JPH0579911B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a melting furnace for melting and smelting scrap raw materials, and in particular to a method for recovering exhaust gas from a melting furnace in which scrap raw materials are preheated with gas discharged from the melting furnace. and its apparatus.

[Prior Art] Conventionally, a melting furnace such as an electric arc furnace using an arc as a main heat source has been used to melt and refine scrap raw materials, but the cost of electricity accounts for a high proportion of the refining cost. For this reason, it is common practice to preheat the scrap raw material that is fed into the melting furnace.

Conventionally, scrap raw materials are preheated using the heat of the exhaust gas discharged from the melting furnace. Most of this exhaust gas is air that has entered the furnace, and the rest is some gas from the combustion of the arc electrode and the auxiliary burner in the furnace, and its temperature is 500%.
There is almost no latent heat at ~800℃.

[Problem to be solved by the invention] For this reason, the preheating temperature of the scrap raw material is 300~300℃.
The temperature is around 400°C, so no significant power saving effect can be expected. In addition, when scrap raw materials with oil and other adhesion are preheated using exhaust gas at a temperature of about 500 to 800℃, odors and harmful substances are generated during preheating, and since the temperature has not reached the temperature to thermally decompose them, the gas after preheating is There are problems that require separate pollution prevention measures such as removing harmful substances.

The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to provide a method and apparatus for recovering exhaust gas from a melting furnace, which can save or remove electricity, and can preheat scrap raw materials at a high temperature.

[Means for Solving the Problems] In order to achieve the above object, the present invention supplies carbonaceous material and oxygen to the molten material in the melting furnace, and directs the combustible gas generated in the melting furnace to the combustion chamber. It is introduced and combusted to produce a combustion gas of 1000 to 1200℃, and the scrap raw material to be supplied to the melting furnace with the combustion gas is 500 to 800℃.
This method involves preheating the scrap raw material at a high temperature at a high temperature, thermally decomposing the oil, etc. attached to the scrap raw material, and then exchanging heat between the exhaust gas and the air supplied to the combustion chamber. , a means for supplying carbonaceous materials and oxygen to the melting furnace, a combustion chamber for introducing combustible gas generated in the melting furnace, normal temperature air and preheated air, and combusting the combustible gas, and charging the melting furnace to the melting furnace. a preheating chamber that accommodates scrap raw materials and preheats the scrap raw materials by introducing combustion gas from the combustion chamber; a preheating chamber that exchanges heat between the exhaust gas discharged from the preheating chamber and the air supplied to the combustion chamber; This device is equipped with an air preheater.

[Function] According to the above configuration, by supplying carbonaceous material and oxygen into a molten material such as molten steel, the heat of reaction between the carbonaceous material and oxygen is used as a heat source of the melting furnace, reducing arc input power or It can completely eliminate combustible gases such as CO and _H2 generated in melting furnaces by 1000%.
By using combustion gas of ~1200℃ and preheating the scrap raw material at a high temperature of 500~800℃, it thermally decomposes the odor and harmful substances such as oil attached to the scrap raw material and renders them harmless. By supplying the exhaust gas to the air preheater to preheat the air supplied to the combustion chamber, the temperature of the combustion gas in the combustion chamber and the preheating temperature can be accurately controlled, and heat can be recovered efficiently.

[Embodiment] A preferred embodiment of the melting furnace exhaust gas recovery method and device according to the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a melting furnace in which scrap raw material is melted by a three-phase arc electrode 2, and the furnace body 3 is provided with a tapping port 3a for discharging molten material 4.

The three-phase arc electrode 2 is made up of three arc electrode bodies 5, and the upper end is attached to the lifting device 7 via a support 6, so that the arc electrode 2 can be moved in and out of the furnace body 3, and each arc electrode 2 has a It is connected to the power cable 8. A nozzle 9 is provided at the bottom of the furnace body 3, and a means 10 for supplying carbonaceous material and oxygen into the melt 4 is connected through the nozzle 9. The nozzle 9 may be provided at the bottom of the furnace body 3 as shown, or may be provided so as to blow carbon and oxygen into the melt 4 from the side of the furnace body 3.

An exhaust port 11 for discharging combustible gas generated within the melting furnace 1 is provided on the upper side of the furnace body 3, and a combustion chamber 12 for introducing combustible gas is connected to the exhaust port 11. A normal temperature air supply pipe 13 for supplying room temperature air to the combustion chamber 12 and a preheated air supply pipe 14 for supplying preheated air are connected to the combustion chamber 12 .

The combustion gas exhaust pipe 15 of the combustion chamber 12 is connected to the preheating chamber 16
connected to. Scrap raw material 17 is charged into this preheating chamber 16 by a scrap raw material charging device (not shown), and the scrap raw material 17 in the preheating chamber 16 is appropriately supplied to the melting furnace 1. The exhaust gas pipe 18 of the preheating chamber 16 is connected to an air preheater 19, and the preheated air supply pipe 14 is connected to the air preheater 19.

In the above process, the scrap raw material charged into the melting furnace 1 is melted by the arc of the arc electrode 2. In this melt 4, carbonaceous material and oxygen supply means 1
Carbon materials such as pulverized coal, char, and coke and oxygen are blown into the tank from the nozzle 9. At this time, in the melt 4, for example, carbon contained in the charged scrap raw material such as carbon in pig iron, blown carbon material and blown oxygen react, and the reaction causes combustible gas (such as CO gas). , a mixture of CO and _H2 ) is generated. This reaction is an exothermic reaction, and the electric power required for arc input to melt the scrap raw material can be saved.

Combustible gas generated in the melting furnace 1 is led to the combustion chamber 12 through the exhaust port 11, where the preheated air supply pipe 1
It is combusted with the preheated air from step 4, resulting in combustion gas of 1000-1200℃. In this case, in order to maintain the temperature of the combustion gas at a certain temperature, room temperature air is appropriately introduced into the combustion chamber 12 from the room temperature air supply pipe 13 to control the temperature.

The combustion gas generated in the combustion chamber 12 is introduced into the preheating chamber 16 through the exhaust pipe 15, where the scrap raw material 17 in the preheating chamber 16 is preheated to a high temperature of 500 to 800°C.

The preheated gas flowing into the discharge pipe 18 from the preheating chamber 16 has a temperature of about 600 to 900°C, and this gas is introduced into the air preheater 19, where the preheated air supply pipe passes through the air preheater 19. After preheating the air inside 14, it is discharged into the atmosphere.

The molten material 4 that has been smelted in the melting furnace 1 is tapped at the tap port 3.
a, and then lift the arc electrode 2 upward from the furnace body 3 using the lifting device 7 and remove it.
The scrap raw material 17 is preheated in the preheating chamber 16.
is charged and smelted in the same manner as above.

Further, the scrap raw material 17 is preheated in the preheating chamber 16 so that the temperature of the combustion gas from the combustion chamber 12 is about 1200° C. at the initial stage of preheating.
At the end of preheating, the temperature of the gas coming out of the preheating chamber 16 can be reduced by preheating with combustion gas of about 1000℃.
Can be maintained at over 600℃. In other words, at the initial stage of preheating, the scrap raw material 17 is at a low temperature.
A combustion gas of 1200℃ is supplied to keep the gas temperature after preheating at 600℃ or higher, and at the end of preheating, since the scrap raw material 17 has been preheated to about 500 to 800℃, the combustion gas temperature is kept at 1000℃. Reduce it to a certain degree. In this case, if the combustion gas temperature is below 1000°C, the gas after preheating the scrap raw material 17 cannot be maintained at a temperature above 600°C at which the odor from oil etc. adhering to the scrap raw material 17 can be thermally decomposed;
At temperatures above 1200° C., some combustible materials are contained in the scrap raw material, and partial melting occurs, making it difficult to convey the preheated scrap raw material 17 to the melting furnace 1.

In the example shown in Fig. 1, electric power and heat generated by the reaction with carbonaceous material and oxygen are used together to melt the scrap raw material in the melting furnace 1, but this is different from the initial melting by the arc. This is to accelerate the melting process, shorten the melting time, and generate combustible gas necessary for high-temperature preheating.The supply ratios of arc current, carbonaceous material, and oxygen are as follows.

Arc: 200-300kwh/t-steel Carbonaceous material: 20-40Kg/t-steel Oxygen: 15-35Nm/t-steel If melting is performed using only arc current, power consumption of 400kwh or more is required per ton of steel. However, in this embodiment, it is possible to save power to about half of that.

In addition, by providing a combustion chamber 12 for combustible gas separately from the melting furnace 1, it is possible to reduce consumption of the graphite electrode for the arc, reduce the heat load on the melting furnace, and reduce heat loss compared to when combustion is performed in the furnace. Furthermore, by combusting near the preheating chamber 16, heat loss is eliminated and an optimal design for the combustion chamber 12 is possible.

[Modified Embodiment] FIG. 2 shows a modified embodiment of the present invention, which is different from the embodiment shown in FIG. This is an example of dissolving scrap raw materials simply by blowing in oxygen.

In this case, in order to accelerate the melting of the scrap raw material, some of the molten material 4 is left in the furnace body 3 without being completely discharged, and the heat of the remaining molten material 4 is used to make carbon material. After the reaction of oxygen is promoted or after all of the molten material 4 is discharged, carbonaceous material and oxygen may be supplied from the supply means 10 to the melting furnace 1, and at the same time, the molten metal may be injected.

In this example, since no arc current is used, the amounts of carbonaceous material and oxygen supplied are increased accordingly. Also combustion chamber 1
Since the amount of combustible gas in step 2 also increases to some extent, the temperature of the combustion gas supplied to the preheating chamber 16 is adjusted to 1000 to 1200° C. by controlling the temperature in the room temperature air supply pipe 13.

FIG. 3 shows yet another modification of the invention.

In FIG. 3, the melting furnace 1 can be used as a heat source using both the arc electrode 2 and the reaction heat of carbonaceous material and oxygen as explained in FIG. It may be possible to use only the heat of reaction as the heat source.

In this example, only the amount of combustible gas generated in the melting furnace 1 necessary for preheating the scrap raw material 17 is introduced into the combustion chamber 12 in the preheating chamber 16, and the rest is introduced into the combustion chamber 12 through the exhaust port 1.
1 and stored in the gas holder 20 and used as other fuel gas. That is, the exhaust port 11 of the melting furnace 1
A preheating control valve 21 that supplies combustible gas to the combustion chamber 12 and a storage control valve 2 that supplies combustible gas to the gas holder 20 are provided.
2 are connected to each other, and the opening degree of each of the control valves 21 and 22 is controlled by temperature sensors 23 and 24 provided before and after the preheating chamber 16 via a control device 25.

Further, since the combustible gas has a high temperature when sent to the gas holder 20, an auxiliary air preheater 26 is provided, and the sensible heat of the combustible gas is used to preheat the auxiliary air supply pipe 27 to be supplied to the combustion chamber 12.

In this example, the temperature of the combustion gas entering the preheating chamber 16 is detected by the temperature sensor 23, and the temperature of the gas after preheating is detected by the temperature sensor 24. Based on the temperature, the control device 25 controls the preheating control valve 21 and the storage. By controlling the valve opening degree of the control valve 22, it is possible to secure only the amount of combustible gas generated in the melting furnace 1 necessary for preheating the scrap raw material 17, and store the rest in the gas holder 20 for use as another heat source. can.

[Effects of the Invention] As is clear from the above detailed description, the present invention exhibits the following excellent effects.

(1) Supply carbonaceous materials and oxygen into the melt in the melting furnace, and combustible gas generated in the melting furnace
Since the combustion is performed at 1200℃ and the scrap raw material is preheated at a high temperature of 500 to 800℃ using the combustion gas, the preheating temperature can be increased compared to conventional methods, reducing arc power consumption in the melting furnace and the amount of carbon material and oxygen sucked in. reduction is possible.

(2) Out of the thermal energy of sensible heat and latent heat of the combustible gas generated in the melting furnace, the latent heat is used to preheat the scrap raw material by combustion in the combustion chamber as sensible heat, and after further preheating, is supplied to the combustion chamber. By preheating the air that is being heated, the degree of heat utilization within the system can be increased.

(3) Since the scrap raw material can be preheated at a higher temperature than the conventional preheating method, the burden of input energy in the melting furnace can be reduced, thereby shortening the melting and smelting time and improving productivity.

(4) Since the scrap raw material is preheated at a high temperature, it is possible to thermally decompose bad odors and harmful substances generated from oil adhering to the raw material, thereby preventing pollution.

(5) By supplying the exhaust gas after preheating the scrap raw material to an air preheater to preheat the air supplied to the combustion chamber, efficient heat recovery can be achieved and accurate temperature control of combustion gas temperature and preheating temperature can be achieved. can.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of a melting furnace exhaust gas recovery method and apparatus according to the present invention, FIG. 2 is a diagram showing a modified embodiment of the present invention, and FIG. 3 is a diagram showing another modified embodiment of the present invention. It is a figure which shows an example. In the figure, 1 is a melting furnace, 4 is a melt, 10 is a carbon material and oxygen supply means, 12 is a combustion chamber, 16 is a preheating chamber,
17 is scrap raw material.

Claims (1)

[Claims] 1. Carbon material and oxygen are supplied to the molten material in the melting furnace, and the combustible gas generated in the melting furnace is introduced into the combustion chamber and combusted to produce combustion gas at 1000 to 1200°C. Using the combustion gas, the scrap raw material to be supplied to the melting furnace is preheated at a high temperature of 500 to 800°C, and oil etc. adhering to the scrap raw material is thermally decomposed and removed, and the exhaust gas and the air supplied to the combustion chamber are heated. A method for recovering exhaust gas from a melting furnace, characterized by replacing the gas. 2. A melting furnace for melting scrap raw materials, a means for supplying carbonaceous materials and oxygen to the melting furnace, and a combustion system for introducing combustible gas generated in the melting furnace, as well as normal temperature air and preheated air, and burning the combustible gas. a preheating chamber that accommodates scrap raw material to be charged into the melting furnace and preheats the scrap raw material by introducing combustion gas from the combustion chamber, and exhaust gas discharged from the preheating chamber and air that is supplied to the combustion chamber. An exhaust gas recovery device for a melting furnace, comprising: an air preheater that exchanges heat with the air to produce the preheated air.