汽煤比对煤气化过程中微量元素迁移规律的影响研究

采用氢化物发生器和原子荧光光谱法联用 (HG -AFS)和电感耦合等离子发射光谱法 (ICP -AES) ,测定了常压流化床煤气化产物中As、Cd、Co、Cr、Cu、Mn、Mg、Ni、Hg、Pb、V、Se、Sr、Zn 1 4种微量元素含量 ,分析了汽煤比对微量元素在气化产物中迁移规律的影响。结果表明 :随着汽煤比增加 ,在旋风高温焦中Co、Cu的相对富集系数 (REs)先减小再增加 ;Cd、Ni的REs先增加再减小 ;Pb、Zn的REs减小 ;Cr、Mn、Mg、V和Sr的REs受汽煤比的影响很小 ;易挥发性元素As、Hg、Se的REs在高汽煤比条件下略微有上扬的趋势。随着汽煤比增加 ,在布袋低温焦中Cd、Co、Cu、Ni的REs先增加后减小 ;As、Hg、Pb、Se、Zn的REs减小。底渣中易挥发性元素As、Hg、Se的REs受汽煤比的影响不及部分挥发性元素Cd、Cr、Cu、Ni、Pb、Zn那么明显。随着汽煤比增加 ,在煤气中As、Cr、Zn的含量减小 ,Co、Cu的含量先增加后减小。     

循环流化床煤燃烧产物中微量元素分布特征

利用清华大学小型循环流化床对黔西南坑硫煤进行燃烧实验，研究循环流化床燃烧过程中煤中微量元素在燃烧产物中的重新配置和对环境的影响，以及固硫添加剂对煤中部分有害微量元素排放的控制作用，结果表明，循环流化床灰中，As、Sb、Pb、Cu、Be与Zn等在细粒灰中富集，Pb、As、Sb、Se、Th、Ni与Cr等在磁性灰中富集。除尘器后烟道灰中富集Zn、As、P、Ni、Cr、Mo、Be、Pb、Th、Hg与F等，而Nb、Rb与Zr等明显亏损。在煤中加入固硫添加剂燃烧后比较发现，As、Se、Sg与Zn等在细粒流化床灰中富集能力降低，As、Se、Li、Be、Mo、Cr、Co与Ni等在除尘器后烟道灰中含量降低，烟道喷淋水中Cu、Zn、Cr、Pb、Co、Ni、F与Se等的含量降低。循环流化床燃烧过程中，固硫添加剂不仅降低SO2的排放，而且对部分有害微量元素（As、Se、Be、Cr、Co、Ni、Pb、Zn与F等）的排放有一定的控制作用。     

部分痕量元素在煤粉炉中赋存特性

定量测定了1台220t/h煤粉炉进口煤样、底渣、飞灰中Mn、Cr、Pb、As、Se、Zn、Cd、Hg8种痕量元素的含量,分析了飞灰粒径、炉膛温度、含氧量以及痕量元素自身性质对痕量元素赋存、挥发特性的影响。根据痕量元素的赋存、挥发特性,将元素分成3类：第一类元素为Hg;第二类元素为Pb、Zn和Cd;第三类元素为Mn,Se介于第一类元素和第二类元素之间;Cr同时表现出第一类和第三类元素性质。研究发现,除Mn外,其它元素在飞灰中的富集程度随飞灰粒径的减小而增加;飞灰对各痕量元素吸附机理不同;炉膛温度升高能促进部分痕量元素的挥发;除Mn和Cr外,其它元素在飞灰中相对富集系数大于底渣;含氧量低并非促进所有痕量元素挥发;痕量元素分类应视具体情况而定。     

不同添加剂/吸附剂对循环流化床燃烧痕量元素迁移的影响规律

在6,k Wth流化床实验装置上进行了贵州烟煤的燃烧实验,采用电感耦合等离子体质谱仪(ICP-MS)研究不同添加剂/吸附剂对11种痕量元素(Be、Cr、Mn、Co、Cu、As、Mo、Cd、Sb、Ba、Pb)在燃烧产物中的富集规律.结果表明:活性炭和稻壳焦对痕量元素都有一定的吸附作用,稻壳焦可增加Be、Mn、Co、Cu、As、Mo、Cd、Sb、Ba、Pb这些元素在飞灰中的富集程度,降低了Cr在飞灰中的富集程度;活性炭对Cr、Mn、Cu、Mo、Cd、Sb、Pb的富集都有一定的促进作用.原煤中掺混Ca Cl2能提高Mn、Sb和Ba在飞灰中的富集程度,同时抑制了其他元素在飞灰中的富集;掺混NH4Cl对Co和Cu在飞灰中的富集有抑制作用,但作用很小,对其他的痕量元素在飞灰中的富集都有一定的促进作用,其中对Mo、Cd和Sb的促进最为明显.     

煤气化过程中微量元素挥发动力学

煤气化过程中,与矿物质有关的微量元素挥发时包含3个连续步骤:微量元素在熔化的矿物质内部质量扩散;微量元素在矿物质熔化表面挥发,以及逆反应凝聚过程;气态微量元素在灰尘中扩散.不同微量元素的挥发过程由上述3个不同步骤控制.数学模型计算结果表明,饱和蒸气压力较小的元素(如Co、Cr、Cu、Mn、Ni、V、Sr、Mg和Pb等)挥发速率常数主要由熔融矿物质表面微量元素挥发和熔融矿物质内微量元素质量扩散共同控制;饱和蒸气压力较大的元素(如As、Cd、Hg、Se、Zn等)挥发速率常数由熔融矿物质内微量元素质量扩散所控制;气化温度对微量元素挥发速率影响很大;所有微量元素挥发速率常数随着气化温度的增加而增加;元素的饱和蒸气压力越大,气化温度对其挥发速率影响也越明显.     

垃圾焚烧炉飞灰熔融处理前后的重金属分布特性

研究探讨了熔融温度、熔融时间、碱基度对飞灰熔融处理前后重金属分布特性的影响．结果表明,熔融温度为1 200℃时Ni、Cr、Cu、As的固溶率最高,除Zn外,熔融温度对Pb、Cd、Hg挥发率影响较小．随熔融时间的增加,Ni、Cr、Cu、As的固溶率在90 min后趋于稳定,Pb、Cd、Hg的挥发率在30 min内达95％以上,接近完全挥发;碱基度较高有利于重金属Ni、Cu、As、Cr的固溶,碱基度变化对Pb、Cd、Hg的挥发率影响较小,低碱基度对Zn的挥发影响较为显著．     

某燃煤电厂废弃灰场土壤中重金属污染评价研究

对某燃煤电厂废弃灰场土壤中的Cr、Hg、As、Cu、Pb、Cd、Zn、Ni等重金属进行测定分析,并以国家二级质量标准为评价标准来评价其环境质量状况。结果表明:该灰场土壤中Hg、Pb、Zn为非污染水平,As为轻污染水平,Cr为中污染水平,Cu、Cd、Ni为重污染水平,该地块综合污染指数为24.69,达到重污染程度。     

地球化学原生晕在玲珑金矿中的应用——以47号矿体为例

玲珑金矿位于山东省招远市与周边县城的交界处,是我国最重要的一种金矿类型。在所得样品的测试数据的基础上,对Au、Ag、As、Bi、Co、Cu、Hg、Mn、Mo、Ni、Pb、Sb、Th、U、V、Zn 16种元素进行了分析,并绘制相应元素相关图件。最终结合矿体原生晕分带序列,研究了该金矿床的元素相关性特征和地球化学参数变化规律。其中,元素相关性特征包括:Au、Ag、As、Bi、Cu、Co、Pb、Mo是金矿的最佳指示元素;Hg、Mn、Ni、V、Zn等与Au元素有一定的相关性;Sb、Th、U与Au相关性不大,无明显的指示意义。经过计算,得出47号矿体的原生晕分带序列自上而下分别为As、Pb、Ag、Cu、Hg、Sb、M、Ni、T、V、U、Mn、Zn、Bi、Co、Au。其中,近矿元素Au、Ag、Bi、Pb、Zn中的大多数出现在序列的尾部,这一反常的特征,在一定程度上可以预测在深部有隐伏矿体的存在。     

城市污泥流化床焚烧炉飞灰中重金属迁移特性

对120 t/d城市污泥循环流化床焚烧炉飞灰中重金属迁移富集特性进行试验研究,对污泥、飞灰及不同温度、取样点的飞灰中Cr、Mn、Ni、Cu、Zn、As、Cd和Pb 8种重金属迁移富集特性进行了分析。试验结果表明:飞灰、底渣及入炉污泥中主要化学成分为Si O_2、Fe_2O_3、Ca O、Al_2O_3和P_2O_5,"Si0_2-Ca O-Al_2O_3-金属氧化物"体系构成了重金属吸附的载体,也为不同形态重金属的吸附提供了活性空间。Cd、As为易挥发性重金属,在炉膛内挥发的Cd、As及其化合物蒸气在503℃和475℃时几乎全部富集于飞灰颗粒;Cr、Mn、Cu、Zn主要通过夹带富集于飞灰颗粒,它们在尾部烟道不同温度区域飞灰颗粒上的富集程度相当,为难挥发性重金属。     

部分痕量元素在油页岩中的富集特性及挥发行为

选取吉林桦甸、广东茂名、吉林汪清、辽宁大平4个矿区的油页岩为研究对象,用电感耦合等离子发射光谱技术和原子荧光技术对油页岩中14种痕量元素的含量进行了测定.结果表明,油页岩中的痕量元素含量明显高于中国煤中对应元素的平均含量,特别是Mn、P、Ti.与国外煤相比,痕量元素As、Mn、Zn、V、Cu和Cr在我国桦甸油页岩中表现出高含量特性.与地壳丰度相比,油页岩中痕量元素具有比较明显的富集亲硫元素、贫亲铁和亲石元素的特征.同时,研究了燃烧温度对油页岩中痕量元素的挥发行为的影响.结果表明:所研究元素的挥发性均随燃烧温度的升高而增大,其中As、Pb和Zn表现出较强的挥发行为,茂名油页岩中的痕量元素在燃烧过程中表现出较高的稳定性.     

Emission of trace toxic metals during pulverized fuel combustion of Czech coals

A study of the trace elements emission (As, Se, Cd, Co, Cr, Cu, Zn, Hg, Tl, Pb, Ni, Sn, Sb, V, Mn and Fe) from pulverized coal combustion has been made at six heating and power stations situated in the Czech Republic. The amount of chlorine in coal has considerable influence on volatilization of some elements such as Zn, Cu, Pb, Hg and Tl, which is explained by the formation of thermodynamically stable compounds of these elements with chlorine. Generally, the affinities for Cl follows the order Tl > Cu > Zn > Pb > Co > Mn > Sn > Hg. The experimental data indicates enrichment of some of the trace toxic elements in the emissions (Cu, Zn, As, Se, Cd, Sn, Sb, Hg and Pb) and good agreement was obtained by thermodynamic equilibrium calculations with a few exceptions. In the case of Fe, Mn, Co, Cr and Sn calculated values are overestimated in the bottom ash and there are zero predicted amounts of these elements in the fly ash. In comparison, the results from experiments show up to 80% of these elements retained in fly ash. This implies that there exist additional steps leading to the enrichment by Fe, Mn, Co, Cr and Sn of small particles. Such mechanisms could include the ejection during devolatilization of small inorganic particles from the coal of bottom ash particles, or disintegration of the char containing these metals to small particles of fly ash. On the other hand, there are slightly overestimated or similar values of relative enrichment factors for As, V, Cu, Cd, Sb, Tl and Pb in the fly ashes and zero predicted values for bottom ashes. Our experimental results show about 5% or less of these elements are retained in bottom ashes, so they probably remain in the bottom ash inside unburned parts of coal. Copyright © 2003 John Wiley & Sons, Ltd.     

Determination of major and minor ash-forming elements in solid biofuels

The development of reliable and appropriate methods for the accurate determination of major (Al, Ca, Fe, K, Mg, Na, P, Si, Ti) and minor (As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Tl, V, Zn) ash-forming elements in solid biofuels was the major goal of Task III.2 of the EU project BioNorm. For this purpose, wood+bark, straw and olive residues were analysed using several digestion and determination methods. The digestion methods included wet decomposition in closed vessels with different acid mixtures as well as dry-ashing techniques. The determination systems included FAAS, GFAAS, CVAAS, ICP-OES, ICP-MS, XRF as well as direct Hg-determination. Tests were carried out to optimise the methods applied. To summarise the outcomes of these tests, different digestion procedures were developed for major and minor elements. Digestion with H₂O₂/HNO₃/HF followed by neutralisation with H₃BO₃ was validated for major element analyses, while digestion with H₂O₂/HNO₃/HF was validated for minor element analyses. The validation results show that the applied digestion methods can be recommended for solid biofuel analyses. For the determination of the elements investigated in solid biofuels, the following detection systems can be recommended: FAAS for Ca, Fe, K, Mg, Na, Si, Mn, Zn; ICP-OES for Al, Ca, Fe, K, Mg, Na, P, Si, Ti, Mn, Zn, Ba, Cr, Cu, Mn, Ni, V, Zn; GFAAS for Cd, Cr, Cu, Ni, Pb; ICP-MS: P, Ti, As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, V, Zn and direct determination as well as CVAAS for Hg.     

Major and trace-element enrichments in the Karapınar coals (Konya,Turkey)

Ten major oxides and 27 trace elements were determined in 21 samples collected from four holes that were drilled into the fault-controlled coals of the Karap?nar (Turkey) basin. On the basis of X-ray diffraction analyses, the coals contain, in order of abundance, calcite, quartz, dolomite, feldspar, mica, clay minerals, and gypsum. In samples from the study area, a high level of correlation was determined between Mo, Sb, As, U, and V, and S and TOC (Mo, r = 0.697; Sb, r = 0.902; As, r = 0.927; U, r = 0.653; V, r = 0.721). Relative to coals of the world, USA, Turkey, and China, coals of the study area are seen to be enriched up to 1,000 times with respect to Mg, Ca, Na, and K. The Karap?nar coals were determined to be enriched in Pb, U, Ba, Cs, Nb, Y, Sr, Rb, Ni, Co, V, and Sc relative to average Turkish coals; in Mn, Na, Ca, Mg, Cs, Sr, Ni, and Cr relative to average Chinese coals; in Ti, K, Na, Ca, Mg, U, Ta, Ba, Cs, Sr, Rb, As, Ni, Co, V, and Cr relative to average worldwide coals; in Mn, P, Ti, K, Na, Ca, Mg, Si, U, Ta, Ba, Cs, Nb, Zr, Sr, Ni, Co, V, and Cr relative to average USA coals; and in Mn, P, Ti, K, Ca, Mg, Fe, Sb, Nb, Zr, Sr, Rb, Zn, Cu, Ni, Co, and Sc relative to crustal averages (Clarke values). The aim of the present study was to determine the enrichment factors of the major- and trace-element contents of the Karap?nar coals relative to coals of the world, USA, China, and Turkey, and to crustal averages.     

Mass Balance of Major and Trace Elements in a Coal-Fired Power Plant

The Soma power plant in western Turkey consists of six 165-MW units (B1–4 and B5–6), of which the first four units (B1–4) burn Early-Middle Miocene feed coals from the lower seam in central mines (southern Soma village), and later, two units (B5–6) use Early-Middle Miocene and Upper Miocene feed coals from the lower and upper seams in Denis mines (northern Soma village). A total of 48 samples, feed coals (FCs), fly ashes (FAs) and bottom ashes (BAs), which were systematically collected once a week over an eight-week period from both group boiler units, B1–4 with 660 MW and B5–6 with 330 MW capacity from Soma power plant, have been evaluated for major and trace elements (Al, Ca, Fe, K, Mg, Mn, Na, Ti, S, As, B, Ba, Be, Bi, Cd, Co, Cr, Cu, Cs, Ga, Ge, Hf, Hg, Li, Mo, Nb, Ni, P, Pb, Rb, Sb, Sc, Se, Sn, Sr, Ta, Th, Tl, U, V, Y, Zn, Zr, and REEs) to get information on behavior during coal combustion. This study indicates that some elements such as Hg, Bi, Cd, As, Pb, Ge, Tl, Sn, Zn, Sb, B show enrichments in FAs relative to the BAs in both group boiler units. In addition to these, Cs, Lu, Tm, and Ga in Units B1–4 and S in Units B5–6 also have enrichments in FAs. Elements showing enrichments in BAs in both group boiler units are Ta, Mn, Nb. In addition to these, Se, Ca, Mg, Na, Fe in Units B1–4 and Cu in Units B5–6 also have enrichments in BAs. The remaining elements investigated in this study have no clear segregation between FAs and BAs. Mass balance calculations with the two methods show that some elements, S, Ta, Hg, Se, Zn, Na, Ca in Units B1–4, and Hg, S, Ta, Se, P in Units B5–6, have volatile behavior during coal combustion in the Soma power plant. This study also implies that some elements, Sb and Tb in Units B1–4 and Sb in Units B5–6, have relatively high retention effects in the combustion residues from the Soma power plant.     

Distributions of environmentally hazardous elements in the Tertiary oil shale deposits from NW Anatolia,Turkey: A statistical analysis

The environmentally hazardous element concentrations (As, Cd, Cr, Cu, Hg, Mn, Pb, S, and Zn) and element–organic matter relations of the oil shale deposits in six different fields in NW Anatolia, Turkey, were investigated and the characteristics of fields were compared. The enrichment factor (EF) for most of the trace elements in the studied oil shales generally show enrichment patterns for all the fields. Only Cr, Hg, and Pb for oil shale samples from the Bahçecik field samples and Hg for oil shale samples from the Gölpazar? field samples are depleted. Arsenic in the Bahçecik field samples and Hg in the Himmeto?lu field samples are neither depleted nor enriched. The lowest and highest element enrichments in these fields are determined to be Hg and S, respectively. In general, all elements have high concentrations in the Beypazar? and Seyitömer fields and low concentrations in the Himmeto?lu, Bahçecik, and Gölpazar? (except for As) fields. A positive correlation at significance level of p ≤ 0.05 was observed for total organic carbon content with Cd in four of the fields, with Cu and S in two fields and with Cr, Mn, and Zn in only one field.     

O_2_CO_2气氛下痕量元素迁移特性试验研究

在管式炉上进行徐州烟煤的燃烧试验,采用电感耦合等离子体光谱质谱联用仪(ICP-MS)对燃烧剩余灰渣进行测定.研究了不同温度和不同燃烧气氛(空气气氛和O2/CO2气氛)下痕量元素的迁移特性.结果表明,煤燃烧过程中,痕量元素Cr、Mn、Ni、Zn、Cd、Pb在灰渣中富集,As挥发率达70%以上.随着温度的升高,大部分痕量元素在灰渣中的含量降低,Mn、Ni、Cr在灰渣中的含量相对比较稳定.O2/CO2气氛下,各元素随温度的变化趋势并未受到影响,但整体上O2/CO2气氛下各痕量元素在灰渣中的含量要大于空气气氛下的,随着温度的升高,O2/CO2气氛和空气气氛下痕量元素在灰渣中的含量越来越接近,说明燃烧气氛对痕量元素迁移的影响随温度升高而减弱.     

Physiochemical and leaching characteristics of fly and bottom ash

Bottom ash and fly ash are the by-products of coal in thermal power plants. They are the combustion wastes and contain many elements that may harmful to the environment. The present study investigates the physiochemical, mineral, and leaching characteristics of an Indian coal ash (bottom ash and fly ash). From the characterization of bottom ash and fly ash, it is found that the ash samples are enriched predominantly in silica, alumina, and iron oxides. A series of leaching experiments have been performed to analyze the tracing elements of metal at the different liquid to solid ratio (L/S). The L/S varies from 20:1 to 80:1. From the leaching results of the fly ash and bottom ash data, it is observed that the tracing elements of Mn, Mg, Cr, Zn, Ni, Pb, Fe, and Cu are the most abundant elements, while Hg, Mo, and Co are the least abundant elements.