INTERPRETATION OF FLOW NONUNIFORMITY AND HYSTERESIS WITH A CAPILLARY ARRAY MODEL

A novel capillary array model is proposed to shed light on the development of themaldistribution of cocurrent downward gas-liquid flow and the hysteretic performance behavior in apacked column.The model is based on the principle of nonequilibrium thermodynamics and incombination with lateral random walk of elemental liquid rivulets.The liquid distribution over aone-dimensional array of capillaries is simulated and the basic features of gas-liquid flow in packedbeds are demonstrated.With proper correspondence of hysteresis branches with nonuniformity of flowdistribution assumed,the experimentally observed hysteresis in pressure drop,liquid holdup and masstransfer rate can be qualitatively simulated.Strenuous efforts are still required for further developingthis model into a predictive tool for the evaluation of performance of packed-bed type devices.     

液相合成甲醇催化剂活性的研究

The effects of reduction procedure, reaction temperature and composition of feed gas on the activity of a CuO-ZnO-Al2O3 catalyst for liquid phase methanol synthesis were studied. An optimized procedure different from conventional ones was developed to obtain higher activity and better stability of the catalyst. Both CO and CO2 in the feed gas were found to be necessary to maintain the activity of catalyst in the synthesis process. Reaction temperature was limited up to 523K, otherwise the catalyst will be deactivated rapidly. Experimental results show that the catalyst deactivation is caused by sintering and fouling, and the effects of CO and CO2 on the catalyst activity are also investigated. The experimental results indicate that the formation of water in the methanol synthesis is negligible when the feed gas contains both CO and CO2. The mechanism for liquid-phase methanol synthesis was discussed and it differed slightly from that for gas-phase synthesis.     

滴流床中流体分布的研究现状及展望

回顾了滴流床流体分布研究的历史和技术进步,分析了测量液体分布大尺度和小尺度均匀性的方法,讨论了改善流体分布均匀性的措施,指出了滴流床操作特性的非线性与小尺度不均匀性的关系,最后对值得深入的工作提出了建议。     

The Relationship Between Hysteresis and Liquid Flow Distribution inTrickle Beds

Experiments were conducted on a trickle bed with 0.283 m ID to eluddate the relation-ship between hysteretic phenomena and liquid distribution. The hysteresis of pressure drop and the variance of radial liquid distribution were observed simultaneously. Residence time dlstribu-tion (KTD), holdup and mean residence time (RT) of liquid phase were also found to demonmtrate hystereels of the same nature. RTD, liquid holdup and mean RT calculated with a simple model from the distribution of liquid flow rate show chaxacteristic consistant with the experlmeataJ data, suggesting that the hyteretic phenomena originate from the multiplicity and nonuniformity of liquid flow distribution.