Investigation of granulation calcined under the eutectic temperature in the fluidized bed

•A two-process clinker manufacturing system with fluidized bed reactors is shown.•Sintering is the main driving force for granulation under the eutectic temperature.•Granulation process of cement raw meal consists of agglomeration and sintering. A new two-process cement calcination method using fluidized bed reactors to substitute rotary kilns was employed for cement manufacturing. Granulation of cement raw meal in the first calcination process under the eutectic temperature determined the quality of clinkers produced in the second process and the feasibility of the method. Therefore, the granulation process and the factors affecting granulation were investigated by comparing the morphology of different granules. X-ray diffraction and X-ray fluorescence tests verified CaO as a significant constitute for granulation. Morphological comparison between CaO and cement raw meal confirmed that sintering rather than solid-phase reactions was the main driving force of granulation. Thin layers of reaction zones contributed to the bonding of different clusters. Granulation was depicted as a two-step process involving agglomeration and sintering. Fluidized gas velocity, initial weight of cement raw meal and clinker amount all influenced granulation. An increase in the fluidized gas velocity suppressed granulation, while an increase in the initial weight of cement raw meal and clinker amount contributed to granulation. This study explains the granulation process of cement raw meal and the main driving force for granulation, and suggestions are also provided for granulation control.