Pressure Swing Adsorption System Research Articles

Six-Tower Pressure Swing Adsorption Demonstration Animation

The Pressure Swing Adsorption (PSA) technique is a widely embraced automated method for gas separation within the industrial sector, prized for its operational simplicity and substantial economic benefits. In practice, the process typically involves the use of multiple towers to facilitate the completion of the PSA cycle. However, with the increasing number of towers in a PSA system, the intricacies of the cyclic process tend to amplify, posing challenges for novices attempting to grasp the mechanics of a six-tower PSA cycle. Utilizing animation can facilitate the process of comprehending these complex techniques by presenting them in a simplified and visually engaging format. Therefore, our research group has designed an animated depiction of a six-tower PSA device, predicated on the prototype established in our laboratory. This animation furnishes an inclusive demonstration of a complete cycle, encompassing twelve steps, pertaining to the operation of a six-tower PSA. It is our aspiration that this tool will prove advantageous for those who are embarking on the journey of understanding multi-tower PSA, as well as for seasoned professionals engaged in the field of pressure swing adsorption.

Minimum work associated with separating nitrogen from air: An exergy analysis

Background Nitrogen is essential for a variety of industries, including heat treatment, laser cutting, fire protection, and food packaging. Many companies in these industries obtain nitrogen via on-premises air separation processes. The three main processes for separating nitrogen from ambient air are cryogenic distillation, membrane separation, and pressure-swing adsorption (PSA). Improvements to these processes will likely focus on increasing efficiency, resulting in reduced environmental impact owing to less electrical power demand and opportunities for economic incentives. Regardless of the process utilized, a minimum theoretical amount of work input is required to obtain nitrogen gas at different pressures and concentrations compared to ambient conditions. Methods An equation was derived to evaluate the total exergy (including thermo-mechanical and chemical exergy) of product and exhaust mixtures resulting from air separation, indicating the minimum theoretical work input as a function of the product pressure, purity, and process recovery rate. This analysis considered an air separation system as a black box, with the input, output, and exhaust assumed to be ideal gas mixtures of nitrogen and oxygen at 15°C. The analysis applies to cryogenic distillation if the product and exhaust mixtures return to the gas phase. Results In general, the minimum required work input increases with product purity and recovery rate. Plots of minimum theoretical work versus product purity and recovery rate were made for two product pressures (atmospheric and 800 kPa) to show the behavior of the derived equation. Conclusions The analysis allows for direct efficiency (based on the second law of thermodynamics) comparisons between existing processes and future technological innovations in the field of air separation. Actual air separation systems have low efficiencies compared to ideal systems; actual PSA systems were estimated to have second law efficiencies of 5.5–11.2%. Therefore, there is great potential for improvements to current air separation systems.

Competitive multi-component bio-syngas separation for hydrogen production: breakthrough dynamics, thermal effects, and adsorbent stability analysis under practical operating conditions

The present work experimentally investigates the ability of zeolite 13X to purify H2 from a multi-component bio-syngas feed [composition (mol%): H2/CH4/CO/CO2 – 51.7/3.4/13.2/31.7] in a bench scale, glass wool insulated column simulating a near-industrial adiabatic environment. The column breakthrough dynamics and thermodynamic interactions are studied as a function of total pressure and feed flow rate. The adsorbent showed excellent separation characteristics with the highest affinity for CO2 followed by CO and CH4, and completely restricts their propagation for pure H2 production. The non-isothermal operation results in forming two distinct temperature fronts and manifests itself by broadening the mass transfer zone, decreasing loadings, and causing an early breakthrough of various adsorbates. The competitive adsorption is confirmed through the presence of roll-ups with a slowly moving CO2 concentration front displacing pre-adsorbed CH4 and CO over the duration of the experiment. Further, dynamic adsorption and desorption (sweep gas: He and CO2) experiments are respectively employed to measure competitive equilibrium loadings of heavy (CO2) and light components (CH4, CO). Additionally, the variation in breakthrough time, adsorbate propagation rate, column peak temperature, breakthrough and effective loading, and competitive selectivities are analyzed and discussed. Finally, a novel methodology to design H2 purification systems is proposed and put to practical use by developing and long duration (∼1500 cycles) testing a pilot scale (feed flow rate: 100 Nm3/h) vacuum pressure swing adsorption system. The cyclic separation unit while generating fuel-cell grade H2, displayed complete operational repeatability, with minimal deviation (<6 %) in adsorbent textural properties and crystalline structure.

Modeling and simulation of dynamic characteristics of a green ammonia synthesis system

Green ammonia production system driven by renewable electricity will be under frequent dynamic operation due to the fluctuation of renewable energy. The nonlinear dynamic model of a green ammonia synthesis system is developed and the dynamic responses of PEM (proton exchange membrane) electrolysis subsystem, PSA (Pressure swing adsorption) subsystem and ammonia synthesis subsystem during the start-up process and under the fluctuation of renewable electrical current are analyzed. The start-up dynamic results show that the hydrogen production rate of PEM electrolysis system is positively correlated to the current. The nitrogen output of PSA system is affected by the adsorption time, adsorption pressure, bed length, and air velocity. A start-up period of 300 min from the warmed-up state to the design state can maintain the temperature rise rate of the ammonia synthesis reactor at approximately 40 K/h. The dynamic results under step fluctuations of electrical current show that the PEM electrolysis subsystem and the PSA subsystem response fast compared to the ammonia synthesis reactor and buffer tanks. Using large buffer tanks to smooth the fluctuation allows the system to slide with the variation of renewable current to some extent, resulting in a higher outlet ammonia fraction when the current increases. Different volume ratios of the hydrogen tank to the nitrogen tank volume can lead to different variations of the hydrogen/nitrogen ratio. PID controllers can effectively maintain the bed temperatures, hydrogen/nitrogen ratio, and pressure of the ammonia synthesis reactor at their set points despite fluctuations in renewable electrical current. Buffer tanks are necessary to compensate for the imbalance between the flow rate fluctuation caused by current change and the flow rate regulation caused by PID controllers.

Optimized hydrogen purification for fuel cell quality from quinary coke oven gas via layered pressure swing adsorption under non-isothermal conditions

Coke oven gas from steel industries offers a valuable hydrogen rich fuel but is accompanied by impurities, such as CH4 and CO2, that contribute to the environmental footprint. The process of extracting H2 from coke oven gas not only provides clean energy from the alternative source, but also prevents the release of these impurities. Motivated by the promising H2 source alternative, a 2-bed, 6-step pressure swing adsorption system operating under non-isothermal conditions was used to purify H2 from coke oven gas. A validated multi-component adsorption model was developed via Aspen Adsorption to simulate and optimize the process. The validated model revealed strong correlations between the factors (adsorption pressure, adsorption temperature, adsorption time, and H2 concentration) and responses (purity and recovery of H2). The findings indicated that increasing the H2 feed concentration resulted in an improvement in H2 purity but a decline in recovery. Conversely, an extended duration of adsorption exhibited an adverse influence on both the purity and recovery of H2. Furthermore, the study indicates that higher adsorption pressure and temperature were correlated with lower H2 purity but improved recovery performance. To optimize the pressure swing adsorption process, the desirability function was applied within the response surface methodology model, enabling the determination of optimal conditions for the purification process. The optimized H2 purity and recovery were found to be 99.995% and 62.758%, respectively, at H2 feed concentration of 49%, adsorption time of 160 s, pressure of 6 atm, and adsorption temperature of 293 K.

Research on Pure Hydrogen Production Using a Fuel-Processing System Combined with a PSA System

Research was conducted to improve the system efficiency of a fuel-processing system combined with a hydrogen-purification system to supply hydrogen to a 10 kW residential building proton-exchange membrane fuel cell (PEMFC). The system consists of a steam-reforming reactor, a water–gas shift reactor, heat exchangers and a pressure swing adsorption (PSA) system, increasing the purity of the produced hydrogen by over 99.97%. Aspen Plus® and Aspen adsorption® simulators were used to optimize operating conditions by calculating thermal efficiency and hydrogen-production yield under various temperature and pressure conditions in the reformer. To optimize the hydrogen-production system, simulations were performed under conditions of 1 to 10 atm and 600 to 1000 °C, and simulations were also performed while maintaining the PSA pressure at 9 atm. The overall system efficiency was expressed as a function of methane conversion, and the methane conversion was expressed as a function of reformer temperature and pressure. The fuel-processing system showed the highest thermal efficiency of 82.40% at a pressure of 1 atm and a temperature range of 800 °C. For the combined system of a fuel-processing system and a hydrogen-purification system, the highest hydrogen-production yield was 43.17% at 800 °C and 1 atm.

Adaptive digital twin for pressure swing adsorption systems: Integrating a novel feedback tracking system, online learning and uncertainty assessment for enhanced performance

This paper presents a novel approach to digitizing and modeling pressure swing adsorption (PSA) processes using an uncertainty-aware digital twin. PSA modeling presents unique challenges due to its complex and cyclic behavior, which lacks a steady state. By contributing to the literature on periodic systems, we provide valuable insights into the potential applications of artificial intelligence and digital twins beyond the field of cyclic processes. Our proposed methodology can enhance the understanding and optimization of complex systems across various industries and applications. The proposed digital twin is uncertainty-aware and reliable, continuously updating itself through online learning and utilizing a novel feedback tracker to accurately represent the PSA system. This robust and adaptable methodology supports optimal PSA system operation and facilitates informed decision-making for enhanced process operation. The results demonstrate that the proposed approach yields a reliable digital twin for the PSA unit, capable of tracking the process’s complex dynamics and adapting to changes, including adsorbent degradation, which is a significant challenge in PSA operations. Overall, this work highlights the potential of advanced technologies, such as digital twins and artificial intelligence, to improve performance and efficiency in the field of process engineering. This work contributes to the ongoing efforts to optimize industrial processes and support sustainable development by providing a reliable and adaptable methodology for digitizing PSA processes.

Small-scale medical oxygen production unit using PSA technology: modeling and sensitivity analysis

This study presents a solid approach for small-scale medical oxygen production unit using pressure swing adsorption (PSA) technology. The objective of this research is to develop a mathematical model and conduct a sensitivity analysis to optimise the design and operating parameters of the PSA system. Based on the simulation results, an optimal set of operational parameter values has been obtained for the PSA beds. The result shows that the binary system produced oxygen with a purity of 94%, at the adsorption pressure 1 bar and temperature of 308K. The findings demonstrate the effectiveness of the proposed small-scale PSA system for medical oxygen production, highlighting the impact of key parameters and emphasising the need for careful optimisation. The findings serve as a guide for the design and operation of small-scale PSA systems, enabling healthcare facilities to produce their own medical oxygen, thereby improving accessibility and addressing critical shortages during emergencies. Future research may explore the integration of large scale PSA units in hospitals in Morocco.

Hydrogen production through agro-residue gasification and adsorptive separation

The present work reports on the characterization of mixed agro-residue pellets and their subsequent use for syngas generation in a laboratory-scale downdraft gasifier utilizing the mixture of oxygen and steam as the gasifying agent (equivalence ratio/steam to biomass ratio: 0.21/2.15). Pure hydrogen is realized in a vacuum pressure swing adsorption system using zeolite 13X adsorbent. Regarding pellets, the high ash content (11.46 ± 0.38 wt%) and the presence of inorganic elements (potassium, silicon, calcium) dictate gasification process level interventions. The key requirement established experimentally is maintaining the reactor temperature under 900 °C for a clinker-free operation. This prerequisite, accomplished through an optimized char-ash extraction rate, enables the consistent production of hydrogen-rich (42.2 ± 0.9 vol%) syngas with a lower heating value of 8.3 ± 0.2 MJ/Nm3 at a gross cold gas efficiency of 78.9%. The cyclic separation system operates at a pressure ratio of 7.5 and continually generates pure hydrogen with minimal contaminants. The oxy-steam gasification of high ash feedstock in a near-ambient fixed-bed reactor and its integration to a low-pressure swing adsorption system for practical multi-specie syngas separation with quality assessment of the produced hydrogen are the main novelty features.

Evaluation of ZIF-7 media for biogas upgrading into vehicular fuel quality standard by pressure swing adsorption through experiment and dynamic simulation under non-isothermal conditions

Biomethane (bioCH4) has gained increasing attention as a potential alternative to traditional fossil fuels due to its environmentally friendly and sustainable nature. An evaluation was carried out to determine the suitability of ZIF-7 as an adsorbent for capturing CO2 from a biogas mixture in pressure swing adsorption (PSA) under non-isothermal conditions. ZIF-7 was prepared and characterized using various analytical techniques such as SEM, BET, FTIR, XRD, TGA, particle size distribution, and TPD. Subsequently, a numerical model was created to effectively illustrate the dynamic behavior of the ZIF-7 adsorbent during methane enrichment. The development of the model took into account the characterization outcomes of ZIF-7, as well as the geometry of the adsorption bed, which was adjusted using the extended Langmuir model to consider multicomponent adsorption. Aspen Adsorption platform was utilized to perform a dynamic simulation, which was then corroborated against experimental breakthrough data of CH4 and CO2 loading over ZIF-7. The experiment and simulation results of biogas upgrading performed under comparable PSA operating conditions and bed dimensions to ensure consistency. Following this, the model was utilized to analyze the impact of specific parameters such as CH4 concentration, bed pressure, and outside wall temperature on the purity of the biomethane. The CCD and desirability property into Design of Experts platform were applied to analyze and optimize the interaction effects of the studied factors on the separation performance. According to the findings indicate that the PSA system and ZIF-media were capable of producing high-grade bioCH4 to meet the quality standard of a vehicle fuel with the most stringent emission regulation. The purity and recovery of the bioCH4 after the optimization from Aspen simulation were 99.96% and 96.5% at optimum conditions of 28 °C outside wall temperature, 2 bar adsorption pressure, and 60% initial CH4 content in the biogas feed stream with feed flowrate 55 mL/min.

Green route for biomethane and hydrogen production via integration of biogas upgrading using pressure swing adsorption and steam-methane reforming process

Biogas is a cornerstone within a clean and sustainable energy portfolio, while hydrogen production from biogas is a key enabler for methane conversion and carbon dioxide valorization for greenhouse gases emissions mitigation. In this work, pressure swing adsorption (PSA) configuration of two vessels-four adsorption beds connected in series was tested for upgrading low-grade biogas (50% CH4 and 50% CO2). To resolve CH4 spillage issue, steam-methane reforming (SMR) plant was proposed as a green route for converting CH4 and portion of CO2 in the waste stream of PSA system into hydrogen. The integrated system (PSA-SMR) was performed on two stages i.e., PSA runs were conducted experimentally in lab while SMR system was simulated using Aspen Hysys software under operating conditions from a real plant. Response surface methodology was applied into Design Expert software to optimize the effects of system pressure, CH4 concentration, and biogas/steam flowrate ratio on H2, CO2, H2O, and CO molar fractions in the product. The results revealed that four adsorption beds in serial configuration successfully recorded ultrapure CH4 of 99.9% and recovery of 84.9% along with average CO2 content of 60% in the waste stream. For SMR system, produced syngas comprised of 42.2% H2, 28.46% CO2, 13.84% N2, 8.88% H2O, and 6.66% CO with 100% conversion of the CH4 and about 52.56% conversion of the CO2. The optimum conditions that achieved the highest H2 content of 51% from SMR were system pressure below 32 bar, methane content in feed stream ≥61%, and biogas/steam ratio in the range of 0.41–0.66 to record H2.

Techno-economic analysis of methanol synthesis from syngas derived from steam reforming of crude glycerol

AbstractDue to the large amount of crude glycerol produced as a by-product by the biodiesel industry, alternative technologies for converting glycerol to value-added fuels such as syngas have been proposed. By employing four main processes, the syngas could further be used to produce methanol. The first process is steam reforming (STR) where the crude glycerol is converted into syngas. The next step is a three-unit pressure swing adsorption (PSA) system which is employed to condition the syngas into the required stoichiometric ratio. The final two process are the methanol synthesis and methanol purification processes. The effects of STR temperature, steam-to-glycerol ratio (SGR), methanol synthesis temperature and pressure were all investigated. The results obtained shows that 0.29 kgMeOH/kgCG can be obtained through this process at STR of 650 ℃, SGR of 9, and methanol synthesis temperature and pressure of 250 ℃ and 80 bar respectively. In addition, a methanol production plant capacity of 6.8 tonnes/hr of crude glycerol feed for a 20-year plant life was investigated. The result from the economic analysis carried out shows that production of methanol from glycerol is economically feasible with net present value (NPV), return on investment, (ROI), discounted payback period (DPBP) and net production cost (NPC) of $74.2 million, 17%, 4.59 years, and 85₵/kgMeOH respectively. The sensitivity analysis results show that the revenue from sales of methanol and byproducts (hydrogen and methane), the manufacturing cost, the cost of raw materials, as well as fixed capital investment (FCI) were the most sensitive economic parameters.

Modeling study on a two-stage hydrogen purification process of pressure swing adsorption and carbon monoxide selective methanation for proton exchange membrane fuel cells

A two-stage hydrogen purification process based on pressure swing adsorption (PSA) and CO selective methanation (CO-SMET) is proposed to meet the stringent requirements of H2-rich fuel for kW-scale skid-mounted or distributed proton exchange membrane fuel cell systems. The reforming gas is purified using dynamic adsorption model of PSA with activated carbon for initial purification and then kinetic model of CO-SMET with 50 wt% Ni/Al2O3 for CO deep removal. Sensitive analyses of the gas hourly space velocity, adsorption time and adsorption pressure etc. are studied. The results show that excellent H2 purity and CO concentration below 1000 ppm for the initial target using the three-bed and four-bed PSA system at shorter adsorption time and higher pressure, and then CO concentration below 10 ppm with H2 purity over 99.94% on CO-SMET. This work provides a small-scale and hydrogen-saving process for hydrogen purification can be achieved by the two-stage process.

The Production of Industrial-Grade Oxygen from Air by Pressure Swing Adsorption

Oxygen, an odorless and colorless gas constituent of the atmosphere, is a vital gas component for the Earth, as it makes up 21% of the composition of the air we breathe. Apart from the importance of oxygen for human breathing, its highly pure form is demanding for industrial applications. As such, several technologies have been established to increase the oxygen purity from 21% to somewhat higher than 95%. One of the competitive technologies for producing this high-purity oxygen from the air is through pressure swing adsorption (PSA), which has the advantages of low cost and energy while being highly efficient. Also, PSA is a simple and flexible system due to its ability to start up and shut down more rapidly since its operation occurs at ambient temperature, which is enabled through the use of adsorbents to bind and separate the air molecules. The enhancement of the PSA’s performances was reported through the modification of PSA step cycles and material (zeolite) tailoring. A simplified complete set of a mathematical model is included for modelling the PSA system, aiming to ease the experimental burden of the process design and optimization of an infinite modification of PSA step cycles. Finally, some technological importance of oxygen production via PSA, particularly for onboard oxygen generation system and oxy-enriched incineration of municipal solid waste, was discussed. Continuous development of PSA will make significant contributions to a wide range of chemical industries in the near future, be it for oxygen production or other gas separation applications.

Feature-based statistical process monitoring for pressure swing adsorption processes

Pressure swing adsorption (PSA) is a widely used technology to separate a gas product from impurities in a variety of fields. Due to the complexity of PSA operations, process and instrument faults can occur at different parts and/or steps of the process. Thus, effective process monitoring is critical for ensuring efficient and safe operations of PSA systems. However, multi-bed PSA processes present several major challenges to process monitoring. First, a PSA process is operated in a periodic or cyclic fashion and never reaches a steady state; Second, the duration of different operation cycles is dynamically controlled in response to various disturbances, which results in a wide range of normal operation trajectories. Third, there is limited data for process monitoring, and bed pressure is usually the only measured variable for process monitoring. These key characteristics of the PSA operation make process monitoring, especially early fault detection, significantly more challenging than that for a continuous process operated at a steady state. To address these challenges, we propose a feature-based statistical process monitoring (SPM) framework for PSA processes, namely feature space monitoring (FSM). Through feature engineering and feature selection, we show that FSM can naturally handle the key challenges in PSA process monitoring and achieve early detection of subtle faults from a wide range of normal operating conditions. The performance of FSM is compared to the conventional SPM methods using both simulated and real faults from an industrial PSA process. The results demonstrate FSM’s superior performance in fault detection and fault diagnosis compared to the traditional SPM methods. In particular, the robust monitoring performance from FSM is achieved without any data preprocessing, trajectory alignment or synchronization required by the conventional SPM methods.

Techno-economic analysis of PSA separation for hydrogen/natural gas mixtures at hydrogen refuelling stations

Logistics of hydrogen is one of the bottlenecks of a hydrogen economy. In this study, a pressure swing adsorption (PSA) system is proposed for the separation of hydrogen from natural gas, co-transported in the natural gas grid. The economic feasibility of hydrogen supplied by a PSA system at a refuelling station is assessed and compared with other alternatives. The adsorbent material is key to the design of a PSA system, which determines the operation performance and cost. It is concluded that a refuelling station with hydrogen supplied by a PSA system is economically feasible. The final hydrogen price including hydrogen supply, compression, storage, and dispensing is compared with two other hydrogen supply methods: on-site electrolysis and tube-trailer transported hydrogen. Currently, PSA supplied hydrogen is a more economical option. On-site electrolysis can become a more economical option in the future with improved cell efficiencies and reduced electricity prices. Tube-trailer transported hydrogen is highly influenced by the distance travelled. The findings of this study will help with more efficient distribution of hydrogen.

Oxygen separation via chemical looping of the perovskite oxide Sr0.8Ca0.2FeO3 in packed bed reactors for the production of nitrogen from air

A redox chemical looping process is investigated as an add-on deoxygenation unit for the production of high-purity nitrogen from air using pressure swing adsorption systems. A material screening study indicated the non-stoichiometric perovskite oxide Sr0.8Ca0.2FeO3−δ as a promising candidate redox material with fast kinetics and a 75% greater gravimetric oxygen capacity compared to state-of-the-art SrFeO3 at the desired process conditions. Granules of Sr0.8Ca0.2FeO3 were manufactured and characterised according to their thermodynamic and kinetic redox properties. A lab scale packed-bed reactor was experimentally tested as proof-of-concept and used to validate a convection–diffusion model of mass transfer within the reactor. The model was further applied for scaling up to a production of 1000 Nm3h−1 of high-purity nitrogen. The results indicate good performance of the packed-bed configuration and a favourable energy demand compared with existing nitrogen production technologies. The proposed technology could greatly extend the useable oxygen impurity range of pressure swing adsorption systems for nitrogen production.

Mass transfer approaches for CO2 separation in non-isothermal and non-adiabatic pressure swing adsorption system for biomethane upgrading

The mass transfer of CO2 over solid materials can be quite complex. The complexity arises as a result of the adsorbent’s complex surface morphology and dynamic process operating conditions. In this study, a new model was proposed to predict the mass transfer behavior of CO2 over silica gel in biogas upgrading process in which three mass transfer systems (lumped, micro-/macropore, and particle) were introduced. An overview for such mathematical models for CO2 mass transfer was conducted and then a new non-adiabatic and non-isothermal model for pressure swing adsorption (PSA) that is different from the existing models in the literature, i.e., adiabatic and isothermal models, was built and assessed. The new model was executed using Aspen Adsorption and validated using experimental data reported previously over silica gel bed. The validation was performed by comparing molar fractions of CH4 and CO2, temperature profile of silica gel bed, and bio-CH4 purity and recovery with previously reported experimental data. The particle mass transfer system, which estimated the adsorption rate and gas concentration profile in the adsorbent’s particle, recorded the highest bio-CH4 purity of 99.12%. Lumped approach, which comprised mass transfer resistances in one overall resistance and ignored the dispersion effect, recorded bio-CH4 purity of 97.63% followed by micro-/macropore, which accounted micro and macropore resistance individually, with purity of 84.65%. Particle mass transfer approach yielded the highest bio-CH4 recovery of 96.745%, followed by lumped (95.41077%), and micro/macropore (82.433%) systems. Particle mass transfer was one of the most realistic systems in predicting the CO2 diffusion over silica gel due to its comprehensive heat/mass transfer consideration along with its assumption of uniform pore structure that fitted well with the true nature of the microporous silica character.

Surrogate-assisted evolutionary multi-objective optimisation applied to a pressure swing adsorption system

The complexity of chemical plant systems (CPS) makes optimising their design and operation challenging tasks. This complexity also results in analytical and numerical simulation models of these systems having high computational costs. Research demonstrates the benefits of using machine learning models as surrogates or substitutes for these computationally expensive simulation models during CPS optimisation. This paper presents the results of our study, extending recent research into optimising chemical plant design and operation. The study explored the original surrogate-assisted genetic algorithms (SA-GA) in more complex variants of the plant design and operation optimisation problem. The more complex plant design variants include additional parallel and feedback components. The study also proposes a novel multivariate extension, surrogate-assisted NSGA (SA-NSGA), to the original univariate SA-GA algorithm. The study evaluated the SA-NSGA extension on the popular pressure swing adsorption (PSA) system. This paper outlines our extensive experimentation, comparing various meta-heuristic optimisation techniques and numerous machine learning models as surrogates. The results in both more complex plant design variants and the PSA case show the suitability of genetic algorithms combined with surrogate models as an optimisation framework for CPS design and operation in single and multi-objective scenarios. The analysis further confirms that combining a genetic algorithm framework with machine learning surrogate models as a substitute for long-running simulation models yields significant computational efficiency improvements, 1.7–1.84 times speedup for the increased complexity examples and a 2.7 times speedup for the pressure swing adsorption system. The discussion successfully concludes that surrogate-assisted evolutionary algorithms can be scaled to increasingly complex CPS with parallel and feedback components.

Site trials of methane capture from low-concentration coalbed methane drainage wells using a mobile skid-mounted vacuum pressure swing adsorption system

Coalbed methane (CBM) emissions account for a large part of methane (CH4) emission in the fossil energy area, and vacuum pressure swing adsorption (VPSA) is an effective method to recover low-concentration CBM. However, CBM supply can fluctuate in quality or quantity because of the constantly changing geological conditions, thus permanent large-scale factory mode is economically inappropriate. In this work, a highly integrated mobile skid-mounted prototype VPSA system was designed and installed, and site trials of low-concentration CH4 capture were, for the first time, carried out in a coal mine site of Huayang New Material Technology Group Co. Ltd in China. Site trials including breakthrough tests and VPSA experiments were conducted in a fluctuating range of CH4 (16–30%). The effects of flow rate, adsorption pressure, and feed concentration on the separation process were revealed using a breakthrough process, and their effects on the dynamic parameters were also analyzed. After purification, the CH4 content in product gas was increased from 16–30% to 43.3–70.7% which all meet the requirements of 4T grade city gas in China, and maximum CH4 productivity of 43.6 × 10−3 m3/(kg·h) can be achieved. More importantly, multicycle breakthrough tests demonstrated that superhydrophobic zeolite TUTJ-1 is more resistant to the effects of water and has more potential for capturing CH4 under humid conditions than activated carbon.