Ammonia Production Process Simulation in Nitrogen Fertilizers Plants and Case study about ammonia converter conversion percent.

1. Ammonia Production
& Applications
Under supervision of :-
Prof. Abeer Shoaib

2. Group members
1) Abd‐Elrahman Shaaban Hussein
2) Abeer Elsayed Abbas
3) Karim Hosny Tawfik
4) Mohamad Ahmed Tawfik
5) Mohamad Hassan Abd‐Elmoula
6) Tassneem Hassan Salem

3. Introduction
• Growth in world population
• The need to increase the agriculture production
• Synthetic fertilizers is the solution
• Why fertilizers derived from Ammonia ?

4. Main uses of Ammonia

5. Fertilizers derived from ammonia:
1‐Urea fertilizer:
• Reactions :
NH3 + CO2 NH2COONH4
NH2COONH4 NH2CONH2 + H2O
2‐Ammonium nitrate
• Reaction :
HNO3 (l) + NH3 (g) NH4NO3 (aq)
3‐Ammonium phosphates
• Reactions :
2NH3 + H3PO4 (NH4)2HPO4 ( DAP )
NH3 + H3PO4 NH4H2PO4 ( MAP )

6. Other Ammonia Applications
• Explosive Industry
• Textile Industry
• Petroleum Industry
• Antimicrobial agent for food products
• Amines manufacture
• CO2 EOR

7. Ammonia Production

8. Ammonia properties
• colorless.
• its density being 0.589 times that of air
• It is miscible with water
• Melting point = ‐77.7 0C
• Boiling point = ‐33.3 0C

9. Ammonia Process
History:
A process for synthesizing ammonia from nitrogen and hydrogen‚ using
high temperatures and pressures and an iron‐containing catalyst‚ was
invented by Fritz Haber at BASF in 1908
N2+3H2 2NH3
In 1909‚ C. Bosch of BASF built a pilot plant
The Haber‐Bosch process has been continuously improved and is still
of major importance worldwide

11. Ammonia Process Steps
• Desulfurization :
• Sulfur content in N.G <10 ppm
• Preheating from 52 oC to 370 oC
1. Hydrogenation :
• convert the organic sulphur species
to H2S over a hydrodesulphurization
catalyst (CO‐MO)
• RSH + H2 RH + H2S
2. H2S removal :
• Zno+ H2S ZnS+H2O

12. Primary Reformer
• Steam Reforming :
• is the reaction of a hydrocarbon, such as methane with water and/or
carbon dioxide, to produce a mixture of carbon monoxide and hydrogen.
• Mixing Desulfurized stream with MP Steam , Preheating to 540 OC
CH4 + H2O CO + 3H2
CO + H2O H2 + CO2
• 90 % of CH4 is converted into synthesis gas (CO + H2)
• Excess steam is used to avoid side reactions such as:
CH4 2H2 + C
2CO CO2 + C

14. Convection Bank
• It`s used to heat :
• Steam ( 380 to 510 ) oC
• Combustion Air ( 50 to 250 ) oC
• Process Air ( 170 to 450 ) oC

15. Secondary Reformer
• A portion of the product gas is burned in the Secondary Reformer with
added air or oxygen so that the gas mixture reaches a temperature that is
over 1,000°C
• Methane reacts with steam at this temperature until only an insignificant
amount remains (0.2 to 0.3 vol %)
CH4 + H2O 3H2 + CO
2H2 + ( N2+O2 ) 2H2O + N2
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
CH4 + O2 2CO + H2 + H2O

17. Waste Heat Boiler

18. Aspen Hysys Tech.
V.8.3Aspen Hysys Version
Actual Data (E.F.C) company Input Data
1‐ Ping Robinson fluid package
2‐ Steam reforming :
• One Equilibrium reactor represent
primary and secondary reformers
3‐ HTS & LTS are Equilibrium reactor
4‐ Methanator is Conversion reactor
5‐ Co2 removal is MDEA unit
6‐ Ammonia Converter is plug flow
reactor
Assumption
Calculated by Hysys Program Results

19. Data Given: Component list of
involved compounds
• Methane
• Ethane
• Propane
• I –Butane
• N ‐Butane
• I – Pentane
• N‐ Pentane
• C6H14
+
• Argon
• Hydrogen
• Nitrogen
• Ammonia
• Oxygen
• H2O
• CO
• CO2
• Sulfur

20. N.G feed
Feed Conditions
• Temp : 30 0C
• Pressure : 32.5 bar_a
• Mwt : 17.99
• Vol flow : 1584.2 m3/h
• Vapour Fraction : 1
Feed Composition
Mole FractionStream
0.9251Methane
0.0367Ethane
0.0177Propane
0.0049I –Butane
0.0051N –Butane
0.0019I – Pentane
0.0012N‐ Pentane
0.0033C6H14
+
0.0041CO2
< 10 ppmSulfur

21. Required :
Ammonia converter feed is 25% N2 & 75% H2 to
produce NH3

22. Reformer Outlet
Conditions Composition

23. Carbon Monoxide Shift
• removes most of the carbon monoxide (CO) & produces more
hydrogen.
CO + H2O H2 + CO2
• The “shift” from carbon monoxide to carbon dioxide generally
occurs in two steps :
1. High Temperature Shift Conversion
• The synthesis gas is passed through a bed of iron
oxide/chromium oxide catalyst at around 400°C and a
pressure of 25 to 28 bar.
• The CO content of the gas is reduced to about 3% (on a dry
gas basis).

24. 2.a Low Temperature shift conversion
• Adding a LT‐shift (adiabatic reactor, inlet
temperature 205 °C) to a HT‐shift reactor
(adiabatic reactor, inlet temperature 370 °C)
• when a Low Temperature Shift (LTS)
converter is installed :
The gas from the HTS is cooled to increase
the conversion, and then it is passed through
the LTS converter
( 99.8 % of CO is converted into CO2)

26. High & Low Temperature Shift
Converter

27. High & Low Temperature Shift
Converter Outlet
Conditions Composition

28. CO2 Removal step
Benfield Process :
• The Benfield (Benson and Field)process removes carbon dioxide,
and other acid gases from industrial gas streams by scrubbing with
hot aqueous potassium carbonate :
K2CO3 + CO2 +H2O 2KHCO3
K2CO3 + H2S KHS + KHCO3
•The aqueous scrubbing solution contains 40% K2CO3 and is circulated
at 110°C in the absorber
• The CO2 is released in the stripper at atmospheric pressure by
heating the solution to 230°C
KHCO3 K2CO3 + CO2

30. MDEA Process
The AMDEA (Activated Methyl Di ethanol amine)process
removes Co2 & H2S and trace sulfur compounds from natural
gas and synthesis gas via pressurized wash with activated
Methyl di ethanolamine
• Advantages:
• Low vapor pressure ( low losses)
• Non toxic
• No crystallization (no need to reclaimer)
• Lowest energy consumption
• No need to corrosion inhibitor (not corrosive ).

31. Amine Plant (Co2 removal)

32. Amine Unit outlet

33. Final Purification of Synthesis Gas
Methanation:
• The synthesis gas at 300 oC still contains 0.1% to 0.2 mole % CO and Co2
impurities in outlet product at 339 oC can be reduced to about 5 ppm
• All of the oxygen compounds must be completely removed TO :
1. avoid poisoning the ammonia synthesis catalyst
2. remove the inert gases (methane‚ argon‚ etc.) to achieve a higher
synthesis conversion per pass
CO + 3H2 H2O + CH4
CO2+ 4H2 2H2O + CH4

34. Methanator

35. Methanator outlet
Conditions Composition

36. Ammonia Synthesis Section
N2+3H2 2NH3
• At the usual commercial converter operating conditions: the
conversion achieved per pass is only 14% to 16%
• The range of pressure is : 150 to 250 bar
• The range of temperature is : 350°C to 550°C
• The Haber recycle loop process is still used to give substantially
complete conversion of the synthesis gas.
• The ammonia is separated from the recycle gas by cooling and
Condensation.

38. Ammonia converter
3 bed one converter 3 bed 2 converters

39. Ammonia Synthesis section

40. Synthesis gas Feed
Conditions Composition

41. Synthesis gas Outlet
Conditions Composition

42. Conversion Discussion
• Today, the maximum conversion of Ammonia
Synthesis reaction according to UDHE design is
16 % .
• This conversion depends on:
• Pressure
• Temperature
• Type of catalyst
• Space velocity

43. Using Aspen HYSYS simulation
program (V8.3)
• We simulated the true ammonia
reactor process using a dynamic
case with many different values
of pressure and temperature
inside these ranges:
• Range of P (50 bar_a : 600 bar_g)
• Range of T (25 C : 395 C)
• Range of Conversion :
Results (0.00 : 38.86)%
• And here is some of these
results in the following table
ConvTP
22.04935285180
21.19854295180
20.28123305180
19.36659315180
18.46488325180
17.57734335180
2.808962245190
5.291055255190
17.19902265190
23.1368275190

44. Effect of pressure on conversion

45. Effect of temperature on conversion

46. Effect of Pressure Drop on conversion

47. Effect of pressure and temperature on
conversion

48. Effect of pressure and temperature on
conversion

49. • Each pressure has an
optimum temperature
that gives the maximum
conversion at this
pressure
• By increasing pressure ,
the optimum
temperature decrease &
Conversion increase.
Conversion Optimum
Temperature
Pressure
5.36238050
13.44320100
19.54295150
23.39280200
26.51265250
29.33250300
31.47240350
32.97235400
35.26220450
36.09220500
37.74210550
38.86205600

50. MS Excel Equation Analysis
• Using the results of Aspen Hysys optimizer V8.3
and Equation analysis tool of MS Excel 2007 ,
Conversion can be calculated from the following
empirical equation:
•
• Where :
• P = Inlet feed pressure in (bar_g)
• T = Inlet feed temperature in (oC)

52. Effect of Catalyst on conversion
• Because of some construction constraints that limit the conversion
percentages which are :
• 1‐ catalyst maximum activity conditions:
• The KATALCOJM S6‐ 10 series and 35‐series catalysts operate at
temperatures in the range 350‐530°C and at pressures of 100‐600
bar.
• The KATALCOJM 74‐series offers superior activity for low pressure
plants, i.e. those in the range 80‐120 bar and has been chosen for
UHDE Dual Pressure process for ammonia plants producing more
than 3,000 mtpd.
• 2‐ Material of construction limits are higher than catalyst limits .
• The main difference between UHDE & KBR ammonia converter is
that KBR uses a new ruthenium‐based catalysts with higher
conversion but UHDE uses Iron‐based catalysts

53. Troubleshooting

54. Reformer
1. Flame impingement:
 Direct
 Indirect
• Causes:
 flue gas misdistribution
 poor burner design
 blockage of ports in burners
2. Metal dusting:
• temperature range “400:800”
• Contact with gases with high carbon activity
 Recommendation :
• Sulfur addition
• Al2O3 coating

55. 3. Bowed tube :
• Causes :
Differential amount of heat
• Recommendation :
change tube according to GBHE recommendation
4. Hot bands :
• Causes :
‐ loss of activity
‐ poor heat transfer
‐ Localized high voidage
‐ Too low steam/carbon ratio
• Recommendation :
‐ The affected tube must be niped

56. Ammonia Synthesis
1) Failure of ammonia level valve
• Cause :
‐ Suddenly level transmitter damage
• Recommendation :
‐ Put valve in manual mode.
‐ Observe the ammonia level by level local site.
‐ Put LHS key on override mode to prevent trip G.
‐ Fix transmitter and return to control mode
2) High pressure synthesis gas
• Cause :
‐ High amount of inert gas.
• Recommendation :
‐ Increase purge gas flow rate.
‐ Blow of stack.

57. SAFETY

58. • IN AMMONIA PRODUCTION THREE POTENTIAL
HAZARD EVENTS CAN BE IDENTIFIED:
1‐ Fire/explosion hazard from the hydrocarbon feed
system.
2‐ Fire/explosion hazard due to leaks in the synthesis gas
generation and purification, Compression, or synthesis
section (75 % hydrogen).
3‐ Toxic hazard from release of liquid ammonia from the
synthesis loop.
• The severe impacts of rare events with explosions
seem to be confined to a radius of around 60 m .
• The ignition temperature is 651 0C.
AMMONIA PRODUCTION AND STORAGE
HAZARDS