6. • Ammonia is a compound of nitrogen and hydrogen.
• It is a colorless gas at ambient conditions with a characteristic
pungent smell.
• Formula: NH3
• Density: 0.68 kg/m³
• Boiling point: -33.34 °C
• Molar mass: 17.031 g/mol
• Melting point: -77.73 °C
PROPERTIES OF AMMONIA
8. PROCESS DESCRIPTION
• Ammonia is produced from Syn. gas containing H2 & N2 in
the ratio of 3:1
• Source of H2 is De-mineralized water & hydrocarbons in
natural gas.
• The source of N2 is atmospheric air.
• Source of CO2 is hydrocarbons in natural gas feed.
14. N.G. GAS BOOSTERS
• Feed and fuel gas header pressure boosting site.
• Feed and fuel gas headers are combined and pressure is
increased from 13 kg/cm2 to 32 kg/cm2, with help of 07
Engine driven Reciprocation compressors.
• In second step a portion of this gas is further compressed to
increase pressure up to 55 kg/cm2 for use as feed gas with
help of 04 Engine Driven Reciprocating compressors.
22. CATALYST
A catalyst is a substance ,which alters the rate of a chemical
reaction with out being consumed in the reaction .
Thus, a small amount of catalyst is able to catalyze the reaction
to a large amount of reactant.
A catalyzed reaction has lower activation energy than an un-
catalyzed reaction.
23. • Sulphur is a poison to several catalysts in the process & must
be removed .
• There are two reactors each has two Zinc oxide beds.
• Adsorbent trade name HTZ-3 and HTZ-51 (Haldor Topsoe)
• Elimination of traces of Sulphur.
• This is achieved in zinc oxide beds (350-410 °C & 38 kg/cm2)
𝑍𝑛𝑂 + 𝐻2𝑆 → 𝑍𝑛𝑆 + 𝐻2𝑂
• Sulphur reduction from 5ppm to≤ 2.0 µg/NMC.
Desulphurization
24. DESULPHURIZATION
Reactions
COS + H2 CO + H2S
ZnO + H2S ZnS + H2O ΔH=-76kJ/mol
H2 + CO2 H2O + CO ΔH=+41kJ/mol
Parameters;
NG contains 4 – 5 mg/Nmc Sulphur
NG contains both H2S and organic Sulphur
NG
Feed
De-Sulphurized NG
Temp:
350-410°C
Pressure:
38 kg/cm2
Sulphur Slip:
< 5 µg/Nmc
27. Primary Reforming
In primary reforming reaction between Methane and steam
over Nickel catalyst (780 °C & 36 kg/cm2 )
CH4 + H2O CO + 3H2 ∆H = - 206 KJ/mol
CO + H2O CO2+H2 ∆H = + 41.1 KJ/mol
Methane is reduced from 70% to 9%.
Favorable conditions for methane conversion are;
Low pressure
High temperature
High steam to carbon ratio
28. PRIMARY REFORMER
28
Reactions
CH4 + H2O CO + 3H2 ΔH = +206 kJ/mol
CO + H2O CO2 + H2 ΔH = -41 kJ/mol
Process Steam
De-Sulphurized
NG
Fuel NG
Process Gas
9 – 11 %
CH4
29. Primary Reformer
Primary reformer is a heart of synthesis gas generation plant.
Primary reformer is a heat exchanger. Its function is to heat up
process gas.
Consists of a radiant section having two fire boxes each
containing a single row of catalyst tubes (filled with Ni catalyst).
Side wall burners on either side of the tubes discharging hot
gases into the convection section through smoke hood.
Convection section has several coils which recovers heat from
flue gases leaving the radiant section for various processes and
utilities duties.
30. PRIMARY REFORMER
Fire boxes 02
Total tubes 288
Total Burners 648
Induced draft Blower
Convection Section
07 Coils
34. Secondary Reformer
Air is introduced at this stage as source of N2 necessary
for ammonia synthesis (Ratio = 1:3). Air is injected
through a mixing device called burner.
Combustion reaction increases temp ~ 1550 °C
2H2 + O2 2H2O ∆H = + 242 KJ/mol
CH4+2O2 CO2+2H2O
2CO+O2 2CO2
Reforming reaction over Nickel catalyst
(1350 - 900 °C & 31.8 kg/cm2)
CH4 + H2O CO + 3H2 ∆H = -206 KJ/mol
CO + H2O CO2+H2 ∆H = +41.1KJ/mol
Methane is reduced up to 0.75 %
Process
Air
Process
Gas
09% CH4
Process Gas
0.75% CH4
38. Waste heat recovery
The gas from the secondary
reformer is cooled by recovering the
waste heat for Production of high
pressure steam at 110 kg/cm2
Process gas outlet temperature after
passing waste heat boiler reduces
from 915 °C to 350 °C
39. Shift Conversion
• CO is not required. Oxides will damage ammonia reactor
catalyst.
• CO is converted into H2 and CO2 , as per following reaction:
• CO+H2O CO2+H2 +Heat [Exothermic]
• Reaction carried in two stages:
• High Temperature shift (HTS) converter, loaded with an iron -
chromium catalyst. Gas enters at 320 - 350 °C
• Low temperature shift (LTS) converter [Catalyst: Copper
Oxide] gas enters at 195°C and leaves at 225°C
• CO at exit of LTS is reduced up to 0.12 – 0.15 %.
• Low temperature and high steam to carbon ration is favorable
for conversion of CO to CO2
41. Shift Conversion
Shift Converters Comparison
Reactor Catalyst
Base
Metal
Temperature
Range(ºC)
Pressure
Range
(Kg/cm2)
High
temperature
Shift
converter
SK-201-2 Iron 350-420 33
Low
temperature
shift
Converter
Katalco83
-3
Copper 195-225 32
44. 44
BLHP
H2=74%,N2=24 %
99% CO2 to urea plant
From LTS
R-205
MP-301A/B
XP-301
E.CONSERVATION T
B/F LOW HEAT
PROJECT
B/F RICH
SOLUTION
HOT B/F
40%
60 %
COLD
B/F
LEAN
SOLUTION
CO2 Removal System
45. CO2 Removal System
Potassium carbonate solution used for CO2 removal.
CO2 absorption at high pressure and low temp. (64°C & 28
kg/cm2 ).
K2CO3 + CO2 + H2O 2KHCO3
CO2 stripping at low pressure & high temp (122 °C & 0.32
kg/cm2 ).
2KHCO3 K2CO3 + CO2 + H2O
CO2 produced is sent to urea plant.
CO2 slip with process gas is up to 800 ppm
48. Methanator
CO and CO2 are poison for the ammonia synthesis catalyst
Residual CO and CO2 are converted to methane over
Nickel catalyst (300 °C & 26 kg/cm2 )
CO2 + 4H2 CH4 + 2H2O ∆H = + 165 KJ/mol
CO + 3H2 CH4 + H2O ∆H = +206 KJ/mol
CO/CO2 content reduce from 0.2-0.3% to ≤ 5 ppm.
49. SYN. GAS COMPRESSOR
04 – Stage
Compressor
Speed :13,200 rpm
Pressure Increase
from 25kg/cm2to
245 kg/cm2
50. AMMONIA SYNTHESIS
The ammonia synthesis takes place in the ammonia
converter R-501 according to the following reaction.
3H2 + N2 ↔ 2NH3 + heat
3 volumes of hydrogen +1 volume of nitrogen react to
give 2 volumes of ammonia .
51. AMMONIA SYNTHESIS
Operating conditions for plant-I
Pressure : 245 Kg / cm2
Temperature : 380 °C - 520 °C
Catalyst is KM1R Base metal Fe contains 94 % Fe3O4
(magnetite)
Common poison for catalysts is oxygen in the form of water,
carbon monoxide and carbon dioxide.
52. Ammonia Synthesis
The synthesis unit R-501 is constructed for a maximum pressure
of 295 kg/cm2 and the normal pressure is about 245 kg/cm2 .
The reaction temperature in the catalyst bed is 380C -520C.
Synthesis gas after compression to about 245 kg/cm2 pressure
is passed over iron catalyst in a radial flow reactor.
A part of the synthesis gas about 17% is converted to ammonia.
53. Ammonia Synthesis
The synthesis unit R-501 is constructed for a maximum pressure
of 295 kg/cm2 and the normal pressure is about 245 kg/cm2 .
The reaction temperature in the catalyst bed is 380C -520C.
Synthesis gas after compression to about 245 kg/cm2 pressure
is passed over iron catalyst in a radial flow reactor.
A part of the synthesis gas about 17% is converted to ammonia.
54. Ammonia Synthesis
Converter effluent gas is cooled in BFW pre heater from 370°C
to 204°C.
Gas is then cooled in hot heat exchanger to 80°C by preheating
converter feed gas.
The syn. gas is cooled to 41°C in water cooler & to 21°C in cold
exchanger, by preheating converter feed gas.
Final cooling/ liquefaction of gas takes place in 1st & 2nd Amm.
Chiller.
The condensed NH3 is separated from syn. gas in ammonia
separator.
56. Ammonia Recovery Unit
Purge Gas
Off Gas
(V-502 & V-510)
(From Loop)
Saturated Steam
Purge Gas to
Utilities
Off Gas to
Utilities Off Gas
Absorber Distillation
Column NH3 Reflux Drum
NH3 Condenser
NH3 Reflux
Pump
Liquid NH3 to V-502
Reboiler
Steam Cond.
HP
Circulation
Pump
LP Circulation Pump
Lean
Solution
Cooler Rich/Lean
Solution
Exchanger
57. AMMONIA STORAGE T-5101
Product ammonia storage is at atmospheric pressure and
-33oC with tank pressure controlled by compressors. Pressure
safety valves are installed for protection against high pressure
and vacuum breaker against very low pressure.
Capacity = 5000 MT
Operating Pressure = 250-500mmwc
Operating Temperature = -33C
58. Ammonia Storage T-5101 / T-1101
• Temperature and pressure conditions maintained by a set of
two reciprocating compressors K-1101 A/B, K-5101 A/B.
• One of which is diesel and the other motor driven.
• Ammonia vapors from storage top are sucked by compressors,
compressed, cooled / condensed and fed back to the storage
maintaining operating temperature and pressure conditions.
