多效膜蒸馏技术用于果汁浓缩

利用自制的具有高效内部热量回收功能的多效膜蒸馏组件对西瓜汁、梨汁、柚子汁和苹果汁4种果汁进行了浓缩试验,考察了进料温度、浓度和料液流量对膜通量和造水比的影响。浓缩试验中选用温度为75℃的热水作为低品位热源以保障果汁经历的最高温度不超过70℃。在浓缩过程中膜平均通量约为3 L/（m2.h）,造水比约为7.5,相当于九效蒸发器的节能效果。选取苹果汁为料液,利用上述单因素、浓缩试验后的膜组件进行了周期为2个月的多效膜蒸馏浓缩操作稳定性试验,试验期间所用膜组件的操作性能没有明显下降。

Concentration of Fruit Juices by Multiple-Effect Membrane Distillation

Multiple-effect membrane distillation(MEMD) was used to concentrate fruit juices such as watermelon juice,pear juice,grapefruit juice and apple juice,which possessed characteristics of mild operation conditions,high enrichment ratio,low capital cost and high thermal efficiency.The influences of various experimental conditions such as feed-in concentration,feed-in flow rate,and heating temperature on the trans-membrane flux and gained output ratio(GOR) were studied.In the initial stage of concentrating fresh juices by MEMD process,both GOR and trans-membrane flux were less influenced by the concentration of sugars in the juice and,the average water permeate flux achieved 3 L/(m2·L),the GOR achieved 7.5 when the temperature of heating resource was 75 ℃.In a long-term stability test lasting for 60 days,the MEMD module and operation kept in good condition through the whole experiment.