Fabric Filters Baghouses

Baghouses separate fly ash from flue gas in separate compartments containing tube-shaped or pocket-shaped bags or fabric filters. Baghouses are effective in controlling both total and fine particulate matter. They can filter fly ash at collection efficiencies of 99.9% on pulverized, coal-fired utility boilers. Other baghouse applications include building material dust removal, grain processing, oil mist recovery in workplace environments, soap powders, dry chemical recovery, talc dust recovery, dry food processing, pneumatic conveying, and metal dust recovery.

The main parameters in baghouse design are the pressure drop and air-to-cloth ratio. Pressure drop is important because higher pressure drops imply that more energy is required to pull gas through the system. The air-to-cloth ratio determines the unit size and thus, capital cost. This ratio is the result of dividing the volume flow of gas received by a baghouse by the total area of the filtering cloth and is usually expressed as acfm/ft2. This ratio is also referred to as the face velocity. Higher air-to-cloth ratios mean less fabric, therefore less capital cost. However, higher ratios can lead to high pressure drops forcing energy costs up. Also, more frequent bag cleanings may be required, increasing downtime. Fabric filters are classified by their cleaning method or the direction of gas flow and hence the location of the dust deposit.

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