微波协同化学助剂强化脱除煤中硫

硫是煤中主要有害元素,煤炭利用过程中硫的排放是酸雨的重要成因,脱硫是煤炭洁净利用的研究热点之一。微波具有促进反应发生、加快反应速率的作用,微波协同化学助剂脱硫是煤炭脱硫的重要手段。本文通过微波辐照结合3种化学助剂研究煤中硫的脱除效果,利用正交试验考察微波辐照时间、化学助剂种类和煤种对脱硫效果的影响。结果表明,煤种对微波协同不同助剂的脱硫效率影响较大,所选3种煤样的最佳辐照时间各不相同;硝酸与微波联合的脱硫效果最好,其中贵州(GZ)煤在微波协同硝酸作用下,全硫脱除率可达71. 2%。形态硫测试分析表明煤样经脱硫后无机硫脱除效率较高,最高可达90. 5%,有机硫脱除效率在20%～40%。XRD谱图分析显示微波协同化学助剂脱硫后,煤中主要矿物和煤质结构没有明显变化,微波在脱除煤中硫分的同时可保持煤炭基质稳定。XPS谱图分析表明,煤样硫醚(醇)类有机硫脱除效果较好,脱除率可达49. 4%,亚砜类略低,脱除率为23%～28%,噻吩类有机硫脱除效果最差,脱除率在10%～20%。     

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。     

沥青中硫、氮元素脱除的研究进展北大核心

随着环保形势的日益严峻以及高端炭材料对原料沥青中硫、氮元素含量的严苛要求,导致高硫、氮沥青的应用受到了极大的限制,因此降低沥青中硫、氮元素的含量非常必要。基于沥青中硫、氮的赋存形态,从加氢法和溶剂法两个方面论述了沥青中硫、氮元素脱除的研究进展,并对沥青中硫、氮元素脱除技术的发展方向进行了展望。     

煤中硫的赋存状态及成因

煤中硫的赋存形态和结构对煤的脱除效率有很大影响,重点对煤中硫的化学形态进行了综述,详细讨论了煤中黄铁矿、有机硫的赋存状态、结构及成因,以加深对硫的认识,为脱除硫提供可靠的理论依据。     

用重力——化学法使煤脱硫

Meyers法是一种工艺,它借助于温和的氧化处理,使煤中所有黄铁矿硫基本上得到化学脱除。痕量元素铅、镉及砷这些重要的污染物也可同时被脱除。已经得知:这一方法对于给工业锅炉和较小型的电厂提供合格煤,以及对于在采煤和洗煤操作中所弃去的粉煤的回收和脱硫,都特别经济有效。它是氧化脱硫(用氧气或空气处理煤和水形成的浆液,化学脱除煤中的硫)新技术中最先进的一类。为适应对这一工艺进行判明的需要,     

安太堡矿各层煤洗选脱硫性研究

通过对安太堡矿各煤层煤岩、黄铁矿硫赋存和浮沉大样各密度组分形态硫及煤芯５０￣０．１５ｍｍ粒度，１．６ｋｇ／ｍ＾３密度浮上物形态硫的分析，结合安太堡矿洗煤工艺，研究了各煤层洗选脱硫性及其原因。     

湿法磷酸净化预处理的实验研究

研究了以化学沉淀法对湿法磷酸进行预处理,脱除湿法磷酸中的硫酸根以及重金属砷。考察了搅拌速度、脱硫剂种类、脱硫剂用量、脱砷剂用量等因素对湿法磷酸中硫、砷的脱除率及磷收率的影响。实验结果表明,化学沉淀法可以有效降低湿法磷酸中的硫及砷的含量,磷酸经化学沉淀法预处理后,脱硫率可达60%,脱砷率可达73%。     

高硫煤热解脱硫技术研究现状

归纳了煤中硫赋存形态,阐述了热解脱硫研究的意义;根据热解过程脱硫方式,将热解脱硫分为不同气氛下热解脱硫和添加物共热解脱硫。不同气氛下热解脱硫方面,分析了惰性、氧化性、还原性3种气氛下热解脱硫效果,结果表明,还原性气氛下脱硫效果最佳,且被脱除的硫多以H2S形态逸出;炼焦煤热解形成焦炭,还原性氢仅与表面含硫化合物反应,脱硫效果有限,因此难以工业化应用。添加物共热解脱硫方面,分析了有机和无机添加物共热解的脱硫效果,结果表明,某些有机和无机添加物与煤共热解时具有脱硫效果,但对于脱除哪类形态硫及各形态硫脱除机理研究甚少;最后提出了热解脱硫技术研究的可能性方向。     

高硫炼焦煤中硫元素赋存形态的XANES分析

硫是自然界中最为活跃的元素之一,赋存形态多样。炼焦煤中有机硫的高效脱除是近年来的研究热点。以山西两种高硫炼焦煤为研究对象,采用X射线吸收近边结构光谱(XANES)对煤中硫元素赋存形态进行表征。结果表明,两种高硫炼焦煤中硫的赋存形态基本一致,噻吩环、巯基(-SH)、亚硫酰基(S=O)是两种煤样中硫元素的主要赋存形态,其中噻吩环类硫占60%以上。     

淮南煤田张集矿山西组煤中锑含量和赋存状态及富集成因

以淮南煤田张集矿山西组煤为研究对象，刻槽采集煤样，采用电感耦合等离子体质谱仪、X射线荧光光谱仪、X射线衍射仪、偏光显微镜、扫描电镜等手段，结合相关性分析和逐级化学提取实验，探讨了张集矿山西组煤中锑的含量分布、赋存状态及其富集成因。结果表明：张集矿山西组煤中锑含量范围为2.49μg/g～4.57μg/g,平均3.13μg/g,高于世界煤背景值，富集系数为3.4,属于轻度富集；同煤层中锑含量变化较大，在垂向上，顶部和底部煤样中锑含量高；张集矿山西组煤中锑主要赋存在硅铝酸盐矿物中，其中顶部和底部煤样中的锑还赋存于黄铁矿中；成煤盆地受陆源碎屑输入作用越强，淮南煤中锑含量越大，因此推断煤中锑的富集主要与物源区的陆源物质输入有关；此外，煤中锑元素的富集还受地下水活动和围岩作用影响。     

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.     

Partitioning of minerals and elements during preparation of Taixi coal, China

Mineralogy, sulfur and 40 other element contents were determined on eight samples of the Taixi coal and its preparation products from the Rujigou mining district, China. INAA, ICP-AES, CV-AAS, GAAS, XRD, SEM/EDX, conventional chemical and maceral analysis were carried out on the samples. This study is focused on the partitioning behavior of the minerals and elements during the coal cleaning, and the main factors influencing the partitioning behavior of elements were also discussed.The clay minerals (kaolinite, illite, montmorillonite and chlorite), quartz and, to a lesser extent, carbonate minerals (calcite, dolomite and siderite) dominate the mineralogy of Taixi coal. There is also minor amounts of pyrite and trace amounts of gypsum and feldspar. The quartz is dominantly epigenetic in origin, and clay minerals were modified by the thermal metamorphism. They are easily liberated from the coal by cleaning. However, although the majority of carbonate minerals are also mainly epigenetic in origin, its degree of removal is relatively low, especially with respect to dolomite and siderite, which are often finely dispersed in coal macerals, so that they are mostly retained in cleaned coal. Most of the elements studied could be removed effectively during the cleaning processes, especially for the elements predominantly hosted in coarse, epigenetic minerals. Compared with other sized cleaned coals, the coarse-grained cleaned coal is cleanest and has a relatively low potential of environmental risk. The majority of the potentially hazardous elements are notably enriched in the coal waste so that the waste is not feasible to be used as fuel. The partitioning of elements during the coal cleaning processes is essentially controlled by some factors such as the modes of occurrence of elements, maceral type, grain size and textural relation of minerals, and types of cleaning technique used.     

Organic sulfur and hap removal from coal using hydrothermal treatment

Coal is still the major source of power for electrical generation worldwide and will continue to be in the foreseeable future. However, the inorganic elements in coal that qualify as hazardous emissions upon combustion of the coal become an increasingly important concern. Primary emphasis has been on postcombustion cleanup of these emissions, with no technology achieving overwhelming success. The precombustion technique reported here shows promise for removing trace elements as well as sulfur prior to burning the coal. This study shows that hydrothermal treatment need not be carried out at extreme conditions to effect such removal. The sulfur content and selected trace elements of some coals are reduced by 50% or more by water at conditions above the critical temperature but below the critical pressure. The study also shows that the technique was more effective on some coals than others. Results from a pilot-scale test are included in addition to bench-scale data.     

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.     

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.     

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.     

Concentration and distribution of sixty-one elements in coals from DPR Korea

Fifty coal samples (28 anthracite and 22 lignites) were collected from both main and small coal mines in DPR Korea prioritized by resource distribution and coal production. The concentrations of 61 elements in 50 coal samples were determined by several multielement and element-specific techniques, including inductively coupled plasma atomic emission spectrometry (ICP-AES), and inductively coupled plasma mass spectrometry (ICP-MS), ion chromatogram (IC), cold-vapor atomic absorption spectrometry (CV-AAS), and hydride generation atomic absorption spectrometry (HGAAS). The ranges, arithmetic means and geometric means of concentrations of these elements are presented. A comparison with crustal abundances (Clarke values) shows that some potentially hazardous elements in the coals of DPR Korea are highly enriched Li, B, S, Cl, Zn, As, Se, Cd, Sn, Sb, W, Te, Hg, Ag, Pb, and La, Ce, Dy, Tm, Ge, Mo, Cs, Tl, Bi, Th and U are moderately enriched. A comparison of ranges and means of elemental concentrations in DPR Korea, Chinese, and world coals shows the ranges of most elements in DPR Korea coals are very close to the ranges of world coals. Arithmetic means of most elements in DPR Korea coals are close to that of American coals. Most elements arithmetic means are higher in Jurassic and Paleogene coals than coals of other ages. In DPR Korea coals, only seven elements in early Permian coals are higher than other periods: Li, Zn, Se, Cd, Hg, Pb, and Bi. Only five elements B, As, Sr, Mo, W in Neogene coals have arithmetic means higher than others. SiO₂ and Al₂O₃ in ashes are more than 70% except six samples. The correlation between ash yields and major elements from high to low is in the order of Si>Al>Ti>K>Mg>Fe>Na>Ca>P>S. Most elements have high positive correlation with ash (r>0.5) and show high inorganic affinity.     

Distributions of trace elements in Western Canadian coal ashes

Concentrations of 52 minor elements in coal ash were determined using spark source mass spectroscopy. Hg levels in raw coal were investigated by cold vapour atomic absorption spectrophotometry. The concentration of elements are compared to other available data and to levels in the Earth's crust. F levels in coal ash exceed 500 μ g^?1 and may be greater than 1 wt% in raw coal. Approximately half the elements (B, S, Ni, Zn, Ga, Ge, Se, Sr, Y, Mo, Sn, Sb, I, Ba, Pr, Nd, Sm, Eu, Ho, Hf, Pt, Hg, Pb, Tl, Bi, U) investigated are enriched in the coal ash with respect to the Earth's crust. The ranges in minor element concentrations in coal ash and coal from different global regions are very similar.     

Experimental study of chemical treatment of coal fly ash to reduce the mobility of priority trace elements

Coal fired electric power plants produce large volumes of fly ash and other coal combustion by-products (CCBs) every year. Although almost 50% of the fly ash produced in the US is recycled for beneficial use, most of the ash material is disposed in dry landfills and ash lagoon impoundments. Fly ash may contain hazardous leachable trace elements such as As, B, Cr, Mo, Ni, Se, Sr and V which have a negative impact on the environment due to potential leaching by acid rain and groundwater with time. Many of the older CCB disposal facilities are unlined and unmonitored and as a result the EPA is currently developing national standards for monitoring CCB disposal sites. The cost to the US electric power industry could exceed one billion dollars if existing and closed CCB disposal facilities come under regulation. Thus simple, low-cost and effective in situ chemical treatment techniques are needed to stabilize hazardous leachable trace elements in the coal combustion by-product (CCB) materials. This paper reports the results of experiments designed to chemically treat fly ash with ferrous sulfate solutions to immobilize hazardous leachable trace elements after disposal.The current study is focused on three acidic and one alkaline fly ash samples collected from electric power plants located in the southeastern United States that were treated with two ferrous sulfate treatment solutions. The first treatment solution contained ferrous sulfate (FS) to give 322 mg/L of dissolved iron, while the second treatment solution contained the same concentration of ferrous sulfate along with excess calcium carbonate (FS + CC) to buffer the pH. Fly ash treatment experiments were carried out at solid:liquid (S:L) ratios of 1:3 and 1:30. The effectiveness of the treatment methods was evaluated by sequentially leaching the treated and the untreated fly ash samples using a synthetic acid rain (SAR) solution (US EPA Method 1312B SPLP fluid) as the leachate. The best overall treatment result was shown by the unbuffered ferrous sulfate solution at the 1:30 S:L ratio, which substantially reduced the mobility of the oxyanion trace elements. The overall mobility reduction achieved for As was 23-72%, B mobility was reduced by 43-80%, Cr by 45-77%, Mo by 21-90%, Se by 41-85% and V by 41-53% The unbuffered ferrous sulfate treatment was not effective for immobilization of the cationic trace elements Ni and Sr.