共查询到19条相似文献,搜索用时 140 毫秒
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挥发分组成及其析出过程对煤的着火特性的影响 总被引:2,自引:0,他引:2
一、引言 目前,在利用热分析法研究煤的热力特性方面,重点是研究TGA、DTA、DTGA三条曲线,从中归纳出反映煤质特性的指标,如T_i、W_c、E、C、D、S,据此判别煤的热力特性的优劣。以往的试验结果表明,着火温度T_i基本上随挥发分增多而降低。但也有些挥发分含量相近的煤种,T_i和燃烧速度(dW/dτ)_(max)却有较大的差别。这说明仅 相似文献
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在沉降炉上制备了不同燃烧气氛、不同燃尽程度的半焦,采用低温氮吸附仪和扫描电子显微镜测定了其孔隙结构和表面形态.结果表明,所取的半焦试样均具有完整且连续的孔结构体系;但在相同的操作条件下,O_2/CO_2气氛下半焦试样的孔结构参数及其分形维数均小于相同O_2浓度的O_2/N_2气氛下的情况;两种气氛下煤焦的燃尽过程中,孔隙结构参数(S_(BET)、V_(BJH)和d_(pore))随燃尽率的增加均呈减小趋势;SEM图像的定性分析结果与N_2吸附的定量测量吻合较好.研究结果为深入认识O_2/CO_2气氛下煤粉的孔隙结构与其燃烧特性的关系提供了基础. 相似文献
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Vl. V. Salomatov V. A. Karelin Vas. V. Salomatov 《Journal of Engineering Thermophysics》2016,25(4):485-494
Innovation development of coal power engineering, besides qualitative improvement of traditional technologies, should be based also on invoking novel methods and means both in preparation and efficient combustion of coal and for reduction of toxic emissions. The most activating action on coal fuel is provided by microwave radiation. A microwave field intensifies energy-consuming processes such as drying of coal, its dispersion, removal of impurities, qualitative heating, combustion with improved ecological characteristics, etc. Base information for development of microwave technologies in coal power engineering is a temperature field. In this paper we study approximately analytically a mathematical model of flat coal mass heating when the heat release source, due to absorption of microwave energy, obeys the Bouguer law. A specific feature of this model is the presence of nonlinearity caused by dissipation of energy from the mass surface due to heat radiation. The obtained dependences on the temperature field are the base for calculation of ignition and burnout of coal substance, search for the optimal microwave regimes, estimation of thermal destruction parameters, etc. The present paper is a continuation of authors’ publication in this journal [1]. 相似文献
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煤焦燃烧反应动力学的通用规律研究 总被引:4,自引:0,他引:4
本文提出了有关煤焦燃烧反应动力学的新思想,即认为煤焦反应动力学参数E(活化能)与煤质无关,它只是煤焦温度的函数;但其反应频率因子k0,ch与煤质有密切关系。本文中首次给出了煤焦燃烧反应动力学参数E/k0,ch与煤的工业分析基值的通用关系。这样可以根据煤质的工业分析基值,就可获得一确定的E/k0,ch值。从而避免了前人关于E/k0,ch值与煤质无通用关系的状况。本文还揭示了反应频率因子不仅与煤质有关,而且还与其燃烧状态有关的物理本质,并给出了它们之间的定量关系。 相似文献
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Mohamed E. Mostafa 《Proceedings of the Combustion Institute》2019,37(3):3053-3060
Fluorescence interference in Raman spectrum is a big barrier for rapid and precise analysis of coal structures by Raman spectroscopy. Dealing with fluorescence interference suitably is one of the key tasks before efficient application of Raman spectroscopy in coal assessment. In this study, Raman spectra and coal combustion characteristics of 32 kinds of Chinese coals were respectively obtained in a micro-Raman spectrometer and Thermal Gravimetric Analyzer. The degree of fluorescence interference in Raman spectrum was firstly defined and quantified as the drift coefficient α using a simple method without curve-fitting the spectrum. The correlations between the degree of fluorescence interference and coal property, coal combustion characteristics were set up and multivariable analysis was done. The results indicate that the degree of fluorescence interference is well related to the coal structures, and it is synthetically determined by volatile, moisture and ash content in coal. With the increase of volatile, moisture content in coal, the fluorescence interference increases continuously, and it can be reduced but not eliminated by drying the moisture in coals. Significant mathematical relations between the drift coefficient α and volatile, moisture content, coal combustion characteristic temperatures have been found. Coal with more evident fluorescence interference in Raman spectrum usually has lower degree of coalification, more polar functional groups, and burns at a lower temperature. The drift coefficient α can act as an efficient probe for coal property and coal combustion characteristics. This study provided a new and simple approach for evaluating coal property and coal combustion characteristics by fluorescence interference in Raman spectrum. 相似文献
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Carboxyl groups play an important role during the development of coal self-heating. The real-time changing characteristics of carboxyl groups were obtained using an in situ Fourier Transform Infrared Spectroscopy method. They are significantly influenced by reaction atmospheres. Under dry-air atmosphere, their quantity obviously decreases before reaching 120°C and then increases with temperature rise. Under oxygen-free atmosphere, it decreases before reaching 80°C and then increases with temperature rise. In contrast with direct oxidation process, the quantity of carboxyl groups is smaller and the decrease phenomenon at the beginning almost disappears during the oxidation process following oxygen-free reaction. The results indicate that the carboxyl groups have different reaction pathways during coal self-heating. These pathways can be divided into two kinds, that is, oxidation pathways and self-reaction pathways. The study proposed the reaction sequences of carboxyl groups during coal self-heating, which are helpful for revealing the mechanism of coal spontaneous combustion. 相似文献
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Char characteristics and particulate matter formation during Chinese bituminous coal combustion 总被引:3,自引:0,他引:3
Yun Yu Minghou Xu Hong Yao Dunxi Yu Yu Qiao Jiancai Sui Xiaowei Liu Qian Cao 《Proceedings of the Combustion Institute》2007,31(2):1947-1954
The characteristics of char particles and their effects on the emission of particulate matter (PM) from the combustion of a Chinese bituminous coal were studied in a laboratory-scale drop tube furnace. The raw coal was pulverized and divided into three sizes, <63, 63–100, and 100–200 μm. These coal samples were subjected to pyrolysis in N2 and combusted in 20 and 50% O2 at 1373, 1523, and 1673 K, respectively. Char samples were obtained by glass fiber filters with a pore size of 0.3 μm, and combustion-derived PM was size-segregated by a low pressure impactor (LPI) into different sizes ranging from 10.0 to 0.3 μm. The characteristics of char particles, including particle size distribution, surface area, pore size distribution, swelling behavior and morphology property, were studied. The results show that, coal particle size and pyrolysis temperature have significant influence on the char characteristics. The swelling ratios of char samples increase with temperature increasing from 1373 to 1523 K, then decrease when the temperature further increases to 1623 K. At the same temperature, the swelling ratios of the three size fractions are markedly different. The finer the particle size, the higher the swelling ratio. The decrease of swelling ratio at high temperature is mainly attributed to the high heating rate, but char fragmentation at high temperature may also account for the decrease of swelling ratio. The supermicron particles (1–10 μm) are primarily spherical, and most of them have smooth surfaces. Decreasing coal particle size and increasing the oxygen concentration lead to more supermicron-sized PM formation. The influence of combustion temperature on supermicron-sized PM emission greatly depends on the oxygen concentration. 相似文献
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本文应用强旋湍流气一固两相流动和煤粉燃烧的数学模型,对新型涡旋燃烧炉内的流动、传热和燃烧过程进行了系统的模拟和分析,得到了与实验相符合的结果。结果表明,涡旋燃烧炉内的湍流空气动力场分布具有强旋、回流和正在发展流的特点。水冷壁总吸热量随燃烧热负荷的增大成比例地增加。煤粉颗粒在炉内的平均停留时间随初始粒径的增大而加长。炉内可实现煤粉的低温、强旋、高效率和高强度燃烧。 相似文献
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Eleanor Binner Lian Zhang Chun-Zhu Li Sankar Bhattacharya 《Proceedings of the Combustion Institute》2011,33(2):1739-1746
This work investigates the fundamental and practical implications of the application of drying technologies to Victorian brown coal combustion. The base case of 60% moisture content coal preheated prior to combustion is compared with partially dried coal (with or without pre-heating) and coal dried to equilibrium moisture content (10–15%). Pulverised coal was combusted in a drop tube furnace and in-situ observations of combustion phenomena, particle temperature and gas temperature were made. An ignition delay was found to occur when partially dried coal was combusted without pre-heating. Flame stability was also decreased when wet coal was combusted without pre-heating. No ignition delay was observed when the water in coal was heated prior to entering the furnace, as in current boilers. The peak particle temperature was found to be higher than the wall temperature by around 130 °C for dried coal, 80 °C for preheated wet coal and 40 °C for non-preheated partially dried coal. The gas temperature profile in the furnace was measured and found to lag behind the particle temperature peak. It was concluded that the evolution and evaporation of water in the wet case lead to an ignition delay, cooler peak particle temperatures and prolonged char combustion. The difference in particle temperatures between preheated wet coal and dried coal and the gas temperature behaviour was attributed to the steam gasification reaction, although studies to elucidate reasons for the differences are ongoing. The quantified results on ignition delay and particle temperatures have important implications for the design of new technologies, in particular the boilers and feed size preparation, for power generation from high-moisture brown coals. 相似文献