Study On Conversion Characteristics Of Electric Arc Furnace Dust For Solar Thermochemistry

The limitation of fossil energy and the environmental problems caused by the use of fossil energy have made people turn to the development and utilization of sustainable energy,of which solar energy is an ideal alternative energy source.However,solar energy has the shortcomings of low energy density,intermittent,uneven distribution,etc.In order to overcome these shortcomings,people began to develop solar thermal chemical conversion technology,which converts solar energy into fuel chemical energy.There are many methods of solar thermochemical conversion technology.Among them,the two-step thermochemical cycle method based on metal oxides is particularly potential.The promising metal oxides of this method include zinc oxide and ferrite,and the main components of electric steelmaking furnace dust are Iron oxide and zinc oxide are suitable as a medium for solar fuel conversion.The organic combination of electric furnace dust and solar fuel conversion process is undoubtedly of great significance for the treatment of circuit dust waste or the conversion and utilization of solar fuel.At present,since the mechanism of electric furnace dust used for solar fuel conversion is not clear,this paper uses density functional theory calculations and transition state theory to study the conversion mechanism of circuit dust and methane fuel,including the reaction of zinc oxide and iron oxide in electric furnace dust with methane kinetic research,came to the following conclusions:(1)Exploring the four reaction paths of a single zinc oxide molecule reacting with methane molecules,the reaction along path c(that is,the process from b-IM1 to c-IM5)is more favorable in terms of reaction kinetics.(2)The decisive step of the reaction of methane molecules on the surface of Zn O crystal is the fourth dissociation of methane from H;among the two paths of generating H₂,the one along the path A(that is,the process of combining H adsorbed on O site and H adsorbed on Zn site to synthesize H₂)is more favorable in kinetics.(3)Among the six reaction paths of single iron oxide molecule and methane molecule,the reaction along path a(i.e.the process from IM1/a to IM9/a)is more advantageous in terms of reaction kinetics.(4)The decisive step for the reaction of methane molecules on the surface of zinc oxide crystals is the second dissociation of H by methane.The presence of OH groups on the surface of iron oxide crystals will limit the dissociation of methane and increase the energy barrier for dissociation of H.The energy barrier of methane and iron oxide selectively converted to water is lower than that of hydrogen,so the conversion to water is more advantageous in kinetics.The energy barrier for the reaction of methane and iron oxide to be converted to CO is lower than that of CO₂,so conversion to CO is more favorable in terms of kinetics.This paper studies the reduction process and oxidation process law of the thermochemical cycle of electric furnace dust through thermodynamic analysis,and draws the following conclusions:(1)In the reduction step,the iron oxide and zinc oxide in the electric furnace dust interact with each other,The temperature at which the iron oxide is completely reduced increases,while the temperature at which the zinc oxide starts to be reduced increases slightly,while the temperature at which it is completely reduced remains unchanged.The optimum material ratio of electric furnace dust for solar fuel conversion is n(Fe₂O₃):n(Zn O):n(CH₄)=a:b:(3a+b).In the oxidation step,the reaction of Fe with water vapor is more sensitive than that of Zn with water vapor,which is greatly affected by the amount of water vapor and oxidation temperature.(2)As the reduction temperature increases,the solar fuel conversion efficiency first increases and then decreases;as the oxidation temperature increases,the solar fuel conversion efficiency gradually decreases.As the proportion of iron oxide in electric furnace dust increases,the conversion efficiency of solar fuels gradually declines.