Internship FFC Mirpur Methelo Process Report 2019

HANZLA IMRAN | Internship Report | July 25, 2019
Fauji Fertilizer Company Ltd.
FFC Mirpur Mathelo

1
FAUJI FERTILIZER COMPANY LTD.2019
INTERNSHIP REPORT
(Production Unit)
Prepared for
Technical Training Centre (TTC)
Fauji Fertilizer Company Ltd. (FFC)
Mirpur Mathelo, District Ghotki (Sindh)
Prepared by
Muhammad Hanzla Imran
Department of Chemical and Polymer Engineer
University of Engineering & Technology Lahore
(Faisalabad Campus)
Email: hanzlaimran.30@gmail.com
Contact: +92-331-7376667

2
Acknowledgements
Author is thankful to
Almighty Allah,
For His unlimited blessings and bounties,
And for keeping him sane, sound and successful;
His parents and friends,
For all their support and trust in him and his aims;
His teachers and guides,
For teaching him things he knew not;
Mr. Intkhab Alam,
For bringing the opportunity of this excellent learning and exposure;
And last but never the least
Management and Staff of Fauji Fertilizer Company Mirpur Mathelo
Especially Unit Managers, Shift Engineers, Supervisors and Operators,
For their utmost help, guidance and time
Which made author make most of his internship at plant site;

3
FFC MM PLANT AREA DESCRIPTION
Area Number Unit Area
Area No. 1 Urea Urea Section
Area No. 2 Ammonia Synthesis Gas Preparation
Area No. 3 Ammonia Carbon dioxide removal
Area No. 4 Ammonia Compression Section
Area No. 5 Ammonia Ammonia Synthesis & Refrigeration
Area No. 6 Utilities Turbo Generator
Area No. 7 Utilities Boiler
Area No. 8 Utilities Cooling Tower
Area No. 9 Utilities Pre-treatment and treatment
Area No. 10 Utilities Instrument Air
Area No. 11 B & S Urea Storage
Area No. 12 B & S Urea storage and fresh feed belts
Area No. 13 B & S Urea screening and recycling
Area No. 14 B & Storage Urea packing and dispatch
Area No. 15 Utilities Natural Gas
Area No. 16 Utilities Waste Water Treatment
Area No. 17 Utilities Diesel Storage

4
Contents
Declaration ........................................................................................................................................................ 7
Production Unit.................................................................................................................................................8
List of Acronyms................................................................................................................................................9
Utilities Unit.....................................................................................................................................................10
Water Treatment (Area 09) .............................................................................................................................12
Pretreatment Section....................................................................................................................................12
Hardness of water: ..................................................................................................................................... 12
Chemical Dosage........................................................................................................................................14
Lime softening............................................................................................................................................14
TURBIDITY: ............................................................................................................................................... 15
Filtration ....................................................................................................................................................16
Demin Lines ..................................................................................................................................................16
Cooling Tower System (Area 08).....................................................................................................................19
Types of Cooling Towers:..............................................................................................................................19
Categorization by air-to-water flow.............................................................................................................19
Crossflow:...................................................................................................................................................19
Counterflow:.............................................................................................................................................. 20
Components of Cooling Tower:................................................................................................................... 20
Corrosion reducing chemicals:.................................................................................................................... 20
Instrument Air Compression (Area 10)............................................................................................................23
The major parts of an instrument air supply system are:............................................................................23
Inlet Air Filter (Pre-Filter)..........................................................................................................................23
Compressor: ...............................................................................................................................................23
Cooler: ........................................................................................................................................................23
Drying Section:.......................................................................................................................................... 24
Desiccant Air Dryers.................................................................................................................................... 24
Purpose of Desiccants:.............................................................................................................................. 24
Types of Desiccant air dryers.................................................................................................................... 24
Air Filtration:................................................................................................................................................ 24

5
Air Distribution System:.............................................................................................................................. 24
Natural Gas Station (Area 15).......................................................................................................................... 25
Old Line:....................................................................................................................................................... 25
New Line:...................................................................................................................................................... 25
Steam Generation (Area 06) ........................................................................................................................... 26
De-aerator (V-603):...................................................................................................................................... 26
Types of De-aerator:..................................................................................................................................27
Boilers:.......................................................................................................................................................... 27
Types of Boilers: ........................................................................................................................................ 28
Steam Drum: ................................................................................................................................................ 28
Combustion Zone:........................................................................................................................................ 29
De-Superheated Zone: ................................................................................................................................. 29
Super-Heating Zone:.................................................................................................................................... 29
Power Generation (Area 07)............................................................................................................................ 30
Turbo-Generator:......................................................................................................................................... 30
Critical Speed:............................................................................................................................................ 30
Emergency Diesel Generator (EDG): ........................................................................................................... 31
Gas Turbine:..................................................................................................................................................32
Waste Water Disposal (Area 16) ......................................................................................................................33
Ammonia Unit................................................................................................................................................. 34
Area 02 ............................................................................................................................................................. 36
Desulfurization Section: .............................................................................................................................. 36
Reforming Section.........................................................................................................................................37
PRIMARY REFORMER:............................................................................................................................. 38
SECONDARY REFORMING:......................................................................................................................41
Gas Purification Section (Area 03).................................................................................................................. 43
Shift Conversion:.......................................................................................................................................... 43
HTS-Convertor (R-204):............................................................................................................................ 44
LT S – Convertor (R-205):.......................................................................................................................... 44
AREA 03 ...........................................................................................................................................................46
CARBON DIOXIDE REMOVAL SECTION (BENFIELD SOLUTION) ..........................................................46

6
CO2 Absorbents:...........................................................................................................................................46
Process Description:.....................................................................................................................................46
Benfield Solution Recovery:.........................................................................................................................48
METHANATION:.........................................................................................................................................48
AREA 05 ........................................................................................................................................................... 50
AMMONIA SYNTHISIS AND REFRIGERATION SECTION ......................................................................... 50
Process:......................................................................................................................................................... 50
Description:.................................................................................................................................................. 50
AREA 04........................................................................................................................................................... 52
COMPRESSORS SECTION ............................................................................................................................. 52
Air Compressor (TK-421): ............................................................................................................................ 52
Ammonia Compressor (TK-441):..................................................................................................................53
UREA................................................................................................................................................................ 54
AREA 01............................................................................................................................................................ 55
High Pressure Section:................................................................................................................................. 56
Ammonia Receiving:.................................................................................................................................. 56
Carbon Dioxide Receiving: ........................................................................................................................ 56
Continuous Heating in HP section: .......................................................................................................... 56
PROCESS DISCRIPTION: ......................................................................................................................... 56
Medium Pressure Decomposition:.............................................................................................................. 58
Lower Pressure Decomposer: ...................................................................................................................... 59
Vacuum Section: ..........................................................................................................................................60
Waste Water Treatment Section:.................................................................................................................61
Bagging and Shipment Unit............................................................................................................................ 62

7
Declaration
July 07, 2019
TO WHOM IT MAY CONCERN
Respected Sir:
Submitted for your review is the report of my six weeks internship at Production
Unit of Fauji Fertilizer Company Ltd. Mirpur Mithalo plant, during June-July 2019.
It is hereby declared that the report is compiled in long report format, as per the guidelines and is
based upon the literature review; plant manuals and standard operating procedures; process flow
diagrams and sharing and learning from management and staff of the company. Maximum
possible references from literature are cited and sources are mentioned.
It is anticipated that response will be reflected.
Regards
Muhammad Hanzla Imran
Undergraduate Student
Department of Chemical & Polymer Engineering
University Of Engineering And Technology Lahore (FSD Campus)
3.5 KM. Khurrianwala – Mukkuana Bypass Road, Faisalabad
2016-CH-431
Email: hanzlaimran.30@gmail.com
Contact: +92-331-7376667

8
Production Unit
Production unit of an industry manages product production in field in coordination with process unit
(which does the desk job for same). The sole responsibility of the unit is to ensure maximum production
through overcoming the problems and issue coming up on daily routine on plant. The unit manages process
parameters like temperature, pressure, flow rate etc to achieve production targets, while guaranteeing the
safety of personnel and plant. The plant is monitored / controlled through a controlling centre (CCR at
FFC MM) where shift engineers work under the supervision of a coordination engineer and achieve the set
goals.
At FFC MM, production unit works under a Production Manager and is sub-divided into four sub-units, as
per their working goals. These include:
1. Utilities Unit; provides utilities like instrument air, cooling water, electricity to other
2. units
3. Ammonia Unit; provides raw materials i.e. ammonia and carbon dioxide for urea section
4. Urea Unit; produces the product urea (trade name: Sona Urea)
5. Bagging and Shipment Unit; bags urea and dispatch it to consumer market
Each of the unit has a UM which works with a team of engineers and other technical staff to manage smooth
run of unit. Shift starts with a coordination meeting of production manager, Unit Managers, staff engineers
and engineers; discussing and addressing the problems to be encountered. Shift engineers coordinate with
board men (operators of DCS monitoring facility at CCR) and operators (at respective areas) for following
the agreed plan of action for the shift or day.

9
List of Acronyms
BFW Boiler Feed Water
CCR Central Control Room, FFC MM
DCS Distributed Control System
DMW De-mineralized Water
DO Dissolved Oxygen
DS Dissolved Solids
EDG Emergency Diesel Generator
EPA Environment Protection Agency
FFC MM Fauji Fertilizer Company Ltd. Mirpur Mathelo
FFC Fauji Fertilizer Company Private Limited
HP High Pressure
HS High Steam
IMS Integrated Management System
LP Low Pressure
LPD Low Pressure Decomposer
LS Low Steam
LTA Lost Time Accident
MC Medium Condensate
MP Medium Pressure
MPD Medium Pressure Decomposer
MS Medium Steam
NEQS National Environment Quality Standards
NSC National Safety Council, USA
OSHA Occupational Safety and Health Administration
PLC Programmable Logical Control
QPM Quality Procedures Manual
SDV Shut Down Valve
SOP Standard Operating Procedures
SOV Solenoid Operating Valve
TDS Total Dissolved Solids
TG Turbo Generator
TTC Technical Training Centre, FFC MM
UM Unit Manager
WTCR Water Treatment Control Room

10
Utilities Unit

11
The objective of utilities unit is:
• To provide desired quantity and quality of certain utilities to the ammonia and urea units for
smooth functioning. These utilities include electricity, cooling water, instrument air, fuel gas and
steam network.
Water, air and natural gas are the basic utility raw materials, which are processed and improved to meet
the plants’ criterion of quality and ensure a longer life and safety of equipment.
PLANT UTILITIES DIVISION
Water Air Natural gas
1. Cooling water
2. Steam
3. Utility / service water
4. Drinking water
1. Instrument air
2. Utility / service air
Process air
1. Process stream
2. Fuel stream
Utilities unit is a pre-requisite for other units because their smooth running depends upon the utilities
supplied by it. In case of utility failure plant must face an emergency shutdown. Major sub-divisions of
utility section are:
• Water Treatment
• Cooling Tower System
• Waste Water Disposal
• Instrument Air Compression
• Natural Gas Station
• Power Generation
• Auxiliary Boilers and Steam Network

12
Water Treatment (Area 09)
The core purpose of the installation is to produce two main types of water:
• Make-up water for the cooling tower
• De-mineralized water for boiler feed
The section is controlled through the PLC based system in WTCR (Water Treatment Control Room)
located next to installations in area 09. WTCR also manages the preparation of different chemicals in
desired qualities, needed for water treatment. These include ammonium hydroxide, chlorinated water,
ferrous sulfate, lime solution, sodium hydroxide, sulfuric acid etc. At FFC MM, sources of water are
Masuwah canal flowing from Guddu Barrage and tube wells. Canal water has the main usage, whereas tube
wells are used in case of canal supply is suspended.
Water from canal is collected in a collection pit under gravity or pumped (when canal is flowing below
routine level) by four motor driven centrifugal pumps called Canal Bank Pumps (MP-950 G/H/I/J). A mesh
is used to prevent litter and garbage from coming inside the pit. Water is pumped to clarifier (ME-920 also
called Italfloc) at a flow rate of 250 m3/hr through six motor driven Canal Bank Pumps (MP-950
A/B/C/D/E/F), connected in series. In case of tube well (thirty-one units installed on the other side of N5)
service, motor driven MP-950 D/E/F pumps are used pump water from tube wells to collection pit.
Water treatment is further sub divided into:
• Pretreatment Section
• Demin Lines
Pretreatment Section
The pretreatment section produces filtered water from source water through:
• Clarification
• Filtration
Hardness of water:
Water becomes hard by being in contact with soluble divalent metallic cation (positive
ions having valency 2 i.e. salts of calcium, magnesium, barium, aluminum, manganese and iron).the
two main cations that causes water hardness are Ca and Mg. Ca is dissolved as it passes over and
through lime stone deposits. Mg is dissolved as it passes over and through dolomite and other Mg
bearing formations. Since the concentration of calcium and magnesium salts is usually much higher
than concentrations of other compounds which impart hardness, it is customary to consider only the
hardness caused by these salts. Removing these two hardness compounds hardness associated with
other compounds like iron, manganese, aluminum and barium is also removed.

13
Hardness Classification:
• Temporary Hardness
• Permanent hardness
Temporary Hardness:
Temporary hardness is due to calcium and magnesium alkaline salts such as calcium
and magnesium carbonates and bicarbonates so temporary hardness is also known as carbonate
hardness. Mostly temporary hardness in raw water is due to bicarbonates of calcium and
magnesium anent Hardness.
Permanent hardness:
Permanent hardness is due to neutral salts of calcium and magnesium which include
chlorides, sulfates, nitrates, and fluorides of calcium and magnesium. Permanent hardness is also
known as “non carbonate hardness” or “non alkaline hardness”. Any alkalinity present in the raw
water besides alkaline calcium and magnesium salts is due to sodium and potassium alkaline salts.
In Clarification, raw water is fed to 1800 m3
capacity clarifier (ME-920) at a flow rate of 1200 m3
/hr by
means of canal intake pumps (MP-950), mixed in line with ferrous sulfate and chlorinated water, for
enhanced mixing and oxidation of iron from ferrous to ferric. Chemical (lime and polyelectrolyte) dosage
is automatically adjusted according to the feed water rate.
The mixture enters the reaction zone of clarifier (ME-920) and is mixed with recycled sludge and
suspension of lime slurry. Mixing and recycling are ensured by a dual stirrer (MM-920 A) moving at 2 – 6
rpm. Through high activity of particles in reaction zone, suspended particles are held together to make
flocs and settle down to the bottom of clarifier. A bottom scrapper (MM-920 B) moving at 0.06 rpm
prevents building up of deposits and scales by conveying the sludge towards the extraction cone, where it
is withdrawn by gravity and recycled in some quantity to the reaction zone. The main flow from the
reaction zone to the upper portion passes to the upper flocculation area and finally flows in to the outer
clarification zone. During the final passage, it goes through the bed of pre-formed sludge (also called sludge
blanket), where it deposits both impurities and suspended particles. Clarifier has a residence time of
approximately 95 minutes and is equipped with several sampling points for testing the concentration of
the sludge at different levels. Clarifier is set to maintain a sludge bed height at bottom, on exceeding, the
blow down will automatically start.
CLARIFIER SPECIFICATIONS
Number 1
Name of Manufacturer ITAL-FLOC
Type Sludge Blanket
Design flow rate 660 -1320 m3
/hr
Recirculation Flow Rate 1200 to 4000 m3
/hr

14
Impeller Rotation Speed 2-6 rpm
Reaction Zone Residence Time 30 minutes
Total Residence Time 95 minutes
Chemical Dosage to a clarifier could be divided into three types: coagulants (ferrous sulfate and chlorine),
flocculants (polyelectrolyte) and softeners (lime). Sometimes, natural iron present in raw water is used to
supply the part of coagulant. When iron salts are used, the best flocs are formed when the pH value is
between 10.2 to 10.4. Therefore, if dissolved iron content exceeds 4 to 5 ppm, it is not necessary to add
ferrous sulfate. Chlorination may be considered as a coagulant aid since it reduces many of the organic
substances present in water which inhibit floc formation (M. Yaqoob Ch., 1987). Chlorinated organic
compounds are more readily removable by the floc and therefore, final quality of effluent is lower in
organics.
Polyelectrolyte is anionic polymer that attracts the neutralized suspended particles through its positive
charge and provides them with a nucleus to deposit on. This leads to floc formation and settling. Lime
reacts with soluble hardness molecules and reduces them to insoluble. Lime dose is a function of pH of raw
water and is regularly adjusted.
Lime softening
Is the process used to reduce temporary hardness of water by treatment with lime. The addition
of lime softens the water by removing carbonate hardness as calcium carbonate and magnesium hydroxide
precipitates, with some of these remaining in solution depending upon their solubility at a temperature.
The result of this operation is not only a considerable reduction in hardness, but also the elimination of
dissolved CO2, turbidity, and the reduction of silica, iron and manganese levels.
Reactions of lime with:
1. Carbonate Hardness

15
2. Non-Carbonate Hardness
TURBIDITY:
Turbidity is defined as,
“Reduction of transparency of water due to presence of particulate matter”.
OR
“A suspension of fine inorganic, organic & other suspended impurities in water that cause cloudiness”.
CHEMICAL DOSAGE IN CLARIFIER
Chemicals % by weight Mass Flow Rate
Ferrous sulfate 25 1200 kg/hrs
Chlorine 99.5 7.8 kg/hr
Polyelectrolyte 0.3 0.6 kg/hr
Lime 5 675 kg/hrs
Following (M. Yaqoob Ch., 1987) modifications are achieved to the quality of water in a clarifier:
• Turbidity reduction
• Color and organic matter reduction
• Lime softening
o Calcium reduction
o Magnesium reduction
• Alkalinity reduction
• Partial demineralization
• Free carbon dioxide reduction (up to zero level)
• Iron reduction (up to zero level)
• Silica reduction
Clarified water is collected into radial channels, flowing in to annular channels outside the basinand finally
into the feeding channels of the collection basin ME-926. The basin with a capacity of 800 m3, corresponds
to an average retention time of 45 minutes at nominal flow, to shadow the effects of excess chlorine dosage.
Through pumps P-926 (capacity 500 m3/hr) a certain amount of clarified water is withdrawn from the

16
collection basin for cooling towers make-up, while the remaining is pumped to the filtration section
through P-923 A/B/C.
CLARIFIED WATER PARAMETERS
Parameter Quantity
Turbidity Lss than 5 NTU
pH 9.9 – 10.2
Free chlorine Less than 0.2 ppm
Iron Less than 0.2 ppm
Alkalinity 2 p = m
Filtration is done to remove residual turbidity of clarified water. The flow rate of fed to filters from clarified
water tank is proportional to the requirement of treatment section. Filtration encounters the suspended
matter in water with sand bed in filters which finally becomes clogged and demands periodic regeneration
after particular operational time.
Clarified water at 70 m3/hr flow rate is delivered to battery of four gravel filters (V-920 A/B/C/D) connected
in parallel. At odds, flow rate is regulated by a valve LIC-02-V actuated through the level controller 09-LIC-
2 located into the filtered water storage tank T-920. Thus the flow rate of water to the filter is proportional
to actual requirement of users i.e. treatment section. Filters are filled with 18 tons of light grey bright quartz
sand particles with 97% silica.
During filtration, suspended matters contained in the water are retained inside the filtering bed which
becomes clogged and the pressure increases to a maximum value (approx 1.0). Clogging however doesn’t
depend only upon the total quantity of retained particles, but also upon the time of operation. At a time,
two filters are in operation and two are on regeneration. Back washing water collected in back-washing pit
is sent to clarifier after mud settling, to reduce water losses. Filter water is stored in storage tank 09 (T-
920) having capacity 600 m3/hrs.
Demin Lines
The purpose of the Demin lines is:
• To remove permanent hardness producing ions from the filtered water
• To remove dissolved carbon dioxide
Raw water contains many minerals in varying concentrations. When minerals dissolve in water they form electrically
charged particles called ions. These are cations (positively charged ions) and anions (negatively charged ions) present
in relatively low concentrations and permit the water to conduct electricity. They are sometimes referred to
electrolytes. These ionic impurities can led to problems in cooling and heating systems, steam generation and
manufacturing.

17
Therefore, their removal is necessary. Certain natural and synthetic materials (called ion exchange resins) have the
ability to remove mineral ions from water in exchange for others.
These resins are usually small beads that compose a bed several feet deep through which the water is passed. Ion
exchange resin is an insoluble polymeric matrix containing labile ions capable of exchanging with ions in the
surrounding medium.
MINERAL IONS IN WATER
Cations Anions Other
Aluminum
Barium
Calcium
Magnesium
Potassium
Sodium
Bicarbonate
Chloride
Sulfate
Nitrite
Silica
Carbon dioxide
Demin Line (Area 09)

18
Demin lines (de-mineralization section) comprise of two trains of ion exchangers, each with a capacity of
130 m3/hr and consist of strong cationic exchanger, weak anionic exchanger and a strong anionic exchanger.
Both trains have a common forced draft degasifier (filled with rushing rings) for decarbonation of
decationized water.
Filtered water stored in tank (T-920) is fed by the pump P-925 A/B/C to the cation exchangers V-940 A/B
and percolating on the resin bed, exchanges ions like calcium, magnesium, sodium, potassium with
hydrogen ion.
Water is stored in T-940 along with steam condensate, de-oiled by activated carbon filters V-980 A/B/C.
De-ionized water is fed by pumps P-941 A/B/C to mixed beds V-9444 A/B/C, where final polishing is
performed. Water leaving the mix bed is stored in de-mineralized water tanks T-901. Regeneration of
vessels is done by 2 % and 4 % of sulfuric acid (strong cationic resin), 4 % sodium hydroxide solution
(strong and weak anionic resins).
Water treatment plant has been designed mainly for tube well water and keeping in consideration the canal
water. Regeneration of cation exchanger in counter current according to econex system is definitely needed
because tube well water has sodium content as high as 85%. To avoid any movement in resin bed during
counter current phase, the resin is held fixed by filling the free space above the resin with polyethylene
beads. This material is called ECONEX and is completely inert from chemical point of view.

19
Cooling Tower System (Area 08)
The cooling tower is one of the most important device in chemical industries for example when the hot
water come from heat exchanger we use the cooling tower to cool it. The purpose of cooling tower is to
cool relatively warm water by contacting with unsaturated air. The evaporation of water mainly provides
cooling.
Types of Cooling Towers:
• Mechanical draft cooling tower.
• Atmospheric cooling tower.
• Hybrid draft cooling tower.
• Air flow-characterized cooling tower.
• Construction-characterized cooling tower.
• Shape characterized cooling tower.
• Cooling tower based on method of heat transfer.
Categorization by air-to-water flow
• Crossflow
• Counterflow
Crossflow:
In the counter flow induced draft design, hot water enters at the top, while the air is introduced
at the bottom and exits at the top. Both forced and induced draft fans are used.
Advantages:
• Low pumping head, thus lower operational cost.
• Accepts variations in water flow without changing the distribution system
• Easy maintenance access to vital parts.
• Reduced drift loss due to the absence of water droplets.
• Lower in noise due to absence of water noise.
Disadvantages:
• Larger foot print of the tower.
• Large air inlet surface makes icing difficult to control.
• Tendency of uneven air distribution through the infill due to the large
inlet surface.

20
Counterflow:
In cross flow induced draft towers, the water enters at the top and passes over the fill. The
air, however, is introduced at the side either on one side (single-flow tower) or opposite sides
(double-flow tower). An induced draft fan draws the air across the wetted fill and expels it through
the top of the structure.
Advantages:
• The coldest water comes in contact with the driest air maximizing
tower performance.
• Smaller foot print of the tower
• Smaller tower height due to compact infill.
• More efficient air/water contact due to droplet distribution.
Disadvantages:
• Noise production due to spraying and falling water.
• Direct sunlight in the tower basin might trigger algae growth.
• Water distribution system might clog due to water borne debris.
• Uneasy maintenance of water distribution system.
• Drift loss due to droplet distribution system.
• Icing of the air inlet louvers in winter time.
Components of Cooling Tower:
• Cooling tower packing
• Drift separators
• Gear and fans
• Water distribution system
• Air inlet louvers
• Other cooling tower parts
Corrosion reducing chemicals:
• Phosphate and ortho-phosphate
• Calcium Carbonate
• Organic Phosphate
• Corrosion Inhibitor
• Bio-Dispersant

21
The tower is splash-type cross flow and induced air cooling. It consists of 8 cells separated by gates with a
common water collection basin. Each cell comprises of six louvers and space between the consecutive
louvers is filled with 12 layers of poly propylene filling. A cell comprises of three portions with a fan on the
top. The fan is located at the center of the cell and is motor driven. Inside the two portions of cell special
type polypropylene assemblies are placed. These assemblies are called drift eliminators. There are five
pumps for cooling water circulation.
• 1 is motor driven.
• 4 are Turbo (Turbine) driven.
The turbines for pumps are condensing turbines. The exhaust steam from all the turbines is condensed in
a condenser equipped with vacuum system. Another tower with 2 cells was later constructed to improve
the performance of cooling tower.
Hot water at 42°C from unit returning to cooling towers in enters hot water channel of cooling towers at
31,000 m3
/hr flow rate and rises up through risers located in the center of each of the 10 cells. Water is
distributed to 2 pits and each having 240 nozzles through which water is showered into the cells, by gravity.
The water falling down strikes the polypropylene packing that increases the water surface area in contact
with water and residence time, resulting in efficient cooling. Evaporation causes cooling and cooled water
is collected in 6900 m3
basin, from where it returns to exchanger for heat duty.
COOLING TOWER DESIGN DATA
Type Induced Draft / Cross Flow
Flow rate 31000 m3/h
Basin capacity 6900 m3
Number of cells 8 + 2
Ambient air temperature 25°C
Cold water inlet temperature 43 °C
Cold water outlet
temperature
32°C
Wet bulb 28°C
Dry bulb 47.8°C
Heat load 341 G cal/h
Air relative humidity 80%
Make up 803 m3/h
Blow down 158 m3/h
Drift losses 0.1 % (31 m3/h)
Evaporative losses 2 % (614 m3/h)
Drift eliminator Polypropylene
Packing Splash type
Nozzle Static / Turbo

22
Water is the most common and nearly universal solvent known. Solvent property varies widely and is the property
that causes problems for operators. Water evaporation increases the TDS content of what is left behind ready to scale.
In order to keep the quantity of salts like calcium, magnesium, sulfates or silicates minimum, a portion of
concentrated water is removed and make-up water is added. Removal of concentrated water is called Blow Down.
There are two types of blow down: continuous and batch. Continuous blow down removes the sludge produced in the
water basin to waste disposal (Area 16). While batch blow down is me to time manually to get the samples for the
laboratory tests.
Corrosion is controlled through addition of corrosion inhibitors; zinc, phosphates, polyphosphates, ortho-
phosphates etc. Water in cooling tower is also treated and filtered to remove impurities, to maintain the
pH level, to avoid rusting, and corrosion and biological microorganisms. Several chemical like Zinc
Phosphate (corrosion inhibitor), sulfuric acid (maintains pH) etc. are dozed to keep water quality constant.
A slime measuring unit is also employed to measure the quantity of slime (waste of micro-organisms) in
water.

23
Instrument Air Compression (Area 10)
The term “Instrument Air” refers to an extremely clean supply of compressed air that is free from
contaminates such as moisture & particulates. A system may utilize instrument air for various types of
pneumatic equipment, valves & electrical controls. The area is of extreme importance because in case of its
failure, plant might lead to shut down.
The major parts of an instrument air supply system are:
• Electric Motor
• Compressor
• Inlet Air Filter (Pre-Filter)
• After Cooler
• Moisture Separator
• Condensate Trap
• Air Receiver
• Safety Relief Valve
• Pressure Gauge
• Oil Remover
• Dryers
• Air Distribution System
Inlet Air Filter (Pre-Filter)
Air inlet of air compressor is connected to the pre-filter. Pre-filter is used to filter out dirt particles from
entering airline and connected instruments. The Pre-filter are effective solid particle filters, which
removes solid particles down to microns from inlet air to compressor.
Compressor:
Air from process gas compressor in area 04 K-421, at a pressure of 8.5 kg/cm2
is fed to ammonia receiver
tank, during normal running of ammonia compression section. However, the Area has two stages,
double acting, non-lubricating, Y-shaped, motor driven two stand-by compressor MK-1001/2. The
compressor takes air from atmosphere in its first stage amd discharges at the pressure of 1kg/cm2.
Compression heats the air to 160°C, which is than cooled to 45°C in inter cooler before feeding to the
second stage of compression. The second stage discharges at 8 kg/cm2
and 175°C. Compressed air is
then passed through a damping vessel V-1003/4, fitted with baffles to remove any condensate.
Cooler:
Air is then passed through an after cooler E-1002B/3B, where it is cooled down to 50°C. Downstream
of after cooler is fitted with cyclone separator to remove the condensate water produced as a result of
cooling. Cooling is automatically operated through SDV, while the pressure is controlled by PCVs.

24
Drying Section:
In the industry we use both types of regenerative Desiccant Air Dryers
Desiccant Air Dryers
They adsorb moisture from the air stream and onto a desiccant material in a reversible process. They
produce low dew points, so they are a good choice in subfreezing conditions or when processes require
extremely dry air.
Types of desiccant used in Desiccant air dryers are:
1. Activated Alumina
2. Silica Gel
3. Molecular Sieve
Purpose of Desiccants:
The process of adsorption begins as the water vapor,
which is more highly concentrated in the compressed
air stream, moves into an area of lower water vapor
concentration in the pores of the desiccant. Once inside the pores, a natural attraction of the vapor
molecules to the solid surface of the desiccant causes water vapor molecules to build up on the surface of
the desiccant.
Types of Desiccant air dryers
• Heated Desiccant air dryers
• Heatless Desiccant air dryers
The compressed air from V-1001 is sent to air drying section through a cooler E-1001 and condensate
separator V-1002. The air cools down to 37°C while passing through the final cooler E-1001 and condensate
is separated in V-1002. The compressed air is then fed to air dryers MD-1001 A/B (one in service and other
on regeneration), where in moisture is absorbed in activated alumina.
Air Filtration:
Dried air is finally passed through air filters ME-1001 A/B, where sub-micron particles are removed from
air.
Air Distribution System:
Transporting the compressed air without losing pressure, quality and quantity of air. Thus, distribution
has direct impact on the performance of the compressors. So there should be no pressure lose during
distribution.

25
Natural Gas Station (Area 15)
The purpose of natural gas station is to supply natural gas after filtration to meet the demands:
• Process gas
• Fuel gas
• Township supply
There are two lines that are being used for the purpose of transport of Methane.
• Old Pipe-Line
• New Pipe-Line
Old Line:
This is 16-inch line which is used to supply 2.5kg/cm2
of methane to FFC township. It has a low
pressure as compared to the new line. Initially when we didn’t have new line this line was used for both
purposes to supply township and plant as well and now after installing the new line this only used for
township (household) purposes.
New Line:
It is also 16-inch line that are being used to supply compressed high-pressure Methane to the
Plant. FFC have applied the compressor at the place of origin of gas so that they can increase the pressure
of gas and can fulfil the plant requirements.
Natural gas is drawing from the Mari Gas Field through 16’’ diameter header. Distance between plant and
Mari Gas field is about 20km. Pressure of this natural gas is about 31.5 kg/cm2
. Gas is passed through the
two gas filters ME-1501 A/B (one in service, other in standby), which allow on less than 5 microns size
particles to pass through them. Gas circulates centrifugally due to which velocity increases and heavy
particles and mainly liquids are settled down. The condensate consists of Iron, Manganese and Chlorides.
Each filter consists of 18 elements as filter media. Process gas is then fed to steam reformer F-201 at 46
kg/cm2
. Fuel gas to boilers and furnaces is supplied at 5.6 - 6 kg/cm2
. Natural gas to township is supplies
at 2.5 kg/cm2
after adding odorizing agent tetra thiophene (THT) to it.

26
Steam Generation (Area 06)
This area further divided into 4 different sections:
• De-aerator (V-603)
• BFW pumps (P-601 A/B/C)
• 02 Auxiliary Boiler
• 01 Heat recovery steam generator
De-aerator (V-603):
A deaerator is a device that removes oxygen and other dissolved gases from water, such as
feedwater for steam-generating boilers. Dissolved oxygen in feedwater will cause serious corrosion damage
in a boiler by attaching to the walls of metal piping and other equipment and forming oxides (rust).
Dissolved carbon dioxide combines with water to form
carbonic acid that causes further corrosion. Most deaerators
are designed to remove oxygen down to levels of 7 ppb by
weight (0.005 cm³/L) or less, as well as essentially eliminating
carbon dioxide.
There are two types of separations done in De-aerator:
• Mechanical (Steam) Method
• Chemical Method
In mechanical method we just provide the heat using steam to rise the temperature of feed water up-to
saturation point without reducing the pressure the purpose of this to evacuate the dissolved gases from the
deaerator almost 75-80% separation done in this section after that BFW forward to the chemical dosing
tank where we add chemicals to remove dissolved gases from the BFW. In this plant initially, we use
Hydrazine but the consequences of this chemical is very harmful for workers but now we have alternate
for this now we use Eliminox which have higher efficiency and no harmful effect using these chemicals we
remove 94-96% dissolved gases from BFW remaining quantity of gases is bearable.
De-Aerator Specifications
Name of Manufacturer ROSSETTI
Type of de-aerator Pressurized
Design water flow 480m3
/cm2
Accumulator Capacity 118m3
Design pressure 4.5kg/cm2
Number of nozzles 16
Vent rate 998kg/hr
Feed Water Temperature 110-120o
C

27
Types of De-aerator:
1. Spray Type Deaerator
2. Tray Type Deaerator
BFW Pumps (P-601 A/B/C)
Number of Pumps 3
Name of Manufacturer Halberg
Type of Pumps Centrifugal
RPM 2980
Rated/Maximum Capacity 310 m3/hr
Design Temperature 118 °C
Discharge pressure 146.7 kg/cm2
Prime mover (2) Turbine (2500 HP) + (1) Motor
(2000 KW)
The purpose of these pumps to provide the DM pre-heated water to boilers where boilers produce steam.
Boilers:
Boilers are basically used to produce the steam to run the generators and further generators produce
electricity to run the plant. In FFC MM we use Auxiliary Water Tubes Boilers to produce steam. There are
four types of steam produced in our plant.
Sr# Types Properties Areas
1 KS Temperature: 510o
C
Pressure: 105 kg/m2
Utility section (Area 06)
2 HS Temperature: 380o
C
Pressure: 38 kg/m2
Letdown station (Area 06)
3 LS Temperature: 150 – 200o
C
Pressure: 3.5 kg/m2
Area 06
4 MS Temperature:
Pressure:
Urea Plant

28
Types of Boilers:
➢ According to the Contents in the Tubes The major sections of boiler are following as:
1. Fire Tube Boiler
2. Water Tube Boiler
➢ According to the Number of Tubes:
1. Single Tube Boiler
2. Multitube Boiler
➢ According to the Position of the Furnace:
1. Internally Fired Boiler
2. Externally Fired Boiler
➢ According to the Axis of the Shell:
1. Vertical Boiler
2. Horizontal Boiler
➢ According to the Methods of Circulation of Water and Steam
1. Natural Circulation Boiler
2. Forced Circulation Boiler
➢ According to the use:
1. Stationary Boiler
2. Mobile Boiler
The major sections of Auxiliary boiler are following as:
• Steam Drum
• De superheating Zone
• Superheating Zone
• Combustion Zone
Steam Drum:
The steam drum is cylindrical with two flat plates of equal thickness. Because of the internal
pressure, the flat plates are mutually connected by vertical solid stays. The steam drum is furnished
with the necessary internal fittings to ensure an even distribution of the feed water, of the
circulation water from the exhaust boiler and to ensure enough dryness of steam.
BFW entered the boiler has some specification like the pressure of it about 150kg/cm2
, the
temperature is 110 – 120o
C and the flow rate about 300m3
/hr.
The temperature of water in the drum is 325 – 350o
C it also helpful for the boiler because it increases
the efficiency of the boiler so less heat required to generate the super-heated steam.

29
Combustion Zone:
Natural Gas, Synthesis Gas, Purge Gas are use for burning to take combustion process complete and
there are four burners in each boiler two having purge gas as a fuel and other two use natural gas
as fuel source. As we know for the combustion three elements required.
Pre-Heated air provide to boiler to make air fuel mixture and the
main purpose of pre-heated air to increase the efficiency of boiler.
The fuel gas methane also pre-heated and initial ignition produced
by the burners. Compressed air provide to boilers has capacity
110 ton/hr.
Air to Fuel Ratio = 1 : 9
De-Superheated Zone:
The primary function of a desuperheater is to lower the temperature of superheated steam or other
vapors. This temperature reduction is accomplished because of the process vapor being brought
into direct contact with another liquid such as water. The injected water is then evaporated.
Super-Heating Zone:
The combustion zone is the most important part of a boiler. Its primary function is to
provide adequate space for fuel particles to burn completely and to cool the flue gas to a
temperature at which the convective heating surfaces can be operated safely.
There are three super-heaters installed in series that increase the temperature up to 510o
C.
Fire Triangle
Heat
Source
Fuel
Air

30
Power Generation (Area 07)
FFC has capacity to produce 32.5MW power that easily meet the consumption of plant and
township as well. There are three power generation sources in FFC MM.
1. Turbo Generators (TG-701 A/B)
2. Gas Turbine (GT-703)
3. Emergency Diesel Generator (EDG)
Turbo-Generator:
A turbo generator is the combination of a turbine directly connected to an electric generator for
the generation of electric power. Large steam-powered turbo generators provide the majority of
the world's electricity and are also used by steam-powered turbo-electric ships.
Turbines are also divided by their principle of operation and can be:
1. Impulse Turbine
2. Reaction Turbine
3. Gravity Turbine
Turbo Generators (TG) are the turbine driven for the production of electricity. There are the major source
of electricity for all the plant having a capacity of 16 Mega Watts (2 generators each has capacity 8 Mega
Watts). TG have 15 stages turbine in first stage is impulsive and the other 14 are reaction stages and from
the 14 reaction stages 8 are High pressure and 6 are Low pressure stages.
The impellers are connected on a single shaft. The KS Saturated steam at 105 kg/cm2
Pressure and 510°C
temperature is injected in the turbine impeller chamber on the first stage. The steam apply force on the
impellers and get its velocity lower. The velocity head is converted into pressure head on having large area.
Again, the steam enters to the next impeller via nozzles. The pressure head is converted into velocity head
and this mechanism continue till the discharge of the steam from the turbine. Then exit stream is
condensed and send to boiler for reuse.
The turbine is connected with gear box that reduce the rotating speed from 11,478 RPM to 1500 RPM
because the generator design for this limit. So, a gear box in installed to reduce the RPM and the gear ratio
is 7.65. These are just like a control valve that controls the steam quantity depending upon the load of
generator.
The Critical Speed of Generator about 7400 RPM.
Critical Speed:
Critical speed of the turbine is the rotor speed at which natural frequency of the assembled
rotor (rotor shaft with discs, blades, shrouding strips etc. in assembled condition) becomes equal
to the operating speed. This is usually a expressed as a range (critical speed range). There are

31
multiple critical speeds. However, the operating speed of the turbine may be above or below the
first / lowest critical speed. Accordingly, it is called as a flexible or a rigid rotor.
In TG we use Artificial Magnet (electric magnets) are mounted on a shaft and are connected to the electric
power supply (DC). When the electricity is switched on, the electric magnets create powerful magnetic
fields. This magnet made of special kind of steel. Coils of wire are mounted around the shaft. As the shaft
with the magnets rotates, the coils of wire are exposed to changing magnetic fields, and an electric current
is generated in the wires (The process of generating a magnetic field by means of an electric current is
called excitation).
When 1 million lines of electromagnetic force lines cuts than it produces 1 volt. There are carbon graphite
slip rings that allows the transmission of power and electrical signals from a stationary to a rotating
structure. A slip ring can be used in any electromechanical system that requires rotation while transmitting
power or signals. It can improve mechanical performance, simplify system operation and eliminate
damage-prone wires dangling from movable joints.
Main Generator parameters
Voltages 6.3kV
Current Produces 916A
Phases 3 (120o
phase difference applied)
Frequency 50Hz
Emergency Diesel Generator (EDG):
EDG ME-702 is a V-shaped four stroke; single acting engines
with 16 cylinders arranged eight on each side of V-shape. It works on diesel cycle, coupled with electric
generator that make the initial rotations and the self combustion of Diesel Engine start at 70RPM. Full
load consumption is 400L/hr and no gear box required to control rotation. Output provided by EDG is
6.3kV and current produced is 174A.
EDG Parameters
Number of generators 1
Name of Manufacturer SACM + UNILIC
Type of Engine 16 Cylinder V shape
Rated/Maximum Capacity 1500 KW
RPM 1000
Fuel Diesel
Fuel consumption (full load) 400 Liters/hr
Starting system Compressed air
Dependency Independent Unit

32
Gas Turbine:
The gas turbine is the engine at the heart of the power plant that produces electric
current. A gas turbine is a combustion engine that can convert natural gas or other liquid fuels to
mechanical energy. This energy then drives a generator that produces electrical energy.
Initially we have just two turbo generators but when the time goes on and production increases
the more energy required so for the major and more efficient source of energy we get Gas Turbine.
This GT-703, 14 axial stages these are the mixture of impulse and reaction turbines and first 6
stages are impulsive and the 8 are reaction turbines. Natural gas use as fuel gas and the minimum
pressure that we introduced in the turbine has pressure 20bar. The GT has maximum capacity
about 15MW and produce 11200RPM which is further attached to reduction gear box the reduce
it rotations up to 1500RPM. After combustion the outlet temperature of gases leaving from the
GT has temperature about 585o
C so, it is very large amount of heat loss so to reduces these heat
losses we HRSG system to utilize this massive amount of heat.
Air and fuel required for consumption is about 1.5Nmc air for 6000Nmc methane gas.
GT-703 Parameters
Name of Manufacturer Turbo Mach
Type Annular
Rated/Maximum Capacity 15MW
Turbine stages 3
Compressor stages 14
Min gas pressure 20bar
Number of fuel nozzles 21
Fuel Natural Gas
RPM 11200
Gear ratio 7.46
Generator Capacity 13.6MW
Efficiency 33%
Air to fuel ratio 25

33
Waste Water Disposal (Area 16)
The section ensures that the effluent disposal from plant is within safety limits and regulations
set by EPA or NEQS. Waste water is disposed to two places:
• Masuwah Canal; when parameters are in permissible range
• Evaporation ponds; when parameter are out from the set values
Effluents from various plants are in general collected in a common pit and treated before disposal into
Masuwah canal. The effluents of major concern are from ammonia, urea and water treatment plants. The
effluents from boilers, carbon dioxide, and absorption unit are mostly diluents.
Waste water from all plant sites at a flow rate of 250 – 300 m3/h is collected in pit A, where it is neutralized
with sulfuric acid. The dosing of sulfuric acid is controlled by the pH transmitter controller. It controls the
pH between 6.5 -8.5. A stirrer in the pit helps the neutralization reaction. The neutralized water overflows
in the next pit B. Water from the settling ponds (if any) also mixes up with neutralized water in pit B. Waste
water is pumped to canal by means of P-1603-A/B. In case of effluent not being within the permissible range,
waste is directed to the evaporation pond, to save canal from polluting.
Waste water is sampled at an interval of every 4 hour for lab testing to verify the chemical dosage for
neutralization.

34
Ammonia Unit

35
Ammonia is one of the most highly produced inorganic chemicals. There are numerous large-scale
ammonia production plants worldwide, producing a total of 144 million tons of nitrogen (equivalent to 175
million tons of ammonia) in 2016.
The core purpose of ammonia unit is to provide the raw materials for urea unit. They are:
• Liquid ammonia at – 4 °C
• Carbon dioxide gas (by-product)
For producing these urea raw materials, unit needs a mixture of hydrogen and nitrogen gas in ration 3:1. A
limited degree of inert gases like argon and methane are also present. Source for hydrogen are generally
hydrocarbons in the form of natural gas. The source for nitrogen is atmospheric air, both cheap and
abundantly available. The following processes take place in different sections of unit:
➢ Desulfurization section; removes sulfur content of natural gas
➢ Reforming section
1. Primary reformer; cracks natural gas to give hydrogen
2. Secondary reformer; eliminates oxygen from air leaving nitrogen
➢ Gas purification section
1. Shift Conversion; converts carbon monoxide to carbon dioxide
2. Carbon dioxide Removal; separates carbon dioxide by absorption in Benfield sol.
3. Methanation; convert residual carbon dioxide to methane convert
➢ Ammonia synthesis section; hydrogen and nitrogen react to give ammonia
➢ Cooling and Storage; product is compressed, cooled and stored

36
Area 02
Desulfurization Section:
The section removes the sulfur compounds from the natural gas feedstock to avoid poisoning of
catalyst in primary reformer (F-201) and Low Temperature Carbon Monoxide Shift (R-205). The
desulphurization section has been designed to reduce to about 0.1ppm Sulphur by volume. The max
permissible Sulphur concentration at reformer inlet is 0.5 ppm and it should preferably be lower (0.2 ppm).
Sulphur absorption takes place in the two vessels R-201A & R-201B, containing each 21m3
of HTZ-5 catalyst
(Zinc oxide in two equal beds of 2.15 m each). The normal operating temperature is 350 – 400oC, but also
at low temperatures the catalyst will react with H2S.
The key reaction is:
ZnO + H2S ZnS + H2O (i)
Natural gas coming from Maripur gas field through Natural Gas Station (Area 15) has compositions
(Molecular Mass 20.91):
NATURAL GAS COMPOSITION
H2 0.1 %
N2 19.5 %
CO2 9 %
CH4 71 %
C2H6 0.2 %
Natural gas at a flow rate of 36472 Nm3/h at 30 kg/cm2 and at 38°C is
compressed in natural gas compressor K-411 to 40 kg/cm2 and 72°C
and mixed with a recycled synthesis (short: syn) gas stream and the
mixture is then pre-heated to 310°C in process gas pre-heater E-204 B
and then to 400°C in process gas pre-heater E-204 A (both in
convection zone of primary reformer). Despite the fact that key
reaction of conversion of inorganic sulfur to zinc sulfide is possible at
ambient temperature conditions, stream is pre heated to:
• Convert organic sulfur to inorganic sulfur (350°C)
• Promote reaction of absorption bed with carbonyl sulfide (310°C)
ZnO + COS ZnS + CO2 (ii)
• Enable reaction of sulfides and disulfides with sulfur absorption catalyst (330°C – 440°C)
• Increase the absorption capacity of catalyst (350°C)

37
SYN GAS RECYCLE COMPOSITION
H2 74.4 %
N2 24.74 %
Ar 0.23 %
CH4 0.92 %
The endothermic reaction reduces the sulfur content according to the following rate of reaction:
KI = 2.5 x 10-6
at 380°C KII = 4 x 10-9
at 380°C
The rate of reaction increases with increase in temperature:
KI = 4 x 100
at 400°C KII = 7 x 10-9
at 400°C
Fresh or sulfide catalyst neither reacts with hydrogen nor oxygen at any practical temperature. HTZ-3 has
several advantages in comparison with other sulfur absorbents like activated iron mass. The absorption
capacity (expressed in weight of sulfur absorbed per volume of absorbent) is more than twice as high for
HTZ-3 as far iron oxide. Methanation of gas containing carbon mono or dioxides will not occur using zinc
oxide catalyst. The catalyst does not become pyrophoric during operation and therefore its disposal
presents no problems. The operation temperature could vary from ambient to 50 kg/cm2 (700psig) or
even higher. The normal operating temperature ranges from 350°C to 400°C. Absorption capacity of
catalyst is 39 kg sulfur per 100 kg of catalyst or 545 kg of sulfur per cubic meter or reactor volume.
Reforming Section
The section produces synthesis gas containing necessary compounds (hydrogen and nitrogen in
ratio 3:1) for ammonia synthesis by catalytic steam reforming of natural gas and addition of atmospheric
air to give nitrogen content to mixture.
The reaction between hydrocarbons and steam is one capable of producing a wide range of gases depending
upon the operating conditions. The reactions common ones can be represented.
Reaction (1) Absorbs a great amount of heat but reaction (2) is slightly exothermic, i.e. it gives out heat.
Ideally these reactions would go to completion to give the overall reaction:
The reaction starts at 500o
C temperature for higher hydrocarbons and for methane it starts at 600o
C. The
reaction take place in two steps in the two reformers, basically raw material hydrogen and nitrogen
produced in these reformers. In primary reformer hydrogen produce and in secondary reformer nitrogen

38
produce, these reactions take place in the presence of catalyst. From experimentation it has been found
that metallic nickel is the best catalyst. The catalyst RKS-1 contains about 17% nickel-oxide.
The filling density of RKS catalyst depends on the diameter of the reactor and on the catalyst particle size:
• For primary reformer with 4" I.D. tubes:
• Filling density or bulk density = 1.06 kg/l (66 lbs/ft3)
• Using catalyst particle size: 16.6.5 X 16mm
PRIMARY REFORMER:
Basically, primary reformer is the furnace where we produce heat energy in very huge
amount. In FFC MM we have Induced draft furnace. As we know large amount of heat of heat energy
produced so we can’t waste this huge amount of energy. So, we use this energy for different processes like
steam generation, pre-heating etc.
Activation of Catalyst:
There is 31.8m3
catalyst used in reforming section in the form of rings and
this catalyst must be activated at the startup of the plant, done by reduction at a temperature
between 600o
C and 800o
C, depending on the reducing medium (for methane 860o
C required and
for hydrogen 600o
C required). Excess amount of steaming of very high temperature should be avoid
because it may over heat the catalyst and pressure should kept below the 5kg/cm2
. As for our
requirement temperature should be below than 700o
C and greater than 350o
C because the
temperature below than 350o
C steam may condense and liquid water formed which harm the
catalyst.
The catalyst regenerated by oxidation reaction, Full oxidation of the catalyst is expected after a
continuous flow of steam for 5 hours at a temperature of 600°C after use of 5~15 kg Steam/kg
Catalyst.
Primary reformer Specifications
Number of tubes 288
Number of burners 648
Catalyst 31.8m3
RKS catalyst (TOPSOE) ceramic
rings.
16/16.5 mm by 16 mm high.
Catalyst Improver RKG-2

39
FURNACE DETAILS:
It consists of two identical radiant-box chambers placed side by side in a
duplex arrangement functioning as one unit. The tubes are heated by 324 burners in each radiation
chamber, arranged in 6 horizontal rows with 27 burners in each along the length of catalyst tubes
on both sides. Flue gases flow upwards with a common flue gas collector between the two
radiation chambers, the draft being maintained by an induced draft fan mounted at the end of the
flue gas heat recovery section and connected to the stack. Natural gas is used as fuel and the flue
gases leaving radiation chamber are at about 1000 °C.
Furnace Specifications
Type of Furnace Induced Draft Fan
Number of Tubes 144 each
Number of Burners 324 each
Catalyst Tubes
Length Approx. 11m
Internal Dia 122mm
Outer Dia 150.4mm
FLUE GAS HEAT RECOVERY SECTION:
It consists of L Shaped section with a vertical and a horizontal leg with,
different duty coils in each leg. In the vertical section, sensible heat of flue gases is utilized for pre-
heating of 4 coils, respectively from the top, natural gas/steam, process air, KS steam super heating
and natural gas heating.
Then the flue gases from the auxiliary steam super-heater F-202 area also introduced in the main
horizontal flue gas heat recovery section. The heat contents of the mixed flue-gas are then utilized
for respectively, KS-steam production, for preheating of natural gas and finally for preheating
boiler feed water.

40
SPECIFICATIONS OF COILS IN FLUE GAS HEAT:
On the Basis of working only
E-201 Process gas and Steam Pre-
Heater
E-202 Process Air Pre-Heater
E-203 KS-Steam Super-Heater
E-204A Process Gas Pre-Heater
E-204B Process Gas Pre-Heater
E-205 KS-Steam Production
E-206 BFW
E-207 DMW

41
SECONDARY REFORMING:
The purpose of secondary reforming in reactor R-203 is primarily to feed
stoichiometrically process air to have 3:1 Hydrogen to Nitrogen ratio, and secondly; maximum
efficiency of the overall reforming operation requires that as much reforming as possible be done
in this partial combustion step also reducing the inerts in the synthesis loop to the desired
minimum level.
The methane feed in the primary reforming section didn’t use completely so the remaining
amount of methane that leaving the reforming section further utilize for combustion process in
the secondary reformer (about 7.03% CH4 remaining). The pressure of natural gas also reduces to
30-33kg/cm2
so for proper mixing and complete combustion same pressure air introduce in the
secondary reformer. No burner required in this reforming section and combustion produce by
using amount of energy carried by flue gases leaving the primary reforming section.
There are three points that we talk about when it comes to ignition of substances and they are as
follows:
1. Flash Point: - The flash point is the minimum temperature at which fuel favour is
momentarily ignited in air by an external ignition source. However, this will not necessarily
sustain combustion and produce a fire.
2. Flame or Fire point: - The flame or fire point is the minimum temperature at which enough
vapor is produced to allow continued combustion. This is usually a few degrees higher than
the flash point
3. Spontaneous Ignition Point: - The spontaneous ignition point, also known as the auto-
ignition point, is the lowest temperature at which a substance will ignite without any
external ignition source.
The reaction mixture will contact the catalyst an about 1100 – 1200 °C. In the temperature range
of 1100 to 1350 °C, some catalyst activity will be lost during the first period of time (will be only
significant if the catalyst is operated at a lower temperature later). When the catalyst has been
operated for some time at high temperatures, the further activity decrease will be very slow. In the
temperature range of 1400 – 1500 °C, the catalyst begins to sinter. 35m3
of RKS-2 catalyst use in
the form of rings in secondary reformer.
GAS COMPOSITION (MOL%) LEAVING REFORMING
SECTION
H2 55.93
N2 22.15
CO 12.40
CO2 9.02

42
Ar 0.20
CH4 0.30
Gas from secondary reformer is cooled in a waste heat boiler E-208, to 380°C. As the stream contains
considerable amount of carbon mono and dioxides, there is a probability of carbon formation, when the
gas is cooled.
2CO → CO2 + C (soot)

43
Gas Purification Section (Area 03)
The section prepares a syn gas containing hydrogen and nitrogen in ratio of 3:1 by purification.
Only inert gases like methane and argon are permissible in lowest possible concentrations. Carbon
monoxide is converted in two shift convertors R-204 and R-205 according to the following reaction
to reduce the concentration to (0.4 % on dry basis).
CO + H2O ↔ CO2 + H2 + (heat)
Reaction increases the hydrogen yield with formation of carbon dioxide which is more easily
removable. After cooling of gas and condensation of water content, carbon dioxide is removed up
to 0.1 %, which is then converted to methane methanator R-311, at the cost of expensive hydrogen.
CO + 3H2 ↔ CH4 + H2O + (heat)
CO2 + 4H2 ↔ CH4 + 2H2O + (heat)
Shift Conversion:
Shift conversion of carbon monoxide to carbon dioxide is an equilibrium reaction with
low temperature and more water supporting the forward move. However, higher temperature will give a
higher reaction rate. More water can apparently give a lower reaction rate due to bigger total volume giving
a shorter contact time. An optimum temperature is therefore needed to give the best conversion.
Conversion is performed in two steps:
• High temperature shift (HTS); to increase the rate of reaction
• Low temperature shift (LTS); to favor equilibrium conditions
It is the conversion of carbon mono-oxide by water gas shift reaction:
CO + H2O CO2 + H2 H = -9.84 KCal

44
HTS-Convertor (R-204):
In HTS we use SK-12 (Chromium promoted iron oxide Fe2O3) in the form of
cylindrical tablets. The catalyst is reduced in reformed gas (CO2, CO, H2, Steam), reducing
conditions are controlled such that Fe2O3 is reduced to Fe3O4, without possibility of further
reduction to metallic Fe.
Reactions:
3Fe2O3 + H2 2Fe3O4 + H2O
3Fe2O3 + CO 2Fe3O4 + CO2
Methane is not an inert for the catalyst and reduces it to be spoiled by carbon deposits. Catalyst is
therefore not exposed with reducing agents like hydrogen or carbon monoxide unless absolutely
cold. Catalyst is activated by reduction at 250°C with a mixture of hydrogen and carbon monoxide
after being preheated with steam (inert for catalyst).
The gas from HTS convertor is then cooled in trim heater E-205, HP waste boiler E-210
and BFW pre-heater E-211 to 220°C before being sent to LTS convertor.
GAS COMPOSITIONS AFTER HTS CONVERTOR R-204
H2 59.66
N2 20.28
CO 3.0
CO2 16.73
Ar 0.19
CH4 0.127
LT S – Convertor (R-205):
The purpose of LTS convertor is to reduce the carbon mono oxide content in the process gas after HTS
convertor from about 3 % to 0.38 %
CO + H2O CO2 + H2 + Heat
The reaction is the same as in HTS convertor, but because of low temperature and more active catalyst
much lower CO content in the exit gas are obtained.
The LTS convertor R-205 consists of specially prepared zinc and chromium oxides catalyst with much
higher activity and therefore is used at lower temperatures of 220°C – 240°C. Catalyst loses its activity if
temperature is higher than 250°C – 270°C. 85m3
of LSK catalyst is distributed on two beds each 2.8m high.
The gas leaves the vessel at 235°C and 29 kg/cm2
.

45
GAS COMPOSITIONS AFTER LTS CONVERTOR R-205
H2 50.54
N2 19.78
CO 0.08
CO2 18.75
Ar 0.18
CH4 0.27

46
AREA 03
CARBON DIOXIDE REMOVAL SECTION (BENFIELD SOLUTION)
CO2 Absorbents:
CO2 was once a waste gas and of little interest but today it is important as a raw
material for urea production, which now supplies about 30% of the world’s fertilizer nitrogen.
There are many absorbents used or were used for the absorption of CO2 gas.
• MEA
• Hot Potassium carbonate
• DEA
• Water
• Sulfinol
• mDEA process(commonly used in latest plants)
There are three processes use hot carbonate for absorption of CO2 gas.
1. Vetrocoke
2. Catacarb
3. Benfield
The difference is only the use of activator, catacarb uses borates and DEA, Vetrocoke uses more
efficient activator Arsenic trioxide and Benfield uses DEA only. Absorption of CO2 depends upon
• Partial pressure of CO2 in feed gas.
• Temperature of absorption system
• Pressure of absorption units.
• Degree of regeneration required.
• Quantity of heat required for regeneration.
At low pressure (about atmospheric) MEA is economical but as pressure is increased process like
K2CO3 is favored. Whereas MEA is expensive, requires more heat for regeneration, require more
solution flow and have higher cooling duties) Out of many. Nowadays hot carbonate is being used
widely as absorbent. At our plant Benfield process use about 30% K2CO3 and 2.5 % DEA.
Process Description:
The gas mixture containing about 18.7% CO2 at the temperature of 236°C and at a pressure
of 29 Kg/cm2 at the exit of R-205 (low temperature CO-shift converter) flows to the
absorption unit. At first flows through the tube side of E-301, (Lowpressure. steam boiler

47
for the generation of LP steam which is ultimately used for the regeneration of B / solution
as shown in figure below.
The gas is cooled up to its dew point 160°C. The condensate is removed in V-305 (Knockout
drum) to sewer. Then the gas flow through tube side of E-302 A/B (Horizontally placed re-
boilers) where gas heat is utilized for evaporation in regenerators the gas temperature
drops up to 125°C, after which the gas pressure through Demin water pre-heater E-304,
where gas is further cooled down up to 110°C. Then it enters from the bottom of absorber
tower C-302 at 27.7 kg/cm2
steel where absorption takes place in a counter current flow of
catalyzed hot potassium carbonate with carbon steel/ stainless steel reaching rings
according to the following reaction.
K2CO3 + CO2 + H2O → 2KHCO3 + Heat (Absorber)
The gas leaving from top of the absorber C-302 contains about 0.1 mole % of CO2 at the
temperature of 70°C. CO2 enriched solution leaves the bottom of the absorber at 120°C & 27.7 Kg
/cm2
pressure for regenerator, but the part of energy is recovered in the hydraulic turbine by
facilitating MP-301 a run at lower energy consumption. The XP-301A discharge pressure is ~ 11
Kg/cm2
.

48
ABSORBER SPECIFICATIONS
Internal Dia. of tower at Top 2.5m
Internal Dia. of tower at Bottom 3.5m
No. of beds 04
Bed height 7.7m
Operating temperature 150/110o
C
Operating Pressure 30/27.7kg/cm2
Pall ring size 50mm
Upper two beds volume 76m3
Lower two beds volume 148m3
Total tower volume 448m3
Benfield Solution Recovery:
The Benfield solution is flashed at the top of regenerator where CO2 strips out as a result
of pressure reduction, but remaining CO2 in solution is removed by the counter current
flow of stripping steam, which is directly supplied by E-301 and indirectly by E-302 AB.
2 KHCO3 → K2CO3 + CO2 + H2O (Stripper)
Stripper Specifications
Tag No. C-301 Mitsubishi
Internal Dia. of tower 4.5m
No. of beds 04
Bed height 7m
Operating temperature 160/119o
C
Operating Pressure 2.5/03kg/cm2
Pall ring size 50mm
Total packing volume 450m3
METHANATION:
The traces of carbon dioxide are poison to reactor catalyst and therefore are converted to methane
(inert) in methanator R-311. Methanation is just the reverse of reforming, supported by lower temperatures.
CO + 3H2 ↔ CH4 + H2O + (heat)
CO2 + 4H2 ↔ CH4 + 2H2O + (heat)

49
The reaction is based more upon the activity of catalyst rather than other parameters. Efficiency is
increased through higher temperature conditions but also reduces the life of the catalyst. The reactor
reduces the combined carbon mono and dioxides compositions to less than 10 ppm with a temperature
rise of 30°C. Methanator R-311 contains 30 m3
of PKR catalyst in the form of spheres in a single bed of 3.1m
height. The catalyst has approximately similar characteristics as reforming catalyst but great activity due
to reaction at lower operating temperatures.
Process gas stream from the top of the Benfield absorber C-302 passes through separator V-302 to remove
the traces of potash solution. Passing through the shell of gas-gas exchanger E-311 and trim heater E-205,
its temperature is increased to 320°C and fed to methanator R-311.
Methanated gas at 351°C is passed through the tubes of gas-gas exchanger E-311 and final gas cooler E-312,
it is fed to a separator V-311; from where it leaves for ammonia synthesis section at 39°C and 25 kg/cm2
.
GAS COMPOSITION AFTER METHANATOR R-311
H2 74.4 %
N2 24.74 %
Ar 0.23 %
CH4 0.92 %

50
AREA 05
AMMONIA SYNTHISIS AND REFRIGERATION SECTION
The ammonia synthesis takes place in the ammonia convertor R-501 with a catalyst bed,
according to the reaction:
3H2 + N2 ↔ 2NH3 + (heat)
This reaction is volume reduction and exothermic reaction and high pressure and low temperature favor
it. Huge amount of energy released during this reaction. The operating pressure of this unit about
260kg/cm2
and maximum pressure is 295kg/cm2
.
A furnace also installed just by the side of ammonia reactor the purpose of this furnace is just provide the
initial startup temperature to reactor when plant stat-up after shut down because ammonia production is
exothermic reaction so large amount of heat produced during this reaction but when plant just start and
reactor is at normal atmospheric temperature we need external amount of energy for suitable conditions
for ammonia production.
Process:
Synthesis gas after compression about 260kg/cm2
pressure is passed over iron catalyst at
temperature about 350-380o
C in an axial radial flow convertor a part of synthesis gas about 17% is
converted to ammonia in per cycle. The reaction effluent are cooled ammonia liquified and
separate the unreacted gas is recycled.
Main steps involved:
1. Synthesis gas compression and recycling of unreacted gas.
2. Synthesis loop cooling and purging.
3. Separation of ammonia and refrigeration.
4. Ammonia absorption section distillation section for ammonia recovery.
5. Ammonia storage.
Description:
After absorption chamber syn gas sent to compressor where its pressure increases from
29kg/cm2
to 250kg/cm2
. This Syn gas compressor consist of two turbines extraction and condensing fed
by 100kg//cm2
steam produced in ammonia plant.
The synthesis loop consists ammonia synthesis reactor R-501, re-circulating
compressors (integrated with synthesis gas compressor), BFW pre-heat; for cooling the syn gas
and Internship condensation and separation of ammonia. The synthesis loop is operated at 380°C
– 520°C and 270 kg/cm2, with promoted iron catalyst containing small amounts of non-reducible
oxides.
The convertor R-501 is a radial type convertor with the gas flowing through the three catalyst
beds in a radial direction. It contains a total of 33 m3
catalyst, distributed in three beds with bed height 5
m3
, 10 m3
and 18 m3
respectively. Catalyst size decreases downward in beds, increases the catalytic activity

51
of smaller particles. The catalyst is stable in air below 100 °C, while above 100°C it reacts and spontaneously
heat up.
The reactor is so designed to increase the temperature of an inlet gas through exchangers up
to 400°C, where it enters the first catalyst bed from bottom. As the gas passes through the catalyst bed, the
temperature is increased to a maximum temperature at the outlet from the first bed. The temperature here
is about 520°C, which is normally the highest in the convertor and is called “The Hot Spot”. The gas from
the first bed is quenched with cold gas to 400°C – 420°C before the second bed. After the second bed, the
outlet temperature is about 500°C.
Convertor effluent gas from the convertor exit at 325°C and 265 kg/cm2 is cooled to 195°C in
BFW pre-heater E-501 A/B, then in the hot heat exchanger E-502 to 79°C and in the water cooler E-503,
where condensation of ammonia starts. Further cooling and condensation takes place in the cold heat
exchanger E-504 to 25°C, in the first ammonia chiller E-505 to 11°C , and finally in the second ammonia
chiller to 0°C. The condensed ammonia is separated from the circulating syn gas in the ammonia separator
V-501. Make-up gas is introduced between the two chillers.
Ammonia liquid stream from ammonia separator V-501 goes to a let-down vessel V-502 to for
further removal of gaseous contents, from where it is further directed to ammonia spheres S-501 and S-502
or the Urea Unit.
AMMONIA COMPOSITIONS AFTER LET-DOWN VESSEL V-502
NH3 99.94 %
H2 0.015 %
N2 0.015 %
Ar 0.015 %
CH4 0.015 %

52
AREA 04
COMPRESSORS SECTION
In this area all compressors are held. There are total 5 compressors in which 2 Turbo Compressors
which generally use for Natural gas and 1 Air compressor, 2 Syn-Gas compressors and 1 is Ammonia
compressor.
K-211 is the natural gas compressor, TK-431 and TK-432 are Syn-gas compressors and TK-441 is the
ammonia compressor and the last TK-421 air compressor.
Air Compressor (TK-421):
Borsig centrifugal compressor driven by steam turbine is used to compress
the atmospheric air to the design conditions of reforming up-to a pressure of 38040kg/cm2
as processed air is used for combustion in secondary reformer.
This compressor has two casings. The first casing is Low Pressure (LP) has
three stages, each with two impellers arranged in such a manner that thrust of each stage
tend to cancel out. In the second casing High Pressure (HP), contains two stages each with
two impellers arranged back to back in such a manner to minimize the thrust force.
In the LP and HP casings there are inter cooler are installed between them.
The rotor of LP casing rotate at 7050 R.P.M and after filtration achieve 8.56kg/cm2
pressure
and after through intercoolers in HP casing the pressure reached about 37kg/cm2
. The
speed of HP casing rotor is about 16100 R.P.M after compression when it leaves the
temperature of the outlet steam is 157o
C.
BORSIG AIR COMPRESSOR SPECIFICATIONS
Low Pressure Casing
Medium Air
Suction Volume 49750m3
/hr
Suction Pressure 0.947 bar
Discharge Pressure 8.32 bar
Normal Speed 7050 R.P.M
Maximum Speed 7403 R.P.M
1st
Critical Speed 3010 R.P.M
2nd

53
High Pressure Casing
Medium Air
Suction Volume 4880 m3
/hr
Suction Pressure 8.22 bar
Discharge Pressure 36.775 bar
Speed 16100 R.P.M
1st
2nd
Ammonia Compressor (TK-441):

54
UREA

55
AREA 01
The unit manages the urea production from raw materials:
• Ammonia (liquid)
• Carbon dioxide (gas)
These raw materials are provided by the ammonia unit, are reacted to form ammonium
carbamate, which dehydrates to give urea. Urea synthesis is divided into following sections:
1. High pressure section
• Urea synthesis
• Stripping
• Carbamate recovery
2. Medium pressure/Low pressure section
• Ammonia recovery
• Carbon dioxide recovery
3. Vacuum section
• Urea concentration
• Prilling
4. Waste water treatment section
Optimum temperature conditions and retention time in process are extre3mely important
because high temperature and more residence time causes:
• High biuret content
• More energy input
• More water circulation
• Overloading of vacuum condensers and ejectors
• Pressure increase in system
• Reduced efficiency
These highly disturb the economics of the process and are always prevented.

56
High Pressure Section:
The purpose of the section is to synthesize urea from the reaction of liquid ammonia
and carbon dioxide in the urea reactor R-101 and to decompose the unconverted carbamate in the stripper
to carbon dioxide, ammonia and water, which are then condensed, absorbed and recycled back to the
reactor with the help of an ejector system.
Ammonia Receiving:
The liquid ammonia coming from plant at -4°C and 24 kg/cm2
, is collected in
ammonia receiver tank V-101 after pre-heating to nearby ambient temperature in the ammonia pre-heater
E-109. From V-101 it is fed through ammonia booster pump P-105 to the high pressure motor driven
ammonia pumps P-101 A/B/C. The three low speed, heavy duty reciprocating pumps boost the pressure to
260 kg/cm2
. Before entering the reactor, ammonia is used as a driving fluid in carbamate ejector EJ-101,
where carbamate coming from the bottom of the carbamate separator MV-101 is injected in to the reactor
R-101 along with ammonia.
Carbon Dioxide Receiving:
The carbon dioxide received from urea plant at 51°C and 0.29 kg/cm2
is compressed
by a centrifugal compressor K-101 to 100°C and 160 kg/cm2
. A small quantity of air is added to passivate
the stainless steel surfaces of HP synthesis section, protecting from the corrosive action of ammonium
carbamate.
Continuous Heating in HP section:
HP section is heated uniformly prior to start-up. This prevents the thermal stresses
in materials and avoids the possibility of crystallization due to cold piping. The rate of heating is monitored
not exceed more than 40°C/hr till 100°C and 15 – 20°C/hr for 100 – 150°C.
PROCESS DISCRIPTION:
Reactor Section
In the reactor R-101, the ammonia and carbon dioxide react to form ammonium carbamate,
a portion of which dehydrates to form urea and water. The reactions are as follows:
2 NH3 + CO2 ↔ NH2COONH4 ∆H = 37.65 kcal
NH2COONH4 ↔ NH2CONH2 + H2O ∆H = 6.3 kcal
At synthesis conditions, of 188°C and 155 kg/cm2
the first reaction is instantaneous and
goes to completion, the second reaction occurs slowly and determines the volume of
reactor. The fraction of ammonium that dehydrates is determined by the ratios of various
reactants, operating temperature and residence time. The mole ratio of ammonia to carbon
dioxide is 3.6:1 and the mole ratio of water to carbon dioxide is 0.6:1. Excess water will

57
reduce the urea conversion. The reactor volume is such as to give the residence time of
about 45 minutes at full capacity.
SOLUTION COMPOSITION AFTER REACTOR R-101
NH3 32.13 %
CO2 15.82 %
H2O 19.67 %
Urea 32.38
Total 280403 kg/hr
Stripping Section:
The reaction products leaving the reactor enter the stripper E-101, which operates as the same
pressure as reactor. The mixture is heated by MS as it flows down the falling film exchanger. The
carbon dioxide content of the solution is reduced by stripping action of ammonia as it boils out of
the solution. Almost 80 % of carbamate is decomposed in stripper. The over head gases from the
top of the stripper enter the carbamate mixer ME-106 along with carbonate solution from the
discharge of MP carbonate pumps P-102 A/B. Mixed phase then enters the kettle type carbamate
condensers E-105 A/B, where the total mixture, except for few inerts is condensed and recycled back
to the reactor. Inerts are removed through carbamate separator MV-101, which sends them to the
medium pressure decomposer holder ME-102, to passivate the equipment. The bottom product of
stripper goes to the MPD top separator MV-102.
SOLUTION CONCENRTATION AFTER STRIPPER E-101
NH3 25.03 %
CO2 6.75 %
H2O 24.53 %
Urea 43.69 %
Inets 0.1%
Total 207641 kg/h
Medium/ Low Pressure Section:
The purpose of the section is to purify urea by recovering ammonia and carbon dioxide for being recycled
to the reactor.
The section is divided into:
• Medium Pressure Decomposer
• Low Pressure Decomposer

58
The exchangers where urea is purified are called decomposers because the residual carbamate
is decomposed in them giving ammonia and carbon dioxide.
Medium Pressure Decomposition:
The solution with low residual carbon dioxide content, leaving the bottom of the stripper is
expanded at the pressure of 18 ata and enters the MPD E-102 (falling film type). MPD is divided in
to three parts:
• Top separator MV-102; released flash gases are removed before the solution enters the tube
bundle.
• Decomposing Exchanger E-102; residual carbamate is decomposed and the required heat is
supplied by means of MC flowing out of the stripper.
• Bottom Holder ME-102; holds the solution to avoid their escape to LP section.
The ammonia and carbon dioxide rich gases ay 134°C and 17.2 ata leaving the top separator are sent to the
medium pressure condenser E-107 through the shell of E-150, where they are partially absorbed in aqueous
carbonate solution coming from the recovery section. The absorption heat is removed by cooling water. A
tempered water circuit is provided to prevent carbamate solidification and to keep a suitable cooling water
temperature at MP condenser inlet re-circulating the cooling water by means of the in-line pump P-116.
In the mixture, the carbon dioxide is almost totally absorbed. The mixture from E-107 flows to the MP
absorber C-101 where the gaseous phase coming up from the solution enters the rectification section.
The column is a bubble cap trays type and performs carbon dioxide absorption and ammonia rectification.
The trays are fed by pure reflux ammonia which eliminates residual carbon dioxide and water contained in
the inert gases. Reflux ammonia is drawn from the ammonia receiver V- 101 and sent to the column by
means of the centrifugal pumps P-105.
A current of inert gases saturated with ammonia with minimum carbon dioxide residue (20 –100 ppm)
comes out from the top of the rectification section. The bottom of the solution is recycled by the low speed
reciprocating pump P-102 to mixer ME-106 in the synthesis recovery section.
Ammonia with inert gases leaving the column top is mostly condensed in the ammonia condenser E-110,
where the condensation heat is removed by cooling water. From here the two phases are sent to the
ammonia receiver V-101 through two different lines. The inert gases, saturated with ammonia, leaving the
receiver, enter the ammonia pre-heater E-109 where an additional amount of ammonia is condensed and
the condensation heat is recovered by heating the cold ammonia from the urea plant.
The condensed ammonia is recovered in V-10. The inert gases with the residue ammonia contents are sent
to the MP falling film absorber E-111. Where they meet counter current flow of water which absorbs gaseous
ammonia. The absorption heat is removed by MP absorber C-101 by means of centrifugal pump P-107. The
upper part of the medium pressure absorber consists of three valve trays (C-103) where the inert gases are
submitted to a final washing by means of the same absorption water. This way, inerts are vented practically
free from ammonia. Level in holder ME-102m from where bottom products are fed to LPD section; is very

59
important because a low level will result in breakthrough of HP gases to LP section and a high level will
increase the residence time followed by biuret formation.
SOLUTION CONCENTRATIONS AFTER MPD E-102
NH3 6.83 %
CO2 1.86 %
H2O 28.97 %
Urea 62.34 %
Total 145530 kg/h
Lower Pressure Decomposer:
The solution leaving the bottom of MPD is expanded at 4.5 ata pressure and entered in LPD E-103
(falling film type). LPD is also divided in to three parts:
• Top separator (MV-103); where the released flash gases are removed before the solution enters the
tube bundle.
• Decomposition section (E-103); where the last residual carbamate is decomposed and the required
heat is supplied by means of steam saturated at 4.5 Ata.
• Bottom holder (ME-103); where gases are prevent from their escape to vacuum section.
The gases leaving the top separator are sent to low pressure condenser E-108 where they are absorbed in
an aqueous carbonate solution coming from the waste water treatment section. The absorption heat is
removed by cooling water. From the condenser bottom the liquid phase, with the remaining inert gases, is
sent to the carbonate solution tank V-103. From here the carbonate solution is recycled back to the medium
pressure condenser E-107 by means of centrifugal pump P-103.
The inert gases, which essentially contain ammonia vapor, flow directly into the low pressure falling film
absorber E-112 where the ammonia is absorbed by a countercurrent water flow. The inert gases, washed
through the low pressure inert washing tower C-104, are collected to vent practically free from ammonia.
SOLUTION COMPOSITIONS AFTER LPD E-103
NH3 1.67 %
CO2 0.76 %
H2O 28.71 %
Urea 68.87 %
Total 131729 kg/h

60
Vacuum Section:
The urea solution after removal of ammonia and carbon dioxide is concentrated through
evaporation of water in pre-concentrator E-150 and vacuum separators MV-106 and MV-107.
Vacuum separators are employed due to their functioning at low temperature conditions and less
steam consumptions. Further they also reduce the probability of biuret formation.
The solution leaving the low pressure decomposer bottom with about 69% urea is sent to the pre-
concentrator E-150 in which a considerable amount of moisture is flashed off at a near vacuum pressure of
0.4 ata. Then in the second chamber of the pre-concentrator the solution exchanges heat with MPD top
gases thus causing more water to vaporize.
SOLUTION COMPOSITIONS AFTER PRE-CONCENTRATOR E-150
NH3 0.38 %
CO2 0.1 %
H2O 16.24 %
Urea 83.28 %
Total 108928 kg/hr
Then the bottom product with water content and concentrated urea is sent to first vacuum separator
exchanger E-114 operating at 0.4 Ata. The mixed phase coming out from E-114 enters the gas-liquid
separator MV-104, while the solution enters the second vacuum concentrator E-115 operating at the
pressure of 0.04 Ata.
The mixed phase coming out from E-115 enters the gas-liquid separator MV-107 where from the vapours are
extracted by the second vacuum system ME-105 while the melted urea is separated in the holder ME-107.
The water thus removed is sent to the tank T-102, the water production ratio with carbon dioxide inlet is
0.67:1.
The melted urea leaving the second vacuum separator MV-107 is sent to the prilling bucket ME-109 by
means of centrifugal pump P-108.The urea coming out from the bucket in the forms of drops falling along
the prilling tower ME-108 and encounters a cold air flow which causes its solidification. The vapor coming
from the top of the tower is condensed into the overhead condenser E-117
SOLUTION CONCENTRATIONSS AFTER VACUUM SEPARATOR MV-106 AND MV-107
Urea 99.62 %
H2O 0.38 %
Total 90291 kg/hr
The carbonate solution is collected in the accumulator V-110. By means of the centrifugal pump P-115 part
of this solution is recycled back to the top of the tower as reflux, the remaining part of the low pressure

61
condenser E-108. This distilled water containing only traces of ammonia, after cooling in E-118, is sent to
the urea battery limits by means of the centrifugal pump P-114.
An injection of a small quantity of air in the bottom of the tower is provided to passivate the tower itself
and the overhead condenser. The air is collected to vent from V-110. The tower is provided with five motor
driven conveying belts (ME-112 A/B/C/D/E) that transports urea to the bagging section.
Waste Water Treatment Section:
The water containing ammonia and carbon dioxide coming from the first and second vacuum
separators MV-106 and MV-107 respectively is collected in waste water collector tank T-102. It is
then pumped to waste water distillation tower C-102 operating at pressure of about 2.5 ata. Before
entering the top of the column, the solution is pre-heated in a heat exchanger E-118 by means of the
distilled water flowing out from the bottom of the tower. In the column ammonia and carbon
dioxide are stripped by means of vapor produced in the re-boiler E-116. Column is divided by a
chimney tray which directs the bottom product of top section to a hydrolyser R-102 through a heat
exchanger E-119 A/B. The pump P-121 is used for service. Hydrolyser decomposes the remaining
amount of carbon dioxide and ammonia and sprays it again in the distillation tower.

62
Bagging and Shipment Unit
Urea from urea plant is transferred to bagging unit through belt conveyers.
There are three areas in unit:
• Area 12 ( storage + fresh feed belts)
• Area 13 ( cleaning system or screening and recycling)
• Area 14 ( dispatching area , packing , stitching)
Urea is fed to hoppers in area 12, there are two main kinds of hopper:
1. Hopper for fresh feed
2. Hopper for both fresh and recycle feed
Hopper feed urea to feeders for being transferred to the belts. Bags used for packing are woven poly-
propylene bags. Inside covering of bag is made of nylon to prevent incoming and outgoing of moisture. In
order to remove dust there is a suction air system of cleaning. In air cleaning system SOVs operate and
separate air from dust by pressure.
Certain securities concerned in urea transferring include:
• Misalignment switches
• Pull card
• Speed monitors
• Thermal overload
Usually every belt has different capacity and speed. Fresh feed belts are have above 90 ton capacity.

Internship FFC Mirpur Methelo Process Report 2019

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Internship FFC Mirpur Methelo Process Report 2019

Similar to Internship FFC Mirpur Methelo Process Report 2019 (20)

Recently uploaded

Recently uploaded (20)

Internship FFC Mirpur Methelo Process Report 2019