Fabric Filters: Uses and Advantages
When it comes to cleaning industrial gases of particulate matter, filtration is one of the most efficient and versatile techniques ever discovered. The process depends mainly on the use of filter fabrics (also referred to as tube filers, cartridge filters and sleeve filters, among many others) which are made of a felted or woven material shaped like a flat supported envelope or cylindrical bag.
Filter fabrics come in a unit that includes a gas inlet and outlet connections, a dust collection hopper, and a system that gets rid of the collected dust periodically. As gas passes through the filter, dust may be trapped in the fabric through different mechanisms, such as diffusion, inertial impaction and direct interception.
Advantages of Fabric Filters
There are a number of advantages to using fabric filters, and here are the most important:
> Notably high collection efficiency (up to 99.9+%) with more variations in terms of inlet grain loadings and particle size; Under certain limits, fabric collectors can maintain static pressure and efficiency for more particle concentrations and sizes compared to other alternatives.
> Collection efficiency is unaffected by the combustion fuel’s sulfur content, as in ESPs
> Less particle size distribution sensitivity
> No voltage requirements
> Collects flammable dust
> Removes smoke and fumes at sub-micron levels using special fibers or filter aids
> Come in a whole range of configurations, inlet/outlet locations and sizes
Types of Fabric Materials
The two main materials used to make fabric filters include tissue and felt. As a two-dimensional network woven in many possible ways, tissue offers varying degrees of permeability and pliability. The properties of tissue are also affected by the individual characteristics of the thread or fibre used, the coating and the surface treatment. The filter qualities of tissue mainly depend on the dust cake that is left on the filter.
Because felt is a three-dimensional fiber network, it is more effective for filtration. With felt’s higher mechanical strength compared to tissue, high fabric loading can be done while a small filer installation is adequate.
Polytetrafluorethylene and ryton are two examples of materials that filter fabrics in flue gas applications are made of, and they all have specific advantages and disadvantages related to temperature, chemical resistance, mechanical strength and even cost.
Fabric filters have several applications where limitations are easily overcome simply with the right choice of filter material. This technique also allows the removal of acid components or the absorption of dioxins by injecting lime or carbon, respectively, into the fume channel. Catalytic fabric filters can remove dioxins too.
Today, there are man industries where the use of fabric filters is prevalent, ranging from metal processing to cattle-feed.