Product recovery in gas-solids reactors

Abstract

A gas-solids reaction system is provided for improving product recovery in a multiple reactor reaction system. The solids of the product gas-solids flows from the multiple reactors are separated out in a separation vessel having a baffled transition zone. Additional product vapor is stripped from the solids as the solids pass through the baffled transition zone. The solids are then returned to the multiple reactors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a reaction system according to an embodiment of the invention.

FIGS. 2A and 2B schematically show a portion of a reaction system according to an embodiment of the invention.

FIG. 3 shows expected performance characteristics for an apparatus according to an embodiment of the invention.

FIG. 4 schematically shows another portion of an apparatus according to an embodiment of the invention.

FIG. 5 shows results of operation of an apparatus according to an embodiment of the invention.

FIG. 6 shows results of operation of an apparatus according to an embodiment of the invention.

FIG. 7 shows results of operation of an apparatus according to an embodiment of the invention.

FIG. 8 shows results of operation of an apparatus according to an embodiment of the invention.

Claims

1. A method for separating solids from a gas-solids flow comprising: producing a plurality of product gas-solids flows by performing an oxygenate to olefin conversion reaction in a plurality of reactors;separating each of the plurality of product gas-solids flows into a corresponding higher density flow and lower density flow, each higher density flow comprising a majority of the solids contained in the corresponding product gas-solids flow;receiving the solids from each higher density flow in a transition zone;flowing a displacing gas, from one or more displacing gas inlets within the transition zone, countercurrently through the received solids while passing the received solids through the transition zone; andreturning the received solids to the plurality of reactors via standpipes, the entry locations for each standpipe being separated from the one or more displacing gas inlets by a separation distance.

2. The method of claim 1, wherein the transition zone comprises a plurality of baffle layers.

3. The method of claim 2, wherein the one or more displacing gas inlets comprise a lowest layer of baffles in the baffled transition zone.

4. The method of claim 1, wherein the transition zone comprises at least one pair of baffle layers.

5. The method of claim 4, wherein an orientation of one layer of the pair of baffle layers is rotated by 90 degrees relative to the second layer of the pair of baffle layers.

6. The method of claim 1, wherein a superficial velocity of the displacing gas within the transition zone is 0.03 m/sec or greater.

7. The method of claim 1, wherein a superficial velocity of the displacing gas within the transition zone is 0.15 m/sec or greater.

8. The method of claim 1, wherein flowing the displacing gas leads to increased reactor effluent prime olefin selectivity and reduced coke selectivity.

9. The method of claim 1, wherein the stripping efficiency within the transition zone is at least 50%.

10. The method of claim 1, wherein the displacing gas is steam.

11. The method of claim 1, wherein the separation distance is at least 25 cm.

12. The method of claim 1, wherein the separation distance is at least 50 cm.

13. The method of claim 1, wherein the separation distance is at least 90 cm.

14. The method of claim 1, wherein returning the received solids to the plurality of reactors comprises returning the received solids to at least 4 reactors.

15. The method of claim 1, wherein receiving the solids from each higher density flow further comprises receiving regenerated solids returned from a regenerator.

16. The method of claim 1, wherein a catalyst flux in each standpipe is at least 488 kg/m2*sec.

17. The method of claim 1, wherein a catalyst flux in each standpipe is at least 976 kg/m2*sec.

18. The method of claim 1, wherein a catalyst flux in the transition zone is 488 kg/m2* sec or less.

19. The method of claim 1, wherein a catalyst flux in the transition zone is 122 kg/m2* sec or less.

20. The method of claim 1, wherein a catalyst flux in the transition zone is at least 5 kg/m2*sec.

21. The method of claim 1, wherein a catalyst flux in the transition zone is at least 49 kg/m2*sec.

22. The method of claim 1, wherein a ratio of a distance from a center of the transition zone to a center of a standpipe versus a diameter of the transition zone is at least 0.2.

23. The method of claim 1, wherein a ratio of a distance from a center of the transition zone to a center of a standpipe versus a diameter of the transition zone is at least 0.3.

24. The method of claim 1, wherein a catalyst residence time within the transition zone is 10 minutes or less.

25. The method of claim 1, wherein a catalyst residence time within the transition zone is 1 minute or less.

26. The method of claim 1, wherein a catalyst residence time within the transition zone is at least 5 seconds.

27. The method of claim 1, wherein a catalyst residence time within the transition zone is at least 30 seconds.

28. The method of claim 1, wherein a catalyst density gradient within the transition zone is 525 kg/m3-m or less.

29. The method of claim 1, wherein a catalyst density gradient within the transition zone is 53 kg/m3-m or less.

30. The method of claim 1, wherein a volume fraction of vapor bubbles at the standpipe entry locations is at least 0.00005.

31. The method of claim 1, wherein a volume fraction of vapor bubbles at the standpipe entry locations is at least 0.0002.

32. An apparatus for performing oxygenate to olefin reactions, comprising: a plurality of oxygenate to olefin reactors; anda separation vessel for receiving a product gas-solids flow from each of the oxygenate to olefin reactors, the separation vessel comprising:a plurality of separation devices;a transition zone;one or more displacing gas inlets within the transition zone; anda plurality of standpipe entry locations for returning solids to each of the plurality of oxygenate to olefin reactors, the plurality of standpipe entry locations being separated from the one or more displacing gas inlets by a separation distance.

33. The apparatus of claim 32, further comprising: a regenerator for regenerating a portion of the solids from the product gas-solids flow and for returning the regenerated portion to the separation vessel.

34. The apparatus of claim 32, wherein the transition zone comprises a plurality of baffle layers.

35. The apparatus of claim 34, wherein the one or more gas inlets comprise a baffle layer of the baffled transition zone.

36. The apparatus of claim 32, wherein the transition zone comprises at least one pair of baffle layers.

37. The apparatus of claim 36, wherein an orientation of one layer of the pair of baffle layers is rotated by 90 degrees relative to the second layer of the pair of baffle layers.

38. The apparatus of claim 36, wherein one layer of the pair of baffle layers is offset relative to the second layer of the pair of baffle layers.

39. The apparatus of claim 32, wherein the separation distance is at least 25 cm.

40. The apparatus of claim 32, wherein the separation distance is at least 50 cm.

41. The apparatus of claim 32, wherein the separation distance is at least 90 cm.

42. The apparatus of claim 32, wherein the plurality of oxygenate to olefin reactors comprise riser reactors.