JPS6011085B2 - Decarburization measurement device in vacuum decarburization furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring exhaust gas, particularly carbon emissions, by analyzing exhaust gas using a mass spectrometer during a vacuum refining process using a vacuum descaling furnace.

In general, carbon in steel plays an important role in the quality and mechanical properties of the steel, so it is an important issue to match the end point carbon value to the product target carbon value in the steelmaking process, especially in the final refining process.

Therefore, a lot of research has recently been conducted to control this end point carbon value, and this research is particularly active in converters, and dynamic control methods that model the exhaust gas amount and exhaust gas composition, etc. are being carried out. There is.

On the other hand, in the process of manufacturing stainless steel, a method of decarburizing using vacuum (reduced pressure) is used to reduce the loss of chromium due to oxidation.

In this method, stabilizing the end point carbon value is simply C
This method is important not only for improving the quality of the steel, but also for lowering the oxygen concentration in the molten steel and reducing its dispersion, thereby producing clean keys. By the way, the method of controlling the end point carbon value in a vacuum decarburization furnace according to this invention has not been studied as thoroughly as in the case of a converter, and there are various drawbacks in measuring the amount of decarburization. There is. That is, conventionally, the absolute amount of exhaust gas is determined using a venturi tube or the like, but in this case, there are problems with the response characteristics and the accuracy is not sufficient. There is also leakage from the vacuum equipment, and the leakage changes depending on the temperature, making it difficult to detect the amount of leakage. Furthermore, it is difficult to control errors caused by fluctuation factors during vacuum refining. Due to these circumstances, the actual situation is that in the past, the amount of decarburization has not been measured with good accuracy and end point carbon control has not been performed well. In view of this situation, we have developed an innovative method that uses a mass spectrometer type gas analyzer to add a tracer gas and uses this as a measurement medium to measure the amount of exhaust gas from the measurement gas and the partial pressure value of this tracer gas. (Tokusei Showa 50-9
No. 9592 proposes a method and apparatus for measuring the amount of gas generated in a gas generation chamber.

This invention aims to provide a decarburization amount measuring device that can accurately implement this new method in a vacuum decarburization furnace. That is, this invention provides a valve mechanism that can vary the conductance in a sampling path through which carbon gas and tracer gas to be measured are sampled into a gas analyzer, and the pressure inside the gas analyzer (mass spectrometer) is controlled by the operation of this valve mechanism. This is a decarburization amount measuring device that is always in the optimum state.

The present invention will be described below according to embodiments shown in the drawings. FIG. 1 is a schematic diagram of a measuring device according to the present invention, FIG. 2 is an enlarged view of the main part, and FIG. 3 is a diagram showing a modified embodiment.

1 is a vacuum descaling furnace, and a ladle 2 containing molten steel 3 is placed inside.

This vacuum decarburization furnace 1 is exhausted by an ejector 6 via an exhaust duct 5. 7 is a capacitor.

When the inside of the furnace 1 reaches a predetermined degree of vacuum due to this evacuation, gaseous oxygen is blown out by the lance pipe 4, but at this time, before and during the blowing of the gaseous oxygen, some of the carbon and elements in the molten steel are removed from the steel. Reacts with dissolved or gaseous oxygen to produce all CO
Alternatively, it becomes C02 gas and is exhausted through the exhaust duct 5. 8 indicates the position where the gas sampling pipe 10 is connected to the exhaust duct 5, and 16 indicates the position where the tracer gas is supplied to the exhaust duct 5.

9 is a cylinder for tracer gas, that is, an inert gas such as argon gas.

The terminal end of the collection tube 10 is connected to a mass spectrometer 15 for gas analysis, and 11 is a dust trap interposed in this tube. Reference numeral 12 denotes a variable conductance valve, which is a feature of the present invention, and is interposed in the sampling pipe 10, and its conductance is adjusted by a signal from a vacuum gauge 18 installed in the exhaust duct 5.

Reference numeral 10' denotes a sampling tube for introducing exhaust gas from the condenser 7 into the mass spectrometer 15 via a valve 19 and a sampling tube 10.

13 is a mass spectrometer 1 for the gas sampled from the exhaust duct 5.
5 is a vacuum pump for introducing the mass spectrometer, and 14 is a mass spectrometer exhaust pump.

Reference numeral 17 denotes a valve for supplying the tracer gas, which is operated when supplying the tracer gas to the exhaust duct 5 to perform continuous supply or intermittent supply. With the above configuration, when the tracer gas is supplied to the exhaust duct 5, the gas is mixed with the gas from the furnace 1, and is uniformly distributed and exhausted.

Sample gases (exhaust gas and tracer gas) are then sampled through the sampling tube 10 (or sampled from the sampling tube 10');
It varies from 760 Torr) to 0.1 Torr.
Therefore, in the conventional case, when such a pressure change occurs, the amount of sample gas introduced into the mass spectrometer 15 changes. However, the optimal condition for the analysis pressure of the mass spectrometer 15 is 1
0-5 to 10-orr, and therefore, the above-mentioned fluctuation not only lowers the accuracy of analysis, but also causes a rise in pressure within the analyzer, leading to deterioration of the heating filament of the analysis tube. The present invention completely solves the problems of this conventional method.

That is, the introduction of the sample gas into the mass spectrometer is adjusted according to the pressure change at the introduction part of the sample gas into the mass spectrometer 15, and as shown in FIG. This is done by the valve 12. This valve 12 is regulated by the pressure in the exhaust duct 5. Therefore, a constant amount of sample gas can always be introduced into the mass spectrometer 15 even when the pressure changes. FIG. 3 shows a modified embodiment of the present invention in which the conductance of one valve 12 is not adjusted, but a plurality of valves 12-1 to 12-3 each having a different conductance are connected to the sampling path 10 in parallel. In this embodiment, a vacuum gauge 18 is provided to control the start of these operations using a signal from a vacuum gauge 18.

As for the valve mechanism that can vary the conductance in this way, various modified embodiments can be mentioned. Various other modified embodiments other than those shown in the drawings may be made regarding the exhaust system and sampling system. As explained above, the present invention ensures that the mass spectrometer analyzes the sample gas with high precision, and therefore can measure the amount of exhaust gas, that is, carbon, with high precision, making it an excellent decarburization furnace. The present invention provides a device for measuring the amount of decarburization.
By adjusting the conductance variable range of the valve mechanism, the optimum analysis conditions for the mass spectrometer can be obtained, and the analysis accuracy and ultimately the measurement accuracy can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a measuring device according to the present invention, FIG. 2 is an enlarged view of the main part, and FIG. 3 is a diagram showing a modified embodiment. 1...Vacuum decarburization furnace, 5...Exhaust duct, 7
...... Capacitor, 10,10'...
Collection tube, 12...variable conductance valve,
13... Vacuum pump, 15... Mass spectrometer, 18... Vacuum gauge. 1 diagram, 2 diagrams, 3 diagrams

Claims (1)

[Claims] 1 The carbon monoxide, carbon dioxide, and tracer gas emitted during the vacuum refining process using the vacuum decarburization furnace are analyzed using a mass spectrometer, and the amount of decarburization is measured from the partial pressure of each gas and the amount of tracer gas supplied. In this apparatus, a valve mechanism capable of varying the conductance is installed in the sampling path through which each of the gases is sampled from the exhaust duct of the vacuum decarburization furnace to a mass spectrometer, and the conductance is sequentially adjusted in the process of depressurizing the vacuum decarburization furnace. 1. A decarburization amount measuring device in a vacuum decarburization furnace, characterized in that a valve mechanism is operated to reduce changes in sampled gas pressure on the mass spectrometry side to increase decarburization.