Catalytic Cracking - RFCC
A Residue FCC (RFCC) unit expands the versatility and profitability of an FCC to crack a wider variety of feedstock:
- Traditional FCC feedstocks
- Deeply Deasphalted Oil
- Atmospheric Residue
- Vacuum Residue
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 often advantageous to either partially or fully hydrotreat the feedstock to improve the hydrogen content and reduce the level of contaminants.
When processing residues containing high levels of metals (Ni, V and Na) and ConC values of 3-10 wt%, more sophisticated FCC designs are required. The reaction section will be designed to inject and efficiently crack heavier molecules. The regenerator section is designed to burn more coke, minimize catalyst deactivation in the presence of high metals loading on the catalyst, and control the heat balance by using a two-stage regenerator design (R2R).
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 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 of particularly interest currently and the several solutions to increase propylene production have been developed in a dedicated section.
For expanded product flexibility, the RFCC unit can be integrated with upstream units such as resid hydrotreating/ 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.