JPH11319773A - Continuous decomposition of pcb and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously decomposing PCB and a device therefor in which PCB is continuously subjected to detoxification treatment without generating corrosive gas and heat loss is reduced and running costs are decreased. SOLUTION: Mixed liquid of both a PCB solution and a PCB decomposer consisting of sodium ethoxide, a surfactant and a carbonate is mixed and heated in a reaction tank 22 to produce an emulsionlike reaction medium. A neutralizer and the emulsionlike reaction medium are vaporized in a thermal decomposition tank 42 and subjected to a catalytic contact reaction. Thereby, sodium chloride and a gaseous reaction medium are separated. This sodium chloride is scraped by a screw drum 66 and discharged from a discharged means 70. Further, the gaseous reaction medium is cooled by a condenser 86 and separated into decomposition oil and the neutralizer in a separation tank 90. Accordingly, PCB is efficiently subjected to detoxification treatment and heat loss is reduced and both energy consumption and running costs are decreased and load of maintenance and inspection is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for continuously decomposing a PCB.

[0002]

2. Description of the Related Art In recent years, PCBs contained in insulating oil for transformers, cutting oils, lubricating oils, press oils, heating media for heat treatment, additives for paints and printing inks, or solvents for carbonless paper have been developed. An incineration method has been attempted as a method of treating PCB solution, but toxic gas such as dioxin is generated, and has not been put to practical use.

[0003] US Patent No. 5,075,017 ('01
Patent No. 7) discloses a continuous treatment method of an organic chlorine compound using supercritical water. In a supercritical state, in a reactor, a large amount of hydrogen chloride gas or chlorine gas is generated during the reaction and significantly corrodes a metal portion, so that the life of the equipment is extremely short, so that practical use is difficult. In order to prevent this, it is conceivable to inject alkali into the reactor as a neutralizing agent.However, even in such a case, the corrosive gas generated during decomposition may abnormally damage metal parts under high temperature and high pressure. Life cannot be extended to a practical level. In addition, solids such as sodium chloride are produced as reaction products in the reactor, which adhere to and accumulate on the inner wall of the reactor, and eventually block the inside of the apparatus, so that maintenance and
The burden of inspection is heavy.

US Pat. No. 5,558,783 ('78)
No. 3 patent), the reactor has a double tube structure of an outer tube and an inner tube, and an inner tube is formed by a ceramic porous material, and supercritical water is jetted into the inner tube to cause a reaction. The corrosive gas generated in the above will damage the inner tube and corrode the outer tube. Therefore, the equipment cannot be operated continuously for a long time. Although cooling water is jetted downstream of the reaction zone to prevent salt from adhering to the inner tube, heat loss is large.

[0005]

The '017 patent and'
In any of the 783 patents, it is difficult to solve a trouble caused by a large amount of corrosive gas generated in the reactor at a high temperature and a high pressure. Second, in the '783 patent, cooling water for salt dissolution is supplied to the lower part of the reaction zone, so that water consumption and heat loss are large and running costs are high.

The present invention minimizes the generation of corrosive gas in the reaction vessel, extends the life of the equipment to a practical level, prevents solids from adhering in the reaction vessel,
PC that can continuously detoxify PCB for long term
An object of the present invention is to provide a continuous decomposition method of B and an apparatus therefor.

[0007]

Means for Solving the Problems In the first invention of the present application, a PCB solution and a PCB decomposing agent comprising sodium ethoxide, a surfactant and a carbonate are reacted in a reaction vessel at 100 ° C. to 25 ° C.
Heating and mixing at 0 ° C. to produce an emulsified reaction medium;
Supplying a pyrolysis tank maintained at 250 ° C. to 450 ° C. with at least one reaction accelerator selected from tannin and wood vinegar and a neutralizing agent comprising a sodium hydroxide solution;
Contacting the emulsified reaction medium and the neutralizing agent in the pyrolysis tank to separate sodium chloride and the gaseous reaction medium, and discharging the gaseous reaction medium and sodium chloride from the upper and lower parts of the pyrolysis tank, respectively And a step of producing a cracked oil and a neutralizing agent in the upper and lower phases of the separation tank by cooling and liquefying the gaseous reaction medium, respectively.
This is a continuous decomposition method of CB.

[0008] The second invention of the present application is a PC solution comprising a PCB solution, a sodium ethoxide, a surfactant and a carbonate.
A reaction vessel for producing an emulsified reaction medium by heating and mixing the B-decomposing agent, a thermal decomposition vessel connected to the reaction vessel, at least one reaction accelerator selected from tannin and wood vinegar, and sodium hydroxide First supply means for supplying a neutralizing agent composed of a solution to the thermal decomposition tank, second supply means for supplying the emulsified reaction medium to the thermal decomposition tank, and the emulsified reaction medium and the neutralizing agent in the thermal decomposition tank. A stirring means for causing a contact reaction while stirring to separate and generate a gaseous reaction medium with sodium chloride, a screw means for discharging sodium chloride adhering to the inner wall of the pyrolysis tank from the lower part while scraping the same, and an upper part of the pyrolysis tank This is a continuous cracking apparatus for PCB, which is connected to a liquefied gaseous reaction medium and separates a decomposed oil and a neutralizing agent into an upper phase and a lower phase, respectively.

[0009]

In the method and apparatus for continuously decomposing PCB of the present invention, an emulsified reaction medium is produced by heating and mixing a PCB solution and a PCB decomposing agent comprising sodium ethoxide, a surfactant and a carbonate. , 98% or more of the organochlorine compound is supplied to a pyrolysis tank, and further reacted with a reaction accelerator and a neutralizing agent containing a sodium hydroxide solution in the pyrolysis tank to form PCB.
Since the decomposition treatment is performed at 99% or more, it is possible to minimize the generation of corrosive gas in the thermal decomposition tank and extend the life of the equipment to a practical level. Moreover, sodium chloride and the gaseous reaction medium are separated and generated in the pyrolysis tank,
The former is continuously taken out from the lower part of the pyrolysis tank by screw means, while the latter is taken out from the upper part of the pyrolysis tank and liquefied and separated into separated oil and neutralizing agent, so that heat loss is reduced and processing is performed. The cost can be significantly reduced. The reaction accelerator has a strong chelating agent effect in the thermal decomposition tank, and has a function of effectively replacing the chlorine in unreacted PCB in the emulsified reaction medium to make the PCB harmless.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a schematic diagram of a continuous decomposition apparatus according to a first embodiment for executing a continuous decomposition method of a PCB according to the present invention. PCB is contained in waste oil and the like generated at the stage of producing agricultural chemicals such as transformer insulating oil, cutting oil, lubricating oil, and herbicide, but is described here as a PCB solution. The continuous decomposition apparatus 10 includes a storage tank 12 for storing a PCB solution, a pump 14, and a feed tank 16 for supplying the PCB solution. The PCB solution is supplied from a feed tank 16 to a reaction tank 22 via a pump 18 and a control valve 20. To the reaction tank 22, sodium ethoxide, a surfactant, and a carbonate as PCB agents are supplied from supply tanks 24, 26, and 28 via rotary valves 24a, 26a, and 28a, respectively. The weight ee of the sodium ethoxide, the surfactant, and the carbonate is preferably about 10: 0.5: 1. The surfactant is selected from higher fatty acids such as palmitic acid, stearic acid and oleic acid, and the carbonate is selected from sodium carbonate and sodium hydrogen carbonate. The mixing ee ratio of the PCB decomposing agent to the PCB solution is 5 to 5 by weight ee.
25% is desirable. If the PCB decomposer is less than 5%, P
If the CB solution is insufficiently emulsified and gelled, if it exceeds 25%, not only the treatment effect does not change but also the treatment cost increases. The reaction tank 22 includes a motor-driven stirrer 30 for stirring the PCB solution and the PCB decomposing agent, and a heating unit 32. The heating means 32 converts the mixed solution in the reaction tank 22 to 100 to 25.
Heat to a temperature of 0 ° C. Heat mixing is performed for 5 to 10 minutes. At this time, the PCB solution reacts with the PCB decomposing agent to be emulsified and gelled, and about 98% of the organic chlorine compound is decomposed, thereby generating an emulsified reaction medium. The emulsified reaction medium is press-fitted into a pyrolysis tank 42 through a press-fitting means 39 comprising check valves 34 and 36 and a plunger pump 38 and a control valve 40. A hydrothermal solvent is supplied from a hydrothermal solvent tank 44 into the thermal decomposition tank 42. The hydrothermal solvent tank 44 stores a neutralizing agent comprising a mixed solvent of a sodium hydroxide solution and a reaction accelerator. A reaction accelerator is mixed in the sodium hydroxide solution at a ratio of 1 to 10% by weight. The reaction accelerator comprises at least one solution selected from tannin and wood vinegar having a strong chelating action. As described above, the neutralizing agent composed of the mixed solution of the reaction accelerator and the sodium hydroxide solution is supplied to the check valve 46,
After being supplied to the heating means 56 through the press-fitting means 54 comprising the pressure pump 48 and the high-pressure pump 52 and heated to 250 ° C. to 450 ° C., it is press-fitted into the pyrolysis tank 42 through the control valve 58. The thermal decomposition tank 42 includes a reaction vessel 62 heated to 250 ° C. to 450 ° C. by a heating means 60 such as a band heater, a stirring blade 64 and a screw drum 66. The stirring plate 64 functions to stir and mix the emulsified reaction medium and the neutralizing agent vaporized in the reaction vessel 62 and scrape sodium chloride adhering to the inner wall of the vessel. The screw drum 66 forms an annular reaction chamber 68 with the reaction vessel 62 for thermally decomposing the emulsified reaction medium by 99.99%, and simultaneously scrapes sodium chloride adhering to the inner wall of the reaction vessel 62 while lowering it. It has the function of discharging to As described above, the pyrolysis tank 42 has a function of separating the emulsified reaction medium into the gaseous reaction medium and the solid sodium chloride. The lower part of the pyrolysis tank 42 is provided with a salt discharge port 42a, in which a motor driven extrusion screw 70 for forcibly discharging the scraped sodium chloride to the lower part is arranged. Extrusion screw 7
The discharge side of the discharge tank 7 through the rotary valve 72
The outlet of the discharge tank 74 is provided with a rotary valve 76 from which sodium chloride is discharged.

[0011] Among the reaction products in the pyrolysis tank 42, solids are discharged from the salt discharge port 42a, and the gaseous reaction medium is supplied to the condenser 86 through the outlet 42b, where it is cooled by cooling water. The pressure is reduced by the pressure reducing valve 88 and discharged to the separation tank 90. In the separation tank 90, the decomposed oil 92
And the neutralizing agent 94 composed of a sodium hydroxide solution and a reaction accelerator separate into an upper phase and a lower phase, respectively. After the cracked oil 92 is taken out through the valve 96, the PCB concentration in the oil is measured, and if the PCB concentration is equal to or higher than the reference value, the separated oil is circulated again to the storage tank 12, mixed with the PCB solution, and recycled. To process. On the other hand, a level switch 98 is attached to the lower side of the separation tank 90.
When the liquid level of the neutralizing agent comes into contact with, the level switch 98 is operated to open the control valve 100. At this time, the neutralizing agent is supplied to the concentration adjusting tank 104 with a stirrer via the pump 101 and the pipe 102. The neutralizing agent in the tank 104 is partially discharged through a valve 106. When the concentrations of the reaction accelerator and the alkali in the neutralizing agent are lower than a predetermined value, a pump 110 and a control valve 1
A high concentration solution of the reaction accelerator and the sodium hydroxide solution is supplied to the concentration adjusting tank 104 via 12 to adjust the concentrations of the reaction accelerator and the alkali to a predetermined value. The neutralized agent composed of the sodium hydroxide solution and the reaction accelerator whose concentration has been adjusted is circulated to the hydrothermal solvent tank 44 via the pump 114 and the control valve 116 to be reused.

FIG. 2 is a schematic view of a continuous PCB disassembling apparatus according to a second embodiment of the present invention. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals, and similar parts are denoted by single apostrophes. PCB continuous decomposition device 10 '
, The reaction tank 22 ′ and the thermal decomposition tank 42 ′ are heated at 280 ° C. to 450 ° C.
Heated. The PCB solution is supplied from tank 16 to reaction vessel 22 'via control valve 20, and sodium ethoxide, surfactant and carbonate are supplied from tanks 24, 26 and 28, respectively, to rotary valve 24a,
26a and 28a, and supplied to the reaction tank 22 '.
The mixture is heated and mixed with the solution B to form an emulsified reaction medium.
The emulsified reaction medium is a fixed-quantity feeding device 1 composed of a screw or the like.
24 feeds to a pyrolysis tank 42 '. Pyrolysis tank 4
2 ′ is supplied with a neutralizing agent comprising a mixed solution of a reaction accelerator and sodium hydroxide from the concentration adjusting tank 104. The emulsified reaction medium is thermally decomposed in the annular reaction chamber 68 'to separate the sodium chloride and the gaseous reaction medium. The sodium chloride is scraped off the inner wall of the reaction vessel 62 ′ by a screw drum and transported downward, where it is discharged to a discharge tank 74 via an extrusion screw 70 and a rotary valve 72. Gaseous reaction medium is outlet 4
2′b is supplied to the separation tank 90 via the condenser 86,
The cracked oil 92 and the mixed solution 94 are separated. Separation tank 90
Separation oil 92 is supplied to control valve 96 and pump 12
The fuel is supplied to the fuel oil tank 130 via the valve 6 and the valve 128, mixed with other fuel oil at an appropriate ratio, and then supplied to the burner 120 by the pump 132.

[0013]

As described above, according to the present invention, the PC
Since B is decomposed by 98% or more in the reaction tank and then pyrolyzed in the pyrolysis tank, the generation of hydrogen chloride gas and chlorine gas is suppressed, the damage to the equipment is reduced, and the PCB is decomposed efficiently and continuously. can do. Moreover, the solid by-product sodium chloride, which is a by-product of the reaction, was completely separated from the other reaction medium at the time of thermal decomposition, and sodium chloride was discharged from the lower part of the reaction tank by screw means.
The operation of dissolving the salt with the cooling water and the subsequent separation operation are not required, so that the thermal efficiency of the pyrolysis tank is significantly improved, and the running cost can be greatly reduced. In addition, since it is not necessary to supply cooling water for dissolving the salt in the reaction vessel, consumption of a large amount of water can be prevented and heat loss can be minimized.

[Brief description of the drawings]

FIG. 1 is a view showing a continuous decomposition apparatus and a reaction system of a PCB according to a first preferred embodiment of the present invention.

FIG. 2 is a view showing a continuous PCB decomposition apparatus and a reaction system according to a second preferred embodiment of the present invention;

[Explanation of symbols]

16 Feed tank 22
Reaction tank 24 Sodium ethoxide supply tank 26
Surfactant supply tank 28 Carbonate 32
Heating means 42 Pyrolysis tank 44
Hydrothermal solvent supply tank 46 Oxidant supply tank 62
High temperature and high pressure vessel 64 Stirrer blade 66
Screw drum 68 Annular reaction chamber 70
Extrusion screw 74 Salt discharge tank 86
Condenser 90 Separation tank 104
Concentration adjusting tank 108 Alkaline solution tank 120
Burner 122 Heating furnace 124
Metering device

Claims (5)

[Claims] (1) a step of heating and mixing a PCB solution and a PCB decomposing agent comprising sodium ethoxide, a surfactant and a carbonate at 100 ° C. to 250 ° C. in a reaction vessel to form an emulsified reaction medium; A step of supplying at least one reaction accelerator selected from tannin and wood vinegar and a neutralizing agent comprising a sodium hydroxide solution to a pyrolysis tank maintained at a temperature of from 450 ° C to 450 ° C; Contacting the medium with a neutralizing agent to separate sodium chloride from the gaseous reaction medium; discharging the gaseous reaction medium and sodium chloride from the upper and lower parts of the pyrolysis tank, respectively; Cooling the reaction medium to liquefy it to produce cracked oil and a neutralizing agent in the upper and lower phases of the separation tank, respectively. 2. The method for continuously decomposing PCB according to claim 1, further comprising the step of adjusting the concentrations of the reaction accelerator and the sodium hydroxide solution in the neutralizing agent and circulating them in the neutralizing agent supply step. 3. The continuous PCB decomposing method according to claim 1, further comprising a step of scraping sodium chloride adhering to the inner wall of the thermal decomposition tank with a screw drum. 4. A reaction tank for producing an emulsified reaction medium by heating and mixing a PCB solution and a PCB decomposing agent comprising sodium ethoxide, a surfactant and a carbonate, and a thermal decomposition tank connected to the reaction tank. First supply means for supplying at least one reaction accelerator selected from tannin and wood vinegar and a neutralizing agent comprising a sodium hydroxide solution to the pyrolysis tank; and supplying an emulsified reaction medium to the pyrolysis tank. A second supply means, a stirring means for causing a contact reaction between the emulsified reaction medium and the neutralizing agent in the pyrolysis tank while stirring to separate and generate sodium chloride and a gaseous reaction medium, and adhering to the inner wall of the pyrolysis tank. A screw means for discharging sodium chloride from the bottom while scraping off, and a liquefied gaseous reaction medium connected to the upper part of the pyrolysis tank to separate cracked oil and neutralizer into upper and lower phases, respectively. Separation tank and PCB continuous decomposition device equipped. 5. The reaction vessel according to claim 4, wherein a pyrolysis tank is rotatably disposed in the reaction vessel, a screw drum for scraping sodium chloride adhering to the inner wall, and between the reaction vessel and the screw drum. A continuous decomposition apparatus for PCB, comprising: a formed annular reaction chamber; and a screw drum that feeds the lower part of the high-pressure vessel while scraping off sodium chloride adhering to the inner wall of the annular reaction chamber.