JPH02156012A - Method for reducing dust in exhaust gas in converter blowing - Google Patents

Abstract

PURPOSE:To suitably restrain generating rate of dust in exhaust gas by continuously measuring the generating rate of the dust in the exhaust gas, rising the lance height when the generating speed of the dust becomes more than the setting upper limit value and mixing inert gas into top blowing gas. CONSTITUTION:In the blowing with a combined blowing converter 1, the flow rate of the exhaust gas is measured at downstream of a flue 5. On the way of the flue 5, the exhaust gas and the dust are sucked with a suction pipe 6 and introduced to a dust concn. meter 7 to measure the generating rate of the dust. From the values of this dust concn. and the exhaust gas flow rate, the generating speed of the dust is continuously displayed to the dust generating rate detector and controller 9. At the time of exceeding the setting value of the generating speed of the dust or the setting pattern, the height of the lance top-blowing the oxygen is risen. At the same time, the inert gas is mixed into the top blown oxygen gas. By this method, the generating ratio of the dust in the exhaust gas is reduced and the yield of the steelmaking is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for reducing dust in exhaust gas in converter blowing.

<Prior art> Dust in the exhaust gas generated during converter refining is composed of Hiem dust, which is the evaporation of metal components in molten iron, and bubbles generated by supplying oxygen gas to the steel bath using methods such as top blowing or bottom blowing. It is broadly classified into burst type dust.

In order to suppress dust in the exhaust gas generated during converter refining, methods such as lowering the height of the top blowing lance and enlarging the hole diameter of the top blowing lance are well known. However, these methods cannot detect dust generation without waiting time, so they cannot be a timely and appropriate control measure for dust suppression. also affects other metallurgical operating factors, so
Dust suppression may not always be the top priority.

Furthermore, in Japanese Patent Application Laid-Open No. 60-262912, Dust Brother 1
A method is disclosed in which the lance height is changed according to information on the dust generation rate from the lance, or water vapor is sprayed from the lance. However, the appropriate lance height is determined not only by the amount of dust, but also by the metallurgical factors of the pond, as mentioned above.In addition, spraying water vapor significantly increases the hydrogen concentration in the steel.
It becomes necessary to provide additional axilons for dehydrogenation. It is necessary to avoid operations that reduce decarburization oxygen efficiency or introduce impurity components into the steel.

<Problem to be solved by the invention> In converter blowing, even if the oxygen supply pattern and lance height are the same, if the molten iron composition, temperature, and timing of adding auxiliary materials are changed, the blowing behavior will be different. Therefore, the amount of dust generated will also vary. Each blowing process is different, and under unfavorable conditions, there are often cases in which the above-mentioned conventional techniques are not very effective.

The present invention solves the problems of the prior art described above, detects dust I in the exhaust gas generated during converter blowing in almost real time, and thereby suppresses the amount of dust generated in the exhaust gas in a timely and appropriate manner. It is an object of the present invention to provide a method for reducing dust in exhaust gas in converter blowing, which can improve the process and also sufficiently deal with non-reproducibility of blowing.

Means for Solving the Problems> The method for reducing dust in exhaust gas in converter blowing of the present invention to achieve the above object continuously measures the rate of dust generation in exhaust gas in converter blowing. , when the measured value exceeds the upper limit set for the dust generation rate, the height of the lance for upward blowing of oxygen gas is raised, and at the same time, an inert gas is mixed with the oxygen gas blowing upward from the lance. It is characterized by training.

As mentioned above, in order to carry out the present invention, it is necessary to: i) measure the dust flow during blowing in real time;

ii) Determine whether an arbitrarily set dust scene upper limit value has been exceeded.

iii) Take control measures when excess das1-fit occurs.

It is necessary. Furthermore, the measures to be taken in case of excessive dust amount are: i) Raise the height of the top blowing lance.

it) 0 from the top blowing lance to the steel bath, N inside!
.

^ ``Or mix in an inert gas such as COl.

The present invention requires a device (hereinafter referred to as a dust meter) that continuously measures the amount of dust generated. The dust in the flue gas may be collected in the converter flue gas flue or inside the furnace.The probe for dust collection is water-cooled or air-cooled, and the dust is kept in the probe until it is introduced into the dust meter. The structure should be such that it does not accumulate.

There are various types of dust meters, such as light transmission type or scattering type measuring devices that aspirate sample gas and measure the sample gas optically, measuring devices using ultrasonic waves, and measuring devices using radiation, which one should you use? Even in such cases, the amount of dust generated can be determined by knowing the flow rate of the exhaust gas entrained with dust and the dust concentration in the exhaust gas.

In this way, the amount of dust generated is continuously measured during converter blowing, and when the amount exceeds an arbitrary set value, suppression measures are taken. There are various suppression measures, but the most sensitive response can be achieved when the following two measures are taken at the same time.

) Increasing the top blowing lance height The lance height is increased to the extent that other operating factors do not change significantly from the normal lance height setting. If the amount of dust generated still exceeds the set value, the lance height is raised again to gradually reduce the amount of dust generated.

ii) Top blow 0! Inert mixed gasification and changing of the mixed gas ratio cool the fire point with a top-blown gas jet to achieve dust rot control. Vary the inert gas mixture ratio depending on the set dust bond or rate of increase in generated dust bond. 0 depending on the type of gas. and change the ratio of mixed gas.

As the inert mixed gas, there is NZ+Ar+cot, and after the amount of dust generation decreases, the ratio of the mixed gas may be lowered or pure oxygen gas may be used.

In any case, the dust suppression method according to the present invention continuously measures the dust generation π without deteriorating the metallurgical properties, and when the dust generation rate exceeds the set upper limit value, the above-mentioned two dust suppression methods are applied. Actions are taken at the same time. The set upper limit value is constant throughout the blowing time, but °ζ may also be changed depending on the blowing time.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. 1st
In the figure, 2BOL of molten iron 2 is charged into the top and bottom blowing converter 1, and 0.0BOL of pure molten iron is charged from the bottom blowing tuyere 3. Gas is blown into the molten iron 2, and normally pure 02 gas is blown onto the molten iron 2 from the top blowing lance 4 for blowing.

The pure Ot gas supplied to the lance 4 is controlled by a valve tea, but it is possible to mix inert gas through a valve tab.

In addition, the height of the lance 4 can also be changed, and in this example, pure Shima gas was blown in at 16 ONd/gu from the bottom blowing tuyere 3, and normal pure Ot gas was blown in at 550 to 750 Nd/gu from the top blowing lance 4. The lance height is set to 2 when the amount of dust is below the set value.
．． It was set to 5m. The exhaust gas and dust pass through the exhaust gas flue 5, are cooled with water, and then separated.

The exhaust gas flow rate is measured downstream of the flue 5. i.e. flue 5
During the process, exhaust gas and dust are sucked in by a suction pipe 6 and introduced into a dust concentration meter 7 to measure the amount of dust generated. The dust concentration meter 7 is of a light nk scattering type.

Based on the dust concentration continuously measured by the dust concentration meter 7 and the value of the exhaust gas flow meter (not shown) installed downstream of the flue 5, the dust generation rate is continuously detected and controlled.Total 9 will be displayed. The dust generation amount detection and control meter 9 also has the role of a control meter, and instructs to change the lance height and the mixed gas ratio for top blowing according to the set amount or set pattern of the dust generation rate. Note that 8 indicates a cable.

Figure 2 shows the change over time in the dust generation rate of the inventive example obtained in the above system along with that of the comparative example.In the comparative example (2), the lance height was set to 2.0 mm at the same gas flow rate as in the example. 5
When m was kept constant, the amount of dust generated gradually increased after the start of blowing, and after about 7 minutes, the upper limit set by the present invention was 4 kg/m/m.
At a high level exceeding l, the value becomes almost constant, and in the second half of blowing 1
It starts to decrease after about 5 minutes.

On the other hand, in the example, the dust generation rate was 4 kg/am/
When the set upper limit of l is exceeded, the pure O of top blowing lance 4 is
CO in t gas! The gases are mixed at a ratio of ox/co□=4/1, and the lance height from the surface of the molten iron 2 is 2.5.
m to 3.0 m, and this state was continued for a period of ■.

As a result, the dust generation rate decreased, so in the following period ■, CO□ mixing in the top blowing lance 4 was discontinued, and the height of the lance 4 was lowered from 3.0 m to the original 2.5 m, so that only pure island gas could be used. We performed blowing. During the period (2), the dust generation rate gradually increased, and the dust generation rate exceeded 4 kg/m/L again, so the top blowing lance 4 was pure 0! Add Ar gas to the gas
While mixing at a ratio of /Ar=3/4, the height of the lance 4 was raised from 2.5 m to 2.9 m, and period C was continued in this state. Then, at the end of the blowing period after the CM period, the lance height was returned to the normal height of 2.5 m, but since it was the end of the blowing period, the dust generation rate remained below 4 kg/m/.

In Comparative Example (2), the same oxygen supply pattern as in the Example was used, and only the lance height was increased from 2.5 m to 3.0 m at the time of (3). However, the amount of dust generated did not fall below the set upper limit. Therefore, at the time of ■, CO was sent to top-blown Junshima gas as Axigon! Although gas was mixed at a ratio of 3/1, dust was not suppressed. That is, the lance height rise and H2, Ar.

It can be seen that CO2 must be mixed into 02 at the same time.

In order to clarify the present invention example and comparative example explained above,
I! Table 1 shows the basic conditions and their effects.

Table 1 shows that the method of the present invention makes it possible to freely control the dust generation rate without adversely affecting the metallurgical reaction compared to the method of the comparative example, and the dust generation rate can be kept below the set upper limit. It can be seen that the layers can be suppressed.

<Effects of the Invention> As explained above, according to the method of the present invention, the dust generation layer in the exhaust gas during converter blowing can be significantly reduced, the steelmaking yield can be improved, and the labor spent on dust treatment can be reduced. You can get the effect of being able to work.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a graph showing changes in dust generation rate over time during the blowing process for the present invention and a comparative example. 5... Wandering girth flue, 6... tJP gas and dust suction pipe, 7... Dust concentration meter, 8... Cable, 9... Dust generation agitation detection and control fl meter, 10... ·valve.

Claims (1)

[Claims] In converter blowing, the dust generation rate in the exhaust gas is continuously measured, and when the measured value exceeds the upper limit set for the dust generation rate, the height of the lance for upward blowing of oxygen gas is raised. A method for reducing dust in exhaust gas in converter blowing, characterized by simultaneously blowing by mixing an inert gas with oxygen gas blown upward from the lance.