Riser regenerator

Fig. 4. Quick contact reactor, concurrent downflow cracker. Modified from P. K. Niccum and D. P. Bunn, U. S. Pat. 4,514,284 (1985). 1, catalyst storage 2, recirculating pipe 3, quick contact reactor 4, steam stripper 5, riser regenerator.

Several types of FCC testing equipment are described in literature, varying from the more traditional standardized micro activity test (MAT) and fluidised bed reactors to complete riser-regenerator combinations. Also other designs such as a pulse reactor, or a very short contact time reactor have been reported in literature (7-9). 

Model I Side-by-side configuration Fast fluidized upflow riser regenerator Low pressure High elevation external cyclones Catalyst coolers Full feed pre-vaporization... 

Butane oxidation to maleic anhydride over a VPO catalyst following the riser regenerator approach... 

Du Pont has suggested to separate the two steps in space by the so called Riser-Regenerator Concept . The (fast) reaction of butane to MA is performed in a transport reactor where a narrow residence time distribution of the particles is achieved. The reoxidation of the catalyst is performed in a bubbling fluidized bed to ensure a maximum oxygen uptake. Temperatures of reaction and reoxidation can be optimized separately and no attention has to be paid to explosion limits because gas phase oxygen and butane are never fed simultaneously. 

A validation of this approach should be possible by using in situ DR (Diffuse Reflectance) Vis spectroscopy to monitor the color of the VPO under process conditions. Following Rodemerck et al., this should reflect the oxidation state of the catalyst. It is noteworthy that Golbig and Werther [9] report different colors of the VPO catalyst behind the riser (brown) and behind the regenerator (dark green) in their lab-scale riser-regenerator experiments. Preliminary experiments with high temperature (< 600°C) fiber optics show satisfactory spectral and temporal resolution. 

Golbig KC, Werther J. Selective synthesis of maleic anhydride in a riser-regenerator system. In Kwauk M, Li J, eds. Circulating Fluidized Bed Technology V. Beijing Science Press, 1996, pp 394-399. 

This approach can be conveniently used in order to enhance the efficiency in the selective oxidation of hydrocarbons hy the spatially- or time-resolved separation of the reduction and re-oxidation step of the catalyst, by the application of the riser-regenerator concept (commercially realized by DuPont for the oxidation of hutane to maleic anhydride) or by a periodic or cyclic reactor operation (Fig. 15.4). This oxidation approach should ... 

Specifically, Section 4.1 gives the motivation of this chapter. Section 4.2 describes the typical FCC process, including both riser-regenerator complex... 

Earlier work in this area has focused mostly on isolated parts (kinetic model, riser/regenerator, gas plant) of the FCC process. In this work, we show how to use routinely collected plant data with well-known commercial software tools to present an integrated process model that includes both reaction and fractionation... 

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