Comparison of hollow fiber membranes in direct contact and air gap membrane distillation (MD)

摘要

Hollow fiber microporous membranes was used for seawater desalination in direct contact membrane distillation (DCMD) and air gap membrane distillation (AGMD) configurations. The efficiencies of hollow fiber membranes with different membrane materials and pore size were compared in a laboratory-scale DCMD system. The water flux and salt rejection were shown to be different depending on the membrane properties. The apparent permeabilities for water vapor and NaCl ion were estimated to determine the optimum membrane distillation (MD) membranes. A novel AGMD membrane module utilizing hollow fiber membranes was designed, and its prototype was fabricated using a 3D printer. Using this AGMD module, the performance of the hollow fiber membrane was examined and compared with the results from DCMD experiments. The water flux in AGMD configuration was less than 40% of that in DCMD configuration due to high mass transfer resistance and insufficient cooling plate area. However, it holds promise for practical applications of hollow fiber MD due to the higher thermal efficiency of AGMD than that of DCMD.