Process for producing a pulp
AssigneeLenzing Aktiengesellschaft
InventorsHerbert Sixta, Andrea Promberger, Andrea Borgards, Ronald Möslinger
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Abstract
The invention relates to a process for producing a dissolving pulp from a cellulosic starting material using the kraft process, comprising the step of cooking the starting material with a cooking liquor. The process according to the invention characterized in that the starting material is exposed to a steam treatment prior to cooking and that the pulp obtained by cooking is subjected to cold caustic extraction (CCE) in the course of further processing.
Claims34
A process for producing a dissolving pulp from a cellulosic starting material using the kraft process, comprising the step of cooking the starting material with a cooking liquor, wherein the starting material is exposed to a steam treatment prior to cooking and wherein the pulp obtained by cooking is subjected to cold caustic extraction (CCE) in the course of further processing.
The process according to any of the preceding claims, wherein the starting material is subjected to an impregnation prior to cooking.
The process according to any of the preceding claims, wherein the cooking, the steam treatment and optionally the impregnation of the starting material are carried out in the same cooker.
The process according to any of the preceding claims, wherein the cooking is carried out in the form of continuous batch cooking (CBC).
The process according to any of the preceding claims, wherein at least a portion of the press liquor forming in the cold caustic extraction stage is purified using a membrane separation process, preferably nano- or ultrafiltration.
The process according to any of the preceding claims, wherein it is linked to a process for producing a paper pulp and at least a portion of the press liquor forming in the cold caustic extraction stage and/or at least a portion of the retentate of a membrane separation process performed on the press liquor is/are supplied to the cooking liquor of a cooking process carried out for the production of paper pulp.
The process according to any of the preceding claims, wherein the pulp obtained by cooking in the course of further processing, in addition to a bleaching step which has optionally been carried out, is subjected to a treatment for adjusting the degree of polymerization (DP).
The process according to any of the preceding claims, wherein the cooking step of the pulp is carried out in two stages, and wherein, in the first stage, a delignification using a first cooking liquor to a kappa number of from 35 to 70 in case of softwoods as the starting material and to a kappa number of from 30 to 60 in case of hardwoods as the starting material is carried out and, in the second stage, the cooking is continued to the desired degree of purity of the pulp, using a second cooking liquor.
Dependencies are inferred from the claim text.