Numerical modeling of a rotary cement kiln with improvements to shell cooling

Numerical models are developed by researchers to analyze and understand the trends occurring within rotary kilns, and allow for improvements in terms of energy quantification and usage. The present study develops a one-dimensional kiln model using elements of existing models and then links the model to the surroundings via a composite resistance model and a forced convection model that enables proper inclusion of the effects of shell-cooling fans. Shell-cooling fans are common in industry and allow for a reduction in shell temperature and promotion of internal coating formation. Thermal conductivity through the kiln shell is treated as a calibration parameter to allow for a more accurate shell temperature profile to be generated, while a forced convection model developed for a bank of jets impinging on a large cylinder is implemented to quantify the external convective resistance. The governing heat transfer and chemistry equations are implemented into the Matlab R2014a software to produce one-dimensional solutions of the temperature distributions and species mass fractions observed in a rotary cement kiln. A validation study is performed against an existing one-dimensional model showing reasonable quantitative and qualitative results of temperature profiles and species outputs. Using operational parameters from a partner organization, a profile of internal and external temperature profiles and the corresponding axial development of species products is also presented. Scanned shell temperature data is then compared against the results of the model considering only free convection, and forced convection from the kiln shell cooling fans in operation. An error of ⩾20% was observed when the effects of forced convection on the kiln shell are neglected.