The three-dimensional propagation of a horizontal gas jet injected into a gas-solid crossflow is described by a model based on the mass and momentum balances for both phases. The potential core close to the nozzle, the kidney-shaped cross-section of the jet and the region of rapidly increasing jet volume are taken into account. Viscous and turbulent stresses within the gas phase as well as the momentum exchange with the solid phase are considered. Several parameters are determined empirically by experimental data obtained by measurements in a dilute circulating fluidized bed. The comparison of calculated with experimental data shows good agreement concerning the shape of the jet axis and the solid phase concentration.