Method for manufacturing a heating element of a gas heater

Abstract

The present invention relates to a method for manufacturing a heating element of a gas heater, wherein the heating element (1) of the gas heater has at least one electric heating element in a monolith (12), a carrier and channel structure (11) with a plurality of channels is formed in the monolith (12), the electric heating element is guided through the channels of the carrier and channel structure (11), and heat can be transferred from the electric heating element within the channels to the gas flowing through the channels to heat the gas and / or to achieve a high gas temperature. The method is characterized by the following steps: shaping the electric heating element; at least partially or completely coating the electric heating element with at least one coating material (3); introducing the coated electric heating element into a mold (5, 6) for manufacturing the monolith; manufacturing the monolith (12) surrounding the coated electric heating element; and removing the coating material (3) of the electric heating element.

Description

Field of the Invention

[0001] The present invention relates to a method for manufacturing a heating element of a gas heater, wherein the heating element of the gas heater has at least one electric heating element in a single block, a carrier and channel structure with a plurality of channels is constructed in the single block, and the electric heating element is guided in the channels of the carrier and channel structure, and heat can be transferred from the heating element into the gas flowing through the channels to heat the gas and / or achieve a high gas temperature. Background Art

[0002] Gas heaters are specifically designed for vertical flow-through, but are also used for horizontal applications, and are specifically designed for gas temperatures of 800°C to 1200°C. Here, gas heaters are superior to conventional heaters in terms of reliably achieving the desired gas temperature within the said temperature range and at the same time having a relatively long operating time until the heating wire fails due to their geometry.

[0003] The design of the heating element of the gas heater is based on the patent EP 2 926 623 B2 "Heating Element and Process Heater", wherein the manufacturing process is completely new.

[0004] Document EP 2 926 623 B2 discloses a heating element for heating a gas to a high temperature, which has at least one tube designed for the flow-through of hot or gas to be heated and an electric heating wire in the tube, and the electric heating wire is designed to transfer heat to the gas flowing through the heating wire.

[0005] Similarly, this document also relates to a process heater, which has a housing, the housing has a gas inlet and a gas outlet, a heating space between the gas inlet and the gas outlet for accommodating the heating element and an electrical connection for at least one heating element. Corresponding heating elements have long been known. They consist of at least one tube through which gas can flow, and the tube is open on both sides for the purpose of flow-through, and a heating wire is arranged in the tube, and the gas flows through the heating wire and is heated by direct contact with the heating wire.

[0006] According to EP 2 926 623 B2, the term "heating wire" as a generic term is used not only for relatively thin coiled wires but also for the heating rods according to the present invention, the heating rods have a corresponding longitudinal axis, the longitudinal axis extends substantially along or parallel to the axis of the tube and fills the tube to such an extent that only a relatively small net spacing is left between the heating rod and the tube wall, the spacing is at most 10 mm and preferably even significantly smaller, even if the spacing can be larger in spots.

[0007] The term "duct" is defined in document EP 2 926 623 B2 as a cavity with an inlet and an outlet opening, which corresponds to the carrier and channel structure in this document.

[0008] Different types of heating elements and different manufacturing methods are known from the prior art.

[0009] The heating element in EP 2 926 623 B2 is currently made of a bent heating wire and an extruded ceramic rod, which forms a gas channel, so this also seems to be the only feasible variant. The ceramic rods are then arranged side by side with as little intermediate space as possible, thus forming a very small bypass flow. The gas to be heated flows along the heating wire through the ceramic rods. In order to avoid bypass flow, a multi-drilled ceramic block can also be used instead of a single ceramic rod. Additionally, this document alternatively proposes hermetically filling the intermediate space between the ceramic rods with a suitable material or using a cover plate.

[0010] Especially due to the small-component structure and cost-intensive ceramics, the manufacture of the heating element for a gas heater entails high manufacturing effort and high manufacturing costs in relation to the manufacturing and materials used. The vertical installation of the heating element and the vertical gas flow-through are technically complex and thus also costly to manufacture. A large, high-performance gas heater cannot be realized practically and economically using the prior art manufacturing methods for the heating element according to EP 2 926 623 B2. The content of EP 2 926 623 B2 is also known from document DE 10 2014 102 474 A1.

[0011] Document DE 101 42 768 A1 describes a method for manufacturing a ceramic brake disc from a green body, which is made of SMC, reinforcing fibers, and subsequent pyrolysis and melt infiltration. In order to produce an integral green body with a very complex internal cavity after pyrolysis, the method includes manufacturing the green body in a die under pressure and temperature loading from a sandwich structure consisting of SMC, a thermoplastic insert, and SMC in one working step, where the insert fills the green body over its entire surface and is designed by perforations such that the upper SMC layer and the lower SMC layer are at least partially connected to each other.

[0012] In this document, the ceramic is produced by sintering the green body. The cooling channels required in the ceramic brake disc are generated by burning out a sacrificial material. This document only relates to the manufacture of ceramic brake discs. By burning out the sacrificial material, the cooling channels are exposed, and these cooling channels are only used for this purpose. No heating wire is introduced into the channels of the ceramic body.

[0013] Document DE 24 51 175 A1 discloses complex ceramic heating elements having a suitable geometry and a cross-section with a favorable resistance moment, wherein a metal heating conductor having a determinable power for single-phase to three-phase connection types is sintered as an energy conductor for heating liquids, gases, and solid substances into a dense, temperature-resistant and temperature-change (shock)-resistant, corrosion-resistant, physiologically neutral, dielectric ceramic material. The heating elements can be immersed in these media and / or be flowed through by these media. The heating capacity and service life of these heating elements exceed those of conventional designs. Manufacturing methods and suitable ceramic materials are described herein.

[0014] In this document, the ceramic heater-heating wire composite product is manufactured by a continuous casting method and by sintering the ceramic. Flow channels are formed into the ceramic as separate channels. The space around the heating wire is explicitly stated to be sealed to avoid contact with the medium to be heated. The flow channels are not produced by melting / burning out sacrificial material, but are formed into the ceramic by a continuous casting method.

[0015] Document EP 1 191 002 A1 describes the manufacture of a sintered body of aluminum nitride having excellent mechanical strength, wherein the detachment of ceramic particles from the surface and / or sides of the particles is prevented and thus the generation of free particles is suppressed. The sintered aluminum nitride sintered body contains sulfur.

[0016] The sintered body is used for manufacturing a ceramic heater and is manufactured by a ceramic die-casting method. The ceramic heater is used as a radiation heater for heating silicon wafers. Due to the high purity requirements for silicon wafers, a special selection of the ceramic material is made.

[0017] This document only relates to a radiation heater for silicon wafers and does not relate to a gas heater. Airflow channels are not produced by burning out sacrificial material.

[0018] Document US 2016 / 273 801 A1 discloses a gas heater heating element having a monolith / monolithic body in a carrier and channel structure and at least one heating element guided through the carrier and channel structure in the monolith.

[0019] A gas heater heating element of this kind is also known from document GB 499 074 A. However, no suitable manufacturing method for such a gas heater heating element is given.

[0020] The problems in the prior art mainly lie in that the manufacture of heating elements for gas heaters is both time-consuming and cost-intensive, and the installation is technically complex. Summary of the Invention

[0021] The object of the present invention is to provide a manufacturing method for a heating element of a gas heater, which is feasible for manufacturing heating elements of gas heaters that are not only small but also large and high-power, and can be economically implemented due to reduced manufacturing costs and reduced production costs.

[0022] This object is achieved by a manufacturing method for a heating element of a gas heater according to the present invention.

[0023] A manufacturing method for a heating element of a gas heater, wherein the heating element of the gas heater has at least one electric heating element in a single block, a carrier and channel structure with a plurality of channels is constructed in the single block, the electric heating element is guided in the channels of the carrier and channel structure, and heat can be transferred from the electric heating element to the gas flowing through the channels in the channels to heat the gas and / or achieve a high gas temperature, characterized by the following steps:

[0024] Form the electric heating element;

[0025] Coat the electric heating element at least partially or completely with at least one coating material;

[0026] Introduce the coated electric heating element into a mold for monolithic manufacturing;

[0027] Manufacture a single block surrounding the coated electric heating element; and

[0028] Remove the coating material of the electric heating element.

[0029] By this method, the corresponding heating elements of gas heaters can be manufactured cost-effectively for the first time. In particular, the size is no longer important, because the disclosed method enables the economic realization of both large and small heating elements of gas heaters.

[0030] Manufacturing the channel structure before actually manufacturing the monolithic structure can prove to be a particular advantage of the manufacturing method disclosed herein. By removing the coating material after manufacturing the monolithic structure, it is not necessary to introduce channels into the monolithic structure into which the corresponding electric heating elements must then be assembled after the monolithic structure is manufactured. Therefore, simply coating the electric heating element before manufacturing the monolithic structure is a special manufacturing step for defining the subsequent intermediate space by the coating to be removed.

[0031] The manufacturing process for a heating element of a gas heater according to the present invention has achieved a significant cost reduction in manufacturing heating elements of gas heaters, because the manufacturing costs and manufacturing time have been reduced. Now, continuous, i.e., integral and also mechanically manufactured, heating elements of gas heaters can be used.

[0032] Compared with manufacturing load-bearing and channel structures using ceramic rods known in the prior art, a significant reduction in the number of components is achieved. A self-supporting structure can be realized, which means that the electric heating element is combined with the load-bearing and channel structures in one component. In addition, other possible functional combinations are given, such as thermal insulation, electrical insulation, gas guiding or catalyst-bearing structures.

[0033] The following describes further design variants of the manufacturing method, which can further improve the method shown previously and also further specialize the method.

[0034] The electric heating element can in particular be configured as a heating wire and / or as a heating wire with a varying diameter and / or as a heating wire with a varying geometric structure and / or as a plurality of different heating wires and / or as a heating grid and / or as a heating grid structure. Thereby, different amounts of heat can be introduced into the individual regions or sections of the gas heater heating element according to the heating element geometry. In particular, the electric heating element can be arranged and / or shaped uniformly or non-uniformly or locally uniformly and locally non-uniformly in order to meet the corresponding requirements for the required heat.

[0035] The electric heating element and in particular the heating wire can be shaped arbitrarily and arranged with different densities. In a special variant, a non-uniform distribution of the electric heating elements within the gas heater - heating device can also be achieved, which can suppress, for example, possible non-uniform gas heating in the edge regions of the heater. For this purpose, the heater with the electric heating elements can be designed according to the flow profile. In order to further homogenize the temperature distribution, reflection elements for reflecting thermal radiation can be embedded or installed in the edge regions and / or outer regions of the monolithic structure.

[0036] As the electric heating element, heating wires, heating plates, heating rods, heating grids and combinations of the above elements are considered. However, other special design solutions are also possible.

[0037] In addition, the electric heating element can consist of three sections, namely: a first connecting section, which is formed outside the monolith and on the gas inlet side; a channel section, which is formed within the monolith; and a second connecting section, which is formed outside the monolith and on the gas outlet side. Thereby, the individual heating wires or heating elements within the monolith or monolithic structure are electrically connected correspondingly outside the monolithic structure. The mechanical connection between the multiple sections can also be achieved thereby, or can also be achieved within the channels of the monolithic structure.

[0038] In order to manufacture the monolith, a mold can be used, and for this purpose, the manufacturing method can in particular have the following steps:

[0039] - Place the formed and coated electric heating element into a mold;

[0040] - Fill the mold with a removable filling material until the first connection section of the coated electric heating element is completely covered;

[0041] - Cure the removable filling material;

[0042] - Pour the mold with a material that can be cured, is heat-resistant at temperatures above 800 °C, and has high resistance and high thermal conductivity, such that the second connection section of the coated electric heating element remains unpoured, and

[0043] - Remove the removable filling material and burn the heat-resistant material.

[0044] As the heat-resistant material for pouring the mold, for example, concrete can be used or other suitable ceramic embedding materials can also be used. The material is introduced into the mold by pouring and then fully hardened for subsequent process steps until it reaches the required strength. In this way, the channels and load-bearing structures to be formed are prevented from deforming uncontrollably during the removal of the filling material or the burning process.

[0045] In addition, alternatively, the monolith can be manufactured in a pressing mold and particularly has the following steps:

[0046] - Load the formed and coated electric heating element into a pressing mold;

[0047] - Fill the pressing mold with a pressure transfer material until the first connection section of the coated electric heating element is completely covered;

[0048] - Fill the pressing mold with a sintering material such that the second connection section of the coated electric heating element remains unfilled, the sintering material forms a green body, is heat-resistant at temperatures above 800 °C, and has high resistance and as high thermal conductivity as possible;

[0049] - Fill the second connection section of the coated electric heating element with a pressure transfer material;

[0050] - Press the entire loose material including the placed coated electric heating element;

[0051] - Remove the pressure transfer material;

[0052] and

[0053] - Sinter the heat-resistant sintering material.

[0054] For example, sand or other corresponding materials are suitable as pressure transfer materials. As sintered materials, for example, ceramic powders can be used or other materials meeting the requirements can also be used.

[0055] In a preferred variant, the removal of the coating of the electric heating element can be carried out by melting and / or by burning off and / or by chemical removal. Depending on the coating material used, the corresponding method steps can be carried out. For example, paint can be removed quite well by chemical removal. And wax can be removed well by melting.

[0056] In an implementation variant, the step of removing the coating of the electric heating element and / or the step of removing the removable filling material and / or the burning or sintering of the heat-resistant material can be combined in one method step.

[0057] The filling material usually has to be removed. Particularly preferably, the removable filling material and the coating of the heating wire can be removed in the same process step. Therefore, in relation to the removal step, the filling material should be selected to preferably have material properties similar to those of the coating. For example, casting resin or wax can be used as the filling material.

[0058] If, for example, wax is used, melting can also be carried out without direct contact with air / oxygen. The wax can melt and flow into / permeate the pressure transfer material. In contrast, if it is removed by burning off, contact with air / oxygen is required.

[0059] Furthermore, depending on which material is used as the sintered material and how the pressing process is carried out, if the green compact together with the embedded heating wire or electric heating wire has sufficient stability, the pressure transfer material is removed before sintering and simultaneously removing the coating, especially by burning off.

[0060] Alternatively, the coating or the filling material can be removed before burning.

[0061] Furthermore, the at least one coating material can be selected such that it has a lower melting point and a lower ignition point than the heat-resistant material.

[0062] Furthermore, the shaping of the electric heating element in the form of a heating wire can be achieved by bending and / or winding the heating wire into a heating wire row and / or by folding it into a heating wire pack. This is a very simple way to manufacture the required electric heating element.

[0063] In particular, the electric heating element can be constructed as a heating wire, particularly preferably as a single continuous heating wire.

[0064] The shaping of the heating wire includes both bending or winding the heating wire into a heating wire row and subsequently folding it into a heating wire pack, so as to obtain different variants in terms of the length and shape of the shaped heating wire, and the appearance of the completed shaped heating wire can be optimized as required.

[0065] If the heating wire is bent into a heating wire row, a limited side length of the heating wire is obtained in a method- or machine-determined manner. When the heating wire is wound around a mandrel, the side length can be variably adjusted according to the size of the mandrel. The heating wire can also be bent by other winding methods, such as the double-pin winding method.

[0066] Furthermore, thermal bending or stress-relieving annealing can be carried out as required, where this depends on the dimensions of the overall structure and whether the overall structure will be deformed or sheared due to stress.

[0067] If a centering profile is applied to the non-bent section of the heating wire generally or especially after stress-relieving annealing of the heating wire or generally of the electrical heating element and before coating of the heating wire / electrical heating element, the heating wire or electrical heating element is better centered in subsequent channels and carrier structures. This enables an optimized flow of gas through the carrier and channel structures. Furthermore, guiding elements can be used in which shaped heating wires can be used in order to hold the heating wire in its shape.

[0068] In particular, at least one of the materials wax and / or plastic and / or gel and / or paint can be used as the coating material.

[0069] In a further improved embodiment, the coating material can include at least one layer consisting of a viscous or pasty release agent and at least one layer consisting of a non-sticky material. As the non-sticky material, in particular polyethylene or other suitable polymers can be used.

[0070] Furthermore, the heating wire can be coated with a material or material system having a lower melting point or ignition point, where "lower" or "lower" is relative to the material filling the mold.

[0071] The temperature required for melting or burning off the coating depends in particular on the type of coating material, in particular on its melting point and / or ignition point. Since, for example, wax and / or plastic are used as low-melting or flammable coating materials, the temperature required for melting or burning off the coating can be significantly lower than the temperature required for sintering or burning of the monolith. This enables the removal and burning or sintering steps to be advantageously combined in one method step.

[0072] By forming a monolith around the finally shaped continuous heating wire, different carrier and channel structures can be formed according to the shape of the coated heating wire. The cross-section of the flow channel is adjustable along the gas flow direction, and the thicker the coating of the heating wire is constructed, the larger the cavity formed between the heating wire and the monolith body, i.e., the final gas channel.

[0073] For a specific manufacturing method of a heating wire that selects a material with a lower melting point compared to the material selected for casting, the lower region of the mold can be filled up to cover the bend with the same material or a similar material or a material having at least similar properties with respect to the removal step. If, for example, resin or wax is used, the region around the bend can be melted or burned away together with the coating of the heating wire.

[0074] In another design variant, the coating material can be configured to be at least locally non-uniform in thickness on the electric heating element. Here, different thicknesses can be formed on the electric heating element, which results in non-uniform structures of the channels and load-bearing structures in the monolithic structure. In particular, a large variability can be achieved in the design of the channels and load-bearing structures that can be formed in this way. Larger spaces can be designed in the inner region of the channel structure, and the larger spaces can then have a positive effect on the heating of the flowing gas overall. However, complex internal channel structures can also be formed, for example, to calm the flow or deliberately design the flow to be turbulent. By means of a coating of variable thickness of the heating wire, the cross-section of the flow channel can be adjusted purposefully. If a material system consisting of at least one non-sticky material and at least one sticky material is used, the non-sticky material can be used in terms of its thickness to define the diameter of the channels and load-bearing structures to be formed, while the sticky material serves as a release agent between the heating wire coated with the non-sticky material and the heat-resistant material and thus facilitates processing.

[0075] A gas heater heating element manufactured according to one of the methods for manufacturing a gas heater heating element according to the invention has, in its arrangement, a monolith / monolithic body with load-bearing and channel structures, wherein the load-bearing and channel structures are constructed during the monolithic manufacturing process and are not introduced afterwards, and at least one continuous electric heating element is guided through the load-bearing and channel structures in the monolith.

[0076] The load-bearing and channel structures of the monolith / monolithic body can be shaped at least locally non-uniformly with respect to the inner diameter of the load-bearing and channel structures.

[0077] Furthermore, the load-bearing and channel structures of the monolith / monolithic body can be shaped at least locally non-uniformly with respect to the spacing of the channels in the channel sections of the load-bearing and channel structures.

[0078] Furthermore, the gas heater heating element can have one or more heating elements with their respective load-bearing and channel structures and corresponding electric heating elements. Here, the monoliths can be arranged side by side or one after the other.

[0079] Since the single block can also be variably designed in terms of its shape, the gas heater heating element can be integrated into different housings. In addition, the vertical integration of the gas heater heating element can be carried out simply. Furthermore, the single block can have a reflector element for reflecting thermal radiation, which is embedded or mounted in the edge region and / or the outer region of the single block structure. Description of the Drawings

[0080] Embodiments of the present invention will be described in detail below with reference to the drawings in the description of the drawings, wherein the embodiments are intended to illustrate the present invention and should not be considered restrictive:

[0081] In the figures:

[0082] Figure 1 Schematic diagram showing a bent heating wire;

[0083] Figure 2 Schematic diagram showing a bent heating wire folded into a heating wire bundle;

[0084] Figure 3 Schematic diagram showing a wound heating wire;

[0085] Figure 4 Schematic diagram showing a wound heating wire folded into a heating wire bundle;

[0086] Figure 5 Schematic diagram showing a heating wire bundle after coating;

[0087] Figure 6 Schematic diagram showing a centering profile;

[0088] Figure 7 Schematic diagram showing a coated heating wire bundle fixed in a mold;

[0089] Figure 8 Schematic diagram showing a coated heating wire bundle fixed and cast in a mold;

[0090] Figure 9 Schematic diagram showing a coated heating wire bundle fixed and cast outside the mold before melting and burning;

[0091] Figure 10 Schematic diagram showing a coated heating wire bundle fixed in a pressing mold;

[0092] Figure 11 Schematic diagram showing a coated heating wire bundle fixed in a pressing mold filled with sintered material;

[0093] Figure 12 Schematic diagram showing a coated heating wire bundle in a fully covered pressing mold;

[0094] Figure 13 Schematic diagram showing the pressing for producing a green body of a heating wire packet;

[0095] Figure 14 Schematic diagram showing the green body of the heating wire packet after removing the non-pressed pressure transfer material and before melting and sintering;

[0096] Figure 15a Schematic diagram showing the completed gas heater heating element with the gas channel structure opened after melting and combustion or sintering;

[0097] Figure 15b Magnified schematic diagram showing the completed gas heater heating element with the gas channel structure opened after melting and combustion or sintering; and

[0098] FIG. 16 shows in detail three partial views a, b, c of the gas heater heating element in a monolithic structure. DETAILED DESCRIPTION

[0099] In the following description of the drawings, components having the same function are provided with a unified reference numeral.

[0100] In Figure 1 a bent heating wire 21 in the form of a heating wire row is shown. In this manufacturing variant of the heating wire row, there is a limited side length.

[0101] Figure 2 Shown Figure 1 in

[0102] in Figure 3 a wound heating wire 22 in the form of a heating wire row is shown. In this manufacturing variant of the heating wire row, there is a variable side length depending on the mandrel used. The mandrel can be variably designed in terms of size and shape. Other winding methods can also be used for manufacturing.

[0103] Figure 4 Shown Figure 3 in

[0104] in Figure 5 a wound heating wire 22 can be seen, and the wound heating wire 221 is folded into a heating wire packet. Figure 9A heating wire package composed of a wound heating wire 221 after a coating 3 of a material with a low melting point or a low ignition point. The coating 3 shown by hatching is applied to the heating wire with a uniform outer radius. As an alternative, the coating can be shaped with a non-uniform thickness or a varying outer radius and / or be composed of a material system including a plurality of materials having a melting point or an ignition point sufficiently smaller than that of the embedding material. In the following drawings, for the sake of clarity, the hatching of the coated heating wire is omitted, although the heating wire is coated according to the corresponding embodiments.

[0105] In Figure 6 a possible embodiment of a centering profile 4 is shown, which is used to better center the heating wire in a subsequent load-bearing and channel structure 11. Before or after applying the coating 3 to the heating wire and before a further manufacturing step, the centering profile 4 is placed at predetermined intervals on the vertical section of the heating wire.

[0106] Figure 7 A half-shell of a mold 5 is shown, and a coated heating wire package composed of a wound heating wire 221 is fixed in the half-shell. The mold 5 is poured with a removable filling material 7 to such an extent that the lower bending part of the coated heating wire package composed of the wound heating wire 221 is completely covered.

[0107] In Figure 8 In Figure 7 the mold 5 in

[0108] Figure 9 is shown a coated heating wire package composed of a wound heating wire 221 in Figure 8 after being removed from the mold 5 and before the melting and / or burning-off of the removable filling material and the coating of the wire package. The coated heating wire package is poured into the removable filling material 7 and a heat-resistant / ceramic embedding material 9. The heat-resistant / ceramic embedding material 9 has solidified or has been solidified before removing the mold.

[0109] Figure 10A half-shell of the extrusion die 6 is shown. The coated heating wire bundle formed by the wound heating wire 221 is fixed in this half-shell with a pressure transfer material 8, such as sand. The pressure transfer material 8 is filled to such an extent that the lower bending part of the coated heating wire bundle formed by the wound heating wire 221 is completely covered. The pressure transfer material is poured into the pressing die 6 and then compacted. To ensure sufficient fixation of the wound heating wire 221, one or more holding devices can be used in the corresponding manufacturing step. The pressure transfer material can be compacted, for example, by vibration and / or pressing.

[0110] In Figure 11 the Figure 10 pressing die 6 is filled with a sintering material 10, such as ceramic powder, to such an extent that the upper bending part of the coated heating wire 221 is not filled.

[0111] In Figure 12 the Figure 11 pressing die 6 is filled with the pressure transfer material 8 to such an extent that the coated heating wire bundle is completely covered. Thus, the pressing die 6 containing the coated heating wire bundle formed by the wound heating wire is filled with three stacked layers (pressure transfer material - sintering material - pressure transfer material).

[0112] Figure 13 Schematically shown is the force action F13 acting on the coated heating wire bundle in the fully filled pressing die 6 during the pressing process. During the pressing process, the sintering material 10 is pressed into a green body in the pressing die 6.

[0113] Figure 14 Shown is the green body containing the coated heating wire bundle 221 after removing the pressing die 6 and the pressure transfer material 8 and before removing the coating and sintering the green body 10.

[0114] Figure 15a Shown is the completed gas heater heating element 1, which has a monolith 12 with a carrier and channel structure 11, and the heating wire bundle formed by the wound heating wire 221 extends through the carrier and channel structure. To complete the gas heater heating element 1, the coating 3 is removed from Figure 9 the coated and cast heating wire bundle formed by the wound heating wire 221 in Figure 14 or from the green body containing the coated heating wire bundle in

[0115] Figure 15b ShownFigure 15a An enlarged view of the completed gas heater heating element 1 in []. The openings of the carrier and channel structure 11 can be clearly seen, from which the windings of the wound heating wire 221 extend. The monolith is penetrated by a channel structure that has an opening near the bend of the electrical heating element and through which gas can be guided for heating purposes.

[0116] The structure of the gas heater heating element 1 is self-supporting. The heating wire is combined with the carrier and channel structure 11 in one component. It is characterized in that the monolith 12 containing the carrier and channel structure 11 is formed in one process, as illustrated in the above figures. Other functional combinations such as thermal insulation, electrical insulation, gas guiding or catalyst carrier structures are possible.

[0117] Figure 16a and Figure 16b Shows the coated heating wires 211 / 221 in the bulk material of the monolith 9 / 10 before removal of the coating by melting / ablation and combustion / sintering of the bulk material. The heating wires 211 / 221 are only coated with the material 3 in [], and in [] shows a coating structure composed of a material system consisting of two layers 3 and 3'. Figure 16a in [] Figure 16b shows a coating structure composed of a material system consisting of two layers 3 and 3'. Figure 16c Shows the heating wires 211 / 221 exposed after removal of the coating by melting / ablation and combustion / sintering of the bulk material, such that the carrier and channel structure 11 is formed in the monolith 12.

[0118] The previously mentioned embodiments are intended to illustrate the invention but do not limit the scope of protection of the invention.

[0119] List of reference numerals

[0120] 1 Gas heater heating element

[0121] 21 Bent heating wire

[0122] 211 Heating wire package composed of bent heating wire

[0123] 22 Wound heating wire

[0124] 221 Heating wire package composed of wound heating wire

[0125] 3, 3' Coating

[0126] 4 Centering profile

[0127] 5 Mold

[0128] 6 Pressing die

[0129] 7 Removable filling material

[0130] 8 Pressure transfer material

[0131] 9 Heat-resistant materials / Ceramic investment materials

[0132] 10 Sintered materials

[0133] 11 Load-bearing and channel structures

[0134] 12 Monolith

[0135] 13 Force F

Claims

1. Method for manufacturing a heating element of a gas heater, wherein, The gas heater heating element (1) has at least one electric heating element in a monolith (12), and a carrier and channel structure (11) with a plurality of channels is constructed in the monolith (12). The electric heating element is guided in the channels of the carrier and channel structure (11), and heat can be transferred from the electric heating element to the gas flowing through the channels within the channels to heat the gas and / or achieve a high gas temperature. It is characterized by the following steps: Form an electric heating element; Coat the electric heating element at least partially or completely with at least one coating material (3); Introduce the coated electric heating element into a mold (5, 6) for monolith manufacturing; Manufacture a monolith (12) surrounding the coated electric heating element; and Remove the coating material (3) of the electric heating element.

2. The method for manufacturing a gas heater heating element according to claim 1, characterized in that, The electric heating element is configured as a heating wire.

3. The method for manufacturing a gas heater heating element according to claim 1, characterized in that, The electric heating element is configured as a heating wire with a varying diameter.

4. The method for manufacturing a gas heater heating element according to claim 1, characterized in that, The electric heating element is configured as a heating wire with a varying geometric structure.

5. The method for manufacturing a gas heater heating element according to claim 1, characterized in that, The electric heating element is configured as a plurality of different heating wires.

6. The method for manufacturing a gas heater heating element according to claim 1, characterized in that, The electric heating element is configured as a heating grid.

7. The method for manufacturing a gas heater heating element according to claim 1, characterized in that, The electric heating element is configured as a heating grid structure.

8. The method for manufacturing a gas heater heating element according to any one of claims 1 to 7, characterized in that, The electric heating element is arranged and / or formed in a uniform or non-uniform or locally uniform or locally non-uniform manner.

9. The method for manufacturing a gas heater heating element according to any one of claims 1 to 7, characterized in that, The electric heating element consists of three sections, namely A first connection section, which is constructed outside the monolith and on the gas inlet side, A channel section, which is formed within the monolith, and A second connection section, which is constructed outside the monolith and on the gas outlet side.

10. The method for manufacturing a gas heater heating element according to claim 9, characterized in that, The manufacturing of the monolith (12) is carried out by means of a casting mold (5) and has the following steps: Place the shaped and coated electric heating element into the casting mold (5); Fill the casting mold (5) with a removable filling material (7) until the first connection section of the coated electric heating element is completely covered; Cure the removable filling material (7); Pour the casting mold (5) with a material that can be cured, is heat-resistant at temperatures above 800°C, and has a high resistance and high thermal conductivity, such that the second connection section of the coated electric heating element remains un-poured, and Remove the removable filling material (7) and burn the heat-resistant material (9).

11. The method for manufacturing a gas heater heating element according to claim 9, characterized in that, The manufacturing of the monolith (12) is carried out in a pressing mold (6) and has the following steps: Place the shaped and coated electric heating element into the pressing mold (6); Fill the pressing mold (6) with a pressure transfer material (8) until the first connection section of the coated electric heating element is completely covered; Fill the pressing mold (6) with a sintering material (10) that forms a green body, is heat-resistant at temperatures above 800°C, and has a high resistance and as high a thermal conductivity as possible, such that the second connection section of the coated electric heating element remains unfilled; Fill the second connection section of the coated electric heating element with the pressure transfer material (8); Press all the bulk materials including the placed coated electric heating element; Remove the pressure transfer material (8); And A sintered heat-resistant sintered material (10).

12. A method for manufacturing a gas heater heating element according to any one of claims 1 to 7, characterized in that, The removal of the coating (3) of the electric heating element is carried out by melting and / or burning off and / or chemical removal.

13. A method for manufacturing a gas heater heating element according to any one of claims 1 to 7, characterized in that, The following steps: Removing the coating (3) of the electric heating element and / or Removing the removable filling material (7) and / or Burning or sintering the heat-resistant material is carried out in one method step.

14. The method for manufacturing a gas heater heating element according to claim 13, characterized in that, The at least one coating material (3) is selected such that it has a lower melting point and a lower ignition point than the heat-resistant material.

15. The method for manufacturing a gas heater heating element according to claim 2, characterized in that, The electric heating element is formed in the form of a heating wire by bending the heating wire into a heating wire row.

16. The method for manufacturing a gas heater heating element according to claim 2, characterized in that, The electric heating element is formed in the form of a heating wire by winding the heating wire into a heating wire row.

17. The method for manufacturing a gas heater heating element according to claim 2, characterized in that, The electric heating element is formed in the form of a heating wire by folding the heating wire into a heating wire pack.

18. The method for manufacturing a gas heater heating element according to claim 2, characterized in that, The electric heating element constructed as a heating wire is constructed as a single continuous heating wire.

19. A method for manufacturing a gas heater heating element according to any one of claims 1 to 7, characterized in that, Wax and / or plastic and / or gel and / or paint is used as at least one material of the coating material (3).

20. The method for manufacturing a gas heater heating element according to any one of claims 1 to 7, characterized in that, The coating material (3) includes at least one layer composed of a viscous or pasty release agent and at least one layer composed of a non-sticky material.

21. The method for manufacturing a gas heater heating element according to any one of claims 1 to 7, characterized in that, The coating material (3) is constructed such that it is at least locally non-uniformly shaped in terms of its thickness on the electric heating element.

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