Study On Thermodynamics And Kinetics Of Separating Zinc From Iron In The Gas Dust Of No.4Blast Furnace At An Steel

Metallurgical zinc—bearing dust mainly includes blast furnace zinc—bearingdust, Rotary hearth furnace zinc—bearing dust and Electric arc furnace zinc—bearingdust. Blast furnace zinc—bearing dust is divided into gas dust and gas sludge. Undernormal conditions gas dust and gas sludge each accounts for about50%of the blastfurnace zinc—bearing dust. Metallurgical zinc—bearing dust has a large quantity ofproduction and serious pollution to the environment. The accumulation process ofMetallurgical zinc—bearing dust is not only a waste of resources but also taking upspace. If it is directly returned to the iron plant as raw material, it will cause seriousdamage to the blast furnace. Therefore it is imperative to carry on the comprehensiverecycling for metallurgical zinc—bearing dust.The No.4blast furnace gas dust of An Steel is selected in this thesis. First of all,the chemical and physical properties of the gas dust were studied. To lay thefoundation for the laboratory study, the work was started from the chemicalcomposition, physical properties (particle size, bulk density),and other basicproperties.Secondly, thermodynamic analysis on ZnO, Fe2O3, Fe3O4,FeO and C waslaunched. It is concluded that zinc can be restored in897.8℃and can quickly leavethe system in the form of zinc vapor. Iron has reduction step by step, and all of thereduction products continue to persist in the dust in solid.Making the reactiontemperature above900℃can reach the experimental purpose of separating zinc fromiron in the gas dust.The briquetting experiments for gas dust showed that the average of each dropstrength is3.1times. The average of each compressive strength is11.85N, andexplosion temperature reaching about550℃,they can reach the national standard.Finally, pellets containing carbon reduction roasting method is employed to thekinetics experiment. Results showed that the metallization rate, dezincing rate andweightlessness rate increase with the extension of reaction time as well as the rise oftemperature. But the change of temperature is the decisive factor. When the reactiontemperature is above1100℃with the reaction time above20min, zinc evaporationrate can meet the requirements of gas dust dezincification process. Previous kineticsequation is ln[1r(t)]13303.73e144.26/RTt， For later kinetics equation is[1(1r(t))1/3]212436.61e177.65/RTt。On the basis of the experiment, we expanded the scale of the research. As thezinc content of An Steel zinc—bearing dust is3~7%, while zinc oxide content is1.17%of the dust selected in this study. Therefore, the original dust should be joinedwith additional zinc oxide to make the zinc content among the range of3~7%. Theexperimental results showed that, without considering metallization rate, dezincification process parameters can be classified as the reaction temperature above1100℃with the reaction time between20min and30min, at the same time dezincingrate can reach90%.