基于枝条形分布器的气固流化床固体浓度分布的冷模研究

Solid Concentration Distribution in a Gas-solid Fluidized Bed Based on a Branched Pipe Distributor

实验在内径0.284m、高度6.000mm的气固流化床冷模装置中进行,采用PC6D型光纤粉体浓度测试仪来检测固体浓度。实验系统由有机玻璃筒体、气体分布器、气体缓冲罐、冷冻干燥机、流量计、光纤测试仪和旋风分离器组成。使用开孔率均为0.5%的枝条形气体分布器,以直径为154×10-6～180×10-6m、密度为2550kg·m-3的砂子为固体颗粒,压缩空气为流化气体,在静床高为0.6～1.5m,表观气速为0.3～0.6m·s-1的情况下,考察了时均固体浓度在空间的分布。实验结果表明,表观气速的增加会使密相区的固体浓度减小。静床高较小(0.6m和0.9m)时,床层密相区的固体浓度的分布比较简单,随着径向位置的增加而增加,随着轴向位置的增加而减少。静床高较大(1.2m和1.5m)时,床层密相区的固体浓度的分布比较复杂:径向仍然呈现中心稀边壁浓的规律;从轴向来看,整体上满足下浓上稀的分布,但是中间存在波动,床层高度H=0.4～0.8m区域固含率的等值线近似为椭圆。实验结果能够为工业流化床反应器优化设计提供基础数据。

The solid concentration distribution in a gas-solid fluidized bed was studied by using fiber optical probes as detecting apparatus. The experimental system was composed of an acrylic column with a branched pipe type gas distributor, a compressor, a series of knock-out drums, a freeze dryer, a fiber optical probe detecting system and a series of cyclones. The experiments were conducted at ambient condition; the air and the mixture of sands with diameter of （154-180） ×10^-6 m and average density of 2550 kg·m^-3 were used as fluidizing gas and fluidizing particles separately. Under different operating conditions, such as the superficial gas velocities of 0.3-0.6 m·s^-1, the initial bed heights of 0.6-1.5 m, the effects of superficial gas velocity and initial bed height on the solid concentration distribution along the radial direction and axial direction of the column were measured and discussed. The experimental results show that the time-averaged solid concentration in the dense phase area decreases with the increase of superficial gas velocity. When the initial bed height is small （0.6 - 0.9 m）, the time-averaged solid concentration decreases axially and increases radically; while when the initial bed height is higher （1.2 -1.5m）, the time-averaged solid concentration still increases radically and in the axial direction it decreases on the whole, but there is a fluctuation, which leads the equal value lines of the time-average solid concentration to form a series of elliptic contours in the axial position of 0.4-0.8 m and causes this area has higher possibility of appearing bubbles. The results of this study can provide basic data for the design and optimization of industrial fluidized reactors.