AN ENGINEERING MODEL FOR DILUTE RISER FLOW

To facilitate understanding of the hydrodynamic behaviour of CFBs, a o ne-dimensional model for the riser tube of a CFB has been developed. T he model describes steady state hydrodynamic key variables (i.e. cross -sectional averaged values of pressure, solids concentration and veloc ities of both phases) for developing axi-symmetrical flow as a functio n of the axial position in the riser tube. Calculated results have bee n compared with experimental data obtained from a small scale CFB unit which could be operated at pressures up to 6 bar. Despite the simplic ity of the model, it turned out that the model was capable of predicti ng the effect of changes in operating conditions (i.e. gas velocity, s olids mass flux, operating pressure and particle diameter). The model neglects the existence of clustering of particles, lateral solids segr egation and solids downflow near the tube wall, which limits the appli cability to dilute systems (epsilon(s)<0.04).