GB325570A - Improvements in or relating to the extraction of celiulose - Google Patents

Abstract

325,570. Thiriet, A. Nov. 20, 1928. Pulp, preparation of.-In the extraction of cellulose from vegetable material by a process wherein the material is treated in one of a series of vats, the material remaining stationary in the vat and being subjected therein to a series of treatments with hot soda lye in successively increasing concentrations, the lye having already been used in other vats of the series, the material is treated under atmospheric pressure and the lye is caused to circulate continuously through the whole series of vats so that the cellulose is ultimately liberated in a soda solution free from organic matter. The treating plant comprises a series of vats 1 having perforated false bottoms 4, circulating pumps 6, calorifiers 8 fed with steam through piping 30, multi-way cocks 9, decanting troughs 20 for the purification of water, water and soda distributing troughs 23, 25 and connecting piping arranged as shown. All the vats other than those being loaded or emptied, or in which the pulp is being washed, form a closed circuit in which the lyes circulate. When a vat in which the treatment is completed receives washing water through the piping 14 an equal amount of lye is displaced and forced into the next vat. Soda as required is added to this next vat through piping 15. The lye so displaced from this vat is pumped into the next vat and the circulation continues throughout the series of vats, completely used lye which has passed through the entire circuit being discharged from the last vat. For straw, spanish grass &c. the lye is maintained at 70-95‹ C. To purify the water, alkaline-earth salts are cold precipitated therefrom by small amounts of caustic soda in the troughs 20, the water and caustic soda being distributed respectively from troughs 23, 25. Specifications 306,072 and 318,868 are referred to.