JPH0743344B2 - Oxygen analysis method and oxygen analysis device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to various metals, various alloys, semi-metals such as tellurium,
The present invention relates to a method and apparatus for quantitatively analyzing the amount of oxygen contained in various compounds and the like.

(Prior Art) As a method and apparatus for quantitatively analyzing the amount of oxygen contained in various metals, various alloys, semi-metals such as tellurium, various compounds, etc., there are conventionally known Japanese Patent Laid-Open Nos. 60-187854 and Sho-187854. 62-55552
No. 6, JP-A-62-56853, JP-A-62-71839-71845,
JP-A-62-75252, JP-A-62-78101, JP-A-62-80
550, JP-A-62-80551, JP-A-62-138745, JP-A-62-138746 and JP-A-63-200759-200762 are known. There is. They are,
In both cases, a closed gas passage in which the carrier gas circulates, a sample melting furnace and an electrochemical oxygen pump using a solid electrolyte are interposed, and the carrier gas is circulated in the closed gas passage while the carrier gas is circulated. The oxygen in the inside is discharged to the outside of the closed gas channel by an oxygen pump to make the inside of the closed gas channel a sufficiently low constant oxygen partial pressure, and then the sample is introduced into the closed gas channel.
Dissolve and release oxygen in the sample into the closed gas flow channel, discharge the released oxygen to the outside of the closed gas flow channel by the oxygen pump, and determine the amount of released oxygen, that is, The amount of oxygen is calculated. However, such methods and devices have
When a sample containing carbon monoxide or carbon dioxide is analyzed, there is a problem that the analysis accuracy becomes low.

That is, when the sample contains carbon, when the sample is dissolved, the carbon may react with oxygen in the sample to generate carbon monoxide or carbon dioxide. However, since the electrochemical oxygen pump using the solid electrolyte has no pumping function for carbon monoxide and carbon dioxide, these,
Carbon monoxide and carbon dioxide remain as they are in the closed gas passage. However, when the carbon monoxide is carried to the oxygen pump, it is chemically decomposed into carbon monoxide and oxygen, and the oxygen generated at that time is discharged to the outside of the closed gas flow path by the oxygen pump. However, carbon monoxide still remains. Therefore, the analytical value is lower than the true value because oxygen remains in the closed gas flow path in the form of carbon monoxide. Further, although the sample may originally contain carbon monoxide or carbon dioxide, if these are released into the closed gas flow channel, an error will occur in the analysis value for the same reason as above.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method and an apparatus capable of highly accurately analyzing even a sample containing carbon, carbon monoxide, or carbon dioxide.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention circulates a carrier gas in a closed gas flow channel while oxygen in the carrier gas is electrochemically converted using a solid electrolyte. After the oxygen gas is discharged to the outside of the closed gas channel to make the inside of the closed gas channel a sufficiently low constant oxygen partial pressure, the sample is introduced into the closed gas channel and dissolved in the sample. The oxygen in the closed gas flow channel, and the released oxygen is discharged to the outside of the closed gas flow channel by the oxygen pump to determine the amount of released oxygen, and the closed gas flow after introduction and dissolution of the sample. An oxygen analysis method, characterized in that an increase in carbon monoxide in the road is obtained, an oxygen amount forming carbon monoxide in the increase is obtained, and the oxygen amount and the released oxygen amount are added. I will provide a.

In addition, the present invention is a closed gas channel for circulating a carrier gas, and a sample introduction device for introducing a sample to be analyzed into the closed gas channel, which is interposed in series in the closed gas channel. A. A sample melting furnace for melting the sample introduced into the closed gas channel, and c. An electrochemical using a solid electrolyte for discharging oxygen in the closed gas channel to the outside of the closed gas channel. Dynamic oxygen pump, and d. A carbon monoxide meter for determining an increase in carbon monoxide in the closed gas flow channel due to introduction of a sample into the closed gas flow channel, An oxygen analyzer is provided.

Here, as the carrier gas, an inert gas such as argon gas or nitrogen gas, or a reducing gas such as argon gas or nitrogen gas containing 0.1 to 10% by volume of hydrogen is used.

Further, the sample introduction device is configured to introduce the sample into the closed gas flow path by dropping it into a sample melting furnace described later, for example.

Further, as the sample melting furnace, one having a sample melting tube made of quartz glass or the like and a heater for heating the sample melting tube to an arbitrary temperature is usually used. The heating temperature by the heater is set according to the type of sample.

Further, an electrochemical oxygen pump is a solid electrolyte having oxygen ion conductivity, for example, zirconia, yttria,
A solid electrolyte such as magnesia and calcia, which is solid-dissolved, is provided with a porous electrode made of platinum or the like on both sides of a cylindrical solid electrolyte, and the solid electrolyte exhibits oxygen ion conductivity. When a DC voltage of arbitrary magnitude is applied between the electrodes while being heated to about 500 to 1000 ° C, oxygen can be moved from one side of the solid electrolyte to the other side according to the polarity of the voltage. is there. Such an oxygen pump uses a solid electrolyte oxygen concentration battery based on the Nernst equation as a pump, not as a battery, and is well known. The amount of oxygen transferred by the oxygen pump as described above can be obtained from the amount of electricity required for transfer, as is well known.

Carbon monoxide meters include infrared absorption carbon monoxide meters such as distributed or non-dispersive infrared carbon monoxide meters, heat conduction carbon monoxide meters, and constant potential electrolysis carbon monoxide meters. Can be used. However, the carbon monoxide meter needs to be of a continuous type.

To determine the amount of oxygen in carbon monoxide from the increase in carbon monoxide obtained by a carbon monoxide meter, introduce carbon monoxide into the closed gas flow path prior to analysis and use the following formula to calculate the amount of oxygen. Find the relationship between the amount of carbon introduced and the increase in the indicated value of the carbon monoxide meter.

y = K ・ x ……… where y: Carbon monoxide introduction amount (mol) x: Incremental value of carbon monoxide meter (ppm) K: Constant And carbon monoxide meter instruction after sample introduction If the increase in value is x ₁ , the increase in carbon monoxide accompanying sample introduction
y ₁ from above, the _{y 1 = K · x 1 .........} . Therefore, the amount of oxygen forming carbon monoxide
w ₁ (g) is w ₁ = M · y ₁ …………, where M is the atomic weight of oxygen. The above-described formula creation and formulas and formula calculations may be performed by a microcomputer or the like.

(Embodiment) In the drawings, in a closed gas flow path 1, a carrier gas circulation pump 2, a four-way switching valve 3, a sample introduction device 4, a sample melting furnace are sequentially arranged along a carrier gas circulation method indicated by a thick arrow. 5, a microsyringe type carbon monoxide introducer 6, an electrochemical oxygen pump 7, a carbon monoxide meter 8, a four-way switching valve 9 and a flow controller 10 are provided. A carrier gas outlet pipe 13 having a filter 11 and a carrier gas suction pump 12 is connected to the four-way switching valve 3, and the four-way switching valve 9 is connected via a carrier gas introducing pipe 15 having a filter 14. It is connected to a carrier gas supply source (not shown). Further, the four-way switching valves 3 and 9 are connected to each other via a bypass pipe 16.

The sample introduction device 4 has a dish 4 a on which the sample 17 is placed. This plate 4a can be rotated as shown by the arrow.

Further, the sample melting furnace 5 has a sample melting tube 5a and a heater 5b for heating the sample melting tube 5a. Then, the cooling fan 18 is provided above the sample dissolving tube 5a.

Further, the electrochemical oxygen pump 7 has a cylindrical solid electrolyte 7a having porous electrodes on both sides, and a heater 7b for heating the solid electrolyte 7a.

To explain the operation of the above-mentioned device, first, the closed gas flow path 1
The inside is replaced with a carrier gas. This replacement is performed by introducing the carrier gas from the carrier gas supply source into the closed gas flow path 1 through the carrier gas introduction pipe 15 having the filter 14 and the four-way switching valve 9 as shown by a thin arrow. To do. The introduced carrier gas flows through the closed gas flow path 1, then passes through the four-way switching valve 3, and further passes through the carrier gas outlet pipe 13 including the filter 11 and the carrier gas suction pump 12 to the outside of the system. Flow out. After continuing such an operation for an arbitrary time, the four-way switching valves 3 and 9 are switched so that the carrier gas from the carrier gas supply source has a carrier gas introducing pipe 15 having a filter 14, a four-way switching valve 9, a bypass pipe 16, and a four-way It is made to flow out of the system through the switching valve 3, and further through the carrier gas outlet pipe 13 having the filter 11 and the carrier gas suction pump 12. Thus, the inside of the closed gas channel 1 is replaced with the carrier gas.

The carrier gas in the closed gas passage 1 is circulated in the closed gas passage 1 by the carrier gas circulation pump 2.
The flow rate at this time is adjusted by the flow rate controller 10. Then, the oxygen pump 7 is operated while continuing such an operation, and oxygen in the carrier gas is continuously discharged to the outside of the closed gas flow path 1. Then, the inside of the closed gas channel 1 has a sufficiently low constant oxygen partial pressure, for example, 10 ⁻²¹ atm or less.

After the inside of the closed gas channel 1 has a sufficiently low constant oxygen partial pressure, a known amount of carbon monoxide is introduced from the carbon monoxide introducer 6 into the closed gas channel 1, and The relationship with the indicated value of the carbon oxide meter 8 is obtained. Now that the analysis is ready, the relationship between the amount of carbon monoxide introduced and the indicated value of the carbon monoxide meter 8 does not have to be calculated each time.

Now, the analysis of the sample 17 is carried out when the inside of the closed gas flow path 1 has a sufficiently low constant oxygen partial pressure.
The dish 4a is rotated in the direction of the arrow to drop the sample 17 into the sample melting tube 5a of the sample melting furnace 5. Then, the sample 17 is dissolved, and the nitrogen contained therein is released into the closed gas flow reactor 1 and is carried by the carrier gas to reach the oxygen pump 7. Is discharged to. A current flows through the oxygen pump 7 during discharging, and the amount of discharged oxygen, that is, the amount of released oxygen from the sample 17 can be known from the amount of electricity required for discharging. At this time, although it may not be possible to discharge the entire amount by one discharging operation, since the released oxygen is circulated in the closed gas passage 1 by the carrier gas, the released oxygen passes through the oxygen pump 7 many times. Therefore, there is no problem because the discharge operation is performed for that reason. The cooler 18 cools the sample dissolution tube 5a,
Heat transfer from the sample melting furnace 5 side to the sample introducer 4 side is prevented, and metal vapor or the like generated with melting of the sample 17 is condensed so that it does not flow out to the downstream side.

Now, if carbon is contained in sample 17, as it dissolves,
Part of oxygen in the sample is combined with carbon to form carbon monoxide or carbon dioxide. Even when the sample 17 contains carbon monoxide and carbon dioxide, the carbon monoxide and carbon dioxide are released into the closed gas channel 1. Of these, carbon dioxide is electrochemically represented by a reaction formula, CO ₂ → CO + 1 / 2O ₂ , since the oxygen pump is heated to about 500 to 1000 ° C. when it is conveyed to the oxygen pump 7. It decomposes into carbon monoxide,
Oxygen generated by this decomposition is discharged to the outside of the closed gas passage 1 by the oxygen pump 7. Meanwhile, sample 17
The amount of carbon monoxide generated by the combination of a part of oxygen and carbon during dissolution, the amount of carbon monoxide originally contained in Sample 17, and the amount of carbon monoxide generated by the decomposition of carbon dioxide. Is measured by the carbon monoxide meter 8, and the increased amount is caused by the introduction of the sample 17. Therefore, the oxygen amount can be known by calculation from the increased amount. Then, by adding this and the above-mentioned released oxygen amount, the total oxygen amount contained in the sample 17 can be known.

In the embodiment described above, the carbon monoxide meter is provided on the downstream side of the oxygen pump in the method of circulating the carrier gas, but this makes the path from the sample melting furnace to the oxygen pump as short as possible. This is to reduce the diffusion of released oxygen and improve the level of the electric signal accompanying the discharge by the oxygen pump. Further, when carbon dioxide exists in the closed gas flow path, the carbon dioxide is decomposed into carbon monoxide and oxygen by the oxygen pump as described above, but in order to quickly detect the change in the amount of carbon monoxide. Is because it is more convenient on the downstream side than on the upstream side.

(Effects of the Invention) The present invention relates to a closed gas flow path for circulating a carrier gas,
A. A sample introduction device for introducing a sample to be analyzed into the closed gas flow passage, which is interposed in series in the closed gas flow passage, and b. To dissolve the sample introduced into the closed gas flow passage. A sample melting furnace, c. An electrochemical oxygen pump using a solid electrolyte that discharges oxygen in the closed gas channel to the outside of the closed gas channel, and d. While the carrier gas is being circulated in the closed gas flow path by an oxygen analyzer equipped with a carbon monoxide meter for determining the increase in carbon monoxide in the closed gas flow path due to the introduction, Oxygen in the closed gas flow passage is discharged to the outside of the closed gas flow passage by an electrochemical oxygen pump using a solid electrolyte so that the inside of the closed gas flow passage has a sufficiently low constant oxygen partial pressure. Introduce the sample into the sample and dissolve it to release the oxygen in the sample into the closed gas channel. Therefore, the released oxygen is discharged to the outside of the closed gas channel by the oxygen pump to obtain the amount of released oxygen, and the increase of carbon monoxide in the closed gas channel after introduction and dissolution of the sample is obtained. , The amount of oxygen forming the carbon monoxide in the increased amount is obtained, and the amount of oxygen and the amount of released oxygen are added, so that a sample containing carbon, carbon monoxide, or carbon dioxide is used. Even so,
The total oxygen content can be analyzed with high accuracy.

[Brief description of drawings]

The drawings are schematic flow diagrams showing an embodiment of the present invention. 1: Closed gas flow path 2: Carrier gas circulation pump 3: Four-way switching valve 4: Sample introducer 4a: Dish 5: Sample melting furnace 5a: Sample melting tube 5b: Heater 6: Carbon monoxide introducer 7: Electrochemistry Oxygen pump 7a: Solid electrolyte 7b: Heater 8: Carbon monoxide meter 9: Four-way switching valve 10: Flow controller 11: Filter 12: Carrier gas suction pump 13: Carrier gas outlet pipe 14: Filter 15: Carrier gas Introduction piping 16: Bypass piping 17: Sample

Claims (2)

[Claims] 1. A closed gas flow path, wherein oxygen in the carrier gas is discharged to the outside of the closed gas flow path by an electrochemical oxygen pump using a solid electrolyte while circulating the carrier gas in the closed gas flow path. After setting the oxygen partial pressure in the flow channel to a sufficiently low constant value, the sample is introduced into the closed gas flow channel and dissolved to release oxygen in the sample into the closed gas flow channel, and the released oxygen is released. Is discharged to the outside of the closed gas flow path by the oxygen pump to determine the amount of released oxygen, and the increase of carbon monoxide in the closed gas flow path after introduction and dissolution of the sample is determined, and the increase in An oxygen analysis method, wherein the amount of oxygen forming carbon monoxide is obtained, and the amount of oxygen and the amount of released oxygen are added. 2. A closed gas flow path for circulating a carrier gas,
A. A sample introduction device for introducing a sample to be analyzed into the closed gas flow passage, which is interposed in series in the closed gas flow passage, and b. To dissolve the sample introduced into the closed gas flow passage. A sample melting furnace, c. An electrochemical oxygen pump using a solid electrolyte that discharges oxygen in the closed gas channel to the outside of the closed gas channel, and d. An oxygen analyzer, comprising: a carbon monoxide meter for determining an increase in carbon monoxide in the closed gas flow channel due to introduction.