Process of fixed bed catalytic cracking

  • Heavy oil is heated in preheated to a temperature of about 425-4500C. the resulting vapours oil is charge is then forced through the catalytic chamber.
  • The catalytic chamber is maintained at a temperature of 425-4500C and 1-5 kg/cm2 pressure. Artificial clay mixed with zirconium oxide is used as a catalyst.
  • About 40% of the charge is converted to gasoline and 2-4 is deposited over the catalyst bed as carbon.
  • The vapours containing heavy oil as well as cracked gasoline pass into the fractionating column where heavy oil condenses.
  • The uncondensed vapour containing the cracked fraction is led to the coolers where some of the vapour condense to form uncondensed gases dissolved in gasoline.
  • Gasoline containing dissolved gases is then sent through stabilizer where dissolved gases are removed and pure gasoline is obtained.
  • After 8-10 hours of operation, the catalyst gets deactivated and has to be reactivated the catalyst tower is heated to about 5000C whereby the carbon deposited burns reactivating the catalyst.
  • The process can be converted to a continues one by having catalyst towers. While the first tower in operation the second tower is being regenerated and vice-versa.

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