Patent ID: 8685685
Filing Date: 2014-04-01
Classification: C05F,C08B,C08H,C10L,C12P,C13K,F23G,Y02E,Y02P,Y02W

Abstract:
1. A process for producing fermentable hemicellulosic sugars and 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) hydrolyzing said hemicellulosic oligomers contained in said extract liquor, under effective hydrolysis conditions, to produce fermentable hemicellulosic sugars, wherein said effective hydrolysis conditions release acetyl groups to generate additional acetic acid; (f) 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 fermentable hemicellulosic sugars; (g) recycling at least a portion of said vapor stream from step (f), 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); (h) recovering said fermentable hemicellulosic sugars; and (i) drying said dewatered solids to produce said low-ash biomass.