Crusher-dryer and method of crushing

Abstract

An improved apparatus for the simultaneous crushing and drying of materials, such as coal with high moisture content, which includes a hammermill crusher having parallel top inlets for the material and a rapid flow of hot air. The material drops into the impactor impact circle of the hammermill crusher prior to any substantial mixing with the flow of hot air. The flow of hot air is selectively directed into the crushing chamber, behind the breaker plates or in parallel to both locations, to dry the material during crushing. A substantially unobstructed bottom outlet permits high flow rates through the apparatus. A method of crushing and drying high moisture content material is also disclosed.

Description

This is a continuation of application Ser. No. 746,379, filed Dec. 1, 1976, and now abandoned.

BACKGROUND OF THE INVENTION

In recent years, utility companies operating steam generating units powered by pulverized coal have experienced a variety of problems relating to fuel supplies. Curtailment of the availability of natural gas and oil as fuels; decline in coal reserves due to environmental restrictions on mining and to increased foreign purchases; increased costs of spot purchases in the coal market; and related factors have played a part. Moreover, environmental requirements for low sulfur-dioxide emissions have increased the demand for bituminous coals of low hammermillhammermill impactor comprises a housing 10 within which a shaft 12 is rotatably mounted. Shaft 12 carries a plurality of rotor plates 14 on which a plurality of impact members such as swing hammers 16 are pivotably mounted. As rotor 14 turns, hammers 16 move outward to their illustrated positions thereby defining a hammer an impact circle 18 in the familiar manner. Of course, other rotor types could also be used. Located closely adjacent to hammer impact circle 18 are a pair of conventional breaker plates 20 mounted on pivots 22 which are located in support arms 24 attached to housing 10. Although single piece breaker plates are illustrated, multiple piece units with several pivots may also be used. The space between breaker plates 20 comprises the crushing volume or zone of the mill crusher. A pair of jack screws 26 are provided for adjusting the positions of breaker plates 20 relative to hammer impact circle 18 via pivots 28, to change the hammer to breaker plate clearance.

Housing 10 is completely open to at its upper end to receive the lower portion of an inlet chute 30 for coal or other moist material to be crushed and dried. Chute 30 is preferably arranged essentially vertically so that material dropping through the chute will have an unobstructed path for obtaining the necessary velocity to penetrate hammer impact circle 18; however, it is permissible to angle the chute somewhat from the vertical so long as the necessary material velocity is achieved by the time the material reaches hammer impact circle 18. An adjustable bottom collar 32 is telescopically received on the lower end of inlet chute 30. Normally, collar 32 is positioned so that it terminates above hammer impact circle 18 by a distance slightly larger than the maximum size of inlet material anticipated. This prevents the air from undesirably interfering with the falling material before the material reaches the area just above the impact circle. As viewed in FIG. 1, chute 30 has a width of approximately one-fourth to one-third the diameter of hammer impact circle 18 to provide an efficient delivery of material to the hammers. If the chute is substantially wider than this, the hammers tend to throw a considerable amount of material back up the chute, thereby impeding the downward flow of new material; whereas, if the chute is substantially narrower than this, the inlet feed rate is limited unnecessarily. As shown in FIG. 2, chute 30 extends substantially across the width of the rotor as measured along its rotational axis in order to deliver material to all of the rotor hammers and thereby equalize hammer wear across the rotor.

An air inlet duct 34 surrounds inlet chute 30 and is essentially concentric with it. Duct 34 is provided to deliver high temperature, high velocity air to the interior of housing 10. Simultaneously the walls of inlet chute 30 are heated to raise the temperature of the coal as is approaches the crushing area. In practice, air at 600° to 700° F. and as much as 28,000 cfm is mixed with coal moving at approximately 54 tons per hour, using 20.5 pound hammers rotating at 1050 rpm. At the lower end of duct 34, a pair of adjustable air dampers 36 are provided, one on either side of inlet chute 30. Dampers 36 are sized to permit full or partial closure of duct 34 on each side of inlet chute 30 so that the flow of air through duct 34 may be directed to the crushing volume between breaker plates 20, to the path between breaker plates 20 and housing 10 or to some combination of both locations. The path between the breaker plates and the housing on each side preferably is sized to pass the entire air flow in cases where little or no air is directed through the crushing chamber. Depending upon the flow rate and temperature of the inlet air, the moisture contect content of the coal or other material and similar factors, the flow of air through the crushing volume may be adjusted as necessary to produce the desired characteristics in the outlet product. The bottom outlet of the mill crusher is preferably centrally located; however, it may be set off to one side or the other as desired so long as bridging by the material and reduced air flow capacity are not induced to an unacceptable extent. A plurality of bottom breaker bars 38 may be located below the outlet from the rotor in position to receive material flung off by hammers 16 without substantially obstructing air and material flow out of the crushing zone. By "without substantially obstructing" it is meant that bars 38 would be spaced so that material passes through the crushing zone without recirculation. Means for adjusting the spacing of bars 38 may be provided if desired (not shown). Also, vanes or deflectors such as 36 may be positioned in housing 10 to deflect air moving behind breaker plates 20 into the stream of material leaving the crushing chamber, thereby aiding in drying the material. As shown in FIG. 2, shaft 12 of the hammermill impactor is supported in a pair of bearings 40 which are mounted on a support frame 42 in the conventional fashion.

FIG. 3 shows a further embodiment of the invention in which a one way or non-reversible hammermill impactor is utilized. In this embodiment, the inlet chute 44 for coal or other moist material is also preferably vertically arranged but is located to one side of the center line of the rotor on the down-running side, as indicated. The off center location of chute 44 is permissible in the one way mill crusher since the depth of penetration through the hammer impact circle is not as important to the effective operation of a one way mill crusher as it is in a reversible mill crusher. The size of material leaving the one way mill crusher may be varied effectively by adjusting the position of breaker plate 20 as will be understood by those skilled in the art. For the same reasons as in the previous embodiment, an adjustable bottom extension 46 is provided at the lower end of inlet chute 44 to permit the location at which material leaves the chute to be modified in use. An air inlet duct 48 is located outboard of inlet chute 44 relative to the center line of the rotor so that the air flow does not interfere with hammer movement on the up-running side of the mill crusher, and that "foul balling" up the air inlet duct is avoided. At the lower end of air inlet duct 48, an adjustable air damper 50 is provided for controlling air flow in the manner previously discussed.

In the embodiments shown in FIGS. 1 to 3, the positioning of adjustable collar 32 and adjustable bottom extension 46 is important to the operation of the invention. As mentioned previously, material leaving the lower end of the material chute should have attained a velocity to ensure optimum penetration of the hammer impact nd○ If the lower end of the chute is located too far away from the hammer impact circle, the high velocity air moving in the area will adversely affect the movement of material into the crushing volume. However, because the movement of material and air in this area will naturally tend to wear away the bottom of the chute and because the preferred clearance to the hammer impact circle will vary depending on operating conditions, an adjustable collar or extension is necessary to maintain the preferred clearance between the chute and the hammer impact nd○ The adjustable air dampers 36 and 50 help to control the effects of the moving air on coal entering the crushing zone. In addition, the presence of dampers 36 and 50 in air inlet ducts 34 and 48 prevents material flung off by hammers 16 from flying back up the air ducts by deflecting the material back down into the crushing volume.

FIG. 4 shows a view of an actuating linkage suitable for positioning adjustable air dampers 36 and 50. The dampers are mounted on shafts 51 which are rotatably mounted through the walls of ducts 34 and 48 via stuffing boxes 52. A pair of crank arms 53 and 54 are actuated by hydraulic or pneumatic cylinders or screws 56 and 58 mounted on the sides of the air inlet ducts by brackets not illustrated. In use, the dampers on either side of coal chutes 30 and 44 may be operated independently or in tandem as desired.

FIG. 5 shows a perspective view of a linkage suitable for adjusting collar 32 and extension 46. A pair of support rods 60 and 62 are attached to collar 32 or extension 46 as indicated. These rods are passed out through a cover plate 64 mounted in the wall of air duct 34 or 48, through a pair of guide slots 66 and 68. A pair of links 70, one on each side of the air inlet chute, join support rods 60 and 62 and are supported by a pair of yokes 72 mounted on a pair of screw jacks 74. By operating screw jacks 74, the position of collar 32 or extension 46 may be adjusted as necessary during operation.

FIG. 6 shows a schematic view of one application of the invention in a coal crushing system for a commercial power plant. A coal feeder 76 feeds coal as required through a cut off valve 77 which opens into the upper end of inlet chute 30 or 44 at about 16 feet above the hammer impact circle to ensure adequate penetration. The discharge from the crusher dryer according to the invention is to an outlet duct 78 which leads to a commercial ball mill or other pulverizer of known design. High temperature air for inlet duct 34 may be withdrawn from the stack of the power plant to conserve heat.

Claims

1. An improved apparatus for crushing and drying materials, such as moist coal, comprising:

a housing having an inlet opening located; in the upper portion thereof and an outlet opening located in the lower portion thereof;

a rotor mounted for rotation in said housing, said rotor having impact members thereon for striking and crushing material falling through said inlet opening and passing through the impact circle defined by the outer extremities of said impact members;

a first inlet duct means entering said inlet opening and terminating a short distance above said hammer impact circle, for causing said material to drop through said inlet opening above said impact circle to be struck by said impact members;

a second inlet duct means entering said inlet opening for conveying hot air into said housing without substantially interfereing interfering with said material until just prior to entry of said material into said impact circle;

at least one breaker plate mounted within said housing in position to be impacted by material thrown off by said impact members; and

means located within said second inlet duct for selectively directing the flow of hot air through said second inlet duct to pass between said breaker plate and said rotor; behind said breaker plate; or both.

2. Apparatus according to claim 1 in which said first inlet duct means comprises a duct having a lower end terminating a short distance above said impact circle, and means for adjusting the clearance between said lower end and said impact circle.

3. Apparatus according to claim 1, wherein said first inlet duct extends substantially across the axial width of said rotor to direct material to be crushed to the axial width thereof.

4. Apparatus according to claim 1, wherein said first inlet duct means is concentrically located within said second inlet duct means.

5. Apparatus according to claim 4 wherein said rotor is reversible to crush material in either direction of rotation, further comprising at least one additional breaker plate mounted within said housing opposite to said at least one breaker plate, and means for deflecting the flow of hot air further being effective to direct air flow between said additional breaker plate and said rotor; behind said breaker plate; or both.

6. Apparatus according to claim 1, wherein said first and second inlet ducts share a common wall through which heat from said air is conducted to said material to induce at least partial drying thereof.

7. Apparatus according to claim 1, wherein said first and second inlet duct means are located on the down-running side of said rotor with said first inlet duct means located between the center of said rotor and said second inlet duct means.

8. Apparatus according to claim 4, wherein said first and second inlet duct means are centered above the center of said rotor.

9. Apparatus according to claim 4 wherein said means for directing the flow of hot air comprises first and second flapper valve means located on opposite sides of said first inlet duct means within said second inlet duct means, further comprising means for closing either one of said valve means as the other opens.

10. A method of crushing and drying moist materials such as coal and other materials, comprising the steps of:

causing said material to drop through a first essentially vertically oriented duct;

causing said material to leave said first duct at a short distance above the impact circle defined by the outer extremities of the impact members of a crushing machine having a housing, a rotor mounted for rotation on an axis in said housing, impact members mounted on said rotor for striking and crushing material falling through said impact circle and at least one breaker plate mounted in said housing in position to be impacted by material thrown off by said impact members;

passing a flow of hot air into said crushing machine in parallel with said material through at least one second duct spaced outboard of said first duct on the down-running side of said rotor; and

selectively directing said flow of hot air through said crushing machine and between said breaker plate and said rotor; behind said breaker plate; or both.

11. A method according to claim 10, further comprising the step of adjusting the distance at which said material leaves said first duct.

12. A method according to claim 10, wherein said material is directed substantially across the axial width of said rotor.

13. A method according to claim 10, further comprising the steps of causing heat from said air to be conducted to said material in said first duct to induce at least partial drying thereof.

14. A method according to claim 10, wherein said material is caused to leave said duct on the downrunning side of said rotor. 15. A method according to claim 10, wherein said material is directed across a width of approximately one-fourth to one-third of the diameter of said impact circle.

16. Apparatus according to claim 1, wherein said first inlet duct has a width of approximately one-fourth to one-third the diameter of said impact circle.

17. An improved apparatus for crushing and drying materials, such as moist coal, comprising:

a housing having an inlet opening located in the upper portion thereof and an outlet opening located in the lower portion thereof;

a rotor mounted for rotation in said housing, said rotor having impact members thereon for striking and crushing material falling through said inlet opening and passing through the impact circle defined by the outer extremities of said impact members;

a first inlet duct means entering said inlet opening and terminating a short distance above said impact circle, for causing said material to drop through said inlet opening above said impact circle to be struck by said impact members;

a second inlet duct means entering said inlet opening for conveying hot air into said housing without substantially interfering with said material until just prior to entry of said material into said impact circle; and

means located within said second inlet duct for selectively directing the flow path of hot air entering said housing without substantially affecting

material flow through said first inlet duct means. 18. Apparatus according to claim 17, further comprising at least one breaker plate mounted within said housing in position to be struck by material thrown by said impact members.

19. Apparatus according to claim 17, in which said first inlet duct means comprises a duct having a lower end terminating a short distance above said impact circle, and means for adjusting the clearance between said lower end and said impact circle.

20. Apparatus according to claim 17, wherein said first inlet duct means extends substantially across the axial width of said motor to direct material to be crushed to the axial width thereof.

21. Apparatus according to claim 17, wherein said first inlet duct means is concentrically located within said second inlet duct means.

22. Apparatus according to claim 18, wherein said rotor is reversible to crush material in either direction of rotation, further comprising at least one additional breaker plate mounted in said housing opposite to said at least one breaker plate. 23. Apparatus according to claim 17, wherein said first and second inlet ducts share a common wall through which heat from said air is conducted to said material to induce at least partial drying thereof. 24. Apparatus according to claim 17, wherein said first and second inlet duct means are located on the downrunning side of said rotor with said first inlet duct means located between the center of said rotor and said second inlet duct means.

25. Apparatus according to claim 21, wherein said first and second inlet duct means are centered above the center of said rotor.

26. Apparatus according to claim 21, wherein said means for directing the flow of hot air comprises first and second flapper valve means located on opposite sides of said first inlet duct means within said second inlet duct means, further comprising means for closing either one of said valve means as the other opens.

27. Apparatus according to claim 17, wherein said first inlet duct has a width of approximately one-fourth to one-third the diameter of said impact circle.

28. An improved apparatus for crushing and drying materials, such as moist coal, comprising:

a housing having an inlet opening located in the upper portion thereof and outlet opening located in the lower portion thereof;

a rotor mounted for rotation in said housing, said rotor having impact members thereon for striking and crushing material falling through said inlet opening and passing through the impact circle defined by the outer extremities of said impact members;

a first inlet duct means entering said inlet opening and having a lower end terminating a short distance above said impact circle, for causing said material to drop through said inlet opening above said impact circle to be struck by said impact members;

a second inlet duct means entering said inlet opening for conveying hot air into said housing without substantially interfering with said material until just prior to entry of said material into said impact circle; and

means for adjusting the clearance between said lower end and said impact circle.

29. Apparatus according to claim 28, wherein said first inlet duct means extends substantially across the axial width of said rotor to direct material to be crushed to the axial width thereof.

30. Apparatus according to claim 28, wherein said first inlet duct means is concentrically located within said second inlet duct means.

31. Apparatus according to claim 28, further comprising at least one breaker plate mounted in said housing in position to be struck by material thrown off by said impact members.

32. Apparatus according to claim 31, wherein said rotor is reversible to crush material in either direction of rotation, further comprising at least one additional breaker plate mounted within said housing opposite to said at least one breaker plate. 33. Apparatus according to claim 28, wherein said first and second inlet ducts share a common wall through which heat from said air is conducted to said material to induce at least partial drying thereof. 34. Apparatus according to claim 28, wherein said first and second inlet duct means are located on the downrunning side of said rotor with said first inlet duct means located between the center of said rotor and said second inlet duct means.

35. Apparatus according to claim 30, wherein said first and second inlet duct means are centered above the center of said rotor.

36. Apparatus according to claim 30, wherein said means for directing the flow of conveying hot air comprises first and second flapper valve means located on opposite sides of said first inlet duct means within said second inlet duct means, further comprising means for closing either one of said valve means as the other opens.

37. Apparatus according to claim 28, wherein said first inlet duct has a width of approximately one-fourth to one-third the diameter of said impact circle.

38. A method of crushing and drying moist materials, such as coal and other materials, comprising the steps of:

causing said material to drop through a first essentially vertically oriented duct;

causing said material to leave said duct at a short distance above the impact circle defined by the outer extremities of the impact members of a crushing machine having a housing, a rotor mounted for rotation on an axis in said housing and impact members mounted on said rotor for striking and crushing material falling through said impact circle;

passing a flow of hot air into said crushing machine in parallel with said material through at least one second duct spaced outboard of said first duct; and

selectively directing the path of said flow of hot air through said crushing machine.

39. A method according to claim 38, further comprising the step of adjusting the distance at which said material leaves said first duct.

40. A method according to claim 38, wherein said material is directed substantially across the axial width of said rotor.

41. A method according to claim 38, further comprising the step of causing heat from said air to be conducted to said material in said first duct to induce at least partial drying thereof.

42. A method according to claim 38, wherein said material is caused to leave said duct on the downrunning side of said rotor.

43. A method according to claim 38, wherein said material is directed across a width of approximately one-fourth to one-third the diameter of said impact circle.

44. A method of crushing and drying moist materials, such as coal and other materials, comprising the steps of:

causing said material to drop through a first essentially vertically oriented duct having a lower end;

causing said material to leave said duct at a short distance above the impact circle defined by the outer extremities of the impact members of a crushing machine having a housing, a rotor mounted for rotation on an axis in said housing and impact members mounted on said rotor for striking and crushing material falling through said impact circle;

passing a flow of hot air into said crushing machine in parallel with said material through at least one second duct spaced outboard of said first duct; and

adjusting the clearance between said lower end and said impact circle.

45. A method according to claim 44, wherein said material is directed substantially across the axial width of said rotor.

46. A method according to claim 44, further comprising the step of causing heat from said air to be conducted to said material in said first duct to induce at least partial drying thereof.

47. A method according to claim 44, wherein said material is caused to leave said duct on the downrunning side of said rotor. 48. A method according to claim 44, wherein said material is directed across a width of approximately one-fourth to one-third the diameter of said impact circle.