Methanol Reformer Designs


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Three major types of reformer
Each tackles the duty in different ways
No clear best choice
Choice dictated by Contractor history

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Methanol Reformer Designs

  1. 1. Gerard B. Hawkins Managing Director, CEO C2PT Catalyst Process Technology
  2. 2.  Three major types of reformer  Each tackles the duty in different ways  No clear best choice  Choice dictated by Contractor history
  3. 3. Top Fired Usually Single box with Multiple rows of tubes. Heat load for a Top fired, is in the top one third of the reforming section. Peak tube wall temperature is is this region Pencil Type Flames required Side Fired/Foster Wheeler Side Fired Reformers are usually made up of several identical cells, with each having a single row of tubes The aim of the side fired design is to achieve a more even heat flux profile over the length of the tube, by locating burners the full height of the box.
  4. 4. Top Fired KTI Jacobs ( H & G) Kellogg Lummus Uhde Side Fired Topsoe Selas Howe Baker Chiyoda ICI (Hybrid) Foster Wheeler
  5. 5.  Majority of plants have Top Fired Reformers  Some have Foster Wheeler Reformers  A few have Side Fired Furnaces  Lurgi plants often have an oxygen blown secondary  A few plants have a pre reformer (Statoil and M5000)
  6. 6.  Methanol reformers are large  Largest reformer has 960 tubes  Two to three times the size of an ammonia reformer  Many reformers in the range 600-900 tubes  Why is this ?  All reforming is done in this reformer  There is no secondary  Therefore choose the cheapest design and easiest to scale up  Therefore use Top Fired - Why ?
  7. 7.  Capital Cost  For a reformers of the same size a Top Fired furnace has less equipment than Side Fired or Foster Wheeler  FW and SF duplicate a lot of equipment as there are 2 cells  Side fired are generally less heavily loaded - they have a higher capacity
  8. 8.  Operational Costs  Top fired have a higher radiant efficiency  Typically 50-60%  Side fired furnaces have a lower efficiency  Typically 40-45%  Maintenance Costs  Side Fired reformers have more burners  By a factor of 5 over Top Fired  By a factor of 2 over Foster Wheeler  Side Fired refractory temperatures are higher
  9. 9. Name Methanol Ammonia Steam to Carbon 2.8-3.2 3.0-3.4 Pressure (bara) 15-20 30-35 Exit 1y Temperature (°C) 860-880 740-780 Exit 2y Temperature (°C) n/a 960-980 Tube Count 900-1000 300-400 Maximum TWT (°C) 900-950 800-850 H2 70-73 54-58 CO 14-16 10-12 CO2 7-9 8-10 CH4 2-3 0.1-1.0 N2 0-1 22-26 Comparison of Flowsheets Typical Conditions
  10. 10.  On most methanol plants we only have a primary reformer  Therefore must minimize methane slip from primary  Methane is an inert in the loop  Just like ammonia  Represents an inefficiency  Must be purged out - lose reactants  Purge is burned in reformer  Typically 2/3 of the reformer fuel  (Some plant do sell it !)
  11. 11.  Must therefore run at highest outlet temperature  There is no secondary to drop slip down to very low levels  A steam to carbon of 2.8 to 3.3 allows MPS to be used from steam turbine  Balances out MPS balance  Run at low pressure to minimise methane slip  Does increase compression costs
  12. 12.  No requirement for nitrogen to be added to the process  In fact do not want nitrogen  It’s an inert and will reduce loop efficiency  Oxygen plants are traditionally expensive  Oxygen blown secondary’s have a poor track record  Many failures due to poor burner design  Many failures due to poor vessel/refractory design  Flame temperature is very high (2000°C)
  13. 13.  Historically plants were never built with them  No need for feedstock flexibility  Licensed contractors have their own primary reformer design - based on JMC design in many cases  Topsøe do include them - problems with MgO hydration  Similar to ammonia plants  Therefore there is no great driving force for inclusion  Until now  Mega plants are at limit of reformer design
  14. 14. TopBottomSide Wall
  15. 15.  Nearly all heat transfer is by radiation  Radiation from the fluegas to the tubes  Little direct radiation from refractory to tube  Refractory acts as a reflector  Radiation from flame to tube at tube top
  16. 16. Tube Support Pigtail Burner Tube Coffins Exit Header
  17. 17. Side Fired Furnace
  18. 18. ICI Methanol Foster Wheeler Reformer
  19. 19.  Same for both types  Nearly all heat transfer is by radiation from flames and refractory  Major portion is from refractory  Some from flame (especially in FW)  Some from fluegas  Heat is transferred from flame to the walls  By convection
  20. 20.  Typical catalyst is VSG-Z101  Required to prevent carbon formation  Heat fluxes are very high 100-160 kW/m²  For plants with really high heat fluxes us VSG-Z101  Only two plant shave giant installed  Pressure drop is not an issue (no air compressor)  Heat transfer and carbon formation ARE issues
  21. 21. Weld Hot Band
  22. 22.  Exit temperatures are higher  Therefore inside tube wall temperatures are higher  Heat fluxes are higher  Top fired between 100-140 kW/m²  But some in range 140-160 kW/m²  Ammonia plants typically 80-120 kW/m²  These conditions favor carbon formation
  23. 23.  Several N American Operators had failures at bottom of the tubes  Simulations said lots of margin  New peepholes installed and temperatures measured  Must hotter than expected
  24. 24.  Found in Canada  Unusual Temperature distribution  Checked using dry powder  Up flow at walls  Flame impingement  Modelled using CFD
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