Osmotic membrane distillation regeneration of liquid desiccant solution used for air-conditioning: A proof of concept

Liquid desiccant air-conditioning (LDAC) has emerged as a promising technology to meet the increasing demand for indoor thermal comfort. In LDAC systems, regeneration of liquid desiccant solution is a critical step. Direct contact membrane distillation (DCMD) has been explored for regeneration of liquid desiccant solutions used in LDAC systems, but faces technical challenges caused by the hyper salinity of the solutions. Osmotic membrane distillation (OMD) is a variant of DCMD that can treat hyper saline waters. In this study, a proof of concept of OMD regeneration of liquid desiccant solution was experimentally demonstrated. Compared to DCMD, the OMD process exhibited significantly higher water flux due to reduced water vapor pressure on the permeate side of the membrane. Indeed, the OMD process of the liquid desiccant 20 LiCl solution feed achieved water flux two-fold higher than that of the DCMD process under the same operating conditions. Given its increased water flux, the OMD process could regenerate the LiCl solution of much higher concentration: The OMD process with the initial 20 CaCl2 solution osmotic agent concentrated LiCl solution from 20 to 38.4 after a continuous 8-hour operation. © 2023, Publishing House of Natural Science and Technology, VAST. All rights reserved.