JPH05273112A - Precision maintaining method for dust concentration measuring sensor and device - Google Patents

Abstract

PURPOSE:To maintain a measuring sensor at high precision over a long period by forming an auxiliary gas duct, and providing opening/closing valves at the front and rear of the dust sensor. CONSTITUTION:The unscattered light within the light from a light emitting unit 21 reaches a light receiving unit 22, and the dust concentration is measured by a dust concentration output device 23. Opening/closing valves 17, 18 at the front and rear of a dust sensor are normally kept opened, the valves 17, 18 are closed by the instruction signal of dust collector control device at each fixed time, the outside clean air is fed between the valves 17, 18 by a compressor 20, and the portion between both opening/closing valves 17, 18 is filled with the clean gas. The dust concentration is measured in this state. If the light emitting unit 21 and the light receiving unit 22 deteriorate, a change is generated on the current value, the difference between this current value and the reference current value stored in the dust collector control device is calculated, and the dust sensor output value is corrected by this difference to calculate the dust concentration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for maintaining the accuracy of a dust sensor for measuring the dust concentration of exhaust gas generated from a melting furnace, a heating furnace or the like, and an apparatus for implementing the method.

[0002]

2. Description of the Related Art A melting furnace, a heating furnace and the like generate a large amount of dust during operation. When this dust is discharged to the outside from the factory where the above equipment is installed, the air will be polluted and cause pollution.Therefore, a dust collector is usually installed in such equipment to suck the dust and place it in an appropriate place. Pollution is prevented by landfilling and other methods. Dust can be sucked in by attaching a dust collector directly to the place where dust is generated or by installing a hood under the roof of a building where dust-generating equipment is installed to suck dust. Appropriate method is taken according to the occurrence situation of.

However, no matter which method is used to collect dust, a large amount of electricity is consumed to treat dust, and therefore it is necessary to urgently proceed with technological development for reducing the amount of electricity used. ing.

In order to use electricity efficiently, the amount of dust generated is accurately grasped, the power of the dust collector is adjusted little by little according to the amount of dust generated, and the dust is collected with power exceeding the required strength. It is necessary to control the machine so that it does not operate.
In order to solve such a problem, the present inventor has invented a melting furnace for melting steel or the like, a method called "dust melting dust collecting method" (Japanese Patent Application No. 3-162257), and determines the amount of dust. We have clarified an efficient operation method that measures at any time and collects dust with a suction amount according to that amount.

[0005]

Dust sensors for measuring the amount of dust produced include light transmission type, light scattering type,
Various sensors such as β-ray absorption type and electrostatic type are commercially available. Of these, the light transmission type and light scattering type sensors are most suitable for daily dust amount management because they can measure the average smoke concentration in the flue and can measure it continuously. It is a sensor. Therefore, in order to accurately grasp the dust generation amount, operate the dust collector with the strength according to the amount, and use electricity efficiently, it is extremely necessary to establish the accuracy control technology of the dust sensor using light. It becomes important.

In order to use the light transmission type or light scattering type sensor with high accuracy for a long period of time, the following problems must be solved. That is, a dust sensor utilizing light is composed of three parts, a light source part, a light receiving part, and a dust concentration output device, but if the surfaces of the light source part and the light receiving part are contaminated by dust or the like, the light is blocked by the dirt. Therefore, the measured dust concentration becomes higher than the actual dust concentration. The light source part and the light receiving part are designed so as not to come into contact with the exhaust gas by taking measures such as blowing in protective air, but it is inevitable that the light source part and the light receiving part will become dirty with the passage of time. There is a need to. In addition, since the illuminance of the lamp used in the light source unit decreases with the lapse of time, it is necessary to periodically make a correction in consideration of the illuminance decrease amount.

The present invention has been made to solve the above problems, and an object thereof is a method and apparatus for maintaining accuracy of a dust concentration measuring sensor capable of maintaining high measurement accuracy for a long period of time. To provide.

[0008]

Means for Solving the Problems The present invention, which was made to solve the above-mentioned problems, provides a method for measuring the dust concentration in a flue with a dust sensor of a light transmission type or a light scattering type.
An open / close valve was installed in front of and behind the dust sensor provided in the middle of the flue, and the output corresponding to the dust concentration was measured with the open / close valve closed and the inflow of exhaust gas to the light passage position of the dust sensor blocked. A method for maintaining accuracy of a dust concentration measuring sensor, characterized in that the dust concentration value obtained from the dust sensor is corrected based on the amount of change of the output value from the output value at the time of initial setting.

[0009] Further, by putting clean gas into the flue with the open / close valve closed, the dust concentration at the light emitting position of the light source is surely lowered, and then the output corresponding to the dust concentration is measured. The dust concentration value may be corrected.

Here, the time interval for reviewing the accuracy is
It changes depending on the operating status of the target equipment, and it is desirable to set an appropriate interval for each equipment. Further, the dust sensor must be in a measurable state at all times during operation of the facility, but if the accuracy of the present invention is reviewed during facility operation, it becomes impossible to measure the dust concentration in the exhaust gas. Attach to multiple locations,
It is desirable to always be able to measure at more than one place.

Furthermore, if the on-off valve is closed and the dust stops flowing in the flue, the dust collection itself becomes impossible.
It is desirable to apply the method of the present invention by providing a bypass from the main flue and installing an opening / closing valve and a dust sensor in the middle thereof. That is, in order to efficiently carry out the method of the present invention, a secondary flue provided as a bypass from the main flue, and a light transmission type or light scattering type dust measuring the dust concentration of the exhaust gas flowing in the auxiliary flue. A sensor,
It is possible to manufacture an accuracy maintaining device for a dust concentration measuring sensor, which includes an opening / closing valve which is provided in the middle of the auxiliary flue and before and after the dust sensor to prevent the exhaust gas from flowing into the dust concentration measuring position.

Further, a device for supplying a clean gas to this device may be provided at an intermediate position between the two opening / closing valves to surely reduce the dust concentration and review the measurement accuracy as described above.

In the present invention, the normal range of the dust concentration output value measured with the on-off valve closed is set in advance, and if the output value is out of the range, a buzzer, a lamp, etc. are used. It is also possible to give an alarm to inform the operator of the abnormality.

[0014]

1 is a system diagram showing an outline of a dust collection system when the present invention is applied to an electric furnace for melting steel, and FIG. 2 shows a dust concentration measuring sensor according to an embodiment of the present invention. It is an enlarged view of a precision maintaining device (hereinafter referred to as a precision maintaining device) 12 and its vicinity. As shown in FIG. 1, the electric furnace 1 is provided with a suction port 5 for sucking exhaust gas containing dust, and a suction elbow 6 which is a curved pipe is provided therein. The exhaust gas sucked by the suction elbow 6 is delivered to the main flue 9, the combustible gas in the exhaust gas is burned in the combustion tower 7, and then cooled by the cooling tower 8 to a temperature at which the subsequent equipment is not damaged. The cooled exhaust gas is sent to the bag house 16 by the air exhauster 13, where dust is captured by the filter cloth.

The gas generated from the electric furnace 1 is sent to the bag house 16 by the exhaust fan 13 as described above, and the efficient control of the rotation speed of the exhaust fan 13 is the key to reducing the power cost. Becomes The rotation speed control method in this embodiment will be described below.

A power supply device 2 for supplying electric power to the electric furnace 1.
Are controlled by the electric furnace control device 3. The electric furnace control device 3 constantly sends a timing signal to the dust collector control device 11 during the operation of the electric furnace to inform when the current operation corresponds to the melting operation. This is because the accuracy of the dust sensor, which will be described later, is reviewed at an appropriate time in consideration of the operation time and time.

A precision maintaining device 12 is provided in the middle of the auxiliary flue 10 provided as a bypass of the main flue 9.
The dust concentration in the passing exhaust gas is measured and the data is sent to the dust collector control device 11. As described below,
Since the dust concentration cannot be measured during a review of the dust accuracy, two secondary flues 10 are installed in parallel, and a dust sensor is installed in the middle of each auxiliary flue 10 so that at least one dust sensor can always be measured. I am trying to be in a state. The dust collector control device 11 determines the rotation speed based on the timing signal obtained from the electric furnace control device 3 and the dust concentration obtained from the accuracy maintenance device 12, and sends an instruction to the rotation speed controller 15 to generate the dust amount. The exhaust fan 13 rotates at an appropriate rotation speed according to the above, and efficient use of electricity becomes possible.

Next, the accuracy maintaining device 12 will be described with reference to FIG. As shown in FIG. 2, a light transmission type dust sensor is attached in the middle of the auxiliary flue 10 provided as a bypass from the main flue 9. The dust sensor is
It consists of a light emitter 21, a light receiver 22, and a dust concentration output device 23, and a part of the light emitted from the light emitter 21 that is not scattered by the dust reaches the light receiver 22, and the dust concentration output device 23 The dust concentration can be measured by converting the current value according to the amount of received light. Before and after the dust sensor, open / close valve 17,
18 is provided and is normally in an open state, a part of the exhaust gas sucked from the electric furnace 1 flows in, and the dust concentration thereof is measured.

When a certain period of time has passed and it is time to reassess the accuracy of the dust sensor, an instruction signal is sent from the dust collector control device 11 to open / close the valves 17, 18.
Is closed. Even after the on-off valves 17 and 18 are closed, the exhaust gas can freely flow in the main flue 9, so that there is no hindrance to the operation of the dust collector. Also,
Since the measurement of the dust concentration can be continued by the remaining accuracy maintaining device 12, the accuracy described below can be reviewed while continuing the efficient dust collector control.

After the opening / closing valves 17 and 18 are closed, clean air outside is made to flow between the opening / closing valves 17 and 18 by the compressor 20. This is because the exhaust gas containing dust left between the two opening / closing valves 17 and 18 is discharged outside from the light passage position of the dust sensor. The exhaust gas left inside is pushed by the clean gas, passes through the gas discharge port 19, and is returned to the auxiliary flue 10 from the light passage position of the sensor. In this way, the opening / closing valve 17
The space between and 18 is filled with clean gas, which is almost free of dust.

In this state, the light emitter 21 emits light toward the light receiver 22, and the dust concentration output device 23
It is converted into a current value corresponding to the amount of light reaching the light receiver 22, and the result is sent to the dust collector control device 11. If the light emitter 21 is deteriorated and the illuminance is lowered, or if the surfaces of the light emitter 21 and the light receiver 22 are dirty, the amount of light reaching the optical sensor inside the light receiver 22 is reduced, and the current value changes. Occurs. A difference ΔA between this current value and a reference current value obtained in advance (stored in the dust collector control device 11) is calculated. After this, the output value obtained by the dust sensor is corrected by the value of ΔA to calculate the dust concentration. When ΔA exceeds a certain value, a buzzer, a lamp, etc., give an alarm to notify the operator that it is time to inspect and clean the dust sensor, and immediately
By cleaning and replacing parts as needed,
Work for maintaining the performance of the dust sensor can be efficiently performed.

As described above, the accuracy of the dust sensor is reviewed regularly and automatically in accordance with an instruction from the dust collector control device 11, so that the dust concentration can be accurately measured for a long period of time. It can greatly contribute to energy saving of the dust collector.

Although the present example is applied to an electric furnace used for melting steel, the method of the present invention is not limited to the electric furnace, and the dust generation amount in the flue is measured by a dust sensor in all cases. Can be effectively applied to equipment.

[0024]

According to the method and apparatus for maintaining the accuracy of the dust concentration measuring sensor according to the present invention, the accuracy of the dust concentration measuring sensor is automatically reviewed at regular intervals, so that the accuracy of the dust concentration measuring can be kept high for a long period of time. it can. Therefore, by applying the present invention, it is possible to configure a dust collecting system that can efficiently suck dust.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a dust collecting system of a melting furnace that is an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an embodiment of an accuracy maintaining device for a dust concentration measuring sensor according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric furnace 2 ... Power supply device 3 ... Electric furnace control device 4 ... Electrode 5 ... Suction port 6 ... Suction elbow 7 ... Combustion tower 8 ... Cooling tower 9 ... Main flue 10 ... Sub flue 11 ... Dust collector control device 12 ... Accuracy maintaining device 13 ... Exhaust air blower 14 ... Motor 15 ... Rotation control machine 16 ... Bag house 17, 18 ... Open / close valve 19 ... Gas discharge port 20 ... Compressor 21 ... Light emitting device 22 ... Light receiving device 23 ... Dust concentration output device

Claims (4)

[Claims] 1. When measuring the dust concentration in a flue with a light transmission type or light scattering type dust sensor, an opening / closing valve is provided before and after a dust sensor provided in the middle of the flue, and the opening / closing valve is closed to close the dust sensor. The output corresponding to the dust concentration is measured with the inflow of the exhaust gas to the light passage position of, and based on the amount of change from the output value at the time of initial setting of the output value, the dust concentration obtained from the dust sensor thereafter. A method for maintaining accuracy of a dust concentration measuring sensor, which is characterized by correcting a value. 2. The method for maintaining accuracy of a dust concentration measuring sensor according to claim 1, wherein a clean gas is introduced into the flue with the on-off valve closed, and then an output corresponding to the dust concentration is measured. 3. A secondary flue provided as a bypass from the main flue, a dust sensor of a light transmission type or a light scattering type for measuring the dust concentration of exhaust gas flowing in the auxiliary flue, and a midway of the secondary flue. An accuracy maintenance device for a dust concentration measurement sensor, comprising: an opening / closing valve that is provided before and after the dust sensor to prevent the exhaust gas from flowing into a dust concentration measurement position. 4. The dust concentration according to claim 3, further comprising a clean gas supply device capable of supplying clean gas into the auxiliary flue from an intermediate position of two opening / closing valves provided before and after the dust sensor. Accuracy maintenance device for measurement sensor.