JP2023183054A - Detoxification treatment method of low concentration pcb waste - Google Patents

Abstract

To provide a treatment method of low concentration PCB waste capable of applying detoxification treatment to various types of low concentration PCB waste by stably securing combustion temperature of 1,100°C or higher and retention time.SOLUTION: A treatment method of PCB waste includes: a heating step of heating waste containing PCB to evaporate PCB from PCB waste; and an exhaust gas processing step of heating exhaust gas discharged by the heating step to detoxify the exhaust gas. In the heating step, a refractory material is supplied together with the PCB waste to a rotary combustion furnace.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a method for treating PCB-containing waste for rendering low-concentration PCB waste harmless.

PCB (polychlorinated biphenyls) has excellent heat resistance, insulation properties, and is difficult to decompose, so it was once widely used as insulating oil, etc. However, due to its high toxicity to the human body and the environment, it is no longer manufactured. , import and use are prohibited. Furthermore, according to the PCB Special Measures Law, existing equipment that uses PCBs must be rendered harmless and disposed of by March 2027.

Conventionally, PCB waste has been treated by solvent cleaning or vacuum heating separation. For example, Patent Document 1 discloses a method for decomposing liquid or solid waste containing low concentration PCBs at 850° C. or higher to render them harmless. Note that PCB waste refers to waste that contains PCBs and requires specially designated storage and disposal. Specific examples of PCB waste include transformers and capacitors that use PCBs as insulating oil.

However, in recent years, it has been newly discovered that pressure-sensitive paper and the like contain more than 5,000 mg/kg of PCBs. Along with this, the PCB Special Measures Law was revised, and sludge, paper waste, wood waste, fiber waste, and waste containing PCBs of 5,000 mg/kg (0.5%) or more and 100,000 mg/kg (10%) or less were revised. Plastics have been certified as revised low-concentration PCB waste, and can now be detoxified at a general certified detoxification facility.

Japanese Patent Application Publication No. 2010-75848

For the revised low-concentration PCB waste, which has a higher concentration than the conventional low-concentration PCB waste, treatment standards have been established for the residence time of 2 seconds or more at 1,100℃ or higher, based on a detoxification verification test conducted by the Ministry of the Environment. . However, conventional detoxification treatment, such as the method disclosed in Patent Document 1, involves treatment at 850° C. for 2 seconds or more, and cannot treat revised low-concentration PCB waste.

In addition, at conventional treatment facilities, permitted items such as waste rags, sludge/activated carbon, sawdust, paper waste, wood chips, absorbent cotton, textile waste, and waste plastics, which have been certified as revised low-concentration PCB waste, are treated with pressure-sensitive paper. , paint films (containing Pb), combustible solids, non-combustible solids, oil sludge, and other low-concentration PCB contaminants. There is a problem that it cannot be done.

The present invention was made in view of the above problems, and is capable of stably securing a combustion temperature of 1,100°C or higher and a residence time, and detoxifying a wide variety of low-concentration PCB wastes. The purpose is to provide a method for processing low-concentration PCB waste.

In order to solve the above problems, the present invention provides a heating process in which PCB-containing waste is heated to volatilize PCBs from the PCB waste, and an exhaust gas in which the exhaust gas discharged from the heating process is heated and detoxified. A method for detoxifying low-concentration PCB waste, the method comprising: a treatment step, wherein in the heating step, a refractory is supplied to a rotary combustion furnace along with the PCB waste. I will provide a.

It is preferable that the refractory has a melting temperature of 1200° C. or higher. Further, it is preferable that the refractory contains 90% or more of the upper part of the sieve having a mesh opening of 50 mm and the lower part of the sieve having a mesh opening of 200 mm.

The refractory may be supplied at a rate of 0.04 to 0.3 kg/MJ depending on the combustion gas calorie of the rotary combustion furnace.

The weight of the refractory may be 2 to 20 times the weight of the PCB waste supplied to the rotary combustion furnace. PCB waste having a high combustion rate and PCB waste having a low combustion rate may be mixed and supplied to the rotary combustion furnace. Further, the solid PCB waste may be supplied to the rotary combustion furnace with a side of 400 mm or less.

The PCB waste may have a PCB concentration of 5000 mg/kg or more and 100,000 mg/kg or less.

According to the present invention, it is possible to stably secure a combustion temperature of 1,100° C. or higher and a residence time in a rotary combustion furnace.

1 is a schematic diagram showing an example of a processing facility for low-concentration PCB waste according to an embodiment of the present invention. FIG. 2 is a sectional view showing the internal state of the rotary kiln and the secondary combustion chamber.

Embodiments of the present invention will be described below with reference to the drawings. Note that in this specification and the drawings, elements having substantially the same functional configuration are designated by the same reference numerals and redundant explanation will be omitted.

FIG. 1 shows an example of a low-concentration PCB waste treatment facility according to the present invention. In this embodiment, it is assumed that the low-concentration PCB waste to be treated contains 5,000 mg/kg to 100,000 mg/kg of PCBs. The treatment device 1 includes a waste incineration unit 11 that performs a heating process to volatilize PCBs from low-concentration PCB waste, and an exhaust gas treatment unit 12 that performs an exhaust gas treatment process to detoxify exhaust gas generated in the heating process. ing. The waste incineration unit 11 includes a rotary kiln 21, which is an example of a rotary combustion furnace that burns the low-concentration PCB waste 9, and a secondary combustion chamber 22 connected to the outlet of the rotary kiln 21. The exhaust gas treatment unit 12 includes a tertiary combustion furnace 23 that burns and processes the exhaust gas generated in the secondary combustion chamber 22, and a cooling tower 24 that cools, neutralizes, and removes dust from the exhaust gas containing soot and dust treated in the tertiary combustion furnace 23. A first cleaning tower 25, a second cleaning tower 26, a first wet electrostatic precipitator 27, and a second wet electrostatic precipitator 28 are arranged in this order. In addition to the rotary kiln, the rotary combustion furnace includes a rotary stoker type incinerator.

FIG. 2 is a diagram showing the inside of the rotary kiln 21 and the secondary combustion chamber 22. One end of the rotary kiln 21 (the left end in FIG. 2) is an entrance 31 for the low-concentration PCB waste 9. The other end (downstream side) is an outlet 32, and the outlet 32 is connected to the side of the secondary combustion chamber 22. The rotary kiln 21 is equipped with a burner (not shown) that heats the inside to a predetermined temperature, for example, 600° C. to 1300° C., and heats the low-concentration PCB waste 9, which is the material to be treated, while conveying it in the discharge direction.

The low-concentration PCB waste 9 is fed from a supply hopper 20 (FIG. 1) into a rotary kiln 21 together with refractory bricks 10, which are an example of a refractory. The low-concentration PCB waste 9 that is the object to be treated is pressure-sensitive paper, paint film (containing Pb), combustible solids, non-combustible solids, oil mud, etc., and these may be mixed. In the case of solid materials, in order to smoothly supply them, it is preferable to crush them into particles with a particle size of 400 mm or less before supplying them. Furthermore, it may be difficult to stably treat PCB waste such as oil sludge, which burns at a high rate, only by controlling the supplied heat load amount. In such a case, the PCB can be reliably volatilized by including a rag or the like in the package and reducing the combustion rate by burning the solid surface.

The refractory brick 10 preferably has a melting temperature of 1200° C. or higher to prevent melting and sticking in a furnace at 1100° C. or higher. In addition, if the particle size is too small, many parts become softened and molten, making it easy to form clinker, which may reduce the effectiveness of preventing waste from scattering, and the waste may be masked by the refractory bricks 10 and oxidized. It may become depleted and combustion may be hindered. Furthermore, if the particle size is too large, troubles during feeding may increase, and the inside of the furnace wall may be damaged. Therefore, it is preferable that the material contains 90% or more of the upper part of the sieve with a mesh opening of 50 mm and the lower part of the sieve with a mesh opening of 200 mm. Furthermore, the amount of refractory bricks 10 to be supplied is 0.04 to 0.3 kg per waste combustion calorie, considering the total amount of heat (combustion gas calories) of combustion gas supplied to the rotary kiln 21 for heating purposes. It can be adjusted within the range of MJ. At this time, the weight of the refractory bricks 10 may be about 2 to 20 times the weight of the supplied waste. Alternatively, it can be supplied at a rate of 1 t to 2 t/h.

Furthermore, if necessary, a combustion improver such as kerosene, which is conventionally used when incinerating PCB waste, is supplied into the rotary kiln 21.

By supplying the low-concentration PCB waste 9 together with the refractory bricks 10, the heat capacity is improved, and the flue 33 of the secondary combustion chamber 22 is supplied from the vicinity of the outlet of the rotary kiln 21, for example, from a position 3 m from the outlet 32 as shown in FIG. It is possible to stably maintain a temperature of 1100° C. or higher over a period of time. Therefore, the PCBs can be completely decomposed by causing the low concentration PCB waste 9 to undergo convection at a temperature of 1100° C. or higher for 2 seconds or more. Therefore, the amount of combustion improver that was conventionally used can be reduced. Further, since the low concentration PCB waste 9 comes into contact with the high-temperature firebrick 10 and burns while being stirred, the PCB can be reliably decomposed and volatilized.

Furthermore, if the low-concentration PCB waste 9 is in the form of paper, its contact with the refractory bricks 10 has the effect of suppressing the paper-like waste from being scattered inside the furnace by the combustion air from the kiln inlet. . In addition, the refractory bricks 10 prevent the cinders and the like of the low concentration PCB waste 9 from melting and solidifying, creating gaps, thereby exhibiting the effect of suppressing unburnt combustion due to oxygen deficiency. That is, it is possible to promote the decomposition of PCBs in the low-concentration PCB waste 9 and to suppress troubles in the discharge system.

Note that the refractory brick 10 used in the present invention can be manufactured at low cost since it is possible to use chiseled items generated during refractory repair work.

The burnt remains of the low-concentration PCB waste 9 burned in the rotary kiln 21 are discharged from the outlet 34 at the bottom of the secondary combustion chamber 22, and the exhaust gas is sent to the tertiary combustion furnace 23 through the flue 33 of the secondary combustion chamber 22. be discharged. In the tertiary combustion furnace 23, the exhaust gas is burned at a predetermined temperature and residence time, and the exhaust gas containing soot and dust burned at a high temperature is sent to a cooling tower 24, a first cleaning tower 25, a second cleaning tower 26, a first wet electrostatic precipitator 27, and a second cleaning tower 25. After sequentially passing through a double-wet electrostatic precipitator 28 to be cooled, neutralized, and dust removed, it is released into the atmosphere. Note that in the present invention, the exhaust gas treatment section 12 is not limited to the configuration shown in FIG.

As described above, according to the present invention, the combustion efficiency is improved by co-firing the low concentration PCB waste 9 and the refractory bricks 10, and the low concentration PCB waste 9 of 100,000 mg/kg or less is stably rendered harmless. It becomes possible to process. Furthermore, it is possible to process the low concentration PCB waste 9 without crushing it, and furthermore, by conveying the low concentration PCB waste 9 in the rotary kiln 21 while contacting the refractory bricks 10, it is possible to process the low concentration PCB waste 9 with a wide variety of properties. Low concentration PCB waste 9 can be treated. Furthermore, by mixing PCB waste 9 with a fast combustion rate and PCB waste 9 with a slow combustion rate and supplying the mixture to the rotary kiln 21, it is possible to handle a wide range of low-concentration PCB wastes 9 with a wide range of calorific values, such as oil sludge and paint film debris. be able to. Here, examples of PCB waste with a fast combustion rate include combustible PCB waste, such as oil sludge and waste plastics, and examples of PCB waste with a slow combustion rate include nonflammable sludge.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such examples. It is clear that those skilled in the art can come up with various changes or modifications within the scope of the technical idea described in the claims, and these naturally fall within the technical scope of the present invention. It is understood that it belongs to For example, the constituent features of the above embodiments can be combined arbitrarily. This arbitrary combination naturally provides the effects and effects of the respective constituent elements of the combination, as well as other effects and effects that will be apparent to those skilled in the art from the description of this specification.

Further, the effects described in this specification are merely explanatory or illustrative, and are not limiting. In other words, the technology according to the present disclosure can have other effects that are obvious to those skilled in the art from the description of this specification, in addition to or in place of the above effects.

Note that the following configurations also belong to the technical scope of the present disclosure.
(1) PCB waste that has a heating process in which PCB-containing waste is heated to volatilize PCBs from the PCB waste, and an exhaust gas treatment process in which the exhaust gas discharged from the heating process is heated and detoxified. A method of processing,
A method for detoxifying low-concentration PCB waste, characterized in that in the heating step, a refractory is supplied to a rotary combustion furnace together with the PCB waste.
(2) The method for detoxifying low-concentration PCB waste according to (1) above, wherein the refractory has a melting temperature of 1200° C. or higher.
(3) The refractory contains 90% or more of the upper part of the sieve with an opening of 50 mm and the lower part of the sieve with an opening of 200 mm. processing method.
(4) The refractory according to any one of (1) to (3) above, characterized in that the refractory is supplied at a rate of 0.04 to 0.3 kg/MJ depending on the combustion gas calorie of the rotary combustion furnace. A method for detoxifying low-concentration PCB waste.
(5) The refractory according to any one of (1) to (4), wherein the weight of the refractory is 2 to 20 times the weight of the PCB waste to be supplied to the rotary combustion furnace. A method for detoxifying concentrated PCB waste.
(6) The method according to any one of (1) to (5) above, characterized in that PCB waste with a fast burning rate and PCB waste with a slow burning rate are mixed and supplied to the rotary combustion furnace. A method for detoxifying low-concentration PCB waste.
(7) The detoxification treatment of low-concentration PCB waste according to any one of (1) to (6) above, characterized in that the solid PCB waste is supplied to the rotary combustion furnace with a side of 400 mm or less. Method.
(8) The PCB waste is a low-concentration PCB waste according to any one of (1) to (7) above, characterized in that the PCB concentration is 5000 mg/kg or more and 100,000 mg/kg or less. Detoxification treatment method.

[Example 1]
As shown in Table 1, 1260 kg of low-concentration PCB waste 9 with a PCB concentration of 5,500 to 65,000 mg/kg was prepared, and each type was refilled into 40 L capacity medical pails (471 mm x 320 mm x 354 mm). The material was fed from the supply hopper 20 through the loading port 31 into a rotary kiln 21 having a total length of 8.3 m. Note that the low-concentration PCB waste 9 was crushed into pieces with a side of 400 mm or less as necessary, and then packed into medical pails by type.

The combustion gas calorie of rotary kiln 21 was 6,437 MJ. Refractory bricks 10 (melting temperature 1400 ° C., 95% of the upper part of the sieve with an opening of 50 mm and the lower part of the sieve with an opening of 200 mm) were supplied at 1870 kg/h, the low concentration PCB waste 9 was supplied at 103 kg/h, Burning treatment was performed. The weight of the refractory brick 10 was 18.2 times the weight of the supplied low concentration PCB waste.

When the low-concentration PCB waste 9 was incinerated at a high temperature of 1,100° C. or higher in the rotary kiln 21, as shown in Table 2, a residence time of 2 seconds or more of the exhaust gas was ensured. Moreover, the PCB decomposition rate was 99.9997%.

In addition, we measured the PCB concentration in the flue gas, the PCB elution concentration in cinders and soot, the PCB concentration in wastewater, the PCB concentration in the air surrounding the site, and the PCB concentration in the air around the outside of the site. . As a result, all of the results were below standard values, confirming that the low-concentration PCB waste was completely decomposed by the sample injection and high-temperature combustion at 1,100°C or higher.

[Example 2, Example 3]
As Example 2, 10 refractory bricks (average particle diameter of about 35 mm) under the sieve with an opening of 50 mm were supplied in the same weight as in Example 1, and the same operations as in Example 1 were repeated to carry out the combustion treatment. did. In addition, as Example 3, 10 refractory bricks (average particle size of about 500 mm) on a sieve with an opening of 200 mm were supplied in the same weight as in Example 1, and the same operations as in Example 1 were repeated except for the combustion. Processing was carried out.

As a result, in both Examples 2 and 3, as in Example 1, the exhaust gas was below each standard value, etc., and it was confirmed that the low concentration PCB waste was completely decomposed.

However, in Example 2, since the refractory bricks 10 under the sieve with an opening of 50 mm were supplied, there were places where the refractory bricks 10 and cinders were melted and fixed in the lower part of the rotary kiln 21 and the secondary combustion chamber 22. Further, in Example 3, since the refractory bricks 10 on a sieve with an opening of 200 mm were supplied, malfunctions occurred in the supply hopper 20 and the damper during supply, which required countermeasures.

[Comparative example 1]
As a comparative example, combustion treatment was carried out by repeating the same operation as in Example 1 except that the refractory brick 10 was not supplied. As a result, the exhaust gas temperature was less than 1100°C, which did not meet the treatment standards for PCB waste.

Table 3 shows the measurement results of the furnace temperature at four points in a rotary kiln with a total length of 8.3 m in each of the case where the refractory brick of Example 1 was supplied and the comparative example 1 where no refractory brick was supplied. In addition, in the case of Example 2 and Example 3, the temperature inside the furnace was the same as in Example 1.

In Examples 1 to 3 in which refractory bricks were supplied, the temperature exceeded 1100°C on the downstream side after 2 m from the entrance, but in Comparative Example 1, the temperature did not reach 1100°C over the entire length. That is, in Examples 1 to 3, which are examples of the present invention, the combustion efficiency is improved by co-firing with refractory bricks, and low concentration PCB waste can be stably incinerated at 1100°C or higher for 2 seconds or more, and 100,000mg/ It was found that detoxification treatment of modified low-concentration PCB contaminants weighing less than 1 kg can be carried out reliably. In Comparative Example 1, the same amount of combustion gas as in Examples 1 to 3 was supplied to the rotary kiln 21, but the temperature inside the rotary kiln 21 was lower than in Examples 1 to 3.

INDUSTRIAL APPLICABILITY The present invention can be applied as a method for high-temperature combustion treatment of waste and the like.

1 Treatment device 9 Low concentration PCB waste 10 Refractory bricks 11 Waste incineration unit 12 Exhaust gas treatment unit 20 Supply hopper 21 Rotary kiln 22 Secondary combustion chamber 23 Tertiary combustion furnace 24 Cooling tower 25 First cleaning tower 26 Second cleaning tower 27 First wet type electric precipitator 28 Second wet type electric precipitator 31 Inlet 32 Exit 33 Flue 34 Discharge port

Claims (8)

A method for treating PCB waste, comprising: a heating step of heating waste containing PCBs to volatilize PCBs from the PCB waste; and an exhaust gas treatment step of heating exhaust gas discharged in the heating step to detoxify it. And,
A method for detoxifying low-concentration PCB waste, characterized in that in the heating step, a refractory is supplied to a rotary combustion furnace together with the PCB waste. 2. The method for detoxifying low-concentration PCB waste according to claim 1, wherein the refractory has a melting temperature of 1200° C. or higher. 3. The method for detoxifying low-concentration PCB waste according to claim 1 or 2, wherein the refractory contains 90% or more of the upper part of the sieve with an opening of 50 mm and the lower part of the sieve with an opening of 200 mm. The detoxification of low-concentration PCB waste according to claim 1 or 2, wherein the refractory is supplied at a rate of 0.04 to 0.3 kg/MJ depending on the combustion gas calorie of the rotary combustion furnace. Processing method. The method for detoxifying low-concentration PCB waste according to claim 1 or 2, wherein the weight of the refractory is 2 to 20 times the weight of the PCB waste supplied to the rotary combustion furnace. . 3. The detoxification treatment for low-concentration PCB waste according to claim 1 or 2, characterized in that PCB waste with a high burning rate and PCB waste with a slow burning rate are mixed and supplied to the rotary combustion furnace. Method. 3. The method for detoxifying low-concentration PCB waste according to claim 1, wherein the solid PCB waste is supplied to the rotary combustion furnace in a size of 400 mm or less on a side. 3. The method for detoxifying low-concentration PCB waste according to claim 1, wherein the PCB waste has a PCB concentration of 5000 mg/kg or more and 100,000 mg/kg or less.

Images