APPARATUS FOR MIXING AND APPLYING PARTICULATE MATTER AND FOAM

Abstract

In an apparatus for applying rock dust with foam to a mine wall to suppress mine fires and prevent explosions, foam and air-entrained rock dust are separately conveyed to a combination nozzle and mixing device. The air-entrained rock dust moves axially through a passage into an enlarged chamber while foam moves through an array of openings surrounding the passage that direct the foam in a helical path. The helical movement of the foam, and the reduction of the velocity of the air-entrained rock dust resulting from its movement into the enlarged chamber, enhance mixing. The mixture passes from the enlarged chamber through a restricted nozzle to increase the velocity of the mixture for effective spraying. The restricted nozzle has an array of internal flow-interrupting baffles that further promote mixing by generating turbulence, condense the stream, and shape the spray pattern.

Claims

1. Apparatus for mixing a foam with particulate matter and air to produce a mixture, and for spraying the mixture, the apparatus comprising: an elongated passage extending along a longitudinal axis, said passage having a first inlet opening at one end thereof, facing along the direction of said longitudinal axis, for receiving a stream of air and particulate matter passing through said first inlet opening in the direction of said longitudinal axis, and an outlet opening at an opposite end thereof for spraying said mixture; a second inlet opening facing in a direction transverse to said longitudinal axis for receiving a stream of flowable foam directed through said second inlet opening toward said longitudinal axis; and a ring adjacent said first inlet opening, the ring having a central opening forming a part of said elongated passage, an annular channel on the exterior of the ring, the channel being positioned to receive flowable foam passing through said second inlet opening, and a circular flange extending around the ring and forming a boundary of the annular channel on the side thereof closer to said outlet opening, said flange having passage means for the movement of flowable foam from said channel into said elongated passage for admixture with air and particulate matter passing though said central opening of the ring; wherein said elongated passage comprises a chamber located on the side of said ring remote from said first inlet opening, and a tubular portion extending from said chamber to said outlet opening, said chamber having a maximum cross-sectional area transverse to said longitudinal axis larger than the maximum cross-sectional area of the central opening of the ring, whereby the velocity of the stream of air and particulate matter is reduced as it passes from said central opening of the ring into said chamber and more complete mixing of foam with air and particulate matter can take place in said chamber; and wherein the cross-sectional area transverse to said longitudinal axis of at least a portion of the length of said tubular portion is smaller than said maximum cross-sectional area of said chamber, whereby the velocity of a mixture of foam, air and particulate matter through said outlet opening exceeds the maximum velocity of the mixture of foam, air and particulate matter flowing through said chamber.

2. The apparatus according to claim 1, in which the passage means of said flange comprises a plurality of circumferentially distributed through holes.

3. The apparatus according to claim 1, in which the passage means of said flange comprises a plurality of circumferentially distributed through holes, said holes being skewed in relation to said longitudinal axis in directions to cause foam exiting from said through holes to flow in a helical pattern.

4. The apparatus according to claim 1, in which the passage means of said flange comprises a plurality of circumferentially distributed through holes, each hole having an inlet end for receiving foam from said annular channel and an outlet end for delivery of foam to said chamber, said holes being skewed in relation to said longitudinal axis in directions to cause foam exiting from said through holes to flow in a helical pattern, and the outlet end of each of said holes being closer than the inlet end thereof to said axis.

5. The apparatus according to claim 1, in which said chamber includes a cylindrical tube having an inner diameter greater than the maximum dimension of said portion of the length of said tubular portion.

6. The apparatus according to claim 1, in which said tubular portion includes a plurality of flow-interrupting baffles for promoting turbulence in the flow of said mixture through said tubular portion.

7. The apparatus according to claim 1, in which said tubular portion has an inner wall and includes a plurality of flow-interrupting baffles extending inward from said inner wall for promoting turbulence in the flow of said mixture through said tubular portion.

8. The apparatus according to claim 1, in which said tubular portion has a cylindrical inner wall and includes a plurality of flow-interrupting baffles extending inward from said inner wall from locations on an imaginary helix on said cylindrical inner wall for promoting turbulence in the flow of said mixture through said tubular portion.

9. The apparatus according to claim 1, in which said tubular portion has a cylindrical inner wall and includes a plurality of flow-interrupting baffles extending inward from said inner wall from locations on an imaginary helix on said cylindrical inner wall for promoting turbulence in the flow of said mixture through said tubular portion, each of said flow-interrupting baffles being in the form of a twisted plate secured to said inner wall by a fastener, and extending obliquely from the location of said fastener toward said axis and toward said outlet opening.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a perspective view of the mixing and applying device in accordance with the invention;

[0015] FIG. 2 is a first longitudinal cross-sectional view of the mixing and applying apparatus, taken on a first longitudinal section plane;

[0016] FIG. 3 is another longitudinal cross-sectional view of the mixing and applying apparatus, taken on a second section plane perpendicular to the first section plane;

[0017] FIG. 4 is an elevational view showing the outlet end the mixing and applying apparatus;

[0018] FIG. 5 is an elevational view showing details of a ring, at the inlet end of the apparatus, having multiple foam passages for directing foam into a mixing chamber in which the foam is combined with rock dust that passes through a central opening in the ring;

[0019] FIG. 6 is an elevational view of ring as seen from the right side of FIG. 5; and

[0020] FIG. 7 is a partial elevational view of the right side of the ring in FIG. 5, illustrating the configuration of the foam passages.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The apparatus in accordance with the invention can be in the form of a hand-held assembly as shown in FIG. 1, comprising an inlet 10 for connection to a first flexible hose for carrying particulate matter, e.g., limestone dust entrained in air, an inlet 12 for connection to a second flexible hose for carrying foam, and a nozzle 14 for directing the mixture of air, particulate matter, and foam at a surface, such as the wall of a coal mine.

[0022] The flexible hoses connect respectively a remote source for combining air and particulate matter and a remote foam generator. The remote source for combining air and particulate matter can be, for example, a rock dust system as described in U.S. Pat. No. 10,071,269, and the foam generator can be the foam/air mixing device described in the same patent. The disclosure of U.S. Pat. No. 10,071,269 is here incorporated by reference.

[0023] The flexible hoses allow the assembly of FIG. 1 to be carried by an individual, who can aim the nozzle at a desired target area on a mine wall or other surface. As an alternative, the apparatus can be transported and aimed toward a target area by mechanical means such as a remotely controlled boom on a vehicle or by a robotic carrying apparatus.

[0024] The apparatus includes a combining section 16 for bringing the foam introduced through the foam inlet 12 into contact with the air-entrained particulate matter introduced through inlet 10. The air which entrains the particulate matter necessarily flows into the inlet 10 at a high velocity, whereas the foam flows more slowly. The foam, particulate matter, and air move from the combining section 16, through an expansion section 18 into a chamber 20. having a diameter larger than that of the opening of inlet 10. In the chamber 20, expansion of the air reduces its velocity to a level more closely approaching the velocity of the foam so that thorough mixing takes place, i.e., substantially all of the particulate matter is absorbed into the foam.

[0025] Because of the reduction in velocity in the chamber 20, the mixture cannot be propelled directly from the chamber 20 toward a target surface. However, the chamber 20 is followed by a reduction section 22 and a the nozzle 14, which is in the form of a tubular section 24 having an internal diameter substantially smaller than that of chamber 20, e.g., a diameter comparable to that of the opening of the inlet 10 through which air-entrained particulate matter passes into the apparatus. The velocity of the mixture thus increases, and the mixture can be propelled from nozzle opening 26 toward a target area, which can be at a considerable distance from the apparatus. A typical rate of flow of the air entering the apparatus is in the range from approximately 75 to 100 cfm, and the pressure is typically approximately 10 psi. Under those conditions, the mixture exiting the nozzle opening 26 can be sprayed through a distance of approximately eight meters.

[0026] FIGS. 2 and 3 show the interior structure of the apparatus of FIG. 1. The inlet 10 directs air-entrained limestone dust along the direction of a central axis 28, and through a central opening 30 of a ring 32 inside the combining section 16. (Details of the ring 32 are shown in FIGS. 5-7.) Foam introduced through foam inlet 12 is received in an annular channel 34 formed between flanges 36 and 38 on the exterior of the ring 32. The foam flows around the ring, filling channel 34, and exits from the channel through an array of openings 40 in flange 38.

[0027] The foam and the air-entrained limestone dust come together in a tapered passage 42 in the combining section 16, and the mixture then flows through expansion section 18 into chamber 20.

[0028] As shown in FIGS. 5, 6 and 7, the holes 40 are cylindrical and their axes are disposed at angles such that their outlet ends 43 are closer than their inlet ends 44 to the central axis 28 (FIGS. 2 and 3) of the apparatus. As shown in FIGS. 6 and 7, each of the holes 40 is formed so that its axis is directed toward one side of the central axis 28. FIG. 7 shows the relationship between a central axis 46 of one of the holes 40 and a radial plane 48 in which axis 28 lies. The axes of the other ones of holes 40 are similarly disposed in order to produce a helical flow of foam in the tapered passage 42 for more effective mixing of foam with the air-entrained limestone dust.

[0029] Mixing continues to take place in chamber 20 (FIGS. 2 and 3), and the mixture of foam, air and limestone dust then passes through reduction section 22 into the tubular section 24 of nozzle 14.

[0030] Inside the nozzle 14, a plurality of flow-interrupting baffles 50 extend inward from the inner wall of the tubular section to promote turbulence in the flow of the foam, air and limestone dust mixture through the nozzle for continued mixing. The baffles 50 can be secured to the inner wall of the tubular section 24 by rivets or other suitable fasteners, and are preferably in the form of twisted sheets of metal or synthetic resin.

[0031] Because the diameter of the passage inside the nozzle 14 is smaller than the diameter of the interior of the chamber 20, the velocity of the mixture increases as it passes from the chamber 20 into the nozzle, and the mixture can then be projected from the nozzles. The flow-interrupting baffles are preferably arranged in a helical pattern, and promote mixing, condense the stream, and shape the spray pattern of the mixture for application to a mine wall.