Removal of Ca2+, Mg2+, Ba2+ and Sr2+ from shale gas flowback water from the Sichuan Basin in China by chemical softening under the guidance of OLI Stream Analyzer: precipitation behaviors and optimization study | Zendy

Wenshi Liu | Zendy; Lingru Sun | Zendy; Sha Tao | Zendy

Open Access

Removal of Ca2+, Mg2+, Ba2+ and Sr2+ from shale gas flowback water from the Sichuan Basin in China by chemical softening under the guidance of OLI Stream Analyzer: precipitation behaviors and optimization study

Author(s) -

Wenshi Liu,

Lingru Sun,

Sha Tao

Publication year - 2020

Publication title -

water science and technology

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 0.406

H-Index - 137

eISSN - 1996-9732

pISSN - 0273-1223

DOI - 10.2166/wst.2020.355

Subject(s) - reverse osmosis , water softening , desalination , precipitation , produced water , shale gas , oil shale , softening , wellbore , chemistry , environmental science , petroleum engineering , environmental engineering , membrane , materials science , waste management , geology , engineering , biochemistry , physics , meteorology , composite material

The disposal of flowback water is recognized as a key issue for the sustainable shale gas development and discharge after reasonable treatment is considered as a feasible pathway. One of the challenges during treatment is the severe mineral scaling potential in reverse osmosis desalination, especially with high amounts of Ca2+, Mg2+, Ba2+ and Sr2+ in flowback water. In this study, precipitation behaviors of Ca2+, Mg2+, Ba2+ and Sr2+ during traditional chemical softening was evaluated so as to achieve optimal chemical dosage. Both jar tests and OLI Stream Analyzer simulation revealed that the main precipitates were CaCO3, SrCO3 and BaSO4 during Na2CO3 addition, and Ba2+ could not be removed efficiently by Na2CO3 unless a high dosage was applied since Ba2+ would react after the precipitation of Ca2+ and Sr2+. Reverse Osmosis System Analysis simulation indicated that Ba2+ was a concern because Ba2+ would form tenacious BaSO4 scale on the reverse osmosis membranes. Finally, the Na2SO4-NaOH-Na2CO3 process was proposed for chemical softening as it has a high removal efficiency and low chemical cost. Overall, this study presents an effective chemical softening method and OLI Stream Analyzer could serve as a reliable tool for the calculation, which would finally improve the design and operation of shale gas flowback water treatment.

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