(538d) Validation of Electrostatic Model in Gas-Solid Fluidized-Beds

Authors: 
Rokkam, R. G., Iowa State University
Sowinski, A., University of Ottawa
Fox, R. O., Iowa State University
Mehrani, P., University of Ottawa
Muhle, M. E., Univation Technologies


Electrostatics are known to influence the fluidized-bed dynamics. Electrostatic charge generation in fluidized-beds is due to particle-particle, particle-wall and gas-particle contacts. In this work an electrostatic model developed (Rokkam et al., 2010) is validated using published experiments (Sowinski et al. 2010). In their study an online faraday cup method is used to quantify electrostatic charge generation in three key areas in gas-solid fluidized-beds, namely the bed particles (dropped particles), the particles that adhered to the column wall (wall particles), and particles that were entrained from the column (fines). Experiments were performed in a lab-scale fluidized-bed reactor and at two fluidization regimes: bubbling and slug flow regime. The mass, charge and particle size distribution of fines, dropped and wall particles were measured.

A multi-fluid CFD model coupled with the electrostatic model is used to predict the qualitative and quantitative trends observed in the lab-scale fluidized-bed reactor experiments. The multi-fluid model solves for one gas phase and three solid phases. The three solid phases are fine, wall and dropped particles. The mass, particle size and charge from experiments are used as an input to the coupled CFD model. Kinetic theory of granular flow and frictional theory are used for computing particle phase pressure and viscosities. Simulations predicted the height of wall coatings and particle phase segregation inside the fluidized-bed reactor.

References

Sowinski A., Miller L. and Mehrani, P., Investigation of electrostatic charge distribution in gas-solid fluidized-beds, Chemical Engineering Science, 65, 2771-2781, 2010.

Rokkam R. G., Fox R. O. and Muhle M. E., Computational fluid dynamics and electrostatic modeling of polymerization fluidized-bed reactors, Powder Technology, In press.