Numerical investigation of the impact of coating layers on RDF combustion and clinker properties in rotary cement kilns

•CFD-simulations of rotary cement kilns considering coating layers are conducted.•Numerical models for RDF, coating and clinker bed are presented and combined.•The impact of coating regions on RDF combustion and clinker properties is investigated.•Light and evenly distributed coating profiles are found to be beneficial for the process.•Heavy and locally concentrated coating can result in a high free lime content of 2 wt%.