Filter cake washing is a common way of improving the quality in purity of particulate products in solid-liquid separation processes. In industrial applications, this process step is usually treated as a black box where optimization is performed through trial and error. Decisive progress has been made in academia by the development of physical models to describe the washing phenomena inside a porous structure such as filter cakes. Although some models have led to a better understanding of the process, experimental efforts are still inevitable for determining optimization strategies. This contribution is an empirical approach to investigate the influence of important process parameters of washing pre-deliquored cakes with the focus on the wash liquor and filtrate flow rate. In washing a pre-deliquored cake, low moisture content at the time of wash liquor addition can be very disadvantageous for the wash efficiency due to inhomogeneous flow. This can be the result of a poor re-wetting process while washing at low wash liquor flow rates. An increase of the flow rate was observed to be very advantageous to set higher moisture content of the filter cake and therefore enforce a homogeneous distribution of the wash liquor. A homogeneous distribution of the wash liquor inside the cake is generally required for good washing. ᭧
Technologie in Pfinztal für die Bestimmung der Tropfengröûenverteilung mittels Laserstreuung und der Volkswagen-Stiftung für die finanzielle Unterstützung (I/75 682).
This contribution aims to bridge two different fields of science, viz., geoecology and mechanical process engineering. The study reports on the application of mechanical washing processes especially filter cake washing, on calcium-ion removal from peat, which is a natural material that is used in different fields of application such as agriculture, medicine, cosmetics, etc. The interesting properties of peat such as its porous structure and the sorption behavior influence the distribution of liquid inside the bulk and the liquid flow behavior through the porous structure. Experimental results are obtained from filtration tests using differential gas pressure in a filter nutsche. The washing efficiency is determined for different pressures and specific amounts of applied wash liquor. It is found that the water repellent phenomena that occurs when peat has been dried, affects the washing efficiency in a very negative way. The results obtained are compared to the conventional filter cake washing process.
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