From the Navier-Stokes equations and the Newtonian equations, which describe gas flow and the movement of a single particle respectively, a two-phase model describing gas-solid flow macroscopically in fluidized beds was derived by using volume averaging and the parameters of the model were determined. This general model can be reduced to several forms of simpler models reported in the literature. An improved interphase slip algorithm (IPSA) method based on finite volume approach was used in the solution of the model equations. The influences of the velocity of the central jet, height of the bed and superficial gas velocity in the bed on jet penetration height were obtained by numerical simulation. The computed flow patterns of the binary mixture were also obtained. The theoretical prediction was verified against the experiments made on a two-dimensional jet fluidized bed with both unitary and binary component materials. Under the operating conditions of an industrial ash-agglomerating coal gasifier, the arithmetical mean based upon particle number was introduced to calculate the mean diameter of the binary components. Thus the simulation of the binary components was simplified. All the computed jet penetration heights under various conditions were in good agreement with experimental and literature data.