JP2002105517A - Method for operating blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for operating a blast furnace by which the ventilation in the furnace is kept satisfactory and a stable operation can be performed in the injecting operation of pulverized fine coal. SOLUTION: In the blast furnace operation performed by injecting >=180 kg/ton of molten iron of pulverized fine coal, the amount of blasted air and the amount of oxygen enrichment supplied into the blasting air, are controlled so as to satisfy the conditions in the following relations (1) and (2) in accordance with a coke strength after hot-reaction (CSR): (1) in the case the CRS of the coke charged into the furnace is <60%, Vbosh/Vin <=2.05, and (2) in the case the CSR of the coke charged into the furnace is >=60%, Vbosh/Vin <=2.20. Here, Vbosh/Vin is the ratio of the amount of gas in the bosh part of the blast furnace to the inner volume of the blast furnace defined by ([the blasting air amount (Nm3/min)]×0.79+2×[the blasting air amount (Nm3/ min)]×0.21+2×[the amount of oxygen enrichment (Nm3/min) into the blasting air]/[the inner volume in the blast furnace (m3)].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to
The present invention relates to a method for operating a blast furnace by blowing more than kg / ton of hot metal.

[0002]

2. Description of the Related Art Normally, in blast furnace operation, ore and coke are charged alternately from the furnace top, and coke is burned with hot air of about 1200 ° C. blown from tuyeres at the bottom of the furnace, and the ore is generated by the generated gas. It is to obtain hot metal by reduction. In recent blast furnace operations, pulverized coal is injected from the tuyere instead of coke for the purpose of extending the life of the coke oven and reducing hot metal cost, and the amount of injection is increasing year by year. .

[0003] In a high pulverized coal injection operation in which pulverized coal is blown by 180 kg or more per ton of hot metal, the charged material layer is increased by increasing the ratio (O / C ratio) of the amount of ore charged to the amount of coke charged per ton of hot metal. Due to the decrease in the porosity of the furnace, the rise in the furnace gas temperature due to the decrease in the heat capacity ratio (heat flow ratio) between the charge and the furnace gas per ton of hot metal, and the resulting increase in the furnace gas flow velocity. It is known that this causes an increase in ventilation resistance and pressure loss.

[0004]

When such a condition occurs, a remarkable increase in the blowing pressure and a blow-through phenomenon in which the charged material is blown up to the upper portion of the furnace without being stably lowered, and as a result, the blast furnace Stable operation is greatly impaired, and operation elasticity is significantly reduced. Therefore, in order to realize stable operation under high pulverized coal injection operation, it is extremely important to maintain good furnace air permeability. Accordingly, an object of the present invention is to provide a method for operating a blast furnace, which maintains a good air permeability in a furnace in a high pulverized coal blowing operation and enables a stable operation.

[0005]

Means for Solving the Problems The present inventors have conducted a detailed study on the improvement of air permeability in a furnace in a high pulverized coal injection operation, particularly in a high pulverized coal injection operation in which pulverized coal is injected at 180 kg or more per ton of hot metal. , As a result, Vbosh
/ Vin, ie, [blast air volume (Nm ³ / min)] × 0.
79 + 2 × [blowing air amount (Nm ³ /min)]×0.21+
2 × [oxygen enriched amount in blast air (Nm ³ / min)] /
There is a clear correlation between the ratio of the gas amount in the blast furnace bosh section (morning glory) defined by [Blast furnace internal volume (m ³ )] to the blast furnace internal volume, and the ventilation resistance in the furnace.
The Vbosh / Vin is controlled within a predetermined level or less according to the strength CSR after the hot reaction of the coke charged into the furnace by controlling the air permeability in the furnace. By controlling, it was found that the air permeability in the furnace in the operation of blowing high pulverized coal was kept good and a stable operation could be performed.

The present invention has been made based on such findings, and the features thereof are as follows. [1] In the operation of a blast furnace in which pulverized coal is blown at a rate of 180 kg / ton or more of hot metal, strength after hot reaction of coke CSR
A method for operating a blast furnace, comprising controlling the amount of blown air and the amount of oxygen enriched in the blown air so as to satisfy the following conditions (1) and (2) according to (1) When the strength of the coke introduced into the furnace after hot reaction is less than 60% CSR Vbosh / Vin ≦ 2.05 (2) When the strength of the coke after hot reaction of the coke introduced into the furnace is 60% or more Case Vbosh / Vin ≦ 2.20 Here, Vbosh / Vin: ratio of the gas amount in the blast furnace bosh portion and the internal volume of the blast furnace, which is defined by the following formula ([air volume of blown air (Nm ³ /min))×0.79+2 × [blown air amount (Nm ³ / min)] [oxygen enrichment of the blast air (Nm ³ / min)] × 0.21 + 2 ×) / [ blast furnace volume ^(m 3)

[2] In the operation method according to the above [1], at least one of the oxygen enrichment amount in the blast air, the blast temperature, and the blast humidity is controlled so that the theoretical tuyere tip combustion temperature becomes 1950 ° C. or more. A method for operating a blast furnace, comprising:

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, 180 kg /
In the operation of a blast furnace in which more than a ton of hot metal is blown, Vbosh / Vin, that is, the following equation, according to the hot strength index of coke charged into the furnace interior, ([blast air volume (Nm ³ /min)]×0.79+2×[blast Blast furnace Bosch portion defined by (air amount (Nm ³ /min))×0.21+2×[oxygen enrichment amount in blown air (Nm ³ / min)] / [blast furnace inner volume (m ³ )] ( Control the amount of air blown and the amount of oxygen enriched in the blown air so that the ratio of the gas volume in the morning glory to the volume inside the blast furnace (total volume inside the blast furnace) satisfies the following conditions (1) and (2): . (1) Strength CSR after hot reaction of coke in furnace interior is 60%
If less than Vbosh / Vin ≦ 2.05 (2) The strength CSR after hot reaction of coke inside furnace is 60%
In the above case, Vbosh / Vin ≦ 2.20

In the present invention, Vbosh / Vin is controlled under different conditions in accordance with the post-hot-strength CSR (hereinafter, simply referred to as “CSR”) of the coke contained in the furnace interior. This is because the amount of coke breeze generated in the furnace and the degree of particle size reduction are different. here,
Coke's CSR (coke strength after reaction)
After heating coke having a particle size of 20 ± 1 mm in a CO ₂ atmosphere at 1100 ° C. for 2 hours, an I-type drum test (20 rpm × 60 minutes) was performed at room temperature, and the particle size after the test was 9.5 m
It is represented by the ratio (%) of coke of m or more.

FIG. 1 shows that pulverized coal is weighed at 180 kg / tonne of hot metal or less.
Vbo based on the data of the actual operation of the blast furnace that was blown up
An example of the relationship between sh / Vin and the ventilation resistance in the furnace
is there. Here, the blowing pressure Pb (kg / cm²) And furnace top pressure
Force Pt (kg / cm²Pb-Pt, which is the difference from
This is an index indicating the ventilation resistance. According to FIG.
If the coke CSR is less than 60%, Vbosh /
Vin ≦ 2.05, coke CSR inside furnace is 6
In the case of 0% or more, Vbosh / Vin ≦ 2.20 is satisfied
Thereby, Pb-Pt which is an index of the ventilation resistance in the furnace is
1.6kg / cm ²It can be suppressed to the following. Also,
When coke with CSR of 60% or more is used, Pb-
Pt is reduced overall and is effective for improving airflow resistance.
I understand.

Here, Vbosh / Vin can be controlled, for example, by adjusting the amount of oxygen enrichment in the blown air. In general, in the blast furnace operation, the oxygen consumption rate is determined according to the hot metal production volume. Therefore, if the production volume is fixed, the higher the oxygen enrichment rate in the blast air, the higher the Vbosh
The value of / Vin decreases. In the present invention, the lower limit of Vbosh / Vin is not particularly specified, but from the viewpoint of ensuring the stability of gas flow in the blast furnace, it is preferable to set the lower limit to about 1.50.

When the amount of pulverized coal blown into the blast furnace is increased, it is generally considered that the ventilation resistance in the furnace increases due to the following factors. When the pulverized coal injection amount is increased, the pulverized coal injection density increases, so that the contact efficiency between pulverized coal and oxygen decreases, and the combustion efficiency of pulverized coal decreases. As a result, a large amount of unburned coal (unburned char) is generated. However, since the solution loss reaction (CO ₂ + C → 2CO) by the unburned coal consumes CO ₂ in the furnace, it is generated by coke pulverization. Coke powder is less likely to be consumed by the solution loss reaction. For this reason, coke powder stays and accumulates in the furnace core, and the ventilation resistance in the furnace increases.

[0013] Since the replacement of coke with pulverized coal has a limit, increasing the amount of pulverized coal blow inevitably increases the fuel ratio (coke ratio + pulverized coal ratio). Accordingly, the unit air volume for blowing increases, so that the gas flow rate in the furnace increases, and as a result, the ventilation resistance in the furnace increases. As mentioned above, as a result of the increase in the fuel ratio and the basic unit of blast,
Since the heat supply amount is large, the cohesive zone shifts to the upper region side of the furnace, and accordingly, the surface area of the cohesive zone increases, so that the ventilation resistance in the furnace increases. Since the ratio (O / C ratio) of the charged amount of ore to the charged amount of coke per ton of hot metal increases, the porosity in the charged layer decreases, and the ventilation resistance in the furnace increases. Since the slag ratio increases with an increase in the fuel ratio, the ventilation resistance in the furnace increases accordingly.

In the present invention, Vbosh / Vin is adjusted to the above (1) and
By controlling to the condition (2), it is considered that the in-furnace airflow resistance is reduced by the following actions, and the in-furnace air permeability is improved. (a) As a result of relatively increasing the oxygen enrichment rate in the blast air, the combustion efficiency of pulverized coal in the furnace is improved, the amount of unburned coal is reduced, and the solution loss reaction due to unburned coal is suppressed. As a result, the coke powder generated by the coke pulverization (the amount of coke
(Depending on R) is easily consumed by the solution loss reaction, the amount of stagnation and accumulation of coke powder in the furnace core decreases, and the ventilation resistance in the furnace decreases.

(B) Since the combustion efficiency of pulverized coal in the furnace is improved, the replacement ratio of coke by pulverized coal is improved, and the fuel ratio (coke ratio + pulverized coal ratio) can be reduced. Along with this, the unit air volume decreases, so that the gas flow rate in the furnace decreases, and as a result, the ventilation resistance in the furnace decreases. (c) As described above, as a result of reducing the fuel ratio and the basic unit of air blowing, the heat supply amount is reduced, so that the cohesive zone can be maintained at the lower region side of the furnace, and as a result, the ventilation resistance in the furnace is reduced. I do. (d) Since the slag ratio also decreases as the fuel ratio decreases, the ventilation resistance in the furnace decreases accordingly.

Further, in the blast furnace operation of the present invention, at least one of the oxygen enrichment amount, the blowing temperature, and the blowing humidity in the blown air is adjusted so that the tuyere tip combustion temperature (hereinafter referred to as TFT) becomes 1950 ° C. or more. It is preferable to control one. Here, the TFT is a flame temperature when coke and pulverized coal burn at the tuyere tip, and this flame temperature has a great influence on furnace heat. This TFT is calculated by the following equation (ram's equation). TFT = (2450 + Qf + Qb + Qc) / (Cg · V
g) However, Qf: blast fuel reaction heat (kcal / kgC, C:
Cb burning at the tuyere tip) Qb: Sensing blast heat (kcal / kgC, C: C burning at the tuyere tip) Qc: Coke sensible heat flowing into the combustion zone at the tuyere tip (kca)
l / kgC, C: tuyere burned in C) Cg: product gas pressure specific heat ^{(kcal / Nm 3 · ℃)} Vg: the product gas volume ^{(Nm 3 / kgC, C:} C to burn at tuyere)

By setting the temperature of the TFT to 1950 ° C. or higher, the flammability of the pulverized coal is maintained, the improvement of the air permeability in the furnace is more effectively promoted, and the securing of the supplied heat is also promoted. FIG. 2 shows the relationship between the TFT and the amount of pulverized coal blown. When the amount of pulverized coal blown is increased, Qf decreases due to VM (volatile matter) decomposition heat, and the TFT decreases. When the temperature of the TFT becomes 1950 ° C. or lower, the instability of the furnace condition becomes apparent.

In order to avoid the instability of the furnace condition by increasing the TFT, it is effective to increase the oxygen enrichment rate. As a result, the increase in the oxygen concentration in the blast air promotes the generation of CO combustion heat. A decrease in Qf due to an increase in the amount of pulverized coal injected is suppressed. It is also effective to raise the temperature of the blown air, to reduce the moisture added to the blown air, and the like to raise the TFT. By controlling one or more of these, a desired TFT can be obtained.

[0019]

EXAMPLE In a blast furnace of an actual machine, a high-pulverized coal injection operation was carried out under the conditions shown in Table 1. The results are shown in Table 1.

[0020]

[Table 1]

[0021]

As described above, according to the method of the present invention, in a high pulverized coal blowing operation in which pulverized coal is blown into a blast furnace at 180 kg / ton or more of hot metal, airflow resistance in the furnace is effectively reduced and stable Operation can be implemented.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between Vbosh / Vin based on actual operation data of a blast furnace and the ventilation resistance in the furnace.

FIG. 2 is a graph showing a relationship between a pulverized coal injection amount and a TFT.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Shimomura 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Hoshihisa Mori 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. F-term (reference) 4K012 BE01 BE06 BE09

Claims (2)

[Claims] In a blast furnace operation in which pulverized coal is blown in at a rate of 180 kg / tonne of hot metal or more, blast air is supplied so as to satisfy the following conditions (1) and (2) in accordance with the post-hot reaction strength CSR of coke. A method for operating a blast furnace, characterized by controlling the amount and oxygen enrichment in the blast air. (1) When the strength of the coke introduced into the furnace after hot reaction is less than 60% CSR Vbosh / Vin ≦ 2.05 (2) When the strength of the coke after hot reaction of the coke introduced into the furnace is 60% or more Case Vbosh / Vin ≦ 2.20 Here, Vbosh / Vin: ratio of the gas amount in the blast furnace bosh portion and the internal volume of the blast furnace, which is defined by the following formula ([air volume of blown air (Nm ³ /min))×0.79+2 × [blown air amount (Nm ³ / min)] [oxygen enrichment of the blast air (Nm ³ / min)] × 0.21 + 2 ×) / [ blast furnace volume ^(m 3) 2. The method according to claim 1, wherein at least one of the amount of oxygen enrichment in the blown air, the blown temperature, and the blown humidity is controlled so that the tuyere tip theoretical burning temperature is 1950 ° C. or more. Operating method of the blast furnace described.