(350d) A Novel Seawater Desalination Based On Self-Heat Recuperation

The demand for potable water has been increasing recently due to the rise in population and industrialization of developing country. There are two well-known desalination processes, thermal and membrane processes. Thermal process which separates potable water from seawater by evaporation can be divided into several types such as Multi Stage Flash and Multi Effect Desalination. Thermal desalination consumes large energy due to the heat requirement of water evaporation. But there are also merits; the contents of feed water do not strongly affect the desalination operation, and the salinity concentration of the product water is relatively low.

On the other hand, membrane processes such as Reverse Osmosis (RO) which separates portable water from brine water by semipermeable membrane is the most widely used desalination technique. Its reason is merely because it consumes less energy than conventional thermal process. Thus, most newly desalination plant is constructed based on RO process. However, when feed seawater contains large amount of dissolved solids and impurities, they damage the membrane. For this reason RO requires a greater degree of pretreatment than the thermal desalination process.

Summing up, thermal desalination does not need the greater degree of pretreatment but requires large amount of energy.

To overcome the problem, we proposed an energy efficient thermal desalination process based on self-heat recuperation. In a thermal process based on self-heat recuperation, both latent heat and sensible heat are recirculated into the process without any heat addition. As a result, energy requirement is drastically reduced.

In this study, the energy consumption of thermal process based on self-heat recuperation in the steady state has been calculated using a process simulator. We obtained some results; the energy consumption grows with increase of the minimum temperature difference in the heat exchangers, and increased quantities of production flow rate make the specific energy consumption smaller. The desalination based on self-heat recuperation consumes approximately 1/4 of the energy compared to the conventional thermal desalination process when the minimum internal temperature difference in heat exchangers is assumed to be 5 K and the percentage of the product in the feed stream is assumed as 30%.

By applying the self-heat recuperation technology to the thermal desalination process, we proposed an innovative thermal desalination process.