hariom report
TRANSCRIPT
Birla Institute of Technology & Science, Pilani. 1
A
REPORT ON
TO CARRY OUT THE ENERGY BALANCE OF UREA PLANT
&
SIMULATION OF MEDIUM PRESSURE ABSORBER(C-01)
BY
Name of the Student ID No. Discipline
Hariom Sharma 2009H101015P M.E Chemical Engineering
Prepared in Partial Fulfillment of the
Practice School-II Course No. BITS G639
AT
TATA CHEMICALS LIMITED, BABRALA
A Practice School-II Station of
BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI
(June, 2011)
Birla Institute of Technology & Science, Pilani. 2
BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE,
PILANI (RAJASTHAN)
Practice School Division
Station: Tata chemicals Limited Centre: Babrala
Duration: From: 06 Jan. 2011 To: 18 June 2010.
Date of Submission: 13 June 2011
Title of the Project: To Carry out the energy balance of Urea plant & Simulation of
Medium Pressure (MP) Absorber (C-01) in an Urea Plant.
ID No.: Name of Student: Discipline:
2009H101015P Hariom Sharma M.E. Chemical Engineering
Name of Expert: Mr U.P .SINGH Designation: Manager-Urea Plant
Name of the PS Faculty: Prof. R. K. Tiwary
Key Words: Study,Analysis,Calculation,Simulation,Aspen
Project Areas: Designe
Abstract: The first part of the report looks at one of the problem which was assigned to me.
During the course of this assignment I done the energy balance of all section of Urea Plant.
The second part of report deals with the simulation of Medium Pressure Absorber(C-01) of
urea plant in aspen plus ,commercial process simulation software.The detailed results and the
curves can be accessed by running the simulation files which are attached with the soft copy
of this report.
Signature of Student Signature of PS Faculty
Date: Date:
Birla Institute of Technology & Science, Pilani. 3
BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCE
PILANI (RAJASTHAN)
PRACTICE SCHOOL DIVISION
Response Option Sheet
Station: Tata Chemicals Ltd. Center: Babrala
ID No: 2009H101015P Name: Hariom Sharma
Title of the Project: To Carry out the energy balance of Urea plant & Simulation of
Medium Pressure (MP) Absorber (C-01) in an Urea Plant.
Usefulness of the project to the on-campus courses of study in various disciplines. Project should
be scrutinized keeping in view the following response options. Write Course No. and Course
Name against the option under which the project comes.
Refer Bulletin for course no and course name.
Code No. Response Option Course No. & Name
1 A new course can be designed out of this project.
2 The project can help modification of the course
content of some of the existing courses.
Process Plant Simulation
(CHE G541).
3 The project can be used directly in some of the
existing Compulsory Discipline Courses (CDC)/
Discipline Courses Other than Compulsory
(DCOC)/ Emerging Area (EA) etc. courses
Advanced Separation
Processes (CHE G615).
4 The project can be used in preparatory courses
like Analysis and Application Oriented Courses
(AAOC)/ Engineering Science (ES)/ Technical
Art (TA) and Core courses.
5 This project cannot come under any of the above
mentioned options as it relates to the professional
work of the host organization.
Signature of student Signature of Faculty
Date: Date:
Birla Institute of Technology & Science, Pilani. 4
ABSTRACT
The first part of the report looks at one of the problem which was assigned to me.
During the course of this assignment I done the energy balance of all section of Urea Plant.
The second part of report deals with the simulation of Medium Pressure Absorber(C-01) of
urea plant in aspen plus ,commercial process simulation software.The detailed results and the
curves can be accessed by running the simulation files which are attached with the soft copy
of this report.
Signature of Student Signature of PS Faculty
Signature of Guide Signature of General Manager
Date:
Place:
Birla Institute of Technology & Science, Pilani. 5
ACKNOWLEDGEMENTS
I would like to thank my mentor Mr. U.P. Singh for guiding me all through my project. I am
overwhelmed in all humbleness and gratefulness to acknowledge my debt to Mr. Azaz Ali,
Mr.Avineesh, Mr. Sanjay Kumar, Mr. Siva Prasad, Mr. Kamakhya and Mr. Adarsh for their
support and timely help. A special thanks to Captain K. Santosh, Mr. Rajendra Singh and Mr.
Thomas Varghese for taking care of us at TATA Chemicals Ltd. I would also like to thank Mr.
C. K. S. Raman and Mr. Mahenderpal for providing us freedom to refer books and avail the
software facilities in the Technical Library and Documentation Centre.
I am also indebted to BITS, Pilani for providing me the opportunity in the form of practice
school to enrich my practical knowledge. And of course, this project would never have been
complete without the immense motivation by our PS Faculty Mr. R. K. Tiwary.
Last but not the least; I would like to thank my parents for their blessings.
Hariom Sharma
2009H101015P
Birla Institute of Technology & Science, Pilani. 6
INDEX
Abstract
i
Acknowledgement ii
Index iii
List of Tables v
List of Figures v
Name Page Number
1. Introduction 1
1.1) Introduction to Tata Chemicals Limited, Babrala 1
1.2) Credentials of Tata Chemicals Limited, Babrala. 2
1.3) TCL Babrala: The Nation‘s Conceit 3
1.4) Milestones of Tata Chemicals Limited, Babrala 3
1.5) Composition of Tata Chemicals Limited, Babrala 4
1.6) Salient Features of Tata Chemicals Limited, Babrala 6
2. Fire and Safety 8
2.1) Fire Chemistry 8
2.2) Fire Prevention 8
2.3) Classification of Fires 9
2.4) Fire fighting Gadgets and Appliances 10
2.5) Safety Programme at T.C.L 11
2.6) Safety Provisions 11
Birla Institute of Technology & Science, Pilani. 7
3. Brief Introduction of Urea Plant 12
3.1) Raw Material Required for Urea Production 12
3.2) Manufacturing Procedure 14
3.3) Steam and Condensate Steam 18
3.4) Flushing Network 20
4. Project 21
4.1) To Carry Out The Energy Balance of Urea Plant 21
4.2) Simulation of Medium Pressure Absorber (C-01) 30
5. Conclusions and Recommendations 59
6. References 61
Birla Institute of Technology & Science, Pilani. 8
1. INTRODUCTION
1.1) INTRODUCTION TO 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 is India'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 tones per annum. Tata Chemicals makes urea at its fertilizer
complex in Babrala. The complex has an installed capacity of 13, 14,000 metric tones 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.
Birla Institute of Technology & Science, Pilani. 9
1.2) CREDENTIALS OF TATA CHEMICALS LIMITED BABRALA
AWARDS:
Prestigious Industry Award, Govt. of UP., 1995.
National Energy Conservation Award, Ministry of Power, 1997.
National Energy Conservation Award, Ministry of Power, 1998.
Best Production Performance Award for Nitrogenous Fertilizers, Fertilizers Association of
India.
Second best productivity performance in Nitrogenous Fertilizers Industry, 1997-98.
Yogyata Praman Patra Award, 1998.
Jawaharlal Nehru memorial National Award for Pollution Control and Energy Conservation,
2000-01.
Golden Peacock Environmental Management Award, World Environment Foundation, 2001-
02.
Best Technical Innovation Award, Fertilizer Association of India, Dec.2004.
Excellence in Safety, Fertilizer Association of India, Dec.2—4.
Commendation Certificate for Strong Commitment to TQM, CII-Exim Bank Award for
Business Excellence, Nov.2004.
5 Star Rating in Safety, British Safety Council, UK, Safety Gold Awards, Greentech
Foundation, Delhi.
Indian Chemical Council (ICC) confers the ICC award for social responsibility 2005-06.
NSCI safety award for 2006.
ICC Aditya Birla Award for Best Responsible Care Committed Company and ICC Award for
Social Responsibility for 2005-06.
Fertilizers Association of India Award for the Best Technical Innovation 2007.
Nine ABCI (Association of Business Communicators of India) Awards, 2008.
Birla Institute of Technology & Science, Pilani. 10
1.3) TCL BABRALA: THE NATION’S CONCEIT
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 about 4 million tones/year.
First major steps towards the fulfillment 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 tons of Urea achieving a capacity of 113% in the
year1995-96, and produced 9, 51,764 tones of Nitrogenous Urea in year 1996-97.
Now produce capacity of 13, 14,000 metric tons of Urea per year, which constitutes nearly
12 per cent of the total urea produced by India's private sector.
Total production of urea at Babrala is 3300 tons/day maximum and 2600 tons/day average.
Current maximum capacity is 146%.
The Babrala facility, among the best of its kind in India and comparable to the best in the
world, has set new standards in technology, energy conservation, productivity and safety
It is the only fertilizer plant in the country to use dual feedstock: natural gas or naphtha, or a
combination of both.
Birla Institute of Technology & Science, Pilani. 11
1.4) MILESTONES OF TATA CHEMICALS LIMITED, BABRALA
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 certificates obtained in October 2000.
ISO 14001 certificate for Babrala township obtained in 2004.
Birla Institute of Technology & Science, Pilani. 12
1.5) COMPOSITION OF TATA CHEMICALS LIMITED, BABRALA
1. AMMONIA PLANT
Capacity: 2000 MTPD
Technology: HALDOR TOPSE Process, DENMARK
Plant (Single Stream) Production: 2000 tons/ 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
Birla Institute of Technology & Science, Pilani. 13
2.UREA PLANT
Capacity: 2 X 1750 MTPD
Technology: SNAMPROGETTI Process, ITALY
Carbon Dioxide requirements supplied from ammonia plant.
Two urea strings have a common Prilling section.
Maximum Urea production: 3600 tons per day
Basic scheme involves the following steps:
Urea Synthesis
Waste Water Treatment section
3.OFFSITE AND UTILITIES
S. N. UNIT CAPACITY TECHNOLOGY
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 Technofab Engg. Ltd.
Birla Institute of Technology & Science, Pilani. 14
1.6) SALIENT FEATURES OF TATA CHEMICALS LIMITED, BABRALA
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:2000 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.
Birla Institute of Technology & Science, Pilani. 15
UNIQUE FEATURES OF TATA CHEMICALS LIMITED, BABRALA
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 LIMITED
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.
2. FIRE AND SAFETY
2.1) 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‖.
Birla Institute of Technology & Science, Pilani. 16
2.2) 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/biddies/matches/lighter etc. in
the following areas is a serious offence. All non-smoking areas should carry ―NO
SMOKING‖ signboards.
Friction and overheated 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.
Birla Institute of Technology & Science, Pilani. 17
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.
2.3) 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
categorized as class ―B‖ fire. Blanketing is a useful first aid fire control for ―B‖ class fire. Water
Birla Institute of Technology & Science, Pilani. 18
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. 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, aluminum, 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.
2.4) 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.
2.5) SAFETY PROGRAMME AT T.C.L
Birla Institute of Technology & Science, Pilani. 19
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 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.
2.6) SAFETY PROVISIONS
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.
Fencing of machinery.
Devices for cutting of power.
Hoists and lifts.
Birla Institute of Technology & Science, Pilani. 20
3. BRIEF INTRODUCTION OF UREA PLANT
Tata Chemicals owns fertilizer complex at Babrala. It has adopted Snapgrogetti NH3
stripping process for the production of urea. It has two identical units (11 and 21) of the
same nameplate capacity 1750 MTPD each, so the total capacity is 3500 MTPD.
3.1) RAW MATERIAL REQUIRED FOR UREA PRODUCTION
The raw material condition at the battery limit is as under:
Ammonia:
NH3 min - 99.5%wt
Oil - 10 ppm max
Water - 0.5% wt
Carbon dioxide:
CO2 (dry basis) - 98.76% vol. min
H2 - 0.3% vol min
H2O - Saturated
Utilities characteristics
Cooling water:
Pressure (norm/design) - 3.5/6.0 kg/cm2g
Inlet temperature - 35° C
Outlet temperature - 45° C
Fouling factor - 0.0004 m2 h ° C/kcal
Electric power:
Birla Institute of Technology & Science, Pilani. 21
Alternating current - 11KV 50 Hz 3ph
- 3.3 KV 50 Hz 3ph
- 415 V 50 Hz 3ph
Direct Current - 115 V 1Ph
Service air:
Moister - saturated
Pressure (norm/degn) - 7/11 kg/cm2
Temperature - 40 ° C
Instrument air:
Pressure - 7/11 kg/cm2
Temperature - 40 ° C
Type - Oil free
Dew Point - -20 ° C max at 7 kg/cm2
Polished water:
Conductivity - ≤ 0.2 µs/cm
Silica (reactive) - ≤ 0.02 µs/cm
Fe - 0.01 ppm
TDS - ≤ 0.1 ppm
Oil - ≤ 0.5 ppm
pH - 7
Birla Institute of Technology & Science, Pilani. 22
Nitrogen:
Nitrogen plus noble gas - 99.6 % vol
CO2 - 20 ppm max
Water - 20 ppm max
Oxygen - 200 ppm max
Pressure (min/ norm) - 5/7 kg/cm2
Temperature - ambient
3.2) MANUFACTURING PROCEDURE
Urea is commercially manufactured by direct synthesis of gaseous CO2 and liq. NH3.
The urea production involves following steps:
1. Urea synthesis and pressure recovery.
2. Urea purification and medium low pressure recovery.
3. Urea concentration
- pre vacuum concentration
- Vacuum concentration
4. Urea prilling
5. Waste water treatment
1. UREA SYNTHESIS AND HIGH PRESSURE RECOVERY
For urea production raw materials (liquid ammonia and gaseous carbon dioxide) are supplied by
ammonia Plant. The liquid ammonia is pumped at high pressure through an ejector in to the
reactor. The ejector serves as drive less pump to recycle back ammonia and CO2 mixture at high
pressure known as carbamate into the Synthesis loop.CO2 mixed with small but measured
quantity of air is compressed in a fourstage compressor up to synthesis pressure. CO2 from the
Birla Institute of Technology & Science, Pilani. 23
compressor outlet is fed to the reactor. The NH3 and CO2 react in the reactor to form an
intermediate product, ammonium carbamate (NH4 COONH 2). This intermediate product
dehydrates to form urea and water. The oxygen in the air forms a passive oxide layer on the inner
surface of the vessel to prevent corrosion by carbamate and urea.
The reaction products from the reactor overflow to the stripper where the unconverted carbamate
is decomposed back in to the constituents with the help of the heat supplied by MP steam. The
stripper is basically a falling film exchanger with urea solution on the tube side and MP steam on
the shell side. The Urea solution obtained at the bottom flows to MP section through a level
control valve. The vapours from the stripper top enter the HP carbamate condenser along with
the carbamate solution Again and in the process releasing a large amount of heat of
condensation, which is utilized to generate the low-pressure steam on the shell side. Vapours
consisting mainly of inerts are sent from the carbamate separator to the bottom of the MP
decomposer to passivate the MP section.
2. UREA PURIFICATION
Urea purification takes places in two stages. One is known as MP section and the other is known
as LP Section.
MEDIUM PRESSURE SECTION
Urea solution from the bottom of the stripper enters the MP decomposer. During the expansion
most of the remaining carbamate flashes forming the NH3 and CO2 vapours, thereby
concentrating the urea solution. The vapours from the MP decomposer top flow to pre vacuum
concentrator shell side and from pre vacuum Concentrator to MP condenser shell side. Prior to
the entry of the vapours in the pre vacuum concentrator the vapours get mixed with the low
concentration carbamate solution from the LP section. The partly condensed gas mixture from
MP condenser outlet goes to MP absorber where the CO2 is stripped from the NH3 vapors and
the pure NH3 vapors from the MP absorber flow to ammonia condenser. The solution at the
Birla Institute of Technology & Science, Pilani. 24
bottom of the MP absorber provides the suction for the HP carbamate pump. Ammonia
condenser has cooling water on tube side.
From ammonia condenser both vapour and liquid flow to the ammonia receiver tank. The
receiver tank receives fresh ammonia from the ammonia plant. The inert gases saturated leaving
the receiver enter the ammonia recovery tower.
Here ammonia is further condensed by direct contact with cold ammonia from the battery
limit.The inert with residual ammonia from the tower are sent to MP inert wash tower via a
condenser. The ammoniacal solution collected at the bottom is recycled back to the MP absorber.
LOW PRESSURE RECOVERY
The urea solution from MP decomposer bottom enters the LP decomposer after expansion
through a level controller. Consequently most of the residual carbamate is decomposed and in
the process urea solution gets concentrated. The remaining carbamate is decomposed in falling
film exchanger, which is a part of LP decomposer.
The vapours from the LP decomposer enter the LP condenser where they get cooled and
liquefied. Prior to entry of LP off gases in LP condenser the vapours get mixed with aqueous
solution from wastewater section. The vapours thus formed get condensed in LP condenser goes
to carbonate solution tank from where it is sent back to MP condenser. The inert gases in the
tank contain considerable amount of ammonia and thus are absorbed in cool condensate before
being sent to the vent stack. The urea solution at the bottom of LP decomposer is sent to pre
vacuum concentrator through a level controller valve.
3. UREA CONCENTRATION
PRE VACUUM CONCENTRATOR
The urea solution from LP decomposer enters the pre vacuum concentrator, which is an
exchanger with urea solution from the LP section on tube side and MP decomposer off-gases on
the shell side. The MP decomposer off-gases give their heat and the urea solution gets
concentrated in the process. The pre vacuum concentrator operates under vacuum and the
Birla Institute of Technology & Science, Pilani. 25
vapours from the top are condensed in the pre vacuum condenser. The vapours condensing in the
pre vacuum condenser are collected at the bottom in vacuum system tank and the liquid is sent to
the wastewater section. The concentrated urea solution at the bottom is sent to the vacuum
concentrated section.
VACUUM CONCENTRATION
The urea solution from the pre vacuum section bottom gets further concentrated up to the
concentration required for prilling in two vacuum concentrators in series. The heat for
concentrating the urea solution is supplied by low-pressure steam. The vacuum is maintained in
both the stages with the help of ejectors and condensers. The urea solution from the outlet of
second vacuum concentrator has 99.7 % (w/w) concentrations and is pumped to prilling section.
The vapours from both the stages get condensed in the condensers and are sent to the wastewater
section.
4. UREA PRILLING
The urea melt from the second vacuum concentrator is sent to the prilling bucket. The urea melt
comes out from the bucket in the form of liquid drops and they fall along the prilling tower. The
drops get solidified and cooled by the countercurrent flow of air from the bottom of prilling
tower. The solidified urea melt drops known as urea prills, fall on the prilling tower bottom.
These prills are collected by a rotating scrapper and are sent to the bagging plant with the help of
belt conveyors. The heated air containing few ppm of NH3 is released from the top in to the
atmosphere.
5. WASTE WATER TREATMENT
The liquid waste containing water, urea, ammonia and carbon dioxide from the process, the
condensate from vacuum and pre vacuum concentration ejector/condensers are collected in a
wastewater tank. From here it is transferred to the distillation tower where it is fed in the upper
portion of the distillation tower. The stripping medium is low-pressure steam fed at the bottom of
the tower. The ammonia stripped wastewater is then pumped to the hydrolyser where the urea in
the wastewater is hydrolyser to be converted back in to ammonia and carbon dioxide. The
hydrolyzation takes place with the help of the superheated steam. The wastewater from the
Birla Institute of Technology & Science, Pilani. 26
hydrolyser outlet contains only few ppm of urea but still has ammonia in it. So the wastewater
from the hydrolyser outlet is again fed to the lower portion of the distillation column where the
remaining ammonia is stripped off and the wastewater at the distillation tower at the bottom
contains only few ppm of ammonia and urea.
This treated water is sent to O&U plant for reuse. The vapours from the distillation tower and
hydrolyser get condensed in the overhead condenser and are recycled back to the LP section and
a part of it is used as reflux for distillation column. The distillation column is a tray column
PROCESS FLOW DIAGRAM
Fig.3.2.1. Process Flow Diagram of Urea Plant
3.3) STEAM AND CONDENSATE SYSTEM
The steam networks provided in the urea plant are:
1. Superheated steam (KS) network at P = 110 kg /cm2
g & T = 510°C
Birla Institute of Technology & Science, Pilani. 27
2. Superheated steam (HS) network at P = 37 kg /cm2
g & T = 381°C
3. Saturated steam (MS) network at P = 22 kg /cm2
g & T = 219°C
4. Saturated steam (LS) network at P = 3.5 kg /cm2
g & T = 147°C
5. Saturated steam (KS) network at P = 4.7 kg /cm2
g & T = 160°C
KS NETWORK:
The steam is available at urea plant battery limit and is utilized to drive the CO2 compressor
turbine. It may be used to provide the MS steam in case of failure of turbine extraction steam.
HS NETWORK
This steam is available at the point battery limit and is utilized in hydrolyzer.
MS NETWORK
This steam is extracted from the carbon dioxide compressor turbine and is the superheated to
make it saturated. This steam is utilized in the stripper and MP decomposer.
LS NETWORK
This steam is produced in the HP carbamate condenser shell & is used in the following
equipment / systems:
1. LP decomposer
2. First vacuum concentrator
3. Second vacuum concentrator
4. distillation tower bottom
5. Prevacuum / vacuum system ejectors
6. Steam tracing
7. Steam jackets
8. MP start up lines
9. MP inert gas wash tower vent line
Birla Institute of Technology & Science, Pilani. 28
10. Steam condensate collector tank
11. Blow down vents, ME-14,ME-15, ME-21
12. PSV flushing
13. Mechanical seal / jacket flushing of P-08, P-09, & P-20
14. utilities points
LMS NETWORK:
This steam is produced by boosting LS pressure with the help of an ejector with MS as motive
fluid. The steam is utilized in the MP decomposer.
CONDENSATE COLLECTION
Turbine condensate is exported to O&U for steam generation. MS & HS condensate known as
MC & HC respectively is utilized for LS generation in HP carbamate condenser shell. LS
condensate known as LC from all the sources in the plant is collected in a common tank as steam
condensate tank. From where it is used for flushing purpose and the excess condensate is
exported to O&U.
3.4) FLUSHING NETWORK
Condensate in the steam condensate tank is utilized to provide flushing water requirement in all
the section of the plant. There are three types of network:
KW Network: Flushing water at pressure of about 180 kg /cm2 a
HW Network: Flushing water at pressure of about 25 kg /cm2 a
LW Network: Flushing water at pressure of about 10 kg /cm2 a
Birla Institute of Technology & Science, Pilani. 29
Birla Institute of Technology & Science, Pilani. 30
4) PROJECT
4.1) To Carry out the energy balance of Urea plant
Birla Institute of Technology & Science, Pilani. 31
TO CARRY OUT THE ENERGY BALANCE OF UREA PLANT
PROJECT SUMMARY
The project assigned to me is ‗To Carry Out The Energy Balance of Urea Plant‘.I was assigned
this project by Mr.Azaz Ali, the head of department of urea plant.Now the urea plant here at Tata
Chemicals Limited has two exactly identical units viz. 11 and 21 within the plant.Both the units
work on the same load of raw materials and energy and have the same installations.Therefore it
is prudent to surmise that both the units would have the same or nearly same concentration of
gases in the flows analogus to both the sister units.
The process used here for urea manufacturing is Snamprogetti process.
The urea production involves following steps:
1 Urea synthesis and pressure recovery.
2 Urea purification and medium low pressure recovery.
3 Urea concentration
4 pre vacuum concentration
Vacuum concentration
5 Urea prilling
6 Waste water treatment
The material balance of every section has already done in detail manner.Now the task was to
Carry Out The Energy Balance of Urea Plant.
Birla Institute of Technology & Science, Pilani. 32
Approach:
The way forward for tackling this problem was to first get a design data sheet of the plant.Since
the plant was updated to a new capacity of 2*1750 MTPD as against the old 2*1225 MTPD it
was imperative only to work with the new design data sheet.The idea was to first find the design
flowrates of various components at various points and then to find out the temperature at various
points.
FLOWRATES OF PROCESS FLUID
The flowrates of process fluids were obtained from the Control room as well as from the
PROCESS FLOW DIAGRAMS(PFD).
TEMPERATURE MEASUREMENTS
The temperature of process fluids were obtained from the Control room as well as from the
PROCESS FLOW DIAGRAMS(PFD).
SPECIFIC HEAT DATA
The specific heats of various components were obtained from the data sheets in the technical
library.Since there is a small variation in Cp value with temperature.I assume Cp of any
component at three diff. temperature ,then I get three variable with three equations and after
solving them I get the value of a,b.and c .
Hence,although this approach may not be entirely accurate ,it will still be within an extremely
small range of error of the actual value.
PROCEDURE
The heat exchanged by the process side is calculated by the formulae:
Q = mcp(Tin – Tout) [mass flowrate*specific heat *temp.difference]
Birla Institute of Technology & Science, Pilani. 33
Material Balance Of Urea Plant.
Urea production per day = 3800 MTPD
CO2 conversion = 64%
CO2 requirement per day = 57954 kg/hr
NH3 requirement per day = 127804 kg/hr
Compound Chemical formula Molecular Weight(kg/kmol)
Ammonia NH3 17
Carbon di oxide CO2 44
Ammonium Carbamate NH2COONH4 78
Water H2O 18
Urea NH2COONH2 60
Table 1 Compound in Urea Manufacturing
Input ratio to reactor NH3:CO2
Molar ratio 4: 1
Weight ratio 68: 44
Reactions involved in the process
2 NH3 + CO2→ NH2COONH4 + HEAT
Birla Institute of Technology & Science, Pilani. 34
Sch 2 1 1
Mass 34 44 78
Wt% 0.436 0.564 1.000
NH2COONH4 + HEAT → NH2CONH2 + H2O
Sch 1 1 1
Mass 78 60 18
Wt% 1.000 0.769 0.230
5.0 Heat Balance Calculation
5.1 Main Process Energy Balance
2 NH3 + CO2 NH2COONH4 + HEAT -84 KJ/mol
NH2COONH4 + HEAT NH2CONH2 + H2O +23 KJ/mol
2NH3 + CO2 NH2CONH2 + H2O -60 KJ/mol
Ammonia Liquid
T (ºC) 60 80 112
Cp (KJ/KgK) 5.6 5.87 8.6
Ammonia Vapour
T (ºC) 87 127 167 207
Cp (KJ/KgK) 2.2 2.3 2.37 2.44
Birla Institute of Technology & Science, Pilani. 35
CO2(g)
T (ºC) 27 127 227
Cp (KJ/KgK) 0.84 0.94 1.01
Urea Vapour
T (ºC) 80 120 200
Cp (KJ/KgK) 1.26 1.36 1.56
Urea Liquid
T (ºC) 80 120 200
Cp (KJ/KgK) 1.4 1.6 2.1
Urea Solid
T (ºC) 27 77 127
Cp (KJ/KgK) 1.56 1.8 2.04
Water Liquid
T (ºC) 27 127 177
Cp (KJ/KgK) 4.18 4.26 4.39
Cp of the Carbamate = 2.3 KJ/KgK
Birla Institute of Technology & Science, Pilani. 36
For NH3 liquid
Cp = a + bT + cT2
5.6 = a + 333b + 3332 c (1)
5.87 = a + 353b + 3532 c (2)
8.6 = a + 385b + 3852 c (3)
From (1), (2) & (3)
a = 163.44 b = - 0.9338 c = 1.38*10-3
For NH3 gas
Cp = a + bT + cT2
2.2 = a + 360b + 3602 c (4)
2.3 = a + 400b + 4002 c (5)
2.44 = a + 480b + 4802 c (6)
From (4), (5) & (6)
a = 0.4 b = 7.25*10-3
c = -6.25*10-6
For CO2 gas
Cp = a + bT + Ct2
0.84 = a + 300b + 3002 c (7)
0.94 = a + 400b + 4002 c (8)
1.01 = a + 500b + 5002 c (9)
From (7), (8) & (9)
a = 0.36 b = 2.05*10-3
c = -1.5*10-6
For Urea
Cp = a + bT + cT2
1.4 = a + 353b + 3532 c (10)
1.6 = a + 393b + 3932 c (11)
2.1 = a + 473b + 4732 c (12)
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From (10), (11) & (12)
a = 1.08 b = -2.77*10 -3
c = 1.04*10-5
Reactor (R-01)
Urea formation heat by decomposing Ammonium Carbamate
∆Hf = 79279 *
= 30390.28 kJ/hr
Ammonium Carbamate production in the reactor
= *79279
= 103,062.7 Kj/hr
Ammonium Carbamate formation heat
∆Hf = 103062.7* = -110990.6 KJ/hr
Heat required to increase raw material from 178°C to 188°C
= (12,7804)*[ ∫(163.44 – 0.9338T + 1.38 * 10-3T2)dT ] +(23333)*(461-451) +
(57954 + 42,284)*[∫(0.36 + 2.05*10-3T ― 1.5*10-6T2)dT]
= 3818763.96 KJ/hr
Energy required to reactor = 30390.28 – 110990.6 + 3818763.96
= 3738163.66 KJ/hr
Stripper (E-01)
Decomposition energy of Ammonium Carbamate
(251373 )* = 270,709.38 Kj/hr
Heat absorbed by Carbamate by temp.increase from 461K to 477K
Birla Institute of Technology & Science, Pilani. 38
= (79,279)*[∫(1.08 – 2.77*10-3
T + 1.04 *10-5
T2)dT ]+
(45,665)*[ ∫(163.44 – 0.9338T + 1.38 * 10-3T2)dT] + 43,007*4.4*(477-461) +
(12,843)*[∫ (0.36 + 2.05*10-3T ― 1.5*10-6T2)dT]
= 79,279*32.5 + 45,665*390.7 + 3,027,692.8 + 204,414.58
= 2577186.6 + 206852657.8 + 3,027,692.8 + 204,414.58
= 212,661,951.8 Kj/hr
Heat absorbed by carbon Dioxide by increasing the temp. from 461°C to 463°C
= (12843)*∫10.36(463-461) + 2.05*0.001*0.5*(4632 – 461
2) – 1.5 *10*-6*(463
3 -461
3)*0.333
= 12843*21.98
=282,289.14 Kj/hr
Heat absorbed for Ammonia Vapourisation
= 37214*160
= 5954240 Kj/hr.
Energy required for stripper = 270,709.38 + 212,661,951.8 + 282,289.14 + 5954240
= 219,169,190.3 Kj/hr
Carbamate Condenser:(E-05)
Heat absorbed by Carbamate by temp.increase from 368K to 428K
(13169)*∫(0.36 + 2.05*0.001T – 1.5 *10-6
T2)dT + (28138)*[∫(163.44 – 0.9338T + 1.38*10
-
3T
2)dT] + 19283*4.4*(428-368)
= 742,731.6 + 42,550,976.92 +50,90,7 12
Heat released by CO2 =
29257*∫(0.36 + 2.05*0.001T – 1.5 *10-6
T2)dT
= -1001871.7 Kj/hr
Birla Institute of Technology & Science, Pilani. 39
Heat released by water
= 19263*4.4*(428-463)
= -2969,582 Kj/hr
Condensation heat & Sensible heat released by NH3 =
37,214*760 + 37,214*[∫(0.4+(7.25*10-3
)T-1.5*10-6
T2)dT]
= 37214*760 + 37,214*-116.72
= 23,939,021.92 Kj/hr.
Heat released from water
= 4,110*4.4*(428-463)
= -632,940 kj/hr.
Heat released from Carbamate condenser =
742,731.6 +42,550,976.92 + 5090,712 -1001871.7 -2,969,582 +23,939,021.92-632,940
= 67,719,048.72 Kj/hr.
Carbamate Separator(MV-O1) :
Heat released from up flow (190°C to 155°C)
= 4501*[∫(163.44 – 0.9338T + 1.38*10-3
T2)dT]
= -5,934,540.99 Kj/hr
Heat released from down flow (190°C to 155°C)
60,581*[∫(163.44 – 0.9338T + 1.38*10-3
T2)dT]
+ 42,284*[*∫(0.36 + 2.05*0.001T – 1.5 *10-6
T2)dT
+23,251*4.4*(428-463)
= - 85,345,693.06 Kj/hr
Energy loss = -5,934,540.99 - 85,345,693.06 = -91,280,234.05 Kj/hr
Birla Institute of Technology & Science, Pilani. 40
Low pressure Decomposer (E-03):
Decomposition energy of Ammonium Carbamate
= 123723*84/78 = 133,240.15 KJ/hr
Heat absorbed for Ammonia Vapourization
= 6006 *210 = 1261260 KJ/hr
Heat released from Urea (160°C - 142°C)
= (79279)*[∫(1.08 – 2.77*10-3
T + 1.04 *10-5
T2)dT ]
= 79,279*-31.62 = - 2506,951.85 KJ/hr
Heat released by Ammonia (160°C - 142°C)
= 7849*[∫(163.44-0.9338T + 1.38*10-3
T2)dT]
= -2080,640.037 KJ/hr
Heat released from water (160°C - 142°C)
= 34459*4.3*(415-433)
= - 2,667,126.6 KJ/hr
Heat released from carbon – di-oxide (160°C - 142°C).
= 2136*[∫(0.36 + 2.05*10-3T ― 1.5*10-6T2)dT]
= -36,179.28 KJ/hr
Heat released by LPD = 133,240.15 +1261260 - 2506,951.85 -2080,640.037
- 2,667,126.6 -36,179.28
= -5,896,397.61 KJ/hr
Birla Institute of Technology & Science, Pilani. 41
MP Decomposer (E-02 A/B):
Decomposition energy of Ammonium Carbamate
= (180794 – 123723)* = 61,461.07 KJ/hr.
Heat absorbed for Ammonia vapourisation
= 42317*210 = 8886570 KJ/hr
Heat released from Urea (204°C - 160°C)
= (79279)*[∫(1.08 – 2.77*10-3
T + 1.04 *10-5
T2)dT ]
= 79,279*-117.54 = -9318998.45 KJ/hr
Heat released from water (204°C - 160°C)
= 43007*4.3*(160-204) = -8136924.4 KJ/hr
Heat released by Ammonia (204°C - 160°C)
= 45665*[∫(163.44-0.9338T + 1.38*10-3
T2)dT]
= 45665*-1808.4 = -8258104.39 KJ/hr.
Energy loss = 61,461.07 + 8886570 – 9318998.45 – 8136924.4 – 8258104.39
= -16,765,996.17 KJ/hr
Birla Institute of Technology & Science, Pilani. 42
M.P.Absorber(C-01):
Condensation heat released by NH3
= (50308-29713)*(-200)
= -4119000 kj/hr
Energy loss due to reduce temperature from 85°c to 80°c
= 28138*[∫(163.44 – 0.938T + 1.4*10-3
T2)dT] + 13169[(0.36+ 2.05*10
-3T -1.5*10
-6T
2)dT ]
+ 17783*4.4*(80-85)
= 28138*-22.18 +13169*-8.15 + 17783*4.4*(80-85)
= -1122,654.19 Kj/hr.
Energy released from M.P.ABSORBER(C-01)
= -4119000 -1122,654.19 = -5,241,654.19 Kj/hr
Prevacuum Separator(MV-29/E-29)
Heat released from UREA =
79279*1.96*(102-142) = -6,215,473.6 KJ/hr
Heat released from Water =
(29745+8690)*4.25*(102-142) = -6,533,950 KJ/hr
Heat absorbed by water Vapourisation =
15856*2,258 = 35,802,848 KJ/hr
Total Heat gain = -6215,473.6-6,533,950 + 35,802,848
= 23,053,424.4 KJ/hr
M.P Steam load
S6 *1972 = 23,053,424.4
S6 = 11,690.38 KJ/hr
Birla Institute of Technology & Science, Pilani. 43
1st Vacuum Separator (MV-06/E-14):
Heat absorbed by water vapourisation
= 9720*2702.4 = 26,267,328 KJ/hr
Heat absorbed by Urea & Water
= 79,279*2*(128-102) + 13,889*4.25*(128-102)
= 4,122,508 + 1,534,734.5 = 5,657,242.5 KJ/hr
Energy loss = (26,267,328 + 5,657,242.5)*0.01 = 319,245.71 KJ/hr
Total energy requirement
= (26,267,328 + 5,657,242.5 + 319,245.71) KJ/hr
= 32,243,816.21 KJ/hr
3.5 kg/cm2
LS steam load
S7 * 2109 = 32,243,816.21
S7 = 15,288.68 KJ/hr
2nd
Vacuum Separator (MV-07/E-15):
Heat absorbed by water vapourisation
= 5115*2706.28 = 13,842,622.2 KJ/hr
Heat absorbed by Urea & Water
= 79,329*2*(138-128) + 5,313*4.25*(138-128)
= 1,586,580 + 225,802.5 = 1,812,382.5 KJ/hr
Energy loss = (13,842,622.2+ 1,812,382.5)*0.01 = 156,550.047 KJ/hr
Total energy requirement
= (13,842,622.2+ 1,812,382.5 + 156,550.047) KJ/hr
= 15,811,554.75 KJ/hr
3.5 kg/cm2
LS steam load
S8* 2109 = 32,243,816.21
Birla Institute of Technology & Science, Pilani. 44
S8 = 7,497.18 KJ/hr
Prilling Tower (ME-06)
Heat removed from Prilling Tower =
79,329*2*(128 – 138) + 5,313*4.25*(128 – 138)
= -1,586,580 – 225,802.5
= - 1,812,382.5 KJ/hr
Process Waste water treatment unit.
Heat requirement of waste water treatment unit =
58396 * 4.2*(147-128) + 58,396*2258
= 63,000.5 + 131,858,168
= 131,921,168.5 KJ/hr
Birla Institute of Technology & Science, Pilani. 45
8.0 Tabulated heat balance
Input Energy KJ/hr
Heat supplied to reactor 3738163.66
Heat supplied to stripper 219,169,190.3
Heat out from Carbamate Condenser 67,719,048.72
Heat supplied to HPD
Heat supplied to prevacuum separator 23,053,424.4
Heat supplied to 1st vacuum separator 32,243,816.21
Heat supplied to 2nd
vacuum separator 15,811,554.75
Total input energy 340,735,198
Output Energy KJ/hr
Heat out from Separator 91,280,234.05
Heat out from Carbamate Condenser
Heat out from MPD 16,765,996.17
Heat out from Absorber 5,241,654.19
Heat out from prilling tower 1,812,382.5
Heat out from waste water 131,921,168.5
Heat out from LPD 5,896,397.61
Total output energy 251,286,689
Difference between input and output energy = 89,448,508.98
Total heat input is greater than total heat output.So this difference
is due to heat generated in the reaction.But the amount of theoretical heat generated in the
reaction is much higher than this value.That difference between actual and theoretical value is
happens because of heat losses ocuured during the reaction.
Birla Institute of Technology & Science, Pilani. 46
5) CONCLUSIONS AND RECOMMENDATIONS
Birla Institute of Technology & Science, Pilani. 47
4.1) SIMULATION OF MEDIUM PRESSURE ABSORBER(C-01):
This project deals with the steady state simulation of ‗Medium Pressure Absorber(C-01)‘ of the
urea plant using Aspen plus simulator. Aspen plus is a process modeling tool for conceptual
design, simulation, optimization and performance monitoring for chemical, polymer, specialty
chemical, metals and minerals, and coal power industries. The unique combination of sequential-
modular and equation-oriented solution technologies in Aspen plus facilitate simulation of wide-
scale, integrated chemical processes. Aspen plus can predict the output conditions based on the
given input and process conditions and hence we can use it as a tool in process improvisation.
We can also optimize a process using Aspen Plus's various in-built optimization algorithms.
Using these optimization techniques we can improve the performance of various processes by
manipulating the operating variables.
The purpose of the simulating this absorber is to calculate the amount of absorption of carbon
dioxide and water contained in the vapors of mixed stream coming from medium pressure
condenser (E-07) outlet enter into the medium pressure absorption column (C-01), so as to
increase recovery of ammonia from the process. In this project, the simulations are carried out
based on design conditions. The saved aspen simulation files can be used by anyone to predict
the behavior of the simulated sections
The first step in simulation is to build the process flow diagram in the user interface. Fig. 4. 1.1
shows the process flow diagram of the medium pressure absorber (C-01). The process mixed
stream from medium pressure condenser (E-07) outlet enters the absorber, from the middle of the
column. The vapors containing ammonia, carbon dioxide, water and inerts are separated out from
liquid and rises towards top of the column. Fresh ammonia and ammonia solution are entered on
tray 1 and 2 resp. from top of the column. Whenever reflux gets contacted with rising vapors, it
absorbs carbon dioxide and water. Vapors are drawn from the top of column containing
ammonia, inerts and few ppm of carbon dioxide and water. Liquid solution is drawn from bottom
of the column containing ammonia, carbon dioxide and water.
In this case the equilibrium steady state simulation of medium pressure absorber (C-01) is carried
out. The RADFRAC ABSORBER model from the steady-state simulator ASPEN PLUS, version
2006 was taken to simulate the process. RADFRAC is based on a rigorous equilibrium-stage
model for solving the MESH (Material balance, vapor – liquid Equilibrium, mass fraction
Summations and Heat balance) equations.
Birla Institute of Technology & Science, Pilani. 48
Simulation of the design data on Absorber Column (C-01):
The input data for the components entering from shell side of Pre Vacuum Column (E-29) shell
side:
Temperature = 85°C
Pressure = 18.22 kg/cm2g
Ammonia flow rate = 78996 kg/hr
Carbon di-oxide flow rate = 13169 kg/hr
Water flow rate = 16917 kg/hr
The input data from the M.P Ammonia absorber (E-11)
Temperature = 37°C
Pressure = 23.00 kg/cm2g
Ammonia flow rate = 5837 kg/hr
The input data from the Ammonia Solution
Temperature = 50°C
Pressure = 18.00 kg/cm2g
Ammonia flow rate = 1385 kg/hr
The M.P absorber input is :
Height : 9 m
Dia. : 1.74 m
No.of Trays : 4
Type of Trays :Bubble cap
Properties Specified : ELECNRTL (Electrolytic Non Random Two Liquid)
Birla Institute of Technology & Science, Pilani. 49
Simulation was run on the above input data and the following results were obtained.The
results are tabulated on the following page.
Fig. 4. 1. 1. Medium Pressure Absorber (C-01)
Birla Institute of Technology & Science, Pilani. 50
Table 4. 1. 1: Streams Results
Birla Institute of Technology & Science, Pilani. 51
Table 4. 1. 2: Mass and Energy Balance
Table 4. 1. 3: Top stage parameters
Table 4. 1. 4: Bottom stage parameters
Table 4. 1. 5: Split fraction of components
Birla Institute of Technology & Science, Pilani. 52
Table 4. 1. 6: Temperature, Pressure and Flow rate Profiles
Table 4. 1. 7: Vapor Compositions of Components
Table 4. 1. 8: Liquid Compositions of Components
Birla Institute of Technology & Science, Pilani. 53
Table 4. 1. 9: K-Value Profiles
Birla Institute of Technology & Science, Pilani. 54
Some of the plots for various simulation results are as follows:
Fig. 4. 1. 2. Variation of temperature with stages
Birla Institute of Technology & Science, Pilani. 55
Fig. 4. 1. 3. Variation of column pressure with stages
Fig. 4. 1. 4. Variation of total liquid flow rate with stages
Birla Institute of Technology & Science, Pilani. 56
Fig. 4. 1. 5. Variation of total vapor flow rate with stages
Birla Institute of Technology & Science, Pilani. 57
Fig. 4. 1. 6. Liquid composition profiles
Fig. 4. 1. 7. Vapor composition profiles
Birla Institute of Technology & Science, Pilani. 58
5) CONCLUSIONS AND RECOMMENDATIONS
For 3500 MTPD capacity; ranges are found for column pressure would be 17 to 18 kg/cm2 a.
P5NH3 flowrate would be 5500 to 6500 kg/hr and C1mixin temperature would be 84°C to 87 °C.
Output of C1vapor temperature would be in the ranges of 42.4°C to 44.5°C and corresponding
C1vapor flow rate would be in the ranges of 31100 to 31700 kg/hr. Output of C1liquid
temperature would be in the 78°C to 81°C and corresponding C1 liquid flow rate would be in the
ranges of 55600 to 56500 kg/hr.
Birla Institute of Technology & Science, Pilani. 59
6) REFERENCES
1) Urea Manual, TATA Chemicals Ltd, Babrala, 1999.
2) Fire and Safety manual of TCL, Babrala.
3) ASPEN plus Manual 2006.
4) McCabe Warren L., Smith Julian C., Harriott Peter, Unit Operations of Chemical
Engineering, 6th
Edition, McGraw-Hill Book Co.-Singapore, International Edition, 2001.
5) Richardson, J. F.; Harker, J. H.; Buckhurst, J. R., Particle Technology and Separations
Processes, Vol. 2, 5th
Edition, Butterworth-Heinemann, Elsevier, 2006.
6) Perry, R.H., and Green, D.W., Perry’s Chemical Engineering Handbook, 7th
Edition,
Tata McGraw-Hill, 1999
7) Treybal, R.E., Mass Transfer Operations, 3rd
Edition, Tata McGraw-Hill, 1980
8) Smith, J.M., Abbott, M.M., Vanhess, H.C., Chemical Engineering Thermodynamics, 6th
Edition, Tata McGraw-Hill, 2003.
9) MARTYN S. RAY;DAVID W. JOHNSTON – Chemical engineering Design Project:
A Case Study Approach
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