JPH0994423A - Gas passing method for pressure swing adsorption type gas separating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the upper limit of space velocity to decrease the diameter of a column by preventing the fluidization of an adsorbent in a pressure swing adsorption type(PSA) as separating device. SOLUTION: In the PSA gas separating device provided with adsorption columns 1A, 1B for executing an adsorption process for obtaining a production gas by adsorbing a separating component in a stock gas to the adsorbent under pressure and a desorption process for desorbing the adsorbed separating component from the adsorbent under reduced pressure, the fluidization of the adsorbent is prevented by making the gas flow in the adsorption columns 1A, 1B downward flow through full processes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas passing method of a pressure swing adsorption type (hereinafter referred to as PSA) gas separator.

[0002]

2. Description of the Related Art A conventional gas separation technique using a PSA gas separation apparatus is shown in FIGS. FIG. 6 is a system diagram of a conventional apparatus, and FIG. 7 shows a gas separation process by the conventional system. The parts indicated by A to D in the lower part of FIG. 7 are the arrows indicating the directions of the gas flows flowing in the adsorption towers 1A and 1B in the steps indicated by A to D in the upper part of FIG. is there.

In this PSA gas separator, the raw material gas is blown by the raw material air blower 2 through the raw material gas line 4 connected to the lower part of the adsorption towers 1A and 1B.
B is fed to B (upflow), and the adsorbent filled between the upper and lower porous discs in the adsorption tower adsorbs the separated components under pressure (adsorption step) and sends the production gas to the production gas line 7. When the amount of adsorption by the adsorbent reaches saturation, the vacuum pump 3 exhausts the inside of the adsorption tower through the desorption line 6 (downflow) to regenerate the adsorbent (desorption process). The adsorption towers 1A and 1B are arranged in parallel, the adsorption step and the adsorption step are alternately performed in the adsorption towers 1A and 1B, and
It is supposed to be repeated.

When one adsorption tower, for example the adsorption tower 1A, completes the adsorption step and the other adsorption tower, for example the adsorption tower 1B, completes the desorption step, the production gas lines of both adsorption towers 1A, 1B are connected. Through the pressure equalizing line 5, a gas is desorbed from the adsorption tower 1A having a high pressure and transferred to the adsorption tower 1B having a low pressure by performing the adsorption step, and a pressure equalization step for equalizing the pressures of both adsorption towers 1A and 1B is performed. .

The adsorption step in the adsorption towers 1A and 1B,
The pressure equalization step and the desorption step are alternately repeated in the adsorption towers 1A and 1B by operating a valve provided in each line, and between the adsorption step and the desorption step. A pressure equalization process is performed.

[0006]

In the conventional PSA gas separation apparatus, as shown in FIG. 6, the raw material gas flow flowing in the adsorption towers 1A and 1B from the raw material gas line 4 to the manufacturing gas line 7 flows upward. Therefore, the flow resistance force that the adsorbent receives and the gravity work in a direction of canceling each other, and when the speed of the raw material gas flow increases, the flow resistance is more predominant and the flow of the adsorbent occurs. This causes pulverization of the adsorbent, which has a significant adverse effect on the performance such as deterioration of the adsorbent performance and inclusion in the product gas.

In the past, in order to prevent fluidization of the adsorbent, it was necessary to reduce the superficial velocity by increasing the column diameter of the adsorption column. For this reason, the degree of freedom of the shape of the adsorption tower is low, and the tower diameter becomes excessively large, especially in the case of a large-capacity machine, and there have been problems such as an arrangement space problem and an excessive weight, resulting in high cost.

The present invention is intended to provide a gas passage method for a PSA gas separation apparatus which can solve the above problems.

[0009]

Means for Solving the Problems The gas passing method of the PSA gas separation apparatus of the present invention takes the following means. (1) An adsorption tower is provided which performs an adsorption step of adsorbing a separation component in a raw material gas under pressure to an adsorbent to obtain a production gas, and a desorption step of desorbing the separated component adsorbed from the adsorbent under reduced pressure. In the pressure swing adsorption type gas separation device,
It is characterized in that the gas flow in the adsorption tower is a downward flow in all steps of adsorption and desorption. (2) In the gas passing method according to (1) above, a plurality of adsorption towers are provided in parallel, the adsorption step and the desorption step are alternately repeated in each adsorption tower, and a plurality of adsorption steps are performed between the adsorption step and the desorption step. In addition to the adsorption and desorption steps, the flow of gas in each adsorption tower of the pressure swing adsorption type gas separation device that performs the pressure equalization step for equalizing the pressure in the tower can be made to be a downflow also in the pressure equalization step. Characterize. (3) In the gas passing method of (2) above, the inside of the plurality of adsorption towers is formed by a pressure equalizing line connecting a line connecting the raw material gas supply lines of the plurality of adsorption towers and a production gas line discharging the production gas. It is characterized by equalizing pressure. (4) In the gas passing method according to (1) or (2) above, a porous empty cylinder connected to a desorption gas line is arranged in the center of the adsorption tower, and desorption gas is introduced from the center of the adsorption tower in the desorption step. Is discharged.

Since the present invention has the above-mentioned constitution, the gas flow in the adsorption tower becomes a downward flow through the adsorption step and the desorption step, or the desorption step, the adsorption step and the pressure equalization step, It is possible to prevent fluidization of the adsorbent in the adsorption tower, increase the superficial velocity in the adsorption tower, and reduce the tower diameter of the adsorption tower.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 1 is a system diagram thereof, FIG. 2 is a cross-sectional view of an adsorption tower in the same embodiment, and FIG. 3 is a gas separation process diagram of the same embodiment.
The portion indicated by D is an arrow indicating the direction of the gas flow flowing in the adsorption towers 1A, 1B in the steps indicated by A to D in the upper portion.

Reference numerals 1A and 1B are cylindrical vertical adsorption towers each containing an adsorbent and arranged in parallel as will be described later.
As shown in FIG. 1, in the adsorption towers 1A and 1B, support plates 11 and 12 composed of perforated plates which are arranged substantially horizontally above and below are provided, and the support plates 11 and 12 are in air under pressure under pressure. Is filled with an adsorbent that adsorbs N ₂ or O ₂ .

Reference numeral 2 is a raw material air blower for supplying raw material air, and a raw material gas line 4 on the discharge side thereof has a valve V, respectively.
The lines 4A and 4B having A-1 and VB-1 are branched, and the lines 4A and 4B are connected to the upper portions of the adsorption towers 1A and 1B above the support plate 11, respectively. Valves VA- are provided below the adsorption plates 1A and 1B below the support plate 12, respectively.
Lines 7A and 7B having 3, VB-3 are connected, and these lines 7A and 7B join to form a production gas line 7.

At the central position of the adsorption towers 1A and 1B,
An empty cylinder 13 is provided, which extends upward from the bottom of the adsorption towers 1A, 1B through the support plates 12, 11 and has its closed upper end slightly above the support plate 11.
The portion between the support plates 11 and 12 is porous, and the porosity of the zero portion is larger than that of the lower portion. The lower end of the empty cylinder 13 is connected to lines 6A and 6B having valves VA-2 and VB-2, respectively, and the lines 6A and 6B join to form a desorption gas line 6 connected to the vacuum pump 3. There is.

Further, one equalizing line 5 is provided,
The lower end of the pressure equalizing line 5 is connected via valves VA-4 and VB-4 to the adsorption towers 1A and 1B of the lines 7A and 7B and the valve VA-.
3 and VB-3, and the upper end of the pressure equalizing line 5 is connected to the adsorption towers 1A and 1B of the lines 4A and 4B and the valve VA via valves VA-5 and VB-5. -1, VB
It is connected to the part between -1 and -1.

In this embodiment, as in the conventional PSA gas separator shown in FIGS. 6 and 7, when the adsorption tower 1A is in the adsorption step, the adsorption tower 1B is in the desorption step and the adsorption tower 1A is desorbed. In the process, the adsorption tower 1B is in the adsorption process, and both adsorption towers 1B are in between the adsorption process and the desorption process.
A pressure equalizing step for equalizing the pressure between A and 1B is performed, and these steps are repeatedly performed in both adsorption towers 1A and 1B.

The case where the adsorption tower 1A is in the adsorption step and the adsorption tower 1B is in the desorption step will be described. Valves VA-1, VA-3, V
B-2 is opened and the other valves are closed. The raw material air is pressurized by the raw material air blower 2 and is fed to the raw material gas line 4 and the valve V.
A-1 enters the upper part of the adsorption tower 1A through the opened line 4A and flows as a downward flow in the adsorption tower 1A, N ₂ or O ₂ in the raw material air is adsorbed by the adsorbent, and N ₂ Alternatively, the O ₂ -rich production gas flows in the production gas line 7 through the line 7A in which the valve VA-3 is opened. On the other hand, the inside of the adsorption tower 1B is connected to the vacuum pump 3 via the line 6B in which the valve VB-2 is opened and the desorption gas line 6 to become a low pressure, and the N ₂ or O ₂ adsorbed by the adsorbent is adsorbed. The desorbed gas is desorbed from the adsorbent to regenerate the adsorbent, and the desorbed gas flows from the portion filled with the adsorbent into the porous empty column 3 provided in the center of the adsorbent tower and surely flows downward in the adsorbent tower 1B. And flows through the line 6B and the desorption gas line 6 and is discharged to the outside of the system by the vacuum pump 3.

The adsorption step of the adsorption tower 1A ends, and the adsorption step of the adsorption tower 1B ends (point X in FIG. 3).
Then, the pressure equalizing step between the adsorption towers 1A and 1B is performed. In this case, the valves VA-4 and VB-5 are opened and the other valves are closed. The adsorption tower 1A has been subjected to the adsorption step and has a high pressure, and the adsorption tower 1B has been subjected to the desorption step and have a low pressure. Therefore, the manufacturing gas remaining in the adsorption tower 1A passes through the pressure equalizing line 5 due to this pressure difference,
The lower part of the adsorption tower 1A enters the upper part of the adsorption tower 1B. As a result, the gas flows in the adsorption towers 1A and 1B both become downward flows. In the adsorption tower 1A, the residual production gas is discharged to the adsorption tower 1B and the pressure is reduced so that the next desorption process can be started smoothly.
The production gas remaining in the adsorption tower 1A is transferred to the chamber and the pressure is increased, so that the next desorption process can be performed smoothly.
Moreover, the production gas can be flown to the production gas line 7 without loss.

When the above pressure equalization process is completed, the adsorption tower 1A
The desorption step is performed in the adsorption tower 1B, and the adsorption step is performed in the adsorption tower 1B. This is because the adsorption step is performed in the adsorption tower 1A and the desorption step is performed in the adsorption tower 1B. Since it corresponds to the reverse, the description thereof is omitted.

Also in the case of the pressure equalization step between the adsorption towers 1A and 1B after the desorption step is performed in the adsorption tower 1A and the adsorption step is performed in the adsorption tower 1B, the relationship between the adsorption towers is as described above. The description is omitted because it corresponds to the case where the relationship between the two adsorption towers in the pressure equalization step after the adsorption step is performed in the adsorption tower 1A and the desorption step is performed in the adsorption tower 1B is reversed.

The gas separation process in the adsorption towers 1A and 1B described above is shown in FIG. 3, and A in the lower part of FIG.
Arrows in the adsorption towers 1A and 1B in ~ D indicate the gas flow directions in AD in the upper part of the figure.

As described above, in the present embodiment, in each adsorption tower, the gas flow can be always made a downward flow through the adsorption step, the desorption step and the pressure equalization step. Therefore, in order to make the flow resistance of the adsorbent downward in the same vertical direction as the motion through each process, it is possible to prevent the fluidization of the adsorbent, and to raise the upper limit of the superficial velocity in the adsorption tower to increase the adsorption tower. The size of the tower can be reduced and the flexibility of the tower shape can be increased.

Incidentally, the conventional 0.5-0.6 mm / se
In the present embodiment, the upper limit of the superficial velocity of the adsorption tower set to c can be set to 1 m / sec or more, and the tower diameter of the adsorption tower is correspondingly reduced to improve the flexibility of the tower shape. Can be made.

A second embodiment of the present invention will be described with reference to FIG. The present embodiment uses a single tower type adsorption tower, which has a built-in adsorption tower and has an empty space blower 2 and a valve V-1 above an adsorption tower 1 having a structure similar to that shown in FIG. Is connected to a raw material gas line 4, a desorption line 6 having a valve V-2 and a production gas line 7 having a valve V-3 are connected to the lower part of the adsorption tower 1, and the desorption line 6 is vacuumed. No pump is provided.

In this embodiment, the adsorption process and the desorption process are performed as in the first embodiment of the present invention, but the pressure equalization process is not performed (see FIG. 4 (b)). Also,
Since the raw material gas line 4 is connected to the upper part of the adsorption tower 1 and the desorption line 6 and the production gas line 7 are connected to the lower part of the adsorption tower 1, as shown by the arrow in FIG. The gas flow inside can always be a downward flow.

A third embodiment of the present invention will be described with reference to FIG. This embodiment is the second embodiment of the present invention.
The same single-column type adsorption tower as in the above embodiment is used, but in addition to the source gas line 4, desorption line 6 and production gas line 7 of the adsorption tower 1 in the second embodiment of the present invention, , Pressure equalization lines 21 and 22 connected to the upper part and the lower part of the adsorption tower and having valves V-4 and V-5, respectively, and pressure equalization lines 21 and 22 are provided, and a vacuum pump 6 is provided in the desorption line 6. Has been.

In this embodiment, the adsorption step and the desorption step are performed in the same manner as in the second embodiment of the present invention, but when the pressure of the adsorption tower 1 is reduced, the valve V-5 is opened and the inside of the adsorption tower 1 is opened. Of the gas is discharged to the atmosphere through the pressure equalizing line 22 (see C in FIG. 5B).
(Equal pressure equalization), and when the pressure in the adsorption tower 1 is restored, the valve V-4 is opened to suck the atmosphere into the adsorption tower 1 through the equalization line 21 (A equalization pressure in FIG. 5B). Also in this embodiment, FIG.
(A) As shown by the middle arrow, the gas flow in the adsorption tower 1 can always be a downward flow.

[0028]

As described above, according to the present invention, the fluidization of the adsorbent can be prevented through each step by always making the gas flow in the adsorption tower downward. by this,
The upper limit of the superficial velocity in the adsorption tower can be increased to reduce the diameter of the adsorption tower, and the degree of freedom of the tower shape can be improved. In addition, along with this, it is possible to reduce the weight and cost of the adsorption tower, and it is possible to design an adsorption tower of a free form that fits the arrangement space, and it is easy to apply it to a large capacity machine.

[Brief description of drawings]

FIG. 1 is a system diagram of a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the adsorption tower of the same embodiment.

FIG. 3 is a gas separation process diagram in the same embodiment.

FIG. 4 shows a second embodiment of the present invention, and FIG.
Is a system diagram thereof, and FIG. 4B is a process diagram thereof.

FIG. 5 shows the third embodiment of the present invention, and FIG.
Is a system diagram thereof, and FIG. 5 (b) is a process diagram thereof.

FIG. 6 is a system diagram of a conventional PSA gas separation device.

FIG. 7 is a gas separation process diagram of the conventional PSA gas separation device.

[Explanation of symbols]

 1, 1A, 1B Adsorption tower 2 Raw material air blower 3 Vacuum pump 4 Raw material gas line 5 Pressure equalizing line 6 Desorption gas line 7 Production gas line 13 Porous empty cylinder V1 to V5 valve VA-1 to VA-5 valve VB- 1-VB-5 valve

Claims (4)

[Claims] 1. An adsorption tower which performs an adsorption step of adsorbing a separation component in a raw material gas under pressure to an adsorbent to obtain a production gas, and a desorption step of desorbing the adsorbed separation component from the adsorbent under reduced pressure. In the pressure swing adsorption type gas separation apparatus comprising the above, the gas flow in the pressure swing adsorption type gas separation apparatus is characterized in that the flow of gas in the adsorption tower is made a downward flow in all steps of adsorption and desorption. 2. A pressure equalizing device in which a plurality of adsorption towers are provided in parallel, the adsorption step and the desorption step are alternately repeated in each adsorption tower, and the pressures in the plurality of adsorption towers are equalized between the adsorption step and the desorption step. The gas flow in each adsorption tower of the pressure swing adsorption type gas separation device adapted to perform the steps is made to be a downflow also in the pressure equalization step in addition to the adsorption and desorption steps. Of the pressure swing adsorption type gas separation device of the above. 3. The pressure in the plurality of adsorption towers is equalized by a pressure equalizing line connecting a line connecting the raw material gas supply lines of the plurality of adsorption towers and a production gas line discharging the production gas. The gas passing method of the pressure swing adsorption type gas separation device according to claim 2. 4. The desorption gas is discharged from the center of the adsorption tower in the desorption step by disposing a porous hollow cylinder connected to the desorption gas line in the center of the adsorption tower. 2. The gas passing method of the pressure swing adsorption type gas separation device according to 2.