Radiative Heat Transfer Conditions in a Rotary Kiln Test Furnace Using Coal, Biomass, and Cofiring Burners

Journal article, 2017

This work studies the radiative heat transfer in a 580 kW(th) pilot scale test furnace that resembles a full-scale rotary kiln for iron ore pellet production. The aim is to quantify the radiative heat transfer in coal and cofiring flames and also to study the possibility to model the radiative heat transfer for such combustion conditions. Three combustion cases of coal and cofiring are studied, and an evaluation is made using a detailed radiation model. The test furnace is cylindrical and refractory lined but does not rotate and no iron ore pellet bed material is included. In-flame measurements of temperature, gas composition, particle concentration, radiative intensity, and radiative heat flux are conducted for the different fuels and fuel combinations. Overall, the differences in measured radiative intensities and heat fluxes among the three studied fuel cases are minor, which implies that introduction of renewable fuels by cofiring in a full-scale rotary kiln should be feasible with respect to heat transfer conditions. In the model, the furnace is treated as an axisymmetric and infinitely long cylinder, and gas properties are calculated with a statistical narrow-band model, while particle properties are calculated using Mie theory. The modeling results show reasonable to good predictivity compared to the measured intensity data. This indicates that the experimental data is of good quality but also indicates the potential use of the model in full-scale rotary kiln calculations in future work.