Computational investigation of slugging behaviour in gas-fluidised beds

A computational study has been carried out of the slugging behaviour in fluidised beds using a two-fluid continuum model. According to this approach, the two phases are treated as separate interpenetrating continuums, respectively described by the governing equations and coupled through an interfacial momentum exchange term. The computations are started from minimum fluidisation or bubbling flow conditions for two-dimensional and symmetrical three-dimensional fluidised beds. The well-known SIMPLE algorithm is employed to numerically solve the gas–solid two-phase governing equations. The validity of the approach is confirmed by comparing the model predictions with experimental measurements in the literature. The computational results are presented mainly in terms of porosity contours to illustrate the formation, growth, rising and bursting of slugs. With prescriptions of various wall conditions, round-nosed, square-nosed and wall slugs are predicted in the framework of the numerical simulations, where significant factors such as superficial gas velocity, wall or boundary condition and bed geometry are identified through a parametric study. It is also demonstrated that the slug rising velocity, length and frequency, and the bed expansion can be predicted by the proposed approach, and the particle–wall friction is a key factor responsible for the deficiency of the empirical correlations in the literature.