Assessment of mixing quality for an industrial pulp mixer using electrical resistance tomography

Abstract

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.La qualité de mélange d'une suspension de pâte et d'une solution de ClO2 par un mélangeur statique dans un stade de blanchiment industriel aétéévaluéeà l'aide de la tomographie par résistanceélectrique (ERT) en fonction du processus d'exploitation de conditions, y compris le débit de solution, débit de suspension et la concentration de fibre. L'uniformité aété quantifiée par un indice de mélange basé sur le coefficient de variation des valeurs individuelles de conductivité dans chaque pixel de l'image. Une augmentation de l'indice de mélange, indiquant une qualité inférieure de mélange, aété observée lorsque le débit de solution a augmenté. En outre, la qualité du mélange diminue avec une diminution de la vitesse d'écoulement de suspension. En revanche, une diminution de la concentration de fibre dans la suspensionà un débit constant de suspension volumétrique a donné un mélange de meilleure qualité. Les résultats montrent que l'ERT peutêtre utilisée pourévaluer sur le plan industriel le rendement du mélangeur et pour surveiller la qualité du mélange sous différentes conditions d'exploitation. Les résultats sont en bon accord avec ceux de la littérature basée sur d'autres techniques de mesure pour des installations de mélangeur similaire

Application of high-frequency impedancemetry approach in measuring the deposition velocities of biomass and sand slurry flows in pipelines

“…and costly, and data collection strategies and image reconstruction algorithms are difficult to apply. In addition, the ERT approach, to be applicable, requires a significant electrical conductivity difference between solid particles and fluid (Yenjaichon et al, 2011).…”

Gas–liquid mixing in dual agitated vessels in the heterogeneous regime

“…The technique has multiple advantages over other imaging techniques, such as high speed, low cost, non-intrusive, and no radiation hazard. Thus ERT has become one of the most promising tomography techniques in monitoring and analysing various industrial flow processes (Aw et al, 2014;Rodgers et al, 2011;Yenjaichon et al, 2011). The fundamental of ERT is to take numbers of surface voltage measurements from multiple electrodes mounted in an arbitrary geometric pattern, generating an image showing distribution of electrical resistivity or conductivity.…”

Assessing Blending of Non‐Newtonian Fluids in Static Mixers by Planar Laser‐Induced Fluorescence and Electrical Resistance Tomography

“… used ERT to validate CFD simulations of the blending of two non‐Newtonian fluids flowing in SMX static mixers. The same technique was employed for measuring velocity profiles of shampoo in pipelines and to evaluate mixing of industrial pulp in static mixers . Recent applications of ERT in pipe flows demonstrated potential for in‐line rheometry measurements (ERR) .…”