A study on the applicability of adsorption desalination cum cooling cycles in zero liquid discharge process

Abstract

Adsorption Desalination cum Cooling (ADC) process is a cost effective and environmental-friendly fresh water resource. In contrast to the conventional thermal desalination systems such as multi-stage flash (MSF) and multi-effect distillation (MED), the evaporation of feed water (seawater or brackish water) occurs at lower temperatures, typically from 5°C to 30°C. The salient advantages of the ADC cycle over the other desalination technologies are: (i) it can be powered by a low-temperature heat source, (ii) it has almost no major moving parts, (iii) it has low maintenance, (iv) it is environmental-friendly with lowest CO2 emission at 0.64 kg/m3 of water, 5 times lesser emission than a RO plant, and more than 10 times lesser with the MSF, (v) it utilizes zero chemicals in the pretreatment step and (vi) it can achieve high recovery ratio (over 80%). ADC cycles utilize the lowtemperature heat sources to perform simultaneous desalination and cooling power production, i.e., 8 to 22 m3 per day and 24 to 35 Rton per ton of silica gel. The implementation of adsorption-desorption principles to evaporation-condensation of seawater enables the AD cycles to achieve low specific energy consumption of 1.38 kWh/m3. In this study, it has been shown that AD cycle can be operated at higher feed salinity compared to conventional thermal- or membrane-based desalination technologies, thus could play a pertinent role in zero liquid discharge process.