Abstract:
In a dust extraction apparatus, impeller means, such as a fan, draws dust-laden air through a water reservoir. Baffles cause the air to divert into sinuous undulating lateral paths through the water without significant turbulence. The air passed through the water is allowed to separate from lateral curtains of water and rises into a grid of plates which strip water from the air prior to its discharge.

Description:
This application is a continuation, of copending application Ser. No. 964,195, filed on Nov. 28, 1978, and now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates in general to a dust control apparatus. More particularly, the invention relates to apparatus for collecting or extracting dust from air and to a method of collecting or extracting dust from air employing such apparatus. The apparatus with which this invention is concerned is particularly useful in underground mining installations, although the apparatus can be used in quarries or other industrial premises where air is prone to carry dust. 
     One form of known dust collection apparatus is described in my U.K. Pat. specification No. 1,355,908. In this known apparatus, dust-laden air is passed over the surface of water in a reservoir and air turbulence is deliberately created by baffles to generate water spray above the water surface. Large particles of dust pass directly into the water, while smaller particles are entrained in the turbulent air and are removed subsequently. The present invention seeks to improve the previously known apparatus. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, the apparatus comprises an air inlet means adapted to receive air carrying dust therein, air outlet means for discharging the air after cleansing, a water reservoir, means for directing the air from the inlet means towards the water reservoir and baffle means for constraining the air which passes through the water in the reservoir in at least one sinuous or tortuous path. Preferably, stripping means is provided above the water reservoir for stripping residual water from the air emerging from the reservoir and baffle means, the water being returned back to the reservoir. 
     In contrast to the previously known apparatus of this type, there is no significant turbulence in the air as it passes through the baffle means and water reservoir and the air passes therethrough in a lateral undulating path or paths. 
     The present invention also provides a method of collecting or extracting dust from air utilizing apparatus as described above and comprising passing dust-laden air through baffle means and a water reservoir in a sinuous or tortuous path and thereafter passing the air through stripping means to remove residual water from the air. 
     It is desirable to arrange for the air emerging from the baffle means and the reservoir to separate from lateral curtains of water at the sides of the reservoir since this is a particularly efficient arrangement for cleaning the air. 
     Preferably, a fan or blower is used to draw or force the air through the apparatus. 
     The baffle means can be designed to constrain the air to reverse its direction of flow, some at least twice, and preferably three times, so that the air initially passes down into the water, reverse direction to pass up again, reverses direction to pass down again and finally emerges again in the upward direction. This promotes efficient cleaning or scrubbing of the air. 
     The stripping means preferably comprises a series of narrowly-spaced plates arranged as a grid to deflect the air flowing between the plates through a series of sharp angles. In this way, the successive deflections of the air as it passes through the stripping means forces the water to be deposited onto the plates from where it is allowed to drip back into the reservoir. 
     Preferably, the reservoir has means for draining off the sediment or sludge which forms at the bottom of the reservoir from time to time. To promote the efficient removal of the sludge, water can be periodically passed directly through the reservoir in a flushing operation. 
     The invention may be understood more readily and various other features of the invention may become apparent from consideration of the following description. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings wherein: 
     FIG. 1 is a side elevation of apparatus made in accordance with the invention; 
     FIG. 2 is an end elevation of the apparatus as viewed from the outlet; 
     FIG. 3 is an end elevation of the apparatus as viewed from the inlet; 
     FIG. 4 is a cross-section taken along the line IV--IV FIG. 1, and 
     FIG. 5 is a side elevation of the scrubber unit of the apparatus. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     As shown in the drawings, the apparatus has a base structure or a skid 10 which is preferably provided with a number of jacks (not shown) for adjusting the level of the apparatus. Brackets 5 are also provided to enable the apparatus to be suspended, for example, from a monorail. An inlet duct 11 is provided at one end of the apparatus and an outlet duct 12 provided at the opposite end. A fan (not shown) is provided, preferably at the outlet, to draw air through the apparatus from the duct 11 to the duct 12. 
     A water reservoir 13 is formed in a chamber 9 at the base of the apparatus. 
     Within and above the water reservoir 13 is a scrubber unit 14 depicted in FIGS. 4 and 5. This scrubber unit 14 has a main channel 20 with a rectilinear side and upper walls 22,21 as shown in FIG. 4. This channel 20 communicates with the inlet duct 11. As shown in FIG. 5, the upper wall 21 of the channel 20 is tapered downwardly towards the water reservoir. This ensures that the air passed into the inlet duct 11 is guided progressively downwardly towards the water reservoir 13. The scrubber unit 14 additionally comprises baffle means 15. This baffle means 15 consists of wedge members 16 at the lower ends of the side walls 22 of the channel 20, upstanding plates 17 with inwardly-bent flanges mounted to the bottom of the chamber 9 and a further set of shaped plates 18 mounted to the exterior of the side walls 22 of the channel 20. The upper level of the water in the reservoir 13 is generally denoted by dotted lines L and the flow path of the air is generally denoted by the full lines A. 
     The members 16 define a gap 16&#39; therebetween through which the dust-laden air is initially directed into the water in the reservoir 13. The members 16 also combine with the plates 17 to define a second set of gaps or channels 17&#39; through which the air and water is allowed to rise. A final set of gaps or channels 18&#39; is defined between the plates 18,17. The plates 18 serve to direct the air and water rising through the gaps 17&#39; downwardly towards the sides of the reservoir 13 and the air separates from lateral curtains C of water extending over the length of the scrubber unit 14. The air is then allowed to rise at arrows P at the sides of the apparatus for further treatment. 
     The overall construction of the baffle means 15, as described, thus constrains the air to pass along a sinuous, tortuous path and, more particularly, the air flows through lateral undulating paths (as shown at A) without causing a great deal of turbulence of the water and air. 
     After the air has been forced through the water in the reservoir 13 and constrained by the baffle means 15 of the scrubber unit 14, it is allowed to rise into stripping means 39, mounted at the top of the apparatus. The stripping means 39 is designed to remove the residual water from the air. The stripping means 39 comprises a grid or framework of plates 40 bent in the manner as shown in the drawing (FIG. 1) so that the air passes successively through narrow angles 41 in the order of 30°-45°. The water is thus stripped from the air and deposited on the plates 40 from whence the water drips into the water reservoir 13. 
     A series of upstanding plates 59 extend across the apparatus and serve to guide the rising air into the stripping means 39. The plates 59 also inhibit undue turbulence of the air. 
     The sludge or slurry which builds up at the bottom of the water reservoir 13 can be flushed out from time to time by opening drain valves or cocks 51 (FIG. 3) which also permit the reservoir 13 to be emptied for other purposes. As shown in FIGS. 1 and 2, water is supplied to an inlet connection 52 and thence to flexible hoses 53,54. A stop cock or valve 55 is provided in the hose 53 and this hose 53 feeds nozzles at the floor of the reservoir 13 which are only used for flushing out the reservoir 13. In the other branch, i.e. hose 54, a pressure reducing valve 56 is provided and this hose 54 feeds control means 50 in the form of a float valve 70 which is damped with a dash pot 76 and serves to automatically charge the reservoir 13 with water whenever necessary to maintain a desired level. This level can be inspected visually with the aid of an inspection window 57. A further inspection door 58 and window 58&#39; allow access and inspection of the control means 50. For safety purposes, an overflow pipe 61 is provided to drain off water which rises too high above the desired level. One or more filters, such as that indicated by reference numeral 60, can be incorporated in the water system. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.