What is the most economical way to extract magnesium chloride from brine water?.?

Question

Magnesium chloride sinks to the bottom of a brine pit. Would it be better to filter or reduce to smaller tank and evaporate if it is an 80 acre pond 10ft deep?

Answer 1

Dow Chemical used a sea water process in Freeport Texas (up to 1998) . This this consisted of adding calcined dolomite to sewater to produce magnesium hydroxide which was then filtered and reacted with Hydrochloric acid. The magnesium chloride produced was further purified then dehydrated to MgCL2. x 1.5-2 H20. The partially dehydrate magnesium chloride was then electrolysed.
Magnesium International in Austrailia hopes to build a plant using thie same dehydration and electrolysis technology.

The process does use large amounts of energy (Electrolysis alone approx 18 kWhe/kg magnesium,).


Another potential magnesium route would be to add slaked lime to
sea water (or better yet desalination concentrated brine) to produce magnesium hydroxide . Then roast to form magnesium oxide
Magnesium oxide (magnesia low tech process widely used good web page on http://www.psi-net.org/chemistry/s2/magnesiumoxide.pdf) . The Magnesium oxide could then be thermally reduced with Ferrosillicon using the Pidgeon process. The principal energy source could now be thermal, coal or natural gas. The magnesium plant could be located next to a large middle east desalination plant , recent plants tend to have gas fired power stations adajacent to the sites. The cost of natual gas in the middle east can be very low (I believe the Saudi price to the fertilliser industry is as low as $0.75/GJ)