JP4408222B2 - Detoxification equipment for soil contaminated with chemical agents - Google Patents

Description

  The present invention relates to a treatment technique for detoxifying soil contaminated with chemical agents for chemical weapons by heating.

  In recent years, chemical weapons that have been abandoned underground by the former Japanese army and chemical weapons in glass bottles have been discovered. For this reason, there is concern about contamination of the surrounding soil by chemical agents leaking due to shell erosion or glass bottle breakage. Soil contaminated with such chemical agents (hereinafter referred to as “chemical agent-contaminated soil” or simply “contaminated soil”) may cause serious environmental pollution if left unattended, and must be detoxified immediately. .

  As an example of detoxifying soil contaminated with chemical agents, there is an example of chemical treatment by spraying neutralizing agent on contaminated soil in the United States.

In addition, in the United States, although not contaminated soil, equipment such as shells contaminated with a chemical agent is heated and detoxified (see Non-Patent Document 1). In this method, the chemical agent-contaminated equipment is exposed to the atmosphere maintained at 540 ° C. by burning the fuel in a heating furnace for at least 15 minutes to evaporate and remove the chemical agent adhering to the surface. Since the vapor of the agent is still toxic, it passes through the afterburner maintained at 1090 ° C. to be oxidatively decomposed and rendered harmless.
Graham Pearson, et al, “Critical Evaluation of Proven Chemical Weapon Destruction Technologies”, Pure and Applied Chemistry (Pure and Applied Chemistry), IUPAC, 2002, Vol. 74, No. 2, p.187-316

In the United States, there are few examples of using chemical agents containing arsenic in chemical weapons, but chemical weapons manufactured by the former Japanese army include Louisite (CH ₂ ClCHAsCl ₂ ), diphenylchloroarsine ((C ₆ H ₅ ) 2AsCl ) And diphenylcyanoarsine ((C ₆ H ₅ ) ₂ AsCN) are often used. Here, diphenylchloroarsine and diphenylcyanoarsine among organic arsenic compounds are decomposed into diphenylarsinic acid, which is also an organic arsenic compound, when they come into contact with groundwater in soil. For this reason, many chemical agents containing an organic arsenic compound exist in the chemical agent-contaminated soil as decomposition products such as diphenylarsinic acid. For soil contaminated with chemical agents containing arsenic (including decomposition products of chemical agents; the same applies hereinafter), detoxification could not be realized by the conventional treatment method. That is, even if a soil contaminated with a chemical agent containing arsenic is chemically treated with a neutralizing agent, an arsenic component remains in the soil even after the treatment, and thus a fundamental solution cannot be achieved. In addition, when soil contaminated with arsenic-containing chemicals is heat-treated in a heating furnace by fuel combustion, arsenic components evaporated and removed from the soil combine with oxygen components in the air for fuel combustion, resulting in harmful solid phases. Or there is a problem that liquid arsenic oxide (particles) is generated and adheres to the soil again (in the case of equipment, even if arsenic oxide reattaches to the surface, it can be removed relatively easily, In the case of soil, the removal of arsenic oxide and the soil is difficult because they are all united.)

  Then, an object of this invention is to provide the processing method and its apparatus which can implement | achieve detoxification of the soil contaminated with the chemical agent (including the decomposition product of a chemical agent) containing arsenic.

The invention according to claim 1 is a heating furnace for evaporating and removing the chemical agent by heating the chemical agent-contaminated soil contaminated with the chemical agent containing arsenic in an airtight state where oxygen intrusion is blocked, and A ventilator that exhausts the evaporated chemical agent from the heating furnace, and further, an oxygen-containing gas is added to the exhaust gas of the heating furnace discharged from the heating furnace between the heating furnace and the exhaust fan. An oxidative decomposition furnace for oxidatively decomposing the evaporated chemical agent, a gas cooler for cooling the oxidative decomposition furnace exhaust gas discharged from the oxidative decomposition furnace, and a gas cooler exhaust gas discharged from the gas cooler A detoxification treatment device for chemical agent-contaminated soil, which comprises a dust collector for removing arsenic oxide generated by the oxidative decomposition from the furnace, the charging portion of the chemical agent-contaminated soil into the heating furnace and the heating Drainage section of treated soil from the furnace Wherein each, while maintaining the airtight state of the heating furnace, that double damper is provided as airtight maintaining means for enabling the discharge of the charging and the processed soil of the chemical agent contaminated soil It is a detoxification processing device for chemical agent-contaminated soil.

The invention according to claim 2, wherein the heating furnace is a detoxification apparatus chemical agents contaminated soil according to claim 1 is a rotary kiln externally heated.

According to the present invention, when a soil contaminated with a chemical agent containing arsenic is heated in an airtight heating furnace in which oxygen intrusion is blocked, the double damper is used to change the airtight state in the heating furnace. By discharging the treated soil together with the heating furnace exhaust gas from the heating furnace while maintaining it, it becomes possible to evaporate and remove the chemical agent from the contaminated soil without generating arsenic oxide, and in the removed chemical agent Since the arsenic component is prevented from being oxidized and reattached to the soil being treated, decontamination of the contaminated soil can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic explanatory view showing a detoxification treatment apparatus for chemical agent-contaminated soil according to an embodiment of the present invention. Detoxification apparatus of this example, and evaporation contaminated soil receiving hopper 1 for temporarily holding a chemical agent contaminated soil a _1, a chemical agent by heating the contaminated soil a ₁ cut out from the contaminated soil accepting hopper 1 A rotary kiln (hereinafter also simply referred to as “kiln”) 2 as a heating furnace to be removed and an exhaust fan 3 for exhausting the chemical agent evaporated and removed from the rotary kiln 2 are provided.

Further, between the rotary kiln 2 and the exhaust fan 3, the chemical agent evaporated and removed by adding the air c, which is an oxygen-containing gas, to the kiln exhaust gas b ₁ , which is the heating furnace exhaust gas discharged from the rotary kiln 2. The oxidative decomposition furnace 4 for oxidative decomposition, the gas cooler 5 for cooling the oxidative decomposition furnace exhaust gas b ₂ discharged from the oxidative decomposition furnace 4, and the gas cooler exhaust gas b ₃ discharged from the cooler 5 And a filtering dust collector 6 as a dust collector for removing arsenic oxide generated by oxidative decomposition.

The rotary kiln 2 is an external heating type. That is, the rotary kiln 2, the outer tube 21 of the fixed against rotation, has a double structure consisting of the tube 22. Of that rotates to transport while maintaining the contaminated soil a _1, instrumentation of contaminated soil a ₁ is inclined downward gradient toward the join the club side to the discharge side of the treated soil a _2. A plurality of burners 23 is provided in the space between the inner tube 22 and outer tube 21, by heating the inner tube 22 from the outer peripheral surface side, so as to indirectly heat the contaminated soil a ₁ It has become. A double damper 24 and a contaminated soil feeder 25 are provided in the charging section of the contaminated soil a ₁ to the rotary kiln 2, and a treated soil cooler is disposed in the discharge section of the treated soil a ₂ from the rotary kiln 2. 26 and a double damper 27 are provided, and the soil a ₁ and a ₂ that are the objects to be treated can be charged and discharged online while ensuring airtightness in the heating furnace (rotary kiln) 2.

The oxidative decomposition furnace 4 is provided with a burner 41 for adding air as an oxygen-containing gas together with fuel into the rotary kiln exhaust gas b ₁ . The gas cooler 5, the spray nozzles 51 for spraying water directly is provided in the oxidative decomposition furnace exhaust gas b _2.

  Next, a method for detoxifying a chemical agent-contaminated soil using the detoxification processing apparatus will be described with reference to FIG.

Chemical agent-contaminated soil a ₁ that is to be treated includes leucite (CH ₂ ClCHAsCl ₂ ), diphenylchloroarsine ((C ₆ H ₅ ) 2 AsCl), diphenyl cyanoarsine ((C ₆ H ₅ ) ₂ AsCN), etc. The target is soil contaminated with chemical agents containing organic arsenic compounds. In order to increase the removal efficiency of the chemical agent that is a contaminant, it is desirable that the rocks and lump in the contaminated soil a ₁ that is the object to be treated are sieved in advance and crushed or crushed by a crusher or the like. The contaminated soil a ₁ thus pretreated is temporarily held in the contaminated soil receiving hopper 1. Then, the contaminated soil a ₁ is cut out from the contaminated soil receiving hopper 1 and charged into the inner cylinder 22 of the rotary kiln 2 by the contaminated soil supply machine 25 through the double damper 24. Contaminated soil a ₁ was charged into the inner cylinder 22 by the rotation of the inner cylinder 22 sequentially transported to the kiln outlet with stirring, indirectly heated to for example 540 ° C. In the heat of combustion of the burner 23, preferably 900 ° C. The temperature is raised to and maintained at that temperature for at least 15 minutes. Accordingly, the chemical agent adhering to the contaminated soil a ₁ evaporates. The evaporated chemical agent is sucked by the exhaust fan 3 and discharged from the kiln 2. At this time, the inside of the inner cylinder 22 is maintained in an airtight state by the double dampers 24 and 27 and indirect heating is also used for heating, so that oxygen does not enter the inner cylinder 22 and the evaporated chemical agent The arsenic component is not oxidized. Therefore, solid-phase arsenic oxide is not generated, and the arsenic component is discharged from the kiln 2 together with the kiln exhaust gas b ₁ without reattaching to the soil being treated. The treated soil a ₂ from which the chemical agent as a pollutant has been removed and detoxified is cooled to near room temperature by indirect water cooling in the treated soil cooler 26 and then discharged out of the system through the double damper 27. The

In addition, although the contaminated soil a ₁ normally contains water, it is not necessary to dry it when charging the kiln 2. It is desirable to charge with some moisture. That is, the moisture is heated and evaporated in the inner cylinder 21 of the kiln 2 to form an air flow made of water vapor in the inner cylinder 21. As a result, the chemical agent evaporated by heating is discharged out of the kiln 2 on the air stream made of the water vapor, so that the chemical agent can be removed more efficiently. When the water content of the contaminated soil a ₁ is small, it is also preferable to spray water before charging the contaminated soil receiving hopper 1 to prevent dust scattering.

Since the chemical agent vapor in the kiln exhaust gas b ₁ is still harmful, the kiln exhaust gas b ₁ is introduced into the oxidative decomposition furnace 4 and burned by adding air as an oxygen-containing gas together with fuel by the burner 41, for example at 1090 ° C. Oxidative decomposition of chemical vapor at temperature. This detoxifies chemical agents such as mustard ((CH ₂ CH ₂ Cl) ₂ S) that do not contain arsenic, but arsenic oxides generated from chemical agents such as leucite (CH ₂ ClCHAsCl ₂ ) Phase) is toxic. Therefore, the oxidative decomposition furnace exhaust gas b ₂ containing arsenic oxide is introduced into the gas cooler 5, and water is sprayed by the spray nozzle 51 to lower the exhaust gas temperature, thereby condensing the arsenic oxide into a solid phase. . Then, the gas cooler exhaust gas b ₃ containing the solid phase arsenic oxide is passed through the filtration dust collector 6 to remove the arsenic oxide, and a neutralizing agent is added in the exhaust gas cleaning tower. After exhaust gas is cleaned and detoxified, it is released to the atmosphere. The arsenic oxide recovered by the filtering dust collector 6 is mixed with the dust of the soil a ₁ scattered in the kiln 2 along with the exhaust gas, but the amount is very small. Therefore, the mixture of the arsenic oxide and the soil a ₁ recovered by the filtration dust collector 6 is greatly reduced in volume compared to the original contaminated soil a _1. It can be disposed of simply and safely by landfilling in a landfill.

(Modification)
In the above embodiment, the loading / discharging of the soil is performed online, but may be performed in batch. However, in this case, it should be noted that although the double damper is not required on both the charging side and the discharging side, it is easy to ensure airtightness, but the processing capacity is reduced as compared with the above embodiment. Moreover, although air was used as the oxygen-containing gas added to the kiln exhaust gas, oxygen-enriched air or pure oxygen may be used. Moreover, although the filtration-type dust collector was used as a dust collector, you may use a cyclone, an electric dust collector, or what combined these.

  In order to confirm the effect of the present invention, an experiment was conducted in which the chemical agent-contaminated soil containing arsenic was heated in an atmosphere in which oxygen-containing gas was blocked to remove the chemical agent. As the chemical agent-contaminated soil containing arsenic, simulated contaminated soil prepared by mixing about 1 g of diphenylchloroarsine and diphenylcyanoarsine, which is a decomposition product of diphenylchloroarsine, with about 100 g of pure sand soil was used. About 4 g of this simulated contaminated soil was placed on a boat and placed in a small electric heating furnace, and heat-treated in a nitrogen stream at 900 ° C. for 15 minutes. As a result, the arsenic content in the simulated contaminated soil was about 2000 mg / kg soil before the heat treatment, but decreased to about 240 mg / kg soil after the heat treatment, and the arsenic removal rate was about 88 % And a high value were obtained.

It is a schematic explanatory drawing which shows the detoxification processing apparatus of the chemical agent contamination soil which concerns on embodiment.

Explanation of symbols

1: Contaminated soil receiving hopper 2: Heating furnace (rotary kiln)
3: Ventilator 4: Oxidation cracking furnace 5: Gas cooler 6: Dust collector (filter type dust collector)
21: Outer cylinder 22: Inner cylinder 23: Burner 24: Double damper 25: Contaminated soil feeder 26: Treated soil cooler 27: Double damper 41: Burner 51: Spray nozzle a ₁ : Chemical agent contaminated soil a ₂ : Treated soil b ₁ : kiln exhaust gas b ₂ : oxidation cracking furnace exhaust gas b ₃ : gas cooler exhaust gas

Claims (2)

A heating furnace for evaporating and removing the chemical agent by heating the chemical agent-contaminated soil contaminated with a chemical agent containing arsenic in an airtight state where oxygen intrusion is blocked, and the heating and removing the chemical agent removed by evaporation A ventilator for exhausting from the furnace, and further adding an oxygen-containing gas to the heating furnace exhaust gas discharged from the heating furnace between the heating furnace and the exhaust fan to remove the chemical agent removed by evaporation. An oxidative decomposition furnace for oxidative decomposition, a gas cooler for cooling the oxidative decomposition furnace exhaust gas discharged from the oxidative decomposition furnace, and an arsenic oxidation produced by the oxidative decomposition from the gas cooler exhaust gas discharged from the gas cooler A chemical agent-contaminated soil detoxification device comprising a dust collector for removing matter, wherein the chemical agent-contaminated soil is charged into the heating furnace, and the treated soil is discharged from the heating furnace. Each of the heating furnaces The while maintaining the airtight state, the chemical agent contaminated soil, characterized in that the double damper as airtight maintaining means for enabling the discharge of the charging and the processed soil of the chemical agent contaminated soil is provided Detoxification processing equipment. The chemical furnace-contaminated soil detoxification apparatus according to claim 1 , wherein the heating furnace is an externally heated rotary kiln.

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