Patent ID: 8518672

Claim:
A process for producing hemicellulose sugars and energy from cellulosic biomass, said process comprising: (a) extracting hemicelluloses from cellulosic biomass by a batch or continuous extraction reactor in the presence of steam, to produce a cellulose-rich solids stream and a liquid extract comprising water, wherein hemicelluloses and acetyl groups are released from the cellulosic biomass; (b) concentrating said liquid extract in a first evaporation stage that removes a majority of said water from said liquid extract, to produce a low-solids extract, wherein said first evaporation stage is operated at a pH of 4.8 or less, wherein a first amount of acetic acid, is obtained from acetyl groups released from the cellulosic biomass, and wherein the first amount of acetic acid is evaporated from said first evaporation stage; (c) hydrolyzing said low-solids extract from step (b) in the presence of sulfuric acid, heat, or hemicellulase enzymes, to produce a hydrolyzate comprising hemicellulose sugars and additional acetyl groups released during said hydrolyzing said low-solids extract; (d) introducing said hydrolyzate to a second evaporation stage, to produce a concentrated extract, wherein said second evaporation stage is operated at a pH of 4.8 or less, wherein a second amount of acetic acid, derived from said acetyl groups released during said hydrolyzing said low-solids extract, is evaporated from said second evaporation stage, and wherein said concentrated extract comprises said hemicellulose sugars; (e) recovering or further processing said hemicellulose sugars; (f) dewatering said cellulose-rich solids stream from step (a), to produce dewatered solids; and (g) combusting said dewatered solids, to produce energy.