高温鼓泡流化床的压力波动

Pressure Fluctuations in a Bubbling Fluidized Bed at High Temperature

在内径82mm,高1500mm的不锈钢流化床中,采用4种不同粒径加压流化床灰为实验物料,通过统计分析,功率谱分析和小波分析研究了流化床操作温度由室温至1000℃变化时压力波动行为。研究显示,灰在不同温度下随着流化数增加压力波动偏差增大。B类颗粒,流化数相同时,床层温度升高,压力波动标准偏差减小不明显。D类灰,当流化数相同时,床层温度升高使得压力波动标准偏差减小。在同样的温度下,随着流化数的增加,主频减小。高温鼓泡流化床压力波动信号包含低频成份和高频成份,高频成份较小。压力信号通过离散小波变换可分解为5尺度的近似信号和1到5尺度的细节信号,5尺度细节信号图上幅值大于平均幅值的尖峰数代表了气泡生成数。

Pressure fluctuations are investigated in an 82 mm i.d. and 1500 mm high stainless steel bubbling fluidized bed at a temperature ranging from ambient temperature to 1000°C, using four coal ashes of various average size as fluidized materials. Pressure fluctuation signals are analyzed by using statistics analysis, power spectrum density function analysis, and wavelet analysis. Experimental results indicate that pressure fluctuation standard deviation (PFSD) increases with increasing fluctuation number at various temperatures. At the same fluidization number, for Geldart B ash, there is little variation of PFSD with an increase of bed temperature. For Geldart D ash, PFSD decreases with increasing bed temperature. Major frequency in power spectrum density function (PSDF) decreases with increasing fluidization number. Pressure fluctuation signals consist of low frequency components and high frequency component with small fraction. On basis of discrete wavelet transform, an original signal is resolved into five detailed scale signals (from detailed scale 1 to detailed scale 5) and a fifth analogue signal. The peak number per second in detailed scale 5 is agreement with the bubble formation frequency.