Gas Mixing in the Reactor Section of Fluid Cokers

The gas flow structure in the reactor section of a fluid coker cold model was investigated using helium as the tracer gas. Gas residence time distributions indicate intensive gas mixing. The mean residence time from the feed nozzles decreased when the same flow of air was distributed from three rings of nozzles rather than six. When steady state measurements were carried out by injecting helium through a feed ring in the middle of the reactor section, the downstream radial profile of helium concentration formed a bell-shaped curve above the jet region near the tracer injection level and became nearly uniform with increasing height due to radial dispersion. Upstream, the helium concentration was higher in the wall region because of descending solids. The core-annulus flow structure disappeared toward the bottom of the reactor section.