A process for the preparation of half chemical agent by means of alkaline cooking liquor, green liquor, with na deep 2 s and na deep 2 co deep 3 as a basic constituents

摘要

1396132 Pulp manufacture DEFIBRATOR AB 25 May 1972 [4 June 1971] 24634/ 72 Heading D2W Pulp is made from lignocellulosic material in a yield of 65-90% by impregnating the lignocellulosic material with a digesting liquor comprising sodium sulphide and sodium carbonate, digesting the impregnated material in the vapour phase in an atmosphere of steam at 159-190‹C, cooling the resulting pulp and liquor to not less than 100‹C, adding molecular oxygen sulphur compounds therefrom, separating the pulp from the liquor, and recovering chemicals from the liquor. The latter step is carried out by concentrating the liquor by evaporation, and burning the concentrated liquor to yield a smelt consisting substantially of sodium sulphide and sodium carbonate, and dissolving the smelt in water to form fresh digesting liquor. As shown, wood chips are fed via conveyor 1 into a vessel 2 in which they steamed and then into a digester 7. The digesting liquid is supplied to the vessel via pipe 47 and steam via pipe 17. Digested chips and liquor are then fed into vessel 10 which is supplied with compressed air via line 12 from compressor 13, and subsequently blown therefrom into a centrifugal cleaner 20. Pulp removed from the bottom of the cleaner is defibrated by difibrator 25 and passed to a filter 26 for separation of liquor, liquor recovered in tank 28 is concentrated in evaporator 43, and burnt in furnace 44. The smelt obtained is dissolved in tank 45 and the fresh digestion liquor recirculated via line 47. The digested chips may be cooled during thier transfer from digester 7 to vessel 10 by using a watercooled conveyor.