Liquor free pre-pulping stage for cellulose material - uses recovered white liquor or gaseous hydrogen sulphide in absence of free liquor

摘要

A new process for pulping in which the cellulose contg. material is treated in an extra step to obtain the highest possible sulphide conc. The extra step takes place essentially without free liquor, with a sulphide enriched liquor, or hydrogen sulphide in gaseous form at 70-170, pref. 90-150 deg.C for 20-120 pref. 60-100 mins. Sulphide conc. in the extra step is 5-50, pref. 15-30 kg/cu m. Gaseous hydrogen is used at a pressure of 2-10 bar and a --temperature of 90-150 deg.C. The following pulping process may be any combination of known chemical processes.