Abstract: A method for recovering sodium from a spent cooking liquor used in a kraft pulping process employing sodium hydroxide as a cooking agent resulting in the presence of sodium and sulfur combined with various elements in the spent cooking liquor. Black liquor is converted to green liquor, and the green liquor is reacted with lime in a causticizer to produce caustic and calcium carbonate. The caustic is recovered for use as a cooking liquor and the calcium carbonate is heated in a lime kiln to provide a source of lime. Flue gases containing free lime evolved from the lime kiln are contacted with a sodium carbonate solution in a scrubber to convert lime to caustic.

Abstract: A method and apparatus for removing solids from the porous surface of a rotating vacuum drum. Such drums are used to separate the solid and liquid phases of a slurry, such as a calcium carbonate containing mud slurry. Doctor blades are often used to scrape the drum exterior surface of excess mud to minimize the build up of solids thereon. Nonetheless a cake eventually forms on the drum and clogs the porous surface and stops the vacuum action. The drum is stopped and the drum backwashed by water to dislodge the cake. According to this invention, a jet of water from a nozzle is substantially tangentially directed against the drum surface to thereby eliminate stopping the drum for cake dislodgement. The nozzle is located beneath and moves with a reciprocating secondary doctor blade, the secondary doctor blade being of a length less than the width of the drum. A stationary, main doctor blade spans the entire width of the drum.

Abstract: A one-step slaking/causticizing method for producing white liquor from unslaked lime and clarified green liquor comprising introducing a feed slurry of unslaked lime and clarified green liquor into a pressurized slaker/causticizer reaction zone and maintaining the mixture in the zone at a temperature, under sufficient pressure and for a time sufficient, in one step to slake the lime and to convert the slaked lime to a white liquor containing product slurry.