JPS61263523A - Method and device for measuring the rate of flow of pulverized/granular substance - Google Patents

Abstract

PURPOSE:To provide high-precision measurement by sensing the rate of flow of a pulverized/ granular substance in a pipe, correcting the sensed value for the in-pipe rate of flow with a specific correction factor, which is to be determined from said sensed rate of flow and the differentiated value of the sensed value for the weight of tank discharging the pulverized/ granular substance, and thereby eliminating ill influence of possible turbulence to occur on the occasion of replacement of tank. CONSTITUTION:The sensed signal for the weight of fine pulverized coal in tanks obtained through load cells 7A, 7B mounted on feedout tanks 2A, 2B is put into a differentiating device 20, and the differentiated signal thereby Q2 is fed in a rate-of-flow calculator 21, while the flow sensing value for the main pipe 10 measured by a flow meter 4 is corrected with said output signal Q2 from the differentiating device 20, whereby the operation is free from any ill influence even when the discharge of the fine pulverized coal is switched over from the tank 2A to 2B or vice versa. Therefore, said calculator 21 corrects a signal Q1 with the correction factor C to be determined on the basis of relationship between the signal Q2 and the signal Q1 given by the flow meter 4 during normal time without influence of switching between the tanks 2A, 2B, which should accomplish determination of the rate of flow of fine pulverized coal with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for measuring the flow rate of pneumatic granular material, that is, granular material transported by a pressurized carrier gas.
More specifically, in the case where a plurality of tanks for discharging powder and granules are provided, and the powder and granules are continuously supplied by pneumatically feeding the powder and granules while sequentially switching between these tanks (, 7
- This invention relates to a method and device for measuring the flow rate of powder or granular material, which can accurately measure the flow rate of powder or granular material even when switching tanks.

[Prior art]

For example, conventional blast furnaces for steelmaking have used coke inserted from the top of the furnace and heavy oil as auxiliary fuel injected through the tuyeres. However, in recent years, a technique has been developed in which pulverized coal is blown through the tuyeres using pressurized carrier gas such as nitrogen (N2) gas instead of heavy oil. When injecting pulverized coal into a blast furnace as auxiliary fuel, it is necessary to accurately measure the amount of pulverized coal injected into the blast furnace.However, accurately measuring the flow rate of powder and granules requires measuring the gas flow rate, liquid flow rate, etc. This is different from the measurement of the flow rate of granular materials, which is not easy, and for this reason, various techniques have been proposed for measuring the flow rate of powder and granular materials.

For example, in Japanese Patent Application Laid-open No. 56-61227, the detection signal of a load cell for detecting the weight of a tank from which pneumatically fed powder and granules are pressurized and discharged is time differentiated, and this time differential value is used to calculate the weight of powder and granules. A device has been proposed that measures body flow rate (strictly speaking, the flow rate discharged from a tank).

For example, JP-A No. 59-108917 discloses a method for determining the flow rate of powder and granular material from the carrier gas flow rate and the pressure loss value of the pneumatic powder and granular material in the curved pipe section of the pipe through which the powder and granular material is pneumatically fed. is proposed. Furthermore, JP-A-58-1546
No. 22 proposes a method of detecting the density of the pneumatic powder using microwaves and measuring the flow rate of the powder based on this and the flow rate of the pneumatic powder in a pipe.

[Problem that the invention seeks to solve]

However, Japanese Patent Application Laid-Open No. 56-61227 proposes to measure the powder flow rate from the time differential value of the M amount detection signal of the tank mentioned above.
The invention of No. 1 can be expected to have relatively high measurement accuracy of ±1 to 3% under normal conditions.

However, for example, in the case of an equipment configuration in which multiple tanks are installed and the powder or granules are continuously supplied by discharging the powder or granules from one of the tanks while switching between them as appropriate, when the tanks are switched, the Discharging of powder and granular material from the tank that was previously used is stopped, and discharging of powder and granular material from the tank that will be used next is started. As a result, the pressure in both tanks suddenly changes, causing distortion of the tanks and other causes, which causes a large disturbance to the detected value of the load cell. As a result, as shown in FIG. 4, there is a problem in that the measured value of the powder flow rate obtained by differentiating the detected value of the load cell is also greatly disturbed. According to the inventor of the present invention, the disturbance in the measured value of the load cell when switching the tank is at most about ±30%, as shown in Fig. 4, and the duration of the effect is about 5 minutes. The observation results have been obtained.

Furthermore, in the inventions of the above-mentioned JP-A-59-108917 and JP-A-58-154622, the above-mentioned JP-A-56-
Problems like No. 61227 are avoided, but the measurement accuracy is
Since the accuracy is about 6 to 10%, which is about 1710 lower than that of the invention of JP-A No. 56-61227, there are many practical difficulties.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and
When switching between multiple tanks loaded with powder and granules and continuously supplying the powder, the weight of the tank from which the pneumatic powder is discharged is detected and differentiated with respect to time, and the flow rate is By detecting the flow rate of the pneumatic powder and granular material with a meter, determining a correction coefficient from the relationship between the two, and correcting the detected value of the flowmeter using this correction coefficient to determine the flow rate of the pneumatic powder and granular material, high accuracy can be achieved. Flow rate measurement of powder and granular materials that makes it possible to measure the flow rate of powder and granular materials, and also makes it possible to eliminate the influence of disturbances on the weight detection means of pressurized tanks that occur when switching tanks for discharging powder and granular materials. The purpose is to provide a method and apparatus.

The present invention is a method for measuring the flow rate of powder or granular material discharged from one of a plurality of tanks and pneumatically conveyed through a pipe, in which the flow rate in the pipe is detected at an appropriate position in the pipe, and the weight of the powder or granular material is measured. The weight of the tank discharging the powder to be detected is detected, the detected value of this weight is differentiated with respect to time, a correction coefficient is determined according to the relationship between this time differentiated value and the detected value of the flow rate in the pipe, and the correction is performed. The method is characterized in that the flow rate of the powder or granular material is determined by correcting the detected value of the flow rate in the pipe using a coefficient.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 1 is a block diagram showing the configuration of an apparatus for implementing the method for measuring the flow rate of powder or granular material according to the present invention, that is, the apparatus of the present invention. In the embodiment of the present invention, a case will be described in which pulverized coal in the form of granules is injected into a blast furnace.

In the figure, IA and IB are hoppers for storing pulverized coal, which is particulate matter, and the stored pulverized coal is cut out and supplied to tanks 2A and 2B, respectively.

The cut-out tanks 2A and 2B are pressurized tanks for discharging and pneumatically transporting pulverized coal, which is a particulate material, using a carrier gas. For example, pressurized N2 gas is supplied as a carrier gas to the cut-out tanks 2A and 2B, and the inside thereof is in a high-pressure state in which pulverized coal and carrier gas are mixed. In addition, a mechanical discharge device, for example, a rotary feeder 3.3, is provided at the bottom of each of the cutting tanks 2A and 2B (note that other hydrodynamic discharge devices may be used in place of the rotary feeder). Of course). The pulverized coal discharged from the rotary feeder 3.3 in a mixed state with the pressurized carrier gas is sent to the main pipe 10 equipped with a flow meter 4, and is sent to the branch pipes 11, 11, . . . by the distributor 5, respectively. It is distributed and blown into the blast furnace 6 through its tuyeres.

The flow meter 4 is a known one, such as a differential pressure type, a microwave type,
An appropriate one may be used, such as a capacitance type, and the detection signal Q1 of the flow meter 4 is given to the flow rate calculator 21.

In addition, in this embodiment, the cutting tanks that are pressurized tanks and the hoppers for supplying pulverized coal to them are IA and 2A.
It is equipped with two sets of pulverized coal, IB and 2B, and while pulverized coal is discharged from one cut-out tank, for example 2A, and supplied to the blast furnace 6 by pneumatically conveying it through the main pipe 10, the pulverized coal is discharged from the hopper IB to the other cut-out tank 2B. It is configured to switch between the two to supply charcoal. Thereby, pulverized coal can be continuously supplied to the tuyeres of the blast furnace 6.

On the other hand, load cells 7A and 7B are installed in the cut-out tanks 2A and 2B to detect the amount of M in each tank, and these detection signals are used to detect the amount of pulverized coal charged in each tank 2A and 2B. A signal representing the total weight is given to the differentiator 20. In other words, the amount of change in the output signals of load cells 7A and 7B is equal to that of tank 2A.
Or it represents the weight change of pulverized coal in 2B.

Differentiator 20 time-differentiates the input signal and converts the result into signal Q
It is configured to output as 2.

'-Therefore, the output signal Q2 of the differentiator 20, ie, the time differential value of the detection signals of the load cells 7A, 7B, represents the flow rate of pulverized coal discharged from the cutting tank 28 or 2B. The output signal Q2 of this differentiator 20 is given to a flow rate calculator 21.

The flow rate calculator 21 corrects the output signal Q1 of the flow meter 4, that is, the detected value of the flow rate in the main pipe 10 by the flow meter 4, using the output signal value of the differentiator 20.

Specifically, the detected value of the flow rate of pulverized coal by the flow meter 4 is:
As explained in the [Prior Art] section, ±6 to 10
Although the accuracy is relatively low at about %, it will not be affected even if the discharge of pulverized coal is cut out and the tank is switched from 2A to 2B or vice versa. Therefore, the flow rate calculator 21 calculates the correction coefficient C based on the relationship between the detection signal Q1 of the flowmeter 4 and the output signal Q2 of the differentiator 20 in normal times when no influence from switching between the cut-out tanks 2A and 2B appears. The detection signal Q of the flowmeter 4 is corrected using this correction coefficient C while being calculated in a time-shifting manner, and when switching the cut-out tanks 2A and 2B, the correction coefficient calculated immediately before is used during the period in which the effect continues. By correcting the detection signal Q1 of the flowmeter 4 at C, the cut-out tanks 2A, 2
The purpose is to obtain the flow rate of pulverized coal with almost the same accuracy as when the MWt of the cutting tanks 2A and 2B is obtained by time differentiation, without being affected by the switching of B, and even under normal conditions. .

Figure 2 is a schematic diagram showing the waveforms of each signal Q, Q2, etc.
The figure is a flowchart showing the processing contents of the flow rate calculator 21.
The correction calculation according to No. 1 will be specifically explained.

The flow rate calculator 21 calculates a period other than a predetermined time (5 minutes in this embodiment) (hereinafter referred to as
(referred to as a normal period), the detection signal Q1 of the flowmeter 4 and the output signal Q of the differentiator 20 at a predetermined sampling period.
2 is being read, and its sampling timing i
The ratio Xi = (Ql/Q
2) Find and memorize.

Next, the flow rate calculator 21 calculates the moving average of the ratio Xi of both signals Q1+Q2 at the past 0 sampling timings (from i-n+1 to the current i), and uses this as the correction coefficient C4 at the sampling timing i. shall be. Then, the detection signal Q1 of the flow meter 4 is corrected using the following equation (11) using this correction coefficient Ci, and the flow rate Qo of pulverized coal is calculated.

QO=Q1/Ci-(1) For example, during the normal period before the tank switching point indicated by the arrow in FIG. 2, the detection signal Q of the flowmeter 4,
and the output signal Q2 of the differentiator 20 have substantially similar waveforms. Therefore, Xi maintains a substantially constant value, and the correction coefficient C is substantially linear.

Therefore, in a normal period, the detection signal Q1 of the flowmeter 4
is corrected by this correction coefficient C.

As shown in the bottom row of FIG. 2, has a similar waveform that is almost proportional to the detection signal Q1 of the flowmeter 4.

On the other hand, for about 5 minutes after the tank is switched (hereinafter referred to as the switching period), the flow rate calculator 21 reads only the detection signal Q1 of the flow meter 4 at a predetermined sampling period. Then, the flow rate calculator 21 corrects the detection signal Q1 of the flow meter 4 using the correction coefficient Ci obtained immediately before the tank was switched, and obtains the corrected flow rate Qo. Through such arithmetic processing, as shown in FIG. 2, for example, during the tank switching period, the output signal Q2 of the differentiating circuit 4 indicates an increase greater than the increase in the detection signal Q of the flowmeter 4 (as described above). As shown, load cell 7 when switching tanks
QI+
The ratio Xi of Q2 also varies greatly (actually, sampling of Q2 is not performed during the switching period, so the ratio Xi of Q2 is not calculated). However, during the 5-minute switching period after tank switching, the flow rate calculator 21
The differentiator 20 uses the correction coefficient C4 immediately before the switching period starts to correct the detection signal Q1 of the flowmeter 4.
The amount of increase in the flow rate Qo after correction is relatively small compared to the amount of increase in the output signal Q2.

Then, during the normal period after the switching period ends when approximately 5 minutes have passed since the tank switching, the correction coefficient d is calculated again in the same manner as described above, and the result -1- is approximately a straight line as described above. , the corrected flow rate QO has a waveform substantially similar to the detection signal Q1 of the flowmeter 4.

The corrected flow rate Qo of pulverized coal calculated by the flow rate calculator 21 in this manner is given to the flow rate control device 22. Note that this flow rate control device 22 adjusts the flow rate of pulverized coal, in other words, the amount of pulverized coal injected into the blast furnace 6, to a target value based on the corrected pulverized coal flow rate QO determined by the above-mentioned flow rate calculator 21. It is configured to control the opening degree of the row feeder 3 so as to match the opening degree.

〔effect〕

As described in detail above, according to the present invention, in the case of continuously supplying powder or granules by switching the tank for discharging powder or granules between a plurality of tanks, the disturbance caused by switching the tank can be avoided. It is possible to accurately measure the flow rate of powder and granules regardless of the situation, and under normal conditions when switching between tanks does not affect the flow rate of powder or granules, It is possible to measure the body flow rate, and also avoids external disturbances such as vibrations from devices placed around the body.

In the above embodiments, pulverized coal is used as the powder, but it goes without saying that the present invention is also applicable to various other powders and granules.

In addition, in the above embodiment, there are two tanks for supplying powder and granular material, and these are used by switching alternately. The present invention is also applicable to the configuration used.

Further, in the above embodiment, the ratio of the detected value Q1 of the flow meter to the time differential value Q2 of the weight of the pressurized tank, that is, the moving average value of Q+/Q2, is used as the correction coefficient, but the present invention is not limited to this. Instead, it is possible to employ various other mathematical techniques.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a block diagram showing the configuration of the device of the present invention, FIG. 2 is a waveform diagram for explaining correction calculation by the flow rate calculator, and FIG. 3 is a flow rate diagram. FIG. 4 is a flowchart showing the procedure of correction calculation by the arithmetic unit, and is an explanatory diagram of the prior art. 2A, 2B... Cutout tank (pressurized tank)
4...Flowmeter 6...Blast furnace 7A, 7B...
Load cell 10... Main pipe 20... Differentiator
21...Flow rate calculator time Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono 3 Reasons $ 4 Figure

Claims (1)

[Claims] 1. In a method for measuring the flow rate of powder or granules discharged from any one of a plurality of tanks and pneumatically conveyed through a pipe, the in-pipe flow rate is detected at an appropriate position in the pipe, while the powder or granules are In order to detect the weight of the body, the weight of the tank discharging the granular material is detected, the detected value of this weight is differentiated with respect to time, and a correction coefficient is calculated according to the relationship between this time differentiated value and the detected value of the flow rate in the pipe. A method for measuring the flow rate of a powder or granular material, characterized in that the flow rate of the powder or granular material is determined by correcting a detected value of the flow rate in a pipe using the correction coefficient. 2. A flow rate measuring device for powder and granular material discharged from any one of a plurality of tanks and pneumatically fed through a pipe, which includes: a flow meter installed at an appropriate position in the pipe; and a flow meter installed in each of the tanks to measure the weight of each tank. a differentiator for time-differentiating the detection signal of the weight detector of the tank discharging the powder, and a time-differentiated value obtained by the differentiator and the flowmeter. a calculation device that calculates a correction coefficient according to the relationship with the in-pipe flow rate determined by the calculation device; and a calculation device that corrects the detected value of the flowmeter using the correction coefficient calculated by the calculation device to calculate the flow rate of the powder and granular material. A flow rate measuring device for powder or granular material, characterized in that it is equipped with a calculation device.