Process for high severity catalytic cracking of crude oil
In an FCC process and system, a whole crude oil feedstock is directly converted into light olefins and other products. The feed is separated into a high boiling fraction and a low boiling fraction, and each fraction is processed in separate FCC downflow reactors. The catalyst, combined from both downflow reactors, is regenerated in a common vessel. The low carbon content in the catalyst particles from the low boiling fraction downflow reactor is insufficient to provide the necessary heat. By combining catalyst particles from the high boiling fraction having high carbon content helps to provide additional heat for regeneration.
1. A method for processing a crude oil feedstock having total metals (Ni+V) content of less than 5 ppm and Conradson carbon residue of less than 5 wt % comprising:
fractionating the feedstock into a low boiling fraction and a high boiling fraction, wherein fractionating is conducted in a range temperature conducive to produce the high boiling fraction having less than 10 wt % Conradson Carbon and less than 10 ppm total metals;
cracking the low boiling fraction in a first downflow reaction zone of a fluid catalytic cracking unit in the presence of a predetermined amount of catalyst to produce a first cracked product stream and spent catalyst;
cracking the high boiling fraction in a second downflow reaction zone of the fluid catalytic cracking unit in the presence of a predetermined amount of catalyst to produce a second cracked product stream and spent catalyst;
wherein each of the first and second downflow reaction zones includes a mixing zone, a separation zone and a catalyst-stripping zone,
and
regenerating spent catalyst from both the first and second downflow reaction zones in a common regeneration zone and recycling the regenerated catalyst back to the first and second downflow reaction zones; and
recovering the first and second cracked product streams,
wherein heat formed by combustion of coke formed on catalyst particles having increased coke formation from the high boiling fraction reaction zone overcomes limitations associated with reduced coke formation on catalyst particles from the low boiling fraction reaction zone.
2. The process of claim 1 , wherein the catalyst-oil ratio in the first downflow reaction zone is in the range of 20:1 to 60:1.
3. The process of claim 1 , wherein the catalyst-oil ratio in the second downflow reactor is in the range of 20:1 to 40:1.
4. The process of claim 1 , wherein the temperature in the first downflow reaction zone is in the range of 500° C. to 704° C.
5. The process of claim 1 , wherein the temperature in the first downflow reaction zone is in the range of 550° C. to 700° C.
6. The process of claim 1 , wherein the temperature in the second downflow reaction zone is in the range of 500° C. to 704° C.
7. The process of claim 1 , wherein the temperature in the second downflow reaction zone is in the range of 500° C. to 650° C.
8. The process of claim 1 , wherein the residence time in the first downflow reaction zone is in the range of 0.2 s to 5 s.
9. The process of claim 1 , wherein the residence time in the second downflow reaction zone is in the range of 0.2 s to 2 s.
10. The process of claim 1 , further comprising separating cycle oil and/or slurry oil from the recovered first and second cracked product streams.
11. The process of claim 10 , wherein a portion of separated cycle oil and/or slurry oil is recycled to the first downflow reaction zone.