The swirling fluidised bed examined in this work is a variant of a fluidised bed and featured a shallow annular bed with diverging cross-section, angular injection of fluidising air and swirling motion of bed material in an annular path. The principle of operation was based on the fact that a horizontal component of air velocity in the bed creates a swirling motion of the solids that suppresses elutriation. Recognising the need for a Residence Time Distribution (RTD) model which represents the physical bed behaviour and has enough flexibility to accurately fit the experimental data, a multi-parameter two-layer residence time distribution model was proposed for the RTD of solids. The model consisted of two parallel layers. The bottom layer obeyed a general recycle model and represented the swirling motion of the bottom layer of the bed. The top layer represented the conventional fluidised layer. The proposed model had six independent parameters and one dependent parameter. It was concluded that the model was versatile and capable of representing a range of widely different mixing conditions in the bed.