Patent ID: 9085494
Filing Date: 2015-07-21
Classification: C05F,C08B,C08H,C10L,C12P,C13K,F23G,Y02E,Y02P,Y02W

Abstract:
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.