High-temperature-steam-driven, varied-pressure, humidification-dehumidification system coupled with reverse osmosis for energy-efficient seawater desalination

The specific thermal energy consumed by steam driven thermal desalination systems can be decreased significantly by reducing the total entropy rate of steam used per unit mass of distilled water produced in the system. This specific entropy rate can be reduced by using a high pressure, saturated steam at a low specific entropy and high specific enthalpy. However, the temperature of steam that can be used is limited owing to scale formation considerations. In this manuscript, we propose a novel carrier gas based desalination cycle which can use steam at a high temperature (>> 120 °C) without causing formation of hard scales. This system is based on the principle of HDH (humidification dehumidification) desalination. Various salient features of this cycle are analyzed in this paper bringing out its merits and demerits. Important system and component parameters are identified to facilitate optimal operation and design. The energy performance of this new system is compared with all existing desalination systems including MSF, MED, MVC and RO. It has been found that the performance of the new system is comparable to existing thermal desalination systems and is much higher than conventional HDH systems.

► A novel carrier gas based thermal desalination system using steam at a low entropy rate is described.
► This system is appropriate for medium scale, stand-alone, decentralized seawater desalination.
► A GOR (Gained-output-ratio) of 20 can be attained.
► Outstanding embodiment of the system using off-the-shelf components is detailed.
► A detailed parametric analysis identifying the important design variables has been reported.