Effect on the Concentration of Alkaline Solution in the Hot Alkaline Refining

Abstract

The hot alkaline refining of prechlorinated sulphite pulp was studied with the various concentrations of alkaline solutions. The results are as follows : 1) If an equal amount of sodium hydroxide based on moisture-free pulp is used in the treatments, higher refining effect is obtained with increase in pulp consistency.2) The refining reaction scarcely goes on, when the concentration of sodium hydroxide solution is reduced to 0.05% or less on the course of hot alkaline treatment.3) A certain correlation seems to exist between the yield and the alpha cellulose content of refined pulp, and the amount of dissolving from pulp is a function of the amount of alkali consumed in the treatment. Therefore, the highest alpha cellulose content of pulp, expected within a range of adopted conditions, may be determined by the amount of sodium hydroxide based on moisture-free pulp using in the hot alkaline refining.4) The velocity of refining reaction during the hot alkaline treatment is influenced by the amount of remained pulp and the concentration of alkaline solution.5) The higher the concentration of alkaline solution adopted, the quicker the reaction takes place, and the velocity does not reduce to the corresponding level, even if the alkali concentration falls down on the course of refining. This is due to the fact that the structure of cellulose fiber is loosened by the higher alkaline solution at the beginning of treatment.