A three-tower series pressure swing adsorption device and adsorption process

Abstract

The present invention discloses a three-tower series pressure swing adsorption device and adsorption process. The device employs a set of pressure swing adsorption devices and three adsorption towers for simultaneous adsorption, significantly improving yields and reducing energy consumption and equipment investment while ensuring product gas quality. The three-tower series pressure swing adsorption process provided by the present invention is used for pressure swing adsorption hydrogen extraction. While ensuring that the product hydrogen purity and impurity content meet high-purity hydrogen requirements, the product hydrogen yield is significantly higher than that of existing single-stage pressure swing adsorption hydrogen extraction devices. The three-tower series pressure swing adsorption process provided by the present invention is used for pressure swing adsorption oxygen and nitrogen production. While ensuring that the oxygen purity and nitrogen purity meet basic parameter requirements, the unit oxygen production power consumption and unit nitrogen production power consumption are significantly lower than the minimum index requirements in relevant standards.

Description

Technical Field

[0001] The present invention relates to a pressure swing adsorption gas separation technology, and in particular to a three-tower series pressure swing adsorption device and an adsorption process. Background Art

[0002] Pressure swing adsorption (PSA) technology has been used in gas separation and purification for over 70 years and is widely used in various industries requiring gas separation. Examples include PSA nitrogen production (for separating nitrogen from air), PSA oxygen production (for separating oxygen from air), and PSA hydrogen production (for separating and purifying hydrogen from refinery gas). PSA technology utilizes a PSA unit. Most currently used PSA units, when in the adsorption state, require the feed gas to pass through only one adsorption tower, from the time it enters the adsorption tower to the time the target product gas is obtained. Alternatively, some systems utilize multi-stage PSA units. However, these units are essentially two or more PSA units connected in series, with the intermediate product gas produced by the preceding PSA unit and the target product gas produced by the final PSA unit. Therefore, during PSA operation, the feed gas actually passes through only one adsorption tower.

[0003] Most pressure swing adsorption devices currently in use, when in the adsorption state, from the time the raw gas enters the adsorption tower to the time the target product gas is obtained, the raw gas only passes through one adsorption tower. This is also true for multi-stage pressure swing adsorption devices. A multi-stage pressure swing adsorption device is actually two or more pressure swing adsorption devices connected in series, rather than a series connection between adsorption towers within a single device. The intermediate product gas is obtained through the front-stage pressure swing adsorption device, and then the target product gas is obtained through the last-stage pressure swing adsorption device. There are some authorized patents for the technology of having two or more adsorption towers connected in series when in the adsorption state. The patent content is as follows:

[0004] The invention patent with application number ZL00113035.8 discloses a "back and forth pressure swing adsorption process" that operates multiple adsorption towers in series, so that the amount of adsorbent flowing through the raw gas remains unchanged, while the total amount of adsorbent is reduced, the equipment size is correspondingly smaller, and the operating energy consumption is also reduced. The adsorption step is divided into two or more stages, and the direction of the adsorbed effluent gas changes back and forth according to a certain rule. In addition, when the depressurized effluent gas of the adsorption tower flows into the adsorption tower, the distribution position of the easily adsorbed components in the adsorption tower is more reasonable. When the adsorption towers of this patent are connected in series, the outlet of the first adsorption tower where the raw gas enters is connected to the outlet of the second adsorption tower, the inlet of the second adsorption tower is connected to the inlet of the third adsorption tower, the outlet of the third adsorption tower is connected to the outlet of the fourth adsorption tower, and so on. In this patent, the series connection between the adsorption towers is carried out in a manner of connecting the inlets to the inlets and the outlets to the outlets. At the same time, in addition to being connected in series, the adsorption towers in the adsorption state may also be connected in parallel. Each adsorption tower has multiple adsorption states, which are carried out continuously. The flow direction of the gas in the adsorption tower needs to be reversed when it is in the adsorption state at different stages. When the method in this patent is used, when the difficult-to-adsorb component is used as the product gas, the purity of the product gas is variable, and it is difficult to ensure high purity, and the product gas flow is discontinuous. In this patent, the adsorbent is already saturated or near saturation before the adsorption tower is depressurized. When depressurizing, the gas in the adsorption tower is first discharged into multiple empty tanks, and then pressure-equalized with other adsorption towers. When the gas is discharged into the empty tanks, a large amount of easily adsorbed components will be desorbed from the adsorbent and discharged into the empty tanks. When pressure equalization is performed, a large amount of components discharged into the pressure-equalizing and boosting adsorption tower are easily adsorbed gases, which results in the purity of the difficult-to-adsorb component product gas failing to meet the high-purity gas quality requirements.

[0005] Publication number CN103695063A discloses a "method for concentrating low-concentration methane gas." This method concentrates low-concentration methane gas with a CH4 concentration ≤30% V and a pressure ≤0.5 MPa.G via a pressure swing adsorption process. The method employs N (N ≥ 3) adsorption towers, each filled with adsorbent. During one adsorption cycle, N adsorption stages are cycled through, with each tower performing N-1 adsorption cycles in series. After the pressure of the N adsorption towers is equalized in each adsorption stage, the tower that has performed N-1 adsorption cycles is flushed and replaced, then vacuumed for desorption. The pressure of the next N-1 adsorption towers is then reversed to the adsorption pressure and adsorption continues. This cycle completes one adsorption cycle. The beneficial effects of this invention are that this method significantly improves the CH4 yield from methane gas concentration, significantly increases the CH4 concentration, and reduces investment and operating costs. The adsorption towers in this patent are connected end-to-end, and the number of adsorption towers in series is the total number of adsorption towers minus one. This patent uses the easily adsorbable component as the target product gas, which can greatly increase the content of the easily adsorbable component in the target product gas. When the purity of the difficult-to-adsorb component is not high, the easily adsorbable component in the target product can obtain a higher yield. If the difficult-to-adsorb component is to have a high purity, the yield of the easily adsorbable component in the target product gas will inevitably decrease; the airflows of the easily adsorbable component and the difficult-to-adsorbable component obtained by the process technology in this patent are discontinuous, which may cause certain fluctuations in the pressure of the airflow of the easily adsorbable component and the airflow of the difficult-to-adsorbable component; when the pressure is equalized and reversely increased between the adsorption towers, the raw gas does not enter any adsorption tower, which will cause the raw gas pressure to be high; this patent can only perform pressure equalization once, and cannot significantly improve the yield of the difficult-to-adsorbable component.

[0006] The utility model patent with publication number CN202237712U provides "a device for concentrating coal mine ventilation gas by a multi-tower pressure swing adsorption method". The device obtains product gas from the desorption stage through the method of pressure swing adsorption. In order to increase the volume fraction of methane in the product gas as much as possible under a lower pressure difference and maintain a high recovery rate, a multi-tower parallel and series process is used in the adsorption process. After the raw gas is adsorbed by the adsorption tower, the high-pressure gas flowing out from the exhaust end of the adsorption tower enters the next adsorption for adsorption. The mass transfer zone in the adsorption process can be reduced and the adsorption tower can be completely removed, thereby increasing the volume fraction of the product gas. Coal mine ventilation gas can be enriched at a lower energy consumption, realizing the utilization of methane gas in ventilation gas and reducing greenhouse gas emissions. This patent uses the easily adsorbable component as the target product gas, and the series connection between the adsorption towers is carried out in an end-to-end manner. However, when in the adsorption state, only a small part of the time the two adsorption towers are in the series adsorption state, and most of the time only one adsorption tower is in the adsorption state; the process method in this patent does not control the purity of the difficult-to-adsorb component, nor can it control the purity of the difficult-to-adsorb component; using the method in this patent, the content of the target component in the target product gas is only doubled compared with the content of the target component in the feed gas, from 0.2% to 0.4%~0.42%, and the concentration effect is not obvious. This patent adopts the method of directly equalizing the pressure of the adsorption tower that needs to be desorbed on the adsorption tower that needs to be pressurized. Because the adsorbent in the adsorption tower that needs to be desorbed is already in an adsorption saturation state before equalization, when equalization is performed, a large amount of desorbed easily adsorbed component will flow into the adsorption tower that needs to be pressurized, thereby causing the difficult-to-adsorb component to be unable to achieve a high purity and unable to effectively control the purity of the difficult-to-adsorb component; and there is only one equalization process, which cannot significantly improve the yield of the difficult-to-adsorb component.

[0007] The invention patent with publication number CN102423602A discloses "a series adsorption gas separation process in which the product gas discharged from the adsorption tower always maintains a high concentration." This solves the problem in the prior art that the product gas purity is low due to the gas adsorption passing through the adsorption tower once and then discharging the product gas. A total of at least 6 adsorption towers are combined to achieve cyclic adsorption. At the same time, each adsorption tower completes one process. The raw gas enters the first adsorption tower in a forward direction through the valve. The impurities are adsorbed by the adsorbent to obtain intermediate gas. The intermediate gas flows out through the valve and flows to the second adsorption tower. In the second adsorption tower, the impurities are adsorbed by the adsorbent to obtain product gas. The product gas flows out of the second adsorption tower through the valve and enters the next process section. The raw gas is adsorbed once to obtain intermediate gas, and the intermediate gas is adsorbed again to obtain product gas, so that the purity of the product gas can be achieved at a high level. This patent targets difficult-to-adsorb components as product gas. According to the patent claims and the description in the invention content, the adsorption towers are connected end to end when in the adsorption state. However, according to the description in the specific implementation method, only one adsorption tower is in the adsorption state, and there is no working condition where two adsorption towers are connected in series. The specific implementation method example also has the following description: A series adsorption gas separation process, a total of at least 6 adsorption towers are combined to achieve cyclic adsorption, namely the first adsorption tower 1, the second adsorption tower 2, the third adsorption tower 3, the fourth adsorption tower 4, the fifth adsorption tower 5, and the sixth adsorption tower 6. At the same time, each adsorption tower completes a process, and the six processes are adsorption, depressurization, venting, vacuuming, pressurization, and stamping. Taking the adsorption of the first adsorption tower as an example, the series adsorption is carried out. At this time, the second adsorption tower is stamping, the third adsorption tower is pressurizing, the fourth adsorption tower is vacuuming, the fifth adsorption tower is venting, and the sixth adsorption tower is depressurizing. According to this description, there are 6 adsorption towers, and the 6 adsorption towers are in different processes, and there is no working condition where two adsorption towers are in the adsorption state at the same time.

[0008] Patent publication number CN113426245A discloses a "high-purity gas production method based on pressure swing adsorption." While retaining the pressure-equalizing regeneration of the adsorption towers, this method connects multiple adsorption towers in series along the adsorption path, effectively improving product gas purity. During regeneration, the regenerated adsorption tower is connected in series to the adsorption path, and the first-stage adsorption tower in the original adsorption path is disconnected for regeneration. This approach reduces the impact of tower replacement on product gas purity. At the same time, the adsorption towers retain the advantages of the original pressure-equalizing operation, maintaining a high adsorption pressure, reducing pressure drop, and reducing airflow fluctuations, effectively improving gas yield. This patent uses difficult-to-adsorb components as target product gas; when in the adsorption state, the adsorption towers are connected in series in an end-to-end manner; the adsorption state of each adsorption tower is carried out continuously; when equalizing the pressure, the adsorption tower that has completed the adsorption state is directly equalized with the adsorption tower that needs equalization. Since a large number of easily adsorbable components will be desorbed from the adsorbent during the equalization and pressure reduction process, a large number of easily adsorbable components will enter the adsorption tower that needs equalization and pressure increase during the equalization. Therefore, this method will have a certain improvement in the yield of difficult-to-adsorb components. However, a large number of easily adsorbable components enter the adsorption tower that is about to enter the adsorption state, which is not conducive to the purity of the product gas with difficult-to-adsorb components as the product. If the purity of the product gas is to be guaranteed, it is necessary to try to control the entry of too many easily adsorbable components into the adsorption tower that is about to enter the adsorption state during the equalization process, otherwise the yield cannot be improved. Summary of the Invention

[0009] To solve the above technical problems, the present invention proposes a three-tower series pressure swing adsorption device and adsorption process. While ensuring that the product gas quality meets the high-purity gas quality requirements, only a single-stage pressure swing adsorption device can be used, so that the product gas yield reaches or exceeds the product gas yield of the two-stage or above pressure swing adsorption devices commonly used in the prior art.

[0010] The objective of the present invention is achieved through the following technical solution: A three-tower series pressure swing adsorption device comprises: at least 8 adsorption towers and corresponding valve pipe fittings, wherein the adsorption towers are connected in series and in parallel.

[0011] Each adsorption tower is controlled by 14 valves to switch between various states.

[0012] Among them, the lower interface and the upper interface of the adsorption tower are each connected to 7 valves.

[0013] Preferably, the seven valves connected to the lower interface of the adsorption tower include:

[0014] 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 valve of each adsorption tower is connected in parallel through the adsorption pipeline 2;

[0015] Secondary adsorption air inlet valve: the gas from the outlet of the tertiary adsorption tower enters the secondary adsorption tower through the secondary adsorption air inlet valve. The secondary adsorption air inlet valve of each adsorption tower is connected in parallel through the adsorption pipeline 1;

[0016] The raw gas enters the tertiary adsorption tower through the tertiary adsorption inlet valve. The tertiary adsorption inlet valve of each adsorption tower is connected in parallel through the raw gas pipeline;

[0017] Reverse-down exhaust valve: when the adsorption tower is in the reverse depressurization process, the gas in the adsorption tower is discharged from the adsorption tower through the reverse-down exhaust valve. The reverse-down exhaust valves of each adsorption tower are connected in parallel through the reverse-down pipeline;

[0018] Pumping and exhaust valve: when the adsorption tower is in a vacuum and pressure-reducing state, the gas in the adsorption tower is discharged from the adsorption tower through the pumping and exhaust valve. The pumping and exhaust valves of each adsorption tower are connected in parallel through the pumping and exhaust pipeline;

[0019] The gas from the outlet of the secondary pressure-equalizing and pressure-reducing adsorption tower enters the primary pressure-equalizing and pressure-reducing adsorption tower through the primary pressure-equalizing and pressure-reducing air inlet valve. The primary pressure-equalizing and pressure-reducing air inlet valves of each adsorption tower are connected in parallel through the pressure-equalizing pipeline 2;

[0020] Secondary equalizing air inlet valve: the gas from the outlet of the tertiary equalizing and pressure-reducing adsorption tower enters the secondary equalizing and pressure-reducing adsorption tower through the secondary equalizing air inlet valve. The secondary equalizing air inlet valve of each adsorption tower is connected in parallel through the pressure-equalizing pipeline 1.

[0021] Preferably, the seven valves connected to the upper interface of the adsorption tower include:

[0022] The gas in the tertiary adsorption tower is discharged into the secondary adsorption tower through the tertiary adsorption exhaust valve. The tertiary adsorption tower is connected in series with the secondary adsorption tower and the primary adsorption tower through the tertiary adsorption exhaust valve, the secondary adsorption air inlet valve, the secondary adsorption exhaust valve and the primary adsorption air inlet valve. The tertiary adsorption exhaust valve of each adsorption tower is connected in parallel through the adsorption pipeline 1.

[0023] 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 valve of each adsorption tower is connected in parallel through the adsorption pipeline 2;

[0024] The gas in 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 valve of each adsorption tower is connected in parallel through the difficult-to-adsorb component product gas pipeline;

[0025] The gas in the three-way pressure-equalizing and pressure-reducing adsorption tower is discharged into the secondary pressure-equalizing and pressure-reducing adsorption tower through the three-way pressure-equalizing and pressure-reducing exhaust valve; the three-way pressure-equalizing and pressure-reducing adsorption tower and the secondary pressure-equalizing and pressure-reducing adsorption tower and the primary pressure-equalizing and pressure-reducing adsorption tower are connected in series through the three-way pressure-equalizing and pressure-reducing exhaust valve, the secondary pressure-equalizing and pressure-reducing air intake valve, the secondary pressure-equalizing and pressure-reducing exhaust valve, and the primary pressure-equalizing and pressure-reducing air intake valve; the three-way pressure-equalizing and pressure-reducing exhaust valve of each adsorption tower is connected in parallel through the pressure-equalizing pipeline 1;

[0026] Secondary pressure-equalizing exhaust valve: the gas in the secondary pressure-equalizing and pressure-reducing adsorption tower is discharged into the primary pressure-equalizing and pressure-reducing adsorption tower through the secondary pressure-equalizing exhaust valve; the secondary pressure-equalizing exhaust valve of each adsorption tower is connected in parallel through the pressure-equalizing pipeline 2;

[0027] The gas in the primary pressure-equalizing and pressure-reducing adsorption tower is discharged into the pressure-equalizing and pressure-boosting adsorption tower through the primary pressure-equalizing and pressure-reducing exhaust valve. The primary pressure-equalizing and pressure-reducing exhaust valves of each adsorption tower are connected in parallel through the pressure-equalizing and pressure-boosting pipeline;

[0028] Reverse rising flushing valve, reverse rising pressurized gas or flushing gas enters the adsorption tower that needs to be reversely pressurized or flushed through the reverse rising flushing valve, and the reverse rising flushing valve of each adsorption tower is connected in parallel through the reverse rising flushing gas pipeline.

[0029] In addition to providing a three-tower series pressure swing adsorption device, the present invention further provides an adsorption process using the above-mentioned adsorption device, comprising the following steps:

[0030] In a three-tower series pressure swing adsorption device, three adsorption towers are always in the adsorption state during one cycle;

[0031] The three adsorption towers are connected in series in an end-to-end manner; the raw gas enters the adsorption tower from the lower interface of the first adsorption tower, and the adsorption tower is equipped with one or more adsorbents that have a good adsorption effect on the components to be adsorbed (easy to adsorb components), such as carbon molecular sieves in the pressure swing adsorption nitrogen production device, oxygen molecular sieves in the pressure swing adsorption oxygen production device, activated carbon or silica gel with a good adsorption effect on carbon dioxide, 5A molecular sieve with a good adsorption effect on carbon monoxide, etc. in the pressure swing adsorption hydrogen production device; after the raw gas contacts the adsorbent bed, the easily adsorbed components are adsorbed by the corresponding adsorbent and separated from the raw gas, and most of the components that do not need to be adsorbed (difficult to adsorb components) and a small amount of easily adsorbed components flow to the adsorption bed. The gas flows out from the upper interface of the attached tower; it continues to enter the adsorption tower from the lower interface of the second adsorption tower in the adsorption state, most of the easily adsorbable components contained in the gas entering the second adsorption tower are adsorbed by the adsorbent, and most of the difficultly adsorbable components and a small amount of easily adsorbable components contained in the gas entering the second adsorption tower flow out from the upper interface of the adsorption tower; it continues to enter the adsorption tower from the lower interface of the third adsorption tower in the adsorption state, most of the easily adsorbable components contained in the gas entering the third adsorption tower are adsorbed by the adsorbent, and most of the difficultly adsorbable components and a trace amount of easily adsorbable components contained in the gas entering the third adsorption tower flow out from the upper interface of the adsorption tower, thereby obtaining a difficultly adsorbable component product gas that meets the quality requirements of high-purity gas;

[0032] When the adsorption tower is in the adsorption state, the adsorbent in the adsorption tower will show three state areas. The adsorbent bed that has reached the saturated adsorption amount is the saturated area; the adsorbent bed that has adsorbed some easily adsorbable components but has not yet reached the saturated adsorption amount is the mass transfer area; the adsorbent bed that has not yet adsorbed easily adsorbable components is the blank area; the three state areas are arranged in sequence along the direction of airflow; as the adsorption time increases, the three state areas gradually move toward the upper interface of the adsorption tower;

[0033] In one cycle, each adsorption tower undergoes three adsorption states; the adsorption tower into which the raw gas directly enters is in the tertiary adsorption state, the adsorption tower into which the gas flowing out of the adsorption tower in the tertiary adsorption state enters is in the secondary adsorption state, and the adsorption tower into which the gas flowing out of the adsorption tower in the secondary adsorption state enters is in the primary adsorption state;

[0034] In one cycle, there are always three adsorption towers in series adsorption state, so the obtained difficult-to-adsorb component product gas flow that meets the high-purity gas quality requirements is continuous;

[0035] When the mass transfer zone has moved out of the adsorption tower in the tertiary adsorption state and transferred to the adsorption tower in the secondary adsorption state, the adsorption state of the three adsorption towers ends; at this time, the adsorbent bed in the first adsorption tower where the raw gas directly enters has become a saturated area and no longer has the adsorption function. The gas components remaining in the gaps of the adsorption tower are equivalent to the raw gas and also contain a large amount of difficult-to-adsorb components. If these gases are directly discharged from the device, a large amount 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 provided after the end of this adsorption state;

[0036] During pressure equalization, the gas in the adsorption tower with high pressure will flow into the adsorption tower with low pressure, and the pressure in the adsorption tower with high pressure will decrease, which is called pressure equalization and decompression, and the pressure in the adsorption tower with low pressure will increase, which is called pressure equalization and decompression. During pressure equalization and decompression, the easily adsorbed components adsorbed on the adsorbent will gradually desorb from the adsorbent as the pressure decreases, and the desorbed easily adsorbed components will push and follow the gas in the adsorption tower gap to move to the upper interface of the adsorption tower. Since the adsorbent in the adsorption tower originally in the tertiary adsorption state has no adsorption capacity, the desorbed easily adsorbed components will follow the original gas in the adsorption tower gap to flow out of the adsorption tower. At the end of the pressure equalization state, a large amount of desorbed easily adsorbed components will flow out of the adsorption tower. At this time, most of the gas in the adsorption tower gap is easily adsorbed components, and also contains a small amount of difficultly adsorbed components. If the adsorption tower that has just ended the secondary adsorption state is chosen to directly equalize the pressure of the adsorption tower that needs pressure equalization and decompression, a large amount of easily adsorbed components will flow into the adsorption tower that needs pressure equalization and decompression, thereby causing a great impact on the purity of the difficultly adsorbed component product gas.

[0037] When the pressure is equalized, the three adsorption towers that have ended the adsorption state continue to be connected in series, but the three adsorption towers are disconnected from the raw gas pipeline and the product gas pipeline respectively, and the upper interface of the adsorption tower originally in the primary adsorption state is connected to the upper interface of the adsorption tower in the equalization and pressure boosting state through the equalization and pressure boosting pipeline; the easily adsorbed components and the difficultly adsorbed components flowing out of the adsorption tower originally in the tertiary adsorption state enter this adsorption tower from the lower interface of the adsorption tower originally in the secondary adsorption state, pushing and following the gas in the gap of this adsorption tower and the gas desorbed from the adsorbent of this adsorption tower to move to the upper interface of the adsorption tower. Because the adsorbent near the lower interface of this adsorption tower is in the transfer state before the pressure is equalized, the adsorption tower is in the transfer state. The mass transfer zone and the upper part of the mass transfer zone still have most of the adsorbent bed layer belonging to the blank zone. The easily adsorbable components entering this adsorption tower and the easily adsorbable components desorbed from the mass transfer zone will be adsorbed by the adsorbent in the blank zone; when the easily adsorbable component is a gas with a smaller adsorption amount, after the adsorption tower originally in the three adsorption states completes the equalization and pressure reduction state, if the pressure in the adsorption tower is not lowered low enough, the amount of the easily adsorbable component desorbed from the adsorbent will not be enough to push most of the gas existing in the gap of the adsorption tower before the pressure reduction out of the adsorption tower, which will result in a certain amount of difficult adsorbable components still existing in the gap of the adsorption tower after the equalization and pressure reduction state is completed. This part of the difficult adsorbable components will be in the subsequent pressure reduction and desorption process. The gas will be discharged from the pressure swing adsorption device, resulting in the difficult-to-adsorb component product gas unable to achieve a high yield; if a higher yield is to be obtained, the pressure in the adsorption tower must be lowered even further after the equalization and pressure reduction state is completed. The pressure in the adsorption tower originally in the secondary adsorption state will also become lower, and the amount of easily adsorbed components that can be adsorbed by the adsorbent in its blank area will also be reduced accordingly. As a result, the amount of adsorbent in the blank area cannot adsorb most of the easily adsorbed components that have entered and originally existed in this adsorption tower, resulting in a part of the easily adsorbed components flowing out of this adsorption tower. If this part of the easily adsorbed components enters the adsorption tower in the equalization and pressure increase state, it will greatly affect the purity of the difficult-to-adsorb component product gas. Therefore, the present invention adopts the method of connecting three adsorption towers in series, so that when the pressure is equalized and reduced, the easily adsorbable components and the difficultly adsorbable components flowing out from the upper interface of the second adsorption tower enter the third adsorption tower through the lower interface of the third adsorption tower. Most of the easily adsorbable components will be adsorbed by the adsorbent in the third adsorption tower, and most of the gas flowing out from the upper interface of the third adsorption tower is difficultly adsorbed components, and at the same time contains trace amounts of easily adsorbable components, the quality of which is equivalent to that of the difficultly adsorbable component product gas. This part of the gas flows into the adsorption tower in the equalized pressure boosting state, and will not affect the quality of the difficultly adsorbable component product gas; thereby ensuring that the difficultly adsorbable component product gas that meets the high-purity gas quality requirements can always be obtained.

[0038] When the equalizing pressure reduction state ends, most of the difficult-to-adsorb components and a part of the easily adsorbable components in the adsorption tower originally in the tertiary adsorption state are discharged from the upper interface of the adsorption tower, and the easily adsorbable components will be adsorbed by the adsorbent in the adsorption tower originally in the secondary adsorption and primary adsorption states. Most of the difficult-to-adsorb components enter the adsorption tower originally in the secondary adsorption and primary adsorption states and the adsorption tower in the equalizing pressure boosting state, and are not discharged from the pressure swing adsorption device, so that the product gas recovery rate of the difficult-to-adsorb components reaches or exceeds the product gas recovery rate of the currently commonly used two-stage or two-stage or above pressure swing adsorption devices; at the same time, it can ensure that the product gas quality of the difficult-to-adsorb components meets the high-purity gas index requirements.

[0039] After the pressure is reduced by equal pressure, the pressure inside the adsorption tower originally in the primary adsorption, secondary adsorption, and tertiary adsorption state is the same as the pressure inside the adsorption tower after the pressure is increased by equal pressure; the adsorption tower originally in the tertiary adsorption state will continue to perform other pressure reduction steps after the pressure is reduced by equal pressure to maximize the desorption of the easily adsorbed components adsorbed on the adsorbent, so as to realize the adsorption function in the next cycle; the adsorption tower originally in the primary adsorption and secondary adsorption states will also perform the secondary adsorption and tertiary adsorption in this cycle respectively after the pressure is reduced by equal pressure, but the pressure inside the adsorption tower does not meet the requirements for entering the adsorption state, so after the pressure is reduced by equal pressure, a reverse pressure increase state is set to pressurize the two adsorption towers with the difficultly adsorbed component product gas. When the pressure inside the adsorption tower reaches the adsorption state pressure, it can be put into the adsorption state; the total length of time from the end of the primary adsorption state to the start of the secondary adsorption state of the adsorption tower originally in the primary adsorption state and the total length of time from the end of the secondary adsorption state to the start of the tertiary adsorption state of the adsorption tower originally in the secondary adsorption state are both the same as the adsorption (referring to the primary adsorption or secondary adsorption or tertiary adsorption) state length;

[0040] In one cycle, each adsorption tower goes through the following states in sequence: one adsorption, one equalizing pressure reduction, two reverse pressure increases, two adsorptions, two equalizing pressure reductions, three reverse pressure increases, three adsorptions, three equalizing pressure reductions, or / and reverse pressure reductions, or / and vacuum pressure reductions, or / and flushing, equalizing pressure increase, one reverse pressure increase, and then enters the first adsorption state again; the above states are repeated in a cycle;

[0041] Each adsorption tower is in different states at different times to ensure that the entire device can be operated continuously and periodically;

[0042] The three adsorption towers that are in the adsorption state at the same time, according to the flow of raw gas, the first one is in the tertiary adsorption state, the second one is in the secondary adsorption state, and the third one is in the primary adsorption state; when the three adsorption towers that are in the adsorption state at the same time end the primary adsorption state, the secondary adsorption state, and the tertiary adsorption state respectively, the other three adsorption towers that were previously in the tertiary reverse boosting state, the secondary reverse boosting state, and the primary reverse boosting state respectively, enter the series adsorption state at the same time, among which the adsorption tower that was previously in the tertiary reverse boosting state enters the tertiary adsorption state, the adsorption tower that was previously in the secondary reverse boosting state enters the secondary adsorption state, and the adsorption tower that was previously in the primary reverse boosting state enters the primary adsorption state, thereby ensuring that the obtained difficult-to-adsorb component product gas flow is continuous.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] In the prior art, if the easily adsorbed component is a medium with a smaller 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 use requirements, some working conditions often require the use of two or three-stage pressure swing adsorption devices in series, and the number of adsorption towers required is also increased accordingly. The present invention adopts a set of pressure swing adsorption devices, by setting a multi-step pressure equalization process and adopting the method of simultaneous adsorption in two adsorption towers, while ensuring the quality of the product gas, significantly improving the yield, reducing energy consumption and equipment investment.

[0045] For a pressure swing adsorption hydrogen extraction device, while ensuring that the product hydrogen purity (≥99.999%) and impurity content (N2≤5ppm, CO≤1ppm, CO2≤1ppm, CH4≤1ppm, H2O≤3ppm) meet the high-purity hydrogen requirements in GB / T3634.2-2011, the product hydrogen yield is significantly higher than that of existing single-stage pressure swing adsorption hydrogen extraction devices. For example, for a chlor-alkali gas hydrogen purification device, the product hydrogen yield of an existing pressure swing adsorption device is approximately 92% at most. By adopting the method of the present invention, the product hydrogen yield can reach more than 98%. The product hydrogen yield value is obtained by analyzing the purity of the feed gas and product hydrogen using a gas chromatograph, measuring the feed gas flow rate and product hydrogen output using the volumetric method in Appendix A of GB / T19773-2005, and then dividing the product hydrogen output by the amount of hydrogen in the feed gas to obtain the product hydrogen yield value. For pressure swing adsorption oxygen and nitrogen production equipment, under the premise that the oxygen purity (≥90%) and nitrogen purity (≥99.5%) meet the basic parameter requirements of JB / T6427-2015, the unit oxygen production power consumption and unit nitrogen production power consumption are significantly lower than the minimum index requirements of JB / T6427-2015; for example: for product oxygen pressure of 0.2Mpa and gas production of 200m 3 / h PSA oxygen generator, the unit oxygen production power consumption in the standard is ≤1.0kW·h / m 3, using the method of the present invention, the unit oxygen production power consumption is ≤0.6kW·h / m 3 ; For product oxygen pressure of 0.005Mpa and gas production of 8000m 3 / h axial flow VPSA oxygen generator, the minimum power consumption per unit oxygen production in the standard is 0.35kW·h / m 3 , using the method of the present invention, the unit oxygen production power consumption is ≤0.25kW·h / m 3 ; For gas production of 3000m 3 / h PSA nitrogen production device, the unit nitrogen production power consumption in the standard is ≤0.43kW·h / m 3 By adopting the method of the present invention, the power consumption per unit nitrogen production is ≤0.29kW·h / m 3 The above power consumption values ​​per unit oxygen production and per unit nitrogen production are obtained by measurement and calculation in accordance with the provisions of JB / T6427.

[0046] In the prior art, some pressure swing adsorption devices with relatively high adsorption pressures often require a large number of pressure equalization steps to ensure the yield of difficult-to-adsorb components, and the number of adsorption towers required also increases accordingly. The three-tower series pressure swing adsorption device and adsorption process provided by the present invention can reduce the number of adsorption towers while improving the yield, thereby reducing equipment investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A three-tower series pressure swing adsorption device and an adsorption process flow chart of the present invention;

[0048] Figure 2 The operation sequence of each adsorption tower in the embodiment of the present invention adopts the 8-tower 3-absorption 1 average reverse-decline process;

[0049] Figure 3 This is the operating sequence of each adsorption tower when the 8-tower 3-absorption 1-average pumping-down process is adopted in the embodiment of the present invention;

[0050] Figure 4 This is the operating sequence of each adsorption tower when the 8-tower 3-absorption 1 average reverse down washing process is adopted in the embodiment of the present invention. DETAILED DESCRIPTION

[0051] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0052] The technical solution of the present invention provides a three-tower series pressure swing adsorption device and an adsorption process. The three-tower series pressure swing adsorption device applicable to the process is as follows:

[0053] It comprises at least 8 adsorption towers and corresponding valve pipe fittings, and the adsorption towers are connected in series and parallel.

[0054] Among them, each adsorption tower is controlled by 14 valves to complete the switching between various states.

[0055] The 14 valves are numbered 1-14. The complete position number of the valve is obtained by appending the code of the adsorption tower to which they belong before the numbers 1-14, such as A1, A2, ..., A14, B1, B2, ..., B14. Valves with the same number have the same function. Their connection methods and functions are as follows:

[0056] There are 7 valves connected to the lower interface of the adsorption tower, namely:

[0057] The gas from the outlet of the secondary adsorption tower enters the primary adsorption tower through the primary adsorption inlet valves A5, B5, ..., I5 (J5, K5). The primary adsorption inlet valves of each adsorption tower are connected in parallel through the adsorption pipeline 2.

[0058] Secondary adsorption air inlet valves A6, B6, ..., I6 (J6, K6), the gas from the outlet of the tertiary adsorption tower enters the secondary adsorption tower through the secondary adsorption air inlet valve, and the secondary adsorption air inlet valve of each adsorption tower is connected in parallel through the adsorption pipeline 1;

[0059] The raw gas enters the tertiary adsorption tower through the tertiary adsorption inlet valves A1, B1, ..., I1 (J1, K1). The tertiary adsorption inlet valves of each adsorption tower are connected in parallel through the raw gas pipeline;

[0060] Reverse-down exhaust valves A2, B2, ..., I2 (J2, K2). When the adsorption tower is in the reverse depressurization process, the gas in the adsorption tower is discharged from the adsorption tower through the reverse-down exhaust valve. The reverse-down exhaust valves of each adsorption tower are connected in parallel through the reverse-down pipeline;

[0061] Pumping and exhaust valves A14, B14, ..., I14 (J14, K14). When the adsorption tower is in a vacuum and pressure reduction state, the gas in the adsorption tower is discharged from the adsorption tower through the pumping and exhaust valves. The pumping and exhaust valves of each adsorption tower are connected in parallel through the pumping and exhaust pipeline;

[0062] The gas from the outlet of the secondary pressure-equalizing and pressure-reducing adsorption tower enters the primary pressure-equalizing and pressure-reducing adsorption tower through the primary pressure-equalizing and pressure-reducing inlet valves A3, B3, ..., I3 (J3, K3). The primary pressure-equalizing and pressure-reducing inlet valves of each adsorption tower are connected in parallel through the pressure-equalizing pipeline 2.

[0063] Secondary equalizing air inlet valves A4, B4, ..., I4 (J4, K4), the gas from the outlet of the tertiary equalizing and pressure-reducing adsorption tower enters the secondary equalizing and pressure-reducing adsorption tower through the secondary equalizing air inlet valves, and the secondary equalizing air inlet valves of each adsorption tower are connected in parallel through the pressure-equalizing pipeline 1.

[0064] There are 7 valves connected to the upper interface of the adsorption tower, namely:

[0065] 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 is connected in series with the secondary adsorption tower and the primary adsorption tower through the tertiary adsorption exhaust valves, the secondary adsorption air inlet valves, the secondary adsorption exhaust valves, and the primary adsorption air inlet valves. The tertiary adsorption exhaust valves of each adsorption tower are connected in parallel through the adsorption pipeline 1.

[0066] Secondary adsorption exhaust valves A8, B8, ..., I8 (J8, K8), the gas in the secondary adsorption tower is discharged into the primary adsorption tower through the secondary adsorption exhaust valves; the secondary adsorption exhaust valves of each adsorption tower are connected in parallel through the adsorption pipeline 2;

[0067] The gas in the primary adsorption tower is discharged from the adsorption tower through the primary adsorption exhaust valves A13, B13, ..., I13 (J13, K13) and discharged into the difficult-to-adsorb component product gas 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;

[0068] The gas in the tertiary pressure-equalizing and pressure-reducing adsorption tower is discharged into the secondary pressure-equalizing and pressure-reducing adsorption tower through the tertiary pressure-equalizing and pressure-reducing exhaust valves A9, B9, ..., I9 (J9, K9); the tertiary pressure-equalizing and pressure-reducing adsorption tower is connected in series with the secondary pressure-equalizing and pressure-reducing adsorption tower and the primary pressure-equalizing and pressure-reducing adsorption tower through the tertiary pressure-equalizing and pressure-reducing exhaust valves, the secondary pressure-equalizing and pressure-reducing air intake valves, the secondary pressure-equalizing and pressure-reducing exhaust valves, and the primary pressure-equalizing and pressure-reducing air intake valves; the tertiary pressure-equalizing and pressure-reducing exhaust valves of each adsorption tower are connected in parallel through the pressure-equalizing pipeline 1;

[0069] Secondary pressure-equalizing exhaust valves A10, B10, ..., I10 (J10, K10), the gas in the secondary pressure-equalizing and pressure-reducing adsorption tower is discharged into the primary pressure-equalizing adsorption tower through the secondary pressure-equalizing exhaust valves; the secondary pressure-equalizing exhaust valves of each adsorption tower are connected in parallel through the pressure-equalizing pipeline 2;

[0070] The gas in the primary pressure-equalizing and pressure-reducing adsorption tower is discharged into the pressure-equalizing and pressure-boosting adsorption tower through the primary pressure-equalizing and pressure-reducing exhaust valves A11, B11, ..., I11 (J11, K11); the primary pressure-equalizing and pressure-reducing exhaust valves of each adsorption tower are connected in parallel through the pressure-equalizing and pressure-boosting pipeline;

[0071] Reverse rising flushing valves A12, B12, ..., I12 (J12, K12), reverse rising pressurized gas or flushing gas enters the adsorption tower that needs to be reversely pressurized or flushed through the reverse rising flushing valves, and the reverse rising flushing valves of each adsorption tower are connected in parallel through the reverse rising flushing gas pipeline.

[0072] like Figures 1 to 4 As shown, in one embodiment of the present invention, a three-tower series pressure swing adsorption device includes 8 adsorption towers. Based on this device, the technical solution of the present invention provides a three-tower series pressure swing adsorption process, which is specifically as follows:

[0073] A cycle can be divided into 16 steps, which are described as follows:

[0074] Step 1: The adsorption tower A that has finished the three-time reverse boosting state, the adsorption tower C that has finished the two-time reverse boosting state, and the adsorption tower E that has finished the one-time reverse boosting state enter the adsorption state at the same time. Valves A1, A7, C6, C8, E5, and E13 are opened. The raw gas enters the adsorption tower A from the lower interface of the adsorption tower through the A1 valve. The adsorption tower A enters the three-time adsorption state. The easily adsorbed component is adsorbed by the adsorbent, and the difficultly adsorbed component and a part of the easily adsorbed component flow out of the adsorption tower A from the upper interface of the adsorption tower. The raw gas flows out of the adsorption tower A through the A7 valve, adsorption pipeline 1, and C6 valve from the lower interface of the adsorption tower C. The interface enters adsorption tower C, and adsorption tower C enters the secondary adsorption state. The easily adsorbable components in the gas are adsorbed by the adsorbent, and the difficultly adsorbable components with a small amount of easily adsorbable components flow out of the adsorption tower from the upper interface of adsorption tower C, and enter adsorption tower E from the lower interface of adsorption tower E through C8, adsorption pipeline 2, and E5 valve. Most of the easily adsorbable components are adsorbed by the adsorbent, and the difficultly adsorbable components and trace amounts of easily adsorbable components flow out of adsorption tower E from the upper interface of the adsorption tower, and enter the difficultly adsorbable component product gas pipeline through E13 valve, and are sent to the pressure swing adsorption device through subsequent equipment, such as product gas buffer tanks, etc. When adsorption towers A, C, and E enter the adsorption state, adsorption towers H, B, and D remain in series and connected to adsorption tower F for pressure equalization; at the same time, adsorption tower H may enter the vacuum pressure reduction state, such as Figure 2 、 Figure 3 As shown, or enter the flushing state, such as Figure 4 shown.

[0075] Step 2: After the pressure equalization state among adsorption tower H, adsorption tower B, adsorption tower D, and adsorption tower F is completed, adsorption tower B, adsorption tower D, and adsorption tower F enter the reverse pressure increase state together, and adsorption tower H enters the reverse pressure reduction state, such as Figure 2 、 Figure 4 At the same time, adsorption tower A, adsorption tower C, and adsorption tower E continue to maintain the series adsorption state; at the same time, adsorption tower G either continues to be vacuumed and depressurized, or enters a blank waiting state before equalizing and increasing the pressure.

[0076] Step 3: When the adsorption mass transfer zone moves out of adsorption tower A and enters adsorption tower C, adsorption tower A ends the tertiary adsorption state, adsorption tower C ends the secondary adsorption state, adsorption tower E ends the primary adsorption state, and valves A1, A7, C6, C8, E5, and E13 are closed; at the same time, adsorption towers B, D, and F enter the series adsorption state. At the same time, valves A9, C4, C10, E3, E11, and G11 are opened, and adsorption tower A, adsorption tower C, and adsorption tower E remain in a series state and are connected to adsorption tower G. Adsorption tower A enters a three-time equalizing pressure reduction state, adsorption tower C enters a two-time equalizing pressure reduction state, adsorption tower E enters a single-time equalizing pressure reduction state, and adsorption tower G enters an equalizing pressure boost state; the gas in the gap of adsorption tower A and the desorbed easily adsorbed components enter the adsorption tower C from the lower interface of adsorption tower C through the upper interface of the adsorption tower via the A9 valve, the equalizing pressure pipeline 1, and the C4 valve. Most of the easily adsorbed components are adsorbed by the adsorbent, and the difficultly adsorbed components and a small amount of easily adsorbed components flow out from the upper interface of adsorption tower C via the C10 valve, and enter the adsorption tower E from the lower interface via the equalizing pressure pipeline 2 and the E3 valve. The vast majority of the easily adsorbed components are adsorbed by the adsorbent, and the difficultly adsorbed components and trace easily adsorbed components flow into the adsorption tower G from the upper interface of the adsorption tower via the E11 and G11 valves. At the same time, the adsorption tower H may enter a vacuum and pressure reduction state, such as Figure 2 、 Figure 3 As shown, or enter the flushing state, such as Figure 4 shown.

[0077] Step 4: After the pressure in adsorption tower A, adsorption tower C, adsorption tower E, and adsorption tower G is balanced, adsorption tower A ends the three-time pressure equalization and pressure reduction state, or enters the reverse pressure reduction state, such as Figure 2 and Figure 4 As shown, or enter the blank waiting state before vacuuming and depressurizing, such as Figure 3As shown in the figure, adsorption tower C ends the secondary equalization and pressure reduction state and enters the tertiary reverse pressure increase state; adsorption tower E ends the primary equalization and pressure reduction state and enters the secondary reverse pressure increase state, while adsorption tower G simultaneously enters the primary reverse pressure increase state; after the equalization state is completed, valves A9, C4, C10, E3, E11, and G11 are closed. When adsorption tower A is reverse pressure reduction, valve A2 opens, and the gas in the adsorption tower is discharged through the reverse pressure reduction pipeline; when adsorption tower A is vacuuming and pressure reduction, valve A14 opens, and adsorption tower A is connected to the vacuum pump either through a vacuum tank or directly to the vacuum pump, and the gas in the adsorption tower is pumped out by the vacuum pump through the vacuum pressure reduction pipeline. Adsorption tower C, adsorption tower E, and adsorption tower G are reversely pressurized at the same time, valves C12, E12, and G12 are opened, and adsorption tower C, adsorption tower E, and adsorption tower G are connected to the reverse rising flushing pipeline through the upper interface. The product gas of the difficult-to-adsorb component enters adsorption tower C, adsorption tower E, and adsorption tower G from the upper interface through the reverse rising flushing pipeline through valves C12, E12, and G12 respectively. When the pressure in the adsorption tower rises to the adsorption pressure, the three reverse rising states of adsorption tower C are completed, the two reverse rising states of adsorption tower E are completed, and the one reverse rising state of adsorption tower G is completed, and valves C12, E12, and G12 are closed. At the same time, adsorption tower B, adsorption tower D, and adsorption tower F continue to maintain the series adsorption state. At the same time, adsorption tower H may continue to be vacuumed and depressurized, such as Figure 2 、 Figure 3 As shown; or enter the blank waiting state before voltage equalization and voltage boost, such as Figure 4 shown.

[0078] Step 5: The adsorption state of adsorption tower B, adsorption tower D, and adsorption tower F is completed; at the same time, adsorption tower B, adsorption tower D, and adsorption tower F are kept in series and connected with adsorption tower H for pressure equalization. Adsorption tower B enters the three-times equalization and pressure reduction state, adsorption tower D enters the two-times equalization and pressure reduction state, adsorption tower F enters the one-time equalization and pressure reduction state, and adsorption tower H enters the equalization and pressure boosting state. At the same time, valves C1, C7, E6, E8, G5, and G13 are opened, and adsorption tower C, adsorption tower E, and adsorption tower G enter the series adsorption state, adsorption tower C enters the three-times adsorption state, adsorption tower E enters the two-times adsorption state, and adsorption tower G enters the one-time adsorption state. At the same time, the valve of adsorption tower A or A2 is closed to end the reverse pressure reduction state, and valve A14 is opened to enter the vacuum pressure reduction state, such as Figure 2 As shown; or A14 valve is opened to enter the vacuum and pressure reduction state, such as Figure 3 As shown; or enter the flushing state, such as Figure 4 As shown, A2 remains open, A12 valve is opened, and the product gas of the difficult-to-adsorb component flows from the reverse-ascending flushing pipeline through the A12 valve and enters the adsorption tower A from the upper interface. The gas in the gap of the adsorption tower A is blown into the reverse-descending pipeline from the lower interface through the A2 valve by the product gas of the difficult-to-adsorb component and discharged.

[0079] Step 6: The pressure equalization process of adsorption tower B, adsorption tower D, adsorption tower F, and adsorption tower H is completed; at the same time, adsorption tower B may enter the reverse pressure reduction state, such as Figure 2 、 Figure 4 As shown, or enter the blank waiting state before vacuuming and depressurizing, such as Figure 3 As shown; at the same time, adsorption tower D enters the three-time reverse boost state, adsorption tower F enters the two-time reverse boost state, and adsorption tower H enters the one-time reverse boost state. When the pressure in the adsorption tower rises to the adsorption pressure, the reverse boost state is completed. At the same time, adsorption towers C, E, and G continue to maintain the series adsorption state. At the same time, adsorption tower A continues to be vacuumed and depressurized, as shown Figure 2 、 Figure 3 As shown; or the A12 valve and A2 valve are closed to end the flushing state, such as Figure 4 As shown, it enters the blank waiting state before voltage equalization and voltage boosting.

[0080] Step 7: After the adsorption mass transfer zone is moved from adsorption tower C to adsorption tower E, adsorption tower C ends the tertiary adsorption state, adsorption tower E ends the secondary adsorption state, adsorption tower G ends the primary adsorption state, and valves C1, C7, E6, E8, G5, and G13 are closed. At the same time, the valve of adsorption tower A or A14 is closed to end the vacuum decompression state, or end the blank waiting state; at the same time, valves C9, E4, E10, G3, G11, and A11 are opened, and adsorption tower C, adsorption tower E, and adsorption tower G remain in series and connected to adsorption tower A. Adsorption tower C enters the tertiary equalizing pressure reduction state, adsorption tower E enters the secondary equalizing pressure reduction state, adsorption tower G enters the primary equalizing pressure reduction state, and adsorption tower A enters the equalizing pressure boosting state. At the same time, adsorption tower D, adsorption tower F, and adsorption tower H enter the series adsorption state. At the same time, adsorption tower B ends the reverse decompression state and enters the vacuum decompression state, such as Figure 2 As shown; or directly enter the vacuum decompression state, such as Figure 3 As shown; or enter the flushing state, such as Figure 4 shown.

[0081] Step 8: After the pressures of adsorption towers C, E, G and A are balanced, valves C9, E4, E10, G3, G11 and A11 are closed, the three equalizing and reducing pressure states of adsorption tower C are completed, the two equalizing and reducing pressure states of adsorption tower E are completed, the one equalizing and increasing pressure state of adsorption tower G is completed, and the equalizing and increasing pressure state of adsorption tower A is completed; at the same time, valve A12 is opened to cause adsorption tower A to enter the one reverse increasing pressure state, valve E12 is opened to cause adsorption tower E to enter the three reverse increasing pressure states, valve G12 is opened to cause adsorption tower A to enter the one reverse increasing pressure state, valve G12 is opened to cause adsorption tower E to enter the three reverse increasing pressure states, and valve G12 is opened to cause adsorption tower A to enter the one reverse increasing pressure state. The auxiliary tower G enters the secondary reverse pressure-raising state, and the product gas of the difficult-to-adsorb component enters the adsorption tower A, adsorption tower E, and adsorption tower G respectively through the reverse rising flushing pipeline through the A12 valve, E12 valve, and G12 valve from the upper interface of the adsorption tower. After the pressure in the adsorption tower A, adsorption tower E, and adsorption tower G rises to the adsorption pressure, the first reverse pressure-raising state of the adsorption tower A is completed, the third reverse pressure-raising state of the adsorption tower E is completed, and the second reverse pressure-raising state of the adsorption tower G is completed. The A12 valve, E12 valve, and G12 valve are closed. At the same time, the adsorption tower C may enter the reverse pressure-reducing state, such as Figure 2 、 Figure 4 As shown, the C2 valve is opened, and the gas in the adsorption tower is discharged from the reverse-down pipeline through the C2 valve; or enters the blank waiting state before vacuuming and depressurization, such as Figure 3 At the same time, the adsorption tower B continues to be vacuumed and depressurized, as shown in FIG. Figure 2 、 Figure 3 As shown; or end the flushing state, such as Figure 4 As shown, it enters the blank waiting state before pressure equalization and pressure boosting. At the same time, adsorption tower D, adsorption tower F, and adsorption tower H continue to maintain the series adsorption state.

[0082] Step 9: When the adsorption mass transfer zone moves from adsorption tower D to adsorption tower F, the tertiary adsorption state of adsorption tower D ends, the secondary adsorption state of adsorption tower F ends, and the primary adsorption state of adsorption tower H ends; at the same time, adsorption towers E, G, and A enter the series adsorption state, valves E1, E7, G6, G8, A5, and A13 are opened, adsorption tower E enters the tertiary adsorption state, adsorption tower G enters the secondary adsorption state, and adsorption tower A enters the primary adsorption state. At the same time, adsorption tower B ends the vacuum decompression state, such as Figure 2 、 Figure 3 As shown, or end the blank waiting state, such as Figure 4 As shown; at the same time, adsorption tower D, adsorption tower F, and adsorption tower H remain in series and connected to adsorption tower B. Adsorption tower D enters the three-time equalization and pressure reduction state, adsorption tower F enters the two-time equalization and pressure reduction state, adsorption tower H enters the one-time equalization and pressure reduction state, and adsorption tower B enters the equalization and pressure increase state. At the same time, the valve of adsorption tower C or C2 is closed to end the reverse pressure reduction state, and the valve C14 is opened to enter the vacuum pressure reduction state, as shown Figure 2 As shown; or open the C14 valve and enter the vacuum and pressure reduction state directly, such as Figure 3As shown, the adsorption tower C is connected to the vacuum pump through a vacuum tank or directly connected to the vacuum pump, and the gas in the adsorption tower is pumped out by the vacuum pump through the pumping pipeline; or enters the flushing state, such as Figure 4 As shown, the C2 valve continues to remain open, the C12 valve is opened, and the difficult-to-adsorb component product enters the adsorption tower C from the upper interface of the adsorption tower through the reverse rising flushing pipeline through the C12 valve. The gas in the gap of the adsorption tower C is blown into the reverse descending pipeline from the lower interface through the C2 valve by the difficult-to-adsorb component product gas and discharged.

[0083] Step 10: After the pressures of adsorption tower D, adsorption tower F, adsorption tower H, and adsorption tower B reach equilibrium, the three equalizing pressure reduction states of adsorption tower D are completed, the two equalizing pressure reduction states of adsorption tower F are completed, the one equalizing pressure reduction state of adsorption tower H is completed, and the equalizing pressure boosting state of adsorption tower B is completed. At the same time, adsorption tower B enters the one reverse boosting state, adsorption tower F enters the three reverse boosting states, and adsorption tower H enters the two reverse boosting states; after the pressures in adsorption towers B, adsorption tower F, and adsorption tower H rise to the adsorption pressure, the one reverse boosting state of adsorption tower B is completed, the three reverse boosting states of adsorption tower F are completed, and the two reverse boosting states of adsorption tower H are completed. At the same time, adsorption tower D may enter the reverse depressurization state, such as Figure 2 、 Figure 4 As shown, or enter the blank waiting state before vacuuming and depressurizing, such as Figure 3 At the same time, the adsorption tower C continues to be vacuumed and depressurized, as shown in FIG. Figure 2 、 Figure 3 As shown; or end the flushing state, such as Figure 4 As shown, valves C2 and C12 are closed, and the system enters a blank waiting state before pressure equalization and pressure boosting. At the same time, adsorption towers E, G, and A continue to maintain a series adsorption state.

[0084] Step 11: When the adsorption mass transfer zone moves from adsorption tower E to adsorption tower G, the tertiary adsorption state of adsorption tower E ends, the secondary adsorption state of adsorption tower G ends, and the primary adsorption state of adsorption tower A ends. Valves E1, E7, G6, G8, A5, and A13 are closed. At the same time, adsorption towers F, H, and B enter the series adsorption state, with adsorption tower F entering the tertiary adsorption state, adsorption tower H entering the secondary adsorption state, and adsorption tower B entering the primary adsorption state. At the same time, the valve of adsorption tower C or C14 is closed to end the vacuum decompression state. Figure 2 、 Figure 3 As shown, or end the blank waiting state, such as Figure 4As shown; at the same time, adsorption tower E, adsorption tower G, and adsorption tower A are kept in series and connected to adsorption tower C. Valves E9, G4, G10, A3, A11, and C11 are opened. Adsorption tower E enters the three-time equalizing pressure reduction state, adsorption tower G enters the two-time equalizing pressure reduction state, adsorption tower A enters the one-time equalizing pressure reduction state, and adsorption tower C enters the equalizing pressure boost state. At the same time, adsorption tower D ends the reverse pressure reduction state and enters the vacuum pressure reduction state, as shown Figure 2 As shown; or directly enter the vacuum decompression state, such as Figure 3 As shown; or enter the flushing state, such as Figure 4 shown.

[0085] Step 12: After the pressures of adsorption tower E, adsorption tower G, adsorption tower A, and adsorption tower C reach equilibrium, valves E9, G4, G10, A3, A11, and C11 are closed, the three equalizing pressure reduction states of adsorption tower E are completed, the two equalizing pressure reduction states of adsorption tower G are completed, the one equalizing pressure reduction state of adsorption tower A is completed, and the equalizing pressure boosting state of adsorption tower C is completed; at the same time, valve C12 is opened to allow adsorption tower C to enter the one reverse boosting state, valve G12 is opened to allow adsorption tower G to enter the three reverse boosting states, valve A12 is opened to allow adsorption tower A to enter the two reverse boosting states, and after the pressures in adsorption towers C, adsorption tower G, and adsorption tower A rise to the adsorption pressure, the one reverse boosting state of adsorption tower C is completed, the three reverse boosting states of adsorption tower G are completed, the two reverse boosting states of adsorption tower A are completed, and valves C12, G12, and A12 are closed. At the same time, valves in adsorption tower E or E12 are opened to enter the reverse pressure reduction state, such as Figure 2 and Figure 4 As shown; or enter the blank waiting state before vacuuming and depressurizing, such as Figure 3 At the same time, the adsorption tower D continues to be vacuumed and depressurized, as shown in FIG. Figure 2 、 Figure 3 As shown; or end the flushing state, such as Figure 4 As shown, it enters the blank waiting state before pressure equalization and pressure boosting. At the same time, adsorption tower F, adsorption tower H, and adsorption tower B continue to maintain the series adsorption state.

[0086] Step 13: When the adsorption mass transfer zone moves from adsorption tower F to adsorption tower H, the tertiary adsorption state of adsorption tower F ends, the secondary adsorption state of adsorption tower H ends, and the primary adsorption state of adsorption tower B ends; at the same time, adsorption tower G, adsorption tower A, and adsorption tower C enter the series adsorption state, valves G1, G7, A6, A8, C5, and C13 are opened, adsorption tower G enters the tertiary adsorption state, adsorption tower A enters the secondary adsorption state, and adsorption tower C enters the primary adsorption state. At the same time, the valve of adsorption tower D or D14 is closed to end the vacuum decompression state, as shown in FIG. Figure 2 、 Figure 3 As shown, or end the blank waiting state, such as Figure 4As shown; at the same time, adsorption tower F, adsorption tower H, and adsorption tower B are kept in series and connected to adsorption tower D. Adsorption tower F enters the three-time equalization and pressure reduction state, adsorption tower H enters the two-time equalization and pressure reduction state, adsorption tower B enters the one-time equalization and pressure reduction state, and adsorption tower D enters the equalization and pressure increase state. At the same time, the valve of adsorption tower E or E2 is closed to end the reverse pressure reduction state, and the valve E14 is opened to enter the vacuum pressure reduction state, as shown Figure 2 As shown; or open the E14 valve and enter the vacuum and pressure reduction state directly, such as Figure 3 As shown; or enter the flushing state, such as Figure 4 As shown, the E2 valve continues to remain open, the E12 valve is opened, and the difficult-to-adsorb component product enters the adsorption tower E from the upper interface of the adsorption tower through the reverse rising flushing pipeline through the E12 valve. The gas in the gap of the adsorption tower E is blown into the reverse descending pipeline from the lower interface through the E2 valve and discharged.

[0087] Step 14: After the pressures of adsorption tower F, adsorption tower H, adsorption tower B, and adsorption tower D reach equilibrium, the three equalizing pressure reduction states of adsorption tower F are completed, the two equalizing pressure reduction states of adsorption tower H are completed, the one equalizing pressure reduction state of adsorption tower B is completed, and the equalizing pressure boosting state of adsorption tower D is completed; at the same time, adsorption tower D enters the one reverse boosting state, adsorption tower H enters the three reverse boosting states, and adsorption tower B enters the two reverse boosting states. After the pressures in adsorption towers D, adsorption tower H, and adsorption tower B rise to the adsorption pressure, the one reverse boosting state of adsorption tower D is completed, the three reverse boosting states of adsorption tower H are completed, and the two reverse boosting states of adsorption tower B are completed. At the same time, adsorption tower F may enter the reverse depressurization state, such as Figure 2 and Figure 4 As shown; or enter the blank waiting state before vacuuming and depressurizing, such as Figure 3 At the same time, the adsorption tower E continues to be vacuumed and depressurized, as shown. Figure 2 、 Figure 3 As shown; or end the flushing state, such as Figure 4 As shown, valves E2 and E12 are closed, entering a blank waiting state before pressure equalization and pressure boosting. At the same time, adsorption towers G, A, and C continue to maintain a series adsorption state.

[0088] Step 15: After the adsorption mass transfer zone is moved from adsorption tower G to adsorption tower A, valves G1, G7, A6, A8, C5, and C13 are closed, the tertiary adsorption state of adsorption tower G ends, the secondary adsorption state of adsorption tower A ends, and the primary adsorption state of adsorption tower C ends; at the same time, adsorption towers H, B, and D enter the series adsorption state, adsorption tower H enters the tertiary adsorption state, adsorption tower B enters the secondary adsorption state, and adsorption tower D enters the primary adsorption state. At the same time, the valve of adsorption tower E or E14 is closed to end the vacuum decompression state, as shown in FIG. Figure 2 、 Figure 3As shown, or end the blank waiting state, such as Figure 4 As shown; at the same time, adsorption tower G, adsorption tower A, and adsorption tower C are kept in series and connected to adsorption tower E. Valves G9, A4, A10, C3, C11, and E11 are opened. Adsorption tower G enters the three-time equalizing pressure reduction state, adsorption tower A enters the two-time equalizing pressure reduction state, adsorption tower C enters the one-time equalizing pressure reduction state, and adsorption tower E enters the equalizing pressure boost state. At the same time, adsorption tower F ends the reverse pressure reduction state and enters the vacuum pressure reduction state, as shown Figure 2 As shown; or directly enter the vacuum decompression state, such as Figure 3 As shown; or enter the flushing state, such as Figure 4 shown.

[0089] Step 16: After the pressures of adsorption tower G, adsorption tower A, adsorption tower C, and adsorption tower E reach equilibrium, valves G9, A4, A10, C3, C11, and E11 are closed, the three equalizing pressure reduction states of adsorption tower G are completed, the two equalizing pressure reduction states of adsorption tower A are completed, the one equalizing pressure reduction state of adsorption tower C is completed, and the equalizing pressure boosting state of adsorption tower E is completed; at the same time, valve E12 is opened and adsorption tower E enters the one reverse boosting state, valve A12 is opened and adsorption tower A enters the three reverse boosting states, valve C12 is opened and adsorption tower C enters the two reverse boosting states, after the pressures in adsorption towers E, adsorption tower A, and adsorption tower C rise to the adsorption pressure, the one reverse boosting state of adsorption tower E is completed, the three reverse boosting states of adsorption tower A are completed, and the two reverse boosting states of adsorption tower C are completed. At the same time, adsorption tower G may enter the reverse depressurization state, such as Figure 2 and Figure 4 As shown; or enter the blank waiting state before vacuuming and depressurizing, such as Figure 3 At the same time, the adsorption tower F continues to be vacuumed and depressurized, as shown in FIG. Figure 2 、 Figure 3 As shown; or end the flushing state, such as Figure 4 As shown, it enters the blank waiting state before pressure equalization and pressure boosting. At the same time, adsorption tower H, adsorption tower B, and adsorption tower D continue to maintain the series adsorption state.

[0090] At this point, one cycle is completed. In the above embodiment, the focus is on describing the corresponding valve switch states when adsorption towers A, C, and E are in different states. When the remaining adsorption towers are in the same state as adsorption towers A, C, and E, the corresponding valve switch states are the same as the switch states of the same position numbers in adsorption towers A, C, and E.

[0091] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A three-tower series pressure swing adsorption device, characterized in that: The device comprises at least 8 adsorption towers and corresponding valves and pipe 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; Among them, the lower interface and upper interface of the adsorption tower are each connected to 7 valves; The 7 valves connected to the lower interface of the adsorption tower include: 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 valve of each adsorption tower is connected in parallel through the adsorption pipeline 2; Secondary adsorption air inlet valve: the gas from the outlet of the tertiary adsorption tower enters the secondary adsorption tower through the secondary adsorption air inlet valve; the secondary adsorption air inlet valve of each adsorption tower is connected in parallel through the adsorption pipeline 1; The raw gas enters the tertiary adsorption tower through the tertiary adsorption inlet valve. The tertiary adsorption inlet valve of each adsorption tower is connected in parallel through the raw gas pipeline; Reverse-down exhaust valve: when the adsorption tower is in the reverse depressurization process, the gas in the adsorption tower is discharged from the adsorption tower through the reverse-down exhaust valve. The reverse-down exhaust valves of each adsorption tower are connected in parallel through the reverse-down pipeline; Pumping and exhaust valve: when the adsorption tower is in a vacuum and pressure-reducing state, the gas in the adsorption tower is discharged from the adsorption tower through the pumping and exhaust valve. The pumping and exhaust valves of each adsorption tower are connected in parallel through the pumping and exhaust pipeline; The gas from the outlet of the secondary pressure-equalizing and pressure-reducing adsorption tower enters the primary pressure-equalizing and pressure-reducing adsorption tower through the primary pressure-equalizing and pressure-reducing air inlet valve. The primary pressure-equalizing and pressure-reducing air inlet valves of each adsorption tower are connected in parallel through the pressure-equalizing pipeline 2; Secondary pressure-equalizing air inlet valve: the gas from the outlet of the tertiary pressure-equalizing and pressure-reducing adsorption tower enters the secondary pressure-equalizing and pressure-reducing adsorption tower through the secondary pressure-equalizing air inlet valve. The secondary pressure-equalizing air inlet valves of each adsorption tower are connected in parallel through the pressure-equalizing pipeline 1; The 7 valves connected to the upper interface of the adsorption tower include: 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 air intake valve, the secondary adsorption exhaust valve, and the primary adsorption air intake valve; the tertiary adsorption exhaust valve of each adsorption tower is connected in parallel through the 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 Inside, the secondary adsorption exhaust valve of each adsorption tower is connected in parallel through the adsorption pipeline 2; The gas in 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 valve of each adsorption tower is connected in parallel through the difficult-to-adsorb component product gas pipeline; Three-way pressure reduction exhaust valve, three-way pressure reduction adsorption tower and two-way pressure reduction adsorption tower, one-way pressure reduction adsorption tower The three equalizing exhaust valves, the two equalizing intake valves, the two equalizing exhaust valves, and the one equalizing intake valve are connected in series; the three equalizing exhaust valves of each adsorption tower are connected in parallel through the pressure equalizing pipeline 1; Secondary pressure-equalizing exhaust valve: the gas in the secondary pressure-equalizing adsorption tower is discharged into the primary pressure-equalizing adsorption tower through the secondary pressure-equalizing exhaust valve; the secondary pressure-equalizing exhaust valve of each adsorption tower is connected in parallel through the pressure-equalizing pipeline 2; The gas in the primary pressure-equalizing and pressure-reducing adsorption tower is discharged into the pressure-equalizing and pressure-boosting adsorption tower through the primary pressure-equalizing and pressure-reducing exhaust valve. The primary pressure-equalizing and pressure-reducing exhaust valves of each adsorption tower are connected in parallel through the pressure-equalizing and pressure-boosting pipeline; Reverse rising flushing valve, reverse rising pressurized gas or flushing gas enters the adsorption tower that needs to be reversely pressurized or flushed through the reverse rising flushing valve, and the reverse rising flushing valve of each adsorption tower is connected in parallel through the reverse rising flushing gas pipeline.

2. A three-tower series pressure swing adsorption device and adsorption process, characterized by: Using the adsorption device according to claim 1, the following steps are performed: In a three-tower series pressure swing adsorption device, three adsorption towers are always in the adsorption state during one cycle; The three adsorption towers are connected end to end in series. 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 an adsorption effect on the components to be adsorbed. After the feed gas contacts the adsorbent bed, the easily adsorbed components are adsorbed by the corresponding adsorbent and separated from the feed gas. Most of the components that do not need to be adsorbed and a small amount of easily adsorbed components flow to the upper interface of the adsorption tower. It flows out from the upper interface and continues to enter the adsorption tower from the lower interface of the second adsorption tower in the adsorption state. Most of the easily adsorbable components contained in the gas entering the second adsorption tower are adsorbed by the adsorbent, and most of the difficultly adsorbable components and a small amount of easily adsorbable components contained in the gas entering the second adsorption tower flow out from the upper interface of the adsorption tower; it continues to enter the adsorption tower from the lower interface of the third adsorption tower in the adsorption state. Most of the easily adsorbable components contained in the gas entering the third adsorption tower are adsorbed by the adsorbent, and most of the difficultly adsorbable components and a trace amount of easily adsorbable components contained in the gas entering the third adsorption tower flow out from the upper interface of the adsorption tower, thereby obtaining a difficultly adsorbable component product gas that meets the quality requirements of high-purity gas; When the adsorption tower is in the adsorption state, the adsorbent in the adsorption tower will show three state areas. The adsorbent bed that has reached the saturated adsorption amount is the saturated area; the adsorbent bed that has adsorbed some easily adsorbable components but has not yet reached the saturated adsorption amount is the mass transfer area; the adsorbent bed that has not yet adsorbed easily adsorbable components is the blank area; the three state areas are arranged in sequence along the direction of airflow; as the adsorption time increases, the three state areas gradually move toward the upper interface of the adsorption tower; In one cycle, each adsorption tower undergoes three adsorption states; the adsorption tower into which the raw gas directly enters is in the tertiary adsorption state, the adsorption tower into which the gas flowing out of the adsorption tower in the tertiary adsorption state enters is in the secondary adsorption state, and the adsorption tower into which the gas flowing out of the adsorption tower in the secondary adsorption state enters is in the primary adsorption state; The three adsorption towers that are in the adsorption state at the same time, according to the flow of raw gas, the first one is in the tertiary adsorption state, the second one is in the secondary adsorption state, and the third one is in the primary adsorption state; when the three adsorption towers that are in the adsorption state at the same time end the primary adsorption state, the secondary adsorption state, and the tertiary adsorption state respectively, the other three adsorption towers that were previously in the tertiary reverse boosting state, the secondary reverse boosting state, and the primary reverse boosting state respectively, enter the series adsorption state at the same time, among which the adsorption tower that was previously in the tertiary reverse boosting state enters the tertiary adsorption state, the adsorption tower that was previously in the secondary reverse boosting state enters the secondary adsorption state, and the adsorption tower that was previously in the primary reverse boosting state enters the primary adsorption state, thereby ensuring that the obtained product gas flow of the difficult-to-adsorb component is continuous; When the mass transfer zone has been pushed out of the adsorption tower in the tertiary adsorption state and transferred to the adsorption tower in the secondary adsorption state, the adsorption state of these three adsorption towers ends.

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