JPH0480652A - Apparatus for measuring moisture and oxygen simultaneously and continuously - Google Patents

Abstract

PURPOSE:To enable the measuring of concentrations of moisture and oxygen simultaneously and continuously with oxygen sensors by providing one measuring probe tube with two oxygen sensors of the same structure. CONSTITUTION:At a zirconia sensor section 27 for measuring concentrations of moisture, an output (electromotive force) is generated in an oxygen sensor corresponding to a difference in concentration of oxygen between a gas A to be measured which flows continuously to contact a measuring electrode and a dry gas to be measured which is made to pass continuously to the side of a reference electrode and concentrations of moisture can be measured in the gas A. At a zirconia sensor section 26 for measuring concentrations of oxygen, an output is generated in the oxygen sensor corresponding to a difference in concentration of oxygen between an external reference gas (atmospheric air, dry atmospheric air or the like) which flows continuously to the side of the measuring electrode through an external gas introduction tube and a dry gas B to be measured which is made to pass continuously to the side of the reference electrode and concentrations of oxygen in the gas A to be measured can be measured. This enables the measuring of moisture and oxygen simultaneously with a simple construction.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a device for simultaneously and continuously measuring moisture and oxygen concentrations in gas, in which two oxygen sensors of the same structure are arranged in one probe tube. The present invention relates to a device that can simultaneously and continuously measure moisture and oxygen concentrations in each oxygen sensor.

(Prior art and its problems) Conventionally, oxygen concentration (or The technology of detecting oxygen partial pressure and feeding it back to the combustion side pressure of industrial furnaces and boilers is already known.

Moisture measurement in the combustion exhaust gas of various industrial furnaces and boilers, especially pulverized coal boilers, is extremely difficult to quantitatively understand due to variations in the properties of the coal used, or the daily thermal efficiency management of the boiler must be improved. , is important for maintaining and improving thermal efficiency.

Further, the oxygen concentration in the combustion exhaust gas is essential for the purpose of low-oxygen operation from the viewpoint of energy saving.

For this purpose, a moisture measuring method is disclosed, for example, in Japanese Patent Application Laid-Open No. 57-178154. In this method, a measurement gas is brought into contact with an electrode on one side of a solid electrolyte element exhibiting oxygen ion conductivity, and a measurement gas after water removal is brought into contact with an electrode on the other side, and the gas generated between these two electrodes is brought into contact with the measurement gas. It measures the moisture concentration in the measurement gas using electromotive force.

However, this method only uses the measurement gas from which moisture has been removed as a reference gas, and has the disadvantage that the oxygen concentration in the measurement gas cannot be measured continuously and simultaneously.

(Problems to be Solved by the Invention) It is an object of the present invention to have a very simple configuration, economically low cost, and to provide moisture concentration and oxygen concentration (partial pressure) in a gas to be measured such as combustion exhaust gas. An object of the present invention is to provide a device that can measure both simultaneously and continuously.

(Means for Solving the Problems) The present invention includes a measurement probe fixed so as to be in contact with the flow of a gas to be measured in a duct; a dehumidifier that converts the gas into gas; a suction pump that sucks the gas to be measured and sends it to the dehumidifier, and further sends the dry gas to be measured into the inside of the measurement probe; and a suction pump that makes contact with the gas to be measured. comprising a measurement electrode and a reference electrode facing into the measurement probe and in contact with the dry gas to be measured, the electrode being caused by a difference between the oxygen concentration of the gas to be measured and the oxygen concentration of the dry gas to be measured. configured to be able to measure the moisture concentration of the gas to be measured from the electromotive force,
and a zirconia sensor unit for measuring moisture concentration fixed to the measurement probe; a measurement electrode in contact with an external reference gas whose oxygen concentration is known; and a measurement electrode facing into the measurement probe and in contact with the dry gas to be measured. a reference electrode that is configured to be able to measure the oxygen concentration of the gas to be measured from an electromotive force generated due to the difference between the oxygen concentration of the external reference gas and the oxygen concentration of the dry gas to be measured; This invention relates to a simultaneous and continuous measuring device for moisture and oxygen, which has a zirconia sensor section for measuring concentration and a zirconia sensor section for measuring oxygen concentration fixed to a measurement probe at a predetermined interval.

(Example) FIG. 1 is a configuration explanatory diagram showing an apparatus for simultaneously and continuously measuring moisture and oxygen according to an example of the present invention.

In this figure, l is a measurement probe that is inserted and installed into the flow of combustion exhaust gas, which is the gas to be measured. A sensor section 26 and a zirconia sensor section 27 for measuring water concentration are provided.

In each of these sensor sections 26 and 27, an oxygen sensor 1O shown in FIG. 2 is attached to the inside of the filter cover 2, respectively. Further, a sensor back cover 3 is provided on the opposite side of the filter cover 2 so that the oxygen sensor 10 can be attached to the measurement probe 1 and replaced. When attaching and detaching the oxygen sensor IO, the sensor back cover 3 is removed, and the oxygen sensor is attached and detached through its opening. A mounting flange 5 and a terminal box 8 are provided in the mounting section of the measurement probe 1, and the measurement probe 1 is fixed to a furnace wall flange 6 provided on a furnace wall 7 by the mounting flange 5. The terminal box 8 is provided with wiring and a wiring hole 9.

A gas suction pipe 2 is installed between the zirconia sensor section 26 for oxygen concentration measurement and the zirconia sensor section 27 for water concentration measurement.
The gas suction port 8 is positioned, and the gas to be measured is sucked in the direction of the arrow by the suction pump 29 and taken out to the outside of the duct. The extracted gas to be measured has its moisture content removed by the dehumidifier 30, and is vented into the measurement probe 1 as a dry gas to be measured. Thereafter, it is discharged into the duct as shown by arrow B from the discharge port 4 located at the tip of the measurement probe 1. This series of operations (extraction of the gas to be measured to the outside - suction bomb dehumidifier - ventilation inside the measurement probe - discharge) is performed continuously.

Therefore, the inside of the measurement probe, that is, the reference electrode side of the oxygen sensor, is always filled with an atmosphere of dry gas to be measured, and the series of operations is performed continuously, so the concentration of each component in the dry gas is This means that it constantly responds to changes in concentration in the gas to be measured.

The distance between the zirconia sensor section 26 for oxygen concentration measurement and the zirconia sensor section 27 for water concentration measurement is 100 mm in order to reduce the influence of uneven distribution of gas concentration in the flue duct.
The gas suction port of the gas suction pipe 28 is preferably located between the sensor portions 26 and 27. That is, within a duct for carrying combustion exhaust gas, etc., there is a concentration distribution of the concentration of each component gas in the width and depth directions.

Therefore, by making the distance between the oxygen sensors as short as possible and placing the gas suction port in the middle position between the two oxygen sensors, the influence of uneven distribution of each concentration can be eliminated and the measurement of moisture and oxygen concentrations can be performed with high accuracy. This is because it is possible to ensure the

Next, details of the structures of the oxygen sensors that constitute the zirconia sensor section 26 for measuring oxygen concentration and the zirconia sensor section 27 for measuring water concentration will be explained with reference to FIGS. 2 to 5.

FIG. 2 shows the mounting structure of the oxygen sensor on the measurement probe 1. As shown in FIG. In this figure, an oxygen sensor 10 in the shape of a cylinder with a bottom made of a solid electrolyte is arranged so that the space inside the cylinder with a bottom communicates with the space of the gas flow to be measured (that is, the opening of the cylinder with a bottom is directed toward the combustion exhaust gas flow). ) are located. To attach the oxygen sensor 10 to the measurement probe 1, first, the sensor clasp 11 is airtightly fixed around the opening of the bottomed cylindrical oxygen sensor 10 by, for example, a shrink-fitting method. Tightening is achieved by fixing the sensor holder 12 fitted to the S-bulb 1 via a metal O-ring 17. Further, in the oxygen sensor lO mounted in this manner, a double cylindrical heater holder 14 (these constitute a heater unit) containing a built-in heater 13 is fitted from the inside to the sensor fastener 11, and cemented. is integrally fixed by. Therefore, the oxygen sensor 10, the sensor fastener 11 and the heater 13
and the heater holder 14 (that is, the heater unit) are integrated to form a sensor unit.

In order to prevent the inflow of dust, a filter unit consisting of a filter 15 and a filter holder 16 is connected to the side of the oxygen sensor 10 that comes into contact with the gas to be measured, and a filter cover 2 is further provided on the outside thereof. This prevents dust from directly hitting the filter 15 and prevents the filter 15 from clogging. The filter cover 2 is provided with, for example, four gas inflow holes 24 divided equally at an angle of 90 degrees (see Fig. 3).
, the gas to be measured is introduced into the oxygen sensor via the filter 15. Furthermore, in order to introduce an external reference gas (with known oxygen concentration) for calibrating the output (electromotive force) of the oxygen sensor 10, an external gas introduction pipe 18 introduced from outside the furnace wall is arranged along the outside of the measurement probe 1. The opening 19 of the external gas inlet pipe 18 is connected to the external gas inlet 20 provided in the sensor holder 12, and this communicates with the gas inlet/outlet 25 provided in the filter holder 16 and the internal space 21. This forms a gas passage through which the above-mentioned calibration gas or external reference gas can be introduced into the internal space. Also,
The sensor holder 12 is provided with a gas exhaust port 22 on the side opposite to the side where the external gas inlet 20 is provided. Furthermore, a corner portion of the filter holder 16 that contacts the sensor fastener 11 is machined to form a gas passage 23 on the circumference of the filter holder 16 (see FIG. 4).

This gas passage 23 communicates the internal space 21 with the measured gas space in the duct via the gas inlet/outlet 25 and the gas exhaust port 22, and also communicates the external gas with the internal space of the external gas introduction pipe 18. It communicates via an inlet 20.

Therefore, the gas to be measured, the calibration gas, or the external reference gas existing in the internal space 21 can be quickly discharged to the outside.

Note that the oxygen sensor 10 shown in FIG. 2 may have a flat plate shape or the like in addition to a cylindrical shape with a bottom, and can be appropriately selected depending on the application.

In the zirconia sensor section 27 for water concentration measurement (see Figures 1 and 2), the gas to be measured flows into and comes into contact with the inner surface of the bottomed cylinder (measuring electrode side) of the oxygen sensor 10, and the dry gas flows into the reference electrode side. The gas to be measured comes into contact with it.

On the other hand, in the zirconia sensor section 26 for oxygen concentration measurement, an external reference gas (for example, atmospheric air) with a known oxygen concentration, introduced from the external gas introduction pipe 18, flows into and comes into contact with the measurement electrode side of the oxygen sensor 10. The dry gas to be measured comes into contact with the electrode side. Moreover, both sensor parts 26 and 27 are
Introducing a calibration gas through a suitable external gas introduction pipe 18,
Perform proofreading.

Next, the inflow and discharge of the gas to be measured to the measurement electrode side of the zirconia sensor section 27 for measuring water concentration will be further described.

As shown in the plan view and cross-sectional view of the state in which the filter cover is attached in FIGS. It enters through the hole 24 , passes through the filter 15 , and flows into the internal space 21 above the oxygen sensor 10 .

From this internal space 21 to the measurement electrode provided deep inside the bottomed cylindrical oxygen sensor 10, gas replacement is performed by gas diffusion and thermal convection due to the difference in concentration of the measurement gas. Other gases to be measured are shown in Figure 4 (A) and (B).
As shown in (omitting the filter cover), the gas is discharged to the outside through the gas inlet/outlet 25, the gas passage 23, and the gas outlet 22.

Next, regarding the inflow and discharge of the external reference gas to the measurement electrode side in the zirconia sensor section 26 for oxygen concentration measurement, the fifth
This will be described with reference to Figures (A) and (B).

However, in order to clarify the drawing, the filter cover is omitted from the illustration. First, the external reference gas passes through the external gas inlet pipe 18 from outside the furnace wall, passes through the external gas inlet 20 and the gas inlet/outlet 25, and fills the internal space 21. At this time, since the internal space 21 is in a positive pressure state, the inflow of the gas to be measured is blocked. A part of the external reference gas filling the internal space 2I gradually reaches the deep part of the oxygen sensor 10 by being introduced under pressure and comes into contact with the measurement electrode. As shown in FIG. 5(A), other external reference gases are discharged from the gas outlet 22 through the gas passage 23 when the internal space becomes a negative pressure state with respect to the pressure of the gas atmosphere to be measured. Ru.

Next, regarding the effects obtained by the device of this example,
I will explain them one by one.

(1) In the zirconia sensor section 27 for water concentration measurement (see Figure 1), a gas to be measured continuously flows into and comes into contact with the measurement electrode side, and a dry gas to be measured is continuously vented to the side of the reference electrode. Based on the difference in oxygen concentration, an output (electromotive force) is generated in the oxygen sensor correspondingly, and the moisture concentration in the gas to be measured can be measured.

The output of the oxygen sensor at this time is as follows.

Here, E is the output of the oxygen sensor: Constant T: Oxygen sensor heating temperature (absolute temperature) PO2 (W): Oxygen partial pressure in the measured gas PO2 (D)
:Oxygen partial pressure in dry measured gas and moisture concentration (H
2O) (vo1%), the oxygen concentration in the measured gas was set to [0
□(W) ) (vo1%), and the oxygen concentration in the dry gas to be measured is [0□(D) ) (vo1%), then the following relationship holds true.

[0□(W) ) 100- (H2O) Therefore, from the above ■, equation 2, (H2O) = (110"") X100(Vo1
%) In this way, the moisture concentration in the gas to be measured can be calculated from the difference between the oxygen partial pressure in the gas to be measured and the partial pressure of oxygen in the dry gas to be measured.

(2) In the zirconia sensor section 26 for oxygen concentration measurement (see Fig. 1), an external reference gas (air, dry air, etc.) continuously flows into the measurement electrode side through the external gas introduction pipe I8, and an external reference gas (air, dry air, etc.) flows into the measurement electrode side. Due to the difference in oxygen concentration between the dry gas to be measured and the dry gas to be measured which is continuously vented, a corresponding output is generated to the oxygen sensor, and the oxygen concentration in the gas to be measured can be measured.

The output of the oxygen sensor at this time is as follows.

E2: Oxygen sensor output 0.206: Oxygen concentration in the atmosphere Therefore, the oxygen concentration in the dry measured gas is 02 (D) =
(0,206/10”'K”) X100 (vo1%)
The oxygen concentration 0□(D) measured here is the oxygen concentration in the dried gas to be measured, but the oxygen concentration in the gas to be measured before drying can also be easily calculated by the following formula using the above three formulas. can be asked for.

UU (3) The important thing here is that, as shown in Figure 1,
- When attaching two oxygen sensors to a measuring probe, dry gas to be measured is vented into the measuring probe, one oxygen sensor is connected to the gas to be measured in a wet gas state, and the other oxygen sensor is connected to an external reference gas. This makes it possible to simultaneously measure moisture and oxygen using an extremely simple configuration. This is extremely advantageous because only one mounting seat is required for the measurement probe on the duct wall, and equipment costs and costs can be reduced.

Therefore, if the device of this embodiment is applied to the measurement of moisture and oxygen concentrations in the flue gas of various industrial furnaces and boilers, especially pulverized coal boilers, it will be possible to improve boiler thermal efficiency management, maintain and improve thermal efficiency, and improve electricity consumption at low cost. Highly efficient operation of dust collectors,
It is extremely effective in preventing corrosion of flues, etc.

(4) In the device of this embodiment, in the zirconia sensor section for measuring water concentration, a measurement gas flow path from the inflow to the outflow of the gas to be measured is provided on the measurement electrode side.
Further, in the zirconia sensor section for measuring oxygen concentration, a gas flow path is provided on the measuring electrode side from the inflow to the outflow of the external reference gas introduced from the external gas introduction pipe. Therefore, the gas to be measured or the external reference gas is quickly introduced into the internal space 21 (see Figure 2), and gas replacement can be performed while maintaining a nearly balanced state at the measurement electrode of the oxygen sensor. While maintaining high responsiveness, protection against thermal shock can be provided at the same time. As a result of increasing the responsiveness of the oxygen sensor in this way, time delays and deviations can be effectively prevented when measuring moisture and oxygen simultaneously and continuously.

In the above example, in FIG. 1, the zirconia sensor section 26 for oxygen concentration measurement is provided above the zirconia sensor section 27 for water concentration measurement, but this positional relationship may be reversed, and each sensor section 26, 27 It is also possible to provide a plurality of each.

(Effects of the Invention) According to the simultaneous and continuous measurement device for moisture and oxygen according to the present invention, the measurement electrode contacts the gas to be measured, and the reference electrode faces the inside of the measurement probe and contacts the dry gas to be measured. and has a zirconia sensor section for measuring moisture concentration configured to be able to measure the moisture concentration of the gas to be measured from the electromotive force generated by the difference between the oxygen concentration of the gas to be measured and the oxygen concentration of the dry gas to be measured. Therefore, the water concentration in the gas to be measured can be measured continuously.

It also has a measurement electrode that contacts an external reference gas whose oxygen concentration is known, and a reference electrode that faces the inside of the measurement probe and contacts the dry gas to be measured. It has a zirconia sensor for measuring oxygen concentration that is configured to measure the oxygen concentration of the gas to be measured from the electromotive force generated due to the difference between the oxygen concentration of the gas to be measured, so the oxygen concentration in the gas to be measured can be continuously measured. Can be measured accurately.

The zirconia sensor section for measuring water concentration and the zirconia sensor section for oxygen concentration measurement are fixed to the tube wall of the measurement probe at a predetermined interval, which eliminates the need for a mounting seat for the probe tube, reducing equipment costs. Costs can be significantly reduced.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the configuration of the device according to the present invention, Fig. 2 is a sectional view of the main part showing the installation state of the oxygen sensor, and Fig. 3 (A) shows the state in which the gas to be measured flows into the oxygen sensor. 4 (A) is a front view showing the state in which the gas to be measured flows out from the oxygen sensor; FIG. 5 (B) is a longitudinal sectional view; (A) is a cross-sectional view showing a state in which the external reference gas flows into and out of the oxygen sensor, and (B) is a longitudinal cross-sectional view. 1...Measuring probe 2...Filter cover 3...Sensor back cover 4...Air outlet 5.
...Mounting flange 6...Furnace wall flange 7...
・Furnace wall 8...Terminal box 9...Wiring・
Piping hole 10...Oxygen sensor 11...Sensor clasp 12...Sensor holder 13...Heater 14...Heater holder 15...Filter 17...0 ring 19...Opening 21... Internal space 23... Gas passage 25... Gas inlet/outlet 26... Zirconia sensor section for oxygen concentration measurement 27...
- Zirconia sensor section for measuring water concentration 28...Gas suction pipe 29...Suction pump 30...Dehumidifier 16...Filter holder 18...External gas introduction pipe 20...External gas introduction port 22...Gas outlet 24...Measurement gas inflow hole Fig. 2 Fig. 3 (A) (B) Fig. 4 (A) (A)

Claims (1)

[Claims] 1. A measurement probe fixed so as to be in contact with the flow of the gas to be measured in the duct; and a dehumidifier that substantially removes the moisture from the gas to be measured to dry the gas to be measured. a suction pump for sucking the gas to be measured and sending it to the dehumidifier and further sending the dry gas to be measured into the inside of the measurement probe; a measurement electrode in contact with the gas to be measured; a reference electrode that faces the inside of the measurement probe and contacts the dry gas to be measured; It is configured to be able to measure the moisture concentration of the measurement gas,
and a zirconia sensor unit for measuring moisture concentration fixed to the measurement probe; a measurement electrode that contacts an external reference gas with a known oxygen concentration; and a measurement electrode that faces into the measurement probe and contacts the dry gas to be measured. a reference electrode,
The oxygen concentration of the gas to be measured can be measured from the electromotive force generated due to the difference between the oxygen concentration of the external reference gas and the oxygen concentration of the dried gas to be measured, and A simultaneous and continuous measurement device for moisture and oxygen, which includes a zirconia sensor section for oxygen concentration measurement fixed to a measurement probe at intervals.