JPH07107174B2 - Solid fuel injection method and injection device for electric furnace and converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention preheats the above raw materials in an electric furnace or a converter for melting molten raw materials such as scrap iron to produce molten steel,
The present invention relates to a melting method and preheating and melting equipment suitable for carrying out the method, and more particularly, to improvement of an electric power consumption rate when a solid fuel is used in an electric furnace, and a low-cost heat compensation method in a converter.

[Conventional technology]

Conventionally, in an electric furnace that manufactures molten steel by melting scrap iron, etc., there is a method of blowing heavy oil or kerosene into the furnace with an auxiliary combustion burner, or enriching oxygen, as a method for reducing the electric power consumption rate. . For example, by enriching the amount of oxygen blown with 1.3 to 1.4 times the theoretical amount of oxygen, the electric power consumption rate is reduced by 3 to 5 kwH / t. Taking the operation of an electric furnace of 20 T / H as an example, when the maximum kerosene of 500 l / h is injected, the electricity consumption rate will decrease by about 10%.

3 and 4 show such a conventional apparatus, in which 1 is an electric furnace in which a furnace lid 1b is openably and closably mounted on the upper surface of a furnace body 1a lined with a refractory material, The electrode 6 is inserted into the furnace. Note that 1c is a flue that guides the exhaust gas to the chimney. A large number of auxiliary burners 2 are arranged on the side wall of the furnace main body 1a toward the raw materials in the furnace, and further toward the upper surface of the molten steel 3. The auxiliary burner 2 has a structure in which an air nozzle 2a and an oil nozzle 2b are arranged at the center thereof, and an oxygen nozzle 2c is arranged outside thereof, and the outside is surrounded by a cooling water casing 2d.

In this conventional apparatus, heavy oil or kerosene and air are blown from the upper surface of the molten steel 3 in the electric furnace 1 by the auxiliary combustion burner 2,
Further, oxygen is blown into the molten steel 3 by the oxygen blowing lance to enrich the oxygen. As a result, the electric power consumption rate is reduced according to the preheating and oxygen enrichment by the auxiliary burner 2.

[Problems to be solved by the invention]

However, in the above conventional device, the electric power consumption rate cannot be reduced so much even if the injection amount of heavy oil or kerosene is increased.
The reason is considered as follows. That is, in the above conventional apparatus, since heavy oil or kerosene is blown into the furnace and burned in the furnace, low temperature scrap iron is hit with heavy oil or the like, and it is difficult for these temperatures to rise, or unburned smoke is generated. This is because it is difficult to completely combust the above heavy oil and the like because the inside of the furnace is in a reducing atmosphere in general and the sensible heat of the heavy oil and the like cannot be effectively used.

The object of the present invention is to eliminate the above-mentioned conventional problems and to effectively utilize the sensible heat of the auxiliary fuel for injection, to significantly improve the electric power consumption rate in the electric furnace, and in the converter to refine the iron scrap at low cost. It is an object of the present invention to provide an electric furnace, a method for injecting solid fuel in a converter, and an injecting device capable of performing the above.

[Means for solving problems]

Therefore, the first invention of the present application is a solid fuel injection method for an electric furnace or a converter, in which solid fuel is primarily burned outside the furnace of the electric furnace or the converter at an air-fuel ratio of 1.0 or less, and the unburned gas is further burned. Is secondarily combusted in the vicinity of the inlet of the electric furnace, and high-temperature exhaust gas produced by the second-stage combustion is blown into the furnace.

A second aspect of the present invention is, in a solid fuel injection device for an electric furnace or a converter, a primary combustion in which solid fuel and primary air are supplied to the outside of the electric furnace or the converter to burn at an air-fuel ratio of 1.0 or less. A chamber is formed, and secondary air is supplied to the unburned gas from the primary combustion chamber for secondary combustion at the inlet of the electric furnace or the converter, and high-temperature exhaust gas due to this two-stage combustion is generated. The feature is that a secondary combustion chamber blown into the furnace is formed.

[Action]

According to the method and apparatus for injecting solid fuel in the electric furnace and the converter according to the present invention, the solid fuel is firstly burned outside the furnace at an air-fuel ratio of 1.0 or less, and then secondarily burned at the inlet of the electric furnace. In other words, since the two-stage combustion is performed, the solid fuel can be almost completely burned, and the scrap iron and the like can be preheated and melted by the high-temperature exhaust gas due to this complete combustion. The utilization ratio of preheat and sensible heat of the auxiliary fuel for melting can be greatly improved as compared with the case of blowing into the interior, and as a result, the power consumption rate can be reduced.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a fixed fuel injection device for an electric furnace according to an embodiment of the second invention of the present application. In the figure, the same reference numerals as those in FIG.
The next combustion chamber 4 is installed. The primary combustion chamber 4 has a cylindrical shape whose inner surface is lined with a refractory material, and its axis is directed to the center of the molten steel 3 in the furnace. Further, air blowing pipes 4a, 4a for blowing the primary air or oxygen in the circumferential direction are connected to the side wall of the primary combustion chamber 4. A burner 4c for blowing pulverized coal is inserted in the air blowing pipes 4a, 4a. An ash pot for collecting ash produced from the solid fuel is provided on the lower surface of the primary combustion chamber 4.
4b is formed.

A secondary combustion chamber 5 is connected to the tip of the primary combustion chamber 4. The axis of the secondary combustion chamber 5 is on the same line as the axis of the primary combustion chamber 4, and the blow-in port 5a is directed toward the molten steel level near the center of the furnace through the opening 1d of the furnace body 1a. Further, two blow pipes 5b for blowing secondary air are connected to the secondary combustion chamber 5, and the blow pipes are connected to each other.
The blowing nozzle following 5b extends into the furnace.

Next, a case where the method of the first embodiment of the present invention is carried out in the apparatus of the above embodiment will be described.

Burner 4 with a specified amount of pulverized coal (350 kg / H) in the primary combustion chamber 4
The air is blown from c through the air blowing pipe 4a, and the primary air is blown from the air blowing pipe 4a so that the air-fuel ratio becomes, for example, 0.65. As a result, the pulverized coal in the primary combustion chamber 4 swirls along the inner wall and is subsequently burned. At this time, the heavy ash content adheres to the inner wall of the primary combustion chamber 4 and is collected by the ash pot 4b. This air-fuel ratio of 0.65 1
The combustion exhaust gas generated by the secondary combustion is completely combusted in the secondary combustion chamber 5 with the secondary air mixed therein. The high-temperature exhaust gas from which ash has been removed by this complete combustion is blown onto scrap iron or the like in the furnace, whereby the scrap iron or the like is preheated and melted.

As described above, in the present embodiment, the solid fuel is burned in two stages, so that complete combustion is easy, and it is possible to efficiently preheat it by blowing high-temperature exhaust gas with good thermal efficiency onto scrap iron, and the required power amount Can be reduced and the power consumption rate can be significantly reduced. Further, in this case, since the ash content is collected in the ash pot 4b, it is possible to eliminate the adverse effect of the ash content on the molten steel.

In the above embodiment, the amount of secondary air in the secondary combustion chamber 5 is set so that the unburned gas can be completely combusted. However, in this case, the amount of secondary air should be 0.35 or less. As a result, the exhaust gas produced by the secondary combustion can be converted into a reducing gas and blown into the electric furnace 1. By doing so, the formation of slag (Fe ₂ O ₃ ) can be prevented, and C + Co ₂
It has an effect of preventing the oxidation of the electrode 6 due to 2CO.

FIG. 2 shows a modified example of the above embodiment, which is an example in which combustion exhaust gas is blown into the furnace from the bottom of the furnace.

In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts, and the primary combustion chamber 4 and the secondary combustion chamber 5 are connected by an exhaust gas passage 8, and the blowing port 5a of the secondary combustion chamber 5 is a furnace. It is connected to the opening 1e formed in the bottom.

In this modified example, the heat of the exhaust gas can be applied to the scrap iron or the like that is located away from the electrode 6 and is difficult to be energized, and the molten steel can be agitated, so that the whole can be heated more uniformly.

In addition, although the electric furnace has been described in the above embodiments, the present invention is not limited to the electric furnace of the present invention and can be applied to a converter.

〔The invention's effect〕

As described above, according to the electric furnace, the method for injecting the solid fuel in the converter, and the injecting apparatus according to the present invention, since the solid fuel is burned in two stages, complete combustion is easy and thermal efficiency is good. High-temperature exhaust gas can be blown into the electric furnace or converter, and the sensible heat of solid fuel can be effectively used to preheat and melt scrap iron to a high temperature. Therefore, the converter has the effect of enabling low-cost thermal compensation.

[Brief description of drawings]

FIG. 1 is a view for explaining a solid fuel injection device for an electric furnace according to an embodiment of the second invention of the present application, FIG. 1 (a) is a sectional side view thereof, and FIG. 1 (b) is A transverse sectional view of the primary combustion chamber, FIG. 2 is a sectional side view showing a modified example of the above embodiment, FIG. 3 is a sectional side view of a conventional electric furnace, and FIG. 4 (a) is a cross section of the burner. A plan view and FIG. 4 (b) are longitudinal sectional views of the burner. In the figure, 1 is an electric furnace, 4 is a primary combustion chamber, and 5 is a secondary combustion chamber.

Claims (6)

[Claims] 1. A method for preheating and melting the raw material by blowing fixed fuel in an electric furnace or a converter for melting raw material such as scrap iron to produce molten steel, wherein the solid fuel is air-fuel ratio outside the furnace. It is characterized in that primary combustion is carried out at 1.0 or less, air or oxygen is supplied to the unburned gas in the vicinity of the furnace inlet to carry out secondary combustion, and exhaust gas by the second-stage combustion is blown to the raw materials. Solid fuel injection method for electric furnaces and converters. 2. A solid fuel blowing method for an electric furnace or a converter according to claim 1, wherein the combustion exhaust gas is blown from an upper surface of a raw material in the electric furnace or the converter. 3. The method for injecting solid fuel in an electric furnace or converter according to claim 1, wherein the combustion exhaust gas is blown from the bottom of the electric furnace or converter. 4. An electric furnace or a converter for melting raw materials such as scrap iron to produce molten steel, which is an apparatus for preheating and melting the raw materials by blowing fixed fuel into the electric furnace or the converter. Solid fuel and primary combustion air are blown outside the furnace to form a primary combustion chamber for primary combustion of the solid fuel at an air-fuel ratio of 1.0 or less, and the primary combustion chamber is provided at the inlet of the electric furnace or converter. Secondary combustion air is supplied to the unburned gas from the secondary combustion chamber to perform secondary combustion, and a secondary combustion chamber for introducing the exhaust gas from the second stage combustion into the electric furnace or the converter is formed. Solid fuel injection device for electric furnaces and converters. 5. The electric furnace according to claim 4, wherein the outlet of the secondary combustion chamber faces the upper surface of the raw material in the electric furnace or the converter, and the solid material of the converter. Fuel injection device. 6. The solid of the electric furnace or the converter according to claim 4, wherein the outlet of the secondary combustion chamber faces the bottom of the electric furnace or the converter. Fuel injection device.