基于国内实测燃煤电厂烟气汞排放估算的不确定度

参照测量不确定度评定与表示的国家技术规范,基于近年来我国燃煤电厂常规污控设备协同脱汞的现场测试数据(文献报道和实测值)及各省原煤w(汞)的实测值,初步构建了国内燃煤电厂烟气汞排放不确定度的计算方法,并以2010年的燃煤量、污控方式布局为基础,计算了该年度汞排放的不确定度. 结果表明:2010年我国燃煤电厂烟气汞排放的总不确定度为48.8t,占平均排放总量的34.3%;其中60.2%源于污控设备脱汞效率的不确定度,39.8%源于原煤w(汞)的不确定度;采用ESP(静电除尘)、ESP+WFGD(静电除尘+湿法脱硫)、SCR+ESP+WFGD(选择性催化还原脱硝+静电除尘+湿法脱硫)和FF(袋式除尘)大气污控组合的机组各存在6.0、32.2、9.7和0.9t的烟气汞排放不确定度,分别占各对应机组烟气汞排放量的19.3%、32.8%、84.6%和53.6%,其中SCR+ESP+WFGD污控组合烟气汞排放的相对不确定度最大. 随着我国烟气脱硝工作全面推行,2015年以后,SCR+ESP+WFGD污控措施(组合)的机组所占比例将会提高到66%以上,如果仍以现有数据为基础,则来自SCR+ESP+WFGD污控措施(组合)机组的烟气汞排放不确定度将会大幅增加,因此急需增加对该类装置脱汞效率的实测样本数量.      

碳汞比对燃煤烟气中Hg脱除影响的实验研究

利用吸附反应器和袋式除尘器联合脱汞系统,研究了活性炭喷射对模拟烟气中元素汞的脱除影响。实验表明,吸附反应器对元素汞的脱除起主要作用,并且脱汞效率随碳汞比的增加而提高;碳汞比的变化对除尘器的脱汞效率影响不大。在碳汞比为4 000、6 000、8 000下,系统的脱汞效率分别为39.9%、42.5%、47.3%。实验同时探讨了除尘器滤袋上粉尘层的存在对脱汞效率的影响,结果表明:在表面过滤速度为0.98 m/min的实验条件下,在碳汞比为4 000、6 000、8 000下,粉尘层的脱汞效率分别为:3.65%、3.20%、3.66%。     

燃煤烟气脱汞处理技术

论述了燃煤烟气中汞的来源、存在形态、危害和脱除效率,综述了除尘装置、选择性催化还原(SCR)脱硝装置、脱硫装置对脱汞效率的作用,固体氧化物催化剂、卤素添加剂对单质汞的催化氧化的影响,探讨了单质汞催化氧化剂类型和脱硫中汞被还原的技术研究难点。燃煤电厂的监测数据表明脱汞中的重点问题有:如何提高SCR催化剂催化氧化单质汞的氧化效率,如何改进催化剂的抗硫性及稳定性,设备防腐蚀问题,如何改善湿法脱硫系统吸收效率以及吸收溶液中的汞沉淀分离技术:这些都是燃煤烟气汞污染控制技术的重点研究内容。     

新型SCR脱硝催化剂对汞的催化氧化研究

现有脱汞技术存在成本高、对设备有腐蚀的问题,通过对传统SCR催化剂进行改性,提高汞氧化性能,开发出同时脱硝脱汞新型催化剂,考察了NH3以及HCl等对脱汞性能的影响。结果表明:SCR催化剂改性后零价汞氧化率可达40%以上,NH3对零价汞的催化氧化有抑制作用;HCl对零价汞的催化氧化基本无影响。     

利用现有设备和技术控制燃煤烟气汞污染研究进展

就当前国内外利用现有气体净化设备和传统的脱汞技术进行燃煤电站汞污染控制研究进展进行了综述,并对各类设备与技术的脱汞特点进行了比较和分析,提出了适合我国国情的研究方向建议。     

旋流雾化脱硫塔除尘效果试验研究

在研究传统湿法脱硫塔的除尘效果基础上,提出了一种基于旋流雾化的协同脱硫除尘技术。该技术利用切圆布置旋流雾化器的湍流与雾化作用,使得烟气与浆液产生强烈碰撞,混合更加均匀,强化了细微颗粒湍流凝并作用,同时加剧了微细颗粒的相变凝并,提高了脱硫效率、雾滴及粉尘捕集效率。采用该技术对某300 MW火电机组进行脱硫除尘改造,现场测试结果表明:使用该技术的脱硫效率可达到99%以上,粉尘排放浓度由脱硫塔入口的50~60 mg/m~3降低到6~12 mg/m~3,旋流雾化技术在脱硫塔内具有脱硫降尘的双重作用。     

燃煤电厂烟气汞的排放及控制研究

随着环保意识的增强,燃煤电厂汞污染越来越受到人们的关注,对燃煤电厂烟气汞污染的控制也逐渐成为热点。介绍了燃煤电厂烟气中汞的排放形态及特性,分析了燃煤电厂烟气汞形态转化的影响因素,综述了有关燃煤电厂烟气中汞污染控制技术及研究进展,讨论了燃烧前脱汞、燃烧中脱汞和燃烧后脱汞技术,特别分析了利用现有烟气脱硫设备吸收法脱汞、吸附法脱汞、催化氧化脱汞的技术,并对燃煤电厂烟气脱汞技术的前景进行了展望,提出结合现有烟气净化设备同时脱汞的设想。     

燃煤锅炉烟气汞污染控制技术浅析

燃煤锅炉烟气是最大的人为汞排放源。通过对燃煤锅炉烟气汞分布及脱汞技术的分析,提出利用现有的烟气污染控制设备以提高汞的脱除效率,走复合式污染控制之路是目前我国经济技术上可行的选择。     

基于声波团聚的热脱附装置除尘的关键影响因素研究

针对土壤热脱附装置存在着严重的扬尘问题，将声波团聚联合喷雾的方法应用于热脱附装置的除尘，研究了声频、粉尘初始浓度、声压级和喷雾流量等对除尘效果的影响(粉尘的平均粒径小于10μm)。实验发现，在声频为1 400 Hz、喷雾浓度为1.0 L·m^-3的条件下，团聚室的除尘效率在60 s内达到98%;声压级从145 dB提高至153 dB后，除尘效率提高了38%;SEM结果表明，声波处理后的颗粒被碾碎并团聚；添加喷雾可以提高除尘效率，但不同的喷雾浓度对最终的除尘效率影响不大，施加喷雾后的最佳声频仍为1 400 Hz;粉尘和喷雾的初始浓度越大，团聚前期的除尘速率和最后的除尘效率越大，当喷雾浓度为2.0 L·m^-3时比没有喷雾时的除尘效率提高了44%,说明声波团聚对高浓度气溶胶的使用效果更好，研究结果可为热脱附装置除尘技术的研发提供参考。     

基于监测数据的我国燃煤电厂汞排放分析

燃煤是最大的人为汞排放源之一,我国已加强对燃煤电厂的汞排放控制要求。通过对16家燃煤电厂32台机组的汞排放情况进行全要素监测,分析总结出符合我国燃煤电厂特点的汞排放情况:我国燃煤机组中的汞质量平衡范围在70%~130%是合理的;燃烧后的汞经过烟气污染物处理设施后,70%以上进入粉煤灰和脱硫石膏,经烟气排入外环境的平均不足30%;安装SCR脱硝装置有助于烟气中汞的去除;除尘、脱硫设施对烟气中汞平均去除效率为38.5%、52.5%;各污染物控制设施对烟气中汞的总协同去除效率平均为74.1%,说明我国燃煤机组现有的污染物处理设施的协同控制对降低烟气中的汞排放有较好的作用。     

Effects of two sludge application on fractionation and phytotoxicity of zinc and copper in the soil

The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the effect of two sludges on fractionation of Zn and Cu in soil and their phytotoxicity to pakchoi. The loamy soil was mixed with 0%, 20%, 40%, 60% and 80% (by weight) of digested sewage sludge (SS) and composted sludge (SC). The additions of both sludges caused a significant raise in all fractions, resulting in that exchangeable (EXCH) and organic bound (OM) became predominance of Zn and organic bound Cu occupied the largest portion. There was more available amount of Zn and Cu in SS treatments than SC treatments. During the pot experiment, the concentration of Zn in EXCH, carbonate (CAR) and OM and Cu in EXCH and OM fractions decreased in all treatments, so their bioavailability reduced. Germination rate and plant biomass decreased when the addition rate was high and the best yield appeared in 20% mixtures at the harvest of pakchoi. The two sludges increased tissue contents of Zn and Cu especially in the SS treatments. Zn in pakchoi was not only in relationship to ΔEXCH and ΔCAR forms but also in ΔOM forms in the sludge-soil mixtures. Tissue content of Cu in pakchoi grown on SC-soils could not be predicted by ΔEXCH. These correlation rates between Zn and Cu accumulation in pakchoi and variation of different fractions increased with time, which might indicate that sludges represented stronger impacts on the plant in long-term land application.     

Intraspecific differences in effects of co-contamination of cadmium and

A hydroponic experiment was carried out to study intraspecific differences in the effects of different concentrations of cadmium (Cd)(0-10 mg/L) and arsenate (As(V)) (0-8 mg/L) on the growth parameters and accumulation of Cd and As in six wheat varieties Jing-9428, Duokang-1, Jingdong-11, Jing-411, Jingdong-8 and Zhongmai-8. The endpoints of wheat seedlings, including seed germination,biomass, root length and shoot height, decreased with increasing the Cd and As concentrations. Significant differences in seed germination, biomass, root length, shoot height and the accumulation of Cd and As were observed between the treatments and among the varieties (p ＜ 0.05). The lethal dosage 50% were about 20, 80, 60, 60, 80 and 20 mg As/L for Jing-9428, Duokang-1, Jingdong-11,Jing-411, Jingdong-8 and Zhongmai-8, respectively, and the corresponding values for Cd were about 30, 80, 20, 40, 60 and 10 mg Cd/L, respectively. Among the six varieties, Duokang-1 was found to be the most resistant to Cd and As toxicity, and Zhongmai-8 was the most sensitive to Cd and As co-contamination. The resistance of the six varieties was found dependant on the seedling uptake of Cd and As. Duokang-1 was the most suitable for cultivation in Cd and As co-contaminated soils.     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

Effect of sorbed and desorbed Zn(Ⅱ) on the growth of a green alga (Chlorella pyrenoidosa)

Toxic effect of Zn(Ⅱ) on a green alga (Chlorella pyrenoidasa) in the presence of sepiolite and kaolinite was investigated.The Zn-free clays were found to have a negative impact on the growth of C.pyrenoidosa in comparison with control samples (without adding any clay or Zn(Ⅱ)).When Zn(Ⅱ) was added,the algae in the presence of clays could be better survived than the control samples,which was actually caused by a decrease in Zn(Ⅱ) concentration in the solution owing to the adsorption of Zn(Ⅱ) on the clays.When the solution system was diluted,the growth of algae could be further inhibited as compared to that in a system which had the same initial Zn(Ⅱ) concentration as in the diluted system.This in fact resulted from desorption of Zn(Ⅱ) from the zinc-contaminated clays,although the effect varied according to the different desorption capabilities of sepiolite and kaolinite.Therefore the adsorption and desorption processes of Zn(Ⅱ) played an important part in its toxicity,and adsorption and desorption of pollutants on soils/sediments should be well considered in natural eco-environmental systems before their risk of toxicity to aquatic organisms was assessed objectively.