A MODEL FOR AGGLOMERATION IN A FLUIDIZED-BED

Experiments indicate that at a fixed superficial gas velocity, defluidization, as a result of massive agglomeration of the particles in a fluidized bed, occurs sharply when the bed temperature reaches a certain value. At a given temperature, the defluidization velocity is defined to be the minimum superficial gas velocity needed to avoid defluidization. In this report, an estimate of the defluidization velocity is developed using a two-particle collision model and a model for the granular energy of the bed. Using the available data on the material properties of coal ash as a function of temperature, the defluidization velocity is expressed as a function of bed temperature and particle and gas properties. A comparison with experimental data is made, and a simplified formula suitable for correlation studies is suggested.