JPS6229709B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for pre-treating raw material scrap from an electric furnace or the like using high-temperature exhaust gas.

Originally, in order to improve thermal efficiency, raw material scrap was preheated using high-temperature exhaust gas from an electric furnace. That is, as shown in Fig. 1, the exhaust gas discharged from the electric furnace 1 is passed through the secondary air intake 2 necessary to burn the CO gas from the furnace.
The high-temperature exhaust gas discharged from the combustion chamber 4 is guided along with the secondary air from the combustion chamber 4 through the inlet pipe 3 to a pair of preheating chambers 6a and 6b through the exhaust conduit 5, and stored therein. The raw material scrap is preheated and heat exchanged in the preheating chamber, and the low temperature exhaust gas is
Although not shown, the gas is directly fed into the gas cooler 7, cooled to a required temperature, and then fed to the dust collector 9 by the exhaust fan 8, where the dust is removed and then released into the atmosphere. However, among the raw material scraps, there are scraps that generate bad gases that emit foul odors and white smoke, such as dry powder, engine blocks, shredders, etc., and when they are mixed with good quality scraps in the same bucket and preheated, , it inevitably generates bad odor and white smoke, which are difficult to remove with a dust collector, and therefore it is inappropriate from the environmental hygiene point of view to release it into the atmosphere through the above process.

As a means of eliminating this foul odor and white smoke, it may be possible to introduce the gas back into the electric furnace and burn it, but introducing a large amount of low-temperature gas that has left the preheating chamber into the electric furnace will lower the temperature inside the furnace and Introducing the combustion chamber 4 into the combustion chamber 4 as another means would hinder the operation.
The temperature of the exhaust gas from the chamber decreases, and if a sufficient temperature rise is not achieved in the preheating chamber and a large amount of low-temperature gas is introduced into the combustion chamber, the temperature of the combustion chamber itself decreases and the above-mentioned harmful gas generating substances There are drawbacks such as insufficient decomposition of .

Therefore, as shown in FIG. 1, the preheating chamber 6a,
An afterburning method is adopted in which the exhaust gas from the combustion chamber 6b is guided to the mixing chamber 11 by the booster fan 10, and a part of the high temperature exhaust gas from the combustion chamber 4 is supplied to the mixing chamber 11 and combusted in the chamber. In the figure, 12 is the control panel, and the preheating chamber 6
a, 6b and the exhaust gas distribution regulating valves 13, 14 to the mixing chamber 11 are controlled.

However, in this case, it is necessary to introduce a considerable amount of high-temperature gas in order to bring the temperature inside the mixing chamber 11 to a high temperature necessary for decomposing and burning the harmful gas-generating substances.

For example, the temperature of the exhaust gas discharged from the combustion chamber is 800
℃, discharge temperature from preheating chamber 6a (or 6b) 400
℃, the temperature of the mixing chamber 11 is the above decomposition combustion temperature.
When the temperature is 600° C., approximately 50% of the exhaust gas from the combustion chamber 4 needs to be introduced into the mixing chamber 11. In other words, the high temperature exhaust gas from the combustion chamber 4 is
The remaining 50% can only be used for preheating the scrap, which is extremely uneconomical.

The present inventor has determined that the above-mentioned amount of bad gas generation scrap is:
Depending on the situation, it is usually
The present invention was developed by focusing on the fact that the amount of waste gas is approximately 20%, and in which a part of the high-temperature exhaust gas is used to form a circulation circuit, and in this circuit, only the scrap that generates bad gas is pretreated. This method is designed to combust the bad gas generated by the above-mentioned electric furnace or combustion chamber in a high-temperature exhaust gas generating means such as the above-mentioned electric furnace or combustion chamber.The amount of high-temperature exhaust gas used for pretreatment is only the bad gas generation scrap, so only a small amount is required. The purpose is to increase as much as possible the amount of high-temperature exhaust gas supplied to the preheating chamber.

The present invention will be described below based on embodiments shown in the drawings.

In Fig. 2, A is a high temperature exhaust gas supply means;
The electric furnace 1 and the exhaust gas from the electric furnace are
It consists of a combustion chamber 4 where the secondary air from the secondary air intake port 2 necessary for combustion of CO gas is introduced through an introduction pipe 3 and completely combusted. , preferably into a pair of preheating chambers 6a and 6b. The preheating chambers 6a and 6b (hereinafter collectively referred to as simply 6) are filled with high quality scrap, preheated by the high temperature exhaust gas, and the low temperature exhaust gas is passed through the exhaust pipe 20 by the booster fan 10.
The exhaust gas is sent to the gas cooler 7 via the exhaust fan 8 and cooled to a predetermined temperature or lower, and is sent to the dust collector 9 by the exhaust fan 8, where the dust is removed and then released into the atmosphere.

A branch pipe 21 is connected to the discharge pipe 5,
The branch pipe 21 is equipped with an air supply fan 22, which is connected to a pretreatment furnace 23, and the exhaust side of the furnace 23 and the electric furnace 1 or combustion chamber 4 in the high-temperature exhaust gas supply means A are The provided return pipe 25 is connected, and the branch pipe 21 and the return pipe 25 constitute a circulation path B. The pretreatment furnace 23 is designed to heat the scrap that generates bad gas as described above, and the discharge conductor 5 and the branch pipe 21 are provided with regulating valves 2, respectively.
6 and 27 are provided to regulate the supply amount to the branch pipe 21 side. sent to
It is heated by high temperature exhaust gas supplied from the branch pipe 21. Bad gases such as white smoke generated by heating are returned to the combustion chamber 4 or the electric furnace 1 through the return pipe 25 by the intake fan 24 and incinerated.

The pre-treated scrap W2, which has been heated for the required time in the pre-treated furnace 23 and has undergone the decomposition treatment of harmful gas-generating substances, is carried out by a carrying means 30 such as an electromagnet, and the scrap is directly stored in the pre-heating chamber 6 or in a storage area. sent.

In this case, the bad gas-generating scrap treated in the pre-treatment furnace 23 is approximately equal to the raw material scrap as described above.
Therefore, the high-temperature exhaust gas sent to the branch pipe 21 accounts for about 10% of the total amount of exhaust gas from the combustion chamber 4.
%, and based on this, the amount reduced from the pretreatment furnace including white smoke, etc. generated via the return pipe 25 is approximately the same, and the temperature change due to this is not affected much, so Bad gas is completely incinerated.

As described above, when using the method of the present invention, a part of the high-temperature exhaust gas sent out from the high-temperature exhaust gas supply means such as a combustion chamber is guided to the circulation path formed by the branch pipe and the return pipe, and the bad gas-generating scrap is pretreated. However, the generated bad gas is treated by the above-mentioned high-temperature exhaust gas supply means, and the amount of bad gas-generated scrap to be treated is small compared to the total amount of scrap, so the high-temperature exhaust gas required for pretreatment is Since only a part of the total amount of high-temperature exhaust gas is required, the influence on the atmosphere such as temperature drop in the high-temperature exhaust gas supply means is small, and the decrease in the amount of supply to the preheating chamber can be kept as small as possible. Pretreatment of scrap that generates bad gas has the advantage that it can be carried out at an appropriate time during operation of the electric furnace.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of a known afterburning method, and FIG. 2 is a block circuit diagram showing an embodiment of the method of the present invention. 1... Electric furnace, 4... Combustion chamber, 6a, 6b...
Preheating chamber, 21...branch pipe, 23...pretreatment furnace, 2
5...Return pipe, A...High temperature exhaust gas supply means, B...
...Circulation path, W1... Bad gas generation scrap.

Claims (1)

[Claims] 1. The high-temperature exhaust gas sent out from an electric furnace or a high-temperature exhaust gas supply means such as an exhaust gas combustion chamber connected thereto is guided to a preheating chamber to preheat the raw material scrap, and a part of the high-temperature exhaust gas sent out is again heated to the high temperature. forming a circulation circuit that returns to the exhaust gas supply means, disposing a pretreatment furnace in the circuit,
The scrap that generates bad gas is heated in this pretreatment furnace, and the generated bad gas is incinerated and decomposed in the high-temperature exhaust gas supply means, and the flow rate of the high-temperature exhaust gas to the circulation circuit is regulated according to the amount of scrap that generates bad gas. A scrap pretreatment method using high-temperature exhaust gas characterized by: