Numerical and experimental investigation of olive pomace oxy-combustion in a laminar flow drop tube furnace

The paper deals with the development and validation of a computational fluid dynamics model for olive pomace combustion. The model was implemented in Ansys/Fluent software. The combustion model is based on three reactions for solid and three reactions for gaseous phase. The kinetic data for the former was obtained experimentally, while for the latter was taken from literature. Presented combustion model was kept simple so it can easily be scaled to industrial combustion systems while maintaining its efficiency. The developed model was validated against experimental data. The experiments were conducted in a laboratory-scale entrained flow reactor. There the combustion was performed for N2-O2 and CO2-N2 mixtures over a range of temperatures and oxygen concentrations representative of oxy-MILD (Moderate or Intense Low-oxygen Dilution) conditions. The whole combustion process took place under laminar flow conditions. Such conditions put additional pressure on the kinetic data, which control the conversion process. Good agreement between experiment and numerical model was obtained for major components in flue gases, fuel conversion and NOx emissions. The model, however, underpredicts the outlet CO content. Additional analyses using other gas phase reaction schemes did not improved the results. Overall, the results indicated that increased oxidizer dilution and lower operating temperatures promote more uniform reaction zones and reduced temperature gradients, confirming the transition toward MILD combustion conditions. The proposed framework offers a validated and computationally efficient approach for modelling biomass oxy-combustion, elucidating the impact of MILD combustion conditions on flame behaviour and emission characteristics, and contributing to the design of efficient, low-emission industrial combustion technologies compatible with carbon capture.