JPH0450980B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in an oxygen analyzer using an electrochemical oxygen pump.

[Prior Art] Recently, a new type of oxygen analyzer 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. was developed (Shinya Otsuka, Zensaku Kozuka, Transaction of the
Japan Institute of Metals.Vol−25, No.9, 639
pp. 648, published September 1984).

For example, as shown in FIG. 3, this oxygen analyzer includes a closed gas passage 31 for circulating carrier gas
As shown in FIG. 4, an electrochemical oxygen pump 32 using a solid electrolyte 35 made of, for example, zirconia in which a stabilizer such as yttria, calcia, or magnesia is dissolved is interposed. By applying a constant DC voltage V, oxygen is discharged from the closed gas flow path 31 so that the oxygen partial pressure within the closed gas flow path 31 can be maintained at a sufficiently low constant value. . Before measurement, 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.
In this state, the sample 33 is introduced into the closed gas flow path 31. The introduced sample 33 is melted in the sample melting furnace 34, and the oxygen gas in the sample 33 flows through the closed gas flow path 31.
released within. The released oxygen is carried by the carrier gas to the oxygen pump 32, and is discharged outside 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. . By measuring the amount of electricity of the oxygen pump 32 required for this oxygen evacuation (for example, via the current i), the amount of oxygen in the sample 33 can be measured in absolute value quickly and with high precision.

[Problems to be Solved by the Invention] In the oxygen analyzer configured as described above, in order to increase the resolution of oxygen content analysis of the sample 33 and maintain high measurement accuracy, it is necessary to close the closed gas flow path before starting the measurement. It is desirable that the oxygen partial pressure in the sample 31 and the oxygen partial pressure in the oxygen releasing section (in the sample melting furnace 34) from the sample 33 under measurement be as small as possible.

However, in the configuration shown in FIG. 3, a certain amount of oxygen leaks into the closed gas flow path 31 from the atmosphere in the piping system between the oxygen pump 32 and the sample melting furnace 34 when viewed in the flow direction of the carrier gas. Hard to avoid. Therefore, there is a problem in that the oxygen partial pressure in the sample melting furnace 34 is higher than the oxygen partial pressure in the oxygen pump 32, and the resolution of oxygen content analysis is correspondingly lowered.

The present invention focuses on the above-mentioned problems, and aims to improve the resolution of oxygen content analysis of a sample by lowering the oxygen partial pressure in the sample melting furnace to the same level as the oxygen partial pressure in the oxygen pump section. purpose.

[Means for Solving the Problems] The oxygen analyzer of the present invention that meets this objective includes a closed gas flow path in which a carrier gas is circulated, and a sample is placed in the closed gas flow path along the circulation direction of the carrier gas. a sample introduction means for introducing the sample; a sample melting furnace for melting the sample from the sample introduction means and releasing oxygen in the sample into the closed gas flow path; In an oxygen analyzer, an electrochemical oxygen pump using a solid electrolyte is disposed in series in this order, and an electrochemical oxygen pump using a solid electrolyte is disposed on the downstream side of the oxygen pump with respect to the circulation direction of the carrier gas, and upstream of the furnace, electrically in parallel to the electrochemical oxygen pump;
Another electrochemical oxygen pump using a solid electrolyte is provided, and a means for measuring the total amount of current of the two electrochemical oxygen pumps is connected to these two electrochemical oxygen pumps. made up of things.

[Function] By installing another oxygen pump upstream of the sample melting furnace, the oxygen that has leaked up to that point is discharged out of the closed gas flow path by this oxygen pump.
A carrier gas with a low oxygen partial pressure is sent to the sample melting furnace. In the sample melting furnace, oxygen is released from the sample into the carrier gas whose base state is a low oxygen partial pressure state, so the resolution of analysis is increased accordingly. Then, as will be described in detail later, by measuring the total amount of current of the two electrochemical oxygen pumps, the amount of oxygen released from the sample can be accurately measured.

[Embodiments] Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an oxygen analyzer according to an embodiment of the present invention. The figure shows the overall configuration of the oxygen analyzer, and each directional switching valve shows the state during oxygen content analysis of a sample.

In FIG. 1, the path indicated by the thick line indicates a closed gas flow path 1 through which a carrier gas such as argon gas containing 0.01 to 10% hydrogen is circulated during oxygen content analysis of a sample. Each direction switching valve 2,
3 and 4 consist of four-way valves in this embodiment,
When analyzing the oxygen content of a sample, as shown in the figure, the carrier gas in the closed gas flow path 1 is flowed in the direction of the thick line arrow A, and when initially replacing the gas in the closed gas flow path 1 with the carrier gas, it is flowed in the direction of the solid line arrow B. flow to.

The closed gas flow path 1 includes a circulation pump 5 for circulating carrier gas along the carrier gas circulation direction A during measurement, and a sample 6 made of a metal, an alloy, a compound thereof, or a semimetal such as selenium or tellurium. A sample introducing means 7 that introduces the sample into the closed gas flow path 1, a sample melting furnace 10 that melts the sample 6 in a sample melting tube 9 by heating it with a heating device 8 and releases oxygen in the sample 6, and a carrier gas released from the sample 6. An electrochemical oxygen pump 12 using a solid electrolyte 11 is interposed in series to discharge oxygen carried by the gas to the outside of the closed gas flow path 1. This oxygen pump 12 has exactly the same structure as that described in FIG.

A flow meter 13 capable of measuring the flow rate 4 (flow velocity) of the carrier gas circulated by the circulation pump 5 is provided upstream of the circulation pump 5 . Further, a carrier gas inlet 14 for introducing carrier gas into the closed gas flow path 1 is connected between the oxygen pump 12 and the circulation pump 5, and the carrier gas is introduced through the filter 15 and the directional control 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, 3, and 4 are switched as shown by arrow B, but a reduced pressure suction port 16 is connected to the end of the path. Closed gas flow path 1 that has been driven out by carrier gas supply
The gas inside is discharged to the outside of the system via a filter 17 and a suction pump 18.

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 19 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 20 are provided to suppress outflow to the downstream side.

In the system of such a closed gas flow path 1, the position as close to the sample melting furnace 10 as possible on the downstream side of the oxygen pump 12 and the upstream side of the sample melting furnace 10 with respect to the carrier gas circulation direction A, in this embodiment, Introduction means 7
Another electrochemical oxygen pump 22 that uses a solid electrolyte 21 similarly to the oxygen pump 12 is provided immediately upstream of the oxygen pump 12 . Similar to the oxygen pump 12, this oxygen pump 22 applies a constant DC voltage between the inner and outer surfaces of the solid electrolyte 21, so that the oxygen in the closed gas flow path 1 is transferred through oxygen ion conduction in the solid electrolyte 21. can be discharged from the system.

In this embodiment, as shown in FIG.
The oxygen pump 22 and the oxygen pump 12 are connected in parallel to a DC power supply 23 so that the same voltage is applied to them. Note that R in FIG. 2 represents a microresistance, and V represents a voltmeter, so that the current I flowing through this circuit can be measured.

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

First, before measuring the amount of oxygen in the sample, the oxygen pump 1
2 and 22, oxygen is exhausted from the carrier gas, and the oxygen partial pressure within the closed gas flow path 1 is maintained at a sufficiently low constant value. In this state, the sample 6 is placed in the sample melting furnace 1.
0, the sample 6 is dissolved and the oxygen in the sample 6 is released. The released oxygen is carried by the carrier gas to the oxygen pump 12, and is discharged to the outside of the closed gas flow path 1 by the oxygen pump 12, and the amount of oxygen is measured from the amount of electricity of the oxygen pump required for this discharge.

However, due to the capacity of the oxygen pump 12, oxygen that cannot be exhausted in one circulation flows directly to the downstream side. In addition, some amount of oxygen is thought to leak into the closed gas flow path 1 in the piping system from the oxygen pump 12 to the sample introduction means 7, and as mentioned above, oxygen may leak into the closed gas flow path 1 through the solid electrolyte 11 of the oxygen pump 12. It is also possible that the leakage of Therefore, the sample melting furnace 10
In this case, the oxygen partial pressure is about to become slightly higher than that in the 12th part of the oxygen pump. However, in the present invention, since another oxygen pump 22 is provided immediately upstream of the sample introduction means 7, the oxygen that has leaked and has not been completely exhausted by the oxygen pump 12 is exhausted by the oxygen pump 22. The oxygen partial pressure in the sample melting furnace 10 is maintained at a desirable and sufficiently low value.
in a carrier gas with a constant oxygen partial pressure low enough to
Since oxygen is released from the sample 6 and the amount of electricity required for the oxygen pump to discharge the released oxygen is measured, the analytical performance of the analysis is improved.

In this oxygen pump electrical quantity measurement, the total current of the two oxygen pumps 12 and 22 is measured. In other words, even before sample measurement, oxygen leaks from the piping system of the closed gas flow path 1, and these leaked oxygen are pumped into the oxygen pump 12 and the oxygen pump 2.
2 and is discharged out of the system, and the inside of the closed gas flow path 1 is brought into an equilibrium state of a sufficiently low constant oxygen partial pressure.
At this time, a constant base current is flowing through the oxygen pumps 12 and 22. In this state, oxygen is released from the sample 6, the released oxygen is exhausted to the outside of the system by the oxygen gas 12, and the released oxygen that cannot be completely exhausted is exhausted to the outside of the system by the oxygen pump 22. The amount of electricity required for the oxygen pump is the value obtained by subtracting the total base current from the rise of the total current of the oxygen pump 12 and the oxygen pump 22. Therefore, by measuring the total current of the oxygen pumps 12 and 22, the amount of oxygen released from the sample 6 can be accurately measured.

In addition, by applying the same voltage to the oxygen pump 12 and the oxygen pump 22 as in the circuit shown in FIG.
It becomes possible to bring the immediately downstream side of the oxygen pump 22 into a sufficiently low oxygen partial pressure state similar to that of the oxygen pump 12, and the resolution of measurement can be improved as described above.

[Effects of the Invention] As explained above, when using the oxygen analyzer of the present invention, another oxygen pump is provided upstream of the sample melting furnace to adjust the oxygen partial pressure of the carrier gas circulated to the sample melting furnace. Since the value can be set to a sufficiently low value in the same manner as in the conventional oxygen pump section provided on the upstream side, it is possible to obtain the effect that the resolution of the oxygen content analysis of the sample can be improved.

Furthermore, since it is a two-stage extraction mechanism in which two oxygen pumps are arranged in series, it is possible to improve the ability and speed of exhausting oxygen to the outside of the closed gas flow path, thereby shortening the measurement time.

Furthermore, the newly installed oxygen pump upstream of the sample melting furnace can also be used to check for oxygen leaking into the closed gas flow path further upstream. It also has the effect of providing a self-diagnosis monitoring function for checking performance.

Furthermore, as is well known, a solid electrolyte oxygen pump can be used as an oxygen meter by measuring electromotive force instead of applying a voltage to it, so the oxygen pump upstream of the sample melting furnace can be used as an oxygen meter if necessary. It can also be used to monitor the oxygen concentration in the carrier gas just before it enters the sample melting furnace.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an oxygen analyzer according to an embodiment of the present invention, FIG. 2 is an electric circuit diagram of the oxygen pump shown in FIG. 1, and FIG. 3 is an overall diagram of a conventionally known oxygen analyzer. FIG. 4 is an enlarged sectional view of the oxygen pump of the apparatus shown in FIG. 3. DESCRIPTION OF SYMBOLS 1... Closed gas flow path, 2, 3, 4... Directional switching valve, 5... Circulation pump, 6... Sample, 7... Sample introduction means, 10... Sample melting furnace, 11, 21...
Solid electrolyte, 12, 22...Oxygen pump, A...
Carrier gas circulation direction.

Claims (1)

[Claims] 1 Sample introduction means for introducing a sample into the closed gas flow path through which carrier gas is circulated along the circulation direction of the carrier gas, and a sample introduction means for dissolving the sample from the sample introduction means to remove oxygen in the sample. A sample melting furnace that discharges oxygen into a closed gas flow path and 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 are connected to each other in this order. In the oxygen analyzer arranged in series, downstream of the oxygen pump with respect to the circulation direction of the carrier gas and upstream of the sample melting furnace, electrically parallel to the electrochemical oxygen pump. , another electrochemical oxygen pump using a solid electrolyte is provided, and a means for measuring the total current of the two electrochemical oxygen pumps is connected to these two electrochemical oxygen pumps. An oxygen analyzer characterized by: