JP2002200410A - Method for isolating and recovering inert gas, and device for performing the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for performing the method in which an inert gas is isolated and recovered from the inert gas containing an impure gas and a contaminated gas by applying an adsorption method and the inert gas is reused as a high purity one. SOLUTION: As indicated in Fig. 3, a contaminated nitrogen discharged continuously from a reaction tank 31 in which chemical reaction is performed under the presence of gaseous nitrogen is introduced to an adsorption tower 37A and returned to the reaction tank 31 as a high purity nitrogen and reused in circulation. A purge air is introduced from D-1 to the adsorption tower 37A after switching to desorption and sent to a separation vessel via D-2 and subjected to gas-liquid separation, then a liquefied gaseous contaminated component is taken out from D-4 to the outside of system, and uncondensed gas is discharged from D-3 and disposed as waste gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for isolating and recovering an inert gas from an inert gas containing an impurity gas or a pollutant gas, and an apparatus for performing the method. Impurity gas or contamination unavoidably mixed in the above manufacturing process for the purpose of recycling high-purity inert gas such as nitrogen, chlorofluorocarbons and paraffin hydrocarbons widely used in factories and semiconductor manufacturing factories. The present invention relates to a method and an apparatus for efficiently separating gases, such as olefin hydrocarbons, aromatic hydrocarbons, and diene polymer substances, from inert gas, and reusing the inert gas.

[0002] Specifically, the present invention relates to an impurity gas or a contaminant gas accompanying a reaction in the presence of an inert gas.
(Impurity gas or pollutant gas such as volatile reactant or unreacted raw material or reaction product), for example, benzene, toluene, methyl ethyl ketone, trichloroethylene,
The present invention relates to a purification process of an inert gas containing a volatile impurity gas or a pollutant gas such as octadiene or hexene, and a component concentration of the impurity gas or the pollutant gas accompanying the inert gas is 100 ppm or less, preferably 10 ppm or less. And then
In other words, the present invention relates to a method and an apparatus for reusing the inert gas with the purity of the inert gas being desirably 99% or more.

[0003]

2. Description of the Related Art There are said to be 20,000 kinds of chemical products currently used in Japan, and most of them are manufactured in chemical factories, petrochemical factories, pharmaceutical factories and the like. That is,
Basic chemicals such as aromatics, aliphatics, heterocyclics,
Organic halogen-based basic organic chemicals are used as raw materials, and they are reacted under a catalyst to obtain a target product. In the reaction step at this time, the reaction often proceeds in the presence of an inert gas such as nitrogen, carbon dioxide, carbon monoxide, or paraffin-based gas. And after this reaction, the used inert gas is contaminated with the reaction product and cannot be reused,
Currently, it is currently disposed of as it is. Also, in a semiconductor manufacturing plant or the like, many etching agents used for etching are composed of gas components which are difficult to dispose similarly to the above.

On the other hand, if the polluted inert gas is released into the atmosphere as it is, benzene, toluene, methylene chloride, methyl ethyl ketone, trichloroethylene, which are one of the main pollutants of air pollution as impurity gas or pollutant gas.
The entrainment of harmful gases such as chlorofluorocarbons would violate legal regulations on emission levels. For this reason,
At present, each of the above-mentioned factories has difficulty in handling the inert gas after the reaction.

Conventionally, as a method of treating an inert gas after completion of the reaction, the inert gas is washed with water or an acid or alkali, and then washed with a high boiling point sponge oil (for example, heavy oil). Was returned to a clean state and reused, or mixed gas such as impurity gas was separated by adsorption method using activated carbon, and as a method for regenerating activated carbon, it was treated by a general method using steam. . Activated carbon cannot be used as a mixed impurity gas or pollutant gas if it contains a polymerizable gas component such as a diene.In this case, the emission regulation value stipulated by the regulations of each local government is passed. It was diluted in the air to disperse it as it was, although it was a palliative measure.

However, in the case of using steam for washing with water, washing with acid or alkali, or washing with heavy oil, and also for regenerating activated carbon, wastewater treatment equipment is indispensable. Even when activated sludge treatment is performed, the BOD value passes the drainage standard, but a large amount of aeration is required because the COD value does not decrease. In this case, the impurity gas or the contaminant gas released into the drainage and mixed into the water is re-emitted into the atmosphere together with the aeration. Although this concentration depends on the amount of aeration, it is usually relatively thin, less than 100 ppm, and satisfies the "emission concentration regulation value of 250 ppm or less (in the case of Tokyo)" defined by the conventional local government. Did not occur.

However, in April 2002 (April 2002)
The “PRTR Law”, which is stipulated to be implemented after March, 2009, is a law on the improvement of management and control of emissions of specific chemical substances into the environment, the so-called “PRTR Law”. In addition, this is a total emission control for the entire factory, and as described above, it becomes impossible to discharge a large amount of air during aeration. In light of this situation,
The inventors of the present invention did not disclose the impurity gas or polluted gas mixed in the inert gas into the atmosphere, not from the viewpoint of preventing pollution, but rather from the viewpoint of separation, recovery, and reuse of the target inert gas. From the point of view of the present invention.

The source of the inert gas that needs to be reused is a chemical reaction tank performed in a batch system or a contact reaction tank performed in a continuous system, or nitrogen in order to increase product purity. There are a wide variety of processes, such as a process of cleaning and removing contaminants with a gas, and a treatment of an inert gas leaking from a chemical storage tank requiring a seal.

As a method for isolating an inert gas for the above-mentioned purpose, techniques such as cryogenic separation, distillation, absorption and the like have been conventionally used. Regarding the adsorption separation method, known methods widely used in this field include (1) gas separation membrane method + adsorption method, and (2) adsorption method using activated carbon, zeolite, hydrophobic silica gel, or the like. For example, Japanese Patent Publication No. Hei 4-23568,
No. 84623, JP-A-57-14687, JP-A-57-42319
Japanese Patent Publication No. JP-B-59-50715, JP-B-59-50716, JP-B-2-46630, etc., have no number.

[0010] Such an adsorption method includes a conventional means for switching between adsorption and desorption, and is not particularly novel, but it cannot be said that the conventionally known adsorption method has always achieved the purpose of isolation. In the case of using activated carbon, which is a combustible solid adsorbent, for example, if the mixed "impurity gas or pollutant gas (contaminant component)" is a diene, olefin, etc., a large number of active carbons present in the activated carbon Inspired by spots, such compounds readily polymerize, and the heat of polymerization poses the problem of risk of ignition and explosion.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above problems, and its object (problem) is to first apply an adsorption method to “impurity gas or Inert gas is isolated and recovered from "inert gas containing pollutant gas" and reused as "high-purity inert gas". "A method for isolating and recovering an inert gas from an inert gas containing an impurity gas or a pollutant gas, and an apparatus for performing the method" for efficiently separating the "impurity gas or the pollutant gas". It is in.

[0012]

According to the present invention, there is provided a method for isolating and recovering an inert gas according to the present invention.
(Technical configuration) As a technical configuration to achieve the above, using "adsorption device having an adsorbent layer that alternately performs adsorption and desorption", using pre-coated synthetic zeolite and / or hydrophobic silica gel as this adsorbent layer, The "impurity gas or pollutant gas mixed with inert gas" is passed through the adsorbent layer to adsorb the "impurity gas or pollutant gas", and the inert gas substantially free from the impurity gas or pollutant gas is removed. Isolate and recover ".

That is, the method for isolating and recovering an inert gas according to the present invention comprises the following steps: an "adsorber having an adsorbent layer" for alternately adsorbing and desorbing is used, and one of the adsorbing apparatuses is provided with an impurity gas or contamination An inert gas containing a mixture of gases is allowed to pass therethrough, and the adsorbent layer in the adsorption device adsorbs the impurity gas or the contaminant gas. A method for isolating an inert gas comprising switching the other adsorber to desorption during that time, wherein the adsorbent layer is pre-coated with the impure or contaminated gas and / or a synthetic zeolite and / or A layer filled with a nonflammable solid sorbent made of hydrophobic silica gel,
At the time of desorption, a vacuum pump and a purge gas are used in combination, the switching time between suction and desorption is set to 1 to 30 minutes, and the purge exhaust gas of the vacuum pump is cooled to liquefy the impurity gas and take it out of the system. , Is characterized.

Further, the method for isolating and recovering an inert gas according to the present invention includes the following steps: (a) an inert gas containing an impurity gas or a contaminated gas to be introduced into the adsorption device is previously converted into an absorbing solution or a cleaning solution; After the treatment, an adsorption treatment is performed (Claim 2). An adsorption treatment is performed under a pressurized state of an “inert gas containing an impurity gas or a contaminated gas” introduced into the adsorption device (Claim 2). Item 3) The purge gas introduced into the adsorption device is dehumidified dry air and / or nitrogen (Claim 4). The uncondensed gas when the purge exhaust gas is cooled is removed by the adsorption device. (Claim 5).

[0015] On the other hand, the device according to the present invention comprises the above-mentioned claim
An apparatus for carrying out a method for isolating and recovering an inert gas according to any one of claims 1 to 5, wherein the adsorbent layer in the adsorption device has a plurality of independent adsorbent layers having different adsorption characteristics. Separated or separated into a plurality of independent adsorbent layers, and the plurality of independent adsorbent layers are superposed and coordinated (claims 6 and 7); Wherein the exhaust pipes are buried between the independent adsorbent layers and connected to a vacuum pump. (Claim 8) The adsorbent layer in the adsorption device comprises a single adsorbent layer ,
A plurality of exhaust conduits are embedded in the adsorbent layer, and the conduits are connected to a vacuum pump (claim 9).

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail including embodiments of the present invention. (In the following description, the “inert gas containing an impurity gas or a contaminant gas” which is a target of the present invention may be simply referred to as an “impurity gas-containing inert gas”.)

In the conventional "adsorption method using activated carbon", as described above, when the mixed "impurity gas or pollutant gas (contaminant component)" is a diene, olefin or the like, a large number of activated carbons present in the activated carbon are present. Inspired by the spots, such compounds readily polymerize, and the heat of polymerization poses a risk of ignition and explosion.

In order to solve the above problem, the present inventors have used a non-combustible solid adsorbent, specifically a synthetic zeolite and / or hydrophobic silica gel, instead of activated carbon, It has been found that by closing the active sites present in the macropores using a pre-coating means in advance, the above-mentioned risk associated with isolation can be avoided. As a result, adsorption and desorption rely only on mass transfer within the pores of the macropores and mesopores of the adsorbent.
Inevitably, the switching time between suction and desorption is shortened. However, for this time, for example, when a chemical reaction is carried out in a reaction vessel by filling an inert gas, the time required for the reaction is predetermined and the switching time follows.
For this reason, if this time is extended with a margin, an enormous amount of adsorbent is required. Therefore, the present inventors have limited this time to 1 to 30 minutes from economic considerations.

In the operation for switching between suction and desorption,
At the time of adsorption, it is extremely preferable that the impurity gas-containing inert gas introduced into the adsorption device is kept in a pressurized state, and at the time of desorption, it is also preferable to heat the purge gas and / or the adsorption tower (desorption tower). That is. Further, it is preferable to use air and / or nitrogen as a purge gas, and purge gas (air and / or nitrogen) at the time of desorption.
Is preferably dehumidified. The advantage of dehumidifying the purge gas is that the load on the vacuum pump used for regeneration is reduced, and the capillary condensation of water that enters the adsorbent layer during desorption is prevented. Further, it is also a preferred embodiment of the present invention to return the uncondensed gas when the purged exhaust gas is cooled to the inlet of the adsorption device. Alternatively, adsorption treatment after treatment with a cleaning liquid or after pressurization is also a preferred embodiment of the present invention.

It is also known to use a purge gas in combination with a vacuum pump at the time of desorption. However, the present inventors have found that the adsorbent layer in the adsorption device described above has a different (a) adsorption characteristic. To a structure that is coordinated separately to a plurality of independent adsorbent layers, or (b) separated into a plurality of independent adsorbent layers having different adsorption characteristics, and the plurality of independent adsorbent layers Having a structure in which the adsorbent layers are superposed and coordinated, and / or
By providing a plurality of exhaust ports in the adsorbent layer in the adsorption device and connecting the exhaust ports to a vacuum pump, a remarkable desorption effect not found by the conventional method was successfully obtained.

By the way, solid adsorbents such as activated carbon, synthetic zeolite, and silica gel used as adsorbents are originally also used as heat insulators. Therefore, when these adsorbents are used in a packed state, they may be about 4 inches to 5 inches (about 1 inch) depending on the particle size and temperature.
With a thickness of 0 cm to 15 cm), it is difficult to transfer heat to its outer layer. In other words, 10cm ~ 15
Within a thickness of cm, heat is transmitted.

Therefore, for example, even if hot air at about 100 ° C. is used as a purge gas at the time of desorption, if the adsorbent layer is formed as a single layer having a height of 50 cm or more, it is supplied from the hot air. The heat is dissipated to the atmosphere through a metal jacket surrounding the adsorbent layer, and hardly contributes to promoting desorption. In addition, the rate of desorption of the impurity gas or contaminant gas adsorbed on the adsorbent layer is reduced in proportion to the thickness of the layer, which may result in an increase in the capacity of the vacuum pump. That is, the present inventors have previously proposed a method in which three adsorption towers are used to reduce the pressure in one tower, and the other tower is divided into adsorption and purging. Although a remarkable effect can be obtained in increasing the concentration of, this is not always economically advantageous. From the viewpoint of absorption and desorption, the decompression step can be said to be useless time.

By the way, according to the present inventors' operating experience with actual equipment, the diffusion speed of the individual adsorbent in the adsorbent layer in the pores is extremely smaller than the exhaust speed of the vacuum pump. Do you get it. The diffusion rate can be easily estimated from the theoretical calculation result of the adsorption model. Therefore, it is more effective to take the amount of purge air and the time required for purging sufficiently than to use a vacuum pump in order to perform the desorption well. As a result, the desorption effect is improved, and the purity of the inert gas recovered from the outlet of the adsorption tower is improved.

However, if the purging is performed sufficiently, the "purity of the target inert gas" recovered from the adsorption tower,
That is, instead of increasing the degree of purification, the concentration of the impurity gas or the contaminant gas in the purge exhaust gas decreases. Since the present invention aims to improve the purity of the inert gas so that the inert gas can be reused, the purge exhaust gas containing the impure gas dilutely may be directly emitted into the atmosphere and discarded. Conflicts with national legal regulations. For this reason, it is desirable to enrich the impurity gas in the purge exhaust gas and to liquefy and remove the impurity gas for easy handling. For this purpose, instead of relying solely on the purge air, the individual adsorbents are finely divided. Means for increasing the diffusion speed in the pores will be required. A number of known methods have been proposed for this adsorption / desorption operation, but novel means for improving the diffusion rate of the individual adsorbents in the pores include:
Not found so far.

Conventionally, a large amount of purge air is used,
Heat desorption using a large amount of steam has been a common practice. Therefore, as described above, in order to simultaneously satisfy the conflicting objectives, the present inventors have made the adsorbent layer in the adsorption tower into a plurality of adsorbent layers, preferably an independent adsorbent layer having a thickness within 20 cm. Using adsorption towers with separate and coordinated structures, providing conduits that can supply hot air from outside independently to each adsorbent layer, and desorbing gas from each adsorbent layer into vacuum The connection was made by a conduit leading to the suction hole of the pump.

With the above configuration, a remarkable desorption effect, which cannot be achieved by the prior art, has been successfully obtained. That is, in the prior art, the desorption is based on "the expensive and high-performance vacuum pump is used and the purge gas is simply supplementarily used", whereas in the present invention, the "expensive and high-performance vacuum pump is used" And the purge gas is mainly used. "

It should be noted that even if the above-mentioned plurality of adsorbent layers are of a cartridge type that can be taken out from each, it does not depart from the object of the present invention. In addition, as described above, without separating into separate adsorbent layers, a plurality of conduits interlocked with a vacuum pump were provided at respective positions from the upper part to the lower part of the single adsorbent layer, and the adsorption was performed via this conduit. A structure for sucking impure gas is another aspect of the present invention.

Further, as described above, the smaller the individual adsorbent particles, the larger the adsorbent surface area per unit volume, and the diffusion rate in the pores is inversely proportional to the square of the particle size. The rise can be easily analogized in theory, but on the other hand, there is a downside that the pressure loss of the adsorbent layer increases in inverse proportion to the square of the adsorbent diameter. Some ingenuity will be needed. That is, in order to improve the target inert gas to “reusable purity”, the desorbed impurity gas or contaminated gas is completely separated from the desorption tower within a predetermined time and the next step is performed. The method of preparing for the adsorption operation is unique, and the treatment of the desorbed gas must be considered secondarily.

Therefore, any of the above-mentioned means can be used for the combustion treatment as it is, without recovering the impurity gas or the polluted gas in the purge exhaust gas. It is desirable to take out the liquid in a state where it can be carried out. For that purpose, a method of cooling to a temperature close to the dew point and returning the uncondensed purge exhaust gas to the inlet of the adsorption tower and recirculating it, or pressurizing the purge exhaust gas to increase the dew point, is often used alone. Although it is a known method, a further effect can be exhibited by combining it with the method intended by the present invention. In particular, 0.
It is the most desirable embodiment to use a fine adsorbent of about 5 to 1.5 mm in combination.

The embodiment of the present invention will be described below. The adsorbent used in the present invention is a noncombustible solid adsorbent, and is a synthetic zeolite and / or hydrophobic silica gel. In a pre-coated state, each adsorbent is used in multiple layers. As the pre-coating agent, it is preferable to use the same kind of component gas as the impurity gas or the contaminant gas in the "inert gas containing the impure gas or the contaminant gas" which is the gas to be treated.

As a preferred embodiment of the above-mentioned "noncombustible solid adsorbent" used in the present invention, in particular, "nitrogen (N ₂ )
For the purpose of "isolation", the hydrocarbon to be removed is
In the case of low boiling points such as methane, ethylene and propylene, and in the case of high boiling points such as pentane, hexene and benzene,
It is necessary to use different adsorbents stacked in multiple layers. As a specific example, A type hydrophobic silica gel is used for removing low boiling hydrocarbons, and B type is used for removing high boiling hydrocarbons.
A type of hydrophobic silica gel is used. Then, at the top, a Y-type synthetic zeolite having a high silica ratio or a synthetic zeolite having a high alumina ratio (trade name of Toso Co., Ltd .: zeolam) is coordinated. The reason is that the pore diameter of A-type hydrophobic silica gel is 30 °, and the pore diameter of B-type hydrophobic silica gel is 60 °. In the case where is low, it is based on the fact that A-type hydrophobic silica gel (30 °) has a larger adsorption amount. The reason that it is preferable to coordinate a synthetic zeolite (zeolam) with a high alumina ratio at the top is that zeolam is hydrophilic, but selectively adsorbs methane and ethylene if water is not present. This is due to the nature of The reason why the purge gas is dehumidified is to take into consideration the property that it dislikes moisture.

In the present invention, the adsorption / desorption operation is not for exhausting gaseous hydrocarbons in the air, which are conventionally widely used, to a level below the legally regulated value, but obtains a single component with high purity. This is a unit operation similar to the distillation operation or absorption operation used for the purpose. However, basically, if each technique is individually taken up, it belongs to a known technique. Here, a specific example of an apparatus for performing the method is shown in FIG. 1 (1 of the apparatus according to the present invention). FIG. 2 (adsorption tower showing another example of the apparatus according to the present invention)
The present invention will be described in detail with reference to FIGS.

An adsorption tower 10 showing one example of the apparatus according to the present invention.
As shown in FIG. 1, the adsorbent layers 11a and 11
b and 11c are divided and coordinated, and each adsorbent layer 11
The exhaust conduits 12a,
12b and 12c are provided, and the exhaust pipes 12a, 12b and 12c are connected to a vacuum pump 13. In FIG. 1, 14
Reference numerals a, 14b, and 14c denote purge air conduits. Also,
A-1 is a line of an inert gas containing an impurity gas, A-2 is a line of an isolated inert gas, B-1 is a line of a purge gas, and B-2 is a line of a purge exhaust gas. Line ".

An adsorption tower 20 showing another example of the apparatus according to the present invention.
As shown in FIG. 2A, the adsorbent layer 21 is composed of a single adsorbent layer, and the exhaust pipes 22a, 22b,
22c is embedded and connected to the vacuum pump 23.
2 (A) comprises a ring 24 having a hole 25 as shown in FIG. 2 (B). FIG. 2 (A)
A-1, A-2, B-1, and B-2 in FIG. 1 are the same as those in FIG.

Hereinafter, the present invention will be described in detail with reference to FIG. 1. An inert gas intended for reuse, for example, nitrogen gas sealed in a reaction tank in an organic synthesis plant in a chemical plant is contaminated with impurities. Then, in order to regenerate the nitrogen gas, the gas is introduced into the adsorption tower 10 from A-1 (inert gas line including the impure gas) of FIG. 1 connected to the reaction tank. Although not shown in FIG. 1, a desorption tower is provided separately from the adsorption tower 10, and each of them is alternately switched at a cycle of about 5 minutes.

In the interior of the adsorption tower 10, adsorbent layers are independently formed.
a, 11b and 11c are arranged in three stages. There is no particular limitation on the height of each step, but it is preferable that
A range of １５15 cm is preferred. The reason for this is that, as described above, the height range of each step is "the length of the range in which heat can be transferred to the outer layer of the adsorbent". The spatial distance separating the adsorbent layers 11a, 11b, 11c is not particularly limited, but is preferably as wide as possible. The reason is that the gas flow passing through the adsorbent layer is sufficiently diffused so as not to be biased to one side.

In the space, exhaust pipes 12a, 12b, and 12c directly connected to a vacuum pump 13 for desorbing contaminant gas contained in nitrogen gas are provided. It is desirable that a plurality of the exhaust conduits 12a, 12b, 12c be provided. When the vacuum pump 13 operates, the automatic valves (not shown) of the exhaust conduits 12a, 12b, and 12c are opened, and are closed during adsorption. Similarly, purge air is also supplied to the purge air conduit 14.
The adsorbent layers 11a, 11b, and 11c are individually obtained from a, 14b, and 14c.
Is introduced into the adsorption tower 10 downward from above. As the purge air, heated air is more desirable.

A-1 (inert gas line including impure gas)
The nitrogen gas introduced from the column is removed from the nitrogen gas by the impurity gas such as cyclohexene and benzene being adsorbed by the adsorbent in the adsorption tower 10, and the clean nitrogen gas is
From exit 10 without exposure to air,
-2 (isolated inert gas line) and returned into the reaction vessel (not shown), and the regeneration cycle is repeated.

On the other hand, the adsorption tower 10 after being switched to desorption
The lower and upper automatic valves (not shown) are closed, and the desorption operation is started from a closed state. That is, for the first few minutes, the automatic valve (not shown) of the suction port of the vacuum pump 13 is opened, and the operation of only the vacuum pump 13 is started without using purge air. A few minutes later, after the degree of vacuum of the vacuum pump 13 has decreased to a predetermined pressure, B-1 (purge gas line)
The automatic air valve (not shown) is opened, and purge air is introduced into the adsorption tower 10 in an auxiliary manner.

The switching is performed by using a time control method. The vacuum pump 13 and the purge air are stopped one to two minutes before the desorption is completed, and then the pressure equalizing operation for returning the desorption tower 10 to the atmospheric pressure is performed. Perform for 1 minute to prepare for the next adsorption operation.

Next, the present invention will be described in detail with reference to FIGS. 2A and 2B. This figure shows an example in which an existing adsorption tower is applied to the method intended in the present invention. That is, a ring 24 having a large number of holes 25 shown in FIG. 2B is embedded in an existing adsorption tower 20 (an adsorption tower 20 having a single adsorbent layer 21), and this ring 24 is connected to an exhaust pipe. This embodiment shows an embodiment in which the adsorption tower 20 is connected to a vacuum pump 23 via 22a, 22b, and 22c, respectively.

As described in detail above, the present invention uses an adsorption / desorption operation as a means for reusing an inert gas, and is not intended to recover an impure gas. Therefore, if a large amount of purge air is used to increase the purity of nitrogen gas, a load is applied to the vacuum pump and the pump becomes large in capacity. Novel inert gas isolation method, including economical effect of achieving a desired purpose with a vacuum pump having as small a capacity as possible by increasing the diffusion rate in the gas, and an apparatus for performing the method Is provided.

[0043]

Next, the present invention will be described in detail with reference to examples of the present invention. However, the present invention is not limited only to Examples 1 to 3 below.

<Embodiment 1> FIG. 3 is a schematic flow sheet diagram of a nitrogen gas recovery system according to an embodiment of the present invention. This flow sheet is used for operating a large commercial plant based on the present invention. It is related to. The purpose of the first embodiment is to “contaminated nitrogen” continuously discharged from a reaction tank that performs a chemical reaction in the presence of nitrogen gas (inert gas).
Is taken out of the system and reused again.

FIG. 3 shows a process in which benzene, butadiene, and styrene are used as raw materials and are reacted under high pressure to obtain a desired reaction product. C-1 (impurity gas-containing nitrogen gas line) ", the contaminated nitrogen discharged at a high temperature during the production was cooled by a cooler 32 in advance, and then 3.5 kg by a circulating compressor 33. / Cm ² (gauge pressure). The purity of the contaminated nitrogen is about 97%, and the impurities (including unreacted raw material components) contained therein are benzene, butadiene, cyclohexane, toluene, 4-vinylcyclohexane, cyclooctadiene and the like.

The contaminated nitrogen compressed by the circulating compressor 33 passes through a water separator 34 and is cooled by a cooler 35 to condense and remove most of the contained saturated water. The contaminated nitrogen from which water has been removed under high pressure filters the contained dust and mist by passing through a filter (filter cloth) 36, and then leads to the adsorption tower 37A (37B).

In the adsorption tower 37A (37B), the adsorbent layer shown in FIG.
Exhaust conduits are respectively arranged in the lower space of each adsorbent layer,
An adsorber having a structure in which the exhaust pipe was connected to a vacuum pump was used. The thickness of each adsorbent layer was set to 15 cm. The adsorbent filled in the adsorbent layers was Fuji Silysia Chemical. "Q-6" (trade name: hydrophobic silica gel) manufactured by the Company was prepared by grinding to about 1.0 mm, and a product precoated with a contaminant component (benzene) in contaminated nitrogen was used.

In the first embodiment, the adsorption tower has two towers operated alternately (see 37A and 37B in FIG. 3), and the adsorption and desorption are alternately performed by a solenoid valve (not shown). Switch. The switching time is 10 minutes, and the adsorption tower 37A
When the adsorption of the adsorption tower 37A is completed, the electromagnetic valve of the inlet gas pipe of the adsorption tower 37A is automatically turned "OFF".
Switch to B and continue the suction operation.

The high-purity nitrogen released from the adsorption tower 37A (37B) at the time of adsorption is finally purified by a filter (activated carbon) 38 and then passed through C-2 (high-purity nitrogen gas line) to the reaction tank 31.
, And reuse by circulation.

On the other hand, the adsorption tower 37A after the switching is connected to a solenoid valve (not shown) of a pipe (not shown) connected to the vacuum pump 39.
Is turned "ON" to operate the vacuum pump 39. Five minutes after operating the vacuum pump 39, purge air is introduced from D-1 (purge air line). The exhaust gas from the vacuum pump 39 is introduced into the condenser 40 via D-2 (purge exhaust air line). This condenser 40
And then gas-liquid is separated by the separator 41, and the liquefied impurity gas or contaminated gas is taken out of the system by the pump 42 [D-4
(Recovered liquid line)], the uncondensed gas is disposed (processed) from D-3 (uncondensed gas line) as waste gas. The uncondensed gas may be returned to the inlet of the adsorption tower 37A (37B) based on a known method.

Table 1 below summarizes operating conditions and operating results obtained based on the above-described operating method in a table for easy understanding. In addition, benzene (BZ) is used as an impurity gas or a pollutant gas (including a raw material component gas) contained in the polluted nitrogen.
And the concentrations of cyclohexane (C-HX) were measured.

[0052]

[Table 1]

As can be seen from Table 1, at 13:45 (measurement time), three days after the start of operation, the impurity gas or contaminated gas in the high-purity nitrogen to be recovered was released as gas released from the adsorption tower. “174.20 ppm (155.00 ppm + 19.20 ppm)”, and the purity of the obtained high-purity nitrogen was “99.9% or more”. Although not described in Table 1, the result of continuous operation after that is that the component ratio of the impurity gas or the contaminant gas eventually becomes “10 ppm or less”, which is a result that is more than expected by the present invention. It was confirmed that was obtained.

<Embodiment 2> In this embodiment 2, in order to improve the purity of the product obtained from the reaction layer in the petrochemical plant, the recovery of the contaminated nitrogen after bubbling or aeration with nitrogen is performed. Aim. In particular, the difference from the first embodiment is that the gas to be treated is contaminated nitrogen containing a large amount of low-boiling hydrocarbons such as propane and propylene. That is, the composition of this gas (contaminated nitrogen) is as follows. N ₂ (nitrogen) 88.4% C ₃ (propane) 1.4% C ₃ (propylene) 5.5% C ₄ (butane) 0.4% C ₅ (pentane) 0.1% C ₆ or higher (hexene Etc.) 1.7% H ₂ O (water) 2.5%

In the second embodiment, the processing gas amount is 1000 m
^{At 3} / hr, the target nitrogen purity was 99% or more. For the adsorbent layer used for this purpose, an adsorbent layer of about 1000 kg of A-type hydrophobic silica gel and an adsorbent layer of about 500 kg of Y-type synthetic zeolite were laminated thereon. Each of them is a pre-coated agent (pre-coating agent: mainly pentane). The capacity of the vacuum pump used is 30
The operation was performed at m ³ / min (at 25 torr) and the switching time between absorption and desorption was 5 minutes. The dew point of the purge gas is -35C.

The result of operating under the above conditions is that the purity of the obtained recovered nitrogen is 99.9%, and the adsorbent to be used is selectively used in multiple layers (or multiple stages) as in Example 2. The present inventors succeeded in efficiently removing a wide range of hydrocarbons from low boiling point to high boiling point from contaminated nitrogen gas to obtain recyclable pure nitrogen.

<Example 3> In Example 3, an experiment was conducted for the purpose of purifying impure nitrogen gas containing ethylene and hexene to obtain pure nitrogen by using a bench-scale experimental device. The adsorption tower (desorption tower) has a diameter of 20 cm and a height of 7 cm.
0 cm. As the adsorbent layer, a synthetic zeolite having a high alumina ratio (trade name: Zeolam F, manufactured by Toso Co.)
9) 3 kg, under which 3 kg of A-type hydrophobic silica gel (trade name: Carrierct Q-3 manufactured by Fuji Silysia Chemical Co., Ltd.) Q-6) 7 kg each was filled to form a multilayer structure. The composition of the contaminated nitrogen to be treated is as follows. N ₂ (nitrogen) 91.2% C ₂ (ethylene) 0.5% C ₆ (hexene) 7.5% H ₂ O (moisture) 0.8%

The experimental conditions were as follows: After confirming that the pre-coating of the adsorbent was completed (pre-coating agent: mainly hexene), 50 L of the above gas (contaminated nitrogen) was introduced into the adsorption tower.
/ Min, and switched to the desorption tower after 5 minutes. That is, the switching time between the suction and the desorption was set to 5 minutes. The suction pressure of the desorption tower was 20 torr, and the amount of purge gas was 2 L /
Minutes.

As a result of operating under the above conditions, the purity of the obtained recovered nitrogen was 99.8%, the ethylene removal rate was about 80%, and the hexene removal rate was 100%. In this experiment, it was found that even if the impurities contained in the contaminated nitrogen contained hydrocarbons having a very low boiling point, recyclable pure nitrogen could be obtained.

[0060]

According to the present invention, as described in detail above, the "inert gas containing an impure gas or a pollutant gas" is obtained by applying the adsorption method.
"High purity inert gas" by isolating and recovering inert gas from
As a result, a remarkable effect of efficiently reusing can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an adsorption tower showing one example of an apparatus according to the present invention.

FIG. 2 is an adsorption tower showing another example of the apparatus according to the present invention, wherein (A) is a sectional view of the adsorption tower, and (B) is an enlarged plan view of a portion C of (A). It is.

FIG. 3 is a "schematic flow sheet diagram of a nitrogen gas recovery system" showing one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Adsorption tower 11a, 11b, 11c Adsorbent layer 12a, 12b, 12c Exhaust conduit 13 Vacuum pump 14a, 14b, 14c Purge air conduit 20 Adsorption tower 21 Adsorbent layer 22a, 22b, 22c Exhaust conduit 23 Vacuum pump 24 Ring 25 Hole A-1 Line of inert gas containing impurity gas A-2 Line of isolated inert gas B-1 Line of purge gas B-2 Line of purge exhaust gas 31 Reaction tank 32 Cooler 33 Circulating compressor 34 Water separation Container 35 Cooler 36 Filter (filter cloth) 37A, 37B Adsorption tower 38 Filter (activated carbon) 39 Vacuum pump 40 Condenser 41 Separator 42 Pump C-1 Impure gas-containing nitrogen gas line C-2 High-purity nitrogen gas line D-1 Purging Air line D-2 Purge exhaust air line D-3 Uncondensed gas line D-4 Recovered liquid line

Continuation of the front page (72) Inventor Hiroshi Nochi 4-2-43-601, Shiohama, Ichikawa-shi, Chiba Prefecture (72) Hideki Sakuma 4-6-29 Namamugi, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Terms (reference) 4D012 CA11 CA20 CB16 CD07 CE03 CF01 CG01 CH04 CH06 CJ02 4D020 AA08 4G066 AA22B AA61B BA24 CA04 CA32 CA33 CA51 DA01 DA05 GA06 GA14

Claims (9)

[Claims] 1. Use of an "adsorption device having an adsorbent layer" for alternately performing adsorption and desorption, and allowing one of the adsorption devices to pass an inert gas containing a mixture of an impurity gas or a pollutant gas. To adsorb the impurity gas or the contaminant gas to the adsorbent layer, collect the inert gas substantially free of the impurity gas or the contaminant gas at the outlet of the adsorber, and switch the other adsorber to desorption during that time A method for isolating and recovering an inert gas comprising: adsorbent layer filled with a noncombustible solid adsorbent made of synthetic zeolite and / or hydrophobic silica gel precoated with said impure gas or contaminant gas. A vacuum pump and a purge gas are used at the time of desorption, and the switching time between suction and desorption is set to 1 to 30 minutes. How to recover isolated inert gas, characterized in that issue Ri. 2. The method according to claim 1, wherein an inert gas mixed with an impurity gas or a pollutant gas introduced into the adsorption device is treated with an absorbing liquid or a cleaning liquid in advance, and then subjected to an adsorption treatment. A method for isolating and recovering the above-mentioned inert gas. 3. The adsorption process according to claim 1, wherein an inert gas mixed with an impurity gas or a contaminant gas introduced into the adsorption device is subjected to an adsorption treatment in a pressurized state. A method for isolating and recovering an inert gas. 4. A purge gas introduced into the adsorption device,
The method for isolating and recovering an inert gas according to any one of claims 1 to 3, which is dehumidified dry air and / or nitrogen. 5. An inert gas according to claim 1, wherein uncondensed gas produced when the purged exhaust gas is cooled is returned to an inlet of the adsorption device. how to. 6. Apparatus for carrying out the method according to claim 1, wherein the adsorbent layer in the adsorber is separately coordinated into a plurality of independent adsorbent layers. An apparatus for performing a method for isolating an inert gas, characterized in that the method has an unstructured structure. 7. An apparatus for carrying out the method according to claim 1, wherein the adsorbent layer in the adsorption device is provided with a plurality of independent adsorbent layers having different adsorption characteristics. An apparatus for carrying out a method for isolating an inert gas, characterized in that the method comprises separating and coordinating the plurality of independent adsorbent layers in a superposed manner. 8. The exhaust pipe according to claim 6, wherein an exhaust pipe is buried between a plurality of independent adsorbent layers in the adsorption apparatus, and the exhaust pipe is connected to a vacuum pump. An apparatus for carrying out the method for isolating an inert gas described in 1. 9. An apparatus for carrying out the method according to claim 1, wherein the adsorbent layer in the adsorption device comprises a single adsorbent layer, and wherein the adsorbent layer contains a single adsorbent layer. An apparatus for performing a method for isolating an inert gas, comprising a plurality of exhaust conduits embedded therein and connected to a vacuum pump.