Methane Steam Reformer
Re-Tube Evaluation
By
Gerard B. Hawkins
Managing Director, CEO
Contents
 Design methodology applied
• Mechanical design
• Process design
 Case studies
 Why work with GBHE ?
Introduction
 The tubes in a primary reformer are a key
consumable
 Different to the majority of hardware on a
synthesis...
Design Methodology
 Understand present operation
 Base Case - simulate existing reformer
• At normal conditions
• Using ...
Design Methodology
 Then select a tube material to use
• Always go for an improved metallurgy
 Select a catalyst type to...
Design Methodology
 Must be careful with stress data
 Some tests have been conducted over a short
period of time
• May n...
Design Methodology
Average Reported
Stress
Design Curve
80% of Average
Reported Stress
Temperature
Stress
Design Methodology
 Deduct off a margin to give Maximum Allowable
Operating Temperature (MAOT)
 Check if MAOT is greater...
Typical Options
 Typical to upgrade to a modified micro-alloy
 Such as H39WM, XM or KHR35CT
 Use minimum sound wall thi...
Typical Tube Compositions
HK40 Alloy HK40 20% Ni 25% Cr
IN519 Alloy IN519 24% Ni 24% Cr 1% Nb
36X Manaurite 36X (Pompey) 3...
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
Temperat...
Typical Tube Upgrades
 If using HK40 or similar
• Replace with HP or HP Mod
• Can get a large change in performance due t...
Options for Catalyst Optimization
 A re-tube can allow for an optimization of the
catalyst loading since the tube ID can ...
Options for Catalyst Optimization
 Pressure drop will be reduced
• Can reduce even further by installing larger
catalyst ...
Example - Ammonia Plant
 By optimizing both the tube ID and catalyst
combination, achieved,
• Reduction in ATE
• Reduced ...
Example - Methanol Plant
Name Units Case 1 Case 2 Case 3 Case 4
Tube material n/a HK40 Microalloy Microalloy Microalloy
Pl...
Example - Methanol Plant
 Can reduce ATE and hence methane slip
 Increase production to realise between 5 and
15% extra ...
Why Work with GBHE ?
 GBHE has operating experience of steam
reformers
 GBHE has design experience of steam
reformers an...
Why Work with GBHE ?
 This model include
rigorous modelling of
• Heat transfer on
fluegas and process
gas side
• Kinetic ...
Details of VULCAN REFORMER
SIMULATION
 Also includes effect of
• Process conditions changes on tube life
• Coffins
• Tunn...
Other Issues
 If the re-tube allows for a plant rate increase
then must consider other parts of the plant
 Fluegas rate ...
Other Issues
 What will the effect be on the downstream
catalytic units ?
• For example - HTS/LTS
 What will happen to p...
Middle Eastern Ammonia Plant
 During discussions re-tube was mentioned
 Conducted 3 phase approach
 Process design - US...
Conclusions
 GBHE has an un-paralleled experience is
design and operation of steam reformers
 GBHE has project managemen...
Methane Steam Reformer Re-tube Studies
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Methane Steam Reformer Re-tube Studies

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Design methodology applied
Mechanical design
Process design
Case studies
Why work with GBHE ?

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Methane Steam Reformer Re-tube Studies

  1. 1. Methane Steam Reformer Re-Tube Evaluation By Gerard B. Hawkins Managing Director, CEO
  2. 2. Contents  Design methodology applied • Mechanical design • Process design  Case studies  Why work with GBHE ?
  3. 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. 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. 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 (σ) and use Larsen-Miller plot to determine design temperature
  6. 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. 7. Design Methodology Average Reported Stress Design Curve 80% of Average Reported Stress Temperature Stress
  8. 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. 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. 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. 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. 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. 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. 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. 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 40°C • Increase radiant box efficiency • And can increase through put by 3%
  16. 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. 17. Example - Methanol Plant  Can reduce ATE and hence methane slip  Increase production to realise between 5 and 15% extra capacity worth US$330,000-1,000,000 per year  Reduce pressure drop by 1/3rd  Increase radiant reformer efficiency
  18. 18. Why Work with GBHE ?  GBHE has operating experience of steam reformers  GBHE has design experience of steam reformers and in particular re-tubes  GBHE understands the problems and issues associated with re-tubes  This means that GBHE is in a unique position to help with reformer re-tubes
  19. 19. Why Work with GBHE ?  This model include rigorous modelling of • Heat transfer on fluegas and process gas side • Kinetic models for • Carbon prediction • Pressure drop • Full tube stress
  20. 20. Details of VULCAN REFORMER SIMULATION  Also includes effect of • Process conditions changes on tube life • Coffins • Tunnel port effects • Naphtha feeds  This means that VULCAN REFORMER SIMULATION is becoming a leading primary reformer simulation package
  21. 21. Other Issues  If the re-tube allows for a plant rate increase then must consider other parts of the plant  Fluegas rate will increase • Can the fluegas duct coils cope with the increased duty ?  Process gas rate through the reformed gas cooling train will rise • Can the reformed gas cooling train cope ?
  22. 22. Other Issues  What will the effect be on the downstream catalytic units ? • For example - HTS/LTS  What will happen to plant production  GBHE has models to perform this analysis  Can simulate all unit operations in detail and determine performance post re-tube
  23. 23. Middle Eastern Ammonia Plant  During discussions re-tube was mentioned  Conducted 3 phase approach  Process design - US$ 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. 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

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