Effects of obstacles and deposited coal dust on characteristics of premixed methane–air explosions in a long closed pipe

An experimental system including pressure transducer, electric spark ignition device, data acquisition and control unit was set up to investigate methane–air explosions in a horizontal pipe closed at both ends with or without the presence of obstacles and deposited coal dust. The experimental results show that explosion characteristics depended on the methane content, on the layout of obstacles, and on the deposited coal dust. Pressure fluctuation with a frequency of 150 Hz appeared in its crest when the methane content was close to the stoichiometric ratio (9.5% methane percentage by volume). The pressure rise rate increased locally when a single obstacle was mounted in the pipe, but it had little effect on the pressure peak. Repeated obstacles mounted in the pipe caused the pressure to rise sharply, and the mean maximum explosion overpressure increased with the increase of the obstacle’s number. The amplitude of pressure fluctuation was reduced when deposited coal dust was paved in the bottom of the pipe. However, when repeated obstacles were arranged inside, the maximum overpressures were higher with coal dust deposited than pure gas explosions.     

Potential ecological and health risk assessment of different kiwifruit orchards in Qianjiang district,Chongqing city,China

Environmental Science and Pollution Research - Heavy metal (HM) pollution in orchards is becoming serious in many countries, and some fruit HMs exceed the safety limits. In this study, contents of...     

江西省环境保护产品发展现状分析

本文依托2011年江西省环境保护及相关产业基本情况调查,对江西省环境保护产品经营现状进行分析,研究了环境保护产品经营规模、行业分布、质量状况、产值等经营现状,并剖析了江西省环境保护产品经营存在的问题。     

双铝电极电絮凝-微滤法去除饮用水中细菌的实验研究

天然水体中的细菌多以游离形式存在，主体物质为蛋白质，一般带有负电荷。本实验采用电絮凝-微滤法对饮用水进行杀菌实验的研究，并探讨了电流密度、极板间距、pH值、氯离子对杀菌效率的影响及杀菌机理。实验表明电絮凝-微滤杀菌效果显著，且在电流密度为15．8A／m^2，极板间距为1．0cm，pH值在酸性范围内杀菌效果比较好，此外氯离子的存在有利于除菌。     

渝西经济区土壤地球化学基准值与背景值及元素分布特征

基于渝西经济区多目标区域地球化学调查资料,采用正态和对数正态法,获得了土壤54种元素(指标)的地球化学基准值和背景值,并研究其分布特征;同时分析了岩石风化成土过程元素的富集贫化规律,以及表层土壤元素分布特征。结果表明,与全国土壤相比,该区重金属元素Cd、Cr、Hg、Ni基准值较高,As较低,Pb、Zn、Cu与全国值相当;多数重金属元素和植物营养元素背景值偏高,仅K、Mn、P、Cl元素背景值低于全国水平。对比土壤背景值与基准值,发现多数元素(指标)背景值与基准值相当,说明表生作用和人为活动对表层土壤影响较小;而Se、Hg、S、N等14种元素在表层土壤富集,人为输入作用显著。不同母岩区表层土壤元素(指标)分布表现为,碳酸盐岩区多数元素含量较高;就不同pH值范围而言,CaO、MgO、K2O、P以及除Hg以外的重金属元素均在碱性环境含量较高,SiO2在酸性环境含量高,较多元素(指标)在中性环境中趋于稳定。