220MW热电联产锅炉中痕量元素的迁移及分布特性

本实验在北京某220 MW热电联产锅炉上进行。采用承重撞击器系统对该锅炉SCR前、ESP前以及FGD前的颗粒物进行采集,研究了痕量元素在烟道沿程上的迁移特性,另外,还给出了痕量元素在各固体燃烧产物中的分布。结果表明：ESP前的颗粒物上As、Cd、Cr和Pb的浓度明显高于SCR前的浓度;在从SCR到ESP的过程中,As、Cd、Cr、Pb从气态迁移到固态的质量分别占到了原煤中总质量的26 %、16 %、12 %和11 %;从ESP到FGD的过程中,颗粒物上As与Cd的浓度有略微增加,而Cr和Pb的浓度几乎不变;Mn在三个采样点的浓度几乎一致;绝大部分痕量元素存在于ESP捕获的飞灰中,在ESP出口处,As、Cd、Cr、Pb在<10 μm的四个粒径段上的质量随着粒径的减小而增大,而Mn的质量分布与颗粒物质量分布类似。     

660MW燃煤锅炉细微颗粒物中次量与痕量元素的分布特性

应用承重撞击器(DGI)采样系统在南昌某电厂2^#锅炉电除尘器前进行颗粒物采集,并同时采集了原煤样和底灰样。对飞灰的质量粒径分布、底灰和飞灰中次量与痕量元素的分布特性进行了分析。结果表明PM_1.0和PM_2.5质量分别占PM₁₀质量的16.0%~17.4%和46.9%~50.6%;Na、Mg、P、S主要富集在亚微米颗粒物中,Al、Si、Ca、Ti、Fe、K主要富集在超微米颗粒物中;随着颗粒物粒径的减小,As、Cd、Cr、Pb的浓度逐渐增大,且在亚微米颗粒物中的增幅大于超微米颗粒物,Mn在各级颗粒物中浓度相近;As、Cd、Cr、Pb大量富集于亚微米颗粒物之上,Mn在各级颗粒物中富集特性无明显差异,且各痕量元素挥发特性存在以下规律:As>Cd>Cr>Pb>Mn;文中给出了无控制条件下痕量元素的排放因子,PM_1.0中各元素排放比例存在以下规律:As>Cd>Cr>Pb>Mn。     

320 MW燃煤电厂痕量元素的分布、脱除及排放特性

燃煤电厂痕量元素的排放已经引起了世界的广泛关注。在一台配置选择性催化还原(SCR)+静电除尘器(ESP)+湿法脱硫装置(WFGD)的320MW燃煤电厂上进行了12种痕量元素(Cr、Mn、Co、Ni、Cu、Zn、As、Mo、Cd、Sb、Ba、Pb)排放特性的实验研究,使用了US EPA Method 29对4个测点烟气痕量元素进行同时取样,考察了痕量元素在电厂中的分布、协同脱除以及在烟囱中的排放。结果表明:锅炉、SCR、ESP、WFGD和整个系统的痕量元素质量平衡率均在可接受的范围内。这12种痕量元素主要分布在底渣和飞灰中,分别占据底渣、ESP灰、WFGD脱除及烟囱排放痕量元素总量的1.90%~27.6%和72.3%~98.0%,然而,它们在烟囱和被WFGD脱除的部分所占比例较少,两者之和仅占0.11%~0.66%。ESP和WFGD对烟气痕量元素的脱除率分别为99.39%~99.95%和40.39%~78.98%,SCR+ESP+WFGD对烟气痕量元素的总体脱除率为99.79%~99.99%。ESP对痕量元素较高的脱除效率是APCDs系统具有较高的协同脱除效率的主要原因。烟囱排放的痕量元素浓度及排放因子分别为0.01~12.88μg·m-3和(0.002~4.57)×10~(-12)g·J~(-1)。应进行更多的燃煤电厂痕量元素排放的研究,以便为中国燃煤电厂痕量元素的排放预测模型的建立以及相关标准的制定提供参考。     

320MW燃煤电厂痕量元素的分布、脱除及排放特性

燃煤电厂痕量元素的排放已经引起了世界的广泛关注。在一台配置选择性催化还原（SCR）+静电除尘器（ESP）+湿法脱硫装置（WFGD）的320MW燃煤电厂上进行了12种痕量元素（Cr、Mn、Co、Ni、Cu、Zn、As、Mo、Cd、Sb、Ba、Pb）排放特性的实验研究,使用了US EPA Method 29对4个测点烟气痕量元素进行同时取样,考察了痕量元素在电厂中的分布、协同脱除以及在烟囱中的排放。结果表明：锅炉、SCR、ESP、WFGD和整个系统的痕量元素质量平衡率均在可接受的范围内。这12种痕量元素主要分布在底渣和飞灰中,分别占据底渣、ESP灰、WFGD脱除及烟囱排放痕量元素总量的1.90%～27.6%和72.3%～98.0%,然而,它们在烟囱和被WFGD脱除的部分所占比例较少,两者之和仅占0.11%～0.66%。ESP和WFGD对烟气痕量元素的脱除率分别为99.39%～99.95%和40.39%～78.98%,SCR+ESP+WFGD对烟气痕量元素的总体脱除率为99.79%～99.99%。ESP对痕量元素较高的脱除效率是APCDs系统具有较高的协同脱除效率的主要原因。烟囱排放的痕量元素浓度及排放因子分别为0.01～12.88 μg·m^-3和（0.002～4.57）×10^-12 g·J^-1。应进行更多的燃煤电厂痕量元素排放的研究,以便为中国燃煤电厂痕量元素的排放预测模型的建立以及相关标准的制定提供参考。     

ICP-MS法测定煨粉葛中17种痕量元素

考察中药饮片煨粉葛中Pb、Cu、As、Cd、Hg、Mn等17种痕量元素的含量情况,以达到控制煨粉葛的质量和药效的目的。采用ICP-MS法测定煨粉葛中Pb、Cu、As、Cd、Hg、Mn等17种痕量元素的含量,从而评价不同产地煨粉葛的质量,为指导临床用药安全提供科学依据。采用ICP-MS法测得各痕量元素的线性关系良好,r在0. 9990～0. 9999,检测限0. 000493～0. 369619 ng/mL,加样回收率96. 6%～101. 9%。该方法灵敏度高,专属性好,可用于中药饮片痕量元素的定量分析。     

ICP-AES法同时测定卤鸭肉制品中的9种微量元素

采用湿法消解卤鸭肉样品,ICP-AES测定Cd、Cr、Cu、Fe、Mn、Ni、Pb、Zn 8种元素,对于痕量As,使用HG-ICP-AES测定。优化了ICP-AES的工作条件,探究了氢化物发生最佳条件。As的检出限为0.00027 mg/L。回收率范围为92.5%~108.0%,大部分元素的RSD在5%之内。     

电感耦合等离子体-原子发射光谱法同时测定水中9种微量元素

建立了电感耦合等离子体-原子发射光谱法同时测定水中As、Ba、Cu、Se、Zn、Mn、Cd、Cr、Pb等9种微量元素的检测方法。结果表明,9种元素的检出限均低于0.008 mg/L。在0.05~1.50 mg/L质量浓度范围内,9种元素的线性相关系数均大于0.999 0。精密度实验中,9种元素的极差值均小于0.007 mg/L。3个加标水平下,9种元素的平均回收率均在89.0%~113.6%范围内,相对标准偏差均小于5%。结果表明,该方法具有较高的灵敏度高,并具有良好的线性关系、精密度和准确度。该方法可作为水中As、Ba、Cu、Se、Zn、Mn、Cd、Cr、Pb等9种微量元素定量分析方法。     

呼和浩特市城区环境空气颗粒物中重金属含量时间分布特征

于2021年7月至12月，为揭示呼和浩特市城区环境空气颗粒物中重金属含量时间分布特征，使用中流量大气采样器采集环境空气中PM₁₀、PM_2.5样品，选择毒性效应较强的Cr、Mn、Fe、Ni、Cu、As、Cd和Pb等8种重金属作为研究对象，采用ICP-MS测定了其含量。结果表明：(1)2021年7月至12月，除Cu以外，其他重金属在PM₁₀和PM_2.5中的质量浓度变化趋势基本相同；(2)PM₁₀中Cr、Pb呈现出冬季>夏季>秋季的特点；Mn、Fe、As呈现出冬季>秋季>夏季的特点；Cu、Cd呈现出夏季>冬季>秋季的特点；Ni呈现出秋季>夏季>冬季的特点；PM_2.5中Cr、Mn、Fe、As、Cd、Pb呈现出冬季>秋季>夏季的特点；Ni的季节变化与PM₁₀相同，即秋季>夏季>冬季的特点；Cu呈现出秋季>冬季>夏季的特点。PM₁₀和PM     

微波消解-ICP-MS法同时测定海南椰子水中重金属元素铜、铅、锰、镉、铬

建立了微波消解-ICP-MS法测定椰子水中Cu、Mn、Pb、Cr、Cd五种元素的方法。椰子水样品经微波消解处理后,分别选用63Cu、208Pb、55Mn、52Cr、111Cd作为Cu、Pb、Mn、Cr、Cd的分析同位素,选择187Re为内标校正Pb、Cd,74Ge为内标校正Cu、Mn、Cr,Cu、Pb、Mn、Cr这4种元素。使用本法时Cu、Pb、Mn、Cd、Cr检出限分别为4.11、0.219、2.21、0.023、0.119 ng/mL,RSD分别为3.6%、3.2%、2.6%、4.6%、4.5%,试剂样品的加标回收率在86%～105%之间,该方法满足椰子水中重金属元素铜、铅、锰、镉、铬的分析要求。     

合肥市初夏PM2.5中重金属元素污染特征分析

大气颗粒物的污染目前已经成为大气污染的首要问题。选择合肥市滨湖新区、董铺水库、琥珀山庄、高新区四个监测点PM2.5为研究对象,对重金属元素Cu、Ni、Zn、Pb、Mn、Cr、Co、Cd的含量、富集系数、可能来源展开研究。结果表明,合肥市初夏时节PM2.5中重金属元素质量浓度含量最高的是Zn。滨湖新区、琥珀山庄和高新区的Cu元素污染显著。根据SPSS软件分析推测滨湖新区Cu和Cd可能来自交通领域污染源,董铺水库的Fe和Mn可能来源于自然因素,琥珀山庄的Pb和Cd可能来自交通污染源,高新区的Ni和Cr可能来源于工厂的电镀操作。     

Trace elements (Mn,Cr, Pb,Se, Zn,Cd and Hg) in emissions from a pulverized coal boiler

The concentrations of seven trace elements (Mn, Cr, Pb, Se, Zn, Cd, Hg) in raw coal, bottom ash and fly ash were measured quantitatively in a 220 tons/h pulverized coal boiler. Factors affecting distribution of trace elements were investigated, including fly ash diameter, furnace temperature, oxygen concentration and trace elements' characteristics. Modified enrichment factors show more directly element enrichment in combustion products. The studied elements may be classified into three groups according to their emission features: Group 1: Hg, which is very volatile. Group 2: Pb, Zn, Cd, which are partially volatile. Group 3: Mn, which is hardly volatile. Se may be located between groups 1 and 2. Cr has properties of both Groups 1 and 3. The smaller the diameter of fly ash, the higher is the relative enrichment of trace elements (except Mn). Fly ash shows different adsorption mechanisms of trace elements and the volatilization of trace elements rises with furnace temperature. Relative enrichments of trace elements (except Mn and Cr) in fly ash are larger than that in bottom ash. Low oxygen concentration will not always improve the volatilization of trace elements. Pb forms chloride more easily than Cd during coal combustion.     

Characteristics of coal combustion products (CCP's) from Kentucky power plants, with emphasis on mercury content

The Center for Applied Energy Research conducts a survey of Kentucky's coal-fired power plants every five years. The last survey was conducted in 2002 and covered most units at all of the plants in Kentucky. Special emphasis was placed on the spatial distribution of ash products, with each row of ESP's or baghouses samples wherever possible. In this manner, we can track the change in concentration of trace elements with relative temperature of the flue gas. Certain elements, such as Zn, Pb, and As, are known to be temperature dependent. The behavior of Hg, while also temperature dependent, is more complex owing to the adsorption of Hg on fly ash carbon. The survey provides a wide array of coal sources, ESP/baghouse collection temperatures, and fly ash carbon composition, all important in determining the behavior of Hg in the flue gas. In addition, many plants have FGD systems, allowing an assessment of the efficiency of FGD in capturing Hg from the post-ESP flue gas.     

Behavior of trace elements during pyrolysis of coal in a simulated drop-tube reactor

Release behavior and chemical form distribution of As, Pb, Cr, Cd and Mn in Datong coal during pyrolysis was studied in a simulated drop-tube reactor at a heating rate of about 1000 °C/s, including effects of temperature (300-1000 °C), atmosphere (N₂ and H₂), and holding time (0.3-10 min). Results show that the bleeding ratios of As, Pb, Cr, Cd and Mn increase with increasing pyrolysis temperature and holding time. Reductive environment results in higher emission of the elements. Among the five trace elements, As, Pb and Cd show similar behavior with volatilities higher than that of Cr and Mn at 1000 °C. The five trace elements in the coal and coal-derived chars are separated into five fractions through an extraction procedure. Ion exchangeable form of the elements is not found in the coal and the chars, and the elements remained in the residue fraction is the most dominant occurrence form in the coal and the chars for As, Pb, Cd and Cr. All the forms for all the elements undergo transformation in the pyrolysis resulting in reduced content in the chars.     

Trace element evaporation during coal gasification based on a thermodynamic equilibrium calculation approach

Thermodynamic equilibrium calculations using the HSC-Chemistry program were performed to determine the distribution and mode of occurrence of potentially toxic and corrosive trace elements in gases from coal gasification processes. The influence of temperature, pressure and gas atmospheres on equilibrium composition was evaluated. In these reducing conditions, the behaviour of the trace elements is complex, but some form of organization can be attempted. Elements were classified into three groups. Group A includes those elements that, according to thermodynamic data at equilibrium, could probably be condensed in coal gasification. Mn is classified in this group. Group B contains those elements that could be totally or partially in gas phase in gas cleaning conditions, and can be divided into two subgroups, depending on whether the cleaning conditions are hot or cold. Co, Be, Sb, As, Cd, Pb, Zn, Ni, V, Cr are elements in this group. Group C contains those elements that could be totally in gas phase in all the possible conditions, including flue gas emissions. Se, Hg and B are the elements that make up this group.     

Fine particle and trace element emissions from an anthracite coal-fired power plant equipped with a bag-house in China

Fine particle and trace element emissions from energy production are associated with significant adverse human health effects. In this investigation, the fine particles and trace elements emitted from the combustion of pulverized anthracite coal at a 220 MW power plant were determined experimentally in the size range from 30 nm to 10 μm with 12 channels. The particulate size distributions and morphological characteristics before and after the bag-house were evaluated. The uncontrolled and controlled emission factors of particles are compared with the calculated values from the US Environment Protection Agency, AP-42. Size-classified relative enrichment factors of As, Hg, Se, Cd, Cr, Cu, Al, V, Zn, Mn, Fe were obtained. Relative distributions of trace elements between bottom ash, fly ash and flue gas are determined by mass balance method. The bag-house collection efficiencies of particles and trace elements in the particulate phase are obtained. Finally, the controlled and uncontrolled emission factors of elements of different particulate size fractions are obtained, which will provide useful information for PM_2.5 and PM₁₀ emission inventory development, toxic and hazardous pollutant emission estimates and emission standards established for metal-based pollutants from a pulverized coal-fired boiler.     

Prediction of trace element volatility during co-combustion processes

The behaviour of some selected trace metals (Hg, Cd, As, Pb, Sb, Cr, Co, Cu, Mn, Ni and V) during co-combustion processes of bio-waste materials (sewage sludge, waste wood, refused derived fuel) and coal has been predicted by thermodynamic equilibrium calculations using the HSC-Chemistry 4.0 software. The influence of temperature, flue gas composition, trace element concentration and minor fly ash components on equilibrium composition was evaluated. For most of the elements, an increase in the HCl concentration favours the formation of gaseous species while increasing concentration of SO₂ in the gas composition enhances the formation of condensed species. Trace element interactions with minor fly ash components were predicted. From results obtained in this study it may be concluded that, from a thermodynamical point of view, the addition of a secondary fuel in combustion processes does not produce an increase in trace element emissions to the environment. Generally, trace elements are captured in ashes avoiding that these elements reach the stack.     

热处理条件对大同煤中微量有害元素变迁规律的影响

在自行设计的加压密闭热解反应器中研究了大同煤中As、Pb、Cr、Cd和Mn等微量有害元素在氮气条件下随温度（300～700℃）、压力（0.1～4MPa）和停留时间的变化规律,同时也考察了热解气氛（氮气和氢气）的影响.结果表明：这5种元素的析出率均随热解温度的升高而升高,随停留时间的延长而增大;反应压力的升高抑制了微量元素的释放;长停留时间,氢气气氛有利于微量元素的挥发; 热解过程中As和Cd较其他3种元素表现了较强的挥发性.