Dust collector#Fabric filters

With a surface- filter dust (and bonded thereto, pollutants such as dioxins / furans) from flue gases, but also useful products (e.g., meal) from a carrier gas stream separated. The separation efficiency with respect to the particles is usually well over 99%. Of actual separation effect is in contrast to the deep-bed filter is not caused by the filter media, but rather by the filter cake formed on the filter.

Function

Surface filters are filters houses - consisting of several chambers - used which gas stream containing exhaust gases or recyclable materials are in use. There are several rows of cylindrical filter bags, which are stabilized by means of an embedded support cage or are provided with support rings in each chamber. The particulate laden gas flows through the filter bags generally from the outside towards the inside, whereby the surface of the filter medium, a dust layer ( filter cake) is built, which itself acts as the thickness as a highly effective filter. However, the structure of the dust layer produces an increase in the differential pressure, and thus an increase of the consumed during the flow through the hose energy. For this reason, the hose must be cleaned regularly (in practice, this is done either after a certain time or when a defined differential pressure ). Cleaning is performed mostly by Drucklufteindüsung in the tubes, thereby replacing the layer of dust and drops down into a collection hopper. This hopper is emptied via a rotary.

For the removal of gaseous contaminants from the gas stream also called sorbents (such as activated carbon, sodium bicarbonate or calcium hydroxide) may be injected upstream of the filter. The sorbent particles contact the filter cake from the well, whereby when flow through the filter cake, a reduction of the contaminant concentration ( by adsorption or chemical reaction) is effected. With a correspondingly high concentration of sorbents, the adsorption takes place before reaching the filter in the air stream to a large extent.

Application

Surface filters are for example used in the industry for flue gas cleaning, especially in power plants, cement plants and incinerators. Another application is the removal of swarf. Add the flour mills is often conveyed pneumatically, here surface filters are used for the recovery of the flour from the gas stream.

Filter medium

The filter medium come at low temperatures ( below 250 ° C) usually needled felts for use. Partly also fine fabrics are used, due to the lower collection efficiency of a nude fabric but with a declining trend. In addition, can be applied to improve the deposition upstream, an ePTFE membrane on the fabric / the needle felt. For filter media with ePTFE membrane glass fabric are used as carriers in addition to needle felting often.

Particularly in high temperature applications, rigid ceramic ( ceramic particle or fiber ceramic) or metallic used (e.g., sintered metal ) filter media, in which case the filter cartridge name is used instead of the filter bag. In order to reduce pollutants (eg dioxins ), such media can also be coated with catalysts.

Disposal

The filter dust and the filter material must be disposed of as hazardous circumstances. This depends on the filtered dust, the deposited pollution gases and the added sorbent.