JPS5877622A - Measuring method for flow rate of powder and granule - Google Patents

Abstract

PURPOSE:To obtain measured values continuously and accurately by measuring the flow rates of the gas in a transport pipe and the pressure drop of the fluid mixture between two places in a straight pipe part from a hopper during a prescribed period. CONSTITUTION:The flow rate of the powder and granules flowing in a transport pipe 1 is operated in an arithmetic circuit 15 (the operated value thereof is Gs) in accordance with the measuring signal of the flow rate of the air in the pipe 1 and the measuring signal of the pressure drop of the gaseous mixture of the powder and granules and the air in the pipe 1 from a differential pressure gage 14. On the other hand, the change in the weight of the powder and granules in a hopper 2 is measured continuously with a load cell 3, and the powder and granules are repeatedly supplied from a hopper 5 into the hopper 2 in such a way that the signal value thereof moves back and forth between WUU and WLL. The ratio (k) between the weighed value W of the powder and granules supplied into the pipe 1 determined from the signal values WU-WL of the cell 3 and the integrated value S in the prescribed period of the value GS is operated and is outputted to a multiplier 19. Here, a new operated value G's=kXGs is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the flow rate of powder or granular material, which allows extremely accurate measurement.

For example, when transporting granular materials such as pulverized coal by air,
It is necessary to know the supply amount of powder or granular material by some means, and conventionally, as a device for determining the supply amount of powder or granular material, a powder or granular material applying the so-called loss-in-weight method as shown in Figure 1 has been used. Feeding devices are known. As shown, 1
is a transport pipe, and a pressure air supply source (not shown) is connected to one end of the transport pipe 1, and air is sent toward the other end.

2 is a hopper; 3 is a hopper connected to hopper 2;
2 is a load cell for weighing the weight of the powder and granules supplied into the hopper 2; 4 is a four-tary pulp installed at the bottom of the hopper 2; through the rotary pulp 4, the powder and granules in the hopper 2 are Transport pipe 1 through which air for body transport flows
From the middle of, it is supplied into it. A sub-hopper 5 is arranged above the hopper 2 to which powder and granules are supplied from the outside. It is fed into the hopper 2. 4' is an expansion joint for connecting the transport pipe 1 and the rotary pulp 4 provided directly below the rotary pulp 4, and 6' is an expansion joint provided directly below the rotary pulp 6.

The rotary pulp 6 is controlled as follows, and when the rotary pulp 6 is closed, the weight of the powder and granules supplied into the transport pipe 1 through the rotary pulp 4 is equal to the weight of the powder in the hopper 2. It is determined by the signal from the load cell 3 that weighs the granules.

That is, the weighing signal from the load cell 3 is input to the differentiator 8 and the control circuit 9 through the amplifier 7.

In the control circuit 9, the upper and lower limits of the weight of the powder or granular material in the hopper 2 are set in advance, and this control circuit 9 controls the weighing value of the load cell 3 when starting to supply the powder or granular material into the popper 2. The rotary pulp 6 is opened until the value reaches the upper limit, and then the load cell 3
When the weighing value of the load cell 3 reaches the upper limit, the rotary pulp 6 is closed, and then, when the weighing value of the load cell 3 reaches the lower limit, the rotary pulp 6 is opened again until the weighing value of the load cell 3 reaches the upper limit. do. In addition, rotor IJ /<
The loop 4 continues to open regardless of whether the rotary pulp 6 is opened or closed, and supplies the granular material in the hopper 2 into the transport pipe 1. On the other hand, the weighing signal of the load cell 3 input to the differentiator 8 is differentiated in the differentiator 8, and the thus obtained differentiated signal is controlled by the control signal from the control circuit 9 while the rotary pulp 6 is closed. , the signal from the differentiator 8 passes through the hold circuit 10 as it is, and is output to a recorder or the like (not shown) as a calculation signal of the flow rate of the powder and granular material supplied from the inside of the hopper 2 to the transport pipe 1. be done. While the rotary pulp 6 is open (the rotary pulp 4 is continuously open), the weight of the powder and granules supplied from the sub-hopper 5 to the hopper 2 through the rotary pulp 6 is unknown (i.e., The load cell 3 cannot weigh the granular material in the hopper 2 unless either one of the two rotary pulps 4.6 is closed, so the load cell 3 is transported through the rotary pulp 4. It is not possible to measure the weight of the granular material supplied to the tube 1. Therefore, while the rotary pulp 6 is open, the hold circuit 10 holds the differential signal value of the differentiator 8 at the time when the rotary pulp 6 starts to open (
) and outputs this value as an estimated value of the flow rate of the powder and granular material supplied from the hopper 2 into the transport pipe 1.

Therefore, in the above configuration, there is a drawback that the flow rate of the granular material supplied into the transport pipe 1 cannot be accurately measured while the rotary pulp 6 is open.

Considering these points, the powder and granular material is supplied from inside the hopper into the transport pipe through which the gas for transporting the powder and granular material is flowing, and the flow rate of the gas in the transport pipe and the transport, pipe are controlled. The pressure loss of the mixed fluid of the granular material and the gas in the transport pipe is measured between two straight pipe parts, and based on the measurement results, the pressure loss of the granular material flowing in the transport pipe is determined. A method for measuring the flow rate of powder and granular materials was proposed to calculate the flow rate.
-134400, Special Publication No. 52-2630).

According to this flow rate measurement method, there is no need to measure the weight of the powder in the hopper, so it is possible to continuously accurately measure the flow rate of the powder supplied from the hopper into the transport pipe. For example, an example of a calculation method for implementing this flow rate measurement method is as follows. That is, the pressure loss ratio α and the mixing ratio m between two straight pipe portions in the middle of the transport pipe have a relationship of m=K (α−1).

(Here, s ”” /Ga G5: Calculated value Ga of the flow rate of granular material (in the mixed fluid) flowing in the transport pipe Ga: Calculated value Ga of the flow rate of gas (in the mixed fluid) flowing in the transport pipe = C0.5I ΔPad: Measured value of differential pressure of gas flowing in the transport pipe by the flowmeter 11 α-17/ΔP3 ΔPT: Particles and gas in the transport pipe between two straight pipe parts of the transport pipe Pressure loss of mixed fluid Ua: Gas flow rate between two straight pipe parts of the transport pipe, Ua=C, -Ga ΔPa: Pressure of only the gas in the transport pipe between two straight pipe parts of the transport pipe Loss, △Pa=c3 @r mUa (imAq) CI, C2, C3: constant of proportionality r: air density) Therefore, if JK is determined in advance by verification (actual measurement), GS is determined by Gs=m@Ga. You can ask for it.

However, in the above flow measurement method,
As described above, and C3 change due to wear on the inner surface of the transport pipe due to changes over time, changes in the physical properties of the powder (for example, particle size, humidity), etc. Therefore, there is a problem in that an error occurs in the above-mentioned calculation, and accurate measurement cannot be performed.

Therefore, this invention was made to solve the above-mentioned problems, and the granular material is supplied from inside the hopper into a transport pipe through which gas for transporting the granular material is flowing, and Measure the flow rate of the gas and the pressure loss of the mixed fluid of the granular material and the gas in the transport pipe between two straight pipe parts of the transport pipe, and based on the results of both measurements, In a method for measuring the flow rate of powder and granular material that calculates the flow rate of powder and granular material flowing in a transport pipe, the powder supplied from the hopper into the transport pipe during a predetermined period is measured by a weighing means connected to the hopper. Weighing the weight of the granular material, and integrating the calculated value of the flow rate of the granular material during the predetermined period, and then calculating a new flow rate of the granular material flowing through the transport pipe after the elapse of the predetermined period. The value G's is expressed as G's m=kxQs [where GS is the value of the granular material flowing in the transport pipe, which is determined based on the measurement result of the flow rate of the gas and the measurement result of the pressure loss of the mixed fluid. The calculated value of the flow rate: a weighed value W of the weight of the powder or granular material during the predetermined period;
It is characterized in that it is determined based on the ratio of the Gs to the integral value S at the end of the predetermined period, that is, the ratio of the Gs to the integral value S.

The present invention will be described below based on embodiments and with reference to the drawings.

FIG. 2 is a schematic configuration diagram showing one embodiment of a powder/granular material flow rate measuring device for carrying out the present invention (the same reference numerals as in FIG. 1 indicate the same parts), and FIG. It is a figure showing an example of a time chart. As shown in FIG. 2, in the transport pipe IVc, an air flow meter 11 is provided upstream of the supply point of the powder and granular material from the hopper 2, and a flow rate control valve 12 is provided further upstream thereof. The flow control valve 12 is controlled by a valve control circuit 13. The valve control circuit 13 inputs the signals of the air flow rate 8 meter 11, and controls the flow rate control valve 12 so that the signal becomes a preset flow rate value.
Thus, the air flow rate in the transport pipe 1 on the downstream side of the flow rate control valve 12 is controlled to be constant.

Reference numeral 14 denotes transportation in a section downstream from the supply point of the powder or granular material in the transport pipe 1, where a mixed fluid of air and granular material flows in a steady state (a section in which the movement of the powder or granular material is stable). tube 1
This is a differential pressure gauge for measuring the pressure loss (differential pressure) of a mixed fluid of air and powder in a transport pipe 1 provided between two locations. The signal from the differential pressure gauge 14 and the signal from the air flow meter 11 are input to the arithmetic circuit 15, and the arithmetic circuit 15 performs the calculation as described above, that is, Ga = C, ·FΣ, and Ua = C2 · Ga. ΔPa=c3 a r *Ua'. =ΔPTmP3 m =K(α-1) Gs =m·Ga is performed, and the flow rate Gs of the powder and granular material flowing through the transport pipe 1 is calculated.

On the other hand, the signal from the load cell 3 connected to the hopper 2 passes through the amplifier 7 to the control circuit 9 and the correction control circuit 1.
6 is input.

As shown in FIG. 3, the control circuit 9 controls the signal value of the load cell 3 to be Wr unless a correction signal to be described later is input.
, b (the lower limit value that does not hinder continuous supply of the powder and granular material in the hopper 2 into the transport pipe 1), the rotary pulp 6 is opened (ONL), and the signal value from the load cell 3 becomes WUU. The rotary pulp 6 is closed (turned OFF) when it reaches (the upper limit that can accommodate powder and granular material in the hopper 2).
This operation is repeated (during this time, the rotary pulp 4 is open regardless of whether the rotary pulp 6 is open or closed).

The output signal (calculation signal) of the calculation circuit 15 is input to the integrator 18 via the multiplier 19 and the switch 17. The output signal of the integrator 18 is output to the divider 21 through the hold circuit 20.

Reference numeral 22 denotes a correction command switch circuit, and this circuit outputs a correction signal to the correction control circuit 16 at an arbitrary time (for example, at a fixed time once or several times a day, or at a time arbitrarily selected by the operator). The correction control circuit 16 operates as follows based on the correction signal. That is, (1), the point in time when the correction signal is first input is the state in which the rotary pulp 6 is open (the third
(Refer to Figure ■) (The determination of whether the rotary 1 valve 6 is - or closed is determined by the control circuit 9's opening or closing of the rotary pulp 6.
(obtained by inputting the control signal for closing operation) is
Once the rotary pulp 6 is closed (OFF) and the signal value of the load cell 3 reaches wU (a value smaller than wUU by a predetermined value), the switch 17 that was open until then is closed (Fig. 3 @ reference). In addition, if the rotary pulp 6 is in a closed state (see Fig. 3 a) at the time when the correction signal is input, the rotary pulp 6 is immediately closed.
A command to open the circuit is output to the control circuit 9. the result,
The rotary pulp 6 is opened and the signal value of the load cell 3 is W.
The rotary pulp 6 is closed (OFF) when TJU is reached.
Then, when the signal value of the load cell 3 becomes WU, the switch 17, which had been open until then, is closed (
(See Figure 3 O'). (2) Next, when the signal value of the load cell 3 reaches Wy, (a value larger than WLI- by a predetermined value ζ°), the switch 17 is opened and the hold circuit 20 is turned on (hold). , and divider 21
, wU-wL, that is, the signal value of load cell 3 is wtr
The measured value (weighed value) W of the weight of the powder and granular material supplied from the inside of the hopper 2 into the transport pipe 1 during the subtraction from W to WL is input (this Wtr-Wr, = VJ is entered in advance in the divider 21). (You may remember it.)

The integrator 18 is connected to the arithmetic circuit 1 by closing the switch 17.
Integration of the 5 calculation signals (Gs) is started, and then the integration is stopped by opening the switch 17 (Fig. 3 θθ'
reference).

The hold circuit 20 holds the integral signal of the integrator 18 as it is when it is OFF, and outputs the O from the correction control circuit 16.
It is turned ON when the N signal is input, holds the integral signal value from the integrator 18 at that time, and inputs this (S) to the divider 21.

The divider 21 receives a hold signal from the hold circuit 20,
That is, the integral value S at the time when the integration ends when the switch 17 is opened
and the weighed value W to be equal to 1, and output this to the multiplier 19.

The multiplier 19 converts the thus inputted k into the next new k
The product of the computed value Gs of the computed signal from the computing circuit 15 and k, that is, kaQs, is used as the new calculated value G' of the flow rate of the powder and granular material flowing in the transport pipe 1. S (note that when starting this powder/granular material flow measuring device, it is set as 1 (=l)).

With the above configuration, the flow rate of the powder flowing through the transport pipe 1 is determined by the air flow rate measurement signal in the transport pipe 1 from the flow meter 11 and from the differential pressure gauge 14.

It is calculated in the calculation circuit 15 based on the pressure loss measurement signal of the mixed fluid of powder and air in the transport pipe 1 (the calculated value is Qs).

On the other hand, the weight change of the granular material in the hopper 2 is continuously measured by the load cell 3, and the granular material in the hopper 2 is stored in the sub-hopper 5 so that the signal value reciprocates between WUU and WjLJ, 4. is repeatedly supplied from

Then, when the correction signal is inputted to the correction control circuit 16 by the correction command switch circuit 22 (see ■, ■' in Fig. 3), (if the rotary pulp 6 is closed (OFF), it is immediately opened), The rotary pulp 6 continues to be opened (ON) until the signal value of the load cell 3 becomes wUU, and then the rotary pulp 6 closes when the signal value of the load cell 3 becomes WTJIT.

Next, when the signal value of the load cell 3 reaches wU for the first time, the switch 17 is closed and the integrator 18 is switched to the arithmetic circuit 1.
(See Figure 3 @, @')
, then the signal value of load cell 3, becomes WL for the first time
, the switch 17 opens and the integrator 18
The hold circuit 2° holds the integrated value S of the calculated value Gs of the calculated signal at that time, and divides it into the divider 21.
(see ○, O' in Figure 3).

Then, the divider 21 calculates the ratio between the weight value W of the weight of the powder and granular material supplied into the transport pipe 1 and the integral value S, which is calculated from the signal values wU to IWL of the load cell 3 during the integration period. k is calculated and outputted to the multiplier 19. The multiplier 19 holds k until the next new signal is also input to the divider 21, calculates the product of this k and the calculated value Gs of the calculated signal of the calculation circuit 15, and calculates the calculated result. of,
Output as a new calculation value of the flow rate of powder and granular material in transport pipe 1 (
See Figure 3 θ, θ'. Note that the process from the end of the integration until the divider 21 outputs k and the multiplier 19 outputs a new sum value based on k is instantaneous).

In this way, the calculated value Gs of the calculation signal of the calculation circuit 15
is corrected by the signal from the divider 21 and used as the new calculated value G's, but the new calculated value G's corrects the error (with respect to the true flow rate) of the calculated value Gs. The reason for this is as follows. That is, while the rotary pulp 6 is closed, the load cell 3 weighs the hopper 2.
The weight of the powder and granules fed into the transport pipe 1 from within is accurate.

Therefore, the weighed value W (weight of the granular material supplied from the inside of the hopper 2 into the transport pipe 1) by the load cell 3 during the corresponding integration period while the rotary pulp 6 is closed,
Ratio k of the calculated value Gs of the calculation signal of the calculation circuit 15 to the integral value S at the end of the integration period (i.e., the calculation value of the weight of the powder and granular material flowing through the transport pipe 1 during the integration period) The calculated value Gs of the calculation signal of the calculation circuit 15 is
, the new calculated value G's is the calculated value G
Compared to s, it is possible to show a more accurate measured value of the flow rate of the powder and granular material flowing through the transport pipe 1.

FIG. 4 is a schematic configuration diagram showing another embodiment of a powder/granular material flow rate measuring device for carrying out the present invention (the same parts as in FIG. 2 are indicated by the same reference numerals). 23 is a pressure gauge for measuring the absolute pressure of the fluid in the transport pipe 1, which is installed in the supply path of the powder and granular material into the transport pipe 1 directly below the rotary pulp 4 at the lower part of the hopper 2; The signal from the pressure gauge 23 is output to the weight correction circuit 24 . The weight correction circuit 24 is further input with the signal from the amplifier 7, and the correction control circuit 2
The signal No. 4 is output to the control circuit 9 and the correction control circuit 16.

Between the signal of the pressure gauge 23 and the signal of the load cell 3,
For example, there is a relationship as shown in FIG. That is, if there is a difference in area (passage cross-sectional area) between the two expansion joints f6' and 4' above and below the hopper 2 (the expansion joint 4' has a larger area), then this area difference and the hopper 2 The hopper 2 receives upwardly the force multiplied by the pressure in the transport pipe 1, which causes the measured value of the load cell 3 to be shown as a value lighter than the true weight of the hopper 2 and the granular material therein. (In addition, the air pressure in the transport pipe 1 is supplied to the hoppers 2 and 5 through a pressure equalizing pipe, etc., so that the pressure inside the hoppers 2 and 5 is equal to the pressure inside the transport pipe 1.) be)
. Figure 5 shows that under the condition that the weight of the powder in the hopper 2 is not changed, the area difference between the two expansion joints 4' and 6' is 139.9.
25 (CI) is a diagram showing an example of the relationship between the pressure in the transport pipe 1 and the signal of the load cell 3. From the diagram, it is clear that the two are substantially proportional. In the diagram, the straight line is the least squares approximation straight line, Y=-145,80
- It can be expressed as X+284.64 (correlation coefficient r=0.9963, number of data 30).

Therefore, in the weight correction circuit 24, Wa' giant Wa C4op (however, WIa double double positive correction circuit 24 force, that is, the measured value Wa of the weight of the powder and granular material in the hopper 2: the output of the amplifier 7 (measured value of load cell 3) P: measured value of pressure gauge 23 C4: constant) By calculating The measured value of the weight of the powder or granular material in the hopper 2 can be given to the control circuit 9 and the correction control circuit 16 without receiving the weight.

As explained above, in the present invention, the flow rate of the powder or granular material flowing through the transport pipe can be measured continuously and extremely accurately.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a powder supply device to which a conventional loss-in-weight method is applied, and FIGS. 2 and 4 show different examples of a powder and granule flow rate measuring device for carrying out the present invention. FIG. 3 is a diagram showing an example of a time chart of the apparatus shown in FIG. 2, and FIG.
It is a figure which shows an example of the relationship between the signal of a load cell and the pressure in a transport pipe in the case where there is an area difference between the upper and lower expansion joints. 1...Transport pipe, 2...Hotsuno (-13
11, load cell, 4.6... rotary pulp, 9.
...Control circuit, 10.20...Hold circuit, 14...Differential pressure gauge, 15...Arithmetic circuit, 16
...correction control circuit, 17...switch, 18.
... Integrator, 19... Multiplier, 21... Divider, 22... Correction command switch circuit, 23.
...Pressure gauge, 24...Weight correction circuit. Applicant Nippon Kokan Co., Ltd. Applicant Sankyo Dengyo Co., Ltd. Agent Keitabe Tsutsumi

Claims (2)

[Claims] (1) From inside the hopper, granular material is supplied into a transport pipe through which gas for transporting the granular material is flowing, and the flow rate of the gas in the transport pipe and the two straight pipe portions of the transport pipe are controlled. measuring the pressure loss of the mixed fluid of the powder and granular material and the gas in the transport pipe between the steps, and calculating the flow rate of the powder and granular material flowing in the transport pipe based on the measurement result. , a method for measuring the flow rate of powder or granular material, the weight of the powder or granular material supplied from the hopper into the transport pipe during a predetermined period is weighed by a weighing means connected to the hopper; The calculated value of the flow rate of the granular material is integrated during the predetermined period, and then the new calculated value G's of the flow rate of the granular material flowing in the transport pipe after the elapse of the predetermined period is calculated as G's = k X Gs [However, GS: The calculated value of the flow rate of the powder and granular material flowing in the transport pipe, which is determined based on the measurement result of the flow rate of the gas and the measurement result of the pressure loss of the mixed fluid: During the predetermined period A method for measuring the flow rate of a powder or granular material, characterized in that the flow rate is determined based on a ratio of a weighed value W of the weight of the powder or granular material to an integral value S of the Gs at the end of the predetermined period, that is, 5]. (2) The method for measuring the flow rate of powder or granular material according to claim (1), characterized in that the weighed value of the weighing means is corrected based on the measured value of the fluid pressure in the transport pipe. .