Characterization and simulation of displacement washing processes in filter cakes

B. Hoffner*, University of Applied Sciences Mannheim, Germany

Displacement washing of filter cakes is common in various industrial fields. The objective is to separate dissolved substances from the filter cake like salts, acids, bases, and colorants by means of a wash liquid. The wash liquid penetrates the filter cake and displaces the mother liquor largely. This paper refers only to gas differential pressure driven processes.

The displacement washing process is usually applied to filter cakes that do not show shrinkage, cracks, and wall detachment. In other cases, dilution washing processes are applied. However, due to the low specific wash liquid consumption a displacement washing is the first choice to be considered. An additional benefit of a displacement washing process is the easy integration into a process chain consisting of the cake formation step followed by one or several subsequent washing and dewatering steps.

Typical machines of operation are continuously and batch-wise operated filter equipment such as belt filter, drum filter, nutsch filter, filter press …

The progress of the washing process is commonly characterized by means of a washing curve: The amount of residuals is plotted as a function of the amount of wash liquid used. This type of curve shows usually three distinct regions, reflecting the different mass transport mechanisms, commonly named as...

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

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