Device and process for secondary adsorption of PSA (Pressure Swing Adsorption) separated finished product gas participating in pressure-equalizing reflux

Abstract

The invention discloses a device and a process for secondary adsorption of PSA (Pressure Swing Adsorption) separated finished product gas participating in pressure-equalizing reflux, the device comprises an adsorption tower group, the adsorption tower group is mainly composed of two adsorption towers connected in parallel, and the adsorption tower group is connected with a gas inlet end and an emptying end and can complete a cyclic adsorption process; comprising a plurality of valves, the valves are connected through pipelines, the flow direction and flow of fluid in the pipelines can be controlled by controlling opening and closing and opening degrees of the valves, and then part of finished gas participates in pressure-equalizing backflow to perform a secondary adsorption process, so that energy consumption is reduced; comprising a plurality of indicating instruments and measuring instruments; and safe and efficient operation of the process can be ensured through indication of the instrument and measured parameters. According to the invention, part of finished gas participates in the pressure-equalizing reflux process, and adsorbed gas can be prevented from penetrating too early so as to ensure full play of an adsorbent; and compared with the traditional PSA nitrogen-making system, the system has the advantages that the operation energy consumption can be reduced by about 10%, and the productivity can be improved by about 10%.

Description

Technical Field

[0001] The invention relates to the technical field of industrial separation and nitrogen production, in particular to a device and a process for secondary adsorption of finished gas after PSA separation by pressure equalization reflux. Background Art

[0002] At present, PSA technology, as one of the main technologies for industrial nitrogen production, has the characteristics of wide application and many process influencing factors. Among them, process energy consumption and adsorbent regeneration capacity are two extremely important factors limiting the development of PSA technology. Whether the PSA process energy consumption can be reduced and the adsorbent regeneration capacity can be improved during process operation is the key to whether PSA technology can maintain process advancement and create greater production benefits.

[0003] However, for PSA technology, the pressure during process operation is high, which leads to high energy consumption, and the air flow at the bottom of the adsorption tower is easy to penetrate, resulting in a decrease in adsorbent efficiency.

[0004] Therefore, reducing process energy consumption and improving adsorbent regeneration capacity are of great significance to PSA technology. According to a large-scale VPSA nitrogen and oxygen cogeneration device with multiple towers proposed in the publication number: CN114849424A, a technical solution of multiple towers for nitrogen and oxygen production is adopted. When the incoming gas volume is large, the efficiency is high. However, when the incoming gas flow is small, the process system investment return rate is low and the problem of adsorption penetration is not considered. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies in the prior art and to provide a device and process for secondary adsorption in which the finished gas after PSA separation participates in pressure equalization reflux. By allowing part of the finished gas to reflux and perform a two-tower pressure equalization process, the energy consumption of the process operation can be reduced, the adsorbent regeneration capacity can be improved, and the production capacity can be increased.

[0006] The present invention is achieved through the following technical solutions:

[0007] A device for secondary adsorption of finished gas after PSA separation by pressure equalization reflux, comprising: a group of adsorption towers, multiple valves, a buffer tank, and indicating instruments and measuring instruments. The adsorption tower group is mainly composed of an adsorption tower (one) and an adsorption tower (two) connected in parallel; each of the valves is connected by a pipeline; the indicating and measuring instruments include a pressure indicating instrument, a purity detection instrument, and a flow detection instrument.

[0008] As a further improvement of the technical solution of the invention, the adsorption tower (one), the adsorption tower (two) and the buffer tank are connected via pipelines and valves (nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen), and the adsorption tower (one) and the adsorption tower (two) are connected to the air inlet end and the exhaust end via pipelines and valves (four, five, six, seven, nineteen, twenty).

[0009] As a further improvement of the technical solution of the invention, when the adsorption tower (one) is performing adsorption, valves (four, five, eleven) are opened, valves (six, twelve) are closed, and low-pressure air enters the adsorption tower (one) from the air inlet end through valves (four, five) for adsorption; at the same time, the adsorption tower (two) is performing desorption, valve (twenty) is opened, valve (nineteen) is closed, and the adsorbed material in the adsorption tower (two) is extracted from the exhaust end to achieve desorption.

[0010] As a further improvement of the technical solution of the invention, the finished gas in the adsorption tower (one) will flow out through the valve (eleven). At this time, the valves (thirteen, twelve, and twenty-one) are opened. It can also flow out through the valve (nine). At this time, the valves (fourteen, fifteen, and sixteen) are opened and the valve (ten) is closed. A part of the finished gas flows into the buffer tank through the valve (thirteen) as the product, and then passes through the valve (twenty-one). After the purity and flow are detected by the purity detection instrument and the flow detection instrument, it flows out; the other part of the finished gas flows into the adsorption tower (two) through the valve (twelve). At this time, the valves (seven and eighteen) are opened, and the two towers are connected to each other to complete the equalization of pressure drop and equalization of pressure rise respectively.

[0011] As a further improvement of the technical solution of the invention, when the pressures of the two towers are balanced, that is, when the pressures indicated by the pressure indicating instrument (eight) are consistent, the valves (five and twenty) are closed, the valves (six and nineteen) are opened, the adsorption tower (one) begins to be evacuated, and the adsorption tower (two) finally increases the pressure and then begins the adsorption process, and this cycle is repeated.

[0012] As a further improvement to the technical solution of the invention, all valves are controlled and switched by PLC according to the process sequence.

[0013] As a further improvement to the technical solution of the invention, the finished gas reflux ratio and reflux rate can be determined according to process requirements.

[0014] As a further improvement of the technical solution of the invention, a process of secondary adsorption of the product gas after PSA separation by pressure equalization reflux includes the following steps:

[0015] Step S1: The purified raw air is compressed to a certain pressure by a low-pressure air compressor and enters the process system to provide it with continuous and stable airflow and pressure;

[0016] Step S2: Special molecular sieves are installed in the adsorption tower (1) and the adsorption tower (2), and the opening and closing of the valves are controlled by the PLC control system. When the purified compressed air enters the air inlet end of the adsorption tower (1) and flows to the air outlet end through the molecular sieve, the product gas flows out from the air outlet end of the adsorption tower because the adsorption capacity of the product gas on the molecular sieve is relatively small; at the same time, the adsorption tower (2) performs a desorption process, and the adsorbed material in the adsorption tower (2) is extracted from the emptying end to achieve desorption;

[0017] Step S3: A portion of the finished gas flowing out of the adsorption tower (I) enters the buffer tank as a product, and then flows out of the process system after purity detection and flow detection, and the other portion of the finished gas flows into the adsorption tower (II) through a valve for pressure equalization reflux process. At this time, the valve between the two adsorption towers is opened, and the two towers are interconnected to complete pressure equalization and pressure equalization respectively.

[0018] Step S4: When the pressures of the two towers are balanced, that is, the pressures indicated by the pressure indicating instruments are consistent, valves (five and twenty) are closed, valves (six and nineteen) are opened, the adsorption tower (one) begins to be evacuated, and the adsorption tower (two) finally increases the pressure and then begins the adsorption process, and this cycle continues.

[0019] In summary, the present invention has the following beneficial effects:

[0020] 1. The process of the present invention can prevent the airflow from penetrating the bottom of the adsorption tower by allowing part of the finished gas to reflux, thereby ensuring that the adsorbent efficiency can be better exerted and effectively increasing the production capacity by about 10%.

[0021] 2. The process of the present invention uses pressure equalization operation to allow the two towers to communicate with each other, achieving equal pressure drop and equal pressure increase, which can effectively reduce the energy consumption of the process operation and can reduce energy consumption by about 10%.

[0022] 3. The process of the present invention performs secondary adsorption by having the finished gas participate in the equalized pressure reflux, so as to realize the interaction of the adsorption and desorption processes of each adsorption tower in the adsorption tower group through the equalized pressure drop and equalized pressure increase operation of the two towers, thereby ensuring that the adsorption and desorption are carried out smoothly and continuously, and the gas flow product is continuously output.

[0023] 4. The process of the present invention is universal to a certain extent and is suitable for the separation and purification of most gases, and has a wider range of applications.

[0024] 5. The overall operating pressure of the process of the present invention is low, does not meet the pressure vessel management level requirements, and is safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of a system for secondary adsorption of finished gas after PSA separation by pressure equalization reflux (finished gas is introduced before the tank) according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of a system for secondary adsorption of finished gas after PSA separation by pressure equalization reflux (the finished gas is introduced into the tank body) according to an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the structure of a system for secondary adsorption of finished gas after PSA separation in an embodiment of the present invention by pressure equalization reflux (finished gas is introduced after the tank);

[0028] Figure 4This is a schematic diagram of a process flow of secondary adsorption of product gas after PSA separation by pressure equalization reflux according to an embodiment of the present invention.

[0029] The numbers in the figure are:

[0030] 1- Adsorption tower one; 2- Adsorption tower two; 3- Buffer tank; 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21- Valves; 8- Pressure indicating instrument; 22- Purity detection instrument; 23- Flow detection instrument. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0032] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, upper end, lower end, top, bottom...) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0033] In the present invention, unless otherwise clearly defined and limited, the term "connection" should be understood in a broad sense, for example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features; in addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0035] The following is combined with Figure 1-4 The present invention is described in further detail.

[0036] A system for secondary adsorption of finished gas after PSA separation by pressure equalization reflux includes a set of adsorption towers, multiple valves, a buffer tank, and indicating instruments and measuring instruments. The adsorption tower set is mainly composed of an adsorption tower 1 and an adsorption tower 2 connected in parallel; the valves are connected by pipelines; and the indicating and measuring instruments include a pressure indicating instrument (8), a purity detection instrument (22), and a flow detection instrument (23).

[0037] Specifically, in the present embodiment, the adsorption tower 1, the adsorption tower 2 and the buffer tank (3) are connected via pipelines and valves (9, 10, 11, 12, 13, 14, 15, 16, 17, 18), and the adsorption tower 1 and the adsorption tower 2 are connected to the air inlet end and the exhaust end via pipelines and valves (4, 5, 6, 7, 19, 20).

[0038] Specifically, in the present embodiment, when adsorption tower 1 is performing adsorption, valves (4, 5, 11) are opened, valves (6, 12) are closed, and low-pressure air enters adsorption tower 1 from the air inlet end through valves (4, 5) for adsorption; at the same time, adsorption tower 2 is performing desorption, valve (20) is opened, valve (19) is closed, and the adsorbed material in adsorption tower 2 is extracted from the exhaust end to achieve desorption.

[0039] Specifically, in the present embodiment, the finished gas in the adsorption tower 1 will flow out through the valve (11). At this time, the valves (13, 12, 21) are opened. It can also flow out through the valve (9). At this time, the valves (14, 15, 16) are opened and the valve (10) is closed. A part of the finished gas flows into the buffer tank (3) through the valve (13) as the product, and then flows out through the valve (21) and passes through the purity detection instrument (22) and the flow detection instrument (23) for purity and flow detection; the other part of the finished gas flows into the adsorption tower 2 through the valve (12). At this time, the valves (7, 18) are opened, and the two towers are connected to each other to respectively complete the pressure drop and pressure rise.

[0040] Specifically, in the present embodiment, when the pressures of the two towers are balanced, that is, when the pressures indicated by the pressure indicating instrument (8) are consistent, the valves (5, 20) are closed, the valves (6, 19) are opened, the adsorption tower 1 begins to be evacuated, and the adsorption tower 2 finally increases the pressure before the adsorption process begins, and this cycle continues.

[0041] Specifically, in this embodiment, a secondary adsorption process is performed by subjecting the product gas after PSA separation to pressure equalization reflux, including the following steps:

[0042] Step S1: The purified raw air is compressed to a certain pressure by a low-pressure air compressor and enters the process system to provide it with continuous and stable airflow and pressure;

[0043] Step S2: Special molecular sieves are installed in the adsorption tower 1 and the adsorption tower 2, and the opening and closing of the valves are controlled by the PLC control system. When the purified compressed air enters the air inlet end of the adsorption tower 1 and flows to the air outlet end through the molecular sieve, the product gas flows out from the air outlet end of the adsorption tower because the adsorption capacity of the product gas on the molecular sieve is relatively small; at the same time, the adsorption tower 2 performs a desorption process, and the adsorbed material in the adsorption tower 2 is extracted from the emptying end to achieve desorption;

[0044] Step S3: A portion of the finished gas flowing out of the adsorption tower 1 enters the buffer tank as a product, and then flows out of the process system after purity detection and flow detection, and the other portion of the finished gas flows into the adsorption tower 2 through a valve for pressure equalization reflux process. At this time, the valve between the two adsorption towers is opened, and the two towers are interconnected to complete pressure equalization and pressure equalization respectively.

[0045] Step S4: When the pressures of the two towers are balanced, that is, the pressures indicated by the pressure indicating instruments are consistent, valves (5, 20) are closed, valves (6, 19) are opened, adsorption tower 1 begins to be evacuated, and adsorption tower 2 finally increases its pressure before the adsorption process begins, and this cycle continues.

[0046] Embodiment 1:

[0047] Reference Figure 1-4 A system for secondary adsorption of finished gas after PSA separation by pressure equalization reflux includes an adsorption tower group, multiple valves, a buffer tank, and indicating instruments and measuring instruments. The adsorption tower group is mainly composed of an adsorption tower 1 and an adsorption tower 2 in parallel; the valves are connected by pipelines; the indicating and measuring instruments include a pressure indicating instrument (8), a purity detection instrument (22) and a flow detection instrument (23).

[0048] The adsorption tower 1, the adsorption tower 2 and the buffer tank (3) are connected via pipelines and valves (9, 10, 11, 12, 13, 14, 15, 16, 17, 18), and the adsorption tower 1 and the adsorption tower 2 are connected at the air inlet end and the exhaust end via pipelines and valves (4, 5, 6, 7, 19, 20).

[0049] When adsorption tower 1 is performing adsorption, valves (4, 5, 11) are opened, valves (6, 12) are closed, and low-pressure air enters adsorption tower 1 from the air inlet end through valves (4, 5) for adsorption; at the same time, adsorption tower 2 is performing desorption, valve (20) is opened, valve (19) is closed, and adsorbed material in adsorption tower 2 is extracted from the exhaust end to achieve desorption.

[0050] The finished gas in the adsorption tower 1 will flow out through valve (11). At this time, valves (13, 12, 21) are open. It can also flow out through valve (9). At this time, valves (14, 15, 16) are open and valve (10) is closed. A part of the finished gas flows into the buffer tank (3) through valve (13) as a product, and then flows out through valve (21) and passes through purity detection instrument (22) and flow detection instrument (23) for purity and flow detection; another part of the finished gas flows into the adsorption tower 2 through valve (12). At this time, valves (7, 18) are open, and the two towers are connected to each other to complete the pressure drop and pressure rise. Figure 1-3 As shown, the finished gas can flow back before, after or at the tank body of the buffer tank (3).

[0051] When the pressures of the two towers are balanced, that is, the pressures indicated by the pressure indicating instrument (8) are consistent, the valves (5, 20) are closed, the valves (6, 19) are opened, the adsorption tower 1 begins to be evacuated, and the adsorption tower 2 finally increases the pressure before the adsorption process begins, and this cycle continues.

[0052] In this embodiment, a secondary adsorption process is performed by pressure equalization reflux of the product gas after PSA separation, including the following steps:

[0053] Step S1: The purified raw air is compressed to a certain pressure by a low-pressure air compressor and enters the process system to provide it with continuous and stable airflow and pressure;

[0054] Step S2: Special molecular sieves are installed in the adsorption tower 1 and the adsorption tower 2, and the opening and closing of the valves are controlled by the PLC control system. When the purified compressed air enters the air inlet end of the adsorption tower 1 and flows to the air outlet end through the molecular sieve, the product gas flows out from the air outlet end of the adsorption tower because the adsorption capacity of the product gas on the molecular sieve is relatively small; at the same time, the adsorption tower 2 performs a desorption process, and the adsorbed material in the adsorption tower 2 is extracted from the emptying end to achieve desorption;

[0055] Step S3: A portion of the finished gas flowing out of the adsorption tower 1 enters the buffer tank as a product, and then flows out of the process system after purity detection and flow detection, and the other portion of the finished gas flows into the adsorption tower 2 through a valve for pressure equalization reflux process. At this time, the valve between the two adsorption towers is opened, and the two towers are interconnected to complete pressure equalization and pressure equalization respectively.

[0056] Step S4: When the pressures of the two towers are balanced, that is, the pressures indicated by the pressure indicating instruments are consistent, valves (5, 20) are closed, valves (6, 19) are opened, adsorption tower 1 begins to be evacuated, and adsorption tower 2 finally increases its pressure before the adsorption process begins, and this cycle continues.

[0057] Compared with the prior art, the present invention provides a process for secondary adsorption in which the finished gas after PSA separation participates in pressure equalization reflux, and the process mainly includes adsorption, part of the finished gas refluxes to participate in the pressure equalization process, pressure drop and pressure increase, and desorption. The system includes two adsorption towers, a buffer tank, connecting pipes, control valves, indicating instruments and measuring instruments. By allowing part of the finished gas to reflux to participate in the pressure equalization adsorption operation, the adsorption and desorption processes can be carried out simultaneously, and switched synchronously according to the timing control; compared with the traditional PSA nitrogen production system, it can reduce the operating energy consumption by about 10% and increase the production capacity by about 10%. The present invention has the following beneficial effects:

[0058] 1. The process of the present invention can prevent the airflow from penetrating the bottom of the adsorption tower by allowing part of the finished gas to reflux, thereby ensuring that the adsorbent efficiency can be better exerted and effectively increasing the production capacity by about 10%.

[0059] 2. The process of the present invention uses pressure equalization operation to allow the two towers to communicate with each other, achieving equal pressure drop and equal pressure increase, which can effectively reduce the energy consumption of the process operation and can reduce energy consumption by about 10%.

[0060] 3. The process of the present invention performs secondary adsorption by having the finished gas participate in the equalized pressure reflux, so as to realize the interaction of the adsorption and desorption processes of each adsorption tower in the adsorption tower group through the equalized pressure drop and equalized pressure increase operation of the two towers, thereby ensuring that the adsorption and desorption are carried out smoothly and continuously, and the gas flow product is continuously output.

[0061] 4. The process of the present invention is universal to a certain extent and is suitable for the separation and purification of most gases, and has a wider range of applications.

[0062] 5. The overall operating pressure of the process of the present invention is low, does not meet the pressure vessel management level requirements, and is safer.

[0063] Embodiment 2:

[0064] This embodiment takes nitrogen production as an example. Figure 1 , 4 A system for secondary adsorption of finished gas after PSA separation by pressure equalization reflux includes an adsorption tower group, multiple valves, a buffer tank, and indicating instruments and measuring instruments. The adsorption tower group is mainly composed of an adsorption tower 1 and an adsorption tower 2 in parallel; the valves are connected by pipelines; the indicating and measuring instruments include a pressure indicating instrument (8), a purity detection instrument (22) and a flow detection instrument (23).

[0065] The adsorption tower 1, the adsorption tower 2 and the buffer tank (3) are connected via pipelines and valves (9, 10, 11, 12, 13, 14, 15, 16, 17, 18), and the adsorption tower 1 and the adsorption tower 2 are connected at the air inlet end and the exhaust end via pipelines and valves (4, 5, 6, 7, 19, 20).

[0066] When adsorption tower 1 is performing adsorption, valves (4, 5, 11) are opened, valves (6, 12) are closed, and low-pressure air enters adsorption tower 1 from the air inlet end through valves (4, 5) for adsorption; at the same time, adsorption tower 2 is performing desorption, valve (20) is opened, valve (19) is closed, and adsorbed material in adsorption tower 2 is extracted from the exhaust end to achieve desorption.

[0067] Since O2 has a greater adsorption capacity on molecular sieves than nitrogen, it is adsorbed preferentially; O2, CO2 and H2O are adsorbed, and the finished nitrogen gas in adsorption tower 1 will flow out through valve (11). At this time, valves (13, 12, 21) are opened. It can also flow out through valve (9). At this time, valves (14, 15, 16) are opened and valve (10) is closed. A portion of the finished nitrogen gas flows into the buffer tank (3) through valve (13) as a product, and then passes through valve (21). It is then passed through purity detection instrument (22) and flow detection instrument (23) for purity and flow detection before flowing out; another portion of the finished nitrogen gas flows into adsorption tower 2 through valve (12). At this time, valves (7, 18) are opened, and the two towers are connected to each other to complete equal pressure drop and equal pressure rise respectively. Figure 1-3 As shown, the finished gas nitrogen can be refluxed before, after or at the tank body of the buffer tank (3).

[0068] When the pressures of the two towers are balanced, that is, the pressures indicated by the pressure indicating instrument (8) are consistent, the valves (5, 20) are closed, the valves (6, 19) are opened, the adsorption tower 1 begins to be evacuated, and the adsorption tower 2 finally increases the pressure before the adsorption process begins, and this cycle continues.

[0069] Table 1 below is a comparison table of different PSA processes.

[0070] Table 1: Comparison of different PSA processes

[0071]

[0072] It can be seen from the table that compared with the traditional PSA process, the operating energy consumption of the process of the present invention is 10% lower than that of the existing process, and the production capacity is increased by about 10%.

[0073] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A device for secondary adsorption of product gas after PSA separation by pressure equalization reflux, characterized in that: The invention comprises an adsorption tower group, a plurality of valves, a buffer tank (3) and indicating and measuring instruments; the adsorption tower group is mainly composed of an adsorption tower 1 (1) and an adsorption tower 2 (2) connected in parallel; the plurality of valves are connected by pipelines; the adsorption tower 1 (1), the adsorption tower 2 (2) and the buffer tank (3) are connected by pipelines and valves (9, 10, 11, 12, 13, 14, 15, 16, 17, 18); the adsorption tower 1 (1) and the adsorption tower 2 (2) are connected at the air inlet end and the air discharge end by pipelines and valves (4, 5, 6, 7, 19, 20).

2. The device for secondary adsorption of the product gas after PSA separation by pressure equalization reflux according to claim 1, characterized in that: The indicating and measuring instruments include a pressure indicating instrument (8), a purity detection instrument (22) and a flow detection instrument (23).

3. The device for secondary adsorption of the product gas after PSA separation by pressure equalization reflux according to claim 1, characterized in that: When the adsorption tower 1 (1) is performing adsorption, the valves (4, 5, 11) are opened, the valves (6, 12) are closed, and low-pressure air enters the adsorption tower 1 (1) from the air inlet end through the valves (4, 5) for adsorption; at the same time, the adsorption tower 2 (2) is performing desorption, the valve (20) is opened, the valve (19) is closed, and the adsorbed material in the adsorption tower 2 (2) is extracted from the exhaust end to achieve desorption.

4. The device for secondary adsorption of the product gas after PSA separation by pressure equalization reflux according to claim 2, characterized in that: The finished gas in the adsorption tower 1 (1) will flow out through the valve (11). At this time, the valves (13, 12, 21) are opened. It can also flow out through the valve (9). At this time, the valves (14, 15, 16) are opened and the valve (10) is closed. A part of the finished gas flows into the buffer tank (3) through the valve (13) as a product, and then flows out through the valve (21) after being tested for purity and flow by the purity detection instrument (22) and the flow detection instrument (23); another part of the finished gas flows into the adsorption tower 2 (2) through the valve (12). At this time, the valves (7, 18) are opened, and the two towers are interconnected to respectively complete the pressure drop and pressure increase.

5. The device for secondary adsorption of the product gas after PSA separation by pressure equalization reflux according to claim 4, characterized in that: When the pressures of the adsorption tower 1 (1) and the adsorption tower 2 (2) are balanced, that is, when the pressures indicated by the pressure indicating instrument (8) are consistent, the valves (5, 20) are closed, the valves (6, 19) are opened, the adsorption tower 1 (1) begins to be evacuated, and the adsorption tower 2 (2) finally increases its pressure before starting the adsorption process, and this cycle continues.

6. The device for secondary adsorption of the product gas after PSA separation by pressure equalization reflux according to claim 1, characterized in that: Each of the valves is controlled and switched by PLC according to the process sequence.

7. The device for secondary adsorption of the product gas after PSA separation by pressure equalization reflux according to claim 1, characterized in that: The product gas reflux ratio and reflux rate are determined according to process requirements.

8. A process for secondary adsorption of product gas after PSA separation by pressure equalization reflux, characterized in that: The following steps are involved: Step S1, the purified raw air is compressed to a certain pressure by a low-pressure air compressor and enters the process system to provide it with continuous and stable airflow and pressure; Step S2, adsorption tower 1 (1) and adsorption tower 2 (2) are equipped with special molecular sieves, and the opening and closing of the valves are controlled by a PLC control system. When the purified compressed air enters the air inlet of adsorption tower 1 (1) and flows to the air outlet through the molecular sieve, the product gas flows out from the air outlet of the adsorption tower because the adsorption capacity of the product gas on the molecular sieve is relatively small; at the same time, the adsorption tower 2 (2) performs a desorption process, and the adsorbed material in the adsorption tower 2 (2) is extracted from the exhaust end to achieve desorption; Step S3, a part of the finished gas flowing out of the adsorption tower 1 (1) enters the buffer tank as a product, and then flows out of the process system after purity detection and flow detection, and the other part of the finished gas flows into the adsorption tower 2 (2) through a valve to perform a pressure equalization reflux process. At this time, the valve between the two adsorption towers is opened, and the two towers are connected to each other to respectively complete the pressure drop and pressure increase; Step S4: When the pressures of the two towers are balanced, that is, the pressures indicated by the pressure indicating instruments are consistent, the valves (5, 20) are closed, the valves (6, 19) are opened, the adsorption tower 1 (1) starts to be evacuated, and the adsorption tower 2 (2) finally increases the pressure and starts the adsorption process, and the cycle continues.

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