A control system to prevent fluidization of a pressure swing adsorption bed

Abstract

The utility model relates to industrial gas separation and purification equipment technical field especially relates to a control system of preventing pressure swing adsorption bed layer fluidization, including raw material gas inlet main pipe, product gas discharge main pipe and a plurality of adsorption purification devices, and adsorption purification device contains raw material gas inlet branch pipe, adsorption tower, product gas discharge branch pipe, and the control system still includes the pressure cylinder of adsorption tower top, pressure sensor and process control regulating valve on product gas discharge branch pipe, the forward depressurization branch pipe and pressure equalizing orifice plate of intercommunication adjacent device. The utility model eliminates fluidization space through the pressure cylinder compaction adsorbent top surface, and process control regulating valve and pressure equalizing orifice plate cooperate and regulate and control pressure difference and flow velocity, solve the adsorbent fluidization pulverization in the operation of pressure swing adsorption device, pipeline vibration and the problem of high cost and high failure rate of existing control scheme, be applicable to all pressure swing adsorption device, especially to large -scale pressure swing adsorption device of low hydrogen raw material gas or macromolecular weight product gas, the effect is particularly remarkable.

Description

Technical Field

[0001] This utility model relates to the technical field of industrial gas separation and purification equipment, specifically to a control system for preventing laminar fluidization of a pressure swing adsorption bed. Background Technology

[0002] Pressure swing adsorption (PSA) gas separation and purification technology has become an independent operating unit in industrial production, and is widely used in the separation and purification of hydrogen, carbon monoxide, carbon dioxide, oxygen, nitrogen, argon, and hydrocarbon gases in mixed gas sources. Its core principle is to utilize the differences in adsorption capacity of the adsorbent for different gas components under pressure changes, and to achieve gas separation through periodic pressure regulation. A complete adsorption cycle typically includes six steps: adsorption, forward depressurization, forward desorption, desorption regeneration, reverse pressurization, and final pressurization. Forward depressurization and reverse pressurization can be set to one or more steps depending on process requirements. Desorption regeneration can be divided into reverse depressurization regeneration, rinsing regeneration, or vacuum regeneration.

[0003] With the large-scale application of pressure swing adsorption (PSA) units and the expansion of their feed gas sources, technical problems such as adsorbent fluidization and pulverization, and pipeline vibration have gradually emerged in actual operation, seriously affecting the safe and stable operation of the units. Large-scale PSA units using low-hydrogen feed gas or product gas as the adsorbent phase generally have large adsorption tower volumes. During the initial stage of forward depressurization, under conditions of high pressure differential and high flow rate, the adsorbent is prone to fluidization in the adsorption bed. After fluidization, the adsorbent particles wear down, producing powder, i.e., adsorbent pulverization, which affects the adsorbent's service life and poses safety hazards to the unit. For example, in a low-hydrogen-content feed gas PSA hydrogen purification unit using raw coal gas as feedstock, due to the high impurity content in the raw coal gas, a two-stage PSA series hydrogen production process is usually adopted. The first-stage PSA outlet gas molecules have high kinetic energy, making it highly susceptible to adsorbent pulverization and significant pipeline vibration during forward depressurization. After the adsorbent pulverizes, the powder is carried by the equalizing gas and washes against the sealing surface of the control valve, causing damage to the valve's sealing surface. This further disrupts the pressure in various states of the adsorption tower, posing a safety hazard of cross-contamination between high and low pressure gases. Simultaneously, the high kinetic energy of the equalizing gas molecules causes high-frequency, low-amplitude vibrations in the pipeline during the forward depressurization process, especially noticeable at the beginning of the forward depressurization. This pipeline vibration causes the control valve and its associated instrument gas supply fittings to vibrate as well. Prolonged operation can easily lead to the instrument fittings detaching, rendering the control valve malfunction. Similar problems are also prominent in PSA units that use adsorbed phases such as carbon monoxide, methane, and carbon dioxide as product gases.

[0004] To address the aforementioned issues, existing technologies have attempted to control the PSA process. For example, utility model patent CN215138394U discloses a system for precisely controlling the pressure swing adsorption, equalization, forward discharge, and rinsing processes. This system achieves automatic control of the equalization rate by installing regulating valves at the connection points of two rows of equalization programmable valves. However, this technology has significant limitations: firstly, it requires two rows of equalization programmable valves and associated instruments, twice the number required by conventional solutions, significantly increasing equipment investment; secondly, the equalization regulating valves need to operate continuously during the equalization process, with the highest operating frequency in the system. This high-frequency operation easily leads to increased valve failure rates, increasing maintenance costs and the risk of system downtime, making it difficult to meet the long-term stable operation requirements of large-scale PSA units.

[0005] Therefore, for PSA units with low-hydrogen feed gas or adsorption phase as product gas, there is an urgent need to develop a control system that can effectively suppress adsorbent fluidization and pulverization, reduce pipeline vibration, and lower equipment investment and operational failure rate, so as to ensure the safe and efficient operation of the unit. Utility Model Content

[0006] This invention provides a control system for preventing fluidization of a pressure swing adsorption bed. This control system reduces fluidization and pulverization of the adsorbent, lowers the failure rate of the programmable valve, and improves the stability and service life of the system.

[0007] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0008] This utility model provides a control system for preventing laminar fluidization of a pressure swing adsorption (PSA) bed, comprising a raw material inlet main pipe, a product gas outlet main pipe, and several adsorption purification devices. Each adsorption purification device includes: a raw material inlet branch pipe with one end connected to the raw material inlet main pipe; an adsorption tower with one end connected to the raw material inlet branch pipe; and a product gas outlet branch pipe with one end connected to the top of the adsorption tower and the other end connected to the product gas outlet main pipe. The control system further includes: a pressing cylinder disposed at the top of each adsorption tower, the pressing plate of the pressing cylinder contacting the top surface of the adsorbent in the adsorption tower; a pressure sensor and a process control regulating valve disposed on each product gas outlet branch pipe, the pressure sensor and the process control regulating valve being electrically connected to form a regulating loop; and a forward pressure reducing branch pipe for connecting the product gas outlet branch pipes of adjacent adsorption purification devices, the forward pressure reducing branch pipe being provided with a pressure equalization orifice plate.

[0009] Preferably, the forward depressurization branch pipe includes a first branch pipe and a second branch pipe. One end of the first branch pipe is connected to the product gas emission branch pipe, and the other end is connected to the corresponding branch pipe of the adjacent adsorption purification device. A third programmable valve is provided on the first branch pipe. One end of the second branch pipe is connected to the product gas emission branch pipe, and the other end is connected to the corresponding branch pipe of the adjacent adsorption purification device. A fourth programmable valve is provided on the second branch pipe. Two equalizing orifice plates are provided, respectively located near the inlet ends of the third and fourth programmable valves. The second branch pipe 22 has a dual function: firstly, in the forward depressurization stage, the fourth programmable valve 23 is opened to achieve a second forward depressurization between adjacent adsorption towers, forming a stepped pressure difference control with the first forward depressurization of the first branch pipe 20, further reducing the pressure difference gradient of a single depressurization; secondly, in the forward discharge stage, the opening and closing of the fourth programmable valve 23 controls the forward discharge gas to enter the forward discharge gas storage tank 7 through the forward discharge gas pipe 8, realizing the recovery and utilization of the forward discharge gas. The two functions are switched by the timing control of the fourth programmable valve 23 through the control system, without the need for additional hardware modifications.

[0010] Preferably, each of the adsorption purification devices further includes: a first programmable valve disposed on the raw material inlet branch pipe; a second programmable valve disposed on the product gas outlet branch pipe, the second programmable valve being located between the process control regulating valve and the product gas outlet main pipe; the connection point of the first branch pipe is located on the product gas outlet branch pipe between the process control regulating valve and the second programmable valve.

[0011] Preferably, the pressing cylinder includes an instrument air-driven piston assembly and the pressure plate, the piston assembly driving the pressure plate to move axially along the adsorption tower to eliminate the empty space on the top surface of the adsorbent.

[0012] Preferably, the process control regulating valve is located in the horizontal section of the product gas discharge branch pipe and close to the outlet end of the adsorption tower, and the flow characteristic of the process control regulating valve is equal percentage.

[0013] Preferably, the orifice diameter of the pressure equalizing plate is not less than 68% of the orifice diameter of the third programmable valve, and it is made of stainless steel.

[0014] Preferably, each of the adsorption purification devices further includes a third branch pipe, one end of which is connected to the product gas emission branch pipe and the other end is connected to the flushing gas pipe, and a fifth programmable valve is provided on the third branch pipe.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. This invention achieves precise control of pressure difference and velocity during pressure swing adsorption (PSA) through the synergistic effect of a process control regulating valve and a pressure equalizing orifice plate. The process control regulating valve is positioned near the adsorption tower outlet and, in conjunction with a pressure sensor, monitors the operating conditions in real time. It can dynamically adjust the pressure gradient for forward pressure reduction and reverse pressure increase based on fluctuations in the feed gas source. The pressure equalizing orifice plate, with an orifice diameter of no less than 68% of the programmable valve's diameter, achieves mechanical flow restriction of the gas flow rate. The combination of these two features allows for manual setting of the pressure difference distribution and endpoint pressure for each forward pressure reduction, significantly improving the adaptability of the PSA unit to complex operating conditions such as low-hydrogen feed gas and high-molecular-weight product gas.

[0017] 2. This invention fundamentally solves the problems of adsorbent fluidization and pulverization through structural innovation of the clamping cylinder and flow-limiting components. The clamping cylinder at the top of the adsorption tower continuously compacts the top surface of the adsorbent through a pressure plate, eliminating fluidization space; the pressure equalization orifice plate of the forward pressure-reducing branch pipe and the process control regulating valve work together to control the airflow velocity, avoiding severe adsorbent disturbance caused by the large pressure difference in the initial stage of forward pressure reduction. In practical applications, the adsorbent service life is more guaranteed, the wear rate of the control valve sealing surface caused by pulverization is reduced by 99%, the annual cost of adsorbent replacement and valve maintenance is reduced by more than one million yuan, and the continuous stable operation cycle of the device exceeds 8000 hours.

[0018] 3. This utility model achieves a balance of low cost, high reliability, and wide applicability through simplified structural design and optimized control logic. Compared to existing technologies that require doubling the number of equalizing process control valves, this system only requires a single process control regulating valve in the product gas discharge branch, reducing investment costs by 35%. Furthermore, the regulating valve only adjusts during forward depressurization and forward discharge (maintaining 95% opening for other steps), reducing the operating frequency by 60% and the failure rate to below 0.5 times per year. Simultaneously, this system is adaptable to various scenarios such as raw coal gas to hydrogen production and CO / CO2 / CH4 purification, and is particularly suitable for large-scale PSA units with high gas molecule kinetic energy and equalizing pressure differences exceeding 0.4 MPa, covering complex gas source conditions that cannot be met by existing technologies. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the control system for preventing fluidization of the pressure swing adsorption bed in an embodiment of this utility model.

[0020] Figure 2 This is a schematic diagram of the adsorption purification device in an embodiment of this utility model.

[0021] Figure 3 This is a partially enlarged schematic diagram of the adsorption purification device in an embodiment of this utility model.

[0022] The reference numerals in the above figures are explained as follows:

[0023] 1. Raw material inlet main pipe; 2. Adsorption purification device; 3. Raw material inlet branch pipe; 4. Adsorption tower; 5. Product gas discharge branch pipe; 6. Product gas discharge main pipe; 7. Forward venting gas storage tank; 8. Forward venting gas pipe; 9. Flushing gas pipe; 10. Desorbed gas storage tank; 11. Reverse venting desorbed gas outlet pipe; 12. Flushing desorbed gas outlet pipe; 13. Desorbed gas outlet main pipe; 14. Flow regulating valve; 15. Pressure regulating valve; 16. Pressure boosting pipe; 17. Pressure boosting flow control valve; 18. First programmable valve; 19. Second programmable valve; 20. First branch pipe; 21. Third programmable valve; 22. Second... Branch pipe; 23. Fourth control valve; 24. Third branch pipe; 25. Fifth control valve; 26. First outlet branch pipe; 27. Sixth control valve; 28. Second outlet branch pipe; 29. ​​Seventh control valve; 30. Equalizing orifice plate; 31. Pressure sensor; 32. Process control regulating valve; 33. Pressing cylinder; 34. Adsorption tower A; 35. Adsorption tower B; 36. Adsorption tower C; 37. Adsorption tower D; 38. Adsorption tower E; 39. Process control regulating valve A; 40. Process control regulating valve C; 41. Third control valve C; 42. Third control valve D; 43. Eighth control valve. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings.

[0025] Example

[0026] like Figure 1-3As shown, this utility model provides a control system for preventing laminar fluidization of a pressure swing adsorption (PSA) bed. It includes a main feed gas inlet pipe 1 for conveying feed gas, which is connected to the bottom of five adsorption purification devices 2 (at least four devices) via five feed gas inlet branch pipes 3, achieving uniform distribution of feed gas to each adsorption tower 4. Each adsorption purification device 2 has a product gas discharge branch pipe 5 connected to its top. The five product gas discharge branch pipes 5 converge and connect to the main product gas discharge pipe 6 for centralized external transmission of the purified product gas. A forward venting gas storage tank 7 is connected to the product gas discharge branch pipe 5 via a forward venting gas pipe 8 and a flushing gas pipe 9, temporarily storing the gas discharged during the forward venting process. A desorption gas storage tank 10 is connected to the feed gas inlet branch pipe 3 via a reverse venting desorption gas outlet pipe 11 and a flushing desorption gas outlet pipe 12, collecting the gas generated during desorption. The desorption gas storage tank 10 is also connected to the desorption gas outlet pipe 13, allowing the desorption gas to be externally transmitted to subsequent processing stages. An eighth control valve 43 is installed on the venting pipe 8, located between the fourth control valve 23 and the venting gas storage tank 7. This valve controls the flow of venting gas from the second branch pipe 22 into the venting pipe 8. When the second branch pipe 22 performs the forward depressurization function, the eighth control valve 43 closes to prevent gas from flowing into the venting gas storage tank 7. When performing the venting function, the eighth control valve 43 and the fourth control valve 23 open synchronously to ensure that the venting gas enters the storage tank in a directional manner. The eighth control valve 43 completely isolates the airflow paths of the forward depressurization and venting functions, preventing gas cross-flow between different process steps.

[0027] The flow-stabilizing valve 14 installed on the flushing gas pipe 9 can stabilize the flow rate of the flushing gas and ensure uniform flushing and regeneration effect; the pressure-stabilizing valve 15 on the reverse release desorption gas outlet pipe 11 can control the pressure change rate during the reverse release process and avoid sudden pressure drops that could impact the adsorbent. A pressure boosting pipe 16 is also provided between the adsorption purification device 2 and the product gas discharge main pipe 6. One end of the pipe is connected to the product gas discharge branch pipe 5, and the other end is connected to the product gas discharge main pipe 6. The pressure boosting flow control valve 17 on the pipe can adjust the gas flow rate during the final pressure boosting stage, so that the pressure of the adsorption tower 4 can be steadily increased to the adsorption pressure.

[0028] The adsorption purification device 2 includes: a first programmable valve 18 on the raw material inlet branch pipe 3 for controlling the flow of raw material gas into the adsorption tower 4; one end of the adsorption tower 4 is connected to the raw material inlet branch pipe 3, and the other end is connected to the product gas outlet branch pipe 5, and the tower is filled with a specific adsorbent to selectively adsorb impurities in the raw material gas; a second programmable valve 19 on the product gas outlet branch pipe 5 for controlling the flow of product gas output. A first branch pipe 20, a second branch pipe 22, and a third branch pipe 24 are also connected to the product gas outlet branch pipe 5 between the second programmable valve 19 and the adsorption tower 4: the first branch pipe 20 connects the product gas outlet branch pipe 5 to the pressure boosting pipe 16; the third programmable valve 21 on the pipe controls the flow of gas during the pressure equalization and boosting process; the connection point of the first branch pipe 20 is selected between the process control regulating valve 32 and the second programmable valve 19, allowing for the pre-regulation of the forward depressurization airflow using the process control regulating valve 32. The equalizing gas is buffered by the regulating valve before entering the adjacent adsorption tower to avoid the high pressure difference directly impacting the sealing surface of the programmable valve. At the same time, it forms a "double valve isolation" with the second programmable valve 19 to improve system safety. The second branch pipe 22 connects the product gas discharge branch pipe 5 and the forward discharge gas pipe 8. The fourth programmable valve 23 on the pipeline is used to control the gas path opening and closing during the forward discharge process. The third branch pipe 24 connects the product gas discharge branch pipe 5 and the flushing gas pipe 9. The fifth programmable valve 25 on the pipeline is used to control the gas path opening and closing during the flushing process.

[0029] On the raw material inlet branch pipe 3 between the first programmable valve 18 and the adsorption tower 4, there are also a first outlet branch pipe 26 and a second outlet branch pipe 28: one end of the first outlet branch pipe 26 is connected to the raw material inlet branch pipe 3, and the other end is connected to the reverse release desorption gas outlet pipe 11. The sixth programmable valve 27 on the pipeline is used to control the gas path opening and closing during the reverse release process; one end of the second outlet branch pipe 28 is connected to the raw material inlet branch pipe 3, and the other end is connected to the flushing desorption gas outlet pipe 12. The seventh programmable valve 29 on the pipeline is used to control the gas path opening and closing during the flushing desorption gas discharge.

[0030] The first branch pipe 20, the second branch pipe 22, the third branch pipe 24, the first outlet branch pipe 26 and the second outlet branch pipe 28 of each adsorption purification device 2 are respectively connected to the corresponding branch pipes of the adjacent adsorption purification device 2 to form a parallel pressure equalization channel, which can realize the pressure balance between multiple towers.

[0031] To limit the gas flow rate at the initial stage of forward pressure reduction, equalizing orifice plates 30 are provided at the inlet ends of the first branch pipe 20 and the second branch pipe 22 for forward pressure reduction, near the third program control valve 21 and the fourth program control valve 23. The equalizing orifice plates 30 are made of stainless steel, and their thickness needs to withstand the maximum pressure difference on both sides of the program control valve and frequent pressure alternation. Moreover, the aperture diameter is not less than 68% of the corresponding program control valve diameter. By means of mechanical flow limiting, the speed of the gas flowing through the branch pipe is reduced, and the erosion of the adsorbent is decreased. Those skilled in the art can understand that the aperture diameter of the equalizing orifice plate 30 is the key to achieving the balance between flow limiting and ensuring equalizing efficiency. Through experimental verification, when the aperture diameter is too small (for example, less than 68% of the corresponding program control valve diameter), it will lead to too long equalizing time and affect the overall process efficiency; when the aperture diameter is too large, the gas flow rate at the initial stage of forward pressure reduction cannot be effectively limited, and the inhibition effect on pipeline vibration and adsorbent fluidization is weakened. Therefore, setting the aperture diameter to be not less than 68% of the program control valve diameter is the preferred range for achieving a technical balance between ensuring process efficiency and inhibiting fluidization effect.

[0032] A pressure sensor 31 and a process control regulating valve 32 are provided on the product gas discharge branch pipe 5. The pressure sensor 31 can monitor the outlet pressure of the adsorption tower 4 in real time, and the process control regulating valve 32 dynamically adjusts the opening degree according to the pressure signal. This regulating valve adopts an equal percentage flow characteristic, and has the characteristics of high precision, high sensitivity and high pressure difference resistance. It can accurately control the pressure change curve during the forward pressure reduction and forward blowdown processes, and avoid excessive pressure fluctuations.

[0033] A pressing cylinder 33 is installed at the top of the adsorption tower 4. Its diameter and piston stroke are matched with the diameter of the adsorption tower 4 and the outlet pipe diameter. It is driven by instrument air. The pressing plate of the pressing cylinder 33 is always in close contact with the upper surface of the adsorbent, eliminating the empty space at the top of the adsorbent, preventing the adsorbent from fluidizing structurally, and ensuring the stability of the adsorbent bed layer.

[0034] The specific working principle of this control system is as follows:

[0035] The pressing cylinder 33 at the top of the adsorption tower 4, the process control regulating valve 32, and the equalizing orifice plate 30 are the core combined hardware components of the control system for preventing the fluidization of the pressure swing adsorption bed layer. The software control method of the process control regulating valve 32 is the program control software supporting the control system for preventing the fluidization of the pressure swing adsorption bed layer.

[0036] The pressure swing adsorption process includes steps such as adsorption, forward pressure reduction, forward blowdown, regeneration, reverse pressure boost, and final pressure boost. Now, taking the adsorption tower A34 as an example to describe the entire process of the main flow, the processes of the adsorption tower B35, the adsorption tower C36, the adsorption tower D37, and the adsorption tower E38 are exactly the same as that of the adsorption tower A34. The process and principle are as follows:

[0037] (1) Adsorption

[0038] The raw material gas enters the adsorption tower A34 through the raw material inlet main pipe 1 and the first programmable valve 18. The adsorbent phase components are sequentially adsorbed by the various adsorbents packed in the adsorption tower A34. The resulting product gas is discharged from the top of the adsorption tower A34 through the second programmable valve 19 to the product gas discharge branch pipe 5, and finally merges into the product gas discharge main pipe 6. As the adsorption time progresses, when the adsorption front rises to a certain height close to the adsorption bed, the first programmable valve 18 and the second programmable valve 19 are closed to stop the adsorption.

[0039] In this embodiment, the internal structure of the upper end cap of the pressure swing adsorption tower 4 is a filter cartridge. The top surface of the adsorbent is filled to the lower end of the filter cartridge and is flush with or leaves a small distance from the lower end. There is empty space around the filter cartridge inside the upper end cap of the adsorption tower 4. Once the gas flow velocity through the particles reaches the critical velocity of adsorbent fluidization, adsorbent fluidization will occur on the top surface of the adsorbent because there is empty space around the filter cartridge on the top surface of the adsorbent.

[0040] In the control system of this embodiment, a clamping cylinder 33 is installed at the top of the adsorption tower 4. Most of the space in the upper end cap of the adsorption tower 4 can be filled with adsorbent, making the space utilization rate of the adsorption tower 4 higher. The pressure plate of the clamping cylinder 33 is pressed firmly against the top surface of the adsorbent by the piston at all times, so that under abnormal circumstances, the top adsorbent cannot fluidize when it reaches the fluidization critical velocity because there is no fluidization space.

[0041] Throughout the entire adsorption process, the opening of the process control valve 32 is maintained at 95%.

[0042] (2) Forward pressure reduction

[0043] The third programmable valve 21 of adsorption tower A34 and the third programmable valve C41 of the reverse pressurization adsorption tower C36 system are opened. Then, by dynamically adjusting the opening of the process control regulating valve A39 of adsorption tower A34 and under the action of the pressure equalizing orifice plate 30, the gas pressure in the two adsorption towers is made to reach the same level within a given time.

[0044] The process control valve has two control modes to choose from during this process:

[0045] The first mode is the automatic PID control mode: Within a given time period, based on the difference between the actual pressure drop monitored by pressure sensor 31 and the set differential pressure value, the control valve is automatically controlled to operate between the minimum and maximum set values, ensuring that the difference reaches the allowable error range at the end of the given time. The set differential pressure value is set by the operator and is less than or equal to the differential pressure value when process control valve A39 is fully open. During this process, process control valve C40 of adsorption tower C36 remains at 95% opening.

[0046] The second mode is the automatic linear control mode: the process control valve A39 linearly opens from the minimum set opening to the maximum set opening within a given process time, and then returns to the minimum opening in the last 5 seconds of the given time. During this process, the process control valve C40 of the adsorption tower C36 always maintains a 95% opening.

[0047] In the initial stage of the forward depressurization, the pressure difference between adsorption towers A34 and C36 is at its maximum. At this time, the gas velocity flowing through the adsorbent particles in adsorption tower 4 is at its maximum. The process control valve A39 is kept at its minimum opening to limit the flow velocity from approaching the critical fluidization velocity of the adsorbent particles and prevent fluidization. Specifically, the flow velocity is limited to ≤0.8 m / s (based on 13X molecular sieve adsorbent). As the pressure difference between the two towers decreases, the opening of the process control valve A39 is gradually increased, but the gas velocity flowing through the top adsorbent particles in adsorption tower 4 still needs to be kept below the critical fluidization velocity of the adsorbent particles.

[0048] Based on the characteristics of pressure swing adsorption, the diameter of the adsorbent cross-section at the top of adsorption tower A34 and the diameter of the product gas discharge branch pipe 5 are larger than the diameters of the first branch pipe 20 and the third programmable valve 21. The velocity of the same volume of forward depressurized gas flowing through the first branch pipe 20 is the velocity of the product gas discharge branch pipe 5 multiplied by the arithmetic square of the ratio of the diameters of the product gas discharge branch pipe 5 and the first branch pipe 20. This velocity is much greater than that of the product gas discharge branch pipe 5, which can easily cause high-frequency, low-amplitude vibrations in the horizontal section of the first branch pipe 20 connecting adsorption tower A34 and adsorption tower C36. At this time, the velocity and flow rate of the gas flow can be limited by the pressure equalization orifice plate 30 set at the inlet of the third programmable valve 21, which can both reduce the frequency and amplitude of the vibration and further reduce the flow velocity of the gas through the adsorbent particles.

[0049] The process control regulating valve A39 is installed on the horizontal section of the product gas discharge branch pipe 5 and at the shortest distance from the outlet pipe of the adsorption tower A34 to prevent the fluidization of the adsorbent at the top of the adsorption tower A34 from occurring momentarily when the third programmable valve 21 is opened.

[0050] The minimum and maximum set opening of the aforementioned process control regulating valve A39 are manually set by the operator. The minimum opening is not less than 5%, and the maximum opening is not greater than 95%. By adjusting the minimum and maximum set openings, the pressure difference for each forward pressure reduction can be manually adjusted to match the diameter of the first branch pipe 20 and reduce pipeline vibration during forward pressure reduction.

[0051] During the forward depressurization process, the pressure plate of the top pressing cylinder 33 of the adsorption tower A34 is pressed firmly against the top surface of the adsorbent by the piston at any time. This prevents the top adsorbent from failing to fluidize due to a lack of fluidization space when the speed of the gas flowing through the top adsorbent particles in the adsorption tower 4 approaches the critical speed of fluidization of the adsorbent particles during the forward depressurization process.

[0052] Forward pressure reduction can be performed once or multiple times, depending on the specific process requirements, with each forward pressure reduction lasting ≤30 seconds.

[0053] (3) Place in order

[0054] Open the fourth programmable valve 23 of adsorption tower A34. The process control regulating valve A39 adopts the automatic PID regulation mode to store the gas in adsorption tower A34 into the gas storage tank 7 at a constant speed through the second branch pipe 22 and the gas discharge pipe 8. The gas discharge is then returned to the previous section for recovery.

[0055] After setting the minimum opening, maximum opening, and discharge termination pressure, the process control valve A39 opening is automatically calculated and output based on the discharge time, the pressure difference between the current discharge pressure and the termination pressure. The opening is calculated and output in real time based on changes in time and pressure difference to meet discharge requirements. The output opening is adjusted via PID control between the minimum and maximum opening. Similar to forward depressurization, the process control valve A39 opening is minimized during the initial stage of discharge when the pressure difference is at its maximum, preventing momentary fluidization of the adsorbent at the top of adsorption tower A34.

[0056] During the sequential placement process, the pressure plate of the top pressing cylinder 33 of the adsorption tower A34 is pressed firmly against the top surface of the adsorbent by the piston at any time, so that the top adsorbent cannot be fluidized when the fluidization conditions are met because there is no fluidization space.

[0057] (4) Reverse playback

[0058] Open the sixth programmable valve 27 of adsorption tower A34, and the pressure regulating valve 15 adopts the automatic adjustment mode. The gas in adsorption tower A34 is uniformly reversed to the desorption gas storage tank 10 through the first gas outlet branch pipe 26 and the reverse desorption gas outlet pipe 11, and finally discharged through the desorption gas outlet main pipe 13. The process control regulating valve A39 is fixed at 95%.

[0059] (5) Regeneration:

[0060] Open the fifth programmable valve 25 and the seventh programmable valve 29 of the adsorption tower A34. The flow regulating valve 14 adopts the automatic adjustment mode. The gas in the flushing gas pipe 9 is introduced into the adsorption tower A34 for flushing and regeneration. The desorbed gas generated by flushing enters the desorbed gas storage tank 10 through the second gas outlet branch pipe 28 and the flushing desorbed gas outlet pipe 12. The process control regulating valve A39 is fixed at 95%.

[0061] (6) Reverse boost:

[0062] The reverse pressurization corresponds to the forward pressurization. The third control valve 21 of adsorption tower A34 and the third control valve D42 of adsorption tower D37 are opened. The gas in adsorption tower A34 is used to reverse pressurize adsorption tower D37 through the first branch pipe 20. The process control regulating valve A39 is fixed at 95%.

[0063] (7) Final boost:

[0064] Open the third programmable valve 21 of adsorption tower A34, and the pressure boosting flow control valve 17 adopts the automatic adjustment mode. The product gas enters adsorption tower A34 through the pressure boosting pipe 16 and the first branch pipe 20 to finally boost the pressure of adsorption tower A34. The process control regulating valve A39 is fixed at 95%.

[0065] To better enable those skilled in the art to fully understand and implement this utility model, the following supplementary explanation of the implementation principle of this device is provided in conjunction with a specific application scenario. In the field of industrial gas separation, although pressure swing adsorption (PSA) technology is widely used for the purification of mixed gases, it often faces problems such as adsorbent fluidization and pulverization, and high-frequency pipeline vibration when processing low-hydrogen feed gas or high-molecular-weight product gas. Taking the scenario of producing hydrogen from raw coal gas via a conversion unit as an example, the feed gas composition is complex and methane needs to be recovered separately. Traditional PSA systems are prone to adsorbent fluidization in the initial stage of forward depressurization due to the large pressure difference and high flow rate. Simultaneously, pipeline vibration affects the stability of the programmable valve. This control system effectively solves these problems through structural optimization and precise control.

[0066] Hydrogen is produced from raw coal gas via a conversion unit. The feed gas conditions for the PSA system are shown in Table 1.

[0067] Table 1. Data on the composition of feed gas

[0068] Components <![CDATA[H2]]> CO <![CDATA[CO2]]> <![CDATA[CH4]]> <![CDATA[N2]]> <![CDATA[C m H n ]]> <![CDATA[H2O]]> Vol,% 30.52 0.8 22.03 5.37 40.2 0.62 0.46

[0069] The operating pressure is 1.2 MPaG, and the operating temperature is 40℃. Methane needs to be recovered separately for use as feedstock in LNG production. A two-stage PSA process is employed in series. The first-stage PSA mainly removes methane and carbon dioxide, with an outlet gas molecular weight of 14.8 (main components are H2 and N2, with volume contents of 50.6% and 47.8%, respectively). The second-stage PSA mainly removes nitrogen from the outlet gas of the first stage, yielding hydrogen with a purity of 99.9%. This control system is primarily used in the first-stage PSA section.

[0070] The first-stage PSA process includes steps such as adsorption, forward depressurization, forward degassing, vacuuming, reverse pressurization, and final pressurization. The specific process is as follows:

[0071] (1) Adsorption

[0072] The raw material gas enters the adsorption tower A34 via the first programmable valve 18 on the raw material inlet main pipe 1 and the raw material inlet branch pipe 3. The adsorption phase components, namely CO2 and CH4, are sequentially adsorbed by various adsorbents packed in the adsorption tower A34. The resulting product gas is discharged from the top of the adsorption tower A34 via the second programmable valve 19 on the product gas discharge branch pipe 5 and merges into the product gas discharge main pipe 6. As adsorption progresses, when the adsorption front rises to a certain height close to the adsorption bed, the first programmable valve 18 and the second programmable valve 19 are closed, stopping the adsorption. A pressing cylinder 33 is installed at the top of the adsorption tower 4. Its diameter and piston stroke are matched to the diameter of the adsorption tower 4 and the outlet pipe diameter. Driven by instrument air, it allows most of the space in the upper head of the adsorption tower 4 to be used for filling with adsorbent, improving space utilization. The pressure plate of the pressing cylinder 33 is always pressed firmly against the top surface of the adsorbent by the piston, preventing fluidization even when the top adsorbent reaches the fluidization critical velocity due to lack of free space. During the adsorption process, if the operating pressure of the subsequent stage fluctuates abnormally, the adsorbent in adsorption tower 4 may experience instantaneous fluidization due to pressure difference. The clamping cylinder 33 can effectively mitigate this risk. Throughout the entire adsorption process, the opening of the process control regulating valve A39 on the product gas discharge branch pipe 5 is consistently maintained at 95%.

[0073] (2) Forward pressure reduction

[0074] This embodiment sets up seven forward depressurization steps according to process requirements. Taking the first step as an example: the third programmable valve 21 on the first branch pipe 20 of adsorption tower A34 and the third programmable valve C41 on the corresponding branch pipe of adsorption tower C36 (for reverse pressure boosting) are opened. Under the coordinated action of process control valve A39 and the pressure equalization orifice plate 30 on the first branch pipe 20, adsorption tower A34 completes forward depressurization within ≤30 seconds. After on-site adjustment, process control valve A39 linearly opens from the minimum set opening of 32% to the maximum set opening of 95% within a given time, and returns to the minimum opening of 32% in the last 5 seconds. During this process, process control valve C40 of adsorption tower C36 maintains a 95% opening. Each forward depressurization requires adjusting the minimum and maximum opening of process control valve A39 according to the valve diameter to match the set pressure difference. By adjusting the opening, the pressure difference and final pressure of each depressurization can be manually controlled, changing the gas flow rate and velocity, which is applicable to different PSA units.

[0075] In this embodiment, the comparison of forward pressure reduction data when the process control regulating valve A39 is fully open and when the opening is controlled is shown in Tables 2 and 3. It can be seen that with control, the pressure difference during each pressure reduction can be effectively adjusted. The process control regulating valve A39 has both automatic linear and manual modes. During operation, the automatic linear mode is used to precisely control the gas flow rate and tower pressure, preventing fluidization and pipeline vibration. Because the diameter of the product gas discharge branch pipe 5 (DN250) is larger than that of the first branch pipe 20 and the third programmable valve 21 (DN150), the velocity of the same volume of gas flowing through the first branch pipe 20 is 2.78 times (DN250) that of the product gas discharge branch pipe 5.2 / 150 2 This can easily cause pipeline vibration. In this case, adjusting the opening of process control valve A39 to reduce the pressure difference, combined with the flow restriction by the pressure equalization orifice plate 30 at the inlet of the third control valve 21, can mitigate vibration and reduce the adsorbent scouring velocity. Process control valve A39 is installed in the horizontal section of the product gas discharge branch pipe 5 and near the outlet of adsorption tower A34 to prevent instantaneous fluidization of the adsorbent when the third control valve 21 is opened. Simultaneously, the pressure plate of the clamping cylinder 33 always compacts the top surface of the adsorbent, eliminating fluidization space. The forward pressure reduction when process control valve A is fully open is shown in Table 2.

[0076] Table 2. Pressure drop during each forward flow when process control regulating valve A is fully open.

[0077]

[0078]

[0079] The forward pressure reduction during each control operation of process control valve A is shown in Table 3.

[0080] Table 3. Forward pressure reduction during process control valve A opening control.

[0081] Minimum opening % Maximum opening % Initial pressure (MPa) End pressure (MPa) Pressure difference (MPa) First forward pressure reduction 32 95 1.31 1 0.31 Secondary forward buckling 24 85 1 0.78 0.22 Three forward depressurizations 24 90 0.78 0.6 0.18 Four anterograde blood pressure reductions 28 95 0.6 0.47 0.13 Five anterograde depressors 28 95 0.47 0.36 0.11 Six anterograde depressors 33 95 0.36 0.24 0.12 Seven antegrade blood pressure reductions 28 80 0.24 0.11 0.13

[0082] (3) Place in order

[0083] The fourth programmable valve 23 on the second branch pipe 22 of adsorption tower A34 is opened. The process control regulating valve A39 adopts PID automatic adjustment mode, and the gas is uniformly stored in the venting gas storage tank 7 through the second branch pipe 22 and the venting gas pipe 8. The venting gas can be returned to the previous section for recovery. The parameters are set to a minimum opening of 20%, a maximum opening of 50%, and an end pressure of 0.08MPa. Based on the venting time and the pressure difference between the current pressure and the end pressure, the opening of the process control regulating valve A39 is calculated and output in real time to ensure uniform gas flow without peaks. At the initial stage of venting with the maximum pressure difference, the regulating valve opening is at its minimum to prevent instantaneous fluidization of the adsorbent, and the clamping cylinder 33 always compacts the top surface of the adsorbent to eliminate fluidization space.

[0084] (4) Reverse playback

[0085] Open the sixth programmable valve 27 on the first outlet branch pipe 26 of the adsorption tower A34. The pressure regulating valve 15 on the reverse release desorption gas outlet pipe 11 automatically adjusts and releases the gas at a uniform speed through the first outlet branch pipe 26 and the reverse release desorption gas outlet pipe 11 to the desorption gas storage tank 10. Finally, the gas is discharged through the desorption gas outlet main pipe 13. During the process, the process control regulating valve A39 is kept at 95% opening.

[0086] (5) Vacuuming

[0087] Open the seventh programmable valve 29 on the second outlet branch pipe 28 of adsorption tower A34, and use a vacuum pump to evacuate the adsorption bed to achieve adsorbent desorption. The process control regulating valve A39 is fixed at 95%.

[0088] (6) Reverse boost

[0089] Corresponding to the forward depressurization, the third programmable valve 21 on the first branch pipe 20 of adsorption tower A34 and the third programmable valve D42 on the corresponding branch pipe of adsorption tower D37 are opened, and the gas in adsorption tower A34 is used to reverse the pressure of adsorption tower D37 through the first branch pipe 20. The process control regulating valve A39 is kept at 95% opening.

[0090] (7) Final boost

[0091] Open the third programmable valve 21 on the first branch pipe 20 of adsorption tower A34. The pressure boosting flow control valve 17 on the pressure boosting pipe 16 will automatically adjust and introduce the product gas into adsorption tower A34 through the pressure boosting pipe 16 and the first branch pipe 20 to complete the final pressure boost. The process control regulating valve A39 is at a fixed opening of 95%.

[0092] Each adsorption tower 4 alternately performs the above adsorption and regeneration processes to achieve continuous purification of the raw gas, effectively solving the technical problems of traditional PSA systems in the treatment of complex gas sources.

[0093] The above embodiments are merely one of the preferred embodiments of this utility model and should not be used to limit the scope of protection of this utility model. Any modifications or refinements made to the main design concept and spirit of this utility model that are not of substantial significance, but solve the same technical problem as this utility model, should be included within the scope of protection of this utility model.

Claims

1. A control system for preventing laminar fluidization of a pressure swing adsorption bed, comprising a raw material inlet main pipe (1), a product gas outlet main pipe (6), and a plurality of adsorption purification devices (2), each of the adsorption purification devices (2) comprising: A raw material inlet branch pipe (3) connected at one end to the raw material inlet main pipe (1); An adsorption tower (4) with one end connected to the raw material inlet branch pipe (3); A product gas discharge branch pipe (5) with one end connected to the top of the adsorption tower (4) and the other end connected to the product gas discharge main pipe (6); The control system is characterized in that it further includes: A pressing cylinder (33) is installed at the top of each of the adsorption towers (4), and the pressure plate of the pressing cylinder (33) is in contact with the top surface of the adsorbent inside the adsorption tower (4). A pressure sensor (31) and a process control regulating valve (32) are installed on each of the product gas discharge branch pipes (5), and the pressure sensor (31) and the process control regulating valve (32) are electrically connected to form a regulating loop; And a forward pressure-reducing branch pipe for connecting the product gas discharge branch pipe (5) of the adjacent adsorption purification device (2), wherein the forward pressure-reducing branch pipe is provided with a pressure equalization orifice plate (30).

2. The control system according to claim 1, characterized in that, The forward pressure reducing branch pipe includes a first branch pipe (20) and a second branch pipe (22). One end of the first branch pipe (20) is connected to the product gas emission branch pipe (5), and the other end is connected to the corresponding branch pipe of the adjacent adsorption purification device (2). A third programmable valve (21) is provided on the first branch pipe (20). One end of the second branch pipe (22) is connected to the product gas emission branch pipe (5), and the other end is connected to the corresponding branch pipe of the adjacent adsorption purification device (2). A fourth programmable valve (23) is provided on the second branch pipe (22). Two equalizing orifice plates (30) are provided, which are respectively located near the air inlet end of the third programmable valve (21) and the fourth programmable valve (23).

3. The control system according to claim 2, characterized in that, Each of the aforementioned adsorption purification devices (2) also includes: The first programmable valve (18) is installed on the raw material inlet branch pipe (3); The second programmable valve (19) is installed on the product gas discharge branch pipe (5), and the second programmable valve (19) is located between the process control regulating valve (32) and the product gas discharge main pipe (6); The connection point of the first branch pipe (20) is located on the product gas discharge branch pipe (5) between the process control regulating valve (32) and the second programmable valve (19).

4. The control system according to claim 1, characterized in that, The pressing cylinder (33) includes an instrument air-driven piston assembly and the pressure plate. The piston assembly drives the pressure plate to move axially along the adsorption tower (4) to eliminate the empty space on the top surface of the adsorbent.

5. The control system according to claim 1, characterized in that, The process control regulating valve (32) is located in the horizontal section of the product gas discharge branch pipe (5) and close to the outlet end of the adsorption tower (4). The flow characteristic of the process control regulating valve (32) is equal percentage.

6. The control system according to claim 2, characterized in that, The orifice diameter of the equalizing orifice plate (30) is not less than 68% of the orifice diameter of the third programmable valve (21), and it is made of stainless steel.

7. The control system according to claim 3, characterized in that, Each of the adsorption purification devices (2) further includes a third branch pipe (24), one end of which is connected to the product gas discharge branch pipe (5), and the other end is connected to the flushing gas pipe (9). A fifth programmable valve (25) is provided on the third branch pipe (24).

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