JPH08128928A - Gas concentration measuring equipment - Google Patents

Abstract

PURPOSE: To provide gas concentration measuring equipment capable of measuring gas concentration at quick response and accurately calibrating a sensor with a small amount of calibrating gas. CONSTITUTION: When the concentration of combustion gas is measured, a control means 6 rotates a gas flow rate regulating plate 3 so as to be parallel in the lengthy direction of a sampling pipe 1a through a regulating plate driving means 4 to directly introduce a sampling gas into an oxygen concentration sensor 2. When the sensor is calibrated, the control means 6 rotates the gas flow rate regulating plate 3 so as to be vertical in the lengthy direction of the sampling pipe 1a through the regulating plate driving means 4 to shut off the sampling gas, drives a valve 5a through a valve driving circuit 5b and ejects the calibrating gas in the oxygen concentration sensor 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas concentration measuring device for measuring the concentration of a specific gas, such as oxygen gas or carbon monoxide gas, in a flue gas.

[0002]

2. Description of the Related Art In an industrial plant or the like, measuring the concentration of a specific gas such as oxygen gas or carbon monoxide gas in a combustion gas is an important factor in monitoring the operation of the plant such as monitoring the combustion state. .

In such a case, in the gas concentration measuring device in which the probe and the gas sensor for sampling by utilizing the dynamic pressure of the sample gas are integrally formed, as shown in FIG.
The sampling pipe 21a is attached to 0a, the combustion gas flowing through the flue 21b is taken in as sampling gas from the gas sampling port 21b, and the concentration is measured by the gas concentration sensor 22 arranged inside. Then, a calibration gas having a known concentration is injected from the calibration gas tube 23 to the gas concentration sensor 22 at a predetermined cycle, for example, before starting the plant or every one week, and the output change of the gas concentration sensor 22 is calibrated with time. Was being done.

[0004]

However, when the gas concentration of the gas to be measured is measured using the gas concentration measuring device having the configuration shown in FIG. 7, the higher the dynamic pressure of the gas to be measured, the higher the response speed and the more accurate the measurement. It is possible to measure various concentrations, but Fig. 7
In the configuration in which the combustion gas collected from the flue 20b is brought into direct contact with the gas concentration sensor 22 as described above, the calibration gas cannot be accurately calibrated due to the influence of the sampling gas unless a large amount of the calibration gas is injected during the calibration of the sensor. was there.

Therefore, in order to solve such a problem, the present invention aims to provide a gas concentration measuring device capable of measuring a gas concentration at a fast response speed and capable of accurately calibrating a sensor with a small amount of calibration gas. And

[0006]

In order to achieve the above object, the present invention relates to a gas concentration for taking in a gas to be measured and measuring the concentration of the gas to be measured taken in by a gas concentration sensor arranged in a sampling pipe. In the measuring device, a calibration gas injection means for injecting a calibration gas to the gas concentration sensor, and a flow rate adjusting means disposed near the gas concentration sensor for adjusting the flow rate of the measured gas reaching the gas concentration sensor, It is characterized by having.

[0007]

The operation of the present invention will be described with reference to FIG. 1. When measuring the concentration of the combustion gas, the control means 6 causes the gas flow rate adjusting plate 3 to move through the adjusting plate driving means 4 to the sampling pipe 1.
It is rotated so as to be parallel to the longitudinal direction of a and the sampling gas is brought into direct contact with the oxygen concentration sensor 2. On the other hand, at the time of sensor calibration, the control means 6 rotates the gas flow rate adjusting plate 3 through the adjusting plate driving means 4 so as to be perpendicular to the longitudinal direction of the sampling pipe 1a, shields the sampling gas, and controls the valve driving circuit 5b. The valve 5a is driven via the valve to inject the calibration gas into the oxygen concentration sensor 2.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic view of a gas concentration measuring apparatus according to the present invention, wherein 1a is a cylindrical sampling pipe,
The combustion gas in the flue 11 is fixed to the flue pipe 10 via the mounting flange 1d, taken in as sampling gas from the gas sampling port 1c, and discharged from the gas exhaust port 1d. The inside of the sampling pipe 1a is partitioned by the guide plate 1b into the gas sampling port 1c side and the gas discharge port 1d side so that the sampling gas taken in does not become stagnant in the sampling pipe 1a.

The sampling pipe 1a is arranged so as to project from the flue pipe 10 to the outside as compared with the normal state, whereby the gas flow rate adjusting plate 3 can be attached easily.

Reference numeral 2 is a zirconia type oxygen concentration sensor which is one of the gas concentration sensors and detects the oxygen concentration in the combustion gas. As shown in FIG. 2, this oxygen concentration sensor 2 is configured such that one side is in contact with the sampling gas side, which is the gas to be measured, and the other side is in contact with the air taken in from the air intake port 2b, with the zirconia 2a as a boundary wall. By utilizing the characteristic of the zirconia 2a that generates an electromotive force according to the difference in oxygen concentration between the air and the measurement gas, a signal corresponding to the oxygen concentration of the measurement gas is output.

Reference numeral 3 denotes a disc-shaped gas flow rate adjusting plate, which is arranged in an airtight manner in the sampling pipe 1a and is rotated by an adjusting plate driving means 4 such as a motor. When the plate surface is parallel to the paper surface, the sampling gas exerts a dynamic pressure directly on the oxygen concentration sensor 2, and when the plate surface is perpendicular to the paper surface, the sampling gas is shielded and directly moves to the oxygen concentration sensor 2. It does not exert pressure.

FIG. 3 shows a case where the gas flow rate adjusting plate 3 is airtightly arranged in the sampling pipe 1a. First, the plate surface portion 3a of the gas flow rate adjusting plate 3 is sampled in the sampling pipe 1a.
The large-diameter threaded portion 3d of the mounting bolt 3c, which is inserted through the insertion port 1e formed in the above, and penetrates the rotary shaft 3b of the gas flow rate adjusting plate 3 through the through hole 3f, is screwed into the thread groove formed in the insertion port 1e. Next, an airtight pipe 3g having O-rings 3h on both sides is inserted between the through hole 3f of the mounting bolt 3c and the rotating shaft 3b, and then the small diameter screw portion 3 of the tightening nut 3i is inserted.
k is screwed onto the small-diameter screw portion 3e of the mounting bolt 3c. As a result, the inside of the sampling pipe 1a is O
It is kept airtight by the ring 3h.

In FIG. 1, reference numeral 5a denotes a valve, which is driven by valve driving means 5b, and when the valve is opened, the calibration gas in the calibration gas cylinder 5e is injected from the gas discharge port 5d to the oxygen concentration sensor 2 through the gas tube 5c.

Reference numeral 6 is a control means for controlling the rotation of the gas flow rate adjusting plate 3 via the adjusting plate drive means 4 and for controlling the drive of the valve 5a via the valve drive means 5b. Reference numeral 7 denotes an arithmetic means for calculating the actual concentration of the sampling gas and calibrating the oxygen concentration sensor 2 based on the detection signal from the oxygen concentration sensor 2.

Next, the operation of the present invention will be described based on the flowchart of FIG. 4 showing the operation of the control means 6. Wait for a calibration instruction from the computing means 7, and if there is a calibration instruction (S
1), the gas flow rate adjusting plate 3 is set to 9 via the adjusting plate driving means 4.
While rotating 0 ° (S2), valve driving means 5b
The valve 5a is opened via the and the calibration gas is injected into the oxygen concentration sensor 2 (S3).

FIG. 5 shows this state. Since the sampling gas is shielded by the gas flow rate adjusting plate 3, the oxygen concentration sensor 2 is not directly subjected to dynamic pressure, but the calibration gas is shielded by the sampling gas. Instead, it fills the vicinity of the oxygen concentration sensor 2. Therefore, the concentration of the calibration gas can be accurately detected by the oxygen concentration sensor 2 without injecting a large amount of the calibration gas, and accurate sensor calibration can be performed.

When the drive control of the gas flow rate adjusting plate 3 and the valve 5a is completed, the calculation means 7 is instructed to that effect (S).
4).

Here, the calibration operation of the oxygen concentration sensor 2 performed by the calculation means 7 will be described. As shown in FIG. 6, the calibration curve for obtaining the oxygen concentration from the detection signal of the oxygen concentration sensor 2 is usually a detection value N1 for oxygen gas having a known concentration, for example, 9% concentration and 1% concentration in advance.
, N2, and linear approximation of these is used. Then, based on this calibration curve, the calibration gas cylinder is filled with oxygen gas having a concentration of, for example, 9 percent, and when the detected value is N2 'at the time of calibration, as shown in FIG. Calibration is completed by translating. In addition, in the above-described embodiment, an example in which the sensor is calibrated with one calibration gas having a known concentration has been described. However, a plurality of calibration gas cylinders are used to sequentially apply two or more calibration gases having known concentrations to the oxygen concentration sensor 2. By injecting, a plurality of detection values can be obtained, so that a more accurate calibration curve can be obtained.

When the calibration operation is completed, the calculation means 7 notifies the control means 6 of that fact, and the control means 6 waits for this notification (S5). Contrary to the operations of S2 and S3, the valve drive means is activated. The valve 5a is closed through 5b (S6),
The gas flow rate adjusting plate 3 is further connected via the adjusting plate driving means 4.
Rotate 0 °. (S7).

FIG. 5b shows this state, in which the sampling gas is not blocked by the gas flow rate adjusting plate 3 and exerts a dynamic pressure directly on the oxygen concentration sensor 2, so that the oxygen concentration can be measured at a high response speed. Becomes

Although the gas flow rate adjusting plate 3 is used for calibrating the oxygen concentration sensor 2 in the above-described embodiment, it may be used for cleaning the oxygen concentration sensor 2. That is, since the combustion gas flowing in the flue 11 is in direct contact with the oxygen concentration sensor 2, dust such as flue gas is very likely to adhere, but if a large amount of these adheres, the detection accuracy of the sensor is greatly adversely affected. give. Therefore, it is necessary to regularly clean the oxygen concentration sensor 2. However, according to the present invention, the gas flow can be controlled by appropriately moving the gas flow rate adjusting plate 3 at the time of cleaning. The sensor can be cleaned. For example, if the calibration gas is injected from the state of FIG. 5a to the oxygen concentration sensor 2 from the state of FIG. 5a, and the state is gradually shifted to the state of FIG. Since the calibration gas directly collides with the oxygen concentration sensor 2 and bounces off the gas flow rate adjusting plate 3a and collides with the entire oxygen concentration sensor 2, dust and the like adhering to the oxygen concentration sensor 2 are efficiently cleaned. Then, after a predetermined time, the gas flow rate adjusting plate 3 is gradually rotated to the state of FIG. 5b, and the dust washed off from the oxygen concentration sensor 2 is discharged from the discharge port 1d together with the sampling gas. By disposing the gas flow rate adjusting plate in the vicinity of the oxygen concentration sensor 2 as described above, the oxygen concentration sensor 2 can be calibrated more accurately, and the oxygen concentration sensor 2 can be efficiently cleaned.

Further, in the above-mentioned embodiment, the control of the gas flow rate adjusting plate 3 and the valve 5a is configured to be performed by the control means 6 in conjunction with the operation of the computing means 7, but the present invention is not limited to this. Instead, the valve 5a and the gas flow rate adjusting plate 3 may be manually moved at the time of calibration.

Further, in the above-mentioned embodiment, the zirconia type oxygen concentration sensor 2 is shown, but any type of sensor such as a carbon monoxide concentration sensor which detects the gas concentration by directly contacting with the gas can be used. Good.

[0025]

According to the present invention, since the flow rate adjusting means for adjusting the flow rate of the gas to be measured reaching the concentration sensor is provided in the vicinity of the gas concentration sensor, the combustion gas is directly supplied when the gas concentration is measured. The combustion gas can be shielded by contacting the gas concentration sensor and calibrating the gas concentration sensor. For this reason,
It is possible to measure the gas concentration with a fast response, and moreover, when calibrating the sensor, it is possible to accurately calibrate the gas concentration sensor with a small amount of calibration gas. Further, if the flow rate adjusting plate is moved appropriately, the gas concentration sensor can be cleaned efficiently by only injecting the calibration gas.

[Brief description of drawings]

FIG. 1 is an embodiment of a gas concentration measuring device according to the present invention.

FIG. 2 is a schematic diagram of a zirconia-type oxygen concentration sensor.

FIG. 3 is a view showing a case where a gas flow rate adjusting plate according to the present invention is airtightly attached to a sampling pipe.

FIG. 4 is a flowchart showing the operation of the present invention.

FIG. 5 is a diagram showing a case where the gas flow rate adjusting plate according to the present invention is operated.

FIG. 6 is a diagram showing a calibration curve of a gas concentration sensor.

FIG. 7 is a schematic view of a conventional gas concentration measuring device.

[Explanation of symbols]

 1a ... Sampling pipe 2 ... Oxygen concentration sensor 3 ... Gas flow rate adjusting plate 5a ... Valve 5d ... Gas discharge port

Claims (1)

[Claims] 1. A gas concentration measuring device for taking in a gas to be measured and measuring the concentration of the gas to be measured taken in by a gas concentration sensor arranged in a sampling pipe, wherein a calibration gas is injected into the gas concentration sensor. A gas concentration measuring device comprising: an injection unit; and a flow rate adjusting unit that is disposed in the vicinity of the gas concentration sensor and adjusts the flow rate of the gas to be measured that reaches the gas concentration sensor.