Ammonia plant flowsheets
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The document discusses various aspects of ammonia production processes including: 1) Simplified block diagrams of typical ammonia, methanol, and hydrogen production plants showing the main process units. 2) Modern conventional ammonia plant flowsheets have the same main process steps but differ in equipment designs between vendors. 3) Other flowsheet options for ammonia production including the Braun Purifier process, ICI AMV, ICI LCA, dual pressure Uhde process, and Linde LAC process. 4) Additional process modifications and options such as gas turbine drives, pre-reformers, heat recovery techniques, synthesis gas driers, and booster converters.
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Ammonia plant flowsheets
- 2. Chemistry of the Ammonia Process
- 3. Simplified Block Diagram of a Typical 1000 t/d Ammonia Plant
- 4. Simplified Block Diagram of a 2000 MTPD Methanol Flowsheet Methanol Purification Reforming Compression Distillation Synthesis Steam Raising Feedstock (CH ) 4 Water VHT-S103 20 m³ VSG-EZ200 VSG-Z101 40 m³ VSG-Z101 40 m³ VSG-A101 200 m³
- 5. Simplified Block Diagram of a Hydrogen Flowsheet Desulfurization Primary Reforming High Temperature CO Shift VHT-S101 VSG- Cl101 VSG- EZ200 VSG- Z101 VSG- F101 PSA etc SteamNatural Gas Feed Hydrogen
- 6. Simplified Flowsheet for a Typical Ammonia Plant Natural Gas Steam superheater Air Steam 30 bar Steam Steam raising 350 C 200 C Heat Recovery Steam raising Cooling Cooling Reboiler CO Cooling Preheater Heat Recovery Steam Boiler Process Condensate Quench Quench Liquid Ammonia H Hydrodesulphuriser Primary Reformer Secondary Reformer High Temperature Shift Low Temperature Shift Ammonia SynthesisMethanator Carbon Dioxide Purge Gas Cooling 400 Co 390 Co 2 790 C o 550 Co 1000 Co o 420 Co 150 C o 400 Co 470 C o o 220 C o 290 Co 330 Co 2 CO Removal2 220 bar Refrigeration Condensate Cooling Ammonia Catchpot
- 7. Modern Conventional Flowsheets Main process steps are the same for all plants Main differences in equipment design Uhde Top fired reformer Proprietary exit header design Secondary reformer has a riser HP loop with radial flow converter
- 8. Modern Conventional Flowsheets HKBR Primary reformer with manifold/riser Haldor Topsøe Side fired reformer Radial flow converter S-200 S-250
- 9. Other Flowsheet Options Braun Purifier ICI AMV ICI LCA Dual Pressure Uhde Process HKBR KAAP (with/without purifier) Linde LAC H2 Recovery is used on most modern plants
- 10. Braun Purifier Process Primary reformer exit temperature is 700°C Excess air is added to the secondary reformer Methane slip typically around 2-2.5 mol % Excess nitrogen (and methane) cryogenically removed downstream of methanator Also removes water - ammonia synthesis catalyst poison Improved synthesis lives Can reduce SC ratio to 2.7-3.0 Small primary
- 11. Braun Purifier Process Cold Box Purified Syn Gas Waste Gas Raw Syn Gas Feed Effluent Exchangers
- 12. ICI AMV Process As with Braun - utilizes excess air to secondary Excess nitrogen is passed to the loop Loop runs at low pressure (80-110 bara) Use ICI LP Catalyst (74- Series) Uses a saturator to saturate feed gas This raises around 50% of the required steam Can use SC ratio of 2.8 H2 Recovery in loop at loop pressure
- 13. ICI LCA Process Aim at small plant capacities (500 mtpd) Uses the GHR-Secondary concept Excess air is utilized to close heat balance Utilizes an ITS rather than HTS and LTS A saturator for steam raising A PSA system to remove the CO2 and excess N2 A low pressure loop (80 bara) A tube cooled converter or Casale converter No longer actively marketing
- 14. Dual Pressure Uhde Process PGR Unit Make up gas from frontend H2O Ammonia from once through conversion HP- steam C.W.NH3 NH3 C.W. C.W. C.W. HP- steam NH3 NH3 Off-Gas Ammonia from HP loop HP casing LP casing First ammonia converter Second ammonia converter Once through ammonia converter HP- steam Note: Molecular Sieves not shown
- 15. Dual Pressure Uhde Process Benefits of such a scheme realised at 3,000 mtpd + Although this is large capacity - all equipment is proven Note the low pressure converter between stages of synthesis gas machine Makes machine smaller Makes loop pipework 24” Uses Comp. J catalyst
- 16. HKBR Purifier and KAAP Primary Reformer Secondary Reformer Shift & CO2 Removal Purifier CompressionKAAP Meth’n Dryers Recycle Purge To Fuel Feed
- 17. Linde LAC Key features are No secondary reformer Nitrogen is generated cryogenically and added after a PSA unit No HTS/LTS - only Isothermal (ITS) shift No methanation
- 18. Linde LAC Desulfurization Primary Reformer Isothermal Shift PSA Nitrogen Unit Ammonia Synthesis
- 19. Other Flowsheet Options Use Gas Turbine to drive process air compressor Can use effluent as combustion air Has 16-17% O2 and is at 500°C Braun plants Install pre reformer HT Retrofit Many other reasons Remove heat from duct Uprate plant
- 20. Other Flowsheet Options Synthesis Gas driers Reduces H2O in syn gas H2O is a poison Activity increases Ammonia Wash As per Syn Gas driers Booster converters Drop load on loop and allow overall output increase Quenches in Shifts
- 21. Ammonia Flowsheet Data Analysis Tool - VULCAN CERES Looks at all catalytic unit operations Highlights potential issues/in-correct data items Functionality to address flowsheet options Kellogg risers Differential flowsheet conditions (Braun) Use as a basis for Predictions of future performance Predictions of new catalyst options Uprates