OXYGEN DELIGNIFICATION PROCESS

摘要

1449828 Pulp manufacture CANADIAN INDUSTRIES Ltd 25 April 1974 [26 April 1973 31 Dec 1973] 19794/73 and 60303/73 Heading D2W A process for making pulp comprises (a) treating lignocellulosic material in a closed reaction vessel with a liquor comprising alkali metal hydroxide with or without alkali metal sulphide at 160-195‹C for not longer than 120 minutes to provide a pulp yield of 52-65%, the pulp having a Kappa number not less than 40, (b) displacing the liquor from the lignocellulosic material with water or an aqueous alkali metal hydroxide solution, (c) treating the lignocellulosic material without prior defiberisation in aqueous suspension at a consistency of 2-30% with 2-20% by wt. of alkali metal hydroxide at 20-90‹C, (d) treating the resulting lignocellulosic material in an aqueous medium at a consistency of 3-35% with oxygen or an oxygen-containing gas for 10-120 minutes at 80-140‹C and a partial pressure of oxygen of 30-200 lbs/square inch. In a modification, the process comprises (a) treating lignocellulosic material with a liquor comprising alkali metal hydroxide with or without alkali metal sulphide at 160-195‹C for not longer than 90 minutes to provide a pulp yield of 55-65%, (b) displacing the liquor from the lignocellulosic material with water, or an aqueous alkali metal hydroxide solution, (c) treating the lignocellulosic material without prior defiberisation in aqueous suspension at a consistency of 2-15% by wt. for 0.5-30 minutes at 20-90‹C with 2-20% by wt. of alkali metal hydroxide, and (d) treating the resulting lignocellulosic material in an aqueous medium at 3-35% with oxygen or an oxygencontaining gas for 10-120 minutes at 80-140‹C and a partial pressure of oxygen of 50-200 lbs/ square inch. Deliquification may be accelerated by the addition of anthraquinone mono- or disulphonic acid, or an alkali metal salt thereof,- to the initial pulping liquor. Preferably, a magnesium salt e.g. magnesium chloride or magnesium sulphate is added to the alkali metal hydroxide of step (c) above. The oxygentreated product may be subjected to a conventional sequential bleaching process.