ASSESSMENT OF THE MIXING EFFICIENCY OF HC MIXERS IN HIGH-CONSISTENCY BLEACHPLANTS

摘要

A non-radioactive method was optimised and approved for measuring the mixing efficiency of a chemical mixture,i.e. the evenness of chemical distribution in a pulp sample, using lithium chloride as tracer.With a laboratory kneader, mixing efficiencies in the range of 91- 96% were obtained. Further, it was shown that alower mixing efficiency leads to a reduced bleaching effect, which demonstrated that the method as described is asuitable measure for assessing the mixing efficiency.The mixing efficiency of industrial-scale HC mixers was between 86 and 94% and thus, well within the range of thelaboratory mixer.Calculations demonstrated that the peroxide consumption in a HC bleach plant is 5% higher at a mixing efficiency of80%, compared with ideal mixing.The measuring method described above allows us to measure the mixing efficiency of almost every available mixerand to quantify possible savings in chemicals achieved by improving the mixing efficiency.