Process for sequestering sodium chloride and calcium chloride from a non-saleable salt waste product produced from oil and gas produced wastewater

A system for sequestering calcium chloride and/or sodium chloride from a solid salt mixture, the system comprising:

• a mix tank which receives and mixes a combination of water, solid salt comprising sodium chloride and calcium chloride, and sequesters solid sodium chloride precipitate from liquid calcium chloride, and further provides sodium chloride brine;
• a calcium chloride clarifier in liquid communication with the mix tank to receive the liquid calcium chloride;
• a sodium chloride clarifier in liquid communication with the mix tank, to both receive sodium chloride brine from the mix tank, and provide clarified sodium chloride brine back to the mix tank;
• a dewatering system in communication with the mix tank to receive the solid sodium chloride, and further in fluid communication with the sodium chloride clarifier to provide any brine resulting from a dewatering process to the sodium chloride clarifier;
• and
• a drying system coupled with the dewatering system to receive and dry the sodium chloride precipitate.

A method for treating solid waste mixtures including calcium chloride, sodium chloride and particulate impurities, the waste mixtures resulting from the process of desalinating wastewater, and producing from such waste saleable products including a calcium chloride liquid and a solid sodium chloride, the method comprising the steps of:

• in a calcium chloride sequestration step, adding at least a portion of the solid salt waste mixture and water in a mixing tank to form a heterogeneous mixture;
• lightly mixing the heterogeneous mixture to release the calcium chloride from the sodium chloride particles into the water, forming a calcium chloride-water solution, wherein the calcium chloride is maintained in the mixture at a concentration of no less than 30% w/w;
• allowing the mixture to settle, causing the sodium chloride particles to settle out of the mixture at the bottom of the mixing tank, the particulate impurities settle out of the mixture in a layer above the sodium chloride particles and a layer of calcium chloride-water solution above the sodium chloride particles;
• and
• decanting the calcium chloride-water solution and the particulate impurities from the mixing tank;
• and
• in a depuration step:
• adding additional water to the mixing tank to form a second heterogeneous mixture;
• lightly mixing the second heterogeneous mixture to release additional calcium chloride from the sodium chloride particles into the water, wherein a small portion of the sodium chloride also dissolve into the water;
• allowing the second mixture to settle, causing the remaining sodium chloride particles to settle out of the second mixture at the bottom of the mixing tank and a layer of a brine comprising sodium chloride, calcium chloride and water above the sodium chloride particles;
• and
• decanting the brine from the mixing tank;
• following one or more repetitions of the depuration step, adding additional water to the mixing tank to form a third heterogeneous mixture, lightly mixing the third heterogeneous mixture, and allowing the third mixture to settle, causing the remaining sodium chloride particles to settle out of the third mixture;
• separating and removing the particulate impurities from the decanted calcium chloride-water solution;
• and
• removing the sodium chloride particles from the mixing tank.