Claims
- 1. A process for stripping hydrocarbons from spent FCC catalysts said process comprising:
- a) transferring a mixture of catalyst and hydrocarbon containing gas to an FCC reactor vessel;
- b) at least partially separating gas from said catalyst in said vessel and directing a first stream of catalyst containing entrained and sorbed hydrocarbons from said reactor vessel into a rejection zone having a length less than the diameter of said reactor vessel;
- c) passing a first stream of stripping gas upwardly through said catalyst in an upper section of said rejection zone to at least partially remove entrained hydrocarbons from said catalyst stream;
- d) passing a second stream of catalyst particles from said upper section of said rejection zone to a lower section of said rejection zone and contacting said second stream of catalyst particles with a second stripping gas stream, consisting essentially of stripping medium for a first average residence time to maintain a dense bed of catalyst in said lower section of said rejection zone and passing stripping gas from said lower section into said upper section of said rejection zone to provide a portion of said first stripping gas stream;
- e) withdrawing a third stream of at least partially stripped catalyst from the side of said rejection zone through a sloped passageway and disengaging stripping gas from said stripped catalyst while transferring said catalyst along a lower surface of said passageway to a stripping zone contained in an elongated stripping vessel;
- f) countercurrently contacting said third catalyst stream with a third stripping gas stream in said stripping zone for a second average residence time of less than 60 seconds;
- g) recovering stripped catalyst particles from the bottom of said stripping zone;
- h) collecting stripping gas at the top of said stripping zone and passing said stripping gas as a fourth stripping gas stream through said passageway to the top of the upper section of said rejection zone to provide a portion of said first stripping gas stream.
- 2. The process of claim 1 wherein said gases have a superficial velocity of from 0.05 to 0.3 m/sec in said rejection zone.
- 3. The process of claim 1 wherein at least a portion of said fourth stripping gas is passed into an annular gas chamber and radially discharged into contact with said catalyst in said upper section of said rejection zone.
- 4. The process of claim 1 wherein said passageway slopes downwardly at an angle that does not exceed 45.degree. from horizontal.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation in part of U.S. Ser. No. 696,384, filed May 6, 1991 which is a continuation in part of U.S. Ser. No. 285,694, filed Dec. 16, 1988, now abandoned.
US Referenced Citations (13)
Continuation in Parts (2)
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Number |
Date |
Country |
Parent |
696384 |
May 1991 |
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Parent |
285694 |
Dec 1988 |
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