Kvaerner Pulping Technologies Ab

Kvaerner Pulping Aktiebolag

Bjorn Dillner

Ake Backlund

Stig Andtbacka

Goran Tidstam

Hans Arne

Provided is a method for reducing resin content in sulfite pulp, in an ozone bleaching process where the sulfite pulp is bleached using ozone, at a pulp concentration of about 6 to about 14% by weight, and at a pH of less than about 7. The process includes the steps of alkalizing the sulfite pulp to a pH of greater than about 7 after ozone bleaching and then mechanically processing the sulfite pulp to press resin out of the sulfite pulp.

Method of reducing the resin content in sulfite pulp

A process is disclosed for bleaching pulp without chlorine containing chemicals and for greatly reducing total washing filtrate discharge, comprising the steps of: 1) sending pulp that has been subjected to continuous digestion, oxygen-delignification and then washing, through a washing press; 2) treating, with agitation, the delignified washed pulp with sulfuric acid and a chelating agent; 3) washing the pulp in a washing apparatus; 4) bleaching with hydrogen peroxide in a reaction vessel; 5) washing the hydrogen peroxide bleached pulp; 6) adding sulfuric acid and ozone with mixing of the pulp; 7) reacting the pulp with ozone in a reaction vessel; and 8) washing the ozone reacted pulp, wherein the majority of liquid filtrate from the bleaching process that is waste not to be recycled is drawn off from the washing apparatus of step 3, the washings in step 3 and 5 have at least 85% efficiency, filtrate from washing step 5 is recirculated to the washing apparatus of step 3, and filtrate from the washing apparatus of step 8 is recirculated and used in the washing apparatus for the washing of pulp after oxygen-delignification.

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Saffle, Sweden

Bjorn Dillner