CPFD Simulation of a Full-Scale Calciner Operating with Refuse Derived Fuel

In this work, a full-scale cement calciner firing refuse derived fuel (RDF) has been simulated using computational particle fluid dynamics (CPFD). To accurately predict the aerodynamics and conversion of RDF particles, a series of sub-models have been developed. A physical characterization framework has been established to quantify the size and shape distribution of the RDF particles. This framework is based on aerodynamic separation in a wind sieve followed by mass measurement and 2D photographing of individual particles. A proper drag model based on the terminal velocity of particles is adopted. Besides, a reliable iso-thermal model for conversion of plastic particles in suspension condition is developed based on the experiments in a single particle combustor (SPC).

The CPFD simulation results are compared with detailed temperature and gas composition measurements in the full-scale calciner. It has been observed that the overall trends of all measured (i.e., gas temperature and O₂ and CO₂ concentrations) and estimated (i.e., calcination degree and fuel burnout) parameters are well-predicted along the calciner. The burnout degree of fuel particles in the calciner is well-predicted as compared to the measurements. The fuel burnout mainly takes place in the calciner lower and upper vessels and is nearly completed when the particles exit the calciner. The calcination degree, on the other hand, is underpredicted; and in general, the non-uniformity of cross-sectional profiles is overpredicted.