Thermal and electrical insulation of electrically heated reaction tubes

Abstract

An electrified reactor includes a reactor coil that is electrically connected to an electric power source, a first insulating layer that is electrically connected to the reactor coil, and a second insulating layer that is thermally connected to the first insulating layer. The first insulating layer is an electric insulating layer, and the second insulating layer is a thermal insulating layer.

Description

85993-WO-PCT / DOW 85993 WO1THERMAL AND ELECTRICAL INSULATION OF ELECTRICALLY HEATED REACTION TUBESCROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Application Serial No. 63 / 719,768 filed November 13, 2024, the entire disclosure of which is hereby incorporated by reference.BACKGROUND

[0002] Ethylene is widely used as an intermediate in the petrochemical industry and its production exceeds that of any other organic compound. Much of ethylene production goes to the manufacture of ethylene oxide, ethylene dichloride and polyethylene, which are precursors to a multitude of everyday consumer products. Despite various improvements over the years in thermal efficiency, reliability and safety, steam-cracking furnaces used to form hydrocarbons such as ethylene remain heavily reliant on combustion of fossil fuels to provide process heat leading to substantial greenhouse gas emissions.

[0003] The steam cracking process to produce ethylene requires roughly half the energy required of competing processes (e.g., direct Ci conversion technologies) and is projected to remain as the most energy efficient process. CO2 emissions from steam cracking of ethane ranges from 0.76 to 1.06 ton-CCh per ton-ethylene produced and is lower than steam cracking of naphtha and alternates Ci-based routes to ethylene. At projected rates of ethylene production, CO2 emissions from conventional steam cracking could exceed 300 Mta-CCh in the coming years. About 85% of the CO2 emissions in the steam cracking process are emitted in the radiant combustion furnace section. In conventional radiant furnaces, numerous fuel gas burners are deployed to efficiently radiate heat from the combustion process through tubular reactor walls containing flowing feedstocks (e.g., hydrocarbon and steam) and product gases, providing heat to perform the required endothermic chemical reactions.

[0004] The growth and availability of renewable electricity creates an opportunity to use renewable energy in the formation of ethylene, eliminating the need to burn fossil fuels, and achieve a lower emission process. Various electric heating technologies such as impedance, induction, plasma, and microwaves may be used in place of combustion fired heating to generate and effectively transfer heat into the radiant coils of steam cracking furnaces. However, needs still exist for systems that can form ethylene and other hydrocarbons via heating with renewable electric sources.85993-WO-PCT / DOW 85993 WO2BRIEF SUMMARY

[0005] In electrical cracking systems (e-crackers), a considerable fraction of the direct electric resistance heat generated in the tubular reactor wall may be lost to the atmosphere if not appropriately addressed. This heat loss is undesirable as it reduces the efficiency of ethylene production. In some e-crackers, an enclosure may be positioned surrounding the tubes, which will primarily act as secondary containment during accidental scenarios such as coil rupture. However, a secondary role of the enclosure may be to minimize heat loss to the atmosphere. While the enclosure does help with heat management, further improvements can be made if heat insulation is provided closer to the heat generation source, such as directly on the reaction tube, as disclosed in embodiments herein.

[0006] In the conversion between steam cracking systems and e-crackers, electric arcing between adjacent tubular reactors may also be a concern if not appropriately spaced. However, even if the spacing between the adjacent tubular reactors (also called pitch) is initially appropriate, electric arcing may again become an issue after a period of time. Particularly, after a period of operation such as a few years, the spacing between the adjacent tubular reactors may again become tight due to tube deformation and creep. One way to address this problem is to keep the pitch between the tubes large to begin with so that that even after deformation, the tubes will not contact each other. However, this approach is not ideal because a larger initial pitch necessitates a larger overall footprint and volume, which is undesirable from a heat-loss and cost perspective. Therefore, an alternate method of electric arc prevention is desirable.

[0007] Accordingly, embodiments herein address this desire by providing reactor coils, in at least some embodiments, having an electric insulating layer overlaying the reactor coil and a thermal insulation layer overlaying the electric insulating layer, or a combination electric and thermal insulation layer overlaying the reactor coil. This may be beneficial as conventional thermal insulators are normally not sufficient for use in e-crackers because they are electrically conductive. Further, in the case of the former configuration, the use of the thermal insulation layer overlaying the electric insulating layer may permit an electric insulator of high thermal conductivity to be used without risking heat loss to the atmosphere / enclosure. This may be of benefit in distributing heat away from hot spots in the reactor coils (potentially reducing coking) to cold spots (increasing desired product yield) and evening heat distribution across the reactor coils.85993-WO-PCT / DOW 85993 WO3

[0008] In embodiments, one or more embodiments disclosed herein are directed to an electrified reactor comprising: a reactor coil that is electrically connected to an electric power source; a first insulating layer that is electrically connected to the reactor coil; and a second insulating layer that is thermally connected to the first insulating layer, wherein the first insulating layer is an electric insulating layer, and the second insulating layer is a thermal insulating layer.

[0009] One or more embodiments disclosed herein is directed to an electrified reactor comprising: a reactor coil that is electrically connected to an electric power source; and an insulating layer that is electrically and thermally connected to the reactor coil, wherein the reactor coil comprises: a thermal conductivity measured at 1000 °C that is from 20 W / m-K to 40 W / m-K; and an electrical resistivity that is from 10'8-m to 10'4-m, and the insulating layer comprises: a thermal conductivity measured at 1000 °C that is from 0.5 W / m-K to 1.0 W / m-K; an electrical resistivity that is from 108-m to 1010-m, and a dielectric strength that is from 1.5 kV / mm to 2.5 kV / mm.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0011] FIG. 1A is a schematic of a first side view of an electric cracking system;

[0012] FIG. IB is a schematic of a second side view of an electric cracking system;

[0013] FIG. 2A is a schematic of a first perspective view of a reactor coil in an electric cracking system;

[0014] FIG. 2B is a schematic of a second perspective view of a reactor coil in an electric cracking system;

[0015] FIG. 3 is a schematic of a cross-section of a reactor coil and insulation layer according to embodiments disclosed and described herein;

[0016] FIG. 4 is a schematic of a cross-section of a reactor coil, first insulating layer, and second insulating layer according to embodiments disclosed and described herein;

[0017] FIG. 5 is a schematic depicted a side view of an insulated reactor coil having a varying insulation layer thickness according to embodiments disclosed and described herein;85993-WO-PCT / DOW 85993 WO4

[0018] FIG. 6A is a schematic showing the simulated heat loss in the reactor coil of a comparative example; and

[0019] FIG. 6B is a schematic showing the simulated heat loss in the insulated reactor coil of the example according to embodiments disclosed and described herein.DETAILED DESCRIPTION

[0020] An exemplary electrical cracking system (e-cracker) is described in WO / 2024 / 084253, which is incorporated herein by reference in its entirety. However, it should be understood that embodiments disclosed and described herein can be used with any e-cracker that includes reactor coils, such as tubular reactor coils. An exemplary e-cracker, which is not intended to limit embodiments disclosed and described herein, will now be described with reference to FIG. 1 A, FIG. IB, FIG. 2A, and FIG. 2B.

[0021] The above heating apparatus 100 according to embodiments disclosed and described herein will now further be defined with reference to FIG. 1A and FIG. IB, which are side views of the heating apparatus according to one or more embodiments. As shown in FIG. 1 A, grounded connections 140 are electrically connected to the left and right side of the first electrically conductive tube 220a. Moreover, a positive conductor 124 is connected to the middle of the first electrically conductive tube 220a, which is positioned in an enclosure 102, to provide an electrical current to the first electrically conductive tube 220a. As a result of the electrical resistance of the first electrically conductive tube 220a, applying electrical current via the positive conductor 124 to the first electrically conductive tube 220a causes the temperature of the first electrically conductive tube 220a to increase, thereby heating the first portion of the hydrocarbon fluid 202a that enters the first electrically conductive tube 220a on the left side of FIG. 1A. The first portion of the hydrocarbon fluid 202a reacts within the first electrically conductive tube 220a to form a product stream 204.

[0022] As shown in FIG. IB, grounded connections 140 are electrically connected to the left and right side of a second electrically conductive tube 220b, which is positioned in the enclosure 102. Moreover, a negative conductor 126 is connected to the middle of the second electrically conductive tube 220b to provide an electrical circuit with the first electrically conductive tube 220a and the positive conductor 124 depicted in FIG. 1 A. With reference again to FIG. IB, as a result of the electrical resistance of the second electrically conductive tube 220b, applying electrical current via the circuit formed by the positive conductor 124, the first electrically85993-WO-PCT / DOW 85993 WO5conductive tube 220a, the second electrically conductive tube 220b, and the negative conductor 126 causes the temperature of the second electrically conductive tube 220b to increase, thereby heating the second portion of the hydrocarbon fluid 202b that enters the second electrically conductive tube 220b on the left side of FIG. IB. The second portion of the hydrocarbon fluid 202b reacts within the second electrically conductive tube 220b to form a product stream 204. As also shown in FIGS. 1A-1B, the first and second electrically conductive tubes 220a / 220b may be secured or hung in the heating apparatus through one or more coil hangers 206 as well as one or more guide legs (not shown).

[0023] An e-cracker according to embodiments disclosed and described herein will further be defined with reference to FIG. 2A and FIG. 2B, which are perspective views of an e-cracker according to one or more embodiments, without the surrounding enclosure 102 illustrated.

[0024] As shown in FIG. 2A, a first electrically conductive tube 220a and second electrically conductive tube 220b are each fluidly connected to a feed channel 210 (which may also be referred to as an inlet header) on the left side of FIG. 2A, where a first portion of hydrocarbon fluid 202a (not shown) enters the first electrically conductive tube 220a and a second portion of hydrocarbon fluid 202b (not shown) enters the second electrically conductive tube 220b. Similarly, the first electrically conductive tube 220a and the second electrically conductive tube 220b are fluidly connected to a product channel 214 (which may also be referred to as an outlet header) where product stream 204 (not shown) exits the first electrically conductive tube 220a and the second electrically conductive tube 220b.

[0025] The positive conductor 124 is electrically connected to the first electrically conductive tube 220a to provide electrical current to the first electrically conductive tube 220a, thereby causing the temperature of the first electrically conductive tube 220a to increase as a result of its electrical resistance. A first current bridge link 118a and a second current bridge link 118b electrically connect the first electrically conductive tube 220a and the second electrically conductive tube 220b, thereby allowing electrical current to more easily flow between the first electrically conductive tube 220a and the second electrically conductive tube 220b.

[0026] It should be appreciated that the first current bridge link 118a and the second current bridge link 118b may be present in the embodiments shown in FIG. 1A and FIG. IB, but would not be visible in a side view. Referring again to FIG. 2A, grounded connections 140 are electrically connected to the first current bridge link 118a and the second current bridge link 118b. The second electrically conductive tube 220b is electrically connected to a negative85993-WO-PCT / DOW 85993 WO6conductor 126, thereby completing an electrical circuit between the positive conductor 124, the first electrically conductive tube 220a, the first current bridge link 118a, the second current bridge link 118b, the second electrically conductive tube 220b, and the negative conductor 126.

[0027] As shown in FIG. 2B, a plurality of first electrically conductive tubes 220a and a plurality of electrically conductive tubes 220b (illustrating that the heating apparatus 100 may be scaled to any number of electrically conductive tubes 220a / 220b) are each fluidly connected to a feed channel 210 on the left side of FIG. 2B where a first portion of hydrocarbon fluid 202a enters the plurality of first electrically conductive tubes 220a and a second portion of hydrocarbon fluid 202b enters the plurality of second electrically conductive tubes 220b.

[0028] Similarly, the plurality of first electrically conductive tubes 220a and the plurality of second electrically conductive tubes 220b are fluidly connected to a product channel 214 where product stream 204 exits the plurality of first electrically conductive tubes 220a and the plurality of second electrically conductive tubes 220b. A plurality of positive conductors 124 are electrically connected to the plurality of first electrically conductive tubes 220a to provide electrical current to the plurality of first electrically conductive tubes 220a, thereby causing the temperature of the plurality of first electrically conductive tubes 220a to increase as a result of their electrical resistance.

[0029] Still referring to FIGS. 2A-2B, a plurality of first current bridge links 118a and a plurality of second current bridge links 118b electrically connect the plurality of first electrically conductive tubes 220a and the plurality of second electrically conductive tubes 220b, thereby allowing electrical current to more easily flow between the plurality of first electrically conductive tubes 220a and the plurality of second electrically conductive tubes 220b. Grounded connections 140 are electrically connected to the plurality of first current bridge links 118a and the plurality of second current bridge links 118b. The plurality of second electrically conductive tubes 220b are electrically connected to a plurality of negative conductors 126, thereby completing an electrical circuit between the plurality of positive conductors 124, the plurality of first electrically conductive tubes 220a, the plurality of first current bridge links 118a, the plurality of second current bridge links 118b, the plurality of second electrically conductive tubes 220b, and plurality of the negative conductors 126.

[0030] As noted above, a considerable fraction of the direct electric resistance heat generated in the tubular reactor wall may be lost to the atmosphere in an e-cracker if not appropriately addressed. However, conventional thermal insulators may not be sufficient for use in e-cracking85993-WO-PCT / DOW 85993 WO7systems because they are, generally, electrically conductive, which can lead to arcing. In particular, as the reactor coils, such as reactor coil 320, deform with use, the spacing between reactor coils 320 may decrease, which can promote arcing. For this reason, conventional insulating layers used in other cracking systems (such as steam cracking and the like) are not suitable for use in e-crackers. Moreover, it is desired to keep the insulating layers close to the heat generation source, i.e., the reactor coils, to decrease the footprint of the e-cracker and maintain thermal efficiencies. However, these insulating layers should not transmit electricity.

[0031] Embodiments of e-crackers having one or more thermal and electrical insulating layers will now be described with reference to FIG. 3, which is a cross-section view of a reactor coil 320 having an insulating layer 330. As shown in FIG. 3 and as described above, the reactor coil 320 depicted in FIG. 3 has a tubular shape with a hollow center forming a reaction zone 310 traversing through the reactor coil 320. The embodiment depicted in FIG. 3 shows an insulating layer 330 positioned on the outer diameter of the reactor coil 320. Put differently, where the center of the reaction zone 310 is the origin, the reactor coil 320 has an inner radius Ri corresponding with an inner diameter of the reactor coil 320 and an outer radius R2 corresponding to an outer diameter of the reactor coil 320. Likewise, where the center of the reaction zone 310 is the origin, the insulating layer 330 has an inner radius R3 corresponding to an inner diameter of the insulating layer 330 and an outer radius R4 corresponding to an outer diameter of the insulating layer 330. As shown in FIG. 3, the reactor coil 320 and the insulating layer 330 may be in close proximity to one another and / or may be in direct contact.

[0032] According to embodiments, the reactor coil 320 may have a thermal conductivity (measured at 1000 °C) greater than 10 watts per meter per degree Kelvin (W / m-K) or from 10 W / m-K to 40 W / m-K, such as from 10 to 20 W / m-K, 20 to 30 W / m-K, 30 to 40 W / m-K, or combinations of the previous ranges or smaller ranges therein, such as from 12 to 18 W / m-K. The thermal conductivity of the coil may be measured according to ASTM Cl 77.

[0033] According to embodiments, the reactor coil may have an electrical resistivity (volumetric) of from 10'8ohm meters (Q-m) to 10'4Q-m, such as from 10'8Q-m to 10'7Q-m, from IO'7Q-m to 10'6Q-m, from 10'6Q-m to 10'5Q-m, from 10'5Q-m to 10'4Q-m, or any combinations of the previous ranges or smaller ranges therein, such as from from 10'7Q-m to 10'5Q-m, or approximately 10'6ohm Q-m. In embodiments, the electrical resistivity may be determined utilizing a linseis unit or any other resistivity measuring system known in the art.85993-WO-PCT / DOW 85993 WO8

[0034] In the embodiments depicted in FIG. 3, the reactor coil 320 is thermally and electrically connected to the insulating layer 330. In one or more embodiments, at least a portion of the outer reactor coil 320 physically contacts the insulating layer 330. In embodiments, substantially all of the reactor coil 320 may physically contact the insulating layer 330, such as from greater than 50%, greater than 90%, from 50-80%, from 80-90%, from 90-99%, from 99-100% or any combinations of the previous ranges or small range therein, such as from 90-100%). For example, all or a portion of the outer diameter of the reactor coil 320 may physically contact all or a portion of the inner diameter of the insulating layer 330. It should be understood that in embodiments an intermediate layer or coating (not shown) may be present between the reactor coil 320 and the insulating layer 330, such as an adhesive layer or coating, a lubricating layer or coating, or the like.

[0035] As previously stated, the insulating layer 330 of embodiments may be both thermally and electrically insulating because the resistive heating of the reactor coils 320 with electricity in e-cracking systems tends to result in more heat loss than traditional cracking systems (such as steam cracking and the like) and arcing can occur between the reactor coils 320 if they are not electrically insulated from adjacent reactor coils 320. Accordingly, the insulating layer 330 according to embodiments should have sufficient electrical and thermal resistivity.

[0036] According to embodiments, the insulating layer 330 may have a thermal conductivity (measured at 1000 °C) that is less than 1.0 W / m-K, such as from 1.0 to 0.8 W / m-K, from 0.8 to 0.6 W / m-K, from 0.6 to 0.4 W / m-K, from 0.4 to 0.2 W / m-K, from 0.2 to 0.1 W / m-K, from 0.1 to 0.05 W / m-K, from 0.05 to 0.01 W / m-K, or any combination of the previous ranges or smaller ranges therein, such as from 0.05 W / m-K to 1.0 W / m-K. Accordingly, the insulating layer 330 according to embodiments has a thermal conductivity that is 50 to 300 times lower than typical insulators used in traditional cracking systems, such as steam cracking and the like. This low thermal conductivity is desirable in e-cracking systems because significant amounts of heat can be lost when heating the reactor coil 320 via electrical resistivity.

[0037] According to embodiments, the insulating layer 330 may have an electrical resistivity (volumetric) that is greater than from 106Q-m, such as from 106Q-m to 107Q-m, from 107Firn to 108Q-m, from 108Q-m to 109Q-m, from 109Q-m to 1010Q-m, or any combination of the previous ranges or smaller range therein, such as from 106Q-m to 1010Q-m or from 108Q-m to 1010Q-m. Accordingly, the electrical resistivity of the insulating layer 330 according to85993-WO-PCT / DOW 85993 WO9embodiments is significantly higher than the 10'6-m used in traditional reactor coils and cracking systems, such as steam cracking.

[0038] According to embodiments, the insulating layer 330 may have a dielectric strength of greater than 50 kilovolts per millimeter (kV / mm) or from 50 kV / mm to 200 kV / mm, such as from 50 to 75 kV / mm, from 75 to 100 kV / mm, from 100 to 120 kV / mm, from 120 to 125 kV / mm, from 125 to 130 kV / mm, from 130 to 150 kV / mm, from 150 to 200 kV / mm, or combinations of the previous ranges or smaller ranges therein, such as from 120 kV / mm to 150 kV / mm. Without being limited by theory, if the dielectric strength is too low, the insulating layer 330 may not be able to withstand the conditions it is subjected to when electrically connected to the reactor coil 320. In embodiments, the dielectric strength may be measured according to ASTM D149-20 or IEC 60243-1:2013.

[0039] The insulating layer 330 may be applied to the reactor coil 320 by any suitable method. In embodiments, the insulating layer 330 is constructed from a material that is capable of being wrapped around the reactor coil 320, such as a pliable sheet or a material that is formed or molded in a shape that is similar to the shape of the reactor coil 320 and can be fitted to the reactor coil 320. It should be understood that the insulating layer 330 wrap material could be applied to one or more portions of the reactor coil 320 or to the entirety of the reactor coil 320 as desired, as well as associated components such as but not limited to the bridge linkages, the coil hangers, the guide legs, the positive conductors, the negative conductors, the internal lining of the enclosure itself, or combinations thereof. In such embodiments, exemplary materials for the insulating layer 330 wrap may include ceramic fiber blankets, boards, papers, textiles, bulk fibers, and wraps of the same.

[0040] The thickness of the insulating layer 330 wrap may, in embodiments, be from 0.1 inches to 5 inches, such as from 0.1 to 1 inch, from 1 to 2 inches, from 2 to 3 inches, from 3 to 4 inches, from 4 to 5 inches, or any combination of the previous ranges or smaller range therein, such as from 2 to 4 inches or from 1 to 5 inches, for example.

[0041] In embodiments, the insulating layer 330 may be applied as a coating to the outer diameter of the reactor coil 320. The insulating layer 330 coating may be applied by any suitable method and in embodiments spray coating, dip coating, sputtering, and plating methods may be used to apply the insulating layer 330 coating to the outer diameter of the reactor coil 320.

[0042] In one or more embodiments, the insulating layer 330 coating may be applied to the outer surface of the reactor coil 320 by applying the coating material to the inner surface of a85993-WO-PCT / DOW 85993 WO10mold that is used to form the reactor coil 320. In this way, when the reactor coil 320 is formed in the mold, the insulating layer 330 coating material may be transferred from the inner surface of the mold to the outer surface of the reactor coil 320. It should be understood that the coating may be applied to a portion of the outer surface of the reactor coil 320 or to the entire outer surface of the reactor coil 320 as desired. Exemplary coating materials that may be applied to the outer surface of the reactor coil 320 include ceramic coatings, such as, but not limited to, zirconia coatings (e.g., Zircoat-HT and Zircoat-M available from Jyoti ceramics) or aluminum nitride coatings

[0043] In at least embodiments wherein the insulating layer is a coating, the thickness of the insulating layer 330 coating may be greater than 20 microns, such as from 20 to 30 microns, from 30 to 50 microns, from 50 to 100 microns, from 100 to 150 microns, from 150 to 200 microns, or any combination of the previous ranges or smaller range therein, such as from 20 to 200 microns.

[0044] Regardless of whether the insulating layer 330 is constructed from an insulating layer 330 wrap or an insulating layer 330 coating, the insulating layer 330 should be able to withstand the reaction conditions present in e-cracking processes. For example, the insulating layer in embodiments may be chemically and thermally stable up to reaction temperatures of about 1100 °C, such as but not limited to stable in an oxidizing environment at temperature of up to 1100 °C.

[0045] Additional embodiments will now be described with reference to FIG. 4. According to one or more embodiments, the insulating layer may be comprised of a first insulating layer 330a and a second insulating layer 330b. The first insulating layer 330a is positioned in close proximity to the outer diameter of the reactor coil 320 such that the first insulating layer 330a is electrically and thermally connected to the reactor coil 320. In embodiments, one or more portions of the first insulating layer 330a is in direct, physical contact with the reactor coil 320. In some embodiments, the entirety of the first insulating layer 330a is in direct, physical contact with the reactor coil 320. It should be understood that in embodiments, an intermediate layer, such as an adhesive layer or a lubricating layer may be positioned between the reactor coil 320 and the first insulating layer 330a.

[0046] According to one or more embodiments, the first insulating layer 330a may be a material or alloy having a high thermal conductivity and a low electrical conductivity, such as but not limited to aluminum nitride, such that the first insulating layer 330a is an electrical85993-WO-PCT / DOW 85993 WO11insulating layer. In embodiments, the first insulating layer 330a has a thermal conductivity that is greater than the thermal conductivity of the reactor coil 320. Thus, the first insulating layer 330a will electrically insulate the reactor coil 320 to prevent arcing and the like while allowing heat to evenly dissipate from the reactor coil 320. As previously stated, this combination of high electrical insulation and high thermal conductivity may thereby mitigating localized thermal spots on the reactor coil 320, such as hot spots that form from localized coking at the inner diameter of the reactor coil 320. Particularly, due at least to the high thermal conductivity of the first insulating layer 330a, heat may be distributed from the hot spots to cooler areas of the coils, thereby minimizing localized over-cracking and thereby coke formation. This may be shown in FIG. 6A as compared to FIG. 6B, as well as explained in further detail herein.

[0047] According to embodiments, the first insulating layer 330a may have a thermal conductivity (measured at 1000 °C) that is greater than 50 W / m-K, such as from 50 to 100 W / m-K, from 100 to 200 W / m-K, from 200 to 300 W / m-K, from 300 to 500 W / m-K, from 500 to 1000 W / m-K, or any combination of the previous ranges or smaller range therein, such as from 100 to 300 W / m-K. Accordingly, the first insulating layer 330a according to embodiments may have a thermal conductivity that is at least 5 times greater than the thermal conductivity of the reactor coil 320, such as from 5 to 8 times greater, from 8 to 10 times greater, from 10 to 20 times greater, from 20 to 30 times greater, or combinations of the previous ranges or smaller ranges therein, such as from 5 times greater to 10 times greater than the thermal conductivity of the reactor coil 320.

[0048] According to embodiments, the first insulating layer 330a may have an electrical resistivity (volumetric) that is greater than 106Q-m, such as from 106Q-m to 108Q-m, from 108Q-m to 1010Q-m, from 1010Q-m to 1012Q-m, from 1012Q-m to 1014Q-m, or any combination of the previous ranges or smaller range therein, such as from 106Q-m to 1014Q-m. Accordingly, the electrical resistivity of the first insulating layer 330a according to embodiments is significantly higher than the 10'6Q-m used in traditional cracking systems, such as steam cracking.

[0049] According to embodiments, the first insulating layer 330a may have a dielectric strength of greater than 50 kilovolts per millimeter (kV / mm) or from 50 kV / mm to 150 kV / mm (depending on the voltage and safety factor), such as from 50 to 75 kV / mm, from 75 to 100 kV / mm, from 100 to 120 kV / mm, from 120 to 125 kV / mm, from 125 to 130 kV / mm, from 130 to 150 kV / mm, from 150 to 200 kV / mm, or combinations of the previous ranges or smaller85993-WO-PCT / DOW 85993 WO12ranges therein, such as from 120 kV / mm to 150 kV / mm. Without being limited by theory, if the dielectric strength is too low, the first insulating layer 330a may not be able to withstand the conditions it is subjected to when electrically connected to the reactor coil 320.

[0050] In embodiments, the first insulating layer 330a may be applied as a coating to the outer diameter of the reactor coil 320. The first insulating layer 330a coating may be applied by any suitable method and in embodiments spray coating, dip coating, sputtering, and plating methods may be used to apply the first insulating layer 330a coating to the outer diameter of the reactor coil 320. In embodiments, the first insulating layer 330a coating may be a low emissivity coating that is applied to the outer diameter of the reactor coil 320 at process temperatures. This application process reduces heat losses from the outer diameter of the reactor coil 320 to the surroundings and will increase the temperature of the inner diameter of the reactor coil 320, thereby lowering heat generation that is required by Joule heating in the reactor coil 320 (z.e. , the electrical current supplied to the reactor coil 320 can be reduced, which results in improved energy efficiency. It should be understood that the coating may be applied to a portion of the outer surface of the reactor coil 320 or to the entire outer surface of the reactor coil 320 as desired. Exemplary coating materials that may be applied to the outer surface of the reactor coil 320 include aluminum nitride.

[0051] As previously stated, the first insulating layer 330a may be applied as a coating. However, in at least some embodiments, the first insulating layer 330a may be applied as a wrap, similar or identical to the wrap described with respect to FIGS. 1A-3. The wrap may also have a similar thickness range to the aforementioned coating for the first insulating layer 330a.

[0052] According to embodiments where the first insulating layer 330a is applied as a coating, the thickness of the first insulating layer 330a may be greater than 100 microns, such as from 100 to 200 microns, from 200 to 400 microns, from 400-1000 microns (1 mm), from 1 mm to 3 mm, from 3 mm to 5 mm, or any combination of the previous ranges or smaller ranges therein, such as from 100 microns to 5 mm.

[0053] As previously stated, a second insulating layer 330b may be positioned in close proximity to the first insulating layer 330a, such that the second insulating layer 330b is thermally connected to the first insulating layer 330a. In embodiments, the at least a portion of the second insulating layer 330b is in direct, physical contact with the first insulating layer 330a. In other embodiments, the entirety of the second insulating layer 330b is in direct, physical contact with the first insulating layer 330a. It should be understood that in embodiments, an85993-WO-PCT / DOW 85993 WO13intermediate layer, such as an adhesive layer or a lubricating layer may be positioned between the second insulating layer 330b and the first insulating layer 330a.

[0054] The second insulating layer 330b, according to embodiments, has a low thermal conductivity and, thus, is a thermal insulating layer. In embodiments, the thermal conductivity of the second insulating layer 330b is less than the thermal conductivity of the reactor coil 320. By positioning the thermally insulating second insulating layer 330b in thermal contact with the thermally conductive first insulating layer 330a, heat can dissipate from the reactor coil 320 through the first insulating layer 330a and yet overall system heat losses that can cause system inefficiencies can be prevented by thermally insulating second insulating layer 330b.

[0055] According to embodiments, the second insulating layer 330b may have a thermal conductivity (measured at 1000 °C) that is less than 1.0 W / m-K, such as from 1.0 to 0.8 W / m-K, from 0.8 to 0.6 W / m-K, from 0.6 to 0.4 W / m-K, from 0.4 to 0.2 W / m-K, from 0.2 to 0.1 W / m-K, from 0.1 to 0.05 W / m-K, from 0.05 to 0.01 W / m-K, or any combination of the previous ranges or smaller ranges therein, such as from 0.05 W / m-K to 1.0 W / m-K.

[0056] Accordingly, the second insulating layer 330b according to embodiments may have a thermal conductivity that is at least 10 times less than the thermal conductivity of the reactor coils 320, such as from 10 to 15 times less, from 15 to 20 times less, from 20 to 30 times less, from 30 to 50 times less, from 50 to 100 times less, or combinations of the previous ranges or smaller ranges therein, such as from 10 to 20 times less than the thermal conductivity of the reactor coil 320, such as from 50 times to 300 times less than the thermal conductivity of the reactor coil 320.

[0057] According to embodiments, the second insulating layer 330b may have an electrical resistivity (volumetric) that is greater than 102-m, such as from 102-m to 103-m, from 103-m to 104Q-m, from 104-m to 105Q-m, from 105-m to 106Q-m, from 106-m to 107firn, from 107-m to 108Q-m, or any combination of the previous ranges or smaller range therein, such as from 102-m to 108-m. However, it should be understood that the electrical resistivity of the second insulating layer 330b is not particularly limited since it is positioned adjacent to the electrically insulating first insulating layer 330a.

[0058] According to embodiments, the second insulating layer 330b may have a dielectric strength of greater than 50 kilovolts per millimeter (kV / mm) or 50 kV / mm to 200 kV / mm (depending on the voltage and safety factor), such as from 50 to 75 kV / mm, from 75 to 100 kV / mm, from 100 to 120 kV / mm, from 120 to 125 kV / mm, from 125 to 130 kV / mm, from 13085993-WO-PCT / DOW 85993 WO14to 150 kV / mm, from 150 to 200 kV / mm, or combinations of the previous ranges or smaller ranges therein, such as from 120 kV / mm to 150 kV / mm. Without being limited by theory, if the dielectric strength is too low, the second insulating layer 330b may not be able to withstand the conditions it is subjected to when electrically connected to the reactor coil 320.

[0059] In embodiments, the second insulating layer 330b may be applied as a coating similar to or identical to the first insulating layer, i.e., the second insulating layer 330b may be applied to an inner surface of a mold as a first coating, the first insulating layer 330a may then be applied to the first coating as a second coating, and the reactor coil may then be applied to the second coating as a third coating to form the coil. However, in at least some embodiments, the first insulating layer 330a may alternatively or additionally comprise a wrap that is applied to the outer diameter of the first insulating layer 330a, similar or identical to the wrap described with respect to FIGS. 1 A-3. However, in at least some embodiments, the second insulating layer 330b may alternatively or additionally be applied to the outer diameter of the first insulating layer 330a using a prefabricated clam-shell insulation held in place with a fastener, such as, but not limited to, banding straps. It should be understood that other second insulating layer 330b wraps made by other methods and applied to the outer diameter of the first insulating layer 330a are included in embodiments disclosed and described herein.

[0060] In conjunction with the embodiments and solutions previously stated, it may be contemplated to over-size the second (thermal) insulating layer 330b to theoretically minimize total heat loss to the environment from the system. However, as insulation thickness, and thereby surface area, increases, there theoretically comes a point at which heat loss to the second insulation layer exceeds any further minimization of heat loss to the environment to the system. Further as previously stated, footprint of the system and cost are also concerns in reactor design.

[0061] Accordingly, it may be desired to balance the thickness of the second insulating layer 330b such that heat loss to the environment is balanced with heat loss to the insulation itself. Such a thickness of the second insulating layer 330b may determined by calculating a ‘balanced’ insulation thickness and applying the balanced insulation thickness as the maximum thickness of the second insulating layer 330b. The balanced insulation thickness may be calculated by the following equation:85993-WO-PCT / DOW 85993 WO15where t is the thickness of the insulating layer in meters, k is the thermal conductivity of the material used in the second insulating layer 330b in W / m-K, and h is the expected maximum convective heat coefficient in W / m2'K of the outer surface of the dual layer insulating layer 330 (z. e. , the maximum convective heat coefficient of the outer surface of the second insulating layer 330b). As an example, for natural convective heat transfer conditions on the outside of the second insulating layer 330b, h equals 2 W / m2'K. Accordingly, assuming the thermal conductivity (k) of the second insulating layer 330b is 0.1 W / m-K, the balanced insulation thickness equals 0.05 m (5 cm). Accordingly, in this example, the thickness of the second insulating layer 330b would be set to 5 cm to balance heat loss with excess insulation application. In embodiments, the balanced insulation thickness may generally be in the range of 1 to 8 cm, such as from 1 to 2 cm, from 2 to 5 cm, from 5 to 8 cm, or combinations of the previous ranges or smaller ranges therein, such as from 1 to 5 cm. Without being limited by theory, the presence of the first insulating layer 330a may not impact the balanced insulation thickness calculation due at least to the greater thermal conductivity of the first insulating layer 330a as compared to the reactor coil 320.

[0062] In embodiments, steps may be taken to decrease the theoretical balanced insulation thickness of the second insulating layer 330b. In one exemplary embodiment, applying external forced convective cooling may increase the convective heat transfer coefficient h, thereby decreasing the balanced insulation thickness. For example, adding CO2 to the recirculating air in the enclosure 102 in amounts from 1 vol% to 50 vol%, such as from 10 vol% to 40 vol%, or from 20 vol% to 30 vol%, would increase the convective heat transfer coefficient h. This CO2 could be sourced from carbon captured from an onsite process to reduce the carbon footprint of the site. In addition, using insulation materials with a lower thermal conductivity k would decrease the balanced insulation thickness. As previously stated, using the balanced insulation thickness, a balance of material costs for the material comprising the second insulating layer 330b (z.e., increased material cost vs. decreased thickness) may be made when designing the insulating layer(s) 330. In addition, a balance between decreased thickness and the energy for forced convective cooling may be made when designing the insulating layer 330.

[0063] With reference now to FIG. 5, in embodiments, the thickness of the insulating layer 330 may vary along the length L of the reactor coil 320. As shown by the dashed lines in FIG. 5, which depict the outline of the reactor coil 320 within the insulating layer 330, the diameter of the reactor coil 320 is constant along the length L of the reactor coil 320. However, the thickness85993-WO-PCT / DOW 85993 WO16of the insulating layer 330 is greater at a first end of the reactor coil 502 than at a second end of the reactor coil 504. Embodiments where the thickness of the insulating layer 330 varies across the length L of the reactor coil 320 allows one to modify the amount of insulation according to the local heat flux in the reactor coil 320. For example, in a preheated zone, the feed stream is rapidly heated to the reaction temperature and, thus, the heat transfer from the inner diameter of the reactor coil 320 to the relatively cold feed stream is higher than the heat transfer in the reaction zone where the temperature of gases in the process stream are closer to the temperature. In areas of high heat flux (heat transfer) of the reactor coil 320, the thickness of the insulating layer 330 may be less thick than the insulating layer 330 in areas of low heat flux in the reactor coil 320. So, in FIG. 5 it follows that the heat flux at the second end of the reactor coil 504 is greater than the heat flux at the first end of the reactor coil 502 and, thus, the thickness of the insulating layer 330 is greater at the first end of the reactor coil 502 than the thickness of the insulating layer 330 at the second end of the reactor coil 504.

[0064] In the embodiment depicted in FIG. 5 the thickness of the insulating layer 330 varies uniformly along the length L of the reactor coil 320, as evidenced by the constant slope of the outer surface 506 of the insulating layer 330 along the length L of the reactor coil 320. However, it should be understood that in embodiments, the change in the thickness of the insulating layer 330 along the length L of the reactor coil 320 may not be uniform, and the thickness of the insulating layer 330 may be varied according to any heat flux profile within the reactor coil 320.

[0065] In embodiments where the insulating layer 330 comprises a first insulating layer 330a and a second insulating layer 330b, the first insulating layer 330a being an electrical insulating layer positioned next to the reactor coil 320 and the second insulating layer 330b being a thermal insulating layer positioned next to the first insulating layer 330a, the thickness of the first insulating layer 330a may be uniform along the length L of the reactor coil 320 and the thickness of the second insulating layer 330b may vary along the length of the reactor coil 320.

[0066] For example, and in embodiments, the thickness of the second insulating layer 330b may vary along the length of the reactor coil by at least 20% or by at least 50% from the thickest point of the second insulating layer 330b to the thinnest point of the second insulating layer 330b, such as by from 20 to 25%, from 25 to 30%, from 30 to 50%, from 50 to 75%, from 75 to 100%, or any combinations of the previous ranges or smaller ranges therein, such as varying from 20% to 100% from the thickest point of the second insulating layer 330b to the thinnest point of the second insulating layer 330b. Without being limited by theory, it may be85993-WO-PCT / DOW 85993 WO17advantageous for the thickness of the second insulating layer to decrease as a function of distance from the positive conductor 124, due at least to voltage loss across the length of the coil.

[0067] One or more embodiments disclosed herein is directed to an electrified reactor comprising: a reactor coil that is electrically connected to an electric power source; a first insulating layer that is electrically connected to the reactor coil; and a second insulating layer that is thermally connected to the first insulating layer, wherein the first insulating layer is an electric insulating layer, and the second insulating layer is a thermal insulating layer.

[0068] One or more embodiments disclosed herein is directed to an electrified reactor comprising: a reactor coil that is electrically connected to an electric power source; and an insulating layer that is electrically and thermally connected to the reactor coil, wherein the reactor coil comprises: a thermal conductivity measured at 1000 °C that is from 20 W / m-K to 40 W / m-K; and an electrical resistivity that is from 10'8Q-m to 10'4Q-m, and the insulating layer comprises: a thermal conductivity measured at 1000 °C that is from 0.5 W / m-K to 1.0 W / m-K; an electrical resistivity that is from 108Q-m to 1010Q-m, and a dielectric strength that is from 1.5 kV / mm to 2.5 kV / mm.EXAMPLES

[0069] Embodiments will be further clarified by the following non-limiting example.

[0070] A direct electric heated (EDH) furnace (as shown in FIG. 1A and FIG. IB) was simulated using a computational fluid dynamics (COD) model in Any’s Fluent v23.1. The DEH furnace consisted of two reactor coils, each having an inside diameter of 1.5 inches, a wall thickness of 0.25 inches, and total heated length of 65.6 ft. The coil metal had an electric resistivity of 1.2 pQ-m and thermal conductivity of 26 W / m-K. The furnace box has an internal dimension of 2 m x 2.5 m x 4.6 m (L x W x H) and 18 inch thick high temperature ceramic fiber insulation material (thermal conductivity = 0.3 W / m-K) attached to the furnace box casing. A total process flow consisting of 188 kg / hr ethane and 101 kg / hr of steam was fed to the two coils with an inlet temperature of 670 °C. Outside of the coils, a purge airflow with a flow rate of 100 kg / hr continuously flowed through the furnace box. The pair of coils were electrically energized with an electric potential difference of 58 V. The heat generated from DEH was 231 kW.85993-WO-PCT / DOW 85993 WO18

[0071] Two scenarios were analyzed using the CFD model. For the comparative example, both reactor coils were bare coils installed in the DEH furnace. For the example, the reactor coils were wrapped with two layers of insulation materials. The first insulating layer was positioned next to the reactor coil and was an electric insulating material that had a thickness of 0.5 inches, an electric resistivity of IO10Q-m, and a thermal conductivity of 150 W / m-K. The second insulating layer was positioned next to the first insulating layer and was 3 -inch thick thermal insulating material that had a thermal conductivity of 0.1 W / m-K.

[0072] Both the comparative example and the example were modeled using CFD. FIG. 6A shows the simulated outer surface temperature of the bare reactor coils for the comparative example and FIG. 6B shows the simulated outer surface temperature of the insulated reactor coils of the example (where the outer surface temperature represents the temperature of the insulation material outer surface wrapped around the reactor coils).

[0073] It can be seen that the dual-layer insulation material of the example greatly reduced the temperature of the outer surface (on the exterior surface of the coil vs. on the exterior surface of the insulation) of the tube assembly (from 915 °C down to 280 °C). The total heat loss was reduced from 42 kw (18%) down to 9 kw (4%). In this example, heat loss was reduced by 79%.

[0074] The singular forms “a,” “an” and “the” include plural referents, unless the context clearly dictates otherwise.

[0075] Throughout this disclosure ranges are provided. It is envisioned that each discrete value encompassed by the ranges are also included. Additionally, the ranges which may be formed by each discrete value encompassed by the explicitly disclosed ranges are equally envisioned.

[0076] As used in this disclosure and in the appended claims, the words “comprise,” “has,” and “include” and all grammatical variations thereof are each intended to have an open, nonlimiting meaning that does not exclude additional elements or steps.

[0077] As used in this disclosure, terms such as “first”, “second”, “third”, etc. are arbitrarily assigned and are merely intended to differentiate between two or more instances or components. It is to be understood that the words “first”, “second”, “third”, etc. serve no other purpose and are not part of the name or description of the component, nor do they necessarily define a relative location, position, or order of the component. Furthermore, it is to be understood that the mere use of the term “first”, “second”, or “third” does not require that there be any “fourth” component, although that possibility is contemplated under the scope of the present disclosure.85993-WO-PCT / DOW 85993 WO19

[0078] For the purposes of describing and defining the present embodiments it is noted that the terms “substantially” and “approximately” are utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The terms “substantially” and “approximately” are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

[0079] Having described the subject matter of the present disclosure in detail and by reference to specific embodiments, it is noted that the various details disclosed in the present disclosure should not be taken to imply that these details relate to elements that are essential components of the various embodiments described in the present disclosure. Further, it will be apparent that modifications and variations are possible without departing from the spirit and scope of the present disclosure, including, but not limited to, embodiments defined in the appended claims. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.

Claims

85993-WO-PCT / DOW 85993 WO20CLAIMS1. An electrified reactor comprising:a reactor coil that is electrically connected to an electric power source;a first insulating layer that is electrically connected to the reactor coil; anda second insulating layer that is thermally connected to the first insulating layer, wherein the first insulating layer is an electric insulating layer, andthe second insulating layer is a thermal insulating layer.2 The electrified reactor of claim 1, wherein:the first insulating layer has a thermal conductivity that is at least 5 times greater than a thermal conductivity of the reactor coil; andthe second insulating layer has a thermal conductivity that is at least 10 times less than the thermal conductivity of the reactor coil.3 The electrified reactor of claim 1 or 2, wherein the reactor coil comprises:a thermal conductivity measured at 1000 °C that is from 10 W / m-K to 40 W / m-K; and an electrical resistivity that is from 10'8-m to 10'4-m.4 The electrified reactor of any one of claims 1 to 3, wherein the first insulating layer comprises:a thermal conductivity measured at 1000 °C that is greater than 50 W / m-K;an electrical resistivity that is greater than 106-m; anda dielectric strength that is greater than 50 kV / mm.5 The electrified reactor of any one of claims 1 to 4, wherein the second insulating layer comprises:athermal conductivity measured at 1000 °C of less than 1.0 W / m-K;an electrical resistivity that is greater than 102-m; anda dielectric strength that is greater than 50 kV / mm.6 The electrified reactor of any one of claims 1 to 5, wherein the first insulating layer is a coating.85993-WO-PCT / DOW 85993 WO217. The electrified reactor of any one of claims 1 to 6, wherein the second insulating layer is a material that is wrapped around the first insulating layer.

8. The electrified reactor of any one of claims 1 to 7, wherein: a maximum thickness of the ksecond insulating layer satisfies the equation td=where ta is the thickness of the second insulating layer in meters, k is the thermal conductivity of the material of the second insulating layer in W / m-K, and h is the expected maximum convective heat coefficient in W / m2'K of the outer surface of the second insulating layer.9 The electrified reactor of any one of claims 1 to 8, wherein a thickness of the second insulating layer varies along a length of the reactor coil.10 The electrified reactor of any one of claims 1 to 9, wherein:the first insulating layer is in physical contact with at least a portion of the reactor coil, andthe second insulating layer is in physical contact with at least a portion of the first insulating layer.11 An electrified reactor comprising:a reactor coil that is electrically connected to an electric power source; andan insulating layer that is electrically and thermally connected to the reactor coil, wherein:the reactor coil comprises a thermal conductivity measured at 1000 °C that is greater than 10 W / m-K and an electrical resistivity that is from 10'8Q-m to 10'4-m, andthe insulating layer comprises a thermal conductivity measured at 1000 °C that is less than 1 W / m-K, an electrical resistivity that is greater than 106-m, and a dielectric strength that is greater than 50 kv / mm.12 The electrified reactor of claim 11, wherein at least a portion of the insulating layer is physical contact with at least a portion of the reactor coil.85993-WO-PCT / DOW 85993 WO2213. The electrified reactor of claim 11 or 12, wherein the insulating layer is a material that is wrapped around the reactor coil.

14. The electrified reactor of claim 11 or 12, wherein the insulating layer is a coating formed on the reactor coil.

15. The electrified reactor of any one of claims 11 to 14, wherein a thickness of the insulating layer varies along a length of the reactor coil.

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