Minimum and terminal velocity in fluidization of coal gasification materials and coal blending of gasification under pressure

Fluidization plays an important role in the chemical process of fluidized bed coal gasification. Experiments have been conducted with gasifier discharge of pilot plant and industrial demonstration plant to investigate fluidization fundamentals on the condition that pressures up to 2.5 MPa and nitrogen as the fluidizing gas. Both a three-dimensional bed (60-mm-i.d.) and a two-dimensional bed (30 × 300 mm) are used in the experiments. The fundamentals of high pressure fluidization examined in this study include minimum fluidization velocity, terminal (entrainment) velocity and jetting bubbling behavior. Several simplified correlations derived from the Ergun equation were investigated for determining minimum fluidization velocity. The effects of pressure upon entrainment velocity and flexibility were analyzed. Jetting bubble and coal blending were also studied over a range of pressures. Experimental results indicate that the diameter of coal should be decreased in the process of blending coal with increasing pressure.