循环流化床制取流体冰中液滴碰撞-聚并实验研究  

Experimental study on collision-coalescence of drops in circulating fluidized bed for ice slurry production

作　　者：彭正标[1] 梁坤峰[1] 袁竹林[1] 徐大勇[1] 何张陈[1] 

机构地区：[1]东南大学能源与环境学院,南京210096

出　　处：《东南大学学报（自然科学版）》2007年第5期826-832,共7页Journal of Southeast University：Natural Science Edition

基　　金：教育部高等学校博士点专项科研基金资助项目(20060286034)

摘　　要：对雾化液滴在液-液循环床体内碰撞-聚并现象进行了研究.在相同喷速下,通过改变载冷介质流量和温度,考察了影响液滴聚并发生频率的关键因素;采用高分辨率数码摄像仪实时采集床内颗粒在同一工况下不同高度处的流动状态,应用图像处理与数值计算相结合的方法,分析了颗粒平均粒径沿床高的变化趋势;对载冷介质温度最低时实验所获得的冰晶进行粒径的测量与统计整理,探讨了抑制液滴聚并的方案.结果表明,液滴聚并严重地影响了冰晶尺寸及其分布;在载冷介质流量较小时,液滴聚并频率大大降低,而在载冷介质温度较低时,液滴表面局部破碎及快速冻结导致颗粒平均粒径沿床高呈减小的变化趋势.在保证经济性及不冰堵的条件下,可以通过降低载冷介质温度和减小其流量来改善所制取流体冰冰晶的质量.The phenomena of drops coalescence were studied in liquid-liquid circulating fluidized bed. Critical factors that influenced the frequency of drops-coalescing were investigated through varying the mass flow rate and temperature of the carded oil-medium at same velocity of jetting. The high-resolution digital CCD （charge couple device） camera was employed to acquire the drops flow regime in real-time at different heights. The variation tendency of the mean particle-size along the bed was analyzed via image processing and numerical calculation. Ice particles produced at the lowest temperature of the oil-medium were measured manually and then the results were sorted. Based on these the scheme to restrain drops-coalescing was explored. Final results show that the influence of drops coalescence on the distribution of the ice-particle size is strong and intense, and the dropscoalescing frequency decreases with decreasing the mass flow rate of the oil-medium. However, partial surface breakup and swift freezing-out of drops make the mean particle-size decrease along the bed when the oil-medium temperature is lower. The quality of crystals produced for ice slurries can be improved by means of prescribing reasonable temperature and flow rates for the cold oil-medium, taking cost related factors into account and promising no ice-agglomeration.

关 键 词：液-液循环流化床 液滴聚并 流体冰冰晶 

分 类 号：TQ027.35[化学工程]