Metso Chemical Pulping Oy

Metso Paper Pori Oy

Valmet Chemical Pulping Oy

Mikael Svedman

Päivi Uusitalo

Thomas Fant

Jukka Vaistomaa

Panu Tikka

Asko Paakki

Hannu Haaslahti

Seppo Martikainen

A method for the preparation of pulp by means of alkaline cooking, in which method spent liquor is transferred to pressurized tanks, and at least one liquor is expanded corresponding to a temperature difference of 1 to 5&#xb0; C. The generated steam is led to turpentine recovery. Thus, the removal of turpentine and gases dissolved in said liquor is effective, the amount of recovered turpentine increases, and pulp of better washability and higher quality is obtained.

Method for improved turpentine recovery from modern cooking plants

Methods for producing chemical pulp from lignocellulose-containing material in processes for kraft pulp production are disclosed including charging the lignocellulose-containing material to a digester, initially treating the lignocellulose-containing material with an impregnation liquor, and then treating the impregnated lignocellulose-containing material with hot liquor and displacing calcium-containing spent liquor from the digester during that treatment, heating and cooking the heated lignocellulose-containing material to produce cooked lignocellulose-containing material and cooking liquor and displacing the cooking liquor from the digester using at least a portion of the displaced calcium-containing spent liquor.

Batch process for producing chemical pulp by removing and reintroducing calcium-containing spent liquor in the digester

A method for producing chemical pulp from cellulosic material by means of alkaline cooking, including cooking the material to pulp at cooking temperature in a digester, reducing the temperature at the end of the cook, substantially relieving the overpressure in the digester and then discharging the pulp from the digester by means of pumping. The method is characterized in that the pulp is cooled to essentially 85&deg; C. to 70&deg; C. before pumping cooked material as a fluid suspension from the digester, and that the temperature of the cooked material is maintained in the same temperature range and at a pH level being between 10 and 13, between the digester and a first delignification/bleaching stage, thus avoiding mechanical damage of cellulosic material.

Method for avoiding mechanical damage of pulp

A method for preparing pulp from lignin-containing cellulosic material is disclosed, including a step for acid cleaning of the lignocellulosic material, followed by alkaline delignification. The acidic step removes undesired components such as metal ions and side groups of polysaccharides, which may have adverse effects on the process especially when extensive recycling of liquors is employed within the plant.

Method for the production of precleaned pulp

A process for the production of pulp using alkaline delignification is disclosed, wherein cellulosic material is initially treated with steam, and a chelating agent is added in connection with the steam treatment. The end pH of the steam treatment stage is below 5. Liquors containing chelated, so-called non-process compounds are not recycled in the pulping process, but expelled therefrom for further processing where non-process compounds are eliminated.

Growing community of inventors

Pori, Finland

Mikael Svedman