Dewatering and imbibition effects on the multi-stage cake washing

A. Brückner*, T. Sprott, B. Hoffner, University of Applied Sciences Mannheim, Germany

The continuous multistage cake filtration is used in many industrial sectors (e.g. chemical, pharmaceutical, energy). In order to reduce the amount of wash liquid and filtrate by having a high concentration of filtrate at the same time, the wash liquid is frequently conducted in countercurrent washing.

A dewatering step after cake formation (pre-dewatering) and an intermediate dewatering step between the washing steps are technically unavoidable. However, they can be used to remove contaminated liquid. Through an intense undersaturation in the pre-dewatering step, the contamination discharge of the filter cake reduces significantly. The filter cake can be dewatered to an equilibrium saturation. In order to describe the impact of dewatering on the whole washing process, it has been proven effective to simultaneously regard the contamination and the cake saturation as a function of process time. The parameters saturation (S), contamination (X*), washing ratio (W), time (t) must, therefore, be determined after each experiment. When the filter cake passes the washing steps (W1, W2,…), it will be filled up with wash liquid leading to a saturation increase. For a rewatered filter cake could also be determined an equilibrium saturation.

The influence of pre-dewatering and intermediate dewatering between the single washing steps were investigated in laboratory experiments with the nutsch filter. The effects of dewatering on a multistage filter cake washing can be..

Session: L7 - Cake Filtration – Particle Washing
Day: 23 October 2019
Time: 13:00 - 14:15 h

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