Multi-tower efficient pressure swing adsorption purification hydrogen production system and process thereof

Abstract

The present application belongs to the technical field of pressure swing adsorption device and hydrogen purification, and particularly relates to a multi-tower efficient pressure swing adsorption hydrogen purification system and process thereof. The system comprises a first adsorption tower, a second adsorption tower, a third adsorption tower, a fourth adsorption tower, a vacuum pump, a raw gas buffer tank, a desorption gas buffer tank, a product gas buffer tank, an equalizing tank and a sequential tank. By changing the path of product gas, the system realizes simultaneous adsorption of two adsorption towers under the condition of only four adsorption towers, increases the production capacity of the device, and adopts a combination of vacuum pumping and flushing for adsorbent regeneration, thereby relieving the current situation that simultaneous adsorption of multiple towers can only be realized by not less than six beds of pressure swing adsorption, and solving the problem that the regeneration effect is weakened at the end of vacuum pumping regeneration and the adsorbent regeneration effect is not complete in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of pressure swing adsorption (PSA) devices and hydrogen purification technology, specifically relating to a multi-tower high-efficiency PSA purification hydrogen production system and its process. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Hydrogen is one of the most ideal energy sources for the future, possessing advantages such as high efficiency, cleanliness, pollution-free operation, and renewability. Pressure swing adsorption (PSA) technology is currently the main technique for hydrogen purification and preparation. It is a novel technology that uses pressure swing adsorption to separate gases, and it is of great significance for the preparation of high-purity hydrogen. PSA offers advantages such as simple process flow, operational flexibility, high reliability, high operational adaptability, and high degree of automation.

[0004] In existing pressure swing adsorption (PSA) processes, single adsorption towers are intermittent because the adsorbent requires regeneration. Industrially, two or more adsorption beds are used, alternating between adsorption and regeneration. However, since the adsorption tower spends more time in a generalized regeneration state than in an adsorption state, and pressure equalization is required, achieving simultaneous adsorption operation of two adsorption towers at certain points in the PSA cycle is only possible in PSA processes with at least six beds. For example, the commonly used industrial six-tower operation with two towers in adsorption mode, while the remaining towers are in a generalized regeneration state.

[0005] Simultaneous feeding of multiple towers can increase the production capacity of the equipment, but it requires the addition of multiple adsorption towers, which will increase the overall equipment cost. At the same time, it will increase the number of pipelines and control valves, which will increase the risk of equipment failure and make it difficult for later management and maintenance.

[0006] Meanwhile, in actual engineering operation, it was found that in existing pressure swing adsorption (PSA) processes, even with vacuum regeneration, the regeneration effect weakens towards the end of the vacuum period, resulting in incomplete adsorbent regeneration and reduced product gas purity and hydrogen recovery rate. Furthermore, if the vacuum system malfunctions, adsorbent regeneration cannot occur, and the entire PSA unit will cease operation.

[0007] In summary, given the current high cost and limited production capacity of the six-tower-two-tower adsorption system, there is an urgent need to develop a system that allows simultaneous adsorption in two adsorption towers using only four adsorption towers, thereby increasing the plant's production capacity. Summary of the Invention

[0008] To address the aforementioned issues, this invention provides a multi-tower high-efficiency pressure swing adsorption (PSA) hydrogen purification system and its process. The system alters the product gas path; after adsorption, the product gas is first partially released to the equalization tank via a primary pressure equalization drop, and then released to other adsorption towers via a secondary pressure equalization drop. This two-stage release and the buffering effect of the equalization tank extend the adsorption time, enabling simultaneous adsorption in two adsorption towers with only four adsorption towers, thus increasing the unit's production capacity. Furthermore, the system employs a combined vacuum and flushing method for adsorbent regeneration, alleviating the limitation of existing processes requiring at least six PSA beds for simultaneous multi-tower adsorption. It also solves the problem of weakened regeneration efficiency and incomplete adsorbent regeneration in existing technologies that rely solely on vacuum processes.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a multi-tower high-efficiency pressure swing adsorption purification hydrogen production system, comprising: at least four adsorption towers;

[0011] The inlet end of each adsorption tower is connected to the air inlet pipe and the vacuum pipe, respectively, and the outlet end of each adsorption tower is connected to the equalization tank and the flow tank, respectively.

[0012] Two adsorption towers are in the adsorption state simultaneously during each time period.

[0013] In some embodiments, the pressure equalization tank performs one pressure drop equalization and one pressure rise equalization on the adsorption tower;

[0014] In some embodiments, the parallel discharge tank is used to parallel discharge and purge the adsorption tower.

[0015] In some embodiments, the raw material gas enters the first adsorption tower, the second adsorption tower, the third adsorption tower, and the fourth adsorption tower from the raw material gas buffer tank.

[0016] In some embodiments, the system further includes a vacuum pump, which, after the forward discharge is completed, reversely evacuates the adsorbed impurity gas in the adsorption tower and discharges it as desorption gas through a desorption gas buffer tank.

[0017] In some embodiments, after the vacuuming is completed, the adsorption tower is connected to the forward discharge tank. The gas in the forward discharge tank flows into the adsorption tower from the forward discharge tank, is extracted by the vacuum pump as purging exhaust gas, and is discharged through the desorption gas buffer tank.

[0018] In some embodiments, after purging, the connection between the adsorption tower and the discharge tank is disconnected, and the adsorption tower is connected to other adsorption towers for a secondary pressure equalization boost.

[0019] In some embodiments, after the secondary pressure equalization is completed, the adsorption tower is disconnected from other adsorption towers, and the adsorption tower is connected to the pressure equalization tank for a first pressure equalization.

[0020] In some embodiments, after the first pressure equalization is completed, the connection between the adsorption tower and the pressure equalization tank is disconnected, so that the raw material gas can be used to finally pressurize the adsorption tower through the inlet pipe.

[0021] In some embodiments, valves are provided on each device and the pipelines between devices.

[0022] A second aspect of the present invention also provides a multi-tower high-efficiency pressure swing adsorption (PSA) purification hydrogen production process, employing the above-mentioned system for hydrogen production, comprising:

[0023] The raw gas is passed through a raw gas buffer tank at room temperature and a certain pressure and then enters the adsorption tower. Each adsorption tower is filled with adsorbent. Each adsorption tower goes through the following steps in sequence: adsorption, pressure drop equalization, cascading, vacuuming, purging, pressure increase equalization, and final pressure increase. At each time period, two adsorption towers are in the adsorption state at the same time. The process is repeated in a cycle to obtain the product.

[0024] The product gas is first released into the equalization tank through a primary pressure equalization drop, and then released into other adsorption towers through a secondary pressure equalization drop.

[0025] In some embodiments, the pressure fluctuation of the vacuum pump is controlled within 35 to 50 kPaA.

[0026] A third aspect of the present invention also provides the application of the above-described multi-tower high-efficiency pressure swing adsorption purification hydrogen production system in gas processing.

[0027] Beneficial effects of the present invention

[0028] This invention provides a multi-tower high-efficiency pressure swing adsorption (PSA) hydrogen production system and its process. By designing different process flows through the selection of steps, the production capacity of the device can be increased, investment reduced, and the purity of the product gas and hydrogen recovery rate improved simultaneously. Specifically, the advantages of this invention are:

[0029] 1. This invention utilizes an equalizing tank and a forward discharge tank in conjunction with an adsorption tower to simulate a multi-tower PSA cycle process for purifying hydrogen, which greatly reduces the production cost of multi-tower systems. At the same time, by controlling the opening and closing of valves to set the process sequence of the four towers, simultaneous adsorption of two towers can be achieved, which improves the system's production capacity, reduces investment and operating costs, and lowers the risk of equipment failure.

[0030] 2. The adsorbent regeneration process of this invention adopts a regeneration method combining vacuuming and purging. Vacuuming and purging are performed simultaneously in the later stages of adsorbent regeneration, resulting in more thorough regeneration, lower impurity content, and better regeneration effect. Even if the vacuum system malfunctions, the reverse release and purging process can be run to ensure stable operation of the pressure swing adsorption system.

[0031] 3. The pressure swing adsorption technology used in this invention cycles through adsorption, primary pressure equalization, secondary pressure equalization, forward discharge, vacuuming, purging, secondary pressure equalization and increase, primary pressure equalization and increase, and final pressure increase. Furthermore, the pressure equalization tank, inter-tower pressure equalization tank, and forward discharge tank are used to achieve three pressure reductions, thereby reducing the pressure fluctuation range of the system process and thus reducing the pressure fluctuation and noise of the vacuum pump.

[0032] 4. The system and process of the present invention can achieve gas separation under normal temperature and low pressure conditions, and also have the characteristics of miniaturized equipment, high production capacity, high product gas purity, high degree of automation, low failure risk, and low maintenance cost. Attached Figure Description

[0033] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0034] Figure 1 This is a schematic diagram of a multi-tower high-efficiency pressure swing adsorption purification hydrogen production system and its process.

[0035] A. First adsorption tower; B. Second adsorption tower; C. Third adsorption tower; D. Fourth adsorption tower; 1. Raw material gas buffer tank; 2. Product gas buffer tank; 3. Desorption gas buffer tank; 4. Equalizing tank; 5. Forward discharge tank; 6. Vacuum pump. Detailed Implementation

[0036] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0037] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0038] like Figure 1 As shown, this embodiment provides a multi-tower high-efficiency pressure swing adsorption purification hydrogen production system and its process, including a first adsorption tower A, a second adsorption tower B, a third adsorption tower C, a fourth adsorption tower D, a raw material gas buffer tank 1, a product gas buffer tank 2, a desorption gas buffer tank 3, a pressure equalization tank 4, a forward discharge tank 5, and a vacuum pump 6, as well as pipes and valves connected to each part.

[0039] The raw material gas inlet is connected to the inlet end of the raw material gas buffer tank 1. The outlet end of the raw material gas buffer tank 1 is connected to the bottom inlet end of the first adsorption tower A, the second adsorption tower B, the third adsorption tower C, and the fourth adsorption tower D via inlet pipes. The bottom inlet ends of the first adsorption tower A, the second adsorption tower B, the third adsorption tower C, and the fourth adsorption tower D are all connected to vacuum pipes, which are connected to the inlet end of the vacuum pump 6. The outlet end of the vacuum pump 6 is connected to the inlet end of the desorption gas buffer tank 3. The first adsorption tower A, the second adsorption tower B, the third adsorption tower C, and the fourth adsorption tower D are connected to the bottom inlet end of the buffer tank 3 via inlet pipes. The top outlet of adsorption tower D is connected to the inlet of product gas buffer tank 2 via an outlet pipe; the top outlets of the first adsorption tower A, the second adsorption tower B, the third adsorption tower C, and the fourth adsorption tower D are all connected to the inlet of pressure equalization tank 4 via a primary pressure equalization pipe; the top outlets of the first adsorption tower A, the second adsorption tower B, the third adsorption tower C, and the fourth adsorption tower D are all connected to the secondary pressure equalization pipe; the top outlets of the first adsorption tower A, the second adsorption tower B, the third adsorption tower C, and the fourth adsorption tower D are all connected to the inlet of the flow tank via a flow pipe.

[0040] The cycle sequence of the pressure swing adsorption system and its process used in this embodiment is shown in Table 1.

[0041] Table 1 - Cycle Time Sequence of Four-Tower High-Efficiency Pressure Swing Adsorption Hydrogen Production Process

[0042]

[0043] Note: A is adsorption, ED / ER equal pressure drop / equal pressure rise, PP is released in the forward direction, V is vacuum, P is purging, FR is final pressure rise;

[0044] As shown in Table 1, each tower operates in a different state during each time period of the pressure swing adsorption (PSA) process, ensuring that two adsorption towers are simultaneously in the adsorption state during each time period. Each adsorption tower undergoes the same cycle sequence. Taking tower A as an example, the PSA process for this segment is explained as follows:

[0045] (1) Adsorption: Open the inlet control valve of tower A. The raw gas enters tower A after passing through the raw gas buffer tank 1. Impurities in the raw gas are adsorbed by the adsorbent under the adsorption pressure. Unadsorbed hydrogen enters the product gas buffer tank 2 through the product gas inlet control valve. When the adsorption front of the impurity component reaches a certain position in the adsorption tower, close the inlet control valve. The raw gas stops entering tower A, and the pressure inside the tower is maintained during adsorption.

[0046] (2) First pressure equalization: After stopping the adsorption step of tower A, open the programmable valve connecting tower A and equalization tank 4 to connect the outlet of tower A to equalization tank 4. The gas in the dead space of tower A flows into equalization tank 4 from the outlet of tower A through the programmable valve. At the end of this step, the pressure of tower A and equalization tank 4 is basically balanced. (3) Second pressure equalization: After the first pressure equalization of tower A is completed, close the programmable valve connecting tower A and equalization tank 4, and open the programmable valve connecting tower A and tower D to connect the outlet of tower A to the outlet of tower D, which has just finished regeneration. The gas in the dead space of tower A flows into tower D from the outlet of tower A. At the end of this step, the pressure of towers A and D is basically balanced.

[0047] (4) Forward discharge: After the secondary pressure equalization and reduction step of tower A is stopped, close the programmable valve of the pipeline connecting tower A and tower D, and open the programmable valve of the pipeline connecting tower A and forward discharge tank 5, so that the outlet end of tower A is connected to the inlet end of forward discharge tank 5, and the dead air in tower A flows into forward discharge tank 5 from the outlet end of tower A. When this step is completed, the pressure of tower A and forward discharge tank 5 is basically balanced.

[0048] (5) Vacuuming: After the A tower is discharged in the forward discharge step, close the programmable valve of the pipeline connecting the A tower and the forward discharge tank 5, open the programmable valve of the pipeline connecting the A tower and the vacuum pump, and start the vacuum pump 6 to perform reverse vacuuming on the adsorbed impurity gas in the tower. The gas is discharged as the desorption gas through the desorption gas buffer tank 3. During this process, most of the adsorbed impurity gas is desorbed and the adsorbent is regenerated to a certain extent.

[0049] (6) Purging: After the vacuuming step is completed, open the programmable valve of the pipeline connecting tower A and the forward discharge tank 5 to connect the outlet end of tower A with the inlet end of forward discharge tank 5. Keep the vacuum pump 6 running, and the gas in the forward discharge tank flows into tower A from the outlet end of the forward discharge tank. It is then extracted by the vacuum pump as purging waste gas and discharged from the system through the desorption gas buffer tank 3. When this step is completed, the regeneration of tower A is finished.

[0050] (7) Secondary pressure equalization: Close the control valve of the pipeline connecting tower A and the forward discharge tank 5, close the control valve of the pipeline connecting tower A and the vacuum pump, and open the control valve of the pipeline connecting tower A and tower B to connect the outlet end of tower A and the outlet end of tower B. Gas in tower B flows into tower A to equalize the pressure in tower A. After this step, the pressures of tower B and tower A are basically equal.

[0051] (8) First Pressure Equalization Rise: After tower A completes the second pressure equalization and pressurization process, it is ready for further pressurization. Close the control valve of the pipeline connecting tower A and tower B, and open the control valve of the pipeline connecting tower A and pressure equalization tank 4, so that the outlet end of tower A is connected to pressure equalization tank 4. The pressure equalization tank contains the gas that flowed into tower B during the first pressure equalization drop in the previous sequence. At this time, the gas in pressure equalization tank 4 enters tower A to equalize the pressure of tower A. After this step is completed, the pressure of pressure equalization tank 4 and tower A are basically equal.

[0052] (9) Final pressurization: After the pressure equalization step, the pressure inside column A has not yet reached the working pressure of the adsorption step. At this time, the programmable valve of the pipeline connecting column A and the pressure equalization tank 4 is closed, and the programmable valve of the column A inlet pipeline is opened. The raw material gas is used to finally pressurize column A until the pressure of column A basically reaches the adsorption pressure. At this point, all steps of column A in one cycle are completed, and the next cycle begins immediately.

[0053] Furthermore, the pressure fluctuation of vacuum pump 6 is controlled within 35–50 kPaA.

[0054] This invention provides a multi-tower high-efficiency pressure swing adsorption (PSA) hydrogen production system and its process. By designing different process flows for four adsorption towers in conjunction with equalizing tanks and cascading tanks, it is possible to achieve simultaneous adsorption by two adsorption towers at any time sequence, reducing investment while increasing the production capacity of the device. The adsorbent regeneration method, which combines vacuuming and purging, makes the adsorbent regeneration more thorough, improving the purity of the product gas and the hydrogen recovery rate. The device is simple to operate, with smooth pressure rise and fall and low vacuum pump noise, making it suitable for industrial production.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-tower high-efficiency pressure swing adsorption (PSA) purification and hydrogen production system, characterized in that, include: At least four adsorption towers; The inlet end of each adsorption tower is connected to the air inlet pipe and the vacuum pipe, respectively, and the outlet end of each adsorption tower is connected to the equalization tank and the flow tank, respectively. Each adsorption tower sequentially undergoes the processes of adsorption, pressure equalization and drop, sequential discharge, vacuuming, purging, pressure equalization and increase, and final pressure increase. At each time period, two adsorption towers are simultaneously in the adsorption state, and a second pressure equalization and drop is performed between the towers. The pressure equalization tank performs one pressure drop equalization and one pressure rise equalization on the adsorption tower. The parallel placement tank is used to parallel place and purge the adsorption tower; After the vacuuming is completed, the adsorption tower is connected to the forward discharge tank. The gas in the forward discharge tank flows into the adsorption tower and is extracted by the vacuum pump as purging exhaust gas. It is then discharged through the desorption gas buffer tank.

2. The multi-tower high-efficiency pressure swing adsorption purification and hydrogen production system as described in claim 1, characterized in that, The raw gas enters the first adsorption tower, the second adsorption tower, the third adsorption tower, and the fourth adsorption tower from the raw gas buffer tank.

3. The multi-tower high-efficiency pressure swing adsorption purification and hydrogen production system as described in claim 1, characterized in that, Also includes: After the vacuum pump finishes its forward discharge, it reversely evacuates the adsorbed impurity gas in the adsorption tower and discharges it as desorption gas through the desorption gas buffer tank.

4. The multi-tower high-efficiency pressure swing adsorption purification and hydrogen production system as described in claim 1, characterized in that, After purging, disconnect the adsorption tower from the feed tank, connect the adsorption tower to other adsorption towers, and perform a second pressure equalization boost.

5. The multi-tower high-efficiency pressure swing adsorption purification and hydrogen production system as described in claim 1, characterized in that, After the second pressure equalization is completed, disconnect the adsorption tower from other adsorption towers, connect the adsorption tower to the pressure equalization tank, and perform the first pressure equalization.

6. The multi-tower high-efficiency pressure swing adsorption purification and hydrogen production system as described in claim 1, characterized in that, After the first pressure equalization is completed, disconnect the adsorption tower from the pressure equalization tank, and allow the raw material gas to be pressurized in the adsorption tower through the inlet pipe.

7. The multi-tower high-efficiency pressure swing adsorption purification and hydrogen production system as described in claim 1, characterized in that, Valves are installed on each device and on the pipelines between devices.

8. A multi-tower high-efficiency pressure swing adsorption process for hydrogen purification, characterized in that, Hydrogen production using the system according to any one of claims 1-7, comprising: The raw gas is passed through a raw gas buffer tank at room temperature and a certain pressure and then enters the adsorption tower. Each adsorption tower is filled with adsorbent. Each adsorption tower goes through the following processes in sequence: adsorption, pressure drop equalization, cascading, vacuuming, purging, pressure increase equalization, and final pressure increase. At each time period, two adsorption towers are in the adsorption state at the same time. The process is repeated to obtain the product. In this process, the product gas in the adsorption tower is first partially released to the pressure equalization tank through a primary pressure equalization drop, and then released to other adsorption towers through a secondary pressure equalization drop.

9. The multi-tower high-efficiency pressure swing adsorption purification hydrogen production process as described in claim 8, characterized in that, The pressure fluctuation of the vacuum pump is controlled within 35~50 kPa.

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