JPS63128109A - Control method for de-phosphorization in converter refining - Google Patents

Abstract

PURPOSE:To execute the de-phosphorization in molten steel at high accuracy by continuously measuring composition of converter exhaust gas at the time of refining steed in the converter, converting changing with passing of time to time series changing of parameter by the ARMA system and controlling the converter operational condition by comparing this with the standard pattern. CONSTITUTION:At the time of refining molten iron to steel having the aimed quality by executing de-siliconization, de-manganization, de-sulfurization, de- phosphorization and de-carburization through oxygen blowing, the contents of CO, CO2, H2, O2 in the exhaust gas and flow rate of the exhaust gas from the converter during refining operation are continuously measured. The changes with passing time of the measured values is converted to the time series changing of parameter by ARMA system and this is compared with the standard pattern to quickly and quantitatively represent the difference of the operational condition, and by controlling oxygen lance height and oxygen injecting velocity from the lance, the P content in the molten steel produced is refined as de-phosphorizing to the aimed value with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dephosphorization control method that accurately matches the phosphorus content contained in molten steel at the time of converter blow-off to a target value.

[Conventional technology]

In the converter during blowing, reactions such as C9 removal, Si removal, Mn removal, and P removal mainly proceed. Of these reactions,
Regarding removal of C1, removal of Si, and removal of Mn, it is possible to control the progress of the reaction relatively easily.

However, the dephosphorization reaction is greatly influenced by the properties of converter slag, but the technology to continuously analyze the properties of this slag has not yet been established. The dephosphorization reaction is controlled based on the estimated value.

For example, in the method disclosed in JP-A-55-161012, residual oxygen (O5) in the slag is taken as an indicator of slag activation, and Pa1m is removed. In other words, the exhaust gas is periodically sampled, and the residual oxygen (O5) in the slag is calculated approximately every 2 seconds from this exhaust gas information, and the time-series changes in the calculated value are used to determine the optimum operation in which the dephosphorization reaction is promoted. The conditions are determined and the lance height etc. are controlled based on the conditions.

[Problem that the invention seeks to solve]

However, the method disclosed in Japanese Patent Application Laid-open No. 55-161012 only focuses on the residual oxygen 1 (Os) in the slag.

However, the dephosphorization reaction in a converter is mainly controlled by the ease with which P in the molten steel reacts with oxygen in the slag, and therefore the dephosphorization reaction in the converter is simply controlled by the residual oxygen I (Os) in the slag.
) as control information does not result in control that accurately grasps the properties of the slag. Therefore, in order to further stabilize and improve P removal, it is desired to improve control accuracy.

Therefore, the present invention was developed in response to such demands, and it is possible to obtain various information from the exhaust gas, grasp the progress state of the dephosphorization reaction in the converter accordingly, and accurately perform the target dephosphorization. The purpose is to finish molten steel to a phosphorus content.

[Means and actions for solving the problems] In order to achieve the object, the dephosphorization control method of the present invention controls the CO content of the exhaust gas discharged from the converter.

CO, containing 1. Continuously measure Ht content, 0□gold content, and exhaust gas flow rate, convert the temporal changes in these measured values into time-series changes in parameters in the ARMA formula, and use the time-series changes in the parameters as a standard. It is characterized by controlling operating conditions by comparing with patterns.

Hereinafter, the present invention will be specifically explained along with its effects.

First, unnecessary carbon C contained in molten steel reacts with oxygen to generate CO gas. A part of this co gas reacts with oxygen again to become cot gas. The mechanism of COt gas generation is complex, but the thickness of the slag has a great influence. The thickness of this slag is closely related to the properties of the slag.

Therefore, by understanding changes in the amount of CO gas and COt gas generated, it is possible to understand qualitative changes such as increases and decreases in slag thickness, trends, and properties.

In addition, the flow rates of I11 gas, 0□ gas, and exhaust gas are also closely related to the progress of the blowing reaction, so when these flow rates are incorporated as control factors, the blowing reaction can be controlled with finer precision. I can do it.

For this reason, CO is included in the exhaust gas! , co, content.

The H8 content, 0□ content, and exhaust gas flow rate are determined, and their temporal changes are calculated using ARM A (Auto-Regr.
The parameters of the blowing reaction model equation expressed in the Movable Average) format are sequentially identified, and the exhaust gas information is converted into time-series changes in these parameters, thereby quickly and quantitatively expressing differences in operating conditions. , the lance height, oxygen delivery rate, etc. are controlled accordingly to obtain the optimum operating conditions.

Here, to explain the model in which the blowing reaction is expressed as an ARMA equation based on exhaust gas information, the content of each component of the exhaust gas and the exhaust gas flow rate at the current moment k are the exhaust gas composition and the oxygen supply amount at the stage before (k-1). It is expressed as the accumulation of

CO+t+ ”a+co+w-++ +azCOn-u
” °゛°”aacOTk-ml...(11 COt(*+ =e+C(h+++-++ +czCO
t(m-□)+...+cscOtn-s+...(
2) Hz n)=e+Hz 1k-11+etHt (*-
x+ + 9 °-+eIIHto+-ur・・・・(
3) Ox on -grot 10gtoz n-t
> ” ' 0 °”gwo! (k-wl・ ・ ・
・(4) F(ml −j+Fn−u ”jtFn−t+ + °
°°＋jyFn−1)・・・・・(5) However, CO□): CO content COz of exhaust gas at time k
(Ill: CO□ content of exhaust gas at time k H1
(ml: H2 content of exhaust gas at time k is 0!(.

2 Content of exhaust gas at time k F0): Amount of exhaust gas at time k FOg on : Amount of oxygen supplied at time k M: Amount of hot metal a+tl+C+d+fl+Lg+h+J+Il: Parameters to be identified Also, (k-1), (k-2 )...
etc. represent the time at which exhaust gas is periodically measured prior to time k.

Therefore, the CO content 1. co, content.

Hz content, 03 content, and exhaust gas flow rate are accumulated, and by substituting into the above equations (11 to (5)), using the sequential least squares method,
Each parameter a+ b, C+d+ e+ L L h
+J+II is determined at each sampling time.

For example, Figure 1 shows that when molten steel for ordinary steel is refined,
Parameters a and C when components are mixed at the time of converter blow-off
On the other hand, Figure 2 shows the time-series changes in parameters a and C when molten steel with approximately the same composition is refined and when the compositions are not mixed.These figures are compared. When doing so, no particular difference is observed for parameter a, but for parameter C, the initial stage 1! ! )(0~l
The values at 0 min) are significantly different. It is considered that this difference is accumulated, and the target dephosphorization rate is reached in the case of FIG. 1, and the target dephosphorization rate is deviated from the target dephosphorization rate in the case of FIG.

Therefore, each parameter a+ b, C+ d+ e+ f
Regarding +L h+j, -, time-series changes in an example of operation in which P removal has progressed well as shown in FIG. 1 are determined in advance from past operation data, and this is used as a standard pattern.

Then, from the current refining operating conditions, the formula ill ~
Parameter a+ b+ C- found by (5)
+ d+e+ L g+ h+ J+ Comparing the time-series changes in II with the standard pattern of parameter changes,
Find the deviation.

Next, this deviation is calculated as a change in operating conditions such as lance height and feed MN, and the refining reaction is controlled so that the dephosphorization reaction proceeds along a predetermined course.

〔Example〕

The following table shows C4,0%, 5i3oxto-”%, Mn
30 X 10-”%, P85X10-3%, 514
It shows the changes in each parameter when hot metal of xlO-3% is refined in a converter. In addition, Fig. 3 shows the time series of lance gear 7 (distance from the tip of the lance to the molten steel surface) to control the proportion of oxygen reacting with molten steel and slag in response to changes in this parameter. It also shows changes. In this way, by making the changes in each parameter follow the standard pattern, 16=1.5 x
It was possible to achieve the target phosphorus content at the time of blow-off at a high darkness of 1O-''%.

Table: Time-series changes in parameters [Effects of the invention] As explained above, in the dephosphorization control method of the present invention, various information is obtained from the exhaust gas, and the dephosphorization reactivity of slag is grasped from this. , the operating conditions are controlled to match the optimal course of the dephosphorization reaction. This made it possible to accurately match the final dephosphorization rate at the time of converter blow-off to the target value.

[Brief explanation of the drawing]

Figure 1 shows the parameters a and C when the components are connected.
Figure 2 shows the time series changes of parameters a and C in the case where the components are not connected;
The figure shows time-series changes in the lance gap.

Claims (1)

[Claims] 1. CO content of exhaust gas discharged from the converter, CO_2
Continuously measure the content, H_2 content, O_2 content, and exhaust gas flow rate, and record the temporal changes in these measured values using AR.
1. A dephosphorization control method in converter refining, characterized in that operating conditions are controlled by converting parameters in an MA formula into time-series changes and comparing the time-series changes in the parameters with a standard pattern.