Hydraulic fracturing flowback and produced water as a feedstock for mineral carbonation

  • Author / Creator
    Zhu, Bizhou
  • Hydraulic fracturing and produced water or FPW has potential use as a feedstock to supply divalent Ca and Mg cations for mineral carbonation at standard temperature and pressure. The carbonation potential of real FPW samples produced by oil and gas companies has not previously been tested in laboratory environments under ambient conditions. As such, the effects of pH and pCO2 on the rate and efficiency of mineral carbonation reactions under ambient conditions were tested in this thesis. The results of this work show that calcite (CaCO3) and aragonite (CaCO3) precipitate from FPW at alkaline pH conditions (i.e., 8.5–12.0) under ambient conditions and atmospheric pCO2 (i.e., 0.04%). These minerals sequester CO2 from air. Brucite [Mg(OH)2] and occasional portlandite [Ca(OH)2] precipitate at greater pH from the residual CO2-depleted FPW and both minerals have potential to capture additional CO2 owing to their high reactivity. The resulting high purity Ca-carbonate and Ca- and Mg-hydroxide minerals could be used to maximum effect for Carbon Dioxide Removal as part of a Ca- and Mg-looping operation, where the hydroxide precipitates could be regenerated by calcining while CO2 is stored in underground sedimentary reservoirs. When a higher pCO2 gas (10%) is injected into FPW titrated to pH 10.5, precipitation of calcite is promoted at the expense of brucite dissolution. The mineral carbonation reactions reach steady-state within 40 minutes of CO2 injection under these conditions. Although brucite and hydrated Mg-carbonate minerals are undersaturated at pCO2 = 10%, the maximum amount of CO2 captured by precipitates was 8 higher than that measured in experiments at atmospheric pCO2 after 24 hours. Residual Ca remained unreacted in experiments conducted at pCO2 = 10%, which implies that alkalinity in the FPW limits the extent of CO2 capture. Therefore, step-wise alkalinity swings, or maintenance of pH >10.5, could be used to drive the carbonation reaction to completion. In addition, the experiments showed that B, Ba, Fe, Mn, Ni, Pb, S, Si, Sr, and Zn are immobilized by the precipitates during mineral carbonation, which offers an opportunity to recover valuable elements and sequester potentially toxic elements from FPW. Lastly, an assessment of FPW resources suggests that the FPW produced in Canada in 2020 could be used to sequester 151 kt CO2/year with a value of ~7.55 M CAD under federal carbon pricing which will reach 50 CAD/t in 2022.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.