Steam Reforming - Types of Reformer Design

Steam Reforming - Types of Reformer Design

1. 1. Types of Reformer Design Gerard B. Hawkins Managing Director GBH Enterprises Ltd.
2. 2.  Four main types • Pre reformers • Primary reformers ◦ Main different designs • Secondary reformers • Compact reformers WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
3. 3. • Need ◦ To contain the catalyst - use tubes ◦ High heat transfer area - lots of narrow ID tubes ◦ To supply heat - combustion of fuel ◦ To distribute feed - headers ◦ To collect effluent - headers ◦ To supply fuel/combustion air - headers & duct ◦ To contain combustion gases - casing ◦ To recover heat - flue gas duct and coils WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
4. 4. • Three main types considered ◦ Top Fired ◦ Foster Wheeler Terrace Wall ◦ Side Fired • Many other types ◦ Not considered ◦ Not encountered frequently ◦ Same principles still apply WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
5. 5. TopBottom Side Wall WWW.GBHENTERPRISES.COMWWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
6. 6. Tube Support Pigtail Burner Tube Coffins Exit Header WWW.GBHENTERPRISES.COM
7. 7. Transfer Line Risers Tubes WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
8. 8.  Nearly all heat transfer is by radiation  Radiation from the flue gas to the tubes  Little direct radiation from refractory to tube  Refractory acts as a reflector  Radiation from flame to tube at tube top WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
9. 9. Top Fired Temperature Profiles 800 900 1000 1100 1200 1300 1400 1500 1600 0 20 40 60 Distance Down Tube (ft) ProcessandOutside TubeWall Temperature(°F) 1400 1600 1800 2000 2200 2400 2600 2800 FluegasTemperature (°F) Outside Tube Wall Temperature Process Gas Temperature Fluegas Temperature WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
10. 10. • The key advantages of this design are • Small catalyst volume • A relative small number of burners • Combustion air preheat is simple to install • The key disadvantages of this design are ◦ High heat fluxes at the top of the tubes can lead to carbon formation and hence to hot bands • The heat flux down the tube can not be varied • Burner control is coarse due to the low number of burners used on top fired reformers • A temperature pinch between the flue gas and process gas at the exit of the tubes WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
11. 11. Air BFW MP Steam HP Steam Fuel NG Feed WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
12. 12. Upper Firing Level Lower Firing Level Convection Section Fluegas Fans Cell 1 Cell 2 Tubes WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
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14. 14. • Nearly all heat transfer is by radiation from flames and refractory ◦ Major portion is from refractory ◦ Some from flame ◦ Some from flue gas • Heat is transferred from flame to the walls ◦ By convection/radiation Radiative heat flows Convection WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
15. 15. Foster Wheeler Temperature Profiles 800 1000 1200 1400 1600 1800 2000 0 20 40 60 Distance Down Tube (ft) Temperature(°F) FluegasTemperature (°F) Outside Tube Wall Temperature Process Gas Temperature Fluegas Temperature WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
16. 16. • The key advantages of this design are, ◦ Ability to alter the firing between the two levels to either,  Reduce methane slip,  Or increase the flue gas temperature and hence raise more steam, ◦ A low heat flux which means carbon formation should not be an issue. • The key disadvantages of this design are, ◦ Relatively high catalyst volume, ◦ The feed and fuel gases must be balanced between the two cells, ◦ A large number of burners. WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
17. 17.  Convection section is placed above transfer duct  Elevated - makes modifications difficult  Long tubes in coil  Multiple fans in some cases  Can include auxiliary burners WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
18. 18. Pigtail Tube Burner Outlet Collector Peephole Burner Burner Burner Fluegas Extraction WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
19. 19. Tubes Peephole Burners WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
20. 20. Staggered Single Lane WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
21. 21. • Nearly all heat transfer is by radiation from flames and refractory ◦ Major portion is from refractory ◦ Some from the flames - less than for Foster Wheeler • Some from flue gas • Heat is transferred from flame to the walls ◦ By convection/radiation Convection Radiative heat flows WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
22. 22. Side Fired Temperature Profiles 800 900 1000 1100 1200 1300 1400 1500 1600 1700 0 10 20 30 40 Distance Down Tube (ft) ProcessandOutside TubeWall Temperature(°F) 1400 1500 1600 1700 1800 1900 2000 2100 2200 FluegasTemperature (°F) Outside Tube Wall Temperature Process Gas Temperature Fluegas Temperature WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
23. 23. • The key advantages of this design are, ◦ Ability to alter the firing between the burner levels to either,  Reduce methane slip,  Or increase the flue gas temperature and hence raise more steam, ◦ A low heat flux which means carbon formation should not be an issue. • The key disadvantages of this design are, ◦ Relatively high catalyst volume, ◦ The feed and fuel gases must be balanced between the two cells, ◦ A large number of burners. WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
24. 24. WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
25. 25.  Issues • Variation of tube wall temperature • Tubes are at different distances from burners • Leads to high methane slip • Variability of tube life WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
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28. 28. • Most of these reformers are ◦ Upfired ◦ Upflow ◦ Therefore same as a top fired reformer • Small plant capacities • Always have uneven heat flux and therefore un-even temperatures • One side hotter than the other WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
29. 29.  Offered by • Howmar ◦ Now designing Top Fired furnaces • Howe Baker ◦ Now designing Top Fired furnaces • Chemico WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
30. 30. WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
31. 31. • Use low grade heat from flue gas duct to preheat air • Maximize efficiency as stack temperature is reduced • Minimizes fuel used • No preheating in primary of the combustion air • Must ensure symmetry ◦ Prevents mal-distribution WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
32. 32. Burner Tube Feed Header WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
33. 33. Burner Tube WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
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38. 38. Burner Tube Fuel Header WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
39. 39. Burner Tube WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
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41. 41. WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
42. 42.  Main types include • Gas Heated Reformer (GHR) • Advanced Gas Heat Reformer (AGHR) • Enhanced Heat Transfer Reformer (EHTR) • KRES WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
43. 43.  Aim is to • Minimize plot area ◦ Eliminate large fired box ◦ Eliminate convection section • Maximise heat integration • Eliminate HP steam system WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
44. 44. • Developed for ammonia process - LCA • Early 1980’s - Paper exercise • Mid 1980's - Sidestream unit at Billingham • Mid 1980's - LCA design developed • Late 1980's - ICI Severnside plants start up • 1991 - BHPP LCM plant designed • 1994 - BHPP plant start up • 1998 - AGHR Start Up • 1998 - MCC Start Up WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
45. 45. Purifier Saturator GHR Secondary Converter Preheater Purge to fuel Topping Column Refining Column Process condensate water Fusel oil Natural gas OxygenSteam Refined methanol Purge Crude methanol WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
46. 46. Steam Secondary Reformer Steam + Gas Air / Oxygen GHR WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
47. 47. Secondary Reformer GHR Syngas Gas/steam 425`C 701`C 975`C 515`C 742`C 21,000 Nm3/Hr Oxygen30`C 1200`C 2,590 Nm3/Hr 43.7 Barg 39.2 Barg 38.6 Barg 37.9 Barg 22.0% Methane 16.6% Methane 0.4% Methane 40.6 Barg WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
48. 48. • Shellside heat transfer usually poor • Minimize tube count with expensive alloys • Tubes are externally finned • Designed as double tubes • Sheath tube • Produces much smaller tube bundle • Allows scale up to higher capacities Catalyst tube Fins Double tube Hot shellside gas WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
49. 49. Gas & Steam Scabbard Tube Catalyst Bayonet Tube Support Grid End Cap Hot Reacted Gas WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
50. 50. Gas/SteamHot gas Twin tubesheets Refractory Syngas WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
51. 51. WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
52. 52. • GHR operates in extremely corrosive duty • Metal dusting - catastrophic carburization • Need for materials research • Suitable high temperature alloys identified • Many years of operation in LCA plants • Also confirmed in Methanol plant WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
53. 53. • Retain • Series reforming scheme • Shellside heat transfer enhancement • Mechanical & process design methods • Change to • Non bayonet design • Hot end tubesheet • Sliding seal system WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
54. 54. • Novel seal system • Prevents leakage from tubeside to shellside • Not sensitive to wear of sliding surfaces • Allows independent tube expansion • Proven in full scale pilot plant tests WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
55. 55. • Easier to replace tubes • Easier to load catalyst • Capacity of up to 6,500 mtpd in single shell ◦ Would need 2 conventional primaries WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
56. 56. WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
57. 57. • APCI / KTI • EHTR • Kellogg • KRES • Uhde • CAR • GIAP • Tandem • Johnston Matthey • GHR WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
58. 58. Feed & Steam In To Heat Recovery Catalyst Tube Perforated Distributor Reformer Effluent Cylindrical Distributor WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.