Analysis of the electrochemical processes during the production of liquid iron by Molten Oxide Electrolysis

Abstract : Molten oxide electrolysis (MOE) is an ambitious technique for the production of liquid iron by the use of renewable energies and thus lower CO2 emissions in the steel industry. In this concept, electrolysis is used to produce gaseous O2 and liquid iron metal at temperatures above 1810 K. In the experimental study presented here the key-parameters of the electrochemical reactions in a magnesio-aluminosilicate electrolyte and at the electrodes during MOE are investigated. A significant amount of liquid iron metal was produced during experiments of several hours. SEM-EDS analysis of the deposit revealed an alloy of iron metal and of the cathode material, which thereby indicates high process selectivity. Investigation of the electrolyte’s response in dependence of cell voltage and iron concentration inferred a diffusional limitation at low iron oxide concentrations at potentials below 1.5 V. The cathode half-reaction was identified as the reduction of ferrous iron to liquid iron metal. Using Tafel interpretation reaction-transfer coefficients close to 0.6 and an order of reaction around 1 were determined. The analysis of the anode half-reaction showed that in low iron bearing molten oxides, oxide anions were firstly oxidized into O2 gas. At high iron concentrations the charge transfer is conducted in the entire cell voltage range by the oxidation of ferrous iron. The participation of oxide anions in the charge transfer was only witnessed at high cell voltages. In the entire compositional range a limitation of the measured current due to the anode half reaction was not observed
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Theses
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http://docnum.univ-lorraine.fr/ulprive/DDOC_T_2017_0329_WIENCKE.pdf
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https://hal.univ-lorraine.fr/tel-01909411
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Submitted on : Wednesday, October 31, 2018 - 10:20:19 AM
Last modification on : Wednesday, September 4, 2019 - 2:06:04 PM

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  • HAL Id : tel-01909411, version 1

Citation

Jan-Christian Wiencke. Analysis of the electrochemical processes during the production of liquid iron by Molten Oxide Electrolysis. Materials Science [cond-mat.mtrl-sci]. Université de Lorraine, 2017. English. ⟨NNT : 2017LORR0329⟩. ⟨tel-01909411⟩

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