JPS6115127B2 - - Google Patents

Description

[Detailed description of the invention]

This invention focuses on the fact that there is a strong correlation between the steel bath carbon concentration at the end of blowing and the decarburization rate in converter oxygen blowing, and calculates the end of the blowing decarburization rate to the decarburization rate curve at the end of blowing. The above-mentioned correction is made to the exhaust gas decarburization rate obtained moment by moment from the exhaust gas analysis of the converter at the end of blowing, which is calculated from the multiple regression equation based on the operating conditions divided by patterns, the actual exhaust gas correction value, and the fluctuation correction value depending on the operating conditions. It is characterized by successively monitoring the calculated decarburization rate in addition to the above, and when the above-mentioned blowout conditions based on the blowout decarburization rate are satisfied, the blowing is terminated to control the steel bath carbon concentration at the time of blowout. The present invention relates to a converter blowing control method. When controlling the decarburization reaction in a converter, most methods estimate the blowing process from information on the exhaust gas during blowing (decarburization rate) and control the end-of-blown carbon concentration. ₂ ) and the amount of decarburization (decarburization rate) is calculated sequentially by continuous measurement of the exhaust gas flow rate, and the remaining carbon concentration in the steel bath is estimated to determine the amount of oxygen for blowing. In this method, good control accuracy cannot be obtained because the measurement errors in the measurement or changes over time of the process measurement values and the accumulated errors thereof are not negligible. It is an object of the present invention to advantageously overcome these problems and realize accurate control of the blow-up carbon concentration in a manner suitable for actual operation of a converter. The method of this invention is applied to actual converter operation as described below, and achieves appropriate control of the blow-up operation concentration (C%). This invention will be specifically explained below. In this invention, in the early stage of converter blowing, the expected blowing oxygen amount (O
Find _E ). Next, from the final stage of blowing using this amount of oxygen, the exhaust gas decarburization rate (dc/do or dc/d
t) is the decarburization rate A over unit time (e.g. seconds)
Then, the decarburization rate B is continuously measured and calculated over a coarser period (for example, in minutes). Since this exhaust gas decarburization rate is generally strongly influenced by measurement errors in process measurements and variability due to operating conditions, these are corrected and the calculated decarburization rates after correction are designated as A ^* and B ^* , respectively. , sequentially displayed on a display device (for example, a CRT display device). The above correction is performed as follows. A ^* =k ₁・k ₂・A ………(1) B ^* =k ₁・k ₂・B ………(2) Here k ² =k ₂ ² /k ₁ ¹ , however, k ₁ is Exhaust gas performance correction value (previous charge performance decarburization amount/exhaust gas decarburization amount),
k ₂ is the variation correction value of k ₁ obtained from the multiple regression equation depending on the operating conditions, k ₂ ¹ is the estimated correction value of the previous charge, and k ₂ ² is the estimated correction value of the main charge. Regarding the actual exhaust gas correction value _k1 , the previous charge actual decarburization amount and the exhaust gas decarburization amount are determined by the following equations (3) and (4), and the main charge estimated correction value is given by the equation (5). Actual decarburization amount = 10 {10 _HM・W _HM +4.2W _CI −C _S・W _S }+9.6W _CaO ……(3) where C _HM : Hot metal C concentration (%), W _HM : Hot metal weight (ton), W _CI ; Cold pig iron weight (ton), C _S ; Molten steel blowout C concentration (%), W _S ; Weight of produced steel (wton), W _Ca
O ; Burnt lime weight (ton) However, Q(t+τ ₁ ); exhaust gas flow rate (Nm ³ /h) at time (t+τ ₁ ), CO (t+τ ₂ ), CO ₂ (t
+τ ₂ ); Exhaust gas analysis CO at time (t + τ ₂ );
CO ₂ component (%vol), K: constant, t _O ; blowing start time, t _E ; blowing end time,

[Table] However, T _HM : Hot metal temperature (℃), Si _HM : Hot metal Si concentration (%), S _HM : Hot metal S concentration (%), W _ORE : Iron ore weight (ton), Wacale : Scale weight (ton) ,
C _F : Molten steel blow-off C concentration (%), T _F : Molten steel blow-up temperature, O _S : Blowing cumulative oxygen amount (Nm ³ ), and the estimated blow-off decarburization rate A ^* _F of this charge is as follows ( 7) given by Eq. However, Mn _HM : Hot metal Mn concentration (%), HR: Hot metal blending ratio, N _LD : Number of furnaces, O _t : Oxidation amount (Nm ² /t). The curve locus of the coal speed B ^* is determined according to several kinds of predetermined curve pattern determination conditions as shown in FIG. 1, and the decarburization curve pattern of the main charge is determined. On the other hand, the estimated blowout decarburization rate A ^* _F of the main charge is determined from the multiple regression equation based on the operating conditions of the blowout decarburization rate, which is divided in advance by the decarburization rate curve pattern, and the target blowout decarburization rate is calculated as follows. Let the coal speed be A ^* _E . A ^* (E) = A ^* _F (6) This target blow-off decarburization rate A ^* (E) is also displayed on the display device. The calculated decarburization rate A ^* and the target blow-off decarburization rate A ^* (E) are monitored successively, and the blowing is terminated when the next blow-off condition is satisfied. Condition (1) A ^* (E)A _* <(1+α)A ^* (E) 0<α<1 (2) β・O _E <O _S (1+β)O _E 0<β<1 However, O _S ; Cumulative oxygen amount for blowing, O _E ; Planned oxygen amount for blowing (according to furnace reaction model) Example A case will be described in which the method of the present invention is applied to the operation of a 100 ton converter. Target carbon concentration is 0.070% before main charge blowing.
According to the furnace reaction model, the expected amount of oxygen for blowing O
_E was calculated and O _E =5120 Nm ³ was obtained. The exhaust gas integral correction value _k1 , which is the correction coefficient for the exhaust gas decarburization rate, is calculated from the actual value of the previous charge using equations (3) and (4).
k ₁ = 0.99 was calculated, and the correction value k ₂ for the fluctuation of k ₁ due to operating conditions was obtained from equation (5) using the operating condition data of the previous charge and main charge as k ₂ = k ₂ ² /k ₂ ¹ = 1.11. . After the start of blowing, the exhaust gas decarburization rates A and B were measured and calculated from time to time by exhaust gas analysis, and the calculated decarburization rates A ^* = 1.099A, B ^* = after correction of k ₁ and k ₂ mentioned above.
Display 1.099B on the CRT screen. Figure 2 shows these calculated decarburization rate trends. 75% to 88 of the planned oxygen amount for blowing O _E (=5120Nm ³ )
The curve pattern of the calculated decarburization rate B ^* for about 3 minutes between 3840 and 4506 Nm ³ was shown in FIG. 1a. After recognizing the pattern, the estimated blow-off decarburization rate A ^* _F of this pattern is determined using the multiple regression equation (7) under the blow-off target conditions of the main charge, and A ^* _F = 55.5Kg・
C/min was obtained. This value was displayed on the CRT screen as the target blow-off decarburization rate A ^* (E) for the main charge. (2) According to formula A ^* = 1.099A, the calculated decarburization rate A ^* that is calculated and displayed every moment is (1) If α = 0.2 empirically, then A ^* (E) = 5.55Kg・C /minA ^* 66.6Kg・C/min, and then the blowing was stopped when the cumulative oxygen amount O _S of blowing met the condition of 4870Nm ³ <O _S (2) β = 0.95. The end carbon concentration (C _F ) _ACT was 0.066% or less, which is extremely close to the target carbon concentration of 0.070%. Figure 3 shows the effect when the method of this invention is applied to blowing control of a 100 ton converter. This is 763 heats over 20 days (38 average per day)
Target carbon concentration in the steel bath at the end of blowing (C _F ) _AIM and actual carbon concentration (C _F ) _ACT obtained for blowing with heat)
The deviation is expressed in days as σ defined by the following formula. However, n is the number of heats per day.For comparative reference, the data of blowing controlled only by static charge calculation before applying the method of this invention are also shown in FIG. Comparing the σ values of the two, it is 0.025% to 0.034% based on static charge calculation, whereas it is 0.002% to 0.005% according to this invention, about 1/10 of the former, and the It can be said that the concentration accuracy rate is significantly higher than that of the conventional method. The effects of this invention are summarized as follows. 1. The blowing control calculation formula such as the in-furnace reaction formula model alone can greatly improve the blow-stop performance, and is particularly effective for converter blowing control without sublance equipment. Of course, it will be even more effective if used in combination with a converter equipped with sublance equipment. 2. Conventional exhaust gas analysis methods measure and calculate the decarburization rate, estimate the carbon concentration in steel, and perform integral calculations to estimate the blowing oxygen amount up to the blow-off carbon concentration, which is extremely inaccurate, but this method This is a very simple method that only requires calculation of the decarburization rate.
Furthermore, the accuracy of measurement and calculation of the decarburization rate can be improved by various corrections.

[Brief explanation of the drawing]

Fig. 1 a to e are explanatory diagrams illustrating patterns of decarburization rate curves, Fig. 2 is a decarburization rate transition diagram showing an example of the present invention, and Fig. 3 is a decarburization rate control in a stopper steel bath. This is a comparison graph of the effects of

Claims (1)

[Claims] 1. In the converter oxygen blowing process, the exhaust gas decarburization rate is calculated using a known exhaust gas analysis method, and in order to eliminate the effects of measurement errors in the process measurement values and variability of operating conditions, the exhaust gas decarburization rate of each pre-charge Calculated decarburization rates A ^* and B ^* corrected by the exhaust gas integral correction value of the actual decarburization amount with respect to the actual decarburization amount and the fluctuation correction value obtained from the multiple regression equation depending on the operating conditions are successively determined. automatically recognizing and determining the decarburization rate B ^* curve pattern for the period during which the decarburization rate B* curve pattern is determined from several types of curve pattern determination conditions; Calculate the estimated blow-off decarburization rate A ^* _F for this charge from the multiple regression equation, and use this as the target blow-off decarburization rate A ^* (E) for this charge, and calculate the calculated decarburization speed A ^* and the target. Compare and monitor the blow-off decarburization rate A ^* (E) while sequentially displaying it on the display device, and make sure that the calculated decarburization rate A ^* satisfies the blow-off condition of the target blow-off decarburization rate A ^* (E). , and controlling the end point of blowing based on the blowing cumulative oxygen amount satisfying the blowing oxygen amount blowing condition according to the in-furnace reaction model. How to control concentration.