PREPARATION OF PULP FROM HARDWOOD (BIRCH) BY KRAFT PRCESS

Abstract

Studies on the possible utilization of hardwoods by kraft process have beencarried out. It is concluded that from the standpoint of cooking time, yield and strength, it is best to use hardwoods with conifers in 50-50 proportion in weight or about 40% of hardwoods in volume mixed with conifers. The following are some of the results.
1) It takes less time to cook hardwoods than soft woods inspite of the hardness.
2) Pulp yield is about 5% higher in the case of hardwoods.
3) Alkali consumption per digester is higher for hardwoods. Chlorine No. 5 of hardwoods corresponds to chlorine No. 10 of conifers approximately.
4) Heart-wood and sap-wood usually result in lack of uniformity even under the same cooking condition.
5) Pulp made from hardwoods gives maximum strength at around chlorine No. 5. Breaking length and bursting strengths are about the same as conifer-pulp but tearing strength drops to 2/3 of conifer-pulp.
6) The maximum strength is observed when the proportion of mixture of hardwoods and conifers is 50-50 with anexception of tearing strength.