Electrochemical Conversion And Resource Utilization Of Metallurgical Gas In Carbonate Melts

In many human industrial activities,a large amount of greenhouse gases emitted by the metallurgical production have caused tremendous environmental pressure.Due to the sintering,pelletizing and coking processes in traditional blast furnace ironmaking,a large number of greenhouse gases are produced inevitably.The abovementioned problems can be partly alleviated through the recent proposal of all-oxygen metallurgy.However,low CO2 gas utilization and large pollution will be caused due to the high CO2 concentration in the flue gas generated during the pre-reduction stage.Therefore,it is important to solve the problem of extraction and separation and the resource utilization of CO2 for clean and efficient production of all-oxygen metallurgy in the flue gas.In this paper,the metallurgical flue gas is used as the raw material,then the CO2 in it is absorbed and electrochemically converted by molten salt electrochemistry method.First,according to thermodynamic calculation,it was determined that it is more feasible to absorb and electrochemically reduce CO2 by alkaline earth metal carbonates(such as MgCO3,CaCO3,SrCO3 and BaCO3).considering the reserves.prices and safety of each metal carbonate,the compound system containing metal lithium was abandoned.This paper focuses on the electrochemical conversion and resource utilization of CO2 in the Na2CO3-K2CO3-CaCO3 system.The effects of electrolysis temperature and voltage on the morphology and electrochemical performance of electrolysis product are investigated.The results show that the carbon deposited at 3.0V under 710? has the largest specific surface area,and its morphology is mainly in the form of flakes.The electrochemical performance of the carbon flakes prepared under this condition was tested and the results show that a specific discharge capacity of 301 F/g(0.1 A/g)was achieved when used as a supercapacitor.As used in lithium-ion and sodium-ion batteries electrode,the discharge specific capacities of deposited carbon can reach 768.5 mAh/g and 210 mAh/g,respectively,both of which show excellent electrochemical performances.In addition,benefiting by a laboratorymade Ni11Fe10Cu alloy inert anode,oxygen was successfully obtained on the anode during the electrochemical reduction of CO2,and the green conversion of CO2 to carbon and oxygen was truly achieved.Finally,the mechanism of CO2 reduction in molten salt was in-depth investigated and it was found that the reduction of CO2 inside molten salt was mainly dominated by the conversion of the intermediate CO32-,and the reduction of CO2 at "gas CO2/liquid molten salt/solid electrode" three-phase interline is mainly based on the reduction of gaseous CO2 molecules.