Effect of CaCO3 on volatilization of self-reduced zinc from blast furnace dust

To solve the problem of low reduction extraction rate of zinc from blast furnace dust, the effects of CaCO3 addition, reduction temperature, and reduction time on self-reduction zinc extraction were studied through high-temperature reduction experiment, and the mechanism of how CaCO3 addition promotes zinc ferrite reduction was analyzed. The zinc removal rate can reach 98.82% when the blast furnace dust is reduced at 1000 degrees C for 25 min by adding 10 mass% CaCO3. At low temperature, CaCO3 can enhance the reduction and decomposition of ZnFe2O4 (which is difficult to reduce) into ZnO and low-valent iron oxides. After CaCO3 is decomposed at high temperature, CO2 is produced to undergo gasification reaction with carbon in blast furnace dust, and CO is generated to provide more reducing agents for the whole reduction system. CaO generated by decomposition can also catalyze the gasification reaction of carbon, thus improving the removal rate of zinc in the reduction process of dust.

Automated summary

Through high-temperature reduction experiments, it was found that adding CaCO3 can improve the reduction rate of zinc in blast furnace dust, especially at lower temperatures. The decomposition of CaCO3 generates CO2 and CO, which provide more reducing agents and enhance the zinc removal rate in the entire reduction system.