Rotary kiln process: An overview of physical mechanisms, models and applications

• Solid transport, heat transfer and thermochemical transformation are discussed in detail. • The heat and mass transfer modeling process in rotary kilns is summarized. • The commonly used correlations involving rotary kilns are categorized by application. • The solid-wall heat exchange coefficient is examined. • The current status, challenges and future direction of this technology are highlighted. The heat and mass transport occurring through a rotary kiln has many industrial applications, such as organic or mineral materials manufacturing. The originality of this review is to explore the various works that have led to a better understanding of rotary kiln process modeling. The paper also details the set of works carried out on the solid load (granular flow regimes, load profile, mean residence time), heat transport (conduction, convection, radiation exchanges) and thermochemical conversion processes (endo- and exothermic reactions). Beginning with the research conducted on directly heated rotary kilns for cement applications, this review extends the scope of application to other fields, including waste, biomass.