JPH08136163A - Exhaust gas controller for scrap preheater - Google Patents

Abstract

PURPOSE: To safely operate by controlling the flow of exhaust gas in an exhaust gas controller for preheating scrap by the gas. CONSTITUTION: A scrap preheater has a preheating chamber 10 provided on an arc furnace 1 to contain scrap to pass the exhaust gas of the furnace 1 through a preheating chamber 11, and comprises a pressure sensor provided in the exhaust gas channel of the chamber 10, and a bypass passage 26 provided to directly exhaust the gas to the furnace 1 without intermediary of the chamber 10, wherein the part of the gas of the furnace 1 is directly exhausted via the passage 26 so that the static pressure detected by the sensor is always held at a predetermined value or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas control device for a scrap preheating device in an arc furnace for melting metal scrap.

[0002]

2. Description of the Related Art A scrap preheating device has been known in which the residual heat of exhaust gas discharged from an arc furnace is effectively used for preheating scrap (metal material) to contribute to energy saving. For example, in the scrap preheating device disclosed in Japanese Examined Patent Publication No. 6-46145, the scrap is held in the flue opening to the ceiling of the arc furnace so that the scrap can be preheated by exhaust gas and radiation in the furnace.

[0003]

By the way, in the preheating device having the structure in which the exhaust gas flows through the scrap as described above, the pressure in the arc furnace depends on the scrap filling condition because the scrap interferes with the discharge of the exhaust gas. However, there was a risk that the exhaust gas would leak into the factory building as it was. Further, carbon monoxide in the exhaust gas from the arc furnace may significantly increase the carbon monoxide concentration in the exhaust gas in an incompletely burned state, causing abnormal temperature rise in the arc furnace,
In some cases, the temperature rise loss in the scrap preheating chamber was increased. Also, scraps of various sizes are mixed and, for example, metal shavings (Dalai powder) and the like are easily melted, so that they may be melted and oxidized in the preheating chamber, and the ventilation path is narrowed by welding to further increase the pressure loss. There was a problem.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above problems, and a preheating chamber capable of accommodating scrap is provided on the arc furnace so that the exhaust gas of the arc furnace flows through the preheating chamber. In the scrap preheating device, a gas sensor for detecting the concentration of carbon monoxide in the exhaust gas is provided in the exhaust gas passage of the preheating chamber, and a flow rate adjusting damper for controlling the amount of air or oxygen introduced into the arc furnace is provided. The damper is automatically opened / closed so that the concentration of carbon monoxide detected by is kept below a certain value.

Further, the present invention similarly provides a scrap preheating apparatus in which a preheating chamber capable of accommodating scrap is provided on the arc furnace so that exhaust gas of the arc furnace flows through the preheating chamber. A pressure sensor for detecting static pressure is provided, and a bypass passage for directly discharging exhaust gas without passing through a preheating chamber is provided in the arc furnace so that the static pressure detected by the pressure sensor is always kept above a certain value. In addition, a part of the exhaust gas of the arc furnace is directly discharged through the bypass passage.

Further, the present invention similarly provides a scrap preheating apparatus in which a preheating chamber capable of accommodating scrap is provided on the arc furnace so that exhaust gas of the arc furnace flows through the preheating chamber. Along with the temperature sensor, the arc furnace is provided with a bypass path for directly discharging the exhaust gas without going through the preheating chamber, and the exhaust gas of the arc furnace is kept so that the temperature detected by the temperature sensor is always kept below a certain value. Is partially discharged through the bypass passage. The preheating chamber may be divided into a plurality of sections.

[0007]

[Effect] Even if the preheating chamber is provided, the exhaust gas of the arc furnace can be discharged as required, and the operation can be performed safely.

[0008]

EXAMPLE Next, an example of the scrap preheating apparatus according to the present invention will be described with reference to FIGS. In the figure, 1 is an arc furnace provided on a base 2 so as to be tiltable via rollers 6, 3 is a tap hole of the arc furnace 1, 4 is an electrode supporting device 5 and the tip is inside the arc furnace 1. It is an electrode that hangs down.

Numeral 7 is a supporting base provided on both sides of the arc furnace 1. A rail 8 is laid on the supporting base 7 and wheels 30 are attached to the lower end of the frame 9 so as to be movable along the rail 8.
Is provided. Further, a cylindrical preheating chamber 10 and a preheating chamber 11 penetrating vertically in the frame 9 are supported, and the preheating chamber 10 and the preheating chamber 11 are supported by the frame 9 in a vertically stacked state on the arc furnace 1. 12 is the upper preheating chamber 1
A pair of fork-shaped breathable bottom plates pivotally attached to the bottom portion of 0 so as to be deployed downward by the operation of the cylinder 13. Further, 14 is a cylinder 15 at the bottom of the lower preheating chamber 11.
Is a pair of fork-shaped breathable bottom plates pivotally attached so as to be able to be deployed downward by the operation of. The opening edge of the extension cylindrical portion 16 extended to the lower end of the preheating chamber 11 is formed in an arc shape that matches the upper edge opening of the arc furnace 1 and is in sliding contact with each other to allow the tilting of the arc furnace 1. . A pair of shutters 18 which can be opened and closed by a cylinder 17 are provided at the upper end opening of the preheating chamber 10. In addition, 19 is a bucket stand projectingly provided on the upper end of the frame 9, and 20 is a clamshell type bucket suspended by a crane wire for carrying scrap.

The scrap carried by the bucket 20 can fall into the preheating chamber 10 by opening the shutter 18. By opening the bottom plate 12 of the preheating chamber 10, the scrap in the preheating chamber 10 falls into the preheating chamber 11, and by opening the bottom plate 14 of the preheating chamber 11, the scrap in the preheating chamber 11 is scraped by the arc furnace 1. Can fall inside.

Reference numeral 21 is a circulation duct that connects the side wall of the extension cylinder portion 16 and the side wall of the preheating chamber 10 so as to guide the exhaust gas of the arc furnace 1 to the preheating chamber 10. An exhaust gas outlet 23 is opened on the side wall of the preheating chamber 11, and the exhaust gas outlet 23 communicates with an exhaust gas duct 24. Therefore, in this scrap preheating device, the exhaust gas generated in the arc furnace 1
At the same time, the scrap in 1 is discharged to the exhaust gas duct 24, and at the same time, it directly flows to the preheating chamber 10 through the circulation duct 21, and the scrap in the preheating chamber 10 flows from top to bottom and is discharged to the exhaust gas duct 24. .

FIG. 3 shows a system diagram of the exhaust gas control device of the scrap preheating device. In FIG. 3, the same reference numerals as those in FIGS. 1 and 2 indicate the same parts. A detection device 25 is provided near the exhaust gas outlet 23 and includes a pressure sensor that detects the static pressure of the exhaust gas, a gas sensor that detects the carbon monoxide concentration in the exhaust gas, and a pressure sensor that detects the exhaust gas concentration. Further, 26 is a side wall of the extension cylinder portion 16 and the exhaust gas duct 2
4 is a bypass passage that directly communicates with 4, and a reference numeral 27 is a flow rate adjusting damper that can adjust the amount of exhaust gas directly discharged from the arc furnace 1 provided in the bypass passage 26 through the bypass passage 26. Further, 28 is a flow rate adjusting damper provided in the air supply passage 29 for controlling the amount of air introduced into the arc furnace 1.

In this device, however, the opening degree of the flow rate adjusting damper 27 is adjusted so that the detection value of the static pressure of the exhaust gas by the detection device 25 is always kept above a certain value. That is,
When the static pressure is abnormally reduced, the pressure loss due to scrap in the preheating chamber 10 or the preheating chamber 11 is large and the air permeability is extremely poor. In such a case, the flow rate adjusting damper 27 is opened and the arc is opened. By directly discharging the exhaust gas of the furnace 1 to the exhaust gas duct 24 through the bypass passage 26, the inside of the arc furnace 1 is kept at a negative pressure and the leakage of the exhaust gas into the factory building is prevented.

Further, the opening of the flow rate adjusting damper 28 is adjusted so that the detected value of the carbon monoxide concentration by the detecting device 25 is always kept below a certain value. That is, when the concentration of carbon monoxide in the exhaust gas near the exhaust gas outlet 23 rises, it is recognized that the combustible components in the exhaust gas in the preheating chamber 10 or the preheating chamber 11 are incompletely burned, so the flow rate adjusting damper 28 is opened. By supplying more air or oxygen into the arc furnace 1 through the air supply path 29, the combustion is promoted, and the combustion is effectively used for preheating the scrap, and the exhaust gas is purified to facilitate the exhaust treatment. Let's train.

Further, the flow rate adjusting damper 27 is so arranged that the temperature detection value of the exhaust gas detected by the detection device 25 is kept below a certain value.
Adjust the opening of. That is, when the exhaust gas temperature near the exhaust gas outlet 23 rises abnormally, the preheating chamber 10 or the preheating chamber 1
Since there is a risk that the scrap will be melted in 1 and the oxidation and pressure loss will be further increased by the melting, the flow rate adjustment damper 27 should be avoided in order to avoid such a situation.
And the exhaust gas of the arc furnace 1 is directly discharged to the exhaust gas duct 24. The scrap preheated by allowing the exhaust gas to flow through in the preheating chamber 11 in this way is put into the arc furnace 1, and the scrap preheated in the preheating chamber 10 is transferred to the preheating chamber 11 to be preheated to a sufficient temperature to be further heated in the arc furnace 1. 1
Be thrown into.

In the embodiment shown in FIG. 3, the exhaust gas of the arc furnace 1 was passed through the preheating chamber 10 and the preheating chamber 11 in parallel and discharged, but in the embodiment shown in FIG.
Exhaust gas duct 24 provided on the side wall of the preheating chamber 10 by passing the exhaust gas of the preheating chamber 11 in series in the order of the preheating chamber 10
The exhaust gas is discharged to. In this case, the exhaust gas outlet 23
A detection device 25 is provided in the vicinity or in the preheating chamber 11 to detect the static pressure, carbon monoxide concentration, temperature, etc. of the exhaust gas, and according to the detected values, the flow rate adjusting damper 27 and the air supply passage 29 are provided in the same manner as in the above embodiment. The opening is automatically adjusted to ensure ventilation and ensure safety. In the above, the example in which the two preheating chambers are arranged vertically is shown, but it goes without saying that the arrangement and number of preheating chambers are not limited to these examples. Further, the detection device 25 is not limited to the vicinity of the exhaust gas outlet 23 as shown in the embodiment, and may be in the preheating chambers 10 and 11 or the circulation duct 21 and the exhaust gas duct 24 depending on the detection purpose.
May be provided.

[0017]

As described above, according to the present invention, it is possible to detect the abnormality of the exhaust gas system in the apparatus for preheating scrap by the exhaust gas flow through the arc furnace in advance and always safely preheat the scrap. In addition, there is a beneficial effect that the combustion heat can be effectively used by complete combustion and the heat loss is reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a scrap preheating device showing an embodiment of the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a system diagram of an exhaust gas control device of a scrap preheating device according to the present invention.

FIG. 4 is a system diagram showing another embodiment of FIG.

[Explanation of symbols] 1 arc furnace 10 preheating chamber 11 preheating chamber 12 breathable bottom plate 14 breathable bottom plate 21 circulation duct 23 exhaust gas outlet 24 exhaust gas duct 25 detector 26 bypass passage 27 flow rate adjustment damper 28 flow rate adjustment damper 29 supply air passage

Claims (4)

[Claims] 1. A scrap preheating apparatus in which a preheating chamber capable of accommodating scrap is provided on the arc furnace so that the exhaust gas of the arc furnace flows through the preheating chamber. A gas sensor for detecting the carbon concentration is provided, and a flow rate adjusting damper for controlling the amount of air or oxygen introduced into the arc furnace is provided so that the carbon monoxide concentration detected by the gas sensor is kept below a certain value. An exhaust gas control device for a scrap preheating device, which automatically opens and closes the damper. 2. A scrap preheating device in which a preheating chamber capable of accommodating scrap is provided on the arc furnace so that exhaust gas of the arc furnace flows through the preheating chamber, and static pressure is detected in an exhaust gas passage of the preheating chamber. Along with the pressure sensor, the arc furnace is provided with a bypass passage for directly discharging the exhaust gas without passing through the preheating chamber, and the static pressure detected by the pressure sensor is always maintained at a constant value or more so that the static pressure of the arc furnace is maintained. An exhaust gas control device for a scrap preheating device, characterized in that a part of the exhaust gas is directly discharged through the bypass passage. 3. A scrap preheating apparatus in which a preheating chamber capable of containing scrap is provided on the arc furnace so that exhaust gas of the arc furnace flows through the preheating chamber, and a temperature sensor is provided in an exhaust gas passage of the preheating chamber. By providing a bypass passage in the arc furnace that directly discharges the exhaust gas without going through the preheating chamber,
An exhaust gas control device for a scrap preheating device, wherein a part of the exhaust gas of the arc furnace is directly discharged through the bypass passage so that the temperature detected by the temperature sensor is always kept below a certain value. 4. The exhaust gas control device of the scrap preheating device according to claim 1, 2 or 3, wherein a plurality of preheating chambers are vertically divided and provided on the arc furnace.