posted on 2019-02-03, 00:00authored bySeyed A. Dastgheib, Hafiz H. Salih
A two-stage
supercritical (SC) desalination system is proposed
to treat highly saline brines to high-purity steam that could be used
in power generation. Highly saline brines with up to ∼20% salt
content are pressurized and heated to SC conditions of 500 °C
and 3500 psi to rapidly precipitate the dissolved salts and generate
SC steam containing ∼100 ppm salts. Two highly saline brines,
collected from an oil field and a deep saline formation, and two concentrated
NaCl solutions were treated in the SC desalination system. A SC membrane
separation system with carbon filters is developed and used to purify
the SC steam to a high purity level. Promising carbon filters or membranes
prepared and tested for purifying SC steam included a porous graphite
disk, a flexible graphite sheet, and a carbon nanotube-based membrane.
The best performing membranes exhibited a very high water flux of
∼200–800 kg/m2·h, with a salt rejection
of >90%.