Sustainable integration of a refrigerant hydrate-based desalination system with a dual-effect absorption refrigeration cycle

Innovative desalination technologies are emerging as critical solutions to address the escalating challenges of freshwater scarcity. Among these, gas hydrate-based desalination is a promising approach because it is independent of water salinity and the total amount of dissolved solids. Gas hydrate-based desalination involves forming ice-like structures, known as gas hydrates, from a hydrate former (typically gas) and water under specific conditions, separating pure water into crystals and leaving behind a concentrated brine solution. However, conventional hydrate formers often require near-zero temperatures and high pressures, leading to high energy consumption and operational costs. To address these challenges, this study proposes the use of gas hydrate-based desalination with an R-152a refrigerant as the hydrate former. When using vapor compression refrigeration cycles, refrigerant hydrate-based desalination reduces specific energy consumption by 70% compared to using propane. Energy analysis highlights the dominance of compressors and pumps in total energy consumption, emphasizing the need to replace vapor compression refrigeration systems with more sustainable integrations. Therefore, a dual-effect absorption refrigeration cycle powered by waste heat dissipated from an exothermic hydrate formation reaction is proposed. Integrating this cycle with refrigerant hydrate-based desalination not only decreases the energy requirement to nearly zero but also reduces carbon dioxide emissions by 65%. Economic analysis indicates that integrating the dual-effect absorption refrigeration cycle with refrigerant hydrate-based desalination further reduces the total annualized cost by 33% compared to vapor compression refrigeration combined with refrigerant hydrate-based desalination, which has a total annualized cost of $0.46 million.