多孔球形材料阻火抑爆性能影响因素数值模拟研究

为探究影响多孔球形材料阻火抑爆性能的主要因素,采用气体爆炸模拟软件FLACS建立多孔球形结构中湍流燃烧模型,对填充多孔球形材料后丙烷/空气预混气体燃烧爆炸过程进行数值模拟。研究结果表明:多孔球形材料能够有效衰减爆燃压力波、阻隔火焰传播,起到阻火抑爆作用,且压力波衰减程度和火焰阻隔效果与多孔球形材料的尺寸、孔径及填充密度密切相关。当多孔球形材料的直径为25 mm、孔径为3 mm、填充密度为20层时,压力波衰减程度最大,火焰阻隔效果最明显,说明直径和孔径越小,填充密度越大,材料的阻火抑爆性能越强。     

我国城市扬尘污染现状及控制对策

目前颗粒物已经成为我国城市大气污染的首要污染物 ,在颗粒污染物中来源于工业烟尘和粉尘的数量在逐年减少 ,而来源于扬尘的颗粒物在颗粒污染物总量中所占的比重却在逐年增加 ,目前已成为造成城市颗粒物污染的首要因素。本文分析了我国城市扬尘污染的现状、来源、扬尘污染控制中存在的问题 ,并提出了控制城市扬尘污染的几点对策和措施。     

济南市道路尘中类二噁英类多氯联苯残留情况

通过采集济南市区主要路段道路尘样品,用气相色谱-电子俘获检测器(GC-ECD)方法分析了济南市区主要路段道路尘中毒性较高的12种类二噁英类多氯联苯(DL-PCBs)的残留情况,并对样品中DL-PCBs的含量、污染水平及同系物的组成进行了详细研究。结果发现,DL-PCBs在各采样点均有检出,残留总浓度在0.20～22.84ng/g(干重)范围内,平均值为0.0051ng/kg,同系物PCB81的检出率最高为90%,而同系物PCB189未被检出。计算的毒性当量(TEQ)值显示,对毒性当量贡献最大的是同系物PCB126,其TEQ值高达117.100pg/g(干重)。由平均残留百分含量较大的同系物结构分析可知,济南市区主要路段道路尘中非邻位氯取代的剧毒类二噁英类PCBs含量相对较大。     

港口起尘影响因素分析及粉尘污染控制措施与建议

介绍了港口粉尘污染类型,港口粉尘污染包括静态污染和动态污染,容易产生粉尘污染的常见固体散货码头有煤炭码头、矿石码头和水泥码头等,对煤炭、矿石等固体散货码头的起尘影响因素进行了分析,不同货物的种类和粒径、含水率、风力及储存方式等均对港口起尘产生影响,从码头和堆场装卸过程、港口物料输送过程、堆场和港区内道路等角度分别介绍了粉尘污染控制措施,对前沿的防尘方式,如防风网和筒仓的抑尘机理及在国内外的应用情况进行了介绍,并从港口选址、平面布置、管理、监测和科研等角度对港口污染防治提出建议。     

基于模糊综合识别技术的粉尘危害评价应用研究

针对目前粉尘危害评价存在的不足,采用最优权法确定各评价指标的权系数,利用模糊识别技术对粉尘危害程度进行综合评价,初步建立了粉尘危害评价指标体系和评价分级标准.结合某矿山实例,对粉尘危害进行模糊综合评价.评价结果表明,模糊综合识别技术能够较好反应实际情况,是一种有效的评价方法,对粉尘防治工作具有一定的指导意义.     

提高电除尘器除尘效率措施的研究进展

电除尘器在粉尘治理领域发挥着极其重要的作用.简要介绍了影响电除尘器除尘效率的主要因素.综述了近年来提高电除尘器效率措施的研究进展.着重介绍了几种新型电除尘器的除尘机制及除尘试验结果,评论了其除尘性能和应用前景,并对进一步的研究方向提出了看法.     

一次强沙尘过程对江苏省空气质量的影响研究

2021年3月15—17日,江苏省自北向南经历了一次严重沙尘污染过程,在此期间对连云港和苏州2市的PM_(10)和PM_( 2.5)质量浓度,以及退偏振比参数进行连续观测,结合后向轨迹(HYSPLIT)模型对沙尘气团来向进行分析。结果表明,本次沙尘过程起源于蒙古国南部,起沙之后自西北至东南传输,约24 h后开始影响江苏省。受其影响,江苏省3月16日4市达重度污染,沙尘对苏北和苏南城市影响差异较大,连云港市PM_(10)质量浓度短时高达978μg/m^( 3),近地面至高空2 km退偏振比值达0.3左右,沙尘特征较明显;苏州市受沙尘影响时间较连云港滞后约14 h,PM_(10)质量浓度峰值仅为155μg/m ^(3),以浮尘天气为主。     

Numerical study of dust lifting in a channel with vertical obstacles

In the paper, several results of numerical computation of multiphase flows in a channel with complex geometry are considered. The objective of the research was to study the dust lifting process from a layer behind a shock wave in a rectangular channel with vertical obstacles in the upper part of the tube. It is to be shown that that kind and also any sort of geometry may crucially change the whole phenomena of dust enhancement and of combustion. This is very important for safety in, for example, coal mines where channels are usually of more sophisticated structure than is usually assumed by most researchers.     

Flameless venting of dust explosion: Testing and modeling

Flameless venting is a sort of dual mitigation technique allowing, in principle, to vent a process vessel inside a building where people are working without transmitting a flame outside the protected vessel. Existing devices are an assembly of a vent panel and a metal filter so that the exploding cloud and the flame front is forced to go through the filter. Within the frame of ATEX Directive, those systems need to be certified. To do so a standard (NF EN 16009) has been issued describing which criteria need to be verified/measured. Among them, the “efficiency” factor as defined earlier for standard vents. This implies that flameless venting systems are basically considered as vents. But is it really so? This question is discussed on the basis of experimental results and some implications on the practical use and certification process are drawn. The practical experience of INERIS in testing such systems is presented in this paper. Schematically, with a flameless vent the pressure is discharged but not the flame so that combustion is proceeding to a much longer extent inside the vessel than with a classical vent so that the physics of the explosion is different. In particular it is shown that besides the problem of the unloading of the confined explosion, there is a highly complicated fluid mechanics problem of a fluid-particle flow passing through a porous media (the flameless device grids arrangement in the filter), which passing surface is progressively reduced. To characterize Flameless venting the problem can be addressed sequentially, considering separately the vent panel and the flameless mesh. A model is proposed to estimate the overall venting efficiency of the flameless vent. However, it does not address the flame quenching issue, which is a different problem of heat exchange between the devices and the evacuated burnt products.     

Determination of heterogeneous reaction mechanisms: A key milestone in dust explosion modelling

Reaction kinetics is fundamental for modelling the thermal oxidation of a solid phase, in processes such as dust explosions, combustion or gasification. The methodology followed in this study consists in i) the experimental identification of the reaction mechanisms involved in the explosion of organic powders, ii) the proposal of simplified mechanisms of pyrolysis and oxidation, iii) the implementation of the model to assess the explosion severity of organic dusts. Flash pyrolysis and combustion experiments were carried out on starch (22 μm) and cellulose (53 μm) at temperatures ranging from 973 K to 1173 K. The gases generated were collected and analyzed by gas chromatography. In this paper, a semi-global pyrolysis model was developed for reactive systems with low Damköhler number. It is in good agreement with the experimental data and shows that both carbon monoxide and hydrogen are mainly generated during the pyrolysis of the solid, the generation of the latter compound being greatly promoted at high temperature. A simplified combustion model was also proposed by adding two oxidation reactions of the pyrolysis products. In parallel, flame propagation tests were performed in a semi open tube in order to assess the burning velocity of such compounds. The laminar burning velocity of cellulose was determined to be 21 cm s⁻¹. Finally, this model will be integrated to a predictive model of dust explosions and its validation will be based on experimental data obtained using the 20 L explosion sphere. The explosion severity of cellulose was determined and will be used to develop and adjust the predictive model.