Online blockage treatment and prevention method and system for bed layer of PSA (Pressure Swing Adsorption) pre-adsorption tower

Abstract

The invention relates to the technical field of gas separation and purification, and discloses an online blockage treatment and prevention method and system for a bed layer of a PSA pre-adsorption tower, and the method comprises the following steps: (1) adopting a plurality of pre-adsorption towers to run in parallel, and carrying out dense-phase filling on an adsorbent in each pre-adsorption tower by adopting a multi-layer gradient structure, large-particle activated carbon, activated aluminum oxide and small-particle activated carbon are sequentially filled from bottom to top; (2) monitoring the bed pressure difference of the pre-adsorption towers in real time, and when the pressure difference reaches 0.1-0.2 MPa, switching out the faulted pre-adsorption tower; (3) carrying out on-line water washing on the fault pre-adsorption tower, and alternately carrying out purging and vacuumizing; and (4) re-feeding the qualified regenerated pre-adsorption tower. Through three-dimensional cooperation of facility addition, program optimization and adsorbent improvement, online blockage treatment and prevention are achieved, the pressure difference is effectively reduced, and finally the purposes of prolonging the service life of the adsorbent and guaranteeing the operation stability and economical efficiency of the PSA device are achieved.

Description

Technical Field

[0001] This invention relates to the technical field of gas separation and purification, and in particular to an online method and system for preventing and controlling clogging of a PSA pre-adsorption tower bed. Background Technology

[0002] Pressure swing adsorption (PSA) technology is a gas separation and purification process widely used in petrochemical, metallurgical, and hydrogen production fields. Its core principle is to achieve efficient separation by utilizing the differences in adsorption capacity of adsorbents for various components in a gas mixture under different pressures. During the operation of a PSA unit (hydrogen purification unit), trace amounts of alkaline impurities such as ammonia often contain in the feed gas. These impurities readily react with acidic gases such as hydrogen chloride to form crystalline ammonium salts such as ammonium chloride. With long-term operation, these ammonium salt crystals continuously precipitate and accumulate on the surface of the adsorbent particles, in the bed voids, and at the bottom inlet screen, causing severe blockage of the gas flow channels and leading to a continuous increase in the pressure differential of the pre-adsorption tower bed.

[0003] An abnormal increase in bed pressure differential is a key challenge in the operation of PSA units. It not only significantly increases energy consumption of power equipment and exacerbates adsorbent wear and pulverization, shortening its lifespan, but more seriously, it can lead to fluctuations in product gas purity, reduced unit processing capacity, and even unplanned shutdowns requiring manual cleaning or complete adsorbent replacement, causing significant losses to production continuity and economic efficiency. Therefore, effectively controlling and reducing bed pressure differential is a core challenge for ensuring the long-term, efficient, and stable operation of PSA units.

[0004] Currently, the mainstream treatment methods for the problem of increased pressure differential in PSA beds have obvious limitations: (1) Adjusting process parameters, such as reducing the treatment load or adjusting the adsorption temperature, has limited effect and often comes at the cost of sacrificing the efficiency of the equipment; (2) Regularly shutting down for maintenance, physical cleaning or replacement of the adsorbent, although this method is direct, the downtime is long, the labor intensity is high, and the economic loss is serious; (3) Pre-treatment of the raw gas at the front end, adding purification facilities to remove impurities such as ammonia, although this method has a certain preventive effect, the investment and operating costs are high, and it cannot solve the problem of crystal blockage that has already formed inside the bed. In summary, the existing technology lacks an efficient and economical treatment solution that can be implemented online, does not require a complete system shutdown, and can specifically dissolve and remove the formed ammonium salt crystals.

[0005] Furthermore, patent CN210765202U discloses a coke oven gas purification device with multi-stage inlet regeneration adsorbent to prevent blockage. At least two layers of adsorbent beds are spaced apart along the distribution direction of the inlet and outlet within the tower body, with cavities formed between adjacent adsorbent beds. Several high-temperature regeneration gas pipes are connected at one end to the main high-temperature regeneration gas pipe, and the other ends of these pipes are connected to corresponding cavities. By connecting the high-temperature regeneration gas branches to the cavities of the adsorbent beds at both ends, the temperature drop of the packing material from top to bottom is offset, effectively preventing the condensation and crystallization of impurities that could cause blockage of the outlet pipe. However, this traditional adsorbent loading scheme is insufficient to resist deep blockage caused by ammonium salt crystallization. How to optimize the selection of adsorbents and the bed structure design from a hardware perspective to improve their anti-blockage performance and achieve a synergistic effect with the online regeneration process remains a problem that has not yet been properly solved in the existing technology. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an online method and system for preventing and controlling clogging in PSA pre-adsorption tower beds. This solution achieves online clogging control and prevention through three-dimensional synergy of facility addition, program optimization, and adsorbent improvement, effectively reducing pressure differential and ultimately extending adsorbent lifespan and ensuring the operational stability and economy of the PSA unit.

[0007] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides an online method for preventing and controlling clogging of a PSA pre-adsorption tower bed, comprising the following steps: (1) Several pre-adsorption towers are operated in parallel. The adsorbent in each pre-adsorption tower is packed in a dense phase using a multi-layer gradient structure. From bottom to top, large-particle activated carbon, activated alumina and small-particle activated carbon are packed in sequence. The particle size of the large-particle activated carbon is Φ4-6×5-10 mm and the bulk density is 0.40-0.48 g / mL. The particle size of the activated alumina is 3-5 mm and the bulk density is 0.68-0.78 g / mL. The particle size of the small-particle activated carbon is Φ2-3×3-5 mm and the bulk density is 0.45-0.55 g / mL. (2) Monitor the pressure difference of the pre-adsorption tower bed in real time. When the pressure difference reaches 0.1-0.2 MPa, cut off the faulty pre-adsorption tower. (3) The faulty pre-adsorption tower is washed online with water, and then purged and vacuumed alternately; (4) Re-enter the qualified pre-adsorption tower.

[0008] To enhance anti-clogging capability from the source, this invention optimizes the adsorbent loading scheme in the pre-adsorption tower. A multi-layer gradient structure is adopted, specifically, the bottom layer consists of large-particle activated carbon, the middle layer of activated alumina, and the top layer of small-particle activated carbon, using a dense-phase loading process. This structure forms a synergistic system of graded filtration and adsorption, significantly enhancing the bed's mechanical strength, scale-holding capacity, and regeneration efficiency. Gradient filtration effectively protects against scale buildup.

[0009] The advantages of using this multi-layer gradient structure for filling are mainly reflected in the following aspects: First, the bottom layer of large-particle activated carbon: As a support layer and coarse adsorption layer, the large-particle activated carbon not only evenly distributes the gas flow entering the pre-adsorption tower, avoiding direct impact on the upper fine-particle adsorbent, but its large pore size and interparticle spacing also constitute a "coarse filtration" system. It can trap solid particles that may be carried in the feed gas and preferentially adsorb heavy hydrocarbons with larger molecular diameters. This provides a huge fouling capacity for the entire bed, confining the most likely clogging heavy pollutants to the bottom of the bed and preventing them from penetrating deeper. Simultaneously, due to its large particle size and high porosity, the pressure drop in this area is extremely low, laying the foundation for pressure drop control throughout the pre-adsorption tower.

[0010] If the activated carbon particles used in this layer are too large, the specific surface area will be severely insufficient, resulting in poor coarse adsorption. A large amount of hydrocarbons will directly penetrate to the upper layer, increasing the load on the upper adsorbent and shortening the overall adsorbent lifespan. If the particle size is too small, it will completely lose its significance as a support layer and low-pressure-drop zone, resulting in a very high initial pressure drop for the entire pre-adsorption tower. It will also be prone to rapid failure due to clogging, becoming a bottleneck in the system. Its interception function may even turn into a filtration function, leading to rapid clogging itself.

[0011] Second, the intermediate layer of activated alumina: After the bottom layer purification, most of the heavy hydrocarbons in the gas have been removed. At this point, the gas comes into contact with activated alumina, which specializes in dehydration. Alumina can lower the dew point of the feed gas to an extremely low level. The dry environment greatly inhibits the upward migration of ammonium salts. Placing activated alumina in the middle layer protects it from contamination by oil and heavy hydrocarbons (protected by the bottom layer), maintaining its highly efficient dehydration performance.

[0012] The limitation on the particle size of activated alumina is to ensure a balance between mechanical strength and adsorption kinetics. Larger particle sizes are less prone to pulverization under loading and airflow impact, while the size is not so large as to severely affect the mass transfer rate of water molecules diffusing into the particle interior, thus ensuring its efficiency as the main dehydrating agent. If the alumina particle size is too large, the specific surface area decreases, the adsorption capacity decreases, and more seriously, the water molecule adsorption mass transfer zone becomes longer, reducing dehydration efficiency. If the alumina particle size is too small, although the specific surface area increases, the porosity between particles is significantly reduced, leading to a sharp increase in bed pressure drop. Simultaneously, small particles have poor mechanical strength and are easily pulverized; the pulverized material migrates and exacerbates bed blockage. Furthermore, by controlling an appropriate bulk density, not only is the static adsorption capacity ensured, but it also helps to form a stable bed, reducing airflow disturbance and providing a certain degree of impact resistance. If the bulk density is too low, the strength is insufficient, the structure is loose, and it is easily worn and generates dust under high-speed airflow. The bed is also prone to channeling, causing gas short-circuiting and reducing treatment efficiency. If the bulk density is too high, the pore structure between the activated alumina will be underdeveloped, the adsorption capacity will be low, and the performance of the adsorbent per unit weight will be poor.

[0013] Third, the upper layer of small-particle activated carbon: The gas after dehydration and removal of heavy hydrocarbons finally passes through the upper layer of small-particle activated carbon. Utilizing its high specific surface area, it performs fine adsorption on light hydrocarbons (such as methane and ethane) with smaller molecular sizes and any remaining trace impurities. The role of this layer is to ensure that the feed gas entering the PSA main adsorption tower is as clean as possible, reducing the load on the main tower adsorbent and extending its regeneration cycle and lifespan. Limiting its particle size to a smaller size means a larger specific surface area and a shorter internal mass transfer path, enabling efficient and deep removal of remaining light hydrocarbons, some sulfides, and trace impurities. Excessively large particle sizes lead to a decrease in adsorption rate and deep purification capacity, resulting in poor fine adsorption and potentially causing trace hydrocarbons to penetrate and contaminate the molecular sieves in the downstream PSA main adsorption, causing irreversible poisoning and deactivation. While excessively small particle sizes enhance adsorption capacity, they significantly increase the pressure drop in the upper part of the bed, becoming a major contributor to the increase in system pressure differential.

[0014] Therefore, the multi-layer gradient structure packing method and the synergistic control of particle size and bulk density in this invention enable the entire adsorbent bed to form a more compact whole, which is key to achieving efficient adsorption, low pressure drop operation, and long-term stability. The adsorption bed has higher mechanical strength, better withstands airflow impact, and reduces friction and movement between adsorbent particles, thereby significantly reducing the adsorbent pulverization rate. Pulverization is another important cause of increased bed pressure differential; this process physically inhibits this process.

[0015] Meanwhile, this adsorption bed also provides a stable bed structure foundation for the effective implementation of subsequent online declogging (washing, regeneration) methods. The pressure difference between the beds of each pre-adsorption tower is monitored in real time. When the pressure difference exceeds a preset threshold, the control system automatically and safely disconnects the faulty tower from the PSA sequence, ensuring continuous operation of the main system. The disconnected faulty tower undergoes online water washing to dissolve and crystallize. After washing, a programmed deep regeneration process is executed. This process employs a synergistic mode of alternating heating and purging with vacuuming. Purging removes most of the moisture and some adsorbed hydrocarbon impurities, while vacuuming deeply desorbs residual moisture and strongly adsorbed impurity molecules. The above purging and vacuuming steps are repeated multiple times according to a preset program to ensure thorough bed drying and restoration of adsorption performance.

[0016] The optimized adsorbent loading method, together with online washing and programmed regeneration, constitutes a comprehensive solution. It not only improves purification efficiency through staged adsorption, but also enhances the anti-clogging ability and operational stability of the pretreatment bed through source control (dehydration) and structural optimization (dense phase loading, gradient particles). This lays a solid foundation for the effective implementation and long-term effectiveness of the online treatment system.

[0017] Preferably, in step (1), the filling height ratio of the large-particle activated carbon, activated alumina and small-particle activated carbon is 1-2:1:7-9.

[0018] Preferably, in step (1), the specific surface area of ​​the large-particle activated carbon is 850-1200 m². 2 / g; the specific surface area of ​​the activated alumina is 95-350 m² / g. 2 / g; the specific surface area of ​​the small granular activated carbon is 1100-1300 m². 2 / g.

[0019] Preferably, in step (3), the online washing includes: controlling the level of the cleaning solution to overflow the inlet screen of the pre-adsorption tower and part of the large-particle activated carbon adsorbent, and soaking for 20 minutes or more; the cleaning solution is demineralized water.

[0020] Inject cleaning fluid into the cut-out faulty tower. By controlling the flow rate and liquid level, the liquid level completely covers the high-occurrence area of ​​blockage (the inlet screen of the pre-adsorption tower and the bottom adsorbent). Through thorough soaking, the crystalline ammonium salt and other soluble impurities are dissolved in a targeted manner.

[0021] Preferably, in step (3), the purging is performed using hydrogen gas at 80-100°C with a flow rate of 800-1200 Nm³. 3 / h, purging time is 1-2 h.

[0022] Preferably, in step (3), the vacuuming is to reduce the pressure inside the pre-adsorption tower to absolute pressure of 20-25 kPa and maintain it for 10-20 min.

[0023] Preferably, in step (4), the criterion for determining whether the pre-adsorption tower is qualified for regeneration is that the dew point of the regenerated gas is consistently below -5°C for at least 5 minutes.

[0024] Purging stage: The product hydrogen, heated by an electric heater, is used to purge the bed in a penetrating manner to remove most of the moisture and some of the adsorbed hydrocarbon impurities.

[0025] Vacuuming stage: Start the vacuum pump unit to reduce the pressure inside the tower to the set low vacuum level, and deeply desorb residual moisture and strongly adsorbed impurity molecules.

[0026] The above purging and vacuuming steps are repeated multiple times according to the preset program until the dew point of the gas at the outlet of the pre-adsorption tower is stably below -5℃ (or the moisture content is qualified), ensuring that the bed is thoroughly dried and the adsorption performance is restored.

[0027] Secondly, the present invention also provides a system for online anti-clogging and anti-blocking of PSA pre-adsorption tower bed. The system includes a pre-adsorption tower unit, a water washing unit, a regeneration unit, and a DCS control unit. The pre-adsorption tower unit includes several pre-adsorption towers connected in parallel. The pre-adsorption towers are filled with adsorbents with a multi-layer gradient structure, which includes, from bottom to top, a large-particle activated carbon layer, an activated alumina layer, and a small-particle activated carbon layer. The water washing unit includes a water metering tank connected to the bottom of the pre-adsorption tower. The regeneration unit includes an electric heater connected to the top of the pre-adsorption tower and a vacuum pump unit connected to the bottom of the pre-adsorption tower. The DCS control unit is connected to the pre-adsorption tower unit, the water washing unit, and the regeneration unit respectively.

[0028] Preferably, the water washing unit further includes a waste liquid collection tank; the waste liquid collection tank is connected to the bottom of the pre-adsorption tower via a pipeline and an isolation valve group installed on the pipeline.

[0029] Preferably, the regeneration unit further includes a desorption gas buffer tank and a fuel gas pipeline connected in sequence to the vacuum pump group.

[0030] Preferably, the pre-adsorption tower unit further includes a hydrogen pipeline network connected to the top of the pre-adsorption tower. A branch pipe connected to the inlet of the electric heater is provided on the pipeline connecting the pre-adsorption tower to the hydrogen pipeline network, and the outlet of the electric heater is connected to the outlet pipeline at the top of the pre-adsorption tower.

[0031] Compared with the prior art, the present invention has the following beneficial effects: (1) It has achieved true online governance and production continuity. Through the "single tower cut-out, offline governance" model, it has fundamentally avoided the production loss and economic loss caused by unplanned shutdowns. (2) The combined process of “water washing and dissolution + programmed gas heat - vacuum regeneration” can target and remove ammonium salt crystals, and deeply dry and activate the bed, with a treatment effect far exceeding that of a single method; (3) It has the synergistic effect of short-term treatment and long-term prevention. By combining dynamic online cleaning and regeneration with static adsorbent loading optimization, it can not only effectively solve the blockage problem that has occurred, but also delay the re-formation of blockage through the optimized bed structure, which significantly extends the adsorbent replacement cycle and the overhaul cycle of the device. (4) The entire process is completed automatically by the control unit, which is precise and efficient, minimizing human intervention and operational errors. In addition, the product gas produced by the PSA adsorption bed can be used as the regeneration purge gas, which has low energy consumption and high industrial promotion value and comprehensive economic benefits. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the online anti-clogging system for the PSA pre-adsorption tower bed in this invention.

[0033] The attached diagram is labeled as follows: 1. Water metering tank; 2. Water pump; 3. Isolation valve assembly; 4. Waste liquid collection tank; 5. Electric heater; 6. Pre-adsorption tower; 7. Vacuum pump assembly; 8. Desorption gas buffer tank; 9. Fuel gas pipeline; 10. Hydrogen pipeline. Detailed Implementation

[0034] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0035] like Figure 1 As shown, the PSA pre-adsorption tower bed online anti-clogging system of the present invention includes a pre-adsorption tower unit, a water washing unit, a regeneration unit, and a DCS control unit.

[0036] The pre-adsorption tower unit consists of four pre-adsorption towers connected in parallel (6). Figure 1 The example shown only shows one pre-adsorption tower; in reality, there are four pre-adsorption towers connected in parallel (each using the same connection method as pre-adsorption tower 6) and a hydrogen pipeline 10 connected to the top outlet of pre-adsorption tower 6. The hydrogen produced at the outlet of pre-adsorption tower 6 is all fed into the hydrogen pipeline 10. The tower body of pre-adsorption tower 6 is made of Q345R steel, and pressure transmitters are installed at the inlet and outlet of pre-adsorption tower 6. Each pre-adsorption tower 6 has an isolation valve assembly 3 installed on its bottom pipeline. The isolation valve assembly 3 includes several valves, respectively located on the raw material inlet pipeline, waste liquid collection pipeline, and vacuum pipeline connected to the bottom pipeline. All valves are pneumatically controlled programmable valves with valve position status feedback signals.

[0037] Each pre-adsorption tower 6 is filled with an optimized multi-layer gradient structure of adsorbent. The multi-layer gradient structure, from bottom to top, includes a large-particle activated carbon layer, an activated alumina layer, and a small-particle activated carbon layer. The layers are filled sequentially from bottom to top as follows: Bottom layer: Large-particle activated carbon, particle size Φ4-6×5-10 mm, bulk density 0.40-0.48 g / mL, specific surface area 850-1200 m². 2 / g, mainly serving as support and coarse filtration; Intermediate layer: activated alumina, particle size 3-5 mm, bulk density 0.68-0.78 g / mL, specific surface area 95-350 m² / mL. 2 / g, mainly used for removing moisture and some hydrocarbons, and has a strong scale-holding capacity; Top layer: small granular activated carbon, particle size Φ2-3×3-5 mm, bulk density 0.45-0.55 g / mL, specific surface area 1100-1300 m² 2 / g, used for fine adsorption and protection of the main adsorbent. The packing height ratio of large granular activated carbon, activated alumina, and small granular activated carbon is 1-2:1:7-9. All adsorbents are packed using a dense-phase packing process to ensure high bed density and stability.

[0038] The water washing unit includes a water metering tank 1, a water pump 2, and a waste liquid collection tank 4. The water metering tank 1 is connected to the bottom of the pre-adsorption tower 6 via a water washing water injection pipe, on which the water pump 2 is installed. The volume of the water metering tank 1 is 3 m³. 3 The material is 304 stainless steel and equipped with a level gauge. Water pump 2 is a metering pump with a flow rate adjustment range of 0-10 m³ / h. 3 / h. Waste liquid collection tank 4 is connected to the bottom of pre-adsorption tower 6 via a waste liquid collection pipeline. The volume of waste liquid collection tank 4 is 8 m³. 3 It is made of 304 stainless steel.

[0039] The regeneration unit includes an electric heater 5, a vacuum pump assembly 7, a desorption gas buffer tank 8, and a fuel gas pipeline 9. A branch pipe connected to the inlet of the electric heater 5 is located on the pipeline connecting the pre-adsorption tower 6 and the hydrogen pipeline 10. The outlet of the electric heater 5 is connected to the top outlet pipeline of the pre-adsorption tower 6 for reverse purging. During reverse purging, the valve on the pipeline connecting the pre-adsorption tower 6 and the hydrogen pipeline 10 is in an isolated closed state. The electric heater 5 heats the product hydrogen from room temperature to 80-100℃ to purge the adsorption bed. The electric heater 5 has a power of 80 kW and is equipped with anti-dry-burning interlock protection and a temperature sensor. The vacuum pump assembly 7 is connected to the bottom of the pre-adsorption tower 6 via a vacuum pumping pipeline. The vacuum pump assembly 7 is a liquid ring vacuum pump with an ultimate vacuum level of 15 kPa. The desorption gas buffer tank 8 is connected to the vacuum pump assembly 7 and has a volume of 120 m³. 3It is equipped with a pressure control system, and the desorption gas buffer tank 8 is connected to the fuel gas pipeline 9 to stably deliver the regenerated waste gas to the downstream fuel gas pipeline 9. An online moisture analyzer is installed on the pipeline connecting the pre-adsorption tower 6 and the vacuum pump group 7 to monitor the dew point of the regenerated gas in real time.

[0040] The DCS control unit employs a distributed control system (DCS). All pressure transmitters (especially PDTs used to monitor bed pressure differentials), temperature sensors, flow meters, moisture analyzers, and valve position feedback signals from the pre-adsorption tower unit, water washing unit, and regeneration unit are connected to the DCS. The start and stop of all programmable valves, pumps, and electric heaters are controlled by the DCS according to preset programs.

[0041] Example 1 The above system is used for online anti-clogging and anti-fouling of the PSA pre-adsorption tower bed (a pressure swing adsorption unit for 150,000 cubic meters / hour of hydrogen). The specific method includes the following steps: (1) Four pre-adsorption towers are operated in parallel. The adsorbent in each pre-adsorption tower is packed in a dense phase with a multi-layer gradient structure. The layers are packed from bottom to top as follows: bottom layer: large granular activated carbon, with a filling height of 1020 mm, a particle size of 4 mm (Φ4×6 mm), and a filling amount of 4.22 tons; middle layer: activated alumina, with a filling height of 940 mm, a particle size of 3-5 mm, and a filling amount of 5.58 tons; top layer: small granular activated carbon, with a filling height of 7800 mm, a particle size of 2 mm (Φ2×3-5 mm), and a filling amount of 35.89 tons.

[0042] (2) Real-time monitoring of bed pressure difference of pre-adsorption tower. When the DCS control unit detects through the pressure transmitter that the bed pressure difference of a certain pre-adsorption tower continues to exceed the preset threshold of 0.15 MPa, the DCS control unit issues an instruction to adjust the switch status of the programmable valve of the system in a preset order, so as to smoothly cut off the faulty pre-adsorption tower from the adsorption sequence. This process ensures that the faulty tower is completely isolated from other towers in operation, and the remaining 3 pre-adsorption towers continue to operate without affecting production.

[0043] (3) Perform online water washing on the faulty pre-adsorption tower. The DCS control unit starts the water washing program, opens the water injection control valve leading to the faulty tower, and starts the water injection pump; the injection flow rate of the cleaning solution (room temperature demineralized water) is precisely controlled to 3m³ using a flow meter. 3 / h, injection volume 2 m 3 Ensure that the inlet screen and bottom adsorbent of the pre-adsorption tower are soaked (the bottom of the faulty tower is isolated by a three-valve group during water injection to prevent internal leakage of the valves from affecting the operating tower). Stop water injection and soak for 20 minutes to dissolve the adsorbent. Repeat this water washing-soaking operation twice. After water washing, the DCS control unit opens the drain valve to discharge the waste liquid containing dissolved ammonium salts to the waste liquid collection tank for centralized treatment.

[0044] (4) Then, alternately purge and vacuum the faulty pre-adsorption tower: Purging Phase: The DCS control unit opens the valve on the top pipeline of the pre-adsorption tower, allowing product hydrogen to flow into the electric heater, which then heats the hydrogen to 90°C. The heated hydrogen then flows at 1000 Nm³. 3 The air enters from the top of the fault pre-adsorption tower and performs a penetration purging of the moist bed for 1 hour.

[0045] Vacuuming stage: After the purging is completed, the DCS control unit closes the purging gas path and starts the vacuum pump group to evacuate the faulty tower until the pressure inside the tower drops to absolute pressure of 21 kPa and is maintained for 15 minutes to deeply desorb moisture. At the same time, the water vapor and a small amount of hydrocarbons purged out enter the desorption gas buffer tank through the vacuum pipeline at the bottom of the pre-adsorption tower.

[0046] (5) The above purging-vacuuming process is repeated multiple times, and the dew point of the regenerated outlet gas is monitored in real time by an online moisture analyzer in the regeneration unit. When the moisture analyzer detects that the gas dew point is stably below -5℃ for 5 minutes, the DCS control unit determines that the regeneration is qualified, automatically stops the regeneration unit, and closes all valves of the faulty tower, putting it in a pressure-holding standby state. When the system needs to put the tower into operation, the DCS control unit will re-enter the qualified pre-adsorption tower into the adsorption sequence, and the system will return to the full-process operation of 4 towers.

[0047] The pre-adsorption tower using the above system experienced an increasing pressure differential after approximately 23 months of operation. Through this embodiment, the system can address the issue of rising bed pressure differential without a complete shutdown. The total time from disconnection to regeneration and reintegration into the system for a single tower is approximately 8-10 hours, significantly reducing production loss compared to traditional full-line shutdowns for maintenance (typically 5-8 days). After treatment, the bed pressure differential of the faulty tower can be restored to a normal level below 0.04 MPa, and the purity of the product hydrogen remains stable. Simultaneously, the optimized adsorbent packing structure effectively slows down the rate of pressure differential increase, and the adsorbent lifespan is expected to be extended by more than 30%.

[0048] Example 2 The difference from Example 1 is that a packing structure of large-particle activated carbon-activated alumina-small-particle activated carbon is used, but the particle size and packing height are different. Specifically, the adsorbent in each pre-adsorption tower is packed in a dense phase using a multi-layer gradient structure, from bottom to top as follows: bottom layer: large-particle activated carbon, packing height 1140 mm, particle size 5 mm (Φ5×5 mm); middle layer: activated alumina, packing height 1030 mm, particle size 3-5 mm; top layer: small-particle activated carbon, packing height 7590 mm, particle size 3 mm (Φ3×3-5 mm).

[0049] The pre-adsorption tower using the above system showed an increasing pressure differential after approximately 24 months of operation. Through this embodiment, the system can address the issue of rising bed pressure differential without a complete shutdown. The total time for a single tower, from disconnection to regeneration and reintegration into the system, is approximately 8-10 hours. After treatment, the bed pressure differential of the faulty tower can be restored to a normal level below 0.04 MPa, and the purity of the product hydrogen remains stable. Simultaneously, the optimized adsorbent packing structure effectively slows down the rate of pressure differential increase, and the adsorbent lifespan is expected to be extended by more than 30%.

[0050] Comparative Example 1 The difference from Example 1 is that the pressure swing adsorption device with a capacity of 150,000 cubic meters per hour of hydrogen is used for bed pressure differential treatment.

[0051] The specific configuration of the PSA pre-adsorption tower bed clogging control system in this comparative example is as follows: four pre-adsorption towers are connected in parallel, and a traditional filling scheme is adopted. The pre-adsorption towers are filled from top to bottom with ceramic balls, activated carbon, silica gel, activated alumina, and activated carbon. The control unit of the system has basic sequential control functions, but there is no dedicated online water washing and regeneration module or corresponding hardware facilities.

[0052] After 18 months of operation, operators discovered that the total differential pressure of the PSA system had gradually increased from the normal 0.05 MPa to 0.15 MPa, and continued to rise, causing fluctuations in the purity of the product hydrogen. Attempts were made to adjust process parameters, such as appropriately reducing the processing load. The upward trend in differential pressure slowed slightly, but could not be reversed, forcing the unit to operate at reduced efficiency. When the total differential pressure exceeded the upper limit of 0.2 MPa, seriously threatening normal production, the entire unit had to be shut down urgently.

[0053] After the shutdown, the faulty tower system was first isolated and purged with nitrogen, a process that took approximately 12 hours. Upon opening the manhole of the pre-adsorption tower, inspection revealed a large amount of white ammonium salt covering the inlet screen and the surface of the bottom adsorbent. Manual entry into the tower was required to mechanically clear the screen using tools. Because the silica gel and other adsorbents had partially pulverized and deactivated due to ammonium salt crystallization and moisture, it was decided to replace the adsorbent in all four pre-adsorption towers. After replacing the adsorbent, the manholes were sealed, an airtightness test was conducted, and the towers were subsequently put back into operation. The entire overhaul process, from shutdown to resumption of normal production, took a total of 7 days (168 hours).

[0054] Comparative Example 2 The difference from Example 1 is that a packing structure of small granular activated carbon-activated alumina-small granular activated carbon is adopted. Specifically, the adsorbent in each pre-adsorption tower is packed in a dense phase using a multi-layer gradient structure, from bottom to top as follows: bottom layer: small granular activated carbon, packing height 1020 mm, particle size 2 mm (Φ2×3-5 mm), packing amount 4.69 tons; middle layer: activated alumina, packing height 940 mm, particle size 3-5 mm, packing amount 5.58 tons; top layer: small granular activated carbon, packing height 7800 mm, particle size 2 mm (Φ2×3-5 mm), packing amount 35.89 tons.

[0055] In this comparative example, after approximately 21 months of system operation, the system pressure differential began to rise abnormally and rapidly, accompanied by fluctuations in the purity of the product gas. The pre-adsorption tower was regenerated using the method described in Example 1, with a regeneration time of approximately 11 hours. The pressure differential of the regenerated pre-adsorption tower was 0.05 MPa, indicating a relatively poor regeneration effect.

[0056] Comparative Example 3 The difference from Example 1 is that a packing structure of large-particle activated carbon-activated alumina-small-particle activated carbon is used, but instead of dense-phase packing, a loose packing is used. The packing is as follows from bottom to top: bottom layer: large-particle activated carbon, packing height 1020 mm, particle size 4 mm (Φ4×6 mm), packing amount 3.84 tons; middle layer: activated alumina, packing height 940 mm, particle size 3-5 mm, packing amount 5.13 tons; top layer: small-particle activated carbon, packing height 7800 mm, particle size 2 mm (Φ2×3-5 mm), packing amount 32.66 tons.

[0057] Dense-phase packing and loose packing are two fundamentally different adsorbent packing processes, with the core difference lying in packing density, uniformity, and the stability of the final bed. Dense-phase packing allows adsorbent particles to be oriented and tightly packed within the container, minimizing inter-particle voids, and its packing density can be 8-12% higher than that of loose packing. In this invention, the bed after dense-phase packing exhibits higher adsorption capacity per unit volume and mechanical stability. Loose packing relies on gravity for natural accumulation, which easily leads to particle size segregation (separation of large and small particles) and uneven initial voids. After packing, the settling rate of dense-phase packed beds is extremely low (typically <0.5%), while loose-packed beds experience significant settling (up to 2%-5% or higher) due to airflow scouring in the initial stages of operation, resulting in bed loosening and channeling.

[0058] In this comparative example, after approximately 20 months of system operation, the system pressure differential began to rise abnormally and rapidly, accompanied by fluctuations in product gas purity. The pre-adsorption tower was regenerated using the method described in Example 1, with a regeneration time of approximately 14 hours. The pressure differential of the regenerated pre-adsorption tower was 0.08 MPa, indicating relatively poor regeneration performance. Subsequent refrigerant replacement revealed severe pulverization of the activated carbon due to friction and collision. Loose packing led to uneven gas distribution and channeling, preventing some adsorbent from effectively participating in adsorption.

[0059] Comparative Example 4 The difference from Example 1 is that although dense-phase packing is used, the packing height ratio of each adsorbent layer is changed to: large particle activated carbon layer: activated alumina layer: small particle activated carbon layer = 0.5 : 1 : 8.9 (the ratio in Example 1 is ≈1.1 : 1 : 8.3). Specifically, the adsorbent in each pre-adsorption tower is packed in a multi-layer gradient structure in a dense phase, from bottom to top as follows: bottom layer: large particle activated carbon, packing height 460 mm, particle size 4 mm (Φ4×6mm), packing amount 1.90 tons; middle layer: activated alumina, packing height 940 mm, particle size 3-5 mm, packing amount 5.58 tons; top layer: small particle activated carbon, packing height 8360 mm, particle size 2 mm (Φ2×3-5 mm), packing amount 38.47 tons.

[0060] In this comparative example, the system's differential pressure was normal during initial operation. However, after approximately 19 months of operation, the system's differential pressure exhibited intermittent fluctuations and an upward trend. After regeneration and restart, the differential pressure stabilization period was shorter than in Examples 1 and 2, requiring retreatment after approximately 17-18 months. An unreasonable packing height ratio disrupted the balance of the gradient structure design. Insufficient packing of large-particle activated carbon reduced the mechanical strength of the adsorption bed, the progressive interception of impurities, and the scale-holding capacity. Furthermore, the penetration of ammonium salts and hydrocarbons into the small-particle activated carbon layer significantly reduced the regeneration effect.

[0061] Through a thorough comparison of Embodiment 1 of the present invention with the four comparative examples, the significant progress achieved by the present invention in terms of technical effectiveness, economic benefits, and operational safety can be clearly seen: Comparing Example 1 with Comparative Example 1 (traditional full-line shutdown solution), when the pressure differential in Comparative Example 1 rose to a level that endangered production, a full-line shutdown was forced, requiring high-risk, high-intensity manual labor for cleaning and adsorbent replacement. The entire process took up to 7 days, resulting in significant production losses and only addressing the symptoms, not the root cause. In contrast, the online treatment system in Example 1 achieved the following: shortening the multi-day full-line shutdown to a single-tower offline regeneration of a few hours, ensuring long-term stable operation of the production unit; fully automated programmed operation completely eliminated the high-risk work of personnel entering confined spaces, greatly reducing labor intensity and safety hazards; and by restoring adsorbent performance online, it avoided the high material and disposal costs associated with frequent adsorbent replacements.

[0062] A comparison of Example 1 with Comparative Examples 2, 3, and 4 (different packing schemes) shows that Comparative Examples 2, 3, and 4 used the same online treatment method as Example 1, but due to defects in the adsorbent packing structure, the final treatment effect was significantly reduced. Comparative Example 2 (non-gradient packing) demonstrated the indispensability of large-particle activated carbon as a bottom support. The small-particle structure at the bottom could not effectively disperse the airflow or resist blockage, leading to a rapid increase in pressure differential and poor regeneration effect (pressure differential still reaching 0.05 MPa). This highlights the crucial role of the gradient packing design of this invention in providing primary protection and maintaining low bed resistance. Comparative Example 3 (loose packing) demonstrated the importance of the dense-phase packing process. The gas channeling and adsorbent pulverization caused by loose packing not only made the regeneration process longer and less effective (pressure differential reaching 0.08 MPa), but also directly led to premature adsorbent failure, proving that the high-density, stable bed of this invention is a prerequisite for ensuring the effectiveness of the method and the long lifespan of the adsorbent. Comparative Example 4 (changing the loading ratio) demonstrates that a ratio imbalance will significantly reduce the system's anti-clogging ability and regeneration recovery effect.

[0063] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An online anti-clogging and anti-fouling method for PSA pre-adsorption tower bed, characterized in that, Includes the following steps: (1) Several pre-adsorption towers are operated in parallel. The adsorbent in each pre-adsorption tower is packed in a dense phase using a multi-layer gradient structure. From bottom to top, large-particle activated carbon, activated alumina and small-particle activated carbon are packed in sequence. The particle size of the large-particle activated carbon is Φ4-6×5-10 mm and the bulk density is 0.40-0.48 g / mL. The particle size of the activated alumina is 3-5 mm and the bulk density is 0.68-0.78 g / mL. The particle size of the small-particle activated carbon is Φ2-3×3-5 mm and the bulk density is 0.45-0.55 g / mL. (2) Monitor the pressure difference of the pre-adsorption tower bed in real time. When the pressure difference reaches 0.1-0.2 MPa, cut off the faulty pre-adsorption tower. (3) The faulty pre-adsorption tower is washed online with water, and then purged and vacuumed alternately; (4) Re-enter the qualified pre-adsorption tower.

2. The online anti-clogging and anti-fouling method for the PSA pre-adsorption tower bed according to claim 1, characterized in that, In step (1), the loading height ratio of the large-particle activated carbon, the activated alumina and the small-particle activated carbon is 1-2:1:7-9; the specific surface area of the large-particle activated carbon is 850-1200 m 2 / g; the specific surface area of the activated alumina is 95-350 m 2 / g; and the specific surface area of the small-particle activated carbon is 1100-1300 m 2 / g.

3. The online anti-clogging and anti-fouling method for the PSA pre-adsorption tower bed according to claim 1 or 2, characterized in that, In step (3), the online washing includes: controlling the level of the cleaning solution to overflow the bottom inlet screen of the pre-adsorption tower and part of the large-particle activated carbon adsorbent, and soaking for 20 minutes or more; the cleaning solution is demineralized water.

4. The online anti-clogging and anti-fouling method for the PSA pre-adsorption tower bed according to claim 1, characterized in that, In step (3), the purging is performed using hydrogen gas at 80-100°C with a flow rate of 800-1200 Nm³. 3 / h, purging time is 1-2h.

5. The online anti-clogging and anti-fouling method for the PSA pre-adsorption tower bed according to claim 1 or 4, characterized in that, In step (3), the vacuuming is to reduce the pressure inside the pre-adsorption tower to absolute pressure of 20-25 kPa and maintain it for 10-20 min.

6. The online anti-clogging and anti-fouling method for the PSA pre-adsorption tower bed according to claim 1, characterized in that, In step (4), the criterion for determining whether the pre-adsorption tower is qualified for regeneration is that the dew point of the regenerated gas is consistently below -5°C for at least 5 minutes.

7. A system for online anti-clogging and anti-fouling of PSA pre-adsorption tower bed using the method described in any one of claims 1-6, characterized in that, The system includes a pre-adsorption tower unit, a water washing unit, a regeneration unit, and a DCS control unit. The pre-adsorption tower unit includes several pre-adsorption towers connected in parallel. Each pre-adsorption tower is filled with an adsorbent with a multi-layer gradient structure, which, from bottom to top, includes a layer of large-particle activated carbon, a layer of activated alumina, and a layer of small-particle activated carbon. The water washing unit includes a water metering tank connected to the bottom of the pre-adsorption tower. The regeneration unit includes an electric heater connected to the top of the pre-adsorption tower and a vacuum pump unit connected to the bottom of the pre-adsorption tower. The DCS control unit is connected to the pre-adsorption tower unit, the water washing unit, and the regeneration unit.

8. The system according to claim 7, characterized in that, The washing unit also includes a waste liquid collection tank; the waste liquid collection tank is connected to the bottom of the pre-adsorption tower via a pipeline and an isolation valve group installed on the pipeline.

9. The system according to claim 7 or 8, characterized in that, The regeneration unit also includes a desorption gas buffer tank and a fuel gas pipeline network that are connected in sequence to the vacuum pump group.

10. The system according to claim 7 or 8, characterized in that, The pre-adsorption tower unit also includes a hydrogen pipeline network connected to the top of the pre-adsorption tower.

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