Fabric Filters: Uses and Advantages
Filtration is one of the most efficient and versatile methods of eliminating particulate mater from industrial gases. 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 are placed in a housing with a gas inlet and outlet connections, collection hopper, and a mechanism that periodically removes the collected dust from the fabric. As gas passes through the filter, dust may be trapped in the fabric through different mechanisms, such as diffusion, inertial impaction and direct interception.
Why Fabric Filters?
There are a number of advantages to using fabric filters, and here are the most important:
> Remarkably high collection efficiency (maximum of 99.9 plus %) with more particle size and inlet grain loading variations 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
> Works with wider particle size distribution
> No specific 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. In addition, tissue properties are also dependent on the individual properties of the fibre or thread, the surface treatment and the coating. Tissue’s filter qualities are largely determined by the dust cake that gathers on the filter.
Because felt is a three-dimensional fiber network, it is more effective for filtration. High fabric loading is possible with felt, which is mechanically stronger than felt, while a smaller filter installation works fine.
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 method absorbs dioxins or gets rid of acid components when activated carbon or lime, respectively, is injected into the fume channel. Through catalytic fabric filters, dioxins can be removed as well.
Fabric filters are currently used in various industries, such as chemicals, metal processing, food, waste processing and cattle-feed.