Desalinating a Real Hyper-Saline Pre-Treated Produced Water via Direct-Heat Vacuum Membrane Distillation

Yiming Liu, Jingbo Wang, Bongyeon Jung, Unnati Rao, Erfan Sedigni, Eric Hoek, Nils Tilton, Tzahi Cath, Craig Turchi, Michael Heeley, Y. Ju, David Jassby

Research output: Contribution to journalArticlepeer-review

9 Scopus Citations

Abstract

Membrane distillation (MD) is an emerging thermal desalination technology capable of desalinating waters of any salinity. During typical MD processes, the saline feedwater is heated and acts as the thermal energy carrier; however, temperature polarization (as well as thermal energy loss) contributes to low distillate fluxes, low single-pass water recovery and poor thermal efficiency. An alternative approach is to integrate an extra thermal energy carrier as part of the membrane and/or module assembly, which can channel externally provided heat directly to the membrane-feedwater interface and/or along the feed channel length. This direct-heat delivery has been demonstrated to increase single-pass water recovery and enhance the overall thermal efficiency. We developed a bench-scale direct-heated vacuum MD (DHVMD) process to desalinate pre-treated oil and gas “produced water” with an initial total dissolved solids of 115,500 ppm at a feed temperature ranging between 24 and 32 °C. We evaluated both water flux and specific energy consumption (SEC) as a function of water recovery. The system achieved a 50% water recovery without significant scaling, with an average flux >6 kg m–2 hr–1 and a SEC as low as 2,530 kJ kg−1. The major species of mineral scales (i.e., NaCl, CaSO4, and SrSO4) that limited the water recovery to 68% were modeled in terms of thermodynamics and identified by scanning electron microscopy and energy-dispersive X-ray spectroscopy. In addition, we further developed and employed a physics-based process model to estimate temperature, salinity, water transport and energy flows for full-scale vacuum MD and DHVMD modules. Model results show that a direct-heat input rate of 3,600 W can increase single-pass water recovery from 2.1% to 3.1% while lowering the thermal SEC from 7,800 kJ kg−1 to 6,517 kJ kg−1 in an unoptimized module. Finally, the scaling up potential of DHVMD process is briefly discussed.

Original languageAmerican English
Article numberArticle No. 118503
Number of pages12
JournalWater Research
Volume218
DOIs
StatePublished - 30 Jun 2022

Bibliographical note

Publisher Copyright:
© 2022 Elsevier Ltd

NREL Publication Number

  • NREL/JA-5700-82946

Keywords

  • Brine
  • Hyper-saline water
  • Membrane distillation
  • Mineral scale
  • Pre-treated produced water
  • Process modeling

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