Fluid Catalytic Cracking (FCC)
Fluid Catalytic Cracking Units (FCCUs) are used to break, or crack, large hydrocarbon chains into smaller chains, which are suitable for use in gasoline blending. FCC is the most common catalytic cracking process and involves a catalyst section and a fractionation section.
How FCCUs Work
A fine, powder-like catalyst is fluidized by oil vapors, air, and steam, and is continuously circulated in the reactor and regenerator using standpipes and risers. To crack the oil, preheated hydrocarbons are mixed with hot, freshly regenerated catalysts entering the riser that leads to the reactor. Combined with a recycle stream in the riser, the process stream is vaporized and heated by the catalyst. The mixture travels up the riser where it is eventually cracked at pressures between 10-30 psi. Modern fluid catalytic cracking units (FCCU) crack the oil solely in the riser, and rely on the reactor as a cyclone holding vessel. Cyclones in the reactor are used to separate the cracked oil vapors from the catalyst, creating a product stream that can be separated into fractions when it is charged to a fractionation, or distillation, column. Residual heavy oil that did not crack is recycled back to the riser to undergo the process another time. A catalyst stripper is used to separate the catalyst from the process stream so that it can be regenerated. The catalyst regenerator will remove coke that formed during the cracking process. Spent catalyst is removed and fresh catalyst is mixed with regenerated catalyst to allow the process to continue with optimize results.