Combustor for a secondary reformer

Abstract

A burner for a two-stage reformer, comprising: an oxidizer channel (22) for an oxidizer stream (4) and a swirler (7) located in the oxidizer channel; the swirler comprising: an inner body (16) having a central passage (30) arranged axially with respect to the oxidizer channel; an outer body (15) coaxial with respect to the inner body and external to the inner body; a first set of fixed vanes (14) extending from the inner body; a second set of fixed vanes (13) extending from the outer body; each set of vanes being arranged to induce a swirl of the oxidizer stream.

Description

Technical Field

[0001] This invention relates to the field of burners for two-stage converters. Background Technology

[0002] The burners in the two-stage reformer are designed to feed process gases and oxidizers into the combustion chamber. Process gases are typically partially converted gases from the first-stage reformer, including, for example, methane, hydrogen, carbon monoxide, and carbon dioxide. The oxidizer is typically air, oxygen-enriched air, or oxygen of desired purity. The process gases are at a high temperature of approximately 700-800°C, while the air is at a lower temperature, typically around 450°C to 600°C.

[0003] The burner is mounted vertically on top of the pressure vessel of the second-stage converter, above the combustion chamber. The burner essentially comprises an oxidizer channel arranged coaxially with the process gas channel. Typically, the process gas channel is an annular channel arranged coaxially around the oxidizer channel. The process gas and oxidizer remain separated as they flow through the coaxial channel of the burner and mix at the burner outlet.

[0004] A known practice is to provide a cyclone separator located in the oxidant channel. The cyclone separator is designed to cause the oxidant to swirl around a vertical axis to improve mixing with the process gas at the combustion chamber inlet, where a diffuse flame is formed.

[0005] In a common design of the prior art, a hydrocyclone includes a straight central passage surrounded by an annular channel, the annular channel comprising a group of rotating blades. The central passage does not include the rotating blades, such that the incoming flow of the oxidant is divided into two parts: an un-rotated internal flow through the central passage; and an external flow rotated by the blades through the annular channel. The internal and external flows merge downstream of the hydrocyclone.

[0006] The reason for this design is that the angle of the swirling blades relative to the axis (vertical axis) of the flow is determined by the manufacturing technique of forming the blades from a sheet of metal and subsequently welding them to the machined body. Therefore, the blade angle is typically larger than the optimal value for fluid dynamics, resulting in a larger swirling motion than desired. Excessive swirling motion of the flow can cause highly undesirable backflow of the mixture from the combustion chamber into the burner body, with the associated risk of flame rise within the burner, which can damage or destroy the burner.

[0007] To avoid this risk, existing burners are designed with a relatively large central passageway, having a cross-sectional area of ​​approximately 10% of the area of ​​the annular channel. Considering the varying pressure drops, the non-swirling internal flow typically constitutes about 20% to 30% of the total flow. Given that only a small portion passes through the blades, the internal flow reduces overall swirl; secondly, the non-swirling internal flow acts as a deterrent against the formation of recirculation along the burner axis, thereby preventing the synthesis gas from flowing back into the combustion chamber.

[0008] However, the above-described design of the hydrocyclone is far from optimal. In most cases, the swirling flow supplied to the external stream is higher than desired, which is then balanced by mixing with the internal stream. This process is inherently inefficient and causes a large pressure drop, increasing the energy consumption for compressing the oxide.

[0009] As a further drawback, the current design involves hand-finishing the blades from sheet metal and then welding them to the intermediate body. This fabrication process is time-consuming and error-prone. The manual fabrication and welding process of the blades can lead to significant risks associated with an asymmetric cyclone structure. This asymmetry can cause vibrations in the burner, resulting in uneven flame and temperature fields in the combustion chamber. Furthermore, it can lead to inconsistent cooling of the burner surface, which can adversely affect burner life, potentially causing damage to the refractory lining of the converter and pressure vessel, and increasing methane escape.

[0010] US 5,252,447 discloses an air-fuel mixer specifically for a gas turbine combustor, wherein the mixer includes an internal rotating cyclone and an external counter-rotating cyclone, the internal rotating cyclone and the external counter-rotating cyclone being independently rotatable and separated by a hub. WO 2023 / 227547 discloses a combustor for a conversion reactor. Summary of the Invention

[0011] The purpose of this invention is to overcome the aforementioned problems and limitations of the prior art. Specifically, this invention aims to address the problems of suboptimal hydrocyclone design and related drawbacks, including large pressure drops.

[0012] The objective of this invention is achieved using the burner as described in claim 1.

[0013] The burner of this invention includes a swirler located in an oxidant channel, and the swirler features an improved design compared to the prior art. The swirler includes two sets of blades that allow for a lower pressure drop in the oxidant flow and reduce backflow problems. In a very preferred embodiment, the swirler is manufactured using additive manufacturing (AM), which eliminates the disadvantages of hand-finishing from metal sheets.

[0014] This invention discloses a burner for a secondary reformer, comprising an oxidant channel (e.g., an oxidant conduit) coaxial with a process gas channel. Typically, the process gas channel is an annular channel surrounding the oxidant channel. The process gas channel may be a portion of the burner or a portion of the upper neck of the reformer vessel.

[0015] The oxidant can be air, oxygen-enriched air, or oxygen, while the process gas can be the effluent from a partial conversion process (e.g., the effluent from a primary converter or the effluent from a gas-heated converter located upstream of a secondary converter).

[0016] The term "two-stage converter" as used in this specification and claims may also include an autothermal converter (ATR).

[0017] The cyclone separator located in the oxidant channel comprises an inner body and an outer body. The inner body has a central passage for the oxidant flow. The outer body is arranged around the inner body and is coaxial with respect to the inner body. Therefore, the cyclone separator has: a first annular passage located between the inner and outer bodies; and a second annular passage located outside the outer body and within the oxidant channel. The inner and outer bodies preferably have a cylindrical shape.

[0018] The hydrocyclone includes: a first set of blades (inner blades) extending from the inner body in a first annular passage; and a second set of blades (outer blades) extending from the outer body in a second annular passage.

[0019] Each set of blades is arranged to cause swirling of the oxidant flow. In a preferred embodiment, each inner blade is arranged in a helical manner around an inner body, and / or each outer blade is arranged in a helical manner around an outer body. The inner blades may extend radially through part or all of the first annular passage; similarly, the outer blades may extend radially through part or all of the second annular passage. In some embodiments, the outer blades may be connected to an outer ring (shroud).

[0020] The blade inclination can be defined relative to the hydrocyclone axis. The hydrocyclone axis is the central axis of the hydrocyclone and is coaxial with the oxidant passage and process gas passage. In most applications, the burner is mounted vertically on top of the pressure vessel, and therefore the axis is a vertical axis. The first and second sets of blades are fixed (i.e., the blades do not move or rotate) such that the blades define a fixed swirling path for the oxidant flow. The first and second sets of blades are configured to cause swirling with the same direction of rotation. The direction of rotation is understood as the direction of rotation (clockwise or counterclockwise) given by the blades, and the direction of rotation is the same for both the first and second sets of blades.

[0021] In a preferred embodiment, each of the inner blades has a first tilt angle relative to the hydrocyclone axis of less than 65°, preferably in the range of 40° to 60°, and even more preferably in the range of 45° to 55°. Each of the outer blades preferably has a second tilt angle relative to the hydrocyclone axis of less than 75°, more preferably in the range of 50° to 70°, and even more preferably in the range of 55° to 65°.

[0022] The inner and outer blades are arranged to cause the oxidant flow to swirl in the same direction (clockwise or counterclockwise). According to various embodiments, the first and second tilt angles may be the same or different. The above upper limits are not limiting and can be exceeded in specific cases where high swirl is required.

[0023] In a preferred embodiment, the cross-sectional area of ​​the central passage is preferably 0.2% to 5.0%, more preferably 0.5% to 3.0%, and even more preferably 0.5% to 1.0% (e.g., about 0.8% or 0.8%) of the cross-sectional area of ​​the first annular passage. The cross-sectional area of ​​the first annular passage is preferably 10% to 25%, more preferably 15% to 25%, and even more preferably about 20% or 20% of the cross-sectional area of ​​the second annular passage. The cross-sectional area of ​​the passage is understood as the area in a plane perpendicular to the axis of the hydrocyclone.

[0024] The central passage within the internal body is a free passage without rotating blades. Therefore, a portion of the oxidant flowing into the central passage bypasses the swirling process. More specifically, the oxidant flow through the cyclone separator of the present invention is divided into three flows: an internal flow, which flows through the central passage and is not swirled; an intermediate flow, which flows through the first annular passage and is swirled by the internal blades; and an external flow, which flows through the second annular passage and is swirled by the external blades.

[0025] This invention allows for the fabrication of cyclones with a smaller central passage than those in the prior art, while still avoiding the risk of backflow. In embodiments of this invention, the internal flow is less than 10% or less than 5% of the total oxidant flow through the oxidant passage.

[0026] A further aspect of the invention is a method for feeding process gas and oxidant to a two-stage reformer using a burner as described above, wherein the oxidant flow through the central passage is less than 10% of the total oxidant flow.

[0027] The present invention has the following advantages.

[0028] For a given swirling effect, the present invention allows for a smaller tilt angle of the swirler blades than in the prior art, thanks to the provision of two sets of blades, and the invention is even more particularly relevant in embodiments for additive manufacturing.

[0029] This invention allows for the same swirl level as prior art designs, but with a smaller blade angle, resulting in reduced pressure drop. The inner body is retained for ease of construction and provides a small, non-swirling internal flow, preventing even small recirculation regions from forming in front of the inner blades. The outer body serves to finely adjust the angle of the outer blades, thereby enabling control of the flow distribution between the first and second annular passages and determining the desired swirl level. By optimizing the angles of the inner and outer blades, pressure drop can be minimized. As a result, the new design provides a significant reduction in pressure drop of approximately 10% to 30% compared to conventional designs.

[0030] In the embodiments, the proposed design is constructed using additive manufacturing (AM). AM eliminates the constraints on blade angles imposed by conventional manufacturing, allowing for lower angles and mitigating the risk of recirculation along the cyclone axis. Furthermore, by relying on additive manufacturing, the risks of asymmetric construction and all other construction-related problems outlined in the prior art description are eliminated.

[0031] In a preferred embodiment, a portion of the conduit defining the oxidant channel, located around the hydrocyclone, is integrally manufactured with the hydrocyclone via additive manufacturing. The workpiece, including the conduit and hydrocyclone portions, can be joined (e.g., welded) to one or more portions of a conventional conduit used to create the oxidant channel. A related advantage is that it simplifies the construction and reduces the number of welds compared to existing technologies, since the object integrally manufactured by AM requires no welding. Attached Figure Description

[0032] Figure 1 This is a sketch of a two-stage converter.

[0033] Figure 2 and Figure 3 A cyclone separator according to an embodiment of the present invention is shown.

[0034] Figure 4 express Figure 2 and Figure 3 The longitudinal section of the hydrocyclone.

[0035] Figure 5 and Figure 6 Different projections on the front plane of the new cyclone design are shown.

[0036] Figure 7 is a longitudinal cross-section of a conventional hydrocyclone in the prior art.

[0037] Figure 8 Another embodiment of the present invention is shown.

[0038] The accompanying drawings are given by way of illustration only and are therefore not intended to limit the invention. Detailed Implementation

[0039] Figure 1 A two-stage converter is shown, having a burner 1 located above a combustion chamber 2. The burner 1 includes an oxidant conduit 22 arranged coaxially with a process gas passage 21. The oxidant conduit 22 is connected to an oxidant inlet 41, and the process gas passage is connected to a process gas inlet 51.

[0040] Oxidant inlet 41 is connected to a suitable source of oxidant flow 4 (e.g., an air compressor). Oxidant 4 can be air, oxygen-enriched air, or oxygen. Process gas inlet 51 is connected to upstream equipment (e.g., a primary converter or a gas-heated converter) to provide partially converted process gas 5.

[0041] The process gas passage 21 includes a process gas distributor 6, and the oxidant conduit 22 includes a cyclone separator 7. The gas passage 21 may be part of a burner, or in some embodiments, the gas passage 21 may be formed in the upper neck of the refractory vessel of a two-stage converter.

[0042] Oxides 4 entering through inlet 41 are guided to combustion chamber 2 via oxidant conduit 22 and swirled around vertical axis AA by cyclone separator 7. At the outlet of conduit 22, oxides 4 encounter process gas 5, thereby forming diffusion flame 8 in combustion chamber 2. Arrows in the combustion chamber indicate gas recirculation. The converter may include a catalytic bed 3 for completing the conversion reaction.

[0043] The hydrocyclone axis AA passes through the center of the hydrocyclone and is also the axis of the oxidant pipe 22.

[0044] Figure 2 and Figure 3 A cyclone separator 7 according to a preferred embodiment of the invention is shown. The cyclone separator includes a coaxial inner body 16 and an outer body 15. The inner body 16 is a hollow conduit defining a central passage 30. The outer body 15 defines a first annular passage 40 located between the inner body 16 and the outer body 15, and a second annular passage 50 located outside the outer body 15. The second annular passage 50 may be externally defined by the inner surface 101 of the oxidant conduit 22. Figure 4 ).

[0045] The hydrocyclone 7 has a group of internal blades 14 and a group of external blades 13. The internal blades 14 are located in a first annular passage 40 and extend from an internal body 16. The external blades 13 are located in a second annular passage 50 and extend from an external body 15.

[0046] Preferably, the inner blades 14 are arranged in a spiral around the inner body 16, and the outer blades 13 are arranged in a spiral around the outer body 15, such as... Figure 2and Figure 3 As shown.

[0047] As shown in the figure, the inner blade 14 and the outer blade 13 follow the same (simultaneous) direction of rotation. The first set of blades and the second set of blades are configured to cause rotation along the same direction of rotation. The direction of rotation is understood as the direction of rotation (clockwise or counterclockwise) given by the blades, and the direction of rotation is the same for the first set of blades and the second set of blades.

[0048] Preferred materials for the hydrocyclone 7 include: Cr-Ni alloy; Fe-Ni-Cr alloy; stainless steel.

[0049] like Figure 4 As shown, the oxide flow 4 is divided into three separate flows: the outer flow 17 in channel 50, the intermediate flow 18 in channel 40, and the innermost flow 19 in the central passage 30. Flows 17 and 18 are rotated by the outer blade 13 and the inner blade 14, respectively; the inner flow 19 (“bypass flow”) is not rotated because there are no blades inside the small channel 30.

[0050] Figure 5 This represents the projection of the inner blade 14 onto the plane, and shows the tilt angle V1 of the blade 14 relative to the axis AA. Similarly, Figure 6 The projection of the outer blade 13 onto the plane is shown, and the tilt angle V2 of the blade 13 relative to the axis AA is also shown.

[0051] Figure 7 shows a cross-sectional view of a conventional hydrocyclone design. A conventional hydrocyclone includes a single set of blades 9 and a fairly large bypass channel 60. By comparing Figure 7 and... Figure 4 As can be seen, the central passage 30 of the hydrocyclone 7 of the present invention is significantly smaller than the central passage of a known hydrocyclone. Therefore, the bypass flow (which crosses the hydrocyclone without being swirled) is smaller.

[0052] Figure 8 This is an example of an embodiment in which a portion of the oxidant conduit 101 is integrally formed with the hydrocyclone 7 by additive manufacturing. Figure 8 The objects (including the hydrocyclone 7) are individual workpieces made of AM, and these individual workpieces can be welded to other parts of the oxidant pipeline.

Claims

1. A burner (1) for a two-stage converter, comprising: Oxidizing channel (22), the oxidizing channel (22) is arranged to feed oxidizing agent flow (4); A hydrocyclone (7) is located in the oxidant channel (22); The cyclone separator includes: An internal body (16) having a central passage (30). An outer body (15) is coaxial with respect to the inner body (16) and outside the inner body (16), defining a first annular passage (40) between the inner body and the outer body and a second annular passage (50) outside the outer body (15) within the oxidant channel (22). A first set of fixed blades (14) extends from the inner body in the first annular passage (40); a second set of fixed blades (13) extends from the outer body in the second annular passage (50); the first set of blades and the second set of blades are arranged to cause rotation having the same rotational direction as the oxidant flow (4).

2. The burner according to claim 1, wherein, The cross-sectional area of ​​the central passage (30) is between 0.2% and 5.0% of the cross-sectional area of ​​the first annular passage (40), preferably between 0.5% and 3.0% of the cross-sectional area of ​​the first annular passage (40), and more preferably about 0.8% of the cross-sectional area of ​​the first annular passage (40).

3. The burner according to claim 1 or 2, wherein, The cross-sectional area of ​​the first annular passage (40) is between 10% and 25% of the cross-sectional area of ​​the second annular passage (50), preferably between 15% and 25% of the cross-sectional area of ​​the second annular passage (50), and more preferably about 20% of the cross-sectional area of ​​the second annular passage (50).

4. The burner according to any one of the preceding claims, wherein, The hydrocyclone is manufactured using additive manufacturing.

5. The burner according to claim 4, wherein, The portion of the conduit (101) that defines the oxidant channel around the hydrocyclone (7) is integrally formed with the hydrocyclone (7) by additive manufacturing.

6. The burner according to any one of the preceding claims, wherein, The inner body (16) and the outer body (15) have a cylindrical shape.

7. The burner according to any one of the preceding claims, wherein, Each blade in the first set of blades (14) is arranged in a spiral around the inner body (16).

8. The burner according to any one of the preceding claims, wherein, Each blade in the first set of blades is arranged around the inner body (16) at a first tilt angle (V1) relative to the hydrocyclone axis (AA), wherein the first tilt angle (V1) is less than 65°, preferably in the range of 40° to 60°, and even more preferably in the range of 45° to 55°.

9. The burner according to any one of the preceding claims, wherein, Each blade in the first set of blades (14) extends from the inner body (16) toward the outer body (15).

10. The burner according to any one of the preceding claims, wherein, Each blade in the second set of blades (13) is arranged in a spiral around the outer body (15).

11. The burner according to any one of the preceding claims, wherein, Each blade in the second set of blades is arranged around the outer body (15) at a second tilt angle (V2) relative to the hydrocyclone axis (AA), wherein the second tilt angle (V2) is less than 75°, preferably in the range of 50° to 70°, and even more preferably in the range of 55° to 65°.

12. The burner according to any one of the preceding claims, wherein, Each blade in the second set of blades (13) extends from the outer body (15) toward the oxidant channel (22).

13. The burner according to any one of the preceding claims, wherein, The first group of blades and the second group of blades are arranged in the same direction, either clockwise or counterclockwise.

14. A method for feeding process gas (5) and oxidant (4) to a two-stage reformer using a burner according to any one of the preceding claims, wherein, The oxidant flow (4) through the central passage (30) is less than 10% of the total oxidant flow through the oxidant channel (22), preferably less than 5%.

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