Electric air heater

Abstract

The present disclosure provides an electric air heater system including a first electric air heater module. The first electric air heater module includes: an outer housing having an inner surface, a first end, and a second end; the fire-resistant heat insulation layer is tightly communicated with the outer shell; the inner cavity is positioned in the fire-resistant thermal insulation layer; and a plurality of tubes extending through the lumen from the first end to the second end, the plurality of tubes each having an outer surface. Each tube is fixed relative to the outer housing at the first end, and each tube has an electrical connection disposed at the first end. The plurality of tubes are arranged in one or more tube bundles, wherein each bundle includes two or more tubes having a plurality of fins extending radially from the outer surface and a heating element axially through a hollow interior of the tubes.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to high capacity electric air heater systems capable of heating a gas or other fluid to temperatures in excess of 343°C. Background Art

[0002] Electrical heating of the gas can be done using an intermediate heat transfer fluid such as hot oil or molten salt. However, such systems have a maximum operating temperature of 400° C. Electrical heating of gas at higher temperatures is usually achieved via one of two types of electric heater systems.

[0003] First, electrical heating can be achieved by using a gas heater assembly that relies on convective heating of the gas. Gas heater assemblies are widely commercially available, however current designs are limited in their ability to heat large volumes of air to high temperatures in a single enclosure with a low pressure drop. Additionally, currently available gas heater modules are also characterized by small channel sizes, direct contact between the heating element and the process gas, and low watt density due to the high temperatures of the heating element that need to be dissipated. This, in turn, can lead to overheating and premature failure of the heating element.

[0004] Alternatively, furnace tube assemblies are also currently commercially available. A furnace tube assembly is a modular assembly that features discrete heating device segments mounted into a housing. The furnace tube assembly transfers heat radiatively between the heating element and the furnace tube, and then from the furnace tube to the workpiece. Attempts to increase the surface area by adding extended surfaces have only provided modest improvements due to the low view factor between the extended surface and the workpiece being heated radiatively.

[0005] Current solutions are often characterized by a number of undesirable factors. First, the process gas is often directly exposed to the heating element. This can limit the number of different process gases that can be heated within the heater assembly. In particular, process gases that are corrosive, flammable, or otherwise difficult to use are precluded from use with such heater assemblies. Furthermore, the flow of gas directly through the heating element can cause the heating element to vibrate or otherwise move. This can result in short circuits or breaks at the connection points. Furthermore, current solutions also involve flowing the process gas directly through tubes within larger conventional heater assemblies.

[0006] Currently available electric heaters are also limited in that they include flow passages having relatively small cross-sections and high flow resistances. This reduces the suitability of the heater for heating large volumes of gas while maintaining a low pressure drop. Summary of the invention

[0007] This summary is provided to introduce a series of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to help limit the scope of the claimed subject matter.

[0008] In one or more aspects, embodiments disclosed herein relate to an electric air heater system, which includes a first electric air heater module. The first electric air heater module includes: an outer shell having an inner surface, a first end, and a second end; a fire-resistant insulation layer, which is closely connected to the outer shell; an inner cavity, which is located within the fire-resistant insulation layer; and a plurality of tubes extending from the first end through the inner cavity to the second end, each of the plurality of tubes having an outer surface. Each tube is fixed relative to the outer shell at the first end, and each tube has an electrical connector disposed at the first end. The plurality of tubes are arranged into one or more tube bundles, wherein each bundle includes two or more tubes having a plurality of fins extending radially from the outer surface and a heating element axially extending through the hollow interior of the tube, and a sleeve, which supports each of the plurality of tubes at the second end of the outer shell.

[0009] In another aspect, embodiments disclosed herein relate to an electric air heater. The electric air heater comprises: an outer shell having an inner surface defining an inner cavity, a first end, and a second end; a fire-resistant insulation layer, which is in close communication with the outer shell; and a plurality of tubes extending axially from the first end through the inner cavity to the second end, each of the plurality of tubes having an outer surface. The plurality of tubes are radially arranged around the axial center of the inner cavity. Each tube is fixed relative to the outer shell at the first end, and each tube has an electrical connector disposed at the first end. Each tube has a plurality of fins arranged radially extending from the outer surface, an electric heating element axially disposed through the hollow interior of the tube, and a sleeve supporting each of the plurality of tubes at the second end of the outer shell.

[0010] In yet another aspect, embodiments disclosed herein are directed to a method of heating air. The method includes directing a volume of air into an electric air heater having an interior cavity, directing the volume of air through the interior cavity, and heating the volume of air.

[0011] Other aspects and advantages of the claimed subject matter will become apparent from the following description and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Specific embodiments of the disclosed technology will now be described in detail with reference to the accompanying drawings. For consistency, similar elements in the various drawings are represented by similar reference numerals. The size and relative position of the elements in the drawings are not necessarily drawn to scale. For example, the shapes and angles of the various elements are not necessarily drawn to scale, and some of these elements can be arbitrarily enlarged and positioned to improve the readability of the drawing. In addition, the specific shapes of the drawn elements are not necessarily intended to convey any information related to the actual shapes of these specific elements, and they are selected only for ease of identification in the drawing. In addition, a single reference numeral can be used to represent flow lines and process flows within flow lines.

[0013] Figure 1A and Figure 1B An electric air heater module is shown according to one or more embodiments.

[0014] Figure 2A and Figure 2B An electric air heater module is shown according to one or more embodiments.

[0015] Figure 3 A cross-sectional view of a tube within an electric air heater module is shown according to one or more embodiments.

[0016] Figure 4 A cross-sectional view of a tube within an electric air heater module is shown according to one or more embodiments.

[0017] Figure 5 A cross-sectional view of a tube within an electric air heater module is shown according to one or more embodiments.

[0018] Figure 6 A cross-sectional view of a tube within an electric air heater module is shown according to one or more embodiments.

[0019] Figure 7 A cross-sectional view of an electric air heater module is shown in accordance with one or more embodiments.

[0020] Figure 8 A cross-sectional view of an electric air heater module is shown in accordance with one or more embodiments.

[0021] Fig. 9 A cross-sectional view of an electric air heater module is shown in accordance with one or more embodiments.

[0022] Fig.10 A cross-sectional view of an electric air heater module is shown in accordance with one or more embodiments.

[0023] Fig.11 A cross-sectional view of an electric air heater module is shown in accordance with one or more embodiments.

[0024] Fig.12 A flow chart of a method according to one or more embodiments is shown. DETAILED DESCRIPTION

[0025] In the following detailed description of the embodiments of the present disclosure, many specific details are set forth in order to provide a more thorough understanding of the present disclosure. However, it will be apparent that one of ordinary skill in the art can practice the present disclosure without these specific details. In other cases, well-known features are not described in detail to avoid unnecessarily complicating the description.

[0026] Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives for elements (i.e., any noun in the application). The use of ordinal numbers does not imply or create any particular order of elements, nor does it limit any element to only a single element, unless explicitly disclosed, such as using the terms "before," "after," "single," and other such terms. Instead, ordinal numbers are used to distinguish elements. For example, a first element is different from a second element, and a first element may encompass more than one element and be after (or before) a second element in the ordering of elements.

[0027] In the following Figures 1 to Fig.12 In the description of the various embodiments disclosed herein, any component described with respect to a figure may be equivalent to one or more similarly named components described with respect to any other figure. For the sake of brevity, the description of these components will not be repeated for each figure. Therefore, each embodiment of the components of each figure is incorporated by reference and assumed to be optionally present in each other figure with one or more similarly named components. In addition, according to the various embodiments disclosed herein, any description of the components of the figures should be interpreted as an optional embodiment, which can be implemented as a supplement, combination or replacement for the embodiment described in any other figure with respect to the corresponding component of the same name.

[0028] It should be understood that the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an "electric heater module" includes reference to one or more of such electric heater modules.

[0029] Terms such as "about", "substantially" and the like mean that the listed characteristics, parameters or values ​​need not be achieved precisely, but the amount of deviation or variation (including, for example, tolerances, measurement errors, measurement precision limitations and other factors known to those skilled in the art) that may occur does not prevent the effect that the characteristic is intended to provide.

[0030] It should be understood that one or more of the steps shown in the flowchart may be omitted, repeated and / or performed in an order different from the order shown. Therefore, the scope of the disclosure herein should not be considered limited to the specific arrangement of the steps shown in the flowchart.

[0031] Although multiple dependent claims are not introduced, it will be apparent to a skilled person that the subject matter of the dependent claims of one or more embodiments may be combined with other dependent claims.

[0032] Disclosed herein are embodiments of electric air heater systems that can withstand high temperatures, particularly temperatures exceeding 343° C. In one or more embodiments, the electric air heater system can heat a large volume of air or any other fluid to a temperature of up to 760° C. In some embodiments, the air, steam, or other fluid can be heated to temperatures of up to 900° C., 950° C., 1000° C., 1050° C., 1100° C., or even up to 1400° C. Additionally, disclosed herein are embodiments of electric air heater systems that combine radiative heat transfer from the heating element to the tubes and convective heat transfer from the tubes to the process gas flowing through the electric air heater system.

[0033] In addition, embodiments of electric air heater systems using two or more sets of tubes are disclosed herein. Each set of tubes may have a different power load, wherein the total power of the electric air heater system is significantly higher than commercially available systems. In contrast, currently available systems require multiple heaters to be connected in series or in parallel to achieve the same total power.

[0034] Figure 1A and Figure 1B An electric air heater module 100A, 100B is depicted according to one or more embodiments. The electric air heater module 100A, 100B can have a central portion 110A, 110B that is rectangular or square (110A) in shape. However, the central portion can also have many other geometric shapes, such as cylindrical (110B). The electric air heater module 100A, 100B can also have two tapered ends 112A, 112B extending from opposite sides of the central portion 110A, 110B.

[0035] The central portion 110A, 110B can house the internal components of the electric air heater module. For example, multiple rows 108A, 108B of tubes 102A, 102B can be arranged so that the tubes 102A, 102B extend through the central portion 110. In one or more embodiments, there can be 25 rows 108A, 108B of tubes 102A, 102B arranged in the central portion 110A, 110B and there are more than 5 tubes 102A, 102B in the same row. However, in other embodiments, there can be between 5 and 50 rows of 108A, 108B arranged in the central portion 110A, 110B. The number of rows used can depend on the desired temperature rise (heating) of the fluid passing over and around the tubes, and more than 50 rows, such as 60, 70, 80, 90, 100 or more rows, can be used in some embodiments.

[0036] Now turn to Figure 2A and Figure 2B , Figure 2A A cross-sectional view of an electric air heater module is shown and Figure 2B A side view of an electric air heater module 100 according to one or more embodiments is shown. The electric air heater module 100 can have an outer shell 104 and a fire-resistant insulation layer 106 in close communication with the interior of the outer shell 104. In one or more embodiments, close communication can mean that the fire-resistant insulation layer 106 and the outer shell 104 can have a negligible spacing between the insulation layer 106 and the outer shell 104. A plurality of corbels 105 can be arranged around the inner surface of the fire-resistant insulation layer 106. An internal cavity 114 can extend through the outer shell 104 so that the module is hollow.

[0037] In one or more embodiments, a gas (such as air 120 or another process gas) can be directed through the inner cavity 114, where the gas can be heated. In one or more embodiments, the electric air heater module 100 can have a rectangular, square, cylindrical, or any combination thereof geometry. In embodiments where particularly high pressures are present, the electric air heater module 100 can have more than one outer shell 104 layer, which can cascade operating pressures and minimize shell deflection. In addition, embodiments with more than one outer shell 104 layer can add an additional safety factor to the heater operation and can maintain insulation integrity.

[0038] A plurality of tubes 102 may be arranged in multiple rows throughout the inner cavity 114. The tubes may have similar or different outer diameters and may be arranged in the inner shell of the heater module using uniform or non-uniform spacing. In one or more embodiments, the tubes 102 may be made of an alloy suitable for high furnace temperatures. However, since the gas flow through the electric air heater module 100 may cool the tubes 102, the alloy may be selected for a design temperature lower than the design temperature required when the tubes 102 themselves are resistive heating elements. For example, in one or more embodiments, the tubes 102 may be made of 304 stainless steel or INCONEL alloy. For modules having curved geometries, such as cylindrical inner shells, the effective length of the tubes disposed within the inner shell may vary, such as where the length of the tubes passing near the center of the cylindrical shell is longer than the length of the tubes passing near the sides of the cylindrical shell.

[0039] Each tube 102 may have a plurality of fins 103 arranged circumferentially on the outer surface of the tube. In one or more embodiments, a plurality of fins 103 extend radially from the outer surface of each tube 102. Alternatively, there may be an embodiment in which a plurality of fins 103 are arranged in a tight spiral pattern around the outer surface of each tube 102. A plurality of fins 103 may increase the surface area for convective heat transfer between each tube 102 and the gas directed into the electric air heater module 100 for heating. In one or more embodiments, the fins 103 may be circular fins. However, in other embodiments, the fins 103 may be solid fins, serrated fins, or stud fins. In one or more embodiments, the fins may have an outer diameter, fin frequency, fin height, and fin thickness, all of which may be selected to suit the heating needs of the situation and promote turbulence within the heater. Fin height, fin thickness, the number of fins per unit length, and other fin variables may vary between tubes. For example, the fins provided on the tubes near the inlet of the heater module may be different from the fins near the outlet of the heater module. In some embodiments, for example, the fins may be made of 18-chromium-8-nickel alloy or 11-13 chromium alloy. However, it should be understood that these are merely examples and many other alloys may be used without departing from the scope of the present disclosure.

[0040] Each tube 102 may also have a heating element 101 extending axially through the interior of the tube 102. There may be many different types of heating elements 101 that may be used within the tube 102. In one or more embodiments, the heating element 101 may be an iron-chromium-aluminum wire or a nickel-chromium wire. However, in other embodiments, the heating element 101 may be a silicon carbide rod-type heating element or a molybdenum disilicide heating element. In one or more embodiments, the heating element 101 may be bent into a U-shape or a hairpin shape so that a circuit is formed between the two ends of the element. In addition, the individual heating elements 101 may be grouped into bundles that may be supported by ceramic spacers installed along the length of the tube 102. Depending on the type of element and the needs of the situation, the individual heating elements 101 may be combined in parallel, in series, or in both configurations.

[0041] In one or more embodiments, the heating element 101 can radiatively heat the tube 102. As the cooler process gas passes through the tube 102, the tube 102 can convectively dissipate heat, thereby reducing the temperature of the tube 102. Heat dissipation can also be enhanced by installing fins 103, which increase the effective surface area for convective heat transfer. In addition, convective heat transfer can reduce the temperature of both the tube 102 and the heating element 101, allowing the heating element 101 to maintain a higher watt density than would otherwise be possible.

[0042] Now turn to Figure 2B , the inner cavity 114 can extend from the first end 116 to the second end 118 of the electric air heater module 100. Each tube 102 can be fixed at the first end 116, wherein the fixed connection also serves as an electrical connection point. In one or more embodiments, a cable 107a can extend from each heating element 101 to an electrical connector 107 disposed on the outer surface of the outer shell 104. Each tube 102 can float at the second end 118, allowing expansion during heating. In one or more embodiments, each tube 102 can have a corresponding support member located at the second end 118. In one or more embodiments, one or more cables 107a and connector 107 can be placed on the end 118 opposite to another cable 107a and connector 107 so that the cables and connectors are distributed on both ends.

[0043] In one or more embodiments, various sensors and connections may be installed within the electric air heater module 100. For example, in some embodiments, thermocouples and / or pressure sensors / connections may be installed within the electric air heater module as desired.

[0044] Figure 3 1 shows a cross-sectional view of a tube 102 within an electric air heater module according to one or more embodiments. More specifically, Figure 3A detailed cross section of the tube 102 at the first end 116 of the outer housing 104 is shown. The heating element 101 can extend axially through the tube 102. In one or more embodiments, the heating element 101 can be a single element. However, there are many embodiments in which the heating element 101 can be a bundle of individual heating elements fixed together in parallel, in series, or both, and the appropriate electrical connections for a particular embodiment.

[0045] At the first end 116, the tube 102 can be fixed with a sealing flange 222, which can be welded to the tube 102 and the sleeve 209. The cable 107a can extend from the sealing flange 222 to the heating element 101. The sealing flange 222 can have a central opening that is large enough to insert and remove the heating element 101. An end cap 223 can be provided to hold the heating element in place. In one or more embodiments, the end cap 223 can be external to the fire-resistant insulation layer 106. An electrical direct connection 221 can be provided that passes through the end cap 223 and enters the tube 102. The portion of the tube 102 through which the cable 107a extends can be referred to as an unheated length 224.

[0046] In one or more embodiments, a plurality of ceramic element supports 213 may be spaced throughout the tube 102 such that the heating element 101 is supported within the tube 102. The ceramic element supports 213 may be equally spaced throughout the tube 102, although embodiments may exist where the ceramic element supports 213 are not equally spaced.

[0047] In one or more embodiments, a plurality of fins 103 may be arranged circumferentially around the outer surface of the tube 102. The plurality of fins 103 may help dissipate heat from the heating element, thereby improving heating of the air within the electric air heater module.

[0048] The sleeve 209 can fit tightly around the tube 102 in the unheated length 205. In one or more embodiments, the sleeve 209 can define an outer portion of the fire-resistant insulation layer 106, which can be positioned at the first end 116 of the outer shell 104. The sleeve 209 can extend from the outer shell 104 and through the insulation layer 106. In one or more embodiments, the insulation layer 106 can be a fire-resistant type insulation material such as a castable, ceramic fiber, insulation board, or any other type of high temperature insulation material.

[0049] Figure 4 1 shows a cross-sectional view of a tube 102 within an electric air heater module according to one or more embodiments. More specifically, Figure 4 1 shows a detailed cross-section of the tube 102 at the first end 116 of the outer shell 104. In one or more embodiments, as shown in FIG. Figure 4As shown, the refractory insulation layer 106 can fit tightly to the exterior of the outer shell 104. In one or more embodiments, the refractory insulation layer 106 can be a castable fiber or a ceramic fiber, where the ceramic fiber refers to an internal ceramic fiber insulation layer installed in the liner. In addition, in some embodiments, the end cap 223 can be in line with the outer shell 104, eliminating the need for a sleeve 209 and shortening the unheated length.

[0050] Now turn to Figure 5 , Figure 5 1 shows a cross-sectional view of a tube 102 within an air heater module according to one or more embodiments. More specifically, Figure 5 A detailed cross section of the tube 102 at the second end 118 of the outer shell 104 is shown. The second end 118 can have a feature that the tube 102 floats within the electric air heater module. In one or more embodiments, the sleeve 209 can define a space within the fire-resistant insulation layer 106 in which the tube 102 can freely expand axially during heating. The terminal end of the heating element 101 can also be spaced apart from the end of the tube 102 to allow the heating element to expand freely within the length of the tube 102.

[0051] The radial expansion of the tube 102 may cause an increase in the radius of the tube. In one or more embodiments, the expansion may be on the order of millimeters. However, the magnitude of the expansion may vary depending on the specific application and use of the electric air heater module.

[0052] In one or more embodiments, a vibration damper 411 can be used to support the tube 102 at the second end 118. In addition, the vibration damper 411 can allow for thermal expansion of the tube 102 and reduce or prevent vibration of the tube 102 due to flow-induced vibrations. In one or more embodiments, a housing portion or cover 410 can be installed to seal the furnace environment from the external environment. The housing portion or cover 410 can have a variety of designs and geometries and can be insulated externally or internally as the situation requires.

[0053] Now turn to Figure 6 In one or more embodiments, the intermediate support 512 can be installed at a midpoint between the first end 116 and the second end 118 of the outer shell 104 (see FIG. 2 ). In such embodiments, the tube 102 can be divided into a first section 102a and a second section 102b, wherein the intermediate support 512 is installed in the space between the two sections 102a, 102b. This can allow the tube to expand at a midpoint, rather than at the second end 118 of the outer shell 104.

[0054] Vibration dampers 411 may be mounted at the end of the first section 102a and at the end of the second section 102b. In addition, a sleeve 209 may be installed from the end of the first section 102a to the beginning of the second section 102b to provide support for each section. In one or more embodiments, the tube 102 may have electrical connectors 107 mounted at both the first end 116 and the second end 118 so that the tube 102 is fixed at both the first end 116 and the second end 118. When a large electric air heater module volume is required, or to reduce the unsupported length of the tube 102, a sleeve such as Figure 6 Embodiments such as the embodiments shown.

[0055] Figure 7 A cross-sectional view of an electric air heater module according to one or more embodiments is shown. More specifically, Figure 7 2 to 3. A radial electric air heater module 700 is shown. The radial electric air heater module 700 may have an inner cavity 714 extending axially through a cylindrical outer shell 704, which may be hollow. Figure 6 A plurality of tubes 702 similar to the tube 102 described above can be arranged radially around the inner cavity 714. In one or more embodiments, the plurality of tubes 702 can be arranged in circular rows or layers such that each successive row has a larger radius than the previous row. In addition, each successive row can have a different wattage level than the previous row. The inner cavity 714 can have a plurality of axial perforations 711 machined into its outer wall to allow air to flow outward through the rows of tubes 702.

[0056] In one or more embodiments, a baffle 708 may be mounted in the center of the outer shell 704 and the inner cavity 714 so as to prevent air from flowing from one side of the radial electric air heater module 700 to the other side. In such embodiments, the air 120 may be directed into either end of the inner cavity 714, where each inner cavity 706 opening may serve as an inlet 716, 718. The positioning of the baffle 708 may force the air entering each inlet 716, 718 to flow through multiple rows 702 to reach the outlet 710. The air temperature in the upper half (i.e., the half closest to the outlet) of the radial electric air heater module 700 may be higher than the air temperature in the lower half. However, in one or more embodiments, additional internal baffles may be installed to promote air flow around the entire tube 702, not just those in the upper half of the radial electric air heater module 700.

[0057] Figure 8 A cross-sectional view of an electric air heater module according to one or more embodiments is shown. More specifically, Figure 8 A radial electric air heater module 800 is shown according to one or more embodiments. Figure 72 to 3. As shown in the radial electric air heater module 700, the radial electric air heater module 800 may include an inner cavity 814 extending axially through the hollow outer shell 804. The inner cavity 806 may have an inlet 807 disposed at one end and an outlet 810 located at the opposite end. Figure 6 A plurality of tubes 802 similar to the tube 102 described may be arranged in a row radially around an inner cavity 814. The inner cavity 814 may have a plurality of axial perforations 811 machined into its outer wall to allow air to flow outwardly through the row of tubes 802.

[0058] The baffle 808 can be mounted in the center of the radial electric air heater module 800. In one or more embodiments, the baffle 808 can extend completely through the interior of the outer housing 804 and the inner cavity 814. In such embodiments, the baffle 808 can have a plurality of perforations in the surface area around the inner cavity 806 so that air can flow through the perforations. In other embodiments, the baffle 808 can be disposed only in the inner cavity 814 so that the air 120 can freely flow through the interior of the outer housing 804 outside the inner cavity 814.

[0059] In one or more embodiments, the air 120 may be directed into the inlet 807 of the inner cavity 814 and then forced out of the axial perforations 811 due to the presence of the baffle 808 that blocks air flow directly through the inner cavity 814. The air 120 may then be forced through the row of tubes 802 so that the air may flow through the entire interior of the outer shell 804. In one or more embodiments, there may be additional internal baffles (not shown) mounted within the interior of the outer shell 804 to ensure uniform air flow through the entire interior of the outer shell 804, avoiding air flow concentration through a given section of the interior of the outer shell.

[0060] After the air is forced through the row of tubes 802, it may re-enter the interior cavity 814 behind the baffle 808 through the plurality of axial perforations 811. The air 120 may then flow out of the radial electric air heater module 800 via the outlet 810.

[0061] Now turn to Fig. 9 , Fig. 9 900 is a cross-sectional view of an electric air heater module according to one or more embodiments. Specifically, Fig. 9 902 according to one or more embodiments. The electric air heater module 900 may be installed with multiple rows 908 of tubes 902. For example, there may be some embodiments where 25 rows 908 are installed, such as Fig. 9 As shown, each row 908 includes 16 tubes 902 in each row (not shown). However, alternative numbers of installed rows 908 and tubes 902 may be used, and it should be understood that the number of installed rows 908 and tubes 902 per row may be changed as circumstances require.

[0062] In one or more embodiments, multiple rows 902 may be grouped together to form a bundle 906. Within a bundle 906, row spacing 904 may refer to the distance between each row 908. Bundle spacing 910 may refer to the distance between each bundle 906. The rows 902 and bundles 906 may be spaced and arranged to provide a tortuous flow path through the cavity while also providing sufficient spacing for expansion of the tubes 902 and fins and maintaining a relatively low pressure drop.

[0063] The electric air heater module 900 may have a height 912, which may be defined as the distance between an inlet 914 and an outlet 916. Additionally, the electric air heater module 900 may have a width 918, which may be defined as the distance between fire-resistant insulation layers 920. An effective row height 922 may refer to the distance between the first and last rows 908 arranged within the electric air heater module 900. Similarly, an effective tube length 924 may refer to the length of each tube 902.

[0064] The number of tubes per row within a bundle may vary, such as having a greater or lesser number of tubes in a first row compared to a second row. For example, a row near the inlet of the heater may have a smaller number of center rows, taking into account the development of eddies and flow within the heater from the inlet to a region of fully developed flow, which may have a greater number of tubes per row. Additionally, the number of tubes, the number of tubes per row, may vary between a first bundle and a second bundle within an electric air heater module, similarly taking into account the development of flow and the changing flow dynamics and fluid properties as the gas passing through the heater is heated.

[0065] The row spacing within a bundle can be uniform or non-uniform, and can vary, such as being spaced closer to the inlet of the heater and closer to the outlet of the heater, or vice versa. Similarly, the row spacing in multiple bundles can be similar or different. As described above, the bundle configuration can vary from the heater inlet to the heater outlet to take into account not only the flow development, but also the flow dynamics and changes in fluid properties through the heater.

[0066] For embodiments with fins on the tubes, fin height, fin thickness, number of fins per unit length, and other fin variables may vary between tubes within a row, between rows of a bundle, or between bundles. For example, a first row or first bundle within a heating module may have a different fin configuration than a second row or second bundle, respectively, within the heating module.

[0067] For heaters having two or more modules arranged in series, the modules may have similar designs or different designs, taking into account fluid flows and properties, as described above. Each module may be designed to have an appropriate configuration with respect to one or more of the following in order to provide the desired heat exchange: module height, module width, row height, tube spacing, tube height, tube diameter, tube length, number of tubes per row, number of tubes per module, number of fins per unit length of tube, fin height, fin thickness, structural material, etc.

[0068] In one or more embodiments, multiple spare rows 926 can be installed. In one or more embodiments, spare rows 926 can also be referred to as empty rows. Spare rows 926 can refer to rows 908 of tubes 902 in which no heating elements are installed or in which no heating elements are powered. For example, in some embodiments, three spare rows 926 can be installed, wherein spare rows 926 are scattered among bundles 906. Spare rows 926 can be used in the event of failure of one or more heating elements in rows 908. For example, if row 908 has one or more tubes 902 with failed heating elements, a new heating element can be inserted into the tube 902 of one of the spare rows 926, or the heating element that is not powered can be powered. Spare rows 926 can then function in the same manner as any other rows 908. In addition, the failed heating element can be removed to create a new spare row 926. In this way, the heating element can be repaired while the electric air heater module 900 is still running at full capacity, including installation and removal. In embodiments where the heating element is to be removed, the weld on the sealing flange may need to be cut and re-welded according to techniques known in the art.

[0069] Now turn to Fig.10 , Fig.10 1 shows a cross-sectional view of an electric air heater module 1000 according to one or more embodiments. More specifically, Fig.10 An illustrative example of an electric air heater module 1000 according to one or more embodiments is shown. The electric air heater module 1000 can have an inlet 1006 and an outlet 1004, between which a plurality of rows 1008 of tubes 1002 are arranged. Each tube 1002 can contain a heating element (not shown). At the inlet 1006, an inlet temperature 1010 can be measured. At the outlet 1004, an outlet temperature 1012 can be measured. The rows 1008 can be arranged into five bundles 1014, 1016, 1018, 1020, 1022.

[0070] The first bundle 1014 can have a tube metal temperature (TMT), which refers to the temperature of the tube 1002. The first bundle 1014 can also have an internal temperature (internal T), which can refer to the temperature of a heating element (such as a heating element) within the tube 1002. Figure 2A101). In addition, the first bundle 1014 can have a power. In one or more embodiments, each tube bundle 1002 can have a different power. However, there may be other embodiments in which some of the tube bundles 1002 have the same power.

[0071] Similarly, each of the second to fifth bundles 1016, 1018, 1020, 1022 may have a TMT value, an internal T value, and a power value. In one or more embodiments, the corresponding TMT value, internal T value, and power value of each of the bundles 1014, 1016, 1018, 1020, 1022 may be different. However, there may be some embodiments in which one or more values ​​are the same or substantially similar. In one or more embodiments, the electric air heater module 1000 may have a limited air flow rate to ensure maximum heating and total load.

[0072] Table 1 shows an exemplary example of an electric air heater module 1000, and the approximate ranges of each parameter associated with the various components within the electric air heater module 1000. Although Table 1 describes one exemplary example, there may be many exemplary examples, each having different parameter ranges without departing from the scope of the present disclosure.

[0073]

[0074]

[0075] Table 1

[0076] In one specific example, the electric air heater module 1200 may have an air flow rate of 313,800 kg / h and a total load of 25.8 MMkcal / h. In the same example, the inlet temperature 1210 may be 394°C and the outlet temperature 1212 may be 714°C. The first bundle 1214 may have a TMT of 635°C, an internal T of 660°C, and a power of 80kW per heating element. The second bundle 1216 may have a TMT of 700°C, an internal T of 725°C, and a power of 80kW per heating element. The third bundle 1218 may have a TMT of 765°C, an internal T of 790°C, and a power of 80kW per heating element. The fourth bundle 1220 may have a TMT of 800°C, an internal T of 840°C, and a power of 80kW per heating element. The fifth bundle 1222 may have a TMT of 830°C, an internal T of 850°C, and a power of 60kW per heating element.

[0077] In one or more embodiments, the internal T value may be higher than the TMT value. In addition, the power value may vary between beams. Although one example is given above, it should be understood that many other examples may be used without departing from the scope of the present disclosure. Fig.10 The electric air heater module is shown.

[0078] Now turn to Fig.11 , Fig.11 A cross-sectional view of an electric air heater system 1100 according to one or more embodiments is shown. In one or more embodiments, the electric air heater system 1100 may include a first portion 1104 of the electric air heater 1100 and a second portion 1106 of the electric air heater 1100 connected in series. The electric air heater system 1100 may also include a connection point 1108 disposed between the first portion and the second portion of the electric air heaters 1104, 1106. In one or more embodiments, a portion may refer to a segment of the electric air heater system 1100 in which one or more tube bundles 1102 are configured in a single direction. The connection point 1108 may refer to a change in the configuration of the tube bundles such that the tube bundle disposed in the first portion 1104 extends axially at an angle to the tube bundle disposed in the second portion 1106.

[0079] In one or more embodiments, the first electric air heater portion and the second electric air heater portion 1104, 1106 can be stacked at an angle so that one electric air heater portion faces one direction and the second electric air heater portion faces another direction. In one or more embodiments, the first electric air heater portion and the second electric air heater portion can be offset by 90 degrees. In these embodiments, the tube of the first electric air heater portion 1104 can be oriented at a 90-degree angle to the tube of the second electric air heater portion 1106. However, it should be understood that this angle is only an example, and the first electric air heater portion and the second electric air heater portion 1104, 1106 can be arranged to have an offset of any angle between 0 and 90 degrees without departing from the scope of the present disclosure. In addition, the tube of the first electric air heater portion 1103 can be oriented at a 180° angle to the tube of the second electric air heater portion 1106. The power connections of the portions 1104 and 1106 can then be located at opposite ends. Arranging the continuous electric air heater portion at an angle to the previous portion can provide more open space for power connections and more space for heater maintenance activities.

[0080] In one or more embodiments, the tube bundles 1102, and in particular how many tubes are included in a bundle, can be determined based on the desired total power. For example, each tube bundle 1102 can be a 5 MW unit, such that the power supply connected to the tube bundle 1102 is associated with a 5 MW transformer. However, this is just one example, and there can be many different transformers with varying power outputs that can be associated with each tube bundle 1102. In some embodiments, by independently powering each tube bundle 1102, a single electric air heater system 1100 can provide over 170 MW of energy.

[0081] Fig.11 An example of an arrangement of tubes 1102 within a first electric air heater section 1104 is shown. In this embodiment, the tubes 1102 are arranged in a parquet style (i.e., an arrangement in which the tubes are arranged at 90° relative to the previous row or tube bundle). However, there are other embodiments in which the tubes 1102 can be arranged in a brick-and-mortar style. In one or more embodiments, the tubes 1102 can be positioned in a staggered arrangement. However, there are other embodiments in which the tubes 1102 are positioned in an in-line arrangement. In one or more embodiments, a fin tube cleaning door or access door can be installed between the first and second electric air heater sections 1104, 1106.

[0082] In one or more embodiments, the tubes 1102 in the first electric air heater module 1104 may be made of the same material as the tubes 1102 in the second electric air heater module 1106. However, in other embodiments, the tube material between the first and second electric air heater modules 1104, 1106 may be different.

[0083] Now turn to Fig.12 , Fig.12 A flow chart 1200 of a method for heating a volume of air within an electric air heater module is depicted. Initially, in step 1202, a volume of air may be directed into an electric air heater, such as the electric air heater module 100. Next, in step 1204, a volume of air may be directed through an interior cavity of the electric air heater module 100. Within the electric air heater module 100, multiple rows of tubes may be arranged according to one or more of the embodiments described herein. A volume of air may be forced through the multiple rows of tubes so that the air may be heated, as described in step 1206.

[0084] In one or more embodiments, the electric air heater module may be a radial electric air heater module such as Figure 7 and Figure 8In these embodiments, the method may further include directing a volume of air through the lumen to a baffle disposed in the center of the lumen and forcing the volume of air outward from the center of the lumen and through the one or more layers of tubes.

[0085] In one or more embodiments, the electric air heater module may include one or more tube bundles, such as Fig. 9 The tube bundle 906 is shown. The bundle may include one or more tubes, where the number of tubes used is selected based on the desired total power. Each bundle may have a power accordingly, and the electric air heater module may have a total power composed of the combination of the powers of each bundle. As a result, in some embodiments, a single electric air heater module can provide more than 170 MW of energy.

[0086] Embodiments of the present disclosure may provide at least one of the following advantages. In currently available commercial heaters, the maximum temperature must be limited to avoid overheating of the heating element. In addition, as the gas flows through a continuous element, the gas heats to a temperature at which it is difficult to dissipate the heat. Therefore, the heater element at the hottest part of the heater assembly must be operated at a much lower watt density than desired. In addition, in many currently available air heaters, the heating element is exposed within the heater so that the gas flows directly through the element.

[0087] In contrast, embodiments of the present disclosure allow for higher temperatures and watt densities without causing overheating or failure of the heating element. In addition, embodiments of the present disclosure allow for easy repair and replacement of the heating element during operation of the electric air heater. Since the heating element is completely enclosed within the tube, which can be considered a controlled environment, a stable oxide layer can be maintained on the surface of the heating element, thereby extending the life of the element. In addition, placing the heating element within a controlled environment allows for the heating of corrosive, flammable, or otherwise difficult product gases.

[0088] Embodiments of the present disclosure may also allow large volume flows of gas (e.g., mass flow rates greater than 100,000 kg / h) to be heated from a nominal preheat temperature of 343°C to over 760°C at low pressure. However, embodiments of the present disclosure are not limited to a maximum inlet temperature or a minimum inlet temperature of 343°C. In addition, embodiments of the present disclosure may allow large volume heating while maintaining a pressure drop of less than 13.8 kPa. In some embodiments, the pressure drop may also be limited to less than 7 kPa.

[0089] Embodiments of the present disclosure may also allow overheating of the heating element to be avoided. The heat transfer from the heating element to the tube is primarily radiative and is controlled by cooling the tube by the gas flowing through the inner cavity of the electric air heater module. The heat transfer may be further improved by adding fins to the outer periphery of the tube, thereby increasing the effective surface area for convective heat transfer, which improves the dissipation of heat from the tube and the cooling of the tube.

[0090] Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications may be made to the exemplary embodiments without substantially departing from the present invention. Therefore, all such modifications are intended to be included within the scope of the present disclosure as defined by the following claims.

Claims

1. An electric air heater system comprising: a first electric air heater module; Wherein the first electric air heater module comprises: an outer shell having an inner surface, a first end and a second end, a fire-resistant heat-insulating layer, which is in close communication with the outer shell; an inner cavity located within the fire-resistant insulation layer; a plurality of tubes extending from the first end through the lumen to the second end, the plurality of tubes each having an outer surface, wherein each tube is fixed relative to the outer shell at the first end, and each tube has an electrical connector disposed at the first end; wherein the plurality of tubes are arranged into one or more tube bundles, wherein each bundle comprises two or more tubes; wherein each tube has a plurality of fins extending radially from the outer surface, and wherein each tube has a heating element extending axially through the hollow interior of the tube; and A sleeve supports each of the plurality of tubes at the second end of the outer shell.

2. The electric air heater system of claim 1 further comprising a second electric air heater portion rotated at an angle to the first electric air heater portion.

3. An electric air heater system according to claim 2, wherein each of the one or more bundles is connected to an individually controlled power supply group.

4. The electric air heater system of claim 3, wherein the heating element of the first electric air heater portion is a different type of heating element than the heating element of the second electric air heater portion.

5. The electric air heater system of claim 1, wherein the plurality of tubes are arranged in two or more rows and one or more rows of tubes are not powered. 6 . The electric air heater system of claim 1 , wherein the first electric air heater module has a rectangular cross-section or a cylindrical cross-section.

7. The electric air heater system of claim 6, wherein the first electric air heater module having the cylindrical cross-section comprises: a cylindrical outer shell; a rectangular inner housing configured to receive a flow of air; and The fire-resistant heat-insulating layer covers the rectangular inner shell.

8. An electric air heater comprising: an outer shell having an inner surface defining an inner cavity, a first end and a second end, a fire-resistant heat-insulating layer, which is in close communication with the outer shell; a plurality of tubes extending axially through the lumen from the first end to the second end, the plurality of tubes each having an outer surface, wherein the plurality of tubes are radially arranged around the axial center of the inner cavity, wherein each tube is fixed relative to the outer shell at the first end, and each tube has an electrical connection disposed at the first end, wherein each tube has a plurality of fins extending radially from the outer surface, and wherein each tube has an electrical heating element disposed axially through the hollow interior of the tube; and A sleeve supports each of the plurality of tubes at the second end of the outer shell.

9. An electric air heater according to claim 8, wherein the electric heating element disposed axially through each tube comprises a plurality of heating elements and electrical wires arranged in parallel or in series.

10. An electric air heater as claimed in claim 8, wherein each heating element is supported by at least one ceramic element support.

11. An electric air heater as claimed in claim 8, wherein each heating element is selected from the group consisting of: iron-chromium-aluminum wire, nickel-chromium wire, silicon carbide rod and molybdenum disilicide heating element.

12. The electric air heater of claim 8, wherein the geometry of the plurality of fins is selected from the group consisting of: round solid fins, serrated fins, or stud fins.

13. The electric air heater of claim 8, wherein the refractory insulation layer comprises a castable refractory material, ceramic fibers, or insulation board.

14. The electric air heater according to claim 8, wherein the electric air heater comprises an inner shell disposed inside the outer shell, and wherein the fire-resistant insulation layer is in close communication with an outer surface of the outer shell or the inner shell.

15. The electric air heater of claim 8, further comprising a vibration damper disposed around each of the plurality of tubes at the second end of the outer shell.

16. The electric air heater of claim 8, wherein the plurality of tubes are connected to the outer housing at the first end.

17. The electric air heater of claim 16, further comprising a thermal expansion zone at the second end.

18. The electric air heater of claim 8, further comprising a support mounted in the center of the interior cavity.

19. The electric air heater of claim 18, wherein one or more of the plurality of tubes comprises two tube segments arranged around the support and wherein the thermal expansion zone of each of the two tube segments is located at the support.

20. The electric air heater of claim 8, wherein the electric air heater has a first portion and a second portion, each portion having one or more tubes and wherein the first portion and the second portion rotate relative to each other.

21. A method of heating air, comprising: Directing a volume of air into an electric air heater, Wherein the electric air heater comprises: outer shell; an inner cavity disposed through the outer shell; a fire-resistant insulating material which is closely fitted to the outer shell; and a plurality of tubes extending through the lumen, wherein the plurality of tubes are arranged in one or more layers; directing the volume of air through the interior cavity; and The volume of air is heated.

22. The method of claim 21, further comprising: directing the volume of air through the interior cavity to a baffle disposed in the center of the interior cavity; and The volume of air is forced outward from the center of the lumen and through one or more layers of tubes.

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