From Gasification to Syngas – Design Considerations

iChemE: Gasification 2014, Rotterdam, Holland, March 10-13, 2014Speaker: Rasmus Trane-Restrup, Email: ratr@topsoe.dk

Agenda

• Gasifier technology• Sour shift• Benchmarking study• Topsøe SSK-10 catalyst• Sulfur polishing

Key findings• Partial quench gasifier + optimal sour shift technology

• Enhances efficiency• Up to 10 % reduction in OPEX (Methanol)

• Reduces CO2 emissions

Topsøe is devoted to…

• Research and development in heterogeneous catalysis• Production and sale of catalysts• Licensing of technology• Equipment supply• Engineering and construction of plants based on catalytic processes

Business areas

• Fertilizer industry• The heavy chemical and petrochemical industries• The refining industry• The environmental and power sector

… and a leading market player

•Market share between 15–25% for established products•Supplier of solutions for 50% of new ammonia plants built within

the last decade•More than 60% of ammonia is produced worldwide on

Topsøe catalyst•Supplier of 40% of catalysts for production of ultra-low sulfur

diesel•>30% market share of hydrogen catalysts•Leading environmental catalysts and technologies•>35% market share of sulfuric acid catalysts•30% market share of FCC pretreatment catalysts

Typical layout for coal gasification plant

AirSeparationUnit

AirSeparationUnit

GasificationGasification Sour shiftSour shiftAcidGasRemoval

AcidGasRemoval

SulfurRecoveryUnit

SulfurRecoveryUnit

SynthesisSynthesis

O2

CO2

CO2/H2S

Sulfuric acid or sulfur

Air

H2O

MethanolDMEAmmoniaGasolineSNG

Coal

HPSteam

H2Oquench

HPSteam

Cooling of the raw syngas from gasifier

•Full quench• Low capital cost• Standard design• Low energy efficiency

•Partial quench• Higher capital cost• Material and maintenance

considerations• High pressure steam production

Sour shift reaction

• CO + H2O ↔ CO2 + H2 + Q• The shift reaction is limited by equilibrium• CO conversion increases with

• High steam content• Low temperature

Equilibrium curve

Temperature

CO

conc

entra

tion

By-product formation

• Methane• CO + 3 H2↔ CH4 + H2O + Q

• Very exothermic reaction• Risk of runaway

• Proprietary Topsøe kinetics for the CH4 formation• Allows optimal and reliable design

Reactor length

H2

Temperature

CH4

Desired sour shift catalyst properties

• Full quench (operation at high S/DG ratio)• S/DG is high,

• Shifts equilibrium towards CO2 and H2

• Limits CH4 formation

• Partial quench (operation at minimum S/DG ratio)• High activity

• Can operate at low S/DG levels• Active at low temperature to reach high conversion

• High selectivity• Low methane formation even at low S/DG

Study of gasifier technology in combination with sour shift

• Comparison of partial and full quench gasifier• Combination with sour shift for production of H2, methanol/FT, and SNG

• Objectives• Evaluate changes in OPEX• Evaluate changes in CO2 emissions

• Assumption• Lower steam export is compensated by aux. boilers

• Higher consumption of coal

Basis for study

Gasifier type Full Quench Partial QuenchOperating temperature, °C 1450 1450Pressure, Bar abs 68 68Radiant cooling, °C n.a. 730Water quench cooling, °C 250 250Steam generated Shift Shift + GasifierCO2 from Aux. Boiler, ton/ton steam 0.375 0.375

Value of steam (118 bar abs) 15 USD/MTSyngas efficiency in MeOH loop 93%

Gas composition from Polk Power Station IGCC, Technical Report,http://www.netl.doe.gov/research/coal/major-demonstrations/clean-coal-technology-development-program/baepgig-tampaig

Hydrogen/ammonia production – Sour shift layout

• High CO conversion is required

• Two or three reactors in series• Inter-reactor cooling by steam production and feed preheating

Equilibrium curve

Temperature

CO

conc

entra

tion

Two stage sour shift unit

MP steam

Shifted gas

2nd sour shiftreactor

1st sour shiftreactor

Feed gas

MP steam

Steamdrum

Coolingtrain

Hydrogen/ammonia production – Results

Hydrogen/ammonia production – Results

• Partial quench + 2 sour shift reactors• Value of additional steam export: $11 per 1000 Nm3 of H2

• Reduced CO2 emissions: 16%

• Partial quench + 3 sour shift reactors• Value of additional steam export: $12 per 1000 Nm3 of H2

• Reduced CO2 emissions: 17%

Study results – Summary

• SNG plant – Partial quench + 2 sour shift reactors• Value of additional steam export: $60 per 1000 Nm3 of CH4

• Reduced CO2 emissions: 28%

• Methanol plant – Partial quench + 2 sour shift reactors• Value of additional steam export: $35 per ton of methanol• Reduced CO2 emissions: 33%

• Hydrogen plant – Partial quench + 2 sour shift reactors• Value of additional steam export: $11 per 1000 Nm3 of H2

• Reduced CO2 emissions: 16%

Features of sour shift catalyst SSK-10

• Active at low temperatures• Allows high CO conversion at low steam/dry gas

• High selectivity at low steam to dry gas ratio• Methanation reaction is limited

• Proprietary kinetics for the CH4 formation• Sour shift can be designed for minimum steam/dry gas ratio without risk of

temperature run away

• Guard beds for carbonyls from gasifiers

SSK-10 high activity at low temperaturesIndustrial example: 3rd bed in an ammonia plant

X(CO)=59 %

SSK-10 high activity at low temperaturesIndustrial example: 3rd bed in an ammonia plant

X(CO)=59 %

X(CO)=86 %

Topsøes SSK-10catalysts

SSK-10 high activity at low temperaturesIndustrial example: 3rd bed in an ammonia plant

X(CO)=59 %

X(CO)=86 %

X(CO)=78 %Topsøes SSK-10catalysts

Sulfur polishing – After acid gas removal

• Sulfur slip from AGR: 100 ppbv to 1 ppmv

• Max. total sulfur to synthesis step: 10 ppbv

• H2S removed by ZnO• ZnO + H2S ⇔ZnS + H2O

• COS• Hydrolyze to H2S: COS + H2Oà H2S + CO2

• Promoted ZnO – HTZ-51

• Mercaptans, CS2 and COS• Copper based catalyst – Haldor Topsøe ST series• Low temperature to inhibit side reactions like methanol formation

Industrial cases – Sulfur polishing

• Qinghua SNG plant – World’s largest SNG plant• Required S removal to < 10 ppbv – preferably lower• Mercaptans, H2S, and CS2 ( ~100 ppb S)• HTZ-5 for H2S and ST-101 for the remaining

• Xianyang methanol plant• Required S removal to < 10 ppbv – preferably lower• COS and H2S ( ~100 ppb S)• Small amounts of H2O added for hydrolysis of COS to H2S• HTZ-51

Final comments

Key findings:• Optimal shift technology enhances efficiency and reduces CO2 emissions

for gasification projects

• Partial quench gasification technology improves overall OPEXsignificantly for FT/MeOH, SNG, H2 and NH3 plants

• Topsøe SSK-10 catalyst provides

• Lower CO2 emissions

• Reduced OPEX

Thank you for your attention!