A Simplified Model Accounting for the Combustion of Pulverized Coal Char Particles in a Drop Tube Furnace

A simple model is proposed, which predicts the evolutions versus time of the temperature and of the carbonaceous material conversion of a coal char particle during its combustion in a drop tube furnace under a very high heating rate of 1500 K/s. The values of the intrinsic reactivity parameters arc obtained performing thermogravimetric analyses of the coal char particles in a thermobalance under a low heating rate of 10 K/min. In this simple model, the local evolutions of the particle porosity and density are not accounted for as only their mean values are considered at any time of the combustion process. The oxygen concentration gradient within the particle is accounted for, once a particle effectiveness factor related to the Thiele modulus is estimated. Comparisons between the experimental and simulated temperatures of the particle are performed for three regulation temperatures of the drop tube furnace, and the combustion regimes are analyzed in terms of the effectiveness factor of the particle.