(70a) Riser Dynamics –  a Comparison of Scale

Risers in gas-solids circulating systems are used extensively in the petrochemical and energy industries as well as being proposed for advanced technologies from chemical looping combustion/gasification. The performance of these units has been linked to the meso-scale and the dynamic behavior of the flow field. New experimental data has been obtained in a 0.1 m diameter riser with a 5.3 m height. The particle is an 850 µm high density polyethylene with a density of 860 kg/m². Experiments were conducted primarily in the core-annular regime. In addition to standard differential pressure measurements along the riser, three-dimensional measurements of the solids volume fraction were obtained using a Tech4Image Electrical Capacitance Volume Tomography (ECVT) system. The dynamic structure of the riser solids fraction is obtained by analyzing the time series data for each voxel in the flow field. Specifically, the data were analyzed using higher level statistics (skewness and kurtosis) as well as chaotic correlation dimension and the entropy. These values are compared with published ECVT data using the same material from a 0.3 m diameter riser with a 16 m height. The effect of system scale is analyzed and discussed.