Belt filter systems are very versatile and are used in the chemical industry, in pharmacy, the food industry and environmental engineering. They are furthermore ideally suited for the separation of solids from liquids in the manufacturing process of paints and pigments, in the mineral industry as well as in mining and metalworking. The filter media are either continuous filter belts made of different plastic/stainless steel fabrics or filter nonwovens as rolled goods. The filter medium can be arranged horizontally,
inclined or semicircular. Belt filters in basic designs work with gravity. More complex versions can also work with overpressure or reduced pressure/vacuum. There are very small belt filters with filter surfaces of less than one square meter as well as variants with more than 250 m². Best filtration performances are achieved in applications with a solids content of 3 to 40 % at particle sizes between 1 and 100 µm. Here is a short overview of the different variants with filter fleece and filter nonwoven recommendations.
Gravity belt filters are the easiest and cheapest version of industrially used belt filter systems. They are easy to operate and, because of their low mechanical requirements for the nonwovens, flexible in regard to their selection. Despite their fully automated function they are very robust and due to low acquisition costs and low-maintenance construction, they are cost-efficient for many applications. Because only small water columns with low pressure can form, the filter nonwovens are not ideally used. Resulting in a large space requirement we recommend them mainly for water-based applications.
|Nonwoven recommendations:||Viscose nonwoven S-CV, Needle felt S-PES-N, |
Waterjet fleece S-PES-W
This belt filter is also called belt drum filter. The filter medium which is in contact with the contaminated suspension is arranged semicircular. This leads to a water column as well as problems with the discharge of the filter cake. Special filter nonwovens - calendered on one side, fleecy on the other side - can solve this problem. The requirements for the nonwovens are generally high with respect to the usable dimensions as well as the needed tensile strenghts. That and the intensive maintenance due to agglutinating sensors or leakages in the fringe area lead to higher operating costs in addition to high acquisition costs. On the other hand there is the compact and space saving design which is possible because of a very good utilization of the filter fleece due to the hydrostatic pressure.
|Nonwoven recommendations:||Viscose nonwoven S-CV, Needle felt -PES-N, |
Waterjet fleece S-PES-W
Vacuum belt filters are often used as central units. Because of the pressure difference the filter fleece is optimally utilized which results in a good filter cake. In contrast there are similar disadvantages like for the compact belt filter which are even more pronounced: Very high investment and maintenance costs, complex fine tuning of filtration parameters necessary, high filter fleece costs due to specific requirements.
|Nonwoven recommendations:||Spunbond S-PES-F, Needle felt S-PES-N, Waterjet fleece S-PES-W, BICO-Nonwoven S-PES-B|
Whereas the inclined bed filter corresponds functionally to a gravity belt filter with additional water column, the volume flow in the hydrostatic filter is further increased by applying a negative pressure. The pressure caused by the water column allows a better utilization of the nonwoven. Therefore, only certain, tear-resistant filter nonwovens are usable.
|Nonwoven recommendations:||Spunbond S-PES-F, Needle felt S-PES-N, |
Waterjet fleece S-PES-W, BICO-Nonwoven S-PES-B
The operating principle of a pressure belt filter works, in contrast to the described vacuum filter systems, with an overpressure on the dirt side. These plants are often used for the purification of contaminated cooling lubricants. Due to high feasible throughput capacities of up to 10 m³/min they are especially suited as central units. Because of the good and clocked operation of the filter nonwoven due to high differential pressures, separation efficiencies in the single-digit µm-range are achieved. At the same time one obtains a very dry filter cake.
|Nonwoven recommendations:||Needle felt S-PES-N, BICO-Nonwoven S-PES-B, |
Polypropylene nonwoven S-PP