JPS61163204A - Converter blowing method - Google Patents

Abstract

PURPOSE:To recover efficiently secondary dust by precharging the wet secondary dust generated in the operating stage of a converter into a top and bottom blown converter and drying the dust by the remaining heat of the converter in an inert gaseous atmosphere then charging a molten iron into the converter and subjecting the same to oxygen blowing. CONSTITUTION:The dust contg. an iron-component is contained in the waste gas generated during refining for steel making by the converter and is therefore recovered by a wet process dust collector. The dust 5 contg. such moisture and iron-component is put into the top and bottom blown converter 1 after the end of refining and the inert gas 3 such as N2 is blown from a bottom blowing nozzle 2 into the converter to maintain the non-oxidizing atmosphere in the converter and thereafter the mouth of the converter is closed by a cap 4 and the wet dust is dried by utilizing the remaining heat of the converter. The molten iron is then charged into the converter and is subjected to decarburization refining by oxygen blowing to produce a molten steel. The iron oxide in the dust is utilized as an oxidizing agent for Si, C, etc. during this time, by which Fe is reduced and is incorporated into the molten steel. The yield of Fe is thus safely improved with the less energy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for operating a converter, which aims to effectively recover secondary dust generated during the operation of a converter.

Conventional technology Conventionally, as a method for recovering the secondary dust, a method of pelletizing blast furnace dust or converter dust as the main raw material using heavy oil or gas in a rotary kiln or the like [Tetsu-to-Hagane Vou, 7B]
(1!37B) 344B), or cold pellets using solid materials such as cement for the purpose of reducing fuel costs.
Cutting technology [Tetsu to Hagane VasL, 76 (197B) S4
[32] reported a dust recovery method in which the obtained pellets are used in a blast furnace or converter.

Problems to be solved by the invention During converter operation, approximately 5
0 to 80 mmg/m'' dust is included, and approximately 60% of the dust component is iron, so 1 of the total iron charged in the converter is
．． Iron loss of around 4 to 1.6% occurs, which is a factor in deteriorating the steel production yield and has a large impact on manufacturing costs. In other words, collecting the generated dust and reusing the dust improves the yield of steel production by recovering the iron content, leading to a reduction in manufacturing costs. For these reasons, it is extremely important to recover the iron content of the generated dust.

However, since the collected dust is collected by a wet dust remover, it retains about 20 to 30% moisture even after dehydration treatment, and it is extremely dangerous to use it by directly inserting it into high-temperature hot metal. .

Therefore, in the conventional method, drying is carried out in the sun for the purpose of removing moisture, and during drying, the component FeO in the dust undergoes an oxidation reaction and becomes Fe2.
Utilizing the transition to O3, it is used as a substitute for iron ore by charging it into the furnace from above the furnace, but since it is a powder, it is suspended in the raw material hopper, and the raw material yield decreases at the time of charging. There was a problem with dust during handling.

In order to solve these problems, there is a method of using a solid material such as cement, or sintering it and using it in a solid state, but due to the influence of the component (S) of the solid material, etc. It has drawbacks such as being difficult to use for all charges during operation and increasing processing costs.

Means for Solving the Problems The present invention aims to eliminate these drawbacks and provide an excellent method for easily and inexpensively reusing dust, improving the yield of molten steel, and reducing manufacturing costs. The gist is that the wet secondary dust I generated during converter operation is pre-charged into a top-bottom blowing converter, and then heated in an inert atmosphere with a bottom-blowing inert gas. This is a converter blowing method characterized by dehydrating the wet secondary dust using the residual heat of the furnace body after the previous blowing, and then charging and blowing hot metal.

action The present invention has the following features.

(a) Maintaining the inside of the top-bottom blowing converter furnace in an inert gas atmosphere,
Due to the residual heat of the furnace body after the previous blowing of wet secondary dust in the furnace,
This method is much simpler than the conventional method, in which hot metal is charged after dewatering the wet secondary dust.

(b) By suppressing the oxidation of FeO in the used dust with an inert gas, the cooling coefficient is lowered and when iron ore is replaced, the amount used increases compared to the conventional method, so the yield of molten steel is improved. It has the advantage of being highly effective.

(c) Raw material cost as it can be used without any processing)・
It also has the advantage of being low, the effective ingredients in the dust can be reused effectively, and the influence of impurities (S) etc. is small.

(d) Since the FeO in the dust used can be used in an unoxidized state, pre-charging is possible, and it is a highly safe usage method that does not cause abnormal reactions during charging of hot metal.

Next, an example of an apparatus used to carry out the method of the present invention will be explained. In Fig. 1, wet dust is charged into a top-bottom blowing converter l, an inert gas 3 is blown in from a bottom-blowing nozzle 2, the inside of the furnace is sealed with a furnace cover 4, and the furnace body after the previous blowing is After the wet secondary dust is heated by the residual heat and the dust moisture is removed, hot metal is charged and the operation is carried out.

Next, examples of the method of the present invention will be given.

Example 1 In a converter, a bottom-blowing nozzle protective gas (N2
) to maintain an inert atmosphere inside the furnace and remove dust components (w
t%): T-Fe 54.19. FeO45,
8, Fe2O318,3, CaO9,1, SO,0
13, C2,3, Mn 1.8, moisture 5.5 After charging 4.1 with wet secondary dust, the furnace mouth was sealed using the furnace mouth cover, and the furnace atmosphere temperature was 650°C. Dry.

Next, the hot metal blending ratio was 86.7%, and the hot metal temperature was 1357°C.
1.As a result of charging and blowing hot metal with a Si concentration of 27X10-2%, the molten steel yield was 1.
We were able to obtain an increased effect of 21%. The blow-off component of this charge had no problems, and the slag formation was also good.

Comparative Example 1 170 was placed in a converter, and the inside of the furnace was kept in an inert atmosphere using protective gas in the same manner as in Example 1. Dust components (wt%): T-Fe 53.77, F
e00.4, Fe2O373,? , Can 10.3,
SO, 05, CO, 4, Mn 1. [l, moisture 1.
After charging the sun-dried dust No. 5 to No. 4.4, it was force-dried in the furnace in the same manner as in Example 1.

Next, the hot metal blending ratio was 87.5%, and the hot metal temperature was 1341”0.
When hot metal with a Si concentration of 22 x 10-2% was charged, an abnormal reaction occurred on the charging surface and a large amount of flames were generated, creating a very dangerous situation. This seems to be a decomposition reaction of Fe2O3, in which (C) in the hot metal reacted with decomposition 0.

In addition, the molten steel yield was increased by 1.23% compared to the comparison material (normally operated material without using dust, conducted N = 15 times). Furthermore, there were no problems with the blow-off component and slag properties.

However, this method caused flames to occur during the process, making it difficult to operate on a regular basis, and clogging of the hopper occasionally occurred during the supply of powder, making it unsuitable for stable, regular operation.

Comparative Example 2 Pellet material obtained by solidifying 170 using cement material in a converter was charged into the auxiliary raw material hopper on the furnace, and pelletized dust component (wt%): T-Fe 49.8, F
ee O,4, Fe2O387,? , Ga015.8,
S O,+4, C0036, Mn L, S, dust with a moisture content of 1.0 was used as a substitute for iron ore in the furnace.

Next, the hot metal blending ratio was 97.0%, and the hot metal temperature was 1360°C.
1 Si concentration in hot metal 32X10-2%, S 30 Xl
As a result of charging 0-2% hot metal, performing blowing, and using pellet dust as the primary charge from the top of the 5.4 t/ch furnace, the molten steel yield was lower than that of the comparative material (normal operation without using dust). wood,
We were able to obtain an increase effect of 1.08% compared to the test (N = 15 times), but the blowout component (S) value was 60XIO-
The result was a high after-plow of 2%.

Effects of the Invention According to the converter blowing method of the present invention, dust can be reused in a simpler and cheaper manner than conventional methods, and the active ingredients in the dust can be recovered to improve the yield of molten steel and reduce the unit consumption of quicklime. , increased LDG recovery, etc., and the effect on manufacturing costs is extremely large.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an example of an apparatus used to carry out the method of the present invention. l...Top and bottom blowing converter, 2...bottom blowing nozzle, 3...inert gas, 4 fists...furnace mouth cover, 5, Φ, dust.

Claims (1)

[Claims] The wet secondary dust generated during converter operation is pre-charged into a top-bottom blowing converter, and is then heated in an inert atmosphere created by bottom-blowing inert gas.
A converter blowing method characterized in that the wet secondary dust is dehydrated using the residual heat of the furnace body after the previous blowing, and then hot metal is charged and blowing is performed.