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Wood Chemistry PSE 406

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Wood Chemistry PSE 406

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  1. Wood ChemistryPSE 406 Bioenergy-Pretreatment

  2. Agenda • Bioconversion to ethanol process • Pretreatment • Steam explosion • Organosolv pulping

  3. Bioconversion to ethanol Pretreatment Hydrolysis Biomass Ethanol Fermentation Distillation

  4. Pretreatment –”disruption” • Possible methods: • Mechanical (milling) • Chemical (acid and base) • Biological (white rot fungi) • Combination

  5. Steam explosion • Treatment of biomass with high-pressure steam for a short period of time followed by sudden decompression • Acid (H2SO4, SO2) impregnation of wood increases SE efficiency • Typical conditions: • Pressure: 1.2-1.7 MPa (12-17atm) • Temperature: 170-250oC, 338-482 F • Time: 10sec-10min

  6. Steam explosion (2) • One of the most cost effective and efficient pretreatment for agricultural, hardwood and softwood residues • 3 variables: time, temperature and pH • Use of SO2 as catalyst: reaction time and temperature enzyme accessibility to cellulose recovery of hemicellulose

  7. Steam gun Receiving vessel Karin Fill valve Receiving vessel Steam valve Blow valve Pretreated corn stover

  8. Organosolv pulping • Separation of the hemicellulose, lignin and cellulose • Lignin as a co-product • 4 variables: time, temperature, pH and ethanol concentration

  9. Pretreatment methods-organosolv pulping Carmen Screening Pressure vessels Rotary digester

  10. Process flow Organosolv pulping Steam explosion Lignocellulose Lignocellulose ethanol, water, H2SO4 SO2 Steam explosion Cooking Unwashed pulp Water dilution Spent liquor Filtration Fractionation Pulp Precipitation Warm ethanol and water wash Filtration Washed pulp Precipitate Filtrate Disintegration Water wash Screening Lignin fraction Liquid fraction Solid fraction Solid fraction Liquid fraction SSF SSF Ethanol Ethanol

  11. Severity factor (Log Ro) Log Ro=t*e(Tr-Tb)/14.75 -t: time (min), Tr: reaction temperature, Tb: reference temperature (100°C) (Overend and Chornet, 1987) Low (log Ro=2.1) Med (log Ro=3.4) High (log Ro=4.5) 150oC or 302F 190oC or 374F 230oC or 446F

  12. Optimization of pretreatments Low severity fermentation yield solids hydrolysis Medium severity good fermentation yield good solids hydrolysis High severity fermentation yield solids hydrolysis

  13. Conditions for pretreatment of corn fibre (surface response modeling) Increasing Severity

  14. Recovery of hemicellulose after pretreatment (monomers-corn fibre) 190-220oC 6-8 min

  15. Total sugar recovery after pretreatment and enzymatic hydrolysis (corn fibre) 185-205oC 3-6% SO2

  16. Optimization of pretreatments Low severity fermentation yield solids hydrolysis Medium severity good fermentation yield good solids hydrolysis High severity fermentation yield solids hydrolysis Cornfibre:190ºC, 5 min, 3% SO2, Bura et al., 2003 Cornstover:190ºC, 5 min, 0% SO2, Bura et al., 2005 Hybrid poplar:200ºC, 5 min, 3% SO2, Bura et al., 2006 Hybrid poplar:180ºC, 60 min, 1.25% H2SO4, 60% E, Pan et al., 2006* BKLP:205ºC, 5 min, 4% SO2, Ewanick et al., 2006 BKLP:180ºC, 60 min, 1.25% H2SO4, 60% E, Pan et al., 2006* Douglas-fir:195ºC, 4.5 min, 4.5% SO2, Boussaid et al., 2000

  17. Beetle Killed Lodgepole Pine

  18. Overall sugar recovery (BKLP)

  19. Steam explosion (SE)/Ethanol pulping (EP) Sugar to ethanol yield 80% yield SE 244 g of ethanol 1 kg BKLP 35% yield EP 152 g of ethanol

  20. Ethanol pulping versus SE