The concept of a rotating chimney for rotating fluidized beds is
introduced. The rotating chimney consists of multiple blades with
openings to the chimney in between them and rotates in the same
sense as the particle bed, but at rotational speeds higher than the
average particle bed rotational speed. As such, the rotating chimney
increases locally, in the immediate vicinity of the chimney, the
centrifugal force. This makes it more difficult for the particles to be
entrained by the gas into the chimney.
Experimental measurements with 1G-Geldart B particles at given
solids loading and fluidization gas flow rate show a significant
reduction of the rate of solids losses via the chimney with increasing
chimney rotational speed. Consequently, for given solids feeding and
fluidization gas flow rates, increasing chimney rotational speeds allow
operating rotating fluidized beds at higher solids loadings. At
sufficiently high solids loadings, the particle bed freeboard approaches
the rotating chimney which then allows to increase the particle bed
density, the rotating chimney essentially acting as a compressor on the
particle bed. The densification of the particle bed at higher solids
loadings is reflected in a non-linear increase of the particle bed
pressure drop with increasing solids loading.
By increasing the particle bed density and solids loading in the
fluidization chamber, bubbling can be suppressed, allowing to obtain
quite uniform rotating fluidized beds of 1G-Geldart B particles over a
wide range of particle bed rotational speeds.