ON THE MANUFACTURE OF PULP BY AMMONIUM SULPHITE PROCESS. (No. 2)
On the cooking of beech by neutral ammonium sulphite process.
1953 Volume 7 Issue 5 Pages 324-332,395
Details
1953 Volume 7 Issue 5 Pages 324-332,395
After the model of the previous report, the cooking of beech by neutral ammonium sulphite liquor is investigated, and at the same time the comparision between NH3 and Na base cooking is made, the results of which are as follows : -
1. Beech is cooked easier than Abies Sachaliensis by this process, and when the cooking time is limited for 5 hours, the optimum cooking temperature is found 160°C.The maximum yield of pulp is 55%, and in higher yield range the pulping is not complete. The pulp includes 23.4% pentosan, showing its Roe number 8.4, the holocellulose yield 92.6%, easy bleachability and good mechanical strength ; these are suitable for paper making. To complete the pulping, the concentration of total SO2 of liquor is needed more than 4.5% at the cooking tempreature.
2. In the case of cooking by 165°C, 2.5% SO2, the last pH of liquor drops to 4.5, and the resulting pulp is slightly burned, showing only 43.5% yield : similarly, by 170and 180°C series cooking, lower pulping yield results. The degree of pH drop in the case of beech cooking is more remarkable than Abies Sachaliensis.
3. The cooking velocity is greatly effected by the pH of liquor, and NH3 base cooking shows tendncy to lead liquor to lower pH than Na base.
4. The cooking velocity by NH3 base is greater than that by Na base at the same pH condition.
5. Although the pulps resulted by both NH3 and Na bases give nearly the same qualities for the same yield, the former pulp is slightly superior to the latter in its Roe number, lignin content, holocellulose % and mechanical strength, but somewhat inferior in its color, so it may be said that NH3 base pulp is more suitable than Na base one for obtaining the bleached pulp.
