Simulação computacional da influência de parâmetros operacionais sobre a pressão estática do escoamento gás-sólido em fornalha piloto de leito fluidizado circulante

Abstract

Circulating fluidized beds (CFBs) used as furnaces are multiphase systems characterized by operating in fast fluidization regime. Due to their constructive and functional aspects, they have good combustion efficiency, low emission of nitrogen oxides (NOx), and high rates of heat and mass transfer. In addition, they are attractive for operating with fuels of different physical and chemical properties. In order to predict the static pressure profile of the gassolid flow for stable operation of a pilot scale CFB furnace currently being installed at the Laboratory of Thermochemical Processes of the UTFPR-Campus Ponta Grossa, this work develops a computational code from a semiempirical modeling approach available in the literature to anticipate and guide the planning of future experiments. Initially, the code developed in this work was compared with that presented by other authors, and later, it was applied to simulate the pressure static profile in the pilot CFB furnace. The main results obtained showed that the solids inventory used in simulations has a significant influence on the pressure drop in the CFB loop, reacting proportionally to the increase of the mass of solids loaded into the system. It was also noticed that the particle diameter was the parameter that most influenced the results of the simulations, leading to greater pressure drops and problems in the convergence of solutions, mainly when simulating with particles of 200 μm or further. On the other hand, the results of the pressure drop variation when changing the fluidization velocity in the riser and standpipe were not as expected. Nevertheless, the solid circulation rate promoted an appropriate response, whereby the pressure drop in the riser and the standpipe grew up with the increase of both simulation parameters. Even though the code implemented in the EES® software satisfactorily represents the physics of the gassolid dynamics under the conditions tested in the circulating fluidized bed system, it is still necessary to introduce some improvements for experimental validation before being applied.