Fluidization in two-dimensional beds with a jet. 2. Hydrodynamic modeling

The object of this investigation is to develop an experimentally verified hydrodynamic model to predict solids circulation around a jet in a fluidized bed gasifier. Hydrodynamic models of fluidization use the principles of conservation of mass, momentum, and energy. To account for unequal velocities of solid and fluid phases, separate phase momentum balances are developed. Other fluid bed models used in the scale-up of gasifiers do not employ the principles of conservation of momentum. Therefore, these models cannot predict fluid and particle motion. In such models solids mixing is described by means of empirical transfer coefficients. A two-dimensional unsteady-state computer code was developed to give gas and solid velocities, void fractions, and pressure in a fluid bed with a jet. The growth, propagation, and collapse of bubbles was calculated. Time averaged voi fractions were calculated that showed good agreement with void fractions measured with a ..gamma..-ray densitometer. Calculated gas and solid velocities in the jet appeared to be reasonable.