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Entropy 2019, 21(4), 395; https://doi.org/10.3390/e21040395

Energy Use of Flux Salt Recovery Using Bipolar Membrane Electrodialysis for a CO2 Mineralisation Process

Thermal and Flow Engineering Laboratory, Åbo Akademi University, Piispankatu 8, 20500 Turku, Finland
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Received: 28 February 2019 / Revised: 2 April 2019 / Accepted: 10 April 2019 / Published: 12 April 2019
(This article belongs to the Special Issue Thermodynamics of Sustainability)
PDF [1089 KB, uploaded 12 April 2019]

Abstract

Mineral carbonation routes have been extensively studied for almost two decades at Åbo Akademi University, focusing on the extraction of magnesium from magnesium silicates using ammonium sulfate (AS) and/or ammonium bisulfate (ABS) flux salt followed by carbonation. There is, however, a need for proper recovery and recirculation of chemicals involved. This study focused on the separation of AS, ABS and aqueous ammonia using different setups of bipolar membrane electrodialysis using both synthetic and rock-derived solutions. Bipolar membranes offer the possibility to split water, which in turn makes it possible to regenerate chemicals like acids and bases needed in mineral carbonation without excess gas formation. Tests were run in batch, continuous, and recirculating mode, and exergy (electricity) input during the tests was calculated. The results show that separation of ions was achieved, even if the solutions obtained were still too weak for use in the downstream process to control pH. Energy demand for separating 1 kg of NH4+ varied in the range 1.7, 3.4, 302 and 340 MJ/kg NH4+, depending on setup chosen. More work must hence be done in order to make the separation more efficient, such as narrowing the cell width.
Keywords: bipolar membrane electrodialysis; ammonium sulfate; ammonium bisulfate; CO2 sequestration; mineral carbonation bipolar membrane electrodialysis; ammonium sulfate; ammonium bisulfate; CO2 sequestration; mineral carbonation
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Koivisto, E.; Zevenhoven, R. Energy Use of Flux Salt Recovery Using Bipolar Membrane Electrodialysis for a CO2 Mineralisation Process. Entropy 2019, 21, 395.

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