Strength Propeties Of Eucalyptus Mixed Pulp In ECF Bleaching Process

Importing the foreign goods wood always is one of the important wood material resources to pulp in our country. However some defects such as low strength of pulp and high degree of dust still limit the application of imported goods wood. So as far as possible to overcome the bad effect, a series of inquiry about strength are proceed according to the characteristics of the raw material quality in this paper. The paper explores the characteristic of imported wood based on the conventional pulping process. Then the adaptive process optimization scheme is put forward. And finally the loss of eucalyptus pulp strength in the bleaching process is explored.At first, when the mixed eucalyptus wood chips of a large pulp mill in Guangdong were used in kraft pulping and bleaching, the strength loss became a more serious problem.The optimum parameters in ECF bleaching process for kraft pulp of eucalyptus wood were obtained via orthogonal experiments. When the final stage was chosen, the whiteness and kappa number would be better by hydrogen peroxide bleaching while the bleaching effect of D1 stage refered to the chlorine dioxide whitening stage was better in strength of pulp and viscosity. So when the strength of pulp was the chieflyindicator, Di stage was the first choice of final bleaching stage.Then the rule for performance of pulp needed to be understood in ECF bleaching process of eucalyptus mixed pulp:the whiteness of bleaching pulp was 87.72%, after bleaching process of O-D0-Ep-D1, and the whiteness meet the standard of bleaching pulp which was explicitly stipulated by QB/T 1678—2007. After oxygen delignification the carboxyl content of pulp was 75.45mmol/kg which was the equivalent of carboxyl content for unbleached pulp two times, while the carboxyl content dropped to 44.66mmol/kg when the subsequent bleaching stages were carried out.The rule about strength of pulp for conventional kraft pulp in ECF bleaching p rocess was introduced in this paper. The rank of loss about tensile and tear index o f pulp in the bleaching process was described below:oxygen delignification>D1>D 0>Ep and loss of strength was the most serious in oxygen delignification stage.At last, the characteristics of performance about pulp in ECF bleaching were listed, which pulp was prepared by Lo-solids cooking and conventional kraft cooking, respectively. Pulp prepared by Lo-solids cooking had better performance in whiteness, viscosity and pulp strength.