| 摘要 |
An oxygen delignification method and apparatus in which a charge of heated wood pulp is reacted with oxygen in the presence of a charge of caustic soda in a plurality of reaction stages 28, 30 and 32 which alternate with mixing stages 22, 24 and 26 in which caustic is mixed with the wood pulp. The use of the plurality of mixing stages reduces peak pH exposure of the wood pulp that would otherwise occur if the charges of caustic soda and wood pulp were mixed all at once. Moreover, the caustic soda mixed in such manner replenishes neutralized caustic soda and ensures that the average pH level is increased above that in conventional oxygen delignification. The increase in average pH level favours an increase in the delignification. Effluent liquor from a reacted wood pulp washing stage 24 is introduced into the mixing stages 22, 24 and 26 to prevent wood pulp degradation. Oxygen is mixed within the wood pulp by a wood pulp mixer that employs coaxial perforate passageways between which the wood pulp is retained and driven but which allow the oxygen to pass in an inward radial direction of the passageways to mix with the wood pulp. <IMAGE> |
