Measuring turbulence in a circulating fluidized bed using PIV techniques

This study utilized the particle image velocimetry （P1V） technique, non-invasively near the wall, in the developing region, for the measurements of laminar and turbulent properties during circulation of Geldart B type particles in the U.S. Department of Energy （DOE） National Energy Technology Laboratory （NETL） riser. A novel method was used to measure axial and radial laminar and turbulent solids dispersion coefficients using autocorrelation technique. The instantaneous and hydrodynamic velocities for the solid phase were measured simultaneously in the axial and radial directions using a CCD camera, with the help of a colored rotating transparency. The measured properties, such as laminar and Reynolds stresses, laminar and turbulent granular tempera- tures, laminar and turbulent dispersion coefficients and energy spectra exhibited anisotropy. The mixing in the riser was on the level of clusters. The total granular temperatures were in reasonable agreement with the literature values. However, the axial and radial solids dispersion coefficients measured near the wall were slightly lower than the radially averaged values in the literature.

Improving circulating fluidized bed dehydrogenation technology through optimization of fluidization

The dehydrogenation of light alkanes to corresponding light olefins is an important industrial process.The present work involved the assessment of a commercial alkane dehydrogenation circulating fluidized bed (CFB) reactor unit that had been underperforming and exhibiting higher than expected catalyst losses over a long period of time.Several aspects of this unit related to fluidization,catalysis,and process engineering were investigated to understand and resolve these issues.The primary focus was on the fluidization aspects of the process,along with a comparison of equipment design and operating conditions to accepted best practices in the industry.The designs of key equipment in the reactor and regenerator,including feed distributors,fuel gas distributors,cyclones,baffles,strippers,transfer lines,risers,riser terminations,and refractories,were studied in detail.The attrition rates of different types of catalysts used in the unit were also examined.Several recommendations and improvement opportunities were proposed to significantly increase light olefins production and reduce catalyst losses,and were accepted and implemented.This study provides insights into means of improving fluidization behavior and highlights the viability of employing a systematic approach to determine the underlying root causes of issues in a commercial CFB reactor unit.