JP3969372B2 - Organochlorine compound decomposition accelerator and decomposition method - Google Patents

Description

  The present invention is used for dioxins (polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar PCBs), PCBs, polychlorinated ethylenes used as cleaning agents, agricultural chemicals, and the like. Incineration ash, incineration fly ash, molten fly ash, lake and river silt, incineration contaminated with polychlorinated phenols, polychlorinated benzenes, and organic chlorine compounds such as brominated dioxins generated by incineration of flame retardants The present invention relates to a method for decomposing organochlorine compounds that can be applied to detoxification treatment such as furnace demolition residues.

Aromatic organochlorine compounds such as dioxins that are extremely toxic for exhaust gas, fly ash and incineration ash (also called main ash and furnace ash) generated from waste incinerators such as general waste and industrial waste It is included.
In addition, aliphatic organochlorine compounds such as trichlorethylene and tetrachloroethylene are used in a wide range of fields such as degreasing and dry cleaning of metal products such as precision machinery.
Since these organochlorine compounds are toxic, chemically stable, and hardly decomposable, the problem of pollution of air, water, soil, etc. due to their emission is in a serious situation. In particular, it is said that 70 to 80% of the total discharge amount of dioxins is discharged from a waste incinerator, most of which is discharged in the state contained in fly ash. The fly ash generated by incineration of waste contains dioxins. Therefore, the soil around the waste incineration plant may be contaminated by the fall of fly ash contained in the exhaust gas discharged from the chimney. In order to prevent the accumulation of dioxins in the environment, it is necessary to decompose and detoxify the dioxins in the waste incineration fly ash generated every day. In addition, PCBs that were once used as stable insulating oil may contaminate soil due to leakage or the like in factories that manufacture or use electrical equipment.

Conventionally, various methods have been proposed as techniques for decomposing and detoxifying organochlorine compounds contained in fly ash and soil.
(1) A method of heating fly ash directly under a flow-through system under oxygen-deficient conditions has been proposed (see, for example, Patent Document 1).
(2) A method of heating the fly ash by adding an amine compound has been proposed (see, for example, Patent Documents 2 and 3).
(3) A method in which a substance containing an organic substance is added to and mixed with a solid substance contaminated with an aromatic halogen compound, and the mixture is heated to 300 ° C. to 450 ° C. to decompose the aromatic halogen compound. The substance containing the organic compound is selected from humus soil, compost, powdered starch or sucrose, sodium formate, formic acid water, or the like (see, for example, Patent Document 4).
Japanese Patent Publication No. 6-38863 Japanese Patent No. 3287298 Japanese Patent No. 3287301 JP-A-8-52454

However, the prior art has the following problems.
In the method (1), sufficient decomposition of dioxins cannot be achieved unless an oxygen-deficient state is established. In order to establish an oxygen-deficient state, the reactor is a closed system that prevents air from entering, and in order to replace the intruding air inside the reactor, an inert gas supply facility such as nitrogen is required. This causes an increase in equipment costs. The method (1) is a technique for decomposing dioxins using a part of the transition metal salt contained in the fly ash as a catalyst, which decomposes at a lower temperature than when dioxins are thermally decomposed alone. Can be achieved. However, in order to advance the decomposition reaction of dioxins, it is necessary to contact the dioxins with the catalyst. However, in the method (1), the hardly volatile dioxins and the metal salt acting as the decomposition catalyst are both fly ash. Since they are mixed inside the particles, there is a problem that the contact efficiency between them is low and the decomposition reaction does not easily proceed. In general, it is difficult to achieve sufficient contact efficiency in a solid-solid reaction.

  In addition, organochlorine compounds typified by dioxins contained in objects to be treated such as fly ash are chemically stable, and heat treatment at a high temperature is necessary to compensate for the low contact efficiency described above. Generally, in order to sufficiently decompose fly ash dioxins generated by incineration of waste, a reaction temperature of 400 ° C. or higher, preferably about 450 ° C., and a reaction time of about 30 minutes or longer are required. On the other hand, fly ash generated by incineration of waste contains high concentrations of salts such as sodium chloride, potassium chloride, and calcium chloride. In steel materials, as shown in FIG. 1, it is known that corrosion caused by salts in fly ash is accelerated at a temperature range of 400 ° C. or higher. Therefore, in the method (1), there is a problem that the maintenance cost is greatly increased due to corrosion of the equipment.

  Furthermore, alkali metal chlorides such as sodium chloride have a low melting point, and the above-described method may cause troubles such as sticking and discharge failure due to melting of fly ash that is a treatment product inside the reactor. Compared with general incineration fly ash, gasification melted fly ash and molten fly ash generated by melting of ash have a higher alkali metal chloride concentration and are particularly likely to cause similar troubles.

  In the method (1), dioxins are detoxified by dechlorination reaction, but if the treated fly ash after the reaction is discharged out of the system as it is and then slowly cooled, the dioxin inherent in fly ash Dioxins may be re-synthesized due to synthesis ability. Therefore, generally, a method of quenching by providing a cooler after the reactor is employed. However, due to the effect of moisture adsorbed on the fly ash, which is the raw material, the atmospheric gas inside the reactor is highly humid, so condensation occurs inside the cooler, which also causes sticking of fly ash and corrosion problems of the equipment. There was a risk of inviting.

  The amine compound proposed in the prior art (2) is capable of efficiently decomposing dioxins in a material to be treated such as fly ash under mild temperature conditions of high temperature corrosion of steel materials by chloride. Is possible. However, due to the chemicals used and their decomposition products, the exhaust gas and the treated fly ash will generate a specific odor. Moreover, generation | occurrence | production of the tar-like decomposition product is also seen. Therefore, it is necessary that the exhaust gas from the heat treatment apparatus for fly ash be led to the combustion chamber of the incinerator using a duct kept warm enough to prevent the tar components from condensing, so that the odor components can be oxidatively decomposed.

  Of the substances containing organic substances described in the prior art (3), sodium formate exhibits an effective promoting action on the decomposition of some fly ash dioxins. However, for the purpose of removing hydrochloric acid gas contained in the exhaust gas, fine powdery calcium-based neutralizing agent is sprayed on the flue upstream of the dust collector, and fine powdery activated carbon or fine powdery active coke is used for the purpose of adsorption removal of gas phase dioxins. In the case of fly ash containing calcium chloride and activated carbon, which are reaction products, or fly ash generated from an ash melting furnace in the dust collection fly ash, the formic acid is added and heated to 300 to 450 by heat treatment. It was found that it was difficult to decompose dioxins in the temperature range of 0 ° C., and as shown in Comparative Example 3 described later, the resynthesis was promoted to significantly increase the dioxins concentration.

  The present invention has been made in view of the above circumstances, and a method for decomposing an organic chlorine compound capable of decomposing an organic chlorine compound such as dioxins at a high decomposition rate even if it is an object to be treated such as activated carbon or activated coke. The purpose is to provide.

In order to achieve the above object, the present invention is a method for decomposing an organic chlorine compound contained in a material to be treated by heating the material containing carbon, wherein calcium is added to the material as a neutralizing agent. Without adding an alkali metal salt by spraying into flue exhaust gas, and adding an alkali metal salt of a carboxylic acid having 1 to 3 carbon atoms as an organic chlorine compound decomposition accelerator, Provided is a method for decomposing an organochlorine compound, characterized by heating.
In the method of the present invention, the carbon is preferably activated carbon or activated coke added to an object to be treated as an adsorbent for an organic chlorine compound.
In the method of the present invention, the neutralizing agent may be one or more selected from the group consisting of sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, potassium carbonate, potassium hydrogen carbonate, and potassium hydroxide. preferable.
In the method of the present invention, the organochlorine compound decomposition accelerator is preferably one or more selected from the group consisting of sodium formate, potassium formate, sodium acetate, and potassium acetate.
In the method of the present invention, the treatment object to which the neutralizing agent and the organochlorine compound decomposition accelerator are added is a continuous indirect heating kiln reactor, a continuous fluidized bed reactor, a continuous vertical multistage. It is preferable to heat to 200 to 400 ° C. in a pyrolysis reactor selected from the group consisting of a heating furnace reactor, an autoclave, and a batch fluidized bed reactor.
In the method of the present invention, it is preferable to add 1 to 20% by mass of the organochlorine compound decomposition accelerator to the object to be treated.
In the method of the present invention, an anti-caking agent selected from the group consisting of zeolite, porous silica, porous alumina, diatomaceous earth, perlite, calcium carbonate, slaked lime, quicklime, sodium carbonate, and sodium bicarbonate is used as the decomposition accelerator. It may be added.
In the method of the present invention, it is preferable to add the organochlorine compound decomposition accelerator to the object to be treated before heating the object to be treated.
In the method of the present invention, by spraying the decomposition accelerator of the organochlorine compound on the flue at the dust collector inlet for collecting the finely processed object, the object to be processed and the decomposition accelerator are collected together. A decomposition accelerator may be added to and mixed with the workpiece.
In the method of the present invention, when the object to be treated is heated, it is preferable to remove the water vapor evaporated in the thermolysis reaction apparatus by air replacement.
In the present invention, the object to be treated is fly ash generated from waste incineration equipment, incineration ash, gasification fusion fly ash generated in gasification melting equipment, fusion fly ash generated by melting treatment of fly ash or incineration ash It is preferably one or a mixture of two or more selected from the group consisting of

According to the present invention, an alkali metal salt is added as a neutralizing agent to an object to be treated, and an alkali metal salt of a carboxylic acid having 1 to 3 carbon atoms is added as a decomposition accelerator for an organic chlorine compound. Even when treating a carbon-containing material such as activated carbon or activated coke, the re-synthesis of dioxins is prevented, and organic chlorine compounds such as dioxins in the material are efficiently used. Can be decomposed well.
According to the present invention, the dioxins contained in the object to be treated such as fly ash are dechlorinated and detoxified by heat treatment at a temperature of 200 to 400 ° C. for about 30 minutes or less, and a toxic equivalent amount ( Dioxins decomposition rate of 60% or more can be achieved at Toxic Equivalent (TEQ) concentration.
According to the present invention, since the processing temperature is 400 ° C. or lower, high temperature corrosion of steel materials by chloride contained in fly ash can be prevented, and maintenance costs can be reduced. Further, even fly ash having a low melting point due to a high chlorine concentration can be treated in a stable state without causing fixation due to melting.
In addition, even if oxygen is contained in the treatment atmosphere at the time of decomposition, there is little influence on the decomposition of organic chlorinated compounds such as dioxins, so there is no need for the thermal decomposition reaction device to have a sealed structure, and a purge to prevent air intrusion Since the production equipment for the inert gas is not required, the equipment cost can be reduced.
In addition, by allowing air to flow through the thermal decomposition reaction apparatus, it is possible to prevent condensation of moisture that is adsorbed and accompanied by an object to be processed such as fly ash.
In addition, since the decomposition accelerator works effectively even in an oxygen-deficient atmosphere, the reaction temperature can be lowered to 400 ° C. or lower in a sealed apparatus, and a sufficient decomposition rate can be obtained under the conditions of a reaction time of 30 minutes or less.
Since the decomposition accelerator having the poisoning action of the dioxin-producing catalyst in the object to be processed is used, there is no possibility of recombining dioxins without rapidly cooling the object to be processed after the heat treatment.

  The present invention is used for dioxins (polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar PCBs), PCBs, polychlorinated ethylenes used as cleaning agents, agricultural chemicals, and the like. Organic that can be applied to detoxification treatments such as incineration ash, incineration fly ash, molten fly ash, lake and river silt, and incinerator residue from incineration contaminated with organochlorine compounds such as polychlorinated phenol and polychlorinated benzene A method for decomposing chlorine compounds is provided. In particular, in the present invention, dioxins are easily re-synthesized during heat treatment, and even if the object to be treated contains carbon such as activated carbon or activated coke, dioxins are prevented from being re-synthesized and the dioxins are decomposed at a high decomposition rate. It relates to a method capable of performing decomposition. In the following description, the method of the present invention will be described by taking as an example the decomposition treatment of dioxins contained in fly ash such as incineration fly ash, but the method of the present invention is not limited to this, and the above-described various objects to be treated It can be applied to the decomposition treatment of organic chlorine compounds.

As shown in Comparative Example 1 to be described later, the high temperature corrosion of the steel material induced by contact with chloride is mild, and in a temperature range of 400 ° C. or less that does not cause trouble on handling due to melting of fly ash, Moreover, sufficient decomposition of dioxins in the fly ash cannot be achieved only by heat treatment in a period of less than 30 minutes.
Also, in the waste incinerator, waste pyrolysis gasification melting furnace or ash melting furnace, spraying fine activated carbon for the purpose of adsorbing and removing dioxins contained in the exhaust gas, and absorbing and removing hydrochloric acid gas. There are many examples of adopting an exhaust gas treatment method in which a calcium-based neutralizing agent (slaked lime, quicklime, etc.) is sprayed. Fly ash generated in such facilities is collected by a filtration dust collector or an electric dust collector. Such dust collection fly ash contains activated carbon or activated coke and a salt content mainly composed of calcium chloride. The fly ash exhibits remarkable dioxin resynthesis when heat-treated at 200 to 400 ° C. for the purpose of decomposing dioxins. Moreover, it was confirmed that even when sodium formate was added for the purpose of promoting the decomposition of dioxins, the resynthesis of dioxins could not be suppressed due to the influence of calcium chloride, and the decomposition could not be made harmless.
In particular, the incineration fly ash of waste and the molten fly ash generated by melting of ash are produced in an air atmosphere by the action of chlorination catalysts such as copper chloride, which are also contained from the residual carbon and salts contained therein. When heated at a temperature of about 200 to 400 ° C., there are not a few that show a tendency to generate dioxins. Such a production process of dioxins is called resynthesis or denovo synthesis. Incinerated fly ash and molten fly ash, which easily re-synthesize dioxins by simple heating, are dioxin pollutants that are particularly difficult to detoxify.

In the fly ash containing activated carbon or activated coke, in which the re-synthesis of dioxins is remarkable by heating, the present inventors have no fear of high-temperature corrosion of steel materials due to chloride, and have a low temperature of 400 ° C. or less without fixation due to melting. Research was conducted on dioxin degradation-promoting agents capable of efficiently decomposing dioxins even in an oxygen-deficient state.
As a result of research, an alkali metal salt is used instead of calcium-based alkali as a neutralizer for exhaust gas, an alkali metal salt of a carboxylic acid having 1 to 3 carbon atoms is added as a decomposition accelerator, and the mixture is heated to 200 to 400 ° C. Can prevent the re-synthesis of dioxins even when treating carbon-treated materials such as activated carbon or activated coke, and efficiently decompose organic chlorine compounds such as dioxins in the materials to be treated The present invention has been completed.

  In the present invention, as shown in FIG. 1, by heating for less than 30 minutes in a temperature range of 200 to 400 ° C., which is mild against high temperature corrosion of steel materials by chlorides, the activated carbon-containing fly with high re-synthesis ability of dioxins is obtained. It is possible to achieve a sufficient dioxin decomposition rate in ash. Here, the sufficient decomposition rate means a decomposition rate of 60% or more in terms of the decomposition rate based on the toxic equivalent concentration concentration of dioxins.

  In the present invention, various alkali metal salts can be used as the alkali metal salt added to the fly ash as a neutralizing agent, particularly sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, potassium carbonate, potassium hydrogen carbonate, water. One or more selected from the group consisting of potassium oxide are preferred. The neutralizing agent is finely powdered and sprayed into the flue exhaust gas. The spray amount is about 1.2 to 2.5 times equivalent to hydrochloric acid contained in the combustion exhaust gas. If the spray amount of the neutralizing agent is less than the above range, the neutralizing effect of the exhaust gas may be insufficient, which is not preferable. On the other hand, when the spray amount of the neutralizing agent exceeds the above range, the neutralizing effect reaches its peak, which is not preferable because it causes an increase in capacity after treatment with the neutralizing agent and an increase in cost. At this time, the neutralizing agent and its reaction product contained in the collected fly ash are 15 to 80% by mass, and more generally 20 to 60% by mass.

  In the present invention, the alkali metal salt of a carboxylic acid having 1 to 3 carbon atoms added as a decomposition accelerator to fly ash includes carboxylic acid such as formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, acrylic acid, and lactic acid. Can be selected from salts of alkali metals such as sodium and potassium, and from the viewpoint of promoting the decomposition of dioxins, handleability and price, from sodium formate, potassium formate, sodium acetate, potassium acetate 1 type or 2 types or more selected from the group which consists of are preferable, and sodium formate is especially preferable among these. This decomposition accelerator such as sodium formate is preferably finely powdered and added to fly ash. In the following description of the present invention, the decomposition accelerator may be described as sodium formate.

  Usually, the amount of sodium formate added is in the range of 1 to 20% by mass, preferably 3 to 15% by mass with respect to fly ash. If the amount of sodium formate added is less than 1% by mass, the effect of promoting the decomposition of dioxins may be insufficient. Even when sodium formate in an amount exceeding 20% by mass is added, there is no problem in the decomposition of dioxins in the fly ash, but in view of economy, addition of 20% by mass or more is not preferable.

In the present invention, the carbon added as an adsorbent for dioxins in the exhaust gas includes finely divided activated carbon or activated coke. Activated carbon or activated coke is used in fine powder form. The pore diameter is not particularly limited as long as it has a pore size suitable for adsorption of dioxins, and can be appropriately selected from various commercially available products. Usually, activated carbon is sprayed in exhaust gas at a concentration of about 50 to 300 mg / Nm ³ . If the spray amount of the activated carbon is less than the above range, the dioxins adsorption removal rate in the exhaust gas may be insufficient, which is not preferable. On the other hand, when the spray amount of the activated carbon exceeds the above range, the dioxin adsorption removal rate reaches a peak, which causes an increase in dose after treatment with activated carbon and an increase in cost. At this time, the activated carbon contained in the collection fly ash is 1 to 15% by mass, more generally 2 to 10% by mass.

  In this invention, after adding a neutralizer, a decomposition accelerator, activated carbon, and activated coke to fly ash, these are heated at 200-400 degreeC within a thermal decomposition reaction apparatus. This thermal decomposition can be performed in either an oxygen-containing atmosphere or an oxygen-bonded atmosphere.

  In this thermal decomposition, the temperature of the thermal decomposition reactor is in the range of 200 to 400 ° C, preferably in the range of 250 to 400 ° C. By setting the temperature of this thermal decomposition within the above range, as shown in FIG. 1, the thermal decomposition can be performed under a condition where the corrosion rate of the heated portion of the thermal decomposition treatment apparatus is low. If the temperature is lower than the above range, the corrosion rate is high, the reaction rate of dioxins is low, and decomposition may be insufficient. If the temperature exceeds the above range, the corrosion rate becomes high and the equipment maintenance cost becomes high, which is not preferable.

  In this thermal decomposition, the heating time is not particularly limited, but is preferably about 5 to 60 minutes, preferably about 10 to 35 minutes. If the heating time is less than the above range, decomposition of dioxins may be incomplete. If the heating time exceeds the above range, the treatment efficiency is deteriorated, which is not preferable.

  To-be-processed objects such as fly ash exhibit different properties such as the composition of the main component and the content of dioxins depending on the waste quality and incineration conditions during incineration. Therefore, a small amount of fly ash was used in advance to determine the optimal drug mixing ratio of neutralizer, decomposition accelerator, activated carbon, etc. (hereinafter sometimes referred to as drugs) added to fly ash. It is preferable to determine the optimum mixing ratio in a preliminary test. Moreover, you may determine an optimal value also about heating temperature and a heating time by such a preliminary test.

  An apparatus for heating an object to be processed after the addition of a chemical in which an appropriate amount of chemical has been added to the object to be processed such as fly ash need not be strictly defined. For example, it is possible to use a continuous indirect heating kiln reactor, a fluidized bed reactor, a vertical multi-stage furnace reactor, or a batch indirect heating reactor such as an autoclave or a fluidized bed. According to the present invention, decomposition is possible even in an atmosphere in which oxygen is present, and it is not necessary to provide a special mechanism such as preventing air from entering in order to exhibit a sufficient decomposition effect of dioxins. In the present invention, it is advantageous to circulate air for the purpose of preventing moisture condensation at the temperature-lowering site due to partial cooling inside the reactor. Prevention of condensation of moisture adsorbed on fly ash is preferable in preventing corrosion of the apparatus and avoiding problems such as reaction inhibition and emission inhibition due to solidification of fly ash.

  The method of adding sodium formate to fly ash is not strictly defined, and a method of adding it in a transfer line such as a storage tank or a conveyor in front of the heating device can be adopted. In order to obtain a stable decomposition rate of dioxins, it is preferable not only to add sodium formate but also to mix well with fly ash. When adding chemicals to the primary storage tank at the fly ash heating reactor inlet, methods such as mixing with a mechanical stirrer or introducing gas into the storage tank to form a fluidized bed are effective. It is. Moreover, a screw conveyor, a screw feeder, etc. can be utilized as a method of mixing a chemical | medical agent in transfer processes, such as a conveyor. These can stably mix fly ash and chemicals.

  FIG. 2 is a configuration diagram illustrating a first example of a method of adding and mixing sodium bicarbonate as a neutralizing agent and sodium formate as a decomposition accelerator in fly ash (object to be treated) in the method of the present invention. In the first example, a baking soda supply line for spraying baking soda is provided in the middle of a pipe for sending combustion exhaust gas containing fly ash to the dust collector 1, and sodium bicarbonate is sprayed into the incineration exhaust gas. Fly ash, baking soda, and sodium chloride as a reaction product in the incineration exhaust gas are collected by the dust collector 1. Dust collection fly ash collected by the dust collector 1 is sent to the quantitative supply hopper 3 of the thermal decomposition reaction device 4 and mixed with sodium formate quantitatively supplied from the sodium formate quantitative supply hopper 2, in the range of 200 to 400 ° C. Is heated for a certain time in the thermal decomposition reaction apparatus 4 set at a temperature of 1 to decompose dioxins in fly ash. In this first example, the fly ash supply device itself of the thermal decomposition reaction device 4 has a mixing effect, and sodium formate is supplied into the thermal decomposition reaction device 4 and mixed with the dust collection fly ash.

  The place for adding sodium formate is not limited to that shown in FIG. 2. For example, sodium formate may be supplied from the sodium formate quantitative supply hopper 2 to the quantitative supply hopper 3 of the thermal decomposition reaction apparatus 4.

  Furthermore, in the waste incinerator, hydrochloric acid gas is contained in the incineration exhaust gas. As a method for removing this, the present invention is premised on a method in which fine powders such as sodium hydrogen carbonate (sodium bicarbonate) and sodium carbonate are sprayed onto the flue. Yes. Similarly, for the purpose of adsorbing and removing dioxins in the exhaust gas, a method of spraying finely powdered activated carbon or activated coke is employed. In such facilities, sodium formate is sprayed onto the flue along with fine powdered alkali components and activated carbon, and this is collected with a dust collector together with fly ash, and the collected fly ash containing sodium formate is heated to decompose dioxins. The method of leading to can be adopted. In this method, it is not necessary to separately provide a sodium formate supply device or a stirrer in a storage tank or a measuring tank provided at the inlet of the dioxins thermal decomposition apparatus. Therefore, the present invention is particularly suitable for an existing heating apparatus for decomposing fly ash dioxins. This is particularly effective when the drug proposed in (1) is applied.

  FIG. 3 is a block diagram for explaining a second example of a method of spraying and adding sodium bicarbonate as a neutralizing agent and sodium formate as a decomposition accelerator in fly ash (object to be treated). In this method, a line for sending a chemical mixed with sodium bicarbonate, sodium formate, activated carbon and the like is connected to the combustion exhaust duct 8 for sending incineration exhaust gas containing fly ash to the dust collector 1, and the chemical stored in the chemical storage hopper 6 Dust collection in which fly ash, baking soda, activated carbon and sodium formate are mixed by conveying with airflow introduced from blower 7 and supplying a certain amount of fine powdery chemical to combustion exhaust gas duct 8 and collecting with dust collector 1 It becomes fly ash. The dust collection fly ash is sent to the quantitative supply hopper 3 and supplied to the thermal decomposition reaction device 4 in a fixed quantity. The dust collection fly ash supplied to the thermal decomposition reaction apparatus 4 is heated for a certain time in the thermal decomposition reaction apparatus 4 set to a temperature in the range of 200 to 400 ° C. to decompose dioxins in the fly ash.

  In FIG. 3, baking soda, decomposition accelerator, activated carbon, and the like are mixed in advance. However, not limited to this, sodium bicarbonate and the decomposition accelerator are put in separate quantitative supply hoppers. You may make it spray.

  It is also possible to put the neutralizing agent, activated carbon and the like and the decomposition accelerator all in separate quantitative supply hoppers, put them on an air transportation line, and spray them on the flue. In this case, when there is a concern about solidification due to moisture of the dioxin decomposition accelerator, it is advisable to mix a solidification inhibitor in advance.

  When sodium formate is used, when the drug is stored in a supply hopper or the like, the drug may be solidified by moisture in the air. In such a case, if necessary, an anti-caking agent can be added to the drug in advance and used. The anti-caking agent to be added may be any substance that preferentially adsorbs moisture and is effective in adsorbing and solidifying the dioxins decomposition accelerator with moisture, and does not inhibit the dioxins decomposition promoting effect. For example, by using a mixture of zeolite, porous silica, porous alumina, diatomaceous earth, pearlite, calcium carbonate, slaked lime, quicklime, sodium carbonate, sodium hydrogen carbonate, etc., preventing solidification caused by moisture in the air Is possible.

  The mixing rate of the anti-caking agent is not strictly defined, but when mixing at the inlet of the dioxin heat decomposition apparatus, the mixing rate of the anti-caking agent is 1 to 30 with respect to the dioxin-decomposing agent. It is 1 mass%, Preferably it is 1-20 mass%, More preferably, it is 1-10 mass%. The increase in the mixing ratio of the anti-caking agent exceeding 30% by mass and the anti-caking effect due to moisture are not in a first-order proportional relationship, and when the mixing ratio exceeds a certain level, the improvement in the anti-caking effect reaches equilibrium. From such a viewpoint, a mixing ratio exceeding 30% by mass is not preferable. Furthermore, since the greatest merit of incineration in the waste treatment technology is volume reduction, it is not preferable to mix more than necessary anti-caking agent into fly ash.

  When spraying sodium formate on the flue, it is preferable to use it in advance mixed with a neutralizing agent for removing hydrochloric acid contained in the exhaust gas or finely powdered activated carbon for adsorbing and removing gas phase dioxins. This is because sodium-based neutralizers for absorbing hydrochloric acid and activated carbon for gas phase dioxin adsorption also act as anti-caking agents for fly ash dioxin decomposition accelerators. In this case, the addition amount of the decomposition accelerator can be determined according to the amount of collected fly ash, and the mixing ratio of the neutralizing agent can be determined according to the hydrochloric acid gas concentration. Use of a neutralizing agent or finely powdered activated carbon as an anti-caking agent for sodium formate is preferable without incurring excessive fly ash increase.

Sodium formate undergoes a dechlorination reaction efficiently even in an oxygen-containing atmosphere. It is possible to prevent condensation of moisture brought in by adsorbing to the fly ash by substituting the inside of the thermal decomposition apparatus for dioxins with air.
Furthermore, since the re-synthesis reaction of dioxins is suppressed, the concentration of dioxins does not increase without rapid cooling of the treated fly ash, which is effective as a detoxification technique for dioxins.

According to this method, a neutralizer such as sodium bicarbonate is added to fly ash, a decomposition accelerator such as sodium formate is added, and the fly ash containing activated carbon is treated by heating to 200 to 400 ° C. Even so, re-synthesis of dioxins is prevented, and dioxins in fly ash can be efficiently decomposed.
According to this method, the dioxins contained in the fly ash are dechlorinated and detoxified by heating at a temperature of 200 to 400 ° C. for about 30 minutes or less, and the toxic equivalent (TEQ) concentration is 60. % Of dioxins decomposition rate can be achieved.
According to this method, since the treatment temperature is 400 ° C. or less, high-temperature corrosion of the steel material due to chloride contained in fly ash can be prevented, and maintenance costs can be reduced. Further, even fly ash having a low melting point due to a high chlorine concentration can be treated in a stable state without causing fixation due to melting.
In addition, even if oxygen is contained in the treatment atmosphere at the time of decomposition, there is little influence on the decomposition of dioxins, etc., so there is no need for the heat decomposition reaction apparatus to have a sealed structure, and an inert gas for purging to prevent air from entering Since no manufacturing equipment is required, the equipment cost can be reduced.
Further, by allowing air to flow through the thermal decomposition reaction apparatus, it is possible to prevent condensation of moisture adsorbed and accompanied by fly ash.
In addition, since the decomposition accelerator works effectively even in an oxygen-deficient atmosphere, the reaction temperature can be lowered to 400 ° C. or lower in a sealed apparatus, and a sufficient decomposition rate can be obtained under the conditions of a reaction time of 30 minutes or less.
Since sodium formate having the poisoning action of the dioxins production catalyst in the fly ash is used, there is no possibility of recombining dioxins without quenching the fly ash after the heat treatment.

  The following sample fly ash was prepared, and sample fly ash alone or 5% by mass of sodium formate was added thereto, followed by heat treatment at 350 ° C. for 10 minutes.

(1) Raw material fly ash Neutral fly ash, which was collected from a stoker furnace type municipal waste incinerator operated continuously for 24 hours and was not sprayed with a neutralizing agent for chlorine gas treatment, was used as the raw fly ash. Furthermore, since this facility does not perform activated carbon spraying on exhaust gas, the fly ash does not contain activated carbon.
Table 1 shows the main component composition and dioxin concentration of the raw fly ash.

(2) Sample preparation Add calcium chloride corresponding to the reaction product when calcium-based neutralizer is used as raw material fly ash as neutralizer, or to reaction product when sodium-based neutralizer is used Corresponding sodium chloride was added, and activated carbon as a carbon source was added to each of the two types of samples. 1 and 2 fly ash was prepared and a heating experiment was conducted. The heating reactor is open to the atmosphere and is not purged with an inert gas such as nitrogen gas. Therefore, the reaction field is basically an air atmosphere.

(3) Experimental results <Comparative example 1>
The raw fly ash was heat-treated at 350 ° C. for 10 minutes without adding any chemicals. As a result, the concentration of dioxins in the fly ash after the treatment was 4.1 ng-TEQ / g, a decomposition rate of 21.8%, and a sufficient decomposition rate of dioxins could not be obtained.

<Comparative example 2>
Sample No. No. 1 fly ash was heat-treated at 350 ° C. for 10 minutes without adding any chemicals. As a result, the dioxins concentration of the fly ash after the treatment was 30 ng-TEQ / g (the raw fly ash was 5.2 ng-TEQ / g), and a large increase was observed due to resynthesis.

<Comparative Example 3>
Sample No. 5 mass% of sodium formate was added to 1 fly ash and heat-treated at 350 ° C. for 10 minutes. As a result, the concentration of dioxins in the fly ash after treatment was 23 ng-TEQ / g (the raw fly ash was 5.2 ng-TEQ / g), and a large increase was observed due to resynthesis. Thus, in the fly ash containing calcium chloride that is a reaction product of activated carbon and hydrochloric acid of a calcium-based neutralizer, sodium formate cannot exhibit an effective dioxin decomposition effect.

<Comparative example 4>
Sample No. 1 mass% of sodium acetate was added to the fly ash, and heat treatment was performed at 350 ° C. for 10 minutes. As a result, the dioxins concentration of the fly ash after the treatment was 20 ng-TEQ / g (the raw fly ash was 5.2 ng-TEQ / g), and a large increase due to resynthesis was observed. Thus, in fly ash containing calcium chloride, which is a reaction product of activated carbon and hydrochloric acid of a calcium-based neutralizer, sodium acetate cannot exert an effective dioxin decomposition effect.

<Comparative Example 5>
Sample No. No. 2 fly ash was heat-treated at 350 ° C. for 10 minutes without adding any chemicals. As a result, the concentration of dioxins in the fly ash after treatment was 23 ng-TEQ / g (the raw fly ash was 5.2 ng-TEQ / g), and a large increase was observed due to resynthesis.

<Example 1>
Sample No. 2 mass% of sodium formate was added to the fly ash of No. 2 and heat-treated at 350 ° C. for 10 minutes. As a result, the concentration of dioxins in the fly ash after treatment was 0.12 ng-TEQ / g (the raw fly ash was 5.2 ng-TEQ / g), and a decomposition rate of 96% of dioxins was obtained. In this way, even for fly ash containing activated carbon, the neutralizing agent for absorbing hydrochloric acid is changed to sodium, and heat treatment is performed by adding sodium formate as a decomposition accelerator to re-synthesize dioxins. It became possible to decompose dioxins at a high decomposition rate while preventing the above.

<Example 2>
Sample No. 2 mass% of sodium acetate was added to the fly ash of No. 2 and heat-treated at 350 ° C. for 10 minutes. As a result, the dioxins concentration of the fly ash after the treatment was 0.26 ng-TEQ / g (the raw fly ash was 5.2 ng-TEQ / g), and a decomposition rate of 91% of dioxins was obtained. In this way, even for fly ash containing activated carbon, the neutralizing agent for absorbing hydrochloric acid is changed to sodium, and heat treatment is performed by adding sodium acetate as a decomposition accelerator to re-synthesize dioxins. It became possible to decompose dioxins at a high decomposition rate while preventing the above.

It is a graph which shows the relationship between the temperature of steel materials in the presence of chloride, and the corrosion rate. It is a block diagram which shows the 1st example of the method of adding a neutralizing agent and a decomposition accelerator to fly ash in this invention. It is a block diagram which shows the 2nd example of the method of adding a neutralizing agent and a decomposition accelerator to fly ash in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dust collector 2 Sodium formate fixed supply hopper 3 Fixed supply hopper 4 Thermal decomposition reaction device 5 Mixing part 6 Chemical storage hopper 7 Blower 8 Incineration exhaust gas duct

Claims (11)

A method of decomposing an organochlorine compound contained in a treatment object by heating the treatment object containing carbon,
While not adding calcium as a neutralizing agent to the object to be treated , an alkali metal salt is sprayed and added to flue exhaust gas, and an alkali of a carboxylic acid having 1 to 3 carbon atoms as an organic chlorine compound decomposition accelerator. A method for decomposing an organochlorine compound, comprising adding a metal salt and heating to 200 to 400 ° C.   2. The method for decomposing an organic chlorine compound according to claim 1, wherein the carbon is activated carbon or activated coke added to an object to be treated as an adsorbent for the organic chlorine compound.   The neutralizing agent is one or more selected from the group consisting of sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, potassium carbonate, potassium hydrogen carbonate, and potassium hydroxide. 2. The method for decomposing organochlorine compounds according to 2.   The decomposition accelerator for the organic chlorine compound is one or two or more selected from the group consisting of sodium formate, potassium formate, sodium acetate, and potassium acetate. Of decomposition of organochlorine compounds.   An object to be treated to which the neutralizing agent and an organic chlorine compound decomposition accelerator are added is a continuous indirect heating kiln reactor, a continuous fluidized bed reactor, a continuous vertical multi-stage heating furnace reactor, The organochlorine compound according to any one of claims 1 to 4, wherein the organochlorine compound is heated to 200 to 400 ° C in a thermolysis reactor selected from the group consisting of an autoclave and a batch fluidized bed reactor. Disassembly method.   The method for decomposing an organic chlorine compound according to any one of claims 1 to 5, wherein 1 to 20% by mass of a decomposition accelerator for the organic chlorine compound is added to the object to be treated.   A solidification inhibitor selected from the group consisting of zeolite, porous silica, porous alumina, diatomaceous earth, pearlite, calcium carbonate, slaked lime, quicklime, sodium carbonate, and sodium bicarbonate is added to the decomposition accelerator. The decomposition | disassembly method of the organochlorine compound in any one of Claims 1-6.   The method for decomposing an organic chlorine compound according to any one of claims 1 to 7, wherein a decomposition accelerator for the organic chlorine compound is added to the object to be processed before the object to be processed is heated.   Spraying the decomposition accelerator of the organochlorine compound onto the flue at the dust collector inlet that collects the finely processed material to be processed, and collecting the processed material and the decomposition accelerator together to accelerate the decomposition of the processed material The method for decomposing an organochlorine compound according to any one of claims 1 to 8, wherein an agent is added and mixed.   The method for decomposing an organic chlorine compound according to any one of claims 1 to 9, wherein when the object to be treated is heated, water vapor evaporated in the thermal decomposition reaction apparatus is replaced with air.   From the group consisting of the fly ash generated from waste incineration equipment, incineration ash, gasification fusion fly ash generated in gasification melting equipment, fly ash or fusion fly ash generated by melting treatment of incineration ash It is a 1 type, or 2 or more types of mixture selected, The decomposition | disassembly method of the organochlorine compound in any one of Claims 1-10 characterized by the above-mentioned.

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