JPH08188808A - Blast furnace operation method - Google Patents

Abstract

(57) [Summary] [Object] The present invention maintains good ventilation in the lower part of a blast furnace even when a large amount of pulverized coal is injected.
The present invention relates to a method for always maintaining the core of a blast furnace in an active state. [Composition] During operation of the blast furnace, the lower K value is obtained from the blast pressure of the blast furnace tuyeres, the pressure of the bosh section of the blast furnace and the Bosch gas amount of the blast furnace, and the lower K value is higher than the standard lower K value of the blast furnace by 10% or more. In the case of the above, a method for operating a blast furnace, which comprises charging coke having a CRI of less than 20 to 26 into the center of the blast furnace.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for reducing the ventilation resistance of the core of a blast furnace and operating the blast furnace in a stable state.

[0002]

2. Description of the Related Art In recent years, the amount of pulverized coal blown into a blast furnace has increased, and in Japan, the amount of pulverized coal blown per t of pig iron is at a level of 200 kg / t, although it is a test level. Especially in Europe, 200 kg / t even in normal operation
There is also a blast furnace with a proven track record. In the all coke operation, the coke ratio is about 500 kg / t, whereas in the operation of pulverized coal 200 kg / t, the coke ratio is 300 kg / t.
Before and after.

On the other hand, the core portion of the blast furnace is also a site where coke powder generated in the raceway and unburned char that has not burned in the raceway are easily deposited. The accumulation of such fine powder deteriorates the air permeability and liquid permeability in the blast furnace, and causes a so-called inactive state. This causes a rise in the temperature of the packed bed due to gas, so it is desirable to keep the core in a healthy state so that the gas always flows. It is desired that the coke forming the furnace core be kept in a large particle size with good ventilation and liquid permeability.

It has been clarified from the solid flow experiments or simulations that the core coke is mainly the coke charged in the center of the blast furnace. By the way, the particle size of the coke charged in the upper part of the blast furnace is reduced by the solution loss reaction (2). C + CO ₂ = 2CO (2) The solution loss reaction amount per pig iron t is close to 100 kg in coke. In the all coke operation, the solution loss reaction is 100 kg / t reduction with respect to the coke ratio of 500 kg / t, but if the pulverized coal injection rate is 200 kg / t level, it is 300.
Since 100 kg / t of the coke ratio of kg / t is the weight loss due to the solution loss reaction, the weight loss rate, that is, the particle size reduction rate becomes larger than that in the all coke operation.

As described above, particularly in the pulverized coal blowing operation, the reduction in the particle size of coke becomes apparent. As a result, the decrease in the particle size of the coke forming the core causes inertness of the core. It was difficult to maintain the coke grain size of the furnace core sound with the conventional technology.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention maintains good ventilation in the lower part of the blast furnace even when a large amount of pulverized coal is blown into the blast furnace. The present invention relates to a method for always maintaining the core in an active state. The purpose of this is to allow gas, solids, and liquids in the blast furnace to flow smoothly, and to operate the blast furnace in a stable manner.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a blast furnace tuyere pressure (P1), a blast furnace bosh pressure (P2) and a blast furnace Bosch during blast furnace operation. The lower K value is calculated from the gas amount (G) by the equation (1), and when the lower K value is 10% or more higher than the reference lower K value of the blast furnace, the coke having a CRI of 20 to less than 26 is the center of the blast furnace. It is a method of operating a blast furnace, which is characterized in that it is charged into the section.

K = (P1 ² −P2 ² ) / G ^1.7 (1) P1: Blower pressure (g / cm ² ) P2: Bosh pressure (g / cm ² ) G: Bosch gas amount of blast furnace ( Nm ³ / min) Here, the reference lower K value is an average value of the lower K value of the blast furnace during stable operation for one month.

[0009]

The present invention relates to a method of increasing the coke particle size in the furnace core in order to reduce the ventilation resistance in the furnace core when the ventilation resistance in the lower part of the blast furnace is increased. By supplying the coke from the top of the blast furnace to the center of the blast furnace, it is possible to suppress the reduction of coke until the coke charged from the furnace top reaches the core, and to supply the coke with a large particle size into the core. It is in.

The reactivity of coke in the furnace is usually determined by a CRI (Coke Reactivate) test by testing outside the furnace.
y Index). The method for measuring CRI will be described below. Grain size 20 ± 1m in a small reactor
m coke sample 200 ± 2 g was charged, and CO ₂ gas was 5
After reacting at a temperature of 1100 ° C. for 120 minutes with Nl / min, the reaction rate is measured. The CRI reaction rate is represented by CRI = (weight reduction amount after reaction (g) / 200 (g)) × 100 (%) (3).

Usually, this CRI value is about 26 to 30 (%). This CRI value can be adjusted to a target numerical value by changing the combination of coal species of coal that is a raw material for coke. Lowering the CRI value leads to lowering the reaction amount of coke and at the same time increasing the strength of the coke after the reaction. Therefore, for the coke in the furnace core, there is a dual effect of increasing the particle size and improving the strength. .

At the same time, the gas utilization rate (ηC
O = CO ₂ / (CO + CO ₂ )) is generally low, but suppressing the reaction of C + CO _{2 in} the lower part of the furnace also has the effect of increasing the gas utilization rate in the central part of the furnace.

The ventilation resistance in the lower part of the blast furnace is expressed and managed by an index called the lower K value. K = (P1 ² −P2 ² ) / G ^1.7 (1) where P1: blast pressure (kg / cm ² ) P2: lower pressure of blast furnace (pressure of bosh) (kg / cm ² ) G: blast furnace Velocity of gas passing through the morning glory (kg / m
² s). In normal management, the following values are often used as simpler input values. P1: Blower pressure (kg / cm ² ) × 1000 + 1033
(G / cm ² ) P2: Bosh area pressure (kg / cm ² ) × 1000 + 103
3 (g / cm ² ) G: Bosch gas amount in blast furnace (Nm ³ / min)

With respect to the amount of Bosch gas in the blast furnace, the oxygen in the gas reacts with the coke with respect to the amount of gas blown from the tuyere, and CO
It represents the amount of gas after becoming gas, and the amount of Bosch gas is about 1.2 times the amount of air blown from the tuyere. Usually lower K value is 1.4-
Although it takes about 1.4, when the ventilation resistance of the furnace core increases, the lower K value increases.

It is said that among the cokes charged at the top of the blast furnace, the coke charged within a radius of 1 m from the center (hereinafter referred to as center coke) forms the furnace core. Therefore, when the lower K value is monitored and rises, the CRI value of the central coke can be lowered from the normal value to increase the coke size of the furnace core.

The lower K value is 1 from the standard lower K value of the blast furnace.
When it is higher than 0%, it can be judged that the ventilation resistance in the lower part of the blast furnace has increased, and it is necessary to operate to lower the ventilation resistance. Therefore, by charging a coke having a CRI of less than 20 to 26 into the center of the blast furnace, the solution loss reaction amount is smaller than that of the coke having a normal CRI of 26 to 30,
The grain size of coke in the furnace core is larger than that of normal coke, and the ventilation resistance in the lower part of the blast furnace can be improved.

Coke having a CRI of 26 or more is not preferable because the solution loss reaction amount is large and the air permeability of the furnace core cannot be improved. Coke with a CRI of less than 20 is difficult to produce. In addition, in terms of improving the air permeability, the total amount of coke charged to the blast furnace should be 20 to 26 CRI.
Although coke may be used, it is preferable to charge it in the center of the blast furnace when improvement of air permeability is required because of high production cost.

The gist of the present invention will be described below with reference to the drawings.
FIG. 1 shows an outline of the method of the present invention. The pressure detecting end 2 at the lower part of the blast furnace 1 is attached to the lower part of the shaft, the abdomen of the furnace, or the furnace wall at the morning glory. Pressure detection end 3 for detecting blow pressure
, Which are usually installed in the blower main pipe or the annular pipe 4, but also include those installed in the tuyere nozzle section 5. Pulverized coal is usually blown from the powder blowing portion 7 of the blast furnace tuyere 6, but powders such as iron oxide and flux are also included. In the case of pulverized coal, it burns in the raceway 8, and the unburned chain enters the furnace core 10.

The turning chute type charging device 11 has a function of charging coke only in the center.
When the charging device is a bell type, a special charging device 12 having a function of charging mainly coke is provided.
Usually, the coke 13 within a radius of 1 m from the center of the furnace descends in the cohesive zone 16 in the blast furnace while undergoing the solution loss reaction shown in the equation (2) and enters the core of the furnace.

Normally, the differential pressure detecting device 18 detects the differential pressure between the pressure 2 at the bosh and the blowing pressure 3 to control the operation of the blast furnace. The lower K value is calculated from the blast pressure, the bosh pressure, and the Bosch gas amount in the blast furnace according to the equation (1). The lower K value and the average particle diameter (Dp) of the coke in the furnace core have the relationship of the equation (4). K 1 / Dp K / K ₀ = Dp ₀ / Dp (4) where, Dp: average particle size of coke in the furnace core (mm) K ₀ : reference K value DP ₀ : furnace at reference K value Average particle size of coke in the core (mm)

Dp can be increased by lowering the CRI of the coke charged into the blast furnace, but the operating conditions differ depending on the blast furnace, so if the relationship between Dp and CRI was investigated beforehand, the lower K value increased. In this case, the optimum CRI value can be determined.

[0022]

EXAMPLES The present invention will be described in detail below based on examples.
FIG. 2 shows changes in the pulverized coal injection amount, the reactivity of the central coke, the estimated core particle size of the coke, and the lower K value in the actual blast furnace. Here, in this blast furnace, usually, the CRI of the charging coke was 28%, the Dp was 30 mm, and the reference value of the lower K value under stable operation was 1.7.

The amount of pulverized coal blown from 120 to 190
The effect of the reactivity of the central coke was investigated in the process of increasing it significantly to (kg / t-pig). The K value in the lower part of the furnace is calculated from equation (1) from the blast pressure and the pressure difference in the middle part of the furnace side. During the process of increasing the amount of pulverized coal blown in, the pressure loss in the lower part of the furnace increased, and at the level of 150 (kg / t-pig), the lower K value exceeded the control standard of 1.7, and the value of 190 (k
(g / t-pig) increased by about 12% from the control standard.
Rose to 9.

During this period, since the production volume was constant, the blast volume was almost constant, and therefore, the gas flow velocity level in the furnace did not change significantly. Therefore, it was determined that this increase in pressure was caused by the decrease in the core coke particle size. . Therefore, CRI of central coke
Was reduced from 28% to 24%. As a result, Dp is 38
The pressure loss was reduced by this action, and the blast furnace returned to the stable operation area. The effect of coke reactivity at this time is that the lower K value was lowered by 0.1 when the CRI was lowered by 1%. Thus, controlling the reactivity of the central coke is extremely effective in controlling the ventilation of the lower part of the blast furnace.

[0025]

EFFECTS OF THE INVENTION According to this method, the ventilation of the blast furnace is valuable because it can be one of the few control means of controlling the coke particle size of the furnace core through the reactivity control of the coke. Further, this method can be a control means having a quick effect on deterioration of ventilation in the lower part of the blast furnace. And it is possible to prevent delay in the action of the blast furnace. With such a simple principle, the activation of the blast furnace, which has been considered impossible in the past, can be achieved in a relatively short period of time. It is an innovative technology in that it can have a means to escape from a blast furnace malfunction.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing the principle of the present invention.

FIG. 2 is a view showing a blast furnace operation result of one example of the present invention.

[Explanation of symbols]

1 Blast furnace 2 Pressure detection end 3 Blow pressure detection end 4 Annular pipe part 5 Tuyere nozzle 6 Tuyere 7 Powder injection part 8 Raceway 9 Coke forming the core 10 Blast furnace core 11 Swirling chute type charging device 12 Center charging device 13 Coke within a radius of 1 m from the center 14 Falling trajectory of solids after charging in the upper part 15 Flow line of gas generated in combustion zone 16 Fusion zone 18 Differential pressure detector 19 Lower K value calculation Calculator 20 Calculator for estimating core coke diameter 21 Calculator for optimum core coke particle size 22 Indicator for calculating the optimum differential pressure value and instructing the amount of pressure change 23 Calculator for CRI value of central coke 24 CRI value Calculator for instructing the blending of coal based on the indicated value of 25 Coke charge indicator for central charging coke

Claims (1)

[Claims] 1. A blast furnace tuyere pressure (P
1) From the pressure (P2) of the bosh section of the blast furnace and the Bosch gas amount (G) of the blast furnace, the lower K value is calculated by the equation (1), and the lower K value becomes 10% or more higher than the standard lower K value of the blast furnace. In this case, a coke having a CRI of less than 20 to 26 is charged into the center of the blast furnace, which is a method for operating the blast furnace. K = (P1 ² -P2 ² ) / G ^1.7 (1) P1: blast pressure (g / cm ² ) P2: bosh pressure (g / cm ² ) G: blast furnace Bosch gas amount (Nm ³ / min)