Systems and methods for producing regenerant brine and desalinated water from high temperature produced water

A process for treating high temperature produced water derived from hydrocarbon production operations, the process comprising:

• a. passing a produced water feed stream at a feed temperature from 70° C. to 95° C. and having a total dissolved solids concentration less than 15,000 mg/L and a hydrogen sulfide content of up to 1000 ppm to an electrocoagulation unit or an electroflotation unit;
• b. passing the produced water feed stream from the electrocoagulation unit or the electroflotation unit to a first direct contact membrane distillation unit wherein:
• i. the produced water feed stream contacts a hydrophobic membrane on a membrane feed side;
• and
• ii. an inlet product side stream comprising deionized water contacts the hydrophobic membrane on a membrane product side at a temperature of from 15° C. to 35° C.;
• such that a first distilled water stream is recovered from the produced water feed stream and collected with the inlet product side stream on the membrane product side to form an exit product side stream;
• and a volume-depleted exit produced water stream is formed on the membrane feed side of the hydrophobic membrane;
• c. passing the exit product side stream in a pass through a heat recovery heat exchanger wherein the exit product side stream transfers heat to the volume-depleted exit produced water stream to form a return inlet produced water stream;
• d. returning the return inlet produced water stream from the heat recovery heat exchanger to a location upstream of the first direct contact membrane distillation unit for an additional pass through the first direct contact membrane distillation unit, thereby recovering additional water from the membrane feed side to the membrane product side;
• e. repeating steps (c) and (d) as needed to achieve a recovery of from 15 to 45 vol % of the produced water feed stream and to form a final exit produced water stream leaving the first direct contact membrane distillation unit having a temperature of from 40 to 60° C., a total oil and grease content no greater than 500 mg/L, and a suspended solids content no greater than 200 mg/L;
• f passing a first portion of the first distilled water stream from the first direct contact membrane distillation unit to a brine tank at a temperature of from 55 to 80° C. wherein the first portion of the first distilled water stream is combined with sodium chloride to form a concentrated brine solution comprising from 8 wt % to 18 wt % brine;
• and
• g. utilizing the concentrated brine solution to regenerate used ion exchange resin in a water softening system wherein monovalent sodium ions in the brine solution displace multivalent ions on the ion exchange resin.