Ammonia Process

1. Dawood Hercules Chemicals Limited
Ammonia Unit

2. Some Basics
 Technology M.W. Kellogg
 Year of built 1970
 Capacity 815 MTPD
 BMR 1991
 Steam per Ton NH3 4.9 MT
 Steam per Ton urea 1.4 MT
 NH3 per ton of urea 0.58 MT

3. Raw Materials
CO2
+
Ammonia
Steam
Natural Gas
Air

4. Natural Gas
Natural gas is received from SNGPL.
Its contents are;
 CH4 87 %
 N2 9.2 %
 CO2 1.8 %
 Other HC 0.4 %
 T. Sulfur 7ppm

5. Natural Gas
 N.G. Pressure at battery Limit = 590psig
 PRe-35 indicates & records the battery limit pressure.
 It is increased by a Positive Displacement Compressor
1102-J.
 It is double acting single stage reciprocating PD
Compressor.
 It is provided with a knock out drum to prevent
Naphtha to enter into the compressor.
 PICe-202 is provided to control discharge pressure.

6. 1102-J
 Suction Press. = 590 psig
 Disch. Press. = 690 psig
 Motor = HP
 RPM =

7. Feed Gas
 Feed Gas is to heat at required temperature.
 After 1102-J feed gas passes through 1139-C and then
through Feed Pre Heat Coil of 101-B.
 At this stage temperature = 700°F
 After feed pre heat coil feed gas is passed through 103-
B (Feed Gas Preheater).
 Then gas is entered into Hydrotreater 101-D.

8. Hydrogen Injection
 H2 is injected into Feed Gas for Hydrotreating.
 H2 is injected from LP discharge of Syn Gas
Compressor 1103-J.
There are three pints for H2 injection.
1. Before 1139-C
2. After 1139-C
3. After Feed Pre Heat Coil.
Now a days before 1139-C point is used.

9. Hydrotreating
 This is the first step to remove Sulfur from natural gas.
 Sulfur compounds in N.G are reacted with H2 to form
H2S.
 This reaction is carried out in HYDROTREATER 101-D
 The reactions are;
 RHS + H2 → H2S + RH
 COS + 3H2 → H2S + CS3OH

10. Hydrotreater 101-D
 Catalyst Cobalt Molebdenum (CoMo)
 Inlet Temperature 700ºF
 Pressure 580#
 ΔP across 101-D 4.5#
 Total volume of catalyst 750 ft3
 Height 30 ft
 Diameter 6 ft

11. Desulphurization
 H2S produced in Hydrotreater is reacted with ZnO
catalyst in Desulphurizers. (102-DA/DB)
The reaction is;
 H2S + ZnO → ZnS + H2O
 Total life expectancy
of catalyst is one year.
 102-D out pressure is 565psig.
After 102-D in feed gas
Total Sulfur = 0.05 ppm
H2S = NIL

12. Desulphurizers 102-DA/DB
 Catalyst Zinc oxide (ZnO)
 Inlet Temperature 680°F
 Pressure 575#
 ΔP across 101-D 4 - 5#
 Total volume of catalyst 410 ft3
 Height 19.5 ft
 Diameter 8.5 ft

13. The second raw material Steam is mixed in DS Gas and
mixed feed is entered in Primary Reformer 101-B
575# Steam
FRCe-102
DS Gas
Primary
Reformer
101-B

14. Saturator Coil
FICe-504A FICe-504E FICe-504F
FICe-504C FICe-504D
FICe-504B
FIe-502C
FIe-502E
FIe-502F
FIe-502A
FIe-502D
FIe-502B

15. Saturator Coil
1139-F
390°F
575# steam
FRCe-102
Condensate
Mixed
Feed
Coil
Saturator
Coil

16. Primary Reformer
 After Mixed Feed Coil, feed gas is entered in Primary
Reformer 101-B
Mixed Feed
Coil
101-B
850°F

17. Primary Reformer
It is Induced Draft Furnace
 Headers 6
 Tubes in each header 44
 Tubes 264
 Burner rows 7
 Burners 140
An induced draft fan is
provided to pull out flue
gases from out of furnace
and thus create draft in
furnace.

18. Primary Reformer
 In primary reformer steam is reacted with methane to give CO2
and H2O.
The reactions are;
CH4 + H2O → CO + 3H2 (Endothermic)
CO + H2O → CO2 + H2 (Exothermic)
CH4 + 2H2O → CO2 + 4H2 (Endothermic)
Overall reaction is endothermic, so a lot of heat input is
required for reforming reactions.
Ni
Ni

19. Primary Reformer Convection
Section Coils Auxiliary
Heater
Steam Air
Coil
Mixed Feed
Coil
HOT
SUPRHTR
BFW HT
BFW LT
Feed Preheat
Fuel
Preheat
Saturator
Coil
COLD
SUPRHTR
Flue Gases
Arch Burner Rows
Tunnel Burners
S.H Burners
ID Fan

20. Primary Reforming
Reforming reaction is favored with…
High
Temperature
1460°°F
500 #
Low
Pressure
High
S/C Ratio
3.1 – 3.5

21. Secondary Reformer
103-D
101-B
Transfer Line
1107-D
Steam
+
Air

22. H2 + O2 → H2O (Exothermic)
CH4 + 2H2O → CO2 + 4H2 (Endothermic)
Secondary Reformer
 Two reactions occurred in 103-D.
Ni

23. Secondary Reformer
 In first portion, combustion of H2 takes place as air is
entered in the vessel on high temperature.
 This reaction is highly exothermic and H2O is
produced along-with a lot of heat.
 Then produced steam is reacted with the methane
coming from 101-B.
 The second reaction is similar to as primary reforming
reaction.
 Heat produced in 1st reaction is used for the 2nd
endothermic reaction.

24. Secondary Reformer
 Catalyst Nickel (Ni)
 Catalyst Volume 710 ft3
 Inlet temperature 1485°F
 Outlet temperature 1780°F
 The vessel is water jacketed to keep the metal
temperature in safe limit.
 In normal steam condensate is in water jacket.
 In emergency conditions, cooling water or fire water
may be used.

25. Waste Heat Boiler
 The effluent of 103-D contains a huge amount of heat.
 This quantity of heat is used to produce 1500psig
steam.
 A Waste Heat Boiler 1101-C / 1101-F is provided for this
purpose.
 By this 320,000 lb/hr steam is generated.

26. 1101-F
1101-C
1500# Steam
320,000 lb/hr
HTS
104-D
From
103-D
BFW

27. K
O
D
Feed
Pre Heat
Coil
1102-J 1139-C 103-B
101-D
102-D
A
102-D
B
Mixed
Feed
Coil
FRCe-101
FRCe-102
101-B
103-D
1101-F
1101-C
Mixed
Feed
Coil
FRCe-103
MICe-10
1500#
steam
102-D
B
103-D
102-D
A
102-D
B
103-D
101-D
102-D
A
102-D
B
103-D
103-B
101-B

28. Shift Conversion
 At the exit of 103-D, feed gas contains 11.6% CO
 We are to convert this CO into CO2.
 Conversion of CO into CO2 is called shift reaction.
The reaction is;
CO + H2O → CO2 + H2 (Exothermic)
This shift reaction is carried out in two separate vessels.
1. High Temperature Shift Converter (104-D)
2. Low Temperature Shift Converter (108-D)

29. High Temperature Shift Converter (104-D)
 Feed gas at temp. of 640°F is entered in HTS.
 TRCe-610 controls the temp. of HTS in.
 HTS reaction is exothermic.
 Catalyst in HTS Fe
 Catalyst Volume 1450 ft3
 Outlet temp. 740°F
 ΔP across vessel 6 psig
 After HTS CO 2%

30. Low Temperature Shift Converter (108-D)
 After HTS feed gas temp is 740°F,
 At the inlet of LTS, 400°F temp is required.
 So feed gas is passed through a series of Heat Exchangers.
 Catalyst in LTS Cu
 Catalyst Volume 1490 ft3
 After HTS CO 0.15 %
 Max. allowable temp. 500°F
 Poisons for catalyst Chlorine and Sulphur

31. HTS
104-D LTS
108-D
103-C
1104-C
1112-C
400°F
740°F
MOV-1 MOV-2
TRCe-11
435°F
HCV-2
From
1101-C

32. CO2 Removal System
After LTS, feed gas contains;
 CO2 18%
 CO 0.15%
 H2 60%
 N2 20%
This CO2 is to be separated from the feed gas.
CO2 is removed in CO2 Removal System.

33. CATACARB System
 After LTS, feed gas of temp 435°F is passed through
De-Super Heater.
 Steam condensate is injected and temp of gas is
lowered to 356°F.
 Then gas exchanges its latent heat in CO2 Stripper
Gas Exchanger 1105-CA/CB.
 After 1105-C, Raw Gas Separator (102-F) collects
process condensate from the Gas Stream.
 Then Gas enters into the CO2 Absorber.

34. CO2 Absorber 101-E
 In CO2 Absorber, gas flows upward through 4 beds of
Polypropylene packing.
 From top of Absorber, catalyzed solution of Potassium
Carbonate (CATACARB Solution) is showered and
contacts counter currently with the up coming Gas.
 CO2 is absorbed in Catacarb Solution (Rich Solution)
and this rich soln. is transferred to the top of CO2
Stripper (102-E).
 Level of Absorber is controlled with LICe-6 A, C & D
valves.

35. CO2 Absorber 101-E
 Catalyzed solution of potassium carbonate absorbs
CO2 by chemical reaction;
CO2 + H2O → H2CO3
H2CO3 + CO2 → 2HCO3
 This reaction takes place under high pressure (400#)
and low temperature (180°F top, 256°F bottom)
conditions.

36. Factors Affecting CO2 Absorption
High
Pressure
400psig
Low
Temperature
180°F top
256°F bot.
Solution
Strength
Normality
Catalyst
Volume
11-12 %

37. FRCe-12
FRCe-5
Rich Solution
Semi Lean Solution
Lean Solution
Raw Synthesis Gas
From 102-F
CO 2 Absorber
101-E

38. CO2 Absorber 101-E
 Temperature Top 178°F
 Bottom 256°F
 Operating Pressure 410#
 Setting of PSV 435#
 No. of Beds 4
Rings material
 1st bed Poly Propylene Pall Rings
 2nd, 3rd & 4th bed Stainless Steel

39. CO2 Stripper (102-E)
 CO2 absorbed in Catacarb Solution is separated in
CO2 stripper (102-E).
 Rich Solution enters into the stripper from its top.
 While coming down through the stripper, CO2 is
separated from the solution under high temperature
(222°F top, 265°F bottom) and low pressure (5#).
 CO2 product is exited from the top of the Stripper at a
pressure of 5psig.
 Pressure is controlled by PICe-24.

40. CO2 Stripper (102-E)
 Reflux water is entered at the top of the Stripper above
first bed.
 This reflux water prevent any carry over of Catacarb
Solution with CO2 product.
 CO2 product is cooled in 110-C1A/B and C2A/B.
 113-F collects the condensate from CO2 Product.
 This condensate is pumped with 108-J/JA as reflux
water at the top of the Stripper..

41. CO2 Stripper 102-E
 Temperature Top 222°F
 Bottom 265°F
 Operating Pressure 5#
 Setting of PSV 435#
 No. of Beds 5
Rings material
 1st, 2nd & 3rd bed Stainless Steel
 4th & 5th beds Poly Propylene Pall Rings

42. Rich Solution
Semi Lean
Solution
Lean Solution
CO2 Product
98.40%
113-F
108-J
110-C1A/B
C2A/B

43. 107-JHT
 Hydraulic turbine 107-JHT is installed for energy
conservation point of view.
 High pressure energy of Absorber is used to run the
Hydraulic Turbine while solution transfer to low
pressure Stripper.
JT
JHT 107-J
A steam turbine is also provided with 107-J Semi-Lean
Solution Pump to support JHT

44. Flasher 1103-E
 Rich solution is entered into Flasher after discharge of
Hydraulic Turbine.
 The purpose of Flasher is to decrease H2 in CO2
Product.
H2 in CO2 Product;
 When Flasher is in service 0.20 %
 When Flasher is out of service 1.0 %

45. 1103-E
PICe-101B
1160-
F
PICe-101A
LICe-102
1141-C
LICe-101
To C-2111
To Cold
Vent

46. LICe-1A
1103-E
109-C
JHT
LICe-101
107-J
FRCe-12
107-JA
DMW
CO2 Slippage

47. Absorber Over Head
 Gas free of CO2 is exited from the top of the 101-E.
 Entrained Catacarb Solution is separated in 116-F.
This gas contains;
 CO2 0.25%
 CO 0.2%
 H2 74%
 N2 24%

48. Why CO2 slippage is dangerous?
 Oxides are poison for NH3 Converter catalyst.
 Ammonium Carbamade is produced in 9th wheel of
103-J HP case which is highly corrosive.
So
 It is necessary to convert CO & CO2 into CH4 which is
inert for NH3 Converter catalyst.
 This process is called Methanation.

49. Methanation
 From top of Absorber syn gas is to be entered in
Methanator.
 CO & CO2 present in it are converted into CH4 which is
inert for NH3 converter catalyst.
Methanation reaction is;
CO + H2 → CH4 + H2O
CO2 + H2 → CH4 + H2O
These reactions are highly exothermic.

50. Methanator 106-D
 Manufacturer DESCON Engineering
 Design pressure 435psig
 Design temperature 850°F
 Catalyst volume 600 ft3
 Catalyst poison Sulfur & Chlorine
 Methanator is tripped in case of high beds
temperature.
 HTA-12 & 13 are provided which closes V-17 (inlet valve
of Methanator) at 750°F.

51. 116-F
Methanator
106-D
1104-C
1136-C
HCV-3
TRCe-12
101-E
PICe-205
600°F
180°F
V-17

52. Methanator Effluent
After Methanator, syn gas contains;
 H2 74 %
 N2 24 %
 CO2 7ppm
 After 106-D, syn Gas temp is 650°F which is cooled
upto 105°F in 114-C & 115-C.

53. Synthesis Section
 After Methanator, synthesis gas is to be compressed up
to required pressure for NH3 synthesis reaction i.e. 1880
psig.
 1103-J Synthesis Gas Compressor is provided for this
purpose.
 High temperature Methanator effluent gas is to be
cooled before suction of 1103-J.
 114-C, 115-C & a K.O.D 104-F are provided for cooling
and removing moisture from the syn gas.

54. 104-F
Methanator
106-D
114-C
115-C
650°F
105°F
LP suction
of 1103-J

55. Synthesis Gas Compressor 1103-J
 It is two stage centrifugal compressor driven by two
steam turbines, one is condensing and the other is
non-condensing.
 Its LP case receives syn gas at pressure of 370# and
105F.
 Discharge pressure of LP case is 970# and 340F

56. 1103-J
 Suction Pressure 370#
 Suction Temperature 105°F
 Discharge Pressure 940#
 Discharge Temperature 340°F
 No. of wheels 1st stage 9
 No. of wheels 2nd stage 9
 RPM 10200

57. Molecular Sieve Drier 1109-D
 After LP case discharge, syn gas is cooled in a series of
exchangers i.e. 1136-C, 116-C & 129-C.
 Then it passes through Molecular Sieve Drier 1109-
DA/DB
 It is to remove any moisture or CO2 content present in
syn gas.
After 1109-D,
 Moisture 0.05 ppm (on AR-820)
 CO2 4 ppm

58. Ammonia Converter 1105-D
 Synthesis gas at pressure 1880# and temperature 270F
enters in to the Ammonia Converter 1105-D.
Ammonia Synthesis reaction;
N2 + 3H2 → 2NH3
 Efficiency of Ammonia Converter is 14%.
 Ammonia Converter Catalyst is Fe.

59. 121-C
1134-F
1105-D
Ammonia
Converter
HP discharge
of 1103-J
650°F
Converter Effluent
Gases
NH3 14.9%
140°F 270°F

60. Factors Affecting Synthesis Reaction
High
Pressure
1880psig
High
Temperature
680°F 1st bed
705°F 2nd bed
Inert
Level
>12%
Space
Velocity

61. Ammonia Converter 1105-D
Converter inlet gases contains;
 H2 64%
 N2 22%
 NH3 1.5%
Converter outlet gases contains;
 H2 52%
 N2 18%
 NH3 14.9%

62. Ammonia Converter 1105-D
 Manufacturer Halder Topsoe
 Model S-200
 Type Radial Flow Type
 Catalyst beds 2
 Catalyst in 1st bed KMR
 Volume 14.6 m3
 Catalyst in 2nd bed KM1
 Volume 59.8 m3

63. After Converter
 After converter, Ammonia which is almost 15% in
converter effluent gases, is separated from converter
effluent gases.
 This separation is done by refrigeration of the effluent
gases.
 For this purpose, a refrigeration system is designed in
which Ammonia is used for refrigeration.
 After separation of Ammonia, remaining gas is
recycled to 103-J HP Case 9th wheel for synthesis.

64. 1105-D
Ammonia
Converter
1103-J
Refrigeration
system
Product Ammonia
Recycled Gas

65. Product Ammonia
 Refrigerated Ammonia is collected in 106-F at -13°F &
1650 psig.
 From 106-F, it is transferred to 107-F through LC-12
and its pressure reduced to 225 psig.
 From 107-F, ammonia is transferred to 111-F & 112-F
through FICe-14 & LC-13.

66. 121-C
106-F
1105-D
Ammonia
Converter
1123-C
1124-C 120-C
117-C
118-C 119-C
HCV-3
650°F
-13°F

67. 106-F
107-F
112-F
111-F
Purges
109-J To TK-601
&
Urea Unit

68. 128-C
LP
HP
110-F 111-F 112-F
109-F
127-C
A/B/C
FICa-11 FICa-10 FICa-9
117-C 118-C 119-C
LC-15
Refrigeration System