JPH06108126A - Operation of blast furnace - Google Patents

Abstract

PURPOSE:To recover the temp. in coke layer without considerably raising fuel ratio and to avoid the lowering of production caused by bad ventilation and increase in the fuel ratio, in the case of temp. drop in the coke layer at the center part in the furnace lower part of a blast furnace (temp. in the furnace core). CONSTITUTION:The high strength coke having >=85% cold strength (DI 150/15) and >=60% hot strength (CSR) and/or the large grain size coke having >=60mm average grain size are charged into the center part of the furnace top in the quantity of 0.02-0.07 times of the ordinary coke charging quantity from a movable armor or a swinging chute or an exclusive chute.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention maintains the temperature in a coke layer (referred to as a core) in the lower center of a blast furnace during the operation of blowing hot air or hot air and auxiliary fuel from the tuyere of the blast furnace. , Blast furnace operation method to maintain productivity and fuel ratio.

[0002]

2. Description of the Related Art In blast furnace operation, hot air or hot air and auxiliary fuel are blown from the tuyere to blow hot metal. However, as an alternative to coke, a cheap fuel with good combustibility and high calorific value ( Pulverized coal, petroleum, heavy oil, naphtha, etc.) is blown from the tuyere to reduce the hot metal production cost and improve the productivity, and the technique is disclosed in Japanese Examined Patent Publication No. 40-23763. In particular, in recent years, the injection of pulverized coal has become the mainstream in terms of price, which reduces the combustion ratio (cost reduction),
It greatly contributes to productivity improvement.

The auxiliary fuel blown in this way burns in the blast furnace instead of a part of the coke, and produces a large amount of reducing gas at a high temperature due to its good combustibility and high calorific value, which is efficient. Various reduction reactions. Therefore, the iron ore charged from the furnace top is quickly reduced to a metal state and is melted to form high-temperature hot metal, and the furnace heat of the blast furnace is high and the productivity is improved.

[0004]

When a large amount of pulverized coal is blown in the operation of the blast furnace and the ratio of iron ore and coke charged from the furnace top becomes high (abbreviated as O / C), the center of the furnace top is It is more likely that iron ore will be overcharged.
In the conventional blast furnace operation, when the iron ore is excessively charged in the central portion of the furnace top, the central gas flow is suppressed, the iron ore in the central portion is not sufficiently reduced by heating, and FeO is large and the fluidity is low at a low temperature. A large amount of bad melt is dripped into the center of the lower part of the blast furnace. Since a large amount of endothermic reaction of molten FeO occurs rapidly in the center of the lower part of the furnace, the coke layer in the center of the lower part of the blast furnace (called the core)
The liquid permeability of the melt at the time of flowing down is deteriorated, and the temperature in the furnace core is lowered.

When a large amount of auxiliary fuel, especially pulverized coal, is blown in, the entire amount of pulverized coal blown in is not burned and some unburned char is generated, and this unburned char is trapped in the furnace core. The liquid permeability of the melt flowing down the portion is deteriorated, which in turn impairs the gas permeability of this portion, and the temperature inside the furnace core also decreases. If these conditions continue, the melt will begin to solidify and eventually solidify. In either case, the productivity of the blast furnace will drop significantly. At this time, it is assumed that the blast pressure, which shows the air permeability of the entire blast furnace, increased and the core temperature decreased.

When it is assumed that the blast pressure rises and the temperature in the core falls, the O / C at the central portion is lowered and instead the O / C at the intermediate portion to the peripheral portion is increased. When there is no room to increase the O / C from the middle part to the peripheral part, the total O / C
C is lowered. When the auxiliary fuel, especially pulverized coal, is being blown, the blowing amount is reduced or cut, and the overall O / C is lowered instead. In either case, the fuel ratio will increase significantly and the production volume will decrease.

In view of the above, the present invention aims to recover the temperature of the core without significantly increasing the fuel ratio when the temperature inside the furnace core is decreased, and to prevent the production rate from being lowered due to poor ventilation and increase in the fuel ratio. And

[0008]

Means for Solving the Problems The present invention is to solve the above problems, in which iron ore and coke are charged in layers from the furnace top, and hot air or hot air and auxiliary fuel are blown from the tuyere to blow hot metal. In the blast furnace operating method for blowing, the blast furnace operating method is characterized in that when the temperature in the furnace core decreases, high-strength or / and large-grain coke is charged in the central portion of the furnace top. It is also characterized in that the amount of high-strength or / and large-grain coke charged in the central portion of the furnace top is 0.02 to 0.07 times the normal amount of coke charged.

[0009]

In the present invention, the central portion of the furnace top refers to the radius of the furnace top of 0.
It is defined as a region of 0.20 times. The furnace core is the depth of the raceway.
(0 mm) indicates the area of the circle toward the center of the blast furnace. Since the high-strength coke charged in the center of the furnace top is less likely to deteriorate due to wear or the like as it descends in the furnace, it remains large in size when it reaches the core. The large-grain coke charged in the center of the furnace top has a large grain size when it reaches the furnace core. When a large-grain coke is charged into the furnace core, the porosity of the coke layer is secured and the
Since the liquid permeability becomes good, the high temperature gas and the melt pass through the inside of the furnace core, and the temperature inside the furnace core is recovered.

The high-strength coke in the present invention means cold strength (DI 150/15) of 85% or more (usually 83).
.About.84%), and a hot strength (CSR) of 60% or more (usually 55 to 57%). The large grain size coke means an average grain size of 60 mm or more (usually 45 to 50 mm).

The amount of high-strength and / or large-grain coke charged to the center of the furnace top is usually 0.0
2 to 0.07 times. If it is less than 0.02 times, the amount is too small to exhibit the effect, or it takes a long time for the effect to be exhibited. When it exceeds 0.07 times, the central gas flow is overdeveloped and the peripheral gas flow is reduced, resulting in insufficient heating and reduction of the peripheral portion. As a method for charging high-strength or / and large-grain coke into the center of the furnace top, a method of charging into the center with a movable armor or a swirling chute is generally used. You may enter.

[0012] In order to produce a coke having a high strength and / or a large grain size, it is necessary to give special consideration to the blending of the raw coal, and thus the production cost is generally high. Therefore, in order to eliminate this, the coking coal composition during normal coke production is changed to reduce the production cost of normal coke. As a result, the strength decreases, but there is no problem even if the strength of the normal coke charged from the middle part of the furnace top to the peripheral part slightly decreases.

Whether or not the temperature inside the furnace core has decreased may be judged by an increase in the blowing pressure, or a thermometer may be installed in the core to detect the temperature. It is also possible to determine whether or not the melt is solidified by inserting a gold rod from the tuyere or the lower part of the shaft. It takes about 1 month to recover the temperature by significantly increasing the fuel ratio when the temperature inside the conventional core decreases, whereas it takes 7 to 10 days to recover according to the operation method of the present invention. The period is shortened.

[0014]

EXAMPLES The features of the present invention will be specifically described with reference to the following examples. Table 1 shows the operation results.

[0015]

[Table 1]

[0016] Example 1 since blowing pressure is increased from the state which has been operating in the normal 3.5 ± 0.05kg / cm ² about the 3.8 ± 0.08kg / cm ^2, cold strength (DI 0.99 / 15) Decrease the strength of 84% normal coke to 83% and reduce the cold strength (D
I 150/15) 86% coke was produced, and with a movable armor, 10 kg / t (per ton of pig iron, the following “/ t” is the same) (coke ratio 500 kg / t.
(02 times) was charged into the center of the furnace top, and the blast pressure returned to the normal 3.6 ± 0.04 kg / cm ² after 7 days.

Example 2 Since the blast pressure was increased from 3.9 ± 0.09 kg / cm ² to 3.9 ± 0.09 kg / cm ² , the hot strength (CSR) was 57. % Coke strength is reduced to 55%, hot strength (CSR) 63% coke is produced, and 20 kg / t (0.04 times the coke ratio of 500 kg / t) is swirled into the center of the furnace top. After 8 days, the blast pressure was 3.4 ±
This is an example of an operation in which the pressure has returned to 0.04 kg / cm ² .

Example 3 Since the thermometer installed in the furnace core was lowered to 1200 ± 80 ° C. from the state where it was normally operated at about 1400 ± 50 ° C., cold strength (DI 150/15) 84%, average The strength of normal coke with a particle size of 47 mm is reduced to 83%, the cold strength (DI 150/15) is 87% and the average particle size is 6
A 2mm coke is manufactured, and 15kg / t (coke ratio of 500kg / t is 0.03 with a special chute installed).
Was added to the center of the furnace top, and after 9 days, the temperature inside the furnace core returned to the normal 1400 ± 60 ° C., which is an operation example.

[0019] Example 4 increased from the state in which the blowing pressure was operating in the normal 3.5 ± 0.05kg / cm ² approximately in 3.95 ± 0.08kg / cm ^2, when inserting the Kanabo from tuyere Since it was confirmed that the melt had solidified, the hot strength (CSR) 57
%, The strength of ordinary coke having an average particle size of 47 mm is reduced to 55%, the hot strength (CSR) is 60%, and the average particle size is 6%.
Manufacture 0 mm coke, 25 kg from a turning chute
/ T (0.05 times the coke ratio of 500 kg / t) was charged into the center of the furnace top, the blast pressure returned to the normal 3.55 ± 0.05 kg / cm ² after 10 days, and the tuyere This is an example of operation in which the solidification of the melt disappears when the gold rod is inserted more.

Example 5 Since the thermometer installed in the furnace core dropped from 1250 ± 70 ° C., which was normally operating at 1400 ± 50 ° C., the average particle size was 47 mm and the average coke size was 65 mm. 35 kg / t (coke ratio of 500 kg / t 0.0
(7 times) was charged in the central part of the furnace top, and after 7 days, the temperature in the furnace core returned to the normal 1400 ± 50 ° C., which is an operation example.

[0021] Since Comparative Example blowing pressure is increased from the state which has been operating in the normal 3.5 ± 0.05kg / cm ² about the 3.8 ± 0.08kg / cm ^2, to reduce the central portion O / C The whole O /
This is an example of operation in which C is lowered (3.8 → 3.6). Thirty
Blast pressure is normal 3.55 ± 0.05 kg / cm after day
Returned to ² . Compared with Examples 1 to 5, the amount of tapped iron is small and the fuel ratio is high.

[0022]

As described above, according to the present invention, when the temperature of the melt dropped in the center of the furnace is lowered and the melt solidifies and the temperature inside the furnace core starts to decrease, or the powder inside the furnace core begins to fall. When the melt is solidified and the core temperature begins to drop due to deterioration of air permeability and liquid permeability, high strength or / and large particle size coke is charged in the center of the furnace top to form a coke layer. Ventilation and liquid permeability are improved by ensuring the porosity, so that high-temperature gas and melt pass through the furnace core, and the temperature inside the furnace core is recovered. Therefore, defective ventilation can be avoided, productivity can be improved, fuel ratio can be reduced, and stable hot metal supply can be achieved.

Claims (2)

[Claims] 1. A blast furnace operating method in which iron ore and coke are charged in layers from the furnace top, hot air or hot air and auxiliary fuel are blown from the tuyere to blow hot metal, and the temperature in the furnace core decreases. In addition, a high-strength and / or large-grain coke is charged in the center of the furnace top, which is a blast furnace operation method. 2. High-strength or / or high-strength charging at the center of the furnace top
The method of operating a blast furnace according to claim 1, wherein the amount of coke having a large grain size is 0.02 to 0.07 times the amount of the normal coke charged.