【作者】 张凯；

【导师】 由长福；

【作者基本信息】 清华大学 ， 动力工程及工程热物理， 2012， 博士

【摘要】 针对清华大学提出的具有自主知识产权的基于水平移动床工艺的褐煤提质技术，采用实验测量与理论分析手段，开展褐煤提质过程的机理与模型研究，为完善水平移动床褐煤提质技术提供理论基础。本文首先从单个大颗粒褐煤干燥和热解两方面着手，获得单个大颗粒褐煤干燥和热解过程的微观机理。针对单个大颗粒褐煤干燥过程，首先搭建了大颗粒褐煤对流干燥实验台，完成单颗粒褐煤干燥实验。同时建立基于褐煤物性参数的热质耦合模型，所建模型与实验数据进行对比，证实了模型具有较好的精度。利用校验后的热质耦合模型计算获得不同工况下的大颗粒褐煤干燥数据，利用数值回归的方法得到简单且便于耦合计算的大颗粒褐煤集总参数干燥模型，并论证了该集总参数模型的适用性。针对大颗粒褐煤热解过程，通过建立准确描述褐煤热解机理的平行反应模型，发展了适用于单个大颗粒褐煤热解的数学模型。其次，以水平移动床褐煤提质技术所涉及的堆积态（固定床和移动床堆积态）干燥过程为目标，开展了褐煤提质过程的堆积态干燥模型与规律研究。对于固定床堆积态褐煤干燥过程，利用多尺度方法进行数学建模，在计算宏观的气相与颗粒表面的传热、传质的同时，通过瞬时边界条件计算颗粒内部微观的传热、传质过程。基于单个大颗粒褐煤集总参数干燥模型，建立了固定床集总参数干燥模型。上述两个固定床干燥模型与实验数据定量符合较好。对于提出的水平移动床工艺，利用集总参数模型进行了中试规模水平移动床装置运行参数研究，最终获得水平移动床中试装置合理的运行参数及优化建议，为大型化褐煤干燥提质工艺的开发提供理论指导。最后，从干燥提质产物的自燃倾向性和水分复吸特性两方面着手，探索能够保证提质产物安全、长期堆放的水含量范围。针对干燥褐煤自燃倾向性问题，利用搭建的联合国标准篮和氧化动力学测试实验台对不同水分含量褐煤提质产物的自燃倾向性进行了详细的表征工作，明确了水分对褐煤自燃倾向性的影响规律，以常见烟煤作为参考，提出不易发生运输与应用时自燃的水含量范围。对于提质产物的水分复吸特性，发展了现有的的平衡水含量模型，并提出了平衡水含量与初始水含量及储存条件的定量关系式。上述研究为褐煤提质过程的目标控制与存储条件确定提供了理论依据。更多还原

【Abstract】 For the lignite upgrading technology based on the principle of horizontal movingbed which proposed by Tsinghua University the mechanism and model research hadbeen carried out by experimental measurements and theoretical analysis, and the finalgoal of the research is to provide theories and guidelines for the lignite upgradingtechnology.First, single coarse lignite particle drying and hydrolysis mechanism was studied.The drying kinetics of single coarse lignite particles in hot air were investigatedexperimentally, and a coupled heat and mass transfer mathematical model for the dryingof single particles was developed assuming local thermodynamic equilibrium. Thenumerical results agree well with the experimental data verifying that the mathematicalmodel can evaluate the drying performance of porous lignite particles, and a lumpeddrying model for single coarse lignite particle was established by simulation resultsfrom the coupled heat and mass transfer mathematical model. The lumped drying modelfor single particle is available for air and flue gas, and it is simple and can be easilycoupled for drying of packed lignite particles. The mathematical model of the pyrolysisof single coarse lignite particles was established using a parallel reaction kinetics modelcoupled with a heat transfer model.Then, the drying process of packed lignite particles (packed bed and moving bed)was studied. A multi-scale model was used in a numerical investigation of ligniteparticle drying in a fixed bed. The multi-scale model simultaneously analyzed amacroscopic thin bed layer and a microscopic thin particle layer. The macroscopic heatand mass transfer between the drying gas and the lignite particle surfaces was calculatedin conjunction with the microscopic intra-particle heat and mass transfer using transientboundary conditions. Meanwhile, a lumped drying model of fixed bed was establishedbased on the lumped drying model of single coarse lignite particle. Compared withexperimental results of drying of fixed bed it can be found that the both drying model offixed bed are available for drying process simulation of packed lignite particles. Forproposed horizontal drying technology, the influence of operating parameters wasstudied using lumped drying model, and suitable parameters and optimationrecommendations were determined. Finally, the spontaneous combustion propensity and water vapour readsorptioncharacteristics were studied, and the range of water content of the lignite upgradingproduct was determine to ensure secure and long-term stacking. For the spontaneouscombustion UN basket method and oxidation kinetics testing method were used toresearch the influence of water content on spontaneous combustion of the ligniteupgrading product. The bituminous coal was selected as benchmark, so the watercontent of upgraded lignite product can be calculated to avoid the spontaneouscombustion. For the water vapour readsorption characteristics, considering the effect ofinitial water content the equilibrium water content model was developed. The goal ofthe above research is to provide theoretical guidelines for the target control of theupgrading process and storage conditions.更多还原