Abstract:

The processes of mixing and heat transfer between oil shale ash particles and oil shale particles in a non-reacting rotary retorting were investigated by using discrete element method combined with particle thermal conduction model. The mixing index, the average temperature of particles and the standard deviation of temperature were used as the quantitative indexes to evaluate the effect of mixing and heat transfer. The influences of fill ratio of particles, rotational speed of vessel, diameter of the oil shale particles and flights form on particles mixing and heat transfer characteristics were analyzed. Results indicated that the rotational speed of vessel and the diameter of the oil shale particles are the main factors which influence the mixing and heat transfer effect between particles, but the fill ratio and the flights form are relatively minor. When rotary retorting without flights equipped, with the increasing of the fill ratio or the diameter of oil shale particles, the more serious segregation phenomenon between two kinds of particles occurs, the worse the mixing and heat transfer performance are. But it goes up firstly then down with the increasing of vessel speed. Compared with the rotary retorting without flights, the flights forms have influence of disturbance on particle mixing inordinately, so that the mixing and heat transfer effect between particles can be improved remarkably.

Key words: rotary retorting, discrete element method (DEM), numerical simulation, mixing, heat transfer

摘要：

将离散元方法与颗粒热传导模型相结合，研究了页岩灰颗粒与油页岩颗粒在回转干馏炉内的混合传热过程，采用混合指数、颗粒平均温度和温度标准偏差作为评价混合传热效果的指标，分析了填充率、炉体转速、油页岩粒径及抄板形式对颗粒间混合传热特性的影响规律。结果表明，炉体转速和油页岩粒径是影响颗粒混合传热效果的主要因素，而填充率和抄板形式对混合传热效果的影响相对较小。当炉内未设抄板时，随着填充率和油页岩粒径的增大，颗粒间分层现象使混合传热效果变差，而随炉体转速的提高传热效果呈现出先增强后减弱的趋势；设抄板时，抄板形式对炉内颗粒间的混合起到不同程度的扰动作用，从而使传热效果得到显著改善。

关键词: 回转干馏炉, 离散元方法, 数值模拟, 混合, 传热