Estudo de leito fluidizado circulante com fluxo de ar pulsante

Abstract

Circulating fluidized bed (LFC) has been employed in several industrial processes, such as in combustion, gasification and pyrolysis. The LFC is mainly composed of riser, cyclone, standpipe and solid recirculation valve, such as loop-seal. This valve is divided into two chambers, the supply and recycle chambers, which require aeration for the fluidization of the particles in this region. However, the gas-solid contact in the loop-seal valve is sometimes not as effective. On the other hand, pulsed air has been widely used to improve fluidization quality. In this sense, the objective of the present work was to study the fluid dynamics behavior with the injection of pulsed air in the supply and recycling chamber and to compare the results obtained in the two systems. For this purpose, six experimental tests (three in the supply chamber and three in the recycling chamber) were performed using continuous flow, and pulse rate of 1 Hz and 2 Hz for each chamber studied. The pulsed air flow was controlled by a solenoid valve. The material used for the tests was casting sand, with an average diameter Sauter of 183 μm and an apparent density of 2712 kg m-3. In all experiments, the solids inventory was 4 kg and the surface air velocity was maintained at 4 m s-1. The results showed that the addition of pulsed air improved the hydrodynamics in the loop-seal valve, requiring less amount of air for the fluidization. For the two analyzed chambers it became possible to work with low aeration rates, thus proving the efficiency of the application of pulsed air to the loop-seal valve.