陕北低阶烟煤显微组分结构特征及分子结构模型

为了更好地利用我国丰富的低阶煤资源,以变质程度较低的陕北低阶烟煤镜质组、惰质组富集物作为研究对象,采用常规的煤质分析、傅立叶变换红外光谱、高分辨固体13C核磁共振、X射线衍射等分析表征手段,对样品结构进行全面分析,得到了陕北低阶烟煤显微组分分子结构特征及结构参数,建立了镜质组和惰质组的部分分子结构模型。结果表明,陕北低阶烟煤镜质组和惰质组氧含量均较高,硫含量很低,所选镜质组的芳碳率为0.634,平均缩合环数约为2.98个;惰质组的芳碳率为0.734,平均缩合环数约为3.15个;相对于镜质组,惰质组的缩合程度更高,芳核尺寸更大,排列也更加规则有序。今后低阶烟煤加工转化工艺的研究应从分子层面揭示其不同显微组分结构特征的差异性,为低阶烟煤清洁高效利用新工艺的开发奠定基础。     

神东煤显微组分与基本结构特征研究

对神东煤显微组分及其反射率分布特征进行了详细阐述．利用工业分析和元素分析结果及结构经验公式,研究了神东煤的结构特征与煤岩组成的关系．利用^13C-NMR对神东煤显微组分进行了分析测试．结果表明,神东煤显微组分及其亚组分具有各自不同的反射率分布范围,煤中低反射率的惰质组含量较高．挥发分、氢含量、氮含量和氢碳比随惰质组含量的增加而下降,碳含量、芳碳率和缩合环数随惰质组含量的增加而增加．^13C-NMR测得镜质组和惰质组的芳碳率分别为0．67和0．81．     

石马洼煤显微组分结构特征的红外光谱分析

通过显微组分富集物的红外光谱分段分峰拟合对比和结构参数对比,分析镜质组和惰质组结构上的差异.分段分峰拟合对比结果:两者羟基氢键的分配既有相似之处,又有区别;镜质组较惰质组含有更高比例的CH2,CHx和CO基团吸收峰,同时含有更低比例的R3CH,CC和—O—基团吸收峰;惰质组较镜质组芳环结构的取代方式更复杂.结构参数对比结果:镜质组芳香度和缩合环指数均较惰质组低;脂氢与芳氢比,镜质组较惰质组要高;氧化程度参数,镜质组较惰质组更高;芳构化参数比较,惰质组缩合比较镜质组缩合比高,而脂肪比较镜质组脂肪比低.因此可得出:石马洼煤惰质组较镜质组芳构化程度更高,脂肪链长度较短,支链较多,且氧化程度较弱.     

宁夏庆华煤镜质组和惰质组显微组分的分子结构及对比分析

使用密度梯度离心法对宁夏庆华煤的显微组分进行分离,获得煤的镜质组和惰质组。通过元素分析、X射线光电子能谱（XPS）、固体¹³C核磁共振（¹³C NMR）技术、傅里叶变换红外光谱（FTIR）和X射线衍射（XRD）技术等表征手段对不同显微组分进行物性表征。进一步基于统计平均的分子结构近似结合分子模拟计算,确定庆华煤镜质组和惰质组显微组分的分子结构可分别表示为C₂₆₉H₁₉₆N₄O₁₃S和C₂₅₅H₁₇₉N₃O₁₄S。通过FTIR光谱与¹³C NMR光谱验证,从而实现了不同显微组分的分子结构描述。对两种显微组分的分子模型和结构参数进行了系统对比分析,发现镜质组的芳碳百分数为51.95,惰质组的芳碳百分数为62.16。镜质组模型中芳碳结构数目较少,脂肪碳结构丰富,不饱和度较小,还原度最大。惰质组模型中芳碳结构数量最大,脂肪碳结构数目少,不饱和度最大,煤化程度高。镜质组在原煤中含量高,是原煤的主要组成。惰质组的含量少且大分子结构缩合度高,分布在镜质组构成的基体中。     

3种沥青中正戊烷沥青质及其亚组分的分子特性研究

以3种沥青为研究对象,从中分离出正戊烷沥青质(As-5),又进一步从正戊烷沥青质(As-5)中分离出正庚烷沥青质(As-7)和重胶质两种亚组分,并分别对3种沥青的正戊烷沥青质、正庚烷沥青质和重胶进行了元素分析(EA)、凝胶色谱分析(GPC)、核磁共振氢谱分析(¹H NMR)的表征分析。结果表明：每种沥青的3种组分中均是正庚烷沥青质的C/H原子数比、重均分子量M_w和大小分子(LMS/SMS)含量比最大,同时具有最大的芳碳率f_A、芳环缩合程度和结构单元分子量usw。而重胶质的C/H原子数比、重均分子量M_w和大小分子(LMS/SMS)含量比均最小,同时具有最小的芳碳率f_A、芳环缩合程度和结构单元分子量usw。正戊烷沥青质的以上平均结构参数均处于其分离出的正庚烷沥青质和重胶质二者之间。在这些表征结果的基础上,对3种沥青中3种组分的溶解度参数δ进行计算,进一步分析了沥青组分的平均分子结构与溶解度参数之间的关系。     

神东上湾煤及其显微组分富集物结构特征研究

采用13C-CP/MAS NMR和FTIR测试手段对神东上湾煤及其显微组分富集物进行了分析表征,并对其相关结构特征进行了讨论.结果表明,惰质组富集物较原煤和镜质组富集物有较高的芳香度,桥头芳碳(faB)也较高,大分子芳香结构以萘和蒽结构为主;镜质组富集物有较多的烷基化取代芳碳和脂肪碳,氢含量相对较多,结构中富含链状烷烃、环状烷烃和芳甲基等,大分子芳香结构以苯结构为主;原煤结构中含有较多的faHl(季碳、CH和CH2)和faOl(氧接脂碳),原煤芳香结构以萘结构为主.三个煤样结构中羟基缔合程度都比较大,有较强的CC骨架伸缩振动峰,镜质组富集物的Hal/Har为2.18,远远高于原煤(1.52)和惰质组富集物(1.36),说明镜质组富集物有较多的脂肪结构;与原煤相比,镜质组和惰质组富集物大分子结构中有较多伸缩振动的—CH2.     

煤显微组分对气化过程的影响

利用浮选法探究浮选的最优条件,得到富集率为65.2%、30.7%的镜质组和惰质组。利用元素分析、SEM、XRD技术等表征手段探究煤显微组分气化差异性。结果表明,由于惰质组表面存在孔隙,气化反应前煤粒内部热解产生的气体扩散快;聚合芳环的含量高,热稳定性较差,导致气化起始温度低。惰质组碳、氢含量低,芳香结构较多,灰分较大以及高温下硅铝酸盐熔体会对气化反应起到抑制作用,进一步导致其气化反应性差。     

矿物质对不同还原程度煤显微组分半焦燃烧特性影响

在热重分析仪上考察了内在矿物质和三种无机组分(CaO、Fe_2O_3和Al_2O_3)对不同还原程度煤显微组分半焦燃烧反应性的影响。结果表明,弱还原性煤显微组分半焦的燃烧反应性高于还原性煤显微组分半焦;内在矿物质降低了镜质组半焦的起燃温度,但对惰质组半焦燃烧有明显抑制作用;三种外加矿物质对还原性煤显微组分半焦燃烧均有抑制作用,抑制顺序为Al_2O_3CaOFe_2O_3,而CaO对弱还原性煤显微组分半焦燃烧有一定催化作用,并且Al_2O_3和Fe_2O_3对弱还原性煤显微组分半焦燃烧抑制作用也低于对还原性煤显微组分半焦燃烧的抑制作用。     

中低煤阶镜煤/暗煤大分子结构及对甲烷吸附的影响

为研究中低阶煤不同宏观煤岩组分微观结构及对甲烷吸附的影响，采集黄陇煤田郭家河、大佛寺、园子沟及黄陵矿区的四种不同煤样，手工剥离不同宏观煤岩成分(镜煤和暗煤),通过傅立叶红外光谱(FTIR)分析、X射线衍射(XRD)分析和等温吸附实验探究中低阶煤分子结构特征及其对甲烷吸附能力的影响。结果表明：同一煤样中镜煤的水分和挥发分产率高于暗煤的水分和挥发分产率，而暗煤的灰分产率和固定碳含量高于镜煤的灰分产率和固定碳含量。镜煤的显微组分中镜质组含量较大、惰质组含量较低，暗煤则相反。红外光谱分析结果表明，同一煤层的镜煤和暗煤红外光谱吸收峰形态相似，官能团类型和含量接近。煤分子结构中主要含氧官能团按含量由高到低依次为C—O,COOH,■,脂肪侧链按含量由高到低依次为CH₂,CH₃,CH。对比煤的准晶体结构发现，中低阶煤煤化程度低，γ带的峰面积整体较大。受煤化作用和压实作用影响，暗煤的堆砌度和堆砌层数大于镜煤的堆砌度和堆砌层数。分子结构特征对甲烷吸附量的影响显著。镜煤的最大甲烷吸附量与芳碳率和缩合度均呈正相关，暗煤的最大甲烷吸附量与芳碳率和缩合度均呈负相关。镜煤...     

低阶煤煤岩组分性质分析及其制备活性炭的实验研究

低阶煤制取活性炭是低阶煤清洁高效利用的有效途径之一。对陕北某矿低阶煤进行了煤岩显微组分分析，其镜质组质量分数为70.32%，惰质组质量分数为29.18%；通过浮选法探索了矿浆pH值对不同显微组分富集率的影响，结果表明：煤岩组分富集率与矿浆pH值存在非线性关系，当pH=4时，镜质组和惰质组的富集率相对较高，分别约为75%和60%。对镜质组及惰质组进行了X-射线分析及热重分析，发现惰质组的芳构化程度和缩合环数相对镜质组更高，脂肪结构更少；以惰质组为原料、KOH为活化剂，采用化学活化法制备活性炭，分析了惰质组富集率对活性炭吸附性能及微观形貌的影响，结果表明：惰质组含量高时更易生成微孔发达的活性炭。     

Study on the structure and pyrolysis characteristics of Chinese western coals

The structure and pyrolysis characteristics of three inertinite-rich Chinese western coals were researched and compared with one relative vitrinite-rich Chinese middle coal by means of XRD, TG-DTG and fixed-bed reactor. The results show that the atomic ratio O/C, aromaticity factor, even ring condensation number and ring condensation index increase and atomic ratio H/C decreases with increasing inertinite content in coal; inertinite contains more aromatic ring structure than that of vitrinite; the crystallite structure order of coal char increases slightly with increasing heat treatment temperature. The higher inertinite content in coal is, the lower pyrolysis reactivity of coal is at lower temperature, and yet they have obvious second pyrolysis reactivity in higher temperature. The pyrolysis reaction in primarily devolatilisation phase that comes mainly from the decomposition of containing hydrogen function groups and the secondary devolatilisation at high temperature is mainly the decomposition of stable containing oxygen function groups in coal matrix with higher inertinite.     

Study on the structure and gasification characteristics of selected South African bituminous coals in fluidised bed gasification

The gasification characteristics of three South African bituminous coals were investigated in a bubbling fluidised bed reactor. The three coals are similar in rank, but two are inertinite-rich coals and the third has a high vitrinite content. The microstructural characteristics of the parent coals and their resultant chars were determined using XRD, FT-IR, Raman and petrographic analysis. The microstructural changes that occurred in the organic (maceral) and the inorganic (mineral) fractions of the selected coals were evaluated. The change in the carbon structure was correlated to the proportions of inertinite and vitrinite macerals in the coals. High vitrinite content resulted in an increase in the order of the disordered carbon structure after gasification and this leads to greater graphitised ordered carbon structures. While a high inertinite content resulted in low or no structural transformation of the chemical structure. The transformation of inorganic mineral constituents of the coal was correlated to the amount of inertinite present in the selected coals. Higher proportions of inertinite macerals and inertinitic chars resulted in higher proportions of melted minerals. Char samples with low proportions of organic matter resulted in higher proportion of melted minerals covering the char surface.     

Coal microlithotype response to froth flotation in selected Western Kentucky coals

Seven coals representing four western Kentucky coal seams and the coal rank range from high volatile C to high volatile A bituminous were selected for bench-scale froth flotation processing. Each coal was represented by two splits of the run-of-mine coal: a 12.7 mm × 0 fraction (crushed to 28 mesh × 0) and a 28 mesh × 0 fraction. The original 28 mesh × 0 split was found to be higher in the inertinite macerals fusinite and semifusinite than the coarser fraction. The separation of the inertinite macerals, expressed as the microlithotype inertite, from the vitrinite-rich vitrite and clarite microlithotypes proved to be markedly rank dependent. In the higher rank coals vitrite and clarite were concentrated in the clean coal while inertite was concentrated in the clean product in the high volatile C coals. Whereas in gravity-based coal cleaning only the finest pyrite usually remains in the clean coal, in this study no consistent trend in pyrite-size or pyrite-quantity partitioning was noted.     

Exploring the possibilities of using Brazilian subbituminous coals for blast furnace pulverized fuel injection

The current study investigates the combustion and blast furnace injection performance of three Brazilian subbituminous coals (Mina do Recreio) and their beneficiation products using laboratory scale combustion tests. The coals have relative high ash yields (up to 40 wt%) that were reduced stepwise to levels as low as 12 wt%, dry basis. The reduction of ash yields is paralleled by a significant decrease in sulphur and inertinite contents.The combustion tests were performed in a drop tube reactor operating at 1300 °C using two different atmospheres (2.5 and 5% O₂). The chars exhibited preferentially rounded shapes with thick walls and abundant secondary porosity for the 2.5% O₂ chars, whereas the 5% O₂ chars showed very thin walls as a consequence of extensive burnout. The intrinsic reactivities of both set of chars were similar. The differences in conversion between the two working atmospheres were 24-37% and roughly tend to increase with increasing mineral matter content. Conversions as high as 76-81% were reached operating under 5% O₂ indicating that the coals are easy to burn. The small differences in burnout among the coals and their beneficiation products cannot be clearly attributed neither to mineral matter or inertinite content. A rough inverse relationship was found between the intrinsic reactivity of the chars and the inertinite content of the parent coal indicating that the char material derived from inertinite was intrinsically less reactive than that derived from vitrinite. These differences were no longer relevant at high temperature.Blast furnace injection performance was studied through thermobalance experiments using CO₂ atmosphere and 1050 °C temperature. It is apparent that the beneficiation process has no effect on the reactivity of the coals from Recreio Mine. The only exception is the low ash coal-2-LabB (11.5 wt%), for which a higher reactivity is indicated. The reactivity tests show also that the coals have adequate properties to be used together with imported coal blends in pulverized coal injection in the blast furnace (PCI).     

Micrinite and exudatinite in some Australian coals,and their relation to the generation of petroleum

The occurrence and microscopic features of micrinite and exudatinite in some Australian coals are reported. The origin of these macerals and also the significance of their occurrence are discussed in connection with hydrocarbon genesis. In Australia, micrinite occurs in bituminous and sub-bituminous coals which are very rich in inertinite, and also in brown coal rich in inertinite. One of the possible progenitors of micrinite is oxidized porigelinite. There is little reason to conclude that micrinite was formed from resinite and other macerals at an early stage of coalification and that liquid hydrocarbons were formed during this process. Exudatinite occurs in sub-bituminous and high-volatile bituminous coals in the Gippsland Basin. There is no positive evidence of a genetic relation between liquid hydrocarbons, exudatinite, micrinite and liptinite macerals. The formation of liquid hydrocarbons from solid liptinite etc. may take place just before and during Teichmüller's so-called ‘2nd coalification jump’.     

Carbonization reactions of inertinite macerals in Australian coals

Widespread disagreement about the degree of reactivity of the inertinite group of macerais is related to variations in experimental conditions of assessment and failure to appreciate technological modifications imposed on similar macerals by dissimilar source materials and depositional conditions. This has resulted in the constant under-estimation of the coking potential of post-Carboniferous inertinite-rich coals by predictive methods developed for vitrinite-rich Carboniferous coals. Coking tests up to 1000 °C have been carried out on 20 coals of different rank in such a manner that coked portions of the samples could be correlated with their uncoked equivalents. It has been found that an inverse relationship exists between the level of precarbonization reflectance (PCR) of inertinite and the reflectance and bireflectance of its coke. The increase in the latter parameter is non-linear and involves a sudden jump which is taken as the boundary between reactive (high bireflectance) and non-reactive (low bireflectance) inertinite. In relation to coal rank a reactivity field for inertinite has been delineated which can be subdivided into two areas of high and moderate reactivity, respectively. On the whole, the proportion of reactive inertinite is larger than allowed for in most petrography-based coke stability calculations.     

An Electrokinetic Study on the Oil Flotation of Oxidized Coal

Abstract

The objective of this investigation was to study the electrokinetic behavior of oxidized coals and of hydrocarbon emulsion droplets of flotation reagents to indicate the feasibility of separating the oxidized coals from ash materials and pyrite by an oil flotation process. The effects of surfactants and hydrolyzed metal ions were also included. The electrokinetic behavior of the oxidized coals and the hydrocarbon emulsion droplets were studied by an electrophoresis technique. Generally the isoelectric point (IEP) of the coals decreased with increasing degree of oxidation.

A model of selective flotation of oxidized coal is postulated on the basis of the electrokinetic results. This model simply states that in the presence of a suitable amount of collector and frother, the optimal selective flotation of oxidized coal will occur at the IEP of the oxidized coal. To achieve this condition at the coal surface, it is necessary to adsorb heavy metal hydroxide ions prior to flotation and to absorb hydrocarbon oil droplets containing positively charged organic functional groups during flotation. Oxidized coal becomes more hydrophobic at its IEP because most of its surface is relatively non-polarizable. In contrast, pyrite and ash minerals have relatively polarizable surfaces and remain in suspension even when they are at an IEP.     

Study on coal liquefaction characteristics of Chinese coals

The New Energy and Industrial Technology Development Organization (NEDO) has implemented the collaborative research work with China Coal Research Institute (CCRI) on the liquefaction of Chinese coals for about 20 years. A total of 53 runs in a 0.1 t/d bench scale coal liquefaction plant installed at the CCRI were made on 27 kinds of coal selected among coals existing throughout China. The bench plant was operated in a direct hydrogenation (DH) mode and NEDOL mode. In the DH mode, 25 MPa of reaction pressure was employed with decrystallized anthracene oil used as the solvent, while 17 MPa of reaction pressure was employed and hydrogenated solvent was used in the NEDOL mode. This study confirmed that the NEDOL mode, which uses comparatively mild in liquefaction conditions, can liquefy each coal with the high oil yield more efficiently, and is capable of liquefying about 60% of inertinite in high inertinite coals.     

Studies on the combustion behaviour of blends of Indian coals by TGA and Drop Tube Furnace

Combustion behaviour of blends of two Indian coals of same rank with wide variation in mineral matter content were studied using Thermogravimetric Analyzer (TGA) and Drop Tube Furnace (DTF). The characteristic TGA parameters determined from the burning profiles showed both additive and non-additive behaviour. The burnout temperature and peak temperature showed a linearly decreasing trend with the increasing proportion of the high ash coal. Deviation from the linear trend was observed in the case of the reactivity parameter. The high ash coal showed better TGA reactivity than the low ash coal. The higher TGA reactivity could arise from the combined effect of mineral matter and the nature and distribution of the macerals, particularly those of the inertinite group.The burnout in DTF showed a nonlinear effect. The burnout behaviour of the coals and their blend observed in DTF was not similar to that reflected in TGA. Coal blends with less than 50% of high ash coal showed better burnout than the individual coals.