High-pressure grinding roller with radar monitoring function

Abstract

The invention relates to a high pressure grinding roller (HPGR) machine. These machines have rollers provided with columns. In order to monitor the condition of the column during operation of such a machine to detect wear of the column, fracture of the column, absence of the column, and / or breakage of the column, a radar system (44a) is provided on the linear drive (46a). The radar system (44a) is arranged to transmit a radar beam onto an outermost surface of the roller (14) and to generate a radar system output indicative of a distance between the radar system and the outermost surface of the roller. The HPGR machine also includes a monitoring system including a processing device connected to the radar system and configured to analyze the radar system output and determine a condition of the outermost surface of the roller.

Description

Technical Field

[0001] The present disclosure relates to a high-pressure grinding roll for radar monitoring with rolls. Background Art

[0002] High pressure grinding rolls (HPGR) are used in the mining and mineral processing industries to crush rocks and minerals. HPGR uses two parallel cylinders (rolls) that are spaced apart to form a gap between their outer surfaces. When the cylinders rotate in opposite directions, the material to be ground or crushed is fed into the gap. The material in the gap is crushed by the pressure between the two rolls.

[0003] In some designs of HPGR, a plurality of studs are formed on the outer surface of one or both rolls. These studs are typically made of a material harder than the cylinder. The studs help grind the rock. The studs also help form an autogenous layer of grinding material that adheres to the surface of the cylinder between the studs. This autogenous layer can protect the surface of the cylinder from wear. If a stud breaks from its mounting position on the cylinder, it can cause substantial damage to the surface of the cylinder due to its hardness. It is desirable to monitor the condition of the studs during the operation of the HPGR to detect wear of the studs, breakage of the studs, missing studs, and / or fracture of the studs. Summary of the Invention

[0004] The invention is further defined herein below. Preferred additional embodiments are listed herein.

[0005] Thus, a high-pressure grinding roll (HPGR) machine for grinding materials, as claimed and described herein, includes a first roll and a second roll, each roll having a longitudinal axis of rotation and a cylindrical outer surface. The first roll and the second roll are arranged such that their longitudinal axes are parallel and such that a gap is formed between the outer surfaces of the rolls. The high-pressure grinding roll (HPGR) machine further includes a plurality of first studs. The plurality of first studs are mounted on the outer surface of the first roll and extend radially outward from the outer surface of the first roll. A first radar system is also provided, the first radar system being arranged to emit a radar beam onto the outermost surface of the first roll and to produce a first radar system output that indicates the distance between the radar system and the outermost surface of the first roll. The outermost surface of the first roll includes one or more of the following: the outer surface of the first roll, the plurality of studs, and an autogenous layer of crushed material that adheres to the outer surface of the roll. The HPGR machine further includes a monitoring system that includes a processing device that is connected to the radar system and is configured to analyze the first radar system output and determine the condition of the outermost surface of the first roll.

[0006] In the HPGR machine, the first radar system is preferably a synthetic-aperture radar.

[0007] According to the claimed HPGR machine, the radar system can be mounted on a linear drive, which is arranged to move the radar system along an axis parallel to the longitudinal axis of rotation of the first roll. The range of movement preferably allows the first radar system to scan the entire axial length of the first roll. Even more preferably, the monitoring system is configured to use the position information from the linear drive in the process of determining the condition of the outermost surface of the first roll.

[0008] In an arrangement with a linear drive or in another arrangement allowing the capture of the entire axial length of the first roll, the HPGR machine can also include a first speed sensor for determining the rotational speed of the first roll. The first speed sensor will then be communicatively connected to the monitoring system. If the monitoring system is configured to use the speed data from the first speed sensor to calibrate the data received from the first radar system and from the linear drive, a height map of the outermost surface of the roll can be formed.

[0009] According to the claimed HPGR machine, the processing device is configured to have a first operating mode and a second operating mode.

[0010] The first operating mode is preferably a continuous scanning mode, in which the current distance measured between the first radar system and a given position on the outermost surface of the roll is compared with the previously measured distance between the first radar system and the given position during a previous rotation of the roll. Even more preferably, the monitoring system is configured to output an alarm when the current distance differs from the previously measured distance by more than a predetermined amount, the alarm indicating the position on the roll corresponding to the given position. The predetermined amount can be about 2 mm, but can be greater or less than 2 mm.

[0011] The second operating mode is preferably a wear measurement mode performed when the roll is rotating and there is no grinding material in the gap. Then, even more preferably, the processing device is first configured to identify the distance from the first radar system to each of a plurality of posts and determine the height of each post above the outer surface of the roll with an accuracy greater than 0.5 mm, and secondly to compare the determined height of each post with the expected height obtained from a post in a new condition. This allows the wear condition of each post to be calculated based on the difference between the determined height and the expected height. Still more preferably, the processing device is then configured to identify a set of worn posts and output the position of each post in the set of worn posts on the outer surface of the roll. In the context of the present disclosure, a worn post is understood to be a post with a wear condition below a predetermined threshold.

[0012] The HPGR machine claimed and described herein may also include a second radar system arranged to monitor a plurality of second posts on the outer surface of the second roll. If so, the second radar system will preferably be configured to produce a second radar system output to the monitoring system. The second radar system output may indicate, for example, the distance between the second radar system and the outermost surface of the second roll.

[0013] The HPGR machine claimed and described herein may also include a housing and a skew control mechanism to hold the rolls at a desired distance, preferably also maintaining the distance and angle relative to each other.

[0014] The skew mechanism will act on at least one longitudinal axis of the roll, preferably on one longitudinal axis of the roll. In this preferred embodiment, the first roll is fixed relative to the housing and the second roll is movable relative to the housing such that the size of the gap between the surfaces of the rolls is variable. Then, the second roll is operatively connected to the skew control mechanism and the skew control mechanism will be configured to control the movement of the longitudinal axis of the second roll, thereby controlling the size of the gap. Alternatively, the longitudinal axis of the second roll may be fixed relative to the housing and the longitudinal axis of the first roll may be movable relative to the housing such that the size of the gap is variable. Then, the first roll will be operatively connected to the skew control mechanism and the skew control mechanism will be configured to control the movement of the longitudinal axis of the first roll, thereby controlling the size of the gap. In either of these alternatives, the skew control mechanism may also be configured to keep the longitudinal axes of the rolls parallel to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 An HPRG machine is shown;

[0016] Figure 2 A perspective view of two rolls of an HPGR machine is shown;

[0017] Figure 3 A perspective view of two rolls within an HPGR machine is shown;

[0018] Figure 4 A cross-section of two rolls is shown;

[0019] Figure 5 and Figure 6 each depicts one roll;

[0020] Figure 7 A monitoring system for monitoring the rolls is shown;

[0021] Figure 8 and Figure 9 A radar system and a linear drive for monitoring the rolls are shown;

[0022] Figure 10 Depicts a linear drive and a linear drive controller;

[0023] Figure 11 Shows a radar unit;

[0024] Figures 12 - 14 Shows a radar system, each radar system including two radar units;

[0025] Figure 15 Shows a linear drive;

[0026] Figure 16 Is a height map of the outermost surface of the roll measured using the radar system;

[0027] Figure 17A Shows a part of the roll with posts and some self - generating layers;

[0028] Figure 17B Is determined by Figure 17A The radar data of the roll part shown in;

[0029] Figure 18A Depicts a worn post;

[0030] Figure 18B Is determined by Figure 18A The radar data of the worn post of;

[0031] Figure 19 Is another height map determined by the radar data of the outermost surface of the roll;

[0032] Figure 20 Is another height map including the monitoring of one or more end plates of the roll;

[0033] Figure 21 Is another monitoring system for monitoring the roll;

[0034] Figure 22 Shows three height maps generated using different compensation methods to compensate for the variable roll speed during rotation; and

[0035] Figure 23 Shows a speed sensor and the metal parts detected by it during roll rotation.

[0036] List of reference numerals

[0037] HPGR 10

[0038] Hopper 12

[0039] First roll 14

[0040] First roll rotation axis 14a

[0041] Rotation direction of the first roller 14b

[0042] Cleaning area (outer surface of the roller) 14c

[0043] Second roller 16

[0044] Axis of rotation of the second roller 16a

[0045] Rotation direction of the second roller 16b

[0046] Gap 18

[0047] Drive motors 20, 22

[0048] Skew control system 24

[0049] End plate 26

[0050] Column 28

[0051] Self-generated layer 30

[0052] Monitoring system 40

[0053] First speed sensor 42a

[0054] Second speed sensor 42b

[0055] First radar system 44a

[0056] Second radar system 44b

[0057] Metal part 45

[0058] First linear drive 46a

[0059] Second linear drive 46b

[0060] First linear drive controller 47a

[0061] Second linear drive controller 47b

[0062] Control unit 48

[0063] Computer 49

[0064] Radar unit 50a

[0065] RF board 52

[0066] Plano-convex lens 54 Detailed implementation

[0067] Figure 1 The high-pressure grinding roll (HPGR) 10 machine is shown. The HPGR 10 includes being mounted on Figure 2 , Figure 3 andFigure 4 The hopper 12 (or chute) above the two rollers 14, 16 depicted in Figure 4 . Each of the rollers 14, 16 has a respective axis of rotation 14a, 16a. The rollers 14, 16 are arranged such that their axes of rotation 14a, 16a are parallel to each other. In this arrangement, a gap 18 is formed between the two rollers 14, 16. The gap 18 is defined herein as the narrowest point between the two rollers 14, 16. Briefly referring Figure 4 , during operation, the material to be crushed is fed from the top side of the rollers 14, 16 (i.e., from the hopper 12) in the direction marked by the arrow R to the rollers 14, 16. The material may briefly be located in the region defined between the vertically uppermost part of the rollers and the gap. The rollers 14, 16 rotate in the directions shown by the curved arrows 14b, 16b such that at the gap 18, the outer surface of each of the rollers 14, 16 moves downward. This movement pulls the material located in the aforementioned region into the gap 18 to be crushed.

[0068] Each of the rollers 14, 16 is rotated by a respective drive motor 20, 22 ( Figure 1 ). The first roller 14 of the two rollers is mounted such that its axis of rotation 14a is fixed relative to the ground and relative to the hopper 12. The second roller 16 of the two rollers is mounted such that its axis of rotation 16a is floating, such that the linear distance between the two axes 14a, 16a is variable. A skew control system 24 is provided. In this embodiment, the skew control system is mechanical. The skew control system supports the second roller 16 to allow the second roller to float (i.e., to allow the linear distance to vary), while also maintaining the two axes 14a, 16a parallel to each other. Thus, the size of the gap 18 varies within limits determined by the skew control system 24.

[0069] The two rollers 14, 16 have substantially equal lengths. The two rollers 14, 16 are arranged such that the first end of the first roller 14 is axially aligned with the first end of the second roller 16, and such that the second end of the first roller 14 is axially aligned with the second end of the second roller 16.

[0070] The typical length of the rollers is between 250 mm and 2000 mm. The typical diameter is between 800 mm and 4000 mm.

[0071] Each roll may be provided with one or more end plates 26 to ensure that the material from the hopper 12 enters the gap 18 and does not fall from an axial end of either of the rolls 14, 16. Typically, there will be two sets of one or more end plates, with one set positioned adjacent to the first end of the roll and the other set positioned adjacent to the second end of the roll. The one or more end plates 26 on one roll (e.g., the first roll 14) describe an annular or circular profile having a radius greater than that of the first roll 14. The radius of this profile is equal to or greater than the sum of the radius of the first roll and the maximum dimension of the gap 18. This ensures that the one or more end plates 26 on the first roll 14 overlap the second roll 16. This overlap prevents the material from falling out of the axial ends of the gap 18 or from the axial ends of the rolls above the gap 18. In some examples, a roll has end plates 26 at either axial end. In other examples, one roll has an axial plate at one axial end and the other roll has an axial plate at the other axial end.

[0072] In some examples, the roll is provided with a single axial end plate that describes a complete ring. However, since the diameter of the rolls in an HPGR can be several meters, the overall end plate must also have a diameter of several meters. Such a large overall end plate may be difficult to construct, install, maintain, and / or replace. Thus, in other examples, a plurality of end plates 26 may be provided, where each end plate describes a segment of the complete ring such that the individual end plates 26 can be constructed, installed, and / or replaced separately from the other end plates 26 that form the ring.

[0073] Figure 5 and Figure 6 is a depiction of the first roll 14 in the HPGR 10. The illustrated roll is part of a machine that is a test model. The test model is designed to be smaller than a full - scale HPGR, which can have a roll diameter of several meters, in accordance with the principles of dimensional analysis. Except for this change in diameter, the operation of the test model is the same as that of a full - scale HPGR.

[0074] Figure 5 The first roll 14 is shown having a plurality of posts 28 mounted on its outer surface. The first roll 14 has end plates 26 at either axial end of the roll 14. Figure 6 The first roll 14 after use (with the end plates 26 removed) is shown, where an autogenous layer 30 has formed between the posts 28. The autogenous layer 30 is formed by the broken material that accumulates between the posts 28 during operation. Due to the pressure from the broken material, the autogenous layer 30 is compacted onto the outer surface of the roll 14.

[0075] Figure 6 Also shown are worn posts 28w. The posts 28 are made of a hard material such as tungsten carbide. This material of the posts 28 is typically harder than the material of the outer surfaces of the rolls 14, 16.

[0076] The post 28 is a replaceable component and can be replaced when a given post 28 is excessively worn or when the post 28 breaks. Since the post 28 is made of a material harder than the outer surfaces of the rollers 14, 16, a broken post pulled into the gap 18 may cause substantial damage to the outer surfaces of the rollers 14, 16. Accordingly, it is desirable to monitor the condition of the post 28 during operation of the HPGR 10.

[0077] Figure 7 The HPGR 10 with a monitoring system 40 is schematically depicted. In some examples, the monitoring system 40 may monitor only one roller of the HPGR 10. In other examples, the monitoring system may monitor both rollers of the HPGR 10.

[0078] The main components of the monitoring system 40 will now be described in relation to monitoring one roller (the first roller 14) of the HPGR 10. However, this description also applies to the monitoring of the second roller 16 or both rollers. The monitoring system includes a first speed sensor 42a for monitoring the rotational speed of the first roller 14. The speed sensor 42a may be located at or beyond the axial end of the first roller 14. For example, the speed sensor 42a may monitor the rotational speed of the shaft of the first roller 14, and this may be converted to the rotational speed of the outer surface of the roller 14. For example, the shaft may have a plurality of metal pieces (optionally, magnetic metal pieces) circumferentially spaced apart at equal angles around it, and the speed sensor may include an inductive sensor fixed in a position such that as the roller 14 rotates, each metal piece passes sequentially by the inductive sensor. The passage of each metal piece is detected by the inductive sensor as a pulse. The timing between the pulses and / or the width of the pulses may be converted to the rotational speed of the roller 14. One metal piece may have a central gap such that it generates two signals in the inductive sensor in quick succession. This signal, different from the signals generated by the other metal pieces, may allow determination that a complete rotation of the roller has occurred.

[0079] The monitoring system 40 further includes a first radar system 44a mounted to a first linear drive 46a. The first radar system 44a and the first linear drive 46a are communicatively connected to a control unit 48. The first speed sensor 42a is also communicatively connectable to the control unit 48. In this example, the first linear drive 46a is controlled by a first linear drive controller 47a which is communicatively connected to the control unit 48. The first linear drive controller 47a may transmit the position of the linear drive to the control unit 48 which gives the position of the radar system 44a relative to the rotational axis 14a of the roller 14.

[0080] The control unit 48 can be communicatively connected (e.g., via a wired connection or a wireless connection) to a computer 49, such as a laptop or a PC.

[0081] The first radar system 44a is arranged on a side of the roll 14 that is substantially opposite to the gap 18. This ensures that the first radar system 44a is spaced apart from any material (rocks, minerals, etc.) from the hopper 12 to the gap 18, and also from any material leaving the gap 18 on the lower side of the rolls 14, 16. In Figure 7 the schematic illustration shown, if the position of the narrowest part of the gap defines the 0° position of the first roll 14, the first radar system is spaced apart from the gap by an angle equal to or greater than 90° and equal to or less than 270° in the counterclockwise circumferential direction of the first roll 14, as Figure 7 shown. Such a position facilitates the installation of the radar system 44a onto the monitoring system 40. In this arrangement, the material from the hopper 12 will contact the first roll 14 between the 0° position and the <90° position (i.e., the uppermost vertical part of the first roll 14).

[0082] As described below, a second radar unit 44b can be provided. In Figure 7 the schematic illustration shown, if the position of the narrowest part of the gap defines the 0° position of the second roll 16, the second radar system 44b is spaced apart from the gap 18 by an angle equal to or greater than 90° and equal to or less than 270° in the clockwise circumferential direction of the second roll 16, as Figure 7 shown. Such a position facilitates the installation of the radar system 44b onto the monitoring system 40.

[0083] Figures 8 - 10 The first radar system 44a and the first linear drive 46a are shown. The first radar system 44a is mounted to the first linear drive 46a. The first linear drive 46a is arranged to linearly move the first radar system 44a along an axis parallel to the rotational axis 14a of the first roll 14. The first radar system 44a includes at least one radar unit 50a that points to the outer surface of the roll 14 (see Figures 12 - 14 ). The radar unit 50a is configured to transmit a radar beam onto the outermost surface of the roll and receive the radar beam reflected from the outermost surface of the roll. The radar unit is designed such that the radar beam forms a point on the roll 14. In some examples, the point of the radar beam has a diameter between 7 mm and 13 mm on a surface defined by the outermost points of the complete and unworn cylinder of the roll.

[0084] In operation, the outermost surface of the roll 14 can consist of any one or all of the following: the outer surface of the roll 14, the posts 28, and the self - generated layer 30. That is, when the roll 14 is completely clean, for example, before first use or after refurbishment, the outermost surface detected by the radar unit 50a will include the outer surface of the roll 14 and the posts 28. After a short period of use, the self - generated layer 30 may have accumulated between some but not all of the posts 28, such that some of the outer surface of the roll remains exposed. In this case, the outermost surface detected by the radar unit 50a will include some portions of the outer surface of the roll 14, the posts 28, and some portions with the self - generated layer 30. After more use, the self - generated layer 30 can completely cover the outer surface of the roll and can even extend just over the top of some of the posts 28 in some places. In this case, the outermost surface detected by the radar unit 50a includes the self - generated layer 30 and some (or all) of the posts 28.

[0085] The first linear drive 46a is mounted at a fixed distance from the axis 14a of the roll 14. This means that, in the case of no wear on the outer surface of the roll 14, the radar system 44a is maintained at a fixed distance from the outer surface of the roll 14. This fixed distance is preferably set between 5 cm and 30 cm. The posts 28 extend above the outer surface of the roll 14 such that the distance between an unworn post 28 and the radar system 44a is less than this fixed distance. The self - generated layer 30 extends above the outer surface of the roll such that the distance between the self - generated layer 30 and the radar system 44a is less than this fixed distance.

[0086] During operation of the HPGR 10, the first linear drive 46a moves the first radar system 44a back and forth along the axial length of the roll 14. In some examples, the first linear drive 46a moves the first radar system in a continuous motion. During this time, the roll 14 rotates. Thus, the points of the radar beam describe a helical shape on the outermost surface of the roll 14. By adjusting the rotational speed of the roll 14, in particular the back - and - forth scanning speed of the first linear drive 46a, the radar system 46a is able to map the entire outermost surface of the roll 14.

[0087] Alternatively, the first linear drive 46a can be configured to move the radar system 44a in a step - by - step manner. For example, it can move the first radar system in fixed increments after an integer number of complete rotations of the roll 14 (e.g., after one complete rotation of the roll 14 or after two complete rotations of the roll 14, etc.). In this case, the points of the radar beam will sweep through a series of axially adjacent circles on the outermost surface of the roll 14. In Figure 9 In the test unit shown, the linear drive is a Rexroth linear drive, typically model number Model MKK - 065 - NN - 3R030544889, with a total length of 131 cm and a drive length of 75 cm. This linear drive is also inFigure 15 is shown in

[0088] In some examples, the first linear actuator 46a may move the first radar system 44a in steps of 1 mm per revolution of the roller 14. In other examples, it may move the first radar system 44a in steps of 2 mm. In the illustrated example roller, the posts 28 are arranged in a regular repeating pattern, showing clearly spaced rows, each row spaced apart by a row distance. The first linear actuator 46a may be configured to move the first radar system 44a in steps equal to the row distance such that the radar system obtains one measurement (e.g., taken from the center of each post) of the surface of each post 28 in a given row before moving to the next row of posts 28. Compared to more closely spaced measurements, this exemplary process may miss some fine details of the height map but may allow for a faster generation of a map of the entire outermost surface of the roller. This process may be particularly useful when only interested in quickly identifying missing or shortened posts 28 across the entire roller.

[0089] Figure 11 is a photograph of an exemplary radar unit 50a. The illustrated radar unit 50a has an FWCW radar chip mounted on an RF board 52 and a plano-convex lens 54. The radar unit 50a may be configured to operate at a frequency of 120 - 140 GHz. Figure 11 The radar unit shown in

[0090] is a silicon radar, a 120 - 140 GHz radar unit, such as the Indie Semiconductor TRA_120_045. In other examples, an elliptical lens may be used instead of the plano-convex lens. Figures 12 - 14 The radar system 44a may include two radar units 50a arranged adjacent to each other, and these examples are shown in Figures 12 - 14 The first of the radar units 50a may be configured to transmit a radar beam having a first polarization (e.g., polarized along the x direction), and the second of the radar units 50a may be configured to transmit a radar beam having a second polarization orthogonal to the first polarization (e.g., polarized along the y direction). This may overcome noise in the signal and compensate for backscatter losses. Since waves are scattered based on surface differences, cross or angled polarization can help improve the signal rx / tx quality.

[0091] The radar unit 50a or each radar unit 50a provides an output signal that is processed to determine the distance between the radar unit and the outermost surface of the roll 14. The output signal can be processed into a distance by the first radar system 44a or by the control unit 48. The control unit 48 is configured to combine the distance data with the speed data from the speed sensor 42a and the position data from the first linear drive 46a to determine any one or all of the following: wear of the post 28, breakage of the post (which may manifest as a significantly reduced post height or a post that is completely missing from its expected position on the roll), thickness of the autogenous layer 30, wear on the outer surface of the roll 14. The control unit 48 can be configured to generate a height map of the outermost surface of the roll 14. Figure 16 An example height map is shown. Alternatively, the height map can be generated by a computer 49 based on data received from the control unit 48.

[0092] In the test unit, the following components are used for signal processing of the output from the radar unit: a processor demonstration board (Zynq ZC702) and an ADC demonstration board (AD7606CFMC) and a custom adapter board. MATLAB is used to process the data into a height map.

[0093] The first radar system 44a can operate as a synthetic aperture radar.

[0094] In Figure 16 the height map in the upper part, the post 28 is clearly visible as a blue circle. The map is calibrated such that when the radar system detects a distance equal to a fixed distance (which is the outer surface of the roll 14), the map shows white. In the height map, some areas of the autogenous layer 30 are also visible as speckles between the posts 28.

[0095] Figure 16 the height map in the lower part of Figure 16 is a 3D pseudo-color rendering of the height map in the upper part of

[0096] Figure 17A A photograph of a portion of the roll is shown, where the post 28 and some of the autogenous layer 30 are visible, and where there is a clean area 14c between four posts such that the outer surface of the roll 14 is visible. Figure 17B Shows Figure 17A from the same portion of the roll as shown in Figure 17B The above four posts appear clearly defined above the outer surface of the roll (i.e., relative to the clean area 14c which is the bare outer surface of the roll 14). Other areas of the height map show different amounts of the autogenous layer 30 between other posts 28.

[0097] Figure 18A A photograph of a fractured post 28 is shown. Figure 18BA height map of the same fragmented column 28 is shown. In the height map determined from the radar data Figure 18B the uneven upper surface of column 28 can be clearly discerned.

[0098] Figure 19 A height map of another part of roller 14 is shown, in which a plurality of columns 28 are clearly visible, as are the cleaning areas 14c of the outer surface of roller 14 and some areas having the self-generated layer 30.

[0099] Figure 20 Another height map of the outermost surface of the roller is shown. In this case, the roller has one or more end plates 26 at one axial end. These are shown on the figure as Figure 20 continuous horizontal blue lines at the top of. Thus, the radar system additionally allows monitoring of one or more end plates 26, for example, to detect wear or breakage of one or more end plates 26.

[0100] Figure 21 An alternative arrangement is shown, in which there is no separate linear drive controller 47a, but rather the first linear drive 46a is directly connected to the control unit 48, and the control unit 48 is configured to control the first linear drive 46a. All other features of this alternative arrangement are the same as those of the arrangement described above with respect to Figures 1 - 19 described arrangement.

[0101] The first linear drive 46a preferably has a length that encloses the entire axial length of each roller, such that the radar system 44a can be moved to scan the entire outermost surface of the roller 14. The first linear drive 46a may also preferably have a length that additionally encloses any end plates 26 of the roller (if present, which may be only at one end of the roller or at both ends of the roller), such that the first radar system 44a additionally scans on the end plates 26. In addition to monitoring the outermost surface of the roller 14, this can also allow the control unit 48 to additionally monitor wear or damage on one or more end plates 26.

[0102] The monitoring system 40 has been described above in relation to monitoring one roll (the first roll 14). In some examples, the monitoring system 40 may be configured to monitor only the second roll 16 or both the first roll 14 and the second roll 16. In such a case of monitoring two rolls 14, 16, a second radar system 44b is provided mounted on the second linear drive 46b. A second speed sensor 42b is provided which is arranged to measure the rotational speed of the second roll 16. The second linear drive 46b is mounted at a second fixed distance from the outer surface of the second roll 16, which second fixed distance may be the same as or different from the first fixed distance. The second linear drive unit 46b is arranged to move the second radar system 44b along an axis parallel to the axis of rotation of the second roll 16. In use, the second linear drive 46b causes the second radar system 44b to scan back and forth across the axial length of the second roll 16. The second radar system 44b outputs distance data to the control unit 48 in the same manner as described above for the first radar system 44a. Thus, in this example, the control unit 48 can monitor both rolls 14, 16 simultaneously. Again, the control unit 48 may be communicatively connected to an external computer 49 (laptop, PC, etc.) and the height map may be graphically generated only by the computer 49.

[0103] As described above, the second speed sensor 42b may have the same construction as the first speed sensor 42a. As described above, the second radar system 44b may have the same construction as the first radar unit 44a. As described above, the second linear drive 46b may have the same structure as the first linear drive 46a. As described above, the second linear drive controller 47b may have the same structure as the first linear drive controller 47a.

[0104] During operation of the HPGR 10, a large amount of airborne dust is generated from the comminuted material. Radar (especially radar in the frequency range of 120 - 350 GHz, or more preferably 120 - 140 GHz or 250 - 300 GHz) may be able to penetrate the airborne dust and reliably measure the distance to the outermost surface of the roll. This is in contrast to existing monitoring schemes using visible light, which is easily scattered by airborne dust, which may make precise measurement difficult.

[0105] In one test, while the radar system 44a remained stationary, the roll 14 was rotated multiple times so that the repeatability of the measurement could be determined by scanning the same set of columns multiple times. The radar system was found to have a repeatability of the order of 0.01 mm. That is, the results of multiple measurements of the height of the same column made over multiple rotations of the roll were equal to the order of 0.01 mm. The pure distance measurement accuracy of the broadband millimeter-wave FMCW radar is of the order of a few tens of micrometers.

[0106] During operation, the two rollers 14, 16 experience vibrations due to the significant forces involved in crushing materials such as rocks and minerals. Therefore, preferably, a linear drive is firmly mounted relative to the roller rotation axis (whether a fixed roller or a movable / floating roller) such that any movement of the rotation axis also causes movement of the linear drive, so that the relative position of the roller and the linear drive is fixed as much as possible.

[0107] During operation, for example, the rotational speed of the roller can vary due to variations in the material being crushed at any given moment. Therefore, it is preferred that the instantaneous rotational speed of the roller is accurately measured and this data is used when forming the height map. This allows the interval between different radar measurements to be accurately determined. In one example, a speed sensor is configured to make four speed measurements per revolution of the roller. This is achieved by providing four metal pieces on the shaft of the roller, which are spaced at equal angles (i.e., 90 degrees in this example) to be detected by an induction-based speed sensor. It has been found that this provides sufficiently accurate speed information of the roller during use, where the roller has some variation in rotational speed during each revolution, such that the height map can be accurately generated.

[0108] Figure 22 A comparison of height maps generated using different methods of determining the roller rotational speed is shown. In height map A, no compensation algorithm is used, i.e., the map is generated assuming a constant rotational speed of the roller. Height map B is generated using a compensation algorithm that uses data from a speed sensor that detects a single point (i.e., a single metal piece) on the roller, i.e., a single roller speed measurement is made during each complete revolution. Height map C is generated using a compensation algorithm that uses data from a speed sensor that detects four equally spaced points (i.e., four metal pieces) on the roller, i.e., four roller speed measurements are made during each complete revolution. By comparing the three maps, it can be seen that the true circular profile of column 28 appears clearer in map C compared to maps A and B. This indicates that four speed measurements per revolution provide a reasonable height map.

[0109] Figure 23 is a photograph showing the speed sensor 44a and the aforementioned metal piece 45 with a central notch. This metal piece causes the speed sensor 44a to detect two closely spaced peaks, which enables easy determination that this particular metal piece is passing the sensor, which indicates a complete revolution of the roller, since there is only one metal piece with a central notch on the roller shaft.

[0110] An alarm system can be implemented in the monitoring system 40. The alarm system can be generated in the control unit 48 or the computer 49 or both. The control unit (or the computer) is configured to continuously monitor any feature change of more than 1 mm (in any direction) between successive scans of the same part of the roll. For example, a change > 2 mm can indicate that a given column 28 has broken or has broken off from the roll. The alarm system can identify the fault point associated with the actual roll surface. That is, the alarm can not only indicate that one or more columns have broken or fractured, but also identify which specific column(s) have broken or fractured, enabling the technician to quickly locate the damaged column on the actual roll and replace it. Although this is preferably not preferred, when a broken column is detected, the alarm system can optionally output an emergency stop signal to stop the rotation of the rolls 14, 16.

[0111] The monitoring system 40 can be configured to have a wear measurement mode, which will be performed when the HPGR machine is running (i.e., the rolls are rotating) but not grinding material. In this mode, the amount of wear of the columns 28 and the outer surface of the roll can be measured with an accuracy of 0.1 mm variation in the height direction. Columns with wear exceeding a predetermined amount (e.g., exceeding 1 mm) can be identified by the monitoring system 40, and their positions on the actual roll surface can be indicated. This can allow the technician to quickly locate the worn columns on the actual roll surface and replace them during a maintenance period.

Claims

1. A high pressure grinding roller machine for grinding materials, comprising: a first roller having a longitudinal axis of rotation and having a cylindrical outer surface, a plurality of first posts mounted on the outer surface of the first roller and extending radially outward from the outer surface of the first roller; a second roller having a longitudinal axis of rotation and having a cylindrical outer surface, The first roller and the second roller are arranged such that their longitudinal axes are parallel to form a gap between outer surfaces of the first roller and the second roller; a first radar system arranged to transmit a radar beam onto an outermost surface of the first roller and to generate a first radar system output, the first radar system output being indicative of a distance between the first radar system and the outermost surface of the first roller; wherein the outermost surface of the first roller comprises one or more of: an outer surface of the first roller, the plurality of first pillars, and an autogenous layer of crushed material adhered to the outer surface of the first roller; and the machine further comprises: A monitoring system includes a processing device connected to the first radar system and configured to analyze the first radar system output and determine a condition of the outermost surface of the first roller.

2. The high pressure grinding roller machine according to claim 1, wherein: The first radar system is a synthetic aperture radar.

3. The high pressure grinding roller machine according to any one of claims 1 or 2, wherein: The first radar system is mounted on a linear drive, wherein the linear drive is arranged to move the first radar system along an axis parallel to the longitudinal rotational axis of the first roller to allow the first radar system to scan the entire axial length of the first roller, wherein the monitoring system is configured to use position information from the linear drive in determining the condition of the outermost surface of the first roller.

4. The high pressure grinding roller machine of claim 3, further comprising a first speed sensor for determining a rotational speed of the first roller, the first speed sensor being communicatively connected to the monitoring system; wherein, The monitoring system is configured to use velocity data from the first velocity sensor to calibrate data received from the first radar system and from the linear drive to form a height map of the outermost surface of the first roller.

5. A high pressure grinding roller machine according to any one of the preceding claims, wherein: The processing device is configured to have a first mode of operation and a second mode of operation.

6. The high pressure grinding roller machine according to claim 5, wherein The first operating mode is a continuous scanning mode in which a current distance measured between the first radar system and a given location on the outermost surface of the first roller is compared to a previously measured distance between the first radar system and the given location measured during a previous rotation of the first roller, and wherein, The monitoring system is configured to output an alarm when the current distance differs from the previously measured distance by more than a predetermined amount, the alarm indicating a position on the first roller corresponding to the given position, optionally wherein the predetermined amount is 2 mm.

7. The high pressure grinding roller machine according to claim 5 or 6, wherein The second operation mode is a wear measurement mode performed when the first roller and the second roller are rotating and no abrasive material is present in the gap, wherein: The processing device is configured to identify the distance from the first radar system to each of the plurality of poles and determine the height of each pole above the outer surface of the roller with an accuracy greater than 0.5 mm; wherein the processing device is also configured to compare the determined height of each pole with an expected height obtained from the pole in a new condition, and calculate the wear condition of each pole based on the difference between the determined height and the expected height.

8. The high pressure grinding roller machine according to claim 7, wherein: The processing device is configured to identify a set of worn posts, the set of worn posts being posts having a wear condition below a predetermined threshold, and output a position of each post in the set of worn posts on the outer surface of the roller.

9. A high pressure grinding roller machine according to any one of the preceding claims, further comprising a second radar system arranged to monitor a plurality of second posts on the outer surface of the second roller and configured to generate a second radar system output to the monitoring system, wherein The second radar system output is indicative of a distance between the second radar system and an outermost surface of the second roller.

10. A high pressure grinding roller machine according to any one of the preceding claims, wherein: The high pressure grinding roller machine includes a housing and a skew control mechanism.

11. A high pressure grinding roller machine according to any one of the preceding claims, wherein: The longitudinal axis of the first roller is fixed relative to the shell, and wherein the longitudinal axis of the second roller is movable relative to the shell so that the size of the gap is variable, wherein the second roller is operably connected to the skew control mechanism, wherein the skew control mechanism is configured to control the movement of the longitudinal axis of the second roller, thereby controlling the size of the gap.

12. The high pressure grinding roller machine according to any one of claims 1 to 10, wherein: The longitudinal axis of the second roller is fixed relative to the shell, and wherein the longitudinal axis of the first roller is movable relative to the shell so that the size of the gap is variable, wherein the first roller is operably connected to the skew control mechanism, wherein the skew control mechanism is configured to control the movement of the longitudinal axis of the first roller, thereby controlling the size of the gap.

13. The high pressure grinding roller machine according to any one of claims 10 to 12, wherein: The skew control mechanism is also configured to maintain the longitudinal axes of the rollers parallel to each other.

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