Claims
- 1. In a delayed coking process carried out in a coker unit comprised of a coker furnace, a coke drum and a coker fractionator, wherein coker feedstock and recycle material are heated to coking temperature in said furnace and then passed to said coke drum where coke and overhead vapors are formed, wherein said overhead vapors are passed to said fractionator, wherein a portion of said overhead vapors are condensed and combined with said feedstock as heavy recycle, wherein the amount of said overhead vapors condensed is sufficient to provide good fractionator operation and sufficient to provide enough heavy recycle to effectively prevent coke formation on the tubes of said furnace, and wherein the coke yield is higher than is desired, the improvement comprising:
- operating with an amount of heavy recycle that is not sufficient to effectively prevent coke formation on the furnace tubes, and adding to said feedstock as additional recycle a distillate hydrocarbon material having a boiling range which is at least in part lower than the boiling range of said heavy recycle, said distillate hydrocarbon material being added in an amount which, when combined with said heavy recycle, is effective to prevent coke formation on the tubes of said furnace, whereby coke formation on the tubes of said furnace is effectively prevented, the yield of liquid products from the process is increased, and the coke yield from the process is decreased.
- 2. The process of claim 1 wherein said distillate hydrocarbon material is recovered from a coker fractionator, combined with said coker feedstock and fed to the bottom of said coker fractionator.
- 3. The process of claim 1 wherein said distillate hydrocarbon material has a boiling range between about 335.degree. and about 850.degree. F.
- 4. The process of claim 1 wherein said distillate hydrocarbon material has a boiling range between 450.degree. and about 750.degree. F.
- 5. The process of claim 1 wherein said distillate hydrocarbon material has a boiling range between about 510.degree. and about 650.degree. F.
- 6. The process of claim 1 wherein the amount of said distillate hydrocarbon material added is from about 1.0 to about 5.0 times the amount of heavy recycle used.
- 7. The process of claim 6 wherein heavy coker gas oil is used to quench coke drum vapors between the coke drum and the fractionator and to condense coke drum vapors and remove entrained material entering said fractionator, and the combined amount of said heavy gas oil used is sufficient to generate from about 5 to about 15 parts of heavy recycle for each 100 parts of fresh coker feed.
- 8. The process of claim 7 wherein the amount of said distillate hydrocarbon material added is from about 15 to about 30 parts for each 100 parts of fresh coker feed.
- 9. The process of claim 8 wherein said coker feedstock is a resid having an API gravity of less than 10 and a sulfur content of more than 2.0 percent by weight.
- 10. In a delayed coking process carried out in a coker unit comprised of a coker furnace, a coke drum and a coker fractionator, wherein coker feedstock and recycle material are heated to coking temperature in said furnace and then passed to said coke drum where coke and overhead vapors are formed, wherein said overhead vapors are passed to said fractionator, wherein a portion of said overhead vapors are condensed and combined with said feedstock as heavy recycle, wherein the amount of said overhead vapors condensed is sufficient to provide good fractionator operation and sufficient to provide enough heavy recycle to effectively prevent coke formation on the tubes of said furnace, and wherein the coke yield is higher than is desired, the improvement comprising:
- operating with an amount of heavy recycle that is not sufficient to effectively prevent coke formation on the furnace tubes, said amount of heavy recycle being at least partially generated by contact of said overhead vapors with heavy gas oil which has been previously withdrawn from said fractionator, and adding to said feedstock as additional recycle a distillate hydrocarbon material having a boiling range which is at least in part lower than the boiling range of said heavy recycle, said distillate hydrocarbon material being added in an amount which, when combined with said heavy recycle, is effective to prevent coke formation on the tubes of said furnace, whereby coke formation on the tubes of said furnace is effectively prevented, the yield of liquid products from the process is increased, and the coke yield from the process is decreased.
- 11. The process of claim 10 wherein said distillate hydrocarbon material is recovered from a coker fractionator, combined with said coker feedstock and fed to the bottom of said coker fractionator.
- 12. The process of claim 10 wherein said distillate hydrocarbon material has a boiling range between about 335.degree. and about 850.degree. F.
- 13. The process of claim 10 wherein said distillate hydrocarbon material has a boiling range between about 450.degree. and about 750.degree. F.
- 14. The process of claim 10 wherein said distillate hydrocarbon material has a boiling range between about 510.degree. and about 650.degree. F.
- 15. The process of claim 10 wherein the amount of said distillate hydrocarbon material added is from about 1.0 to about 5.0 times the amount of heavy recycle used.
- 16. The process of claim 15 wherein heavy coker gas oil is used to quench coke drum vapors between the coke and the fractionator and to condense coke drum vapors and remove entrained material entering said fractionator, and the combined amount of said heavy gas oil used is sufficient to generate from about 5 to about 15 parts of heavy recycle for each 100 parts of fresh coker feed.
- 17. The process of claim 16 wherein the amount of said distillate hydrocarbon material added is from about 15 to about 30 parts for each 100 parts of fresh coker feed.
- 18. The process of claim 17 wherein said coker feedstock is a resid having an API gravity of less than 10 and a sulfur content of more than 2.0 percent by weight.
- 19. In a delayed coking process carried out in a coker unit comprised of a coker furnace, a coke drum and a coker fractionator, wherein coker feedstock and recycle material are heated to coking temperature in said furnace and then passed to said coke drum where coke and overhead vapors are formed, wherein said overhead vapors are passed to said fractionator, wherein a portion of said overhead vapors are condensed and combined with said feedstock as heavy recycle, wherein the amount of said overhead vapors condensed is sufficient to provide good fractionator operation and sufficient to provide enough heavy recycle to effectively prevent coke formation on the tubes of said furnace, and wherein the coke yield is higher than is desired, the improvement comprising:
- operating with an amount of heavy recycle that is not sufficient to effectively prevent coke formation on the furnace tubes, and adding to said feedstock as additional recycle a distillate hydrocarbon material recovered from said fractionator above the heavy gas oil draw, said distillate hydrocarbon material being added in an amount which, when combined with said heavy recycle, is effective to prevent coke formation on the tubes of said furnace, whereby coke formation on the tubes of said furnace is effectively prevented, the yield of liquid products from the process is increased, and the coke yield from the process is decreased.
- 20. The process of claim 19 wherein said distillate hydrocarbon material has a boiling range between about 335.degree. and about 850.degree. F.
- 21. The process of claim 19 wherein said distillate hydrocarbon material has a boiling range between about 450.degree. and about 750.degree. F.
- 22. The process of claim 19 wherein said distillate hydrocarbon material has a boiling range between about 510.degree. and about 650.degree. F.
- 23. The process of claim 19 wherein the amount of said distillate hydrocarbon material added is from about 1.0 to about 5.0 times the amount of heavy recycle used.
- 24. The process of claim 23 wherein heavy coker gas oil is used to quench coke drum vapors between the coke drum and the fractionator and to condense coke drum vapors and remove entrained material entering said fractionator, and the combined amount of said heavy gas oil used is sufficient to generate from about 5 to about 15 parts of heavy recycle for each 100 parts of fresh coker feed.
- 25. The process of claim 24 wherein the amount of said distillate hydrocarbon material added is from about 15 to about 30 parts for each 100 parts of fresh coker feed.
- 26. The process of claim 25 wherein said coker feedstock is a resid having an API gravity of less than 10 and a sulfur content of more than 2.0 percent by weight.
- 27. In a delayed coking process carried out in a coker unit comprised of a coker furnace, a coke drum and a coker fractionator, wherein coker feedstock, which from the time it leaves its source unit until it reaches said coker unit, including any intermediate storage time, by virtue of its composition or its temperature or a combination thereof always has a viscosity such that it can be readily pumped without the necessity of adding diluent to maintain pumpability, is combined with recycle material and heated to coking temperature in said furnace and then passed to said coke drum where coke and overhead vapors are formed, wherein said overhead vapors are passed to said fractionator, wherein a portion of said overhead vapors are condensed and combined with said feedstock as heavy recycle, wherein the amount of said overhead vapors condensed is sufficient to provide good fractionator operation and sufficient to provide enough heavy recycle to effectively prevent coke formation on the tubes of said furnace, and wherein the coke yield is higher than is desired, the improvement comprising:
- operating with an amount of heavy recycle that is not sufficient to effectively prevent coke formation on the furnace tubes, said amount of heavy recycle being at least partially generated by contact of said overhead vapors with heavy gas oil which has been previously withdrawn from said fractionator, and adding to said feedstock as additional recycle a distillate hydrocarbon material recovered from said fractionator above the heavy gas oil draw, said distillate hydrocarbon material being added in an amount which, when combined with said heavy recycle, is effective to prevent coke formation on the tubes of said furnace, whereby coke formation on the tubes of said furnace is effectively prevented, the yield of liquid products from the process is increased, and the coke yield from the process is decreased.
- 28. The process of claim 27 wherein said distillate hydrocarbon material has a boiling range between about 335.degree. and about 850.degree. F.
- 29. The process of claim 27 wherein said distillate hydrocarbon material has a boiling range between about 450.degree. and about 750.degree. F.
- 30. The process of claim 27 wherein said distillate hydrocarbon material has a boiling range between about 510.degree. and about 650.degree. F.
- 31. The process of claim 27 wherein the amount of said distillate hydrocarbon material added is from about 1.0 to about 5.0 times the amount of heavy recycle used.
- 32. The process of claim 31 wherein heavy coker gas oil is used to quench coke drum vapors between the coke drum and the fractionator and to condense coke drum vapors and remove entrained material entering said fractionator, and the combined amount of said heavy gas oil used is sufficient to generate from about 5 to about 15 parts of heavy recycle for each 100 parts of fresh coker feed.
- 33. The process of claim 32 wherein the amount of said distillate hydrocarbon material added is from about 15 to about 30 parts for each 100 parts of fresh coker feed.
- 34. The process of claim 33 wherein said coker feedstock is a resid having an API gravity of less than 10 and a sulfur content of more than 2.0 percent by weight.
RELATED APPLICATION
This application is a continuation-in-part of co-pending application Ser. No. 353,671, filed Mar. 1, 1982, now abandoned.
US Referenced Citations (10)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
353671 |
Mar 1982 |
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