JPH0694565B2 - Injection method of auxiliary fuel into blast furnace - 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 auxiliary fuel into a blast furnace, and more particularly, it is a method of co-firing solid fuel such as pulverized coal and liquid fuel such as heavy oil and tar, which generally have different combustibility. Alternatively, the present invention relates to a method for injecting auxiliary fuel into the blast furnace to obtain stable blast furnace operation when co-firing solid fuel and gas fuel such as coke oven gas and natural gas.

[0002]

2. Description of the Related Art In the blast furnace, a shift to an all-coke operation in which heavy oil that had been injected as an auxiliary fuel was completely stopped was triggered by a significant rise in the price of oil. Since then, pulverized coal injection, which has a high economic effect as a stabilization of blast furnace operation and an alternative to coke, has attracted attention and has now been adopted by the majority of blast furnaces in Japan.

However, powdered fuels such as pulverized coal have the disadvantage that they have poorer combustibility than heavy oil and contain ash, so that various measures must be taken in blowing.

Under these circumstances, the applicant of the present invention has long been making diligent research and development in order to establish an effective method for injecting powdered fuel such as pulverized coal. For example, Japanese Patent Publication No. 60-53081.
No. 6, Japanese Patent Publication No. 63-32842, Japanese Patent Publication No. 1-29846.

In Japanese Examined Patent Publication No. 60-53081, the injection position of the powdered fuel is defined as a means for satisfying both the two requirements of improving the burning rate of powdered fuel such as pulverized coal and preventing ash from adhering to the blow pipe. It is the one that has moved to the upstream side in the blow pipe.

In addition, Japanese Patent Publication No. 63-32842 and Japanese Patent Publication 1-2
In 9846, in order to sufficiently increase the combustion rate of pulverized fuel such as pulverized coal even when using hot air at a temperature lower than 1050 ° C, pulverized coal such as coke oven gas or natural gas is used. It was proposed to co-combust 2% or more in terms of calorie from the outer periphery of the furnace, or to perform oxygen-enriched combustion so that the oxygen concentration in hot air was 23% or more by volume.

[0007]

By the way, in the case of a blast furnace operation in which a powdered fuel such as pulverized coal is used as an auxiliary fuel, there are restrictions on the supply and demand balance of the auxiliary fuel, fluctuations in fuel cost, or failure of the pulverized coal injection facility. In some cases, multiple auxiliary fuels may be blown into the blast furnace simultaneously during maintenance. For example, a steel mill may generate a large amount of by-product gas such as coke oven gas and converter gas, which may be excessive due to the balance of usage within the steel mill, and these gases may be blown into the blast furnace as auxiliary fuel. is there. Further, natural gas or tar, which is cheaper and easier to obtain than coke, may be blown as an auxiliary fuel to reduce the coke ratio. That is, in the operation of the blast furnace, different auxiliary fuels may be injected at the same time. In this case, the injection amount of the auxiliary fuel was small and was 50 kg / ton of pig iron or less in coke conversion, and the difference in combustibility did not affect the operation of the blast furnace. Therefore, the injection method such as the injection position is not changed, paying attention to the difference in the combustibility of the auxiliary fuel, and different auxiliary fuel is injected from the same tuyere at the same position.

However, in recent years, it has become the most important issue to blow various auxiliary fuels in large amounts of 100 kg / ton of pig iron or more to lower the coke ratio and reduce the pig iron cost.

[0009] Above all, the price of coal is about half that of coke, and coking coal (coking coal) is used for blowing blast furnace pulverized coal.
The present invention is not limited to the above, and steam coal can be used. Therefore, if more pulverized coal can be injected from the viewpoints of both economic efficiency and diversification of coal sources, the advantage will be even greater.
Furthermore, if a large amount of auxiliary fuel other than pulverized coal can be blown, the coke ratio can be greatly reduced and the pig iron cost can be greatly reduced.

However, at the same injection position, different auxiliary fuel is supplied to different tuyere at 50 kg / coke conversion.
If more than a ton of pig iron is blown, the gas fuel and heavy oil fuel with good combustibility will raise the hot air temperature significantly due to combustion in the tuyere, and the tuyere tip velocity will also greatly increase. As a result, the pressure in the blow pipe also increases significantly. On the other hand, in the tuyere blowing pulverized coal, which has poor combustibility, the rise in hot air temperature is small. Therefore, if the same amount of auxiliary fuel with different flammability is blown from different tuyere, the hot air pressure in the hot air main is equal, so the amount of hot air at the tuyere blowing the fuel with good flammability is small and the fuel with poor flammability The amount of hot air at the tuyere blowing in the air increases, and the air volume balance at each tuyere is disrupted, and blast furnace operation becomes unstable.

Therefore, in view of the above circumstances, the present invention provides a method for injecting auxiliary fuel into a blast furnace, which enables stable blast furnace operation even if a plurality of auxiliary fuels having different combustibility are simultaneously blown into the blast furnace. That is the purpose.

[0012]

In order to achieve the above object, a method for injecting auxiliary fuel into a blast furnace according to the present invention comprises:
When simultaneously blowing a plurality of auxiliary fuels of different combustibility from the wall of the blast furnace tuyere or the hot-air blowing blow pipe connected to the blast furnace tuyere, while blowing from each independent tuyere or blow pipe for each auxiliary fuel, The gist of the invention is to blow the auxiliary fuel so that the injection position of the auxiliary fuel having good combustibility is inside the furnace from the injection position of the auxiliary fuel having poor combustibility.

A plurality of auxiliary fuels having different combustibility may be blown alternately from the tuyere or the blow pipe on the circumference.

Further, when a plurality of auxiliary fuels having different combustibility are blown from different tuyere or blow pipe, the blowing position may be adjusted so that the blower pressure loss of each tuyere and blow pipe is substantially equal.

Further, when pulverized coal, C heavy oil, or coke oven gas is used as a plurality of auxiliary fuels having different combustibility, C heavy oil is 1
50-250 mm, coke oven gas should be blown from 250-350 mm downstream from the inside of the oven.

[0016]

[Operation and Examples] The structure and operation of the present invention will be described in detail below with reference to the experimental process and analysis results. FIG. 2 is a schematic view of the apparatus used in the combustion experiment, which is designed in a structure similar to the actual tuyere of the blast furnace. Powder fuel (pulverized coal) A is conveyed from the ground hopper 1 to the coal bin 3 by the screw conveyor 2. A powder fuel quantitative feeder 4 is provided below the coal bin 3, and the powder fuel A cut out by a fixed amount in this portion is sent to a burner 7 by a transport pipe 6 together with transport air 5. On the other hand, the hot air obtained in the high-temperature hot-air stove 8 is sent from the blower pipe 9 to the combustion test furnace 12 via the blow pipe 10 and the water-cooled tuyere 11. 13 in the figure
Is a chimney.

The fuel injection part of the blast furnace is completely different from a general combustion device and is composed of the blow pipe 10 and the water-cooled tuyere 11. Therefore, this experimental device is at normal pressure, and the pressure is lower than that of the actual blast furnace injection. Although the shape is low, the shape is approximated. Further, the combustion test furnace 12 is provided with a large number of viewing windows for observing the combustion state and the ignition state of the powdered fuel, and for measuring the temperature inside the furnace, the gas composition inside the furnace, the dust inside the furnace, the amount of flame radiation, etc. An inspection hole is provided, and a peep window 14 for observing the adhesion state of ash to the wall surface of the blow pipe 10 is provided at the upstream bend of the blow pipe 10.

The conditions in a series of experiments described below using this apparatus are as follows. Liquid fuel: C fuel oil Gas fuel: Coke oven gas Powder fuel: Coal (volatile content 34% by weight, ash content 1
0.5% by weight) Auxiliary fuel injection amount: 148 kg / 1 ton of pig iron (T-
P) Hot air temperature: 1200 ° C Auxiliary fuel injection position L: Based on the boundary position between the tuyere 11 and the blow pipe 10, upstream (negative sign) L = -200 mm ~ downstream (positive sign) L = +496 mm (furnace inner blade (In the mouth)

First, the present applicant, after finding out the above-mentioned various problems, conducted an experiment in order to clarify the cause of the occurrence of these various problems. The results will be described below.

FIG. 3 is an enlarged view of the auxiliary fuel injection section.
The structure of the main injection part is the same as that of the actual injection part of the blast furnace, and is composed of a blow pipe 10, a water-cooled tuyere 11, and an auxiliary fuel injection burner 7. A blow pipe pressure measuring hole 15 is provided upstream of the auxiliary fuel injection burner 7 so that the blow pipe rising pressure ΔP due to the auxiliary fuel injection.
Was measured.

FIG. 1 shows the blow pipe pressure when pulverized coal, heavy fuel oil C and coke oven gas are simply blown from the auxiliary fuel blowing burner 7. The blow pipe pressure was measured by changing the auxiliary fuel injection position L under the same conditions of the auxiliary fuel injection amount and the hot air amount. As is clear from this figure, in the case of coke oven gas or C heavy oil with good combustibility, when the auxiliary fuel injection position is L = -200 mm to +200 mm, combustion occurs rapidly in the blow pipe and tuyere, and the hot air becomes hot. Blow pipe pressure increases significantly. However, when the auxiliary fuel injection position is moved into the furnace on the downstream side, the blow pipe pressure gradually decreases. Therefore, pulverized coal, C heavy oil,
When the coke oven gas is blown at the same position of the auxiliary fuel injection position L = 0, the blow pipe pressure is 84 for the coke oven gas.
0 mm H ₂ O, becomes 580mmH ₂ O in 800mmH ₂ O, pulverized coal in fuel oil C. Since the actual blast furnace operates at high pressure, this pressure difference becomes even larger. In this case, in the actual blast furnace, since the pressure of the hot air mains is the same, a large amount of hot air is supplied to the tuyere blowing pulverized coal, so a large amount of hot air is supplied, and tuyere blowing C heavy oil and coke oven gas. A small amount of hot air will flow from the tuyere blowing pulverized coal. That is,
In this case, the amount of hot air greatly differs depending on each tuyere, and the circumferential balance of the blast furnace is disturbed and the furnace condition becomes unstable.

Therefore, in the present invention, it was considered to keep the pressure loss of each tuyere constant and to make the air flow distribution to each tuyere uniform. The specific method is to blow a plurality of auxiliary fuels with different combustibility simultaneously from the wall of the blast furnace tuyere or the hot-air blowing blow pipe connected to the blast furnace tuyere, in which independent tuyere or In addition to blowing from the blow pipe, the auxiliary fuel with good combustibility should be blown inside the furnace from the auxiliary fuel with poor combustibility, and the auxiliary fuel should be blown so that the pressure loss at each tuyere is almost equal. In this way, the circumferential condition of air flow in the blast furnace is maintained and the furnace condition is stabilized.

For example, in FIG. 1, pulverized coal is L = + 20
By blowing at 0 mm, blowing C heavy oil at L = + 400 mm and / or blowing coke oven gas at L = + 500 mm, the blow pipe pressure becomes almost equal at each tuyere, and the air volume is kept circumferentially balanced.

In the above example, the hot air temperature is 1200 ° C. However, if the hot air temperature is lowered, the combustion in the tuyere or the blow pipe is delayed and the blow pipe pressure is naturally lowered. However, the decreasing tendency of each fuel is similar to the above-mentioned example where the hot air temperature is 1200 ° C, and if the injection position of pulverized coal is taken as the reference, the heavy fuel oil for C is 150 to 250 m.
m, coke oven gas was blown from 250 to 350 mm downstream from the inside of the furnace, and it became clear that the difference in blow pipe pressure due to fuel was not a problem and was optimal.

In an actual blast furnace operation, even if the pressure loss and the burning rate in the tuyere are the same, the amount of unburned carbon flowing into the raceway is the largest in pulverized coal, followed by C heavy oil and coke oven gas. It decreases in order. Therefore, when auxiliary fuels with different combustibility are simultaneously blown into the blast furnace, by alternately blowing them from the tuyere or blow pipe on the circumference of the blast furnace, the circumference of the unburned carbon amount flowing into the raceway is increased. The balance becomes better.

[0026]

As described above, according to the method for injecting auxiliary fuel into the blast furnace of the present invention, a plurality of auxiliary fuels having different combustibility are maintained without deteriorating the furnace condition while keeping the tuyere pressure loss of hot air equal. A large amount of fuel can be injected into the blast furnace at the same time.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a blow pipe pressure and an auxiliary fuel injection position L.

FIG. 2 is an explanatory diagram of an experimental furnace applied to the method of the present invention.

FIG. 3 is an enlarged view of a main part (auxiliary fuel injection part) of FIG.

[Explanation of symbols]

7: Auxiliary fuel injection burner 8: High temperature hot stove
9: Blower pipe 10: Blow pipe 11: Water-cooled tuyere 12: Combustion test furnace 14: View window 15: Blow pipe pressure measurement hole

Claims (4)

[Claims] 1. An independent tuyere or blow pipe for each auxiliary fuel when simultaneously blowing a plurality of auxiliary fuels having different combustibility from the wall of a blast furnace tuyere or a hot-air blowing blow pipe connected to the blast furnace tuyere A method for injecting auxiliary fuel into a blast furnace, characterized in that the auxiliary fuel having good combustibility is blown into the furnace from the injection position of auxiliary fuel having poor inflammability . 2. The method for injecting auxiliary fuel into a blast furnace according to claim 1, wherein a plurality of auxiliary fuels having different combustibility are alternately blown from tuyere or blow pipe on the circumference. 3. When blowing a plurality of auxiliary fuels having different flammability from different tuyere or blow pipe, the blowing position is adjusted so that the blower pressure loss of each tuyere and blow pipe is substantially equal. The method for injecting auxiliary fuel into the blast furnace according to claim 1, wherein 4. When using pulverized coal, heavy fuel oil C, or coke oven gas as a plurality of auxiliary fuels having different combustibility,
Based on the injection position of pulverized coal, C heavy oil is 150 to 250 m
The method for injecting auxiliary fuel into a blast furnace according to claim 1, wherein m and coke oven gas are blown from a downstream side inside the oven of 250 to 350 mm.