Electric gas heater

Abstract

The electric gas heater 2 includes a housing 4, a number of thin-walled tubes 16 arranged in a bundle 18 inside the housing 4, and a protective member 20 configured to support the number of thin-walled tubes 16 separated and electrically insulated from one another. Each tube 16 of the number of thin-walled tubes 16 is made of an electrically resistive material, and the protective member 20 includes a fibrous material.

Description

[Technical Field]

[0001] This invention relates to an electric gas heater. Furthermore, this invention relates to a method for heating gas in an electric gas heater. [Background technology]

[0002] A through-flow type electric gas heater is known, which includes an electrically heated tube through which the gas to be heated is guided.

[0003] US927173 discloses an electric heater having a resistive member constructed of nickel tubing. In the housing, a very large number of thin-walled nickel tubings are placed on a lateral sheet metal wall through a protective body. These nickel tubings are interposed in series through suitably arranged sheet metal strips to form a continuous conductor for current.

[0004] US4233494 discloses a through-flow heater for fluids, in particular an air heater used for regenerating carbon dioxide adsorbents in an air rectification system. Air is fed from an upper chamber in a cylindrical housing through a parallel group of Ni-Cr steel heating tubes to a lower chamber communicating with carbon dioxide adsorbents. The groups of tubes protrude at their upper ends into each of the openings in a carrier plate and are subsequently suspended from each of Al2O3 ceramic holder plates, which are mounted on flanges that are removablely fixed inside the housing. The tubes in each group are connected in series to a voltage source, and the lower ends of the tubes in one group are held by molded ceramic spacers that are slidably inserted into pipe sections aligned in a support plate and associated openings in the upper carrier plate, thereby ensuring electrical insulation of these tubes. The holder plates and openings are formed as circular or circular cross-sections.

[0005] A different type of gas heater includes one or more electrically heated wires extending through a number of tubes arranged in parallel, such as those disclosed in US2018 / 098385. This type of gas heater is distinctly different from the above-described type of fluid heater which includes electrically heated tubes. That is, the tubes through which the electrically heated wires extend must be electrically insulated. This also means that these tubes may be placed in contact with each other in a bundle of tubes. Furthermore, the gas is heated firstly by the electrically heated wires and secondly by the tubes which are indirectly heated by the electrically heated wires.

[0006] To ensure the proper operation of an electric gas heater, it is crucial that the heater's tubes are isolated from one another. Therefore, the suspension of electric gas heater tubes is complex, sometimes requiring intricate suspension configurations to satisfy both the suspension requirements and electrical insulation requirements. [Overview of the project]

[0007] It would be preferable to realize an improved electric gas heater that overcomes or at least mitigates at least some of the above-mentioned drawbacks. In particular, it would be desirable to enable efficient suspension of the tubes of the electric gas heater. To better address one or more of these concerns, an electric gas heater having the features defined in one of the independent claims is provided.

[0008] According to one aspect of the present invention, an electric gas heater is provided. This electric gas heater includes a housing, a number of thin-walled tubes arranged in a bundle inside the housing, protective members configured to support the number of thin-walled tubes separated from each other and electrically insulated from each other, a conductor configured to connect the number of thin-walled tubes to an external power source, and inside the housing, an inlet chamber upstream of the number of thin-walled tubes and an outlet chamber downstream of the number of thin-walled tubes. A gas flow path extends from the inlet chamber through the inside of the number of thin-walled tubes to the outlet chamber. The individual tubes of the number of thin-walled tubes are made of aluminum oxide molded electrical resistance material or molybdenum-based alloy.

[0009] The electric gas heater includes protective members configured to support a number of thin-walled tubes that are separated from each other and electrically insulated from each other, so that the tubes of the number of thin-walled tubes are insulated from each other and supported individually.

[0010] Electric gas heaters may, for the purposes of this text, be referred to simply as gas heaters or heaters. Electric gas heaters may be used to heat gas in industrial processes. The heated gas may be used, for example, in industrial processes, and / or it may be used as an energy carrier in industrial processes and / or as a heat source in industrial processes.

[0011] A gas heater provides a principle of a gas heater with a simple structure, where there are tubes that are electrically heated directly and tubes to which energy is directly applied, and these are the spaces for any additional heating elements. This gas heater has a simple structure, requiring only a few different components. This heater may contain hundreds of individual tubes, but the number of these tubes of their types may be limited. This, above all, results in an operationally reliable gas heater.

[0012] These thin-walled tubes have a small diameter and a thin wall thickness. A very large number of these tubes may therefore be provided for a gas heater of a given capacity. Thus, these thin-walled tubes provide efficient use of the housing of this capacity, and therefore efficient heat transfer to the gas being heated.

[0013] Furthermore, since many of the thin-walled tubes are configured to be connected to an external power source, and because the thin-walled tubes are made of aluminum oxide molded electrical resistance material or molybdenum-based alloy, these thin-walled tubes are electrically heated directly. Thus, the supplied electrical energy is efficiently converted into heat, which is then transferred to the gas being heated in the electric gas heater.

[0014] These thin-walled tubes provide a passage for the gas to be heated. There are no heating elements extending through the inside of the thin-walled tubes. In other words, the inside of the thin-walled tubes is empty, meaning there is nothing inside. They do not have any internal elements, such as wire heating elements, extending through them.

[0015] Here, these thin-walled tubes may be referred to simply as tubes.

[0016] Here, these numerous tubes arranged in a bundle may be alternatively referred to as a bundle of tubes, or simply a bundle. In this bundle, these thin-walled tubes are arranged in parallel, separated from one another.

[0017] A gas heater includes a housing that not only protects the bundle of tubes but may also be additionally designed as a pressure vessel, with a bundle of tubes arranged inside. If the housing is designed as a pressure vessel, this means that the individual tubes of the multitude of tubes do not need to be able to withstand any pressure difference between their inside and outside that exceeds the pressure drop caused by the gas flow. Therefore, additionally, tubes with a rated pressure are not required.

[0018] The external power source may include main power or may be connected to the main power via a transformer for adapting the voltage of the current supplied to the electric gas heater.

[0019] During use of the gas heater, the inlet chamber functions as a manifold for distributing the collective gas stream into individual tubes. The outlet chamber functions as a manifold for combining the heated gas in the individual tubes into one collective gas stream.

[0020] The electrical resistance material is a conductor. When current flows through the electrical resistance material, it heats the electrical resistance material. As described above, the electrical resistance material is an aluminum oxide forming material. The aluminum oxide forms a protective layer, whereby a number of thin-walled tubes can withstand both high temperatures and other harsh environmental conditions, and thus may enable heating of the gas to a high temperature. Further as described above, the thin-walled tubes may alternatively be made of a molybdenum-based alloy. Such an alloy may be utilized when the gas to be heated is a non-oxidizing gas such as hydrogen or nitrogen.

[0021] According to some embodiments, the protective member may include a fiber material. In this way, a relatively lightweight support member for a number of tubes may be provided.

[0022] The protective member, which may include a fiber material, may be configured to support a number of thin-walled tubes separated from each other in a bundle of tubes inside the housing. The protective member including the fiber material may form the only support member of the gas heater for supporting a number of thin-walled tubes against the housing.

[0023] Alternatively, the protective member may include a (non-fibrous) refractory material in a compact shape. The refractory material may include aluminum oxide and / or silicon oxide and / or magnesium oxide.

[0024] According to some embodiments, the protective member may seal the inlet chamber away from the outlet chamber, and the gas flow path may constitute the main gas flow path from the inlet chamber to the outlet chamber. In this way, the protective member may also perform the sealing task between the inlet chamber and the outlet chamber, and no additional sealing between the inlet and outlet chambers may be required.

[0025] According to some embodiments, the fibrous material may include a vacuum-formed fibrous material. In this way, the protective member can be produced efficiently.

[0026] According to some embodiments, the vacuum-formed fibrous material may be selected from Al2O3 fibers and / or SiO2 fibers, but other ceramic fibers may be used. The protective member may be configured to withstand temperatures above 1400°C, for example, 1650°C or 1750°C. Thus, many thin-walled tubes may be electrically heated to the corresponding high temperature, for example, 1300°C. An electric gas heater may be configured to heat the gas to a maximum temperature of about 1250°C.

[0027] According to some embodiments, the electrical resistance material may be an iron-chromium-aluminum (FeCrAl) alloy containing at least 3 wt% aluminum. Examples of these include, but are not limited to, those marketed by the company Kanthal as Kanthal® APMT or Kanthal® APM.

[0028] In this way, the previously defined alloy containing FeCrAl forms a layer of Al2O3, which is, in particular, a very heat-resistant oxide in itself. Therefore, the Al2O3 protects the FeCrAl alloy from aluminum degradation even when the thin-walled tube is heated to high temperatures, for example, up to 1300°C or in the range of 900 to 1250°C.

[0029] Additionally, another advantage of using aluminum oxide molding material is that Al2O3 itself does not react with a wide variety of gases and is therefore relatively resistant to them. A further advantage is that Al2O3 is not a conductive material. Therefore, these tubes can be placed close to each other. Also, any Al2O3 that would be lost from these tubes would not cause any potential problems of short-circuiting them. Finally, these tubes made of FeCrAl alloy will be heat-resistant and thermally stable.

[0030] Therefore, the numerous tubes may be configured to heat the gas to a high temperature, for example, a maximum gas temperature of about 1150°C. This means that individual tubes of the numerous tubes may be heated to even higher temperatures, for example, a maximum temperature of 1400°C. However, higher temperatures for the numerous tubes shorten their operating life. A maximum temperature of 1300°C or 1250°C for individual tubes may provide a considerably longer operating life for the numerous tubes, for example, by further heating the gas to a maximum temperature of 1100 to 1150°C, depending on the gas flow through these tubes.

[0031] Therefore, according to some embodiments, the numerous thin-walled tubes may be configured to be electrically heated to a temperature of 1300°C. According to some alternative embodiments, the numerous thin-walled tubes may be configured to be electrically heated to a temperature of 1250°C, for example, in the range of 900 to 1250°C. Within these high-temperature ranges, the gas heater described herein offers the advantage of being an efficiently electrically direct-heating gas heater that can be provided in a compact format. However, it should be noted that, depending on the application and use of the heater, the numerous thin-walled tubes may be heated to lower temperatures.

[0032] Molybdenum-based alloys may also be used in this disclosure. An electric current applied to thin-walled tubes of molybdenum-based alloys heats those tubes. These alloys are suitable for service temperatures up to 1800°C. Molybdenum-based alloys are also known to have good creep strength at high temperatures, possessing good thermal conductivity, electrical conductivity, a low coefficient of thermal expansion, high-temperature strength, low vapor pressure, and wear resistance.

[0033] According to some embodiments, the housing may form a pressure vessel. In this way, the individual tubes of the multitude of tubes do not need to be able to withstand any pressure difference between their inside and outside. Therefore, the electrical resistance material or molybdenum-based alloy does not need to have any particular pressure difference strength and does not need to have a rated pressure.

[0034] According to some embodiments, the housing may include a sealable opening, sized such that a number of thin-walled tubes arranged in a bundle can be pulled out of the housing as a single unit through the opening. In this way, the bundle of tubes can be easily placed inside the housing as a single unit. Furthermore, pre-assembling the bundle before placing it in the housing may be much easier than assembling the bundle as is inside the housing. Similarly, after being in operation for its entire lifespan, the bundle inside the housing can be easily replaced with a new bundle of tubes through the opening.

[0035] According to some embodiments, depending on the composition of the gas used and the pressure of the gas used, the individual thin-walled tubes in the bundle may have a pressure of, for example, 70 W / cm². 3 Up to, or 100W / cm² 3 Up to, or 40 to 70 W / cm² 3 Up to the range of 30 to 60 W / cm² 3 They may be arranged for energy transfer within a certain range. In this way, efficient energy / heat transfer from individual tubes to the gas may be achieved.

[0036] In particular, in some embodiments where the resistive material is an FeCrAl alloy, such high energy transfer can be achieved as described above.

[0037] A further aspect of the present invention provides a method for heating gas in an electric gas heater according to any one of the embodiments and / or models described herein. This method is By supplying gas to the inlet chamber, the gas is guided along the gas flow path through the inside of numerous thin-walled tubes to the outlet chamber. The process involves supplying electric current to numerous thin-walled tubes in order to heat those numerous thin-walled tubes, The process continues to guide the gas along the gas flow path, through the inside of those numerous thin-walled tubes, to the outlet chamber. To release the gas from the outlet chamber and Includes.

[0038] Further features of the present invention and the advantages thereof will become apparent when considering the appended claims and the following detailed description.

[0039] Various aspects and / or embodiments of the present invention, including their particular features and advantages, will be readily apparent from the exemplary embodiments described in the following modes for carrying out the invention and from the accompanying drawings shown below. [Brief explanation of the drawing]

[0040] [Figure 1a-1b] Two diagrams of electric gas heaters are shown. [Figure 2] A cross-sectional view showing the passage through an electric gas heater is shown. [Figure 3a-3c] Embodiments of the tubes of an electric gas heater and their arrangement in bundles inside the housing of the gas heater are shown. [Figure 4] This document describes a method for heating gas in an electric gas heater. [Modes for carrying out the invention]

[0041] Various aspects and / or embodiments of the present invention will be described in detail below. Throughout this specification, similar reference numerals indicate similar components. Well-known functions or structures will not necessarily be described in detail for the sake of brevity and / or clarity.

[0042] Figures 1a and 1b show two diagrams of an electric gas heater 2 according to several embodiments.

[0043] The electric gas heater 2 includes a housing 4. The gas to be heated flows through the housing 4 from the inlet 6 to the outlet 8. The heater 2 further includes a number of thin-walled tubes bundled together inside the housing 4. See Figures 2 to 3c for further reference. A conductor 10 is provided to connect the number of thin-walled tubes to an external power source.

[0044] In some embodiments shown herein, the housing 4 has a tubular shape, the inlet 6 is radially connected to the housing 4, and the outlet 8 extends axially from the housing 4. The inlet 6 is supplied to an inlet pipe 12 that extends radially from the housing 4. The outlet 8 is supplied by the tubular housing 4. A lid 14 closes the housing 4 axially on the inlet side of the housing 4. The conductor 10 extends axially through the lid 14 to the tubular housing 4.

[0045] However, the present invention is not limited to these embodiments shown herein. The gas heater housing may have any preferred shape that accommodates a bundle of tubes, connects conductors to the tubes, and allows a gas flow through the housing. For example, the inlet may be axially oriented instead of radially oriented, as with the outlet 8 shown in Figures 1a and 1b, and / or the outlet may be radially oriented.

[0046] Figure 2 shows a cross-sectional view passing through the electric gas heater 2 along line II in Figure 1b.

[0047] Figure 2 clearly shows a number of thin-walled tubes 16 arranged in a bundle 18 inside the housing 4. The tubes 16 are made of electrical resistance material or a molybdenum-based alloy. The tubes 16 are directly heated by the current supplied to them through the conductor 10. As this current flows through the electrical resistance material or molybdenum-based alloy, it heats the electrical resistance material or molybdenum-based alloy.

[0048] The gas heater 2 includes protective members 20 configured to support a number of thin-walled tubes 16 that are separated from each other and electrically insulated from each other. The protective members 20 also support the tubes 16 within the housing 4.

[0049] In some embodiments shown herein, the protective member 20 extends substantially along the entire axial length of the bundle 18 of tubes 16. For example, the protective member 20 may extend along at least 90% of the length of the tubes 16, for example, along the entire length of the tubes 16. In this way, the thin-walled tubes 16 may be firmly supported and electrically heated to a temperature that reduces the strength of the tubes 16. Furthermore, in this manner, the protective member 20 may protect the inside of the housing 4 from heat from the tubes 16.

[0050] The protective member 20 may include a number of individual members 20'. In some embodiments shown herein, the individual members 20' are arranged adjacent to each other and in contact with one another. Alternatively, the individual members 20' may be arranged apart from each other, or some of the individual members 20' may be in contact with each other and some may be arranged apart from each other. Thus, according to some embodiments, the protective member 20 formed by the individual members 20' may extend along at least 50% of the length of the tube 16.

[0051] In this way, the protective member 20 supporting the tube 16 provides a gas heater 2 that can be placed at any required location within the factory.

[0052] The protective member 20 may include a fibrous material. The fibrous material provides a relatively lightweight protective member 20 relative to the tube 16. This may be important if the protective member 20 extends over a substantial portion of the length of the tube 16, for example, along at least 50% of the length of the tube 16, or even further, along more than 90% of the length of the tube 16.

[0053] The fiber material may include vacuum-formed fiber material.

[0054] The vacuum forming process for producing vacuum-formed fiber materials is known, and therefore its explanation will be omitted here.

[0055] According to one embodiment, the vacuum-formed fibrous material may be fully cured after manufacturing, meaning that all the fibers of the fibrous material are bound together via a binder, and the protective member 20 has no parts containing unbound fibers. In this way, it may be ensured that the protective member 20 can support the tube 16. Alternatively, holes for the tube 16 may be easily drilled in the protective member 20 or individual members 20'.

[0056] According to one embodiment, the vacuum-formed fibrous material may contain more than 40% Al2O3 fibers in a balanced manner with SiO2 fibers and binder residue. Alternatively, the vacuum-formed fibrous material may contain more than 50% Al2O3 fibers in a balanced manner with SiO2 fibers and binder residue, or more than 60% Al2O3 fibers in a balanced manner with SiO2 fibers and binder residue.

[0057] The vacuum-formed fiber material may be a relatively lightweight material. The density of the vacuum-formed fiber material is 250 kg / m³, therein, in order to provide a protective member configured to support a number of thin-walled tubes 16 in the housing 4 of the heater 2.3 It can be extremely high. The upper limit of the density range is approximately 500 kg / m³. 3 That's fine.

[0058] As described above, the protective member 20 may include, for example, a compact (non-fibrous) fire-resistant material if a heavier gas heater 2 is acceptable.

[0059] Inside the housing 4, an inlet chamber 22 is located upstream of a number of thin-walled tubes 16, and an outlet chamber 24 is located downstream of the number of thin-walled tubes 16. The gas flow path extends from the inlet chamber 22 through the inside of the tubes 16 to the outlet chamber 24. In Figure 2, the gas flow path is indicated by thick arrows in the inlet and outlet chambers 22 and 24, and by thin arrows in some of the tubes 16.

[0060] The inlet chamber 22 can be thought of as forming a manifold for distributing a collective stream of gas to individual tubes 16. Similarly, the outlet chamber 24 can be thought of as forming a manifold for merging the gas streams distributed to the tubes 16 back into a single collective stream of gas. Thus, in the gas flow path extending from the inlet chamber 22 to the outlet chamber 24, a distributive flow path is provided through the inside of the tubes 16. In the distributive flow path inside the tubes 16, the gas is heated.

[0061] According to some embodiments, a flow limiter may be provided at the inlet of each individual tube 16. That is, the upstream portion of each tube 16 may have a smaller inner diameter compared to the downstream portion of that tube 16. In other words, at high gas flows, the gas flow is distributed uniformly among the individual tubes 16, regardless of whether a flow limiter is provided on the tubes 16. However, at low gas flows, such a flow limiter can contribute to the uniform distribution of the gas flow from the inlet chamber 22 to the tubes 16, among the individual tubes 16 of the bundle 18. Therefore, such a flow limiter may be preferable in gas heaters where the gas flow changes over a wider flow range during use.

[0062] The protective member 20 seals the inlet chamber 22 from the outlet chamber 24 to such an extent that the gas flow path constitutes the main gas flow path from the inlet chamber 22 to the outlet chamber 24. Therefore, the protective member 20 does not necessarily have to provide a gas-sealing seal between the inlet and outlet chambers 22 and 24. However, the protective member 20 provides a sufficiently high pressure drop, i.e., gas flow resistance, so that the gas flowing from the inlet chamber 22 to the outlet chamber 24 flows mainly through the inside of the tube 16 instead of the outside. For example, at least 90% of the gas may flow through the inside of the tube 16 from the inlet chamber 22 to the outlet chamber 24. Certain gas flow along the outside of the tube 16 may be permitted because the gas may be heated along the outside of the tube 16. However, any gas flow along the inner surface of the housing 4 should be prevented by the protective member 20. This is because the gas is not heated there. If the seal along the inside of housing 4 is not good, this will allow some of the gas to escape along this inside from the inlet chamber 22 to the outlet chamber 24, where it will not be heated.

[0063] Protective elements 26, 26' may be provided inside the inlet and outlet chambers 22, 24. The protective elements 26, 26' may be positioned adjacent to the housing 4 to protect the housing 4 from warm gases in the inlet and outlet chambers 22, 24. According to some embodiments, the protective members 26, 26' may contain the same type of fibrous material as the protective member 20.

[0064] In this context, it can be said that gas heater 2 is suitable for raising the temperature of an already hot gas. For example, the gas flowing into the inlet chamber 22 may have a temperature in the range of 300 to 900°C.

[0065] Figures 3a to 3c show an embodiment of the tubes 16 of the gas heater 2 and their arrangement in a bundle 18 inside the housing 4 of the gas heater 2. The gas heater 2 may be the gas heater 2 described above with reference to Figures 1a to 2.

[0066] Figure 3a shows the heater 2 to the inlet chamber 22. Figure 3b shows a partial view of the inlet chamber 22. Figure 3c shows the two tubes 16.

[0067] The gas heater 2 includes a number of thin-walled tubes 16. To illustrate purely as an example, the number of tubes 16 may be, for example, 50 to 500 tubes or 200 to 300 tubes. Each of the numerous thin-walled tubes 16 is made of an electrical resistance material or a molybdenum-based alloy and is electrically insulated from one another by being supported by protective members.

[0068] The tubes 16 are electrically connected to each other at their ends via conductive connectors 28. The connectors 28 provide parallel connections between some of the tubes 16 and series connections between some of the tubes 16. Depending on the voltage connected to the conductor 10 and the electrical resistivity of the individual tubes 16, a suitable configuration of parallel and series connections between the tubes 16 may be provided.

[0069] The tubes 16 are connected directly or indirectly to the main power via the conductor 10. For example, the tubes 16 may be connected to each other so that a 400V main power can be supplied to the tubes 10 via the conductor 10.

[0070] The thin-walled tube 16 has a small diameter and a thin wall thickness.

[0071] According to some embodiments, the individual thin-walled tubes 16 of the bundle 18 may have an inner diameter in the range of 7 to 30 mm, for example, 9 to 20 mm, and a wall thickness in the range of 1 to 3 mm, for example, 1.5 to 2.5 mm. In this way, good heat transfer to the gas being heated may be achieved along each of the individual tubes 16 without excessive pressure drop.

[0072] The protective members 20 supporting the individual thin-walled tubes 16 allow the tubes 16 to be of such low dimension, even if their length is long. In particular, this may be the case in embodiments where the protective members 20, such as those formed by the individual members 20', extend along at least 50% of the length of the tubes 16. Purely as an example, the length of the individual tubes 16 may be in the range of 0.5 to 2.5 m, or in the range of 1 to 2 m.

[0073] An electrical resistance material is a material that forms at least one heat-resistant oxide. As mentioned above, an electrical resistance material is an aluminum oxide (i.e., alumina) molded alloy.

[0074] For example, the alumina forming alloy is an FeCrAl alloy containing at least 3 wt% aluminum. Thus, the tube 16 may be configured to be electrically heated to a temperature of 1250°C while maintaining a practical operating life for the tube 16.

[0075] The bundle of tubes 16, 18 in total, has a load capacity of 5 MW / m 3configured for energy transfer up to, or higher than, this, and according to one embodiment, this energy transfer may be in the range of 2 to 5 MW / m 3 That is, the electric gas heater 2 described herein provides a spatially efficient transfer of energy / heat from the bundle 18 of tubes 16 to the gas being heated. This spatial efficiency may be achieved by the arrangement of a number of thin-walled tubes 16 that are separated and supported from each other by the protective member 20. It should be noted that only the volume of the bundle 18 of tubes 16 is included in their energy transfer numerical values. The volumes of the inlet and outlet chambers 22, 24 are excluded.

[0076] To illustrate purely by way of some examples, larger gas heaters are designed for 5 to 10 MW and the volume of the bundle 18 may be on the order of about 1.5 to 2.0 m 3 where the bundle 18 may include hundreds of tubes 16, which may be arranged within a range of 20 to 30 mm from each other. Relatively small gas heaters are designed for 0.5 to 1 MW and the volume of the bundle 18 may be on the order of about 0.2 m 3 where the tubes 16 within the bundle 18 may be arranged within a range of 10 to 20 mm from each other. The above arrangement of the tubes 16 from each other relates to the range of the distance between the outer diameters of adjacent tubes 16 in the bundle 18.

[0077] Within the respective above distance ranges of 20 to 30 mm and 10 to 20 mm, discharge and / or short circuit between individual tubes 16 are avoided. The voltage applied to the tubes 16 is relevant in the context of the distance between the tubes 16. Generally, the higher the rated power for the gas heater, the higher the voltage applied to the tubes 16. Thus, the distance range between the tubes 16 for a gas heater 2 with a higher rated power is wider than that for a gas heater 2 with a lower rated power.

[0078] According to some embodiments, the individual tubes 16 of the thin-walled tubes 16 arranged in the bundle 18 may be arranged so that the outer diameters of adjacent tubes 16 are within a range of 10 to 30 mm from each other.

[0079] According to some embodiments, the individual tubes 16 of the bundle 18 are 70 W / cm 3 Up to, or 100W / cm² 3 Up to, or 40 to 70 W / cm² 3 Up to the range of 30 to 60 W / cm² 3 It may be positioned for energy transfer within a certain range.

[0080] Efficient energy / heat transfer from individual thin-walled tubes 16 to the heated gas is achieved in the gas heater 2. The thin-walled tubes 16 may be suitable for the above scale. The upper limit range is 100 W / cm 3 Energy transfer in this manner may result in a high pressure drop as the gas flows through tube 16, and may be achieved for some gases, such as hydrogen, and / or under specific operating conditions, which may include operation under high pressure and / or at one or more lower outlet temperatures, such as 600 degrees Celsius. A more reasonable pressure drop is 40 to 70 W / cm². 3 and 30 to 60 W / cm² 3 The energy transfer values ​​may be realized within a range of these values. Furthermore, these energy transfer values ​​depend on the gas being heated and the conditions under which the gas heater 2 operates beneath it.

[0081] Another way to specify energy transfer is to define energy transfer area by area inside the thin-walled tube 16. For example, a value of 60 W / cm². 3 In an embodiment of the gas heater 2, the power consumption is approximately 15 W / cm². 2 This corresponds to [the above].

[0082] The following non-limiting example relates to a gas heater 2 that operates at atmospheric pressure and provides a tube 16 having outer and inner diameters of 17.15 and 12.53 mm and positioned at a center-to-center distance of 35 mm. A surface temperature of 1250 degrees Celsius is provided for the tube 16, and a maximum pressure drop of 100 mBar is permitted. The gas to be heated is air with an inlet temperature of 20 degrees Celsius.

[0083] In the above embodiment, the gas heater 2 is designed with an outlet temperature of 600 degrees Celsius and a power output of approximately 18 W / cm². 2 Energy transfer can be achieved. Alternatively, if it is supplied by a gas heater with an outlet temperature of 1100 degrees Celsius, then approximately 3 W / cm² 2 Lower energy transfer rates may be achieved. Operating the gas heater 2 under pressure and / or allowing higher pressure drops will improve the numerical values ​​of their energy transfer.

[0084] Therefore, the power output is between 2 and 20 W / cm². 2 It can be easily predicted that the energy transfer values ​​within this range can be achieved in the gas heater 2 by operating it using air at atmospheric pressure.

[0085] The housing 4 may form a pressure vessel. Instead of individual tubes that can withstand the pressure difference between their inside and outside, the housing 4 is designed to withstand the pressure difference between its inside and outside. Depending on the relevant pressure level, temperature level, and type of gas being heated, the housing 4 may include low-carbon non-alloys, low-alloys, alloys, or stainless steel suitable for forming a pressure vessel. Furthermore, in embodiments in which the housing forms a pressure vessel, the gas heater 2 may be used in direct connection to the industrial process in which the gas to be heated is pressurized.

[0086] To illustrate purely as an example, the pressure vessel may be designed to withstand gas pressures inside the housing 4 ranging from 10 to 15 bar, or even up to 30 or 40 bar, depending on the industrial process in which the heater 2 is used.

[0087] Some examples of industrial processes in which a gas heater 2 with pressure vessel properties may be used include: Energy storage using heated gas, comprising a bed of metal or ceramic pellets, or a bed containing natural materials such as rocks or volcanic rocks, which heats a bed that provides back pressure to the gas being heated in a gas heater. Direct reduction of iron pellets using hydrogen or natural gas to produce directly reduced iron (DRI). In this process, the high gas temperature achieved in the gas heater 2 may be particularly beneficial. Gas heated to a temperature in the range of 1000 to 1100°C, or higher, for example, up to 1250°C or 1300°C, is suitable for this direct reduction process. By using the gas heater 2, this is achieved in a compact format gas heater 2 with high energy density, which can heat high gas flow. In the gas heater 2, this is made possible by the use of molded aluminum oxide electrical resistance material in the thin-walled tube 16 which is electrically heated directly, which also gives the gas heater 2 a compact format with fewer components. Various chemical processes, such as Fischer-Tropsch synthesis.

[0088] The use of heater 2 is not limited to these process examples. Furthermore, heater 2 may be used to heat an unpressurized or low-pressure gas.

[0089] Gas heater 2 is particularly suitable for heating large gas flows. 0.2m 3 Even in the gas heater illustrated earlier, a bundle 18 of tubes 16 having a capacity of 400 to 500 m is provided. 3The gas flow per hour may be heated to a temperature in the range of 900 to 1250°C. Furthermore, 1.5 to 2.0 m 3 A bundle 18 of tubes 16 having a capacity of 3000m is provided. The gas heater illustrated earlier is provided. 3 The gas flow up to 1 / hour may be heated to a temperature in the range of 900 to 1250°C. 15000 to 20000 m 3 Even with much larger flows, such as over a certain period of time, heating is expected to be achieved by larger capacity versions of the gas heater.

[0090] For easy installation, replacement, and service of the tubes 16, the housing 4 may include a sealable opening, sized to allow the tubes 16, arranged in bundle 18, to be pulled out of the housing 4 as a single unit through the opening. In these exemplary embodiments, see, for example, Figures 1a and 2, the opening of the housing 4 is covered by a lid 14 during use of the gas heater 2. The lid 14 seals the opening and is removably attached to the tubular portion of the housing 4, for example, via nuts and bolts.

[0091] If the housing 4 forms a pressure vessel and includes one or more lids 14, as in these exemplary embodiments, see, for example, Figure 1a, then the lids 14 must close the housing 4 to satisfy the requirements of a pressure vessel.

[0092] Figure 4 shows one of the embodiments and / or models described herein, for example, a method 100 for heating gas in an electric gas heater 2, relating to the gas heater 2 described earlier with reference to Figures 1a to 3c. Therefore, please also refer to Figures 1a to 3c below.

[0093] A method 100 for heating gas in an electric gas heater 2 is: By supplying gas to the inlet chamber 22 102, the gas is guided along the gas flow path through the inside of numerous thin-walled tubes 16 to the outlet chamber 24. 104 to supply current to a number of thin-walled tubes 16 to heat those number of thin-walled tubes 16, The gas continues to be guided along the gas flow path through the inside of numerous thin-walled tubes 16 to the outlet chamber 24 106, Let the gas flow from outlet chamber 24 108 This includes the following steps.

[0094] The gas will begin to flow as soon as it is supplied to the inlet chamber, and in this way it will be guided along the gas flow path through these bundles of tubes.

[0095] Method 100 may be used to heat a gas in an industrial process.

[0096] According to some embodiments of Method 100, the gas may be, but is not limited to, air, hydrogen, nitrogen, carbon dioxide, synthesis gas, or pyrolysis gas. In this way, a gas suitable for the relevant industrial process may be heated in the gas heater 2.

[0097] According to some embodiments of Method 100, step 102 of supplying gas to the inlet chamber 22 may include supplying the gas to the inlet chamber 22 at a temperature in the range of 300 to 900°C. In this way, the property of the gas heater 2 to raise the temperature of an already heated gas to an even higher temperature may be utilized in an industrial process.

[0098] The above describes various exemplary embodiments, and it will be understood that the present invention is defined solely by the appended claims. Those skilled in the art will recognize that these exemplary embodiments may be modified, and different features of these exemplary embodiments may be combined to create other embodiments not described herein, without departing from the scope of the present invention as defined by the appended claims.

Claims

1. Housing (4) and A plurality of thin-walled tubes (16) are arranged in a bundle (18) inside the housing (4), A protective member (20) comprising a fibrous material, which supports the plurality of thin-walled tubes (16) so that the plurality of thin-walled tubes (16) are separated from each other and electrically insulated from each other, A conductor (10) configured to connect the plurality of thin-walled tubes (16) to an external power supply, The housing (4) includes an inlet chamber (22) upstream of the plurality of thin-walled tubes (16) and an outlet chamber (24) downstream of the plurality of thin-walled tubes (16), The gas flow path extends from the inlet chamber (22) through the inside of the plurality of thin-walled tubes (16) to the outlet chamber (24). Each of the plurality of thin-walled tubes (16) is made of an iron-chromium-aluminum (FeCrAl) alloy, which is a material that forms a layer of aluminum oxide. To support the plurality of thin-walled tubes (16), the fibers in the fibrous material of the protective member (20) are bound together via a binder, and the protective member (20) is provided with holes through which the plurality of thin-walled tubes (16) are inserted. Each of the plurality of thin-walled tubes (16) is made of an iron-chromium-aluminum (FeCrAl) alloy containing at least 3% by weight of aluminum. Each of the plurality of thin-walled tubes (16) has an inner diameter in the range of 7 to 30 mm and a wall thickness in the range of 1 to 3 mm. The individual tubes (16) of the bundle (18) are arranged to enable energy transfer up to 100 W / cm³, and the distance between the outer circumferences of adjacent thin-walled tubes (16) is in the range of 10 to 30 mm. Electric gas heater (2).

2. The electric gas heater (2) according to claim 1, wherein the protective member (20) is configured to provide gas flow resistance to the outside of the plurality of thin-walled tubes (16) such that at least 90% of the gas flows inside the plurality of thin-walled tubes (16) from the inlet chamber (22) to the outlet chamber (24).

3. The electric gas heater (2) according to claim 1 or 2, wherein the fiber material includes a vacuum-formed fiber material.

4. The electric gas heater (2) according to claim 3, wherein the fibrous material comprises Al₂O₃ fibers and / or SiO₂ fibers.

5. The fibrous material comprises more than 40% Al₂O₃ fibers together with the remainder SiO₂ fibers and binder residue. It contains more than 50% Al₂O₃ fibers, along with the remainder SiO₂ fibers and binder residue, or The electric gas heater (2) according to claim 4, comprising more than 60% Al₂O₃ fibers together with the remainder SiO₂ fibers and binder residue.

6. The electric gas heater (2) according to any one of claims 3 to 5, wherein the density of the vacuum-formed fiber material is greater than 250 kg / m³ and less than or equal to 500 kg / m³.

7. The electric gas heater (2) according to any one of claims 1 to 6, wherein the protective member (20) extends along 50% or more of the length of the thin-walled tube (16).

8. The electric gas heater (2) according to any one of claims 1 to 7, wherein the plurality of thin-walled tubes (16) are configured to be electrically heated to a temperature of 1250°C.

9. The electric gas heater (2) according to any one of claims 1 to 8, wherein the plurality of thin-walled tubes (16) are configured to be electrically heated to a temperature of 1300°C.

10. The electric gas heater (2) according to any one of claims 1 to 9, wherein the housing (4) forms a pressure vessel.

11. The electric gas heater (2) according to any one of claims 1 to 10, wherein the housing (4) includes a sealable opening, the sealable opening being sized to allow the plurality of thin-walled tubes (16) arranged in the bundle (18) to be pulled out of the housing (4) as a single unit through the opening.

12. The individual thin-walled tubes (16) of the bundle (18) are 70 W / cm ３ Up to, or 40 to 70 W / cm² ３ Up to the range of 30 to 60 W / cm² ３ An electric gas heater (2) according to any one of claims 1 to 11, which is arranged to enable energy transfer within a certain range.

13. The electric gas heater (2) according to any one of claims 1 to 12, wherein the individual thin-walled tubes (16) of the bundle (18) have an inner diameter in the range of 9 to 20 mm and a wall thickness in the range of 1.5 to 2.5 mm.

14. The electric gas heater (2) according to any one of claims 1 to 13, wherein the individual thin-walled tubes (16) of the bundle (18) are arranged such that the distance between the outer circumferences of adjacent thin-walled tubes (16) is in the range of 10 to 20 mm.

15. By supplying gas to the inlet chamber (22) (102), the gas is guided along the gas flow path through the inside of the plurality of thin-walled tubes (16) to the outlet chamber (24), The current is supplied to the plurality of thin-walled tubes (16) to heat the plurality of thin-walled tubes (16) (104), The process continues (106) in which the gas is guided along the gas flow path, through the inside of the plurality of thin-walled tubes (16), to the outlet chamber (24), The gas is flowed from the outlet chamber (24) (108) A method (100) for heating gas in an electric gas heater (2) according to any one of claims 1 to 14, including the above.

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