Optical fiber probes for the measurement of local solids concentration
must be accurately calibrated with defined limits and, in such a way,
optimized for the flow densities to be measured. In this study, a mul
ti-fiber optical reflection probe was uniquely calibrated in a downer
to obtain quantitatively precise solids holdup. An iteration procedure
was utilized to modify the initial calibration curves, which was veri
fied both theoretically and practically. Calibrations using two differ
ent batches of FCC particles, with different carbon contents, indicate
that these probes are sensitive to minor variations of particle colou
r and reflective properties; however, the characteristic shape of the
calibration curves remains unchanged and a simple linear relationship
exists between the curves from different batches of FCC particles. (C)
1998 Elsevier Science S.A. All rights reserved.