Vacuum Pressure Swing Adsorption Research Articles

Vacuum pressure swing adsorption intensification by machine learning: Hydrogen production from coke oven gas

Hydrogen is a vital resource in the fight against climate change, and it has the potential to revolutionize the energy sector. Our research focused on optimizing the production of high-purity hydrogen using coke oven gas (COG), a valuable hydrogen source in the steel industry. By leveraging advanced artificial neural networks (ANNs), we can predict the performance and exergy efficiency of a 6-bed 12-step vacuum pressure swing adsorption (VPSA) process accurately and efficiently. The Pareto fronts were addressed by combining the evolutionary algorithm with ANNs, and the effects of operating parameters were discussed in detail. Importantly, we found that our VPSA process can achieve a hydrogen purity of 99.99% with 45.2% exergy efficiency. We also demonstrated that using ANNs can significantly enhance VPSA process optimization, making it a valuable tool for extracting high-purity hydrogen from COG.

Upgrading of Biogas Generated from Shrimp Processing Effluent Using Vacuum Pressure Swing Adsorption

Upgrading of Biogas Generated from Shrimp Processing Effluent Using Vacuum Pressure Swing Adsorption

Plateau-Adapted Single-Pump, Single-Bed Vacuum Pressure Swing Adsorption Oxygen Generation Process Simulation and Optimization

To enhance the oxygen guarantee capacity in high altitude areas and address the challenges of traditional pressure swing adsorption oxygen generation fixed equipment with large volume and multiple device modules, a novel single-reversible-pump single-bed vacuum pressure swing adsorption (VPSA) oxygen generation process was proposed and simulated. This study investigated the effects of purge on oxygen productivity, purity, recovery, and energy consumption, determining that the optimum ratio of total oxygen in the purge gas to the total oxygen in the feed gas (P/F) was 0.176. A set of principle prototypes was developed and validated in plains. The process performance was then simulated and studied at altitudes of 3000 m, 4000 m, and 5000 m. Finally, the optimization was carried out by adjusting the product flow rate and feed flow rate, revealing that the best performance can be achieved when the oxygen purity exceeded 90% with lower energy consumption or larger productivity than the optimization goal. This study serves as a valuable reference for the optimization of the VPSA oxygen generation process in a plateau environment.

Multi-objective optimization of a hybrid carbon capture plant combining a Vacuum Pressure Swing Adsorption (VPSA) process with a Carbon Purification unit (CPU)

The imperative challenge posed by climate change requires urgent actions to counteract the harmful effects of greenhouse gas emissions, particularly CO2, which contributes to approximately 80 % of emissions responsible for global warming. A hybrid system combining Vacuum Pressure Swing Adsorption (VPSA) unit with a Cryogenic Carbon Purification Unit (CPU) is evaluated to enhance recovery and purity of CO2captured from flue gas containing CO2concentration ranging from 5 % to 20 %. VPSA preconcentrates the CO2and CPU completes the separation and purifies the CO2. The study uses surrogate models for multi-objective optimization, considering energy consumption, cost, and CO2recovery, providing a time-efficient approach for investigating computationally demanding processes. Results from the study indicate that the hybrid system achieves over 90 % recovery for flue gas concentration range considered, while ensuring the production of high-purity CO2(>99.99 %) suitable for transportation. A trade-off analysis reveals the balance between recovery, electricity consumption, and economic viability. A sensitivity analysis identifies parameters influencing recovery and energy consumption, providing guidance for future optimization efforts. The techno-economic analysis highlights the impact of electricity prices and carbon taxes on total costs, identifying an optimum towards higher recovery values under rising carbon taxes. Furthermore, the research underscores concentration-dependent economic feasibility, emphasizing the attractiveness of concentrations above 10 % compared other technologies, which require higher concentrations. For an electricity price of 75 €.MWh−1, the total cost of the CO2capture hydride system considering CO2emissions with carbon tax of 100 €.tCO2-1for concentrations ranging from 10 % to 20 % is from 123 to 80 €.tCO2-1, respectively. The analysis of the electricity source shows the importance of a low-carbon emission energy mix for optimal carbon emissions reduction.

Green Hydrogen Recovery from Natural Gas Grids by Vacuum Pressure Swing Adsorption

Green Hydrogen Recovery from Natural Gas Grids by Vacuum Pressure Swing Adsorption

Techno-economic analysis of vacuum pressure swing adsorption process for a sustainable upgrading of biogas

Vacuum pressure swing adsorption (VPSA) has demonstrated promising features for the upgrading of biogas to biomethane. In this study, a biogas upgrading plant, comprised of a hybrid of an N-column VPSA unit (2 ≤N ≤ 6) with a combined heat and power (CHP) engine, was developed and its techno-economic characteristics were assessed via a mathematical approach. Moreover, the techno economic analysis was used for the state-of-the-art VPSA configuration (a sophisticated configuration) and compared with the developed hybrid process. The prominent parameters including feedstock transport, biogas production, desulfurization, drying, upgrading, combustion, and grid injection were considered in the analyses of the plant for the upgrading capacity in the range of 100–6500 Nm3/h. Sensitivity analysis of the most influencing parameters, i.e., electricity price, gas price, and feed processing revenues, was conducted for the developed models. Beside comparing upgrading cost of the sophisticated VPSA with other upgrading technologies, a detailed comparison with the best available membrane unit for biogas upgrading was conducted. The limitations of adsorption process and VPSA in reducing the upgrading cost were also investigated. The results showed that in the absence of subsidies and requirements for CO2 capture, the hybrid plant outperforms the sophisticated VPSA units. Also, higher market price of natural gas or feedstock processing revenues were necessary in order to render the plant profitable. The results showed that, at flowrates larger than 175 Nm3/h, the sophisticated VPSA unit required a lower investment cost than the membrane unit for identical outputs. The results also show that even at the most idealistic conditions in the adsorption process, the upgrading is not economically favorable without subsidies. The findings of this study shed light on the importance of process design for biogas upgrading.

Optimization of hydrogen purification from biomass‐derived syngas via water gas shift reaction integrated with vacuum pressure swing adsorption for energy storage

AbstractBiomass is one of the promising sources to produce green H2, which can be considered an energy storage medium. To produce high‐purity H2 from biomass‐derived syngas, this study implemented a two‐stage H2 purification process. In the first stage, a water gas shift reaction (WGSR) was performed to enhance the H2 concentration in the syngas. The Taguchi method was employed to analyze the influence of the operating conditions and maximize the H2 concentration in the water gas shift reaction product. The results suggested that reaction temperature is a more dominant factor for enhancing the H2 concentration than the molar steam/carbon monoxide (S/CO) ratio. In the second stage, vacuum pressure swing adsorption was employed to obtain the high‐concentration H2 using the product from the water gas shift reaction having the optimum H2 concentration. Using the adsorption pressure as the primary parameter, it was found that high H2 purity and recovery could be obtained from vacuum pressure swing adsorption operated at low adsorption pressures. Based on this study's results, the vacuum pressure swing adsorption unit's best outcome occurs during an adsorption pressure of 2 kg·cm−2 and a flow rate of 17 L·min−1. Under these conditions, 93.61% H2 purity, 31.63% H2 recovery, 4.86 mol H2·(kgads·h)−1 productivity, and 448.14 kJ·(kg H2)−1 energy consumption are obtained.

High throughput screening of pure silica zeolites for CF4 capture from electronics industry gas.

The capture and separation of CF4 from CF4/N2 mixture gas is a crucial issue in the electronics industry, as CF4 is a commonly used etching gas and the ratio of CF4 to N2 directly affects process efficiency. Utilizing high-throughput computational screening techniques and grand canonical Monte Carlo (GCMC) simulations, we comprehensively screened and assessed 247 types of pure silicon zeolite materials to determine their adsorption and separation performance for CF4/N2 mixtures. Based on screening, the relationships between the structural parameters and adsorption and separation properties were meticulously investigated. Four indicators including adsorption selectivity, working capacity, adsorbent performance score (APS), and regenerability (R%) were used to evaluate the performance of adsorbents. Based on the evaluation, we selected the top three best-performing zeolite structures for vacuum swing adsorption (LEV, AWW and ESV) and pressure swing adsorption (AVL, ZON, and ERI) processes respectively. Also, we studied the preferable adsorption sites of CF4 and N2 in the selected zeolite structures through centroid density distributions at the molecule level. We expect the study may provide some valuable guidance for subsequent experimental investigations on adsorption and separation of CF4/N2.

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.

Design and assessment of a novel mobile carbon capture system: Energy and exergy analyses

In this work, we designed a mobile carbon capture (MCC) system that can effectively capture CO2 from the exhaust gas of diesel engines for applications in commercial vehicles. We present the results of energy and exergy analyses conducted on this system, which includes an energy recovery unit, a cooling unit, CO2 adsorption and desorption units, and a CO2 liquefaction unit. Three processes were considered to capture CO2: temperature vacuum swing adsorption (TVSA), vacuum pressure swing adsorption (VPSA), and vacuum swing adsorption (VSA). Energy is produced using turbines and generators, which supply the necessary power to run the MCC system, thus overcoming the limitation of mobile devices, i.e., lack of energy source. The energy requirement for each process was found to be in the order of VPSA > TVSA > VSA. In terms of specific energy consumption (SEC) and exergy efficiency, VSA was the most suitable process. As an MCC system, the VSA process consumes a small amount of energy in the designed system, and CO2 can be captured, liquefied, and stored by utilizing the energy contained in the exhaust gas. Because the TVSA process is expected to operate with less additional energy input, it can be used as an MCC system to improve the efficiency of each process unit. Our study can serve as a basis for advancing carbon capture technologies that can be implemented in commercial vehicles to reduce the greenhouse effect and help control global warming.

Development of hybrid surrogate model structures for design and optimization of CO2 capture processes: Part I. Vacuum pressure swing adsorption in a confined space

Design and optimization of CO2 capture processes have become a tremendously active area of research particularly in the past decade. In this context, development of intelligent techniques on the basis of first-principles models coupled with data-driven algorithms for such purpose looks very promising. In a series of works, we intend to present mechanism approaches in order to develop applicable structures for design and optimization of the CO2 capture processes of interest via hybrid models. A systematic method is presented for optimizing a process for capturing CO2 from a confined space through a Vacuum Pressure Swing Adsorption (VPSA) operation using a Hybrid Surrogate Model (HSM) and Non-dominated Sorting Genetic Algorithm (NSGA-III). The surrogate model is structured based on the VPSA process model offered in the Aspen Adsorption® environment and an artificial intelligence (AI) data-driven algorithm. The developed HSM is then used to predict the key process outputs including CO2 purity, air recovery ratio and energy consumption rate. Accordingly, the optimized parameters are re-substituted into the VPSA process simulator for further data processing. It is demonstrated that the proposed model architecture provides considerable computational efficiency for the process optimization with only 48 h to complete the corresponding evolutionary search, while the optimization time by the conventional NSGA-direct method is close to 1129 h. The optimization results also show that the CO2 purity changes from 1000 ppm to 399 ppm, the air recovery ratio remains at 93 %, and the energy consumption per unit product (ECP) decreases by 38.5 % to 99.7 kJ·Nm−3 air after an optimized air purification operation. The idea of chemical mechanism and industrial data twin modeling in this study holds substantial importance for the development of digital chemical twin systems and the process optimization of intelligent factory.

Comparative Evaluation of PSA, PVSA, and Twin PSA Processes for Biogas Upgrading: The Purity, Recovery, and Energy Consumption Dilemma

The current challenges of commercial cyclic adsorption processes for biogas upgrading are associated with either high energy consumption or low recovery. To address these challenges, this work evaluates the performance of a range of configurations for biogas separations, including pressure swing adsorption (PSA), pressure vacuum swing adsorption (PVSA), and twin double-bed PSA, by dynamic modelling. Moreover, a sensitivity analysis was performed to explore the effect of various operating conditions, including adsorption time, purge-to-feed ratio, biogas feed temperature, and vacuum level, on recovery and energy consumption. It was found that the required energy for a twin double-bed PSA to produce biomethane with 87% purity is 903 kJ/kg CH4 with 90% recovery, compared to 961 kJ/kg CH4 and 76% recovery for a PVSA process. With respect to minimum purity requirements, increasing product purity from 95.35 to 99.96% resulted in a 32% increase in energy demand and a 23% drop in recovery, illustrating the degree of loss in process efficiency and the costly trade-off to produce ultra-high-purity biomethane. It was concluded that in processes with moderate vacuum requirements (&gt;0.5 bar), a PVSA should be utilised when a high purity biomethane product is desirable. On the other hand, to minimise CH4 loss and enhance recovery, a twin double-bed PSA should be employed.

Optimization of hydrogen purification via vacuum pressure swing adsorption

An experimental study was performed for hydrogen purification using the vacuum pressure swing adsorption (VPSA) process, commonly adopted in gas mixture separation using hollow fiber materials. This study aimed to examine the effects of the operating pressure and the H2 concentration in the H2/CO2 mixture on the H2 purity (HP) and H2 recovery (HR). A design of experiment (DoE) based on central composite design (CCD) was adopted to develop the response of the experimental domain and determine the optimal operating conditions of the process. The highest HP and HR obtained were close to 99.99 % and 72.39 %, respectively. However, the two responses, HP and HR, cannot reach the maximum values simultaneously in their response surfaces; one should compromise on the other. HP increased, but HR decreased as the operating pressure and H2 concentration increased. With the operating pressure of 1 kg∙ cm−2 and H2 concentration of 50 %, optimum HP and HR were found to be 99.17 % and 32.03 %, respectively. Analysis of variance (ANOVA) revealed that the built quadratic models consisting of the primary and interaction terms predicted the acceptable results for HP and HR based on p-values and R2. In addition, beyond the principle of a larger F-value and a p-value less than 0.05, the H2 concentration was identified as a more significant factor than the operating pressure.

Air preoxidation and Fe-catalyzed cooperative effect for preparation of high-performance coal-based granular activated carbon: Enhancing low-concentration CH4 recovery and utilization

Low-cost and efficient recovery of low-concentration CH4 is important in enhancing energy utilization and mitigating climate issues. The primary objective of this study was to develop a novel coal-based granular activated carbon through an improved preparation process. By utilizing anthracite as a precursor and coal tar as a binder, the present investigation highlights the cooperative effects of air preoxidation and Fe catalysis on the development and regulation of the pore structure in activated carbon. The efficiency of the modified activated carbon in separating CH4/N2 was tested and compared to that of commercial activated carbon. The modified activated carbon ACAFe exhibited an equilibrium separation factor of 3.23 for CH4/N2 at 25 °C. At 25 °C and 400 kPa, a single-column vacuum pressure swing adsorption (VPSA) process enriched CH4 from 40 mol% to 53.49 mol% and provided a CH4 recovery rate of 76.39%. ACAFe also demonstrated excellent cyclic regenerability. In conclusion, the cooperative effect of air preoxidation and Fe catalysis is an operationally simple, cost-effective, and highly efficient process with considerable industrial potential for recovering and utilizing low-concentration methane from unconventional natural gas sources.

How Can (or Why Should) Process Engineering Aid the Screening and Discovery of Solid Sorbents for CO2 Capture?

ConspectusAdsorption using solid sorbents is emerging as a serious contender to amine-based liquid absorption for postcombustion CO2 capture. In the last 20+ years, significant efforts have been invested in developing adsorption processes for CO2 capture. In particular, significant efforts have been invested in developing new adsorbents for this application. These efforts have led to the generation of hundreds of thousands of (hypothetical and real) adsorbents, e.g., zeolites and metal-organic frameworks (MOFs). Identifying the right adsorbent for CO2 capture remains a challenging task. Most studies are focused on identifying adsorbents based on certain adsorption metrics. Recent studies have demonstrated that the performance of an adsorbent is intimately linked to the process in which it is deployed. Any meaningful screening should thus consider the complexity of the process. However, simulation and optimization of adsorption processes are computationally intensive, as they constitute the simultaneous propagation of heat and mass transfer fronts; the process is cyclic, and there are no straightforward design tools, thereby making large-scale process-informed screening of sorbents prohibitive.This Account discusses four papers that develop computational methods to incorporate process-based evaluation for both bottom-up (chemistry to engineering) screening problems and top-down (engineering to chemistry) inverse problems. We discuss the development of the machine-assisted adsorption process learning and emulation (MAPLE) framework, a surrogate model based on deep artificial neural networks (ANNs) that can predict process-level performance by considering both process and material inputs. The framework, which has been experimentally validated, allows for reliable, process-informed screening of large adsorbent databases. We then discuss how process engineering tools can be used beyond adsorbent screening, i.e., to estimate the practically achievable performance and cost limits of pressure vacuum swing adsorption (PVSA) processes should the ideal bespoke adsorbent be made. These studies show what conditions stand-alone PVSA processes are attractive and when they should not be considered. Finally, recent developments in physics-informed neural networks (PINNS) enable the rapid solution of complex partial differential equations, providing tools to potentially identify optimal cycle configurations. Ultimately, we provide areas where further developments are required and emphasize the need for strong collaborations between chemists and chemical engineers to move rapidly from discovery to field trials, as we do not have much time to fulfill commitments to net-zero targets.

Process modeling and optimization of vacuum pressure swing adsorption for ethane and ethylene separation using Cu(Qc)2 MOF

The separation of ethylene from ethane/ethylene mixtures is of prime significance, and replacing the energy-intensive cryogenic distillation used in the petrochemical industry is challenging. The aim of this study is to separate ethane and ethylene using a vacuum pressure swing adsorption (VPSA) process on a Cu(Qc)2 metal–organic framework (MOF) synthesized as a spheroidal adsorbent. To quantify the adsorption equilibrium, single isotherms of ethane and ethylene were measured at 283 and 298 K up to 5 bar. A Quadratic Langmuir adsorption model was employed to predict equilibrium adsorption. Dynamic adsorption experiments were conducted for a single-component and a binary mixture of different feed compositions and flow rates. The mass-transfer coefficients of ethane and ethylene were estimated to be 0.1 sec−1 and 1.0 sec−1, respectively. Based on these parameters, a two-bed, five-step VPSA mathematical model was developed, and the nominal operating conditions were determined from the length of the unused bed. It showed ethylene purity, recovery, and productivity of 99.68 mol%, 65.28%, and 1.84 mol/kg/hr. Sensitivity analyses of purity and recovery were performed using six critical operating variables. The time and rate of the rinse step had the most significant influence on the results, followed by those of the PU, AD and BLW steps. The particle swarm optimization methodology was applied to optimize the operating variables to maximize ethylene recovery. After optimization, the ethylene purity, recovery, and productivity were attained at 99.60 mol%, 76.57%, and 1.98 mol/kg/hr.

Thermodynamic modeling on multi-stage vacuum-pressure swing adsorption (VPSA) for direct air carbon capture with extreme dilute carbon dioxide

Thermodynamic modeling on multi-stage vacuum-pressure swing adsorption (VPSA) for direct air carbon capture with extreme dilute carbon dioxide

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.

Hydrogen production from low pressure coke oven gas by vacuum pressure swing adsorption

Hydrogen is a major component of coke oven gas (COG) and can be used in gas-based direct reduction iron processes to help the steel industry achieve the carbon peaking and carbon neutrality goals. However, the high compression power consumption is the main drawback of the current PSA cycle since the COG needs to be compressed from atmospheric pressure to ∼18 bar to achieve a hydrogen production with purity >99.9% and recovery < 85%. Here in this study, we experimentally demonstrate by using a 4-bed 12-step lab-scale VPSA rig filled with activated carbon RB3 and can obtain a hydrogen product with a purity of 99.67% and a recovery of 91.97% at a feed pressure of only 5.17 bar. We then constructed a non-isothermal non-adiabatic VPSA model using our in-house code and validated the model against experimental breakthrough and VPSA cycles. Parametric optimization produced a H2 product of 99.995% purity and 92.29% recovery at a slightly increased adsorption pressure of 6 bar and a vacuum pressure of 0.02 bar with 10.21 mol.H2/kg.ads/hr productivity and 7.09 kJ/mole.H2 specific power. We also confirmed that light product purge at vacuum pressure can effectively improve the H2 purity and the gas flow direction of the pressure equalization step has a significant effect on the mass transfer front. Our research presents the success of low-pressure hydrogen production from COG, which will greatly accelerate the transformation of COG utilization and promote the decarbonization of the iron and steel industry.

Purification of hydrogen as green energy with pressure-vacuum swing adsorption (PVSA) with a two-layers adsorption bed using activated carbon and zeolite as adsorbent

Today, hydrogen is produced in refineries and petrochemicals using the methane reforming process, followed by a water gas shift reaction stage. The hydrogen produced has a purity of approximately 75%, and is purified further through an adsorption process. In this project, the feasibility of achieving a purity level greater than 90% through the use of a more effective adsorbent and the periodic process of pressure vacuum swing adsorption (PVSA) with a double-layer bed of active carbon and zeolite will be investigated. The design, simulation, and optimization of the hydrogen purification unit will also be conducted. The results of this study indicate that the proposed process can achieve a purity level of up to 97% for the output hydrogen.