A system for recycling tail gas of pressure swing adsorption and a propane dehydrogenation device

Abstract

The utility model relates to chemical industry process tail gas recovery technical field, concretely relates to a kind of pressure swing adsorption tail gas recycling system and propane dehydrogenation device, including the clean gas compressor, pressure swing adsorption unit, tail gas compressor and tail gas utilization unit sequentially communicated by main pipeline, still include circulation pipeline, its inlet end is connected in the outlet side main pipeline of the tail gas compressor, its outlet end is connected in the inlet side main pipeline of the clean gas compressor;The circulation pipeline is used to send the tail gas discharged from the pressure swing adsorption unit to the inlet of the clean gas compressor, and is combined with raw material gas leading to the clean gas compressor;The utility model can effectively improve hydrogen recovery rate, reduce tail gas emission and reduce external resource consumption.

Description

Technical Field

[0001] This utility model relates to the field of chemical process tail gas recovery technology, specifically to a pressure swing adsorption tail gas recycling system and a propane dehydrogenation device. Background Technology

[0002] In the petrochemical industry, propane dehydrogenation (PDH) units are crucial for the production of propylene and hydrogen. The pressure swing adsorption (PSA) unit is a key component in hydrogen purification, and its operating efficiency directly impacts the overall economics and resource utilization of the plant. In existing PDH processes, the tail gas from the PSA unit still contains a high concentration of hydrogen. Taking the plant in this case as an example, the hydrogen fraction in the tail gas is over 70%. Under current technology, only a small portion of this hydrogen-rich tail gas can be effectively utilized as stripping gas in downstream units; the remainder is typically mixed with gaseous propane and other fuels before being transported to the fuel gas pipeline for combustion. The PSA unit is the critical link in hydrogen purification in this process.

[0003] However, directly using hydrogen-rich exhaust gas as low-value fuel is essentially a waste of valuable resources, which is not only uneconomical but also poses safety hazards due to the properties of hydrogen. Furthermore, mixing this exhaust gas into the fuel gas pipeline network typically requires additional resources such as propane for mixing and transportation, further increasing operating costs. Therefore, how to efficiently recover and utilize residual hydrogen in pressure swing adsorption (PSA) exhaust gas, improve the overall recovery rate of the entire hydrogen purification system, and reduce or even eliminate dependence on the fuel gas pipeline network, thereby reducing material and energy consumption, has become a pressing technical problem to be solved in this field. Utility Model Content

[0004] This invention provides a pressure swing adsorption tail gas recycling system and a propane dehydrogenation device that can effectively improve hydrogen recovery rate, reduce tail gas emissions and reduce external resource consumption.

[0005] This utility model provides a pressure swing adsorption tail gas recycling system, which includes a clean gas compressor, a pressure swing adsorption unit, a tail gas compressor and a tail gas utilization unit connected in sequence through a main pipeline. It also includes a circulation pipeline, the inlet end of which is connected to the outlet side main pipeline of the tail gas compressor and the outlet end of which is connected to the inlet side main pipeline of the clean gas compressor. The circulation pipeline is used to transport a portion of the exhaust gas discharged from the pressure swing adsorption unit to the inlet of the gas purifier compressor, where it is combined with the raw material gas flowing to the gas purifier compressor.

[0006] In one embodiment of the present invention, an air intake separator is provided on the main pipeline on the inlet side of the air purifier compressor, and the outlet end of the circulation pipeline is connected to the air intake separator.

[0007] In one embodiment of the present invention, a first pressure control component and a first flow monitoring component are provided on the main pipeline between the exhaust gas compressor and the exhaust gas utilization unit; a second flow control component is provided on the circulation pipeline.

[0008] In one embodiment of the present invention, the first pressure control component includes a pressure detection element, a control valve, and a first controller electrically connected to both, for stabilizing the exhaust gas pressure sent to the exhaust gas utilization unit.

[0009] In one embodiment of the present invention, the second flow control component includes a flow detection element, a flow control valve, and a second controller electrically connected to both, for precisely adjusting the flow rate of the recirculating exhaust gas.

[0010] In one embodiment of the present invention, process monitoring points are provided at the inlet of the air purification compressor, the circulation pipeline and / or the main pipeline leading to the exhaust gas utilization unit. The process monitoring points are configured to allow the installation of online analyzers or for instrument calibration.

[0011] In one embodiment of the present invention, the exhaust gas utilization unit includes at least one of a stripping unit, a fuel gas pipeline network, and a fuel gas preparation system.

[0012] In one embodiment of the present invention, a safety branch pipe is also connected to the circulation pipeline, the safety branch pipe leads to the flare system, and a shut-off valve is provided on it.

[0013] In one embodiment of the present invention, an exhaust gas heater and a temperature monitoring component are further provided on the main pipeline between the exhaust gas compressor and the exhaust gas utilization unit.

[0014] This utility model also provides a propane dehydrogenation device, characterized in that it integrates the aforementioned pressure swing adsorption tail gas recycling system.

[0015] The beneficial effects of this invention are as follows: This invention proposes a pressure swing adsorption (PSA) tail gas recycling system and a propane dehydrogenation device. By introducing the recycling pipeline, a physical recycling channel is constructed, redirecting a portion of the hydrogen-rich tail gas originally intended for discharge into the fuel gas network back to the inlet of the purified gas compressor. This allows this portion of tail gas to be combined with the feed gas, pressurized by the purified gas compressor, and then re-enter the PSA unit. By optimizing adsorption parameters (such as adsorption time), further purification of residual hydrogen in the tail gas can be achieved. Through structural improvements, this system alters the tail gas treatment path, enabling the recycling and recovery of residual hydrogen in the tail gas, thereby potentially increasing the total hydrogen recovery rate. Specifically, the implementation of this system can significantly improve the total recovery rate of the PSA unit. Simultaneously, since most of the tail gas is recycled, the amount of tail gas discharged into the fuel gas network is significantly reduced or even completely eliminated. This not only reduces dependence on the fuel gas network but also avoids the additional consumption of gaseous propane and corresponding steam for mixing the tail gas, achieving the dual goals of resource conservation and consumption reduction. The entire system has a clear structure and is easy to modify. By adding key circulation pipelines between existing mature equipment units, the process flow is optimized and energy efficiency is improved. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0017] In the attached diagram: Figure 1 A simplified structural diagram of a pressure swing adsorption tail gas recycling system provided in an embodiment of this utility model; Figure 2 This is a schematic diagram of the structure of a pressure swing adsorption tail gas recycling system provided in one embodiment of the present invention; The attached diagram is labeled as follows: Main pipeline 1, Clean gas compressor 2, Pressure swing adsorption unit 3, Tail gas compressor 4, Tail gas utilization unit 5, Circulation pipeline 6, Inlet gas separator 7, First pressure control component 8, First flow monitoring component 9, Second flow control component 10, Process monitoring point 11, Safety branch pipe 12, Flare system 13, Tail gas heater 14, Temperature monitoring component 15, Product hydrogen 16, Pressure swing adsorption tail gas 17, Regeneration gas scrubbing tower 18, Hydrogen pipeline source port 19. Detailed Implementation

[0018] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0019] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0020] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the present invention. However, it will be apparent to those skilled in the art that embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the present invention.

[0021] The PDH unit, or propane dehydrogenation unit, is an important facility for producing propylene and hydrogen. It dehydrogenates propane (C3H8) in the presence of a catalyst to produce propylene (C3H6) and hydrogen (H2). Propylene is an important chemical raw material, while hydrogen is a byproduct.

[0022] PSA (Pressure Swing Adsorption) unit: Its core is to utilize the characteristic that specific adsorbents (such as molecular sieves and activated carbon) have different adsorption capacities for different gases under different pressures.

[0023] Adsorption stage: Under high pressure, the mixed feed gas is passed into an adsorption tower filled with adsorbent. The adsorbent will preferentially adsorb strongly adsorbable components (such as methane, ethane, propane, propylene, carbon monoxide, etc. in this case), while weakly adsorbable components (such as hydrogen) pass through smoothly and are output as product gas (high-purity hydrogen).

[0024] Regeneration stage: When the adsorbent is near saturation, the adsorbed impurities are desorbed from the adsorbent by reducing the pressure (or even creating a vacuum). This gas is called the tail gas. The adsorbent is thus regenerated and ready for the next adsorption cycle.

[0025] A complete PSA unit typically consists of multiple adsorption towers, which are precisely controlled by programmable valves. Some towers are in the adsorption step, while others are in the regeneration step, thus ensuring a continuous and stable output of product hydrogen and exhaust gas.

[0026] The PSA (Pressure Swing Adsorption) unit is a key component in a PDH (Pulse-Driven Hydraulic) system for purifying hydrogen. For example, in one embodiment, the original recovery rate was 87%, meaning that 13% of the hydrogen in the feed was lost to the tail gas. By recycling a portion of the tail gas back to the unit and optimizing the adsorption time, the recovery rate was increased to 91% or higher.

[0027] Stripping gas: Gas used in the stripping process. Stripping is a separation technique that removes volatile components from a liquid by injecting a gas (such as hydrogen). In this case, the PSA tail gas can be used as stripping gas in downstream units, possibly for purging or purification equipment.

[0028] Clean Gas Compressor 2: Located upstream of the PSA unit, this booster unit's main function is to pressurize the pre-purified feed gas from the preceding process to the optimal operating pressure required by the PSA unit. The PSA process requires a specific pressure range to achieve ideal separation results; therefore, Clean Gas Compressor 2 is a key device for ensuring the PSA feed conditions.

[0029] In this case, a circulation pipeline 6 is installed between the outlet of the exhaust gas compressor 4 and the inlet of the clean gas compressor 2, so that the clean gas compressor 2 in this case no longer needs to process only the raw material gas, but the mixture of the raw material gas and the recycled PSA exhaust gas.

[0030] Exhaust Gas Compressor 4: A booster unit located downstream of the PSA unit; the exhaust gas desorbed from the PSA has a low pressure and cannot be directly sent to subsequent systems. The function of Exhaust Gas Compressor 4 is to boost this low-pressure exhaust gas to meet the pressure required by downstream users (such as units used for stripping gas) or fuel gas pipelines.

[0031] In this case, the exhaust gas compressor 4 provides the necessary pressure for the recirculation of a portion of the exhaust gas, enabling it to overcome pipeline resistance and enter the inlet of the clean gas compressor 2. The recirculation pipeline 6 is led out from the outlet of the exhaust gas compressor 4. After being pressurized, part of the exhaust gas can continue downstream along the original path for stripping or other uses, while the other part has sufficient pressure to overcome the resistance of the pipeline and equipment and is forced back to the inlet of the higher-pressure clean gas compressor 2, thus achieving recirculation.

[0032] Stripping hydrogen heater: This is a process heating device. Stripping is a mass transfer separation operation that typically uses a gas (stripping gas) to drive out lighter components from a liquid. When PSA tail gas is used as stripping gas, in some processes, this gas needs to be heated to a certain temperature to improve stripping efficiency. The stripping hydrogen heater is a device specifically designed to heat this PSA tail gas used as stripping gas; it may use steam or electricity as a heat source.

[0033] Adsorption time: In the PSA process, this refers to the time period during which the adsorbent adsorbs impurities. Adjusting the adsorption time can optimize adsorption efficiency and prevent adsorbent oversaturation or insufficient regeneration.

[0034] Fuel gas preparation system: In petrochemical plants, the fuel gas preparation system is a subsystem used to collect, blend, and transport combustible gases as fuel. These gases are sent to various heating furnaces, boilers, and other equipment within the plant to provide the heat source required for combustion.

[0035] Previously, the PSA tail gas contained as much as 70% hydrogen, making its use as fuel gas neither economical nor safe. It was uneconomical because hydrogen is a higher-value product; and unsafe because hydrogen has a high flame velocity and a wide explosion range, placing higher demands on the pipeline system. After the successful implementation of this proposed solution, the amount of PSA tail gas will be reduced to just enough for downstream stripping gas use, eliminating the need for excess tail gas to enter the fuel gas production system. This simplifies the plant's overall material balance and improves both economic efficiency and safety.

[0036] Flare tube: The flare system 13 is a critical safety facility in chemical plants. A flare tube is a pipeline system that transports flammable and toxic waste gases that cannot be recovered or treated during plant start-up, shutdown, accident conditions, or emergencies to a high-altitude flare head for combustion and destruction. Its purpose is to ensure the safe and environmentally friendly release of pressure under abnormal operating conditions.

[0037] Under normal operation, PSA tail gas is utilized as a useful feedstock (stripping gas or fuel gas) and should not enter the flare. However, if downstream users (such as stripping gas users or fuel gas pipelines) experience problems, or if the unit itself experiences fluctuations, excess tail gas may need to be sent to the flare for combustion to prevent it from accumulating in the system and causing safety accidents such as overpressure. This invention reduces the total amount of tail gas through recycling, reduces the unit's dependence on downstream systems, thereby reducing the risk of tail gas being forced into the flare, and improving the unit's operating efficiency and environmental friendliness.

[0038] Regeneration Gas Scrubber 18: This is a piece of equipment closely related to the PSA unit. During the PSA process, the adsorbent (such as molecular sieves or activated carbon) needs to be "regenerated" to restore its adsorption capacity after adsorbing impurities. Regeneration is usually achieved by reducing pressure (reverse venting and vacuuming). The gas desorbed from the adsorption tower is called regeneration gas; the function of the regeneration gas scrubber 18 is to purify this regeneration gas. The regeneration gas may contain concentrated impurity components (such as hydrocarbons like methane, ethane, and propylene in the tail gas composition), and sometimes may also carry a small amount of adsorbent dust. The scrubber typically uses a liquid (such as water or a specialized solvent) to contact the regeneration gas counter-currently to remove harmful components or particulate matter, meeting the environmental protection requirements for subsequent treatment or emissions.

[0039] Inlet Separator 7: This is a gas-liquid separation device installed at the compressor inlet. Its main function is to protect the compressor and prevent liquids (such as water, condensed hydrocarbons, or lubricating oil) from being carried into the cylinder. When the PSA exhaust gas enters the separator, the flow rate decreases and the flow direction changes. Heavier droplets are separated from the gas by gravity and the action of built-in demisters and other components, settling to the bottom of the tank and then periodically discharged. The clean, dry gas enters the clean gas compressor 2 from the top. In this case, the inlet separator 7 needs to process the mixture of the feed gas and the recirculated exhaust gas. Ensuring that this mixture is clean and dry before entering the clean gas compressor 2 is crucial for the long-term stable operation of the compressor and the downstream PSA unit.

[0040] Process monitoring point 11: In chemical plants, process monitoring point 11 refers to a pre-set location on pipelines or equipment for sample collection, instrument installation, or online measurement. It is typically a short pipe joint with a valve. Process monitoring point 11 can be installed on the circulation pipeline to analyze the composition and flow rate of the circulating tail gas, or on the main pipe entering the PSA to monitor the composition of the mixed feed gas, providing crucial data support for adjusting and shortening the PSA adsorption time. For example, process monitoring point 11 can be installed on the PSA product hydrogen 16 and the final tail gas pipeline to verify whether the recovery rate has increased from 87% to 91%.

[0041] Figure 2In this utility model, the abbreviations for the instruments involved are as follows: PI pressure indicator, used to display (indicate) the instantaneous value of pressure locally or in the control room; PIC represents pressure indicating controller, which is a device with pressure display function and can automatically output control signals (such as to valves) according to set values; PT represents pressure transmitter, used to measure pressure and convert it into a standard electrical signal for remote transmission to the control system for monitoring, recording, or automatic control; PG represents pressure gauge, used to mechanically display pressure values ​​on-site without power supply, but the data cannot be transmitted remotely; FV represents flow control valve, used to precisely regulate the flow rate of fluid in a pipeline by changing the valve core opening; FI represents flow indicator, used to display the instantaneous value of flow rate, allowing people to see how much flow is being measured; FT represents flow transmitter, used to be installed on a pipeline to measure fluid flow rate in real time and convert it into a standard signal (such as 4-20mA) for remote transmission to the control system; FE represents flow element, which generates a physical signal (such as differential pressure) related to the flow rate and is the source of flow measurement; PV represents pressure control valve, which is a... A valve driven by a control signal opens and closes to control the pressure within the pipeline. FC indicates fault-closed; when the power source driving the valve (such as instrument air or electricity) fails, the valve will automatically and safely move to the fully closed position. Under normal use, at a preset pressure / flow rate, the valve opening automatically decreases when the pressure / flow rate is high and automatically increases when the pressure / flow rate is low, automatically adjusting according to the pressure / flow rate. TT indicates a temperature transmitter, used to measure temperature and transmit the signal to the control room. TI indicates a temperature indicator, used to display the instantaneous temperature value. TE indicates a temperature element, which directly senses temperature; it is the physical element itself that is in contact with the measured medium and senses temperature changes, and is the source of temperature measurement. RH indicates a flare, used to safely handle flammable gases that cannot be recovered by the plant or are emitted in accident situations, converting them into harmless substances through combustion; it is the most important safety and environmental protection equipment in chemical plants.

[0042] Currently, the total feed rate of PSA pressure swing adsorption unit 3 is 58,000 Nm³ / h, the hydrogen production rate is 50,000 Nm³ / h, the tail gas rate is 8,000 Nm³ / h, and the overall recovery rate of PSA pressure swing adsorption unit 3 is 87%. The PSA feed composition is shown in Table 1, in which the hydrogen gas fraction is 95.61%; the tail gas composition is shown in Table 2, in which the hydrogen gas fraction is 70%.

[0043] Table 1: PSA Feed Composition Statistics

[0044] Table 2: PSA Exhaust Gas Composition Statistics

[0045] The PSA pressure swing adsorption (PSA) tail gas (17) only requires about 5500 Nm3 / h to be used as stripping gas in downstream units. The remaining tail gas needs to be mixed with gaseous propane and sent to the Sirbon fuel gas pipeline network. Since the PSA tail gas still contains more than 70% hydrogen, using PSA tail gas as fuel gas is neither economical nor safe.

[0046] This utility model relates to a pressure swing adsorption (PSA) tail gas recycling system. Through structural improvements, this system effectively solves the technical problems of low utilization rate, safety hazards, and high operating costs associated with existing propane dehydrogenation units where the PSA tail gas 17 is rich in hydrogen. The technical solution, implementation principle, and technical effects of this utility model are described in detail below.

[0047] Please see Figure 1 Alternatively, this utility model provides a pressure swing adsorption tail gas recycling system, including a clean gas compressor 2, a pressure swing adsorption unit 3, a tail gas compressor 4 and a tail gas utilization unit 5 connected in sequence through a main pipeline 1, and also includes a circulation pipeline 6, the inlet end of which is connected to the outlet side main pipeline 1 of the tail gas compressor 4, and the outlet end of which is connected to the inlet side main pipeline 1 of the clean gas compressor 2. The circulation pipeline 6 is used to transport a portion of the exhaust gas discharged from the pressure swing adsorption unit 3 to the inlet of the air purification compressor 2, where it is combined with the raw material gas flowing to the air purification compressor 2.

[0048] It should be noted that the main pipeline 1, serving as a transport channel for process fluids, can utilize conventional pressure pipelines in the art, such as seamless steel pipes or stainless steel pipes. In this case, a circulation pipeline 6 is installed, with its inlet end connected to the outlet side of the main pipeline 1 of the exhaust gas compressor 4, and its outlet end connected to the inlet side of the main pipeline 1 of the clean gas compressor 2. This connection method means that the circulation pipeline 6 is connected in parallel between the outlet of the exhaust gas compressor 4 and the inlet of the clean gas compressor 2, providing a new flow direction option for the material. The circulation pipeline 6 can be implemented as a branch pipe directly welded to the main pipeline 1, or as an independent pipe section connected by detachable connectors such as flanges or compression fittings. Its core function is to form a physical channel that can guide a portion of the exhaust gas discharged from the self-pressure adsorption unit 3 and pressurized by the exhaust gas compressor 4 back from downstream to the inlet of the clean gas compressor 2 upstream. There, this portion of the circulating exhaust gas is fully combined and mixed with the fresh raw material gas (i.e., dry gas from the preceding process) leading to the clean gas compressor 2.

[0049] In existing technologies, the hydrogen-rich pressure swing adsorption (PSA) tail gas 17 passes through the system in a single pass, with a large amount of hydrogen ultimately entering the fuel gas pipeline. This invention, however, changes the final destination of this tail gas by introducing the recirculation pipeline 6. Specifically, during operation, a portion of the tail gas originally destined for the tail gas utilization unit 5 (such as the fuel gas pipeline) can be diverted and returned via the recirculation pipeline 6. This returned tail gas mixes with the feed gas at the inlet of the purified gas compressor 2, is then pressurized by the purified gas compressor 2, and subsequently enters the PSA unit 3 for further processing along with the main feed stream. Since the tail gas still contains a high concentration of hydrogen, its return and mixing with the feed essentially increases the hydrogen load in the PSA unit 3 feed. The system configuration allows for improved recovery rates through optimized adsorption parameters, enabling this returned hydrogen to be re-adsorbed and purified, rather than being lost with the tail gas. This process achieves multiple, cyclical recovery of residual hydrogen in the tail gas, fundamentally improving the overall hydrogen extraction efficiency.

[0050] This invention effectively solves the resource waste problem of using hydrogen-rich tail gas as low-value fuel, as described in the background art, as well as the resulting poor economic efficiency and safety hazards. Through structural improvements, this system achieves the technical effects of increasing hydrogen recovery rate, reducing tail gas emissions, and lowering external resource consumption. First, by recycling hydrogen from the tail gas, the total hydrogen recovery rate of the pressure swing adsorption unit 3 is significantly improved, enabling the device to produce more high-purity hydrogen products with the same raw material input, directly improving the economic efficiency of the process. Second, since most of the hydrogen-rich tail gas is recycled internally, the total amount of tail gas that ultimately needs to be discharged from the system and enter the fuel gas pipeline is greatly reduced, even achieving zero emissions under certain operating conditions. This not only reduces dependence on and impact on the downstream fuel gas pipeline but also fundamentally reduces the safety risks associated with directly burning hydrogen as fuel gas. Finally, the reduction in tail gas volume means that it is no longer necessary to consume large amounts of resources such as gaseous propane to mix with it to meet the requirements of fuel gas calorific value, thereby saving materials and energy required for mixing and transportation, achieving a simultaneous reduction in material and energy consumption.

[0051] Please see Figure 1 Alternatively, in an optional embodiment of this utility model, an air intake separator 7 is provided on the main pipeline 1 on the inlet side of the air purifier compressor 2, and the outlet end of the circulation pipeline 6 is connected to the air intake separator 7.

[0052] It should be noted that the inlet separator 7 can be a conventional gas-liquid separation device in the art. Its specific structural form may include, but is not limited to, a separator with internal baffles to achieve gravity sedimentation separation, or a cyclone separator that uses centrifugal force to achieve gas-liquid separation. The connection between the circulation pipeline 6 and the separator can also be achieved through various feasible industrial methods. For example, it can be connected by opening an interface on the upper part of the separator body and using a flange connection, or it can be connected to the existing inlet main pipe of the separator. These specific implementation variations can all achieve the core function of introducing the circulating exhaust gas into the separator for subsequent treatment.

[0053] In this case, the exhaust gas returning from the recirculation pipeline 6 needs to be thoroughly and uniformly mixed with the raw material gas from the preceding process before entering the air purification compressor 2, and may carry a small amount of liquid droplets or solid particles. The inlet separator 7, acting as a centralized mixing chamber, provides sufficient space and flow conditions for the recirculated exhaust gas and fresh raw material gas to achieve stable and uniform mixing, thereby ensuring that the gas composition entering the air purification compressor 2 is uniform and avoiding adverse effects on the compressor's operational stability and the subsequent pressure swing adsorption unit 3 due to composition fluctuations. More importantly, the separator utilizes the density differences between gas and liquid / solid particles, through physical mechanisms such as gravity settling, centrifugal separation, or collision aggregation, to effectively remove trace amounts of liquid droplets and solid impurities that may be carried in the gas flow. This significantly reduces the risk of these impurities causing erosion or scaling on the high-speed rotating impeller of the air purification compressor 2, and also prevents them from entering the subsequent pressure swing adsorption unit 3, avoiding contamination of the adsorbent bed and ensuring the long-term service life and separation efficiency of the adsorbent.

[0054] By introducing the intake separator 7 and integrating the circulation pipeline 6 into it, the problems of equipment reliability and system stability that may be caused by uneven gas mixing and medium cleanliness are effectively solved. This ensures the homogeneity and cleanliness of the mixed gas, providing a basic guarantee for the long-term, stable and efficient operation of the gas purification compressor 2 and the pressure swing adsorption unit 3, thereby indirectly supporting the stable achievement of the hydrogen recovery rate target.

[0055] Please see Figure 1 Alternatively, in an optional embodiment of this utility model, a first pressure control component 8 and a first flow monitoring component 9 are provided on the main pipeline 1 between the exhaust gas compressor 4 and the exhaust gas utilization unit 5; a second flow control component 10 is provided on the circulation pipeline 6.

[0056] It should be noted that the first pressure control component 8, as a key component for maintaining downstream pressure stability, can be implemented using, for example, a closed-loop control circuit consisting of a pressure transmitter and a pneumatic diaphragm regulating valve, or a system consisting of a pressure sensor, an electric regulating valve, and a controller. The first flow monitoring component 9 is used to measure the instantaneous and cumulative flow of the exported exhaust gas. Its implementation can include, for example, a differential pressure flow meter using a combination of a standard orifice plate and a differential pressure transmitter, or directly installing a vortex flow meter or other mature flow meters in the field. Correspondingly, the second flow control component 10, installed on the circulation pipeline 6, is responsible for accurately distributing the circulating gas volume and the total exhaust gas volume. Its specific configuration can be an integrated flow controller, or it can be a form in which a separate flow sensor (such as a turbine flow meter) and a regulating valve are installed separately and work in conjunction with the control system. The first pressure control component 8 continuously detects the outlet pressure of the exhaust gas compressor 4 and compares it with the set value, automatically adjusting the opening of the control valve to ensure that the exhaust gas pressure sent to the exhaust gas utilization unit 5 (such as a stripping tower or fuel gas pipeline) remains constant within a safe range that meets the downstream operating requirements. This is a prerequisite for ensuring that downstream users receive materials stably. The first flow monitoring component 9 provides accurate data on the external exhaust gas flow rate, providing crucial information for material balance and performance evaluation of the entire system. The most critical component is the second flow control component 10, which dynamically adjusts the valve opening on the circulation pipeline 6 based on a preset circulation ratio or a feed signal from upstream, thereby precisely controlling the exhaust gas flow rate returning to the inlet of the clean gas compressor 2. This proactive flow allocation mechanism allows operators to flexibly and accurately distribute the external exhaust gas and the circulating exhaust gas according to the unit load and the optimal operating window of the PSA unit.

[0057] Please see Figure 2 As an optional embodiment of the present invention, the first pressure control component 8 includes a pressure detection element, a control valve, and a first controller electrically connected to both, for stabilizing the exhaust gas pressure sent to the exhaust gas utilization unit 5.

[0058] It should be noted that the pressure sensing element monitors the pressure signal in real time, and the first controller outputs a control signal according to the set value to drive the control valve to maintain pressure stability. For example, the pressure sensing element (such as a pressure transmitter) collects the pressure signal in the pipeline in real time and transmits it to the first controller. The first controller compares the measured value with the set value and then outputs a control signal to the actuator (such as a pneumatic or electric control valve) to drive the valve core to change the flow area of ​​the pipeline, thereby realizing automatic pressure regulation and effectively resisting pressure disturbances caused by compressor operating condition fluctuations or changes in downstream gas consumption. For example, the first pressure control component 8 includes a pressure transmitter, a pressure indicating controller, and a pressure control valve. The pressure transmitter and the pressure control valve are installed in the main pipeline, and both the pressure transmitter and the pressure control valve are electrically connected to the pressure indicating controller.

[0059] Please see Figure 2 As an optional embodiment of the present invention, the second flow control component 10 includes a flow detection element, a flow control valve, and a second controller electrically connected to both, for precisely adjusting the flow rate of the circulating exhaust gas.

[0060] It should be noted that the flow detection element measures the flow rate, and the second controller compares it with the set value and outputs a command to adjust the opening of the flow control valve, thus precisely controlling the circulating flow rate. This control method ensures both the recovery effect and avoids excessive system load. For example, the flow detection element (such as the differential pressure signal generated by the orifice plate flow meter, which is converted into a standard electrical signal by the transmitter, or the pulse / current signal directly output by the vortex flow meter) transmits the real-time flow rate value to the controller. The controller compares this value with the desired circulating flow rate set value and calculates the control command, which then drives the flow control valve (such as an equal percentage characteristic regulating valve) to operate, forming a negative feedback closed loop. Ultimately, the flow rate of the circulating tail gas is stabilized near the set point, thereby ensuring that the amount of hydrogen entering the circulation is precisely managed. This maximizes hydrogen recovery to improve the overall yield while preventing the feed load and composition of the PSA unit from exceeding its design operating range due to excessive circulation volume, thus maintaining the stable and optimized operation of the entire PSA unit and even the upstream PDH unit. For example, the second flow control component 10 includes a flow element, a flow transmitter, a flow indicator, and a fault switch. The flow element and the flow control valve are disposed in the circulation pipeline 6. The flow element is provided with a flow transmitter. The flow transmitter and the fault switch are both electrically connected to the flow indicator.

[0061] Please see Figure 2 As an optional embodiment of this utility model, process monitoring points 11 are provided on the inlet of the air purification compressor 2, the circulation pipeline 6 and / or the main pipeline 1 leading to the exhaust gas utilization unit 5. The process monitoring points 11 are configured to allow the installation of online analyzers or for instrument calibration.

[0062] It should be noted that the process monitoring point 11 is essentially a pre-reserved interface conforming to standard engineering specifications on the corresponding pipeline. Its specific implementation can take various forms; for example, it can be a pre-welded standard nozzle with a root valve for subsequent installation; or it can be a sampling port or instrument interface with a quick-connect fitting. The core function of these monitoring points is to provide access conditions for process monitoring and maintenance. Their configuration allows for the installation of online analyzers or for calibrating existing instruments. For example, an online hydrogen concentration analyzer can be installed at the monitoring point at the inlet of the clean gas compressor 2 to monitor the mixing composition of the circulating gas and raw material gas entering the compressor in real time; a portable ultrasonic flow meter can be connected to the monitoring point on the circulating pipeline 6 for periodic comparison and calibration of the existing second flow control component 10 on the pipeline; and an online calorific value analyzer can be installed at the monitoring point on the main pipeline 1 leading to the exhaust gas utilization unit 5 to monitor the quality of the externally supplied fuel gas. This setup, by providing structural assurance, achieves real-time sensing of key process parameters and accurate and reliable measurement instruments. By setting standardized monitoring points at key system nodes, a physical basis is provided for introducing advanced analysis and detection methods. Online analyzers can continuously provide parameters that directly reflect the process status, such as gas composition and the content of key impurities, providing real-time data support for operation optimization and fault diagnosis. Meanwhile, monitoring points used for instrument calibration ensure the long-term accuracy of existing flow, pressure, and other measuring elements in the system, maintaining the reliability of the entire control system and the accuracy of process calculations.

[0063] This invention effectively solves the potential technical problems of opaque operating status, delayed operation adjustments, and undetected instrument drift caused by the lack of real-time data at key locations during the implementation of tail gas recycling by introducing flexibly configurable process monitoring points 11. This improves the observability, controllability, and maintainability of the entire system. It allows operators to optimize the circulating gas volume and adsorption process parameters based on more comprehensive and accurate data, ensuring that hydrogen recovery efficiency remains at a consistently high level. Simultaneously, the convenient instrument calibration function ensures the long-term stability and reliability of the control system, avoiding material distribution imbalances or pressure fluctuations caused by measurement inaccuracies, and providing crucial data support for the long-term safe and stable operation of the device and continuous economic benefits.

[0064] Please see Figure 1 As an optional embodiment of this utility model, the exhaust gas utilization unit 5 includes at least one of a stripping unit, a fuel gas pipeline network, and a fuel gas preparation system.

[0065] It should be noted that the stripping unit is a process unit that uses gas as the stripping medium, and the fuel gas pipeline network is a pipeline system for distributing combustible gases. The tail gas utilization unit 5 can be a single entity, for example, sending all remaining tail gas to the stripping unit or all to the fuel gas pipeline network; it can also be a combination, where a portion of the tail gas prioritizes the needs of the stripping unit, and the excess is discharged to the fuel gas pipeline network. This limitation provides a flexible and reliable outlet for the final tail gas and clarifies the integration scheme between the system and downstream facilities. Listing the stripping unit as one of the destinations reflects the deep utilization of the remaining value in the tail gas, while the fuel gas pipeline network serves as a necessary buffer and final disposal route, ensuring that the unit can still operate safely and continuously when the usage of the stripping unit decreases, avoiding the risk of tail gas pressure buildup, and thus ensuring the integrity and operational flexibility of the entire tail gas treatment chain.

[0066] Please see Figure 1 Alternatively, as an optional embodiment of this utility model, a safety branch pipe 12 is also connected to the circulation pipeline 6, the safety branch pipe 12 leads to the flare system 13, and a shut-off valve is provided on it.

[0067] It should be noted that the safety branch pipe 12 can be led out from the main pipe of the circulation pipeline 6 via a tee, and the shut-off valve can be a pneumatic shut-off valve or a gate valve, etc. During normal operation, the shut-off valve is closed, and the circulation pipeline 6 operates according to the set process. In case of abnormal pressure increases in the circulation pipeline 6 or downstream equipment shutdowns, the shut-off valve can be quickly opened via interlocking or manual operation to guide the gas to the flare system 13 for safe combustion. This safety branch pipe 12 provides a controlled and safe venting path for the circulation loop, effectively preventing the risk of system overpressure or gas accumulation, significantly enhancing the system's safety, reliability, and operational flexibility, and conforming to the inherent safety design principles of chemical plants.

[0068] Please see Figure 1 Alternatively, as an optional embodiment of this utility model, an exhaust gas heater 14 and a temperature monitoring component 15 are also provided on the main pipeline 1 between the exhaust gas compressor 4 and the exhaust gas utilization unit 5.

[0069] It should be noted that the exhaust gas heater 14 can be a shell-and-tube heater or an electric heater, and the temperature monitoring component 15 includes a temperature sensor, transmitter, and display instrument. The exhaust gas heater 14 raises the exhaust gas to a suitable temperature through heat exchange, ensuring its process efficiency as stripping gas and preventing the condensation and precipitation of heavier hydrocarbon components during transportation. The temperature monitoring component 15 automatically adjusts the heater's heat load by providing real-time temperature feedback, ensuring the exhaust gas temperature remains stable within the required range. This setup guarantees the process quality and transportation reliability of the exported exhaust gas, eliminating potential operational failure points such as pipeline corrosion or equipment damage caused by low-temperature condensation.

[0070] Furthermore, a pressure gauge is installed on the intake separator 7, connected to a pressure transmitter, which in turn is connected to a pressure indicator. A fault shut-off valve, a pressure control valve, and a flare are installed on the main pipeline between the intake separator 7 and the purified gas compressor 2. This configuration, through multi-parameter collaborative monitoring and control, achieves comprehensive monitoring of the gas state entering the purified gas compressor 2. The pressure gauge, pressure transmitter, and pressure indicator form a complete pressure monitoring chain, reflecting the pressure status within the separator in real time and providing crucial information for system pressure balance. The fault shut-off valve and pressure control valve form a cascade control loop, automatically adjusting the gas pressure according to system load changes to ensure that the gas parameters entering the compressor remain stable within the set range. Each monitoring and control unit is linked by signals to form an organic, integrated control system. This solves the problems of compressor instability and liquid carryover risk caused by the lack of precise monitoring of the intake state in traditional systems. By implementing comprehensive monitoring and automatic control, the automation level and operational reliability of the system have been significantly improved, ensuring that the clean gas compressor 2 always operates under optimal conditions, thereby providing a stable and reliable gas source for the subsequent pressure swing adsorption unit 3 and ensuring the long-term stable and efficient operation of the entire exhaust gas recirculation system.

[0071] This invention provides a propane dehydrogenation device that integrates a pressure swing adsorption tail gas recycling system as described above.

[0072] It should be noted that this device integrates the pressure swing adsorption (PSA) tail gas recycling system described in any of the above embodiments. This integration means that the tail gas recycling system is an integral part of the propane dehydrogenation unit. Its feed comes from the dry gas produced in the PDH reaction separation sequence, while its product hydrogen and residual tail gas are respectively fed into or returned to the corresponding sections of the PDH unit. This system is directly connected to the main equipment of the PDH unit via pipelines, achieving synergy between materials and energy. By introducing efficient hydrogen recovery technology into the propane dehydrogenation process and utilizing the unit's own dry gas as feedstock, the unique recycling structure significantly improves the total yield of hydrogen products, changing the fate of tail gas as a low-value fuel. This integrated device effectively improves resource utilization and economic efficiency, producing more high-value hydrogen while consuming the same amount of propane feedstock, and reducing tail gas emissions and external fuel consumption.

[0073] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A pressure swing adsorption (PSA) tail gas recycling system, characterized in that, It includes a purified gas compressor, a pressure swing adsorption unit, a tail gas compressor, and a tail gas utilization unit, which are connected sequentially through a main pipeline, and also includes: The circulation pipeline has its inlet end connected to the main pipeline on the outlet side of the exhaust gas compressor, and its outlet end connected to the main pipeline on the inlet side of the clean gas compressor. The circulation pipeline is used to transport a portion of the exhaust gas discharged from the pressure swing adsorption unit to the inlet of the gas purifier compressor, where it is combined with the raw material gas flowing to the gas purifier compressor.

2. The pressure swing adsorption tail gas recycling system according to claim 1, characterized in that, An air intake separator is installed on the main pipeline on the inlet side of the air purifier compressor, and the outlet end of the circulation pipeline is connected to the air intake separator.

3. The pressure swing adsorption tail gas recycling system according to claim 1, characterized in that, A first pressure control component and a first flow monitoring component are installed on the main pipeline between the exhaust gas compressor and the exhaust gas utilization unit; a second flow control component is installed on the circulation pipeline.

4. The pressure swing adsorption tail gas recycling system according to claim 3, characterized in that, The first pressure control assembly includes a pressure sensing element, a control valve, and a first controller electrically connected to both.

5. The pressure swing adsorption tail gas recycling system according to claim 3, characterized in that, The second flow control component includes a flow detection element, a flow control valve, and a second controller electrically connected to both.

6. The pressure swing adsorption tail gas recycling system according to claim 1, characterized in that, Process monitoring points are provided at the inlet of the clean gas compressor, the circulation pipeline, and / or the main pipeline leading to the exhaust gas utilization unit. These process monitoring points are configured to allow the installation of online analyzers or for instrument calibration.

7. The pressure swing adsorption tail gas recycling system according to claim 1, characterized in that, The exhaust gas utilization unit includes at least one of a stripping unit, a fuel gas pipeline network, and a fuel gas preparation system.

8. The pressure swing adsorption tail gas recycling system according to claim 1, characterized in that, The circulation pipeline is also connected to a safety branch pipe, which leads to the flare system and is equipped with a shut-off valve.

9. The pressure swing adsorption tail gas recycling system according to claim 2, characterized in that, An exhaust gas heater and a temperature monitoring component are also installed on the main pipeline between the exhaust gas compressor and the exhaust gas utilization unit.

10. A propane dehydrogenation apparatus, characterized in that, It integrates a pressure swing adsorption tail gas recycling system as described in any one of claims 1 to 9.

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