The CREC-GS-Optiprobes and its focal region: Gas–solid flow measurements in down flow reactors

The Chemical Reactor Engineering Center – Gas Solid – Optiprobes (CREC-GS-Optiprobe) can be used to determine particle cluster properties in down flow reactors. These properties include solid hold-up, cluster size and cluster velocity. Critical to this task is the determination of the “focal region”. It is established in this study that the CREC-GS Optiprobes display an “effective focal region” smaller than the focal region calculated using geometrical and optical considerations. In this respect, an “effective focal region” of 118 μm with a standard deviation of 34 μm is established on the basis of different considerations including experimental observations. The existence of this “effective focal region” is most valuable in downer units given it makes the CREC-Optiprobe a suitable tool for measurements of clusters sizes with an average diameter of 84 μm FCC particles as well as local solid concentration.