Page 23 - Fluid Catalytic Cracking Handbook

Process Description

Vent to Main Column

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Slurry

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Feed Preheater

Figure 1-5. Typical feed preheat system.

increasing preheat temperature allows increased throughput. The effects
of feed preheat are discussed in Chapter 6.

RISER—REACTOR—STRIPPER

The reactor-regenerator is the heart of the FCC process. In a modern
cat cracker, virtually all the reactions occur in 1.5 to 3.0 seconds
before the catalyst and the products are separated in the reactor.
From the preheater, the feed enters the riser near the base where it
contacts the regenerated catalyst (see Figure 1-6). The ratio of catalyst-
to-oil is normally in the range of 4:1 to 9:1 by weight. The heat
absorbed by the catalyst in the regenerator provides the energy to heat
the feed to its desired reactor temperature. The heat of the reaction
occurring in the riser is endothermic (i.e., it requires energy input). The
circulating catalyst provides this energy. The typical regenerated catalyst
temperature ranges between 1,250°F to 1,350°F (677°C to 732°C).