Belt filter

Belt filter

A belt filter, also called vacuum or gravity filter, is a mechanical system to filtrate contaminated suspensions using a filter fleece. The filter fleece is stretched between two or more rollers running through the filter body either horizontally or by forming a slope depending on the filter type. Belt filters are divided into vacuum and gravity filters. This form of filtration is particularly used in the food industry, e.g. for smokehouses or frying lines, and in metal processing, for example on welding, soldering or milling machines.

In vacuum filters, e.g. carrier belt filters or cycle belt filters, the filter fleece runs over two opposite rollers attached to an elastic carrier belt. So the filter fleece forms a continuously moving filter belt. Laterally mounted bars next to the filter belt create a flat basin for the contaminated suspension. Solid particles in the suspension sink through gravity tor are extracted by a vacuum below the filter belt. At the end of the carrier belt, the filter fleece is separated to remove the filter cake. The fleece can then be cleaned, reused or recycled. Belt filters are particularly used for particle filtration.

Gravity filters also use a combination of carrier belt and filter fleece. In contrast to vacuum filters, however, the fleece does not run horizontally, but is led down into a deep basin forming a gradient slope. The suspension flows into the basin. The contained impurities are then separated through gravity and get caught in the filter fleece. The gradient slope allows for various contaminants to be picked up directly, e.g. oil and fat containing contaminants on the surface, solid particles at a lower level. In gravity filters, the filter belt is controlled through a float switch – when the filter cake has reached a certain size it blocks the filtration fleece causing the suspension level to rise. The float switch is released, the filter belt is moves along and an unused piece of fleece enters the basin. At the end of the carrier belt, the filter fleece is separated to remove the filter cake. The fleece can then be cleaned, reused or recycled.

As part of the exhaust air purification process, belt filters are often used for the filtration of washing water or other liquid suspensions. KMA Umwelttechnik combines belt filters with its high-performance exhaust air filter systems to separate the washing water produced during the cleaning process in the fully automatic filter cleaning system (CIP).