JPH03262512A - Pressure swing adsorbing type gas separation apparatus and operation thereof - Google Patents

Abstract

PURPOSE:To enhance the recovery of product gas by connecting the product gas outlet parts of a plurality of adsorbing cylinders by a pressure equalizing conduit and connecting the product gas outlet parts and the raw material gas inlet parts of other adsorbing cylinders by a series pressure equalizing conduit. CONSTITUTION:In the operation method of a pressure swing adsorbing type gas separation apparatus separating gas by changing over a plurality of adsorbing cylinders A, B packed with an adsorbent to an adsorbing process and a regenerating process, the product gas outlet part of the adsorbing cylinder A after the completion of the regenerating process and the product gas outlet part of the adsorbing cylinder B after the completion of the adsorbing process are allowed to communicate with each other by an outlet part pressure equalizing conduit 10 having outlet part pressure equalizing valves 10a, 10b. The raw material gas inlet part of the adsorbing cylinder A and the product gas outlet part of the adsorbing cylinder B are respectively allowed to communicate by a series pressure equalizing conduit 11 having a series pressure equalizing valve to perform a series pressure equalizing process moving gas. By this method, a pressure equalizing process can be performed until the pressures of both cylinders reach pressure near to perfectly equal pressure and many gases can be recovered.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pressure fluctuation adsorption type gas separation device and an operating method thereof, and more particularly, to a pressure fluctuation adsorption type separation device that can perform an efficient pressure equalization process. The present invention relates to an apparatus and a method of operating a pressure equalization process in the apparatus.

[Conventional technology]

Conventionally, as a means of separating specific components in a mixed gas or removing impurity components, pressure fluctuation adsorption gas separation is used to separate gases by sequentially switching multiple adsorption cylinders filled with adsorbent into an adsorption process. (hereinafter referred to as PSA) is used. This PSA is configured to perform a regeneration process on an adsorption cylinder that has completed an adsorption process, and to continuously produce product gas by sequentially switching between the adsorption process and the regeneration process.

The above PSA is - adsorbed, pressure equalized and regenerated within the membrane.

The pressure equalization and pressure charging steps are treated as one cycle, and are carried out sequentially for each adsorption column. That is, one adsorption column is used for the adsorption process in which pressurized raw material gas is introduced and product gas is derived, and the amount of gas (number) cg remaining in the adsorption column is
/ cd G) into another adsorption column after the regeneration step, a depressurization regeneration step of reducing the pressure inside the adsorption column to a lower pressure than during the adsorption step, and/or the adsorption column. A purge regeneration step in which a part of the product gas is reversed to promote regeneration, a pressure equalization step in which gas from another adsorption column whose adsorption step has been completed is introduced into the adsorption column after the regeneration step, and a pressure equalization step in which the gas from another adsorption column whose adsorption step has been completed is introduced into the adsorption column after the regeneration step has been completed. The system is set to sequentially perform each step of the pressurization step in which product gas is introduced into the cylinder to raise the pressure inside the cylinder to the operating pressure for the adsorption step.

Here, the pressure equalization step is performed for the purpose of improving the recovery rate of product gas, and the gas is moved using the pressure difference between the adsorption column where the adsorption step has been completed and the adsorption column where the regeneration step has been completed. While reducing the pressure in one adsorption column to an intermediate pressure,
The other adsorption cylinder is charged to an intermediate pressure. This pressure equalization process is carried out by the exit part (upper part) pressure equalization method in which the product outlets of the adsorption column that has completed the adsorption process and the product outlet part of the adsorption column that has completed the regeneration process are communicated with each other, and the pressure equalization method that is carried out by connecting the product outlet parts of the adsorption column that has completed the adsorption process and the product outlet part of the adsorption column that has completed the regeneration process. The pressure equalization method at the inlet (lower part) is carried out in a continuous manner, the simultaneous pressure equalization method (simultaneously at the top and bottom) where the outlet and inlet pressures are equalized at the same time, and the outlet section of the adsorption column where the adsorption process has been completed and the regeneration process has been completed. A series pressure equalization method is used in which the artificial part of the adsorption cylinder is communicated.

Which pressure equalization method to use among the above pressure equalization methods is determined by PS.
It varies depending on the configuration of A and its operating method, especially the regeneration method and the amount of gas recovered by the pressure equalization process.

[Problem to be solved by the invention]

However, in any of the above pressure equalization methods, there is a recovered gas amount at which the product gas purity is the highest, and if the pressure equalization step is performed in excess of that gas amount, the product gas purity will decrease. Therefore, it is common to not perform so-called complete pressure equalization, in which pressure is equalized until the pressures in both cylinders match. Since this is disadvantageous from the viewpoint of pressure recovery, a pressure equalization method is desired that can increase the amount of pressure equalized recovery gas as much as possible without reducing the product gas purity.

Therefore, the present invention aims to perform an operation that can increase the amount of equalized pressure recovery gas as much as possible without reducing the product gas purity, improve the recovery ratio of product gas to raw material gas, and reduce the production cost of product gas. The purpose of the present invention is to provide a PSA that can be used and a method for operating the same.

[Means to solve the problem]

In order to achieve the above object, the PSA of the present invention provides a pressure fluctuation adsorption type gas separation device that separates gas by switching a plurality of adsorption cylinders filled with adsorbent between an adsorption process and a regeneration process. The product gas outlet parts of the adsorption cylinders are communicated with each other by an outlet pressure equalization conduit having an outlet pressure equalization valve, and the product gas outlet part of the adsorption cylinder and the raw material gas inlet part of the other adsorption cylinder are connected in series, each having a pressure equalization valve. They are characterized by being connected to each other through series pressure equalizing conduits.

In addition, the method of operating the PSA of the present invention is such that the product gas outlet of the adsorption column where the regeneration step has been completed is communicated with the product gas outlet of the adsorption column where the adsorption step has been completed to equalize the pressure at the outlet to move the gas. After performing the process, a series pressure equalization process is carried out in which the raw gas inlet of the adsorption column where the regeneration operation has been completed is communicated with the product gas outlet of the adsorption column where the adsorption process has been completed to move the gas. There is.

[For production]

By configuring the PSA as described above and performing the operation method as described above, the gas with high product purity remaining in the adsorption column after the adsorption process can be efficiently introduced into the adsorption column after the regeneration process, and evenly. In the pressure process, the pressure in both cylinders is approximately the same,
That is, it becomes possible to carry out the pressure equalization process to a pressure that is completely equalized or close to completely equalized pressure, and more gas can be recovered without reducing the purity of the product gas.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on an embodiment shown in the drawings.

Figure 1 shows a two-cylinder PSA that produces nitrogen gas using air (a mixture of nitrogen and oxygen) as a raw material.
The insides of A and B are filled with molecular sieve charcoal (MSC).

This PSAI is provided with a pair of adsorption cylinders A and B, an air tank 2 on the feed air introduction side, a product tank 3 on the product gas supply side, and a vacuum pump 4 and blow valve 5 used during adsorption cylinder regeneration. In addition, large-mouth valves 5g, 6b% outlet valves 7a, 7b, and regeneration outlet valves 8a, 8b are provided for each adsorption cylinder A, B, and both adsorption cylinders A, B
The inlet portions At and Bi of the adsorption tubes have an inlet communication conduit 9 that communicates the inlet portions At and Bi of the adsorption cylinders, and the outlet portions Ao and Bo of both adsorption cylinders A and H have an outlet portion Ao of both adsorption cylinders. , Bo are provided with outlet pressure equalizing conduits 10 for communicating with each other, and the inlet communicating conduit 9 is provided with inlet pressure equalizing valves 9a, 9.
b, the outlet pressure equalizing conduit 10 has outlet pressure equalizing valves 10a, 1
0b are provided corresponding to adsorption cylinders A and B, respectively,
Further, between each valve of both conduits 9 and 10, a flow rate control valve 11 is provided.
A series pressure equalizing conduit 11 that communicates both conduits 9 and 10 via a.
is provided. Note that an air compressor, purification equipment, etc. (not shown) are installed upstream of the air tank 2, and the product tank 3
A product supply valve 3a is provided on the supply side.

This PSA includes steps 1 to 6 shown in FIG. 2 as one cycle. Note that during each process period, the valves other than the valves being described and the flow rate control valve 11a are closed.

Step 1 First, when one adsorption cylinder A is in the adsorption process and the other adsorption cylinder B is in the regeneration process, pressurized air that has been pressurized to a predetermined pressure is passed through the air tank 2 to the large mouth valve 6a attached to the adsorption cylinder A. The nitrogen gas is introduced into the adsorption column A, where oxygen is preferentially adsorbed and removed by the MSC in the column, and nitrogen is concentrated on the side of the adsorption column outlet Ao. The concentrated nitrogen is stored in the product tank 3 via the outlet valve 7a, and is supplied to the consumer as product nitrogen gas from the product supply valve 3a.

During this time, the regeneration process is being performed in the other adsorption cylinder B, and the regeneration outlet valve 8b of the adsorption cylinder B is opened, and the gas in the cylinder is discharged from the blow valve 5 to the atmosphere, and then the vacuum pump 4 By evacuation, the gas (mainly oxygen gas) adsorbed by the adsorbent in the cylinder is desorbed. In addition, in purge regeneration, a part of the product nitrogen gas is caused to flow back from the outlet valve 7b to the adsorption cylinder B and is discharged from the regeneration outlet valve 8b, the blow valve 5, or the vacuum pump 4, so that the nitrogen gas is not adsorbed by the adsorbent in the cylinder. Desorbs the gas.

Step 2 Each adsorption step and regeneration step are performed for a certain period of time, and when the adsorption of one adsorption cylinder A has progressed and the regeneration process of the other adsorption cylinder B has been completed, the population valve 5a, the outlet valve 7a, and the regeneration output valve are closed. 8b is closed, the outlet pressure equalizing valves 10a and 10b are opened to allow the outlet sections Ao and Bo of both adsorption cylinders A and B to communicate with each other. As a result, the nitrogen gas present at the outlet Ao of the adsorption column A moves to the outlet Bo of the adsorption column B (outlet pressure equalization step).

Continuously, with the outlet pressure equalizing valve 10a on the adsorption cylinder A side open,
The outlet pressure equalizing valve 10b on the adsorption cylinder B side is closed, and the inlet pressure equalizing valve 9b on the adsorption cylinder B side is opened. As a result, the gas with high nitrogen concentration present at the outlet Ao of the adsorption cylinder A is transferred to the inlet part Bi of the adsorption cylinder B at a predetermined flow rate via the flow rate control valve 11a.
(Series pressure equalization process).

The amount of gas transferred by the outlet pressure equalization process and the amount of gas transferred by the series pressure equalization process can be controlled by the communication time by opening and closing each valve or the opening degree of the flow rate control valve 1.1a, Similar control is also possible by inserting a diaphragm plate in the middle of the pipe.

By performing the pressure equalization process during the regeneration process as described above with the outlet pressure equalization process and the series pressure equalization process that follows, the high nitrogen concentration present at the outlet AO of the adsorption column A after the adsorption process has been completed. Gas can be efficiently introduced into the adsorption cylinder B where the regeneration process has been completed.

That is, the outlet part Ao of one adsorption cylinder A where the adsorption process has been completed.
By introducing the gas with the highest nitrogen concentration existing in the adsorption column B from the outlet Bo of the adsorption column B that has undergone regeneration processing, the desorption gas (oxygen) remaining in the adsorption column B is moved to the inlet Bl and the adsorbent is can be adsorbed to. Further, by subsequently introducing gas with a relatively high nitrogen concentration into the adsorption column A from the artificial part B1 of the adsorption column B, pressure equalization can be proceeded while removing oxygen in the gas.

Therefore, even if the pressure equalization process is performed to bring the adsorption cylinder A, which has undergone the adsorption process, and the adsorption cylinder B, which has undergone the regeneration process, to the same pressure,
In the series pressure equalization step that follows the pressure equalization step, gas with a higher nitrogen concentration than the feed air is introduced into the cylinder from the inlet Bf of the adsorption column B, so that more nitrogen is introduced toward the outlet BO of the adsorption column B. Highly concentrated gas can be placed.

The time for the above pressure equalization step varies depending on the configuration of the PSA, the volume of the adsorption cylinder, the type and filling amount of the adsorbent, the type and purity of the product gas, and other conditions, but it depends on the rate of gas adsorption to the adsorbent. PS using MSC that separates gases using differences
In case A, it is within 30 seconds, preferably within 20 seconds. Furthermore, the time for the outlet pressure equalization step during the pressure equalization step is 5
It is preferably within seconds, particularly within 3 seconds. For example, if the outlet pressure equalization process takes a long time, gas with low nitrogen purity will be introduced from one adsorption column after the adsorption process to the outlet of the other adsorption column, reducing the purity of the product nitrogen gas. There is a risk that it may cause

In addition, if the pressure equalization process time is set for a long time, the oxygen gas desorbed from the adsorbent in the adsorption column where the adsorption process has finished will be transferred to the adsorption column where the regeneration process has finished, which will also reduce the purity of the product gas. It ends up.

The method of the present invention performs separation using the difference in adsorption rate.
It is particularly effective for adsorbents such as SC that have a relatively slow adsorption rate (rate separation type adsorbents). In other words, in this type of adsorbent, since the adsorption speed is slow, the change in the purity of the gas in the adsorption column after the adsorption process is completed is gradual from the inlet to the outlet, and the so-called adsorption breakthrough zone is long. Therefore, when the gas existing in the upper part of the adsorption column is recovered under equal pressure into the adsorption column after the regeneration process has been completed, the method of the present invention is particularly effective because it allows the gas with higher purity to be arranged toward the outlet. .

Step 3 In order to perform depressurization regeneration of adsorption column A, regeneration outlet valve 8 ar
When the blow valve 5 is opened to lower the cylinder pressure to around atmospheric pressure (blowdown), the regeneration valve 7b is opened to raise the pressure in the adsorption cylinder B to the adsorption operating pressure. Introducing the product nitrogen gas in the product tank 3 from the outlet BO,
And/or the artificial valve 6b is opened to introduce the raw material air in the air tank 2 into the adsorption tower B (pressurizing step). Through this pressure charging process, gas with the same purity as the product nitrogen gas can be placed on the side of the adsorption cylinder outlet Bo, and a decrease in the nitrogen concentration of the gas sent from the adsorption cylinder B to the product tank 3 at the beginning of the next adsorption process can be prevented. be able to.

Step 4 Next, by opening the large mouth valve 6b while leaving the outlet valve 7b open, or by leaving the inlet valve 6b open, the adsorption cylinder B enters the adsorption process, and the blow valve 5 is closed to operate the vacuum pump 4. By doing so, adsorption cylinder A enters the regeneration process. Hereinafter, in steps 5 and 6, the same operations as those in steps 2 and 3 are performed by replacing the adsorption cylinders A and B, and after step 6, the process returns to step 1 and each step is repeated.
This nitrogen gas can be obtained.

Here, the results of an experiment comparing the apparatus of this embodiment in which the above steps were performed and a conventional apparatus in which the upper pressure equalization and the upper and lower pressure equalization were performed simultaneously will be described.

Using a PSA having the configuration shown in FIG. 1, the adsorption pressure was set at 7.0 kg/cd G using air as the raw material gas, and regeneration was performed by reducing the pressure to 100 Torr using a vacuum pump. The adsorption step and the regeneration step were each conducted for 90 seconds, and the product purity and recovery rate were measured when 1 ONrri'/h of product nitrogen gas was continuously taken out. The results are shown in Table 1, Table 2, and Figure 3.

Table 1 shows the product purity (expressed as the concentration of residual oxygen contained in the product nitrogen) and recovery rate when the equalization recovery pressure (the pressure at the end of pressure equalization in the adsorption cylinder pressurized by pressure equalization) is changed. Figure 3 is a graph of this. Furthermore, Table 2 shows the equalization recovery pressure and recovery rate when the pressure equalization step was performed to obtain a product nitrogen gas with a purity of 0.070% residual oxygen.

The recovery rate depends on the equalization recovery pressure when the steps other than the pressure equalization process are the same, and the higher the equalization recovery pressure, the higher the product recovery rate (see Figure 3).

As is clear from Table 1, Table 2, and Figure 3 above, when the product recovery rate is made the same by performing the pressure equalization process using the apparatus of this embodiment The product purity can be improved, and when the product purity is kept the same, the product recovery rate can be improved and the equalization recovery pressure can also be increased.

Note that the present invention is not limited to the PSA shown in the above embodiments, but can also be applied to a PSA equipped with three or more adsorbers and a PSA that produces or purifies other product gases using other adsorbents. It is particularly effective when used in PSA using a velocity separation type adsorbent.

In addition, this pressure equalization method is applicable not only to vacuum regeneration using a vacuum pump as described above, but also to other types of regeneration methods, such as the normal pressure regeneration method that performs regeneration by opening it to the atmosphere, and the purge regeneration method that performs regeneration using product gas. It is valid regardless.

〔Effect of the invention〕

As explained above, the device of the present invention allows the product gas outlet sections of a plurality of adsorption cylinders to communicate with each other through an outlet pressure equalization conduit having an outlet pressure equalization valve, and also connects the product gas outlet sections with other adsorption cylinders. By communicating the raw material gas inlet with a series pressure equalizing conduit having a series pressure equalizing valve, the pressure equalizing process shown in the method of the present invention, that is, the product gas outlet of the adsorption column after the regeneration process has been completed, and the adsorption process can be communicated with each other. After performing an outlet pressure equalization process in which the product gas outlet of the completed adsorption column is communicated with the product gas outlet section to move the gas, the feed gas intake section of the adsorption column whose regeneration operation has been completed and the adsorption column whose adsorption process has been completed are then connected. By implementing the method of the present invention, the gas with high nitrogen concentration remaining in the adsorption cylinder after the adsorption process can be efficiently removed. It can be easily introduced into an adsorption column that has completed the regeneration process.

This allows the pressure in both cylinders to be approximately the same during the pressure equalization process.
That is, it becomes possible to perform the pressure equalization process to a pressure that is completely equalized or close to completely equalized pressure, and more gas can be recovered without causing a decrease in product gas purity.

Therefore, compared to PSA using the conventional pressure equalization method, it is possible to increase the product recovery rate when generating product gas of the same purity, reduce the supply amount of raw material gas, and reduce the equipment cost of the compressor. Operation costs etc. can be reduced. In addition, in the conventional pressure equalization method, product purity drops significantly when the pressure is equalized to near complete pressure equalization in the pressure equalization process, whereas in the method of the present invention, pressure equalization close to complete pressure equalization or complete pressure equalization is performed. Also, since the reduction in product gas purity is very small, more gas can be recovered, which is also advantageous from the viewpoint of pressure recovery, that is, energy recovery.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing one embodiment of the apparatus of the present invention, FIG. 2 is an explanatory diagram showing the operating steps in order, and FIG. 3 is a graph showing experimental results. 1... Pressure fluctuation adsorption separator (PSA) 2... Air tank 3... Product tank 4... Vacuum pump 5...
・Blow valve 6a, 6b...Inlet valve 7a.

Claims (1)

[Scope of Claims] 1. In a pressure fluctuation adsorption type gas separation device that separates gas by switching a plurality of adsorption cylinders filled with adsorbent between an adsorption process and a regeneration process, the product gas outlet portion of the plurality of adsorption cylinders of,
They were communicated with each other by an outlet pressure equalizing conduit having an outlet pressure equalizing valve, and the product gas outlet of one adsorption column and the raw material gas inlet of another adsorption column were communicated with each other by a series pressure equalizing conduit having a series pressure equalizing valve. A pressure fluctuation adsorption type gas separation device characterized by: 2. The pressure fluctuation adsorption type gas separation device according to claim 1, wherein the adsorbent is molecular sieve charcoal. 3. In the method of operating a pressure fluctuation adsorption type gas separation device in which gas is separated by switching a plurality of adsorption cylinders filled with adsorbent between an adsorption process and a regeneration process, the product gas outlet part of the adsorption cylinder after the regeneration process has been completed. After performing an outlet pressure equalization process in which gas is transferred by communicating the product gas outlet of the adsorption column where the adsorption process has been completed, the product gas inlet of the adsorption column where the regeneration operation has been completed and the product gas outlet of the adsorption column where the adsorption process has been completed are carried out. A method of operating a pressure fluctuation adsorption type gas separation device, characterized by performing a series pressure equalization process in which gas is moved by communicating with the product gas outlet of an adsorption column. 4. The pressure fluctuation adsorption gas separation method according to claim 1, wherein the adsorbent is molecular sieve carbon. 5. The total time of the outlet pressure equalization step and the series pressure equalization step is within 30 seconds, and the time of the outlet pressure equalization step is 5.
5. The method of operating a pressure fluctuation adsorption type gas separation apparatus according to claim 4, wherein the pressure fluctuation is within seconds.