Saltworks Technologies recently helped a mining client achieve solid salt production in a new membrane-chiller hybrid plant, lowering capital and energy by using ultra-high pressure reverse osmosis (UHP-RO) technology to replace a thermal evaporator.
The company’s engineers hybridised UHP-RO with a chilled crystalliser system, in a semi-closed loop that concentrates water, extracts solid salt, and repeats the cycle. The UHP-RO system concentrates certain salts (e.g. sodium sulphate) to over 20% by mass.
The concentrated brine solution then enters the chilled crystalliser, which takes advantage of steep solubility changes with temperature. There, the solution cools, resulting in the formation of salt crystals, which are separated and removed.
After cooling and salt extraction, the residual brine liquor has a lower dissolved salt content (~10%) and is warmed and recycled through the UHP-RO system. A heat pump simultaneously cools one part of the circuit while heating the other. As the loop operates, it continuously produces reverse osmosis quality permeate and solid salt crystals, while being replenished with make-up wastewater. Examples of suitable ions include Na+, K+, NH4+, CO32-, and SO42-.