Heat and mass transfer analysis of a high-pressure TGA with defined gas flow for single-particle studies

Abstract The test reactor HITECOM was designed to study in situ the conversion of an isolated particle in a well-defined gas flow at a gas temperature up to 1400  ° C and a pressure up to 40 bar. As is typical of high-temperature, high-pressure systems, the temperature field inside the reactor is not perfectly constant and causes natural convection, which interferes with the gas flow in the test rig. To gain a deeper insight into the complex flow field and temperature and species distribution, a detailed CFD study was carried out and the results validated against experimental data. The numerical model comprised reactive gas flow, heat and mass exchange with a reactive char particle, convective and radiative heat transfer in the reactor and heat conduction in the solid parts of the reactor. The present study revealed that, depending on the operating conditions, the flow field shifts from an idealized parabolic profile to a complex, buoyancy-driven flow. It could be shown that comprehensive CFD modeling is necessary to identify critical operating conditions and estimate the real species and temperature distribution around the reacting particle, facilitating an improved evaluation of the experimental data.