Bag filters. Purpose and principle of work
Bag filters are special equipment, the purpose of which is the cleaning of polluted air. They are used for dry separation of dust particles or for the extraction of useful dust from streams air. Usually contamination at the outlet after the cleaning process is not more than 10 mg/m3, while the purity of air after the process filtration reaches 99.99%.
These filters are widely used in various industries production, such as:
- removal of dust from transport companies, for example, in cement industry;
- processing of ferrous and non-metallic materials, for example, in foundry;
- removing the dust from the kettle settings, in biomass burning;
- as a filter product for mills, for example, for a coal.
The main privileges of bag filters are efficiency, profitability, reliability and, accordingly, durability. Filter for cleaning the compressed air is installed in dust collection systems and aspiration.
The main element of the bag filter is the filtering sleeves, which require replacement and often wear out. The material from which the sleeve is made is selected depending on the conditions of its use. The important role in reliable operation of such sleeves is played by quality of material and tailoring, because during the work they go through many regenerations, that is, they are affected by different shaking mechanisms, pulses of compressed air and cleaning by blow. To ensure the reliability of these filters, the sleeves should have high technological properties and pass the test for strength, stability and durability.
The configuration of filter has a rather simple composition. It consists of two parts (upper and lower). The lower part can be open and closed, that is, with or without a sewn bottom. An upper part is open and usually includes fixing elements (springs, metal fastening rings and other sealing elements). Longitudinal seam is a connecting element to which is given special attention. The seam is made not by one piercing line, but several, and it provides the seam with 100% reliability. It stands a greater load than the filter cloth.
To ensure high quality sleeves, as well as reliability operation of a seam filter, stitching of collars, cords and springs are done on specialized equipment.
Filter bags have a cylindrical or rounded shape and made of filter cloth or needle-punched fabric. Filter fabric must meet the requirements of the industrial process, chemical gas and dust characteristics, technical characteristics of a factory.
Ways of regeneration (cleaning) of filter bags:
- Purge via reverse push of air. There are used continuous low-pressure air flows in the cells for removal of collected solids.
- Mechanical shaking or vibration actions for cleaning from dust.
- Pulse regeneration – there are used the compressed streams of the air at high pressure to remove the solid particles. Such type of cleaning is used in the sleeves with metal framework.