涡旋式流化床生物滤器水力特性试验

为把流化床生物滤器应用于循环水养殖系统,探讨其较佳的设计与运行参数,研制了一种涡旋式流化床生物滤器,并对其水力特性进行了试验研究。试验装置使用石英砂作为填料,设计了0.18～0.25、>0.25～0.425和>0.425～0.6mm3组不同粒径范围的石英砂和40、50、60、70、80和90cm6组不同初始砂床高度的双因素试验,探讨了石英砂粒径和初始床层高度对砂床流化性能的影响。结果表明:3组不同粒径范围石英砂的临界流化速度分别为(0.061±0.0088)、(0.25±0.011)、(0.48±0.014)cm/s。砂床要保持良好的流化状态,初始砂床高度与床层直径的比值(高径比)需分别大于1.43,1.78和2.14,且高径比与石英砂粒径大小成正比;在相同的膨胀率下,当初始砂床高度增加时,表面流速基本保持不变。床层压降测量显示,3组不同粒径范围石英砂单位床高的压降值分别为(7530.66±215.98)、(6925.66±364.58)和(6790.08±277.95)Pa/m,使用0.18～0.25mm石英砂测得的压降试验值与理论值较为接近,误差在2%～3%。基于Ergun方程,采用回归拟合方法得出涡旋式流化砂床临界流化速度的数学模型,可为流化床的设计和应用提供技术依据。

Hydraulic characteristics of swirling fluidized-sand biofilter

In order to evaluate the working performance of fluidized sand biofilter, and determine the optimal design parameter, a swirling fluidized-sand was designed, which used quartz sand as media. This paper discussed the effect of size and initial thickness of sand bed on the fluidizing performance. Double factor test was designed with different ranges of quartz sand (0.18 to 0.25, >0.25 to 0.425 and >0.425 to 0.6 mm) and different initial thickness of sand bed (40, 50, 60, 70, 80 and 90 cm). The results showed that the minimum fluidization velocities in three groups of different sizes range for quartz were (0.061±0.0088) cm/s, (0.25±0.011) and (0.48±0.014) cm/s, respectively. To keeping sand bed at optimum fluidized state, the ratios of initial thickness of sand bed to the diameter of circular vessel should be greater than 1.43, 1.78 and 2.14, respectively, and the ratio was proportional to the size of quartz sand. The superficial velocity remained constant, while the initial thickness of sand bed increased at the same expansion ratio state. The pressure drop test showed that the pressure drop values per unit sand bed thickness for different sizes of quartz sand were (7530.66±215.98), (6925.66±364.58) and (6790.08±277.95) Pa/m, respectively. The measured value was close to the theoretical value under the condition of quartz sand with 0.18 to 0.25 mm, and error was 2% to 3%. Based on Ergun equation, the mathematical model of minimum fluidization velocity was proposed according to the measured value by regression method, and it can provide a technical basis for the design and application of fluidized-sand biofilter.