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Difference between revisions of "Baghouses"
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[[Category:Filtration]]{{Knoppen}} | [[Category:Filtration]]{{Knoppen}} | ||
[[File:Baghouses_01.gif|thumb|right|Baghouse]] | [[File:Baghouses_01.gif|thumb|right|Baghouse]] | ||
[[File:Baghouses_03.jpg|thumb|right|Baghouse model]] | [[File:Baghouses_03.jpg|thumb|right|Baghouse model]] | ||
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==Operation of Baghouses== | ==Operation of Baghouses== | ||
Most baghouses use long, cylindrical bags (or tubes) made of woven or felted fabric as a filter medium. (For applications where there is relatively low dust loading and gas temperatures are 250°F or less, pleated, nonwoven cartridges are sometimes used as filtering media instead of bags.) Dust-laden gas or air enters the baghouse through hoppers (large funnel-shaped containers used for storing and dispensing particulate) and is directed into the baghouse compartment. The gas is drawn through the bags, either on the inside or the outside depending on cleaning method, and a layer of dust accumulates on the filter media surface until air can no longer move through it. When sufficient pressure drop (delta P) occurs, the cleaning process begins. Cleaning can take place while the baghouse is online (filtering) or is offline (in isolation). When the compartment is clean, normal filtering resumes. | Most baghouses use long, cylindrical bags (or tubes) made of woven or felted fabric as a filter medium. (For applications where there is relatively low dust loading and gas temperatures are 250°F or less, pleated, nonwoven cartridges are sometimes used as filtering media instead of bags.) Dust-laden gas or air enters the baghouse through hoppers (large funnel-shaped containers used for storing and dispensing particulate) and is directed into the baghouse compartment. The gas is drawn through the bags, either on the inside or the outside depending on cleaning method, and a layer of dust accumulates on the filter media surface until air can no longer move through it. When sufficient pressure drop (delta P) occurs, the cleaning process begins. Cleaning can take place while the baghouse is online (filtering) or is offline (in isolation). When the compartment is clean, normal filtering resumes. | ||
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===Sonic Horns=== | ===Sonic Horns=== | ||
Some baghouses have sonic horns installed to provide supplementary vibration cleaning energy. The horns, which generate high intensity, low frequency sounds waves, are turned on just before or at the start of the cleaning cycle to help break the bonds between particles on the filter media surface and aid in dust removal. | Some baghouses have sonic horns installed to provide supplementary vibration cleaning energy. The horns, which generate high intensity, low frequency sounds waves, are turned on just before or at the start of the cleaning cycle to help break the bonds between particles on the filter media surface and aid in dust removal. | ||
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Two main sequence types are used to clean baghouses: | Two main sequence types are used to clean baghouses: | ||
*Intermittent (periodic) cleaning | *Intermittent (periodic) cleaning | ||
*Continuous cleaning. | *Continuous cleaning. | ||
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*Pressure drop is the resistance to air flow across the baghouse. A high pressure drop corresponds with a higher resistance to airflow. Pressure drop is calculated by determining the difference in total pressure at two points, typically the inlet and outlet. | *Pressure drop is the resistance to air flow across the baghouse. A high pressure drop corresponds with a higher resistance to airflow. Pressure drop is calculated by determining the difference in total pressure at two points, typically the inlet and outlet. | ||
*Filter drag is the resistance across the fabric-dust layer. It is the pressure drop per unit of velocity. | *Filter drag is the resistance across the fabric-dust layer. It is the pressure drop per unit of velocity. | ||
*An understanding of the term air-to-cloth ratio is vital to understand the mechanics of any baghouse system regardless of the exact type used. This ratio is defined as the amount of air or process gas entering the Baghouse divided by the sq. ft of cloth in the Baghouse. Units of measure are (ft3/min)/ft2 or (cm3/sec)/cm2. | *An understanding of the term air-to-cloth ratio is vital to understand the mechanics of any baghouse system regardless of the exact type used. This ratio is defined as the amount of air or process gas entering the Baghouse divided by the sq. ft of cloth in the Baghouse. Units of measure are (ft3/min)/ft2 or (cm3/sec)/cm2. | ||
*Commonly, baghouses are designed with 99.9% collection efficiency. Oftentimes, cleaned air is recirculated back into the plant for heating. | *Commonly, baghouses are designed with 99.9% collection efficiency. Oftentimes, cleaned air is recirculated back into the plant for heating. | ||
===Baghouse Filter Media=== | ===Baghouse Filter Media=== | ||
Fabric filter bags (sometimes referred to as envelopes) are oval or round tubes, typically 15–30 feet and 5 to 12 inches in diameter, made of woven or felted material. Depending on chemical and/or moisture content of the gas stream, its temperature, and other conditions, bags may be constructed out of cotton, nylon, polyester, fiberglass or other materials. | Fabric filter bags (sometimes referred to as envelopes) are oval or round tubes, typically 15–30 feet and 5 to 12 inches in diameter, made of woven or felted material. Depending on chemical and/or moisture content of the gas stream, its temperature, and other conditions, bags may be constructed out of cotton, nylon, polyester, fiberglass or other materials. | ||
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==Components of a Baghouse== | ==Components of a Baghouse== | ||
*Bags, fabric & support | *Bags, fabric & support | ||
*Housing or shell | *Housing or shell | ||
*Collection hoppers | *Collection hoppers | ||
*Discharge devices | *Discharge devices | ||
*Filter cleaning device | *Filter cleaning device | ||
*Fan | *Fan | ||
==Related topic== | ==Related topic== | ||
[[Electrostatic Precipitators]] | |||