Steam Reforming - Types of Reformer Design
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Four main types Types of Reformer Design Pre reformers Primary reformers Main different designs Secondary reformers Compact reformers
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Steam Reforming - Types of Reformer Design
- 1. Types of Reformer Design Gerard B. Hawkins Managing Director GBH Enterprises Ltd.
- 2. Four main types • Pre reformers • Primary reformers ◦ Main different designs • Secondary reformers • Compact reformers WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
- 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. • 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.
- 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. 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. • 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.
- 12. Upper Firing Level Lower Firing Level Convection Section Fluegas Fans Cell 1 Cell 2 Tubes WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
- 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. 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. • 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. 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. Pigtail Tube Burner Outlet Collector Peephole Burner Burner Burner Fluegas Extraction WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
- 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. 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. • 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.
- 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.
- 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. Offered by • Howmar ◦ Now designing Top Fired furnaces • Howe Baker ◦ Now designing Top Fired furnaces • Chemico WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
- 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. Burner Tube Feed Header WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
- 38. Burner Tube Fuel Header WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
- 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. 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. • 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. 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. Steam Secondary Reformer Steam + Gas Air / Oxygen GHR WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
- 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. • 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. Gas & Steam Scabbard Tube Catalyst Bayonet Tube Support Grid End Cap Hot Reacted Gas WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
- 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. • 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. • 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. • 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.
- 57. • APCI / KTI • EHTR • Kellogg • KRES • Uhde • CAR • GIAP • Tandem • Johnston Matthey • GHR WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.
- 58. Feed & Steam In To Heat Recovery Catalyst Tube Perforated Distributor Reformer Effluent Cylindrical Distributor WWW.GBHENTERPRISES.COM GBH Enterprises Ltd.