Patent ID: 7666637
Filing Date: 2010-02-23
Classification: C12P,Y02E,Y02P

Abstract:
1. A process of treating and fractionating a lignocellulosic feedstock into high-purity fermentable sugars and lignin to produce ethanol, wherein the feedstock is selected from the group consisting of a softwood and a hardwood, the process comprising: (a) obtaining logs and separating said logs into hardwood and softwood logs; (b) chipping the separated logs of step (a) into wood chips having a length or width of approximately ¼ inch to 1 inch and a thickness of ¼ inch; (c) pre-hydrolyzing, said pre-hydrolyzing comprising: (d) centrifuging and draining the acid-presoaked wood chips obtained from step (c) to consistency of approximately 30% solids; (e) preheating the centrifuged-and-drained material obtained from step (d) in a series of steam mixers; (f) screw-feeding the preheated material into a pressurized reactor, wherein the reactor is pressurized to a reactor pressure of 150 psi to 1000 psi and heated to a reactor temperature of 150° C. to 300° C. by injecting into the reactor direct live steam and a gas selected from the group consisting of nitrogen, carbon dioxide, oxygen, and air; and then maintaining the screw-fed material in the pressurized reactor at said temperature and said pressure for a period of time of 1 minute to 30 minutes; (g) blowing the steam-pressure-treated material obtained from step (f) into a series of blow tanks or flash tanks, thereby disintegrating the material into lignocellulosic solids comprising impregnable fibers and fiber bundles, wherein steam is recovered from the blow tanks and recycled into the steam mixers of step (e); (h) pressing the lignocellulosic solids containing the impregnable fibers and fiber bundles thereby separating a pre-hydrolysate liquor from the solids, wherein said pressing further comprises recovering from the impregnable fibers and fiber bundles of said solids trapped hemicellulosic xylose, arabinose, galactose, mannose, and glucose by washing the solids in a series of counter-current washers; (i) neutralizing the pre-hydrolysate liquor and a filtrate obtained from the counter-current washers obtained from step (h) by treating the liquor and the filtrate with lime at a pH of 8 to 10, at a temperature of 40° C. to 80° C., and for a period of time of about 30 minutes to about 180 minutes, thereby precipitating compounds which are toxic to fermentation, the precipitated compounds selected from the group consisting of furfural, a phenol-containing compound, and acetic acid; (j) delignifying and deresinating the washed solids obtained from step (h) wherein said washed solids further comprise lignin, cellulose, and extractives, said delignifying and deresinating comprising either: (k) further delignifying and purifying the purified cellulose solid material obtained from step (j)(ib) or the extracted-and-washed solid obtained from step (j)(ii) by mixing therewith a solution selected from the group consisting of chlorine-and-chlorine dioxide having a chlorine dioxide amount of 30% to 50% of the total chlorine in the solution or sodium chlorite-and-anhydrous acetic acid, wherein when a chlorine-and-chlorine dioxide solution or the sodium chlorite-and-anhydrous acetic acid solution is mixed at 120° F. and for a period of time of 3 hours, thereby providing a solids consistency of 3% to 10% solids and producing a cellulose solid product; (l) washing the cellulose solid product of step (k) in a three-stage counter-current washer train to produce a purified cellulose solid product and a lignin-containing liquid filtrate; (m) evaporating the lignin-containing liquid filtrate obtained from step (j)(ib) or step (l) by multiple-effect evaporators to 50% to 70% solids content, thereby recovering said lignin; (n) enzymatically saccharifying or acid-hydrolyzing the purified cellulosic solids of step (l), thereby converting the purified cellulosic solids into a fermentable glucose; and (o) fermenting the glucose obtained from step (n) and the xylose and arabinose from step (h) with a yeast or a bacterium, thereby producing said ethanol.