Fluid Catalytic Cracking Unit (FCCU), Residue Fluid Catalytic Cracking (RFCCU) or Residue Catalytic  Cracking Unit (RCCU) is a “similar” process unit that functions as a process unit for heavy fraction of  hydrocarbon cracking into a lighter fraction with the help of finely heated catalyst granules which is driven like a liquid fluid (fluidization), in the setting of the pressure, temperature and conditions of a particular  process parameter.