Pyro processing cement kiln bypass dust : enhancing clinker phase formation

The valorisation of cement kiln bypass dust (CBPD) is explored for sustainable production of cementitious clinker phases. CBPD can replace the calcareous component in cement manufacture and allow for a reduction in CO2 emissions, as the calcium component in CBPD is mostly decarbonised. CBPD was heated with/out the addition of alumina or silica at temperatures of 900 – 1100 °C to produce clinker phases. Belite and mayenite formed at temperatures as low as 900 °C, while alite formation was achieved at 1200 °C, which is significantly lower than is conventional (~1450 °C). Alite is thermodynamically stable only above 1250 °C; thus, the reduced temperature is potentially owing to the presence of chloride found in the CBPD (as KCl) which was also simultaneously removed through pyro processing at 1100 – 1200 °C. The investigation also confirmed that the formation of belite is enhanced in the presence of molten KCl.