JP5109028B2 - Method for purifying a large amount of exhaust gas containing lean volatile hydrocarbons - Google Patents

Description

The present invention relates to a method for purifying exhaust gas containing dilute volatile hydrocarbons (hereinafter abbreviated as “VOC”), and in particular, VOC in a large amount of exhaust gas containing very dilute VOC that is diffused into the atmosphere. It is related with the method of collect | recovering as it is, without burning. More specifically, the present invention does not diffuse carbon dioxide (CO ₂ ), which has been regarded as a problem as a warming gas, by burning the exhaust gas containing VOCs into the atmosphere as in the prior art. From the viewpoint of prevention of global warming and pollution prevention, a large amount of exhaust gas containing the VOC related to the adsorption system for purifying the exhaust gas to zero emission and efficiently separating and reusing VOC from the exhaust gas It relates to a purification method.

  Conventionally, many methods for treating exhaust gas containing VOC have been proposed. In other words, as a method for removing VOC in exhaust gas so as to satisfy the legally required VOC emission concentration regulation value for pollution prevention, a combustion method, an adsorption method, an absorption method, a pressurized membrane separation method, etc. have been conventionally used. Are known.

However, the above method is limited to the case where the amount of exhaust gas to be processed is several hundred to several thousand m ³ per hour and the concentration of VOC contained is relatively high on the order of%. Among them, as a method for treating a large amount of exhaust gas containing dilute VOC in the order of ppm, a high-silica zeolite is used as an adsorbent, and a dilute VOC is turned into several thousand ppm by a honeycomb rotor rotating by alternately repeating adsorption and desorption. Many combustion methods have been adopted, apart from whether the catalyst is burned after being concentrated to the above concentration or directly burned. However, such a combustion method has become extremely difficult to apply due to the recent tightening of greenhouse gas (carbon dioxide) emission regulations.

In light of these circumstances, adsorption methods, absorption methods, pressurized membrane separation methods, and fibrous activated carbon methods have attracted attention as methods that can recover VOCs without burning them, but most of these methods are It is known. In particular, the adsorption methods that can be efficiently recovered in a dry state without using steam when desorbing the adsorbed VOC are also disclosed, for example, in Patent Documents 1 to 5 below. Moreover, as described above, the application method of the adsorption method disclosed in these patent documents is limited to exhaust gas treatment of several hundred m ³ to several thousand m ^{3 at} most including rich VOC. . The reason is that if the rising speed of the exhaust gas passing through the adsorbent layer is too fast (the limit is about 30 cm per second), the adsorbent with a small particle size rises and causes flooding phenomenon, so that the processing is performed at the limit per second. This is because the size of the apparatus becomes extremely large and does not hold economically.

Therefore, the present inventors applied a method of using honeycomb mesopore activated carbon instead of a granular adsorbent as an adsorbent that does not cause the flooding phenomenon as described above, and the latter stage was concentrated. The invention of the method of collect | recovering VOC with the well-known technique which the present inventors developed is proposed (refer the following patent document 6). That is, a method of pre-concentration and post-recovery, which is proposed as a preferable method for treating a large amount of exhaust gas containing dilute VOC of several hundred to several thousand ppm and exceeding 10,000 m ³ per hour. It is.
JP 09-047635 A JP 09-057060 A JP 09-215908 A Japanese Patent Laid-Open No. 11-071584 Japanese Patent Application Laid-Open No. 11-077496 JP 2007-038201 A

  The invention disclosed in the above-mentioned Patent Document 6 can cope with the greenhouse gas (carbon dioxide) emission regulation that has become a hot topic recently, and does not generate carbon dioxide in order not to burn VOC, As a method for recovering VOC as it is, it has an excellent effect. On the other hand, from an economic point of view, in order to be able to be used as a marketable device, improvements are made to the simplification of the individual equipment configuration and arrangement used in these methods, and the operation method, and a simple device is finished. There is a need.

  That is, according to experiments by the inventors, as in a large amount of exhaust gas purification method including VOC disclosed in Patent Document 6, the adsorption / desorption is caused to swing by a rotor using honeycomb-shaped mesopore activated carbon. Obtaining exhaust gas that has been concentrated to some extent by passing through a pre-concentration process that has been completed, and moving the exhaust gas that has been concentrated to some extent to a subsequent processing device to achieve zero emissions is not necessarily the best equipment configuration. It was found. That is, in the method for purifying a large amount of exhaust gas containing VOC disclosed in Patent Document 6, a vacuum pump is required as a desorption means in the previous concentration step, and converted from the VOC concentration discharged into the atmosphere during adsorption. This is because the VOC recovery rate does not exceed 80%.

The reason is that the greatest merit of adopting the honeycomb-shaped adsorbent layer is that the adsorbent layer is passed at a speed exceeding 1 m / sec and the adsorption is completed in 1 to 2 seconds with the adsorbent. Contrary to this, the breakthrough of the adsorbent (a honey-comb honeycomb having a bulk specific gravity of about 0.1) is fast. Incidentally, the bulk specific gravity of conventionally used granular activated carbon is around 0.4, and has an adsorption capacity 4 to 5 times that of the honeycomb-like adsorbent layer. However, the concentration ratio of the honeycomb-shaped adsorbent layer depends on the composition of the honeycomb-shaped adsorbent layer to be used, but when the main material is mesopore activated carbon, it is about 5 to 10 times (VOC in the exhaust gas is 2). In the case of 1,000 ppm, 10,000 PPm or 20,000 ppm), that is, the obtained VOC concentration is about 1 vol% to 2 vol%. With this level of concentration, VOC can be recovered almost 100% by the post-stage recovery apparatus using a large amount of exhaust gas purification method containing VOC described in Patent Document 6 above, but several hundreds of VOCs are contained in the exhaust gas. Considering the case where the gas is further diluted to ppm and is processed at several thousand to several tens of thousands of m ³ per hour, whether or not the apparatus is configured to recover at the subsequent stage after the concentration is completed at the previous stage is questioned.

  As one of the reasons, as conventionally known, two towers made of a honeycomb-like adsorbent layer were provided, and adsorption / desorption operations were alternately performed, and suction was performed using a vacuum pump used for desorption. After cooling the purge exhaust gas, the method of repeatedly returning the uncondensed gas to the one honeycomb-shaped adsorbent layer is that the capacity of the apparatus becomes very large because the adsorption capacity of the honeycomb-shaped adsorbent layer is small. It is done. In short, as described above, the recovery rate of VOC in the air diffused into the atmosphere after the operation because the breakthrough is early is less than 80%.

To solve the above problems, method for purifying large quantities of exhaust gas containing dilute VOC of the present invention, as described in claim 1, filling the mesopores activated carbon was Pureko Bok volatile hydrocarbon as adsorbent Using an adsorption device that alternately adsorbs and desorbs , allows exhaust gas containing VOC to pass through one of the adsorption devices, adsorbs VOC to the adsorbent layer in the adsorption device, and removes exhaust gas that does not contain VOC. A method for treating VOC-containing exhaust gas, which comprises discharging from the outlet of the adsorption device and switching the other adsorption device to desorption during that time, taking out the VOC previously adsorbed out of the system, cooling it, and collecting it as a liquid in the honeycomb or corrugated adsorbent layer consisting of mesopores activated carbon pre-coated with volatile hydrocarbons at the top of the suction device, in granular volatile hydrocarbons to lower plecos Using an adsorption apparatus equipped with an adsorbent layer filled with at least one of the bets the mesopore activated carbon and volatile particulate hydrophobic silica gel pre-coated with hydrocarbons, and the supply position of raw exhaust gas, middle layer in communication with the upper and lower It is located in.

Further, according to the method for purifying a large amount of exhaust gas containing the diluted VOC according to the present invention, as described in claim 2, a vacuum pump is used from the lower part of the adsorption device in which the upper part and the lower part are integrated at the time of desorption. At least one of suctioning and using a small amount of air or nitrogen as the purge gas from the top, the adsorption / desorption switching time is set to 1 to 30 minutes, and the obtained purge exhaust gas is cooled and taken out as a liquid outside the system The uncondensed gas at this time is returned to the bottom of the adsorption device.

  According to the method for purifying a large amount of exhaust gas containing a dilute VOC according to the present invention, an upper unit is obtained by making an upper part a purification part by a honeycomb and a lower part by a granular activated carbon and / or a concentration part by hydrophobic silica gel. The processing gas passing through the honeycomb-shaped adsorbent layer is increased to a speed of 1 to 2 m per second and is concentrated about 5 to 10 times here. At the time of desorption, the concentrated gas is absorbed by the lower granular adsorbent by a vacuum pump. By desorbing the VOC that has been adsorbed again as it passes through the layer, it becomes a richer gas. By repeating this adsorption and desorption, the lower particle size adsorbent communicating with the upper part has an equilibrium adsorption amount. A so-called cascade adapter that accumulates the corresponding VOCs (an adsorption tower that collects and concentrates uncondensed VOCs in this column without returning them to the raw material for each desorption) It becomes possible to play a role. With such an apparatus configuration and operation method, VOC contained in the purge exhaust gas can be easily liquefied even at about room temperature and recovered as a liquid. Therefore, the VOC concentration in the gas discharged to the atmosphere can be reduced to almost zero ppm. The cascade adapter is disclosed in detail in the above-mentioned Patent Document 2 by the present inventors.

  Further, in the method for purifying a large amount of exhaust gas containing the diluted VOC according to the present invention, as described above, the means for desorption of the adsorption / desorption device is sucked and / or used from the lower part of the integrated device using a vacuum pump. A small amount of air or nitrogen is used as a purge gas from the top, the adsorption / desorption switching time is set to 1 to 30 minutes, and the obtained purge exhaust gas is cooled and taken out as a liquid outside the system. And by returning the uncondensed gas at this time to the bottom of the integrated apparatus, the above-mentioned problems, in particular, the honeycomb part intended for the pre-stage concentration and the adsorption / desorption part intended for the post-stage recovery are separated. By eliminating almost all of the VOCs contained in the raw material gas and achieving zero emissions, eliminating the disadvantages of operating in a cost-effective manner and preventing pollution The above viewpoints can be cleared together.

  The method of returning the raw material exhaust gas to the intermediate position of the adsorption tower integrated above and below is not a novel means, for example, as there is a known example used when concentrating dilute carbon dioxide gas. It is also used universally for the separation operation of the distillation column during purification. However, in any known example, the target component is still concentrated in the lower part of the tower, and in the case of petroleum refining, while maintaining the vapor-liquid equilibrium of each stage using the difference in boiling point, Light components are dropped on the top and heavy components are dropped on the bottom, but in the case of carbon dioxide enrichment, since the raw material gas is air containing very thin carbon dioxide, the adsorbent that adsorbs only carbon dioxide, namely Union Showa Concentrated using a 13X (trade name) particle size zeolite from Co., Ltd. However, carbon dioxide gas concentrated (adsorbed) to 13X cannot be desorbed by a vacuum pump, and it is necessary to always use purge gas (air). Moreover, since the amount of the purge gas is large and comparable to the amount of the raw material gas, a vacuum pump and a purge gas (reflux purge) are used in the same 13X layer separated from the upper adsorbent layer and disposed at the lower portion. The carbon dioxide gas thus obtained is compressed to a high pressure and returned to the adsorbent layer. The partially concentrated gas is taken out.

  In the method according to the above known example, the present inventors were also involved at the time, but the intended purpose could not be achieved. This method is fundamentally different from the present inventors' large-scale exhaust gas purification method including a dilute VOC. First, the adsorbent is different. The method according to the above-mentioned known example does not use a honeycomb-like adsorbent layer, and the recovery target component itself is greatly different from the present invention. Further, the method according to the above-mentioned known example is different from the present invention in the apparatus configuration and the operation method. That is, the method for purifying a large amount of exhaust gas containing the diluted VOC according to the present invention is an adsorption tower that communicates vertically with the VOC recovery. This is a method in which the VOC concentrated in the upper part and the lower part is drawn out from the bottom part of the bottom of the slab at once and cooled, and only the uncondensed gas is returned to the bottom part of the original adsorption tower.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples and drawings. However, the examples described below are intended to limit the present invention to those described herein. Rather, the present invention can be equally applied to a variety of modifications without departing from the technical idea shown in the claims.

  In addition, FIG. 1 is a figure which shows schematic structure of the apparatus which can be used with the exhaust gas purification method of an Example. FIG. 2 is a flow sheet diagram when the adsorption process is performed in the A system in the exhaust gas purification method of the embodiment. FIG. 3 is a flow sheet diagram when the adsorption process is performed in the B system in the exhaust gas purification method of the embodiment. FIG. 4 is a diagram showing a schematic configuration of another apparatus that can be used in the exhaust gas purification method of the embodiment.

  The method for purifying a large amount of exhaust gas containing a diluted VOC according to the present invention uses an adsorbing device in which a pair of adsorbent layers are integrated separately. This adsorber is provided with a honeycomb-like adsorbent layer that concentrates the diluted VOC contained in the exhaust gas about 5 to 10 times on the upper part. This honeycomb-shaped adsorbent layer is a stationary honeycomb or corrugated mesopore activated carbon pre-coated with the above-mentioned VOC and having a mesopore activated carbon having an adsorption pore diameter of 1 nm to 10 nm held by a ceramic carrier. A silica gel corrugate can also be used in combination.

  The VOC concentrated about 5 to 10 times in the upper honeycomb adsorbent layer is taken out of the system by a vacuum pump together with the VOC accumulated in the lower adsorbent layer at the time of desorption. Similarly, the adsorbent layer of VOC is composed of an adsorbent layer filled with pre-coated granular mesopore activated carbon having an adsorption pore diameter of 1 to 10 nm and / or granular hydrophobic silica gel specializing in an average adsorption pore diameter of 4 to 6 nm. It is used by pre-coating. Since this granular adsorbent layer has an adsorption capacity several times that of the honeycomb adsorbent layer, VOC accumulated at the bottom of the lower adsorbent layer, that is, return of uncondensed gas by the previous operation. As a result, the concentrated VOC is present in the lower adsorbent layer, but this concentrated VOC and the VOC adsorbed on the honeycomb-shaped adsorbent layer join together and are taken out together by a vacuum pump as purge exhaust gas. .

  If such an operation is repeated by switching between a pair of adsorption devices, the VOC concentration in the purge exhaust gas becomes extremely high, and there is an advantage that a large amount of VOC can be recovered as a liquid without lowering the cooling temperature so much. Since the upper and lower adsorbing towers are connected to each other up and down in this way, the idea that the retan gas is at the bottom of the tower and the raw material gas is at an intermediate position is created, and the dilute VOC contained in the purge exhaust gas is reduced to ultra-low temperatures. Therefore, it can be easily liquefied.

  In the method for purifying a large amount of exhaust gas containing the diluted VOC according to the present invention, the switching time of the adsorption / desorption operation of the pair of adsorption devices is 1 to 30 minutes, preferably about 5 minutes, and a vacuum pump is used for the purge operation. And / or normal temperature air or nitrogen is used together as a purge gas. The purge exhaust gas obtained at the time of the purge operation is cooled and taken out of the system, and the contained VOC is recovered as a liquid, and the uncondensed gas is subjected to an adsorption treatment of the pair of adsorption devices. Return to the bottom of the side adsorber. The type of the empty pump to be used is not limited, but a liquid ring rotary pump is desirable, and the ultimate vacuum is sufficient if it is 3.5 to 5 Kpa.

[Exhaust gas targeted by the present invention]
The target gas in the present invention is a large amount of exhaust gas of several thousand to several tens of thousands m ^{3 /} h discharged from a painting factory, a semiconductor factory, a manufacturing process for handling chemical products, and the like, and a lean VOC (for example, Olefin hydrocarbons such as ethylene and propylene, alcohols such as methanol, aromatic hydrocarbons such as benzene and toluene, diene polymer materials such as butadiene, hexene and styrene, trichlene, methylene chloride and ethyl acetate As well as hazardous substances regulated by the Pollution Control Ordinance. Moreover, preferably, the exhaust gas having a concentration of several thousand m ³ or more per hour whose concentration does not exceed the% order is targeted, but the present invention is not limited to this.

  An example of an apparatus that can be used in a method for purifying a large amount of exhaust gas (air) containing a lean VOC according to the present embodiment will be described with reference to FIG. This apparatus includes a raw material exhaust gas supply line 1 using a blower, and a pair of adsorption towers 1A, 1B, lower lines 2A, 2B, purge exhaust gas lines 3, vacuum pumps 4, coolers 5a, drains filled with different adsorbent layers. A tank 5b, an uncondensed gas return line 7, a recovered liquid take-out line 6, a gas line 9 that diffuses to the atmosphere, and a purge gas supply line 9A are provided. Note that 10A, 10B, 11A, 11B, 12A, 12B, 13A, 13B, 14A, and 14B are all electromagnetic valves. In the following, the constituent part including the adsorption tower 1A is referred to as A system, and the constituent part including the adsorption tower 1B is referred to as B system.

  In this embodiment, a honeycomb made of mesopore activated carbon and / or a corrugated made of hydrophobic silica gel is used as the adsorbent layers 1Aa and 1Ba filled in the upper parts of the adsorption towers 1A and 1B, and the adsorbent layers 1Ab filled in the lower part are used. As the 1Bb, a pre-coated granular mesopore activated carbon and / or hydrophobic silica gel, or a pre-coated operation before operating the adsorption towers 1A and 1B is used. Specifically, as the adsorbent layers 1Aa and 1Ba filled in the upper part, a honeycomb-like adsorbent layer made of Nippon Noritto's mesopore activated carbon (trade name: GF-45) can be used. Adsorbent layer made of granular activated carbon (trade name: GH-1) of Kiyara and / or granular hydrophobic silica gel (trade name: S-3, S-6) of Fuji Silysia Chemical Co., Ltd. is used as the agent layers 1Ab and 1Bb. Can do.

  FIG. 2 illustrates the flow of gas or liquid when an adsorption process is performed in the A system and a desorption process is performed in the B system in a large amount of exhaust gas purification method including VOC of the present embodiment. Note that among the solenoid valves in FIG. 2, those that are blacked out indicate solenoid valves that are in the “closed” state, and those that are outlined are those that are in the “open” state (Note that this also applies to FIG. 3).

  In the A system, the raw material exhaust gas from the raw material exhaust gas supply line 1 blown by the blower is introduced into the intermediate portion of the adsorption tower 1A through the electromagnetic valve 12A, and VOC is adsorbed while passing through the honeycomb-shaped adsorbent layer 1Aa. The purified raw material exhaust gas is discharged into the atmosphere through the upper line 8A, the electromagnetic valve 10A, and the gas line 9 that diffuses into the atmosphere. On the other hand, in the B system, the purge gas (for example, air) supplied from the purge gas line 9A is introduced into the adsorption tower 1B via the electromagnetic valve 11B and the upper line 8B, and adsorbed in advance while passing through the honeycomb adsorbent layer 1Ba. The VOC that has been removed is further desorbed and enters the lower granular adsorbent layer 1Bb together with the purge gas, and the lower line 2B, solenoid valve 13B, purge exhaust gas line 3 and vacuum pump 4 together with the VOC adsorbed on the granular adsorbent layer 1Bb. Then, it is introduced into the cooler 5a.

  The VOC partially liquefied by the cooler 5a is gas-liquid separated by the drain tank 5b, the liquid component is taken out through the recovered liquid take-out line 6, and the purge gas containing the non-condensed component of the VOC is taken out by the uncondensed gas return line. 7. It is introduced into the lower part of the A-system adsorption tower 1A through the electromagnetic valve 14A and the lower line 2A. The purge gas containing uncondensed components of VOC introduced into the lower part of the A-type adsorption tower 1A is adsorbed and removed while passing through the granular adsorbent layer 1Ab, and the remaining purge gas is introduced from the raw material exhaust gas supply line 1 The raw material exhaust gas is introduced into the honeycomb-like adsorbent layer 1Aa. In this way, the adsorption process is performed in the A system and the desorption process is performed in the B system.

  In the exhaust gas purification method including a large amount of VOC according to the present embodiment, before the honeycomb adsorbent layer 1Aa of the adsorption tower 1A breaks through, the electromagnetic valve is switched, and the desorption process in the A system and the desorption process in the B system. An adsorption process is performed. The flow of gas or liquid when performing the desorption process in the A system and the adsorption process in the B system will be described with reference to FIG.

  In the B system, the raw material exhaust gas from the raw material exhaust gas supply line 1 blown by the blower is introduced into the intermediate portion of the adsorption tower 1B through the electromagnetic valve 12B, and VOC is adsorbed while passing through the honeycomb-shaped adsorbent layer 1Ba. The purified raw material exhaust gas is discharged into the atmosphere through the upper line 8B, the electromagnetic valve 10B, and the gas line 9 that diffuses into the atmosphere. On the other hand, in the A system, the purge gas (for example, air) supplied from the purge gas line 9A is introduced into the adsorption tower 1A through the electromagnetic valve 11A and the upper line 8A and adsorbed in advance while passing through the honeycomb adsorbent layer 1Aa. The VOC that has been removed is further desorbed and enters the lower granular adsorbent layer 1Ab together with the purge gas, and the lower line 2A, solenoid valve 13A, purge exhaust gas line 3 and vacuum pump 4 together with the VOC adsorbed on the granular adsorbent layer 1Ab. Then, it is introduced into the cooler 5a.

  The VOC partially liquefied by the cooler 5a is gas-liquid separated by the drain tank 5b, the liquid component is taken out through the recovered liquid take-out line 6, and the purge gas containing the non-condensed component of the VOC is taken out by the uncondensed gas return line. 7. It is introduced into the lower part of the B-type adsorption tower 1B via the electromagnetic valve 14B and the lower line 2B. The purge gas containing uncondensed components of VOC introduced into the lower part of the B-type adsorption tower 1B is adsorbed and removed while passing through the granular adsorbent layer 1Bb, and the remaining purge gas is introduced from the raw material exhaust gas supply line 1 The raw material exhaust gas is introduced into the honeycomb adsorbent layer 1Ba. In this way, the adsorption process is performed in the B system and the desorption process is performed in the A system.

In this embodiment, air containing 2,000 ppm of ethyl acetate is fed from the source gas supply line 1 to the middle stage of the adsorption towers 1A to 1B at a rate of 8 m ³ per hour. Precoat with the gas. Further, the air feeding speed of the air passing through the raw material gas line 1 was about 1.5 m per second, and the switching time was about 10 minutes.

  As a verified result, the result of testing under the above conditions is that, for example, when the adsorption treatment is performed in the A system, the concentration of ethyl acetate concentrated in the honeycomb adsorbent layer 1Aa at the top of the adsorption tower 1A is about 15,000 ppm. It was found to be concentrated about 7 to 8 times. In this adsorption tower 1A, after 10 minutes, the adsorption process is cut so that it is performed in another adsorption tower 1B, and the process proceeds to the desorption process. In this case, the vacuum pump 4 is operated and air is used as a purge gas. Use. The amount of air supplied from the purge gas supply line 9A is 8 L / min, and the purge coefficient (α) corresponds to about 2. The degree of vacuum is 3 KPa. At that time, about 15,000 ppm of ethyl acetate concentrated in the upper adsorbent layer 1A passes through the granular adsorbent layer 1Ab filled in the lower portion. Although the amount of ethyl acetate contained in the purge exhaust gas that is adsorbed by the vacuum pump 4 is small, the operation returns to the bottom of the adsorption tower 1A (returns to the bottom of the adsorption tower). The concentration of ethyl acetate in the purge exhaust gas begins to gradually increase, and in a steady state, even when the cooling temperature of the purge exhaust gas in the cooler 5a is almost normal temperature, the entire amount of ethyl acetate is recovered in the liquid state become able to. In a steady state, it was confirmed that the concentration of ethyl acetate in the exhaust gas diffused into the atmosphere from the gas line 9 diffused into the atmosphere was almost zero ppm.

  In the above embodiment, as the adsorption towers 1A and 1B, those having the honeycomb adsorbent layers 1Aa and 1Ba in the upper portion and the granular adsorbent layers 1Ab and 1Bb in the lower portion are used. The adsorbent layer and the granular adsorbent layer may be disposed in separate adsorption towers. A modification in which such a honeycomb adsorbent layer and a granular adsorbent layer are arranged in separate adsorption towers will be described with reference to FIG. In FIG. 4, the same constituent elements as those shown in FIGS. 1 to 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

  4 differs from that shown in FIGS. 1 to 3 in that the honeycomb adsorbent layers 1Aa and 1Ba are disposed in the first adsorption towers 1A ′ and 1B ′, respectively. The granular adsorbent layers 1Ab and 1Bb are respectively arranged in the second adsorption towers 1A "and 1B", and the first A adsorption tower 1A 'and the second adsorption tower 1A "of the A system are communicated with each other by a connection pipe 15A. The B-type first adsorption tower 1B ′ and the second adsorption tower 1B ″ are communicated with each other by a connection pipe 15B, the electromagnetic valve 12A is communicated with the connection pipe 15A, and the electromagnetic valve 12B is communicated with the connection pipe 15B. It is only a point. The operation method and effect of the apparatus of the modification shown in FIG. 4 are the same as those shown in FIGS. 1 to 3, and detailed description thereof will be omitted.

  In this way, by treating a large amount of exhaust gas containing lean VOC by the above-mentioned means and by a new method that is economically excellent, the above-mentioned gas can be purified to zero emission. Since it can be applied not only to the case of ethyl but also to other organic compounds in general, it is also an epoch-making invention as a technique for preventing global warming gas, and can fully meet social needs.

It is a figure which shows schematic structure of the apparatus which can be used with the exhaust gas purification method of an Example. It is a flow sheet figure at the time of implementing an adsorption process by A system in an exhaust gas purification method of an example. It is a flow sheet figure at the time of implementing an adsorption process by B system in an exhaust gas purification method of an example. It is a figure which shows schematic structure of the other apparatus which can be used with the exhaust gas purification method of an Example.

Explanation of symbols

  1: Raw material exhaust gas supply line 1A, 1B: Adsorption tower 1A ', 1B': First adsorption tower 1A ", 1B": Second adsorption tower 1Aa, 1Ba: (Honeycomb) Adsorbent layer 1Ab, 1Bb :( Granular) Adsorbent layer 2A, 2B: Lower line 3: Purge exhaust gas line 4: Vacuum pump 5a: Cooler 5b: Drain tank 6: Recovery liquid take-out line 7: Uncondensed gas return line 8A, 8B: Upper line 9: Air Gas line 9A: Purge gas supply line 10A-14A, 10B-14B: Solenoid valve 15A, 15B: Connection piping

Claims (3)

Comprising an adsorbent layer ing of a layer filled with pre-coated mesopore activated carbon as an adsorbent, using a suction device which performs alternating adsorption and desorption, passed through an exhaust gas containing volatile hydrocarbons in one adsorber, the Volatile hydrocarbons are adsorbed on the adsorbent layer in the adsorber, and exhaust gas that does not contain volatile hydrocarbons is released from the outlet of the adsorber, while the other adsorber is switched to desorption and adsorbed first. In a method for purifying a large amount of exhaust gas containing dilute volatile hydrocarbons, the volatile hydrocarbons are taken out of the system, cooled, and recovered as a liquid.
As the suction device, a honeycomb or corrugated adsorbent layer consisting of mesopores activated carbon pre-coated on the top, an adsorbent layer filled with at least one hydrophobic silica particulate was mesopore activated charcoal and precoat precoated beads for lower A method for purifying a large amount of exhaust gas containing dilute volatile hydrocarbons, characterized by using an adsorbing apparatus connected in the vertical direction and having a feed gas supply position located between the upper part and the lower part of the adsorbing apparatus. The suction device, a small amount of air or nitrogen since and top sucking with a vacuum pump from the bottom of the adsorber is performed at least one of be used as purge gas during desorption, the switching time of the adsorption and desorption 1-30 The purged exhaust gas obtained is cooled and the volatile hydrocarbons contained in the system are taken out of the system and recovered, and the uncondensed gas at this time is returned to the bottom of the adsorption device in the adsorption process. A method for purifying a large amount of exhaust gas containing volatile hydrocarbons according to claim 1.   The method for purifying a large amount of exhaust gas containing volatile hydrocarbons according to claim 1 or 2, wherein the concentration of volatile hydrocarbons in the exhaust gas discharged from the outlet of the adsorption device is substantially zero ppm.

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