Residue from the chloride bypass de-dusting of cement kilns: Reduction of the chloride content by air classification for improved utilisation

In many cement kiln systems a chloride bypass is required in order to avoid operational problems caused by the deposition of alkali chlorides. The dust collected from the bypass gas often has to be discharged to landfill sites because it is enriched in chloride. In this study classification of cement kiln bypass dust (CKBD) for chloride removal was investigated. Through air classification a fine fraction which was enriched in chloride, and somewhat less enriched in potassium, was separated from the bulk of the CKBD, thus reducing the concentration of these components in the coarse fraction of the material. This coarse fraction could be returned to the cement production process. The fine chloride-enriched fraction could be discharged to landfill sites or fed to a leaching process for the production of potassium chloride. The approximately 2–3 times higher chloride concentration of the feed material should improve the profitability of such a process. Other components enriched in the fine fraction were sodium, lead, cadmium and copper.