KR101012686B1 - gas concentration method - Google Patents

Abstract

The present invention relates to a method for obtaining a concentrated gas by applying a pressure difference to the adsorbent, and more particularly to a method for obtaining a concentrated gas having a low concentration and a high flow rate rather than a high concentration. The present invention is not intended for application to large industrial gas separation processes or to produce medical oxygen, but for application to air conditioners and the like used in daily life. The adsorption step by this method is carried out at the pressure difference between the vacuum pressure and the atmospheric pressure by the main vacuum pump means, but the end of the adsorption bed where gas is produced has a different pressure history. The desorption step is performed by the vacuum pressure by the main vacuum pump means, but the vacuum pressure by a separate concentrated gas discharging means is used as auxiliary in the desorption step. Apparatus according to the present method has the advantage that can be implemented to maximize the production at low noise, high flow rate and low cost.

Gas concentration

Description

Gas concentration method

1 is a schematic view of a gas concentration module which is an embodiment according to the method of the present invention.

Figure 2 is a pressure change over time of the adsorption bed according to the method of the present invention.

3 is a schematic representation of an apparatus having two adsorptive beds according to the method according to the invention.

Explanation of symbols on the main parts of the drawing

1 ... adsorption bed 2 ... vacuum pump means

3.Filter means 4.Euro switching valve

5.Valve means 6 ... Gas supply means

7 ... Output 8 ... Input

9 ... Adsorption bed 10 ... Pressure means

11.check valve means

The present invention relates to a gas concentration method of increasing a concentration of a specific gas from an input gas by separating a specific gas from a mixed gas by applying a pressure difference to an adsorbent having a selective adsorption force for each gas.

In the concentration method of increasing the concentration of a specific gas by using an adsorbent, a compressed gas of a predetermined pressure or more is supplied into an adsorption bed including an adsorbent, and the specific gas adsorbed in the adsorption bed is desorbed and discharged at atmospheric pressure and relatively adsorbed. Pressure Swing Adsorption (PSA), which produces inferior gases, has evolved since the 1950s and is commonly used. In addition to producing specific gases for large-scale industrial use, they separate nitrogen from the air and are small, and are mainly used for supplying oxygen to medical spaces and confined spaces in offices and homes, and wastewater treatment plants and farms.

Conventional compression swing adsorption method as described above usually uses a pressure between about 2 and 4 atm, in the case of oxygen separation in the air oxygen concentration of 90% or more for medical use, 40% or more for general use. In the case of using high pressure as described above, the efficiency is small in the case of small size, and has relatively advantages, but the noise problem, the heat problem, and the durability of the air compressor due to the use of high pressure are shown as the biggest problems.

In the conventional large industrial production facilities, the vacuum swing method (VSA, Vacuum Swing Adsorption), which does not operate between atmospheric pressure and high pressure, but operates between a vacuum pressure below atmospheric pressure and a low pressure of several hundred mmAq slightly higher than atmospheric pressure (VSA) The method is also used in consideration of the initial equipment cost, equipment cost, and maintenance cost. Such a vacuum swing method has a low efficiency in the case of a small size, but is practically limited, but the noise and durability problems of the PSA due to the use of low pressure do not occur.

When oxygen is enriched from air to obtain oxygen-enriched air, high-purity oxygen is required for medical use for patients, but in general, gas concentrators are used for the purpose of ventilation at home or office and for the purpose of creating a pleasant environment. When used, the oxygen concentrator is used to increase the oxygen concentration slightly, so high purity does not mean much, and the total oxygen flow to the room determines the indoor oxygen concentration. Therefore, the oxygen concentration of the small-capacity oxygen concentrator combined with the household air cleaner or the air conditioner is preferably designed according to the final oxygen concentration increase of the target space. In other words, the increase in concentration of about 21% to 23% is enough for people to feel comfortable, so theoretically, the supply oxygen concentration can be higher than this. For this reason, commercially available oxygen concentrators use a lot of methods for supplying indoors with low concentration and high flow rate by mixing purified air.

The gas enrichment plant is strategically designed on the basis of first, concentration, second, productivity, and third recovery rates, and as described above, conventional devices are designed with priority on concentration. In the case of PSA, RPSA (Rapid PSA) was developed to continuously incubate the gas in consideration of the concentration and the total production, thereby increasing productivity based on the basic stages of pressurization, delay, and production. This process is fast, with several steps in seconds, enabling continuous production on a single bed.

Recently, these devices are rapidly being applied to small devices as the gas separation membrane has been applied to the small size to produce oxygen enriched air of 50% or less. The separation method by gas separation membrane cannot produce high concentration in the case of oxygen concentration, but it can be more advantageous in terms of air conditioning because it can be configured at a lower cost than the method using an adsorbent.

Regardless of the concentration, there are no high-productivity processes based on VSA, and for the purpose of air conditioning, a process to increase only the total yield has not been applied to small devices.

The present invention has been made to solve this problem, and relates to a method for effectively producing a low concentration of incubation gas rather than a high concentration of gas based on the vacuum swing adsorption (VSA, a kind of conventional PSA method). will be.

An object of the present invention is to construct a compact gas concentrator that does not have the noise and durability problems of the PSA system. It is also an object of the present invention to provide a method for separating oxygen from air, in particular for low concentration, high flow rate and continuous gas separation.

It is also an object of the present invention to provide a device that can effectively overcome the problem of low efficiency of the VSA by utilizing the pressure distribution in the adsorption bed containing the adsorbent.

Unlike the conventional VSA, the present invention is not operated between the vacuum pressure and the pressure slightly higher than the atmospheric pressure in the case of air separation, but is operated between the predetermined vacuum pressure and the atmospheric pressure, and the suction end of the adsorption bed reaches the atmospheric pressure, but hatches. The gas production stage is operated at a pressure slightly below atmospheric pressure. This is because the purpose of the present invention is not to produce a high purity incubation gas, but to continuously produce a low purity, high flow incubation gas, thereby minimizing the pressure difference applied to the adsorbent to solve the noise and durability problems, and again. By optimizing this, the method of maximizing efficiency in terms of the total output is used.

The present invention is based on the method according to the prior application by the present applicant, the object is to further improve to minimize the capacity of the main vacuum pump and to maximize the yield of the hatching gas.

The present invention can add a separate pressurization means to increase the concentration, in this case can be used for a particular application because it can obtain a certain high concentration, high flow rate.

The apparatus according to the method of the present invention is not intended to be widely used for pre-gas concentration, but for the purpose of increasing the concentration of oxygen in a small amount or increasing the concentration of a specific gas, such as the use of an oxygen concentrator. It is preferably used in combination with a purifier or air conditioner.

Each step of the method according to the invention is explained on the basis of the components described below.

The present invention provides an adsorptive bed comprising an adsorbent, a vacuum pump means for applying a vacuum pressure to the adsorbent, a flow path switching valve for converting a vacuum pressure and an atmospheric pressure, and preventing a backflow to the adsorptive bed. The check valve means and the incubation gas supply means for supplying the incubation gas produced to the target space are essential components.

The invention is described in detail with reference to the embodiments of the accompanying drawings.

1 is a schematic representation of the essential components constructed in accordance with the method according to the invention. That is, the adsorption bed 1 including an adsorbent such as zeolite or carbon molecular material therein, the vacuum pump means 2 for discharging the gas and impurities adsorbed in the adsorption bed 1 to the outside, moisture and impurities The filter means (3) for filtering, the flow path switching valve (4) for switching the flow path, and the product gas passing through the adsorption bed (1) and is mainly used as a check valve used for pressure and concentration control in the adsorption bed (1) The valve means 5 is configured, and the gas supply means 6 for injecting the produced concentrated gas into the target space.

The method according to the invention consists of the following steps. First, the vacuum pump means (2) applies a vacuum pressure to the adsorption bed (1) containing the adsorbent to create a vacuum pressure in the adsorption bed (1), and the adsorption bed (1) by the flow path switching valve (4) The pressure of the mixed gas which is cut off from the vacuum pump means 2 and passes through the filter means 3 is introduced into the adsorption bed 1 so that the specific gas is adsorbed to the adsorbent. It is provided with a gas supply means (6) capable of generating a very low pressure vacuum pressure without being provided to apply a vacuum pressure to the upper end of the adsorption bed (1) where the concentration of the production gas is increased to discharge the production incubation gas to the outside Include a step as a required step.
The gas supply means 6 preferably has a low vacuum pressure of 200 mmHg or less.
At this time, the step of forming the vacuum pressure in the vacuum pump means (2) in the adsorption bed (1) overlaps with the gas supply means (6) for supplying the production gas from the adsorption bed (1) for a certain time. Typically, the conventional method is to close the valve means 5 after the completion of the production step and proceed with the desorption, but in the present invention, the production is continued for a certain time even after the desorption starts. This is to reduce the pressure in the adsorption bed (1) in parallel with the desorption and production, the production will continue even during the desorption process. This decreases the concentration but allows the production of large amounts for a given cycle. That is, in some respects, the gas supply means 6 may also be regarded as a kind of vacuum pump means, so that the desorption action may be performed in the initial stage of desorption. If the vacuum pressure in the adsorption bed 1 is greater than the sum of the vacuum pressure of the gas supply means 6 and the pressure caused by the self-pressure of the valve means 5, which is mainly a check valve, the valve means 5 is closed so that the vacuum pump means ( 2) only serves to create a vacuum pressure in the adsorption bed (1). This overlap time initially helps to form a rapid vacuum pressure in the adsorption bed 1, and the gas supply means 6 supplies the production gas and at the same time contributes to the desorption process in the adsorption bed 1 as much as the vacuum pressure it has. To maximize productivity.
As described above, the vacuum pump means (2) by applying a vacuum pressure inside the adsorption bed (1) containing the adsorbent to create a vacuum pressure inside the adsorption bed (1), and passed through the filter means (3) The adsorption step in which the mixed gas is introduced into the adsorption bed 1 by the pressure difference between the pressure of the mixed gas and the vacuum pressure inside the adsorption bed 1 and the specific gas is adsorbed to the adsorbent is carried out over the same time period. For example, it is preferable to have a desorption time of 2 to 5 seconds to have a fast vacuum swing cycle.
In addition, as described above, the production step of discharging the concentrated production gas to the outside by applying a vacuum pressure to the upper end of the adsorption bed (1) having a higher concentration of the production gas, the vacuum pump is provided with a separate check valve means (5) Preferably, this check valve means is closed by closing during the desorption process by means (2).

A series of such processes are shown in FIG. 2, where A represents the pressure change over time of the mixed gas input stage 8 of the adsorptive bed 1 and B represents the output stage 7 on the gas supply means 6 side. ) Shows the approximate pressure change at time of). X represents a pressure reference line through which the gas supply means 6 can pull out the production gas from the adsorption bed, and thus, if the pressure of B is higher than the reference line X, the gas supply means 6 supplies the production gas. C and D represent the pressure change with time of the input end and the output end of the other adsorption bed 9 in the embodiment when two adsorption beds are used as shown in FIG. 3 and are symmetrical with A and B. The vertical dashed line Y is the baseline at which the adsorption bed 1 stops production, while the other adsorption bed 9 starts the production gas at the same time or at least prior to the start of this line so that the two beds are continuously produced. Will be achieved. Of course, the expansion to a multibed system using multiple beds is apparent to those skilled in the art. 2 and 3 again, one adsorption bed 1 starts a desorption process in which pressure drops rapidly while the other adsorption bed 9 starts an adsorption process in which a mixed gas is introduced. At this time, one adsorption bed 1 still produces the target gas, where the adsorption bed 9 produces the target gas until the output end portion connected to the gas supply means 6 is below the vacuum pressure of the gas supply means. The internal pressure increases without doing so. When the upper end of the adsorption bed 9 has an absolute pressure higher than the vacuum pressure of the gas supply means 6, the adsorption bed 9 starts producing the target gas, and the adsorption bed 1, which produced the target gas, stops production. It stops and undergoes the desorption process by the vacuum pump means (2) only.

As described above, the production of the target gas simultaneously with the desorption process by the vacuum pump means 2 during the desorption process is aimed at maximizing the yield, and rapidly reducing the pressure in the adsorption bed 1 initially. It has the effect of shortening the entire cycle, and it is difficult to achieve high concentration of the production gas, but it is a process of continuously obtaining low concentration and high flow rate of production gas.

During the above steps, the pressure distribution in the adsorption beds (1, 9), the side (A, C) into which the mixed gas is introduced, the vacuum pressure by the vacuum pump means (2) and the pressure of the mixed gas ( Air does not exceed atmospheric pressure), and the upper end portions B and D, which supply the production gas, are placed at the vacuum pressure of the upper end generated by the production gas supply means to supply the production gas. That is, the upper end and the lower end undergo different pressure history, and the upper end, which is a supply end, operates between the vacuum pressure by the vacuum pump means 2 and the vacuum pressure provided by the gas supply means 6. The lower end of the adsorption bed 1 through which the mixed gas is sucked is the part with the largest pressure difference, and receives the pressure (atmospheric pressure in the case of air) due to the vacuum pressure by the vacuum pump means 2 and the flow of the mixed gas directly. Therefore, the operating pressure difference decreases from the lower end, which is the input end of the suction bed, to the upper end, which is the output end.

Oxygen-enriched air is usually suitable up to about 40% when constituting the apparatus according to the present invention, and if it is desired to further increase the concentration, it is provided with a separate pressurizing means 10 and used in the adsorption step (1, 9). The pressure inside the can be increased above atmospheric pressure, so that a higher concentration can be obtained. In this case, it should be determined in consideration of the economic aspect and the application object, and in general, the pressurizing means 10 is a slight pressure increase means, so that a small size is sufficient. The check valve means 11 prevents pressure from leaking to the outside when the pressurizing means 10 pressurizes into the adsorption beds 1 and 9.

In the case of the valve means 5, a solenoid valve or a check valve that opens only at a predetermined pressure or the like is used in the case of the PSA method. However, in the vacuum method such as the apparatus, the above method is not suitable. This is fine in the case of a conventional VSA method, in which a pressure method of raising the pressure in the adsorption bed 1 slightly above atmospheric pressure in the case of air is used. When only the pressure of is used, it is not preferable to generate high flow rate and low concentration of oxygen. Therefore, a very open, for example, thin rubber membrane, which is normally only slightly open and closes only when the vacuum pressure at the upper end of the bed, which is a part for outputting the production gas, is above a certain level above the vacuum pressure provided by the gas supply means 6 Concise check valve means are preferred.

By using the valve means 5 as described above, the burden on the gas supply means 6 is greatly reduced, and in addition to a vacuum pump having a large vacuum pressure or a blower having a medium vacuum pressure, a dust generator such as a bubble generator which generates very small vacuum pressure A pneumatic vibrator can be used as the gas supply means 6. Therefore, the structure of the low vibration, low cost, and high durability by the low vacuum pressure of the gas supply means 6 becomes possible relatively.

Since the pressure distribution in the adsorption bed 1 is different from the lower end and the upper end as described above, it is preferable to use a multi-layer adsorption bed which is used in consideration of adsorbents having different adsorption performance. This is different from the pressure difference in the adsorption bed in the PSA method, which does not change much according to the bed length. Therefore, it is better to use the adsorbent with good adsorption force at the lower end and the adsorbent with lower adsorption force at the upper end. Is advantageous in It is, of course, also possible to arrange the adsorbents in reverse and economically optimize them.

When the device according to the present invention is installed in a building or used for oxygen supply to a motor vehicle, the vacuum pump means 2 uses a separate vacuum pump in parallel or independently of a vacuum source already present in the building or motor vehicle. It is available. For example, in the case of automobiles, since there is a vacuum pressure due to the suction force of the engine, when connected thereto, a separate vacuum pump means (2) is not required, or a very small vacuum pump means (2) can be configured. In the case of a building, the vacuum pump means 2 can be miniaturized by using a vacuum source existing in the air conditioning apparatus.

In addition to the embodiments of the present invention, those skilled in the art will recognize that in addition to the two commonly used adsorption bed system, various modifications or changes, such as other multi-bed systems, can be configured without departing from the basic scope of the present invention. will be.

The method according to the present invention can produce a large amount of low concentration, high flow of the target gas, especially in the case of the oxygen concentrating device configured by the present method as an air conditioner to comfort the room and to a level of air slightly higher than normal oxygen concentration. It can make a difference. In addition, it is possible to implement a device of low noise and high durability by operating between low vacuum pressure without using high pressure air.

It is possible to produce low concentration and high flow rate without separate purifying air mixing device, so it is excellent to combine with home and office air purifier and air conditioner. In addition, by considering the pressure difference according to the length of the adsorption bed, it is possible to configure a compact and lightweight device.

Claims (13)

In the method of making the enriched gas enriched by the pressure difference using an adsorbent having a selective adsorption force for a particular gas from the mixed gas, The method comprises a vacuum pump means for making a pressure difference, Desorption step of the vacuum pump means to apply a vacuum pressure inside the adsorption bed containing the adsorbent to create a vacuum pressure inside the adsorption bed; The adsorption bed is blocked by the flow path switching valve and the mixed gas is introduced into the adsorption bed by the pressure difference between the pressure of the mixed gas passing through the filter and the vacuum pressure inside the adsorption bed, and the specific gas is absorbed into the adsorbent. Adsorption step is adsorbed, It includes a production step of discharging the concentrated production gas to the outside by applying a vacuum pressure to the upper end of the adsorption bed having a high concentration of the production gas having a gas supply means capable of generating a low pressure vacuum pressure, The desorption step starts before the end of the production step, and the production takes place for a certain time in parallel with the desorption step, and the gas supply means shortens the desorption process, thereby reducing the pressure in the adsorption bed by the vacuum pump means and the gas supply means within a short time. Gas concentration method characterized in that the dropping. According to claim 1, wherein two or more adsorption beds are provided so that one adsorption bed starts the desorption step while the other adsorption bed starts the adsorption step so that the production step in one adsorption bed is finished or Gas concentration method, characterized in that the production step is made in the other adsorption bed during the continuous production. The input stage of the adsorptive bed into which the mixed gas is input is operated between the pressure of the mixed gas and the vacuum pressure of the vacuum pump means, and the output end to which the production gas is supplied is a vacuum pressure provided by the gas supply means. And a vacuum pressure provided by the vacuum pump means. 4. The gas concentration method according to claim 3, wherein the mixed gas is ordinary air, and the oxygen-enriched air is obtained by adsorbing nitrogen from the air. 4. The gas concentration method according to claim 3, wherein the gas supply means has a low vacuum pressure of 200 mmHg or less. 4. The gas concentration method according to claim 3, wherein the desorption step and the adsorption step are the same time and have a fast vacuum swing cycle having a desorption time of 2 to 5 seconds. 4. The gas concentration method according to claim 3, further comprising a separate check valve means, in which the check valve means is closed during the desorption process by the vacuum pump means. In the method of making the enriched gas enriched by the pressure difference using an adsorbent having a selective adsorption force for a particular gas from the mixed gas, The method comprises a vacuum pump means for making a pressure difference, Desorption step of the vacuum pump means to apply a vacuum pressure inside the adsorption bed containing the adsorbent to create a vacuum pressure inside the adsorption bed; The adsorption bed is blocked by the flow path switching valve and the mixed gas is introduced into the adsorption bed by the pressure difference between the pressure of the mixed gas passing through the filter and the vacuum pressure inside the adsorption bed, and the specific gas is absorbed into the adsorbent. An adsorbent for adsorbing the adsorbent, and adsorbing the adsorbent for adsorbing the adsorbent onto the adsorbent bed by means of a separate pressurization means. It includes a production step of discharging the concentrated production gas to the outside by applying a vacuum pressure to the upper end of the adsorption bed having a high concentration of the production gas having a gas supply means capable of generating a low pressure vacuum pressure, The desorption step starts before the end of the production step, and the production takes place for a certain time in parallel with the desorption, and the gas supply means shortens the desorption process, thereby reducing the pressure in the adsorption bed by the vacuum pump means and the gas supply means within a short time. Gas concentration method characterized in that floating. The method of claim 8, wherein two or more adsorption beds are provided so that one adsorption bed starts a desorption step while the other adsorption bed starts an adsorption step so that the production step in one adsorption bed is finished or Gas concentration method, characterized in that the production step is made in the other adsorption bed during the continuous production. 10. The gas concentration method according to claim 8 or 9, wherein the mixed gas is ordinary air, and the oxygen-enriched air is obtained by adsorbing nitrogen from the air. The gas concentration method according to claim 10, wherein the gas supply means has a low vacuum pressure of 200 mmHg or less. The gas concentration method according to claim 10, wherein the desorption step and the adsorption step are the same time and have a fast vacuum swing cycle having a desorption time of 2 to 5 seconds. 11. The gas concentration method according to claim 10, further comprising a separate check valve means, in which the check valve means is closed during the desorption process by the vacuum pump means.

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