JP2005193148A - Method and apparatus for separating volatile organic compound in wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To separate a volatile organic compound such as trichloroethylene or tetrachloroethylene which is contained in wastewater such as underground water or industrial wastewater from the wastewater in a high separation ratio at a low running cost. <P>SOLUTION: Air is mixed with the wastewater containing the volatile organic compound. The wastewater is introduced into a hermetically closed tank 1 having a packed bed 2 provided therein and internally held to pressure lower than saturated vapor pressure at the temperature of the wastewater and injected on the upper side of the packed bed 2 while discharged from the lower side of the packed bed 2. The vapor passed through the packed bed 2 from above to below is guided to a condenser 9 to condense the vapor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides a method for efficiently 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 thereof. It is about.

  In Patent Document 1 as a prior art, as one of the separation methods, a packed bed is provided in the aeration tower, and waste water containing a volatile organic compound is supplied to the upper side of the packing in the aeration tower. Then, while flowing down through the packed bed, air compressed by a blower is blown into the lower side of the packing in the aeration tower, and this air is discharged from the upper side of the packing in the aeration tower. It is described that the volatile organic compound in the wastewater is volatilized and separated in the air by contacting the wastewater and air as a counterflow in the packed bed.

  And in this prior art separation method, the exhaust gas of the air containing a volatile organic compound is discharged | emitted from the said aeration tower.

Since discharging this exhaust gas as it is to the atmosphere will contaminate the atmosphere with the volatile organic compounds contained therein, Patent Document 1 discloses that the exhaust gas from the aeration tower is used as an activated carbon adsorption tower. Through the purification process, the volatile organic compound in the exhaust gas is adsorbed and removed by activated carbon, and then released into the atmosphere.
Japanese Patent Laid-Open No. 5-92181

  However, in the prior art separation method, in order to increase the separation rate of volatile organic compounds, the amount of air blown into the aeration tower must be excessively increased. In addition to the significant increase in the amount of gas, the concentration of volatile organic compounds in the exhaust gas is considerably reduced. Therefore, when the exhaust gas is purified by the activated carbon adsorption tower as described above, The activated carbon adsorption tower is not only significantly increased in size, but also has a problem in that the running cost is significantly increased.

  In addition, when the exhaust gas from the aeration tower is led to a combustion furnace and decomposed by combustion, the amount of the exhaust gas is remarkably large, resulting in a large combustion furnace and a significant increase in running cost. The problem is invited.

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

In order to achieve this technical problem, the separation method of the present invention, as described in claim 1,
“Air is mixed with wastewater containing volatile organic compounds, and then the wastewater is provided with a packed bed inside, and the inside is kept at a reduced pressure lower than the saturated vapor pressure at the temperature of the wastewater. Among these, after ejecting to the upper side of the packed bed, it is discharged from the lower side of the packed bed, while air and steam passing through the packed bed from the top to the bottom are led to a condenser to condense the steam. "
It is characterized by that.

Moreover, as described in claim 3, the separation device of the present invention is
“A means for mixing air with wastewater containing volatile organic compounds, a sealed tank provided with a packed bed therein and maintained at a reduced pressure lower than the saturated vapor pressure at the temperature of the wastewater, and a steam condenser A spray nozzle for ejecting the waste water on the upper side of the packed bed in the sealed tank, and an outlet for treated waste water on the lower side of the packed bed in the sealed tank. The condenser was connected to the lower side of the packed bed in the tank so that air and vapor that passed through the packed bed from the top to the bottom were led to the condenser.
It is characterized by that.

  When the wastewater mixed with air is ejected into a closed tank that is maintained at a reduced pressure lower than the saturated vapor pressure at the temperature of the wastewater, the air bubbles mixed with the wastewater burst, and at the same time, the wastewater evaporates at a boiling point.

  Due to the bursting of air bubbles in the wastewater, volatile organic compounds contained in the wastewater are gasified along with the bursting air bubbles and separated from the wastewater together with the air.

  In addition, when the wastewater is boiled and evaporated, the volatile organic compound contained in the wastewater is gasified along with the vapor that boils and is separated from the wastewater together with the vapor. The boiling evaporation is performed even while the waste water flows down from the packed bed to the bottom. In other words, the separation of the volatile organic compound by boiling evaporation causes the waste water to flow down the packed bed from the top. It is done during the process.

  Thereby, the separation efficiency of the volatile organic compound from the wastewater can be greatly promoted, and the treated wastewater after the separation of the volatile organic compound is sealed after passing through the packed bed from top to bottom. It is discharged out of the tank.

  On the other hand, the air separated from the waste water and the vapor boiled and evaporated from the waste water are led to the condenser after passing through the packed bed together with the waste water, and in this condenser, As the steam is condensed, the exhaust gas from the condenser is almost only air mixed with the waste water, and the amount of the exhaust gas is remarkably reduced. In the same manner as in the prior art, even if the purification treatment is performed in the activated carbon adsorption tower, not only a small activated carbon adsorption tower is required, but also the running cost can be greatly reduced, and the exhaust gas is led to the combustion furnace. Even in the case of performing the combustion treatment, the enlargement of the combustion furnace can be avoided and the running cost can be significantly reduced.

  In particular, as described in claim 2, the air bubbles mixed with the waste water are sprayed through the spray nozzle so that the air bubbles mixed with the air are refined by the spray nozzle. Therefore, there is an advantage that the separation efficiency of the volatile organic compound from the wastewater can be further promoted.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing an embodiment of the present invention. FIG. 2 is a diagram showing a state before reaching the present invention.

  In FIG. 1, reference numeral 1 denotes a sealed tank in which a packed layer 2 such as a Raschig ring is provided inside, and waste water is placed in the packed bed 2 above the packed layer 2 in the sealed tank 1. A spray nozzle 3 is provided for jetting toward the waste water. Waste water containing a volatile organic compound such as trichlorethylene or tetrachloroethylene is supplied to the spray nozzle 3 from a transfer pump 4 via a waste water supply line 5. In addition, an air supply pipe 7 for mixing the air compressed by the blower 6 with the waste water in the waste water supply pipe 5 is connected in the middle of the waste water supply pipe 5 to the spray nozzle 3. Has been.

  On the other hand, an outlet pipe 8 of the treated wastewater from the sealed tank 1 is connected to the lower side of the packed bed 2 in the sealed tank 1.

  Further, in FIG. 1, reference numeral 9 denotes a steam condenser using cooling water or atmospheric air as a cooling source. The steam condenser 9 is lower than the packed bed 2 in the sealed tank 1. A steam duct 10 from the side is connected, and further a vacuum generation source such as a vacuum pump 11 is connected, so that the pressure in the sealed tank 1 is changed to the temperature of the wastewater supplied through the wastewater supply pipe 5. Maintain a reduced pressure below the saturated vapor pressure.

  The waste water supplied through the waste water supply pipe 5 is mixed with the air from the air supply pipe 7 and then reaches the spray nozzle 3, where the air bubbles are refined and then the sealed tank 1. It ejects toward the packed bed 2 inside.

  Due to the ejection of the waste water into the sealed tank 1, the air bubbles mixed with the waste water burst, and at the same time, the waste water boils and evaporates.

  Due to the bursting of air bubbles in the wastewater, volatile organic compounds contained in the wastewater are gasified along with the bursting air bubbles and separated from the wastewater together with the air.

  In addition, when the wastewater is boiled and evaporated, the volatile organic compound contained in the wastewater is gasified along with the vapor that boils and is separated from the wastewater together with the vapor. The boiling evaporation is performed even when the waste water flows down from the top to the bottom of the packed bed 2. In other words, the separation of the volatile organic compound by the boiling evaporation causes the waste water to move down the packed bed 2 from the top. It is also performed in the middle of flowing down.

  Thereby, the separation efficiency of the volatile organic compound from the wastewater can be greatly promoted, and the treated wastewater after separating the volatile organic compound is discharged after passing through the packed bed 2 from top to bottom. It is discharged from the conduit 8.

  On the other hand, the air separated from the waste water and the vapor boiled and evaporated from the waste water are guided to the steam condenser 9 through the steam duct 10 after passing through the packed bed together with the waste water from the top to the bottom. In addition, since the steam is condensed in the steam condenser 9, most of the exhaust gas discharged from the steam condenser 9 by the vacuum pump 11 is only air mixed with the waste water. Become.

  By the way, in the experimental apparatus before reaching the present invention, as shown in FIG. 2, the steam duct 10 ′ to the steam condenser 9 is connected to the upper part of the sealed tank 1 above the packed bed 2. It was configured to do.

  On the other hand, in the case of the apparatus of the embodiment shown in FIG. 1, the steam duct 10 to the steam condenser 9 is connected to a portion below the packed bed 2 in the sealed tank 1. The separation rate of the volatile organic compound from the wastewater can be improved to about 1.2 times that of the experimental apparatus shown in FIG.

  The exhaust gas from the vacuum pump 11 is purified by an activated carbon adsorption tower or a combustion furnace and then released into the atmosphere. On the other hand, the condensed water discharged from the steam condenser 9 through the conduit 12 Since some volatile organic compounds are contained, the volatile organic compounds are decomposed by ultrasonic irradiation or the like, or condensed water discharged from the pipe 12 is supplied to the waste water supply pipe 5. Configure to return.

It is a figure which shows embodiment of this invention. It is a figure which shows before reaching this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sealing tank 2 Packing bed 3 Spray nozzle 4 Waste water pump 5 Waste water supply line 6 Blower 7 Air supply line 8 Outlet line of treated waste water 9 Steam condenser 10 Steam duct 11 Vacuum pump

Claims (3)

  The air is mixed with the wastewater containing the volatile organic compound, and then the wastewater is provided with a packed bed inside, and the inside is kept at a reduced pressure lower than the saturated vapor pressure at the temperature of the wastewater. , After being ejected from the upper side of the packed bed and discharged from the lower side of the packed bed, the air and steam that have passed through the packed bed from top to bottom are guided to a condenser to condense the steam. A method for separating volatile organic compounds from wastewater.   2. The method for separating volatile organic compounds in waste water according to claim 1, wherein the waste water mixed with air is ejected to the upper side of the packed bed through a spray nozzle.   Means for mixing air with wastewater containing volatile organic compounds, a sealed tank comprising a packed bed inside and holding the interior at a reduced pressure lower than the saturated vapor pressure at the temperature of the wastewater, a steam condenser, A spray nozzle for ejecting the waste water on the upper side of the packed bed in the sealed tank, and an outlet for treated waste water on the lower side of the packed bed in the sealed tank. Volatility in waste water, characterized in that the condenser is connected to the lower side of the packed bed so that air and vapor passing through the packed bed from the top to the bottom are led to the condenser. An apparatus for separating organic compounds.

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