JPS6270508A - Method for controlling recovering of waste gas from converter - Google Patents

Abstract

PURPOSE:To efficiently control the recovery of a waste gas from a converter by detecting the generation of abnormal decarburization from the full opening of a damper for adjusting the recovery of the waste gas, stepwise reducing the rate of the oxygen to be passed and restoring the rate of oxygen when the abnormal decarburization settles down. CONSTITUTION:The waster gas generated from the converter 9 is induced by an induced draft fan 12 into a recovery system and the damper 4 is operated in the open direction by a device 18 for controlling the recovery of the waste gas via an operating device 5 to prevent the overflow of the waste gas from the converter throat part 16. The rate of deceleration to command the throttling of the rate of the oxygen to be passed is added to the output value of an oxygen flow rate program setter 20 by a block 21 for suppressing the abnormal decarburization when the damper 4 attains a full open region upon abnormal progression of the decarburization reaction. A controller 19 for the rate of the oxygen to be passed decelerates the rate of the oxygen to be passed to an oxygen lance 7 by such command and makes this operation stepwise to move the damper 4 in the close direction until the damper is moved to the outside of the full open region. The throttled rate of the oxygen is stepwise restored to the previous rate when the abnormal decarburization settles down. The deceleration restoration deceleration are thus repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an exhaust gas recovery control method in the field of converter refining in iron manufacturing (steel manufacturing process).

[Conventional technology] In converter refining, 2C+
The decarburization reaction of O,→2GO generates exhaust gas containing a high concentration of combustible gas. In order to recover this exhaust gas in an unburned state with high efficiency, various improvements and devices have been made in the past.One example is JP-A-58-1011, which uses an exhaust gas recovery device to blow oxygen and input auxiliary materials. A method is disclosed in which exhaust gas is recovered with high efficiency by operating an exhaust gas adjustment damper in accordance with the increase or decrease in exhaust gas generated by the exhaust gas.

[Problems to be Solved by the Invention] However, after 3 to 5 minutes have passed after the start of refining, the decarburization reaction rapidly progresses, and sometimes an abnormal decarburization phenomenon occurs in which exhaust gas is generated in excess of the exhaust gas recovery capacity. For this reason, a problem arose in that the amount of gas that could not be recovered overflowed to the outside of the recovery system, reducing the exhaust gas recovery rate. Particularly in recent years, the peracid rate has sometimes been significantly increased to improve productivity, which has resulted in frequent blow-off of exhaust gas, which can cause operational troubles.

[Means for Solving the Problems] The present invention focuses on the fact that when the amount of exhaust gas is generated due to abnormal decarburization than the recovery capacity, the exhaust gas adjustment damper is in a fully open region, and the exhaust gas adjustment damper is If the full-open range is rapidly reached, reduce the amount of acid in stages,
We came up with a method to suppress the decarburization reaction of 2C+02→2CO. By restoring the reduced amount of oxygen once the decarburization reaction has been suppressed and the abnormal decarburization has subsided, the main purpose of converter refining is decarburization and the effect on steel bath temperature rise is avoided. In addition, since the total amount of acid passing is almost the same, there is no disadvantage that the refining time is longer than before and the production efficiency is lowered. That is, the feature of the present invention is that, in the exhaust gas recovery control method for an oxygen converter, the occurrence of abnormal decarburization is detected by sensing the full opening of the exhaust gas recovery adjustment damper, and the amount of superacid is gradually reduced. The aim is to restore the amount of oxygen that has been squeezed out once the abnormal decarburization has subsided. What is an oxygen converter here?
A converter that mainly uses pure oxygen to make and refine steel by top-blowing, top-bottom blowing, or bottom-blowing.

The gist of the present invention will be explained below by way of example. During normal operation, the exhaust gas recovery adjustment damper
The opening is adjusted to 40%, but since the exhaust induction fan normally operates at a constant speed, it is fully open, or 85%.
Reaching the above range means that the suction capacity is full, and if the amount of gas generated from the converter continues to increase further, a phenomenon of excess gas blowing out from the furnace mouth will naturally occur. That is,
The fully open state of the damper is a critical point in exhaust gas recovery control and the starting point of action. It is necessary to narrow down the amount of peracid in stages.

In other words, the deceleration of the overacid rate should not have a negative effect on the blowing time, decarburization, and temperature rise.

The deceleration command per time is, for example, 200 to 300, and 5000 Nrn'/Hr for charging blowing. The damper opening degree is not determined for 10 seconds after issuing the command.

This is to wait for the effect of the deceleration operation.

After 10 seconds, the damper opening degree is determined again. If the abnormal decarburization has not subsided and the damper opening is still in the region of 85% or more, the above-described deceleration operation is performed again. In actual practice, the abnormal decarburization phenomenon can be suppressed by performing deceleration operations within 3 times.
%, it is necessary to supply again the amount of decelerating oxygen that was not blown in due to the restriction of the peracid rate. This volume increase operation is to recover the decarburization reaction and temperature rise that were slightly delayed by the squeezing operation.
By adding the above deceleration amount to the current peracid rate, in a stepwise manner in the opposite manner to the deceleration operation, 20% in one operation.
If blowing from 0 to 300, 5000 Nri
When the amount is increased by '/Hr and reaches the level before deceleration, an amount commensurate with the amount of deceleration superacid is further added, and then the power restoration operation is performed.

By performing power restoration operations, it is possible to avoid the effects of decarburization and temperature rise caused by controlled deceleration operations to suppress abnormal decarburization.

[Effect] Hereinafter, the present invention will be explained based on actual examples.

FIG. 1 is an overall diagram showing a converter exhaust gas recovery control method according to the present invention, and a characteristic point is that an abnormal decarburization suppression block 21 is added to the conventional exhaust gas recovery control method.

The command from the abnormal decarburization suppression block 21 is added to the command from the oxygen flow rate program setting device 20 to become a setting signal for the superacid amount controller 19.

FIG. 2 is a detailed diagram of the abnormal decarburization suppression block 21 in FIG. 1.

The following description is based on the general diagram of the converter wandering gas recovery control method shown in FIG. As the converter refining progresses, the exhaust gas recovery control device 18 draws the generated exhaust gas into the recovery system using the exhaust gas induction fan 12, and gradually operates the damper to prevent gas from overflowing at the converter mouth 16. A command is issued to the device 5 to operate the exhaust gas regulating damper 4 in the opening direction. After 3 to 5 minutes have passed after the start of refining, the refining reaction mode becomes mainly a decarburization reaction (2G+02→2GO), and the decarburization reaction reaches its peak. At this time, the decarburization reaction may progress abnormally and generate exhaust gas that exceeds the exhaust gas recovery capacity for several minutes. The present invention is a technique for avoiding this phenomenon through the following control. In this case, the exhaust gas recovery control device 18 issues a command to the damper operating device 5 to fully open the exhaust gas adjustment damper 4, and when the exhaust gas adjustment damper 4 reaches the fully open region, the abnormal decarburization suppression block 21 A deceleration amount is added to the output value of the oxygen flow rate program setting device 20 to instruct narrowing down to one oxygen flow amount.

The peracid amount controller 19 slows down the amount of peracid supplied to the blown oxygen lance 7 based on this command. This control is 2C+O, →2
This suppresses the decarburization reaction of CO. When the abnormal decarburization continues and the reaction cannot be suppressed by the above-mentioned operation amount alone, the abnormal decarburization suppression block 21 issues a similar command again. By performing the deceleration operation an average of 2.5 times (25 seconds), the previous abnormal decarburization can be suppressed and the amount of exhaust gas generated can be kept within one recovery capacity.

Because the decarburization reaction of 2C102→2GO is rapidly suppressed due to the decrease in the amount of peracid, the exhaust gas recovery control system @18
A command is issued to the damper operating device 5 to move the exhaust gas adjusting damper 4 in the closing direction.

Due to this command, the state of the exhaust gas regulating damper 4 moves in the closed direction, so that it is out of the fully open region. Therefore, the abnormal decarburization suppression block 21 sends a command to the output side of the oxygen flow rate program setting device 20 to perform the process of restoring the amount of overacid narrowed down in the overacid amount recovery block in FIG. 2-3. , and operates in the direction of canceling out the amount of deceleration. The peracid amount regulator 19 restores the peracid from the oxygen lance 7 by blowing in the amount commanded from the abnormal decarburization suppression block 21, and has the effect of reinforcing the decarburization reaction. Abnormal decarburization suppression block 21
However, with the fully open area of the exhaust gas adjustment damper 4 as the threshold,
By decelerating the amount of superacid in the blown oxygen lance → reducing the amount → reducing the amount → returning the power, it works so that exhaust gas recovery control can always be performed within the recovery capacity.

[Example 3] Fig. 3 shows the results of exhaust gas recovery control based on the present invention. In conventional exhaust gas control, when the damper fully open region 4 is reached, a blowout 5 is generated from the furnace mouth, but according to the present invention, when the damper fully open region 4 is reached, the amount of superacid 1 is gradually narrowed down, so that the blowout is Exhaust gas recovery control can be realized without causing 5.

[Effects of the Invention] To describe the effects of the present invention as an example, since the present invention prevents converter exhaust gas from blowing out from the furnace mouth, the recovery unit of converter exhaust gas is reduced compared to before implementation. Approximately 2 N
rn'/t-611 (heat value converted to 2000 Kcal) was improved, and a considerable effect could be achieved. Furthermore, there was no extension of steelmaking time and no decrease in productivity.

[Brief explanation of drawings]

Fig. 1 is an overall diagram showing the converter exhaust gas recovery control method of the present invention. Fig. 2 is a detailed diagram of the abnormal decarburization control block 21 in Fig. 1. Fig. 3 is a comparison of the exhaust gas control method of the present invention with the conventional method. This is a diagram showing

Claims (1)

[Claims] In the exhaust gas recovery control method for oxygen converters, the occurrence of abnormal decarburization is detected by sensing when the damper for exhaust gas recovery adjustment is fully opened, and the amount of oxidation is reduced in stages, until the abnormal decarburization has subsided. A converter exhaust gas recovery control method characterized by restoring the amount of oxygen.