Experimental investigation on oxidation of sulfurized rust in oil tank

Oxidation of sulfurized rust in oil tank is complicated, and it is influenced by numerous factors such as water content, air humidity, operating temperature etc. The paper focuses on the oxidation process of sulfurized rust in the wild. Firstly, samples collected from a petrochemical company were put into the sulfurization & oxidation experimental apparatus to gain wet and dry sulfurized rusts. Their chemical compositions and phase were analyzed by Energy Dispersive X-ray Spectrometer (EDS) -scanning electron microscope (SEM) technique. The results showed that both wet and dry sulfurized rusts had S, Fe₂O₃, Fe₃S₄ and FeS₂, whereas FeS only existed in wet sulfurized rust. The two kinds of rusts gave a short length of side, diamond appearance and a large pore size in structure. Then oxidation of wet sulfurized rust was investigated, which included electrochemical reaction stage, electrochemical & chemical reaction coexisting stage and chemical reaction stage. The final oxidation product of wet sulfurized was determined to be Fe₂O₃. On the basis of this study, an indicator for monitoring and early-warning was proposed to prevent plants in vicinity of the accidental vessel or tank from fire and explosion.     

Extinguishment of hydrogen laminar diffusion flames by water vapor in a cup burner apparatus

Transient computations with full hydrogen chemistry were performed to reveal the flame structure and extinguishment process of co-flow, hydrogen diffusion flame suppressed by water vapor. As the concentration of water vapor was increased, the flame detached away from the burner brim and formed an edge flame at the flame base. Water vapor showed larger chemical inhibition effect than nitrogen when extinguishing hydrogen flame, which was attributed to its enhanced third body effect in the reaction H + O₂ + M = HO₂ + M. The minimum extinguishing concentration (MEC) of water vapor and nitrogen was predicted by Senecal formula and perfectly stirred reactor (PSR) model respectively. The MECs predicted by PSR model agree with the MECs calculated by Fluent, which shows that 1) the flame extinction is controlled by the flame base, and 2) radiation absorption is negligible. The measured MECs are in a reasonable agreement with the values calculated by Fluent, which demonstrates the accuracy of the CFD model. A simple model was used to investigate the relative importance of extinguishing mechanisms of water vapor. The results show that in a co-flow configuration the thermal cooling and chemical inhibition effect are the main extinguishing mechanisms in suppressing hydrogen diffusion cup burner flame.     

Thermal radiation from vapour cloud explosions

The current study estimates the radiation flux emitted from hot extended gas clouds characteristic of vapour cloud explosions along with the corresponding level of irradiance posed on particles suspended in the unburnt part of the cloud ahead of an advancing flame front. The data presented permits an assessment of the plausibility of combustion initiation by such particles due to forward thermal radiation. The thermal radiation will depend on the emissivity of the burned volume, which relates to the concentration of gaseous and particulate combustion products. A sensitivity analysis has been carried out to account for variations in the equivalence ratio, mixture pressure and radiative heat losses. The spatial distribution of irradiance ahead of the flame front has been computed by introducing appropriate geometrical factors to explore the impact of cloud size. Using fuel rich ethylene-air mixtures it has been shown that high flame emissivities can be achieved at path lengths of order 1 m even in the presence of very low soot volume fractions. The emissivity of gas-soot mixtures will hence be mainly determined by the soot concentration and to a lesser extent by the mixture temperature. Our analysis suggests that the role of forward thermal radiation as a contributing factor to flame propagation in large scale vapour cloud explosions can not currently be ruled out.     

A transportation-location problem model for pedestrian evacuation in chemical industrial parks disasters

A successful emergency management for chemical industrial parks (CIPs) accidents includes the route and shelter selection. Both of them are based on the collection of chemicals, atmosphere, geographic and population databases of CIPs. This decision process can be considered as a kind of transportation-location problem (TLP). In this paper, a conceptual model of emergency decision system for TLP of CIPs has been reported and a new multi-objective TLP model of pedestrian evacuation has also been proposed. The model includes sub-criteria, and the affected areas are categorized into a priority hierarchy based on human vulnerability model (HVM). The model can be used to design shelter places and guide the evacuation of the affected people. Besides, it can maximize the total time satisfaction level of evacuees combined with the routes passable probabilities. Finally, a case study shows that this model is flexible and applicable to various scenarios and risk measures.     

高原环境对车辆动力性的影响及动力提升措施

在总结我国高原气候和地理环境特点的基础上,从反映车辆动力性能的指标出发,以加速时间、最大爬坡度和最高车速入手,理论分析了对整车高原动力性影响较大的因素,主要包括有效热效率、循环喷油量、滚动阻力系数、空气密度对空气阻力的影响等。通过分析高原环境对这些因素的影响,总结出了高原环境对车辆动力性的影响机理,并进一步提出了整车高原动力性改进的技术措施,认为先进增压、燃烧优化、高压共轨燃油喷射、高原环境标定、热平衡控制和富氧进气燃烧等技术措施成为提高车辆动力性的有效技术措施。     

建筑火灾过渡区域数值模拟选取计算区域的判据研究

在建筑火灾的计算机模拟中,计算区域的选取密切关系到计算结果的合理性。已有研究针对单一开口小室在火灾燃料控制阶段和通风控制阶段时计算区域如何选取进行了分析并得到了定量的结论,该文在此基础上改进结果处理的方法,提出一种新的定量分析计算区域合理选取的方法,对单一开口小室在火灾两阶段间的过渡区域如何选取计算区域进行了定量分析。     

The role of pH in the fermentative H2 production from an acidogenic granule-based reactor

The role of pH in the fermentative H(2) production from an upflow acidogenic granule-based reactor was investigated in this study. Experimental results show that all H(2) partial pressure, H(2) production rate and H(2) yield were pH-dependent, in the range of 2.8 x 10(4)-5.2 x 10(4)Pa, 61-145 ml-H(2)l(-1)h(-1) and 0.68-1.61 mol-H(2)mol-glucose(-1), respectively. The maximum H(2) partial pressure was observed at pH 3.4, while both maximum H(2) production rate and H(2) yield were found at pH 4.2. Acetate, propionate, butyrate, i-butyrate, valerate, caporate and ethanol were present in the effluent of this UASB reactor, and their distribution was also pH-dependent. As pH was decreased from 4.2 to a lower level of 3.4 or increased to a higher level of 6.3, the fermentative type of this H(2)-producing reactor would shift from butyrate-type to caporate- or ethanol-type. Thermodynamic analysis was performed to explore the possible metabolic pathways of caproate and valerate formation. The metabolic pathway of caproate formation was pH-dependent, while that of valerate formation was pH-independent. A neural network model was designed, trained and validated. It was able to successfully describe the daily variations of H(2) partial pressure and H(2) yield of the reactor, and to predict its steady state performance at various pHs.     

Observation study of pedestrian flow on staircases with different dimensions under normal and emergency conditions

Compared with horizontal motion, there were several characteristics in staircase movement. This study focused on the movement characteristics in staircases of typical student crowds and the quantitative relations of flow rate-speed-density in different dimensions of staircases and different circumstances were obtained. Basic data concerning daily movement when classes were over and an evacuation drill for college students was collected through analysis of video observation. From the analysis, the following conclusions can be given: some typical characteristics of pedestrian movement in staircases were found, such as queuing behavior at platform, merging flow at staircase entrance, and subgroup behavior. Movement on stairs was markedly slower than the horizontal motions. In normal condition, the number and initial speed of students entering the staircase affected observably the pedestrians flow, and the impact of staircase attributes (riser, tread, slope, etc.) cannot be neglected. In different conditions, the characteristics of pedestrian movement were quite different, and the influence of the speed on the density was more significant in the emergency condition. The study highlighted the amassment phenomenon at the bottom of the staircase and the potential influence of stair widths to evacuation efficiency in evacuation drill.     

基于模式生物秀丽隐杆线虫的环境污染物生殖毒性研究进展

由于人类社会的发展,环境污染也越来越严重,研究环境污染物对生态及人类健康的影响极为重要。生殖系统是人和动物繁衍后代的重要系统,常见环境污染物对生殖系统的影响正引起研究人员的广泛关注。秀丽隐杆线虫具有身体透明、品系丰富和遗传背景清楚等优点,为生殖毒理学研究提供了一个便利的平台。以秀丽隐杆线虫为模型已对多种环境污染物的生殖毒性进行了评价。本文重点叙述了重金属、纳米材料、有机物等化学污染,辐射、磁场等物理污染,以及病毒等生物污染对秀丽线虫生殖系统的影响,并归纳讨论了环境污染物造成生殖功能障碍的几种主要机制,如氧化应激、DNA损伤、内质网应激以及神经损伤等,但不同类型污染物的毒性效应与其自身的物化性质紧密相关。环境污染物诱导的生殖毒性中不同响应机制之间的关联性、不同发育阶段的敏感性差异、污染物的传代效应以及有效的缓解方式的筛选等都有待进一步的开展。     

2017~2021年苏皖鲁豫交界区域PM2.5和O3时空变化特征及影响因素

苏皖鲁豫交界区域是长三角和京津冀及周边两大大气污染治理重点区域的连接带,揭示该区域PM_2.5和O₃污染特征对推动区域大气污染联防联控有着重要意义.基于2017~2021年苏皖鲁豫交界区域22个地市的国家空气环境监测网络观测数据,探讨了该区域PM_2.5和O₃浓度的时空变化特征及气象影响.结果表明：①2017~2021年区域PM_2.5浓度呈现逐年下降趋势,PM_2.5浓度月均值呈现“U型”分布,冬季PM_2.5浓度仍维持高位.O₃-8h-90%浓度呈现波动下降趋势,O₃-8h-90%浓度月均值变化呈“M型”分布,夏秋季O₃污染程度未有好转.②与2017年相比,2021年PM_2.5-O₃复合污染天数减少了52 d,但PM_2.5污染仍占主导地位.③PM_2.5和O₃污染区域主要集中在区域中部和北部城市,且中部城市PM_2.5和O₃污染程度均改善显著.④采用Moran''s I指数和LISA指数分析了区域PM_2.5和O₃-8h-90%浓度的全局和局部空间自相关性,PM_2.5和O₃-8h-90%浓度均具有空间相关性,PM_2.5浓度主要表现为高值-高值聚集或低值-低值聚集现象,且高值-高值聚集有从中部向西部转移的现象,2020年和2021年O₃-8h-90%浓度表现为高值-高值聚集或低值-低值聚集现象.⑤结合气象要素数据,利用KZ滤波方法量化排放源与气象条件对区域PM_2.5和O₃-8h浓度的贡献,两者主要受到污染物排放影响,贡献率分别为101.0%和99.3%,表明污染物减排是驱动区域空气质量改善的主要因素.此外,气象条件对PM_2.5浓度的贡献在一、四季度为正值,二、三季度为负值,而对O₃-8h浓度的影响则反之,且气象条件对不同城市PM_2.5和O₃-8h浓度的影响程度存在较大差异.