JP3133988B2 - Equipment for treating lean gaseous hydrocarbons contained in waste gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for treating a lean gaseous hydrocarbon contained in waste gas, and more particularly to a method for treating a waste gas containing harmful gaseous hydrocarbons that cause air pollution. The present invention relates to a processing apparatus for performing a method of efficiently separating hydrogen and detoxifying the hydrogen. In particular,
Regarding the treatment of waste gas containing gaseous hydrocarbons such as benzene, toluene, methyl ethyl ketone, trichloroethylene, and chlorofluorocarbon, which are carcinogenic and one of the substances causing air pollution, as harmful gaseous hydrocarbons, The concentration of hydrocarbons is 100 ppm or less (preferably 10 pp
m or less), and relates to the above-described processing apparatus for exhausting to the atmosphere.

[0002]

2. Description of the Related Art Gaseous hydrocarbons such as benzene, toluene, methyl ethyl ketone, trichloroethylene, and chlorofluorocarbon, which are one of the main causes of air pollution, are released into the atmosphere in developed countries such as the United States, Europe, and Japan. Regulations are strictly regulated. The level of regulatory values varies depending on the circumstances of each country, but in developed countries except Japan,
For example, benzene is “5 ppm or less”, and in Japan, it has been regulated to “30 ppm or less” according to the Notification of the Environment Agency No. 5 (February 6, 1997).

[0003] By the way, a particularly problematic source of such gaseous hydrocarbons is a large amount of dilute waste gas of about 5000 ppm or less generated in a printing factory, a cleaning factory, a painting factory, and the like. This is waste gas generated not only at factories but also at the time of unloading and unloading from tanks storing them.

"Prior art related to waste gas treatment method" As a method for detoxifying waste gas containing gaseous hydrocarbons as described above, the following methods have been widely used. (1) Gas separation membrane method + Adsorption method (2) Adsorption method using activated carbon, zeolite, hydrophobic silica gel, etc.

[0005] Of the above methods, the method (1) is a mainstream technology in Europe. When a large amount of waste gas is used, the treatment after the gas separation membrane method (pressurized membrane method) is performed as a polishing step. It uses an adsorption method. In Japan, as disclosed in Japanese Patent Publication No. 23568/1992 and Japanese Patent Application Laid-Open No. Hei 7-284623, a technique belonging to this field is disclosed. On the other hand, the method most widely adopted in the United States is the above-mentioned adsorption method (2), particularly the adsorption method using activated carbon. This method is disclosed in JP-A-57-146.
No. 87, JP-A-57-42319, Japanese Patent Publication No. Sho 5
Japanese Patent Publication No. 9-50715, Japanese Patent Publication No. 59-50716, and Japanese Patent Publication No. 2-46630.

In the current state of the art, the above-mentioned activated carbon is required to treat a large amount of waste gas containing a dilute gaseous hydrocarbon so that the concentration of hydrocarbons in the clean gas released to the atmosphere is 1000 ppm or less. The adsorption method using is the best industrial means. (Note that the catalytic combustion method is also a simple and effective means, but depending on the concentration of gaseous hydrocarbons in the waste gas, there is a danger of an explosion. .)

However, in the conventional adsorption method using activated carbon, "steam" is usually used as a purge gas at the time of desorption. The amount of steam required for desorption is about three times the amount of the adsorbent used, and requires a large amount. In addition, hydrocarbons are entrained and mixed in when this steam is condensed into water.Therefore, in order to clear strict water quality standards, there is a disadvantage that a considerable burden is imposed on wastewater treatment equipment such as the activated sludge method. . For this reason,
As a purge gas at the time of desorption, a method of circulating and using "nitrogen heated to high temperature" instead of steam has been proposed. However, for separation of lean gaseous hydrocarbons accumulated in circulating nitrogen, It requires a large refrigerator and must be cooled to a low temperature of 0 ° C. or lower, which is rather uneconomical.

As means for solving the above-mentioned problems, as disclosed in Japanese Patent No. 2,823,835, prior to recovering gaseous hydrocarbons from purge exhaust gas,
Through a cascade-type concentration adsorption tower (adapter), dilute gaseous hydrocarbons in the purged exhaust gas are concentrated,
Removing from the concentration adsorption tower (adapter) is also one of the solutions. When the adsorption tower is switched to the desorption tower and suction is performed by the vacuum pump, the gas is discharged in a state where the gaseous hydrocarbons in the purged exhaust gas have been concentrated by applying a substitution purge means to the desorption tower in advance. A method of cooling and liquefying and separating the obtained purge exhaust gas is also one of the solutions.

In any of the above means, liquefaction of gaseous hydrocarbons in the purge exhaust gas is possible only by cooling the purge exhaust gas, but involves means for concentrating the gaseous hydrocarbons in the purge exhaust gas. In addition, it can be said that the concentration means itself is complicated. Also,
In any of the above-mentioned means, when hydrocarbons having a low boiling point are used, they are not easily cooled and require a powerful refrigerator, so that they are complicated as means for concentrating a dilute gaseous hydrocarbon.

Accordingly, in order to overcome the above drawbacks, in the activated carbon adsorption method has been widely used conventionally, when processing a large amount of gas that per minute hundred m ^3, are used primarily the fibrous activated carbon, On the other hand, as an apparatus, an "adsorption apparatus in which a large number of cylinders or boxes are arranged inside" in which the adsorbent layer made of the fibrous activated carbon is thinly surrounded by a thickness of several cm to several tens cm has been used. For example, "K-Filter (trade name, manufactured by Toyobo)" or "Pyromex (trade name, manufactured by Toho Rayon Co.)" is used.

According to this method, the dilute hydrocarbon is adsorbed over a long period of time of tens of minutes to several hours without being concentrated as in the present invention which will be described in detail later, and then is simply desorbed with steam. is there. However, this method is characterized by devising an "adsorption device having an adsorbent layer" so that a large amount of gas can be treated. However, the concentration of hydrocarbons in the gas discharged to the atmosphere is "100 ppm or less". It is difficult to do.

"Prior art relating to means for switching between suction and desorption"
On the other hand, in the method for treating waste gas containing gaseous hydrocarbons by the adsorption method, switching between adsorption and desorption is controlled by time control via an electromagnetic valve. However, when switching is performed by time control, it is necessary to know in advance the time required for the adsorption tower to break through experiments and experiences. In addition, although switching by time control is straightforward, when the amount and concentration of gaseous hydrocarbons at the inlet of the adsorption tower constantly fluctuate greatly, the adsorbent may be charged more than necessary and then switched earlier. I will be forced. Therefore, there has been a problem that the adsorbent is not used effectively.

In order to solve the above problem, a method of performing "detection of breakthrough" of an adsorption tower using various measuring instruments and switching to desorption when the concentration reaches a level at which breakthrough can be detected has been performed. Have been. However, according to the recent severe air pollution control law, the concentration at the time of breakthrough is a trace concentration of several tens of ppm or less, so that the concentration requiring detection before that is on the order of 1-2 ppm or less. Requires a fairly large and precise measuring instrument.

[0014] Also, various proposals have been made for the above detection method since ancient times. For example, JP-A-55-3599
No. 6 discloses a method using a double tower PSA purifier for adsorption and desorption, and using an adsorption tower of 5 to 10 kg / c without using a vacuum pump.
The moist gas is adsorbed while pressurized to m ² , and the dry gas is diffused from the top of the column. On the other hand, the desorption is performed by discharging the adsorbed gas by returning the pressure of the column to normal pressure. In the dehumidification method, the operating conditions of each part including the gas flow rate passing through the adsorption tower, the inlet and outlet temperatures of the adsorption tower, the inlet and outlet pressures of the adsorption tower, and the regeneration pressure of the desorption tower are stored in the microcomputer as data. Then, the material balance and heat balance are calculated instantaneously, the desorption time is controlled based on the results, and the timing of indirectly switching between adsorption and desorption is automatically controlled. Is disclosed.

The method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 55-35996 is characterized in that the switching between adsorption and desorption is not controlled by time, but by an instruction from a microcomputer in which the operation status of the apparatus is stored. Although it was a periodical proposal, the simulation method could not be used at that time because there was no superior adsorption model as at present. That is, the idea of “predicting the breakthrough concentration by simulation of an adsorption model” was not reached.

Thereafter, before the breakthrough occurs, the concentration of the component to be adsorbed in the gas is detected promptly from the measurement port embedded in the adsorbent layer, and when the concentration reaches a certain level, the solenoid valve is automatically activated. Switching methods have been proposed. However, when the adsorbent has a diameter of 5 to 100 °, such as granular activated carbon or silica gel, the concentration and the temperature also vary locally, so that “the adsorbent layer does not shift along the gas flow, There is no guarantee that it will rise toward the exit with a uniform width, "and therefore it is difficult to identify the position to be measured. If the measurement port is inserted at a position that is too deep from the top, it is hard to say that this method is superior to time control. For this reason, at present, the mainstream technology for switching between absorption and desorption is simple time control.

[0017]

SUMMARY OF THE INVENTION The present invention relates to the problems of the prior art described in the above-mentioned "prior art relating to the method of treating waste gas" and "prior art relating to the means for switching between adsorption and desorption".
The present invention has been made in view of the drawbacks, and is an attempt to further improve the prior art. And, the present invention concentrates the dilute gaseous hydrocarbons contained in a large amount of waste gas, extracts it as an extremely small amount of gas as a whole, and incurs an economic burden when incinerating or industrially disposing or liquefying it. The objective (technical issue) is to significantly reduce it.

Further, the present invention provides an apparatus for detoxifying a large amount of waste gas containing a dilute gaseous hydrocarbon, wherein the waste gas is treated using a solid adsorbent such as hydrophobic silica gel, activated carbon and synthetic zeolite. It can safely, easily, and efficiently separate harmful hydrocarbons and can reduce the concentration of residual gaseous hydrocarbons in waste gas released into the atmosphere after treatment to 100 ppm or less. To carry out a method for treating a lean gaseous hydrocarbon. Still another object of the present invention is to provide an apparatus which can be made portable so that the system can be integrated and mounted on a skid when the above method is implemented.

[0019]

The invention according to claim 1 of the present invention uses an "adsorber having an adsorbent layer which alternately performs adsorption and desorption", and supplies gaseous hydrocarbon to one of the adsorbers. Containing waste gas, allowing gaseous hydrocarbons to be adsorbed by the adsorbent layer in the adsorption device, and releasing waste gas substantially free of gaseous hydrocarbons into the atmosphere, while the other adsorption device Is switched to desorption, and the gaseous hydrocarbons adsorbed on the adsorbent layer in the adsorption device are sucked and desorbed by a vacuum pump, and the gaseous hydrocarbons contained in the waste gas are transferred to purge exhaust gas. A method for treating hydrogen, in which all or most of the purge exhaust gas is returned to the waste gas to be treated, thereby increasing the hydrocarbon concentration in the adsorbent layer and desorbing before the adsorbent layer breaks through. Switching If some of the gaseous hydrocarbon in the purge gas is liquefied, consists of the said liquid hydrocarbon is combusted, or, detoxifies as industrial waste,
As an apparatus for carrying out the method of processing dilute gaseous hydrocarbons contained in waste gas, wherein in said device "adsorption unit having an adsorbent layer" is, surrounds the adsorbent layer, and adsorption
A dilute gas contained in the waste gas, characterized by comprising an adsorption device in which components that allow the waste gas to pass laterally from the outer cylinder of the agent layer toward the adsorbent layer are incorporated. Hydrocarbon processing equipment. "Is a feature (a matter specifying the invention).

The invention according to claim 1 of the present invention provides:
As described above, the entire or most of the purged exhaust gas is returned to the waste gas to be treated, and the hydrocarbon concentration in the adsorbent layer is increased (first method).
Switch to desorption before the adsorbent layer breaks through (second
Features of the), consisting of, is an apparatus for performing a method for treating a lean gaseous hydrocarbon contained in waste gas,
This allows safe, easy, and efficient treatment of hydrocarbons from waste gas, and reduces the concentration of residual hydrocarbons in the gas released into the atmosphere to 100 ppm after treatment.
Hereinafter, it can be particularly set to “20 ppm or less”.

Further, the invention according to claim 1 of the present invention is as follows: When a part of the gaseous hydrocarbon in the purge exhaust gas is liquefied, the liquid hydrocarbon is burned or detoxified as industrial waste. Processing (third feature);
This is an apparatus for carrying out a method for treating a lean gaseous hydrocarbon contained in waste gas, thereby avoiding complicated means associated with the recovery of gaseous hydrocarbon.

Further, the invention according to claim 1 of the present invention provides:
The “adsorption device having an adsorbent layer” surrounds the adsorbent layer , and moves in a lateral direction from the outer cylinder of the adsorbent layer toward the adsorbent layer
(4th feature point) , which comprises a multiplexed component capable of venting waste gas into
As described later in detail, a suction device in which such components are multiplexed contains several hundred meters per minute.
It is possible to provide an adsorption device that can be applied to a case where a large amount of waste gas of ³ is processed.

[0023] The invention according to claim 2 of the present invention is characterized in that the component is a cylindrical component, a box component or a honeycomb component, and is a suction device in which the components are multiplexed. The invention according to claim 3 of the present invention is characterized in that the adsorbent layer is formed of a layer filled with fine adsorbent having a diameter of 0.1 to 1 mm. in the case of processing a large amount of waste gas of one hundred m ^3,
A more suitable adsorption device can be provided.

[0024] The invention according to claim 4 of the present invention is characterized in that the adsorbent layer comprises a layer of activated carbon and / or hydrophobic silica gel, and an adsorption layer made of synthetic zeolite is disposed on top of the layer. By combining such adsorbents, the temperature in the adsorbent layer can be easily and promptly kept close to room temperature, and the performance of the adsorbent can be fully exhibited without waste.

The invention according to claim 5 of the present invention is characterized in that the adsorbent or the adsorbent layer filled in the adsorption device is pre-coated with gaseous hydrocarbon, whereby
Prevents adsorption of nitrogen gas and oxygen gas in waste gas, which is originally preferentially adsorbed, as well as moisture, effectively adsorbs gaseous hydrocarbons in waste gas, and makes the adsorbent layer extremely effective Can be used.

According to a sixth aspect of the present invention, as means for releasing gaseous hydrocarbons adsorbed on an adsorbent layer in an adsorption device, air or liquid "water" heated above the boiling point of the hydrocarbons to be adsorbed is used. "Is used. However, the case where heated air is used is the case where an adsorbent other than activated carbon is used. When non-flammable hydrophobic silica gel other than activated carbon is used, air having a high temperature of up to 250 ° C. can be used as a purge gas. Also,
In particular, when liquid “water” is used, the water can be vaporized inside the desorption device by using the vacuum pump together with the vacuum pump to exert the same effect as the purge gas. In the case of using steam, there is a remarkable effect that the gas can be purged with a small gas amount of "several tenths".

In the invention according to claim 7 of the present invention, as means for switching to desorption before the adsorbent layer breaks through, a temperature detection port is provided at the top of the adsorbent layer, and The electromagnetic valve is automatically switched when the temperature stops rising, and the invention according to claim 8 of the present invention is also a means for switching to desorption before the adsorbent layer breaks through. , The adsorber obtained during the adsorption operation, "inlet gas flow", "hydrocarbon concentration in the inlet gas" and "desired hydrocarbon concentration in the outlet gas (assumed value)" is read into the chip as numerical data, The switching time is set in advance by using a simulation model for control incorporated in the chip. By adopting these means, the breakthrough point of the adsorbent layer is automatically detected. Come, it is possible to automatically perform the switching of the adsorption and desorption.

According to the first to eighth aspects of the present invention, the concentration of hydrocarbons in the clean gas discharged from the adsorption device to the atmosphere can be reduced to 100 ppm or less.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus according to the present invention (hereinafter simply referred to as "the present invention") is as described above. Increasing the hydrogen concentration (Part 1
Switch to desorption before the adsorbent layer breaks through (second
When a part of the gaseous hydrocarbons in the purge exhaust gas is liquefied, the liquid hydrocarbons are burned or detoxified as industrial waste (third characteristic point). This is an apparatus for carrying out a method for treating lean gaseous hydrocarbons contained in waste gas. As described above, the present invention is an apparatus for implementing the “method for treating a lean gaseous hydrocarbon contained in waste gas” having the technical features of the first to third features. Hereinafter, embodiments of the first to third features presupposed in the present invention will be described in detail, together with their functions and effects.

(Summary of Action and Effect) The technical configuration of the first and second features presupposed in the present invention enables safe, easy and efficient treatment of hydrocarbons from waste gas. After the treatment, the concentration of the remaining hydrocarbons in the gas released into the atmosphere is reduced to 1
It can be set to 00 ppm or less, particularly “20 ppm or less”. In addition, since the technical configuration of the third feature presupposed in the present invention does not aim at recovering gaseous hydrocarbons in waste gas, it is possible to avoid complicated means associated with the recovery. .

First, the first feature of the present invention will be described. In one embodiment, the entire amount of the purge exhaust gas is returned to the waste gas to be treated, but the hydrocarbon concentration in the purge exhaust gas is extremely low. If it is too high, the adsorbent layer will break through in a very short time, which will adversely affect the treatment of waste gas. Therefore, as another embodiment of the present invention, when the hydrocarbon concentration is extremely high, a part of the purge exhaust gas is taken out, subjected to a detoxification process, for example, a combustion process, and the remaining purge exhaust gas is subjected to a treatment. When the gaseous hydrocarbons in the purged exhaust gas are partially liquefied, the liquid hydrocarbons are separated, and the liquid hydrocarbons are separated and burned or detoxified as industrial waste (→ No. 3).

Next, the second characteristic feature of the present invention, that is, "switching to desorption before the adsorber breaks through" will be described.
Basically, it is based on a circuit chip incorporated in the apparatus. However, since a very small chip, which has been remarkably advanced recently, is used, the above-mentioned known technology (Japanese Patent Application Laid-Open No. 55-359) is used.
No large-scale microprocessor for the purpose of calculation as described in Japanese Patent Application Laid-Open No. 96-96 is not required. Moreover, according to a preferred embodiment of the present invention, rather than just picking up data obtained during operation and only calculating the material and heat balances, the adsorption model
The point of trying to control the adsorption system by predicting breakthrough concentration, preferably in units of seconds, by inputting the data into the OM and reading the data during operation, which is constantly changing, as a logger signal into a personal computer and simulating it. This is completely different from the prior art. In other words, this is clearly different from the idea of “predicting breakthrough concentration by simulation of an adsorption model” which is a preferred embodiment of the present invention.

Various "adsorption models" have been proposed. Among them, the physical properties of the adsorbent, that is, "adsorption isotherm curve and adsorption pressure inside the adsorption tower, degree of vacuum of vacuum pump, degree of vacuum inside the tower, Frozen gas flow rate, height of adsorbent layer, purge coefficient, and variable “inlet gas flow rate and concentration” changing every moment, or switching time or outlet of adsorbent layer The so-called “Frozen” is calculated by inputting the concentration (breakthrough concentration) to the chip as an assumed value.
The "equilibrium model," which is time-consuming but has excellent accuracy, is also known, but the "adsorption model" used in the present invention is not particularly limited to these.

The second feature of the present invention, namely, "switching to desorption before the adsorber breaks through" is an essential component, and the first feature of the present invention, "purge". Return all or most of the exhaust gas to the waste gas to be treated,
Increase the concentration of hydrocarbons in the adsorbent layer ". That is, in the case where the amount of waste gas to be treated and the concentration of gaseous hydrocarbons contained therein are not constant and change every moment, and it is difficult to estimate in advance the time until breakthrough, By mixing the uncondensed purge exhaust gas into the waste gas (by adopting the first feature point), the hydrocarbon concentration in the adsorber inlet gas and the hydrocarbon concentration in the adsorbent layer in the adsorber are both increased. This is because it further changes, which makes it even more difficult to predict the time until breakthrough. Therefore, in order to solve this problem, the above-mentioned second characteristic point is an essential component.

However, the present invention does not exclude the switching means based on time control which has been performed conventionally. If the concentration of gaseous hydrocarbons contained in the inlet gas of the adsorption tower (waste gas + the uncondensed purge exhaust gas) is substantially constant over time, the operation of the adsorption tower is started to break through. This is because it is one of the convenient methods to determine in advance the time up to this time and to use the time as a guide in the next suction operation.

As described above, when the flow rate and the concentration of the inlet gas fluctuate, according to a preferred embodiment of the present invention, the concentration of the gaseous hydrocarbon adsorbed on the adsorbent layer is reduced to just before the breakthrough. It can be automatically concentrated to a high concentration. Then, after taking out this as a small amount of purge exhaust gas, as described above, a part of this purge exhaust gas can be taken out and subjected to, for example, a combustion process, and gaseous hydrocarbons in the purge exhaust gas can be removed. It is separated as a liquid hydrocarbon and burned or detoxified as industrial waste (→ third feature).

However, while having such an advantage, the disadvantage is that if the time required for adsorption and the time required for desorption are too different, for example, it takes several days to reach just before breakthrough due to adsorption, On the other hand, in the case where the desorption process takes several hours, it is not necessarily a preferable method from the viewpoint of a person managing the work.

Therefore, when the "proper adsorbent" is properly filled, the amount of gaseous hydrocarbons to be adsorbed is extremely small near the top of the adsorbent layer. The amount of heat of adsorption generated is extremely small, and
The amount of heat exceeding that will be dissipated outside from the cooling water and the tower wall of the adsorption tower. As a result, the signal from the measurement port inserted near the top to capture data into the chip,
That is, the indicated temperature stops, and the temperature gradually decreases over time. If the means for automatically switching the suction / desorption switching valve (electromagnetic valve) at this time is used in combination, the above-mentioned disadvantage can be solved, and this is also included in the present invention.

The "appropriate adsorbent" refers to a region where the diameter of the adsorption hole is controlled to a certain size, the amount of adsorption is hardly uneven locally, and the relative humidity in the waste gas is as high as about 50% or more. However, it is an adsorbent that does not easily adsorb moisture, and for example, an adsorbent such as synthetic zeolite is optimal. Therefore,
An example of a preferred embodiment of the present invention is to dispose an adsorbent layer made of synthetic zeolite on the top of the adsorbent layer, and arrange a temperature detection port in the adsorbent layer made of this synthetic zeolite. Means for automatically switching the solenoid valve when the temperature from the temperature detection port stops its rise. As the adsorbent to be filled in the lower part of the adsorbent layer made of the synthetic zeolite, precoated activated carbon or similarly precoated hydrophobic silica gel is preferable.

Here, the technical significance of the above-mentioned “pre-coat” which is a preferred embodiment of the present invention will be described. The degree to which gaseous hydrocarbons are concentrated in the adsorbent layer is theoretically "760/25" if only the hydrocarbons are adsorbed at a vacuum degree of 25 mmHg, that is, "about 25".
The density is twice as high, but usually a large amount of air coexists, and the molecular diameter of nitrogen gas and oxygen gas in this air is extremely smaller than the molecular diameter of hydrocarbons.
Nitrogen gas and oxygen gas are adsorbed in preference to hydrocarbon gas. As a result, it is empirically known that the concentration can be reduced to only four times the hydrocarbon concentration at the inlet.

Further, the solid adsorbent such as activated carbon, synthetic zeolite, and hydrophobic silica gel used in the present invention is not an adsorbent that does not adsorb moisture at all, as shown in FIG. The water absorption varies greatly depending on the relative concentration. When the gas to be adsorbed is moist air, almost no moisture is adsorbed when the relative humidity is about 40% or less,
If it exceeds 0%, water will be rapidly adsorbed (see FIG. 6). Although FIG. 6 shows a water adsorption isotherm of activated carbon, the same can be said for other hydrophobic adsorbents.

Therefore, in order to prevent the adsorption of nitrogen gas, oxygen gas, and moisture in waste gas which is originally preferentially adsorbed,
It is desirable to pre-coat the adsorbent layer. As the pre-coating means, for example, the liquid hydrocarbon is dropped onto the waste gas to be treated, specifically, the liquid hydrocarbon is sprayed on a conduit of the waste gas to be treated, thereby pre-coating the adsorbent layer. be able to. Further, as the precoat agent, other than the above-mentioned liquid hydrocarbon, for example, a substance such as a hydrocarbon having an affinity for water and having a higher boiling point than water can be used.

As described above, the inventor of the present invention has developed a system technology for processing a large amount of waste gas containing gaseous hydrocarbons by using an elemental technology on a hardware surface called a "loga signal" which is a means for capturing data. By using a new method on the so-called soft side, called "simulation of a ROM-based adsorption model", which is incorporated in the control system, and in a control system, a short period of time can be achieved regardless of changes in the hydrocarbon concentration at the inlet. The concentration in the adsorbent layer was easily and promptly kept constant at around room temperature by easily estimating the breakthrough concentration in the solution and selecting an appropriate adsorbent.

As a result, the performance of the adsorbent is wasted by leaving the time of switching from adsorption to desorption to be determined by a personal computer (software) incorporating the "adsorption model" instead of simply setting the time cycle. No, it was possible to make full use. For this reason, it concentrates the dilute hydrocarbons in the purge exhaust gas to just before breaking through,
And, it became possible to take out as an extremely rich hydrocarbon with a very small amount of purge exhaust gas.

(Regarding Adsorbent) The adsorbent used in the present invention may be any solid adsorbent which is compatible with hydrocarbon gas in waste gas, regardless of whether the material is flammable or nonflammable. can do. However, the concentration of hydrocarbons in the waste gas is 5000p
When it is as low as about pm, desirably, hydrophobic silica gel which is inexpensive and easily available is desirable. The reason is that the temperature of the purge gas can be increased to about 250 ° C. for use.

When non-combustible silica gel is used, those which have been rendered hydrophobic by a silane coupling agent such as trimethylchlorosilane, those which have been rendered hydrophobic and lipophilic by being treated at a high temperature for a long time, or ethylene glycol Adsorbents precoated with high boiling hydrocarbons such as equol and heptane are preferred. However, the most suitable adsorbent is R
Even if H is 50% or more, the solid adsorbent absorbs only a few% of water. In the first place, solid adsorbents such as activated carbon, synthetic zeolite, silica gel, and activated alumina used as adsorbents have strong affinity for gaseous hydrocarbons,
It is also heavily used as a heat insulator. In addition, apart from synthetic zeolite, other adsorbents have a wide distribution of adsorption pore diameters, so that the concentration at adsorption sites is not uniform, and local heating is likely to occur.

Generally speaking, in the case of hydrophobic silica gel or granular activated carbon, depending on the particle size and temperature rise, when the thickness is about 4 inches or more, the heat of adsorption is transferred to the cooling water layer in a short time. It is said that it cannot be done. Therefore, when the thickness is 4 inches or more, the heat transfer in the circumferential direction cannot be expected so much, and the heat transfer carried out by the gas flowing in the vertical direction is relied on. For this reason, it is a problem whether or not the adsorption layer having a certain width uniformly and uniformly moves toward the outlet of the adsorption tower under the influence of the temperature distribution in the adsorption tower. That is, there is no problem when the concentration at the time of breakthrough is detected at the outlet of the adsorption tower, but there is a problem when the concentration is detected at a detection port disposed at a position embedded in the adsorbent.

The recommended means for avoiding this is to put the synthetic zeolite on the top of the adsorbent layer, that is, at a position near the outlet. For example, Y-type zeolite "360HUD (product name of Tosoh Corporation)" or the like is used. Synthetic zeolites, unlike hydrophobic silica gel or granular activated carbon, have a pore size that is strictly controlled to a certain size.Depending on the material selected, some varieties cover almost the entire molecular diameter of gaseous hydrocarbons. . In addition, although the ratio of adsorbing gaseous hydrocarbons is 15 to 20% by weight, the amount of water adsorbed is 10% or less even for a gas having an RH of 50% or more. . For this reason, there is no deviation in the adsorption band having a certain width moving in this layer.

The port for detecting the concentration and temperature taken in as a data logger signal needs to be arranged at the center of the synthetic zeolite layer. With this configuration, in addition to the above-described means for detecting the breakthrough point, it is possible to use the instruction of the temperature at the center thereof as a guideline for switching when the temperature rise due to the heat of adsorption is stopped. Such synthetic zeolites preferably have a SiO ₂ / Al ₂ O ₃ ratio of 20 or more and have a pore size of about 8 Å.

(Regarding Adsorption Apparatus) Next, an embodiment of the “adsorption apparatus having an adsorbent layer” used in the present invention will be described. Prior to that, a reference example of the adsorption apparatus will be described first.

(Reference Example of Adsorption Apparatus) As a reference example, “an adsorption apparatus having an adsorbent layer”,
In order to locally uniform the temperature and concentration of the adsorbent layer, the heat of adsorption generated in the adsorbent layer is quickly moved laterally from the adsorbent layer to remove gaseous hydrocarbons. And a cooling water layer for cooling the adsorbent layer, which is adjacent to a "double cylinder or multi-cylindrical adsorption tower".
In consideration of the tendency of static electricity generated in the adsorbent layer to gather at the center of the layer, use of an adsorption tower having a structure in which a metal cylinder is arranged at the center to release static electricity for cooling. can do.

The specific adsorption tower of the reference example will be described with reference to FIG. 3. This adsorption tower 1a (1b) comprises an outer cylinder 2a (2b), an adsorbent layer 3a (3b), and an inner cylinder 4a. (4b),
It is constituted by cooling water 5. The adsorption tower 1a (1
b) is an adsorption tower used in a comparative example described later, in which 3-1a (3-1b) is activated carbon, and 3-2a (3-2b) is Y
It is a synthetic zeolite.

One of the points to be noted as the adsorption tower 1a (1b) is that if the pressure inside the adsorption tower is increased, the effective adsorption amount of hydrocarbons adsorbed by the adsorbent will be significantly increased. Since it is natural from the theory of the PSA method, it is extremely desirable to operate the internal pressure of the adsorption tower 1a (1b) at a gauge pressure "1 kg / cm ² or less" which does not conflict with the "high pressure regulations".

(Embodiment of Adsorption Apparatus of the Present Invention) Next, an adsorption apparatus and an embodiment of the present invention will be described. Prior to this, as compared with a conventional adsorption tower,
The adsorption device of the present invention will be described in more detail.

The conventional tower type, which is a tower type,
Adsorption device with a densely packed adsorbent inside (conventional adsorption tower)
Then, a problem arises when the amount of waste gas to be treated is large. To explain this problem in detail, for example, when processing waste gas of "36000 m ³ " per hour, the conventional adsorption tower requires a tower diameter of about 10 m.

The reason is that the passing speed of waste gas passing through the adsorbent layer (that is, the time of contact with the adsorbent (SV value)) is limited from the viewpoint of adsorption efficiency. Generally, this speed is set to a value below which the adsorbent particles do not flow,
Usually, it is “10 to 20 cm / sec”. If the average value of the gas passage speed is calculated as "15 cm / sec (0.15 m / sec)", it will be "10 m" as shown by the following equation. Formula: πR ² × 0.15 = 36,000 / 3,600 =
10 In the present invention, it is not practical to use an adsorption tower having such a column diameter.

On the other hand, the adsorption efficiency is closely related to the size of the adsorbent particles. For example, when comparing the case where a large particle size adsorbent and a small particle size adsorbent are packed in an adsorbent layer having the same capacity, it is obvious that the smaller the particle size is, the higher the efficiency is. If it is too small, there is a problem. For this reason, the diameter of the conventionally used adsorbent depends on the type and shape of the adsorbent, but it is appropriate that the diameter is 2 to 3 mm. The adsorbent that avoids the flow of the adsorbent and is densely packed has a structure in which a cross of fibrous activated carbon is coordinated inside the adsorber, and waste gas flows in a direction across the cloth. Specific examples thereof include the above-mentioned "K-filter (trade name, manufactured by Toyobo)" and "Pyromex (trade name, manufactured by Toho Rayon Co., Ltd.)".

The adsorber having the above structure has an advantage that a large gas passage area can be obtained, but has a thin adsorbent layer.
It has the disadvantage that the contact time is short and the dilute hydrocarbons in the waste gas cannot be sufficiently collected. Moreover, as a desorption means in this apparatus, it is conceivable to use only a steam, and a vacuum pump cannot be used together.

According to the adsorption theory, the adsorption efficiency is “Kf
av ”, that is,“ the value of the overall mass transfer capacity coefficient (1 / sec). ”From the experiments performed by the inventor and the analysis of the operation results of the industrial equipment constructed by the inventor, Kfav was obtained.
When the adsorbent having a particle size of 2 to 3 mm is used,
Although it depends on the properties of the gaseous hydrocarbon, it is substantially in the range of "3 to 6". On the other hand, when fibrous activated carbon is used, it is in the range of "15 to 25", and the adsorption performance is several times better. Specifically, the contact time between the gas and the adsorbent is "about 1/5".

By paying attention to this point, the present inventor has developed a new and economical adsorption apparatus which can be applied even when the amount of waste gas to be treated is large. The novel and economical adsorption device of the present invention (adsorption tower according to the embodiment),
As described above, the adsorbent layer is surrounded and outside the adsorbent layer.
It is characterized by comprising an adsorber in which components capable of venting waste gas in the lateral direction from the cylinder toward the adsorbent layer are multiplexed, and the component is a cylindrical component, a box component or a honeycomb component. It is characterized by the following.

As the adsorbent to be filled in the adsorption device of the present invention, fine particles of 0.1 to 1 mm (preferably 0.2 to 1 mm) are used.
0.5 mm), thereby shortening the contact time with the gas and increasing the coordination of the adsorbent layer in the adsorber in order to increase the gas passage area. As described above, by using fine particles of 0.1 to 1 mm as the adsorbent, the contact time is reduced by about 1 /
An excellent function and effect can be obtained in that the thickness can be reduced to "5". Further, the fact that the thickness can be reduced to "about 1/5" means that the thickness of the adsorbent layer becomes "about 1/5". That is to say.

All conventional commercial plants are of single-column type and have a thickness (layer height) of “1 to 2 m”. However, in the adsorption apparatus of the present invention, the thickness of the adsorbent layer is “about 1/5”. ", The thickness becomes" 20cm ~ 40cm ",
As a result, an excellent operation and effect is obtained in that the adsorbent layer does not need to be cooled in principle. The reason is,
Since the hydrocarbon gas contained in the large amount of waste gas passing through the adsorbent layer is extremely dilute and mostly air, the heat of adsorption exceeding the amount of heat carried out by the air does not remain in the adsorbent layer. It is.

In addition, in the above-mentioned conventional adsorption apparatus using a fibrous activated carbon layer, the waste gas ends up in a single pass through this adsorbent layer, so that the concentration of the adsorbed hydrocarbon is extremely low, and as a means for desorption, I couldn't think of anything but steam. However, in the adsorption device of the present invention, the entire or most of the purged exhaust gas can be returned to the waste gas to be treated, so that the hydrocarbon concentration in the adsorbent layer can be increased. This makes it possible to use a vacuum pump that has not been used. In addition, by using a vacuum pump together, water can be used as a purge medium at the time of desorption. (Refer to the following for "Use of vacuum pump" and "Use of water as purge medium")

Referring to FIGS. 4 and 5 (A) and 5 (B), a description will be given of a specific adsorption tower of a novel and economical adsorption apparatus which exhibits the above-mentioned remarkable functions and effects of the present invention.
The adsorption tower 41a (41b) has an adsorbent layer 43a (43b)
Outer tubes 42a (42b) and 42a '(42
b '). And the waste gas is
As shown by the arrow lines in FIG. 4 and FIG. 5 (B), the gas passes through the adsorbent layer 43a (43b) and thus the gas passage area is widened. The adsorption tower 41a (41b) is an adsorption tower used in an embodiment of the present invention described later. In the drawing, 43-1a (43-1b) is crushed activated carbon, and 43-2a (43-2b) is It is a Y-type synthetic zeolite.

(Regarding the Integration of the System) Further, as a result of earnest research, the present inventor has tried to integrate the adsorption device of the present invention as a system and to make the device portable so that it can be mounted on a skid. This has led to the present invention. That is, Patent No. 28 which the inventor has already obtained
No. 40563, Patent No. 2,766,793, Patent No. 282
Instead of using the adapter method or the displacement purge method disclosed in No. 3835, and in recovering the gaseous hydrocarbons of the purge exhaust gas, without using a method of washing with a hydrocarbon liquid of the same quality, the desorbed gas is further removed. It is not intended to recover gaseous hydrocarbons from the gas as a liquid by using a complicated cooling means after recycling and enriching the hydrocarbon concentration in the adsorption tower, but simple and economical in which the recovery means is omitted. BRIEF SUMMARY OF THE INVENTION An adsorption device for performing a method is provided.

(Regarding Desorption Means) In the present invention, air or water heated above the boiling point of the hydrocarbon to be adsorbed can be used as means for releasing the gaseous hydrocarbon adsorbed on the adsorbent layer. Of these, use of "water" is particularly preferable (see below). (Note that
As this air, a part of a clean gas discharged into the atmosphere from the adsorbent layer can be used. )

Conventionally, the field of application of the present invention is "a means for detoxifying lean hydrocarbons contained in a large amount of waste gas".
, The adsorption method has been used. The adsorbents used are, with exceptions, granular activated carbon or fibrous activated carbon. However, this type of activated carbon has an excellent adsorption capacity as compared with other adsorbents, but has a drawback that it is extremely difficult to desorb. For this reason, at the time of desorption as described above, at present, a large amount of steam, which is about three times the amount of charged activated carbon, is used. In addition, at present, the hydrocarbons entrained in the steam are rendered harmless by wastewater treatment means such as an activated sludge treatment device together with water.

Desorption using a large amount of heated air instead of steam as a purge gas may cause the activated carbon to burn, and the use of activated carbon other than room temperature air or non-combustible nitrogen is permitted by the Fire Service Law. It has not been. However, when nonflammable hydrophobic silica gel is used as the adsorbent, there is no such danger. For this reason, it has become possible to use air having a high temperature of up to 250 ° C. as a purge gas. (Note that the concentration of gaseous hydrocarbons is determined to be lower than the lower explosive limit. Therefore, it should preferably be lower than about 5000 ppm.)

In the present invention, the gaseous hydrocarbon desorbed along with the heated purge gas is a gas suitable for burning as it is as a purge exhaust gas. Furthermore,
When a vacuum pump is used as an auxiliary means for desorption, when the amount of heated air, that is, the purge coefficient is large, not only the load on the vacuum pump is reduced, but also desorption is sufficiently performed. The degree of vacuum is “60-150T
orr "is sufficient. It can be said that this is a remarkable effect of the application of the present invention because the vacuum pump is expensive.

On the other hand, when activated carbon is used as the adsorbent, the purge gas at the time of desorption is as described above.
In the past, there was no choice but to use a large amount of steam (or nitrogen gas), but the present invention has found that liquid "water" is used. By injecting water into the desorption tower, not only can it be vaporized inside the desorption tower with the help of a vacuum pump and exert the same effect as the purge gas,
A remarkable effect is obtained in that the vaporized gas amount can be purged with a small gas amount of "several tenths" in the case of using conventional steam.

When "water" is used in the present invention, a water ring vacuum pump is preferable as the vacuum pump used at that time. The reason for this is that the concentrated hydrocarbon gas is mixed with the water in the water ring to produce wastewater and wastewater suitable for industrial waste treatment.

Although the embodiment of the present invention has been described in detail above, in the “method for treating lean gaseous hydrocarbons contained in waste gas” presupposed in the present invention, a known PSA method is used. And the PTSA method can be applied. In addition, the present invention can be applied to the VSA method, the VTSA method, and the like, and these applications are also included in the present invention. The present invention also provides an apparatus for carrying out a treatment method for concentrating and separating a dilute gaseous hydrocarbon contained in a waste gas, wherein the dilute multi-component hydrocarbon generated at the time of coating is provided. Not only hydrocarbon gas, but also benzene, toluene,
It is widely applied to a single-component rare gas such as trichloroethylene, methyl ethyl ketone, and chlorofluorocarbon.

[0073]

EXAMPLES Next, comparative examples and examples of the present invention will be described.
The present invention will be specifically described, but the present invention is not limited to the following examples.

FIG. 1 is a flow sheet diagram for explaining a “method of treating a lean gaseous hydrocarbon in waste gas” presupposed in the present invention, and FIG. 2 is a flow sheet diagram of the flow sheet shown in FIG. "Control panel for grasping and controlling operating conditions"
It is a figure showing an example of. FIG. 3 is a longitudinal sectional view showing an adsorption tower (comparative example) used in the flow sheet shown in FIG.

(Comparative Example) In the comparative example, as shown in FIG. 3, the inner cylinder 4a (4b) through which the cooling water 5 circulates and the outer cylinder 2a (2b) filled with the adsorbent layer 3a (3b) outside. Tower 1a composed of a double cylinder
(1b) was used. The cooling water 5 flowing through the inner cylinder 4a (4b) was made to flow in a turbulent manner and flow countercurrent to the waste gas flowing through the adsorbent layer 3a (3b). In addition, granular activated carbon (granular Shirasagi Ichigo: trade name of Takeda Pharmaceutical Co., Ltd.) and Y
Synthetic zeolite (360 HUD: trade name, manufactured by Tosoh Corporation) was used. Then, as shown in FIG. 3, the Y-type synthetic zeolite 3-2a (3-b) is placed on top of the granular activated carbon 3-1a (3-1b).
2b) is packed in the adsorption tower 1a (1b), and the adsorbent layer 3a (3b)
It was provided for implementation. The granular activated carbon used was pre-coated with benzene vapor in advance.

A comparative example using the adsorption tower shown in FIG. 3 and performing the “method for treating lean gaseous hydrocarbons in waste gas” shown in FIG. 1 will be described in detail. Waste gas generated from a waste gas generation source (not shown) (waste gas containing about 5000 ppm of benzene: 2)
0 liter / min gas) with a gauge pressure of 1 kg / cm ²
Air is sent to the adsorption tower 1a from a waste gas air pipe 11 by a blower (not shown) or a self-pressure to be compressed below. At this time, the gas velocity passing through the adsorbent layer 3a (3b) is "about 10 cm /
Seconds after the adsorption process.
From the top of the adsorption tower 1a (after switching to the desorption step, the adsorption tower 1b), it is discharged into the atmosphere as air (clean gas) containing 20 ppm or less of benzene vapor via the discharge pipe 12.

The adsorption towers 1a and 1b operate while alternately switching between the above-mentioned adsorption step and the desorption step described later. At this point in time, the adsorbent layers in the adsorption towers 1a and 1b break through. Before, and the valve (d), shown in FIG.
This is done by automatically opening and closing (d). That is, the valves (e) and (e) for switching between suction and desorption are opened and closed. The "inlet gas flow rate""J" and the "inlet gas concentration""H" of the adsorption towers 1a and 1b are shown in FIG. "Estimated breakthrough time" indicating the result of calculation by the CPU (calculation) 22 of the adsorption model read in the memory 21 and previously written in the memory (adsorption model) 23; and a temperature detection button disposed above the adsorbent layer. (Not shown), the "temperature""F" in the adsorbent layer taken out of the Y-type synthetic zeolite 3-2a (3-2b) [see FIG.
The point at which "G" stops rising is automatically switched.

On the other hand, the adsorption tower 1a after the completion of the adsorption step
(After the switching to the desorption step, the adsorption tower 1b), the water is supplied to the adsorption tower 1a via the water pipe 13 (the tower switched to desorption).
And a water-sealed vacuum pump 14 (Nash pump: trade name, manufactured by Kurimura Seisakusho) for suction and detachment. In this comparative example, the water ring vacuum pump 14 is operated at about 60 Torr to reduce the pressure (vacuum) in the adsorption tower 1a (the tower switched to desorption). As a result, the supplied water becomes steam in the adsorption tower 1a and becomes a purge gas. Then, the exhaust gas is taken out from the purge exhaust gas supply pipe 15 through the water ring vacuum pump 14 as purge exhaust gas.

For cooling the purge exhaust gas sucked by the water ring vacuum pump 14, industrial water at room temperature was used. That is, the purge exhaust gas is sent to the gas-liquid separator 16. The gas-liquid separator 16 is cooled by industrial water flowing through a cooling pipe (not shown) provided therein. At this time, the benzene vapor in the purge exhaust gas is sent to the gas-liquid separator 16 connected to the lower part.
It is condensed and liquefied by mixing with water in a water seal and separated from uncondensed gas. The accumulated water and benzene are taken out of the system and are subjected to industrial waste treatment by the industrial waste treatment device 17.

Since benzene vapor remains in the exhaust gas not condensed by the gas-liquid separator 16, the benzene vapor is returned to the waste gas air pipe 11 again via the return gas air pipe 18, and is returned together with the waste gas. To perform the adsorption process. The uncondensed gas contains high-concentration residual benzene, and returning the entire amount to the waste gas air pipe 11 further increases the benzene concentration in the adsorption tower. Then, by using the above-mentioned means, the time when the adsorbent layer in the adsorption tower breaks through is predicted, the switching time of the valve (e) is set, and the operation is automatically switched to the desorption operation.

"A to J" shown in FIG. 1 indicate the positions of the instruments provided for grasping the operation status, while (A) to (D) indicate the operation control. 3 shows the position of a valve provided for the purpose. FIG. 2 shows a control panel 20 for grasping and controlling the operating state in the flow shown in FIG. 1 and comprises a memory 21, a memory (suction model) 23 and a CPU (calculation) 22. Is what is being done. In FIG. 2, only data necessary for switching between absorption and desorption are shown as "X" as data signals to be read into the memory 21. (Reading of other data signals was omitted.)

In this comparative example, as described above, since the switching between the adsorption and the desorption is performed by detecting the data logger signal before the adsorption tower breaks through, the concentration of the gaseous hydrocarbon is reduced when the gaseous hydrocarbon is lean. By devising a cooling means that can concentrate several times in the tower and remove heat generated in the adsorbent layer
(Refer to FIG. 3 described above), local heating was avoided, and the temperature of the adsorbent layer during the operation period was almost room temperature. Further, the benzene concentration in the gas discharged into the atmosphere from the discharge pipe 12 was substantially 20 ppm or less.

(Example) FIG. 4 is a longitudinal sectional view of an adsorption tower used in an example of the present invention. FIGS. 5A and 5B further illustrate the adsorption tower of FIG. 4, wherein FIG. 5A is a sectional view taken along line AA of FIG. 4, and FIG. 5B is a partially enlarged detailed view of FIG. In the present embodiment, as shown in FIGS. 4 and 5A and 5B, the adsorbent layer 43a (43
b) -filled outer cylinders 42b (42b) and 42a '(42
The adsorption tower 41a (41b) composed of the double cylinder of b ') was used.

As the adsorbent, crushed activated carbon having a particle diameter of 0.4 mm (HC42: trade name of Tsurumi Coal) and Y-type synthetic zeolite having a particle diameter of 1.0 mm (360 HU)
D: trade name, manufactured by Tosoh Corporation). Then, as shown in FIGS. 4 and 5B, the crushed activated carbon 43-1a (43-
1b), the Y-type synthetic zeolite 43-2a (43-2b) is filled in the adsorption tower 41a (41b), and the adsorbent layer 43a (43
This was used as b). The crushed activated carbon used was pre-coated with benzene vapor in advance.

In this embodiment, the above-described FIGS.
Except for using the adsorption tower 41a (41b) shown in (A) and (B), and using the above-mentioned crushed activated carbon and Y-type synthetic zeolite, the waste gas (about 5
(A waste gas containing 000 ppm of benzene: a gas amount of 300 liter / min). In this case, the gas velocity passing circumferentially through the adsorbent layer 43a (43b) is
“1.5 cm / sec”.

In this embodiment, the concentration of benzene in the gas discharged into the atmosphere from the discharge pipe 12 (see FIG. 1) is such that it cannot be detected by a commercially available portable HC concentration detection tube (converted to isobutane). It was a trace amount.

In the comparative example, while the benzene concentration in the gas released into the atmosphere is 20 ppm or less,
In this example, as described above, the amount is so small that it cannot be detected and detected, and it can be understood that it is superior to the comparative example. Further, in the present embodiment, it can be understood that a large amount of waste gas of "300 liters / minute (18 m ³ / hour)" can be effectively treated.

As described above, the embodiment of the present invention uses the multi-cylindrical adsorption tower shown in FIGS. 4 and 5 described above. However, the present invention is not limited to such a multi-cylindrical column. It is also possible to use an adsorption device configured by filling the adsorbent into a honeycomb-shaped core and bundling the core, or an adsorption device configured by packing the adsorbent in a box and stacking it. Other requirements are not limited to the above-described embodiment, and various embodiments are possible within the scope of the features of the present invention (items limiting the invention).

[0089]

As described in detail above, the present invention relates to a method for treating a lean gaseous hydrocarbon contained in waste gas, which is premised in the present invention. All or most of the exhaust gas is returned to the waste gas to be treated, thereby increasing the hydrocarbon concentration in the adsorbent layer (first characteristic point). ・ Switching to desorption before the adsorbent layer breaks through (second characteristic)
This makes it possible to safely, easily and efficiently treat hydrocarbons from waste gas, and to reduce the concentration of residual hydrocarbons in the gas released into the atmosphere after treatment to 100 ppm or less. In particular, "20 ppm or less".

Therefore, according to the present invention, in the removal treatment of gaseous hydrocarbons, which are air pollutants, the benzene concentration of benzene specified in the amendment of the Air Pollution Control Law (publicly reported on February 6, 1997) Not only can the emission standard "30 ppm or less" be completely cleared, but even if the numerical value is less than half as severe, it can sufficiently cope with it.

Further, in the “method of treating lean gaseous hydrocarbons contained in waste gas” presupposed in the present invention, it is possible to: • When a part of the gaseous hydrocarbons in the purge exhaust gas is liquefied, Combustion treatment of hydrocarbons or detoxification treatment as industrial waste (third characteristic point), characterized in that it is not intended to recover gaseous hydrocarbons in waste gas Therefore, it is possible to avoid complicated means associated with this collection.

Further, according to the present invention, as an “adsorption device having an adsorbent layer”, the adsorbent layer is surrounded and outside the adsorbent layer.
It is characterized by comprising an adsorber with multiple built-in components capable of passing waste gas in the lateral direction from the cylinder toward the adsorbent layer . In this way, the adsorbent layer in the adsorber is expanded to increase the gas passage area. By multiplexing coordination,
In particular, it is possible to provide an adsorption device that can be applied to a case where a large amount of waste gas of several hundred m ³ is processed per minute.
In addition, in principle, an excellent effect of eliminating the need to cool the adsorbent layer is produced.

In addition, when the above-described method presupposed in the present invention is implemented as an apparatus, the method can be made portable so that the system can be integrated and mounted on a skid.

[Brief description of the drawings]

FIG. 1 is a flow sheet diagram for explaining a “method of treating a lean gaseous hydrocarbon in a waste gas” presupposed in the present invention.

FIG. 2 is a diagram showing an example of a “control panel for grasping and controlling an operating state” in the flow sheet shown in FIG. 1;

FIG. 3 is a longitudinal sectional view of an adsorption tower used in a comparative example.

FIG. 4 is a longitudinal sectional view of an adsorption tower used in an embodiment of the present invention.

5 is a diagram further illustrating the adsorption tower of FIG. 4, and FIG.
4A is a cross-sectional view taken along the line AA in FIG. 4, and FIG.
FIG.

FIG. 6 is a graph showing “water adsorption isotherm of activated carbon”.

[Explanation of symbols]

 1a, 1b Adsorption tower 2a, 2b Outer cylinder 3a, 3b Adsorbent layer 3-1a, 3-1b Activated carbon 3-2a, 3-2b Y-type synthetic zeolite 4a, 4b Inner cylinder 5 Cooling water 10 Waste gas generation source 11 Disposal Gas air pipe 12 discharge pipe 13 water pipe 14 water ring vacuum pump 15 purge exhaust gas air pipe 16 gas-liquid separator 17 industrial waste treatment equipment 18 return gas air pipe 20 control panel 21 memory 22 CPU (calculation) 23 memory (adsorption) Model) 41a (41b) Adsorption tower 42a (42b), 42a '(42b') Outer cylinder 43a (43b) Adsorbent layer 43-1a (43-1b) Crushed activated carbon 43-2a (43-2b) Y-type synthetic zeolite

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideki Sakuma 27-5, Niiisogo-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Niigata Construction Co., Ltd. (56) References 4-114697 (JP, A) JP-A-9-57060 (JP, A) JP-A-51-35675 (JP, A) JP-A-11-71584 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 53 / 72,53 / 04 D06F 43/08

Claims (8)

(57) [Claims] 1. An adsorber having an adsorbent layer which alternately performs adsorption and desorption is used. One of the adsorbers is made to pass a waste gas containing gaseous hydrocarbons. The gaseous hydrocarbons were adsorbed, and waste gas substantially free of gaseous hydrocarbons was released into the atmosphere, during which time the other adsorber was switched to desorption and adsorbed on the adsorbent layer in the adsorber. A method for treating a lean gaseous hydrocarbon contained in waste gas, which comprises sucking a gaseous hydrocarbon by a vacuum pump to separate the gaseous hydrocarbon, and transferring the gaseous hydrocarbon to a purged exhaust gas. To the waste gas to be treated, thereby increasing the hydrocarbon concentration in the adsorbent layer and switching to desorption before the adsorbent layer breaks through. The part liquefies In this case, the apparatus is used as an apparatus for performing a method for treating a lean gaseous hydrocarbon contained in waste gas, which comprises burning the liquid hydrocarbon or detoxifying the liquid hydrocarbon as industrial waste. The above “adsorption device having an adsorbent layer” surrounds the adsorbent layer and directs the adsorbent layer from the outer cylinder of the adsorbent layer
A device for treating lean gaseous hydrocarbons contained in waste gas, characterized by comprising an adsorption device having multiple components capable of aerating the waste gas in the horizontal direction . 2. The waste gas according to claim 1, wherein the component is a cylindrical component, a box component, or a honeycomb component, and the component is an adsorption device in which the components are multiplexed. Equipment for the treatment of lean gaseous hydrocarbons contained. 3. The waste gas according to claim 1, wherein the adsorbent layer comprises a layer filled with fine adsorbent having a diameter of 0.1 to 1 mm. Equipment for processing lean gaseous hydrocarbons. 4. The adsorbent layer according to claim 1, wherein said adsorbent layer comprises a layer of activated carbon and / or hydrophobic silica gel, and an adsorbent layer comprising synthetic zeolite is disposed on top of said layer. An apparatus for treating a lean gaseous hydrocarbon contained in waste gas according to any one of the above. 5. The waste gas according to claim 1, wherein the adsorbent filled in the adsorption device or the filled adsorbent layer is pre-coated with a gaseous hydrocarbon. Equipment for the treatment of lean gaseous hydrocarbons contained. 6. The method according to claim 1, wherein the means for releasing gaseous hydrocarbons adsorbed on the adsorbent layer in the adsorber uses air or water heated to a boiling point or higher of the hydrocarbons to be adsorbed. An apparatus for treating a lean gaseous hydrocarbon contained in waste gas according to any one of claims 1 to 5. 7. As a means for switching to desorption before the adsorbent layer breaks through, a temperature detection port is disposed at the top of the adsorbent layer, and the temperature from the temperature detection port stops rising. 7. The apparatus for treating a lean gaseous hydrocarbon contained in waste gas according to claim 1, wherein the solenoid valve is automatically switched at a point in time. 8. As means for switching to desorption before the adsorbent layer breaks through, “adsorption gas flow rate”, “inlet gas hydrocarbon concentration” and “outlet gas concentration” of the adsorption device obtained during adsorption operation. The desired hydrocarbon concentration (assumed value) is read into the chip as numerical data, and the switching time is set in advance using a simulation model for control incorporated in the chip.
An apparatus for treating a lean gaseous hydrocarbon contained in waste gas according to any one of claims 1 to 6.