Biomass Pyrolysis in DNS of Turbulent Particle-Laden Flow

Biomass is important for co-firing in coal power plants thereby reducing CO2 emissions. Modeling the combustion of biomass involves various physical and chemical processes, which take place successively and even simultaneously [1, 2]. An important step in biomass combustion is pyrolysis, in which virgin biomass is converted into char. In this paper a point-particle model for the pyrolysis of biomass particles based on Haseli [3] is developed, which is coupled to a direct numerical simulation of the turbulent flow of gas in a channel with heated walls, using two-way coupling of mass, momentum and energy. We do not model combustion and gasification of biomass, but focus on pyrolysis, in particular on the effect of particle-gas interaction on the conversion time, i.e. the time needed to convert biomass into char. This is the first attempt in modeling the pyrolysis of biomass in a 3D flow framework. Gas-particle interaction affects the conversion time, which shows a characteristic dependence on particle size and concentration as shown in the results presented in this paper. In the following, the model of the biomass pyrolysis and of the gas with details on the way the two phases are coupled are introduced.