JPS59231389A - Method of controlling atmosphere in furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the atmosphere in a furnace, and is characterized in that the atmosphere in the furnace, which undergoes temperature changes, can be accurately and inexpensively controlled using an oxygen sensor.

Recently, oxygen sensors have been used to analyze and control the atmosphere inside the furnace instead of infrared gas measuring instruments, dew point sensors, etc.

Since the oxygen sensor is inserted directly into the furnace, unlike the conventional splitter, it does not require a sampling device or its maintenance, and has the advantage of extremely quick response.

The analysis of the furnace atmosphere using the oxygen sensor is performed using the fact that the electromotive force from the oxygen sensor has a certain relationship with 00.2/Co in the furnace atmosphere and the furnace temperature.

That is, a zirconia solid electrolyte (Zr
When an oxygen sensor coated with platinum electrodes on the inner and outer surfaces of Or) is placed in the furnace atmosphere, the force of the platinum electrodes on the inner and outer surfaces increases depending on the difference in oxygen concentration between the inside (reference air) and the outside (furnace atmosphere). arise.

If the temperature inside the furnace is given to the above electromotive force, the amount of oxygen inside the furnace can be determined.

Furthermore, the atmosphere inside the furnace contains CO+%0. ! --------(1)2C
Since the equilibrium relationship of O* C+ 0C1z -m---(2) exists, the carphon potential is calculated from a certain relationship between the amount of oxygen in the furnace, the temperature in the furnace, and the carhon potential of the atmosphere. It is something that can be done.

That is, the electromotive force from the oxygen sensor varies depending on the temperature, and when the temperature inside the furnace changes, it is difficult to accurately calculate the carbon potential of the atmosphere.

For this reason, in the past, the temperature inside the furnace was kept constant and the signal (electromotive force) from the oxygen sensor was linearly sliced and output, which required a large computer.

The present invention uses a commercially available microprocessor-based regulator to analyze the atmosphere with temperature changes and thereby control the furnace atmosphere.

As already mentioned, the Cahon potential of the atmosphere calculated from the electromotive force from the oxygen sensor and the temperature inside the furnace is a quadratic curve.

In order to linearly rice the image in its original state, the above-mentioned commercially-available computational power is insufficient. That is, it does not have the arithmetic function -. Therefore, in the present invention, linear lining is performed using broken line approximation.

The above-mentioned polygonal line approximation is performed at a specific temperature that is most used, and even if the temperature inside the furnace changes, it is linearly sliced as the oxygen sensor output at that temperature.

Next, a temperature correction signal is obtained by subjecting the furnace temperature detected by the thermocouple to a predetermined calculation. The temperature correction is carried out using a mathematical formula experimentally determined by Cheetah, which states that the quadratic curve shifts according to the temperature inside the furnace, and that changes in the temperature inside the furnace are proportional to changes in the oxygen concentration inside the furnace. Then, the Cahon potential is calculated by calculating the corrected temperature signal and the voltage signal by the above-mentioned broken line approximation, and the subsequent control is carried out using conventional methods, for example, by comparing the above-mentioned calculated value and the target value to obtain the target value. The supply amount of enriched scum is controlled in accordance with the above, and the atmosphere inside the furnace is controlled.

Example 1 A polygonal line approximation of the oxygen sensor output was performed at the most frequently used temperature, specifically 926.7°C (1700'F),
Even if the temperature inside the furnace changes, the linear rice is processed using the oxygen sensor output at the temperature of 926.7°C.

Next, the proportional relationship between the temperature change in the furnace and the oxygen concentration in the furnace is determined based on the fact that when the temperature in the furnace shifts by 14°C, the oxygen concentration in the furnace changes by 05%.

As a result, the in-furnace oxygen concentration is 5 A (/14 (1-926,7)), where the output signal linearized by the oxygen sensor sensor is calculated and the in-furnace temperature detected by the thermocouple is t. -----f
3).

Temperature correction is performed using the above equation (3), and the Cahon potential of the furnace atmosphere is calculated by calculating the temperature correction signal △A and the output signal A linearly sliced by the oxygen sensor, and the calculated value and the target The values are compared, the enrichment gas supply is controlled, and the furnace atmosphere is sterilized.

FIG. 2 shows a block diagram for implementing the method of the invention.

In the figure, (1) is the oxygen sensor, (2) is the adder, and (3) (
(4) is a thermocouple, (5) is a subtracter, (6) is a multiplier, (7) is a broken line counter, (8) is a carphone potential calculation m, and t9+ is a target setting device. , (10) is an enriched gas control section.

That is, one aspect of the present invention adds and subtracts the output from the oxygen sensor (1) to linearly slice the oxygen sensor output at the constant temperature.

On the other hand, the detected temperature from the thermocouple (4) is subtracted and multiplied according to the above equation (3), and is added to the polygon line counter (7) together with the corrected output of the oxygen sensor (1), The carbon potential of the atmosphere inside the furnace is calculated.

-D, the calculated value of 'c and the target setter (9) are compared in the enriched gas control section (10), and the supply amount of the enriched gas is controlled so as to meet the target value.

As mentioned above, the present invention calculates the carbon potential of the atmosphere inside the furnace by calculating the signal obtained by linearly arranging the output of the oxygen sensor using polygonal approximation and the temperature correction signal obtained by performing a predetermined calculation on the temperature inside the furnace. + It controls the supply amount of enriched gas by comparing it with the target setting value, and since it uses broken line approximation, it is easy to change the linear rice of the oxygen sensor output, and it is also easy to correct the temperature. It can be used accurately and inexpensively, and it is possible to achieve the effect of being able to control the atmosphere with temperature changes.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and Figure 1 is a diagram showing the relationship between oxygen sensor output, temperature, and carbon potential, and Figures 2 and 2 are block diagrams of the present invention. (1)...Oxygen sensor, (4)...Aging pair, (7
)... Broken line Seki Keiki, (8)... Carbon potential calculation section, (9)... Target setting device, 00)... Enrich gas control section. Figure 1

Claims (1)

[Claims] Calculate the Cahon potential of the furnace atmosphere by using the signal obtained by linearizing the oxygen sensor output using a polygonal approximation and performing a predetermined calculation on the furnace temperature to calculate the appropriate temperature correction signal, and set the calculated value as the target. A method for controlling an atmosphere in a furnace, characterized by controlling the amount of enriched sludge charged in comparison with a value.