Abstract:

A comprehensive numerical model coupled two correlative one-dimensional unsteady heat conduction equations of spherical particle with distributed activation energy model has been developed for heat and mass transfer mechanism in lignite pyrolysis with solid heat carrier. The finite volume method and the genetic algorithm optimization toolbox based on Matlab software were employed to calculate the thermal and dynamic parameters, separately, and the reliability of the predictions was further validated by thermogravimetric data of the Hulunbuir lignite and temperature measuring experiment on a laboratory-scale fixed bed reactor, respectively. It was found that the variations in mass and heat transfer during lignite pyrolysis with solid heat carrier showed a complex coupling characteristic. The time-dependent rules of temperature field in radial direction have been obtained by varying operation conditions, such as coal particle radius, the initial temperature and feed amount of solid heat carrier. Besides, the relationship between the releasing rate of pyrolytic products and temperature field revealed that the change of temperature field with heating time in lignite pyrolysis was the primary cause of different distribution of the pyrolytic products.

Key words: solid heat carrier, lignite pyrolysis, heat transfer, mass transfer, numerical simulation

摘要：

为揭示在固定床反应器中固体热载体法快速热解褐煤工艺过程中的热、质传递机理,建立了固体热载体法褐煤热解过程中的传质传热模型。模型包括球型颗粒的一维非稳态导热方程和基于分布活化能模型的动力学模块,分别采用有限容积法与Matlab软件中遗传算法工具箱对二者进行数值计算。通过呼伦贝尔褐煤热重实验数据与温度测定实验数据分别验证了预测的动力学参数及颗粒传热模型结果。研究发现,热、质变化在固体热载体法褐煤热解工艺中呈现复杂的耦合特性。此外,考察了在不同初始温度、热载体进料比与煤颗粒半径条件下,褐煤在热解过程中颗粒内部温度场在径向上随时间的变化规律,并分析了产物释放速率与温度场的关联性,结果表明热历程改变是工艺条件对热解产物分布造成影响的根本原因。

关键词: 固体热载体, 褐煤热解, 传热, 传质, 数值模拟