JPH0692872B2 - Exhaust gas heat recovery method and apparatus in dual melting furnace - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for recovering exhaust gas heat in a dual melting furnace having a plurality of furnace bodies mainly made of scrap (scrap iron) and an apparatus therefor. is there.

“Prior art” In a scrap melting furnace, it is an important issue to save energy and reduce melting cost by recovering the high temperature exhaust gas energy generated from the furnace body during the operation of the scrap melting furnace. Therefore, various means have been conventionally taken for heat recovery of exhaust gas.

As such a means, for example, a heat recovery means in a double arc furnace provided with two furnace bodies that are alternately operated is known. This guides the high-temperature exhaust gas generated from the operating furnace body to the waiting furnace body before releasing it to the atmosphere, and the scrap (raw materials) charged in the waiting furnace body due to this exhaust gas heat It is to preheat. According to this
The operation time can be shortened, the exhaust gas heat is recovered by preheating the scrap, and energy can be saved when the preheated scrap is processed.

"Problems to be solved by the invention" However, in the heat recovery means in the above-mentioned double-arc furnace, since the exhaust gas used for preheating is directly discharged to the atmosphere, the odor component generated from scrap during preheating May be released into the atmosphere along with the exhaust gas, so 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 heat recovery method and an apparatus therefor which do not require odor treatment or limitation of scrap types in a double melting furnace.

"Means for Solving Problems" In the heat recovery method of the first invention, scrap is charged into a standby furnace body out of a plurality of furnace bodies that are alternately operated, and the standby furnace body is charged with the scrap. After preheating the scrap in the standby furnace body by guiding a part of the exhaust gas generated from the furnace body in operation, the exhaust gas used for this preheating and the rest of the exhaust gas generated from the furnace body in operation The feature is that they are merged.

The heat recovery device according to the second aspect of the present invention includes a preheating duct that guides the exhaust gas generated from the operating furnace body to the waiting furnace body, a discharge duct that discharges the guided exhaust gas to the atmosphere, and both of these. A bypass duct connected to the duct, the bypass duct having an exhaust gas flow rate control damper for bypassing a part of the exhaust gas generated from the furnace body in operation, and the discharge duct and the bypass duct being connected to each of these ducts. It is characterized in that a merging portion is provided for merging the exhaust gases respectively guided by.

Further, the heat recovery device of the third invention is a preheating duct for guiding the exhaust gas generated from the operating furnace body to the waiting furnace body, a discharge duct for discharging the guided exhaust gas to the atmosphere, and both of these ducts. And a bypass duct provided with an exhaust gas flow rate control damper for bypassing a part of the exhaust gas generated from the furnace body in operation, and the exhaust gas and air which are provided in the middle of the discharge duct and heat the exhaust gas passing through the discharge duct. A heat exchanger that heats the air by exchanging the exhaust duct, and a connecting portion for connecting the discharge duct and the bypass duct is provided with a merging portion for merging the exhaust gas guided by each of these ducts. It has a feature.

[Operation] According to the present invention, exhaust gas heat is recovered by being used for preheating scrap. Also, the exhaust gas used for preheating and containing the odor component generated from scrap merges with the exhaust gas that is directly guided by bypassing the furnace body in operation from the furnace body in operation at the confluence part, where the odor component is bypassed. It is thermally decomposed by high temperature exhaust gas. further,
In the third aspect of the invention, the heat is also recovered from the exhaust gas discharged into the atmosphere through the heat exchanger. That is, by guiding air to a heat exchanger provided in the middle of the discharge duct to exchange heat with the exhaust gas, the air is heated and used as, for example, combustion air or preheating air.

"Embodiment" An embodiment in which the present invention is applied to a three-phase AC arc furnace 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 the figure, reference numerals 1 and 2 are a pair of two furnace bodies in a double-type arc furnace.
These furnace bodies 1 and 2 have a common power supply facility (transformer for furnace) 3
And the secondary side conductors 4 are selectively connected to operate alternately, and when one is operating, the other is on standby.

Each of these furnace bodies 1 and 2 is provided with a pair of connection ports 5, 6 and 7, 8 for connecting an exhaust gas duct. A preheating duct 13 is connected to the connection port 5 of the furnace body 1 and the connection port 7 of the furnace body 2 via break flanges 9 and 10 and dampers 11 and 12. Further, discharge ducts 16 and 17 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 14 and 15, respectively.
These discharge ducts 16 and 17 are connected to each other via dampers 18 and 19, and further, a discharge duct 20 is connected to this connecting portion, and a dust collecting device 21 is connected to the tip of this discharge duct 20.
Is provided.

Further, one end of a bypass duct 22 having an exhaust gas flow rate control damper 29 is connected between the dampers 11 and 12 of the preheating duct 13, and the other end of the bypass duct 22 is connected to the discharge ducts 16, 17, 20. Connected to the department. The connection portion where the discharge ducts 16, 17, 20 and the bypass duct 22 are connected to each other forms a merging portion A where the exhaust gas guided by the discharge duct 16 or 17 and the exhaust gas guided by the bypass duct 22 merge, The exhaust gas that has merged at the junction A is discharged into the atmosphere by the discharge duct 20.

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 dampers 11 and 12 of the preheating duct 13 and the damper 19 of the discharge duct 17 are opened, and the damper 18 of the discharge duct 16 is closed.

Therefore, in this state, a part of the high temperature exhaust gas generated by the operation of the furnace body 1 is guided to the furnace body 2 from the connection port 5 through the preheating duct 13 as shown by the solid line arrow in the figure, Therefore, after the scrap in the furnace body 2 is preheated, it is guided to the merging portion A through the discharge duct 17. The rest of the exhaust gas from the furnace body 1 passes through the bypass duct 22, bypasses the furnace body 2, and joins with the exhaust gas from which the scrap has been preheated at the joining portion A. The exhaust gas flow rate control damper 29 controls the flow rate of the exhaust gas to be bypassed. After that, the exhaust gas that has merged at the merge section A is collected from the duct 20 through the dust collector.
It is released into the atmosphere via 21.

Thereby, the exhaust gas heat is recovered by preheating the scrap in the furnace body 2. Further, the odorous component generated during preheating is thermally decomposed in the merging portion A and the discharge duct 20 by joining with the high-temperature exhaust gas bypassing the furnace body 2, and the odorous component is released into the atmosphere. It will not be done.

After the operation of the furnace body 1 as described above is completed, the break flanges 9 and 14 are opened to fix the furnace body 1 to the preheating duct 13 and the discharge duct 16.
Then, the furnace body 1 is tilted and the steel is tapped. Then, the secondary side 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, 18, and 19 are closed, and the exhaust gas generated from the furnace body 2 is discharged into the atmosphere through the bypass duct 22. When the preparation work of the furnace body 1 is completed, open the dampers 11 and 18,
The exhaust gas is passed through as indicated by the dashed arrow in the figure. As a result, contrary to the operation of the furnace body 1, a part of the exhaust gas generated from the furnace body 2 passes through the inside of the furnace body 1, and the rest passes through the bypass duct 22 to join them at the merging portion A. Then release.

By repeating the above procedure and operating furnace bodies 1 and 2 alternately, the steelmaking cycle time can be shortened, and heat recovery of exhaust gas can be performed with high efficiency without limiting odor treatment and scrap types. You can

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, preheating chambers 23 and 24 are provided in the discharge ducts 16 and 17, respectively. These preheating chambers 23 and 24 are
Scrap is stored inside and ducts 16 and 17
The exhaust gas flowing inside is made to pass through.

Further, a combustion chamber 25 for burning the exhaust gas is provided in the middle of the preheating duct 13, and a heat exchanger 26 is provided in the middle of the discharge duct 20. The heat exchanger 26 heats the exhaust gas by recovering the exhaust gas heat by exchanging heat with the exhaust gas of the combustion air (that is, oxygen) introduced from the duct 27 and sent to the combustion chamber 25 by the duct 28.

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 is flowing in the direction of the solid line arrow. At this time, the preheating chamber 24 stores scrap to be additionally charged into the furnace body 1 in operation. Further, the exhaust gas flowing from the furnace body 1 to the furnace body 2 is passed through the combustion chamber 25, and unburned gas such as carbon monoxide in the exhaust gas is burned there. As the combustion air required in the combustion chamber 25, the air heated through the heat exchanger 26 is used.

As a result, the exhaust gas generated from the furnace body 1 has its thermal energy increased by burning the unburned gas in the combustion chamber 25.
The scrap in the furnace body 2 and the scrap in the preheating chamber 24 can be preheated. Therefore, according to this apparatus, the scrap additionally charged into the furnace body 1 is also preheated at the same time, and the combustion air required in the combustion chamber 25 is recovered by the heat exchanger 26 from the exhaust gas discharged into the atmosphere. Since the temperature is increased by increasing the temperature, the heat recovery efficiency can be further increased as compared with the first embodiment.

When the operation in the furnace body 1 is completed, the furnace body 2 is immediately operated, and the exhaust gas is circulated in the reverse direction (the direction of the arrow indicated by the broken line), as in the case of the above-described first embodiment, and the furnace body 2 is additionally mounted. The scrap is preheated in the preheating chamber 23 and the furnace body 1 in which the incoming scrap is stored, and thereafter, the above procedure is repeated.

If it is not necessary to additionally load the scrap preheated in the preheating chambers 23 and 24 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. When it is sufficient to use only scraps that do not generate odorous components during preheating, the preheating chamber may be installed in the duct 22 or 20. Further, the high temperature air obtained by the heat exchanger 26 is used as the combustion air in the combustion chamber 25, as well as the preheating chambers 23,2.
It may be used for preheating of scrap by leading it to 4, or may 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 preheating chamber, the combustion chamber, and the heat exchanger do not necessarily have to be provided together, and the operating conditions and the economical efficiency are improved. 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.

Although the above-mentioned embodiments have been described for the case where the number of the furnace bodies is two, the present invention can be similarly applied to the multiple arc furnace constituted by a larger number of furnace bodies. 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 heat recovery method of the first invention, a part of the exhaust gas is guided to the standby furnace body to preheat the scrap, and then from the furnace body in operation. Since it was made to join with the exhaust gas of, the odor component generated from the preheated scrap will be thermally decomposed, and the effect that the heat recovery of the exhaust gas can be performed without the need to treat the odor or limit the type of scrap Play.

Further, according to the heat recovery device of the second invention, the preheating duct for guiding a part of the exhaust gas to the standby furnace body, the discharge duct for discharging the exhaust gas, and the bypass duct are provided, and the discharge duct and the bypass duct are provided. Since a merging part is provided at the connection part with
It is possible to easily carry out the above method.

Further, according to the heat recovery device of the third invention, a heat exchanger for heating the air by exchanging heat between the exhaust gas and the air is provided in the middle of the discharge duct, and the air heated by the heat exchanger is By utilizing it for combustion air, preheating air, or other uses, it is possible to recover heat from the exhaust gas discharged, and it is possible to further improve the heat recovery efficiency.

[Brief description of drawings]

1 and 2 are views showing the first and second embodiments of the present invention, respectively. 1,2 …… Furnace body, 13 …… Preheating duct, 16,17,20 …… Discharge duct, 22 …… Bypass duct, 26 …… Heat exchanger, 29 ……
Exhaust gas flow rate control damper, A ...... Merging section.

Claims (3)

[Claims] 1. A method for recovering heat from high-temperature exhaust gas generated from a furnace body during operation, which is used in a double melting furnace having a plurality of furnace bodies that are alternately operated, said plurality of furnace bodies After preheating the scrap in the standby furnace by introducing scrap into the standby furnace, and introducing part of the exhaust gas generated from the operating furnace to the standby furnace A method for recovering heat of exhaust gas in a double melting furnace, characterized in that the exhaust gas used for this preheating and the rest of the exhaust gas generated from the furnace body in operation are merged. 2. A heat recovery device for exhaust gas in a double melting furnace comprising a plurality of furnace bodies that are operated alternately, and a preheating duct that guides the exhaust gas generated from the operating furnace body to the standby furnace body. , A discharge duct that discharges the guided exhaust gas to the atmosphere, and a bypass duct that is connected to both of these ducts and that has an exhaust gas flow control damper that bypasses a part of the exhaust gas generated from the furnace body in operation A heat recovery device for exhaust gas in a double melting furnace, characterized in that a confluence part is provided at a connection part between the discharge duct and the bypass duct to combine exhaust gases respectively guided by these ducts. 3. A heat recovery device for exhaust gas in a double melting furnace comprising a plurality of furnace bodies that are operated alternately, and a preheating duct that guides the exhaust gas generated from the operating furnace body to a standby furnace body. A discharge duct that discharges the guided exhaust gas to the atmosphere, a bypass duct that is connected to both of these ducts and that has an exhaust gas flow rate control damper that bypasses a part of the exhaust gas generated from the furnace body in operation; A heat exchanger that is provided in the middle of the discharge duct and heats the air by exchanging heat between the exhaust gas passing through the discharge duct and the air is provided. A heat recovery device for exhaust gas in a double melting furnace, characterized in that a confluence part is provided for combining the exhaust gases respectively guided by the ducts.