Analyses of the Dynamic Processes of Liquid Metal Filtration

The dynamic processes of liquid metal filtration with reticulated ceramic filters prior to filter "ripening" were analyzed theoretically by examining the changes in the filter coefficient as a function of its independent variables during the filter aging period. Correlations relating the filter coefficient and pressure gradient to the specific deposit (volume fraction of nonmetallic particles captured within the filter) were derived and then solved numerically to simulate the dynamic behavior of liquid aluminum filtration. Simulated results showed that the particle-capture process within the filter possesses an autocatalytic behavior. The filtration efficiency of, and pressure gradient within, the filter were found to increase with filtration time and with particle concentration within the melt. These increases were, however, negligibly small for the first 2-hour period of filtration if the particle concentration within the melt was lower than I ppm by volume; when the particle concentration reached 10 ppm, increases in filtration efficiency became appreciable. This corresponds to a passage of about 160,000 kg of 10ppm liquid aluminum per square meter of filter area.