JP2002035542A - Method for treating lean gaseous hydrocarbon contained in waste gas and apparatus for practicing the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste gas treatment method whereby a large amount of a waste gas containing lean gaseous hydrocarbons can be safely, easily, and efficiently treated to separate the gaseous hydrocarbons, the remaining gaseous hydrocarbon concentration of the waste gas discharged into air after the treatment can be decreased to 100 ppm or below, if possible, to zero-emission and to provide an apparatus for practicing the method. SOLUTION: This method comprises (1) using adsorption towers 1a and 1b; (2) packing each of the towers 1a and 1b with an oxide-catalyst-carrying hydrophobic silica gel and zeolite Y laid thereon; (3) allowing each tower to alternately perform adsorption and desorption, the changeover between which is performed by automatically actuating a valve (ii) according to the command of 'the concentration at break-through of the adsorbent layer' predicted from the data log in the form of an electric signal taken from the control panel; and (4) during desorption, using preheated air having a purge effect as a combustion medium gas to catalytically combusting the gaseous hydrocarbons held in the adsorbent layer into harmless gases, which are then discharged into the atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating lean gaseous hydrocarbons contained in waste gas, and more particularly to a method for treating waste gas containing harmful gaseous hydrocarbons that cause air pollution. The present invention relates to a method and an apparatus for efficiently separating and detoxifying the hydrocarbon. Specifically, as a harmful gaseous hydrocarbon, for example, carcinogenic,
Benzene and toluene, which are one of the substances causing air pollution,
The present invention relates to the treatment of waste gas containing gaseous hydrocarbons such as methyl ethyl ketone, trichloroethylene, chlorofluorocarbon, olefin, etc., wherein the concentration of the hydrocarbons is reduced to 100 ppm or less (preferably zero emission), and the above-mentioned treatment method for discharging into the atmosphere. Related to the device.

[0002]

2. Description of the Related Art For gaseous hydrocarbons, such as benzene, toluene, methylene chloride, methyl ethyl ketone, trichloroethylene, chlorofluorocarbons, and olefins, which are one of the main causes of air pollution, developed countries such as the United States, Europe, and Japan. Strictly regulates the concentration of air emitted into the atmosphere. Although the level of the regulation value varies depending on the circumstances of each country, in advanced countries other than Japan, for example, benzene is “5 ppm or less”, and even in Japan, the Environment Agency Notification No. 5 (February 1997) 6th) "30ppm or less"
Became regulated. Furthermore, in July 1999, a law (PRTR Law) was enacted to promote the improvement and improvement of the management and management of the release of specified chemical substances into the environment, which would require companies to report their emissions. Was. It will shift from the conventional regulation of emission concentration to regulation of total emission.

[0003] By the way, as a source of the generation of such gaseous hydrocarbons, a particular problem is, for example, emission from the ducts of printing factories, cleaning factories, painting factories, factories that widely perform manufacturing, and the like into the atmosphere. Large and about 50
It is a waste gas of less than 00 ppm and is generated not only at factories but also at the time of unloading and unloading from tanks storing them.

[0004] "Prior art related to waste gas treatment method" [0004] As a method for detoxifying waste gas containing gaseous hydrocarbons as described above, a method widely used in the past is as follows: (1) Gas separation membrane method + Adsorption method (2) Room temperature absorption and reduced pressure regeneration method (3) Adsorption method using activated carbon, zeolite, hydrophobic silica gel, etc.

[0005] Of the above methods, the method (1) is a mainstream technology in Europe, and 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. Even in Japan,
As disclosed in Japanese Patent Application Laid-Open No. 4-23568 and Japanese Patent Application Laid-Open No. 7-284623, a technique belonging to this field is disclosed. In Japan, the technology that has occupied the mainstream so far is
As described in JP-B-54-8632 and JP-B-58-022503, gaseous hydrocarbons in waste gas are washed with a special absorbent, and a vacuum pump is used to recycle the absorbent (2 ).

On the other hand, the most widely adopted method in the United States is the above-mentioned adsorption method (3), particularly the adsorption method using activated carbon. This method is disclosed in Japanese Patent Application Laid-Open No. 577-14687.
Japanese Patent Application Laid-Open No. 57-42319, Japanese Patent Publication No. 59-50715, 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 into the atmosphere is 100 ppm or less. The adsorption method using is the best industrial means. However, in the conventional adsorption method using activated carbon, "steam" is usually used as a purge gas at the time of desorption. And the amount of steam required for desorption is about three times the amount of adsorbent used,
Requires a large amount. Moreover, since the steam is condensed and mixed with water when the steam is condensed into water, there is a drawback that a considerable burden is imposed on wastewater treatment equipment such as the activated sludge method in order to clear strict water quality standards. Therefore, a method has been proposed in which "high-temperature heated nitrogen" is used instead of steam as a purge gas at the time of desorption, and this is used in a circulating manner. Separation requires a large refrigerator.
It must be cooled to a low temperature of less than ℃, which is rather uneconomical.

As means for solving the above-mentioned problems, Japanese Patent No.
Prior to the recovery of gaseous hydrocarbons from the purged exhaust gas, as disclosed in the specification of 2823835, the lean gaseous hydrocarbons in the purged exhaust gas were removed through a cascade-type concentrated adsorption tower (adapter). Concentration and removal from the concentration adsorption tower (adapter) are 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-mentioned 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. In addition, any of the above-mentioned means is not economical as a means for concentrating a dilute gaseous hydrocarbon because hydrocarbons having a low boiling point are not easily cooled and require a powerful refrigerator. It's not an easy way.

Therefore, in order to solve the above-mentioned drawbacks, in the activated carbon adsorption method which has been widely used, when treating a large amount of gas of several hundred m ³ per minute, fibrous activated carbon is mainly used. 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.

In the above method, the adsorption is performed over a long period of time of several tens of minutes to several hours, and thereafter, it is merely desorbed by steam. The feature of this method is that the "adsorption device having an adsorbent layer" is devised so that a large amount of gas can be treated, but the hydrocarbon concentration in the gas discharged into the atmosphere is reduced to "100 ppm or less". It is extremely difficult to do so.

"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, a trace concentration of several tens of ppm or less becomes a problem, and the concentration that needs to be detected before that, that is, before the breakthrough, is required. It is on the order of 1 to 2 ppm or less, and requires an expensive measuring instrument requiring precision.

[0014] Also, various proposals have been made for the above detection method since ancient times. For example, JP-A-55-3599
No. 6, there is a description that "adsorption tower is 5 to 10 kg / cm using a two-column PSA purification apparatus for adsorption and desorption without using a vacuum pump.
^In the state of pressurizing to ² , the wet gas is adsorbed and the dry gas is diffused from the top of the tower.On the other hand, desorption is performed by discharging the adsorbed gas by returning the pressure of the tower to normal pressure. In the dehumidifying method, the operating state of each part including the gas flow rate passing through the adsorption tower, the inlet and outlet pressures of the adsorption tower, and the regeneration pressure of the desorption tower is stored in the microcomputer as input data, and the material balance is obtained. And instantaneously calculate the heat balance, control the desorption time based on the results, and automatically indirectly control the timing of switching between adsorption and desorption. 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, at the time, there was no excellent adsorption model as at present, and the simulation method could not be used. That is, the idea of "controlling the operating state of the apparatus according to the instruction of the calculation result on the personal computer incorporated in the control panel using the simulation method of the adsorption model with the breakthrough concentration" has not been reached. After that, the concept of "adsorption model" was born as a theoretical calculation problem required for the design of the adsorption device, and many studies have been made so far. For example, a frozen model, an equilibrium model, etc. are detailed in "Chemical Engineering" (Journal of the Society, August 1988). However, although there are many points that should be referred to as design data of the adsorption device, control of the device under the operation state proposed by the present inventors, that is, adsorption and desorption intended by the present invention, As a switching means, there is no description and no technical disclosure about the idea of taking out a calculation result of a simulation model on a personal computer incorporated in a control panel as an electric signal and linking it with an on / off valve.

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 of switching between adsorption and desorption is to perform simple time control, but the present inventors have found that the gas rising in the adsorbent layer is applied to the tower wall side. In order to prevent the phenomenon of passing through to the top, that is, the “wall effect (wall effect) phenomenon”, a wrapper is provided inside the adsorption tower to prevent slipping, and further, the adsorbent layer is provided on the top. A zeolite layer having an almost uniform adsorption pore diameter was coordinated, and the time in which the temperature did not fluctuate was detected, and a method for switching the adsorption operation to the desorption operation was found.

[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. Then, the present inventors argued that "the gaseous hydrocarbon contained in a large amount of waste gas is adsorbed on the adsorbent layer in the adsorption device, and the adsorbed gaseous hydrocarbon is not taken out of the system. Combustion using an oxygen-containing gas or a light source in the presence of an oxidation catalyst or a noncombustible solid adsorbent carrying titanium oxide, or in the presence of an oxidation catalyst and a noncombustible solid adsorbent (catalytic combustion) Or oxidatively decompose it into the atmosphere as a harmless gas,
After the completion of combustion or oxidative decomposition, the desorption tower is switched to the adsorption operation. "

The object (technical problem) of the present invention is, firstly, to solve the above-mentioned problems and disadvantages of the prior art, and to remove a large amount of waste gas containing harmful gaseous hydrocarbons that cause air pollution. The object of the present invention is to provide a "method for treating a lean gaseous hydrocarbon contained in waste gas and an apparatus for carrying out the method" for efficiently separating and detoxifying the hydrocarbon. Hazardous hydrocarbons in waste gas are safely, easily and efficiently exhausted as flameless combustion gas, and the concentration of residual gaseous hydrocarbons in waste gas released to the atmosphere during adsorption is 100 ppm or less. The third object of the present invention is to provide the above-described processing method and apparatus capable of achieving zero emission as an expected value. Third, it is possible to generate air pollutants such as NOX usually contained in combustion exhaust gas due to catalytic combustion. There is to provide the above-described processing method and apparatus, the fourth, is to provide the above-described processing method and apparatus capable of processing a large amount of waste gas that per minute hundred m ^3, the fifth, Since there is no need for a conventional desorption process using a vacuum pump or a desorption process using a steam, it is an object of the present invention to provide the above-described processing method and apparatus that can easily switch between suction and desorption.
The switching timing can be performed by opening and closing the valve according to the instruction of the temperature in the zeolite layer provided on the top of the adsorbent layer, or the instruction from the calculation result on the personal computer incorporating the adsorption model. It is an object of the present invention to provide a method and an apparatus which can be made portable so that they can be integrated on a skid.

[0019]

According to the present invention, there is provided a processing method for achieving the above objects (the first to sixth objects).
The technical configuration uses an "adsorption device having an adsorbent layer that alternately performs adsorption and desorption", and allows waste gas containing gaseous hydrocarbons to pass through one of the adsorption devices to form an adsorbent layer in the adsorption device. Adsorb gaseous hydrocarbons and release waste gas substantially free of gaseous hydrocarbons into the atmosphere, while switching the other adsorber to desorption. In the method for treating gaseous hydrocarbons, at the time of the switching, the gaseous hydrocarbons adsorbed on the adsorbent layer in the adsorption device are not taken out of the system,
In the presence of an oxidation catalyst or titanium oxide supported on the adsorbent, or in the presence of an oxidation catalyst and a non-combustible solid adsorbent,
A method for treating a lean gaseous hydrocarbon contained in waste gas, which comprises burning or oxidatively decomposing using an oxygen-containing gas or a light source. (Claim 1) is a feature (a matter specifying the invention), and thereby the following effects are obtained.

That is, according to the treatment method of the present invention, the adsorbed gaseous hydrocarbon is burned using the oxidation catalyst or titanium oxide (photocatalyst; oxidation catalyst in a broad sense).
(Catalytic combustion), oxidative decomposition to treat, high combustion efficiency can be obtained, and because it is flameless combustion, the oxidation temperature is lower than in the case of direct combustion, and it does not locally increase, so Stable combustion is obtained. In addition, the most significant feature of the "catalytic combustion or oxidative decomposition" according to the present invention is that not only is there no emission of air pollutants such as NOX normally contained in flue gas, but also it is contained in exhaust gas that is released into the atmosphere after treatment. The effect is that the gaseous hydrocarbon concentration can be reduced to almost zero, not to mention 100 ppm or less.

[0021] In the above treatment method according to the present invention, specifically, the oxidation catalyst comprises at least one of platinum, palladium, vanadium, titanium and a transition metal, and the radical is excited by light. Is titanium oxide, the non-combustible solid adsorbent supporting the oxidation catalyst or the non-combustible solid adsorbent coexisting with the oxidation catalyst is hydrophobic silica gel and / or synthetic zeolite, and the combustion temperature is 30 to 500. ° C (preferably 50 to 150 ° C) (Claim 2), and safely, easily and efficiently disposes harmful hydrocarbons in waste gas as harmless combustion gas. The concentration of residual gaseous hydrocarbons in the waste gas released into the atmosphere during adsorption is 100 pp
m or less, the expected value can be made substantially zero. In particular, in the case of titanium oxide used as an oxidation catalyst excited by light, when the hydrocarbon gas concentration in the inlet gas is 100 ppm or less as a guide, a non-combustible solid adsorbent layer supporting titanium oxide at normal temperature Alternatively, zero emission can be easily achieved by irradiating the non-combustible solid adsorbent layer coexisting with the oxidation catalyst (including the catalyst layer filled with the oxidation catalyst) with a wavelength of 380 nm or less, for example, ultraviolet rays. However, when the concentration exceeds 100 ppm, the hydrocarbon can be easily burned with an oxygen-containing gas at a high temperature of 300 ° C. or higher, as a standard, similarly to ordinary catalytic oxidation.

Further, in the treatment method according to the present invention, as means for burning or oxidatively decomposing gaseous hydrocarbons adsorbed on the adsorbent layer in the adsorber, (1) the adsorbent layer is kept at atmospheric pressure or lower. Hold or tightly enclose the adsorbent layer or catalyst layer with fine metal particles with good electrical conductivity
(Claim 3), (2) Combustion using an oxidation catalyst (catalytic combustion)
In the case of making the adsorbent layer adsorbing gaseous hydrocarbons a closed system, circulating and burning an oxygen-containing gas, and oxidative decomposition or switching to a release system at the end of combustion,
Air is introduced to cool the adsorbent layer, and thereafter, the process proceeds to an adsorption treatment. On the other hand, when a titanium oxide catalyst is used, the titanium oxide catalyst is irradiated with light having a wavelength of 380 nm or less to be excited and generated. It is characterized in that it is decomposed by active oxygen (free radical) and then shifts to an adsorption treatment (claim 4), thereby producing the following effects.

That is, as a means for burning or oxidatively decomposing gaseous hydrocarbons adsorbed on the adsorbent layer in the adsorber, for example, without using a medium such as a purge gas, a vacuum pump or steam as in the prior art, By passing a preheated oxygen-containing gas through the adsorbent layer holding the gaseous hydrocarbons and bringing them into contact (purge effect),
It can be exhausted as harmless gas.

In particular, in the method (1), the adsorbent layer (including the catalyst layer) is densely surrounded by fine particles of a metal (for example, sponge aluminum) having good electric conductivity and excellent heat insulation. In addition, the danger of explosive combustion can be avoided when contacting with a heated oxygen-containing gas.

Further, in the case of "combustion using an oxidation catalyst (catalytic combustion)" in the above method (2), it is difficult to sufficiently burn the oxygen-containing gas simply by passing it from top to bottom in an open system. Therefore, in order to complete the time required for catalytic combustion within a short time, the desorbent layer is closed and the oxygen-containing gas is recycled. When the operation is switched to the adsorption operation, a sufficient adsorption effect cannot be obtained with the adsorbent layer while maintaining the high-temperature state. Means for cooling the adsorbent layer and thereafter shifting to the adsorption treatment is employed. If the time required for this cooling process is long (if the desorption time exceeds the time required for adsorption), a method of adding a small amount of water to the above air and using the latent heat of vaporization to accelerate the cooling effect is also cooling. One of the means and this is possible because the adsorbent is hydrophobic. As a particularly effective method, as described in the fifth aspect of the present invention, "a concentrated adsorption by cascade method for the purpose of obtaining efficient combustion by increasing the hydrocarbon concentration in the adsorbent layer. A method of separately providing a tower (adapter) and switching the tower to a desorption tower for the purpose of oxidative combustion ”is recommended. In this case, it is sufficient for the switching means to be an inexpensive suction means such as a blower.

On the other hand, in the case of using the titanium oxide catalyst in the above method (2), a light source such as a xenon lamp, a mercury lamp, or a fluorescent lamp may be provided in the tower, at the lower part of the tower, or near the outlet. . By the above methods (1) and (2), harmful hydrocarbons in the waste gas are safely, easily and efficiently exhausted as harmless combustion gas, and after switching to the adsorption operation, the efficiency is reduced. The process can be shifted to the adsorption process.

Further, in the treatment method according to the present invention, the adsorbent layer is preferably a layer filled with (a) a non-combustible solid adsorbent having a diameter of 0.1 to 2 mm and carrying an oxidation catalyst; b) a layer filled with a mixture of an oxidation catalyst and a noncombustible solid adsorbent, or (c) at least two layers of a layer filled with an oxidation catalyst and a layer filled with a noncombustible solid adsorbent. Features (claim 6).

As described above, in addition to the above (a) and (b), another embodiment of the processing method of the present invention includes the above (c)
By separately disposing the adsorbent layer into a non-combustible solid adsorbent layer and a catalyst layer as described above, that is, the catalyst layer filled with a solid support supporting an oxidation catalyst is By arranging the catalyst at a position in contact with the gaseous hydrocarbon displaced by the oxygen-containing gas from the agent, more efficient catalytic combustion can be performed, and thus the temperature during catalytic combustion can be reduced to 30 ° C. Combustion while maintaining at ℃ ~ 500 ℃
(Catalytic combustion) .On the other hand, when switching to adsorption, the temperature in the adsorbent layer can be easily and promptly kept close to room temperature, and the performance of the adsorbent can be maintained without waste. Can be demonstrated.

In this case, an important problem to be considered is the problem of "how to safely burn a lean gaseous hydrocarbon whose concentration is within the explosion limit value". In other words, if the burning rate is rapid, an explosion may occur, but the problem of how to reduce the burning rate must be solved. Empirically, it is widely known that safe combustion can be achieved if the pressure during combustion is maintained at or below atmospheric pressure.However, for combustion under normal pressure, low-temperature catalytic combustion without a flame using a catalyst is used. There is no way to take it. In view of the fact that the main cause of the explosion of lean gaseous hydrocarbons so far has been spark discharge due to static electricity generated in towers and tanks having a wide gap, the present inventors have used a general purpose to prevent explosion. As a result, it was found that the risk of explosion combustion can be avoided by densely surrounding the oxidation catalyst layer with metal particles having high electric conductivity as described above. (Claim 3).

Further, in the above-mentioned treatment method according to the present invention, the adsorbent layer has a diameter of 0.1 mm for supporting an oxidation catalyst.
A layer filled with a non-combustible solid adsorbent of 1 mm to 2 mm, or a layer not supporting an oxidation catalyst, having a diameter of 0.1 m
characterized in that a layer filled with non-combustible solid adsorbent M～2mm (Claim 6), by using an adsorbent such fine, particularly, mass of per minute hundred m ³ waste While it is possible to efficiently concentrate and adsorb a dilute gaseous hydrocarbon of about several hundreds to several tens of ppm contained in the gas, shorten the contact time with the oxygen-containing gas,
Efficient catalytic combustion can be obtained.

On the other hand, in the treatment method according to the present invention, the operation is switched from combustion (catalytic combustion) to oxidative decomposition operation before the adsorbent breaks through (claim 7). A terminal for detecting the temperature (temperature detection port) is disposed at the top of the layer, and the valve is automatically switched when the temperature indicated by the temperature detection port stops rising (claim 8).・ The "inlet gas flow rate", "hydrocarbon concentration in the inlet gas" and "desired hydrocarbon concentration in the outlet gas (assumed value)" of the adsorption device obtained during the adsorption operation are provided in the control panel as numerical data. By reading this value into a simulation model for the purpose of control in which the value is written in the ROM of the personal computer and calculating the value, the switching time of the valve is made to follow the instruction of the calculation result ( According to claim 9), it is possible to automatically detect the breakthrough point of the adsorbent layer and automatically switch between adsorption and desorption.

According to the treatment method 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, and the expected value can be set to zero emission. ).

An apparatus according to the present invention is an apparatus for carrying out the above-mentioned treatment method, wherein: an adsorbing device having an adsorbent layer surrounds the adsorbent layer, and the adsorbent is transferred from an outer cylinder of the adsorbent layer to the adsorbent. An adsorber having a plurality of components capable of passing waste gas laterally toward the layer (claim 11); the component is a box-shaped component, a cylindrical component or a honeycomb-shaped component; The above object (first to sixth objects) can be achieved by being a suction device that incorporates multiple components (claim 12).

That is, it is possible to provide an apparatus suitable for treating a large amount of waste gas of several hundred m ³ per minute, and it does not require a desorption step using a conventionally widely used vacuum pump. In addition, the switching operation between suction and desorption can be easily performed, and the switching can be performed only by an inexpensive butterfly valve (on-off valve) without using an expensive solenoid valve or vacuum pump. Further, the entire system can be mounted on a skid by integrating the system so as to be portable.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the method and apparatus according to the present invention will be described including the effects thereof, and the present invention will be described in more detail.

The processing method according to the present invention, as described above,
When the adsorption device is switched to desorption, the gaseous hydrocarbons adsorbed on the adsorbent layer in the adsorption device are not taken out of the system, and are kept in the adsorbent layer.
(In the presence of a non-combustible solid adsorbent carrying titanium oxide), or (b) in the presence of a mixture of an oxidation catalyst and a non-combustible solid adsorbent, catalytic combustion or light by an oxygen-containing gas. Oxidative decomposition by irradiation, or (c) without desorbing the gaseous hydrocarbons adsorbed on the adsorbent layer in the adsorber, after desorbing the gaseous hydrocarbons adsorbed on the adsorbent layer without taking out the system The catalyst layer is characterized by catalytic combustion by an oxygen-containing gas or oxidative decomposition by light irradiation.

According to the above-mentioned processing methods (a) to (c), high combustion efficiency is obtained, and since the flameless combustion is performed, the oxidation temperature is lower than that in the case of direct combustion, and the combustion is locally performed. Since the temperature does not rise, stable combustion can be obtained. As an example, comparing the “catalytic oxidation onset temperature” of various organic compounds with a noble metal based oxidation catalyst and the “non-catalytic ignition temperature”, the “catalytic oxidation onset temperature” of toluene, acetone, methyl ethyl ketone, etc. is “100 ° C. 〜150 ° C., whereas the “catalyst-free ignition temperature” of the material is as high as 500 ° -700 ° C.

(About Combustion Means) In a preferred embodiment of the treatment method according to the present invention, a gaseous hydrocarbon adsorbed on the adsorbent layer is burned using an oxygen-containing gas which has been heated in advance.
(Catalytic combustion). The combustion treatment temperature is 30 to 500 ° C, preferably 50 to 150 ° C. As the oxygen-containing gas, it is preferable to use air that is extremely easily available or air in which a small amount of oxygen or moisture is contained in advance. (Note that, as the air, a part of the clean gas discharged into the atmosphere from the adsorbent layer can be used.) Also, an inert gas (nitrogen, carbon dioxide gas) containing a small amount of oxygen is used. This use is also included in the present invention. When the oxidation catalyst is titanium oxide, the above-mentioned means can be applied as it is when the concentration of the gaseous hydrocarbon is relatively high, but when the concentration is as low as several tens ppm, the wavelength is 38.
The objective can be sufficiently achieved only by irradiating light of 0 nm or less.

The adsorbent layer adsorbing the gaseous hydrocarbons is a layer filled with a non-combustible solid adsorbent supporting an oxidation catalyst. The adsorbent layer is closed, and the oxygen-containing gas is circulated for combustion. When the combustion is completed, the system is switched to an open system, air is introduced to cool the adsorbent layer, and thereafter,
It is desirable to shift to the adsorption process. The reason is as follows.

That is, when the gaseous hydrocarbon held in the desorbing layer is catalytically combusted with the oxygen-containing gas, the time required for the combustion depends on the oxygen concentration in the oxygen-containing gas, the combustion temperature, and the time required for the combustion. Determined by the concentration of gaseous hydrocarbons present. For this reason, in a system where the oxygen-containing gas is released,
Simply circulating in the tower does not always ensure sufficient combustion. Therefore, in order to finish the time required for catalytic combustion in a short time, it is necessary to make the desorption layer a closed system and to recycle the heated oxygen-containing gas. The catalytic combustion temperature according to the invention is between 30 and 500 ° C., preferably between 50 and 1 ° C.
Although the temperature is 50 ° C., as a heating means, air heated by electric heating or an electromagnetic induction fluid heating device (trade name: dual pack heater manufactured by Seta Kosan Kako Co., Ltd.) is used.

On the other hand, when the operation is switched to the adsorption operation, a sufficient adsorption effect cannot be obtained with the adsorbent layer kept at a high temperature. For this reason, means for switching to an open system at the time of completion of combustion, introducing air to cool the adsorbent layer, and thereafter shifting to adsorption treatment is employed. As a result, harmful hydrocarbons in the waste gas can be safely, easily, and efficiently exhausted as harmless combustion gas, and after switching to the adsorption operation, the process can be efficiently shifted to the adsorption process.

In addition, the cooling means may be to introduce water or refrigerant into the cooling coil, close the valve during adsorption operation, open the valve during catalytic combustion, and rapidly cool the temperature in the tower after desorption. However, it is easier and more economical to use sensible heat brought out by a large amount of air than to arrange a large number of cooling coils inside the adsorbent layer. In addition, if the cooling coil is arranged inside, there is a possibility that the temperature rise required for catalytic combustion may be hindered.
This cooling means is not necessarily a preferred embodiment of the present invention. As a preferred embodiment, as described above, when it takes too much time to cool the desorption layer, three operations of “adsorption, desorption, and cooling” are performed efficiently.
A means for separately providing a concentration adsorption tower (adapter) tower is suitable.

Here, the present invention will be described in detail by comparing the processing method according to the present invention with the conventional processing method. Conventionally,
In the field of application of the present invention, "the means for detoxifying lean gaseous hydrocarbons contained in a large amount of waste gas"
The adsorption method has always been used. The adsorbents used are, with exceptions, granular activated carbon or fibrous activated carbon. On the other hand, “the means for detoxifying rich gaseous hydrocarbons” is an adsorption method using a hydrophobic and nonflammable solid adsorbent which has already been developed by the present inventors. I have.

Although the above-mentioned activated carbon has excellent adsorption capacity as compared with other adsorbents, it has the drawback that it is flammable and 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. Moreover, the hydrocarbons entrained in the steam are mixed with the wastewater and made harmless by a wastewater treatment means using an activated sludge treatment device or an aeration device, but the COD cannot be reduced.
If a large amount of heated air is used as a purge gas instead of steam to perform desorption, there is a risk that the activated carbon may burn, and the fire gas is used as a purge gas when using activated carbon except for air at room temperature or non-combustible nitrogen. Unauthorized.

However, when a non-combustible solid adsorbent is used as the adsorbent, there is no danger as described above. For this purpose, in the processing method according to the present invention,
The use of a non-combustible solid adsorbent is an essential requirement, which enables the use of high-temperature air at a maximum of 500 ° C. as a combustion medium gas (oxygen-containing gas) having a purging effect. (Note that the concentration of gaseous hydrocarbons is specified to be lower than the lower explosion limit.
If desired, it should be below about 5000 ppm. )

(Regarding the Noncombustible Solid Adsorbent) The noncombustible solid adsorbent used in the present invention has a material that is nonflammable and has an affinity for hydrocarbon gas in waste gas.
Any solid adsorbent carrying an oxidation catalyst can be used. However, if the concentration of hydrocarbons in the waste gas is as low as "5000 ppm or less",
Inexpensive and easily available hydrophobic silica gel and / or synthetic zeolite are preferred, and the use of hydrophobic silica gel is particularly preferred. The reason is that the temperature of the purge gas is about 500 ° C.
This is because it can be used up to a maximum. The above-mentioned titanium oxide is also an oxidation catalyst in a broad sense, and depending on whether the concentration of the gaseous hydrocarbon to be treated is high or low, it is used under light at normal temperature or under high temperature. There is a difference between using air.

As the hydrophobic silica gel, non-combustible silica gel obtained by subjecting a non-combustible silica gel to a hydrophobic treatment with a silane coupling agent such as trimethylchlorosilane or a high temperature treatment for a long time to impart hydrophobicity and lipophilicity. Any of these can be used, but the most suitable adsorbent is a non-combustible solid adsorbent that absorbs only a few percent of water and adsorbs hydrocarbons well even if the RH is 50% or more. is there.

In the first place, solid adsorbents such as synthetic zeolite, silica gel and activated alumina used as adsorbents have strong affinity for gaseous hydrocarbons and are also used heavily as heat insulating agents. 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. Among them, a hydrophobic silica gel having a narrow distribution range around an adsorption hole diameter of 100 mm (trade name: Caractact Q-10, manufactured by Fuji Silysia Chemical Ltd.)
Is one of the preferred adsorbents for practicing the present invention. The reason is that, despite the fact that water is most difficult to adsorb among hydrophobic silica gels, it selectively adsorbs gaseous hydrocarbons well, and the material has heat resistance of 600 ° C. or higher and is very easy to desorb. This is because it is a hydrophobic silica gel having properties.

Generally speaking, in the case of hydrophobic silica gel or synthetic zeolite, it depends on the particle size and the temperature rise, but it is about 1 hour.
It is said that when the thickness is 0 cm or more, the heat of adsorption cannot be transferred to the cooling water layer in a short time. Therefore, 1
At a thickness of 0 cm or more, heat transfer in the circumferential direction cannot be expected so much, and it depends on heat transfer carried out by gas flowing in the vertical direction. 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, when the concentration at the time of breakthrough is directly detected at the outlet of the adsorption tower, there is no problem. ("Detection port
(See below for “

In order to avoid this, in a preferred embodiment of the present invention, the synthetic zeolite is placed at the top of the adsorbent layer, that is, at a position near the outlet from which gaseous hydrocarbons flow. For example, Y-type zeolite "360H"
UD (product name manufactured by Tosoh Corporation) ", etc. Synthetic zeolites, unlike hydrophobic silica gel or granular activated carbon, have a strictly controlled pore size to a certain size, and depending on the material selected, gaseous hydrocarbons Some varieties cover almost all of the molecular diameter of R. Further, although the ratio of adsorbing gaseous hydrocarbons is 15 to 20% by weight, R
The amount of water adsorbed is 1 even for gas with H of 50% or more.
0% or less. For this reason, there is no deviation in the adsorption band having a certain width moving in this layer.

Further, a concentration and temperature detection port to be taken into the control panel as an electric signal (data logger signal) from a sensor disposed inside the tower needs to be disposed at the center of the synthetic zeolite layer. In this way, in addition to the above-described means for detecting the breakthrough point, the instruction of the temperature at the center thereof is
The point at which the temperature rise due to the heat of adsorption is stopped can be used as a guide for switching. Such synthetic zeolites are SiO 2
It is desirable that the ratio of ₂ / Al ₂ O ₃ be 20 or more and have a pore size of about 8 Å. (Refer to the following for "Body for detecting density and temperature taken in as data logger signal")

(Regarding Oxidation Catalyst) In the treatment method according to the present invention, a non-combustible solid adsorbent carrying an oxidation catalyst is used. Examples of the oxidation catalyst include platinum, palladium, vanadium, and titanium (including titanium oxide). One or more of the obvious oxidation catalysts, including transition metals, can be used, and conventional noble metal loading, spraying, slurry,
The non-combustible solid adsorbent can be supported (attached) by any means such as a method, a sol-gel method, and a coupling method.

(Means for Switching to Combustion Step Before Adsorbent Layer Breakthrough) In the treatment method according to the present invention,
A preferred embodiment is to switch to a combustion step (catalytic combustion step) before the adsorbent layer breaks through, as described above: a temperature detection port is set at the top of the adsorbent layer. The valve is automatically switched at the time when the temperature indication from the temperature detection port stops its rise, the "inlet gas flow rate" of the adsorption device obtained during the adsorption operation,
The “hydrocarbon concentration in the inlet gas” and the “desired hydrocarbon concentration in the outlet gas (assumed value)” are read as numerical data by a personal computer provided in the control panel.
The switching time is automatically set according to the instruction of the calculation result in conjunction with the simulation model for the purpose of controlling the burned-in M. This enables the breakthrough point of the adsorbent layer to be automatically detected. Another object of the present invention is to enable automatic switching between the adsorption step and the combustion step.

Next, embodiments (first and second embodiments) of an "adsorption device having an adsorbent layer" used in the present invention will be described.

(First Embodiment of Adsorbing Apparatus) The first embodiment of the "adsorbing apparatus having an adsorbent layer" used in the present invention is intended to locally uniform the temperature and concentration of the adsorbent layer. As means for quickly moving the heat of adsorption generated in the adsorbent layer in the lateral direction from the adsorbent layer and removing it, an adsorbent layer for adsorbing gaseous hydrocarbons and cooling of the adsorbent layer It is preferable to use a “double cylinder or multi-cylinder adsorption tower” that is adjacent to a cooling water layer for performing the treatment. 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. Is desirable.

The specific adsorption tower of the first embodiment used in the present invention will be described with reference to FIG. 3. The adsorption tower 1a (1b) comprises an outer cylinder 2a (2b) and an adsorbent layer 3a.
(3b), the inner cylinder 4a (4b), and the cooling water 5.
The adsorption tower 1a (1b) is an adsorption tower used in Examples 1 and 3 of the present invention described later, and 3-1a in FIG.
(3-1b) is an impregnated hydrophobic silica gel (Examples 1 and 3 described below).
3-2a (3-2b) is a Y-type synthetic zeolite (see Examples 1 and 3 described later).

One of the points to be noted as the adsorption tower 1a (1b) of the present invention is that if the pressure inside the adsorption tower is increased, the hydrocarbon adsorbed on the adsorbent (hydrophobic silica gel impregnated) is increased. The remarkable increase in the effective adsorption amount of
Since it is natural to say from the theory of the law, the internal pressure of the adsorption tower 1a (1b) is also set to the "high pressure regulation" when the present invention is carried out.
It is extremely desirable to operate at a gauge pressure "1 kg / cm or less" which does not conflict with

(Second Embodiment of Adsorption Apparatus) In the present invention, a conventionally used "tower-type adsorption apparatus in which an adsorbent is tightly packed inside" can be used. In the case where the amount of waste gas to be treated is large, a problem arises in this conventional type. To explain this problem in detail, for example, when processing waste gas of "36,000 m ³ " per hour, the conventional type requires a column 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 in terms 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". When the average value of the gas passage speed is calculated as "15 cm / sec (0.15 m / sec)", the tower diameter becomes "10 m" as shown by the following equation. Formula: πR ² × 0.15 = 36,000 / 3,600 = 10 In the present invention, it is economically impossible to use an adsorption tower having such a diameter, and it is not practical.

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-described 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 in the industrial equipment constructed by the inventor, KFav
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".

The present inventor has paid attention to this point, and has developed a novel and economical adsorption apparatus [the adsorption apparatus having an adsorbent layer used in the present invention] which can be applied even when the amount of waste gas to be treated is large. Second Embodiment of Apparatus "]. As a novel and economical adsorption device of the present invention (adsorption tower according to the second embodiment), as the adsorbent to be filled,
0.1-2 mm fines (preferably 0.4-1 mm fines) are used, thereby reducing the contact time with the gas,
In addition, the configuration of the adsorbent layer in the adsorption device is multiplexed in order to increase the gas passage area.

As described above, 0.1 to 2 m
By using the fine particles of m, there is an excellent effect that the contact time can be reduced to "about 1/5" as compared with the conventional means. In addition, the fact that the thickness can be reduced to "about 1/5" means that the thickness of the adsorbent layer is also reduced to "about 1/5".
/ 5 ".

Conventional commercial plants are all single-column systems, and the thickness (layer height) is “1-2 m”. In the adsorption apparatus of the present invention, the thickness of the adsorbent layer is “about 1 / From the point of "5", the thickness becomes "20 cm to 40 cm", and as a result, an excellent action and effect is obtained in that the adsorbent layer does not need to be cooled in principle. The reason is that the hydrocarbon gas contained in the large amount of waste gas passing through the adsorbent layer is extremely dilute, and most of it is air, so the heat of adsorption that exceeds the calorific value of the air remains in the adsorbent layer. Because there is nothing.

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. I couldn't think of anything but steam. However, in the adsorption device of the present invention, the gaseous hydrocarbons adsorbed on the adsorbent layer are not taken out of the system, and are catalytically burned at normal pressure while being held. This eliminates the need for using an expensive vacuum pump or an elaborate electromagnetic valve that requires airtightness at the time of switching, thereby enabling the use of an inexpensive butterfly valve (on-off valve).

A specific adsorption tower of a novel and economical adsorption apparatus [the second embodiment of the "adsorption apparatus having an adsorbent layer" used in the present invention] which exhibits the above-mentioned remarkable effects and effects of the present invention. Referring to FIG. 4 and FIGS. 5A and 5B, the adsorption tower 41a (41b) includes an adsorbent layer 43.
outer cylinders 42a (42b) and 42
a '(42b'). Then, the waste gas flows into the adsorbent layer 43 as shown by the arrow line in FIG.
a (43b), and thus the gas passage area is increased. In addition, this adsorption tower 4
1a (41b) is an adsorption tower used in Example 2 of the present invention described later, and 43-1a (43-1b) in the figure is a hydrophobic silica gel supporting a metal oxide. Also, 43-2a (4
3-2b) is a Y-type synthetic zeolite. (← See Example 2 below)

(About system integration)
The inventor of the present invention has conducted intensive studies to integrate the device proposed in the present invention as a system and to make the device portable so that it can be mounted on a skid. That is, Patent No. 2840563 which the inventor has already obtained
, Patent No. 2,676,793, Patent No. 2,823,835, and Japanese Patent Application No. 9-245318, etc., do not use the adapter method or the displacement purge method. Without using a method of washing with a hydrocarbon liquid of the same quality, and further, after recycling the desorbed gas to increase the hydrocarbon concentration in the adsorption tower, the gaseous hydrocarbon is removed from the gas using a complicated cooling means. Instead of recovering as a liquid, a simple and economical method with no recovery means is provided.

Although the embodiment according to the present invention has been described in detail above, the method according to the present invention employs a known PS.
A method and PTSA method can be applied.
The method can be applied to the A method, the VTSA method, and the like, and these applications are also included in the present invention. Further, the present invention provides a method of concentrating a lean gaseous hydrocarbon contained in waste gas, burning it by catalytic oxidation and treating it as a harmless gas, and an apparatus for carrying out the method. Not only dilute multi-component hydrocarbon gas generated during coating, but also benzene, toluene, trichloroethylene, methyl ethyl ketone, and a single component such as chlorofluorocarbon, especially reactive gas such as olefin It is suitably applied to the treatment of hydrocarbons.

[0070]

Next, the present invention will be specifically described with reference to examples of the present invention.

(Embodiment 1) FIG. 1 shows an embodiment of the present invention, "Method for treating lean gaseous hydrocarbons in waste gas".
FIG. 2 is a flow sheet diagram for explaining FIG.
FIG. 6 is a diagram showing an example of a “control panel for grasping and controlling an operating state” in the flow sheet shown in FIG. FIG.
2 is a longitudinal sectional view showing an example (Example 1) of the structure of the adsorption tower used in the flow sheet shown in FIG.

In the first embodiment, 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. An adsorption tower 1a (1b) composed of a heavy cylinder was used. The inner cylinder 4a (4
The cooling water 5 flowing through the adsorbent layer 3a (3)
b) was made to flow in countercurrent to the flowing waste gas. Also,
As an adsorbent, vanadium oxide is 4 wt% in weight ratio,
Hydrophobic silica gel carrying 14.9% by weight of potassium sulfate
(Prototype manufactured by Fuji Silysia Chemical Ltd .: impregnated hydrophobic silica gel Q-10) and Y-type synthetic zeolite (360 HUD:
(Trade name, manufactured by Tosoh Corporation). Then, as shown in FIG. 3, Y is placed on top of the attached hydrophobic silica gel 3-1a (3-1b).
The type-synthesized zeolite 3-2a (3-2b) was packed in the adsorption tower 1a (1b), and used as an adsorbent layer 3a (3b). The hydrophobic silica gel used was precoated with benzene vapor in advance.

Hereinafter, the first embodiment will be described in detail with reference to FIG. 1. A waste gas generated from a waste gas generation source (not shown) (a waste gas containing about 5000 ppm of benzene: a gas of 20 liters / minute) (Amount) is compressed under a gage pressure of 1 kg / cm ² by a blower (not shown)
From 1, air is sent to the adsorption tower 1a. At this time, the adsorbent layer 3a
The gas velocity passing through (3b) was "about 10 cm / sec". The treated waste gas that has completed the adsorption step is supplied to the adsorption tower 1a.
(After switching to the desorption step, from the top of the adsorption tower 1b), it is discharged into the atmosphere as air (clean gas) containing 20 ppm or less of benzene vapor through the discharge pipe 12.

The adsorption towers 1a and 1b are operated while alternately switching between the above-mentioned adsorption step and a combustion step (desorption step) described later.
This is performed before the adsorbent layer in b goes through, and by automatically opening and closing the valves (b) and (b) shown in FIG. That is, the valves (b) and (b) for switching between suction and desorption are opened and closed. The "inlet gas flow rate""F" and the "inlet gas concentration""E" 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""C" in the adsorbent layer taken out of the Y-type synthetic zeolite 3-2a (3-2b) [see FIG.
Automatic switching is performed in combination with the time when "D" stops rising.

On the other hand, the adsorption tower 1a after the completion of the adsorption step
In, via a water pipe (not shown), supply and cool water,
At the same time, the pre-heated air 13 is supplied via the flow control valve (a). At this time, the adsorption tower 1a is closed, and the combustion air 13 is circulated for catalytic combustion.
When the combustion is completed, the system is switched to an open system, and air is introduced to cool the adsorption tower 1a.

In Example 1, the temperature of the preheated air was about 150 ° C., and the flow rate was about 1.5 in terms of a purge coefficient conversion formula. As a result, the hydrocarbons held in the adsorption tower are catalyzed and burnt out of the system as carbon dioxide.

The measure of the completion of the combustion was a time when the temperature in the adsorption tower became constant by temperature measurement. 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 (b) is set, and the operation is automatically switched to the desorption operation.

A to F shown in FIG. 1 indicate the positions of instruments provided for grasping the operation status. On the other hand, (A) and (B) indicate the operation control. 2 shows the position of the valve provided in the first embodiment. 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 the first embodiment, as described above,
Since the switching of desorption is detected by the data logger signal before the adsorption tower breaks through, if the gaseous hydrocarbon is lean,
By concentrating the concentration several times in the adsorption tower, and by devising cooling means to remove the 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 2 FIG. 4 is a longitudinal sectional view of an adsorption tower used in Example 2. FIG. 5 is a diagram further illustrating the adsorption tower of FIG. 4, wherein (A) shows A of FIG.
FIG. 4A is a cross-sectional view, and FIG. In the second embodiment, as shown in FIGS. 4 and 5A and 5B,
Outer cylinder 42b (42b) filled with adsorbent layer 43a (43b)
And an adsorption tower 41a (41b) composed of a double cylinder of 42a '(42b').

As an adsorbent, hydrophobic silica gel Q-10 supporting vanadium oxide having a particle size of 0.4 mm was used.
(Trade name, manufactured by Fuji Silysia Chemical Ltd.) and YZ type synthetic zeolite HSZ-360 (trade name, manufactured by Tosoh Corporation) were used. Then, as shown in FIGS. 4 and 5 (B), the Y-type synthetic zeolite 43-2a (43-2b) is placed on the top of the attached hydrophobic silica gel 43-1a (43-1b), and the adsorption tower 41a (41b). And used as an adsorbent layer 43a (43b). The adsorbent used was precoated with benzene vapor in advance.

In the second embodiment, FIGS.
Same as Example 1 except that the "hydrophobic silica gel supporting vanadium oxide" and the "Y-type synthetic zeolite" were used using the adsorption towers 41a (41b) shown in (A) and (B). A waste gas (a waste gas containing about 5000 ppm of benzene: a gas amount of 300 liters / minute) was treated under the conditions and means described above. At this time, the gas velocity passing in the circumferential direction through the adsorbent layer 43a (43b) was "1.5 cm / sec".

In the second embodiment, the concentration of benzene in the gas discharged into the atmosphere from the discharge pipe 12 (see FIG. 1) is determined by using a commercially available portable HC concentration detection tube (isobutane conversion).
Was too small to detect.

In the first embodiment, the benzene concentration in the gas released into the atmosphere is 20 ppm or less, whereas in the second embodiment, as described above, a very small amount that cannot be detected and detected. It can be understood that this is superior to Example 1. In the second embodiment, “3”
It can be understood that a large amount of waste gas of "00 liter / minute (18 m ³ / hour)" can be effectively treated.

Example 3 In Example 3, the adsorption tower 1a (1b) used in FIG. 3 of Example 1 was diverted as it was.
Instead of the oxidation catalyst used in Example 1 and Example 2, it was filled with titanium oxide and subjected to a catalytic combustion experiment using high-temperature heated air. The reason is that, according to the known literature, a very small amount of hydrocarbons of less than a few ppm contained in dilute gaseous hydrocarbons can be converted to titanium oxide by a method in which the novel system and the system of the apparatus according to the present invention are different. This is because the silica gel is adsorbed on a hydrophobic silica gel carrying, and the adsorbent is oxidized and decomposed by irradiating the adsorbent with ultraviolet rays at room temperature to achieve zero emission. (See JP-A-11-138017)

In the hydrophobic silica gel impregnated in Example 3, the oxidation catalyst supported on the hydrophobic silica gel (Q-10) is titanium oxide. Similarly, the synthetic zeolite impregnated is made of a Y-type synthetic zeolite ( HUD-360), on which titanium oxide is supported. The experimental conditions were the same as those in Example 1 for comparison, but when the temperature of the combustion air was 250 ° C. or lower, the combustion was not sufficiently performed.
It was confirmed that the emission exceeded 0 ° C. and reached zero emission at around 400 ° C.

Example 4 In Example 4, as shown in FIG. 6 (longitudinal sectional view of the adsorption tower used in Example 4), the inside of the adsorption tower 6a (6b) The adsorbent layer 63a (63b) was arranged in the upper layer, the layer (hollow body filling layer) 65a (65b) in which the hollow layer of fine aluminum balls was filled in the middle layer, and the catalyst layer 66a (66b) in the lower layer. The adsorption tower 6a (6b) was used.
In FIG. 6, 62a (62b) indicates an outer cylinder, 64a (64b) indicates an inner cylinder, and 5 indicates cooling water. Then, combustion air (not shown) is supplied from the upper part of the adsorption tower 6a (6b), and the benzene adsorbed on the adsorbent layer 63a (63b) disposed on the upper layer is released by the purge effect. The benzene vapor is burned by passing through a catalyst layer 66a (66b) disposed at a lower portion, and benzene in the air to be diffused is reduced to zero emission.

The oxidation catalyst used in Example 4 was an ID type hydrophobic silica gel (trade name: manufactured by Fuji Silysia Chemical Ltd.)
Q-10) with palladium impregnated at 1% by weight.
It is spherical particles of 0 to 30 mesh, and the adsorbent used is a synthetic zeolite most suitable for benzene adsorption.
(Trade name: ZSM-5, manufactured by Tosoh Corporation) 9 to 10 mesh cylindrical particles. The aluminum hollow body has a diameter of about 2 mm which is commercially available. The reason for arranging such hollow aluminum fine particles in the middle layer is that it has excellent electrical conductivity and is provided as a safety measure to control excessive combustion rate (explosion) by tightly sealing between combustions. is there.

The experimental conditions were as described in Example 1 for comparison.
That is, as in Example 1, the waste gas containing about 5,000 ppm of benzene was used as the waste gas.
(L / min gas volume), and conducted in accordance with Example 1. It was confirmed that benzene was oxidized by the catalyst even at a relatively low temperature of combustion air of about 200 ° C., resulting in almost zero emission. did. Further, in order to lower the temperature of the combustion air, an experiment was conducted by adding a small amount of oxygen to the combustion air, and as a result, the emission was completely zero even at 120 ° C. At this time, a small amount of oxygen (supplied from the cylinder)
The experiment was carried out with the oxygen concentration in the combustion air maintained at about 40% by constantly adding the combustion air from above the hollow body filling layer 65a (65b) (see "← O ₂ " in FIG. 6). Was.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments 1 to 4,
Various embodiments are possible within the scope of the features of the present invention (items limiting the invention). For example, as the first and third embodiments, the double-cylindrical adsorption towers 1a and 1b shown in FIG. 3 were used. However, the present invention is not limited to such a double cylinder, and other examples are given. Alternatively, a double-cylinder or multi-cylinder type adsorption tower in which an adsorbent is filled in an inner cylinder and water for cooling the adsorbent layer is circulated outside the inner cylinder may be used. Further, although the multi-cylinder adsorption tower shown in FIGS. 4 and 5 was used as the second embodiment of the present invention, the present invention is not limited to such a multi-cylinder adsorption tower. It is also possible to use an adsorption device configured by filling a core in a shape and bundling the core, or an adsorption device configured by packing an adsorbent in a box and stacking it. Other requirements are not limited to the above-described first to fourth embodiments, and the features of the present invention described above (items limiting the invention).
Various embodiments are possible within the range described above.

[0091]

As described in detail above, the present invention provides a method for removing gaseous hydrocarbons adsorbed on an adsorbent layer in an adsorber without switching out the adsorbent when the adsorber is switched to desorption. In the presence of an oxidation catalyst or titanium oxide supported on, or in the presence of an oxidation catalyst and a non-combustible solid adsorbent,
It is characterized by combustion or oxidative decomposition using an oxygen-containing gas or a light source, thereby safely and easily and efficiently treating hydrocarbons from waste gas,
After the treatment, the concentration of the residual hydrocarbon in the gas released into the atmosphere can be reduced to 100 ppm or less, and the emission can be set to zero emission as an expected value.

Further, according to the present invention, high combustion efficiency can be obtained, and flameless combustion is performed.
Since the oxidation temperature is low and the temperature is not locally high, stable combustion can be obtained. In addition, there is no emission of air pollutants such as NOX normally contained in flue gas, and it is released into the atmosphere after processing. The concentration of gaseous hydrocarbons contained in the exhaust gas can be reduced to almost zero as well as 100 ppm or less.

Therefore, according to the present invention, in the removal treatment of gaseous hydrocarbons, which are air pollutants, the benzene concentration specified by the revision 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 it is also possible to sufficiently cope with the case where the numerical value is less than half as severe. Also, the present invention can be made portable so that the system can be integrated and mounted on a skid when the method according to the present invention is implemented as an apparatus.

[Brief description of the drawings]

FIG. 1 is a flow sheet diagram for explaining a “method for treating lean gaseous hydrocarbons in waste gas” which is one embodiment of 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 Example 1 of the present invention.

FIG. 4 is a longitudinal sectional view of an adsorption tower used in Embodiment 2 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 longitudinal sectional view of an adsorption tower used in Embodiment 4 of the present invention.

[Explanation of symbols]

 1a, 1b 6a, 6b Adsorption tower 2a, 2b 62a, 62b Outer cylinder 3a, 3b 63a, 63b Adsorbent layer 3-1a, 3-1b Hydrophobic silica gel impregnated 3-2a, 3-2b Y-type synthetic zeolite 4a, 4b 64a, 64b Inner cylinder 65a, 65b Hollow body filling layer 66a, 66b Catalyst layer 5 Cooling water 10 Waste gas generation source 11 Waste gas air pipe 12 Discharge pipe 13 Combustion air 15 Combustion gas air pipe 20 Control board 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) Adsorbed hydrophobic silica gel 43-2a ( 43-2b) Y-type synthetic zeolite

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 53/86 ZAB (72) Inventor Hirofumi Nochi 4-2-43-601 (72) Shiohama, Ichikawa-shi, Chiba ) Inventor Hideki Sakuma 27-5 Shinisogo-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 4D002 AA21 AA22 AA33 AA40 AB03 BA04 BA05 BA12 CA07 DA11 DA45 DA46 EA08 GA01 GA02 GA03 GB01 GB02 GB03 GB08 HA01 4D048 AA11 AA17 AB01 BA07X BA11X BA23Y BA30Y BA31X BB01 DA01 DA02 EA01

Claims (12)

[Claims] 1. An adsorber having an adsorbent layer which alternately performs adsorption and desorption is used. One of the adsorbers is made to pass waste gas containing gaseous hydrocarbons, and the adsorbent layer in the adsorber is passed through the adsorbent layer in the adsorber. Lean gas contained in waste gas comprising adsorbing gaseous hydrocarbons and releasing waste gas substantially free of gaseous hydrocarbons into the atmosphere while switching the other adsorber to desorption In the method for treating gaseous hydrocarbons, at the time of the switching, the gaseous hydrocarbons adsorbed on the adsorbent layer in the adsorber are not taken out of the system, and the presence of an oxidation catalyst or titanium oxide carried on the adsorbent. Below or in the coexistence of an oxidation catalyst and a non-combustible solid adsorbent, the use of an oxygen-containing gas or a light source to combust or oxidatively decompose dilute gaseous hydrocarbons contained in waste gas. Processing method. 2. The oxidation catalyst comprises at least one of platinum, palladium, vanadium, titanium and a transition metal, and the oxidation catalyst excited by light is titanium oxide. The non-combustible solid adsorbent layer coexisting with the above is hydrophobic silica gel and / or synthetic zeolite, and the combustion treatment temperature is 30 ° C.
The method for treating lean gaseous hydrocarbons contained in waste gas according to claim 1, wherein the temperature is 500 ° C. 3. A method for burning or oxidatively decomposing gaseous hydrocarbons adsorbed on the adsorbent layer in the adsorber, wherein the adsorbent layer is maintained at an atmospheric pressure or lower, or
3. The method for treating a lean gaseous hydrocarbon contained in waste gas according to claim 1, wherein the adsorbent layer or the catalyst layer is densely surrounded by fine particles of a metal having excellent electric conductivity. . 4. As means for burning or oxidatively decomposing gaseous hydrocarbons adsorbed on the adsorbent layer in the adsorbent layer,
The adsorbent layer that has adsorbed gaseous hydrocarbons is a closed system,
Oxygen-containing gas is circulated for combustion, and when the combustion is completed, the system is switched to a release system, air is introduced to cool the adsorbent layer, and then the process proceeds to adsorption treatment, or light irradiation is performed to oxidize and decompose. 4. The method for treating a lean gaseous hydrocarbon contained in waste gas according to claim 1, wherein the process is shifted to an adsorption treatment after the treatment. 5. A cascade-type enrichment adsorption tower (adapter) is provided as a means for increasing the hydrocarbon concentration in the adsorbent layer and burning or oxidatively decomposing the gaseous hydrocarbon in the purge exhaust gas. Hydrogen is accumulated in this and concentrated, and the concentrated adsorption tower is switched to a desorption tower for the purpose of combustion or oxidative decomposition, which is contained in the waste gas according to any one of claims 1 to 4. A method for treating lean gaseous hydrocarbons. 6. The adsorbent layer is a layer filled with a non-combustible solid adsorbent having a diameter of 0.1 to 2 mm carrying an oxidation catalyst, or a mixture of an oxidation catalyst and a non-combustible solid adsorbent. The waste gas according to any one of claims 1 to 5, comprising at least two layers of a packed layer or a layer filled with an oxidation catalyst and a layer filled with a nonflammable solid adsorbent. For treating lean gaseous hydrocarbons contained in water. 7. The method for treating a lean gaseous hydrocarbon contained in waste gas according to any one of claims 1 to 6, wherein a combustion or oxidative decomposition operation is performed before the adsorbent layer breaks through. A method for treating lean gaseous hydrocarbons contained in waste gas, characterized by switching. 8. As a means for switching before the adsorbent layer breaks through, a temperature detection port is provided at the top of the adsorbent layer, and a point in time at which the temperature from the temperature detection port stops its rise is stopped. 8. The method for treating a lean gaseous hydrocarbon contained in waste gas according to claim 7, wherein the valve is automatically switched. 9. As means for switching before the adsorbent layer breaks through, the “gas flow rate at the inlet”, the “hydrocarbon concentration in the inlet gas”, and the “desired gas in the outlet gas” of the adsorption device obtained during the adsorption operation. Of the hydrocarbon concentration (assumed value) as numerical data into a personal computer provided in the control panel, and burned in the ROM of the personal computer.
The method according to claim 7, wherein the switching time is automatically set in conjunction with an application model. 9. 10. The disposal according to claim 1, wherein the concentration of hydrocarbons in the clean gas discharged from the adsorption device to the atmosphere is 100 ppm or less, and the expected value is zero emission. A method for treating a lean gaseous hydrocarbon contained in a gas. 11. An apparatus for carrying out the treatment method according to claim 1, wherein an “adsorption apparatus having an adsorbent layer” in the apparatus surrounds the adsorbent layer. ,
And a lean gaseous hydrocarbon contained in the waste gas, characterized by comprising an adsorber in which components capable of aerating the waste gas laterally from the outer cylinder of the adsorbent layer toward the adsorbent layer are multiplexed. Processing equipment. 12. The waste gas according to claim 11, wherein the component is a box-shaped component, a cylindrical-shaped component or a honeycomb-shaped component, and the component is an adsorption device in which the components are multiplexed. Equipment for the treatment of lean gaseous hydrocarbons contained.