JPH10137544A - Treatment of organic halogen compound waste gas containing fluorine and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously treating an organic halogen compound waste decomposition waste gas containing fluorine with a small quantity of water and capable of recovering valuable CaF2 . SOLUTION: The method is by allowing HF and HCl in the decomposition waste gas continuously supplied from a decomposition device 20 of, for example, chlorofluorocarbon 12 to contact with an alkali solution continuously supplied from an alkali tank 40 and containing Ca(OH)2 in a prescribed concentration to form a neutralized material of insoluble CaF2 and soluble CaCl2 , circulating the alkali solution containing the neutralized material to return to the tank 40, taking out a fixed quantity of the alkali solution containing the neutralized material from the alkali tank 40 on the other hand to remove and recover CaF2 by a dehydrator 51, returning the separated water separated by the dehydrator 51 to the tank 40 after discharging a part thereof, supplying Ca(OH) 2 in the quantity corresponding to the quantity of the returned water by an alkali constant quantity feeder 44 and further supplying new water in the quantity corresponding to the discharged quantity of the separated water and Ca(OH)2 to the alkali tank 40 to regulate CaCl2 in the tank 40 to a prescribed concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the treatment of gas generated when an organic halogen compound containing fluorine is decomposed.

[0002]

2. Description of the Related Art In recent years, chlorofluorocarbon (CFC) has been completely abolished by 1996 in the Montreal Protocol as a substance that destroys the ozone layer.
Hydrochlorofluorocarbon (HCFC) is 202
It has been decided that it will be completely abolished by year 0. On the other hand, perfluorocarbon (PFC), sulfur hexafluoride (SF ₆ ), and hydrofluorocarbon (HFC), which have low ozone depletion potential but large warming potential, are not regulated at present, but will With the increase in prevention, countermeasures are needed. Therefore, various techniques for decomposing these substances have been studied, and studies on a catalytic decomposition method, a plasma decomposition method, and a combustion decomposition method have been conducted so far. In any of these decomposition methods, hydrogen fluoride and hydrogen chloride are generated as decomposition products. For example, Freon 12, a refrigerant that is being recovered from waste refrigerators at each local body in the country,
When decomposed together with water vapor at a freon concentration of 3 vol% (carrier gas: air), about 6 vol% of hydrogen fluoride and about 6 vol% of hydrogen chloride are generated.

[0003] Hydrogen fluoride and hydrogen chloride are highly corrosive,
Since it is a harmful substance, its emission is strictly regulated by the Air Pollution Control Law. Therefore, an exhaust gas treatment facility after the decomposition is required in the decomposition apparatus.

In particular, in the case of hydrogen fluoride, the emission concentration is set to 11 ppm or less in order to prevent air pollution. It is difficult to use exhaust gas equipment (dry type, wet type) in general incinerators, and a method of increasing the contact between the flue gas of Freon 12 and water, such as a washing tower (spray tower, packing tower) using a large amount of water or an alkaline solution, etc. Otherwise it cannot be removed. Therefore, a large amount of water is required, and a large-scale exhaust gas treatment facility is required to obtain a contact time. Further, also in the device material, an expensive material having corrosion resistance to strongly corrosive hydrogen fluoride and hydrogen chloride must be used.

[0005] Since water used for cleaning the flue gas decomposed with chlorofluorocarbon 12 contains fluorine ions, it must meet the effluent standards in order to be discharged out of the system. The discharge of wastewater containing fluoride ions requires a fluorine concentration of 15 according to national wastewater standards.
Under ppm, municipal ordinances, etc., strictly regulate drainage.

In wastewater containing fluorine ions, calcium salts are used to reduce the fluorine ion concentration to below the standard value. I have. Therefore, a large amount of undissolved calcium fluoride is generated in the wastewater. In the case of Freon 12, 1 kg of Freon is decomposed,
After exhaust gas treatment, calcium fluoride finally becomes 0.6
Generates 5 kg. This calcium fluoride is a highly useful substance as a raw material for industrial use, for example, it is used as a fluidizing material for slag in iron making and as a raw material for the glass industry.

However, calcium fluoride generated from an organic halogen compound containing fluorine is settled in a wastewater treatment facility, then dehydrated and recovered in the form of a dehydrated cake. Since it contains water, it cannot be reused as a valuable resource in this state, and is currently buried as it is. For this reason, even if an organic halogen compound containing fluorine is treated, secondary waste is generated, which impairs the economic efficiency of the decomposition treatment facility. In addition, dewatered cakes must be disposed of in a managed landfill, and landfills are becoming increasingly difficult under the current situation where the remaining capacity of landfill facilities is insufficient.

[0008] The wastewater from which calcium fluoride has been removed is usually temporarily stored in a tank of a wastewater treatment facility, adjusted to pH, and discharged outside the system. Since a large amount of water is used in the treatment of the exhaust gas from decomposition of an organic halogen compound containing fluorine, if the water is discharged without being reused, the wastewater treatment equipment including tanks for storage becomes large-scale.

Thus, in a large-scale exhaust gas treatment facility,
Under the current situation where exhaust gas treatment is performed using a large amount of water and secondary waste is generated, the practical use for decomposition treatment of organic compounds containing fluorine is lacking.

[0010]

As described above, according to the conventional exhaust gas treatment method, it is necessary to efficiently remove hydrogen fluoride generated by decomposition of an organic halogen compound containing fluorine.
There is a problem that a large amount of water is required, and the drainage equipment becomes large. In addition, calcium fluoride that is finally generated is buried as secondary waste and is not effectively used.

The present invention has been made to solve such a conventional problem. A first object of the present invention is to convert a hydrogen fluoride gas generated by decomposing an organic halogen compound containing fluorine into an alkaline solution. When contacting and removing as a neutralized product, the used alkaline solution is reprocessed and used as water for the alkaline solution, thereby reducing the required water amount. Is to provide.

A second object of the present invention is to provide a method for removing hydrogen fluoride gas generated by the decomposition of an organic halogen compound containing fluorine as a neutralized product by contacting the gas with an alkaline solution containing calcium. The treated alkaline solution is reprocessed and used as water for the alkaline solution, so that the required amount of water can be reduced, and at the same time, the fluorine-containing organic halogen compound exhaust gas which can be recovered in a form in which calcium fluoride can be used as a valuable material is recovered. It is an object of the present invention to provide a processing method and apparatus.

[0013]

Means for Solving the Problems The organic halogen compounds containing fluorine (hereinafter abbreviated as organic halogen compounds) which are the object of the present invention include chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), and hydrofluorocarbon (HFC). And perfluorocarbon (PFC). Examples of the method for treating the target halogen organic compound include a catalytic method, a plasma method, and an incineration method.

When the treatment amount is large, the decomposition treatment of the organic halogen compound and the exhaust gas treatment are performed continuously for 24 hours. For this purpose, the exhaust gas treatment is made continuous, the supply of alkali is continuously supplied, and the alkali solution is continuously regenerated, thereby reducing the size of the exhaust gas treatment apparatus and reducing the amount of water used.

In order to achieve the first object, the first “method of treating an organic halogen compound exhaust gas containing fluorine (hereinafter abbreviated as“ method of treating a halogen compound exhaust gas ”)” according to the first aspect of the present invention comprises: Hydrogen fluoride continuously supplied as an exhaust gas from a decomposition device that decomposes a halogen compound is brought into contact with an alkali solution having a predetermined concentration continuously supplied from an alkali bath to generate a neutralized product. The alkaline solution is circulated so that the alkaline solution containing the neutralized substance is returned to the alkaline tank.On the other hand, the alkaline solution containing the neutralized substance is taken out from the alkaline tank in a fixed amount and dehydrated. This is a method in which the alkali is returned to the alkali bath, and (3) alkali is supplied so as to have a predetermined concentration in accordance with the amount of the returned water.

The second method for treating exhaust gas of a halogen compound according to the present invention is the first method for treating exhaust gas of a halogen compound, wherein the organic halogen compound is hydrofluorocarbon or perfluorocarbon, and the turbidity of calcium hydroxide is used as an alkaline solution. The solution is used to produce a neutralized product of insoluble calcium fluoride, (1)-
The processing of (3) is the same.

Further, the third method for treating a halogen compound exhaust gas according to the present invention is characterized in that (1) hydrogen fluoride and hydrogen chloride contained in the exhaust gas continuously supplied from a decomposer for decomposing chlorofluorocarbon or hydrochlorofluorocarbon. Is contacted with an alkaline solution that is continuously supplied from an alkaline tank and turbidates calcium hydroxide at a predetermined concentration to produce a neutralized product of insoluble calcium fluoride and soluble calcium chloride, (2) The alkaline solution containing the neutralized substance is circulated so as to return the alkaline solution to the alkaline tank. (3) On the other hand, the alkaline solution containing the neutralized substance is taken out from the alkaline tank in a fixed amount and dehydrated to remove calcium fluoride. Then, after partially discharging the separated water separated by the dehydration treatment, the separated water is returned to the alkali bath, and (4) calcium hydroxide is adjusted to a predetermined concentration in accordance with the amount of the returned water. And (5) a method in which water corresponding to the amount of separated water partially discharged is newly supplied to the alkaline tank, and calcium chloride in the alkaline water stored in the alkaline tank is maintained at a predetermined concentration. It is.

As in the first to third halogen compound exhaust gas treatment methods, by circulating the alkaline solution, the exhaust gas can be continuously treated, and the water separated from the spent alkaline solution by the dehydration treatment. By reusing, the amount of water for the alkali solution required for removing the halogen gas can be secured, and the amount of water discharged out of the system can be reduced.

The second object is achieved in the second and third methods for treating a halogen compound exhaust gas, wherein the calcium fluoride removed by the dehydration treatment is dried and recovered in powder form. Is done. If the powdered calcium fluoride is granulated, handling of the calcium fluoride is further facilitated.

If the exhaust gas contains halogen other than fluorine (here, chlorine) as in the second method for treating a halogen compound exhaust gas, hydrogen chloride can be neutralized with an alkaline solution. Since the neutralized product of hydrogen chloride (chloride) is soluble, it does not become a sedimentable solid, but when the separated water separated by the dehydration treatment is returned, the chloride gradually increases in the alkaline tank, and the water quality is reduced. It gets worse. When the water quality deteriorates, the efficiency of removing the acidic gas also decreases, and the exhaust gas treatment is hindered. Therefore, a certain amount of water is supplied to the alkaline tank, and a certain amount of water separated by the dehydration treatment is discharged out of the system in accordance with the supply of the water. Here, the amount discharged to the outside of the system is the minimum amount of water necessary to suppress an increase in soluble substances in the alkaline tank. By this method, the concentration of the soluble substance in the alkaline solution is kept constant, the deterioration of water quality can be prevented, and the equipment of tanks for discharging the discharged alkaline solution out of the system is downsized. it can.

Thus, in the continuous exhaust gas treatment, the exhaust gas treatment equipment can be miniaturized, the amount of water used can be reduced as much as possible, and the acidic gas in the exhaust gas can be efficiently removed.

The solid containing calcium fluoride removed by dehydration contains about 50 to 90% by weight of water and soluble substances. In this state, it cannot be used as valuables and must be landfilled as secondary waste. However, by removing water and the water of calcium fluoride containing soluble substances, it becomes calcium fluoride that can be used as an industrial raw material. Calcium fluoride for industrial use
Usually, it is used in powdered or granulated form. Therefore, as a method for removing water, the powder can be made into a powder by controlling the water content of calcium fluoride to 10 wt% or less by drying. The powdered calcium fluoride can be used as a valuable resource as it is, but it may be scattered during transportation. Therefore, granulation is performed to further increase the value of the valuable resource. By granulation, handleability is improved, and the volume during transportation can be reduced.

In order to achieve the first object, a first apparatus for treating an organic halogen compound exhaust gas containing fluorine (hereinafter referred to as an apparatus for treating a halogen compound exhaust gas) according to the present invention comprises: A decomposer for continuously supplying hydrogen fluoride gas, an alkali tank for storing an alkali solution having a predetermined concentration, a cooling chamber for cooling hydrogen fluoride gas from the decomposer with an alkali solution introduced from the alkali bath, A removing device for flowing hydrogen fluoride gas from the cooling chamber, flowing an alkaline solution from the alkaline bath, neutralizing the hydrogen fluoride gas with the alkaline solution, and returning the alkaline solution containing the neutralized product to the alkaline bath; A dehydrator for dehydrating an alkaline solution containing a neutralized substance supplied from the alkaline tank and supplying the neutralized substance and separated water, and an alkaline tank separated by the dehydrator. Characterized in that it is composed of, and alkali supply device for supplying alkali to a predetermined concentration commensurate with the amount of separated water returned.

In order to achieve the second object,
The second halogen compound exhaust gas treatment device of the present invention is provided with a dryer for drying the neutralized product separated by the dehydrator to powder in addition to the first halogen compound exhaust gas treatment device. is there. Further, a granulator for granulating the powder of the neutralized product dried by the dryer may be provided.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited thereto.

[0026]

Embodiment 1 A decomposition gas treatment method for decomposing a fluorine-containing organic halogen compound (hereinafter referred to as a halogen compound) and continuously treating a decomposition gas generated at that time is shown in FIG.
This will be described below. Here, the decomposition treatment of Freon 12 (CF ₂ Cl ₂ ), which is a halogen compound, is performed using a catalyst.
The decomposition treatment of Freon 12 is performed by using a carrier gas for adjusting the Freon concentration as air, 10 kg / h of Freon 12 under the conditions of space velocity SV = 1,500 h- ¹ , Freon concentration 3.0 vol%, and catalyst layer temperature 450 ° C. (83 mol / hr).

Air serving as a carrier gas is supplied to the heater (11) at about 60 Nm ³ / h. The water required for the decomposition of CFCs is 7.5k by a metering pump (12) such as a diaphragm pump.
g / h (415 mol / hr) (2.
The heater (1) is supplied together with air to allow for a 5-fold margin.
Supply to 1). The air and water are heated to about 500 ° C. by the heater (11), and become heated air and superheated steam at the outlet of the heater (11). The supply of Freon 12 is adjusted to 10 kg / h by the Freon flow control valve (13a) and supplied to the downstream side of the heater (11),
The mixed gas of the heated air and the superheated steam becomes a mixed gas of about 450 ° C. and is supplied to the catalyst container (20).

The mixed gas supplied to the catalyst container (20) under predetermined conditions is decomposed with chlorofluorocarbon by the catalyst, and
(HF): 3.3 kg / h, hydrogen chloride (HCl): 6.0 kg / h, carbon dioxide (CO ₂ ): 3.6 kg / h.

The gas after decomposition is led to a cooling chamber (31) provided below the catalyst container (20), and is cooled by spraying an alkaline solution. The spray in the cooling chamber (31) rapidly cools the decomposition gas temperature from about 450 ° C. to 100 ° C. or less to prevent generation of harmful organic halogen compounds such as dioxin. Further, by setting the decomposition gas temperature to 100 ° C. or lower, a low-cost and corrosion-resistant plastic material can be used for the material of the cooling chamber (31). Decomposed gas after cooling is supplied to the cooling chamber (3
Water is separated by a baffle provided in 1), and only gas is supplied to the removal tower (32). In the removal tower (32), the acidic gases (HF, HCl) are completely removed by spraying the alkaline solution, and only the air and carbon dioxide (CO ₂ ) are discharged out of the system by the exhaust fan (15). In the cooling chamber (31), the purpose is to cool the decomposed gas, but a part of the acid gas in the decomposed gas is also removed by spraying, similarly to the removal tower (32).

The cooling chamber (31) and the removing tower (32) are supplied with an alkali solution of 22 m ³ / h from the alkali tank (40) by the circulation pump (41) and sprayed by the spray nozzle (35). Spray flow rate of the cooling chamber (31) is needed to be set in the flow rate which can be neutralized in boiling not flow and partial decomposition gas by contact with the cracked gas of from about 450 ° C., in this embodiment 5 m ³ / h.

The alkaline solution used for gas cooling and neutralization is returned to the alkaline tank (40), and is again supplied to the cooling chamber and the removal tower by the circulation pump (41) to cool and neutralize the decomposition gas. Used for

The alkali required for neutralization is supplied from an alkali hopper (43) to an alkali tank (40) by an alkali metering device (44). The supply amount of the alkali is adjusted depending on the type of the halogen compound to be decomposed and the decomposition amount, and the supply amount is 1.3 times the equivalent required for neutralization of the acid gas. As the alkali, sodium hydroxide, calcium hydroxide, calcium carbonate, or the like can be used, but calcium hydroxide is used from the viewpoints of handleability, neutralization performance, and ease of drainage from the system. Calcium hydroxide (C
a (OH) ₂ ), 16 kg / h (216 mol / h) is metered from the alkali metering machine (44) to the alkali tank (40),
The calcium hydroxide concentration in the alkaline tank (alkaline solution: about 3 m ³ ) is always 5 wt%. The alkali metering device (44) employs a screw feeder capable of strictly controlling the supply amount to prevent excessive addition of alkali.
The alkaline tank (40) contains calcium hydroxide as an insoluble substance and calcium fluoride (Ca) as a neutralization product.
F ₂ ) is constantly stirred by a stirrer (45) so as not to settle at the bottom of the alkaline tank (40).

As the removal tower (32) of the present embodiment, a spray tower that does not cause blockage inside the removal tower (32) due to calcium hydroxide and calcium fluoride contained in the alkaline solution is employed. A demister (36) is installed at the top of the removal tower to prevent mist containing insoluble substances from being discharged out of the system along with the air. The demister (36) has a water spray tank to prevent clogging due to adhesion of insoluble substances.
About 48 L / h of water is supplied from (33) by a water spray pump (34) to perform washing.

The hydrogen fluoride (H) removed in the removal tower (32)
F) and hydrogen chloride (HCl) are neutralized in an alkaline bath (40), and are insoluble calcium fluoride (6.5 kg / h), soluble calcium chloride (9.2 kg / h), water ( 6.0 kg / h). Note that hydrogen fluoride (HF) and hydrogen chloride (HC
l) A reaction formula for neutralizing each with calcium hydroxide (Ca (OH) ₂ ) is expressed as 2HF + Ca (OH) ₂ → CaF ₂ + 2H ₂ O 2HCl + Ca (OH) ₂ → CaCl ₂ + 2H ₂ O.

The concentration of calcium fluoride and calcium chloride in the alkaline tank (40) is determined by adding an alkaline solution to the alkaline tank (40).
Via the circulation pump (41), the cooling chamber (31), the removal tower (32)
If it is used in a closed loop after returning to the alkaline tank (40), it will gradually rise. Removal tower when the concentration of calcium fluoride or calcium chloride increases (32)
In this case, the performance of removing acidic gas at the time is reduced, and clogging of pipes and spray nozzles due to calcium fluoride as an insoluble substance occurs. From the performance of the alkaline tank (40) for the purpose of preventing these performance degradation and blockage, the dehydrator supply pump (55) continuously supplies a 350 kg / h alkaline solution to the dehydrator (51),
Calcium fluoride (6.5 kg / h) and unreacted calcium hydroxide (about 3 kg / h) are removed by a dehydrator (51).
The solid content dehydrated by the dehydrator (51) contains 50%
Contains ~ 70% water.

The operation of the dehydrator supply pump (55) is controlled by a level switch (46) provided in the alkaline tank (40).
ON / OFF by liquid level high / low signal
drive.

The alkali solution from which non-soluble substances have been removed by dehydration is led to a separation liquid tank (60). Separation liquid tank (60)
In, about 300 L / h of the alkaline solution is returned to the alkaline tank (40) by the separation liquid supply pump (56), and is reused as the alkaline solution for the decomposition gas treatment. Separation liquid supply pump
The operation in (56) uses a constant flow rate of 300 L / h. In the separation liquid tank (60), about 48 L / h of the alkaline solution is partially discharged from the overflow line provided above the separation liquid tank (60) to the settling tank (62). This overflow keeps the concentration of calcium chloride in the reused alkaline solution constant by discharging the soluble calcium chloride contained in the alkaline solution together with water to about 9 kg / h sedimentation tank (62). In the case of the present embodiment, the concentration of calcium chloride in the alkaline solution is about 20% by weight.

From the separation liquid supply pump (56) to the alkaline tank (40)
About 48 L / h of the alkali solution supplied to the settling tank (62) is discharged from the separating liquid tank (60) to the shortage of water. Therefore, it is necessary to supply the same amount of fresh water into the system. The supply location may be directly to the alkaline tank (40), but in the present embodiment, the shortage of water is supplied to the system while also washing the demister (36) in the removal tower (32). We are trying to streamline.

Calcium fluoride (CaF ₂ ) in the solid content discharged from the dehydrator (51) can be used as a valuable resource. Therefore, in order to increase the added value as a product, moisture is removed by drying. After the powder is formed, the powder is formed into pellets by a granulator (54) for easy handling.

Since the alkaline solution discharged from the overflow line of the separation liquid tank (60) to the settling tank A (61) or the settling tank B (62) contains a trace amount of insoluble substance, In order to release them outside the system, it is preferable to separate and discharge these trace amounts of insoluble substances. For this reason, two sedimentation tanks (61) are provided and one sedimentation tank (61) receives the separated liquid from the separation liquid tank (60) while the other sedimentation tank (61) sediments the insoluble matter and sets the supernatant. The liquid is discharged to the adjusting tank (63). This operation is performed alternately in the two sedimentation tanks (61) to control the adjustment tank (6).
Insoluble solids of the separated liquid discharged to 3) can be further removed. The alternate operation of the settling tank (61) is performed by switching valves provided before and after the settling tank (61). In addition, since the spontaneous settling of the insoluble substance requires 8 to 12 hours, each settling tank (61) does not overflow even if it is drained from the separation liquid tank (60) for more than 48 L / h. The capacity is about 3 m ³ . In the present embodiment, the insoluble solid is separated by natural sedimentation. However, it is also possible to separate a small amount of the insoluble substance by flotation and discharge only the separated liquid to the adjustment tank (63).

The insoluble substance settled at the bottom of the settling tank (61) is removed from the pipe provided at the bottom of the settling tank (61) once every two to three weeks by using a dehydrator feed pump (55). Transfer to (51), dehydrate again, separate solids and discharge out of the system.

The alkali solution from which a small amount of insoluble material has been separated in the settling tank (61) is discharged to the adjusting tank (63), and the adjusted tank (63)
After adjusting the pH and confirming the concentration of fluorine (F), water is drained out of the system by a drain pump (64). The acid used for adjusting the liquid to be drained is preferably hydrochloric acid, and the alkali is preferably calcium fluoride. This is because the substance produced by the neutralization is the same as the calcium chloride contained in the alkaline solution.

In the present embodiment, the treatment of the exhaust gas decomposed of chlorofluorocarbon Freon 12 (CF ₂ Cl ₂ ) has been described. However, the treatment of the exhaust gas decomposed of hydrochlorofluorocarbon can be similarly performed.

[0044]

Embodiment 2 FIG. 2 shows a C ₂ F ₆ (perfluorocarbon) decomposition treatment system using a catalyst in which the decomposition gas treatment is a continuous treatment. In the first embodiment, since the decomposition target gas is Freon 12, calcium chloride having high solubility is generated by neutralization of the decomposition gas. For this reason, it was necessary to drain a certain amount of water out of the system in order to adjust the concentration of calcium chloride in the alkaline solution. However, in this embodiment, since the gas to be decomposed does not contain chlorine, the equipment for draining out of the system according to Embodiment 1 (a settling tank (61), a regulating tank (63), a drainage pump (64), a slaked lime tank) (65), hydrochloric acid tank (66)) becomes unnecessary.

The decomposition process of the C ₂ F ₆ had a carrier gas to adjust the C ₂ F ₆ concentration of ^{air, SV = 1,500h ~ 1, C} 2
C ₂ F ₆ at a F ₆ concentration of 3.0 vol% and a catalyst layer temperature of 800 ° C.
Of 10 kg / h (72.5 mol / h). Air as a carrier gas is supplied to the heater (11) at about 60 Nm ³ / h. About 9.8 kg / h (544 mol / h) of water is supplied to the heater (11) together with air at a rate 2.5 times the amount required for the decomposition of C ₂ F ₆ by the metering pump (12). C ₂ F ₆ is a flow control valve (13
After being adjusted to 10 kg / h by a), the mixture is supplied downstream of the heater (11), and is supplied to the catalyst container (20) as a mixed gas together with the heated air and steam.

The gas mixed under the predetermined conditions is decomposed by the catalyst, and hydrogen fluoride (HF) is converted to 8.7 kg / h (435 mol / h).
l / h) and carbon monoxide (CO) at 2.0 kg / h (72.5 mol / h).
h), carbon dioxide (CO ₂ ) is 3.2 kg / h (72.5 mol / h)
Occur. The cracked gas is supplied to the cooling chamber (3) as in the first embodiment.
It is led to 1) and is cooled to 100 ° C. or less by spraying. Here, since the decomposition gas temperature is as high as about 800 ° C., the spray amount of the cooling chamber (31) is set to 10 m ³ / h as a spray amount capable of reducing the high-temperature decomposition gas to 100 ° C. or less. The cooled cracked gas is removed after removing hydrogen fluoride (HF) in the removal tower (32).
The air is exhausted out of the system by the air exhauster (15).

Calcium hydroxide (Ca (OH) ₂ ) used for neutralization of the removed hydrogen fluoride (HF) is supplied to an alkali tank (40) by an alkali metering device (44). The amount of calcium hydroxide to be added is 20 kg / h, which is 1.3 times the amount required for neutralizing hydrogen fluoride. The alkali solution adjusted to a constant concentration in the alkali tank (40) is sprayed quantitatively into the cooling chamber (31) and the removal tower (32) via the circulation pump (41), and collected again in the alkali tank (40). Cycle in a closed loop as shown. In the alkaline tank (40), hydrogen fluoride (HF) is neutralized and calcium fluoride (CaF ₂ ), which is an insoluble substance, is dissolved.
Is produced at 16 kg / h.

From the alkaline tank (40), the circulating pump (41) supplies the alkaline solution to the cooling chamber (31) and the spray of the removal tower (32), while the dehydrator supply pump (55) supplies approximately 9% of the alkaline solution.
00L / h is supplied to the dehydrator (51). Here, insoluble substances (calcium fluoride, unreacted calcium hydroxide) are removed. The removed solids are dried and granulated to be recovered as valuable resources.

The alkaline solution from which non-soluble substances have been removed is
The separated liquid is returned from the separated liquid tank (60) to the alkaline tank (40) by the separated liquid supply pump (56), and is reused as an alkaline solution for treating the decomposed gas.

When only an insoluble substance is produced by neutralization as in the present embodiment and the soluble substance is hardly contained in the alkali solution after dehydration, the system for adjusting the concentration of the soluble substance is out of the system. There is no need to discharge and the entire amount can be reused.

However, since the solid content of the dehydrated non-soluble substance contains 50 to 70% of water, it is necessary to replenish the system with about 18 L / h of water corresponding to it.
As the supply method, it is reasonable to supply the demister (36) in the removal tower (32) also for washing as in the first embodiment. As a supply method, continuous supply may be used, but in this case, since the supply amount is as small as about 18 L / h,
Supply a large amount of supply instantaneously as intermittent supply,
Demister by supplying 18L per hour (36)
It is rational to improve the washing efficiency.

In this way, in the decomposition gas treatment by decomposition of a fluorine compound containing no halogen other than fluorine, wastewater is not discharged to the outside of the system, so that only a small amount of water is used and drainage equipment for discharging outside the system is not required. Simplifies the system.

In this embodiment, the treatment of the decomposition exhaust gas of perfluorocarbon C ₂ F ₆ has been described, but the treatment of the decomposition exhaust gas of other types of perfluorocarbon and hydrofluorocarbon can be similarly performed.

[0054]

Embodiment 3 FIG. 3 shows a decomposition processing system for chlorofluorocarbon 12 (CF ₂ Cl ₂ ) using a combustor, in which a decomposition gas processing method is a continuous processing. Freon 12 is 10 kg / h (83 mol / h
h) Supply. City gas is supplied as a combustion aid and air is supplied as an oxidant. First, Freon 12 is a Freon cylinder (1
From 3), adjust the flow rate to 10kg / h (83mo) with the CFC flow control valve (13a).
l / h), mix with city gas and supply to combustor (22). For city gas, the flow rate is controlled by the city gas flow control valve (15a) to 2.5 times the theoretical molar ratio of the amount of methane required for CFC decomposition.
It is adjusted and controlled to 4.7 Nm ³ / h (210 mol / h) which is twice as high.
The air is adjusted and controlled to about 6 Nm ³ / h by air flow control valve (10a) so that the air-fuel ratio becomes 1.2 times.
Supply to (22).

In the combustor (22), air and city gas are burned by a combustion burner (23). Freon 12 has a temperature of 800 ° C.
When it becomes the above, it is thermally decomposed, reacts with hydrogen generated by combustion of propane gas, and reacts with hydrogen fluoride (HF), hydrogen chloride (HCl),
It becomes carbon dioxide (CO ₂ ).

Since the type and amount of the acidic gas generated by the decomposition of the chlorofluorocarbon 12 are the same as in the first embodiment, the decomposition gas treatment is also performed in the same processing system as in the first embodiment. The cracked gas is led to a cooling chamber (31), and is rapidly cooled to 100 ° C. or less by spraying. Here, the spray amount of the cooling chamber (31) is set to a water amount of 10 m ³ / h which is sufficient to reduce the decomposition gas temperature from 800 ° C. to 100 ° C. or less. The cooled decomposition gas is discharged outside the system after removing hydrogen fluoride and hydrogen chloride in the removal tower (32).

Hydrogen chloride (HCl) and hydrogen fluoride (HF)
Calcium fluoride neutralized by alkaline bath (40)
(CaF ₂ ) and calcium chloride (CaCl ₂ ). Calcium hydroxide (Ca (OH) ₂ ) used for neutralization is supplied to an alkali tank (40) by an alkali quantitative supply device (44).
The amount of calcium hydroxide added is 1.3 times (16 kg / h) the amount required for neutralizing hydrogen fluoride and hydrogen chloride. The alkaline solution whose concentration has been adjusted in the alkaline bath (40) is supplied to the circulation pump (4
Spray nozzle in cooling chamber (31) and removal tower (32) via 1)
A fixed amount is sprayed from (35) and circulated through a closed loop so as to be collected again in the alkaline tank (40).

On the other hand, from the alkaline tank (40), about 350 kg / h is supplied to the dehydrator (51) by the dehydrator supply pump (55), where the non-soluble substances (calcium fluoride, unreacted hydroxide) are supplied. Calcium) is removed. The solid content of the removed insoluble substance is recovered as valuable resources by drying and granulating.

The alkali solution from which non-dissolved substances have been removed by dehydration is returned from the separation solution tank (60) to the alkali tank (40) by the separation solution pump (56), and is reused as an alkali solution for treating the decomposition gas. . Further, in the separation liquid tank (60), separately from the line returning to the alkali tank (40), the separation liquid tank (60) overflows from the upper part and is supplied to the settling tank. This is because a certain amount of soluble substance (CaCl ₂ )
By this, the increase in the concentration of the soluble substance in the alkaline tank (40) due to the reuse of the alkaline solution is suppressed. The amount of the alkaline solution in the alkaline tank (40) depends on the amount of the separated solution tank (6).
Since it is reduced by the amount discharged from 0) to the sedimentation tank (61), it is necessary to replenish insufficient water. The replenishment of the insufficient water is supplied from the top of the removal tower.

In the settling tank (61), solids are settled over one day, and only the supernatant after settling is supplied to the adjusting tank (63). In the adjustment tank (63), after adjusting the pH of the water and checking the fluorine concentration,
Discharge outside the system.

[0061]

Fourth Embodiment FIG. 4 shows a decomposition processing system for chlorofluorocarbon 12 (CF ₂ Cl ₂ ) using arc plasma by using a decomposition gas processing method as continuous processing. Freon 12 is 10kg / h
(83 mol / h). Water is supplied at 7.5 kg / h (415 mol / h), which is 2.5 times the molar ratio required for the decomposition of CFCs.

The flow rate of the Freon 12 is adjusted and controlled by a Freon flow rate control valve (13a), mixed with water and mixed with a plasma torch (24).
Supply to Water is supplied as steam at 100 ° C. from the steam generator (14).

In the plasma torch (24), a plasma generator locally generates 10,000 plasma using an arc plasma.
Create a high temperature of 0 ° C. In such a high temperature state, Freon 12 takes the form of a fluorine atom, a chlorine atom, and a carbon atom.
These atoms react with hydrogen and oxygen atoms from water to form stable hydrogen fluoride (HF), hydrogen chloride (HCl), and carbon dioxide (CO ₂ ).

Since the type and amount of the acidic gas generated by the decomposition of the chlorofluorocarbon 12 are the same as in the first embodiment, the decomposition gas treatment is also performed by the same processing system as in the first embodiment. The cracked gas is led to the cooling chamber, where it is sprayed.
It is quenched below 00 ° C. Here, the spray amount of the cooling chamber (31) is set to a water amount of 20 m ³ / h, which is sufficient to lower the decomposition gas temperature of 1000 ° C. or more to 100 ° C. or less. The cooled cracked gas (HF, HCl, CO ₂ ) is supplied to the removal tower (32) by hydrogen fluoride.
After removing (HF) and hydrogen chloride (HCl), it is discharged out of the system.

Hydrogen chloride (HCl), hydrogen fluoride is (HF),
Calcium fluoride neutralized by alkaline bath (40)
(CaF ₂ ) and calcium chloride (CaCl ₂ ). Calcium hydroxide (Ca (OH) ₂ ) used for neutralization is supplied to an alkali tank (40) by an alkali quantitative supply device (44).
The amount of calcium hydroxide added is 1.3 times (16 kg / h) the amount required for neutralizing hydrogen fluoride and hydrogen chloride. The alkaline solution whose concentration has been adjusted in the alkaline bath (40) is supplied to the circulation pump (4
Spray nozzle in cooling chamber (31) and removal tower (32) via 1)
A fixed amount is sprayed from (35) and circulated through a closed loop so as to be collected again in the alkaline tank (40).

From the alkaline tank (40), about 350 kg / h is supplied to the dehydrator (51) by the dehydrator supply pump (55), and the insoluble substances (calcium fluoride, unreacted calcium hydroxide) are supplied. ) Is removed. The solid content of the removed insoluble substance is recovered as valuable resources by drying and granulating.

The alkali solution from which non-dissolved substances have been removed by dehydration is returned from the separation liquid tank (60) to the alkali tank (40) by the separation liquid pump (56), and is reused as an alkali solution for decomposition gas treatment. In the separation liquid tank (60), an alkaline tank
Separately from the line returning to (40), overflow from the upper part of the separation liquid tank (60) is supplied to the settling tank. This removes a certain amount of a soluble substance (CaCl ₂ ) from the alkali solution after dehydration, thereby suppressing an increase in the concentration of the soluble substance in the alkaline bath (40) due to reuse of the alkaline solution. In addition,
Since the amount of the alkaline solution in the alkaline tank (40) decreases by the amount discharged to the settling tank (61), it is necessary to replenish insufficient water. The replenishment of the insufficient water is supplied from the upper part of the removal tower (32).

In the sedimentation tank (61), solids are sedimented over one day, and only the supernatant after sedimentation is supplied to the adjustment tank (63). In the adjustment tank (63), after adjusting the pH of the water and confirming the fluorine concentration, the water is discharged out of the system.

[Test of Acid-Resistant Material I] FIG. 5 shows the result of a material selection test performed on a part where a hydrofluoric acid solution and a hydrochloric acid solution come into contact with each other in an acidic gas removing apparatus and an alkaline bath.

In this test, three types of specimens were used: Inconel and Hastelloy, a Ni-based alloy having excellent corrosion resistance, and vinyl chloride as a resin material, and each specimen was immersed in an acidic solution for 100 hours. Was measured for the amount of corrosion. (Test conditions) Liquid temperature: 30 ° C., 50 ° C., 70 ° C. Acid solution: pH 0.1 or less Immersion time: 100 hours The acid solution is a gas generated when Freon 12 (3 vol%) is decomposed with a catalyst. (Hydrogen fluoride: about 6 vol%, hydrogen chloride: about 6 vol%) was absorbed in an alkaline solution.

The specimen immersed in the acidic solution for 100 hours was taken out, and the amount of corrosion was measured (FIG. 5). As a result, corrosion occurred at each temperature for both Ni-based alloys, Inconel and Hastelloy. The corrosion amount tended to increase in proportion to the temperature.

On the other hand, no corrosion was observed at all temperatures of vinyl chloride, and it was found that vinyl chloride had corrosion resistance to hydrogen fluoride and a hydrogen chloride solution. However, since vinyl chloride has a heat-resistant temperature of 100 ° C., it is required that the usage condition of the material be 100 ° C. or less.

From these results, in the decomposition gas treatment of the organic halogen gas containing fluorine, the temperature of the device material in the portion in contact with the hydrogen fluoride solution and the hydrogen chloride solution after the removal of the acidic gas was suppressed to 100 ° C. or less. It was confirmed that vinyl chloride could be used.

The exhaust gas treatment systems according to Embodiments 1 to 4 of the present invention provide a method for suppressing the temperature of the liquid at a portion where the acidic gas is removed from the portion in contact with the hydrogen fluoride solution and the hydrogen chloride solution to 100 ° C. or less. This makes it possible to use PVC as a device material.

[Corrosion Resistance Test of Acid-Resistant Materials II] Material selection test conducted on materials used in high-temperature acidic gas (hydrogen fluoride, hydrogen chloride) atmosphere after decomposition of organic halogen compounds containing fluorine and before exhaust gas treatment equipment Table 1 shows the results.

[0076]

[Table 1]

In this test, three types of Ni-base alloys, Inconel, Hastelloy, and stainless steel, which are excellent in corrosion resistance, were used as specimens, and each specimen was treated with a catalyst using fluorocarbon 1
2 (3 vol%) After the decomposition, the sample was exposed to a high-temperature acidic gas atmosphere (400 ° C., hydrogen fluoride: 6 vol%, hydrogen chloride: 6 vol%) for 1,000 hours, and the weight change of the specimen was measured. (Test conditions) Gas composition: 6 vol% of hydrogen fluoride, 6 vol% of hydrogen chloride (fluorocarbon 12 (3 vol%) decomposed gas) Gas temperature: 400 ° C Exposure time: 1,000 hours Exposure time: 1,000 hours I checked the condition. As a result, no abnormalities were found in both Inconel and Hastelloy of the Ni-based alloy, and the test was continued for 1,000 hours. On the other hand, in the case of stainless steel, the specimen itself had disappeared due to corrosion at the time of exposure for 100 hours.

In the weight measurement at the 1,000th hour, the weight of both Inconel and Hastelloy increased, and as a result of a detailed analysis of the increase, it was found that not the corrosion products but the deposits from upstream of the apparatus. I found it.

Thus, in the exhaust treatment of the decomposition gas of the organic halogen compound containing fluorine, the acid (hydrogen fluoride, hydrogen chloride) gas having a temperature of 1,000 or less from the decomposition treatment device to the exhaust gas treatment device is used. In an atmosphere, Inconel and Hastelloy of a Ni-based alloy can be used as a device material.

[0080]

According to the present invention, a method and an apparatus for treating a fluorine-containing decomposed exhaust gas containing an organic halogen compound are circulated by circulating an alkaline solution having a predetermined concentration for neutralizing an acidic gas contained in the decomposed exhaust gas, thereby producing a neutralized product. The dehydrated alkali solution was dehydrated by a fixed amount, and the alkali was added to the separated water at this time so as to have a predetermined concentration and circulated again to neutralize the acidic gas contained in the exhaust gas. Thus, the processing of the decomposition exhaust gas can be performed.

In the above method and apparatus, by using an alkali containing calcium, it is possible to separate calcium fluoride by dehydration treatment of an alkali solution containing a neutralized product, and to recover the calcium fluoride as a valuable substance. it can.

[Brief description of the drawings]

FIG. 1 shows a system for treating flue gas decomposed by catalysis by continuous wastewater treatment.

FIG. 2 shows a catalytic C ₂ F ₆ decomposition exhaust gas treatment system by continuous waste water treatment.

FIG. 3 shows a combustion type chlorofluorocarbon decomposition exhaust gas treatment system by continuous wastewater treatment.

FIG. 4 shows a plasma-type CFC decomposition exhaust gas treatment system using continuous wastewater treatment.

FIG. 5 shows the results of a material selection test of a portion in contact with a hydrogen fluoride solution and a hydrogen chloride solution.

[Explanation of symbols]

 10a Air flow control valve 11 Heater 12 Metering pump 13a Freon flow control valve 15 Exhaust air 15a City gas flow control valve 20 Catalyst container 22 Combustor 23 Combustion burner 24 Plasma torch 31 Cooling room 32 Removal tower 33 Spray water tank 34 Spray water Pump 35 Spray nozzle 36 Demister 40 Alkaline tank 41 Circulation pump 42 Heat exchanger 43 Alkaline hopper 44 Alkali quantitative feeder 45 Stirrer 51 Dehydrator 53 Dryer 54 Granulator 55 Dehydrator supply pump 56 Separator pump 60 Separator tank 61 sedimentation tank a 62 sedimentation tank b 63 control tank 64 drainage pump 65 slaked lime tank 66 hydrochloric acid tank

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshihiro Mori 3-18-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Ibaraki Hitachi Information Service Co., Ltd. (72) Inventor Hisao Yokoyama 3-chome, Sachimachi, Hitachi City, Ibaraki Prefecture No. 1 within Hitachi Engineering Co., Ltd. (72) Inventor Takayuki Toyama 3-10-2 Bentencho, Hitachi City, Ibaraki Prefecture Within Hitachi Kyowa Engineering Co., Ltd.

Claims (11)

[Claims] 1. A method in which hydrogen fluoride continuously supplied as an exhaust gas from a decomposer for decomposing an organic halogen compound containing fluorine is brought into contact with an alkali solution of a predetermined concentration continuously supplied from an alkali bath to dissolve it. A neutralized product is generated, and the alkaline solution containing the neutralized product is circulated so as to return the alkaline solution containing the neutralized product to the alkaline bath. On the other hand, a certain amount of the alkaline solution containing the neutralized product is taken out of the alkaline bath and dehydrated. Returning the water separated by the dehydration treatment to an alkali bath, and supplying an alkali so as to have a predetermined concentration corresponding to the amount of the returned water, a method for treating an organic halogen compound exhaust gas containing fluorine. . 2. An alkaline solution which continuously supplies hydrogen fluoride contained in exhaust gas continuously supplied from a decomposer for decomposing hydrofluorocarbons or perfluorocarbons from an alkaline tank and cloudes calcium hydroxide at a predetermined concentration. To produce a neutralized product of insoluble calcium fluoride, and circulate the alkaline solution so as to return the alkaline solution containing the neutralized product to the alkaline bath, while containing the neutralized product from the alkaline bath. A certain amount of the alkali solution is taken out and dehydrated to remove calcium fluoride, the separated water separated by the dehydration treatment is returned to the alkali tank, and the hydroxide is adjusted to a predetermined concentration according to the amount of the returned water. A method for treating an organic halogen compound exhaust gas containing fluorine, which comprises supplying calcium. 3. Hydrogen fluoride and hydrogen chloride contained in exhaust gas continuously supplied from a decomposition device for decomposing chlorofluorocarbon or hydrochlorofluorocarbon,
The calcium hydroxide which is continuously supplied from the alkali bath is brought into contact with an alkali solution which is turbid at a predetermined concentration to produce a neutralized product of insoluble calcium fluoride and soluble calcium chloride, and contains the neutralized product The alkaline solution was circulated so as to return the alkaline solution to the alkaline bath, while a certain amount of the alkaline solution containing the neutralized product was taken out from the alkaline bath and dehydrated to remove calcium fluoride, and separated by the dehydration process. After partially discharging the separated water, return to the alkaline tank, supply calcium hydroxide so as to have a predetermined concentration in accordance with the amount of the returned water, and further newly add water corresponding to the amount of the separated water partially discharged. A method for treating an exhaust gas of an organic halogen compound containing fluorine, the method comprising supplying an alkaline tank and maintaining a predetermined concentration of calcium chloride in alkaline water stored in the alkaline tank. 4. The organic halogen containing fluorine according to claim 2, wherein fresh water having an amount of water contained in the calcium fluoride to be removed and calcium hydroxide having a predetermined concentration of the water are supplied. A method for treating compound exhaust gas. 5. The method for treating an organic halogen compound exhaust gas containing fluorine according to claim 2, wherein the calcium fluoride removed by the dehydration treatment is dried and recovered in a powder form. 6. The method for treating an exhaust gas of an organic halogen compound containing fluorine according to claim 5, wherein the powdery calcium fluoride is granulated. 7. A decomposer for continuously supplying hydrogen fluoride gas as an exhaust gas of an organic halogen compound containing fluorine, an alkali tank for storing an alkali solution having a predetermined concentration, and an alkali tank for supplying hydrogen fluoride gas from the decomposer. A cooling chamber for cooling with an alkaline solution introduced from the reactor, a hydrogen fluoride gas flowing from the cooling chamber, an alkaline solution flowing from the alkaline bath, and neutralizing the hydrogen fluoride gas with the alkaline solution to produce the neutralized gas. A removing device for returning the alkaline solution containing the substance to the alkaline tank, a dehydrator for dehydrating the alkaline solution containing the neutralized substance supplied from the alkaline tank in a fixed amount and separating the neutralized substance and the separated water, and a dehydrator. An organic halo containing fluorine, comprising: an alkali supply device for supplying alkali so as to have a predetermined concentration in accordance with the amount of separated water returned to the alkali tank. Gen compound exhaust gas treatment equipment. 8. The apparatus for treating flue gas of an organic halogen compound containing fluorine according to claim 7, further comprising a drier for drying the neutralized product separated by the dehydrator into powder. 9. The apparatus for treating an exhaust gas of an organic halogen compound containing fluorine according to claim 8, further comprising a granulator for granulating a powder of the neutralized product dried by the dryer. 10. The apparatus for treating an exhaust gas of an organic halogen compound containing fluorine according to claim 7, wherein a portion of the removing device that comes into contact with the alkali and a material of the alkaline tank are vinyl chloride. 11. The organic halogen compound containing fluorine according to claim 7, wherein the material of the decomposing device, the cooling chamber, and the part in contact with the high-temperature exhaust gas in the conduit connecting the both are made of inconel or hastelloy of a Ni-based alloy. Exhaust gas treatment equipment.