【作者】 石金明；

【导师】 向军； 孙路石；

【作者基本信息】 华中科技大学 ， 热能工程， 2010， 博士

【摘要】 我国是世界上最大的煤炭生产国和消费国,也是世界仅有的几个以煤为主要能源的国家之一。煤烟型污染是我国大气污染的主要特点,提高我国煤炭利用效率、减少煤炭利用带来的环境污染的根本途径是研制和推广应用煤炭优化利用技术,这已成为煤炭工业的发展方向。应用煤气化技术是减少环境污染、节能、发展工业的重要措施。虽然国外己有多种煤气化技术开发成功,但我国的先进煤气化技术还处于开发阶段,与世界先进技术相比差距甚远。因此,对适用于我国煤炭资源和国情的煤气化技术的研究,具有特别重要的现实意义。论文系统总结和分析了国内外有关煤热解气化方面的研究进展,明确了影响煤气化过程的各种关键因素,进而确定了研究对象和思路。主要从以下几个方面开展了研究：采用热重分析仪与便携红外联用对典型煤种热解过程进行了反应动力学和热解过程中气体产物的分析,系统研究了热解温度和煤质特性等因素对煤热解过程的影响,着重分析了热解过程中可燃气体产物和污染性气体产物的析出特性。利用管式炉制取了快速热解焦和慢速热解焦,并对原煤样进行酸洗脱灰处理,分别采取热重与便携红外联用、管式炉与便携红外联用等仪器对煤气化特性进行了详细分析,研究了煤气化过程中气化温度、煤种、脱挥发分、酸洗脱矿物质、煤粉细度和反应速率等因素对煤气化过程中气体产物析出的影响。热重气化实验表明：与原煤和慢速热解焦的气化相比,快速热解焦气化过程中,矿物质对气化反应的影响更加显著；研究发现煤粉细度对气化反应性有明显影响,当粒度大于0.15mm时,CO2气化反应转化率差别较小,而小于0.074mmm的煤粉CO2气化实验结果差别明显；提高气化剂CO2的浓度,可以提高原煤气化过程中可燃气体产物的析出浓度,同时也提高了污染物NO和SO2的析出浓度。通过对污染气体产物的析出特性研究,分析了气化过程中CO与污染气体产物析出的反应机理。利用快速比表面积及中孔/微孔分析仪、低温灰化仪和傅立叶变换显微红外光谱仪对样品的表面物理结构和表面化学结构进行分析,能很好的关联煤的表面特性与热解气化实验结果。通过比表面分析和低温灰化实验,对不同煤阶的原煤样和焦样进行表面物理结构及灰分分析,发现灰分高的煤种在高温下很容易黏结,严重影响热解气化反应的进行,然而制取的煤焦内会孔型很丰富。挥发分快速释放会形成更多的孔隙,但是形成的孔隙会发生坍塌,使得比表面减小。通过傅立叶红外吸收光谱分析,对原煤样和焦样进行了煤表面化学结构分析,研究了煤种、脱矿物质、制焦温度和升温速率等多种因素对煤/焦的表面化学结构的影响。研究发现酸洗主要脱除的是晶态Si02和可溶性盐；随着煤阶的增加,煤中的矿物质与煤分子结构结合更紧密,使得洗煤脱灰难度增大；煤化程度越低,煤结构中的基团越复杂,基团缔合现象越严重；酸洗、制焦温度和升温速率对煤中的基团的影响都有选择性。通过对煤表面分子结构变化进行红外表征,发现洗煤会影响某些基团,但对煤分子结构影响较小。贫煤和无烟煤中脂肪度都很低,且主要以芳环碳骨架为主,而褐煤中存在很多支链结构；贫煤和无烟煤中的氧主要来自于与不同桥氧原子相连的SiO4四面体的Si—O—Si和Si—O—中,而褐煤中还有脂肪族C=O和芳香族C=O,且后者较少；在气化过程中,芳香结构的裂解和缩合协同作用提高了高温气化半焦富氢程度；温度较低时脂肪结构不会脱落,芳环也不受影响,随着温度的升高,煤焦中原始脂肪结构脱落,但芳香度不变,而高温下芳环开链成脂肪结构也逐渐脱落,同时增加了脂肪链长的程度和支链化程度。基于上述实验研究,确定了典型煤热解气化动力学参数,运用多步热解反应机理模型对煤热解气化过程进行了数值模拟,模拟结果与实验结果有很好的相关性,对研究煤气化反应机理有重要指导意义。更多还原

【Abstract】 Flue gas of coal power plant is the main resourcese of atmospheric pollution in China, and the fundamental way to improve the efficiency of coal utilization and reduce environmental pollution caused by coal utilization is to research and develop optimal utilization technologies, which has become the development direction of the coal industry, one of the possible ways is to research, develop and apply the coal gasification technology. Although various coal gasification technologies had been developed successfully in foreign countries, advanced coal gasification technology in China is still in development stage. Therefore, the research of coal gasification technology that suitable for our country’s situations is of particular practical significance to satisfy the requirement of the economic development to coal clean utilization.This thesis provided an overview of the present researches on coal gasification. It revealed the key factor of the coal gasification process. The following investigations are made in this thesis:Thermal gravimetric analyzer STA 409C with portable infrared spectrometry (FTIR) GASMET DX-4000 is used to investigate the pyrolysis processes of some typical coals, including the reaction kinetics and the analysis of gas products. A comprehensive study on pyrolysis temperature and coal properties is analyzed, at the same time, pyrolysis products of the combustible gases and pollutants are mainly detected in this chapter.Rapid-pyrolysis cokes and slow-pyrolysis cokes are made in a tube furnace, and coal samples are dematerialized by pickling. Thermal gravimetric analyzer and tube furnace are used to perform coal gasification characteristic respectively with the help of FTIR on-line measurement, to study the impact of gasification temperature, coal property, devolatilization, demineralization by pickling, the coal particle size and the reaction rate on the yields of the product gas in the gasification progress. According to the TGA gasification experiments, it’s indicated that, compared with coal and slow-pyrolysis cokes, rapid-pyrolysis cokes gasification can make the mineral influence more remarkable. It points that when the coal particle size is over 0.15mm, instead of smaller than 0.074mm, the differences of CO2 gasification conversion rates are not obvious. Meanwhile the study also indicated that raising the concentration of CO2 in the coal gasification process can increase the concentration of combustible gas products and pollutants NO and SO2.The physical structures of coals with different ranks have been studied by surface area analysis and low-temperature ashing experiments. It finds that high ash coal is very easy to felt at high temperatures, seriously affecting the pyrolysis and gasification reaction. In the char-making process, there are multi-molecular layer adsorption and capillary condensation phenomenon in the inner of char, and the pore types are various. The Fourier transform infrared spectroscopy have also been used to studied the chemical structures of coal and char. Detailed characteristics of coal properties, demineralization, char-making temperature and heating rate on coal/char chemical structure are studied. It pointed that pickling process mainly removed crystalline SiO2 and soluble salt. With the increase of coal rank, minerals in coal are in combination with the molecular structure more closely, resulting in dematerializing by pickling more difficult. Moreover, the lower the coal rank is, the more complex the coal structure is, the more serious peaks association is. In addition, the effects of pickling, char-making temperature and heating rate on the coal groups are selectivity. Comparing with the infrared parameters to characterize the molecular structure of coal, it is found that pickling would affect certain groups, but has little effect on the molecular structure of coal.Based on the experiments, kinetics parameters of typical coals pyrolysis were detemined, and a multi-step reaction mechanism of pyrolysis was used to simulate coal pyrolysis. There is good correlation between the experiments and the simulation results. It is important to investigate the reaction mechanism of pyrolysis and gasification.更多还原