Conceptual Design of a Sustainable Hybrid Desalination Process Using Liquefied Natural Gas Cold Energy

Abstract

To counter growing shortages in water supply and the energy crisis, a sustainable hybrid desalination process using liquefied natural gas (LNG) cold energy is proposed in this study. The newly proposed dual-expander organic Rankine cycle-hydrate-based desalination (dual-expander ORC-HBD) process with a reverse osmosis (RO) system consists of two expanders to utilize LNG cold energy and pressure energy simultaneously and can cogenerate electricity and pure water. To analyze the feasibility of the proposed dual-expander ORC-HBD process, computational modeling was performed using liquid-phase and gas-phase hydrate formers (propane, R125A, R141B, and cyclopentane). Thereafter, optimization, energy, and sensitivity analyses were also conducted. The dual-expander ORC-HBD process using propane resulted in a negative product cost to yield a profit of up to 0.521 $/ton of pure water while producing 82.5 tons/h of pure water and electricity (25.4 kWh/ton of pure water). These profits could be further increased to 3.095 $/ton of pure water with free external heat. These values are superior to many RO technologies in terms of energy, exergy, and economics. Therefore, the dual-expander ORC-HBD process with the RO system has a strong potential for resolving the water shortage and electricity generation crises simultaneously.