The document provides an overview of the urea manufacturing process used at FFC plants in Pakistan. It describes the key stages of urea production, including CO2 compression, urea synthesis in the high pressure section, and decomposition and recovery in the medium and low pressure sections. The final stages involve vacuum concentration to increase the urea concentration to 99.7% for prilling, and a waste water treatment section. The document is intended as training material for staff on the urea production process.

1. UREA PLANT DESCRIPTION :
(Basic Course for Staff Trainees)
PRESENTED BY:
ABDUL RASHEED
1

2. CONTENTS
 Introduction
 Fertilizers
 Urea fertilizers
 Physical properties of urea
 Uses of urea
 FFC urea plants
 Raw materials
 Urea synthesis
 Urea processes
 CO2 compression
 High pressure section
 Medium and low pressure section
 Vacuum concentration and prilling section
 Waste water treatment section

3. LECTURE : 1
3

4. INTRODUCTION
Urea Manufacturing Industries In Pakistan :
 Pak Arab Fertilizer (Snamprogetti - 400 MTPD)
 FFC – I (Snamprogetti - 2105 MTPD)
 FFC – II (Snamprogetti - 1925 MTPD)
 FFC – III (Snamprogetti - 2175 MTPD)
 Engro Enven 1.3 (Snamprogetti - 3700 MTPD)
 FFBL (Stamicarbon - 1750 MTPD)
 Fatima Fertilizer (Stamicarbon -1200 MTPD)
 Engro (Toyo Process - 2800 MTPD)
 Pak American Fertilizer (Toyo Process - 1000 MTPD)
 Dawood Hercules (Mitsui Process- 1000 MTPD)
4

5. INTRODUCTION
Fertilizers:
 Provide essential nutrients (N,P,K ) to crops
 Nitrogen is required to promote protein formation which
helps healthy growth, high yields and keep plants green
(Urea, CAN, AN)
 Phosphorus accelerates seeding and fruit formation (SSP,
DAP)
 Potassium is essential for the development of starch/
sugar/fibers of plants (Potassium phosphate, NPK blended)
Urea Fertilizers :
 Highly soluble in water
 Low transportation cost / ton of nitrogen
 Prills ( 1.5 ~ 2.1mm) / Granular ( 2.0 ~ 3.0mm)
 Most Concentrated dry source of Nitrogen(46%) 5

6. Physical Properties of Urea :
Other Names:
 Carbamide
Physical State:
 Solid at ambient conditions , Hygroscopic
Appearance:
 White , Odorless
 Melting /boiling Point : 132.7 / 196.6 °C at 760 mm of Hg
 Molecular Weight : 60.056 g/mol, Density :1.32 g/ml
Uses of Urea :
 Fertilizer , Feed for cattle , Adhesives
 Melamine Production , Deicing agent for airports runway
 Urea-Formaldehyde Resin , NOx removal from flue gas
INTRODUCTION

7. 7
FFC Urea Plants :
INTRODUCTION
2140

8. FFC PLANTS COMPARISION
8
Plant -II
 CO2 COMPRESSOR
 01 centrifugal
 COMPRESSOR TURBINE
 KS Driven
 HP AMMONIA PUMP
 02 Centrifugal
 PRILL TOWER
 Cone
 CONTROL SYSTEM
 Honey well TDC-3000
 PCT/HYDROLYSER
 Since Commissioning
Plant -I
 CO2 COMPRESSOR
 01centrifugal+1Reciprocating
 COMPRESSOR TURBINE
 HS Driven
 HP AMMONIA PUMP
 03 Reciprocating
 PRILL TOWER
 Belts
 CONTROL SYSTEM
 Foxboro 200 / DCS Invensys
 PCT / HYDROLYSER
 Since 1985
FFC Plants Salient Features :
 Energy Efficient Process , Total Recycle Process
 Ammonia Stripping Process , Passivation With Air

9. UREA SYNTHESIS
Raw Materials:
 Carbon Dioxide , Ammonia
Utilities:
 Electric Power , Cooling Water
 Steam , Treated Water
 Instrument Air , Utility Air
Reaction of Urea Synthesis :
 Liquid Ammonia : pressurized up to 240 ATA via HP
reciprocating pumps and feed to the REACTOR for reaction
 CO2 : is pressurized up to 160 ATA via two compressors , one
driven by HS STEAM while other one driven by ELECTRIC
MOTOR and feed to the REACTOR for reaction

10. UREA SYNTHESIS
First Reaction :
2NH3 + CO2 ↔ NH2 CO2 NH (Ammonium Carbamate)
Exothermic
Second Reaction :
NH2 CO2 NH4↔ NH2CO NH2 + H2O
Endothermic
Overall Reaction :
2NH3 + CO2 ↔ NH2CO NH2+ H2O
(liq) (g) (liq) (liq)
Exothermic,
Pressure = 140 ~ 150 Kg / cm2 , Temperature = 172 ~ 190 ºc
Favourable conditions :
High Pressure - 150 Kg/cm2 , High Temperature - 190 ºC
High NH : CO ratio - 3.3 : 1 , Low H2O : CO ratio - 0.55 :1

11. Urea processes licensers :
 Snam progetti : Italy
 Stamicarbon : Holland
 Toyo engineering : Japan
 ACES- Advanced process for Cost and Energy saving) :
Japan
Urea processes :
 Once Through Processes.
 Partial Recycle .
 Total Recycle.
UREA PROCESSES

12. UREA PROCESSES
ONCE THROUGH PROCESS :
 It is simplest and less expensive (in both capital investment
and operating cost) , unconverted NH3 and CO2 is not
recycled to the reactor
 It is least flexible and cannot be operated unless some
provision is made to utilize the large amount of off-gas NH3
PARTIAL RECYCLE PROCESS :
 In this partial unconverted NH3 and CO2 is recycled to the
reactor
TOTAL RECYCLE PROCESS :
 Most of the new plants use total recycle process
 All the unconverted NH3 and CO2 is recycled
 This is the most flexible process
 It is expensive in investment & operating costs 12

13. ADVANTAGES
Advantages of Snamprogetti Urea Process :
 Total recycle process
 Ammonia stripping process
 Passivation with air
 Energy efficient process
13

14. LECTURE : 2
14

15. STAGES OF UREA PLANT
Main Stages fo Snamprogogetti Urea Process are:
1. CO2 compression section .
2. Urea synthesis and high pressure recovery section .
3. Medium pressure recovery section .
4. Low pressure recovery section .
5. Urea solution concentration section .
6. Prilling section .
7. Waste water treatment section .
15

16. BLOCK DIAGRAM OF SNAMPROCESS :

17. UREA
REACTOR
144 kg/cm2
NH3
CO2
Urea Solution:
Urea = 31 % ,
Bottom : 172 ,Top :182 °C
PRILLING
Urea = 99.7%
Moisture= 0.3%
UREA
STRIPPER
143 kg/cm2
Urea = 42 %
Bottom : 203 ,Top :188 °C
NH3, CO2, H2O
LP
DECOMPOSER
3.5 kg/cm2
Urea = 71 %
Bottom : 138
,Top :125 °C
NH3, CO2, H2O
MP
DECOMPOSER
16 kg/cm2
Urea = 62 %
Bottom : 158 ,Top :140°C
NH3, CO2, H2O
PRE
CONCENTRATOR
0.5 kg/cm2
Urea = 85%
Bottom : 106 °C
H2O
1ST
CONCENTRATOR
0.3 kg/cm2
H2O
2ND
CONCENTRATOR
0.03 kg/cm2
H2O
Urea = 95 %
Bottom : 127 °C
Urea = 99.7 %
Bottom : 137 °C
17

18. BLOCK DIAGRAM OF SNAM PROCESS
HP
SECTION
144 Kg/cm2
NH
3
CO
2
2ND EFFECT
VACUUM
0.03 Kg/cm2
WWT / PCT
SECTION
2.5 Kg/cm2
IST EFFECT
VACUUM
0.3 Kg/cm2
H2O
UREA
DUS
T
PRE-CON
CENTRATION
0.5 Kg/cm2
INERT
S
MP
SECTION
16 Kg/cm2
LP
SECTION
3.5 Kg/cm2
PRILLIONG
(ATM)
INERT
S

19. CO2 COMPRESSION
CO2 Compressor :
 CO2 gas available from NH3 plant is compressed to 160 ATA
pressure for feeding into the urea reactor
 The compression is done in a four stage centrifugal compressor
driven by turbine and a four stage reciprocating compressor
driven by electric motor
 The heat of compression is removed in intercoolers after each
stage of compression except the final one
19

20.  Manufacturer : NOUVOPIGNONE
 Type : CENTRIFUGAL
 No. of stages/ casings : FOUR/ two
Capacity :
 Normal/maximum (m³/hr)=30000/31500
Pressure :
 Discharge (normal/maximum) ATA : 157/160
 Suction(min/normal/max) ATA : 1.2/1.3/1.35
 Speed (RPM) Normal/max. : 6220/13900
CO2COMPRESSOR FEATURES
20

21. H.P PURIFICATION AND RECOVERY
Purpose :
 To synthesize urea in the reactor
 To decompose unconverted carbamate in the stripper
 To recover unconverted CO2 and ammonia
 The Residence time of the REACTOR has been reduced from 45
to 35 minutes after DBN (debottle necking )project
 About 80% of the carbamate is decomposed into NH3 & CO2 in
HP urea stripper
 The stripper top gases are condensed partially in HP carbamate
condenser , separated in HP carbamate separator and recycled
back to the REACTOR for reaction
 Reactor out let urea concentration is up to 31 %
21

22. Stripper
E-101
LP STEAM
CO2 COMPRESSOR
MS
LRC-1V
R101
CARBAMATE
FROM MP SCETION
TO MP SECTION
CARBAMATE
SEPARATOR
TO MP SECTION
HP
AMMONIA
PUMP
NH3
CARBAMATE PUMP
CARBAMATE EJECTOR
CARBAMATE CONDENSERS
240
Kg/cm2 23 Kg/cm2
144
Kg/cm2
HIGH PRESSURE LOOP
STRIPPER
REACTOR
E-101
22

23. LECTURE : 3
MEDIUM AND LOW PRESSURE
DECOMPOSITION AND RECOVERY :
23

24. MP DECO. AND RECOVERY
Purpose :
 Medium pressure purification section is fed by 42 % urea
solution coming from the HP section after preheating in pre
– decomposer
 In this section, by heating, un-reacted carbamate and excess
NH3 are vaporized and then condensed for re-use in
process reaction
 In this way all un reacted reagents are vaporized and
recovered
 liquid ammonia collected in ammonia receiver and recycled
to the H.P. Section
24

25. NH3
FROM B/L
TO HP SECTION
TO CARBAMATE PUMP
FROM STRIPPER
BOTTOM
TO LP SECTION
CWS CWR
MP
CONDENSER
CWS
CWR
AMMONIA RECEVIER
VENT
CO2
ABSORBER
Urea = 62.0%
AMMONIA
CONDENSER
MEDIUM
PRESSURE
DECOMPOSER
PRE-CONCENTRATOR
FROM LP SECTION
MEDIUM PRESSURE LOOP
25

26. L.P DECOMPOSITION AND REVOVERY
Purpose :
 The section is feed by 62 % urea solution coming from the M.P.
section
 Surplus NH3 and CO2 are recovered in vapour phase from L.P
decomposer
 The recovered gases are condensed in L.P .condenser and
collected in the LP carbonate solution vessel .
 This carbonate solution is recycled to MP section while the urea
solution 71 % is fed to the vacuum section
26

27. FROM MP
SECTION
TO
PRE-CONETRATOR
SHELL SIDE
TO PRECONETRATOR
INERTS
Urea = 71.0 %
CWS CWR
CARBONATE ACCUMULATOR
LOW PRESSURE
DECOMPOSER
LP
CONDENSER
LS
LOW PRESSURE LOOP
27

28. LECTURE : 4.
VACUUM CONCENTRATION AND PRILLING :
28

29. Purpose :
 MP decomposer bottom urea solution 71 % is fed to the
vacuum section
 The surplus water is removed under vacuum collected in Waste
water tank
 Vacuum concentrator separator last effect outlet urea
concentration is achieved to 99.7 % for prilling requirements
29
3 STEPS OF VAC. CONCENTRATION

30. VACUUM SYSTEM
TO WASTE WATER
TREATMENT SYSTEM
PRE- CONCENTRATOR
1st VACUUM
STAGE
2nd VACUUM
STAGE
FROM LP
DECOMPOSER
TO PRILL
TOWER
Urea = 85.0%
Urea = 95.0 % Urea = 99.7 %
LS
LMS
30
3 STEPS OF VAC. CONCENTRATION

31. 3 STEPS OF VAC. CONCENTRATION
First step vacuum pre- concentrator separator:
 L-P decomposer bottom effluents are sent to vacuum pre –
concentration separator .
 Vapors are sucked by ejector , condensed in pre - concentrator
condenser and sent to waste water tank .
 Urea solution 85% achieved is sent to 1st stage vacuum concentrator
separator
Second step 1st stage vacuum concentrator separator:
 This 85% effluent after heating with L.S steam sent to 1st stage
vacuum concentrator separator , Vapors are sucked by a set of
ejectors , condensed in condenser and sent to waste water tank .
 Urea solution 95% achieved is sent to 2nd stage vacuum concentrator
separator
31

32. 2ND STAGE VACUUM CONCENTRATION
Third step 2nd stage vacuum concentrator separator:
 1st stage vacuum concentrator separator outlet is heated with
LMS and feed to 2nd stage vacuum concentrator separator
 Vapors from 2nd stage vacuum concentrator separator sucked by
a booster ejector and sent to a set of 2nd stage vacuum
condensers
 Condensate is sent to waste water tank and uncondensed vapors
with inserts vented to atmosphere
 Urea concentration achieved 99.7% sent for prilling
32

33. PRILLING TOWER OPERATION
33
Purpose :
 Molten urea prilled in prilling bucket in the form of droplets ,
cool , solidify and collected at the bottom of the tower and
transported by means of conveyor belts to storage or loaded
for transportation
 Prilling bucket RPM are adjusted to have fine droplets
showering downwards
 In prilling tower air comes in contact with hot urea droplets ,
removes their heat & moisture and moves upward where as
fresh air enters from bottom louvers
 Prilling tower effective height (from belts to bucket) is 80
meters

34. PRILL TOWER OPERATION
AIR
INLET
Bucket
AIR
INLET
AIR
OUTLET
AIR
OUTLET
34

35. BULK
STORAGE
From Urea Melt Pump
Urea Conveyor Belts
Prill Tower
PRILL TOWER OPERATION
35
BAGGING & SHIPMENT

36. PRODUCT QUALITY CONTROL
Product Quality Control :
 Factor : Design Limit Dispatch Limit
 Moisture : 0.3% 0.45%
 Biuret : 0.9% 1.0%
 Max. Fines : 5% 3.5%
 Prill Size : 1.8 mm >1.7mm
36

37. PRODUCT QUALITY CONTROL
Moisture :
 Low recycle load
 Adequate vacuum in vacuum section
 Proper prill tower operation
Biuret :
 Low temperature , Low residence time
Prill Size :
 Prill bucket holes diameter , Prill tower height
 Fines:
 Prill Size , Prill Strength
 Moisture
37

38. LECTURE : 5
WASTE WATER TREATMENT SECTION :
38

39. WASTE WATER SECTION
Purpose :
 To recover all the unreacted reagents left in the reaction
Waste water treatment process :
 Waste water from waste water tank contains about 1.5 % urea, 5-
6% NH3 and 1-2% CO2
 It is feed to the distillation column after preheating with treated hot
water
 LS steam is introduced as a stripping agent in bottom of the
column
 Solution from middle of the column is taken out and sent to
hydrolyzer where urea molecule breaks into NH3 and CO2 in the
presence of H.P steam under the high pressure system ( 37ATA &
235 °C )
39

40. WASTE WATER RECOVERY
Waste water treatment process (continue …..):
 The hydrolyzed solution from this reactor is taken back
into the distillation column for separation gases and liquid .
 Vapors from the hydrolyzer are combined with gases from
top of the distillation column and condensed in the
condenser
 The recovered NH3 and CO2 in the form of weak solution
from the condenser is collected in waste water accumulator
and recycled to LP section
 While The uncondensed gases / inserts are vented to the
atmosphere.
40

41. WASTE WATER LOOP
41
235
36
Legend
Temperature
(ᵒC)
Pressure
(kg/cm2)
2.5

42. 42
CO2
P-101A/B/C
NH3
V-102
EJECTORS
CONDENSERS
To
Prilling
Bucket
MS
V-105
Tank
HP
RECOVERY
MP
RECOVERY
LP
RECOVERY
WASTE WATER
RECOVERY
MS
LS

43. 43