JPH0513575B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a simultaneous oxygen and hydrogen analyzer which is an improvement of an oxygen analyzer using an electrochemical oxygen pump.

[Prior Art] Recently, a new type of oxygen analysis layer has been developed that can measure the amount of oxygen contained in metals, alloys, their compounds, semimetals such as selenium and tellurium, etc. with high precision and in absolute value. (Shinya Otsuka, Zensaku Kozuka, Transaction of the
Japan Institute of Metals, Vol−25, No.9639~
684 pages, published September 1984).

As shown in FIG. 7, this oxygen analyzer has an eighth
As shown in the figure, for example, an electrochemical oxygen pump 32 using a solid electrolyte 35 formed by dissolving a stabilizer such as calcia, magnesia, or ittria in zirconia is interposed, and the oxygen pump 32
By applying a constant DC voltage V to the closed gas flow path 31, oxygen is exhausted from the closed gas flow path 31.
This makes it possible to maintain the oxygen partial pressure inside the tank at a sufficiently low constant value. Before measurement, the oxygen in the carrier gas is exhausted and the inside of the closed gas flow path 31 is maintained at a sufficiently low constant oxygen partial pressure, and the sample 33 is introduced into the closed gas flow path 31 in this state. Oxygen released from the introduced sample 33 (in the case of a sample with a high melting point, oxygen is quickly released by melting it in the sample melting furnace 34) is transported to the oxygen pump 32 by a carrier gas. The oxygen is discharged to the outside of the closed gas flow path 31 by the oxygen pump 32, and the inside of the closed gas flow path 31 is again maintained at a constant low oxygen partial pressure. Oxygen pump 32 required for this oxygen discharge
By measuring the quantity of electricity (for example via the current i), the amount of oxygen in the sample 33 is determined quickly and precisely in absolute value.

In such an oxygen analyzer, it is convenient to use a reducing gas containing hydrogen as the carrier gas. If hydrogen is contained in the carrier gas, especially when measuring oxygen contained in a sample such as a metal, the oxygen in the sample will react with the hydrogen in the carrier gas to form H ₂ O gas, and the oxygen in the sample will be removed. Efficient release occurs and this H ₂ O gas is carried by the carrier gas to the oxygen pump. Again at the interface of the closed gas flow path of the solid electrolyte using the oxygen pump.
The H ₂ O is reduced to release oxygen, which is pumped out of the closed gas flow path by an oxygen pump.

Next, the hydrogen pump will be described below.

Proton-conductive solid electrolytes containing strontium oxygen or cerium oxide as main components can be transferred from one side of the solid electrolyte partition wall to the other in a hydrogen or water vapor atmosphere by applying a DC voltage to both sides of the solid electrolyte partition wall. It is known that hydrogen can be transferred (Solid State Ionics 9 & 10, 1983
(2013, pp. 1021-1026).

As an example of a hydrogen pump, as shown in FIG. 9, a hydrogen ion conductive solid material 40 made of cerium strontium trioxide is used as a partition wall, and both sides of the hydrogen ion conductive solid material 40 are sandwiched between ceramic tubes 43. There is a glass patch between 4
4 to form a gas chamber A and a gas chamber B. The solid electrolyte 40 is housed in a heating furnace 45, and Pt porous electrodes 4 are provided on both sides of the solid electrolyte 40.
6 is provided, and a lead wire 47 is connected thereto.
A mixed gas of argon and hydrogen flows in the gas chambers A and B, and when a DC voltage is applied through the lead wire 47, one side of the solid electrolyte 40 ( or the other side) to the other side (or one side),
Hydrogen ions move within the solid electrolyte 40. That is, hydrogen in one gas chamber (or the other gas chamber) can be moved to the other gas chamber (or one gas chamber) due to the hydrogen ion conductivity of the solid electrolyte 40.

In this invention, the principle of such a hydrogen pump is applied to a conventional oxygen analyzer.

[Problems to be solved by the invention] In the oxygen analyzer as described above, H ₂ O
Since the released oxygen from the sample 33 carried in the form of is reduced in the oxygen pump 32 section and only the original _H2 remains in the closed gas flow furnace 31, the hydrogen in the carrier gas is essentially not consumed. However, while using the oxygen analyzer for a long time, hydrogen in the carrier gas may leak or diffuse permeate from the piping etc. that make up the closed gas flow path 31, resulting in hydrogen concentration in the carrier gas. may fall below a predetermined range. If the hydrogen concentration decreases too much, the efficiency of releasing oxygen from the sample 33 as described above will decrease, so it is necessary to always maintain the hydrogen concentration in the carrier gas within a predetermined range.

Furthermore, when the carrier gas containing hydrogen flows through the oxygen pump for a long time, the closed gas flow path side of the oxygen pump solid electrolyte is reduced by hydrogen, which may reduce the performance of the oxygen pump.

As a result of focusing on and considering these issues, we found that
It has been found that these problems can be solved by adding an electrochemical hydrogen pump to the oxygen analyzer mentioned above, and it is also possible to measure the absolute value of not only the oxygen concentration but also the hydrogen concentration in the sample. The inventor has discovered that there is.

The present invention can prevent a decrease in the efficiency of releasing oxygen from a sample, and can also prevent a decrease in the performance of the oxygen pump due to reduction of the closed gas flow path side of the oxygen pump solid electrolyte by hydrogen in the carrier gas. It is an object of the present invention to provide an oxygen and hydrogen analyzer that can prevent such problems and simultaneously measure the absolute values of oxygen and hydrogen concentrations in a sample.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a closed gas flow path for circulating carrier gas,
sample introduction means for introducing a sample into the closed gas flow path;
In an analyzer in which an electrochemical oxygen pump using a solid electrolyte that discharges oxygen in the closed gas flow path to the outside of the closed gas flow path is arranged in series with the sample introduction means in the gas circulation direction. Provided is a simultaneous oxygen and hydrogen analysis device, characterized in that electrochemical hydrogen pumps using solid electrolytes are provided in the closed gas flow paths on the upstream and downstream sides of the gas flow path. In addition, in order to achieve the above object, the present invention includes a sample introduction means for introducing a sample into the closed gas flow path in which a carrier gas is circulated, and a sample introduced from the sample introduction means is dissolved. A sample melting furnace that releases oxygen in the sample into a closed gas flow path and an electrochemical pump using a solid electrolyte that discharges oxygen in the closed gas flow path outside the closed gas flow path are connected in series with each other. in the oxygen analyzer disposed in the oxygen analyzer, wherein electrochemical hydrogen pumps using solid electrolytes are provided in the closed gas flow paths on the upstream and downstream sides of the sample melting furnace with respect to the gas circulation direction, respectively. A simultaneous oxygen and hydrogen analyzer is provided.

[Example] Hereinafter, one embodiment of the apparatus of the present invention will be described with reference to the drawings for the case where oxygen and hydrogen contained in metals and the like are simultaneously analyzed.

FIG. 1 shows a simultaneous oxygen and hydrogen analysis device (hereinafter referred to as the present device) according to an embodiment of the present invention. The figure shows the overall configuration of this device.
Each directional switching valve indicates the state at the time of analysis of the oxygen content and hydrogen content of the sample (hereinafter referred to as the time of analysis).

In FIG. 1, a path indicated by a thick line indicates a closed gas flow path 1 through which a carrier gas such as argon gas is circulated during analysis of a sample. Each of the directional switching valves 2 and 3 is a four-way valve in this embodiment, and when analyzing a sample, the carrier gas in the closed gas flow path 1 is made to flow in the direction of the bold arrow A, as shown in the figure, and the closed gas is initially When replacing the gas in the flow path 1 with the carrier gas, the gas is caused to flow in the direction of the solid line arrow B.

The closed gas flow path 1 includes, along the carrier gas circulation direction A during measurement, a circulation pump 4 that circulates carrier gas, an electrochemical hydrogen pump 21 (hereinafter referred to as hydrogen pump) that introduces hydrogen into the system, and a metal pump. ,
A sample introduction means 7 for introducing a sample 6 made of an alloy or a compound thereof into the closed gas flow path 1, and a sample 6
A sample melting furnace 10 melts the sample 6 in a sample melting tube 9 by heating with a heating device 8 to release oxygen and hydrogen in the sample 6, and a closed gas flow path in which the hydrogen released from the sample 6 and carried by the carrier gas is melted in a sample melting tube 9. 1 Hydrogen pump 2 using a solid electrolyte 22 discharged to the outside
3. Electrochemical oxygen pump 12 using a solid electrolyte 11 that discharges oxygen released from the sample 6 and carried by the carrier gas to the outside of the closed gas flow path 1
(hereinafter referred to as oxygen pumps) are arranged in series.

A flow meter 5 that can measure the flow rate (flow velocity) of the carrier gas circulated by the circulation pump 4 is provided upstream of the circulation pump 4 . Further, a carrier gas inlet 13 for introducing carrier gas into the closed gas flow path 1 is connected between the oxygen pump 12 and the circulation pump 4, and the carrier gas is introduced through the filter 14 and the directional switching valve 2. It is becoming more and more like this. When replacing this closed gas flow path 1 with carrier gas, the directional control valves 2 and 3 are switched as shown by arrow B, but a reduced pressure suction port 15 is connected to the end of the path to supply carrier gas. The gas in the closed gas flow path 1 that has been expelled by the pump is discharged to the outside of the system via the filter 16 and the suction pump 17.

The sample introducing means 7 is configured in the shape of a container that can be sealed against the atmosphere, and is provided with a sample receiver 18 on which the sample 6 is placed and allows the sample 6 to fall downward by rotation or the like. A sample melting furnace 10 is connected to the lower part of the sample introducing means 7. There is a space between the heating device 8 of the sample melting furnace 10 and the sample introducing means 7 to suppress heat transfer from the heating device 8 side to the sample introducing means 7 side and to condense metal vapor etc. from the sample melting furnace 10. Appropriate cooling means 19 are provided to suppress outflow to the downstream side.

As shown in FIG. 2, the above-described hydrogen pump 21 includes a heating furnace 21a and a cylindrical solid electrolyte 20 housed within the heating furnace 21a. On the inner and outer surfaces of the solid electrolyte 20, porous electrodes a1, a
2 is provided, and each electrode has a lead wire a.
5 and a6 are connected. Lead wire a5, a6
A DC power supply a3 serving as a voltage applying means is connected between the two, and an ammeter a4 serving as a current measuring means is connected in series with the DC power supply.

Argon gas containing, for example, 0.01 to 10% hydrogen is constantly flowing through the outer surface of the solid electrolyte 20 of the hydrogen pump 21, and a negative DC voltage is applied to the inner electrode of the solid electrolyte 20 and a positive DC voltage to the outer electrode. As a result, hydrogen in the hydrogen-containing argon gas flowing near the outer surface of the solid electrolyte 20 can be introduced into the closed gas flow path through hydrogen ion conduction of the solid electrolyte 20.

Next, as shown in FIG. 3, the hydrogen pump 23 includes a heating furnace 23b and a cylindrical solid electrolyte 22 housed within the heating furnace 23b. Porous electrodes b1, b are provided on the inner and outer surfaces of the solid electrolyte 22.
2 is provided, and each electrode has a lead wire b
5 and b6 are connected. Lead wires b5, b6
A DC power supply b3 as a voltage applying means is connected between them, and an ammeter b4 as a current measuring means or a electricity meter (not shown) as a means for measuring an electrical quantity is connected in series with the DC power supply. has been done.

Then, by constantly flowing, for example, argon gas through the outer surface of the solid electrolyte 22 of the hydrogen pump 23, and applying a positive DC voltage to the inner electrode of the solid electrolyte 22 and a negative DC voltage to the outer electrode,
The hydrogen in the carrier gas flowing in the closed gas flow path is
The solid electrolyte 22 can be discharged to the outside of the closed gas flow path through hydrogen ion conduction.

Next, as shown in FIG. 4, the oxygen pump 12 includes a heating furnace 12c and a cylindrical solid electrolyte 11 housed within the heating furnace 12c. Porous electrodes c1, c are provided on the inner and outer surfaces of the solid electrolyte 11.
2 is provided, and each electrode has a lead wire c
5 and c6 are connected. Lead wire c5, c6
A DC power supply c3 as a voltage applying means is connected between them, and an ammeter c4 as a current measuring means or a electricity meter (not shown) as a means for measuring an electrical quantity is connected in series with the DC power supply. has been done.

By applying a positive DC voltage to the outer electrode of the solid electrolyte 11 of the oxygen pump 12 and a negative DC voltage to the inner electrode, oxygen in the carrier gas flowing in the closed gas flow path is transferred through oxygen ion conduction of the solid electrolyte 11. It is designed to be able to be discharged outside the closed gas flow path.

The operation of the embodiment device configured as described above will be explained below.

First, before analyzing a sample, oxygen is discharged from the carrier gas by the oxygen pump 12, and the oxygen partial pressure in the closed gas flow path 1 is kept at a sufficiently low constant value. Current is flowing.

FIG. 5 shows the current flowing through the solid electrolyte 11 corresponding to the current flowing through the lead wires c5 and c6, and how the current component changes with respect to time t. A constant electron current Ie ^* corresponding to the applied voltage and independent of time t always flows through the solid electrolyte 11. The ionic current due to oxygen released from the solid electrolyte 11 is virtually independent of time t under the above measurement conditions and can be regarded as constant, and also slightly leaks from the atmosphere into the closed gas flow path 1. The ionic current accompanying the discharge of oxygen is also constant and independent of time t. Therefore, if the ionic current that constantly flows during the measurement due to these two contributions is I' ₀ , then the current that always flows through the solid electrolyte 11 during the measurement is I ₀ ∽=Ie ^* +I' ₀ .

Furthermore, hydrogen is constantly introduced into the closed gas flow path 1 by constantly supplying a constant current to the hydrogen pump 21. This hydrogen passes through the melting furnace together with the carrier gas and reaches the hydrogen pump 23, where it is discharged out of the closed gas flow path 1 by the hydrogen pump 23. Therefore, the hydrogen concentration in the carrier gas flowing through the melting furnace is always kept within a certain predetermined range, and the carrier gas without hydrogen flows through the oxygen pump. At this time, a constant base current I _H ∽ flows through the hydrogen pump 23. Figure 6 shows lead wires b5 and b.
6 shows the current I flowing through the solid electrolyte 22 corresponding to the current flowing through the solid electrolyte 22 and how the current component changes with respect to time t. In the solid electrolyte 22, in addition to the hydrogen ion current I _H ' due to the discharge of hydrogen in the carrier gas, there is also a constant electron current I'e that does not depend on time t,
Other charge carriers may include current I'ion due to oxygen ions, etc., which also does not depend on time t. Therefore, if the current constantly flowing during the measurement due to these two contributions is I', the current constantly flowing through the solid electrolyte 22 during the measurement is I _H ∽=I _H ′+I′.

In this state, the sample 6 is dropped into the sample melting furnace 10, the sample 6 is melted, and the oxygen and hydrogen in the sample 6 are released. Hydrogen released from the sample is carried by the carrier gas to the hydrogen pump 23 and discharged to the outside of the closed gas flow path 1 by the hydrogen pump 23.
At this time, the current of the hydrogen pump 23 rises rapidly, and as hydrogen is discharged by the pumping function of the hydrogen pump 23, it quickly returns to the original base current I _H ∽ after time t' ₂ . Here, if the average hydrogen ion transfer number of the solid electrolyte 22 is Tp, the following equation holds theoretically.

T _H = I _H / (I _H + Ie) where I _H : Ion current flowing through the hydrogen pump 23 due to the released hydrogen when the released hydrogen is discharged outside the closed gas flow path 1 Ie: Depends on the ionic current I _H Therefore, when the hydrogen pump is operated under the condition of T _H ≈1, all of the current I _H that increases from a constant current value I _H ∽ can be considered to be due to the hydrogen in the sample 6. Therefore, the quantity of electricity Q _H due to the hydrogen ion current I _H at that time is Q _H = X H・F, where the amount of hydrogen generated from sample 6 is X _H grams, Faraday's constant is F _, and the atomic weight of hydrogen is M _H. /M _H =∫ ^t2 ′ _t1 ′I _Hdt , and from this, the hydrogen concentration in sample 6 can be determined. Under conditions where the condition of T _H ≒ 1 cannot be satisfied, calibrate in advance and use the correction coefficient K at that time to obtain Q _H = K・X _H・F/M _H =∫ ^t2 ′ _t1 ′I _Hdt , From this, the hydrogen concentration in sample 6 can be determined.

In addition, the oxygen released from the sample is transported to the oxygen pump 12 by a carrier gas.
At this time, as shown in FIG. 5, the current of the oxygen pump 12 rises rapidly and as oxygen is discharged by the pumping function of the oxygen pump 12, the current of the oxygen pump 12 is discharged to the outside of the closed gas flow path 1. After ₂ , the current returns to the original base current. Here, if the average oxygen ion transfer number of the solid electrolyte 11 is T ₀ , the following equation holds theoretically.

T ₀ = I ₀ / (I ₀ + Ie) where I ₀ : Ion current flowing through the oxygen pump 12 by the released oxygen when the released oxygen is discharged outside the closed gas flow path 1 Ie: Depends on the ionic current I ₀ Therefore, when the oxygen pump is operated under the condition of T ₀ ≈1, the current I ₀ that increases from the constant current value I ₀ ∽ can be considered to be entirely due to the oxygen in the sample 6. Therefore, the quantity of electricity Q ₀ due to the oxygen ion current _{I 0} at that time is _{Q 0 =} X ₀・2F/ M ₀ =∫ ^t2 _t1 I ₀ dt From this, the oxygen concentration in the sample 6 can be determined.

In the above, the case of measuring the concentration of oxygen and hydrogen contained in metal etc. has been explained, but according to the apparatus of the present invention, the concentration of oxygen and hydrogen in gas can be measured in exactly the same way. . However, in that case, use a sample injector that can inject a certain amount of gas.

A sample melting furnace is not required.

[Effects of the Invention] The device of the present invention employs a closed gas flow path, and an oxygen pump and a hydrogen pump equipped with lead wires are disposed in the closed gas flow path, so that the solid electrolyte and electrodes on the gas flow path side are Since the chemical potential at the interface with the solid electrolyte can be kept constant at all times, and the sample is introduced in that state, in the case of an oxygen pump, the electronic conductivity of the solid electrolyte and the oxygen released from the solid electrolyte itself can be kept constant. Oxygen concentration can be measured without being affected by oxygen leaking from the air or the atmosphere, and in the case of hydrogen pumps, hydrogen concentration can be measured without being affected by electron current flowing through the solid electrolyte or current by other charge carriers. Concentration can be measured. Therefore, the measurement sensitivity and measurement accuracy are excellent, and the absolute values of oxygen concentration and hydrogen concentration can be measured without any need for a standard sample.

In addition, hydrogen is introduced into the closed gas flow path by a hydrogen pump installed upstream of the sample melting furnace, and hydrogen is discharged outside the closed gas flow path by a hydrogen pump installed downstream of the sample melting furnace. The hydrogen concentration in the carrier gas flowing through the sample dissolving section is always maintained within a predetermined concentration range. Therefore, oxygen in the sample reacts with hydrogen in the carrier gas to form H ₂ O gas, so that oxygen in the sample is efficiently released. In addition, since a very small amount of oxygen is always present in the carrier gas, the hydrogen in the sample reacts with the oxygen in the carrier gas to form H ₂ O gas, so the hydrogen in the sample is efficiently released. become.

Further, since a carrier gas that does not contain hydrogen flows through the oxygen pump, the closed gas flow path side of the oxygen pump solid electrolyte is not reduced by hydrogen, and the performance of the oxygen pump can be maintained at all times.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a simultaneous oxygen and hydrogen analysis device including a partial cross section, showing an embodiment of the present invention for analyzing oxygen and hydrogen contained in metals, etc. FIG. 2 and FIG. is the above first
FIG. 4 is a schematic vertical cross-sectional view of the electrochemical hydrogen pump shown in FIG. 1, FIG. 5 is a schematic vertical cross-sectional view of the electrochemical oxygen pump shown in FIG. A graph showing changes in I with respect to time t, FIG. 6 is a graph showing changes in current I generated in the hydrogen pump with respect to time t, FIG.
The figure is an overall configuration diagram of a conventionally known oxygen analyzer, FIG. 8 is a schematic vertical sectional view of the oxygen pump of the device in FIG. 7, and FIG. 9 is a diagram of a conventionally known hydrogen pump. It is a schematic longitudinal cross-sectional view. 1... Closed gas flow path, 2, 3... Directional switching valve, 4
... Circulation pump, 5 ... Flow meter, 6 ... Sample, 7
... Sample introduction means, 8 ... Heating device, 9 ... Sample melting tube, 10 ... Sample melting furnace, 11 ... Solid electrolyte, 12 ... Oxygen pump, 13 ... Carrier gas inlet, 14 ... Filter, 15...Decompression suction port, 16...Filter, 17...Suction pump, 1
8...Sample receiver, 19...Cooling means, 20...Solid electrolyte, 21...Hydrogen pump, 22...Solid electrolyte, 23...Hydrogen pump.

Claims (1)

[Scope of Claims] 1. Sample introducing means for introducing a sample into a closed gas flow path through which carrier gas is circulated, and discharging oxygen in the closed gas flow path to the outside of the closed gas flow path. In an analyzer in which an electrochemical oxygen pump using a solid electrolyte is arranged in series with each other, a solid electrolyte is provided in the closed gas flow path on the upstream side and the downstream side of the sample introducing means with respect to the gas circulation direction. A simultaneous oxygen and hydrogen analysis device characterized by being equipped with an electrochemical hydrogen pump. 2. A sample introduction means for introducing a sample into a closed gas flow path through which carrier gas is circulated, and a sample for dissolving the sample from the sample introduction means and releasing oxygen in the sample into the closed gas flow path. a melting furnace, and discharging oxygen in the closed gas flow path to the outside of the closed gas flow path;
An electrochemical oxygen pump using a solid electrolyte,
In oxygen analyzers arranged in series with each other, electrochemical hydrogen pumps using solid electrolytes are provided in the closed gas flow paths upstream and downstream of the sample melting furnace with respect to the gas circulation direction, respectively. Features: Oxygen and hydrogen simultaneous analyzer.