Experimental investigation of the interactions between the flame and the particles in packed beds
In this project, we propose to examine the interactions between particles of a packed bed reactor and a flame propagating in between the particles. To be representative of bulk solids of industrial relevance and also allow for highly resolved diagnostics, a two-dimensional geometry based on an array of parallel cylinders representing the particles and a slit burner is proposed. This project will focus on investigating the two-way coupling between the particles and the flame. The particles influence the flame through preheating, heat losses, radical quenching, catalytic effects and the release of gas resulting from the particle chemical conversion. In return, the flame dictates the particle transformation rate via the particle temperature and the gas composition. The first funding period will focus on the interactions of the particles with a premixed methane-air flame. Several optical measurement techniques will be applied including chemiluminescence imaging, two-component laser Doppler velocimetry, coherent anti-Stokes Raman spectroscopy and phosphor thermometry for the respective determination of the flame reaction zone location, two-component flow velocities, gas phase species concentration, and gas and surface temperature. First, the investigation will be carried out at steady-state conditions in an array of water-cooled steel cylinders. Uncooled alumina cylinders will then be used as thermally thick particles with higher outer surface temperatures significantly altering the flame-particles interaction. Both steady state and transient measurements will be performed to assess the heat transfer rates, and observe the effect of particle surface temperature on the flame properties. Finally, reactive cylinders made of magnesite (MgCO3) will be used to probe the influence of the calcination reaction on the flame.