FCC riser reactor

Although this test clearly had its advantages, the deviation from actual FCC riser reactor operating conditions still remained too large as illustrated in figure 1 ... 

Fluidized bed catalytic cracking (FCC) Riser reactor fast-fluidized bed regime... 

Ranade, V.V. (1999), Modelling of gas-solid flows in FCC riser reactor fully developed flow, 2nd International Conference on CFD, Melbourne. 

Theologos et al. [1997] used the Eulerian-Eulerian gas-solid flow model and the 10-lump kinetic model of Jacob et al. [1976] to carry out 3D simulations of FCC riser reactors. Extensions of the flow model to account for the details of the feed atomization were studied by Theologos et al. [1999] and by Simonin and co-workers [Saulnier et al., 2005]. 

Figure 2. Model Components for Aspen FCC (Riser/Reactor/Regenerator)...

The basic problem lies in the fact that in the MAT unit the catalyst remains fixed while in a FCC riser reactor the catalyst moves along with the hydrocarbon vapours. Mott (1987) describes this in terms of the number of active sites. In the MAT unit the number of active sites is fixed while in real operation the number of active sites delivered to the riser per unit of feed is dynamic and will change according to the heat requirements and the combined coke-making tendencies of the feed and catalyst. Thus, the most effective FCC catalyst should be determined by the number of active sites it can bring to the reactor per mass of feed which may not necessarily be the catalyst with the highest MAT activity (Mott, 1987). 

The results described in this review demonstrate the importance of novel tools for kinetic modelling and catalyst development. In this context it is proposed to adopt the Riser Simulator to effectively represent the catalytic cracking reactions which take place in a FCC riser reactor. The technique allows for similar conditions to be used such as temperature, catalyst to oil ratio, partial pressure of hydrocarbons, solids loading and reaction time as those used in commercial units. Moreover, the contacting of the hydrocarbons with the catalyst is more representative of riser cracking where the catalyst moves in time with the vapours, than that achieved in the MAT test. 

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