JP2009023907A - Gas separation method and gas separation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a product gas having higher purity in the case when the product gas is separated and recovered through adsorption onto an adsorbent. <P>SOLUTION: A raw material gas containing carbon monoxide is supplied into adsorption columns 16A, 16B and thereafter, carbon monoxide is separated and recovered by desorbing carbon monoxide from an adsorbent. At this time, the pressure of the adsorption columns 16A, 16B is reduced by an ejector 18 operated with steam as a primary fluid (driving fluid) and carbon monoxide (secondary fluid) desorbed from the adsorbent is discharged together with steam (primary fluid) while being sucked into the ejector 18. Then, the discharged fluids are cooled to an ordinary temperature or near to the ordinary temperature to condense steam. The discharged fluids are thereby vapor-liquid separated and carbon monoxide being a gas component is recovered as the product gas. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gas separation method and apparatus for separating a target gas from a raw material gas.

  Conventionally, a pressure swing adsorption separation method (“PSA method”) is generally known as one of methods for obtaining a target gas (referred to as a product gas) from a raw material gas. In this method, pressurized source gas is supplied into an adsorption tower filled with an adsorbent to adsorb impurities to the adsorbent, thereby separating and recovering the target gas (product gas) (adsorption process), and then adsorbing The adsorbent is regenerated (desorption process) by depressurizing the inside of the column and desorbing impurities from the adsorbent, and the product gas can be continuously taken out by repeating this adsorption process and desorption process alternately. It is.

In the PSA method, the product gas is generally separated by adsorbing impurities to the adsorbent as described above, but on the contrary, the product gas is adsorbed on the adsorbent and is separated from the adsorbent in the desorption process. The product gas is also separated by desorbing the product gas (Patent Document 1). For example, when carbon monoxide is separated as a product gas from a mixed gas of carbon monoxide (CO) and nitrogen (N ₂ ), there is currently no effective adsorbent that adsorbs only nitrogen (N ₂ ). Therefore, in such a case, carbon monoxide is adsorbed on an adsorbent and separated and recovered by desorbing it from the adsorbent in a desorption step.
JP-A-2-283608

  In the PSA method, in the desorption process, the inside of the adsorption tower is usually sucked by using a vacuum pump, and thereby the adsorbate desorbed from the adsorbent is recovered by depressurizing the inside of the tower. There are the following problems when separating and recovering by adsorbing to the catalyst. In other words, because of the structure of the vacuum pump, there is a risk that outside air may enter (air leak) from moving parts such as bearings. Therefore, when collecting the product gas desorbed from the adsorbent, the outside air is mixed into the product gas. As a result, the purity of the product gas may be reduced. For example, when carbon monoxide is separated and recovered as a product gas, if outside air is mixed with this, the outside air component and carbon monoxide are close in vaporization temperature, and then it is necessary to go through many steps to separate them. It is extremely difficult. Therefore, it has been practically difficult to obtain a product gas having a high purity of, for example, 99.9% or more.

  The present invention has been made in view of the above circumstances, and a product gas with higher purity can be obtained when the product gas is separated and recovered by adsorbing the product gas to the adsorbent as described above. The purpose is to do so.

  In order to solve the above-mentioned problems, the gas separation method of the present invention supplies a raw material gas composed of a plurality of components including carbon monoxide gas to an adsorption tower filled with an adsorbent, and then depressurizes the inside of the adsorption tower. In the method for separating and recovering the carbon monoxide gas desorbed from the adsorbent as a product gas, an ejector is used as means for reducing the pressure in the adsorption tower, and water vapor is supplied to the ejector as a primary fluid. The ejector is operated to reduce the pressure in the adsorption tower, and the carbon monoxide gas desorbed from the adsorbent by this pressure reduction is sucked into the ejector as a secondary fluid and discharged from the ejector together with the primary fluid. The discharged fluid is gas-liquid separated at room temperature or a temperature close thereto to recover the gas component (claim 1).

  According to the method of depressurizing the inside of the adsorption tower using the ejector as described above, since the ejector does not have a moving part such as a bearing such as a vacuum pump, the carbon monoxide gas desorbed due to the depressurization in the adsorption tower is used. On the other hand, outside air is not mixed due to equipment factors (that is, equipment that depressurizes the inside of the adsorption tower). When the ejector is used, the primary fluid and the secondary fluid (carbon monoxide gas) are mixed with each other. As described above, water vapor is used as the primary fluid, and the discharge fluid discharged from the ejector is used as the primary fluid. Since the gas component is recovered by gas-liquid separation at room temperature and near normal pressure, the carbon monoxide gas can be easily and reliably separated from the primary fluid and recovered.

  More specifically, water vapor is generated, the water vapor is supplied to the ejector as a primary fluid, and the discharge fluid discharged from the ejector is cooled to condense the water vapor contained in the discharge fluid. Carbon monoxide gas is separated from the fluid (claim 2).

  If water vapor is supplied to the ejector as the primary fluid in this way, the primary fluid can be ejected from the ejector's built-in nozzle at a higher speed, and the negative pressure suction force (degree of vacuum) by the ejector, that is, adsorbed by the adsorbent This is advantageous in increasing the desorption capacity of the carbon monoxide gas produced. Further, since the discharge fluid from the ejector is cooled to condense the water vapor, the discharge fluid can be satisfactorily gas-liquid separated to recover the carbon monoxide gas.

In the above method, the carbon monoxide gas desorbed from the adsorbent by the reduced pressure in the adsorption tower is dehydrated in the dehydration tower, and is supplied to the adsorption tower after the supply of the source gas and before the pressure reduction. It is preferable that the carbon monoxide after the dehydration is directly refluxed from the dehydration tower to wash the adsorption tower (claim 3).

According to this method, a gas other than carbon monoxide adsorbed on the adsorbent can be favorably desorbed (washed) using the product gas (carbon monoxide).

On the other hand, the gas separation device of the present invention comprises an adsorption tower filled with an adsorbent and a decompression means for depressurizing the inside of the adsorption tower, and the raw material gas comprising a plurality of components including carbon monoxide gas in the adsorption tower. In the apparatus for separating and recovering carbon monoxide gas desorbed from the adsorbent as a product gas by reducing the pressure in the adsorption tower, an ejector is provided as the pressure reducing means, and water vapor is primarily supplied to the ejector. The ejector is operated as a side fluid to depressurize the inside of the adsorption tower, and the carbon monoxide gas desorbed from the adsorbent due to the depressurization is sucked into the ejector as a secondary side fluid. It is configured to be discharged together with the primary fluid, and the discharged fluid discharged from the ejector is gas-liquid separated at room temperature or a temperature close to this to produce the gas component. Is provided with a recovery means for recovering a gas (claim 4).

According to this apparatus, when the primary fluid is supplied to the ejector using water vapor as the primary fluid, the inside of the adsorption tower is depressurized by the ejector, and carbon monoxide desorbed from the adsorbent is sucked into the ejector by this decompression. While being discharged from the ejector together with the primary side fluid. The gas component is recovered as product gas while the discharged fluid discharged from the ejector is gas-liquid separated by the recovery means at room temperature or a temperature close thereto. Therefore, it is possible to satisfactorily implement the gas separation method according to the first to third aspects .

Each gas separation device includes a circulating means for circulating the primary fluid to the ejector by supplying the primary fluid contained in the discharge fluid discharged from the ejector to the ejector again. (Claim 5 ).

  By repeatedly using the primary side fluid for operating the ejector in this way, it is possible to effectively use the primary side fluid and reduce the running cost.

In the above apparatus, the dehydration tower for dehydrating the carbon monoxide gas desorbed from the adsorbent by the reduced pressure in the adsorption tower, and the adsorption tower after the supply of the source gas and before the pressure reduction And means for directly refluxing the carbon monoxide gas after dehydration by the dehydration tower from the dehydration tower (Claim 6).

According to this apparatus, gases other than carbon monoxide adsorbed by the adsorbent can be favorably desorbed (washed) using the product gas (carbon monoxide).

  According to the gas separation method and the gas separation apparatus of the present invention, it is possible to prevent outside air from being mixed into carbon monoxide due to equipment factors by reducing the pressure in the adsorption tower using an ejector. While purifying carbon monoxide desorbed from the product as a product, its purity can be effectively increased.

  A first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows a circuit diagram of a first embodiment of a gas separation apparatus according to the present invention (a gas separation apparatus in which a gas separation method according to the present invention is implemented). The apparatus shown in this figure includes a raw material gas containing carbon monoxide, specifically, hydrogen (H ₂ ), argon (Ar), oxygen (O ₂ ), nitrogen (N ₂ ), carbon dioxide (CO ₂ ) and carbon dioxide. Carbon monoxide is separated and recovered from a source gas containing carbon oxide (CO) based on a so-called pressure swing adsorption separation method (“PSA method”).

  In the figure, L1 is a supply line for supplying the source gas to the first adsorption unit 12. The line 10 is provided with a compressor 10, and the raw material gas is pumped to the first adsorption unit 12 by the operation of the compressor 10.

  The first adsorption unit 12 adsorbs and removes carbon dioxide from the source gas, and is provided with two adsorption towers 12A and 12B. Each of the adsorption towers 12A and 12B is filled with an adsorbent of carbon dioxide such as zeolite, and a raw material gas is introduced into each of the adsorption towers 12A and 12B through the line L1, whereby carbon dioxide is absorbed by the adsorbent. Is adsorbed and separated and removed from the source gas.

  A line L2 including a vacuum pump 14 and a line L3 leading to the second adsorption unit 16 are connected to each of the adsorption towers 12A and 12B. Thereby, during operation of the apparatus, the source gas is supplied to the second adsorption unit 16 through the line L3 while the source gas is introduced only into the adsorption tower 12A (or 12B) on the one side through the line L1, while the adsorption on the other side is performed. As for the column 12B (or 12A), the inside of the column is depressurized by driving the vacuum pump 14, and thereby desorption of carbon dioxide (that is, regeneration treatment of the adsorbent) is performed. That is, the adsorption and desorption (regeneration treatment) of carbon dioxide by the adsorbent are alternately performed at regular time intervals between the adsorption towers 12A and 12B, whereby carbon dioxide is continuously separated and removed in the first adsorption unit 12. To be able to be.

  The second adsorption unit 16 adsorbs and removes carbon monoxide from the source gas, and the second adsorption unit 16 is also provided with two adsorption towers 16 </ b> A and 16 </ b> B like the first adsorption unit 12. Each adsorption tower 16A, 16B is filled with, for example, a carbon monoxide adsorbent in which a copper compound is added to an alumina carrier, and a raw material gas is introduced into each adsorption tower 16A, 16B through the line L3. Carbon monoxide is adsorbed by this adsorbent and separated from the raw material gas.

  An off gas line L4 and a line L5 leading to the ejector 18 are connected to the adsorption towers 16A and 16B, respectively, so that the adsorption and desorption of carbon monoxide are performed in the respective adsorption towers in the same manner as the first adsorption unit 12. It is performed alternately between 16A and 16B. That is, during operation of the apparatus, the raw material gas is introduced only into the adsorption tower 16A (or 16B) on one side through the line L3, and only carbon monoxide is adsorbed among the components while the other gas components are introduced into the atmosphere through the line L4. In the meantime, the adsorption column 16B (or 16A) on the other side is depressurized by the operation of the ejector 18 to desorb carbon monoxide.

  The ejector 18 is a so-called steam ejector that operates with water vapor as a primary fluid (driving fluid). As shown in FIG. 2, the water ejected from the internal nozzle 18b through the line L7 into the steam inlet 18a through the line L7. The gas is allowed to flow into the diffuser 18d while being ejected, and at this time, the inside of the adsorption towers 16A and 16B is sucked using the negative pressure generated in the suction chamber 18c provided between the nozzle 18b and the diffuser 18d. . The suction action reduces the pressure in the adsorption towers 16A and 16B through the line L5, desorbs carbon monoxide from the adsorbent, and sucks the desorbed carbon monoxide into the ejector (suction chamber 18c) as a secondary fluid. However, it is discharged from the diffuser 18d to the line L6 together with the water vapor that is the primary fluid.

  The downstream end of the line L6 is connected to the condenser 26. The condenser 26 comprises a heat exchanger, and a mixed gas (mixed gas of water vapor and carbon monoxide; discharged fluid) discharged from the ejector 18 is introduced into the condenser 26 and cooled to room temperature or in the vicinity thereof. . As a result, water vapor in the mixed gas is condensed and gas-liquid separated, and the gas component, that is, carbon monoxide, is taken out through the line L9.

  An upstream end of the line L7 is connected to the condenser 26, and a pump 22 and a boiler 24 are interposed in the line L7, whereby the condensed water in the condenser 26 is regenerated as water vapor and supplied to the ejector 18 again. It has come to be. That is, in the present embodiment, the circulation means according to the present invention is configured by the line L7, the pump 22, the boiler 24, and the like, and is configured to circulate water vapor (primary fluid) to the ejector 18. . Note that reference numeral L8 in the figure is a makeup water line for replenishing the condenser 26 with steam water, so that steam water that decreases as the water vapor is taken out through the line L9 can be replenished.

  The downstream end of the line L9 is connected to the dehydrating unit 30 through the blower 28. The dehydration unit 30 adsorbs and removes water (water vapor) taken out from the condenser 26 together with carbon monoxide, and is provided with two dehydration towers 30A and 30B. Each dehydration tower 30A, 30B is filled with an adsorbent such as zeolite, for example, and carbon monoxide is introduced into each dehydration tower 30A, 30B through the line L9, so that moisture contained therein is adsorbed and removed. Is done.

  A line L10 for taking out carbon monoxide as a product and an off-gas line L12 are connected to each dehydration tower 30A, 30B, respectively, and moisture adsorption (dehydration) and desorption (adsorbent regeneration process) are performed. The dehydration towers 30A and 30B are alternately arranged. That is, during operation of the apparatus, carbon monoxide is introduced only into the dehydration tower 30A (or 30B) on one side through the line L9, and is introduced into a product tank (not shown) through the line L10 as product gas while adsorbing and removing moisture. In the meantime, the dehydration tower 30B (or 30A) on the other side is desorbed by supplying air through the line L12. In this embodiment, the line L6, the condenser 26, and the like constitute the recovery means according to the present invention.

  The line L10 that guides carbon monoxide as a product gas to the product tank is provided with a line L11 that branches from the middle of the line L10 to reach the adsorption towers 16A and 16B of the second adsorption unit 16. After the adsorption of carbon monoxide, specifically, part of the product gas is refluxed to the adsorption tower 16A (16B) before desorption, thereby washing the adsorbent, that is, adsorbed by the adsorbent. A process for desorbing a gas other than carbon monoxide is performed.

  In the gas separation apparatus configured as described above, after the raw material gas is compressed by the compressor 10 and first introduced into the adsorption tower 12A (or 12B) of the first adsorption unit 12 through the line L1, the carbon dioxide is removed. Then, it is introduced into the adsorption tower 16A (or 16B) of the second adsorption unit 16 through the line L3. And here, only carbon monoxide in the raw material gas is adsorbed and separated, and the other gas components are exhausted to the atmosphere. The carbon monoxide adsorbed by the adsorbent in the adsorption tower 16A (or 16B) is desorbed from the adsorbent by the action of the ejector 18 and is introduced into the condenser 26 together with water vapor as the primary fluid. Then, water vapor is condensed into water and carbon monoxide by condensing water vapor here, and only carbon monoxide which is a gas component is taken out and introduced into the dehydration tower 30A (or 30B) of the dehydration unit 30. Here, after the dehydration treatment is performed, the product gas is recovered.

  As described above, in this gas separation apparatus (gas separation method), the raw material gas is introduced into the adsorption towers 16A and 16B, the carbon monoxide contained in the raw material gas is adsorbed by the adsorbent, and then the adsorption tower 16A, The inside of 16B is depressurized and carbon monoxide is desorbed from the adsorbent to separate and recover carbon monoxide from the raw material gas. At this time, as described above, the ejector 18 is used to suck the inside of the adsorption towers 16A and 16B. Therefore, outside air is not mixed into the carbon monoxide desorbed from the adsorbent as in the conventional apparatus using a vacuum pump. That is, since the ejector 18 does not have a mechanical movable part, there is no possibility that outside air may be mixed from the movable part unlike a vacuum pump having a mechanical movable part such as a bearing, and therefore, it is accompanied by the mixing of outside air. And carbon monoxide can be desorbed from the adsorbent.

  Moreover, water vapor is used as the primary fluid (driving fluid) of the ejector 18, and after desorption, the mixed gas (mixed gas of water vapor and carbon monoxide) discharged from the ejector 18 as described above is at or near room temperature. Only the water vapor is condensed by cooling, and the mixed gas is gas-liquid separated into water and carbon monoxide so that only the carbon monoxide is recovered. Only carbon oxide can be separated and recovered.

  Therefore, according to the gas separation device (gas separation method) described above, carbon monoxide can be separated and recovered with higher purity than the conventional gas separation device (gas separation method). In this gas separation apparatus (gas separation method), the condensed water in the condenser 26 is supplied to the ejector 18 by the pump 22 while regenerating the water vapor as the water vapor. However, since the pump 22 is a positive pressure pump, it is like a vacuum pump. Outside air is not sucked into the pump from moving parts such as bearings and mixed. Therefore, the outside air hardly enters the carbon monoxide through the primary side fluid.

  By the way, in the said embodiment, although water vapor | steam is used as the primary side fluid (driving fluid) of the ejector 18, gaseous bodies other than water vapor | steam can also be used as a primary side fluid. For example, oil vapor obtained by vaporizing oil can be used as the primary fluid. In addition, when using oil vapor | steam as a primary side fluid in this way, each dehydration tower 30A, 30B of the dehydration part 30 is filled with a lipophilic adsorbent, and what is necessary is just to perform a deoiling process here.

  Further, in addition to using a gaseous body such as water vapor or oil vapor as the primary fluid, a liquid such as water (pure water) may be used. In this case, the boiler 24 is omitted in the configuration of the gas separation apparatus of the above embodiment, a tank or the like is provided in place of the condenser 26, and the mixed gas discharged from the ejector 18 is introduced into the tank and water and Carbon monoxide may be separated. However, since the ejector 18 generates the suction force (negative pressure) by using the velocity energy by ejecting the primary side fluid at a high speed, high velocity energy can be obtained with a small amount of power when generating a strong suction force. It is preferable to use a gaseous body such as water vapor or oil vapor which can be used as the primary fluid.

  The primary fluid of the ejector 18 may be a fluid other than water vapor, oil vapor, or water, and in short, it may be a liquid at room temperature and normal pressure. In other words, any fluid that can be gas-liquid separated into liquid and carbon monoxide at normal temperature or a temperature close to the mixed fluid (fluid in which the primary fluid and carbon monoxide are mixed) discharged from the ejector 18 is used. Good.

Next, an embodiment related to the present invention will be described.

Figure 3 schematically shows an embodiment of a gas separation equipment in the circuit diagram. Note that the gas separation device shown in the figure does not directly specify the present invention, but will be described as a second embodiment for convenience of explanation.

  In the gas separation device according to the second embodiment, carbon monoxide, which is a product gas, is used as the primary fluid (driving fluid) of the ejector 18. Compared with the gas separation device according to the first embodiment. The configuration is different in the following points. First, a cooler 32 composed of a heat exchanger is provided instead of the condenser 26 in the first embodiment, and a line L10 is branched and led out from a portion between the cooler 32 and the pump 22 in a line L7. Further, the boiler 24, the blower 28, the dewatering unit 30, the lines L8 and L9, and the line L12 are not provided.

  In this gas separation apparatus, carbon monoxide, which is a product gas, is introduced into the ejector 18 through the line L7 as a primary fluid. As a result, the carbon monoxide adsorbed by the adsorbent in the adsorption tower 16A (or 16B) is desorbed from the adsorbent by the action of the ejector 18 and is discharged into the line L6 while being sucked into the ejector 18 to the cooler 32. be introduced. The discharged gas (carbon monoxide) is recovered as it is through the line L10 as a product gas, and a part thereof is supplied to the ejector 18 through the line L7 by the pump 22, whereby a part of the product gas is supplied to the primary fluid. It has come to be used as.

  According to such a gas separation device (gas separation method) of the second embodiment, the inside of the adsorption towers 16A and 16B is decompressed using the ejector 18, and therefore, due to equipment factors as in the first embodiment. Carbon monoxide can be desorbed from the adsorbent without mixing outside air.

  In addition, since the same carbon monoxide as the product gas is used as the primary fluid of the ejector 18, the mixed gas discharged from the ejector 18 (that is, the mixed gas of the primary fluid and the secondary fluid) is used as it is as the product gas. It can be recovered. Therefore, as compared with the first embodiment, the apparatus configuration can be rationally simplified by the amount that the post-processing equipment such as gas-liquid separation and further dehydration of the mixed gas discharged from the ejector 18 is unnecessary. There is an effect.

  Further, in this apparatus (method), a part of the carbon monoxide discharged from the ejector 18 is extracted and recirculated to the ejector 18 as a primary fluid, so that the product gas is directly supplied to the primary side of the ejector 18. There is also an effect that the ejector 18 can be operated with a rational configuration used as a fluid.

  The gas separation devices (gas separation methods) of the first and second embodiments described above are some examples of preferred embodiments of the present invention, and the specific configuration or method thereof is the gist of the present invention. As long as it does not deviate from the above, it can be appropriately changed. For example, a configuration in which the ejectors 18 are provided in multiple stages in order to enhance the pressure reduction effect in the adsorption towers 16A and 16B can be employed.

In the first and second embodiments described above, when an example has been described for separating and recovering the carbon monoxide as a product gas, said apparatus (method), of course, that this is to separate and recover the gas component other than Also effective.

The implementation mode of the gas separation apparatus according to the present invention (viable gas separation apparatus gas separation method according to the present invention) is a circuit diagram showing. It is sectional drawing which shows the structure of an ejector. Is a circuit diagram showing the gas separation equipment in connection with the present invention.

Explanation of symbols

12 1st adsorption part 12A, 12B adsorption tower 16 2nd adsorption part 16A, 16B adsorption tower 18 ejector 26 condenser 30 dehydration part 30A, 30B dehydration tower

Claims (4)

After supplying the raw material gas composed of a plurality of components including carbon monoxide gas to the adsorption tower filled with the adsorbent, the carbon monoxide gas desorbed from the adsorbent by reducing the pressure in the adsorption tower is the product gas. In the method of separating and recovering as
An ejector is used as a means for depressurizing the inside of the adsorption tower. By supplying water vapor as a primary fluid to the ejector, the ejector is operated to depressurize the inside of the adsorption tower, and the depressurization is desorbed from the adsorbent. Carbon monoxide gas is sucked into the ejector as a secondary fluid and discharged from the ejector together with the primary fluid, and the discharged fluid is separated into gas and liquid at room temperature or a temperature close thereto to recover the gas component. Characterized gas separation method. The gas separation method according to claim 1,
Carbon monoxide gas is generated from the discharge fluid by generating water vapor, supplying the water vapor as a primary fluid to the ejector, cooling the discharge fluid discharged from the ejector, and condensing the water vapor contained in the discharge fluid. The gas separation method characterized by isolate | separating. An adsorption tower filled with an adsorbent and a decompression means for depressurizing the inside of the adsorption tower, and after supplying a raw material gas comprising a plurality of components including carbon monoxide gas to the adsorption tower, In an apparatus for separating and recovering carbon monoxide gas desorbed from the adsorbent by reducing the pressure as product gas,
An ejector is provided as the decompression means, and the ejector is operated to depressurize the inside of the adsorption tower by supplying water vapor to the ejector as a primary fluid, and the first desorbed from the adsorbent accompanying this decompression. Carbon dioxide gas is sucked into the ejector as a secondary fluid and discharged together with the primary fluid, and the discharged fluid discharged from the ejector is gas-liquid separated at or near normal temperature. And a gas separation device provided with a recovery means for recovering the gaseous component as product gas. The gas separator according to claim 3, wherein
A gas separation device comprising a circulation means for circulating the primary fluid to the ejector by supplying the primary fluid contained in the discharge fluid discharged from the ejector to the ejector again.

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