Two vessel reactor system and method for hydrolysis and digestion of wood chips with chemical enhanced wash method

摘要

A processing system for converting cellulosic material to pulp comprises a first pressurized reactor vessel (10) operating at a pressure above atmospheric pressure. The first reactor vessel (10) includes: a material input receiving cellulosic material and a material discharge (56) for the material, wherein the cellulosic material flows from the material input to the material discharge (56); a heat energy input port in an upper portion of the first reactor vessel (10); an extraction screen (48) having an outlet for extracting hydrolysate and liquid from the first reactor vessel (10); a first region of the first reactor vessel (10) between the material input and the liquid extraction screen (48), wherein the first region is maintained at a hydrolysis temperature in the cellulosic material; a wash liquid input (52) to the first pressurized reactor vessel (10) and below the extraction screen (48), wherein the wash liquid input (52) is connected to a source of wash liquid including a source of cool wash water (50) and a source of at least one of sodium hydroxide and essentially sulfur free white liquor (82); and a second region of the first reactor vessel (10) between the liquid extraction screen (48) and the discharge (56) in which a temperature is below the hydrolysis temperature and the hydrolysis reaction is substantially suppressed. A transport pipe (62) provides a flow conduit from the discharge (56) to a second reactor vessel (12) which is a continuous digesting vessel. The continuous digesting vessel (12) receives the cellulosic material discharged from the first reactor vessel (10).