GB2621678A

GB2621678A - Mining apparatus and methods

Info

Publication number: GB2621678A
Application number: GB2309007.9A
Authority: GB
Inventors: Davies Robert
Original assignee: Adeptomines Ltd
Current assignee: Adeptomines Ltd
Priority date: 2022-06-17
Filing date: 2023-06-16
Publication date: 2024-02-21
Also published as: GB202208984D0

Abstract

A method of determining the grindability of rock at a site 10 being excavated, comprises collecting a sample of rock from a location at or near at least one planned or actual first blasting hole 30 within the site being excavated; determining from the collected sample at least one first grindability value of the sample; analysing drilling data obtained during the drilling of the or each first blasting hole to determine at least one first drill penetration rate; comparing the or each first grindability value to the first drill penetration rate to determine a correlation; analysing drilling data obtained during the drilling of at least one second blasting hole 40 to determine at least one second drill penetration rate; and determining at least one second grindability value from the second drill penetration rate and the correlation of the first grindability value and the first drill penetration rate. The grindability values may comprise a Bond work index (BWi) value. The method may include determining a predicated throughput of the comminution phase. A method of at a specific mining site is also claimed.

Description

MINING APPARATUS AND METHODS

The present invention relates to the field of mining. In particular, but not exclusively, the present invention relates to methods and apparatus for determining rock properties to predict and/or optimise the performance of the comminution phase.

Mining is the extraction of ore bearing rocks and minerals from the earth. The comminution phase of mining (crushing and milling of the excavated rock) is the largest single user of power within the mining process. Certain rocks and minerals pass through the crushers and mills more quickly than others due to differing levels of resistance to grinding. Assuming constant metal grades, revenues will increase and decrease linearly with changes in the throughput rate. However, comminution circuits often receive rock of highly variable grindability resulting in large fluctuations in throughput and thus revenue. It is common to have throughput deficits of between 5% to 20% and these deficits are directly attributable to the variations in rock grindability.

A small percentage change in throughput (e.g. 1-5%) can have a significant impact on revenue and profitability of mining operations.

It is known to take samples of the rock from the mining site using drilling techniques known as diamond coring. This provides cylinders of rock, which are sent to a laboratory for testing to determine the hardness and grindability of the rock. Typically, dozens of holes are drilled and the test result data is used to generate a 3D model, which attempts to map out variations in comminution characteristics of the rock (e.g. grindability) to allow effective forecasting and proactive mine planning.

However, this is very expensive and it is known that, even with a comprehensive sampling programme, it is not possible to represent the full natural variance within an ore body using core sampling and laboratory testing. There is also a lag time between collecting the samples and being able to implement remedial action in an operational setting of the comminution phase.

The laboratory test data is commonly used to determine the grindability of rocks. Rock grindability is defined using various standard indices, such as Bond work index (BWi). The test work methods are standardised and indices such as BWi are known across the mining industry. BWi is a measure of how much energy is required to reduce the grain size of rock from one set size to another. The higher the index value, the more energy that is needed to complete the set grinding requirement. It is known that the BWi is related to the throughput (Thp) of a Ball Mill. Ball Mill's take crushed rock from the crushing circuit and grind it to produce a powder. It is typically the part of the circuit that defines the overall comminution circuit throughput The relationship between BWi and Ball Mill Thp is known to be as follows: Thp =E1( I 0*BWi*( I /SQRT(P80)-I /SQRT(F80))) Where E = Energy Consumption (kW), F80 = feed particle size (F80 in pm) and P80 = product particle size (P80 in pm).

In mining, explosives are frequently used to break up the rock, which is then excavated and hauled to the crushing plant Blasting holes are drilled by drilling rigs for siting the explosives throughout the rock mass. The blasting holes are typically drilled 1m to 10m apart in a grid arrangement. Increasingly, drilling rigs are being provided with multiple sensors capable of capturing various drilling data. This is known as Measurements Whilst Drilling (MWD). The drilling data is digital and can be stored or transmitted for analysis. The drilling data has been used for various purposes, in particular to plan for future drilling operations.

It has been found that the drilling data can be used to determine the grindability of the rock which can then be used to predict the throughput of the comminution phase and thus revenues.

W02022/016207 describes a method of characterising rock properties using MWD data. However, the MWD data is used to determine an optimal blasting operation, such as the spacing of the blasting holes and the type of explosive to use.

Furthermore, the MWD data is used to derive a rock hardness variable. This is of limited use for optimising comminution phase parameters since rock hardness and grindability are distinct properties. For example, rock hardness primarily depends on the compression strength of the rock, whereas grindability depends on other properties such as the shear strength of the rock.

It is desirable to provide a method of determining the grindability of rock at a site being excavated for ores, so that comminution phase parameters can be optimised.

According to a first aspect of the present invention there is provided a method of determining the grindability of rock at a site being excavated, the method comprising: collecting a sample of rock from a location at or near at least one planned or actual first blasting hole within the site being excavated; determining from the collected sample at least one first grindability value of the sample; analysing drilling data obtained during the drilling of the or each first blasting hole to determine at least one first drill penetration rate; comparing the or each first grindability value to the first drill penetration rate to determine a correlation; analysing drilling data obtained during the drilling of at least one second blasting hole to determine at least one second drill penetration rate; and determining at least one second grindability value from the second drill penetration rate and the correlation of the first grindability value and the first drill penetration rate.

Some aspects and embodiments are based on a system using the penetration rate of a blasting rig to predict the grindability of intact rock.

Some aspects and embodiments are configured specifically for implementation in the real world i.e. a mine environment.

Some methods include a step of drilling twinned holes. Twin drillholes may be used on the mine to prepare an actual (non-theoretical) correlation model.

Some methods/systems calculate through-put for the material in-situ i.e. calculate how the rock will actually perform in the mill.

Some methods/systems calculate mill throughput for material under standardised conditions.

Some methods/systems include a step of producing a 3D grid of points, which can, for example, be automatically imported into mining software (rather than a thematic map, for example). A 3D grid of points is more useful in a real mine environment than a thematic map.

Some embodiments are based on penetration rate correlation with BWI (Relative Bond Work Index BWi / Comparative Grindability).

Some methods and systems make use of rock from a specific mine and actual blast hole data For example some methods and systems require the use of rock from a specific mine and apply a model to actual/real blast hole data.

In some embodiments the system twins blastholes with diamond cored holes, so that samples of the material that is being drilled for blasting is analysed (e.g. sent for BWI test work). The correlation may then be created between real blast hole penetration rates and real BWi results for that actual rock, in that specific mine.

Some systems calculate how the rock would respond to the comminution circuit under standard conditions (i.e. if blast energy was not changed).

Some embodiments calculate how the rock would respond in the comminution circuit under standard conditions, so that the operator can blend from different areas in the mine to ensure that the hard to soft rock blend is optimised for their comminution circuit.

System in accordance with the present invention may be used to optimise blast energy in holes to improve fragmentation.

The collection of samples for generating the correlation may be done with twinning of diamond drill holes.

Optionally, a plurality of samples is collected. Optionally, each sample comprises a column of rock. Optionally, the sample is obtained using diamond core drilling.

Optionally, a plurality of first grindability values is determined from each sample. Optionally, a first grindability value is determined for each of a plurality of vertical depths of the sample.

Optionally, a plurality of first blasting holes is drilled and at least one first drill penetration rate is determined for each blasting hole. Optionally, the spacing between each of the first blasting holes is less than 10 m. Optionally, the spacing between each of the first blasting holes is around 1 m.

Optionally, a plurality of first drill penetration rates is determined for each first blasting hole, each first drill penetration rate determined from a different vertical drilling depth.

Optionally, a plurality of first grindability values is determined. Optionally, the method includes generating a 3D model of the site being excavated, the model displaying the first grindability value at a plurality of locations of the site being excavated.

Optionally, the method includes including the second grindability values in the 3D model.

Optionally, the drilling data comprising one or more of: easting, northing and elevation for the site being excavated; vertical depth; the actual penetration rate; the force on the drill bit; the rotational speed of the drill bit; air pressure; torque; and vibrational data.

Optionally, the first drill penetration rate is an adjusted penetration rate. Optionally, the second drill penetration rate is an adjusted penetration rate. Optionally, the adjusted penetration rate is the actual penetration rate adjusted for at least one of the force on the drill bit, the rotational speed of the drill bit and air pressure.

Optionally, the first grindability value comprises a Bond work index (B\Ni) value.

Optionally, the second grindability value comprises a Bond work index (BVVi) value, or other grindability indices used in the mining industry.

Optionally, the step of comparing the or each first grindability value to the first drill penetration rate to determine a correlation comprises generating at least one regression formula.

Optionally, the at least one second grindability value is determined from the second drill penetration rate and the regression formula.

Optionally, the step of determining the at least one second grindability value from the second drill penetration rate and the correlation is carried out in real time or close to real time.

Optionally, the method includes determining a predicted throughput of the comminution phase from the correlation of the grindability value and the drill penetration rate.

Optionally, the method includes determining a predicted process energy consumption of the comminution phase from the correlation of the grindability value and the drill penetration rate.

Optionally, the method includes adjusting at least one parameter of the comminution phase based on the predicted throughput.

Optionally, the method includes optimisation of selected feed and feed blends to comminution phase based on the predicted throughput A further aspect provides a method to determine grindability of rock at a specific mining site being excavated, the method comprising: drilling twinned holes; collecting a sample of rock from a location at or near at least one planned or actual first blasting hole within the site being excavated; determining from the collected sample at least one first grindability value of the sample; analysing drilling data obtained during the drilling of the or each first blasting hole to determine at least one first drill penetration rate; comparing the or each first grindability value to the first drill penetration rate to determine a correlation; analysing drilling data obtained during the drilling of at least one second blasting hole to determine at least one second drill penetration rate; and determining at least one second grindability value from the second drill penetration rate and the correlation of the first grindability value and the first drill penetration rate.

Methods may further comprise the step of determining a correlation between real blast hole penetration rates and real BWi results for the actual rock, in the specific mine so as to determine how the rock would respond to a comminution circuit under standard conditions.

Different aspects and embodiments of the invention may be used separately or together.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with the features of the independent claims as appropriate, and in combination other than those explicitly set out in the claims. Each aspect can be carried out independently of the other aspects or in combination with one or more of the other aspects.

The present invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure I is a perspective view of an excavation site; Figure 2 is a flowchart of a method according to the invention; and Figure 3 is a graph plotting drill penetration rate against BWi.

Example embodiments are described below in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.

Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.

The terminology used herein to describe embodiments is not intended to limit the scope. The articles "a," "an," and "the" are singular in that they have a single referent, however the use of the singular form in the present document should not preclude the presence of more than one referent In other words, elements referred to in the singular can number one or more, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including," when used herein, specify the presence of stated features, items, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, items, steps, operations, elements, components, and/or groups thereof Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealized or overly formal sense unless expressly so defined herein.

Referring first to Figure 1, there is shown an excavation site 10. A grid arrangement of blasting holes has been drilled using a drilling rig (not shown) where the blasting holes are typically 5m to 8m apart. Also shown are holes 20 created during diamond core drilling to obtain a sample of rock. Each of these holes 20 is located near a blasting hole, typically within 1 m from the blasting hole. These blasting holes which are next to the holes 20 created to obtain a sample will be referred to as first blasting holes 30. The remaining blasting holes will be referred to as second blasting holes 40.

Figure 2 shows a flowchart of a method a method of determining the grindability of rock according to the present invention.

In step 100, samples of rock are collected, each sample from a location near a first blasting hole 30. The samples are carefully labelled including their location within the excavation site. Each sample comprises a column of rock and is obtained using diamond core drilling. The column of rock will vary in its properties across its length which represents the vertical depth of drilling. Each sample provides multiple sample points. Typically, the sample points are 1 m apart.

In step 110, each sample is tested and a set of first grindability values are determined.

Preferably, this testing is carried out at or near the excavation site 10. The grindability values are determined by testing for the BWi. Each determined first grindability value corresponds to a particular sample and also a particular vertical depth of that sample. Therefore, each determined first grindability value corresponds to a particular known 3D location within the excavation site.

In step 120, drilling data obtained during the drilling of each first blasting hole is analysed. The drilling data is MWD data which may have been stored at the site or transmitted to a remote location. The MWD data includes 3D data (easting, northing and elevation for the site being excavated and the vertical drilling depth), as well as the actual penetration rate, the force on the drill bit, the rotational speed of the drill bit, air pressure, torque and vibrational data. The 3D location of each first grindability value is also known. Therefore, each first grindability value can be matched to a particular drill penetration rate obtained from a location in close proximity (typically within I m to 2 m horizontally or vertically) to the location of the sample point giving that first grindability value.

The actual drill penetration rate is adjusted so that it is as representative of the grindability of the rock as possible. Therefore, it is adjusted to take account of the force on the drill bit, the rotational speed of the drill bit and the air pressure.

The adjusted penetration rate is a normalised penetration rate that removes the influence of drilling parameters, for example (but not limited to) feed force and torque.

The adjusted penetration rate is a more representative proxy for the character of the rock mass than penetration rate alone.

The adjusted penetration rate (APR) is calculated as follows: APR = PR/(force/average of all force records)*SQRT(torque/average of all torque records) *100 In step 130, each first grindability value is compared to the corresponding first drill penetration rate to determine a correlation. The relationship between grindability and drill penetration rate can be plotted and an example is shown in Figure 3.

In Figure 3, the 'X's are from test results providing the BWi value (X value) and the matched drill penetration rate (Y value). It has been found that there is a strong (inverse) linear correlation between the drill penetration rate and grindability. The gradient of a regression line (or line of best fit) through the data points provides a regression formula (or conversion factor) between the two variables. Once this is known, a predicted grindability value can readily be obtained for any other drill penetration rate.

Once the correlation between grindability and drill penetration rate is known, grindability values can be predicted for other locations within the excavation site as explained below. This substantially decreases the amount of sampling and testing that is required which significantly lowers the cost involved.

In step 140, drilling data (MWD data) obtained during the drilling of the second blasting holes is analysed to determine corresponding second drill penetration rates.

The MWD data can be received and analysed in real time or near real time.

In step 150, from the second drill penetration rates a set of second grindability values are readily determined using the correlation of the first grindability values and the first drill penetration rates. Referring again to Figure 3, the '0' is a predicted BWi using the second drill penetration rate obtained from MWD data at a nearby location and using the known regression formula.

The blasting holes are typically between 1m to 10m apart. Also, the drill penetration rate is known at each stage of the drilling so that discrete values are available for, say, each 1 m step if vertical depth. Therefore, it is possible to generate a 3D model of the site being excavated, the model displaying first and second grindability values and having a 1 m vertical and 1 to 10m horizontal resolution.

As stated, BWi (grindability) is a measure of how much energy is required to grind the material to a particular size. Therefore, at known energy input and BWi, the throughput of the comminution circuit associated with rock from each point in the 3D model can be estimated.

Similarly, for known throughput values, the energy required at each point in the 3D model can be estimated. This can be summated to provide a value for the total energy that will be required during the comminution phase.

A predicted throughput of the comminution phase can be determined using the equation previously stated. This allows revenues to be predicted in advance of the comminution phase (during which the majority of the energy will be expended).

Also, during the comminution phase, operators knowing the local location and the local values of grindability of a batch of material can optimise the operational settings of the comminution phase. The improved performance will result in increases in revenues.

Optimisation could include selection and blending of feed material, optimisation of blasting and crushing parameters, as well as optimisation of milling parameters, such as mill speed, grinding media size, shape and type, and level of solids loading.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims

CLAIMSI. A method of determining the grindability of rock at a site being excavated, the method comprising: collecting a sample of rock from a location at or near at least one planned or actual first blasting hole within the site being excavated; determining from the collected sample at least one first grindability value of the sample; analysing drilling data obtained during the drilling of the or each first blasting hole to determine at least one first drill penetration rate; comparing the or each first grindability value to the first drill penetration rate to determine a correlation; analysing drilling data obtained during the drilling of at least one second blasting hole to determine at least one second drill penetration rate; and determining at least one second grindability value from the second drill penetration rate and the correlation of the first grindability value and the first drill penetration rate.
2. A method as claimed in Claim I, wherein a plurality of samples is collected.
3. A method as claimed in Claim I or 2, wherein a plurality of first grindability values is determined from each sample.
4. A method as claimed in Claim 3, wherein a first grindability value is determined for each of a plurality of vertical depths of the sample.
5. A method as claimed in any preceding claim, wherein a plurality of first blasting holes is drilled and at least one first drill penetration rate is determined for each blasting hole.
6. A method as claimed in any preceding claim, wherein the spacing between each of the first blasting holes is less than 10 m.
7. A method as claimed in Claim 6, wherein the spacing between each of the first blasting holes is around I m.
8. A method as claimed in any preceding claim, wherein a plurality of first drill penetration rates is determined for each first blasting hole, each first drill penetration rate determined from a different vertical drilling depth.
9. A method as claimed in any preceding claim, wherein a plurality of first grindability values is determined.
10. A method as claimed in Claim 9, wherein the method includes generating a 3D model of the site being excavated, the model displaying the first grindability value at a plurality of locations of the site being excavated
I I. A method as claimed in Claim 10, wherein the method includes including the second grindability values in the 3D model.
12. A method as claimed in any preceding claim, wherein the drilling data comprising one or more of: easting, northing and elevation for the site being excavated; vertical depth; the actual penetration rate; the force on the drill bit; the rotational speed of the drill bit; air pressure; torque; and vibrational data.
13. A method as claimed in any preceding claim, wherein the first drill penetration rate is an adjusted penetration rate.
14. A method as claimed in Claim 13, wherein the second drill penetration rate is an adjusted penetration rate.
15. A method as claimed in Claim 13 or 14, wherein the adjusted penetration rate is the actual penetration rate adjusted for at least one of the force on the drill bit, the rotational speed of the drill bit and air pressure.
16. A method as claimed in any preceding claim, wherein the first grindability value comprises a Bond work index (BWi) value.
17. A method as claimed in any preceding claim, wherein the second grindability value comprises a Bond work index (BWi) value.
18 A method as claimed in any preceding claim, wherein the step of comparing the or each first grindability value to the first drill penetration rate to determine a correlation comprises generating at least one regression formula.
19. A method as claimed in any preceding claim, wherein the at least one second grindability value is determined from the second drill penetration rate and the regression formula.
20. A method as claimed in any preceding claim, wherein the step of determining the at least one second grindability value from the second drill penetration rate and the correlation is carried out in real time or close to real time.
21. A method as claimed in any preceding claim, wherein the method includes determining a predicted throughput of the comminution phase from the correlation of the grindability value and the drill penetration rate.
22. A method as claimed in any preceding claim, wherein the method includes determining a predicted process energy consumption of the comminution phase from the correlation of the grindability value and the drill penetration rate.
23. A method as claimed in any preceding claim, wherein the method includes adjusting at least one parameter of the comminution phase based on the predicted 30 throughput.
24. A method to determine grindability of rock at a specific mining site being excavated, the method comprising: drilling twinned holes; collecting a sample of rock from a location at or near at least one planned or actual first blasting hole within the site being excavated; determining from the collected sample at least one first grindability value of the sample; analysing drilling data obtained during the drilling of the or each first blasting hole to determine at least one first drill penetration rate; comparing the or each first grindability value to the first drill penetration rate to determine a correlation; analysing drilling data obtained during the drilling of at least one second blasting hole to determine at least one second drill penetration rate; and determining at least one second grindability value from the second drill penetration rate and the correlation of the first grindability value and the first drill penetration rate.
25, A method as claimed in claim 24, comprising the step of determining a correlation between real blast hole penetration rates and real BWi results for the actual rock, in the specific mine so as to determine how the rock would respond to a comminution circuit under standard conditions.