JPH01250753A - Oxygen analyzing apparatus - Google Patents

Abstract

PURPOSE:To expedite the substitution of gas, to improve the responsiveness of measurement and to enable the protection of a measuring electrode from thermal impact, by providing a gas channel from inflow to outflow of a gas to be measured which passes in the vicinity of the base end part of an oxygen sensor formed of a solid electrolyte. CONSTITUTION:A plurality of oxygen sensors 10 fitted to a main pipe 1 are set in the flow of a gas to be measured. The gas enters an internal space 21 through a filter 15 from gas inflow ports 24 provided in four spots of a filter cover 2 of a sensor 10, and the substitution of the gas is implemented by gas diffusion and thermal convection due to a difference in concentration of the gas, in a place from the internal space to a measuring electrode. The other part of the gas passes through a gas inlet-outlet port 25, a gas passage and a gas exhaust port 22 and is released outside. When a calibration gas is introduced through an introduction pipe 18, it is passed through an introduction port 20 and the inlet-outlet port 25 and filled up in the space 21. Since the space 21 is put in a state of positive pressure on the occasion, the inflow of the gas to be measured is prevented. Part of the calibration gas is brought into contact with the measuring electrode by pressure introduction. The other part of the calibration gas is exhausted from the exhaust port 22 through the gas passage at the time point where the space 21 is put in a state of negative pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in an apparatus for measuring oxygen partial pressure or oxygen concentration.

(Prior Art) Conventionally, solid electrolytes such as zirconia that have oxygen ion conductivity at high temperatures have been used, and the principle of oxygen concentration batteries that utilize electrochemical reactions has been used in various steelmaking furnaces, other industrial furnaces, and boilers. Detects the oxygen concentration (or oxygen partial pressure) in the combustion exhaust gas emitted from the furnace, etc.
It is known to control the combustion state of a boiler.

The gas to be measured, such as the combustion exhaust gas from industrial furnaces, which is measured by conventional oxygen sensors that utilize such electrochemical reactions, flows in a layered manner in passages such as flues. It is recognized that the value of oxygen concentration varies greatly depending on the depth.

Japanese Unexamined Patent Publication No. 60-85360 discloses a measurement method in which a plurality of oxygen sensors are arranged at a predetermined distance in the depth direction of the flow of gas to be measured, and the oxygen partial pressure is determined at different locations in the longitudinal direction. Alternatively, a measuring device for effectively determining oxygen concentration has been disclosed.

(Problem to be Solved by the Invention) However, in this known measuring device, since there is no gas flow path from the inflow to the outflow of the gas to be measured, gas replacement in the space inside the filter is slow, and therefore gas measurement is difficult. Responsiveness (time) also becomes worse (slower). Moreover, when calibration gas is introduced during calibration, the measurement electrode is rapidly cooled, which causes a large change in sensor temperature between measurement and calibration gas introduction, creating the problem that highly accurate calibration cannot be obtained. was.

The present invention has been made to solve these problems.

(Means for Solving the Problems) In the oxygen analyzer of the present invention, the base end of the bottomed cylindrical solid electrolyte is positioned in the gas atmosphere to be measured, and the outer periphery is airtightly attached to the main pipe wall. The gist is that a flow path for a gas to be measured passing through the vicinity of the proximal end of the solid electrolyte is provided.

(Function) In the oxygen analyzer of the present invention, since a gas flow path is provided from the inflow to the outflow of the gas to be measured, the replacement of the gas to be measured is fast, and therefore the responsiveness (time) of gas measurement is good (fast). Become. Moreover, because the base end of the solid electrolyte is placed in contact with the atmosphere of the gas to be measured, the gas to be measured does not blow directly onto the measurement electrode, which is located deep inside the solid electrolyte. well protected from

Similarly, even if a calibration gas is introduced during calibration, the measurement electrode will not be cooled down. Therefore, the change in sensor temperature between the time of ° measurement and the time of introducing the calibration gas is reduced, making it possible to perform calibration with higher accuracy.

(Example) Embodiments of the present invention will be described based on the drawings.

FIG. 1 shows the configuration of a main pipe in which a plurality of oxygen sensors can be arranged at predetermined distances apart in the depth direction. In this figure, 1 is a main pipe that is inserted and installed into the flow of combustion exhaust gas, which is the gas to be measured.
A plurality of oxygen sensors 10 are mounted on the filter cover 2 at predetermined intervals.
is installed inside. In addition, this oxygen sensor 1
An opening is formed in the main pipe portion facing the filter cover 2, and the sensor back cover 3 is placed over the opening so that the sensor 0 can be attached to the main pipe 1 and replaced. When attaching and detaching the oxygen sensor 10, the sensor back cover 3 is removed, and the oxygen sensor is attached and detached through its opening.

The oxygen sensor 10 is arranged at a predetermined distance from the main pipe 1 in the pipe axis direction, and the predetermined distance is generally 50 m.
cm or more is accepted. A mounting flange 5 and a terminal box 8 are provided at the base of the main pipe 1, and the mounting flange 5 is attached and fixed to a furnace wall flange 6 provided on a furnace wall 7. The terminal box 8 is provided with wiring and piping holes 9.

An air outlet 4 is provided at the tip of the main pipe 1, and a standard gas such as air (atmosphere) continuously introduced into the main pipe 1 through an air valve (not shown) is supplied to the air outlet 4.
It is made to be continuously released from.

FIG. 2 shows the mounting structure of the oxygen sensor on the main pipe 1. In this figure, a bottomed cylindrical oxygen sensor 10 made of a solid electrolyte is installed in a predetermined position on a main pipe 1 so that the space inside the bottomed cylinder communicates with the combustion exhaust gas flow space (i.e., the bottomed The cylindrical opening is oriented toward the flue gas flow. To attach the oxygen sensor 10 to the main pipe 1, first, the sensor clasp RII is airtightly fixed around the opening of the bottomed cylindrical oxygen sensor 10 by, for example, the boundary method. Tightening is achieved by fixing the fitted sensor holder 12 via a metal O-ring 17. The oxygen sensor 10 mounted in this manner is further fitted with a double cylindrical heater holder 14 containing a heater 13 (these constitute a heater unit), which is fitted into the sensor fastener 11 from the inside and cemented. is integrally fixed by. Therefore, the oxygen sensor 10, the sensor clasp 11, the heater 13, and the heater holder 14 (ie, the heater unit) are integrated into a sensor unit.

On the side of the oxygen sensor 10 exposed to the gas to be measured,
In order to prevent the inflow of dust, a filter unit consisting of a filter 15 and a filter holder 16 is fitted together.
Furthermore, a filter cover 2 is provided on the outside to prevent dust from directly hitting the filter 15 and to prevent the filter 15 from clogging. By the way, this filter cover 2 has, for example, four gas inflow holes 24 to be measured.
They are equally divided at an angle of 90 degrees so that the gas to be measured can be introduced into the oxygen sensor through the filter 15. Furthermore, in order to calibrate the output (i.e., electromotive force) of the oxygen sensor 10, a calibration gas introduction pipe 18 introduced from outside the furnace wall is arranged along the outside of the main pipe 1, and an opening 19 of this calibration gas introduction pipe 18 is provided. is connected to the calibration gas inlet 20 provided in the sensor holder 12, and this and the gas inlet/outlet 25 provided in the filter holder 16 together form a gas passage communicating with the internal space 21. The calibration gas is introduced into the The sensor holder 12 has a gas outlet 22 on the side opposite to the side where the calibration gas inlet 20 is provided.
is provided.

Further, a corner portion of the filter holder 16 in contact with the sensor fastener 11 is processed to form a gas passage 23 on the circumference of the filter holder 16.

This gas passage 23 communicates the internal space 21 with an external measured gas space via a gas inlet/outlet 25 and a gas outlet 22, and also introduces a calibration gas into the internal space of the calibration gas inlet pipe 18. It communicates via the port 20. Therefore, the gas to be measured and the calibration gas existing in the internal space 21 can be quickly discharged to the outside.

As is already known, the oxygen sensor 10 has a structure in which a measurement electrode is provided on one side of a solid electrolyte that conducts oxygen ions at high temperatures, and a reference electrode is provided on the other side.As this solid electrolyte, For example, zirconium oxide with calcium oxide as a solid solution, zirconium oxide with yttrium oxide as a solid solution, thorium oxide with yttrium oxide as a solid solution, cerium oxide with lanthanum oxide as a solid solution, etc. be. In addition to the shape of a cylinder with a bottom as shown in FIG. 2, the shape of the solid electrolyte can be a flat plate or the like, and can be appropriately selected depending on the application.

In addition, the measurement electrode provided in such a solid electrolyte is generally a porous metal electrode, such as platinum, platinum, etc.
It is formed from metal materials such as rhodium alloy, platinum/palladium alloy, silver, and platinum/silver alloy.

For an oxygen sensor having such a predetermined shape, the gas to be measured such as combustion exhaust gas is brought into contact with the electrode surface on one side, and the reference oxygen partial pressure or concentration is placed on the electrode surface on the other side. Standard comparison gas, or normal atmosphere (air). For example, when the oxygen sensor has a cylindrical shape with a bottom as in this example, it is particularly configured so that the gas to be measured is brought into contact with its inner surface, and the reference atmosphere is brought into contact with its outer surface.

In the oxygen analyzer configured in this manner, for example, four oxygen sensors 10 are installed at predetermined intervals in the longitudinal direction of the main pipe 1, and are installed in the flow of gas to be measured such as in a flue. Each comes into contact with the gas to be measured at different locations. This will be explained in more detail based on FIG. As shown in the plan view and cross-sectional view of the filter cover with the filter cover 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 (8) 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. Therefore, in the device of the present invention, since the gas flow path is provided from the inflow to the outflow of the gas to be measured, the gas to be measured is quickly introduced into the internal space, and moreover, the gas to be measured is introduced into the measurement electrode of the oxygen sensor almost in an equilibrium state. By performing gas replacement while maintaining the temperature, the responsiveness of the oxygen sensor 10 can be maintained high and protection against thermal shock can be provided at the same time.

Next, the case where a calibration gas is introduced in order to calibrate the output of the oxygen sensor will be described based on FIGS. 5(8) and 5(B). However, in order to clarify the drawing, the filter cover is omitted from the illustration. First, the calibration gas passes through the calibration gas inlet pipe 18 from outside the furnace wall, passes through the calibration 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 calibration gas filling the internal space 21 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 Figure 5 (8), other calibration gases are added to the gas passage 2 when the internal space becomes a negative pressure state with respect to the pressure of the gas atmosphere to be measured.
3 and is discharged from the gas outlet 22. therefore,
Since the calibration gas does not directly hit the measurement electrode of the oxygen sensor 10 when introduced, and therefore is not rapidly cooled, the temperature change at the measurement electrode of the oxygen sensor between when measuring the gas to be measured and when the calibration gas is introduced. This allows for highly accurate calibration.

(Effects) As is clear from the above description, in the present invention, while effectively removing dust from the gas to be measured, the gas to be measured passes through the base end of the solid electrolyte and enters the flow of the gas to be measured again. By providing a gas flow path for discharging, gas replacement of the gas to be measured is performed quickly, and furthermore, it is gradually performed from the base end of the solid electrolyte to the deep inside by gas diffusion and thermal convection, so rapid heating is possible. It effectively protects the measurement electrode of the oxygen sensor from thermal shocks such as rapid cooling, improves responsiveness to the gas being measured, and increases the accuracy of the oxygen sensor by reducing changes in the temperature distribution of the oxygen sensor. be able to.

[Brief explanation of the drawing]

Fig. 1 is an external view showing an example of a device according to the present invention, Fig. 2 is a vertical cross-sectional view showing the oxygen sensor installation part of such a device, and Figs. 3 to 5 show how gas to be measured flows into and out of the oxygen sensor. FIG. 3 is a cross-sectional view of a fir tree showing how the calibration gas flows and how the calibration gas flows in and out. ■... Main pipe 2... Filter cover 3
...Sensor back cover 4...Air release port 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
16... Filter holder 17... 0 ring
18...Calibration gas introduction pipe 19...Opening
20... Calibration gas inlet 21... Internal space 22... Gas outlet 23... Gas passage
24...Measurement gas inlet hole 25...Gas inlet/outlet Patent applicant: Tokyo Electric Power Co., Ltd. Same applicant: Nippon Insulator Co., Ltd. Figure 1 Figure 2 Figure 3 (A) (B)

Claims (1)

[Claims] 1. A standard comparison gas that is inserted and installed in the depth direction of the flow of the gas to be measured and is continuously introduced into the flow of the gas to be measured through the discharge port. At least one main pipe configured to discharge continuously so that the pressure of the standard comparison gas in the pipe is approximately equal to the pressure of the gas to be measured, and a main pipe whose distal end is closed and whose proximal end is open. It has a bottom cylindrical solid electrolyte with oxygen ion conductivity, a measurement electrode provided on one side thereof, and a reference electrode provided on the other side, and the measurement electrode flows outside the main pipe. The reference electrode is attached to the wall of the main pipe at a predetermined distance in the pipe axis direction so that it is brought into contact with the gas to be measured, and the reference electrode is brought into contact with a standard comparison gas flowing through the main pipe. In an oxygen analyzer that includes a plurality of oxygen sensors and measures oxygen partial pressure or concentration at different locations in the measurement depth direction using the plurality of oxygen sensors, the proximal end of the oxygen sensor is connected to the gas to be measured. Oxygen analysis characterized in that the outer circumferential portion of the oxygen sensor is airtightly attached to the main pipe wall in a posture located in an atmosphere, and further a flow path for the gas to be measured passing near the base end of the oxygen sensor is provided. Device. 2. The oxygen analyzer according to claim 1, wherein the oxygen sensor is provided with a heating means and has an integral structure so that the solid electrolyte is heated to a predetermined temperature by the heating means.