II International Symposium on Carbon for Catalysis ABSTRACTS

STABILITY OF A CARBON CATALYST FLUIDIZED BED
PP-<strong>II</strong>-10
Isakov V.P., Vlasov N.M., Zaznoba V.A.
FSUE SRI SIA Luch, Podolsk
e-mail: dvp@luch.podolsk.ru
Maximum heat and mass transfer of catalytic apparatuses can be provide in a fluidizedbed
(FB) reactor with carbon spherical particles. Efficiency of a FB reactor (level of
conversion) is increased with increasing of FB height. At the same time, in process of FB
height increase (and differential pressure), FB itself becomes unstable and undergoes
sequentially the following perturbations: spouting, formation of bubbles of Davidson, "piston"
boiling [1].
This work is intended to analyse a stability of catalytic FB reactor, to give
recommendations how to increase stability when FB height is increased and to check
recommendations in experiments with glass models of FB reactors with pyrocarbon catalyst
particles 600 µm in diameter. The glass reactor consists of a feeding tube, conic diffuser and
cylinder with internal diameter 30 mm. Argon was used as fluidizing gas.
The investigations of FB instability, which has been carried out on glass models, have
shown that when the fluidization rate is 0.5-2.0 km/s (Reynolds number of a flow (Re)
130-520, respectively) catalyst particles oscillate under action of turbulent pulsations which
intensity is maximum in a FB bottom area (transition from cone to cylinder). The amplitude
and frequency of the catalyst particles fluctuations in the top area of FB measured with use of
a movie camera were 5 mm and 2 Hz, respectively.
Occurrence of turbulence in the interval of Reynolds numbers when their values is
significantly less than 2100-2300 (transition of laminar mode in turbulent in a cylindrical
pipe) is explained by the gas rate jump in the cylindrical reactor entrance providing
occurrence of turbulence at Re = 81,49 (Orr-Zommerfeld task [2]). If a catalysis process
temperature is 300-600ºС then additional rate jump is observed due to expansion of gas,
therefore bottom area of FB is located in an area of transition from cone to cylinder due to the
maximum turbulence of gas that corresponds to the maximum front of its flowing.
As gas movement is in progress along height of a chemical reactor, stabilization of its
temperature, rate hold and composition occurs, the scale of turbulent pulsations decreases,
and the flat front of flow becomes parabolic (Gagen-Poiseuille flow in a cylindrical pipe [2]).
243