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United States Patent

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United States Patent 3,785,123
Leith January 15, 1974

ROTATING CONCENTRIC "HOMOGENEOUS TURBULENCE" FABRIC BAG GAS CLEANER METHOD


Abstract

This invention relates to the application of couette motion caused by centrifugal forces in a rotating concentric "homogeneous turbulence" fabric bag gas cleaner, to provide uniform separation of gaseous, liquid, and solid particulates in a carrier fluid, by adjustable levels of imposed discrete "homogeneous turbulence" established by Taylor circular couette motion with a multiple array of secondary flow cellular vortices in the annulus between the inner perforated cylinder and the outer perforated cylinder, with both cylinders rotating in the same direction. When the outer cylinder rotates in the opposite direction to the inner cylinder, an adjustable level of imposed discrete spiral band of turbulence in a travelling wave, will ripple the fabric bags, will move either up or down in the annulus, and will clean the collected material from the inner surface of the fabric bags.


Inventors: Leith; William Cumming (Seattle, WA)
Appl. No.: 05/223,851
Filed: February 7, 1972

Current U.S. Class: 95/282 ; 55/293; 55/301; 55/302; 55/341.1; 55/341.2; 95/286
Current International Class: B01D 46/04 (20060101); B01d 046/04 ()
Field of Search: 55/96,97,286,287,291,293,301,302,304,400-403,341 210/332,333


Foreign Patent Documents
532,467 Jan., 1941 GB
Primary Examiner: Nozick; Bernard

Claims



The embodiments of the invention in which an exclusive property or privilege is claimed are defined as the following improvements:

1. The method of utilizing Taylor circular couette motion in a fluid to clean a porous filter positioned in the annular area between inner and outer rotary perforated cylinders and rotating said cylinders in opposed directions to provide a spiral band of turbulence in a travelling wave to ripple the filter.

2. The method of claim 1 further including filtering particulate matter from a fluid by passing said fluid through said filter while the perforated cylinders are rotating in the same direction.

3. The method of claim 2 wherein said filter is a bag filter.
Description



PERTINENT PRIOR ART

1. c. orr, Particulate Technology, MacMillan Co, New York, 1966

2. M.M. Couette, Annals Chim Phys, ser VI, Vol 21, 1890, p 433

3. G.I. Taylor, Phil Trans Roy Soc London, ser A, vol 223, 1923, p 289

4. D. Coles, J. Fluid Mech, 1965, vol 21, part 3, pp 385-425

SUMMARY

This present invention consists essentially in the method of utilizing Taylor circular couette motion caused by centrifugal forces in a rotating concentric "homogeneous turbulence" fabric bag gas cleaner to provide uniform separation of gaseous, liquid, and solid particulates in a carrier fluid, by adjustable levels of imposed discrete "homogeneous turbulence" established by a multiple array of secondary flow cellular vortices in the annulus between the inner perforated cylinder and the outer perforated cylinder, with both cylinders rotating in the same direction. When the outer cylinder rotates in opposite direction to the inner cylinder, an adjustable level of imposed discrete spiral band of turbulence in a travelling wave, will ripple the fabric bags, will move either up or down in the annulus, and will clean the collected material from the inner surface of the fabric bags.

This invention utilizes the basic functions of a fabric bag gas cleaner as described historically by Orr in reference 1; but this invention depends on centrifugal forces between rotating concentric cylinders to initiate couette motion as reported initially by Couette in reference 2; and depends on criteria for hydrodynamic instability as reported by Taylor in reference 3; and depends on regiemes of stabilized couette motion as given by Coles in reference 4.

This invention utilizes the stabilized boundary layer of couette motion to dampen out non-uniformities in the supply flow of a carrier fluid with gaseous, liquid, and solid particulates at present in use in fabric bag gas cleaners, which are due to variable levels of steady, random, and cyclic excitation forces initiated by disturbance energy sources from hydrodynamic origins in the fluid, hydroelastic origins in the structure, and thermodynamic origins in the pressure-temperature environment.

DESCRIPTION OF DRAWINGS

The accompanying drawings illustrate the following detailed specifications:

FIG. I shows a plan view of a rotating concentric "homogeneous turbulence" fabric bag gas cleaner 1, with the dirty gas inlet 2, and the clean gas outlet 3, and the fabric bags 4.

FIG. II shows a front sectional elevation of a rotating concentric "homogeneous turbulence" fabric bag gas cleaner 1, with the fabric bags 4 supported by a frame 5. The fabric bags 4 are nested in the annulus between the outer cylinder 6 and the inner cylinder 11. The outer perforated cylinder 6, is supported by a bearing 7, and driven by a gear 8, supported by a bearing 9, and a motor 10. An inner perforated cylinder 11, is supported by bearings 12 and 14, and driven by a shaft 13, and a motor 15. The gaseous, liquid, and solid particulates in the dirty inlet gas 2, sweep into the fabric bag 4, where the Taylor circular couette motion provides a uniform separation by secondary flow cellular vortices, with both cylinders rotating in the same direction. When the outer cylinder rotates in the opposite direction to the inner cylinder, a spiral band of turbulence in a travelling wave, will ripple the fabric bags, will move either up or down, and will remove the collected material from the fabric bags.

FIG. III is a partial sectional view of the annulus between the two cylinders 6 and 11, showing the multiple array of secondary flow cellular vortices.

FIG. IV shows the specific regieme of stabilized couette motion given by Coles in reference 4, with the multiple array of secondary flow cellular vortices when both cylinders turn in the same direction, and the spiral band of turbulence when the outer cylinder rotates in the opposite direction to the inner cylinder.

DETAILED DESCRIPTION

The object of the invention is the application of couette motion caused by centrifugal forces in a rotating concentric "homogeneous turbulence" fabric bag gas cleaner to provide a laminar flow with adjustable levels of imposed discrete "homogeneous turbulence" in the radial direction, which promotes the uniform separation of gaseous, liquid, and solid particulates in a carrier fluid, with a multiple array of secondary flow cellular vortices in the annulus between the perforated cylinders, with both cylinders rotating in the same direction. When the outer cylinder rotates in the opposite direction to the inner cylinder, a spiral band of turbulence in a travelling wave, will ripple the fabric bags, will move either up or down in the annulus, and will clean the collected material from the inner surface of the fabric bags.

The mathematical basis for the present invention is given in references 3 and 4, in which an imposed hydrodynamic instability can lead usual laminar flow to another state of imposed laminar flow, rather than the expected turbulent flow. In the case of a rotating concentric "homogeneous turbulence" fabric bag gas cleaner, Taylor circular couette motion caused by centrifugal forces impose a steady secondary flow in the annulus between the two cylinders by establishing a multiple array of secondary flow cellular vortices when both cylinders rotate in the same direction; or it will impose a spiral band of turbulence in a travelling wave, which will ripple the fabric bags, will move either up or down in the annulus, and will clean the collected material from the inner surface of the fabric bags, when the outer cylinder rotates in the opposite direction to the inner cylinder.

Couette motion between rotating concentric cylinders is well known, but this invention is related to perforated cylinders with radial flow thru the perforated cylinders, rather than the usual couette motion with stagnant or longitudinal flow in the annulus between the cylinders.

This invention utilizes the basic functions of a fabric bag gas cleaner as described historically by Orr in reference 1; but this invention depends on centrifugal forces caused by flow between rotating concentric cylinders to initiate couette motion as reported by Couette in reference 2; and depends on the criteria for hydrodynamic instability as reported by Taylor in reference 3; and depends on the detailed study of various regiemes of couette motion as given by Coles in reference 4 in which a multiple array of secondary flow cellular vortices is established when both cylinders rotate in the same direction, or a spiral band of tubulence is established when the outer cylinder rotates in the opposite direction to the inner cylinder.

This invention utilizes the stabilized boundary layer of couette motion to dampen out the non-uniformities in the supply flow of a carrier fluid with gaseous, liquid, and solid particulates at present in use in fabric bag gas cleaners, which are due to variable levels of steady, random, and cyclic excitation forces initiated by disturbance energy sources from hydrodynamic origins in the fluid, hydroelastic origins in the structure, and thermodynamic origins in the pressure-temperature environment which are expected from operating transients at startup, emergency shutdown, and maintenence shutdown in metallurgical operations with particulates of typical metals such as lead, zinc, copper, iron, and uranium.

This invention differs from the usual classical couette motion with stagnant or longitudinal flow between the rotating concentric cylinders, in that this invention utilizes radial flow thru the perforated cylinders.

This invention is an improvement on present day fabric bag gas cleaners handling a carrier gas polluted with gaseous, liquid, and solid particulates having non-uniformities in concentration, density, and velocity produced by the dirty gas jetting into the fabric bag, in that this invention utilizes a final uniform separation by couette motion in addition to the usual fabric bag separation.

This invention differs from the usual fabric bag gas cleaner in that a uniform separation by couette motion produces an imposed residence time for uniform separation of gaseous, liquid, and solid particulates in the carrier fluid.

The rotation speed, the number and diameter of the perforations together with the perforation pattern and percent perforated area can be optimized for a specific separation of gaseous, liquid, and solid particulates in a carrier fluid, such as the metallurgical particulates of lead, zinc, copper, iron, and uranium.

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