Membrane-based skid-mounted high-efficiency hydrogen extraction system for hydrogenation purge gas.

Abstract

This invention discloses a skid-mounted high-efficiency hydrogen extraction system for hydrogenation purge gas based on membrane separation, relating to the field of hydrogenation purge gas recovery technology. The system includes a feed pretreatment unit, a membrane separation unit, a multi-dimensional sensing module, a feedforward-cascade decoupled control subsystem, and a product collection module. A feedforward signal matrix is ​​constructed through the multi-dimensional sensing module at the inlet to monitor feed composition, temperature, and pressure parameters in real time. The feedforward-cascade decoupled control subsystem, based on a membrane separation characteristic model, proactively decouples and regulates the feed heater and back pressure valve, and performs cascade fine-tuning based on the hydrogen purity on the permeate side, achieving proactive prevention of feed disturbances and avoiding membrane unit exposure and puncture. The standardized product collection module separates hydrogen products from tail gas, and the tail gas treatment unit further improves resource utilization. This system is adaptable to various hydrogenation unit purge gas recovery scenarios, effectively improving hydrogen extraction efficiency, system stability, and operational reliability.

Description

Technical Field

[0001] This invention relates to the field of hydrogenation purge gas recovery technology, specifically a skid-mounted high-efficiency hydrogen extraction system for hydrogenation purge gas based on membrane separation. Background Technology

[0002] Hydrogenation is a core process in petrochemical, fine chemical and other fields. During the reaction, a large amount of hydrogenation off-gas is generated. Its main components are light hydrocarbons such as hydrogen, methane, ethane, and propane, as well as a small amount of heavy hydrocarbons and impurities. Due to its high hydrogen content, it has significant recycling value. After hydrogen extraction, it can be recycled back to the hydrogenation reaction, which can reduce hydrogen consumption costs, reduce waste gas emissions, and realize resource recycling.

[0003] Currently, the mainstream technologies for hydrogen extraction from hydrogenation purge gas include membrane separation, pressure swing adsorption, and cryogenic separation. Among them, membrane separation has become the dominant technology for skid-mounted hydrogen extraction systems due to its advantages such as simple operation, low energy consumption, compact equipment, high separation efficiency, and no secondary pollution. Skid-mounted systems adopt an integrated design, integrating the equipment into the skid body. They are characterized by convenient installation, flexible transportation, and small footprint, and are suitable for small and medium-sized hydrogenation units or mobile hydrogen extraction scenarios. This is a key technology direction for the recovery and utilization of hydrogenation purge gas.

[0004] Existing skid-mounted hydrogen extraction systems based on membrane separation still have significant technical shortcomings in industrial applications. On the one hand, the feed composition, flow rate, pressure, and temperature parameters of the hydrogen extraction gas fluctuate drastically due to the operating conditions of the upstream hydrogenation unit. Especially towards the end of the hydrogenation catalyst's lifespan, extreme conditions such as a sudden drop in hydrogen content and a significant increase in the proportion of heavy hydrocarbon components can easily occur. However, existing systems generally adopt a hysteresis feedback control mode based on the hydrogen purity on the permeate side, which only triggers adjustments when the membrane separation effect is abnormal or the product purity does not meet the standards. This fails to proactively control feed disturbances, making it easy for heavy hydrocarbon components in the feed to condense due to insufficient temperature. The condensate adheres to the membrane surface, clogging the membrane pores and even causing dew point puncture of the membrane material, leading to irreversible degradation of membrane separation performance and a significant reduction in membrane lifespan. On the other hand, existing systems mostly adopt a single-loop independent control mode, which has strong dynamic coupling characteristics between the temperature regulation of the feed heater and the pressure regulation of the membrane permeation side back pressure valve. When the feed parameters fluctuate greatly, problems such as mutual interference of regulation actions, system coupling oscillation, and slow response speed are very likely to occur. It is impossible to ensure the stable operation of the membrane separation unit in a wide range of operating conditions and it is difficult to continuously maintain the stable hydrogen purity on the permeation side. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a skid-mounted high-efficiency hydrogen extraction system for hydrogenation purge gas based on membrane separation. This system includes a feed pretreatment unit, a membrane separation unit, a multi-dimensional sensing module, a feedforward-cascade decoupled control subsystem, and a product collection module. The multi-dimensional sensing module at the inlet constructs a feedforward signal matrix to monitor feed composition, temperature, and pressure parameters in real time. The feedforward-cascade decoupled control subsystem, based on a membrane separation characteristic model, proactively decouples and regulates the feed heater and back pressure valve, and performs cascade fine-tuning based on the hydrogen purity on the permeate side, achieving proactive prevention of feed disturbances and avoiding membrane unit exposure and puncture. The standardized product collection module separates hydrogen products from tail gas, and the tail gas treatment unit further improves resource utilization. This system is adaptable to various hydrogenation unit purge gas recovery scenarios, effectively improving hydrogen extraction efficiency, system stability, and operational reliability.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a skid-mounted high-efficiency hydrogen extraction system for hydrogenation purge gas based on membrane separation, the system comprising: a feed pretreatment unit, a membrane separation unit, a multi-dimensional sensing module, a feedforward-cascade decoupled control subsystem, and a product collection module; The feed pretreatment unit is used to pretreat the hydrogenated purge gas, remove impurities and adjust the initial state of the feed, and its output end is connected to the input end of the membrane separation unit. The membrane separation unit is used to separate hydrogen from other components in the hydrogenation purge gas. It is equipped with a feed heater at the feed end, a back pressure valve on the permeate side, and a hydrogen purity detection element at the permeate outlet. The multidimensional sensing module is deployed at the hydrogen purge gas inlet of the skid-mounted main body. It includes an online laser Raman gas component analyzer, a temperature sensor, and a pressure sensor, which work together to form a feedforward signal matrix for real-time detection of the component parameters, temperature parameters, and pressure parameters of the feed, and transmits the detection signals to the feedforward-cascade decoupled control subsystem. The feedforward-cascade decoupled control subsystem is used to receive the detection signal from the feedforward signal matrix, calculate the optimal operating point of the membrane separation unit in advance, decouple and adjust the temperature setpoint of the feed heater and the opening of the back pressure valve, and simultaneously receive the detection signal from the hydrogen purity detection element. Using the hydrogen purity on the permeate side as the cascade secondary loop, the system fine-tunes and corrects the adjustment effect. The product collection module is connected to the permeate side outlet and the retrieval side outlet of the membrane separation unit, respectively, and is used to collect the concentrated hydrogen product and the retrieval tail gas.

[0007] Furthermore, the feedforward-cascade decoupling control subsystem includes a feedforward control module, a cascade control module, and a decoupling module; The feedforward control module is used to receive the detection signal from the multi-dimensional sensing module, calculate the optimal operating point in advance based on the preset membrane separation characteristic model, and output the feed heater temperature setting value adjustment signal and the back pressure valve opening adjustment signal. The decoupling module is used to decouple the two adjustment signals output by the feedforward control module to avoid mutual interference of adjustment actions; The cascade control module is used to receive the detection signal from the hydrogen purity detection element, compare the actual value of hydrogen purity on the permeation side with the preset target value, output a fine-tuning signal, and correct the adjustment parameters of the feed heater and the back pressure valve.

[0008] Furthermore, the feedforward control module continuously receives feed hydrogen content, heavy hydrocarbon content, feed temperature, and feed pressure signals transmitted by the laser Raman gas component online analyzer, temperature sensor, and pressure sensor. These signals are then synchronously input into a preset membrane separation characteristic model. This model is based on the inherent separation parameters of the membrane module and incorporates the correlation between the feed component ratio, feed temperature, and feed pressure on the hydrogen permeation rate and the critical temperature for heavy hydrocarbon condensation. Through mapping relationships, the optimal operating range of the membrane separation unit under the current feed condition is solved. This determines the target temperature rise value of the feed heater and the target opening degree of the back pressure valve to maintain a reasonable pressure difference across the membrane and prevent heavy hydrocarbon condensation. Finally, corresponding temperature setpoint adjustment signals and back pressure valve opening adjustment signals are generated, completing the output of advance control commands for the feed heater and back pressure valve.

[0009] Furthermore, the feedforward control module solves for the optimal operating range of the membrane separation unit under the current feed state through a mapping relationship. Firstly, it uses a correction formula based on the critical temperature of heavy hydrocarbon condensation. First, calculate the correction value for the critical condensation temperature of heavy hydrocarbons under the current feed pressure and heavy hydrocarbon content; second, rely on the formula of the target temperature rise setpoint of the feed heater. The target temperature setpoint for the feed heater is determined, and a hydrogen content deviation correction term is introduced to balance hydrogen separation efficiency; thirdly, the membrane permeation side pressure is calculated using the formula... Derive the target pressure on the permeation side and combine it with the back pressure valve opening mapping formula. Solve for the target opening degree of the back pressure valve, where, This is the correction value for the critical condensation temperature of heavy hydrocarbons under the current feed conditions. It is the basic condensation critical temperature of heavy hydrocarbons under standard atmospheric pressure. It is a pressure correction factor, obtained by fitting the pressure-condensation temperature correlation curve provided by the membrane module manufacturer. It is the actual feed pressure, which is collected in real time by a pressure sensor; It is standard atmospheric pressure. This is a correction factor for heavy hydrocarbon content, calibrated based on on-site process tests. It is the volume fraction of heavy hydrocarbons in the feed, which is detected in real time by an online laser Raman gas component analyzer. This is the target temperature rise setting value for the feed heater; This is a safety temperature margin, a temperature allowance reserved to prevent the condensation of heavy hydrocarbons. It is the hydrogen content deviation correction coefficient, used to fine-tune the heating temperature according to the deviation between the actual hydrogen content and the target value; This is the target value for the integral number of the feed hydrogen gas; It is the actual hydrogen gas integral of the feed, which is detected in real time by an online laser Raman gas composition analyzer. It is the target pressure on the membrane permeation side, a core pressure parameter for maintaining the driving force of hydrogen permeation; It is the basic ratio coefficient of feed pressure - permeation side pressure. It is the correction factor for the heavy hydrocarbon content relative to the pressure ratio. It is the optimal operating pressure difference across the membrane; It is the target opening degree of the back pressure valve. It is the back pressure valve opening adjustment coefficient; This is the membrane permeate side pressure setpoint; It is the basic opening degree of the back pressure valve.

[0010] Furthermore, the decoupling module receives the feed heater temperature setpoint adjustment signal and the back pressure valve opening adjustment signal from the feedforward control module in real time. Combining the temperature-pressure coupling characteristics of the membrane separation unit, it constructs a bivariate decoupling correlation matrix using a fuzzy decoupling algorithm based on on-site operating conditions, calculates the cross-coupling gain between the two adjustment signals, and cancels in real time the interference component of temperature regulation on the pressure difference across the membrane and the influence component of pressure regulation on the stability of the feed temperature. Then, the purified adjustment signal after decoupling is output to the feed heater temperature control actuator and the back pressure valve pneumatic actuator, respectively, so that the two adjustment actions are executed independently and accurately, thereby ensuring the stable control of the operating parameters of the membrane separation unit.

[0011] Furthermore, the specific steps of the decoupling module in constructing a bivariate decoupling correlation matrix using a fuzzy decoupling algorithm based on on-site operating condition calibration are as follows: Through full-range calibration tests under different feed components, pressures, and temperatures at the hydrogen extraction site using purge gas, coupled response data of the feed heater temperature regulation and the back pressure valve opening regulation are collected. Based on this, a temperature-opening bivariate fuzzy membership function is constructed. Then, using the influence coefficient of membrane separation unit temperature regulation on permeate side pressure and the disturbance coefficient of opening regulation on feed temperature as core parameters, a bivariate decoupling correlation matrix is ​​established. After receiving the temperature regulation signal and opening regulation signal output by the feedforward control module in real time, the cross-coupling components of the two signals are quickly solved through matrix operations. Pressure disturbance components caused by temperature regulation and temperature disturbance components caused by opening regulation are simultaneously eliminated. Then, amplitude and rate corrections are performed on the two signals according to the dynamic response characteristics of the membrane module. Finally, independent control commands without interactive interference are output and sent to the feed heater and back pressure valve actuators, respectively.

[0012] Furthermore, the cascade control module uses the hydrogen purity on the permeate side as the control parameter. It receives the actual hydrogen purity value on the permeate side from the hydrogen purity detection element in real time, calculates the difference between the actual value and the system's preset hydrogen purity target value, obtains the purity deviation signal, and then completes the calculation through an incremental PID adjustment algorithm to generate a corresponding purity correction fine-tuning amount. This fine-tuning amount is then synchronously superimposed on the feed heater heating setpoint and back pressure valve opening adjustment parameters processed by the decoupling module to form a closed-loop fine-tuning correction. When the actual hydrogen purity value is detected to be lower than the preset target value, the feed heater heating setpoint is increased and the back pressure valve opening is increased to enhance the hydrogen permeate separation effect and quickly raise the purity. When the actual hydrogen purity value is higher than the preset target value, the heater heating setpoint is decreased and the back pressure valve opening is reduced. Finally, a corrected and stable adjustment signal is output to correct the operating parameters of the membrane separation unit.

[0013] Furthermore, the cascade control module completes the calculation process using an incremental PID control algorithm, the formula of which is: ,in, It is the first The hydrogen purity correction fine-tuning increments output in each control cycle correspond to the feed heater temperature rise fine-tuning amount and the back pressure valve opening fine-tuning amount, respectively. It is a proportionality coefficient. It is the integral coefficient. These are differential coefficients. It is the first Periodic hydrogen purity deviation, It is the first Periodic hydrogen purity deviation, It is the first Periodic hydrogen purity deviation.

[0014] Furthermore, the feedforward-cascade decoupled control subsystem also includes a data storage module and an alarm module. The data storage module is used to store the detection data and adjustment parameters of the multi-dimensional sensing module, and the alarm module is used to issue an audible and visual alarm signal when the feed parameters exceed the preset range, the membrane separation unit malfunctions, or the hydrogen purity on the permeate side is substandard.

[0015] Furthermore, the product collection module includes a hydrogen collection tank and a tail gas collection tank. The hydrogen collection tank is connected to the permeate-side outlet of the membrane separation unit and is used to store concentrated hydrogen products. The tail gas collection tank is connected to the retrieval-side outlet of the membrane separation unit and is used to store retrieval tail gas. The hydrogen collection tank is equipped with a pressure monitoring element and a discharge valve, and the tail gas collection tank is equipped with a liquid level monitoring element and a discharge valve.

[0016] Compared with existing technologies, this skid-mounted hydrogenation purge gas high-efficiency hydrogen extraction system based on membrane separation has the following advantages: This invention utilizes a multi-dimensional sensing module deployed at the skid-mounted inlet to capture real-time fluctuations in the composition, temperature, and pressure of the hydrogen purge gas. Combined with a feedforward-cascade decoupled control subsystem, it can preemptively calculate and adjust the optimal operating point before feed disturbances affect membrane separation performance. Especially when heavy hydrocarbon content increases and hydrogen partial pressure decreases, it can promptly raise the feed temperature to prevent heavy hydrocarbon condensation, avoiding dew point puncture in the membrane separation unit and effectively extending the membrane module's lifespan. Furthermore, the decoupling module eliminates the mutual interference between the feed heater temperature and the back pressure valve opening adjustment, resolving the regulation oscillations and slow response issues common in traditional single-loop control. The system addresses the slow performance issue by combining cascade control with fine-tuning of hydrogen purity, providing dual assurance that the hydrogen purity on the permeation side remains stable and meets standards. This solves the problem of purity non-compliance caused by the lag in traditional feedback regulation, significantly improving the quality of the hydrogen product and the stability of system operation. The product collection module in the system can collect the concentrated hydrogen product and the retained tail gas separately and in a standardized manner, avoiding mixing and leakage. This not only ensures the purity of the hydrogen product but also facilitates the subsequent purification and recycling of the retained tail gas, reducing safety hazards and improving the practicality of the system. Overall, it improves the economy, reliability, and safety of hydrogen purge gas recovery and utilization.

[0017] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0019] Figure 1 This is a structural block diagram of a skid-mounted hydrogenation purge gas high-efficiency hydrogen extraction system based on membrane separation; Figure 2 This is a structural block diagram of the feedforward-cascade decoupled control subsystem of a skid-mounted hydrogenation purge gas high-efficiency hydrogen extraction system based on membrane separation; Figure 3 This is a flowchart of a skid-mounted hydrogenation purge gas high-efficiency hydrogen extraction system based on membrane separation. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0021] This invention provides a skid-mounted high-efficiency hydrogen extraction system for hydrogenation purge gas based on membrane separation, including a feed pretreatment unit, a membrane separation unit, a multi-dimensional sensing module, a feedforward-cascade decoupled control subsystem, and a product collection module. A feedforward signal matrix is ​​constructed through the multi-dimensional sensing module at the inlet to monitor feed composition, temperature, and pressure parameters in real time. The feedforward-cascade decoupled control subsystem, based on a membrane separation characteristic model, proactively decouples and regulates the feed heater and back pressure valve, and performs cascade fine-tuning based on the hydrogen purity on the permeate side, achieving proactive prevention of feed disturbances and avoiding membrane unit exposure and puncture. The standardized product collection module separates hydrogen products from the retained tail gas, and the tail gas treatment unit further improves resource utilization. This system is adaptable to various hydrogenation unit purge gas recovery scenarios, effectively improving hydrogen extraction efficiency, system stability, and operational reliability.

[0022] The feed pretreatment unit is used to pretreat the hydrogenation purge gas discharged from the hydrogenation unit, remove droplets and solid impurities from the gas phase, and adjust the initial pressure and flow rate of the feed to provide feed that meets the operating requirements of the subsequent membrane separation unit. Its output end is connected to the input end of the membrane separation unit through a process pipeline.

[0023] In specific implementation, the feed pretreatment unit is sequentially equipped with a gas-liquid separator, a precision filter, a buffer tank, and a feed regulating valve along the feed flow direction. The gas-liquid separator is a cyclone gas-liquid separator used to remove liquid hydrocarbons and free water carried in the hydrogenation purge gas, preventing the liquid phase from entering the subsequent membrane module and causing membrane fiber damage and performance degradation. The precision filter has a filtration accuracy of not less than 0.01μm and is used to intercept solid particles and tiny droplets in the gas phase, providing pre-protection for the membrane module. The buffer tank is used to stabilize the feed flow rate and pressure, eliminate pulsation fluctuations in the feed gas source, and ensure stable feed conditions. The feed regulating valve is installed at the outlet of the buffer tank to coarsely adjust the initial feed pressure and cooperate with the subsequent control system to achieve pre-stabilization of the feed pressure.

[0024] The membrane separation unit is used to achieve efficient separation of hydrogen from other components such as methane, heavy hydrocarbons, and CO in the hydrogenation purge gas by taking advantage of the difference in permeation rates of different gas components in the membrane material, so as to obtain high-purity hydrogen products. Its feed end is connected to the output end of the feed pretreatment unit, and the permeate side outlet and the interception side outlet are respectively connected to the product collection module.

[0025] In practical implementation, the membrane separation unit includes at least one membrane module. The membrane module is a polyimide hollow fiber gas separation membrane module with a separation coefficient of not less than 50 for hydrogen / methane, exhibiting excellent hydrogen selectivity and permeation stability. A feed heater is installed on the feed pipeline of the membrane separation unit. The feed heater is an explosion-proof electric heater used to precisely heat the pretreated feed gas. This avoids the condensation of heavy hydrocarbon components on the membrane surface and contamination of the membrane module, and also allows for adjustment of the hydrogen permeation rate, optimizing the separation efficiency.

[0026] The membrane module's stubble-side outlet is connected to the stubble-side pipeline, and the permeate-side outlet is connected to the permeate-side pipeline. A back pressure valve is installed on the permeate-side pipeline to precisely regulate the pressure on the permeate side of the membrane, maintain a stable osmotic pressure difference across the membrane, and provide the core driving force for hydrogen separation. A hydrogen purity detection element is installed on the pipeline between the permeate-side outlet and the back pressure valve. The hydrogen purity detection element adopts an online thermal conductivity hydrogen purity analyzer with a detection accuracy of not less than 0.1%, which is used to collect the purity data of the hydrogen produced on the permeate side in real time and transmit the detection signal to the feedforward-cascade decoupled control subsystem in real time.

[0027] The multidimensional sensing module is deployed at the hydrogen venting gas inlet of the skid-mounted main body, specifically installed on the front-end inlet pipeline of the feed pretreatment unit. It is used to collect the full-dimensional operating parameters of the feed in real time before the feed enters the pretreatment and membrane separation stage, providing advanced signal input for feedforward control and forming a feedforward signal matrix in concert.

[0028] In specific implementation, the multi-dimensional sensing module includes a laser Raman gas component online analyzer, a temperature sensor, and a pressure sensor. The signal output terminals of all three are electrically connected to the input terminal of the feedforward-cascade decoupled control subsystem. The laser Raman gas component online analyzer is used to detect the volume fraction of each component in the feed gas, such as hydrogen and methane, in real time, with a detection response time of no more than 5 seconds, enabling rapid online monitoring of the feed components. The temperature sensor uses a platinum resistance temperature sensor with a measurement accuracy of no less than ±0.2℃, used to acquire the actual temperature of the feed in real time. The pressure sensor uses a high-precision diffused silicon pressure transmitter with a measurement accuracy of no less than 0.1%, used to acquire the actual pressure of the feed in real time. The feed component parameters, temperature parameters, and pressure parameters acquired synchronously by these three sensors are transmitted synchronously to the feedforward-cascade decoupled control subsystem in real time.

[0029] The feedforward-cascade decoupled control subsystem receives the detection signal from the feedforward signal matrix, calculates the optimal operating point of the membrane separation unit in advance, decouples and adjusts the temperature setpoint of the feed heater and the opening of the back pressure valve, and simultaneously receives the detection signal from the hydrogen purity detection element. Using the hydrogen purity on the permeate side as a cascade secondary loop, it fine-tunes and corrects the adjustment effect to ensure that the hydrogen extraction system can still stably produce hydrogen products that meet the purity requirements when the feed conditions fluctuate, while avoiding membrane module fouling and damage.

[0030] In practical implementation, the hardware carrier of the feedforward-cascade decoupling control subsystem adopts an explosion-proof PLC controller, which is adapted to the explosion-proof requirements of the skid-mounted device. The system has built-in feedforward control module, decoupling module, and cascade control module, and is also equipped with data storage module and alarm module. All control algorithms and mathematical models are integrated into the PLC controller for execution.

[0031] The feedforward control module receives real-time feed condition detection signals transmitted by the multi-dimensional sensing module. Based on a preset membrane separation characteristic model, it calculates the optimal operating point of the membrane separation unit in advance and outputs the corresponding adjustment signal to achieve advance control of feed fluctuations and solve the adjustment lag problem of traditional feedback control.

[0032] In practical implementation, the feedforward control module continuously and synchronously receives the feed hydrogen integral number and heavy hydrocarbon volume fraction transmitted by the online laser Raman gas component analyzer, the actual feed temperature transmitted by the temperature sensor, and the actual feed pressure signal transmitted by the pressure sensor. It then synchronously inputs these multi-dimensional signals into a preset membrane separation characteristic model. This model is based on the inherent separation parameters of the membrane module provided by the membrane module manufacturer (including hydrogen permeability coefficient, component selectivity coefficient, etc.), and is established by combining the correlation between the feed component ratio, feed temperature, and feed pressure on the hydrogen permeation rate and the critical temperature for heavy hydrocarbon condensation. Through a built-in mapping relationship, it solves for the optimal operating range of the membrane separation unit under the current feed condition, clarifying the target temperature rise value of the feed heater and the target opening degree of the back pressure valve that can simultaneously maintain a reasonable osmotic pressure difference across the membrane, prevent heavy hydrocarbon condensation from contaminating the membrane module, and ensure hydrogen separation efficiency. Finally, it generates corresponding temperature setpoint adjustment signals and back pressure valve opening adjustment signals, completing the output of advance control commands for the feed heater and back pressure valve.

[0033] Specifically, the process of finding the optimal operating range of the feedforward control module includes the following steps: Based on the heavy hydrocarbon condensation critical temperature correction formula, the correction value of the heavy hydrocarbon condensation critical temperature under the current feed pressure and heavy hydrocarbon content is calculated to prevent heavy hydrocarbon condensation within the membrane module from the source. The heavy hydrocarbon condensation critical temperature correction formula is as follows: In the formula, This is the correction value for the critical condensation temperature of heavy hydrocarbons under the current feed conditions. It is the basic condensation critical temperature of heavy hydrocarbons under standard atmospheric pressure. It is a pressure correction factor, obtained by fitting the pressure-condensation temperature correlation curve provided by the membrane module manufacturer. It is the actual feed pressure, which is collected in real time by a pressure sensor; It is standard atmospheric pressure. This is a correction factor for heavy hydrocarbon content, calibrated based on on-site process tests. It represents the volume fraction of heavy hydrocarbons in the feed, which is detected in real time by an online laser Raman gas component analyzer.

[0034] The target temperature rise setpoint for the feed heater is determined based on the formula, taking into account both heavy hydrocarbon condensation and hydrogen separation efficiency. The formula for the target temperature rise setpoint for the feed heater is: In the formula, This is the target temperature rise setting value for the feed heater; This is a safety temperature margin, a temperature allowance reserved to prevent the condensation of heavy hydrocarbons. It is the hydrogen content deviation correction coefficient, used to fine-tune the heating temperature according to the deviation between the actual hydrogen content and the target value; This is the target value for the integral number of the feed hydrogen gas; It is the actual hydrogen gas integral of the feed, which is detected in real time by an online laser Raman gas composition analyzer.

[0035] The target pressure on the permeate side is derived by using the membrane permeate side pressure calculation formula, and then the target opening of the back pressure valve is solved by combining it with the back pressure valve opening mapping formula. The membrane permeate side pressure calculation formula is as follows: In the formula, It is the target pressure on the membrane permeation side, a core pressure parameter for maintaining the driving force of hydrogen permeation; It is the basic ratio coefficient of feed pressure - permeation side pressure. It is the correction factor for the heavy hydrocarbon content relative to the pressure ratio. It is the optimal operating pressure difference across the membrane.

[0036] Combining the back pressure valve opening mapping formula To determine the target opening degree of the back pressure valve, the formula is as follows: It is the target opening degree of the back pressure valve. It is the back pressure valve opening adjustment coefficient; This is the membrane permeate side pressure setpoint; It is the basic opening degree of the back pressure valve.

[0037] The decoupling module is used to decouple the two regulation signals output by the feedforward control module, avoiding mutual interference between regulation actions and ensuring the independent and precise execution of the two regulation actions. In specific implementation, the decoupling module receives the feed heater temperature setpoint regulation signal and the back pressure valve opening regulation signal output by the feedforward control module in real time. Combining the temperature-pressure coupling characteristics of the membrane separation unit, a two-variable decoupling correlation matrix is ​​constructed using a fuzzy decoupling algorithm based on field operating conditions calibration. The cross-coupling gain between the two regulation signals is calculated to cancel the interference component of temperature regulation on the pressure difference across the membrane and the influence component of pressure regulation on the stability of the feed temperature in real time. Then, the purified regulation signal after decoupling is output to the feed heater temperature control actuator and the back pressure valve pneumatic actuator, respectively, so that the two regulation actions are executed independently and precisely, thereby ensuring the stable control of the operating parameters of the membrane separation unit.

[0038] Specifically, the decoupling module constructs a bivariate decoupling correlation matrix and performs decoupling processing in the following steps: Through full-range calibration tests under different feed components, feed pressures, and feed temperatures at the hydrogen extraction site using hydrogen purge gas, multiple sets of coupled response data on the adjustment of feed heater temperature rise and back pressure valve opening were collected. This included data on permeation side pressure fluctuations caused by temperature adjustment actions and feed temperature disturbances caused by opening adjustment actions, forming the basic calibration database for the decoupling algorithm.

[0039] Based on the calibration database, a temperature-opening bivariate fuzzy membership function is constructed, and the fuzzy universe and membership of the temperature adjustment, opening adjustment, and coupling disturbance are set respectively to adapt to the changes in coupling characteristics under different working conditions.

[0040] Establish a bivariate decoupling correlation matrix: Using the influence coefficient of membrane separation unit temperature control on permeate side pressure and the disturbance coefficient of opening control on feed temperature as core parameters, establish a bivariate decoupling correlation matrix.

[0041] After receiving the temperature regulation signal and opening regulation signal output by the feedforward control module in real time, the system quickly calculates the cross-coupling components of the two signals through matrix operations of the decoupling correlation matrix, and simultaneously eliminates the pressure disturbance component caused by temperature regulation and the temperature disturbance component caused by opening regulation. Then, according to the dynamic response characteristics of the membrane module and the actuator, the system performs amplitude and rate correction on the two decoupled signals to avoid overshoot of the regulation action. Finally, it outputs independent control commands without interactive interference, which are sent to the actuators of the feed heater and the back pressure valve, respectively.

[0042] The cascade control module receives the detection signal from the hydrogen purity detection element, compares the actual value of hydrogen purity on the permeation side with the preset target value, outputs a fine-tuning signal, and corrects the adjustment parameters of the feed heater and back pressure valve. This compensates for the deviation of the feedforward control model and unpredictable operating disturbances, ensuring that the purity of the hydrogen product remains stable and meets the standards.

[0043] In specific implementation, the cascade control module uses the permeate-side hydrogen purity as the primary controlled parameter and the feed heater temperature and back pressure valve opening as secondary controlled parameters, forming a cascade secondary loop to achieve closed-loop fine-tuning correction of hydrogen purity. Its specific working process is as follows: the cascade control module receives the actual permeate-side hydrogen purity value collected by the hydrogen purity detection element in real time, calculates the difference between this actual value and the system's preset hydrogen purity target value to obtain a purity deviation signal; the purity deviation signal is input into an incremental PID control algorithm to complete the calculation and generate a corresponding purity correction fine-tuning amount; this fine-tuning amount is then synchronously superimposed onto the feed heater temperature setpoint and back pressure valve opening adjustment parameters processed by the decoupling module, forming a closed-loop fine-tuning correction.

[0044] When the actual hydrogen purity is detected to be lower than the preset target value, the cascade control module outputs a positive fine-tuning amount, increasing the feed heater temperature setting and the back pressure valve opening to raise the membrane separation temperature and the osmotic pressure difference across the membrane, thereby enhancing the hydrogen permeation separation effect and rapidly increasing the product hydrogen purity. When the actual hydrogen purity is higher than the preset target value, the cascade control module outputs a negative fine-tuning amount, lowering the heater temperature setting and reducing the back pressure valve opening to reduce system energy consumption and hydrogen loss while ensuring that the purity meets the target.

[0045] The incremental PID control algorithm formula used in the cascade control module is as follows: In the formula, It is the first The hydrogen purity correction fine-tuning increments output in each control cycle correspond to the feed heater temperature rise fine-tuning amount and the back pressure valve opening fine-tuning amount, respectively. It is a proportionality coefficient. It is the integral coefficient. These are differential coefficients. It is the first Periodic hydrogen purity deviation, It is the first Periodic hydrogen purity deviation, It is the first Periodic hydrogen purity deviation.

[0046] In practice, the feedforward-cascade decoupling control subsystem is also equipped with a data storage module and an alarm module.

[0047] The data storage module uses industrial-grade storage chips to store real-time detection data from the multi-dimensional sensing module, adjustment parameters of various parts of the system, product hydrogen purity detection data, and equipment operating status data for a long time. It supports the query and export of historical data, providing data support for system operation and maintenance, process optimization, and fault tracing.

[0048] The alarm module is linked with all detection elements and actuators in the system. It presets the normal operating thresholds for each parameter. When the feed parameters exceed the preset range, the operating parameters of the membrane separation unit are abnormal, the hydrogen purity on the permeate side is consistently below standard, or the actuator malfunctions, it immediately issues an audible and visual alarm signal. At the same time, it can upload the alarm information to the plant's DCS system to remind maintenance personnel to handle the situation in a timely manner.

[0049] The product collection module is connected to the permeate-side outlet and the retrieval-side outlet of the membrane separation unit, respectively, and is used to collect the concentrated hydrogen product and the retrieval tail gas.

[0050] In practical implementation, the product collection module includes a hydrogen collection tank and a tail gas collection tank, both of which are skid-mounted integrated pressure vessels that comply with pressure equipment safety regulations. The inlet of the hydrogen collection tank is connected to the permeate-side outlet of the membrane separation unit via a permeate-side pipeline, and is used to store concentrated high-purity hydrogen product. The hydrogen collection tank is equipped with a pressure monitoring element, a safety valve, and a discharge valve. The pressure monitoring element is used to monitor the tank pressure in real time, the discharge valve is used to transport qualified hydrogen product to downstream hydrogen refueling units or hydrogen storage equipment, and the safety valve is used for overpressure safety protection. The inlet of the tail gas collection tank is connected to the retentate-side outlet of the membrane separation unit via a retentate-side pipeline, and is used to store the separated retentate tail gas. The tail gas collection tank is equipped with a pressure monitoring element, a liquid level monitoring element, a safety valve, and a discharge valve. The discharge valve is used to transport the retentate tail gas to the plant's fuel gas pipeline network or flare system, realizing the resource utilization or compliant disposal of the tail gas.

[0051] The specific workflow of the skid-mounted high-efficiency hydrogen extraction system based on membrane separation for hydrogenation purge gas provided by this invention is as follows: Feed pretreatment: The hydrogenation purge gas discharged from the hydrogenation unit first enters the feed pretreatment unit, and then undergoes gas-liquid separation, precision filtration, and pressure stabilization treatment in sequence to remove liquid impurities and solid particles, stabilize the feed conditions, and then the pretreated gas is transported to the membrane separation unit.

[0052] Multidimensional sensing and feedforward advance control: While the hydrogen purge gas enters the system, the multidimensional sensing module collects the composition, temperature and pressure parameters of the feed in real time and transmits them synchronously to the feedforward control module of the feedforward-cascade decoupled control subsystem; the feedforward control module calculates the optimal operating parameters in advance based on the membrane separation characteristic model and outputs temperature and opening adjustment signals.

[0053] Decoupling process: The decoupling module performs decoupling operations on the two regulation signals output from the feedforward, eliminates cross-coupling interference, and outputs independent control commands to the actuators of the feed heater and the back pressure valve to complete the advance regulation.

[0054] Hydrogen extraction via membrane separation: The pretreated gas is precisely heated by the feed heater and then enters the membrane module. Under the action of the osmotic pressure difference on both sides of the membrane, hydrogen gas preferentially permeates through the membrane module, and high-purity hydrogen gas is enriched on the permeate side. Other components that do not permeate form retrieval tail gas on the retrieval side.

[0055] Cascade closed-loop calibration: The hydrogen purity detection element collects hydrogen purity data from the permeate side in real time and transmits it to the cascade control module. Based on the purity deviation, the cascade control module generates a fine-tuning calibration amount through an incremental PID algorithm, which is added to the temperature and opening adjustment parameters to perform closed-loop fine-tuning of the operating parameters of the membrane separation unit, ensuring that the hydrogen purity of the product is stable and meets the standards.

[0056] Product collection: High-purity hydrogen produced on the permeation side is transported to a hydrogen collection tank for storage and then transported downstream for use via a discharge valve; tail gas from the interception side is transported to a tail gas collection tank and then transported to the subsequent pipeline network for treatment via a discharge valve.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A skid-mounted high-efficiency hydrogen extraction system for hydrogenation purge gas based on membrane separation, characterized in that, The system includes: a feed pretreatment unit, a membrane separation unit, a multi-dimensional sensing module, a feedforward-cascade decoupled control subsystem, and a product collection module; The feed pretreatment unit is used to pretreat the hydrogenated purge gas, remove impurities and adjust the initial state of the feed, and its output end is connected to the input end of the membrane separation unit. The membrane separation unit is used to separate hydrogen from other components in the hydrogenation purge gas. It is equipped with a feed heater at the feed end, a back pressure valve on the permeate side, and a hydrogen purity detection element at the permeate outlet. The multidimensional sensing module is deployed at the hydrogen purge gas inlet of the skid-mounted main body. It includes an online laser Raman gas component analyzer, a temperature sensor, and a pressure sensor, which work together to form a feedforward signal matrix for real-time detection of the component parameters, temperature parameters, and pressure parameters of the feed, and transmits the detection signals to the feedforward-cascade decoupled control subsystem. The feedforward-cascade decoupled control subsystem is used to receive the detection signal from the feedforward signal matrix, calculate the optimal operating point of the membrane separation unit in advance, decouple and adjust the temperature setpoint of the feed heater and the opening of the back pressure valve, and simultaneously receive the detection signal from the hydrogen purity detection element. Using the hydrogen purity on the permeate side as the cascade secondary loop, the system fine-tunes and corrects the adjustment effect. The product collection module is connected to the permeate side outlet and the retrieval side outlet of the membrane separation unit, respectively, and is used to collect the concentrated hydrogen product and the retrieval tail gas.

2. The skid-mounted high-efficiency hydrogen extraction system based on membrane separation for hydrogenation purge gas according to claim 1, characterized in that, The feedforward-cascade decoupling control subsystem includes a feedforward control module, a cascade control module, and a decoupling module. The feedforward control module is used to receive the detection signal from the multi-dimensional sensing module, calculate the optimal operating point in advance based on the preset membrane separation characteristic model, and output the feed heater temperature setting value adjustment signal and the back pressure valve opening adjustment signal. The decoupling module is used to decouple the two adjustment signals output by the feedforward control module to avoid mutual interference of adjustment actions; The cascade control module is used to receive the detection signal from the hydrogen purity detection element, compare the actual value of hydrogen purity on the permeation side with the preset target value, output a fine-tuning signal, and correct the adjustment parameters of the feed heater and the back pressure valve.

3. The skid-mounted high-efficiency hydrogen extraction system based on membrane separation for hydrogenation purge gas according to claim 2, characterized in that, The feedforward control module continuously receives feed hydrogen content, heavy hydrocarbon content, feed temperature, and feed pressure signals transmitted from the laser Raman gas component online analyzer, temperature sensor, and pressure sensor. These signals are then synchronously input into a preset membrane separation characteristic model. This model is based on the inherent separation parameters of the membrane module and incorporates the correlation between the feed component ratio, feed temperature, and feed pressure on the hydrogen permeation rate and the critical temperature for heavy hydrocarbon condensation. Through mapping relationships, the optimal operating range of the membrane separation unit under the current feed condition is solved. This determines the target temperature rise value of the feed heater and the target opening degree of the back pressure valve to maintain a reasonable pressure difference across the membrane and prevent heavy hydrocarbon condensation. Finally, corresponding temperature setpoint adjustment signals and back pressure valve opening adjustment signals are generated, completing the output of advance control commands for the feed heater and back pressure valve.

4. The skid-mounted high-efficiency hydrogen extraction system based on membrane separation for hydrogenation purge gas according to claim 3, characterized in that, The feedforward control module solves for the optimal operating range of the membrane separation unit under the current feed state through a mapping relationship. Firstly, it uses a correction formula based on the critical temperature of heavy hydrocarbon condensation. First, calculate the correction value for the critical condensation temperature of heavy hydrocarbons under the current feed pressure and heavy hydrocarbon content; second, rely on the formula of the target temperature rise setpoint of the feed heater. The target temperature setpoint for the feed heater is determined, and a hydrogen content deviation correction term is introduced to balance hydrogen separation efficiency; thirdly, the membrane permeation side pressure is calculated using the formula... Derive the target pressure on the permeation side and combine it with the back pressure valve opening mapping formula. Solve for the target opening degree of the back pressure valve, where, This is the correction value for the critical condensation temperature of heavy hydrocarbons under the current feed conditions. It is the basic condensation critical temperature of heavy hydrocarbons under standard atmospheric pressure. It is a pressure correction factor, obtained by fitting the pressure-condensation temperature correlation curve provided by the membrane module manufacturer. It is the actual feed pressure, which is collected in real time by a pressure sensor; It is standard atmospheric pressure. This is a correction factor for heavy hydrocarbon content, calibrated based on on-site process tests. It is the volume fraction of heavy hydrocarbons in the feed, which is detected in real time by an online laser Raman gas component analyzer. This is the target temperature rise setting value for the feed heater; This is a safety temperature margin, a temperature allowance reserved to prevent the condensation of heavy hydrocarbons. It is the hydrogen content deviation correction coefficient, used to fine-tune the heating temperature according to the deviation between the actual hydrogen content and the target value; This is the target value for the integral number of the feed hydrogen gas; It is the actual hydrogen gas integral of the feed, which is detected in real time by an online laser Raman gas composition analyzer. It is the target pressure on the membrane permeation side, a core pressure parameter for maintaining the driving force of hydrogen permeation; It is the basic ratio coefficient of feed pressure - permeation side pressure. It is the correction factor for the heavy hydrocarbon content relative to the pressure ratio. It is the optimal operating pressure difference across the membrane; It is the target opening degree of the back pressure valve. It is the back pressure valve opening adjustment coefficient; This is the membrane permeate side pressure setpoint; It is the basic opening degree of the back pressure valve.

5. The skid-mounted high-efficiency hydrogen extraction system based on membrane separation for hydrogenation purge gas according to claim 2, characterized in that, The decoupling module receives the feed heater temperature setpoint adjustment signal and the back pressure valve opening adjustment signal from the feedforward control module in real time. Combining the temperature-pressure coupling characteristics of the membrane separation unit, it constructs a two-variable decoupling correlation matrix using a fuzzy decoupling algorithm based on on-site operating conditions, calculates the cross-coupling gain between the two adjustment signals, and cancels in real time the interference component of temperature regulation on the pressure difference across the membrane and the influence component of pressure regulation on the stability of the feed temperature. Then, the purified adjustment signal after decoupling is output to the feed heater temperature control actuator and the back pressure valve pneumatic actuator, respectively, so that the two adjustment actions are executed independently and accurately, thereby ensuring the stable control of the operating parameters of the membrane separation unit.

6. The skid-mounted high-efficiency hydrogen extraction system based on membrane separation for hydrogenation purge gas according to claim 5, characterized in that, The specific steps of constructing a bivariate decoupling correlation matrix using a fuzzy decoupling algorithm based on on-site operating condition calibration in the decoupling module are as follows: Full-range calibration tests are conducted at the hydrogen extraction site under different feed components, pressures, and temperatures. Coupled response data of the feed heater temperature regulation and back pressure valve opening regulation are collected. Based on this, a temperature-opening bivariate fuzzy membership function is constructed. Then, using the influence coefficient of membrane separation unit temperature regulation on permeate-side pressure and the disturbance coefficient of opening regulation on feed temperature as core parameters, a bivariate decoupling correlation matrix is ​​established. After receiving the temperature regulation signal and opening regulation signal output by the feedforward control module in real time, the cross-coupling components of the two signals are quickly solved through matrix operations. Pressure disturbance components caused by temperature regulation and temperature disturbance components caused by opening regulation are simultaneously eliminated. Then, amplitude and rate corrections are performed on the two signals according to the dynamic response characteristics of the membrane module. Finally, independent control commands without interactive interference are output and sent to the feed heater and back pressure valve actuators, respectively.

7. The skid-mounted high-efficiency hydrogen extraction system based on membrane separation for hydrogenation purge gas according to claim 3, characterized in that, The cascade control module uses the hydrogen purity on the permeate side as the control parameter. It receives the actual hydrogen purity value on the permeate side from the hydrogen purity detection element in real time. It calculates the difference between the actual value and the preset hydrogen purity target value to obtain the purity deviation signal. After processing by an incremental PID control algorithm, it generates a corresponding purity correction fine-tuning amount. This fine-tuning amount is then synchronously superimposed on the feed heater temperature setting and back pressure valve opening adjustment parameters processed by the decoupling module to form a closed-loop fine-tuning correction. When the actual hydrogen purity value is detected to be lower than the preset target value, the feed heater temperature setting is increased and the back pressure valve opening is increased to enhance the hydrogen permeate separation effect and quickly raise the purity. When the actual hydrogen purity value is higher than the preset target value, the heater temperature setting is decreased and the back pressure valve opening is reduced. Finally, a corrected and stable adjustment signal is output to correct the operating parameters of the membrane separation unit.

8. The skid-mounted high-efficiency hydrogen extraction system based on membrane separation for hydrogenation purge gas according to claim 7, characterized in that, The cascade control module performs calculations using an incremental PID control algorithm, the formula of which is: ,in, It is the first The hydrogen purity correction fine-tuning increments output in each control cycle correspond to the feed heater temperature rise fine-tuning amount and the back pressure valve opening fine-tuning amount, respectively. It is a proportionality coefficient. It is the integral coefficient. These are differential coefficients. It is the first Periodic hydrogen purity deviation, It is the first Periodic hydrogen purity deviation, It is the first Periodic hydrogen purity deviation.

9. The skid-mounted high-efficiency hydrogen extraction system based on membrane separation for hydrogenation purge gas according to claim 1, characterized in that, The feedforward-cascade decoupled control subsystem also includes a data storage module and an alarm module. The data storage module is used to store the detection data and adjustment parameters of the multi-dimensional sensing module, and the alarm module is used to issue an audible and visual alarm signal when the feed parameters exceed the preset range, the membrane separation unit malfunctions, or the hydrogen purity on the permeate side does not meet the standard.

10. The skid-mounted high-efficiency hydrogen extraction system based on membrane separation for hydrogenation purge gas according to claim 1, characterized in that, The product collection module includes a hydrogen collection tank and a tail gas collection tank. The hydrogen collection tank is connected to the permeate-side outlet of the membrane separation unit and is used to store concentrated hydrogen product. The tail gas collection tank is connected to the retrieval-side outlet of the membrane separation unit and is used to store retrieval tail gas. The hydrogen collection tank is equipped with a pressure monitoring element and a discharge valve, and the tail gas collection tank is equipped with a liquid level monitoring element and a discharge valve.

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