TOTAL CHLORINE-FREE BLEACHING OF SULFATE HARDWOOD PULP WITH HYDROGEN PEROXIDE

The work is devoted to the study of the possibility and feasibility of environmentally safe bleaching of sulfate hardwood pulp by TCF-technology without the use of traditional oxygen and ozone as a delignifying reagent. The TCF-technology of sulphate hardwood pulp bleaching (scheme Pa-EP-Pd-Aac-P-A) was developed with only one oxidizing reagent – hydrogen peroxide. It is proposed to carry out of pulp delignification with hydrogen peroxide in an acid medium conditions, additional delignification and bleaching – with hydrogen peroxide in an alkaline medium conditions. Soft oxidizing effect of hydrogen peroxide used at all stages of bleaching provides selectivity of the process along with ecological compatibility of the scheme. The mechanical strength of pulp varies during bleaching in accordance with the change of the degree of delignification and is very moderate, and the total loss of pulp fibers is only 6.1%. Production of hardwood sulfate pulp, as well as sulfite, is associated with difficulties caused by a "harmful" resin at a small proportion of extractives. The proposed scheme of bleaching provides a high degree of resin removal and contributes to the depitching, i.e. decision of very important problems in sulphate hardwood pulp production.