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Because of the fast heat transfer and the low pressure drop, the technology of moving-bed adsorption for carbon dioxide capture is gathering the momentum in the last decade. The primary aim of this paper is to investigate the influence of various parameters on the energy-efficiency performance of moving-bed adsorption for CO2 capture. The relevant parameters involve desorption temperature, desorption pressure, CO2 capture rate and CO(2 )mole fraction of flue gas. The energy efficiency assessment of moving bed is performed and compared in the light of the minimum separation work and the second-law efficiency. Moreover, two evaluation approaches, which are the thermodynamic carbon pump model and regeneration separation model, are employed and compared as well. Results indicate that the values of minimum separation work for CO(2 )capture by moving bed, which are calculated by regeneration separation model, are about 15% higher than those of thermodynamic carbon pump model under the same conditions. Furthermore, the second-law efficiencies of both models are approximately 10% under the given conditions. It is also found that the regeneration separation model is closer to real status owing to the additional consideration of the adsorption isotherm equilibrium data., QC 20210614

An open circuit voltage-based model for state-of-health estimation of lithium-ion batteries is proposed and validated in this work. It describes the open circuit voltage as a function of the state-of-charge by a polynomial of high degree, with a lumped thermal model to account for the effect of temperature. When applied for practical use, the model requires a prior learning from the initial charging or discharging data for the sake of parameter identification, using e.g. a nonlinear least squares method, but it is undemanding to implement. The study shows that the model is able to estimate the state-of-health of a LiFePO4 cell cycled under conditions where the temperature has fluctuated significantly with a relative error less than 0.45% at most. A short part of a constant current profile is enough for state-of-health estimation, and the effect of size and location of voltage window on the model's accuracy is also studied. In particular, the reason of accuracy change with different voltage windows is explained by incremental capacity analysis. Additionally, the versatility and flexibility of the model to different chemistries and cell designs are demonstrated., QC 20200303

CO2 adsorption capture, which could be driven by various forms of energy, has been widely studied in recent years due to the equipment is easy to control with low energy consumption required. However, the existing research on the energy-efficiency aspects of temperature/vacuum swing adsorption (TVSA) for CO2 capture are primarily focus on the quantification of input energy in specific cases. As a classical concept in thermodynamics, entropy has been widely applied in researches on the energy conversion process, which could benefit an in-depth understanding on the mechanism of "heatgeneralized chemical energy" conversion. However, an integrated thermodynamic research framework, which could clarify how to conduct a reasonable energy-consumption analysis of TVSA, has not been established yet. In this paper, a simplified thermodynamic cycle of 4-step TVSA was established, with the assumption of CO2 in adsorbed phase as loop fluid. With the application of the thermodynamic research framework proposed in this paper, the entropy analysis on the thermodynamic cycle was conducted. This study is concerned with application of thermodynamics concept to the CO2 adsorption engineering, which is mainly based on classical thermodynamics but also relying on adsorption physics to supply insight into the energy conversion and energy-efficient mechanism of TVSA technologies., QC 20190814

Carbon dioxide capture from the post-combustion flue gas via temperature swing adsorption is supposed to be a valid technology to mitigate carbon emissions. With regard to the adsorbent development and process improvement, the technologies of temperature swing adsorption for post-combustion carbon dioxide capture have been reviewed and compared in terms of fixed bed, fluidized bed and moving bed. A comprehensive evaluation framework of fixed-bed temperature swing adsorption for CO2 capture has been established. In a four-step fixed-bed cycle, a shortcut model has been utilized. Four typical adsorbent materials, such as activated carbon, zeolite 13X, zeolite NaUSY and Mg-MOF-74, have been chosen in this assessment. The comparative study has been conducted under the same operating conditions, from four aspects using eight performance indicators. Results indicate that Mg-MOF-74 and zeolite 13X reveal excellent performance among the four selected adsorbents. Thereinto, Mg-MOF-74 performs well at four indicators including purity, productivity, specific thermal energy consumption and second-law efficiency; zeolite 13X excels in the other four indicators such as selectivity, recovery, minimum separation work and capture cost. Future work will complete a thorough assessment criterion in evaluating the TSA process for CO2 capture., QC 20191127

As a huge reserve for potential energy, natural gas hydrates (NGHs) are attracting increasingly extra attentions, and a series of researches on gas recovery from NGHs sediments have been carried out. But the slow formation and dissociation kinetics of NGHs is a major bottleneck in the applications of NGHs technology. Previous studies have shown that nanobubbles, which formed from melt hydrates, have significant promotion effects on dissociation and reformation dynamics of gas hydrates. Nanobubbles can persist for a long time in liquids, disaccording with the standpoint of classical thermodynamic theories, thus they can participate in the hydrate process. Based on different types of hydrate systems (gas + water, gas +water +inhibitors/promoters, gas + water + hydrophilic/hydrophobic surface), the effects of nanobubble evolution on nucleation, dissociation, reformation process and "memory effect" of gas hydrates are discussed in this paper. Researches on the nanobubbles in hydrate process are also summarized and prospected in this study., QC 20190927

This paper presents a techno-economic study to seek the feasibility about the proposed system that integrating solar-assisted pressure-temperature swing adsorption (PTSA) into an 800MWe coal-fired power plant. Solar energy has the potential to supply thermal energy demand for carbon capture, which can avoid the energy consumption of the traditional method such as the steam extraction. The performance of the proposed system is largely affected by the climatic conditions and solar collector's types. The assessment criteria include carbon emission intensity (CEO, levelized cost of electricity (LCOE) and cost of CO2 avoidance (COA). By the parametric analysis, the results show that CEI of the novel system with solar thermal collectors is approximately 2g/kWh lower than that of the referenced power plant with CO2 adsorption capture. In addition, CEI of the novel system can be further decrease with the decline of desorption temperature, adsorption pressure and desorption pressure. For the sake of lower LCOE and COA, the prices of the power plant capacity, adsorbents and solar collectors should be reduced. Specifically, LCOE of the system with evacuated tube collector will be lower than that of the reference system with CO2 capture as the price of solar field is lower than 46.08 USD/m2., QC 20190315

Abrupt climate change such as the loss of Arctic sea-ice area urgently needs negative emissions technologies. The potential application of direct air capture of carbon dioxide from indoor air and outdoor air in closed buildings or crowded places has been discussed in this paper. From the aspects of carbon reduction and indoor comfort, the ventilation system integrating a capture device is of great value in practical use. For ultra-dilute carbon dioxide sources, many traditional separation processes have no cost advantages, but adsorption technologies such as temperature vacuum swing adsorption is one of suitable methods. Thermodynamic exploration has been investigated regarding minimum separation work and second-law efficiency at various concentrations in the air. The influence of concentration, adsorption temperature, desorption temperature and desorption pressure on the energy efficiency has also been evaluated. Results show that the minimum separation work for the level of 400 ppm is approximately 20 kJ/mol. The optimal second-law efficiencies are 44.57%, 37.55% and 31.60%, respectively for 3000 ppm, 2000 ppm and 1000 ppm. It means that a high energy-efficiency capture device in buildings merits attention in the exploration of the possibility of approaching negative carbon buildings., QC 20190403

Because of the ability to utilize the low-grade solar thermal energy for regeneration, a CO2 capture system characterized by solar-assisted pressure temperature swing adsorption (SOL-PTSA) is studied on the effects of adsorbent materials. A detailed cycle description is firstly presented within the diagram of adsorption isotherm for the energy-efficiency analysis. Typical adsorbent materials, including zeolites and chemical adsorbent, are assessed in terms of sensible heat and latent heat, etc. Then, the energy consumption and the second-law efficiency, which can be considered as lumped indicators from such material parameters, are chosen as performance indicators as well. The influence of separation temperature, desorption temperature, CO2 concentration and CO2 adsorption pressure on system performance are finally obtained. For the chosen three adsorbent materials, the energy consumption of SOL-PTSA system is at the range of 25.96-87.76 kJ/mol, and the corresponding second law efficiencies are at the range of 9.18-26.89%. The effect of adsorbent materials on the energy-efficiency of SOL-PTSA system mainly depends on specific heat, CO2 working capacity and cycle design. In addition, the integration options of solar energy into PTSA technology are also discussed from the standpoint of the utilization of solar grade heat due to two energy loads required for PTSA's operation., QC 20180801

This study explores the impacts of materials, such as adsorbents and electrodes, on the energy efficiency of a 4-step ESA cycle for CO2 capture. Three types of adsorbents including activated carbon honeycomb monolith (ACHM) and two hybrid adsorbents are compared, and two kinds of electrodes such as aluminum and brass are combined for comparative analysis. Process description of ESA cycle, including feed, electrification, electrification with purge and cooling, is presented via the adsorption isotherm diagram. By the theory of thermodynamic carbon pump, sensitivity analysis of cycle parameters is evaluated in terms of the second-law efficiency (Eff(2nd)) and the electrical heating efficiency (Eff(ele)). The results show that Eff(2nd) of the employed adsorbents is in the range of 1.17%-6.15%, and Effele of the selected electrodes is between 27.46% and 60.91%. Among the three adsorbents, Eff(2nd) of ACHM is the lowest one compared to the others. Similarly, Effele of the combination with brass is superior to that of the groups with aluminum. However, the actual efficiency of ESA cycle is the production of both Eff(2nd) and Eff(ele), which is approximately 1.03%-3.66%. Typical measures are proposed to reduce the heat loss of the adsorbents and electrodes as well for future work., QC 20180807