Process for manufacturing the high a content by a - cellulose, a multiple stages of cooking, comprising a préhydrolyse acid

摘要

Process for the production of special pastes having an increased alpha-cellulose content, suitable for chemical processes and for types of special papers, by means of a multiple stage digestion characterised in that (a) in the first stage, wood shavings, 20-21mm long are treated with steam at 110-120 deg.C for 5-10 mins. (b) then in a pre-hydrolysis stage, 1-2 wt.% (based on the weight of the wood) of a strong acid is added, so that the ratio of liquid to wood is 1 to 2.5-3.5 and the shavings are maintained at 140-150 deg.C, for 30-60 mins., leading to dissolution of 20-30% of the dry weight of the wood; (c) the hydrolysate is removed from the reactor and evacuation is completed by counter-current washing of the wood shaving; (d) white liquor is added and the shavings submitting to a relatively gentle sulphate cooking at 156-170 deg.C, with the help of an addition of 14-15 Na20 active alkali (based on the dry weight of the wood). High quality wood pastes having a high alpha-cellulose content for production of special paper and for use in the chemical industry are obtd. The hydrolysate (contg. mostly mono- and di-saccharides has only a low furfural content) is neutralised to acids and concentrated by evaporation to give a dry solid content of 60-70%. This product is suitable for use in animal feeds and as a starting material in the chemical industry.