JPH025463B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] This invention applies to powder particles in an air-flow type pulverizer, which accelerates powder particles with a particle size of several hundred microns or less using a high-speed jet air stream and pulverizes them into fine particles through mutual friction and collision between the powder particles. The present invention relates to a body supply amount control device. [Prior Art] An example of this type of prior art is the one described in Japanese Patent Publication No. 54-13631. That is, in this prior art shown in FIG. A jet air stream e is ejected, and the detector 5 detects the propulsive force generated when this jet air stream and the ascending particle stream f of the powder particles that are accompanied by it touch the baffle plate 3. The level c of the powder layer 2 is kept constant by converting it into an electric signal and controlling the powder supply machine using this electric signal. That is, as the thickness of the powder layer 2 gradually increases from the empty state, the amount of powder that rises along with the jet airflow increases. Therefore, the propulsive force applied to the baffle plate 3 gradually increases. However, when this height exceeds a certain height and the height of the granular material layer becomes high, the granular material ceases to flow, and therefore the driving force to the baffle plate 3 rapidly decreases. Therefore, the propulsive force increases in proportion to the height of the powder layer 2 from the empty state to the appropriate powder layer, so
This changing propulsive force is converted into an electrical signal, and when the propulsive force is the largest, the amount of powder and granular material supplied is controlled to be reduced. Further, similar control is possible even if the baffle plate 3 is replaced with a capacitance type level meter. [Problems to be Solved by the Invention] However, in the former case, it is difficult to sensitively detect changes in the driving force with respect to minute changes in the thickness of the powder. The reason for this is that a centrifugal air classifier is usually installed in the upper part of the crushing container, and the return powder flow m of the return powder (unclassified) from this classifier is caught up in the rising particle flow f. , are suspended in the crushing container 1, and the suspended particles reach a certain concentration, which reduces the driving force applied to the baffle plate 3 and changes the concentration. However, mechanically detecting this minute change in driving force cannot be used because of large errors, and in the latter case, detection is difficult due to the physical properties of the powder, such as relative dielectric constant. Therefore, the present invention detects the level of the powder with high precision, regardless of the state of grinding in the grinding container and regardless of the physical properties of the powder, thereby determining the height of the layer of the staying powder. An object of the present invention is to provide a powder supply amount control device for an air flow type pulverizer, which can maintain the pulverization efficiency at a constant level and thereby significantly improve the pulverization efficiency. [Means for Solving the Problems] In order to solve the above-mentioned problems, this invention detects the pressure of a pressure detection tube inserted into a predetermined position in the granular material of a crushing container in an air flow crusher, and A device that controls the powder supply machine to the grinding container so that the reference pressure set based on the pressure of the airflow space of It consists of a pressure detection tube on the powder and granule side and a static pressure detection tube on the space side that communicates from the side wall of the crushing container to the space above the powder and granule layer. The present invention provides a supply amount control device that controls a powder or granular material feeder so that the powder and granular material feeder matches the set value. [Function] First, the function of the first invention will be described. Powder is fed into a crushing container by a powder feeder. On the other hand, air generated from a compressed air source is injected into the accumulated powder layer using a jet nozzle to accelerate the powder, and the particles are finely pulverized in the powder layer due to mutual friction and collision between the particles. . The finely pulverized particles are air classified into fine powder and fine powder by an air classifier, and the fine powder is returned to the crushing container, and the fine powder is sent to the dust collector along with the air flow, where it is separated into fine powder and air, and the fine powder is separated into fine powder and air. taken out as a product,
Air is exhausted via an exhaust fan. During the above operation, if the level of the powder layer increases or decreases due to an imbalance between the amount of pulverization and the amount of supply, the pressure within the detection tube changes due to this increase or decrease. This change in pressure is guided to a pressure conversion regulator, which detects the difference from the set pressure, converts this difference into an electrical signal, inputs this signal to the control unit, and controls the control unit based on the commands from the control unit. It is something to do. That is, the rotational speed of a constantly rotating electric motor is controlled, and the supply amount is controlled by the powder supply machine. Then, the number of revolutions of the electric motor is increased or decreased until the difference becomes zero, and the amount of powder or granular material to be fed is increased or decreased. When the level of the powder layer reaches the original level, the pressure in the detection tube also returns to the original pressure, and the rotation of the electric motor becomes steady rotation. In this way, the increase or decrease in the level of the powder layer is detected by the pressure of the detection tube embedded in the powder layer, so it is not affected by the grinding state in the grinding container, and the Layer level accuracy can be significantly increased. Next, to explain the operation of the second invention, the pressure inside the detection tube in the powder layer and the pressure at the static pressure outlet in the crushing container are detected, and the detected pressure is guided to the pressure conversion regulator. Detect the pressure difference, detect the difference between the pressure difference and the set pressure, convert this difference into an electrical signal, input this signal to the motor control section, convert it to voltage etc. By controlling the rotation speed, the amount of powder and granule supplied by the powder and granule feeder is controlled. By detecting the difference between the detection tube pressure and the static pressure inside the container in this way, if the static pressure inside the container pulsates for some reason, the detection tube pressure will also pulsate, so the pulsation will cause an error. No movement occurs. Furthermore, it is effective in cases where the absolute value of static pressure changes over time due to changes in pressure loss in the dust collector. [Embodiment] In the embodiment shown in FIGS. 1 and 2, A indicates an airflow pulverizer for pulverizing powder and granules (hereinafter referred to as raw material), and includes a pulverization container 11 and a centrifugal air classifier 1.
A raw material supply pipe 13 is provided near the bottom of the crushing container 11, and raw materials from a raw material feeder 14 are supplied into the crushing container 11 through this supply pipe 13. Further, the feeder 14 is driven using a variable speed electric motor 15, and the rotational speed of the electric motor 15 is controlled by a control section 16 so that the feed amount can be freely controlled. Furthermore, a jet air jet nozzle 17 is provided at the lower end of the crushing container 11, and this nozzle 17
is connected to a compressed air source 18 such as a compressor. The upper part of the peripheral wall of the centrifugal air classifier 12 is communicated with a dust collector 19, and the dust collector 19 is communicated with an exhaust fan 20. The above configuration is similar to the conventional device,
The raw material is supplied to a raw material feeder 1 driven by an electric motor 15.
4 into the crushing container 11 of the crusher A through the supply pipe 13, and when this raw material reaches a predetermined level C as shown in FIG. The airflow generated by this process is injected through the jet airflow jetting nozzle 17, and the raw material is pulverized by this jet airflow e. The crushed fine powder particles flow into the upper space 2 along with the rising particle flow f.
Rise 2. The fine powder particles rising in the upper space 22 are conveyed together with the suction airflow by the exhaust fan 20, and are first classified into fine powder and fine powder by the air classifier 12, and the fine powder is returned as a powder flow m. Returning to the crusher, the fine powder enters the dust collector 19 along with the airflow, where it is separated into fine powder and air.
The fine powder is taken out as a product through the discharge valve 23, and the air is discharged from the exhaust fan 20. In the air flow type crusher A as described above, reference numeral 25 denotes a pressure detection tube provided diagonally downward from the side wall of the crushing container 11, and the lower end opening 26 is embedded in the raw material layer 21 by a required amount. This detection tube 2
The installation angle (θ) of 5 should be 60° or more, and the detection tube 2
Let the embedding depth (h) of No. 5 be the distance between the level C of the raw material layer 21 and the lower end opening 26. The lower end opening 26 of the detection tube 25 is located at a location where it does not directly affect the flow of the jet air stream e blown into the raw material layer 21, and is obliquely cut to prevent clogging of the raw material. Further, the detection tube 25 is slidably attached to the attachment part of the container 11, and can be fixed in any position by an adjustment bolt 27, and the attachment part is kept airtight by a seal cover 28. Reference numeral 30 in FIG. 2 is a pressure conversion regulator, and the upper end of the pressure detection tube 25 and a static pressure side detection tube 31 whose inner end is open near the upper part of the peripheral wall of the crushing container 11 are connected to the regulator 30. do. In the above embodiment, the raw material is supplied to the raw material feeder 14.
When the level of the raw material layer 21 reaches the appropriate level after being supplied into the crushing container 11, the jet airflow generated by the compressed air source 18 is applied to the raw material layer 21 inside the crushing container 11 while maintaining the raw material supply. The raw material is pulverized by this air flow. While the amount of pulverization and the amount of raw material supplied are balanced by the above-described action, the variable speed electric motor 15 for the feeder rotates at a constant speed to supply a fixed amount. If the level of the raw material layer 21 increases or decreases for some reason during the quantitative supply, the pressure change in the detection tube 25 buried in the raw material layer 21 and the detection pressure of the static pressure detection tube 31 due to this increase or decrease will occur. The pressure conversion regulator 30 detects the pressure difference, converts the difference between this differential pressure and a preset set pressure into an electrical signal, and controls the controller 1.
6, the electric motor 15 is controlled based on the command from the control unit 16, and the amount of raw material supplied from the raw material feeder 14 is controlled. In other words, if the supply of raw materials is insufficient, the electric motor 1
By increasing the number of revolutions of the motor 5 to increase the amount of input, and when it becomes too large, the number of revolutions of the electric motor 15 is lowered to reduce the amount, so that the difference between the differential pressure detected as described above and the set pressure is always zero. control so that Furthermore, raw material supply control will be explained in detail. Here, it is assumed that the amount of raw material supplied is small relative to the crushing capacity. The static pressure in the upper space 22 of the crushing container 11 is -80 m/mAq (this is because the crushed particles are sucked (airflow) and transported by the exhaust fan 20). At the start, the raw material layer 21 is at the highest level, and the detection tube 25 is in the raw material layer 21 (installed at a pre-measured embedding position). Therefore, the pressure in the detection tube 25 is 0 m/mAq (because the raw material is not affected by the static pressure in the head space and the jet air flow). As time passes from the above state, the supply amount becomes insufficient in spite of the constant supply of the raw material relative to the amount of pulverization as assumed. Naturally, the level C of the raw material layer 21 will be lowered by the amount that the supply amount is insufficient. As the level C decreases, the raw material around the detection tube 25 becomes easier to flow due to the action of the jet air flow, and the static pressure inside the crushing container 11 begins to affect the detection tube 25.
The pressure ranges from 0 m/mAq to 40 m/mAq, for example.
becomes. Furthermore, as time passes and the raw material starts to flow around the detection tube 25, the value becomes -60m/mAq, and when the detection tube 25 is completely in a flowing state, that is, the lower end opening 26 of the detection tube 25 is at the raw material level. When it matches C, it becomes the same as the static pressure in the upper space 22,
-80m/mAq. At this time, the amount of change in the raw material layer level C from the start is 65 m/mAq. Therefore, the pressure between the detection tube 25 pressure and the static pressure inside the container 11 is detected by the pressure conversion regulator 30, so the pressure difference at the start is 80 m/mAq, and the detection tube 25 pressure is detected.
The pressure difference when the lower end opening 26 coincides with the raw material level C is 0 m/mAq. These relationships are shown in the table below.

〔effect〕

The present invention provides the following effects through the above configuration and operation. Since the pressure within the raw material layer can be accurately detected and the level of the raw material layer can be detected with high precision, the fluctuation range of the increase/decrease level can be made as small as possible, and the pulverization efficiency can be significantly increased. Therefore, the level can be detected regardless of the state of pulverization in the pulverization container, and no error occurs in the detected pressure. In addition, since minute changes can be detected sensitively, the grinding efficiency can always be maintained at its best.One detection tube is buried in the raw material layer and its pressure is detected, so the Increases and decreases in the raw material layer level due to unbalance between supply and crushing can be kept constant. It is disturbed by changes in the pulverization condition, such as changes in the diameter of the nozzle used to detect the pressure difference between the raw material layer and the pulverization container, and changes in the rotation speed of the classifier, as well as changes in the performance of the dust collector. Accurate level control is possible without any problems, and grinding efficiency can be maintained at its best under any conditions. Since there are no restrictions due to the physical properties of the raw material, highly accurate level detection is possible. Since the pressure is detected using a detection tube, there is no need for complicated principles found in conventional level meters such as capacitance type, rotary vane type, and ultrasonic type, and instruments that apply them. Therefore, it is highly reliable and can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view showing essential parts of the device of the present invention, FIG. 2 is a circuit diagram of the same, and FIG. 3 is a longitudinal sectional front view of the conventional device. 11...Crushing container, 17...Jet air jet nozzle, 21...Raw material layer, 25...Pressure detection tube,
30...Pressure conversion regulator, 31...Static pressure side detection tube.

Claims (1)

[Scope of Claims] 1. A pneumatic pulverizer comprising a pulverizing container storing granular material and a jet air jet nozzle provided below or on the side of the pulverizing container, in which the pulverizing material in the granular material in the pulverizing container is The powder supply machine to the grinding container is controlled so that the reference pressure set based on the pressure of the pressure detection tube inserted at a predetermined position and the pressure of the airflow space of the grinding container is always maintained. A powder supply amount control device for an airflow type crusher, characterized by the following. 2. In an air-flow pulverizer consisting of a pulverizing container storing granular material and a jet air jet nozzle installed below or on the side of the pulverizing container, a predetermined amount of powder is embedded into the granular material from the side wall of the pulverizing container. It consists of a powder-side pressure detection tube and a space-side static pressure detection tube that connects from the side wall of the crushing container to the space above the powder layer. 1. A powder supply amount control device for an air flow type pulverizer, characterized in that the powder supply amount controller is controlled so as to match a set value.