Gas passage module for a high-temperature furnace

Abstract

The invention relates to a gas passage module for installation in a radiation shield (3) of a high-temperature furnace (1), wherein the gas passage module (2) has a plurality of planar guiding devices (6) which are spaced apart from one another and extend at least in part between two opposing walls (7, 72), wherein at least some of the guiding devices (6) form, with at least part of the walls (7, 72), at least one channel (K) through which gas (G) can flow along a longitudinal axis (L) of the gas passage module (2) at least temporarily and / or at least in sections, wherein the guiding devices (6) extend, at least temporarily and / or at least in sections, obliquely to the longitudinal axis (L) so as to substantially prevent direct passage of radiation through the gas passage module (2).

Description

[0001]1119 Text Foreign Countries 09.01.2024 GAS PASSAGE MODULE FOR A HIGH-TEMPERATURE FURNACE The present invention relates to a gas passage module for a high-temperature furnace having the features of the preamble of claim 1. The invention further relates to a radiation shield having a gas passage module and to a high-temperature furnace having a gas passage module. A high-temperature furnace comprises a generally water-cooled furnace shell, also called a boiler, which encloses a furnace chamber. A radiation shield is formed within the furnace chamber, which encloses a process chamber and thermally insulates it from the furnace shell. In metallic high-temperature furnaces, the radiation shield is formed by shielding plates (also called radiation plates) arranged parallel to one another and spaced apart. This arrangement effects shielding against radiant heat through multiple reflection at the shielding plates and thus acts as insulation.Metallic high-temperature furnaces are described, for example, in EP0303420 (A1) or WO2020 / 120147 (A1). This form of all-metallic insulation is used particularly for high-temperature furnaces with high requirements for the purity of a process atmosphere or for vacuum furnaces. "High temperature" is usually referred to when process temperatures exceed approximately 800°C. Radiation shielding typically consists of several shielding modules, i.e., individual components that are joined together to form the radiation shield. This makes it possible to create various cross-sectional shapes of process spaces using geometrically simple shielding modules. An assembly of a radiation shield together with heating conductors is referred to as a heating insert (hot zone). The heating insert of a high-temperature furnace is crucial for the temperature distribution, purity, and energy consumption of high-temperature processes.During operation of high-temperature furnaces, it is often necessary to feed process gas or cooling gas into the process chamber and then discharge it again. High-temperature furnaces are therefore often equipped with a gas system that allows gas exchange between the process chamber and a furnace chamber located beyond the radiation shielding. A gas-carrying connection can also be implemented through the furnace shell. Process gas is understood to be a gas composition that supports the heat treatment of a annealing material or even enables it in the first place, such as inert or reducing atmospheres. Another motivation for a gas system can be the forced cooling of the annealing material using a cooling gas. The cooling gas is usually fed into the process chamber and thus to the annealing material via gas inlets. The gas, which is cool relative to the annealing material, absorbs heat from the annealing material and cools it.The heated gas then leaves the heating element via a gas outlet. The heated gas is then fed to a heat exchanger installed on the furnace side, which cools the gas. The gas circuit is typically driven by a fan, which is also installed on the furnace side. Gas inlets and outlets are provided on the heating element for gas exchange to ensure gas flow over the annealing material. Gas inlets and outlets essentially represent openings in the radiation shielding and thus cause significant energy losses. In addition, gas inlets and outlets represent local weak points in the radiation shielding and lead to temperature inhomogeneity in the furnace. Measures must therefore be taken to ensure that gas inlets and outlets have as little resistance as possible while simultaneously minimizing thermal losses.The solutions for a gas system known from the prior art have a number of disadvantages which are explained in more detail below: In the case of horizontal metallic heating inserts, a gas outlet according to the prior art is usually located on a rear wall and thus directly in front of a fan and / or heat exchanger of the furnace. The gas inlets are usually arranged around the circumference of the heating insert or axially, i.e. on the side opposite the rear wall. x Gas outlet on a rear wall of the radiation shield - deficiency 1 According to the current state of the art, the gas outlet on the rear wall is realized, for example, by a circular opening in the shield. In order to still achieve a certain shielding effect, a spaced-off shielding package is located in front of (i.e. on the side facing the process chamber) or behind the opening, which shielding package is usually larger in extent than the opening itself.This is to ensure that no direct radiation path leads from the interior of the heating insert to the boiler wall or other steel components. This type of design is cost-intensive because the shielding package has to be held in place by a complex support structure. With an internal shielding package, particularly temperature-resistant materials must be used. A further disadvantage of this design is that additional mass has to be heated up and cooled down. x Gas outlet on a rear wall of the radiation shield - Deficiency 2 If the gas outlet is implemented via an opening and a spaced-apart shielding package, a certain installation depth is required, which must also be provided on the furnace side, i.e. on the boiler. The size of the boiler is a major cost driver for high-temperature furnaces.x Gas outlet on a rear wall of the radiation shielding - Defect 3 If the gas outlet is realized via an opening and a shielding package spaced outwards, the first shielding layers of this shielding package are located outside (behind) the plane of the rest of the shielding. Radiation reflected from there hits the rest of the shielding from behind, which is why it has to be designed to be particularly temperature-resistant and therefore expensive. To understand this, it should be explained that shielding plates that are located further out with respect to the process chamber, i.e. towards the furnace wall, are exposed to lower temperatures than layers of radiation shielding further in. Therefore, shielding plates located further out can, if necessary, be made of heat-resistant steel, while shielding plates located further in are usually made of refractory metal. The use of tungsten may be necessary for the innermost layers.The following layers on the outside can be made of molybdenum, for example. x Heat losses – Deficiency 4 In general, openings in the insulation of the heating insert significantly impair the shielding effect. Heat is transported to the outside through these openings by radiation. The higher the temperature inside the heating insert, the greater the losses of the heating insert. The increased losses through openings in the insulation must be compensated for by higher (heating) outputs, in contrast to systems without openings in the insulation. The energy efficiency of systems with openings is lower. A heater with a correspondingly higher output must be provided. x Temperature inhomogeneities – Deficiency 5 An opening in the insulation also represents a source of temperature inhomogeneities inside the heating insert.It has been shown that a lower temperature prevails on the inside of an opening than on the inside of a closed shield. This inhomogeneity continues inwards and can lead to different temperatures in the annealing material. This is undesirable since a temperature distribution that is as homogeneous as possible is a prerequisite for a uniform annealing result. The object of the present invention is to provide a device for gas exchange in a high-temperature furnace with which the disadvantages of existing solutions described above are eliminated or at least mitigated. In particular, the conflicting objectives of low-resistance flow through a gas passage while at the same time achieving a high shielding effect is to be overcome. This object is achieved by a gas passage module with the features of claim 1 or by a radiation shield with a gas passage module, or by a high-temperature furnace with at least one gas passage module.Preferred developments are specified in the dependent claims. By the gas passage module comprising: a plurality of flat, spaced-apart guide devices which extend at least partially between two opposite walls, wherein at least some of the guide devices form, with at least some of the walls along a longitudinal axis of the gas passage module, at least temporarily and / or at least partially at least one channel through which gas can flow, wherein the guide devices run at least temporarily and / or at least partially obliquely to the longitudinal axis in such a way that direct radiation passage through the gas passage module is essentially prevented, a favorable shielding effect is ensured while at the same time ensuring good flow. The deficiencies described above are eliminated or at least significantly reduced by the invention.The gas passage module is designed to be inserted into an opening in the radiation shielding of a high-temperature furnace, which radiation shielding surrounds a process chamber and is thermally insulated from a furnace wall. In an installed position, the gas passage module is oriented in particular such that the longitudinal axis of the gas passage module runs parallel to a local shielding direction of the radiation shielding surrounding the gas passage module in the installed position. As a rule, a plane normal to the surrounding radiation shielding can be set as the local shielding direction of the radiation shielding. The longitudinal axis of the gas passage module typically runs orthogonal to an end face of the gas passage module. An end face refers in particular to that side of the gas passage module which, in an installed position in a high-temperature furnace, faces into the process chamber.Typically, the gas passage module is installed flush with the surrounding shielding. The front side of the gas passage module is then preferably coplanar with an inner layer of the shielding. It is understood that the "front side" does not represent a closed surface like a cover, but rather refers to a geometric plane that forms the front side of the gas passage module. In this context, an "oblique" course of the guide devices means that at least sections of the guide devices run at an angle to the longitudinal axis of the gas passage module. The angle is in particular between 10° and 80°. An angle of 90° would mean that the relevant section of the guide device is perpendicular to the shielding direction. A large angle is advantageous in terms of the shielding effect, but disadvantageous in terms of flow resistance.The orientation of the guide devices essentially prevents direct radiation passage along the longitudinal axis through the gas passage module. This means that the gas passage module is designed in such a way that it prevents direct passage of thermal radiation. Therefore, no straight line can be constructed parallel to the longitudinal axis of the gas passage module along which the gas passage module can be traversed from a front to a rear end without crossing or at least touching a guide device. In particular, there is no straight line along which the gas passage module can be traversed from a front to a rear end without crossing or at least touching a guide device – regardless of the direction of the path. This means that even lines running at any angle to the longitudinal axis of the gas passage module touch or cross at least one guide device.A gas can flow through the gas passage module from a front to a rear end face. To ensure flow through the gas passage module, it is advantageous if the guide devices are not angled too steeply. Sections with an orientation of 90° to the longitudinal axis of the gas passage module are therefore particularly unfavorable, as they cause impingement of the flow. Further preferred and favorable for both aspects is an orientation of the guide devices in the range of 45° ± 10°, more preferably 45° ± 5°, relative to the longitudinal axis. The guide devices are in particular flat. They can comprise flat partial surfaces and / or be curved. From a manufacturing perspective, the formation of flat partial surfaces can be advantageously achieved by bending sheet metal strips. The guide devices can comprise sections that run along, i.e. parallel to, the longitudinal direction of the gas passage module.It is preferably provided that guide devices run at least partially obliquely in opposite directions in planes which follow one another in the longitudinal direction of the gas passage module. This can be designed, for example, such that guide devices are arranged one behind the other in the longitudinal direction of the gas passage module with their orientation mirrored. This can, for example, make it possible to create a meandering course of channels. In particular, this development allows the use of identical parts. In particular, the gas passage module is at least 90% opaque along its longitudinal axis. “Opaque” means that no uninterrupted radiation path can be constructed which runs from the front to the back of the gas passage module. 90% opaque would mean that direct passage of radiation in the longitudinal direction is possible at 10% of the cross-section, based on an end face.Opacity further specifies the feature according to which direct radiation passage through the gas passage module is essentially prevented. The feature of opacity is associated with the effect that the gas passage module prevents direct passage of thermal radiation. In particular, the gas passage module is 100% opaque. In particular, it is provided that the gas passage module includes several shielding layers along the longitudinal direction. This means that along a fictitious straight path through the gas passage module along the shielding direction, a plurality of at least two guide devices will pass through. In other words: if a straight line is constructed through the gas passage module, the line will be interrupted by at least two guide devices. In the context of orientations in the gas passage module, a "longitudinal direction" means a direction parallel to the longitudinal axis of the gas passage module.It is preferably provided that a free flow cross-section in the gas passage module amounts to at least 30% of a cross-section of the gas passage module. In other words, a cross-section normal to the longitudinal axis is only filled with material to a maximum of 70%. Preferably, along the longitudinal direction, which generally also corresponds to the flow direction, all cross-sections normal to the longitudinal axis have a free flow cross-section of at least 30%. In other words, a cross-section is only filled with material to a maximum of 70%. More preferably, the free flow cross-section is more than 80%, more preferably more than 90%, in particular more than 95%. It is further preferably provided that more than 80% of all cross-sections normal to the longitudinal axis of the gas passage module have a free flow cross-section of at least 80% of a cross-section of the gas passage module.This means that only a small proportion of cross-sections normal to the longitudinal axis of the gas passage module, in particular only less than or equal to 20% of all cross-sections, fall below a free flow cross-section of 80%. This clarification expresses that it can be provided to allow a smaller free flow cross-section at a few cross-sections in order to improve the shielding effect. However, at the majority of cross-sections the free flow cross-section is more than 80% of the cross-sectional area. To ensure good flowability, it can further be provided that the free flow cross-section is free of constrictions along one flow direction. In other words, it is preferred that the channel formed from walls and guide devices has a substantially constant cross-sectional area along its extent.Essentially constant here means that the cross-sectional area varies by less than 25% along its extent. It is preferably provided that a free flow cross-section is essentially constant in the flow direction. It is preferably provided that the guide devices extend between two opposite walls from one end to the other end. This means that the guide devices extend preferably completely, more preferably without a gap, between two opposite walls. It is preferably provided that the guide devices are flush with the walls. This means that the guide devices bear against the walls essentially along their entire end surfaces and, in particular, are gap-free along the contact point. The guide devices and walls form channels for guiding a gas flow through the gas passage module.The channels are in particular discrete and geometrically well-defined, i.e. they are formed by geometrically defined surfaces. This is favorable for low-resistance flow. If the guide devices are designed to be movable, the above feature relates to the operating state of the gas passage module with deflected guide devices, i.e. the operating state open for flow. The channels formed by guide devices and walls are preferably at least 60%, preferably greater than 80%, more preferably more than 90% enclosed by material. Associated with this feature is the effect that the channels allow low-resistance flow. As they are closed to ^ 60%, preferably ^ 80%, more preferably ^ 90%, there is little fluid communication between adjacent channels.If the guide devices are designed to be movable, the above feature relates to the operating state of the gas passage module with deflected guide devices, i.e. the operating state open for flow. In a further development, the channels are completely enclosed by material. In particular, the channels can preferably be formed monolithically from guide devices and walls, i.e., free of joining zones. With regard to flowability, it is advantageous if the channels are designed to deflect a gas flow as rarely as possible. The gas flow is preferably deflected twice. In this way, the flow resistance is kept low while maintaining a shielding effect. It can be provided that the orientation of at least some of the guide devices is designed to be variable. This expresses the fact that the guide devices are not necessarily rigidly fixed.Rather, it can be provided that guide devices are aligned differently depending on the operating conditions. One conceivable embodiment is to suspend the guide devices so that they can be moved. In a further development, it can be provided that the guide devices are designed so that they can be deflected by a mechanical device or by a gas flow. This opens up the possibility of keeping the gas passage module closed for operating states without flow, thus achieving a high shielding effect. In the case of flow, this further development could have a particularly low flow resistance. In a further development, the guide devices could be suspended in such a way that the gas passage module can only be flowed through in one direction. This can create a valve effect. Preferably, a reset of the guide devices by gravity when the gas flow ceases is provided.A flap solution increases the cooling effect when open to flow, as the gas passage module offers little shielding effect against thermal radiation in this state. The gas passage module can be provided with several cassettes that are arranged in series along the shielding direction and / or parallel to one another transversely to the shielding direction. This means that a gas passage module is designed in segments in a further development. Cassettes are understood here to be frames in which guide devices are fixed and which, in a stacked assembly, form the gas passage module. A construction using cassettes has the advantage that guide devices do not have to span the entire dimension of the gas passage module. This stiffens the construction. The modular design in the form of cassettes also allows gas passage modules of different sizes to be constructed from identical parts.In particular, cassettes consist of metal sheets parallel to the longitudinal axis, between which guide devices are arranged. The cassettes forming the gas passage module can also have different geometric designs. The cassettes can also be arranged one behind the other and consist of different materials, for example, a particularly temperature-stable material on the inside and a less temperature-stable material on the outside. Designs and arrangements of cassettes are explained in more detail with reference to the figures. It is preferably provided that the gas passage module is one-piece, such that guide devices are formed integrally with walls. According to this variant, guide devices and walls are not connected to one another by a joining process, but are formed monolithically during the primary shaping. In particular, this variant can be realized using additive manufacturing processes.In particular, the gas passage module is formed by a melting process, preferably the Laser Powder Bed Fusion (LPBF) process. In melting processes, powder particles are locally melted under the influence of an energy beam, such as a laser or electron beam. Beam melting processes have the particular advantage of enabling high geometric precision and thin walls. Alternatively, the gas passage module can be produced using a binder-based additive manufacturing process. Binder-based means that a metal powder used for the additive manufacturing process is prepared with at least one organic binder component. Known binder-based additive manufacturing processes include, in particular, filament printing with feedstock filaments, extrusion, selective laser sintering (SLS) with feedstock granulate powder, lithography processes with feedstock, and binder jetting with mixed, pre-alloyed, or granulated metal powders.Binder-based additive manufacturing processes can also be used advantageously for non-metallic materials such as graphite or ceramic. The advantage of a one-piece construction, particularly through an additive manufacturing process, lies, among other things, in the design options for the free flow cross-section. A channel with favorable flow characteristics can be created. Protection is also sought for a heating insert for a high-temperature furnace with at least one gas passage module according to the invention. Protection is also sought for a high-temperature furnace with a gas passage module according to the invention. In addition to the described use of the gas passage module for ensuring gas exchange in a high-temperature furnace, other uses are conceivable: Another conceivable application is use for the preferential separation of contaminants during a cleaning annealing run.The gas passage module could be designed in such a way that it interrupts the direct beam path, thus allowing a high temperature to be reached, but at the same time remains as cool as possible - at least in sections. This could be achieved, for example, by a strongly radiating surface on the outer surface of the heating element. The goal here is to use the gas passage module as a type of cold trap, on which contaminants can precipitate as condensate. This is achieved by making the gas passage module cooler than the surrounding areas, particularly if the gas (and the contaminants transported with it) is forced over the cold component. In particular, with this development, temperatures in some sections of the gas passage module are lower than or equal to the dew point of the gas flow. This can be technically implemented by installing the gas passage module on the cold side, i.e.Located on the outside of the heating element, it has a large, radiating surface and is thus cooled (= cooling fins). This can be facilitated by a high-emissivity layer. This allows impurities that evaporate inside the heating element to condense preferentially on the replaceable gas passage module. The gas passage module can therefore be used as a type of condensation trap. After the cleaning run, this special gas passage module is removed and can be cleaned outside the furnace. The gas passage module can then be reinstalled or replaced with a new gas passage module. In summary, the invention achieves the following advantages: 1.Reduction of thermal losses by eliminating a direct radiation path from the interior of the heating insert to the outside (applies primarily to the design of gas passage modules as gas nozzles, since direct radiation is currently possible here). This results in increased energy efficiency compared to the state of the art. 2. Reduction of thermal losses by increasing the shielding effect compared to the state of the art at comparable or lower costs (applies to gas passage modules used on the rear wall of a radiation shield, since the state of the art uses a spaced-apart shielding package here). This results in increased energy efficiency compared to the state of the art. 3. Realization of interchangeability. The invention can be designed as an insert for gas nozzles or as an insert in a rear wall.This makes it possible to specifically adapt the gas inflow direction to the furnace load (particularly applicable to gas passage modules used as gas nozzles). Gas nozzle and rear wall inserts can also be subsequently replaced without removing the entire heating insert from the furnace. This provides greater serviceability compared to the state of the art. Inserts can also be removed entirely, or the openings completely closed. 4. Compact design (particularly applicable to gas passage modules used as inserts in the rear wall of a radiation shield). The inventive design of the rear wall requires a smaller installation space than a state-of-the-art solution. This allows for a smaller boiler with the same charge space (particularly interesting for new systems) or a larger charge space with the same boiler (particularly interesting for retrofits). 5.Increased temperature homogeneity (particularly applies when using gas passage modules in a rear wall shielding). By avoiding local thermal losses through openings in the shielding, the temperature homogeneity inside the heating insert is increased. 6. Ensuring a shielding effect in all operating conditions (gas nozzles and rear wall). Unlike known flap solutions, the design according to the invention ensures a shielding effect in all operating conditions. Hot spots on the boiler wall are thus avoided. The inventive design of gas nozzles and rear wall enables flow while providing simultaneous thermal shielding. 7. Combination of a static and a dynamic system (rear wall). In one possible design variant, a static system (fixed guide devices) is combined with a dynamic system (deflectors as flaps).This ensures that no direct beam path is possible from a hot (internal) area, while the benefit of flaps, in particular the particularly low flow resistance, can be utilized. Since the flaps are arranged in a cooler area, long-term operability is guaranteed. 8. Independence of the geometry of the gas inlet and outlet. The invention can be used for all possible shapes of gas inlets and outlets. Axial flow through a heating insert is also possible with clever arrangement. It is also possible to apply the concept of gas passage modules to the gas inlet. 9. The use of the invention is not limited to metallic heating inserts. All types of high-temperature systems in which thermal shielding with simultaneous flow through is to be achieved are possible areas of application.The gas passage modules according to the invention can be used in graphitic or ceramic insulation. The invention is explained in more detail with reference to the attached figures. Therein: Fig. 1a-b shows a schematic representation of a generic high-temperature furnace Fig. 2a-b shows a schematic representation of an external gas outlet according to the prior art Fig. 3 shows a high-temperature furnace with a gas passage module according to a first embodiment Fig. 4 shows a gas passage module according to a further embodiment Fig. 5 shows a guide device according to a first example Fig. 6 shows a guide device according to a further example Fig. 7 shows a gas passage module according to a further embodiment Fig. 8a-8c shows a gas passage module according to a further embodiment Fig. 9a-b shows a gas passage module in further embodiments Fig. 10a-b shows a gas passage module in further embodiments Fig.11a-b shows a channel in a gas passage module according to the exemplary embodiment of Figure 9a. Fig. 12 shows a channel in a gas passage module according to the exemplary embodiment of Figure 10a. Fig. 13 shows a schematic representation of an additive manufacturing process for a gas passage module. Fig. 14 shows a gas passage module according to a further exemplary embodiment. For basic orientation, Figures 1a and 1b schematically show a generic high-temperature furnace 1, wherein Figure 1a shows a schematic longitudinal section and Figure 1b shows a schematic cross-section. In this example, a cylindrical furnace shape in a lying (horizontal) design is shown. The invention is of course also applicable to other furnace shapes such as rectangular or polygonal shapes. The high-temperature furnace 1 comprises a furnace shell 11, also called a boiler, which is generally designed as a steel shell and is usually water-cooled.The high-temperature furnace 1 can be closed by covers at its front ends. The high-temperature furnace 1 comprises a process chamber 4, which is insulated from the furnace shell 11 by a radiation shield 3. In this case, the radiation shield 3 comprises a side shield 32 circumferentially surrounding the process chamber 4 and cover shields 31 at the front ends. The radiation shield 3 is constructed from spaced-apart radiation plates 33. Only two radiation plates 33 are shown here in a schematic and simplified manner. As a rule, many more radiation plates 33 are arranged in parallel, one behind the other, for example, between five and ten radiation plates 33. In particular, all or some of the radiation plates 33 are made of refractory metal, in particular molybdenum or tungsten or alloys thereof. Alternatively or additionally, insulation layers can be made of graphite and / or ceramic.Layers facing away from the process chamber 4 can optionally be made of high-temperature-resistant steel. As can be seen in Figure 1b, in this example the side shield 32 is formed as a polygonal line made up of several interconnected shielding modules which together approximate a cylindrical shape. In the example of a high-temperature furnace 1 shown, an approximately circular cross-section of the process chamber 4 is realized. Alternatively, for example, a rectangular cross-section could also be formed by shielding modules arranged perpendicular to one another. Figures 2a-b show schematic representations of a gas outlet according to the prior art. Figure 2a shows a cross-section through a radiation shield 3. The radiation shield 3 surrounds a process chamber 4. For gas exchange with a furnace chamber surrounding the process chamber 4, an opening 5 is introduced into an end-face shield 31 or structurally recessed.According to this solution known from the prior art, an opening 5 of the frontal shield 31 is provided with an additional shield - VA ^ with a diameter D, which projects beyond the opening 5 in terms of its diameter - D. VAin front. The additional shielding - VA ^ is basically constructed in the same way as the front shielding 31 or the side shielding 32, namely from a stack of parallel, spaced-apart radiation plates 33. The front shielding - VA ^ is connected to the front shielding 31, for example, via a support structure and is thus suspended from it. The front shielding - VA ^ is spaced from the front shielding 31 by an annular gap of width B. A radiation shield 3 serves to insulate the process chamber 4 by reflecting heat radiation from the process chamber 4 back into the process chamber 4 via multiple reflection at the radiation plates 33. A local shielding direction ^ R ^ can be defined as a direction parallel to a local plane normal of a respective shield, here the front shielding 31. The radiation plates 33 are accordingly perpendicular to the local shielding direction R .Arrows indicate exemplary directions of radiation paths. It can be seen that a considerable amount of radiation can escape through the annular gap. The extent of radiation loss can be described, for example, by an exit angle D, within which radiation can escape through the annular gap. Even if this angle is 0°, there are losses due to multiple reflections and radiation from the shielding itself. The width - B ^ of the annular gap cannot be reduced arbitrarily, since the best possible gas exchange should take place via the opening 5 and the annular gap. It can also be seen that a portion of the radiation that does not strike the front shielding VA exactly parallel to the shielding direction R is reflected by the shielding onto the back of the front shielding 31.In addition to the energy losses, this is particularly disadvantageous because the rear side of the frontal shield 31 is subjected to high thermal stress. Figure 2b shows a design that is at least thermally improved compared to the solution in Figure 2a, as is also known from the prior art. It includes an additional cylindrical shield ZZ ^ surrounding the annular gap. As is easily conceivable geometrically, this reduces the angular range in which radiation occurs through the annular gap. However, this improvement comes at the cost of a costly design. The additional cylindrical shield ZZ is complex to manufacture. In addition, a separate suspension for the additional cylindrical shield ZZ ^ must be provided. These gas passage designs known from the prior art therefore have significant deficiencies.In the following, exemplary embodiments of the invention are described by which the deficiencies are eliminated or at least mitigated. Figure 3 shows a high-temperature furnace 1 with a gas passage module 2 according to a first exemplary embodiment. Shown is a section through the frontal shield 31 with a gas passage module 2 arranged in an opening 5. The gas passage module 2 is in this case embedded flush with the inner plane of the frontal shield 31. In particular, it can be provided that several gas passage modules 2 are embedded in the radiation shield 3 of the high-temperature furnace 1. An arrangement on opposite sides of the radiation shield 3 can be particularly advantageous, so that a flow through the high-temperature furnace 1 is enabled. The gas passage module 2 comprises a plurality of flat, spaced-apart guide devices 6. The guide devices 6 serve both for gas guidance and for thermal shielding.The guide devices 6 extend between walls 7, which in the present illustration run parallel to the plane of the drawing and are not shown. The guide devices 6 form, with walls 7, at least one channel K through which gas G can flow. Gas G can flow through the gas passage module 2, in particular along a longitudinal axis L. This does not mean that channels K must extend exactly along the longitudinal axis L. Rather, it is provided that gas G can be flowed through between its end faces 22, 23. In this exemplary embodiment, the guide devices 6 are formed from folded sheet metal strips. In particular, the guide devices 6 are made of refractory metal, in particular molybdenum or tungsten or alloys thereof. In the context of the present invention, refractory metals are the metals of group 4 (titanium, zirconium and hafnium), group 5 (vanadium, niobium, tantalum) and group 6.Group (chromium, molybdenum, tungsten) of the periodic table, as well as rhenium. Refractory metal alloys are alloys containing at least 50 at.% of the respective element. These materials exhibit, among other things, excellent dimensional stability at high operating temperatures. If lower temperature resistance requirements are applicable, guide devices 6 can optionally be formed from a high-temperature-resistant steel, for example only in sections. The guide devices 6 extend, at least in sections, at an angle E to a longitudinal axis L of the gas passage module 2 and are dimensioned such that essentially no direct radiation passes through the gas passage module 2 along the longitudinal axis L, while gas - G - can flow through the gas passage module 2. The longitudinal axis L runs parallel to the local shielding direction R.In particular, no straight path can be created through the gas passage module 2 that passes through it without contact (i.e., without encountering at least one guide device 6). This prevents direct radiation passage, and the gas passage module 2 acts as a shield against thermal radiation. Furthermore, the guide devices 6 are thin and optionally interrupted, which keeps heat conduction losses to a minimum. The special design of the guide devices 6 essentially prevents direct radiation passage through the gas passage module 2. Geometrically, this feature can be described by the degree of opacity. In particular, the gas passage module 2 is at least 90% opaque. "Opaque" means that no direct radiation path can be constructed that extends from the side of the gas passage module 2 facing the process chamber 4 to the rear of the gas passage module 2.Further preferably, the gas passage module 2 is 100% opaque. Sections of the guide devices 6 can also extend in the direction of the longitudinal axis L, as is the case in the present exemplary embodiment. The gas passage module 2 according to the invention considerably increases the number of reflections until radiation emerges compared to existing concepts, which leads to a reduction in energy losses. With previously known gas passages in a shield, for example in a rear wall, the radiation can emerge after only one reflection; with the inventive concept, a similar number of radiation paths is required as in the radiation shield itself. Previously known gas inlets / outlets have a considerably poorer shielding effect than the actual radiation shielding of the high-temperature furnace. The invention also makes it possible to achieve the same shielding effect on the gas passage module 2 as on the radiation shield itself.The shape of the gas passage module 2 can be selected according to the circumstances. A cuboid shape is shown here. Figure 4 shows a section of the gas passage module 2 from Figure 3 in detail. The gas passage module 2 and thus the guide devices 6 are shown in cross-section. For ease of understanding, an installation situation of the gas passage module 2 opposite a process chamber 4 is indicated. In this example, a front end face of the gas passage module 2 points towards the process chamber 4, and an opposite rear end face of the gas passage module 2 points towards the furnace shell (not shown). A wall 7 is indicated, which in the present view runs parallel to the plane of the drawing. The guide devices 6 extend between walls 7, so that the guide devices 6 are enclosed by walls 7 at their end faces. The guide devices 6, together with the walls 7, form at least one channel K through which gas G can flow along the longitudinal axis L.Along the longitudinal axis L, several levels E of guide devices 6 are arranged one behind the other along a depth t of the gas passage module 2; in the present section, three levels E1, E2 and E3 are shown. The gas passage module 2 preferably comprises at least three levels E and up to ten levels E. Typically and preferably, five to eight levels E are provided. The arrangement and number of guide devices 6 is carried out with the aim of multiple interruption of the radiation path from the inside to the outside from all angles of incidence. This interruption of the radiation path should be present as frequently as possible, while at the same time providing the lowest possible resistance for the gas flow and the lowest possible heat conduction from the inside to the outside. A local free flow cross-section b1 of a channel K results from the distance between two adjacent guide devices 6 orthogonal to the direction of the gas flow.To determine the local free flow cross-section b1 of a channel K, an imaginary sectional plane SE is laid orthogonal to the longitudinal axis L through the gas passage module 2. Local free flow cross-sections bi of a channel K lie between the guide devices 6. Only the distances along which the sectional plane SE intersects guide devices 6 are filled with material. Since the distances between guide devices 6 can be variable, an average free flow cross-section b is preferably specified, which can be determined as the average over all local free flow cross-sections bi along a section with the sectional plane SE. It is preferably provided that an average free flow cross-section b in the gas passage module amounts to at least 30% of a cross-section of the gas passage module. In other words, a cross-section through the gas passage module 2 normal to the longitudinal axis L is only filled with material to a maximum of 70%.More preferably, an average free flow cross-section b in the gas passage module is over 80%. It is further preferably provided that over 80% of all cross-sections normal to the longitudinal axis of the gas passage module have a free flow cross-section of at least 80% of a cross-section of the gas passage module. This means that in most cross-sections parallel to the sectional plane SE shown here, an average free flow cross-section b is at least 80% of a cross-section of the gas passage module 2. It can be provided to allow a smaller free flow cross-section b for a few cross-sections in order to improve the shielding effect. A large average free flow cross-section is desired. Relative to a cross-section of the gas passage module 2, the value also reflects a measure of the "porosity" of the gas passage module 2, i.e. how much of a volume of the gas passage module 2 is not filled with material.A high porosity value, i.e., a low material fill, is advantageous due to the associated low heat capacity and low heat conduction. In addition, a large mean free flow cross-section promotes permeability, i.e., the permeability to gas flow. Preferably, the gas passage module 2 is filled with material to a maximum of 20%. The volume of the gas passage module 2 can be determined from its external dimensions. Knowing the material composition of the guide devices 6 and the walls 7, the material fill can thus be determined gravimetrically, for example. At the same time, the gas passage module 2 must be designed to be stable against high application temperatures, thermally induced stresses, loads due to gas pressure, abrasion, and the like. For the guide devices 6, sheet wall thicknesses between 0.1 mm and 2 mm have proven particularly suitable.For low-resistance flow, i.e. high permeability, it is advantageous if a free flow cross-section b varies little or not at all along a depth of the gas passage module 2. It is preferred if deviations of a free flow cross-section along a flow path P are less than 10%. The deflection angle of the flow should be as small as possible, i.e. the gas flow should not hit surfaces perpendicularly if possible. It can also be seen that the guide devices 6 run at least in sections obliquely to the longitudinal axis L. “Oblique” means in particular that the guide devices 6 are inclined at least in sections at an angle E to the longitudinal axis L. In the present exemplary embodiment, the guide devices 6 of the first plane E1 are inclined in sections at a first angle E1 to the longitudinal axis L.The guide devices of the second plane E2 extend in sections at a second angle E2 to the longitudinal axis L. An orientation of guide devices 6 in the range of 45° ± 15°, more preferably 45° ± 5° relative to the longitudinal axis L is advantageous. Partial sections of guide devices 6 can extend partially parallel to the longitudinal axis L. Partial sections of guide devices 6 can run normal to the longitudinal axis L. Furthermore, an arrangement of guide devices 6 in a plane E such that they overlap in the direction of the longitudinal axis L is advantageous. This means that in the case of an imaginary straight incidence of thermal radiation along the longitudinal axis L, the thermal radiation always hits a surface of a guide device 6 of a plane Ei and therefore not as far as the following plane E. i+1The guide devices 6 act similarly to shielding plates of a radiation shield. In the present embodiment, the guide devices 6 of the different levels Ei are of identical design. The guide devices 6 of adjacent levels E iare arranged mirrored along the longitudinal axis L. The second angle here corresponds in magnitude to the first angle. This preferred embodiment allows the same components to be used for all guide devices 6. The guide devices 6 can also have multiple sections running at different angles. Furthermore, the guide devices 6 do not need to be formed from flat partial sections, as in the example of the folded sheet metal strips. Rather, curved guide devices 6 are also conceivable, in particular sinusoidal, wave-shaped or circular (segment-shaped) profile cross-sections. The angle(s) of the inclined section and the shape of the guide devices 6 are dimensioned according to the requirements of the shielding effect and / or flowability of the gas passage module 2. The dimensions of the gas passage module 2 in the illustrated embodiment with a cuboid basic shape were approximately 400 x 400 mm edge length with a depth t of approximately 200 mm.The width of a channel K was approximately 15 mm. Figure 5 shows a schematic diagram of a guide device 6 from the previously discussed embodiment. The guide device 6 is designed as a folded sheet metal strip. Figure 6 shows a schematic diagram of a guide device 6 in an alternative design. The guide device 6 is designed here as a profile with a sinusoidal shape in sections. This means that in cross-section or in a side view of an end face 61, the guide device 6 has a sinusoidal shape. Mixed forms of guide devices 6 are also possible: A guide device 6 can be composed of straight and curved sections in cross-section. A gas passage module 2 can also comprise differently shaped guide devices 6. With regard to the radiation path of thermal radiation, it should be noted that this does not, at least not exclusively, occur according to the angle of incidence ^ angle of reflection, as in optics.Rather, hot surfaces of radiation plates and guide devices form diffuse radiators that emit heat radiation in all spatial directions. Figure 7 shows a schematic representation of a gas passage module 2 according to a further exemplary embodiment. The exemplary embodiment shown here comprises several cassettes 21 which, in a stacked assembly, form the gas passage module 2 of depth t. The cassettes 21 typically have side walls 7, between which the guide devices 6 extend. The gas passage module 2 has a front end face 22 and a rear end face 23. The side walls 7 are preferably sheets made of refractory metal. The guide devices 6 are connected to the side walls 7 at their end faces. Welding is an example of a joining technique. The guide devices 6 could also be inserted into correspondingly shaped slots in the side walls 7 and fixed via a positive connection.For the sake of clarity and purely schematically, only three guide devices 6 are shown in the drawing on the front of the two cassettes 21 shown. An arrangement of guide devices 6 within a cassette 21 can be as shown in Figure 4, for example. The cassettes 21 can additionally have covers 8 and / or bases 9. Cassettes 21 can be connected to one another along the side walls 7, whereby gas passage modules 2 of different dimensions can be easily realized. A connection can be made, for example, using rivets 71. Identical or different cassettes 21 can be connected to one another. A further advantage is that the guide devices 6 in this design do not have to span the entire width of an opening 5 in a radiation shield 3. Rather, the gas passage module 2 is divided into segments via the cassettes 21. Alternatively, an arrangement of cassettes 21 with respect to the longitudinal axis L orthe flow direction one after the other. Figures 8a-c show different views of a gas passage module 2 according to a further embodiment and this in different operating states. Figure 8a shows a parallel perspective (cavalier perspective) of a section of a gas passage module 2, Figure 8b a cross-section. In the present example, guide devices 6 are suspended via bolts 10 between side walls 7 and are movably mounted. The direction parallel to the longitudinal axis L corresponds to the shielding direction R. Figures 8a and 8b show a closed state of the gas passage module 2. In this position of the guide devices 6, the gas passage module 2 shielding direction R is blocked against flow and has a high shielding effect ^ comparable to a conventional shielding with a corresponding number of layers.In the operating state according to Figure 8c, the guide devices 6 are deflected and the gas passage module 2 is open to the flow of gas G opposite to the shielding direction R (i.e., in the negative shielding direction R). In the deflected position, the flow resistance is comparable to that of a simple opening in the radiation shield. This configuration would, for example, allow a process chamber 4 to be supplied with gas G, while the gas passage module 2 blocks flow in the (positive) shielding direction R. Of course, the reverse case is also conceivable, in which the guide devices 6 are deflectable in the shielding direction R. In any case, a valve effect can be generated via this movable arrangement of guide devices 6. Preferably, static and movable guide devices 6 are combined in a gas passage module 2.It is particularly advantageous to provide movable guide devices 6 on the "cold" side, i.e. the side facing away from a process chamber 4 during use, while static guide devices 6 are used on the hot side. In this way, a valve effect can be created without using a mechanically more vulnerable movable suspension on the hot side. The movable guide devices 6 are also preferably made of refractory metals such as molybdenum or tungsten. When installed in a furnace, it is preferred that the gas passage module 2 can be inserted into the radiation shield 3 from the side of the process chamber 4. This makes subsequent replacement easy. By replacing the gas passage modules 2, the preferred gas inflow direction can be adjusted. This makes it conceivable to specifically influence the cooling of a defined batch.Thus, completely different flow conditions can be created in an otherwise structurally unchanged furnace by using different gas passage modules 2. The gas flow can be directed and focused. When replacing a module, only parts of a gas passage module 2 can be replaced, for example only an internal cassette 21 which shows greater wear. The fact that the entire gas passage module 2 or even the entire rear wall does not always have to be replaced results in cost and resource savings. To extend their service life, the cassettes 21 can also be replaced or rotated (e.g., according to a rotation principle from inside to outside, or by 180° around the vertical axis). Figures 9a and 9b show further embodiments of gas passage modules 2 in a perspective view. For the sake of clarity, reference symbols identifying the same elements are not shown in all figures.The circular-cylindrical gas passage modules 2 are shown sectioned centrally and parallel to the longitudinal axis L, so that each half-cylinder with a depth t is visible. In the exemplary embodiments, the gas passage modules 2 are designed as a single piece, such that guide devices 6 are formed integrally with walls 72. This design can be achieved in particular through additive manufacturing. In the present design, guide devices 6 and walls 72 form channels K that extend continuously between the end faces of the gas passage module 2. In the present case, the channels K have a curved shape, as can be seen in the section along the contour of the end face 61 of a guide device 6. The monolithic design, together with the continuous, in particular edge-free, course of the channels K, ensures particularly low-resistance flow through the gas passage module 2.Particular advantages of producing the gas passage modules 2 using additive manufacturing processes are: - thin, achievable wall thicknesses Æ low heat conduction losses - complex, stackable geometry. High shielding effect with a shallow installation depth - aerodynamically advantageous design Æ allows, for example, a focusing of the gas flow - one-piece solution Æ low assembly effort - geometrically flexible design Æ adaptable to different shapes of the gas inlet and outlet opening In particular, the channels formed by the guide devices 6 and walls 72 are closed across their entire circumference. In this further development, there is therefore no fluid communication between channels K. In summary, it can be stated that by designing the gas passage modules 2 using additive manufacturing processes, it is advantageous to realize a particularly "large number of walls" along an installation depth, which creates a high shielding effect. At the same time, a low flow resistance can be achieved through the aerodynamically advantageous design of the channels formed by the guide devices 6 and walls 72.In principle, connections between channels K could be formed via openings in guide devices 6 and / or walls 72. However, from a flow-technical perspective, a disturbance-free course of the channels K is more advantageous. It is preferred if the curved course of the channels K has exactly one apex over the depth t of the gas passage module 2. This is intended to express that there are not unnecessary many deflections of a flow. Nevertheless, a good shielding effect can be ensured. It is understood that the degree of curvature, the amplitude of the curvature and the clear width of a channel K are coordinated such that no direct radiation occurs. As with the previously discussed embodiments, a measure of open "porosity" can also be specified for the variant of one-piece gas passage modules 2. The wall thicknesses for one-piece gas passage modules 2 are preferably between 0.1 mm and 0.5 mm.Values ​​below this are not sensible for mechanical reasons. Thicker walls lead to higher heat conduction and increase manufacturing costs because more material is used. A free flow cross-section is preferably greater than 80% of a cross-section of the gas passage module 2. A specific example of an additively manufactured gas passage module 2 had the following dimensions: The wall thickness of the guide devices 6 was 0.15 mm. The radius of the gas passage module 2 was 25 mm, with five walls lying along the radial radius. This resulted in a free flow cross-section of around 98% based on the cross-section of the gas passage module 2. A channel width was around 5 mm. Relative to the entire volume of the gas passage module 2, the open "porosity" is naturally somewhat lower, since the above calculation does not take into account a possibly thicker cladding layer and walls 72.In the exemplary embodiments of Figures 9a and 9b, it can further be seen in longitudinal section that the channels K run essentially parallel to one another in the radial direction - r. In other words, the cross-sectional end faces 61 of the guide devices 6 form a set of essentially parallel curves. The walls 72 run flat and radially. Figuratively speaking, a cylinder sector (piece of a pie) contains radially stacked, sinusoidal channels K that become wider and / or larger towards the radial outside. In the exemplary embodiment according to Figure 9b, there are more walls 72, i.e., the gas passage module 2 is divided into cylinder sectors with smaller opening angles than the example according to Figure 9a. The smaller channel size produces a shielding effect comparable to that in the previous exemplary embodiment with a smaller installation depth (thus less material required, lower costs), but with higher flow resistance.The embodiments according to Figures 10a and 10b are also one-piece variants of gas passage modules 2. Compared to the embodiments in Figures 9a and 9b, the arrangement of the channels K is different here: If the cylindrical basic shape of the gas passage module 2 is considered as a shell-shaped arrangement of hollow cylinders (circular ring cylinders), then the channels K are each arranged within a hollow cylinder and parallel to one another in the circumferential direction U. Compared to the embodiment according to Figure 9, the entire cross-section is used here. In the design according to Figure 9, volume is wasted in the center and at the edge, since no flow can pass through these. This embodiment of one-piece gas passage modules 2 is particularly advantageous due to the small cross-sectional variation of the channels K. The channels K are, in particular, edge-free. In particular, the channels K have a constant cross-section over a depth t of the gas passage module 2.This can be achieved particularly advantageously using additive manufacturing processes. In a further development, locally different channel sizes can be provided, e.g. larger channels in the center, in order to adapt the local flow resistance to the parabolic course of the flow velocity of a pipe flow when used in a pipe flow. Values ​​between 0.1 mm and 0.5 mm have proven advantageous as wall thicknesses for the guide devices 6. An additive manufacturing process is preferably used to produce one-piece (monolithic) gas passage modules 2. In particular, the LPBF process is proposed. Figures 11a and 11b each show an individual channel K from the exemplary embodiment according to Figure 9a. In Figure 11a, the channel K is shown non-transparent, while in Figure 11b the same channel K is shown partially transparent. As already described for Figure 9a, a channel is formed by walls 72 and guide devices 6.In this embodiment, the walls 72 extend in the radial direction r. The exemplary embodiment of Figure 9a comprises, in a cylinder sector (pie slice), radially stacked, curved, in particular sinusoidal channels K, which visibly become wider and / or larger towards the radial outside. A channel K is preferably designed such that no path—and thus no radiation path—can be represented parallel to the longitudinal axis L of the gas passage module 2 that runs through the channel K without contact. In other words, the channel K has a curved course such that the channel K is opaque and thus prevents direct radiation passage in a shielding direction. In particular, no straight path can be laid through the channel K that does not intersect a wall of the channel K. Figures 12a and 12b each show an individual channel K from the exemplary embodiment according to Figure 10a.In Figure 12a, channel K is shown non-transparent, while in Figure 12b the same channel K is shown partially transparent. Here, too, it is envisaged that channel K has a curved course such that no contact-free path parallel to the longitudinal axis L can be defined through channel K. Contact-free would mean that the path runs through the gas passage module 2 without touching a wall of channel K. Preferably, all channels K of a gas passage module 2 are designed in such a way that they do not allow direct passage of radiation. Figure 13 shows a schematic and highly simplified principle of additive manufacturing of a gas passage module 2. It shows production using the LPBF process with melting by laser radiation. The base material is applied in powder form to a base plate. The powder P is melted by the action of a laser beam LS at the locations of the later walls.After solidification, a solid material bond is created. The base plate is lowered (symbolized by the block arrow "Z"), and another layer of powder P is applied. This process is repeated until the component is obtained. In this way, particularly advantageous geometries of channels K of gas passage modules 2 can be created. Figure 14 illustrates another embodiment of a gas passage module 2 with a serial arrangement of cassettes 21 relative to the longitudinal axis L. According to this variant, walls 7, in this example four walls 7 each, form a frame in which the guide devices 6 extend in a slat-like manner. In the example, the gas passage module 2 is formed by two cassettes 21, which, in series, result in a depth t along the longitudinal axis L. An offset of the guide devices 6 in successive cassettes 21 is advantageous.In the present case, the orientation of the guide devices 6 in successive cassettes 21 is mirrored, so that a deflection occurs when the flow passes through.

Claims

Claims 1. A gas passage module for installation in a radiation shield (3) of a high-temperature furnace (1), wherein the gas passage module (2) has a plurality of flat, spaced-apart guide devices (6) that extend at least partially between two opposite walls (7, 72), wherein at least some of the guide devices (6) form, with at least some of the walls (7, 72), at least temporarily and / or at least partially along a longitudinal axis (L) of the gas passage module (2), at least one channel (K) through which gas (G) can flow, wherein the guide devices (6) extend at least temporarily and / or at least partially obliquely to the longitudinal axis (L) in such a way that direct radiation passage through the gas passage module (2) is substantially prevented.

2. The gas passage module (2) according to claim 1, wherein the gas passage module (2) is at least 90% opaque along the longitudinal axis (L). 3.Gas passage module (2) according to one of the preceding claims, wherein a free flow cross-section (b) amounts to at least 30% of a cross-section of the gas passage module (2).

4. Gas passage module (2) according to one of the preceding claims, wherein at least some of the guide devices (6) are designed so that their orientation can be changed.

5. Gas passage module (2) according to one of the preceding claims, wherein the gas passage module (2) comprises a plurality of cassettes (21) arranged in series along the longitudinal axis (L) and / or parallel to one another transversely to the longitudinal axis (L).

6. Gas passage module (2) according to one of the preceding claims, wherein the gas passage module (2) is in one piece, such that guide devices (6) are formed integrally with walls (7).

7. Gas passage module (2) according to claim 6, wherein guide devices (6) together with walls (7) form closed channels (K) that extend through the gas passage module (2).

8. Gas passage module (2) according to claim 7, wherein at least some of the channels (K) have a curved course along the longitudinal axis (L) of the gas passage module (2) such that no contact-free path parallel to the longitudinal axis (L) through the channel (K) can be defined.

9. Gas passage module (2) according to one of the preceding claims, wherein a volume of the gas passage module (2) is filled with material to a maximum of 20%.

10. Gas passage module (2) according to one of the preceding claims, wherein at least a portion of the guide devices (6) is formed from refractory metal or a refractory metal alloy. 11.Gas passage module (2) according to one of the preceding claims, wherein at least some of the guide devices (6) are made of graphite or ceramic.

12. Radiation shield (3) for a high-temperature furnace (1), wherein the radiation shield (3) has an opening (5) into which a gas passage module (2) according to one of the preceding claims is inserted.

13. A high-temperature furnace (1) with a radiation shield (3) surrounding a process chamber (4) and thermally insulated from a furnace wall (11), wherein the radiation shield (3) has an opening (5) into which a gas passage module (2) according to one of the preceding claims is inserted.

14. Use of a gas passage module (2) according to one of the preceding claims as a gas nozzle for an inlet or outlet of gas (G) in a high-temperature furnace (1).

15. A method for producing a gas passage module (2) according to one of the preceding claims 1-11 using an additive manufacturing process.

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