Abstract: The flow regimes and pressure fluctuations of powdered coal gas-solid two-phase flow in a fluidized-bed are experimentally studied by using five different particle size distributions of powdered coal.The flow patterns under different operating parameters are determined.The effects of different operating conditions on the pressure distribution and the pressure fluctuation are investigated.The critical fluidization velocity was analyzed by a new method, which is based on the curve of the pressure difference between two adjacent points at the bottom of the fluidized-bed.The initial turbulent fluidization velocity is determined by the fluidization velocity of the maximum value of the pressure standard deviation.The relation formulas between the Reynolds numbers of the critical fluidization and the initial turbulent fluidization on the particle size of powdered coal are proposed.The internal relation between the pressure variations and the evolution of the flow regimes is revealed.The results show that the smaller particle size of powdered coal is, the smaller critical velocity of each flow regime is.When slugging fluidization or turbulent fluidization occurs in fluidized-bed, the pressure fluctuation of fine powdered coal is slight, while the pressure fluctuation of coarse powdered coal is severe.The pressure difference between two adjacent points and pressure standard deviation at the bottom of the fluidized-bed increase first and then decrease with the increase of fluidization velocity.

Key words: fluidized-bed, fluidization, flow regime, powders, hydrodynamics

摘要： 采用5种不同粒径分布的粉煤对流化床内粉煤气固两相流动形态和压力波动进行了实验研究。确定了不同操作参数下的流动形态，考察了不同操作条件对压力分布和压力波动的影响，采用了一种新方法——通过流化床底部相邻两点压差关于流态化气速的曲线来分析临界流态化速度，通过压力标准偏差最大值对应的流态化速度来确定起始湍动流态化速度，提出了临界流态化和起始湍动流态化雷诺数关于粉煤粒径的关系式，揭示了压力变化与流态演变的内在联系。结果表明，粉煤颗粒粒径越小，各流动形态的临界速度越小；当床内出现节涌流态化或湍动流态化时，细颗粒粉煤的压力波动较小，而粗颗粒粉煤的压力波动比较剧烈；流化床底部相邻两点压差和压力标准偏差均随着流态化速度的增大先增加后减小。

关键词: 流化床, 流态化, 流域, 粉体, 流体动力学