Co-firing biomass and coal-progress in CFD modelling capabilities

This paper discusses the development of user defined FLUENT™ sub models to improve the modelling capabilities in the area of large biomass particle motion and conversion. Focus is put on a model that includes the influence from particle size and shape on the reactivity by resolving intra-particle gradients. The advanced reaction model predicts moisture and volatiles release characteristics that differ significantly from those found from a 0-dimensional model partly due to the processes occurring in parallel rather than sequentially. This is demonstrated for a test case that illustrates single particle conversion patterns. The improved model will impact the simulation capabilities of biomass fired boilers in the areas of thermal conditions, NOx formation and particle deposition behaviour.