Simulação do perfil axial de pressão na coluna riser de um leito fluidizado circulante

Abstract

Gas-solid flows in circulating fluidized bed systems are very common in industrial processes, being a research subject in recent years because of its highly complex nature. The study of parameters related to the hydrodynamics characteristics of this flow, such as the static pressure profile along the column in fast fluidization, can show the way to prevent undesired situations found in processes of the chemical and petroleum industry, as well as in boilers for power generation. Despite the existence of several studies conducted on the subject, there are differences in the results pointed out by several authors. Thus, in order to contribute to a better understanding of the phenomenon of gas-solid flow in fast fluidization regime, this study aimed to model and simulate the gas-solid multiphase flow inside a riser of a circulating fluidized bed by using computational fluid dynamics, in order to determine the axial pressure profile under different operating conditions. Therefore, the finite volume method, through ANSYS-FLUENT™ v.16.0-commercial software was applied to analyze the hydrodynamics of the gas-solid flow inside the riser. In addition to the pressure profile, simulations determined the solid and gas velocity fields, and also the distribution of the solids holdup, among other parameters of interest. To validate the computational model, the results obtained from simulations of the axial pressure drop across the riser column were compared with experimental data obtained in a pilot system, which had its geometry reproduced in the simulations. The results obtained showed good agreement between the values of the simulations and those available from experimental data.