JP4371375B2 - Method and apparatus for separating volatile organic compounds from wastewater - Google Patents

Description

  The present invention relates to a method for separating a volatile organic compound from wastewater when the wastewater such as groundwater or industrial wastewater contains a volatile organic compound such as trichlorethylene or tetrachloroethylene, and an apparatus therefor.

  The present inventor proposed a separation method described below in Patent Document 1 as a prior art regarding a technique for separating a volatile organic compound from waste water.

This separation method is
“To-be-processed wastewater containing volatile organic compounds is sprayed and supplied to the inside of a sealed separation vessel, while the inside of the separation vessel is connected to a vacuum generating means such as a vacuum pump connected via an indirect heat exchanger. The volatile organic compound is separated from the wastewater to be treated by degassing or flash-evaporating the wastewater to be treated into a separation vessel while maintaining the pressure lower than atmospheric pressure. The treated wastewater is heated in an indirect heat exchanger using steam generated in the separation vessel as a heat source so that its temperature approaches the saturated vapor temperature in the separation vessel.
It is something.

According to this prior art separation method, the heat of water vapor generated in the separation vessel can be recovered by heating the wastewater to be treated supplied to the separation vessel. Separation is possible with high thermal efficiency.
JP 2004-337567 A

  However, in the indirect heat exchanger described above, it is necessary to always maintain a temperature difference between the heating side and the heated side for performing a predetermined amount of heat transfer through the heat transfer body. As in the separation method in the prior art, when the heat of steam generated in the separation container is recovered by the indirect heat exchanger to be heated to the wastewater to be treated, the wastewater to be treated Cannot be brought close to the saturated steam temperature in the separation container by the temperature difference.

  Therefore, the degassing or flash evaporation in the wastewater to be treated in the separation container is lowered by the amount that the temperature of the wastewater to be supplied to be supplied cannot be brought close to the saturated steam temperature in the separation container. The separation rate of volatile organic compounds from wastewater was low.

  Moreover, the water vapor in the separation vessel is sucked into the vacuum generating means such as a vacuum pump without being cooled to the saturated vapor temperature in the indirect heat exchanger, so that the vacuum generating means such as the vacuum pump Since the amount of suction increased, a large-capacity vacuum generation means had to be used.

  In particular, when the vacuum generating means is a vacuum pump, the condensed water of water vapor generated in the separation container is sucked into the vacuum pump together, leading to problems such as an increase in load. It was.

  An object of the present invention is to provide a separation method and an apparatus for solving these problems.

In order to achieve this technical problem, the separation method of the present invention comprises:
“The inside of the sealed separation vessel is maintained at a reduced pressure lower than atmospheric pressure by a vacuum generating means connected through a sealed heat exchange vessel, and the inside of the separation vessel contains a volatile organic compound. Waste water is jetted and supplied from the separation vessel after direct contact with water vapor generated in the separation vessel in the heat exchange vessel.
It is characterized by that.

Moreover, the separation method of the present invention comprises:
“The insides of the sealed first separation container and the second separation container are maintained at a reduced pressure lower than the atmospheric pressure by a vacuum generating means connected to them through a sealed heat exchange container, and the first separation container The waste water to be treated containing a volatile organic compound is supplied into the heat exchange vessel after being directly brought into contact with the water vapor generated in each separation vessel in the heat exchange vessel, while being treated in the first separation vessel. Waste water is indirectly heated using the exhaust from the vacuum generating means as a heat source, and then sprayed into the second separation container and discharged from the second separation container .
It is characterized by that.

Next, the separation device of the present invention comprises:
“A sealed separation container, a sealed heat exchange container connected to the separation container so as to introduce water vapor in the separation container, and a pressure lower than atmospheric pressure through the heat exchange container. And a vacuum generating means for sucking so as to maintain the waste water to be treated, which includes a volatile organic compound, in the heat exchange container, after directly contacting the steam generated in the separation container, It was configured to supply and discharge from this separation vessel . "
It is characterized by that.

Moreover, the separation device of the present invention comprises:
“A sealed first and second separation vessel, a sealed heat exchange vessel connected to each of these separation vessels so as to introduce water vapor in each of the separation vessels, and this heat exchange vessel A vacuum generating means for sucking so that the inside of each separation container is maintained at a pressure lower than atmospheric pressure, and an indirect heat exchanger connected to the exhaust side of the vacuum generating means, and containing a volatile organic compound The waste water to be treated is configured to be directly supplied to the steam generated in the separation container in the heat exchange container and then sprayed into the first separation container. The treatment wastewater is indirectly heated by using the exhaust from the vacuum generating means as a heat source in the indirect heat exchanger, and then jetted and supplied to the inside of the second separation container, and is discharged from the second separation container. did "It is characterized in that.

  By configuring as described in claims 1 and 3, the wastewater to be treated to be supplied to the separation vessel is a water vapor generated by degassing or flash evaporation in the separation vessel in advance in the heat exchange vessel. The wastewater to be treated can be heated to a temperature close to the saturated steam temperature in the separation vessel, in other words, the temperature of the wastewater to be treated Thus, the temperature difference between the temperature of the wastewater to be treated and the saturated steam temperature can be almost eliminated so as to be closer to the saturated steam temperature in the separation container than in the case of indirect heating. The deaeration or flash evaporation of the wastewater to be treated in the inside becomes vigorous, and the separation rate of the volatile organic compound in the separation container can be greatly improved.

  In the prior art described above, since the separation rate of volatile organic compounds in the separation vessel is low, in order to increase this separation rate, the wastewater to be treated supplied to this separation vessel is preliminarily supplied with a gas such as air. However, in the present invention, the separation rate of volatile organic compounds in the separation container can be greatly improved as described above. Dissolving the gas can be omitted.

  On the other hand, the water vapor generated in the separation container is condensed in the wastewater to be treated by directly contacting the wastewater to be treated in the heat exchange container. As compared with the prior art, the capacity of the vacuum generating means can be reduced. Further, when the vacuum generating means is a vacuum pump, it is possible to avoid sucking condensed water into the vacuum pump.

  In addition, since the separation of the volatile organic compound from the wastewater to be treated is repeated in two stages by configuring as described in the second and fourth aspects, the separation rate is determined by the effect of the first and second aspects. Therefore, the heat of the exhaust exhausted from the vacuum generating means can be converted into wastewater to be treated into the second separation container. Since the heat can be recovered by heating, the separation rate of the volatile organic compound in the second separation container can be improved, and the overall thermal efficiency can be improved.

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

  FIG. 1 shows a first embodiment.

  In this figure, reference numeral 1 denotes a sealed separation container, and reference numeral 2 denotes a heat exchange container also having a sealed structure, and inside thereof, packed layers 1a and 2a made of packing such as Raschig rings are provided. The separation vessel 1 and the heat exchange vessel 2 are provided with a passage 3 so as to introduce water vapor generated in the separation vessel 1 into the heat exchange vessel 2 below the packed beds 1a and 2a. It communicates through.

Reference numeral 4 denotes a wastewater tank for receiving treated wastewater containing a volatile organic compound such as trichlorethylene. The treated wastewater in the wastewater tank 4 is pumped out by the treated wastewater supply pump 5 and treated wastewater. By supplying to the spray nozzle 7 provided in the upper part in the said heat exchange container 2 via the supply line 6, after ejecting from this spray nozzle 7 to the said packed bed 2a, the pump 8 from the lower part of this packed bed 2a The waste water to be treated pumped out from the heat exchange container 2 by the pump 8 is supplied to the spray nozzle 10 provided in the upper part in the separation container 1 through the pipe 9, thereby pumping from the nozzle 10 to the outside of the separation container 1 in the process from the lower completion wastewater pump 11 of the filling layer 1a After ejection the filling layer 1a (discharge That) is configured so as.

  Reference numeral 12 denotes a vacuum pump as a vacuum generating means. The vacuum pump 12 sucks from the upper part of the heat exchange vessel 2 so that the inside of the heat exchange vessel 2 and the inside of the separation vessel 1 are brought to atmospheric pressure. It is configured to maintain a low vacuum.

  In this configuration, the waste water to be treated in the waste water tank 4 is ejected from the spray nozzle 7 in the upper part of the heat exchange container 2 by the pump 5, so that in the heat exchange container 2, in the separation container 1. In direct contact with water vapor generated by degassing or flash evaporation, the temperature is raised so as to approach the saturated vapor temperature in the heat exchange vessel 2 and in the separation vessel 1.

  Next, the wastewater to be treated whose temperature has been raised in the heat exchange vessel 2 is ejected from the spray nozzle 10 in the upper portion of the separation vessel 1 by the pump 8 and degassed or flash evaporated. Volatile organic compounds such as trichlorethylene contained in the wastewater to be treated are separated from the wastewater to be treated and are sucked into the vacuum pump 12 through the heat exchange container 2 along with the water vapor generated at this time.

  As described above, the wastewater to be treated supplied to the separation container 1 is brought into direct contact with water vapor generated in the separation container 1 in the heat exchange container 2 in advance. , And can be heated to a temperature closer to the saturated steam temperature in the separation container 1, in other words, the temperature of the wastewater to be treated is further increased even when the temperature is indirectly heated as in the prior art. Since the temperature difference between the temperature of the wastewater to be treated and the saturated steam temperature can be almost eliminated so as to approach the saturated steam temperature in 1, the degassing or flash evaporation of the wastewater to be treated in the separation vessel 1 can be eliminated. As a result, the separation rate of volatile organic compounds in the separation container 1 can be greatly improved.

  On the other hand, the water vapor generated in the separation container 1 is condensed in the wastewater to be treated by directly contacting the wastewater to be treated in the heat exchange container 2. Is smaller than in the case of the prior art, and it is possible to reduce the capacity of the vacuum pump 12 and to avoid sucking condensed water into the vacuum pump 12.

  The exhaust gas discharged from the vacuum pump 12 through the exhaust pipe 12a is guided to the gas-liquid separator 13 to be separated into a liquid and a gas, and the separated liquid is received by the post-treatment layer 14.

  The separated gas is guided to the photocatalyst decomposer 15 where the volatile organic compound in the gas is harmlessly decomposed by the action of the photocatalyst and then guided to the upper part of the post-treatment tank 14. The post-treatment layer 4 is neutralized by the liquid circulated by the pump 14b between the packed bed 14a provided above the post-treated layer 4, while being washed while passing through the packed bed 14a. To be released.

Further, the treated waste water pumped out (discharged) from the bottom of the separation container 1 by the treated waste water pump 11 is a switching means such as a valve provided in a transfer pipe 17 from the treated waste water pump 11. at 18, the the case is returned to the waste water tank 4, and is configured to selectively switched between when the output sent to other locations.

  Furthermore, the liquid neutralized in the post-treatment tank 14 is configured to be appropriately mixed with the wastewater to be treated to the heat exchange vessel 2 via the pipe line 19.

  Next, FIG. 2 shows a second embodiment.

  In the second embodiment, two separation containers, that is, a first separation container 1 ′ and a second separation container 1 ″ are used as the separation containers in the first embodiment. 1 ', 1 "are provided with packed beds 1a', 1a" and spray nozzles 10 ', 10 ", and the spray in the upper part of the first separation container 1' out of the two separation containers 1 ', 1". The wastewater to be treated in the wastewater tank 4 is supplied to the nozzle 10 ′ and ejected, while the wastewater to be treated that collects at the bottom of the first separation container 1 ′ is pumped out by the pump 20, and then the treated wastewater supply pipe Through the passage 21, the water is supplied to the spray nozzle 10 ″ in the upper part of the second separation container 1 ″ and ejected, while the water vapor in both the separation containers 1 ′ and 1 ″ is supplied to the heat exchange container 2. Introduce in.

  Further, an indirect heat exchanger 22 is provided in the middle of the exhaust pipe 12a from the vacuum pump 12 and the wastewater supply pipe 21 to be treated to the second separation container 1 ″. In the exchanger 22, waste water to be treated to the second separation container 1 ″ is configured to be indirectly heated by using the exhaust from the vacuum pump 12 as a heat source, and other configurations are the same as those in the first embodiment. It is the same as the form.

  According to the second embodiment, the separation of the volatile organic compound from the wastewater to be treated can be performed in two stages of the first separation container 1 ′ and the second separation container 1 ″. While the separation rate can be further improved, the heat of the exhaust from the vacuum pump 12 can be recovered by heating the wastewater to be treated to the second separation container 1 ″, so that the thermal efficiency can be further improved, and The separation rate of the volatile organic compound in the second separation container 1 ″ can be improved.

It is a figure which shows 1st Embodiment. It is a figure which shows 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separation container 1 '1st separation container 1 "2nd separation device 2 Heat exchange container 3 Steam duct 4 Waste water tank 5 Untreated waste water supply pump 6 Untreated waste water supply line 7, 10 Spray nozzle 12 Vacuum pump 12a Exhaust line from vacuum pump 22 Indirect heat exchanger

Claims (4)

The inside of the sealed separation container is maintained at a pressure lower than atmospheric pressure by a vacuum generating means connected to the sealed separation container, and the wastewater to be treated containing a volatile organic compound is contained inside the separation container. In the heat exchange vessel after directly contacting with the water vapor generated in the separation vessel and then discharged from the separation vessel, and separating the volatile organic compounds in the waste water. The inside of the sealed first separation container and the second separation container is maintained at a reduced pressure lower than the atmospheric pressure by a vacuum generating means connected to the first and second separation containers through a sealed heat exchange container. The wastewater to be treated containing volatile organic compounds is supplied into the heat exchange vessel after being directly brought into contact with the water vapor generated in each of the separation vessels, and then supplied to the wastewater in the first separation vessel. Volatile organic compounds in waste water, wherein the exhaust gas is indirectly heated using the exhaust from the vacuum generating means as a heat source, jetted into the second separation container, and discharged from the second separation container How to isolate. A sealed separation vessel, a sealed heat exchange vessel connected to the separation vessel so as to introduce water vapor in the separation vessel, and the pressure inside the separation vessel is reduced to a pressure lower than atmospheric pressure via the heat exchange vessel. A vacuum generating means for sucking so as to maintain the waste water to be treated containing volatile organic compounds after being brought into direct contact with water vapor generated in the separation container in the heat exchange container and then sprayed into the separation container And the apparatus which isolate | separates the volatile organic compound in a wastewater characterized by being comprised so that it may discharge | emit from this separation container . The sealed first and second separation containers, a sealed heat exchange container connected to each of these separation containers so as to introduce water vapor in each of the separation containers, and the heat exchange container Vacuum generating means for sucking each separation container so as to maintain a reduced pressure lower than atmospheric pressure, and an indirect heat exchanger connected to the exhaust side of the vacuum generating means, and containing a volatile organic compound. The treatment wastewater is configured to be sprayed and supplied into the first separation container after directly contacting the steam generated in the separation container in the heat exchange container, while being treated in the first separation container The waste water is indirectly heated using the exhaust from the vacuum generating means as a heat source in the indirect heat exchanger, and then jetted into the second separation container and discharged from the second separation container . This Apparatus for separating volatile organic compounds in the waste water characterized by.

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