Energy storage is one of the most critical factors for maximising the availability of renewable energy systems while delivering firm capacity on an as- and when-required basis, thus improving the ...balance of grid energy. Chemical and calcium looping are two technologies, which are promising from both the point of view of minimising greenhouse gas emissions and because of their suitability for integrating with energy storage. A particularly promising route is to combine these technologies with solar heating, thus minimising the use of fossil fuels during the materials regeneration steps. For chemical looping, the development of mixed oxide carrier systems remains the highest impact research and development goal, and for calcium looping, minimising the decay in CO2 carrying capacity with natural sorbents appears to be the most economical option. In particular, sorbent stabilisers such as those based on Mg are particularly promising. In both cases, energy can be stored thermally as hot solids or chemically as unreacted materials, but there is a need to build suitable pilot plant demonstration units if the technology is to advance.
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•Calcium and chemical looping can potentially be deployed at commercial scale within the next two decades.•Both technologies have the potential for energy storage, either by means of sensible heat or as chemical energy.•A critical requirement for such development is construction and testing of suitable pilot and demonstration plants.•Both technologies can be combined with solar power to provide thermochemical energy storage.
•The economics of retrofitted sorption enhanced steam methane reforming is investigated.•The levelised cost of H2 ranges from £1.90–2.80/kg.•The cost of CO2 avoided ranges from £33-69/tonne CO2.•The ...results provide flexible options for blue and carbon-negative H2 production.
Hydrogen is an attractive energy carrier that will play a key role in future global energy transitions. This work investigates the techno-economic performance of six different sorption enhanced steam methane reforming (SE-SMR) configurations integrated with an indirect natural gas or biomass-fired calciner, oxy-fuel combustion and chemical-looping combustion for large-scale blue and carbon-negative hydrogen production. The techno-economic performance of the proposed cases was evaluated by their net efficiency, CO2 capture efficiency, levelised cost of hydrogen (LCOH), and costs of CO2 avoided and removal. A sensitivity analysis was also conducted to evaluate the key parameters and explore existing uncertainties that can affect the economic performance of the proposed SE-SMR processes. The results revealed that the proposed systems were comparable with conventional steam methane reforming (SMR) with carbon capture and storage (CCS). The LCOH of the proposed SE-SMR plants ranged from £1.90–2.80/kg, and the costs of CO2 avoided and removal ranged from £33-69/tonne and £58-107/tonne, respectively. By applying a carbon price (£16/tonne CO2), the costs of CO2 avoided and removal for the proposed SE-SMR processes could be significantly reduced. The results of cumulative discounted cash flow of SE-SMR plants at a hydrogen selling price of £3.00/kg indicated that all the investment of the proposed cases could be paid back after eight years, even if the carbon tax is zero.
Research from a variety of scientific fields suggests that physical activity in nature and feelings of connection to nature enhance psychological health and well-being. This study investigated the ...psychological health and well-being impact of the physical activity environment for those already undertaking the recommended weekly amount of physical activity. This topic is important for the design of health and well-being environments and interventions involving physical activity. Participants (
= 262) aged 18-71 years (
= 34.5,
= 13.1) who met the UK physical activity guidelines completed the Nature Relatedness Scale, the trait section of the State Trait Inventory for Cognitive and Somatic Anxiety and the Psychological Well-Being Scale. Analysis via Multivariate ANOVA indicated that participants who engaged in outdoor physical activity reported significantly lower somatic anxiety levels and higher Nature Relatedness experience (NRexp). Significant results were not evident for wellbeing. Hierarchical regressions revealed that the psychological well-being facet of autonomy, NRexp, and outdoor physical activity predicted lower somatic anxiety, whereas indoor physical activity predicted higher somatic anxiety. Results indicate that somatic anxiety is lower for outdoor physical activity participation, and that outdoor activity, in conjunction with autonomy and NRexp, predicts lower anxiety levels. The findings extend previous work by demonstrating the impact of the physical activity environment on anxiety levels, as well as the contribution of outdoor physical activity and well-being facets to the previously established Nature Relatedness-anxiety relationship.
Mental toughness (MT) is an umbrella term that entails positive psychological resources, which are crucial across a wide range of achievement contexts and in the domain of mental health. We ...systematically review empirical studies that explored the associations between the concept of MT and individual differences in learning, educational and work performance, psychological well-being, personality, and other psychological attributes. Studies that explored the genetic and environmental contributions to individual differences in MT are also reviewed. The findings suggest that MT is associated with various positive psychological traits, more efficient coping strategies and positive outcomes in education and mental health. Approximately 50% of the variation in MT can be accounted for by genetic factors. Furthermore, the associations between MT and psychological traits can be explained mainly by either common genetic or non-shared environmental factors. Taken together, our findings suggest a 'mental toughness advantage' with possible implications for developing interventions to facilitate achievement in a variety of settings.
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•Six retrofitted SE-SMR processes are simulated and investigated.•A sensitivity analysis and competitiveness study are conducted.•The results offer flexible options for blue H2 ...production scale up.•The integration of SE-SMR with PSA and CLC can achieve CO2-free, pure H2 production.
Clean and carbon-free hydrogen production is expected to play a vital role in future global energy transitions. In this work, six process arrangements for sorption enhanced steam methane reforming (SE-SMR) are proposed for blue H2 production: 1) SE-SMR with an air fired calciner, 2) SE-SMR with a Pressure Swing Adsorption (PSA) unit, 3) SE-SMR thermally coupled with Chemical-Looping Combustion (CLC), 4) SE-SMR+PSA+CLC, 5) SE-SMR+PSA with an oxy-fired calciner, 6) SE-SMR+PSA with an indirect H2 -fired calciner. The proposed process models with rigorous heat exchanger network design were simulated in Aspen Plus to understand the thermodynamic limitations in achieving the maximum CH4 conversion, H2 purity, CO2 capture efficiency, cold gas efficiency and net operating efficiency. A sensitivity study was also performed for changes in the reformer temperature, pressure, and steam to carbon (S/C) ratio to explore the optimal operating space for each case. The SE-SMR+PSA+H2 recycle process (Case 6) can achieve a maximum of 94.2% carbon capture with a trade-off in cold gas efficiency (51.3%), while a near 100% carbon capture with the maximum net efficiency of up to 76.3% is realisable by integrating CLC and PSA (Case 4) at 25 bar. Integration of oxy-fuel combustion lowers the net efficiency by 2.7% points due to the need for an air separation unit. In addition, the SE-SMR with the PSA_process can be designed as a self-sustaining process without any additional fuel required to meet the process heat utility when the S/C ratio is ~3–3.5.
The pyrolysis behaviors of three types of biomass (cellulose, sawdust and straw) in three cases (no catalyst, Ni-CaO-Ca2SiO4 and Ni-Ca2SiO4) were investigated by non-isothermal thermogravimetric ...analysis. The non-isothermal pyrolysis was implemented with four different heating rates: 20, 30, 40 and 50 °C/min and the yield rates of the produced gases were measured by TG-MS. For kinetic analysis, the activation energy was obtained using four isoconversional analysis methods (Flynn-Wall-Ozawa (FWO) method, Kissinger-Akahira-Sunose (KAS) method, Starink method, and the Miura distributed activation energy model (DAEM)). Ni-CaO-Ca2SiO4 and Ni-Ca2SiO4 was found to intensify the decomposition of biomass to produce more H2 and CO. The correlation R2, of all fitting lines in all cases, was above 0.9 which demonstrated that FWO, KAS, Starink methods and DAEM were suitable for calculating the activation energy of the biomass catalytic pyrolysis. Ni-CaO-Ca2SiO4 showed the obvious catalytic effects in the decrease of activation energy of biomass pyrolysis to produce additional H2 and CO from the breakage of light organic molecules.
•Ni-CaO-Ca2SiO4 and Ni-Ca2SiO4 enhanced the gas yields from biomass pyrolysis.•Isoconversional methods are suitable to describe kinetics of catalytic pyrolysis.•Activation energy from different methods showed similar trend with catalysis.•Ni-CaO-Ca2SiO4 significantly decreased activation energy of biomass pyrolysis.
Oil refineries are responsible for 4–6% of global CO2 emissions, and 20–35% of these emissions released from the regenerator of Fluid Catalytic Cracking (FCC) units, which are the essential units for ...the conversion of heavier petroleum residues (vacuum gas oil) into more valuable products. Chemical looping combustion (CLC) has been recently proposed to mitigate the CO2 emissions released from the regenerator of FCC units with a lower energy penalty. However, a detailed experimental and modelling investigation is still necessary in order to identify the hydrodynamics in the regenerator of chemical looping combustion integrated with fluidised catalytic cracking (CLC-FCC). A computational fluid dynamic (CFD) study was conducted to understand the hydrodynamic behaviours of gas-solid two-phase flow in the regenerator of the CLC-FCC unit, based on a three-dimensional multiphase model (Eulerian-Eulerian) with the kinetic theory of granular flow.
The results provide a useful insight into regenerator hydrodynamics, in terms of oxygen carrier modified FCC catalysts and FCC coke distribution profiles, in the regenerator of CLC-FCC. The conventional drag models (Syamlal-O'Brien and Gidaspow) predict a bed density profiles of a dense phase (250–300 kg/m3) at the dense phase (0–0.25 of h/H), and a dilution phase from h/H = 0.25 to 0.50 of regenerator. The bed density profile is indistinguishable from the industrial data provided for conventional FCC regenerators. The fluidisation gas (CO2) passes through the centre of the regenerator where the fluidisation gas splits the catalyst particles from the centre to the walls, to create a dilute particle phase in the centre and a dense particle-phase near the wall, which is one of the characteristic flow regimes in circulating fluidised bed reactors. The particles in the centre demonstrate an upward flow trend with a particle velocity above 3.0 m/s while the dense particles near the wall tend to go down with relatively low particle velocity of <0.5 m/s, which creates vortexes and a non-uniform particle distribution in the regenerator. The distribution of the fluidising gas provides better mixing of solid particles in the entrance and the optimisation of the superficial gas velocities (1.0 m/s) to create a distributed flow regime with developed vortexes through the dense and dilute phases. Furthermore, the laminar and turbulent flow models demonstrated no significant differences in terms of axial bed density profile in the regenerator of the CLC-FCC concept. These findings demonstrated that the hydrodynamics of catalysts in the CLC-FCC regenerator successfully predicted with CFD modelling and the prediction results aligned well with the conventional FCC regenerator.
•Predicted the hydrodynamics of catalysts in the novel CLC-FCC regenerator.•CLC-FCC regenerator demonstrated similar bed density profiles with conventional FCC.•Demonstrated the characteristic flow regimes in CLC-FCC regenerator.•Demonstrated the effects of gas distribution in CLC-FCC regenerator hydrodynamics.
•A NaNO2-promoted MgO for CO2 capture was prepared and characterized.•Doped NaNO2 induced significant quantities of hydroxide sites and carbonate species.•These desirablefeatures facilitated surface ...chemisorption processes.•The surface chemisorption process was not dependent on temperature.
Alkali metal nitrate-/nitrite-promoted MgO sorbents are promising candidates for intermediate-temperature (200–500 °C) CO2 capture. However, the structure-performance relationship and kinetic characteristics of NaNO2-promoted MgO remain unclear. Here the effects of physical-chemical properties on the CO2 sorption performance of NaNO2-promoted MgO and the sorption kinetics were comprehensively studied to elucidate the detailed role of NaNO2. Samples were characterized by X-ray diffraction, scanning electron microscopy, N2 adsorption, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The sorption kinetics were obtained by isothermal thermogravimetry and elucidated using a double exponential model. Compared with pure MgO and NaNO3-promoted MgO, NaNO2-modified MgO had a lower initial sorption temperature and a unique bimodal sorption characteristic. Characterization results revealed that such bimodal sorption was due to the presence of double promoters (mixture of NaNO2 and NaNO3) which implies that some of the nitrite was oxidized to nitrate during the preparation process. Deposition of double promoters further reduced the amounts of hydroxide and carbonate species for pure MgO while still preserving more hydroxide and carbonate species on the surface as compared with NaNO3-promoted MgO. The kinetics analysis demonstrated that the double exponential model can describe the sorption process well for both NaNO3- and NaNO2-promoted MgO, suggesting that the entire sorption occurs as a double process (surface chemisorption and product layer diffusion). Significant differences were seen from NaNO3-promoted MgO, and the surface chemisorption process of NaNO2-promoted MgO was independent of temperature, which suggests that an increased presence of hydroxide and carbonate species provides more active sites for greatly facilitating surface chemisorption.
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