Fluid catalytic cracking data processing

Table 6.7.2 Data on chemical media and reaction conditions ofthe fluid catalytic cracking (FCC) process.

The scale-up and design configurations of fluid-bed chemical reactors have evolved rapidly and empirically. An example is fluid catalytic cracking (FCC) [13]. The general fluid-bed concepts developed early. However, the correlations describing the various rate processes and other operational phenomena developed slowly because they could not easily be related back to already established data bases developed for other systems in the case of trickle-bed reactors, data developed for packed-bed absorption towers were utilized. 

The catalysts used in Fluid Catalytic Cracking (FCC) are reversibly deactivated by the deposition of coke. Results obtained in a laboratory scale entrained flow reactor with a hydrowax feedstock show that coke formation mainly takes place within a time frame of milliseconds. In the same time interval conversions of 30-50% are found. After this initial coke formation, only at higher catalyst-to-oil ratios some additional coke formation was observed. In order to model the whole process properly, the coke deposition and catalyst deactivation have to be divided in an initial process (typically within 0.15 s) and a process at a larger time scale. When the initial effects were excluded from the modeling, the measured data could be described satisfactory with a constant catalytic activity. 

Among the five modes of OCE reactor operation quoted by ARCO, the one with two-fluid-beds was chosen for all studies except one because its operation, which is similar to a FCC (Fluid Catalytic Cracking) operation, was judged to be most practical. Unfortunately, no process data of this mode are available in the public domain. For this study, the conversion and selectivity of a cyclic fixed-bed mode were adopted for this mode. 

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