Processes for producing low-ash biomass for combustion or pellets

摘要

This invention provides processes and apparatus to convert biomass, including wood and agricultural residues, into low-ash biomass pellets for combustion, alone or in combination with another solid fuel. Some embodiments provide processes for producing low-ash biomass from cellulosic biomass, comprising providing an aqueous extraction solution with acetic acid; extracting the feedstock to produce an extract liquor containing soluble ash, hemicellulosic oligomers, acetic acid, dissolved lignin, and cellulose-rich solids; dewatering and drying the cellulose-rich, lignin-rich solids to produce a low-ash biomass; hydrolyzing the hemicellulosic oligomers to produce hemicellulosic sugars, wherein additional acetic acid is generated; removing a vapor stream comprising vaporized acetic acid from the extract; and recycling the vapor or its condensate to provide some starting acetic acid for the extraction solution. The disclosed processes can produce clean power from biomass. Co-products may include fermentable sugars, fermentation products such as ethanol, fertilizers, and lignin.

主权项

1. A process for producing low-ash biomass from cellulosic biomass, said process comprising:
(a) providing a feedstock comprising cellulosic biomass; (b) providing an extraction solution comprising steam and/or hot water, and starting acetic acid; (c) treating said feedstock with said extraction solution under effective extraction conditions to produce an extract liquor containing soluble ash, hemicellulosic oligomers, acetic acid, dissolved lignin, and cellulose-rich solids; (d) separating at least a portion of said cellulose-rich solids from said extract liquor, to produce dewatered solids containing cellulose and lignin; (e) concentrating said extract liquor in an intermediate evaporation stage at a pH of 4.8 or less to release vaporized acetic acid, and recycling at least a portion of said vaporized acetic acid derived from said intermediate evaporation stage back to said extraction solution; (f) hydrolyzing said hemicellulosic oligomers contained in said extract liquor, under effective hydrolysis conditions, to produce hemicellulosic sugars, wherein said effective hydrolysis conditions release acetyl groups to generate additional acetic acid; (g) removing a vapor stream comprising water and vaporized acetic acid from said extract liquor in at least one evaporation stage at a pH of 4.8 or less, to produce a concentrated extract liquor comprising said hemicellulosic sugars; (h) recycling at least a portion of said vapor stream from step (g), or a condensed form thereof, back to step (b) to provide at least some of said starting acetic acid for said extraction solution and to provide heat for step (c); and (i) drying said dewatered solids to produce said low-ash biomass.