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Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
Hydrogen Plant - Normal Operations
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Hydrogen Plant - Normal Operations

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Typical controlled variables …

Typical controlled variables
Plant Data analysis
Approach to equilibrium
Prediction of remaining catalyst life
Tube wall temperature measurement

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  • 1. Normal Operation of Steam Reformers on Hydrogen Plants By: Gerard B. Hawkins Managing Director, CEO
  • 2. Contents  Typical controlled variables  Plant data analysis  Approach to equilibrium  Prediction of remaining catalyst life  Tube wall temperature measurement
  • 3. Typical Controlled Variables  Process gas exit temperature  Process gas and steam inlet temperature  Steam/carbon ratio  Process pressure  Furnace parameters • Air preheat temperature • Excess air
  • 4. ExitMethaneSlip(mol%Dry) Catalyst Activity 40% 200% Plant Rate 130% 80% Exit Pressure -1 bar +1 bar Exit Temp(oC) -10 -20 +20 +10 Steam Ratio -10% -8% +8% +10% 5 4 3 2 1 0 Reformer Optimization : Hydrogen Reformer (Top-Fired) Exit Temperature 856oC (1573oF) Note relatively small changes in exit temperature or steam to carbon ratio can have significant effect on exit Methane slip Catalyst activity has relatively less impact
  • 5. Catalyst Activity40% 60% 80% 150% 200% Exit Temp(oC) +10 -20 Steam Ratio +10% -10% Exit Pressure -1bar +1bar Plant Rate 120% 110% 90% 80% 8 6 4 2 Methane-SteamApproach Temperature(oC)Reformer Optimization : Hydrogen Reformer (Top-Fired) Exit Temperature 856oC (1573oF) Catalyst activity has relatively more impact on methane-steam approach to equilibrium temperature
  • 6. MaximumTubeWall TemperatureoC(oF) Catalyst Activity40% 200% 60% Plant Rate 110% 90% 80% 120% Exit Temp(oC) -10 -20 +10 +20 Steam Ratio (Small effect) 890 (1634) 880 (1616) 870 (1598) 860 (1580) 850 (1562) Exit Pressure (Small effect) Reformer Optimization : Hydrogen Reformer (Top-Fired) Exit Temperature 856oC (1573oF) If exit temperature remains constant, then catalyst activity has relatively more impact on maximum tube wall temperatures
  • 7. Monitoring Operations  Furnace Inspection • tube appearance • refractory condition  external hot-spots • burns  flame characteristics  Steam reformer exit temperature measurement • subheader/pigtail temp, measurements  burner trimming  Feedstock purification performance  sulfur/chlorides etc
  • 8. Hot Band Hot Tube SettlingGiraffe Necking Tiger Tailing Reformer Tube Appearance
  • 9. Contents  Typical controlled variables  Plant data analysis  Approach to equilibrium  Prediction of remaining catalyst life  Tube wall temperature measurement
  • 10. Plant Data Analysis  Important to cross-check measured data • gas compositions  inlet steam reformer  exit steam reformer  exit shift reactors(s) • pressures/temperatures at these points • flowrates  recycle hydrogen  hydrocarbon feedstocks  steam (need also steam/BFW HTS feed quench)  fuel & air
  • 11. Plant Data Analysis  Match measured plant data with heat/mass balance • if good match, then data accurate • if poor match, then errors in plant data  Total plant data computer fitting program • can use product rates and compositions etc for cross-checking of data • can suggest likely sources of measurement error
  • 12. Plant Data Analysis  Total plant data fitting • CO conversion across shift converter(s)  temperature increase very accurate due to multiple thermocouples  cross-checks CO analysis AND steam rate • Product rate/composition (methanator exit or PSA product and offgas)  cross-checks feed rate, steam rate and methane in reformer exit analysis • Methanator temperature rise  cross-checks CO slip from LTS and CO2 slip from CO2 removal system
  • 13. Steam Reformer Feed flow (Nm3/hr) Steam flow (tonne/hr) Exit gas temperature (oC) Exit gas composition (mol % dry) H2 N2 CH4 CO CO2 Exit gas flow (Nm3/hr) Steam : dry gas ratio Equilibrium temperature (oC) Approach to M/S equilb.(oC) Steam : carbon ratio Measured Value 1975 11.2 750.0 65.27 - 4.65 9.02 21.05 7.009 Best Fit Value 2459 11.1 765.0 71.37 0 3.23 8.63 16.77 8634 1.1745 755.5 9.5 5.575 Percentage Error 24.5 -1.1 1.4 -9.3 - 30.5 4.3 20.3 Plant data Verification - Poor Fit
  • 14. Plant Data Verification - Poor Fit  Poor fit  Areas to check • feed flowrate • exit methane • exit CO/CO2 Feed flowrate originally quoted as 1.156 tonne/hr naphtha - Revised to be 1.59 te/hr naphtha
  • 15. Plant Data Verification - Revised Fit Steam Reformer Feed flow (Nm3/hr) Steam flow (tonne/hr) Exit gas temperature (oC) Exit gas composition (mol % dry) H2 N2 CH4 CO CO2 Exit gas flow (Nm3/hr) Steam : dry gas ratio Equilibrium temperature (oC) Approach to M/S equilb.(oC) Steam : carbon ratio Measured Value 2644 11.2 750.0 65.27 - 4.65 9.02 21.05 5.244 Best Fit Value 2554 11.2 758.0 71.33 0 3.23 8.68 16.76 8954 1.1384 758.1 0 5.442 Percentage Error -3.4 0.3 0.8 -9.3 - 30.4 3.8 20.4
  • 16. Plant Data Verification - Revised Fit  Better fit for flowrate  Significant error still on reformer exit gas analysis  CH4  CO/CO2 Methane slip originally quoted as 4.65 mol %(dry) - Revised to 3.56 mol % (dry)
  • 17. Plant Data Verification - Final Fit Steam Reformer Feed flow (Nm3/hr) Steam flow (tonne/hr) Exit gas temperature (oC) Exit gas composition (mol % dry) H2 N2 CH4 CO CO2 Exit gas flow (Nm3/hr) Steam : dry gas ratio Equilibrium temperature (oC) Approach to M/S equilb.(oC) Steam : carbon ratio Measured Value 2644 11.2 750.0 69.86 - 3.56 8.24 18.34 5.244 Best Fit Value 2554 11.2 758.0 71.33 0 3.23 8.68 16.76 8954 1.1384 758.1 0 5.442 Percentage Error -3.4 0.3 0.8 -2.1 - 9.4 5.3 8.6
  • 18. Plant Data Measurement - Problem Areas  Sampling/analysing exit gas compositions  Exit temperature from reformer  Flow measurement
  • 19. Exit Gas Composition  CO shift reaction can occur if not quench cooled quickly  CO2 may dissolve in water • dry gas analysis!  Analysis of sample must be taken in the same time frame as the process data recording
  • 20. Exit Reforming Catalyst (mol % dry) "Shifted" Sample Analysis (mol % dry) CH4 4.4 4.2 CO 13.8 10.3 CO2 8.6 11.4 H2 71.9 72.8 N2 1.3 1.3 CO>CO2 CO<CO2 “Shifting” in Gas Sample Note also reduction in CH4
  • 21. Exit Temperature  Heat/mass balance requires temperature exit catalyst  Plant temperature measurement often at inlet to waste heat boiler • large heat losses possible  outlet pigtails, headers, transfer mains Top-fired : 10-20oC (18-36oF) heat loss Side-fired : 25-35oC (45-63oF) heat loss (Air ingress at base of steam reformer can lead to further cooling)
  • 22. Note that hydrocarbon composition variations may effect the metered accuracy and also the steam/carbon ratio calculation Flow Measurement  Hydrocarbon feedstock generally high accuracy • “costing” meter • multiple feed streams may be less accurate  Steam flow often less accurate • error in steam/carbon ratio can have a significant effect on heat/mass balance
  • 23. Plant Data Analysis  Best to record trends • relative changes partially remove  measurement errors  Monitor monthly/quarterly • measures of catalyst activity  methane slip  assuming constant operating conditions • approach to equilibrium • tube wall temperature
  • 24. Plant Data Analysis
  • 25. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 10 20 30 40 MethaneSlip(mol%) Months on line Plant Data Analysis NaturalGasRate(x1000 Nm3/hr) 8 6 4 2
  • 26. Contents  Typical controlled variables  Plant data analysis  Approach to equilibrium  Prediction of remaining catalyst life  Tube wall temperature measurement
  • 27. Approach Tms = Actual T gas - Equilibrium T gas (A.T.E.) Measured Calculated • Measure of catalyst activity • If ATE = O, system at equilibrium • As catalyst activity decreases, ATE increases Approach to Equilibrium CH4 + H2O CO + 3H2⇔
  • 28. Calculation of Approach to Equilibrium 1. Take gas samples and record steam reformer exit temperature 2. Calculate wet reformer exit composition - Hydrogen atom molar balance (inlet/exit) - Calculate steam in exit gas - Convert exit dry gas to wet gas composition 3. Calculate equilibrium temperature corresponding to this exit composition - Use tables or equations 4. Calculate approach to equilibrium
  • 29. Contents  Typical controlled variables  Plant data analysis  Approach to equilibrium  Prediction of remaining catalyst life  Tube wall temperature measurement
  • 30. Case Study  Terraced wall reformer  How much longer will catalyst last (from Jan’08)  Change-out when? • September ‘08 • April ‘09 • September ‘09
  • 31. 11/Apr/06 03/Oct/06 27/Mar/07 18/Sep/07 12/Mar/08 1,320 1,340 1,360 1,380 1,400 1,420 6 7 8 9 10 Date MethaneSlip(m Outlet Temperature Methane Slip Steam Reformer Performance GBH Enterprises Ltd.
  • 32. 10/Feb/04 22/Dec/05 02/Nov/05 12/Sep/06 24/Jul/07 04/Jun/08 0 Design EOR Design SOR Catalyst On- line: Oct ‘02 01/Apr/03 10 20 30 40 Date ApproachtoEquilibrium(oF) Catalyst Performance Monitoring GBH Enterprises Ltd.
  • 33. 1,300 1,400 1,500 1,600 1,700 Date 01/Apr/05 26/May/06 20/Jul/07 12/Sep/08 06/Nov/09 Design temperature Tube wall temperatures (Top) Tube wall temperatures (Bottom) Tube Wall Temperatures TubeWallTemperature(oF) GBH Enterprises Ltd.
  • 34. 0 0.2 0.4 0.6 0.8 1260 1360 1460 1560 Fraction down Tube (%) Tube Wall Temperature Process Gas Delta T 1 Tube Wall Temperatures GBH Enterprises Ltd.
  • 35. Bottom minus Top 01/Apr/06 26/May/07 20/Jul/08 12/Sep/08 06/Nov/09 0 20 40 60 80 100 120 140 -9oF/year Tube wall Temperatures Date GBH Enterprises Ltd.
  • 36. June 06 June 07 June 08 Sep 08 Sep 09 Exit CH4 (mol% dry) 7 7 7 7 7 Exit Temp oC (oF) 787 (1432) 789 (1452) 795 (1463) 795 (1463) 795 (1463) Max Tube Temp oC (oF) 829 (1524) 831 (1528) 838 (1540) 838 (1540) 838 (1540) M/S Equilib. Approach oC (oF) 10 (18) 12 (22) 13 (23) 14 (25) 15 (27) Steam Reformer Data Looks OK to September ‘09 BUT……..….
  • 37. 0 0.2 0.4 0.6 0.8 1 500 600 700 800 900 Fraction from inlet of tube Carbon Formation Catalyst ageing New catalyst Carbon Formation GBH Enterprises Ltd.
  • 38. Activity Decay Factor  Need to consider carbon formation • Accurate model of catalyst activities needed to correctly simulate catalyst ageing  Take data at different times and calculate relative activity • for terraced wall reformer  (i) top 30% slowly poisoned  (ii) middle 30% very slowly poisoned  (iii) bottom 40% sinters very slowly (i) and (ii) account for delta T (iii) accounts for increased approach GBH Enterprises Ltd.
  • 39. Jan 02 May Sep Jan 03 May Sep Jan 04 May Sep Jan 05 May Sep 0 50 100 150 200 250 Today September ‘04 September ‘05 Carbon margin Date CarbonMargin(oF) Carbon Margin with Time GBH Enterprises Ltd.
  • 40. Activity (arbitrary) Time (years) Carbon forming region Initial sintering "Stable" activity Margin Period where carbon can be formed at anytime due to variation in process conditions Catalyst Deactivation (Schematic) GBH Enterprises Ltd.
  • 41. Conclusions #1  In terms of M/S Approach and Tube Wall Temperatures, can run till September ‘05  Concern about carbon margin from April ‘05 onwards • options  change April ‘05 - CHOSEN OPTION  OR run with spare on site and change September ‘05 GBH Enterprises Ltd.
  • 42. Conclusions #2 • Sometimes difficult for operator to predict change-out requirement – Couldn’t rely on M/S Equilibrium Approach and Tube Wall Temperature trending – Needed complex reformer simulation • HOWEVER, recording of historic data from start-of-run conditions allowed accurate assessment by the catalyst vendor – Take data from SOR! GBH Enterprises Ltd.
  • 43. Contents  Typical controlled variables  Plant data analysis  Approach to equilibrium  Prediction of remaining catalyst life  Tube wall temperature measurement GBH Enterprises Ltd.
  • 44. Importance of Tube Wall Temperature Measurement  Need accurate information • Tube life ! • Artificial limitation on plant rate GBH Enterprises Ltd.
  • 45. TubeLife(Years) 850 (1560) 900 (1650) 950 (1740) 1000 (1830) 0.1 0.2 0.5 1 2 5 10 20 Design Effect of Tube Wall Temperature on Tube Life Temperature oC (oF) + 20oC + 36oF GBH Enterprises Ltd.
  • 46. Tube Wall Temperature Measurement  Contact • surface Thermocouple  “Pseudo-contact” • Gold Cup Pyrometer  Non-contact • disappearing filament • infra-red optical pyrometer • laser pyrometer GBH Enterprises Ltd.
  • 47. Surface Thermocouples  Continuous measurement, by condution  “Slotting” can weaken tube wall  Spray-welding leads to high readings  Short, unpredictable lives (6-12 months) Not commonly used for steam reformer tubes GBH Enterprises Ltd.
  • 48. Disappearing Filament  Hand held instrument  Tungsten filament superimposed on image of target  Current through filament altered until it “disappears”  Current calibrated to temperature  Range 800-3000oC (1470 - 5430oF) Very operator sensitive Largely displaced by IR GBH Enterprises Ltd.
  • 49. Infra-red Pyrometer  Easy to use  Need to correct for emissivity and reflected radiation  Inexpensive GBH Enterprises Ltd.
  • 50. Radiation Methods  Measure emitted energy at given wavelength  Use Planck’s Law to give temperature  Correction factors needed • target emissivity  real versus black body • reflected radiation GBH Enterprises Ltd.
  • 51. Tw "e" is the emissivity of the tube Target Tube Tt Refractory Wall Measured Temperature Tm Flame Tf e The Effect of Reflected Radiation from Target Surroundings
  • 52. Measured True Averaged target target background temperature temperature temperature e = emissivity r = reflectance = (1-e) Temperature Correction E (Tm) = e E (Tt) + r E (T’w) GBH Enterprises Ltd.
  • 53. 0.7 0.75 0.8 0.85 0.9 0.95 1 Difference in wall and target temperature oC (oF) 300 200 100 Deg C Deg F (540 F) (360 F) (180 F) 200 150 100 50 0 392 302 212 122 0 Target Emissivity Error in measured tube temperature Theoretical Effect of Wall Temperature (0.9 micron pyrometer) GBH Enterprises Ltd.
  • 54. Laser Pyrometers  Laser pulse fired at target and return signal detected  Can determine target emissivity  Must correct for background radiation  High speed selectivity  Very accurate for flat surfaces GBH Enterprises Ltd.
  • 55. TUBE Laser Pyrometer Laser Pyrometer - Angle of Incidence Scattered laser pulse GBH Enterprises Ltd.
  • 56. Gold Cup Pyrometer  Excludes all reflected radiation  Approximates to black body conditions  High accuracy/reproducibility  But….. • limited access • awkward to use GBH Enterprises Ltd.
  • 57. Tube Furnace Wall Water Cooling To Recorder Gold Cup Lance * Gold Cup Pyrometer GBH Enterprises Ltd.
  • 58. Accurate Temperature Measurement  Combination of IR pyrometer and Gold Cup • Gold Cup allows us to calculate “e” • Full accurate survey of reformer possible with IR GBH Enterprises Ltd.
  • 59. • Measure Tt using Gold Cup • Measure Tm and Tw using Infra Red Pyrometer • Calculate e Calculate "e"Use IR to give Tt with measured T’w and Tm and calculated e Accurate Temperature Measurement E (Tm) = e E (Tt) + (1-e) E (T’w) GBH Enterprises Ltd.
  • 60. A a (Nearby tubes)2 Background Temperature Measurement Background Measurement for Tube A a1 Refractory Wall GBH Enterprises Ltd.
  • 61. 950 900 850 800 750 1742 1652 1562 1472 1382 Temperature(oC) Temperature(oF) 0 0.2 0.4 0.6 0.8 1 Uncorrected Pyrometer Corrected Pyrometer Calculated = Gold Cup Measurements Fraction down tube Comparison of IR pyrometer and Calculated Tube Wall Temperature Measurements GBH Enterprises Ltd.
  • 62. Tube Wall Temperature Measurement - Conclusions  IR typically reads high • top-fired reformer 32oC (58oF) • side-fired reformer 50oC (90oF)  IR with Gold Cup “calibration” • top-fired reformer 2oC (4oF) • side-fired reformer 16oC (29oF) GBH Enterprises Ltd.
  • 63. Summary  Effect of operating variables on performance  Plant data analysis • fitting plant data • problem areas  reformer exit temperature  flow errors  sample analysis shifting  Approach to equilibrium  Prediction of remaining catalyst life  Tube wall temperature measurement GBH Enterprises Ltd.

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