In general, the post-combustion capture of CO2 is costly; however, swing adsorption processes can reduce these costs under certain conditions. This review highlights the issues related to ...adsorption-based processes for the capture of CO2 from flue gas. In particular, we consider studies that investigate CO2 adsorbents for vacuum swing or temperature swing adsorption processes. Zeolites, carbon molecular sieves, metal organic frameworks, microporous polymers, and amine-modified sorbents are relevant for such processes. The large-volume gas flows in the gas flue stacks of power plants limit the possibilities of using regular swing adsorption processes, whose cycles are relatively slow. The structuring of CO2 adsorbents is crucial for the rapid swing cycles needed to capture CO2 at large point sources. We review the literature on such structured CO2 adsorbents. Impurities may impact the function of the sorbents, and could affect the overall thermodynamics of power plants, when combined with carbon capture and storage. The heat integration of the adsorption-driven processes with the power plant is crucial in ensuring the economy of the capture of CO2, and impacts the design of both the adsorbents and the processes. The development of adsorbents with high capacity, high selectivity, rapid uptake, easy recycling, and suitable thermal and mechanical properties is a challenging task. These tasks call for interdisciplinary studies addressing this delicate optimization process, including integration with the overall thermodynamics of power plants.
Biogas is a biorenewable energy resource that has the potential to serve as a possible replacement for fossil fuels, especially natural gas and as a hydrogen carrier. However, raw biogas produced via ...anaerobic digestion process contains a large number of impurities such as hydrogen sulfide and carbon dioxide. Thus, upgradation and purification of the raw biogas by capturing CO2 before its application are necessary. In this regard, swing adsorption (pressure/vacuum/temperature/electrical) technologies have received considerable attention from the research community worldwide as compared to other techniques because of flexibility in operation, high auto-control degree, low energy consumption, and less capital investment. Thus, this review provides a detailed mechanistic insight into the effect of various factors such as type of adsorption technologies, different kinds of adsorbents, bed configuration, source and composition of the biogas, time cycle, and operating conditions on the efficiency of biogas purification process via pressure swing adsorption technologies. Moreover, an overview of the fundamentals of the pressure swing adsorption (PSA) process is provided by focussing on different innovative engineering approaches that contribute to the continuous improvement in process performance.
•Biogas enrichment technologies have been discussed.•Special attention has been given to the swing adsorption technologies.•A tutorial review on PSA isotherms, column dynamics, bed configuration.•Parameters affecting selection of adsorbent performance materials is highlighted.
•Novel hybrid zeolite-carbon monolith used in electrical and vacuum swing adsorption.•Improved carbon capture purity achieved.•Low electrical swing adsorption energy requirement.
Electrical swing ...adsorption (ESA) is an interesting cyclic adsorption technology which relies on rapid Joule heating of the adsorbent to liberate adsorbed molecules such as CO2. In this study we used a novel hybrid zeolite/activated carbon honeycomb to implement ESA and compared it to conventional vacuum swing adsorption (VSA) for CO2 capture. We then combined electrical and vacuum swing adsorption (VESA) to assess the merits of this dual regeneration technology for recovering CO2 from a 15% CO2/N2 gas stream at low pressure. With a simple VSA-only cycle, a CO2 downstream purity of only 17–23% was achievable when the desorption pressures varied from 30 to 10 kPa. This was primarily due to the adsorbent’s poor adsorption characteristics which provided little change in CO2 adsorption capacity over this pressure range. A CO2 product purity of 15–34% and a recovery of 29–78% was achieved with ESA as the electrification time was extended from 30 s to 180 s. The combined VESA process provided a CO2 purity of 33% and recovery of 72% with a short electrification time of 30 s at a mild desorption pressure of 10 kPa. Energy calculations indicate that the total specific energy for VESA was lower than ESA alone but still higher than VSA, although the latter suffered from low purity.
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•N-doped porous carbon (NPC) was fabricated via a novel one-step solvent-free melt polycondensation.•Potassium citrate served as both a template and an activator to create abundant ...microporous structure.•NPC delivered an excellent CO2 adsorption capability at 4.16 mmol·g−1 at 100 kPa.•NPC exhibited a fast adsorption kinetics and an outstanding uninterrupted recyclability.•The CO2 adsorption mechanism on NPC was ascribed to multi-layer adsorption by the micropore filling.
Heteroatomic doped porous carbon (HPCs) is a promising advanced material, showing great application potential in greenhouse gas capture. Here, in-situ N-doped porous carbon (NPC) was developed via a novel and readily scalable strategy − one-step solvent-free melt polycondensation assisted by organic potassium salts, followed by pyrolysis and activation. As both a template and an activator, the added C6H5K3O7 played an important role to create abundant microporous structure. The as-fabricated NPC-650–0.5 showed a rich N content (6.11 at.%), abundant narrow micro-porosity (0.3437 cm3·g−1), and a high surface area (1209.37 m2·g−1) and delivered an excellent CO2 static adsorption capacity (4.16 mmol·g−1 and 8.40 mmol·g−1 at 100 and 500 kPa), a fast adsorption kinetics (circa 98% of balance capacity in 12 min), moderate heat of adsorption (25 to 30 kJ/mol), high selectivity of CO2/N2, and outstanding uninterrupted recyclability. Both the narrow micropore volume and N-doping sites had strong effects on the CO2 adsorption capacity, indicating a physical and chemical adsorption process with the mechanism being multi-layer adsorption by the micropore filling. This work highlights the great potential of the NPC-650–0.5 for capturing CO2 and offers new insights into a green activator and a simple and easy-to-scale method for preparing HPCs.
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.
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•Simulation of a hydrogen purification.•Changes in pressure drop along the bed are estimated using the Ergun equation.•Using Activated carbon and Zeolite as adsorbent.
Modern compact and low power sensors and systems are leading towards increasingly integrated wearable systems. One key bottleneck of this technology is the power supply. The use of energy harvesting ...techniques offers a way of supplying sensor systems without the need for batteries and maintenance. In this work we present the development and characterization of two inductive energy harvesters which exploit different characteristics of the human gait. A multi-coil topology harvester is presented which uses the swing motion of the foot. The second device is a shock-type harvester which is excited into resonance upon heel strike. Both devices were modeled and designed with the key constraint of device height in mind, in order to facilitate the integration into the shoe sole. The devices were characterized under different motion speeds and with two test subjects on a treadmill. An average power output of up to 0.84 mW is achieved with the swing harvester. With a total device volume including the housing of 21 cm3 a power density of 40 W cm−3 results. The shock harvester generates an average power output of up to 4.13 mW. The power density amounts to 86 W cm−3 for the total device volume of 48 cm3. Difficulties and potential improvements are discussed briefly.
In this study, a novel enhanced anti-swing control method is proposed for underactuated overhead crane systems, which shows superior anti-swing control performance than most existing control methods. ...In particular, to increase the anti-swing control performance of overhead crane systems, an improved damping anti-swing signal is investigated based on a swing-related storage function. Subsequently, based on the anti-swing signal, a constructive Lyapunov function candidate is introduced and a new non-linear anti-swing control method is proposed straightforwardly, and the equilibrium point of the overall closed-loop system is proven to be asymptotically stable by Lyapunov techniques and LaSalle's invariance theorem. Some experimental results are provided to demonstrate the feasibility and effectiveness of the proposed control method. In addition, to illustrate the superior control performance of the proposed method, a comparison study between the designed control method and the existing control methods is provided as well.
The Artemis program has gathered further attention due to the transfer trajectories to the Moon and beyond. Trajectories such as weak stability boundary and ballistic lunar transfer are known as ...low-energy transfer toward the vicinity of the Moon. Among these categories, using the Moon swing-by contributes to the reduction of fuel consumption. In this study, we investigate trajectory design with the Moon swing-by as a constraint, and propose a methodology that projects swing-by parameters onto a conventional B–plane to facilitate the efficient analysis and design of post swing-by trajectories. This proposed approach not only enables a comprehensive understanding of all candidate solutions at each swing-by, but also provides flexibility in response to varied swing-by conditions. As illustrative examples, this paper demonstrates transfer problems to periodic orbits in the Earth–Moon system.
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