Abstract:
A system for cleaning at least one filter in a baghouse and an associated method for providing the system. The at least one filter separate a dirty gas chamber from a clean gas chamber, and filters at least one substance from a gas. The system includes a supply of compressed air and a blowpipe to direct the air at the at least one filter to dislodge a collected amount of the at least one substance from the at least one filter. The blowpipe has a cross-sectional flow area through which the compressed air flows. A valve controls provision of the compressed air. The valve has a cross-sectional flow area though which the compressed gas flows. The cross-sectional area of the valve is smaller than the cross-sectional area of the blowpipe to provide for air pressure at the valve to be greater than air pressure at the blowpipe.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a system for cleaning filters in a baghouse, and more particularly, to a piping arrangement for pulse jet dust collectors for cleaning filters in a baghouse. 
     2. Discussion of the Prior Art 
     Filters for removing particulates from a particulate-laden gaseous stream flowing through a baghouse are known. The particulates are typically generated by an industrial process and carried to the filters in the gas flow stream. The filters include media that is formed into filter cartridges or filter bags, etc. The particulate-laden gas flows through the filters from outside towards inside. The particulates are separated from the gas stream at the outer side of the filters. The filtered gas stream flows through the media and exits the filter through an open end. The filtered gas stream then is conducted to subsequent plant uses or the atmosphere. 
     Over time, an increasing buildup of accumulated particulates forms on the outer sides of the filters. This increasing buildup of particulates causes an increase in pressure drop across the filters. This increased pressure drop may result in increased operation cost because more power is consumed to generate an effective flow of gas through the filters. 
     The filters are periodically cleaned to remove the particulate buildup and reduce the pressure drop across the filters. To clean the filters, a pressurized fluid, such as air, is blown into the open end of the filters to dislodge the particulate buildup adhering to their outer sides. Known cleaning systems typically provide a pulse of compressed air into the filters at a supplied pressure in the range of about 60 psi to 100 psi (414 kilopascals to 690 kilopascals). 
     Some known baghouses require a large volume of pressurized fluid in order to obtain a desired filter cleaning. The large volume of fluid is provided by large pressurized tanks that store the fluid prior to use. Only a limited number of manufacturers and testing facilities can build and test the large tanks. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The following presents a simplified summary of the invention in order to provide a basic understanding of some example aspects of the invention. This summary is not an extensive overview of the invention. Moreover, this summary is not intended to identify critical elements of the invention nor delineate the scope of the invention. The sole purpose of the summary is to present some concepts of the invention in simplified form as a prelude to the more detailed description that is presented later. 
     In accordance with one aspect, the present invention provides a system for cleaning at least one filter in a baghouse. The baghouse has a dirty gas chamber and a clean gas chamber. The at least one filter separate the dirty gas chamber from the clean gas chamber. The at least one filter filtering at least one substance from a gas as the gas passes from the dirty gas chamber to the clean gas chamber through the at least one filter. The system includes a supply of compressed air and a blowpipe to direct the compressed air at the at least one filter to dislodge a collected amount of the at least one substance from the at least one filter. The blowpipe has a cross-sectional flow area through which the compressed air flows. A valve is interposed between the supply of compressed air and the blowpipe for controlling provision of the compressed air from the supply. The valve has a cross-sectional flow area though which the compressed gas flows. The cross-sectional area of the valve is smaller than the cross-sectional area of the blowpipe to provide for air pressure at the valve to be greater than air pressure at the blowpipe. 
     In accordance with another aspect, the present invention provides a method of providing a system for cleaning at least one filter in a baghouse. The baghouse has a dirty gas chamber and a clean gas chamber. The at least one filter separate the dirty gas chamber from the clean gas chamber. The at least one filter filtering at least one substance from a gas as the gas passes from the dirty gas chamber to the clean gas chamber through the at least one filter. The method includes providing a supply of compressed air. The method provides a blowpipe to direct the compressed air at the at least one filter to dislodge a collected amount of the at least one substance from the at least one filter. The blowpipe has a cross-sectional flow area through which the compressed air flows. The method provides a valve interposed between the supply of compressed air and the blowpipe for controlling provision of the compressed air from the supply. The valve has a cross-sectional flow area though which the compressed gas flows. The cross-sectional area of the valve is smaller than the cross-sectional area of the blowpipe to provide for air pressure at the valve to be greater than air pressure at the blowpipe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other aspects of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic illustration of an example baghouse arrangement that includes a system for cleaning in accordance with one aspect of the present invention; 
         FIG. 2  is a schematic example illustration of a portion of a prior art system for cleaning; 
         FIG. 3  is a schematic illustration similar to  FIG. 2 , but shows an embodiment in accordance with an aspect of the present invention; and 
         FIG. 4  is an enlarged portion of the embodiment shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Example embodiments that incorporate one or more aspects of the present invention are described and illustrated in the drawings. These illustrated examples are not intended to be a limitation on the present invention. For example, one or more aspects of the present invention can be utilized in other embodiments and even other types of devices. Moreover, certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. Still further, in the drawings, the same reference numerals are employed for designating the same elements. 
     The invention relates generally to a system for cleaning at least one filter in a baghouse with reverse pulses of the pressurized air. In one specific example, the system may be integrated into an initial construction of a baghouse. In another specific example, the system may be a retrofit into an existing baghouse. Such choice (i.e., initial construction or retrofit) is not a limitation on the present invention. 
     Turning to the shown example of  FIG. 1 , a baghouse  10  incorporating a filter cleaning system  12  is schematically illustrated. It is to be understood that the following provides a description of one example baghouse  10 , and that the filter cleaning system  12  in accordance with the present invention can be utilized in various baghouses having various configurations. Particulate-laden gas  18  flows into the baghouse  10  from an inlet  20 . The particulate-laden gas  18  is filtered by a plurality of filters  22  located within the baghouse  10 . The filters  22  may be of varied construction. Typically, the filters are generally cylindrical in shape. One example type of filters is referred to as a candle filter. Filtered or clean gas  26  exits through an outlet  28  of the baghouse  10 . 
     The baghouse  10  is divided into a “dirty gas” plenum or chamber  30  and a “clean gas” plenum or chamber  32  by a tubesheet  34  made from a suitable material, such as sheet metal. The tubesheet  34  supports the filters  22  such that the filters extend into the dirty gas chamber  30 . The inlet  20  is in fluid communication with the dirty gas chamber  30 . The outlet  28  is in fluid communication with the clean gas chamber  32 . The dirty gas chamber  30  of the baghouse  10  may also have an accumulation chamber defined by sloped walls  38  located at a lower end of the dirty gas chamber  30 . The accumulation chamber receives and temporarily stores particulates and other debris that separate from the particulate-laden gas  18  or fall off of the filters  22 . The stored particulates and debris may exit the accumulation chamber through an opening or the like. 
     In one example, the tubesheet  34  includes a plurality of openings (not shown) extending there through. A respective one of the filters  22  is installed in each respective one of the openings. Each of the filters  22  is mounted within the respective opening so it seals against the tubesheet  34  and isolates the dirty gas chamber  30  from the clean gas chamber  32 . While the filters  22  are illustrated as being mounted to extend in a substantially vertical direction, the filters could be mounted to extend in any direction, for example horizontally or at an angle. By way of example and not limitation, a circumferential resilient mounting band (not shown) can be located in each one of the openings in the tubesheet  34 . The band provides the seal between the respective filter  22  and the opening in the tubesheet  34 , and any suitable mounting structure may be used to attach, support and seal the filters  22  to the tubesheet  34 . 
     As mentioned, the filters  22  filter particulates from the particulate-laden gas  18  as the gas passes through each filter. Each filter  22  can include conventional bags and cages, and/or may include pleated filter media. For example, the filter media can be formed into a tubular configuration with a circular cross section. It will be apparent that the filters  22  may be any desired length in order to meet the filtering requirements of the baghouse  10 . The filter media may be constructed of any suitable material for desired filtering requirements and operating conditions. For example, materials such as polyester, acrylic and polypropylene are generally acceptable for operating temperatures in the range of 180° F. to 225° F. (82° C. to 107° C.). Aramid and PPS are suitable for up to 375° F. (191° C.). Fiberglass is suitable for use up to 450° F. (232° C.). 
     The filters  22  are illustrated as having retention devices  42  ( FIG. 1 ) extending circumferentially about the pleated filter media. It is to be understood that conventional filters using bags and cages generally do not include such retention devices  42 . However, where pleated filter cartridges are used, the retention devices  42  serve to hold the pleated filter media in place during reverse pulse cleaning of the filters  22 . Specifically, the retention devices  42  limit movement of the pleated filter media in a radial outward direction during reverse pulse cleaning. The retention devices  42  may be in the form of a strap or an extruded elastomer. 
     The example embodiment of the filter cleaning system  12  is a reverse pulse cleaning system and includes at least one blowpipe  44 . The number of blowpipes  44  may be varied and may be dependent upon the number of filters  22  used within the baghouse  10 . A baghouse  10  that has a multitude of filters  22  that may be arranged in an array may include multiple blowpipes  44 . The blowpipes  44  are arranged in cooperation with the filters  22 . Specifically, the blowpipes  44  are routed/directed so that each blowpipe extends in close proximity to a group of filters. Thus, each group of filters has an associated blowpipe. For ease of visualization,  FIG. 1  only shows a single blowpipe and a single group of associated filters. It is to be appreciated that multiple blowpipes and multiple groups of associated filters may be present in the example of  FIG. 1 . 
     Located on each blowpipe is a plurality of nozzles  46 . Each nozzle  46  is associated with a filter  22  and is oriented/pointed such that air flowing from the blowpipe  44  through the nozzle is directed into the respective filter. Associated with each blowpipe  44  is a valve  48 . Thus, there is a plurality of valves  48  within the filter cleaning system  12 . In one example, the valves  48  are pulse valves, however it is possible that other valves could be used. Going forward, the valves  48  are described as pulse valves with the understanding that the invention may not be so limited. For ease of visualization,  FIG. 1  only shows a single pulse valve  48  with the shown single blowpipe  44 . It is to be appreciated that a different number of pulse valves  48  may be present in the example of  FIG. 1 . 
     The pulse valve  48  is connected to a header pipe  50 , which in turn is connected (shown schematically) to a pressurized air supply  52 . The header pipe  50  may be connected to multiple pulse valves  48  which are in turn connected to multiple blowpipes  44 . In the alternative there may be a singular correspondence between a header pipe  50  and a pulse valve  48  and thus there may be plural header pipes for plural pulse valves. 
     With regard to the pressurized air, the content thereof is not to be a limitation on the present invention. For example, the pressurized air may contain or include various gasses and/or combinations thereof. For example, additive gases may be included with atmospheric air. The phrase “pressurized air” is to be interpreted to include such variations. The phrase “pressurized air” is only used for ease of reference. 
     Going forward for swiftness, further discussion will be directed to just the single header pipe  50 , the single pulse valve  48 , the single blowpipe  44 , the single group of associated filters  22  and associated structure. However, it is to be appreciated that such discussion may be equally applicable to the multiples of the pulse valves, blowpipes, filter groups, associated structures, etc. as may be present. 
     The general operation of the filter cleaning system  12  is based upon the use of air from the pressurized air supply  52  to clean off accumulated particulate matter from the filters  22 . The pressurized air is transmitted to the pulse valve  48  via the header pipe  50 . The pulse valve  48  is controlled to open, which allows the pressurized air to travel along the blowpipe  44  and be discharged from the nozzles  46 . This discharge from the nozzles  46  is a pulse of air that is transmitted into the filters  22 . This pulse of air dislodges particulate that has accumulated upon the filters  22 . The dislodged particulate may proceed down within the accumulation chamber (i.e., along the sloped walls  38 ) for removal there from as discussed above. This can be referred to as the cleaning process. 
     It is to be appreciated that in order to achieve the desired result during the cleaning process, it is necessary to have a sufficient volume of air and with a sufficient force due to pressure, emitted from the nozzles  46  to cause the particle dislodgement or cleaning. Of course, the volume of air will be somewhat dependent upon the particulars of the baghouse  10 . Such particulars may include size of the filters  22 , configuration of the blowpipes  44  and filters, etc. Even the type, size and volume of the particulate accumulation may be a factor in the needed volume of air for cleaning. 
     In a known prior arrangement, the sufficient volume of air was provided via a provision of a rather large vessel for containing the pressurized air supply, and a rather large header pipe distribution to rather large pulse valves. Some details of an example of such a known prior arrangement are shown in  FIG. 2 . Specifically, a 14 inch (36 cm) header pipe  50 ′ transmits pressurized air at 45 psi (310 kilopascals). A 4 inch (approx. 10.2 cm) pulse valve  48 ′ is connected directly to a 4 inch (approx. 10.2 cm) blowpipe  44 ′. The 4 inch (approx. 10.2 cm) blowpipe  44 ′ transmits pressurized air through the nozzles  46 ′. It is to be appreciated that the pipes shown in the example have circular cross-sections and the cross-sectional flow areas are related to the diameters. Of course, the pipes may have cross-sections that are other than circular. 
     When the relatively large pulse valve  48 ′ is open, the flow of pressurized air is 45 psi (310 kilopascals) within the blowpipe  44 ′. However, it is to be appreciated that the relative large components, and in particular the vessel and the header pipe  50 ′, have commensurate large material and construction aspects. Such large material and construction aspects may be associated with commensurate large costs. Such large costs may be a factor of cost for constituent materials, such as steel. 
       FIG. 3  shows one example embodiment of components of the filter cleaning system  12  (shown in  FIG. 1 ) in accordance with the present invention. The header pipe  50  is smaller than the counterpart shown within  FIG. 2 . In the specific shown example, the header pipe  50  has a diameter of 8 inches (approx. 20.3 cm). The pulse valve  48  is also smaller than the counterpart shown in  FIG. 2 . In the specific example, the pulse valve  48  is a 2 inch (approx. 5.1 cm) pulse valve. In the shown example, the blowpipe  44  is still 4 inches (approx. 10.2 cm). However, a nipple plate  60  has been included between the pulse valve  48  and the blowpipe  44 . In the shown example, the nipple plate  60  has a circular cross-section and has a 2 inch (approx. 5.1 cm) diameter. 
     In the shown example, pressurized air is provided from the supply at 90 psi (620 kilopascals). Thus, the air pressure from the supply is greater than as provided within the known prior arrangement. The pressure within the header pipe and the pulse valve is 90 psi (620 kilopascals). Upon actuation of the pulse valve  48 , the pressurized air at the greater pressure is transmitted through the valve and along the nipple plate  60 . As can be seen in  FIG. 4 , at the junction between the nipple plate  60  and the blowpipe  44 , the pressurized air encounters an increased cross-sectional area within which to proceed. Specifically, air is transitioning from the 2 inch (approx. 5.1 cm) nipple plate  60  to the 4 inch (approx. 10.2 cm) blowpipe  44 . The area of the blowpipe  44  immediately adjacent to the nipple plate  60  may be referred to as an expansion zone  62 . In the shown example, the desired pressure of 45 psi (310 kilopascals) is achieved via the use of smaller components up-stream of the blowpipe and the use of increased pressure from the pressurized air supply  52 . 
     The smaller header pipe  50  requires less material, such as steel, to construct as compared to the header pipe  50 ′ of the known prior arrangement of  FIG. 2 . Also, a smaller pressurized air supply could be employed as compared to the air supply of the known prior art arrangement. The smaller vessel would be configured to retain the pressurized air at the greater pressure. Similar to the reduction in size of the header pipe, the reduction in size of the vessel would require less material, such as steel, to construct as compared to the vessel of the known prior arrangement. 
     The invention has been described with reference to the example embodiments described above. Modifications and alterations will occur to others upon a reading and understanding of this specification. Examples embodiments incorporating one or more aspects of the invention are intended to include all such modifications and alterations insofar as they come within the scope of the appended claims.