Washing, bleaching and characterization of eucalyptus pulp from ethanol pulping

摘要

The present study analyzed eucalyptus pulp produced by the ethanol-based organosolv process submitted to different bleaching strategies. Washing tests with ethanol and alkaline solution, cold caustic extraction (CCE), oxygen delignification and bleaching through D_(hot)(EP)DP bleaching sequence were performed. Different washing strategies were investigated. In washings with NaOH solution, different charges, times and temperatures were tested. The best result was obtained with NaOH charge of 40 kg/t, 3 min and 90℃, reducing the kappa number by 33 %. CCE of the brown stock resulted in a reduction of the kappa number by 29%. The highest kappa number reduction was reached by bleaching with the O/OD_(hot)(EP)DP sequence. Delignification degree in the oxygen stage was 79.2%, indicating no need for prior treatments as ethanol or alkaline solution. The final bleached pulp had a brightness of 91.7% ISO, viscosity of 546 cm~3/g and low content of hemicelluloses.