JP3176680B2 - Blast furnace operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injecting a large amount of pulverized coal into a blast furnace from the tuyere of a blast furnace. The blast furnace operation method for achieving

[0002]

2. Description of the Related Art In blast furnace operation, inexpensive, highly flammable and high calorific value fuel (pulverized coal, petroleum, heavy oil, naphtha, etc.) is blown from the tuyere as an alternative to coke to reduce hot metal production cost and production. To improve the quality,
No. 23,763 discloses the technique. Particularly recently, pulverized coal injection has become the mainstream in terms of price, which greatly contributes to a reduction in fuel ratio (reduction of hot metal production cost) and improvement in productivity.

[0003] The pulverized coal injected in this way burns as a substitute for some coke in the blast furnace, and because of its good flammability and high calorific value, generates a large amount of reducing gas at high temperatures and is efficient. Perform a suitable reduction reaction. Therefore, the iron ore charged from the furnace top is rapidly reduced to a metallic state, and is melted into high-temperature hot metal. The furnace heat of the blast furnace is increased as a whole, so that productivity is improved.

[0004]

In the conventional blast furnace operation, if a large amount of pulverized coal is blown, the whole amount of the pulverized coal does not burn, and some unburned char is generated. Since this unburned char is discharged from the furnace top on the rising gas flow,
It lowers the replacement ratio of pulverized coal to coke, causing an increase in fuel ratio and a decrease in production. In addition, since the unburned char is trapped in the coke layer (furnace core) at the center of the lower part of the blast furnace, it impairs the liquid permeability of hot metal and slag flowing down this part, and consequently the gas permeability of this part. And the productivity of the blast furnace further decreases.

For the above reasons, there is an upper limit to the amount of pulverized coal to be blown, and the following excess oxygen ratio is maintained at 1.0 or more during operation. (Excess oxygen rate) = (Air blown from the tuyere, pure oxygen, amount of oxygen in pulverized coal) / (necessary to burn carbon and hydrogen in pulverized coal to CO ₂ and H ₂ O) Oxygen content)

When the excess oxygen ratio is 1.0 or more, the total amount of carbon and hydrogen in pulverized coal is C + O ₂ = CO ₂ , 2H + (1 /
2) O ₂ = H ₂ O reacts to CO ₂ , H ₂ O,
This is the total amount of coke in the raceway and CO ₂ + C = 2
CO, H ₂ O + C = H ₂ + CO, CO, H ₂
Therefore, no unburned char is generated. However, when the excess oxygen ratio is less than 1.0, the entire amount does not become CO ₂ and H ₂ O, and a part of C (unburned char) is generated. As described above, this unburned char causes a reduction in the replacement rate and poor ventilation.

[0007] The blast furnace has a maximum blast temperature of about 1300 ° C. However, when pulverized coal is blown into the blast furnace by inserting a burner from the side wall of the blast tube, the thermal decomposition of the pulverized coal (gas and char Generation), combustion of the generated gas, and combustion of the generated char. Gas burning is very fast, but char burning slowly. As a result, the gas almost completely burns in the ventilation duct, but the char continues burning even after entering the raceway. When the excess oxygen ratio is less than 1.0, unburned char is generated, and the char has low flammability and reactivity. Therefore, the char is released outside the raceway without reacting with CO ₂ and H ₂ O. Will be.

When the excess oxygen ratio is 1.0, the pulverized coal injection amount is 170 kPa when the fuel ratio of the blast furnace is 500 kg / t.
g / t, which is the blowing limit. That is, this value is the limit of blast furnace production and fuel ratio, and further improvement in productivity and reduction in fuel ratio cannot be expected. Therefore, the present invention aims to secure the flammability of unburned char even when pulverized coal is blown at 170 kg / t or more, and to maintain the production amount and the fuel ratio even if the replacement ratio for coke is increased. The purpose is to provide a method that enables it.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a blast furnace operating method in which pulverized coal is blown into a blast furnace from a tuyere by using a double-pipe burner.
When fuel gas is injected from the inner pipe of the heavy pipe and pulverized coal is injected from the outer pipe
Both are characterized in that the fuel gas injection amount is adjusted such that the ambient temperature at the discharge position of the pulverized coal blown from the outer pipe into the air blowing branch pipe is 1500 to 2000 ° C.

[0010]

In the present invention, the burner inserted from the side wall of the blower branch pipe is a double pipe, and fuel gas is blown from the inner pipe of the double pipe and pulverized coal is blown from the outer pipe. Due to the heat of combustion of the fuel gas blown from the inner pipe of the double pipe, the ambient temperature at the discharge position of the pulverized coal blown from the outer pipe becomes 1500 to 20
The fuel gas injection amount is adjusted so as to be 00 ° C. 1
In a high-temperature field of 500 ° C. or more, pyrolysis of pulverized coal occurs rapidly, and the amount of generated gas having a higher combustion rate than that of normal 1300 ° C. increases (that is, the amount of generated char decreases). The char also expands, increasing its burning rate.

[0011] Therefore, the gas whose generation amount is increased substantially completes combustion in the blower branch pipe, the amount of char combustion in the blower branch pipe increases, and the amount of char entering the raceway decreases. In addition, this char is flammable,
Because of its high reactivity, it easily reacts with CO ₂ and H ₂ O,
Since CO and H ₂ are formed by the reaction of CO ₂ + C = 2CO and H ₂ O + C = H ₂ + CO, no unburned char is generated even when the excess oxygen rate is less than 1.0. In other words, all unburned chars disappear in the raceway, and are discharged from the furnace top,
There is no capture in the furnace core. For this reason, the replacement rate of coke does not decrease and poor ventilation does not occur.

If the ambient temperature at the pulverized coal discharge position is less than 1500 ° C., the above-described increase in the amount of gas with a high combustion rate (decrease in the amount of char generation) and the increase in the combustion rate due to expansion of the generated char will occur. It does not occur and has little effect. When the ambient temperature is 1500 ° C. or higher, the effect is higher as the temperature is higher.
Limited to 00 ° C or less. That is, the injection amount of the fuel gas becomes too large, and since the combustion of the fuel gas also requires oxygen, the excess oxygen ratio of the pulverized coal is significantly reduced,
This is because unburned chars are generated. The following equation can be used for calculating the ambient temperature, but the temperature may be actually measured.

(Atmospheric temperature; ° C.) = ｛(Calorific value of fuel gas; kcal / Nm ³ ) × (fuel gas blowing amount; Nm ³
/ Min) + (air volume; Nm ³ ) x (air temperature; ° C) x 0.
345 ° / [｛(fuel gas combustion exhaust gas amount; Nm ³ / min)
+ (Blowing amount; Nm ³ /min)｝×0.360]

(Fuel gas combustion exhaust gas amount; Nm ³ / min) =
(Fuel gas injection amount; Nm ³ / min) × ｛(C amount in gas;
kg / Nm ³ ) × (22.4 / 12) + (H content in gas;
kg / Nm ³ ) × (22.4 / 2)｝

As the fuel gas, any gas having a high calorific value may be used, and natural gas (LNG), coke oven gas (COG), propane gas (LPG) and the like can be used.

Further, the reason why the method of injecting fuel gas from the inner pipe of the double pipe burner and pulverized coal from the outer pipe is adopted is that when the fuel gas is blown from the outer pipe, the fuel gas is burned. This is because oxygen is consumed, and oxygen-deficient gas surrounds the pulverized coal blown from the inner pipe, and the oxygen required for pulverized coal combustion is extremely insufficient, and unburned char is generated.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be specifically described below with reference to embodiments. Table 1 shows the operation results.

[0018]

[Table 1]

Example 1 Pulverized coal 2 at a blast temperature of 1300 ° C. and an excess oxygen ratio of 0.70
At the time of blowing 00 kg / t, natural gas was blown from the inner pipe of the double pipe burner and pulverized coal was blown from the outer pipe, and natural gas (calorific value = 9600 kcal / Nm)
³ , C content in gas = 0.62kg / Nm ³ , H content in gas =
0.19kg / Nm ³ ) 75-100Nm ³
/ Min (calculated atmospheric temperature: 1600-1700 ° C.).

Example 2 Pulverized coal 2 at a blast temperature of 1300 ° C. and an excess oxygen ratio = 0.70
When blowing 00 kg / t, the coke oven gas was blown from the inner pipe of the double pipe burner and pulverized coal was blown from the outer pipe, and the coke oven gas (calorific value = 4750 kc)
al / Nm ³ , C content in gas = 0.23 kg / Nm ³ , H content in gas = 0.11 kg / Nm ³ )
160 Nm ³ / min (calculated atmospheric temperature 1600 to 1700
° C). When only the coke oven gas was blown, a thermocouple was inserted to measure the gas temperature, and it was confirmed that the ambient temperature was 1500 to 1600 ° C. in the same manner as the calculated value.

Example 3 Pulverized coal 2 at a blast temperature of 1300 ° C. and an excess oxygen ratio = 0.70
At the time of injecting 00 kg / t, the operation is such that propane gas is blown from the inner pipe of the double pipe burner and pulverized coal is blown from the outer pipe, and propane gas (calorific value = 21800 kca)
1 / Nm ³ , C content in gas = 1.61 kg / Nm ³ , H content in gas = 0.36 kg / Nm ³ )
Nm ³ / min (calculated atmospheric temperature 1900 to 2000 ° C.).

Example 4 Pulverized coal 2 at a blast temperature of 1300 ° C. and an excess oxygen ratio of 0.70
At the time of blowing 00 kg / t, natural gas was blown from the inner pipe of the double pipe burner and pulverized coal was blown from the outer pipe, and natural gas (calorific value = 9600 kcal / Nm)
³ , C content in gas = 0.62kg / Nm ³ , H content in gas =
0.19 kg / Nm ³ ) Blowing amount is 10 to 125 Nm ³
/ Min (calculated atmospheric temperature 1700-1800 ° C.).

Example 5 Pulverized coal 2 at a blast temperature of 1300 ° C. and an excess oxygen ratio of 0.70
At the time of injecting 00 kg / t, the operation is such that propane gas is blown from the inner pipe of the double pipe burner and pulverized coal is blown from the outer pipe, and propane gas (calorific value = 21800 kca)
1 / Nm ³ , C content in gas = 1.61 kg / Nm ³ , H content in gas = 0.36 kg / Nm ³ ) The blowing amount is 55-60
Nm ³ / min (calculated atmospheric temperature 1800 to 1900 ° C.).

Comparative Example 1 is a case where the fuel gas was not blown when pulverized coal was blown at a blowing temperature of 1300 ° C. and an excess oxygen rate = 0.70 and 200 kg / t was blown. The blowing pressure, which indicates the ventilation, is high, the tapping amount is small, and the fuel ratio is high. Comparative Example 2 has a blowing temperature of 1300.
° C, excess oxygen rate = 1.0, when pulverized coal is blown at 170 kg / t, and no fuel gas is blown. Compared with Examples 1 to 5, the blowing pressure is almost the same, but the tapping amount is Low, high fuel ratio.

[0025]

As described above, in the present invention, fuel gas is blown together with pulverized coal in order to eliminate unburned char generated when a large amount of pulverized coal is blown in the raceway. As a result, it is possible to avoid a decrease in the replacement rate and poor ventilation, improve the productivity, and reduce the fuel ratio, thereby enabling a stable hot metal supply.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-11608 (JP, A) JP-A-4-268003 (JP, A) JP-B-63-32842 (JP, B1) (58) Field (Int. Cl. ⁷ , DB name) C21B 5/00 319 C21B 7/00 309

Claims (1)

(57) [Claims] In a blast furnace operating method in which pulverized coal is blown into a blast furnace from a tuyere, a blowing burner is double-pipe.
When fuel gas is injected from the inner pipe of the heavy pipe and pulverized coal is injected from the outer pipe
In both cases, the discharge position of the pulverized coal blown from the outer pipe into the air duct
The ambient temperature in the place will be 1500-2000 ° C
A blast furnace operating method characterized by adjusting the amount of fuel gas injected .