煤炭洗选脱除煤中有害微量元素的实验研究

利用浮沉试验研究了通过煤炭洗选技术脱除煤中有害微量元素的可能性。结果表明,煤中有害微量元素在选煤过程中的行为取决于其有机亲和性。大多数煤中As、Cr、Hg、Mn、Ga、Ta、Ti、W、Cs等元素均可得到较高的理论脱除率,而B、Mo、Y等元素理论脱除率在各种煤中均较低。Be、Se、Pb等元素理论脱除率在不同煤中变化幅度较大,主要是由于其在不同煤中赋存状态不同而造成的。     

霍林河14~#煤中微量元素的分布赋存特征研究

运用反射偏光显微镜和扫描电镜等手段研究霍林河14#煤中矿物分布特征,运用浮沉实验和煤岩组分定量统计方法研究了煤中6种微量元素的分布赋存特征以及有机亲和性.结果表明,霍林河14#煤中矿物含量较高,以伊利石黏土矿物为主;霍林河煤中微量元素As,Cr和Hg含量较高,Pb,Cd和Se含量较低;元素As,Cr,Hg和Pb明显富集于矿物中,主要为无机态,与有机组分亲和性较低,而元素Cd和Se与有机组分亲和程度比其他4种元素高,基本上均匀分布于有机组分和矿物中.     

煤中微量有害元素洗选洁净的研究进展

阐述了煤中微量有害元素的赋存状态和洗选脱除机理,指出微量有害元素在选煤过程中的迁移行为取决于其赋存状态和有机亲和性,以无机态或矿物质结合态为主的有害元素大部分能被脱除,总结概括了常规洗选方法脱除煤中微量有害元素的研究状况,指出常规洗选方法一定程度上脱除煤中微量有害元素,重点分析了磁选脱除煤中有害微量元素的研究进展.     

ICP-MS用于测定特定地区饮用水中金属元素总量

运用电感耦合等离子体质谱法(ICP-MS)对大同市饮用水金属元素总量进行检测。结果表明,共发现16种金属元素,排名前五的金属元素分别为:Ba为39.51μg/L、Zn为12.03μg/L、Sb为3.43μg/L、Cr为2.30μg/L、Ni为2.10μg/L;As、Sb超标;Co与Ni、Mn,Ni与Cu、As、Ti、T1,Cu与As、Ti、T1,As与Ti、T1,Zu与Cd,Ti与T1之间均显著相关(P0.01),同时Be与Cr,Co与Cu、As、Ti、A1,Ni与V,Be与Cu、T1之间有相关相关性(P0.05)。得出结论,大同市饮用水部分元素含量较高,大部分金属元素具有共同来源,必须引起重视。     

乌鲁木齐市商品燃煤中汞等有害微量元素含量及分布特征

对乌鲁木齐市13个煤矿、22个用煤单位商品燃煤中Hg、As、Pb、Co、Zn、Ni、Cd、Cu和Cr含量,相关性及区域分布特征进行了研究。结果表明,各元素含量均在中国煤各元素含量范围内,Cu和Cr含量算术平均值略高于中国煤中算术平均值,其他微量元素含量算术平均值低于中国煤中算术平均值;各元素含量之间无高度相关,两组元素含量之间显示中度正相关,6组元素含量之间显示低度正相关;南部煤矿Hg和As算术平均值明显高于其他区域,西部煤矿Cd算术平均值明显低于其他区域,各区域各元素含量范围多数差异较大,未显示出区域一致性。     

贵州省煤中有害微量元素的地球化学特性

对贵州省主要产煤区特别是西南部高污染无烟煤进行了系统采样,应用电感耦合等离子体原子吸收光谱(ICP-AES)、原子荧光光谱(AFS)、离子选择性电极和化学方法测定了煤中As,Hg,F,Cl,Cr,Cd,Mo等有害微量元素和形态硫的含量特性,应用等离子体低温灰化仪分离出煤中的无机矿物质,测试结果表明,煤中As,Hg,F,Cr,Cd,Mo等元素的含量均显著高于我国煤中的平均值,含量异常高的煤主要分布在贵州省的西南部.微量元素与矿物质总量之间的相关性并不十分明显,Hg与As与黄铁矿之间显著相关.     

煤中有害微量元素的洁净潜势分析

为降低煤中有害微量元素含量,提高商品煤质量,以大河边矿原煤为对象进行分步释放浮选试验,测定有害微量元素在分步浮选产物中的含量,研究矿物质的迁移特征;对4个选煤厂的8个煤样采用电感耦合等离子体质谱测定其中有害微量元素含量,计算有害微量元素脱除率,研究有害微量元素的迁移特性和洁净潜势。结果表明,煤中矿物质大多集中在灰分中,基本可以随灰分的脱除而脱除;有害微量元素与矿物质之间的相关系数均大于0.708,说明两者存在高度相关性。煤中有害微量元素大多数以无机矿石的形态赋存,其迁移规律主要受控于无机矿物的迁移,少数有害微量元素以有机态存在,普通物理分选对其脱除效果较差;还有一些有害微量元素赋存状态多样,脱除率表现在较宽范围内。     

应用ICP-MS同时测定矿泉水中22种微量金属

研究结果表明应用ICP-MS可以同时测定饮用天然矿泉水中的Li、Be、B、Al、Ti、V、Cr、Mn、Co、Ni、Cu、Zn、Ge、As、Se、Sr、Mo、Ag、Cd、Sb、Ba、Pb、等微量金属元素.ICP-MS法具有快速、准确、处理简单、干扰少等优点.     

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.     

ICP-MS测定银杏叶茶中的多种微量元素的研究

采用微波消解银杏叶茶样品,电感耦合等离子体质谱法(ICP-MS)同时测定试样中As、Cr、Cu、Co、Pb、Hg、Bi、Ba、Be、Li、Ni、Sr、Ti、V、Zn、Mn、Mo、Sb、Se微量元素含量,同时对方法学进行考察。结果表明,此方法测定的各元素的相对标准偏差在1.22%~9.75%之间,加标回收率在91.9%~103.9%之间,此方法具有较高的精密度和加标回收率,适用于生物样品中多种金属元素的测定。ICP-MS法为银杏叶的开发和利用提供了科学依据。     

西部煤中环境敏感性痕量元素的燃烧迁移行为

应用仪器中子活化( INAA)、电感耦合等离子体原子发射光谱( ICP- AES)和原子吸收光谱( AAS)对我国西北部五个电厂原煤、底灰和飞灰中环境敏感性痕量元素的含量进行了系统测定,通过不同电厂原煤与燃烧产物中痕量元素的含量变化特征,揭示了痕量元素在不同燃烧产物中的相对富集规律.以痕量元素在不同燃烧产物中的相对富集系数为评价标准,建立了燃烧产物中痕量元素的分配模型.结合痕量元素的原始赋存状态,总结了痕量元素燃烧的迁移富集机理和环境效应.     

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.     

Geochemical distribution of trace elements in coal: modelling and environmental aspects

The present work consists of verifying a theoretical model based on mass distribution of trace elements in coal. Many versions of the model were tested using 42 elements in 8 different coals (5 American, 2 Brazilian and 1 Spanish). The calculated partial concentrations of elements in organic and inorganic (sulfide, carbonate and sulfate) fractions were obtained. These results could be summarised as following: B, Be, Br, Ge and V are associated to organic coal fraction while As, Cd, Co, Cu, Dy, Hg, Lu, Mo, Ni, Pb, Se, W and Zn occur mainly in sulfide minerals and Ba, Cr, Cs, Ga, Mn, Rb, Sb, Sn, Sr, Ta, U and Zr are distributed in the non-sulfide fraction. Finally, the volatility of trace elements was estimated using the calculated partial concentrations in organic and sulfide fractions. The applicability of this parameter in related environmental problems was discussed, comparing model results with experimental and theoretical literature data of the mobilisation of these species into atmosphere.     

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.     

Distribution of potentially hazardous trace elements in coals from Shanxi province, China

Shanxi province, located in the center of China, is the biggest coal base of China. There are five coal-forming periods in Shanxi province: Late Carboniferous (Taiyuan Formation), Early Permian (Shanxi Formation), Middle Jurassic (Datong Formation), Tertiary (Taxigou Formation), and Quaternary. Hundred and ten coal samples and a peat sample from Shanxi province were collected and the contents of 20 potentially hazardous trace elements (PHTEs) (As, B, Ba, Cd, Cl, Co, Cr, Cu, F, Hg, Mn, Mo, Ni, Pb, Sb, Se, Th, U, V and Zn) in these samples were determined by instrumental neutron activation analysis, atomic absorption spectrometry, cold-vapor atomic absorption spectrometry, ion chromatography spectrometry, and wet chemical analysis. The result shows that the brown coals are enriched in As, Ba, Cd, Cr, Cu, F and Zn compared with the bituminous coals and anthracite, whereas the bituminous coals are enriched in B, Cl, Hg, and the anthracite is enriched in Cl, Hg, U and V. A comparison with world averages and crustal abundances (Clarke values) shows that the Quaternary peat is highly enriched in As and Mo, Tertiary brown coals are highly enriched in Cd, Middle Jurassic coals, Early Permian coals and Late Carboniferous coals are enriched in Hg. According to the coal ranks, the bituminous coals are highly enriched in Hg, whereas Cd, F and Th show low enrichments, and the anthracite is also highly enriched in Hg and low enrichment in Th. The concentrations of Cd, F, Hg and Th in Shanxi coals are more than world arithmetic means of concentrations for the corresponding elements. Comparing with the United States coals, Shanxi coals show higher concentrations of Cd, Hg, Pb, Se and Th. Most of Shanxi coals contain lower concentrations of PHTEs.     

Leaching of ashes and chars for examining transformations of trace elements during coal combustion and pyrolysis

One sub-bituminous coal and two bituminous coals were subjected to the combustion and pyrolysis by slow heating to a temperature ranging 550-1150 °C. Leaching of raw coals, ashes and chars with dilute HCl and HNO₃ was carried out, and leachate concentrations of major and trace elements were determined. Such a comparative leaching method was validated for characterizing the modes of occurrence of trace elements in coal and their transformations upon heating. Leaching results suggested that Be, V, Co, Cr and Ni were partially associated with organic matter, and As was partially associated with pyrite. During the ashing at 550-750 °C, the organically associated trace elements in coal formed some acid-soluble species. After the ashing at 1150 °C, Be, Co, Cr and Ni, together with Mn, Zn, and Pb, were immobilized in ash against leaching, whereas As was not immobilized. After pyrolysis, the organically associated trace elements in chars remained insoluble in both acids, and some HNO₃-soluble As in coal turned to a HNO₃-insoluble species.     

Mineralogy, elemental composition and modes of occurrence of elements in Canadian feed-coals

Feed-coals used in some Canadian power plants were examined for their mineralogical and elemental composition. The mode of occurrence of elements (organic/minerals) in these samples were determined using sequential leaching by H₂O, NH₄OAc and HCl.Canadian feed-coals examined in this study are subbituminous to bituminous rank (calorific values: 19.62-29.88 MJ/kg). The sulphur content of these coals is 0.32-3.55%.Quartz and aluminosilicates (clay minerals and feldspar) dominate the mineralogy of these samples. The accessory minerals consists of pyrite, sphalerite, barite, calcite, anhydrite, chromite, zircon, biotite, and monazite, which occur as both primary and secondary cell filling types. An interesting mineral found in one of the subbituminous feed-coals is the gorceixite that is normally associated with degraded volcanic ash.The sulphur content of the feed-coals is an indication of their geological setting with feed-coal formed in a fresh water setting containing the least amount of S and those associated with evaporites having the highest S content.The concentrations of Cd, Cr, Cu, Hg, Ni, Se, V, and Zn in these Canadian feed-coals are low compared to world coals. Mercury content of these feed-coals ranges from 0.04 to 0.16 ppm. Mercury is mostly associated with the pyretic portion of coal and has direct correlation to As and S content in these coals. Arsenic in low sulphur coals is mostly associated with coal macerals and in higher sulphur coals with pyrite. About 47% of As in high sulphur coal is removed after leaching by HCl.Water soluble elements consist of Co, Ni and Mn, which are associated only with bituminous feed-coals. The removal of these elements by water is possibly due to an increased acidity of leaching solution and presence of soluble Cl and S.Beryllium and vanadium in low S coals are mostly removed after leaching by HCl, indicating a possible association with clay minerals. Limited Be and V is removed from lower clay mineral content coals; however, in high S content coals, more Be and V are removed.The speciation of As, Cr and Ni indicates that As is mostly present in the less-toxic form As⁺⁵ and Cr is present entirely as Cr³⁺, an essential human trace nutrient, found in both subbituminous and bituminous ranked coals. Nickel is present mostly as Ni²⁺ in oxygen coordination in these milled coals and carcinogenic compounds of nickel are not present in these feed-coals.     

Behaviour of elements and minerals during preparation and combustion of the Pernik coal,Bulgaria

The chemical and mineral composition, including major (Al, Ca, Fe, K, Mg, S, Si, Ti), minor (Na, P) and trace (Br, Cl, Co, Cr, Cu, Li, Mn, Ni, Pb, Rb, Sr, Zn) elements and different minerals, of the Pernik subbituminous coals and their preparation and combustion solid waste products were studied. Feed coals, upgraded coals (high-grade and low-grade coals) and their waste products, namely coal slimes and host rocks generated from the Pernik coal preparation plant, as well as combustion waste products such as bottom ashes, fly ashes and lagooned ashes resulted from the Republica coal-fired thermoelectric power station were characterized. The occurrence and behaviour (partitioning, volatilization, condensation, capture and retention) of the above-mentioned elements and various minerals during coal preparation and combustion are described. The results indicate some technological problems and possible environmental pollution of the air, water, soil and vegetation with certain elements in the areas surrounding both thermoelectric power station and coal preparation plant.     

Certification of the contents of some trace elements in a coal

The preparation of a coal reference material to be used in trace element analysis is described, as well as the tests to ascertain the homogeneity and stability of the material. Several analytical methods were applied by several laboratories to certify the contents of As, Cd, Cr, Co, F, Mn, Hg, Ni, Pb and Zn. The procedure followed for certification is explained.