Study on Preparation of Dissolving Grade Pulp and its Kinetics of Prehydrolysis

The possibilities of dissolving grade pulp production from reed were investigated in this paper. Two - stage prehydrolysis - kraft pulping and CEHA bleaching process of reed for preparation of dissolving grade pulp were studied in laboratory. The optimum cooking and bleaching conditions were found out. The mechanism and its kinetics of reed in prehydrolysis process were also discussed. The results showed that under the laboratory conditions the rate for removal of materials at about 175 degrees C follow approximately a pseudo first order law with two distinct phrases: the bulk removal and the residual removal of the materials. The prehydrolysis-factor (P-factor) was established. The advantage of using P-factor is predict compensating adjustments in cooking time and/or temperature to give the same degree of pulping and to produce pulp with predetermined characteristics. It is found that three distinct delignification rate stages about 75% of pentosans and about 50% of lignin were removed. A CEHA four stage bleaching is used for dissolving grade pulp. Total chlorine charge in bleaching is 6% (to oven-dry pulp). The results show that all of the indices fitted the quality standards of dissolving grade pulp.