超低排放燃煤电厂颗粒物脱除特性

在京津冀某660 MW超低排放发电机组,通过低压撞击器(DLPI)颗粒物取样系统对选择性催化还原装置(SCR)、低低温省煤器(LLTe)、静电除尘器(ESP)、高效湿法脱硫塔(WFGD)、湿式静电除尘器(WESP)进出口烟气中的颗粒物取样,通过滤膜取样系统对WFGD、WESP进出口颗粒物进行同步取样。获得了超低排放改造后,不同烟气处理设备对PM1、PM1~2.5、PM2.5~10的脱除效率。结果表明,SCR能够明显增加PM1的质量浓度,PM1增加了52.11%;LLTe能够显著提高ESP的脱除效率,尤其是0.1~1μm范围内的颗粒物;WFGD能够协同脱除SO2和颗粒物,但会增加PM1的排放,PM1质量浓度增加了59.41%,PM10中水溶性Mg2+、Cl-、SO42-组分增加;WESP对PM1、PM1~2.5、PM2.5~10均有较高的脱除效率,能够进一步降低颗粒物质量浓度。超低排放技术路线下,该燃煤电厂最终排放的PM10质量浓度为2.04 mg·Nm-3。     

超低排放改造后燃煤电厂细颗粒物排放特征

超低排放改造后,燃煤电厂细颗粒物排放特征发生了变化,为定量评估颗粒物中各组分的排放特征及环保设备对细颗粒物的影响选取了3台超低排放机组为研究对象利用DGI分级撞击采样器对湿法烟气脱硫装置(WFGD)、湿式静电除尘器(WESP)进、出口颗粒物取样并用多种指标分析研究.结果表明,3台机组出口处排放的PM_1、PM_(2.5)和PM_(10)质量浓度范围分别为0.25～0.38、0.31～0.42和0.42～0.57 mg·m~(-3)两种改造工艺下排放的PM_(10)质量浓度相当,但是颗粒物粒径分布和成分组成存在差异相比FP1和FP2机组,FP3机组PM_(2.5)/PM_(10)比值最高,可能原因是FP3机组安装了WESP,对粒径2.5μm以上的颗粒有更好地脱除效果.FP2和FP3机组排放的PM_(2.5)中水溶性离子总浓度分别为0.20 mg·m~(-3)和0.06 mg·m~(-3),FP2机组排放水溶性离子以Ca~(2+)和SO_4~(2-)为主,FP3机组以NH_4~+和SO_4~(2-)为主.FP2机组WFGD进出口颗粒物分析结果显示,WFGD过程会通过夹带含石灰石、石膏的脱硫浆液增加水溶性离子排放.在WFGD后加WESP能有效去除PM_(25)、PM_(10)颗粒物,降低水溶性离子对大气环境的影响.     

山西某电厂燃煤烟气SO_3与颗粒物排放特征

某330 MW电厂燃煤机组的污染物脱除设备(SCR脱硝塔、电除尘器、湿式电除尘器)进行了改造,并进行了污染物排放检测,得到SO_2、NO_x、颗粒物排放浓度分别为5.1,4.1,4.2 mg/m3,符合超低排放的标准。运用虚拟撞击采样器对湿式电除尘器进行了颗粒物分级浓度检测,得到PM_(2.5)、PM_(2.5~10)、PM_(>10)的脱除效率分别为83.29%、93.06%、96.51%,湿式电除尘器对PM_(2.5)脱除效果明显。对电除尘器进出口灰样进行元素分析和粒径分析,得到SO_3与颗粒物中碱性物质结合协同脱除效率为10.09%,粒径>13μm颗粒物在除尘器内部趋近于完全脱除。     

基于现场实测的湿电除尘器颗粒物特性变化研究

采用自主设计的固定源细颗粒物稀释采集系统以及根据GB/T 16157—1996方法对陕西关中地区某燃煤电厂湿电除尘器(WESP)进出口的颗粒物开展了现场实测与特性分析。结果表明:WESP对PM_(2.5)、PM_(10)和颗粒物的脱除效率分别为67.85%、43.57%、40.88%;WESP前后质量浓度峰值均出现在积聚模态,但由双峰(1.764、0.649μm)变成单峰(1.764μm),峰值移至大粒径段,数浓度峰值出现在爱根核模态和积聚模态,但由多峰(0.017、0.129、0.384、1.764μm)变成双峰(0.017、0.073μm),峰值移至小粒径段;经WESP,PM_(2.5)积聚模态大多粒径段颗粒物的质量浓度与数浓度均在下降(如在质量浓度和数浓度下降粒径段中,0.129μm处下降率均最少(均为59.03%)),爱根核模态大多粒径段颗粒物的质量浓度与数浓度均在上升(如在质量浓度和数浓度上升粒径段中,0.017μm处上升率均最少(均为55.36%)),但无论是WESP前或后,PM_(2.5)的主要质量浓度均集中在大粒径段、主要数浓度均集中在小粒径段;WESP对PM_(2.5)中大粒径段颗粒物的去除效果要优于小粒径段颗粒物。     

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.      

湿式静电除尘技术研究及应用

燃煤烟气细颗粒物排放的高效控制是控制雾霾天气的重要手段之一,为此国家颁布了世界上最严格的标准之一:《火电厂大气污染物排放标准》(GB13223-2011),要求火电厂粉尘排放浓度低于30 mg/m3,重点地区低于20 mg/m3。干式静电除尘器由于反电晕和二次扬尘等问题,对亚微米级颗粒物脱除效率较低,难以完全满足新标准的要求。湿式静电除尘技术(WESP)通过水膜清灰方式代替振打清灰,可有效控制湿法脱硫塔后细颗粒物的排放,实现燃煤烟气细颗粒物的深度脱除。该文详细阐述了湿式静电除尘器在粉尘脱除效率、材料润湿、抗腐蚀特性及多种污染物协同脱除等方面的最新研究进展,重点介绍了湿式静电除尘技术在燃煤电厂中的应用现状,并在此基础上对我国湿式静电除尘技术的发展做了总结和展望。     

湿式除尘器多种污染物协同脱除效果分析

为掌握湿式除尘器多种污染物协同脱除的效果,依托已投运的37台湿式除尘器机组,系统研究了湿式除尘器粉尘和雾滴去除能力、SO_3和PM_(2.5)的协同脱除效果,以及本体阻力和废水产生量,得出湿式除尘器具有较高的除尘效率,可以实现烟尘超低排放,除尘效率随入口烟尘浓度增加而增大;同时可以有效降低烟气中的雾滴含量,并具有80%左右的SO_3和PM_(2.5)脱除效率,但不同材质其废水产生量差别较大,需考虑废水进一步处理措施。因此湿式除尘器不仅是烟尘超低排放的有效手段,也是下一步控制SO_3和PM_(2.5)的有效措施之一。     

不同空气质量等级下环境空气颗粒物及其碳组分变化特征

为研究不同空气质量等级下环境空气颗粒物及其碳组分变化特征,于2016年3月在廊坊市对环境空气中PM_(10)、PM_(2.5)和PM1质量浓度及PM_(2.5)中碳组分质量浓度进行了在线监测.结果表明,监测期间廊坊市PM_(10)、PM_(2.5)和PM1质量浓度较高,其分别为204.1、107.9和87.8μg·m~(-3),日变化趋势呈双峰型分布.总体来说,当空气质量越好,PM_(10)、PM_(2.5)、PM1及其碳组分(OC、EC、SOC和POC)质量浓度越低,PM1/PM_(2.5)、PM1/PM_(10)和PM_(2.5)/PM_(10)比值越小.但"中度污染"时,PM_(10)质量浓度最高,且PM1/PM_(10)和PM_(2.5)/PM_(10)达到谷底值;同时OC质量浓度比"轻度污染"略低,而明显低于"重度污染",且主要出现在13:00~23:00,表明"中度污染"时细颗粒物和超细颗粒物占比下降,与其对应的首要污染物相一致.此外,OC/EC比值大于2.0,通过最小OC/EC比值法估算PM_(2.5)中SOC和POC,其浓度均值分别为12.2μg·m~(-3)和5.0μg·m~(-3).     

烧结过程细微颗粒物排放特征与控制方法

针对钢铁行业对大气环境质量的影响问题,对烧结过程中微细颗粒的排放特征、粉尘成分、PM_(2.5)成因及形貌、化学组成等进行总结分析,并对目前采用较普遍的湿式静电除尘器(WESP)和电袋除尘器(HPC)除尘效果进行了对比。分析研究得出:烧结过程中PM_(2.5)细微颗粒包括一次来源和二次来源,一次来源是由烧结过程直接排放,二次来源是气态污染物经过物理或化学变化而生成二次污染粒子,主要为硫酸盐、硝酸盐等。通过对比WESP和HPC的经济性和适用性,发现HPC适用于烧结厂新建除尘项目和旧除尘器的改造项目,不受烟气湿度的影响,与WESP相比具有较大优势。     

焦粉配比对烧结烟气中颗粒物排放的影响

从源头减排角度入手,通过烧结杯实验,在烧结原料固定碳为3.6%的条件下,使用Andersen 8级撞击器采样研究了焦粉配比分别为100%、75%、50%、0%时烧结烟气中颗粒物排放特性。结果表明:各组焦粉配比实验中排放的颗粒物质量浓度为98.66～134.04 mg/m~3,经旋风除尘器净化后,颗粒物质量浓度降至68.49～112.34 mg/m~3,总体颗粒物脱除率在16.19%～30.59%。烧结烟气中颗粒物以2.63μm以下细颗粒物为主。旋风除尘器前后的颗粒物质量浓度粒径分布均呈单峰分布,峰值出现在0.88μm附近。在烧结烟气的PM_(10)中,PM_1占比在78%以上,PM_(2.5)占比在94%以上。焦粉配比的改变对烧结烟气颗粒物排放的质量浓度粒径分布影响较小。     

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.     

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.     

基于综合水质标识指数和对应分析法的校园河道水质评价

以三峡大学的校园河道求索溪为研究对象,利用综合水质标识指数法确定求索溪水质类别,分析其水质时空变化规律,并利用对应分析法得出求索溪中不同监测点的主要污染因子.研究结果表明:求索溪整体的综合水质标识指数为7.423,整体水质为劣V类(地表水环境质量标准GB 3838-2002)且黑臭.从时间变化来看,求索溪4月份的水质最差,5月份次之,4、5月份所有监测点的水质都劣于V类且黑臭;8月份水质最好,水质为Ⅳ类;从空间分布来看,8个监测点综合水质标识指数均超过6.0,水质为劣V类,其中6号监测点的水质相对最好,监测点3号的水质相对最差;对应分析法得出求索溪的整体水体污染程度受总氮因子的影响最大,其次为总磷.该研究拟为求索溪及类似校园河道的水环境治理研究提供基础依据和参考.     

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. venicillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.     

Removal of cadmium using MnO2 loaded D301 resin

MnO2 loaded weak basic anion exchange resin D301 （Anion exchange resin, macroreticular weak basic styrene） as adsorbent has been prepared and applied to the removal of cadmium. The adsorption characteristics have been investigated with respect to effect of pH, equilibrium isotherms, removal kinetic data, and interference of the coexisting ions. The results indicated that the Cd^2＋ could be efficiently removed using MnO2 loaded D301 resin in the pH range of 3-8 from aqueous solutions with the co-existence of high concentration of alkali and alkaline-earth metals ions. The saturate adsorption capacity of the Cd^2＋ was 77.88 mg/g. The adsorption process followed the pseudo first-order kinetics. The equilibrium data obtained in this study accorded excellently with the Langmuir adsorption isotherm.     

Evaluation of phytoextracting cadmium and lead by sunflower, ricinus, alfalfa and mustard in hydroponic culture

Soil contaminated with heavy metals cadmium(Cd)and lead(Pb)is hard to be remediated.Phytoremediation may be a feasible method to remove toxic metals from soil,but there are few suitable plants which can hyperaccumulate metals.In this study,Cd and Pb accumulation by four plants including sunflower(Helianthus annuus L.),mustard(Brassica juncea L.),alfalfa(Medicago sativa L.), ricinus(Ricinus communis L.)in hydroponic cultures was compared.Results showed that these plants could phytocxtract heavy metals, the ability of accumulation differed with species,concentrations and categories of heavy metals.Values of BCF(bioconcentration factor)and TF(translocation factor)indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals.Changes on the biomass of plants,pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures.Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals,such as pH and Eh regulations,and so forth.     

Effect of coagulation pretreatment on the fouling of ultrafiltration membrane

The purpose of this study is to understand the effect and mechanism of preventing membrane fouling, by coagulation pretreatment, in terms of fractional component and molecular weight of natural organic matter （NOM）. A relatively higher molecular weight （MW） of hydrophobic compounds was responsible for a rapid decline in the ultrafiltration flux. Coagulation could effectively remove the hydrophobic organics, resulting in the increase of flux. It was found that a lower MW of neutral hydrophilic compounds, which could remove inadequately by coagulation, was responsible for the slow declining flux. The fluxes in the filtration of coagulated water and supernatant water were compared and the results showed that a lower MW of neutral hydrophilic compounds remained in the supernatant water after coagulation could be rejected by a membrane, resulting in fouling. It was also found that the coagulated flocs could absorb neutral hydrophilic compounds effectively. Therefore, with the coagulated flocs formed on the membrane surface, the flux decline could be improved.     

Penetration analysis of elements and bioleaching treatment of spent refractory for recycling

Acidithiobacillus ferrooxidans ATCC23270 and Acidithiobacillus thiooxidans TM-32 were used for bioleaching of spent refractories of aluminium and copper melting furnaces for their recycling.Firstly,penetration of elements into aluminium melting furnace refractory was investigated and it was found that up to 7 cm from surface was contaminated.Comparison on leaching efficiency by the strains ATCC23270 and TM-32 found that the strain ATCC23270 could treat larger amount of the refractories than the strain TM-32 could do.In the experiment of bioleaching of spent refractory aluminium melting furnace by the strain ATCC23270,high leaching efficiency were obtained on Al,Si,and Ca,and extremely low leaching performance was,however,shown on the rest of elements i.e.,Na,Mn,and Zn.Under the strain TM-32 use,relatively high leaching performance was recognized on Al,Si,Ca,Na,Mn,and Zn.In the experiment of bioleaching for spent refractory copper melting furnace,almost the same leaching trends were shown on Cu,Zn,Al,and Si under the strains ACTT23270 and TM-32 uses.