A single, sharp peak with low solids holdup existed in
the central region of the conventional CFB riser.
The low solid holdup peak disappeared
and a relatively wider peak
with higher solid holdup appeared in a radial position near the wall.
The variation in radial position of the probability peak in a cross section shows the segregation of gas phase from the solids phase
(gas tends to pass through the center and solids tend to aggregate at the wall), leading to a low gas–solids contact efficiency