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。     

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选择性催化还原（SCR）前、电子除尘（ESP）前以及烟气脱硫（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3个采样点的浓度几乎一致;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4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。     

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     

燃煤电厂煤粉炉及CFB锅炉PM2.5产生及排放特性的现场实验研究

采用稀释采样方法对一台220 MW煤粉炉(锅炉A)及一台300 MW的CFB锅炉(锅炉B)电袋复合式除尘器前后PM_2.5进行现场采样。通过ELPI测定PM_2.5的粒径分布;采用SEM分析PM_2.5的显微结构;采用EDX及ICP-OES分别对分级PM_2.5中次量及痕量元素含量进行了检测。结果表明,锅炉A和B除尘前后对应的PM_2.5粒数及质量浓度分布均不同;锅炉A和B产生的PM_2.5分别以较为光滑球形和不规则形状为主,锅炉A除尘后PM_2.5呈表面粗糙球形,锅炉B除尘后PM_2.5单颗粒形貌特征不变;锅炉A和锅炉B产生的PM_2.5除尘前后在各粒径段中Si、Al、Fe、Ca和Mg含量基本一致,As、Cd和Se含量随着粒径的减小而增大;除尘后锅炉A产生PM_2.5中As和Se含量增加,且在亚微米PM_2.5中As和Se含量的增加更明显,锅炉B除尘后PM_2.5中As和Se含量基本不变。     

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。     

燃煤锅炉SCR对颗粒物排放特性影响

我国电厂多数采用选择性催化还原（SCR）脱硝技术降低电厂NO_x排放,目前关于电厂中SCR对颗粒物排放特性的影响研究十分匮乏。本研究对一热电联产锅炉SCR前后颗粒物和飞灰进行取样,分析颗粒物质量粒径分布以及化学成分。采用计算机控制扫描电镜（CCSEM）对飞灰进行分析,获得颗粒物单颗粒成分。结果表明SCR前后PM₁₀均呈双峰分布。经过SCR后,PM_0.21浓度降低约62%（质量）,而PM_0.21-1浓度升高19%（质量）;PM₁中SO₂相对含量增加约6%（质量）,SiO₂和Al₂O₃相对含量降低,而CaO相对含量没有明显变化;经过SCR后,PM_1-10浓度降低约17%（质量）,成分基本没有变化,但是颗粒成分变得更均一,说明经过SCR后,PM_1-10发生交互作用。因此经过SCR后PM_1-10浓度降低不仅由于颗粒物在SCR中发生沉积,更有可能是颗粒物之间交互作用导致。     

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。     

湿法脱硫装置对燃煤锅炉PM2.5排放特征的影响

采用二级稀释采样方法对1台电厂煤粉炉、1台电厂CFB锅炉和2台工业层燃炉配备的WFGD前后烟气中PM_2.5进行现场采样。采用ELPI分析PM_2.5的数量及质量浓度粒径分布;通过SEM分析PM_2.5的显微结构,通过XRF、ICP-OES和离子色谱法分别对PM_2.5中次量、痕量元素及水溶性离子含量进行测定。研究结果表明,相比于WFGD前,煤粉炉和CFB锅炉WFGD后PM_2.5质量浓度减少,而层燃炉WFGD后PM_2.5质量浓度增加。WFGD后PM_2.5中存在大量块状、层状、片状、细小柱状和球形颗粒聚合体的结构,浆液成分及脱硫产物的附着会使PM_2.5的外观形貌特征发生显著变化。脱硫后由于脱硫浆液的参与,PM_2.5中Ca、S及相应Ca²⁺、SO₄^2-含量显著增加,Si和Al的含量下降;气相的As、Se和Hg也会发生不同的化学变化从而进入PM_2.5。湿法脱硫过程中浆液会捕集烟气中颗粒物,但脱硫浆液成分及脱硫产物会经由干化作用直接形成颗粒或与原有颗粒经碰撞聚合形成新颗粒。     

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。     

矿物质化合物对含油污泥焚烧过程中重金属迁移转化的影响

为了厘清矿物质化合物对含油污泥焚烧过程中重金属迁移转化的影响规律,以胜利油田罐底含油污泥为研究对象,在水平管式炉上分别进行了含油污泥添加CaO、Fe₂O₃、Al₂O₃、MgO后的焚烧实验,对获得的焚烧底灰分别进行了重金属总量、浸出特性以及风险性分析。研究结果表明：矿物质在焚烧过程中形成的残渣对重金属均有一定的吸附作用,CaO对Cu、Cr、Pb和As的吸附效果最好,其中Cu的残留率达到93.40%。不同矿物质化合物对重金属浸出的抑制效果不同,其中Al₂O₃对Cr、Zn、Pb、As、Cd的浸出特性表现出了最强的抑制效果,且Zn、Pb和As的浸出率均低于5%。矿物质对重金属风险性影响的规律性不强,CaO和Al₂O₃对降低Zn和As的风险性效果较为显著,Zn和As生物有效态含量均低于18%。     

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.     

The characteristics of inorganic elements in ashes from a 1 MW CFB biomass gasification power generation plant

This paper investigated the characteristics of inorganic elements in ashes from biomass gasification power generation (BGPG) plant. The ash samples of the gasifier ash, separator ash and wet scrubber ash were collected in a 1 MW circulating fluidized bed (CFB) wood gasification power generation plant. Particle size distribution of ashes was determined by gravimetric measurement and super probe analyzer. The concentrations of trace elements and major ash-forming elements, such as As, Al, Ca, Cd, Cr, Cu, K, Mg, Na, Ni, Pb, Ti in different ashes as a function of particle size were determined by Inductive Coupled Plasma Spectrometer. The concentrations and distribution coefficient and enrichment factors of the inorganic elements in ashes were studied. X-ray fluorescence spectrometer and X-ray powder diffraction were used to provide information on the characteristics of the ashes. The results showed that most of the trace elements had an enrichment tendency in the finer size particles. A considerable amount of the ashes was residual carbon. Most of the volatile e.g. halogen elements and alkali elements existed mainly in wet scrubber ash and enriched in fly ash. Most of the Si, Ni, Pb, Zn, Cr, Cd were found in separator ash, indicating an enrichment of heavy metal elements in separator ash. K, S, Mn, Cu mainly existed in gasifier ash.     

Volatility and chemistry of trace elements in a coal combustor

The volatility of 16 trace elements (TEs) (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Se, Sn, Te, Tl, V, Zn) during coal combustion has been studied depending on the combustion conditions (reducing or oxidizing) and type of coal (high- or low-ash coal), together with their affinities for several active gaseous atoms: Cl, F, H, O, and S.

The elements can be divided into three groups according to their tendencies to appear either in the flue gases or in the fly ashes from a coal combustor:

Group 1: Hg and Tl, which are volatile and emitted almost totally in the vapor phase.

Group 2: As, Cd, Cu, Pb and Zn, which are vaporized at intermediate temperature and are emitted mostly in fly ashes.

Group 3: Co, Cr, Mn and V, which are hardly vaporized and so are equally distributed between bottom ashes and fly ashes. In addition, Sb, Sn, Se and Te may be located between Groups 1 and 2, and Ni between 2 and 3.

At 400 and 1200 K, the 16 TEs behave differently in competitive reactions with Cl, F, H, O and S in a coal combustor.     

The fate of trace elements and bulk minerals in pulverized coal combustion in a power station

The behaviour of 15 trace elements (As, Ba, Cr, Cu, Mn, Mo, Nb, Ni, Pb, Rb, Sr, V, Y, Zn and Zr) and 10 major and minor elements (Al, Ca, Fe, K, Mg, Na, P, S, Si and Ti) in coal during combustion in a power station has been studied. Synchronized sampling of pulverized coal, bottom ash and fly ash was undertaken over a limited time period. Fly ash morphology was studied by SEM and the mineral composition was studied by EDX and XRD. Major, minor and trace elements were determined by XRF and AAS. Differences between the composition of the ashes of pulverized coal, bottom ashes and fly ashes have been observed. As, Cu, Mo, Pb and Zn were concentrated in the fly ash. The relationship between the composition of the fly ashes and their particle size was studied. Enrichment factors were calculated for each element in different size fractions. As the particle sizes of fly ash decrease, the concentrations of As, Cu, Mo, Pb and Zn increase. From the different composition of bottom ashes and fly ashes (and relying on the results of the characterization of the feed coal carried out in previous work), it can be assumed that pyrite and carbonates make a greater contribution to the furnace bottom ashes. Quartz carries through into the fly ash. This mineral is almost absent in the finest fractions, reflecting the absence of small quartz particles in the feed coal.     

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.