JPS6017692A - Method of preheating scrap - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preheating raw material scrap in an electric arc furnace for rice production. By using this gas as a heat medium and circulating it and using it for preheating, the 44G material contained in the scrap decomposes due to preheating, and the odor and smoke generated are released to the outside. ! It is designed to prevent the occurrence of cloudy weather.

In electric furnaces such as arc furnaces, which purify scrap using exhaled energy, preheating of scrap using exhaust gas has been widely practiced in recent years in order to save energy by recovering heat from the exhaust gas. But 1. C is also
In this preheating method, the organic matter contained in the scrap is decomposed by preheating, causing secondary pollution such as bad odors and smoke pollution, so there are currently only a few examples of it operating satisfactorily.

FIG. 1 (al to cl indicate conventional scrap preheating devices, respectively).

In the fat type shown in Fig. 1, the exhaust gas discharged from the arc furnace 1 is sent through the exhaust gas duct 2 into the combustion tube 3, where it is combusted to raise the exhaust gas temperature, and then passed through the scrap preheating tank 4 as it is. The scrap is preheated at the preheating stage, and the exhaust gas from the preheating stage is discharged to the outside via a dust collector.

This is the simplest method, but the foul odor and smoke generated by the decomposition of organic matter in the scrap due to preheating are emitted to the outside, leading to complaints.

ijJ Figure 1 (The one shown in BL leads a part of the exhaust gas discharged from the arc furnace 1 to the scrap preheater 4,
``J4 ``lr'' The exhaust gas that comes out is recycled to the combustion tube 3 by the fan 5 and mixed with the high temperature gas from the arc furnace 1, resulting in malodorous components, oil mist; heat content of %lγ! 11. It is designed to promote combustion. With this method, it is possible to reduce the unpleasant odor and smoke that is discharged to the outside, but only a portion of the heat of the exhaust gas can be used; most of the high-temperature gas is not used for preheating and is discharged to the outside as is. As a result, the heat recovery rate is extremely low. In addition, the temperature of the exhaust gas from the arc furnace 1 changes rapidly, and the period when the temperature exceeds the temperature of f and c, which is necessary for the amount of odor components, etc. + 4 yen, is unfortunately short, and the odor components, oil mist, etc. are scraped and preheated. Furthermore, it is difficult to completely thermally decompose and burn the total N.

Figure 1 (CL) uses a part of the exhaust gas from the arc furnace 1 exclusively for scrap preheating 4fI4, and the exhaust gas after the scrap preheating is passed through the pyrolysis furnace 7 to high-temperature exhaust gas directly led from the arc furnace 1. The pyrolysis furnace 7 is equipped with a burner 8 to maintain combustion.

Since the exhaust gas leaving the pyrolysis furnace 7 is at a high temperature, the heat exchanger 9
The air sent by the fan 10 is preheated, and the preheated air is supplied from the break flange portion 11 at the outlet of the arc furnace 1 into the exhaust gas duct 2 as combustion air, and the combustion condition in the combustion tube 3 is improved. By increasing the exhaust gas temperature by increasing the temperature, the scrap preheating temperature and the temperature of the pyrolysis furnace 7 are maintained at high temperatures. This method can reduce the amount of bad odors and smoke emitted to the outside, but it is expensive to set up and requires 8 burners to be used once a month.
This has the disadvantage of increasing running costs.

This invention was made in consideration of the above-mentioned problems, and it is an object of the present invention to provide a scrap preheating method that has a relatively simple design, can prevent smoke emission, and has a good heat recovery rate. It is something to do.

According to this invention, the exhaust gas from the arc furnace is not brought into direct contact with the scrap, but instead the heat exchange is twisted to heat the gas that becomes the heat medium, and the scrap is preheated by this gas, and the gas after preheating is It is heated to t[ by rl+ and exhaust gas.

Hereinafter, embodiments of the present invention will be explained with reference to the accompanying drawings.

In FIG. 2, exhaust gas discharged from an arc furnace 1 is sent into a combustion tube 3 through an exhaust gas duct 2, where it is combusted to increase its temperature, and then sent to a ν group exchanger 12. A pipe 14 through which preheating gas passes is led to the heat exchanger 12, and the preheating gas is heated by the Jll' gas.The heated preheating gas is passed through a pipe 15 to the preheating tank 4. After preheating the scrap, the preheating gas is discharged from the preheating tank 4, and the fan 13
t14 is reduced to 1JFJ and sent to the heat exchanger 12, where it is heated and used again to heat the scrap. In this way, the preheating gas is transferred from the heat exchanger 12 to the piping 15 to the preheating tank 4.
It is circulated as follows: → fan 13 → distribution #14 → heat exchanger 12 → and so on, and is not discharged to the outside.

- After the exhaust gas has undergone 16'C heat exchange in the heat exchanger 12, it is discharged to Li't 15 via a dust collector.

According to the above purchase, during the preheating process, the scrap odor, smoke, etc. are generated, and the "C" is also circulated in the above circulation path and is discharged to the outside, so it is possible to prevent the occurrence of pollution. Furthermore, since all the exhaust gas is passed through the heat exchanger 12 and used to heat the preheating gas, a high heat recovery rate can be obtained.In addition, the installation rtfi is relatively simple.

In addition to air, the preheating gas should be an inert gas such as nitrogen gas if there is a risk of ignition due to the gas generated from the scrap.

FIG. 3 shows another example of the present invention. This is applied when a large amount of gas is generated from scrap), and a gas duct is installed in the middle of the circulation path (for example, at the position of the trowel of heat exchanger J2 as in this example). Connect 16 and circulate! By supplying the surplus gas in the path into the arc furnace l and burning it, the energy of the scrap bath l'l'r is reduced to -1 quintillion degrees Celsius.
It was designed to be used. Also, top, 1 firefly 16'
As shown in the figure, the exhaust gas duct 2 is
If the paper is burned in °C, the exhaust gas temperature can be raised and the scrap preheating temperature can be increased. In this way, the gas generated from scrap can also be effectively utilized, so that the energy utilization rate can be further increased.

As mentioned above, according to the present invention, the 16-joint scrap is preheated with the exhaust gas from the electric furnace.
First, the preheating gas is heated with the heat of the exhaust gas, and the scrap is preheated by the heated preheating machine (body), and the preheating gas is circulated and used. Therefore, it is possible to prevent bad odors, smoke, etc. generated from scrap from being discharged to the outside, and the generation of 1,000 yen can be prevented.In addition, all the exhaust gas can be used to heat the preheating gas. Since it can be done, the heat recovery can be improved.In addition, the installation cost is relatively 111'4 $-, and since the burner N is not used safely, the running cost is low. The combustible gas produced can also be reused as a heat source.

[Brief explanation of the drawing]

Figure 1 (at, tbl, (cl) indicates the conventional electric furnace scrap preheating method, system N, system 2, respectively.
Figure 283 is a system diagram showing an embodiment of this invention, and Figure 283 is a system diagram showing another embodiment of this invention. 1... Electric furnace, 2... Exhaust gas duct, 3... Combustion tube, 4... Scrap preheating 41.516, 10.
x3...Fan, 7...Pyrolysis furnace, 8...Burner, 11...Break flange, 12...Heat exchanger, 14, 15...Circulation path arrangement a, 16° 16'・
...Gas exhaust duct.

Claims (1)

[Claims] A method for preheating scrap, characterized in that a preheating gas in a circulation path is heated by exhaust gas discharged from an electric furnace, and the scrap is preheated by the heated preheating gas.