Tracking the histories of individual fuel particles in packed bed combustion

Abstract

This paper introduces a simple technique for sampling individual fuel particles at various stages in overfeed packed bed combustion. A particle is secured to the end of a thin stainless steel rod, which is then used to track the motion of the particle and to remove it from the bed for sampling at the desired time. The particles so tracked provide a record of changes in mass, volume, density, and individual dimensions as combustion proceeds in the bed. Results of a number of experiments of this sort on the packed bed combustion of parallelepipedal wood particles are presented, which among other things show that particle shrinkage during pyrolysis is generally – but not always – largest along the direction of the wood grain and less in the cross-grain directions. The “tracker rod” technique has the advantage over single particle experiments in a furnace that the particles are exposed to the varying and non-uniform conditions in the actual packed bed of fuel; it is, however, only suited to fixed beds, not fluidized or moving beds.