| Summary: | 碩士 === 淡江大學 === 化學工程與材料工程學系碩士班 === 96 === Membrane distillation is a separation operation employing porous hydrophobic membrane and utilizing the vapor pressure difference across the membrane due to temperature difference. This thesis investigates the application for desalination via simulation. Direct contact membrane distillation (DCMD) and air gap membrane distillation (AGMD) are studied. Simulation model is built on Aspen Plus® with a user defined unit operation written for the two types of membrane distillation, respectively. The model is different from reported in that the bulk phase mass resistances are included. Large scale modules for practical industrial applications are simulated and studied for the effects of design and operation variables, as well as the importance of heat and mass transfers of each phase. Response surface method is adopted to establish the performance-variable quadratic model and optimization is further accomplished.
Analysis results indicate that the most significant variables are hot liquid inlet temperature, hot liquid inlet flow rate, cold liquid inlet flow rate and the membrane thickness or pressure of the air gap. The optimal operation should use minimum hot liquid flow rate, maximum hot liquid temperature, maximum cold liquid flow rate and minimum membrane thickness for DCMD with efficiency of 8.2% can be obtained and use minimum hot liquid flow rate and maximum hot liquid temperature for AGMD with efficiency of 5.8% can be obtained.
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