INLET ASSEMBLY FOR AN ABATEMENT ASSEMBLY AND METHOD OF CONVEYING AN EFFLUENT TO AN ABATEMENT CHAMBER

Abstract

An inlet assembly for an abatement apparatus includes: an effluent stream conduit configured to convey an effluent stream along a major direction of flow within the effluent stream conduit; an inlet nozzle fluidly coupled with the effluent stream conduit and configured to convey the effluent stream received from the effluent stream conduit to an abatement chamber of the abatement apparatus; and a baffle interposed between the effluent stream conduit and the inlet nozzle, the baffle being shaped and configured to redirect flow of the effluent stream from the effluent stream conduit into the inlet nozzle by inhibiting effluent stream flow along the major direction of flow into the inlet nozzle. A line-of-sight flow from the effluent stream conduit into the inlet nozzle is prevented by the baffle and the effluent stream instead follows a non-line-of-sight or diversionary path from the effluent stream conduit into the inlet nozzle, which improves DRE.

Claims

1. An inlet assembly for an abatement apparatus, comprising: an effluent stream conduit configured to convey an effluent stream along a major direction of flow within said effluent stream conduit; an inlet nozzle fluidly coupled with said effluent stream conduit and configured to convey said effluent stream received from said effluent stream conduit to an abatement chamber of said abatement apparatus; and a baffle interposed between said effluent stream conduit and said inlet nozzle, said baffle being shaped and configured to redirect flow of said effluent stream from said effluent stream conduit into said inlet nozzle by inhibiting effluent stream flow along said major direction of flow into said inlet nozzle.

2. The inlet assembly of claim 1, wherein said baffle is shaped and configured to redirect flow of said effluent stream away from said major direction of flow into said inlet nozzle.

3. The inlet assembly of claim 1 or 2, wherein said baffle is shaped and configured to encourage turbulent flow of said effluent stream upstream of said inlet nozzle.

4. The inlet assembly of any preceding claim, wherein said baffle is shaped and configured to encourage laminar flow of said effluent stream into said inlet nozzle.

5. The inlet assembly of any preceding claim, wherein said baffle is shaped and configured to encourage a uniform axial rate of flow within said inlet nozzle.

6. The inlet assembly of any preceding claim, wherein said baffle is shaped and configured to inhibit increased axial rate of flow within said inlet nozzle proximate said effluent stream conduit and inhibit decreased axial rate of flow within said inlet nozzle distal said effluent stream conduit to obtain said uniform axial rate of flow within said inlet nozzle.

7. The inlet assembly of any preceding claim, wherein said baffle comprises a baffle conduit positioned within a plenum configured to receive said effluent stream from said effluent stream conduit, said baffle conduit defining at least one aperture positioned for fluid communication between said plenum and said inlet nozzle.

8. The inlet assembly of claim 7, wherein said at least one aperture is located away from a position on said baffle conduit which is aligned with incident effluent stream travelling along said major direction of flow.

9. The inlet assembly of claim 7 or 8, wherein said at least one aperture is located towards at least one axial end of said baffle conduit.

10. The inlet assembly of any one of claims 7 to 9, comprising a plurality of said apertures.

11. The inlet assembly of any one of claims 7 to 10, wherein a cross-sectional area of an aperture proximate to said effluent stream conduit is smaller than a cross-sectional area of an aperture distal from said effluent stream conduit.

12. The inlet assembly of any one of claims 7 to 11, wherein said baffle conduit is shaped to redirect flow of said effluent stream in said plenum to a direction transverse to said major direction of flow.

13. The inlet assembly of any one of claims 7 to 12, wherein said apertures are shaped to redirect flow of said effluent stream to convey said effluent stream radially into said baffle conduit.

14. The inlet assembly of any one of claims 7 to 13, wherein said baffle conduit is shaped to redirect flow of said effluent stream to convey said effluent stream in an axial direction along said baffle conduit into said inlet nozzle.

15. The inlet assembly of any one of claims 7 to 14, wherein said effluent stream conduit is shaped and configured to deliver said effluent stream along said major direction of flow which is transverse to said axial direction.

16. The inlet assembly of any preceding claim, wherein said effluent stream conduit follows a curved path.

17. The inlet assembly of any one of claims 7 to 16, wherein at least one of said baffle conduit and said inlet nozzle comprises coaxial lance positioned therewithin.

18. The inlet assembly of claim 17, wherein a helical structure is configured to extend along said axial direction beyond said lance.

19. The inlet assembly of any one of claims 7 to 18, wherein said baffle conduit extends along said axial direction for at least 5 times its internal diameter.

20. An abatement apparatus comprising an inlet assembly as claimed in any preceding claim and said abatement chamber.

21. A method, comprising: conveying an effluent stream along a major direction of flow within an effluent stream conduit; coupling an inlet nozzle with said effluent stream conduit to convey said effluent stream received from said effluent stream conduit to an abatement chamber of said abatement apparatus; and interposing a baffle between said effluent stream conduit and said inlet nozzle to redirect flow of said effluent stream from said effluent stream conduit into said inlet nozzle by inhibiting effluent stream flow along said major direction of flow into said inlet nozzle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

[0063] FIG. 1 illustrates an inlet assembly for an abatement apparatus according to one embodiment;

[0064] FIG. 2a is a computational fluid dynamics analysis showing the velocities experienced within the inlet assembly without the baffle;

[0065] FIG. 2b is a computational fluid dynamics analysis showing the velocities experienced within the inlet assembly with the baffle;

[0066] FIG. 3a illustrates the contours of the fuel mass fraction on a plane which is located downstream of the fuel lance without the baffle;

[0067] FIG. 3b illustrates the contours of the fuel mass fraction on a plane which is located downstream of the fuel lance with the baffle;

[0068] FIG. 4 is a graph demonstrating the difference in DRE and NOx with and without the baffle;

[0069] FIG. 5 demonstrates the performance of an abatement apparatus with one, two and six inlet assemblies feeding the abatement chamber;

[0070] FIG. 6 shows the baffle with orifices located at different positions;

[0071] FIG. 7 is a graph demonstrating the DRE, NOx and CO produced as the orifice apertures move down the baffle;

[0072] FIG. 8a shows the position of the standard length fuel lance;

[0073] FIG. 8b shows the position of the longest length fuel lance;

[0074] FIG. 9 is a graph showing the DRE, CO and NOx performance with varied fuel lance lengths;

[0075] FIG. 10 is a graph showing the DRE, CO and NOx performance with varied spring lengths;

[0076] FIG. 11a is a CFD of the inlet assembly with the baffle;

[0077] FIG. 11b is a CFD of the inlet assembly without the baffle; and

[0078] FIG. 12 illustrates an inlet assembly for an abatement apparatus according to one embodiment.

DETAIL DESCRIPTION

[0079] Before discussing the embodiments in any more detail, first an overview will be provided. Embodiments provide an arrangement which helps to facilitate mixing between a gas (for example, a fuel, an oxidant or another compound) and an effluent stream and increases the residence time of the mixed gas and effluent stream prior to entering an abatement chamber which increases DRE and can decrease fuel consumption. This is achieved by inhibiting the effluent stream from following a flow path which limits the amount of mixing that occurs and reduces residence time and instead causes the effluent stream to follow a flow path which facilitates such mixing and increases residence time. In particular, a structure is positioned into the effluent stream flow to prevent the effluent stream following a direct, line-of-sight path from the effluent stream conduit into the inlet nozzle which reduces mixing and residence time since a reduction in mixing and residence time causes a reduction in destruction rate efficiency (DRE). The effluent stream is sometimes delivered obliquely to the inlet nozzle which causes non-uniform flow of the effluent stream within the inlet nozzle, with greater flow and less mixing occurring in that portion of the nozzle proximate to the inlet providing the effluent stream. This results in non-uniform mixing of the effluent stream and the gas, which results in a less than optimal DRE. Although different structures are possible, in an arrangement which uses an inlet nozzle to deliver the mixed effluent stream and gas to an abatement chamber, a baffle can be positioned to intersect the flow of the effluent stream when being delivered to the inlet nozzle. The baffle may have one or more apertures therein. The effluent stream therefore has its direction of flow diverted by the baffle. The effluent stream then flows through these apertures and into the inlet nozzle. The baffle can then re-establish a uniform flow of the effluent stream within the nozzle for mixing with the fuel.

Inlet Assembly

[0080] FIG. 1 illustrates an inlet assembly 10 for an abatement apparatus according to one embodiment. The inlet assembly 10 has an inlet nozzle 20 comprising an elongate cylindrical conduit having a coaxially located fuel lance 30 therewithin. A concentrically located helical spring 40 is positioned between an outer surface of the fuel lance 30 and an inner surface of the inlet nozzle 20. The fuel lance 30 can be provisioned in this example with three different lengths, A, B or C. A further concentrically located lance 55 is provided which delivers a gas (such as fuel or oxidant) provided to a port 65. In an upper portion of the inlet nozzle 20 there is provided a baffle 50. The baffle 50 comprises a cylindrical tube having a number of apertures 60 formed through its wall. The wall of the inlet nozzle 20 has an aperture 70 which receives an effluent stream conduit 80. The effluent stream conduit is provided with an oxygen inject 90 which is arranged to inject oxygen into the effluent stream conduit 80.

[0081] In operation, an effluent stream 100 is conveyed into the effluent stream conduit 80. When activated, the oxygen inject 90 conveys oxygen into the effluent stream 100 as it passes through the effluent stream conduit 80 towards the aperture 70. The baffle 50 presents a cylindrical surface to the incident effluent stream 100 being conveyed through the aperture 70. The baffle 50 seals the upper portion of the inlet nozzle 20 and the only way for the effluent stream 100 to progress through the inlet nozzle 20 is via the apertures 60. Accordingly, the effluent stream 100 passes through the aperture 70 and into a plenum 110 defined by an outer surface of the baffle 50 and an inner surface of the upper portion of the inlet nozzle 20. The main directional flow of the effluent stream is thus diverted towards the apertures 60. This redirection of flow causes turbulence which assists in mixing the oxygen into the effluent stream 100. An annular chamber 120 is defined between the inner surface of the baffle 50 and an outer surface of the fuel lance 30. The annular chamber 120 redirects the flow of the effluent stream 100 along the elongate axis of the annular chamber 120. These redirections of flow cause turbulence which assists in mixing the oxygen into the effluent stream 100. As the effluent stream 100 travels along the elongate axis of the annular chamber 120, a generally laminar flow is restored. As the effluent stream 100 passes the end of the fuel lance 30, mixing between fuel 130 delivered via the fuel lance 30 and the effluent stream 100 commences. Mixing continues until the mixed fuel and effluent stream 140 exits the inlet nozzle 20 into the abatement chamber (not shown) surrounded concentrically by the gas delivered from the lance 55. To facilitate mixing and improve the stability of the mixed fuel and effluent stream 140, the spring 40 imparts a rotational component to the mixed fuel and effluent stream 140 as it passes along the annular chamber 120.

[0082] As can be understood from FIG. 1, were the baffle 50 not present then the effluent stream 100 delivered through the aperture 70 would enter the inlet nozzle 20 at an oblique angle and travel past the end of the fuel lance 30 when in position A in a non-uniform way, which would lead to non-uniform mixing and suboptimal DRE. In contrast, with the baffle 50 present, the effluent stream 100 travels uniformly along the annular chamber 120 which allows for uniform distribution of the fuel (typically by diffusion) into the annular column of effluent stream 100 passing through the annular chamber 120. The presence of a uniform distribution of fuel helps to improve the DRE. As mentioned above, the arrangement of the effluent stream conduit, the aperture 70 and the baffle 50 gives improved DRE by primarily removing the line-of-sight gas flow into the inlet nozzle 20. The arrangement forces the main gas flow to distribute evenly around the lance fuel, resulting in stable, consistent and repeatable DRE and NOx readings.

Velocities

[0083] FIG. 2 is a computational fluid dynamics analysis showing the velocities experienced within the inlet assembly 10. FIG. 2A shows the arrangement without the baffle 50 and FIG. 2B shows the arrangement with the baffle 50.

[0084] As can be seen, in the arrangement in FIG. 2A, the velocity of the effluent stream as it enters the inlet nozzle 20 is relatively low and the flow is biased towards the lower portion of the aperture 70 proximate the fuel lance 30. However, as can be seen in FIG. 2B, pre-reaction mixing is improved because the baffle 50 helps to provide a uniform distribution of the effluent stream 100 within the inlet nozzle 20, a smooth flow of the effluent stream through the inlet nozzle 20 and aids mixing between the fuel and the effluent stream together with a longer residence time for the mixed fuel and effluent stream 140 before entering the abatement chamber. The presence of the baffle 50 gives the effluent stream 100 a higher velocity, the baffle 50 forces the effluent stream 100 up into a smaller surface area and therefore increases its velocity, which may assist in mixing of the fuel 130 and the effluent stream 100.

Mixing

[0085] FIG. 3 illustrates the contours of the fuel mass fraction on a plane which is located downstream of the fuel lance when at position A. FIG. 3A shows the mass fractions with no baffle 50 present, while FIG. 3B shows the mass fraction with the baffle 50 present. As can be seen, the fuel mixing is significantly improved in the arrangement where the baffle 50 is present. In particular, in FIG. 3A, due to the inclined entry of flow from the effluent stream conduit 80 into the inlet nozzle 20, the maximum flow of fuel is concentrated at a region under the circled area and hence the mass fraction is higher at this location. In FIG. 3B, the flow is travelling straight in a downward direction and hence the flow is distributed across the plane and the mass fraction is more uniform.

[0086] FIG. 4 is a graph demonstrating the difference in DRE and NOx with (line 1 which shows DRE and line 3 which shows NOx) and without (line 2 which shows DRE and line 4 which shows NOx) the baffle 50 with increasing flow of oxygen. As can be seen, the performance with the baffle 50 when achieving 95% DRE generates 15 ppm NOx compared to the performance without a battle where 23 ppm NOx is generated at 95% DRE.

[0087] FIG. 5 demonstrates the performance of an abatement apparatus with one, two and six inlet assemblies 10 feeding the abatement chamber with increasing flow of oxygen. As can be seen, they each achieve consistent performance.

[0088] FIG. 6 shows the baffle 50 with orifices located at different positions designated positions 1, 2, 3, 4 and 5.

[0089] As can be seen in FIG. 7, which is a graph demonstrating the DRE, NOx and CO produced as the orifice apertures 70 move down the baffle 50 (at positions 1, 2, 3, 4 and 5 shown in FIG. 6), CF4 DRE reduces—this is a consequence of the effluent stream 100 entering the line-of-sight area of the inlet nozzle 20 from the effluent stream conduit 80. As the apertures 70 continue down, the effluent stream 100 leaves this area and the CF4 DRE returns to its normal performance. As result, it is important that the baffle 50 removes the line-of-sight gas flow from the effluent stream conduit 80 into the inlet nozzle 20, other variations where the baffle 50 either forces the effluent stream 100 to sweep around the baffle 50 into the plenum 110 and up or down into the annular chamber 120 significantly improves abatement performance.

[0090] FIGS. 8A and 8B show the positions of a standard length fuel lance 30 (FIG. 8A) and the longest length fuel lance 30 (FIG. 8B) with appropriately sized springs 40, as mentioned in FIG. 1 above.

[0091] FIG. 9 is a graph showing the DRE, CO and NOx performance with varied fuel lance 30 lengths when operating with 9 SLM lance fuel, 2.5 SLM coaxial fuel, 15 SLM 02 and 26 LPM CDA. As can be seen in FIG. 9, there is a clear trend that as the length of the fuel lance 30 increases, the DRE increases and therefore it is preferred to incorporate a short fuel lance 30. The short fuel lance 30 gives an increased residence time of fuel and mixed fuel and effluent stream 140 within the annular chamber 120 and the distance of the lance fuel from the coaxial flame is important for CF4 DRE. Also, the analysis shown in FIG. 2 suggest that the lance fuel velocity is extremely disruptive, the shortest fuel lance 30 allows the lance fuel to interact with the mixed fuel and effluent stream 140 with the added benefit of residence time for the flows to smooth out, creating a more laminar flow into the coaxial flame.

[0092] FIG. 10 is a graph showing the DRE, CO and NOx performance with varied spring 40 lengths (with the shortest fuel lance 30 installed), with 9 SLM of lance fuel, 2.5 SLM of coaxial fuel, 15 SLM of 02 and 26 LPM of CDA. From the data shown, it seems that as the length of the spring 40 increases, more turbulent gas flows interact with the swirling effect within the annular chamber 120, as shown in FIG. 11, resulting in an increased mixing with oxygen from the available CDA and consequently reducing NOx and CO emissions.

[0093] FIG. 11 (which is a CFD comparison of the inlet assembly 10 with (FIG. 11B) and without (FIG. 11A) the baffle 50 also shows due to the increased inertia produced by the baffle 50, the mixed fuel and effluent stream 140 have an increased swirl as they exit the inlet nozzle 20.

[0094] Accordingly, it can be seen that the swept effluent stream conduit 80 and baffle 50 controls the gas path of the effluent stream 100 into the abatement chamber.

[0095] This arrangement meets the need to improve CF4 DRE and thus the distribution of the effluent stream around the fuel lance 30 to in turn help mix the lance fuel with the incoming process gas (CF4, O2 and typically 50 slm of N2). The swept effluent stream conduit 80 removes the process flow gas bias, aids better mixing of the lance fuel and incoming process gas and allows a longer residence time of the resulting mixture before entering the coaxial flame.

[0096] FIG. 12 illustrates an inlet assembly 10′ for an abatement apparatus according to one embodiment. This arrangement is similar to that described with reference to FIG. 1 but the effluent stream 100′ is delivered axially. The inlet assembly 10′ has an inlet nozzle 20′ comprising an elongate cylindrical conduit having a coaxially located fuel lance 30′ therewithin. A concentrically located helical spring (not shown) may be positioned between an outer surface of the fuel lance 30′ and an inner surface of the inlet nozzle 20′. The fuel lance 30′ can be provisioned with different lengths as mentioned above. A further concentrically located lance 55′ is provided which delivers a gas (such as fuel or oxidant). In an upper portion of the inlet nozzle 20′ there is provided a baffle 50′. The baffle 50′ comprises a cylindrical tube having a number of apertures 60′ formed through its wall. An effluent stream conduit 80′ receives an effluent stream 100′ and is located upstream of a feed structure 150′ which sits in the effluent stream conduit 80′. The feed structure 150′ conveys a fuel 130′ to the fuel lance 30′ and has apertures 75′ to allow the effluent stream 100′ to be conveyed from the effluent stream conduit 80′ to a plenum surrounding the baffle 50′

[0097] In operation, the effluent stream 100′ is conveyed into the effluent stream conduit 80′. When activated, an oxygen inject (not shown) conveys oxygen into the effluent stream 100′ as it passes through the effluent stream conduit 80′ towards the feed structure 150′. The effluent stream 100′ passes through the apertures 75′ and undertakes multiple changes of direction as the only way for the effluent stream 100′ to progress through the inlet nozzle 20′ is via the apertures 60′. Accordingly, the main directional flow of the effluent stream 100′ is thus diverted towards the apertures 60′. This redirection of flow causes turbulence which assists in mixing the oxygen into the effluent stream 100′. An annular chamber 120′ is defined between the inner surface of the baffle 50′ and an outer surface of the fuel lance 30′. The annular chamber 120′ redirects the flow of the effluent stream 100′ along the elongate axis of the annular chamber 120′. These redirections of flow cause turbulence which assists in mixing the oxygen into the effluent stream 100′. As the effluent stream 100′ travels along the elongate axis of the annular chamber 120′, a generally laminar flow is restored. As the effluent stream 100′ passes the end of the fuel lance 30′, mixing between fuel 130′ delivered via the fuel lance 30′ and the effluent stream 100′ commences. Mixing continues until the mixed fuel and effluent stream 140′ exits the inlet nozzle 20′ into the abatement chamber (not shown) surrounded concentrically by the gas delivered from the lance 55′. To facilitate mixing and improve the stability of the mixed fuel and effluent stream 140′, the spring may impart a rotational component to the mixed fuel and effluent stream 140′ as it passes along the annular chamber 120′.

[0098] Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

[0099] Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

[0100] Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.