Design, development, experimental and CFD analysis of a prototype fluidized bed stripper ash cooler

Abstract

In this study, a novel stripper ash cooler for Circulating Fluidized Bed (CFB) boiler has been designed and a cold test rig has been fabricated. Pressure drop characteristics and the flow pattern of ash have been captured using a cold test rig. Numerical analysis using the Eulerian Eulerian multiphase model coupled with closures from the kinetic theory of granular flow has been used to simulate the flow pattern and heat transfer characteristics. The model has been validated using the experimental data. The influence of particle size and the fluidization velocity of ash on the flow pattern and heat transfer performance have been studied. The results show that there is a reduction in bubble diameter on increasing the particle size. The motion of the solid particles around the immersed heat exchanger has been predicted. The variations in the instantaneous heat transfer coefficient with particle size and fluidization velocity has been presented. The effect of Ranz- Marshall and the Gunn model on the wall-to bed heat transfer coefficient has also been analyzed. It has been observed that the heat transfer coefficient varies in the range of 250–400W/m2K and the heat transfer coefficient is highest for a fluidization velocity of 4m/s and a particle size of 600μm among all cases considered.