Transesterification of waste vegetable oil under pulse sonication using ethanol,methanol and ethanol–methanol mixtures

This study reports on the effects of direct pulse sonication and the type of alcohol (methanol and ethanol) on the transesterification reaction of waste vegetable oil without any external heating or mechanical mixing. Biodiesel yields and optimum process conditions for the transesterification reaction involving ethanol, methanol, and ethanol–methanol mixtures were evaluated. The effects of ultrasonic power densities (by varying sample volumes), power output rates (in W), and ultrasonic intensities (by varying the reactor size) were studied for transesterification reaction with ethanol, methanol and ethanol–methanol (50%-50%) mixtures. The optimum process conditions for ethanol or methanol based transesterification reaction of waste vegetable oil were determined as: 9:1 alcohol to oil ratio, 1% wt. catalyst amount, 1–2 min reaction time at a power output rate between 75 and 150 W. It was shown that the transesterification reactions using ethanol–methanol mixtures resulted in biodiesel yields as high as >99% at lower power density and ultrasound intensity when compared to ethanol or methanol based transesterification reactions.     

Optimization of recertification intervals for PSV based on major accident risk

Overpressure is a major hazard in the process industry with the potential to lead to a major accident. Pressure Safety Valves (PSVs) are often used as the last layer of protection against such a hazard and require regular recertification in order to be dependable. The valve safely vents gas from a vessel when the pressure becomes excessive. It is often the practice in industry to apply one or two years as the normal recertification interval of PSV. However, experience from the Norwegian oil and gas industry is that the recertification process several times have caused leaks of gas. The process thus represents a certain risk in itself and the question is then whether the recertification intervals presently being used actually are optimal from a risk point of view? The objective of this paper is to look into this problem, applying typical data from an oil and gas installation. An optimal recertification interval will be calculated based on minimization of risk to personnel.     

Learning from the Bhopal disaster to improve process safety management in Singapore

The Singapore process industry is mainly made up of chemical and energy companies such as Mitsui Chemicals, Clariant, Exxon Mobil, Shell, Sumitomo, Petrochemical Corporation of Singapore and Infineum. Majority of these companies are located on Jurong Island, southwest of Singapore. Jurong Island houses nearly 100 leading petroleum, petrochemicals and specialty chemicals companies and the total investment is about S$42 billion in total. With a land surface area of only 716 km² and a high concentration of process plants, the Singapore government places strong emphasis on safety and risk management. In this paper, four process industry veterans from the government, academic and private sectors were interviewed. Through the interviews, the authors sought to understand the veterans’ perspectives on lessons that the Singapore process industry should learn from the Bhopal disaster. The veterans expanded their thoughts beyond the Bhopal disaster and provided many insights and suggestions critical to process safety management in Singapore and other countries. A systemic model of process safety management was derived from the interviews and key elements of operational process safety management were identified. In addition, a research agenda was identified based on the inputs from the veterans.     

膜法处理垃圾渗滤液新技术实验研究

将改进间歇式活性污泥法与FIL-MAX膜组合处理工艺相结合,应用于沈阳某垃圾场垃圾渗滤液处理工程实例中。通过实验,分析了COD、NH3-N等指标的处理效率以及影响因素,最终得出改进间歇式活性污泥法与FIL-MAX组合工艺处理在一定程度上改善膜污染、膜堵塞等常见问题。     

基于油水分离的餐饮废水破乳化技术研究

餐饮废水中乳化油的分离处理一直是一个技术难题,文章分别采用物理机械方法和物理化学方法对餐饮废水进行了破乳化研究。通过对比试验结果和分析破乳机理,总结出各方法不同的破乳特点。结果表明,温度越高分离效果越好,但在实际应用中,保持在50～60℃即可。低功率的超声波可以促进破乳效果,但超过30W,又会使溶液发生乳化反应。小分子醇类的加量越多,破乳化作用越强;醇类单链越长,分离效果越好。加入无机盐,在一定程度上可以加快破乳化速度,但效果并不明显。     

Process analysis of PM2.5 pollution events in a coastal city of China using CMAQ

US EPA's Community Multiscale Air Quality modeling system(CMAQ) with Process Analysis tool was used to simulate and quantify the contribution of individual atmospheric processes to PM_(2.5) concentration in Qingdao during three representative PM_(2.5) pollution events in the winter of 2015 and 2016. Compared with the observed surface PM_(2.5) concentrations, CMAQ could reasonably reproduce the temporal and spatial variations of PM_(2.5) during these three events. Process analysis results show that primary emissions accounted for 72.7%–93.2% of the accumulation of surface PM_(2.5) before and after the events.When the events occurred, primary emissions were still the major contributor to the increase of PM_(2.5) in Qingdao, however the contribution percentage reduced significantly,which only account for 51.4%–71.8%. Net contribution from horizontal and vertical transport to the accumulation of PM_(2.5) was also positive and its percentage increased when events occurred. Only 1.1%–4.6% of aerosol accumulation was due to PM processes and aqueous chemical processes before and after events. When the events occurred,contribution from PM processes and aqueous chemistry increased to 6.0%–11.8%. Loss of PM_(2.5) was mainly through horizontal transport, vertical transport and dry deposition, no matter during or outside the events. Wet deposition would become the main removal pathway of PM_(2.5), when precipitation occurred.     

Role of adsorption behavior on metal build-up in urban road dust

Metal pollution of stormwater runoff can cause potential toxic impacts on the receiving water environment and human health. Effective pollution mitigation requires accurate stormwater quality modeling. Even though a significant knowledge base exists on the factors influencing metal build-up on urban roads, very limited studies have investigated how metal–particulate interaction influences metal build-up. This study quantitatively assessed the influence of particulate characteristics, together with vehicular traffic and land use, on the build-up of Zn, Cu, Pb, Cr, Ni and Cd on urban roads. The study outcomes revealed that the variability in metal build-up is highly influenced by the variability associated with metal adsorption to particulates. The percentage contribution from particulate properties influencing metal adsorption in the case of 150 μm size road dust particles was found to be higher(Zn 44%, Cu 52%, Cr 16%, Ni 27% and Cd 45%) when compared to traffic and land use characteristics(Zn 21%, Cu 13%, Cr and Ni 10% and Cd 34%). Similar adsorption behavior was noted for metals associated with 150 μm size road dust particles. Among different particulate properties influencing metal adsorption, effective cation exchange capacity showed a strong positive relationship with the build-up of Cd compared to other metals,highlighting the potential role of Cd in stormwater quality as a readily available metal. The build-up of metals such as Cr and Ni are highly influenced by metal oxides of Al, Fe and Mn and clay forming minerals, indicating that Cr and Ni are relatively stable in nature.     

基于改进层次分析法的城中村火灾风险评估及防控对策研究

为更好的预防与控制城中村火灾风险,本文将事故树、层次分析法、模糊综合评价相结合,通过FTA建立AHP模型,从防火能力、灭火能力、安全疏散能力、安全管理水平4个维度出发构建了城中村火灾风险评估指标体系,并计算了各评价指标权重,通过实例研究证明,该方法能够较好的分析评价城中村火灾风险安全等级,最后提出相对应的对策与建议,有利于城中村火灾风险的预防与控制,为提高城中村火灾消防安全管理水平奠定了理论基础。     

豆奶粉废水生物处理技术

维维集团第二生产基地污水处理设施为全国第一套豆奶粉废水处理设施。该设施采用了“ＵＡＳＢ（ＡＦ）—活性污泥法”工艺。其中ＵＡＳＢ（ＡＦ）反应器是国内最大规模的生产性ＵＡＳＢ装置之一。     

难降解毒性有机物污水的高级氧化处理

高级氧化技术是目前水处理实践方面很有发展前途的一个方向，特别是对含难降解有机物的废水处理。文中介绍了在水处理中常见的几种高级氧化过程和它们的应用现状，分析了它们的特点，并指出该领域的发展趋势。