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What Is a Belt Filter?

Dan Cavallari
Dan Cavallari

A belt filter is a machine used in many industry applications to separate liquids from solids. It is often used in sewage treatment and filtration to obtain reclaimed water or to safely dispose of harmful solids. The machine is so named because it uses a belt or series of belts run through rollers to separate the materials. Materials are fed into the belt filter from a hopper, and the belts run through several rollers in a scattered configuration. As the belts process the materials, solids and liquids are separated, and the solid matter can be scraped from the belts and fed into a container system.

While the specific configuration of the belt filter can vary from machine to machine, most filters can be broken down into three sections: the first section is the gravity component, in which liquid is allowed to drain naturally from the material. Vacuum pumps may be used at this stage to facilitate quicker removal of liquids. The second section of the belt filter process is a preparation stage, in which the materials are prepared for compression or pressure application. The third and final section is a belt system in which varying degrees of pressure are applied to the materials for the most adequate separation.

Man with a drill
Man with a drill

Before the sludge or material is fed into the machine, it may be treated with a chemical that will further facilitate the separation of liquids and solids. The gravity feed zone, in which liquid is initially drained from the solids by using gravity and vacuum forces, will often consist of a rapidly rotating drum or a vacuum cylinder that sucks water downward. A high percentage of the liquid will be drained off during this stage in the belt filter. Once this initial stage is complete, the materials will be fed by the belt into the series of rollers.

The initial rollers are large diameter components that apply light and medium pressure. This presses out remaining liquid and prepares the material for further pressurization. The next series of rollers will be increasingly smaller in diameter, allowing higher levels of pressure to be applied to the materials. By the time the belts have fed the materials through the rollers, most of the liquid will have been removed and the materials in solid form can be fed out of the machine. Spray bars must be used to continually clean the belts with fresh water to prevent binding and cake build-up.

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