Fluid Catalytic Cracking
Fluid Catalytic Cracking (FCC) is the most important material conversion process in the oil processing industry and is used by some 400 refineries worldwide. In particular, heavy residues from vacuum distillation are processed and brought into contact with fluidised, solid catalyst material. There are different designs, but as a rule the plant consists of two fluidised bed reactors. In addition to the actual cracker, which is often designed as a riser reactor, the catalyst used must be treated and conditioned in a second reactor, the so-called regenerator (see figure).
Main products of the FCC process are naphtha fractions, which are mainly used for the production of gasoline and other fuels. In addition, gaseous products are formed from which liquefied petroleum gas (LPG) is recovered after separation of unsaturated hydrocarbons.
Since the catalyst cools during the cracking process, it must be removed cyclically and brought back up to the required temperature of about 700 °C. In addition, coke forms during the cracking reactions and settles on the catalyst surface quickly deactivating it. The catalyst thus needs to be regenerated. For this it is brought into contact with blown-in air in the regenerator at temperatures of 600 - 700 °C where the adherent coke is burned off.
Using oxygen-enriched air for this process can increase the efficiency of the coke burn off and thus increase the capacity of the regenerator. The use of oxygen in the regenerator has the following advantages compared to pure air operation:
- Possibility to increase capacity
- Processing of cheaper crude oil qualities
- Greater flexibility in operation