Fluid burner head and use of the fluid burner head

Abstract

A fluid burner head (9) for a fluid combustion unit (1) and the use of the fluid burner head (9) in the fluid combustion unit (1) are provided. The fluid burner head (9) comprises a body (11) having a hollow tube (13) for carrying a fluid to be combusted to a combustion chamber (5), and a cap (15) at least partially closing an upper end (25) of the tube (13). A wall (17) of the tube (13) comprises a plurality of rows (29) of holes (27), the rows (29) extending about a central longitudinal axis (C) of the fluid burner head (9). The holes (27) allow for combustion of a flow of fluid from an interior (49) to an exterior (51) of the tube (13). The fluid burner head (9) is further characterized by comprising an annular first projection (39) extending about the central longitudinal axis (C) of the fluid burner head (9). A first projection (39) projects diagonally upward from the outer surface (43) of the body (11) above the top row (29a) of holes (27) in the tube (13) at an angle α relative to the central longitudinal axis (C) of the fluid burner head (9), where 0<α<90 degrees.

Description

[Technical field]

[0001] The present invention relates to a fluid burner head for a fluid combustion unit, and to its design. The present invention also relates to the use of such a fluid burner head in a fluid combustion unit for burning boil-off gas from a fuel tank on board a ship. [Background technology]

[0002] In various situations, it may be necessary to combust a fluid, such as a gas or a mixture of gas and liquid. For example, gas combustion units are typically on board LNG carriers, i.e. tank vessels arranged to transport liquefied natural gas (LNG). The LNG, whose vaporization temperature is -160 °C at atmospheric pressure, is contained in tanks. Even if these tanks are insulated, evaporation of the LNG inevitably occurs, forming the so-called boil-off gas. This boil-off gas increases the pressure inside the tank and must be vented from the tank for safety reasons. Once removed from the tank, the boil-off gas can be re-liquefied and returned to the tanks to be used as fuel on board the LNG carrier or burned by the gas combustion unit.

[0003] A gas combustion unit may typically include a gas burner head extending into a combustion chamber. Gas to be burned is supplied to the combustion chamber through the gas burner head, where it is ignited and burned. Known gas burner heads include a perforated tube having an end closed by a cap. Gas is conveyed through the tube and through the perforations in the tube to the combustion chamber, where combustion takes place in a flame. When the gas pressure is relatively high, the gas is supplied through the perforations at a high velocity, and a flame is generated at some distance from the gas burner head. Furthermore, the gas flow in the tube cools the gas burner head. As a result, the temperature of the gas burner head is kept low enough to avoid damage to the gas burner head. However, when the gas pressure is relatively low, the gas is supplied through the perforations at a low velocity, and as a result, a flame is generated closer to the gas burner head. Also, cooling of the gas burner head by the gas flow in the tube is reduced. This can cause the temperature in the gas burner head to become very high, which can damage the gas burner head, usually in the area close to the closed end of the tube. Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to provide a fluid burner head and a use of the fluid burner head that at least partially solves the above problems. The basic idea of ​​the present invention is to provide the fluid burner head with a means for forcing the burning fluid, and therefore the combustion flame, further away from the fluid burner head. The fluid burner head and the use of the fluid burner head to achieve the above object are defined in the appended claims and are discussed below. [Means for solving the problem]

[0005] A fluid burner head for a fluid combustion unit according to the invention comprises a body. The body comprises a hollow tube or pipe for conveying a fluid to be burned to a combustion chamber and a cap at least partially closing an upper end of the tube. The tube further comprises a lower end for receiving a fluid within the tube, i.e. inside the tube. The wall of the tube comprises a plurality of rows of holes, the rows extending around a central longitudinal axis of the fluid burner head. The holes allow a flow of the fluid to be burned from the inside of the tube to the outside, i.e. through the wall of the tube. The fluid burner head is characterized in that it further comprises an annular first projection or protrusion extending around the central longitudinal axis of the fluid burner head. The first projection protrudes obliquely from the outer surface of the body in a direction away from the lower end of the tube, i.e. upwards, above the top row of holes of the tube, at an angle α to the central longitudinal axis of the fluid burner head, where 0<α<90 degrees. The top row of holes is the row of holes that is located closest to the cap.

[0006] The first projection can include opposed first and second edges. The first and second edges can be annular and extend along one another. The first projection can directly or indirectly engage the body at and along the first edge, and the second edge can be free.

[0007] The terms "combustion" and "combustion" and variations thereof are used herein and are intended to have the same meaning.

[0008] The fluid may be a gas or a mixture of gas and liquid. As an example, the fluid may be boil-off gas from an LNG tank, such as methane or a mixture of methane and nitrogen.

[0009] The tube may include a mesh formed into a cylindrical shape.

[0010] The tube may be a perforated tube and the opening may be a perforation in the tube.

[0011] The tube may be elongated and may have any suitable wall thickness and any suitable cross-section, such as circular, oval or polygonal.

[0012] The tube may be made of any suitable material, such as a metal, for example, carbon steel, stainless steel or aluminum.

[0013] The central longitudinal axis of the fluid burner head may be coincident with the central longitudinal axis of the tube.

[0014] Multiple rows here means two or more rows.

[0015] The holes, openings, apertures or perforations in the tube may or may not all have the same size and / or shape, they may have any suitable size and shape, such as circular, oval or polygonal, and the holes may or may not be equidistantly spaced.

[0016] "Annular" does not necessarily mean a circular longitudinal extent, but may mean any closed longitudinal extent, such as an elliptical or polygonal extent.

[0017] As used herein, "top," "top," "bottom," "bottom," "upper," "lower," etc., refer to the fluid burner head when oriented in normal use. Additionally, "top" / "bottom" refers to the location furthest / closest from the ground or surface on which the fluid combustion unit containing the fluid burner head is positioned.

[0018] As noted above, the cap at least partially closes the top end of the tube, where a top end that is only partially closed can mean, for example, that gas can pass from inside the tube to outside it, through an opening in the cap, or between the tube and the cap.

[0019] The first projection may or may not have a uniform cross-section, e.g., a constant width and / or thickness, along its longitudinal extent. As an example, the first projection may be formed as a skirt or flange. If the width and thickness are zero along one or more portions of the longitudinal extent, the first projection may be considered to be discontinuous.

[0020] The first protrusion is positioned to force the fluid to burn away from the fluid burner head to reduce the temperature of the fluid burner head even when the fluid is supplied through the tube hole at a relatively slow velocity, thereby reducing the risk of damage to the fluid burner head.

[0021] The tube and cap may be integrally formed, however, in accordance with one embodiment of the present invention, the tube and cap are formed separately, allowing the tube and cap to be replaced independently of one another, if necessary.

[0022] The tube and the cap can be made of the same material. However, according to one embodiment of the present invention, the cap and the tube are made of different materials. This may allow for a more flexible construction of the fluid burner head. The cap can be made of any suitable material, such as refractory concrete or metal, for example carbon steel, stainless steel or aluminum.

[0023] The first protrusion may be located anywhere between the top row of holes in the tube and the top end of the fluid burner head. However, according to one embodiment of the present invention, the first protrusion protrudes from the outer surface of the body at the interface between the tube and the cap. If the first protrusion is not in place, the local temperature at the interface between the tube and the cap will tend to be relatively high. Thus, by locating the first protrusion at the tube-cap interface, the risk of damage to the fluid burner head can be minimized.

[0024] The fluid burner head may be configured such that the tube and the first protrusion are formed separately, such that when the first protrusion wears, it can be replaced with a new protrusion without having to discard the tube and possibly the cap.

[0025] The tube may have a cross-section that varies along its central longitudinal axis, however, in accordance with one embodiment of the present invention, the upper portion of the tube, including the hole, has a substantially uniform cross-section along the central longitudinal axis of the fluid burner head, which may facilitate easier manufacture of the fluid burner head.

[0026] The fluid burner head may further include an annular support extending about a central longitudinal axis of the fluid burner head. The support may be connected to the first projection and engage with the body of the fluid burner head to secure the first projection to the body. Such a design may facilitate placement of the first projection on the body. As with the first projection, the support may or may not have a uniform cross-section along its longitudinal extent and may be continuous or discontinuous.

[0027] The fluid burner head may further include an annular second protrusion extending about a central longitudinal axis of the fluid burner head. The second protrusion may protrude from an outer surface of the body between the top row of tube holes and the first protrusion. The first protrusion may or may not protrude beyond the second protrusion. The second protrusion may serve to force the fluid to burn away from the fluid burner head to further reduce the temperature of the fluid burner head even when the fluid is fed through the tube holes at a relatively low velocity, thereby further reducing the risk of damage to the fluid burner head.

[0028] The second protrusion may extend from the outer surface of the tube to locally shield the tube in areas where the tube temperature tends to be relatively high, thereby minimizing the risk of damage to the tube.

[0029] As described above, the fluid burner head may include an annular support extending about a central longitudinal axis of the fluid burner head, the support being connected to both the first and second projections and capable of engaging a body of the fluid burner head to secure the first and second projections to the body.

[0030] Regardless of whether the support is connected only to the first prong or also to the second prong, the support may engage with the body in various ways. As an example, it may be screwed into the body with a tight fit so that it stays in place by friction. However, according to one embodiment of the present invention, the support is clamped between the cap and the tube. This may allow for a precise positioning of the first prong, and possibly also the second prong, along with a secure engagement between the support and the body of the fluid burner head.

[0031] The cap can be designed in various ways. According to one embodiment of the present invention, it comprises a top and a bottom, the bottom protruding into the tube. This allows for a secure and precise engagement between the cap and the tube.

[0032] The bottom of the cap may include a portion that tapers away from the top of the cap. For example, the bottom may be conical, or in some cases, frustum of a cone. This may result in a flow area within the tube that is perpendicular to the central longitudinal axis of the tube, decreasing in a direction toward the cap, i.e., toward the top end of the tube. This, in turn, may increase the fluid flow rate within the tube in a direction toward the cap, i.e., toward the top end of the tube. As a result, this design may allow the fluid, and thus the combustion flame, that is delivered through the top hole of the tube to be forced further away from the fluid burner head. This may allow the temperature of the fluid burner head to be further reduced, and the risk of damage to the fluid burner head to be further reduced, especially when the fluid is delivered through the tube at a relatively low pressure.

[0033] The fluid burner head can be designed so that the outer periphery of the top of the cap is larger than the inner periphery of the tube, which can prevent the top of the cap from being received into the tube and allow for a precise and secure engagement between the cap and the tube.

[0034] The fluid burner head according to the present invention may be used in a fluid combustion unit for combusting boil-off gas from a fuel tank on board a marine vessel.

[0035] The above discussed advantages of the different embodiments of the fluid burner head according to the invention are naturally transferable to the different embodiments of the use according to the invention.

[0036] Further objects, features, aspects and advantages of the present invention will become apparent from the following detailed description and drawings.

[0037] The invention will now be described in more detail with reference to the accompanying schematic drawings. [Brief description of the drawings]

[0038] [Figure 1] 1 shows a schematic cross-section of a fluid combustion unit. [Diagram 2] 2 is a schematic perspective view of a fluid burner head of the fluid combustion unit of FIG. 1; [Diagram 3] FIG. 3 is a schematic side view of the fluid burner head of FIG. 2. [Figure 4] FIG. 3 is a schematic cross-sectional view of the fluid burner head of FIG. 2. [Diagram 5] FIG. 5 is an enlarged view of a portion of the cross section of FIG. [Figure 6a] FIG. 3 is a schematic side view of the fluid burner head arrangement of FIG. 2. [Figure 6b] FIG. 6b is a schematic top view of the arrangement of FIG. [Figure 6c] FIG. 6b is a schematic cross-sectional view of the arrangement of FIG. 6a. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] In FIG. 1, a fluid combustion unit 1, more specifically a gas combustion unit, is shown. The fluid or gas combustion unit 1 is arranged on board a ship (not shown), more specifically an LNG carrier, for burning boil-off gas from one or more LNG tanks of the ship. The fluid combustion unit 1 comprises a fluid burner system 3, an air supply system (not shown), a combustion chamber 5, and a stack 7. Boil-off gas from the LNG tank is fed to the fluid burner system 3 and further to the combustion chamber 5, where it is ignited and burned. The combustion products leave the combustion chamber 5 and are mixed with cool air in the stack 7 before leaving the fluid combustion unit 1. The structure and function of a fluid combustion unit are well known in the art and will not be described in further detail herein.

[0040] The fluid burner system 3 includes a fluid burner head 9, more specifically a gas burner head, which is shown in further detail in Figures 2-6. The fluid burner head 9 includes a body 11, which includes a hollow elongated stainless steel tube 13 and a solid cap 15 of refractory concrete. The tube 13 and cap 15 are separate separable elements having circular peripheries as viewed along the central longitudinal axis C of the fluid burner head 9.

[0041] The tube 13 has a wall 17 of uniform thickness along and about the central longitudinal axis C of the fluid burner head 9. Referring to FIG. 4, it includes a lower end 19, a lower portion 21, an upper portion 23 and an upper end 25 arranged successively along the central longitudinal axis C. The upper portion 23 of the tube 13 includes a number of circular holes 27 extending through the wall 17 of the tube 13. The holes 27 are arranged equidistantly in rows 29. The rows 29 of holes 27 are parallel to one another and extend equidistantly about the central longitudinal axis C of the fluid burner head 9.

[0042] 5, the cap 15 comprises a top portion 31 and a bottom portion 33 arranged concentrically about the central longitudinal axis C of the fluid burner head 9. The boundary between the top and bottom portions 31, 33 of the cap 15 is indicated by a dashed line. The top portion 31 has the basic shape of a disk with a constant cross-section along the central longitudinal axis C. The bottom portion has the basic shape of a truncated cone with a circular cross-section that decreases along the central longitudinal axis C in a direction away from the top portion 31 of the cap 15. The maximum cross-section of the bottom portion 33 is smaller than the cross-section of the top portion 31.

[0043] As can be seen from the drawings, and in particular from FIG. 5, the cap 15 closes the upper end 25 of the tube 13. The bottom part 33 of the cap 15 has a maximum circumference smaller than the inner circumference of the tube 13 and is received inside the tube 13. The top part 31 of the cap 15 has a circumference substantially equal to the outer circumference of the tube 13 and larger than the inner circumference of the tube 13. The top part 31 of the cap 15 is disposed outside the tube 13 and adjacent its annular edge which defines the upper end 25 of the tube 13. Due to the above-defined relative dimensions of the tube 13 and the cap 15, an annular groove 35 is formed between the bottom part 33 of the cap 15 and the tube 13.

[0044] With reference to Figures 5 and 6a-c, the fluid burner head 9 further comprises an annular support 37 in the form of a flat circular ring of stainless steel, an annular first projection 39 in the form of a circularly extending skirt of stainless steel, and an annular second projection 41 made of stainless steel in the form of a very short tube having a circular cross section. The support 37, the first projection 39 and the second projection 41 are arranged concentrically with respect to the longitudinal central axis C of the fluid burner head 9. The first projection 39 projects upwards and outwards from the outer edge of the support 37, while the second projection projects downwards from the outer edge of the support 37. The support 37, the first projection 39 and the second projection 41 are integrally formed in an arrangement designed to cooperate with the body 11 of the fluid burner head 9. More specifically, the support 37 is positioned and clamped between the tube 13 and the cap 15 with the first and second projections 39 and 41 projecting from the outer surface 43 of the body 11 (Figure 3). The first projection 39 has mutually extending annular first and second longitudinal edges 39a and 39b (Fig. 6a). The first projection 39 engages with the body 11 indirectly, more specifically via the support 37, at and along the first edge 39a, while the second edge 39b is free. The second projection 41 has mutually extending annular first and second longitudinal edges 41a and 41b (Fig. 6b). The second projection 41 surrounds the body 11 and its inside contacts the outer surface 43 of the body 11 between the first and second edges 41a and 41b. The tube 13 and the cap 15 are connected by elements not shown in the drawings. Thereby, the support 37 and the first and second projections 39 and 41 extend about the central longitudinal axis C of the fluid burner head 9 at the interface 45 between the tube 13 and the cap 15 (FIG. 5), i.e. above the top row 29a of the rows 29 of holes 27 (FIG. 3). Further, with particular reference to FIGS. 5 and 6c, the support 37 is clamped between the tube 13 and the cap 15 such that the first projection 39 projects obliquely upwards at an angle α=30 degrees relative to the central longitudinal axis C of the fluid burner head 9, while the second projection 41 projects downwards from the outer surface 47 of the tube 13 so as to surround the top of the tube 13.

[0045] The fluid burner head 9 is arranged to convey the boil-off gas to be combusted into the combustion chamber 5 of the fluid combustion unit 1 (FIG. 1). More specifically, referring to FIG. 4, the boil-off gas is arranged to be fed into the interior 49 of the tube 13 of the fluid burner head 9 via the lower end 19 of the tube 13, then upward through the lower portion 21 of the tube 13, then into the upper portion 23 of the tube 13, and further through the holes 27 in the tube wall 17 to the exterior 51 of the tube 13, and thus into the combustion chamber 5 (FIG. 1). Inside the combustion chamber 5, the boil-off gas is ignited and combusted in a flame, as previously described. The first and second protrusions 39, 41 are arranged to force the boil-off gas, and thus the combustion flame, away from the body 11 of the fluid burner head, so that the temperature of the fluid burner head remains low enough to avoid melting damage of the tube 13 and cracking damage of the cap 15, even if the pressure of the boil-off gas and the velocity of the boil-off gas through the holes 27 are relatively low. The frusto-conical shape of the bottom 33 of the cap 15 is arranged to increase the velocity of the boil-off gases through the holes 27 close to the top end 25 of the tube 13, helping to reduce the temperature of the body 11 and therefore minimising damage to the body 11. The first and second protrusions 39 and 41 protect and shield the body 11 of the fluid burner head 9 from exposure to harsh environments. In the event that the first and second protrusions 39 and 41 are damaged, the arrangement consisting of the support 37 and the first and second protrusions 39 and 41 can be replaced with a new one, whilst the tube 13 and cap 15 may be further used.

[0046] The above-described embodiments of the present invention should be considered as examples only: those skilled in the art will recognize that the described embodiments can be varied in several ways without departing from the concept of the present invention.

[0047] As an example, the fluid burner head need not include the second protrusion, but may only include the first protrusion.

[0048] As another example, the fluid burner head need not include a support for fastening the first protrusion, and possibly the second protrusion, to the body of the fluid burner head. Instead, the first protrusion, and possibly the second protrusion, can be fastened directly to the body of the fluid burner head.

[0049] As yet another example, the support need not be secured to the body of the fluid burner head by being clamped between the tube and the cap. In an alternative embodiment of the invention, the support can be located on the outside of the tube and / or cap such that it fits tightly to stay in place by friction. Thus, the first and second protrusions need not be located at the interface between the tube and the cap.

[0050] The first and second projections do not have to be formed separately from the tube and the cap, but can be formed integrally with the tube and / or the cap. Such a design may compromise the possibility of replacing the first and second projections, and only the support, if present, if they are damaged.

[0051] The angle α between the first protrusion and the central longitudinal axis of the fluid burner head does not have to have the above value, but may be greater or less.

[0052] The tube and cap need not be separately formed and made of different materials, but instead can be integrally formed and / or made of the same material.

[0053] It should be emphasized that details not relevant to the present invention have been omitted and that the figures are merely schematic and not drawn to scale. It should also be mentioned that some figures may be more simplified than others. Thus, some components may be shown in one figure but omitted in another. Finally, as used herein, the prefixes "first", "second", etc. are used only to distinguish different components and do not indicate a requirement regarding relative position or orientation. [Explanation of symbols]

[0054] 1 Fluid Combustion Unit 3 Fluid Burner System 5. Combustion chamber 13 tube 15 Cap 17. Wall 19 Bottom end 21 Lower 23 Upper 25 Top 27 holes 29 columns 33 Bottom 37 Support 39 First protrusion 39a First Edge 39b The second edge 41 Second protrusion 47 Exterior

Claims

1. A fluid burner head (9) for a fluid combustion unit (1) comprising a body (11) including a hollow tube (13) for carrying a fluid to be combusted to a combustion chamber (5) and a cap (15) at least partially closing an upper end (25) of the tube (13), the tube (13) including a lower end (19) for receiving the fluid within the tube (13) and a plurality of rows (29) of holes (27), the rows (29) further including a wall (17) of the tube (13) extending about a central longitudinal axis (C) of the fluid burner head (9), the holes (27) allowing a flow of the fluid to be combusted from an interior (49) to an exterior (51) of the tube (13), the fluid burner head (9) further comprising an annular first projection (39) for projecting the fluid from the interior (49) of the tube (13) to an exterior (51) of the tube (13).

1. A fluid burner head (9), comprising: an annular first projection (39) extending about the central longitudinal axis (C) of the fluid burner head (9) and projecting obliquely from an outer surface (43) of the body (11) away from the lower end (19) of the tube (13) above a top row of holes (29a) of the tube (13) at an angle α to the central longitudinal axis (C) of the fluid burner head (9), wherein 0<α<90 degrees, the top row of holes (29a) being the row of holes (27) located nearest to the cap (15), the first projection (39) having a frusto-conical skirt shape and projecting from the outer surface (43) of the body (11) at a boundary (45) between the tube (13) and the cap (15).

2. 2. The fluid burner head (9) of claim 1, wherein the tube (13) and the cap (15) are formed separately.

3. 3. A fluid burner head (9) as claimed in claim 1 or 2, wherein the cap (15) and the tube (13) are made of different materials.

4. 4. The fluid burner head (9) according to any one of claims 1 to 3, wherein the tube (13) and the first projection (39) are formed separately.

5. 5. A fluid burner head (9) as claimed in any one of claims 1 to 4, wherein the upper part (23) of the tube (13) containing the hole (27) has a substantially uniform cross-section along the central longitudinal axis (C) of the fluid burner head (9).

6. 6. A fluid burner head (9) as claimed in any one of claims 1 to 5, further comprising an annular support (37) extending around the longitudinal central axis (C) of the fluid burner head (9), the support (37) being connected to the first projection (39) and engaging with the body (11) of the fluid burner head (9) to secure the first projection (39) to the body (11).

7. 6. The fluid burner head (9) according to any one of claims 1 to 5, further comprising an annular second projection (41) extending around the longitudinal central axis (C) of the fluid burner head (9) and projecting from the outer surface (43) of the body (11) between the top row (29a) of holes (27) of the tube (13) and the first projection (39).

8. 8. The fluid burner head (9) of claim 7, wherein the second projection (41) protrudes from an outer surface (47) of the tube (13).

9. 9. The fluid burner head (9) of claim 7 or 8, further comprising an annular support (37) extending around the longitudinal central axis (C) of the fluid burner head (9), the support (37) being connected to the first and second projections (39, 41) and engaging with the body (11) of the fluid burner head (9) to secure the first and second projections (39, 41) to the body (11).

10. Fluid burner head (9) according to any one of claims 6 or 9, wherein the support (37) is clamped between the cap (15) and the tube (13).

11. 11. The fluid burner head (9) according to any one of claims 1 to 10, wherein the cap (15) comprises a top (31) and a bottom (33), the bottom (33) projecting into the tube (13).

12. 12. The fluid burner head (9) of claim 11, wherein the bottom (33) includes a portion that tapers in a direction away from the top (31) of the cap (15).

13. Fluid burner head (9) according to claim 11 or 12, wherein the outer periphery of the top part (31) of the cap (15) is greater than the inner periphery of the tube (13).

14. Use of a fluid burner head (9) according to any one of claims 1 to 13 in a fluid combustion unit (1) for combusting boil-off gas from a fuel tank on board a ship.

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