酸性矿井水的治理方法研究进展

酸性矿井水污染已成为全球范围内较为严重的环境污染问题之一,其污染范围广泛,诱因复杂,性质多变,危害深远。酸性矿井水未经处理排放造成江湖河流酸化,地表土壤板结,水中及土壤中的重金属含量超标,导致生物体内重金属过量富集,作物死亡,从而严重地危害了人类的健康和生命安全。对于酸性矿井水的治理意义重大,刻不容缓。讨论了目前国内外常见的酸性矿井水污染的治理技术方法,并对各种方法进行了比较。     

Consequence analysis of premixed flammable gas explosion occurring in pipe using a coupled fluid-structure-fracture approach

A coupled fluid-structure-fracture approach incorporating a high-efficiency detonation modeling algorithm was proposed to study the consequences of premixed flammable gas explosion occurring in pipe. A strain-rate-dependent failure criterion which is the vital prerequisite for accurate consequences prediction was derived based on the failure mechanism of materials at high strain rates and it was applied to account for the fracture of pipe. The simulated pressure time history and fracture patterns were validated against experimental results and good agreements were acquired. The interaction between detonation wave and pipe during crack extension, dynamic fracture processes of pipes with different initial flaws, venting features of detonation products and pressure profiles out of pipe were obtained and discussed in detail. The comparison with existing semi-empirical and CFD methods was performed and it is revealed that the deformation and fracture of pipe have obvious negative influences on the peak overpressure and the rate of pressure increase out of pipe. Because the energy absorption and dissipation due to structural deformation and fracture are well taken into account, the coupled fluid-structure-fracture method is expected to provide more rational consequences prediction and analysis results.     

High efficiency chlorine removal from polyvinyl chloride (PVC) pyrolysis with a gas–liquid fluidized bed reactor

In this research a gas–liquid fluidized bed reactor was developed for removing chlorine (Cl) from polyvinyl chloride (PVC) to favor its pyrolysis treatment. In order to efficiently remove Cl within a limited time before extensive generation of hydrocarbon products, the gas–liquid fluidized bed reactor was running at 280–320 °C, where hot N₂ was used as fluidizing gas to fluidize the molten polymer, letting the molten polymer contact well with N₂ to release Cl in form of HCl. Experimental results showed that dechlorination efficiency is mainly temperature dependent and 300 °C is a proper reaction temperature for efficient dechlorination within a limited time duration and for prevention of extensive pyrolysis; under this temperature 99.5% of Cl removal efficiency can be obtained within reaction time around 1 min after melting is completed as the flow rate of N₂ gas was set around 0.47–0.85 Nm³ kg^?1 for the molten PVC. Larger N₂ flow rate and additives in PVC would enhance HCl release but did not change the final dechlorination efficiency; and excessive N₂ flow rate should be avoided for prevention of polymer entrainment. HCl is emitted from PVC granules or scraps at the mean time they started to melt and the melting stage should be taken into consideration when design the gas–liquid fluidized bed reactor for dechlorination.     

Pyrolysis of waste tyres: A review

Approximately 1.5 billion tyres are produced each year which will eventually enter the waste stream representing a major potential waste and environmental problem. However, there is growing interest in pyrolysis as a technology to treat tyres to produce valuable oil, char and gas products. The most common reactors used are fixed-bed (batch), screw kiln, rotary kiln, vacuum and fluidised-bed. The key influence on the product yield, and gas and oil composition, is the type of reactor used which in turn determines the temperature and heating rate. Tyre pyrolysis oil is chemically very complex containing aliphatic, aromatic, hetero-atom and polar fractions. The fuel characteristics of the tyre oil shows that it is similar to a gas oil or light fuel oil and has been successfully combusted in test furnaces and engines. The main gases produced from the pyrolysis of waste tyres are H₂, C₁–C₄ hydrocarbons, CO₂, CO and H₂S. Upgrading tyre pyrolysis products to high value products has concentrated on char upgrading to higher quality carbon black and to activated carbon. The use of catalysts to upgrade the oil to a aromatic-rich chemical feedstock or the production of hydrogen from waste tyres has also been reported. Examples of commercial and semi-commercial scale tyre pyrolysis systems show that small scale batch reactors and continuous rotary kiln reactors have been developed to commercial scale.     

EFFECTS OF CONTROLLED DRAINAGE ON STORM EVENT HYDROLOGY IN A LOBLOLLY PINE PLANTATION1

ABSTRACT: A paired watershed approach was utilized to study the effects of three water management regimes on storm event hydrology in three experimental watersheds in a drained loblolly pine (Pinus taeda L.) plantation in eastern North Carolina. The regimes were: (1) conventional drainage, (2) controlled drainage (CD) to reduce outflows during spring fish recruitment, and (3) controlled drainage to reduce outflows and conserve water during the growing season. Data from two pit‐treatment years and three years of CD treatment with raised weirs at the watershed outlet are presented. CD treatment resulted in rises in water table elevations during the summer. But the rises were small and short‐lived due to increased evapotranspiration (ET) rates as compared to the spring treatment with lower ET demands. CD treatment had no effect on water tables deeper than 1.3 m. CD treatments, however, significantly (α= 0.05) reduced the stoning outflows for all events, and peak outflow rates for most of the events depending upon the outlet weir level. In some events, flows did not occur at all in watersheds with CD. When event outflows occurred, duration of the event was sharply reduced because of reduced effective ditch depth. Water table depth at the start of an event influenced the effect of CD treatment on storm event hydrology.     

硅锰合金电炉烟气干法净化煤气回收的设计与分析

结合9000kVA硅锰合金电炉烟气净化,对干法烟气净化、煤气回收工艺中烟气参数的选取和控制、安全保证等问题进行了分析,并对其进行了技术经济性评价。     

GC × GC--A New Analytical Tool For Environmental Forensics

Comprehensive two-dimensional gas chromatography, GC 2 GC, is a new analytical tool with a tremendous capability to separate and identify organic compounds in complex environmental samples. GC 2 GC uses two different chromatography columns coupled serially by a modulator to produce a volatility by polarity separation and distribute compound peaks across a two-dimensional retention time plane. The two-dimensional separation produces an order of magnitude more resolved peaks than traditional GC methods. The grouping or ordering of the peaks in the GC 2 GC chromatogram facilitates the identification of unknown compounds and the comparison of complex environmental samples. When a mass spectrometer detector is used, each resolved GC 2 GC peak yields a single-component, interference-free mass spectrum that leads to accurate matching with mass spectral libraries. GC 2 GC examination of marine sediment extracts identified a wide variety of chemical contaminants including polychlorinated biphenyls, p -nonylphenol isomers, polycyclic aromatic hydrocarbons, benzotriazoles, and the alkane, cycloalkane, alkylbenzene, alkylnaphthalene, and biomarker fractions of petroleum. The two-dimensional GC 2 GC chromatogram image permits rapid screening of the sediment extracts for these and other unknown contaminants.     

龙川江楚雄站碳侵蚀通量的动态分析

选取龙川江楚雄水文站进行了为期3年的采样,分析了水体中各形式碳的含量,并估算各碳的输送通量.结果表明:楚雄站3年的碳通量(FTC)分别为27.12×106g·km-2·a-1、24.87×106g·km-2·a-1和10.34×106g·km-2·a-1,分析流域在对碳输送过程中,以输送无机碳为主,分别占输送总量的89.7%、90.3%及91.9%;而汛期碳输送量分别占全年总量的90.9%、84.9%和83.8%,表现出流域汛期对碳的搬运量远远高于非汛期;溶解性有机碳通量(FDOC)与颗粒有机碳通量(FPO C)平均比为0.82,不同季节表现情况不一,非汛期溶解性有机碳(DOC)与颗粒有机碳(POC)含量相当,汛期机械侵蚀作用增强,导致FPO C远远大于FDOC,反映汛期对流域侵蚀作用以机械剥蚀为主,化学侵蚀为辅.研究期内恰遇2008年一场洪水,11月碳的侵蚀通量为8.53×106g·km-2·a-1,其中溶解性无机碳(DIC)、溶解性有机碳(DOC)和颗粒有机碳(POC)的输送量分别为7.37×106、0.36×106、0.80×106g·km-2·a-1,分别占2008年全年相应形式碳总量的33.3%、34.4%和59.9%,为当年非汛期碳侵蚀总量的2.3倍,反映洪水期的碳输出量对流域碳输出总量及构成存在不可忽略的贡献.     

Analysis of gas dispersion and ventilation within a comprehensive CAD model of an offshore platform via computational fluid dynamics

Maintaining an adequate air flow with a desired air quality that is free from hazardous gases is among the most important actions taken toward the improvement of safety in any process plant. Due to the increased focus on the consequences of existing hazardous material on safety, health, and the environment, air quality and sufficient ventilation within a plant has been increasingly considered in the design stage. This paper investigates and analyzes methane and hydrogen sulfite dispersion and the effect of air ventilation within a CAD model of an offshore platform using computation fluids dynamics (CFD). In addition, this method and its principals could be utilized in any other hazardous environment. Simulations of possible hazardous events along with solutions for preventing or reducing their probability are presented to better assess the data. These investigations are performed by considering hypothetical hazardous scenarios which consist of gas leakages from pipes and process equipment under different conditions. After drafting a precise and highly detailed CAD model of the plant and performing CFD simulations on this model, the results of gas behaviors, dispersion, distribution, accumulation, and its possible hazards are investigated and analyzed. The larger amount of details of the actual plant model in CFD simulation are obtained by using a combination of different methods and software. These include PDMS for 3-D drawing of the plan, Rinoceros for geometrical integration of the process equipment and facilities, and Sharc Harpoon which meshes the model. Moreover, the probability of inducing ignitable or toxic concentration of gases within the atmosphere and air ventilation of the unit is considered by these investigations.     

Interactive response of photosynthetic characteristics in Haloxylon ammodendron and Hedysarum scoparium exposed to soil water and air vapor pressure deficits

C₄ plants possess better drought tolerance than C₃ plants. However, Hedysarum scoparium, a C₃ species, is dominant and widely distributed in the desert areas of northwestern China due to its strong drought tolerance. This study compared it with Haloxylon ammodendron, a C₄ species, regarding the interactive effects of drought stress and different leaf–air vapor pressure deficits. Variables of interest included gas exchange, the activity levels of key C₄ photosynthetic enzymes, and cellular anatomy. In both species, gas exchange parameters were more sensitive to high vapor pressure deficit than to strong water stress, and the net CO₂ assimilation rate (A_n) was enhanced as vapor pressure deficits increased. A close relationship between A_n and stomatal conductance (g_s) suggested that the species shared a similar response mechanism. In H. ammodendron, the activity levels of key C₄ enzymes were higher, including those of phosphoenolpyruvate carboxylase (PEPC) and nicotinamide adenine dinucleotide phosphate-malate enzyme (NADP-ME), whereas in H. scoparium, the activity level of nicotinamide adenine dinucleotide-malate enzyme (NAD-ME) was higher. Meanwhile, H. scoparium utilized adaptive structural features, including a larger relative vessel area and a shorter distance from vein to stomata, which facilitated the movement of water. These findings implied that some C₄ biochemical pathways were present in H. scoparium to respond to environmental challenges.