Dust Filter Bags are still one of the most cost effective ways of filtering dust and particulate matter from gas streams caused when industrial processes vent their exhaust. The technology, like all good technologies, is simple and effective. Still relying on fabric bags to do most of the filtering work. Because the major changeable component of a filter (the bag) is relatively inexpensive. The whole filtration system can be very economic to run. An ideal solution to hot gas filtering in the age of recession.
Filters for bags come in a variety of different types and forms. The only common element in all of them being the bag. The way the gas is directed through the filters, and the way the whole filtering unit is operated to ensure continual cleaning even when parts of the filter’s interior are dirty, changes from application to application. Indeed, a bag filter can even contain bag material without actually containing bags. So the gas is filtered through the same kind of woven stuff that a bag would be made of, though not actually collected in a sack.
Simple bag filters allow gas to pass through them by way of a series of hanging bags. The bags choke dust particles out of the gas quite naturally. The gaseous particles can pass through the gaps between the fabric fibres, but the dust particles cannot. The efficacy of a filter actually increases (up to a point) as more dust gets trap. The caked dust rubs gently against the fabric of the bags, which creates an electrostatic charge. That charge attracts more dust to the filter and so speeds up the filtration process.
Naturally enough, bag filters that work like this reach a peak of efficiency (where their electrostatic charge is strong enough to pull in a lot of dust particles, but the material of the bag is not actually clog with dust). Once there is such a concentration of dust on the bag. That gas itself can no longer pass through the fibrous gaps, these have to cleaned.