脉冲流辅助膜蒸馏缓解硫酸钙结垢研究

Study on reduction of calcium sulfate scaling in membrane distillation by pulse flow assisted

膜蒸馏是一种逐渐兴起的热驱动膜技术,近年来在高盐废水的处理中受到了大量关注。然而,膜结垢是制约膜蒸馏工业化应用的瓶颈问题。通过向直接接触式膜蒸馏系统中引入脉冲流场来缓解硫酸钙结垢,分别探讨了脉冲时长与脉冲频率对抑制结垢效果的影响以及通量强化效果。结果表明,在脉冲时长为0.5 s,脉冲频率为5 min-1的最佳条件下,膜蒸馏通量在运行20 h后仍能达到初始通量的70%以上,并且通量强化比(FER)接近于1.3。实验结束后的膜表面形貌分析也表明,最佳脉冲条件下的膜表面结垢较少,仍能够清晰地观察到膜结构,而稳定流下的膜表面则有大量硫酸钙晶体堆积。这是因为,与稳定流条件相比,脉冲流能够促进硫酸钙的均相结晶,并利用形成的膜表面剪切力与膜振动将硫酸钙晶体去除。

Membrane distillation as an emerging heat-driven membrane technology that has attracted a lot of attention in the treatment of high-salty wastewater in recent years.However,the industrialization of membrane distillation has been hampered by membrane fouling.In this study,calcium sulfate scaling was alleviated by introducing pulsed flow field assisted direct contact membrane distillation.The effects of pulse duration and pulse frequency on fouling mitigation and flux enhancement were discussed,respectively.The results showed that under the condition of pulse duration of 0.5 s and pulse frequency of 5 min-1,the membrane distillation flux still maintained more than 70% of the initial flux after 20 h of operation,and the flux intensification ratio was close to 1.3.The morphological analysis of the membrane surface after the experiment also showed that the membrane surface under the optimal pulse condition had less fouling,and the membrane structure could still be clearly observed,while a large amount of calcium sulfate crystals accumulated on the membrane surface under steady flows.Further analysis showed that compared with the steady flow condition,the pulsed flow could promote the homogeneous crystallization of calcium sulfate,and the calcium sulfate crystals could be removed by the formed membrane surface shear force and membrane vibration.