Precise gamma ray measurement of the radial distribution of a cracking catalyst at diluted concentrations in a glass riser

The radial concentration distribution of a cracking catalyst circulating in a glass riser of a cold model was precisely measured in diluted flow regime. Catalyst and compressed air were the components of the fluidized bed system. The gamma transmission measurements were carried out with a 241Am radioactive source and a scintillation NaI(Tl) detector. The gamma ray transmission profile of riser was evaluated and the main effects were identified. The standard uncertainty in the concentration values was evaluated as a function of the photopeak counts. A model was proposed to describe the profile curve of the empty riser as a function of the chordal length that fits experimental data adequately. A calibration of catalyst density carried out in static experiments and an integral evaluation of the radial scan were compared with punctual density. Under flow conditions the radial concentration distribution was measured at (2–16) kg/m3 and at (10–60) kg/m3 intervals. At two different airflow rates, concentration distribution tendency to move from the annular to the core region in the higher airflow, was observed.