Abstract:

At present, many researches on membrane distillation with porous ceramic membranes have been conducted. However, due to the hydrophilic characteristic of the ceramic membrane, hydrophobic modification is required before use. It results in the increase of process and cost, and the hydrophobicity of the membrane gradually weakens with time. Therefore, the membrane distillation of desulfurization wastewater with negative pressure using porous ceramic membrane was proposed. The hydrophilic porous ceramic membrane was directly adopted. The negative pressure of the solution stream was formed by the suction effect of pump, thus the solution was prevented from permeating through the membrane. To explore the heat and mass transfer mechanism of membrane distillation with negative pressure, the performance of hydrophilic and hydrophobic porous ceramic membranes under different operating conditions were experimentally compared. The results showed that when the negative pressure in the membrane tube was lower than the capillary pressure in the membrane pores, the solution transport and water vapor transport occurred respectively in the pores of the hydrophilic and hydrophobic porous ceramic membranes. For air flow rate of 22L/min, wastewater temperature of 50℃ and flow rate of 11L/h, the permeation flux of the hydrophilic membrane was in the range of 1.9—3.9kg/(m·h), while that of hydrophobic membrane was only 0.13—0.25kg/(m·h). The thermal efficiencies of hydrophilic and hydrophobic porous ceramic membranes were about 92% and 55%, respectively. This indicated that thermal efficiency of the hydrophilic membranes was larger, and the high thermal conductivity of ceramic membrane favored the enhancement of the membrane distillation performance. The flow rate of desulfurization wastewater had little effect on the heat mass transfer performance, and the membrane permeation flux increased with the increasing of air flow rate or wastewater temperature.

Key words: porous ceramic membrane, negative pressure, membrane distillation, permeation flux, thermal efficiency

摘要：

目前采用多孔陶瓷膜进行膜蒸馏的技术已有不少研究，但由于膜本身的亲水特性，需要在使用前进行疏水改性，这增加了工序和成本，且疏水性随着使用过程逐渐减弱。因此，提出一种基于多孔陶瓷膜的脱硫废水负压式膜蒸馏方法，直接采用亲水性多孔陶瓷膜，通过泵的抽吸作用使膜内溶液形成负压，以防溶液渗出膜外。为探究负压式膜蒸馏的传热传质机理，通过实验对比了亲、疏水多孔陶瓷膜在不同工况下的传递特性。实验结果表明：当膜内负压值小于膜孔内溶液毛细力时，亲、疏水多孔陶瓷膜的膜孔内分别为溶液输运和水蒸气输运；当空气流量为22L/min、废水温度和流量分别为50℃和11L/h时，亲水膜的渗透通量在1.9~3.9kg/(m²·h)之间，而疏水膜的渗透通量仅为0.13~0.25kg/(m²·h)；亲、疏水多孔陶瓷膜的热效率分别在92%和55%左右，说明亲水性多孔陶瓷膜有着更高的热效率，陶瓷膜的较高热导率有利于提升亲水膜的膜蒸馏性能；脱硫废水流量对热质传递性能影响不大，随着空气流量或者废水温度的增加，膜渗透通量随之增加。

关键词: 多孔陶瓷膜, 负压式, 膜蒸馏, 渗透通量, 热效率