(260c) A Mathematical Model for the Simulation of Binary Gas Fluidized Beds

Particle-size distributions (PSD) are known to play an important role in the behaviour of dense particle phase flows. In gas fluidized beds, a wide size distribution results in a decrease in the minimum fluidization velocity as well as an increase in bed expansion Many researchers involved in the simulation of large-scale dense particle phase flow processes, which have a PSD, use the Eulerian-Eulerian framework. There are two approaches employed within this framework: the first approach is characterized by the use of separate momentum equations to define each particle species. In the second approach, averaged mixture properties from the individual particles are defined and a mixture momentum and granular energy balance are employed.

In this work a new computational fluid dynamics (CFD) model based on the latter approach mentioned above, is proposed for the modelling of binary gas-solid fluidized beds. The model makes use of concepts from the Particle bed Model proposed by Foscolo and Gibilaro (1987). The initial mathematical derivation was for a mono component system, however this has now been extended to cater for ?binary mixtures?. The key features of the new formulation include a new dynamic expression for the elastic force as well as a new interphase transfer function that is independent of the drag co-efficient. Simulations carried out with the proposed model are used to demonstrate some key qualitative and quantitative features of binary fluidization.

REFERENCES

FOSCOLO, P., GIBILARO, L., (1987). Fluid Dynamic Stability of fluidised suspensions: The Particle Bed Model . Chem. Eng. Sci, 42, 1489.