Technical and economic evaluation of seawater freezing desalination using liquefied natural gas

Abstract This article aims to evaluate technical and economic feasibility of the direct contact type seawater freezing desalination (SFD) process proposed by Xie et al. (2018), where the cold energy is provided by regasification of liquefied natural gas (LNG). In the SFD process, the immiscible refrigerant that contains cold energy from LNG regasification is injected into a seawater tank to generate freshwater ice. The freshwater ice is separated and melted to obtain freshwater. Process analysis, integration and optimization are carried out with the aid of detailed material and energy balance models. The influences of some important operating variables of the ice generator, including the inlet temperatures of both refrigerant and seawater, the seawater flow rate and the ratio of seawater that is crystalized into freshwater ice are emphasized in this study. As the main operating cost and income of SFD process are strongly affected by both electricity and water prices, the comparison and effect of these prices in different regions are discussed. Sample calculations with the basis of 1 kg LNG/s show that the optimized SFD process is able to produce 1.64 kg/s of freshwater using 7.83 kg/s seawater when consuming 1.66 kW of electric power.