Metal removal upstream of a mill

Abstract

The present invention relates to an installation for comminuting a mineral material, wherein the installation comprises a coarse material storage unit (10), a conveying device (20), and a comminution device (30), wherein the coarse material storage unit (10) and the conveying device (20) are connected to allow transfer of the material, wherein the conveying device (20) has a discharge end, wherein the discharge end is arranged above the comminution device (30), wherein a free-fall section for the material is arranged between the discharge end and the comminution device (30), wherein at least one metal sensor (40) is arranged above the conveying device (20), wherein the installation comprises a removal device (50), wherein the removal device (50) is arranged below the conveying device (20) and is designed to remove material from the free-fall section, characterised in that the metal sensor (40) is designed as a two-dimensional sensor array consisting of sub-sensors (41), wherein the removal device (50) comprises at least one first partial removal device (51) and one second partial removal device (52), wherein the first partial removal device (51) and the second partial removal device (52) are arranged next to one another.

Description

[0001] Metal removal in front of a mill

[0002] The invention relates to a device for the selective removal of metal upstream of a mill or crusher.

[0003] For example, in the lime and cement industry and the basic materials industry, large quantities of mineral material, such as limestone, are crushed, typically in units with a throughput of several thousand tons per hour. Mineral materials are relatively brittle and prone to breakage. Therefore, metals, such as screws, hammerheads, or similar objects, often pose a significant problem in crushing equipment for such mineral materials. Metals are ductile and therefore do not break. If a metallic object enters the crushing equipment, the rollers of a roller press, for instance, which have considerable inertia due to their very large mass, cannot deflect under the concentrated force exerted by a metallic object. This regularly leads to damage to the rollers.

[0004] Therefore, while electromagnets are regularly used above a conveyor to remove metallic objects, these objects can sometimes be buried so deeply under the mineral material that they cannot be removed. Consequently, it has become standard practice to install a metal detector with a downstream material diversion system above the conveyor. If metal is detected, a material diversion is activated, temporarily diverting all the coarse material containing the metal past the crushing device. This material is optionally separated from the metal and then fed back into the crushing process. This diversion process typically involves several tons of material. This results in an increased amount of material being returned for the subsequent size-selective separation.Unfortunately, there is also the risk that the metal will be circulated in a loop, causing multiple discharges and thus placing a heavy burden on the cycle. The object of the invention is to enable selective and final discharge of the metal and to reduce the discharged material flow.

[0005] This problem is solved by a system with the features specified in claim 1. Advantageous further developments are described in the dependent claims, the following description, and the drawings.

[0006] The system according to the invention is used for comminuting a mineral material, i.e., a material that is primarily brittle and is comminuted under pressure. Therefore, metals, which are ductile and cannot be comminuted by pressure but only deformed to a certain extent, pose a problem. The system comprises a coarse material storage area, a conveying device, and a comminution device. The coarse material storage area and the conveying device are connected for transferring the material. For example, the coarse material storage area is arranged above the conveying device and has a gate at its bottom, so that the material falls from the coarse material storage area onto the conveying device simply by opening the gate due to gravity. Conveyor belts or chutes are particularly suitable as conveying devices. The conveying device has a discharge end, i.e., the end to which the material is transported on the conveying device.At the discharge end, the material is ejected from the conveyor. The discharge end is located above the shredding unit, so that the material ejected from the discharge end falls into the shredding unit. A free-fall section for the material is arranged between the discharge end and the shredding unit. A metal sensor is located above the conveyor. According to the prior art, this sensor is usually designed as a single sensor element that extends across the entire width of the conveyor and thus detects any metal transported by the conveyor. The system includes a discharge device, which is located below the conveyor and is designed to remove material from the free-fall section.Typically, according to the state of the art, the rejection device is a flap that can be folded into the free-fall section, thus preventing the entire material flow from entering the shredding device for a predetermined time after metal detection, diverting it away. To achieve this, the flap is simply folded into the free-fall section and then folded out again. Detection is usually achieved simply by induction. This generates an eddy current in a piece of metal, which can then be detected as a power loss at the inducing coil.

[0007] According to the invention, the metal sensor is designed as a two-dimensional sensor array consisting of sub-sensors. Alternatively, the metal sensor is designed as a one-dimensional sensor array consisting of sub-sensors, and the system additionally includes a velocity sensor. The two-dimensional sensor array enables the determination of at least two pieces of information. Firstly, the position of the metal perpendicular to the conveying direction can be determined, which makes it possible to reject only a portion of the conveying width and thereby reduce the amount of rejected material. Secondly, the movement of the metal along the conveying device can be detected, and therefore the exact time of its passage through the free-fall section can be predicted, thus significantly shortening the rejection time. Alternatively, this can be achieved using two separate sensors: a one-dimensional sensor array and a velocity sensor.The one-dimensional sensor array is arranged transversely to the conveying direction and can therefore also determine the position of the metal perpendicular to the conveying direction. Furthermore, the movement of the metal along the conveying device can be detected by the velocity sensor, allowing the precise time of crossing the free-fall section to be predicted, thus significantly reducing the rejection time. The combination of spatial resolution perpendicular to the conveying direction and precise prediction of the rejection time also leads to a reduction in the amount of material rejected. The rejection device comprises at least a first partial rejection device and a second partial rejection device. The first and second partial rejection devices are arranged side by side.The entirety of all partial discharge devices preferably covers the entire width of the conveyor and free-fall section. This means that, unlike before, only the entire material flow can be discharged, but only the portion covered by the partial discharge device. The greater the number of partial discharge devices, the smaller the amount of material discharged.

[0008] The fact that the discharge device is positioned below the conveying device simply means that it is located below the level of the conveying device, i.e., lower down, or can be inserted there. It does not have to be positioned directly below; it can also be offset laterally, but lower down, thus allowing it to engage with the free-fall section. Similarly, it can be positioned beside or above the conveying device and, for example, be inserted into the free-fall section below it by rotating it. The decisive factor for positioning it below is therefore the duration of the discharge by the discharge device.

[0009] The rejection device, and thus the partial rejection devices, can be designed as air blast devices. The advantage is the highly targeted and precise rejection, which removes only a minimal portion of the material flow. Alternatively, the rejection device, and thus the partial rejection devices, can be designed, for example, as a rotary diverter, i.e., a deflecting device that pivots laterally into the free-fall section. The suspension and axis of rotation of the rotary diverter can also be located next to or even above the conveyor; the important thing is that the effect occurs in the free-fall section and thus below the conveyor, i.e., that a deflector plate is pivoted into this area.Similarly, the ejection device, and thus the partial ejection devices, can be designed, for example, as a chute, which is movable, particularly transversely to the free-fall section, and can therefore be selectively inserted into the free-fall section. Furthermore, the ejection device, and thus the partial ejection devices, can be hydraulically operated, for example. Unlike air, water, due to its greater density, more easily generates a greater momentum, making a stronger deflection easier to achieve. Hydraulic ejection should, of course, be avoided with moisture-sensitive materials, but it is advantageous in other applications. Various detection methods are suitable for the metal sensor. Commonly used metal detectors are inductive, capacitive, magnetic, or infrared. Inductive detection is particularly preferred.

[0010] In another embodiment of the invention, the conveying device is a conveyor belt or a chute, preferably a conveyor belt. With a conveyor belt, it would also be possible to determine the movement of a metal particle from the movement of the conveyor belt using only a line sensor. However, this requires a high degree of integration of various systems, which can be avoided by using a two-dimensional sensor array. With a chute, the movement can only be reliably predicted in this way anyway.

[0011] In a further embodiment of the invention, an intermediate storage area is arranged between the free-fall section and the shredding device. Such intermediate storage areas are already common practice today to bridge the time required for material removal, thus ensuring a continuous supply of material to the shredding device. Accordingly, the intermediate storage area, for example for feeding the shredding device, is designed for a period of usually 10 to 120 seconds.

[0012] In a further embodiment of the invention, the one-dimensional or two-dimensional sensor array has at least as many partial sensors perpendicular to the conveying direction of the conveying device as the system has partial rejection devices. Preferably, the two-dimensional sensor array has at least twice, and preferably three times, as many partial sensors perpendicular to the conveying direction of the conveying device as the system has partial rejection devices. This provides sufficient spatial resolution to achieve targeted partial rejection.

[0013] In a further embodiment of the invention, the two-dimensional sensor array has at least two, preferably at least ten, sub-sensors arranged along the conveying direction of the conveying device. The aim is to predict the metal's motion vector as precisely as possible in order to minimize the ejection time and thus the amount of material ejected. In another embodiment of the invention, the velocity sensor is an optical sensor, for example, a camera. The advantage is simple integration, since there is no interaction with other components.

[0014] In another embodiment of the invention, the comminution device is a bed roller mill.

[0015] In another embodiment of the invention, the comminution device is a crushing device.

[0016] In a further embodiment of the invention, the system includes a metal discharge unit. The discharge device is designed to redirect the material flow in the free-fall section into the metal discharge unit. This is therefore a true discharge and not merely a bypass for the comminution device. This ensures that the metal is reliably removed from the process.

[0017] In a further embodiment of the invention, the system includes a control device. The control device is connected to at least one metal sensor and, if present, to the velocity sensor. The control device is designed to calculate the movement of a metal detected by the metal sensor and to predict when the metal will cross the free-fall section using data transmitted from the metal sensor to the control device. The control device is connected to the partial discharge device for actuation. Selective discharge can thus be carried out according to the prediction. The partial discharge device is only selectively activated when the metal crosses the free-fall section within the operating area of ​​the partial discharge device. This reduces the amount of material discharged, both in terms of time and width. This is centrally evaluated and controlled by the control device.

[0018] In a further embodiment of the invention, the partial discharge devices are air blast devices. This enables particularly selective discharge. In a further alternative embodiment of the invention, the partial discharge devices are mechanical discharge devices, for example, individual flap segments, guide segments, or chute segments.

[0019] In a further aspect, the invention relates to a method for removing a metal from a stream of mineral material. Preferably, the method according to the invention is carried out on the system according to the invention. The method comprises the following steps: a) transporting the mineral material via a conveying device to a free-fall section, b) spatially resolved detection of metal transverse to the conveying device, c) determining the velocity of the metal, d) predicting the location and time of the metal's passage through the free-fall section based on the data acquired in steps b) and c), e) controlling a partial removal device at the location and time predicted in step d) to remove the metal.

[0020] This process differs from conventional methods for crushing mineral materials in that it allows for spatially resolved detection of the metal. This enables a much more precise prediction of the location and time of the metal's passage along the free-fall path. Consequently, the material containing the metal is actually removed from the process in a shorter and more localized manner, rather than simply being passed by the crushing device. This ensures that the metal is truly removed from the cycle.

[0021] In this process, the speed of the metal in step c) can be determined either by means of a speed sensor or by means of a two-dimensional sensor array.

[0022] In a further embodiment of the invention, the ejection in step e) is carried out by means of an air blast. This enables particularly targeted ejection and thus reduces the amount of material ejected. In a further embodiment of the invention, the motion vector of the metal is determined in step d). This can be advantageous, for example, in a slide where accelerated motion occurs.

[0023] The system according to the invention is explained in more detail below with reference to an exemplary embodiment shown in the drawings.

[0024] Fig. 1 Side view, first example

[0025] Fig. 2 Top view, first example

[0026] Fig. 3 Side view, second example

[0027] Fig. 4 Top view, second example

[0028] Figure 1 shows an exemplary system in side view, and Figure 2 shows it from above. The illustrations are highly simplified and not to scale; they serve only to clarify the invention.

[0029] In normal operation, mineral material, for example and especially limestone, falls from the coarse material storage area 10 onto the conveying device 20, here a conveyor belt. The material is conveyed from right to left in the manner shown and falls downwards at the discharge end of the conveyor belt 20, initially into an intermediate storage area 60, which, for example, has space for approximately 1 minute of operation of the crushing device 30 located below it. The crushing device 30 is, for example, a roller mill or a crushing device.

[0030] To detect metal present in the mineral material that could damage the crushing device 30, the system has at least one metal sensor 40, which in the example shown consists of 8x8 sub-sensors 41. When a piece of metal is introduced, it is first detected by one of the rightmost sub-sensors 41 and then by the seven adjacent ones in a row. This data is transmitted from the metal sensor 40 to the control device 80. From these eight data points, it is possible to predict when and at what point the metal piece will pass through the free-fall section. Accordingly, the control device 80 then activates the relevant partial discharge device 51, 52, 53, 54 of the discharge device 50, which thus conveys only a very small proportion of the material containing the metal into the metal discharge 70, for example, by means of an air blast.

[0031] The second example shown in Figs. 3 and 4 differs from the first example shown in Figs. 1 and 2 in that the metal sensor 40 is a one-dimensional sensor array of partial sensors 41 arranged transversely to the conveying direction, and the system additionally includes a speed sensor 90 designed to detect the speed of the metal or the entire conveyed material. For example, the speed sensor 90 is a camera.

[0032] Reference sign

[0033] 10 rough material storage

[0034] 20 Conveyor device

[0035] 30 shredding device

[0036] 40 metal sensor

[0037] 41 partial sensor

[0038] 50 Discharge device

[0039] 51 first partial discharge device

[0040] 52 second partial discharge device

[0041] 53 third partial discharge device

[0042] 54 fourth partial discharge device

[0043] 60 interim storage facilities

[0044] 70 Metal removal

[0045] 80 Control device

[0046] 90 speed sensor

Claims

Patent claims 1. Plant for crushing a mineral material, wherein the plant comprises a coarse material storage area (10), a conveying device (20) and a crushing device (30), wherein the coarse material storage area (10) and the conveying device (20) are connected for transferring the material, wherein the Conveying device (20) has a discharge end, wherein the discharge end is arranged above the comminution device (30), wherein a free-fall section for the material is arranged between the discharge end and the comminution device (30), wherein at least one a metal sensor (40) is arranged, wherein the system has a discharge device (50), wherein the discharge device (50) is arranged below the conveying device (20) and is arranged for the discharge of material from the free-fall section, characterized in that the at least one metal sensor (40) is designed as a one-dimensional sensor array of partial sensors (41) and wherein the system additionally has a velocity sensor (90) or the at least one metal sensor (40) is designed as a two-dimensional sensor array of partial sensors (41), wherein the discharge device (50) has at least one first Partial discharge device (51) and a second partial discharge device (52) comprising the first Partial discharge device (51) and the second Partial discharge device (52) are arranged side by side.

2. System according to claim 1, characterized in that the conveying device (20) is a conveyor belt or a chute, preferably a conveyor belt.

3. System according to one of the preceding claims, characterized in that an intermediate storage (60) is arranged between the free-fall section and the comminution device (30).

4. System according to one of the preceding claims, characterized in that the one-dimensional sensor array or the two-dimensional sensor array transverse to the conveying direction of the conveying device (20) has at least as many partial sensors (41) as the system has partial rejection devices (51, 52, 53, 54).

5. System according to one of the preceding claims, characterized in that the two-dimensional sensor array has at least two, preferably at least ten, partial sensors (41) extending along the conveying direction of the conveying device (20).

6. Plant according to one of the preceding claims, characterized in that the comminution device (30) is a good bed roller mill.

7. Plant according to one of the preceding claims, characterized in that the plant has a metal discharge (70), wherein the discharge device (50) is designed to deflect the material flow in the free-fall section into the metal discharge (70).

8. System according to one of the preceding claims, characterized in that the system comprises a control device (80), wherein the control device (80) is connected to the metal sensor (40) and, if present, to the velocity sensor (90), wherein the control device (80) is configured to calculate the movement of a metal detected by the metal sensor (40) and to predict the passage of the free-fall section for the metal, wherein the control device (80) is connected to control the partial rejection devices (51, 52, 53, 54), wherein the partial rejection device (51, 52, 53, 54) is only selectively activated when the metal passes through the free-fall section in the area of ​​effect of the partial rejection device (51, 52, 53, 54).

9. System according to one of the preceding claims, characterized in that the partial discharge devices (51 , 52, 53, 54) are air blast devices.

10. System according to one of claims 1 to 8, characterized in that the Partial discharge devices (51, 52, 53, 54) mechanical These are discharge devices.

11. Method for removing a metal from a stream of a mineral material, the method comprising the following steps: a) transporting the mineral material via a conveying device (20) to a free-fall section, b) spatially resolved detection of metal transverse to the conveying device (20), c) determining the velocity of the metal, d) predicting the location and time of the metal's passage through the free-fall section based on the data acquired in step b) and step c), e) controlling a partial removal device (51, 52, 53, 54) at the location and time predicted in step d) to remove the metal.

12. Method according to claim 11, characterized in that the ejection in step e) is carried out by means of an air blast.

13. Method according to one of claims 11 to 12, characterized in that in step d) the motion vector of the metal is determined.

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