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Summer Training Report On

“study and calculation of efficiency of centrifugal pump p-309 .”

Submitted To: Submitted By:Mr. U.P SINGH(H.O.D) AKSHAY SAXENA (AMM.DEPTT.) DIPLOMA IN 2ndYEARMr. R.K SRIVASTAVA(AMM. DEPTT.) (CHEM. TECH. FERT.)Mr. MANEESH S ANKHYADHAR(AMM. DEPTT.) GOVT. POLY. BUDAUN

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ACKNOWLEDGEMENT

I would like to express my deep gratitude to Tata Chemicals Ltd., for granting me opportunity to get exposure to industrial environment

I pay my sincere regards to Mr. U.P. SINGH(H.O.D of Ammonia Plant) for his overwhelming support as a project guide; to Mr.R. K. SRIVASTAVA& Mr. MANEESH SANKHYADHAR (AMM DEPTT.) for his benevolent guidance.

I would like to thank Ms. AMITA BAHETI ,Mr.RAJENDER SINGH, HR and to Mr.AKASHDEEP GUPTA(AMM DEPTT.),Mr. SANDEEP GUPTA(F & S DEPTT.) for taking care and making the stay pleasant at TCL, Babrala

I would also like to extend my thanks to my fellow summer trainees for giving their support in completion of this project.

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CONTENTS

Sr. TITLE 1. About TCL, Babrala 2. Fire & Safety 3. Plant Overview

Ammonia production

4. Centrifugal pump

5. Calculation of efficiency of P-309

6. Bibliography.

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ABOUT TATA CHEMICALS LIMITED, BABRALA

Tata Group, India's foremost business conglomerate.Tata Chemicals, by itself, is one of the largest inorganic complexes in the world beginning to TATA Group. Its first plant, which is also called inaugurated establishment of TATA.It isIndia's leading manufacturer and marketer of inorganic chemicals and fertilizers, with a turnover of over Rs. 4000 crores and is part of the Rs 65,000-crore ($14.25 billion) TCL's products and production processes are benchmarked with the best of global touchstones, and meet the most rigorous international specifications., Established in 1939. An ISO-9001/14001 OHSAS 18001 certified company, TCL has a varied user industry base comprising glass, paper, textiles, food additives, petroleum, refining, chemicals, dyes, pesticides, direct farm application etc. The products go into numerous end-use applications in a variety of industries: glass, detergents, paper, textiles, agriculture, photography, pharmaceuticals, food, tanning, rayon, pulp, paints, building and construction, and chemicals.

Tata Chemicals is also one of India's leading manufacturers of urea and phosphatic fertilizers. With an export presence in South and Southeast Asia, the Middle East and Africa, it has set itself the objective of achieving global cost competitiveness in soda-ash. Its foray into phosphatic fertilizers follows the merger of Hind Lever Chemicals Limited into Tata Chemicals Limited. TCL's phosphatic fertilizer complex at Haldia in West Bengal is currently the only manufacturing unit for DAP/NPK complexes in West Bengal. The Haldia plant has production volumes exceeding 1.2 million tons per annum. Tata Chemicals makes urea at its fertilizer complex in Babrala. The complex has an installed capacity of 8, 64,000 tons per year, which constitutes nearly 12 per cent of the total urea produced by India's private sector. Tata Chemicals is among the world's largest producers of synthetic soda ash, with the largest domestic market share, produced at the company's integrated complex at Mithapur on the Gujarat coast in western India.

The fertilizers, sold under the brand name 'Paras', lead the market in West Bengal, Bihar and Jharkhand. TCL is also a pioneer and market leader in the branded, iodized salt segment. Its salt has a purity percentage of 99.8 per cent, the highest in the country.

CREDENTIALS OF TATA CHEMICALS LIMITED BABRALA

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AWARDS:2011-12:

CII-ITC sustainability trophy 2011-12

IFA Green Leaf Award for Excellence in Safety, Health and the Environment in Fertilizer Production 2011-12

CII– Sohrabji Godrej Green Business Centre “Excellence in Water Management-Within the Fence-2011”.

National Awards for Indira Gandhi ParyavaranPurskar – 2011-12

Mother Teresa Award for Corporate Citizen 2011-12

CNBC Asia's India Corporate Social Responsibility Award 2011-12

Product of the Year - 2012 for Tata Swach water purifier

ICC RC Logo use award 2012 Environment Protection Award (Runner-Up) by FAI 2011-12 Surakasha (Safety) Puraskar from NSCI -2011

2012-13

FAI: ENVIRONMENTAL PROTECTION AWARD: NITROGENOUS FERTILIZER PLANT PERFORMA FOR ENTRY 2012-13

Yes Bank Sustainability Award 2012-13

IFA Green Leaf SHE Award – (Runner up) 2012-13

FE-EVI Green Business Leaders Award 2012

'Sustainability Plus' - the world's first corporate sustainability label by CII 2012

Excellence in Safety, Health and Environment by International Fertilizer Association – (1st runner up) 2012

SreshtraSurakashaPuraskar from NSCI -2012

TCL BABRALA: THE NATION’S CONCEIT

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Substituting a part of the imports of Urea, TCL, Babrala is estimated to save the country about Rs. 500 crores in foreign exchange every year and provide the farmer with nitrogenous nutrient, which could help raise the food production by about 4 million tonnes/year.

First major steps towards the fulfilment of a long standing TATA CHEMICALS commitment to provide the farmer with an optimal package of agriculture inputs to safe guard the food security of the company.

Produced more than 100% of the designated production during the first year of commercial production.

Produced more than 8, 40,102.35 tonnes of Urea achieving a capacity of 11.3% in the year1995-96, and produced 9, 51,764 tonnes of Nitrogenous Urea in year 1996-97.

Now produce capacity of 12, 00,000 tonnes of Urea per year, which constitutes nearly 13 per cent of the total urea produced by India's private sector.

Total production of urea at Babrala is 3500 tonnes/day and maximum of 3574 tonnes/day till date.

Current maximum capacity is 102%. It is the only fertilizer plant in the country to use dual feedstock: natural gas or naphtha,

or a combination of both.

MILESTONES OF TATA CHEMICALS LTD. BABRALA

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Commercial Production Started on December 21, 1994

AMMONIA UNIT

First firing of Reformer Furnace for dry out of refractory October 12, 1994

First feed into Primary Reformer October 20, 1994

First Carbon Dioxide for making Urea October 23, 1994

First Ammonia production November 14, 1994

UREA UNIT

Urea Prill Test conducted October 04, 1994

First Prill Test conducted through Unit 2 November 05, 1994

Second Prill Test conducted through Unit 2 December 09, 1994

ISO 14001 certificate obtained in October 2000.

ISO 14001 certificate for Babrala township obtained in 2004.

COMPOSITION OF TATA CHEMICALS LTD. BABRALA

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1. Ammonia PlantCapacity: 2007.16 MTPD

Technology: HALDOR TOPSE Process, DENMARK

Plant (Single Stream) Production: 2007.16 Metric tonnes/ day of liquid Ammonia.

Plant at TCL, Babrala is the first low energy plant in the country.

Basic scheme involves the following steps:

Desulphurization.

Primary and Secondary Reforming.

Carbon Dioxide Shift.

Methanation.

Synthesis and Chilling.

Storage and supply to Urea unit

2.Urea Plant

Capacity: 3500 MTPD

Technology: SNAMPROGETTI Process, ITALY

Carbon Dioxide requirements supplied from ammonia plant.

Two urea strings have a common Prilling section.

Maximum Urea production: 3574 tonnes per day

Basic scheme involves the following steps:

Urea Synthesis

Waste Water Treatment section

3.Offsite and Utilities

S. N. UNIT CAPACITY TECHNOLOGY

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1. Ammonia Storage Tank 2X5000 MT M/S Kaveri Engineering

2. Captive Power Plant 1X110 TPH THERMAX/ L&T

3. Cooling Tower 24000 M3/hr M/S Paharpur Cooling Tower

4. D. M. Water Plant 3X450 M3 TCL, Mithapur

5. Gas Turbine Generator 2X20 MW THOMASSON, Holland

6. Heat Recovery Unit 2X90 TPH L&T

7. Naptha Bulk Storage Tank

3X6300 KL M/S TechnofabEngg. Ltd.

SALIENT FEATURES OF TATA CHEMICALS LTD.BABRALA

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Location Babrala, District Badaun, Rajpura block, Gunnor Tehsil, Uttar Pradesh. Approx. 160km. south-east of Delhi.

Land Area 1519 acres

Plant area:1,069 acres

Township area:350 acres

Green belt: 100 acres

Fuel Natural gas (main)

Naphtha (alternate)

Fuel Source Natural gas supplied by GAIL (HBJ Pipeline)

Naphtha from IOCL, Mathura

Consumptive water source

Six deep bore wells.

Present installed capacity

Ammonia:2007.16 MTPD

Urea: 3500 MTPD

Project cost 1532 crores

Man power Deployment (During Commissioning/ Erecting phase

Total 7,855,128 man-hours.

Peak (month) 405,799 man-hours.

Beneficiary states U.P., Bihar, West Bengal, Punjab, M.P., Assam.

UNIQUE FEATURES OF TATA CHEMICALS LTD. BABRALA

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An integrated energy network, which is the key, factor in achieving high energy efficiency. The flexible range of the ratio of natural gas and naphtha as a fuel/ feed is a major reason for this. The current low operating energy record is 5.055 Gcal/T of Urea.

The second unique feature is common single central control room (CCR) for ammonia, Urea to captive power and steam generation plant (CPSSGP) and other offsite and utility plants. This provides a well coordinated and integrated control of the entire complex from one location and on line inters plant sharing of information. This has been found extremely beneficial especially during plant startups and upsets.

QUALITY POLICY OF TATA CHEMICALS LTD.

To provide customer satisfaction and timely delivery of quality products. Maintain good quality management systems and incorporate regular

improvements to meet our customer changing needs. Continuously upgrade product quality by improvements in process technology. Develop and upgrade employee skills and provide an environment for their

effective participation through teamwork to meet our customer expectations. Take adequate care to ensure safety at the work place, environmental

preservations and to respond to the needs of the community.

FIRE AND SAFETY

FIRE CHEMISTRY: The well known “Fire triangle” requires the three ingredients of fire namely fuel, oxygen and source of ignition.

“A fire is a combination of fuel, oxygen and source of ignition”.

Fire control could thus be carried out by either:

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Cutting the supply of FUEL – STARVATION. Cutting the supply of AIR – SMOTHERING. Lowering the temperature (below the ignition pt.) – COOLING.

2.1 FIRE PREVENTION:

Fire prevention can be done in three ways:

a.) Eliminate sources of ignition.b.) Eliminate combustible substances.c.) Eliminate air excess to combustible substances.

a.) FIRE PREVENTION THROUGH ELIMINATION OF IGNITION SOURCES:To prevent fire the first is to remove the cause of fire. Studies made by fire insurance company shows that majority of fires are caused by following general sources of ignition:

Electrically limited fire: Improper earthing, short circuiting, loose electrical contacts, temporary direct connections without proper fittings, high current, over heating of electrical equipment are among the common cause of electrically initiative fires.

Smoking ignited fire: Smoking or even carrying cigarettes/ beedies/matches/lighter etc. in the following areas is a serious offence. All non-smoking areas should carry “NO SMOKING” signboards.

Friction and over heated material: In flame proof areas, frictional fires can also be started by the friction of moving parts of machinery which are overheated due to excess friction. This is likely in non-lubricated and not well maintained machinery.

b.) FIRE PREVENTION THROUGH ELIMINATION OF COMBUSTIBLE MATERIALS: Waste and combustible materials: All combustible wastes and materials like waste

paper, cotton waste etc. accumulated after a job should be transported to waste bins and is the responsibilities of the person doing the job that creates the wastes.Tins and cans of flammable materials like paints, oils, spirit etc.: These should b handled carefully ensuring that no undue spillages takes place during their uses and any spillages takes place during their use and any spillage should be cleaned immediately.

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Fueling of vehicle tanks: Engine should be always switched off while fueling a vehicle. If diesel or petrol spills over during fueling, dry sand should covered over the spill immediately till only dry sand is visible on the spilled area.

Waste disposal: All combustible waste must be regarded in such a way that can be disposed off as such and not burnt.

c.) PREVENTION THROUGH ELIMINATION OXYGEN SUPPLY:

Smoothening: It is a process of covering the burning area with a non-combustible substance like asbestos or fire proof blanket, wet thick cotton blanket or sand.

2.2 CLASSIFICATION OF FIRES:

Fires are classified according to the nature of fuel burning and fire extinguishing methods that can be applied and the following is the fire classification under the Indian fire code.

CLASS “A” FIRE CLASS “B” FIRE CLASS “C” FIRE CLASS “D” FIRE CLASS “E” FIRE

CLASS “A” FIRE: Fires where the burning fuel is a cellulosic material such as wood, clothing, paper etc. is called class “A” fire.

It can be extinguished by the water and sand. Class “A” fires can also be extinguished by all the available means of extinguishing fires like foam, soda acid, dry chemical powder, carbon dioxide etc.

CLASS “B” FIRE: Fires where the burning fuel is a flammable liquid Naphtha, petrol etc. are categorised as class “B” fire.

Blanketing is a useful first aid fire control for “B” class fire. Water is forbidden as a fire fighting means on class “B” fires. Foam, carbon dioxide, dry chemical powder extinguishers are the desired means of controlling “B” class fires.

CLASS “C” FIRE: Fire involving flammable like natural gases hydrogen are classified as class “C” fire.

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The best means of extinguishing “C” type fire is by stopping the gas supply to the leaking vessels or pipe lines if possible. This must be the intermediate and very first step. Dry chemical powder and carbon dioxide are useful in controlling “C” class fire.

CLASS “D” FIRE: Fire involving material like magnesium, aluminium, zinc, potassium etc. are classified as class “D” fire. Sand buckets are useful in most cases of metallic fires. Special dry chemical powder also works on class “D” fires.

CLASS “E” FIRE: Fires involving electrical equipments are classified as “E” class fires. Only carbon dioxide and D.C.P extinguishers are used on class “E” fires.

2.3 FIRE FIGHTING GADGETS AND APPLIANCES:-

a) CO2:- It contain under pressurized liquid carbon dioxide.

b) SODA ACID:- Contain a double container with sodium bicarbonate solution in outer container and dilute sulphuric acid in the inner container. After the inner container both react and produce a liquid of entrapped CO2.

c) FOAM:- Contain aluminous sulphate in inner container and sodium bicarbonate in outer one. After cracking the container both reacts to produce carbon dioxide and the foam stabilizer makes stable form of carbon dioxide.

d) DRY CHEMICAL POWDER:- It contains an inert dry chemical powder of sodium bicarbonate or potassium bicarbonate or potassium chloride and diammonium phosphate along with liquid carbon dioxide under pressure.

e) HALON/ BROMOCHLOROFLUORO METHANE:-Halon is in the form of a liquid gas under pressure that is released on pressing the knob.

2.4 SAFETY PROGRAMME AT T.C.L

The company conducts regular programmes for safety measures, which not only creates awareness about safety but also maintains it; the fire and safety department of T.C.L organizes many programmes to motivate in this direction and to make the employees aware. National safety day 4th march is being celebrated each year with earnestness and includes

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various awareness programmes, competitions and includes various awareness programmes, competitions etc. some of these are listed below:

1. Training programmes on safety.2. Home safety.3. Use of safety equipments.4. Safety quiz.5. Safety slogan competition.

SAFETY PROVISIONS

1. Personal protective equipment (PPEs ): The various types of PPEs are:- Helmet for head protection. Goggles for eye protection. Ear plugs and muff for ear protection. Safety shoes for foot protection. Gloves for hand protection. Face shields foot protection. Full body protection suits. Hoods for head, neck, face, and, eye protection. Safety belts or life belts or harness. Breathing apparatus or respiratory protection equipment.

2. Fencing of machinery.3. Devices for cutting of power.4. Hoists and lifts.

Introduction

Almost everyone has smelled the sharp, penetrating odor of ammonia, NH3. As the

active product of “smelling salts,” the compound can quickly revive the faint of heart

and light of head. But more than a sniff of this toxic, reactive, and corrosive gas can

make one very ill indeed. It can, in fact, be fatal. Ammonia is pretty nasty stuff.

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Nevertheless, it is also an extremely important bulk chemical widely used in

fertilizers, plastics, and explosives.

Physical Properties of Ammonia:

The melting and boiling points of ammonia, –77.7°C and –33.5°C, respectively, are

both considerably higher than the corresponding properties of its chemical “cousins,”

PH3 and AsH3. This failure of NH3 to follow the usual trend of decreasing melting and

boiling points with decreasing molecular weights indicates abnormally strong

intermolecular attractions. The forces involved stem from hydrogen bonding, a

consequence of the high electronegativity of nitrogen and the small size of the

hydrogen atom

Chemical Propertiesof Ammonia:

The NH3 molecule has a large dipole moment, and this is consistent with its

geometry, a trigonal pyramid.

The electronic arrangement in nitrogen obeys the octet rule. The four pairs of

electrons (three bonding pairs and one non-bonding lone pair) repel each other,

giving the molecule its non-planar geometry. The H–N–H bond angle of 107 degrees

is close to the tetrahedral angle of 109.5 degrees. Because of this, the electronic

arrangement of the valence electrons in nitrogen is described as sp3 hybridization of

atomic orbitals.

The polarity of NH3 molecules and their ability to form hydrogen bonds explains to

some extent the high solubility of ammonia in water. However, a chemical reaction

also occurs when ammonia dissolves in water. In aqueous solution, ammonia acts

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as a base, acquiring hydrogen ions from H2O to yield ammonium and hydroxide

ions.

NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)

The production of hydroxide ions when ammonia dissolves in water gives aqueous

solutions of ammonia their characteristic alkaline (basic) properties. The double

arrow in the equation indicates that equilibrium is established between dissolved

ammonia gas and ammonium ions. Not all of the dissolved ammonia reacts with

water to form ammonium ions. A substantial fraction remains in the molecular form in

solution. In other words, ammonia is a weak base. A quantitative indication of this

strength is given by its base ionization constant:

In contrast, the ammonium ion acts as a weak acid in aqueous solution because it

dissociates to form hydrogen ion and ammonia.

NH4+(aq) NH3(aq) + H+(aq)

The ammonium ion is found in many common compounds, such as ammonium

chloride, NH4Cl. Typically, ammonium salts have properties similar to the

corresponding compounds of the Group IA alkali metals.

Uses of Ammonia:

Ammonia is shipped as a liquefied gas under its own vapor pressure of 114 psig.

The oldest commercial refrigerant known and still in use today. Most extensive use

is in soil fertilization. This application is used in the form of salts, nitrates and urea.

It is the simplest stable compound of these elements and serves as a starting

material for the production of many commercially important nitrogen compounds.

Pure ammonia was first pre-pared by Joseph Priestley in 1774, and its exact

composition was determined by Claude-Louis Berthollet in 1785.

Ammonia is highly soluble in water, forming an alkaline solution called ammonium

hydroxide. Moreover, it becomes highly reactive when dissolved in water and readily

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combines with

many chemicals. Ammonia is easily liquefied by compression or by cooling to about

-33° C (-27.4° F). In returning to the gaseous state, it absorbs substantial amounts of

heat from its surroundings (i.e., one gram of ammonia absorbs 327 calories of heat).

Because of this property, it is frequently employed as a coolant in refrigerating and

air-conditioning equipment.

The chief commercial method of producing ammonia is by the Haber-Bosch process,

which involves the direct synthesis of the compound from its constituent elements.

Ammonia from the

Haber-Bosch process is supplemented by ammonia obtained as a by-product of

coke ovens.

The major use of ammonia is as a fertilizer. It is most commonly applied directly to

the soil from tanks containing the liquefied gas. Additional quantities are converted

into ammonium nitrate,

ammonium phosphate, and other salts that also are utilized primarily in commercial

fertilizers. In the textile industry ammonia is used in the manufacture of synthetic

fibers such as nylon and rayon. In addition, it is employed in the dyeing and scouring

of cotton, wool, and silk. Ammonia serves as a catalyst in the production of Bakelite

and some other synthetic resins. More importantly, it neutralizes acidic by-products

of petroleum refining, and in the rubber industry it prevents the coagulation of raw

latex during transportation from plantation to factory. Ammonia also finds application

in both the ammonia-soda, or Solvay, process, a widely used method for producing

soda ash, and the Ostwald process, a method for converting ammonia into nitric

acid. Ammonia is used in various metallurgical processes, including the nitriding of

alloy sheets to harden their surfaces. Because ammonia can be decomposed easily

to yield hydrogen, it is a convenient

portable source of atomic hydrogen for welding. Finally, among its minor uses

inclusion in certain household cleansing agents.

Nitrogen Cycle:

All life requires nitrogen-compounds, e.g., proteins and nucleic acids.

Air, which is 79% nitrogen gas (N2), is the major reservoir of nitrogen.

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But most organisms cannot use nitrogen in this form.

Plants must secure their nitrogen in "fixed" form, i.e., incorporated in compounds

such as:

nitrate ions (NO3−)

ammonia (NH3)

urea (NH2)2CO

Animals secure their nitrogen (and all other) compounds from plants (or animals that

have fed on plants).

Four processes participate in the cycling of nitrogen through the biosphere:

Nitrogen fixation

Decay

Nitrification

Denitrification

Microorganisms play major roles in all four of these.

Nitrogen Fixation:

The nitrogen molecule (N2) is quite inert. To break it apart so that its atoms can combine with

other atoms requires the input of substantial amounts of energy.

Three processes are responsible for most of the nitrogen fixation in the biosphere:

atmospheric fixation by lightning

biological fixation by certain microbes — alone or in a symbiotic relationship with

plants

industrial fixation

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Atmospheric Fixation:

The enormous energy of lightning breaks nitrogen molecules and enables their atoms to

combine with oxygen in the air forming nitrogen oxides. These dissolve in rain, forming

nitrates, which are carried to the earth.

Atmospheric nitrogen fixation probably contributes some 5– 8% of the total nitrogen fixed.

Industrial Fixation

Under great pressure, at a temperature of 600°C, and with the use of a catalyst, atmospheric

nitrogen and hydrogen (usually derived from natural gas or petroleum) can be combined to

form ammonia (NH3). Ammonia can be used directly as fertilizer, but most of its is further

processed to urea and ammonium nitrate (NH4NO3).

Biological Fixation

The ability to fix nitrogen is found only in certain bacteria.

Some live in a symbiotic relationship with plants of the legume family (e.g.,

soybeans, alfalfa).

Some establish symbiotic relationships with plants other than legumes (e.g., alders).

Some nitrogen-fixing bacteria live free in the soil.

Nitrogen-fixing cyanobacteria are essential to maintaining the fertility of semi-aquatic

environments like rice paddies.

Biological nitrogen fixation requires a complex set of enzymes and a huge expenditure of

ATP.

Although the first stable product of the process is ammonia, this is quickly incorporated into

protein and other organic nitrogen compounds.

Decay:

The proteins made by plants enter and pass through food webs just as carbohydrates do. At

each trophic level, their metabolism produces organic nitrogen compounds that return to the

environment, chiefly in excretions. The final beneficiaries of these materials are

microorganisms of decay. They break down the molecules in excretions and dead

organisms into ammonia.

Nitrification:

Ammonia can be taken up directly by plants — usually through their roots. However, most of

the ammonia produced by decay is converted into nitrates. This is accomplished in two

steps:

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Bacteria of the genus Nitrosomonas oxidize NH3 to nitrites (NO2−).

Bacteria of the genus Nitrobacter oxidize the nitrites to nitrates (NO3−).

These two groups or autotrophic bacteria are called nitrifying bacteria. Through their

activities (which supply them with all their energy needs), nitrogen is made available to the

roots of plants.

Many legumes, in addition to fixing atmospheric nitrogen, also perform nitrification —

converting some of their organic nitrogen to nitrites and nitrates. These reach the soil when

they shed their leaves.

Denitrification:

The three processes above remove nitrogen from the atmosphere and pass it through

ecosystems.

Denitrification reduces nitrates to nitrogen gas, thus replenishing the atmosphere.

Once again, bacteria are the agents. They live deep in soil and in aquatic sediments where

conditions are anaerobic. They use nitrates as an alternative to oxygen for the final electron

acceptor in their respiration

Thus they close the nitrogen cycle.

Are the denitrifies keeping up?

Agriculture may now be responsible for one-half of the nitrogen fixation on earth through

the use of fertilizers produced by industrial fixation

the growing of legumes like soybeans and alfalfa.

This is a remarkable influence on a natural cycle.

Are the denitrifiers keeping up the nitrogen cycle in balance? Probably not. Certainly, there

are examples of nitrogen enrichment in ecosystems. One troubling example: the "blooms" of

algae in lakes and rivers as nitrogen fertilizers leach from the soil of adjacent farms (and

lawns). The accumulation of dissolved nutrients in a body of water is called eutrophication.

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PLANT OVERVIEW

AMMONIA

Properties of ammonia

Molecular weight: 17.03 g/mol

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Melting point: -78oC

Boiling point (1.013 bar): -33.5oC

Latent heat of vaporization (1.013 bar at boiling point): 1371.2 kJ/kg

Latent heat of fusion (1,013 bars, at triple point): 331.37 kJ/kg

Vapor pressure (at 21oC or 70oF): 8.88 bar

Critical point - Critical temperature: 132.4oC - Critical pressure: 112.8 bar

Gas Specific volume (1.013 bar and 21oC (70oF)): 1.411 m3/kg

Gas Ratio of Specific Heats (γ: Cp/Cv) (1.013 bar and 15oC (59oF)): 1.309623

Gas Solubility in water (1.013 bar and 0oC (32oF)): 862 vol/vol

Gas Auto ignition temperature: 630oC

PropertiesLiquid phase

Vapor phase (1.013 bar )250 K 300 K 400 K

Density (1.013 bar at Bp) (kg/m3 ) 669 600 346 0.86

Specific heat capacity (Cp) (kJ/kg.K)

4.52 4.75 6.91

at constant volume (cv) 0.028

at constant pressure (cp) 0.037

Dynamic viscosity (Ns/m2)245 106

141 106 38 106 0.000098 Poise (0oC)

Thermal conductivity (kW/m.K)592 106

477 106

207 106 22.19 (0oC )

Uses of ammonia

Agricultural industries are the major users of ammonia, representing nearly 80% of all ammonia produced.  Ammonia is a very valuable source of nitrogen that is essential for plant growth.  It is used in the production of liquid fertilizer solutions which consist of ammonia, ammonium nitrate, and urea and aqua ammonia. 

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Ammonia and urea are used as a source of protein in livestock feeds for ruminating animals such as cattle, sheep and goats. 

Dissociated ammonia is used in some metal treating operations as nitriding, carbonitriding, bright annealing, furnace brazing, sintering, sodium hydride descaling, atomic hydrogen welding and other applications where protective atmospheres are required.

Ammonia is used in the manufacture of nitric acid; certain alkalies such as soda ash; dyes; pharmaceuticals such as sulfa drugs, vitamins and cosmetics; synthetic textile fibers such as nylon, rayon and acrylics; and for the manufacture of certain plastics such as phenolics and polyurethanes.

Ammonia is used in the mining industry for extraction of metals such as copper, nickel and molybdenum from their ores.

Ammonia is used in several areas of water and wastewater treatment, such as pH control, in solution form to regenerate weak anion exchange resins, in conjunction with chlorine to produce potable water and as an oxygen scavenger in boiler water treatment.

Ammonia is used in stack emission control systems to neutralize sulfur oxides from combustion of sulfur-containing fuels, as a method of NOx control in both catalytic and non-catalytic applications and to enhance the efficiency of electrostatic precipitators for particulate control.

Ammonia is a widely used refrigerant in industrial refrigeration systems found in the food, beverage, petro-chemical and cold storage industries.

Ammonia is used in the rubber industry for the stabilization of natural and synthetic latex to prevent premature coagulation.

Ammonia Manufacturing Technologies

Some well known technologies for ammonia manufacturing are:-

a) HaldorTopsoe Ammonia Processb) Kellogg's Ammonia processc) Kellogg's Advanced Ammonia Process ( KAAP-KRES )d) Linde Ammonia Concept ( LAC )

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e) Brown Purifier Ammonia Processf) ICI's AMV Ammonia Processg) Krupp Uhde ammonia process

At Tata Chemicals, Babrala

Different steps involved in the HALDOR TOPSOE’S process used at TATA CHEMICALS Ltd are:

Desulphurization - sweetening

Naphtha - NPDU

Natural Gas & Naphtha - HDS section

Steam reforming

Pre, Primary and Secondary

Gas purification - shift conversion & CO2 removal

MTS and LTS

GV process

Methanation

Compression

Syn gas compressor

Process air compressor

Ammonia refrigeration compressor

Ammonia synthesis

Ammonia refrigeration

Ammonia recovery

FLOW DIAGRAM OF AMMONIA PRODUCTION PROCESS

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DETAILED PROCESS DESCRIPTION:

Desulphurization

The desulphurization unit consists of three vessels, one containing the hydrogenation catalyst and the other two vessels containing the H2S absorption mass. Over the hydrogenation catalyst the sulphur containing compounds are converted into hydrogen sulphide at a temperature of 380-400.c.

RSH + H2 --------à RH + H2S

After the hydrogenation the process gas passes through the ZnO absorber R 202 A\B for removal of H2S. The two absorption vessels are operates in series. Normally only the first vessel will actually be absorbing H2S while the second vessel will function as a safeguard.

ZnO + H2S ------à ZnS+H2O

With the catalysts installed the sulphur in the raw gas will be removed down to below 0.05 ppm and shall at no time exceed 0.1 ppm by weight.

Note:- There are two states of HDS catalyst in which it is found.

1.Sulphided state: - In this case the methanation activity is nil.

2.Unsulphided state:- If the catalyst is not sulphided or only partly, there is a potential risk of methanation in case the feed gas contains carbon oxides.

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Steam reforming

In the reforming section the gas containing the necessary compound for preparation of the ammonia synthesis gas is produced by the catalytic reforming of a mixture of hydrocarbon and steam and addition of air. The steam reforming of hydrocarbon can be described by the following reactions:

CnHm + nH2O = n CO + (n+m/2) H2-heat

CH4+H2O = CO + 3H2 - heat

CO + H2O = CO2 + H2 + heat

The steam reforming takes place in three steps:

o Adiabatic preconversion

o Primary reforming

o Secondary reforming

Adiabatic preconversion:

The hydrocarbon feed coming from the desulphurization section is mixed with steam and pre-heated in a coil E 201 installed in the flue gas heat recovery section of the primary reformer and taken to the adiabatic preconverter R 206 at 460-480 °C. Virtually all the higher hydrocarbons are decomposed into methane by steam reforming by means of the preconversion catalyst. The preconverter contains RKNGR Topsoe catalyst which is a pre-reduced RKN catalyst especially treated for low temperature operation.

Primary reforming (H 201)

The primary reformer H 201 has a total of 300 vertically mounted tubes installed in two radiant chambers. The process gas is flowing downwards with the gas being distributed to the top of the tubes from a header through hairpins at a temperature of 490-520°C. The gas leaves the tubes through bottom hairpins. The temperature of the gas leaving the reformer will be about 800°C and the hydrocarbon content which is methane only will be about 9-12 mole% .

Secondary reformer

The gas from the primary reformer is passed on to the secondary reformer R 203, through a brick lined transfer line and the gas is admitted to the pear shaped vessel through top dome mixing chamber where it is mixed atmospheric air pre heated to 550°C. In the secondary reformer the partial combustion of process gas will give high temperature at the top of the catalyst bed. The reforming reaction of methane will lower the temperature during passage of the gas mixture through the catalyst bed and at the exit the temperature will be about 1000°C.

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Gas purification - shift conversion & CO 2 removal

Shift conversion

CO + H2O àCO2+ H2 + heat

The above mentioned shift conversion takes place in the converter R 204 and R 205. The equilibrium is favored by lower temperature and more steam while the reaction rate will be higher at higher temperatures. More steam may give an apparently lower reaction rate due to larger total volume resulting in shorter contact time. This means that for each catalyst there will be an optimum temperature depending on the activity and the floe rate which will give optimum conversion. Thus the conversion is performed in two steps.

o Medium temperature CO conversion

The main part of reaction takes place here causing a temperature rise of 90-120°C.

The outlet temperature of up to 340°C is fully acceptable for this catalyst being more rugged than the low temperature shift catalyst used in the second step of shift conversion.

o Low temperature CO conversion

The low temperature shift catalyst consists of specially prepared copper, zinc and aluminum oxide having a much higher activity which means that it can be used in the low temperature range of 180-250°C. The catalyst is les rugged and losses its activity if the temperature exceeds 250-270°C.

Carbon dioxideremoval (GV process)

Carbon dioxide is removed by absorption in the hot aqueous potassium carbonate solution containing approx. 25 wet% potash partly converted into bicarbonate. The solution further contains activator glycine and vanadium oxide as corrosion inhibitor. The reason for keeping the solution hot is to increase the rate of absorption and keep the bicarbonate in solution. Another advantage is that the temperature is approximately the same temperature in the absorber and in the regenerator, thus it is not necessary to supply heat before the regenerator.

The gas is passed to CO2 absorber F 303 which is a column containing stainless steel packing material distributed in six beds. In the absorber the gas flow upward against a descending stream of potash solution. Approximately 15% of the solution is introduced above the top bed at 70°C where as remainder is introduced at about 106°C below the two top beds. Gas is enters from bottom side just after one bed from bottom, this bed prevent the flow of H 2 from

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bottom with down coming stream. The CO2 absorption occurs according to the following reaction.

K2CO3 + CO2 + H2O 2KHCO3

The rich solution leaving the absorber bottom is depressurized through the expansion turbine TG 301which is connected to the semi lean solution pump and its feeds the top of the 1 st

regenerator F 301operating under pressure. A stream of rich solution extract from the top of F 301is depressurized through a control valve and enters the top of the 2nd regenerator F 302 working at low pressure. The regeneration is performed accordingly to the GV two pressure level technologies which foresee that the pressure of F 301 is adjusted to obtain a temperature increase of the solution leaving the bottom of F 301 with respect to the solution entering the top.

The semi lean solution extracted from the intermediary tray of F 301 at 124°C is flashed across the level control valves and enters F 302, operating slightly above atmospheric pressure. The solution is collected on the take off tray and feeds the semi lean solution pump P 301 A/B/C/D. Lean solution transferred from bottom of F 301 at 127°C is flashed across a set of level control valves and enters the bottom of F 302 just below the semi lean solution take off tray. The solution is collected in the bottom of F 302 to feed the lean solution pump P 302 A/B.

The semi lean solution leaving F 302 at 106°C feeds the absorber F 303 by means of P 301A/B/C/D. lean solution drawn from the bottom of F 302 at 109°C is cooled in the DMW pre-heater and pumped by P 302 A/B to the top of the absorber after final cooling to 70°C in the air cooler.

Methanation

After the CO2 removal unit remaining traces of CO and CO2 must be removed since these compounds are poisonous to the ammonia synthesis catalyst. This is done in the methanator and the reactions involved are the reversible of the reforming reaction:

CO + 3H2 CH4 + H2O + heat

CO2 + 4H2 CH4 + 2H2O + heat

Low temperature, high pressure, and low steam content tend to favors the methane formation. However within the allowable temperature range the equilibrium conditions are so favorable that practically only the catalytic activity determines the efficiency of the Methanation. The higher the temperature the better the efficiency but at the same time it means a shorter life time of the catalyst. Furthermore in case of a possible break through of CO2 to methanator, which would result in a significant temperature rise a low inlet temperature is preferable as this limits the temperature rise some what in connection with the lower activity. After the

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methanator the gas normally contains less than 10 ppm of CO and CO2. The temperature rise will normally be about 15-25°C.

Ammonia synthesis

The ammonia synthesis takes place in the two ammonia converters R 501 and R 502 according to the following reaction

N2 + 3H2 2NH3 + heat

However as the reaction rate is very much enhanced by high temperature the choice of temperature is based on a comparison between the theoretical conversion and the approach to equilibrium in a single pass over the catalyst. The result of this relationship is that there is an optimum level for the catalyst temperature at which the maximum production is achieved. At higher temperatures the equilibrium percentage will be too low while at lower temperature the reaction rate will be too slow.

Make-up gas is introduced into the synthesis loop between the 2nd cold heat exchanger E 507, and the 2nd ammonia chiller E 508. At this point a considerable part of the ammonia produced in the converter has been condensed. The mixture of synthesis gas and liquid ammonia passes from the 2ndchiller to the ammonia separator B 501, in which the liquid ammonia is separated. By the ammonia condensation in E 508 traces of impurities in the make-up gas such as H 2O and CO2 are absorbed in the liquid ammonia phase and removed with the liquid ammonia in the separator. Carbon dioxide in the make-up gas reacts with both gaseous and liquid ammonia forming ammonium carbamate. The carbamate formed is dissolved in the condensed ammonia. Carbon monoxide is only slightly soluble in ammonia and will pass with recalculating gas to the 1st ammonia converter, where it is hydrogenated to water and methane. As the water deactivates the ammonia synthesis catalyst the content of carbon monoxide in the make-up gas should be kept as low as possible.

The gas leaving B 501 goes to two cold heat exchangers E 507 and E 505, in which heat exchanger takes place with the gas coming from 1st ammonia chillerE 506, and the water cooler E 504 respectively. After E 505 the gas is taken to the recirculation compressor and then to the hot heat exchanger E 503. In the hot heat exchanger the gas is heated with the gas coming from the BFW pre-heater E 502 to the inlet temperature of the 1st ammonia converter R 501. After R 501 the gas contains about 17.4 mole% ammonia.

The gas is cooled to about 375°C in the waste heat boiler, E 501 A before going to the 2nd

ammonia converter R 502. After R 502 the gas contains about 29.7 mole % ammonia.

A considerable part of the heat content in the gas leaving the converters is recovered in the waste heat boilers, E 501A/B, and in the BFW pre-heater E 502. After the BFW pre-heater the gas is cooled first in the hot heat exchanger E 503, mentioned above and then in the water cooler E 504 where part of the ammonia content is condensed. The gas passes the 1 st cold

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heat exchanger E 505, the 1st ammonia chiller E 506, the 2nd cold heat exchanger E 507, and after addition of make-up gas the 2nd ammonia chiller E 508 and the circuit is repeated.

Compressor section

The compressor section consists of four compressors

The process air compressor K 421

The synthesis gas/recirculation compressor K 431

The ammonia refrigeration compressor K 451

The flash ammonia compressorK 441

Process air compressor

In line with the low energy ammonia plant concept the process air compressor is envisaged to be a high efficiency machine thereby minimizing the power requirement for compression of process air.

During normal operation about 54000 Nm3/hr of atmospheric air is compressed up to 33 Kg/cm2g and after pre-heating added to the secondary reformer as process air. Furthermore, provision has been made for extracting a flow of about 1500 Nm3/hr for use as instrument air back-up. The compressor has no anti surge bypass, but instead an air flow governor vent valve is installed at the compressor outlet. The rotating speed of the compressor is controlled by the turbine speed governor maintaining a constant speed at the set point. At reduced load the speed is maintained at minimum governor speed and the process air flow control is then accomplished by using the air vent valve at the compressor discharge.

Synthesis gas/recirculation compressor

The process gas from methanation section is compressed from about 26 Kg/cm2g to 134 Kg/cm2g before introduction to the ammonia synthesis loop. The compression is carried out by the synthesis gas/recirculation compressor K 431 envisaged to comprise three stages plus recirculation stage.

During normal operation the inlet gas flow is about 162500 Nm3/hr at 41°C and the outlet flow is about 159900 Nm3/hr at 40°C. a flow of about 1840 Nm3/hr hydrogenation gas at min. 42Kg/cm2g is extracted.

The hydrogenation gas is added to the natural gas feed stock upstream of the desulphurization section and before leaving the compressor section it is Desulphurised to about 41 Kg/cm2g. The compressor is provided with anti surge bypass to ensure operation at reduced plant loads.

The recirculation serves to compensate for the pressure drop of the circulated synthesis gas in the ammonia synthesis loop. The flow is about 539000 Nm3/hr at 131 Kg/cm2g and 36°C

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and the discharge pressure and temperature are about 141 Kg/cm2g and 45°C respectively. The recirculation has been provided with a bypass serving primarily as an anti surge device. The steam turbine TK 431 driving the synthesis gas/recirculation compressor consists of two parts. The 1st part is a back pressure turbine driven by HP steam (110 Kg/cm2g, 510°C). The 2nd part is a condensing turbine driven by superheated Mp steam at 40 Kg/cm2g coming from the back pressure part

Ammonia refrigeration compressor

The steam turbine driven ammonia refrigeration compressor K 451 is a two stage centrifugal compressor. When the ammonia product is delivered to the urea plant, it is the only compression facility in operation in the refrigeration circuit. Evaporated ammonia from the 2ndchiller E 508 is compressed from 1.7 Kg/cm2g to about 6.4 Kg/cm2g. The cooled discharge flow is mixed with evaporated ammonia from the highest chiller level (including E 506, E 514 and E 509) before entering the second stage. The discharge pressure from the second stage is about 17.7 Kg/cm2 g and the total flow is about 58 t/hr. both first and second stage are envisaged to a provided with anti surge bypass. The condensation steam turbine TK 451 uses MP steam at 40 Kg/cm2g and 380°C as driving force.

Flash ammonia compressor

When the ammonia product is delivered to the ammonia storage the product needs to be fully refrigerated. This is accomplished by depressurization and flashing in the flash vessel B 503. In order to make the refrigeration compressor K 451 independent of the product destination, all the flashed ammonia from B 503 is compressed from 0.02 Kg/cm2g to 17.7 Kg/cm2g by means of the electric motor driven flash ammonia compressor K 441.

Ammonia refrigeration

The purpose of the refrigeration circuit is to carry out various cooling tasks of the ammonia synthesis loop. The primary task is to condense the ammonia produced in the two converters. Other cooling tasks are cooling of make-up gas and inerts gas. The refrigeration circuit consists of a compressor unit, a condenser, an accumulator, and a number of chillers operating at different temperatures. Liquid ammonia evaporated at 6.4 Kg/cm2g corresponding to a temperature of 15°C. The liquid from E514 is transferred to E 508 where it is further expanded to 1.9 Kg/cm2g corresponding to temperature of -10°C.

Evaporated ammonia from the chiller is compressed by the compressor K 451. The suction pressures correspond to the pressure in the chiller. After compression the ammonia is condensed in E 510 A/B/C and collected in a accumulator B510.

In case the product ammonia is transferred to the storage instead of consumer, the corresponding flash ammonia from B 510 is compressed in K 441 to the discharge pressure of K 451.

In order not to accumulate inert gases liberated with flashing ammonia from B 503 during ammonia to storage operation within the refrigeration circuit a small gas stream is purged

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from the ammonia accumulator B 510. The main part of the ammonia in this purge stream is condensed in the inert gas chiller E 509 by cooling to 20°C and separated in B 509. The condensed ammonia from B 509 is returned to B 510 and the let down gas from B 502 are combined and directed to the off-gas absorber F 522 for further recover of ammonia.

Ammonia recovery

The ammonia recovery section removes and recovers the major part of the ammonia contained in the purge gas from the synthesis loop and the off-gas from the refrigeration section.

Purge Gas Recovery

Hydrogen is recovered from purge gas, and recycled to synthesis loop. Recovery of hydrogen is based on the principle of cryogenic separation.

In the first step of purge gas recovery, the gas stream is cooled down, and condensed water is separated. In the second step all the traces of ammonia and water are removed before going for cryogenic separation. The recovered hydrogen product stream joins the second stage suction of the synthesis gas compressor, while the residual gas stream goes to the reformer fuel.

Moisture removal section:

In this section, the exchanger (water cooler) separator combine removes moisture from the incoming purge gas. It is necessary, as the moisture has a tendency to clog the cryogenic section.

Purification section:

Traces of ammonia and water are removed in this section, so as to avoid freezing of these substances in the cryogenic section. The purge gas is purified in one of two adsorbers. The two adsorbers remain in line or under regeneration alternately. Each adsorber contains one bed of activated alumina (at the bottom) and one bed of molecular sieves (at the top). Alumina is for adsorbing water, while molecular sieve adsorbs traces of ammonia.

Cryogenic separation section: Hydrogen is separated from a mixture of hydrogen, nitrogen, argon and methane, at a cryogenic temperature (-190°C), where other gases except hydrogen liquefy. Nitrogen is also partially recovered, as it is not fully condensed at this temperature. The low temperature is created by reduction of pressure of the gas stream from about 75 kg/cm2g to 3kg/ cm2g. The incoming gas stream exchanges heat with outgoing cold gases (the product hydrogen stream and the residual gases) before being depressurized.The purity of hydrogen obtained is above 90%.

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Absorption

Purge gas from the synthesis loop is introduced at the bottom part of the absorber F 523, where it is washed in the countercurrent with water introduced at the top of the absorber. The purified off-gas leaving the absorber contains about 0.1 mole% ammonia. F 523 is operated at 75 Kg/cm2g, there by facilitating the possible future installation of a PGR unit.

The combined stream of let-down gas and inert vent gas from refrigeration section is introduced at the bottom of the absorber F 522 where it is washed with water. The purified off-gas contains about 0.1 mole% ammonia. The purified off-gases from F 522 and F 523 are directed to the fuel system of the primary reformer H 201, thus reducing the fuel requirement from external source.

Distillation

The ammonia water solution leaving F 522 is pumped by LP circulation pump P 521 A/B, through the rich/lean solution exchanger E 523 A/B, where rich solution is pre-heated to 163°C and then into distillation column F 521. The absorber F 523 is added on the discharge side of P 521 A/B.

The necessary heat for distillation is provided from the re-boiler E 521, where heat is liberated by condensing MP steam. From re-boiler lean solution is returned to the two absorbers after passing the rich/lean solution exchanger E 523 A/B, and the lean solution cooler E 524. For return to the top of F 523 pumping by the HP circulation pump P 522 A/B is required. The distillation is carried out at a pressure of 25 Kg/cm2g and the temperature of the gaseous ammonia leaving the top of the column is about 60°C. This means that the water content in ammonia liquid is returned to the distillation column as reflux. The rest of the liquid ammonia is sent to the let-down vessel B 502.

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Ammonia Manufacturing Process

(Detailed Description Of Operation)

Naphtha Pre-desulfurization:

In the pre-desulfurization process, the organic sulfur compounds are removed from naphtha, by catalytic conversion to hydrogen sulfide, which is separated from naphtha by distillation. The hydrogenation and stripping process is designed to handle a maximum 2500 wt. ppm sulfur in naphtha feed, which is brought down to below 10ppm. The pre-desulfurization step does not yield sufficiently low concentration of sulfur to prevent poisoning of steam reforming catalyst, so a final desulfurization must also be performed.The first hydrogenator R101 is loaded with 15.75 m3 of TK 550 catalyst.

It is a cobalt molybdenum catalyst of HTAS manufacture. On the top of the catalyst there is a

200mm layer of ½” ceramic balls on a stainless steel wire mesh. The bottom layer below the

catalyst is a 200mm layer of ¼ -1/2”

ceramic balls.

TK 550 catalyses the following reactions:

RSH + H2 RH + H2S

R1SSR2 + 3H2 R1H + R2H + 2H2S

R1SR2 + 2H2 R1H + R2H + H2S

(CH)4S + 4H2 C4H10 + H2S

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COS + H2 CO + H2S

Where R is a radical of hydrocarbon.

Besides these reactions, the catalyst also hydrogenates olefins to saturated hydrocarbons.

During start-up, when CO and CO2 are present in the hydrogenation gas, the following

reactions will take place.

CO2 + H2 CO + H2O

CO2 + H2S COS + H2O

and in case of a high CO concentration, Boudouard’sdismutation can take place.

2 CO CO2 + C

In this way, carbon in the form of soot can deposit on the catalyst. The catalyst has however

little activity, for methanation even at low sulfur levels.

The Boudouard reaction and also the methanation reaction do not take place when the

catalyst is in sulfided state. But, Boudouard carbon may still be formed in the feed heating

system and deposit in the inlet layer of the catalyst.

The recommended operating temperature for the catalyst is about 380°C. At temperature

below 330°C a poor hydrogenation will result and at temperatures above 400°C, the

tendency for coking and polymerization on the catalyst increases.

Hydrogen should always be present in the feed, however operation for a few minutes

without hydrogen in the feed does not harm the catalyst. But, prolonged exposure of the

catalyst in this way will result in coking.

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The catalyst is delivered in the oxidized state and the most active state of the catalyst is

obtained when it is sulfided.

In the sulfided state the catalyst is pyriphoric and must not be exposed to air at temperature

above 70°C.

The coking of feed heating system and hydrogenation catalyst will increase, when gum is

formed, an in order to limit this tendency in the feed, a preventive stripping of dissolved

oxygen is performed by means of a small amount of hydrogen.

TK 550 must not be exposed to hydrogen only, as reduction, which takes places then, will

cause a loss of activity for the catalyst.

The following process steps are followed.

1. Oxygen removal from raw naphtha in the deaerator (F101) by stripping with hydrogen

rich gas (introduced through 01FV102), in order to prevent gum formation in the feed

heating system. Deaerated naphtha is transferred by means of the raw naphtha charge

pumps P101A/B.

2. Hydrogenating gas is added to naphtha (through 01FV107) and the mixture is heated

and evaporated in feed effluent exchangers (E101A/B/C/D).

3. After further heating in direct fired heater (H101), the mixture is sent to HDS reactor

(R101), where hydrogenation of sulfur compounds takes place.

4. The reaction mixture is cooled (in E101A/B/C/D and E102) and hydrogenating gas is

separated from naphtha (in B101). A small quantity of gas is purged (by 01PV130) to

avoid build up of inerts. Rest of the gases is recycled to the recycle compressor (K101).

5. Hydrogen sulfide is removed by stripping (in F102) and the pre-desulfurized naphtha is

cooled, depressurized and sent for storage.

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Feedstock for reforming section

Natural gas for feed and fuel

In normal conditions natural gas is delivered at the battery limit at 40kg/cm2g and 30°C. The

process conditions for the incoming natural gas are controlled and measured by 02PC01,

02AT01, 02TI01, and 02FI01 (pressure, density, temperature and flow respectively).

Fuel gas pre-heat and depressurization:

The natural gas part of the fuel for the primary reformer is passed through the fuel gas pre-

heater E219 after getting depressurized through 02PC02 from 39 kg/cm2g to 4 kg/cm2g. Pre-

heating of the fuel gas is done to avoid hydrate formation at low temperature (below 20°C)

due to depressurization.

The heating medium is low pressure (2.8 kg/cm2g, 141°C) condensing steam.

Natural gas feed pre-heating:

Before entering the desulfurization section, the hydrocarbon feed is preheated in two pre-heating coils E204B and E204A, installed in the flue gas heat recovery section H202.In E204B, the natural gas part of the process feed is pre-heated, and after addition of recycle gas and naphtha part of the process feed further pre-heating takes place in E204A. The gas stream at the outlet of E204A has a temperature of 380°C, which is controlled by 02TC17 acting in split range on the bypass valve of 02TV17A of E204B (0-50%) and on the bypass valve 02TV17B of E204A (50-100%).Recycle hydrogen (73 mol %) is added downstream of E204B in order to avoid carbamate formation. The required flow is 0.05 Nm3 of H2/kg of natural gas. This flow is controlled by 02FC10. The source of recycle gas for normal operation is first stage discharge of K431. In case of a trip, it may be supplied from synthesis loop, or inlet or outlet of CO2 absorber.

Process naphtha evaporation and super-heating:The pre-desulfurized naphtha is supplied from sweet naphtha bulk storage tank to sweet naphtha day tank (64T-12), from where it is pumped to the evaporation and desulfurization sections by the sweet naphtha feed pumps 64P12A/B. The flow is controlled by 02FC03. After the flow control valve the recycle hydrogen gas is added through 02FC723 to the liquid naphtha. Recycle gas flow is maitained at the rate of 0.2 Nm3 of H2/kg of naphtha. The mixture is sent to E215A or E215B for evaporation and super-heating of naphtha (up to 220°C at 38 kg/cm2g). The

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heating medium is medium pressure condensing steam, the flow of which is controlled by 02HC111. A knock out drum B204 is installed to prevent liquid carry over from E215A/B.In case evaporation of process naphtha turns out to be difficult, a further reduction of partial pressure of the heavier components of naphtha may be attempted by adding some of the natural gas process feed upstream of E215A/B through 02FC721. The evaporated naphtha from B204 is mixed with natural gas and sent to E204A, where it is heated upto 380°C, controlled by 02TC17.

Desulfurization: Desulfurization takes place in two steps. In the first step, organic sulfur is converted into hydrogen sulfide (H2S) in the HDS reactor (R201). Organic sulfur content is thus reduced to less than 0.05 ppm. In the second step the H2S is absorbed in two ZnO absorbers (R202A/B) connected in series.The natural gas/ naphtha stream mixed with hydrogenation gas from E204A (at about 380°C) passes through R201, R202A/B to get desulfurized.Following reasons can lead to insufficient desulfurization. 1. Too low temperature in hydrogenator.

2. Too low recycle gas flow.

3. The catalyst (TK251) has lost its activity.

Following reasons can lead to insufficient absorption.1. R202A/B beds are loaded with sulfur.

2. Water vapor is present in the feed gas, which gives an unfavorable equilibrium.

The hydro-desulfurization catalyst must be in the sulfided state. It must pick up sulfur corresponding to 5-7% of its weight, from the feed gases in order to be fully active. It must be supplied in a pre-sulfided state (at least partialllY), if; it has to handle a feedstock containing sufficient amount of CO2

and hydrogen. It is necessary to suppress the methanation reaction, which may be favored by the unsulfided catalyst. In a very low sulfur environment, sulfur will tend to strip off the from the HDS catalyst.

Mixing of desulfurized hydrocarbon feed and process steam:

Desulfurized hydrocarbon is mixed with process steam, before final preheating in the waste heat recovery section. The hydrocarbon flow is controlled by 02FC12 and the steam flow is controlled by 02FC19.The process condition for the steam is of 39kg/cm2g pressure and 380°C temperature.

Steam flow is maintained keep steam/carbon (S/C) ratio at 3.2.

Process feed preheat:

The process feed containing the hydrocarbons, recycle gas and the process steam is preheated in E201, situated in the flue gas heat recovery section.The inlet temperature is about 360°C and the outlet temperature is 465°C.

E201 has been rearranged from counter-current to co-current as per mixed feed (natural gas

and naphtha) design. The pre-heated process feed goes to adiabatic pre-reformer (R206)

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Reforming section

Adiabatic pre-converter:

The adiabatic pre-converter (R206) consists of a refractory lined pressure shell containing

26.9m3 RKNGR catalyst which is a pre-reduced RKN type catalyst specially treated for low

temperature operation. Here, all higher hydrocarbons are decomposed into hydrogen,

carbon monoxide, carbon dioxide and methane. The outlet temperature of R206 for normal

mixed operation is expected to be about 445°C. The endothermic reforming reactions are

followed by equilibration of the exothermic methanation and shift reactions. When feedstock

is natural gas, the overall process is endothermic. For heavier feedstock such as naphtha

the process is normally exothermic. The higher the inlet temperature and S/C ratio, the more

dominant will the endothermic reactions be. A pressure drop of 0.5 kg/cm2 across the reactor

is foreseen. The effluent stream from R206 goes to primary reformer.

Primary reformer construction:

The reformer furnace is divided into two chambers. The chambers are placed side by side in a duplex arrangement and function as one unit.The two chambers have a common flue gas channel and a flue gas heat recovery section.

Each furnace chamber contains 150 vertically mounted high alloy Cr-Ni steel (manurite 36X)

tubes filled with catalyst. In total, 300 tubes contain 6.8m3 RKNR on top of 27.3m3 R-67-7H

reforming catalyst. The vertical tubes are mounted in a single row along the centre line of

each chamber. The heated length of the tubes is 12000mm and OD/ID is 134/109.8mm.

The process gas flows downwards with the gas being distributed to the top of the tubes

from a header through the inlet hairpins. After passing the catalyst, the gas leaves the tubes

through bottom hairpins and enters a refractory lined collector through high alloy

intermediary hot collectors.

The tubes are heated by 432 forced draught radiant wall burners located in each side wall

of the furnace chambers and arranged in 6 horizontal rows to provide easy control of a

uniform temperature profile along the length of the catalyst tubes. The flue gas outlet

comprises a common flue gas collector mounted between two radiation chambers. The flue

gas outlet temperature is approximately 1000°C. All hot parts of the reformer are insulated

by ceramic materials to reduce heat loss to a minimum.

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Combustion air supply:

The combustion air to the primary reformer burners is supplied by the blower K202. The

differential pressure across the blower is about 0.05 kg/cm2. Downstream the blower, the air

is pre-heated to about 295°C in the pre-heater E205 situated in the flue gas heat recovery

section. The pressure at the down stream of E205 is controlled by 02PC11, acting on the

guide vanes of the blower K202. Air supply should be at least 5% excess to the

stoichiometric requirement.

Fuel gas control:

The fuel system of primary reformer is designed to operate on the following fuels:a) Natural gas

b) Natural gas in admixture with lean gases

c) Vaporized naphtha

d) Vaporized naphtha in admixture with lean gases

The lean gases originates from purified off-gas (mainly purge gas)from ammonia recovery

section, surplus synthesis gas and tail gases from purge gas recovery(PGR) and naphtha

pre-desulfurization unit(NPDU).

The natural gas fuel flow is controlled by 02FC32 compensating for the deficit in fuel gas.

The off gas flow is controlled by 02PC29 which along with 02FC31 are connected to the low

selector 02FY31/C. The surplus synthesis gas fuel is controlled by 02FC33. Tail gases from

PGR and NPDU are controlled by 07FIC208 and 01FIC155,respectively. In case, the fuel

header pressure decreases to a value equal to the set point of 02PC23, it will take over the

fuel control and maintain the fuel header pressure.

For charging vaporized naphtha as fuel tracing steam has to be in line through 02PC21 and 02PC21A to heat up the fuel pipings. Raw naphtha from bulk storage is supplied to day tank 64T13, from where it is pumped (by P13A/B) to vaporizer E214. The pressure of the vaporized naphtha is controlled by 02PC22 acting at the inlet of E214. E214 is heated by medium pressure condensing steam the flow of which is controlled by 02HC157. A knock out drum B205 is installed to prevent liquid naphtha being carried over to fuel header. The temperature of the vaporized naphtha at the outlet of B205 is kept above 180°C. Steam is charged into E217 through 02TC48 to heat up lean gases so that cold gases on mixing with naphtha vapor do not result in condensation of naphtha. Natural gas fuel is also routed through E217 by 02FC740. The temperature at the outlet of E217 is 180°C.

Primary reforming:

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The pre-reformed gases from R206 enter the primary reformer tubes through inlet hairpin

and passes through the catalyst in the tubes. Temperature of the gas rises mainly through

radiation up to about 800°C, strongly favoring the endothermic reforming reactions. The

reformed process gas containing about 11.3 mole % (dry basis) of methane passes through

outlet hairpin and enters the hot collectors (six in number). From the hot collectors the

process gas enters a common cold collector and the transfer line to secondary reformer.

The heat transferred to the catalyst tubes makes up about 55% of the total heat input. The remaining part of the heat (except heat losses) leaves the combustion chamber with the flue gases as sensible heat. The reformer tubes are designed for a temperature of 910.6°C, any excess of which causes a decrease in the lifetime of the tubes.

Flue gas heat recovery section:The flue gas heat recovery section comprises nine coils located in the following sequence.E201 process feed pre-heaterE202A process air pre-heaterE203A HP steam super-heaterE203B HP steam super-heaterE203C HP steam super-heaterE204A feedstock (natural gas/ naphtha) pre-heaterE202B process air pre-heaterE204B feedstock(natural gas) pre-heaterE205 combustion air pre-heater

The flue gas flow is cooled from about 985°C to 150°C and emitted through stack X201. The flue gas pressure at the inlet of the heat recovery section is controlled by 02PC19

acting on the guide vane of the flue gas fan K201. During normal operation this pressure

(reformer draught) is about –5mmWC. The pressure at the suction of K201 is about –

200mmWC.

Secondary reforming:

The secondary reforming including mixing and combustion of the primary reformed gas with

process air, takes place in the secondary reformer R203.The process gas (31 kg/cm2g,

795°C) enters the secondary reformer at the top, where it is mixed with process air (31

kg/cm2g, 540°C). The mixing of oxygen in air and process gas results in combustion, raising

the temperature to 1200°C. When this gas mixture passes through the catalyst bed

containing 39m3 of RKS-2-7H catalyst the temperature decreases to about 990°C, due to

endothermic reforming reaction, which results in methane content in the gas stream reduced

to 0.3%. The air flow is determined by the desired hydrogen to nitrogen ratio in the synthesis

loop, which should be close to 3:1.

Owing to high temperature inside the secondary reformer the internal parts have been

insulated. The insulation thickness is 300mm and this reduces the heat losses and the skin

42

temperature of the shell reduces to 160°C (design 350°C). Defects in insulation may cause

the skin temperature to exceed design, with possible damage to the shell. In order to warn of

this factor, the shell is coated with thermosensitive paint, which changes color irreversibly

with the increase in the skin temperature, in the range given below.

Original color: Green

Green color : Up to 200°C

Blue color : 200-315°C

White color : 315-500°C

Apart from secondary reformer other pipings with internal insulation like transfer line, cold

collector are also coated with thermosensitive paint.

Process air compression and pre-heat:

Process air leaving the final stage of the air compressor K421 is pre-heated in two pre-heater coils E202A/B, placed in the waste heat recovery section up to about 540°C. The air flow is controlled by 02FC26, which acts on the speed governor of the turbine driving the compressor K421. The outlet temperature of E202A is controlled by 02HC15 acting on the bypass of E202B.

Process gas cooling and HP steam production:

The reformed process gas leaving the secondary reformer, R203 is cooled in three heat

exchangers, arranged in series, recovering heat by HP steam generation (in E206A/B) and

HP steam super-heating (in E207).

The two waste heat boilers are of the fire tube and gravity water circulation type and produce

120kg/cm2g (324°C) saturated steam from preheated boiler feed water sent to the high

pressure steam drum B201. The steam drum is common to E206A/B and Synthesis loop

boiler E501A/B

Process gas from R203 is cooled in E206A from 987°C to a temperature in the range of

575-635°C, depending on the fouling condition of the boiler tubes. The gas then enters HP

steam super-heater E207, provided with a

Bypass. The controller 02TC50 controls the temperature of super-heated steam acting on

the gas side bypass of E207. Process gas is cooled in E207 to the range of 400-450°C. After

mixing, with hot bypass flow the gas from E207, enters E206B and cooled to 330-340°C.

43

Steam drum

06FC0202LC41

02FY41 02FI41

BFW from P601A/B/C HP steam to

E207

06FE02 02FE41

The high-pressure steam production takes place in the shell side of E206A/B. They are

connected with B201 by a number of risers and down-comers. The boiler feed water fed to

the steam drum has a temperature of about 295°C. The level controller of B201 02LC41, is

part of a three element boiler feed water control loop.

The calculation block 02FY41, receives a process value from 02FE41(steam flow) and out

put from 02LC41. The output from 02FY41 serves as a set point to BFW flow controller

06FC02.

The steam drum pressure is controlled by 02PC30, acting on 02PV30 placed in the HP

steam pipe down stream the steam drum. The waste heat boilers and the steam drum have

been provided with four blow-down valves to prevent accumulation of dirt and sludge. The

steam drum has one continuously working blow-down valve, which is anticipated to blow

down 1% of the boiler feed water entering the steam drum. The boiler blow down is sent to

the blow down vessel B602.resulting in saturated LP steam and condensate, which is added

to cooling water return header at E309 cooling water outlet line. The boiler feed water and

steam quality should be treated with great care, as an inferior quality of BFW will cause

scaling on the boiler tube bundles, and high silica content in steam will result in deposits on

the blades of various turbines, etc.

44

HP steam super-heating:

The HP steam super-heating takes place in two steps. First, in E207 by cooling of process gas, where it is heated up to 390°C. Then, in E203A/B/C by cooling of reformer flue gas, where it is heated up to 515°C. To maintain the steam temperature within limit quench water injection controller 02TC52 has been provided at the inlet of E203A. If it is not able to control the temperature another quench controller 02FC27 comes into action which is provided at the inlet of E203B.

CO conversion section

Medium temperature CO conversion:

Before entering the MT CO converter R204, the process gas is cooled down to 200-220°C

by preheating boiler feed water in E209A/B/C. This temperature is controlled by 02TC64,

which acts on a three way valve distributing the BFW between pre-heaters E209 and E210.

The steam to dry gas ratio at the inlet of R204 is 0.53 and the pressure is about 29kg/cm2g.

The dew point of the gas at this point is about 181°C. The MT CO converter contains 124m3

of catalyst. The outlet temperature is in the range 290-310°C, and the corresponding CO

content is 1.11%(end of the run).

Low temperature CO conversion:

The gas leaving MT CO converter is cooled in the boiler feed pre-heater E210A/B, to the

desired inlet temperature of the LT CO converter R205. This temperature is 185- 200°C

depending on start or end of the run conditions, and is controlled by 02TC76 acting on

process gas bypass of E210. The dew point of the process gas at this point is 168°C. The

LT CO converter contains 118 m3 of LK821 catalyst. The outlet temperature is 190-205°C

and the corresponding CO slip is 0.23 mole%(end of the run). The converter is provided with

a full size bypass, which is operated during start-up and shut down. The process gas from

R205 is further cooled to about 160°C by pre-heating BFW in E211A/B. The performance of

this exchanger is controlled by 02TC91, acting on BFW bypass flow rate.

BFW pre-heating:

Part of the sensible heat and the latent heat of condensation is used for pre-heating the high

pressure boiler feed water. The BFW pumps P601A/B/C raises the pressure of BFW to

130kg/cm2g as available at the inlet of E211A/B. The temperature of BFW at this point is

45

122°C. The major part of the BFW passes through E211A/B tubes, remaining part is

bypassed controlled by 02TC91. The outlet temperature in normal operation is in the range

of 165-175°C, which ensures that the process gas inlet temperature of R204 and R205 are

well above the dew point of the gas at respective points.

About 35% of the BFW flow are led to E209A/B/C and the rest is routed through E210A/B,

controlled by 02TC64. The BFW temperature at E209A/B/C outlet is 295°C and the water

goes directly to steam drum from this point.

The temperature at E210A/B outlet is 233°C. The BFW is further preheated in E502 before

being sent to B201.

Carbondioxideremoval section

Carbondioxide absorption:

The shifted process gas contains about 19 mole% of CO2 (dry basis). This content is

reduced to 0.1 mole% by absorption in hot potassium carbonate (HPC) solution. The CO2

rich solution is regenerated, by stripping off CO2 and then recirculated.

Before absorption of CO2, the process gas is cooled to 122°C from about 160°C in the

vetrocokereboilers E302A/B and E305, providing part of the heat required for regeneration of

the HPC or GV solution. The process condensate thus formed is collected in a separator

B303.

The process gas is introduced in the bottom of the vetrocoke absorber (F303) and CO2 is

removed by passing the packed beds in counter-current with the activated HPC solution.

About 85% of the solution (at 109°C) is introduced above the lower three beds, and rest is

cooled to 70°C in the DMW pre-heater E307 and split stream cooler E303and introduced at

the top of the column. The bulk of the CO2 is removed in the lower part of the column. The

residual clean up takes place in the top two beds, where the smaller and colder part of the

solution is added and the gas is cooled to 70°C, thus decreasing the partial pressure of CO2.

The process gas exiting F303 top passes through a separator B304 before passing into the

methanation section. The level in the bottom of F303 is controlled by 03LC24.

Depressurization of HPC solution:

46

Before introduction to the top of the first regenerator (F301), the loaded HPC solution at

116°C is depressurized from 28kg/cm2g to 10.7kg/cm2g. Normally, the main part of the

solution is depressurized by the hydraulic turbineTG301, while a small part is of it

depressurized through the level control valve 03LV24A/B, to take care of the fluctuations in

the solution flow. In case TG301 trips, 03LV24A/B opens to take care of the full solution flow.

The power recovered by TG301 supplies part of the power required to drive the pump

P301A. Rest of the power is supplied by an electric motor. The motor takes up the full load

the pump in case of a trip of TG301.

Stripping of CO2 and regeneration of HPC solution:

The CO2 rich HPC solution enters the first regenerator F301, operating at 1.05Kg/cm2g,

controlled by 03PC03. The solution passes through the packed beds in the column in

counter-current to steam, which comes from the bottom. Steam strips off the CO2, and a

mixture of steam and CO2 leaves F301 from the top. The top temperature is about 108°C.

Major part of the solution is extracted at the higher levels of the regenerator, before

reaching the bottom. About 40% of the solution is extracted below the first bed and

expanded through 03FV01 before entering the second regenerator F302. About 45% of the

solution is drawn from the bottom of the fourth bed and enters F302 through 03LV07A/B.

The strongly regenerated (lean) solution from the bottom of F301 goes to the bottom of F302

through 03LV09A/B. The steam generated from the flashing of lean and semi-lean solutions

is used for stripping the rich solution fed to top of F302. The regeneration input of F301

comes from following sources.

1) In E302A/B by process gas cooling.

2) In the LP reboiler E305 by process gas cooling (suction part of the ejector X301) and

direct steam (motive part of ejector X301).

3) In steam fired reboiler E301 by LP steam condensation.

The operating pressure for F302 is 0.1 kg/cm2g and the top temperature is maintained at

100°C. The pressure of F302 is normally controlled by the anti-surge controller of CO2

blower K301. In case of surplus CO2 production, the pressure may be controlled by 03PC33

and 03PC31 acting on the vent valves 03PV33A/B (on the main CO2 header) and

03PV31(on K301 suction).

Circulation of HPC solution:

47

66

For circulation of HPC solution two pump groups are installed.

Semi-lean solution pumps: P301A/B/C/D

Lean solution pumps: P302A/B

Out of four semi-lean solution pumps normally two (including P301A) are in line and the rest

on standby. Out of P302A/B one stays in line and the other on standby. The semi-lean

solution flow is controlled by 03FC22, and lean solution flow is controlled by 03FC21. The

semi-lean and lean solutions are drawn from two take-off trays at the bottom of F302. The

level of semi-lean and the lean take-off trays are controlled by 03LC07 and 03LC09,

respectively.

In order to avoid accumulation of impurities, it is necessary to filtrate the HPC. A

continuous flow of 5% of total circulation is taken from the suction of P302 A/B or bottom of

F301 and passed through a mechanical filter A301A by pump P304. Part of this also passes

through an activated carbon filter A302. Two mechanical filters A301B and A301C are

provided in the upstream and down stream of A302. This filtered stream goes back to either

P302 suction or F301 bottom.

A small side stream of cold lean solution (cooled in E315 to 40°C) is treated in aeration tank

T305. This flow is about 0.5-1% of total circulation flow and controlled by 03FC61. The

purpose of aeration is to maintain the proper pentavalent to total vanadium ratio, so that the

protective passivation layer in the equipment surfaces remains intact. The solution from

T305 is pumped back to P302A/B suction by P308A/B

Regenerator overhead cooling and separation:

The steam CO2 mixture leaves the first regenerator F301 at about 108°C. This mixture is first

cooled in DMW pre-heater E306 to 95°C. The condensate formed is separated in B305 and

totally recycled to CO2 removal unit through pumps P309A/B. The gas stream from F302 is

cooled in E309A/B by cooling water. The condensate is collected in B302, which also

receives condensate from B301. Part of the condensate from B302 is pumped by P303A/B

to the suction of P302 through 03FV33. The surplus condensate goes to the process

condensate stripping section through 03LV31 controlled by the level controller 03LC31. The

overhead of B301 goes to K301 suction. The discharge of the blower K301 mixes with the

B305 overheads and the final cooling of the acid gas from both takes place in E308A/B,

48

where the gas is cooled to 40°C by cooling water. The condensate is collected in B301 and

sent to B302 through 03LV34 controlled by level controller 03LC34.

The CO2 gas saturated with water vapor and containing minor amount of hydrogen and

nitrogen is sent to the battery limit for consumption in urea plant.

The strength of HPC solution:

The normal composition of fresh solution is;

K2CO3 220-240 g/l expressed as K2O

Glycine 15-20 g/l

Vanadium 5 g/l expressed as V2O5 .

Carbonation index (ratio of CO2 equivalent to alkali equivalent) is a measure to the ability of

absorption of CO2 by the solution.

During normal operation, the carbonation indices are about

1.13 for lean solution

1.31 for semi-lean solution

1.7 for rich solution

Methanation

The process gas after CO2 removal section still contains about 0.1% CO2 and 0.29% CO (on dry basis). As the carbon oxides are poisonous to ammonia synthesis catalyst, they are converted into methane in the methanator R311, by using hydrogen. The inlet temperature of the methanator depends on catalyst activity and has to be increased as the catalyst ages. The methanator inlet temperature (about 320°C in end of run conditions) is obtained by cooling in the exit gas in the gas/gas exchanger E311A/B and, if required, by heating part of the inlet gas in the trim heater E208. The inlet temperature is controlled by 03TC78, acting on the exit gas side bypass of E311A/B. The methanator exit gas at 342°C (end of the run condition) enters the shell side of E311A/B, where it is cooled to about 91°C. It is then further cooled to 41°C in E312 by cooling water before going to the make-up synthesis gas compressor suction. The synthesis gas at the methanator exit contains about 10ppm CO+ CO2 content.

Compressors

Natural gas compressor:

49

The natural gas booster compressor (K411) was installed to take care of low natural gas supply pressure. This is supplied by M/s Atlas Copco (USA). This is a single stage compressor, with overhung open type impeller, designed to boost up the pressure of natural gas from 30.22 bar a to 39.26 bar a. It is driven by an electric motor of 800KW. The natural gas from battery limit comes to the suction of the compressor through a separator B315. The flow through the compressor and the discharge pressure is controlled by an inlet flow controller FCV305, and a recycle (anti-surge) flow controller PCV360. A cooler E355 is provided in the recycle line. A local PLC panel is provided a display screen and key-board for start-up, shut down, monitoring and control. The seal system of the compressor is a combination of dry face seal and labyrinth seal. To save the dry face seal from contamination by liquid from process gas clean buffer gas is provided from compressor discharge through a filter X110. Nitrogen buffer gas is used to ensure that process gas does not contaminate the gearbox. The oil system contains a lube oil console, one main and one auxiliary oil pump (both positive displacement type), oil cooler and oil filter.

Process air compressor: The purpose of process air compressor (K421) is to raise the pressure of atmospheric air to 33-34 kg/ cm2g to introduce it to the secondary reformer. It is a four stage centrifugal compressor, provided with inter-stage coolers E421, E422, E423, and inter-stage separators B421, B422, B423. Separators are provided with level controllers. The compressor consists of HP (2MCL456) and LP (2MCL1006) barrels and is supplied by BHEL. The compressor is driven by an extraction cum condensing steam turbine, also supplied by BHEL. The high-pressure steam inlet conditions are 110 kg/cm2g and 510°C. Low-pressure extraction is taken out at 3.5 kg/cm2g and 190°C. Turbine is provided with a vacuum condenser E402, where vacuum is created with the help of ejector, for which motive fluid is low-pressure steam. The heat of condensation is removed by cooling water. The condenser is provided with condensate transfer pumps P402A/B and level controller. The compressed air flow to R203 is controlled by 02FC26, which acts on the speed governor of the turbine TK421. The anti-surge flow control is through the open to air bleed valve 04FV101, located at 4th stage discharge. A low capacity bleed off valve 04PV101 is provided for controlling pressure during start-up. An inter-stage bleed valve 04HV103 is provided between second and third stages to maintain sufficient flow through the first two stages during start-up. The lube oil system comprises of the lube oil console T421, two lube oil pumps P421A/B (centrifugal), and emergency oil pump P422(centrifugal), an overhead lube oil tank T422 (for safe shut down), lube oil coolers E426A/B and oil filters A421A/B. The lube oil header pressure is controlled by PCV146 and the temperature is controlled by 04TC117, acting on the bypass of E426A/B. An oil accumulator B 427 is provided to take care of sudden jerk in oil pressure during auto changeover of oil pumps. The lube oil also works as the control oil and trip oil for the speed governor of the turbine. A centrifuge X421 is attached to the oil console for purifying the oil from moisture and other impurities..Synthesis gas compressor:The process gas from methanation section is compressed from about 26 kg/cm2g to 134 kg/cm2g before introduction to ammonia synthesis loop in the first three stages synthesis gas compressor K431. It is provided with inter-stage coolers E431, E432, E433, and inter-stage separators B431, B432, B433. The fourth or recirculator stage serves to compensate for the pressure drop of the circulated gas in the synthesis loop (from 131 to 141 kg/ cm2g). The compressor consists of HP and LP barrels (2BCL 408+2BCL508) and is supplied by BHEL. The compressor is driven by an extraction cum condensing steam turbine, also supplied by BHEL. The high-pressure steam inlet conditions are 110 kg/cm2g and 510°C. Medium-pressure extraction is taken out at 40 kg/cm2g and 385°C. Turbine is provided with a vacuum condenser E401, where vacuum is created with the help of ejector, for which motive fluid is low-pressure steam. The heat of condensation is removed by cooling water. The condenser is provided with condensate transfer pumps P401A/B and level controller. The speed of the turbine is governed by 03PC77, which controls the suction pressure of the make-up synthesis gas from methanator. The antisurge flow control for the make up stages is through 04FV604. The recirculator is also provided with a recycle valve 04HV610. The recycle line is provided with a cooler E435. Another recycle valve 04HV602 is provided between the second and the first stages for start up purpose.

50

The lube oil system comprises of the lube oil console T431, two lube oil pumps P431A/B (centrifugal), and emergency oil pump P432 (centrifugal), an overhead lube oil tank T439 (for safe shut down), lube oil coolers E436A/B and oil filters A431A/B. The lube oil header pressure is controlled by PCV676 and the temperature is controlled by 04TC696, acting on the bypass of E436A/B. An oil accumulator B437 is provided to take care of sudden jerk in oil pressure during auto changeover of oil pumps. The lube oil also works as the control oil and trip oil for the speed governor of the turbine. Synthesis gas being a hazardous gas; K431 is provided with a seal oil system, which consists of seal oil pumps P433A/B, seal oil filters A433A/B, seal oil overhead tanks B438A/B, sour oil traps B461A/B, B462A/B, degassifier tanks T432 and T433, and the oil mist separator B464. The seal oil overhead tanks and the sour oil traps are provided with level controllers.The discharge pressure of seal oil pump is controlled by PCV696. A centrifuge X431 is attached to the oil console for purifying the oil from moisture and other impurities.

Ammonia refrigeration compressor:The purpose of ammonia refrigeration compressor K451 is to compress the ammonia vapors from the chillers in the ammonia synthesis and refrigeration loops, which helps in liquefying product ammonia. Ammonia vapor from second ammonia chiller E508 (at 1.8 kg/cm2g), after passing through separator B505, is compressed in the first stage of K451, and cooled in E451. The cooled discharge is mixed with the vapors from E506, E514, E509 (at 6 kg/cm2g), pass through separator B506 and compressed in the second stage of K451. The discharge of the second stage goes to the condensers E510A/B/C, cooled by cooling water. The second stage discharge pressure depends on the cooling water temperature (13-17 kg/cm2g). This is a centrifugal compressor (2MCL458) supplied by BHEL. The compressor is driven by a steam turbine, also supplied by BHEL. The medium-pressure steam inlet conditions are 39kg/cm2g and 380°C. Turbine is provided with a vacuum condenser E403, where vacuum is created with the help of ejector, for which motive fluid is low-pressure steam. The heat of condensation is removed by cooling water. The condenser is provided with condensate transfer pumps P403A/B and level controller. The speed of the turbine is governed by 05PC41, which controls the pressure in chiller E508. Two antisurge control valves 04FV202 and 04FV207 are provided for the two stages. The lube oil system comprises of the lube oil console T451, two lube oil pumps P451A/B (gear type), and emergency oil pump P452 (centrifugal), an overhead lube oil tank T453 (for safe shut down), lube oil coolers E452A/B and oil filters A451A/B. The lube oil header pressure is controlled by PCV255 and the temperature is controlled by 04TC227, acting on the bypass of E452A/B. An oil accumulator B451 is provided to take care of sudden jerk in oil pressure during auto changeover of oil pumps. The lube oil also works as the control oil and trip oil for the speed governor of the turbine. The governor oil pressure is controlled by PCV237. The lube oil also works as seal oil, the seal to reference gas differential pressure is controlled by PDCV243. The pump discharge pressure is controlled by PDCV238. A centrifuge X451 is attached to the oil console for purifying the oil from moisture and other impurities..Flash ammonia compressor:This is a screw type compressor supplied by M/s Howden Compressors (UK), driven by an 1840KW electrical motor. The purpose of this machine 9K441) is to bring down product ammonia pressure and temperature to atmospheric level when it is to be sent to the atmospheric storage facility. The flash vapor from the flash vessel B503 come to B504 and from it goes to K441 suction. The discharge of K441 goes to E510A/B/C for condensation. The discharge pressure depends on cooling water temperature. The flow control is facilitated by a slide valve (from 10-30%) and a recycle valve 04PCV404 (above 30% slide valve opening). A logic unit takes care of the loading and unloading of K441, as per the pressure requirement in B503. The separator B441 also acts as the lube oil reservoir. The oil system also contains oil pumps P441A/B (screw type), oil cooler E442, oil filters A441A/B.The oil supply pressure and temperature are maintained by 04PC413 and 04TC413, respectively.

51

Ammonia synthesis

Addition of Makeup gas:The make up gas from methanation section is added to the synthesis loop through the compressor K431. The quantity of the make up gas is adjusted as per the desired ammonia production. The content of inert gases methane and argon are kept as low as possible. Normally the argon and methane contents in the make up gas are 0.31 and 0.72% respectively. Owing to the addition of hydrogen rich gas from the PGRU, the hydrogen to nitrogen ratio in the make up gas is maintained at about 2.85. This will ensure the stoichiometric ratio of 3.0 at the inlet of ammonia synthesis converter R501. A small change in the H2 to N2 ratio in the make up gas causes much greater change in the ratio in the loop. The make up gas is cooled to about 15-20°C in the make up gas chiller, the condensed moisture is separated in B507. This gas saturated with water vapor is mixed with the circulating synthesis gas and ammonia mixture at the upstream of the second ammonia chiller E508. The water and traces of CO2 are absorbed in the liquid ammonia present and condensed in E508. The liquid ammonia is separated in B501. Thus the water and CO2 are prevented from passing through the catalyst bed of converters R501 and R502. But traces of CO still remains, which cannot be removed. In the design 2ppm of CO has been anticipated in the circulating gas. If the CO content in the make up gas exceeds 10 ppm, the synthesis loop cannot be operated for a long time.

First ammonia synthesis converter:The inlet temperature in the first ammonia converter is controlled by 05TC11 (cold shot) and 05TC03 (bypass of the BFW pre-heater E502). The main inlet valve 05HV 01 should always allow at least 10% of the normal flow to cool the converter shell by flowing through the annular space between the internals and the pressure shell. The design temperature of pressure shell is 370°C. The inlet temperature of the converter first bed is maintained at about 360-380°C and the anticipated second bed temperature is about 365-390°C. The second bed outlet temperature is about 440°C. These temperatures are governed by catalyst activity and a very low inlet temperature will make the reaction unstable. With fresh active catalyst the hot spot temperature is about 500°C.

Second ammonia synthesis converter:The inlet temperature of the second converter R502 is controlled by 05TC36 acting on the bypass of first waste heat boiler E501A. It is maintained in the range of 370-385°C, according to the catalyst activity. The outlet temperature of R502 is kept in the range of 415-430°C. The exit gas is cooled in second waste heat boiler E501B. The design temperature of the pressure shell, out let piping and E501B is 450°C.

Gas composition in the loop: The intended hydrogen/ nitrogen ratio in the synthesis loop is 3.0. It depends on the hydrogen/ nitrogen ratio in the make up gas from methanator and the amount of hydrogen recovered from PGRU. At design conditions the inert level at R501 inlet should be 8 mole%. As methane and argon present in the make up gas does not take part in the ammonia synthesis reaction they keep on accumulating. Their presence reduces the partial pressure of reactants and affects the ammonia production rate. A minor part of the inerts get dissolved in the liquefied product ammonia and removed from the loop. But bulk of the inerts is removed from the loop by purging some of the circulating gas through the flow control valve 05FV42 located down stream of second cold exchanger E507. The purge gas is sent to ammonia recovery section and the ammonia free purge gas is sent to purge gas recovery unit (PGRU). Variation in the ammonia concentration at converter inlet has a considerable effect on the synthesis reaction rate. A decrease in the ammonia concentration in the R501 inlet increases the reaction rate. The ammonia concentration depends on the gas temperature out of the second ammonia chiller E508

52

and on the loop pressure. The shell side temperature of E508 is about –10°C. The gas side outlet temperature of E508 is about –7°C.

Synthesis loop circulation rate and pressure:An optimum circulation rate in the loop is maintained to keep the catalyst temperatures constant and at desired values. The synthesis loop is designed to operate at 134 and 141 kg/cm2g at the make up and recirculation discharge side of K431. The mechanical design is 155 kg/cm2g for the entire synthesis loop. Operating pressure and circulation depends on the catalyst activity.

Ammonia condensation and separation:Condensation of product ammonia starts in water cooler E504 after cooling in E503 with the R501 inlet gas, and continues in the first cold heat exchanger E505, first ammonia chiller E506, second cold heat exchanger E507 and second ammonia chiller E508. The liquid is collected in B501, provided with level controller 05LC42. The liquid ammonia depressurized through 05LV42 to about 25 kg/cm2g and transferred to letdown vessel B502. During pressure release major part of the dissolved gases is released as letdown gas. The letdown gas is sent to ammonia recovery is sent to ammonia recovery along with inert vent gas from B509. The liquid ammonia from B502 is sent to E513 for pre-heating up to 28°C before being delivered to battery limit for consumption in urea plant. The letdown gases are released from B502 through the pressure control valve 05PV51. B502 is provided with two level control valves 05LV52A and 05LV52B, operating in splitting range. Normally, 05LV52B is in line. 05LV52A comes into operation, when ammonia is sent to atmospheric storage, through flash vessel B503 and transfer pump P501A/B.

Refrigeration loop:The refrigeration loop comprises of E506, E514, E509 operating at 6.4 kg/cm2g and E508 operating at 1.9 kg/cm2g. The vapors generated in the shell side of these chillers are compressed by the two stages of K451 and finally condensed in E510A/B/C. The condenaste is collected in B510 and circulated back to chillers through level control valves 05LV31, 05LV137, and 05LV41. E509 is loaded, when ammonia is transferred to storage and vapors and inerts from B503 enter the refrigeration loop through K441 or the new modification line between B503 and B504. The pressure in the separator B509 which separates ammonia from inert gases of the refrigeration loop is controlled by 05PC62. The knock out drums B504, B505, B506 are provided to prevent liquid entrainment from chillers to K451/ K441.

Ammonia recovery

Ammonia absorption:The purge gas from synthesis loop is washed in the in the absorber F523at about 75 kg/cm2g controlled by 05PC72. The absorber bottom level is controlled by 05LC72. The flow of lean wash water is controlled in such away that there is low residual ammonia content (about 0.1%) in the washed purge gas. The lean solution pumped to F523 by the Hp circulation pump P522A/B. The gases vented from B502 and B509 are washed in F522 at about 16.8 kg/cm2g, controlled by 02PC29. The level in absorber bottom is controlled by 05LC73. The level control valve 05LV73 is situated at the discharge of LP circulation pump P521A/B, which circulates the wash solution to the distillation column F521. The flow rate of lean solution to F522 is controlled by 05FC72. The residual ammonia in the exit gas is maintained at 0.1 mole%.

Ammonia distillation: The distillation column F521 is equipped with 20valve trays with the feed being introduced in the tray no. 12. The column is provided with a reboiler E521 heated with de-super-heated MP steam and a water-cooled ammonia condenser E522 for condensing the overheads. The over head condensate (about 99% pure ammonia) is partly returned to the column as reflux and partly sent to B502 as product. The bottom product of F521/E521 is contains 0.1% of ammonia, which is cooled in E523A/B

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by the incoming feed stream from 225°C to 110°C. The lean solution (bottom product) is finally cooled in water–cooler E524 to 41°C. The dissolved gases in the feed are vented through the pressure controller 05PC82. The operating pressure of F521 should higher than that of B502 so that liquid ammonia can be transferred to B502. The temperature controller 05TC99 acting on the ammonia product line determines the amount of reflux and maintains the temperature at the middle of the column corresponding the location of the thermocouple 05TE99. This temperature may be in the range of 70-150°C depending on the location of thermocouple. The steam flow to E521 is controlled by 05FC82. A line connecting the vapor line of E521 and the steam line has been provided (with a valve) to maintain the water content (indicated by E521 shell side level) in the system, by adding steam on discontinuous basis.

Process condensate recovery and BFW preparation:

The process condensate stripping section treats the condensate collected from B303, B311 and B302. The B302 condensate is fed through the pumps P303A/B. The impurities present in the condensates are ammonia, methanol, CO2 and potassium (K+). The amount of impurities widely depending on the operating conditions, catalyst conditions etc. The stripped condensate contains typically 5ppm of ammonia, 10ppm of CO2, 5 ppm of methanol and 1ppm of K+. The stripping agent is de-super-heated LP steam the flow of which is controlled by 06FC21. Stripping steam is also generated by flashing of MP condensate from E214, E215, E217, E4, E105 etc. A significant part of CO2 is stripped off in F602 at a low steam to condensate ratio in preference to ammonia. The stripped gases (mainly CO2), with part of the steam routed through F602 is vented through an orifice at the top of F602. The partly stripped condensate from F602 passes down through the main stripper F601 where is it introduced in the 20th tray, from where the stripping steam for F602 is taken out. Remaining volatile compound are removed in F601. The overhead vapors from F601 are partially condensed in the DMW pre-heater E604. The resulting condensate is recycled to F601 through pumps P602A/B from the separator B603. The vapors from B603 concentrated with volatile impurities are condensed in E605 (cooled by cooling water). The condensate is accumulated in the separator B604 operating at atmospheric pressure. The liquid from B604 is transferred to the process steam line of reformer through pumps P603A/B. The operating pressure (2.3 kg/cm2g) of the stripper is controlled by 06PC23 manipulating the DMW flow through E604. The controller 06FC22 controls the flow of the volatiles from B603 to E605. The stripped condensate is cooled in a series of exchangers E601 (by incoming condensate), E602 (by DMW) and E603 (by cooling water and cooled to 50°C, before being sent to DMW plant.

Pre-heating and deaeration of demineralized water (DMW):Pre-heating of DMW takes place in a series of exchangers E602, E306, E307, and E604 to raise the temperature from 40°C to 110°C. The flow rate of cold DMW is governed by the demand of BFW in ammonia plant as well as the demand for export of pre-heated DMW outside ammonia plant. The distribution of DMW to exchangers is determined by following controllers:06TC27, 06PC23 and 03TC25. The normal set point of these controllers are 110°C, 2.3 kg/cm2g and 80-95°C respectively. The pre-heated DMW is sent to deaerator B601, where most of the dissolved oxygen is stripped off by LP steam. The DMW is introduced from the top of the bed and the steam from the bottom of the bed. The level in the hold up tank below the deaerator, is controlled by 06LC301 acting on the incoming DMW.

BFW preparation:Deaerated DMW is used as feed water for the waste heat boiler. The operating conditions in the deaerator are 1 kg/cm2g and 120°C. The pressure is controlled by 06PC301 acting on the stripping steam. The boiler feed water (BFW) is pumped to the steam drum B201 through pumps P601A/B/C (with two of them in line). The BFW is treated with hydrazine, ammmonia, and phosphate to maintain the desired quality. Dozing pumps P606A/B, P605A/B and P604A/B are installed to add these chemicals to BFW. Hydrazine is dozed in the deaerator itself to minimize the oxygen content.

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Ammonia is also dozed to the deaerator to maintain a pH level higher than 7. Phosphate is added in the steam drum to separate out silica content. The BFW is pre-heated to 295°C from a temperature of 120°C in a series of exchangers E211, E210, E209 and E502, before being sent to steam drum. Medium pressure condensate from steam traps are collected in B605 resulting in saturated LP steam and condensate. The condensate is sent to atmospheric vessel B606 through level control valve 06LV311. In B606 LP condensate is also collected in B606. The level in B606 is controlled by 06LC309, acting on the discharge of pumps P607A/B. The condensate is sent to deaerator B601 through P607A/B.

Purge Gas Recovery unit

Feed preparation:The purge gas from the ammonia recovery section is introduced at 75 kg/cm2g and 55°C. 07FIC201 controls the inlet flow to PGRU. The feed gas is cooled in E 3 to 40°C. The condensed water is collected in B3. The gas leaving B3 flows to two adsorbers R1 and R2. Each of them are filled with two adsorbent beds of activated alumina (at the bottom for adsorbing water) and molecular sieves (at the top for adsorbing ammonia).R1 and R2 come in line one after another in cycles. When one is in line, the other is on regeneration. The gas at the outlet of R1/R2 contains less than one ppm of water or ammonia. A filter F1 prevents any adsorbent dust from being carried away. The regeneration of the adsorbers is carried out by heating part of the fuel gas (controlled by 07FIC323) from the cryogenic section and allowing it to flow through the adsorber bed. The regeneration heater E4 is supplied with de-heated MP steam. The temperature is controlled by 07TIC326. The set point is kept 220°C. During cooling step the regeneration gas bypasses E4, and the moisture content is separated in B4. Each adsorber operates automatically in a cycle in the following steps.1. Isolation with pressure (30seconds)

2. Depressurization (40minutes)

3. Blowing (30seconds)

4. Begin heating (30seconds)

5. Heating (3 hours)

6. Cooling (3.5 hours)

7. Isolation (30seconds)

8. Pressurization (40minutes)

9. Parallel and change over

Hydrogen recovery:The purified purge gas is again cooled in E5 to 40°C, before entering the cryogenic section. This gas is cooled in a special aluminum exchanger (E1 and E2) to -184°C. At this temperature heavier components in the purge gas liquefy and the gaseous phase contains 91.3% pure hydrogen. The separation of gas and liquid takes place in B1. The gaseous stream flows back to E2 and warmed to 38°C and delivered at a pressure of 70.5 kg/cm2g. The Product pressure and flow are controlled by 07PIC318 and 07FIC319.

Fuel gas production:The level in B1 is controlled by 07lLIC409 acting on the throttling valve 07LV409. The pressure is reduced to 4.5kg/cm2g. The depressurized liquid is vaporized in B2 and warmed up in E1. To vaporize the liquid to right temperature level a small part of the hydrogen is leaving B1 is diverted to the residual stream through the expansion valve 07TV410 controlled by 07TIC410. Another expansion valve 07HV411 is provided for start up purpose. The warm fuel gas is sent to reformer fuel circuit at 4 kg/cm2g. The pressure and flow are controlled by 07PIC322 and 07FIC322.

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CENTRIFUGAL PUMP.

Centrifugal pumps are a sub-class of dynamic axisymmetric work-

absorbing turbomachinery.Centrifugal pumps are used to transport fluids by the

conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow.

The rotational energy typically comes from an engine or electric motor. The fluid

enters the pump impeller along or near to the rotating axis and is accelerated by the

impeller, flowing radially outward into a diffuser or volute chamber (casing), from

where it exits.

Common uses include water, sewage, petroleum and petrochemical pumping. The

reverse function of the centrifugal pump is a water turbine converting potential

energy of water pressure into mechanical rotational energy.

HOW IT WORKS :General explanation: Like most pumps, a centrifugal pump converts rotational energy, often from a motor, to energy in a moving fluid. A portion of the energy goes into kinetic energy of the fluid. Fluid enters axially through eye of the casing, is caught up in the impeller blades, and is whirled tangentially and radially outward until it leaves through all circumferential parts of the impeller into the diffuser part of the casing. The fluid gains both velocity and pressure while passing through the impeller. The doughnut-shaped diffuser, or scroll, section of the casing decelerates the flow and further increases the pressure.

Vertical centrifugal pumps

Vertical centrifugal pumps are also referred to as cantilever pumps. They utilize a

unique shaft and bearing support configuration that allows the volute to hang in the

sump while the bearings are outside the sump. This style of pump uses no stuffing

box to seal the shaft but instead utilizes a "throttle bushing". A common application

for this style of pump is in a parts washer.

Multistage centrifugal pumps

Multistage centrifugal pump

A centrifugal pump containing two or more impellers is called a multistage centrifugal

pump. The impellers may be mounted on the same shaft or on different shafts.

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For higher pressures at the outlet, impellers can be connected in series. For higher

flow output, impellers can be connected parallel.

A common application of the multistage centrifugal pump is the boiler feedwater

pump. For example, a 350 MW unit would require two feedpumps in parallel. Each

feedpump is a multistage centrifugal pump producing 150 l/s at 21 MPa.

All energy transferred to the fluid is derived from the mechanical energy driving the

impeller. This can be measured at isentropiccompression, resulting in a slight

temperature increase (in addition to the pressure increase).

Problems of centrifugal pumps.

These are some difficulties faced in centrifugal pumps

Cavitation—the net positive suction head (NPSH) of the system is too low for

the selected pump

Wear of the impeller—can be worsened by suspended solids

Corrosion inside the pump caused by the fluid properties

Overheating due to low flow

Leakage along rotating shaft

Lack of prime—centrifugal pumps must be filled (with the fluid to be

pumped) in order to operate

Surge- Heart Of Pump

- Consist Of Vanes, Shrouds & eye

-Liquid Enters Into Eye, Rotate in The Impeller & Comes Out At Outer Periphery With High Velocity.

-Classified : As Per Construction

*Closed, semi open, open

-As per flow Inside

* Radial , mixed, axial

# Closed Impeller

-Shrouds on both sides of impeller

-Used In Pumps Handling Clear Liquids

#open impeller

-Does not have shroud on any side

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-Used in pumps handling viscous and abrasive liquids

#Semi open impeller

-Shroud on one side of impeller

#CASING:

-Houses the rotating and guides the fluid from inlet to outlet.

-Inlet/outlet nozzles

-Pressure part

-Should be designed as to minimize the loss of kinetic head through eddy formation.

-Generally two types of casing:

a)Volute casing b)Diffusion casing

#Volute casing:

-Spiral type

-Cross section of flow stream gradually increases towards the discharge end.

#Diffusion casing:

-Impeller is surrounded by a guide wheel, consisting of no. of stationary vanes which provides outlet with increasing c/s towards periphery water .

-Angle of guide vane at inlet should coincide with angle of impeller at outlet .

# Casings may also be distinguished as:

(a) Horizontally split:

-Generally for low pressure service

-Brgs. on both side of impeller

(b) Vertically split:

-Split vertically perpendicular to shaft axis.

-High temp. and pressure service .

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(c) Barrel type;

-Must be open from one side to install & repair .

SHAFT:

- Main rotating part on which all rotating elements are mounted.

- Transmits torque and in turn, power from prime mover to impeller .

- Connected to driver with the help of coupling or belts or G/box.

- Should have sufficient strength so that it can withstand various loads coming on it.

STUFFING BOX:

-Main fn. is to arrest the leakage ( i. e. ) the system used to prevent leakage is fitted in this box.

- Gland packing /Mech seal.

BEARING HOUSING:

-houses the brg. for pump & gives support to rotor assembly.

- Provides space for lube. oil for brgs. & very often a cooling jacket also.

BEARINGS:

-Supports rotating shaft.

- Different types:-

According to their function - Radial and thrust According to design requirements of thrust and radial loads friction and anti-friction

-Various types used in c:entrifugal pump:

Ball brg. - both radial & axial load Roller brg. - radial load in much higher capacity Sleeve brg. - high loads Tilted pad - high thrust loads or heavy duty pump

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SLEEVES:

- Protects the shaft from direct corrosion , erosion or wear .- Rotating member along with shaft .

DEFLECTORS:

- Used in brg. hsg. & is mounted on main pump shaft

- To prevent brg oil to come out from chamber along the shaft due to rotation

- Rotating member

WEARING RING:

- For best eff. , stator &rotor clearances must be close , otherwise , back flow of pumped liquid will be there from high pressure zone to low pressure zone.

- For this , separate rings are fitted both on impeller mating dia& in the casing to safe guard the major parts of pump.

- Diff. of 50 BHN min. between the rings.

LANTERN RINGS:

- Prevents air leakage into the pump when the pump is operating below atm. pressure

- Prevent leakage of fluid being pumped

- Cools & lubricate the packing.

TERMS RELATED TO CENTRIFUGAL PUMPS

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#CAPACITY

# PUMP HEAD

# POWER INPUT TO PUMP

# SPECIFIC SPEED

# SYSTEM HEAD

# PIPING HEAD

# CHARACTERSTICS CURVES

# CAVITATION

# NPSH reqd.

# NPSH available

NPSH required

# THE NPSH - NET POSITIVE SUCTION HEAD, IS A STATEMENT OF MINIMUM SUCTION CONDITIONS REQUIRED TO PREVENT CAVITATION OF A PUMP.

# CENTRIFUGAL PUMP NWILL ONLY OPERATE SATISFACTORILY IF THERE IS NO BUILD OF PRESSURE WITHIN THE PUMP.

# IT IS DETERMINED BY TEST & USUALLY STATED BY MANUFACTURER OF PUMP.

NPSH available

# THE AVAILABLE NPSH AT INTALLATION MUST BE AT LEAST EQUAL TO THE REQUIRED NPSH IF CAVITATION IS TO BE PREVENTED

# NPSH SHOULD BE MORE THAN NPSHR BY 0.5M MIN.

CHARACTERSTICES CURVES OF CENTRIFUGAL PUMP

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THESE ARE THE CURVES PLOTTED FROM THE RESULTS OF A NUMBER OF EXPERIMENTS ON THE PUMP, WHILE RUNNING IT AT ITS DESIGN SPEED.

THE CURVES SHOWS THE RELATION BETWEEN EFFICIENCY, BRAKE HORSE POWER , HEAD AND THE DISCHARGE.

CENTRIFUGAL PUMP EFFICIENCY :

Centrifugal Pump Efficiency Calculation Centrifugal pump efficiency is the ratio of Hydraulic power delivered by the pump to the brake horsepower supplied to the pump.

Hydraulic Power (Power Output from Pump):

Centrifugal Pump consumes energy to develop the discharge pressure and to deliver flow. Therefore Hydraulic Horsepower of the Pump depends on these two parameters.

Power Output from Pump = (P2 – P1) * Q

P2: Pump Discharge pressure in N/m2

P1: Pump suction pressure in N/m2

Q: Flow delivered by pump in m3/s

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Brake Horse Power (Power Input to Pump):

This is the power given to the pump through Electric Motor. Power output from the electric driver is calculated by the formula

Power Input to Pump = 1.732 * V * I * PF * Motor Efficiency

V: Measured Voltage of Motor in Volt

I: Measured Current of Motor in Ampere

PF: Power Factor Motor

Efficiency May be considered as design efficiency or may be obtained from Motor efficiency calculation data through tests Coupling Efficiency is obtained from Supplier Manual Centrifugal pump efficiency equation Centrifugal pump efficiency = Power Output from Pump/ Power Input to Pump * 100

Centrifugal Pump Efficiency and Discharge Temperature Actual Power required in pump can also be derived from Heat balance across the pump. Difference in Heat flow Outlet and Heat flow inlet is the actual power required for the pump. This indicates the fall in centrifugal pump efficiency increases the temperature of liquid at the pump discharge.

Factors Influencing Centrifugal Pump Efficiency

1. In Recirculation lines Minimum Thermal flow is maintained to avoid Cavitation during low flow operation of the pump. This will also result in lowering the efficiency.

2. Internal Surface Roughness. Smooth surface finish in pump internals gives high efficiency

3. Increase in Wear Ring Clearances decreases the efficiency of Centrifugal pump. Wear rings are used reduce clearance between Pump impeller and Pump casing

4. Increase in viscosity decreases the pump efficiency

5. Mechanical losses in Couplings, Bearings, Packingsetc will decrease the efficiency

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6. Impeller Trimming will also decrease efficiency.

CALCULATION:

PUMP P-309

LIQUID HANDELED: CONDENSATE WATER +CARBON DI OXIDE

SP.GRAVITY: 0.973

SUCTION PRESSURE:2.2 KG\CM2

DISCHARGE PRESSURE:8.0 KG\CM2

HEAD :59.6 M

NPSH(R):1.8 M

NPSH(A):14 M

VISCOSITY:0.4 CP

IMPELLER DIA:209 MM(FINAL TRIM DIA)

IMPELLER DESIGN:CLOSED

RATED:11.51 KW

HYDRAULIC PRESSURE:63 KG\CM2

MOTOR : 3 PHASE

MOTOR EFFICIENCY:85%

VOLTAGE:415 VOLTS

POWER:11 KW

CTR VALUE : 50

FLC(FULL LOAD CURRENT):20 AMP

RPM:2900

PRESSURE DIFFERENCE = P2 – P1

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=8-2.2=5.8 KG\CM2

OR = 5.8*9.8*10000=568400 N\M2

Δ(P)=H*ρ*g

H=ΔP\ρg

=568400\973*9.8

=59.6 M

Actual current=50*22\100 = 11 Amp

Pump input power:√3*v*i*cosᵩ*ɳ(motor)

=√3*415*11*0.80*0.87

= 5846.9w

Mass Flow Rate:19 ton\hr

=19000\3600

=5.27 kg\sec

Pump efficiency:

ɳ=pump output\pump input

ɳ =m*H*g\pump input

ɳ =(19000\3600)*59.6*9.8\5846.9

ɳ = 52%

DESIGNED EFFICIENCY:56.5%

BIBLIOGRAPHY

1) AMMONIA MANUAL2) MCCABE & SMITH (CHEMICAL ENGINEERING)

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3) PERRY’S HANDBOOK

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