Exploration and Identification of Alternative Raw Materials for Paper and Newsprint Manufacture: Studies on Hardwood Kraft Black Liquors

摘要

Black liquors from some Central Indian hardwood species, eucalyptus tereticornis, Populus deltoides, eta reeds, and Pinus rosburghii have been investigated. The black liquors from the different raw materials varied considerably with respect to their viscosities, burning characteristics and precipitation behavior. Eucalypt black liquor had the highest viscosity at 55% solids, followed by the black liquors from eta reed, mixed hardwoods, populus deltroides, and pine. The mixed hardwood black liquors start precipitating at around 40% solids during evaporation. Analysis of the precipitate formed during evaporation has also been carried out. Hardwood black liquors showed poor burning qualities compared to softwood as revealed by the swelling volume ratio method. The viscosity of black liquor could be reduced effectively by maintaining higher residual alkali by charging slightly more chemical during cooking than by adding fresh sodium hydroxide to the black liquor. An alternative for maintaining the higher residual alkali would be charging fresh sodium hydroxide preferably at 35% concentration of black liquor.