EP2075072A1 - Device and method for monitoring the movement of a grinding ball in a ring ball mill - Google Patents

Abstract

The ball ring mill (99) has a grinder (1) with multiple grinding balls (4), which are guided in a mill track between a grinding ring (2) and a pressure ring (3). The grinding balls are movable along the mill track due to difference of rotational speeds of the grinding and pressure rings. A sensor system (11) is provided for contactless detection of the movement of the grinding balls, where the sensor system has expansion-measuring strips, a radiation source e.g. microwave source and light source, and a radiation detector e.g. microwave detector and light detector. The sensor system is inductive, capacitive, magnetic, optical, acoustic and electromagnetic proximity switches. An independent claim is also included for a method for monitoring a movement of a grinding ball in a ball ring mill.

Description

The invention relates to a device and a method for monitoring the Mahlkugelbewegung in a ball mill.

In ball mill mills, the material to be grounded reaches a grinder via a central feeder. The grinder comprises a plurality of grinding balls, a grinding ring and a pressure ring. The grinding balls are guided in a Mahlspur between grinding and pressure ring, wherein the grinding balls move due to a difference in the rotational speeds of the grinding and pressure ring along the Mahlspur.

The dispatcher brings ground material into the mill. This is then captured by the balls, cut on the lower Mahlring and driven outward from the Mahlring. There it is lifted by a stream of air and fed to a separator. Coarse fractions are fed through this back to the milling process; sufficiently fine ground material can be removed from the mill.

Ball ring mills are mainly used for grinding coarse-grained grinding stock such as coal or gypsum. In particular, when used in large process plants to enforce significant amounts of regrind become. In order to grind coarse-grained meal with a large throughput, the ball ring mills must be made stable. The components of the ball ring mill are large and have a considerable weight.

During operation of the ball ring mill, the grinding balls are set in motion relative to the grinding ring and the pressure ring, and grinding material carried out between the grinding balls and the grinding ring is comminuted. The pressure ring is designed so that it presses the grinding balls against the grinding ring.

The speed at which the grinding balls move relative to the grinding or pressure ring is approximately half the difference between the rotational speeds of the grinding and pressure ring. During operation, blockages can occur, for example due to overfilling of the grinding chamber, so that the grinding balls come to a standstill with respect to the grinding or pressure ring and grind along the respective other ring. A grinding effect can no longer be achieved and it comes to a standstill of the grinding plant and thus production loss.

The invention has for its object to provide a device and a method for monitoring the Mahlkugelbewegung in a ball mill to detect blockages within the grinder can. The object is solved by the features of the independent claims 1 and 14. Advantageous embodiments can be found in the subclaims.

In a ball mill with a grinder, which comprises a plurality of grinding balls, which are guided between a grinding ring and a pressure ring in a milling track, and the grinding balls move along the grinding track due to a difference in the rotational speeds of the grinding and pressure ring, according to the invention at least one sensor system for contactless detection of the passage of a grinding ball past the sensor system is provided.

The method according to the invention provides for monitoring the movement of the grinding balls along the milling track in a ball-ring mill by detecting the passage of a grinding ball past a sensor system from this sensor system.

For ball ring mills, the difference between the rotational speeds of the grinding and pressure ring is generally known. From this, it is possible to determine the rotational speed of one or all grinding balls on the milling track in the event that there is no disturbance, and thus also the setpoint frequency of the passing of one or all grinding balls on the sensor system.

The sensor system provides the actual frequency of passing all the grinding balls on the sensor system in the form of electrical pulses. By comparing this actual frequency with the desired frequency, it is possible to detect a blockage of the grinding balls: If the determined actual frequency falls well below the calculated setpoint frequency, this means a malfunction in the grinding mechanism, as a rule a blockade of the grinding balls.

As an alternative to comparing the frequencies (the number of pulses over a defined period of time), for example, the period between two pulses can also be used as the comparison value. The length of the pulses does not matter. It still does not matter if with the sensor system the grinding balls themselves or the free spaces between two grinding balls are detected. It is only important that a difference between grinding balls and the free spaces between two grinding balls can be determined by the sensor system.

Touch-sensitive switches, which convert a mechanical pulse into an electrical one, are not very suitable for this purpose, because they would have only a short service life due to the many switching operations when used according to the invention. Furthermore, environmental factors, such as dust inside the ball ring mills and possibly high temperatures, when the ball ring mills are used, for example, for calcining gypsum, would further shorten the life of a mechanical sensor system. The invention has recognized this. According to the invention, it is therefore intended to use non-contact sensor system, which are not subject to wear due to the large number of switching operations. Non-contact in this context does not mean that the sensor system must not come into contact with the grinding balls. It simply means that this eventual mechanical contact is not used to generate a switching signal.

The sensor system according to the invention can in principle be designed in one or more parts. The term "one-piece" includes systems in which the excitation and detector components are combined in a common housing, and systems in which only a single component for generating the excitation signal and its detection is provided. A sensor system is then "multi-part" if at least the excitation component can be arranged separately from the detector component.

One-piece sensor systems are preferably known in the prior art proximity switch. These switches trigger a pulse as soon as an object enters its detection area. For this purpose, inductive, capacitive, magnetic, optical, acoustic or electromagnetic (especially in the microwave range) effects are exploited. The final choice of the type of the one-piece sensor system is also influenced by the material to be ground: in the case of electrically conductive materials, no optically operating sensor systems can be used in the microwave range, in the case of light-impermeable material.

Multi-part sensor systems preferably comprise a radiation source and a radiation detector. The radiation source emits radiation that passes along a beam path to the radiation detector and is registered there. The radiation can thereby pass directly from the radiation source to the radiation detector, or be deflected by additional components, such as mirrors, one or more times. According to the invention, however, the beam path is such that it is temporarily interrupted or deflected by the grinding balls. In this context, "interrupting" means that a beam path that runs from the radiation source to the radiation detector in the undisturbed state is disturbed so that no radiation emitted by the radiation source impinges on the radiation detector. The nature of the disturbance is irrelevant. "Redirecting" means that the radiation of the radiation source, which does not impinge on the radiation detector in the undisturbed state, is first deflected by the grinding balls so that it can be registered by the radiation detector.

In multi-part sensor systems, the radiation source may preferably be a microwave source and the radiation detector may be a microwave detector. It can also be provided that the radiation source is a light source and the radiation detector is a light detector.

The sensor system can be arranged with at least one part between the grinding and pressure ring and outside the milling track. Between grinding and pressure ring here means that the part of the sensor system is located on a plane between the grinding and pressure ring. "Outside the milling track" expresses that this part of the sensor system should not interfere with the grinding balls, i. should not get in contact with these. On which side of the Mahlspur the part of the sensor system is arranged, is arbitrary.

It can also be provided to integrate a part of the sensor system in the grinding or pressure ring. If necessary, the fact that the sensor system moves with the grinding or pressure ring must be taken into account when determining the setpoint values for the pulses of the sensor system.

In case of deviations of the desired and actual values for the pulses, an audible and / or visual warning can be issued to the operator of the ball ring mill. It is preferred if the sensor system is connected to the control unit of the ball ring mill. Thus, it can be automatically responded to established blockages of the grinding balls. Since blockages are often associated with an overfilling of the grinding chamber, for example, the Mahlgutzu- and -abfuhr be influenced to prevent blockages or eliminate. Also other parameters such as the rotational speed of grinding and / or rotating ring or the temperature in the ball ring mill can be controlled accordingly.

If a range finder is used instead of a proximity sensor, the speed of each individual grinding ball along the grinding track can be determined individually, depending on the arrangement of the range finder, with continuous measurement. By being able to determine the speed of each grinding ball, in addition to malfunctions such as blockages, the wear of each grinding ball can also be estimated: an uneven speed profile may indicate damage to the ball surface or - generally - a lack of concentricity of a grinding ball.

Such a rangefinder may be based on radar technology. It is also possible in multi-part sensor systems to equip the radiation source with an additional radiation detector. In the cases in which the beam path is interrupted by the radiation source to the actual radiation detector by a grinding ball and reflected back to the radiation source, the additional detector can determine the duration of the radiation and thus the distance of a grinding ball to the radiation source. Continuous measurement can be used to calculate the instantaneous velocity of a grinding ball from the distance values. Speed variations in a grinding ball or comparison to the other grinding balls can indicate problems.

For an explanation of the method according to the invention, reference is made to the above explanations of the device according to the invention.

Fig. 1a,b

eine Vorderansicht und Draufsicht des Mahlwerks einer ersten beispielhaften Ausführungsform einer erfindungsgemäßen Kugelringmühle mit einem einteiligen Sensorsystem;

Fig. 2a,b

eine Vorderansicht und Draufsicht des Mahlwerks einer zweiten beispielhaften Ausführungsform einer erfindungsgemäßen Kugelringmühle mit einem einteiligen Sensorsystem;

Fig. 3a,b

eine Vorderansicht und Draufsicht des Mahlwerks einer dritten beispielhaften Ausführungsform einer erfindungsgemäßen Kugelringmühle mit einem zweiteiligen Sensorsystem;

Fig. 4a,b

eine Vorderansicht und Draufsicht des Mahlwerks einer vierten beispielhaften Ausführungsform einer erfindungsgemäßen Kugelringmühle mit einem zweiteiligen Sensorsystem;

Fig. 5a,b

eine Vorderansicht und Draufsicht des Mahlwerks einer fünften beispielhaften Ausführungsform einer erfindungsgemäßen Kugelringmühle mit einem einteiligen Sensorsystem; und

Fig. 6

eine schematische Ansicht einer erfindungsgemäßen Kugelringmühle mit dem einteiligen Sensorsystem aus Fig. 2.

The invention will be described below by way of example with reference to the accompanying drawings by way of advantageous embodiments. Show it:

Fig. 1a, b

a front view and top view of the grinder of a first exemplary embodiment of a ball mill according to the invention with a one-piece sensor system;

Fig. 2a, b

a front view and top view of the grinder of a second exemplary embodiment of a ball mill according to the invention with a one-piece sensor system;

Fig. 3a, b

a front view and top view of the grinder of a third exemplary embodiment of a ball mill according to the invention with a two-part sensor system;

Fig. 4a, b

a front view and top view of the grinder of a fourth exemplary embodiment of a ball mill according to the invention with a two-part sensor system;

Fig. 5a, b

a front view and top view of the grinder of a fifth exemplary embodiment of a ball mill according to the invention with a one-piece sensor system; and

Fig. 6

a schematic view of a ball mill according to the invention with the one-piece sensor system Fig. 2 ,

In Fig. 1a, b the grinder 1 is shown a ball ring mill. The grinder comprises a Mahlring 2 and a pressure ring 3, and a plurality of grinding balls 4. Both Mahl- 2 as Also pressure ring 3 have a circumferential groove 5, 6, in which the grinding balls 4 are guided. The grinding balls 4 are held by the grooves 5, 6 on the Mahlspur 10. In this embodiment, only the grinding ring 2 rotates, which is indicated by the arrow 7, while the pressure ring 3 rests. The grinding balls 4 roll both on the grinding ring 2 and on the pressure ring 3. They move in the undisturbed state with approximately half the rotational speed 7 of the grinding ring 2 along the grinding track 10, indicated by arrow. 9

Their movement along the grinding track 10 leads the grinding balls 4 past the sensor system 11. The sensor system 11 is designed as a proximity sensor 12. The proximity sensor 12 is disposed between grinding and pressure ring 3 and is located so far away from the grinding track 10 that it does not come into physical contact with the grinding balls 4. However, the minimum distance between grinding balls 4 and proximity sensor 12 is chosen so that the grinding balls 4 pass when passing the proximity sensor 12 in its effective range 13, and thus trigger pulses.

During smooth operation of the grinder 1, the pulses are triggered at the proximity sensor 12 at regular intervals. The desired value for these distances can be calculated from the length of the grinding track 10 and the speed 9 of the grinding balls 4. Deviations of the distances of the pulses of the proximity sensor 12 from this target value mean disturbances of the grinder. The target / actual comparison is performed in a control unit 23 (see FIG. Fig. 6 ), which can also influence the operating parameters of the ball ring mill, such as material feed rate, rotational speed and temperature.

This in Fig. 2 a, b illustrated grinder 1 substantially corresponds to the Fig. 1 from. However, here the pressure ring 3 rotates at the same speed, although in opposite directions to the grinding ring 2, which is indicated by the speed arrows 7 and 8. This has the consequence that the grinding balls rotate 4 in undisturbed operation exclusively and perform little or no translatory movement.

The sensor system 11 is integrated in the pressure ring 3 and moves with this - in the speed 8 - with. The sensor system 11 is designed as a proximity sensor 12 and is arranged in the region of the channel 6 of the pressure ring 3. The proximity sensor 12 can come into direct contact with the grinding balls 4. However, a resulting mechanical contact triggers no impulse. Rather, the grinding balls 4 move through the effective region 13 of the proximity sensor 12, whereby - with smooth operation - regularly a pulse is triggered.

In Fig. 3 a, b is a grinder 1 shown, which is the grinder Fig. 1 a, b corresponds. However, the sensor system 11 is embodied here in two parts and consists of a radiation source 14 and a radiation detector 15. The radiation emitted by the radiation source 14 is - in the illustrated position of the grinder - intercepted by a grinding ball 4 and therefore does not reach the radiation detector 15 So only puts the track 16 back. However, the sensor system 11 is arranged so that - with undisturbed movement of the grinding balls 4 along the grinding track 10 - temporarily the radiation from the radiation source 14 along the beam path 17 can get into the radiation detector 15 and thus triggers a regular pulse will be able to be ascertained about the blockages in the grinder.

The radiation source 14 is equipped with an additional radiation detector 18. Through this detector 18, it is possible to continuously determine the length of the path 16 and thus the distance of the grinding path 17 interrupting the grinding ball 4 to the radiation source 14. From this, the instantaneous speed of the grinding ball 4 interrupting the beam path 17 can be determined. Detected speed variations may indicate problems such as local damage to the grinding ball surface (which can lead to lack of concentricity) or general wear of a grinding ball 4 (which may be reflected in increased slippage of the worn grinding ball against grinding and pressure ring, and thus lower speed).

The sensor system 11 in FIG Fig. 4 a, b is also made in two parts. Unlike the embodiment in Fig. 3 a, b but here the radiation of the radiation source 14 is temporarily deflected by the grinding balls 4 during smooth operation of the grinder 1 so that it impinges on the radiation detector 15 and triggers an impulse. This is illustrated by the beam path 17. In any other positioning of the grinding balls 4 relative to the sensor system 11, the radiation is arbitrary, but not deflected in the manner shown and thus does not trigger a pulse.

The sensor system 11 in FIG Fig. 5 a, b operates with a strain gauge 19. The pressure plate 3 of the grinder 1 presses the balls 4 due to the springs 18 on the Mahlring 2. Since the springs 18 as well as the grinding balls 4 act only selectively on the pressure ring 3, it comes to dynamic deformation of the pressure ring 3. Such deformation is - greatly exaggerated - represented by the lines 20. Via a strain gauge 19, the instantaneous deformation of the pressure ring 3 can be recorded and processed according to the invention into a pulse.

In Fig. 6 a ball mill 99 according to the invention is shown. The illustrated embodiment comprises a sensor system 11 according to the invention Fig. 2 , For explanation of the sensor system, reference is therefore made to the above embodiment.

The material to be grounded passes through the controllable allocator 22 and the supply line 21 into the grinder 1. The regulation takes place via a control unit 23. Their control lines are not shown for reasons of clarity.

The grinder 1 contains grinding balls 4, as well as grinding and pressure ring 2.3. Springs 18 press the pressure ring 3 against the grinding balls 4 and - as a result - the grinding balls 4 against the grinding ring 2. The grinding ring 2 is rotated by a motor 24 in rotation. The motor 24 is controlled and monitored by the control unit 23. The grinding balls 4 roll both on the grinding ring 2 and on the pressure ring 3. They move in the undisturbed state with approximately half the rotational speed of the grinding ring 2. The material to be ground is crushed between grinding balls 4 and grinding ring 3 and carried to the outside.

Outside the grinding ring 2 around is a collecting grid 25 through which also finely ground material does not fall can. Below the collecting grid 25 is a circumferential flow channel 26. At one point of the flow channel 26 air is blown. For this purpose, a blower 27 is provided, which is controllable by the control unit 23. Before the air from the blower 27 enters the flow channel 26, it flows through a heating element 28, in which it can be heated as needed. The heating element 28 is also controlled by the control unit 23.

The air flows through the collecting grid 25 and along a revolving ascending channel 29 into a sifter 30. The milled material lying on the collecting grid 25 is entrained and thus also enters the sifter 30. In the sifter 30, grinding stock is not yet the desired one Has fineness, filtered out and fed to the grinder 1. Coarse material is ground again.

The millbase, which has reached the desired fineness, is passed together with the air through the outlet 31 and can be further processed.

The control unit 23 is connected to the sensor system 11, the allocator 22, the motor 24, the blower 27, the heating element 28 and the classifier 30. All these elements are controlled and monitored by the control unit 23. The control unit 23 is thus able to detect disturbances in the operation of the ball-ring mill 99 and, according to the invention, to control the components of the ball-ring mill 99 in order to eliminate the disturbance, i. on ball mill 99 operating parameters, such as material feed rate, rotational speed and temperature, to influence.

Claims (16)

Ball mill (99) with a grinder (1) comprising a plurality of grinding balls (4) which are guided between a Mahlring (2) and a pressure ring (3) in a Mahlspur (10), wherein the Mahlkugeln (4) due to a difference of the rotational speeds (7, 8) of the grinding and pressure ring (2, 3) move along the Mahlspur (10),
characterized in that
at least one sensor system (11) for non-contact detection of the passing of a grinding ball (4) on the sensor system (11) is provided. Device according to claim 1,
characterized in that
the sensor system (11) is in one piece. Device according to claim 2,
characterized in that
the sensor system (11) is an inductive, capacitive, magnetic, optical, acoustic or electromagnetic proximity switch (12). Device according to claim 2,
characterized in that
the sensor system (11) comprises a strain gauge (19). Device according to claim 1,
characterized in that
the sensor system (11) is multi-part. Device according to claim 5,
characterized in that
the sensor system (11) comprises a radiation source (14) and a radiation detector (15). Device according to claim 6,
characterized in that
a beam path (17) from the radiation source (14) to the radiation detector (15) is direct. Device according to claim 6,
characterized in that
the beam path (17) from the radiation source (14) to the radiation detector (15) is at least temporarily deflected. Device according to one of claims 6 to 8,
characterized in that
the radiation source (14) is a microwave source and the radiation detector (15) is a microwave detector. Device according to one of claims 6 to 8,
characterized in that
the radiation source (14) is a light source and the radiation detector (15) is a light detector. Device according to one of claims 1 to 10,
characterized in that
the sensor system (11) is arranged at least partially between the grinding and pressure ring (2, 3) and outside the milling track (10). Device according to one of claims 1 to 10,
characterized in that
the sensor system (11) is at least partially integrated in the grinding and / or pressure ring (2, 3). Device according to one of claims 1 to 12,
characterized in that
a control unit for the ball ring mill (99) is provided and the sensor system (11) is connected to this control unit. Method for monitoring the movement of grinding balls (4) along a grinding track (10) in a ball-ring mill (99),
characterized in that
the passing of a grinding ball (4) on a sensor system (11) is detected without contact by this sensor system (11). Method according to claim 14,
marked by
Feeding a measurement signal of the sensor system (11) into the control of the ball ring mill (99) and use for parameter determination for the operation of the ball ring mill (99), comprising material feed rate, rotational speed and / or temperature. Method according to claim 14 or 15,
characterized in that a sensor system (11) according to claims 2 to 12 is used as the sensor system (11).

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