(LTS) Low Temperature Shift Catalyst - Comprehensive Overview

5,785 views

Published on

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

Published in: Technology, Business
2 Comments
10 Likes
Statistics
Notes
No Downloads
Views
Total views
5,785
On SlideShare
0
From Embeds
0
Number of Embeds
18
Actions
Shares
0
Downloads
970
Comments
2
Likes
10
Embeds 0
No embeds

No notes for slide

(LTS) Low Temperature Shift Catalyst - Comprehensive Overview

  1. 1. Low Temperature Shift Catalyst By: Gerard B. Hawkins Managing Director, CEO
  2. 2. Conventional Hydrogen Plant
  3. 3. Low Temperature Shift  Purpose  Chemistry  Operating Conditions  Catalyst Activity  Poisons  By-Product Formation  Effects of Water  Catalyst Requirements  VSG-C111/1122 - Series
  4. 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. 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. 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. 7. LTS - Temperature Profile Top Bed Depth Bottom Temperature Ageing Movement • Ageing mechanism is gradual poisoning
  8. 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. 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. 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. 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. 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. 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. 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. 15. Chloride Poisoning of LTS Catalysts Chlorided LTS Non-chlorided LTS Copper clusters normal sizeCopper clusters sintered Lost surface area
  16. 16. Chloride Poisoning of LTS Catalysts Chlorided LTS Sintered Copper ball large surface area loss
  17. 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. 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. 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. 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. 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. 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. 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. 24. Superior Poison Resistance
  25. 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. 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. 27. Equilibrium HCl Concentration
  28. 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. 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. 30. Sulfur Poisoning & Surface Area Competitors VSG-C111/112
  31. 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. 32. Relative Impact of Activity and Poison Base (VSG-C111) +20%act +20%poison
  33. 33. Low By-product Formation (Methanol)
  34. 34. Plant Performance  Optimized alkali promoters to achieve high activity for shift conversion while reducing methanol synthesis --------VSG-C111 ---------VSG-C112 Plant Data
  35. 35. Laboratory Testing Product Methanol Activity VSG-C112 0.18 Comp A low MeOH 0.26 Comp B low MeOH 0.33
  36. 36. High Activity
  37. 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. 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. 39. High Strength
  40. 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. 41. Horizontal Crush Strength after Reduction and Condensing Steam Conditions  Compares relative strength of VSG-C112 and competitive low methanol products VSG-C112
  42. 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. 43. Catalyst Characteristics  VSG-C111 Copper oxide/Zinc Oxide/Alumina  VSG-C112 As above, promoted by alkali metals
  44. 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. 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. 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. 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. 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. 49. Competitive Summary
  50. 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. 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

×