SYSTEM AND PROCESS FOR ONLINE DETERMINATION OF THE CHARACTERISTICS OF WORN BALLS AND BALL FRAGMENTS OF THE SAME

Abstract

The present invention relates to a system and process carried out after a process of separating fragments of steel from pieces of ore that come out of a semi-autogenous grinder for grinding ores, and which consists of a system formed by one or more instruments for capturing images, each one being sensitive to light of different wavelengths, which point to the surface of an element for receiving the steel fragments or a channel that receives the steel balls and the fragments thereof from the separation process, through which the steel balls and fragments thereof move when they are discharged from this process, with the possibility of directing each image sensor such that it is not parallel to the others.

By digitally processing the images obtained with the one or more sensors, the dimensions and morphology of the balls and ball fragments discharged from the separation process can be determined.

Claims

1. A system for detecting worn balls and broken balls discharged from a conveyor belt (15) that receives the oversize material coming out of a semi-autogenous mill (1), where the worn balls and broken balls are separated from said material by at least one magnet, electromagnet (18), acting on the conveyor belt (15), wherein said system comprises: a receiving element (19) whose surface is a screen (24) that receives the worn balls and broken balls when discharged from the electromagnet (18) acting on the conveyor belt (15); at least one visual spectrum camera (16) which captures and records a set of visual images (26), from the surface of said receiving element (19); visual spectrum image data transmission means (17) connected to said at least one visual spectrum camera (16); data processing means (20) with receiving means receiving the visual spectrum image data (17) for processing and generating control data (21); control data transmission means (21) connected to said data processing means (20); and a control center (22) that receives the control data (21) to send corrective instructions (23) towards a control means or operator of the semi-autogenous mill (1).

2. The system for detecting worn balls and broken balls, according to claim 1, wherein the receiving element (19) is a chute.

3. The system for detecting worn balls and broken balls, according to claim 1, wherein the data processing means (20) is a conventional processor.

4. The system for detecting worn balls and broken balls, according to claim 1, wherein the data processing means (20) is a PC computer.

5. The system for detecting worn balls and broken balls, according to claim 1, wherein the data processing means (20) is a Programmable Logic Controller, PLC.

6. The system for detecting worn balls and broken balls, according to claim 1, wherein the visual spectrum image data transmission means (17) are wired.

7. The system for detecting worn balls and broken balls, according to claim 1, wherein the visual spectrum image data transmission means (17) are wireless.

8. The system for detecting worn balls and broken balls, according to claim 1, wherein the processing means (20) comprise: an image conditioning module (27) for conditioning the image by subtracting the geometry of the balls (9, 11) and the ball fragments (12) from the background, performing an intensity adjustment and performing morphological operations; an element identification and tracking module (28); an image analysis module (29) for determining the morphology and dimensions of the balls (9, 11) and ball fragments (12); a discriminating module (30) of balls and fragments of balls; a characterization module (31) where worn balls or fragments of balls are counted, characterizing the sizes and shapes of the balls and fragments of balls (9, 11, 12); an analysis module (32) where the groove sizes of the semi-autogenous mill grates are obtained from the maximum size of balls; and a results module (33) where the output rate of balls and fragments of balls is obtained, with the functionality of emitting an alarm for an anomaly in the size of the balls and fragments of balls and an alarm for an anomaly in the amount of balls and fragments of balls.

9. A process for detecting worn balls and broken balls being discharged from a conveyor belt (15) that receives the oversize material coming out of a semi-autogenous mill (1), where the worn balls and broken balls are separated from said material by at least one electromagnet (18) acting on the conveyor belt (15), wherein comprises the following steps: (a) capturing and recording visual spectrum images (26) from the screen surface (24) of a receiving element that receives the worn balls and broken balls from the conveyor belt (15); (b) transmitting the captured visual spectrum images (26) through visual spectrum image data transmission means (17), to a data processing means (20); (c) conditioning the images by an image conditioning module (27), comprising processing said captured images (26) by: (c1) subtracting the image background, to leave only the image of the worn balls (9) and the broken balls (12); (c2) adjusting the intensity of the images obtained in step (c1); and (c3) performing the operations of determination of morphology of the balls and of the pieces of balls; (d) performing the identification of the fragments of broken balls (12) and the worn balls (9) on the surface of the screen (24) of the receiving element (19) in an element identification and tracking module (28) using the images conditioned in step (c); (e) analyze the morphology and dimensions in an image analysis module (29); (f) perform a characterization of the worn balls (9) and the fragments of broken balls (12) in a characterization module (31), counting the pieces of metal, characterizing the sizes and characterizing the shapes; (g) performing an analysis of the mill operating conditions in an analysis module (32), using the data of grate groove size, reload ball size and process data, conjugated with the data of the mill such as speed, power, weight and noise, previously loaded into a mill data module (34); and (h) display process results in a results display module (33) showing the output rate of worn balls and fragments of broken balls, with the functionality of emitting an alarm due to an anomaly in the size of the identified worn balls, an alarm for an anomaly in the number of balls and fragments of balls detected and an alarm for an anomaly due to the shape of the fragments of balls.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings are included to provide a further understanding of the invention and form part of this description and further illustrate some of the preferred embodiments of this invention.

[0021] FIG. 1 shows a cross section of a prior art semi-autogenous mineral grinding mill, which works by rotating on its axis to produce ore size reduction.

[0022] FIG. 2 shows a longitudinal section of a prior art semi-autogenous mineral grinding mill.

[0023] FIG. 3 shows the schematic of a prior art grate with the charge within the semi-autogenous mill passing through it.

[0024] FIG. 4 shows an enlargement of a perspective view of a grate that has a fracture, causing a hole through which larger balls and ore escape and that should remain in the grinding chamber.

[0025] FIG. 5 shows a longitudinal section of a prior art semi-autogenous mineral grinding mill, where the grate has suffered a fracture of one of its ribs.

[0026] FIG. 6 shows a diagram of the exit of a ball of maximum size added to the mill through the hole caused by the fracture of the grate, and pieces of ore of a larger size can also exit.

[0027] FIG. 7 shows an enlargement of a perspective view of a grate that has a fracture in one of its corners, causing a hole through which larger balls and ore escape and that should remain in the grinding chamber.

[0028] FIG. 8 shows a schematic view of a mill, a classifier and a conveyor belt, carrying worn steel balls and fragments of steel balls together with ore.

[0029] FIG. 9 shows a schematic view of the elements that can be constitutive of the system, to identify, quantify and characterize worn balls and broken balls that are discharged from the separation process with magnets, for example electromagnets.

[0030] FIG. 10 shows a flow chart of the steps that are performed in one of the embodiments of the process of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention refers to a system that works associated with a semi-autogenous mill (1) for ore grinding. The system is installed outside the semi-autogenous mill (1) in an area after the separation process of the steel balls and their fragments from the ore coming out of the semi-autogenous mill (1), which allows observing the surface of a receiving element or chute (19) that receives the discharge from the separation process. From the semi-autogenous mill (1) comes out a material composed of steel balls, fragment of balls and ore after the grinding process, where said material is on a conveyor belt (15) in which acts on the conveyor belt (15) one or more magnets, for example electromagnets (18) suspended on the conveyor belt that capture the balls and fragments of steel that go along with the ore on the conveyor belt (15) from the belt itself. The balls and fragments of steel separated on the conveyor belt (15) by the electromagnets (18) are subsequently discharged in free fall into collection containers and/or bins (25) located below the conveyor belt (15). In the present invention, a receiving element or chute (19) is inserted which receives said balls and fragments of steel captured by the electromagnet(s) on its surfaces before free fall when the electromagnets are discharged, said chute (19) serving as a screen for the detection of balls and fragments of balls, being able to characterize them in shape and size. The chute (19) is necessary in a length that allows the detection of the balls and fragments of balls for an adequate characterization where said length is such that the balls roll on its surface and the fragments of ball can slide and fall without accumulating.

[0032] As shown in FIG. 9, in order to observe the surface of the chute (19), at least one high resolution visual spectrum digital camera (16) is located to determine the dimensions of the oversize balls and ball fragments exiting the semi-autogenous mill. The images obtained with the high-resolution visual spectrum camera (16) are used to determine the dimensions of the balls and larger sized ball fragments that come out of the semi-autogenous mill, since a visual spectrum camera can provide a higher resolution. These cameras are digital cameras that capture the image, either from the infrared spectrum or from the visual spectrum, being recorded in the memory of the data processing means (20).

[0033] The visual spectrum camera (16) has visual spectrum image data transmission means (17), whether wired or wireless. The data transmission means (17) transmits the data to the data processing means (20), being a processor, a PC computer, a PLC programmable logic controller or the like. The data processing means (20) have means for receiving (not shown) the data sent by at least one camera (16).

[0034] The surface of the receiving element of the balls and fragments of balls, for example, of a chute (19) constitutes a fundamental element of this invention. This surface is a screen (24) from which the information for the system emanates. At least one visual spectrum camera (16) is installed pointing towards the surface of the screen (24) of said chute (19) to capture and record the image of the balls and fragments of balls that roll or slide on the surface of the screen (24) of the chute (19) and transmit it with the visual spectrum image data transmission means (17), starting the counting of the balls and fragments of balls discharged from the separation process. This count also discriminates between worn (rounded) and broken (irregularly shaped pieces) balls. To do this, the visual spectrum camera (16) is used that captures and records a high resolution image of the balls (9) showing the contour and size of the worn and broken balls.

[0035] The data processing means (20) processes the visual spectrum image data and transmits the processed data by control data transmission means (21) as information to a control center (22), which determines the actions to be taken, depending on the information delivered by the data processing means (20). The control center (22) sends corrective instructions (23) to a control means or to the semi-autogenous mill operator (1), to correct the problem reported by the data processing means (20).

[0036] As shown in the flow chart in FIG. 10, the digital processing performed by the data processing means (20) starts in the image conditioning module (27), in which background subtraction, intensity adjustment and morphological operations are performed. Then, in the identification and tracking module (28) the balls and fragments of balls are tracked and an operation is performed in an image analysis module (29) by morphology and dimensions.

[0037] The load flow (8) conformed by the ore (10) and the balls (9), which passes through the grooves (5) of the internal grates (4) of the semi-autogenous mill (1), reaches the conveyor belt (15), where at least one electromagnet (18) captures the balls and fragments of steel that go on said conveyor belt (15) allowing said balls and fragments of steel to be separated from the ore (10) that is transported as a whole in a separation process. The balls and fragments of steel are discharged from said at least one electromagnet (18) and reach the surface of the screen (24) of the chute (19), where at least one visual spectrum camera (16) takes a set of visual images (26). Said at least one visual spectrum camera (16) sends the visual images (26) captured through visual spectrum transmission means (17) towards the data processing means (20).

[0038] The images (26) sent through the transmission means (17) are received in an image conditioning module (27), where said captured images (26) are processed. In the module (27) an image conditioning is carried out, where the geometry of the balls (9, 11) and fragments of balls (12) is subtracted with respect to the background, leaving only the image of the worn balls and the broken balls. In this same module (27) the intensity of the image is adjusted to perform the morphology determination operations of the balls (9, 11) and fragments of balls (12). The information generated in the module (27) is transferred to the module (28) of identification and tracking of the elements on the chute (19), whose images have already been conditioned. The information of the balls identified and tracked on the chute (19) is sent to a module (29) where they are analyzed using morphology and sizing determination techniques. The information from this analysis is sent to a discrimination analysis module (30) where the balls (9, 11) and fragments of balls (12) are differentiated.

[0039] The process continues through the characterization module (31) where the worn balls or fragments of balls are counted, characterizing the sizes and shapes of the balls (9, 11) and fragments of balls (12), that is, of the metal that is on the chute (19). From this analysis, the volume of the worn balls and fragments of broken balls is determined, and once the density of the steel is known, the mass of steel that leaves the semi-autogenous mill (1) is determined, and that can be delivered punctually or as mass flow by setting a period of time, such as per hour. Thus, it is possible to know online and in real time the approximate amount of metal that comes out from the semi-autogenous mill (1).

[0040] In the size analysis module (32), balls and fragments of balls are analyzed according to the size of the grate groove. This dimensional analysis corresponds to comparing the size of the worn balls and the fragments of broken ball with the size of the grate groove and if the former are larger, it is deduced that a fracture of the internal grate has occurred. The size of the hole produced can be determined by measuring the largest size of worn balls and fragments of broken ball on the chute (19).

[0041] For this purpose, in the analysis module (32), an analysis is performed to obtain the groove sizes of the grates from the maximum ball size. The analysis is performed using grate groove size data, reload ball size (new ball added to mill), and process data, conjugated with mill data such as speed, power, weight (obtained from load cells and/or oil pressure in breaks) and noise, previously loaded in a mill data module (34). The reload ball size can be entered by the mill operator and process data can be obtained directly in connection with the semi-autogenous mill operational control system (1).

[0042] The module (33) delivers the results of the previously described process, providing information on the output rate of balls and fragments of balls. In the event that the size of the balls is greater than the size of the internal grate groove used, an alarm will be issued for this anomaly. In the same way, if the number of balls in the chute (19) is greater than a preset value or range of values, the system will issue an alarm for this anomaly, so that in the control center (22) a means of control or mill operator take the necessary corrective action for the grinding process. The same happens when there is an excess of broken balls on the chute (19), activating an alarm.

[0043] A sharp decrease in the amount of balls and ball fragments on the chute (19) may indicate a malfunction of said at least one electromagnet (18) acting on the conveyor belt (15) which may result in clogging of crushers used to reduce the size of the pebbles preventing them from being returned to the semi-autogenous mill or sent to the ball mills, which corresponds to the subsequent size reduction stage. A sharp increase in the number of balls and ball fragments on the chute (19) can indicate poor ball quality that may result in excessive wear or breakage or indicate an operating condition that results in damage to the ball load.