Experimental investigation on the performance of air–gap diffusion distillation with foamed ceramics

Abstract

Air-gap diffusion distillation (AGDD) has been proposed as a novel type of thermal distillation technique, in which the hydrophilic porous media is used as a hot stream channel. Polyvinyl alcohol (PVA) sponge was first selected as the porous medium in our previous reports. To improve the thermal, chemical resistance and mechanical strength of the porous medium, some foamed ceramics (FCs) (alumina, zirconia, and silicon carbide foamed ceramic) are selected as the porous mediums which are used as hot stream channels of AGDD in this work. The effect of different FC materials on performances of AGDD is investigated by experiments. That the influence of FCs with pre-wetting and non-wetting treatments on the performances of AGDD is investigated first. Secondly, the influence of operation and structure parameters on the performances of AGDD and the stability of three FCs in long-term operation are explored. And finally, the performances of AGDD used FCs and PVA sponge are compared. Results show that the FC with pre-wetting treatment can improve the performances of AGDD, and the water production flux can rise to 23.7%, especially for the silicon carbide FC with high pore density. Furthermore, among the three FCs, ZrO2 FC can maintain higher water production flux and desalination rate during long-term operation. The desalination rate of AGDD with three different FCs is higher than 99.1%. The AGDD with FC is ideal for high-temperature and high-flow-rate working fluid environments, whereas the AGDD with PVA is suitable for low-temperature and small-flow-rate working fluid environments. This may be used as a reference for the industry to choose porous material for AGDD.