Burner liner

Abstract

The present invention provides a porous burner liner for a gas reduction system. The burner liner includes a hollow body defined by a wall comprising a plurality of interconnected, substantially concentric layers. Each layer of the wall includes a substantially regular perforated network; wherein the substantially regular perforated network of each layer is configured such that it is out of phase with one or more adjacent layers, and wherein the wall includes a sufficient layer configured such that the wall is optically opaque when viewed from the outside in any radially inward direction perpendicular to the wall.

Description

Technical Field

[0001] This invention relates to a gas reduction system radiant burner, and more specifically, to a perforated burner liner, a method for designing a perforated burner liner, and a method for manufacturing a perforated burner liner. Prior Technology

[0002] Radiation burners are known and commonly used to treat exhaust gas streams from one of the manufacturing processes used in, for example, the semiconductor or flat panel display manufacturing industries.

[0003] A known radiant burner uses combustion from an exhaust gas stream to remove compounds. A fuel gas is mixed with the exhaust gas stream, and this gas-gas mixture is conveyed into a combustion chamber laterally surrounded by the outlet surface of a porous gas burner. The fuel gas and air are simultaneously supplied to the porous burner liner to achieve flameless combustion at the outlet surface, wherein the amount of air traveling through the porous burner liner is sufficient to consume not only the fuel gas supply to the burner but also all combustibles in the gas-gas mixture injected into the combustion chamber.

[0004] Generally speaking, porous burner liners are made by layering one of fibers or polyurethane foam (which may be coated with powder and sintered or unsintered in different ways).

[0005] The inventors have discovered that known linings suffer from several drawbacks. For example, both fiber-based linings and foam linings are typically formed from sheets, resulting in the presence of a bonding line that affects their overall macroscopic uniformity. Furthermore, since both the fiber lamination and foam formation processes are random or pseudo-random, altering the properties of burner linings has, to date, relied on operator experience and trial-and-error as elements.

[0006] The present invention at least partially solves these and other problems of the prior art. Summary of the Invention

[0007] In a first embodiment, the present invention provides a porous burner liner for a gas reduction system. The porous burner liner includes a hollow body defined by a wall. The wall includes a plurality of interconnected, substantially concentric layers, each layer of the wall including a substantially regular openwork network. The substantially regular openwork network of each layer is configured such that it is out of phase with one or more adjacent layers. Additionally, the wall includes a sufficient layer configured such that the wall is optically opaque when viewed from the outside in any radially inward direction perpendicular to the wall.

[0008] In a second embodiment, the present invention provides a porous burner liner for a gas reduction system, the burner liner comprising a hollow body defined by a wall comprising a plurality of interconnected layers, wherein one layer comprises at least one right-handed substantially helical strut coupled to at least one left-handed substantially helical strut.

[0009] The present invention further provides a preferred method for manufacturing a porous burner liner according to a prior art by means of lamination.

[0010] Advantageously, the porous burner liner and manufacturing method disclosed herein can provide a regular structure that mimics the random structure of prior art foam and fiber-layered burner liners, thereby allowing burner properties to be controlled in a predictable manner, simplifying optimization and avoiding the need for trial-and-error experiments associated with known burner liner designs.

[0011] The result is a structure that supports combustion, has a uniform inner surface flammability, low back surface temperature, and minimal thickness. Near-blindness can be achieved with as few as six layers, while three times that number is required to provide sufficiently low back surface temperature. One design objective is to achieve minimal thermal conductivity within a single layer while minimizing interlayer conductivity. Typically, in use, the back surface temperature (i.e., the temperature of the outermost wall) will be approximately ambient temperature (e.g., 22ºC). Typically, in use, the inner surface (e.g., the innermost wall) will be at a temperature ranging from approximately 800ºC to approximately 1000ºC. Fuel and air typically flow from the back surface to the inner surface for combustion. Simple Explanation of the Diagram

[0012] The invention will be further described with reference to the following figures, which are intended to be non-limiting. Figures 1 and 2 provide a schematic representation of one type of porous burner layer. Figure 3 shows a single left-handed helix in one of the porous burner linings. Figure 4 shows one left-handed and one right-handed spiral of a porous burner liner. Figure 5 shows one layer of a porous burner liner. Figure 6 shows two layers of a porous burner liner. Figure 7 shows a ten-layer porous burner liner. Figure 8 shows the innermost layer of one of the alternative porous burner liners. Figure 9 shows two layers of a burner liner with an intermediate spacer layer. Figure 10 shows one of the optically opaque walls of a porous burner liner. Figure 11 shows a top-down view of one of the burner lining walls in Figure 10. Figure 12 shows one of the burner liners with an external perforated foil covering. Figure 13 shows the spiral strip used to form the foil covering in Figure 2. Figure 14 shows a section of a conical burner liner. Implementation

[0013] The present invention provides a porous burner liner for a gas reduction system. The burner liner includes a hollow body defined by a wall. The wall includes a plurality of interconnected layers.

[0014] The layers defining the walls of the hollow body may include a substantially regular perforated mesh. Generally, the mesh will include a plurality of supports and nodes arranged to form a porous mesh. The mesh may consist of one or more repeating units, preferably substantially identical, each repeating unit including a plurality of supports and nodes defining one or more holes or voids. Generally, the volume fraction of voids is relatively large compared to the volume fraction of repeating units, preferably most repeating units are voids by volume.

[0015] Preferably, the porous burner liner is optically opaque when viewed from the outside in any radially inward direction perpendicular to the outermost surface of the wall. Therefore, the wall may comprise a sufficient layer configured such that there is no linear radially inward path from one outermost surface of the wall to one innermost surface that is not blocked (i.e., intersected) by at least one pillar and / or node forming a portion of the wall. A perforated mesh has voids or holes providing a linear radially inward path through the entire thickness of the layer. Therefore, a single layer of the porous burner liner wall cannot be optically opaque on its own, even as a perforated mesh.

[0016] The minimum number of layers required to achieve optical opacity can be affected by the diameter of the strut and the phase shift between adjacent layers.

[0017] Preferably, the wall comprises a number of layers greater than the minimum number required to achieve optical opacity, more preferably at least twice the number of layers required to achieve optical opacity, and even more preferably at least three times the number of layers required to achieve optical opacity. Generally speaking, the wall comprises at least three layers, for example, from about 3 to about 20 layers, more preferably from about 4 to about 12 layers, and even more preferably from about 4 to about 9 layers.

[0018] Advantageously, the triple optical opacity provides a sufficiently low back surface temperature (e.g., approximately ambient temperature) during use.

[0019] The perforated mesh of each layer can be configured to be out of phase with one or more adjacent layers. That is, when viewed in a radially inward direction perpendicular to the outer surface of the layer, the repeating cells of adjacent layers are misaligned. Instead, generally speaking, a repeating cell of one layer will be offset from the circumference of a repeating cell of an adjacent layer, such that when viewed in a radially inward direction perpendicular to the outermost layer of the wall, the nodes of the adjacent layer are misaligned.

[0020] Preferably, when viewed in a radially inward direction perpendicular to the outermost layer of the wall, at least a portion of the corresponding struts of the repeating units in adjacent layers will at least partially, but not completely, overlap. The circumferential offset between adjacent layers may be referred to as the interlayer pitch. Generally speaking, the interlayer pitch is from about 5% to about 30% of the strut diameter, with about 10% being an example.

[0021] Preferably, the network is substantially continuous around an entire layer. Advantageously, there may be no bonding lines between layers.

[0022] Preferably, one layer includes at least one right-handed substantially helical strut coupled to at least one left-handed substantially helical strut, and more preferably a plurality of right-handed substantially helical struts coupled to at least one left-handed substantially helical strut.

[0023] When a layer includes two or more right-handed substantially helical struts coupled to two or more left-handed substantially helical struts, the right-handed struts are preferably substantially parallel, and the left-handed struts are substantially parallel.

[0024] Preferably, the right-hand columns of each floor are substantially parallel to the right-hand columns of the other floors. Preferably, the left-hand columns of each floor are substantially parallel to the left-hand columns of the other floors.

[0025] Preferably, the right-hand and left-hand spiral supports of each layer have substantially the same helical pitch. The pitch of a spiral can be defined as the height of a complete helical turn measured parallel to the axis of the spiral.

[0026] The right-hand and left-hand spiral supports of a single layer can also be offset circumferentially up to the pitch within the layer. Generally speaking, the pitch within a layer can be the same as or different from the pitch between layers.

[0027] In this document, a right-handed or left-handed helix may be referred to as an example. A layer of the wall may include one or more examples, typically two or more. Preferably from about 6 to about 400 examples, more preferably from about 8 to about 120 examples. For a given helical pitch and burner liner circumference, reducing the number of examples in a layer will increase the node spacing. The number of examples will generally be higher for burner liners with a relatively high helical pitch (from about 100 to 400 examples) and lower for burner liners with a relatively low helical pitch (from about 6 to about 20 examples). Generally speaking, the higher the number of examples per layer, the lower the number of layers required to achieve optical opacity for a given strut diameter and in-layer pitch.

[0028] As discussed, the intra-story pitch and inter-story pitch can be substantially the same. Preferably, the intra-story pitch is from about 5% to about 30% of the support diameter, with about 10% being an example.

[0029] A pitch greater than zero between layers and within layers ensures that the helical struts can intersect with adjacent helical struts at the nodes and that the number of layers required to contribute to optical opacity is sufficient. That is, the struts overlap at the nodes in a radial direction relative to the longitudinal axis of the burner liner.

[0030] The amount of overlap contributes to both the structural integrity of the wall and the radial thermal conductivity. Therefore, depending on the burner material selection, size, and intended use, and similar factors, a balance can be achieved between these two properties. In particular, in low helical pitch embodiments, an overlap of approximately 10% (preferably from about 5% to about 15%) of the strut diameter in a radial direction relative to the longitudinal axis of the burner liner has been found to be advantageous.

[0031] Conversely, particularly for embodiments with relatively high helical pitch where each layer includes a relatively high number of individual items, it is also found advantageous to overlap within a layer of approximately 100% (e.g., greater than approximately 90% or greater than approximately 95%) the width of a strut.

[0032] For the purposes of this invention, a relatively low helical pitch can be considered as a helical pitch having a pitch angle from about X to about Y.

[0033] Alternatively, a relatively high helical pitch can be considered as a helical pitch having a pitch angle greater than Y (preferably from about V to about W).

[0034] As discussed, in embodiments, each layer may include a plurality of right-handed substantially helical struts coupled to a plurality of spaced left-handed substantially helical struts. Additionally, one or more substantially helical struts of each layer may intersect with and be integrally formed with a substantially helical strut of a neighboring layer. Preferably, each substantially helical strut intersects with and is integrally formed with a substantially helical strut of a neighboring layer.

[0035] In an alternative embodiment, one or more radially extending spacers may couple a first layer to an adjacent layer. Generally speaking, a plurality of circumferentially separated radially extending spacers separate the first layer from the adjacent layers. These radially extending spacers are in the form of one or more intermediate spacer layers, thereby separating the adjacent main layers of the wall.

[0036] Preferably, the spacers are generally uniformly spaced and coupled to the outer inner surface of one of the two layers and the inner outer surface of the two layers. The spacers typically separate one layer from an adjacent layer by a radial distance substantially equal to the diameter and / or radial thickness of the spacer. In the case of multiple intermediate spacer layers in a porous burner, the spacers of adjacent intermediate spacer layers are preferably offset circumferentially. The spacers can advantageously reduce radial / interlayer heat conduction and / or increase the thermal path through the burner, for example, when the internode spacing is relatively low.

[0037] (Several) radially extending spacers may be in the form of a slat, usually in the form of a longitudinally extending slat. Generally speaking, the longitudinally extending slat may be substantially straight, although it may be equivalently in the form of a spiral or part thereof.

[0038] (Several) intermediate spacer layers are typically used in the walls of porous burner liners with low node spacing (e.g., less than about 4 mm, preferably from about 1 mm to about 4 mm).

[0039] As will be known to readers familiar with this art, the size of the wall of a porous burner liner will depend on the intended use and therefore the invention is not intended to be limited to any particular wall geometry. However, typically a porous burner liner wall will be generally tubular, having a substantially annular cross-section. The radial thickness of the wall is typically relatively small relative to the radius of the tube it provides.

[0040] Generally speaking, the wall of a porous burner liner will have an axial length of from about 50 mm to about 500 mm, more preferably from about 60 mm to about 200 mm (about 75 mm and about 150 mm are examples).

[0041] The inner diameter of the wall of the porous burner liner can be from about 50 mm to about 250 mm, preferably from about 100 mm to about 200 mm, with about 150 mm and about 175 mm being examples.

[0042] Generally speaking, the aspect ratio (i.e., the ratio of the inner diameter of the wall to its height) is from about 5:1 to about 1:5, such as from about 3:1 to about 1:3. An aspect ratio greater than 1:1 is preferred, such as from about 1:1 to about 1:5, or more preferably from about 2:3 to about 1:3.

[0043] The radial thickness of the wall of the porous burner liner is preferably from 1 mm to about 10 mm, and more preferably from about 2 mm to about 6 mm.

[0044] Without being bound by theory, the number of helical turns completed by each substantially helical strut in each layer will be determined by its helical pitch and the aspect ratio of the porous burner liner. For example, a relatively low-pitch helix can perform a relatively high number of helical turns for a given length of burner liner, while a relatively high-pitch helix will perform a lower number of helical turns for a burner of the same length.

[0045] A porous burner liner may be provided, wherein one right-handed substantially helical strut and one left-handed substantially helical strut of each layer complete more than one full helical turn. Alternatively, each substantially helical strut may complete a portion of a helical turn, preferably one or fewer helical turns.

[0046] Referring to Figures 1 and 2, for the purpose of understanding, a unfolded layer that has been tiled is shown, wherein: H = Height HP = Helical Pitch <° = Pitch angle = Tan -1(HP / C) C = circumference = π.D D = diameter C / I = circumference divided by the number of terms I = (Example of an LH or RH spiral in one layer) NS = Node spacing = (C² + HP²)⁰.⁵ / (2xI) n = initial angle, which is calculated as ((360 / example) / (offset - 1) = 0, n, 2n, 3n, etc.

[0047] With non-limiting examples, Table 1 illustrates how adjusting various parameters of the burner liner (including inner diameter, height, conductor diameter, intra-layer pitch, example, inter-layer and inter-layer pitch) can improve the control of node spacing, density, and node spacing relative to conductor size. It should be noted, for example, that node spacing can be significantly increased or decreased without affecting the bulk density of the burner liner to the same extent. [Shallow-angled structure] [steep angle] [structure] 1 2 3 4 5 6 7 8 [inner diameter] mm 75 75 75 75 75 75 75 75 [high] mm 75 75 75 75 150 75 75 75 [wire] [diameter] mm 0.3 0.3 0.45 0.6 0.3 0.3 0.45 0.6 [layer] [Inner pitch] mm 0.27 0.27 0.405 0.54 0.27 0 0 0 [Wire turn] 3 3 3 3 6 0.3 0.3 0.3 [spiral] [Pitch] mm 25 25 25 25 25 250 250 250 [Example] twenty four 18 12 9 twenty four 120 90 60 [layer] 11 11 11 11 11 11 11 11 [Start] [angle] [*] n 7.5 10 15 20 7.5 1.5 2 3 [Offset] [**] 3 3 3 3 3 3 3 3 [Radial] [Spacer] [(] [Slats] [)] twenty four twenty four twenty four [Between Floors] [Pitch] mm 0.27 0.27 0.405 0.54 0.27 0.27 0.405 0.54 [density] [(] [About] [) / ] [volume] [%] 75 81 81 82 75 81 78 80 [node] [spacing] mm 4.93 6.58 9.87 13.16 4.93 1.43 1.91 2.86 [Node spacing relative to wire size] 16.45 21.93 21.93 21.93 16.45 4.77 4.24 4.77 [surface] [1] [*] The initial angle is calculated as ((360 / example) / (offset - 1) 0, n, 2n, 3n, etc. **Based on arbitrary parameters used to achieve wire thickness and wire spacing for blindness**

[0048] Therefore, those skilled in this technique can solve one of the problems of identifying known porous burners by tuning the properties of the burner liner in a predictable manner.

[0049] Preferably, the porous burner lining wall has a bulk density of about 65% to about 90%, more preferably about 70% to about 85%. This can be calculated by comparing the calculated mass of the porous structure with the calculated mass of a solid cylinder of the same nominal size.

[0050] Turning to Figure 3, which illustrates a left-handed, essentially helical strut (1). The helix (1) has a height (H) of 75 mm and a helical pitch of 25 mm. Therefore, the illustrated helix (1) has three helical turns. The strut diameter is 0.3 mm.

[0051] Figure 4 shows a right-handed helical strut (2) coupled to the left-handed helical strut (1) of Figure 2 to form a pair of helical pairs (3). The right-handed helix (2) is substantially the same as the left-handed helix (1) except for its isohyet. The interlayer offset is 0.27 mm, such that where the helical struts substantially overlap, their overlap is approximately 10% of their diameter. Preferably, the substantially helical struts of a pair of pairs are joined at one end in an end-to-end face-to-face configuration. In the embodiment shown in Figure 3, the two ends of the helical struts forming the pair of pairs are joined in an end-to-end face-to-face configuration.

[0052] Although not critical, each helical strut of the preferred layer begins at a node (13) and / or ends at a node (14), and each helical strut of each layer of the preferred wall begins at a node and / or ends at a node. This configuration facilitates manufacturing and / or improves structural stability.

[0053] Figure 5 shows one layer of the twelve pairs of examples (twenty-four spiral examples) according to Figure 3. This layer is the innermost layer of a wall. The wall has an inner diameter (D) of 75 mm. All spiral struts have a generally circular cross-section. All spiral struts have substantially the same diameter (e.g., 0.3 mm).

[0054] Figure 6 shows the first layer (4) of Figure 5, which is surrounded by a second layer (5). In the illustrated embodiment, the second layer (5) includes the same number of instances as the innermost layer (4). Generally speaking, each layer will include the same number of instances, although they may be increased or decreased equally in a radially outward direction.

[0055] The interlayer pitch between the first and second layers is 0.27 mm. The intralayer offset is 0.27 mm. Therefore, at the nodes where the supports of adjacent layers form, their overlap reaches approximately 10% of their diameter.

[0056] As can be seen from a second layer (4) offset from the innermost layer, the optical transparency of the burner liner can be reduced. That is, there is a reduction in the area of ​​the outer layer that has a direct, unobstructed path from its longitudinal axis to the burner liner when viewed in a radially inward direction.

[0057] As previously discussed, a preferred porous burner liner includes a sufficient layer to be optically opaque. Advantageously, this means that there is no direct radial path from one outer surface of the burner liner to one inner surface of the burner liner that could lead to localized overheating.

[0058] Figure 7 shows one of the porous burner liner walls (6) comprising ten concentric layers as shown in Figures 5 and 6. This burner liner wall is optically opaque in any radially inward direction perpendicular to the outer surface of the wall.

[0059] Preferably, a porous burner liner comprises at least three times the minimum number of layers required to achieve the optical opacity of a selected layer configuration, each multiplier being individually referred to herein as an opacity group. The minimum number of layers required to achieve the optical opacity can be calculated using finite element analysis. The wall may comprise approximately 9 to approximately 25 layers.

[0060] Advantageously, as can be seen, the porous burner liner does not include bonding lines because the layers are substantially uniform and continuous. The absence of bonding lines improves the macroscopic uniformity of the burner liner and ultimately its performance. In embodiments, the burner liner may be substantially transversely isotropic.

[0061] Figure 8 shows the innermost layer (7) of one of the porous burners with an alternative configuration.

[0062] As illustrated, layer (7) comprises a plurality of left-handed helical struts (8) and right-handed helical struts (9). In this example, the overlap of the helical struts within the layer is approximately 100%. That is, the helical struts travel straight through each other at each node (16). The height of the porous burner liner is again 75 mm; however, the helical pitch is 250 mm, such that each helical strut completes 0.3 helical turns. The helical struts have a diameter of 0.3 mm. There are 120 examples in the layer. This can be considered a relatively steep-angle (high-pitch) structure. Such structures can be advantageous because they can be more easily manufactured by lamination.

[0063] As in the previous embodiment, the spiral struts are substantially connected at one end in a face-to-face configuration.

[0064] Preferably, each helical support of a layer begins at a node and / or ends at a node (15), and preferably each helical support of each layer of the wall begins at a node and / or ends at a node. This configuration facilitates manufacturing and / or improves mechanical strength and structural robustness.

[0065] As can be seen from the figure and Table 1, the node spacing provided by this type of configuration can be significantly smaller than that shown in the configurations in Figures 1 to 7.

[0066] A smaller node spacing can contribute to higher thermal conductivity.

[0067] The illustrated perforated mesh has a repeating unit, which has a rhomboid unit cell. As can be seen in Figures 8 and 9, the illustrated repeating units within a layer are substantially identical. Similarly, the repeating units in each layer are substantially identical to those in adjacent layers.

[0068] In one embodiment, a neighboring layer may be formed directly on the outer surface of one of the inner layers.

[0069] Alternatively, as illustrated in FIG9, the radially adjacent layers (10, 11) may be coupled together using one or more radially extending spacers (12). In the illustrated embodiment, the radially extending spacers (12) are in the form of one or more longitudinally extending slats (12). The illustrated slats are substantially straight.

[0070] The circumferential spacing (CS) of the radially extending spacer (12) is equal to or greater than the node spacing (NS) of (a number of) layers, preferably greater than the node spacing (NS) of the layer, and preferably at least twice the node spacing (NS) of the layer.

[0071] In embodiments, the radially extending spacers (12) can be considered as intermediate spacer layers among the main layers (10, 11) of the separated walls (i.e., main layers formed by substantially helical struts). Preferably, each intermediate spacer layer (12) may include from about 10 to about 50 longitudinally extending strips, more preferably from about 20 to about 30 longitudinally extending strips, 24 being an example. Preferably, the longitudinally extending strips of a spacer layer are substantially uniformly circumferentially separated (i.e., uniformly spaced around the circumference of the layers to which they are attached).

[0072] Preferably, the longitudinally extending slats have a circumferential spacing of about 5 mm to about 20 mm, with 10 mm being an example. The diameter of the slats may be larger or smaller than the diameter of the substantially helical strut, although preferably they are substantially the same.

[0073] Advantageously, the deployment of radially extended spacers can significantly reduce the interlayer thermal conductivity of the wall and / or further increase the tunability of the porous burner lining and / or improve the structural integrity of the wall.

[0074] As illustrated in Figures 9 and 11, due to the out-of-phase nature of adjacent layers (10, 11), the nodes (17, 18) (19, 20) of adjacent layers are offset. That is, a node of one layer does not overlap with a node of an adjacent layer. Preferably, as illustrated, starting from the innermost layer, the nodes of the next outer layer are positioned such that they are substantially radially aligned with the centroid of an unobstructed path (gap) to the center of the burner liner traveling radially inward through all such layers. Generally speaking, the configuration will be repeated from the innermost layer of the wall until optical opacity is achieved. The same configuration can then be repeated traversing any further groups of opacities positioned radially outward.

[0075] As will be understood, the number of layers required to achieve optical opacity will vary depending on the actual thickness (diameter) of the helical column, the number of elements per layer, the form and number of radially extending spacers, and the diameter of the walls. It is preferable to require approximately four or five layers to achieve optical opacity.

[0076] Preferably, the helical strut has a substantially circular cross-section. Preferably, the helical strut has a diameter of about 0.1 mm to about 1 mm, more preferably from about 0.2 mm to about 0.7 mm, with 0.3 mm being an example.

[0077] Preferably, the wall comprises at least three times the minimum number of layers required to achieve optical opacity (i.e., at least three opacity groups). Figure 10 illustrates an optically opaque wall (23) according to one embodiment.

[0078] Increasing the number of opacity groups increases the thermal path from the outermost surface of one of the burner liner walls to the innermost surface of the burner liner wall. Preferably, each opacity group repeats the same interlayer offset pattern used to achieve opacity as its radially inward (several) opacity groups.

[0079] Advantageously, it has been found that such configurations provide expected heat transfer properties commensurate with known burner liners.

[0080] Preferably, when present, the radially extending spacers adjacent to the intermediate spacer layer, and specifically the longitudinally extending strips (21, 22), can also be circumferentially offset. This configuration is illustrated in Figures 8 and 11. Advantageously, this can also increase the heat path and / or reduce the thermal conductivity of the through-wall.

[0081] All the porous burner liners illustrated so far are substantially cylindrical tubes. However, it should be understood that the burner liner according to the invention can take other hollow body forms, such as a hollow truncated conical burner liner as shown in Figure 14. Those skilled in the art will appreciate that the helical path of the struts and the shape of the repeating units can vary within and / or between layers to accommodate non-cylindrical hollow bodies.

[0082] The inventors have also discovered that using struts with uniform circular cross-sections to form a hollow truncated conical burner results in a higher porosity at the blunt end of the cone, which is more pronounced in structures with a large aspect ratio. This can be achieved by varying the cross-section of the struts from one end to the other. For example, a smaller helical strut diameter can be used at the narrow end of a truncated conical burner liner and a larger diameter strut can be used at its wider end, or preferably, helical struts with elliptical cross-sections with different cross-sections can be used, or even more preferably, struts with inclined elliptical cross-sections can be used at the larger end, where the inclination angle matches the cone angle.

[0083] Alternatively, the porous burner liner may further include one or more flow distribution elements, preferably in the form of a pair of counter-rotating spiral bands (26, 27) as illustrated in Figure 13.

[0084] Generally speaking, the spiral pitch and the geometry can be selected such that one of the selected circular patterns is given a controlled open area.

[0085] As shown in Figure 12, the porous burner liner described herein may further include a perforated sheet (24) coupled to one of the outermost (upstream) layers of the wall, which defines one of the outer surfaces of the porous burner liner. Preferably, the pores (25) of the sheet are substantially aligned with the voids in the outermost layer of the wall. The perforated sheet (24) may be integrally formed with or subsequently coupled to the remainder of the burner liner. Alternatively, the perforated foil may be formed from a circular pattern of counter-rotating bands (such as a plurality of counter-rotating bands shown in Figure 13).

[0086] Preferably, (a number of) flow distribution elements provide an open area (e.g., an orifice area) of about 5% and / or an orifice size (e.g., an orifice size) between 0.75 mm² and 1 mm² (such as 0.8 mm²).

[0087] Preferably, the flow distribution element (e.g., a strip and / or a perforated plate) is metallic, preferably comprising a metal or alloy, preferably a high-temperature oxidation-resistant alloy selected from the group consisting of iron-chromium-yttrium alloys, Inconel® 600 and 718, 314 stainless steel and iron-chromium-aluminum alloys.

[0088] Preferably, the porous burner lining is a single-unit structure. It is preferably made of a single material, more preferably a metallic material.

[0089] Preferably, the porous burner liner is manufactured using a powder bed melt deposition process. Preferably, the deposition direction is parallel to the longitudinal axis of the porous burner liner.

[0090] Alternatively, the burner lining can be formed from molten wire.

[0091] Preferably, the burner liner is metallic. More preferably, the burner liner is made of a metal or alloy (preferably a high-temperature oxidation-resistant alloy selected from the group consisting of iron-chromium-yttrium alloys, Inconel 600 and 718 and 314 stainless steels and iron-chromium-aluminum alloys).

[0092] The burner liner of this invention can be fitted into a radiant burner, preferably used in a gas reduction system for inward combustion of flameless combustion. This invention also provides a gas reduction system including a porous burner according to the disclosed embodiments and details. The porous burner liner according to this invention can be installed during the manufacture of a radiant burner or retrofitted to a pre-use radiant burner. Suitable radiant burners are described in EP1773474A and / or sold by Edwards Vacuum (RTM) under the trademark Atlas (RTM).

[0093] To avoid any doubt, features of any of the forms or embodiments described herein may be combined with appropriate modifications.

[0094] It should be understood that various modifications can be made to the illustrated embodiments without departing from the spirit and scope of the invention as defined by the appended invention application as interpreted under patent law.

[0095] 1: Left-hand spiral support 2: Right-hand spiral support 3: Spiral example pairs 4: Innermost layer 5: Second layer 6: Porous burner lining wall 7: Innermost layer 8: Left-handed spiral 9: Right-handed spiral 10: Towards the inner layer 11: Outer layer 12: Longitudinal extension slats 13: Node 14: Node 15: Node 16: Node 17: Node 18: Node 19: Node 20: Node 21: Longitudinal extension slats 22: Longitudinal extension slats 23: wall 24: Perforated film 25: Porosity 26: Spiral ribbon 27: Spiral ribbon 28: Truncated conical porous burner liner CS: Circumferential Spacing D:Inner diameter H: Height HP: Spiral Pitch NS: Node spacing

Claims

1. A porous burner liner for a gas reduction system, the burner liner comprising a hollow body defined by a wall comprising a plurality of interconnected substantially concentric layers; wherein each layer of the wall comprises a substantially regular perforated mesh; wherein the substantially regular perforated mesh of each layer is configured such that it is out of phase with one or more adjacent layers, and wherein the wall comprises a sufficient layer configured such that the wall is optically opaque when viewed from the outside in any radially inward direction perpendicular to the wall; wherein the wall comprises 3 to 20 layers; each substantially helical strut completing a portion of a helical turn; each layer comprising a plurality of circumferentially spaced left-handed substantially helical struts coupled to a plurality of circumferentially spaced right-handed substantially helical struts; and a plurality of radially extending spacers in the form of longitudinally extending offset slats and coupling a first layer to an adjacent layer.

2. The porous burner liner of claim 1, wherein the wall comprises more layers than are required to achieve optical opacity.

3. The porous burner liner of claim 2, wherein the wall comprises at least twice the number of layers required to achieve optical opacity.

4. The porous burner liner of claim 3, wherein the wall comprises at least three times the number of layers required to achieve optical opacity.

5. A porous burner liner as claimed in any of claims 1 to 4, wherein the wall comprises 4 to 9 layers.

6. A porous burner liner as claimed in any of claims 1 to 4, wherein the plurality of interconnecting layers are concentrically arranged.

7. A porous burner liner as claimed in any of claims 1 to 4, wherein the hollow system is substantially tubular or truncated conical.

8. A porous burner liner as claimed in any of claims 1 to 4, wherein one of the outermost layers of the wall is coupled to a perforated sheet defining one of the outer surfaces of the porous burner liner.

9. The porous burner liner of claim 8, wherein the pores of the perforated plate are substantially aligned with the voids in the outermost layer of the wall.

10. A porous burner liner as claimed in any of claims 1 to 4, wherein the burner liner is manufactured using powder bed melting.

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