湍动流化床中气泡行为和压力脉动特性的研究

INVESTIGATION OF BUBBLE BEHAVIOR AND PRESSURE FLUCTUATION IN A TURBULENT FLUIDIZED BED

详细研究了在500mm×30mm×6000mm大型二维湍动流化床中FCC催化剂颗粒的床层轴向空隙率分布和床层的压力脉动。根据床层空隙率变化,建立了1个可以同时适用于鼓泡流化床和湍动流化床的气泡平均直径模型。该模型的计算结果与实验观察和实验测得的床膨胀规律均一致,并且与床层压力脉动的变化趋势也一致。在压力脉动沿床层轴向高度的分布图中,曲线呈水平"S"型。根据压力脉动的变化,床层可以分为分布板影响区、气泡生长区、料面影响区和稀相区4个区。根据床层稀、密相压力脉动的剧烈变化,提出了一种确定稀-密相界面高度的新方法,该方法简单实用。

The axial bed voidage distribution of FCC catalyst particles and the pressure fluctuation in a large two-dimensional turbulent fluidized bed （500 mm × 30 mm×6000 mm） were investigated. First, according to the average bed voidage, a model of average bubble diameter was established, which was suitable for use in both bubble fluidized bed and turbulent fluidized bed. The calculation data of this model were agreed with the experimental observation on bubble diameters and with a similar trend to that of the pressure fluctuation, which could be used to predict the bed expansion with well agreement with the experimental results. Moreover, in the profile of pressure fluctuation along axial of fluidized bed, the curve was of a horizontal ＂S＂ type. According to the pressure fluctuation change, the bed could be divided four regions axially, which were grid region, bubble growing region, surface region and freeboard. According to the rapid change of fluctuation in the interface of dense phase and freeboard, a new method to determine the height of dense phase was developed, which was simple but had a substantial application value.