ➢ Do not expose to eyes use and store only outdoors or in well ventilated place. Eliminate all ignition sources it is safe to do .wear protective gloves and protective clothing to handle it properly. ➢ If it is inhaled take victim to the uncontaminated breathing atmosphere .keep victim warm and rested.in case of physical contact flush affected area for the plenty of water for 15 minutes. ➢ Protective Equipment should be used during the following procedures. •

Manufacture or formation of product.

•

Repair and maintenance of contaminated equipment.

•

Cleanup of leaks.

•

Any situation resulting in hazardous exposure.

101

Table: Material safety information for chemicals and materials used in process. Standard PPE is always assumed.

Name

Sulfuric acid

Phosphoric acid

Ammonia. Anhydrous

Description

Colorless liquid(thick Odorless, oily liquid

Colorless Colorless and pungent

liquid (syrupy liquid liquefied gas Viscous liquid)

Health hazard

Irritation to skin and Irritation to skin and Severely corrosive to eyes. Very toxic when eyes very toxic when eyes, skin and lungs. fumes inhaled.

Exposure

fumes inhaled.

Eye and skin contact, Eye and skin contact, Eye and skin contact, inhalation, ingestion.

First Aid

inhalation, ingestion.

Exposed area Flush Expose with water for 15 Wash minutes.

skin with

Inhalation: Inhalation:

Seek

inhalation, ingestion.

area Exposed area kept water. warm and inhalation

Get

to victim will kept under

medical fresh air. Ingestion: supervision

for

48

attention

Drink water.

hours

Toxicology

High no chronic.

Low no chronic.

High no chronic

Flammability

None

Not Flammable

Extremely flammable

Explosiveness

Risk of explosion of No explosion risk. the

product

presence discharge

of

in static

High explosion risk.

102

Reactivity

Reacts violently with Reacts with metal to Under water

and

alcohol liberate

normal

flammable conditions of storage

especially when water hydrogen gas.

and use.no hazardous

is added to product

reaction

will

not

occur. Storage & Handling

Sulfuric acid stored in In storage container Tightly enclosed in tightly

enclosed with explosion roe closed container.

container Disposal

door.

Hazardous

diluted Hazardous. disposed Hazardous.

and disposed under under the state regulations. Accidental release

Evacuate

the

federal should

regulations

personnel Evacuate

waste not

be

disposed untreated personnel Evacuate

personnel

immediately .Contact immediately .contact immediately .Contact emergency personnel emergency personnel emergency personnel immediately.

immediately

immediately.

103

10.3 HAZOP Analysis for Pre-Neutralizer: Study Node: •

Constant Stirred Tank Reactor

Process Parameters: • Deviation

Flow (Guide Possible Causes

word) None

More

Possible

Action Required

Consequences Blocked pipe

No reaction, no feeds Inspect and unblocke flow to later reactor

pipe

1-Pressure increase

1-Reactor rupture

1-Shut-down process,

2-Temperature

2-Pipe rupture

evacuate area

increase

3-pre-mature reaction 2-Shut down reactor, due

to

inproper inspect

reaction time.

failure.

the

valves

solve

the

problem Less

1-Pressure drop

1-Insuficient

MAP 1-Inspect

reactor,

2-Temperature

conversion in overall piping for leaks.

decrease

process

2-partially open valve

2-Runaway reaction

open completely to achieve required flow rate.

104

Process Parameter: •

Reaction

Deviation(Guide

Possible Causes

Possible

word) More

Action Required

Consequences High

flow

reactants

to

of High pressure and Consider the High temperature in Shut

reactor due to the the reactor.

system.

valves failure.

should

Alarms.

down

the

operator check

this

segment None

No

flow

of Insufficient

Alarms/shut down of

phosphoric acid to conversion in overall the system for low reactor/No flow of process

flow

Ammonia

Plant operator must

to

the

reactor. Less

Low

of

reactant.

check the valve. pressure

in Pre-mature reaction.

Inspect

reactor,

reactor. Less flow of

piping

reactants

leaks/Periodic

to

the

reactor.

for

maintenance

is

required Other

Composition of the Give

off- Verified

acid

Phosphoric acid is specification

composition by the

not as required

inventory control.

product.

105

Process Parameter: •

Temperature

Deviation(Guide

Possible Causes

Possible

word)

Action Required

Consequences

Less

Pre-Mature reaction Pre-Mature product Shut down reactor, due

to

the and off-specification replace valves and

inappropriate flow of product.

periodic

Phosphoric acid

maintenance of the valves required

More

More

flow

phosphoric

of Runaway reaction

Quench reactor

acid

cause high pressure and temperature.

Study Node: •

Reactor wall

Process Parameter: •

Pressure

Deviation(Guide

Possible Causes

Possible

word) None

Less

Action Required

Consequences Reactor or pipeline Hazardous release of Shut rupture

chemical

Minor leak in piping

Low product yield Inspect and

process,

evacuate area reactor

,

premature piping for leaks

reaction. More

High

flow

of Reactor rupture and Shut down process,

phosphoric acid will loss of material

evacuate area, Flow

increase pressure in

controllers

the reactor.

required

are

106

10.4 HAZOP study for Scrubber: There are four condenser of similar category. Study Node: •

Scrubber

Process parameter: •

Temperature

Deviation(Guide

Possible Causes

word) None

Possible

Action Required

Consequences Failure

of

phosphoric valve to open

inlet No separation and Inspect

the

acid loss of anhydrous indicator ammonia

flow and

periodic maintenance

is

required. More

Failure of inlet flow Temperature control

valve

of scrubber

is

of Inspect

the

high indicator

and

phosphoric acid to /decomposition

periodic

adjust flowrate.

maintenance

occurs

flow

required Less

Contamination

Pipe

leakage

or No proper separation Inspect the piping

partial opening of and loss of material.

leakage/repair

valve.

leakage and valve.

Contamination phosphoric acid

in Gives

off Verified

the

acid

specification product composition inventory control.

by

107

10.5 HAZOP study for Storage Vessel: Storage vessel is used for the storage of phosphoric acid and sulfuric acid. Study Node: •

Vessel

Process Parameter: •

Pressure

Deviation(Guide

Possible Causes

Possible

word) None

Action Required

Consequences Leakage or rupture of Low flow or No flow Inspect pipe/Tank rupture

of process material

piping

leakage or rupture and rupture in tank

More

High flow rate

Rupture of vessel

Inspect flow meter /replace flow meter and

periodic

maintenance required. Less

Low

flow

of Low product yield Inspection of piping

stream/plugged line

and reaction.

pre-mature &

flow

meters

/replacement of fail equipments.

108

10.6 HAZOP study for Granulator: MAP to DAP conversion takes place in granulator Study Node: •

Granulator

Process Parameter: •

Flow, Temperature, Pressure

Guide Word

Deviation

Cause

Consequences

No

No Flow

Blockage in the No pipeline

production. Repair

or material

rupture of pipe.

Action

granulator

and

in replacement

of

the pipeline.

decompose No pressure

Rupture

of Premature

Check the flow

granulator or no reaction.

controllers

flow of reactants

granulator.

and

replace if require No Temperature

No

flow

reactants

of No conversion

Consider Alarms

to

and

granulator

operator

should check the flow controls and pipeline.

More

More flow

Failure of flow Not proper time Proper control valves

for the reaction

maintenance

of

valves required. More Pressure

More

flow

of Explode

Pressure

in granulator

indicators

are

granulator cause

required

and

increase

pressure

relief

reactants

pressure

in

valves required

109

More

More

flow

Temperature

reactants

of Product

Flow controllers

to decomposition

are repaired and

granulator

Temperature indicator required.

Less

Low flow

Leakage

of Premature

Verify

periodic

pipeline or partial product

maintenance and

open valve

adequate

conversion

inspection

of

valve required. Low pressure

Inappropriate

Incomplete

Adequate

flow of reactants

reaction

inspection of the flow valves.

Low temperature

Inappropriate

Premature

Adequate

flow of reactants

conversion

inspection of the flow valves.

110

References: 1. http://www.pakinvestorsguide.com/index.php?topic=151.45;wap2 2. Kenneth J. Jardine, V.V.A., Method for producing fertilizer grade DAP having an increased nitrogen concentration from recycle. Jun 5, 2001. 3. Byron R. Parker, B.W.C., Diammonium phosphate produced with a high-pressure pipe reactor. Jul 19, 1988. 4. Max Appl, Dannstadt-Schauernheim, Federal Republic of Germany, Ammonia 5. Ammonia Synthesis Catalysts: Innovation and Practice, Huazhang Liu 6. Chemical Engineering Design Coulson and Richardson Vol # 06 7. Method for producing fertilizer grade DAP having an increased nitrogen concentration from recycle, Kenneth J. Jardine, Vaughn V. Astley,Jun 5, 2001 8. Catalytic Ammonia Synthesis : Fundamentals and Practice 9. William D. Fairchild, Process for producing granular diammonium phosphate 10. Byron R. Parker, Barry W. Curtis, Diammonium phosphate produced with a highpressure pipe reactor, Jul 19, 1988 11. Plant Design and Economics for chemical engineers, 5th Edition by Max S peter and Klaus.D.Timmerhause. 12. Introduction to chemical engineering thermodynamics,6th edition by J.M.Smith 13. Fertilizer Manual by UNIDO Fertilizer Manual published in DEC, 1979 14. Fertilizer manual by neilson. 15. Fertilizer Encyclopedia by Vasant Gowariker 16. Chemical Process Control, by GEORGE STEPHANOPOULOS 17. Elements of Chemical Reaction Engineering, 4th Edition, by H.SCOTT.FOGLER 18. Chemical Reaction Engineering by Octave Leven Spiel, 3rd Edition 19. Fertilizer ammonium phosphate by jhon L.chadwick Manlo park California.94025 20. US4619684Production of diammonium phosphate by pressure reactor by tense valley authority.