A model for heat transfer in a pressurized circulating fluidized bed furnace

A mechanistic model based on cluster renewal approach is proposed to predict bed to wall heat transfer coefficient in a pressurized circulating fluidized bed (PCFB). The model takes into account the effect of pressure on cluster density, cluster thermal conductivity and particle convection heat transfer coefficient. The effect of pressure and bed temperature on bed to wall heat transfer coefficient is investigated. Published information on cluster velocity and bed hydrodynamics are used in the formulation of the model. The effect of cross-sectional average volumetric solids concentration on bed to wall heat transfer coefficient is also reported. The model predictions are validated against the experimental data obtained from a PCFB riser 52.4 mm in diameter and 2020 mm high. The unit is heated by electrical resistance heaters. The experimental results are reported for pressures up to 600 kPa and bed temperatures up to 650°C. The experimental data and model predictions are in reasonable agreement with each other. The model predictions are also validated with the data from the published literature, and a fair agreement is observed.