Technical field

[01] This invention relates to system and method for suppressing dust from a workplace, a modular dust scrubber unit and an assembly of such units.

Background art

[02] There are numerous activities which generate large amounts of dust from a confined location. These include:

• Long wall mining;

• Development mining;

• Bord and Pillar mining;

• Contractor produced dust in U/G applications;

• Hard rock mining;

• Tunnelling;

• Strip Mining;

• Power Stations;

• Other materials handling applications

[03] The invention will be described with reference to the suppression of dust in a long wall underground mine. In underground mines, homotropic ventilation is used. This can influence the operation of systems which use negative fan pressure to extract dust laden air.

[04] Long wall mining involves the driving of a pair of parallel gate roads, referred to as the maingate and the tailgate, in the plane of the mineral ore seam, the gate roads being spaced apart by a distance referred to as the long wall. A mining machine, known as a shearer, then mines the coal face in the long wall by cutting the long wall in a direction transverse to the gate roads. The coal is extracted placed on the Armour Faced Conveyor (AFC) which is then conveyed to the maingate, fed into a crusher and then deposited on a rubber conveyor belt which carries the coal out of the mine. Support and drive means for the mining machine can be mounted in the gate roads.

[05] Respirable dust may be produced by the cutting operation or as the longwall machine moves forward or by associated operations in the mine. In particular, dust maybe created as the longwall machine moves forward. The shield crushes the coal in the roof while it holds the roof up, and, when the machine is to be moved forward, the shield is lowered and the dust is released. It is desirable to remove this dust from the air.

Disclosure of the invention

[06] In a first embodiment, the invention provides an extraction fan housing adapted to house an extraction fan, the housing including inlet ducting adapted to provide directional air inflow into the housing through an air inlet for the air drawn into the inlet ducting by an extraction fan. The housing is adapted to fit under the chock canopy of a long wall mine.

[07] In a second embodiment, the housing includes a particle extraction chamber adapted to house particle extraction means to remove particles from the air drawn in through the inlet ducting by an extraction fan.

[08] In a third embodiment, the particle extraction chamber includes a filter arrangement for removing dust from dust-contaminated air drawn in through the inlet ducting by the extraction fan.

[09] In a fourth embodiment, the assembly includes dust scrubber.

[10] In a fifth embodiment, the dust scrubber includes one or more water nozzles producing a water spray through which the air is passed.

[11] In a sixth embodiment, the filter arrangement includes one or more washable filters.

[12] In a seventh embodiment, the washable filters are washed by the water spray.

[13] In an eighth embodiment, the water and any entrained dust from the water spray is ducted to a sludge outlet.

[14] In a ninth embodiment, the discharge from the sludge outlet is treated in a water recovery system where at least part of the entrained dust is removed from the water and the water is reused in the water spray.

[15] In a tenth embodiment, the air from the outlet ducting is directed between the work area and an operator area.

[16] In an eleventh embodiment, the assembly includes a mist spray which is applied to the scrubbed air before it is directed to the operator area.

[ 17] Preferably, the assembly operates by the use of directional flow velocity rather than by the use of fan generated negative pressure.

[18] preferably, the system is powered by an emulsion or solcenic oil drive.

Brief description of the drawings

[19] Figure 1 shows a schematic view illustrative of the general concept of a long wall mining operation.

[20] Figure 2 shows a modular dust scrubbing unit embodying the invention.

[21] Figure 3 shows a side view of a dust scrubber according to a first embodiment of the invention.

[22] Figure 4 shows a plan view of the dust scrubber of Figure 3.

[23] Figure 5 shows an array of dust scrubbers embodying the invention and arranged for use in a long wall mining operation.

[24] Figure 6 is a schematic representation of a long wall mining plant operating with a dust scrubber of the present invention.

[25] Figure 7 shows a further embodiment of the invention;

[26] Figure 8 schematically illustrates the air flow between extractors of Figure 7.

Description of the invention

[27] The invention will be described with reference to the drawings. In an embodiment of the invention, a modular dust extraction unit includes a plastic hood incorporating a fan, hydraulic motor, filter screens, sludge discharge tube, cleaning sprays, fogging spray and an exhaust discharge acting as an air curtain over the AFC. The dust extraction hood includes deflectors to create directional velocity into each subsequent dust extractor unit.

[28] Figure 1 is a schematic representation illustrative of the general concept of an underground long wall mining operation.

[29] A seam of coal or ore being mined is represented generally as the long wall 100. One or more shearers 104 cut into the wall 100 and may make one or more passes at each "bite" 112, i.e., the horizontal distance the machine advances perpendicular to the wall. Only one shearer 104 is shown, but, in practice, shearers can be provided across the full face of the long wall. The shearer 104 is shown connected to the footing or pontoon 116 of the support posts by articulated/telescopic arm 118.

[30] The roof 100 is supported by a series of beams 106 which are supported at one end by hydraulic supports 108. Shields (not shown) are provided between the beams to support the roof. The distal ends of the beams 106 can be driven into the coal seam so to provide support at that end of the beams. The beams 106 may be driven into the wall 100 to a sufficient depth to permit the mining machine to make one or more traverses across the wall 100 before the beams have to be driven further into the seam. The pontoons are advanced as the coal face is removed.

[31 ] The roof area supported by the beams 106 defines a gallery in front of the wall 100. The mined area behind the gallery is generally not supported. Generally there will be a pair of supported drives at either end of the long wall. These drives are not shown in Figure 1. The

drives are used to service the work area, for example, to provide ventilation and to remove the mined ore.

[32] As the mining machine 104 cuts into the seam, it produces large amounts of dust, and further dust is produced as the coal is loaded onto the AFC. The invention provides an improved means of suppression of the disbursement of the dust within the gallery and gate roads.

[33] In a modification of this system, the beams 106 may be joined to form a chock canopy which is not sunk into the wall 100, and the supports 108, to which the beams 106 are attached, may be mounted on a transport platform so the whole assembly of beams, supports and transport platform can be moved forward simultaneously. A roof or canopy (not shown) and a rear wall (not shown) may also be provided to enclose the gallery. The extractor housing of the invention are shaped and sized so as to be adapted to fit under the canopy.

[34] Figure 2 shows a modular dust scrubbing unit 200 embodying the invention. The unit includes a housing 202 formed of ducting having ^' an air inlet 204, and a scrubbing assembly 212. A fan 208 is driven by a hydraulic motor 201 and draws air in through inlet 204 and forces the air through the scrubbing assembly 212. The upper surface of the unit can be substantially flat, while the lower surface is curved upwardly in a manner which restricts the cross section of the ducting in the vicinity of the fan 208. As best seen in Figure 5, the cross section of the inlet ducting 502 is also tapered horizontally, narrowing from the inlet 204 towards the fan 208. The ducting thus forms an inlet bell mouth which tapers inwardly. This tapered configuration creates flow resistance in the inlet which is overcome by the pressure from the fan 208.

[35] The scrubbing assembly 212 is shown in more detail in Figure 3. A schematic view of the scrubbing assembly is shown generally at 300. The dust contaminated air is drawn into the housing in the direction of th arrows by the fan 306. The air is drawn or blown past a number of water sprays 320, 312, and through a filter 314 where the dust is substantially removed, and finally passes through dehumidifier or mist eliminator 318 which removes a proportion of the moisture from the air.

[36] The scrubbing assembly has a number of zones in which the air is in various conditions. At the inlet zone 302, the air may be heavily contaminated by dust. A first water spray 320 can be provided to dampen the air as it is drawn into the scrubber by the fan 306.

[37] This air is then blown through a spray zone, 310, where the dust is entrapped with water droplets. The water-laden air with entrained dust is blown through filter, 314, where the dust is removed. The filter 314 may be periodically or continuously sprayed with water to clean it. The wash from the filter runs off to a sludge sump and is fed out via a sludge pipe 322.

[38] When the air has passed through the filter 314, and enters zone 316, it retains a high level of moisture. To remove some of the moisture, the air passes through a dehumidifier or mist eliminator 318. The cleaned and dried air can then be returned to the work area or vented to atmosphere.

[39] Preferably the filter 314 has a 99% efficiency for 10 micron particles.

[40] In a preferred embodiment of the invention, the cleaned air is used to form an ^' air curtain between the work area and the rest of the gallery.

[41] Figure 4 illustrates a modular unit 400 assembled to the canopy of a long wall mining gallery 404. The fan 402 is mounted to the canopy 404. Air is drawn in from the workface via the bell inlet 406 and forced through the filters 408 and water sprays 410. The water sprays are directed to the filters and continuously wash the dust collected by the filters into the sludge sump 416 from where it is drained by a sludge pipe not shown. The sludge pipe can be directed to settling tanks where the water can be recovered.

[42] The dust collection unit including the ducting and filters can be assembled as a single unit for ease of installation. The ducting and outer casing can be provided with access openings to facilitate access to the interior of the assembly. With the fan directly mounted on the canopy 404, the ducting unit can be removed without the need to remove the fan.

[43] In Figure 4, a fan 300 is driven by a hydraulic motor 402. The air intake 304 is adapted to draw air from the workface. As best seen in Figures 32 and 3, inlet ducting 202 is used to determine the area from which air will be drawn.

[44] The air drawn in by fan 100 then passes through one or more filters 106. Water sprays 108 are directed onto the filters 106 and continuously wash the collected dust from the filters 106. The water from the screen filters 106 runs off to a sump 110 and thence to a sludge discharge 112.

[45] After passing through the filters 106, the air is then ducted through outlet ducting 114 to filtered air discharge 116. The filtered air is preferably directed back into the gallery behind the workface or over the AFC to form an air curtain. Where the size of the outlet at 114 is smaller than the cross section of the inlet 406, the velocity of the discharged air at 114 will be higher than the velocity of the intake air at 406, ignoring temperature and pressure differences.

[46] Figure 5 shows a plan view of the arrangement of the bell shaped inlet duct 502, the fan 504, the scrubbing unit 506, and the sludge pipe 508.

[47] A number of the modular units described with reference to Figures 2 and 3 can advantageously be grouped to form an assembly of adjacent modular units which works in an additive manner. In particular the units can be assembled as shown in Figure 6. The directional inlet cowling makes it possible for the air flows from adjacent modular units to create directional air flow towards the inlet of an adjacent modular unit.

[48] As seen in Figure 6, the cowling 602 can be extended beyond the fan 604 to provide a section of cowling 606 which influences the air flow into the following unit. In particular, at point 607 the cross section transverse to the air flow at the inlet to the bell shaped ducting is assumed to be A, while the cross section at the narrow end of the bell shaped ducting is assumed to be B. Assume ^" the air velocity at the inlet is V ₁ and the air velocity at the narrow end is V ₂ . Thus, ignoring pressure differences:

V ₂ / V ₁ = A/B.

[49] The bell mouthed deflector cowling can increase the air flow velocity across the workface significantly. In addition, the bell mouthed cowling results in higher velocities within the housing of the unit. Flow resistance due to the reduction in cross section is overcome by the fan produced negative pressure effects.

[50] In addition, as can be seen from the air flow lines in Figure 6, each fan draws in air in the same direction and the flow from the left most fan 608 assists the flow of the next fan 604, and so on. Thus there is an additive effect resulting from the directional flow imposed by the directional inlet cowlings 602. This effect creates an effective air flow across the workface and up into the inlet ducts to improve the efficiency of dust collection from the workface.

[51] As also shown in Figure 6, an additional source of forced airflow 610 can be provided in such a position and oriented so as to aid the airflow of the fans 604. This may be of additional advantage if this secondary flow of forced 612 is applied in a region where the airflow from fans 604 is weaker. This additional source of airflow maybe, for example, external air pumped into the mine. The use of the additional forced airflow reduces the negative air pressure required from the exhaust fans to capture the dust generated at the work face.

[52] An air flow deflector arrangement can also be provided at the base of the workface to recirculate the discharged air curtain from the outlet back towards the fan inlets as illustrated in Figures 7 & 8.

[53] In Figure 7, a deflector cowling 712 is provided to deflect the airflow ins a downward direction at a distance from the workface. The downward airflow strikes a deflector 714 which deflects the airflow back towards the workface as illustrated by arrow 716. Preferably, deflector 714 also imparts an upward direction to the airflow 716. The deflector 714 can be of a "U" shaped section. However, a substantially planar vane angled to deflect the airflow to the work face can be used as the deflector 714, because, the extractor fans will cause the airflow 716 to rise up the workface.

[54] Figure 8 illustrates schematically the flow of air between adjacent extractors 802, 803. Because of the transverse flow created by the extractors, the upward flow from the deflector 814 takes on a spiral path so that the airflow from extractor 802 is directed to the inlet of

extractor 803 after it traverses the workface. Thus the deflector vanes produce an additive airflow.

[55] Where the outlet stream at 414 in Figure 4 is used as an air curtain, additional deflectors placed in the gallery can be used to recirculate the air curtain from 414 to assist the uptake of dust-laden air from the workface.

[56] In an underground environment, ventilation may be provided to force clean air from the surface into the work area. The invention can advantageously utilise the forced exterior ventilation to further increase the effectiveness of the inventive system by directing the external ventilation stream in a direction to further augment the synergistic effect of the directional cowlings.

[57] In one embodiment, the inlet dimensions are of the order of 1500 mm by 280 mm, giving a cross-section of about 0.42 m ² . A fan of 2.5 mVsec will thus produce a directional velocity of the order of 6 m/s is created at the inlet. This velocity is almost twice the face velocity of that generated by systems known to the inventor.

[58] In a further embodiment, the outlet of the velocity deflector has dimensions of the order of 990 mm by 150 mm, giving an area of about 0.15 m ² . Thus a fan of 2.5 m/Vsec will produce a directional velocity of the order of 16.7 m/s. This velocity is greater than the face velocities of systems known to the inventor. This velocity is several times the known face velocities, and can be more than 6 times the known velocities. Resistance created by the reduction in area is overcome by the fan created negative pressure.

[59] Where ever it is used, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of. A corresponding meaning is to be attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear.

[60] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from

the text. All of these different combinations constitute various alternative aspects of the invention.

[61] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein.