During the initial stage of biomass combustion and gasification (so-called devolatilization), biomass particles exchange mass and heat at the surface with surrounding environment; receiving heat from hot gas flow while releasing gas. Recent experimental efforts discovered that both interphase transport phenomena and chemical reactions are affected by the interaction between neighbour particles.
This project will try to elucidate this effect of chemical interaction among pulverised biomass particles by detailed numerical investigation. While many numerical studies exist for particle-laden flow at non-reacting, isothermal conditions, only few studies have investigated the particle interactions including heat transfer and chemical reactions. The major part of this project will focus on the construction of a high-resolution numerical platform of closely located reactive particles (distance: less than 10 times particle diameters) on fluid dynamic simulation. To make the problem simple, the parameter range will be limited to Re_p<20, d_p<1 mm, and T_g=900-1900 K.
The study will be carried out with resolved particle direct numerical simulation (RP-DNS) in OpenFOAM platform. This project is supported by Swedish Research Council in the same project title during 2016-2019. Project has three phases between 2016-2020.
In the first phase, which was partially initiated by SNIC 2016/3-77, the effect of chemical reactions on particle-gas interaction is being investigated with single particle in gas flow. The effect of chemical reactions is imposed in the form of Stefan flow (outgoing mass flow of gas at the particle surface). Specifically, the effect of Stefan flow on the boundary layer is being investigated as a comparison with non-reacting flow conditions. The goal of this phase is to propose the modified correlation for heat, mass, and momentum transport (i.e. Nusselt number, Sherwood number, and drag coefficient) that account for the effect of Stefan flow. This phase is expected to continue throughout 2017.
In the second phase, the numerical platform will be improved to account for more realistic situations in biomass gasification. More specifically, the model will include temperature driven gas-solid reactions (pyrolysis, char gasification and combustion), intra-particle heat and mass transfer, and array of several particles in the computational domain. In this stage, it is expected to gain insight about how the particles interaction with respect to flow field surrounding them affects the progress of chemical reactions. This phase is expected to progress in 2018 and early 2019.
The last phase will introduce reduced kinetic scheme of gas phase reactions including the formation of soot. At this stage, further information about the chemical interaction of closely located particles, including the interaction via chemical reactions in gas phase, will be elaborated. This phase ie expected to progress in 2019-2020.