The invention relates to an improved method for generating clean steam in a digester plant of a chemical pulp mill. By feeding a steam-to-steam converter (SSC) with venting steam from a black liquor flash tank (FT) as well as venting steam from chip steaming (SV) could the volume of clean steam produced be increased by over 40-50%, and to such an extent that the volume of clean steam covers the needs for preheating of chips in the digester system also in severe operational conditions. The total consumption of clean steam from the steam net of the mill may be reduced and used for other purposes such as electricity production, which meets the requirements for converting the pulp mill to an environmental friendly pulp mill.

A method of producing chemical pulp including at least the following steps: a) wood chips or other comminuted ligno-cellulosic fibrous material is treated with a polysulfide-containing cooking liquor in an impregnation stage at a temperature of 90-145 C., and b) slurry of fibrous material from step a) is heated into cooking temperature and cooked for producing pulp having a desired kappa number. After step a) mercaptide ions are added into the slurry of fibrous material and the fibrous material is treated at cooking temperature in step b).

A method of producing chemical pulp including at least the following steps: a) wood chips or other comminuted ligno-cellulosic fibrous material is treated with a polysulfide-containing cooking liquor in an impregnation stage at a temperature of 90-145 C., and b) slurry of fibrous material from step a) is heated into cooking temperature and cooked for producing pulp having a desired kappa number. After step a) mercaptide ions are added into the slurry of fibrous material and the fibrous material is treated at cooking temperature in step b).

A cooking method and a digester system wherein partly digested cellulosic fiber source is compressed during cooking to provide high molecular weight lignin and pulp.

The present invention relates to treatment of unbleached or partially bleached or alkaline extracted dissolving pulp with one or more cellulases. The cellulase treatment results in increased viscosity control, reduced viscosity and/or increased reactivity of the final dissolving pulp.

The present invention relates to treatment of unbleached or partially bleached or alkaline extracted dissolving pulp with one or more cellulases. The cellulase treatment results in increased viscosity control, reduced viscosity and/or increased reactivity of the final dissolving pulp.

A method for feeding a slurry of chips and liquid to a prehydrolysis reactor in the production of dissolving pulp. The slurry is pumped by using at least one pump to the reactor, and alkali is fed into the at least one pump 5 for adjusting the pH of the slurry to a range of 7-10.

A method for feeding a slurry of chips and liquid to a prehydrolysis reactor in the production of dissolving pulp. The slurry is pumped by using at least one pump to the reactor, and alkali is fed into the at least one pump 5 for adjusting the pH of the slurry to a range of 7-10.

The invention relates to an improved method for generating clean steam in a digester plant of a chemical pulp mill. By feeding a steam-to-steam converter (SSC) with venting steam from a black liquor flash tank (FT) as well as venting steam from chip steaming (SV) could the volume of clean steam produced be increased by over 40-50%, and to such an extent that the volume of clean steam covers the needs for preheating of chips in the digester system also in severe operational conditions. The total consumption of clean steam from the steam net of the mill may be reduced and used for other purposes such as electricity production, which meets the requirements for converting the pulp mill to an environmental friendly pulp mill.

The invention relates to an improved method for generating clean steam in a digester plant of a chemical pulp mill. By feeding a steam-to-steam converter (SSC) with venting steam from a black liquor flash tank (FT) as well as venting steam from chip steaming (SV) could the volume of clean steam produced be increased by over 40-50%, and to such an extent that the volume of clean steam covers the needs for preheating of chips in the digester system also in severe operational conditions. The total consumption of clean steam from the steam net of the mill may be reduced and used for other purposes such as electricity production, which meets the requirements for converting the pulp mill to an environmental friendly pulp mill.