JPS5955374A - Method of controlling classifying point of classifier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a classification control method that performs classification by balancing centrifugal force and air resistance.

Many classifiers of this type have been developed and used, but the classification point fluctuates during operation due to external conditions such as temperature, humidity, and pressure. In particular, the classification point fluctuates rapidly with changes in air temperature. For example, when the power of the blower is controlled to be constant, the classification point (cut point) deviates by about 13.5% when comparing the case of 0°C and the case of 30°C.

Therefore, an object of the present invention is to provide a method for controlling a classifier that performs classification by balancing centrifugal force and air resistance so as to maintain a constant classification point even if the air temperature fluctuates. do.

According to the first aspect of the present invention, when controlling to maintain a constant classification point in a classifier that performs classification by balancing centrifugal force and air resistance, the air temperature T in the air circulation line used for classification , detects the air volume signal value Q8, and
When the flow rate of air passing through the classifier, which is a function of Qs, is QT, and the viscosity coefficient of air, which is a function of T, is μT, 819
μTQ is compared with k, which is a predetermined target value.
A classification point control method for a classifier is provided that controls to decrease QT when T>l(, and increase QT when μrQr<k).

According to the second aspect of the present invention, when controlling the classifier that performs classification to maintain a constant classification point using a balance button between centrifugal force and air resistance, the air temperature in the classifier "L" and the classification The air temperature T2 and air volume signal value Qs in the air distribution line used are detected, and the air volume inside the classifier is determined as QT2, which is a function of T2 and Qs, and the viscosity coefficient of air, which is a function of T1, is determined as a function of μT□, QT2, and T1. When the air flow rate in a certain line is QT, compare μTIQ t with a predetermined target value 'A)k, and calculate μTIQ t
There is provided a classification point control method for a classifier which controls to reduce the QT when y>k and increase the QTI when μTIQT is k. Please refer to the attached drawings below for the method for controlling the classifier of the present invention. I will explain it in detail.

FIG. 1 shows diagrammatically the classification system. Feeder 1
The powder supplied from is classified by a rotary classifier 2, coarse powder is discharged from a pulp 3, fine powder is collected by a bag filter 4, and classified air is passed through a line 6 having an orifice 5 inserted in the middle. It is sucked by the proa 7.

A typical structure of a classifier to which the present invention relates is diagrammatically shown in FIG. The powder injected from the powder injection port 8 has an air population of 9.
Due to the airflow from the nine people in the direction indicated by the arrow, classification room 1
The coarse powder is collected from the outlet 11 and the fine powder is collected from the spiral casing 12. The classifier of the present invention thus performs classification based on the balance between centrifugal force and air resistance. By the way, as mentioned above, the classification point of this type of classifier is greatly affected by the air temperature.

Therefore, the present invention performs classification point maintenance control in accordance with temperature changes as described below. First, the following assumptions are made regarding the determination of classification points.

(1) The powder to be classified is spherical.

(2) The air resistance acting on particles is assumed to be in the Stokes region and follows Stokes' law.

(3) The particles entering the classification chamber have a circumferential velocity that is the same as the rotational speed of the rotor.

(4) Particles have no radial velocity at the moment they enter the classification chamber.

T5) Ignore inertia.

Based on the above assumptions, the formula for determining the classification point from the balance of the forces acting on the particles (force) is as follows.

dp: Separation diameter Vo: Rotational speed of classifier R: Distance from center of rotation to classification chamber ρp: True specific gravity of particles μ: Viscosity coefficient of air vr: Radial velocity of air Vo, μ, and Vr in the above equation are constant If so, it is possible to secure a certain classification point. However, among these, although Vo can be kept constant, μ is uniquely determined by the air temperature. Father, Vr also varies depending on the temperature. Air-conditioning the classification room and keeping the air temperature constant is difficult on a general production line. Therefore, the following control is performed.

When the constant term or constant possible term is eliminated from Equation 11), dp = -8, and if the air flow rate inside the classifier is Q, roc
Since Q, equation (1) can be expressed as follows.

dp = k' ward...(2)
Therefore, constant classification point control is possible by controlling μQ ''' const.μ is expressed, for example, by the following equation (T is absolute temperature).

Therefore, in order for μQ == const, it is sufficient to change Q by the amount of change in μ. In conclusion, the change in μ due to temperature is compensated for by adjusting Q, and control is performed such that μQ = const.

A specific control method will be explained with reference to FIGS. 3 and 4. As shown in FIG. 3, the temperature of the air passing through the orifice 50 T
Then, the pressure ΔP at the orifice 5 is measured, and the detected signal is input to a control unit 13 such as a microcomputer, and the control signal operates, for example, a damper 14 to adjust the air volume.

The adjustment is shown in the flowchart of FIG. The detected air temperature signal T and pressure ΔP are input to the control unit, and T
The air volume QT is calculated from ΔP, and μc is calculated from T. The value of μTQt= is determined as a control target. Therefore, control is performed by comparing the calculated value of μTQT and a predetermined value of k.

(1) When μTQT = . No control is required.

(2) When μTQT>k Calculate the value of Qτ'=X, and set QT to μT smaller than Qt. Control is performed to bring it close to the value of QT'.

(31μrQt(When k, calculate the value of k QT a, and control Qt to approach the value of Qd # which is larger than QT.

The control described above is performed when the temperature inside the classifier and the temperature of the air passing through the Orice are the same, but when the two temperature dusts are different, the following control is performed. That is, as shown in FIG. 5, the air temperature T□ inside the classifier 2, the orifice passing air temperature T2, and the orifice pressure ΔP are detected and input to the control unit 13, and the control of the Dan re-14 is controlled by this control signal. conduct.

The control method is shown in the flowchart of FIG.

Input the signal Tl of the detected air temperature inside the classifier, the temperature T2 of the air passing through the orifice 50, and the orifice pressure ΔP to the control section, and set QT2 to T2 and ΔP.
From l, QT is calculated from QT2 and To, respectively. Since the μTQT=lcO value is determined as a control target, control is performed by comparing the calculated μTQT value with the value of k.

(1) When μT□Qt1= No control is required.

(2) Calculate QT2' when μ t I Q t > k, and control the conversion of QT to 9 t 2', which is smaller than QT.

13) When μTIQ↑, <k, calculate the value of QT″=K, and further calculate the value of Qt″ and T2 by 1
Calculate Q and # from μTl, and make 9 guns QT2# larger than Qr.
control conversion.

As is clear from the above explanation, in the present invention, by controlling the temperature change, which has a relatively large influence, by adjusting the air volume, it is possible to eliminate the fluctuation of the classification point due to the temperature change.

Although an orifice is used as the airflow sensor, it is also possible to use a noggle, a power value of a blower, a pitot tube, a hot wire anemometer, etc. as a sensor. In the above-mentioned orifice and nozzle, ΔP is used as the air volume signal value Q8, but
The air volume can also be detected from the power value of the blower. In that case, if the blower power is W and the temperature is T, the airflow amount QT in the classifier can be expressed as QT = f (T, W).

In this way, the air volume signal value Qs is expressed according to the air volume sensor used, and can be used to control the present invention in the same manner as for the orifice described above.

[Brief explanation of drawings]

Fig. 1 is a flowchart of the classification line, Fig. 2 is a partial sectional view of the classifier to which the present invention relates, and Figs. 3 and 4 respectively show when the air temperature inside the classifier and the air temperature passing through the orifice are the same. A control diagram and its control flowchart, FIGS. 5 and 6 are a control diagram and its control flowchart when the air temperature inside the classifier and the orifice passing air temperature are different, respectively. Explanation of symbols 1... Feeder, 2... Classifier, 3... Pulp, 4... Filter, 5... Orifice, 6... Line, 7... Floor - 18... Powder Body input port, 9...
・Air inlet, 10... Classification chamber, 11... Coarse powder outlet, 12... Swirl casing, 13... Control unit, l
4-... Damper patent applicant Nisshin Seifun Co., Ltd. Nisshin Engineering Co., Ltd. Figure 1 Mouse 2 Figure 3

Claims (2)

[Claims] (1) When controlling a classifier that performs classification by balancing centrifugal force and air resistance to maintain a constant classification point, the air temperature T in the air circulation line used for classification
, the air volume signal value Qs is detected, the air flow rate passing through the classifier is QT, which is a function of T and Qs, and the viscosity coefficient of air, which is a function of T, is μT. A classification point control method for a classifier, characterized in that when μtQr>k, Qt is decreased, and when μtQ<k, QT is increased. (2) When controlling a classifier that performs classification by balancing centrifugal force and air resistance to maintain a constant classification point, the air temperature T1 in the classifier, the air temperature T2 in the air distribution line used for classification, and Detects the air volume signal value Qs, and calculates the classified in-machine air volume, which is a function of T2 and Qs, by QT.
2. The viscosity coefficient of air, which is a function of Tl, is μ↑0.9 2.
When the air flow rate in the line, which is a function of Tl, is compared with k, which is a predetermined target value, μT is compared with QTx, and when μf, QT is >k, QT is decreased,
A classification point control method for a classifier, characterized in that control is performed to increase QT□ when μTIQTI < k.