1. Methane Steam Reformer Re-Tube Evaluation By Gerard B. Hawkins Managing Director, CEO

2. Contents Design methodology applied Mechanical design Process design Case studies Why work with GBHE ? 3. Introduction The tubes in a primary reformer are a key consumable Different to the majority of hardware on a synthesis gas plant They have a limited life They fail due to creep damage 4. Design Methodology Understand present operation Base Case - simulate existing reformer At normal conditions Using existing tube design Determines the required minimum performance for all other cases Determines the base line life for all other cases 5. Design Methodology Then select a tube material to use Always go for an improved metallurgy Select a catalyst type to give required benefits Initial select existing catalyst but like for like catalyst change may not be optimal Look at effect of large matrix catalyst and change size Simulate re-tube case Determine pressure and temperature profile Determine stress () and use Larsen-Miller plot to determine design temperature 6. Design Methodology Must be careful with stress data Some tests have been conducted over a short period of time May not be representative GBHE has reviewed manufacturers stress data and eliminated any dubious data There is still a large degree of variation Therefore use a percentage of the average stress data 7. Design Methodology Average Reported Stress Design Curve 80% of Average Reported Stress Temperature Stress 8. Design Methodology Deduct off a margin to give Maximum Allowable Operating Temperature (MAOT) Check if MAOT is greater than maximum predicted temperature Increase/decrease tube wall thickness if required 9. Typical Options Typical to upgrade to a modified micro-alloy Such as H39WM, XM or KHR35CT Use minimum sound wall thickness of 8 mm Keep outside diameter constant Allow inside diameter to be increased Can install smaller catalyst and keep pressure drop below that of base case Or install a larger pellet and generate large pressure drop benefits 10. Typical Tube Compositions HK40 Alloy HK40 20% Ni 25% Cr IN519 Alloy IN519 24% Ni 24% Cr 1% Nb 36X Manaurite 36X (Pompey) 33% Ni 25% Cr 1% Nb H39W Alloy H39W (APV) 33% Ni 25% Cr 1% Nb H39WM Paralloy H39WM 35% Ni 25% Cr 1% Nb + Ti XM Manaurite XM 33% Ni 25% Cr 1% Nb + Ti 11. Relative Allowable Stresses 700 720 740 760 780 800 820 840 860 880 900 920 940 960 980 1000 2 5 10 20 50 100 200 Temperature C HK40 IN519 H39W 36X XM 12. Typical Tube Upgrades If using HK40 or similar Replace with HP or HP Mod Can get a large change in performance due to large reductions in tube wall thickness If using HP Replace with HP Mod Can get smaller changes in performance since the reduction in tube thickness is smaller 13. Options for Catalyst Optimization A re-tube can allow for an optimization of the catalyst loading since the tube ID can be increased If tube wall temperature are limiting Re-tube will reduce peak tube wall temperatures since there is more catalyst and hence more reaction Can install a smaller shape - no increase in pressure drop 14. Options for Catalyst Optimization Pressure drop will be reduced Can reduce even further by installing larger catalyst matrix Allows plant rate increases Reduce flue gas temperature Allows for plant rate increases Remove coil skin temperature limitations Reduced ATE Reduces methane slip 15. Example - Ammonia Plant By optimizing both the tube ID and catalyst combination, achieved, Reduction in ATE Reduced pressure drop by 60% Reduced maximum tube wall temperatures by 40C Increase radiant box efficiency And can increase through put by 3% 16. Example - Methanol Plant Name Units Case 1 Case 2 Case 3 Case 4 Tube material n/a HK40 Microalloy Microalloy Microalloy Plate Rate % 100 100 115 105 Wall Thickness mm 13.5 13.5 8 8 Methane Slip mol % 2.80 2.80 2.80 2.2 Exit Temperature C 869 869 869 869 Approach to Equilibrium C 7.3 7.3 5.5 5.6 Pressure Drop bara 5.2 5.2 3.4 3.44 Maximum Tube Temperature C 921 921 910 925 Fluegas Temperature C 1126 1127 1113 1125 Savings US$/yr n/a n/a 1,000,000 340,000 17. Example - Methanol Plant Can reduce ATE and hence methane slip Increase production to realise between 5 and 15% extra capacity worth US$330,000-1,000,000 per year Reduce pressure drop by 1/3rd Increase radiant reformer efficiency 18. Why Work with GBHE ? GBHE has operating experience of steam reformers GBHE has design experience of steam reformers and in particular re-tubes GBHE understands the problems and issues associated with re-tubes This means that GBHE is in a unique position to help with reformer re-tubes 19. Why Work with GBHE ? This model include rigorous modelling of Heat transfer on fluegas and process gas side Kinetic models for Carbon prediction Pressure drop Full tube stress 20. Details of VULCAN REFORMER SIMULATION Also includes effect of Process conditions changes on tube life Coffins Tunnel port effects Naphtha feeds This means that VULCAN REFORMER SIMULATION is becoming a leading primary reformer simulation package 21. Other Issues If the re-tube allows for a plant rate increase then must consider other parts of the plant Fluegas rate will increase Can the fluegas duct coils cope with the increased duty ? Process gas rate through the reformed gas cooling train will rise Can the reformed gas cooling train cope ? 22. Other Issues What will the effect be on the downstream catalytic units ? For example - HTS/LTS What will happen to plant production GBHE has models to perform this analysis Can simulate all unit operations in detail and determine performance post re-tube 23. Middle Eastern Ammonia Plant During discussions re-tube was mentioned Conducted 3 phase approach Process design - US$ 10,000 : 1 days work Fluegas modelling - US$ 20,000 : 10 days work Detailed tube design - US$ 75,000 Performed by a Engineering Contractor 24. Conclusions GBHE has an un-paralleled experience is design and operation of steam reformers GBHE has project management experience of re-tubes GBHE can determine the effect of a revamp using the world leading VULCAN REFORMER SIMULATION simulation model. GBHE can optimize the catalyst loading using the world leading large matrix catalyst GBHE can determine effect of re-tube on downstream and associated unit operations