Controlled Oxygen Flow Electrolysis for Fe and Study of Corrosion on ZrO2-based Oxygen Ion Membrane
|School||Wuhan University of Science and Technology|
|Course||Physical Chemistry of Metallurgy|
|Keywords||SiO2-CaO-Al2O3-MgO-FeO slag FactSage ZrO2-based oxygen ion membrane slag corrosion metallurgy with controlled oxygen flow|
A ZrO2-based electrolysis cell: graphite rod︱[O]Fe+C saturated︱ZrO2（MgO）︱（FeO）slag︱Ferod was constructed, and the solid metal Fe was extracted from containing FeO slag withcontrolled oxygen flow technology. The results show that: solid Fe dendrite extraction andextending, the change of the cathode active area on the iron crucible wall and ion diffusion inslag will affect the electrochemical reaction speed. Fe2+reduction main appear on new Fedendrite of iron crucible cathode area, and a very small amount of Fe on MZS tube/slaginterface due to electronic conductance of MSZ tube. Electronic current direct through MSZtube has a role of promoting FeO slag electrolysis at earlier stage, but will lower the currentefficiency at later stage. The total final reduction ratio of FeO in slag can achieve98.72%.The corrosion characteristics of FeO molten slag on ZrO2material were investigated byusing the Equilib Module in FactSage software. The results show that: the corrosion of ZrO2increased along with increase of temperature and FeO content in molten acid slag; ZrSiO4andCaZrO3could be formed between molten slag and ZrO2under low and high basicity conditions,respectively. When the molten slag was electrolyzed with controlled oxygen flow, the initialcontent of FeO in slag should be below20%and slag basicity should be between0.23and0.80.Under the controlled oxygen flow reduction process, ZrO2-based oxygen ion membranecould be corroded by slag and Fe+Csaturated. To protect the electrical conductivity andimprove the working life of ZrO2-based oxygen ion membrane, the interface of ZrO2/Fe+Csaturated and ZrO2/slag were analysed by SEM and EDS. The results show that: Under appliyedpotential, it always has ZrSiO4generated at the interface of ZrO2/slag. The ZrSiO4can reducethe ZrO2tube’s penetration and solution by salg, and will reduce ZrO2tube’s electric property aswell. The slag corrosion under open circuit voltage and non-potential condition is more seriousthan appliyed potential. The Fe+Csaturated corrosion under appliyed potential is more seriousthan open circuit voltage. The high basicity slag can cause local leakage on the ZrO2tube, thencause more serious erosion internal ZrO2tube. The measures of reduciong slag erosion are: Theplus potential reduction method should be used, Fe+Csaturated should be changed to inertanode such as silver, etc, the slag basicity in0.43should be used, FeO contents should be nomore than20%.