Heat transfer to the ceiling of the riser of a circulating fluidized bed

Very little information on the heat transfer to the ceiling of a circulating fluidized bed (CFB) boiler is available in the published literature though it constitutes a significant part of the furnace heat absorption. So, to explore this less-known heat transfer process a series of experiments were conducted at four different superficial gas velocities and three external solids circulation rates in a CFB pilot plant with a riser having a height of 5 m and a cross section of 1.0 m x 0.5 m. The experimental results suggest that both solids circulation rates and superficial gas velocities had a significant influence on the local heat transfer to the ceiling close to the riser exit to the gas solids separator. However, on the ceiling, opposite of the exit, solids circulation rates and superficial gas velocities had only a minor influence on the local heat transfer coefficients.