Patent ID: 8017820

Claim:
A continuous process for pre-treating a lignocellulosic feedstock, comprising: (a) providing a pumpable feedstock slurry having a solids concentration of 8% to 30% by weight; (b) pumping the feedstock slurry through a heating train of two, or more than two heating stages, each heating stage including a pump to increase heating stage pressure and a direct steam injection to heat the feedstock slurry; (c) adding acid to the feedstock slurry prior to the heating train, during a heating stage, or after leaving the heating train, the acid added at a concentration of 0.2% to 12% weight of acid on weight of initial feedstock, to produce a heated, acidified feedstock slurry; (d) flowing the heated, acidified feedstock slurry through a pre-treatment reactor at a temperature of 160° C. to 280° C. for a time sufficient to increase efficiency of conversion of cellulose in the feedstock to glucose using cellulase enzymes; (e) cooling the slurry after the slurry exits the pre-treatment reactor, using two, or more than two flashing stages at successively lower pressures, without increasing the steam pressure after flashing; and (f) using at least a portion of the steam energy from two or more than two of the flashing stages to heat the feedstock slurry in the heating train, wherein flash steam from at least one of the flashing stages, from which at least a portion of the flash steam is used in the heating train, has a pressure that is 20% to 99.5% of the inlet slurry pressure to such flashing stage.