Apparatus for treatment of chips with heated black liquor

Apparatus for treating comminuted cellulosic fibrous material to produce kraft pulp, comprising:

• a steaming vessel;
• a generally upright treatment vessel operatively connected to said steaming vessel;
• an upright continuous digester for cooking the comminuted cellulosic fibrous material at a cooking temperature, operatively connected to said treatment vessel, said digester having a material inlet at the top thereof, and a material outlet at the bottom thereof;
• withdrawal screen means located at an intermediate portion of said digester, between the inlet and outlet thereof, for withdrawing black liquor from said digester into a withdrawal conduit;
• heating means for heating the withdrawn black liquor above the cooking temperature in said withdrawn conduit to cause sulfur compounds to separate from the black liquor and be available for reaction with material steamed in said treatment vessel;
• recirculating means for recirculating the heated withdrawn black liquor from said heating means to said treatment vessel at a first point thereof;
• and
• withdrawal means for withdrawing black liquor from said treatment vessel at a second point thereof, vertically below said first point.