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Common problems and solutions in the operation of pressure swing adsorption carbon removal units 1. What are the key points for inspection and adjustment during the operation of pressure swing adsorption carbon removal units? To achieve good operational performance, the following items must be checked and adjusted during operation: (1) Adsorption step – To meet the required CO2 content in the product gas as specified in the design, the pressure in the adsorption step must remain stable. In addition to the need for stable inlet pressure, the adjustment of the final pressure increase flow rate in the adsorption tower directly affects the adsorption pressure. Secondly, an insufficient flow rate of the feed gas can also affect the stability of the adsorption pressure. (2) Pressure equalization step: Due to the presence of resistance, the pressures after equalization between the two towers will not be exactly the same; it is required that the pressure difference after balancing be within 0.05 MPa. The set equalization time only needs to be sufficient to meet the actual time required for equalization to reach equilibrium. Due to the adsorption of the mixed components by the adsorbent, the pressure reached at equilibrium is lower than the theoretical pressure from the aforementioned steps. During pressure equalization, the higher the CO2 concentration in the mixture, the lower the actual pressure after equilibrium is reached. (3) Reverse playback step: The reverse playback process is actually very fast. Too fast reverse flow speed not only generates noise in the system but also causes wear on the adsorbent. The device is equipped with a flow control valve, which allows the vacuum desorption valve to open gradually at the start, enabling the back-pressure to drop slowly to a low level over a specified time under relatively steady conditions; it is required that the pressure reach 0.005–0.01 MPa by the end of the back-pressure release process. (4) Final pressure increase step: The pressure at the end of this pressure increase should essentially reach the adsorption pressure by the time the process switches to the adsorption stage. If the pressure increase is insufficient, at the beginning of the adsorption stage in that column, there will be a short period during which pressure needs to be increased, resulting in an extremely low outlet flow rate and fluctuations in the adsorption pressure ； Too rapid pressurization can cause large fluctuations in the outlet flow rate, as well as fluctuations in the adsorption pressure. The final boost pressure must be controlled to be 0.02~0.04 MPa lower than the adsorption pressure, and the charging speed is adjusted using the additional pressure manual valve. (5) Product purity: An adsorption tower has a fixed capacity to absorb impurities. Therefore, a certain amount of feed gas can be purified in one adsorption regeneration cycle. If the cycle time (period) is too long, an excessive amount of feed gas will lead to an increase in the CO2 content in the product gas ； If the cycle time (period) is too short, increased hydrogen loss occurs due to inadequate utilization of the bed layer (reducing the hydrogen recovery rate). Therefore, when performing timed signaling operations, any adjustment to the cycle time (period) must be carried out carefully. Changes in product concentration will only become apparent after 2 to 3 cycles. (6) Method for restoring the product when its purity is not up to standard: An increase in the CO2 content in the product gas indicates that the entire bed has been contaminated. The impurity components have reached the outlet end of the tower. The cause of this outcome could be improper operation adjustment, or a fault in the device’s automatic control system. Once the cause is identified, normal operation should be restored as soon as possible after taking corrective action. Effective methods for recovery: one is to shorten the cycle time, and the other is to operate at a reduced load (by decreasing the volume of gas being processed) for a period of time. If the two are combined, the effect is even better, and the product purity is restored more quickly. However, it should be noted that the reduced cycle time must still ensure the minimum time required for the evacuation and final voltage boosting steps. 2. What are the key points for the temporary shutdown operation of a pressure swing adsorption carbon removal unit? Upon receiving the notification to stop production, contact the relevant processes before and after, and upon obtaining their approval, proceed with shutdown following these steps: (1) Inform the preceding process to prepare to stop supplying the feed gas, and continuously monitor the operating pressure of the purification system; if overpressure occurs, immediately open the manual vent valve. (2) Shut off the water supply valve for the vacuum pump in the purification system, and inform the previous process to stop supplying the feed gas. (3) After the gas supply is stopped, immediately close the manual valves at the gas inlet and outlet of the system, then quickly shut down some of the vacuum pumps in the purification system, leaving only one vacuum pump operating in that system. (4) Press the (Pause) button on the microcomputer controller of the purification system to stop the program from running, causing the control system to remain at the step it is currently executing; finally, turn off the one vacuum pump that remains in each unit of the purification system. 2. What are the key points for the temporary shutdown operation of a pressure swing adsorption carbon removal unit? Upon receiving the notification to stop production, contact the relevant processes before and after, and upon obtaining their approval, proceed with shutdown following these steps: (1) Inform the preceding process to prepare to stop supplying the feed gas, and continuously monitor the operating pressure of the purification system; if overpressure occurs, immediately open the manual vent valve. (2) Shut off the water supply valve for the vacuum pump in the purification system, and inform the previous process to stop supplying the feed gas. (3) After the gas supply is stopped, immediately close the manual valves at the gas inlet and outlet of the system, then quickly shut down some of the vacuum pumps in the purification system, leaving only one vacuum pump operating in that system. (4) Press the (Pause) button on the microcomputer controller of the purification system to stop the program from running, causing the control system to remain at the step it is currently executing; finally, turn off the one vacuum pump that remains in each unit of the purification system. 3. What are the main types of pressure swing adsorption carbon removal units? Due to different applications, pressure swing adsorption carbon removal units can be divided into three types: units that simply remove carbon dioxide to produce purified gas ； Device for removing carbon dioxide from syngas and producing food-grade liquid carbon dioxide as a by-product ； A device for simultaneously producing decarburized purified gas and carbon dioxide gas with a purity of 98%. (1) PSA decarburization unit: At present, the most commonly used units in small and medium-sized ammonia synthesis plants are still PSA units that simply remove CO2 to produce purified gas, as a replacement for traditional wet decarburization methods. Depending on the specific requirements of ammonia plants, there are two processes: one is a decarburization process aimed at replacing carbonization in order to increase the production of liquid ammonia. After PSA decarburization of the transformed gas, the CO2 content in the purified gas is less than 0.2%, allowing it to proceed directly to the refining process. Currently, the performance of such devices is as follows: the hydrogen recovery rate is >97%, the hydrogen-to-nitrogen ratio in the purified gas is around 3.0, and while removing CO2, it also eliminates most impurities such as CH4, CO, and H2S, thereby reducing the burden on subsequent processing stages. Another is for processes used in conjunction with lyolization units. Since the purified gas is used in the production of dihydroxyalkanes, and considering the lifespan of the methanol synthesis catalyst as well as the need to maximize CO recovery, the CO2 content in the decarburized purified gas is generally kept at a level of 1% to 5%. Currently, the performance of such devices shows a hydrogen recovery rate of >98% and a CO recovery rate of >90%. While removing CO2, the sulfides in the converted gas are also reduced to a level of 0.1 mg/m3 (standard), and trace impurities such as chlorine, ammonia, water, and arsenic present in the feed gas can be removed simultaneously. (2) Decarburization and co-production of liquid CO2 unit: The desorbed gas from the PSA decarburization unit is fed into a compressor at atmospheric pressure; after being pressurized to a certain level, it undergoes pretreatment to remove various sulfides, trace amounts of arsenic, fluorine, chlorine, and saturated water present in the desorbed gas, in order to meet the requirements for food-grade CO2. The pre-treated gas is cooled below 0°C to turn the CO2 in the desorbed gas into a liquid, which then enters a purification tower where CO2 is separated from other gases. Finally, a food-grade liquid CO2 product with a purity of 99.5% to 99.999% is obtained at the bottom of the purification tower. (3) A device for decarburization and simultaneous production of pure CO2, which consists of a purification system and a cleaning system; both systems employ a multi-tower PSA process. The transformed gas passes through a purification system to concentrate the CO2 concentration to over 98.5%, which is then used in the urea production plant. The intermediate gas from the purification system enters the purification unit, where CO2 in this gas is further reduced to levels below 0.2%, in order to meet the requirements of ammonia synthesis. 4. What is the process flow of the device for carbon removal by pressure swing adsorption while simultaneously producing pure CO2? Taking adsorption tower A as an example, the process of adsorption decarburization while simultaneously producing CO2 will be explained separately. The device consists of a purification system and a cleaning system. The transformed gas comes from outside the unit, with a pressure of 10 MPa (varies depending on the design pressure) and a temperature of 40°C or less. After oil and free water are removed via a gas-water separator, it enters the adsorbent bed at the bottom of adsorption tower A in the purification system. Under the condition of selective adsorption by the adsorbent, water (vapor), organic sulfur, inorganic sulfur, and carbon dioxide in the reformate gas are adsorbed in sequence; the components that are not adsorbed are compressed and sent to the purification system for further adsorption. The purified gas, once it meets the required standards, is pressurized using a buffer tank before being sent to the compression section. When the front of the stream containing adsorbed impurities approaches the outlet of the bed, the feed gas valve KV-1A and the outlet gas valve KV-2A of adsorption tower A are closed to stop the adsorption process. Sequentially open the programmable valves KV-3A and KV-4A to perform four equalization voltage drops. On the one hand, the carbon dioxide adsorbed by the adsorbent is desorbed, and gases with a weaker adsorption capacity for carbon dioxide than that of the adsorbent are displaced in the direction of adsorption, thereby increasing the carbon dioxide concentration in the dead space of the bed. On the other hand, fully recover the hydrogen and nitrogen gases in the dead space of the bed. After the uniform pressure reduction, there is still some pressure in the adsorption bed; the gas released is partially recovered and partially vented. When the adsorption bed is at atmospheric pressure, carbon dioxide with a purity of over 98.5% is used to displace and replace most of the gases with weaker adsorption capacity for carbon dioxide that are adsorbed by the adsorbent, as well as gases such as carbon monoxide, methane, nitrogen, argon, and hydrogen present in the dead space of the bed, thereby achieving the purification of the carbon dioxide product. The carbon dioxide from the product is extracted by a vacuum pump, with a purity of over 98.5%, while the adsorbent is fully regenerated. After vacuuming is completed, the bed is pressurized in reverse using equalizing gas and product gas to a pressure close to the adsorption pressure, after which the adsorption bed enters the next adsorption cycle. The operating process of the other eleven absorption towers is exactly the same; they simply differ in time, with each one operating at a different moment according to a specific sequence. The intermediate gas enters the purification system after compression, and the carbon dioxide concentration in the outlet gas of the purification system is less than 0.2%. Once adsorption tower A of the purification system becomes saturated, close the feed gas valve KV-1A and the product gas valve KV-2A of tower A to stop the adsorption process. Sequentially open the programmable valves KV-3A and KV-4A to perform four equalization depressurizations, thereby recovering the product gas from the dead space in the bed through the equalization process. Then, the pressure is reduced in the opposite direction to the adsorption direction, causing the components that are easily adsorbed to be released, thereby achieving preliminary regeneration of the adsorbent. Further vacuum pumping is then used to desorb the residual adsorbed impurities from the adsorbent, resulting in its complete regeneration. After vacuuming is completed, the bed is pressurized in reverse using equalizing gas and product gas to a pressure close to the adsorption pressure, at which point the adsorption bed enters the next adsorption cycle. The operating process of the other seven adsorption towers is exactly the same; they simply differ in time, with each one starting at a specific interval relative to the others. 5. What are the key operating points for the initial startup of a pressure swing adsorption carbon removal unit? (1) Conduct a comprehensive inspection and acceptance of the system’s equipment, management systems, automatic control systems, instruments at various control points, and electrical facilities, in accordance with the installation drawings and plans. (2) In accordance with the setup requirements and relevant regulations, conduct hydraulic strength tests, hydraulic tightness tests, purging or cleaning, pneumatic tightness tests, leakage rate tests, and vacuum degree tests on the equipment and piping systems, and verify that they meet the specified standards. (3) Calibrate the on-site pressure gauges and thermometers as required; within their range of measurement, the accuracy must be no lower than grade 1.5. (4) Calibrate the pressure transmitters as required; within their range of measurement, the accuracy must also be no lower than grade 1.5. Apply a current of 4–20 mA to check whether the zero and full-scale values are correct. For pressure transmitters operating under negative pressure conditions, in addition to positive pressure calibration, accurate vacuum level calibration is also necessary; within the measurement range, the accuracy must be no less than grade 1.5. (5) The CO2 online analyzer was calibrated using a standard gas and passed the inspection. (6) The flow meter shall be calibrated and adjusted in accordance with the requirements of the operating instructions, and the relevant coefficient of the flow meter shall be determined. (7) Check the crisis oil pressure control system. In accordance with the requirements and procedures specified in the instruction manual, carefully check whether there are any errors in the wiring of the solenoid valve, and dynamically verify whether the operation of the programmable valve meets the design specifications. Ensure that all functions of the control system are operating properly, and that the alarm functions meet the design requirements. (8) Electrical interlock test for the vacuum pump and oil pump in the purification and refinement system. In accordance with the requirements of the operating instructions, carry out the electrical interlock tests for the vacuum pump and oil pump of the purification system, the electrical interlock tests for the vacuum pump and oil pump of the purification system, and the interlock tests for the water supply system of the vacuum pump, following the prescribed procedure. During the test, repeated observations are required until the design requirements are met. (9) Performance tests of the vacuum pump in the purification and cleaning equipment, as well as internal leakage tests of the check valve. The vacuum pump performance test and the check valve internal leakage test are carried out after the tests on the hydraulic pipeline system, the process pipeline system, and the calibration of instruments and control systems have been completed. This task includes the following four items: ① Vacuum pump ultimate vacuum test ； ② Vacuum pump pumping capacity test ； ③ Check valve internal leakage test ； ④ Conduct individual testing on equipment such as vacuum pumps. During the above work, it is necessary to strictly follow the instructions and the technical requirements of the equipment manufacturer to ensure that the tests are successful. (10) Fill the adsorption tower with adsorbent in accordance with the requirements of the \"Adsorbent Filling Notice\". (11) Joint trial operation. The hydraulic system and the control system are linked according to the operation timing diagram of the programmable valve, with a cycle time of 3 to 5 minutes, in order to thoroughly remove impurities from the hydraulic system and the cylinders of the programmable valve, until no bubbling occurs within the entire system over a period of 72 hours. (12) Follow the normal startup procedure; once the system has been properly purged, start the operation by feeding in the material. 6. What are the main precautions for the adsorbent loading operation? 1) The following preparatory work must be done before filling: ① Thoroughly clean the entire interior of the adsorption tower ； ② In accordance with the requirements of the \"Adsorbent Loading Notice\", equip all types of adsorbents and transport them to the site ； ③ Prepare specialized loading tools, such as dump trucks or winches, special funnels, bottomless bags, etc ； ④ Prepare personal protective equipment, such as gas masks, dust goggles, boots, gloves, safety helmets, and neck warmers. (2) The purification adsorption tower is generally filled layer by layer from the bottom upwards with three types of adsorbents: activated alumina, activated carbon, and silica gel, while the purification adsorption column is usually filled with only silica gel as the adsorbent. Since adsorbents such as silica gel are sensitive to moisture, they must not be filled on rainy days; it is best to do so on sunny days, and it is strictly prohibited for the adsorbents to become damp. (3) The adsorbent is gradually poured into the adsorption tower through a filling funnel and a bottomless cloth bag; it is important to ensure that during filling, the distance between the already filled adsorbent and the bottom of the cloth bag remains no more than 1 meter. (4) The specifications, quantity, and filling sequence of the adsorbent in the composite bed layer must be strictly followed in accordance with the requirements of the \"Adsorbent Filling Notice\". After loading each type of adsorbent, the top surface of the adsorbent should be leveled, covered with a layer of mesh, and then the second type of adsorbent should be loaded. (5) After the adsorbent bed is filled and compacted, install the filter and cover as specified in the drawings. (6) After filling is complete, use clean nitrogen or air to blow away the dust from the adsorbent in the bed. During purging, it is carried out tower by tower. Its method allows for continuous gas blowing out, that is, the blowing gas is introduced from the raw gas inlet and discharged directly to the top. It is also possible to cover the flange lid and blow off the gas intermittently, that is, first pressurize to 0.2 MPa and then quickly vent from the pipeline at the top of the adsorption tower. (7) After blowing is complete, remove the top flange and ceiling panel, add more adsorbent until it is compact, and then reinstall them. (8) After the adsorbent is loaded, use blind flanges to completely isolate this unit from the preceding and subsequent processes as well as the outside environment. Then, connect the microcomputer controller, programmable valves, hydraulic system, etc. together to reduce the cycle time to 5 minutes, and clean the hydraulic system once again. 7. What are the key points for the proper startup operation of a pressure swing adsorption carbon removal unit? (1) System replacement. Following the operating procedures outlined in the Equipment ‘Operation and Maintenance Manual’, use nitrogen with a purity of over 99.5% to displace the gas within all equipment and pipelines in the system, ensuring that no dead corners remain, until sampling at the designated points shows that the oxygen content in the gas is below 0.5%. (2) After the displacement is complete, release the gas in the gas-water separator, gas buffer tank, and all adsorption towers to atmospheric pressure. (3) Setting of process valves in the purification and cleaning system. Operate in accordance with the requirements of the Operation and Maintenance Manual. (4) Settings for valves in the instrumentation system of the purification and cleaning system. All on-site pressure gauge valves, pressure transmitter sampling valves, manual analysis sampling valves, gas supply sampling valves for online CO2 analyzers, and gas supply valves for control valve instruments in the full-scale purification system. (5) Start the hydraulic system according to the operation manual to close all programmable valves. (6) Re-check repeatedly whether the main program and backup program controlling the solenoid valves in the purification and cleaning system meet the requirements of the process design (check after the microcomputer controller, solenoid valves, hydraulic system, etc. are integrated). (7) Put into operation the instruments and meters in the purification system and cleaning system, such as flowmeters, pressure transmitters, and online CO2 analyzers. (8) Take samples multiple times again to analyze whether the oxygen content in the purification system and the cleaning system is within acceptable limits; these sample analyses will also determine whether the composition of the syngas in the purification system and its oxygen content are satisfactory. (9) Notify the preceding and subsequent processes to prepare for supplying raw gas and receiving purified gas. (10) Start the vacuum pump of the purification and cleaning system in accordance with the procedures. (11) Start the controller for the purification and cleaning system. Start according to the operator’s manual for the purification and cleaning system controller. Bring the programmable control system, which consists of the controller, hydraulic system, and programmable valve, into a normal operating state. Verify once again whether the purification and cleaning procedures are functioning properly; meanwhile, the time for each step in the procedure system should be set at 2 to 3 times the normal operating time. (12) Once all preparations for the purification and cleaning system are complete, the reformate gas can be introduced to put the system into operation. The specific operating steps shall be carried out in accordance with the relevant requirements in the Operation and Maintenance Manual. ① Observe the changes in the CO2 content in the intermediate gas; keep the CO2 content in this intermediate gas within the range of 7% to 12% ； The change in the CO2 content in the purified gas was monitored, with the CO2 level in the purified gas kept below 0.2%. After stabilization, each time the program is switched, the CO2 concentration first decreases and then increases. If such a regular variation is observed, the system is essentially stable. ② If, after the system stabilizes, the CO2 content in the product gas remains above 0.2%, the operating parameters should be adjusted (by shortening the adsorption time or reducing the flow rate) so that when the system is finally stable, the CO2 content is ≤0.2%. ③ When the absorption pressure rises to the normal operating range and the CO2 content in the purified gas is less than 0.2%, the gas can be slowly fed back to the process; the flow rate should be adjusted so as to keep the CO2 content in the purified gas below 0.2%. ④ Based on the gas volume processed by the purification and cleaning system, increase the number of vacuum pumps in operation and adjust the operating time for each step of the program system. Thus, the normal startup process of this system is completed, and the device is put into normal operation. 8. What are the key points for the normal shut-down operation of a pressure swing adsorption carbon removal unit? Upon receiving the notification to stop production, contact the relevant processes before and after, obtain their approval, and then stop production following the procedures below. (1) Notify the previous process to prepare for shutting off the shift gas, and constantly monitor the operating pressure of the purification and cleaning units; in case of overpressure, immediately open the vent valve. (2) Shut off the water supply valve for the vacuum pump in the purification and cleaning unit, and inform the previous operator to stop supplying the feed gas. (3) Once the flow has come to a halt, immediately close the system’s gas inlet and outlet valves as well as the manual control valves connecting section 1 to section 2. Then close the gas inlet and outlet manual valves of the vacuum pump used in the purification unit, and cut off the power supply to that vacuum pump. (4) Turn off the microcomputer controller of the purification system to stop the program from running at the starting position. (5) Change the microcomputer controller of the purification and cleaning system to manual operation; use a reverse pressure valve with lower pressure to manually fill all the vacuum-mounted equipment and pipes in the purification and cleaning unit to atmospheric pressure, and gradually reduce the pressure in each tower to atmospheric pressure. (6) Turn off the power supply to the microcomputer controller of the purification and cleaning unit, and close the pressure-taking valve of the flow meter. (7) Stop the oil pressure system of the purification and purification device. (8) Stop the power supply to the instrument panel of the purification and cleaning unit. (9) Close all manual valves of the purification and cleaning equipment. 9. What are the key points for emergency shutdown operations of a pressure swing adsorption carbon removal unit? In the event of a major leak in the purification and cleaning device system that could lead to a safety accident, or upon receiving an emergency shutdown order from the production control department, shut down the system following the procedures below. (1) Press the emergency stop button on the system controller of the purification and cleaning unit; all programmable valves will close immediately. The relevant manual pressure relief valves should be opened promptly to vent the feed gas and prevent overpressure in the system. Notify the upstream and downstream processes right away, and report to the production management department. (2) Quickly address faults within the purification and cleaning device system. (3) Turn off all vacuum pumps in the purification and cleaning equipment. (4) Close the system gas inlet and outlet valves, as well as the manual control valves from stage 1 to stage 2. 10. How should the restart of a pressure swing adsorption carbon removal unit be carried out after a temporary shutdown? (1) Notify the previous process to prepare the feed gas. (2) Open the manual valve at the system feed gas inlet and the control valve from stage 1 to stage 2. (3) Start 1 vacuum pump each for the purification and cleaning systems, and notify the previous process to supply the feed gas. (4) Press the button on the microcomputer controller of the purification and cleaning system to pause operation, start the running program so that the control system is in the same state it was in during a temporary shutdown, and finally open the outlet valve for the purified gas to supply air to the subsequent process gradually; the amount of air supplied should be such that the adsorption pressure remains at or above the normal operating pressure. (5) Based on the gas volume processed by the purification and cleaning system and the CO2 content at the outlet, increase the number of vacuum pumps operating in the purification and cleaning system and adjust the operation time for each step in the control program. 11. If the raw gas contains too much water, how should the pressure swing adsorption decarburization unit be operated? Due to loss of control in the conversion process prior to this device or operational errors, a large amount of water flowed into the water separator of this device, and even into the adsorption tower, resulting in the deactivation of the adsorbent. At this time, immediately close the system feed gas inlet valve, drain the water from the water separator, and check the water-containing procedure to take appropriate action. If the adsorbent becomes ineffective, it needs to be reactivated or replaced. 12. What should be done with the pressure swing adsorption carbon removal unit in case of a sudden power outage? The sudden power outage caused the system to fail to operate properly; since the microcomputer controller had no output, the programmable valve closed automatically, putting the device into a shut-down state, which is equivalent to an emergency stop. Follow the procedures for emergency stop. 13. What are the main reasons for the decline in the quality of the purified gas due to improper operation of the pressure swing adsorption carbon removal process? How should it be handled? To determine whether the pressure swing adsorption process is operating properly, it is crucial to check whether the regeneration of the tower is functioning well. System operation disorders will immediately or gradually deteriorate the tower regeneration. Since the PSA process is a cyclic process, once the regeneration of one column deteriorates, it will quickly affect and contaminate the other columns, ultimately leading to a decline in the quality of the purified gas. Operational disturbances are often caused by the following two factors. (1) An increase in the gas volume to be treated is not accompanied by a timely reduction in the cycle time. The adsorption capacity of the adsorbent in the absorption tower for impurities is fixed; once the gas volume to be treated increases, the cycle time should be reduced accordingly so that the amount of impurities brought in by the feed gas does not exceed what the adsorbent can handle. If adjustments are not made in time, impurities will quickly contaminate the product. (2) The desorption vacuum level in the adsorption tower does not meet the requirements. In the pressure swing adsorption process, the regeneration of the adsorbent is carried out by reducing pressure (evacuation). If, due to an insufficiently set evacuation time or other issues with the vacuum system, the desorption vacuum level in the adsorption tower does not reach the required value, it will affect the regeneration efficiency of the adsorbent, thereby impacting the quality of the purified gas and the yield. At this point, the time can be adjusted accordingly to lengthen the evacuation time, or issues with the vacuum system can be checked and resolved. 14. What are the production control and consumption metrics for the device that uses pressure swing adsorption for carbon removal while simultaneously producing pure CO2? Raw gas flow rate ≤ designed processing capacity; adsorption temperature ≤ 40°C. Adsorption pressure: 0.8 MPa for purification, 1.35 MPa for cleaning (varies depending on the design pressure). CO2 content in the raw gas: approximately 28%. Total sulfur content in the raw gas ≤ 300 mg/Nm3. CO2 content in the intermediate gas: 6%–12%. CO2 content in the purified gas ≤ 0.2%. Total electricity consumption ≤ 100 kWh/t (NH3). Total sulfur content in the purified gas ≤ 1×10-6. Circulating water consumption ≤ 9 m3/t (NH3). CO2 content in the product ≥ 98.5%. Hydrogen recovery rate ≥ 99.0%. Oil pressure: 4.6–4.8 MPa. Hydrogen recovery rate ≥ 96%. Vacuum level: -0.065–-0.08. Carbon dioxide recovery rate ≥ 75%. Adsorption time > 4.5 minutes (adjustable based on operating conditions). 15. What are the common adsorbents used for pressure swing adsorption decarburization? What issues should be considered when making a choice? Commonly used adsorbents in industry include silica gel, activated alumina, activated carbon, molecular sieves, etc. In addition, there are special adsorbent materials developed for the selective adsorption of certain components.