Counterflow fluidized bed reactor systems and processes

Abstract

Disclosed herein are reactors, systems and methods for performing fluidized gas-solid interactions. An exemplary reactor includes a gas inlet tube, a reaction section, a gas exhaust tube, and a diffuser positioned between the reaction section and the gas exhaust tube and the gas inlet tube. The gas exhaust tube receives the gas inlet tube or is received by the gas inlet tube for allowing transfer of heat from exhaust gas to inlet gas.

Description

[0001] COUNTERFLOW FLUIDIZED BED REACTOR SYSTEMS AND PROCESSES

[0002] BACKGROUND

[0003] As shown in Figure 1, a fluidized bed reactor (FBR) typically consists of a vertically oriented column. Gas flow is introduced from the bottom-up and diffuses through a distributor plate where a bed of material resides. The gas flow velocities act to fluidize the bed of material as it passes through it where a general reaction takes place via gas-solid interactions. The gas then slows down through a free bore space where the column diameter increases. The gas cools and then exits the reactor typically through filters to trap entrained particles. In the FBR the gas stream is poorly utilized because it relies on high gas velocities to fluidize particles. Also, the gas stream has a short dwell time passing through the bed. The FBR requires a large footprint due to necessary free bore volume and filtration to prevent elutriation. Because the distributor plate is flat, poor fluidization in the comers where the plate meets the reactor wall can occur. Additionally, the FBR requires an additional gas pre-heater to improve efficiency for high temperature reactions.

[0004] BRIEF SUMMARY

[0005] In general terms, embodiments are directed to fluidized bed reactors.

[0006] In one aspect, a reactor includes a gas inlet tube, a reactor includes a gas inlet tube, a reaction section, a gas exhaust tube, and a diffuser positioned between the reaction section and the gas exhaust tube and the gas inlet tube. The gas exhaust tube receives the gas inlet tube or is received by the gas inlet tube for allowing transfer of heat from exhaust gas to inlet gas.

[0007] In another aspect, a system includes a gas input device, a gas exhaust device, and a reactor. The reactor includes a gas inlet tube, a reaction section, a gas exhaust tube, and a diffuser positioned between the reaction section and the gas exhaust tube and the gas inlet tube. The gas exhaust tube receives the gas inlet tube or is received by the gas inlet tube for allowing transfer of heat from exhaust gas to inlet gas.

[0008] In still another aspect, an exemplary method includes supplying gas through a first tube to a reactor, expelling the gas from the first tube into a reaction section of the reactor through holes in first section of an attached diffuser causing material residing on the diffuser to fluidize and react with the gas, returning the gas through holes in a second section of the diffuser into a second tube that surrounds the first tube, thereby causing gas to further react with the material, and transferring heat from the returning gas in the second tube to the gas in the first tube due to the first tube residing within the second tube or the second tube residing within the first tube.

[0009] These and other aspects of the invention will be apparent upon reference to the following detailed description.

[0010] iBRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0011] Figure 1 shows a cross-sectional view of a prior art fluidized bed reactor.

[0012] Figure 2 shows a block diagram of a system formed in accordance with embodiments of the present invention.

[0013] Figure 3 shows a partial perspective and cross-sectional view of a counter flow fluidized bed reactor formed in accordance with embodiments of the present invention.

[0014] Figure 4 shows a cross-sectional view of a counter flow fluidized bed reactor formed in accordance with embodiments of the present invention.

[0015] DETAILED DESCRIPTION

[0016] In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments. However, one skilled in the art will understand that the invention may be practiced without these details. In other instances, well-known structures have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments. Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is, as “including, but not limited to.” Further, headings provided herein are for convenience only and do not interpret the scope or meaning of the claimed invention.

[0017] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Also, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

[0018] In various embodiments, as shown in Figure 2, a fluidized bed reactor system 14 includes a counterflow fluidized bed reactor 20, a gas supply device 16, and a gas exhaust device 18. The gas supply device 16 transports the gas to the reactor 20. The gas exhaust device 18 receives gas outputted by the reactor 20 and is configured to properly dispose the outputted gas. The reactor 20 may be part of a larger material processing system.In various embodiments, as shown in Figure 3, the reactor 20 includes an inner tube 24 coupled to the gas supply device 16. The inner tube 24 resides annularly inside an outer tube 26, which is coupled to the gas exhaust device 18. The inner tube 24 acts as a gas inlet and is affixed to a concave-shaped distributor plate 30. Material to be fluidized for reaction with an inlet gas is placed on the concave-shaped distributor plate 30. Gas flows upward from the inner tube 24 through inner holes in the distributor plate 30 fluidizing the material. The gas circulates through a heated, sealed reaction zone headspace 32 then exits back through the distributor plate 30 via outer holes (passing through the material yet again) between the space of the inner tube 24 and the outer tube 26. Exhaust gas acts as a pre-heater for the gas in the inner tube 24. Because the gas enters and exits through the distributor plate 30 there is no need for additional particulate filters in the reactor 20. This is in part made possible by the concave geometry of the distributor plate 30 which keeps the fluidized material in circulation thus preventing the material from blinding / clogging the holes of the distributor plate 30.

[0019] The reactor 20 improves upon the traditional design of a fluidized bed reactor (FBR) by altering the gas inlet flow patterns by having inlet gas flow enter through the inner tube 24 in the center of the concave shaped distributor plate 30. After fluidizing the material, the gas then exits the reactor 20 in a flow direction counter to the inlet flow back out through the holes of the distributor plate 30 to the annulus space between the inner and outer tubes. This type of FBR (counter-flow FBR) improves gas-solid interaction efficiency and uses lets parts / footprint over traditional FBR designs.

[0020] The reactor 20 allows gas to pass through the fluidized medium twice as opposed to once in a traditional FBR, thereby improving thermal efficiency of the gas-solid interaction and gas utilization. The reactor 20 does not need additional particle filters because the distributor plate is also acting as the filter to prevent particle elutriation when the gas exits. The reactor 20 minimizes internal “dead space" because there's no need for free bore space to reduce gas velocity. The hot gas exiting through the annular space acts to pre-heat the gas coming in through the inner annular tube, thus reducing the cost of preheating the inlet gas. The concave design of the distributor plate 30 improves powder turnover efficiency and minimizes convection dead zones, thereby improving gas-solid interaction and fluidization of the particulate medium.

[0021] In alternative embodiments, diameters of the inner tube 24 (I) and the outer tube 26 (x), the radius ( / ) of the curved portion of the distributor plate 30, and the height (Ji) of the reaction headspace 32 can be varied to optimize gas-solid interactions depending on the reaction chemistry, particle sizes, and temperature / pressures desired. For example, the diameter of the inner tube (7) may be 1 / 10th, l / 8th, l / 5th, or 1 / 2 the diameter of the outer tube (x). Also, the height of the reactionheadspace 32 (A) may be equal to 0.5x, x, 1 ,5x, or 2x. The radius (r) value of the distributor plate 30 may be determined by the following equation:

[0022]

[0023] In various embodiments, as shown in Figure 4, the reactor 40 includes an outer tube 46 coupled to the gas supply device 16. An inner tube 44 resides annularly inside an outer tube 46. The inner tube 44 is coupled to the gas exhaust device 18. The outer tube 46 acts as a gas inlet and is affixed to a convex-shaped distributor plate 50. Material to be fluidized for reaction with an inlet gas is placed on the convex-shaped distributor plate 50. Gas flows upward from the outer tube 46 through outer holes in the distributor plate 50 fluidizing the material. The gas circulates through a heated, sealed reaction zone headspace 42 then exits back through the distributor plate 50 via inner holes (passing through the material yet again) above the inner tube 44. The gas exiting via the inner tube 44 acts as a pre-heater for the gas in the outer tube 46. Because the gas enters and exits through the distributor plate 50 there is no need for additional particulate filters in the reactor 40. This is in part made possible by the convex geometry of the distributor plate 50 which keeps the fluidized material in circulation thus preventing the material from blinding / clogging the holes of the distributor plate 50. As shown, an outer section of the distributor plate 50 has a flat crosssection and an inner section of the distributor plate 50 has a convex shape relative to the reaction headspace 42.

[0024] The reactor 20 can be used for any process that involves gas-solid interactions, this includes but is not limited to coatings (chemical vapor deposition (CVD), atomic level deposition (ALD), etc.) on powders, drying materials, chemical synthesis, etc. For example, the reactor 20 may be configured to perform chemical vapor infiltration (CVI) in order to produce composite materials, such as, without limitation, silicon-carbon (Si-C) composite material formed by decomposing a silicon-containing gas in the presence of a solid microporous carbon material.

[0025] In another embodiment, external mechanical forces can be applied to force fluidization of the medium instead of using the gas stream itself (e.g., vibration, rotation, stirring)

[0026] In various embodiments, the reactors 20, 40 may include baffles inside the headspaces 32, 42 to help reduce dwell time and optimize eddy currents therein. This may help improve utilization and gas-solid contact. Various baffle designs may be used.

[0027] Exemplary embodiments include, but are not limited to, the following:Embodiment 1. A reactor comprising a gas inlet tube, a reaction section, a gas exhaust tube connected to the reaction section, the gas exhaust tube being configured to receive the gas inlet tube or be received by the gas inlet tube, and a diffuser positioned between the reaction section and the gas exhaust tube and the gas inlet tube.

[0028] Embodiment 2. The reactor of Embodiment 1, wherein the gas inlet tube is attached to a central portion of the diffuser.

[0029] Embodiment 3. The reactor of Embodiment 2, wherein the diffuser includes an annular portion extending from the central portion to interior walls of the reaction section and the gas exhaust tube.

[0030] Embodiment 4. The reactor of Embodiment 3, the annular portion is at least partially concave towards the reaction section.

[0031] Embodiment 5. The reactor of any of Embodiments 1-4, wherein the diffuser includes an annular portion extending from a central portion to interior walls of the reaction section and the gas inlet tube, wherein the central portion is at least partially convex towards the reaction section.

[0032] Embodiment 6. A system comprising a gas preheater and input device, a gas exhaust device, and a reactor. The reactor comprises a gas inlet tube, a reaction section, a gas exhaust tube connected to the reaction section, the gas exhaust tube being configured to receive the gas inlet tube or be received by the gas inlet tube, and a diffuser positioned between the reaction section and the gas exhaust tube and the gas inlet tube.

[0033] Embodiment 7. The system of Embodiment 6, the gas inlet tube is attached to a central portion of the diffuser.

[0034] Embodiment 8. The system of Embodiment 6 or 7, the diffuser includes an annular portion extending from the central portion to interior walls of the reaction section and the gas exhaust tube.

[0035] Embodiment 9. The system of Embodiment 8, the annular portion is at least partially concave towards the reaction section.

[0036] Embodiment 10. The system of any of Embodiments 6-9, the diffuser includes an annular portion extending from a central portion to interior walls of the reaction section and the gas inlet tube, wherein the central portion is at least partially convex towards the reaction section.

[0037] Embodiment 11. A method comprising supplying gas into a first tube, expelling the gas from the first tube into a reaction section of the reactor through holes in first section of an attached diffuser causing material residing on the diffuser to fluidize and react with the gas; returning the gas through holes in a second section of the diffuser into a second tube that surrounds the first tube, thereby causing gas to further react with the material; and transferringheat from the returning gas in the second tube to the gas in the first tube due to the first tube residing within the second tube or the second tube residing within the first tube Embodiment 12. The method of Embodiment 11, wherein an annular section of the diffuser is at least partially concave towards the reaction section.

[0038] Embodiment 13. The method of Embodiment 11, wherein a central section of the diffuser is at least partially convex towards the reaction section.

[0039] From the foregoing it will be appreciated that, although specific embodiments of the disclosure have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the disclosure.

[0040] All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification, including U.S. Provisional Patent Application No. 63 / 747,724, filed January 21, 2025, to which the present application claims priority are incorporated herein by reference, in their entireties to the extent not inconsistent with the present description. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description.

[0041] From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A reactor compri sing :a gas inlet tube;a reaction section;a gas exhaust tube connected to the reaction section, the gas exhaust tube being configured to receive the gas inlet tube or be received by the gas inlet tube; anda diffuser positioned between the reaction section and the gas exhaust tube and the gas inlet tube.

2. The reactor of Claim 1, wherein the gas inlet tube is attached to a central portion of the diffuser.

3. The reactor of Claim 2, wherein the diffuser includes an annular portion extending from the central portion to interior walls of the reaction section and the gas exhaust tube.

4. The reactor of Claim 3, wherein the annular portion is at least partially concave towards the reaction section.

5. The reactor of Claim 1, wherein the diffuser includes an annular portion extending from a central portion to interior walls of the reaction section and the gas inlet tube, wherein the central portion is at least partially convex towards the reaction section.

6. A system comprising:a gas input device;a gas exhaust device; anda reactor comprising:a gas inlet tube having an exterior diameter;a reaction section;a gas exhaust tube connected to the reaction section and the gas exhaust device, the gas exhaust tube having an interior diameter, the gas exhaust tube being configured to receive the gas inlet tube or be received by the gas inlet tube; anda diffuser positioned between the reaction section and the gas exhaust tube and the gas inlet tube,wherein exhaust gas sent to the gas exhaust device is configured to provide heat to the gas inlet tube while in the gas exhaust tube.

7. The system of Claim 6, wherein the gas inlet tube is attached to a central portion of the diffuser.

8. The system of Claim 7, wherein the diffuser includes an annular portion extending from the central portion to interior walls of the reaction section and the gas exhaust tube.

9. The system of Claim 8, wherein the annular portion is at least partially concave towards the reaction section.

10. The system of Claim 6, wherein the diffuser includes an annular portion extending from a central portion to interior walls of the reaction section and the gas inlet tube, wherein the central portion is at least partially convex towards the reaction section.

11. A method compri sing :supplying gas through a first tube to a reactor;expelling the gas from the first tube into a reaction section of the reactor through holes in a first section of an attached diffuser causing material residing on the diffuser to fluidize and react with the gas;returning the gas through holes in a second section of the diffuser into a second tube that surrounds the first tube, thereby causing gas to further react with the material; and transferring heat from the returning gas in the second tube to the gas in the first tube due to the first tube residing within the second tube or the second tube residing within the first tube.

12. The method of Claim 11, wherein an annular section of the diffuser is at least partially concave towards the reaction section.

13. The method of Claim 11, wherein a central section of the diffuser is at least partially convex towards the reaction section.

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