JPS6358152A - Industrial oxygen concentration measuring apparatus - Google Patents

Abstract

PURPOSE:To enable measurement in a wide temperature range with a smaller size of the measuring apparatus, by providing a smaller detector section which is the integral laminate of a sending cell, a heating element and a thermosensor, at the tip of a probe to be inserted into a gas to be measured. CONSTITUTION:For example, a measuring probe 23 is inserted into a furnace wall of a burning furnace flue and mounted with a flange 35. An oxygen detecting section 21 is provided at the tip of the probe 23 through a ceramic filter 26 and a support 22. The oxygen detecting section 21 is formed by integrally laminating a sensing cell comprising an oxygen concentration cell and an oxygen pump, a heating element and a thermosensor in the form of plates. A reference air introduction tube 28 and a calibration gas introduction tube 27 are provided on the base side of the probe 23. A voltage is detected with the oxygen detecting section 21 corresponding to a difference in oxygen concentration between a gas to be measured from a ceramic filter 26 and a reference air to measure the concentration of oxygen in the gas being measured. Thus, the oxygen detecting section can be miniaturized to be set at the tip of the probe, thereby assuring a higher response time with a reduction in the detection space for the gas being measured.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an industrial oxygen concentration measuring device, and more specifically, it is installed on the furnace wall or exhaust gas 1ltl road wall of various combustion furnaces to measure the inside of the furnace or the exhaust gas. The present invention relates to an industrial oxygen concentration measuring device that measures oxygen concentration in combustion exhaust gas or atmosphere in a passage.

[Conventional technology]

Conventionally, an industrial oxygen concentration measuring device for measuring the oxygen concentration in exhaust gas sampled with a probe using a solid electrolyte is disclosed in JP-A-56-69553.

That is, as shown in FIG. 10, the surface of the oxygen concentration detecting element 1 made of a solid electrolyte in the shape of a cylinder with a bottom, which is in contact with the exhaust gas, collides with the filter 3 and the gas collision plate 5 provided on the gas introduction side of the filter 3. An oxygen concentration detector is disclosed that includes a plate 5 and a gas collector 11 that is provided to surround a filter 3 and has a gas inflow hole 7 and a gas outflow hole 9.

[Problem that the invention seeks to solve]

However, in the above-mentioned oxygen concentration detector, because it uses a nichrome heave heater and a cylindrical oxygen detection element with a bottom, for example, the diameter of the probe is approximately 5.
01 is required, and the entire device becomes large and heavy, and there are disadvantages such as a slow response time, a narrow working temperature range 1, and a narrow measurement concentration range.

The industrial oxygen concentration measuring device of the present invention solves these conventional inconveniences, is small and lightweight, has a simple structure, and can measure a wider temperature and concentration range than conventional devices. The purpose is to provide a device with good response performance.

[Means for solving problems]

The industrial oxygen concentration measuring device of the present invention includes a detection section in which a sensing cell, a heating body and/or a temperature sensing body are laminated and integrally molded into a plate shape, and at least a portion thereof is inserted into a gas to be measured. It is characterized by being provided at the tip of the probe.

[For production]

In the configuration described in Section 2, the sensing cell, heater, and/or temperature sensing body are stacked in a plate shape to form an integral structure, making the sensing part thin, small, and lightweight, which makes it possible to make the tip of the probe of the oxygen concentration measuring device It is possible to prevent the probe diameter from increasing even if it is placed in the
The operating temperature range can be expanded. Furthermore, the detection time for the gas to be measured becomes shorter and the response time becomes faster. Furthermore, if the sensing cell is configured with an oxygen concentration battery and an oxygen pump, the oxygen concentration near the measurement electrode can be controlled by the oxygen pump, and the oxygen concentration can be controlled over a wider oxygen concentration range (from oxidizing atmosphere to reducing atmosphere). ) can be measured.

〔Example〕

A specific embodiment of the industrial oxygen concentration measuring device of the present invention will be described with reference to the drawings.

The industrial oxygen concentration measuring device shown in cross section in FIG. 1 is of the so-called direct insertion type, and reference numeral 23 indicates a cylindrical probe for sampling gas, for example, in the flue of a combustion furnace. It is inserted into a hole formed in the wall, and the installation is done using flange 3.
It is held by 5. This probe 23 is open at both ends, and its material is, for example, metal for use at low temperatures below 600°C, and alumina for use at high temperatures above 600°C. A detection part 21 is connected to the tip side of this probe via a disk-shaped support 22 made of alumina.
is installed. The adhesion between the support 22 and the probe 23 is as follows:
In the case of low-temperature use, for example, shrink fitting, fitting, etc. are used, and in the case of high-temperature use, for example, welding is carried out using limited solder, platinum solder, glass, or the like. In addition, the detection unit 21 and the support 22
The same material is used to fuse the adhesive.

Auxiliary tool 2 for attaching a filter is attached to the tip of the probe 23.
4 with a sealing means such as a heat-resistant O-ring 25,
A porous ceramic filter 26 for dust removal is attached to the other end of this auxiliary tool 24 by means of alumina cement or the like. Also, the side surface of the probe base side, the internal space of the probe 23, the thick part of the probe tip side, and the auxiliary tool 24
A calibration gas introduction pipe 27 is provided that penetrates through the thick part of the calibration gas introduction pipe 2, and the calibration gas introduced from the calibration gas introduction port 34 is passed through the calibration gas introduction pipe 2.
7, and is configured so that it can be supplied to the tip of the detecting section 2].

By doing so, the change in the detection signal of the detection unit 21 due to the high temperature January gas can be measured using the calibration gas, and the output signal can be corrected by the control circuit.

Furthermore, a reference air introduction pipe 28 is provided that penetrates the side surface of the probe 23 facing the calibration gas inlet 34 and extends through the internal space of the probe to the vicinity of the detection section, thereby making it possible to constantly supply reference air to the detection section 21. can.

A terminal portion 29 for drawing out a lead wire is provided at the base end portion of the detection portion 21, and this terminal portion 29 is connected to an external control circuit via a lead wire 30. Terminal section 29
The number of terminals differs depending on the configuration of the detection section, and in this example, it is composed of terminals for an oxygen concentration battery, a terminal for a heating element, and a terminal for an oxygen pump. The material of the lead wire is platinum wire in consideration of heat resistance, but other materials may be used in an atmosphere where heat resistance is not so required. Moreover, the connection between this terminal part 29 and the drawer lead wire 30 is as follows.
For low temperature applications, contact means such as connectors are sufficient, but
In the case of high temperature applications, poor contact occurs with contact means such as connectors, so the platinum lead wire 30 is connected by brazing with silver solder, platinum solder, or the like. The lead wires 30 are individually arranged in an alumina tube 31 in order to insulate each lead wire from each other, and communicated through the aluminum tube to a connector portion 32 at the proximal end of the probe. Not connected to the external control circuit.

2. The overall diagram of the present invention has been explained, but what about soot? 4 quantity is 1, number w/Nm3 when NG is burned, 20 when C heavy oil is burned.
If it is about 0 to 300■/Nm3, the filter should be a cylinder with a bottom and a gas collector installed around it.
It is also possible to adopt a conventional structure as shown in FIG. Further, when the amount of soot and dust is as large as about 20 to 50 g/Nm3, a collector as shown in FIG. 11 may be used. In this case, it is necessary to extend the oxygen concentration measuring device itself in the vertical (earth) direction.

Next, the structure of the oxygen sensor element S constituting the detection section 31 (dimensions: 5 dragons (1) Xl, 5 dragons (thickness) x 30 to 6
01 (length)), Fig. 2 (8'), (B)
This will be explained with reference to FIG.

First, an oxygen pump section P is provided in the upper part, which includes a solid electrolyte body 40 and an upper pump electrode 42 and a lower pump electrode 42 arranged on both upper and lower sides of the solid electrolyte body 40. An upper heating section H1 is provided on the upper surface side of the oxygen pump section P so as to surround the upper pump electrode 41.

Next, similarly to the oxygen pump section P, the solid electrolyte body 43
An oxygen concentration battery section B consisting of a measuring electrode 44 and a reference electrode 45 arranged on both upper and lower sides of this solid electrolyte body 43.
is provided.

Note that between the oxygen pump section P and the oxygen concentration battery section B, an insulator is formed so that a diffusion chamber 46, which is a slit flat space that guides the gas to be measured under a predetermined diffusion resistance, is formed. Space members 47 (47a, 47b) with a predetermined thickness consisting of
is mediated. Further, at a position corresponding to the center of the diffusion chamber 46 in the oxygen pump section P, this diffusion chamber 4
Gas introduction holes 4B (48a, 48b) that connect the gases 6 to the external space where the gas to be measured exists.

48c, 48d) are formed. therefore,
These gas introduction holes 4B (48a, 48b, 48c
, 48d), the gas to be measured is introduced into the diffusion chamber 46.
The oxygen is diffused within the oxygen pump under a predetermined diffusion resistance and comes into contact with the lower pump electrode 42 of the oxygen pump section B. Further, the measurement electrode 44 of the oxygen concentration battery section B also comes into contact with the gas to be measured near (=J) of the lower pump electrode 42.

Next, below the oxygen concentration battery part B, a space member 49 made of a solid electrolyte body and a solid electrolyte body 50 are sequentially provided.
is provided. As a result, the base i1i electrode 45
An air passage 51 is formed in which the air is exposed. This air passage 51 communicates with the atmosphere at the base of the oxygen sensor element S. The reference air, which is the atmosphere, is guided through this air passage 51 and comes into contact with the reference electrode 45 .

In addition, in the air passage 51, a temperature sensing portion T is provided at a position close to both sides of the reference electrode 45 on the lower surface of the solid electrolyte body 43.
is provided.

Further, a lower heating section H2 is provided on the lower side. Therefore, this heating section H2 and the upper heating section 111 sandwich the oxygen pump section P and the oxygen concentration battery section B on both sides of the oxygen pump section P and the oxygen concentration battery section B, so that a predetermined temperature (for example, It can be heated to temperatures above 600°C.

The solid electrolyte bodies 40, 43, 50 and the space member 49 are made of stabilized or partially stabilized zirconia porcelain that exhibits oxygen ion conductivity at high temperatures.

As is well known, this stabilized or partially stabilized zirconia porcelain is obtained by dissolving yttrium oxide, calcium oxide, etc. in zirconium oxide. Further, each of the electrodes 41, 42, 44, and 45 is made of porous platinum or the like. These electrodes 41
, 42 , 44 , and 45 , the upper pump electrode 41 , the lower pump electrode 42 , and the measurement electrode 44 in contact with the gas to be measured are each provided with a porous ceramic layer 52 , 53 made of alumina or the like.

54 are provided in a stacked state. therefore,
The gas to be measured comes into contact with the electrodes 41, 42, and 44 through these porous ceramic layers 52, 53, and 54, respectively.

On the other hand, in the heating section H2, the heater elements 55 and 56 are surrounded by a porous layer 57 (57a) made of alumina or the like having electrical insulation properties.

57b) and 58 (58a, 58b). These porous layers 5
7 (57a.

57b), 5B (58a, 58b) are further provided with airtight layers 59, 6 made of solid electrolyte such as zirconia.
0 is set. As a result, the heater element 5
5 and 56 can be shut off or isolated from the external gas to be measured. In addition, the heater element 5
5 + 56 is formed by, for example, printing and laminating a paste containing alumina powder and platinum powder as main components.

Further, the temperature detection section T has a configuration consisting of a resistor or the like whose electrical resistance changes greatly depending on temperature changes and has a positive or negative temperature coefficient. The temperature sensing element 6I is embedded in a porous layer 62 made of electrically insulating alumina or the like, and is electrically insulated from the surrounding solid electrolyte body 43 and space member 49. The temperature sensing element 61 of the resistor may be a paste mainly composed of ceramic powder such as zirconia or alumina and platinum powder, or a paste mainly composed of ceramic powder such as cermet, zirconia or alumina and platinum powder. 0.1
Paste, cermet, or zirconia with ~0.5% titanium dioxide added.

Printing and laminating a paste or cermet with an aggressively increased temperature coefficient of resistance, such as paste or cermet, which is made by adding manganese, cobalt 1 nickel oxide, etc. to a ceramic powder such as alumina as the main component. It was formed by Further, as the temperature sensing element 61 of the resistor, zirconia porcelain, a platinum wire, a platinum thin film, or the like may be used. Furthermore, instead of the temperature sensing element 61 of the resistor, different metals (for example, platinum, gold) are used.
Alternatively, the thermocouple temperature sensing element 61 may be constructed by printing and laminating a combination of pastes or cermets containing these different metals as a thermocouple.

The oxygen pump section P, oxygen concentration battery section B, heating section old, H2, temperature sensing section T, and space member 47 are stacked as shown in the figure to form an integrated narrow plate-like longitudinal structure. The laminated structure is formed into an integral structure by sintering it. Note that M is an electrical contact terminal on which pump electrodes 41 , 42 , measuring electrode 44 , reference electrode 45 , heater elements 55 , 56 and temperature sensing element 61 are printed.

In the case of this embodiment, the oxygen pump section P and the oxygen concentration battery section B constitute the sensing cell in the present invention.

By the way, when measuring oxygen concentration, the oxygen sensor element S, specifically the oxygen pump part P and the oxygen concentration battery part B, are maintained at a predetermined temperature by the temperature detected by the temperature detection element 61 of the temperature detection part. As such, the heater current is applied to the heater elements 1-55 and 56 of the heating section H2. Then, the measurement starts when the oxygen pump section P and the oxygen concentration battery section B are maintained at a predetermined temperature (for example, 600° C. or higher) or at a time when the temperature is maintained at a predetermined temperature. Note that it takes about 3 minutes for the oxygen sensor element S to be maintained at a predetermined temperature after the start of energization. Further, power consumption is about 8W.

Next, the principle of oxygen concentration measurement using the sensor element S will be explained with reference to the block diagram of FIG. 4.

The measurement electrode 44 is compared with the reference air and the gas to be measured that has entered the diffusion chamber 46 through the gas introduction hole 48 of the oxygen bomb section P by the oxygen concentration battery section B.
An electromotive force E is generated between the reference electrode 45 and the reference electrode 45 in accordance with the oxygen partial pressure ratio between the two. This generated electromotive force E is equal to the comparison voltage V
It is compared with f (generated electromotive force equivalent to air ratio m#1).

The difference voltage between these two (E-Vf) is the oxygen pump current (
IF) is supplied to the controller 63.

This pump current (IP), the controller 63 controls the differential voltage (
i) In the case of E<Vf, the oxygen pump part P pumps the oxygen in the diffusion chamber 46 to the outside as shown by the solid arrow in FIG. , 1i) In the case of E>Vf, the oxygen pump part P removes carbon dioxide C in the gas to be measured.
O□, water 1 (20) is electrolyzed and oxygen is pumped into the diffusion chamber 46 as shown by the dotted arrow in FIG. 11□0
, reacts with CO4+AOz 'Co□. ) is controlling the oxygen pump current (I, ). This brings the oxygen concentration within the diffusion chamber 46 to a predetermined value.

This method of setting the predetermined value sets the oxygen concentration in the diffusion chamber 46 to
The oxygen concentration corresponding to the air ratio m#1, specifically, the oxygen concentration is set to 0%.

Note that since oxygen molecules, -carbon oxide, and hydrogen molecules in the ratio measurement gas each have different diffusion constants with respect to nitrogen gas, the oxygen pump current (■, ) is expressed by the following equation.

1, = K, -POZ -Kg-PCO-K3-PH
Also, K: 2 for the coefficient proportional to the diffusion of oxygen molecules; 3 for the coefficient proportional to the diffusion of carbon oxide molecules; I): the coefficient proportional to the diffusion of hydrogen molecules; Each partial pressure of hydrogen molecules.

Therefore, when the gas to be measured is in the oxidation region, the concentrations of -carbon oxide and hydrogen molecules are 0%, so I, = K, -Po.

becomes.

Furthermore, when the gas to be measured is in the reduction region, the oxygen molecule concentration is 0%, so Ip = -(KzJco + K3·Poz).

To summarize the above principle of oxygen concentration measurement, the oxygen pump current (■,) is controlled so that the oxygen molecule concentration in the diffusion chamber 46 becomes 0% [air ratio mζ1], and the oxygen pump current (I
, ) through a reference resistance (r, ), etc., to measure the oxygen concentration.

This makes it possible to output the excess oxygen concentration in the oxidation region and the oxygen deficiency concentration in the reduction region with a single signal, allowing industrial furnaces in the oxidation/reduction circle region to be operated across the oxidation/reduction region. It will be of great help in building a control system for atmosphere control.

Next, a modification will be described, in which the same reference numerals as in the above embodiment indicate the same contents, and redundant explanation will be omitted.

(First Modification - FIG. 5) The upper heating section 111 and the temperature detection section T are omitted from the previous embodiment. In this case, the lower heating section 11
The temperature of the oxygen sensor element S is detected by the resistance value of the second heater element 56 changing depending on the temperature, and temperature control is performed. The rest is the same as in the previous embodiment.

(Second Modification - FIG. 6) The sensing cell is constituted only by the oxygen concentration battery section B, and the temperature detection section T is provided on two sides of the solid electrolyte body 43. In this case, the oxygen concentration in the gas to be measured is measured by the potential difference between the measurement electrode 44 and the reference electrode 45 using an oxygen concentration cell mechanism. Therefore, basically, the oxygen excess concentration in the oxygen region and the oxygen deficiency concentration in the reduction region cannot be output as one signal.

Note that this oxygen sensor element S is heated to a high temperature by the high-temperature gas to be measured, and the temperature detecting section T reaches a predetermined temperature plate.
Measurement begins after detecting that 2. Therefore, it is suitable for measuring a high temperature gas to be measured.

(Third Modification - Fig. 7) This is the second modification in which a lower heating section +12 is further provided. In this oxygen sensor element S, in accordance with the temperature detected by the temperature detection part T, a heater current is applied to the heating part 112 to maintain the element at a predetermined temperature, as in the previous embodiment. Therefore, it is suitable for measuring low-temperature gases to be measured. The rest is the same as the second modification.

(Fourth modification - FIG. 8) The sensing cell is composed only of the oxygen pump part P, and the temperature detection part T is the solid electrolyte body 40.
It is located on two sides. Further, on each of both sides of the solid electrolyte body 40, upper and lower porous ceramic layers 64 and 65 made of alumina or the like are provided in a laminated manner as shown in the figure as diffusion resistance means. The gas to be measured is configured to diffuse into both porous ceramic layers 64 and 65. In this case, the oxygen concentration is measured by the oxygen pump mechanism by measuring the oxygen pump current. Basically, the oxygen excess concentration in the oxygen region or the oxygen deficiency concentration in the reduction region can be measured. Having only the temperature detection section T is suitable for measuring a high temperature gas to be measured, similarly to the second modification.

(Fifth Modification - FIG. 9) Similarly to the fourth modification, the sensing cell is composed of only the oxygen pump section P. This oxygen pump part P
A space member 66 made of alumina or the like is interposed between the lower heating portion H2 and the lower heating portion H2 as a diffusion resistance means. A temperature detection section T is provided on the upper surface of the lower heating section H2. The gas to be measured is also supplied to the lower surface side of the oxygen pump section P via the porous space member 66.

Therefore, it is supplied to both sides of the oxygen pump section P. In addition, in this modification, the temperature detection part T and the lower heating part ■2
By having this, it is suitable for measuring a low-temperature gas to be measured similarly to the third modification. The rest is the same as the fourth modification.

〔Effect of the invention〕

In the industrial oxygen concentration measuring device of the present invention, the detection section is thin, small and lightweight, and therefore the diameter of the probe is, for example, approximately 2.
It can be made as small as 0n, which shortens the detection space for the gas to be measured, resulting in faster response time.The weight is also reduced, which reduces the overall weight of the device without requiring much strength of the probe. can do.

In addition, by appropriately selecting the components of the sensing cell, there is an advantage that the measurement range can be set using electrical means under a wide range of temperature conditions, and even in an oxidizing atmosphere and a reducing atmosphere.

[Brief explanation of drawings]

1 to 4 are diagrams for explaining a specific embodiment of the industrial oxygen concentration measuring device according to the present invention, in which FIG. 1 is an overall view of the device of the present invention, and FIG. 2 is a detection Figure 3 is an mm-m cross-sectional view in Figure 2, Figure 4 is a block diagram, and Figures 5 to 9 are an exploded perspective view of the oxygen sensor element. FIG. 10 is an explanatory diagram for explaining a conventional example, and FIG. 11 is an explanatory diagram for explaining a modification of FIG. 1. 21...Detection section 23...Probe B...
・Oxygen concentration battery section Ill, +12... Upper and lower heating section P...
・Oxygen pump section T...Temperature detection section Fig. 2 A) Vδi44 ゝU Ninini Ninini 2 (Ninini>Σ, 43: n62 to V
a Te2 = 2 = f6' V522 (A) (B) Figure 11

Claims (4)

[Claims] 1. A detecting section in which a sensing cell, a heating body and/or a temperature detecting body are laminated and integrally molded into a plate shape is provided at the tip of the probe, at least a part of which is inserted into the gas to be measured. Industrial oxygen concentration measuring device. 2. An industrial oxygen concentration measuring device, wherein the sensing cell comprises an oxygen concentration battery. 3. An industrial oxygen concentration measuring device, wherein the sensing cell comprises an oxygen pump. 4. An industrial oxygen concentration measuring device, wherein the sensing cell comprises an oxygen concentration battery and an oxygen pump.