JP4405888B2 - Detoxification method of gas to be processed using electric furnace for steelmaking - Google Patents

Description

  The present invention relates to a gas to be treated such as an HFC compound such as chlorofluorocarbon gas, which has been used as a refrigerant or a cleaning agent in consumer equipment such as refrigerators and air conditioners and industrial equipment such as semiconductor manufacturing equipment (in this specification, simply “ In particular, a steelmaking electric furnace capable of safely and inexpensively decomposing a gas to be processed that has become unnecessary using a steelmaking electric furnace is used. The present invention relates to a method for detoxifying a gas to be treated.

In recent years, chlorofluorocarbon gas that destroys the ozone layer, specifically, chlorofluorocarbon 11 (CCl ₃ F), chlorofluorocarbon 12 (CCl ₂ F ₂ ), chlorofluorocarbon 113 (C ₂ Cl ₃ F ₃ ), chlorofluorocarbon 22 ( Problems with CHClF ₂ ), etc. were raised on a global scale, and the production of these chlorofluorocarbons was discontinued and became virtually unusable.

  On the other hand, chlorofluorocarbons already used as refrigerants and cleaning agents in various equipment are not subject to this regulation, so equipment filled with chlorofluorocarbons was often discarded or left untouched. Then, this problem has been pointed out, and the collection of CFCs that are no longer necessary has been actively carried out.

As a method for detoxifying the recovered chlorofluorocarbon gas, the present applicant has proposed a method in which chlorofluorocarbon gas is introduced into an electric furnace for steel making and the chlorofluorocarbon gas is decomposed in a high-temperature atmosphere formed by an arc when making the steel. (See Patent Document 1).
This detoxification method of chlorofluorocarbon gas decomposes chlorofluorocarbon gas into carbon dioxide (CO ₂ ), hydrogen chloride (HCl), and hydrogen fluoride (HF) in a high temperature atmosphere formed by an arc when steel making. Since the gas can be cooled and neutralized with caustic soda, slaked lime (Ca (OH) ₂ ) can be added to precipitate and separate as calcium fluoride (CaF ₂ ). The generated chlorofluorocarbon gas can be decomposed at low cost.

By the way, in this detoxifying treatment method for chlorofluorocarbon gas, the inside of the furnace is heated by an auxiliary heating device such as an oxygen burner in the initial stage of energization where the temperature in the electric furnace is not stable. Since it stops when the temperature rises, there is a problem that dust tends to stay.
In addition, in order to introduce chlorofluorocarbon into an existing steelmaking electric furnace, it is necessary to install a chlorofluorocarbon gas nozzle separately. This chlorofluorocarbon nozzle is near the molten steel where an arc is generated in order to decompose the chlorofluorocarbon at a high temperature. Therefore, there is a problem that the equipment investment cost is increased, for example, a nozzle cooling facility is required.
JP 11-319484 A

  In view of the problems of the conventional method for detoxifying a gas to be treated, the present invention can prevent the accumulation of dust in the auxiliary heating device, and can eliminate the nozzle for the gas to be treated and its cooling equipment. It aims at providing the detoxification processing method of the to-be-processed gas using the electric furnace for steel manufacture.

In order to achieve the above object, the method for detoxifying a gas to be treated using the electric steel furnace for steel production according to the present invention is a high temperature formed by an arc when the gas to be treated is introduced into the electric furnace for steel making and steel making is performed. In a method for detoxifying a gas to be treated using an electric furnace for steel making that decomposes the gas to be treated in an atmosphere, oxygen gas and the gas to be treated are selectively introduced into an auxiliary heating device disposed in the electric furnace for steel making. When the inside of the electric furnace is below the decomposition temperature of the gas to be treated , oxygen gas is supplied to perform auxiliary heating, and when the inside of the electric furnace exceeds the decomposition temperature of the gas to be treated , the supply of the oxygen gas is stopped. A gas to be treated is supplied.

  In this case, water can be supplied into the steelmaking electric furnace along the outer peripheral surface of the electrode rod.

In this method of detoxifying a gas to be treated using an electric furnace for steelmaking, the gas to be treated is introduced into the electric furnace for steelmaking, and the gas to be treated is decomposed in a high-temperature atmosphere formed by an arc when steelmaking is performed. In the method for detoxifying a gas to be treated using an electric furnace for steel making, oxygen gas and the gas to be treated are selectively introduced into an auxiliary heating device disposed in the electric furnace for steel making, and the inside of the electric furnace is the gas to be treated. When oxygen gas is supplied below, the auxiliary heating is performed by supplying oxygen gas, and when the inside of the electric furnace exceeds the decomposition temperature of the gas to be processed, the supply of the oxygen gas is stopped and the gas to be processed is supplied. A gas to be treated can be supplied into the furnace by using an auxiliary heating device that stops when the temperature in the furnace rises. This eliminates the need for the conventional gas nozzle and its cooling equipment. Introduce treatment gas near hot molten steel Together, it is possible to clean the auxiliary heating device by the processed gas to be supplied to prevent the accumulation of dust.

  In this case, by supplying water into the electric steel furnace for steelmaking along the outer peripheral surface of the electrode rod, the electrode rod can be cooled and moisture as a decomposition substance of the gas to be treated can be supplied into the furnace. it can.

  Embodiments of a detoxification method for a gas to be processed using the electric furnace for steel making according to the present invention will be described below with reference to the drawings.

  1 to 4 show an embodiment of a method for detoxifying a gas to be processed using the electric furnace for steel making of the present invention.

The detoxification treatment method of the gas to be treated using the electric furnace for steelmaking introduces chlorofluorocarbon in the high-temperature atmosphere formed by the arc 12 when the chlorofluorocarbon gas as the gas to be treated is introduced into the electric furnace 1 for steelmaking. And oxygen gas and chlorofluorocarbon gas are selectively introduced into the oxygen burner 2 disposed in the steelmaking electric furnace 1, and the electric furnace has a predetermined temperature , specifically, the decomposition temperature of the gas to be treated. In the following cases, oxygen gas is supplied and auxiliary heating is performed. When the inside of the electric furnace exceeds a predetermined temperature , specifically, the decomposition temperature of the gas to be processed, the supply of the oxygen gas is stopped and the chlorofluorocarbon gas is supplied. I am doing so.

  The facility that performs the detoxification treatment of the chlorofluorocarbon gas is basically an existing steel making facility, and the arc 12 generated from the tip of the electrode rod 11 of the electric furnace 1 is usually used when making steel. The high temperature reaches 5000 to 6000 ° C., and the CFC gas is decomposed in a high temperature atmosphere of about 1600 ° C. near the molten steel 13 formed by the arc 12.

Fluorocarbons used for decomposition are chlorofluorocarbons that are used as refrigerants and cleaning agents in consumer equipment such as refrigerators and air conditioners, and industrial equipment such as semiconductor manufacturing equipment. Freon gas that destroys the ozone layer such as Freon 11 (CCl ₃ F), Freon 12 (CCl ₂ F ₂ ), Freon 113 (C ₂ Cl ₃ F ₃ ), and Freon 22 (CHClF ₂ ), which is called Freon, is targeted. .

On the other hand, as shown in FIG. 3, three oxygen burners 2 are provided so as to equally divide the steelmaking electric furnace 1 as an auxiliary heating device.
As shown in FIG. 2, each oxygen burner 2 includes a fuel injection nozzle 21, a compressed air injection nozzle 22 for atomizing the liquid fuel in the fuel injection nozzle 21, and an oxygen injection nozzle 23 for adjusting the thermal power. And a swirl flow rib 24 is formed at the tip of the oxygen injection nozzle 23 to impart a swirl flow to the supplied oxygen gas.
Further, a water cooling jacket 25 is provided on the outer peripheral portion of the oxygen burner 2, and the cooling water supplied from the water supply port 25a circulates inside and is discharged from the drain port 25b, thereby cooling the oxygen burner 2. be able to.

As shown in FIG. 1, the chlorofluorocarbon gas is introduced from a gas cylinder 3 through a conduit 31 into a compressed air injection nozzle 22 of one of the three oxygen burners 2 ′.
Thereby, the compressed air and the chlorofluorocarbon gas are selectively supplied to the compressed air injection nozzle 22 by switching the control solenoid valve 32.
Further, the chlorofluorocarbon gas can be introduced into the oxygen injection nozzle 23 instead of the compressed air injection nozzle 22. In this case, the oxygen gas and the chlorofluorocarbon gas are selectively supplied to the oxygen injection nozzle 23 by the control solenoid valve 32. To be supplied.
By the way, as shown in FIG. 4, it is preferable to supply the chlorofluorocarbon gas when the inside of the furnace is at or above the decomposition temperature, but conversely, the oxygen burner 2 is used in the furnace at the beginning of energization or during the addition of molten steel material. When the temperature is below the decomposition temperature, auxiliary heating operation is performed, and when the inside of the furnace rises above the decomposition temperature, the operation is stopped.
The present invention uses the operation timing of the oxygen burner 2, and by supplying flon gas into the furnace from the oxygen burner 2 that stops when the furnace temperature rises, the conventional flon gas nozzle and its cooling While eliminating the need for equipment, it is possible to introduce chlorofluorocarbon gas into the vicinity of the high-temperature molten steel 13 and to clean the oxygen burner 2 with the chlorofluorocarbon gas supplied to prevent dust from staying.

On the other hand, as shown in FIG. 3A, moisture (H ₂ O), which is a decomposed substance of chlorofluorocarbon gas, flows from the water supply device 14 equipped with a water flow meter to the outer peripheral surface of the electrode rod 11 of the steelmaking electric furnace 1. In this way, the electrode rod 11 is cooled, and moisture as a decomposing substance of CFC gas is supplied into the furnace.
A mixed gas composed of a decomposition material such as chlorofluorocarbon gas and moisture (H ₂ O) introduced into the steelmaking electric furnace 1 is carbon dioxide (CO ₂ ), hydrogen chloride ( HCl) and hydrogen fluoride (HF) and discharged from the steelmaking electric furnace 1.

As shown in FIG. 1, this exhaust gas is introduced into the combustion tower 4 as necessary, and the combustion tower 4 is maintained at a temperature of, for example, about 800 to 1200 ° C., so that undecomposed chlorofluorocarbon gas is surely obtained. Try to disassemble.
The cracked gas composed of carbon dioxide (CO ₂ ), hydrogen chloride (HCl), and hydrogen fluoride (HF) generated by the decomposition of the freon gas is separated from the dust contained in the cracked gas by the bag filter 5 and then spray tower 6 It is cooled by passing through.
In this spray tower 6, by spraying an aqueous solution of caustic soda, it reacts with the cracked gas, neutralizes harmful hydrogen chloride (HCl) and hydrogen fluoride (HF), and sodium chloride (NaCl) and sodium fluoride ( NaF).

Exhaust air from the spray tower 6 is discharged into the atmosphere after completely removing liquid and solid components through the building fan 7 and the building bag filter 8.
On the other hand, the waste liquid from the spray tower 6 is introduced into the water treatment tank 61 from the drain outlet, and slaked lime (Ca (OH) ₂ ) is added in the water treatment tank 61 to precipitate and separate as calcium fluoride (CaF ₂ ). .
This final product, calcium fluoride (CaF ₂ ), can be effectively used as a desulfurization agent used in steelmaking, and thus the amount of waste can be reduced.

It is to be noted that the detoxification treatment method for chlorofluorocarbon using the electric furnace for steel making of the present invention is as follows, using chlorofluorocarbon 12 (CCl ₂ F ₂ ) and chlorofluorocarbon 113 (C ₂ Cl ₃ F ₃ ) as examples. .

(1) A mixed gas composed of Freon 12 (CCl ₂ F ₂ ) and Freon 113 (C ₂ Cl ₃ F ₃ ) and moisture (H ₂ O) and oxygen gas (O ₂ ) as decomposition substances is used in an electric furnace for steelmaking. 1 is decomposed in a high-temperature atmosphere formed by the arc 12 when steelmaking, and becomes carbon dioxide (CO ₂ ), hydrogen chloride (HCl), and hydrogen fluoride (HF).
CCl ₂ F ₂ + 2H ₂ O → CO ₂ + 2HCl + 2HF
2C ₂ Cl ₃ F ₃ + 6H ₂ O + O ₂ → 4CO ₂ + 6HCl + 6HF

(2) Hydrogen chloride (HCl) is neutralized into sodium chloride (NaCl) by spraying a caustic soda aqueous solution in the spray tower 7.
HCl + NaOH → NaCl + H ₂ O

(3) Hydrogen fluoride (HF) is neutralized to become sodium fluoride (NaF) by spraying a caustic soda aqueous solution in the spray tower 7, and further slaked lime (Ca (OH) _{2 in} a water treatment tank). ) Is added and precipitated and separated as calcium fluoride (CaF ₂ ).
HF + NaOH → NaF + H ₂ O
2NaF + Ca (OH) ₂ → CaF ₂ + 2NaOH
(NaF + Ca (OH) ₂ + H ₂ SO ₄ → CaF ₂ + Na ₂ SO ₄ + H ₂ O)

Thus, the detoxification method of the gas to be treated using the steelmaking electric furnace of the present embodiment is formed by the arc 12 when the freon gas as the gas to be treated is introduced into the steelmaking electric furnace 1 and steelmaking is performed. In the detoxification treatment method for CFCs that decomposes CFCs in a high-temperature atmosphere, oxygen gas and CFCs are selectively introduced into an oxygen burner 2 disposed in the steelmaking electric furnace 1, and the temperature in the electric furnace is below a predetermined temperature. Oxygen gas is supplied to the auxiliary heater, and when the inside of the electric furnace exceeds a predetermined temperature, the supply of the oxygen gas is stopped and the chlorofluorocarbon gas is supplied. Therefore, the oxygen burner is stopped when the temperature in the furnace rises. 2 can be used to supply chlorofluorocarbon gas into the furnace. This eliminates the need for conventional chlorofluorocarbon gas nozzles and cooling equipment, and introduces chlorofluorocarbon gas to the vicinity of the hot molten steel 13. As well as, it is possible to clean the oxygen burner 2 by chlorofluorocarbons supplied to prevent the accumulation of dust.
In this case, the electrode rod 11 is cooled by supplying water into the steelmaking electric furnace 1 along the outer peripheral surface of the electrode rod 11, and moisture serving as a decomposing substance of chlorofluorocarbon gas is supplied into the furnace. Can do.

  As described above, the detoxification treatment method for the gas to be treated using the electric furnace for steel making according to the present invention has been described for the case of treating flon gas, but the present invention is not limited to the configuration described in the above embodiment, In addition, the configuration of the gas to be treated can be changed as appropriate without departing from the scope of the present invention, for example, applicable to not only HFC compounds such as chlorofluorocarbon gas but also compounds such as halon gas.

  The process gas detoxification method using the electric furnace for steel making of the present invention can supply the process gas into the furnace using an auxiliary heating device that stops when the furnace temperature rises, The characteristic of introducing the gas to be treated in the vicinity of high-temperature molten steel while cleaning the auxiliary heating device with the gas to be treated to prevent the accumulation of soot and dust while eliminating the need for the conventional gas to be treated and its cooling equipment Therefore, it can be suitably used for the purpose of safely detoxifying the gas to be treated at low cost using an existing electric furnace for steelmaking.

It is explanatory drawing which shows an example of the equipment used in order to implement the detoxification processing method of the to-be-processed gas using the electric furnace for steelmaking of this invention. An oxygen burner is shown, (a) is a sectional view thereof, and (b) is a rear view. An electric furnace for steel making is shown, (a) is a longitudinal sectional view thereof, and (b) is a transverse sectional view thereof. It is explanatory drawing which shows the timing of the auxiliary | assistant heating operation of an oxygen burner, and the supply of the fluorocarbon gas as to-be-processed gas.

DESCRIPTION OF SYMBOLS 1 Electric furnace for steel making 11 Electrode rod 12 Arc 13 Molten steel 14 Water supply apparatus 2 Oxygen burner (auxiliary heating apparatus)
DESCRIPTION OF SYMBOLS 21 Fuel injection nozzle 22 Compressed air injection nozzle 23 Oxygen injection nozzle 24 Swirling flow rib 25 Water cooling jacket 3 Gas cylinder 31 Conduit 32 Control solenoid valve 4 Combustion tower 5 Bag filter 6 Spray tower 61 Water treatment tank 7 Building fan 8 Building bug filter

Claims (2)

In the detoxification treatment method of a gas to be treated using an electric furnace for steel making, wherein the gas to be treated is introduced into an electric furnace for steel making and the gas to be treated is decomposed in a high temperature atmosphere formed by an arc when steel making is performed, Oxygen gas and gas to be treated are selectively introduced into an auxiliary heating device disposed in an electric furnace for steel making, and when the inside of the electric furnace is below the decomposition temperature of the gas to be treated , oxygen gas is supplied and auxiliary heating is performed. A process gas detoxification method using an electric furnace for steel making, characterized in that when the inside of an electric furnace exceeds a decomposition temperature of the process gas, the supply of the oxygen gas is stopped and the process gas is supplied.   The method for detoxifying a gas to be treated using an electric furnace for steelmaking according to claim 1, wherein water is supplied into the electric furnace for steelmaking along the outer peripheral surface of the electrode rod.

Images