Airflow mill material level control system

Abstract

The present application relates to the technical field of airflow mill, especially to the airflow mill material level control system, which solves the problems in the prior art, comprising a mill cavity, a bottom patch is pasted on the inner side of the bottom of the mill cavity, a plurality of convex parts arranged from top to bottom are welded on the inner side wall of the mill cavity, an electric telescopic rod is installed on the mill cavity in the convex part, a side induction sheet is arranged on the outer side of the telescopic end of the electric telescopic rod, a protection tube is welded on the outer side of the convex part, a cleaning pad is pasted on the inner side of the protection tube, an electrode detection end is connected to the outer surface of the side induction sheet, a detection switch and a potential measuring instrument are arranged between the electrode detection end and the bottom patch, and a sonotrode is installed on the outer side of the mill cavity, the airflow mill material level control system can intuitively and real-timely understand the material level in the mill cavity through the sensor, can realize the dynamic constant material level automatic feeding of the airflow mill, has no material level zero point offset, does not need to be calibrated during long-term operation, does not need to consider the material level problem during the airflow mill with material debugging, and is simple to debug.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of jet mill, in particular to a material level control system of jet mill. BACKGROUND

[0002] The classification wheel of fluidized bed jet mill is a device for screening the speed of particles in the jet mill. It can intercept low-speed large-particle-size powder, and the large-particle-size powder can continue to be broken in the mill cavity to become smaller. The material level of the jet mill will affect the travel of the powder in the mill cavity and the frequency of collision between particles, and then affect the speed of the particles when reaching the classification wheel and the breaking efficiency of the particles. When the material level is low, large-size particles can also reach high speed in the mill cavity and pass through the classification wheel to obtain a product with larger particle size. When the material level is high, small-size particles cannot pass through the classification wheel because of short acceleration travel and slow speed, and a product with smaller particle size is obtained. Fluctuation of the material level will adversely affect the particle size and distribution of the product.

[0003] At present, the mainstream control method in the market is to control the feeding speed or monitor the weight of the mill cavity. Both methods have their own shortcomings. When the feeding speed and the discharge speed of the jet mill reach a balance, the material level in the mill cavity can be considered stable, and a product with stable particle size distribution can be obtained. However, the jet mill uses high-pressure gas as the grinding gas, and the internal gas pressure fluctuates greatly. The weight displayed after the start of the jet mill is inaccurate, and cannot be compared with the discharge weight. Since the raw material itself is a particle, the material density is different when the jet mill feeding bin is at high and low levels. Even if the feeding speed is the same, the actual weight of the material is different. There may be problems such as clogging of the feeding slot and bridging of the material during feeding. In actual production, it is difficult to control the material level by controlling the feeding speed. Monitoring the weight of the mill cavity to control the material level of the jet mill is the mainstream method at present. However, in actual operation, the accuracy of the mill cavity weight is disturbed by the grinding gas flow, the fluctuation amplitude is large, and there is a problem of zero point drift during long-term operation. At this time, the actual material level will deviate from the set value. Therefore, monitoring the weight of the mill cavity requires frequent calibration of the weight, which is complicated to operate. Because of the pressure build-up in the mill cavity, the zero point can only be calibrated at the time of empty blowing, so the zero point is related to the pressure of the grinding gas. Moreover, monitoring the weight of the mill cavity cannot directly reflect the high and low of the material level. Different hardness and density of the product require different grinding gas pressure. Even if you want to control the material level to be the same as before, you cannot calculate the standard material level, and you must carry out material debugging.

[0004] After the material is in a fluidized state, the capacitance value between each electrode of the mill cavity indicates the concentration of the material in the mill cavity. The dielectric constant of the gas in the mill cavity can be calculated from the capacitance value, which has a strong correlation with the concentration of the fluidized material powder. After the jet mill is started, part of the material is blown up and fluidized, and part of the material is not involved in crushing. When the material level is measured by the material level detection sensor, the internal patch is easily worn out due to long-term impact of the material, and the dirt attached to the surface of the patch also affects the accuracy of the detection capacitance of the electrode end, causing the measurement to fail or the data accuracy to decrease, so the internal patch needs to be effectively protected. After the material is added during the feeding process, the top of the material will form a conical structure, causing a certain deviation between the material height and the actual material quantity, thereby affecting the judgment of the remaining material in the mill cavity. SUMMARY

[0005] The purpose of the present application is to solve the problems existing in the prior art.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] The jet mill material level control system comprises a mill cavity, a bottom patch is attached to the inner side of the bottom of the mill cavity, a plurality of convex portions are welded on the inner side wall of the mill cavity in sequence from top to bottom, an electric telescopic rod is installed on the mill cavity in the convex portion, a side sensing sheet is arranged on the outer side of the telescopic end of the electric telescopic rod, a protection tube is welded on the outer side of the convex portion, a cleaning pad is attached to the inner side of the protection tube, an electrode detection end is connected to the outer surface of the side sensing sheet, a detection switch and a potential measuring instrument are arranged between the electrode detection end and the bottom patch, and a sonotrode is installed on the outer side of the mill cavity.

[0008] Preferably, a material level detection sensor is arranged in the mill cavity, the material level detection sensor feeds back the detection result to a control circuit, and the control circuit controls the feeding work of the feeder.

[0009] Preferably, the telescopic end of the electric telescopic rod is clamped in the protection tube, and the outer surface of the side sensing sheet on the outer side of the telescopic end of the electric telescopic rod is in contact with the inner wall of the cleaning pad.

[0010] Preferably, a radially telescopic cleaning pad compression spring is arranged between the cleaning pad and the protection tube, the cleaning pad compression spring can continuously generate a circumferential extrusion force on the side sensing sheet when the side sensing sheet extends to the outside of the protection tube through the cleaning pad, and the cleaning pad is closed to form a plug for sealing the convex portion when the side sensing sheet is retracted out of the cleaning pad.

[0011] Preferably, the material of the cleaning pad is rubber, and the inner wall of the cleaning pad is provided with uniformly distributed grooves.

[0012] Preferably, the feeder is controlled by a variable frequency motor, and the control circuit controls the rotating speed of the variable frequency motor in the feeder.

[0013] The present application has the following advantages:

[0014] 1. The material level control system of the jet mill can intuitively and real-timely understand the material level in the grinding chamber through the sensor, and can realize dynamic constant material level automatic feeding of the jet mill without material level zero point offset, without calibration during long-term operation, without considering material level problem during jet mill with material debugging, and simple debugging.

[0015] 2. The material level control system of the jet mill keeps the material level stable while effectively protecting the side induction patch used for internal detection, avoiding the induction patch being exposed for a long time, avoiding excessive friction of the induction patch caused by material flow, and prolonging the service life.

[0016] 3. The jet mill material level control system is provided with a vibrator outside the grinding chamber. When the jet mill is only started to discharge, the vibrator vibrates to make the material near the discharge port slide down, so that the top of the material is flat, facilitating monitoring of the material level. When the jet mill is working, the material attached to the inner wall of the grinding chamber and the side induction patch can also quickly fall under the action of the vibrator, thereby effectively detecting the internal material amount. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The structure diagram of the jet mill material level control system according to the present application is shown.

[0018] Figure 2 The side induction patch installation structure diagram of the jet mill material level control system according to the present application is shown.

[0019] Figure 3 The side induction patch installation structure diagram of the jet mill material level control system according to the present application is shown.

[0020] Figure 4 The feeder control flow diagram of the jet mill material level control system according to the present application is shown.

[0021] In the figure: 1, material level detection sensor; 2, control circuit; 3, feeder; 4, grinding chamber; 5, bottom patch; 6, convex part; 7, electrode detection end; 8, detection switch; 9, potential measuring instrument; 10, vibrator; 11, electric telescopic rod; 12, side induction patch; 13, protection tube; 14, cleaning pad; 15, cleaning pad compression spring. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0023] In the description of the present application, it is to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0024] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features referred to. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0025] Referring to Figures 1-4 One of the patent embodiments is an airflow grinding material level control system ， This material level control system can be used in a bin or horizontal device, including a grinding cavity 4, a bottom patch 5 is attached to the inside of the bottom of the grinding cavity 4, a plurality of convex portions 6 are welded on the inner wall of the grinding cavity 4, arranged from top to bottom, an electric telescopic rod 11 is installed on the grinding cavity 4 in the convex portion 6, a side induction sheet 12 is provided on the outside of the telescopic end of the electric telescopic rod 11, the material of the side induction sheet 12 is carbon fiber, a protection tube 13 is welded on the outside of the convex portion 6, a cleaning pad 14 is attached to the inside of the protection tube 13, an electrode detection end 7 is connected to the outer surface of the side induction sheet 12, a detection switch 8 and a potential measuring instrument 9 are provided between the electrode detection end 7 and the bottom patch 5, and a sonotrode 10 is installed on the outside of the grinding cavity 4.

[0026] The inside of the grinding cavity 4 is provided with a material level detection sensor 1, the material level detection sensor 1 feeds back the material level detection result to a control circuit 2, the control circuit 2 controls the feeding work of the feeder 3 and in turn controls the material level, the telescopic end of the electric telescopic rod 11 is clamped in the inside of the protection tube 13, the outer surface of the side induction sheet 12 outside the telescopic end of the electric telescopic rod 11 is in contact with the inner wall of the cleaning pad 14, the cleaning pad 14 is made of rubber, the inner wall of the cleaning pad 14 is provided with uniformly distributed grooves, the telescopic end of the electric telescopic rod 11 penetrates and extends to one side outside of the protection tube 13, the cleaning pad 14 controls the side induction sheet 12 to be pressed by the cleaning pad pressing spring, the grooves can increase the friction between the cleaning pad 14 and the side induction sheet 12, ensure the cleaning effect of the side induction sheet 12, and block the protection tube 13 after the side induction sheet 12 is retracted, the feeder 3 is controlled by a variable frequency motor, and the control circuit 2 controls the rotating speed of the variable frequency motor in the feeder 3.

[0027] In the embodiment, the material of the grinding cavity 4 of the airflow mill is an insulating material, so as to avoid affecting the normal detection of the bottom patch 5 and the side induction sheet 12. When the concentration of the internal fluidized material is effectively detected, the electric telescopic rod 11 is first controlled to extend out. When the telescopic end of the electric telescopic rod 11 extends out, the side induction sheet 12 pasted on the outer surface of the telescopic end of the electric telescopic rod 11 extends outwards. At this time, the area between the side induction sheet 12 and the bottom patch 5 is blocked by the material, so as to affect the capacitance size of the detection end of the side induction sheet 12. The material level sensor 12 sends the capacitance value and position information of the side induction sheet to the control circuit, so as to effectively monitor the internal material concentration through the capacitance change, so as to realize the effect that the material level detection sensor 1 judges the material concentration in the grinding cavity 4. The side induction sheets 12 of the grinding cavity 4 are vertically distributed and are single electrodes. The capacitance value between the electrodes indicates the concentration of the material in the grinding cavity 4. The dielectric constant of the gas in the grinding cavity 4 can be calculated through the capacitance value, which has a strong correlation with the concentration of the fluidized material powder. In the material crushing process, the material moves at a very high speed, and the material continuously impacts the side induction sheet 12, which is easy to cause wear of the side induction sheet 12. In addition, the dust in the material is easy to adhere to the surface of the side induction sheet 12, which causes impurities to adhere to the surface of the top part not submerged by the material, so as to affect the resistance and capacitance test, and in turn affect the material level judgment. Therefore, when not detecting, the electric telescopic rod 11 is retracted, the surface of the side induction sheet 12 is rubbed with the cleaning pad 14, the surface impurities of the side induction sheet 12 are removed, and the side induction sheet 12 is effectively protected, so as to avoid wear. After the electric telescopic rod 11 is retracted, the cleaning pad 14 is retracted inwards under the action of the cleaning pad pressing spring 15, so as to block the top end of the protection tube 13, and avoid that dust and other impurities enter the convex part 6.

[0028] The material level in the present application refers to the sum of all materials in the grinding cavity 4, which is calculated on the basis of considering the fluidized material and the material deposited at the bottom of the grinding cavity 4. The sensor in the present application aims to monitor this material level.

[0029] For the settled material, the level can be monitored by the potential. For the fluidized material, the level can be converted by the capacitance. The sum of the two is the total material in the mill chamber 4.

[0030] The settled material is determined by detecting the potential change point. For example, the material level is between A and B points. The voltage will change between A and B points, so the height of the settled material is determined.

[0031] The fluidized material is converted into level information by capacitance. For example, the fluidized material is 10 kg. By detecting the capacitance between multiple side inductors above the B point, the corresponding dielectric constant can be obtained. After shutdown, the fluidized material will be converted into 10 kg level. In this way, the concentration of the fluidized material is marked with the level.

[0032] When the material level detection sensor 1 detects that the internal material is too much, the control circuit 2 controls the variable frequency motor speed of the feeder 3 to slow down, reducing the feeding speed. When the material level detection sensor 1 detects that the internal material is lower than the preset level, the control circuit 2 controls the variable frequency motor speed to increase, thereby speeding up the feeding work of the feeder 3. Since the material top is generally in a conical structure after the feeder 3 feeds, it causes the material top detected by the side inductor 12 to be actually smaller than the actual material amount, so calibration is needed. The mill chamber 4 is externally provided with a vibrator 10. The vibrator 10 knocks the outer wall of the mill chamber 4, thereby causing the conical area of the material top to collapse, and helping the powdery material to shake off the inner wall of the mill chamber 4, so that the top is flat and the inner wall reduces the adhesion of the material, thereby realizing the calibration of the material height and facilitating the effective judgment of the material amount.

[0033] In the embodiment, the QLM-4.5 type jet mill is taken as an example. When the material level is 40 kg, the productivity is about 5 kg / min. When the jet mill is first operated, the properties of the material need to be tested. First, the potential change is monitored to control the feeder 3 to fill the material to slightly above the set level. Then the feeder 3 is stopped, the grinding gas, classification and air induction system is opened, so that the material is fully fluidized. After a few minutes, the material level is only slightly reduced to the standard level. At this time, the air induction and grinding gas are gradually closed, and the material fluidization gradually stops. As the grinding gas decreases, the material gradually falls back to the mill chamber 4. During the process of the material gradually falling, the material level change is monitored by the potential change, and the material concentration in the mill chamber 4 is monitored by the capacitance change. Finally, the material level reaches the maximum value, and the capacitance tends to be the capacitance of air. During the process of closing the grinding gas and air induction, the difference between the material level and the final material level corresponds to the dielectric constant value of the jet mill mill chamber 4. After the next start, the real situation of the mill chamber level can be determined by simultaneously detecting the potential of the level near the electrode and the capacitance between the electrodes far from the bottom electrode, so as to be used as a basis for discharging.

[0034] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. An airflow grinding material level control system, comprising a grinding chamber (4), characterized in that, A bottom patch (5) is attached to the inner side of the bottom of the grinding cavity (4). Several protrusions (6) arranged sequentially from top to bottom are welded to the inner wall of the grinding cavity (4). An electric telescopic rod (11) is installed on the grinding cavity (4) located in the protrusions (6). A side sensing plate (12) is provided on the outer side of the telescopic end of the electric telescopic rod (11). A protective tube (13) is welded to the outer side of the protrusions (6). A cleaning pad (14) is attached to the inner side of the protective tube (13). An electrode detection end (7) is connected to the outer surface of the side sensing plate (12). A detection switch (8) and a potential measuring instrument (9) are provided between the electrode detection end (7) and the bottom patch (5). A vibrator (10) is installed on the outer side of the grinding cavity (4). The telescopic end of the electric telescopic rod (11) is locked inside the protective tube (13), and the outer surface of the side sensor plate (12) on the outside of the telescopic end of the electric telescopic rod (11) is in contact with the inner wall of the cleaning pad (14). A radially telescopic cleaning pad compression spring (15) is provided between the cleaning pad (14) and the protective tube (13). When the side sensing plate (12) extends through the cleaning pad (14) to the outside of the protective tube (13), the cleaning pad compression spring (15) can continuously generate circumferential squeezing force on the side sensing plate (12). When the side sensing plate (12) retracts out of the cleaning pad (14), the cleaning pad (14) closes to form a plug that closes the protrusion (6).

2. The airflow mill material level control system according to claim 1, characterized in that, The grinding chamber (4) is equipped with a material level detection sensor (1), which feeds back the detection result to the control circuit (2), and the control circuit (2) controls the feeder (3) to feed the material.

3. The airflow mill material level control system according to claim 1, characterized in that, The cleaning pad (14) is made of rubber, and its inner wall has evenly distributed grooves.

4. The airflow grinding material level control system according to claim 2, characterized in that, The feeder (3) is controlled by a variable frequency motor, and the control circuit (2) controls the speed of the variable frequency motor in the feeder (3).

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