JP2006314887A - Method and apparatus for heat treatment of contaminated matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detoxify contaminated matter contaminated with a contaminant such as an organohalogen compound or a heavy metal by heating while making it possible to stably perform the detoxification of the contaminated matter and to prevent the contaminant from leaking from the heat treatment process without fail even when the water content of the contaminated matter fluctuates markedly. <P>SOLUTION: The method for heat-treating the contaminated matter comprises the heat treatment step of heat-treating the contaminated matter containing moisture and the exhaust gas treatment step of cleaning exhaust gas produced in the heat treatment step, wherein the flow rate of the exhaust gas sucked from the heat treatment step to the exhaust gas treatment step is controlled according to the measured water content value of the contaminated matter before being fed into the heat treatment step and the pressure value measured in the heat treatment step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat treatment method and a heat treatment apparatus for contaminants contaminated with organic halogen compounds such as PCB and contaminants such as heavy metals.

  Conventionally, as a method for treating contaminants contaminated with organic halogen compounds such as dioxins and polychlorinated biphenyls (PCBs) and contaminants such as heavy metals, the contaminants are heated in a reducing atmosphere and the reducing atmosphere is used. A method is known in which exhaust gas is sucked in such a manner that the lower heat treatment is performed under a negative pressure, and the sucked exhaust gas is purified by an oil cleaning gas cleaning facility or the like (Patent Document 1).

In such a conventional method, pollutants such as organic halogen compounds contained in the pollutants are decomposed or evaporated by heating in a reducing atmosphere, sucked together with the exhaust gas, and then sent to the oil cleaning type gas cleaning device. On the other hand, the object to be treated that has been detoxified and from which the contaminants have been removed is in a clean state and discharged from the reduction heat treatment step.
In addition, according to such a conventional method, since the reduction heat treatment of the contaminant is performed under a negative pressure, there is an advantage that the contaminant is hardly leaked to the outside.

JP 2003-95990 A

  However, in the conventional treatment method as described above, when the amount of water contained in the contaminant is greatly fluctuated, the stable treatment operation is likely to be hindered, and the contaminant may be diffused. That is, when the amount of water contained in the contaminants suddenly increases, a large amount of water vapor is generated from the contaminants supplied to the reduction heating furnace, and the furnace pressure becomes unstable. Further, when the amount of generated water vapor is larger, the pressure in the furnace rises to atmospheric pressure or higher, and contaminants leak out of the furnace.

  The conventional processing method also includes a pressure gauge for measuring the pressure in the furnace, and the exhaust gas suction amount is adjusted so as to keep the pressure in the furnace constant based on the pressure value measured by the pressure gauge. However, since the temperature of the reduction heating furnace is extremely high (for example, 400 to 600 ° C.), it cannot sufficiently cope with the rapid increase in the furnace pressure due to the generation of water vapor.

In addition, a method of operating at a sufficient negative pressure so that it does not become a positive pressure even if there is a pressure fluctuation can be considered,
(1) Contaminants such as agricultural chemicals may evaporate before they are sufficiently pyrolyzed,
(2) Even if heat treatment is attempted in a reducing atmosphere, air may flow from the sealed portion of the furnace, and the oxygen concentration in the furnace may increase.
(3) The capacity of the exhaust fan increases and the amount of dust may increase.
It will cause various problems such as.

  Furthermore, it is conceivable to reduce the water content by dehydrating or drying pollutants with a high water content in advance. However, a device for dehydration or drying or a device for treating exhaust gas generated therefrom is separately provided. There is a problem that it becomes necessary and increases the processing cost of contaminants.

  Therefore, the present invention provides a non-hazardous material for pollutants contaminated with organic halogen compounds and heavy metals, even when the moisture content of the contaminated material fluctuates greatly. It is an object to be able to stably perform the crystallization treatment and more reliably prevent the leakage of contaminants from the heat treatment step.

  In order to solve the above-mentioned problems, the heat treatment method for contaminants according to the present invention includes a heat treatment step for heat treating a contaminant containing moisture, and an exhaust gas treatment step for purifying exhaust gas generated from the heat treatment step. Provided, the suction flow rate of exhaust gas sucked from the heat treatment step to the exhaust gas treatment step, the moisture content measurement value of contaminants before being supplied to the heat treatment step, and the pressure measurement value measured in the heat treatment step It adjusts based on these.

  In the present invention, preferably, the pressure in the heat treatment step is controlled to be −0.1 to 0 kPa (gauge pressure, hereinafter the same).

  Further, the heat treatment apparatus for contaminants of the present invention includes a heat treatment furnace for heat-treating contaminants containing moisture, an exhaust gas treatment apparatus for purifying exhaust gas generated from the heat treatment furnace, and the heat treatment furnace. An exhaust fan for sucking exhaust gas into the exhaust gas treatment device, a moisture meter for measuring the moisture content of contaminants before being supplied to the heat treatment furnace, and a pressure gauge for measuring the pressure in the heat treatment furnace And the exhaust fan is configured to be capable of adjusting the exhaust gas suction flow rate based on a moisture content measurement value obtained by the moisture meter and a pressure measurement value obtained by the pressure gauge.

  In the present invention, the contaminant means an organic halogen compound such as PCB or dioxins, an agrochemical, a heavy metal or other contaminant itself, and the contaminant is a treatment object containing the contaminant, for example, Soil, sludge, waste, etc.

  According to the contaminant treatment method and treatment apparatus of the present invention, when adjusting the exhaust gas suction flow rate, not only the pressure of the heat treatment step but also the moisture content of the contaminants supplied thereto are taken into account. Because the value is reflected in the exhaust gas suction flow rate, even if contaminants with a high water content are supplied, it is possible to predict a large amount of sudden generation of water vapor in advance, and a sudden pressure increase will occur. The furnace pressure can be stabilized so that it does not occur.

  Therefore, according to the heat treatment method and heat treatment apparatus for contaminants according to the present invention, when the contaminants contaminated with contaminants such as organic halogen compounds and heavy metals are detoxified by heating, the moisture content of the contaminants is increased. Even if it fluctuates significantly, the pressure in the heat treatment of the contaminant can be stabilized, and the leakage of the contaminant from the heat treatment step can be more reliably prevented.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic flow diagram showing an embodiment of a contaminant treatment apparatus according to the present invention. As shown in FIG. 1, the contaminant treatment apparatus 10 of the present embodiment supplies a contaminant to the heat treatment furnace 11 for heat treating the contaminant 1 (for example, soil) and the heat treatment furnace 11. A dust collecting device 14, a gas cleaning device 15, and an activated carbon filter 17 are sequentially provided as an exhaust gas processing device for purifying exhaust gas generated from the heat treatment furnace 11, and a supply device 12. Further, the processing apparatus 10 includes an exhaust fan 16 that sucks the exhaust gas 3 so that the furnace pressure of the heat treatment furnace 11 becomes a negative pressure, and guides the sucked exhaust gas 3 to the exhaust gas processing apparatus. The moisture meter 21 for measuring the moisture content of the contaminant 1 in the supply device 12 and the pressure gauge 22 for measuring the furnace pressure in the heat treatment furnace 11 are provided. Then, the moisture measurement value 4 of the contaminant 1 by the moisture meter 21 and the pressure measurement value 5 in the furnace by the pressure gauge 22 are respectively sent to the control device 23, and after a predetermined calculation is performed by the control device 23, The exhaust fan 16 is output as the rotational speed 6, and the exhaust fan 16 is operated at the rotational speed 6.

  The heat treatment furnace 11 is not particularly limited as long as the contaminant 1 to be treated can be heated at a predetermined temperature. As the heat treatment furnace 11, for example, a cylindrical heating device main body, a rotating shaft disposed inside the heating device main body, paddle blades attached to the rotating shaft, and the outside of the heating device main body are covered. And a jacket configured to be supplied with a high-temperature indirectly heated gas can be used. Moreover, it is good also as a structure which a heating apparatus main body rotates, and it may be comprised so that an inert gas may be supplied to a heating apparatus main body so that the inside of the heat processing furnace 11 may be made into a reducing atmosphere. When processing contaminants such as heavy metal contaminated soil, the heat treatment furnace 11 is not an indirect heating furnace as described above, but a so-called direct heating furnace in which a burner is provided in the furnace. May be.

The reducing atmosphere means that it is a low oxygen atmosphere, and preferably has an oxygen concentration of 3 vol% or less (hereinafter simply referred to as%), more preferably 1% or less.
When the pollutant is an organic halogen compound such as PCB, nitrogen gas is supplied as the inert gas, and the oxygen concentration in the heat treatment furnace 11 is 3% or less, preferably 1% or less. The
When the contaminant 1 is heat-treated in the heat treatment furnace 11, the organic halogen compound such as PCB contained in the contaminant 1 is decomposed or evaporated and removed from the object to be processed.

The furnace pressure of the heat treatment furnace 11 is preferably controlled to be −0.1 to 0 kPa, and more preferably −0.01 to −0.001 kPa.
When the pressure in the furnace is 0 kPa or more, the buffer effect is small, and there is a possibility that the pressure change due to expansion of the object to be processed and various substances contained therein may not be supported. On the other hand, if the pressure is -0.1 kPa or less, the inside of the furnace is excessively sucked, dust (dust) is scattered, and there is a possibility that a great burden is imposed on exhaust gas treatment equipment such as a bag filter in the subsequent stage. Furthermore, air will enter the furnace because the sealing performance of the moving parts is insufficient, and it will not be possible to maintain a low oxygen atmosphere, and conversely, to improve the sealing performance to prevent air from entering the moving parts. If so, there is a risk of enormous costs.

When the pollutant is an organic halogen compound, the furnace temperature of the heat treatment furnace 11 is preferably 200 to 700 ° C, and more preferably 400 to 600 ° C. If the temperature in the furnace is lower than 200 ° C, the organic halogen compound contained in the contaminant 1 may remain without being removed. If the temperature in the furnace is higher than 700 ° C, the removal efficiency is not changed. Energy may be wasted.
The residence time of the contaminant 1 in the heat treatment furnace 11 is usually 20 to 180 minutes, preferably 30 to 120 minutes.

Moreover, when a contaminant is a heavy metal, it is preferable that the furnace temperature of the said heat processing furnace 11 shall be 400-1100 degreeC, and it is more preferable to set it as 500-1000 degreeC. If the furnace temperature is lower than 400 ° C, the heavy metal contained in the contaminant 1 may remain without being removed. If the temperature is higher than 1100 ° C, the removal efficiency does not change and heating is required. There is a possibility that energy may be wasted, and there is a possibility that soil or the like to be processed may be slag.
The residence time of the contaminant 1 in the heat treatment furnace 11 is usually 5 to 120 minutes, and preferably 10 to 90 minutes.

  When supplying nitrogen gas as the inert gas, a membrane separation type or PSA type can be used as a nitrogen generator (not shown). The PSA-type nitrogen generator is configured to adsorb oxygen in the air to the adsorbent by bringing air into contact with the adsorbent under high pressure to obtain nitrogen that is difficult to be adsorbed by the adsorbent at a high concentration. By adopting a PSA-type nitrogen generator, 99.99% high-purity nitrogen can be generated. In the PSA system nitrogen generator, the adsorbed gas (mainly oxygen) is separated and separated from the adsorbent by reducing the pressure after the adsorption treatment, and high concentration oxygen having a concentration of 30 to 35% is generated as a by-product. be able to. In the PSA-type nitrogen generator, two or more adsorption towers filled with an adsorbent are arranged, and the above-described adsorption under high pressure and separation and separation under reduced pressure are performed respectively. By performing switching while using a tower, high-concentration nitrogen gas and oxygen gas can be obtained continuously. Moreover, you may comprise so that the high concentration oxygen byproduced by this nitrogen generator may be used as the combustion air of the said indirect heating gas.

  Moreover, although it does not specifically limit as the dust collector 14, It is preferable to employ | adopt what is called a high temperature bag filter which can collect dust, maintaining exhaust gas at high temperature, and can collect only dust by this.

  The gas cleaning device 15 is generated in the heat treatment furnace 11 by bringing the exhaust gas 3 into gas-liquid contact with, for example, hydrocarbon oil, and dispersing or dissolving the organic halogen compound or the like in the exhaust gas 3 in the hydrocarbon oil. The exhaust gas 3 is washed. The hydrocarbon oil that can be used in the gas scrubber 15 is not particularly limited, and is an oil having a boiling point lower than that of the organic halogen compound in the exhaust gas (for example, a hydrocarbon oil having 8 to 15 carbon atoms, preferably 10 to 12 carbon atoms) Among these, normal paraffin is preferable because it easily dissolves the organic halogen compound and is inexpensive.

  The oil and water collected from the lower part of the gas cleaning device 15 are sent to a wastewater treatment facility (not shown) for processing them, and after being cleaned, are reused in the gas cleaning device 15. Or is configured to be discharged as clean wastewater.

  In addition, as the moisture meter 21 provided in the supply device 12, various moisture meters using principles such as a high-frequency measurement method and a dielectric constant measurement method can be used.

  Further, the control device 23 determines the furnace pressure of the heat treatment furnace 11 based on the moisture measurement value 4 measured by the moisture meter 21 and the furnace pressure measurement value 5 measured by the pressure gauge 22. The rotational speed of the exhaust fan 16 is adjusted in order to control within such a predetermined range.

  Specifically, the amount of moisture in the object to be processed per unit volume is calculated from the moisture measurement value, the volume when all of the moisture has changed to gas is calculated, and based on the calculation result, The exhaust amount of the exhaust fan for maintaining the pressure in the furnace is obtained, and the rotational speed of the exhaust fan is changed. The timing at which moisture is supplied into the furnace can be calculated by measuring or setting the supply flow rate of the object to be processed in advance.

  Even in a steady state in which the amount of moisture in the object to be processed does not vary, the pressure in the furnace is constantly monitored by a pressure gauge and is controlled to have a preset pressure value. However, as described above, for example, when the amount of water in the object to be processed has changed significantly, the number of revolutions of the exhaust fan is increased in advance and the inside of the furnace is depressurized before the object to be processed is charged. It is adjusted so that it does not become positive pressure.

Thus, according to the processing apparatus 10 of the present embodiment, the rotational speed of the exhaust fan 16 is determined by the furnace pressure 5 of the heat treatment furnace 11 and the moisture measurement value 4 of the contaminant 1 supplied to the heat treatment furnace 11. That is, the suction flow rate of the exhaust gas 3 is adjusted.
Accordingly, even when an unexpected contaminant 1 having a high moisture content is supplied, the moisture content of the contaminant 1 is detected as a moisture measurement value 4 by the moisture meter 21 in the previous stage of the heat treatment furnace 11, and This is reflected as the suction flow rate of the exhaust gas 3. That is, the rotational speed of the exhaust fan can be increased at an appropriate time before the contaminant 1 having a high water content is supplied to the heat treatment furnace 11, and the contaminant 1 is supplied into the furnace to generate a large amount of water vapor. In this case, since the pressure inside the furnace has already been sufficiently lowered by the exhaust fan 16, it is possible to prevent the inside of the furnace from becoming a positive pressure.
Conversely, when the moisture content of the pollutant 1 is greatly reduced, the same is true. When the pollutant 1 having an extremely low moisture content is supplied to the heat treatment furnace 11, the amount of water vapor generated is greatly reduced. In addition, a rapid pressure drop in the furnace can be prevented.

  Furthermore, since the rotation speed of the exhaust fan is changed in accordance with the timing of the addition of moisture, the inside of the furnace is hardly depressurized beyond a predetermined range due to the increase in the rotation speed of the exhaust fan, and air is not contained in the furnace. There is no risk of mixing.

  Thus, according to the contaminant heat treatment apparatus according to the present embodiment, even when the moisture content of the contaminant contaminated with the contaminant varies significantly, the pressure in the contaminant heat treatment is reduced. Stabilize and reliably prevent leakage of contaminants.

  Further, even when the heat treatment furnace is in a reducing atmosphere, it is not necessary to always operate at a large negative pressure, and the amount of oxygen flowing from the seal portion of the heat treatment furnace can be minimized, so that the heat treatment furnace is stable. Thus, a reducing atmosphere (low oxygen state) can be maintained.

The schematic flowchart which showed one Embodiment of the processing apparatus of the contaminant which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Contaminant 3 Exhaust gas 4 Moisture measurement value 5 Pressure measurement value 6 Exhaust fan rotation speed 10 Waste processing device 11 Heat processing furnace 12 Supply device 16 Exhaust fan 21

Claims (3)

  A heat treatment process for heat-treating contaminants containing moisture, and an exhaust gas treatment process for purifying the exhaust gas generated from the heat treatment process, and suctioning exhaust gas to be sucked from the heat treatment process to the exhaust gas treatment process Contaminant heat treatment method, characterized in that the flow rate is controlled based on the moisture content measurement value of the contaminant before being supplied to the heat treatment step and the pressure measurement value measured in the heat treatment step. .   2. The contaminant heat treatment method according to claim 1, wherein the pressure in the heat treatment step is controlled to be −0.1 to 0 kPa.   A heat treatment furnace for heat-treating contaminants containing moisture, an exhaust gas treatment device for purifying exhaust gas generated from the heat treatment furnace, an exhaust fan for sucking exhaust gas from the heat treatment furnace to the exhaust gas treatment device, A moisture meter for measuring the moisture content of the contaminant before being supplied to the heat treatment furnace, and a pressure gauge for measuring the pressure in the heat treatment furnace, wherein the exhaust fan has a moisture content by the moisture meter. A contaminant heat treatment apparatus characterized in that the exhaust gas suction flow rate can be adjusted based on a measured value and a pressure measured value by the pressure gauge.

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