吸收膜蒸馏的传热传质过程

Heat and mass transfer in osmotic distillation

由于吸收膜蒸馏系统的进料液和吸收液的温度非常接近甚至相同,其传热过程无相变热损失,有可能实现能耗较低的膜蒸馏过程,本文尝试开展吸收膜蒸馏法海水淡化研究。首先分别以葡萄糖水溶液和氯化钙水溶液为吸收液进行吸收膜蒸馏海水淡化实验,结果表明氯化钙吸收液时的膜通量明显高于葡萄糖吸收液时的膜通量。其次建立了吸收膜蒸馏过程的质量和热量传递模型,并对模型进行了计算,模型计算值与实验值非常接近。最后对葡萄糖水溶液和氯化钙水溶液分别作吸收液时对传质系数和极化现象的影响进行了计算分析,结果显示,氯化钙水溶液作吸收液时传质系数约为葡萄糖水溶液的1.7倍;且极化现象造成的蒸气压力差减小的值为后者的1/4左右。

Considering that the temperatures between the both sides of the membrane are quite close or even the same in osmotic distillation system, there is no phase inversion heat loss in this process. It is possible to achieve a lower energy consumption of membrane distillation process. Therefore, the study on seawater desalination by osmotic distillation was carried out. Firstly, the osmotic distillation experiments were proceeded with the seawater as feed solution, the glucose solution and calcium chloride solution as extractant in seawater desalination. The result showed that the membrane flux of calcium chloride solution as extractant was higher than that of glucose solution. Then the heat and mass transfer model of osmotic distillation was founded, based on which the calculation was carried out. The result showed that the model predictions were in good agreement with the experimental data. Thirdly, The impact of glucose solution or calcium chloride solution as extractant to mass transfer coefficient and polarization phenomenon was calculated. The result revealed that the mass transfer coefficient of calcium chloride solution as extractant is 1.7 times of glucose solution and the reduced value of the steam pressure difference by polarization phenomenon is a quarter of that for the latter.