Simulação numérica em CFD de uma câmara de combustão ciclônica para a queima de biomassas de cana-de-açucar pulverizadas

Abstract

The Secondary products generated in the processing of sugarcane; that until a few years ago were mostly discarded, nowadays they have become potential energy resources for the generation of electric energy. However, the use of these available renewable resources requires more efficient technologies for the transformation into thermal energy, and later into electrical energy. With this objective, the company Brayton Energy designed a cyclonic combustion chamber as a fundamental component of a externally fired gas turbine, or EFGT cycle capable of generating 900 kWe of electric energy using different pulverized biomasses as fuel. This cyclonic combustion chamber was studied in this work through numerical computer simulations performed in ANSYS FLUENT, and using pulverized sugar cane bagasse as fuel, to evaluate the fluid dynamics design and the combustion performance of the bagasse particles inside the chamber. The simulations were performed using the turbulence models RMS, RNG k-ε, SST k-ω and Realizable k-ε. The species transport model was used for the combustion and the Finite Rate/Eddy Dissipation was chosen for the iteration of chemical reactions with turbulence. The Discrete Phase Model (DPM) was also used for the tracking of combustible particles and the Discrete Ordinate model for the radiation model. The results of the non-reactive simulations of the cyclonic chamber show the velocity fields and the recirculation zones inside the chamber, which allows to evaluate the fluid dynamics of the chamber design. In addition, the results of the reactive simulations show the distribution of temperature and combustion products within the cyclonic chamber, and provide information on combustion parameters such as temperature, mass, residence time and percentage of burning of bagasse particles along their trajectories through the combustion chamber.