JPH0639629B2 - Scrap melting method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a scrap melting method using a melting furnace equipped with a plurality of furnace bodies that are alternately operated, and in particular, scrap melting capable of odorless preheating of scrap. It is about the method.

"Prior Art" Conventionally, when melting scrap, for example, a double-type arc furnace having two furnace bodies alternately operated,
The high-temperature exhaust gas generated from the operating furnace body is guided to the waiting furnace body before being released to the atmosphere, and the heat of the exhaust gas preheats the scrap charged in the waiting furnace body. ing. According to this, the operating time can be shortened, and energy can be saved when processing the preheated scrap.

"Problems to be solved by the invention" However, in the scrap melting method as described above,
Since the exhaust gas used for preheating is released into the atmosphere as it is, the odorous components generated from scrap during preheating may be released into the atmosphere along with the exhaust gas.Therefore, a separate deodorizing device should be installed. There is also a problem that it is necessary to limit the preheated scraps to those that do not generate odor.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a scrap melting method capable of preheating scraps without the need to treat odors or limit the types of scraps.

"Means for Solving the Problems" The scrap melting method of the present invention, when melting scrap using a double melting furnace equipped with a plurality of furnace bodies that are alternately operated, The charged scrap was preheated by the burner equipped in the furnace body, and the exhaust gas generated by the preheating was introduced into the furnace body during operation to thermally decompose the odorous components in the preheated exhaust gas. It is characterized by that.

In this method, a heat exchanger may be provided in the middle of the exhaust gas duct from the furnace body in operation to heat the combustion air for the burner.

[Operation] According to the present invention, the scrap charged into the furnace body in the standby state is preheated by the burner, and the odorous component generated from the scrap due to the preheating is introduced into the furnace body in operation together with the exhaust gas, After being thermally decomposed here, it is released into the atmosphere.

Moreover, if a heat exchanger is provided in the middle of the exhaust gas duct, the heat can be recovered from the exhaust gas discharged into the atmosphere through the heat exchanger.

[Examples] Examples of the three-phase AC arc furnace of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a diagram showing a first embodiment of the present invention, in which reference numerals 1 and 2 are a pair of two furnace bodies. A common power supply facility (transformer for furnace) 3 and a secondary side conductor 4 thereof are selectively connected to the furnace bodies 1 and 2 to alternately operate, and one of them is operated. Sometimes the other is on standby. Further, in each of the furnace bodies 1 and 2, an auxiliary combustion burner 1a is provided in a so-called cold zone between the electrodes.
, 2a are provided. These combustion burners 1
The a and 2a are mainly used when the furnace body is in a standby state, and preheat the scrap charged in the furnace body.

Each of the furnace bodies 1 and 2 is provided with a pair of connection ports 5, 6 and 7, 8 for connecting an exhaust gas duct. The break flanges 9 and 10 and the damper 11 are provided at the connection port 5 of the furnace body 1 and the connection port 7 of the furnace body 2.
The duct 12 is connected via. Further, discharge ducts 15 and 16 are connected to the connection port 6 of the furnace body 1 and the connection port 8 of the furnace body 2 via break flanges 13 and 14, respectively. These discharge ducts 15 and 16 are connected to each other via dampers 17 and 18, and a discharge duct 19 is connected to this connection portion, and a dust collector 20 is provided at the tip of this discharge duct 19. ing.

Next, the operation mode will be described.

FIG. 1 shows a state in which the secondary conductor 4 from the power supply equipment 3 is connected to the furnace body 1 and the furnace body 1 is in operation, and the furnace body 2 is in a state in which scrap is charged and is on standby. Is shown. At this time, the damper 11 of the duct 12 and the damper 17 of the discharge duct 15 are opened, and the damper 18 of the discharge duct 16 is closed. And the auxiliary burner 2 of the furnace body 2
The scrap is preheated by a ..., and the exhaust gas containing the odorous components generated by this preheating is guided to the furnace body 1 from the connection port 7 through the duct 12 as shown by the solid arrow in the figure, and After being combined with the exhaust gas generated by the operation, the exhaust gas is passed through the discharge ducts 15 and 19 and the dust collector 2
It is released into the atmosphere through 0.

As a result, the scrap in the furnace body 2 can be preheated to a high temperature, and the odorous components generated by the preheating are thermally decomposed in the furnace body 1 during operation and are not released to the atmosphere.

When the operation of the furnace body 1 as described above is completed, the break flanges 9 and 13 are opened to disconnect the furnace body 1 from the duct 12 and the discharge duct 15, and the furnace body 1 is tilted to take out steel. Then, the secondary conductor 4 is immediately moved to the furnace body 2 side to start the operation of the furnace body 2, but the furnace repair work of the furnace body 1 and the preparatory work such as the charging of new scrap into the furnace body 1 are performed. Until the end, the dampers 11 and 17 are closed, the damper 18 is opened, and the furnace body 2 is independently operated to discharge the exhaust gas.
Release through 6,19. When the preparation work of the furnace body 1 is completed, the damper 11 is opened and the auxiliary combustion burner 1a ...
By this, preheating in the furnace body 1 is started, and exhaust gas is passed through as indicated by a dashed arrow in the figure.

As a result, contrary to the operation of the furnace body 1, the exhaust gas containing the odorous components generated by the preheating in the furnace body 1 is guided to the furnace body 2 where the odorous components are thermally decomposed and then the furnace body 1 is heated. It is discharged through the discharge ducts 16 and 19 together with the exhaust gas generated from the gas.

By repeating the above procedure and alternately operating the furnace bodies 1 and 2, the steelmaking cycle time can be shortened, and the scrap can be preheated without the need to treat the odor and to limit the type of scrap. Also, in this arc furnace, when the operation of the furnace body that was on standby (that is, preheated) was started, the so-called cold zone between the electrodes of this furnace body was already heated by the auxiliary combustion burner, Smelting of scrap in this furnace body is performed quickly, which can contribute to energy saving.

Next, a second embodiment will be described with reference to FIG. In the second embodiment, the same components as those in the first embodiment described above are designated by the same reference numerals as those in FIG. 1, and the description thereof will be omitted.

In the second embodiment, the heat exchanger 21 is provided in the middle of the discharge duct 19. Ducts 22 and 23 are connected to the heat exchanger 21, and ducts 24 and 25 are further connected to the duct 23 via dampers 26 and 27. The heat exchanger 21 heats the air taken in through the duct 22 by exchanging heat with the exhaust gas, and the heated air is sent to the preheated furnace body 1 or 2 and the auxiliary combustion burners 1a ..., 2a. Is used as combustion air.

In addition, in the middle of the duct 12 between the furnace bodies 1 and 2, the preheating chamber 2
8 is provided via dampers 29 and 30. The preheating chamber 28 stores scrap therein and allows exhaust gas flowing through the duct 12 to pass therethrough.

Further, a combustion chamber 31 for burning unburned gas contained in the exhaust gas is provided at a connection portion of the discharge ducts 15, 16 and 19.

The operation mode of the second embodiment will be described. FIG. 2 shows a state in which the furnace body 1 is in operation and the furnace body 2 is on standby, and the exhaust gas flows in the direction of the solid line arrow as in the case of the first embodiment. At this time, the furnace body 1 in operation is placed in the preheating chamber 28.
Store the scrap that will be additionally charged in.

Then, the scraps charged in the furnace body 2 are preheated by the auxiliary combustion burners 2a, and the combustion air required for this preheating is the air heated by the heat exchanger 21 through the ducts 23 and 25. Lead to. At this time, the damper 26 is closed. After passing the high-temperature exhaust gas generated by preheating in the furnace body 2 through the preheating chamber 28,
Lead to. As a result, the scrap in the preheating chamber 28 can be preheated by the high-temperature exhaust gas from the furnace body 2, and the odorous components generated in the furnace body 2 and the preheating chamber 28 are thermally decomposed in the furnace body 1.

After that, the exhaust gas generated during the preheating and the exhaust gas generated in the furnace body 1 in operation are guided to the combustion chamber 31, where unburned gas in the exhaust gas is burned, and the heat exchanger 21 and the dust collector 20 are connected to each other. And then released into the atmosphere.

When the operation in the furnace body 1 is completed, the furnace body 2 is immediately operated in the same manner as in the case of the above-described first embodiment, and the auxiliary combustion burners 1a ...
To preheat the scrap in the furnace body 1 (at this time, the damper 27 is closed, the damper 26 is opened, and the combustion air is supplied to the furnace body 1).
Together with the exhaust gas, the exhaust gas is caused to flow in the opposite direction (the direction of the broken line arrow) to preheat the scrap additionally charged into the furnace body 2 in the preheating chamber 28, and the above procedure is repeated thereafter.

As described above, the scrap additionally charged in the furnace body in operation in the preheating chamber 28 can be preheated at the same time. Further, high temperature air obtained by exchanging heat with the exhaust gas is used for the combustion air required by the auxiliary combustion burner, and the exhaust gas that is heat exchanged has energy by burning unburned gas in the combustion chamber 31. Since it is increased, scrap can be preheated efficiently.

In addition, when it is not necessary to additionally load the scrap preheated in the preheating chamber 28 into the furnace body in operation, this scrap may be charged into the furnace body after the operation. In this case, the scrap will be preheated twice and can be preheated to a higher temperature. If it is sufficient to use only scraps that do not generate odorous components during preheating, the preheating chamber 28 may be installed in the middle of the duct 19. Furthermore, the hot air obtained by the heat exchanger 21 is
In addition to being used for the combustion air of the auxiliary combustion burners 1a and 2a, it is also introduced to the preheating chamber 28 and used for preheating the scrap, or the combustion chamber 31
It can also be used as combustion air in, and can also be used for other purposes.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and the heat exchanger, the preheating chamber, and the combustion chamber do not necessarily have to be provided together, and the operating conditions and economical efficiency are not required. It may be appropriately used after considering. Further, although the dust collector blower is not shown in the above embodiment, a blower for circulating the exhaust gas may be further provided if necessary.

In addition, in each of the above-mentioned embodiments, the case where the arc furnace having two furnace bodies is used has been described, but the present invention can be similarly implemented even when a larger number of furnace bodies are provided. . Further, the auxiliary combustion burner can be used not only at the time of preheating the scrap but also at the furnace body during the operation, so as to achieve a quicker melting. Further, although the present invention has been described in the example of the three-phase AC arc furnace, the present invention is not limited to the three-phase AC arc furnace, and the DC arc furnace, the plasma furnace, the combustion furnace, other, fuel, oxygen Of course, it is also possible to use a compound blowing melting furnace by blowing carbonaceous material.

[Effects of the Invention] As described in detail above, according to the scrap melting method of the present invention, preheating is performed by the burner, and the exhaust gas generated by the preheating is guided to the furnace body in operation. The odor component generated at this time is not thermally decomposed and released into the atmosphere. Therefore, there is an effect that preheating can be performed without providing any other deodorizing device or the like and without limiting the type of scrap.

In addition, if a heat exchanger is provided in the duct that discharges the exhaust gas, it is possible to recover the heat of the exhaust gas.

[Brief description of drawings]

1 and 2 are views showing the first and second embodiments of the present invention, respectively. 1, 2 ... Furnace body, 1a, 2a ... Auxiliary burner (burner), 12 ... Duct, 15, 16, 19 ... Discharge duct, 21 ... Heat exchanger.

Claims (2)

[Claims] 1. When melting a scrap by using a double melting furnace having a plurality of furnace bodies that are alternately operated, the scrap charged into the furnace body in the standby state is equipped in the furnace body. The method for scrap melting is characterized in that the odor component in the preheated exhaust gas is thermally decomposed by preheating with a burner and guiding the exhaust gas generated by the preheating to the furnace body in operation. 2. The scrap melting according to claim 1, wherein a heat exchanger is provided in the middle of the exhaust gas duct from the furnace body in operation to heat the combustion air for the burner. Method.