Heat exchanger

Abstract

Heat exchanger (1) with two separate flow paths (2, 3) for a gas flow, wherein a first flow path (2) and a second flow path (3) are separated from each other at least sectionally by a common wall (4), wherein the wall (4) towards both flow paths (2, 3) has a catalytic coating (5).

Description

[0001] The invention relates to a heat exchanger.

[0002] Large amounts of heat are required, particularly in the production of synthetic fuels or in the catalytic conversion of ammonia to hydrogen. This results in a high energy demand. In particular, catalytic processes for producing hydrogen from ammonia require high temperatures to activate the chemical reaction or splitting.

[0003] To achieve these temperatures, catalytic reactors are used and / or material streams are preheated, which may then be directed into the catalytic reactor.

[0004] In such production of synthetic fuels or in the catalysis of ammonia to obtain hydrogen, it is important to provide the required temperatures quickly, without high losses and uniformly.

[0005] Based on this, the object of the invention is to at least partially solve the problems described with reference to the prior art. In particular, it aims to create a method for carrying out a catalytic reaction that requires less energy.

[0006] This problem is solved by the features of the independent claims. Further advantageous embodiments of the invention are specified in the dependent claims. It should be noted that features listed individually in the claims can be combined with one another in any technologically meaningful way and define further embodiments of the invention. Furthermore, the features specified in the claims are specified and explained in more detail in the description, which also presents further preferred embodiments of the invention.

[0007] A heat exchanger with two separate flow paths, each for a different gas stream, contributes to solving this problem. A first flow path and a second flow path are separated from each other, at least partially, by a common wall. The wall facing both flow paths has a catalytic coating.

[0008] The heat exchanger is designed to create a space where thermal energy can be transferred from one gas stream to another. For this purpose, the gas streams are guided through the heat exchanger in separate flow paths. The heat exchanger may be enclosed in a housing with separate connections for the inlet and outlet of the gas streams.

[0009] The two separate flow paths are arranged in the heat exchanger such that heat can be transferred from one gas stream in one flow path to the other gas stream in the other flow path. In particular, one gas stream can heat the other. One gas stream can release heat that was already added to it before entering the heat exchanger or that is generated and / or increased during (exothermic) processes within the heat exchanger. External heat sources and / or reactive, especially catalytic, processes can be used in the heat exchanger.

[0010] The shared wall between the first and second flow paths is designed to be highly thermally conductive. Specifically, the wall is thermally conductive along a predetermined length, allowing heat to be transferred from a gas stream in one flow path to a gas stream in the other. The wall (preferably made of a single material) delimits both flow paths, enabling the gas streams to flow along and be in contact with both sides of the wall.

[0011] The wall has a catalytic coating on each of the two flow paths. The catalytic coating is designed such that the gas flows passing through the flow paths can undergo catalytic conversion. Preferably, at least one of the catalytic coatings is designed such that heat is generated in the gas flow during a catalytic conversion, i.e., an exothermic reaction occurs. Preferably, the heat generated during the catalytic conversion can be transferred from the catalytically heated gas flow through the wall to the other gas flow. The other catalytic coating can then optionally contribute to motivating or initiating a temperature-sensitive chemical reaction in the other gas flow.

[0012] The catalytic coatings can be arranged on opposing sections of the wall. The catalytic coatings can partially or completely overlap each other on the wall. Preferably, the catalytic coatings overlap by at least 75%. This overlapping arrangement of the coatings creates a compact reaction space within the heat exchanger, in which heat can be efficiently generated, transferred, and used for the desired chemical reaction in the other gas stream.

[0013] The wall can be part of a pipe section through which the first flow path extends. The first flow path can extend along an inner surface of the pipe section. The second flow path can extend along an outer surface of the pipe section. It is possible for a gas flow to be directed through the first flow path within the pipe section, while a second gas flow flows along the outer surface of the pipe section. A first catalytic coating for the first flow path can be located directly on the inner surface of the pipe section. A second catalytic coating can be located directly on the outer surface of the pipe section. The first catalytic coating can extend along the entire inner circumference of the pipe section over a predetermined length. The second catalytic coating can extend along the entire outer circumference of the pipe section over a predetermined length.

[0014] The catalytic coating may comprise a possibly amorphous and / or fractured carrier substance, in particular so-called washcoat, which is doped with the desired catalytically active materials.

[0015] The heat exchanger may contain a plurality of (parallel) tube sections, in particular at least 50. The heat exchanger may have a casing that delimits the second flow path. The plurality of tube sections may be provided within the casing. It is possible that the second flow path has a (central or single) inlet to the heat exchanger, wherein the gas flow in the second flow path can be introduced into the heat exchanger towards the tube sections and the catalytic coatings arranged thereon. It is possible that the second flow path has a (central or single) outlet from the heat exchanger, wherein the gas flow in the second flow path can be directed out of the heat exchanger after passing the catalytic coatings. It is possible that the heat exchanger has a tube bundle of tube sections enclosed in the casing.The tube bundle can be designed with a common support for the multiple tube sections, with the tube sections being arranged, for example, on a circle.

[0016] The pipe sections can have an (inner) diameter between 1 mm [millimeter] and 5 mm. The pipe sections preferably have a pipe wall thickness in the range of 0.3 mm to 1.0 mm.

[0017] One or both catalytic coatings facing the flow paths can cover an area of ​​at least 1,000 cm². 2 [square centimeters] The areas preferably have a size of 300 to 10,000 cm². 2 It is possible that the catalytic coatings extend along equally sized wall sections on opposite sides of the pipe sections. It is also possible that one catalytic coating extends over a larger wall section than the other, opposing catalytic coating.

[0018] It is possible, and preferably preferred, that the coatings in the separate flow paths are different, particularly with regard to the catalytically active substances. It is possible that different catalytic reactions are possible on the catalytic coatings. It is possible that one catalytic reaction is possible at a lower temperature than the other catalytic reaction on one side of the wall. In particular, it is possible that the two catalytic reactions on opposite sides of the wall influence each other. Thus, a first catalytic reaction can occur at a lower temperature than a second catalytic reaction. The heat generated in this process can be conducted to the opposite side of the wall and influence and promote the second catalytic reaction.This allows the second catalytic reaction to occur without requiring additional heat input once the first catalytic reaction has taken place. The heat exchanger can be utilized simply by the temperature increase from the first catalytic reaction, which directly influences the second. This makes it possible for the second catalytic reaction to occur with less external heat input. The heat exchanger can be operated by supplying heat to one of the gas streams to a temperature sufficient for the first catalytic reaction. The first catalytic reaction generates waste heat, which raises the temperature of the other gas stream, enabling the second catalytic reaction to occur.

[0019] In the heat-generating reaction, the first gas stream can comprise, for example, HC [hydrocarbon] and CO [carbon monoxide], and react in the presence of a first catalyst, such as Pt [platinum], Pd [palladium], or Rh [rhodium]. Depending on the desired process gases, a suitable second catalyst can be provided.

[0020] In the case of the production of synthetic fuels, the second gas stream can, for example, include HC [hydrocarbon] and H2O [water], and react in the presence of a second catalyst, such as Ni [nickel], Al2O3 [aluminum oxide] to form CO [carbon monoxide] and H2 [hydrogen].

[0021] In the case of catalyzing ammonia to produce hydrogen, the second gas stream can include, for example, NH3 [ammonia] and react in the presence of a second catalyst, such as Ru [ruthenium].

[0022] Each pipe section can have an outer (or single, possibly concentric) jacket pipe extending over the entire length of the pipe section and featuring a catalytic coating on its inner surface. This increases the usable catalytic coating area on the outside of the pipe sections. Consequently, the catalytic reaction can occur not only on the outside of the pipe sections but also on the inner surface of the jacket pipes. This may result in a faster or more significant temperature rise during the catalytic reaction on the outside of the pipe section in combination with the inner surface of the jacket pipes.

[0023] The outer casing tubes can be held in the heat exchanger by one or more inlet plates. The inlet plates may position or align the outer casing tubes around the tube sections. The inlet plates may also prevent the gas flow from bypassing the outer casing tubes. Alternatively, the second gas flow may enter the heat exchanger through the casing inlet and be guided by the inlet plates through the spaces between the outer casing tubes and the tube sections. Finally, the second gas flow may be completely bypassed by the catalytic coatings on the inner surfaces of the outer casing tubes and the outer surfaces of the tube sections.

[0024] It is possible that an electric heater is assigned to or located upstream of the pipe sections. It is possible that the electric heater preheats the second gas stream and (before reaching the second catalytic coating) brings it to a temperature sufficient for a first catalytic reaction to occur on the outer surfaces of the pipe sections and the inner surfaces of the casing pipes.

[0025] The heat exchanger contributes to solving this problem by enabling the efficient conversion of ammonia to hydrogen and nitrogen, or the production of synthetic fuels. In particular, the heat exchanger can be used to catalyze or convert ammonia or other substances in the production of synthetic fuels, requiring less energy than conventional catalysts.

[0026] The heat exchanger offers particular advantages and alleviates the problems mentioned at the outset. The specific advantages and design features described for the heat exchanger are applicable and transferable to the described use of the heat exchanger, and vice versa.

[0027] The invention and the technical context are explained in more detail below with reference to two figures. The illustrations are schematic and not intended to demonstrate scale relationships. The explanations given with reference to individual details of the figure can be extracted and freely combined with facts from the preceding description, unless a person skilled in the art necessarily derives otherwise, or such a combination is explicitly excluded. The figure schematically shows: Fig. 1: a first embodiment of a heat exchanger with a tube bundle, and Fig. 2: A further detailed design of a heat exchanger.

[0028] Fig. Figure 1 shows a heat exchanger 1 with a tube bundle 13. The heat exchanger 1 is shown in a cutaway view. The tube bundle 13 is thus visible. The tube bundle 13 comprises tube sections 6 and surrounding jacket tubes 7. A first flow path 2 runs through each of the tube sections 6. Fig. Figure 1 indicates a catalytic reaction on the first flow path 2, in which NH3 [ammonia] is converted to H2 [hydrogen] and N2 [nitrogen]. It is possible to use heat exchanger 1 for a different catalytic reaction as well.

[0029] The heat exchanger 1 also has a second flow path 3, which is directed into the heat exchanger 1 via an inlet 10 and out of the heat exchanger 1 via an outlet 11. An electric heater 9 is arranged in the inlet 10. The second flow path 3 is guided through one of the jacket tubes 7 in the heat exchanger 1.

[0030] The first flow path 2 and the second flow path 3 are each separated from each other by a wall 4. Heat can be transferred through the wall 4.

[0031] To prevent flow past the casing pipes 7, these also have inlet plates 8. The second flow path 3 thus extends from the inlet 10 to the outlet 11 along the spaces between the inner surface of the casing pipes 7 and the outer surface of the pipe sections 6. The entire heat exchanger 1 is enclosed in a housing 12. The housing 12 also forms an outer boundary of the second flow path 3 before and after the spaces between the casing pipes 7 and the pipe sections 6.

[0032] In Fig. Figure 1 indicates a catalytic reaction on the second flow path 3, in which H₂ [hydrogen], O₂ [oxygen], and H₂O [water] are reacted. It is possible to use heat exchanger 1 for a different catalytic reaction as well. Not apparent in Fig. 1 is also a catalytic coating 5 which is arranged on the inner surfaces of the pipe sections 6, on the outer surfaces of the pipe sections 6 and on the inner surfaces of the casing pipes 7. The catalytic coatings 5 ​​are each adapted to the substances that are to be reacted on the flow paths 2, 3.

[0033] Fig. Figure 2 shows a sectional view of the heat exchanger 1 without the tube bundle 13. The description of the heat exchanger 1 without the tube bundle 13 in Fig. 2 can be analogously transferred to a heat exchanger 1 with tube bundle 13. Fig. Figure 2 shows an inlet 10 and an outlet 11 for the second flow path 3 into and out of the housing 12 of the heat exchanger 1. It also shows Fig.Figure 2 shows the first flow path 2, which extends along the pipe section 6. The second flow path 3 and the first flow path 2 are separated from each other by a wall 4. Also shown are the catalytic coatings 5, which extend along an inner side of the pipe section 6, along an outer side of the pipe section 6, and along an inner side of the casing pipe 7.

[0034] The solution proposed here can at least partially alleviate the problems described with reference to the state of the art. In particular, solutions have been presented that enable a catalytic reaction to be carried out with a lower energy input. Reference sign 1 heat exchanger 2 first flow path 3 second flow path 4 Wall 5 catalytic coating 6 Pipe section 7 Jacket pipe 8 Inlet plate 9 electric heaters 10 Entrance 11 Exit 12 cases 13 tube bundles

Claims

Heat exchanger (1) with two separate flow paths (2, 3) for a gas flow, wherein a first flow path (2) and a second flow path (3) are separated from each other at least sectionally by a common wall (4), wherein the wall (4) towards both flow paths (2, 3) has a catalytic coating (5). Heat exchanger (1) according to claim 1, wherein the wall (4) is part of a pipe section (6). Heat exchanger (1) according to one of the preceding claims, wherein a plurality of tube sections (6) are provided in the heat exchanger (1), in particular at least 12. Heat exchanger (1) according to one of the preceding claims, wherein the pipe section (6) has a diameter between 1 mm and 5 mm. Heat exchanger (1) according to one of the preceding claims, wherein the catalytic coating (5) pointing towards both flow paths (2, 3) each has an area of ​​at least 3,000 cm2. Heat exchanger (1) according to claim 5, wherein the catalytic coating (5) is different in each case. Heat exchanger (1) according to one of the preceding claims, wherein each pipe section (6) has a jacket pipe (7) which extends at least partially over the length of the pipe section (6) and has a catalytic coating (5) on an inner wall. Heat exchanger (1) according to claim 7, wherein the jacket tubes are held in the heat exchanger (1) by at least one inlet plate (8). Heat exchanger (1) according to one of the preceding claims, wherein an electric heater (9) is positioned upstream of the pipe sections. Use of a heat exchanger (1) according to claims 1 to 9 for the efficient conversion of ammonia to hydrogen and nitrogen or for the production of synthetic fuels.

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