Canadian Journal of Chemical Engineering, Vol.89, No.5, 996-1004, 2011
ASSESSMENT OF MIXING QUALITY FOR AN INDUSTRIAL PULP MIXER USING ELECTRICAL RESISTANCE TOMOGRAPHY
The quality of mixing of a pulp suspension and chlorine dioxide by a static mixer in an industrial chlorine dioxide bleaching stage was evaluated using electrical resistance tomography (ERT) as a function of process operating conditions, including chemical flow rate, suspension flow rate, and suspension mass concentration. The uniformity was quantified by a mixing index based on the coefficient of variation of the individual conductivity values in each image pixel. An increase in the mixing index, indicating lower mixing quality, was observed when the chemical flow rate increased. In addition, the mixing quality decreased with a decrease in suspension flow rate. On the other hand, a decrease in the suspension mass concentration at a constant volumetric suspension flow rate gave better mixing quality. The results show that ERT can be used to evaluate industrial-scale mixer performance and to monitor the changes in the mixing quality as a function of process operating conditions. The results are in good agreement with those in the literature based on other measurement techniques for similar mixer installations.