Computational Fluid Dynamics Study of Biomass Combustion in a Simulated Ironmaking Blast Furnace: Effect of the Particle Shape

Biomass is a carbon-neutral fuel and has potential to be used in pulverized coal injection (PCI) technology in ironmaking blast furnaces (BFs). In comparison to pulverized coal particles, biomass particles vary considerably in particle shape, and thus, the change of the aspect ratio of biomass particles may affect the motion and conversion of biomass particles. In this study, a computational fluid dynamics (CFD) model is developed to simulate the flow and thermochemical behaviors related to biomass injection into BFs. The model features non-spherical particle shapes and an improved devolatilization model. The model is then applied to a pilot-scale test of charcoal injection using a pilot-scale PCI test rig under simulated BF conditions for model validation. The burnout comparisons between simulation and measurement indicate that, in comparison to spherical particles, the non-spherical particles show smaller burnouts as a result of the shorter traveling time in the chamber; moreover, the burnouts predicted by the model considering cylindrical particles and improved devolatilization model are more comparable to the measurements. This confirms the model validity and also concludes that it is necessary to include the effect of the particle shape in the modeling of biomass injection in BFs. Then, to give a full picture of charcoal injection, other typical phenomena of flow and combustion behaviors are analyzed in detail for charcoals in cylindrical particle shape, aspects of gas charcoal flow, their temperature distribution, and gas composition distribution. This model provides an effective way for understanding and optimizing biomass injection in BF practice.