Experimental Study on Concentration of Aqueous Lithium Bromide Solution by Vacuum Membrane Distillation Process

摘要

This study aims to investigate the applicability of vacuum membrane distillation for concentrating aqueous lithium bromide solution, and to analyze the feasibility of applying vacuum membrane distillation process to the absorption refrigeration system. Hydrophobic polyvinylidene fluoride (PVDF) was adopted as the membrane material, and was made into hollow fiber membrane module. Commercial aqueous lithium bromide solution with 50% concentration flows through the inner side of membrane thread while the vacuum degree in outer side retain constant from 0.09Mpa to 0.095MPa, the feed temperature varied from 65°C to 90°C. The experiments showed that the permeation flux of vapor water increased quickly when the feed temperature rose from 65°C to 90°C. The permeation flux also increased as the feed flux increased; however, the feed flux was limited by the intensity of PVDF. The permeation flux went up when the vacuum degree of cold side increased, but the tendency went flat as the vacuum degree increased more. Hollow fiber membrane module can provide quite adequate contact area for the feed solution in limited space, and need not heat the solution to boiling point. So it may become a new type of separation device for lithium bromide absorption refrigeration system.