Study of Flow Behavior of Ultrafine Particles

Flow behavior of gas and agglomerates is numerically investigated in the riser based on a transient two-fluid model. The gas phase is modeled by the LES model, and the solid phase uses a kinetic theory model developed from the molecular model coupling the gas-agglomerates interaction and the agglomerates-agglomerates interaction[1]. We assumed that the ultrafine particles move as natural agglomerates rather than single particles in the riser. The energy transfer and dissipation by the instantaneous collisions between the agglomerates of ultrafine particles and gas phase and between agglomerates-agglomerates are considered. The diameter of agglomerates is estimated based on the force model by Li and Tong[2].The distributions of velocity, concentration and diameter of agglomerates, are numerically obtained. The influence of flow and agglomerates in the different operating conditions is also analyzed. The results show that the large agglomerates are rich in the bottom section of the bed. Thus the Fast Fourier Tranform (FFT) is used to get the fluctuated character of the agglomerates in the riser and find the dominant frequency of the agglomerates fluctuation is 0.03-1.26Hz.