JPH04103706A - Method for controlling end-point carbon concentration in top and bottom-blown converter - 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 (Industrial Field of Application) The present invention relates to a blowing end point control method by dynamic control of a converter, in particular, a blowing end point control method using a top-bottom blowing converter to control the amount of carbon at the end point of blowing and the amount of oxygen blown into the converter. and a method for controlling end point carbon concentration by adjusting the amount of coolant input.

(Conventional technology) Even in conventional top-blowing converter blowing, the end point molten steel carbon content,
The next most important task is to bring the molten steel temperature halfway to the target value. Therefore, during blowing, the Guinamisoku end point control method was developed to measure the flow rate and analyze the components of the exhaust gas from the converter, measure the molten steel temperature using a sublance, and measure the amount of carbon in the steel, and modify the blowing conditions based on these measurements. has been done.

Examples of such control methods include the following methods.

(1) A method (special Publication No. 61-54842, No. 61-5484
Publication No. 3).

(2) Starting from the measured values of the molten steel temperature and carbon content at any point during blowing, the molten steel temperature changes based on the exhaust gas flow rate and exhaust gas analysis values measured from time to time, the amount of oxygen supplied, and the gas generated from the auxiliary raw materials input into the furnace. , the change in carbon content and the change in oxygen content in the slag are determined, and compared with the trajectory estimated from the equation for each change calculated in advance, control is performed to minimize the difference between the two, and the target temperature at the end point is determined. A method of estimating the amount of blown oxygen and amount of coolant input necessary for the amount of carbon and performing lance operation (Japanese Patent Publication No. 58-56002).

(3) Measure the respective concentrations of CE1CO2 and N2 in the exhaust gas during converter blowing, and calculate the secondary combustion efficiency of CO in the converter based on those measured values. A method of comparing the secondary combustion efficiency and adjusting the amount of coolant and oxygen supply according to the deviation (Japanese Patent Laid-Open No. 62-224623
Publication No.).

(4) During the blowing period, when the molten steel carbon concentration is 0.1% or more, measure the molten steel carbon concentration with a sublance and estimate the oxygen concentration from that value. The oxygen concentration of molten steel at the end point of blowing is measured from the oxygen concentration increment Δ[01, and the converter blowing control method (JP-A-62-565
Publication No. 11).

(Problem B to be Solved by the Invention) However, these conventional methods have drawbacks such as problems in control accuracy and expensive equipment required for control. Particularly when applied to a top-bottom blowing converter, there was a problem with its accuracy.

That is, the methods (1) and (4) in the previous section do not take into account the bottom blow rate, the fluctuation of the lance action, etc. at the end of blowing, and therefore there is a risk that the control accuracy will be lowered.

In the methods (2) and (3), the control accuracy is good, but the equipment investment is high because of the component analysis of the exhaust gas.

Thus, an object of the present invention is to provide an inexpensive and highly accurate method of controlling end point carbon content in a top-bottom blowing converter.

(Means for Solving the Problem) As a result of various studies to achieve the above object, the present inventors focused on the method (1) described above, simplified the temperature increase rate equation, and calculated the end point oxygen amount. By correlating the end point carbon concentration, we learned that it is effective to simultaneously control the oxygen supply amount and coolant input amount based on the measurement data of molten steel temperature and carbon content, and completed the present invention. did.

Here, the gist of the present invention is to express the oxygen consumption rate at the end of blowing in a top-bottom blowing converter by a polynomial of the carbon content in the steel; The carbon concentration in the obtained steel C8, the required amount of blown oxygen ΔO2 from that point to the end point of blowing, the carbon concentration CE in steel at the end point of blowing, and the amount of coolant WcL introduced during blowing. Determining the correlation equation of the variables of the polynomial based on the data; each time the blowing is performed, the carbon concentration CS in the steel obtained by sublance measurement at an appropriate time before the end point of the blowing, and the target end point carbon concentration CE are calculated from the polynomial. Calculate the required amount of blown oxygen from the point to the end point of blowing; and take into account the reduction efficiency for the coolant that has been added, correct the contributing oxygen amount, and calculate the required amount of oxygen based on this calculation result. This is a method for controlling the end point carbon concentration in a top-bottom blowing converter, which consists of: correcting the amount of oxygen;

As mentioned above, in order to obtain the carbon concentration blowing control equation that indicates the required amount of blown oxygen after coolant is introduced, first collect data for each case without coolant, and then calculate the oxygen consumption rate equation and the variation factor correlation equation. Then, collect data when coolant is introduced after the sublance measurement, calculate the reduction rate of the coolant, and create a relational expression between the end point carbon concentration and the oxygen amount ΔO2 when these operating factors change.

The final stage of blowing is not particularly limited, but -C refers to 15 minutes until the end of blowing.

More specifically, the nodal point carbon concentration control method according to the present invention expresses the oxygen consumption rate and temperature increase rate at the end of blowing by a polynomial of the reciprocal of the carbon concentration in the steel in the top-bottom blowing converter operation. In addition, from the carbon content CS in the steel obtained by sublance measurement at an appropriate time before the end of blowing, the molten steel temperature TS, the amount of oxygen blown into the steel ΔO2 from the said time to the end point of blowing, the amount of temperature increase ΔT, and the amount of temperature increase during the period. iron ore, scale,
Including the amount of cold material such as Mn ore WCL, the carbon concentration CE at the end of blowing, the scrap content ratio, the sublance measurement temperature at the end of blowing, the flow rate of bottom blowing gas, the distance between the lance and the hot water surface, and the amount of input solvent, A formula expressing the correlation between these variables is found, and the target carbon content C4 and target temperature T are determined from the carbon content in the steel and the molten steel temperature obtained by sublance measurement at an appropriate time before the predicted blowing end point for each blowing. Then, the required oxygen injection amount and coolant input amount until the end of blowing are calculated from the above correlation equation, and operations are performed based on the calculation results.

(Function) The amount of coolant input is determined by comparing the target molten steel temperature with the calculated end point molten steel temperature, and the required amount of blown oxygen is calculated in consideration of the coolant input amount.

Next, the present invention will be described in more detail with reference to the accompanying drawings.

First, the blowing control method of the present invention is shown in a flowchart in FIG. FIG. 1(a) shows an example of how the carbon concentration blowing control formula is determined, and FIG. 1(b) shows an example of how the formula is used in actual operation.

As is clear from FIG. 1(a), according to the present invention, a dynamic control formula, that is, an oxygen consumption rate formula is determined in advance, and on the other hand, a relational formula between end point oxygen and end point carbon concentration is determined from past operational results. , based on which the above control equation is corrected.

That is, as shown in FIG. 1(a), the oxygen consumption rate (per molten till) at the final stage of blowing is set as shown in the following equation.

l dO□ W, t dC an-, at: constant related to the operating factors in the previous section C: carbon content in steel (% by weight) Wst: molten steel weight (1).

Integrating from the carbon content in steel C8 (t) at the time of sublance measurement to the carbon content in steel 06~ at the end of blowing, the basic unit Fo (Nm”/l) required for decarburization is Fll (C3ICE)
=ao(CS-CH)+a+log(CS/CH)
+ + + (2). Here, in Equation (2), F from past blowing performance data when no coolant is input from the time of sublance measurement to the end point.
By substituting o, C5, and GE, respectively, determine the optimal values of ao and al.

Next, 6Fo(C3, Ci
)=F6' (CS, Cx)+Σhot(Xi-Xj
k)+P,.

・ ・ ・(3) Here, F o (CS +6): Oxygen consumption after sublance measurement xi: Blowing factor variable Xik: Blowing factor variable reference value Fo' (C5ICE): On the right side of equation (2) ao, a
The value F++o obtained by substituting l is a constant based on the results of the most recent 40 charges.

The blowing factor variable (Xj) is a variable determined by the distance between the lance hot water surfaces, the molten steel temperature at the time of sub-lance measurement, the converted CaO amount input before blowing and before and during blowing, the bottom blowing gas flow rate, etc. , these variables have not been considered in the past.

The optimum value of the influence coefficient hot is determined by substituting actual data into equation (3) in the same manner as in equation (1).

According to a preferred embodiment of the invention, Xi is expressed as follows.

h0 quicklime (X actor life lime - X entertainer life lime reference value) + h
o S/L temperature (Xszt temperature - 13/L temperature reference value)
+h, bottom blowing gas (X bottom blowing gas amount - X bottom blowing gas amount reference value)
+ho Lance hot water surface (X lance hot water surface distance - X lance hot water surface distance standard value) By the way, control of the target 7-water temperature is also necessary from a practical standpoint, and the coolant temperature is an important factor in controlling this. There is an input amount. Therefore, when the coolant is introduced, the required amount of oxygen to be blown needs to be corrected from that point.

First, the temperature increase rate dT/dC is set as shown in the following equation.

to dC Here, (T: molten steel temperature 'C).

Integrating from the carbon content in steel C5(1) at the time of sublancing measurement to the carbon content in steel C6(1) at the end of blowing, the temperature increase ΔT is as follows: ΔT-4E-To=b, (C5-CE) +bllOg(
C5/CE) ・ ・ (5). TE is the end point molten steel temperature, and To is the molten steel temperature at the time of sublance measurement.

Here, in the same manner as described above, the blowing performance data Δ
Substitute T, C3, and GE to determine the optimal values of bo and b+. Next, the relational expression with operational factors is quantified as shown below.

△T = (Tr-TS) =-△T' (C5, CE
)+Σfly, (Xi-Xik)+F, 7...
(6) Here, ΔT: Amount of temperature rise after sublance measurement (C) ΔT゛: Equation (5
) on the right side of Value obtained by substituting sb+ F87: Coefficient based on the results of the last 40 charges, ...: Influence coefficient.

The blowing variation factors are the same as for the oxygen consumption rate. This greatly improves control accuracy.

Next, similarly, from the time of sublance measurement to the end point, blowing data when coolant is introduced and the previously determined a, ~a,, bo ~b +, ho+-hy=
Using the values of , the required amount of blown oxygen (Fo) and the amount of change in molten steel temperature, that is, the amount of temperature rise ΔT are determined as follows.

F+) −(CS, C+:) −poo(CS, CE
)+Σhoi (Xi-Xtk)+Σr o;R;+F
ao HHH(71ΔT=(TE-7s)=Δding'
(CS, Cz) + Σhy* (Xi-Xik) + ΣT a, R, + FfiT ・ ・ ・ (8) Two points, γ. ,
is a coefficient corresponding to the reduction rate of the coolant, and Ri is the basic unit of the coolant.

In fact, based on actual results, these 7oi, 1 gun.

Find the optimal value of.

Based on these data, the carbon concentration blowing control formula is finally determined.

Next, referring to the flowchart of FIG. 1(b), the specific operation sequence of the end point control method according to the present invention will be described.

The end point target carbon content (Cid) and end point target temperature (Tit) are determined for each blowing steel type.Based on the molten steel carbon content CS and molten steel temperature TS measured by the sublance during blowing,
Given TS, CS, and Cty based on equation (6),
Find T.

Here, if h>Tit, an instruction is issued to introduce a coolant such as scale or iron ore. The scale input amount and iron ore input amount are determined by formula (8), but if the scale input amount exceeds 10 kg/l, the coolant can be input during blowing if the remaining amount is used as the iron ore input instruction. .

Next, calculate the oxygen content of the indicated input scale amount and iron ore amount using the formula (
7) to determine the required top-blown oxygen amount F. Calculate and determine the timing of blowing.

Also, if TI=TET, no coolant input instruction is issued,
The required top-blowing oxygen amount P is calculated from equation (3) in the same manner as above.

In addition, in the case of TE<TEt, in equation (6), TEa, TS,
Substitute CS and re-revise the final target carbon concentration GET.

Next, using the obtained CEa, the required top blown oxygen 1iLFo
is calculated using equation (3).

Based on the input coolant amount and the required top-blowing oxygen amount thus obtained, the blowing is terminated.

At the same time as blowing ends, the end point temperature and end point carbon content are measured using a sub-lance, ho+FIT in equations (7) and (8) are updated, and the next blowing is performed.

Next, the present invention will be explained in more detail with reference to Examples.

(Example) An example of a 250-hole top-bottom blowing converter using the control method according to the present invention will be shown.

First, the oxygen consumption curve and temperature increase rate equations (2), (3), (
The optimum values for the coefficients 5), (6), (7), and (8) were found as shown in Table 1 based on the actual results of 150 charges.

The offline blowing calculation results based on the above coefficients are shown in Figure 2 (a) and (b).
90.2% in Nm3, temperature guys:! : 86.3% within 12'C, and the simultaneous success rate was 84.3%.

Figure 3 shows the accuracy of blowing control based on these coefficients.
Shown in a) and (b). End point ICi accuracy is 90.2% within ±0.02%, temperature range 82.3% within ±12°C
82.3% of those who did so at the same time.

This blowing control method has made it possible to achieve high-precision blowing at low cost, speeding up the blowing operation, and greatly improving the no-overturn furnace release ratio.

(Effects of the Invention) As explained above, according to the method of the present invention, the amount of carbon at the end of blowing can be controlled at low cost and with high precision, prevention of component deviation, and rapid steel tapping without blowing. This greatly contributes to improving production efficiency, improving quality, and reducing the unit consumption of refractories.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) show flowcharts of the determination of the carbon concentration blowing control formula and the control operation in actual operation, respectively, of the blowing control method of the present invention. FIGS. 2(a) and 2(b) are graphs showing a comparison between the estimated value and the actual value of the oxygen consumption unit male temperature rise from the time of sublance measurement to the end point, respectively, by off-line analysis. FIG. 3(a), 0)) is a graph showing the online accuracy of the end point carbon concentration and the end point 'If degree, respectively. Figure 1(a)

Claims (2)

[Claims] (1) Expressing the oxygen consumption rate at the end of blowing in a top-bottom blowing converter as a polynomial of the carbon content in the steel; Required amount of blown oxygen ΔO_2 from this point to the end point of blowing, carbon concentration in steel C_ at the end point of blowing
Determining the correlation equation of the variables of the polynomial based on the actual data of E and the amount of coolant input during blowing W_C_L; Each time of blowing, the steel obtained by sublance measurement at an appropriate time before the end point of blowing. Calculate the required amount of blown oxygen ΔO_2 from the above-mentioned time point to the blowing end point from the above-mentioned polynomial as the carbon concentration C_S in the fuel and the target end-point carbon concentration C_E; and take into account the reduction efficiency for the coolant introduced. and correcting the contributing oxygen amount and correcting the required oxygen amount based on the calculated result. (2) Measure the carbon concentration C_S and temperature T_S in the steel by sublance measurement at an appropriate point before the end point of blowing in the top-bottom blowing converter, calculate the end point molten steel temperature T_E,
The top-bottom blowing operation comprises controlling the blowing operation according to the required amount of blown oxygen determined according to claim 1 by comparing this with the target molten steel temperature T_E_T and adding or not adding the required amount of coolant. End point carbon concentration control method in converter.