(83f) CREC-GS-Optiprobe for Measuring Radial Distribution of Clusters in a Downer Reactor

It has been well recognized that particles in downer reactors tend to aggregate into clusters. Therefore, understanding and predicting of cluster velocity and size is one of the fundamental needs for the hydrodynamics of gas-solid flow in such a kind of fluidized bed, especially when the catalyst residence time is a very important issue. With the potentially increasing industrial use of these reactors, the need for accurate local measurement techniques has become apparent. Reflective-type (back scattering) fiber-optic sensors are one of the most effective methods for measuring local particle properties.

The major drawbacks of back scattering fiber-optic sensors are short focal distance, distortion of flow stream due to probe intrusion, low light intensity of the captured reflected light by the receiver fibers and infinite measurement volumes from which the probes collect reflections. By integrating a GRIN lens in a novel and precisely designed CREC-GS-Optiprobe most of these shortcomings were surmounted. More reliable and enhanced results were obtained using this technique.

The radial profiles of local cluster velocities as well as cluster sizes are reported in this paper. The experiment was done in a 2.5 cm downer unit. The operating conditions of the present study were set according to a combination of independent variables such as gas volumetric flow rate and solid mass flux. The gas velocities and solid circulation rates were varied from 0.54 (m/s) to 3.1 (m/s) and from 3 (kg/m²s) to 108 (kg/m²s).