Response of organic aerosol characteristics to emission reduction in Yangtze River Delta region

● The emission reduction causes significant change in organic aerosol composition. ● The atmospheric oxidizing capacity improved during emission reduction. ● The mixed oxygenated organic aerosol contributed higher during emission reduction. Organic aerosol (OA) is a major component of atmospheric particulate matter (PM) with complex composition and formation processes influenced by various factors. Emission reduction can alter both precursors and oxidants which further affects secondary OA formation. Here we provide an observational analysis of secondary OA (SOA) variation properties in Yangtze River Delta (YRD) of eastern China in response to large scale of emission reduction during Chinese New Year (CNY) holidays from 2015 to 2020, and the COVID-19 pandemic period from January to March, 2020. We found a 17% increase of SOA proportion during the COVID lockdown. The relative enrichment of SOA is also found during multi-year CNY holidays with dramatic reduction of anthropogenic emissions. Two types of oxygenated OA (OOA) influenced by mixed emissions and SOA formation were found to be the dominant components during the lockdown in YRD region. Our results highlight that these emission-reduction-induced changes in organic aerosol need to be considered in the future to optimize air pollution control measures.     

加油站火灾爆炸危险指数评价

采用美国道化学公司火灾、爆炸危险指数法对某加油站的单个汽油储罐进行了火灾、爆炸危险指数(FEI)评价及安全措施补偿分析.比较了二者的危害等级,结果表明经安全措施补偿,汽油储罐的安全水平得到很大提高.     

空气加热管路压力损失校核计算

针对自行设计的气体爆炸试验装置中的空气加热管路部分进行了压力损失的计算,并进行了实验验证,通过实验验证该管路达到了设计要求.     

反应性液体紧急泄放面积设计进展

为防止反应失控造成爆炸事故,减少事故损失,在介绍模拟反应失控的实验装置ARC、VSP以及RSST等的基础上,针对不同的紧急泄放类型,如气相系统、蒸气系统和混合系统的紧急泄放研究进展,进行了分析论述,旨在发现解决反应失控紧急泄放问题的更好方法,从而为进一步研究反应失控的紧急泄放问题打下基础.     

事故树在油库静电火灾爆炸分析中的应用

主要分析了引起油库静电火灾爆炸的各种原因和环节,并建立了油库静电火灾爆炸事故树。通过对事故树的定性分析,提出了预防油库静电火灾爆炸事故的对策,给出了具体的防静电措施。     

Fire and explosion disasters occurred due to the Great East Japan Earthquake (March 11, 2011)

The Great East Japan Earthquake (magnitude 9.0 Mw: the moment magnitude scale, based on the seismic moment of the earthquake) occurred at 14:46, March 11, 2011. It triggered huge tsunami waves (seismic sea waves) that reached heights of up to about 20 m. In this paper, the fire and explosion disasters occurred due to the Great East Japan Earthquake are reported shortly. Some fires occurred in seacoast areas after tsunami attacks and some of them were spreading very widely to the tsunami flooded areas. It is important to study the mechanisms of such fires (tsunami fires) for preparing huge tsunami. After the earthquake, a very severe accident happened in the Fukushima Daiichi nuclear power plant. Three reactors experienced full meltdown. During this disaster, hydrogen explosions occurred and made the situation more serious. It has to be realized once again that the countermeasures for hydrogen explosions is indispensable. Also Large scale BLEVEs (Boiling Liquid Expanding Vapor Explosions) happened at LPG storage area in an oil refinery in Chiba Prefecture. This accident started from the falling down of an LPG storage tank by earthquake motions. The tank was heavier than usual, as it was filled with water (1.7 times heavier than LPG) for periodic inspection. Considering these disasters, we have to think about how we prepare the accident of low probability and of very severe consequence. Recently, the risk based approach is widely utilized. However, for such disasters it seems not enough to perform safety management only by risk based approach. Not only probabilistic approach (Risk), but also deterministic approach (Emergency plan, Mitigation technique) should be taken in account.     

Consequence modeling of explosion at Azad-Shahr CNG refueling station

Safety of people has been the most important concern since the onset of commercial use of Compressed Natural Gas¹ as a novel type of vehicle fuel. Provided a car vessel bursts, irreversible consequences will surface. The most important hazard threatening people and their properties in CNG distribution stations is pressurized natural gas in station storage vessels and car vessels. Storage vessels are far from people; however, they may damage other properties such as pipes, valves, electrical equipment, and etc. Owing to the distance between storage vessels and the hive, the risk is not considered a big concern; on the contrary, car storage vessel is very close to the passengers sitting in the car and those standing around the car. The proximity heightens the risk as the consequences caused by vessel burst can be more catastrophic than the former condition. Taken together, the car CNG vessel burst may be regarded as the most hazardous event at CNG distribution centers. It is believed that modeling the mentioned events can illustrate risky conditions. The present study was formulated in order to model one of such accidents occurring in Azad-Shahr in the winter 2010. The obtained results provided useful points and recommendations like the minimum safe distance from rupture center depending on such outcomes as overpressure, types of fire, or toxic release. The recommendations provided by the present study can prevent people from calamitous events and they can be adopted so as to reduce severity of possible events.     

Enhancement effects of methane/air explosion caused by water spraying in a sealed vessel

Experiments about the influence of ultrafine water mist on the methane/air explosion were carried out in a fully sealed visual vessel with methane concentrations of 8%, 9.5%, 11% and 12.5%. Water mists were generated by two nozzles and the droplets' Sauter Mean Diameters (SMD) were 28.2 μm and 43.3 μm respectively which were measured by Phase Doppler Particle Anemometer (PDPA). A high speed camera was used to record the flame propagation processes. The results show that the maximum explosion overpressure, pressure rising rate and flame propagation velocity of methane explosions in various concentrations increased significantly after spraying. Furthermore, the brightness of explosion flame got much higher after spraying. Besides, the mist with a larger diameter had a stronger turbulent effect and could lead to a more violent explosion reaction.     

基于激波管的油气爆炸实验和数据分析

通过对封闭激波管的油气爆炸实验,发现了爆炸时存在"呼吸"现象和震荡现象。通过对爆炸时的压力时间序列分析,除了得到了不同位置压力数量变化特征外,还得到了"呼吸"现象与油气的CH浓度和生成的二氧化碳浓度有关;在不同的CH浓度下,存在三种典型的压力变化曲线;震荡现象与CH浓度有关,没有固定的震荡周期,而且在不同压力变化阶段存在不同的震荡情况等结论。     

空气中爆炸对巷道稳定性影响模拟研究

以西北某铀矿矿床某巷道为依托,针对巷道稳定性及巷道内爆炸问题,运用ANSYS软件对自重应力场下的巷道衬砌及围岩进行静力分析,得出巷道围岩有效应力分布情况及巷道断面上几个典型位置的位移量和等效应力值。在此基础上,再利用LS-DYNA显式分析功能模拟自重应力场下爆炸对计算,获得衬砌结构最大主应力和加速度时程曲线,分析爆炸波在巷道中传播规律,为巷道抗爆性设计提供参考。结果表明,巷道中的爆炸波会产生强烈的多次反射现象,并且在自重应力场下,直墙拐角处往往最先出现破坏。