Removal of the Harmful Elements and Iron Recovery from the Blast Furnace Gas Ash by Chloridizing Roasting

Due to the complexity of Bayan Obo iron ore,the blast furnace gas ash of Baotou steel has low content of iron but is rich in harmful alkali metal oxides like K₂O and Na₂O as well as oxides of Pb and Zn. Two methods named reduction-evaporation-magnetic separation and chlorination-evaporation were introduced in this paper to transform the mentioned oxides into metals or volatile chlorides respectively by the carbon in the ash or adding calcium chloride into the ash,by which the harmful elements can be separated and the residual iron can be recovered from the ash. The results of reduction-evaporation-magnetic separation experiments show that under condition of 1000 ℃ for 2 h the removal rate of Na,Pb and Zn is respectively 94.21%,98.53% and 91.98%,while K cannot be removed by carbon reduction. With the products of reduction-evaporation at 950 ℃ for 2 h as raw materials for magnetic separation,the recovery rate of Fe reaches 90.24% with 0.6 A current. The results of chlorination-evaporation experiments indicate that the removal rate of Pb and Zn can separately reach 99.62% and 85.56% with 1000 ℃ of temperature. Removal of K and Na is barely affected by temperature with both more than 98% of removal rate. K is removed by chlorination reaction. Nevertheless,Na is separated both by carbon reduction and chlorination in which it's easier for the latter.