Air classification of blast furnace dust catcher dust for zinc load reduction at the sinter plant

The off-gas discharged from a blast furnace is de-dusted in a first stage by a dust catcher or a cyclone. The separated dust consists mainly of iron and coke. Therefore, most of this dust is recycled in the sinter plant. A higher Zn content of the dust is undesirable because the allowed Zn content in the sinter feed material is limited. The reduction of the Zn content of the dust by a simple process would be helpful in the case of higher Zn content in the blast furnace dust. In classification experiments, it has been demonstrated that the Zn content of the blast furnace dust increases with decreasing particle size. Thus, air classification of the dust can be applied to separate the Zn-enriched fines. By separating a small fraction of fines (about 10–20 %) from the blast furnace dust, a reduction of the mass of Zn in the remaining coarse fraction for recycling in the range of 40–60 % is possible and only 5–10 % of the carbon is lost.