Syngas cleaning using absorption and adsorption

Syngas cleaning using absorption
and adsorption
Olov Öhrman, ETC
HighBio seminar 2010-05-18
Agenda
• Wash (Chemical or physical absorption)
– Amines
– Alkaline salts
– 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 also
possible 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
used for H2S, CO2,COS and CS2. Lower
vapor pressure (less losses, lower pressure)
• Methyldiethanolamine (MDEA) – tertiary
amine used for high CO2/H2S
concentrations where a high H2S selectivity
is 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
Selectivity
Alkaline salt processes
Elevated temperature
• Benfield process (1950-)–
Hot K2CO3 solution for CO2
removal (and H2S)
• Catacarb – similar to
Benfield
• Flexsorb HP – similar to
Benfield
• Giammarco-Vetrocoke
(1950-) – Na/K arsenite
solution
Ambient temperature
Seaboard Process
Vacuum Carbonate Process
Vacasulf Process
Tripotassium Phosphate
Process
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 pressure
• Organic solvents used in high pressure
applications
• Solubility of H2S and CO2 in the organic
solvents 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 solvents
Process 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 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
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.
• 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
Piteå
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, Sweden
2 Chemrec, Sweden
Presented at 2010 International Chemical Recovery Conference,
March 31, Williamsburg, USA
15
Wash with short time contactor in DP-1
GC sampling
Abs. Liquid
STC1
STC2
STC3
Cyclone
Cyclone
Synthesis gas
35 °C
Cyclone
To Recycle
Acid gas removal with short time
contactors
Diluted green liquor, 300 dm3/h, 50 °C
Adsorption
•
•
•
•
Physical or chemical adsorption
High surface area 500-1000 m2/g
Renegeration thermally or by pressure
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
O. Öhrman, PhD Thesis, LTU (2005)
• Zeolites
– Microporous material
– Use for selective removal, e.g. CO2 from air,
hydrocarbons
– Pressure swing adsorption
– Also a catalyst
A. Mosca, PhD Thesis, LTU (2009)
A. Mosca, PhD Thesis,
LTU (2009)
PBR
Sulfur removal
by ZnO
MFC
PBR
Activated
carbon
MeOH synthesis
GC
Gas purification and conversion to methanol
Methanol removal
from test rig
Activated carbon
Methanol synthesis
H2S removal by ZnO
From SVT Landet runt,
2010-05-02
21
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
gasification
– Swedish Energy Agency
• High Bio
– European Union, European Regional Development
Fund, EU Interreg IV A Nord programme.