Autonomous mill and grinding method

Abstract

The invention relates to a mill comprising an inlet (1) for a product to be ground (P), at least one grinding mechanism (2), an outlet (3) for the ground product (M), at least one particle measuring probe (4) for ascertaining the size of particles passing the particle measuring probe, a control unit and means for adjusting the grinding mechanism (2). The at least one particle measuring probe (4) or a particle removal device connected to the particle measuring probe (4 via a suction device is arranged in the grinding mechanism (2) or between the grinding mechanism (2) and the outlet (3). The control unit is suitable for controlling the means for adjusting the grinding mechanism (2) on the basis of information from the at least one particle measuring probe, in particular a size distribution ascertained on the basis of a plurality of measured values.

Description

[Technical field]

[0001] The present invention relates to an autonomous mill and a method for grinding natural products. [Background technology]

[0002] The purpose of a mill is to grind a coarse material into a fine-grained final product, and the size of the ground particles is often the determining quality characteristic and therefore the reference size for the grinding process. In the mill, the coarse material is usually conveyed between rollers arranged in pairs. In the mill, the coarse material is usually conveyed between roller pairs, so that the rollers of the roller pair are spaced apart with a certain roller gap. The particle size of the resulting ground material depends on the width of the roller gap and can be adjusted by moving the rollers closer to each other or farther apart. In addition to the width of the roller gap, the ambient temperature, the temperature of the product to be ground, the pressure prevailing in the mill, the humidity, the moisture content of the product to be ground, the speed of the rollers, the roller temperature and the vibrations prevailing in the mill can also affect the quality of the ground material or provide information on the performance of the mill. In order to ensure a consistent quality of the ground material and the performance of the mill, it is known in the state of the art to measure these parameters during the grinding process and to adjust them to predetermined target values. To monitor and adjust particle size, ground material is typically extracted from the mill using a sampling scoop, the sample is then analyzed with an external device, and the mill settings are then adjusted according to the measurement results. However, sampling involves significant repetitive labor and material loss, and the time delay due to external measurements does not allow for efficient adjustment and control of the mill settings. Some mill manufacturers have therefore developed automatic measurement systems to determine and adjust the force distribution between the rollers in order to continuously adjust the particle size during the grinding process. However, this method does not directly measure the particle size, but assumes that the force is proportional to the degree of grinding, i.e., to the particle size. While this may be well true for synthetic products, it is not true for natural products, which usually have very heterogeneous properties. For example, the hardness of coffee beans or wheat grains can vary greatly depending on the plant type, the growing location, the growing conditions and / or the drying process, and the size of the particles ground by the rollers will vary accordingly, even if the force distribution between the rollers is identical. Summary of the Invention [Problem to be solved by the invention]

[0003] The invention now sets itself the task of providing an autonomous mill which allows automatic, dynamic and fine regulation of the grinding process and of the particle size of the material to be ground during the grinding process. [Means for solving the problem]

[0004] This problem is solved by an autonomous mill having the features of patent claim 1 and by a grinding method having the features of patent claim 8. Further features and embodiments are indicated in the dependent claims, the advantages of which are explained in the following description. [Brief description of the drawings]

[0005] [Figure 1a] FIG. 1 is a schematic diagram of a mill according to the present invention, in cross-section from the side; [Figure 1b] FIG. 4 is a detailed side cross-sectional view of the nip of the roller pair. [Figure 1c] FIG. 4 is a detailed view of the roller gap between the roller pair, as viewed from below. [Figure 2a] 1 is a schematic diagram of an embodiment of a mill according to the present invention, in cross-sectional side view; FIG. [Figure 2b] 1 is a schematic diagram of an embodiment of a mill according to the present invention, in cross-sectional side view; FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] The drawings illustrate possible embodiments that are described in the following description. In the simplest embodiment of the invention, the autonomous mill comprises an inlet 1 for the product P to be ground, at least one grinding mechanism 2, an outlet 3 for the material M to be ground, at least one particle measuring probe 4, a control unit and means for adjusting the grinding mechanism 2 (Fig. 1a-b). The at least one particle measuring probe 4 is arranged in the grinding mechanism 2 or between the grinding mechanism 2 and the outlet 3 and periodically measures the size of the particles passing through it. The determined sizes are transferred to the control unit which uses these measurements to determine the size distribution. This information is used to control the means for adjusting the grinding mechanism 2. The means for adjusting the grinding mechanism 2 comprise, for example, a drive device which can change the settings of the grinding mechanism 2. Preferably, target or reference values ​​for the desired size distribution of the particles of the grinding material M are stored in the control unit and the measured size distribution of the particles is compared with this information. If the determined size distribution does not correspond to the desired value, the settings of the grinding mechanism 2 are adjusted accordingly. The information for adjusting the settings is stored as predetermined or empirical values ​​depending on the available measurements or the settings are changed using a trial and error method until the desired particle size distribution is achieved. The size distribution of the ground particles is determined by a particle measurement probe 4 and the settings of the grinding mechanism 2 are preferably adjusted continuously, automatically, in real time during the grinding process. This control allows for immediate response to changes in particle size without manual or external intervention to ensure consistent output quality at all times.

[0007] In a preferred embodiment of the invention, the grinding mechanism 2 comprises at least one pair of rollers 21 spaced apart at a certain nip 22 (FIG. 1b). During the grinding process, the rollers 21 rotate relative to one another so that the product P to be ground is conveyed through the nip 22 and ground into smaller particles. A particle measuring probe 4 is arranged after the pair of rollers 21 and determines the size distribution of the resulting particles. Since the size of the particles is an increasing function of the width of the nip 22, the width of the nip 22 is dynamically adjusted by the control unit depending on the measured size distribution of the ground particles. If the particles are too large, the rollers 21 move together and the nip 22 becomes narrower, if the particles are too small, the rollers 21 move apart and the nip 22 becomes wider. Means for adjusting the grinding mechanism 2 are used to move the rollers 21 together and apart and are controlled by the control unit. In order to control the movement of the rollers 21 relative to one another and the width of the nip 22 , a measuring unit can be provided which directly measures either the width of the nip 22 or the position of the axis of rotation of each roller 21 .

[0008] Due to roller wear or contamination, the width of the nip 22 along the rollers 21 may become uneven, leading to uneven particle sizes in the ground material M. Therefore, in an advantageous embodiment of the invention, several particle measuring probes 4 are arranged along the nip 22 (FIG. 1c). If excessive deviations in particle size along the nip 22 are detected by the particle measuring probes 4, the means for adjusting the grinding mechanism 2 can be used to automatically adjust the alignment of the rollers 21 relative to one another in order to compensate for the uneven nip 22.

[0009] This is advantageous when the grinding mechanism 2 has several pairs of rollers 21, where the product P to be ground is ground several times to increasingly finer particles (Figure 1a). Several roller pairs can be arranged, for example, one behind the other or one above the other, so that the product to be ground passes from one roller pair to the next. In this case, the mill can be provided with a particle measuring probe 4 after each pair of rollers 21 to check the particle size and adjust the individual pairs of rollers 21 (Figure 2a). In a simple embodiment of the mill, a single particle measuring probe 4 can also be arranged after the last pair of rollers 21, or in the outlet 3, or between the grinding mechanism 2 and the outlet 3 (Figure 2b). It is expected that the ground final product M is already well mixed by the various pairs of rollers 21 or by conveyors arranged between them, so that this single particle measuring probe 4 can determine representative measurements.

[0010] In one possible embodiment, the mill is equipped with a suction device that can alternately take particle samples at several different points in the grinding mechanism 2 by the particle removal device and transport them to a single particle measuring probe 4. This makes it possible to check particle size at several points in the grinding mechanism 2 and adjust each pair of rollers 21 without having to install multiple particle measuring probes 4 on the mill.

[0011] In addition to particle size, other parameters related to the quality of the ground material M can also be measured and controlled during the grinding process.

[0012] · Temperature: The temperature of the product P to be ground can be monitored by a temperature probe at the inlet 1. If necessary, a pre-treatment of the product P to be ground can be provided in order to bring it to a certain temperature before it reaches the grinding unit 2. The pre-treatment ensures that there are no quality-related deviations in the temperature of the material to be ground in the grinding mechanism 2. The temperature of the grinding material can also be monitored during the grinding process in the grinding unit 2 or at the outlet 3. Controlled heating or cooling means can be provided to maintain the temperature of the grinding material around a predefined target value. Naturally, the same applies to the ambient temperature, which should also be kept as uniform as possible.

[0013] Pressure in the grinding mechanism 2: The pressure in the grinding mechanism 2 can vary depending on the product P to be processed and can rise during the grinding process if outgassing of the grinding material occurs. The pressure prevailing in the grinding mechanism can therefore be monitored and a controlled air extraction system or an external air supply device can ensure constant pressure conditions around a predetermined target value.

[0014] · Moisture content: The moisture content of the product P to be ground can be monitored by a moisture probe at the inlet 1. If necessary, the product P to be ground can be pre-treated to a certain moisture content before reaching the grinding mechanism 2. Pre-treatment ensures that there are no quality-related deviations in the moisture content of the material to be ground in the grinding mechanism 2. The moisture content of the material to be ground can also be monitored during the grinding process in the grinding unit 2 or at the outlet 3. Controlled humidifiers or desiccants can be provided to maintain the moisture content of the ground material around a predefined target value. The humidity inside and outside the mill can also be controlled accordingly and kept as stable as possible.

[0015] In an advantageous embodiment of the mill, parameters providing information about the performance of the mill are also monitored.

[0016] Power consumption of roller motor: If the power consumption of the roller motor changes while the product remains the same, it is assumed that the roller 21 is dirty or worn due to an increase in frictional force.

[0017] Vibration and roller temperature: For the same product, if the vibration or roller temperature or roller coolant temperature change slowly and steadily, it is considered that the product is of poor quality or the roller is dirty. Heating is usually due to insufficient heat dissipation caused by dirt.

[0018] By monitoring one or more of these parameters, defects can be recognized early and necessary repairs of the grinding mechanism 2 can be planned in time or the ideal time to clean or replace the rollers can be calculated.

[0019] Roller contamination can be compensated to some extent by roller gap adjustment. Wear or contamination can result in gradual changes in the setpoint. Such changes are recognized by the system and stored in the control unit as new setpoints immediately after the end of the process.

[0020] In one embodiment of the present invention, the mill is equipped with an automatic roller cleaning system that is automatically activated and controlled by the control unit when contamination of the rollers 21 is detected.

[0021] However, at certain points the rollers must be cleaned or replaced. To do this, the rollers must be removed, cleaned or replaced and reinstalled. The distance between the rollers is then rechecked. Ideally, the baseline setting can be based on empirical values ​​after the rollers have been cleaned or replaced. In some cases. In some cases the rollers must be recalibrated with a test run. After maintenance or cleaning has been performed on the system, the original baseline values ​​are restored.

[0022] According to the invention, it is envisaged that a recipe is compiled prior to the grinding process and one or more of the above mentioned parameters, including at least the desired size distribution of the grinding particles, are defined as target values. In addition to the target values, it is advantageous if recipe-specific tolerances are defined for each parameter. During the grinding process, these parameters are measured and compared to the prescribed target values ​​by the control unit according to the recipe. If all measured values ​​are within the desired range, it can be assumed that the grinding material M is produced with the desired consistent quality. If the measured values ​​do not correspond to the specified target values, the settings of the grinding mechanism 2 are adjusted by the control unit using the means for adjusting the grinding mechanism 2. The determination of the size distribution of the grinding particles by the particle measuring probe 4 and the corresponding adjustment of the settings of the grinding mechanism 2 are preferably performed continuously, automatically and in real time during the grinding process.

[0023] In an advantageous embodiment, the mill outputs a signal during the grinding process containing the measured values ​​or triggers an alarm if the measured values ​​do not correspond to the desired target values. This signal can be, for example, a visual signal displayed on a screen. This signal can also be audio, especially when it functions as an alarm. The signal can also be electrical or electromagnetic and can be transmitted by cable or wirelessly to a separate electronic device such as a central control unit. The mill can be provided with a user interface for inputting the parameters to be monitored and the corresponding set points and tolerances, and / or the mill can receive an electrical or electromagnetic signal from a separate electronic device containing the parameters, set points and tolerances.

[0024] Advantageously, some or all of the values ​​measured during the grinding process are stored in a database and made available for further processing. The collected data can be used to analyze the process retrospectively or live at any time. This allows seamless process monitoring and control as well as more precise definition of target values.

[0025] Advantageously, the product P to be ground can be preweighed or the inlet 1 can be equipped with an in-line quantity measuring device.

[0026] In summary, a new mill and a new grinding process are presented that offer considerable advantages over the state of the art.

[0027] The mill operates virtually without human intervention. All deviations in quality-relevant process parameters are immediately recognized and corrected or directly reported.

[0028] Particle size is measured in a closed system without losses or risks from unnecessary sampling.

[0029] The mill ensures consistent quality by immediately correcting quality-related parameters in case of deviations from specified target values. This means that even natural products can be ground in a controlled and consistent manner.

[0030] Thanks to numerous monitoring systems and data points, downtime during the process is virtually eliminated.

[0031] Mills can be equipped with artificial intelligence that uses machine learning to predict maintenance requirements based on measured parameters and plan them at the ideal times.

Claims

1. A mill comprising an inlet (1) for the product to be ground (P), at least one grinding mechanism (2), an outlet (3) for the material to be ground (M), at least one particle measuring probe (4) for determining the size of the particles passing through, a control unit and means for regulating said grinding mechanism (2), the at least one particle measuring probe (4) or a particle extracting device connected to the particle measuring probe (4) via an extracting device is disposed within the grinding mechanism (2) or between the grinding mechanism (2) and the outlet (3); The control unit is suitable for controlling the means for adjusting the grinding mechanism (2) based on information from the at least one particle measuring probe, in particular a size distribution determined based on a plurality of measurements.

2. 2. The mill according to claim 1, characterized in that a desired value of the desired size distribution of the particles of the grinding material (M) is stored in the control unit, the control unit being suitable for comparing the measured size distribution of the particles with this desired value.

3. 2. A mill according to claim 1, characterized in that the grinding mechanism (2) comprises at least one pair of rollers (21) spaced apart by a roller nip (22).

4. 4. A mill according to claim 3, characterized in that several particle measuring probes (4) are arranged along the nip (22).

5. A mill according to claim 3, characterized in that the grinding mechanism (2) comprises several pairs of rollers (21).

6. 6. A mill as claimed in claim 5, characterized in that the mill has a single particle measuring probe (4) which is positioned after the last pair of rollers (21), or at the outlet (3), or between the grinding mechanism (2) and the outlet (3).

7. 2. A mill according to claim 1, characterized in that the mill has several particle extractors at several points of the grinding mechanism (2), and particle samples can be removed alternately at these several points of the grinding mechanism (2) by the extractors and conveyed to a single particle measuring probe (4).

8. First, a recipe is compiled in which the desired size distribution of the particles of at least the grinding material (M) is defined as a target value; During the grinding process, the size distribution of the particles of the grinding material (M) is measured and compared with a defined target value by the control unit according to the recipe, if the measured particle size distribution of the grinding material (M) does not correspond to the set target value, the settings of the grinding mechanism (2) are adjusted by the control unit using the means for adjusting the grinding mechanism (2); 2. A method for grinding using the mill according to claim 1, characterized by the process steps:

9. the recipe comprises, in addition to the target value of the size distribution of the particles, one or more target values ​​of the following parameters: ambient temperature, temperature of the product to be ground (P), temperature of the grinding material (M), moisture content of the product to be ground (P), moisture content of the grinding material (M), humidity, pressure in the grinding mechanism (2), power consumption of a roller motor, vibration of the grinding mechanism (2), temperature of the rollers (21); During the grinding process, one or more of these parameters are measured and compared with the set target values ​​by the control unit according to the recipe. The method according to claim 8, characterized in that

10. 10. The method according to claim 9, characterized in that contamination or defects of the grinding mechanism (2) are detected by monitoring the power consumption of the roller motor and / or the vibration of the grinding mechanism (2) and / or the temperature of the rollers (21).

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