NZ726144A - Gold theft detection - Google Patents

Abstract

mining system for detecting theft of a material of interest from a mining process, the system including: a first in-line monitoring device for detecting a material of interest in a mining material, the first device including: a plurality of electrodes including at least a first electrode which is a positive or a negative electrode, and second and third electrodes which are opposite in charge from the first electrode, the first electrode being separated from the second and third electrodes by a non-conductive space or spaces through which mining material can pass, the first device configured to detect the presence of the material of interest in the mining material as it passes through the space and forms an electrical connection between the first electrode and at least one of the second or third electrodes, and to provide a first value representative of an amount of the material of interest in the mining material; a second in-line monitoring device for detecting the material of interest in a mining material, the second device being located downstream of the first in-line monitoring device, wherein the second device is configured to monitor a portion of the mining material for the material of interest and to provide a second value representative of an amount of the material of interest in the mining material; a processor configured to determine a loss of the material of interest based on the first value and the second value, and to provide an alarm output indicative of theft of the material of interest if the loss exceeds a threshold value. h is a positive or a negative electrode, and second and third electrodes which are opposite in charge from the first electrode, the first electrode being separated from the second and third electrodes by a non-conductive space or spaces through which mining material can pass, the first device configured to detect the presence of the material of interest in the mining material as it passes through the space and forms an electrical connection between the first electrode and at least one of the second or third electrodes, and to provide a first value representative of an amount of the material of interest in the mining material; a second in-line monitoring device for detecting the material of interest in a mining material, the second device being located downstream of the first in-line monitoring device, wherein the second device is configured to monitor a portion of the mining material for the material of interest and to provide a second value representative of an amount of the material of interest in the mining material; a processor configured to determine a loss of the material of interest based on the first value and the second value, and to provide an alarm output indicative of theft of the material of interest if the loss exceeds a threshold value.

Description

Gold theft detection Field of the invention The invention relates to systems and methods for detecting loss of a material of interest, for example a valuable material such as gold, silver, or other platinum group metals from a mining process, such as due to theft.

Background of the invention The content of PCT application published as WO/2014/100858 on 03 July 2014 and claiming priority from AU 2012905695 is hereby incorporated by reference in its entirety.

Detectors of various types are often used to determine the presence of valuable minerals during prospecting. Two such patents (CA1215743 and CA1188734 – the contents of which are hereby incorporated by reference) disclose the use of electrode probe for the detection of a metal or mineral in a geological formation. Essentially, these operate by detecting the “short circuiting” of conductive grains across a narrow gap between two mutually spaced electrodes.

These types of detectors are suitable for detecting a conductive material. This is because the sensors rely on a conductive material bridging between two electrodes on the probe to short-circuit the electrodes and generate a detection signal. Ideally these types of detectors are suitable for detecting native metal without a non-conducting oxidized layer on the surface.

These detectors have a number of shortcomings which renders them unsuitable for use in a mining process. The detectors disclosed in these documents are point probes that are manually inserted into the ground to detect the presence of an electrically conductive material at that specific location.

The detectors rely on physical contact between the electrode probe and the electrically conductive material. This means that the detectors are only able to detect electrically conductive material in a sampling location if that material is immediately adjacent to the electrodes. This means that the amount of material sampled at each 1001629580 location is very small, and is governed, in part, by the surface area of the electrode probe. If the electrode probe is small, then the amount of material sampled at each location is very little, which lowers the likelihood of detection of an electrically conductive material.

Furthermore, when the electrode portion of the detector is inserted into the ground, the electrically conductive material must align over the narrow gap between the two spaced electrodes in order to short circuit the electrodes and thus generate a detection signal. This means of detection is heavily dependent on the concentration of the conductive material at each sampling location. If there is only a low amount of the conductive material in the soil, then there is a low likelihood that it would come into contact with the electrode probe, or even if it did come into contact with the probe that it would necessarily align correctly with the electrodes to generate a signal.

Another issue with these detectors is that they are only suitable for detecting surface deposits of a conductive material. If the conductive material resides at a reasonable depth below the surface, then these detectors cannot be used.

Additionally, the only information that the detectors report is if the electrode probe has contacted an electrically conductive material or not. The detectors provide no data as to the amount or likely amount of the electrically conductive material in the ground.

Given the above, in order for any meaningful data to be generated, sampling needs to be conducted over potentially thousands of locations. This is both highly labour intensive and time consuming. Therefore these detectors are not suitable for use in a mining operation.

US patent 3316545 discloses a similar system using large co-planar electrodes with a meandering insulating space between them. Whilst such a system may be suitable for analysing material in a batch process it is unsuitable for use with continuous processes. First, the planar electrodes would be highly susceptible to wear. Second, the electrode configuration may generate sufficient levels of inductance in the detection circuit, that when a particle of material bridges the insulating space between electrodes, the level of current that flows will be significantly suppressed making detection of the particle difficult or impossible. 1001629580 The present invention is directed at ameliorating at least one of the problems associated with the prior art.

Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art.

Summary of the invention The above discussed detectors are not suitable for use in continuous mining operations, or for use as in-line monitoring devices. As such, these devices are also unsuitable for use in reporting loss of a material of interest from a mining or mineral extraction process. The inventors have identified the problem of theft of a material of interest (such as valuable metals, e.g. gold) from mining and mineral treatment processes. Thus, certain aspects and embodiments of the invention described herein, is directed to this problem of theft.

In one aspect of the invention, there is provided a mining system for detecting theft of a material of interest from a mining process, the system including: a first in-line monitoring device for detecting a material of interest in a mining material, the first device including: a plurality of electrodes including at least a first electrode which is a positive or a negative electrode, and second and third electrodes which are opposite in charge from the first electrode, the first electrode being separated from the second and third electrodes by a non-conductive space or spaces through which mining material can pass, the first device configured to detect the presence of the material of interest in the mining material as it passes through the space and forms an electrical connection between the first electrode and at least one of the second or third electrodes, and to provide a first value representative of an amount of the material of interest in the mining material; a second in-line monitoring device for detecting the material of interest in a mining material, the second device being located downstream of the first in-line monitoring device, wherein the second device is configured to monitor a portion of the mining material for the material of interest and to provide a second value representative of an amount of the material of interest in the mining material; a processor configured to 1001629580 determine a loss of the material of interest based on the first value and the second value, and to provide an alarm output indicative of theft of the material of interest if the loss exceeds a threshold value.

In another aspect of the invention, there is provided an in-line monitoring process for detecting theft of a material of interest in a mining material, the process including: providing a first in-line monitoring device to a first flow channel for the mining material, the first device including: a plurality of electrodes including at least three electrodes, a first electrode which is a positive or a negative electrode, and second and third electrodes which are opposite in charge from the first electrode; the first electrode being separated from the second and third electrodes by a non-conductive space through which mining material can pass; the first device configured to detect the presence of the material of interest in the mining material as it passes through the space and forms an electrical connection between the first electrode and at least one of the second or third electrodes; transporting the mining material through the flow channel so that at least a portion of the mining material passes through the space; monitoring the portion of the mining material with the first device for the material of interest to determine a first value representative of an amount of the material of interest in the mining material; providing a second in-line monitoring device to either a second flow channel or the first flow channel at a location that is downstream of the first device; monitoring the portion of the mining material with the second device for the material of interest to determine a second value representative of an amount of the material of interest in the mining material; using the first value and the second value to determine a loss of the material of interest; and providing an alarm output indicative of theft of the material of interest if the loss exceeds a threshold value.

The material of interest is preferably a valuable material such as gold and platinum group metals (such as ruthenium, rhodium, palladium, osmium, iridium, and platinum). Additionally, the present invention is also suitable for detecting hard rock copper and silver, and other metals that are in a conductive form, such as after a comminution process (which may break the oxidized layer, or result in comminuted metal particles without an oxidized layer). These materials would not be detected by a point sensor which is inserted into the ground such as those described in the prior art.

This is because an initial treatment stage is required, such as comminution process, to 1001629580 expose conductive particles by breaking the oxidised layer and/or otherwise liberating conductive metal The above system and method is advantageous as it provides a system for monitoring the amount of a material of interest in-line, and comparing this value against an expected amount of the material of interest in-line at a downstream location.

In an embodiment the processor is configured to receive the first and second values continuously from the first in-line monitoring device and the second in-line monitoring device during the operation of the mining process. Preferably the processor is configured to log the first and second values. The processor may log the first and second values continuously, or alternatively the processor may be configured to log the first and second values at a sampling time interval. That is, the processor is configured to average the first and second values over a sampling time interval, and to log the averaged first and second values. The sampling time interval may be of the order of seconds, minutes, or hours etc. depending on the type of process. For example, for a conveyance process where material is being fed through at a constant rate, the sampling time may be of the order of seconds or minutes depending on the speed of the conveyer. Conversely, if a batch process is being monitored then the sampling time interval will be subject to the duration of the batch process, and therefore may be of the order of hours or possibly days. For continuous stirred tank reactors or semi-batch processes an appropriate residence time may be determined and used as the basis of the sampling time interval. The first and second values logged by the processor at the sampling time may be point values, or may be averaged values that have been averaged over the sampling time interval.

In an alternative arrangement, the first and second in-line monitoring devices are configured to report the first and second values at a sampling time interval, and the processor is configured to receive and log the first and second values at the sampling time interval.

An advantage of continuously receiving and logging the first and second values is that it provides for a more accurate historical record of these values. The disadvantage is that it requires significantly more memory to store this information. 1001629580 Conversely, storing data at the sampling time interval reduces the accuracy of the records due to some loss of data, but also requires less memory for data storage.

As generally discussed above, the first value represents the amount of the material of interest passing the location of the first in-line monitoring device, and the second value represents the amount of the material of interest passing the downstream location of the second in-line monitoring device. The processor compares these values and any difference between the amounts represented by the first and second values is indicative that an amount of the material of interest has gone missing.

Again, as discussed above, this invention is broadly applicable to a wide range of mining and mineral extraction processes some In certain embodiments the first value and the second value are compared against each other in real-time at the same sampling time. This may be suitable where there is a relatively constant concentration of the material of interest in the mining material. In other embodiments the processor is configured to factor in a time delay in comparing the first and second values. This time delay factors in the time it takes for the mining material to move from the first in-line monitoring device to the second in-line monitoring device. This time delay may be due to the rate at which the mining material moves through the system or due to the residence time of the mining material in a particular process.

The threshold value takes into consideration expected losses as a result of general process inefficiencies. For example, there may be losses of the material of interest due to some small amount of the material of interest being discarded with a gangue or other waste stream (perhaps due to inability to extract the material of interest due to commercial or technical limitations). The gangue or other waste stream may not be monitored for the material of interest, and even if the gangue or other waste stream was monitored, it may be that the concentration of the material of interest is sufficiently low that it is below accurate detection levels. As such, the threshold value excludes expected loss of the material of interest from process inefficiencies. That is, the threshold is greater than the expected losses as a result of general process inefficiencies. 1001629580 A number of different monitoring strategies may be employed depending on the nature and requirement of the mining or mineral extraction processes.

In one illustrative embodiment, the first value and the second value are compared in real-time against each other. This direct comparison may be appropriate for a particular process or unit process where there is a constant feed of mining material that includes a relatively constant concentration of the material of interest. This allows rapid reporting of an unexpected loss of the material of interest likely due to theft in real-time.

In another illustrative embodiment, the comparison of the first value with the second value is delayed to take into account the residence time of a process operation.

That is, the second value is compared against an historic first value, the first value being taken at time t=0, and the second value being taken at time t=τ . This may be residence suitable in situations where there is variation in the mass flow rate of the mining material, or there is a varied concentration of the mineral of interest in the mining material. Again, this allows rapid reporting of an unexpected loss of the material of interest likely due to theft in near real-time (depending on the residence time of the process operation).

In still another illustrative embodiment, the comparison of the first value and the second value may be in respect of cumulative first and second values over an extended period of time. For example, the cumulative quantity of the material of interest is determined over a period of time, for example a day, a week, or other such appropriate unit of time. The cumulative quantities indicated by the first and second values are then compared and if the difference exceeds a threshold value then the alarm is output. This embodiment may be suitable where the real-time or near real-time losses are below the threshold value, but the cumulative loss is greater than a threshold cumulative value.

Generally, the description above has discussed determining a loss of the material of interest; and providing an alarm output indicative of theft of the material of interest if the loss exceeds the threshold value according to various illustrative operating strategies. It will be appreciated that these embodiments are illustrative only and are not intended to limit the application of this invention in any way. 1001629580 The alarm output can take a variety of different forms. In an embodiment, the alarm is configured to immediately notify an operator or user at the time the loss of the material of interest is determined. Alternatively, the alarm is configured to notify an operator or user sometime after the loss of material is determined. For example, the alarm may notify the operator or user during a standard process report. The alarm may notify the operator or user when the operator or user requests a process report.

The alarm output can simply be a notification to an operator, such as in the form of a computerised notification; and/or the alarm may be a system output that can be used to create this notification. This computerised notification can for example be an email notification, an electronic pop-up notification, a computer generated report, or other notification on a computer screen. Where mine or plant management software is employed (such as SCADA systems or PLC control systems), the mine or plant management software may be configured to display the notification in the context of the process to indicate where the loss of the material of interest has occurred in the process. That is, typically SCADA or PLC systems include a centralised display with an overview of the mining process, and list various process parameters associated with unit processes and/or process trains. Where a loss of material is detected and an alarm is output indicative of theft, the alarm may be in the form of a flashing light, highlight, or change of colour of the unit process and/or process train data displayed by the SCADA or PLC system.

The alarm can be visual, auditory, or both visual and auditory. The alarm may be a siren. A siren may be useful where a large loss of the material of interest is detected in real time.

In an embodiment, the system or process is one in which the mining material is able to be directly accessed by a person in at least a portion of the mining process and/or the mining material is exposed to an external environment. Theft detection is of greater importance in cases where a person is able to easily access the mining material and take the material of interest.

The mining process may be a storage process or a transport process for conveyance of the mining material, for example where transport is through an open chute, open flow channel, conveyer, or by vehicle. 1001629580 In the case where the mining process is a storage process, the mining material may be stored or stockpiled in a heap or in a bin, or using other storage or stockpiling means that are known to those skilled in the art. Theft of the material of interest may easily occur during storage, such as during an operation to load and unload the material from a stockpile, or while the material is present in a stockpile.

In the case where the transport is by vehicle; the first value represents the amount of the material of interest in the mining material being loaded on to the vehicle, and the second value represents the amount of the material of interest in the mining material being offloaded from the vehicle.

Alternatively, the mining process includes at least one unit process or series of unit processes the at least one unit process or the series of unit processes including an inlet and an outlet, the first value represents the amount of the material of interest in the mining material provided to the inlet of the at least one unit process or the series of unit processes, the second value represents the amount of the material of interest in the mining material provided to the outlet of the at least one unit process or series of unit processes; and the mining material is accessible by a person at one or both of the inlet or the outlet, or at a location between the inlet and the outlet.

In an embodiment, the mining process includes a plurality of in-line monitoring devices for monitoring one or more unit process, mining processes, and/or transport processes.

In one case, depending on the specific process operation, there may be plural first devices and/or plural second devices. This may occur where a process stream is bifurcated and the first value is obtained from a position upstream of the bifurcation, and the plural second values are obtained on each stream downstream of the bifurcation. In this case, the bifurcation may be for the purpose of classifying the constituents in the mining stream according to size, in which case a consolidated second value will be compared against the first value, the consolidated second value based on the readings obtained from plural second devices. Similarly, the same applies in the case where plural process streams merge. In such cases, plural first devices may be required upstream of the merge with a single second device downstream of the merge; the 1001629580 second value then being compared against a consolidated first value based on the readings of the plural first devices.

In addition, or alternatively, there may be plural in-line monitoring devices on a single process train but over different process components. For example, first, second, and third; wherein the first device is located on an inlet and each subsequent device is located further downstream. The first device reports a first value, the second device a second value, the third device a third value. The first value is compared with the second value and/or the third value, and the second value is compared with the third value. If one of the comparative values provides a result that exceeds a threshold value then an alarm can be raised which identifies the portion of the process or process train where the unexpected loss or theft has occurred.

In still another embodiment, the mining process is a mining site, and the first device is located to determine the quantity of the material of interest in the mining material as it is conveyed from the location at which it is mined, and the second device is located to determine the quantity of the material of interest in the mining material prior to loading for transport offsite. This arrangement is advantageous as it allows the loss of the material of interest to be monitored over the entire site. This may be useful if loss or theft of small amounts of the material of interest occurs at plural process locations, where each loss or theft may be less than the threshold value associated with local monitoring at each of those process locations; whereas the cumulative loss of the material of interest due to theft across the entire site is sufficient to trigger an alarm.

In an arrangement of this embodiment, the inlet stream to the mining process is at a location near to an extraction site of mining material, and the outlet stream from the mining process is at a processing site where the material of interest can be extracted from the mining material.

It is intended that either of the first or second in-line monitoring devices can be applied on an inlet flow path to a process, an outlet flow path from a process, or an intermediate flow path within a process. The term inlet is intended to encompass an inlet to the overall process, or an inlet to a unit process. Similarly, the term outlet is intended to encompass an outlet from the overall process or an outlet from a unit process. 1001629580 The below discussion relates to the operation of, and describes embodiments and arrangements of the first in-line monitoring device. However, it will also be appreciated that in one or more embodiments, the second in-line monitoring device is of the same type as the first device and/or is characterised as having the same features as the first device including those discussed below.

Preferably the first electrode is configured to form with each of the second and third electrodes a different electrical circuit. Thus when a material of interest forms an electrical connection between the first electrode and the second electrode, a first electrical circuit is established, and when a material of interest forms an electrical connection between the first electrode and the third electrode, a second electrical circuit is established. In this way, it is possible to determine the spatial location of the particle on detection by identifying which circuit has been activated. Furthermore, if there is different electrode spacing between the first electrode and the second electrode as compared with the first electrode and the third electrode (as will be discussed in more detail) size information on the material of interest can be obtained.

Furthermore, this arrangement avoids an issue which can arise where particles become lodged between electrodes. Often conductive particles become lodged and are entrapped between a pair of electrodes. In some instances, the particle will remain lodged there until it is manually removed, for example during a cleaning or servicing operation. If the electrodes are arranged in a single circuit, the presence of the entrapped conductive particle could cause the sensor to malfunction, as the sensor would continue to generate a signal identifying the presence of a conductive particle as long as the jammed particle remained lodged between electrodes. Furthermore, as the pairs of electrodes have been arranged on separate electrical circuits, a false positive signal resulting from the jammed particle may be removed or filtered out electronically or via software.

In an embodiment, the electrodes are arranged in a stack, with the first electrode being located at a first distance in the stack from the second electrode and at a second distance in the stack from the third electrode, the first distance being less than the second distance. Preferably the electrode stack there are more than three electrodes in the plurality of electrodes. More preferably, the electrode stack includes more than four 1001629580 electrodes. Even more preferably, the electrode stack includes more than ten electrodes. In preferred embodiments the electrode stack includes a multiplicity of electrodes, for example the stack may be between 10mm and 500mm in height and contain electrodes spaced from their immediate neighbour by between 5 micrometres and 2000 micrometres. Embodiments may have neighbouring electrodes spaced apart by between 10 micrometres and 1000 micrometres. Most preferably neighbouring electrodes are spaced apart by between 50 and 200 micrometres. In one embodiment electrodes are spaced apart by around 100 micrometres.

This is advantageous as the device is configured to detect a material of interest having a size in at least one dimension corresponding to the first axial distance such that the material of interest forms an electrical connection between the first electrode and the second electrode, and the device is configured to detect a material of interest having a larger size in at least one dimension corresponding to the second axial distance such that the material of interest forms an electrical connection between the first electrode and the third electrode.

Preferably the first electrode forms a first circuit with the second electrode, and the first electrode forms a second circuit with the third electrode, the first and second circuits being electrically separated from each other. In this way, the device is configured to detect and report on approximate sizes of the material of interest in the mining material. In an example, a device includes a first positive electrode arranged in stacked relation with a second and third negative electrodes. The first and second electrode form a first circuit which is separate to a second circuit formed between the first and third electrode. The spacing between the first electrode and the second electrode is 100µm, and the spacing between the first electrode and the third electrode is 200µm. A material of interest having a size of 150µm in one dimension will bridge the gap between the first electrode and the second electrode activating the first circuit, but will not bridge the gap between the first and the third electrodes. However, a material of interest having a size of at least 200µm in one dimension will bridge the gap between the first electrode and the third electrode activating the second circuit. Therefore, depending on which circuits are activated, and based on the space between the electrodes, it is possible to determine a size distribution of the material of interest in the mining material. Increasing the number of electrodes and potential circuits in a stack 1001629580 and having more varied spacing between electrodes on the stack will enhance the resolution of the detector and provide a better estimate as to the size distribution of the material of interest in the mining material.

Preferably, the second and third electrode are electrically separated but adjacent electrodes. The second and third electrodes may for example be electrically separate by a non-conductive separation element such as an insulation layer, or may be separated by a non-conductive space or spacer to electrically isolate the second and third electrodes from each other.

Preferably, the electrodes are in a stepped arrangement, with the third electrode overhanging the second electrode to form the space, the size and shape of the space configured to minimise entrapment of the material of interest and/or mining material.

Preferably electrodes separated by smaller spaces are arranged inwards of electrodes separated by larger spaces. Where the outwards direction is the direction from which the mining material is presented to the electrodes. In this way, larger particles of material of interest are prevented from bridging the more inward smaller spaces between electrodes to minimise double counting of material of interest.

In an embodiment, a non-conductive spacer or spacers defines the space or spaces, and the plurality of electrodes are arranged so as to overlap at least a portion of the non-conductive spacer or spacers, the overlap defining the space or spaces between at least the first electrode and the second and third electrodes.

In an embodiment, the in-line monitoring device includes a plurality of positive and negative electrodes, the positive and negative electrodes separated from each other by the non-conductive spacers.

In an embodiment, the plurality of electrodes are a plurality of conductive plates.

In an arrangement of this embodiment, the plurality of plates are in stacked relation with each other, the non-conductive spacer being a non-conductive plate located between adjacent conductive plates of opposite charge, and wherein adjacent plates of the same charge are electrically separated. Preferably the edges of the conductive plates are bevelled. The inventor has found that the bevelled surfaces assist in preventing particles from lodging between the conductive plates. 1001629580 In an embodiment, the first electrode has a first face which faces a corresponding face of at least one of the second electrode or the third electrode. The faces spaced apart by a non-conductive space and arranged so that mining material can flow there- between. Preferably the first face and the corresponding face each have a surface area that allows an electrical connection to be formed in the presence of the material of interest for sufficient time that an electrical signal can be generated and detected.

Preferably, the surface area is from about 0.008m to about 3.2m . More preferably, the surface area is from about 0.13m to about 1.54m . Even more preferably, the surface area is from about 0.5m to about 1.13m .

In an embodiment, the non-conductive spacer is a portion of a flow channel through which the mining material is transported.

In an embodiment, the plurality of electrodes are mounted to an outer wall portion of the flow channel.

In an embodiment, the plurality of electrodes each include an aperture, and the device further includes a non-conductive shaft, the non-conducting shaft extending through the apertures, and the plurality of electrodes being mounted to the non- conductive shaft.

In an embodiment, the plurality of electrodes are each formed from a material having a hardness of at least 7 on the Mohs scale, but most preferably is greater than 9.

The hardness of the electrodes can be selected based on the minerals present in the deposit being analysed. In an alternative embodiment, the plurality of electrodes are each formed from a resilient material, e.g. material having Shore durometer harness of about D100 or less as defined in ASTM D22400-00. Such electrodes resist damage by yielding In an embodiment, the non-conductive space can be formed from a material having a hardness similar to that of the electrodes with which they are used.

In still a further aspect of the invention, there is provided a mining system for detecting theft of a material of interest from a mining process, the system including: a first in-line monitoring device at a first location within the mining process to determine a first value corresponding to an amount of the material of interest in a mining stream at 1001629580 the first location; a second in-line monitoring device at a second location downstream of the first location within the mining process, to determine a second value corresponding to an amount of the material of interest in a mining stream at the second location; a processor configured to determine a difference in the amount of material of interest at the first location and the second location, and to provide an alarm output if the difference exceeds a threshold value.

In yet another aspect of the invention, there is provided an in-line monitoring method for determining theft of a material of interest from a mining process, the method including: using a first in-line monitoring device at a first location within the mining process to determine a first value corresponding to an amount of the material of interest in a mining stream at the first location; using a second in-line monitoring device at a second location downstream of the first location within the mining process, to determine a second value corresponding to an amount of the material of interest in a mining stream at the second location; determining a difference in the amount of material of interest at the first location and the second location; and providing an alarm output if the difference exceeds a threshold value.

In an embodiment, at least one of the first in-line monitoring device and the second in-line monitoring device includes: a plurality of electrodes including at least three electrodes, a first electrode which is a positive or a negative electrode, and second and third electrodes which are opposite in charge from the first electrode; the first electrode being separated from the second and third electrodes by a non- conductive space through which the mineral stream can pass; the device configured to detect the presence of the material of interest in the mining stream as it passes through the space and forms an electrical connection between the first electrode and at least one of the second or third electrodes. It one or more forms of this embodiment, the in- line monitoring device includes one or more of the features discussed previously.

In one aspect of the invention, there is provided a mining system for detecting theft of a material of interest from a mining process, the system including: a first in-line monitoring device for detecting a material of interest in a mining material, the first device including: a plurality of electrodes including at least a first electrode which is a positive or a negative electrode, and second and third electrodes which are opposite in charge 1001629580 from the first electrode, the first electrode being separated from the second and third electrodes by a non-conductive space or spaces through which mining material can pass, the first device configured to detect the presence of the material of interest in the mining material as it passes through the space and forms an electrical connection between the first electrode and at least one of the second or third electrodes, and to provide a first value representative of an amount of the material of interest in the mining material; a second in-line monitoring device for detecting the material of interest in a mining material, the second device being located downstream of the first in-line monitoring device, wherein the second device is configured to monitor a portion of the mining material for the material of interest and to provide a second value representative of an amount of the material of interest in the mining material; a processor configured to determine a loss of the material of interest based on the first value and the second value, and to provide an alarm output indicative of theft of the material of interest if the loss exceeds a threshold value.

In another aspect of the invention there is provided a mining system for detecting theft of a material of interest from a mining process, the system including: a first device for in-line monitoring of a mining material from a mining process, the device including: at least two conductive electrodes separated by a non-conductive spacer, the conductive electrodes arranged so as to overlap at least a portion of the non-conductive spacer, the overlap defining a spacing between the two conductive electrodes through which alluvial material can pass, the conductive electrodes configured to detect the presence of a material of interest in the alluvial material as it passes therethrough; and to provide a first value representative of an amount of the material of interest in the mining material; a second device for in-line monitoring of a material of interest in a mining material, the second device being located downstream of the first in-line monitoring device, wherein the second device is configured to monitor a portion of the mining material for the material of interest and to provide a second value representative of an amount of the material of interest in the mining material; a processor configured to determine a loss of the material of interest based on the first value and the second value, and to provide an alarm output indicative of theft of the material of interest if the loss exceeds a threshold value. 1001629580 In another aspect of the invention there is provided a method for detecting theft of a material of interest from a mining process, the method including: providing a first device as defined above within a flow path for transporting the mining material, passing at least some of the mining material through the spacing between the two conductive electrodes, the first device providing a first value representative of an amount of the material of interest in the mining material to a processor; providing a second device downstream of the first device within a flow path for transporting the mining material, the second device providing a second value representative of an amount of the material of interest in the mining material to the processor; using the processor to determine a loss of the material of interest based on the first value and the second value, and to provide an alarm output indicative of theft of the material of interest if the loss exceeds a threshold value.

Preferably the conductive electrodes are plate shaped.

Preferably, the in-line monitoring devices and system have one of more of the features discussed previously.

As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps.

Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.

Brief description of the drawings Figure 1 provides an illustration of two rods with different sized spacing between conductive electrodes for determining the presence of a material of interest.

Figure 2 shows an embodiment where the rods of Figure 4A are incorporated in- line into a pipe.

Figure 3 shows an embodiment of a stack of electrodes. 1001629580 Figures 4A and 4B show two solid state electrode stacks able to be used in some embodiments of the present invention.

Figures 5 to 7 illustrate various embodiments of mining processes that include in- line monitors according to various aspects of the invention.

Figures 8 to 9 illustrate various embodiments of a mining process that includes upstream and downstream monitors for use in theft detection.

Detailed description of the embodiments The inventor has found that by incorporating a detector including a series of spaced conductive electrodes in-line in a flow channel, the quantity of a material of interest in a mining stream can be determined. This is because the detectors are constantly in contact with a flow of mining material and therefore are continuously sampling the mining material as it flows by the detector. This means that the detector essentially provides continuous sampling of the mining material. There is a statistical correlation between the number of detection events and the concentration of the material of interest in the mining stream. Thus, even when the material of interest is present only at very low concentrations there is a statistical likelihood of a detection event occurring – although the time between detection events is expected to be large.

Conversely, when the material of interest is present at high concentrations, there will be numerous and frequent detection events.

The detector may be calibrated using a mining stream (or other stream) containing a known concentration of a material of interest. For this known concentration, a frequency of detection events can be recorded. Further known concentrations of the material of interest may be used to provide additional data points to generate a calibration curve. When the detector is used in the field, the frequency of detection events can be compared against the calibration curve to provide an indication of the concentration of the material of interest in the sample.

The calibration will, ideally, also factor in the expected shape and longest dimension of material of interest in the mining stream which can bridge the probe electrodes. Mineral processing is, in part, dependent on these properties as well as a number of other factors. It is likely that these parameters will need to be established 1001629580 through laboratory testing. It is expected that these parameters will vary depending on the source of the material of interest and whether any pre-processing has occurred. For example, it is expected that the shape and dimensions of gold particles will be different between alluvial or crushed hard rock deposits. Laboratory testing can be used to further calibrate or enhance the accuracy of an in-line monitoring process by, for example, providing feedback to the in-line monitoring system.

To improve the accuracy of the system, multiple detectors may be used in the flow channel. The use of multiple sensors increases the sensitivity of the system as it increases the likelihood of a detection event. The use of multiple detectors may be particularly beneficial in mining streams that include only a low concentration of the material of interest.

As will be appreciated, using a sensor system of the present type, which requires physical contact with a conductive particle or grain to detect its presence, even with a large sensor surface area and multiple sensors only a small fraction of the mining stream will be analysed. Therefore statistical methods will typically need to be employed to determine the concentration of the material of interest in the mining stream. A suitable statistical method may be through use of the Poisson distribution.

The inventor has also found that by incorporating rods of conductive electrodes in an inlet and outlet channel, the quantity of the material of interest in a mining stream can be determined and measured against the quantity of the material of interest in the mineral-depleted mining stream (e.g. after mineral extraction).

Ideally a number of rods of conductive electrode plates of different sized spacing are placed on an inlet stream to monitor the concentration of the material of interest in the stream prior to mineral extraction. These rods may be mounted on an inlet that is connected to an ROV, or may be mounted above ground in a pipe, channel, or other flow path that feeds a raw extracted mineral, which may be in the form of a slurry, to the mineral treatment processing plant.

The spacing between the conductive electrode plates is important as different sized spacings will detect different sized particles. In order for particle detection to occur, a particle must come into contact with and bridge the gap between two electrode 1001629580 plates. This bridging results in a short-circuit being established between two electrode plates which results in a detection signal being registered. As such, larger electrode spacing provides for the detection of larger particles, but will limit detection of smaller particles as sufficiently small particles will be unable to bridge the spacing between electrodes.

The conductive electrodes may be formed from a conductive material that is hard to resist wear. Preferably, the hardness of the material is greater than the hardness of the mining material. Preferably the conductive material has a hardness of at least 7 on the Mohs scale, but preferably is even harder, say 9 or above. Suitable conductive materials include metal carbides in a metal matrix, such as tungsten carbide in a cobalt matrix, or silicon carbide. A wide range of hard material can be used is said electrodes if they are conductive (or can be made conductive by doping) including diamond, titanium carbide, titanium nitride, boron nitride, tungsten boride, molybdenum carbide. Such materials may be deposited on an electrode as a surface coating to provide better wear resistance. When the conductive material is silicon carbide, it is preferred that the silicon carbide is doped with a material to provide a surplus of electrons or holes, to improve the conductivity of the silicon carbide. Alternatively, the conductive electrodes may be formed from a conductive material that is resilient such as a conductive plastic or a plastic loaded with a conductive material such as a metal, for example silver. Unlike hard materials described above, such resilient materials are also known to withstand wear as they are able to absorb the impact of the abrasive mining feed material and undergo elastic deformation, then later release that energy and return to their original configuration. Electrodes of this type could, for example be formed from a material having Shore durometer harness of about D100 or less as defined in ASTM D22400-00.

The size, such as a length, of the conductive plates is also important. Larger conductive plates (plates having increased length, such as an increased radius in the case of cylindrical plates) will give rise to increased number and frequency of detection events due to a greater exposed surface area of the plate. The limitation on the size of each electrode is the likelihood of having temporally overlapping interactions with particles between the same set of plates. In some embodiments of the present invention the system cannot distinguish between a single particle bridging a pair of electrodes and 1001629580 multiple particles bridging a pair of electrodes. The likelihood of a particle interacting with a pair of electrodes is related to factors such as: electrode size (larger electrodes being more likely to detect a particle); concentration of the mineral of interest (higher concentration generally means more detection events, subject to particle size distribution as noted below); particle size distribution (a size distribution with more particles of a detectable size range will result in more detection events) flow rate of the material past the detector.

Accordingly the electrodes in the preferred embodiment are sized to avoid simultaneous detection events between electrode pairs.

A similar effect can be achieved by increasing the number of stacks of smaller plates (each with their own electronics) with a lower capacitance per stack. This may be useful for increasing detection events.

The current applied to the electrodes may be DC or AC. In the case of DC, ideally the voltage is less than 3V to prevent electrolysis of materials in the mining feed, which may result in gas generation which can cause dissolution of the electrode material. In some instances, gas generation (which doesn’t lead to electrode dissolution) may be beneficial as, for example, dense gold will tend to be pushed through a H gas layer (which form as microbubbles from nucleation) to provide a clearer signal.

With AC, higher voltages can be used with higher frequencies limiting gas generation and electrode dissolution. Higher frequencies, up to the low kHz range, will generally require that stacks of smaller plates with reduced spacing, each with their own electronics to optimise capacitance effects.

Thus a first electrode is provided with a first face having a first surface area, and a corresponding electrode of opposite charge is provided with a second face having a second surface area. The electrodes are arranged in a stacked arrangement with a space there between. A mining material can flow through this space. The mining 1001629580 material has a residence time in this space that is proportional to the flow rate of the mining material. The residence time is configured so as to provide adequate time for the material of interest to interact and form an electrical connection between the first electrode and the corresponding electrode and to produce a detectable signal. The residence time can be changed by altering the flow rate of mining material through the space. Alternatively or additionally, the residence time may be altered by using electrodes having different surface areas. For example, electrodes with larger surface areas will bound a greater space through which material can flow, thus increasing residence time. Ideally a residence time is selected to enable sufficient opportunity for the electrical contact and thus the generation and detection of an electrical signal.

The electrode spacing may be provided by non-conductive spacers. The non- conductive spacers may be arranged in an alternating arrangement with the conductive electrode plates in a parallel layered type structure. The electrode spacing and/or the thickness of the non-conductive spacers will typically be in the range of 10µm to 200µm.

The non-conductive spacers may be formed from an insulating material that is hard to resist wear. Preferably the non-conductive spacers are formed from a material that has a hardness of at least 7, but preferably 9 on the Mohs scale. Suitable insulating materials include non-conductive diamond, corundum (Al O , sapphire, ruby), or other hard powder (such as boron nitride) in epoxy. Alternatively, the non-conductive spacers may be formed from an insulating material that is resilient such as a nylon urethane.

The insulating material will preferably have a resilience similar to its associated electrodes.

In some embodiments the non-conductive spacer could form part of a wall, floor and/or roof of the pipe or channel. For example, a series of electrode plates be mounted to a sidewall of the pipe or channel, with the electrodes projecting out horizontally from the sidewall. Similarly, from the floor or roof can additionally or alternatively be fitted with the electrodes projecting outwards into the flow of material. This arrangement means has an advantage that an extended sensor (e.g. in the form of a rod) does not project into the centre of the flow channel. Furthermore, as the velocity profile of flow increases towards the centre of a flow channel, use of a wall mounted set of electrodes 1001629580 can be advantageous, as lower flow at the edges means less wear also potentially reduces energy loss as the flow is less hindered.

Hard conductive electrodes may be paired with either hard or resilient non- conductive spacers. Similarly, resilient electrodes may be paired with either hard or resilient non-conductive spacers.

The resistance of the conductive electrodes and the non-conductive spacers to wear is more important when these elements are arranged in an inline monitoring process as compared with the devices disclosed in CA1215743 and CA1188734. The rods of the present invention are exposed to a flow of mining material that, during operation, is constantly flowing past the rods. This means that the rods of the present invention are constantly exposed to wear during operation. In contrast, the devices disclosed in CA1215743 and CA1188734 are simply inserted into the ground at various sampling points. These devices are not exposed to a constantly moving stream of mining material and therefore not subject to a high wear environment.

In an embodiment there are at least two stacks of rods having different sized spacing between the conductive plates. One stack of rods has large spacing, and one stack of rods has small spacing. This arrangement allows different sized mineral particles to be detected, e.g. the rod with the large spacing between conductive elements detects only large mineral particles, whereas the rod with small spacing between conductive elements additionally detects small mineral particles which may not be detected by the rod with large spacing between conductive elements.

For example, one rod stack has a spacing of 10µm for detection of small conductive particles. The other rod stack has a spacing of 100µm for detection of larger conductive particles. Each of the stacks may be provided with their own electronics.

It will be understood that more than two stacks can be used. For example a plurality of stacks may be used, some of which may have different sized electrodes and non-conductive elements. The exact number and configuration of the rod stacks in the plurality of stacks will be dependent on a number of factors such as the type of mining material and the physical and chemical properties of the material of interest. 1001629580 Similarly, rods of conductive plates of different sizes are placed on an outlet stream from the mineral extraction plant to monitor the concentration of the material of interest in the stream after mineral extraction (which operates in the manner described above). This provides an indication on the quantity of the material of interest that is extracted in the mineral extraction stage, and thus provides data on the efficiency of the process.

The skilled person will appreciate that additional rods with varying degrees of spacing may be used depending on the expected size and size distribution of mineral particles within the alluvium.

Figure 1 provides an illustration of two rods 101, 102 stacked with conductive plates 103. The first rod 101 has a non-conductive spacer 104 providing a large gap between the conductive plates 103. The second rod 102 has a non-conductive spacer 105 providing a small gap between the conductive plates 103.

Figure 2 shows an embodiment where the rods 101, 102 are incorporated in-line into a pipe 106. Slurry 107 is pumped through the pipe 106 and passes through the spacers 104, 105 between the conductive plates 103. The rods detect the presence of conductive particles (representing the material of interest – e.g. gold) as the slurry 107 passes by.

Figure 3 provides an illustration of an embodiment of a stack of electrodes 308.

The stack of electrodes 308 includes two positive electrodes 310 and 312 and two negative electrodes 314 and 316. The positive and negative electrodes are separated by a non-conductive spacer element 318. Adjacent positive electrodes 310 and 312 are electrically isolated by a layer, which in this embodiment is a non-conductive spacer 320. Similarly, adjacent negative electrodes 314 and 316 are electrically isolated by a layer, which in this embodiment is a non-conductive spacer 322. Non-conductive layers 320 and 322 are not necessarily the same as non-conductive spacer layer 318. As can be seen in the Figure, the electrodes are of different sizes. Positive electrode 310 and negative electrode 316 are of the same size, with the outer perimeter of these electrodes extending beyond the outer perimeter of electrodes 312 and 314. In this arrangement, four separate circuits can be formed, a first circuit between electrodes 310 1001629580 and 316, a second circuit between electrodes 310 and 314, a third circuit between electrodes 312 and 316, and a fourth circuit between electrodes 312 and 314.

The electrodes are arranged so as to form a flow space 424 for mining material there between.

As can be seen from Figure 3 there are three different electrode spacings, a first electrode spacing between electrodes 310 and 316, a second electrode spacing between electrodes 310 and 314 and electrodes 312 and 316, and a third electrode spacing between electrodes 312 and 314. Due to these different electrode spacings, different size conductive particles will bridge between different electrodes and thus activate different circuits.

Large particles will form a bridge between electrodes 310 and 316 activating the first circuit. Medium sized particles will bridge between either: electrodes 310 and 314, or 312 and 316, activating the second circuit or third circuits. Small particles will bridge between electrodes 312 and 314 activating the fourth circuit. In this way, information as to the size of conductive particles in a mining material can be obtained.

Figure 3 also shows that each of the electrodes 310, 312, 314, and 316 has a bevelled surface. This bevelled surface helps to prevent particulate material from becoming wedged in the flow space 320.

Furthermore, the electrodes 310, 312, 314, and 316 are arranged so that the size of the electrodes sequentially decreases towards the centre of the stack of electrodes.

This arrangement also helps to prevent material from becoming wedged or otherwise entrapped in the flow space 420.

The electrodes shown in Figure 3 may be an entire stack, or only be one portion of the electrodes in a stack. In the latter case, further electrodes may be provided on either side of electrodes 310 and 316 (with appropriate non-conductive material therebetween). These further electrodes may be sequentially larger, thus expanding the range of sizes of the material of interest that can be detected. Alternatively, the further electrodes may be an additional stack of electrodes similar to those of Figure 3 to provide a further stack with the same spacing adjacent to the electrode stack shown in 1001629580 Figure 3. Alternatively, the further stack may be different from the stack shown in Figure 3, and may include a different number or size of electrodes and non-conductive spaces.

Figures 4A and 4B illustrate further embodiments of the present invention which are made using solid state fabrication techniques. In Figure 3 the electrode stack is formed by depositing alternating conductive and insulating layers on a substrate S1, e.g. using chemical vapour deposition or the like. The electrode stack of Figure 4C is formed as follows. The first layer deposited on substrates S1 is a conducting layer in which is formed electrodes E1 and E2. E1 and E2 do not touch each and as such the air gap between them forms a space between the electrodes E1 and E2. On top of this layer an insulating layer is formed to create spacers SP1 and SP2. The spacers SP1 and SP2 leave a small distance at the tips of E1 and E2 exposed to enable contact with mining material in use. This process is repeated to create conductive electrodes E3 and E4 on spacers SP1 and SP2. On top of E3 and E4 further insulating spacers are formed. This continues until the topmost conductive layer is deposited and electrodes formed. Over this topmost conductive layer an optional insulating cover can be deposited to form insulating layers IL1. Each electrode E1 to E8 is connected to the sensor electronics to enable the detection of conductive particles bridging between any pair of opposite polarity electrodes.

Figure 4B is an alternative construction to that of Figure 4A, in that the edges of the deposited layers are the exposed surfaces of the electrodes. In this example, a substrate S1 has deposited on it an conductive layer in which is formed E8. On top of this conductive layer an insulating layer is deposited. This is formed into spacer SP1.

This process of depositing conductive layers and insulating layers continues until electrode E7 is formed. Over this layer an insulating layer IL1 is formed as a cover layer. As with the previous embodiment each electrode formed in the stack is connected to the sensor electronics to enable detection of a conductive particle bridging two of the electrodes.

It will be appreciated that any number of electrodes can be formed in this in any number of layers. For example, multiple electrodes can be formed in a single conductive layer (as illustrated by E1 and E2 in Figure 4A). 1001629580 A wide range of materials can be used to form electrodes, including diamond, silicon carbide, titanium carbide, titanium nitride, boron nitride, tungsten boride, molybdenum carbide, boron, rhenium diboride, stishovite, titanium diboride, carbonado.

These materials can be deposited by vapour deposition (where appropriate) or incorporated as particles in a matrix.

Figure 5 illustrates an embodiment of a simple mining process 500 according to the present invention. An input material 502 is fed through an in-line monitoring system 504 a switch 506 decides where the mining stream is then fed. In the present example, there are two further processing steps, “step A” 508 and “step B” 510. However, it will be understood that further processing steps may be used.

In the present example the in-line monitoring system 504 monitors the input material 502 to determine a concentration of a material of interest in the input material 502. If the concentration of the material of interest is determined to be above a threshold value, the in-line monitoring system 504 uses the switch 506 to divert the input material 502 to further processing step A 508.

Further processing step A 508 may for example be a pre-treatment or extraction step. However, if the concentration of the material of interest is below a threshold value, the in-line monitoring system 504 uses the switch 506 to divert the input material 502 to further processing step B 510.

Further processing step B 510 may for example be a separation step which separates at least some of the gangue from the input material 502 to increase the concentration of the material of interest prior to further processing. Alternatively, step B maybe to reject the input material as tailings due to the concentration of the material of interest being too low to be viable for extraction.

Advantageously, the in-line monitoring system 504 may be used to continuously monitor the input material 502 so that input material 502 that includes a concentration above the desired threshold can be diverted to further processing step A 508, and then if further input material 502 is found to be below the desired threshold, this can be diverted to further processing step B 510, Thus, the in-line monitoring system 504 can provide real time control of the mining process to improve the efficiency of the process. 1001629580 Figure 6 illustrates another embodiment of a mining process 600 that takes an input material 602 and first separates this material according to a number of classification steps 604, 606, and 608. The undersized material 610 from classification step 604 is fed to classification step 606, the undersized material 612 from classification step 606 is fed to 608, the undersized material 614 from classification step 608 is fed to a further processing step 616 which may be a further classification step, a treatment step, or a disposal step.

It is important to note that a variety of classification steps may be used and that the sizes of the constituent components of the input material may vary depending on the nature of the classification step. For example, screening will separate all material into appropriate size ranges. However, other methods, such as the use of a cyclone separator (e.g. a hydrocyclone) will separate material depending on its shape and density. This may result in a situation where you have larger particles that are less dense paired with small particles of a more dense material. By way of example, the oversize/undersize split for a mix of gold and quartz particles may be gold 0.1mm and quartz 1mm.

The oversized material 618 from classification step 604 is fed through an in-line monitoring system 620 which communicates with a switch 622 to divert the material to either further processing step A 624 or further processing step B 626.

Similarly, the oversized material 628 from classification step 606 is fed through an in-line monitoring system 630 which communicates with a switch 632 to divert the material to either further processing step A 634 or further processing step B 636.

The oversized material 638 from classification step 608 is fed through an in-line monitoring system 640 which communicates with a switch 642 to divert the material to either further processing step A 644 or further processing step B 646.

The in-line monitoring steps 620, 630, 640, the switches 622, 632, 642, and the further processing methods 624, 626, 634, 636, 644, 646 may operate in a similar manner to that described above in respect of the process illustrated in Figure 5.

An advantage of this system is that each of the monitoring systems 618, 628, 638 may be fitted with detectors that are optimised and/or calibrated to detect particles in a 1001629580 specific size regime. For example, the detectors may be optimised to have an electrode spacing that is tailored to the expected sizes of the material of interest in the classified input material.

Figure 7 illustrates another embodiment of a mining process 700. In this embodiment an input material 702 is fed to through a grinding/crushing process 704 where the input material is comminuted.

The comminuted material is then fed to a classifier 708 which may generally be as described above with respect to Figure 6. The undersized material 709 is fed to further processing step A 710 which may be a further classification step, treatment step, processing step, or disposal step as generally described above with respect to the other embodiments. The oversized material 712 is fed through an in-line monitoring system 714.

The in-line monitoring system 714 communicates with switch 716 to divert material to either further processing step B 718, or to feed the material back to the grinding/crushing process 704 through a recycle loop 720. As above, further processing step B 718 may be a further classification step, treatment step, processing step, or disposal step as generally described above with respect to the other embodiments.

This embodiment is most likely to be useful with non-alluvial deposits, such as hard rock deposits.

The inventor has also found that the above discussed in-line monitoring device can advantageously be used in systems and methods to monitor unexpected loss of a material of interest (such as a valuable material including gold, silver, copper, and platinum group metals including ruthenium, rhodium, palladium, osmium, iridium, and platinum) due to theft.

Figure 8 provides an illustration of one embodiment of the use of a system for theft detection. In this case, the process includes a black box process 800 which may be any unit process associated with mining or mineral extraction, or alternatively may represent a process train. The process includes an inlet stream 802 with an in-line flow monitoring device 804 and an outlet stream 806 with an in-flow monitoring device 808.

In this embodiment both in-flow monitoring devices 804 and 808 are interfaced with 1001629580 processor 810. Both in-flow monitoring devices 804 and 808 generally operate as discussed previously.

Broadly, in this embodiment, as mining material including the material of interest passes through the in-flow monitoring device 804, a number of detection events will occur. These detection events will be reported to processor 810. Processor 810 will apply an appropriate statistical method to determine the concentration and quantity of the material of interest in the mining material in the inlet stream 802. The mining material is then fed into the black box process. As above, the black box process 800 may be any unit process, such as comminution, classification, various separation processes, or other treatment processes. The black box process 800 may alternatively be a train of processes that includes plural unit processes.

The processed mining material then emerges from the black box process 800 as outlet feed 806. In-line monitoring device 808 will also register a number of detection events corresponding to the concentration and/or quantity of the material of interest in the outlet feed 806. The detection events are reported to processor 810. As above, processor 810 will apply an appropriate statistical method to determine the concentration and quantity of the material of interest in the outlet stream 806.

The processor also compares the difference in the amount of the material of interest determined for the inlet stream 802 against the amount of material of interest determined for the outlet stream 806. If this difference is greater than a threshold difference, then processor 810 will raise an alarm. The alarm may be an audial or visual alarm. However, in this embodiment the alarm is a visual alarm displayed on a computer screen to alert an operator that theft of the material of interest has likely occurred.

There are a number of potential reasons that the amount of the material of interest in the inlet stream 802 and the outlet stream 806 may differ. Setting a threshold value takes these expected differences into account. For example, there may be less material of interest in the outlet stream 806 than in the inlet stream 802 due to (i) samples taken from within the process, (ii) loss due to process inefficiencies, such as outlet waste streams that likely include low concentrations of the material of interest, (iii) margin of error in statistical analysis, etc. 1001629580 That is, a transfer function, residence time distribution, or other probabilistic method is applied to correlate input and output data from the black box process to provide a meaningful comparison between the input and output data while also factoring in the expected losses from the black box process to determine whether an unexpected loss of the material of interest, indicative of theft, has occurred.

In this particular embodiment, the black box process 800 has a residence time τ .

The residence time is the average amount of time that the material of interest takes to pass through the black box process 800. In the case where there is variable feed rate or variable concentration and/or quantity of the material of interest in the inlet feed 802 or the outlet feed 806, the processor 810 delays the comparison between the data reported by in-line monitoring devices 804 and 808 by the residence time.

Furthermore, in some situations, the processor 810 may consider time weighted values representative of the inlet feed 802 and outlet feed 806 concentrations and/or amounts of the material of interest. This may be the case where the inlet feed 802 has a significantly higher mass flow rate than the outlet feed 806 due to, for example, separation and disposal of waste material. In this case, the mass flow in the outlet feed 806 will be substantially lower than the inlet feed 802, and correspondingly the concentration of the material of interest in the outlet feed 806 will be substantially greater than the concentration in the inlet feed 802. In such instances, a time weighted amount of material in the inlet feed 802 may be compared against a time weighted amount of material (the time weightings may be different depending on processing conditions) in the outlet feed 806. Again, the processor will compare the inlet 802 and outlet 806 values and then raise an alarm if this difference exceeds a threshold value while taking into account expected losses.

In still further embodiments, the processor 810 may record inlet 802 and outlet 806 values over extended periods of time and then periodically check the historical amount of the material of interest reported in the inlet feed 802 against the historical amount of the material of interest reported in the outlet feed 806. Again, an alarm will be raised if there is a difference that exceeds the threshold value. The period of time may be over the duration of operation of a particular process or train, and/or may be of the order of hours, days, weeks, months etc. It is expected that extending the period of time 1001629580 over which the reporting and analysis occurs will provide greater accuracy than real- time point comparisons. Thus, different threshold values may be set for comparing data sets compiled over different periods of time to take advantage of the increasing accuracy.

The inlet and outlet in-line monitoring devices 804 and 808 may report detection events continuously, or may be configured to report detection events to the processor 810 at a sampling time interval (which may be of the order of seconds, minutes, or hours depending on the process). Where the in-line monitors 804 and 808 report continuously, the processor 810 can be configured to record and store the corresponding data continuously, or may alternatively be configured to record and store the data at the sampling time interval, for example, although the processor 810 continuously receives data, it only logs data once the sampling time has lapsed. The logged data may be the point data received at that time, or may be averaged over that time. The processor 810 may integrate the data to determine the total amount of the material of interest input and output from the black box process 800 over a period of time.

Figure 9 provides an illustration of another embodiment that includes a first inlet stream 802a with first inlet in-line monitoring device 804a and a second inlet stream 802b with second inlet in-line monitoring device 804b feeding into a black box process 800. The black box process 800 includes only a single outlet stream 806 with outlet in- line monitoring device 808.

In this case, processor 810a is configured to collate data from both inlet in-line monitoring devices 804a and 804b and to determine a total amount of the material of interest that is fed into the black box process 800. This data is then compared against that obtained from the outlet in-flow monitoring device 808 in the same manner as discussed previously. It will be appreciated that additional inlet and outlet streams may be present each with their own in-flow monitoring devices. The processor 810 is configured to rationalise the inlet and outlet data and then compare any difference in the amount of material of interest flowing into the black box process 800 against the amount of material of interest flowing out of the black box process, and to raise an alarm if the difference exceeds a threshold value. 1001629580 Figure 10 provides an illustration of still another embodiment that includes an inlet stream 802 with an in-line monitoring device 804 that feeds a mining material including a material of interest into a black box process 800. The black box process includes two outlet streams, a first outlet stream 806a with a first outlet in-line monitoring device 808a, and a second outlet stream 806b with a second outlet in-line monitoring device 808b. In this case, processor 810b is configured to collate data from both inlet in-line monitoring devices 808a and 808b and to determine a total amount of the material of interest that is fed out of the black box process 800.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention. 1001629580

Claims (26)

1. A mining system for detecting theft of a material of interest from a mining process, the system including: 5 a first in-line monitoring device for detecting a material of interest in a mining material, the first device including: a plurality of electrodes including at least a first electrode which is a positive or a negative electrode, and second and third electrodes which are opposite in charge from the first electrode, 10 the first electrode being separated from the second and third electrodes by a non-conductive space or spaces through which mining material can pass, the first device configured to detect the presence of the material of interest in the mining material as it passes through the space and forms an electrical connection between the first electrode and at least one of the second or third electrodes, and to 15 provide a first value representative of an amount of the material of interest in the mining material; a second in-line monitoring device for detecting the material of interest in a mining material, the second device being located downstream of the first in-line monitoring device, 20 wherein the second device is configured to monitor a portion of the mining material for the material of interest and to provide a second value representative of an amount of the material of interest in the mining material; a processor configured to determine a loss of the material of interest based on the first value and the second value, and to provide an alarm output indicative of theft of 25 the material of interest if the loss exceeds a threshold value.

2. An in-line monitoring process for detecting theft of a material of interest in a mining material, the process including: 1001629580 providing a first in-line monitoring device to a first flow channel for the mining material, the first device including: a plurality of electrodes including at least three electrodes, a first electrode which is a positive or a negative electrode, and second and third electrodes which are 5 opposite in charge from the first electrode; the first electrode being separated from the second and third electrodes by a non-conductive space through which mining material can pass; the first device configured to detect the presence of the material of interest in the mining material as it passes through the space and forms an electrical connection 10 between the first electrode and at least one of the second or third electrodes; transporting the mining material through the flow channel so that at least a portion of the mining material passes through the space; monitoring the portion of the mining material with the first device for the material of interest to determine a first value representative of an amount of the material of 15 interest in the mining material; providing a second in-line monitoring device to either a second flow channel or the first flow channel at a location that is downstream of the first device; monitoring the portion of the mining material with the second device for the material of interest to determine a second value representative of an amount of the 20 material of interest in the mining material; using the first value and the second value to determine a loss of the material of interest; and providing an alarm output indicative of theft of the material of interest if the loss exceeds a threshold value. 25

3. The system of claim 1 or the method of claim 2, wherein the processor is configured to average the first and second values over a sampling time interval, and to log the averaged first and second values. 1001629580

4. The system or method of any one of the preceding claims, wherein the processor is configured to factor in a time delay in comparing the first and second values to account for the rate at which the mining material moves through the system or the residence time of the mining material in the mining process.

5 5. The system or method of any one of the preceding claims, wherein the threshold is greater than the expected losses as a result of general process inefficiencies.

6. The system of any one of the preceding claims, wherein the mining material is able to be directly accessed by a person in at least a portion of the mining process and/or the mining material is exposed to an external environment. 10

7. The system or process of claim 6, wherein the mining process is a storage process, or a transport process for conveyance of the mining material.

8. The system or process of claim 7, wherein the transport process is through an open chute, open flow channel, conveyer, or transported by vehicle.

9. The system or process of claim 8, wherein: 15 the transport process is by vehicle; the first value represents the amount of the material of interest in the mining material being loaded on to the vehicle, and the second value represents the amount of the material of interest in the mining material being offloaded from the vehicle. 20

10. The system or process of claim 6, wherein: the mining process includes at least one unit process or series of unit processes the at least one unit process or the series of unit processes including an inlet and an outlet, the first value represents the amount of the material of interest in the mining 25 material provided to the inlet of the at least one unit process or the series of unit processes, 1001629580 the second value represents the amount of the material of interest in the mining material provided to the outlet of the at least one unit process or series of unit processes; and the mining material is accessible by a person at one or both of the inlet or the 5 outlet, or at a location between the inlet and the outlet.

11. The system or process of any one of the preceding claims, wherein the mining process includes a plurality of in-line monitoring devices for monitoring one or more unit process, mining processes, and/or transport processes.

12. The system or process of any one of the preceding claims, wherein the mining 10 process is a mining site, and the first device is located to determine the quantity of the material of interest in the mining material as it is conveyed from the location at which it is mined, and the second device is located to determine the quantity of the material of interest in the mining material prior to loading for transport offsite.

13. The system or process of any one of the preceding claims, wherein the first 15 electrode is configured to form with each of the second and third electrodes a different electrical circuit.

14. The system or process of any one of the preceding claims, wherein the electrodes are arranged in a stack, with the first electrode being located at a first distance in the stack from the second electrode and at a second distance in the stack 20 from the third electrode, the first distance being less than the second distance.

15. The system or process of any one of the preceding claims, wherein the second and third electrode are electrically separated adjacent electrodes.

16. The system or process of claim 15, wherein the electrodes are in a stepped arrangement, with the third electrode overhanging the second electrode to form the 25 space, the size and shape of the space configured to minimise entrapment of the material of interest and/or mining material.

17. The system or process of any one of the preceding claims, wherein a non- conductive spacer or spacers defines the space or spaces, and the plurality of electrodes are arranged so as to overlap at least a portion of the non-conductive spacer 1001629580 or spacers, the overlap defining the space or spaces between at least the first electrode and the second and third electrodes.

18. The system or process of claim 17, wherein the first device includes a plurality of positive and negative electrodes, the positive and negative electrodes separated from 5 each other by the non-conductive spacers.

19. The system or process of any one claims 17 or 18, wherein the non-conductive spacer is a portion of a flow channel through which the mining material is transported.

20. The system or process of claim 19, wherein the plurality of electrodes are mounted to an outer wall portion of the flow channel. 10

21. The system or process of any one of the preceding claims, wherein the second device is of the same type as the first device and/or is characterised as having the same features as the first device.

22. A mining system for detecting theft of a material of interest from a mining process, the system including 15 a first in-line monitoring device at a first location within the mining process to determine a first value corresponding to an amount of the material of interest in a mining stream at the first location; a second in-line monitoring device at a second location downstream of the first location within the mining process, to determine a second value corresponding to an 20 amount of the material of interest in a mining stream at the second location; a processor configured to determine a difference in the amount of the material of interest at the first location and the second location, and to provide an alarm output if the difference exceeds a threshold value.

23. An in-line monitoring method for determining theft of a material of interest from a 25 mining process, the method including: 1001629580 using a first in-line monitoring device at a first location within the mining process to determine a first value corresponding to an amount of the material of interest in a mining stream at the first location; using a second in-line monitoring device at a second location downstream of the 5 first location within the mining process, to determine a second value corresponding to an amount of the material of interest in a mining stream at the second location; determining a difference in the amount of material of interest at the first location and the second location; and providing an alarm output if the difference exceeds a threshold value. 10

24. The system of claim 22 or the method of claim 23, wherein at least one of the first in-line monitoring device and the second in-line monitoring device includes: a plurality of electrodes including at least three electrodes, a first electrode which is a positive or a negative electrode, and second and third electrodes which are opposite in charge from the first electrode; 15 the first electrode being separated from the second and third electrodes by a non-conductive space through which the mineral stream can pass; the device configured to detect the presence of the material of interest in the mining stream as it passes through the space and forms an electrical connection between the first electrode and at least one of the second or third electrodes. 20 25. A mining system for detecting theft of a material of interest from a mining process, the system including: a first device for in-line monitoring of a mining material from a mining process, the device including: at least two conductive electrodes separated by a non-conductive spacer,

25 the conductive electrodes arranged so as to overlap at least a portion of the non- conductive spacer, the overlap defining a spacing between the two conductive electrodes through which alluvial material can pass, the conductive electrodes 1001629580 configured to detect the presence of a material of interest in the alluvial material as it passes therethrough; and to provide a first value representative of an amount of the material of interest in the mining material; a second device for in-line monitoring of a material of interest in a mining 5 material, the second device being located downstream of the first in-line monitoring device, wherein the second device is configured to monitor a portion of the mining material for the material of interest and to provide a second value representative of an amount of the material of interest in the mining material; a processor configured to determine a loss of the material of interest based on 10 the first value and the second value, and to provide an alarm output indicative of theft of the material of interest if the loss exceeds a threshold value.

26. A method for detecting theft of a material of interest from a mining process, the method including: providing a first device as defined above within a flow path for transporting the 15 mining material, passing at least some of the mining material through the spacing between the two conductive electrodes, the first device providing a first value representative of an amount of the material of interest in the mining material to a processor; providing a second device downstream of the first device within a flow path for 20 transporting the mining material, the second device providing a second value representative of an amount of the material of interest in the mining material to the processor; using the processor to determine a loss of the material of interest based on the first value and the second value, and to provide an alarm output indicative of theft of the 25 material of interest if the loss exceeds a threshold value. 1001629580