JP4017626B2 - Oil-containing wastewater treatment method - Google Patents

Description

  The present invention relates to a method for treating oil-containing wastewater emulsified with a surfactant.

  In factories such as automobiles, machining and metal processing, waste water of water-soluble cutting oil is discharged. This wastewater generally contains n-hexane extract (oil) at a high concentration of several thousand to several tens of thousands mg / L, and is in an emulsion state emulsified with an emulsifier (such as a surfactant). . In addition, the sewage discharge standard for n-hexane extract (oil) based on the Water Pollution Control Law is regulated to 5 mg / L (mineral oil) or less. Therefore, in order to discharge such water-soluble cutting oil wastewater into sewage, it is essential to remove the oil from the wastewater.

  Therefore, in order to treat waste water containing oil as represented by the above-mentioned water-soluble cutting oil (hereinafter referred to as “oil-containing waste water”), several treatment methods (for example, flotation separation method, precipitation separation) Method, microbial treatment method, etc.) have been devised.

  The precipitation separation method is a method in which an oil component is agglomerated and precipitated by adding a flocculant (salt iron, PAC, sulfate band, etc.) to oil-containing wastewater (see Patent Document 1).

  In the floatation separation method, after adding the same flocculant as described above, the specific gravity is smaller than or equivalent to that of water, fine bubbles are attached to reduce the apparent specific gravity, and the oil is separated by floating on the water surface. It is a method (refer patent document 2).

  The microbial treatment method is a method in which oils are decomposed and removed aerobically or anaerobically using microorganisms existing in nature (see Patent Document 3).

JP 2002-58910 A JP 2003-154205 A JP-A-7-303894

  However, in the precipitation separation method described above, the oil recovery rate is as low as 30 to 50%, and many of them can remain in the waste liquid. In the flotation separation method, a large amount of metal microparticles generated by metal cutting may be mixed in the oil-containing wastewater, so that the specific gravity of the oil containing them becomes heavy and it is difficult to float on the liquid surface. There is a risk that the rate will decrease. And in the microbial treatment method, since the mineral oil which is hard to biodegrade is melt | dissolving in oil, the problem that processing takes time has arisen.

  Furthermore, the oil recovered by the precipitation separation method and the flotation separation method contains a large amount of metal microparticles as described above, so that incineration requires a lot of energy and air pollution such as dust. It can also be a cause. In the biological treatment method, a bad odor can be generated along with the biodegradation, and thus a facility such as a deodorizing device may be required.

  Furthermore, in any of the above-described methods, in order to increase the processing capacity, facilities such as a large-scale sedimentation tank, levitation tank, and culture tank are required, and problems with equipment cost and installation location may occur.

  The present invention has been made in view of the above circumstances, and it is possible to quickly and efficiently treat oil-containing wastewater such as cutting oil at a low cost, and does not cause generation of air pollution or odor. A processing method and a processing apparatus are provided.

A first characteristic configuration of the present invention is a method for treating oil-containing wastewater that has been emulsified with a surfactant, wherein the oil-containing wastewater is vaporized, and the gas includes a vaporized component contained in the gas. Heat treatment is performed at a temperature at which the emulsification by the active agent does not occur and the water phase and the gas phase can be separated, and the gas after the heat treatment is condensed and returned to a liquid to be recovered.

[Action and effect]
The oil-containing wastewater that has been emulsified with the surfactant is once vaporized, and then the vaporized component contained in the gas is not emulsified by the surfactant, and the water phase and the gas phase are vaporized. The heat treatment is performed at a temperature that can be separated .

  Therefore, in oil-containing wastewater that is recovered as a liquid by condensing the gas after the heat treatment, the emulsification by the surfactant does not occur. Therefore, the water phase and the oil phase can be easily obtained without using a flocculant or bubbles. It will be in a state that can be separated. As a result, it is possible to efficiently recover oil and water, respectively. Especially for oil, insoluble matters such as metal microparticles are almost separated and removed, and new oil is replenished there, Since it can be reused by adding activator or water, it is not necessary to incinerate.

  Even in the case of incineration, since the oil contains almost no metal microparticles or the like, it can be incinerated without requiring a large amount of energy, and there is no risk of air pollution such as dust.

  Further, since the separated water does not contain insoluble matters such as metal microparticles and contains almost no oil, it can satisfy the drainage standards of the Water Pollution Control Law and can be drained into sewage as it is. In addition, when direct heat treatment is performed on oil-containing wastewater, a large pressure is required to perform the heat treatment at a temperature exceeding the boiling point of water, which requires equipment having a more robust pressure-resistant structure, resulting in high costs. However, in the present invention, such a structure / equipment is not particularly required.

  Also, the oil-containing wastewater can be treated quickly and efficiently because the treatment method is not complicated and the number of steps is small, such as once the oil-containing wastewater is vaporized, heat-treated, condensed and recovered. It is possible, and it is not necessary to prepare a particularly large facility for increasing the processing capacity, and the present invention can be implemented with a small space and a simple structure / equipment.

  The second characteristic configuration of the present invention is to vaporize the oil-containing wastewater by reducing the pressure to below atmospheric pressure.

[Action and effect]
Since the oil-containing wastewater is vaporized by reducing the pressure below the atmospheric pressure, for example, even if the oil-containing wastewater contains components that are difficult to vaporize at normal pressure, it can be easily vaporized (for example, at a lower temperature). possible and will, together with leads to shortening of the running costs of the reduction and processing time, so that can be cold processed, thereby reuse of the oil fraction.

According to a third feature of the present invention, an airtight container capable of storing oil-containing wastewater emulsified with a surfactant and a decompression chamber are connected in communication by a gas transfer path, and a condenser is provided in the gas transfer path. The decompression chamber is decompressed to below atmospheric pressure, the oil-containing wastewater is vaporized, and when the gas is transferred to the decompression chamber via the gas transfer path, the vaporized component contained in the gas is A pyrolysis apparatus that can be heated at a temperature that does not cause emulsification by a surfactant and that can be separated into an aqueous phase and a gas phase is provided in the gastight container or between the gastight container and the condenser. It is in the point provided in the transfer path part.

[Action and effect]
An oil-containing wastewater treatment apparatus capable of executing the treatment method having the operations and effects of the first and second characteristic configurations described above can be provided.

  The 4th characteristic structure of this invention exists in the point which provided the space heating apparatus in the upper space of the said oil-containing wastewater in the said airtight container.

[Action and effect]
Since the space heating device is installed in the upper space of the oil-containing wastewater in the airtight container, the space temperature of the upper space increases and the saturated vapor amount also increases, so that more vaporized molecules may exist in the upper space. Further, the pressure in the upper space increases from Boyle-Charles' law, and a large pressure difference is generated between the airtight container and the decompression chamber. As a result, the gas transfer rate increases and the vaporization rate of the oil-containing wastewater also increases, so that the processing time is further shortened compared to the case where no space heating device is provided. Note that when the airtight container is heated, the oil-containing wastewater may be scorched in the airtight container and the upper space is indirectly heated under reduced pressure, so that the upper space temperature rises. It is difficult to vaporize the oil-containing wastewater smoothly, but there is no such concern in the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment
FIG. 1 is a schematic view showing an apparatus capable of executing an oil-containing wastewater treatment method according to an embodiment of the present invention.

  The hermetic container 2 has an end plate structure at the top and bottom, and has a structure having pressure resistance against the reduced pressure state in the container.

  The side portion of the airtight container 2 is provided with an input port 3 into which the oil-containing wastewater 1 can be input (for example, if the input port is provided with a rotary feeder or the like, the airtight container is kept in a sealed state, It is also possible to automatically and continuously put oil-containing wastewater into an airtight container). Moreover, the lower part of the airtight container 2 is equipped with the discharge port 4, and can discharge | emit the oil-containing wastewater 1 and the residue after a process freely (In this case, for example, the discharge port provided with the rotary feeder etc.) If this is done, it is possible to automatically and continuously discharge oil-containing wastewater and treated residues from the hermetic container while keeping the hermetic container hermetically sealed).

  A space heating device 20 (such as a far-infrared heater) for heating the upper space 20 generated when the oil-containing wastewater 1 is accommodated is provided in the upper part of the airtight container 2.

  Further, a jacket 6 connected to the oil-containing wastewater heating device 5 is provided outside the airtight container 2 so that the oil-containing wastewater 1 can be heated.

  A gas transfer pipe 8 is connected to the end plate-like top plate of the airtight container 2 and is connected to the collection tank 12 in communication.

  The gas transfer pipe 8 that is connected to the airtight container 2 and the recovery tank 12 is connected to the condenser 10 to which the thermal decomposition device 9 and the cooling device 11 are connected in order from the upstream side, with the airtight container 2 being the upstream side, and A valve 21 is provided.

  The recovery tank 12 has an end plate structure at the top and bottom, and has a pressure resistance against the reduced pressure state in the tank. Further, a decompression pipe 22 and a gas transfer pipe 8 of a decompression device 15 (for example, a vacuum pump) are connected to the end plate-like top plate of the recovery tank 12, and a decompression release valve 13 is further provided. . In addition, a drain valve 14 is provided in the lower part of the recovery tank 12 so that the liquid recovered in the recovery tank 12 can be discharged to the separation tank 16.

Next, specific processing steps will be described. First, a predetermined amount of oil-containing wastewater 1 (water-soluble cutting oil discharged from an automobile factory or the like) is introduced into the airtight container 2 through the inlet 3. The input amount at this time is desirably an amount that does not reach the space heating device 7 provided in the upper part of the confidential container 2 at least during processing. This is because when the space heating device 7 and the oil-containing wastewater 1 are in contact with each other, it is difficult to achieve the original purpose of the space heating device for heating the upper space 20, and the space heating device 7 when used, usually oil impregnated in the order temperature used preferably at 80 ° C. to 120 ° C., the resulting in use in a state in which the space heating device 7 and the oil-containing wastewater 1 is in contact, a surface of the space pressurized thermal device 7 This is because the oil content of the wastewater 1 may be burnt. Moreover, even if the oil-containing wastewater 1 is put into the airtight container 2 as a whole, the liquid surface area becomes small, the vaporization rate is slowed, the efficiency is poor, and conversely, if the amount is too small, the inside of the apparatus is decompressed. In this case, it takes a long time, and the efficiency is poor.

  After the oil-containing waste water 1 is introduced, the decompression release valve 13 and the drainage valve 14 are closed, the valve 21 is opened, and the decompression device 15, the cooling device 11 and the thermal decomposition device 9 are operated.

When the decompression device 15 is operated, the inside of the airtight container 2 is decompressed via the recovery tank 12 and the gas transfer pipe 8, and when heated by the oil-containing wastewater heating device 5, vaporization of the oil-containing wastewater 1 is promoted. At this time, if necessary, if operating the spatial pressurized thermal device 7, it becomes possible to promote more efficient vaporization of oil-containing wastewater 1. However, the temperature used in oil-containing wastewater heating device 5 is preferably oil of the oil-containing wastewater 1 is a temperature have kana with burnt airtight container 2.

  As a vaporization component of the oil-containing wastewater 1, an n-hexane extract material (oil content), a surfactant, and water are mainly exemplified.

First, these vaporized components are transferred through the gas transfer pipe 8 to the site where the thermal decomposition apparatus 9 is installed, and are directly heated by the thermal decomposition apparatus 9. Temperature set by the pyrolyzer 9, n- hexane extract (oil) is not interpreted correspondingly, the surfactant is the temperature to be construed min, preferably, 140 ° C. to 160 ° C.. As a result, the only surfactant may be construed min.

  Next, the vaporized component after the heat treatment is transferred to a portion where the condenser 10 connected to the cooling device is installed. Therefore, the vaporized component is condensed and returned to the liquid state again, and is stored in the recovery tank 12 through the valve 21 as it is.

  When the liquid (recovered liquid 23) is stored up to a predetermined amount, the valve 21 is closed, and then the decompression release valve 13 and the drain valve 14 are opened, and the recovered liquid 23 is discharged to the separation tank 16.

Since the recovered liquid 23 discharged to the separation tank 16 is not emulsified by the surfactant, it can be easily separated into the water phase 18 and the oil phase 17 without using any coagulant or bubbles. state becomes (Note that it may the intermediate phase 19 is formed between the aqueous phase 18 and oil phase 17 containing minute construed surfactants).

  As a result, it is possible to efficiently recover oil and water, respectively. Especially for oil, insoluble matters such as metal microparticles are almost separated and removed, and new oil is replenished there, Since it can be reused by adding activator or water, it is not necessary to incinerate. Even in the case of incineration, since the oil contains almost no metal microparticles or the like, it can be incinerated without requiring a large amount of energy, and there is no risk of air pollution such as dust.

  In addition, the separated water does not contain insoluble materials such as metal microparticles and contains almost no oil, so it can meet the wastewater standards of the Water Pollution Control Law and can be drained directly into sewage. There is no need to do so, which leads to cost reduction.

  The residue remaining at the bottom of the airtight container 2 after processing seems to contain a lot of metal microparticles, so it can be recovered from the outlet 4 and reused if possible, or an industrial waste disposal contractor. Appropriate processing is performed, such as whether or not to request.

[Other Embodiments]
1. The thermal decomposition apparatus for oil-containing wastewater in the embodiment is configured to be provided in a gas transfer path portion between the airtight container and the condenser, but is not limited thereto, and the thermal decomposition apparatus is an airtight container. It is good also as a structure provided in the inside.
2. The thermal decomposition apparatus in the embodiment is configured to directly heat the vaporized component, but is not limited to this, and may be configured to indirectly heat by winding a hot wire coil or the like around the gas transfer pipe. .

Schematic which shows the processing apparatus of oil-containing wastewater in embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oil-containing wastewater 2 Airtight container 3 Input port 4 Outlet 5 Oil-containing wastewater heating device 6 Jacket 7 Space heating device 8 Gas transfer pipe 9 Pyrolysis device 10 Condenser 11 Cooling device 12 Recovery tank 13 Decompression release valve 14 Drainage valve 15 Decompression Apparatus 16 Separation tank 17 Oil phase 18 Water phase 19 Intermediate phase 20 Upper space 21 Valve 22 Pressure reducing pipe 23 Collected liquid

Claims (4)

A method for treating oil-containing wastewater that has been emulsified with a surfactant,
The oil-containing wastewater is vaporized , and the gas is heat-treated at a temperature at which the vaporized component contained in the gas does not cause emulsification by the surfactant and can be separated into an aqueous phase and a gas phase , A method for treating oil-containing wastewater in which the gas after the heat treatment is condensed and returned to a liquid for recovery.   The method for treating oil-containing wastewater according to claim 1, wherein the oil-containing wastewater is vaporized by reducing the pressure to below atmospheric pressure in order to vaporize the oil-containing wastewater. An airtight container capable of containing oil-containing wastewater emulsified with a surfactant and a decompression chamber are connected to each other by a gas transfer path, a condenser is provided in the gas transfer path, and the decompression chamber is brought to atmospheric pressure or lower. When the oil-containing wastewater is evaporated under reduced pressure and the gas is transferred to the vacuum chamber via the gas transfer path, the vaporized component contained in the gas is not emulsified by the surfactant. And the oil-containing wastewater which is equipped with the thermal decomposition apparatus which can be heated at the temperature which can be isolate | separated into a water phase and a gaseous phase in the gas- tight passage in the said airtight container or between the said airtight container and the said condenser Processing equipment.   The processing apparatus for oil-containing wastewater according to claim 3, wherein a space heating device is provided in an upper space of the oil-containing wastewater in the airtight container.

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