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 is made possible with the use of filter fabrics – also called baghouse filters, cartridge filters, sleeve filters and many other names – made of woven or felted material.
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.
Fabric Filter Advantages
Fabric filters offer a lot of advantages, including:
> Up to 99.9+% collection efficiency and with more variations in particle size and inlet grain loadings Compared to other types of single dust collectors, fabric filters can have consistent static pressure and efficiency for more particle sizes and concentrations within certain limits.
> Collection efficiency not influenced by the combustion fuel’s sulfur content unlike in ESPs
> Less particle size distribution sensitivity
> No specific voltage requirements
> Filters flammable dust
> Can eliminate smoke and fumes at sub-micron levels with the use of special fibers or filter aids
> Offers wide variety of sizes, configurations and inlet/outlet locations
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. Tissue’s filter qualities are largely determined by the dust cake that gathers on the filter.
Felt is a three-dimensional network of fibers, making it more effective as a filter. High fabric loading is possible with felt, which is mechanically stronger than felt, while a smaller filter installation works fine.
Two examples of basic materials for filter fabrics in flue gas applications are Polyacrylonitril and Polytetrafluorethylene, which come with different advantages and disadvantages in terms of mechanical strength, temperature, chemical resistance and 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. 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.