Method and apparatus for regenerating an iron-based fischer-tropsch catalyst
Solvent extraction is used to remove wax and contaminants from an iron-based Fischer-Tropsch catalyst in a natural circulation continuous-flow system. The wax-free catalyst is then subjected to controlled oxidation to convert the iron to its initial oxidized state, Fe 2 0 3 . Reactivation of the oxide catalyst precursor is carried out by addition of synthesis gas.
1. An apparatus operable for Fischer-Tropsch catalyst regeneration comprising wax extraction, catalyst oxidation and catalyst activation, said apparatus comprising:
a reactor;
a dynamic settler comprising an inlet fluidly connected with the reactor via a first downward sloping conduit and an outlet fluidly connected with the reactor via a second downward sloping conduit, wherein said dynamic settler is operable to separate a substantially catalyst-free liquid stream and a gas stream from a catalyst stream;
heating means functioning to heat inlet gases of said reactor;
first cooling means configured to cool overhead gases from said reactor;
second cooling means configured to condense a first liquid product from said overhead gases;
a first separator configured to separate uncondensed gas from said condensed first liquid product, wherein said first separator is fluidly connected with the reactor via a gas outlet conduit;
a second separator, wherein the second separator is positioned downstream of the flash vessel and fluidly connected therewith such that vapor exiting the flash vessel can be introduced into the second separator and wherein the second separator is configured for separation of a second liquid product from gas;
a flash vessel fluidly connected with the dynamic settler via a clarified liquid conduit configured for removal of the substantially catalyst-free liquid stream from the dynamic settler, wherein the flash vessel is configured for separation of a solvent from Fischer-Tropsch wax during wax extraction; and
a liquid storage vessel positioned downstream of the second separator and connected therewith such that the second liquid product can be stored therein, wherein the liquid storage vessel is fluidly connected with the first separator such that the first liquid product can be stored therein.
2. The apparatus of claim 1 , wherein said reactor comprises a three phase bubble column.
3. The apparatus of claim 1 further comprising gas distribution means functioning to distribute a gas uniformly across a cross section of said reactor during catalyst regeneration.
4. The apparatus of claim 3 , wherein the gas distribution means is a sintered metal plate.
5. The apparatus of claim 4 , wherein the sintered metal plate has a mean pore diameter between about 0.2 and about 2 microns.
6. The apparatus of claim 2 , wherein said three phase bubble column further comprises a heat exchanger.
7. The apparatus of claim 1 wherein the dynamic settler further comprises a gas outlet fluidly connected with the gas outlet conduit upstream of the second cooling means.
8. The apparatus of claim 1 configured for natural circulation of a catalyst slurry from the reactor into the dynamic settler via the first downward sloping conduit and for return of the catalyst stream to the reactor via the second downward sloping conduit.
9. The apparatus of claim 1 further comprising valves on the first and second downward sloping conduits whereby the dynamic settler can be isolated from the reactor during catalyst oxidation.
10. The apparatus of claim 1 wherein the dynamic settler comprises a degassed slurry conduit extending approximately 80% of the height of the dynamic settler from the top thereof.
11. The apparatus of claim 1 wherein the clarified liquid conduit is configured for removal of the substantially catalyst-free liquid stream from a top portion of the dynamic settler.
12. The apparatus of claim 1 further comprising a pressure reduction valve upstream of the flash vessel and downstream of the dynamic settler, said pressure reduction valve configured to reduce the pressure of the substantially catalyst-free liquid stream to a pressure at which a majority of the solvent vaporizes.
13. The apparatus of claim 1 wherein the flash vessel is configured for separation, as a vapor, of a solvent selected from the group consisting of hexane, hexane, heptane, heptene, tetrahydrofuran, Fischer-Tropsch naphtha, and combinations thereof.
14. The apparatus of claim 1 further comprising a wax collection tank downstream of and fluidly connected with the flash vessel and configured for storage of Fischer-Tropsch wax separated from the solvent during wax extraction.
15. The apparatus of claim 1 further comprising a recycle line fluidly connecting the liquid storage vessel with the reactor such that a portion of the first liquid product, a portion of the second liquid product, or a portion of both can be recycled to the reactor.
16. The apparatus of claim 1 further comprising a flare configured for flaring a portion of the uncondensed gas separated from the first liquid product in the first separator, a portion of the gas separated from the second liquid product in the second separator, or both.
17. The apparatus of claim 1 further comprising a recycle line fluidly connecting the first separator, the second separator or both with the reactor, whereby a portion of the uncondensed gas separated from the first liquid product in the first separator, a portion of the gas separated from the second liquid product in the second separator, or both can be recycled to the reactor.