JP2015006672A - Vacuum-evaporation-based voc recovery apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a VOC (volatile organic compound) removal solution regeneration and recovery apparatus in which no heater is used and no gas-permeable membrane is required and therefore volatile substances and the like are not adversely affected when passing through the gas-permeable membrane, and also to provide a VOC removal solution regeneration and recovery method therefor.SOLUTION: The VOC removal solution regeneration and recovery apparatus includes: a liquid feeding pump and a nozzle that spray the VOC removal solution; a vacuum vessel that has the nozzle disposed inside thereof; a vacuum pump that reduces pressure of an interior of the vacuum vessel and performs vacuum-evaporation of the VOC included in the VOC removal solution; a gas introducing mechanism that introduces evaporation enhancing gas into the vacuum vessel; and a liquid discharge mechanism that discharges the processed VOC removal solution from the vacuum vessel. The apparatus further comprises a compressor that compresses air from the outside and generates compressed air having thermal energy and pressure energy. A heat exchanger is provided at a passage from the liquid feeding pump to the nozzle, heat exchange between the VOC removal solution and the compressed air is performed by the heat exchanger, and the thermal energy is supplied to the VOC removal solution. The liquid feeding pump is an air-driven pump that is driven by air pressure as a power source, and the pressure energy of the compressed air is used as the power source of the pump.

Description

  The present invention removes VOC contained in a VOC removal liquid (hereinafter referred to as a removal liquid) used to remove VOC (Volatile Organic Compounds), and collects the removal liquid. The present invention relates to a VOC removal liquid regeneration / recovery device and a regeneration / recovery method.

  For example, it is known that exhaust gas generated in a painting or printing process contains VOC, and if exhaust gas containing VOC is directly discharged into the atmosphere, secondary pollution is caused. Therefore, techniques for removing VOC from exhaust gas have been studied.

As a technique for removing VOC from exhaust gas, for example, there is a technique disclosed in Patent Document 1.
In the technique disclosed in Patent Document 1, an absorption liquid recovery tank that recovers a removal liquid (absorption liquid) that is absorbed by contact with VOC (exhaust gas) is provided. The absorption liquid recovery tank is provided with a heater, and is configured to evaporate and remove VOC from the removal liquid by heating the heater.

Further, as another technique for removing VOC from exhaust gas, Patent Document 2 discloses a technique related to a removal liquid recovery mechanism using a degassing membrane.
The technique disclosed in Patent Document 2 introduces a liquid or volatile substance contained in a liquid by introducing a liquid to be processed into one side of the gas permeable membrane and reducing the gas phase on the other side. It is composed of a module that removes the gas phase chamber. In the technique disclosed in Patent Document 2, an air bleeder for introducing air as a carrier gas into the decompressed gas phase chamber is further provided. The air bleeder is a means for promoting degassing, and the gas introduced from the air bleeder is preferably provided at a position where the volatile substance that has permeated the gas permeable membrane is efficiently carried away. As the gas permeable membrane, a non-porous membrane or a porous membrane such as a flat membrane, a hollow fiber membrane, or a tubular membrane can be applied.

JP 2002-273157 A Japanese Patent No. 2949732

However, since the technique disclosed in Patent Document 1 uses a heater for recovering the removal liquid (absorption liquid), there is a problem that power consumption is large and CO ₂ is discharged more by that amount. Moreover, since the technique disclosed in Patent Document 2 requires a gas permeable membrane, there is a problem that the processing efficiency is poor due to an adverse effect of volatile substances and the like when permeating.

Therefore, in the present invention, since no heater is required, the amount of CO ₂ emission can be reduced by the amount that does not consume the electric power related to the use of the heater, and no gas permeable membrane is required. An object of the present invention is to provide a VOC removal liquid regeneration / recovery device and a regeneration / recovery method in which volatile substances and the like are not adversely affected during permeation.

  In order to solve the above-described problems, in the present invention, a VOC removal liquid regeneration / recovery device that regenerates and collects a VOC removal liquid by removing VOC contained in the VOC removal liquid, and sprays the VOC removal liquid. A liquid feed pump and a nozzle, a vacuum container in which the nozzle is disposed, a vacuum pump for decompressing the inside of the vacuum container to vacuum-evaporate VOC contained in the VOC removal liquid, and an evaporation promoting gas in the vacuum container And a drainage mechanism for discharging the processed VOC removal liquid from the vacuum vessel, and compresses air from the outside to generate compressed air having thermal energy and pressure energy. A heat exchanger is provided on a path from the liquid feed pump to the nozzle, and heat exchange is performed between the VOC removal liquid and the compressed air in the heat exchanger, and the thermal energy is converted to the V energy. And supplying the C remover. The liquid feed pump is an air-driven pump that is driven by air pressure as a power source, and uses the pressure energy of the compressed air as the power source of the pump.

  Thereby, the VOC removal liquid pumped by the liquid feed pump is sprayed from the nozzle in the vacuum container. The inside of the vacuum vessel is depressurized by the action of the vacuum pump, whereby VOC is vacuum evaporated from the VOC removal solution. Since the VOC removal liquid is atomized by spraying, its surface area is dramatically increased as compared with the one that is simply stored. Combined with this, the introduction of the evaporation promoting gas through the gas introduction mechanism improves the efficiency of vacuum evaporation. That is, the regeneration / recovery of the VOC removal liquid is efficiently performed. Here, “vacuum evaporation” refers to a method of reducing the pressure in the gas phase and separating volatile substances and the like from the VOC removal liquid.

  Furthermore, by using the thermal energy of the compressed air for heating the VOC removal liquid, the VOC removal liquid is heated and vacuum evaporation can be performed more efficiently. This is made possible by transferring the thermal energy of the high-temperature and high-pressure compressed air generated by the compressor to the VOC removal liquid using a heat exchanger.

  Further, the pressure energy of the compressed air generated by the compressor is used in order to use the pressure energy of the cooled compressed air after the heat exchange as a drive source of the liquid feeding pump for pumping the VOC removal liquid into the vacuum vessel. Energy can be used effectively without waste.

Therefore, since a heater is not required, the amount of CO ₂ emission can be reduced by the amount that does not consume the electric power associated with the use of the heater, and since no gas permeable membrane is required, volatilization occurs when passing through the gas permeable membrane. Substances are not adversely affected. In addition, the VOC contained therein can be removed from the VOC removal liquid with high efficiency, and the removal liquid can be recovered.

And a storage tank for storing the VOC removal liquid discharged from the drainage mechanism, and compressed air introduction means for introducing the compressed air after heat exchange with the heat exchanger into the storage tank. It is good to provide. Two liquid storage tanks may be provided so that the removal liquid can be stored alternately.
Thereby, the pressure energy which the compressed air produced | generated by the compressor has can be utilized still more effectively.

Moreover, it is good to provide the air tank which stores the compressed air after heat-exchanging with the said heat exchanger.
Thereby, the air tank serves as a buffer for the compressed air, and the pressure energy of the compressed air can be utilized more efficiently.

  The evaporation promoting gas may be compressed air from the compressor instead of the atmosphere. The rapid cooling in the vacuum tank can be suppressed by directly introducing the heated air into the vacuum tank.

  Further, as a method invention for solving the problem, a VOC removal liquid regeneration / recovery method for regenerating / recovering a VOC removal liquid by removing the VOC contained in the VOC removal liquid, the compression generated by the compressor The inside of the vacuum vessel is depressurized by a vacuum pump while spraying the VOC removal solution heated by the heat exchange with the gas inside the vacuum vessel, and further, the VOC removal solution is introduced by introducing an evaporation promoting gas into the vacuum vessel. The VOC contained in is vacuum evaporated. The compressed air after the heat exchange is used as a drive source of a liquid feed pump for spraying the VOC removal liquid.

  Further, the VOC removal liquid after the VOC is vacuum evaporated is stored in a liquid storage tank provided outside the vacuum container, and the VOC removal is performed from the liquid storage tank by the pressure of the compressed air after the heat exchange. The liquid should be drained.

According to the present invention, since no heater is required, the amount of CO ₂ emission can be reduced by the amount that does not consume the electric power related to the use of the heater, and no gas permeable membrane is required. It is possible to provide a VOC removal liquid regeneration / recovery device and regeneration / recovery method in which volatile substances and the like are not adversely affected.

It is a systematic diagram which shows the VOC removal liquid reproduction | regeneration and collection | recovery apparatus in an Example. It is a figure which shows the result of VOC reproduction | regeneration / collection | recovery experiment.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Absent.

FIG. 1 is a system diagram showing a VOC removal liquid regeneration / recovery device in the embodiment.
The VOC removal liquid regeneration / recovery device 1 (hereinafter referred to as the regeneration / recovery device 1) removes VOC from a VOC removal liquid (hereinafter referred to as a to-be-processed removal liquid) containing VOC, and removes the VOC removal liquid ( In the following, this is regenerated / recovered.

First, the structure of the regeneration / recovery device in the embodiment will be described with reference to FIG.
1 includes a storage tank 3, a liquid feed pump 5, a spray nozzle 7, a vacuum vessel 9, a vacuum pump 11, a gas introduction mechanism 13, a drainage mechanism 15, a liquid storage tank 17, a compressor 19, A heat exchanger 21 and an air tank 23 are included.

  The storage tank 3 is a tank that stores a VOC removal liquid (processed removal liquid Ld) drawn from the outside. The storage tank 3 is not provided, and instead of the storage tank 3, the removal liquid Ld to be processed is directly taken out from the VOC removal device (not shown), or the liquid supply pump is provided in the middle of the liquid supply pipe (not shown) of the removal liquid Ld to be processed. 5 can also be provided. The liquid feed pump 5 is for taking out the liquid to be removed Ld stored in the storage tank 3 and pumping it to the nozzle 7. The nozzle 7 is for spraying the to-be-processed removal liquid Ld fed in the vacuum vessel 9. On the exhaust side of the vacuum pump 11, a cooling condensing device 27, which is a VOC processing mechanism, is provided. The compressor 19 generates high-temperature and high-pressure compressed air. The heat exchanger 21 is for heat-exchanging the compressed air generated by the compressor 19 and the removal liquid Ld to be processed which is pressure-fed from the liquid feed pump 5 to the nozzle 7 to raise the temperature of the removal liquid Ld to be processed. is there. The 0 air tank 23 is a tank for storing the compressed air heat-exchanged with the to-be-processed removal liquid Ld in the heat exchanger 21.

  The vacuum container 9 is a cylindrical container whose inside is decompressed by a connected vacuum pump 11. A nozzle 7 is disposed in the upper part of the vacuum vessel 9, a gas introduction mechanism 13 is disposed in the lower part thereof, and a drainage mechanism 15 is disposed in the lowermost part. Further, a mist trap 25 is provided in the middle of the height inside the vacuum vessel 9 and below the nozzle 7 and above the gas introduction mechanism. The mist trap 25 is above the vacuum vessel 9 and above the nozzle 7. 'Is provided. A heat exchanger 21 is provided below the fog trap 25. In this embodiment, the heat exchanger 21 is provided inside the vacuum vessel 9, but may be provided outside the vacuum vessel.

In the present embodiment, the fog trap 25 is composed of a polyurethane foam that is an open-cell foam and a support that supports the foam. Polyurethane foam is lightweight and can be obtained inexpensively. Furthermore, polyurethane foam has a huge surface area (total area of the cell wall) of 1490 m ² per unit volume when its side is a cube of 1 m (ie, volume of 1 cubic meter), and the porosity is 0.97. There is an advantage that there is almost no passage resistance of the VOC removal liquid. Along with this, the total area of the to-be-processed removal liquid Ld adhering to the cell wall also becomes enormous, and this realizes efficient VOC vacuum evaporation. Compared to conventional ceramic gas-adsorbing porous bodies, it is lighter and cheaper (approximately 1/10 or less), and polyurethane foam is very easy to use. However, a foam other than polyurethane foam is adopted as long as the cell wall between adjacent cells communicates with each other and has an air bubble structure in which the removal liquid Ld to be treated can adhere to the cell wall. You can also. The fog trap 25 ′ employs a polyurethane foam in the same manner as the fog trap 25, but other open-cell foams and other members can be employed as long as the purpose of the fog trap can be achieved.

  The support constituting the fog trap 25 is a net-like member and is attached so as to cross the inside of the vacuum vessel 9. By making the said support body mesh-like, the to-be-processed removal liquid Ld can be dripped from the said open cell foam, without staying excessively. Therefore, it is necessary that the mesh of the support is sufficient to support the open-cell foam and is rough enough to smoothly drop the VOC removal liquid. As long as such an object can be achieved, the support can also be constituted by, for example, a cocoon-like one other than the net-like shape, a plate member formed with a large number of small holes such as punching metal, and the like. If the support is not required, such as when the open cell foam has sufficient hardness to be self-supporting, or when a self-supporting member other than the open-cell foam is used as a fog trap, it is supported. The body can be omitted.

  The nozzle 7 is located above the mist trap 25 as described above, and the spray angle, the distance from the mist trap 25, the spray pressure, the spray particle size, etc. so that the to-be-processed removal liquid Ld is spread evenly in the vacuum vessel 9. Adjust. Although the number of the nozzles 7 is one in this embodiment, two or more nozzles 7 may be provided according to the volume of the vacuum vessel 9 and the processing amount per unit time of the removal liquid Ld to be processed.

  The gas introduction mechanism 13 is a leak valve. When this leak valve is opened in a state where the vacuum pump 11 is driven and the inside of the vacuum vessel 9 is depressurized, the gas for promoting evaporation (in FIG. 1 of this embodiment, the introduction of the atmosphere is illustrated, but the compressor 19 is heated). The compressed air may be directly introduced) into the vacuum container 9 by suction. Instead of providing a leak valve, an evaporation promoting gas may be introduced into the vacuum vessel 9 through the nozzle 7. Further, the gas for promoting evaporation may be introduced by both the leak valve and the nozzle 7. In these cases, the nozzle 7 has both the function of spraying the liquid to be treated and the function of the gas introduction mechanism 13.

Next, the operation of the regeneration / collection apparatus in the embodiment will be described with reference to FIG.
According to the regeneration / recovery device 1, the to-be-processed removal liquid Ld stored in the storage tank 3 is pumped by the liquid feeding pump 5, and exchanged with the compressed air from the compressor 19 by the heat exchanger 21 to rise. After being heated, it is sprayed into the vacuum container 9 from the nozzle 7. On the other hand, the compressed air that has been cooled while maintaining a high pressure by exchanging heat with the removal liquid Ld to be treated in the heat exchanger 21 is stored in the air tank 23.
The liquid feed pump 5 is an air-driven pump whose driving source is compressed air. As a drive source for the liquid feed pump, the compressed air stored in the air tank 23 is reduced to an appropriate pressure by the pressure reducing valve 31 and used.

  Further, by driving the vacuum pump 11, the inside of the vacuum vessel 9 is depressurized, and VOC is evaporated from the to-be-treated removal liquid Ld sprayed from the nozzle 7 by the depressurization. Since the to-be-processed removal liquid Ld is atomized by spraying, its surface area is dramatically increased as compared with the liquid just stored. Furthermore, since the to-be-processed removal liquid Ld is heated by the heat exchanger 21, it is more easily evaporated.

  And the mist-like to-be-processed removal liquid Ld arrives at the open cell foam which comprises the fog trap 25, and adheres to the cell wall. The to-be-processed removal liquid Ld adhering to the cell wall further expands its surface area. The surface area of the removal liquid Ld to be processed which has been enlarged is enormous. Combined with these, the introduction of the evaporation promoting gas (air) through the gas introduction mechanism 13 improves the efficiency of vacuum evaporation. That is, the recovery liquid Ld to be treated (recovery removal liquid Lc) is efficiently recovered. The to-be-processed removal liquid Ld becomes the regeneration removal liquid Lc while passing (falling) through the open-cell foam, and drops through the open-cell foam and the support.

  The dropped regeneration removal liquid Lc is discharged out of the vacuum vessel 9 through the drainage mechanism 15 and stored in the liquid storage tank 17. The regeneration removal liquid Lc stored in the liquid storage tank 17 is appropriately discharged from the liquid storage tank 17. When discharging the regeneration removal liquid Lc from the liquid storage tank 17, the discharge valve 18 provided at the lower part of the liquid storage tank 17 is opened, and the compressed air stored in the air tank 23 is supplied to the liquid storage tank 17 through the pipe 33. In this case, the regeneration removal liquid Lc can be easily discharged to the outside by increasing the internal pressure of the liquid storage tank 17. The pipe 33 is provided with a pressure reducing valve 35, a speed controller 37, and a compressed air introduction valve 39. The pressure and amount of compressed air introduced from the air tank 23 to the liquid storage tank 17 can be adjusted by the pressure reducing valve 35 and the speed controller 37, and the introduction of compressed air from the air tank 23 to the liquid storage tank 17 is necessary. When there is no air, the introduction can be stopped by closing the compressed air introduction valve 39.

  In addition, a drain valve 40 is provided in front of the liquid storage tank 17, and the removal liquid discharged from the vacuum vessel 9 can be obtained by using an air operated switching control valve using compressed air from the air tank 23. It can be stored alternately in the two liquid storage tanks 17.

The gas introduction mechanism 13 will be additionally described.
As a premise, the result of the toluene recovery rate from the VOC removal solution according to the conventional technique will be described.
As a conventional method for regenerating a VOC removal solution containing VOC, there is a PV method (pervaporation method) by membrane separation. However, with this method, the recovery rate of toluene from the VOC removal solution is as low as about 0.027%, and it is difficult to regenerate the VOC removal solution in real time.

  Therefore, as shown in FIG. 2A, the VOC evaporation amount can be increased by a vacuum evaporation method using a porous film in order to reduce the permeation resistance of the film. While the evaporation concentration of toluene by the PV method was stable at about 70 ppm and the recovery rate was about 0.027%, toluene by the vacuum evaporation method using a porous film as shown in FIG. The evaporation concentration is stable at about 200 ppm, and the recovery rate is 0.077%, which is a threefold improvement over the PV method. However, even with the vacuum evaporation method using the porous film as shown in FIG. 2A, it is difficult to regenerate the VOC removal solution in real time.

  That is, as described above, it is considered that the conventional method could not efficiently recover the evaporated VOC because there was no air flow because the high vacuum was set to several tens of Pa or less. On the other hand, in the air flow vacuum evaporation method, as shown in FIG. 2 (b), the VOC evaporated by the flow of air is wiped and collected in a state where the vacuum vessel is leaked and air is introduced to lower the degree of vacuum. Is the method. In this method, it was confirmed that VOC can be efficiently recovered when a relatively low vacuum of about several thousand Pa is used for toluene evaporation. In addition, according to the air flow vacuum evaporation method of the present invention in which the removal liquid is sprayed without using a gas permeable membrane, the toluene evaporation concentration was stabilized at about 2900 ppm, and the recovery rate was 93.5%.

  In other words, according to the present invention, the VOC recovery rate is 93.5%, which is a dramatic increase compared to the prior art, and the removal liquid can be regenerated in real time.

  In addition, according to the present invention, by using the thermal energy of the compressed air for heating the treatment removal liquid Ld, the treatment removal liquid Ld is heated and vacuum evaporation can be performed more efficiently. In addition, when the heat energy of the high-temperature and high-pressure compressed air generated by the compressor is transmitted to the treatment removal liquid Ld using a heat exchanger provided in the vacuum vessel, the heating of the treatment removal liquid Ld is performed in the vacuum vessel. The removal liquid Ld to be processed can be heated safely and efficiently without performing it outside.

  Further, the pressure energy of the compressed air whose temperature has been lowered after the heat exchange is used as a drive source of the liquid feed pump 5 for pumping the treated removal liquid Ld into the vacuum vessel, and the separated removal liquid is stored. Since it is used as a pumping function for efficiently discharging from the tank, the energy of the compressed air generated by the compressor can be used effectively without waste.

Therefore, by using compressed air as the heating means for the removal liquid Ld to be treated, it is not necessary to use a heater for heating the removal liquid Ld to be treated, and it is possible to reduce power consumption and CO ₂ emissions associated with the use of the heater. This is possible and the risk of ignition by the heater can be avoided. In other words, it is safe without considering the explosion-proof structure because it uses air pressure.

  Furthermore, by using the pressure energy of the compressed air whose temperature has been lowered after the heat exchange with the removal liquid Ld to be treated, it is possible to effectively discharge the regenerated removal liquid Lc after separation using an air driven pump and air pressure as a series of systems. It can be used to increase the energy efficiency of the entire device.

Since no heater is required, CO ₂ emissions can be reduced by the amount that does not consume the electric power used for the heater, and since no gas permeable membrane is required, a volatile substance or the like can pass through the gas permeable membrane. Can be used as a VOC removal liquid regeneration / recovery device and a regeneration / recovery method that are not adversely affected.

DESCRIPTION OF SYMBOLS 1 VOC removal liquid reproduction | regeneration and collection | recovery apparatus 3 Storage tank 5 Liquid feed pump 7 Nozzle 9 Vacuum container 11 Vacuum pump 13 Gas introduction mechanism 15 Drainage mechanism 17 Liquid storage tank 19 Compressor (compressor)
21 heat exchanger 23 air tank 25, 25 'fog trap

Claims (9)

A VOC removal liquid regeneration / recovery device that regenerates / recovers a VOC removal liquid by removing VOC contained in the VOC removal liquid,
A liquid feed pump and a nozzle for spraying the VOC removal liquid;
A vacuum container having the nozzle disposed therein;
A vacuum pump for depressurizing the inside of the vacuum container and evaporating VOC contained in the VOC removal liquid;
A gas introduction mechanism for introducing an evaporation promoting gas into the vacuum vessel;
A drainage mechanism for discharging the processed VOC removal liquid from the vacuum vessel,
A compressor that compresses air from the outside to generate compressed air having thermal energy and pressure energy;
A heat exchanger is provided on a passage from the liquid feed pump to the nozzle, the VOC removal liquid and the compressed air are heat-exchanged by the heat exchanger, and the thermal energy is supplied to the VOC removal liquid. VOC removal liquid regeneration and recovery equipment.   2. The VOC removal liquid according to claim 1, wherein the liquid feed pump is an air-driven pump that drives air pressure as a power source, and uses the pressure energy of the compressed air as the power source of the liquid feed pump. Regeneration / collection equipment. A liquid storage tank for storing the VOC removal liquid discharged from the drainage mechanism;
3. The VOC removal liquid regeneration / recovery device according to claim 1, further comprising compressed air introduction means for introducing compressed air after heat exchange with the heat exchanger into the liquid storage tank.   4. The VOC removal liquid regeneration / recovery device according to claim 3, wherein two storage tanks are provided so that the removal liquid can be stored alternately.   4. The VOC removal liquid regeneration / recovery device according to claim 3, further comprising an air tank for storing compressed air after heat exchange by the heat exchanger.   6. The VOC removal liquid regeneration / recovery device according to claim 5, wherein compressed air from the compressor is used as the evaporation promoting gas. A VOC removal liquid regeneration / recovery method that removes VOC contained in a VOC removal liquid to regenerate / recover the VOC removal liquid,
While spraying the VOC removal liquid heated by the heat exchange with the compressed gas generated by the compressor, the inside of the vacuum container is depressurized by a vacuum pump, and further, an evaporation promoting gas is introduced into the vacuum container. A VOC removal liquid regeneration / recovery method characterized in that the VOC contained in the VOC removal liquid is evaporated in a vacuum.   8. The VOC removal liquid regeneration / recovery method according to claim 7, wherein the compressed air after heat exchange is used as a drive source of a liquid feed pump for spraying the VOC removal liquid. The VOC removal liquid after the VOC is vacuum evaporated is stored in a liquid storage tank provided outside the vacuum container,
9. The VOC removal liquid regeneration / recovery method according to claim 7 or 8, wherein the VOC removal liquid is discharged from the liquid storage tank by the pressure of compressed air after heat exchange.

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