MTBE装置潜在危险性分析及物料泄漏扩散后果模拟研究

MTBE装置处理的物料（混合C4、甲醇）具有易燃易爆性,若发生物料泄漏,将导致装置发生火灾爆炸。为了确保装置安全平稳、长周期运行,基于MTBE装置工艺技术特点,全面系统分析了装置的潜在危险性,总结出导致装置发生火灾爆炸事故的主要因素-物料泄漏;在此基础上,采用挪威DNV公司的SAFETI定量风险评价软件,建立混合C4、甲醇泄漏扩散模型,对物料泄漏导致的主要事故类型（喷射火、池火等）进行模拟,得出泄漏扩散引发火灾爆炸事故的危害范围。结果表明：该模拟研究能够反映出泄漏扩散过程和破坏范围,取得了较真实的事故影响范围曲线图,可以为设计人员更加详细了解MTBE装置发生事故的危害性及企业加强重点部位监控、制定防范措施、编制事故应急预案提供重要参考依据。     

基于非恒定流的污染物迁移扩散随机模拟

针对目前大部分河流都受到不同程度污染的现状,研究了基于非恒定流的污染物迁移扩散随机模拟方法。通过一维非恒定流数值计算和流场模拟,得到了水库开闸放水后下游各个断面的水位、流量、流速等数据,并以此为基础,利用蒙特卡洛法对水库开闸放水前后下游典型断面的COD和NH3-N等进行污染物迁移扩散随机模拟,并将模型应用于文峪河下游。结果表明,文峪河水库开闸放水后,COD和NH3-N的污染带长度和宽度均有不同程度的减小,污染带向排污一侧岸边集中。研究成果可为解决河流污染现状与水库调度提供参考。     

填埋场内温度场下渗滤液饱和带内硫酸盐还原行为表征

填埋场内渗滤液饱和带是物质交换和生化反应的活跃区域,也是含硫恶臭的主要发生源.本研究探究了填埋场内温度场下渗滤液饱和带内硫酸盐还原行为特征,结果表明,在25～55℃逐步升温的温度场下,渗滤液饱和带内的硫酸盐还原行为逐步增强且差异显著.渗滤液饱和带纵向SO42-和DOC迁移转化规律各异但趋势相同.硫酸盐还原行为主要发生在固液交界区和固相区,且固液交界区的电子供、受体呈特定化学计量关系.电子供体是引起硫酸盐还原行为差异的主要原因.本研究揭示的温度场下渗滤液饱和带内硫酸盐还原行为可为填埋场精准除臭提供重要依据.     

A study on the obstacle-induced variation of the gas explosion characteristics

A study on the variation of the gas explosion characteristics caused by the built-in obstacles was conducted in enclosed/vented gas explosion vessels. It has been well known that the obstacles in pipes and long ducts would accelerate the flame propagation, and cause the transition from deflagration to detonation. In this study, the explosion characteristics and the flame behavior of vented explosions and constant-volume explosions were investigated. Experiments were carried out in a 270-liter and 36-liter hexahedron vessels filled with LPG–air mixture. The explosion characteristics of the gas mixture were determined by using a strain-responding pressure transducer. The flame behavior was recorded by using a high-speed video camera. The shape and the size of the obstacle, and the gas concentration, were adjusted in the experiments.

It can be seen from the experimental results that, instead of being accelerated, the flame propagation inside the explosion vessel is decelerated by the plate obstacles fixed at the bottom of the vessel. Also, the characteristics of the enclosed explosion are not so affected by the built-in obstacles as those of the vented explosion are. It is believed that the eddy-induced turbulence behind the obstacle decelerates the flame propagation.     

Transport of volatile compounds in porous media in the presence of a trapped gas phase

The presence of an immobile gaseous phase in an otherwise-saturated porous medium affects the transport of volatile compounds. The linear theory of partitioning tracers suggests that a volatile tracer introduced into such a system should be retarded with a constant retardation factor. Using high concentrations, however, the saturation of the gaseous phase will change as an effect of the tracer test itself. Competitive gas transfer among all volatile compounds and the change of saturation may lead to tracer concentrations that are temporarily higher than those injected. We analyze the system in the framework of the coherence theory by Helfferich [Soc. Pet. Eng. J. 21 (1) (1981) 51]. The governing equations are formulated as functions of total concentration, i.e., the mass of solutes in all phases per pore volume. Neglecting dispersion and mass-transfer kinetics, we derive the characteristic form of the resulting system of hyperbolic equations. In a system with N volatile compounds, a variation of the concentrations splits up into N waves, each traveling with its own characteristic velocity. If the presence of a gaseous phase is sustained, one wave will be a standing one. We perform numerical model calculations for tracers with various Henry's law coefficients and show that the results agree with the semi-analytical solution obtained by coherence theory.     

城市污水排江工程模型试验的研究

对城市污水排江问题进行了模拟试验,通过对水力模型不同试验工况中改变喷嘴个数、射流速度、射流角度和上升管间距条件下的试验结果分析,结合武汉市污水排江工程问题,确定了黄浦路、平湖门尾水排放中的近区多喷口形式的最佳工程参数,实践证明效果良好。     

煤和瓦斯突出过程中瓦斯作用机理的研究

阐述了瓦斯在煤和瓦斯突出过程中所起的作用 ;指出煤层中瓦斯的存在改变了煤岩体的物理力学性质及响应特性 ,使之成为非稳定介质 ;特别强调在瓦斯突出发生时 ,瓦斯膨胀能起了至关重要的作用 ;由于瓦斯的存在 ,加剧了煤体失稳破坏的过程。     

Estimates of species- and ecosystem-level respiration of woody stems along an elevational gradient in the Luquillo Mountains, Puerto Rico

We measured CO₂ efflux from stems of seven subtropical tree species situated along an elevational gradient in the Luquillo Mountains, Puerto Rico and scaled these measurements up to the landscape level based on modeled and empirical relations. The most important determinants of ecosystem stem respiration were species composition and stem temperature. At a species scale, measured CO₂ efflux per unit bole surface area at a given temperature was highest in the early successional species Cecropia schreberiana and lowest in species that inhabit high elevations such as Micropholis garciniifolia and Tabebuia rigida. Carbon dioxide efflux rates followed a diel pattern that lagged approximately 6 h behind changes in sapwood temperatures. At an ecosystem scale, our simulation model indicates a decreasing trend of stem respiration rates with increasing elevation due to shifts in species composition, lower temperatures and reductions in branch surface area. The highest estimated stem respiration rates were present in the lowland tabonuco forest type and the lowest rates were present in the elfin forest type (mean 7.4 and 2.1 Mg C ha⁻¹ yr⁻¹, respectively). There was slight temperature-induced seasonal variation in simulated stem respiration rates at low elevations, with a maximum difference of 19% between the months of February and July. Our results coincide well with those of Odum and Jordan [Odum, H.T., Jordan, C.F., 1970. Metabolism and evapotranspiration of the lower forest in a giant plastic cylinder. In: Odum, H.T., Pigeon, R.F. (Eds.), A Tropical Rain Forest: A Study of Irradiation and Ecology at El Verde, Puerto Rico. U.S. Atomic Energy Commission, Oak Ridge, TN, pp. I165–I189] for the tabonuco forest type and extend their work by presenting estimates and spatial patterns of woody tissue respiration for the entire mountain rather than for a single forested plot.     

横向风对浮力扩散火焰的振荡影响研究

火焰振荡频率是火灾科学研究领域的一个重要基本参数,对横向风下火焰振荡频率的研究可以为火灾图像探测的参数设置提供理论依据。针对浮力扩散火焰(0.6×10~(-5)弗洛德数Fr2×10~(-2),10~2理查德森数Ri10~5),本研究将横向风条件下火焰结构假设为倾斜的柱状,通过对燃烧产生的浮力和横向风产生的拖曳力进行动力学分析,得出横向风条件下火焰振荡频率表达公式。结合实验结果得出,火焰振荡频率的理论值和实验值均随拖曳系数的增大(即外界风速的增加)而增大,但实验值的上升趋势较理论值平缓.这是因为公式忽略了风速对火焰温度和系数K的影响。     

污泥投配率对污泥中温厌氧消化效果影响的试验研究

试验装置采用半连续流污泥中温厌氧消化反应器,污泥培养接近成熟后开始每天按不同污泥投配率加泥和排泥.结果表明:污泥投配率在3%～10%时,有机物分解率先增大后减小,去除率均在30%以上;污泥投配率在15%和20%时,污泥的有机物去除率非常小;污泥投配率在5%时,有机物分解率最大为41.2%;单位VSS产气量随污泥投配率的增大而呈先急剧上升后逐渐下降的趋势,当污泥投配率为5%时,单位VSS产气量为0.60 L/g,符合美国污水处理厂设计手册标准,其他污泥投配率下该指标均小于0.4 L/g.因此,认为实验用污泥中温消化的最佳污泥投配率为5%,这时污泥的可消化性较好.