Characterization of the lateral gas–solid flow in a circulating fluidized bed boiler using simple mathematical model based on CPFD simulation data

Operation safety, combustion efficiency, and pollutant emissions of circulating fluidized bed (CFB) boilers are significantly affected by the lateral gas–solid flow uniformity, which can be featured by the voidage (ε_g) as well as particle lateral movement velocity (u_p). To obtain abundant data to support quantitative analysis and modeling, the gas–solid flow details in a 170 t/h CFB boiler were numerically simulated using the computational particle fluid dynamics (CPFD) method, which has been validated by field test data. Based on the original simulation data set, simple models for the prediction of lateral profiles of ε_g and u_p were developed. In addition, both theoretical model and genetic algorithm-back propagation (GA-BP) neural network were applied to predict the lateral solids movement behavior. Results show that both two models exhibit excellent prediction accuracy with the coefficient of determination (R₂) exceeding 0.99. While the theoretical model derived from physical equations is relatively simple and has a clear physical meaning. All the simple models developed in this paper can be embedded into the overall CFB mathematical model framework, facilitating the comprehensive analysis of the operational characteristics for large-scale industrial CFB boilers.