JPH111710A - Method for controlling refining furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method of a refining furnace which avoids the bumping of steel bath. SOLUTION: In the control method of the refining furnace blowing at least O2 and coke toward the surface of the steel bath in the furnace body forming the steel bath composed of molten steel and slag by melting iron and steel, the temp. θm of the molten steel and carbon content Cm in the molten steel are calculated, and based on these molten steel temp. θm and carbon content Cm, a bumping iron oxide content F0 in the slag bumping the steel bath, is predicted. The slag is sampled from the steel bath and the actual measured iron oxide content F1 in the slag is obtd., and the coke blowing quantity and the molten steel temp. θm are adjusted so that the actual measured iron oxide content F1 becomes smaller than the bumping iron oxide content F0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a smelting furnace for smelting steel such as scrap.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of resource saving, it has been common practice to dissolve and recycle waste materials of automobile parts and scraps such as empty cans, and then make and reuse steel. Conventionally, an arc furnace for steelmaking (smelting furnace) shown in FIG. 2 has been used as a smelting furnace for melting and refining such scrap.
FIG. 2 is a cross-sectional view of a main part of the steelmaking arc furnace. Reference numeral 1 denotes a furnace body, 2 denotes a throat portion, and 3 denotes a preheating tank.

[0003] The furnace body 1 is a container into which a scrap (iron or steel) 15 to be heated is supplied and melted, and a bottom electrode 5 serving as an anode is provided at the bottom of the furnace body 1. In the furnace body 1, a furnace cover 1a is sandwiched by a scrap charging port 1b.
And two upper electrodes 6 and 6 serving as cathodes, which are attached to the upper electrode, are inserted. By applying a voltage between the bottom electrode 5 and the upper electrodes 6 and 6 to cause arc discharge, the scrap 15 supplied into the furnace body 1 is heated and melted. The steel bath 7 thus melted is stored at the bottom of the furnace body 1. The steel bath 7 is composed of molten steel 7a located on the bottom side of the furnace body 1 and slag 7b deposited above the molten steel 7a. A lance (spray tube) 8 is provided beside the upper electrode 6.

The lance 8 is disposed so as to face the bath surface 12 of the steel bath 7, and coke for primary combustion and O ₂ are jetted from the tip of the lance 8 to the bath surface 12. I have. Further, an air pipe 9 for feeding air for secondary combustion is provided on a side wall of the furnace body 1.

[0005] One end of the throat section 2 is connected to a scrap inlet 1b provided at the top of the furnace body 1,
The other end is connected to the bottom side surface of the preheating tank 3. The throat portion 2 serves as a scrap supply path through which the scrap 15 stored in the preheating tank 3 passes and is supplied to the furnace body 1, and as a path for exhaust gas flowing out of the furnace body 1. In addition, a horizontal cradle part 2 a in which the scraps 15 stored in the preheating tank 3 are temporarily stored is provided above the throat part 2. Further, there is provided an advancing / retracting throat portion extruding device 10 for extruding the scrap 15 retained in the cradle portion 2a and supplying the scrap 15 into the furnace body 1.

[0006] The preheating tank 3 is connected to the upper end of the throat portion 2 and stores the scrap 15. In the preheating tank 3, in addition to the scrap 15, HBI (Hot Briquete Iron) 16 which is reduced iron is mixed. This HBI 16 has a main component of Fe and Sn, C
It does not contain u or the like. Therefore, HBI
16 is mixed with the scrap 15 to relatively reduce the abundance ratio of impurities such as Sn and Cu contained in the scrap 15 and is used for improving the quality of steel obtained by melting the scrap 15. It is something that can be done. The preheating tank 3 is, together with the throat section 2, a passage for exhaust gas flowing out of the furnace body 1. Therefore, the scrap 15 and the HB stored in the preheating tank 3
I16 is preheated by the sensible heat of the exhaust gas. A preheating unit extruding device 11 is provided below the preheating tank 3 for extruding and supplying the stored scrap 15 and HBI 16 to the receiving table 2a.

[0007] An operation method of the steelmaking arc furnace configured as described above will be outlined. The scrap 15 and the HBI 16 stored in the preheating tank 3 are extruded by the preheating unit extruding device 11 to the receiving table 2a, and the throat portion extruding device 1
0 is supplied into the furnace body 1 through the throat section 2.
Scrap 15 and HBI 16 supplied into furnace body 1
Are heated and melted by the arc discharge caused by the bottom electrode 5 and the top electrodes 6,6. The melted steel bath 7 is stored at the bottom of the furnace body 1 and is primarily burned by the lance 8. Since this primary combustion is performed in a shortage of oxygen, it is incomplete combustion, and the combustion gas generated by the primary combustion contains CO. Further, above the steel bath 7, the secondary combustion is performed by the CO contained in the O ₂ and the primary combustion gas contained in the air for secondary combustion supplied by the air pipe 9 are mixed to react . Since the exhaust gas thus obtained is obtained by two-stage combustion consisting of primary combustion and secondary combustion, it is a gas having high temperature sensible heat. The exhaust gas passes through the furnace body 1 and the throat section 2 and flows into the preheating tank 3. Therefore, the scrap 15 and the HBI 16 stored in the preheating tank 3 are preheated by the high-temperature exhaust gas. By preheating the scrap 15 and the HBI 16 in this manner, electric power consumed in the furnace body 1 by arc discharge is reduced.

[0008]

By the way, in the conventional arc furnace for steel making, there was a problem that bumping of the steel bath 7 occurred in the furnace body 1 and the steel bath 7 was blown upward. As shown in FIG. 3, the bumping occurred remarkably in a range where the iron oxide (FeO) amount F in the slag 7b satisfied F ≧ A + B / Cm. Here, A and B are constants given by operation data of the steelmaking arc furnace, and Cm is molten steel 7a.
It is the amount of carbon dissolved in the inside. In addition, when bumping of the steel bath 7 occurs, there has been a problem that the yield of smelted and smelted products is deteriorated.

Accordingly, the present invention has been made in view of the above problems, and has as its object to provide a method for controlling a smelting furnace that avoids bumping of a steel bath.

[0010]

Means for Solving the Problems In the method for controlling a smelting furnace according to the present invention, the following means are employed in order to solve the above problems. The method for controlling a smelting furnace according to claim 1 is characterized in that a steel bath is formed by melting steel and forming a steel bath composed of molten steel and slag deposited above the molten steel. a method of controlling a smelting furnace blowing least O ₂ and coke toward the surface, to calculate the amount of carbon temperature and solution in steel of the molten steel, these molten steel temperature, the steel bath on the basis of the carbon content is bumping the The amount of bumping iron oxide F0 in the slag is predicted, and the slag is sampled from the steel bath to determine the actually measured iron oxide amount F1 of the slag, and the measured iron oxide amount F1 is calculated from the bumping iron oxide amount F0. The amount of coke injected and the temperature of the molten steel are adjusted so as to reduce the temperature.

[0011]

Embodiments of the present invention will be described below. The steelmaking arc furnace according to the present embodiment includes:
Since it is the same as that shown in the prior art, it will be described below with reference to FIG. 2 and the description of each member will be omitted. The power applied between the bottom electrode 5 and the upper electrodes 6, 6 is controlled by a power supply device (not shown). A thermocouple is attached to the temperature of the outlet of the preheating tank 3 so that the temperature can be measured. The weight of the scrap 15 and HBI 16 supplied to the preheating tank 3 is measured at the time of supply. This measured weight,
Since the scrap 15 and the HBI 16 supplied into the furnace body 1 are obtained from the weight extruded by the throat portion extruding device 10 and the preheating unit extruding device 11, the weight of the steel bath 7 in the furnace body 1 is also obtained. ing. Further, the weight of slag and molten steel is determined based on conventional operation data and the like. During the operation of the steelmaking arc furnace, the process in which the scrap 15 and the HBI 16 are supplied into the furnace body 1 and melted by arc discharge in the furnace body 1 is the same as that described in the related art, and a description thereof will be omitted.

The present embodiment is characterized by a method of controlling a steelmaking arc furnace, and this point will be described below. The control method of the steelmaking arc furnace is based on the temperature θ of the molten steel 7a.
m and the amount Cm of carbon dissolved in the molten steel 7a are calculated, and control is performed based on the result. The molten steel temperature θm is calculated by the following calorific value equation. Wh · Qh + Wn · Qn + Σ (Ws · θs · Cs) + Σ (P
· T) = (Wh + Wn + ΣWs) · (Cs · θm)
(1) Here, Wh is the weight of the steel bath remaining in the furnace body 1, Qh is the calorific value of the steel bath weight remaining in the furnace body 1, Wn is the weight of the slag 7b, and Qn is the slag 7
b, the amount of heat, Ws, is the scrap 15 supplied into the furnace body 1.
And the weight of the HBI 16, θs is the temperature of the scrap 15 and the HBI 16 at the outlet of the preheating tank 3, Cs is the specific heat of the scrap 15 and the HBI 16, P is the input power consumed by the arc discharge in the furnace 1, and t is the input power. It is time to be. The amount Cm of carbon dissolved in the molten steel 7a is calculated by the following equation. Cm = ｛Mh + ΣMs + (ΣUb · t−ΣUn · t−ΣUd ·
t)｝ / Wm (2) Here, Mh is the amount of carbon in the steel bath 7 remaining in the furnace body 1, Ms is the amount of carbon in the scrap 15 and the HBI 16, and Ub is from the lance 8 to the steel bath 7. The amount of coke supplied, Un is slag 7b
Ud is the decarburization rate of the molten steel 7a, Wm is the molten steel 7a
Is the weight. The decarburization rate Ud in the equation (2)
Is a function of the molten steel temperature θm. Therefore, the carbon amount Cm is obtained after calculating the molten steel temperature θm. Further, the amount of iron oxide in the slag 7b when bumping of the steel bath 7 occurs, that is, the amount of bumping iron oxide is calculated by the following equation. F0 = A + B / Cm ...
(3) Here, A and B are constants given based on conventional operation data and the like of the steelmaking arc furnace.

A method for controlling a steelmaking arc furnace based on the molten steel temperature θm and the carbon amount Cm will be described with reference to FIG. First, the molten steel temperature θm is calculated by the equation (1). Next, using this molten steel temperature θm, the molten steel 7a
The carbon amount Cm in the medium is calculated. Then, based on the carbon amount Cm, the bumping iron oxide amount F0 is calculated by the equation (3). On the other hand, the slag in the furnace body 1 is sampled by a sampling device (not shown), and the slag 7b is analyzed by the analyzer to obtain the measured iron oxide amount F1 in the slag 7b. Then, the bumping iron oxide amount F0 and the actually measured iron oxide amount F1 are taken into an arithmetic unit (not shown) and compared. If the measured iron oxide amount F1 exceeds the bumped iron oxide amount F0, the slag 7b
In order to reduce the amount of iron oxide therein, coke is blown into the slag 7b to reduce the iron oxide in the slag 7b. Further, by adjusting the input power P, the reduction of iron oxide in the slag 7b is promoted. The measured iron oxide amount F1 is the bumping iron oxide amount F
If it becomes smaller than 0, the operation of the steelmaking arc furnace is continued.

As described above, the molten steel temperature θm and the carbon amount Cm are calculated, and the bumping iron oxide amount F0 is obtained.
By controlling the measured iron oxide amount F1 obtained by sampling b to be smaller than the bumping iron oxide amount F0, the operation in the range in which bumping of the steel bath 7 shown by hatching in FIG. 3 occurs. It can be avoided and bumping of the steel bath 7 can be prevented.

[0015] In the present embodiment, it is configured to blow coke and O ₂ from the lance 8, a plurality of lances 8, each lance 8 Karakara coke,
O ₂ may be blown separately.

[0016]

As described above, according to the smelting furnace control method of the present invention, the following effects can be obtained. The molten steel temperature and the amount of carbon were calculated, and the bumping iron oxide amount F0 was calculated.
And a control method that adjusts the coke injection amount and the molten steel temperature so that the measured iron oxide amount F1 obtained by sampling the slag is smaller than the bumped iron oxide amount F0, so that bumping of the steel bath is avoided. It is possible to do.

[Brief description of the drawings]

FIG. 1 is an embodiment of the present invention and is a view showing a flowchart of a method for controlling a smelting furnace.

FIG. 2 is a cross-sectional view showing a conventional steelmaking arc furnace according to the prior art.

FIG. 3 is a diagram showing a range in which bumping of a steel bath occurs by hatching.

[Explanation of symbols]

 Reference Signs List 1 furnace body 7 steel bath 7a molten steel 7b slag 12 bath surface θm molten steel temperature Cm carbon amount

Claims (1)

[Claims] 1. A furnace in which a steel bath composed of molten steel and slag deposited above the molten steel is formed by melting steel, at least O ₂ and coke are directed toward a bath surface of the steel bath. In the method for controlling a smelting furnace, the temperature of the molten steel and the amount of carbon in the molten steel are calculated, and the amount F0 of bumped iron oxide in the slag in which the steel bath bumps is calculated based on the temperature of the molten steel and the amount of carbon. Predictably, the slag is sampled from the steel bath to determine the measured iron oxide amount F1 of the slag, and the coke injection amount is set so that the measured iron oxide amount F1 is smaller than the bumped iron oxide amount F0. And a method for controlling a smelting furnace, wherein the molten steel temperature is adjusted.