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661.
To explore the inhibitory effects of CF3I and CO2 gas on the explosion pressure and flame propagation characteristics of 9.5% methane, a spherical 20 L experimental explosion device was used to study the effect of the gas explosion suppressants on the maximum explosion pressure, maximum explosion pressure rise rate and flame propagation speed of methane. The results indicated that with a gradual increase in the volume fraction of the gas explosion suppressant, the maximum explosion pressure of methane and maximum explosion pressure rise rate gradually decreased, and the time taken to reach the maximum explosion pressure and maximum explosion pressure rise rate was gradually delayed. At the same time, the flame propagation speed gradually decreased. Additionally, the time taken for the flame to reach the edge of the window and the time taken for a crack as well as a cellular structure to appear on the flame surface was gradually delayed. The fluid dynamics uncertainty was suppressed. The explosion pressure and flame propagation processes were markedly suppressed, but the flame buoyancy instability was gradually enhanced. By comparing the effects of the two gas explosion suppressants on the pressure and flame propagation characteristics, it was found that at the same volume fraction, trifluoroiodomethane was significantly better than carbon dioxide in suppressing the explosion of methane. By comparing the reduction rates of the characteristic methane explosion parameters at a volume fraction of 9.5%, it was observed that the inhibitory effect of 4% trifluoroiodomethane on the maximum explosion pressure was approximately 4.6 times that of the same amount of carbon dioxide, and the inhibitory effect of 4% trifluoroiodomethane on the maximum explosion pressure rise rate and flame propagation speed was approximately 2.7 times that of the same amount of carbon dioxide. The addition of 0.5%–1.5% trifluoromethane to 4% and 8% carbon dioxide can improve the explosion suppression efficiency of carbon dioxide. This enhancing phenomenon is a comprehensive manifestation of the oxygen-decreasing effect of carbon dioxide and the trifluoroiodomethane-related endothermic effect and reduction in key free radicals. 相似文献
662.
Urban safety is significantly impacted by the complexity of urban gas accidents. Although China has put forward the goal of “zero fatalities in accidents” for urban gas, unfortunately, the root causes of the unsound safety culture and imperfect safety management system of urban gas enterprises remain unresolved. Therefore, statistical analysis and 24Model analysis of 160 urban gas accidents in mainland China were performed to investigate the proximate causes of the accidents and the current situation of urban gas safety. The CCPS's risk-based process safety elements were used to identify potential deficiencies in the current urban gas process safety management (UG-PSM). During the analysis, it was observed that insufficient implementation of concealed danger investigation and rectification accounted for 76%, which is the primary proximate cause of urban gas accidents. Stakeholder outreach is the most under-represented competency in urban gas safety management. Based on the results, a novel framework for the UG-PSM system was constructed, and the theory of urban gas safety management was further improved. Furthermore, we evaluated the matching degree between UG-PSM elements and the existing measures of the government, urban gas associations, third-party organizations, and urban gas enterprises. Finally, we analyzed the feasibility, challenges, and development directions of the UG-PSM system. This study establishes a foundation for researchers and practitioners in the future research and practice of urban gas process safety and provides theoretical guidance for preventing high-incidence accidents of urban gas in China. 相似文献
663.
The Biochemical Methane Potential (BMP) test is increasingly recognised as a tool for selecting and pricing biomass material for production of biogas. However, the results for the same substrate often differ between laboratories and much work to standardise such tests is still needed. In the current study, the effects from four environmental factors (i.e. ambient temperature and pressure, water vapour content and initial gas composition of the reactor headspace) on the degradation kinetics and the determined methane potential were evaluated with a 24 full factorial design. Four substrates, with different biodegradation profiles, were investigated and the ambient temperature was found to be the most significant contributor to errors in the methane potential. Concerning the kinetics of the process, the environmental factors’ impact on the calculated rate constants was negligible. The impact of the environmental factors on the kinetic parameters and methane potential from performing a BMP test at different geographical locations around the world was simulated by adjusting the data according to the ambient temperature and pressure of some chosen model sites. The largest effect on the methane potential was registered from tests performed at high altitudes due to a low ambient pressure. The results from this study illustrate the importance of considering the environmental factors’ influence on volumetric gas measurement in BMP tests. This is essential to achieve trustworthy and standardised results that can be used by researchers and end users from all over the world. 相似文献
664.
Many of the products of the reaction of naphthalene (Naph) with the OH radical in a reaction chamber were identified. Previously unidentified products included 1,2-naphthoquinone (NQ), oxygenated indenes and benzopyrones. Possible pathways for the formation of 1,2-NQ and 1,4-NQ are proposed. In the chamber reactions, more 1,2-NQ than 1,4-NQ partitioned to the particle phase. From this result we infer that, in the atmosphere, the percentage of 1,2-NQ in the particle phase should be greater than that for the 1,4-NQ. Because both of these compounds are considered to be toxic, and since they appear in both the gas and particle phases in the reaction chamber, and by implication in the atmosphere, it is considered important that both the gas and particle phases of these two compounds should be measured to assess their impact on human health. 相似文献
665.
The use of flat gas-permeable membranes was investigated as components of a new process to capture and recover ammonia (NH3) in poultry houses. This process includes the passage of gaseous NH3 through a microporous hydrophobic membrane, capture with a circulating dilute acid on the other side of the membrane, and production of a concentrated ammonium (NH4) salt. Bench- and pilot-scale prototype systems using flat expanded polytetrafluoroethylene (ePTFE) membranes and a sulfuric acid solution consistently reduced headspace NH3 concentrations from 70% to 97% and recovered 88% to 100% of the NH3 volatilized from poultry litter. The potential benefits of this technology include cleaner air inside poultry houses, reduced ventilation costs, and a concentrated liquid ammonium salt that can be used as a plant nutrient solution. 相似文献
666.
Schuhfried E Biasioli F Aprea E Cappellin L Soukoulis C Ferrigno A Märk TD Gasperi F 《Chemosphere》2011,83(3):311-317
Sulfides are known for their strong odor impact even at very low concentrations. Here, we report Henry’s law constants (HLCs) measured at the nanomolar concentration range in water for monosulfides (dimethylsulfide, ethylmethylsulfide, diethylsulfide, allylmethylsulfide) and disulfides (dimethyldisulfide, diethylsulfide, dipropylsulfide) using a dynamic stripping technique coupled to Proton Transfer Reaction-Mass Spectrometry (PTR-MS). The experimental data were compared with literature values and to vapor/solubility calculations and their consistency was confirmed employing the extra-thermodynamic enthalpy-entropy compensation effect. Our experimental data are compatible with reported literature values, and they are typically lower than averaged experimental literature values by about 10%. Critical comparison with other freely available models (modeled vapor/solubility; group and bond additivity methods; Linear Solvation Energy Relationship; SPARC) was performed to validate their applicability to monosulfides and disulfides. Evaluation of theoretical models reveals a large deviation from our measured values by up to four times (in units of M atm−1). Two group contribution models were adjusted in view of the new data, and HLCs for a list of sulfur compounds were calculated. Based on our findings we recommend the evaluation and adaption of theoretical models for monosulfides and disulfides to lower values of solubility and higher values of fugacity. 相似文献
667.
Adami G Cabras I Predonzani S Barbieri P Reisenhofer E 《Environmental monitoring and assessment》2007,125(1-3):291-299
Chromium, nickel, copper, zinc and cadmium were determined in sediments of the Niger Delta (Nigeria) in order to discriminate
between natural metal sources and anthropogenic ones. Surface sediments were collected at seven sites along a new gas pipeline
near Port Harcourt, between the New Calabar River and the Bonny River towards Bonny town. Chemical characterisation is obtained
by hydrofluoric–nitric acid digestion procedure, providing the ‘total’ (‘residual’) metal contents. Information about the
anthropogenic metal fraction was obtained by cold diluted hydrochloric acid extraction procedure. This ‘labile’ acid soluble
fraction of metals, perhaps due to relatively recent inputs in the sediments, constitutes the fraction more likely to be available
to marine organisms, and furnishes a first evaluation of the possible toxicity of sediments of this sensitive ecosystem. Zinc
appears to be the most available of all the heavy metals: its ‘labile’ fraction attains 40–50% of the ‘total’ zinc in sediment.
Sites near Port Harcourt city are the most contaminated. All the examined metals are one order of magnitude below the respective
values proposed as a limit for toxicity and are comparable with those observed by other authors in similar Niger Delta areas.
Some anomalous data found near Port Harcourt city suggest that zinc and cadmium are the metals that require further monitoring.
Their anthropogenic source could be derived from urban and industrial sewage. 相似文献
668.
快速溶剂萃取-气相色谱/串联质谱法测定农作物中的有机氯农药 总被引:3,自引:0,他引:3
建立快速溶剂萃取,固相萃取柱净化,气相色谱/串联四极杆质谱检测分析农作物中23种有机氯农药残留的方法。以油菜为样品,加标浓度为5、10、25、50μg/kg时,平均回收率在72%~101%之间,相对标准偏差3%~14%(n=5)。8种农作物(莴笋、黄瓜、蒜苗、辣椒、油菜、茄子、玉米和水稻)加标浓度为25μg/kg时的平均回收率在71%~113%之间,相对标准偏差3%~16%(n=5)。方法检出限0.75~1.76μg/kg之间。 相似文献
669.
670.
务宗伟 《环境监测管理与技术》2008,20(5):48-51
选取传统分流/不分流进样技术与大体积进样技术,结合气相色谱/质谱测定条件,对二者的测定效果和不同进样量的色谱图进行了分析对比。结果表明,使用大体积的进样测定二噁英,在不影响色谱分离度的同时可以大幅度提高仪器分析的灵敏度,可以代替传统分流/不分流进样。 相似文献