Patent ID: 8512979

Claim:
A process for pretreating biomass comprising: a) introducing biomass to a reaction vessel comprising: i) a cylindrical reaction vessel with an opening on at least one end; ii) one or more baffles attached to the interior of said vessel; iii) attrition media comprising pellets free-floating in the interior of the reaction vessel; iv) a cover for said vessel open end comprising one or more ports; and v) an injection lance comprising means for delivering processing reactants, wherein said means is an injection lance extending the length of the reaction vessel and connecting to a first port in the cover of iv); b) contacting said biomass with a process reactant comprising an aqueous solution comprising ammonia to form a biomass-aqueous ammonia mixture in the reaction vessel, wherein the ammonia is present at a concentration at least sufficient to maintain alkaline pH of the biomass-aqueous ammonia mixture but wherein said ammonia is present at less than 12 weight percent relative to dry weight of biomass, and further wherein the dry weight of biomass is at a solids concentration of at least 15 weight percent relative to the weight of the biomass-aqueous ammonia mixture; wherein said processing reactant is assimilated into said biomass by rotating the baffles of the reaction vessel whereby the baffles lift and drop the attrition media to produce a pretreated biomass.