Three-dimensional calculation of a chemically reacting porous particle moving in a hot O2/CO2 atmosphere

Abstract

This work is devoted to the three-dimensional numerical investigation of a chemical reacting porous carbon particle moving in a hot O2/CO2 gas. The porous particle was represented by an agglomerate of small monodisperse spherical particles distributed inside a sphere. The ambient temperature was systematically varied in a range between 1200 and 2500K. To solve the Navier–Stokes equations for the flow field coupled with the energy and species conservation equations, a finite volume solver was applied. In addition to the solid carbon the model incorporates six gaseous chemical species (O2, CO, CO2, H2, H2O, and N2). The reaction mechanism includes semi-global carbon monoxide oxidation, the forward and backward water–gas-shift reaction, and four heterogeneous reactions. The ambient medium was assumed to be nearly dry. The main objective of this work was to understand the char conversion processes inside a porous carbon particle. In particular, the change of regimes depending on the ambient gas temperature and the influence of the flow velocity on the processes inside the porous particle were studied in detail. As a reference case the oxidation of a solid non-permeable sphere moving in a hot O2/CO2 gas was considered, and the results for the porous particle are discussed and compared against the reference case.