JPS61201709A - Method for operating blast furnace to attain low si content - Google Patents

Abstract

PURPOSE:To stabilize the operation of a blast furnace and to reduce the amount of a ferroalloy used in a steel manufacturing stage as well as to increase the amount of Mn in molten pig iron and to reduce the amount of Si by using powdery Mn and MgO sources in the blast furnace after agglomeration. CONSTITUTION:Fine ore contg. Mn, MgO and CaO sources as principal components is kneaded with cement as a binder, molded, crushed and charged into a blast furnace. The crushed product is similar in shape to sintered ore and has a large angle of repose and gas permeability, so it has satisfactory properties as a starting material for a blast furnace. By this method, the productivity is enhanced, the fuel ratio is lowered and the gas permeability in the furnace is increased. As a result, the amount of Si in molten pig iron can be reduced to the desired value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a blast furnace operating method for reducing the St concentration in hot metal for the purpose of stabilizing blast furnace operation and reducing the amount of ferroalloy used in the steelmaking process.

Prior art and its problems In the transfer of St into hot metal in a blast furnace, a gas-metal reaction mediated by SIO gas plays a major role, rather than a sulfur-metal reaction in the hearth sump.

Si transfer into hot metal via SIO gas is as follows:
It is roughly divided into two processes (Tetsu to Hagane vol. 1.5 Si9282
(page 19).

That is, (1) SIO whose main source is ash in coke in the high temperature, low oxygen partial pressure region near the raceway.

The generation process of SIO gas by the reaction between the carbon and the fixed carbon in the coke; ■ The generation process of SIO gas in the hot metal by the reaction between the SiO gas contained in the rising gas flow below the softening cohesive zone and the carbon in the dripping hot metal. This is a transition process, and the reaction equations for both processes are as follows.

■(Sin,) + C= 5iO(f) + Go(
f) ■5IO (f) 10 Ω = 10 GO (f) Here, () is the conventional notation to indicate that the compound is present in the puffer fish, and the underlined element name indicates that the component is present in the hot metal. This is a customary notation to indicate the existence of something. Also, <y
> is a common notation to indicate that the compound is a gas. Therefore, as a method for controlling the Si concentration in hot metal, Si
There is control of the degree of O gas generation and control of the Si transfer reaction into the hot metal.

In actual blast furnace operation, the former control means include controlling the amount of ash in the coke to bring Sin in before the tuyere, controlling the amount, and controlling the SIO gas generation rate by controlling the temperature before the tuyere. The latter control means include controlling the cohesive zone level by controlling the coke ratio based on charge distribution control, and controlling the cohesive zone level by controlling the reducibility and softening and cohesive properties of sintered ore ( Tetsu to Hagane vO Muro Si98
2 p. 129).

In addition to the above-mentioned control method based on the SN transfer mechanism into the hot metal within a high diameter, iron oxide is blown into the furnace from the blast tuyeres, and the following reaction A so-called in-furnace desiliconization means for oxidizing Si in hot metal has been developed (JP-A-53-87908, JP-A-56-29601, JP-A-58-77508, etc.).

■Si + 2FeO = (Sift) + 2Fe Also, with the main purpose of reducing the amount of ferroalloy used in the steelmaking process, manganese ore is charged into the blast furnace based on the economic situation at the time, and Mn in the hot metal is reduced. Conventionally, operations have been carried out to increase the In this operation, the manganese ore charged to the blast furnace is large compared to the appropriate particle size for use in the blast furnace.
It was crushed and sieved, and the top of the sieve (5 to 25 cm) was charged from the top of the furnace as lump ore, and the bottom of the sieve (-5 m, ) was blended as a sintered ore raw material, enriched in Mn more than usual. It is charged into a blast furnace as sintered ore.

Manganese oxide charged into a blast furnace as lump manganese ore or sintered ore has a manganese yield 9 of approximately 75% below the softened cohesive zone, and Mn in the hot metal is enriched according to the amount of manganese charged. Ru. The rate equation of the Si transfer reaction into the hot metal of Equation 0 is shown below, and the enrichment of Mn in the hot metal has the effect of reducing the Si in the hot metal because it increases the activity coefficient/S1 of the hot metal.

■SiO (g) + C = gong + co <y>t asi = /Si - (%5i) 10f/Si = 0.177 (%c) +0.122
(%Si) +0.2Si[%Mn) +0.057
(%S) However, the above-described conventional method for enriching Mn in hot metal has the following problems.

First, when the bottom of the sieve (-5wm) is used as sintered ore raw material, the 4O in the sintered ore raw material increases, and if the coke consumption rate of the sintering machine remains constant, the reduction pulverization index of the finished sintered ore ( R
The reduced pulverization index (R) of finished sintered ore deteriorates.
In order to maintain DI) at a constant KM, it is necessary to increase the coke consumption rate, which leads to an increase in the production cost of sintered ore.

Further, there is a problem in that the effect of reducing 31 in hot metal when manganese magnets are charged from the top of the blast furnace is smaller than when manganese magnet powder is blown into the blast tuyeres. In addition, S in hot metal when manganese magnet powder is blown from the blast furnace tuyere.
The t reduction effect is explained by the fact that iron oxide together with manganese oxide contained in manganese ore causes a desiliconization reaction shown in the following formulas (1) and (2).

■Sf + 2 (MnO) = 2Mn + (SI
Oori ■Si + 2 (Fed) = 2 Fe +
(Sift) An in-furnace desiliconization method in which manganese oxide powder is blown into a blast furnace from a blowing tuyere using the desiliconization reaction described above is known, for example, from Japanese Patent Application No. 57-25983. In the case of tuyere injection, it is necessary to crush the entire amount of manganese ore, which has the disadvantage that the crushing cost is very high.

Purpose of the Invention This invention was made in view of the above-mentioned conventional situation, and it is possible to use powdered Mn ore, powdered MfO source, etc. in the same form as sintered ore and lump coke, and it is economical. The purpose of the present invention is to propose a blast furnace operating method that can increase Mn in hot metal and decrease Si in hot metal.

Structure of the Invention The low SI operation method according to the present invention comprises Mn, WifO
*Powdered ore containing CaOtA as the main component is mixed with semesites as a binder, molded and then crushed to produce high iK.
It is characterized by reducing S171 degrees in hot metal by charging it.

That is, the present invention is a method of reducing the sla degree in hot metal by agglomerating powdered Mn K, powdered MpO sources, etc. in the same way as so-called uncalcined agglomerated ore and using it in a blast furnace.

Cold bonded ore, known as unfired agglomerate used in blast furnaces, is generally manufactured by mixing fine ore or limestone powder with a binder such as cement, then forming it into a block shape, and crushing it. It is.

Because the cold bonded metal produced by this method is crushed, it has a shape similar to sintered ore, has a large angle of repose, and has the same air permeability and state after reduction as sintered ore. It is recognized that it has good properties as a raw material.

1 This invention focuses on the so-called cold bond method in which iron magnets are agglomerated with a cement binder and cold bond ore having the above properties. This method is characterized in that the Mn source, MpO source, and CaO source used to increase MfO and basicity are agglomerated by a cold bond method and used as blast furnace charge.

Figure 1 shows an example of the manufacturing process for blast furnace charge according to the present invention. Therefore, a powdered Mn source, powdered MfO source, powdered CaO source and a binder such as Portland cement are mixed and this is formed into a block shape. After steam curing, crush. here,
As the Mn source, the MgO source, and the CaO source, it is possible to use powdered powder, powdered serpentine, dolomite powder, Ni slag, iron-containing dust, and the like. The powder ore used is as follows:
Considering high temperature properties, 10■ or less and 111111 or more are 1
Preference is given to using ores containing from 0 to 70%. In other words, one or more ores remain as they are and hardly contribute to softening and shrinkage.
If the particle size is 10% or more, a softening property equivalent to that of a normal blast furnace raw material can be obtained, and if it exceeds 70%, the rotational strength becomes lower than the standard rotational strength and becomes unusable.

In this invention, a mixture of a powdered Mn source, powdered MfOg, powdered CaO source, Portland cement as a binder, and moisture if necessary is formed into a block shape using, for example, vibration energy, and after steam curing, a desired size is formed. Crush into pieces. Although it is possible to use a book molded into a block shape in the state 11, it is better to use it after crushing it to improve the angle of repose and ventilation resistance in the blast furnace. That is, the angles of repose of pellets and sintered ore, which are the main blast furnace charges, are 25° and 30°, respectively, and the crushed block-shaped material according to the present invention has an angle of repose of about 31°. , the angle of repose is close to that of sintered ore, which is in good shape, and the charging distribution is improved. Also, because the angle of repose is large, the filling rate in the furnace is low fk! can provide good gas flow.

The particle size after crushing is preferably about 10 to 5 degrees, which is the same as that of sintered ore, which is the main raw material of the blast furnace. In addition, Mn and MpO are the main components of this cold-formed crushed ore.

The content of CaO is not particularly limited.
Mn5~3o%, MP010~40%, Ca010~5
0% is appropriate.

The reason why cold forming is used as a means of producing the blast furnace charge in this invention is because Mn ore and MfO source materials generally have a high melting point.
This is because it poses a quality problem. Also, when mixing raw materials, if solid powder cement is used as a binder, water must be added, but if a liquid binder is used, it is not necessary to add water, so water can be added as necessary. Bye.

Examples Raw materials having the composition shown in Table 1 and the particle size structure shown in Table 2 were mixed, molded into a block shape with a size of 150 to 250 txm, and cured at 50'C for 8 hours. The cold-molded crushed iron having the product properties shown in Table 3 obtained by crushing it to 50cm was crushed into A blast furnace (inner volume 27cm) using the raw material ratio shown in Table 4.
00 d) are shown in Table 4 in comparison with the conventional method.

As is clear from Table 4, compared to the conventional method, the method of the present invention significantly increases productivity, lowers the fuel ratio, and improves the ventilation inside the furnace, and as a result, Si in the hot metal is reduced.

(Leaving space below) Table 1 Composition of raw materials used Table 2 Particle size composition of raw materials used 3 Table Product properties Table 4 Blast furnace raw material ratio Table 5 Results Effects of the invention As is clear from the above examples, this invention According to the method, there is no negative impact on operations, mainly deterioration of sintered ore quality during the sintering process and deterioration of air permeability during blast furnace operation.
Since the amount of Si in the hot metal can be lowered by increasing the Mn in the hot metal, it is highly effective in stabilizing blast furnace operation and reducing the amount of ferroalloy used in the steelmaking process.

[Brief explanation of the drawing]

Claims (1)

[Claims] In a blast furnace operating method for reducing the Si concentration in hot metal, M
This method is characterized by lowering the Si concentration in hot metal by kneading powdered ore mainly composed of n, MgO, and CaO sources with cement as a binder, and charging the crushed product after molding into a blast furnace. A method for operating a blast furnace with low Si.