Kvaerner Pulping Technologies Ab

Kvaerner Pulping Technologies Aktiebolag

Stig Andtbacka

Anders Bergqvist

Ake Backlund

Johanna Svanberg

Sven-Erik Olsson

Bjorn Dillner

Lennart Hagelquist

Elisabeth Andtbacka

Finn Jacobsen

ANGke Backlund

Daniel Panglsson

Gunnar Wernqvist

Method of continuously isothermally cooking of pulp

Recycling of knots in a continuous process for cooking chemical pulp

A method of integrating bleaching and recovery in connection with the production of chemical pulp that has been digested and preferably delignified with oxygen gas using processes that retain the viscosity and strength, to kappa number less than 16 without the use of chemicals containing chlorine, and using a bleaching sequence including at least one step with sequestering agent and/or acid, and a peroxide step. According to the invention spent liquor (5) from the bleaching department is pre-evaporated in one or more evaporation units (20F, 20G), and the spent liquor (24) from the bleaching department thus pre-evaporated is combined with spent liquor (22) from the digestery and/or with pre-evaporated spent liquor (23) from the digestery obtained by pre-evaporating spent liquor (22) from the digestery in one or more evaporation units (20D, 20E) other than said evaporation units (20F, 20G) for pre-evaporating spent liquor (5) from the bleaching department, after which the mixture of spent liquors (23, 24) is subjected to final evaporation in one or more evaporation units (20A, 20B, 20C) other than said evaporation units (20F, 20G, 20D, 20E) used for pre-evaporation.

Method of integrating bleaching and recovery in the production of 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.

Process for bleaching pulp without using chlorine containing chemicals

Growing community of inventors

Karlstad, Sweden

Stig Andtbacka