【作者】 刘彦鹏；

【导师】 王勤辉； 周劲松； 程乐鸣；

【作者基本信息】 浙江大学 ， 工程热物理， 2004， 硕士

【摘要】 煤颗粒在流化床燃烧过程中的灰渣形成特性对锅炉的设计，运行具有很大的影响。不同特性的煤颗粒具有不同的灰渣形成特性，而即使同属一煤种的煤颗粒之间的特性也会存在较大的差异。本文开展了煤颗粒特性对灰渣形成的影响的研究。 本文在概述了国内外关于在流化床燃烧过程中煤颗粒特性对灰渣形成特性影响的研究现状的基础上开展相关研究。通过采用ZnCl₂溶液浮选和筛分的方法把义马烟煤煤样按密度和粒径分成具有不同特性各档颗粒，并在所建的小型流化床燃烧实验台上进行了各颗粒档的多工况燃烧实验。通过对燃烧形成的底渣和飞灰的粒度分布、份额及其含碳量等特性的分析，获得不同密度和粒径下的灰渣形成特性，以及燃烧时间的影响特性。 实验结果表明：（1）同一种煤中，各煤颗粒的性质是不同的，随着密度的增大，煤颗粒的挥发分、碳、氢、氮、氧的含量降低、热值降低，灰分含量增加。（2）对于含灰量较低的低密度颗粒经流化床燃烧后几乎不生成底渣，其燃烧过程主要以单收缩核模式进行；而含灰量较高的密度较高的颗粒则生产大量的底渣，其燃烧过程主要以双收缩核模式进行燃烧。（3）在燃烧时间和入炉粒径相同的条件下，随着密度的增大，底渣份额增加，底渣中细颗粒份额明显减少，底渣的燃尽率下降。（4）随着入炉煤密度的增加，入炉颗粒粒度对底渣粒度分布的影响程度逐渐增加。 在实验研究基础上，以所建的考虑爆裂，破碎及磨损等过程的煤颗粒流化床燃烧模型对燃烧时间为5分钟和20分钟的实验工况下的实验数据进行了拟合，然后预测了各颗粒档在燃烧时间为30分钟时的灰渣特性，预测结果与实验结果总体上吻合。 最后，在一台0.5MW大型循环流化床燃烧试验台上进行了义马烟煤的流化床燃烧特性实验研究，重点讨论了该煤种的灰渣形成特性，并给出燃用该煤种的锅炉的设计和运行建议。更多还原

【Abstract】 Ash formation behaviors of coal partice have great influences on the boiler design and operation for a fluidized bed boiler. The coal particles with differenct properties behave differently on ash formation. Unfortunately, the coal particle properties may be varied form time to time enven for a given coal type. This thesis focuses on the research of effect of particle properties on ash formation.Firstly, a review on the effect of the coal properties on ash formation during f ludized bed combustion is completed. Yima bituminous coal sample is divided into several ranks with different density and size by the ZnCl2 solution floatation and the size sieving processes. Experiments on a bench-scale fluidized bed combustor for every coal rank are completed in different operation conditions. Based on the measurements results, effects of particle density and size on the ash formation behaviors such as ash size distribution, fly ash mass fraction, carbon content in the bottom ash and fly ash are obtained. In additional, effect of burning residence time are discussed.The experimental results indicate that: (1) There are different characteristic particles in the same type of coal. With increasing of coal particle density, the content of ash, volatile matter, C, H, N and 0 and the quantity of heat decreas. (2)As far as the low density particles with low ash content are concerned, there is no bottom ash left after a long term combustion in the fluidized bed. The mode of combustion is "single combusting surface" mode. On the contrary, the high density coal with the high ash content produces large amount of bottom ash and the mode is mainly "two combusting surface" mode. (3)At the condition of the same combustion interval and particle size, with the increasing of coal density, the proportion of bottom ash increases. And the carbon content of fly ash decreases. The proportion of the particle left in the original particle size rank increases distinctly, while the fine particle proportion decreases dramatically. And the burn exhaust ratio decreases. (4)With the increasing of partcle density, the extent of the impact of the particle size distribution to the distribution of bottom ash size graduallyABSTRACTincreases.A simple mathematical model is established based on the single particle coal combustion mode and experimental results. The experimental results of burning for 5min and 20min are matched. The prediction of buring for SOmin is made. The comparison and analysis of model results and experimental results are made.At last, the thesis introduces a combustion experiment carried out on a 0. 5MW circulating f luidized bed combustion test rig. The characteristic of ash formation is discussed through the analysis of experimental results including the ash particle distribution, the propotion of bottom ash and fly ash, ash carbon content and combustion efficency. Some suggestions are provided on the boiler design.更多还原