Revamps for Ageing Ammonia Plants

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This presentation highlights some of the retrofits that can be applied to
Improve efficiency
Increase production

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Revamps for Ageing Ammonia Plants

  1. 1. Revamps for Ageing Ammonia Plants By; Gerard B. Hawkins Managing Director
  2. 2. Introduction  This presentation highlights some of the retrofits that can be applied to • Improve efficiency • Increase production Safety Efficiency Reliability Throughput Environment
  3. 3. Introduction  Why consider a retrofit?  Limitations  Options for retrofits  Problems and Pitfalls  GBHE Catalysts and Retrofits  Conclusions
  4. 4. Why Consider a Retrofit?  Plant is • Inefficient • Has poor economics • Production can be increased by elimination of bottlenecks  Retrofits generally are more cost effective than new plant builds
  5. 5. Plant Limitations  Six main areas that can limit plant performance Primary
  6. 6. Plant Limitations  Six main areas that can limit plant performance Primary Convection Section
  7. 7. Air Compressor and Secondary Plant Limitations  Six main areas that can limit plant performance Primary Convection Section
  8. 8. Plant Limitations  Six main areas that can limit plant performance Primary Convection Section Air Compressor and Secondary Cooling, Shifts and CO2 Removal
  9. 9. Plant Limitations  Six main areas that can limit plant performance Primary Convection Section Air Compressor and Secondary Cooling, Shifts and CO2 Removal Compression
  10. 10. Plant Limitations • Six main areas that can limit plant performance Primary Convection Section Air Compressor and Secondary Cooling, Shifts and CO2 Removal Compression Ammonia Synthesis
  11. 11. Pre-Reformers  Installation of pre-reformer helps to de bottleneck • The primary reformer - reduced box duty • The convection section - heat removal • Eliminates heavies/ poisons  Can increase plant rate by up to 11%  Will affect steam balance
  12. 12. Change Catalyst Shape and Size  By optimizing catalyst size can • Reduce pressure drop by up to 33% • Reduce carbon formation potential  By changing to VULCAN VSG-Z101 can • Reduce ATE/CH4 slip • Reduce Tube Wall Temperatures • Reduce carbon formation potential • Optimize catalyst loading even further
  13. 13. Primary Reformer Re-Tube  By re-tubing reformer can generate large benefits • Reduce pressure drop by 20% • Improve radiant efficiency • Reduce tube wall temperature • Increased plant rate by 3.5% • Further optimize catalyst loading to generate even more benefits
  14. 14. Combustion Air Pre-heat  Installed on many modern plants  Has been retrofitted to many plants  Must have high stack temperature  Allows for large improvements in radiant efficiency • Use less fuel  Can allow for plant increases  Will increase NOx levels • May require NOx reduction system
  15. 15. Options for Secondary Reformers  Install High Intensity Burner Gun  Install improved catalyst • Reduce installed volume - up to 45% • Increase mixing volume  Add excess process air • Requires H2 recovery in loop
  16. 16. VULCAN SG Delta Retrofit for Shift Vessels  By installing a specialized support system we can reduce pressure drop significantly  GBHE can offer the VULCAN SG Delta which can reduce pressure drop by 50%  Allows plant rate increases of up to 0.5%
  17. 17. CO2 Removal Retrofits  Can uprate CO2 removal by • Changing packing • Use more efficient solution  Either will help to reduce reboiler duties • In turn allows reduction in steam to carbon ratio  GBH Enterprises range of catalysts are designed to operate under these lower steam to carbon conditions
  18. 18. Water Removal from Synthesis Gas  Use either molecular sieves or ammonia washing  Can feed synthesis gas to converter inlet • Reduces ammonia content of gas inlet converter therefore increases production • Reduced refrigeration load • No loss of reactants in purge gas
  19. 19. Converter Retrofits  Convert to axial-radial or radial flow  Utilize smaller catalyst • Since reaction is diffusion limited increases reaction rate and therefore increased production • Can improve efficiency by 0.5-1.0 GJ/t • Must look at rest of plant  Converter exit piping and exchangers
  20. 20. Converter Retrofits  Often link with modifications to circulator • Reduce circulation rate and hence power requirement  If converter already modified then can • Modify converter again  Use heat exchange rather than quench • Install high activity catalyst  VULCAN Series VSG-A101 low pressure synthesis  Can be utilized up to 150 bara
  21. 21. Converter Retrofits  Further Options • Add a booster converter  Utilize when main converter has reached limit  Can achieve up to 30% capacity increases  Will need modifications to rest of the plant • Add a synthesis gas converter - for example as done in the Uhde DPUP  Utilize when main converter has reached limit  Can achieve up to 30% capacity increases  Will need modifications to rest of the plant
  22. 22. Hydrogen Recovery  Can increase plant capacity by up to 5% with no other modifications  Either • Cryogenic • Membrane  If adding excess air to the secondary then must install hydrogen recovery • Even greater capacity increases are achievable since methane slip has been reduced
  23. 23. Other Retrofits  Addition of Saturator  Fuel gas preheat  Synthesis gas machine suction chilling  Modification of synthesis gas machine internals  Install AGHR in parallel to existing Waste Heat Boiler  Upgrade utilities
  24. 24. Other Options  There are other options  There are a number of operational modifications that will improve plant performance for no cost • Reduction in steam to carbon • Raising primary exit temperature • Reduce excess air/oxygen in reformer  Energy Audits will help to identify these areas and the benefits of changing process parameters
  25. 25. Plant Revamp Selector Ammonia – Capacity Increases What capacity increase is required ? >15% Front End Catalyst change Re-tube New burner gun VULCAN SG Delta <5% Front End SC Reduction Pre-reformer 5-15% Compression/Loop Syn gas drying High activity catalyst H2 recovery Chill Syn Gas Front End Parallel AGHR Re-tube Loop Booster converter MUG converter
  26. 26. Plant Revamp Selector Ammonia – Efficiency Improvements What efficiency improvement is required ? >1 GJ/t<0.1 GJ/t Front End SC Reduction Fuel preheat CO2 solution change Saturator Chill syngas 0.1-1 GJ/t Front End Combustion air preheat None
  27. 27. Problems and Pitfalls Contractor and Contract  Must carefully select partners • Must have domain knowledge  Design and operations • Must have correct tools • Must be able to supply correct level of detail for study  Must select appropriate contract type • LSTK or Reimbursable • Both have advantages and disadvantages
  28. 28. Problems and Pitfalls Modelling Capability  Must use correct tools  Model the whole plant using a flowsheeting package • Must include all unit operations • Must develop a robust base case • Must validate against plant data • Must understand deviations • Then develop the retrofit case
  29. 29. Problems and Pitfalls Retrofit Details  The customer and engineering contractor must determine • Precise scope for retrofit • Responsibilities • Key deliverables • A detailed and consistent design basis • Time scale and milestones • Review schedules  Summarize as Good Project Management
  30. 30. Problems and Pitfalls Design Basis  Engineering contractor must conduct on site visit • Must work with client • Collect representative plant data • Model and understand plant data • Discuss discrepancies and eliminate • Identify bottlenecks • Identify opportunities for improvement  These form the core of the design basis
  31. 31. Problems and Pitfalls HAZOPs and Commissioning  Must use systematic review method to highlight potential problems with retrofit • HAZOPs are a well proven system • Requires time and buy in from all parties • Results as good as quality of people !  Retrofit will change plant parameters • Must update PFDs and P&IDs • Must update operating instructions • Must take additional care during start up
  32. 32. What Can GBHE Catalysts Offer?  GBHE Catalysts Process Technology has developed a detailed flowsheeting package  GBHE Modelling for AMMONIA includes • Detailed primary reformer model • Models for secondary reformers, shifts, methanation and ammonia synthesis • Can model in detail the synthesis gas machine  Unified, consistent and intelligent process model
  33. 33. What Can GBHE Catalyst Process Technology Offer?  Detail catalyst unit operation models such as the Industry leading VULCAN REFSIM program • Also models for other catalyst unit operations  Detail non-catalyst unit operation models such as • Heat exchange programs • Finite Element Analysis • CFD modelling  One stop shop
  34. 34. What Can GBHE Catalysts Offer?  Domain Knowledge • Operations  Many staff have operations background  Troubleshooting clients plants • Design  Many staff have detailed engineering background  Engineers work on design daily  Work with leading contractors on front end and detailed design issues Catalysts Consulting Services Domain Knowledge
  35. 35. What Can GBHE Catalysts Offer?  Can supply any level of detail for retrofit  Scoping studies • Front End • What are the best options  Front End Engineering • Flowsheets and design of key components  Detailed Engineering • Design of all components of retrofit  A one stop shop for all your revamp requirements
  36. 36. One Stop Shop Case Study Re-tube – Present Model Plant Operator Concept Engineer Tube Supplier Catalyst Vendor Tube Installer Catalyst Handler No Communication Detailed Engineer
  37. 37. One Stop Shop Case Study Re-tube – “One Stop Shop” Model Plant Operator GBHE Concept Engineer Tube Supplier Tube Installer Catalyst Handler Detailed Engineer Seamless Minimum Cost Maximum Benefit
  38. 38. Case Study - How GBHE Works  Strong position due to credibility from previous work  Uprate projects • Feasibility Process Uprate study on Naphtha 115%, 130% or 150% cases • FEEP (Front End Engineering Package, what would be needed?)  115% FEEP adopted • Option evaluations and natural gas feed conversion  Followed by full Engineering Detail Design  Also additional design work on Desulfurization Design Study
  39. 39. Conclusions  Many options for retrofitting an ammonia plant  Must select correct options based on • Require capacity increase • Present bottlenecks  Must select the right contractor  GBHE has all the right expertise and knowledge to develop and design retrofits

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