Gas separation: processes – Filtering – With cleaning of filter
Patent
1996-07-09
1998-12-08
Smith, Duane S.
Gas separation: processes
Filtering
With cleaning of filter
55294, 55302, 553411, 55418, 55419, 95286, B01D 4602, B01D 4604
Patent
active
058463003
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a fabric filter for the removal of particulate matter from a gas stream and more particularly to such a fabric filter having an improved gas inlet geometry.
BACKGROUND OF THE ART
Fabric filters are known in which a gas stream to be cleaned is directed through a group of elongate filter bags from their outside to their inside. The bags are periodically cleaned, such as by periodically injecting into them, against the gas stream, a gas pulse which serves to briefly reverse the direction of gas flow through the filter bags and to thereby remove from the outside of the bags particulate matter that had been retained on the filter bags. U.S. Pat. No. 4,157,899 discloses such a fabric filter.
In fabric filters of this type the group of filter bags is typically disposed in a housing body having a dusty gas section with an inlet thereto and a clean gas section with an outlet therefrom. A porting plate is mounted in the housing body separating the dusty and clean gas sections and has a plurality of concentric rings of ports. A filter bag is supported from each port in the porting plate and hangs into the dusty gas section. A backflushing means are mounted in the clean gas section and are adapted to direct gas pulses to sequentially backflush the filter bags.
In most known fabric filter dusty gas is discharged directly into the dusty gas section of the fabric filter housing. Although inexpensive, this method of entry creates a great deal of turbulence and uneven velocities between filter bags which can result in bag abrasion and re-entrainment of dust following pulsing. It is also known to provide a plenum between the filter bags and a wall of the housing across its width. This allows the dusty gas to enter the housing at lower velocities than would otherwise be the case. Such plenums are, however, wasteful of space and for this reason have not been universally accepted.
SUMMARY OF THE INVENTION
In a first broad aspect, the present invention provides a fabric filter apparatus having a housing defining a dusty gas section with an inlet thereto and a clean gas section with an outlet therefrom, a porting plate mounted in the housing separating the dusty gas section from the clean gas section and a substantially circular array of fabric filter bags depending therefrom; said housing further including a generation/distribution means to generate pulses of backflushing gas and distribute them periodically into the open upper ends of the fabric filter bags through respective ports in the porting plate, wherein at least one duct is provided in the housing, the bottom of the duct being in fluid communication with the inlet, the top of the duct opening into a corner of the housing at a level intermediate the inlet and the porting plate.
The inlet of the inventive fabric filter apparatus may be elongated in the horizontal direction with the duct being in fluid communication with a lateral end of the inlet. It is also possible to provide two such ducts in fluid communication with opposite lateral ends of the inlet.
Preferably, the housing is provided with a plurality of substantially planar sides eg. four planar sides to form a square or rectangle, and is provided with two substantially vertically extending ducts disposed in adjacent corners of the housing.
The inlet of the housing is preferably positioned to open into a downwardly tapering hopper forming the lower end of the housing. A damper may be mounted in the inlet to control gas flow into the housing.
The lower portion of each duct is also preferably provided with a bleed aperture sized to allow particulate matter falling out of the dusty gas stream to escape from the duct.
In a second broad aspect, the present invention provides a method of feeding a dusty gas to a dusty gas section of a fabric filter, said filter further including a clean gas section, a porting plate mounted between the dusty gas section and clean gas section with a circular array of fabric filter bags depending from the porting plate and a generatio
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patent: 4878927 (1989-11-01), Margraf
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patent: 5387406 (1995-02-01), Ruoff
patent: 5514195 (1996-05-01), Durst et al.
Lurgi (Australia) PTY Limited
Smith Duane S.
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