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任何物质的化学反应性质均与其结构有关,煤也不例外.人类对煤研究和利用的历史一直包括对煤的结构与反应的探索,依据从不同层面得到的信息提出了许多煤结构模型并用多种方式表述了煤的反应行为.然而到目前为止,这些探索还没有达到准确解析化学现象所要求的"分子水平".本文简要分析了"煤结构和反应"的认识发展过程,并结合自己的思考和研究结果,试图提出从分子水平进一步发展煤化学的思路和挑战,以供参考. 相似文献
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煤微观结构的X射线衍射原子分布函数分析 总被引:2,自引:0,他引:2
采用在非晶态结构研究中应用的X射线衍射原子分布函数法测试了四种不同煤化程度煤的碳原子平均径向分布,求出了碳原子间距、配位数、芳香度、聚合度和短程有序畴等结构信息,并与文献值进行了以比。结果表明,煤的碳原子间距及对应的配位数介于石墨和金刚石对应的数值之间,随着煤化程度的增加,芳香胺、聚合度和短程有序畴增大,煤的石墨化程度增加。 相似文献
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煤及煤焦微观结构特征与气化反应性 总被引:6,自引:2,他引:4
研究了不同煤化度煤及煤焦的微观结构及其对气化反应性的影响。结果表明,褐煤焦具有丰富的分支孔系统和较大的比表面积,并含有较多对气化有催化作用的可交换阳离子。无烟煤焦分支孔贫乏,比表面积很小。煤焦的总孔容、比表面积和芳核大小之间有很好的对应关系。不同煤化度煤焦气化反应性差异很大,脱矿物质后煤焦反应性差异显著减小,但是脱矿物质前后煤焦的反应性随煤化程度的变化趋势相似。 相似文献
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应用ESR技术对一变质系列煤的自由基特性进行了实验研究,探讨了煤中自由基的起源、性质和数量的变化,并将其与煤的大分子结构相关联。结果表明,煤自由基特性在煤化过程中的规律性较好。 相似文献
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催化剂对煤着火特性的影响Ⅰ.煤性质及煤中矿物质对煤催化着火的影响 总被引:5,自引:0,他引:5
使用可在加压下测定着火点的装置,研究了煤化程度、煤中太物质和煤焦干馏温度对煤或煤焦的催化着火的影响。结果表明,对于煤的催化着火来说,煤化程度、煤焦干馏温度仍是影响煤或煤焦活性的重要因素,但是添加催化剂后,煤的活性顺序也发生了一定的变化;煤中矿物有一定的催化着火作用,催化作用的大小与煤中钙、钾、钠含量及其存在形态、分布状况有关;催化作用的大小与催化剂添加量有关,并且添加量存在一个最佳值,此时着火点最 低。 相似文献
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煤热解过程中含氮气相产物转化规律的实验研究 总被引:3,自引:1,他引:2
为了研究煤在热解过程中含氮气相产物的生成规律,在滴管炉反应系统中对四种原煤以及两种脱除矿物质煤样分别在500℃、700℃、900℃和1100℃进行了实验研究。结果表明,随着温度的升高,作为NO前驱物的HCN和NH3的收率随之增加,N2的收率也增加。煤种对含氮气相产物的生成规律也有着较大的影响,煤化程度比较低的煤在热解过程中,燃料氮向气相含氮产物的转化率较高;煤化程度比较高的煤转化率则偏低,大部分的氮缩聚在多环芳香结构中,成为焦炭氮。煤中的矿物质对燃料氮向N2的转化起到了促进作用,而对燃料氮向HCN和NH3的转化起到了抑制作用。 相似文献
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以煤的大分子结构理论为指导,设置煤化学实验的教学内容,开展实验教学。实验项目的开设以工业分析、元素分析和发热量测定为顺序。教学过程采用主、副板书结合,引导学生运用煤的大分子结构理论分析煤的组成和性质,对比讨论不同煤样的实验结果。这种教学方式突出了煤的大分子结构理论的中心地位,构建了"煤的生成-煤的结构-煤的性质"的知识体系。可循序提高学生的思维能力,即:先整体把握煤的水分、挥发分和固定碳含量随煤化程度的变化规律,再细化分析煤中C、H、O元素在不同煤化阶段的变化特点,最后综合评价煤中可燃质与不可燃质对煤热值的影响。 相似文献
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An in situ ultrasonic diagnostic technique was applied to monitoring the hydrothermal synthesis of zeolite A and X of clear solution extracted from alkaline fused class F coal fly ash. In this context, kinetic evaluations based on in situ ultrasonic diagnostic data displayed an important approach to study the synthesis process. The impact on nucleation and crystal growth was demonstrated by variation of a few relevant parameters such as reaction temperature, amount of water, Na2O and ageing time, including templated colloidal synthesis mixtures as model solution. To complement the kinetic analysis, ex situ techniques such as ICP, X-ray diffraction, scanning electron microscopy and dynamic light scattering were used to investigate liquid phase and reaction products extracted from the reaction mixture during the synthesis. 相似文献
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Schürmann H Unterberger S Hein KR Monkhouse PB Gottwald U 《Faraday discussions》2001,(119):433-44; discussion 445-59
The alkali-metal vapour release during pulverised hard (bituminous) coal combustion was investigated in a semi-technical drop flow reactor in the temperature range 1100-1400 degrees C. Absolute concentrations of total gas-phase sodium and potassium species were determined using the in situ/on-line excimer laser induced fragmentation fluorescence technique (ELIF). Alkali-metal concentrations measured for the untreated coals were found to be in the range 0.1 to 4.7 ppm, depending on the temperature. As well as observing the temperature dependence, the effect of co-feeding defined amounts of silica and clay minerals was studied. In addition, to assist interpretation of ELIF measurements, ash samples were taken and analysed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The additives lead to a pronounced binding of the alkali-metal species and suppression of the sharp temperature dependence observed without co-feeding. Therefore, the use of such getter materials can be confirmed as an effective way to remove corrosive alkali-metal species from the flue gas in pulverised coal combustion. 相似文献
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风化中焦煤结构的变化 总被引:4,自引:1,他引:3
用低温氧化模拟焦煤在自然界的风化过程,借助付里叶变换红外发射光谱法,原位观察了过程中煤结构的变化,并和其成焦性质的下降相关联。所得谱图表明,脂肪族基减少、醚桥键的增多以及羧酸基的出现是氧化焦煤的结构特征。由于脂肪族基的损失以及含氧链的增多,导致用氧化焦煤炼焦时产生的液体产物减少和所形成的胶质体热稳定性降低,以致难以使芳核颗粒间产生良好的熔融缩聚反应,结果使得到的焦饼松散不均一 相似文献
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Baisheng Nie Xianfeng Liu Shaofei Yuan Boqing Ge Wenjie Jia Chunliang Wang Xihui Chen 《Adsorption》2016,22(3):315-325
Enhanced coalbed methane (ECBM) in deep coal seams is being actively investigated around the world. Since the in situ coal seams are always saturated with water, methane sorption behavior on coal in the presence of water can help accurately assess the amount of recoverable methane. Thus, methane sorption isotherms have been measured on a high-rank anthracite, a low-volatile bituminous, a middle-volatile bituminous and a high-volatile bituminous coal with the manometric technology at 30 °C under six different moisture contents. The Dubinin–Astakhov (D–A) equation was used to fit the experimental sorption isotherm data. In all cases, the moisturized coals exhibited lower sorption capacity than the corresponding dry materials and moisture has a significant effect on CH4 sorption capacity. The maximum sorption capacity, V 0, displays a linear decline with the moisture content for the Changcun and Malan samples, but it is nonlinear for the other two coal samples. The net heat of CH4 sorption, βE, is also reduced by the presence of water, but varies only slightly between a relatively small span of about 8.8 and 10.0 kJ mol?1 for the dry samples studied, despite the difference in coal rank. In addition, the maximum sorption capacity of CH4 in dry coals presents the typical “U-shape” trend with coal rank. Moisture has a greater impact on the sorption capacity in low-rank coals than that in high-rank coals. The mechanisms responsible for the effect of moisture on CH4 sorption among various rank coals are also presented. The pore-blocking effect is the main influencing factor for high-rank anthracite, whereas, the competition sorption is dominant for low-rank coals. 相似文献
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Growing environmental concerns and the need for alternatives for oil
and natural gas resulted in intensive researches on ultra clean coal (UCC).
Therefore, the researches related to practice and application of various methods
to produce UCC become more important. Thermal characterization of chemically
demineralized coals by thermogravimetric analysis method is presented in this
study. The aim of the study is to provide thermal data for HF–HNO3
leaching system used for the production of UCC. Coal samples were first physically
enriched by density separation. Then the enriched portion was chemically demineralized
by using HF and HNO3, respectively. Ash content of coal samples were reduced
to a range of 0.12–0.41% by chemical demineralization process. The petrographic,
ultimate and proximate analyses were carried out to determine main features
of samples. Physically and chemically enriched coal samples were then analyzed
in a TG by two different techniques separately. The first technique covered
thermal characterization of samples under non-isothermal conditions. Characteristic
temperatures for each sample were obtained from the TG and DTG data. The second
technique involved the determination of reactivity of in situ produced chars
of each sample. 相似文献
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含铁煤热解过程中HCN形成的主要影响因素 总被引:3,自引:1,他引:2
煤中矿物质和外加含铁化合物对氮氧化物主要前驱体之一HCN在热解过程中的释放具有重要的作用。使用固定床反应器进行了程序升温过程中Ar气氛下的神东、平朔和常村原煤以及相应的脱灰煤、浸渍法加铁煤和沉淀法加铁煤的热解实验,重点研究了HCN释放的影响因素。实验结果表明,煤中的矿物质和外加铁对HCN释放的作用较大程度上取决于煤的变质程度,变质程度越低的煤影响越明显;矿物质和含铁化合物的作用主要出现在升温时挥发分释放的过程,并且因添加方式不同以及煤种不同而对HCN的形成与释放具有不同的作用规律;沉淀法添加的铁在变质程度较低的煤中分散效果较好,对HCN生成量的减少作用明显。同时热解反应温度、煤样粒度和恒温阶段停留时间的长短对HCN释放也有影响。 相似文献
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煤颗粒脱挥发分的数学模拟研究 总被引:2,自引:0,他引:2
煤颗粒脱挥发分的数学模拟研究王国金,李术元,王剑秋,钱家麟,朱亚杰(石油大学化工系,北京100083)关键词煤脱挥发分,煤热解,模拟煤脱挥发分过程是煤的焦化、气化和燃烧等工艺中的基础步骤,开发煤颗粒脱挥发分的数学模型对于煤加工工艺操作参数的制定、生产... 相似文献
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利用电动态平衡技术,将单个带电煤颗粒悬浮在样品池中,可以实现煤颗粒燃烧过程的原位微观研究。本文简要介绍了电动态平衡技术的原理和相关的操作方法,总结了该技术应用于煤燃烧研究的进展,进一步探讨了结合时间分辨光谱技术研究煤燃烧物理化学过程细节的可行性与发展前景。目的在于向国内研究者介绍这一新技术并激发更多的研究兴趣。 相似文献