Three-tower series pressure swing adsorption device and its pressure equalization process

Abstract

The application discloses a three-tower series connection pressure swing adsorption device and a pressure equalization process thereof, adopts a set of pressure swing adsorption device, sets a multi-step series connection pressure equalization process, and adopts a three-tower simultaneous adsorption mode, so that the yield is obviously improved, the energy consumption and equipment investment are reduced, and the product gas quality is guaranteed. The three-tower series connection pressure swing adsorption device is used for pressure swing adsorption hydrogen extraction, the product hydrogen yield is obviously higher than that of an existing first-stage pressure swing adsorption hydrogen extraction device under the premise that the product hydrogen purity and impurity content meet high-purity hydrogen requirements, the three-tower series connection pressure swing adsorption device is used for pressure swing adsorption oxygen production and nitrogen production, and unit oxygen production power consumption and unit nitrogen production power consumption are obviously lower than the minimum index requirements in related standards under the premise that oxygen purity and nitrogen purity meet basic parameter requirements.

Description

Technical Field

[0001] This invention relates to pressure swing adsorption (PSA) gas separation technology, specifically to a three-tower series PSA device and its pressure equalization process. Background Technology

[0002] Pressure Swing Adsorption (PSA) technology has been used in gas separation and purification for over seventy years, and is widely applied in various industries requiring gas separation. Examples include PSA for nitrogen production (separating nitrogen from air), PSA for oxygen production (separating oxygen from air), and PSA for hydrogen production (separating and purifying hydrogen from refinery gas). PSA technology utilizes PSA units. Currently, most PSA units in use, when in adsorption mode, involve the feed gas passing through only one adsorption tower from its entry into the adsorption tower to the acquisition of the target product gas. Additionally, some systems employ multi-stage PSA units. However, multi-stage PSA units are actually two or more PSA units connected in series. An intermediate product gas is obtained through a pre-stage PSA unit, and the target product gas is obtained through a final stage PSA unit. Therefore, in multi-stage PSA units, the feed gas also actually passes through only one adsorption tower.

[0003] Chinese invention patent CN00113035.8 discloses a pressure swing adsorption (PSA) process that uses multiple adsorption towers connected in series to maintain a constant amount of adsorbent while reducing the total amount of adsorbent, resulting in smaller equipment size and lower operating energy consumption. The adsorption process consists of two or more stages, with the direction of the adsorbed gas flow changing back and forth according to a specific pattern. Furthermore, when the depressurized effluent from the adsorption tower flows back into the tower, the distribution of easily adsorbed components within the tower becomes more rational. In this process, the adsorption towers are connected in series by connecting the outlet of the first tower to the outlet of the second tower, the inlet of the second tower to the inlet of the third tower, and the outlet of the third tower to the outlet of the fourth tower, and so on. In addition to series connections, adsorption towers in the adsorption state may also be connected in parallel. Each tower experiences multiple adsorption states, which are continuous. The gas flow direction within the tower needs to be reversed at different adsorption stages. In this method, when the product gas is a difficult-to-adsorb component, the purity of the product gas varies and it is difficult to guarantee a high purity. Furthermore, the product gas flow is discontinuous. In this patent, the adsorbent in the adsorption tower is already saturated or nearly saturated before the pressure is reduced. During the pressure reduction, the gas in the adsorption tower is first discharged into multiple empty tanks, and then pressure is equalized with other adsorption towers. When the gas is discharged into the empty tanks, a large amount of easily adsorbed components will desorb from the adsorbent and be discharged into the empty tanks. When pressure is equalized, a large amount of components discharged into the pressure equalization and boosting adsorption tower are easily adsorbed gases. As a result, the purity of the product gas containing the difficult-to-adsorb component cannot meet the requirements for high-purity gas quality.

[0004] Chinese invention patent CN103695063A discloses a method for concentrating low-concentration methane gas. This method involves concentrating the low-concentration methane gas using a pressure swing adsorption (PSA) process. N (N≥3) adsorption towers are used for adsorption, each containing adsorbent. Within one adsorption cycle, N adsorption stages are performed, with each tower undergoing N-1 series adsorption cycles. After the N towers in series are pressurized in each adsorption stage, the towers that have undergone N-1 adsorption cycles are flushed and replaced, then vacuumed for desorption. The remaining N-1 towers are then pressurized in reverse to the adsorption pressure and undergo adsorption again. This cycle completes one adsorption cycle. In this patent, the adsorption towers are connected end-to-end, and the number of towers simultaneously in series adsorption is the total number of towers minus one. This patent targets easily adsorbed components as the product gas, which can significantly increase the content of these components. Even with low purity of the difficult-to-adsorb components, the easily adsorbed components in the target product can achieve a high yield. However, to ensure high purity of the difficult-to-adsorb components, the yield of the easily adsorbed components in the target product gas will inevitably decrease. The process technology in this patent results in discontinuous gas flows for the easily and difficult-to-adsorbed components, which may cause pressure fluctuations between them. When pressure equalization and counter-pressurization are performed between adsorption towers, the feed gas does not enter any of the adsorption towers, leading to a buildup of feed gas pressure. Furthermore, this patent only allows for one pressure equalization operation and cannot significantly improve the yield of the difficult-to-adsorbed components.

[0005] Chinese invention patent CN102423602A discloses a series adsorption gas separation process that ensures the product gas discharged from the adsorption towers maintains a consistently high concentration. It overcomes the shortcomings of existing technologies where product gas is discharged after only one adsorption tower, resulting in low purity. This process uses at least six adsorption towers working together in a cyclic adsorption process. Simultaneously, each adsorption tower completes one step. The raw material gas enters the first adsorption tower sequentially through a valve, where impurities are adsorbed by the adsorbent to obtain intermediate gas. This intermediate gas then flows out through a valve and into the second adsorption tower, where impurities are adsorbed by the adsorbent to obtain product gas. The product gas then flows out through a valve and enters the next stage. The raw material gas undergoes one adsorption step to obtain intermediate gas, which is then adsorbed again to obtain product gas, resulting in a high purity of the product gas. This patent uses two adsorption towers in series to adsorb easily adsorbed components from the raw material gas, obtaining a product of high purity but difficult-to-adsorb components. However, this technical solution cannot simultaneously guarantee high purity of both easily and difficult-to-adsorb components while achieving extremely high yields for both. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a three-tower series pressure swing adsorption device and its pressure equalization process. While ensuring that the product gas quality meets the requirements for high-purity gas, it can achieve a product gas yield that meets or exceeds the product gas yield of commonly used two- or three-stage pressure swing adsorption devices in the prior art by using only a single-stage pressure swing adsorption device.

[0007] The objective of this invention is achieved through the following technical solution: a three-tower series pressure swing adsorption device includes at least 9 adsorption towers and corresponding valves and fittings, wherein the adsorption towers are connected in series and in parallel.

[0008] Each adsorption tower is controlled by 14 valves to switch between various states.

[0009] The adsorption tower has seven valves connected to both its lower and upper interfaces.

[0010] Preferably, the seven valves connected to the lower interface of the adsorption tower include:

[0011] The gas from the outlet of the secondary adsorption tower enters the primary adsorption tower through the primary adsorption inlet valve. The primary adsorption inlet valves of each adsorption tower are connected in parallel through adsorption pipeline 2.

[0012] Secondary adsorption inlet valve: Gas from the outlet of the tertiary adsorption tower enters the secondary adsorption tower through the secondary adsorption inlet valve. The secondary adsorption inlet valves of each adsorption tower are connected in parallel through adsorption pipeline 1.

[0013] The feed gas enters the adsorption tower through the three-stage adsorption inlet valve. The three-stage adsorption inlet valves of each adsorption tower are connected in parallel through the feed gas pipeline.

[0014] The reverse exhaust valve is used to discharge the gas inside the adsorption tower when the adsorption tower is in the reverse depressurization process. The reverse exhaust valves of each adsorption tower are connected in parallel through the reverse pipeline.

[0015] When the adsorption tower is in a vacuum and depressurization state, the gas inside the adsorption tower is discharged from the adsorption tower through the extraction and exhaust valve. The extraction and exhaust valves of each adsorption tower are connected in parallel through extraction pipelines.

[0016] The gas from the outlet of the secondary pressure equalization and depressurization adsorption tower enters the primary pressure equalization and depressurization adsorption tower through the primary pressure equalization and depressurization inlet valve. The primary pressure equalization and depressurization inlet valves of each adsorption tower are connected in parallel through the pressure equalization pipeline 2.

[0017] The secondary equalization and depressurization inlet valve allows gas from the outlet of the tertiary equalization and depressurization adsorption tower to enter the secondary equalization and depressurization adsorption tower. The secondary equalization and depressurization inlet valves of each adsorption tower are connected in parallel through equalization pipeline 1.

[0018] Preferably, the seven valves connected to the upper interface of the adsorption tower include:

[0019] The gas in the tertiary adsorption tower is discharged into the secondary adsorption tower through the tertiary adsorption exhaust valve. The tertiary adsorption tower, the secondary adsorption tower, and the primary adsorption tower are connected in series through the tertiary adsorption exhaust valve, the secondary adsorption inlet valve, the secondary adsorption exhaust valve, and the primary adsorption inlet valve. The tertiary adsorption exhaust valve of each adsorption tower is connected in parallel through adsorption pipeline 1.

[0020] Secondary adsorption exhaust valve: the gas in the secondary adsorption tower is discharged into the primary adsorption tower through the secondary adsorption exhaust valve; the secondary adsorption exhaust valves of each adsorption tower are connected in parallel through adsorption pipeline 2.

[0021] The gas inside the primary adsorption tower is discharged from the adsorption tower through the primary adsorption exhaust valve and discharged into the difficult-to-adsorb component product gas pipeline as the difficult-to-adsorb component product gas. The primary adsorption exhaust valves of each adsorption tower are connected in parallel through the difficult-to-adsorb component product gas pipeline.

[0022] The gas in the third pressure equalization and depressurization adsorption tower is discharged into the second pressure equalization and depressurization adsorption tower through the third pressure equalization and depressurization exhaust valve; the third pressure equalization and depressurization adsorption tower, the second pressure equalization and depressurization adsorption tower, and the first pressure equalization and depressurization adsorption tower are connected in series through the third pressure equalization and depressurization exhaust valve, the second pressure equalization and depressurization inlet valve, the second pressure equalization and depressurization exhaust valve, and the first pressure equalization and depressurization inlet valve; the third pressure equalization and depressurization exhaust valve of each adsorption tower is connected in parallel through the pressure equalization pipeline 1;

[0023] The gas in the secondary pressure equalization and depressurization adsorption tower is discharged into the primary pressure equalization and depressurization adsorption tower through the secondary pressure equalization and depressurization exhaust valve; the secondary pressure equalization and depressurization exhaust valves of each adsorption tower are connected in parallel through the pressure equalization pipeline 2.

[0024] The gas in the primary pressure equalization and depressurization adsorption tower is discharged into the pressure equalization and boosting adsorption tower through the primary pressure equalization and depressurization exhaust valve. The primary pressure equalization and depressurization exhaust valves of each adsorption tower are connected in parallel through the pressure equalization and boosting pipeline.

[0025] The reverse flushing valve allows reverse pressurized gas or flushing gas to enter the adsorption tower that needs reverse pressurization or flushing. The reverse flushing valves of each adsorption tower are connected in parallel through the reverse flushing gas pipeline.

[0026] Preferably, the two-tower series pressure swing adsorption device includes 9-11 adsorption towers.

[0027] This invention also provides a pressure swing adsorption (PSA) equalization process, which is achieved by using the above-mentioned three-tower series PSA device:

[0028] In the pressure equalization process of the three-tower series adsorption, pressure swing adsorption is used to separate and purify the gas. During the pressure equalization process, four adsorption towers participate in the pressure equalization process simultaneously. Among them, three adsorption towers are in the pressure equalization and depressurization state, corresponding to the first pressure equalization and depressurization, the second pressure equalization and depressurization, and the third pressure equalization and depressurization, respectively, and one adsorption tower is in the pressure equalization and depressurization state.

[0029] Three adsorption towers in pressure equalization and depressurization are connected in series. Before entering the pressure equalization and depressurization state, these three adsorption towers are in a series adsorption state. During pressure equalization and depressurization, their series connection is the same as when the three adsorption towers are in the adsorption state. In the adsorption state, the feed gas enters the adsorption tower from the lower interface of the first adsorption tower. The adsorption tower is filled with one or more adsorbents that have a good adsorption effect on the components to be adsorbed (easily adsorbed components). After the feed gas comes into contact with the adsorbent bed, most of the easily adsorbed components in the gas are adsorbed by the corresponding adsorbents and separated from the feed gas. The components that do not need to be adsorbed (difficult-to-adsorbed components) and a small portion of easily adsorbed components flow to the upper interface of the adsorption tower and flow out of the adsorption tower from the upper interface. This adsorption tower is in a tertiary adsorption state. Gas exiting the adsorption tower in the tertiary adsorption state continues to enter the adsorption tower through the lower inlet of the second adsorption tower, which is also in the adsorption state. Most of the easily adsorbed components in the gas are adsorbed by the adsorbent, while most of the difficult-to-adsorb components and a small amount of easily adsorbed components exit through the upper inlet of the adsorption tower. This adsorption tower is in the secondary adsorption state. Gas exiting the adsorption tower in the secondary adsorption state continues to enter the adsorption tower through the lower inlet of the third adsorption tower, which is also in the adsorption state. Most of the easily adsorbed components in the gas are adsorbed by the adsorbent, while most of the difficult-to-adsorb components and a trace amount of easily adsorbed components exit through the upper inlet of the adsorption tower, resulting in a product gas containing the difficult-to-adsorbed components that meets the high-purity gas quality requirements. This adsorption tower is in the primary adsorption state. After the adsorption state is completed, these three adsorption towers will enter a pressure equalization and depressurization state.

[0030] The difficult-to-adsorb components that were originally in the primary adsorption state in the adsorption tower flowed out of the adsorption tower from the upper interface and flowed directly into the equalization and pressurization adsorption tower from the upper interface of the adsorption tower in the equalization and pressurization state.

[0031] The difficult-to-adsorb components in the voids of the adsorption tower, which were originally in the secondary adsorption state, flow out of the adsorption tower from the upper interface. The easily adsorbed components in the voids of the adsorption tower, which were originally in the secondary adsorption state, and the easily adsorbed components desorbed from the adsorbent during the pressure equalization and depressurization process, are partially adsorbed by the mass transfer zone and blank zone of the adsorbent in the adsorption tower, which were originally in the secondary adsorption state. The remaining part flows out of the adsorption tower from the upper interface along with the difficult-to-adsorbed components, and then flows into the adsorption tower, which was originally in the primary adsorption state, from the lower interface. The easily adsorbed components are adsorbed by the adsorbent, and the difficult-to-adsorbed components and trace amounts of easily adsorbed components flow out of the adsorption tower, which was originally in the primary adsorption state, from the upper interface, and then flow into the pressure equalization and pressurization adsorption tower, which is in the pressure equalization and pressurization state.

[0032] The gas in the voids of the adsorption tower, which was originally in the tertiary adsorption state, and the easily adsorbed components desorbed from the adsorbent during the pressure equalization and depressurization process, flow out of the adsorption tower from the upper interface. Then, they enter the adsorption tower, which was originally in the secondary adsorption state, from the lower interface. Some of the easily adsorbed components are adsorbed by the adsorbent mass transfer zone and the blank zone. The remaining easily adsorbed components, along with the difficult-to-adsorb components, flow out of the adsorption tower from the upper interface. Then, they enter the adsorption tower, which was originally in the primary adsorption state, from the lower interface. The easily adsorbed components are adsorbed by the adsorbent. The difficult-to-adsorb components and trace amounts of easily adsorbed components flow out of the adsorption tower from the upper interface and flow into the pressure equalization and depressurization adsorption tower from the upper interface.

[0033] That is, the gas flow direction in the three adsorption towers under equal pressure and pressure reduction is the same as the gas flow direction when the three adsorption towers are in the adsorption state.

[0034] To ensure that the gas flow of the difficult-to-adsorb components is continuous, three adsorption towers are always in series adsorption state within one cycle; during pressure equalization, three adsorption towers are always in series pressure equalization and depressurization state.

[0035] When the adsorption tower is in the adsorption state, the adsorbent inside the tower will exhibit three state zones: the adsorbent bed that has reached saturation adsorption capacity is the saturation zone; the adsorbent bed that has adsorbed some easily adsorbed components but has not yet reached saturation adsorption capacity is the mass transfer zone; and the adsorbent bed that has not yet adsorbed easily adsorbed components is the blank zone. The three state zones are arranged sequentially along the airflow direction. As the adsorption time increases, the three state zones gradually move towards the upper interface of the adsorption tower.

[0036] Within one cycle, each adsorption tower undergoes three adsorption states. The adsorption tower directly fed by the feed gas is in the third adsorption state; the adsorption tower receiving gas from the third adsorption state is in the second adsorption state; and the adsorption tower receiving gas from the second adsorption state is in the first adsorption state. Correspondingly, within one cycle, each adsorption tower undergoes three pressure equalization and depressurization states. Each regenerated adsorption tower sequentially enters the first, second, and third adsorption states. The pressure equalization and depressurization state after the first adsorption state is called the first pressure equalization and depressurization state; after the second adsorption state, it is called the second pressure equalization and depressurization state; and after the third adsorption state, it is called the third pressure equalization and depressurization state. Before entering the first adsorption state after three pressure equalization and depressurization states, it undergoes two pressure increase states: pressure equalization and pressure increase, and one reverse pressure increase. Before entering the third adsorption state after the second pressure equalization and depressurization state, it undergoes three reverse pressure increase states and one pressure increase state. Before entering the second adsorption state after the first pressure equalization and depressurization state, it undergoes two reverse pressure increase states and one pressure increase state.

[0037] When the mass transfer zone has moved out of the adsorption tower in the tertiary adsorption state and into the adsorption tower in the secondary adsorption state, the current adsorption state of these three adsorption towers ends. At this time, the adsorbent bed in the adsorption tower into which the raw gas directly enters has become a saturated zone and no longer has adsorption function. The gas composition remaining in the gaps of the adsorption tower is the same as that of the raw gas, and it also contains a large number of difficult-to-adsorb components. If these gases are directly discharged from the device, a large number of difficult-to-adsorb components will be discharged, and the yield of difficult-to-adsorb components will be greatly reduced. In order to recover this part of the difficult-to-adsorb components, a pressure equalization process is set after the adsorption state ends.

[0038] During pressure equalization, gas from the high-pressure adsorption tower flows into the low-pressure adsorption tower, causing the pressure in the high-pressure tower to decrease (this is called pressure equalization depressurization), and the pressure in the low-pressure adsorption tower to increase (this is called pressure equalization boosting). During pressure equalization depressurization, easily adsorbed components adsorbed on the adsorbent gradually desorb from the adsorbent as the pressure decreases. These desorbed components push and follow the gas in the adsorption tower's pores towards the upper interface of the adsorption tower. Since the adsorbent in the adsorption tower that was originally in a tertiary adsorption state no longer has adsorption capacity, the desorbed easily adsorbed components flow out of the adsorption tower along with the original gas in the pores. When the pressure equalization state ends, a large amount of desorbed easily adsorbed components will flow out of the adsorption tower. At this point, most of the gas in the pores of the adsorption tower is easily adsorbed, while a small amount of difficult-to-adsorb components are also present. If the adsorption tower that has just finished a tertiary adsorption state is used directly to equalize the pressure of the adsorption tower that needs pressure equalization boosting, a large amount of easily adsorbed components will flow into the adsorption tower that needs pressure equalization boosting, which will significantly affect the purity of the difficult-to-adsorbed component product gas.

[0039] During pressure equalization, the three adsorption towers that have completed their adsorption phase remain connected in series, but are disconnected from the feed gas pipeline and product gas pipeline, respectively. The upper interface of the adsorption tower that was originally in the primary adsorption phase is connected to the upper interface of the adsorption tower in the pressure equalization and boosting phase via a pressure equalization and boosting pipeline. When the adsorption phase ends, the adsorbent in the adsorption tower that was originally in the primary adsorption phase is still in the blank zone, and the gas quality in the void is the same as that of the difficult-to-adsorb component product gas. The adsorbent in the adsorption tower that was originally in the secondary adsorption phase is in the mass transfer zone near the lower interface of the adsorption tower, and the upper part of the mass transfer zone is the blank zone. During pressure reduction, the adsorption tower in the tertiary adsorption state is adjusted to a tertiary pressure reduction state; the adsorption tower in the secondary adsorption state is adjusted to a secondary pressure reduction state; and the adsorption tower in the primary adsorption state is adjusted to a primary pressure reduction state. Easily adsorbed components flowing out of the adsorption tower originally in the tertiary adsorption state, easily adsorbed components desorbed from the adsorbent in the adsorption tower originally in the secondary adsorption state, and easily adsorbed components within the pores of the adsorption tower will be adsorbed by the adsorbent in the blank areas of the adsorption tower originally in the secondary and primary adsorption states, thus ensuring pressure reduction. After the pressure state is completed, only trace amounts of easily adsorbed components flow into the adsorption tower under pressure equalization and boosting along with the difficult-to-adsorb components. The quality of the gas flowing into the adsorption tower under pressure equalization and boosting is equivalent to the quality of the difficult-to-adsorbed component product gas. This portion of gas will not affect the quality of the difficult-to-adsorbed component product gas, thus ensuring that the quality of the difficult-to-adsorbed component product gas always meets the high-purity gas quality requirements. When the adsorption state ends, all the adsorbent in the adsorption tower that was originally in the primary adsorption state is in the blank zone, and all the adsorbent in the adsorption tower that was originally in the secondary adsorption state is also in the blank zone, except for the mass transfer zone near the lower interface. In the blank areas, the adsorbent can adsorb a large amount of easily adsorbed components, thus ensuring that even if the pressure inside the adsorption tower drops very low after the pressure equalization and depressurization process is completed, the quality of the difficult-to-adsorb component product gas will not be affected. After the pressure equalization and depressurization is completed, the lower the pressure inside the adsorption tower, the greater the amount of easily adsorbed components desorbed from the adsorbent in the adsorption tower that was originally in the tertiary adsorption state. When the adsorption state ends, the difficult-to-adsorbed components remaining in the gaps of the adsorption tower that was originally in the tertiary adsorption state are replaced more cleanly by the easily adsorbed components, thus obtaining a higher yield of difficult-to-adsorbed component product gas.

[0040] Under the same partial pressure, different gas components have different adsorption capacities on the adsorbent; some have large adsorption capacities, while others have small adsorption capacities. Similarly, under the same pressure change, the adsorption capacities of different gas components also change differently; some change significantly, while others change little. For gas components with large adsorption capacities and large adsorption capacities, after 1-2 steps of pressure equalization and depressurization, the amount of easily adsorbed components desorbed from the adsorbent in the tertiary pressure equalization and depressurization adsorption tower is sufficient to push most of the gas existing in the adsorption tower voids before pressure equalization and depressurization out of the adsorption tower and into the secondary and primary pressure equalization and depressurization adsorption towers, thus achieving a high yield of the difficult-to-adsorb component product gas. For gas components with small adsorption capacities and small adsorption capacities, the adsorption tower needs to be lowered to a lower pressure. Only then can the amount of easily adsorbed components desorbed from the adsorbent be sufficient to push most of the gas existing in the tertiary pressure equalization and depressurization adsorption tower voids before pressure equalization and depressurization out of the adsorption tower and into the secondary and primary pressure equalization and depressurization adsorption towers, thus achieving a high yield of the difficult-to-adsorb component product gas.

[0041] In this invention, within one cycle, each pressure equalization state can be divided into 2-4 steps. That is, according to the adsorption characteristics of the easily adsorbed components, each pressure equalization and depressurization state can be designed as 2, 3, or 4 steps respectively. The pressure equalization and depressurization state of each adsorption tower corresponds to the pressure equalization and depressurization state of other adsorption towers. Within one cycle, the pressure equalization and depressurization state is also divided into 2, 3, or 4 steps respectively. The number of steps for the first pressure equalization design is the same as the number of steps for the second and third pressure equalization designs.

[0042] During the pressure equalization process, each pressure equalization step involves equalizing the gas between the adsorption tower in the pressure equalization and depressurization state and the adsorption tower in the pressure equalization and depressurization state with the closest pressure. Once the pressure in the adsorption towers participating in the pressure equalization process reaches equilibrium, this pressure equalization step is completed.

[0043] In this invention, the three adsorption towers in the pressure equalization and depressurization state are fixed each time pressure equalization occurs. However, the adsorption towers in the pressure equalization and depressurization state corresponding to each step of the pressure equalization and depressurization state are different. That is, if the pressure equalization is designed in two steps, the first step of pressure equalization and depressurization and the second step of pressure equalization and depressurization correspond to two different pressure equalization and depressurization adsorption towers. If the pressure equalization is designed in three steps, the first step of pressure equalization and depressurization, the second step of pressure equalization and depressurization, and the third step of pressure equalization and depressurization correspond to three different pressure equalization and depressurization adsorption towers. If the pressure equalization is designed in four steps, the first step of pressure equalization and depressurization, the second step of pressure equalization and depressurization, the third step of pressure equalization and depressurization, and the fourth step of pressure equalization and depressurization correspond to four different pressure equalization and depressurization adsorption towers.

[0044] In this invention, within one cycle, each adsorption tower undergoes the following steps: one adsorption, one pressure equalization and depressurization, two reverse pressurization, two adsorption, two pressure equalization and depressurization, three reverse pressurization, three adsorption, three pressure equalization and depressurization, reverse depressurization, vacuum depressurization, pressure equalization and pressurization, one reverse pressurization, and then one adsorption.

[0045] If the equalization design is a 2-step process, then the corresponding equalization pressure reduction states are: first equalization pressure reduction 1, first equalization pressure reduction 2, second equalization pressure reduction 1, second equalization pressure reduction 2, third equalization pressure reduction 1, and third equalization pressure reduction 2; the corresponding pressure increase states are equalization pressure increase 2 and equalization pressure increase 1.

[0046] If the equalization design involves 3 steps, then the corresponding equalization and pressure reduction states are: first equalization and pressure reduction 1, first equalization and pressure reduction 2, first equalization and pressure reduction 3, second equalization and pressure reduction 1, second equalization and pressure reduction 2, second equalization and pressure reduction 3, third equalization and pressure reduction 1, third equalization and pressure reduction 2, and third equalization and pressure reduction 3; the corresponding pressure increase states are equalization and pressure increase 3, equalization and pressure increase 2, and equalization and pressure increase 1.

[0047] If the equalization design involves 4 steps, then the corresponding equalization and pressure reduction states are: first equalization and pressure reduction 1, first equalization and pressure reduction 2, first equalization and pressure reduction 3, first equalization and pressure reduction 4; second equalization and pressure reduction 1, second equalization and pressure reduction 2, second equalization and pressure reduction 3, second equalization and pressure reduction 4; third equalization and pressure reduction 1, third equalization and pressure reduction 2, third equalization and pressure reduction 3, third equalization and pressure reduction 4; the corresponding pressure increase states are equalization and pressure increase 4, equalization and pressure increase 3, equalization and pressure increase 2, equalization and pressure increase 1.

[0048] The three adsorption towers, simultaneously in a pressure equalization and depressurization state, are respectively in the first, second, and third pressure equalization and depressurization states; the correspondence between the pressure equalization and depressurization states of the three adsorption towers and their corresponding pressure equalization and depressurization states is as follows:

[0049] If the equalization design is a 2-step process, the corresponding states are: first equalization pressure reduction 1, second equalization pressure reduction 1, and third equalization pressure reduction 1 correspond to equalization pressure increase 2, and first equalization pressure reduction 2, second equalization pressure reduction 2, and third equalization pressure reduction 2 correspond to equalization pressure increase 1.

[0050] If the equalization and pressure reduction design is 3 steps, the corresponding states are: first equalization and pressure reduction 1, second equalization and pressure reduction 1, and third equalization and pressure reduction 1 correspond to equalization and pressure increase 3; first equalization and pressure reduction 2, second equalization and pressure reduction 2, and third equalization and pressure reduction 2 correspond to equalization and pressure increase 2; and first equalization and pressure reduction 3, second equalization and pressure reduction 3, and third equalization and pressure reduction 3 correspond to equalization and pressure increase 1.

[0051] If the equalization and pressure reduction design is 4 steps, the corresponding states are: first equalization and pressure reduction 1, second equalization and pressure reduction 1, third equalization and pressure reduction 1 correspond to equalization and pressure increase 4; first equalization and pressure reduction 2, second equalization and pressure reduction 2, third equalization and pressure reduction 2 correspond to equalization and pressure increase 3; first equalization and pressure reduction 3, second equalization and pressure reduction 3, third equalization and pressure reduction 3 correspond to equalization and pressure increase 2; and first equalization and pressure reduction 4, second equalization and pressure reduction 4, third equalization and pressure reduction 4 correspond to equalization and pressure increase 1.

[0052] The flow direction of the pressure equalization gas is as follows: the difficult-to-adsorb components in the voids of the primary pressure equalization and depressurization adsorption tower flow directly into the pressure equalization and pressure boosting adsorption tower; the gas in the voids of the secondary pressure equalization and depressurization adsorption tower and the easily adsorbed components desorbed from the adsorbent first flow into the primary pressure equalization and depressurization adsorption tower, where the easily adsorbed components are adsorbed by the adsorbent, while the difficult-to-adsorbed components flow through the primary pressure equalization and depressurization adsorption tower into the pressure equalization and pressure boosting adsorption tower; the gas in the voids of the tertiary pressure equalization and depressurization adsorption tower and the easily adsorbed components desorbed from the adsorbent first flow into the secondary pressure equalization and depressurization adsorption tower, where a portion of the easily adsorbed components are adsorbed by the adsorbent, and the remaining easily adsorbed components, along with the difficult-to-adsorbed components, flow through the secondary pressure equalization and depressurization adsorption tower into the primary pressure equalization and depressurization adsorption tower, where the easily adsorbed components are adsorbed by the adsorbent, while the difficult-to-adsorbed components flow through the primary pressure equalization and depressurization adsorption tower into the pressure equalization and pressure boosting adsorption tower.

[0053] Preferably, to ensure that the pressure swing adsorption device can operate continuously and in a cyclic manner, and to ensure the continuity of the gas flow of the difficult-to-adsorb components, at least 9 adsorption towers are required when the pressure equalization state is designed as a 2-step process; at least 10 adsorption towers are required when the pressure equalization state is designed as a 3-step process; and at least 11 adsorption towers are required when the pressure equalization state is designed as a 4-step process.

[0054] Preferably, the three-tower series pressure swing adsorption unit can be used in pressure swing adsorption oxygen production, nitrogen production equipment or pressure swing adsorption hydrogen production equipment.

[0055] Compared with the prior art, the present invention has the following advantages:

[0056] In existing technologies, if the easily adsorbed component is a medium with a small adsorption capacity, in order to obtain a higher yield of the difficult-to-adsorb component while ensuring that the purity of the difficult-to-adsorb component meets the usage requirements, some operating conditions often require the use of two or three stages of pressure swing adsorption devices in series, which also increases the number of adsorption towers required. This invention uses a single pressure swing adsorption device, sets up a multi-step pressure equalization process, and adopts a method of adsorption by three adsorption towers simultaneously, which significantly improves the yield and reduces energy consumption and equipment investment while ensuring the quality of the product gas.

[0057] In this invention, at the end of the pressure equalization and depressurization state, most of the gas discharged from the adsorption tower that was originally in the tertiary adsorption state is the difficult-to-adsorb component, while a small amount of easily adsorbable components are present. A large amount of the difficult-to-adsorb components enter the adsorption tower that was originally in the secondary adsorption state and the primary adsorption state, as well as the adsorption tower in the pressure equalization and depressurization state, without being discharged from the pressure swing adsorption device. This allows the product gas yield of the difficult-to-adsorb components to reach or exceed the product gas yield of the commonly used two-stage or higher pressure swing adsorption devices. At the same time, it can ensure that the product gas quality of the difficult-to-adsorb components meets the requirements of high-purity gas. For pressure swing adsorption (PSA) hydrogen extraction devices, under the premise that the purity of the product hydrogen (≥99.999%) and the impurity content (N2≤5ppm, CO≤1ppm, CO2≤1ppm, CH4≤1ppm, H2O≤3ppm) meet the requirements for high-purity hydrogen in GB / T3634.2-2011, the product hydrogen yield is significantly higher than that of existing single-stage PSA hydrogen extraction devices. For example, for chlor-alkali gas purification hydrogen extraction devices, the highest product hydrogen yield of existing PSA devices is about 92%, while the product hydrogen yield can reach over 98% using the method of this invention. The method for obtaining the product hydrogen yield value is as follows: the purity of the feed gas and product hydrogen is analyzed by gas chromatography, and the feed gas flow rate and product hydrogen production are measured by the volumetric method in Appendix A of GB / T19773-2005. The product hydrogen yield value is then obtained by dividing the product hydrogen production by the amount of hydrogen in the feed gas. For pressure swing adsorption (PSA) oxygen and nitrogen generators, provided that the oxygen purity (≥90%) and nitrogen purity (≥99.5%) meet the basic parameter requirements in JB / T6427-2015, the unit power consumption for oxygen production and the unit power consumption for nitrogen production are significantly lower than the minimum requirements in JB / T6427-2015; for example, for a product oxygen pressure of 0.2 MPa and a gas production rate of 200 m³ / h... 3 For a PSA oxygen generator with a capacity of [number] m³ / h, the standard specifies a unit oxygen production power consumption of ≤1.0 kW·h / m³. 3 Using the method of this invention, the unit oxygen production power consumption is ≤0.6kW·h / m³. 3 For a product with an oxygen pressure of 0.005 MPa and a gas production rate of 8000 m³ / h... 3 For an axial flow VPSA oxygen generator with a capacity of [number] m³ / h, the minimum power consumption per unit oxygen production in the standard is 0.35 kW·h / m³. 3 Using the method of this invention, the unit oxygen production power consumption is ≤0.25kW·h / m³. 3 For a gas production rate of 3000m³ 3 For a PSA nitrogen generator with a capacity of [number] m³ / h, the standard specifies a unit nitrogen production power consumption of ≤0.43 kW·h / m³. 3 Using the method of this invention, the unit nitrogen production power consumption is ≤0.29kW·h / m³. 3 The above unit oxygen production power consumption and unit nitrogen production power consumption values ​​were obtained by measurement and calculation in accordance with the provisions of JB / T6427. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of a three-tower series pressure swing adsorption device corresponding to the two-step pressure equalization process in an embodiment of the present invention.

[0059] Figure 2 This is a schematic diagram of a three-tower series pressure swing adsorption device corresponding to the three-step pressure equalization process in an embodiment of the present invention;

[0060] Figure 3 This is a schematic diagram of a three-tower series pressure swing adsorption device corresponding to the four-step pressure equalization process in an embodiment of the present invention. Detailed Implementation

[0061] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0062] The present invention provides a three-tower series pressure swing adsorption device:

[0063] There are at least 9 adsorption towers and corresponding valves and fittings, and the adsorption towers are connected in series and parallel.

[0064] Each adsorption tower is controlled by 14 valves to switch between various states.

[0065] The 14 valves are numbered 1-14. The complete valve tag number is formed by prefixing the number with the corresponding adsorption tower code, such as A1, A2, ..., A14, B1, B2, ..., B14. Valves with the same number have the same function, and their connection methods and functions are as follows:

[0066] There are 7 valves connected to the lower interface of the adsorption tower, namely:

[0067] The primary adsorption inlet valves A5, B5, ..., I5 (J5, K5) allow gas from the outlet of the secondary adsorption tower to enter the primary adsorption tower. The primary adsorption inlet valves of each adsorption tower are connected in parallel through adsorption pipeline 2.

[0068] Secondary adsorption inlet valves A6, B6, ..., I6 (J6, K6) allow gas from the outlet of the tertiary adsorption tower to enter the secondary adsorption tower. The secondary adsorption inlet valves of each adsorption tower are connected in parallel through adsorption pipeline 1.

[0069] The three-stage adsorption inlet valves A1, B1, ..., I1 (J1, K1) allow the raw material gas to enter the three-stage adsorption tower. The three-stage adsorption inlet valves of each adsorption tower are connected in parallel through the raw material gas pipeline.

[0070] The reverse exhaust valves A2, B2, ..., I2 (J2, K2) are used to discharge the gas in the adsorption tower during the reverse depressurization process. The reverse exhaust valves of each adsorption tower are connected in parallel through the reverse pipeline.

[0071] The gas inside the adsorption tower is discharged through the extraction and exhaust valves A14, B14, ..., I14 (J14, K14) when the adsorption tower is in a vacuum and pressure reduction state. The extraction and exhaust valves of each adsorption tower are connected in parallel through extraction pipelines.

[0072] Gas from the outlet of the secondary pressure equalization and depressurization adsorption tower enters the primary pressure equalization and depressurization adsorption tower through the primary pressure equalization and depressurization inlet valves A3, B3, ..., I3 (J3, K3). The primary pressure equalization and depressurization inlet valves of each adsorption tower are connected in parallel through the pressure equalization pipeline 2.

[0073] Secondary equalization and depressurization inlet valves A4, B4, ..., I4 (J4, K4) allow gas from the outlet of the tertiary equalization and depressurization adsorption tower to enter the secondary equalization and depressurization adsorption tower. The secondary equalization and depressurization inlet valves of each adsorption tower are connected in parallel through equalization pipeline 1.

[0074] There are 7 valves connected to the upper interface of the adsorption tower, namely:

[0075] The gas in the tertiary adsorption tower is discharged into the secondary adsorption tower through the tertiary adsorption exhaust valves A7, B7, ..., I7 (J7, K7). The tertiary adsorption tower, the secondary adsorption tower, and the primary adsorption tower are connected in series through the tertiary adsorption exhaust valve, the secondary adsorption inlet valve, the secondary adsorption exhaust valve, and the primary adsorption inlet valve. The tertiary adsorption exhaust valve of each adsorption tower is connected in parallel through adsorption pipeline 1.

[0076] Secondary adsorption exhaust valves A8, B8, ..., I8 (J8, K8) allow gas in the secondary adsorption tower to be discharged into the primary adsorption tower; the secondary adsorption exhaust valves of each adsorption tower are connected in parallel through adsorption pipeline 2.

[0077] The primary adsorption exhaust valves A13, B13, ..., I13 (J13, K13) allow the gas inside the primary adsorption tower to be discharged from the adsorption tower as the difficult-to-adsorb component product gas. The primary adsorption exhaust valves of each adsorption tower are connected in parallel through the difficult-to-adsorb component product gas pipeline.

[0078] The gas in the tertiary pressure equalization and depressurization adsorption tower is discharged into the secondary pressure equalization and depressurization adsorption tower through the tertiary pressure equalization and depressurization exhaust valves A9, B9, ..., I9 (J9, K9). The tertiary pressure equalization and depressurization adsorption tower, the secondary pressure equalization and depressurization adsorption tower, and the primary pressure equalization and depressurization adsorption tower are connected in series through the tertiary pressure equalization and depressurization exhaust valve, the secondary pressure equalization and depressurization inlet valve, the secondary pressure equalization and depressurization exhaust valve, and the primary pressure equalization and depressurization inlet valve. The tertiary pressure equalization and depressurization exhaust valves of each adsorption tower are connected in parallel through the pressure equalization pipeline 1.

[0079] Secondary equalization and depressurization exhaust valves A10, B10, ..., I10 (J10, K10) are used to discharge the gas in the secondary equalization and depressurization adsorption tower into the primary equalization and depressurization adsorption tower; the secondary equalization and depressurization exhaust valves of each adsorption tower are connected in parallel through equalization pipeline 2.

[0080] The gas in the primary pressure equalization and depressurization adsorption tower is discharged into the pressure equalization and boosting adsorption tower through the primary pressure equalization and depressurization exhaust valves A11, B11, ..., I11 (J11, K11); the primary pressure equalization and depressurization exhaust valves of each adsorption tower are connected in parallel through the pressure equalization and boosting pipeline.

[0081] The reverse flushing valves A12, B12, ..., I12 (J12, K12) allow reverse pressurization gas or flushing gas to enter the adsorption tower that needs reverse pressurization or flushing. The reverse flushing valves of each adsorption tower are connected in parallel through the reverse flushing gas pipeline.

[0082] The technical solution of the present invention also provides a pressure swing adsorption equalization process, which is achieved by using the above-mentioned three-tower series pressure swing adsorption device.

[0083] like Figure 1 As shown, in one embodiment of the present invention, when the pressure equalization process is designed as a two-step process, the three-tower series pressure swing adsorption device is divided into 9 sections and 27 steps in one cycle, and the specific process sequence is shown in Table 1.

[0084] Table 1. Timing of the Two-Step Pressure Equalization Process

[0085] 1 2 3 4 5 6 7 8 9 A Triple suction Triple suction Triple suction The three averages decreased by 1. All three decreased by 2 Reverse decline Reverse decline Descent Descent B The two averages decreased by 1. The average decreased by 2. Three Reversals Triple suction Triple suction Triple suction The three averages decreased by 1. All three decreased by 2 Reverse decline C Second suction Second suction Second suction The two averages decreased by 1. The average decreased by 2. Three Reversals Triple suction Triple suction Triple suction D One average decrease of 1 One average decrease of 2 Two reversals Second suction Second suction Second suction The two averages decreased by 1. The average decreased by 2. Three Reversals E One inhale One inhale One inhale One average decrease of 1 One average decrease of 2 Two reversals Second suction Second suction Second suction F Average increase 2 One reverse rise One inhale One inhale One inhale One average decrease of 1 One average decrease of 2 Two reversals G Descent All rose by 1 Average increase 2 One reverse rise One inhale One inhale One inhale H Reverse decline Descent Descent Descent All rose by 1 Average increase 2 One reverse rise I The three averages decreased by 1. All three decreased by 2 Reverse decline Reverse decline Descent Descent Descent All rose by 1 10 11 12 13 14 15 16 17 18 A Descent All rose by 1 Average increase 2 One reverse rise One inhale One inhale One inhale B Reverse decline Descent Descent Descent All rose by 1 Average increase 2 One reverse rise C The three averages decreased by 1. All three decreased by 2 Reverse decline Reverse decline Descent Descent Descent All rose by 1 D Triple suction Triple suction Triple suction The three averages decreased by 1. All three decreased by 2 Reverse decline Reverse decline Descent Descent E The two averages decreased by 1. The average decreased by 2. Three Reversals Triple suction Triple suction Triple suction The three averages decreased by 1. All three decreased by 2 Reverse decline F Second suction Second suction Second suction The two averages decreased by 1. The average decreased by 2. Three Reversals Triple suction Triple suction Triple suction G One average decrease of 1 One average decrease of 2 Two reversals Second suction Second suction Second suction The two averages decreased by 1. The average decreased by 2. Three Reversals H One inhale One inhale One inhale One average decrease of 1 One average decrease of 2 Two reversals Second suction Second suction Second suction I Average increase 2 One reverse rise One inhale One inhale One inhale One average decrease of 1 One average decrease of 2 Two reversals 19 20 21 22 23 24 25 26 27 A One average decrease of 1 One average decrease of 2 Two reversals Second suction Second suction Second suction The two averages decreased by 1. The average decreased by 2. Three Reversals B One inhale One inhale One inhale One average decrease of 1 One average decrease of 2 Two reversals Second suction Second suction Second suction C Average increase 2 One reverse rise One inhale One inhale One inhale One average decrease of 1 One average decrease of 2 Two reversals D Descent All rose by 1 Average increase 2 One reverse rise One inhale One inhale One inhale E Reverse decline Descent Descent Descent All rose by 1 Average increase 2 One reverse rise F The three averages decreased by 1. All three decreased by 2 Reverse decline Reverse decline Descent Descent Descent All rose by 1 G Triple suction Triple suction Triple suction The three averages decreased by 1. All three decreased by 2 Reverse decline Reverse decline Descent Descent H The two averages decreased by 1. The average decreased by 2. Three Reversals Triple suction Triple suction Triple suction The three averages decreased by 1. All three decreased by 2 Reverse decline I Second suction Second suction Second suction The two averages decreased by 1. The average decreased by 2. Three Reversals Triple suction Triple suction Triple suction

[0086] like Figure 2 As shown, in one embodiment of the present invention, when the pressure equalization process is designed as a three-step process, the three-tower series pressure swing adsorption device is divided into 10 sections and 40 steps in one cycle, and the specific process sequence is shown in Table 2.

[0087] Table 2. Three-step pressure equalization process sequence

[0088]

[0089]

[0090]

[0091] like Figure 3 As shown, in one embodiment of the present invention, when the pressure equalization process is designed as four steps, the three-tower series pressure swing adsorption device is divided into 11 sections and 55 steps in one cycle, and the specific process sequence is shown in Table 3.

[0092] Table 3. Timing of the Four-Step Pressure Equalization Process

[0093]

[0094]

[0095]

[0096] The following section uses a four-step pressure equalization process as an example to further illustrate the pressure swing adsorption pressure equalization process provided in this invention:

[0097] The four-step pressure equalization process can be divided into 11 sections and 55 steps in one cycle. The adsorption towers simultaneously in the adsorption state are identical in each section. Each section contains 5 steps, and the functional states achieved by different adsorption towers in these 5 steps are different. All the functional states achieved by the 11 adsorption towers in these 5 steps constitute all the functional states experienced by an adsorption tower in one cycle. The following section, steps 1-5, is used as an example to describe the specific correspondence between different functional states and valves and pipelines:

[0098] Step 1: Adsorption tower A, which has completed three reverse-up states, adsorption tower C, which has completed two reverse-up states, and adsorption tower E, which has completed one reverse-pressurization state, simultaneously enter the adsorption state. Valves A1, A7, C6, C8, E5, and E13 are opened. The raw material gas enters adsorption tower A through valve A1 at the lower interface. Adsorption tower A enters the three-stage adsorption state. Easily adsorbed components are adsorbed by the adsorbent, while difficult-to-adsorb components (containing trace amounts or small amounts of easily adsorbed components) flow out of adsorption tower A through the upper interface and enter adsorption tower C through valve A7, adsorption pipeline 1, and valve C6 at the lower interface. When adsorption tower C enters the secondary adsorption state, the easily adsorbed components in the gas are adsorbed by the adsorbent. The difficult-to-adsorb components containing trace amounts of easily adsorbed components flow out of adsorption tower C from the upper interface and enter adsorption tower E from the lower interface through valve C8, adsorption pipeline 2, and valve E5. Adsorption tower E enters the primary adsorption state, where trace amounts of easily adsorbed components in the gas are adsorbed by the adsorbent. The difficult-to-adsorb components containing trace amounts of easily adsorbed components flow out of adsorption tower E from the upper interface and enter the difficult-to-adsorb component product gas pipeline through valve E13. The product gas is then sent out of the pressure swing adsorption unit through subsequent equipment (such as product gas buffer tank).

[0099] While adsorption towers A, C, and E enter the adsorption state, adsorption towers K, B, and D (which have just completed three adsorption cycles), B, and D (which have just completed one adsorption cycle) remain connected in series with adsorption tower F for the first step of pressure equalization. Valves K9, B4, B10, D3, D11, and F11 are opened. Adsorption tower K enters the third pressure equalization and depressurization state 1, adsorption tower B enters the second pressure equalization and depressurization state 1, adsorption tower D enters the first pressure equalization and depressurization state 1, and adsorption tower F enters the pressure equalization and pressurization state 4. The gas in the voids of adsorption tower D, with a quality equivalent to the difficult-to-adsorb component product gas, flows out of the adsorption tower from the upper interface and flows into adsorption tower F through valves D11 and F11 from the upper interface of adsorption tower F. The easily adsorbed components in the voids of adsorption tower B, the easily adsorbed components desorbed from the adsorbent during pressure equalization and depressurization, and the gas from adsorption tower K... The readily adsorbable components flowing in are adsorbed by the adsorbent in the mass transfer zone and the blank zone. The difficult-to-adsorb components in the voids of adsorption tower B containing trace amounts of readily adsorbable components, as well as the difficult-to-adsorbable components flowing in from adsorption tower K, flow out of adsorption tower B through the upper interface and enter adsorption tower D through valve B10, pressure equalization pipeline 2, and valve D3 through the lower interface of adsorption tower D. A small amount of readily adsorbable components are adsorbed by the adsorbent, and the difficult-to-adsorbable components containing trace amounts of readily adsorbable components flow out of adsorption tower D through the upper interface and flow into adsorption tower F through valve D11 and valve F11 through the upper interface of adsorption tower F. The gas in the voids of adsorption tower K and the desorbed readily adsorbable components flow into adsorption tower B through the upper interface of adsorption tower K, valve K9, pressure equalization pipeline 1, and valve B4 through the lower interface of adsorption tower B. When the pressure between adsorption tower K, adsorption tower B, adsorption tower D, and adsorption tower F reaches equilibrium, the first step of the pressure equalization process is completed, and valve F11 is closed.

[0100] While adsorption towers A, C, and E enter the adsorption state, adsorption tower I continues to be evacuated and depressurized, adsorption tower J continues to depressurize in the reverse direction, and adsorption towers G and H are in a blank waiting state.

[0101] Step 2: Adsorption towers A, C, and E continue to be in a series adsorption state;

[0102] Adsorption towers K, B, and D continue to be connected in series for pressure equalization and reduction. Valve G11 is opened and connected to adsorption tower G to perform the second step of pressure equalization. Adsorption tower K enters the third pressure equalization and reduction state 2, adsorption tower B enters the second pressure equalization and reduction state 2, adsorption tower D enters the first pressure equalization and reduction state 2, and adsorption tower G enters the pressure equalization and increase state 3. When the pressure among adsorption towers K, B, D, and G reaches equilibrium, the second step of pressure equalization is completed, and valve G11 is closed.

[0103] Meanwhile, adsorption tower I continues to be evacuated and depressurized, adsorption tower J continues to be depressurized in the reverse direction, and adsorption towers F and H are in a blank waiting state.

[0104] Step 3: Adsorption towers A, C, and E continue to be in a series adsorption state;

[0105] Adsorption towers K, B, and D continue to be connected in series for pressure equalization and reduction. Valve H11 is opened, connecting to adsorption tower H, to perform the third step of pressure equalization. Adsorption tower K enters the third stage of pressure equalization and reduction (stage 3), adsorption tower B enters the second stage of pressure equalization and reduction (stage 3), adsorption tower D enters the first stage of pressure equalization and reduction (stage 3), and adsorption tower H enters the second stage of pressure equalization and increase (stage 2). When the pressure among adsorption towers K, B, D, and H reaches equilibrium, the third step of pressure equalization is completed, and valve H11 is closed.

[0106] Meanwhile, adsorption tower I continues to be evacuated and depressurized, adsorption tower J continues to be depressurized in the reverse direction, and adsorption towers F and G are in a blank waiting state.

[0107] Step 4: Adsorption towers A, C, and E continue to be in a series adsorption state;

[0108] When adsorption tower I finishes its vacuuming and depressurization process, valve I14 closes. Simultaneously, valve I11 opens, connecting adsorption tower I with adsorption towers K, B, and D, which continue to maintain a series pressure equalization and depressurization process, to perform the fourth step of pressure equalization. Adsorption tower K enters the third pressure equalization and depressurization stage 4, adsorption tower B enters the second pressure equalization and depressurization stage 4, adsorption tower D enters the first pressure equalization and depressurization stage 4, and adsorption tower I enters the pressure equalization and pressure increase stage 1. When the pressures among adsorption towers K, B, D, and I reach equilibrium, the fourth step of pressure equalization is complete, and valves K9, B4, B10, D3, D11, and I11 close, thus completing the entire pressure equalization process.

[0109] As adsorption tower I ends its vacuum depressurization state, adsorption tower J ends its reverse depressurization state and valve J2 closes; at the same time, valve J14 opens and adsorption tower J enters its vacuum depressurization state; adsorption tower J is either connected to a vacuum pump through a vacuum tank or directly connected to a vacuum pump, and the gas in the adsorption tower is extracted by the vacuum pump through the depressurization pipeline.

[0110] While the fourth step of the pressure equalization process is being carried out between adsorption towers K, B, D, and I, adsorption towers F, G, and H are in a blank waiting state.

[0111] Step 5: Adsorption towers A, C, and E continue to be in a series adsorption state;

[0112] When valves B12 and D12 are opened simultaneously, adsorption tower B enters a three-stage reverse pressurization state, and adsorption tower D enters a two-stage reverse pressurization state. Simultaneously, adsorption tower F ends its blank waiting state, valve F12 opens, and adsorption tower F enters a one-stage reverse pressurization state. The difficult-to-adsorb component product gas enters adsorption towers B, D, and F respectively through the reverse flushing pipeline via valves B12, D12, and F12 from the upper interface of the adsorption towers. After the pressure in adsorption towers B, D, and F rises to the adsorption pressure, the three-stage reverse pressurization state of adsorption tower B is completed, the two-stage reverse pressurization state of adsorption tower D is completed, and the one-stage reverse pressurization state of adsorption tower F is completed. Then, valves B12, D12, and F12 are closed.

[0113] While adsorption towers B, D, and F enter the reverse pressurization state, adsorption tower K enters the reverse depressurization state. Valve K2 opens, and the gas inside the adsorption tower is discharged through the reverse depressurization pipeline.

[0114] Meanwhile, adsorption tower J continues to be evacuated and depressurized, while adsorption towers G, H, and I are in a blank waiting state.

[0115] At this point, the first phase is complete. The valve position numbers and pipelines corresponding to the different adsorption towers in the other 10 phases when achieving the same functional state are the same as in the first phase, and can be deduced by analogy based on the descriptions in steps 1-5.

[0116] In comparison with this embodiment, the valve switching states, corresponding pipelines, and gas flow states in the one-step, two-step, and three-step pressure equalization processes are completely identical to those in the four-step pressure equalization process when the same functional state is reached. The only difference is the adsorption tower involved. These processes can be described based on the four-step pressure equalization process and will not be elaborated further here.

[0117] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A three-tower series pressure swing adsorption device, characterized in that: The device includes at least 9 adsorption towers and corresponding valves and fittings, wherein the adsorption towers are connected in series and in parallel. Each adsorption tower is controlled by 14 valves to switch between various states; The lower and upper interfaces of the adsorption tower are each connected to seven valves. Seven valves are connected to the lower interface of the adsorption tower, including: The gas from the outlet of the secondary adsorption tower enters the primary adsorption tower through the primary adsorption inlet valve; the primary adsorption inlet valves of each adsorption tower are connected in parallel through adsorption pipeline 2. The secondary adsorption inlet valve allows gas from the outlet of the tertiary adsorption tower to enter the secondary adsorption tower; the secondary adsorption inlet valves of each adsorption tower are connected in parallel through adsorption pipeline 1. The feed gas enters the adsorption tower through the three-stage adsorption inlet valve. The three-stage adsorption inlet valves of each adsorption tower are connected in parallel through the feed gas pipeline. The reverse exhaust valve is used to discharge the gas inside the adsorption tower when the adsorption tower is in the reverse depressurization process. The reverse exhaust valves of each adsorption tower are connected in parallel through the reverse pipeline. When the adsorption tower is in a vacuum and depressurization state, the gas inside the adsorption tower is discharged from the adsorption tower through the extraction and exhaust valve. The extraction and exhaust valves of each adsorption tower are connected in parallel through extraction pipelines. The gas from the outlet of the secondary pressure equalization and depressurization adsorption tower enters the primary pressure equalization and depressurization adsorption tower through the primary pressure equalization and depressurization inlet valve. The primary pressure equalization and depressurization inlet valves of each adsorption tower are connected in parallel through the pressure equalization pipeline 2. The secondary equalization and depressurization inlet valve allows gas from the outlet of the tertiary equalization and depressurization adsorption tower to enter the secondary equalization and depressurization adsorption tower. The secondary equalization and depressurization inlet valves of each adsorption tower are connected in parallel through equalization pipeline 1. Seven valves are connected to the upper interface of the adsorption tower, including: The tertiary adsorption exhaust valve connects the tertiary adsorption tower, the secondary adsorption tower, and the primary adsorption tower in series via the tertiary adsorption exhaust valve, the secondary adsorption inlet valve, and the primary adsorption inlet valve; the tertiary adsorption exhaust valve of each adsorption tower is connected in parallel via adsorption pipeline 1. Secondary adsorption exhaust valve: the gas in the secondary adsorption tower is discharged into the primary adsorption tower through the secondary adsorption exhaust valve. The secondary adsorption exhaust valves of each adsorption tower are connected in parallel through adsorption pipeline 2. The gas inside the primary adsorption tower is discharged from the adsorption tower through the primary adsorption exhaust valve and discharged into the difficult-to-adsorb component product gas pipeline as the difficult-to-adsorb component product gas. The primary adsorption exhaust valves of each adsorption tower are connected in parallel through the difficult-to-adsorb component product gas pipeline. The three equalization and depressurization exhaust valves, the three equalization and depressurization adsorption towers, the two equalization and depressurization adsorption towers, and the one equalization and depressurization adsorption towers are connected in series through the three equalization and depressurization exhaust valves, the two equalization and depressurization inlet valves, the two equalization and depressurization exhaust valves, and the one equalization and depressurization inlet valves; the three equalization and depressurization exhaust valves of each adsorption tower are connected in parallel through equalization pipeline 1. The gas in the secondary pressure equalization and depressurization adsorption tower is discharged into the primary pressure equalization and depressurization adsorption tower through the secondary pressure equalization and depressurization valve; the secondary pressure equalization and depressurization valves of each adsorption tower are connected in parallel through the pressure equalization pipeline 2. The gas in the primary pressure equalization and depressurization adsorption tower is discharged into the pressure equalization and boosting adsorption tower through the primary pressure equalization and depressurization exhaust valve. The primary pressure equalization and depressurization exhaust valves of each adsorption tower are connected in parallel through the pressure equalization and boosting pipeline. The reverse flushing valve allows reverse pressurized gas or flushing gas to enter the adsorption tower that needs reverse pressurization or flushing. The reverse flushing valves of each adsorption tower are connected in parallel through the reverse flushing gas pipeline.

2. The three-tower series pressure swing adsorption device as described in claim 1, characterized in that: The three-tower series pressure swing adsorption device includes 9-11 adsorption towers.

3. A pressure swing adsorption (PSA) equalization process, characterized in that: The three-tower series pressure swing adsorption device according to any one of claims 1-2 is used in accordance with the following steps: In the aforementioned three-tower series pressure swing adsorption device, within one cycle, each adsorption tower undergoes the following steps: first adsorption, first equalization and depressurization, second reverse pressurization, second adsorption, second equalization and depressurization, third reverse pressurization, third adsorption, third equalization and depressurization, reverse depressurization, vacuum depressurization, equalization and pressurization, first reverse pressurization, and then another adsorption. In the pressure equalization process of the three-tower series adsorption, the pressure swing adsorption process is used to separate and purify the gas. During the pressure equalization process, four adsorption towers participate simultaneously. Among them, three adsorption towers are in the pressure equalization and depressurization state, corresponding to the first pressure equalization and depressurization, the second pressure equalization and depressurization, and the third pressure equalization and depressurization, respectively, and one adsorption tower is in the pressure equalization and depressurization state. Three adsorption towers in the pressure equalization and depressurization state are connected in series. Before entering the pressure equalization and depressurization state, these three adsorption towers are in the series adsorption state. When the pressure equalization and depressurization is carried out, their series connection is the same as when these three adsorption towers are in the adsorption state. During pressure equalization, the three adsorption towers that have completed their adsorption phase remain connected in series, but are disconnected from the feed gas pipeline and product gas pipeline, respectively. The upper interface of the adsorption tower that was originally in the primary adsorption phase is connected to the upper interface of the adsorption tower in the pressure equalization and boosting phase via a pressure equalization and boosting pipeline. When the adsorption phase ends, the adsorbent in the adsorption tower that was originally in the primary adsorption phase is still in the blank zone, and the gas quality in the void is the same as that of the difficult-to-adsorb component product gas. The adsorbent in the adsorption tower that was originally in the secondary adsorption phase is in the mass transfer zone near the lower interface of the adsorption tower, and the upper part of the mass transfer zone is the blank zone. During pressure equalization and depressurization, the state of the adsorption tower that was in the tertiary adsorption phase is adjusted to tertiary pressure equalization and depressurization. When the adsorption tower in the secondary adsorption state is adjusted to the secondary pressure equalization and depressurization state, and the adsorption tower in the primary adsorption state is adjusted to the primary pressure equalization and depressurization state, the easily adsorbed components flowing out of the adsorption tower that was originally in the tertiary adsorption state, the easily adsorbed components desorbed from the adsorbent in the adsorption tower that was originally in the secondary adsorption state, and the easily adsorbed components in the pores of the adsorption tower will be adsorbed by the adsorbent in the blank area of ​​the adsorption tower that was originally in the secondary adsorption state and the adsorption tower that was originally in the primary adsorption state. This ensures that after the pressure equalization and depressurization state is completed, only a trace amount of easily adsorbed components flow into the adsorption tower that is in the pressure equalization and depressurization state along with the difficult-to-adsorb components. The quality of the gas flowing into the adsorption tower that is in the pressure equalization and depressurization state is equivalent to the quality of the product gas of the difficult-to-adsorb components. During the pressure equalization process, each pressure equalization step involves equalizing the gas between the adsorption tower in the pressure equalization and depressurization state and the adsorption tower in the pressure equalization and depressurization state with the closest pressure. Once the pressure in the adsorption towers participating in the pressure equalization process reaches equilibrium, this pressure equalization step is completed. The gas flow direction in the three adsorption towers under equalized pressure reduction is the same as the gas flow direction when the three adsorption towers are in the adsorption state.

4. The pressure swing adsorption equalization process as described in claim 3, characterized in that: Within one cycle, each pressure equalization state can be divided into 2-4 steps; the pressure equalization and depressurization state of each adsorption tower corresponds to the pressure equalization and depressurization state of other adsorption towers, and within one cycle, the pressure equalization and depressurization state is also divided into 2, 3, or 4 steps respectively.

5. The pressure swing adsorption equalization process as described in claim 4, characterized in that: When the pressure equalization process is designed as a two-step process, the entire pressure swing adsorption device shall have at least 9 adsorption towers; when the pressure equalization process is designed as a three-step process, the entire pressure swing adsorption device shall have at least 10 adsorption towers; when the pressure equalization process is designed as a four-step process, the entire pressure swing adsorption device shall have at least 11 adsorption towers.

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