基于微波-热烟气联合干燥的褐煤水分协同脱除机理研究

Focusing on the long time, low security and economy of conventinal drying methods due to the high water content and complex water-holding type of lignite, microwave heating is introduced, which has the feature of "internal heating". Through the "selecting heating"for water molecules of microwave, and conbining the hot flue gas drying,the favorable conditions for heat and mass transfer is eatablished, and moisture migration conditions is also improved,then the drying rate of entire drying process has a signicicant increase. For our project,firstly,on the basis of water-holding characteristics of lignite, the drying characteristics of lignites containing different water types are studied on the thermobalance and microwave thermobalance, and drying kinetics models are established to explore the moisture migration characteristics of different water types; exploring the enhanced role of "selective heating" of microwave to water molecule for the migration of water molecules on the basis of analysis of variation of functional groups and pore structure before and after drying, and examining the impacts of variation of lignite structure on the snuff back characteristics, oxidation characteristics (spontaneous combustion characteristics) of dried lignite; numerical simulation of combined drying process of single lignite particle is carried out for exploration of field synergistic strengthening mechanism of moisture removal for predicting the temperature field and moisture migration and diffusion law. Through this research, it can be expected to reveal a new moisture removal mechanism of lignite drying process, get the optimizing configuration parameters of microwave-hot flue gas combining drying. It is of important practical value and significance.

针对褐煤含水量高，持水复杂导致常规干燥方法干燥时间长、安全经济性不高的缺陷，引入具有"内加热"特性的微波加热方法，通过微波对褐煤水分的"选择性加热"，结合热烟气外部干燥，构建加速传热传质的有利环境，改善水分迁移条件，从而大幅提高褐煤干燥速率。拟在获取褐煤持水特性基础上，通过考察不同含水类型褐煤在常规和微波加热下的干燥特性并确定相应的临界含水率，进而研究优化组合工况下褐煤的联合干燥特性，结合干燥中及干燥后褐煤样品的水分、官能团和孔隙结构等分析，揭示褐煤中不同水分的迁移析出特性并明确水分脱除对干燥后褐煤回吸、自燃特性的作用机理；建立单颗粒褐煤双界面蒸发干燥模型，对褐煤中的温度场和水分迁移扩散规律进行预测，探讨褐煤水分脱除的多场协同强化机理。通过本课题研究，预期可以揭示褐煤干燥过程水分脱除的新机理，获得褐煤微波-热烟气联合干燥的优化配置参数，具有重要的实用价值和研究意义。