裤衩腿循环流化床流动特性及翻床机理的研究

Flowing Features and Mechanism of Bed Overturn in Circulating Fluidized Bed with Breeches-legs

基于颗粒动力学两相流方法,建立了裤衩腿炉膛的二维CFD数值计算模型,对流化床内的床料平衡流动状态和非平衡流动状态进行了瞬态数值模拟.计算结果表明:当流化风较小时,流化床处于鼓泡床状态;当流化风较大时,流化床处于快速床状态;裤衩腿流化床内流动存在宏观不稳定性,但当外界条件(回料量、布风板阻力、出口背压等)保持一致时,裤衩腿流化床对这类流动自身波动引起的不平衡具有一定的自平衡能力;当一侧布风板的一些风帽被堵塞且不进行风量主动调节时,左右两侧物料交换量在剧烈波动的同时,出现净交换量,但发生翻床与布风板阻力特性有关.这种特性为裤衩腿流化床稳定流动提供了一种可能的控制方法.

Based on dynamics of granular in two-phase the furnace with breeches-legs was developed, and the the balanced flow state and unbalanced flow state of flow, a two-dimensional CFD numerical model for transient numerical simulation was carried out for the bed material in the fluidized bed. Calculation results show that when the flow rate of the fluidizing air is small, the flow pattern of the fluidizing bed is similar to that of the bubble bed, while there is a fast fluidized bed flow pattern when the flow rate of the fluidizing air becomes large. And the flow in circulating fluidized bed with breeches-legs is macroscopically unsteady. However, if the external conditions （including the amount of the feed back material, resistance of the air distributor, outlet back pressure, etc. ） remain the same, the circulating fluidized bed with breeches-legs has self-balance ability against the unbalance caused by the self-fluctuation of the flow. When some air holes in one side of the actively, mass transfer of the material air distributor are blocked, and the air flow rate can＇t be controlled between left and right side fluctuates violently, and at the same time, net mass transfer occurs. But bed overturn is related to the resistance features of the air distributor. This feature offers a possible control method for the steady flow of the fluidizing in breeches-legs.