Patent ID: 8512512

Claim:
A method for pretreating cellulosic biomass feed stock comprising: pretreating the feed stock in a first pressurized reactor, wherein the feed stock undergoes hydrolysis in the first pressurized reactor, wherein the feed stock in the first pressurized reactor is under a gauge pressure of at least 1.5 bar; transferring the feed stock from the first pressurized reactor to a pressurized sealing device, wherein the feed stock in the pressurized sealing device is under a gauge pressure of at least 1.5 bar; maintaining a vapor phase in the first pressurized reactor by injecting steam into the first pressurized reactor, wherein the injected steam provides heat energy to the feedstock in the first pressurized reactor; washing the feed stock in a downstream region of the first pressurized reactor or in the pressurized sealing device; draining a liquid including dissolved hemi-cellulosic material extracted from the feed stock from at least one of the first pressurized reactor and the pressurized sealing device; discharging the feed stock from the pressurized sealing device through a second pressurized coupling to a second pressurized reactor, wherein the feed stock is maintained at a higher pressure in the second pressurized reactor than in the first pressurized reactor; in the second pressurized reactor, infusing cells of the feed stock with steam or water vapor by injecting steam or water vapor into the second pressurized reactor, and rapidly releasing a pressure applied to the feed stock infused with water to cause steam expansion in the cells of the feed stock and refine the feed stock.