Device for supporting at least two radiant heating pipes in a furnace chamber and industrial furnace

Description

[0001] The invention relates to a device for supporting at least two radiant heating tubes in a furnace chamber of an industrial furnace, wherein each radiant heating tube is connected at one end to a respective burner and is held against a first furnace wall of the furnace chamber, and wherein the free, closed end of the radiant heating tubes protrudes into the furnace chamber. Furthermore, the invention relates to an industrial furnace.

[0002] Radiant heating tubes, also called radiant tubes or radiant heating pipes, are used for the indirect heating of furnace chambers and are heated by burners powered by a liquid or gaseous fuel. Material to be heated in the furnace chamber of an industrial furnace, particularly during a heat treatment process, is thus heated by thermal radiation and does not come into contact with the burner exhaust gases. Typically, several radiant heating tubes are used to heat the furnace chamber. Radiant heating tubes for industrial purposes are used, for example, for annealing metal components, such as sheet metal or pipes. Plants for the heat treatment of steel parts require material temperatures of around 1,000°C. Consequently, the radiant heating tubes are exposed to high thermal loads.

[0003] Radiant heating tubes can be I-shaped, P-shaped, double P-shaped, U-shaped, or W-shaped. I-shaped radiant heating tubes, also called jacketed radiant tubes, typically have a steel jacket tube that concentrically surrounds a flame tube made of a metallic or ceramic material.

[0004] Each radiant heating tube is connected to a burner at one end, usually by a flange. The radiant heating tubes are held at the burner end to a first furnace wall, which is provided with refractory insulation on the inside facing the furnace chamber. I-shaped radiant heating tubes, also called jacketed radiant heating tubes, usually extend through a furnace wall into the furnace chamber and are fixed axially within the furnace wall. The other free end of the radiant heating tube is sealed gas-tight against the atmosphere in the furnace chamber. The combustion exhaust gases from the burner flow towards the free end, where they are deflected and recirculated to be discharged from the radiant heating tube. The radiant heating tubes can be designed for vertical or essentially horizontal operation. Horizontal operation also includes operating modes in which the radiant heating tube is operated at any incline.Radiant heating tubes for horizontal operation in a furnace chamber have a considerable weight, which must be absorbed or supported at the free end to prevent bending, especially of metallic radiant heating tubes.

[0005] The radiant heating tubes can have a pin on the outside of the free end which engages in a holder in the furnace chamber.

[0006] From EP 2 754 958 A1, it is known to provide a welded extension made of steel pipe on the outside of a heating tube body of the radiant heating tube for supporting and intercepting the free end of a radiant heating tube protruding into the furnace chamber. This extension can be pushed into a holder in the furnace wall or onto which a holder engages to support or suspend the free end of the radiant heating tube in order to absorb the weight of the radiant heating tube. However, the free end of radiant heating tubes can also be designed without a spigot and be supported directly by a holder. Sliding support of the free end of the radiant heating tube or its extension can lead to jamming.

[0007] WO 2020 / 003125 A1 discloses, in several embodiments, a holding device for a radiant heating tube of any shape in a heat treatment furnace. In one embodiment for a radiant heating tube with two pipe bends at the end, a brace is located between the two pipe bends. One pipe bend has a shoulder that rests on a furnace-side support or base. The shoulder has rotating means in the region of the support point, which enable movement of the shoulder in the axial direction of the radiant heating tube when the radiant heating tube expands due to thermal stress.

[0008] AT 508 264 A4 shows a heat treatment device with a radiant heating tube unit with two pipe bends at the ends. A bearing journal is located on a bridge that spans both pipe bends. This journal is supported axially displaceably in a support in the furnace chamber. The bridge is formed by two sections that extend at an acute angle to the axis of the central tube of the radiant heating tube and form an obtuse angle with each other. The bridge is intended to absorb thermal expansion of the pipe bends under thermal stress, keeping the connection between the bearing journal and the bridge largely stress-free.

[0009] JP H09 303713 A shows a holder for a W-shaped radiant heating tube with two pipe bends at the end, each provided with a shoulder. In each of the two shoulders, a pin forms a pivot joint, to which rods engage. Both rods are joined at their ends by another pin. The other pin forms another pivot joint and can be moved in a slot in a holder in the furnace wall in the axial direction of the radiant heating tube. Under thermal stress, the articulated holder enables the radiant heating tube to move in the axial direction.

[0010] When converting, modernizing, or upgrading existing systems, it is often necessary to replace at least one existing radiant heating tube, for example a W-shaped radiant heating tube, with two new radiant heating tubes, for example two I-shaped radiant heating tubes, particularly to achieve higher temperatures in the furnace chamber. The free end of the two new radiant heating tubes must be supported in the furnace chamber. The existing bracket for the old radiant heating tube can be used to support the free end of one of the two new radiant heating tubes. An additional bracket must be provided in the furnace chamber for the second new radiant heating tube. This is structurally complex, particularly if the bracket is formed in the refractory insulation of one of the furnace walls and thus requires intervention in the existing refractory insulation.

[0011] The object of the invention is therefore to provide a way to support at least two radiant heating tubes in the furnace chamber of an industrial furnace in a structurally simple manner. One aspect of the object is to enable the replacement of one radiant heating tube with two new radiant heating tubes without providing an additional support in the refractory insulation.

[0012] This object is achieved according to the invention by a device of the type described at the outset by the features of claim 1.

[0013] According to the invention, the device comprises a connecting element with which at least two radiant heating tubes can be connected transversely to the axial direction. The connecting element has a projection that extends in the axial direction of the radiant heating tubes and is designed to rest in the axial direction in a holder in the furnace chamber. According to the invention, the connecting element is designed such that each radiant heating tube is displaceable relative to the connecting element in the axial direction of the radiant heating tubes, and that the projection rests in the holder and / or is or can be firmly connected to the holder.

[0014] This allows thermally induced length changes of the radiant heating tubes, as well as possible thermally induced changes in the first furnace wall (not shown) and the second furnace wall, to be compensated for. Because the axial movement of the radiant heating tubes is ensured, the extension can be connected to the bracket or to components of the bracket in a simple design. In particular, the extension can be welded to the bracket.

[0015] Alternatively, the connecting element can be designed such that a radiant heating tube can be fixed relative to the connecting element in the axial direction of the radiant heating tubes, that each additional radiant heating tube can be displaced relative to the connecting element in the axial direction of the radiant heating tubes, and that the connecting element rests displaceably in the axial direction of the radiant heating tubes by means of the projection in the holder. In this variant, the device according to the invention is movable or displaceable in the furnace chamber with respect to the first and second furnace walls in the axial direction of the radiant heating tubes in order to compensate for heat-related changes.

[0016] Two or more radiant heating tubes, particularly I-shaped radiant heating tubes, can be supported at their free ends in a structurally simple manner, requiring only a single bracket in the furnace chamber. In the common case where the bracket is formed in the refractory insulation, it is not necessary to intervene in the refractory insulation during conversions or retrofits, for example, when replacing one radiant heating tube with two or more radiant heating tubes, which significantly reduces the effort required for conversions or retrofits. A single existing bracket in the furnace chamber can be used to support several individual radiant heating tubes after conversions or retrofits.

[0017] Advantageous and expedient embodiments and further developments of the invention emerge from the claims dependent on claim 1.

[0018] A preferred embodiment, wherein each radiant heating tube has a pin on the outer end face of the free end, is characterized in that the connecting element is designed such that the steel heating tubes can be connected by means of the pins. In other words, the connecting element engages the end pins of the radiant heating tubes. Consequently, the radiant heating tubes are connected by means of the connecting element via the pins.

[0019] The connecting element is preferably rod-shaped. The connecting element is advantageously heat-resistant and is preferably made of metal. The cross-section of the connecting element can be of any shape, for example, as a U-shaped profile. The connecting element can also consist of a rectangular profile, in particular a hollow profile.

[0020] In a preferred embodiment, the connecting element is designed such that each radiant heating tube is rotatable relative to the connecting element, which increases the durability of the radiant heating tubes. This design is particularly advantageous for I-shaped radiant heating tubes or jacketed radiant heating tubes. The connecting element could have tubular receiving elements that serve to receive the free ends of the radiant heating tubes or their end-face pins.

[0021] A particularly advantageous structurally simple development of the invention consists in that the connecting element for each radiant heating tube has a recess for receiving the free end of the radiant heating tube or its front-side pin.

[0022] Preferably, the recess has a half-shell-shaped support surface. Advantageously, the recess is designed as an elongated hole.

[0023] According to the invention, the extension has a substantially rectangular cross-section and is preferably welded to the connecting element, viewed in the operating state, laterally in the direction of the second furnace wall.

[0024] The invention also covers a heating system for an industrial furnace with at least two radiant heating tubes, each radiant heating tube being connected at one end to a burner and being held on a first furnace wall of the furnace chamber (2) and the free closed end of the radiant heating tubes projecting into the furnace chamber, characterized in that the heating system includes a device which has a connecting element with which the radiant heating tubes can be connected transversely to the axial direction (A) and that the connecting element has a projection which extends in the axial direction (A) of the radiant heating tubes and which is designed to rest in a holder in the furnace chamber in the axial direction.According to the invention, the connecting element is designed such that each radiant heating tube is displaceable relative to the connecting element in the axial direction (A) of the radiant heating tubes and that the attachment is designed such that it is firmly connected to the holder in the axial direction (A) of the radiant heating tubes.

[0025] The rod-shaped connecting element is preferably designed such that each radiant heating tube is rotatable relative to the connecting element.

[0026] The invention further provides an industrial furnace with a furnace chamber formed by furnace walls, the furnace walls having a refractory insulation on the inside, at least two radiant heating tubes being arranged in the furnace chamber, each radiant heating tube being connected at one end to a burner and being held on a first furnace wall, the free closed end of the radiant heating tubes protruding into the furnace chamber, characterized by a device according to one of claims 1 to 7 and a holder which is designed to support the device in the furnace chamber.

[0027] Preferably, the holder is formed in the refractory insulation of a second furnace wall opposite the first furnace wall and comprises a bracket, preferably made of metal, in a cavity. Alternatively, the holder can be designed as a bearing suspended in the furnace chamber.

[0028] Preferably, the connecting element rests on the bracket in the refractory insulation with its extension. If the device is designed to be immobile in the axial direction of the radiant heating tubes, the extension of the connecting element could be permanently connected to the bracket. If the bracket is made of metal, the extension can be welded to the bracket.

[0029] Within the scope of the invention, the features explained above can also be used in other combinations or alone. Further details and advantages of the subject matter of the invention will become apparent from the following description in conjunction with the drawing, which illustrates a preferred embodiment of the invention.

[0030] The drawing shows: Figure 1 a schematic representation of a section of the device according to the invention in a furnace chamber of an industrial furnace with two I-shaped radiant heating tubes; Figure 2 a schematic representation of a view of the device according to Figure 1 towards the axis of the radiant heating tubes.

[0031] Figure 1 shows a schematic representation of a device 1 according to the invention in a furnace chamber 2 of an industrial furnace (not shown in detail). The furnace chamber 2 is a space enclosed by furnace walls in which a steel product (not shown) is to be heated as part of a heat treatment process.

[0032] In the furnace chamber 2, there are two I-shaped radiant heating tubes 3, 3', of which only the free end is shown, which protrudes into the furnace chamber 2. The radiant heating tubes 3, 3' serve to indirectly heat the material to high temperatures by means of thermal radiation.

[0033] The radiant heating tubes 3, 3' are intended for horizontal operation in the furnace chamber 2. The two radiant heating tubes 3, 3' are held at one end in a first furnace wall (not shown) in a manner known per se and are each connected to burners (not shown) located outside the furnace chamber 2. The radiant heating tubes 3, 3' are considerably heavy, so that their ends projecting into the furnace chamber 2 must be supported. With increasing temperatures, the mechanical strength values ​​of the radiant heating tubes decrease. The radiant heating tubes expand. Figure 1A portion of a second furnace wall 4 is shown, which is arranged opposite the first furnace wall. The second furnace wall 4 is provided with refractory insulation 5 on the inside, facing the furnace chamber 2. The two radiant heating tubes 3, 3' are aligned in a plane in the furnace chamber 2 approximately perpendicular to the first furnace wall and second furnace wall 4 (not shown).

[0034] The radiant heating tubes 3, 3' have a pin 6, 6', respectively, on their end faces. The pins 6, 6' can be formed as steel cylinders. Thermal insulation can be located inside the pins 6, 6'.

[0035] The device 1 comprises a connecting element 7, which is designed as a heat-resistant, rod-shaped profile with a rectangular cross-section. The connecting element 7 has a recess 8 for the radiant heating tube 3 and a recess 8' in the form of an elongated hole for the radiant heating tube 3'. This is Figure 2which is a schematic representation of a view of the device according to Figure 1 in the direction of the axis of the radiant heating tubes. The pins 6, 6 are rotatably mounted in the recesses 8, 8'. This rotatability serves to increase the durability of the radiant heating tubes. The two radiant heating tubes 3, 3' are connected to one another transversely to the axial direction 9 by means of the connecting element 9. All radiant heating tubes are displaceable in the axial direction relative to the connecting element 7. The pins 6, 6' can move slidably in the connecting element if the length of the radiant heating tubes 3, 3' changes due to temperature changes. This allows thermally induced length changes of the radiant heating tubes 3, 3' as well as possible thermally induced changes in the first furnace wall (not shown) and the second furnace wall 4 to be compensated for.

[0036] The connecting element 7 has a projection 9 which extends in the axial direction of the radiant heating tubes 3, 3' and which is designed to rest in a holder 10 which is located in the refractory insulation 5 of the second furnace wall 4.

[0037] The extension 9 is located near the recess 8. The extension 9 has a substantially rectangular cross-section and is preferably welded laterally to the connecting element 7.

[0038] A holder 10 for receiving the extension 9 is formed in the refractory insulation 5 of the second furnace wall 4. The holder 10 has a metal bracket 12 in a cavity 11 in the refractory insulation 5, on which the extension 9 rests. The shoulder 9 is firmly connected to the bracket 12. Preferably, the extension 9 is welded to the bracket 12. Because the movement of the radiant heating tubes 3, 3' in the axial direction is ensured, the extension 9 can be firmly connected to the bracket 12 in a structurally simple manner.

[0039] The device according to the invention makes it possible to connect two or more radiant heating tubes and to support them at their free end by means of a single holder or a single support point in the furnace chamber.

[0040] Within the scope of the invention, the free ends of several radiant heating tubes can be connected to one another by means of the device according to the invention and can be supported in a simple manner on a single holder in the refractory insulation of a furnace wall.

[0041] Further modifications are possible within the scope of the invention. For example, the radiant heating tubes can be designed without pins at their free ends and can be directly enclosed by the recesses of the connecting element. The connecting element can have any shape, for example, U-shaped or formed as a hollow profile. As an alternative to the recesses in the connecting element, it can be provided with tubular receiving elements for the end of the radiant heating tubes or their pins. List of reference symbols

[0042] 1Device 2Furnace chamber 3, 3'radiant heating tube 4Furnace wall 5Refractory insulation 6, 6'pin 7Connecting element 8, 8'recess 9Approach 10Holder 11Cavity in refractory insulation 12Bracket Axis direction of radiant heating tube

Claims

1. Device for supporting at least two radiant heating tubes (3, 3') in a furnace chamber (2) of an industrial furnace, wherein each radiant heating tube (3, 3') is attached at one end to a respective burner and is held against a first furnace wall of the furnace chamber (2), wherein the free closed end of the radiant heating tubes (3, 3') projects into the furnace chamber (2), wherein the device has a connecting element (7) to which at least two radiant tubes (3, 3') can be connected transversely to the axial direction (A), wherein the connecting element (7) has an attachment (9) which extends in the axial direction (A) of the radiant heating tubes (3, 3') and which is configured to rest in a holder (10) in the furnace chamber (2) in the axial direction, characterized in that the connecting element (7) is configured such that each radiant heating tube (3, 3') is displaceable relative to the connecting element (7) in the axial direction (A) of the radiant heating tubes (3, 3'), wherein the attachment (9) is configured such that it rests immovably in the holder (10) in the axial direction (A) of the radiant heating tubes (3, 3') and / or can be securely connected to the holder (10), or characterized in that the connecting element (7) is configured such that a radiant heating tube (3) can be fixed in the axial direction (A) and each further radiant heating tube (3') can be displaced in the axial direction (A) relative to the connecting element (7), wherein the attachment (9) rests in the holder (10) so as to be displaceable in the axial direction (A) of the radiant heating tubes (3, 3').

2. Device according to claim 1, wherein each radiant heating tube (3, 3') has a pin (6, 6') on the outside of the free end face, characterized in that the connecting element (7) is configured such that the radiant heating tubes (3, 3') can be connected by means of the pins (6, 6').

3. Device according to at least one of the preceding claims, characterized in that the connecting element (7) is configured to be rod-shaped and / or heat-resistant.

4. Device according to at least one of the preceding claims, characterized in that the connecting element (7) is configured such that each radiant heating tube (3, 3') is rotatable relative to the connecting element (7).

5. Device according to at least one of the preceding claims, characterized in that the connecting element (7) for each radiant heating tube (3, 3') has a recess (8, 8') for receiving the free end of the radiant heating tube (3, 3') or its end face pin (6, 6').

6. Device according to claim 5, characterized in that the recess (8, 8') has a half-shell-shaped bearing surface, preferably in that the recess (8, 8') is configured as an elongated hole.

7. Device according to at least one of the preceding claims, characterized in that the attachment (9) has a substantially rectangular cross-section and is preferably welded to the connecting element (7).

8. Industrial furnace with a furnace chamber (2) formed by furnace walls, wherein the furnace walls (4) have a refractory insulation (5) on the inside, wherein at least two radiant heating tubes (3, 3') are arranged in the furnace chamber (2), wherein each radiant heating tube (3, 3') is attached at one end to a burner and is held on a first furnace wall, wherein the free closed end of the radiant heating tubes (3, 3') projects into the furnace chamber (2), characterized by a device according to any one of claims 1 to 7 as well as a holder (10) which is configured to support the device in the furnace chamber (2).

9. Industrial furnace according to claim 8, characterized in that the holder (10) is configured in the refractory insulation (5) of the second furnace wall (2), which is opposite the first furnace wall, in that the holder (10) has a bracket (12) in a cavity (11), which bracket is preferably made of metal and on which the attachment (9) of the connecting element (7) is supported.