JPH04254527A - Method for controlling atmospheric gas in atmospheric furnace for strip - Google Patents

Abstract

PURPOSE:To economically maintain atmospheric gas in the furnace to the prescribed raising pressure reduction atmosphere by adjusting a hydrogen gas feeding quantity based on the actually measured oxygen gas quantity in the furnace while adjusting a nitrogen gas feeding quantity into the furnace based on the actually measured furnace pressure. CONSTITUTION:By arranging atmospheric seals 11, 12 at front and rear parts of the atmospheric furnace 15 for strip, heat treatment is executed to a strip in the furnace made to the reduction atmosphere. In the above method, by controlling a nitrogen gas feeding valve 21 through an arithmetic device 42 based on the actually measured furnace pressure with a furnace pressure gage 41, the nitrogen gas quantity for feeding into the furnace, is adjusted. Together with this, an oxygen gas quantity in the atmospheric gas in the furnace is actually measured with an oxygen gas meter 51. Based on this actually measured valve, a hydrogen gas feeding valve 31 is controlled through an arithmetic device 52. As the other method, the above control can be executed based on the hydrogen gas quantity in the atmospheric gas in the furnace and this dew point. By this method, the feeding quantity of the expensive hydrogen gas is restrained to the necessary min. limit and the atmospheric gas in the furnace is maintained to the prescribed raising pressure reduction atmosphere.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling atmospheric gas in a stripping atmosphere furnace. Atmosphere furnaces for strips are used when surface treating strips of stainless steel, phosphor bronze, etc. The stripping atmosphere furnace is equipped with atmosphere seals before and after the furnace, and is used by feeding nitrogen gas and hydrogen gas into the furnace to maintain the atmosphere gas in the furnace in a pressurized reducing atmosphere.

[0002] The present invention aims to economically maintain the atmospheric gas in the furnace at a predetermined pressure reduction atmosphere by minimizing the amount of expensive hydrogen gas fed into the above-mentioned stripping atmosphere furnace. The present invention relates to a method for controlling atmosphere gas in a furnace.

0003

[Prior Art] Conventionally, as a method for controlling the atmosphere gas in the furnace in an atmosphere furnace for stripping, a premixed gas of nitrogen gas and hydrogen gas is fed into the furnace, and the furnace pressure is controlled by the amount of the mixed gas fed. is being controlled. The atmosphere in the furnace is maintained at an elevated pressure atmosphere by exclusively feeding the mixed gas, and the reducing atmosphere of the atmosphere gas in the furnace is created by mixing a large amount of hydrogen gas when premixing to ensure safety. It is maintained.

However, such conventional furnace atmosphere gas control methods have a drawback in that they use more expensive hydrogen gas than necessary. In addition, the conditions in the furnace, especially the furnace temperature, are different between the start of operation and the time after a predetermined period of time has elapsed since the start of operation of an atmosphere furnace for stripping. The amount of hydrogen gas required to maintain the furnace atmosphere gas in a reducing atmosphere differs depending on the dew point (moisture content) of the furnace atmosphere gas, but a premixed gas mixture is available regardless of the furnace conditions. In the conventional furnace atmosphere gas control method, which feeds hydrogen gas into the furnace, in order to maintain the furnace atmosphere gas in a reducing atmosphere under any furnace conditions, the amount of hydrogen gas when premixing is adjusted to the maximum required amount. They have to be mixed, and in this respect too, expensive hydrogen gas is used more than necessary.

[0005]

[Problems to be Solved by the Invention] The problem to be solved by the present invention is that the conventional furnace atmosphere gas control method uses more expensive hydrogen gas than necessary, which is uneconomical. .

[0006]

[Means for Solving the Problems] The present invention is a method for controlling atmosphere gas in the furnace in a strip atmosphere furnace equipped with atmosphere seals before and after the furnace, and in which gas is controlled to flow into the furnace based on the actually measured furnace pressure. While adjusting the amount of nitrogen gas to be fed, the temperature inside the furnace is adjusted based on the actually measured amount of oxygen gas in the furnace atmosphere gas, or based on the amount of hydrogen gas in the furnace atmosphere gas and the dew point of the furnace atmosphere gas. The present invention relates to a method for controlling atmosphere gas in a furnace atmosphere in a stripping atmosphere furnace, characterized in that the atmosphere gas in the furnace is maintained at a predetermined pressure reduction atmosphere by adjusting the amount of hydrogen gas fed into the furnace.

In the present invention, the furnace pressure is maintained at a predetermined lift pressure mainly by the amount of nitrogen gas fed, and at the same time, the atmospheric gas in the furnace is maintained at a predetermined reducing atmosphere by the amount of hydrogen gas fed. Nitrogen gas and hydrogen gas may be fed into the furnace separately, or a mixture of both gases may be fed into the furnace as a result.

Specifically, the opening degree of the nitrogen gas feed valve is adjusted via a calculation device connected to the furnace pressure gauge so that the furnace pressure actually measured by the furnace pressure gauge becomes a predetermined lift pressure.

At the same time, the realization of a reducing atmosphere in the furnace atmosphere gas is based on the redox equilibrium curve of the furnace atmosphere gas, and the redox equilibrium curve is determined by the amount of oxygen gas ( O2 partial pressure), or the ratio of hydrogen gas amount to moisture content (dew point) to furnace temperature (H2/H2O)
Therefore, the amount of oxygen gas in the furnace atmosphere gas actually measured with an oxygen gas meter against the furnace temperature, or the amount of hydrogen gas in the furnace atmosphere gas actually measured with a hydrogen gas meter against the furnace temperature and the amount actually measured with a dew point meter. via the oxygen gas meter, or the hydrogen gas meter, and an arithmetic device connected to the dew point meter, so as to create a reducing atmosphere close to the oxidation-reduction curve determined from the ratio of the dew point of the furnace atmosphere gas. Adjust the opening of the hydrogen gas supply valve.

In the present invention, by repeatedly adjusting the opening degrees of the nitrogen gas feed valve and the hydrogen gas feed valve as described above, they replenish each other, and as a result, the atmosphere inside the furnace is improved. The gas is maintained at a predetermined pressure reduction atmosphere.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram schematically showing one embodiment of the present invention, and FIG. 2 is a system diagram schematically showing another embodiment of the invention.

In FIG. 1, there are atmosphere seals 11 at the front and rear,
A nitrogen gas feed pipe 23 connected to a nitrogen gas feed source 22 via a nitrogen gas feed valve 21 is installed in the strip atmosphere furnace 13 equipped with a hydrogen gas feed valve 12. A hydrogen gas feed pipe 33 is connected to a hydrogen gas feed source 32 via a valve 31. A furnace pressure gauge 41 is connected to the atmospheric strip furnace 13 , the furnace pressure gauge 41 is connected to a computing device 42 , and the computing device 42 is connected to the nitrogen gas feed valve 21 . Further, an oxygen gas meter 51 is connected to the strip atmosphere furnace 13, and the oxygen gas meter 51 is connected to a calculation device 52, which is connected to the hydrogen gas feed valve 31.
connected to. Although not shown, the furnace temperature is input to the calculation devices 42 and 52.

The furnace pressure is actually measured with the furnace pressure gauge 41, and the actually measured furnace pressure is input to the calculation device 42, and the nitrogen gas supply valve is controlled by a signal issued from the calculation device 42 so that the input furnace pressure becomes the target value. While adjusting the opening degree of 21, at the same time, the oxygen gas amount in the furnace atmosphere gas is actually measured with the oxygen gas meter 51, and the actually measured oxygen gas amount is input to the calculation device 52, and the input oxygen gas amount is set as the target value. (The target value for realizing a reducing atmosphere close to the oxidation-reduction curve in relation to the furnace temperature). be.

In FIG. 2, atmosphere seals 14, 15,
strip atmosphere furnace 16, nitrogen gas feed valve 24,
Nitrogen gas supply source 25, nitrogen gas supply pipe 26, hydrogen gas supply valve 34, hydrogen gas supply source 35, hydrogen gas supply pipe 3
6. The mutual arrangement of the furnace pressure gauge 43 and the calculation devices 44, 55 is the same as in the case of FIG. 1, but in the case of FIG. 53 and a dew point meter 54 are connected, and the hydrogen gas meter 53 and dew point meter 54 are connected to a calculation device 55.

The furnace pressure is actually measured by the furnace pressure gauge 43, and the measured furnace pressure is input to the calculation device 44, and the nitrogen gas supply valve is controlled by a signal issued from the calculation device 44 so that the input furnace pressure becomes the target value. While adjusting the opening degree of 24, at the same time the amount of hydrogen gas in the furnace atmosphere gas is measured using the hydrogen gas meter 53, and the dew point meter 54
The dew point of the atmospheric gas in the furnace is actually measured, and the measured hydrogen gas amount and dew point are input to the calculation device 55, and the ratio (H2/H2O
) is the target value, the opening degree of the hydrogen gas feed valve 34 is adjusted based on a signal issued from the arithmetic unit 55.

Although not shown in the drawings, the arithmetic device 42 and the arithmetic device 52 in FIG.
In this case, the arithmetic device 44 and the arithmetic device 55 can also be used. If they are used in combination, for example, the furnace pressure can be controlled by the total amount of the nitrogen gas feed amount and the hydrogen gas feed amount.

[0017]

Effects of the Invention As is already clear, the present invention described above has the following advantages: In an atmosphere furnace for stripping, the amount of expensive hydrogen gas fed is kept to the necessary minimum, and the atmosphere gas in the furnace can be controlled economically to a predetermined value. This has the effect of being able to maintain a pressurized reducing atmosphere.

[Brief explanation of the drawing]

FIG. 1 is a system diagram schematically showing one implementation state of the present invention.

FIG. 2 is a system diagram schematically showing another implementation state of the present invention.

[Explanation of symbols]

11, 12, 14, 15... Atmosphere seal, 13, 1
6... Atmosphere furnace for stripping, 21, 24... Nitrogen gas feed valve, 31, 34... Hydrogen gas feed valve, 41, 43... Furnace pressure gauge, 42, 44, 52, 55...
...Arithmetic unit, 51...Oxygen gas meter, 53...Hydrogen gas meter, 54...Dew point meter

Claims (2)

[Claims] [Claim 1] A method for controlling atmosphere gas in a strip atmosphere furnace equipped with atmosphere seals before and after the furnace, the method comprising controlling the amount of nitrogen gas fed into the furnace based on the actually measured furnace pressure. , a strip characterized in that the furnace atmosphere gas is maintained at a predetermined pressure reduction atmosphere by adjusting the amount of hydrogen gas fed into the furnace based on the amount of oxygen gas in the furnace atmosphere gas actually measured at the same time. A method for controlling atmosphere gas in a furnace. [Claim 2] A method for controlling atmosphere gas in a strip atmosphere furnace equipped with atmosphere seals before and after the furnace, the method comprising controlling the amount of nitrogen gas fed into the furnace based on the actually measured furnace pressure. At the same time, the amount of hydrogen gas fed into the furnace is adjusted based on the actually measured amount of hydrogen gas in the furnace atmosphere gas and the dew point of the furnace atmosphere gas, so that the furnace atmosphere gas is brought to a predetermined pressure reducing atmosphere. 1. A method for controlling atmosphere gas in a strip atmosphere furnace, characterized in that the atmosphere gas in the furnace is maintained.