The Computation of particle size in Eulerian-Eulerian models of coal combustion by

The calculation of the particle size is one of the main ingredients in the simulation of coal-fired boilers. The particle size (or the specific surface-area) plays a major role in the interphase processes that are the driving force of coal combustion, such as particle drag and turbulent dispersion, heat-up (and hence pyrolysis) and heterogeneous combustion. The size of particles and fly-ash has also a clear influence on the radiative transfer of heat within the boiler.
The inability of Eulerian models of coal combustion to calculate the particle size has been one of their main disadvantages with respect to Lagrangian ones. The present contribution introduces a way of computing the average particle size in the framework of an Eulerian model, with allowance for size diminution due to mass transfer and for a ‘phenomenological’ representation of other mechanisms which may cause a particle-size change, such as devolatilization or particle breakup.
The method is first validated by comparison with a case which has an analytical solution; and then it is applied, in combination with an Eulerian-Eulerian model of coal combustion, to an actual power-production boiler.