Catalytic Cracking - FCC
An FCC unit is a versatile process for the catalytic conversion of a wide range of feedstock:
- Heavy Gas oil,
- Vacuum Gas oil,
- Hydrocracker Unconverted Oil,
- Heavy Coker Gas oil,
- Residue Hydrocracker Gas oil,
- Deasphalted Oil,
- Some Residue (Atmospheric or Vacuum).
The quality of the feed is the main determinant of the yields and product properties. The yield of valuable gasoline and LPG products in the FCC unit will be mainly influenced by the hydrogen content of the feed. Feed contaminants such as sulfur, nitrogen, Conradson Carbon Residue (ConC) and metals also impact the yield and/or product quality. As a result it is increasingly common to either partially or fully hydrotreat the feedstock to improve the hydrogen content and reduce the level of contaminants.
The reaction system is the heart of the process and is defined from the point of catalyst contacting finely atomized feedstock in the reactor-riser, to the catalyst separation system from which product gases are conveyed to the recovery system and spent catalyst is discharged into a stripping zone.
The entire system needs to be designed to work in concert to meet the desired performance objectives:
- Maximum Distillate (low severity)
- Maximum Gasoline
- Maximum Gasoline x Octane number or "Octane-Barrels"
- Maximum LPG and Gasoline or "High Propylene"
- Maximum Propylene
- Maximum Distillate & LPG
During project definition, different modes of operation should be investigated in order to meet current objectives and maintain the flexibility to adapt to market changes or objectives. The high or maximum propylene mode of operation is currently of particular interest and the several solutions to increase propylene production have been developed in a dedicated section.
For expanded product flexibility, the FCC unit can be integrated with upstream units such as Mild Hydrocracking to balance the gasoline and distillate products, or downstream units such as Polynaphtha (FlexEne™ concept) in order to offer higher flexibility toward targeted products (Gasoline, Diesel or Propylene).
Axens provides licensed grassroots designs as well as existing unit revamp services and supply of associated proprietary equipment.