Filter, bag

Bag filters. Bag filters, as discussed in Chap. 3 and illustrated in Fig. 3.66, are probably the most common method of separating particulate materials from gases. A cloth or felt filter material is used that is impervious to the particles. Bag filters are suitable for use in very high dust load conditions. They have an extremely high efficiency, but they suflFer from the disadvantage that the pressure drop across them may be high. ... 

Table 12. Maximum Desirable Operating Temperature for Filter Bags ...

Hydrogen chloride in the lungs can cause pulmonary edema, a life threatening condition. In order for HCl in air to reach the lungs, it must be transported either as an aerosol or as a deposit on soot particles of less than 3 p.m in diameter. A procedure for the removal of 99% of the HCl from municipal waste incinerators has been developed (87). Lime is employed as a dry adsorbent which is collected in a filter bag system. 

PPS fiber has excellent chemical resistance. Only strong oxidising agents cause degradation. As expected from inherent resia properties, PPS fiber is flame-resistant and has an autoignition temperature of 590°C as determined ia tests at the Textile Research Institute. PPS fiber is an excellent electrical iasulator it finds application ia hostile environments such as filter bags for filtration of flue gas from coal-fired furnaces, filter media for gas and liquid filtration, electrolysis membranes, protective clothing, and composites. 

Handling of alumina and coke presents dusting problems. Hoods and exhaust systems collect the dust, which is then separated from the exhaust air either by cyclones, electrostatic precipitators, filter bags, or a combination of these methods, and recycled to the process (see Air pollution control PffiTHODS). 

Fiber from PPS resins has been made in two forms. Monofilament is used in paper machine drier felts to replace polyester, which is attacked by the hot, corrosive conditions of papermaking. Staple fibers are made into filter bags for flue treatment, and are considered a growth area. 

Internal Cake Tube Filters or Liquid Bag Filters This type of filter, such as manufactured by Industrial Filter and Pump Mfg. Co., Rosedale, Illinois, and many others, utihzes one or more perforated tubes supported by a tube sheet or by the hp of the pressure vessel. A cyhndrical filter bag sealed at one end is inserted into the perforated... 

Industrial filtration systems may be of many types. The most common type is the baghouse shown in Fig. 29-3. The filter bags are fabricated from woven material, with the material and weave selected to fit the specific application. Cotton and synthetic fabrics are used for relatively low temperatures, and glass cloth fabrics can be used for elevated temperatures, up to 290 C. 

You wish to design a baghouse to clean 3000 m at a filter ratio of 3 m m of cloth. The filter bags are 15 cm in diameter by 3 m long. If you design a "square" baghouse with... 

Pollutants that require an unusually high level of control or that require the fabric filter bags or the unit itself to be constructed of special materials, such as Gore-Tex or stainless steel, will increase the costs of the system. The additional costs for controlling more complex waste streams are not reflected in the estimates given below. For these types of systems, the capital cost could increase by as much as 75 % and the operational and maintenance (O M cost could increase by as much as 20%. 

The cast grids are made into battery anode and cathode plates by the application of a lead oxide paste of 70 percent lead oxide (PbO) and 30 percent metallic lead. Lead ingots are tumbled in a ball mill with airproducing lead oxide and fine lead dust (referred to as leady oxide ). Leady oxide particulates are entrained in the mill exhaust air, which is treated sequentially by a cyclone separator and fabric filter. The used fabric filter bags are shipped to a RCRA-permitled commercially operated ha2ardous waste landfill located in Colorado. The leady oxide production process does not produce wastewater. 

Abseihebeutel, m. filtering bag. abseihen, v.t. ter, filter off, strain, decant, percolate. 

Press-bemstein, m. amberoid, ambroid, -beu-tel, m. pressing bag, press bag, filter bag (for presses), -blei, n. (Mstal.) inferior lead obtained in the Carinthian process after the addition of charcoal, -druck, m. pressing pressure, press power. 

Seihe,/. strainer, filter Brewing) spent malt, -beutel, m. filtering bag. -boden, m. strainer bottom, perforated bottom, -fass, n. filtering cask or tub. -gefass, n. straining vessel, filtering vessel. -Ibffel, m. straining ladle, strainer. 

Spitz, m. (Metal.) paddle, -becher, m.. -becher-glas, n. sedimenting glass, -beutel, m. triangular filter bag. 

Fabric filters (baghouscs) represent a second accepted method for separating particles from a flue gas stream. In a baghouse, the dusty gas flows into and through a number of filter bags, and the particles are retained on the fabric. Different types are available to collect various kinds of dust with high efficiency. 

This three-dimensional cutaway drawing illustrates the filtering operation of the QAF9 filter-bag pressure filter system, showing the flow patterns of unflltered liquid through a preselected micronrated felt filter bag which renders the desired quality of filtered product. 

Figure 4-73. Flow scheme for GAF filter-bag pressure filter system for liquids. Courtesy of GAF Corporation, Chemicetl Group, Greenwich, Conn.

The open lower ends of shaker-cleaned filter bags are fastened over openings in the tube sheet that separates the lower, dirty-gas inlet chamber from the upper clean-gas chamber. The bags are suspended from supports, which are connected to a shaking device. 

The dirty gas flows upward into the filter bag and the dust collects on the inside surface. When the pressure drop rises to a predetermined upper limit due to dust accumulation, the gas flow is stopped and the shaker is operated. This process dislodges the dust, which falls into a hopper located below the tube sheet. 

As discussed in the preceding section, filter bags must be periodically cleaned to prevent excessive build-up of dust and to maintain an acceptable pressure drop across the filters. Two of the three designs discussed, reverse-flow and reverse-pulse, depend on an adequate supply of clean air or gas to provide this periodic cleaning. Two factors are critical in these systems the clean-gas supply and the proper cleaning frequency. 

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