采用气-液两相流动抑制膜蒸馏浓缩过程的膜污染

采用膜蒸馏技术浓缩中药提取液，在进料侧间歇鼓泡产生两相流。重点考察了气速、通气持续时间、通气频率对膜污染的抑制效果。结果表明间隔时间为30min时, 气速分别为0.06和0.09m³/h时抑制膜污染的效果明显不如气速分别为0.12和0.15m³/h时的效果。通气时间间隔为30min,实验进行到250min时，通气持续时间为3和2min的通量分别为22.0和15.0kg/(m²·h)，前者抑制膜污染的效果明显好于后者。通气频率越高，则两相流抑制膜污染的效果越好。通过两相流技术，可以使跨膜通量在实验进行250min后仅下降5%。

Using gas-liquid two-phase flow to limit membrane fouling in concentration by membrane distillation

The effect of two-phase flow on fouling control in the concentration of extracts of Chinese traditional medicine (TCM) by direct contact membrane distillation (DCMD) has been investigated. The two-phase flow on the feed side of membrane was generated by intermittent gas bubbling in the feed flow. The influences of gas velocity, bubbling duration and the intermission time in gas bubbling on fouling limitation were observed. The results revealed that when the gas velocity was 0.12 or 0.15m³/h, the effects were superior to those observed with velocities of 0.06 or 0.09m³/h. For bubbling durations of 3 and 2min, the permeate fluxes were 22.0 and 15.0kg/(m²·h) respectively over a concentration process lasting 250min. The former bubbling duration gives better fouling control. By applying the two-phase flow technique to the DCMD process in order to limit membrane fouling, the permeate flux was found to decrease by only 5% over a concentration process lasting 250min.