Selective salt recovery from mixed salt brine

Abstract

A process is provided for recovering sodium chloride crystals and sodium carbonate decahydrate crystals from a concentrated brine that results from a gas mining operation where gas and produced water is recovered and the produced water constitutes a brine. An initial pre-concentration process is carried out where the brine is concentrated and in the process carbon dioxide is removed from the brine and at least some sodium bicarbonate is converted to sodium carbonate. In one process, the concentrated brine is directed to a sodium chloride crystallizer where the brine is heated and further concentrated to form sodium chloride crystals which are separated from the brine to yield a product and wherein the resulting brine is termed a first mother liquor. The first mother liquor is then directed to a sodium carbonate decahydrate crystallizer where the first mother liquor is cooled and concentrated resulting in the formation of sodium carbonate decahydrate crystals and a second mother liquor. The second mother liquor is split into two streams where one stream is directed back to the sodium chloride crystallizer while the other stream is wasted or further treated.