JPS5948924B2 - Electrical heating method for floating steelmaking process - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrical heating method for a floating iron manufacturing process, and more particularly to an electrical heating method for a floating direct reduction iron manufacturing process.

The rotary kiln method, the shaft furnace method, the fluidized bed method, etc. are known as direct iron manufacturing methods, and the present invention is classified into the fluidized bed method.

Conventional fluidized bed methods have problems such as poor heat utilization efficiency, low reaction efficiency on the gas side, equipment wear, and powder (raw material) agglomerating and adhering, making operation difficult.

Recently, a floating direct reduction ironmaking process (floating direct ironmaking process) has been proposed as a method to solve these problems (Japanese Patent Application No. 157726/1989, etc.). Carbonaceous materials (coal, coke, char, etc.) are suspended (by gas) in a furnace maintained at high temperatures (800-1000℃) to form a carbonaceous floating fluidized bed (floating layer). Iron oxide raw material (
This is a process in which iron ore powder, etc.) is dropped and reduced while passing through the layer.

For this process, the fluidization flow rate in the furnace is necessarily ○Floating carbonaceous matter ○Falling iron oxide raw materials It is determined by two conditions.

Therefore, the flow rate that satisfies these conditions cannot cover the amount of heat sufficient to maintain the temperature of the floating layer in the furnace at a high temperature, and furthermore, the amount required in terms of material balance is insufficient.

Therefore, in order to cover these two points, that is, ○heat amount ○material balance, by supplying electricity to the carbonaceous floating layer, the temperature inside the furnace is increased using carbonaceous material as a heating medium, and furthermore, Fe20a + 3C = 2Fe + 3CO Alternatively, a process has been proposed in which the direct reduction reaction of Fe2O3+3/2C-2Fe+3/2CO2 is actively promoted, thereby significantly increasing the productivity of the furnace.
1-157727).

The present inventors further studied the above-mentioned floating iron making process and obtained the following two important findings.

i The floating layer in the above process is formed from a carbon-based material (carbonaceous material) and an iron-based material, and there is a relationship shown in FIG. 1 between the electrical resistance of the floating layer and the material forming the floating layer.

ii When the floating layer forming substances are the same, the electrical resistance of the floating layer exhibits negative characteristics with respect to the temperature of the floating layer, as shown in FIG.

Now, in order to increase productivity in the floating steelmaking process, if we increase the gas flow rate in the furnace by sacrificing the piston flow of the iron oxide raw material to some extent, the carbonaceous material and the iron-based material will be almost completely mixed, but the upper part of the floating layer will still be In the lower part of the floating layer, there are many iron-based substances, mainly reduced iron.

At this time, if current heating is performed to compensate for the lack of heat necessary for the reaction system, for example, using an electrode buried in the inner wall of a cylindrical furnace,
The upper part of the floating layer is easily energized and the temperature rises, and the upper part of the floating layer is overheated, and the sintering of reduced iron in the upper part of the floating layer causes the ash in the carbon to melt, causing floating and flow inhibition. I will do it.

In order to prevent this, it is not practical to subdivide the electrodes in the upper and lower directions of the floating layer and control the current flow as appropriate, since this poses a problem in terms of insulation of electrical wiring in a high-temperature furnace.

Furthermore, artificial graphite or the like is practically selected as the material for the electrodes, but at this time the electrodes are consumed by reactions such as C0C02=2CO1 C0H2O-C0+H2, and countermeasures are required to prevent this.

The purpose of the present invention is to provide an electrical heating method that simultaneously solves the above-mentioned electrical properties, insulation structure, and countermeasures against electrode consumption. In the floating iron manufacturing process, which produces reduced iron by floating, multiple phases of electrodes are installed in the furnace at an angle so that the electrical resistance between the electrodes is uniform from the top to the bottom of the floating layer.
The part of each electrode above the surface of the floating layer is purged with an inert gas to prevent the electrode from being consumed by the reducing atmosphere in the furnace, and the floating layer is heated by passing electricity through the electrode, and the floating layer is heated. The present invention relates to an energization heating method for a floating steelmaking process, which is characterized in that electrodes are replenished at any time when the electrodes are consumed.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3 schematically shows an example of an apparatus for carrying out the heating method of the present invention.

1 is a reduction furnace (reaction tower), and at the top of the reduction furnace 1,
A charging hopper 2 is provided for charging iron oxide raw materials (iron ore, oxide pellets, etc.) A and carbon particles B as an example of carbonaceous material into the furnace, and for discharging the furnace top exhaust gas G. A discharge port 3 is provided.

Furthermore, an inlet 4 is provided at the bottom of the furnace 1 for introducing preheated (or heated) gas (reducing gas) C into the furnace.

In addition, a hearth 6 with diffuser holes 5 is installed diagonally in the above-mentioned type 1, and one end of the hearth 6 has reduced iron slag and char (pre-coking) as products. An extraction lower is provided to take out E.

Furthermore, a floating layer F of carbon particles B is formed in the above-mentioned type 1 as described later, and an electrode 8 is provided so that the floating layer F is energized and heated.

The electrodes 8 are consumable electrodes of the required length and the required number of phases, for example, three. It is inserted at an angle.

FIG. 4 is a plan view of the electrode arrangement at the top of the furnace. As shown in the figure, the electrodes 8 are arranged in a triangular shape in plan, and the intervals between the electrodes 8 at the top of the furnace. 1
1 is larger than the distance of 1° between the electrodes 8 and 8 at the bottom of the floating layer F.

Further, the upper part 8a of each electrode 8, that is, the part 8a that is not located in the floating layer F, is inserted and located in a protective tube 9 attached to the top of the furnace, and furthermore, the part 8a of the electrode 8 is prevented from being worn out by the reducing atmosphere in the furnace. In order to prevent this, the portion 8a of the electrode 8 is purged and sealed using an inert gas H such as N2, which is introduced into the protective cylinder 9.

Next, to describe the operation of the iron manufacturing process using this reducing furnace 1, first, during the startup period of the furnace, when preheated (or heated) reducing gas C is blown into the furnace, this reducing gas (reducing atmosphere) C is discharged from the top of the furnace as top exhaust gas G through the vent hole 5, and is circulated into the furnace again.

By repeating this circulation, the reducing performance of the circulating gas increases.

Here, the carbon particles B, which had been charged in advance into the furnace, float in the above-mentioned atmosphere, and a floating fluidized bed of carbon particles B, that is, a floating layer F, is formed in the furnace.

Next, when a voltage is applied between the electrodes 8, 8 from a power source (not shown), the carbon particles B forming the floating layer F are energized, and the temperature in the furnace increases due to Joule heat.

When the iron oxide raw material A is introduced into the furnace in this state, it passes through the floating layer F and descends onto the hearth 6.

When this iron oxide raw material A passes through the floating layer F, the following formula (I
) (II) (III), Fe2O3+3CO=
2Fe+3CO2-(I)Fe203+3C=2Fe
+3CO"・ ke ■)C+CO2-2CO...(II
The reduction reaction shown in I) occurs, and the iron oxide raw material A is transferred to the floating layer F.
While being reduced by carbon monoxide, a reducing atmosphere, that is, a reducing gas containing carbon monoxide is regenerated.

The generated reduced iron oxide and char E are separated and taken out, and the char E is sent to the carbon hopper 4 as carbon particles.

By the way, in the above-mentioned iron-making process, as mentioned earlier, the settling iron-based substances accumulate more in the lower part of the floating layer F than in the upper part of the floating layer F, and as is clear from Fig. Since the electric resistance is larger, if the electrodes are made parallel, the upper part of the floating layer F will be locally heated.

However, in the case of the present invention, since the electrode 8 is inserted and installed at an angle from the top of the furnace, the electrical resistance becomes uniform from the upper part to the lower part of the floating layer F, and the above-mentioned local heating is prevented.
The entire floating layer F is heated uniformly, and the above-mentioned reduction reaction occurs evenly.
and is actively promoted.

In addition, a portion 8 of the electrode 8 other than that located in the floating layer F
A is purged and sealed by a protective tube 9 and an inert gas H, and to prevent the electrode 8 from being consumed in the floating layer F, the electrode 8 can be replaced by successively adding more electrodes.
The number of current-carrying parts can be kept to a minimum, allowing continuous operation over a long period of time.

In summary, since the current heating method of the present invention uses inclined electrodes, the entire floating layer can be heated uniformly, so that the reduction reaction is uniformly and actively promoted throughout the floating layer, making the floating steel manufacturing process more efficient. It exhibits excellent effects such as being able to operate continuously for a long period of time.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the mixing ratio of floating layer forming substances and the electrical resistance of the floating layer, Figure 2 is a graph showing the relationship between the temperature of the floating layer and the electrical resistance of the layer, and Figure 3 is a graph showing the relationship between the floating layer temperature and the electrical resistance of the floating layer. Schematic diagram showing an example of an apparatus for carrying out the energization heating method of the invention, No. 4
The figure is a plan view of the electrode arrangement. 1... Reduction furnace, 8... Electrode, A...
...Iron oxide raw material, B...Carbon particles, D...
...Reduced iron, F...Floating layer, H...
Inert gas.

Claims (1)

[Claims] 1. In the floating iron manufacturing process, in which iron oxide raw materials are introduced into a floating layer formed of carbonaceous material and allowed to settle to produce reduced iron, multiple electrodes are placed in the furnace from the top to the bottom of the floating layer so that the electrical resistance between the electrodes is uniform. The phase electrodes are provided at an angle, and the portion of each electrode above the surface of the floating layer is purged with an inert gas to prevent the electrodes from being consumed by the reducing atmosphere in the furnace, and current is applied to the floating layer from the above electrode. , heating, and replenishing electrodes as needed to prevent electrode consumption in a floating layer.