Ditch the Bag Filters

Barry Perlmutter explains automated clarification technologies

OVER my career in the solid-liquid separation market space, I have seen interesting examples of how to solve a solid-liquid separation problem. In one case, I was at a melamine resin facility where the slurry was in a formaldehyde process and the operators were in a room wearing “masks” opening up a manual plate filter in a room with residential floor fans to dig out the cake from the paper filter media. In another case for zeolites, the client had multiple bag filters to clarify the filtrates following a vacuum belt filter. When the filtrates, the final product, remained cloudy, to my surprise, the client decided to add another set of bag filters!

There are many other examples of process engineers struggling to clarify process liquids. What are some possibilities to automate the clarification processes to improve filtration while minimising operator exposure?

A clarification system is employed after coarse-particle filtration or as a stand-alone system to remove fine particles at low concentrations. These particles are typically less than 5 µm and are in concentrations less than 5% solids down to ppm levels. There are several types of automated, pressure-filtration, clarification technologies that engineers can evaluate. The cake solids structure and the nature of the process determine which type of clarification system is appropriate for an application.