Fabric Filters – Industrial 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 primarily relies on filter fabrics, also known as baghouse filters, compact filters or sleeve filters, among many other names, is made of either felted or woven 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. When gas passes through the fabric, dust can be trapped by way of different mechanisms, the most common of which are direct interception, diffusion and inertial impaction.
Why 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; When pitted against other single dust collector types, fabric collectors, under certain limits, can maintain consistency in static pressure and efficiency for a wider variation of particle concentrations and sizes.
> Collection efficiency not influenced by the combustion fuel’s sulfur content unlike in ESPs
> Less particle size distribution sensitivity
> No voltage requirements
> Picks up flammable dust
> Removes smoke and fumes at sub-micron levels using special fibers or filter aids
> Offers wide variety of sizes, configurations and inlet/outlet locations
Types of Fabric Materials
There are two types of materials used to make fabric filters: tissue and felt. Tissue, a two-dimensional network that may be woven in different ways, can have varied levels of pliability and permeability. In addition, tissue properties are also dependent on the individual properties of the fibre or thread, the surface treatment and the coating. The filter qualities of tissue mainly depend on the dust cake that is left on the filter.
With its three-dimensional fiber network, felt works better for filtration purposes. 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. Dioxins can also be eliminated through catalytic fabric filters.
Today, there are man industries where the use of fabric filters is prevalent, ranging from metal processing to cattle-feed.