JP4725101B2 - Scale charging equipment for arc furnace - Google Patents

Description

The present invention relates to a method and an apparatus for charging a scale generated in a processing process such as rolling and forging of steel to an arc furnace that performs electric furnace steelmaking for recycling.

In many cases, the production of steel using an electric furnace is carried out in the same factory as the subsequent rolling and forging processes, and in this case, the scale generated in the machining process is an iron resource in the steelmaking process. As recycled. Most of the scales are strips mainly composed of oxides, but some of them are also included, so handling thereof is not always easy. The simplest recycling of scales is to charge a steel arc furnace. Conventionally, a large amount of scale has been put in a batch operation after opening the road cover.

However, with this method, the scale is thrown into the periphery of the furnace, where arc heat is difficult, and the arc heat between the electrode and the scale is dissipated and lost, or the refractory on the furnace wall is melted. There is a disadvantage to invite. In addition, it takes time for the scale to melt, and the molten steel temperature must be increased in order to eliminate unmelted residue. Furthermore, since the introduction of scale causes an oxidation-reduction reaction with carbon and metal elements in the molten steel, there are various problems such as unstable operation due to fluctuations in the foamy “foamy” state.

The charging of the scale into the arc furnace is continuous toward the vicinity of the electrode as close to the center of the arc furnace as possible in order to eliminate the various problems described above, even in terms of work efficiency. It is desirable to be able to put in scale. However, batch processing using clamshell or alloy charging equipment is common as a technology for handling the raw material charged in the arc furnace. On the other hand, the scale needs to be charged in a certain amount. It is difficult to finely control the oxidation / reduction in the arc furnace. Regarding scrap, there was a proposal to save heat energy by preheating it with exhaust gas and then putting it in (Patent Literature 1, Patent Literature 2). . Until now, no technology has been tried to put scale into the arc furnace in the above-described manner.
JP-A-62-41582 JP-A 62-41583

The object of the present invention is to respond to the above-mentioned demands, and continuously inject the scale toward the vicinity of the electrode as close as possible to the center of the arc furnace that is in operation, that is, energized. It is to provide a possible scale-in method and an apparatus therefor.

The scale charging method for the arc furnace of the present invention that achieves the above object is preferably converted to oxidized slag that can be effectively used as a roadbed material, or the scale generated in processing steps such as rolling and forging of steel is more preferable. As a processing mode, it is a method for recycling to arc furnace steelmaking in the form of iron resources, where the scale is cut out by an electromagnetic feeder from a scale hopper provided at a position avoiding the position directly above the arc furnace, and the rotational drive is arranged obliquely It is conveyed through a possible rotating cylindrical feeder to a position just above the center of the arc furnace, from which the scale is dropped through a chute penetrating the furnace lid and supplied to the vicinity of the electrode. When the scale is introduced, it is preferable to add an auxiliary material such as a carbon material at the same time, and the present invention naturally includes such an embodiment.

When the scale is charged into the arc furnace according to the present invention, a hopper for storing the scale and an electromagnetic feeder for cutting out the scale from the hopper can be provided at a position avoiding directly above the arc furnace. While avoiding damage, the scale can be moved from above, while the scale taken out in this way is moved laterally by the cylindrical feeder and pulled directly above the arc furnace, From there, it enters the furnace through a chute that penetrates the furnace lid, and is placed in the vicinity of the electrode at the approximate center of the arc furnace. The carbon material or the like that is added at the same time falls together with the scale to the approximate center of the arc furnace and in the vicinity of the electrode, so that it is involved in the reaction efficiently.

In this way, the scale introduced is efficiently dissolved by arc heat and converted to oxidized slag or preferably serves as an iron resource. Since the scale that is continuously added in small amounts is rapidly melted and there is no undissolved residue, it is not necessary to raise the temperature of the molten steel to dissolve it. Since the scale is an oxygen source, it is preferable to add a reducing agent such as charcoal at the same time as the charging, and according to the present invention, it can also be performed continuously under control. The introduction of scale in such a situation does not destroy the foamy state of the slag. Compared to the conventional technology in which the scale is inserted by opening the furnace lid, the basic unit is improved in terms of operating time and power consumption.

The scale charging apparatus of the present invention for carrying out the above-described scale charging method for an arc furnace converts the scale generated in a processing step such as rolling and forging of steel into oxidized slag, or the arc furnace as an iron resource. An apparatus for recycling into steel making, as shown in FIGS. 1 and 2, a scale hopper (4A) provided at a position avoiding the position directly above the arc furnace (1), and an electromagnetic feeder for cutting out the scale connected thereunder (5A), a rotationally driveable cylindrical feeder (6) disposed obliquely at the tip of the outlet of the electromagnetic feeder, its rotational drive means, and a furnace lid (2) just above the center of the arc furnace at the tip of the cylindrical feeder Is a scale charging device for an arc furnace for conveying the scale and supplying it to the vicinity of the electrode (3). In FIG. 1, reference numeral (4B) indicates a hopper for carbon material, (5B) indicates an electromagnetic feeder for cutting out the carbon material, and reference numeral (8) in FIG. 2 indicates an attachment position of the dust collecting duct.

The details of the rotating cylindrical feeder (6) are as shown in FIG. The rotating cylinder feeder (6) is a motor (also these are provided with a cyclo reducer (registered trademark)) in which the rotating cylinder (61) is rotatably supported on a roller (not shown) in the support frame (62). (Not shown) is driven to rotate at a variable speed through the chain (63). The scale from the electromagnetic feeder (5A) enters the upper end (64) of the rotating cylinder, slides through it as the cylinder rotates, exits from the lower end (65), and is supplied to the upper part of the scale chute (7). .

In the present invention, the scale is continuously supplied to the arc furnace little by little. As described above, the scale generated in factories having various processing steps in addition to the steelmaking step is mainly composed of oxides. However, since the individual shapes and dimensions vary, the flow characteristics also vary. Therefore, it is advantageous to intermittently cut out the scale by the electromagnetic feeder from the scale hopper. In order to make it compatible with continuous supply in small quantities, the amount of scale falling through the scale chute can be reduced by adjusting the conveyance speed of the rotating cylindrical feeder, specifically by adjusting the rotation speed. It is preferable to average.

Needless to say, the rotating cylindrical feeder has a larger scale conveyance speed as the angle of inclination is larger and the rotational speed is higher. When the angle of repose was measured for a certain scale, it was 38 degrees. The angle of repose varies slightly depending on the scale, but is about this level. However, in the present invention, as described above, it is intended to adjust the scale supply speed in the rotating cylinder feeder, so by arranging the rotating cylinder with an inclination smaller than the angle of repose and changing the rotating speed, Adjust the feed rate.

For this reason, it is preferable that the tilt angle and the rotational speed of the rotating cylinder (61) with respect to the horizontal direction are variably provided within a certain range. Although the range in which the tilt angle can be changed is not so large due to the structure of the equipment, the rotational speed can be changed within a considerable range. Appropriate combinations can be determined by performing simple experiments in practicing the invention, but usually they can be found in the range of an inclination angle of 3 to 35 degrees and a rotation speed of 0.3 rpm or more. According to the experiences of the inventors based on implementation data described later, the inclination angle is preferably 18 degrees or more and the rotation speed is preferably 2 rpm or more.

The position where the scale chute is provided on the furnace lid is preferably within a circle of 0.4R from the center of the furnace lid, where R is the inner diameter of the arc furnace. If placed in such a position, in a normal arc furnace, most of the scale falls within a circle connecting the outer circumferences of three symmetrically arranged electrodes, and the place intended by the present invention is realized.

In order to build a device that can supply scale to the arc furnace at a maximum rate of 5.5 tons / hour, the dimensions of the rotating cylindrical feeder were determined as follows. (The scale of 5.5 tons / hour is a dissolvable amount when the arc efficiency of this arc furnace is 100%. If the arc efficiency is 60%, the dissolvable amount is 3.3 tons / hour. In other words, a cylinder with an inner diameter of 400 mm and a length of 3 m is selected with an inclination angle of 10 degrees, 15 degrees or 19 degrees with respect to the horizontal, and the rotation speed is selected to be 1 rpm, 2 rpm or 3.2 rpm, and how much the same scale is It was measured whether it could be conveyed.

The conveyance capacity of the rotating cylindrical feeder is determined by the following equation (1).
P = (D2 × π / 4) × L × F × r × (60 / t) (1)
Where P: transport capacity per unit time (ton / hour)
D: Diameter of cylinder (m)
L: Length of cylinder (m)
F: Scale filling rate (%)
r: Scale specific gravity t: Dwell time in cylinder (min)
The in-cylinder residence time t (minutes) in the above equation (1) is expressed by the following equation (2).
t = (k × L) / (D × n × θ) (2)
Where k is a constant determined by the fluidity behavior of the scale and the frictional characteristics of the inner surface of the cylinder n: the rotational speed of the cylinder (rpm)
θ: Inclination angle (degrees)

The result of the experiment was as shown in FIG. From this data, it was found that in order for the rotating cylindrical feeder to have a sufficient transport capability, it is desirable to design the inclination to be 18 to 19 degrees or more and the rotational speed to be about 2 to 6 rpm.

The side view which shows the scale injection | throwing-in apparatus to the arc furnace of this invention with an arc furnace. The top view which shows the preferable position which provides the position of an electrode, the attachment position of a dust collection duct, and a scale chute in the furnace cover of the arc furnace which uses the apparatus of FIG. The side view which showed the detail of the rotating cylindrical feeder which is the principal part of the scale injection | throwing-in apparatus to the arc furnace of this invention, and showed the inside by notching a part. It is the test data of this invention, Comprising: The graph which showed the influence which the rotation speed of a cylinder has with respect to the scale conveyance capability of a rotation cylinder feeder according to the inclination angle of a cylinder.

Explanation of symbols

1 Arc furnace body 2 Furnace lid 3 Electrode 4A Scale hopper 4B Carbon material hopper 5A Electromagnetic feeder (for scale cutting) 5B Electromagnetic feeder (for carbon material cutting)
6 Rotating cylinder feeder 61 Rotating cylinder 62 Support frame 63 Chain 64 Upper end of rotating cylinder 65 Lower end of rotating cylinder 7 Scale chute 8 Dust collection duct position 9 Scale

Claims (2)

A device that recycles the scale generated in processing processes such as steel rolling and forging into iron furnace steelmaking as an iron resource, a scale hopper provided at a position avoiding the top of the arc furnace, and a scale cutout connected below it Electromagnetic feeder, rotationally-rotatable cylindrical feeder disposed obliquely at the tip of the outlet of the electromagnetic feeder and its rotational driving means, and the tip of the rotary cylindrical feeder, when the inner diameter of the arc furnace is R, A scale charging apparatus for an arc furnace for transporting a scale and supplying it to the vicinity of an electrode, comprising a scale chute provided through a furnace lid so as to be located within a circle having a radius of 0.4 R from the center . The scale throwing device according to claim 1 , wherein the rotating cylindrical feeder is arranged at a variable angle of an inclination angle of 3 to 35 degrees with respect to the horizontal direction and is rotationally driven at a variable speed of 0.3 rpm or higher.

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