EFFECTS OF THE WASTE-LIQUOR REUSE OF ASPEN AUTO-CATALYZED ETHANOL-WATER PULPING ON THE PROPERTIES OF PULP

This paper studied the reuse of the ethanol from the waste-liquor of aspen auto-catalyzed ethanol-water pulping by distillation. Recycled ethanol with a certain amount of acetic acid was used to pulp. The results showed that when the reuse of waste-liquor reached the sixth time, the yield of screened pulp decreased from 49.23% to 43.87%, and kappa value decreased from 27.71 to 19.15. At the same time, the waste-liquor pH value decreased from 4.02 to 3.43. Recycled ethanol pH decreased from 4.54 to 4.18, and the content of acetic acid in recycled ethanol increased from 0.23% to 1.12%. In the new preparation of the cooking liquor, acetic acid content increased from 0.07% to 0.28%. This result indicated that acetic acid existing in recycled ethanol promoted the delignification and degradation of carbohydrate in the cooking process to a certain extent. Reducing the cooking temperature was a feasible method. It not only ensured satisfactory yield and kappa value of pulp, but also relieved the high temperature and pressure on the equipments in the process of ethanol pulping. Meanwhile, it could also reduce the energy consumption of cooking process.