The rates of production of CO and CO2 from the combustion of pulverized coal particles in a shock tube

This work presents some results of experiments on coal combustion in a shock tube, as well as a time-dependent model of the boundary layer of a single, burning char particle under similar conditions. The partial pressure of O2 in a shock tube was varied between 0 and 10 bar, with gas temperatures ranging from 1300 to 1850 K. Particle temperatures between 1500 and 2500 K were reached under these conditions. The concentrations of CO and CO2 were measured as functions of time. Together with the equations for a particle's energy and mass, these measurements enable one to determine reaction rates as a function of both the particle's temperature and the partial pressure of O2. Furthermore, the measurement of gaseous reaction products enables fundamental aspects of their formation to be studied. From the rates of production of CO and CO2, kinetic data were obtained, consistent with that from a mass balance on a particle. A comparison of these results with the results from an energy balance on a particle shows hardly any heat transfer from the homogeneous combustion zone to the particle. This heat transfer increases if the rate of the heterogeneous reaction is decreased. These results are supported by modeling calculations, showing the CO combustion takes place in a wide zone surrounding the particle. Furthermore, it is shown that CO can indeed be considered to be the only primary product of heterogenous reaction at the temperatures considered