Unified correlations for vent sizing of enclosures at atmospheric and elevated pressures

Innovative vent sizing technology is presented for explosion safety design of equipment at atmospheric and elevated initial pressures. Unified correlations for vent sizing are suggested. They are modifications of previously reported correlations verified thoroughly for experimental data on vented gaseous deflagrations under different conditions but only at initial atmospheric pressure. Suggested correlations are based on experimental data on vented deflagrations of quiescent and turbulent propane–air mixtures at initial pressures up to 0.7 MPa. Typical values of turbulence factor and deflagration–outflow interaction number are obtained for experimental vented deflagrations at initial pressures higher than atmospheric.

“Blind” examination of new vent sizing technology on another set of experiments with methane–air and propane–air mixtures has shown that predictions by suggested vent sizing technology are better than by the NFPA 68 guide for “Venting of Deflagrations”.

In the development of recently reported results for initial atmospheric pressure it has been concluded that the innovative vent sizing technology is more reliable compared to the NFPA 68 guide at elevated initial pressures as well. Moreover it is crucial that the calculation procedure remains the same for arbitrary deflagration conditions.     

Experiment-based investigations on the effect of ignition energy on dust explosion behaviors

Explosion behaviors of typical light metal and carbonaceous dusts induced by different ignition energies were investigated based on systematic experiments in a Siwek 20 L vessel. Comparative analysis reveals that the explosion mechanism of carbonaceous dust is the volatile combustion, whereas the mechanism for light metal dust mainly features the surface heterogeneous oxidation. Influences of ignition energy on severity and flammability limit are much more significant for carbonaceous dust than light metal, especially for the powder with less volatile. An innovative approach was introduced to derive flame thickness from the pressure–time trace. The relation between explosion induction time and combustion duration of ignitor was also analyzed. Results show inappropriate ignition energy will cause under-/over-driving in the thermodynamic/kinetic characteristic measurements. In this way, a dimensionless parameter pressure ratio was introduced to evaluate the under-driving, while two methods by using flame thickness and induction time respectively, were proposed to evaluate over-driving. To improve the accuracy of dust explosion tests, authors advocate that explosion severity determination should be conducted at the critical ignition energy. Moreover, a comparison between the European and Chinese flammability limit determination procedures was also conducted, indicating that EN 14034-3 is suitable for light metal but not for carbonaceous, while GB/T 16425 appears to be slightly conservative for both carbonaceous and light metal dusts.     

Influence of dustiness on small-scale vented dust explosions

A new safety characteristic the “dustiness” according to VDI 2263 – part 9 (Verein Deutscher Ingenieure, 2008) is investigated. Dustiness means the tendency of a dust to form clouds. The paper deals with the physical reasons for the different behavior of dusts, even if they have similar properties such as particle size and density and the influence of the dustiness on dust explosions. In order to study the effects of the dustiness on dust cloud formation for different dispersion methods experiments in a vertical dust dispersion glass tube apparatus were carried out. Furthermore vented dust explosion experiments were done for two different dispersion methods and two static activation pressures.Experiments show that particle size and density are not the only factors which influence dispersibility. Particle shape, specific surface area, flow and dispersion method have an influence which can outweigh size and density. Preliminary explosion experiments showed that the dustiness has an influence on the reduced explosion pressure and flame speed in a vented 75 L test apparatus. In order to verify the results for applications in the process industries further tests with industrial scale experiments are planned.     

粉尘对电气设备的危害及其防治

冶金生产过程中产生的粉尘对电气设备危害极大,如造成电气设备短路,电气开关按触不良,通风不良等。采取了定期清扫粉尘,定期检查开关设备的触头及接线,提高电气设备的抗尘能力等措施后,取得明显效果。     

Coal dust particle size survey of US mines

The National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA) conducted a joint survey to determine the range of coal particle sizes found in dust samples collected from intake airways of US coal mines. The last comprehensive survey of this type was performed in the 1920s. The size of the coal dust is relevant to the amount of rock dust required to inert the coal dust, with more rock dust needed to inert finer sizes of coal dust.

Dust samples were collected by MSHA inspectors from several mines in each of MSHA's 10 bituminous Coal Mine Safety and Health Districts. Samples were normally collected in several intakes at each mine. The laboratory analysis procedures included acid leaching of the sample to remove the limestone rock dust, sonic sieving to determine the dust size, and low-temperature ashing of the sieved fractions to correct for any remaining incombustible matter. The results indicate that particle sizes of mine coal dust in intake airways are finer than those measured in the 1920s. This finer size coal dust in intake airways would require more incombustible matter to be effectively inerted than the 65% incombustible specified in current regulations.     

煤层注水中水分蒸发现象的研究

对煤层注水的水分蒸发现象进行了研究 ;提出了注入水分蒸发的力学平衡公式 ;研究了影响水分蒸发的各项因素。在此基础上 ,提出了在注水钻孔中添加粘尘棒 ,阻止注入水分过早蒸发的新方法 ,并进行了纯水和粘尘棒溶液在煤体中蒸发的试验。     

南京市道路交通粉尘中重金属的空间分布特征

本次研究以南京市为例,研究道路粉尘中的重金属含量,并分析其空间分布模式。在南京市依据用地类型的不同选取了个22点位采集粉尘样本,并对其中的Cr、Cu、Ni 、Pb、Zn的含量进行检测。结果表明道路粉尘重金属在商业区用地上的含量最高的,在公园绿地区类型上的含量最少,而且粉尘中重金属含量随着样点城市化时间变长而升高。     

由“7·28”南京丙烯管道爆燃事故探讨我国地下管道存在的安全问题

＂7·28＂南京丙烯管道爆燃事故和近期发生的一系列管道事故反映出我国在地下管道安全方面存在的问题。在事故原因分析与共性问题探讨的基础上,结合欧美国家在管道安全管理中的成功做法,从加强法制建设、合理规划城市布局、进行重大危险源普查并建立监测监控系统、强化城镇地面开挖施工安全管理、加强风险沟通提高公众应急能力等方面提出了对策建议。     

氢气爆燃作用下核电站安全壳力学响应数值模拟分析

在核电站严重事故中,由氢气爆燃产生的压力载荷会危及安全壳完整性致其失效,进而造成放射性物质泄漏的严重危害。通过ANSYS/Fluent有限元数值模拟软件,建立了安全壳有限元模型,并对安全壳内氢气爆燃过程以及其力学特性进行了数值模拟研究,获得了氢气爆炸过程中的超压值、升压速率、安全壳变形以及压应力分布。结果表明:爆燃波传递引起压强升高,火焰阵面处压强最高,爆燃波所经区域超压疾速上升随后快速下降;爆燃作用下,顶部壳体和下部筒体连接区域混凝土位移最大,最大压应力也集中分布在该区域,最易受到破坏。获得的结论可为安全壳结构抗爆设计和安全性研究提供理论参考。     

Optimization via response surface methodology of the synthesis of a dust suppressant and its performance characterization for use in open cut coal mines

To relieve dust pollution in open cut coal mines and reduce the hazards of coal dust pollution to the environment and workers we optimized the synthesis of a dust suppressant by graft copolymerization of environmentally friendly soy protein isolate with methyl methacrylate. This dust suppressant could effectively control dust pollution in open cut coal mines. The optimized conditions for graft copolymerization in this case were determined by a response surface experiment designed with Design-Expert 10 software. Characterization by scanning electron microscopy showed a significant morphology change of the dust suppressant and the generation of a rigid and dense layer on its surface after interacting with coal dust. The layer exhibited good bonding and dust suppression performance. The analysis with Fourier-transform infrared spectroscopy revealed the appearance of new absorption peaks near 1300, 1072, and 1631 cm⁻¹, demonstrating effective graft copolymerization. The proposed dust suppressant exhibited excellent wind erosion resistance, with a resistance that exceeded 90% at a wind speed of 6.5 m/sec. The successful graft copolymerization and effective bonding and curing of the dust suppressant on coal dust were experimentally verified. This is of great significance to the control of coal dust pollution.