Valmet Ab

Petteri Kuusisto

Lari Lammi

Stefan Antonsson

Ismo Rosengren

Andreas Engelfeldt

Sannet Minnaar

A method for obtaining a strong hydrolysate from cellulosic material after a hydrolysis in a batch digester is disclosed. According to the invention the cellulosic material is exposed to a 2 stage hydrolysis with a first steam phase hydrolysis followed by a liquid phase hydrolysis, and wherein the steam phase is conducted such that the degree of packing of the cellulosic material results in at least a 20% up to 100% packing increase. The liquid phase hydrolysis includes adding hot and preferably acidified hydrolysis liquid and not establishing a total L/W ratio above 3.5, but sufficient to keep the cellulosic material under the level of the hydrolysis liquid.

Method for recovering concentrated hydrolysate after hydrolysis of cellulose material

The method is for producing pulp. More particularly, a displacement batch cooking process comprises recovery of a first treatment liquid by draining of the digester, preferably not using a displacement liquid. The method may preferably be used in a prehydrolysis step, wherein the recovery of the by-products is improved. In the recovery step, after the target P-factor in the prehydrolysis stage is reached, the hydrolysate is withdrawn by draining in at least one phase obtaining a strong first liquid and thereafter any residual hydrolysate may be displaced.

Method for recovering hydrolysate

The method is for producing pulp in batch digesters. More particularly, the method is for ending a treatment phase of the digester content. In order to obtain a more uniform pulp quality from the process is the treatment phase ended by displacing a liquor volume (WLP) through the digester vessel with an imposed increasing temperature in the displacement liquor added to digester.

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Pori, Finland

Petteri Kuusisto