A new approach to the modelling of gross gas-solids flow through the riser in a circulating fluidized-bed system is proposed in this paper. This approach differs from the previous ones, which are Found to be theoretically incorrect based on a fundamental analysis of the riser process hydrodynamics. Starting from the basic principles, the new approach tackles the modelling problem from both energy and momentum balance perspectives. It also identifies that a riser may be operating in two different flow regimes : the entrainment regime and the dragging regime. Experimental results from a compartmented dense-phase circulating fluidized bed, developed for a continuous coal combustion-gasification process, verified the existence of the two flow regimes.