GB2092910A - Filter for removing particulate material from gases - Google Patents

Abstract

Particle-laden gas passes from an inlet duct through respective inlets 14 to respective deceleration chambers 13, and thence to respective filter units 10 where the entrained particles are removed by filter bags 12. The deceleration chambers 13 communicate with a purge manifold 19 through respective outlets 20 so that periodically the bags 12 in each chamber 13 can be subjected to a reverse gas flow to purge the filtered-out particles therefrom. The inlets 14 are disposed around an axis 15 in a common plane perpendicular to the latter, and are closed off selectively by means of a baffle 16 which rotates about the axis 15 and which has a portion 17 disposed parallel to the aforesaid common plane. The outlets 20 are similarly disposed around an axis 21 and are opened successively by a baffle 22 which rotates around the axis 21. The baffles 16 and 22 are rotated in synchronism such that at any one time the baffle 22 opens the outlet 20 of the particular deceleration chamber 13 whose inlet 14 is closed off by the baffle 16. <IMAGE>

Description

SPECIFICATION Filter device for removing particulate material from gases This invention relates to a filter device for removing particulate material from gases.

According to the invention, a filter device comprisyes an inlet duct through which particle-laden gas is passed in use, a plurality of filter units to which gas passing through the inlet duct is supplied for removal of said particles therefrom, each filter device having associated therewith a deceleration chamber wherein the gas flow is decelerated prior to entry into the filter unit, the deceleration chambers communicating with the inlet duct by way of respective inlets which are disposed in angularly spaced relation around a first axis, a first baffle rotatable about the first axis to close off the inlets successively one or more at a time, and purge means adapted intermittently to apply a reverse gas flow to the filter units to purge said removed particles therefrom, the purge means including a manifold with which the deceleration chambers communicate by way of respective outlets disposed in angularly spaced relation around a second axis, and a second baffle rotatable about the second axis to open the outlets successively one or more at a time in synchronism with the closing of the inlets by the first baffle.

Preferably, the inlets are disposed in a common plane perpendicular to the first axis, and the first baffle includes a portion parallel for said common plane which closes off the inlets successively and one or more at a time as the first baffle is rotated.

The aforesaid portion of the first baffle can extend radially of the first axis, with its radially outer periphery forming a knife-edge. Advantageously, the inlets are arranged in an annular, centered on the first axis.

Similarly, the outlets can be disposed in a common plane perpendicular to the second axis. In this case, the outlets are preferably arranged in an annulus centered on the second axis and the second baffle is in the form of a circular plate also centred on the second axis and having a radial slot therein.

Conveniently, a leading edge of the slot with respect to the direction of rotation of the circular plate is a knife-edge.

Alternatively, the outlets can be disposed on a cylindrical surface co-axial with the second rotation axis. In this case, the second baffle may be in the form of a hollow cap and can have a plate portion and a skirt portion depending from the periphery of the latter, the skirt portion being interrupted to define an opening therein.

Desirably, the first and second baffles are rotated in synchronism by a common drive, in which case both baffles can be mounted on a common rotatable shaft. Alternatively, however, the first and second baffles can be driven separately as long as this is performed synchronously.

The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic sectional side view of a first embodiment of a filter device according to the present invention; Fiure 2 is a part-section taken along the line A-A in Figure 1; Figures 3 to 5 are sections taken respectively along the lines B-B, C-C, and D-D in Figure 1; Figures 6, 7, and 8 are schematic sectional side views of three further embodiments of a filter device according to the present invention; and Figure 9 is a perspective view of a baffle which forms part of the filter device shown in Figure 8.

Referring first to Figures 1 to 5, the filter device shown therein comprises generally a series of wedge-shaped filter units 10 disposed in an annulus and surrounding a central, vertically oriented inlet duct 11. In the illustrated construction, twenty such filter units are provided, and the inlet duct 11 is of round transverse cross-section, although the latter could equally well be square or any other suitable shape. Each filter unit 10 contains a plurality of vertically disposed filter bags 12 which are open at their lower ends. At the bottom of each filter unit 10 there is provided a respective plenum or deceleration chamber 13 which communicates with the lower end of the inlet duct 11 by way of a respective sector-shaped inlet 14. The inlets 14 are arranged in an annulus around an axis 15 and are disposed in a common plane perpendicular to the axis.A blast gate or baffle 16 is rotatable about the axis 15 to close off the inlets 14 successively and one at a time, the baffle 16 including a portion 17 which is parallel to the plane of the inlets 14 and which extends radially of the axis 15. A radially outer periphery 18 of the potion 17, which sweeps around the bottom edge of the inlet duct 11 as the baffle 16 is rotated, forms a knife-edge.

Each deceleration chamber 13 also communicates with a purge manifold 19 by way of a respective sector-shaped outlet 20, the outlets 20 being arranged in an annulus around an axis 21 and being disposed in a common plane perpendicular to the axis 21. A baffle in the form of a circular plate 22 made of highly polished stainless steel is rotatable about the axis 21 to bring a radial slot 23 (Figure 5) therein successively into registration with the outlets 20, such that as the plate 22 is rotated the decelem- tion chambers 13 are successively and one at a time placed in communication with the purge manifold 19. A leading edge 24 of the slot 23 with respect to the direction of rotation of the plate 22 is formed as a knife-edge.The manifold 19 is in turn connected by way of a duct 25 to a fan (not shown) disposed externally of the filter device.

The baffles 16 and 22 are mounted on a common shaft 26 for synchronous rotation by means of a chain drive 27 and an electric motor 28, such that at any given time the deceleration chamber 13 whose inlet 14 is closed off by the baffle 16 is in communication with the purge manifold 19 via the slot 23 in the baffle 22. The shaft 26 is protected from particles entrained in the gas flowing through the device by means of a tube 29.

The above-described filter device operates as follows. Particle-laden gas (such as air from industrial premises) is passed downwardly through the inlet duct 11 and flows through those inlets 14 which are not at that time closed off by the baffle 16 into the respective deceleration chambers 13, where it is decelerated. At this time, any large or relatively heavy particles entrained in the gas flow are deposited by the action of gravity on the upper surface of the baffle 22. As the baffle 22 is rotated, the side walls of the deceleration chambers 13 sweep this surface, and the accumulated particles thereon are deposited into the purge manifold 19 through the slot 23 when the latter comes into registration with the respective chamber 13. From the chambers 13, the particle-laden gas flows upwardly through the filter bags 12 which filter out the entrained particles from the gas stream.The gas, free from particles, which passes through the fabric of the filter bags 12 is discharged through a discharge manifold (not shown).

As the baffls 16 and 22 are rotated, each filter unit 10 is inermittently subjected to a reverse gas flow to purge the filtered-out particles therefrom. This reverse flow occurs when the baffle 16 closes off the inlet 14 of the respective deceleration chamber 13 and the baffle 22 opens the outlet 20 thereof, such that the filter unit 10 is connected to the aforementioned fan by way of the purge manifold 19 and the duct 25. The particles purged from the filter units flow from the duct 25 to a particle separator, such as a cyclone or a high-efficiency grit arrester. The gas in which these particles are entrained can be recirculated.

In the embodiment of Figures 1 to 5, the inlets 14 and the outlets 20 are disposed in radially inner parts of their respective deceleration chambers 13, and only the radially outer side walls 30 of the chambers 13 are inclined to the horizontal. Figure 6 illustrates a modified arrangement wherein both the radially inner and outer side walls of the chambers 13 are inclined, and a duct 31 connects the lowermost point of each chamber 13 to its respective outlet 20. By inclining both of the side walls in this manner, there is little tendency for particles to accumulate in the deceleration chambers 13 during purging.

Figure 7 illustrates a modification of the arrangement shown in Figure 6, wherein the duct 31 associated with each chamber 13 is defined beneath a closed frusto-conical baffle 32 which surrounds the tube 29. It will be manifest that the radially inner side wall of each chamber 13 is formed by the baffle 32 and, as with the arrangement shown in Figure 6, is inclined to reduce particles accumulating in the chamber 13 during purging.

Figure 8 shows an alernative version of the filter device depicted in Figure 7, wherein the shape of the baffle 22 is changed. More particularly, as can be seen to advantage in Figure 9 the baffle 22 is now of hollow cap-like configuration and comprises a circular plate portion 33 having a skirt 34 depending from its periphery, the skirt being interrupted to form an opening 35 which permits each duct 31 to communicate with the purge manifold 19 as the baffle is rotated. As compared with the arrangement shown in Figure 7, it will be seen that the mounting point of the baffle 22 on the shaft 26 is now moved upwardly so that the plate portion 33 is diposed adjacent to the underside ofthefrustoconical baffle 32. Moreover, instead of being positioned in a common plane perpendicular to the rotation axis of the baffle 22, the outlets 20 are now provided on a circular cylindrical surface co-axial with the rotation axis so that they are swept in turn and one at a time by the opening 35 as the baffle 22 rotates.

In all of the above-described embodiments, the baffle 16 closes off one inlet 14 at a time and the baffle 22 opens one outlet 20 at a time. The baffles can, however, be arranged to close off more than one inlet and open more than one outlet at a time.

Also, instead of being driven by a common drive, the baffles can be driven separately as long as synchronism of their rotation is maintained. In either case, the spped of rotation of the baffles will be determined by the type of particles being filtered and also the loading of these particles in the gas.

Claims (14)

1. A filter device comprising an inlet duct through which particle-laden gas is passed in use, a plurality of filter units to which gas passing through the inlet duct is supplied for removal of said particles therefrom, each filter device having associated therewith a deceleration chamber wherein the gas flow is decelerated prior to entry into the filter unit, the deceleration chambers communicating with the inlet duct by way of respective inlets which are disposed in angularly spaced relation around a first axis, a first baffle rotatable about the first axis to close off the inlets successively one or more at a time, and purge means adapted intermittently to apply a reverse gas flow to the filter units to purge said removed prticles therefrom, the purge means including a manifold with which the deceleration chambers communicate by way of respective outlets disposed in angularly spaced relation around a second axis, and a second baffle rotatable about the second axis to open the outlets successively one or more at a time in synchronism with the closing of the inlets by the first baffle.

2. A filter device as claimed in Claim 1, wherein the inlets are disposed in a common plane perpendicularto the first axis, and the first baffle has a portion disposed parallel to said common plane which closes off the inlets successively and one or more at a time as the first baffle is rotated.

3. Afilter device as claimed in Claim 2, wherein the inelts are arranged in an annulus centred on the first axis.

4. Afilter device as claimed in Claim 2 or 3, wherein said portion of the first baffle extends radially of the first axis, and its radially outer periphery forms a knife-edge.

5. Afilter device as claimed in any preceding claim, wherein the outlets are disposed in a common plane perpendicular to the second axis.

6. A filter device as claimed in Claim 5, wherein the outlets are arranged in an annulus centred on the second axis, and the second baffle is in the form of a circular plate also centred on the second axis and having a radial slot therein.

7. Afilter device as claimed in Claim 6, wherein a leading edge of the slot with respect to the direction of rotation of the circular plate is a knife-edge.

8. A filter device as claimed in any one of claims 1 to 4, wherein the outlets are disposed on a cylindrical surface co-axial with the second rotation axis.

9. A filter device as claimed in Claim 8, wherein the second baffle is in the form of a hollow cap and has a plate portion and a skirt portion depending from the periphery of the latter, the skirt portion being interrupted to define an opening therein.

10. A filter device as claimed in any preceding claim, wherein the first and second baffles are rotated in synchronism by a common drive.

11. A filter device as claimed in Claim 10, wherein the first and second baffles are mounted on a common rotatable shaft.

12. After device as claimed in any preceding claim, wherein the first and second rotation axes are co-axial.

13. A filter device as claimed in any preceding claim, wherein the deceleration chambers are angularly spaced around the first and second rotation axes, and at least one of the radially inner and outer sides of each deceleration chamber is inclined to the vertical.

14. A filter device substnatially as hereinbefore described with reference to Figures 1 to 5, or Figure 6, or Figure 7, or Figures 8 and 9 of the accompanying drawings.