JPS60194007A - Converter blowing method - Google Patents

Abstract

PURPOSE:To obtain the best heating-up effect in the stage of top blowing oxygen from a top blowing lance and performing blowing during bottom blowing of a CO-contg. gas from a bottom blowing nozzle by adjusting the hole diameter and blowing speed of the bottom blowing nozzle and the denting condition of the molten metal surface arising from the top blowing of oxygen. CONSTITUTION:Blowing is performed by using a top and bottom blown converter in which a CO-contg. gas is bottom-blown from a bottom blowing nozzle and oxygen is top-blown from a top blowing lance. The hole diameter of said bottom blowing nozzle is set at 1-2 times the nozzle diameter (d) calculated from the equation and the CO-contg. gas is blown from the nozzle at a flow rate of >=0.2Nm<3>/min for each one ton of the molten steel. In the equation, Q; the flow rate (Nm<3>/min) of the bottom blowing gas for each one hole, H; the depth (cm) of the steel bath in the ignition part during blowing, d; the diameter (cm) of the bottom blowing nozzle. The height and oxygen blowing speed of the top blowing lance are so adjusted that the ratio between the dent depth (L) of the steel bath resulting from the top blown O2 jet and static depth (L0) attains >=0.6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a converter blowing method, and more specifically, the present invention relates to a converter blowing method, and in particular, the stirring of a steel bath is promoted by bottom blowing a CO-containing gas, and the copper bath is heated by secondary combustion of the blown CO gas. This is related to the bell blowing method that supplies heat to the

In recent years, there has been a growing demand for higher added value for steel products, and this has led to the elimination of P1 and S after steel extraction from converters in order to produce high-grade copper.
1. Degassing treatment is required.

In order to compensate for the temperature drop in these steps, the average blow-off temperature of converters is becoming higher than before. However, on the other hand, hot metal pretreatment technology aimed at reducing steelmaking costs is also being put into practical use, and desiliconization, dephosphorization, and desulfurization are becoming uniformly performed at the hot metal stage, and as a result, the heat source during converter operation is becoming more common. is on the decline. As a result, normally the blow-stop temperature is secured by lowering the scrap mixing ratio, but the difference between pig iron making, steel making, ingot making, and iron Ml! ! The hot metal supply and scrap consumption balances in the hot metal manufacturing process have been disrupted, and this is becoming a problem in terms of flexible response to crude steel production.

To deal with these problems, various companies are researching ways to increase the blow-off temperature by supplying an external heat source during converter blowing. Such heat source replenishment methods include, for example, (1) charging supplementary fuel (Fe-5is coal, coke, etc.) into the converter or injection into molten steel, (2) injection of liquid fuel, (2)
There is secondary combustion of CO gas generated during blowing, etc. Among these methods, method (2) above burns the supplementary fuel using top-blown oxygen and directly heats the molten steel with the combustion heat, and is extremely effective as a heating means, but Fe-5i
In addition to the problem of high cost in the method of using F6-8L, the sio
In order to compensate for the decrease in slag basicity, quicklime, etc. must be added to the slag, which imposes a double economic burden, and when coal or coke is used as supplementary fuel, The sulfur contained in these is retained in molten steel,
Significantly deteriorate quality. Under these circumstances, method (1) above aims to perform secondary combustion of CO generated during blowing and heat molten steel with the heat generated by this reaction.
At present, method (2) is becoming the mainstream for heat source supply because it does not cause the problems pointed out in methods (1) and (2) above. This method is explained in more detail: 1) A type in which the lance tip of the main lance is modified and oxygen for secondary combustion is injected separately from oxygen for decarburization; 11) A sub-lance is used separately from the main lance, and the sub-lance is There are two types: one type in which oxygen for secondary combustion is injected from the converter, and the other type in which oxygen for secondary combustion is injected by providing a wall at the converter mouth. By the way, the superiority or inferiority of this method depends on how efficiently the heat generated by secondary combustion is transferred to the molten steel, but in the methods l) to 1it) above,
Because secondary combustion occurs above the surface of the slag covering the molten steel surface, the combustion heat is not directly transferred to the molten steel, and the heat transfer efficiency to the molten steel is limited to about 60 to 70% at most, which is sufficient to satisfy the molten steel temperature. You can't raise it to that level. Moreover, since the heat of the exhaust gas blowing upwards in the converter becomes extremely high, there is a problem in that the refractories in the freeboard (the exposed part above the molten steel surface) are significantly eroded and their lifespan is shortened.

Under these circumstances, the inventors of the present invention chose the method (2) above.

We have begun to improve the method, and are now able to efficiently transfer the heat generated by the secondary combustion of CO to the molten steel to sufficiently raise the stop temperature, as well as suppress overheating in the upper part of the converter and extend its life. We have been conducting research in an attempt to establish various technologies. The present invention was completed as a result of such research, and its configuration uses a top-bottom blowing converter, and blows oxygen at the top from a top-blowing lance while bottom-blowing cobalt-containing gas from a bottom-blowing nozzle. When performing refining, the hole diameter of the bottom blowing nozzle is set to 1 to 2 times the nozzle diameter calculated from the following CI) formula, and the melt f! Co-containing gas is injected with a current of at least 0.20 Ntn3/ml n per ton of A, and the specific force (0 ,6
As described above, the gist is that blowing is performed by adjusting the height of the one-hagi lance and the oxygen supply rate.

d=80・Q・(1/1()1・5...(I) However, Q: Bottom blowing gas flow per hole 1kCNm3/m1n) H: Depth of the steel bath to the center of the fire point during blowing (crn) d: Bottom blowing nozzle diameter (crn) The configuration and effects of the present invention will be explained in detail below with reference to the drawings of the embodiments. FIG. 1 is a schematic vertical cross-sectional explanatory view illustrating the converter blowing method of the present invention, in which a converter 1 having two bottom blowing nozzles 2a and 2b at the bottom is used, and hot metal is charged into the converter 1. Blowing is proceeded by blowing oxygen from the top blowing lance 8 while bottom blowing the co-containing gas from the bottom blowing nozzles 2a and 2b. The target position for the improvement blow is co.
It is common to superimpose it on the floating position of the contained gas,
And the most effective. In Fig. 1, two low-blow nozzles and two top-blow lance nozzles are used to dynamically increase the blowing brocade efficiency and temperature raising efficiency, but as shown in Fig. 2. Of course, it is also possible to provide one nozzle for each to perform upward and downward blowing. In any case, in the present invention, CO-containing gas is supplied from the bottom-blowing nozzles 2a, 2b (or reference numeral 2 in FIG. 2), and oxygen is blown upward to generate heat generated by the reaction of [CO+1/20□-Co2:]. The idea was to simplify the temperature rise of the 1iM solution by using the above (in the figure, S indicates slag), but after conducting various laboratory-scale studies, the following facts became clear. First, in order to efficiently burn CO in the bottom-blown gas and top-blown oxygen on the surface of the molten steel, and to efficiently transfer the generated combustion heat to the molten steel M, it is necessary to It is better to blow the CO-containing gas from the bottom toward the position where it hits the surface of the molten steel and causes a reaction with C in the molten steel. A (the so-called atrium state) should be blown from the bottom.However, if the CO-containing gas is blown softly from the bottom so that a bubbling state is formed, the area around the fire point position will be blown before the CO rises to the surface. The amount of reaction with top-blown oxygen on the surface of the molten steel decreases, making it impossible to obtain a temperature-raising effect corresponding to the amount of blowing.However, if CO-containing gas is floated in a blow-through state, CO Since it is intensively supplied to the ignition point and immediately reacts with the top-blown oxygen on the surface of the molten fRM, it is thought that the generated reaction heat is efficiently transferred to the molten steel M, resulting in an excellent temperature-raising effect.

Based on this knowledge, we conducted further research in an attempt to clarify the converter operating conditions that would allow us to obtain the excellent temperature-raising effect described above.
It has become clear that if the concave condition of the surface caused by top-blowing of oxygen is properly smoothed out, the best temperature-raising effect can be obtained depending on the amount of bottom-blowing CO.

First of all, the conditions for making the CO-containing gas float to the surface in the open air state include the gas flow rate, the hole diameter of the bottom blowing nozzle, and the depth of the steel bath. In order to move the atrium to the oxygen fire point position, the hole diameter [d (crn)] of the bottom blow nozzle must be adjusted to the above [d(crn)].
The value calculated from formula 13 should be 1 to 2 times, and the flow rate of bottom blowing gas should be 0.20 Nyyz3/per ton of melt #11.
It was confirmed that the value should be greater than or equal to min. However, if the hole diameter of the nozzle is too large, the blown gas will be in a bubbling state and will diffuse around the fire point position, so the features of the present invention will not be effectively exhibited.On the other hand, if the nozzle diameter is too small,
The necessary length of the atrium and the need for extremely high pressure to secure the gas volume make it impractical.

In addition, the flow rate of the bottom blowing gas is 5, if the absolute amount as a heat source is secured, and the lower limit is determined to ensure the length of the specified blowout, which is 0°20 N m3/ (min @ molten copper If the amount is less than 1 ton, the absolute amount will be insufficient and it will not be possible to raise the temperature of the molten steel sufficiently, and the length of the blowhole will be insufficient and it will not be possible to intensively supply CO to the ignition point position.

Furthermore, the degree of upward blowing of oxygen from the top blowing nozzle is determined by displacing the slag floating on the surface of the molten steel and bringing the oxygen into direct contact with the molten steel, and by increasing the depth of the dent in the molten steel to reach the depth of the molten steel just below the flash point. Figures 1 and 2 and the symbol H of the above CI) formula
), and the atrium is extremely important in bringing the bottom-blown CO gas close to the state into contact with the top-blown oxygen.
As shown in Figure 2, the height of the top blowing lance and the oxygen delivery rate should be adjusted so that the depression depth of the hot water surface (g) and the static depth of the steel bath (Lo) are 0.6 or more. This was confirmed. In this case, it is difficult to check the depression depth L) of the hot water surface from the outside during blowing, but this value can be found almost accurately using the calculation formula shown below.

L=Lh@eXP(-0,78h/Lh) -CI)L
h= ea, o (k-v/n-D)"・rm〕2 L: Dent depth ms) h: Lance height bait) Fo2: Top-blown oxygen flow 11 (Nm3/hr) n: Lance hole The diameter of the lance hole (fin) k: The coefficient depending on the oxygen injection angle and the static depth of the steel bath (Lo) can be calculated from the charged amount of hot metal and scrap, so the lance height and top blowing Control the oxygen flow rate to adjust the depth of the depression on the hot water surface ■
By adjusting the value of L/L0, the value of L/L0 can be easily set to 0.60.
You can do more than that.

The present invention is constructed as described above, and its effects can be summarized as follows.

■Oxygen is blown upward so that the amount of depression on the hot water surface is greater than a predetermined value, and the CO-containing gas is passed through to the ignition point of the top blown oxygen in a state close to that of a blow-through, so that the bottom blown CO
Almost all of the O reacts with oxygen at the flame point, and the reaction heat is efficiently transferred to the molten steel. Therefore, the temperature of molten steel can be effectively raised according to the amount of bottom-blown CO.

■Most of the CO supplied as a heat supply source burns near the hot water surface and does not escape to the top of the converter and then burn to generate reaction heat, so the fireproof wall at the top of the converter is There is no risk of overheating (no problems such as shortening of F? life). There is no risk of an increase in 5ijl or Sjl in the molten steel, unlike methods that use Fe-8i, coal, coke, etc. as a heat source. Therefore, since there is no need to increase the amount of 7 lux, it can be applied to slagless or slag minimum operation without any problem.

Next, experimental examples will be given to further clarify the effects of the present invention.

Experimental example A test converter with one bottom blowing nozzle installed in the center of the furnace bottom (
Using a top blow lance 8 (single hole nozzle, 5.
A Fukitoge experiment was carried out by top-blowing wIRφ). The conditions for improved bottom blowing were as follows.

Resting depth of copper bath (Lo): 40G Cod top blowing lance hole diameter (Lo): 5. On + lance height h
): 400 cod top-blown oxygen flow rate (Fg2): 1.6 Nm/mx
nThe value of (L/Lo> calculated by substituting these values into the formula [■)t(m) is 0.69, which satisfies the requirements of the present invention, and the position of the flame point of top-blown oxygen The depth of the copper bath (to the right below) is 890 x (1-0,69) = 12
It will be in 1st key.

Also, the CO gas flow rate from the bottom blowing nozzle 2 (Q is 0.8ON
m3/min, and this is the depth of the copper bath just below the fire point H.
:121mm) into the above formula (I), d=
2.1 (m), the hole diameter of the bottom blowing nozzle is
It was set to 2.5 vtm', which is 1 to 2 times the above d.

Other operating conditions are shown in Table 1, and operating results are shown in Tables 2 and 8.
Shown in the table.

Table 1 and for comparison, a similar blowing pass experiment was conducted in the same manner as above except that the operating conditions shown in Table 4 below were adopted, with Ar gas being bottom blown from the bottom blowing nozzle.

Table 4 Operating conditions The results are shown in Tables 5 and 6.

In order to simply compare the effect of the present invention (Co bottom blowing method) with the comparative method (Ar bottom blowing method) in the above experiment, Table 2 and Table 5.
If we compare the blow-stopping molten steel temperature in the table, especially the temperature difference (amount of temperature rise due to converter blowing heel), in the Ar bottom blowing method, the temperature difference is +
885°C, whereas the method of the present invention lowers the temperature by 85°C.
A high temperature increase of +870°C was obtained.

Note that this temperature difference is based only on the molten steel temperature at the time of blow-stopping, but when other factors that affect the molten steel temperature are compared in more detail, the temperature difference between the present invention method and the comparative method is as explained below. will become even more popular.

In other words, the temperature rise during converter blowing is determined by: (1) consumption of combustible elements in the hot metal, in other words, calorific value due to combustion of the elements, (2) auxiliary raw materials (
Temperature loss due to heating of flux), Fe in slag
Since it also changes depending on the temperature increase loss due to O, these effects were also compared.

■Calorific value due to combustion of combustible elements in hot metal Table 2 (CO
From Table 5 (Gas bottom blowing method) and Table 5 (Ar gas bottom blowing method), when comparing the consumption of combustible elements during blowing and the heat generation ff1 (equivalent to tapping temperature) by each method, the seventh It is as shown in the table.

Table 7 When the output end temperature conversion values in Table 7 are combined, the result is +8.8°C. That is, assuming that the thermal efficiency is 1oo96, the amount of temperature increase due to combustion of the combustible element should be 8.8° C. higher in the Ar bottom blowing method than in the Co bottom blowing method.

■Temperature rise loss due to heating of auxiliary raw materials The amount of auxiliary raw materials (quicklime + lightly calcined dolomite + rubble stone) used is 82.0 kg for the Ar bottom blowing method and 29.0 kg for the Co bottom blowing method.
2 Kf, the former is 2.8 xg more. Converting this to the tapping temperature is 8.8°C, and the Ar bottom blowing method has a larger temperature increase loss.

■Temperature rise due to reaction heat of FeO formation in slag From Tables 8 and 5, the difference in (T, Fe) in the slag is calculated as follows: (T, Fe) (T-Fe) Co method Ar method = 16 .10-14.22 = 1.88%,
Converting this to the difference in FeOjl, (Fed) = (
T, Fe) X 1.29 = 1.88 X 1
．． 29=2.48 (*). If the difference in F60 fi is converted into the tapping temperature - 2.48 x 4.8 = 10.4 C"C'), it becomes 2.48 The temperature must be 10.4° C. higher for the Ar bottom blowing method.

Comprehending the effects on the tapping temperature shown in ■ to ■ above, (+
8.8-8.8+I O,4) = 9.8, and assuming the thermal efficiency is 10096, the tapping temperature is 9 for the Ar bottom blowing method.
．． It should be 8℃ higher. However, the actual temperature rise of molten steel is 86°C higher with the CO bottom blowing method (method of the present invention).
In the end, the theoretical temperature increase according to the present invention is (86+9.8)=
44.8('C), c.

It can be seen that the temperature increase effect due to bottom blowing is larger than the actual value.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory longitudinal cross-sectional views showing a converter blowing condition according to the present invention. l...Converter, 2.2a, 2b...bottom blowing nozzle, 8...top blowing lance〇Applicant Kobe A Steel Works Co., Ltd.

Claims (1)

[Claims] When using a top-bottom blowing converter and blowing CO-containing gas from the bottom-blowing nozzle and top-blowing oxygen from the top-blowing lance, the hole diameter of the bottom-blowing nozzle is determined as follows ( I) Set it to 1 to 2 times the nozzle diameter calculated from the formula, and
0.20 Nm3/m per ton of melt from the nozzle
Blow CO-containing gas at a flow rate of in or more, and top blow 02
Perform blowing by adjusting the height of the top blowing lance and the oxygen supply rate so that the ratio of the depth of depression in the steel bath due to the jet (L) to the static depth of the steel bath (Lo) is 0.6 or more). The converter blowing pass method is characterized by: d=30・Q-(1/H)'°5 ... [I] However, Q
:1 bottom-blown gas flow per hole! (Net3/m1n
) ■: Depth of the steel bath at the hot spot in the blowgun (crn) d = Bottom blowing nozzle diameter (6n)