多效膜蒸馏技术用于果汁浓缩

Concentration of Fruit Juices by Multiple-Effect Membrane Distillation

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。

Multiple-effect membrane distillation （MEMD） was used to concentrate fruit juices such as wa- termelon juice, pear juice, grapefruit juice and apple juice, which possessed characteristics of mild oper- ation 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 concen- trating 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 last- ing for 60 days, the MEMD module and operation kept in good condition through the whole experiment.