A Model of Naphtha Reforming in a Radial Flow Moving Bed Reactor

Catalytic reforming of naphtha is widely practiced in the petroleum industry to
produce aromatics. Latest technology utilizes novel radial flow moving bed reactors
for the reforming process as well as regeneration of the slowly decaying catalyst.
Catalyst circulation between the reformer and regeneration units makes continuous
operation of reformer-regenerator unit possible. In spite of their extensive use, very
little is known about the performance of radial flow moving bed reformer unit.
The radial flow moving bed reformer consists of four reactor units (R1, R2, RJ
and~) stacked one on top of the other with catalyst flowing downward by gravity as
a moving bed. In each reactor unit the catalyst flows downwards through an annulus
with reactants flowing radially inwards through the moving bed of the catalyst. The
reactants flow through the four units in series and are preheated before entering each
unit. Temperature of the product stream exiting each unit is lower as the reactor is
adiabatic and reactions are net endothermic.
A one dimensional compartment in series multiphase catalytic reactor model
considering the catalyst deactivation is developed to explain the performance of a
radial flow moving bed reformer. The model estimates on the trends of temperature
and composition profiles are in reasonable agreement with the limited industrial
information available. The model is used to simulate various scenarios to identify
possible strategies to improve productivity of aromatics. Feeding the fresh feed in R1
and RJ and recovers the products at R2 and ~ is much better than feeding the fresh
feed in R1 and recovers the products in ~-
Simple models to account for pinning and rate of breakage of catalyst particles
are proposed.