1. TYPE OF TECHNOLOGY
2. RETAINABLE IMPURITIES
Dust particles of all kinds.
3. RETENTION EFFICIENCY
Bag filters can be employed for particles of a large range of sizes, from coarse to submicronic (0.20 – 0.25 μm), achieving a filtering efficiency of over 97%.
4. EQUIPMENT AND PROCESS DESCRIPTION
Bag filters are automated dust collectors designed to operate on a 24/7 schedule, with capabilities of self-regeneration under the action of inverted jets of compressed air. They are used for air concentrations of very fine dust, and afford a particularly high filtering efficiency, even in the case of particles smaller than 1 μm. When constructed out of appropriate materials (e.g. fiberglass filtering material), this type of dust collector can be used in environmental temperatures as high as 200 °C. It features modular structures, so as to be easily transported and assembled, and allows for easy expansion of existing structures. The filtering elements consist of metal cages of different sizes, on which there are mounted bags made out of filtering material of various types, which are suited to particular requirements. The filtering elements are quickly and easily mounted and dismounted, allowing for low cost of maintenance. The parameters of filter’s cleaning cycle can be adapted to particular requirements. Its control panel is designed to allow manipulation of both air-jet cleaning interval duration and frequency. This flexibility allows for the correct regeneration of the filtering material, a process which involves the dislodgement of dirt adhering to the filtering surfaces. In other words, it is possible to calibrate the operation of each filter, depending on the specific needs of each installation, thus affording the highest possible filtering efficiency. In most cases, efficiency can exceed 99%. Dust-laden air enters the filter chamber and is passed through filtering bags from outside within. Filter bags are regenerated through the issue of compressed air jets (at pressures of 6-7 bars) in a direction opposite that of normal operational air-flow (i.e. from within to the exterior). The air jets are triggered by solenoid valves. Each solenoid valve launches compressed air along a line connecting multiple bags, and the lines collectively constitute the complete filter. The valves are operated in a sequential fashion through electrical signals sent by the control panel. Air current is generated by a centrifugal fan required to provide a filtration flow of approx. 0.03 m/s (the filtration flow is the rate at which air passes through the filtering surface). The characteristics of the filter, including the type of filtering material used, the filtering surface, and the number of bags must be suited to particular impurities to be filtered and to air temperature. Suitable bag filter configuration and fan power are determined based on these factors, while taking into account that the pressure drop across the bag filter must not exceed approx. 120 mm H20. Compressed air consumption is situated at approx. 0.15 m³/h per m2 of filtering material.
5. APPLICABLE FIELDS
Bag filters can be used in any industrial process where dust is present: the production and processing of ceramics and paints, the food industry, the chemical industry, rubber manufacturing, sugar refining, extraction mines.