The energy efficiency of different biogas systems, including single and co-digestion of multiple feedstock, different biogas utilization pathways, and waste-stream management strategies was ...evaluated. The input data were derived from assessment of existing biogas systems, present knowledge on anaerobic digestion process management and technologies for biogas system operating conditions in Germany. The energy balance was evaluated as Primary Energy Input to Output (PEIO) ratio, to assess the process energy efficiency, hence, the potential sustainability. Results indicate that the PEIO correspond to 10.5–64.0% and 34.1–55.0% for single feedstock digestion and feedstock co-digestion, respectively. Energy balance was assessed to be negative for feedstock transportation distances in excess of 22
km and 425
km for cattle manure and for Municipal Solid Waste, respectively, which defines the operational limits for respective feedstock transportation. Energy input was highly influenced by the characteristics of feedstock used. For example, agricultural waste, in most part, did not require pre-treatment. Energy crop feedstock required the respect cultivation energy inputs, and processing of industrial waste streams included energy-demanding pre-treatment processes to meet stipulated hygiene standards. Energy balance depended on biogas yield, the utilization efficiency, and energy value of intended fossil fuel substitution. For example, obtained results suggests that, whereas the upgrading of biogas to biomethane for injection into natural gas network potentially increased the primary energy input for biogas utilization by up to 100%; the energy efficiency of the biogas system improved by up to 65% when natural gas was substituted instead of electricity. It was also found that, system energy efficiency could be further enhanced by 5.1–6.1% through recovery of residual biogas from enclosed digestate storage units. Overall, this study provides bases for more detailed assessment of environmental compatibility of energy efficiency pathways in biogas production and utilization, including management of spent digestate.
Any variation in the processing parameters of selective laser melting fabrication could impact the performance of the final product. This study is concentrated on the effects of laser power and ...scanning speed alteration on the microstructure, transformation temperatures, texture, and shape memory response of Ni50.8Ti49.2. In this regard, multiple samples were systematically fabricated to demonstrate that careful selection of process parameters can lead to fabrication of parts with distinctive features and behaviors. The samples processed with low laser power showed significantly higher strain recovery and lower mechanical hysteresis compared to those processed with high laser power. It was demonstrated that the samples fabricated with same energy level, using a combination of different processing parameters each displayed unique responses. The sample fabricated with a laser power of 100 W and scanning speed of 125 mm/s exhibited almost perfect superelasticity with a recovery ratio of 96% and strain recovery of 5.77% in the first cycle. The corresponding stabilized superelastic response demonstrated full strain recovery of 5.5% after 10 cycles.
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Energy efficiency improvement policies have special significance for carbon emissions reduction and the mitigation of the effects of climate change. However the energy rebound effect caused by ...technological progress will indirectly increase energy consumption. The magnitude of the rebound effect largely determines the effectiveness of energy efficiency in mitigating energy consumption. This study reviews the main theory behind estimated methods of energy rebound effect measurement, focuses on constructing a double logarithm energy demand model and an error correction model of the asymmetric demand responses of electricity price changes to empirically analyse the direct rebound effect on residential electricity use in Beijing. It integrates consumer׳s demand theory with the embodied electricity of household spending from a seven-sector environmental energy-input–output (E-I-O) analysis to estimate the indirect rebound effect. The three income-elasticity, weight change, and proportional re-spending scenario simulation results show that: residential electricity use in Beijing exhibits a partial rebound effect, and the long-term direct and indirect rebound effects are 46% to 56%, and the short-term direct rebound effect is 24% to 37%. Finally, the direct and indirect energy rebound effect for various income groups needs further research. An appropriate policy mix should be adopted to mitigate effectively the rebound effect in China’s current lower energy price and lower energy efficiency market.
The ball-milling technology, a highly efficient and cost-effective method, had excellent application prospects for overcoming passivation issues of normal zero-valent iron (ZVI) to enhance the ...decontamination efficiency. In this work, we investigated the effects and mechanisms of pH, process control agents (PCA), and main process parameters on the removal of V5+ using ball-milled zero-valent iron (ZVIbm). The results showed that ZVI was successfully activated due to mechanochemical action. The enhanced proton conductivity of ZVIbm leaded to the rapid production of more Fe2+, thereby resulting in an order of magnitude higher elimination of V5+ by ZVIbm than by ZVI under near-neutral conditions. In addition, the introduction of NaCl in the ball milling process could not only effectively alleviate the agglomeration phenomenon of ZVIbm, but also effectively enhance its activity. Unexpectedly, due to over-compaction and small size effects, excessive energy input weakened the reactivity of ZVIbm on V5+ elimination. Various characterization results confirmed that the removal of V5+ by ZVIbm was dominated by reduction and supplemented by adsorption. This work updated the basic understanding of the critical effects of process parameters and NaCl on ZVIbm in the remediation of vanadium-containing wastewater.
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•ZVI is activated successfully by surface modification.•Two reaction stages exist in the V5 + elimination process.•Introduced NaCl alleviates the ZVIbm agglomeration.•Excessive energy input weakens the activity of ZVI.•The removal mechanism is based on reduction and absorption.
Growing international trade has not only positively affected the People’s Republic of China’s (China’s) economic development, but also expanded the exportation of energy embodied in goods during ...their production. This energy flow out will pose risks to China’s rational utilization of natural resources as well as environmental protection. In this paper, we evaluate the energy embodied in goods produced in China during 1992–2005 and use input–output structural decomposition analysis to identify five key factors causing the changes of energy embodied in exports. (Direct primary energy efficiency, primary energy consumption structure, structure of intermediate inputs, structure of exports, and scale of exports.) For the three sub-periods of 1992–1997, 1997–2002, and 2002–2005, results show that China is a net exporter of energy, and the energy embodied in exports tends to increase over time. The expanding total volume of exports and increasing exports of energy-intensive goods tend to enlarge the energy embodied in exports within all three sub-periods, but these driving forces were offset by a considerable improvement of energy efficiency and changes in primary energy consumption structure from 1992 to 2002 and the effects of structure of intermediate input only in the sub-period from 1992 to 1997. From 2002 to 2005, the sharp augmentation of energy embodied in exports was driven by all the five factors. Our research has practical implications for the Chinese economy. Results of this study suggest that the energy embodied in trade should receive special attentions in energy policies design to limit the energy resource out-flow and pollution generation.
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•Systematic investigation of dispersing conditions on Pickering emulsion properties.•Correlation of Sauter mean diameters with energy density and tip speed.•Pickering emulsion ...filtration at high dispersed phase fractions possible.•Strong membrane-particle-solvent interactions revealed.
Pickering emulsions (PE) are becoming of increasing interest for catalytic multiphase processes. Ultrafiltration of PE is a promising procedure for catalyst recovery to enable continuous processes. Dispersing conditions during production of PE are expected to significantly influence PE characteristics, and control of these properties is essential for robust process design. However, while the impact of PE composition has been studied before, knowledge on dispersing conditions is surprisingly scarce.
The influence of dispersing time, speed and emulsion volume during the preparation of PE with an UltraTurrax (2 dispersing tools) on the drop size distribution, rheology, stability and filtration was investigated.
In this first systematic study of PE preparation conditions, obtained Sauter mean diameters were correlated with energy density (R2 = 0.80), energy dissipation rate (R2 = 0.85) and tip speed (R2 = 0.86). All emulsions were stable for at least 10 weeks. With increasing tip speed (4–13 m/s), the dynamic viscosity first decreased, passed through a plateau value and then increased again. Filtration of concentrated PE was successful but strong membrane-particle-solvent interactions were revealed. This work contributes to a better understanding of PE properties that are essential for a sound application of PE in continuous multiphase catalysis.
Selective Laser Melting (SLM) is a powder bed based technology to fabricate metal parts through laser melting, it provides excellent mechanical properties and freedom. The authors study the influence ...of laser energy on spattering, the investigation analyzed the formation principle, appearance and compositions of spattering. Results indicate that as the laser energy input increases from 0.32×105W/cm3 to 1.30×105W/cm3, the intensity and the quantity of spattering increases, the metal liquid jetted out even reach to the height of 11cm. Major sources of spattering included three types, which were mainly caused by recoil pressure, Marangoni effect and heat effect in molten pool, these three different sources of spattering leading to three types of spattering morphology correspondingly. The solidified spattering particles have an average size of approximately 162μm, much larger than the original powder size of 32μm, and these spatter particles present various appearances. The compositions of spattering powers are almost the same as the original powders, but the contents of O, Si and C increase dramatically. The spattering particles are embedded into the surface and interior of the SLM-fabricated parts. These results are helpful in controlling the intensity of spattering, improving stability and repeatability of the SLM fabrication process.
Formation mechanisms of different types of spatter: (a) morphology of spherical splashing (type-I splashing); (c) morphology of coarse spherical morphology (type-II splashing); (d) morphology of irregular splashing (type-III splashing). Display omitted
•As the laser energy input increases from 0.32×105W/cm3 to 1.30×105W/cm3, the intensity and the quantity of spattering increases, the metal liquid jetted out and reached to the height of 11cm.•Spattering included three types mainly caused by recoil pressure, Marangoni effect and heat effect in molten pool, these three different sources of spattering leading to three types of spattering morphology correspondingly. The compositions of spattering powers are almost the same as the original powders, but the contents of O, Si and C increase dramatically.•Spattering particles have an average size of approximately 162µm compared with the original powder size of 32µm. The spattering particles are embedded into the surface and interior of the SLM-fabricated parts to deteriorate the finial fabricated parts.
In this study, traditional strongly endothermic anaerobic retorting (AR) and relatively novel self‐heating retorting (SHR) processes for oil shale (OS) were investigated and compared in detail. These ...studies mainly involve the structural and quantitative evolution of organic matters in OS during retorting, including varieties of crystallite parameters, carbon framework structure, amounts of various structural carbons and toxic polycyclic aromatic hydrocarbons, and so on. The obtained results well elucidate some reaction pathways in AR and SHR as well as certain differences between the two retorting processes. Moreover, based on our former work that verifies SHR greatly simplifies retorting operation by in situ generating heat to replace external heat carrier/provision, this study further demonstrates that SHR also alleviates the environmental effect of organic toxic residues as compared to AR. The present study provides some critical results not only for penetrating the reaction mechanism but also for assessing or controlling the environmental impact of both retorting processes.
Continuous melt granulation with a planetary roller granulator is a new continuous method based on the orbital motion of planetary spindles driven by a rotating central spindle in a surrounding ...roller cylinder. Here the configuration of the processing section is a central design aspect, which defines the processing conditions and process performance. In this study, the number of applied planetary spindles as part of the module configuration was varied.
As a result, a correlation between direct process parameters, processing conditions and process performance was identified. Hereby, the data normalization relativized successfully the effect of the module configuration. The results are also suitable to identify a module configuration and process settings in the context of a process optimization towards energy input efficiency or energy consumption. Finally, the accounting of the particle modification in terms of size was suitable to link the effect of the investigated parameters to the granulation regime.
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•Planetary roller melt granulation as new continuous method.•Fill level higher and hold-up nearly constant for lower free processing volume.•Normalization of mechanical and thermal energy input.•Energy input efficiency higher for lower specific feed load.•Adaption of granulation regime by process settings.
This paper presents a quantitative assessment of high‐latitude energy input and its partitioning in the polar cap by synthesizing various space and ground‐based observations during the 17 January ...2005 geomagnetic storm. It was found that Joule heating is the primary form of magnetospheric energy input, especially during active times when the hemispheric‐integrated Joule heating can be an order of magnitude larger than the hemispheric‐integrated auroral power. Most of magnetospheric energy is dissipated in the auroral zone rather than in the polar cap. On average, only about 22–25% of the total hemispheric energy input is dissipated into the polar cap region bordered by the convection reversal boundary (CRB) and the poleward auroral flux boundary (FXB). The impact of high‐latitude energy input was also investigated to unveil the causal relationship between Joule heating and the formation of polar cap mass density anomalies. Our numerical simulation demonstrated that thermosphere dynamics readily redistributes composition, temperature, and mass through upwelling and atmospheric gravity waves. The polar cap mass density anomalies observed by the CHAMP satellite during the storm were largely a result of large‐scale atmospheric gravity waves. Therefore, an increase in local thermospheric mass density does not necessarily mean there is direct energy input.
Key Points
The polar cap is not the primary location of high‐latitude energy input
Thermospheric mass density anomalies do not always coincide with direct local energy dissipation
Thermosphere dynamics redistributes mass globally through gradient‐wave adjustment
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