JPS6237310A - Method for preheating metallic scrap in arc furnace - Google Patents

Abstract

PURPOSE:To uniformly preheat the scrap charged into a furnace to a high temp. in a method for blowing a high-temp. gas into the furnace to preheat the scrap by forming a cavity in the scrap by arc melting so that the cavity acts as the passage for the high-temp. gas. CONSTITUTION:Part of the scrap 2 charged into the furnace body 1 is subjected to arc melting by an arc electrode to bore the cavity 3 in the scrap 2. The electrode is then pulled up and moved and a preheating cover 5 is put on the furnace body 1. The high-temp. gas is supplied to the furnace from a duct 4. The high-temp. gas supplied into the body 1 applies heat to the scrap 2 while passing through the spacing of the scrap 2 and gathers particularly at the cavity 3 where the flow passage resistance is low. The gas comes above the scrap 2 by passing through the cavity 3 and is discharged from a gas discharge port 6 to the outside of the furnace body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for preheating metal scrap in an arc furnace for steelmaking.

[Conventional techniques and techniques] In order to save power in an arc furnace for steelmaking, scrap is preheated prior to actual operation. The conventional preheating method is to simply pass high-temperature exhaust gas from an arc furnace or the like or a burner flame vertically or horizontally through the scrap charged into a container.

[Problems to be Solved by the Invention] Therefore, high-temperature gas generally flows along the inner wall of the container, which has less resistance, and hardly flows into the center, so that the thermal energy of the aU gas is effectively used. There was a problem in that the scrap was not recovered, and it was hardly possible to expect an increase in the uniformity heat and average preheating temperature of the scrap.

The present invention allows gas to flow through the center of the scrap charged into the furnace, thereby effectively recovering and utilizing the thermal energy of the high-temperature gas to achieve uniform heating and high-temperature preheating of the scrap. The purpose is to do so.

[Means for solving the problem] The present invention preheats metal scrap by blowing high-temperature gas in an arc furnace. is arc melted to form a cavity in the charged scrap.

The scrap is characterized in that the scrap is preheated by blowing high-temperature gas into the cavity so that it becomes a gas passage.

In the case of a multiple arc furnace, it is desirable to use exhaust gas from the operating furnace as the high temperature gas.

[Operation] If there are cavities in the charged scrap, the gas blown into the furnace will flow so as to gather in the cavities where the flow path resistance is low. (
Therefore, depending on the location of the cavity, the flow of high-temperature gas can be controlled, and gas can pass through the center of the container (furnace), which was previously difficult for gas to pass through, especially inside it.

[Example] An example in which the present invention is applied to a three-phase AC arc furnace,
This will be explained with reference to FIGS. 1 and 2.

FIG. 1 is a plan view showing a state in which a hole is made in the charged scrap by poling by arc melting, and FIG. 2 is a side sectional view showing a state in which a preheating cover is covered. In the figure 1
2 is a hearth, 2 is scrap charged into the hearth 1, 3 is a hole (cavity) polled by arc melting, and 4 is a high temperature gas introduction duct. Further, 5 indicates a preheating cover, 6 indicates a gas exhaust port provided in accordance with the position of the polled hole 3, and 7 indicates an exhaust duct attached to the preheating cover 5.

In this method, during preheating operation, a part of the scrap 2 charged into the furnace body 1 is first arc-melted using an arc electrode, and a hole 3 is made in the charged scrap 2. The depth of the hole 3 may be up to the end of the poling period when the electrode reaches the hearth. When polling is completed, the electrode is pulled up and moved, and then the preheating cover 5 is placed over the furnace body 1, high temperature gas is introduced into the furnace body 1 from the duct 4, and preheating operation begins.

The high-temperature gas introduced into the furnace gives heat to the scrap 2 while passing through the internal gap of the charged scrap 2, concentrates in the poling hole 3 with low flow resistance, and passes through the hole 3 to the scrap 2. The gas flows upward and is discharged from the furnace body 1 through the gas discharge port 6. The arrows in the figure indicate the flow of gas.

As shown by this arrow, the gas also reaches the center of the furnace body 1, so the gas reaches the center, especially the scrap located inside.
The scrap 2 is also sufficiently heated, and the entire scrap 2 is preheated efficiently on average.

When the preheating is completed, the preheating cover 5 is moved, the operating furnace lid is placed on the furnace, and the conventional arc melting operation begins. In this case, when polling is performed at the operating position as shown in FIG. 1, the electrode can be inserted into the hole 3 as it is and the operation can be started. Therefore, arc melting after completion of preheating starts from the time when polling ends, the arc is stabilized from the start time, and large power can be input.

Therefore, rapid dissolution can be performed and flicker is less likely to occur.

FIG. 3 is for explaining another embodiment of the present invention. This embodiment is characterized in that the position of the poling for preheating by electrodes is shifted from the core position during operation and is away from the high temperature gas inlet 4.

In this way, the gas is introduced into the furnace body 1 through the gas inlet 4a! The gas flows toward the hole 3 remote from the inlet 4a, passes through the inside of the charged scrap 2 on the way, and gives heat to the scrap 2 as it passes through. Therefore, more part of the scrap 2 can be uniformly preheated, and when the melting operation is started, the scrap 2 can be quickly melted without worrying that the scrap 2 will hang on the shelf.

Note that the high-temperature gas introduced into the furnace body 1 may be produced by a burner, or high-temperature exhaust gas from another furnace may be used for the purpose of energy saving and exhaust heat recovery. If the present invention is applied to a multiple arc furnace when the exhaust gas of the furnace is utilized, the effect will be extremely large. That is, one of the two furnaces can perform arc melting operation and the other can perform preheating, and the exhaust gas from the operating furnace can be used to preheat the scrap in the other furnace.

Further, in the above embodiments, the present invention was applied to a three-phase AC arc furnace, but the present invention is of course applicable to a DC arc furnace.

[Effect of the invention] The present invention provides the following effects.

■The flow of high-temperature gas can be controlled by the location of the cavity formed in the scrap.

For this reason, high-temperature gas can reach the center of the furnace, particularly into the scrap inside, where preheating gas could not reach with conventional methods. Therefore, the heat of the high-temperature gas can be effectively applied to all the scraps, and the scraps in the furnace can be uniformly preheated to a high temperature.

■゛If the position of the cavity, or hole, formed by arc melting using the city pole is the same position in the core as during the main operation,
When preheating is completed and the main operation begins, arc melting is
It is possible to start from the point at which arc melting during preheating ends. Therefore, the arc is stabilized from the start of arc melting, large power can be applied, rapid melting is possible, and flicker is less likely to occur.

■If the position of the cavity, i.e., the hole, is shifted from the core and located far from the high-temperature gas inlet, preheating can be performed more uniformly, and the phenomenon of scrap hanging on the wall can be prevented. Rapid dissolution can proceed.

(2) By forming cavities, ie, holes, by arcing at multiple locations, uniform preheating and uniform melting can be further promoted.

■If the present invention is applied to a multiple arc furnace that is operated alternately and the high-temperature exhaust gas of the arc furnace on the operating side is used as the high-temperature gas, energy saving and waste heat recovery can be realized more effectively. Ru.

[Brief explanation of the drawing]

1 and 2 are a plan view and a side sectional view, respectively, for explaining one embodiment of the present invention, and FIG. 3 is a plan view for explaining another embodiment of the present invention. 1...Furnace body, 2...Scrap, 3
... Hole), 4 ... High temperature gas introduction duct, 5 ... Preheating cover.

Claims (2)

[Claims] (1) In a method of preheating scrap charged into a furnace by blowing high-temperature gas into the furnace, a cavity is formed in the scrap in the furnace by arc melting, and this cavity is used as a passage for high-temperature gas. A method for preheating metal scrap in an arc furnace, characterized by: (2) A method for preheating metal scrap in an arc furnace according to claim 1, wherein exhaust gas from an operating side of a multiple arc furnace is used as the high-temperature gas.