Heat transfer and bed dynamics study on a swirling fluidized bed under various inlet configurations

Abstract

The present paper aims to study the heat transfer from the wall to the bed in a laboratory-scale swirling fluidized bed with a blade distributor. The experiments were carried out in a swirling fluidized bed reactor with an internal diameter of 10 cm and a total length of 50 cm connected with two different blade-distributors, one with seven blades and another with twelve blades. The heat transfer process represented by the heat transfer coefficient and bed flow dynamics represented by the bed and distributor pressure drops were investigated at different designs and operating conditions, mainly the number of blades, using gas plenum, and using gas plenum with different central bodies. Sand particles (Geldart type D) with a mean diameter of 1.5 mm was used as a bed material fluidized by air. The experiments were carried out at different fluidization number of 2.8, 3.3,4.2, and 4.5 at minimum fluidization velocity of 0.8 m/s. Increasing distributor blades from seven to twelve blades resulted in enhancing the operation of a fluidized bed reactor due to increasing the heat transfer coefficient and reducing the bed and distributor pressure drop. Using gas plenum resulted in decreasing the bed and distributor bed pressure drop and also resulted in decreasing the heat transfer coefficient. Two central bodies with conical and cylindrical shapes were installed in the plenum. The two central bodies had a negative effect on the operation of the fluidized bed that leads to increasing both distributor and bed pressure drops and to decreasing the heat transfer coefficient. For all the cases were studies, the heat transfer coefficient in the horizontal direction had the same behavior; it increased near the walls and it was almost constant at the center region of the reactor. Also, the heat transfer coefficient increased at the lower bed heights and vice versa.