Patent ID: 8444809

Claim:
A method for heating a chip slurry in a pulping system including an impregnation vessel and a chemical digesting vessel, the method comprising: impregnating chips in the impregnation vessel with a liquor; transporting the chips from the impregnation vessel to an upper elevation of the digester vessel; processing the chips through at least one cooking section in the digester vessel and at least one wash section below the at least one cooking section; extracting hot liquor from a lower elevation of the digester vessel, wherein the extracted hot liquor has a temperature substantially higher than a temperature of the chips in the impregnation vessel and the lower elevation is below the at least one cooking section and adjacent at least one wash section of the digester vessel; and adding the extracted hot liquor from the lower elevation of the digester vessel to the chips to be or being transported from the impregnation vessel to the digester vessel, and heating the chips being transported with the heat energy in the extracted liquor.