JPH09281010A - Sampling apparatus for gas to be analyzed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sampling apparatus for a gas to be analyzed, by which a gas inside a tank under a reduced pressure and with a large pressure change can be supplied continuously and stably to a gas snalyzer. SOLUTION: A suction-gas flow-rate regulating means 14 by which the flow rate of a suction gas sucked by a vacuum pump 6 is regulated according to a pressure inside a tank such as a vacuum degassing furnace 1 or the like, a gas-to-be-analyzed flow-rate regulating means 15 which regulates the amount of a gas to analyzed, to the gas analyzer 7 and an evacuation system 16 by which a gas on the upstream side from the gas-to-be-analyzed flow-rate regulating means 15 is discharged according to the pressure on the secondary side of the vacuum pump 6 are installed at a gas-to-be-analyzed supply system 13 by which a gas, which is sucked and sampled by the vacuum pump 6, is supplied to the gas analyzer 7 as a gas to be analyzed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for collecting an analytical gas, for example, in a device such as a vacuum degassing furnace for vacuum degassing stainless steel in which the internal pressure fluctuates greatly under reduced pressure. The present invention relates to a device for collecting an analytical gas for analyzing a gas composition in a tank.

[0002]

2. Description of the Related Art In many industrial processes, a step of performing a chemical or physical reaction in a low-pressure vessel is performed.
For example, in a process for producing high-grade steel such as stainless steel, a vacuum degassing furnace is used mainly in a process for degassing molten metal.

The vacuum degassing treatment of stainless steel using the above vacuum degassing furnace is, for example, as shown in FIG. 2, a ladle 1a containing a molten stainless steel at the bottom of the vacuum degassing furnace 1.
Is fixed by applying a vacuum seal, and the inside of the vacuum degassing furnace 1 is decompressed by the ejector pump 2, while a heating gas (mainly air or argon, sometimes oxygen ) Together with atmospheric gas (carbon dioxide,
Carbon monoxide, nitrogen) is blown in to remove oxygen, hydrogen, nitrogen, etc., which are melted in the molten stainless steel material for purification.

Therefore, the gas composition in the vacuum degassing furnace 1 is a major condition for determining the quality of the obtained product.
It is desirable to constantly monitor the gas composition and feed it back to driving operations such as blowing various gases. For this reason,
The gas in the vacuum degassing furnace 1 is sucked by the vacuum pump 6 through the filter 4 and the valve 5 and supplied to the gas analyzer 7 to analyze the gas composition in the furnace.

[0005]

However, the inside of the vacuum degassing furnace 1 is in a depressurized state at the start of operation, and during operation, the pressure constantly changes due to gas blowing, so that the load on the vacuum pump 6 is reduced. Not only may the vacuum pump 6 constantly change and become overloaded, but the amount of suction gas and the amount of discharge gas in the vacuum pump 6 also change significantly, so that the gas for analysis to the gas analyzer 7 is kept constant. It could not be supplied at a constant flow rate.

Therefore, in the case of analyzing with a normal gas analyzer, accurate data cannot always be obtained due to variations in the flow rate of the analysis gas, and the analysis result cannot be reflected in the driving operation. .

Therefore, the present invention is to collect an analysis gas which can continuously and stably supply the gas in a tank under a reduced pressure and having large pressure fluctuations to the gas analyzer, such as the vacuum degassing furnace. The purpose is to provide a device.

[0008]

In order to achieve the above object, the analytical gas sampling apparatus of the present invention uses a vacuum pump to suction and collect a gas in a tank whose pressure fluctuates, and the collected gas is used for analysis. A suction gas flow rate adjusting means for adjusting the suction gas flow rate sucked by the vacuum pump according to the pressure in the tank in the analysis gas supply system to be supplied to the gas analysis apparatus as gas, and the amount of gas supplied to the gas analysis apparatus. And an exhaust system for exhausting the gas on the upstream side of the analysis gas flow rate adjusting means according to the secondary side pressure of the vacuum pump. Furthermore, the suction gas flow rate adjusting means is to install a plurality of automatic valves having different diameters in parallel and to open and close each automatic valve according to the pressure in the tank, and the exhaust system, Multiple with different calibers With installing the automatic valve in parallel, it is characterized by comprising an exhaust gas flow rate adjusting means for opening and closing the respective automatic valve in accordance with the secondary pressure of the vacuum pump.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 shows an example of the analytical gas sampling apparatus of the present invention, and the present invention is applied to the analysis of the gas composition in the vacuum degassing furnace 1 as described above.

The gas in the vacuum degassing furnace 1 is analyzed by a gas analyzer 7.
Analysis gas sampling device 10 to be supplied to vacuum degassing furnace 1
To the primary side pipe 11 connected to the
A suction gas provided between the secondary gas pipe 12 connected to the gas analyzer 7 and the analysis gas supply system 13 having the vacuum pump 6 and between the valve 5 and the vacuum pump 6. It is composed of a flow rate adjusting means 14, an analysis gas flow rate adjusting means 15 provided in the gas introduction part of the gas analyzer 7, and an exhaust system 16 branched from between the analysis gas flow rate adjusting means 15 and the vacuum pump 6. Has been done.

In the analysis gas supply system 13, a first vacuum gauge 17 is provided between the valve 5 connected to the primary side pipe 11 and the suction gas flow rate adjusting means 14, the suction gas flow rate adjusting means 14 and the vacuum pump 6. Between the second vacuum gauge 18 and the vacuum pump 6
Pressure gauges 19 are respectively provided between the exhaust system 16 and the branch portion of the exhaust system 16, and are configured to open and close each automatic valve described later based on the measured values of these instruments.

The suction gas flow rate adjusting means 14 is provided with a plurality of automatic valves having different diameters, for example, a small diameter automatic valve 14a, a medium diameter automatic valve 14b, and a large diameter automatic valve 14c, which are installed in parallel. The automatic valve is formed so as to be automatically opened and closed by the first vacuum gauge 17 which measures the pressure in the vacuum degassing furnace 1.

Further, the exhaust system 16 is provided with an exhaust gas flow rate adjusting means 20 for adjusting the amount of exhaust gas. This exhaust gas flow rate adjusting means 20 also has a plurality of automatic valves having different diameters, for example, the large-diameter automatic valve 2 as in the above.
0a, a medium-diameter automatic valve 20b, and a small-diameter automatic valve 20c are installed in parallel, and these automatic valves are automatically opened and closed by a pressure gauge 19 that measures the secondary pressure of the vacuum pump 6. Is formed.

As the analyzing gas flow rate adjusting means 15, an appropriate flow rate adjusting means can be used according to the allowable flow rate range in the gas analyzer 7, and when precise flow rate control is required, for example, a mass flow controller. Can be used.

A filter cleaning gas introduction system 21 for backwashing the filter 4 is provided between the filter 4 and the valve 5, and when the filter 4 becomes clogged. By closing the valve 5 to open the valve 22 of the filter cleaning gas introduction system 21 and flowing the gas from the system 21 to the filter 4 in the reverse direction, the filter 4 can be easily cleaned without removing the filter 4. It can be carried out.

Next, the analytical gas sampling apparatus 10 having the above-mentioned structure
The state when the gas in the vacuum degassing furnace 1 is supplied to the gas analyzer 7 will be described with reference to FIG. First, in the vacuum degassing furnace 1, the ejector pump 2 is activated (the ejector pump main valve is closed), and the ejector pump 2 is warmed up. Further, the ladle 1 a is attached to the bottom of the vacuum degassing furnace 1.

At this time, the inside of the vacuum degassing furnace 1 is at atmospheric pressure, and the inside of the system of the analytical gas sampling apparatus 10 is also at atmospheric pressure. In addition, the automatic valves 14a, 14 of the suction gas flow rate adjusting means 14
b and 14c are closed, and the vacuum degassing furnace 1 and the analytical gas sampling apparatus 10 are in a disconnected state.
The valve 5 is opened when the vacuum degassing furnace 1 is started. In this state, the vacuum pump 6 is activated to evacuate the system. At this time, since the secondary pressure of the vacuum pump 6 is in a relatively high state, one of the automatic valves of the exhaust system 16 is opened according to the value indicated by the pressure gauge 19, and the gas in the system is Exhausted through. Further, for some gases, the flow rate adjusting means for analysis gas 1 is set in advance.
The gas is sent to the gas analyzer 7 via 5.

On the other hand, one of the automatic valves of the suction gas flow rate adjusting means 14 is opened according to the indicated value of the first vacuum gauge 17, and the gas in the vacuum degassing furnace 1 is sucked through the automatic valve.
Then, when the discharge of the gas in the vacuum degassing furnace 1 by the ejector pump 2 is started, the gas analysis in the gas analyzer 7 is started. At this time, while the pressure in the vacuum degassing furnace 1 is high and a sufficient amount of gas can be supplied to the gas analyzer 7, one of the automatic valves of the exhaust system 16 opens according to the instruction value of the pressure gauge 19. Therefore, the amount of gas that exceeds the amount required for analysis is discharged from the exhaust system 16.

As the pressure in the vacuum degassing furnace 1 decreases, that is, the value indicated by the first vacuum gauge 17 decreases, the suction gas flow rate adjusting means 14 includes a small diameter automatic valve 14a, an intermediate diameter automatic valve 14b, and a large diameter automatic valve 14b. The automatic caliber valve 14c automatically opens and closes, and thereafter, the automatic valves 1c are changed depending on the pressure in the vacuum degassing furnace 1.
4a, 14b, 14c are automatically switched.

For example, the pressure in the vacuum degassing furnace 1 is 76
Only the small diameter automatic valve 14a is opened between 0 and 200 Torr, only the medium diameter automatic valve 14b is opened between 200 and 50 Torr, and only the large diameter automatic valve 14c is opened between 50 and 1 Torr. Note that each automatic valve may be configured such that two or more automatic valves are opened at the same time without opening only one.

As described above, the suction gas flow rate adjusting means 14 is provided on the primary side of the vacuum pump 6 to adjust the gas flow rate, thereby adjusting the suction gas amount and pressure of the vacuum pump 6 within a certain range. Therefore, the fluctuation of the load of the vacuum pump 6 can be suppressed, the overload state can be prevented, and the gas discharge amount can be stabilized within a certain range.

As described above, the suction gas flow rate adjusting means 14 can stabilize the gas discharge amount of the vacuum pump 6, but it is difficult to make it constant. Therefore, the secondary pressure of the vacuum pump 6 also fluctuates within a predetermined range.

On the other hand, the analysis gas flow rate adjusting means 15 operates so as to keep the gas flow rate sent to the gas analyzer 7 substantially constant, so that when the gas discharge amount of the vacuum pump 6 fluctuates, the secondary of the vacuum pump 6 is changed. Gas will accumulate on the side.

Therefore, the pressure in the secondary side pipe of the vacuum pump 6 is measured by the pressure gauge 19 provided on the secondary side of the vacuum pump 6, and when the pressure exceeds a predetermined value, any of the exhaust system 16 is detected. The automatic valve is opened to discharge excess gas out of the system.

For example, when the pressure in the vacuum degassing furnace 1 is 50 to 1 Torr, which is relatively low, the large-diameter automatic valve 14c of the suction gas flow rate adjusting means 14 is opened and the discharge amount of the vacuum pump 6 is small. Since the indicated value of the pressure gauge 19 is low, the frequency with which each automatic valve of the exhaust system 16 is opened decreases, and almost all of the gas sucked from the vacuum degassing furnace 1 is an analysis gas flow rate adjusting means. Gas analyzer 7 through 15
Will be supplied to.

When various gases are blown into the vacuum degassing furnace 1 and the pressure in the furnace rises, the first vacuum gauge 17
Each valve of the flow rate control unit 14 is switched and opened / closed based on the pressure increase detected in 1., for example, the large diameter automatic valve 14c is closed and the small diameter automatic valve 14a is opened. This allows
Although it is prevented that the gas sucked by the vacuum pump 6 is throttled and the gas discharge amount of the vacuum pump 6 is largely changed, the gas discharge amount of the vacuum pump 6 is increased depending on the degree of increase in the furnace pressure. The secondary pressure of the vacuum pump 6 will rise. The pressure change at this time is measured by the pressure gauge 19, and at least one of the automatic valves 20a, 20b, 20c of the exhaust gas flow rate adjusting means 20 is opened according to the degree of increase in pressure, and the excess gas is discharged. Is discharged to the outside of the system.

Therefore, the suction gas flow rate adjusting means 14 provided on the primary side of the vacuum pump 6 and the exhaust gas flow rate adjusting means 20 provided on the secondary side of the vacuum pump 6 reach the analysis gas flow rate adjusting means 15. The gas flow rate and pressure can be made substantially constant, and the accuracy of flow rate control in the analysis gas flow rate adjusting means 15 can be greatly improved. Thereby, the gas supplied to the gas analyzer 7 can be maintained at a predetermined flow rate, and the gas composition in the vacuum degassing furnace 1 can be grasped in real time. Therefore, the type and amount of the gas blown into the vacuum degassing furnace 1 can be accurately controlled, and the efficiency of the vacuum degassing process can be significantly improved.

As the suction gas flow rate adjusting means and the exhaust gas flow rate adjusting means, a known flow rate controlling means such as a diaphragm type can be used, but as described above, a plurality of automatic valves having different diameters are arranged in parallel. By installing them and forming them so as to open and close (fully open / fully close) within an appropriate range, the facility cost of these gas flow rate adjusting means can be greatly reduced.

Further, in the above embodiment, an example in which the gas in the vacuum degassing furnace is analyzed has been given, but the present invention can be applied to something other than the vacuum degassing furnace and is close to a vacuum. By applying the present invention to various fields in which a material is reacted or processed in a container in a state, the operability can be greatly improved.

[0030]

As described above, according to the analyzer gas sampling apparatus of the present invention, the gas in the tank under reduced pressure and with large pressure fluctuation is automatically and stably supplied to the gas analyzer. Since it is possible to analyze the gas composition in the tank at all times, the analysis results are fed back to control the gas composition in the tank to the desired gas composition, thereby improving and stabilizing the quality of products. Can be planned.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a device for collecting an analysis gas of the present invention.

FIG. 2 is a system diagram showing an example of a conventional analysis gas sampling system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum degassing furnace, 6 ... Vacuum pump, 7 ... Gas analysis device, 10 ... Analysis gas sampling device, 13 ... Analysis gas supply system, 14 ... Suction gas flow rate control means, 15 ... Analysis gas flow rate control means , 16 ... Exhaust system, 17 ... First vacuum gauge, 1
8 ... Second vacuum gauge, 19 ... Pressure gauge, 20 ... Exhaust gas flow rate adjusting means, 21 ... Filter cleaning gas introduction system

Claims (3)

[Claims] 1. A suction suctioned by a vacuum pump in a gas supply system for analysis that sucks and collects a gas in a tank whose pressure fluctuates by a vacuum pump and supplies the collected gas as a gas for analysis to a gas analyzer. A suction gas flow rate adjusting means for adjusting the gas flow rate according to the pressure in the tank, an analysis gas flow rate adjusting means for adjusting the amount of gas supplied to the gas analyzer, and an upstream side of the analysis gas flow rate adjusting means. An analysis gas sampling device, comprising: an exhaust system for discharging gas according to a secondary pressure of a vacuum pump. 2. The suction gas flow rate adjusting means is characterized in that a plurality of automatic valves having different diameters are installed in parallel and each automatic valve is opened and closed according to the pressure in the tank. Item 1. The analysis gas sampling apparatus according to Item 1. 3. The exhaust system is provided with a plurality of automatic valves having different diameters arranged in parallel, and is provided with an exhaust gas flow rate adjusting means for opening and closing each automatic valve according to the secondary pressure of the vacuum pump. The gas sampling device for analysis according to claim 1, characterized in that: