Drilling method and equipment

Abstract

The present disclosure relates to a method and a pulsed power drilling equipment (100) comprising a plurality of electrodes (110) for excavating ore from a rock body (1). The method comprises: - identifying, in the rock body (1), a first rock portion comprising a first rock material and a second rock portion comprising a second rock material, - selecting a first set of electrodes for breaking the first rock portion, - selecting a second set of electrodes for breaking the second rock portion, - breaking the first rock portion by passing a pulsed electric current through the first rock portion using the first set of electrodes, - breaking the second rock portion by passing a pulsed electric current through the second rock portion using the second set of electrodes, and - separating fragmented first rock material from fragmented second rock material by a separation arrangement (130).

Description

[0001] DRILLING METHOD AND EQUIPMENT

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a method for excavating ore from a rock body, a pulsed power drilling equipment, and a drill rig. The disclosed pulsed power drilling equipment and method for excavating ore may for example be applied in rock drilling and continuous mining, such as for selectively extracting valuable ore from the rock body.

[0004] BACKGROUND

[0005] There are currently two main methods that are used for mining of hard rock, namely drill and blast, and mechanical excavation. Both methods typically result in course rock fragments, which are transported from the mine in which the rock fragments were excavated to a processing plant on the ground surface for continued processing. To extract valuable minerals from the excavated rock fragments, the fragments are typically first crushed using jaw, cone, or impact crushing. The crushed material is thereafter ground to very fine particles, which are later separated in a floatation cell, where various chemicals are added to make different minerals adhere to air bubbles.

[0006] Since the same rock fragment may contain valuable ore as well as non-desired waste rock, a lot of waste material is transported to the processing plant together with the valuable ore. The separation at the processing plant therefore typically results in a large amount of waste material that may either be dumped in a waste pile near the processing plant or transported back into the mine for use as backfill.

[0007] Crushing and milling of rock fragments are energy intensive processes. In view of this, there is a desire to reduce the amount of material that has to be subjected to these processes to extract valuable ore from a rock body, and thereby reduce the total energy consumption of the mining process. SUMMARY

[0008] A primary object of the present disclosure is to achieve an in at least some aspect improved method for excavating ore from a rock body, and an in at least some aspect improved pulsed power drilling equipment for excavating ore from a rock body. In particular, it is an object to achieve such a method and drilling equipment that may contribute to a reduction of the total energy consumption of the mining process.

[0009] According to a first aspect of the disclosure, at least the primary object is achieved by the method for excavating ore from a rock body defined in claim 1. The method uses a pulsed power drilling equipment comprising a plurality of electrodes provided on a drill head of the pulsed power drilling equipment. The method comprises: identifying, in the rock body, a first rock portion comprising a first rock material and a second rock portion comprising a second rock material, selecting a first set of electrodes from the plurality of electrodes for breaking the first rock portion, selecting a second set of electrodes from the plurality of electrodes for breaking the second rock portion, breaking the first rock portion by passing a pulsed electric current through the first rock portion using the first set of electrodes, thereby obtaining fragmented first rock material, breaking the second rock portion by passing a pulsed electric current through the second rock portion using the second set of electrodes, thereby obtaining fragmented second rock material, and separating the fragmented first rock material from the fragmented second rock material.

[0010] The disclosed method enables selective breaking of at least two different types of rock material within a rock body, such that the different rock materials may be separated already in connection with drilling. In this way, the amount of energy required for the separation process as a whole may be significantly reduced in comparison with processes involving crushing, milling, and separation in a floatation cell. According to the proposed method, the separation can be achieved without crushing and milling, or at least with crushing and milling of significantly less material. Furthermore, transports of the fragmented rock material from a mine in which the drilling is carried out may be made much more energy efficient, since valuable ore may be separated from waste rock before any of the fragmented material is transported away from the mine. Unnecessary transports of waste rock may hence be avoided.

[0011] The method may be used for breaking and separating more than two different rock portions of a rock body. For example, if three different rock portions are provided comprising three different rock materials, three sets of electrodes may be provided.

[0012] Optionally, separating the fragmented first rock material from the fragmented second rock material is performed below a ground surface of the rock body, such as in a mine. Hence, the separation may be carried out in immediate connection with the drilling, in the mine or at a drill site. It will thereby be possible to, if desired, transport the fragmented first and second rock materials from the mine I drill site to different locations. This will diminish unnecessary transports of fragmented material.

[0013] Optionally, the first rock material comprises a high-grade ore and the second rock material comprises waste rock, wherein the method further comprises transporting the fragmented first rock material to the ground surface. In this way, the valuable high-grade ore may be separated from waste rock already below the ground surface before it is transported up to the ground surface where it is further refined. Since transportation up to the ground surface requires large amounts of energy, it is beneficial when the waste ore can be left behind in the mine, e.g., for use as a filling material, while the high-grade ore is transported to the ground surface.

[0014] Optionally, breaking the first rock portion comprises controlling the first set of electrodes to break the first rock portion into first rock fragments having a first size distribution, and breaking the second rock portion comprises controlling the second set of electrodes to break the second rock portion into second rock fragments having a second size distribution, the first size distribution being different from the second size distribution. In this way, separation of the first and second rock fragments may be performed based on rock fragment size. Standard equipment may be used for such a separation.

[0015] Optionally, the first rock material comprises a high-grade ore and the second rock material comprises waste rock, wherein an average rock fragment size of the first rock fragments is smaller than an average rock fragment size of the second rock fragments. This facilitates transportation of the high-grade ore to the ground surface. Furthermore, the possibility to control the size of the first rock fragments during drilling makes it possible to significantly reduce the energy consumption in connection with crushing and milling of the excavated high-grade ore.

[0016] Optionally, the first set of electrodes are controlled to use a first pulsed electric current for breaking the first rock portion and the second set of electrodes are controlled to use a second pulsed electric current for breaking the second rock portion, the first pulsed electric current differing from the second pulsed electric current in at least one of pulse repetition frequency, pulse duration, pulse voltage, pulse current, and pulse rise time. This enables control of the rock fragment size during breaking of the respective rock portions.

[0017] Optionally, separating the fragmented first rock material from the fragmented second rock material is performed based on rock fragment size.

[0018] Optionally, separating the fragmented first rock material from the fragmented second rock material based on rock fragment size comprises mechanically screening the rock fragments. A sieve may be used for this purpose.

[0019] Optionally, an average electrode-to-electrode spacing within the first set of electrodes is different from an average electrode-to-electrode spacing within the second set of electrodes. The average electrode-to-electrode spacing is the average distance between each two electrodes between which the pulsed electric current is passed. By using different electrode-to-electrode spacings, the rock fragment size may be controlled.

[0020] Optionally, breaking the first and second rock portions comprises controlling the first and second set of electrodes, respectively, to simultaneously break said first and second rock portions. This is suitable when the first and second rock portions can be fragmented into first and second rock fragments of different sizes, respectively, and / or when further properties of the first and second materials may be considered during the separation process after fragmentation, such as magnetic properties, dielectric and / or piezo-electric properties, density, etc.

[0021] Optionally, breaking the first and second rock portions comprises controlling the first and second set of electrodes to sequentially break the first and second rock portions of a rock layer of the rock body. This allows separation of the first and second rock material in cases where separation based on rock fragment size, or material properties, is not possible or not deemed suitable.

[0022] Optionally, separating the fragmented first rock material from the fragmented second rock material comprises removing the fragmented first rock material of the rock layer prior to breaking the second rock portion of the rock layer, or vice versa. Hence, a sequential process of a) breaking using one set of electrodes, b) removing, c) breaking using another set of electrodes, and d) removing rock fragments, is applied in each rock layer.

[0023] Optionally, selecting the first and second set of electrodes is performed based on electrode positions of individual electrodes within the plurality of electrodes relative to the first and second rock portions, respectively. The first set of electrodes may hence be selected among those electrodes that are suitably located for breaking the first rock material, and the second set of electrodes selected among those electrodes that are suitably located for breaking the second rock material.

[0024] Optionally, selecting the first set of electrodes comprises detecting, within the plurality of electrodes, first electrodes that are located directly above the first rock portion, and selecting the first set of electrodes from the first electrodes. This will ensure that a pulsed electric current passed between two electrodes within the first set of electrodes will pass through the first rock portion. The first set of electrodes may comprise all first electrodes, or a subset of the first electrodes.

[0025] Optionally, selecting the second set of electrodes comprises detecting, within the plurality of electrodes, second electrodes that are located directly above the second rock portion, and selecting the second set of electrodes from the second electrodes. This will ensure that a pulsed electric current passed between two electrodes within the second set of electrodes will pass through the second rock portion. The second set of electrodes may comprise all second electrodes, or a subset of the second electrodes.

[0026] Optionally, identifying the first rock portion and the second rock portion, respectively, comprises measuring at least one property of the rock body using at least some of the plurality of electrodes, wherein the at least one property differs between the first and second rock materials. This may be realised by temporarily connecting the electrodes that are to be used for the measurement to a measurement circuit such that they can be used for material characterization. Accurate and rapid identification of the first and second rock portions can thereby be achieved prior to breaking the rock body.

[0027] Optionally, the drilling equipment may comprise sensors for measuring at least one property of the rock body, wherein identifying the first rock portion and the second rock portion, respectively, may comprise measuring the at least one property of the rock body using at least some of the sensors, and wherein the at least one property differs between the first and second rock materials. The sensors may be used to measure the at least one property prior to a drilling operation, and / or during the drilling operation.

[0028] Optionally, identifying the first rock portion and the second rock portion, respectively, comprises using a map of the rock body, such as a map generated through core drilling. Such a map may be generated beforehand and may be useful when it is not possible or suitable to use the electrodes for material characterization.

[0029] According to a second aspect of the disclosure, at least the primary object is achieved by the pulsed power drilling equipment defined in claim 17. The pulsed power drilling equipment for excavating ore from a rock body comprises:

[0030] - a pulsed power generator configured to generate high voltage current pulses,

[0031] - a drill head comprising a plurality of electrodes, each electrode being configured to be selectively electrically connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator to allow for a high voltage current pulse generated by the pulsed power generator to pass between two electrodes among the plurality of electrodes of the drill head via the rock body,

[0032] - an electronic control unit configured to: o identify, in the rock body, a first rock portion comprising a first rock material and a second rock portion comprising a second rock material, o select a first set of electrodes from the plurality of electrodes for breaking the first rock portion, o select a second set of electrodes from the plurality of electrodes for breaking the second rock portion, o control the drill head to break the first rock portion by passing a pulsed electric current through the first rock portion using the first set of electrodes, thereby obtaining fragmented first rock material, o control the drill head to break the second rock portion by passing a pulsed electric current through the second rock portion using the second set of electrodes, thereby obtaining fragmented second rock material, and

[0033] - a separation arrangement arranged to separate the fragmented first rock material from the fragmented second rock material.

[0034] Advantages and advantageous embodiments of the second aspect largely correspond to those of the first aspect.

[0035] Optionally, the separation arrangement is configured to be arranged in a proximity of the drill head, such as at the same vertical level as the drill head with respect to a ground surface of the rock body. This reduces unnecessary transportations of fragmented rock material.

[0036] Optionally, the electronic control unit is configured to control the first set of electrodes to break the first rock portion into first rock fragments having a first size distribution, and to control the second set of electrodes to break the second rock portion into second rock fragments having a second size distribution, the first size distribution being different from the second size distribution, wherein the separation arrangement is a mechanical screening arrangement.

[0037] Optionally, the pulsed power drilling equipment further comprises a transport arrangement arranged to transport the fragmented first rock material to a ground surface of the rock body in connection with the separation. The transport arrangement may be a fluid transportation arrangement comprising a pump or another flow source, or a transport arrangement comprising at least one of a vehicle, a conveyor, a rail, and an elevator.

[0038] According to a third aspect of the disclosure, a drill rig comprising the pulsed power drilling equipment according to the second aspect is provided. The drill rig may be configured for rock drilling and continuous mining, such as for selectively extracting valuable ore from the rock body using the method according to the first aspect.

[0039] Further advantages and advantageous features of the disclosure are disclosed in the following description and in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In the following, the technology disclosed will be described in detail, with reference to exemplifying embodiments and to the enclosed drawings. In the drawings:

[0041] Fig. 1 schematically illustrates a pulsed power drilling equipment according to an embodiment of the disclosure,

[0042] Fig. 2a schematically illustrates first and second portions of a rock body,

[0043] Fig. 2b schematically illustrates a drill head according to an embodiment of the disclosure,

[0044] Fig. 3 schematically illustrates separation of rock fragments according to an embodiment of the disclosure,

[0045] Fig. 4 schematically illustrates a pulsed power drilling equipment according to an embodiment of the disclosure,

[0046] Fig. 5 is a flow-chart illustrating steps of a method according to an embodiment of the disclosure,

[0047] Fig. 6 is another flow-chart illustrating steps of a method according to an embodiment of the disclosure,

[0048] Fig. 7 is another flow-chart illustrating steps of a method according to an embodiment of the disclosure, and

[0049] Fig. 8 is a drill rig comprising a pulsed power drilling equipment according to an embodiment of the disclosure.

[0050] The drawings show diagrammatic, exemplifying embodiments of the present disclosure and are thus not necessarily drawn to scale. It shall be understood that the embodiments shown and described are exemplifying and that the disclosure is not limited to these embodiments. It shall also be noted that some details in the drawings may be exaggerated in order to better describe and illustrate the disclosure. Like reference characters refer to like elements throughout the description, unless expressed otherwise.

[0051] DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE DISCLOSURE The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.

[0052] The present disclosure relates to a method and a drilling equipment for excavating ore from a rock body, such as for excavating ore from an ore deposit within a host rock. Rock bodies are typically heterogeneous and comprise a number of different rock materials, such as different minerals having different chemical compositions. Only some of the rock materials of the rock body may be of interest to excavate. For example, the rock body may contain valuable high-grade ore of different kinds as well as waste rock that has to be mined to access the valuable ore.

[0053] Fig. 1 schematically illustrates a pulsed power drilling equipment 100 according to an embodiment of the disclosure. The drilling equipment 100 is arranged for excavating ore from a rock body 1 by drilling a hole 5. For this purpose, it comprises a pulsed power generator 150 configured to generate high voltage current pulses and a drill head 101 comprising a plurality of electrodes 110. Herein, the plurality of electrodes is illustrated by a first electrode 110 and a second electrode 110’, although the number of electrodes may preferably be larger than two. Each electrode 110, 110’ is configured to be selectively electrically connected to the pulsed power generator 150 and to carry a discharge generated by the pulsed power generator 150 to allow for a high voltage current pulse, generated by the pulsed power generator 150, to pass between two electrodes 110, 110’ among the plurality of electrodes of the drill head 101 via the rock body 1. Some or all of the electrodes 110 may be arranged at fixed positions of the drill head 101. In some embodiments, at least some of the electrodes 110 may be arranged to be movable on the drill head 101, such that the movable electrode(s) can be moved to a desired position prior to passing the high voltage current pulse. A locking arrangement may be provided to lock the movable electrode(s) in desired position(s) on the drill head 101.

[0054] The pulsed power generator 150 illustrated in Fig. 1 comprises a pulse transformer 151 in the form of a bank of capacitors, connected to a power supply, e.g., an alternating current (AC) power supply 152 via a transformer 153. The pulsed power generator 150 comprises a first circuit (not shown) for generating high voltage current pulses and the electrodes 110, 110’ may be connected to the pulsed power generator 150 by closing switches 114, 114’. Using the switches 114, 114’, a short high voltage current pulse generated by use of the first circuit may be transferred to the electrodes 110, 110’. The pulsed power generator 150 is configured for generating high voltage current pulses used for breaking the rock body 1, such as nanosecond (ns) pulses.

[0055] The electrodes 110 are arranged at a front end 102 of the drill head 101. Each one of the first and second electrodes 110, 110’ comprises a solid electrode portion made at least partially of an electrically conductive material, such as a metallic or ceramic material. At least a part of the solid electrode portion must be heat resistant. By way of example, the solid electrode portion may be made of tungsten, stainless steel, aluminum, copper, or ceramics. The electrodes may be identical, or they may have different configurations. The solid electrode portion of one or both electrodes 110, 110’ may be arranged in direct contact with the rock body 1 , or an ionized fluid volume (not shown) may be formed that extends between the rock body 1 and the solid electrode portion of the respective electrode 110, 110’. To prevent discharges from passing between the electrodes 110, 110’ without entering the rock body 1, an isolating volume should be provided between the electrodes 110, 110’, such as between the two ionized fluid volumes. The isolating volume may, e.g., be a non-ionized fluid volume.

[0056] The first and second electrodes 110, 110’ may be galvanically connectable to the pulsed power generator 150 by means of the switches 114, 114’. This is achieved by galvanically connecting the first and second electrodes 110, 110’ to the switches 114, 114’, respectively. A high voltage current pulse generated by the first circuit of the pulsed power generator 110 can thereby pass to the first electrode 110, where a discharge can form between the first electrode 110 and the rock body 1 , either by the solid electrode portion of the first electrode 110 being in direct contact with the rock body 1 , or by an ionized fluid volume as mentioned above extending between the rock body 1 and the solid electrode portion of the first electrode 110. As the switches 114, 114’ are closed, the high voltage current pulse passes between the first electrode 110 and the second electrode 110’ via the rock body 1. As a result, a plasma channel is formed in the rock body 1 and it is broken.

[0057] The drilling equipment 100 further comprises an electronic control unit 140 for controlling operation of the drilling equipment 100, and a separation arrangement 130. The electronic control unit 140 may include a microprocessor, a microcontroller, a programmable digital signal processor or another programmable device. Thus, the control unit 140 comprises electronic circuits and connections (not shown) as well as processing circuitry (not shown) for communicating with different parts and systems of the drilling equipment 100 as well as with any external control unit(s) used to control operation of the drilling equipment. For example, the control unit 140 may be configured for communicating with various sensors, devices, systems and control units of the drilling equipment 100. In the shown embodiment, the control unit 140 controls at least the transformer 153 and the switches 114, 114’. The electronic control unit 140 may be embodied by several separate sub-units configured to communicate with one another.

[0058] The electronic control unit 140 may comprise modules in either hardware or software, or partially in hardware or software, and communicate using known transmission buses such a CAN-bus and / or wireless communication capabilities. The processing circuitry may be a general-purpose processor or a specific processor. The control unit 140 may comprise a non-transitory memory for storing computer program code and data. Thus, the skilled person realizes that the electronic control unit 140 may be embodied by many different constructions.

[0059] Fig. 2a schematically illustrates a portion of a rock layer 2 of the rock body 1, corresponding to a drilled surface, and Fig. 2b schematically illustrates the front end 102 of a drill head 101 of a drilling equipment 100 according to an embodiment of the present disclosure. The rock body 1 is herein seen from the drill head 101, and the portion of the rock layer 2 has the same extension as the front end 102 of the drill head 101. The rock body 1 comprises a first rock portion 3 comprising a first rock material and a second rock portion 4 comprising a second rock material, different from the first rock material. By way of example, the first rock portion 3 may comprise valuable high-grade ore, and the second rock portion 4 may comprise waste rock. The illustrated drill head 101 comprises a plurality of electrodes 110 arranged in a regular pattern at the front end 102 of the drill head 101. When the drill head 101 is located above the portion of the rock body 1 illustrated in Fig. 2a, some of the electrodes 110, illustrated as black circles, will be located above the first rock portion 3, as indicated by the dotted line, and some of the electrodes 110, illustrated as white circles, will be located above the second rock portion 4. The electrodes located above the first rock portion 3 are herein first electrodes comprising a first set of electrodes 111 and the electrodes located above the second rock portion 4 are second electrodes comprising a second set of electrodes 112. The first set of electrodes 111 , selected for breaking the first rock portion 3, may comprise some or all of the first electrodes located above the first rock portion 3. The second set of electrodes 112, selected for breaking the second rock portion, may comprise some or all of the second electrodes located above the second rock portion 4.

[0060] The first and second electrodes may be identical electrodes. Which ones of the electrodes 110 that will be first electrodes and which ones that will be the second electrodes depend only on the positions of the individual electrodes 110 relative to the first and second rock portions 3, 4. Hence, in a rock drilling operation in which the drill head 101 is advanced into the rock body 1 layer by layer, the set of first electrodes 111 may comprise different electrodes for each rock layer 2 depending on the extension of the first rock portion 3 in that particular rock layer 2. Correspondingly, the second set of electrodes 112 may comprise different electrodes for the different rock layers 2.

[0061] The electronic control unit 140 is configured to identify, in the rock body 1, the first rock portion 3 comprising the first rock material and the second rock portion 4 comprising the second rock material. It is further configured to select a first set of electrodes 111 from the plurality of electrodes 110 for breaking the first rock portion 3, and to select a second set of electrodes 112 from the plurality of electrodes 110 for breaking the second rock portion 4. The electronic control unit 140 is further configured to control the drill head 101 to break the first rock portion 3 by passing a pulsed electric current through the first rock portion 3 using the first set of electrodes 111, thereby obtaining fragmented first rock material in the form of first rock fragments, and to control the drill head 101 to break the second rock portion 4 by passing a pulsed electric current through the second rock portion 4 using the second set of electrodes 112, thereby obtaining fragmented second rock material in the form of second rock fragments.

[0062] The separation arrangement 130 is arranged to separate the fragmented first rock material from the fragmented second rock material. The separation arrangement 130 may be configured to be arranged in a proximity of the drill head 101, such as at the same vertical level as the drill head 101 with respect to a ground surface 6 of the rock body 1. A fluid supply arrangement (not shown) may be provided for supplying a flushing fluid, such as water, to the drill head 101. The flushing fluid may be locally ionized to form the ionized fluid volume(s) by using, e.g., a laser beam, a plasma generator, or microwave radiation.

[0063] The identification of the first and second rock portions 3, 4 will now be described in greater detail.

[0064] In order to identify the first and second rock portions 3, 4, the drilling equipment 100 may in some embodiments comprise an arrangement for measuring properties of the rock body 1. Such an arrangement is schematically illustrated in Fig. 4. The arrangement for measuring properties of the rock body 1 may comprise a measurement unit 190 configured to measure at least one property of the rock layer 2 using at least some of the plurality of electrodes 110, wherein the at least one property differs between the first and second rock materials. In one example, the electrodes 110, 110’ of the drill head 101 may be temporarily connected to the measurement unit 190 via switches 115, 115’, where the measurement unit 190 comprises a second circuit for generating radar signals (not shown). As the switches 115, 115’ are temporarily closed during a measurement phase, the radar signals generated by the second circuit are allowed to be transmitted to and subsequently emitted from the connected electrodes 110, 110’. The connected electrodes 110, 110’ are thereby temporarily functioning as antennas for transmitting / emitting a radar signal generated by the second circuit into the rock body 1. Thus, the arrangement for measuring properties of the rock body 1 further temporarily includes the connected electrodes 110, 110’, where each of the connected electrodes 110, 110’ comprises a receiving circuit and a detector (not shown) for receiving reflected waves of the radar signals transmitted from the connected electrodes 110, 110’ included in the arrangement for measuring properties of the rock body 1. The reflected waves detected by the detector and receiving circuit of the respective electrode 110, 110’ indicate properties of the rock body 1. In the example embodiment shown in Fig. 4, each of the first electrode 110 and the second electrode 110’ comprises a receiving circuit and detector for receiving a radar signal reflected from the mineral substrate, i.e., reflected radar waves, and the measurement data obtained from the detection of the reflected radar signals is then transmitted or forwarded to the measurement unit 190. The measurement unit 190 is configured to determine properties of the rock body at least partly based on the measurement data / reflected radar signals, such as reflectance, refraction, and / or absorption.

[0065] The drilling equipment 100 may in other embodiments be configured to determine the at least one rock property by measuring the impedance between selected pairs of electrodes. By measuring the impedance between several combinations of electrodes that are also configured to carry a discharge during a drilling operation, a complete picture of the minerals of the drilled surface can be found and a pair of electrodes for carrying a subsequent discharge, or several pairs of electrodes for carrying the respective discharge in a sequence of subsequent discharges, may be selected based on the measured at least one property.

[0066] In some embodiments, the arrangement for measuring properties of the rock body 1 may comprise dedicated sensors (not shown) that may be used to measure the at least one property of the rock body 1. A combination of measurements using the sensors and the electrodes, respectively, may be used.

[0067] In other embodiments, the electronic control unit 140 may be configured to identify the first and second rock portions 3, 4, respectively, by using a map of the rock body 1, such as a map generated through core drilling. The core drilling may be performed prior to the excavation with the purpose of characterizing the rock body 1 and finding high-grade ore deposits therein. During the core drilling, one or more solid cylinders of rock material is / are extracted from the rock body 1. The cylinder(s) is / are analysed to generate a map of the rock body 1, showing an extension and a location of any ore deposits present within the rock body 1. As an alternative to core drilling, percussion drilling yielding a crushed sample from a drilled hole may be used, wherein the crushed sample comprises rock fragments from a particular depth within the hole. The generated map may be stored in a memory of the electronic control unit 140, or elsewhere where it can be accessed by the electronic control unit 140.

[0068] The separation of the first rock material from the second rock material may be carried out in different ways as will be further explained in the following.

[0069] According to a first example, the separation is performed based on rock fragment size as illustrated in Fig. 3. The electronic control unit 140 is in this case configured to control the first set of electrodes 111 to break the first rock portion 3 into first rock fragments 10 having a first size distribution, and to control the second set of electrodes 112 to break the second rock portion 4 into second rock fragments 20 having a second size distribution. The first size distribution is different from the second size distribution, such that the first and second rock materials can be separated based on rock fragment size. The separation arrangement 130 may be a mechanical screening arrangement, such as a screening arrangement comprising a sieve, configured to separate the rock fragments 10, 20 based on size.

[0070] To control the size of the first and second rock fragments 10, 20, the electronic control unit 140 may be configured to control the first set of electrodes 111 to use a first pulsed electric current for breaking the first rock portion 3 and to control the second set of electrodes 112 to use a second pulsed electric current for breaking the second rock portion 4. The first pulsed electric current may differ from the second pulsed electric current in at least one pulse parameter, such as pulse repetition frequency, pulse duration, pulse voltage, pulse current, and / or pulse rise time to achieve different rock fragment sizes. The selection of pulse parameter(s) may, by way of example, be based on previous tests or historical data relating the pulse parameter(s) to rock fragment size for different materials. The electronic control unit 140 may further be configured to select an average electrode-to-electrode spacing within the first set of electrodes 111 to be different from an average electrode-to-electrode spacing within the second set of electrodes 112. The average electrode-to-electrode spacing is the average distance between each two electrodes between which the pulsed electric current is passed. When the electrodes 110 are evenly distributed across the front end 102 of the drill head 101, such as illustrated in Fig. 2b, the electrode-to-electrode spacing may be varied by selecting the electrodes between which the high voltage current pulse is passed.

[0071] The electronic control unit 140 may in the first example be configured to break the first and second rock portions 3, 4 such that an average rock fragment size of the first rock fragments 10 is smaller than an average rock fragment size of the second rock fragments 20. The first rock material may comprise a high-grade ore and the second rock material may comprise waste rock. In the drill head 101 illustrated in Fig. 2b, this may be achieved by activating neighbouring electrodes within the first set of electrodes 111 to obtain a relatively small rock fragment size, and by activating electrodes located further apart within the second set of electrodes 112 to obtain a larger rock fragment size. In the first example, the first and second set of electrodes 111 , 112, respectively, may be configured to simultaneously break said first and second rock portions 3, 4. In this case, “simultaneously” is to be interpreted as prior to the separation of the first and second rock fragments 10, 20. Hence, the first and second rock portions 3, 4 of a rock layer 2 are fragmented using the first and second sets of electrodes 111 , 112, respectively, prior to the separation of the obtained rock fragments 10, 20. The first and second set of electrodes 111, 112 may not necessarily be controlled such that multiple high voltage current pulses are passed through the rock body 1 at the exact same time, although it may also, depending on drill head configuration, be possible to pass multiple pulses at the exact same time.

[0072] In a second example, the separation is performed based on a material property of the fragmented first and second rock materials, respectively, such as magnetic properties, dielectric and / or piezo-electric properties, density, etc.

[0073] In a third example, the separation is performed based on time rather than size. In this example, the first and second set of electrodes 111, 112 are controlled to sequentially break the first and second rock portions 3, 4 of the rock layer 2 of the rock body 1. The separation arrangement 130 may in this example be arranged to remove the fragmented first rock material of the rock layer 2 prior to breaking the second rock portion 4 of the rock layer 2, or vice versa. By way of example, the control unit 140 may first activate the first set of electrodes 111 to break the first rock portion 3 of the rock layer 2, and subsequently the separation arrangement 130 is used to remove the obtained first rock fragments 10. Only after the first rock fragments 10 have been removed, the second set of electrodes 112 is activated to break the second rock portion 4 of the rock layer 2, whereafter the obtained second rock fragments 20 are removed. Once the second rock fragments have been removed, the drill head 101 may be further advanced into a drilled hole and the process is repeated. The rock layer 2 may herein be understood as a rock layer having a thickness such that it can be fragmented without advancing the drill head 101.

[0074] In all the above examples, the separation arrangement 130 may be connected to a transport arrangement 160 arranged to transport the fragmented first rock material to the ground surface 6 of the rock body 1 in connection with the separation. The transport arrangement 160 may be a fluid-based transport arrangement in which pressurized fluid, such as water or air, is used to transport the first rock material to the ground surface 6. Of course, the transport arrangement may also comprise means for transporting the second rock material to the ground surface 6, if desired, such as a separate fluid-based transport arrangement. In other examples, a vehicle comprising a bucket (not shown) may be provided for transporting at least the first rock material to the ground surface 6.

[0075] A method for excavating ore from a rock body 1 using the pulsed power drilling equipment 100 as described above is illustrated in Fig. 5. The method comprises the following actions:

[0076] Action S1 : identifying, in the rock body 1, a first rock portion 3 comprising a first rock material and a second rock portion 4 comprising a second rock material. This action may, in some examples, be performed by measuring at least one property of the rock body 1 using at least some of the plurality of electrodes 110, wherein the at least one property differs between the first and second rock materials. In other examples, it may be performed using a map of the rock body 1, such as a map generated through core drilling or percussion drilling as described above.

[0077] Action S2: selecting a first set of electrodes 111 from the plurality of electrodes 110 for breaking the first rock portion 1.

[0078] Action S3: selecting a second set of electrodes 112 from the plurality of electrodes 110 for breaking the second rock portion 4.

[0079] The selection of electrodes in actions S3 and S4 may be performed based on electrode positions of individual electrodes 110 within the plurality of electrodes relative to the first and second rock portions 3, 4, respectively. For example, selecting the first set of electrodes 111 may comprise detecting, within the plurality of electrodes 110, first electrodes that are located directly above the first rock portion 3, and selecting the first set of electrodes 111 from the first electrodes. Selecting the second set of electrodes 112 may comprise detecting, within the plurality of electrodes 110, second electrodes that are located directly above the second rock portion 4, and selecting the second set of electrodes 112 from the second electrodes. Reference is made to Figs. 2a and 2b, illustrating selection of the first and second set of electrodes 111 , 112 based on electrode positions relative to the first and second rock portions 3, 4. Action S4: breaking the first rock portion 3 by passing a pulsed electric current through the first rock portion 3 using the first set of electrodes 111 , thereby obtaining fragmented first rock material.

[0080] Action S5: breaking the second rock portion 4 by passing a pulsed electric current through the second rock portion 4 using the second set of electrodes 112, thereby obtaining fragmented second rock material.

[0081] Action S6: separating the fragmented first rock material from the fragmented second rock material. This may comprise separating the first rock fragments 10 from the second rock fragments 20 based on, e.g., rock fragment size.

[0082] As illustrated in Fig. 5, the method may further comprise the following optional actions:

[0083] Action S7: transporting the fragmented first rock material to the ground surface 6. This action may preferably be performed when the first rock material comprises a high-grade ore.

[0084] Action S8: leaving the second rock material below the ground surface 6 while the first rock material is transported to the ground surface 6. This is particularly relevant when the second rock material comprises waste rock, which may be used as a filling material to fill the drilled hole after the ore has been excavated.

[0085] A method according to an embodiment of the disclosure, in which separation is carried out based on rock fragment size, is illustrated in the flow chart in Fig. 6. Following the actions S1-S3 described above, the method according to the illustrated embodiment comprises the following actions:

[0086] Action S4-1 : controlling the first set of electrodes 111 to break the first rock portion 3 into first rock fragments 10 having a first size distribution.

[0087] Action S5-1 : controlling the second set of electrodes 112 to break the second rock portion 4 into second rock fragments 20 having a second size distribution different from the first size distribution. Action S6-1: separating the fragmented first rock material from the fragmented second rock material based on rock fragment size of the first and second rock fragments 10, 20, such as by mechanically screening the rock fragments 10, 20.

[0088] Action S10: Advancing the drill head further down into the drilled hole. This may be performed once the fragmented first and second rock materials have been removed from the drilled surface.

[0089] Action S11 : Determining whether an adjustment of the electrodes used to break the first and second rock portions is necessary. If yes, the method proceeds to the actions S2, S3 of selecting the first and second sets of electrodes 111 , 112, respectively. If no, the method proceeds to the action S4-1.

[0090] The actions may be repeated as many times as desired.

[0091] A method according to another embodiment of the disclosure, in which fragmentation and separation are carried out sequentially, is illustrated in the flow chart in Fig. 7. The method differs from the method illustrated in Fig. 5 in that the action S4 of breaking the first rock portion 3 is immediately followed by an action S6-21 of removing the fragmented first rock material from the drilled surface, after which the action S5 of breaking the second rock portion 4 follows. An action S6-22 of removing the fragmented second rock material from the drilled surface follows immediately, after which the drill head 101 is advanced in the action S10. Although not illustrated, the actions may be repeated as discussed above with reference to Fig. 6.

[0092] Fig. 8 schematically illustrates a drill rig 800 comprising the drilling equipment 100 according to an embodiment of the disclosure, drilling a hole 5 in a rock body 1. The drill rig 800 comprises the power supply, e.g., alternating current (AC) power supply 152, for powering the pulsed power generator 110. It further comprises a compressed gas supply system 830 and a fluid supply system 840 for supplying flushing fluid to the drilled hole. A hydraulic, pneumatic, or electrically actuated arm 810 for at least vertical positioning of the drilling equipment 100 is provided, such as in response to signals from one or more position sensors (not shown) or similar sensing the distance between the electrodes 110, 110’ and the rock surface within the hole 5. The drill rig 800 further comprises ground engaging members 820 for moving the drill rig 800 in a direction parallel with the ground surface 6 of the rock body 1.

[0093] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

Claims

CLAIMS1. A method for excavating ore from a rock body (1) using a pulsed power drilling equipment (100) comprising a plurality of electrodes (110) provided on a drill head (101) of the pulsed power drilling equipment, the method comprising: identifying (S1), in the rock body (1), a first rock portion (3) comprising a first rock material and a second rock portion (4) comprising a second rock material, selecting (S2) a first set of electrodes (111) from the plurality of electrodes for breaking the first rock portion, selecting (S3) a second set of electrodes (112) from the plurality of electrodes for breaking the second rock portion, breaking (S4) the first rock portion by passing a pulsed electric current through the first rock portion using the first set of electrodes, thereby obtaining fragmented first rock material, breaking (S5) the second rock portion by passing a pulsed electric current through the second rock portion using the second set of electrodes, thereby obtaining fragmented second rock material, and separating (S6) the fragmented first rock material from the fragmented second rock material.

2. The method according to claim 1, wherein separating the fragmented first rock material from the fragmented second rock material is performed below a ground surface (6) of the rock body.

3. The method according to claim 2, wherein the first rock material comprises a highgrade ore and the second rock material comprises waste rock, and wherein the method further comprises: transporting (S7) the fragmented first rock material to the ground surface.

4. The method according to any one of the preceding claims, wherein breaking the first rock portion comprises controlling (S4-1) the first set of electrodes (111) to break the first rock portion into first rock fragments (10) having a first size distribution, and breaking the second rock portion comprises controlling (S5-1) the second set of electrodes (112) to break the second rock portion into second rock fragments (20) having a second size distribution, the first size distribution being different from the second size distribution.

5. The method according to claim 4, wherein the first rock material comprises a highgrade ore and the second rock material comprises waste rock, and wherein an average rock fragment size of the first rock fragments (10) is smaller than an average rock fragment size of the second rock fragments (20).

6. The method according to claim 4 or 5, wherein the first set of electrodes (111) are controlled to use a first pulsed electric current for breaking the first rock portion (3) and the second set of electrodes (112) are controlled to use a second pulsed electric current for breaking the second rock portion (4), the first pulsed electric current differing from the second pulsed electric current in at least one of pulse repetition frequency, pulse duration, pulse voltage, pulse current, and pulse rise time.

7. The method according to any one of claims 4-6, wherein separating the fragmented first rock material from the fragmented second rock material is performed based on rock fragment size.

8. The method according to claim 7, wherein separating the fragmented first rock material from the fragmented second rock material based on rock fragment size comprises mechanically screening the rock fragments.

9. The method according to any one of the preceding claims, wherein an average electrode-to-electrode spacing within the first set of electrodes is different from an average electrode-to-electrode spacing within the second set of electrodes.

10. The method according to any one of the preceding claims, wherein breaking the first and second rock portions comprises controlling the first and second set of electrodes, respectively, to simultaneously break said first and second rock portions.

11. The method according to any one of claims 1-9, wherein breaking the first and second rock portions comprises controlling the first and second set of electrodes to sequentially break the first and second rock portions of a rock layer of the rock body.

12. The method according to claim 11, wherein separating the fragmented first rock material from the fragmented second rock material comprises removing the fragmentedfirst rock material of the rock layer prior to breaking the second rock portion of the rock layer, or vice versa.

13. The method according to any one of the preceding claims, wherein selecting the first and second set of electrodes is performed based on electrode positions of individual electrodes within the plurality of electrodes relative to the first and second rock portions, respectively.

14. The method according to any one of the preceding claims, wherein selecting the first set of electrodes comprises detecting, within the plurality of electrodes, first electrodes that are located directly above the first rock portion, and selecting the first set of electrodes from the first electrodes, and / or wherein selecting the second set of electrodes comprises detecting, within the plurality of electrodes, second electrodes that are located directly above the second rock portion, and selecting the second set of electrodes from the second electrodes.

15. The method according to any one of the preceding claims, wherein identifying the first rock portion and the second rock portion, respectively, comprises measuring at least one property of the rock body using at least some of the plurality of electrodes, wherein the at least one property differs between the first and second rock materials.

16. The method according to any one of claims 1-14, wherein identifying the first rock portion and the second rock portion, respectively, comprises using a map of the rock body, such as a map generated through core drilling.

17. A pulsed power drilling equipment (100) for excavating ore from a rock body (1), comprising:- a pulsed power generator (150) configured to generate high voltage current pulses,- a drill head (101) comprising a plurality of electrodes (110), each electrode being configured to be selectively electrically connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator to allow for a high voltage current pulse generated by the pulsed power generator to pass between two electrodes among the plurality of electrodes of the drill head via the rock body,- an electronic control unit (140) configured to: o identify, in the rock body, a first rock portion (3) comprising a first rock material and a second rock portion (4) comprising a second rock material, o select a first set of electrodes (111) from the plurality of electrodes for breaking the first rock portion, o select a second set of electrodes (112) from the plurality of electrodes for breaking the second rock portion, o control the drill head (101) to break the first rock portion by passing a pulsed electric current through the first rock portion using the first set of electrodes, thereby obtaining fragmented first rock material, o control the drill head to break the second rock portion by passing a pulsed electric current through the second rock portion using the second set of electrodes, thereby obtaining fragmented second rock material, and- a separation arrangement (130) arranged to separate the fragmented first rock material from the fragmented second rock material.

18. The pulsed power drilling equipment according to claim 17, wherein the separation arrangement is configured to be arranged in a proximity of the drill head, such as at the same vertical level as the drill head with respect to a ground surface (6) of the rock body (1).

19. The pulsed power drilling equipment according to claim 17 or 18, wherein the electronic control unit is configured to control the first set of electrodes to break the first rock portion into first rock fragments (10) having a first size distribution, and to control the second set of electrodes to break the second rock portion into second rock fragments (20) having a second size distribution, the first size distribution being different from the second size distribution, and wherein the separation arrangement is a mechanical screening arrangement.

20. The pulsed power drilling equipment according to claim 18 or 19, further comprising a transport arrangement (160) arranged to transport the fragmented first rock material to a ground surface (6) of the rock body (1) in connection with the separation.

21. A drill rig (800) comprising the pulsed power drilling equipment (100) according to any one of claims 17-20.

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