Simulação de leito fluidizado via CFD com abordagem Euleriana de escoamento bifásico mediante influência de parâmetros de projeto e operação

Abstract

The fluidization of solid particles is a technology with countless applications, as an example the industries which use biomass, having as advantage the better mixture between solid and gas and low pollutant emissions. Gas-solid flows in systems of fluidized beds have been studied in the last years, due to a heavy and complicated theory. Therefore, the investigation of the fluid dynamics characteristics of the flow inside the fluidized bed is proven to be important, having as base an useful tool of computational simulation for fluid dynamics phenomenon, Computational Fluid Dynamic (CFD). This tool makes it possible the knowledge and identification of the main aspects of project and operation, aiming to improve the components of the reactors, as well as to determine the operational conditions more suited to specific applications. In this work, it was studied the fluidization of a bed with silicon particles, through air flow, under different operation conditions, using the software ANSYS® Fluent, which operates according to the method of finite volume. The approach used here was the biphasic Euler-Euler flow, together with the kinetic theory for granular flow (Kinetic Theory for Granular Flow). It was analyzed the profiles for pressure drop and minimum fluidization velocity, changing the operational parameters (height and initial bed temperatures, as well as the air temperature and the particles granulometry) and project parameters (reactor diameter). To validate the computational model, the results of the simulations were compared with the experimental data through research. The results showed the mathematic/simulation model can represent well the real behavior of the pressure drop inside the bed as function of the inlet velocity, however, for the tests made at temperatures higher than 158 °C, the results had an average error of 19.658%. This error can be justified by some hypothesis to simplify the modelling, such as the initial temperature of the uniform bed, constant temperature of the entrance air and adiabatic reactor walls and without roughness. However, the fluid dynamic behavior could be pictured, following the same tendencies of the experimental tests, with R² = 0,998 and relative average error below 10%.