查看更多>>摘要：Hydrogen fuel cell vehicles (FCVs) have been considered an option for the future zero-emission transport sector. However, there are some safety concerns about FCVs in restricted environments. Risk analysis of possible fire scenarios is an efficient approach to identifying, evaluating, and mitigating the risk from hydrogen fire accidents. Computational fluid dynamics (CFD) simulations were conducted for a 102 m long tunnel to analyse the influence of multiple hydrogen fires having different heat release rates (HRR). The developed model was first validated against published data. A detailed computational analysis of multiple hydrogen fires was then conducted to understand the influence of HRR leakage area, ventilation velocity, the presence of sloping, and the sealing ratio of the tunnel. In the absence of inlet velocity, the high thermal zones are closer to the tunnel ceiling at the fire's location. With increasing the inlet air velocity, the overall ceiling temperature reduces, although the high-temperature zones are pushed further downstream. Increasing the leakage area enhances the HRR, and hence the impact of the heat feedback mechanism becomes more significant since larger HRRs account for higher temperatures, strong flame interactions, and low oxygen concentrations. The results show that the higher sealing ratio of the tunnel leads to an increase in the peak ceiling temperatures. It is also observed that the presence of sloping increases the severity of fires as high-temperature zones and oxygen deficiency is observed at the higher locations of the tunnel from ground level.
查看更多>>摘要：Black carbon (BC) has a large specific surface area and abundant surface functional groups, so it is traditionally regarded as an adsorbent and a metal catalyst carrier. In addition to this, it has recently been found that a variety of BCs can also be used as a metal-free catalyst to mediate the transformation and degradation of specific organic pollutants at room temperature. This paper reviews the recent findings and current developments of the mediating roles of BC in both chemical and microbial degradation of organic pollutants, including azo dyes, nitroaromatic compounds and halogenated hydrocarbons. It starts with a brief overview of the source, properties and sorption characteristics of BC and focuses on the mediating effects and mechanisms of various BCs (such as activated carbon, chars, graphite), as well as types of surface-modified carbon materials, on the transformation and degradation of organic pollutants. Moreover, it also introduces the research on engineered carbon-based nanomaterials (i.e., carbon nanotubes and graphene), which have similar physical and chemical characteristics, for reference. Finally, the application prospects of using BC as a metal-free catalyst to mediate the transformation and degradation of organic pollutants are discussed to provide a reference and expand new ideas for further research in this field.
查看更多>>摘要：Combustible dusts deposited on ground or surfaces present a fire hazard to process industries. It was found that flame spread on an upwardly inclined surface was significantly faster than on a horizontal surface. However, hazard during downward inclined fire spread has been underestimated for dust layers having melting capability. In this paper, the effects of melting fluidity, sample inclination angle, and layer thickness on the fire hazard of four melting dusts were investigated. For sulfur with its excellent melting fluidity, dust layer inclination at a small angle can significantly increase downward flame spread velocity (FSV). For anthraquinone having a moderate melting fluidity, upward or downward dust layer inclination significantly increased FSV. For polystyrene and magnesium having weak melting fluidity, dust layer inclination angle had relatively little effect on flame propagation. Increasing thickness of dust layers significantly enhanced the promotion effect of the inclination angle on the flow of molten material, which in turn affected FSV. As a result, melting fluidity coupled with a large inclination angle and high layer thickness would significantly enhance dust layer fire hazard. These findings should be taken into consideration wherever powders having melting capability are encountered in process industries or in certain public activities.
查看更多>>摘要：Cefradine is a broad-spectrum antibiotic employed in humans to resist bacterial infection. A large amount of cefradine was not fully utilized, which caused harm to aquatic life and aquatic environment. Herein, the toxicity, degradation and metabolic pathway of cefradine to the two microalgal species (Chlorella sp. L166 and Scenedesmus quadricauda) were investigated. The results showed that both microalgae showed excellent degradation performance for cefradine. Chlorella sp. L166 and Scenedesmus quadricauda exposed to 5 mg/L reached the highest removal rates, which were 97.27% and 98.50%, respectively. Although high concentration of cefradine inhibited the growth of both microalgal species, both microalgae showed the capacity to restore growth in high concentration of cefradine. In addition, hydrolysis and biodegradation were regarded as the main mechanisms of cefradine degradation on algae. Seven by-products of cefradine metabolism were identified by HPLC-MS and three metabolic pathways of cefradine in medium were revealed, including decarboxylation, demethylation, hydrolysis, side chain breaking and oxidation processes. These results provide a better understanding of the environmental risks of cefradine in wastewater and the efficient removal of cefradine in wastewater by microalgae.
查看更多>>摘要：The tremendous amount of ash produced from coal-fired power plants must be disposed and utilized in an economically and environmentally sustainable manner. This paper conducted a study on the beneficiation of silo ashes and the risk assessment for land use. Silo ash samples were collected from six Chinese power plants and segregated into five size fractions by a combination of sieving and air classification. The concentration distributions of nine hazardous elements (i.e., As, Cd, Cr, Cu, Hg, Ni, Pb, Se, and Zn) were characterized. The results show that the particle size distributions of hazardous elements in the silo ashes do not exactly agree with the generally accepted models of their release and partitioning in the boiler. Environmental risks were assessed for agricultural and development land use of coal ash, according to related Chinese standards. The results suggest that all the bulk ashes meet the requirements for development land use. Beneficially, for some coal ashes, the coarse fraction (>10 um) can be applied to agricultural land while the remaining fraction (< 10 um) still complies with the standard for development land use. This work demonstrates that a simple air classification is potentially an eco-friendly and value-added approach for the full utilization of coal ash.
查看更多>>摘要：A promising technology has been proposed for the remediation of lead-contaminated soil by using diluted deep eutectic solvents (DESs) in this research. The DESs were synthesized by mixing choline chloride with ethylene glycol, urea, propylene glycol, glycerin and malonic acid. The experiment influences factors on the lead-contaminated soil remediation were investigated, and a response surface analysis was conducted. Scanning electron microscopy (SEM) and X-Ray diffraction (XRD) were applied to detect the mineral phase of contaminated soil before and after remediation. The changes of DESs dissolving lead nitrate (Pb(NO3)2) were analyzed by high resolution mass spectrometry (HRMS) and Fourier transform infrared spectroscopy (FT-IR). The results showed that up to 92.12% of lead could be removed from soil after washing 40 °C for 0.5 h. In the diluted choline chloride-malonate acid (Ch-M) solution, the carboxyl group and the hydrogen bond complex lead ions into complexes such as C3H2O3Pb, [PbChclCOOH] and [Ch-Pb]. Taking the remediation of one ton of lead-contaminated soil (14074.38 mg/Kg), it only costs $41.23 when the Pb removal rate reaches 92.12% using Ch-M as washing agent. This research provided an environmentally friendly and cost-effective remediation method for the lead-contaminated soil.
查看更多>>摘要：Municipal solid waste (MSW) is a persistent burden in many countries. The heterogeneous MSW characteristic requires a transition from the monotonous treatment strategy to a diversified low-carbon waste treatment configuration. Nevertheless, complex mathematical models hinder the policymakers from adopting scientific-based solutions in the decision-making process, and those models seldom link national greenhouse gas reduction targets to local waste policy targets. This study applies two approaches in constructing Carbon Emission Pinch Analysis to either optimize waste treatment system configurations while considering greenhouse gas reduction and waste policy targets or identify the maximum possible national greenhouse gas reduction based on a waste treatment system configuration. Among the seven types of waste treatment systems studied, the carbon emission factor of material recycling is the lowest (-0.19 t CO2-e/t MSW), whereas open landfill is the highest (0.72 t CO2-e/t MSW). The proposed ten waste treatment configurations indicate a 1.0-2.2% reduction of national greenhouse gas emissions, in which the best-case configuration (i.e., carbon sink scenario) contributes to 3.64% of the national electricity consumption in 2030. This study provides a compendious comparison of waste treatment systems integrated with greenhouse gas reduction and waste policy targets for a more circular MSW management in countries facing the waste disposal dilemma.
查看更多>>摘要：The risk assessment of hydrogen-based technologies is necessary in the coming of hydrogen economic society. At present, most studies are focused on the room-temperature hydrogen (about 300 K) and cryogenic hydrogen (30-80 K), Low-temperature (200-300 K) hydrogen storage method is another storage option of hydrogen energy due to its high hydrogen storage density and less energy loss during the cooling process, however, the dispersion characteristics and concentration distribution of unignited low-temperature hydrogen during its sudden release is still unknown. In this work, a series of hydrogen release tests are performed with storage pressure at 0.5 MPa, the dispersion characteristics of unignited low-temperature hydrogen under different temperatures (200 K, 250 K and 300 K) and pinhole nozzles (1.0 mm, 1.5 mm and 2.0 mm) are analyzed. It is found that the concentration on the axis of low-temperature hydrogen jet increases with the decrease of the temperature of the hydrogen and increase of the nozzle diameter. The inverse concentration distribution with various hydrogen temperatures and different nozzle diameters by the scaled distance is obtained. The distances to some key levels of hydrogen concentration such as flammable envelope and safe distances are evaluated and the extrapolation model to other jet conditions is proposed. The results can be available for the improvement of the hydrogen safety codes and standards of low-temperature hydrogen storage.
查看更多>>摘要：Industrial facilities can be severely affected by natural hazards (NHs) often resulting in significant social, environmental, and economic consequences. One of the most serious consequences of Natech's events is the accidental release of hazardous chemicals. While special attention has been paid to leakage prevention of toxic, flammable, or pollutant components to date, the possible effects in terms of green house gas (GHG) emissions have not been thoroughly investigated. NH can trigger, indeed, the release of high global warming potential (GWP) compounds such as fluorinated gases, nitrous oxides and others chemicals from collapsed components and/or structures. Nonetheless, conventional approaches to integrate NHs with LCA of buildings focus mostly on the embodied carbon metric, evaluated as in the Bill of Material procedure. As demonstrated by empirical evidence, these methods do not take into account the possible high-GWP compounds release in the case of extensive damage or collapse, which may lead to a general underestimation of the related carbon footprint. It is worth noticing that current international standards do not explicitly recommend the inclusion of these aspects in LCA procedures for structures. To cope with these issues, we introduce in this paper both the new concept of content release GHG emission potential (CGEP) and, a procedure, capable of integrating these effects with LCA. Finally, we provide some examples of industrial components characterized by a significant CGEP.
查看更多>>摘要：Lithium-ion battery is the main power source of electric vehicles and hybrid electric vehicles due to its excellent properties. However, battery suffers overcharging during its use because of inconsistency among batteries, malfunction of charge control and inappropriate battery management. The failure behaviour, mechanism and diagnosis of battery under slight overcharging cycling are studied in this work. The experimental results indicate that battery capacity is approximately zero after failure. The industrial computed tomography images indicate that the jelly roll is destroyed by internal short circuit. This is the reason of battery failure. Impedances of battery increase much. The results of energy dispersive spectrometer indicate the occurrence of Al3+ ions. It means that the aluminium current collector is corroded. Finally, incremental capacity analysis and resistance estimation can be used to diagnose jelly roll destruction and detect failure battery respectively.
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