Rotary vacuum drum and vacuum belt filters are extensively used on many process filtration operations, to provide filtration, clarification, dewatering or concentration. Moulded thermoplastic vacuum drum filters are particularly suited to providing continuous filtration of corrosive chemicals, without using expensive or hard to obtain exotic metals such as titanium, stainless steel, monel, Hastelloy or rubber covered steels.
Belt press filters for dewatering have found favour in the broader mineral, chemical and metal processing industries, including the treatment of coal refuse, gold and silver tailings, aggregate washing, dewatering of wastewater treatment sludges (primary sludge, waste activated sludge and anaerobically digested sludge), and pulp and paper sludges. Solids must be sufficiently dewatered before being subjected to compression pressures or extrusion from the edges of the belts will occur. This is usually accomplished by a gradual increase in pressure over a fairly long dewatering zone before the solids are finely squeezed between the belts to remove the remainder of the liquid.
Horizontal belt vacuum filters have the advantage of fast filtration cycles, flexibility of operation with either co-current or counter-current washing, and generally low maintenance costs. Typical filtration areas are from 1 to 140m2, with processing capability ranges from a rate of 50 to 9800kg/hm2 depending on the filterability of the material.