DUST SCRUBBER FOR USE WITH CONTINUOUS MINING EQUIPMENT The present invention relates to a continuous mining apparatus comprising means for controlling the dust produced in a continuous mining operation. In a continuous mining operation much dust is produced as the cutting head of the miner cuts coal away from the cutting face of the mine. The dust level present in the air surrounding the continuous mining apparatus must be controlled from both a health standpoint and safety standpoint to prevent explosions. Accordingly, some means must be provided for proper dust control in the cutting areas of continuous mining apparatus.

US-A-4,315,658 discloses a continuous mining apparatus that includes a curtain means for guiding the airborne dust generated by the cutting head toward a passage. The passage directs dust-laden air away from the ventilation air that is supplied to the cutting face of the equipment. Both fans and hydraulic nozzles are provided for inducing ^n air flow in the passage. While means for removing the dust-laden air from the vicinity of the cutting head are disclosed there is no disclosure of any means for removing the dust from t.ie air so that the air can be recirculated within the mine. Instead, US-A- 4,315,658 merely shows discharging the dust-laden air to the rear of the mining apparatus.

In US-A-3,904,246 there is shown a rotary cutting head for use in a continuous mining apparatus that

incorporates air flow inducing devices mounted in the cutting head. In particular, there is shown an air flow guide means in the cutting head with fluid nozzles used for inducing an air flow into the guide means. Again, there is no specific disclosure of any means for removing the dust from the air. The use of nozzles for dispersing a dust suppression fluid in the dust-laden air is mentioned however.

Another continuous miner is shown in US-A-4,037,875 incorporating fans for removing dust-laden air from the vicinity of the cutting heads. The use of nozzles for spraying a liquid into the confined area adjacent the face of the mine is disclosed but there is no specific disclosure of any means for removing dust from the air that is exhausted by the fans.

Three Technology News bulletins of the Bureau of Mines, United States Department of the Interior, No. 117, November 1981; No. 322, January 1989; and No. 337, May 1989, all describe high pressure scrubbers for use with continuous underground mining equipment. All of these scrubbers depend on high pressure water nozzles for producing an air flow through the scrubber and removing dust. This results in a large consumption of water in relation to the air flow produced and creates a water disposal problem. In addition, all of the systems utilize demisters for removing the water and entrained dust from the air before it is returned to the mine atmosphere. The

demisters are screen-type filters that clog after a few hours of use and require frequent cleaning.

From this it can be seen that the need to remove dust-laden air from the vicinity of the cutting head in a continuous mining apparatus has been recognised but an efficient means for removing such dust from the air has yet to be provided. While the use of fluid nozzles has been disclosed for inducing a flow in air removal means or for suppressing dust, there has been no disclosure of specific means for removing dust from dust-laden air so that the cleaned air may be recirculated within the mining operation.

The present invention provides a method and apparatus for removing dust particles from the dust-laden air that is produced in a continuous mining operation. Accordingly, in one embodiment, the invention provides a continuous mining apparatus having a pivoted boom with a cutting head mounted on its free end and a wet scrubber mounted on said boom adjacent said cutting head, said wet scrubber including means adapted in use of said apparatus to induce an air flow through said wet scrubber whereby to remove dust-laden air from the vicinity of the cutting head, to remove dust from said air and to discharge the resulting cleaned air. The apparatus of the invention preferably also comprises an air curtain, said wet scrubber being adapted to discharge cleaned air into said air curtain flow.

The wet scrubber most suitably utilises twin fluid

atomisers, preferably capable of producing a mist of liquid droplets ranging in size from a few micrometers up to 50 micrometers. This size range of liquid droplets will remove substantially all the dust particles from the air that is removed from the vicinity of the cutting head. This particular type of wet scrubber is more particularly described in US-A-5039315.

The efficiency of a wet scrubber employing twin fluid atomizing nozzles provides a compact unit that can be mounted directly on the pivotal boom that supports the cutting head of the miner. The mounting of the wet scrubber directly on the pivotal boom positions it in close proximity to the cutting head of the miner. This eliminates considerable duct means and fan means that are required for removing the dust-laden air from the vicinity of the cutting head. In addition, it improves the removal efficiency and eliminates the need for curtains and other means that are utilized for isolating the cutting head from the remainder of the mine atmosphere. The fluid used in the wet scrubber is preferably water which after contact with the dust-laden air can be discharged directly to the mine floor or, if desired, added to the coal that is being produced by the continuous miner. The twin fluid atomizers used in the wet scrubber have a high efficiency and require very little water for their operation. Thus, there is little water produced by the wet scrubber and this amount can be discharged directly to the

mine without creating a disposal problem.

The wet scrubber preferably includes a parallel plate separator, especially one in which the plates are corrugated, positioned downstream of the twin fluid atomizers. Passage of the scrubbed air through the parallel plate separator enables the removal of water and entrained dust from the air before it is returned to the mine atmosphere. The use of a parallel plate separator eliminates the clog problems that occur when demisters are used.

In a preferred embodiment of the apparatus the wet scrubber includes duct work, said duct work having an open end located in the vicinity of the cutting head and discharge openings located in the opposite end, twin fluid atomizers mounted in said duct work adjacent said open end and discharging toward said discharge openings, and a corrugated parallel plate separator positioned between said twin fluid atomizers and said discharge openings. Such apparatus preferably also comprises exhaust fans mounted adjacent the discharge openings to induce an air flow through the apparatus from the vicinity of the cutting head to the discharge openings. The cleaned air discharged from the wet scrubber, being substantially free of any entrained dust particles, can be circulated to the mine atmosphere, for example directly back to the cutting head of the continuous mining apparatus. The air may be recirculated using the normal flow of the air curtain that is utilized

in continuous miners to remove methane gas that is released during the mining operation.

In another embodiment the invention provides a method for reducing the concentration of dust particles produced during operation of a continuous mining apparatus, which method comprises:- removing dust-laden air from the vicinity of a cutting head of said continuous mining apparatus; treating said dust-laden air with a wet scrubber using twin fluid atomizers, one of said fluids being water and the other fluid being compressed air; and discharging the water and entrained dust particles into the mine while recirculating cleaned air back to the mine atmosphere. The invention will now be described in more detail by reference to the accompanying drawings in which:

Figure 1 is a plan view of a continuous mining apparatus provided with a wet scrubber in accordance with this invention; and Figure 2 is a side view of the apparatus shown in Figure 1.

Referring now to the drawings, there is shown a continuous mining apparatus 10. The apparatus 10 is provided with two separate rotary cutting heads 11 and 12 that are powered by suitable electric motors 13 and 14. The cutting heads 11 and 12 are mounted on a pivoted boom 16 that is supported by a track carriage 15. Suitable

means such as a hydraulic cylinder 17 is used for raising and lowering the boom 16 so that the cutting heads 11 and 12 can traverse a coal face 22 from the floor 20 to the roof 21 of a mine. The track carriage 15 is manoeuvred by a suitable drive means, such as electric motors.

While the above description relates to a continuous mining apparatus that utilizes cutting heads that rotate about a horizontal axis and are mounted on a boom which is pivoted so that they can be raised and lowered, obviously, other arrangements could be used. Many different types of continuous mining equipment are available and they all produce the same problem of dust-laden air. The present invention can be applied to any of these various types of mining equipment by those skilled in the art. The continuous mining apparatus 10 is provided with a wet scrubber 30 mounted on top of the boom 16. Thus, the wet scrubber 30 will be raised and lowered as the boom 16 is manoeuvred so that the cutting heads 11, 12 can cut the complete face 22 of a coal seam. The wet scrubber 30 is provided with duct work which includes a tapered section 31 positioned adjacent the cutting heads 11 and 12. As shown in Figures 1 and 2, the tapered section 31 flares outwardly in Figure 1 so that it will remove dust-laden air from the complete length of the two cutting heads 11 and 12 in the direction indicated by the arrow A. The top surface of the tapered section 31 slopes downwardly as shown in Figure 2 so that as the boom is raised, the cutting heads 11 and 12

can cut to the roof 21 of the mine. In some cases, it may be desirable to include flexible panels in the tapered inlet section 31 of the wet scrubber in order that they may deform when the cutting head is raised to a position where the section 31 contacts the roof 21 of the mine.

The wet scrubber 30 is provided with six twin fluid atomizers 32 as shown in Figure 1. The twin fluid atomizers are supplied with two fluids by means of two separate lines 33 and 34. It is preferable that the fluids be water and compressed air although other combinations can be used. As explained in US-A-5039315, the twin fluid atomizers are preferably designed to supply a liquid mist of atomized droplets having a size range of between a few micrometers and 50 micrometers. This size range of particles has been found to be most efficient for removing dust particles from dust-laden air produced in coal mining operations.

Downstream of the twin fluid atomizers 32 is a reduced cross section 35 of the duct work. The reduced cross section 35 in provided so that the twin fluid atomizers 32 can completely cover the cross sectional area of the duct work with a liquid mist and force all dust- laden air entering the duct work to pass through the mist. Downstream from the reduced cross sectional area 35 is a separator section 36 that is shown as composed of a plurality of corrugated parallel plate members. This type of separator is highly efficient in removing liquids from

the air stream while requiring only a small energy input to produce an air flow across the separator. Water removed from the air stream can be drained through an opening 37 directly onto a conveyor associated with the continuous mining apparatus since the quantity of water required for the wet scrubber is considerably less than that of scrubbers that rely solely upon water sprays for removing dust particles entrapped in an air flow.

The use of parallel plate members eliminates the clogging problems associated with demisters used in the prior art. In addition, they require less energy to produce a given air flow through the separator.

The separator 36 discharges into an exhaust section 40 of the wet scrubber 30. The exhaust section 40 is provided with a diverter element 41 that serves to divert the flow of cleaned air to the sides of the wet scrubber 30. An air flow through the wet scrubber 30 is induced by means of multiple fan elements 42. The fan elements 42 are preferably high efficiency fans that have low noise level to reduce the noise produced by the wet scrubber to permissible limits. The cleaned air discharged from the scrubber 30 can be recirculated in the direction shown by the arrow B. If desired it can be mixed with the air flowing in the air curtain used for removing methane from the mine.

The present invention provides a highly efficient wet scrubber mounted directly on the boom of a continuous

mining apparatus. By mounting the scrubber directly on the boom the need for duct work for removing the dust-laden air to a remote location is eliminated. Further, the cleaned air discharged from the scrubber, being substantially free of any dust particles, can be utilized in the air flow that normally is provided in a mine for maintaining safe operations. As explained in US-A-5039315, the overall removal efficiency of the wet scrubber is above 99.5%. Thus, the cleaned air from the scrubber can be utilized in normal ventilation activities in the mine while the dust- laden water can be discharged directly with the mined coal. The quantity of water required to operate the scrubber is small, i.e. less than 11.4 liters (3 U.S. gallons) per minute for an air flow of 170 m ³ (6000 cubic feet) per minute, and can be supplied from tanks mounted on the miner or other sources. The quantity of compressed air required is less than 0.0283 standard m ³ /S (60 standard cubic feet per minute) and can be supplied from a compressor mounted on the continuous mining apparatus.