【作者】 唐志国；

【导师】 林其钊；

【作者基本信息】 中国科学技术大学 ， 工程热物理， 2009， 博士

【摘要】 煤气化技术是解决未来能源、环境和能源安全战略的核心技术之一,而我国煤炭的特点是高灰熔点煤的储量多,现有的气流床气化技术大都无法满足其高效气化的要求,因此亟待研发适合高灰熔点煤的先进煤气化技术。由于气化炉是煤气化技术中的最关键设备,因此,本文以高灰熔点煤的高效气化为背景,归纳分析了各种先进干煤粉气流床气化炉的炉型结构,将无焰氧化技术应用于粉煤气化,提出了一种基于无焰氧化的新型干法进料煤粉气化炉,进行了炉内冷态、煤粉气化的热态试验和数值计算,分析了高灰熔点煤在该气化炉中的气化特性,并以此为基础,对气化炉的结构进行了优化,提出了无焰氧化分级气化炉,对高灰熔点煤在该气化炉中气化特性进行了数值计算与分析。首先,对各种先进干煤粉气流床气化炉的炉型结构进行了总结与分类,逐一分析了每种类型的炉型结构特点、流场特性、温度分布及优缺点;根据不同形态燃料实现无焰氧化的技术特征和形成机理,归纳得出了实现无焰氧化技术的两条途径。由此设计了一种新型干煤粉气流床气化炉,论证了高灰熔点煤在该气化炉上实现高效气化和液态排渣的可行性进。其次,使用热线风速仪测量了冷态条件下煤粉气化试验炉炉内速度分布,分析了单喷嘴切向进风、双喷嘴错位切向进风和四喷嘴分级错位切向进风三种不同空气入炉方式和不同空气流量情况下的炉内气流流动特性,验证了该煤粉气化炉实现煤粉无焰氧化的可行性。再次,搭建了一套小型煤粉气化试验装置,完成了系统调试,进行了高灰熔点煤干法进料气化试验,观察了炉内气化反应的火焰图像特征;研究了不同工况下的煤气化特性,寻求高灰熔点煤在基于无焰氧化煤粉气化炉中气化的合适工况参数,为后续研究积累了经验。进而,建立煤粉气化炉的物理和数学模型,运用概率密度函数(PDF)方法对高灰熔点煤在基于无焰氧化的煤粉气化炉内的气化过程进行了模拟计算,参照小试的试验工况,验证了气化炉模型;分析了不同氧碳原子比、蒸汽煤比和气化压力对高灰熔点煤气化特性的影响,并可视化地研究在典型工况下高灰熔点煤在该气化炉中气化过程,为进一步炉型结构和气化工艺的优化设计提供依据。最后,将分级气化思想应用于无焰氧化的煤粉气化炉,对基于无焰氧化的煤粉气化炉进行了进一步改进,提出了一种基于无焰氧化的分级气化炉,对高灰熔点干煤粉在该无焰氧化分级气化炉中的气化特性进行了数值计算,分析氧碳原子比、蒸汽煤比和分级进料情况对气化结果的影响,这为后续的中试研究提供参考。更多还原

【Abstract】 Coal gasification technology is one of the key means to account for energy sources, environment and energy safety in the future. However, there is plenty of high ash melting point coal in China which could not be gasified in almost all entrained flow bed gasifier currently, so it’s imperative that a new coal gasification technology should be built out urgently. In coal gasification techniques, the gasifier is the key equipment which directly affects gasification characteristics, therefore flameless oxidant technology was applied to the design of new gasifier for high ash melting coal, and gasification characteristics in the gasifier were carried out by not only experiments under cold state and therma1 state, but also numerical simulations in this paper.Firstly, the all advanced types of dry feeding entrained flow bed gasifiers nowadays at home and abroad were summed up and classified, the structural and flow field characteristics, gasification reaction mechanism, temperature distributing inside the gasifier and the advantages and disadvantages of the the gasifier were detailedly analyzed; at the same time realization conditions, formation mechanism and implementation approaches of flameless oxidation technology also be explored in detail. So, a novel dry pulverized coal gasifier based on flameless oxidant which was applicable to high ash melting point coal was put forward, and the feasibility of high efficiency gasification and slag tapping for the coal on the gasifier were discussed.Secondly, cold state characteristics and aerodynamic field inside the experimental gasifier was tested using hot wire anemometer under three kind conditions, namely single nozzle tangential flow jet, double nozzles tangential flow jet symmetrically and staged-feeding four nozzles tangential flow jet symmetrically, according to the implementation approaches of flameless oxidation technology, so as to demonstrate the feasibility of flameless oxidation in the gasifier.Thirdly, a test system for coal gasifier was designed and built up, subsequently debug experiments were conducted. Then, gasification experiments of high ash melting point coal with dry pulverized coal feeding were carried out on the gasification test system, the flame images were observed to validate the feasibility of flameless gasification inside the gasifier, temperature distributing inner the gasifier and syngas components were measured under different [O]/[C] atom ratio and steam/coal ratio conditions. From these experimental results, the value range of key gasification parameters, including [O]/[C] atom ratio and steam/coal ratio mainly, could be obtained that will accumulate experiences for the subsequent research deeply.Fourthly, physical models and mathematical model of the gasifier were built, then three-dimensional numerical simulation of the gasifier for high ash melting point pulverized coal was conducted by using probability density function (PDF) model. From the simulation results, the veracity and feasibility of numeral gasification model could be verified by compared with the experimental results, the influence rules of [O]/[C] atom ratio and steam/coal ratio on gasification characteristics of high ash melting point coal could be drew, and the flow and components concentration field inner the gasifier could be study visually, that will provide evidences for optimal design further of the gasifier structure and gasification techniques.Finally, staged gasification was applied to the structure design of the gasifier, so a structure improved gasifier, namely staged gasifier based on flameless oxidation was put forward. Then the gasification numerical simulations of high ash melting point coal in the staged gasifier were conducted under different conditions, so as to analyze the effects of [O]/[C] atom ratio, steam/coal ratio and second stage reactants supply ratio on the gasification characteristics in the staged gasifier, all that will somewhat offer references for pilot test subsequently.更多还原