Factors Affecting Filter Cake Pick-Up During Vacuum Filtration

Abstract

Classical theories of filtration, based on the flow of fluids through packed beds of solids, may be confidently applied to ideal systems. However, these same equations may not be directly applicable in operating practice. Thus, it is usually necessary to study the effects of filtration variables on filter performance by leaf and pilot scale experiments. An extensive series of experiments was performed to study the effects of feed variables and filter type on the solids pick-up of a vacuum filter treating fine coal with particular reference to size distribution and the level and type of flocculation. Results of these tests demonstrate the need for careful design of a filter installation to achieve a specific duty. An example is presented of the effects of desliming the feed to a rotary vacuum filter. Theory predicts higher filtrate flows and lower moisture filter cakes. However, in practice the filter simply failed to form coherent filter cakes. The reasons for this are discussed in terms of the effects of feed properties on filter performance.