1. Theory and Operation of Secondary Reformers By: Gerard B. Hawkins Managing Director, CEO

2. Introduction Purpose Key to good performance Problem Areas Catalysts, heat shields and plant up-rates Burner Guns Development of High Intensity Ring Burner Case Studies Conclusions 3. Secondary Reformer Purpose Reduce methane slip to very low levels Around 0.3-0.5 % mol dry For ammonia plants provide feed point for nitrogen required for ammonia synthesis And thereby Ensure optimal H/N ratio Generate heat for transfer for HP steam in Waste Heat Boiler 4. Typical Reforming Configuration Steam Secondary Reformer Steam Steam + Gas Steam Reformer Air / Oxygen500C 780C 450C 1200C 950C 10% CH 4 0.5% CH 4 5. Secondary Reformer Mechanical Details Refractory lined pressure shell Fixed Catalyst bed in lower region Combustion section in upper region Water jackets to keep shell cool Catalyst supported on brick arch 6. Keys to Good Performance Three key components Burner Design Mixing Volume Catalyst All must be designed correctly to maximize performance Air/Oxygen Steam Reformer Effluent To Waste Heat Boiler 7. Keys to Good Performance Again three key components Burner Design Mixing Volume Catalyst - VSG- Z201/202/203 Since using O2 as oxidant, flame temperature is higher Failures are much faster 780C 540`C 2500C 1500C 1100-1200C 975C 1500C 1100-1200C 1300C Note: Oxygen - Methanol Plant Design 8. Secondary Reformer Operation Burner determines mixing performance Air injected at high velocity Forces mixing of air and process gas Combusts only 20% of process gas Must also mix in other 80% Should achieve a uniform mixture Catalyst bed can affect flow patterns 9. Secondary Reformer Combustion Gas feed very hot > 630oC Gas feed contains hydrogen Gas ignites automatically Autoignition >615oC No need for spark or pilot Must maintain gas above 615oC 10. Secondary Reforming Reactions CH4 + 2CO = CO2 + 2H2O 2H2 + O2 = 2H2O Exothermic - gives out heat Flame 2500oC mixed gas 1500oC Steam reforming CH4 + H2O = 3H2 + CO Endothermic - cools down gas Water gas shift CO + H2O = CO2 + H2Slightly exothermic 11. Key Components: Catalyst Problems Catalyst can Exhibit poor activity Unlikely Break up in service Usually linked to a plant upset Suffer physical blockage Alumina vaporization Become overheated and fuse Causes increased pressure drop and gas mal- distribution 12. Key Components: Catalyst Activity Catalyst is exposed to very high temperatures Therefore nickel sinters However once sintered it is very stable Since catalyst operates at high temperature it is difficult to poison Poisons will not stick For ammonia plants will pass through to HTS and then LTS For methanol plants will pass through to methanol synthesis loop 13. Key Components: Catalyst Activity VULCAN Series range of catalysts VSG-Z201/202/203 Size - Mini and Standard plus Elephant Use as a heat shield Shape 5-Hole Quadralobe Quadralobe has +20% more activity than 4-hole Well proven catalysts that are high stable and strong Long lives 14. Key Components: Catalyst Appearance White - loss of nickel Coated in white - alumina vaporization Glazed or blue - very high temperatures Pink crystals - synthetic ruby formation Cause by high temperatures A mixture of refractory and transition metals 15. Key Components: Mixing Performance Good mixing is absolutely essential Poor mixing in mixing zone gives high approach and high methane slip Poor mixing can be due to Poor burner design Insufficient mixing volume Burner gun failure Root cause can be checked with CFD but will not detect burner gun failure 16. Key Components: Burner Gun If burner gun fails then can lead to Wall refractory damage Loss of vessel containment Poor mixing can lead to zones of high temperature Leads to high rate of catalyst sintering Reduction in catalyst activity Increase in approach to equilibrium (ATE) Poor mixing can lead to high flow zones Movement/damage of target tiles or catalyst bed Increased ATE 17. Key Components: Burner Guns Standard Ammonia secondary burners have Small number of large holes Give poor mixing at high rates High risk of overheating bed Methane slip rises rapidly at high rates Burner can be plant limit 18. Key Components: Burner Guns For methanol plants remember that oxidant used in oxygen Gives higher flame temperatures If jet impinges on refractory then refractory will be damaged much more quickly Vessel will fail rapidly As oxidant flow is lower than for an ammonia plant use a different design of burner 19. Key Components High Intensity Ring Burner The high intensity burner differs from the standard burners Large number of small holes: Small flames High degree of mixing: Short mixing distance Oxidant fed evenly into process gas: Good Mixing Insensitive to rate increases Used in ICI Ammonia plants 20. Effect of Operational Changes Air Rate Name Units Base Case Increased Air Rate Plant Rate % 100 100 Air Rate % 100 105 Exit Pressure Bara 39 39 Steam to Carbon to Primary n/a 2.88 2.88 Outlet Temperature C 1000 1026 Methane Slip mol % 0.41 0.41 H/N Ratio n/a 3.00 2.86 Approach to Equilibrium C 14.2 45.1 21. Effect of Operational Changes Pressure Name Units Base Case Increased Exit Pressure Plant Rate % 100 100 Air Rate % 100 100 Exit Pressure Bara 39 40 Steam to Carbon to Primary n/a 2.88 2.88 Outlet Temperature C 1000 1000 Methane Slip mol % 0.41 0.41 H/N Ratio n/a 3.00 3.00 Approach to Equilibrium C 14.2 11.3 22. Effect of Operational Changes Steam to Carbon Ratio Name Units Base Case Decreased Steam to Carbon Plant Rate % 100 100 Air Rate % 100 100 Exit Pressure Bara 39 39 Steam to Carbon to Primary n/a 2.88 2.78 Outlet Temperature C 1000 1002 Methane Slip mol % 0.41 0.41 H/N Ratio n/a 3.00 3.00 Approach to Equilibrium C 14.2 12.2 23. Key Components: Effect of Poor Mixing Poor mixing can be illustrates by assuming a secondary reformer with a high zone of high air flow and a zone with low flow Name Temperature Methane slip Approach Poor Units Too much air Too little air o C 1034 902 Mol % 0.13 1.89 o C 10 10 Mixed 971 0.9 53 Good 957 0.62 10 24. Key Components: Catalytic Heat Shield Bed has to be protected against disturbances Conventional target tiles or alumina lumps used Even these can be moved No longer required: can replace with active catalyst Additional activity improves reforming performance Use VULCAN Series AST Advanced Support Technology Large (35mm) 4-hole shape 25. Key Components Use of CFD for Secondary Reformers CFD modelling very good for secondary reformers BUT time consuming and expensive Building up a library of case studies VULCAN Series Catalysts VSG-Z201/202/203 has extensive experience with CFD for secondary reformers Troubleshooting problems Designing burner guns Validation of modifications Optimization of catalyst quantity 26. Catalyst Bed Air gun Recirculation zones Case Study 1: Insufficient Mixing Volume 1200 C 1400 C 1500 C 1600 - 2100 C Air Gun Catalyst Bed