Claims
- 1. A process for the conversion of petroleum hydrocarbons in the presence of catalyst particles in a fluidized phase in an essentially upflow or downflow tubular reaction zone, said process comprising the steps of:
- steam cracking of a light feedstock having at least one fraction of light hydrocarbons, including at least ethane or propane, in a first, upstream portion of said reaction zone, said steam cracking being carried out by contacting the light hydrocarbons and a quantity of steam equal to at least 20 percent by weight of the quantity of said light hydrocarbons in a fluidized bed of the catalyst particles, the temperature resulting from such contacting ranging from 650.degree. to 850.degree. C. and whereby said contacting results in a hydrocarbon-containing effluent from said first portion which contains olefins including ethylene or propylene, and, said olefins are obtained in excess of alkanes present in the light feedstock;
- atomizing and injecting a heavy feedstock of at least one fraction of heavy hydrocarbons in a second portion of the reaction zone into the effluents from the first, upstream steam-cracking portion of said reaction zone, which effluents include the fluidized catalyst particles, in such a way that the temperature of the resulting mixture ranges from 560.degree. to 650.degree. C. and wherein said temperature on contact is sufficient to vaporize the heavy feedstock;
- immediately downstream of the injection and vaporization of said heavy feedstock in the second portion of the reaction zone, atomizing and injecting into the effluents from said second portion of the reaction zone in a third portion of the reaction zone a hydrocarbon fraction that is completely vaporizable under conditions existing at the exit of the reaction zone so as rapidly to reduce the temperature of the resulting mixture to a more effective catalytic cracking temperature ranging from 475.degree. to 550.degree. C. in the resulting third downstream portion of said reaction zone;
- thereafter, catalytically cracking at least said vaporized heavy hydrocarbons in said third, downstream portion of said reaction zone;
- ballistically separating spent catalyst particles emanating from said third, downstream catalytic cracking portion of said reaction zone;
- regenerating of the separated catalyst particles in at least one zone for combustion of the coke deposited on such particles; and
- recycling the regenerated particles to the intake of the first, upstream cracking portion of said reaction zone.
- 2. A process as defined in claim 1, wherein the light hydrocarbon fractions fed to the first upstream steam-cracking portion of the reaction zone include in addition to ethane or propane, at least one fraction introduced in a downstream part of the first portion and selected from the group consisting of saturated light gases other than the ethane or propane, gasolines, naphthas, gas oils, and middle distillates, wherein said middle distillates are predominantly hydrocarbons having carbon numbers predominantly in the range of C9 to C20 and boiling in the range of approximately 150.degree. C. to 400.degree. C.
- 3. A process as defined in claim 2, wherein the light hydrocarbons are injected successively from upstream to downstream in the steam cracking portion of the reaction zone in the order of increasing boiling points, the lightest fraction being introduced into the hottest zone.
- 4. A process as defined in claim 1, wherein the steam cracking is carried out by contacting the light hydrocarbons and a quantity of steam equal to from 30 to 50 percent by weight of the quantity of light hydrocarbons in a fluidized bed of the catalyst particles.
- 5. A process as defined in claim 1, wherein the heavy feedstock fed to the downstream catalytic cracking portion of the reaction zone includes an atmospheric-residue or a vacuum-residue of which at least 20 percent by weight have a boiling point above 550.degree. C.
- 6. A process as defined in claim 1, wherein the hydrocarbons atomized immediately downstream of the injection of the heavy feedstock are substantially comprised of heavy cycle oil or light cycle oil recycles from a fractionation distillation of the effluents from the reaction zone.
- 7. A process as defined in claim 1, wherein the hydrocarbons injected into the downstream catalytic cracking portion of the reaction zone are atomized to form droplets of which at least 80 percent have a diameter of less than 100 microns.
- 8. A process as defined in claim 1, wherein the catalyst particles are regenerated by combustion of the coke deposited thereon in two separate combustion chambers, each of which has its own means for discharging the gaseous effluents.
- 9. A process as defined in claim 1, wherein the ratio of the quantity of catalyst to the quantity of heavy feedstock to be cracked ranges from 4.0 to 12.0 in the downstream section of the reaction zone.
- 10. A process as defined in claim 1, wherein ethylene from a fractionation of the reaction effluents is sent to an oligomerization reactor whose effluents, other than light gasolines, are recycled to the upstream portion of the reaction zone.
- 11. The process of claim 1, wherein the catalyst to lift gas ratio is about 11.
- 12. The process of claim 1 wherein the ethylene is obtained in a quantity of at least twice the quantity of ethane in the light feedstock.
- 13. The process of claim 12 wherein the propylene is obtained in a quantity of at least six times the quantity of the propane in the light feedstock.
- 14. The process of claim 1 wherein olefins including ethylene and propylene are obtained from the hydrocarbon-containing effluent;
- and the process further comprises subjecting the ethylene thus obtained to oligomerization to obtain an oligomerization product, and recycling the oligomerization product into the light hydrocarbons of the steam cracking step, so that the oligomerization product is selectively cracked into propylene, thereby enhancing the propylene yield of the process.
Priority Claims (1)
Number |
Date |
Country |
Kind |
87 18375 |
Dec 1987 |
FRX |
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Parent Case Info
This application is a continuation of application Ser. No. 07/542,803, filed Jun. 22, 1990, now abandoned, which in turn is a continuation of application Ser. No. 07/292,478, filed Dec. 30, 1988, now abandoned.
US Referenced Citations (14)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0208609 |
Jan 1987 |
EPX |
Non-Patent Literature Citations (1)
Entry |
Wuithier, Le Petrole--Raffinage et Genie Chimique, p. 694, Table III-5.1 (1965). |
Continuations (2)
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Number |
Date |
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Parent |
542803 |
Jun 1990 |
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Parent |
292478 |
Dec 1988 |
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