Patent ID: 6620292
Filing Date: 2003-09-16
Classification: D21C,Y02P

Abstract:
A method of treating lignocellulosic biomass containing lignin to produce purified cellulose, said method comprising:providing a lignocellulosic feedstock; introducing said feedstock into a pressure vessel having at least two reaction zones; heating said feedstock in a first reaction zone to a temperature of from about 180Â° C. to about 240Â° C.; removing hydrolized hemicellulose from the heated feedstock; transferring said heated feedstock from said first reaction zone to a second reaction zone; subjecting said feedstock in said second zone to a counterflow of hot wash water containing dissolved oxygen and having a pH of at least 11 to produce residual solids containing cellulose and a wash water containing lignin and other extractives; and separating the residual solids containing purified cellulose from the filtered wash water, wherein the separated cellulose contains less than 10% lignin.