Concentration of solid particles of ash and inert material present in the combustion chamber of a circulating fluidised-bed boiler is very high, giving rise to some disadvantages. At the same time, the required temperature level in the combustion chamber is guaranteed by circulation of solid particles. In this work numerical simulation of gas-solid particle flow has been performed in the frame of a two-fluid model, namely the Eulerian approach for the dispersed phase, for conditions of the circulating fluidised bed, ranging from moderate to high mass ratios of the flow. An incorporated original model of closure of transport equations of the dispersed phase permitted to account the interparticle collisions which might be indispensable to proper numerical simulation of the process in the circulating fluidised bed under discussion. The results of this work would help to improve the processes occurring in the combustion chamber of the circulating fluidised-bed boiler.