Method for bleaching of cellulosic pulp

In a method of bleaching of cellulosic pulp including the steps of essentially continuously feeding the pulp through a bleaching zone in a straight path and passing a bleaching liquid through the pulp in a direction transverse to the feed direction of the pulp, the improvement in said liquid passing step which consists essentially of the steps of feeding a first portion of bleaching liquid into said zone at a first level with respect to the direction of pulp feed and withdrawing liquid displaced through transversely spaced strainer means located at about said first level so that the passage of the first portion of bleaching liquid through all parts of the pulp flowing along said straight path within said zone through said first level is in a direction transverse to the feed direction of the pulp and feeding a second portion of bleaching liquid into said zone at a second level with respect to the direction of pulp feed and withdrawing liquid displaced through transversely spaced strainer means located at about the second level so that the passage of the second portion of bleaching liquid through all parts of said pulp flowing along said straight path within said zone through said second level is in a direction transverse to the feed direction of the pulp and opposite from the transverse direction through said first level.