Formation of build-up in a cement kiln preheater: qualitative and quantitative mineral characterisation

Extracting more information about the reactions and parameters governing the formation of build-up in the preheater systems of clinker burning lines could be an efficient way of better attenuating build-up formation. In order to control the appearance of build-up, diagnosis steps of mineralogical analysis application for process optimisation (MAA-PO) are suggested. Mineralogical characterisation was carried out on three samples taken from different layers of the same build-up. Qualitative and quantitative X-ray diffraction, chemical analysis and Fourier transform infrared spectroscopy revealed that ternesite is the key mineralogical phase responsible for the growth and consolidation of build-up. Its appearance is governed by solid–solid reactions promoted by the available sulfate liquid phases, mainly calciolangbeinite, as well as C₁₂A₇ and C₄AF. The hot-powder calcination degree, amount of sulfur trioxide, lime saturation factor, silica ratio and alumina ratio are the operational data that were correlated to the mineralogical analysis of build-up. Based on this correlation, it is possible to predict the reaction kinetics involved in each layer formation and to estimate the development time of each. The results showed that MAA-OP is a promising novel approach to optimise the process parameters in clinker production.