Studies on Cyclic Treatment of Alkali Pulp Waste Liquor and Semichemical Pulp Waste Liquor

The manufacture of semichemical pulp by reproduced cooking liquor from kraft pulp black Iiquor was studied. The results are summarized as follows : 1. Carbonation-sulphitation method to manufacture cooking liquor from kraft pulp black liquor was employed in attempt to avoid the formation of Na2S203 which is formed by direct sulphitation of Na2S in black liquor. Reproduced cooking liquor by carbonation-sulphitation method containd 23g/lof Na2S203 and by direct sulphitation contatined 50 g/lof Na2S203.2. Red pine could be pulped to give 5565 % yield of semichemical pulp with Roe number of 1520 by reproduced cooking liquor using carbonation-sulphitation method.