CFD simulation of circulating fluidized bed boiler 30 MW: Effect of primary and secondary air distribution on fluidization behavior

Abstract

The distribution of primary and secondary air on fluidization behavior of Circulating Fluidized Bed (CFB) boiler affects the burning performance. In this paper, Computational Fluid Dynamic (CFD) simulation with Eulerian multiphase model and k-ɛ standard turbulence model is used to study the impact of distribution of primary and secondary air and to observe the optimal value of primary and secondary air distribution as well, in order to achieve good fluidization in a CFB boiler. Fluidization in this study was analyzed from sand volume fraction, air and sand velocity, and pressure of furnace. The simulation was performed on five primary and secondary air distribution variations of (%PA-%SA) 40-60, 50-50, 60-40, 70-30, and 80-20. The simulation indicates that the variation in primary and secondary air distribution significantly affect the fluidization behavior. It is known that the fluidization goes well on primary and secondary air distribution of 50-50 and 60–40, wherein the most optimal is on 50-50. Moreover, the cases with %PA-%SA of 40-60 are not recommended for use because will form static bed. Meanwhile, the fluidization with the primary and secondary air distribution of 70-30 and 80-20 are not recommended to be applied because of a large amount of sand inside the cyclone.