APPARATUS AND PROCESS FOR SEPARATING COMPONENTS OF A MULTIPHASE HYDROCARBON STREAM

Abstract

An apparatus and a process enable separating components of a multiphase hydrocarbon stream. The apparatus may include an outer vessel having a top end with a top outlet and a bottom end with a bottom outlet, with a longitudinal axis extending between the top end and the bottom end. An outer vessel body disposed between the top end and the bottom end has an outer vessel internal volume in fluid communication with the top outlet and the bottom outlet. The outer vessel body may include a first section with a tangential inlet arranged to introduce the multiphase hydrocarbon stream tangentially into the outer vessel internal volume to create a vortex flow, and a second section arranged closer to the bottom end than the first section. The outer vessel internal volume has a smaller cross-sectional circumference in the second section than in the first section. An inner vessel disposed within the outer vessel body includes an inner vessel body having an inner vessel internal volume, and an inner bottom inlet oriented toward the bottom end of the outer vessel and in fluid communication with the inner vessel internal volume and with the outer vessel internal volume. A traversing conduit in fluid communication with the inner vessel internal volume may traverse the outer vessel body.

Claims

1-16. (canceled)

17. An apparatus for separating components of a multiphase hydrocarbon stream, the apparatus comprising: an outer vessel having a top end comprising a top outlet, a bottom end comprising a bottom outlet, with a longitudinal axis extending between the top end and the bottom end, and an outer vessel body disposed between the top end and the bottom end and having an outer vessel internal volume in fluid communication with the top outlet and the bottom outlet; wherein the outer vessel body comprises: a first section comprising a tangential inlet arranged to introduce the multiphase hydrocarbon stream tangentially into the outer vessel internal volume to create a vortex flow, and a second section arranged closer to the bottom end than the first section, wherein the outer vessel internal volume has a smaller cross-sectional circumference in the second section than in the first section; an inner vessel disposed within the outer vessel body, said inner vessel comprising: an inner vessel body having an inner vessel internal volume, and an inner bottom inlet oriented toward the bottom end of the outer vessel and in fluid communication with the inner vessel internal volume and with the outer vessel internal volume, and an inner top outlet oriented toward the top end of the outer vessel and in fluid communication with the outer vessel internal volume and the inner vessel internal volume; and a traversing conduit in fluid communication with the inner vessel internal volume and traversing the outer vessel body, so that a product stream can be conveyed from the inner vessel internal volume outside of the outer vessel, wherein the traversing conduit traverses the outer vessel body at a position that is further down along the longitudinal axis than the inner top outlet of the inner vessel.

18. The apparatus according to claim 17, wherein a ratio of the cross-sectional circumference of the outer vessel internal volume in the second section to the cross-sectional circumference of the outer vessel internal volume in the first section is between 0.05 and 0.95, preferably between 0.1 and 0.9, more preferably between 0.25 and 0.8, even more preferably between 0.4 and 0.7, most preferably between 0.5 and 0.6.

19. The apparatus according to claim 17, wherein the apparatus further comprises a cooling system fluidly connected to the top outlet, wherein the cooling system is adapted to condense a part of a vapor product exiting the outer vessel internal volume via the top outlet and convey the condensed part of the vapor product back into the outer vessel internal volume, preferably wherein the cooling system comprises at least one spray nozzle.

20. The apparatus according to claim 17, wherein the outer vessel internal volume in the first section and/or in the second section is substantially cylindrical or substantially frustoconical, preferably substantially cylindrical.

21. The apparatus according to claim 17, wherein the first section comprises a second tangential inlet arranged to introduce the multiphase hydrocarbon stream tangentially into the outer vessel internal volume to create a vortex flow.

22. The apparatus according to claim 17, wherein the second section comprises a lower tangential inlet arranged to introduce a stream tangentially into the outer vessel internal volume.

23. The apparatus according to claim 17, wherein the inner vessel comprises a barrier arranged between the inner top outlet and the top end of the outer vessel, wherein said barrier is arranged to at least partially block solids from entering the inner vessel internal volume via the inner top outlet but allow fluids to exit the inner vessel internal volume via the inner top outlet.

24. A process for separating components of a multiphase hydrocarbon stream in an apparatus according to claim 17, the process comprising the steps of: introducing the multiphase hydrocarbon stream via the tangential inlet into the outer vessel internal volume to create a vortex flow, whereby a vapor product is separated from the hydrocarbon stream and conveyed to the top outlet; recovering said vapor product from the top outlet; conveying the hydrocarbon stream from the first section to the second section, thereby increasing a tangential velocity of the vortex flow, wherein the hydrocarbon stream is separated into a solid-enriched product stream and a solid-reduced product stream, wherein the solid-enriched product stream is conveyed to the bottom outlet; recovering the solid-enriched product stream from the bottom outlet; conveying the solid-reduced product stream to the inner vessel internal volume via the inner bottom inlet; and recovering the solid-reduced product stream from the inner vessel internal volume via the traversing conduit.

25. The process according to claim 24, wherein the process further comprises the step of condensing a part of the vapor product exiting the outer vessel internal volume via the top outlet and conveying the condensed part of the vapor product back into the outer vessel internal volume.

26. The process according to claim 25, wherein said condensing is achieved by spraying a fluid onto the vapor product, wherein a temperature of said fluid is lower than a temperature of the vapor product, preferably wherein the temperature of the fluid is between 120? C. and 350? C., preferably between 150? C. and 300? C., especially between 180? C. and 250? C.

27. The process according to claim 26, wherein said fluid is obtained by condensing and recycling a part of the recovered vapor product.

28. The process according to claim 24, wherein a temperature of the multiphase hydrocarbon stream at the tangential inlet is between 300? C. and 480? C., preferably between 330? C. and 450? C., more preferably between 350? C. and 420? C., most preferably between 360? C. and 400? C.

29. The process according to claim 24, wherein the multiphase hydrocarbon stream is obtained from depolymerization of plastic materials, preferably plastic waste.

30. The process according to claim 29, wherein the plastic materials comprise polyolefins, preferably selected from polyethylene and polypropylene, and/or polystyrene.

31. The process according to claim 24, wherein the multiphase hydrocarbon stream comprises impurities selected from aluminum powder and/or organophosphorous compounds, especially Tris (2,4-di-tert-butylphenyl) phosphite.

Description

[0052] The present invention is further illustrated by the following figures, without being limited thereto.

[0053] FIG. 1 shows a longitudinal section of a preferred embodiment of the apparatus according to the invention.

[0054] FIG. 2 shows a process flow diagram for a facility for processing plastic waste, comprising a preferred embodiment of the apparatus according to the invention.

[0055] The apparatus shown in FIG. 1 comprises an outer vessel 1 having a top end 2 comprising a top outlet 3, a bottom end 4 comprising a bottom outlet 5, with a longitudinal axis 6 extending between the top end 2 and the bottom end 4. The outer vessel 1 further comprises an outer vessel body 7 disposed between the top end 2 and the bottom end 4 and having an outer vessel internal volume 8 in fluid communication with the top outlet 3 and the bottom outlet 5. The outer vessel body 7 comprises a first section 9 comprising a tangential inlet 10, and a second section 11 arranged closer to the bottom end 4 than the first section 9. In the depicted embodiment, both the first section 9 and the second section 11 are substantially cylindrical. They are connected by a substantially frustoconical third section 12 of the outer vessel body 7. The tangential inlet 10 is arranged to introduce the multiphase hydrocarbon stream 27 tangentially into the outer vessel internal volume 8 to create a vortex flow. This can be achieved by injecting the stream tangentially onto the inner surface of the outer vessel body 7, in order to create a vortex flow on said inner surface, in a similar way as commonly done in cyclonic separators. In addition, in the depicted embodiment, the first section 9 comprises a second tangential inlet 13, which may be similar in nature to the tangential inlet 10. The outer vessel internal volume 8 has a smaller cross-sectional circumference in the second section 11 than in the first section 9, which during operation allows for a higher tangential velocity of the vortex flow in the second section 11 than in the first section 9. In the depicted embodiment, the second section 11 comprises a lower tangential inlet 14, which may be used to introduce a liquid stream to further increase the tangential velocity of the vortex flow in the second section 11.

[0056] The apparatus shown in FIG. 1 further comprises an inner vessel 15 disposed within the outer vessel body 7. The inner vessel 15 comprises and inner vessel body 16 having an inner vessel internal volume 17 and an inner bottom inlet 18 oriented toward the bottom end 4 of the outer vessel 1 and fluidly connecting the inner vessel internal volume 17 with the outer vessel internal volume 8. In addition, in the depicted configuration, the inner vessel 15 comprises an inner top outlet 19 oriented toward the top end 2 of the outer vessel 1 and fluidly connecting the inner vessel internal volume 17 with the outer vessel internal volume 8. A barrier 20 is arranged between the inner top outlet 19 and the top end 2 to at least partially block solids from entering the inner vessel internal volume 17, while allowing fluids, such as vapors, to exit via the inner top outlet 19, for instance to be conveyed to the top outlet 3. The apparatus further comprises a traversing conduit 21 in fluid communication with the inner vessel internal volume 17, which traversing conduit 21 traverses the outer vessel body 7, so that a product stream can be conveyed from the inner vessel internal volume 17 outside of the outer vessel.

[0057] For operating the apparatus depicted in FIG. 1 in the inventive process, a multiphase hydrocarbon stream 27, for instance obtained from the depolymerization of plastic material in a cracking reactor 26 as shown in FIG. 2, may be introduced into the outer vessel internal volume 8 via the tangential inlet 10 and/or the second tangential inlet 13 to create a vortex flow. As a result of centrifugal force, solids and liquids are pushed to the inner surface of the outer vessel body 7, whereas vaporous components are separated by moving radially inward and being conveyed to the top outlet 3. Preferably, the cross-sectional circumference in the first section 9 is low enough to ensure that the axial velocity of the vapor product 30 moving toward the top outlet 3 is low enough to reduce dragging along of liquid droplets. The vapor product 30 exiting the outer vessel internal volume 8 may be partially condensed in a cooling system, for instance by spraying a fluid onto the vapor product 30 using one or more spray nozzles 33. Said fluid may be obtained by condensing and recycling a part of the recovered vapor product 30. The condensation step allows to preferentially condense impurities having a higher boiling point than the desired components of the vapor product 30, for instance undesired organophosphorous compounds commonly found in plastic materials. The condensed part of the vapor product 30 is transferred back into the outer vessel internal volume 8 and may at least partially be removed through the solid-reduced product stream 25 and/or the solid-enriched product stream 28.

[0058] After separation of the vapor product 30, the remaining hydrocarbon stream is conveyed from the first section 9 via the third section 12 to the second section 11, whereby the tangential velocity of the vortex flow is increased due to the decreasing cross-sectional circumference. The higher tangential velocity leads to a shorter residence time, thereby reducing the coking tendency. At the same time, the higher tangential velocity leads to a higher centrifugal force and therefore to a more effective separation. Through this centrifugal force, the hydrocarbon stream is separated into a solid-enriched product stream 28 and a solid-reduced product stream 25. The solid-enriched product stream 28 is conveyed to the bottom outlet. The solid-reduced product stream 25 generates liquid hold-up in the outer vessel internal volume 8 and thereby enters the inner vessel internal volume 17 via the inner bottom inlet 18, eventually reaching the traversing conduit 21, from which it can be recovered. Advantageously, the solid-reduced product stream enters the traversing conduit 21 at an inlet opening 21a and leaves the traversing conduit 21 at outlet opening 21b, whereas the outlet opening 21b is arranged outside the outer vessel body 7 and below the inlet opening 21a. Preferably, the traversing conduit 21 traverses the outer vessel body 7 at a position that is further down along the longitudinal axis 6 than the inner top outlet 19 of the inner vessel 15.

[0059] Advantageously, the recovered solid-reduced product stream 25 can be recycled back to the cracking reactor 26 for further cracking. The solid-enriched product stream 28 is recovered from the bottom outlet and may be supplied to further downstream separation steps, e.g. to a coke catcher 29. A part of the solid-enriched product stream 28 may be recycled and introduced into the lower tangential inlet 14 in order to further increase the tangential velocity of the vortex flow in the second section 11.

[0060] An application of a preferred embodiment of the inventive apparatus in a plastic processing facility can be seen from FIG. 2. Plastic material is supplied to an extruder 23, wherein it is compacted, molten and/or degassed. The molten plastic material, preferably at a temperature between 250? C. and 280? C., is mixed in a static mixer 22 with an external solvent 24, preferably heavy oil, and/or at least a part of the solid-reduced product stream 25 obtained from the inventive apparatus in order to reduce the viscosity of the plastic melt. The resulting mixture is then conveyed to a cracking reactor 26, wherein the plastic is depolymerized, preferably at a temperature between 400? C. and 440? C. From the cracking reactor 26, a multiphase hydrocarbon stream 27 is obtained, which is then introduced into the outer vessel 1 of the inventive apparatus via the tangential inlet 10 as described herein above. At least a part of the solid-reduced product stream 25 obtained from the inventive apparatus may be recycled and supplied to fresh plastic melt, preferably together with solvent 24. The solid-enriched product stream 28 is conveyed to a coke catcher 29 to remove coke particles and at least a part of the resulting stream may be recycled and injected into the lower tangential inlet 14 of the inventive apparatus, as described above. The vapor product 30 obtained from the inventive apparatus is further separated into a light product 31, preferably having a boiling range from 35? C. to 225? C., and a heavy product 32, preferably having a boiling range from 225? C. to 410? C. A part of the heavy product 32 may be recycled to a spray nozzle 33 arranged to cool and condense a part of the vapor product 30, as described herein above.