液-液循环流化床动态制冰特性

Dynamic Behavior of Ice Production in Liquid-liquid Circulating Fluidized Bed

建立了液-液循环流化床制取流体冰的热态试验装置,在多工况条件下对该新技术的动态制冰特性进行了试验研究。通过对所获得的冰晶颗粒进行粒径的测量与统计整理,分析了冰晶粒径分布,并对影响冰晶尺寸的关键因素进行了探讨;通过计算机实时记录循环系统各测点温度,对载冷介质的沿程温变进行了分析;最后考察平衡工况下喷水量与载冷油介质循环量的关系。结果表明,所获得的冰晶粒径呈离散性分布,主要集中在1mm～2mm区间;冰晶粒径与载流介质流量、喷水量及喷嘴内径密切相关,体现为随载流介质流量降低而减小,随喷水量增加呈先增大后减小的变化趋势,在喷水量为120mL·min-1时达到最大值,在喷嘴内径较小时,冰晶粒径明显减小;流化床内载流介质温升梯度沿床高而减小;载流介质循环量随喷水量的增加呈先增大后减小的变化趋势。在液-液雾化中形成体积微小的雾化液滴,是提高系统运行经济性有效的途径。

An experimental apparatus was set up based on the liquid-liquid circulating fluidized bed for ice slurry generation, and the dynamic behavior of this new ice making system was experimentally investigated under different conditions. Ice crystals produced under each condition were measured and the data measured were analyzed. The critical factors that strongly influenced the ice crystal size were discussed. The variation in temperature of the carrier fluid was explored in real time by a data acquisition system. The relationship between the dispersed phase flow rate and the circulated continuum flow rate was analyzed. The results show that the size distribution of the ice crystals displays non-uniform and mainly congregates in the range of 1-2mm. The ice crystal size rests significantly on carrier flow rate, jet velocity and inner diameter （ID） of the spray nozzle. It decreases with the decrease of the carrier flow rate and reaches the maximum at an intermediate flow rate of the dispersed phase of 120 mL·min^-1. At smaller ID of the spray nozzle, the ice crystal size decreases clearly. The increase of the carrier temperature gradient decreases along the bed. In addition, the carrier circulating rate increases first but then decreases with the increase of the jet flow rate.