FI126803B - Method and arrangement for determining the degree of filling of a large mill and large mill - Google Patents

Description

A METHOD AND AN ARRANGEMENT FOR DETERMINING A DEGREE OF FULLNESS OF A LARGE GRINDING MILL, AND A LARGE GRINDING MILL

FIELD OF THE INVENTION

The present invention relates to the field of Mineral and Metallurgical Processes, to Disintegrating in General and to Disintegrating in Tumbling Mills, and more particularly to a method and arrangement for determining the degree of fullness of a large grinding mill, and .

BACKGROUND OF THE INVENTION

One of the most common processes in mining and metallurgy is the comminution processing or disintegrating of ore. When processing material for selective or collective recovery of valuable material components, the processes involved are preceded by comminution processing i.e. mechanical crushing or disintegration of material in a continent to free the valuable components, one from the other. 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 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 a controlled use of explosives and other methods in mining, quarrying and civil engineering. Typically blasting produces particles in the size of having a diameter of 500 mm or more.

Crushing is a 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 shape, of the materials so that pieces of different composition can be differentiated. In the crushing process, the crushing devices hold the material being crushed between two parallel or tangent solid surfaces of a Stronger material and apply sufficient force to bring the surfaces together. Typically, a particle having a diameter of up to 1000 mm is crushed to a particle having a diameter of 5 mm or more.

Grinding is particle size reduction of ore or rock materials in grinding mills. In Hard Rock Mining and Industrial Mineral Operations Requirements for Rotating Mineral and Metallurgical Processing Equipment such as Grinding Mills are very high in terms of grinding efficiency and energy consumption. Typically, a particle having a diameter of up to 1000 mm is grinded to a particle having a diameter of 0.010 mm or more. This conventional grinding of materials results in considerable wear on the grinding bodies present in the mill, due to the hardness of the rock concerned, therewith also results in considerable expense for the provision of such grinding bodies.

The rotating Mineral and Metallurgical processing equipment such as grinding mills are typically very large, having a diameter of several meters. The grinding Mills may be trunnion-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. In a bearing arrangement of a trunnion-supported grinding mill, the support bearings have a relatively small bearing diameter and the trunnion Journals have high consistent stiff journal surfaces, this facilitating the formation of a good bearing lubricant film distribution. The shell-supported grinding mills are more compact, occupy less floor space, and require simpler Foundations than comparable trunnion-supported grinding mills. Because the end plates of the shell-supported grinding mill do not support the structure, the feed and discharge openings can be sized to meet the process conditions without being constrained by trunnion bearing limitations. Ball mill is a typical type of fine grinder. However, rotating Mineral and Metallurgical Grinding Mills are today very often autogenous grinding Mills or semi-autogenous grinding Mills designed for grinding or primary crushed air. Autogenous grinding Mills are so-called due to the self-grinding of the air. In an autogenous grinding mill a rotating drum throws larger rocks of air in a cascading motion which causes impact breakage of larger rocks and compressive grinding of finer particles. In autogenous grinding the actual material itself, i.e. the material to be ground, forms the grinding bodies.

Semi-autogenous grinding balls are similar to autogenous grinding balls, but utilize grinding balls e.g. steel grinding balls to aid in grinding like in a ball mill. Attrition between grinding balls and air particles causes grinding of finer particles. Semi-autogenous grinding mills typically use a grinding ball charge of 8 to 21%, sometimes a grinding ball charge of 5 to 60%. A semi-autogenous grinding mill is generally used as a primary or first stage grinding solution. Semi-autogenous grinding mills are primarily used in gold, copper and platinum mines with applications also in the lead, zinc, silver, alumina and nickel industries.

Autogenous and semi-autogenous grinding Mills are characterized by their large diameter and short length as compared to ball Mills. The rotating Mineral and Metallurgical processing equipment such as autogenous and semi-autogenous grinding mills are typically driven by ring gears, with a 360 ° fully enclosed guard.

The inside of an autogenous or semi-autogenous grinding mill is lined with mill linings. The mill lining materials typically include cast steel, cast iron, solid rubber, rubber-steel Composites or ceramics. The mill linings 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 air charge.

Rotating Mineral and Metallurgical Processing Equipment that is provided with internal lifters is typically difficult to control. 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 grinding efficiency. The change in feed properties is a normal phenomenon that needs to be considered in controlling the rotating Mineral and Metallurgical processing equipment.

In autogenous or semi-autogenous grinding mills, the existing Mineral Deposits seldom have a homogenous structure and a homogenous mechanical strength. Material properties such as hardness, particle size, density and ore type also change constantly and require varying energy input is required.

Conventionally grinding has been controlled on the basis of mill power draw, but particularly in autogenous and semi-autogenous grinding, power draw is extremely sensitive to changes in feed parameters. It has been discovered that the degree of fullness in the mill as percentages of the mill volume is the quantity that is remarkably more stable and much more descriptive as regards the state of the mill. But because the degree of fullness is difficult to infer in an on-line measurement, the measurement of the load mass is often considered sufficient. However, mass measurement has its own problems both in installation and in measurement drift. Moreover, there can be intense variations in the load density, in which case changes in the mass do not necessarily result from changes in the degree of fullness.

As a summary, the degree of fullness is an important parameter that describes the state of the grinding mill. The main challenge with the degree of fullness is that the parameter is difficult to measure online. One prior art method for determining the degree of fullness of a large grinding mill has been to measure the weight of a large grinding mill and use the measured weight to calculate the degree of fullness of a large grinding mill. In this prior art method the weight of the grinding charge has been used as the deciding parameter for controlling the mill. This method is cost-demanding, however, because the weighing equipment needed to register continuously the changes in the weight of the grinding charge that occur during the operation of the mill, which enables the steps necessary to improve preventive operating conditions as quickly as possible. Also the water content of the mill changes constantly, the density, hardness and particle size of the grinding charge changes constantly. Furthermore, the mill linings typically comprise up to 30-50% of the total weight of the mill. As these linings wear off in time this has a significant effect on the weight of the mill. Therefore, the weight of the grinding mill is not a good indication of the degree of fullness in the grinding mill. All in all it has been discovered that the weight of the grinding charge does not correlate good enough with the degree of fullness in the grinding mill as percentages of mill volume.

Another prior art method for determining the degree of fullness of a large grinding mill has been to measure and analyze the power consumption or power intake signal of a large grinding mill and use the measured power consumption to calculate the degree of fullness of a large grinding mill. In patent document US 5,325,027 there is disclosed a method for defining the degree of fullness in a mill is calculated on the basis of the observed variation in power consumption. However, especially in autogenous and semi-autogenous grinding mills, power consumption is extremely sensitive to changing parameters. The energy or power requirement of a large grinding mill depends on several factors, such as the density of the grinding charge, the mill constant, the extent of the mill charge, Replenishment, or the instant volume of charge in the grinding mill, relative mill speed, length and diameter of the grinding mill. Furthermore, it has been discovered that the grinding mill power consumption or the power intake signal does not correlate enough with the degree of fullness in the grinding mill as percentages of mill volume.

In the following, the prior art will be described with reference to the accompanying figures, of which:

Figure 1 shows a cross-sectional view of a large grinding mill according to the prior art;

Figure 2 shows a perspective and partially cut open view of a large grinding mill arrangement according to the prior art.

Figure 1 shows a cross-sectional view of a large grinding mill according to the prior art. In Figure 1, the grinding mill has a drum casing 1, which drum casing 1 is provided with linings. The linings of the drum casing 1 comprise internal lifting means i. lifting bars 2, which lifting bars 2 lift the grinding charge material inside the mill, where it then falls off the lifting bars 2 onto the rest of the grinding charge. The angle in which the grinding charge material inside the mill first hits the lifting bar 2 is called “toe angle” <t> k. Respectively the angle in which the grinding charge material inside the mill first falls off the lifting bar 2 is called “shoulder angle” Φ5.

Figure 2 shows a perspective and partially cut open view of a large grinding mill arrangement according to the prior art. In Figure 2, the grinding mill arrangement has a drum casing 3, which drum casing 3 is provided with linings. As can be seen from the partially cut open view of Figure 2 the linings of the drum casing 3 comprise internal lifting means i.e. lifting bars 4, 5 inside the mill for lifting of the grinding charge material.

The large grinding mill arrangement according to the prior art has a trunnion support with trunnion bearings 6, 7 on both sides of the drum casing 3 of the grinding mill. The large grinding mill arrangement according to the prior art also has a ring gear 8, with a 360 ° fully enclosed guard. The large grinding mill arrangement according to the prior art also has a pinion gear 9 and a pinion bearings 10, 11 on both sides of the pinion gear 9.

In patent document US 6,874,364 a system for monitoring mechanical waves from a moving machine has been presented in which system a sensor arrangement is located on an exterior surface of a grinding mill. The presented sensor arrangement has an acoustic wave sensor for measuring acoustic wave properties and an accelerometer for measuring mechanical waves, viz. vibrational events and low frequency events, event spatial localization, and events occurring on the ends of the mill. The presented mechanical wave monitoring method may also include a step of monitoring the volumetric load in the machine based on the measured mechanical waves. Flowever, even presented on-mill-shell type device measured grinding mill acoustic wave properties do not correlate adequately enough with degree of fullness in grinding mill as percentages of mill volume.

There are also other prior art methods for determining the degree of fullness of a large grinding mill by measuring the acoustic wave properties and using the measured acoustic wave properties, i.e. sound pressure and / or sound intensity to estimate the degree of fullness of a large grinding mill. In these other methods, the acoustic wave property measurement sensors can be a single microphone or series of microphones or microphone Mats that are measuring acoustic wave properties coming from a large grinding mill. Also here, it has been discovered that the measured grinding mill acoustic wave properties provide only a rough estimate on the degree of fullness.

In patent document US 7,699,249 there is disclosed a method for defining the degree of fullness in a mill is calculated on the basis of the measured toe angle, the rotational speed of the mill and the geometrical dimensions of the mill. However, the sensor arrangement presented is not consistently enough to provide straightforward and adequate measurement of sensitivity required for precise degree of fullness in milling mill as percentages of mill volume.

In general, there are some problems with prior art solutions for measuring the degree of fullness of a large grinding mill. So far, the measuring solutions are relatively complex and difficult to provide reliable information. Also measuring accuracy and reliability with prior art measuring solutions has not been adequate enough.

The problem therefore is to find a solution for measuring the degree of fullness of a large grinding mill which can provide a reliable measurement of the degree of fullness of a large grinding mill with better measurement accuracy and reliability.

There is a demand in the market for a method for determining the degree of fullness of a large grinding mill which method would be more reliable and have better measurement sensitivity when compared to prior art solutions. Likewise, there is a demand in the market for an arrangement for determining the degree of fullness of a large grinding mill which arrangement would be more reliable and have better measurement sensitivity when compared to prior art solutions; and also the demand for a large grinding mill having such characteristics.

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 of determining the degree of fullness of a large grinding mill, said grinding mill having a drum casing with internal lifting means arranged inside the drum casing, which method comprises the steps of: - measuring the vibration in the surrounding structures of a large grinding mill drum, said vibration caused by internal lifting means of the drum casing; and - calculating the degree of fullness of the grinding mill based on the measured vibration measurement data.

Preferably, after the step of measuring the method comprises the step of: - analyzing harmonic vibrations from the vibration measurement data.

Preferably, in the step of analyzing the harmonic vibration analysis consists of the analysis of the harmonic vibration caused by main internal lifting means of the drum casing: Further, that in the step of analyzing the harmonic vibration analysis consists of an analysis of the harmonic vibration caused by auxiliary side bars of drum casing.

Preferably, in the step of calculating a toe angle <Pk of the grinding mill drum is first calculated.

Preferably, the step of calculating the calculation procedure comprises one or more of the following phases: - processing of the measured vibration measurement data, - determination of the harmonic vibrations, - observation of the position of the mill drum angle, and - calculating the toe angle <Pk.

Preferably, in the step of calculating the calculation procedure comprises spectral analysis, e.g. Fourier analysis.

Preferably, the step of measuring also the rotational position of the mill drum is measured using at least one accelerometer e.g. synchronization sensor accelerometer attached on rotating mill drum; and that in the step of calculating also the measured rotational position data is utilized. Further preferably, the step of measuring also at least one inclinometer attached on the rotating mill drum is used.

Preferably, the step of measuring also a phase locked loop arrangement is used.

In addition, the objects of the invention are achieved by an arrangement for determining the degree of fullness of a large grinding mill, having a grinding mill having an internal lifting means arranged inside the said drum casing, which arrangement has a vibration sensor arrangement arranged to measure the vibration in the surrounding structures of a large grinding mill drum, said vibration caused by the internal lifting means of the drum casing, and determining the degree of fullness of the large grinding mill based on the measured vibration measurement data.

Preferably, the vibration sensor arrangement is attached to the pinion gear arrangement of the large grinding mill arrangement. Alternatively, the vibration sensor arrangement is attached to the housing arrangement of the trunnion bearings of the large grinding mill arrangement. Further alternatively, the vibration sensor arrangement is attached to the pinion gear arrangement and to the housing arrangement of the trunnion bearings of the large grinding mill arrangement.

Preferably, you received a vibration sensor arrangement consisting of one or more Acceleration sensors. Preferably, the vibration sensor arrangement comprises one or more motion sensors and / or one or more force sensors and / or one or more pressure sensors. Further preferred, said one or more pressure sensors of the said pinion bearing / bearings are used to detect the vibration by measuring the pressure in the surrounding structures of a large grinding mill drum and / or the pressure in the lubrication arrangement of the pinion bearing / bearings.

Preferably, the arrangement comprises a data processing device, said data processing device being physically or wirelessly connected to said vibration sensor arrangement. Further preferably, said vibration sensor arrangement comprises a data processing and transmitting unit for handling raw measurement signals and transmitting the vibration measurement data wirelessly to said data processing device; and that said data processing device comprises a data receiving unit for receiving the vibration measurement data wirelessly from the said vibration sensor arrangement.

Preferably, the vibration sensor arrangement is arranged as a movable unit suitable for placing into multiple measurement positions.

In addition, the objects of the invention are achieved by a large grinding mill, which comprises a drum casing with an internal lifting means arranged inside the said drum casing and an arrangement for determining the degree of fullness of a large grinding mill, said arrangement having a vibration. sensor arrangement arranged to measure the vibration in the surrounding structures of a large grinding mill drum, said vibration caused by the internal lifting means of the drum casing, and determining the degree of fullness of the site large grinding mill based on the measured vibration measurement data.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a cross-sectional view of a large grinding mill according to the prior art;

Figure 2 shows a perspective and partially cut open view of a large grinding mill arrangement according to the prior art;

Figure 3 shows a perspective and partially cut open view of a single embodiment of an arrangement for determining the degree of fullness of a large grinding mill according to the present invention;

Figure 4 shows a perspective and partially cut open view of another embodiment of an arrangement for determining the degree of fullness of a large grinding mill according to the present invention;

Figure 5 shows a perspective and partially cut open view of a third embodiment of an arrangement defining a degree of fullness of a large grinding mill according to the present invention;

Figure 6 shows a perspective and partially cut open view of a third embodiment of an arrangement for determining the degree of fullness of a large grinding mill according to the present invention.

The prior art drawing of Figure 1 to 2 has been presented earlier. In the following, the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings of Figures 3 to 6.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method and an arrangement for registering an instant volume or an instant level of charge in an ore-grinding drum of the kind that is provided with internal lifting means.

The idea of the present invention is to measure the vibration in the surrounding grinding mill drum, said vibration caused by the internal lifting means of the drum casing, and calculating and determining the degree of fullness of the large grinding mill drum on the said vibration.

Figure 3 shows a perspective and partially cut open view of a single embodiment of an arrangement for determining the degree of fullness of a large grinding mill according to the present invention. In Figure 3, the grinding mill arrangement has a drum casing 3, which drum casing 3 is provided with linings. As can be seen from the partially cut open view of Figure 3 the linings of the drum casing 3 comprise internal lifting means i.e. lifting bars 4, 5 inside the mill for lifting of the grinding charge material. The large grinding mill arrangement according to the present invention has a trunnion support with trunnion bearings 6, 7 on both sides of the drum casing 3 of the grinding mill, a ring gear 8, with a 360 ° fully enclosed guard, and a pinion gear arrangement comprising a pinion gear 9 and pinion bearings 10, 11 arranged on both sides of the pinion gear 9.

The presented embodiment of an arrangement for determining the degree of fullness of a large grinding mill according to the present invention also comprises a vibration sensor arrangement 12 attached to the pinion gear arrangement 9 of the large grinding mill arrangement. The said vibration sensor arrangement 12 measures the vibration in the surrounding structures of a large grinding mill drum and provides vibration measurement data.

In the arrangement for determining the degree of fullness of a large grinding mill according to the present invention an important part of the calculations of fullness using this apparatus and method is the knowledge of the rotation of the mill. In the said arrangement this information together with the vibration measurement data measured by the said vibration sensor arrangement 12 is used to calculate the toe angle <Pk of the internal lifting means hitting the grinding charge material and / or the shoulder angle Φ5 and thereafter to calculate the degree of fullness of a large grinding mill. In said calculation a vibration magnitude signal of said measured vibration measurement data may be synchronized in order to calculate the toe angle <Pk of internal lifting means hitting the grinding charge material. Also a trigger e.g. inductive trigger or laser based trigger can be used in said synchronization.

In the arrangement for determining the degree of fullness of a large grinding mill according to the present invention the vibration sensor arrangement 12 may comprise one or more Acceleration sensors for detecting and measuring the vibration in the surrounding structures of a large grinding mill drum. The vibration sensor arrangement 12 may also comprise one or more motion sensors and / or one or more force sensors and / or one or more pressure sensors. In said arrangement, one or more pressure sensors may be used for detecting vibration by measuring the pressure in the surrounding structures of a large grinding mill drum and / or the pressure in the lubrication arrangement of the pinion bearing / bearings 10, 11.

Figure 4 shows a perspective and partially cut open view of another embodiment of an arrangement for determining the degree of fullness of a large grinding mill according to the present invention. In Figure 4, the grinding mill arrangement has a drum casing 3, which drum casing 3 is provided with linings. The linings of the drum casing 3 comprise internal lifting means i.e. lifting bars 4, 5 inside the mill for lifting of the grinding charge material. The large grinding mill arrangement according to the present invention has a trunnion support with trunnion bearings 6, 7 on both sides of the drum casing 3 of the grinding mill, a ring gear 8, with a 360 ° fully enclosed guard, and a pinion gear arrangement comprising a pinion gear 9 and pinion bearings 10, 11 arranged on both sides of the pinion gear 9.

6 to 7 of the large grinding mill arrangement The enclosed another arrangement of the arrangement for determining the degree of fullness of a large grinding mill according to the present invention also comprises a vibration sensor arrangement 13. The said vibration sensor arrangement 13 measures the vibration in the surrounding structures of a large grinding mill drum and provides vibration measurement data.

In the arrangement for determining the degree of fullness of a large grinding mill according to the present invention the knowledge of the rotation of the mill together with the vibration measurement data measured by said vibration sensor arrangement 13 is used to calculate the toe angle <Pk of internal lifting means hitting the grinding charge material and / or the shoulder angle Φ5 and thereafter to calculate the degree of fullness of a large grinding mill.

In the arrangement for determining the degree of fullness of a large grinding mill drum, 13 may comprise one or more Acceleration sensors for detecting and measuring the vibration in the surrounding structures of a large grinding mill drum. The vibration sensor arrangement 13 may also comprise one or more motion sensors and / or one or more force sensors and / or one or more pressure sensors. In said arrangement said one or more pressure sensors may be used for detecting vibration by measuring the pressure in the surrounding structures of a large grinding mill drum and / or the pressure in the trunnion bearing lubrication arrangement.

Figure 5 shows a perspective and partially cut open view of a third embodiment of an arrangement for determining the degree of fullness of a large grinding mill according to the present invention. In Figure 5, the grinding mill arrangement has a drum casing 3, which drum casing 3 is provided with linings. The linings of the drum casing 3 comprise internal lifting means i.e. lifting bars 4, 5 inside the mill for lifting of the grinding charge material. The large grinding mill arrangement according to the present invention has a trunnion support with trunnion bearings 6, 7 on both sides of the drum casing 3 of the grinding mill, a ring gear 8, with a 360 ° fully enclosed guard, and a pinion gear arrangement comprising a pinion gear 9 and pinion bearings 10, 11 arranged on both sides of the pinion gear 9.

The presented third embodiment of an arrangement for determining the degree of fullness of a large grinding mill according to the present invention also comprises a vibration sensor arrangement 9 attached to the housing arrangement of the trunnion bearings 6, 7 of the large grinding mill arrangement. The said vibration sensor arrangement 14 measures the vibration in the surrounding structures of a large grinding mill drum and provides vibration measurement data.

In the arrangement for determining the degree of fullness of a large grinding mill according to the present invention the knowledge of the rotation of the mill together with the vibration measurement data measured by said vibration sensor arrangement 14 is used to calculate the toe angle <Pk of internal lifting means hitting the grinding charge material and / or the shoulder angle Φ5 and thereafter to calculate the degree of fullness of a large grinding mill.

In the arrangement for determining the degree of fullness of a large grinding mill according to the present invention the vibration sensor arrangement 14 may comprise one or more Acceleration sensors for detecting and measuring the vibration in the surrounding structures of a large grinding mill drum. The vibration sensor arrangement 14 may also comprise one or more motion sensors and / or one or more force sensors and / or one or more pressure sensors. In said arrangement said one or more pressure sensors may be used for detecting vibration by measuring the pressure in the surrounding structures of a large grinding mill drum and / or the pressure in the pinion bearing lubrication arrangement and / or the trunnion bearing lubrication arrangement.

Figure 6 shows a perspective and partially cut open view of a fourth embodiment of an arrangement for determining the degree of fullness of a large grinding mill according to the present invention. In Figure 6, the grinding mill arrangement has a drum casing 3, which drum casing 3 is provided with linings. The linings of the drum casing 3 comprise internal lifting means i.e. lifting bars 4, 5 inside the mill for lifting of the grinding charge material. The large grinding mill arrangement according to the present invention has a trunnion support with trunnion bearings 6, 7 on both sides of the drum casing 3 of the grinding mill, a ring gear 8, with a 360 ° fully enclosed guard, and a pinion gear arrangement comprising a pinion gear 9 and pinion bearings 10, 11 arranged on both sides of the pinion gear 9.

The presented fourth embodiment of an arrangement for determining the degree of fullness of a large grinding mill according to the present invention also comprises a vibration sensor arrangement 14 attached to the pinion gear arrangement and to the trunnion bearings housing arrangement of the large grinding mill arrangement. The said vibration sensor arrangement 14 measures the vibration in the surrounding structures of a large grinding mill drum and provides vibration measurement data.

The presented fourth embodiment of an arrangement for determining the degree of fullness of a large grinding mill according to the present invention further comprises a data processing device 15, e.g. a personal computer (PC) 15, said data processing device 15 being physically or wirelessly connected to said vibration sensor arrangement 14.

The received vibration sensor arrangement 14 of the arrangement according to the present invention may comprise a data processing and transmitting unit for handling raw measurement signals and transmitting the vibration measurement data wirelessly to the received data processing device 15. Respectively, the data processing device 15 of the arrangement according to the present invention may comprise a receiving unit for receiving the vibration measurement data wirelessly from the received vibration sensor arrangement 14.

In the arrangement for determining the degree of fullness of a large grinding mill according to the present invention, the vibration sensor arrangement may be arranged as a movable unit which is suitable for placing into multiple measurement positions.

In the arrangement for determining the degree of fullness of a large grinding mill according to the present invention the data processing device 15 calculates the toe angle <Pk of the internal lifting means hitting the grinding charge material and / or the shoulder angle Φ5 by using the knowledge of rotation of the mill together with vibration measurement data measured by said vibration sensor arrangement 14 and thereafter calculates the degree of fullness of a large grinding mill.

In the method and arrangement for determining the degree of fullness of a large grinding mill according to the present invention there is measured the vibration in the surrounding structures of a large grinding mill drum, said vibration caused by the internal lifting means of the drum casing. From the measurement of the vibration, the harmonic vibrations can be detected and analyzed. In this method and arrangement of harmonic vibration analysis procedure consists of analysis of harmonic vibration caused by main internal lifting means of drum casing. Alternatively, the harmonic vibration analysis procedure consists of an analysis of the harmonic vibration caused by auxiliary side bars of the drum casing.

With the help of the measurement of vibration the degree of fullness of a large grinding mill is then calculated. - the processing of measured vibration measurement data, - the determination of the harmonic vibrations, , - observing and / or adjusting for the initial position of the mill drum angle, and - calculating the toe angle {pk and / or the shoulder angle <PS.

Furthermore, the calculation procedure of the degree of fullness of a large grinding mill may comprise spectral analysis, e.g. Fourier analysis.

Furthermore, the arrangement for determining the degree of fullness of a large grinding mill according to the present invention may comprise at least one accelerometer and / or inclinometer attached on the rotating mill drum and arranged to detect and measure the rotational position of the mill drum and arranged to transmit the measured rotational position data wirelessly to the received data processing device 15. The data processing device 15 of the arrangement according to the present invention may then utilize the measured rotational position data in the degree of fullness of a large grinding mill. Furthermore, the arrangement for determining the degree of fullness of a large grinding mill according to the present invention may comprise a phase locked loop arrangement (PLL).

In the method and arrangement for determining the degree of fullness of a large grinding mill according to the present invention, the vibration measurement may be carried out during the start-up of the large grinding mill. Additionally, the vibration measurement may also be carried out during a routine check-up of a large grinding mill. The vibration measurement according to the present invention may also be carried out as an online measurement process. The said online vibration measurement according to the present invention may be carried out as a maintenance procedure and / or as a control procedure and / or as an optimization procedure. The vibration measurement according to the present invention may be carried out as a remotely controlled procedure.

In the method and arrangement according to the present invention, the degree of fullness of a large grinding mill may be calculated e.g. as explained in the following. In the analysis of the measurement results of the phase Θ of the force or power oscillation caused by the lifter bars is calculated by using a sample data P (n) that is equidistant in relation to the angle of rotation and is obtained e.g. on the basis of the mill power draw of one rotation cycle, according to the following formula:

i.e. argument, of a complex number z, N = number of samples in a sample data P (n),

Nn = number of lifter bars in the mill, n = number of sample, and Θ = phase of the oscillation caused by the lifter bars.

The toe angle is calculated from the phase Θ of the power oscillation caused by the lifter bars as follows:

where kn = number of lifter bars remaining between the lifter bar located nearest to the axis x and the lifter bar located nearest to the toe position, <Pk = toe angle, and Φη = angle from the axis x to the lifter bar located nearest to the axis x, so that it has a positive value in the direction of rotation of the mill.

The degree of fullness is calculated from the toe angle and the rotation speed of the mill by means of various mathematical models, such as the model defined in the Julius Kruttschitt Mineral Research Center (JKMRC). Napier-Munn, T., Morrell, S., Morrison, R., Kojovic, T.: Mineral Comminution Circuits, Their Operation and Optimization (Julius Kruttschnitt Mineral Research Center, University) of Queensland, Indooroopilly, Australia, 1999). The calculation formula of the JKMRC model for the degree of fullness in a mill is given in the following formula:

where the degree of fullness is defined by iterating the degree of fullness of the mill in relation to the interior volume of the mill. In the above formula, nc is an experimentally calculated portion of the critical speed of the mill, in which case the centrifugation is complete, np is the rotation speed of the mill in relation to the critical speed, V-, is the previous degree of fullness of the mill, and Vm is the degree of fullness to be defined, in relation to the interior volume of the mill.

The vibration sensor arrangement according to the present invention provides a very sensitive measurement of the vibration in the surrounding structures of a large grinding mill drum. The said measurement is a direct measurement of the reactions caused by the grinding material which is a direct measurement that is not disturbed by any piece of equipment.

As a measurement according to the present invention is a direct measurement of the phenomena and related measurement of the reactions caused by the grinding material, there is no need for calibration. Direct measurement is of particular importance in the analysis and calculation, as this simplifies the calculations significantly and makes the result more reliable. As the measurement solution with sensor arrangements is quite simple and straightforward also installation and maintenance is easy.

With the help of a solution according to the present invention, manufacturers of large grinding mills will be able to provide a grinding mill with a measurement arrangement for the determination of a degree of fullness of a large grinding mill with said measurement arrangement having better measurement sensitivity. The solution according to the present invention may be utilisable in any kind of large grinding mill having lifter bars inside the grinding mill drum.

It will be obvious to a person skilled in the art that, as 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.

Claims (21)

A method for determining the degree of filling of a large refiner with a drum body (3) and internal lifting means (4), (5) fitted inside said drum body (3), characterized in that the method comprises the steps of: in structures, the vibration being caused by the internal lifting means (4), (5) of the drum body (3); and - calculating said filler mill fill rate based on said measured vibration germination data. Method according to Claim 1, characterized in that, after the measuring step, the method comprises the step of - analyzing the vibration measurement data for harmonic vibrations. Method according to claim 2, characterized in that, in the analysis step, the analysis of the harmonic oscillation comprises the analysis of the harmonic oscillation caused by the main internal lifting means of the drum body. A method according to claim 3, characterized in that the analysis step comprises a harmonic oscillation analysis by the additional side bars of the drum body in the analysis step. Method according to one of Claims 1 to 4, characterized in that, in the calculation step, the toe angle Φι <of the grinding mill drum is first calculated. Method according to one of Claims 1 to 5, characterized in that, in the calculation step, the calculation procedure comprises one or more or all of the following steps: - processing the measured vibration measurement data; - determining the period of full revolutions; . Method according to one of Claims 1 to 6, characterized in that, in the calculation step, the calculation procedure comprises spectral analysis, for example Fourier analysis. Method according to one of Claims 1 to 7, characterized in that the measuring step also measures the rotation position of the mill drum by using at least one accelerometer, for example a synchronization sensor accelerometer mounted on a rotary mill drum; and that the measured step also utilizes measured rotation position information. Method according to Claim 8, characterized in that the measuring step also uses at least one inclination meter which is attached to a rotating mill drum. Method according to one of Claims 1 to 9, characterized in that a phase-locked loop arrangement is also used in the measuring step. An arrangement for determining the degree of filling of a large refiner, the refiner having a drum body (3) and internal lifting means (4), (5) fitted inside said drum body (3), characterized by a vibration sensor arrangement (12), (13), (14) adapted to measure vibration in structures surrounding the drum of a large refiner caused by internal lifting means (4), (5) of the drum body (3), and to determine the fill rate of said large refiner based on said measured vibration ripple. An arrangement according to claim 11, characterized in that said vibration sensor arrangement (12) is attached to a traction sheave arrangement (9) of a large refiner mill arrangement. An arrangement according to claim 11, characterized in that said vibration sensor arrangement (13) is fixed to the bearing housing arrangement (9) of the shaft support bearings (6), (7) of the large refining mill arrangement. Arrangement according to Claim 11, characterized in that said vibration sensor arrangement (14) is fixed to the drive wheel arrangement (9) and the bearing housing arrangement (9) of the shaft bearing bearings (6), (7) of the large refiner mill arrangement. An arrangement according to any one of claims 11 to 14, characterized in that said vibration sensor arrangement (12), (13), (14) comprises one or more acceleration sensors. Arrangement according to one of Claims 11 to 15, characterized in that said vibration sensor arrangement (12), (13), (14) comprises one or more motion sensors and / or one or more force sensors and / or one or more pressure sensors. An arrangement according to claim 16, characterized in that said one or more pressure sensors of said vibration sensor arrangement (12), (13), (14) are used to detect vibration by measuring pressure in structures surrounding the drum of a large refiner and / or bearings (10), (11). An arrangement according to any one of claims 11 to 17, characterized in that the arrangement comprises a data processing device (15), which is physically or wirelessly connected to said vibration sensor arrangement (12), (13), (14). An arrangement according to claim 18, characterized in that said vibration sensor arrangement (12), (13), (14) comprises a data processing and transmission unit for processing raw measurement signals and wirelessly transmitting germination data to said data processing device (15); and that said data processing device (15) comprises a data receiving unit for wirelessly receiving background IT information from said vibration sensor system (12), (13), (14). Arrangement according to one of Claims 11 to 19, characterized in that said vibration sensor arrangement (12), (13), (14) is arranged as a movable unit suitable for positioning in a plurality of measuring stations. Large milling mill, characterized in that said large milling mill comprises internal lifting means (4), (5) arranged inside the drum body (3) and an inner drum body (3) and an arrangement according to claim 6 for determining the degree of filling of the milling mill.