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

A reactor vessel system comprising:

• first reactor vessel having an upper material input receiving cellulosic material and a bottom material discharge for the cellulosic material, wherein the cellulosic material flows through the first reactor vessel from the material input to the material discharge;
• a hydrolysate and liquid extraction screen in the first reactor vessel;
• an upper region of the first reactor vessel between the material input and the liquid extraction screen, wherein the upper region is maintained at or above a hydrolysis temperature at which a hydrolysis reaction occurs in the cellulosic material;
• a heat energy inlet port for introducing a heated fluid to the cellulosic material in the upper region of the first reactor vessel;
• a lower region of the first reactor vessel between the liquid extraction screen and the bottom material discharge in which the hydrolysis is substantially suppressed;
• a wash liquid inlet port at a lower region of the first reactor vessel for introducing sufficient wash liquid to the vessel such that the wash liquid flows up through the lower region to the extraction screen, wherein the wash liquid is introduced at a temperature below the hydrolysis temperature and the wash liquid cools and suppresses the hydrolysis reactions in the second region of the reactor vessel;
• a transport pipe having an inlet coupled to the material discharge of the first reactor vessel and an outlet coupled to a second reactor vessel, wherein the cellulosic material flows from the bottom material discharge, through the transport pipe to an upper inlet of the second reactor vessel, and
• the second reactor vessel includes a cooking liquor applied to the cellulosic material, and the second reactor vessel includes a liquid discharge that extracts a portion of liquid from the second reactor vessel and directs the portion of liquid to at least one of a lower inlet of the first reactor vessel or to the transport pipe and
• wherein the wash liquid is a mixture of water and at least one of sodium hydroxide and essentially sulfur free white liquor.

A processing system for converting cellulosic material to pulp, the system comprising:

• a first pressurized reactor vessel operating at a pressure above atmospheric pressure, the first reactor vessel including:
• a material input receiving cellulosic material and a material discharge for the material, wherein the cellulosic material flows from the material input to the material discharge;
• a heat energy input port in an upper portion of the first reactor vessel;
• a first region of the first reactor vessel between the material input and a liquid extraction screen, wherein the first region is maintained at a hydrolysis temperature of at least 150 degrees Celsius in the cellulosic material;
• the extraction screen having an outlet for extracting hydrolysate and liquid from the first vessel, and
• a second region of the first reactor between the liquid extraction screen and the discharge in which a temperature is below the hydrolysis temperature and the hydrolysis reactor is substantially suppressed, and
• a discharge of the first vessel below the second region;
• a transport pipe providing a flow conduit from the discharge to a continuous digesting vessel, and
• the continuous digesting vessel receiving the cellulosic material discharged from the first reactor vessel.

A method to produce pulp from cellulosic material comprising:

• introducing cellulosic material to an upper inlet in a first reactor vessel;
• hydrolyzing the cellulosic material in upper region of the an upper region of the first reactor vessel by adding pressure and heat energy to the vessel;
• extracting hydrolysate from the cellulosic material through an extraction screen below the upper region and in the first reactor vessel;
• introducing a wash liquid to a lower region of the first reactor vessel where the wash liquid suppresses hydrolysis of the cellulosic material in the lower region and said wash liquid flows upward through the cellulosic material to the extraction screen;
• discharging the cellulosic material from a lower outlet of the first reactor vessel;
• introducing the discharged cellulosic material to a second reactor vessel, and
• introducing cooking liquor into the top of the second reactor vessel to digest the cellulosic material to produce pulp.

A method to suppress hydrolysis of cellulosic material comprising:

• introducing cellulosic material in an upper inlet of a first reactor vessel, wherein the material moves downwardly through the vessel;
• adding steam at above atmospheric pressure to the first reactor vessel;
• maintaining at above a hydrolysis temperature the cellulosic material in an upper region of the first reactor vessel;
• extracting hydrolysate from the cellulosic material through an extraction screen below the upper region in the first reactor vessel;
• cooling the cellulosic material below the extraction screen to a temperature below the hydrolysis temperature, and
• discharging the cellulosic material from a bottom outlet of the first reactor vessel.