Full-Scale 3D-Modelling of the Radiative Heat Transfer in Rotary Kilns with a Present Bed Material

Övrigt konferensbidrag, 2018

This work discusses the development and usage of a radiative heat transfer model in 3D of a rotary kiln with a present bed material. Using a discrete-ordinates method to solve the radiative heat transfer equation, radiative properties are calculated using a weighted-sum-of-grey-gases (WSGG) model for gases and Mie and Rayleigh theory for particles including fuel, ash and soot. Measurement data gathered from a pilot scale test furnace, comprising temperature, gas composition and particle concentration, is used to model a pilot-scale rotary kiln and satisfactory agreement to radiative heat flux measurement is shown. Combining measurements, from the same test furnace, with data gathered from an industrial full-scale rotary kiln used for iron ore pelletizing, a full-scale rotary kiln with a present bed material is modelled. Conductive heat transfer within, as well as between, the bed and wall material is included in the model and surface temperatures are calculated within the model. The model also includes heat losses from the outside wall of the rotary kiln due to radiation and convection and a simplified mixing model of the pellet bed. When compared to measurements for the inside and outside wall as well as the bed material, the model predicts the surface temperatures with errors less than 10%. The total heat transfer to the present bed material was also studied showing that more than 90% originated form the radiative heat transfer within the furnace.