Study of wall-to-bed heat transfer in circulating fluidized bed riser based on CFD simulation

[Display omitted] •Hydrodynamics and heat transfer behavior of CFB riser are presented.•Ug, Gs significantly influenced both the hydrodynamics and heat transfer.•Correlation of the heat transfer coefficient based on ρsus was developed.•Modified heat transfer coefficient correlation in terms of Ug, Gs, ds was proposed.•The proposed correlation provides a good prediction and easy to use. Circulating fluidized bed (CFB) riser reactors are widely used in several industrial gas–solid flow systems to achieve a high reaction rate and a high heat of reaction. Thus, understanding wall-to-bed heat transfer is essential for optimizing CFB operation and design. This study aims to analyze the wall-to-bed heat transfer in a CFB riser reactor. A two-fluid model with the kinetic theory of granular flow was used to solve the hydrodynamics and heat transfer behavior in the bed. The wall-to-bed heat transfer coefficient is strongly dependent on the CFB operating conditions, but correlations for the wall-to-bed heat transfer coefficient are often defined in terms the suspension density, which is not an operating parameter. This makes the correlations difficult to use because the solid fraction in the system must be known. Thus, in this study, a correlation was developed that defines the heat transfer coefficient in terms of two operating parameters: the solid circulation rate (Gs) and the superficial gas velocity (Ug). The developed correlation exhibited fairly accurate prediction for several particle sizes because this correlation is based on fluid catalytic cracking (FCC) particles having a specific diameter. To better address the effect of different particle sizes, the correlation was further modified to be a function of the particle diameter in addition to Ug and Gs. The modified correlation can predict the simulated and experimental data within a ±20% deviation and an averaged absolute relative error of 5.72%.