Smoldering combustion of dust layer on hot surface

The critical temperature as well as the critical flux for ignition of a dust layer of cornflour and a mixture of wheatflour and cornflour (80% wheatflour+20% cornflour) on a hot plate have been determined. The moulded sample was cylindrical in shape and of different heights and diameters. The particle size of dusts ranged between 63 μm to 150 μm. The temperature–time histories for self-heating without ignition and with ignition are offered, showing the critical boundaries between them. Also the times to ignition for each dust, showing the effect of sample size on their values, are determined. Certain experimental correlations which relate to times to ignition, as well as the critical temperature for ignition and thermal and geometrical dimensions of sample are presented.     

金隆公司烟尘输送系统的改造

介绍了金隆公司烟尘输送系统的改造过程,着重论述了A烟尘中问仓及双螺旋运输机、布袋收尘器的运行状况、存在的主要问题及改造经过;A、C烟尘系统对接的原因及实施过程。     

我国危险化学品道路运输的现状与对策研究

随着我国工业和经济的发展,危险化学品的需求量越来越大,危险化学品的道路运输也越来越频繁,由危险化学品道路运输而引发的事故也越来越多。为此,必须基于我国危险化学品道路运输的现状,借鉴发达国家在危险化学品道路运输方面较成熟的经验,提出符合我国国情的危险化学品道路运输安全管理的对策,以达到减少危险化学品道路运输事故发生的目的,最大限度地降低由危险化学品道路运输事故引起的生命财产的损失。     

基于主成分分析法的危险货物运输企业安全评价

为更准确地评估危险货物运输企业安全等级以降低其运输风险,提出基于主成分分析法(PCA)的危险货物运输企业BP神经网络安全评价模型;在从人-机-物-环境-管理角度构建危险货物运输企业安全评价指标的基础上,分别利用该模型和其他3种模型对3家实例企业进行仿真评价和对比分析。结果表明,该模型的评价结果与期望值间的相对误差约为0.5%～1.2%,计算精度优于其他模型,且具有计算量小等特点。     

Collecting representative dust samples: A comparison of various sampling methods in underground coal mines

Former methods used in the U.S. to assess hazardous and explosible coal dust date back to the 1950s. As mining technologies advanced, so too have the hazards. Given the results of the recent coal dust particle size survey and full-scale experimental mine explosion tests, the National Institute for Occupational Safety and Health (NIOSH) recommended a new minimum standard, in the absence of background methane, of 80% total incombustible content (TIC) be required in the intake airways of bituminous coal mines, replacing the previous 65% TIC requirement. Most important to monitoring and maintaining the 80% TIC is the ability to effectively collect and analyze representative dust samples that would likely disperse and participate in dust explosion propagation. Research has shown that dust suspended on elevated surfaces is usually finer, more reactive, and more readily dispersible while floor deposits of dust are generally coarser and more difficult to disperse given the same blast of air. The roof, rib, and floor portions of the dust samples were collected and analyzed for incombustible content separately and the results were compared to a band sample of the roof, rib, and floor components. Results indicate that the roof and rib dust samples should be kept separate from floor dust samples and considered individually for analyses. The various experimental collection methods are detailed along with preferred sampling approaches that improve the detectability of potentially hazardous accumulations of explosible dust.     

Flame propagation in lycopodium/air mixtures below atmospheric pressure

Industrial processes are often operated at conditions deviating from atmospheric conditions. Safety relevant parameters normally used for hazard evaluation and classification of combustible dusts are only valid within a very narrow range of pressure, temperature and gas composition. The development of dust explosions and flame propagation under reduced pressure conditions is poorly investigated. Standard laboratory equipment like the 20 l Siwek chamber does not allow investigations at very low pressures. Therefore an experimental device was developed for the investigations on flame propagation and ignition under reduced pressure conditions. Flame propagation was analysed by a video analysis system the actual flame speed was measured by optical sensors. Experiments were carried out with lycopodium at dust concentrations of 100 g/m³, 200 g/m³ and 300 g/m³. It was found that both flame shapes and flame speeds were quite different from those obtained at atmospheric pressure. Effects like buoyancy of hot gases during ignition and flame propagation are less strong than at atmospheric conditions. For the investigated dust concentrations the flame reaches speeds that are nearly an order of a magnitude higher than at ambient conditions.     

基于风险的危险品道路运输安全容量研究

为了确定危险品道路运输安全容量，保障危险品道路运输安全，基于风险理念，使用对比研究方法，提出危险品道路运输个人风险基准，建立改进的危险品道路运输定量风险评估模型。结合提出的风险基准，提出危险品运输安全容量确定方法，解决了单一类别和多种类别危险品运输安全容量确定问题。研究结果表明:在某城市化工集聚区的实例应用该方法，能够大幅度降低危险品道路运输潜在生命损失，有助于保障危险品道路运输安全。     

Evaluating the overall efficiency of a flameless venting device for dust explosions

Results from cornstarch explosion tests using a flameless venting device (mounted over a burst disc) on an 8 m³ vessel are presented and used to determine the overall efficiency of the device, which is defined as the ratio between its effective vent area and the nominal vent area. Because these devices are comprised of an arrestor element mounted over an impulsively-actuated venting device (such as a burst disc), the functional form of the overall efficiency is taken as the product of the area efficiency (i.e., the ratio between the effective vent area of the entire assembly to that of the venting device without the arrestor element) and the burst efficiency (i.e., the ratio of the effective vent area of the venting device without the arrestor element to the nominal vent area). The effective vent areas are calculated from measured overpressures using three different empirical correlations (FM Global 2001, NFPA 2007, and VDI 2002). Furthermore, due to significant variations in the effective reactivity from test to test, a correction factor proportional to the initial flame speed is applied when determining the area efficiency. In general, it was found that the FM Global and NFPA methodologies yield consistent results with less scatter than VDI 3673.     

CFD simulations of dust dispersion in the 1 m3 explosion vessel

According to standard procedures, flammability and explosion parameters for dusts and dust mixtures are evaluated in 20 L and/or 1 m³ vessels, with equivalent results provided a correct ignition delay time (60 ms in the 20 L vessel; 600 ms in the 1 m³ vessel). In this work, CFD simulations of flow field and dust concentration distribution in the 1 m³ spherical vessel are performed, and the results compared to the data previously obtained for the 20 L. It has been found that in the 1 m³ vessel, the spatial distribution of the turbulent kinetic energy is lower and much more uniform. Concerning the dust distribution, as in the case of the 20 L, dust is mainly concentrated at the outer zones of the vortices generated inside the vessel. Furthermore, an incomplete feeding is attained, with most of the dust trapped in the perforated annular nozzle. Starting from the maps of dust concentration and turbulent kinetic energy, the deflagration index K_St is calculated in both vessels. In the conditions of the present work, the K_St is found to be 2.4 times higher in the 20 L than in the 1 m³ vessel.     

基于模糊推理的FRAM事故定量分析方法研究

为有效克服FRAM事故分析中无法进行定量分析的缺陷，提出结合模糊推理技术的Fuzzy FRAM模型。此改进模型基于FRAM识别系统运行状态；依据功能输出要素的时间/精度属性利用Matlab构建2阶模糊推理系统量化功能输出质量；根据通用性能条件(CPC)及功能输入耦合端口构建功能评价体系，针对评价体系中存在的不确定性信息融合及建模问题，采用模糊证据推理技术，通过模糊信度结构建立、数据处理、信息融合测度后获得功能的风险指数;以既有铁路危险品运输事故为例，验证方法的可行性。结果表明:Fuzzy FRAM模型的评估结果较为精确，是FRAM分析方法的有效补充。