JPH0635604B2 - Blast furnace operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention maintains the blast furnace slag basicity CaO / SiO ₂ and the slag Al ₂ O ₃ concentration in a predetermined range in a blast furnace low sinter ratio operation. Accordingly, the present invention relates to a blast furnace operating method capable of reducing the Si concentration in the gun and the S concentration in the gun under stable unloading.

(Prior art and its problems) Regarding the migration of Si into the molten gun in the blast furnace, the gas-metal reaction mediated by SiO gas plays a major role rather than the slag-metal reaction in the hearth pool. There is. Thus, the migration of Si into the melting gun using SiO gas as a medium is roughly divided into the following two processes (“Iron and Steel” Vol. 58, 197).
2, 219-230).

That is, in the high-temperature low-oxygen partial pressure region near the raceway, the production process of SiO gas by the reaction of SiO ₂ mainly containing ash in coke and fixed carbon in coke, in the rising gas flow below the softening cohesive zone It is the process of Si transfer into the gun by the reaction between the contained SiO gas and the carbon in the dropping gun. These two processes can be expressed by the reaction formulas below.
It becomes like a formula.

(SiO ₂ ) + C = SiO (g) + CO (g) ... SiO (g) + C = Si + CO (g) ... In the above formula, () is a conventional notation indicating that the compound is present in the slag. Yes, the underlined element name is a convention that indicates that the component is present in the gun. Further, (g) is a conventional notation indicating that the compound is a gas.

Therefore, as is clear from the above equation, Si in the molten gun
As a method for controlling the concentration, control of the SiO gas generation reaction (
Formula) and control of Si transfer reaction into the molten gun (Formula).

By the way, in the actual operation of the blast furnace, the former control method is to bring in the front of the tuyere by controlling the amount of ash in coke.
Control of the SiO ₂ amount and control of the SiO gas generation rate by controlling the tuyere front temperature are carried out. Further, as the latter control means, control of the cohesive zone level by controlling the coke ratio based on the charge distribution control, reducibility of the sinter, control of the cohesive zone level by controlling the softening fusion property, etc. Yes ("Steel Steel" Vo
68.1982, A129-A132).

However, the control of the ash content in coke by the former control means has a limitation in terms of raw material coal blending.
Further, the latter control means has almost reached the limit in terms of operation and raw materials, and improvement of the properties of the sintered ore leads to an increase in cost.

On the other hand, with regard to the transfer of S into the melting gun in the blast furnace, S in gasified coke and liquid fuel near the raceway is vulcanized into ore at the shaft portion and is mainly slag-below the softening cohesive zone. It is known to be desulfurized by a metal reaction. Below is S between slag and metal
The partition reaction is shown.

S = (S) ... Where T is temperature (K), f _s is activity coefficient of S in the melting gun, and Cs
Represents the desulfurization capacity. Also,
N _CaO , N _SiO2 , N _Al2O3 , and N _MgO represent the mole fraction of the component in the slag.

That is, in the actual blast furnace operation, as a means for reducing the S in the melting gun, the temperature of the melting gun is increased, the amount of charged S is reduced, the amount of slag is increased, or the slag assembly is adjusted, that is, CaO / SiO ₂
Rising, Al ₂ O ₃ lowering, MgO rising are taken. However, the rise in the firing temperature is limited because it leads to an increase in the coke ratio and a rise in Si in the firing gun. In addition, there is a restriction on the reduction of the amount of charged S from the viewpoint of blending of raw coal.

Regarding the increase in the amount of slag, in addition to the increase in the coke ratio, there is a danger that the amount of residual slag will increase and the load will fall in an irregular manner if it is increased transiently. Further, also in adjusting the slag composition, in order to maintain stable operation, it is necessary to maintain the difference between the firing temperature and the melting point of the final slag at a certain value or more.

Here, as a measure for suppressing the SiO gas generation reaction as a means for controlling the Si in the melting gun, it is also effective to reduce the activity a _SiO2 of SiO _{2 in} the slag. In particular, the raceway near high temperature and low oxygen partial pressure atmosphere, and the slag in the SiO ₂ by coke derived SiO ₂ is large activity of a _SiO2 is high, since a vigorous generation region of the SiO gas, in this area Slag CaO / SiO
₂ with decreasing the activity of a _SiO2 in the slag SiO ₂ raises the, reducing the slag year, is an effective control means溶銃in S with the Si溶銃.

The activity a of SiO ₂ in the slag near the raceway
As one means for reducing SiO ₂ , it has been attempted to add quick lime in the process of coke production to increase the CaO content in the product coke (“Coke Circular” Vol. 17, 1968, p. 97). Pp. 103). However, if 5-10% of limestone is added to the high flow synthetic coal,
Although it is possible to produce high-strength blast furnace coke by reducing the proportion of strong coking coal, the coke productivity is considerably reduced, and the limestone erosion of the coke oven wall silica brick due to added limestone is a problem. It

On the other hand, in recent blast furnace operations, most blast furnaces operate at a self-fluxing sinter ratio of 70% or more in order to exert high productivity under stable operation. By the way, most of the sinter CaO / CiO ₂ is 1.6-
It is maintained within the range of 2.0. Accordance connexion, so that CaO / SiO ₂ and Al ₂ O ₃ content of the final slag is maintained within a certain range, CaO / SiO ₂ of the sinter has been determined in accordance with the sinter ratio and coke ratio However, fine adjustment is performed by charging auxiliary materials such as limestone, serpentine, and silica stone together with ores from the furnace top.

In addition, the activity of SiO ₂ in the slag near the raceway a _SiO2
As a second method of reducing the temperature, blowing limestone powder from the tuyere can be mentioned. However, under the above conditions, due to the restrictions on the amount and composition of the final slag, the injectable amount is limited, and a large effect cannot be expected.

On the other hand, in a blast furnace operation with a sinter ore ratio of 70% or more and fuel injection from the tuyere, the sinter ore CaO / SiO ₂ is reduced to 0.6 to 1.0, and the final slag amount and composition are An invention of a method of blowing limestone powder from a tuyere for adjustment is disclosed in Japanese Patent Publication No. 39-8004.
Since this method has a large amount of limestone powder that can be blown from the tuyere, it is advantageous for reducing Si and S in the gun. However, although the drop strength is improved with respect to the properties of the sintered ore, the high temperature property of the sintered ore, that is, The reducibility and softening and fusion properties deteriorate,
Blast furnace operation is at risk of falling unloading irregularly.

The present invention is directed to the activity a of SiO ₂ in slag near the raceway.
_This is done in order to solve the above-mentioned conventional problems in a blast furnace operating method aiming at low Si and low S operation by reducing _SiO2 and adjusting the slag viscosity. Without deteriorating the property
Moreover, it is an object of the present invention to provide a blast furnace operating method capable of injecting a large amount of a slag-forming agent from a tuyere and obtaining a large low-Si and low-S operating effect under a stable load condition. .

(Means for Solving Problems) The present invention provides a powder of a complex compound or a mixture with a CaO source and / or an MgO source as a slag-forming agent in a blast furnace low sinter ratio operation with a sinter ratio of 50% or less. By blowing the tuyere of the body, the blast furnace slag basicity CaO / SiO ₂ is 1.22 to 1.3.
The gist is to adjust the slag Al ₂ O ₃ to 17% or less in the range of 0 to reduce the Si concentration in the gun and the S concentration in the gun.

That is, the present invention, when adjusting the final slag composition in a blast furnace low sinter ratio operation with a sinter ratio of 50% or less,
For example, a method of blowing limestone and serpentine powder as a slag forming agent from the tuyere of a blast furnace.

In the method of the present invention, the reason for adopting the powder blowing method of the slag-forming agent from the tuyere of the blast furnace in the operation of the sinter ore ratio of 50% or less is as follows.

When production is concentrated in a specific steel plant where multiple blast furnaces are operating, and it is necessary to reduce the amount of sinter used in the blast furnace due to the relationship with the sintering machine production capacity, for example, Sintered ore is intensively blended in A and B blast furnaces to maintain the ratio of sinter to 70% or more, and C blast furnace is used to reduce the amount of sinter used to 50% or less. Is performed.

By the way, as compared with the sintered ore, the pellet and the raw ore have lower CaO content and CaO / SiO _{2 as} shown in Table 1 below. Therefore, in the low sinter ratio operation, the final slag CaO / SiO ₂ , Al ₂
O ₃ needs to be adjusted and usually serpentine and limestone are charged from the furnace top. For example, in a low sinter ratio operation with a sinter ratio of 30%, a pellet ratio of 35%, and a raw sinter ratio of 35%,
The final slag composition was CaO / SiO ₂ = 1.26, Al ₂ O ₃ = 14.
Limestone 90kg / P-T, serpentine 30 for 5%
kg / P-T is charged from the furnace top.

On the other hand, in the vicinity of the tuyere, there is a high-temperature strongly reducing atmosphere, and there are many slags with a very low CaO / SiO ₂ content derived from coke ash, so increasing the slag CaO / SiO ₂ in this region is
Leads to a decrease in activity of a _SiO2 in the slag SiO _2, i.e., since SiO gas generation reaction inhibiting effect of the equation is large, the adjustment of the final slag by slag agent is better to conducted in blowing powder from the tuyere The effect of reducing Si and S in the molten gun is great. In particular, in a low sinter ore ratio operation, the amount of slag blowing agent for the final slag adjustment increases,
The controllability of Si and S in the molten gun is great.

When injecting the slag-forming agent from the tuyere, the pre-tuyere coke consumption is calculated by inputting the blast furnace blowing conditions, and a known state diagram (for example, A.Muan, EFOsborn: Phase Eguilibr
ia among Oxides in Steelmaking, ADDISON-W
ESLEY PUBLISHING COMPANY.
INC. The CaO-SiO ₂ -Al ₂ O ₃ melting -MgO 4-element slag tuyere near using pp 1,965.130 to 142) so that the 1600 ° C. or less, limestone, etc. serpentinite Zokasu By controlling the amount of the agent blown in, it is possible to operate with stable unloading.

(Experimental Results) The results of carrying out the method of the present invention in the blast furnace A (internal volume: 2700 m) are shown in Table 2 below in comparison with the conventional method. In addition, limestone and serpentine as a slag forming agent, straw, sinter ore, pellets and raw ore had the compositions shown in Table 1 above.

This experiment is an example of a blast furnace low sinter ratio operation with a sinter ratio of 30% and 0%, and during periods I and II, the slag CaO / SiO ₂ and Al ₂ O ₃ were kept constant as the final slag adjustment by the conventional method. In order to achieve this, massive limestone and serpentine were charged from the top of the blast furnace.

In this conventional method, since the condition of the slag before the tuyere does not change from the base period, the decrease of Si in the melt gun is not obtained, and the increase of MgO in the final slag decreases the viscosity but the slag amount also decreases. As a result, the S in the gun was only slightly reduced.

On the other hand, in the periods III and IV, the method of the present invention is applied,
Slag CaO / SiO ₂ and Al ₂ O ₃ as final slag adjustment in blast furnace low sinter ratio operation with sinter ratio of 30% and 0%
Powdered limestone and serpentine were blown from the tuyere of the blast furnace in order to maintain a constant value. The use of limestone and serpentine at this time was the same as in the conventional method.

When the method of the present invention is applied, CaO / S of the tuyere front slag
iO ₂ rises, the activity of a _SiO2 of SiO ₂ is decreased, C
_{aO-SiO 2 -Al 2 O 3} -MgO 4 also slag melting point of the component decreases and is maintained at 1600 ° C. or less. Therefore, as a result, Si in the molten gun decreases from 0.30% to 0.21% when the sinter ore ratio is 30%, and 0.30% to 0 when the sinter ore ratio is 0%. It fell to 19%. At the same time, S in the molten gun is 0.025% to 0.0 when the ratio of sinter is 30%.
It decreases to 20%, and it is 0.0 when the sinter ratio is 0%.
It decreased from 24% to 0.018%. Furthermore, when the method of the present invention is applied, the number of slips is reduced from 0.1 times / day to 0 times / day, and the load drop situation also tends to be stabilized.

In addition, the results of this experiment show the case where powdered limestone and serpentine were blown from the tuyere as a slag forming agent in the low sinter ore ratio operation, but it was a composite compound with CaO source and / or MgO source. Alternatively, the same effect can be expected when the powder of the mixture is blown from the tuyere.

(Effects of the Invention) As described above, according to the method of the present invention, under the low sinter ore ratio operation, it is possible to effectively utilize the large addition amount of slag necessary for adjusting the final slag, and Alternatively, a high reducing effect of Si in the gun and S in the gun can be obtained by pulverizing the slag forming agent containing the MgO source into powder and stably blowing it in a large amount from the tuyere.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Suyama 1-3-3 Nishi-Nagasumotodori, Amagasaki City, Hyogo Prefecture Sumitomo Metal Industries, Ltd. Central Research Laboratory (56) Reference Japanese Patent Publication Sho 48-3046 (JP, B1) Japanese Patent Publication Sho 59-7327 (JP, B2)

Claims (1)

[Claims] 1. In a blast furnace low sinter ore ratio operation with a sinter ore ratio of 50% or less, powder of a complex compound or mixture with a CaO source and / or MgO source is blown from a tuyere as a slag forming agent, and the blast furnace exits. The slag basicity CaO / SiO ₂ is adjusted to a range of 1.22 to 1.30, and the slag Al ₂ O ₃ is adjusted to 17% or less to reduce the Si concentration and S concentration in the gun. Blast furnace operation method.