Hydrate-based desalination process using CO2 as hydrate forming agent - Modelling and techno-economic analysis

Abstract

The potential of using CO2 for hydrate-based desalination is evaluated in this work. CO2 hydrate formation occurs in a device that uses the NETmix technology and is implemented and modelled in Aspen Plus. To ensure that the vapour-liquid and liquid-liquid equilibria are correctly estimated, the solubility of CO2 in salt water under incipient hydrate formation conditions is predicted by different property models available in Aspen Plus and compared with published models based on experimental data. The energy and economic costs of the process are then assessed for two process flowsheets, which differ in the cold utility source. In one case, heat pump/ refrigeration cycle technology integrates the heat from the hydrate formation and dissociation units, resulting in a Specific Energy Consumption (SEC) within the range of Multi-Stage Flash desalination technologies. In the other case, using the latent heat of natural gas regasification as a cold utility significantly reduced the costs, enabling the production of drinking water with an SEC in the same range as Reverse Osmosis.