JP2007296529A - Method and apparatus for separating volatile organic compound in waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for separating a volatile organic compound in waste water, which can separate a volatile organic compound contained in waste water from the waste water with a high separation efficiency and at a low running cost. <P>SOLUTION: Waste water containing a volatile organic compound is injected into a hermetically sealed vessel 1 kept at a reduced pressure which is lower than the atmospheric pressure through a nozzle 3 in such a state that gas is dissolved in the waste water and the temperature of the waste water is kept at a desired temperature in a range of a temperature which is 5°C above the saturated vapor temperature within the hermetically sealed vessel, to a temperature which is 4°C below the saturated vapor temperature. <P>COPYRIGHT: (C)2008,JPO&INPIT

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.

  Conventionally, when purifying wastewater such as groundwater or industrial wastewater, when separating volatile organic compounds such as trichlorethylene or tetrachloroethylene contained in the wastewater from the wastewater, a large amount of gas such as air is added to the wastewater. However, in order to achieve a high separation rate, the amount of gas such as air that is blown into the wastewater must be significantly increased. In addition to increasing the noise due to the increase in the size of the blower that pumps a large amount of gas, the exhaust gas after bubbling is included in this exhaust gas even though the amount is large. Since the concentration of the volatile organic compound is low, the exhaust gas purification process after bubbling has been troublesome.

In view of this, the present inventor in Patent Document 1 previously filed the patent, put the waste water into a sealed container kept at a reduced pressure below atmospheric pressure from the lower part and flow out from the upper part to appropriately adjust the liquid depth. The waste water collected in the sealed container is boiled and evaporated at a deep part from the surface of the waste water to generate volatile organic compounds contained in the waste water by boiling and evaporation. The method of separating together with steam is proposed.
JP 2002-282844 A

  The separation method of this prior application has a far higher separation rate than the conventional method and has less exhaust gas, so that the downsizing of the apparatus and noise reduction can be achieved. It has the advantage that can be eliminated.

  On the other hand, in the separation method according to the previous application, the waste water stored in a sealed container whose pressure has been reduced is heated and heated in order to boil and evaporate in a deep part from the water surface. The temperature must be higher than the saturated steam temperature in the closed vessel by the boiling and evaporation in the part deeper than the water surface, and energy is required for heating this wastewater. There was a problem that running costs increased by the amount of energy.

  The present invention has a technical problem to reduce the running cost, that is, the problem of the prior application separation method.

The method of the invention for achieving this technical problem is as described in claim 1,
“Waste water containing volatile organic compounds is dissolved in a closed vessel maintained at a reduced pressure lower than atmospheric pressure, and a gas such as air is dissolved in the waste water, and the temperature of the waste water is made higher than the saturated vapor temperature in the closed vessel. It is supplied so as to be ejected while maintaining an arbitrary temperature within a temperature range from a temperature higher by 5 ° C. to a temperature lower by 4 ° C. than the saturated steam temperature. ”
It is characterized by that.

Further, the device of the present invention, as described in claim 2,
“A sealed container, a vacuum generator for maintaining the inside of the sealed container at a pressure lower than atmospheric pressure, a nozzle for injecting waste water containing a volatile organic compound into the sealed container, and further, waste water to the nozzle. The supply line includes a mixing means for dissolving gas in the waste water, and a temperature lower than the saturated steam temperature by 4 ° C. from a temperature higher by 5 ° C. than the saturated steam temperature in the sealed container. Heating means adapted to be maintained at any temperature within the temperature range up to. "
It is characterized by that.

  According to the present invention, as described in claim 1, the waste water containing the volatile organic compound is dissolved in the waste water in a sealed container maintained at a reduced pressure lower than the atmospheric pressure, and the temperature of the waste water is set to the temperature of the waste water. It is supplied so as to be ejected in a state where it is maintained at an arbitrary temperature within a temperature range from a temperature higher by 5 ° C. than the saturated vapor temperature in the sealed container to a temperature lower by 4 ° C. than the saturated vapor temperature. Therefore, it is only necessary to maintain the temperature of the wastewater at any temperature within the above-described temperature range, and the energy added to maintaining the wastewater at any temperature within the above-mentioned temperature range is Because it can be much less than when boiling and evaporating deeper than the water surface as in the previous method, the separation of volatile organic compounds with high separation efficiency and low running cost With the possible effect.

  FIG. 1 shows an apparatus according to a first embodiment of the present invention.

  This apparatus includes a sealed container 1 whose inside is maintained at a reduced pressure lower than atmospheric pressure by a vacuum generator such as a vacuum pump 2, and a spray nozzle 3 is provided in the upper part of the sealed container 1. By supplying wastewater containing volatile organic compounds such as trichlorethylene such as groundwater or industrial wastewater through the wastewater supply line 4, the wastewater is ejected downward to deaerate the wastewater. On the other hand, a discharge pipe 5 is provided at the bottom of the hermetic container 1 for taking out waste water after deaeration.

  The waste water supply line 4 is provided with heating means 6 for maintaining the temperature of the waste water at an appropriate temperature by applying heat energy thereto. When the amount of dissolved gas such as air previously contained in the wastewater supplied through the wastewater supply line 4 is not sufficient, the wastewater supply line 4 is indicated by a two-dot chain line. As described above, a gas mixing means 7 such as air is provided to dissolve a sufficient amount of gas in the waste water.

  In this apparatus, the separation efficiency of the trichlorethylene was actually determined by measuring the trichlorethylene concentration in the wastewater of the supply line 4 and the trichlorethylene concentration in the wastewater of the discharge line 5.

  In this implementation, the temperature T1 of the wastewater supplied to the supply line 4 is adjusted by appropriately adjusting one or both of the temperature of the wastewater in the supply line 4 and the degree of decompression in the sealed container 1. The temperature difference ΔT with the saturated steam temperature T2 in the sealed container 1 was changed in various ways, and the result was as shown in FIG.

  In FIG. 2, when the temperature difference ΔT is in a positive temperature range higher than zero, that is, when the temperature T1 of the wastewater is higher than the saturated steam temperature T2 in the sealed container 1, the wastewater is contained in the sealed container 1. When sprayed from the spray nozzle 3, flash evaporation and deaeration are performed, but when the temperature difference ΔT is zero and in a negative temperature range lower than zero, that is, the temperature T1 of the waste water is When the saturated steam temperature T2 in the sealed container A is equal to or lower than the saturated steam temperature T2 in the sealed container 1, the waste water is removed without flash evaporation when ejected into the sealed container 1 by the spray nozzle 3. Only qi is done.

  As is apparent from FIG. 2, the separation efficiency of trichlorethylene in wastewater is about 92% when the temperature difference ΔT is higher than zero by 5 ° C., that is, + 5 ° C., whereas the temperature difference Even when ΔT reaches + 6 ° C., almost no improvement in the separation efficiency is observed, and the improvement in the separation efficiency in the region exceeding + 5 ° C. is in a flat state. It was observed that the difference ΔT was greatly reduced to 65% or less in a region 4 ° C. lower than zero.

  Therefore, in the above-described apparatus, the wastewater sent through the supply pipe 4 is dissolved into a gas such as air in the wastewater, and the temperature of the wastewater is 5 ° C. higher than the saturated steam temperature in the sealed container. By supplying to the spray nozzle 3 in a state where it is maintained at an arbitrary temperature within a temperature range from a high temperature to a temperature lower by 4 ° C. than the saturated vapor temperature, Trichlorethylene in waste water can be separated with a high separation efficiency of 65 to 92%.

  Next, FIG. 3 shows a second embodiment of the present invention.

  The second embodiment is configured as follows.

  That is, two sealed containers, a first sealed container 11 and a second sealed container 12, are provided, and the inside of both the sealed containers 11 and 12 is filled with Raschig rings or the like for promoting deaeration and flash evaporation described later. The objects 11a and 12a are filled.

  By supplying waste water containing a volatile organic compound such as trichlorethylene and having a temperature of 15 ° C. or less to the spray nozzle 13 provided in the upper part of the first sealed container 11 through the supply pipe 14, the spray nozzle 13 From the bottom of the first airtight container 11 and is taken out by the discharge pump 15.

  The waste water taken out by the discharge pump 15 is supplied to the spray nozzle 17 provided at the upper portion in the second sealed container 12 through the transfer pipe 16, so that the second sealed container 12 is supplied from the spray nozzle 17. After being ejected downward, it is taken out by the discharge pump 18 from the bottom of the second hermetic container 12.

  When the wastewater sent from the supply pipe 14 contains a gas such as air in advance, it is supplied so as to be jetted into the first sealed container 11 as it is. When the gas such as dissolved air is small, as shown by a two-dot chain line, a gas mixing means 19 such as air is provided in the supply pipe 14 to provide a sufficient amount of air or the like for waste water. In the waste water transfer line 16 from the first sealed container 11 to the second sealed container 12, a gas mixing means 20 such as air is provided so as to be sufficient for the waste water. An amount of air or other gas is dissolved.

  A first heat exchanger 21 is disposed in the waste water supply line 14 into the first sealed container 1, and a second heat exchanger 22 is disposed in the waste water transfer line 16 into the second sealed container 12. The steam generated in the second sealed container 12 is introduced into the first heat exchanger 21 through the duct 23, and the temperature of the waste water to the first sealed container 11 is controlled by the steam. The first heat exchanger 21 is configured to be increased.

  By sucking the water vapor and the non-condensable gas in the first heat exchanger 21 with the vacuum pump 25 through the duct 24, the saturated vapor temperature inside the both hermetic containers 11 and 12 is increased. While maintaining the pressure lower than the atmospheric pressure so that the temperature of the waste water in the supply line 14 is higher than the temperature of the waste water (for example, at least about 5 ° C.), for example, about 20 ° C., the vacuum pump 25 By supplying the steam and non-condensable gas to which energy has been added by suction and compression to the second heat exchanger 22 through the duct 26, the temperature of the waste water to the second sealed container 12 is increased. , By the heating in the second heat exchanger 22 and the supply of energy from the drainage pump 15, for example, the maximum temperature is raised to about 25 ° C.

  In this configuration, the temperature of the waste water supplied from the supply line 14 to the first sealed container 11 is determined by using the steam generated in the second sealed container 12 in the first heat exchanger 21 as a heat source. , 12 is raised to, for example, about 19 ° C. so as to approach the saturated vapor temperature, that is, about 20 ° C., and then degassed by being sprayed from the spray nozzle 14 into the first sealed container 11. , Volatile organic compounds such as trichlorethylene contained in the wastewater are separated from the wastewater.

  Waste water taken out from the first sealed container 11 by the discharge pump 15 is raised to about 25 ° C. in the second heat exchanger 22, and further, a gas such as air is mixed and dissolved in the mixing means 20. After that, the volatile organic compound such as trichlorethylene contained in the waste water is separated from the waste water by being ejected from the spray nozzle 17 into the second sealed container 12 and flashing and degassing. Is done.

  That is, in this second embodiment, the separation of volatile organic compounds such as trichlorethylene from wastewater is first performed in the first sealed container 11 so that the temperature of the wastewater becomes the saturated vapor temperature in the first sealed container 11. Any temperature within a temperature range from the equal temperature to a temperature lower by 4 ° C. than the saturated steam temperature, in this embodiment, degassing in a state lower by about 1 ° C. than the saturated steam temperature, 2 In the sealed container 12, any temperature within the temperature range from the saturated steam temperature in the second sealed container 12 to a temperature higher by 5 ° C. than the saturated steam temperature, in this embodiment, This is performed in two steps, flash evaporation and deaeration at a temperature higher by about 5 ° C. than the saturated vapor temperature.

  Next, FIG. 4 shows a third embodiment.

  In the third embodiment, as in the second embodiment, the separation in the first sealed container 11 and the separation in the second sealed container 12, and the separation in the third sealed container 27, the fourth sealed By adding the separation in the container 28 and the separation in the fifth sealed container 29, the separation of the volatile organic compound such as trichlorethylene from the waste water is performed in a total of five stages.

  That is, the third sealed container 27, the fourth sealed container 28, and the fifth sealed container 29 are filled with fillers 27a, 28a, 29a such as Raschig rings for promoting degassing and flash evaporation. And, by being connected to the duct 23 to the first heat exchanger 21 connected to the vacuum pump 25, the inside thereof is about 20 like the first sealed container 11 and the second sealed container 12. It is maintained at a reduced pressure so that the saturated steam temperature is at ° C.

  By supplying the waste water taken out from the second sealed container 12 by the discharge pump 18 to the spray nozzle 31 provided in the upper part in the third sealed container 27 through the transfer pipe 30, the spray nozzle 31 From the bottom of the third hermetic container 27 and is taken out by the discharge pump 32.

  The waste water taken out by the discharge pump 32 is supplied to the spray nozzle 34 provided at the upper part in the fourth sealed container 28 via the transfer pipe 33, so that the fourth sealed container is supplied from the spray nozzle 34. After ejecting downward into the interior 28, it is taken out by the discharge pump 35 from the bottom of the fourth sealed container 28.

  The waste water taken out by the discharge pump 35 is supplied to the spray nozzle 37 provided at the upper part in the fifth sealed container 29 via the transfer pipe 36, so that the fifth sealed container is supplied from the spray nozzle 37. After being ejected downward into 29, it is taken out by the discharge pump 38 from the bottom of the fifth sealed container 29.

  In each of the waste water transfer line 30 to the third closed container 17, the waste water transfer line 33 to the fourth closed container 28, and the waste water transfer line 36 to the fifth closed container 29, The gas mixing means 39, 40, and 41 are provided so that a sufficient amount of gas such as air is dissolved in each waste water.

  On the other hand, a third heat exchanger 42 that uses water vapor and non-condensable gas compressed by the vacuum pump 25 as heat sources is provided in the waste water transfer line 30 to the third sealed container 27, and 3 The temperature of the waste water to the sealed container 27 is increased to about 22 ° C.

  The third heat exchanger 42 uses the water vapor and non-condensable gas compressed by the vacuum pump 25 as the heat source in the same manner as the second heat exchanger 22, and therefore the second heat exchanger 22. And an integrated heat exchanger.

  In this configuration, flash evaporation and deaeration are performed in the second sealed container 12, and waste water taken out from the second sealed container 12 by the discharge pump 18 is heated to about 22 ° C. in the third heat exchanger 42. Furthermore, after a gas such as air is mixed with this by the mixing means 39, it is ejected from the spray nozzle 31 into the third sealed container 27, and is flash evaporated and deaerated. Volatile organic compounds such as trichlorethylene contained in the wastewater are separated from the wastewater.

  The waste water taken out from the third sealed container 27 by the discharge pump 32 is mixed with gas such as air by the mixing means 40 and then ejected from the spray nozzle 34 into the fourth sealed container 28. By deaeration, volatile organic compounds such as trichlorethylene contained in the wastewater are separated from the wastewater.

  The waste water taken out from the fourth sealed container 28 by the discharge pump 35 is mixed with a gas such as air by the mixing means 41, and then is sprayed from the spray nozzle 37 into the fifth sealed container 29. By ejecting and degassing, volatile organic compounds such as trichlorethylene contained in the wastewater are separated from the wastewater.

  In this third embodiment, the sealed container for performing flash evaporation and degassing of waste water is composed of two, the second sealed container 12 and the third sealed container 27, and the waste water is disposed at a later stage. This is a case where the latter sealed container for performing deaeration is constituted by two, a fourth sealed container 28 and a fifth sealed container 29.

  In the first and second embodiments, the second heat exchanger 22 and the third heat exchanger 42 have condensed water and non-condensable gas containing a volatile organic compound such as trichlorethylene. Are discharged from the pipes 43 and 44, which are processed as follows, for example.

  That is, the condensed water is guided to an ultrasonic decomposition tank and irradiated with ultrasonic waves to decompose volatile organic compounds contained therein, while the non-condensable gas guides it to a heating furnace. The volatile organic compounds are thermally decomposed and released into the atmosphere.

It is a figure which shows the apparatus by the 1st Embodiment in this invention. In the apparatus of FIG. 1, it is a figure which shows the relationship between the temperature difference of the temperature of wastewater, and the saturated steam temperature in an airtight container, and the separation efficiency of a volatile organic compound. FIG. 3 shows an apparatus according to a second embodiment of the invention. It is a figure which shows the apparatus by the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 2 Vacuum pump 3,13,17,31,34,37 Spray nozzle 4,14 Waste water supply line 6 Heating means 7,19,20,39,40,41 Gas mixing means 11 First airtight container 12 2nd airtight container 21 1st heat exchanger 22 2nd heat exchanger 25 Vacuum pump 27 3rd airtight container 28 4th airtight container 29 5th airtight container

Claims (2)

  Dissolve gas in the wastewater inside the sealed container maintained at a reduced pressure lower than atmospheric pressure with wastewater containing volatile organic compounds, and the temperature of the wastewater is higher by 5 ° C than the saturated steam temperature in the sealed container A method for separating a volatile organic compound in wastewater, characterized in that the volatile organic compound is supplied so as to be ejected while maintaining an arbitrary temperature within a temperature range from a temperature to a temperature lower by 4 ° C. than the saturated vapor temperature. .   A sealed container, a vacuum generator for maintaining the inside of the sealed container at a pressure lower than atmospheric pressure, and a nozzle for ejecting waste water containing a volatile organic compound into the sealed container, and further, supplying waste water to the nozzle The pipe has a mixing means for dissolving gas in the waste water, and the waste water from a temperature higher by 5 ° C. than the saturated steam temperature in the sealed container to a temperature lower by 4 ° C. than the saturated steam temperature. An apparatus for separating a volatile organic compound in wastewater, characterized by comprising heating means adapted to be maintained at an arbitrary temperature within the temperature range.

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