Exploring Innovative Applications of Evaporative Cooling for High-Total-Dissolved-Solids Produced-Water Treatment

Abstract

Summary This research delves into the pioneering application of evaporative cooling (EC) to address the challenge of reducing total dissolved solids (TDS) in produced water generated during hydraulic fracturing operations in the Permian Basin. In this study, we used a meticulously designed laboratory-scale EC system comprising three cooling pads, a fan, a water reservoir, and a pump. Through a systematic series of experiments, both synthetic and authentic produced-water samples were treated, shedding light on the potential of this novel approach. The EC system efficiently processed untreated produced water, circulating it through the cooling pads, all while closely monitoring crucial variables such as inlet and outlet temperatures, relative humidity, and remaining water volume, utilizing a state-of-the-art temperature and humidity meter. Control experiments were systematically conducted to probe the influence of varying salinities, achieved by introducing NaCl into distilled water, encompassing a wide range from 0 ppm to 70,000 ppm. In addition, we extended our evaluation to real produced-water samples collected from diverse regions within the Permian Basin (Delaware, Northern Midland, and Southern Midland), reflecting the system’s capability to manage high salinity and the diverse impurities inherent to oil and gas production. A comparative analysis of energy consumption was undertaken, positioning EC against conventional thermal evaporation techniques. The findings revealed a compelling insight that differences in EC efficiency between synthetic and real oilfield brines were primarily attributed to the presence of sodium (Na+) and chlorine (Cl-) contents rather than the overall TDS concentration. Across all experiments, the system consistently achieved remarkable TDS removal efficiencies, hovering around the 100% mark for both synthetic and authentic produced-water samples. Moreover, the study unveiled a significant advantage of EC, as it proved to be significantly less energy-intensive when juxtaposed with conventional thermal evaporation methods. In addition, our experiments revealed that divalent ions like CaCl2 tend to lower the treatment efficiency compared to monovalent ions, adding a crucial dimension to our understanding of EC in water treatment. The EC system demonstrated remarkable efficiency, achieving nearly 100% TDS removal in both synthetic and real samples while being significantly less energy-intensive than conventional thermal evaporation methods. This research underscores EC’s potential as an effective, sustainable, and economical solution for high-TDS water treatment, with promising applications in industrial settings. The study also draws parallels between EC and air conditioning systems, suggesting its versatility in various industrial applications.