Particle resolved simulations of carbon oxidation in a laminar flow

Abstract

This work is devoted to the numerical study of the impact of the Reynolds number and the ambient gas temperature on the partial oxidation of a single moving coal particle. The model includes six gaseous chemical species, three semi‐global heterogeneous surface reactions, and three homogeneous gas reactions. The Navier–Stokes equations coupled with the energy and species conservation equations were used to solve the problem. The diameter of the particles considered was set up as 2 mm and 200m. An analysis of the simulations related to the influence of particle Reynolds numbers on integral characteristics such as surface‐averaged carbon consumption rates revealed that the oxidation rate increases with increasing gas velocity, which is logical. However, the increase in the particle Reynolds number leads to the prolongation of the kinetically controlled regime from lower to higher temperatures, which is explained by the enhancement of the mass transfer between the particle and the surrounding gas. Using visualization of the temperature and species mass fraction distributions around the reacting particles predicted numerically, the three well‐known basic oxidation regimes, namely the diffusion‐controlled, transitional, and kinetically controlled regimes are described, taking into account the impact of the particle Reynolds number on the dynamics of oxidation. The influence of radiation in the gas phase on oxidation rates was studied numerically using P1 radiation model. Additionally the behaviour of heterogeneous Damköhler numbers, Thiele modulus and effectiveness factors depending on the ambient temperature and particle Reynolds number was analyzed and discussed.