(696c) Three Dimensional Simulation of Catalytic Cracking Reaction in an Industrial Scale Riser Using a 10-Lump Kinetic Model

Three
Dimensional Simulation of Catalytic Cracking Reactions
in an Industrial Scale Riser Using a 10-lump Kinetic Model

            Fluid Catalytic Cracking (FCC) is
one of the most important processes in the oil refinery. It converts heavy
hydrocarbon petroleum fractions into more usable products such as gasoline,
middle distillates, and light olefins. A FCC unit is composed basically by a
riser reactor, strippers, cyclones and a regenerator. As it is one of the most
profitable operations in a petroleum refining industry, several
researchers have been focused their works on developing mathematical models
that can predict the behavior of this process.

            In this context, the application of
the computational fluid dynamics (CFD) has assumed an important role in the
study of the FCC process. Using appropriate mathematical models, the CFD tools
allow the prediction of properties, such as velocity, temperature and
concentration of the species. In addition it can also reduce enormously the
time-consuming by computational resources and the cost spent for the
improvement of the process and in the development of new projects.

             Many kinetic models have been proposed for the
representation of the cracking reactions that occurs
in the riser reactor. Due to the complexity of the reaction mechanisms and the
large number of chemical species involved in the cracking process, these
species are often grouped into lump, according to their boiling point and/or
molecular characteristics (paraffins, olefins, naphthenic
and aromatics). One of the most widely used lumping models is the ten-lump
model proposed by JACOB et al., 1976 (BARAJAS et al., 2009). By dividing the
feed in five volatile components, it can be used for different charge stocks.
The important characteristic of this model relies on the fact that the feed
composition affects the yield and quality of the gasoline formed during the
process. As shown in the study carried out by CERQUEIRA et al. (1997), for
example, paraffinic and naphthenic feedstock yields more gasoline. On the other
hand, the aromatic feed is the main specie responsible for the formation of
coke.

            The present study applies the
ten-lump kinetic model proposed by JACOB et al. (1976) in the simulation of the
catalytic cracking reactions in an industrial riser reactor.  A three-dimensional model was used to predict
the dynamic behavior inside the riser reactor.

            The results were validated with a
set of plant data and compared with the results obtained by LOPES et al.
(2011), which applied a simplified four-lump kinetic model to simulate the
process in a similar industrial reactor. The use of different feedstock
compositions with ten-lump model showed a more accurate result for the gasoline
yield. Furthermore, it was observed in this study that the influence of
geometric configurations on the flow can drastically affect the reaction
yields.