Catalyst activation process
Catalyst activator, in particular, a catalyst activator for heat conditioning a catalyst. The activator includes a vessel for containing a catalyst charge having an internal diameter of at least 1.2 meters and/or an internal volume of at least 5 m 3 ; a fluidisation grid plate disposed in the vessel, the fluidisation grid plate having an upper major surface and a lower major surface; an array of generally conical depressions in the upper major surface that overlap by less than 17%; and an array of holes perforating the fluidisation grid plate, the holes extending from at least some of the generally conical depressions through the lower surface.
1. A process for activating a batch of polymerisation catalyst which comprises fluidising the batch of polymerisation catalyst in a fluidisation zone of an activator vessel, where the batch size is such that a settled bed of the catalyst in the activator vessel has a bulk volume of greater than 1.5 m 3 and a depth between 1.8 and 3 m.
2. A process according to claim 1 wherein the diameter of the settled bed, which also equates to the internal diameter of the activator vessel, is at least 1.2 meters.
3. A process according to claim or claim 2 wherein the batch size is such that the settled bed of the catalyst in the activation vessel has a bulk volume of greater than 2 m 3 .
4. A process according to claim 1 wherein the height of the fluidised bed of catalyst is at least twice the diameter of the fluidisation zone.
5. A process according to claim 4 wherein the height of the fluidised bed of catalyst is at least three times the diameter.
6. A process according to claim 4 wherein the expansion on fluidisation is above 100%.
7. A process according to claim 1 wherein the catalyst activator vessel comprises:
a) a vessel for containing a catalyst charge having an internal diameter of at least 1.2 meters and/or an internal volume of at least 5 m 3 ;
b) a fluidisation grid plate disposed in said vessel, said fluidisation grid plate and having an upper major surface and a lower major surface;
c) an array of generally conical depressions in said upper major surface that overlap by less than 17%; and
d) an array of holes perforating said fluidisation grid plate, said holes extending from at least some of said generally conical depressions through said lower surface.
8. A process according to claim 7 wherein the array of generally conical depressions are a regular triangular array.
9. A process according to claim 7 wherein the array of generally conical depressions overlap by at least 15.5%.
10. A process according to claim 7 wherein the pitch or spacing, being the distance between the centres of adjacent depressions, is between 2.5 and 5 cm.
11. A process according to claim 7 wherein the nominal thickness of the fluidisation grid plate is in the range 35 to 100 mm.
12. A process according to claim 7 wherein the depths of the generally conical depressions, as measured from the nominal upper surface, are less than 70% of the nominal plate thickness.
13. A process according to claim 1 which comprises:
a) providing said catalyst activator vessel for heat conditioning the catalyst;
b) introducing into said vessel a catalyst charge;
c) introducing a fluidising medium into said vessel through the fluidisation grid plate in order to fluidise said catalyst charge, and
d) heating the fluidised bed of the catalyst to activate said catalyst.
14. A process according to claim 13 wherein the catalyst is a supported chromium oxide polymerisation catalyst.
15. A process according to claim 13 wherein heating the fluidised bed of the catalyst to activate said catalyst comprises heating the fluidised bed of the catalyst particles to a temperature in the range of 50 to 1000° C. and holding for 1 to 72 hours at said temperature.
16. A process according to claim 2 wherein the diameter of the settled bed, which also equates to the internal diameter of the activator vessel, is in the range 1.5 to 2.5 meters.
17. A process according to claim 5 wherein the height of the fluidised bed of catalyst is at least four times the diameter.
18. A process according to claim 9 wherein the array of generally conical depressions overlap in the range 15.6% to 16.5%.
19. A process according to claim 10 wherein the pitch or spacing, being the distance between the centres of adjacent depressions, is in the range 3.5 to 4.5 cm.
20. A process according to claim 11 wherein the nominal thickness of the fluidisation grid plate is in the range from 40 mm and/or up to 65 mm.
21. A process according to claim 12 wherein the depths of the generally conical depressions, as measured from the nominal upper surface, are less than 60% of the nominal plate thickness.
22. A process according to claim 12 wherein the depths of the generally conical depressions, as measured from the nominal upper surface, are less than 50% of the nominal plate thickness.