Abstract: Apparatus (10) for the two stage oxidation of white liquor. The reaction vessel includes a central first stage chamber (24) and a second stage annular outer chamber (26). Heated air is first introduced through the outer second stage chamber (26) by pipes (36) and then directed through elements (38, 40, 44) to the central first stage chamber (24) for completion of the oxidation reaction. Unoxidized white liquor with a small amount of black liquor to catalyze the process is introduced to the first stage of the reaction vessel at a temperature in excess of 185 degrees F. Oxidized white liquor is removed from the second stage chamber and air is venter to atmosphere through the stack at the top of the first stage chamber. The second stage is preferably pressurized for greater efficiency.

Abstract: Method for the recovery of acidic effluent from pulp mill chlorine dioxide generators using the Mathieson or Solvay system. The spent generator acid is directed through a three-stage evaporation/crystallization process in which spent acid from the generator is evaporated and crystallized to produce stage 1 sodium bisulfate crystals. The first stage crystals are then redissolved to form a second solution which is crystallized in order to yield stage 2 sodium sesquisulfate crystals and, finally, the second stage crystals are redissolved in a third stage evaporation/crystallization stage to yield sodium sulfate crystals. Besides salt cake, the system also produces reusable sulfuric acid for the chlorine dioxide generator. No chemicals are added during the recovery steps.

Abstract: Closed water and steam conditioning system for peeler logs in which steam from the boiler house is supplied to an evaporator and clean condensate returned to the boiler. Steam from the evaporator is directed to conditioning tunnels for the peeler logs. Dirty condensate from the conditioning tunnels is delivered to a sump area in which the dirty condensate is screened and at least part of which is directed to shower heads in the conditioning tunnels. The remaining dirty condensate is then directed to the evaporator where steam is generated therefrom. Caustic soda is added to the acidic dirty condensate to maintain a basic pH.