Comparison of bubble eruption models with two-fluid simulations in a 2D gas-fluidized bed

Two-fluid simulations of gas-solid fluidized beds are performed in this work with a threefold aim: (1) explore the capabilities of two-fluid modelling to reproduce realistically bubble eruption patterns in two-dimensional fluidized beds; (2) compare the results obtained from the two-fluid simulations with particle ejection models; and (3) provide information about the mutual interaction of the gas and particle flows during bubble eruption. To fulfil these aims, results from two-fluid simulations concerning the vertical and horizontal velocities of particles in bubble domes, prior to and during bubble eruption, are reported and compared with previously published experimental data taken from a bed of comparable geometry and operating conditions. The comparison shows excellent quantitative agreement. Particle ejection velocities estimated through semi-empirical and theoretical models proposed in the literature are compared with the particle behaviour in the bubble dome obtained from the two-fluid simulations. The results obtained here indicate that the theory based on the potential flow around a cylinder provides a more accurate prediction for the particle velocities in erupting bubbles than semi-empirical relations. For the data reported here it has been found that the velocity of particles in the bubble dome forms an angle with the vertical direction that is twice the angle formed by the radial direction. This observation is contrary to standard models of 2D bubbles, which assume that the particles are ejected radially outwards from the dome. (C) 2011 Elsevier B.V. All rights reserved.