火电厂运煤系统抑尘控制因素探讨

火电厂运煤系统主要工艺过程包括卸煤、贮存、掺烧、煤输送到煤仓等。运煤系统设备及转运站扬尘污染严重,分析了污染发生的原因及解决办法,阐述了运煤系统的优化设计方案。     

半干法烟气脱硫袋式除尘器设计初探

介绍了半干法烟气脱硫工艺及脱硫后烟尘的特点,针对半干法脱硫后烟尘的特点,袋式除尘器设计时采取了一系列的技术措施,从而保证了脱硫系统的正常运行。     

电石炉烟气除尘系统设计探讨与实践

介绍了电石炉的生产工艺和除尘系统的工艺特点,以及电石炉除尘系统设计前和实际工程设计中需要注意的一些问题。     

城市土壤和地表灰尘重金属污染研究进展与展望

随着城市化和工业化的不断推进,城市土壤和地表灰尘重金属污染日趋严重,对城市环境和人类健康构成威胁,已成为国内外城市环境研究的热点问题.从重金属污染水平及其时空特征、污染源解析方法、生态和健康风险这3个主要方面,对国内外城市土壤和地表灰尘重金属研究成果进行了梳理和归纳.分析了当前研究存在的不足,并对未来研究进行了展望,即研究土壤和地表灰尘重金属在不同条件下的相互影响机制,通过丰富验证方法加强重金属来源解析模型结果的可靠性研究,加强来源驱动下重金属化学形态差异和地表灰尘短期累积污染过程的研究,完善暴露参数并深入探究重金属的化学形态对其生态和健康风险的影响,以提高风险预测水平.     

Topical application of synthetic pyrethroids to cattle as a source of persistent environmental contamination

Abstract

Following the application of permethrin or cyhalothrin to cattle for the control of ectoparasites, the occurrence and persistence of these chemicals was assessed on the animals and in their environment. The release of permethrin from ear tags containing 1g of the drug on cattle was followed for 65 days and lead to concentrations of 5 to 35 μg of permethrin per gram of hair on the shoulders. On the flanks of the animals, the corresponding values were 10 times lower. Across the 1.5 acre pasture, high concentrations of permethiin were measured at various locations and long after treatment: 6 μg/g on bark of a birch after one week, 5 μg/g on a pole of the fence after two weeks, 1 μg/g in grass from a resting site of the animal after six weeks, and 0.5 μg/g in bark of a pine tree after three month and two weeks after the animals had left the pasture. In similar assays, cyhalothrin applied to milk cows as a pour‐on preparation was monitored. One week following treatment with 0.2 g/animal, hair cut from the shoulders contained 5 μg/g of the insecticide, which disappeared with a half‐life of 12 days. Dust collected two weeks after the pour‐on treatment from the milk barn where the cows were milked twice daily contained 47 μg/g of cyhalothrin, which disappeared with a half‐life of 44 days. These results show that synthetic pyrethroids used on farm animals can be the source of widespread and persistent contamination.     

京津冀及周边区域PM2.5叠加沙尘重污染过程特征及预报效果分析

选取京津冀及周边区域2018年11月23日至12月4日一次大范围、长时间且PM_2.5叠加两次沙尘传输的复合型重度污染过程开展特征研究,分析了首要污染物PM_2.5和PM₁₀浓度的发展演变,以及污染气象影响因素;结合激光雷达地基和车载走航监测结果,以及HYSPLIT后向轨迹结果,讨论了区域污染传输的情况;并对重污染期间NAQPMS、CMAQ和CAMx这3个空气质量模式的预报效果进行了回顾分析.结果表明,研究时段PM_2.5叠加两次沙尘传输导致区域中南部多数城市达到重至严重污染水平,张家口、北京、石家庄、邯郸和郑州PM₁₀小时峰值分别为1 589、864、794、738和766μg·m^-3,PM_2.5小时峰值浓度分别为239、319、387、321和380μg·m^-3.地面弱气压场、高湿、逆温等静稳条件和沙尘是重要的污染气象和天气因素.激光雷达地基和车载走航监测数据结合HYSPLIT后向轨迹分析表明重污染期间区域西南和东...     

北京市中心城区道路尘土中铂族元素的污染特征

为研究北京市中心城区铂族元素(PGEs)的污染状况,于2009年12月采集了二环道路尘土样品.样品经王水消解和阳离子交换树脂分离纯化后,采用电感耦合等离子体质谱法(ICP-MS)测定了道路尘土中PGEs的含量.结果表明,二环道路尘土中,Pd的含量为17.40～458.75 ng.g-1(平均值为126.66 ng.g-1),Pt的含量为10.04～182.89 ng.g-1(平均值为65.25ng.g-1),Rh的含量为4.00～68.04 ng.g-1(平均值为22.67 ng.g-1).与国内外其它城市相比,Pt含量偏低,Pd和Rh含量处于中等水平.总体而言,近几年道路尘土中Pd含量有了较大幅度的升高.中心城区的PGEs平均含量从大到小的顺序为:西二环≈东二环>北二环>南二环,主要受机动车流量控制.不同粒径的道路尘土中PGEs含量不同,0.125～0.25 mm粒径范围内尘土中的PGEs含量最高,而粒径<0.063 mm的尘土中PGEs含量较低.采用粒径<0.063 mm尘土中的PGEs含量来评价整个道路尘土中的PGEs含量容易导致结果偏低,从而低估其在环境的污染水平.     

裂变产物170Tm的体内蓄积特性诱发骨髓细胞突变效应研究

对裂变产物~(170)Tm的体内蓄积特性和诱发细胞突变效应的监测结果表明,当机体摄入~(170)Tm后,在短时间内即能迅速进入并滞留于骨组织中,其滞留量占体内各器官组织中的首位呈现高度选择性亲骨特征,在机体摄入~(170)Tm后的不同阶段,骨组织中的累积吸收剂量随着观察时间的延长而增升,其诱发骨髓细胞的染色体畸变率亦相应增高。由~(170)Tm内污染所诱发的染色体结构异常为染色单体型畸变,其中主要为染色单体断裂。随着骨组织中累积吸收剂量的增升,可观察到在一个细胞中同时有两个畸变发生,也诱发个别的染色体易位。     

静电旋风水膜除尘系统电晕极优化实验研究*

为了研究电晕极结构对静电旋风水膜除尘系统的影响,采用逐步优化法,对比十字形芒刺电晕极和笼式环形电晕极在不同横向极距、纵向极距、芒刺数下对电场特性的影响。研究结果表明:经优化后,加入芒刺的笼式环形电晕极放电能力优于未加入芒刺的笼式环形电晕极和十字形芒刺电晕极,并在与水膜共同作用时具有较高的除尘效率,其结构参数为:从上至下4层圆环半径依次为107,80,54,28 mm;相邻圆环纵向极距为150 mm,圆环与集尘极的横向极距为90 mm;半径最小圆环上芒刺数为8根,其直径为2 mm,长度为10 mm。优化后的电晕极结构与水膜作用有助于提升静电旋风水膜除尘系统的除尘效率。     

Inerting effect of CaCO3 powder on flame spread of wood dust layer

The effect of CaCO₃ powder, a typical inert dust, on the flame spread characteristics of wood dust layers was studied using an experimental device to understand the ignition characteristics of and develop inert explosion-proof technology for deposited wood dust. The results showed that the flame spread velocity (FSV) of the mixed dust layer was affected by the dispersion effect of CaCO₃ powder and physical heat absorption. As the CaCO₃ powder mass fraction increased, the FSV of the dust layer first increased and then decreased, reaching a peak at a 50% mass fraction. Moreover, the front-end temperature of the flame gradually decreased, and the red spark faded. The combustion reaction of the mixed dust layer could be more completed, and the colour of the combustion residue changed from charcoal black to charcoal grey. The coupling effect of the initial temperature and wind speed can promote an increase in the FSV in the mixed dust layer. The Gauss–Amp model of the FSV of the wood dust layer and mass fraction of CaCO₃ powder showed that the peak of the FSV occurred when the mass fraction of CaCO₃ powder was between 40 and 50%. Thus, a good inerting and explosion-proof effect can be achieved by using CaCO₃ powder with a mass fraction of more than 50%; it can improve the whole inerting process. Inert explosion-proof technology should be considered when assessing fire and explosion risk of dust in real process industry situations.