【作者】 鞠付栋；

【导师】 陈汉平； 杨海平；

【作者基本信息】 华中科技大学 ， 热能工程， 2010， 博士

【摘要】 能源是社会经济发展的重要支柱。鉴于我国富煤少油气的能源国情,大力发展洁净煤技术是实现我国能源安全的重要保证。本文综合了煤气化的基础研究和应用研究两个方面的内容,重点对煤的气化反应行为、高阶煤的催化气化反应特性、煤气化反应器模型库的建立以及催化气化转化代用天然气(substitute natural gas, SNG)等主要方面开展了研究工作。在煤的气化反应行为的研究中发现,压力对煤热解过程中的影响机制与该阶段的热解产物及煤的热物理性质密切相关。实验结果表明热解压力存在一最佳值使得煤焦表面结构的发展最为有利,对于神府煤来说最佳压力为0.8MPa。同时,加压热解也对煤焦的化学结构产生了显著的影响,主要表现为含氧官能团的减少以及骨架结构的生长。利用分形收缩核模型对煤焦的气化反应动力学的分析发现煤焦的气化反应性的影响关键在于表面结构特性,气化反应动力学参数的变化与煤焦的表面结构特性的变化表现出一致性。而对气化反应过程中不同转化率的煤焦表面结构特征的分析发现高变质程度煤倾向于显著的表面发展过程,而低变质程度煤则更趋于立体发展的特点。为了描述煤焦表面结构特性发展的随机性,本文利用分形理论对气化过程中煤焦表面结构特性进行了分析,发现不同孔径范围的孔隙结构具有不同的分形维数和演变特征,主要表现为微观孔隙的生长和宏观孔隙的塌缩。此外,研究发现,灰分在煤焦表面结构发展中具有双重作用,特别是低变质程度煤。考虑到高阶煤气化反应性较差,利用添加催化剂研究高阶煤的气化反应动力学,发现不同的催化剂具有不同的适用温度范围,且催化作用与添加量并不存在明显的线性关系。对碱金属、碱土金属和过渡金属三种金属盐催化剂的综合比较来看,钙盐比较适合作为高阶煤气化反应的催化剂。在煤气化反应器的模拟研究方面,本文建立了基于炉内反应过程和综合热力过程的详细气化炉流程模型和模型库,模拟了运行条件对各典型反应器的运行性能的影响,发现不同的气化炉具有不同的运行性能,这也决定了其运行的经济性及应用领域。最后,围绕国家能源形势,本文综合分析目前各种SNG生产技术,并结合国内外的研究进展指出了工艺改进的方向。利用简化流程模型模拟了煤直接转化运行性能,得到的SNG产率为0.703Nm3/kg煤。通过对比煤与生物质的差异,在直接转化工艺基础上提出了生物质直接转化SNG的工艺,模拟得到的生物质直接转化SNG产率为0.320Nm3/kg生物质。更多还原

【Abstract】 Energy is one of the motivity of the society and economy development. In China, coal is the primary energy supply. Development of Clean Coal Technology (CCT) is the way to protect the energy safety now and hereafter. This thesis focuses on the coal gasification, one of the most important CCTs, and both fundamental research and application research were conducted. In the fundamental research, coal gasification behavior, including coal reactivity, coal surface structure development at atmospheric pressure, coal pressurized pyrolysis characteristics and high rank coal catalysis characteristics, were analyzed. While in the application research part, major gasifier process models based on Aspen Plus and gasification based substitute natural gas (SNG) production technology were developed and simulated to predict the operation performance.Coal gasification behavior is critical in the gasifier design and operation. It is found that pyrolysis pressure influences the volatile evolution process, and the volatile evolution process in different temperature range is closly related to the pyrolysis products and the coal (char) thermal properties and then makes a different char physical surface. The optimum pressure exists which produces a more developed physical structure and this reveals the balance between surface tension and the viscosity. Because of the enlargement of volatile-char reaction time and the increase of char secondary pyrolysis reaction, system pressure also influences char chemical structure, which shows the grow of the skelecton and the decrease of the oxygen contained function group with pressure increase. It is also found that char reactivity is closely related to char surface structure by introducing fractal shringking core model. The characteristics of char from different carbon conversion reveals that char from different rank coal go through different development regime, the high rank coal char shows little trend to interspace development while the low rank coal char physical surface structure experieces the first grow up stage and then the ruin which is inclined to spacial development. The fractal dimensions variations of different pore radius range were found which could be explained by the pore enlargement and breakage. Also, ash plays a key role in char physical structure development, especially for low rank coal. The catalysis effect of AAEM and transition metal salts in high rank coal gasification was also investigated. It is found that, there is less correlation between addtion amont and catalysis effect and different catalysis have different application temperature.In order to verify the performance and the design method of typical coal gasifier process model based on ASPEN PLUS was developed, including the detailed fixed bec gasifier model, fluidized bed gasifier model and entrained flow gasifier model. The detailec gasifier model combines the coal gasification reaction process in the gasifier and the laten heat recovery process and it is shown that different gasifier have different operatior performance, which determines the gasifier application and its operation economy.At last, in view of the trend in China energy supply adjustment, the current substitute natural gas (SNG) production technologies were reviewd. Based on the SNG productior research and development in the world, improvements on Exxon Catalytic Coa Gasification Process (CCG) were proposed. Simulation shows the improved CCG process SNG yield is 0.703 Nm3/kg Coal. Also, it is found that biomass is more suitable for catalytic gasification to produce SNG, and a novel biomass based direct SNG productior process was proposed. The simulated SNG yield is 0.320 Nm3/kg biomass.更多还原