LIGNIN REMOVAL FROM ALCELL(R) PULP BY WASHING WITH ETHANOL AND WATER

Washing of ethanol-based organosolv pulp (Alcell(R) process) in a solu tion of ethanol-water can reduce lignin content significantly. This st udy presents the results of a laboratory study designed to optimize th e washing process for maximum lignin removal. Washing was carried out in a stirred batch reactor and in a displacement-washing cell. Lignin- removal efficiency was much higher in the displacement-washing cell. K ey displacement-washing operating parameters (temperature, superficial velocity, ethanol concentration, and pulp consistency) were varied to determine their effects on lignin removal. The results are interprete d in terms of lignin solubility in the wash liquor and diffusion of di ssolved lignin from the fiber wall. The results show that displacement washing can delignify the organosolv pulp from an initial kappa no. 5 4 to kappa no. 25.