JPH05332986A - Method and device for estimating silicon concentration in blast furnace molten iron - Google Patents

Abstract

PURPOSE:To measure Si concentration in blast furnace molten iron with a high speed and high accuracy for controlling removal of Si so as to dose an appropriate agent for removing Si. CONSTITUTION:An Si activity in blast furnace molten iron 5 that is measured by means of a probe 1 operated with an oxygen concentration battery using solid electrolyte is corrected by using the other solute concentration to improve its accuracy. For example, corrective computation is performed by a process computer 2 to obtain an Si concentration quickly and accurately. Therefore, the dosage of an agent for removing Si can be calculated quickly and accurately, thus improving the accuracy of continuous Si removal control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for accurately estimating the concentration of silicon (hereinafter abbreviated as Si) among solute elements in blast furnace hot metal.

[0002]

2. Description of the Related Art In recent years, hot metal pretreatment, particularly deP treatment, prior to converter refining in a refining process at an iron mill has been emphasized due to demands for higher quality steel and lower refining costs. In the deP treatment, Si in the hot metal becomes a reaction inhibiting factor, so it is desirable to remove Si before the deP treatment. However, since Si also plays a role as a heat source for maintaining the hot metal temperature during the pretreatment,
The concentration of Si in the hot metal of the blast furnace is required to be within a certain range. Si is contained in the raw material, and is generally present in excess over a predetermined range. In this case, de-S
Si removal with the i agent is required, and the amount of the Si removal agent added is calculated based on the Si concentration at that time.

This Si concentration can be known by instrumental analysis. However, in instrumental analysis, a hot metal sample is collected, then solidified, and a sample is prepared for analysis. Therefore, it takes several tens of minutes to obtain an analysis result. Due to this drawback, the result cannot be used for automatic control of the Si removal treatment.

Therefore, as a conventional method for quick measurement,
There has been proposed a technique for electrochemically immediately measuring a solute element such as silicon in hot metal using a probe. For example, in Japanese Unexamined Patent Publication No. 61-142455, the outside of a solid electrolyte having oxygen ion conductivity is coated with a substance having a constant activity of oxide of a solute element to be measured, and the inside is used as a reference substance. A standard electrode having a reference electrode is disclosed. The standard electrode and the measurement electrode are inserted into molten metal, for example, hot metal, and the activity of the solute element is determined from the potential difference between the two electrodes and the hot metal temperature.

[0005]

However, what is measured by such a method is the activity, not the concentration of the solute element itself. The activity is a function of not only the concentration of the solute element to be measured itself but also the concentration of other solute elements. Therefore, there is a problem that the influence of other solute elements appears as an error with respect to the concentration value.

The present invention has been made in order to solve such a problem, and the activity of a solute element that is immediately measured is corrected based on the concentration of another solute element, so that the hot metal in the blast furnace hot metal is corrected. It is intended to improve the measurement accuracy of the Si concentration.

[0007]

Means for achieving this object are an estimation method for correcting the measured Si activity and obtaining a concentration, and an apparatus for executing the estimation method. In estimating the concentration of solute element silicon in blast furnace hot metal by inserting a probe by an oxygen concentration battery using a conductive solid electrolyte into the molten pig iron, the activity of silicon measured by the probe was compared with other solutes. A method for estimating the silicon concentration in blast furnace hot metal that is corrected based on the concentration of elements, and a probe for measuring the silicon activity by an oxygen concentration battery using a solid electrolyte having oxygen ion conductivity, and the measured activity Silicon in Blast Furnace Hot Metal Having Computation Means Performing Computation Based On Means And Storage Means To Store Instrument Analysis Results And Equipped With Process Computer Connected With Instrument Analyzer It is a degree estimation device.

[0008]

First, a probe of an oxygen concentration battery using a solid electrolyte having oxygen ion conductivity will be described with reference to FIG. The probe in the figure is an example, 11 is a reference electrode, 12 is a reference substance, 13 is a solid electrolyte having O ₂ ion conductivity, and 14 is an oxide coating so that the activity of SiO ₂ is constant. , 16 is a measuring electrode, and 5 is hot metal. When the probe is inserted into the hot metal 5, Si and O ₂ in the hot metal 5 and the SiO _{2 of the} oxide coating 14 reach a chemical equilibrium. This chemical equilibrium is represented by Equation 1, and the equilibrium constant K ′ is represented by Equation 2.

[0009]

[Chemical 1]

[0010]

[Equation 1]

Here, aSiO ₂ : SiO ₂ activity (Rawl standard) hSi: Si activity (Henry standard) P _O2 : O ₂ partial pressure.

Since the equilibrium constant K'is made so that the activity of SiO ₂ is constant, O ₂ is maintained unless the temperature changes.
It can be regarded as a function of only partial pressure, and the Si activity is obtained by the equation (3) using a new constant K ″.

[0013]

[Equation 2]

Since the reference substance 12 is contained inside the solid electrolyte 13, a potential difference appears inside and outside the oxide-coated solid electrolyte depending on the difference in O ₂ partial pressure between the hot metal 5 and the reference substance 12. Electricity is generated. That is, since an oxygen concentration cell is formed, if the reference electrode 11 is inserted into the reference substance 12 and the measurement electrode 16 is inserted into the hot metal 5, and the potential difference between the two electrodes is measured, the O 2 on the outer surface of the oxide coating 14 is measured. _{The 2} partial pressure is obtained, and the Si activity in the hot metal 5 that is in equilibrium with this is obtained. This electromotive force is expressed by equation (4).

[0015]

[Equation 3]

Here, E: electromotive force T: temperature F: Faraday constant P _O2 : partial pressure of O ₂ in the hot metal _Pref : partial pressure of O _{2 of the} reference substance R: gas constant

From the equations (3) and (4), the Si activity is
It is expressed as a function of the electromotive force as shown in the equation (5).

[0018]

[Equation 4]

The above is the principle of measuring the Si activity using an oxygen concentration battery using a solid electrolyte. However, Si activity is the measurement most closely related to Si concentration, but at the same time it is related to the concentration of other solute elements. Then, these relationships are expressed by the equation (6).

[0020]

[Equation 5]

Here, hSi: Si activity% Si: Si concentration (%)% i: Concentration of solute element i (%) i: Solute element in hot metal other than Si e (Si, Si): Self of Si Action factor e (i, Si): It is the interaction factor from solute element i to Si. That is, in the conventional method of measuring the activity of Si and using it as the estimated value of the concentration, the term including the concentration of the solute element i in the equation (6) was included in the measurement error.

In the case of hot metal, there are C, P, Mn, Ti, Cr, etc. as solute elements that cause a measurement error, and by correcting the measurement error due to their concentration, the Si concentration measurement accuracy is improved.

To make the correction, it is necessary to know the concentration of the solute element. A desirable method for knowing is to provide a probe for measuring the activity of these solute elements for each, measure simultaneously with Si, and repeat approximate calculation to regress to the concentration value. As a result, the concentrations of other solute elements can be immediately obtained at the same time. However, this method requires many kinds of probes, and currently, it may be difficult in terms of cost and workability.

As the most realistic method, the most important Si
There is a method in which only the probe for the target is provided and the instrumental analysis is used for the concentration of other solutes. This is a method utilizing the properties of hot metal, and it is noted that there is a difference in the state of fluctuation between Si and other solutes.

FIG. 3 shows the changes in the concentration of solutes per day, in which (a) is Si, (b) is C, (c) is P, and (d) is Mn. It is a thing. In the figure, the vertical axis is the concentration, the horizontal axis is the time, and the broken line is the average value of the concentration during the period. The dotted line is obtained by adding and subtracting twice the standard deviation σ to the average value, and shows a rough variation range. Looking at the ratio between the standard deviation and the average value, with respect to Si: 0.269, C: 0.056, P: 0.061, Mn: 0.07.
It is 9.

From this, it can be seen that Si is one of the solute elements.
Although the concentration has a large temporal variation, the concentration of other solute elements is smaller than that of the other solute elements. The reason is that the concentration of solute elements other than Si is almost determined by the mass balance of the blast furnace operation and depends on the raw material properties, whereas the Si concentration is determined by the chemical content of Si in the lower part of the blast furnace and slag. Because it is a physical distribution. That is, the distribution is determined by the chemical reaction among the SiO gas, the hot metal, and the slag, which is greatly affected by the thermal state in the blast furnace, and this thermal state change causes the raw fuel. Because it occurs in a shorter time than the property change of.

Due to the properties of blast furnace hot metal as described above, the concentration values of solute elements other than Si should be used with sufficient accuracy even for instrumental analysis values that require 20 to 40 minutes from the sampling to the determination of the results. You can

The following apparatus is suitable for immediately obtaining the true Si concentration by correcting the Si activity based on these instrumental analysis values. That is, a process computer having a calculation means and a storage means and an instrument analyzer are connected by a data highway,
Moreover, it is an apparatus in which this process computer is connected to the above-mentioned probe for measuring the Si activity. This process computer always stores the latest analysis result by the instrumental analysis sent, and immediately upon receipt of the measured value from the probe, that is, the Si activity, performs the correction calculation based on the equation (6).

[0029]

EXAMPLE Using the apparatus shown in FIG. 1, Si in blast furnace hot metal
The concentration was estimated. Fig. 1 shows the outline of the device.
The probe 1 for measuring the activity is connected to the process computer 2, and the analysis result is sent from the instrument analyzer 3 to the process computer 2 through the general-purpose data highway 4. C, Si, P, Mn, S, Ti, Cr, Cu,
Analytical values such as V are constantly sent from analytical instruments such as emission spectroscopy analysis, fluorescent X-ray analysis, and infrared absorption analysis, regardless of Si measurement by a probe. Sampling for instrumental analysis is every 30 minutes.

The process computer 2 has a storage means for storing analysis values. When the measured Si activity signal in the hot metal 5 is input from the probe 1, the calculation means immediately causes
A correction calculation based on the equation (6) was performed to estimate the Si concentration. In this example, the Si concentration fluctuation graph is displayed on the CRT display 6 and the estimated value is displayed and recorded on the dedicated digital display 7. However, in operation, the estimated value from the process computer 2 passes through the judgment circuit and is released. Used as a signal to the Si agent injection controller.

FIG. 5 shows details of the probe 1 shown in FIG.
A Mo wire is used for the reference electrode 11, a mixture of Cr and Cr ₂ O ₃ is used for the reference substance 12, and Zr is used for the solid electrolyte 13.
MgO containing O ₂ , SiO ₂ for the oxide film 14,
Also, Mo rods are used for the measuring electrodes, and Pt is used for temperature measurement.
-Pt 13% Rh thermocouple was incorporated. In the calculation using equation (6), the solute element i to Si interaction assist coefficient e (i, Si) used the recommended value from the literature at the time of departure. The updated value obtained from time to time was used.

As a result of carrying out the present invention in this way,
When the Si activity signal was input to the process computer 2, the estimated value was immediately displayed on the dedicated digital display 7, and the accuracy of the estimated value was as follows.

The estimated Si concentration is shown in FIG. 2 in comparison with the analysis result of the instrumental analysis sample collected at the same time. (A) is a conventional example in which the correction of the present invention is performed, and (b) is a conventional example in which no correction is performed. In each case, the horizontal axis is the Si analysis value by instrumental analysis and the vertical axis is the corrected Si estimation The value and the Si estimated value without correction.

In the figure (a), the estimated values are distributed very close to the 45 ° straight line, while in contrast, in the figure (b), there is a distribution apart from the straight line. The standard deviation is 0.022 in the standard deviation.
%, While 0.014 in the embodiment of the present invention.
%, And the estimation accuracy was clearly improved.

[0035]

According to the present invention, the shortcoming of the prior art, which is quick but has a problem in accuracy, is solved by using a method of correcting the Si activity by the concentration of a solute element other than Si. Therefore, the Si concentration in the hot metal can be estimated with high accuracy without impairing the speed. This enhances the accuracy of continuous Si removal control in the blast furnace casting floor and makes it possible to rationalize the process including the Si removal agent, and its effect is great.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an apparatus for estimating a silicon concentration in blast furnace hot metal used in an embodiment of the present invention.

FIG. 2 is a correlation diagram of an estimated value and an analytical value comparing the estimation accuracy of the present invention with that of the conventional technique.

FIG. 3 is a diagram showing a temporal variation of each solute concentration for explaining the properties of blast furnace hot metal.

FIG. 4 is an electrode arrangement diagram showing the principle of measuring Si activity by a probe.

FIG. 5 is a diagram showing an outline of a probe used in Examples.

[Explanation of symbols]

 1 Probe 2 Process Computer 3 Analytical Instrument 4 Data Highway 5 Hot Metal 11 Reference Electrode 12 Reference Material 13 Solid Electrolyte 14 Oxide Coating 16 Measuring Electrode 17 Thermocouple

Claims (2)

[Claims] 1. A silicon measured by a probe for charging a probe of an oxygen concentration battery using a solid electrolyte having oxygen ion conductivity into molten pig iron to estimate the concentration of solute element silicon in the blast furnace molten pig iron. Method for estimating silicon concentration in blast furnace hot metal, characterized in that the activity of iron is corrected based on the concentrations of other solute elements. 2. A probe for measuring silicon activity in an oxygen concentration battery using a solid electrolyte having oxygen ion conductivity, a calculation means for performing calculation based on the measured activity, and a memory for storing instrumental analysis results. An apparatus for estimating silicon concentration in blast furnace hot metal, comprising: a process computer having means and connected to an instrument analyzer.