JPS6246607B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for controlling exhaust gas recovery from a closed converter. BACKGROUND TECHNOLOGY There are two main methods for controlling exhaust gas recovery in a converter, one of which is constant furnace pressure feedback control. This method performs feedback control by fixing the optimal control parameters for the most frequently observed fluctuations in the gas generated in the furnace, and the furnace mouth pressure is adjusted by PI adjustment. That is, the well-known formula u(t)=100/P _B (e(t)+1/T _I ∫e
(t) dt) ...(1) Seinosuke Narita, Digital System Control,
1983, p158 (Shokodo), this is feedback control in which the control parameters P _B and T _I are kept constant. Here u(t) is the output of the controller, P
_B is the proportional band, e(t) is the control deviation, and T _I is the integration time. Another control method is the exhaust gas flow rate predictive control method (Japanese Patent Publication No. 56-22926). This method controls based on past macroscopic predictions of the amount generated in the reactor. Problems to be Solved by the Invention The above-mentioned constant furnace mouth pressure control cannot cope with severe fluctuations in the gas generated in the furnace due to slag forming, etc. In such cases, the connection between the exhaust gas collection duct and the furnace mouth is It was necessary to take measures to eliminate fluctuations in the pressure at the furnace mouth by raising a skirt at the relay section that can move up and down, that is, adjust the gap at the furnace mouth. In addition, in the exhaust gas flow rate prediction control method, control delays are unavoidable because the flow rate is predicted using analysis values, and it is difficult to predict forming conditions from gas analysis, etc., and it is relatively microscopic. However, there was a weakness in the ability to respond to short-period gas fluctuations. The present invention provides a closed converter exhaust gas recovery control method that does not have the weaknesses of the above-mentioned conventional techniques. Means for Solving the Problems The configuration of the present invention is as follows: (1) In a method for recovering exhaust gas in a closed converter,
A closed converter exhaust gas recovery method, characterized in that an in-furnace observation device is provided in the furnace body of the closed converter to detect the in-furnace forming status, and an exhaust gas recovery control system is operated according to the detected status, and ( 2) In claim 1, a reference control program is set in advance by determining the correlation between the slag forming situation and the exhaust gas recovery control system for the converter, and the control program is set in advance in accordance with the detection of the slag forming situation. This method implements collection control according to a program. During converter blowing, various reactions such as slag formation, decarburization, dephosphorization, and desulfurization take place, but it is extremely useful to accurately know the conditions inside the furnace, especially the slag formation status. be. The present applicant has applied for a series of patents related to a device for detecting slopping by providing a through hole in the side wall of a converter and installing an inside observation device to observe the condition of the furnace (for example, Japanese Patent Laid-Open No. 60-228931). As shown in Fig. 1, this in-furnace observation device provides an in-furnace observation hole 5 in the side wall of a converter 1, inserts an in-furnace observation probe 6, and converts the in-furnace light received at the tip of the probe into a photoelectric converter. This is a device in which an element 7 converts the signal into an electrical signal, and a slag forming amount detector 9 detects the state of slag forming. Using this equipment, we investigated in detail the correlation between the amount of slag forming and the status of exhaust gas generation, and found that there was an extremely high correlation.Furthermore, fluctuations in the amount of exhaust gas generated can be predicted by forming detection, so it is possible to predict fluctuations in the amount of exhaust gas generated using conventional methods. They learned that much more precise control than controlling the exhaust gas recovery system could be achieved by detecting changes in the furnace mouth pressure at a later time. The magnitude of the slag forming amount is determined in detail as follows. The aforementioned probe 6 has a built-in conductor such as a quartz-based optical fiber that transmits synchrotron radiation emitted from a high-temperature object with low loss, and the tip receives the light inside the furnace while being exposed to high temperature. and transmits it to the photoelectric conversion element 7 located at room temperature.
A photoelectric conversion element has the function of converting light into electrical signals by wavelength in proportion to its intensity.
ITV cameras are one example. Since there is a difference in the relationship between the wavelength and intensity of the light emitted by the slag being blown in the furnace and the gas atmosphere above the slag, the received furnace light is separated by wavelength, and the amount of area by color and the area by color are calculated. The correlation between the size of these two quantities related to a specific color and the slag forming situation is calculated based on a number of results, and the judgment criteria obtained from these are used to determine the forming process through in-furnace observation. It is now possible to detect situations. The amount of area and the amount of change in the amount of area are binarized using a certain threshold value and taken out as signals of 1 and 0, and the criteria for determining the magnitude of these signals and forming are shown in Table 1.

[Table] The slag forming amount detector has the above-mentioned determination function. When the exhaust gas recovery system is controlled by the PI adjustment shown by the above equation (1), it can be qualitatively considered as follows. In other words, when the forming tendency is large, the control gain 100/P _B is increased to speed up the instantaneous response of the damper, and conversely, the steady response of the damper tends to be worse, but the integration time T _I is set longer. ,
It is better to prevent amplification of control deviation due to phase shift. When the forming tendency is small, the control gain does not need to be large, and the integration time does not need to be long. If these are represented in a diagram, it will look like Figure 2. Further, these relationships are quantified from many experimental examples and combined with the above-mentioned Table 1 to obtain Table 2, which includes actual numbers of control parameters as an example. Therefore, by setting a reference control program based on the values in Table 2 and performing recovery control in accordance with the detection of the slag forming situation, stable and extremely efficient exhaust gas recovery can be achieved.

[Table] To explain this using FIG. 1, the information obtained from the slag forming amount detector 9 is
0 and P _B , T _I by the reference control program.
is calculated, and on the other hand, the furnace mouth pressure measurement value is input from the furnace mouth pressure transmitter 4, the calculation of equation (1) is performed, and the result is transmitted to the damper controller 13 and the damper 12
Opens and closes. The method of the present invention will be explained in more detail with reference to Examples. Example In a 170t/ch top-blown closed converter, the above-mentioned furnace observation device was installed to detect the forming situation inside the furnace,
Exhaust gas was recovered while performing converter generated gas recovery control in accordance with a standard control program based on Table 2. The furnace mouth pressure setting value for calculating control deviation is 0 mmAq.
The furnace opening gap was kept constant at 200 mm. The results obtained are shown in FIG. 3 and Table 3. FIG. 3A shows the gas pattern generated in the furnace during slag forming, and one cycle was 8 to 10 seconds. Therefore, one cycle of fluctuating furnace mouth pressure due to this takes 8 to 10 seconds, and it takes at least 8 to 10 seconds to detect abnormal fluctuations during slag forming from the furnace mouth pressure, making it difficult to control the timing. It is clear that there is a risk of loss. The solid line in Figure 3B is the conventional control parameter (P _B = 200%, T _I = 2 seconds)
When using P _B =
This shows the furnace mouth pressure fluctuation corresponding to A when T _I = 20 seconds and 100%, and the difference in amplitude is clear. According to Table 3, each 20
In the operation example, the average furnace mouth pressure maximum value,
Both the minimum absolute value and the variation were smaller in the method of the present invention, and the average furnace combustion rate was also reduced by about 40%, demonstrating the superiority of the method of the present invention.

[Table] Effects of the invention During converter exhaust gas recovery, if slag forming occurs in the furnace and fluctuates the amount of exhaust gas, the fluctuating pressure at the furnace mouth that occurs later causes further damage to the furnace mouth. An attempt was made to deal with the problem by making a comprehensive judgment in conjunction with the brightness and fluctuation of the light, and in the worst-case scenario, the idea was to escape by raising the skirt. The above method cannot be applied to a closed converter, but according to the method of the present invention, the detection status of forming inside the furnace by the inside observation device is directly reflected in the control operation of the exhaust gas recovery control system. , it is possible to respond appropriately mechanically without losing the timing of control system operation, and the furnace combustion rate can also be reduced. As described above, the present invention makes it possible to stabilize the operation of closed converter exhaust gas recovery, which could not be achieved with conventional methods, and contributes to improving the exhaust gas recovery rate.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of exhaust gas recovery control according to the method of the present invention, Fig. 2 is a diagram showing the relationship between the amount of slag forming and control parameters, and Fig. 3A is a diagram showing the gas pattern generated during slag forming. , FIG. 3B is a diagram showing the fluctuation of the furnace mouth pressure corresponding to A. 1... Converter, 2... Skirt, 3... Exhaust gas recovery duct, 4... Furnace pressure transmitter, 5... Furnace observation hole, 6... Observation probe, 7... Photoelectric conversion element, 9 ...Slag forming amount detector, 10...
... Arithmetic processing unit, 11 ... Lance, 12 ... Damper, 13 ... Damper controller, 14 ... Induction fan.

Claims (1)

[Claims] 1. In a method for recovering exhaust gas in a closed converter,
A closed converter exhaust gas recovery method, characterized in that an in-furnace observation device is provided in the furnace body of the closed converter to detect the in-furnace forming status, and an exhaust gas recovery control system is operated in accordance with the detected status. 2 Install an in-furnace observation device in the furnace body of a closed converter to detect the forming situation inside the furnace, and also determine the correlation between the slag forming situation and the exhaust gas recovery control system for the converter, and set a standard control program in advance. and performing collection control according to the program in response to the detection of the slag forming situation.