Patent ID: 6419788
Filing Date: 2002-07-16
Classification: D21C,Y02P

Abstract:
A method of treating lignocellulosic biomass to produce purified cellulose containing less than 20% lignin, said method comprising the steps of:providing a lignocellulosic feedstock having an average constituent thickness of at most 1â€³; introducing said feedstock into a pressure vessel having at least two reaction zones; maintaining said feedstock in the pressure vessel for a residence time; heating said feedstock in a first reaction zone to a temperature of from about 180Â° C. to about 240Â° C. to dissolve hemicellulose; removing said dissolved hemicellulose from the heated feedstock transferring said heated feedstock from said first reaction zone to a second reaction zone; subjecting said transferring feedstock to a counterflow of hot wash water of pH of from about 8 pH to about 13 pH to create residual solids containing cellulose and a wash water containing dissolved materials; and separating the residual solids containing purified cellulose from the filtered wash water, wherein said separated cellulose contains less than 20% lignin.