Pulping and bleaching of mixed southern hardwoods with eucalyptus

Eucalyptus fibers have been used in the manufacture of paper products worldwide. It is a fast growing species which can be grown well in plantations. The projected fiber shortage will increase the demand for eucalyptus and possibly its use in some grades of paperboard, which traditionally have not used this type of fiber. There are about 500 species of eucalyptus, but only a few are used in paper manufacture. The eucalyptus fiber is excellent for printing and writing papers. The objectives of this study were to find out how the addition of eucalyptus to southern mixed hardwoods would affect the pulping, bleaching, refining,and papermaking processes. It was also important to determine the amount of eucalyptus necessary to improve the final pulp and paper properties. Samples of eucalyptus chips, Eucalyptus grandis and Eucalyptus urophylla, were blended at different proportions with southern mixed hardwood chips and pulped using both conventional (CK) and extended delignification (EMCCR). These trial cooks were performed at several kappa numbers ranging from 10-18 to give more data points for our study. After evaluating the initial brownstock pulps, samples were selected for a three stage bleaching study simulating the current mill bleaching sequence. There were no significant affects on the properties of southern mixed hardwood handsheets when the eucalyptus fibers were added. Minor improvements were found in some properties while others demonstrated slight declines in strength. Additional refining will be necessary on the eucalyptus in order to obtain the maximum strengths from these fibers. Bleaching costs were reduced and the solids load in black liquor to the recovery boilers was also lowered.