FIELD OF THE INVENTION

The present invention relates to the field of mineral and metallurgi- cal processes, to comminution processing or disintegrating in general and to comminution processing by crushers and tumbling mills, and more particularly to a method and arrangement for controlling of a comminution process.

BACKGROUND OF THE INVENTION

One of the most common processes in mining and metallurgy is the comminution processing or disintegrating of ore. Comminution is achieved by blasting, crushing and grinding.

In general, there are some problems with the prior art solutions for controlling of a comminution process. The problem therefore is to find a more reliable and accurate solution for controlling of a comminution process.

There is a demand in the market for a method for controlling of a comminution process which method would provide a better controlled comminution process when compared to the prior art solutions. Likewise, there is a demand in the market for an arrangement for controlling of a comminution process which arrangement would have a better controlled comminution process when compared to the prior art solutions.

BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is thus to provide a method and an apparatus for implementing the method so as to overcome the above problems and to alleviate the above disadvantages.

The objects of the invention are achieved by a method for controlling of a comminution process, which method comprises a step of:

- monitoring the flow of ore before entering a grinding circuit of said comminution process, in which said step of monitoring 3D reconstruction measurement data for reconstruction of a three-dimensional image profile of said ore is measured with a imaging system, and

which said method comprises steps of:

- receiving rock size distribution data of said ore said rock size distribution data being calculated based on said measured 3D reconstruction measurement data; and - receiving one or more distinct property values for one or more rock size variables said one or more distinct property values being calculated based on said measured 3D reconstruction measurement data,

- wherein said one or more rock size variables include one or more of the following: a volumetric flow of a certain specified largest percentage of particles, a volumetric flow of a certain specified smallest percentage of particles, a volumetric flow of a certain specified mid-size range of particles, a particle count of a certain specified largest percentage of particles, a particle count of a certain specified smallest percentage of particles, a particle count of a cer- tain specified pebble size range of particles.

Preferably, said method comprises a step of calculating rock size distribution data of said ore based on said measured 3D reconstruction measurement data. Preferably, said method comprises a step of calculating one or more distinct property values for one or more rock size variables based on said measured 3D reconstruction measurement data. Preferably, said ore is conveyed by a conveyor, and that said imaging system is placed in the vicinity of said conveyor.

Preferably, said method comprises a step of detecting oversize ore, e.g. particles with diameter over 200 mm, preferably 400 to 600 mm. Further preferably, said method comprises a step of stopping or slowing the conveyor and removing the detected oversize ore.

Preferably, said method comprises a step of detecting and classifying ore based on size to e.g. fine ore, e.g. particles with diameter under 30 mm and/or pebble ore, e.g. particles with diameter 30 to 80 mm, preferably 60 to 70 mm, and/or lump ore, e.g. particles with diameter 80 to 200 mm. Further preferably, said method comprises a step of controlling grinding mill speed and/or mass feed and/or water addition and/or ball addition and/or pebbles feed to a grinding circuit of said comminution process based on said detected and classified ore.

Preferably, said method comprises a step of receiving comminution process data for controlling said comminution process, said comminution process data including one or more of the following data: mass feed, water addition, ball addition, pebbles feed, grinding mill speed, hardness, density, ore specific gravity, elemental analysis, ore grade, grinding product size, grinding mill power draw, grinding mill torque, grinding mill bearing pressure and grinding mill charge. Furthermore, the objects of the invention are achieved by an arrangement for controlling of a comminution process, said controlling arrangement comprising a system for monitoring the flow of ore before entering a grinding circuit of said comminution process, which

- said monitoring system of said controlling arrangement comprises an imaging system, said imaging system measuring 3D reconstruction measurement data for reconstruction of a three-dimensional image profile of said ore; which

- said controlling arrangement comprises a control block receiving a calculated rock size distribution data of said ore, said rock size distribution data being calculated based on said measured 3D reconstruction measurement data; and which

- said control block receiving one or more distinct property values for one or more rock size variables said one or more distinct property values being calculated based on said measured 3D reconstruction measurement data,

- wherein said one or more rock size variables include one or more of the following: a volumetric flow of a certain specified largest percentage of particles, a volumetric flow of a certain specified smallest percentage of particles, a volumetric flow of a certain specified mid-size range of particles, a par- tide count of a certain specified largest percentage of particles, a particle count of a certain specified smallest percentage of particles, a particle count of a certain specified pebble size range of particles.

Preferably, said imaging system is placed in the vicinity of a conveyor, by which said conveyor said ore is conveyed. Preferably, said imaging system comprises at least one imaging device.

Further preferably, said imaging system comprises a structured light source, and a first imaging device of said at least one imaging device is placed in the angle of 0-150 degrees, preferably 15-60 degrees, more preferably 30- 40 degrees compared to the line laser source, which first imaging device ac- quires 3D reconstruction measurement data for three-dimensional reconstruction from said ore conveyed by said conveyor.

Further preferably, said imaging system comprises a structured light source, and a second imaging device of the at least one imaging device is placed at the opposing side to said first imaging device and in the angle of 0- 150 degrees, preferably 15-60 degrees, more preferably 30-40 degrees compared to the line laser source, which second imaging device acquires 3D re- construction measurement data for three-dimensional reconstruction from said ore conveyed by said conveyor.

Preferably, at least one imaging device acquires 3D reconstruction measurement data for three-dimensional reconstruction from said ore as it is travelling on said conveyor. Alternatively, at least one imaging device acquires 3D reconstruction measurement data for three-dimensional reconstruction from said ore as it is exiting said conveyor. Preferably, said control block detects oversize ore, e.g. particles with diameter over 200 mm, preferably 400 to 600 mm. Further preferably, when oversize ore is detected said arrangement stops or slows the conveyor and removes the detected oversize ore.

Preferably, said control block detects and classifies ore based on size to e.g. fine ore, e.g. particles with diameter under 30 mm and/or pebble ore, e.g. particles with diameter 30 to 80 mm, preferably 60 to 70 mm, and/or lump ore, e.g. particles with diameter 80 to 200 mm. Preferably, said control block controls grinding mill speed and/or mass feed and/or water addition and/or ball addition and/or pebbles feed to a grinding circuit of said comminution process based on said detected and classified ore.

Preferably, said control block has an input for receiving comminution process data for controlling said comminution process, said comminution pro- cess data including one or more of the following data: mass feed, water addition, ball addition, pebbles feed, grinding mill speed, hardness, density, ore specific gravity, elemental analysis, ore grade, grinding product size, grinding mill power draw, grinding mill torque, grinding mill bearing pressure and grinding mill charge.

Preferably, said arrangement further comprises a data storage block, into which data storage block at least some of the calculated process values, i.e. the rock size distribution data and/or the one or more values for the one or more rock size variables are stored. Preferably, at least some of measured process values are stored to a data storage block. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a flow diagram of one example of a comminution process according to the present invention;

Figure 2 shows a side view of one embodiment of an arrangement for monitoring the flow of ore travelling on a conveyor belt from the crusher to the grinding mill according to the present invention; Figure 3 shows a side view of one embodiment of an arrangement for measuring of a three-dimensional image profile of the ore travelling on a conveyor belt from the crusher to the grinding mill of grinding circuit according to the present invention;

Figure 4 shows a backside view of a conveyor belt and a three- dimensional imaging system of one embodiment of an arrangement for measuring of a three-dimensional image profile of the ore travelling on a conveyor belt from the crusher to the grinding mill of grinding circuit according to the present invention;

Figure 5 shows a schematic diagram of one embodiment of an arrangement for controlling of a comminution process according to the present invention;

Figure 6 shows a schematic diagram of another embodiment of an arrangement for controlling of a comminution process according to the present invention;

Figure 7 shows a schematic diagram of one embodiment of a screening circuit of a comminution process according to the present invention;

Figure 8 shows a schematic diagram of one embodiment of a comminution control unit of an arrangement for controlling of a comminution pro- cess according to the present invention;

Figure 9 shows a schematic diagram of another embodiment of a comminution control unit of an arrangement for controlling of a comminution process according to the present invention;

Figure 10 shows one embodiment of a graph diagram of rock size distribution in an arrangement for controlling of a comminution process according to the present invention.

In the following, the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings of Figures 1 to 10. DETAILED DESCRIPTION OF THE INVENTION

Ore comminution is part of mining and metallurgy processing. When processing material for the selective or collective recovery of valuable material components, the processes concerned are preceded by comminution processing i.e. mechanical crushing, grinding, or disintegration of the material in a manner to free valuable from worthless components. Comminution is particle size reduction of materials. Comminution is achieved by blasting, crushing and grinding. After comminution the components are then mutually isolated with the aid of known separation methods, this isolation being contingent on differences in color, shape, density or in differences in their respective surface active and magnetic properties, or other properties.

In comminution processing first ore or rock is excavated, broken down or removed by blasting. Blasting is the controlled use of explosives and other methods in mining, quarrying and civil engineering. Typically blasting produces top size particles of several decimeters or more and can to a degree control particle size distribution through a targeted powder factor.

Crushing is particle size reduction of ore or rock materials by using crushing devices i.e. crushers. Crushers e.g. jaw crushers, gyratory crushers or cone crushers are used to reduce the size, or change the form, of materials. In the crushing process the crushing devices hold material being crushed be- tween two parallel or tangent solid surfaces of a stronger material and apply sufficient force to bring said surfaces together. Typically in a crushing process particles having a diameter up to 1000 mm are crushed to particles having a diameter of 5 mm or more.

Screening is typically carried out after crushing. In screening the ore is passed through a number of screens in a screening station. The screens in a screening station have openings or slots that continue to become smaller and smaller. Screening is used to produce different ore products based on an ore size range.

Grinding is particle size reduction of ore or rock materials in grinding mills such as tumbling, roller, or various types of fine grinding mills which can be arranged in either a vertical or horizontal orientation. In hard rock mining and industrial mineral operations the demands for rotating mineral and metallurgical processing equipment such as grinding mills are very high both in terms of grinding efficiency and energy consumption. Typically in a grinding process particles of a diameter as large as 150mm or more are ground to particles having a diameter of sub-millimeter size or smaller, depending on whether a series of staged size reduction in different types of mills is employed, and depending on the type of mill and its operational setting. This conventional grinding of materials results in considerable wear on sacrificial liners installed inside the mechanical framework of the mill, due to the hardness and associat- ed friction of the rock concerned, therewith also resulting in considerable costs for the provision of such grinding bodies.

Comminution processing equipment such as grinding mill is typically very large, having a diameter of several meters. Grinding mills may be trun- nion-supported or shell-supported. Trunnion support is the most common way of supporting a mill in a mineral processing application, especially in very large grinding mills. Shell-supported grinding mills are more compact, occupy less floor space and require simpler foundations than comparable trunnion- supported grinding mills.

Coarse ore particle grinding mills are commonly either autogenous

(AG) or semi-autogenous (SAG) grinding mills designed for grinding of primary crushed ore. Autogenous grinding mills are so-called due to the self-grinding of the ore. In an autogenous grinding mill a rotating drum throws ore in a cascading motion of the mill content (charge) which causes impact breakage by larger rocks and compressive grinding of particles below the charge surface. In autogenous grinding the actual material itself, i.e. the material to be ground, forms the grinding media.

Semi-autogenous grinding mills are similar to autogenous mills, but utilize grinding media e.g. steel grinding balls to aid in grinding. Impact and attrition between grinding balls and ore particles causes grinding of coarse particles into finer particles. Semi-autogenous grinding mills typically use a grinding ball charge of 8 to 21 %, sometimes the total charge may be higher. Autogenous and semi-autogenous grinding mills are generally used as a primary or first stage grinding solution. They are primarily used at gold, copper and plati- num mines with applications also in the lead, zinc, silver, alumina and nickel industries.

Ball mills are tumbling mills like SAG and AG mills, but are typically employed in a comparably fine grinding duty, often as a second stage behind SAG and AG mills. Like SAG mills, they use steel balls as grinding media, al- beit of smaller diameter than SAG mills.

Autogenous and semi-autogenous grinding mills are characterized by their large diameter and short length as compared to ball mills, which are typically long with a smaller diameter. Tumbling mills are typically driven by ring gears, with a 360° fully enclosing guard. The inside of comminution equipment such as a tumbling mill is lined with sacrificial liners. Mill liner materials typically include steel, cast iron, solid rubber, rubber-steel composites or ceramics. Mill liners include lifters, e.g. lifter bars to lift the material inside the mill, where it then falls off the lifters onto the rest of the ore charge.

Comminution processing equipment that is provided with internal lifters is subject to changes in performance due to the change in liner shape caused by abrasive wear. For example, in autogenous grinding mills or semi- autogenous grinding mills the feed to the mill also acts as a grinding media, and changes in the feed have a strong effect on the grinding performance. Change in the feed properties, i.e. change in the feed parameters is a normal phenomenon that needs to be considered in controlling the comminution pro- cessing equipment.

Mineral deposits rarely have a homogenous structure or a homogenous mechanical strength. In regard to the feed parameters of a grinding process, the ore properties such as hardness, particle size, density and ore type also change constantly and this makes the control of the grinding process cliff i - cult, e.g. a constantly varying energy input is required.

The comminution process of a grinding mill is typically controlled on the basis of mill power draw as a grinding process parameter, yet power draw is sensitive to changes in feed parameters and mechanical properties of the grinding process and is often not a suitable indicator of grinding conditions in- side the mill . Another grinding process parameter is the measurement of mill charge mass. However, mass measurement has its own problems in installation, calibration, and in measurement drift. Moreover, there may be intensive variations in the load density as well as significant variations in liner weight due to wear, in which case changes in the mass do not necessarily result from changes in fill level i.e. the grinding mill charge as percentages of mill volume. Fill level of the mill expressed as percentage of mill volume is a quantity that is very stable, descriptive and useful as an indicator in regards the state of the mill and therefore its efficiency.

It has been discovered that in an optimal grinding process control measured grinding process parameters such as e.g. power draw, torque, bearing pressure, product size and mill load mass and also degree of fullness as percentages of mill volume would also require the knowledge of feed quantity and distribution in a grinding process.

As the grinding process control has a proper knowledge of both the measured grinding process parameters and the feed quantity of the grinding process it can carry out calculations for calculating of the degree of fullness in the mill as percentages of the mill volume and for determining grinding control parameters for controlling the grinding process such as e.g. mass feed, water addition, circulated pebbles, ball addition and speed.

The present invention relates to a method and arrangement for con- trolling of a comminution process, which provides a better controlled and more efficient comminution process when compared to the prior art solutions.

According to the present embodiment a three-dimensional image profile of the ore travelling on a conveyor belt is acquired by using a 3D camera (3D, three-dimensional) for scanning or photographing said ore travelling on a conveyor belt. There are several 3D technologies that can be used to obtain the 3D image profile. One approach is to use a system consisting of a line laser source and a digital imaging sensor, such as e.g. a CCD imaging sensor (CCD, Charge-Coupled Device) or a CMOS imaging sensor (CMOS, Complementary Metal-Oxide-Semiconductor).

Figure 1 shows a flow diagram of a comminution process according to the present invention. A comminution process according to the present invention comprises the process blocks for a crushing circuit 1 , a screening process 2 and a grinding circuit 3. In a comminution process according to the present invention the crushing circuit process block 1 is carried out first. In the crushing circuit 1 the ore or rock material is crushed between two solid surfaces of a stronger material. In crushing the particle size of ore is substantially reduced. The crushing circuit 1 produces crushed ore for the screening process 2.

In screening process block 2 the ore is passed through a number of screens in a screening station. The screens in a screening station have openings or slots that continue to become smaller and smaller. In screening 2 different ore products based on an ore grade or an ore size range are produced.

After the screening process 2 the crushed and screened ore is forwarded to the grinding circuit process block 3. In the grinding circuit 3 the ore or rock material is ground in a grinding mill such as e.g. a tumbling mill, roller mill or a fine grinding mill. In the grinding circuit 3 the particle size of ore is reduced. Typically in a grinding circuit process block 3 particles of a diameter as large as 150mm or more are ground to particles having a diameter of sub- millimeter size or smaller.

Figure 2 shows a side view of an arrangement for monitoring the flow of ore travelling on a conveyor belt from the crusher to the grinding mill according to the present invention. The presented ore monitoring arrangement shows a conveyor belt 4 travelling clockwise from the crusher to the grinding mill. The conveyor belt 4 is first being fed ore 5 from the crusher, thereafter conveyor belt 4 conveys the ore 5 from left to right to the feed of the grinding mill.

In the presented ore monitoring arrangement of Figure 2 there is a laser measurement unit 6 for measuring the surface height of ore travelling on a conveyor belt. The laser measurement unit 6 according to the present invention comprises a laser light source and a laser measurement receiver. The la- ser light source of the laser measurement unit 6 generates laser light pulses towards the ore 5 travelling on a conveyor belt 4 from the crusher to the grinding mill. The generated laser light pulses reflect back from the surface 7 of the ore 5 travelling on the conveyor belt 4.

Figure 3 shows a side view of one embodiment of an arrangement for measuring of a three-dimensional image profile of the ore travelling on a conveyor belt from the crusher to the grinding mill of grinding circuit according to the present invention. The presented three-dimensional image profile measuring arrangement shows a conveyor belt 8 travelling clockwise from a crushing circuit 9 to the grinding mill of grinding circuit 10.

In the presented embodiment of the three-dimensional image profile measuring arrangement according to the present invention the conveyor belt 8 is first being fed ore 1 1 from the crushing circuit 9, thereafter conveyor belt 8 conveys the ore 1 1 from left to right to the feed of the grinding mill of grinding circuit 10. The presented three-dimensional image profile measuring arrange- ment also comprises a three-dimensional imaging system 12 placed above the conveyor belt 8, said three-dimensional imaging system 12 comprising a structured light source, e.g. a line laser source 13, and at least one imaging device 14, 15.

The line laser source 13 of the three-dimensional imaging system 12 generates a laser line and draws a coherent light line on the ore 1 1 travelling on the conveyor belt 8 from the crushing circuit 9 to the grinding mill of grinding circuit 10. The generated laser light reflects back from the surface 16 of the ore 1 1 travelling on the conveyor belt 8.

In the presented embodiment of the three-dimensional surface pro- file measuring arrangement according to the present invention a first imaging device 14, e.g. a CCD imaging sensor 14 or a CMOS imaging sensor 14, of the at least one imaging device 14, 15 is placed in the angle of 0-150 degrees, preferably 15-60 degrees, more preferably 30-40 degrees compared to the line laser source 13. The first imaging device 14 of the at least one imaging device 14, 15 is constantly acquiring measurement data for three-dimensional recon- struction from the ore 1 1 travelling on the conveyor belt 8. The reflected laser line reflected back from the surface 16 of the ore 1 1 and is detected in the three-dimensional reconstructions taken by said first imaging device 14. For example in one three-dimensional reconstruction representing one cross- section of said ore 1 1 travelling on the conveyor belt 8, the location of the laser line may be identified by machine vision algorithms and transformed to the real height of the ore bed for said cross-section.

As the conveyor belt 8 is moving, and the speed of the conveyor belt 8 is known, consequently an enhanced volumetric flow and a three- dimensional image profile of the ore 1 1 travelling on the conveyor belt 8 is ob- tained. The 3D profile image obtained using the presented principle i.e. trian- gulation principle, will inherently include also the shadow areas in the 3D image profile that cannot be detected by the camera. To reduce this effect two cameras can be used.

In the presented embodiment of the three-dimensional surface pro- file measuring arrangement according to the present invention there is also a second imaging device 15, e.g. a CCD imaging sensor 15 or a CMOS imaging sensor 15, of the at least one imaging device 14, 15 is placed at the opposing side to said first imaging device 14, and in the angle of 0-150 degrees, preferably 15-60 degrees, more preferably 30-40 degrees compared to the line laser source 13. Also the second imaging device 15 of the at least one imaging device 14, 15 is constantly acquiring measurement data for three-dimensional reconstruction from the ore 1 1 travelling on the conveyor belt 8. The reflected laser line reflected back from the surface 16 of the ore 1 1 and is detected in the three-dimensional reconstructions taken by said second imaging device 15.

In the present embodiment the imaging devices 14, 15 may be any types of regular imaging devices 14, 15, e.g. based on digital imaging technology. Digital imaging technology is a technology utilizing sensors, e.g. containing grids of pixels, and is widely used in professional, medical, and scientific applications where high-quality image data is required such as in digital cam- eras, in optical scanners, in video cameras and in light-sensing devices. Furthermore, in the present embodiment the ore is travelling on a conveyor leading directly to a grinding mill. Also in the present embodiment the imaging devices are positioned for acquiring measurement data for three- dimensional reconstruction from the ore as it is travelling on a conveyor lead- ing to a grinding mill. However, in an alternative embodiment of the present invention, said comminution process may have several conveyors, screening stations and storage bins. Likewise, in an alternative embodiment of the present invention, said at least one imaging device acquires 3D reconstruction measurement data for three-dimensional reconstruction from said ore as it is travelling on any conveyor in a comminution process or exiting any conveyor in a comminution process.

Figure 4 shows a backside view of a conveyor belt and a three- dimensional imaging system of one embodiment of an arrangement for measuring of a three-dimensional image profile of the ore travelling on a conveyor belt from the crusher to the grinding mill of grinding circuit according to the present invention. In the presented embodiment of the three-dimensional image profile measuring arrangement according to the present invention the conveyor belt 8 conveys the ore 1 1 from the crushing circuit to the feed of the grinding mill. The presented three-dimensional image profile measuring ar- rangement comprises a three-dimensional imaging system 12 placed above the conveyor belt 8, said three-dimensional imaging system 12 comprising a structured light source, e.g. a line laser source, and at least one imaging device. The line laser source of the three-dimensional imaging system 12 generates a laser line and draws a coherent light line on the ore 1 1 travelling on the conveyor belt 8. The generated laser light reflects back from the surface of the ore 1 1 travelling on the conveyor belt 8.

In the presented embodiment of the three-dimensional surface profile measuring arrangement according to the present invention a first imaging device of the at least one imaging device is placed in the angle of 0-150 de- grees, preferably 15-60 degrees, more preferably 30-40 degrees compared to the line laser source of the three-dimensional imaging system 12. The first imaging device of the at least one imaging device is constantly acquiring measurement data for three-dimensional reconstruction from the ore 1 1 travelling on the conveyor belt 8. The reflected laser line reflected back from the surface of the ore 1 1 and is detected in the three-dimensional reconstructions taken by said first imaging device. As the conveyor belt 8 is moving, and the speed of the conveyor belt 8 is known, consequently an enhanced volumetric flow and a three-dimensional image profile of the ore 1 1 travelling on the conveyor belt 8 is obtained.

Furthermore, in the presented embodiment of the three-dimensional surface pro-file measuring arrangement according to the present invention there may also be a second imaging device of the at least one imaging device, which second imaging device is placed at the opposing side to said first imaging device, and in the angle of 0-150 degrees, preferably 15-60 degrees, more preferably 30-40 degrees compared to the line laser source of the three- dimensional imaging system 12.

Figure 5 shows a schematic diagram of one embodiment of an arrangement for controlling of a comminution process according to the present invention. The presented embodiment of an arrangement for controlling of a comminution process according to the present invention comprises a crushing circuit 17, a grinding circuit 19 and a conveyor 18 conveying ore from the crushing circuit 17 towards the grinding circuit 19.

The controlling arrangement according to the presented embodiment also comprises an imaging system 20 for measuring 3D reconstruction measurement data 21 for reconstruction of a three-dimensional image profile of the ore before entering said grinding circuit 19. The imaging system 20 monitors the flow of ore before it enters said grinding circuit 19 of said comminution process. The imaging system 20 of the presented embodiment is placed in the vicinity of said conveyor 18. In the presented embodiment said imaging system 20 measures said 3D reconstruction measurement data 21 from ore conveyed by said conveyor 18 and forwards said measured 3D reconstruction measurement data 21 to a rock size distribution data calculation block 22.

In said rock size distribution data calculation block 22 rock size distribution data 23 is calculated. Furthermore, in said rock size distribution data calculation block 22 there is calculated one or more distinct property values for one or more rock size variables, said one or more distinct property values being calculated based on said measured 3D reconstruction measurement data 21 . The rock size distribution data calculation block 22 forwards said rock size distribution data 23 and said one or more distinct property values towards a control block 27 of the controlling arrangement according to the presented em- bodiment. The one or more rock size variables may include one or more of the following: a volumetric flow of a certain specified largest percentage of parti- cles, a volumetric flow of a certain specified smallest percentage of particles, a volumetric flow of a certain specified mid-size range of particles, a particle count of a certain specified largest percentage of particles, a particle count of a certain specified smallest percentage of particles, a particle count of a certain specified pebble size range of particles.

The controlling arrangement according to the presented embodiment also comprises a separate control value data calculation block 24 for calculation of control value data 26 and for forwarding said calculated control value data 26 to said control block 27. The control value data calculation block 24 according to the presented embodiment receives said rock size distribution data 23 and/or said one or more distinct property values from said rock size distribution data calculation block 22. The control value data calculation block 24 also receives comminution process data 25 from said grinding circuit 19. The comminution process data 25 may include one or more of the following data: mass feed, water addition, ball addition, pebbles feed, grinding mill speed, hardness, density, ore specific gravity, elemental analysis, ore grade, grinding product size, grinding mill power draw, grinding mill torque, grinding mill bearing pressure and grinding mill charge.

In the controlling arrangement according to the presented embodi- ment said control value data calculation block 24 calculates control value data 26 based on the received data and forwards said calculated control value data 26 to said control block 27. The control value data calculation block 24 may also forward the received rock size distribution data 23 and/or the received one or more distinct property values for one or more rock size variables and/or the received comminution process data 25 along with said calculated control value data 26 to said control block 27.

The control block 27 according to the presented embodiment receives said calculated control value data 26 and may also receive said rock size distribution data 23 and/or said one or more distinct property values and/or said comminution process data 25 along with said calculated control value data 26. The control block 27 controls the crushing circuit 17 and/or the grinding circuit 19 by e.g. by sending control signalling and/or data signalling 28, 29 to the crushing circuit 17 and/or to the grinding circuit 19. In an alternative embodiment, said control value data calculation block 24 may be integrat- ed into said control block 27. Furthermore, in an alternative embodiment, said rock size distribution data calculation block 22 and said control value data calculation block 24 may both be integrated into said control block 27.

The control block 27 according to the presented embodiment may control e.g. grinding mill speed and/or mass feed and/or water addition and/or ball addition and/or pebbles feed to a grinding circuit 19 of said comminution process based on said received rock size distribution data 23 and/or the received one or more distinct property values for one or more rock size variables.

Furthermore, in the present embodiment the ore is travelling on a conveyor towards a grinding mill. However, in an alternative embodiment of the present invention, said comminution process may have several conveyors, screening stations and storage bins. Likewise, in an alternative embodiment of the present invention, said at least one imaging device acquires 3D reconstruction measurement data for three-dimensional reconstruction from said ore as it is travelling on any conveyor in a comminution process or exiting any conveyor in a comminution process.

Figure 6 shows a schematic diagram of another embodiment of an arrangement for controlling of a comminution process according to the present invention. The presented another embodiment of an arrangement for controlling of a comminution process according to the present invention comprises a crushing circuit 17, a grinding circuit 19 and a conveyor 18 conveying ore from the crushing circuit 17 towards the grinding circuit 19.

The controlling arrangement according to the presented another embodiment also comprises an imaging system 20 for measuring 3D reconstruction measurement data 21 for reconstruction of a three-dimensional image profile of the ore before entering said grinding circuit 19. The imaging system 20 monitors the flow of ore before it enters said grinding circuit 19 of said comminution process. The imaging system 20 of the presented embodiment is placed in the vicinity of said conveyor 18. In the presented embodiment said imaging system 20 measures said 3D reconstruction measurement data 21 from ore conveyed by said conveyor 18 and forwards said measured 3D reconstruction measurement data 21 to a three-dimensional image profile calculation block 30.

In the controlling arrangement according to the presented another embodiment said three-dimensional image profile calculation block 30 also receives conveyor speed 31 from the conveyor 18. The three-dimensional image profile calculation block 30 then consequently obtains a three-dimensional image profile 32 of the ore travelling on the conveyor 18 based on the received measured 3D reconstruction measurement data 21 and the received conveyor speed 31 . Thereafter, said three-dimensional image profile calculation block 30 forwards said measured 3D reconstruction measurement data 21 including said three-dimensional image profile 32 of the ore to a rock size distribution data calculation block 22.

In said rock size distribution data calculation block 22 rock size distribution data 23 is calculated. Furthermore, in said rock size distribution data calculation block 22 there is calculated one or more distinct property values for one or more rock size variables, said one or more distinct property values being calculated based on said measured 3D reconstruction measurement data 21 including said three-dimensional image profile 32 of the ore. The rock size distribution data calculation block 22 forwards said rock size distribution data 23 and said one or more distinct property values towards a control block 27 of the controlling arrangement according to the presented another embodiment. The one or more rock size variables may include one or more of the following: a volumetric flow of a certain specified largest percentage of particles, a volumetric flow of a certain specified smallest percentage of particles, a volumetric flow of a certain specified mid-size range of particles, a particle count of a cer- tain specified largest percentage of particles, a particle count of a certain specified smallest percentage of particles, a particle count of a certain specified pebble size range of particles.

The controlling arrangement according to the presented another embodiment also comprises a separate control value data calculation block 24 for calculation of control value data 26 and for forwarding said calculated control value data 26 to said control block 27. The control value data calculation block 24 according to the presented embodiment receives said rock size distribution data 23 and/or said one or more distinct property values from said rock size distribution data calculation block 22. The control value data calculation block 24 also receives comminution process data 25 from said grinding circuit 19. The comminution process data 25 may include one or more of the following data: mass feed, water addition, ball addition, pebbles feed, grinding mill speed, hardness, density, ore specific gravity, elemental analysis, ore grade, grinding product size, grinding mill power draw, grinding mill torque, grinding mill bearing pressure and grinding mill charge. In the controlling arrangement according to the presented another embodiment said control value data calculation block 24 calculates control value data 26 based on the received data and forwards said calculated control value data 26 to said control block 27. The control value data calculation block 24 may also forward the received rock size distribution data 23 and/or the received one or more distinct property values for one or more rock size variables and/or the received comminution process data 25 along with said calculated control value data 26 to said control block 27.

The control block 27 according to the presented another embodi- ment receives said calculated control value data 26 and may also receive said rock size distribution data 23 and/or said one or more distinct property values and/or said comminution process data 25 along with said calculated control value data 26. The control block 27 controls the crushing circuit 17 and/or the grinding circuit 19 by e.g. by sending control signalling and/or data signalling 28, 29 to the crushing circuit 17 and/or to the grinding circuit 19. In an alternative embodiment, said control value data calculation block 24 may be integrated into said control block 27. The control block 27 according to the presented another embodiment may control e.g. grinding mill speed and/or mass feed and/or water addition and/or ball addition and/or pebbles feed to a grinding circuit 19 of said comminution process based on said received rock size distribution data 23 and/or the received one or more distinct property values for one or more rock size variables.

Furthermore, in the present embodiment the ore is travelling on a conveyor towards a grinding mill. However, in an alternative embodiment of the present invention, said comminution process may have several conveyors, screening stations and storage bins. Likewise, in an alternative embodiment of the present invention, said at least one imaging device acquires 3D reconstruction measurement data for three-dimensional reconstruction from said ore as it is travelling on any conveyor in a comminution process or exiting any conveyor in a comminution process.

Figure 7 shows a schematic diagram of one embodiment of a screening circuit of a comminution process according to the present invention. The presented embodiment of a comminution process according to the present invention comprises a crushing circuit 33 and a screening circuit, said screen- ing circuit comprising a screening station conveyor 34 and a screening station 35. In the presented embodiment of a comminution process according to the present invention ore is crushed in the crushing circuit 33 and conveyed to the screening station 35 via the screening station conveyor 34.

The screening circuit of a comminution process according to the present invention comprises a fine ore storage bin 37, a pebble ore storage bin 39 and a lump ore storage bin 41 . The screening circuit also comprises a fine ore conveyor 36, a pebble ore conveyor 38 and a lump ore conveyor 40.

In the presented embodiment of a comminution process according to the present invention ore is screened in the screening station 35 and the screened ore is distributed from the screening station 35 to the responsible conveyor, i.e. screened fine ore to said fine ore conveyor 36, screened pebble ore to said pebble ore conveyor 38 and screened lump ore to said lump ore conveyor 40. Respectively, said fine ore conveyor 36 conveys the screened fine ore to said fine ore storage bin 37, said pebble ore conveyor 38 conveys the screened pebble ore to said pebble ore storage bin 39 and said lump ore conveyor 40 conveys the screened lump ore to said lump ore storage bin 41 . In the screening station 35 of the presented embodiment the screened oversize ore 42 is typically returned back to the crushing circuit 33.

The comminution process according to the present invention may also comprise a system for monitoring the flow of ore, said monitoring system comprising an imaging system, said imaging system measuring 3D reconstruction measurement data 21 for reconstruction of a three-dimensional image profile of said crushed ore being conveyed to said screening station 35.

Furthermore, said monitoring system may also comprise an imaging system measuring 3D reconstruction measurement data 21 for reconstruction of a three-dimensional image profile of said screened fine ore being conveyed to said fine ore storage bin 37 and/or an imaging system measuring 3D reconstruction measurement data 21 for reconstruction of a three-dimensional image profile of said screened pebble ore being conveyed to said pebble ore storage bin 39 and/or an imaging system measuring 3D reconstruction measurement data 21 for reconstruction of a three-dimensional image profile of said screened lump ore being conveyed to said lump ore storage bin 41 .

Figure 8 shows a schematic diagram of one embodiment of a comminution control unit of an arrangement for controlling of a comminution process according to the present invention. The comminution control unit 43 ac- cording to the presented embodiment receives comminution process data 44 from the comminution process. The comminution control unit 43 according to the presented embodiment comprises a control block 46 receiving said comminution process data 44 and a data storage block 45 receiving and storing said comminution process data 44.

Furthermore, the comminution control unit 43 according to the pre- sented embodiment comprises a calculation block 47. The calculation block 47 receives measured 3D reconstruction measurement data 21 from an imaging system of the controlling arrangement according to the present invention. The calculation block 47 calculates calculation data 48, said calculation 48 data comprising the three-dimensional image profile of the ore and/or the received rock size distribution data and/or the received one or more distinct property values for one or more rock size variables and/or the control value data. The calculation block 47 forwards said calculation data 48 to said control block 46 and to said data storage block 45. The control block 46 of the comminution control unit 43 according to the presented embodiment controls the comminu- tion process by sending control signalling 49 to the different comminution process blocks, e.g. to the crushing circuit and/or to the grinding circuit.

Figure 9 shows a schematic diagram of another embodiment of a comminution control unit of an arrangement for controlling of a comminution process according to the present invention. The comminution control unit 50 according to the presented another embodiment receives comminution process data 44 from the comminution process. The comminution control unit 50 according to the presented another embodiment comprises a control block 46 receiving said comminution process data 44 and a data storage block 45 receiving and storing said comminution process data 44.

Furthermore, the presented arrangement for controlling of a comminution process according to the present invention comprises a calculation block 51 . The calculation block 51 receives measured 3D reconstruction measurement data 21 from an imaging system of the controlling arrangement according to the present invention. The calculation block 51 calculates calcula- tion data 48, said calculation 48 data comprising the three-dimensional image profile of the ore and/or the received rock size distribution data and/or the received one or more distinct property values for one or more rock size variables and/or the control value data. The calculation block 51 forwards said calculation data 48 to said control block 46 and to said data storage block 45 of said comminution control unit 50 according to the presented another embodiment. The control block 46 of the comminution control unit 50 according to the pre- sented another embodiment controls the comminution process by sending control signalling 49 to the different comminution process blocks, e.g. to the crushing circuit and/or to the grinding circuit.

Figure 10 shows one embodiment of a graph diagram of rock size distribution in an arrangement for controlling of a comminution process according to the present invention. The presented embodi ment of a graph diagram 52 shows the rock size distribution data of ore which has been calculated based on the measurement data of ore, said measurement data measured by the imaging system of the controlling arrangement according to the present inven- tion.

In the presented graph diagram 52 the ore has been classified in classes according to size of ore. In said graph diagram 52 each size class of ore has been shown as a bar, the height of each bar showing the volume of each size class of ore. The controlling arrangement according to the present invention may also calculate one or more distinct property values 53 for one or more rock size variables based on said measurement data of ore and said rock size distribution data of ore. One such distinct property value 53 is shown in the presented graph diagram 52.

The arrangement for controlling of a comminution process according to the present invention may control the crushing circuit by producing crushing control signalling for controlling the crushing process control parameters, that is, by e.g. controlling the screen control and/or the vibrating feeder control so that the desired crushing process output i.e. out coming rock size distribution is sought.

The arrangement for controlling of a comminution process according to the present invention may control the grinding circuit by producing grinding control signalling for controlling the grinding process control parameters so that the desired grinding process output is sought.

In a typical grinding circuit control it is typical to keep the mill charge or the filling of the grinding mill at the constant level by controlling the feed to the mill. As an indication of the filling, the mill power draw and mill bearing pressures are often used. This typical approach works relatively well in case the hardness, the density, and the size distribution of the feed are constant. Unfortunately all of these variables are unknown and changing continuously.

With the obtained rock size distribution data according to the present invention it is possible to assess these disturbances in the grinding circuit control and take the necessary action. For example, in case the upper quartile in the rock size distribution increases, this means that it takes longer time to process the ore. Therefore, the feed to the mill needs to be reduced.

The solution for controlling of a comminution process according to the present invention provides a more accurate and reliable measurement data and information on rock size distribution and quantity of the ore travelling on a conveyor belt from the crusher to the grinding mill. The comminution process can therefore be continuously and adequately controlled, there is no need for frequent calibration.

The solution for controlling of a comminution process according to the present invention provides a more detailed view of the entire comminution process with a thorough knowledge of the ore travelling on a conveyor belt from the crusher to the grinding mill. This enables a substantially better control of a comminution process.

By achieving a substantially better control of a comminution process in general; also the crushing process and more importantly the grinding process can be better and more efficiently controlled. This brings a lot of savings through more efficient use of energy and process ore.

With the help of the solution according to the present invention the manufacturers of comminution process equipment will be able to provide comminution process equipment arrangements with having more reliable measurement data and information on the ore travelling on a conveyor belt from the crusher to the grinding mill of grinding circuit with better measurement accuracy and reliability. The solution according to the present invention may be utilised in any kind of comminution process equipment.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.