Monitoring and visualization of cake dewatering in vacuum filters by temperature measurements

• Thermal imaging enables real-time monitoring of filter cake dewatering in vacuum filtration processes. • Temperature measurements can be used to estimate cake solids content and detect undesirable leakages and cake cracking. • Cake cooling due to evaporation is a clear indicator of cake desaturation when air displaces pore water. • Local differences in air flow can be observed in the thermal images: coolest points at the edges and in cracks of the cake. • The method opens opportunities for energy-efficient control and optimization of industrial vacuum filter operations. The dewatering of filter cakes in continuously operating vacuum belt filters was simulated on a laboratory scale by using a batch vacuum filter, namely a Büchner filter. During the cake desaturation, the gas flow through the cake increases gradually, causing evaporation of the pore liquid, which cools the cake. In this study, two different slurries obtained from industrial processes were filtered using a laboratory-scale Büchner filter, monitoring the progress of cake dewatering with a modern thermal camera, and data acquisition for mass of filtrate, thickness of cake, air flow rate through the cake, and pressure difference. The results of this study show that thermal imaging is a useful technique for investigating the surface temperature patterns of filter cakes, which can be utilized to monitor the progress of the dewatering (cake saturation), as well as to estimate the cake solids content, and to recognize undesirable leakages caused, e.g., by cake cracking.