A pressure swing adsorption oxygen generator

Abstract

The present invention relates to a pressure swing adsorption oxygen generator, in which a part of the oxygen gas flow discharged from the top of the adsorption tank is refluxed into the raw gas tank, mixed with air to form a high-oxygen raw gas for air separation oxygen production. Since the nitrogen content in the raw gas is diluted by the refluxed oxygen, the pressure loss of the gas flow caused by nitrogen adsorption when passing through the bed layer is smaller than that of direct air feeding, thereby ensuring that the molecular sieve particles at the top of the adsorption tank are in a relatively higher pressure environment, thereby having a higher adsorption and separation capacity, and increasing the nitrogen adsorption amount of the entire bed layer; by using molecular sieve particles with gradient particle sizes, the distribution of bed resistance and nitrogen adsorption amount at the bed height is improved, so that the top of the bed layer in the low pressure environment caused by the dual reasons of bed resistance and nitrogen adsorption in the traditional filling scheme has a relatively higher pressure environment and nitrogen adsorption performance (caused by high specific surface area) due to non-pressure reasons; in order to overcome the reverse placement problem caused by the filling layer with gradient particle sizes, a plurality of reverse placement branches are arranged in the adsorption tank to assist in reverse discharge exhaust, which greatly improves the reverse discharge exhaust efficiency.

Description

Technical Field

[0001] The invention relates to a medical device, in particular to a pressure swing adsorption oxygen generator. Background Art

[0002] Oxygen generator is a common medical equipment. At present, conventional medical oxygen generators can be divided into two categories according to their oxygen production principles: one is to produce oxygen by electrolyzing water; the other is to produce oxygen by separating air through molecular sieve adsorption, namely pressure swing adsorption (PSA). The electrolysis of water oxygen production method has low separation cost, low noise, and high oxygen production concentration, but it is easy to cause safety hazards. Although the theoretical maximum concentration of molecular sieve oxygen production is only 96%, which is lower than that of electrolysis of water oxygen production and cryogenic oxygen production (mainly used for large-scale industrial oxygen production), its equipment is simple, safe, and the oxygen production concentration can meet most clinical oxygen needs. Therefore, it is currently the main method for clinical prevention and treatment of patient hypoxia.

[0003] The core component of PSA oxygen production is the molecular sieve adsorption tank. At present, the mainstream molecular sieve adsorption tanks all adopt the fixed bed filling mode, that is, the granular zeolite molecular sieves are stacked and filled in the tank body. During adsorption, the air is allowed to pass through the bed layer in a predetermined direction to achieve the adsorption of nitrogen or oxygen in the air. In this process, in order to ensure the outlet oxygen concentration, it is necessary to ensure sufficient bed thickness (referring to the path of air passing through the bed layer) so that the nitrogen in the air flow is gradually adsorbed completely during the process of air passing through the bed layer. Since the nitrogen content in the air accounts for 78%; there is a significant pressure drop at both ends of the bed, which causes the molecular sieves at both ends of the bed to show different adsorption efficiencies (high pressure on the upstream side, large molecular sieve adsorption capacity; low pressure on the downstream side, small molecular sieve adsorption capacity), which leads to the need to use a larger bed thickness to ensure the outlet oxygen content, and will lead to low utilization of the molecular sieve on the downstream side; furthermore, since the nitrogen content in the airflow contacted by the upstream molecular sieve is relatively large, it will reach adsorption saturation first and lose its separation function; at this time, the upstream molecular sieve is still in a relatively low-pressure working environment due to the large amount of nitrogen in the airflow that has been adsorbed, and its relative adsorption capacity is also close to saturation. Therefore, in order to provide a relatively long adsorption working cycle to allow the desorption and regeneration process of another adsorption tank to be completed, it is necessary to fill the adsorption tank with a sufficient amount of molecular sieve adsorbent to cope with the premature adsorption saturation time of the upstream molecular sieve. However, the excess molecular sieve adsorbent will lead to greater bed resistance, thereby further widening the difference in adsorption capacity between the upstream and downstream adsorbents. Summary of the invention

[0004] In order to solve the problems in the prior art, the present invention provides an oxygen concentrator. The specific scheme is as follows:

[0005] Provided is a pressure swing adsorption oxygen generator, comprising two left and right molecular sieve adsorption tanks, an air compressor and a raw gas tank; the air compressor is connected to the raw gas tank and supplies air thereto; the raw gas tank is connected to the air inlets at the bottom of the left tank and the right tank through left and right raw gas pipes, respectively; the left and right raw gas pipes are respectively provided with air inlet valves; the left and right tanks are filled with molecular sieve adsorbents for adsorbing nitrogen in the raw gas; the exhaust ports at the tops of the left and right tanks are connected to the product gas pipes through left and right exhaust pipes, respectively; the left and right exhaust pipes are respectively provided with exhaust valves; a certain position on the left and right raw gas pipes between the air inlet valve and the air inlet of the corresponding adsorption tank is connected to the reverse pipe through a pipeline with a reverse valve; a certain position on the left and right exhaust pipes between the exhaust valve and the exhaust port of the corresponding adsorption tank is connected through a pressure equalizing pipe with a pressure equalizing valve.

[0006] The oxygen concentrator also includes an oxygen reflux pipe and a reflux oxygen compressor arranged thereon; the lower end of the oxygen reflux pipe is connected to the raw gas tank; the upper ends of the oxygen reflux pipes are connected to the left and right exhaust pipes at a certain location upstream of the exhaust valve through a reflux branch pipe with a reflux valve.

[0007] When the oxygen generator of the present invention is working, part of the oxygen discharged from the top of the adsorption tank is pressurized by the reflux oxygen compressor and enters the raw gas tank, and is mixed with the air delivered by the air compressor to form a high-oxygen raw gas; the high-oxygen raw gas then enters the adsorption tank for air separation and oxygen production. During the adsorption process of the corresponding adsorption tank, oxygen continues to reflux.

[0008] Since oxygen continuously refluxes during operation, the oxygen content in the raw gas entering the molecular sieve adsorption tank is higher than that in normal air; when the airflow passes through the entire molecular sieve adsorption tank, the pressure loss caused by nitrogen adsorption is reduced; for example, without considering the bed resistance, when direct air feed is used, the pressure loss caused by nitrogen adsorption can reach 78%; and when, for example, 50% high-oxygen raw gas feed is used, the pressure loss caused by nitrogen adsorption is only 50%; this allows the molecular sieve located at the upper end of the adsorption tank to be in a higher pressure environment, thereby showing a higher adsorption amount, so that the adsorption capacity of the entire bed is significantly improved.

[0009] The processes of pressure equalization, inversion and regeneration of the molecular sieve adsorption tank can be carried out according to traditional processes.

[0010] Furthermore, in order to improve the bed resistance of the adsorption tank, an improvement on the filling method of the adsorption tank is provided.

[0011] Specifically, the molecular sieve adsorption tank is filled with adsorbent particles with gradually decreasing particle sizes along the airflow direction; the molecular sieve filling layers with different particle sizes are separated by separators to prevent the particles of different layers from migrating to each other, and the separators may be grid plates or wire meshes, etc. The filling thickness of each filling layer may be the same or may gradually decrease along the airflow direction.

[0012] Furthermore, the present invention longitudinally arranges a plurality of reverse branch pipes penetrating the molecular sieve bed layer inside the adsorption tank; the bottoms of the plurality of reverse branch pipes are connected to the manifold through a connecting pipe; the manifold passes through the bottom of the adsorption tank and is connected to the reverse pipe through a reverse auxiliary valve. The reverse branch pipes are closed at both ends, and a vent hole is provided on the side that can intercept the molecular sieve particles but allow reverse exhaust gas to pass through.

[0013] Preferably, each inverted branch pipe is composed of several sections, and each section corresponds to a different filling layer in the adsorption tank. Two adjacent sections of the inverted branch pipe are sealed and connected by a connecting portion. A one-way valve assembly that can only be opened downward is provided at the connection of each section of the inverted branch pipe to allow the passage to be opened during the inverted process to discharge the inverted gas downward, and to close the passage during adsorption to prevent gas crossflow.

[0014] Compared with the prior art, the present invention can at least achieve the following beneficial effects: the present invention returns a part of the oxygen gas flow discharged from the top of the adsorption tank to the raw gas tank, mixes with air to form a high-oxygen raw gas for air separation oxygen production. Since the nitrogen content in the raw gas is diluted by the refluxed oxygen, the air flow pressure loss caused by nitrogen adsorption when passing through the bed is smaller than that of direct air feed, thereby ensuring that the molecular sieve particles at the top of the adsorption tank are in a relatively higher pressure environment, thereby having a higher adsorption and separation capacity, and increasing the nitrogen adsorption amount of the entire bed; at the same time, the present invention improves the distribution of bed resistance and nitrogen adsorption at the bed height by using molecular sieve particles with gradient particle sizes, so that the top of the bed in the low pressure environment caused by the dual reasons of bed resistance and nitrogen adsorption in the traditional filling scheme has a relatively higher pressure environment and non-pressure nitrogen adsorption performance (caused by high specific surface area); in addition, in order to overcome the reverse placement problem brought about by the filling layer with gradient particle sizes, the present invention arranges a number of reversed branch pipes in the adsorption tank to assist in reverse exhaust, which greatly improves the reverse exhaust efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The diagram shows the pipeline connection relationship of the molecular sieve tank;

[0016] Figure 2 This is a diagram showing the filling method of the molecular sieve tank;

[0017] Figure 3 for Figure 2 Schematic diagram of bed resistance in different filling methods;

[0018] Figure 4 It is a schematic diagram of the current equalizing grid;

[0019] Figure 5 This is a schematic diagram of the installation of the reverse branch pipe in the molecular sieve tank;

[0020] Figure 6 This is a diagram for placing the branch pipe in reverse;

[0021] Figure 7 It is a schematic diagram of a single pipe with a branch pipe placed in reverse;

[0022] Figure 8 for Figure 7 A partial enlarged cross-section of the middle circular area is shown. DETAILED DESCRIPTION

[0023] In order to better illustrate the technical concept of the present invention, the scheme of the present invention is further described below in conjunction with the accompanying drawings. It should be noted that the descriptions of "left", "right", "upper" and "lower" used in the present invention are only for the convenience of distinguishing different components in conjunction with the positional relationship shown in the accompanying drawings, and do not represent the left and right position restrictions in actual implementation; and the "upstream" and "downstream" used refer to the front and back relationship distinguished along the gas flow direction.

[0024] Example 1

[0025] See also Figure 1 , provides a pressure swing adsorption oxygen generator, including two molecular sieve adsorption tanks, respectively denoted as left tank 1 and right tank 2; also including an air compressor 3 and a raw gas tank 4; the outlet of the air compressor 3 is connected to the raw gas tank 4 through an air pipe 5; the raw gas tank 4 is connected to the air inlet 17 at the bottom of the left tank 1 and the right tank 2 through a left raw gas pipe 61 and a right raw gas pipe 62 respectively; the left raw gas pipe 61 and the right raw gas pipe 62 are respectively provided with an air intake left valve V1 and an air intake right valve V2; the left tank 1 The interiors of the left and right tanks 2 are filled with molecular sieve adsorbents for adsorbing nitrogen in the raw gas; the top exhaust ports 18 of the left tank 1 and the right tank 2 are connected to the product gas pipe 8 through the left exhaust pipe 71 and the right exhaust pipe 72 respectively; the left exhaust pipe 71 and the right exhaust pipe 72 are provided with a left exhaust valve V10 and a right exhaust valve V11 respectively; a position on the left raw gas pipe 61 between the downstream of the left intake valve V1 and the intake port 17 of the left tank 1 is connected to the reverse pipe 9 through a pipeline with a left reverse valve V3; a position on the right raw gas pipe 61 between the downstream of the right intake valve V2 and the intake port 17 of the right tank 2 is connected to the reverse pipe 9 through a pipeline with a right reverse valve V4; a position on the left exhaust pipe 71 between the left exhaust valve V10 and the exhaust port 18 of the left tank 1 is connected to a position on the right exhaust pipe 72 between the right exhaust valve V11 and the exhaust port 18 of the right tank 2 through a pressure equalizing pipe with a pressure equalizing valve V7.

[0026] Still see Figure 1 , also includes an oxygen reflux pipe 10 and a reflux oxygen compressor 11 arranged thereon; the lower end of the oxygen reflux pipe 10 is connected to the raw gas tank 4; the upper end of the oxygen reflux pipe 10 is connected to the left exhaust pipe 71 through a reflux branch pipe with a left reflux valve V8 at a certain position upstream of the left exhaust valve V10; the upper end of the oxygen reflux pipe 10 is connected to the right exhaust pipe 72 through a reflux branch pipe with a right reflux valve V9 at a certain position upstream of the right exhaust valve V11.

[0027] The working process of this embodiment is as follows: the air compressor 3 first supplies air to the raw gas tank 4 through the air pipe 5; the left air inlet valve V1 and the left reflux valve V8 are opened, and other valves are closed; air enters the left tank 1 from the air inlet 17 through the left raw gas pipe 61; the molecular sieve adsorbent in the left tank 1 adsorbs the nitrogen in the air flow; the oxygen flow is discharged from the exhaust port 18 of the left tank 1; the reflux oxygen compressor 11 is turned on, and the oxygen flow enters the raw gas tank 4 through the oxygen reflux pipe 10 and mixes with the air to become a high-oxygen raw gas; after the oxygen content in the raw gas reaches a predetermined value (which can be selected according to actual conditions, such as 50%, etc.), the left exhaust valve V10 is opened to supply oxygen to the outside, and the oxygen continues to reflux.

[0028] Since oxygen continuously refluxes during operation, the oxygen content in the raw gas entering the molecular sieve adsorption tank is higher than that in normal air; when the airflow passes through the entire molecular sieve adsorption tank, the pressure loss caused by nitrogen adsorption is reduced; for example, without considering the bed resistance, when direct air feed is used, the pressure loss caused by nitrogen adsorption can reach 78%; and when, for example, 50% high-oxygen raw gas feed is used, the pressure loss caused by nitrogen adsorption is only 50%; this allows the molecular sieve located at the upper end of the adsorption tank to be in a higher pressure environment, thereby showing a higher adsorption amount, so that the adsorption capacity of the entire bed is significantly improved.

[0029] The processes of pressure equalization, inversion and regeneration of the molecular sieve adsorption tank can be carried out according to traditional processes.

[0030] Example 2

[0031] In Example 1, due to the adoption of the oxygen reflux process, the overall adsorption performance of the molecular sieve adsorbent bed is greatly improved. In actual operation, the resistance of the airflow through the adsorption bed will also cause a large decompression (pressure reduction); especially after the oxygen reflux process is adopted, if the oxygen supply is to be guaranteed to remain unchanged, the airflow flow in the adsorption tank will increase significantly, which will lead to a greater bed resistance, thereby offsetting part of the reduction in adsorption decompression caused by the oxygen reflux process; that is, the oxygen reflux process can be a reduction in the degree of decompression caused by the nitrogen adsorption process; but the increase in the flow rate in the tank caused by the oxygen reflux leads to a greater degree of decompression caused by the bed resistance; therefore, there is an upper limit to the oxygen reflux amount, exceeding which the increase in decompression caused by the bed resistance will exceed the decrease in decompression caused by the nitrogen adsorption.

[0032] This embodiment provides an adsorption tank filling scheme to further reduce the bed resistance and change the pressure loss distribution caused by the bed resistance, thereby increasing the upper limit of the oxygen reflux rate.

[0033] For details, see Figure 2 . Figure 2 A shows the filling method of the adsorption tank in the prior art, which uses molecular sieve particles with basically uniform particle size, assuming that the particle size is 3. The bed resistance curve along the bed height can be seen in Figure 3 Figure A;

[0034] Figure 2 B is an improved filling method, in which adsorbent particles with gradually decreasing particle sizes are filled in the molecular sieve adsorption tank along the airflow direction; see Figure 4 The layers are separated by a partition 13 to prevent particles from different layers from migrating to each other. The partition 13 may be, for example, a grid plate or a wire mesh. Figure 2 The filling thickness of each layer in B is the same. Figure 2 In B, four layers of molecular sieve filling layers with different particle sizes are arranged from bottom to top. Figure 2 The filling method of B can make the overall bed resistance and Figure 2 A is filled in the same way, see Figure 3 B. However, due to the change in the bed structure, the lower layer uses large-diameter adsorbent particles, which have a relatively low specific surface area and a relatively small amount of nitrogen adsorption; while the upper layer uses small-diameter adsorbent particles, which have a larger specific surface area and a larger amount of nitrogen adsorption.

[0035] After this improvement, Figure 2 In the filling scheme B, the nitrogen adsorption amount in the lower part of the bed intersects Figure 2 Solution A is smaller and the bed resistance is also lower. Figure 2 A is smaller; therefore, when passing through the lower part of the bed, Figure 2The pressure loss of scheme B is small; at the top of the bed, Figure 2 The nitrogen adsorption in Scheme B is Figure 2 A is larger, and the bed resistance is also greater. Figure 2 The pressure loss of the air flow in option B is smaller, so Figure 2 In the B filling scheme, the gas flow still maintains a relatively high pressure in the main nitrogen adsorption area and the upper part of the bed; thus, the nitrogen adsorption of the entire bed is greater than Figure 2 The filling method of A.

[0036] Figure 2 C is a further improvement, which adopts Figure 2 Four layers of molecular sieve particles of the same particle size as in B are filled into the adsorption tank; the difference is that the filling height of each adsorption layer gradually decreases from bottom to top. This filling method can significantly reduce the overall bed resistance of the adsorption tank, see Figure 3 C. However, due to the reduction in the filling height of small-size molecular sieve particles with large specific surface area, the nitrogen adsorption capacity of the entire bed is lower than Figure 2 The filling method in B.

[0037] In actual operation, you can choose according to the specific situation Figure 2 B or Figure 2 The filling method of C can meet different requirements of increasing the bed adsorption capacity and / or reducing the bed pressure drop.

[0038] Example 3

[0039] In Example 2, the distribution of bed resistance and the distribution of nitrogen adsorption amount are improved by providing molecular sieve packing layers of different particle sizes, so that the upper part of the adsorption tank maintains a higher gas flow pressure; at the same time, the pressure is relatively low (compared to the bottom of the tank, not compared to the Figure 2 A) is configured with a small-diameter molecular sieve having a larger adsorption capacity (referring to the molecular sieve particles per unit volume) on the upper part of the tank, thereby improving the overall nitrogen adsorption capacity of the adsorption tank.

[0040] However, since the bed resistance of the small-size molecular sieve packing layer is greater and it is located at the top of the bed, the difficulty of the inversion process will increase. To this end, this embodiment provides the following solution.

[0041] See also Figure 5-6 , a plurality of inverted branch pipes 14 are longitudinally arranged inside the adsorption tank and penetrate the molecular sieve bed layer; the bottoms of the plurality of inverted branch pipes 14 are connected to the manifold 16 through the connecting pipe 15; the manifold 16 passes through the bottom of the adsorption tank. Referring to FIG1 , the manifold 16 of the left tank 1 is connected to the inverted pipe 9 through the left inverted auxiliary valve V5; the manifold 16 of the right tank 2 is connected to the inverted pipe 9 through the right inverted auxiliary valve V6.

[0042] See also Figure 7Each inverted branch pipe 14 is composed of several sections, such as the first section 141, the second section 142, the third section 143 and the fourth section 144 from top to bottom. Each section corresponds to a different filling layer in the adsorption tank.

[0043] See also Figure 8 The two adjacent sections of the inverted branch pipe 14, such as the second section 142 and the third section 143, are sealed and connected by a connecting portion 145; on the side walls of each section, except for the connecting wall 149 corresponding to the connecting portion 145, air holes 148 are provided; the air holes 148 allow the inverted gas to pass through during the inverted process, but prohibit the molecular sieve particles of the corresponding filling layer from passing through.

[0044] Because the molecular sieve particles are not filled in the inverted branch pipe 14, in order to prevent the gas from flowing through the inverted branch pipe 14 during the adsorption process (referring to the gas bypassing the bed layer and flowing directly upward from the inverted branch pipe), a one-way valve assembly that can only be opened downward is set at the connection of each section of the inverted branch pipe 14, so as to allow the passage to be opened during the inverted process to discharge the inverted gas downward, and to close the passage during adsorption to prevent gas from flowing through. The one-way valve assembly includes a retaining ring 146 fixed inside the inverted branch pipe 14 and a valve plate 147 located below the retaining ring.

[0045] In this embodiment, the reverse branch pipe 14 is longitudinally arranged in the bed layer. When the reverse process begins, the reverse passage can be quickly opened, and the reverse gas does not need to overcome the bed resistance to pass through the entire bed layer, so the reverse speed is higher. During the reverse process, the reverse valve and the reverse auxiliary valve can be opened at the same time, and the reverse gas in the bed layer is mainly discharged through the reverse auxiliary valve; the remaining gas can be discharged through the reverse valve, thereby realizing a fast and sufficient reverse process, and the sufficient reverse process can significantly reduce the demand for purge regeneration gas.

[0046] Example 4

[0047] Provided is an oxygen production method based on the above oxygen concentrator, comprising the following steps:

[0048] (1) The air compressor 3 supplies air to the raw gas tank 4 through the air pipe 5; the left air inlet valve V1 and the left reflux valve V8 are opened, and other valves are closed; air enters the left tank 1 from the air inlet 17 through the left raw gas pipe 61; the molecular sieve adsorbent in the left tank 1 adsorbs nitrogen in the air flow; the oxygen flow is discharged from the exhaust port 18 of the left tank 1; the reflux oxygen compressor 11 is turned on, and the oxygen flow enters the raw gas tank 4 through the oxygen reflux pipe 10 and mixes with the air to form a high-oxygen raw gas; after the oxygen content in the raw gas reaches a predetermined value, the left exhaust valve V10 is opened to supply oxygen to the outside, and the oxygen continues to reflux;

[0049] (2) After the left tank 1 is saturated with adsorption, the valve opening mode is switched, and the left reflux valve V8 is closed; the right air inlet valve V2 and the pressure equalizing valve V7 are opened, and the high-pressure and high-oxygen residual gas in the left tank 1 is pressure-equalized in the right tank 2;

[0050] (3) The pressure equalizing valve V7 is closed, and the right reflux valve V9 and the right exhaust valve V11 are opened; the right tank 2 starts to produce oxygen using the high-oxygen raw gas;

[0051] (4) The left reverse release valve V3 and the left reverse release auxiliary valve V5 are opened, and the nitrogen adsorbed in the left tank 1 is quickly discharged through the air inlet 17 and the reverse release branch pipe 14;

[0052] (5) After the left tank 1 is completely inverted, that is, no gas is discharged through the inversion pipe 9, the left inversion auxiliary valve V5 is closed; the equalizing valve V7 is opened, and the oxygen gas flow generated at the top of the right tank 2 is used to purge and regenerate the adsorbent bed in the left tank 1. After the regenerated gas discharged from the inversion pipe 9 is tested and qualified, the equalizing valve V7 is closed, and the regeneration of the left tank 1 is completed.

[0053] (6) Repeat the above steps of adsorption, pressure equalization, reversal, and regeneration to continuously produce oxygen.

[0054] The above is only an example of the best implementation of the concept of the present invention, which should not be understood as a limitation on all feasible implementations of the present invention. A simple replacement of conventional means by a person skilled in the art without creative work also falls within the feasible scope of the present invention. The scope of protection of the present invention shall be subject to the definition of the claims.

Claims

1. A pressure swing adsorption oxygen generator, comprising two adsorption tanks filled with molecular sieve adsorbent, namely a left tank (1) and a right tank (2); the molecular sieve adsorbent can adsorb nitrogen in the air; further comprising an air compressor (3) and a raw gas tank (4); the outlet of the air compressor (3) is connected to the raw gas tank (4) through an air pipe (5); characterized in that: The raw gas tank (4) is connected to the air inlet (17) at the bottom of the left tank (1) and the right tank (2) via a left raw gas pipe (61) and a right raw gas pipe (62), respectively; the left raw gas pipe (61) and the right raw gas pipe (62) are respectively provided with an air inlet left valve (V1) and an air inlet right valve (V2); the exhaust ports (18) at the top of the left tank (1) and the right tank (2) are respectively connected to the product gas pipe (8) via a left exhaust pipe (71) and a right exhaust pipe (72); the left exhaust pipe (71) and the right exhaust pipe (72) are respectively provided with a left exhaust valve (V10) and a right exhaust valve (V11); the left raw gas pipe (61) is located downstream of the left air inlet valve (V1) and is connected to the air inlet (18) of the left tank (1). A position between the right raw material gas pipe (61) and the right raw material gas pipe (7) is connected to the reverse pipe (9) through a pipeline with a left reverse valve (V3); a position between the downstream of the right intake valve (V2) and the intake port (17) of the right tank (2) on the right raw material gas pipe (61) is connected to the reverse pipe (9) through a pipeline with a right reverse valve (V4); a position between the left exhaust valve (V10) and the exhaust port (18) of the left tank (1) on the left exhaust pipe (71) and a position between the right exhaust valve (V11) and the exhaust port (18) of the right tank (2) on the right exhaust pipe (72) are connected through a pressure equalizing pipe with a pressure equalizing valve (V7); and the oxygen reflux pipe (10) and a reflux oxygen compressor (11) arranged thereon are also included; The lower end of the oxygen reflux pipe (10) is connected to the raw gas tank (4); a reflux branch pipe with a left reflux valve (V8) is connected to the upper end of the oxygen reflux pipe (10) at a location upstream of the left exhaust valve (V10) on the left exhaust pipe (71); a reflux branch pipe with a right reflux valve (V9) is connected to the upper end of the oxygen reflux pipe (10) at a location upstream of the right exhaust valve (V11) on the right exhaust pipe (72); Adsorbent particles with gradually decreasing particle sizes are used to fill the molecular sieve adsorption tank along the airflow direction, and adjacent filling layers with adsorbents of different particle sizes are separated by a separator (13), wherein the separator (13) allows airflow to pass through but prohibits adsorbents of different particle sizes from migrating across layers, and the filling thickness of each filling layer is the same, or the filling thickness of each filling layer gradually decreases from bottom to top; A plurality of inverted branch pipes (14) penetrating the molecular sieve bed layer are longitudinally arranged inside the adsorption tank; the bottoms of the plurality of inverted branch pipes (14) are connected to a manifold (16) via a connecting pipe (15); the manifold (16) passes through the bottom of the adsorption tank and is connected to the inverted pipe (9) via a corresponding inverted auxiliary valve; each inverted branch pipe (14) is composed of a plurality of sections spliced ​​together, and each section corresponds to a different filling layer in the adsorption tank.

2. The pressure swing adsorption oxygen generator according to claim 1, characterized in that: Two adjacent sections of the inverted branch pipe (14) are sealed and connected via a connecting portion (145); air holes (148) are provided on the side walls of each section except for a connecting wall (149) corresponding to the connecting portion (145); the air holes (148) allow inverted air to pass through, but prohibit the molecular sieve particles of the corresponding filling layer from passing through.

3. The pressure swing adsorption oxygen generator according to claim 2, characterized in that: A one-way valve assembly that can only be opened downward is provided at the connection between the sections of the reverse branch pipe (14), wherein the one-way valve assembly comprises a retaining ring (146) fixed inside the reverse branch pipe (14) and a valve plate (147) located below the retaining ring.

4. The oxygen production method of the pressure swing adsorption oxygen generator according to claim 3, characterized in that The steps include:

1. The air compressor (3) supplies air to the raw gas tank (4) through the air pipe (5); the left air inlet valve (V1) and the left return valve (V8) are opened, and the other valves are closed; air enters the left tank (1) from the air inlet (17) through the left raw gas pipe (61); the molecular sieve adsorbent in the left tank (1) adsorbs nitrogen in the air flow; the oxygen air flow is discharged from the exhaust port (18) of the left tank (1); the return oxygen compressor (11) is turned on, and the oxygen air flow enters the raw gas tank (4) through the oxygen return pipe (10) and mixes with the air to form a high-oxygen raw gas; after the oxygen content in the raw gas reaches a predetermined value, the left exhaust valve (V10) is opened to supply oxygen to the outside, and the oxygen continues to reflux; 2. After the left tank (1) is saturated with adsorption, the valve opening mode is switched, and the left return valve (V8) is closed; the right air inlet valve (V2) and the pressure equalizing valve (V7) are opened, and the high-pressure and high-oxygen residual gas in the left tank (1) is pressure-equalized in the right tank (2); 3. After the pressure equalization is completed, the pressure equalization valve (V7) is closed, and the right reflux valve (V9) and the right exhaust valve (V11) are opened; the right tank (2) starts to produce oxygen using the high-oxygen raw gas; Fourth, the left reverse release valve (V3) and the left reverse release auxiliary valve (V5) are opened, and the nitrogen adsorbed in the left tank (1) is quickly discharged through the air inlet (17) and the reverse release branch pipe (14); 5. After the left tank (1) is completely reversed, close the left reverse auxiliary valve (V5); open the equalizing valve (V7), and use the oxygen gas flow generated at the top of the right tank (2) to purge and regenerate the adsorbent bed in the left tank (1); after the regeneration gas discharged from the reverse pipe (9) is tested and qualified, close the equalizing valve (V7), and the regeneration of the left tank (1) is completed; 6. Repeat the above steps of adsorption, pressure equalization, reversal and regeneration to continuously produce oxygen.

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