Apparatus for washing pulp

An apparatus for countercurrent washing of pulp, where the pulp moves on a liquid pervious support surface in a first direction and a washing liquid moves in a second direction, said second direction being substantially opposite to said first direction and where washing is performed in a number of washing stages each being divided in at least two washing phases, comprising:

• stationary wall means for separating said washing phases within a washing stage;
• stationary feeding means arranged between said wall means for introducing washing liquid to the pulp layer;
• stationary collecting means arranged on an opposite side of said moving liquid pervious support surface with respect to said feeding means for receiving displaced washing liquid from said washing phases, the number of collecting means corresponding to the number of said phases;
• and
• ducts for feeding washing liquid from said collecting means to said feeding means, said ducts connecting said collecting means of the washing phases of a washing stage in a corresponding order to said feeding means of the washing phases of the preceding washing stage, so that both said washing stages are divided to same number of washing phases.

An apparatus for countercurrent washing of pulp, comprising:

• a rotating cylinder with a liquid-pervious casing surface;
• a stationary shell coaxial with said cylinder and surrounding said cylinder so as to allow said pulp to flow as a layer between said shell and said cylinder with said liquid-pervious casing surface, a washing liquid being suppliable through the shell to the pulp layer;
• at least one inlet pipe for the washing liquid, said inlet pipe being connected to said shell close to a discharge point for the washing liquid;
• compartments disposed under the casing surface of the cylinder for collecting the washing liquid seeping through the pulp;
• a valve system connected to said compartments and having a part rotating with said cylinder and a stationary part disposed against said rotating part;
• a discharge pipe beginning from said stationary part, via which pipe the washing liquid is discharged from the apparatus;
• and
• pipes beginning from said stationary part, said pipes during operation communicating with different compartments of the cylinder and being connected to various points in the shell surrounding the cylinder so as to feed the washing liquid during operation in successive washing stages at said points through the pulp layer while the liquid gradually flows in a direction opposite to the flow direction of the pulp, said pipes passing the washing liquid from one washing stage to another and being disposed between the stationary part of the valve system and shell surrounding the cylinder, and being connected for dividing the washing liquid into two or more partial flows passing alternatively through different washing stages and causing the washing liquid, which has passed through one washing phase, to pass by at least the washing phase preceding it in the flow direction of the pulp.