JP5618606B2 - Plasma melt decomposition method for processing object - Google Patents

Description

  The present invention relates to a plasma melt decomposition processing method in which a processing object such as PCB contaminants is decomposed in a batch manner by air plasma.

  PCB (polychlorinated biphenyl) was once used in insulating oils for electrical equipment such as transformers, condensers and fluorescent ballasts, and heat media such as boilers, but it is currently toxic and persistent. The use of PCB is prohibited, and PCB contamination is being detoxified.

As one of the PCB contaminant detoxification methods, there is a plasma melt decomposition method in which PCB contaminants are decomposed by air plasma (see, for example, Patent Documents 1 and 2).
There are various types of PCB contaminants, such as sludge, waste, pressure-sensitive copying paper, waste activated carbon, and chemical protective clothing. These PCB contaminants are enclosed in a carry-in storage container. And is refilled into a predetermined charging container for each type before the plasma melt decomposition treatment. Then, the charging container is put into a plasma melting and decomposing furnace in units of cans, and decomposed in batch by air plasma.

  However, since the plasma melt decomposition process is performed in a batch manner as described above, there is a problem that the process efficiency is inevitably low and the process time is long. In addition, the amount of gas generated when processing an object to be processed varies greatly depending on the type of object to be processed, but the exhaust treatment facility for processing the gas needs to be a facility corresponding to the maximum amount generated, There was also a problem that the specifications were too large for the average generation amount.

JP 2006-297233 A JP 2007-296415 A

  The problem to be solved by the present invention is to improve the processing efficiency and shorten the processing time in the plasma melt decomposition processing of the processing object performed in a batch system.

  Furthermore, it is intended to reduce the maximum amount of gas generated during the plasma melting decomposition process and to reduce the scale of the exhaust treatment facility.

  In order to solve the above-mentioned problems, the present inventor roughly classifies the object to be decomposed by the plasma melting / decomposing method by melting and decomposing by the transfer of thermal energy mediated by high-temperature plasma, that is, Focusing on the fact that the decomposition process is controlled by the melt rate and the one that is processed by oxidative decomposition rather than melt decomposition because it is firmly bonded at the atomic level, that is, the decomposition process is based on the oxygen supply rate control, By mixing and processing the melt-rate-controlled process object and the oxygen supply-controlled process object, the process by melt decomposition and the process by oxidative decomposition proceed in parallel, improving the processing efficiency compared to individual processing As a result, the present invention has been completed.

  That is, according to the present invention, in a plasma melt decomposition method in which an object to be processed is decomposed batchwise by air plasma, the object to be decomposed is controlled at a melting rate (hereinafter referred to as “melt rate controlled object”), and the decomposition process. Is characterized by being mixed with an oxygen supply rate-determined object to be treated (hereinafter referred to as “oxygen supply rate-determined product”) for decomposition treatment.

Specifically, the plasma melting / decomposing equipment has independent melting / decomposing capability (kg / h) for subjecting the object to be processed to oxidative decomposition (kg / h) for oxidizing / decomposing the object to be processed. Therefore, the melting rate-determining product and the oxygen supply rate-limiting product are mixed and decomposed according to each processing capability . As a result, the processing object can be decomposed by making the best use of the capabilities of each of the plasma melting decomposition processing facilities, so that the processing efficiency is improved.

  More specifically, in the present invention, for example, in the case of a plasma melt decomposition processing facility having a plasma torch with an output of about 1500 kW, a melt rate rate limiting material including auxiliary materials is 30 kg to 120 kg / batch, an oxygen supply rate limiting material (such as waste activated carbon) ) Is preferably mixed in the range of 10 kg to 50 kg / batch. In addition, some oxygen-limited substances (cellulose, olefin polymer compounds) are thermally decomposed and gasified at the start of the treatment, so these are limited to be mixed at 10 kg / batch or less to produce plasma. The exhaust treatment facility at the latter stage of the melt decomposition treatment facility can be made compact.

The present invention mainly treats PCB contaminants as processing objects. Among the PCB contaminants, those that are controlled by the melting rate are fluorescent lamp stabilizers (mainly iron), inorganic sludge (mainly silica), bushings (mainly alumina), etc. with many metal components. It also includes limestone and silica sand necessary to adjust basicity. Examples of oxygen supply rate-limiting products include waste activated carbon, pressure-sensitive copying paper (mainly cellulose), and waste petrochemical products (mainly olefin polymer compounds) such as protective clothing. Among the oxygen supply rate-determined products, waste activated carbon is decomposed by the carbon oxidation reaction (C + O ₂ → CO ₂ ) on the solid surface, which is a typical example of oxygen supply rate-determined products. The processing speed does not increase in proportion to the input of thermal energy. On the other hand, cellulose and olefin-based polymer compounds are pyrolyzed and gasified at the start of the treatment, and the generated gas is discharged out of the plasma melt decomposition treatment furnace, but about 20% remains in the furnace as carbides. This carbide shows the same behavior as waste activated carbon. Furthermore, the fluorescent lamp ballast is a mixture of a melting rate-controlling component (metal component) and an oxygen supply-controlling component, and the melt decomposition treatment and the oxidative decomposition treatment are performed independently, but the processing time is the main component of the metal component. Therefore, the melt decomposition treatment is a rate-determining product.

  As described above, in the present specification, in the plasma melt decomposition process, a component to be melt-decomposed is referred to as a “melt rate-determining component”, and a component to be subjected to an oxidative decomposition process is referred to as an “oxygen supply-determining component”. A processing object that is a mixture and whose decomposition treatment is rate-determined by the melting rate as a whole is referred to as a “melting rate-determining item”, and a processing object that has an oxygen supply rate-determining process is referred to as an “oxygen supply-limiting item”.

  In the present invention, in addition to PCB contaminants, hazardous substances including asbestos, medical waste, or radioactive waste can be treated.

  In the present invention, the melt rate-controlling material and the oxygen supply rate-controlling material are mixed to be the total number of batches (for example, if the melt rate-controlling material before mixing is for 2 batches and the oxygen supply rate-controlling material is for 2 batches, By processing in an input container so that the total amount is 4 batches), the processing by melt decomposition and the processing by oxidative decomposition are not rate-limiting to each other, and the processing efficiency is improved since the process proceeds in parallel. Processing can be performed in a shorter time than adding the time required for processing.

Further, conventionally, when individually processing the melt rate-controlled product and the oxygen supply-controlled product, thermal energy is not effectively used when processing the oxygen supply-controlled product, but in the case of the mixing process of the present invention, the heat energy is melt-rate controlled product. Because it is used for the treatment of heat, the thermal energy can always be used effectively.
Further, when the mixing process as described above is performed, the maximum generation time of the gas accompanying the decomposition process after the start of the process differs due to the difference in the reaction form (decomposition process form) of the mixed processing objects. Therefore, compared with the case where the entire amount of a single processing object is processed, the maximum amount of gas generated is reduced, so that the maximum processing capacity of the exhaust gas processing facility can be reduced, and the scale of the exhaust processing facility can be reduced.

It is a figure which shows the flow of the plasma melt decomposition processing method by this invention. It is a conceptual diagram which shows the progress process of the plasma melt decomposition process of this invention. It is a conceptual diagram which shows the progress process of the plasma melt decomposition process of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to an example in which a PCB contaminant is processed as a processing target by plasma melting and decomposition.

  FIG. 1 is a diagram showing a flow of a plasma melting decomposition processing method according to the present invention. The PCB contamination whose decomposition treatment is controlled by the melting rate and the oxygen supply rate is carried in and stored in a PCB processing facility in a state of being enclosed in a carry-in storage container. These carry-in storage containers are carried into a pretreatment facility in the PCB treatment facility before the plasma melting decomposition treatment. In the pretreatment facility, the carrying-in storage container is opened, and after confirming the contents, the melting rate-determining rate and oxygen supply rate-determined PCB contaminants are refilled into the charging vessel so as to have a predetermined mixing ratio. In other words, the melted rate-limited and oxygen supply-limited PCB contaminants are mixed at a predetermined ratio. Thereafter, the charging container is put into a plasma melting and decomposing furnace and decomposed batchwise by air plasma. This detoxifies PCB contaminants. Gas generated by the decomposition process and decomposition residue slag are discharged from the plasma melting and decomposition furnace. The gas is released into the atmosphere after being subjected to a predetermined treatment in the exhaust gas treatment facility.

  As described above, in the present invention, the plasma melt decomposition treatment is performed by mixing the object to be processed (PCB contamination) having the rate-determined rate and the rate of oxygen supply. FIG. 2 is a conceptual diagram showing the progress of the plasma melt decomposition process of the present invention. In FIG. 2, a melting rate-limiting component (iron, calcium, silicon, aluminum, etc.) is indicated as “component A”, and an oxygen supply rate-limiting component (activated carbon, polymer compound, etc.) is indicated as “component B”.

  Component A and component B have different decomposition mechanisms in the plasma melting decomposition process. That is, component A is melt decomposed, component B is oxidatively decomposed, and these decomposition reactions proceed independently of each other. Therefore, when component A and component B are mixed, the melt decomposition process and the oxidative decomposition process proceed in parallel. In FIG. 2, the time zone in which the decomposition processing of component A and component B proceeds in parallel is indicated by cross diagonal lines, and the processing time can be shortened by that amount compared to the case where component A and component B are processed individually. .

  On the other hand, since component A is rate controlled by the melting rate, in other words, rate of heat transfer, the decomposition reaction proceeds gradually and no pyrolysis gas is generated. On the other hand, the component “B ′ = about 80% by mass of component B” such as a polymer compound in component B that undergoes thermal decomposition and gasification undergoes rapid thermal decomposition and gasification reaction in the air plasma at an early stage. The gas generation amount reaches a peak at the initial stage. Thereafter, the decomposition reaction of the residue containing carbon as a main component (about 20% by mass of component B) becomes the rate of oxygen supply. Strictly speaking, a residue (“component B-component B ′”) containing this carbon component as a main component is an “oxygen supply rate-determining component”.

  Conventionally, the processing object containing these component A and component B is individually put into a charging container and subjected to batch-type plasma melting decomposition treatment. For example, a processing object whose main component is component B ( When an oxygen supply rate-determined product) is processed, and then a processing object whose main component is component A (melting rate-controlled product) is processed, the amount of gas generated is as shown in the upper part of FIG. The initial stage of processing peaks. Therefore, the processing capacity of the exhaust treatment facility for treating the exhaust gas from the plasma melting decomposition treatment furnace needs to be able to cope with the gas generation amount at the peak.

  On the other hand, in the present invention, the melt rate-controlling material (component A) and the oxygen supply rate-controlling material (component B) are mixed and processed. For example, the melting rate-controlling material (component A) and the oxygen supply rate-controlling material (component B) ) Are mixed by half of the conventional method, and the peak value of the gas generation amount is about half that of the conventional method, as shown in the lower part of FIG. This is because, as described above, the component A and the component B are different in the maximum gas generation time after the start of processing, and therefore, gas generation basically does not overlap during the mixing process. Thus, in the method of the present invention, the peak value of the gas generation amount can be lowered as compared with the conventional method, so that the maximum processing capacity of the exhaust treatment facility can be reduced and the scale of the exhaust treatment facility can be reduced.

  Further, as described in FIG. 2, when the melting rate-controlling material (component A) and the oxygen supply-controlling material (component B) are mixed, the decomposition process proceeds in parallel. The total processing time of the melt rate-controlled product (component A) and the oxygen supply controlled product (component B) is shorter in the method of the present invention than in the conventional method.

  In addition, the mixing ratio of the melt rate-controlling material (component A) and the oxygen supply rate-controlling material (component B) is appropriately determined depending on the generation amount, specific type / characteristics, etc., but from the viewpoint of shortening the processing time. It is optimal to mix at a rate such that the processing time of component A during processing and the processing time of component B (strictly, “component B-component B ′”) are equal.

  Comparison of processing time when 60 kg of fluorescent light ballast is used as the melting rate-controlling material (PCB contaminant) and 44 kg of waste activated carbon is used as the oxygen supply-controlling material (PCB contamination) by plasma melting and decomposition using the method of the present invention and the conventional method. did.

  In the method of the present invention, 30 kg of fluorescent lamp stabilizers and 22 kg of waste activated carbon were packed in each can of the input container, and were processed in two steps. The processing time per can was 24 minutes, and processing was possible in a total of 48 minutes.

  On the other hand, in the conventional method, 60 kg of the fluorescent lamp stabilizer and 44 kg of the waste activated carbon are packed in separate charging containers, and individually processed. The treatment time of 60 kg of the fluorescent lamp stabilizer was 30 minutes, and the treatment time of 44 kg of the waste activated carbon was 38 minutes, which took a total of 68 minutes.

  As described above, in the method of the present invention, the processing time can be shortened by 20 minutes. In other words, the ability is improved by 1.4 times.

  Next, the optimum mixing ratio of the fluorescent lamp stabilizer and the waste activated carbon was examined. Therefore, the fluorescent lamp ballast and the waste activated carbon were each treated in the manner shown in Table 1.

  The fluorescent light ballast was processed in a single batch drum by mixing 60 kg alone with a basicity adjusting agent. In this case, the melt rate-limiting component was 80 kg, and the oxygen supply rate-limiting component (carbide base after pyrolysis gasification, that is, the above-mentioned “component B-component B ′”) was 6.7 kg, which was processed in 30 minutes. Here, melting rate-controlling component = fluorescent lamp ballast 60 kg × melting component 43.5% + basicity adjusting agent 54 kg = 80 kg, oxygen supply rate-limiting component = fluorescent lamp ballast 60 kg × combustible component 56% × carbide migration 20% = 6.7 kg, pyrolysis gasification component = 60 kg × combustible component 56% × 80% = 26.9 kg.

  On the other hand, in the treatment of waste activated carbon, it was confirmed that 35 kg was packed in one batch and oxidative decomposition treatment was performed in 30 minutes. That is, the processing time is 30 minutes ÷ 35 kg = 0.857 minutes / kg.

  From the result of this waste activated carbon treatment, the time required for processing one batch of the fluorescent lamp ballast is 30 minutes for the melting rate-controlling component, and the time required for processing the oxygen supply-controlling component is 0.857 × 6. It can be seen that 0.7 kg = 5.7 minutes. Therefore, the optimum mixing ratio when processing 60 kg of the fluorescent lamp ballast is the ratio of mixing the oxygen supply rate-limiting component of 30−5.7 = 24.3 minutes. That is, it is optimal to mix 24.3 ÷ 0.857 = 28.3 kg of waste activated carbon with 60 kg of a fluorescent lamp stabilizer.

  As mentioned above, although the example which processes PCB contaminant as a process target object was demonstrated, the characteristic of this invention exists in carrying out the mixing process of a melting rate rate-control thing and an oxygen supply rate-control thing, and a process target object is PCB contaminant. It is not limited to. For example, in the case where the object to be treated contains harmful substances such as asbestos, medical waste, radioactive waste, etc., it can be decomposed by mixing the melting rate rate-limiting material and the oxygen supply rate-limiting material.

Claims (3)

In a plasma melt decomposition process method in which a processing object that has been refilled into an input container and charged into a plasma melting cracking furnace in units of one can is batch-processed with air plasma and slag is discharged , the cracking is controlled at a melting rate. a processing object, the decomposition process in accordance with the melt decomposition treatment capability of the processing object of the oxygen supply rate-limiting plasma melting decomposition treatment facility (kg / h) and the oxidative decomposition treatment capability (kg / h), the decomposition process is melted The rate-controlled process target is 30 kg to 120 kg / batch, and the decomposition process is oxygen supply-controlled process target is refilled into the input container so that the mixing rate is 10 kg to 50 kg / batch, mixed and decomposed , and decomposed. Plasma melt decomposition treatment is performed batch-wise by placing the processing object whose melting rate is controlled by the treatment and the processing object whose decomposition treatment is the oxygen supply-controlled treatment, respectively, into an input container. Plasma melting cracking process of the processing object, characterized in that to be able to carry out the process in a shorter time than adding the required time that. Plasma melting cracking process of the processing object according to claim 1, wherein the processing object is a PCB contaminant. The method for plasma melting and decomposing a processing target according to claim 1 , wherein the processing target is a harmful substance including asbestos, medical waste, or radioactive waste.

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