Syngas cleaning using absorption and adsorptionand adsorption

Olov Öhrman, ETC

HighBio seminar 2010-05-18

Agenda

• Wash (Chemical or physical absorption)

– Amines

– Alkaline salts

– Physical solvents– Physical solvents

– Example from application in Piteå

• Fixed bed

– Adsorption (physical or chemical)

– Example from application in Piteå

Amines for acid gas removal

• Primary, Secondary, Tertiary

• Hydroxyl group (for water solubility)

• Amine group (for absorption)

• COS and CS2 alsopossible to remove

Examples of amines

• Monoethanolamine (MEA) – used for many years, replaced by better ones. Not suitable for COS and CS2

• MEA-glycol mixtures – dehydration and purification

• Diethanolamine (DEA) – Secondary amine• Diethanolamine (DEA) – Secondary amineused for H2S, CO2,COS and CS2. Lowervapor pressure (less losses, lower pressure)

• Methyldiethanolamine (MDEA) – tertiaryamine used for high CO2/H2S concentrations where a high H2S selectivityis desired. Less corrosive compared to the others and less losses

Alkaline salts for acid gas removal

• Alkaline salt solutions at pH 9-11

• Na2CO3, K2CO3

• Corrosion must be controlled

• Mass transfer, reaction and temperature• Mass transfer, reaction and temperature

• Selectivity

Alkaline salt processes

Elevated temperature

• Benfield process (1950-)–Hot K2CO3 solution for CO2

removal (and H2S)

• Catacarb – similar to

Ambient temperature

Seaboard Process

Vacuum Carbonate Process

Vacasulf Process• Catacarb – similar to

Benfield

• Flexsorb HP – similar to Benfield

• Giammarco-Vetrocoke(1950-) – Na/K arsenitesolution

Vacasulf Process

Tripotassium PhosphateProcess

Sodium Phenolate Process

Alkacid Process

Caustic Wash Processes

Physical and chemical solvents

• Regeneration is important for bulk removal of acid gas

• Organic physical solvents are easy to regenerate by reducing pressureregenerate by reducing pressure

• Organic solvents used in high pressure applications

• Solubility of H2S and CO2 in the organicsolvents are important

• Aromatics tend to accumulate in the solvent

Solubility of gases for different solvents

From Gas Purification by Kohl and Nielsen

Physical and chemical solventsProcess Name Solvent Process Licensor

Fluor Solvent Propylene carbonate Fluor Daniel

Selexol Dimethyl ether of polyethylene glycol (DMEPEG)

UOP

Sepasolv MPE Methyl isopropyl ether of polyethylene glycol (MPE)

Badische (BASF)

Purisol N-Methyl-2-pyrrolidone (NMP)

Lurgi

Rectisol Methanol Lurgi and Linde AG

Ifpexol Methanol Institut Francais du Petrol (IFP)

Sulfinol Sulfolane and DIPA or MDEA

Shell/DIPM

Amisol Methanol and secondary alkylamine

Lurgi

Important parameters

• End use of gas• Capital cost• Gas purity and composition (for Claus plant e.g.)• Loss of hydrocarbons and other valued components• Experience of process supplier• Experience of process supplier• Experience of impurities expected• Experience with operational problems (corrosion,

foaming, clogging)• Cost of initial solvent• Cost of replacement solvent• Energy need/cost

Purisol

• CO2 down to 0.1% and H2S to a few ppm.

• The main applications for the installed Purisol plants are purification of high pressure synthesis gas rich in CO2 for further use in gas turbine integrated 2

gasification combined cycle (IGCC).

Rectisol

• Rectisol process is capable to remove cyanide, aromatics, organic sulfur, gum forming hydrocarbons.

• Gasification of coal and heavy oil.

• The low temperature of the solvent result in a purified gas of less than 0.1 ppm H2S and a few ppm of CO2.less than 0.1 ppm H2S and a few ppm of CO2.

• Two major constellations are used. In the first and standard design, H2S and CO2 is nonselectively absorbed simultaneously. In the other constellation H2S is absorbed in a first step selectively followed by a second absorption step of CO2.

• High plant cost

Summary

From Gas Purification by Kohl and Nielsen

Example of wash experiments in PiteåPiteå

H2S removal with short time contactors in a pressurized black liquor gasification plant

Olov Öhrman 1 and Ann-Christine Johansson 1 and Mats Lindblom 2

1 Energy Technology Centre in Piteå, Sweden2 Chemrec, Sweden

15

Presented at 2010 International Chemical Recovery Conference,March 31, Williamsburg, USA

Wash with short time contactor in DP-1

Synthesis gas35 °C

Abs. Liquid

STC1 STC2 STC3

GC sampling

35 °C

To Recycle

STC1 STC2 STC3

Cyclone Cyclone Cyclone

Acid gas removal with short time contactors

Diluted green liquor, 300 dm3/h, 50 °C

• Physical or chemical adsorption

• High surface area 500-1000 m2/g

• Renegeration thermally or by pressure

• Activated carbon

Adsorption

• Activated carbon– Large organic molecules

– Non polar compounds

• Packed bed (ZnO/Cu/ etc.)– Removal of trace amounts

– ZnO used for H2S removal (Chemical reaction)

Adsorption

• Zeolites

– Microporous material

– Use for selective removal, e.g. CO2 from air, hydrocarbons

O. Öhrman, PhD Thesis, LTU (2005)

hydrocarbons

– Pressure swing adsorption

– Also a catalyst

A. Mosca, PhD Thesis,

LTU (2009)A. Mosca, PhD Thesis, LTU (2009)

MFC

PBRSulfur removalby ZnO

MFCPBRActivatedcarbon

GC

MeOH synthesis

Gas purification and conversion to methanol

21

Activated carbon

H2S removal by ZnO

Methanol synthesis

Methanol removalfrom test rig

From SVT Landet runt,2010-05-02

Acknowledgement

• Sponsors to the BLG2 program– Swedish Energy Agency, Sveaskog, Mistra,

Länsstyrelsen i Norrboten, SmurfitKappa, SCA, Södra and Chemrec

• Sponsor to Catalytic synthesis via black liquor• Sponsor to Catalytic synthesis via black liquorgasification– Swedish Energy Agency

• High Bio– European Union, European Regional Development

Fund, EU Interreg IV A Nord programme.