CEMENT GRINDING MEDIA SORTER AND OPERATING METHOD THEREOF

Technical field

[0001] The present disclosure relates to a cement grinding media sorter and its operating method, wherein the grinding media are alloy steel balls. In detail, the cement grinding ball sorter aims sorting cement grinding balls according to their size, and separates scrap and dust from the grinding media load.

Background Art

[0002] In brief, a cement ball mill is a horizontal cylinder partly filled with alloy steel balls that rotates on its axis, imparting a tumbling and cascading action on the balls. The cement-derived materials are fed through the mill, and afterwards are crushed and milled by the impact/friction between the balls. The grinding media is usually made of steel (e.g. high-chromium steel) or, alternatively, ceramic. Different-sized media are used to ensure an efficient and appropriate grinding of the materials, therefore, is very important to ensure an appropriate mix of different-sized balls. As the grinding media deteriorates with usage, it is necessary to periodically remove the grinding balls, sort them according to their size and condition, and replenish any specific size of grinding balls that is lacking in order to restore the most appropriate mix of different-sized balls.

[0003] Document SU1200976A1 describes a sorter for cement grinding media. Further in detail, a cement grinding ball that sorts cement grinding balls according to their size. The prior art sorter of SU1200976A1 (see figs. 2-4) uses longitudinal partitions/slots and protrusions (3) of varying sizes that create longitudinal gaps with the desired sorting sizes for separating the grinding balls. [0004] The disclosure of SU1200976A1 has the disadvantage of having mixed non- spherical elements interfering with the sorting operation and has a lower sorting precision because the referred slots, not being circular, are prone to misclassification of any grinding media that is not perfectly spherical. For example, a non-spherical grinding ball having a major diameter of 62 mm and a minor diameter of 54 mm may be misclassified by a 55mm slot as being below 55 mm, whereas the larger diameter (62 mm) shows that the grinding ball clearly belongs to the class above 55 mm.

General Description

[0005] It is described a cement grinding media sorter for sorting cement grinding balls according to their size, and for separating scrap and dust, comprising:

a cylindrical surface that rotates on its longitudinal axis and is opened at its two ends; the first end of the cylinder is the inlet for the grinding media and the second end is the outlet for the grinding media;

a motor, or motors, coupled to the cylindrical surface to ensure its rotation movement; wherein the cylindrical surface has consecutive cylindrical segments, and each segment has a plurality of apertures; the apertures of each segment are larger than the largest aperture of the previous segment towards the outlet direction.

[0006] It has been established that a cylindrical surface allows for easier movement of the media along the media sorter and is more robust. Nevertheless, a conical surface could be used alternatively of any of the cylindrical surfaces disclosed in the present document.

[0007] An embodiment, in addition to said cylindrical surface, comprises:

a second cylindrical surface that rotates on its longitudinal axis and is opened at its two ends; the first end of the cylinder is the inlet for the grinding media and the second end is the outlet for the grinding media, wherein the second cylindrical surface has consecutive cylindrical segments, and each segment has a plurality of apertures; the apertures of each segment are larger than the largest aperture of the previous segment towards the outlet direction; a motor, or motors, coupled to the second cylindrical surface to ensure its rotation movement;

a size threshold separator for receiving the grinding media to be sorted and for separating the grinding media into above, or below, a predetermined size threshold; it has its larger size output connected to the inlet of the first cylindrical surface and its smaller size output connected to the inlet of the second cylindrical surface.

[0008] It has been established that by pre-separating the media, a more compact construction can be obtained and each of the subsequent sorters can be constructed more robustly and with less cost having a much reduced range of media size to handle.

[0009] In an embodiment, the apertures of the first segment of the first cylindrical surface are larger than the predetermined size threshold, and the apertures of the last segment of the second cylindrical surface are smaller than the predetermined size threshold. This enables a more efficient setup.

[0010] In an embodiment, the size threshold separator is the first segment of the first cylindrical surface; the apertures of the first segment of the first cylindrical surface have the size of the predetermined size threshold, and the apertures of the second segment of the first cylindrical surface are larger than the predetermined size threshold, plus, the apertures of the last segment of the second cylindrical surface are smaller than the predetermined size threshold. This enhances the efficiency of the setup.

[0011] In an embodiment, the motor, or motors, coupled to the second cylindrical surface and the motor, or motors, coupled to the first cylindrical surface are the same motor or motors.

[0012] In an embodiment, the apertures are circular, facilitating the accurate separation of the grinding media (which is normally circular).

[0013] In an embodiment, the apertures are circular except for the apertures of one, and only one, segment of any such cylindrical surface, which are oblong, in particular this segment being the first inlet segment of said cylindrical surface. This facilitates a faster separation when some debris may be present in the grinding media to be separated.

[0014] In an embodiment, all the apertures of each segment have the same size.

[0015] In an embodiment, the cylindrical surface comprises fins or ribs on the inside of the cylindrical surface for moving the grinding media from the inlet towards the outlet. In an embodiment, said fins or ribs are helical. Alternatively, said fins or ribs are partly helical and partly peripherical.

[0016] In an embodiment, the apertures are offset in respect of the immediate neighbour apertures and, in particular, are offset in respect of the inlet-outlet direction. This enables more apertures for the same separator surface area.

[0017] An embodiment comprises discharge chutes for the sorted grinding balls in the shape of a funnel, and each chute is located below one of the cylindrical segments.

[0018] In an embodiment, the two ends of the cylindrical surface are flat and circular.

[0019] An embodiment comprises a non-spherical media separator at the grinding media inlet. This allows a much more efficient separation of the grinding media, because the separators are not hindered by the non-spherical material present with the grinding media. Furthermore, when combined with circular apertures at the separators, it is even more important to remove non-spherical material, as the circular apertures are more susceptible to non-spherical elements.

[0020] In an embodiment, the non-spherical media separator comprises:

a substantially flat surface arranged to be movable horizontally and for receiving on its top the grinding media to be separated;

a motor, or motors, arranged for moving horizontally the flat surface in a reciprocating fashion such that movement in a first reciprocating direction is substantially faster than in the second inverse reciprocating direction.

[0021] In an embodiment, the flat surface is horizontal or has a slight tilt for promoting the movement of the grinding balls across the surface; in particular the tilt angle is adjustable. [0022] These are configurations that enable a more efficient separation of non- spherical media.

[0023] An embodiment comprises a discharge chute for the separated non-spherical media in the shape of a funnel, and is located below the flat surface.

[0024] An embodiment comprises a separator of scrap and dust at the grinding media inlet. This allows a much more efficient separation of the grinding media, because the separators are not hindered by the scrap or dust material present with the grinding media. Furthermore, when combined with circular apertures at the separators, it is even more important to remove scrap or dust material, as the circular apertures are more susceptible to non-spherical elements.

[0025] In particular the separator of scrap and dust can be located before the non- spherical media separator, if present. Alternatively, the separator of scrap and dust can be located after the non-spherical media separator, if present.

[0026] In an embodiment, the separator of scrap and dust comprises:

a cylindrical surface that rotates on its longitudinal axis and is opened at its two ends; the first end of the cylinder is the inlet for the separator of scrap and dust and the second end is the outlet for the separator of scrap and dust;

a motor, or motors, coupled to the cylindrical surface to ensure its rotation movement; wherein the cylindrical surface has a plurality of apertures; the size of the apertures is large enough such that the dust and scrap material falls through the apertures, however, the size of the apertures is small enough such that the grinding media follows through to the outlet of the separator of scrap and dust.

[0027] In an embodiment, the cylindrical surface of the separator of scrap and dust has two consecutive cylindrical segments; the apertures of each segment are oblong, wherein the apertures of the first segment are at an angle with the apertures of the second stage, in particular, at the angle of 90°.

[0028] In an embodiment, the cylindrical surface of the separator of scrap and dust has two consecutive cylindrical segments; the apertures of one of the segments are oblong and the apertures of the other segment are circular. [0029] These are configurations that enable a more efficient separation of scrap and dust media.

[0030] The oblong apertures mentioned in this document can be stadium-shaped or ellipse-shaped. In an embodiment, the cylindrical surface of the separator of scrap and dust comprises fins or ribs in the inside of the cylindrical surface for moving the grinding media from the inlet towards the outlet. In an embodiment, said fins or ribs are helical. Alternatively, said fins or ribs are partly helical and partly peripherical.

[0031] In an embodiment, the apertures of the cylindrical surface of the separator of scrap and dust are offset in respect to the immediate neighbour apertures and, in particular, are offset in respect to the inlet-outlet direction.

[0032] An embodiment comprises a discharge chute for the separated dust and scrap material in the shape of a funnel; the funnel is located below the cylindrical surface of the separator of scrap and dust.

[0033] In an embodiment, the two ends of the cylindrical surface of the separator of scrap and dust are flat and circular.

[0034] It is also disclosed a method of operating the cement grinding media sorter of the described embodiments, comprising the following steps:

loading the grinding media to be sorted;

separating scrap and dust from the grinding media;

separating non-spherical or asymmetrical elements from the grinding media;

separating the grinding media whether above or below a predetermined size threshold into a larger-size grinding media and a smaller-size grinding media;

sorting the larger-size grinding media by size ranges;

sorting the smaller-size grinding media by size ranges.

[0035] The method can be carried out in successive fashion by re-feeding the previously separated material should any of the separated material have a significant part of wrongly sorted elements. The terms sorter and separator are used interchangeably. Brief Description of the Drawings

[0036] The following figures provide preferred embodiments to illustrate the description and should not be seen as limiting the scope of the disclosure.

[0037] Figure 1: Schematic representation of an embodiment of the cement grinding media sorter.

[0038] Figure 2: Schematic representation of the loading hopper and the scrap/dust separation stage of an embodiment of the cement grinding media sorter.

[0039] Figure 3: Schematic representation of the mid-size threshold separation and larger-size separation stages of an embodiment of the cement grinding media sorter.

[0040] Figure 4: Schematic representation of the smaller-size separation stages of an embodiment of the cement grinding media sorter.

[0041] Figure 5: Schematic representation of the asymmetrical or aspherical scrap separation stage of an embodiment of the cement grinding media sorter.

[0042] Figure 6: Schematic representation of size separation stages of an embodiment of the cement grinding media sorter.

[0043] Figure 7: Schematic representation of the operating method of an embodiment of the cement grinding media sorter.

[0044] Figure 8: Schematic representation of an embodiment of the cement grinding media sorter incorporated in a container, in particular, in a truck container, with a loading hopper at the back of the truck (not shown).

[0045] Figure 9: Schematic representation of the dust and smaller particle separation stage of an embodiment of the cement grinding media sorter.

Detailed Description

[0046] Figure 1 shows an embodiment of the cement grinding media sorter. A loading hopper 1 receives the shovelled grinding media, which has been dumped from the grinding mill. A bucket conveyor 2 picks up the grinding balls from the loading hopper 1 and feeds these into a scrap/dust separator 3. Then the balls are fed into a non- spherical (or asymmetrical) separator 4. After the non-spherical material (e.g. deformed grinding ball) has been removed, the grinding material is fed into a mid-size threshold separator 5 that separates the grinding media into two large classes of diameters: above or below a certain threshold. The larger grinding media goes into a larger size separator 6 while the smaller-size grinding media 7 goes into a smaller size separator. The grinding balls go through each stage of the separators, which sort the grinding media according to the size at each stage. The sorted balls fall into different ball discharge chutes according to the sorted size of the grinding media.

[0047] This has the advantage that the layout is eminently linear enabling a compact construction, which can be placed, for example, in a standard transport container.

[0048] This also has the advantage that the device is transportable.

[0049] This device has the advantage that it is able to process a load of mill balls in a single batch. This device has the further advantage that 80-95 % of sorting balls can be re-used immediately.

[0050] Another advantage is that the present device allows efficient sorting of smaller diameter balls by having the dust/scrap removed.

[0051] Also, by having a mid-size threshold separator and by having two separators of grinding media for two distinct range sizes, each separator can be much more efficient, not having to process such a wide range of sizes as the initial range.

[0052] According to an embodiment, each separator comprises a rotatable cylindrical surface with apertures distributed along its cylindrical face, the separator inlet for the grinding balls is one of the circular faces of the cylinder and the separator outlet is the other circular face of the cylinder. The cylindrical surface may preferably be metallic. An electric engine, or other mean, is provided to ensure the rotation of the cylindrical surface while grinding balls are fed to the separator inlet. [0053] Once the cylindrical surface is normally arranged horizontally when in operation, the flow of material to be separated is ensured by the rotation, and the consequent interaction that the surface causes to the material - tumbling and cascading - and not by having an inclination at the sorting surface. This enables an improved separation since an inclined surface would move the material too quickly along the sorter.

[0054] Figure 2 shows the initial part of an embodiment of the cement grinding media sorter; in particular, shows the scrap/dust separator 3 and the non-spherical separator 4.

[0055] According to an embodiment, the scrap/dust separator comprises a rotatable cylindrical surface with apertures distributed a long its cylindrical face, the separator inlet for the grinding balls at one of the top faces of the cylinder and the separator outlet at the other top face of the cylinder. The cylindrical surface may preferably be metallic. An electric engine, or other means, is provided to ensure the rotation of the cylindrical surface while the grinding balls are fed to the separator inlet.

[0056] The apertures are small enough in order to transport all the grinding media to the next stage, but at the same time the apertures are as large as possible in order to remove the small scrap and dust from the grinding media.

[0057] The embodiment has the overall advantage that an improved separation of dust and scrap is achieved, with less scrap/dust remaining in the grinding media.

[0058] It has been observed that removing scrap/dust more effectively before the sorting of the grinding balls, turns the sorting into a more precise and efficient process, since any leftover scrap/dust interferes with the sorting as will be discussed further below.

[0059] In particular, the scrap/dust separator 3 has a first stage 31 and a second stage 32. The separator stages of the scrap/dust separator can have circular and oblong (e.g. elliptical) apertures, respectively; or can have two stages with oblong (e.g. elliptical) apertures, wherein the refereed apertures of the first stage are positioned with a certain angle to the apertures of the second stage, in particular a square angle. [0060] Oblong apertures have been found to be particularly suited for separating small oddly-shaped scrap materials and, in general, small non-spherical materials. The oblong apertures of the first stage 31 and of the second stage 32 are preferably arranged parallel within each stage and arranged at a square angle in respect to the apertures of the other stage.

[0061] The different angles, and especially when at 90°, have been found out to be the most particularly suited for ensuring an improved separation of scrap materials and smaller non-spherical materials.

[0062] The cylindrical surface may comprise helical ribs or fins arranged on the inside of the cylindrical surface in order to move the material from the inlet to outlet of the separator.

[0063] The apertures are preferably offset {'dicalis') in respect to the immediate neighbour apertures. The immediate neighbours of an aperture are those apertures immediately next to it.

[0064] The non-spherical separator 4 separates grinding media that is deformed (e.g. asymmetrical), and removes these from the grinding media flow.

[0065] It has also been observed that by removing non-spherical or asymmetrical balls before the sorting of the grinding balls turns the sorting into more precise and efficient, since any leftover non-spherical or asymmetrical ball interferes with the ball sorting as will be seen further below.

[0066] Figure 3 shows the mid-size threshold separator 5 that separates the grinding media into two large classes of diameters: above or below a certain threshold. The larger grinding media goes into a larger size separator 6 while the smaller-size grinding media goes into a smaller size separator 7.

[0067] Preferably, the mid-size threshold separator 5 is the first stage of the larger size separator 6 once this has the advantage of providing a more compact construction.

[0068] Having two separators working simultaneously in parallel allows a faster operation. Moreover, having the grinding media separated into two size classes one does not allow interference between very different sized balls in the same separator, besides, the sorting is more efficient because the movements are less chaotic and somewhat more ordered. Furthermore, two cylindrical separators are more easily arranged in a linear fashion what makes the whole equipment to be more suitable for a transport container.

[0069] The larger size separator 6 has a plurality of separating stages for different ranges of ball diameter. The grinding balls are separated and sorted according to the diameter as each stage has a different discharge chute for the balls 61. At the end of the separator the larger grinding balls are dumped to a discharge chute 62.

[0070] Figure 4 shows the smaller size separator 7 of an embodiment. The smaller size separator 7 has a plurality of separating stages 71 for different ranges of ball diameter. The grinding balls are separated and sorted according to the diameter as each stage has a different discharge chute for the balls 72. At the end of the separator the smaller-size grinding balls are dumped to a discharge chute 73.

[0071] Figure 5 shows the non-spherical separator of an embodiment. The non- spherical separator comprises a substantially horizontal and flat surface which is able to be moved horizontally in a reciprocating fashion. In particular, the non-spherical separator is arranged such that the movement in a first reciprocating direction is substantially faster than in the second reciprocating and inverse direction. This reciprocating movement causes different motions to the grinding balls whether these are spherical or not. If the reciprocating movement is asymmetrical, this effect is enhanced. Preferably the surface may be slightly tilted in order to promote the movement of the grinding balls across the surface. If one adjusts the tilting direction of the surface, the separation of the non-spherical balls can be fine-tuned such that non- spherical balls are removed at one end-region of the surface and the spherical balls continue to the next stage.

[0072] Figure 6 shows a view of a ball separator (or sorter) according to an embodiment of the disclosure. This separator can be used for both the larger size separator 6 and the smaller size separator 7, by means of adapting the required sorting sizes.

[0073] According to an embodiment, the grinding ball separator 80 comprises a rotatable cylindrical surface with apertures 81 distributed along its cylindrical face.

[0074] The separator inlet 84 for the grinding balls is at one circular face of the cylinder and the separator outlet 85 is at the other circular face of the cylinder. The cylindrical surface may preferably be metallic. An electric engine, or other means, is provided to ensure the rotation of the cylindrical surface while grinding balls are fed to the separator inlet 84.

[0075] The cylindrical surface comprises helical ribs or fins 82, preferably helical fins, arranged on the inner side of the cylindrical surface in order to move the material from the inlet 84 towards the outlet 85 of the separator 80. The apertures 81 are preferably offset {'dicalis') in respect to the immediate neighbour apertures, in particular in respect to the inlet/outlet direction.

[0076] The apertures 81 at each stage are small enough that grinding media is able to go through to the separator outlet, but dust and scrap material smaller than the aperture falls through the apertures to a ball chute 83.

[0077] For each separator, the apertures 81 of each stage 81a, 81b, 81c and 81d are progressively larger as the grinding balls follows from the inlet to the outlet. As intentional consequence, the balls exiting through the ball chutes 83 are gradually larger at each chute 83a, 83b, 83c and 83d.

[0078] Preferably, the apertures 81 within each stage 81a, 81b, 81c and 81d have all the same size.

[0079] If the apertures are circular, the size of an aperture is defined as its diameter. If the apertures are not circular, the size of an aperture is defined as the diameter of the largest sphere that is able to go through the aperture.

[0080] The separator stages have apertures 81 that are preferably circular apertures. It has been found that other shapes (e.g. oblong shapes) are less precise in separating and sorting the grinding media, even if they may operate faster than circular apertures. This precision is further improved if scrap and/or non-spherical grinding media have been removed beforehand. Irregular materials cause difficulties in sorting the grinding balls as they interfere with the circular apertures. Thus, removing such materials before the sorting is advantageous.

[0081] An example of sizes of the apertures is given below in Table 1 for a grinding media separator such as in Fig. 6.

Table 1

[0082] One can see how the 4-stage separator is able to separate, and sort, the grinding media according to the diameter in 5 classes (<55; 55-65; 65-75; 75-85; >85 mm).

[0083] One can also verify how the output of the first stage can be related or compared to a small size separator that separates the grinding balls below 55 mm. Such separator works as the separator that has just been described as well.

[0084] An example of sizes of the apertures is given below in Table 2 for two grinding media separators such as in Fig. 6, one for larger sizes and the other for small sizes, wherein the output of the first stage of the first separator (larger size separator) is the feeding inlet for the second separator (smaller size separator):

Table 2

[0085] It can be seen how the larger size separator is able to separate, and sort, the grinding media according to the diameter in 5 classes (<55; 55-65; 65-75; 75-85; >85 mm). The smaller class is fed into the smaller size separator, which then sorts the grinding media according to the diameter in 5 classes (<15; 15-25; 25-35; 35-45; 45-55 mm). [0086] In conclusion, the two 4-stage separators are then able to fully separate and sort the grinding media according to the diameter in 9 classes (<15; 15-25; 25-35; 35- 45; 45-55; 55-65; 65-75; 75-85; >85 mm).

[0087] It is possible to "cascade" more separators like this, but it was found out that the benefit of a possible improved precision through the increase of the number stages is damaged with a less compact construction, making the assembly less transportable.

[0088] Figure 7 shows the grinding media flow of an embodiment of the cement grinding media sorter. The grinding media, which has been dumped before from the grinding mill, is loaded onto a loading hopper. The grinding balls are fed into a scrap/dust separator that removes dust and small scraps. The grinding balls are then taken into a non-spherical (or asymmetrical) separator which removes the non- spherical grinding media. After the non-spherical material (e.g. a deformed grinding ball) has been removed, the grinding material is fed into a mid-size threshold separator that separates the grinding media into two classes of diameters: above or below a certain threshold. The larger grinding media follows into a larger size separator while the smaller size grinding media follows into a smaller size separator. The grinding balls go through each stage of the separators, which sort the balls according to their size at each stage. The sorted balls fall into different discharge chutes according to their size.

[0089] Figure 8 shows a schematic representation of an embodiment of the cement grinding media sorter incorporated in a container, in this particular case, a truck container with a loading hopper at the back of the truck (not shown). The grinding ball chutes are placed in the lateral side of the container, according to the sorted sizes.

[0090] Figure 9 shows a view of the scrap/dust separator 90 according to an embodiment of the disclosure. According to an embodiment, the scrap/dust separator comprises a rotatable cylindrical surface with apertures 91 distributed along its cylindrical face, the separator inlet 94 for the grinding balls at one of the circular faces of the cylinder and the separator outlet 95 at the other circular face of the cylinder. The cylindrical surface may preferably be metallic. An electric engine, or other mean, is provided to ensure the rotation of the cylindrical surface while grinding balls are fed to the separator inlet.

[0091] The apertures are small enough in order to allow the passage of the grinding media towards the separator outlet, however, the apertures are as large as possible in order to remove the small scraps and dust from the grinding media. A chute 93 is provided for funnelling the removed scrap and dust.

[0092] The separator stages can have circular and oblong (e.g. elliptical) apertures, respectively; or can have two stages with oblong (e.g. elliptical) apertures, wherein the refereed apertures of the first stage are positioned with a certain angle to the apertures of the second stage, in particular a square angle.

[0093] In particular, the scrap/dust separator 90 may have a first stage and a second stage. The apertures 91a of the first stage and the apertures 91b of the second stage are preferably arranged parallel within each stage and arranged in a square angle in respect to the apertures of the other stage.

[0094] This embodiment has the advantage of supplying an improved separation of dust and scrap, which promotes less remaining scrap/dust in the grinding media flow.

[0095] It has also been observed that removing scrap/dust more effectively before the sorting of the grinding balls turns the sorting into a more precise and efficient process, since any leftover scrap/dust interferes with the sorting as will be discussed further below.

[0096] The cylindrical surface may comprise helical fins arranged on the inside cylindrical surface in order to move the material from the inlet to outlet of the separator.

[0097] The apertures are preferably offset {'dicalis') in respect to the immediate neighbour apertures, in particular in respect to the inlet/outlet direction.

[0098] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0099] It will be appreciated by those of ordinary skill in the art, unless otherwise is indicated herein, and the particular sequence of the described points is only illustrative and can be varied without departing from the disclosure. Thus, the described steps have an unordered meaning and, when is possible, the steps can be performed in any convenient or desirable order, unless otherwise indicated. The disclosure should not be seen in any way restricted to the described embodiments, and a person with ordinary skill in the art will foresee many possibilities of modifications thereof. The above described embodiments are combinable. Further, the following claims point out particular embodiments of the disclosure.