开滦煤洗选过程中稀土元素的迁移和分配特征

以河北开滦矿区晚古生代煤及其洗选产品为研究对象，运用电感耦合等离子体质谱（ICP-MS）和逐级化学提取的方法，对稀土元素的质量分数及其在洗选过程中的迁移和分配特征进行了研究。结果表明，开滦矿区煤中稀土元素没有明显富集；稀土元素在入洗原煤及其洗选产品中，以煤泥中质量分数最高，尾煤次之，在尾煤和煤泥中均相对富集；稀土元素在精煤中的质量分数最低；同原煤相比，中煤的稀土元素质量分数没有明显变化。原煤及其洗选的4种产品中的稀土元素分配模式基本相同，主要差别是质量分数的不同。稀土元素在洗选过程中的分配行为和赋存状态主要受控于黏土矿物，其次是有机质。     

洗选过程对宁武煤中汞迁移和热释放的影响特性

采用逐级化学提取和热分析方法,选取宁武煤田某洗煤厂原煤及洗选产物为研究对象,在汞质量平衡基础上对煤中汞赋存形态进行分类并验证,进而考察了洗选过程对煤中汞迁移行为和热释放的影响特性。结果表明,洗选过程在降低原煤灰分和硫分含量的同时也改变了汞的富集规律,引起了汞的重新分配;样品中汞元素与灰分和硫含量之间的线性相关性分别为0.89和0.99,原煤中汞主要以无机结合态存在,其迁移行为受控于无机矿物质迁移,洗选后矸石总汞绝对含量较原煤增加了322.8%,而精煤汞含量降低至原煤的40%,汞脱除率达到56.4%;洗煤产物中汞富集程度的差异与其在原煤中赋存形态密切相关,其中,矸石中硫化物结合态汞的占比高达56.6%,而精煤和煤泥中有机结合态汞较原煤中均有所提高;相同温度下汞在煤泥中释放率最大,矸石中最小,所有样品中汞至650℃均接近完全析出;煤中汞热释放特性也与其赋存形态密切相关,不同热解温度段汞热释放行为由煤中汞的固有赋存形态所决定,其中,有机结合态汞随有机质分解在300℃已大量逸出,而硫化物结合态汞分解温度主要为400-600℃。     

煤中有害元素的洗选洁净潜势

基于8个洗煤厂实采煤样的测试分析以及2个煤样的模拟洗选实验，对煤炭洗选过程中灰分、硫分及20种有害微量元素的脱除率进行了研究，并系统地探讨了这些有害元素的洁净潜势。结果表明：物理洗选不但能降低煤中的灰分与硫分，还能不同程度地脱除煤中有害微量元素；预测在物理洗选过程中，多数煤中灰分以及有害微量元素As、Co、Cu、Cr、Hg与Mn的脱除率大于50％，硫分的脱除率大于30％，其它有害微量元素Ba、Be、Cd、Cl、Mo、Ni、P、Pb、Sb、Se、Th、U、V与Zn的脱除率相对较低或表现出一个宽的变化范围。     

煤中砷与硫洗选过程迁移和燃烧过程释放特性

以宁武煤田两个洗煤厂原煤及洗选产物为研究对象，采用微波消解与氢化物发生-原子荧光光谱相结合方法考察了洗煤过程硫和砷迁移规律，采用砷质量平衡验证的逐级化学提取法探讨了原煤、精煤、矸石、洗中煤和煤泥燃烧后硫和砷形态转化与释放特性及其依赖性。原煤中20%-28%硫和砷迁移至精煤中，46%-61%迁移至矸石中，Pearson相关系数结果表明，样品中无机矿物质是硫和砷迁移的控制因素。精煤中有机硫和砷提高至30%-50%，而矸石中无机硫和砷占比达90%以上，说明原煤及洗选产物中砷与硫赋存形态具有一定相关性。精煤中较多的有机硫和砷在500℃以下伴随水分和挥发分析出呈现明显释放特征，矸石中以无机态为主的砷则主要在500-1000℃伴随黄铁矿和硫酸盐等矿物质分解与硫一起释放，体现了原煤及洗选产物燃烧时硫与砷释放的同步性。精煤中硫和砷释放速率最快，300和200 s分别达到最大释放率80%-95%和60%-75%；矸石中最慢，300 s时砷达到最大释放率40%-45%，而硫600 s时仍未达最大释放率；洗中煤和原煤介于精煤和矸石之间，样品燃烧时硫和砷赋释放速率差异是由其固有赋存形态差异所致。     

煤中痕量元素在循环流化床锅炉中的迁移行为与富集特性

对天津市某电厂循环流化床(CFB)锅炉燃用的原煤及燃烧产物底灰、飞灰、细飞灰(≤50 μm)进行痕量元素含量的测定,分析了Be、Zn、Hg、V、Cr、Mn、Co、Ni、Cu、As、Se、Cd、Pb 13种痕量元素在燃烧过程中的迁移行为,揭示了痕量元素在CFB锅炉中的分配、富集特性。结果表明,CFB锅炉中,较低的炉温对于痕量元素的迁移富集产生了较大的影响。由相对富集系数得知,Be、V、Co、Se在底灰中耗散,在飞灰中富集,Zn、Mn倾向于在底灰中富集,元素Cd、Pb、Ni、Cu挥发性较强,在底灰和飞灰中均是耗散。As受钙氧化物影响,挥发性表现并不明显。Hg在底灰和飞灰中相对富集系数均很低,表明Hg在整个燃烧过程中以气态形式排放;Hg、As、Se、V、Cr、Mn、Co、Ni、Cu、Zn、Pb均有向小颗粒物中富集的趋势。根据相对富集系数以及研究的13种元素在低温CFB锅炉中的迁移行为,将这些元素分为三类:A类(E_R<0.1),主要是以气态形式排放元素Hg;B类(0.1R≤0.85),较易挥发元素As、Be、Ni、Cu、Se、Cd、Pb、Co、V;C类(E_R>0.85),主要残留在固体产物中元素Zn、Mn、Cr。     

伊敏褐煤中微量元素的地球化学特征及其无机-有机亲和性分析

采用脱矿物质、提取腐殖酸等方法结合ICP-MS对伊敏15_上、16_下煤中的32种微量元素的含量及其赋存特征进行了分析。与地壳克拉克值及中国侏罗-白垩纪煤和世界褐煤中微量元素含量相比,伊敏褐煤中微量元素没有明显富集。脱矿物质处理后,Ni明显富集,As略比原煤高,其他微量元素都低于原煤。原煤提取腐殖酸和脱矿物煤提取腐殖酸中Ni、Mo、Cd、Sn、W明显富集,这表明Ni、Mo、Cd、Sn、W和腐殖酸形成了稳定的有机态化合物。原煤提取腐殖酸残煤和脱矿物煤提取腐殖酸残煤中V、Ni、As富集,表明V、Ni、As与煤的大分子结构形成了稳定的有机态化合物。根据微量元素和灰分的相关性系数,把微量元素分为以下几类:无机富集元素Cr、U;亲无机元素Cu、Cd、In、Sn、Ga、Y、Zr、Hf、Bi、Th;偏无机元素Be、Sc、Rb、Sr、Nb、Cs、Ta、Pb;偏有机元素V、As、Tl、Ba、Se;亲有机元素Li、Co、W;有机富集元素Ni、Zn、Mo、Sb。     

煤中微量元素在燃烧过程中的变化

在分析微量元素燃烧过程中迁移变化机理的基础上,对电厂用煤和煤灰进行了采样测试,分析了电厂燃煤过程中微量元素的析出变化及在各种灰中的分布富集规律,同时用五个不同的温度段分别对煤进行了燃烧实验,研究了在不同温度下,微量元素从煤中析出的浓度和析出率,通过实验分析,。多数有害微量元素在飞灰中的富集浓度高于其它灰中,燃烧时温度的高低是影响微量的高低是影响微量元素迁移析出的重要因素,温度越高,有害微量元素析出率相对越大。     

中煤的煤岩学特征

中煤是煤洗选加工过程的副产品，其煤 组成及特征不同于原煤。煤岩分析表明中煤的煤显微组成中，镜质组及壳质组含量比原煤少，惰质组比原煤多，矿物质则大幅度上升。对中煤的进一步加工最有意义的是中煤的显微煤岩类型组成特征。在中煤中微二合煤含量最高，为７０．６３％，其次是微三合煤，为２５．９４５％，微四合煤为３．４２５％。     

中国煤的硫同位素组成特征及燃煤过程硫同位素分馏

对中国15省区煤的硫同位素组成和硫含量测定表明,中国北方煤以相对高的δ~(34)S值和低的含硫量为特征,而南方煤则以相对低的δ~(34)S值和高的含硫量为特征。工业和民用炉燃煤结果,释放出的二氧化硫总是比原煤相对富集轻硫同位素;而释放出的颗粒物总是比原煤相对富集重硫同位素,本文还讨论了上述结果的环境地球化学意义。     

酸洗脱矿对胜利褐煤热解过程中N迁移转化的影响

在石英管流化床反应器中对胜利褐煤进行快速热解实验,考察了773~1 173 K下酸洗脱矿对胜利褐煤热解过程中N迁移转化规律的影响。通过比较原煤和酸洗后煤中N的不同逸出规律可以得出,影响酸洗前后胜利褐煤热解过程中N迁移转化规律的主要是碱金属Na及碱土金属Ca;热解过程中,煤中的Na和Ca促使煤中的N向NH3转化并有效抑制了HCN的生成,金属离子的存在对催化焦油N转化为NH3的作用较为明显;原煤中的碱金属和碱土金属的赋存使半焦裂解反应加剧,降低了固体半焦的产率,半焦N的产率也随之减少;与原煤相比,酸洗煤热解半焦中的吡啶型N(N-6)含量较多,而吡咯型N(N-5)和季N(N-Q)相对较少。     

INAA of coals from the Midwestern USA

The concentrations of 43 elements were determined in coal samples collected from the state of Missouri using INAA at the University of Missouri Research Reactor. The results of the whole coal analysis reveal that the chemical compositions of Missouri coals are highly variable. Enrichment factors were determined for each of the elements determined in this project to provide a measure of the relative enrichment of the element as compared to the average crustal abundance for that element. Most elements are relatively depleted in coals, however the elements As, Br, B, Ca, Cd, Cl, Fe, Mo, Ni, Sb, S, U, Zn and Zr were found to be enriched in Missouri coals. The determination of the relative enrichment of a given element in coal will allow a greater assessment of the environment impact the will be incurred from the use of that coal.     

Trace element content of some Polish hard and brown coals

Instrumental neutron activation analysis /INAA/ method was applied to measure major, minor and trace elements in 34 samples of hard and brown coal originating from eight Polish coal mines. The elemental concentrations of 38 elements /Na, Mg, Al, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Mo, Ag, Cd, In, Sb, I, Cs, Ba, La, Ce, Sm, Eu, Lu, W, Au and Th/ are presented and compared with published data for coals from various origin. Enrichment factors, calculated relative to iron and the average crustal rock composition, indicated that several elements are highly enriched in Polish coals.     

Concentrations and distributions of trace and minor elements in Chinese and Canadian coals and ashes

A total of 35 trace and minor elements including some of environmental significance were determined in each of a selection of 15 Chinese and 6 Canadian thermal coals and their ashes by using the SLOWPOKE-2 nuclear reactor facility of the University of Toronto. The concentrations and distributions of these constituents among the coals and their combustion products (viz. ash and volatile matter) are presented together with an interpretation of their significance in relation to the large scale combustion of these coals as thermal fuels in industrialized countries such as China and Canada. The detailed results showed wide variations in trace impurity concentrations (up to a factor of 100 and more) among the coals studied with few large differences between those of Chinese and Canadian origin except that the rare earths, Sc, Th, U, I, and Se were much higher in the former, other halogens, As and Na were lower. Values for elemental enrichment factors (EF) relative to normal crustal abundances indicated that only As(EF=13), Br(5.7), I(16), S(230), Sb(11) and Se(320) were appreciably enriched in coal. During static ashing at 750°C most of the halogens, S and Se were volatilized whereas most other inorganic constituents were highly retained and concentrated in the ash by factors of 6 to 11.     

The volatilization of trace elements during oxidative pyrolysis of a coal from an endemic arsenosis area in southwest Guizhou,China

Household coal combustion has caused endemic poisoning in southwest Guizhou Province of China. The mineralogy, geochemistry and mode of occurrence of trace elements (TEs) of coal from this area were examined, and oxidative pyrolysis experiments of the coal were conducted in a box resistance reactor at 300–1200 °C to evaluate the volatilization of trace elements. In coal, As, Sb, Pb, Zn, W, Mo, and Cr are highly enriched when compared to both the world coal and Chinese coal. Cadmium, Sr, and Ba are all slightly higher than the average value for Chinese coal. The volatility of trace elements exhibits a close correlation with the mode of element occurrence. The considerable volatilization of As, Sb, Pb, Zn, Cd and Cr below 450 °C is thought to be related to the organic form of these elements. In the temperature range of 450–1200 °C, the volatility of all trace elements except As increases slowly with temperature because these elements are highly associated with silicates. Among the hazardous trace elements, As is the most volatile, and Sb, Pb, Zn, Cd and Cr are moderately volatile. Arsenic exhibits a uniquely high release at 900–1000 °C, which could be attributed to the high proportion of As association with sulfide. Because TEs are primarily inorganically-associated, the volatilization of TEs is not comparable to the loss of coal weight during pyrolysis. At high temperatures, a significantly low coal weight loss can result in a significant volatility of TEs.     

Neutron activation analysis and natural radioactivity measurements of lignite and ashes from Megalopolis basin,Greece

Elemental concentrations and specific activity values of natural radionuclides were measured in lignite, bottom ash and fly ash samples collected from the Megalopolis power plant A in southern Greece, using nuclear analytical techniques. The results show that the elements As, Br, Mo, Sb, Se, and U were enriched in the lignite samples, the elements Mo, Se and U in bottom ash, while fly ash samples were enriched in As, Mo, Sb, Se and U. Specific activity measurements also show that ²³⁸U (²²⁶Ra) activity values in lignite and both ash samples were high relative to the corresponding data for coal and earth crust given in the literature. As a high quantity of fly ash is produced during the operation of the lignite power plant A, this power plant should be considered as a major source of air particulate pollution and radiation to the population living in the vicinity of lignite burning power plant.     

Trace element composition of atmospheric aerosols in Ankara,Turkey, determined by instrumental neutron activation analysis

Twenty six trace elements were determined by INAA in the aerosol samples collected at two stations in Ankara, Turkey. Industrially derived elements, Se, As, Sb, Zn and Au did not show seasonal dependence and they were not substantially enriched. Elements originating from coal combustion are highly enriched and have higher concentrations in the winter. Correlation factors indicate that motor vehicles, coal and oil combustion are the main sources of aerosols over the city.     

马家塔矿煤层中有害痕量元素的质量分数特性

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）对神华集团马家塔露天矿2-2#煤层中Hg、As、Se、Pb、Be、Cr、Cd、Ni、Th、U、Mn、Mo、Co、Sb和Br共15种有害痕量元素的质量分数进行测定。结果表明，绝大部分痕量元素的质量分数都明显低于中国煤中元素质量分数的平均值，只有Hg和Mn的质量分数偏高，其中Hg的质量分数异常高；通过分析痕量元素在煤层垂向剖面上的质量分数变化特性，揭示出痕量元素在煤层中分布的非均一性,分析了影响痕量元素分布与富集的因素；通过痕量元素之间以及与黄铁矿硫、Fe、Al、Ca、P的聚类分析，研究了痕量元素之间以及与煤中不同矿物组分之间的亲和特性。