From the Navier-Stokes equations and the Newtonian equations, which de
scribe 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 fo
rms of simpler models reported in the literature. An improved interpha
se slip algorithm (IPSA) method based on finite volume approach was us
ed in the solution of the model equations. The influences of the veloc
ity of the central jet, height of the bed and superficial gas velocity
in the bed on jet penetration height were obtained by numerical simul
ation. The computed flow patterns of the binary mixture were also obta
ined. The theoretical prediction was verified against the experiments
made on a two-dimensional jet fluidized bed with both unitary and bina
ry component materials. Under the operating conditions of an industria
l ash-agglomerating coal gasifier, the arithmetical mean based upon pa
rticle number was introduced to calculate the mean diameter of the bin
ary components. Thus the simulation of the binary components was simpl
ified. All the computed jet penetration heights under various conditio
ns were in good agreement with experimental and literature data.