Abstract
A mineral liberation machine comprising vertical wet grinding mill (10) for grinding coarse material comprising a cylindrical housing (14) containing a rotatable shaft (15) creating an annular channel (17) with an input feed (16) for supplying coarse material and an output feed (18) for withdrawing ground product, in which the rotatable shaft (15) is equipped with a plurality of rotor discs (20) and the cylindrical housing (14) is equipped with one or more stators or stator discs (22), the discs (20, 22) on the rotatable shaft (15) and cylindrical housing (14) are interleaved such that the ratio of the height of the housing (14) to the diameter of the housing (14) is low with the diameter to height ratio being between 0.6-1.2.
Claims
1. A mineral liberation machine comprising a vertical wet grinding mill for grinding coarse material, wherein the vertical wet grinding mill comprises a cylindrical housing containing a rotatable shaft creating an annular channel with an input feed for supplying the coarse material and an output feed for withdrawing ground product, wherein the rotatable shaft is equipped with a plurality of rotor discs, and the cylindrical housing is equipped with one or more stator discs, wherein the plurality of rotor discs and the one or more stator discs are interleaved such that a ratio of a height of the cylindrical housing to a diameter of the cylindrical housing is low with the ratio being between 0.6-1.2.
2. The mineral liberation machine according to claim 1, wherein the rotatable shaft is equipped with a rotating drum, wherein the rotating drum holds the plurality of rotor discs.
3. The mineral liberation machine according to claim 2, wherein an inside of the cylindrical housing and an outside of the rotating drum or the rotatable shaft are equipped with vertical grooves.
4. The mineral liberation machine according to claim 1, wherein each of the plurality of rotor discs and the one or more stator discs have one or more blades.
5. The mineral liberation machine according to claim 4, wherein each of the one or more blades have a wedge shape or have triangular raised portions.
6. The mineral liberation machine according to claim 5, wherein an apex of each of the triangular raised portions points towards a centre of the mill.
7. The mineral liberation machine according to claim 5, wherein at a bottom of the mill the wedge shape of each of the one or more blades of the plurality of rotor discs and each of the one or more blades of the one or more stator discs have wedge angles of about 10-12.
8. The mineral liberation machine according to claim 5, wherein close to a top of the mill the wedge shape of each of the one or more blades of the plurality of rotor discs and each of the one or more blades of the one or more stator discs have wedge angles of 20-25.
9. The mineral liberation machine according to claim 4, wherein each of the one or more blades of the plurality of rotor discs including at least two blades, and each of the one or more blades of the one or more stator discs including at least two blades; wherein one or more gaps is formed between the respective at least two blades of each of the plurality of rotor discs and one or more gaps is formed between the respective at least two blades of the one or more stator discs.
10. The mineral liberation machine according to claim 9, wherein each blade of each of the plurality of rotor discs and of the one or more stator discs has a size defined by a horizontal cross-section of the respective blade and each of the gaps between the respective blades comprises 40% to 100% of the size of one of the blades.
11. The mineral liberation machine according to claim 4, wherein the one or more blades of the plurality of rotor discs and the one or more blades of the one or more stator discs cooperate when rotating to create gaps in the annular channel to allow the coarse material to pass through.
12. The mineral liberation machine according to claim 4, further comprising grinding media having a size and wherein the one or more blades of each of the plurality of rotor discs further comprises at least two blades, and the one or more blades of the one or more stator discs further comprises at least two blades of at least two stator blades; and wherein a vertical distance between the at least two blades of the plurality of the rotor discs or between the at least two blades of the at least two stator discs is 10 to 20 times the size of the grinding media and a height of a centre of the blades is 20% to 50% of the vertical distance.
13. The mineral liberation machine according to claim 4, wherein the one or more blades of the plurality of rotor discs and the one or more blades of the one or more stator discs increase in number from a bottom to a top of the mill.
14. The mineral liberation machine according to claim 1, wherein each of the plurality of rotor discs and the one or more stator discs is made from steel material.
15. The mineral liberation machine according to claim 1, wherein the cylindrical housing and the rotatable shaft are sized such that a width of each of the plurality of rotor discs is smaller than a width of each of the one or more stator discs.
16. The mineral liberation machine according to claim 1, wherein the rotatable shaft or a drum on the rotatable shaft forms an outermost inner boundary of the annular channel having a diameter of 0.5R to 0.7R wherein R is an inside diameter of the cylindrical housing.
17. The mineral liberation machine according to claim 16, wherein the diameter of the rotatable shaft or the drum that forms an outermost inner boundary of the annular channel is about 0.6R.
18. The mineral liberation machine according to claim 1, wherein the one or more stator discs further comprises at least two stator discs; and a closest free distance between one of the plurality of rotor discs and one of the at least two stator discs decreases step by step as each stator disc or rotor disc occupies a higher position within the mill.
19. The mineral liberation machine according to claim 18, wherein the closet free distance is reduced from 35 mm near a bottom of the mill to 15 mm close to a top of the mill.
20. The mineral liberation machine according to claim 1, wherein an active milling region is defined below a top one of the one or more stator discs and a top one of the plurality of rotor discs, respectively, to be filled with beads, and an upper region is defined in the mill above the respective top one of the one or more stator discs and the top one of the plurality of rotor discs to accept beads that pass upward through the mill.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Examples of wet grinding mills made in accordance with the present invention will now be discussed hereinbelow with reference to the accompanying drawings, in which:
(2) FIG. 1 shows a cross-sectional plan view of a grinding mill according to the present invention;
(3) FIG. 2 shows the schematic side view of stator and rotor blades according to the present invention in use;
(4) FIG. 3 shows a cross-sectional plan view of a previously proposed grinding mill alongside a similar view of a grinding mill according to the present invention;
(5) FIG. 4 shows a top view of a grinding mill according to the present invention;
(6) FIG. 5 shows a cross-sectional side view of a grinding mill according to the present invention;
(7) FIG. 6 shows a side perspective view of a stack of grinding discs according to the present invention;
(8) FIG. 7 shows a side cross-sectional view of stator and rotor blades according to the present invention;
(9) FIG. 8 shows top plan views of a grinding mill and a rotor blade according to the present invention;
(10) FIG. 9 shows a top plan view and a cross-sectional view of a stator disc according to the present invention;
(11) FIG. 10 shows a top plan view and a cross-sectional view of a rotor disc according to the present invention; and
(12) FIG. 11 shows a cross-sectional plan view of a modified grinding mill according to the present invention; and
(13) FIG. 12 shows a top view of a modified grinding mill according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(14) FIG. 1 shows a side sectional view of a wet grinding mill 10 according to the present invention. The grinding mill 10 comprises a cylindrical housing 14 containing a rotatable shaft 15. The rotatable shaft 15 is equipped with a drum 12. The rotatable shaft 15 is rotated by an external motor not shown. The rotating drum 12 is equipped with a number of rotor discs 20 in this case three. The cylindrical housing 14 is equipped with a number of stators or stator discs 22 in this case three. The discs 20, 22 are interleaved such that the discs 20, 22 next to each other overlap. The space between the rotating drum 12 and the cylindrical housing 14 comprises an annular channel 17. The cylindrical housing 14 is equipped at its bottom with an input channel 16 for supplying coarse material. The coarse material is slowly ground by the action of the rotors and stators 20, 22 as it rises in the annular channel 17. The input channel 16 is supplied by a pump means ensuring a set rate of flow of coarse material 24 into the cylindrical housing 14, when working, filling it to above the top stator or rotor disc 20, 22. The coarse material 24 is given rotational acceleration by the rotors 20 and is moved upwards through the annular channel 17 as more coarse material is added. The compression action between the discs 20, 22 and the gravitation pressure on the coarse material grind it during its pass through the annular channel 17. The ground fine material is withdrawn from the cylindrical housing 14 by output channel 18 on its side, which is above the top rotor or stator 20, 22. This is achieved by the rotational speed imparted to the material by the rotors 20.
(15) FIG. 2 shows diagrammatically the action of rotor and stator blades 20a, 22a, a number of which are attached to each rotor and stator disc 20, 22 when in use. FIG. 2 shows the same section moving from the right-hand side to the left hand side at three different times as the rotor blades 20a rotate. The cross section and shape of rotor and stator blades 20a, 22a vary around their circular discs 20, 22. In the section concerned it will be appreciated the stator blades 22a do not move and therefore their cross-section remains constant. As the varying shape of the rotor blades 20a passes the stator blades 22a the gap between them diminishes compacting the coarse material 24 imparting energy and angular acceleration thereto thus causing grinding to occur.
(16) FIG. 3 shows sections of two grinding mills side-by-side. FIG. 3a is a grinding mill according to the present invention and FIG. 3b is a previously proposed grinding mill. The internal layout of these two mills is substantially as described in FIG. 1. The principal difference is that the cylindrical drum 12 as shown in FIG. 3a is substantially larger in the present invention than the shaft 15 in the previously proposed grinding mill. This results in the horizontal cross-sectional size of the discs 20, 22 being smaller. Furthermore, the cylindrical space between the drum 12 and the annular channel 17 is small. This results in the speed of rotation of coarse material in the annular channel 17 space having less difference between the outside and the inside, with the speed close to the cylindrical housing 14 being 6 m/s and close to the drum 12 being 4 m/s. This leads to considerably more constant grinding action. In the previously proposed grinding mill shown in FIG. 3b the width between the drum 12 and the cylinder 14 is wide, with the result that the speed close to the drum 12 is 5 m/s, in the middle of the space is 10 m/s and on the outside is 20 m/s. This means that significant amounts of energy are used in accelerating the coarse material, rather than achieving grinding.
(17) FIG. 4 shows a view inside the grinding mill 10 looking from the top. This shows the drum or shaft 12 in the centre surrounded on the outside by the cylindrical housing 14. The hatched area in between comprises the grinding or milling zone. The top rotor disc 20 can be seen which comprises four rotor blades 20a, 20b, 20c and 20d below which can be seen the stator disc 22 similarly equipped with four blades 22a, 22b, 22c and 22d. In this instance the blades of the rotor disc 20 and the stator disc 22 effectively fill complete a full circular portion. As shown in the Figure the diameter of the inside of the cylindrical housing 14 comprises a distance R. The diameter of the drum or shaft 12 comprises a range of 0.5 to 0.7 R and preferably 0.6 R.
(18) FIG. 5 shows a sectional view of a modified grinding mill 10 according to the present invention. The rotatable shaft 15 is equipped with three discs 32, which fit directly onto the shaft 15. Between each of the discs 32 is a circular spacer 30 which spaces the discs 32 apart from each other and creates a structure similar to the drum 12 in FIG. 1. The top disc 32 and the bottom disc 32 create the top and bottom of the drum like structure. The distance between the edge of the circular spacers 30 and the edge of the cylindrical housing 14 creates a milling zone. In the case of this embodiment the outlet for the fine material is significantly above the top rotor disc 32. The ground material including the heavy beads here creates a pressure zone. Therefore, the coarse material in the milling zone is put under pressure thereby increasing the grinding effect.
(19) FIG. 6 shows a perspective view of a stack of three rotor discs 20 interleaved with three corresponding stator discs 22. Each rotor disc 20 comprises a central disc part, which joins onto the rotatable shaft 15 or drum 12, which is equipped with three equally spaced blades 20a, 20b, 20c on its outside. Similarly each stator disc 22 comprise a circular outer part, which joins onto the cylindrical housing 14, which is equipped with three equally spaced blades 22a, 22b, 22c on its inside. There is a space between each of the blades to enable coarse material to pass up the milling zone. The structure of each blade can be seen and is similar for both the stator and rotor blades, comprising wedges 40, 42 at front and back of each blade. The purpose of the wedges 40, 42 is to guide and compress the coarse material thus increasing the grinding effect.
(20) FIG. 7 shows a cross-section of the blades 20a, 22a similar to that shown in FIG. 2. The shape of the blades 20a, 22a described in FIG. 6 is clearly visible with the wedges 40, 42 front and back of the blades 20a, 22a. The Figure shows the front of the wedge 40 has an angle of 10 to 25 between the top and bottom surfaces. The distance X between each blade 20a, 20a or 22a, 22a in the stack is 10 to 25 times the diameter of the top beads size. The distance from top to bottom surface of the middle of a blade 20a, 22a is 20 to 50% X.
(21) FIG. 8 shows on the left a section through the grinding mill 10. This shows the inside edge of the cylindrical housing 14 and the outside edge of the drum 12. The space between these two comprises the annular channel 17, which is the milling zone or room. The diameter of the inside of the cylindrical housing 14 is R and the size of the outside of the drum 12 is 0.5 to 0.70 R. On the eft hand side is shown a rotor disc 20. The disc 20 is equipped with four blades 20a, 20b, 20c, 20d. The angular space taken up by each blade comprises X. The distance between each blade 20a, 20b, 20c, 20d is 40 to 100% of X.
(22) FIG. 9 shows a top view of a stator disc 50. The stator disc 50 has a circular space in its centre through which would pass the rotating shaft 15 holding the drum 12. The stator disc 50 has an outside circular part 51 which attaches to the inside of the cylindrical housing 14 and is equipped with three identical blades 53. Each blade 53 has a centre section 54 with a cross-section that matches the circular disc 51 and two wedges 52 on either side. The centre section 54 comprises a triangle with the apex pointing towards the centre axis 62 of the stator disc 50. If a section A-A is examined it can be seen that the edge of the wedge has bisects an angle of 16. Each blade takes up 100 of the circumference of the axis 62 with the spaces 56 comprising 20 each.
(23) FIG. 10 shows a top view of a rotor disc. The rotor disc has through it a rotating shaft 70 surrounded by a part drum 72. The drum part 72 is equipped with three identical blades 74. Each blade 74 has a centre section 78 with a cross-section that matches the circular disc 72 and two wedges 72 on either side. The centre section 74 comprises a triangle with the apex pointing inwards towards the axis of the rotatable shaft 70. If a section A-A is examined it can be seen that the edge of the wedge has bisects an angle of 20. Each blade 74 has edges parallel to the edges of the next blade 74. The edges of the blades 74 are also parallel to the sides of the triangle that forms the centre section 78.
(24) FIG. 11 shows a side sectional view of a modified wet grinding mill 110 according to the present invention. The grinding mill 110 comprises a cylindrical housing 114 containing a rotatable shaft 115. The rotatable shaft 115 is equipped with a drum 112. The rotatable shaft 115 is rotated by an external motor not shown from above. The rotating drum 112 is equipped with eight rotor discs 120. The cylindrical housing 114 is equipped with seven stators or stator discs 122. The discs 120, 122 are interleaved such that the discs 120, 122 next to each other overlap. The space between the rotating drum 112 and the cylindrical housing 114 comprises an annular channel 117. The cylindrical housing 114 is equipped at its bottom with an input channel 116 for supplying coarse material. The input channel 116 is surrounded by an annular slope 119 at the bottom of the cylindrical housing 114, which in conjunction with the bottom of the drum 112 directs the course material into the annular channel 117 and the discs 120, 122. The coarse material is slowly ground by the action of the rotors and stators 120, 122 as it rises in the annular channel 117. As the coarse material rises up the annular channel 117 the size of the beads is reduced by the grinding action. This leads to the ratio of the bead size to the gap between the discs 120, 122 increasing. Thus compression action between the discs 120, 122 and the gravitation pressure on the coarse material grinding it during its passage through the annular channel 117 decreases towards the top of the grinding mill 110. Therefore in this embodiment the distance between each stator and rotor disc 120, 122 is decreased as the top of the mill is reached. Therefore in this embodiment starting at the bottom the gap distances are 55 mm, 55 mm, 50 mm, 50 mm, 45 mm, 45 mm, 40 mm, 40 mm, 35 mm, 35 mm, 30 mm, 30 mm, 25 mm and 25 mm. This leads to a more even grinding effect as the coarse material rises up the mill 110.
(25) FIG. 12 shows a view inside a modified grinding mill 210 looking from the top. This shows a shaft 112 equipped with a drum 212 in the centre surrounded on the outside by a cylindrical housing 214. The inside of the cylindrical housing 214 and the outside of the drum 212 both have vertical grooves 216. When the coarse material is passing up the mill 210 the beads 218 fit into the groove reducing the wear on the beards 218.
