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(LTS) Low Temperature Shift Catalyst - Comprehensive Overview
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(LTS) Low Temperature Shift Catalyst - Comprehensive Overview

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Purpose …

Purpose
Chemistry
Operating Conditions
Catalyst Activity
Poisons
By-Product Formation
Effects of Water
Catalyst Requirements
VSG-C111/1122 - Series

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  • 1. Low Temperature Shift Catalyst By: Gerard B. Hawkins Managing Director, CEO
  • 2. Conventional Hydrogen Plant
  • 3. Low Temperature Shift  Purpose  Chemistry  Operating Conditions  Catalyst Activity  Poisons  By-Product Formation  Effects of Water  Catalyst Requirements  VSG-C111/1122 - Series
  • 4. LTS - Purpose  Generate H2 from steam - improve plant efficiency  Convert CO to CO2 for easier removal • CO is converted to CO2 in two stages of shift conversion  LTS is the second stage of shift conversion to generate H2 • Residual CO conversion - critical to operating economics • Reduce CO levels to typically 0.3 mol% (dry)
  • 5. LTS - Chemistry CO + H2O ⇔ CO2+ H2 ∆H = -41.1 kJ/kgmol • Reaction catalyzed by Cu for LTS • CO lowered from typically 3% to 0.3% • High conversion is favored by – Low temperatures – High steam concentration • Typically accomplished using copper on a zinc-alumina support Cu
  • 6. LTS – Typical Operating Conditions SOR EOR Temp (°F) 356 - 392 410 - 446 CO (vol%) 3 – 5 Temp (°F) 410 - 518 CO (vol%) 0.2 – 0.3 CO + H2O CO2 + H2 Inlet Outlet Inlet temperature ≥ 27°F above dew point
  • 7. LTS - Temperature Profile Top Bed Depth Bottom Temperature Ageing Movement • Ageing mechanism is gradual poisoning
  • 8. LTS - Catalyst Activity  Good, stable catalyst activity • Maximum conversion of CO to CO2 • High kinetic rate at low LTS inlet temperatures  Conversion limited to equilibrium  Operational measure of activity: • temperature gradient through catalyst bed • higher activity gives steeper gradient
  • 9. LTS - Catalyst Activity  Activity is NOT directly related to Cu content or Cu surface area • Cu content must be highly dispersed and stabilised (hence content is not a good measure) • Cu crystal phases and structure important to activity (therefore surface area is not a direct measure)  Only real test is in laboratory under faithfully reproduced plant conditions and on operating plants • Initial activity may not have any relationship with long term activity retention
  • 10. LTS – Catalyst Activity  ATE (approach to equilibrium) is usually very close • CO slip not impacted by activity for most of catalyst life • Does not affect movement of temperature profile through bed  Minimum inlet temperature restricted by dew point • Not always possible to reduce inlet temperature to optimal value to take advantage of activity Not the most important parameter!
  • 11. LTS - Temperature Profile Top Bed Depth Bottom Temperature Ageing Movement • Ageing mechanism is gradual poisoning Goal: Slow the rate of temperature profile movement down the bed
  • 12. LTS – Catalyst Poisons  Sulfur • Powerful poison • Trapped by the catalyst as Cu2S and ZnS  Chloride • Severe poison • Reacts with copper and zinc to form chlorides • CuCl formation provides a mechanism for loss of activity by sintering
  • 13. LTS - Mechanism of Sulfur Poisoning ZnO Cu ZnO Cu Zn2+ Cu ZnO Cu Adsorption on Copper Surface Mobility Surface Sulphide Formation Bulk Sulphide Formation S S ZnS
  • 14. LTS - Chloride Poisoning  Chloride reacts with copper to form CuCl (mp = 430oC)  CuCl formation provides a mechanism for loss of activity by sintering  Requires well dispersed and stabilized copper to minimize the effect of chloride
  • 15. Chloride Poisoning of LTS Catalysts Chlorided LTS Non-chlorided LTS Copper clusters normal sizeCopper clusters sintered Lost surface area
  • 16. Chloride Poisoning of LTS Catalysts Chlorided LTS Sintered Copper ball large surface area loss
  • 17. Effect of Particle Size on Poisons Resistance 0 20 40 60 80 100 Cumulative Chloride Level COconversion(%) 0.3 - 0.6mm 0.6 - 1.0mm 1.18 - 1.4mm 1.4 - 1.7mm •Poisoning reactions with H2S and HCl are strongly diffusion limited •Poisons resistance and activity can be increased by increasing the pellet geometrical surface area
  • 18. LTS - By Product Formation • Methanol – Effect quality of CO2 – Quality of process condensate • Environmental legislation • Increased treatment costs – Odor in CO2 vent • Can produce amines • When vented can be a nuisance – Other oxygenates such as ethanol, ketones
  • 19. LTS - By Product Formation • Methanol Formation CO2 + 3H2 <====> CH3OH + H2O • MeOH increases with – High Temperatures – High inlet CO levels - increases LTS temperature rise – low S:C ratio – Low space velocity / catalyst bed volume • MeOH production decreases rapidly in the first few months of LTS catalyst operation
  • 20. • Condensate – If catalyst is operated at too low temperature • Waste Heat Boiler Leaks – Wetting then evaporation reduces strength significantly – Can cause catastrophic failure due to thermal shock – Loss of activity due to blocking of active sites – Pressure drop increase • catalyst break-up • boiler solids fouling catalyst LTS - Effects Of Water
  • 21. LTS - Effects Of Water • Water will dissolve soluble poisons – wash poisons deep into the bed – Increase affected bed depth – accelerate change-out of the catalyst Remember CuCl2 is soluble in water!
  • 22. Key Performance Requirements  Poisons Resistance • Self guarding capacity  Selectivity • Minimize by-product formation (methanol)  Activity • Minimize CO slip • With minimal catalyst volume  Strength • Withstand upsets such as condensation
  • 23. VSG-C111/112 Superior Poison Resistance Low Methanol By-product Options High Activity High Strength Extended Catalyst Life Short Load Potential to fit T/A Cycles Maximize Hydrogen Production Address Environmental Concern Resilient
  • 24. Superior Poison Resistance
  • 25. Improved Poison Retention using VSG-C111/112 series High sulfur retention Typical = 1% at top & 0.1% at the bottoms Impact of chloride poisoning on CO conversion
  • 26. Extra Chloride Poisons resistance  Applications confirm expected activity for CO and low methanol.  Additional benefit is the enhanced ability to chloride guard. • Caesium and potassium have the highest driving force for chloride. • This is shown by the fact that CsCl and KCl will be formed at very low levels of HCl.
  • 27. Equilibrium HCl Concentration
  • 28. Chloride Guarding Properties of VSG-C111/112 series • Very stable chlorides are formed Chloride Mp (o C) Bp (o C) CuCl 430 1490 ZnCl2 283 732 CsCl 645 1290 KCl 770 1500 subl
  • 29. Mechanism of Chloride Resistance ZnO Cu Adsorption on Potassium HCl CsCl ZnOCs Bulk Chloride Formation K and Cs protect the Cu/ZnO lattice by preferentially reacting with and trapping chloride poison Cu
  • 30. Sulfur Poisoning & Surface Area Competitors VSG-C111/112
  • 31. 2 4 6 8 10 12 14 16 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Sample Depth (ft) Poison Level (%) Cl (%) S (%) Poison Profile for VSG-C111, Chinese Hydrogen Plant Sulfur & Chloride Retention of VSG-C111/112 = 13,000ppm!
  • 32. Relative Impact of Activity and Poison Base (VSG-C111) +20%act +20%poison
  • 33. Low By-product Formation (Methanol)
  • 34. Plant Performance  Optimized alkali promoters to achieve high activity for shift conversion while reducing methanol synthesis --------VSG-C111 ---------VSG-C112 Plant Data
  • 35. Laboratory Testing Product Methanol Activity VSG-C112 0.18 Comp A low MeOH 0.26 Comp B low MeOH 0.33
  • 36. High Activity
  • 37. Activity Comparison (Laboratory) Minimize CO slip 0.20 0.22 0.24 0.26 0.28 0.30 0.32 0.34 0 2 4 6 8 10 Time on-line (years) COslip Com petitor A KATALCO 83-3X Com petitor C ---------- Competitor A ---------- VSG-C112 ---------- Competitor C
  • 38. Case Study: Longer Life (1700 stpd China Ammonia Plant)  Previous competitive charge achieved only 3-yr life before high CO slip (> 0.3 mol%) when 4-yr was expected  Replaced with VSG-C112 and operating 5+ yrs with less than 0.25 mol% $$$ Saved ~ $170,000 + Avoided Unscheduled S/D + 12-month Extension on T/A
  • 39. High Strength
  • 40. Relative Strengths of Fresh and Reduced Catalyst  VSG-C112 series formulated to have high strength after reduction VSG-C112 Competitor A Competitor B
  • 41. Horizontal Crush Strength after Reduction and Condensing Steam Conditions  Compares relative strength of VSG-C112 and competitive low methanol products VSG-C112
  • 42. Conclusions  VSG-C112 excels over all products with • More than adequate activity • Poisons resistance at least equal to a ‘famous and soon to be obsolete’ guard material with claimed ‘unrivalled poisons resistance’ • The lowest by-product Methanol in the industry  So for long life, low CO slip, Low Methanol VSG-C112 is the winner
  • 43. Catalyst Characteristics  VSG-C111 Copper oxide/Zinc Oxide/Alumina  VSG-C112 As above, promoted by alkali metals
  • 44. Lab Based Test Program  Ability of the Topsoe LSK Guard to withstand chloride poisoning relative to VSG-C112  Determined in the laboratory using an accelerated poisoning test.  In the test a guard layer of the catalyst sample is placed above a main bed of VSG-C111 catalyst and the CO conversion is measured using LTS gas containing very low levels (50 ppb in this case) of HCl.
  • 45. Chloride resistance test rig LTS Feed gas (60% H2, 21% N2, 16% CO2, 3% CO) with 50 ppb Chloride poison addition Analysis of CO conversion Standard bed Test bed LSK Analysis of CO conversion Standard bed VSG-C111 Test bed VSG-C112 VSG-C111
  • 46. Chloride poison test results % Conv vs Wt Cl addition (gms) Run No PR133 - 50 ppb HCl addition 0 10 20 30 40 50 60 70 80 90 100 0 0.0005 0.001 0.0015 0.002 0.0025 0.003 0.0035 0.004 0.0045 Wt Cl addition (gms) %Conversion PR133B - U4676 Topsoe LSK PR133C - H1106K Std 83-3XVSG-C111
  • 47. Chloride poison test results TOPSOE LK-823 and LK-821-2 1ppm HCl addition Charged as guard beds (0.2mls) above main beds Std 83-3 (0.4mls) Main Bed SV ~ 127000 0 20 40 60 80 100 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 Wt Cl addition (gm) %conversion PR59 - 83-3X PR59 - LK-823 PR59 - LK-821-2 PR59 - 83-3KVSG-C111
  • 48. Overall comparisons Activity/selectivity on volume comparison Catalyst Relative Activity(v/v) Relative Methanol Make(v/v) LSK 0.52 0.44 LK 821-2 1.20 0.88 VSG-C111 1.18 0.20
  • 49. Competitive Summary
  • 50. Laboratory Poisoning Data Analysis of CO conversion Standard bed Test bed Cat B Analysis of CO conversion Standard bed Test bed Cat C LTS Feed gas (60% H2, 21%N2, 16% CO2, 3% CO) with Chloride poison addition Analysis of CO conversion Standard bed VSG-C111 Test bed Cat A Analysis of CO conversion Standard bed Test bed Cat D VSG-C111 VSG-C111 VSG-C111
  • 51. How do We Compare? Product Relative Poisons Absorption * VSG-C111 1.0 VSG-C112 2.13 Comp A Guard ** 2.1 Comp A std 1.0 Comp A low MeOH 1.28 Comp B std ? Comp B low MeOH 0.70 * Chloride pickup relative to VSG-C!!! measured by CO slip vs time and chloride analysis on spent material ** Guard with almost no sulfur capacity and very low activity

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