Developing a CFD heat transfer model for applying high expansion foam in an LNG spill

Liquefied natural gas (LNG) is widely used to cost-effectively store and transport natural gas. However, a spill of LNG can create a vapor cloud, which can potentially cause fire and explosion. High expansion (HEX) foam is recommended by the NFPA 11 to mitigate the vapor hazard and control LNG pool fire. In this study, the parameters that affect HEX foam performance were examined using lab-scale testing of foam temperature profile and computational fluid dynamics (CFD) modeling of heat transfer in vapor channels. A heat transfer model using ANSYS Fluent® was developed to estimate the minimum HEX foam height that allows the vapors from LNG spillage to disperse rapidly. We also performed a sensitivity analysis on the effect of the vaporization rate, the diameter of the vapor channel, and the heat transfer coefficient on the required minimum height of the HEX foam. It can be observed that at least 1.2 m of HEX foam in height are needed to achieve risk mitigation in a typical situation. The simulation results can be used not only for understanding the heat transfer mechanisms when applying HEX foam but also for suggesting to the LNG facility operator how much HEX foam they need for effective risk mitigation under different conditions.     

污染源以及环境空气中乙酸含量的测定

通过实验建立了测定污染源及环境空气中乙酸的气相色谱分析方法,给出各项指标。实验结果表明该方法分析结果准确、简单实用。并且以PTA装置气体中不同介质组成为例,探讨了含乙酸可燃气含量的测定方法。     

城市排水系统管理创新模式的研究

随着排水行业逐步走向市场化,传统的排水系统管理模式已经成为制约排水行业发展的最突出问题。绍兴市排水管理有限公司通过管理模式创新,创建了国内同行中独一无二的以泵站管理标准化为目标的“无人值守,有人巡视”的现代化排水运行管理模式,取得了显著的社会效益和经济效益,为国内排水行业现代化管理树立了典范。     

A.ferrooxidans对高硫煤矸石去除酸性水体中Cr(VI)的强化作用

本研究考察了Acidithiobacillus ferrooxidans（A.ferrooxidans）联合高硫煤矸石（富含FeS₂）对模拟煤矿酸性水体中Cr（VI）的去除效果.结果表明,处理Cr（VI）初始浓度为50mg/L的模拟煤矿酸性废水（pH=2.5）时,投配率为6.67~33.33g/L高硫煤矸石可使Cr（VI）去除达到良好效果.50mg/LCr（VI）在24h内即可完全被高硫煤矸石中的FeS₂还原成Cr（III）,且在反应终点时（120h）,6.67,13.33,33.33g/L高硫煤矸石对还原产物Cr（III）的吸附去除率分别为7.1%、20.2%、29.1%.然而,在高硫煤矸石的还原和吸附作用下,大部分的Cr仍以Cr（III）形式残留在酸性水体中,且高硫煤矸石的大量投加也给水体带来了Fe²⁺、Fe³⁺、SO₄^2-等二次污染物.在高硫煤矸石-Cr（VI）体系中引入A.ferrooxidans和9K培养基后,A.ferrooxidans介导的Fe²⁺生物氧化及产物Fe³⁺水解矿化过程可促进部分Fe²⁺、Fe³⁺、SO₄^2-等向次生铁矿物（包括施氏矿物和黄钾铁矾）转变,从而使模拟酸性水体中残留的Cr（III）通过次生铁矿物的吸附或共沉淀作用被清除.在A.ferrooxidans强化作用下,模拟煤矿酸性废水中Cr（VI）在96h即可达到99.4%的去除率.     

暗管排水治理渍害田初探

暗管排渍改良低产稻田的试验结果表明,暗管排水显著降低地下水埋探,提高了土壤通透性,减少了土壤中的有毒物质,改善了水稻生长的土壤环境。在宾阳试区和环江试区采用不同水稻品种试验结果表明。与改良前的1989年相比,分别增产53.8％和36.5和36.5％;比同年农艺措施相同的明沟排水田分别增产11.15％和19.93％。     

广场给排水工程设计中的几个问题

本文介绍了校园广场的给排水工程设计特点，提出解决广场排水坡度不能满足设计要求的具体办法探讨了绿地雨水排放中应该注意的几个问题．     

Acid mine-drainage toxicity testing

The BOD inhibition test, the activated sludge respiration inhibition test, and the Microtox® Bioassay procedure were examined for their potential as rapid toxicity screening methods for acid mine drainage (AMD) and for setting toxicity threshold levels in receiving waters. The BOD inhibition test proved to be unsuitable due to the high chemical oxygen demand of the toxicant. The long incubation time (minimum 5 d at 20°C) allowed growth of chemo-autotrophic bacteria and resulted in excessive flocculation and precipitation of metals, making accurate and meaningful measurements of inhibition impossible. The activated sludge respiration inhibition test was successful in measuring AMD toxicity, and for deriving toxicity threshold levels for the basic heterotrophic community in surface waters. However, it is a very time-consuming technique and is not sensitive enough to be used as a routine screening technique. The variability in toxicity was found to be due to the availability of metals as well as the effect of pH on metabolism. Simple linear models were derived to estimate inhibition within surface waters. Prediction of the inhibition caused by AMD can be made as long as the pH of the river water after mixing and the dilution of the AMD are known. Most accurate predictions are made using equations for specific pH ranges, but a useful estimation of inhibition can be obtained using the general equation: inhibition (%) = -2.34 pH + 6.41 AMD (%) + 22.1. The Microtox® Bioassay method, although expensive, was rapid and simple to use. It was the most sensitive test of the three, with the toxic response of marine bacteria increasing notably from 5 to 15 min due to the presence of bivalent metals in the toxicant. The problem of repeatability and reproducibility encountered with the activated sludge inhibition test was overcome with the highly standardised Microtox® method, making it an ideal screening method for AMD. However, the advantage of the activated sludge inhibition test is that the types of heterotrophic micro-organisms found in activated sludge are similar to those found in receiving waters such as the Avoca River and so more meaningful toxicity threshold values can be obtained.     

黄潮土的土壤水渗漏及硝态氮淋溶研究

在黄淮海平原 1hm2 小麦 -玉米轮作田块上 ,利用水量平衡模型对黄潮土的土壤水渗漏和硝态氮淋溶状况进行了定量研究。结果表明 ,黄潮土的土壤水渗漏和硝态氮淋溶状况非常严重 ,全耕作年土壤水渗漏量达到2 73 .9mm ,为灌溉水量的 60 .6% ;硝态氮淋溶达到 81.8kg·hm-2 ,为氮输入总量的 15 .7%。     

The gas-photocatalytic degradation of trichloroethylene without water

The photocatalytic degradation of gaseous trichloroethylene (TCE) without water has been studied. The degradation products were determined to be CO₂, HCl and Cl₂, and the reaction stoichiometry, was described as

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. The degradation rate was found to be linear with 0.16 power of the illumination intensity. When the TCE concentration was low (10¹⁴ mol L⁻¹ or a little more), its degradation rate model could be considered as first order kinetics. A mechanism of valence band hole oxidation was proposed.     

Evaluation of PCDD/F congener distributions in MWI flue gas treated with SCR catalysts

Partitioning of PCDD/F congeners between gaseous and particulate phases and removal efficiencies of the air pollution control devices (APCDs) for PCDD/Fs at an existing municipal waste incinerator (MWI) in Taiwan are evaluated via stack sampling and analysis. The MWI investigated is equipped with electrostatic precipitators (EP), wet scrubbers (WS) and selective catalytic reduction system (SCR) as APCDs. The average PCDD/F concentration of stack gas is 1.49 ng/N m³, and the International Toxic Equivalent Quantity (I-TEQ) is 0.043 ng-I-TEQ/N m³. The EP increases PCDD/F concentration by 174.0% while the average removal efficiency of WS + SCR system for PCDD/Fs reaches 99.1%. In addition, the PCDF removal efficiency achieved with WS + SCR system (97.1–99.8%) is higher than that for PCDDs (96.5–99.3%). The results obtained on gas/particulate partitioning in flue gas indicate that the particulate-phase PCDD/Fs accounted for 65% at the inlet of EP, 20% at the outlet of EP and 50% at the stack, respectively, of the total PCDD/F concentrations. This study also indicates that as the chlorination level of PCDD/F congeners increases, the percentage of PCDD/Fs existing in gas phase decreases in all flue gas samples.