EP4599024A1

EP4599024A1 - Processes for pyrolyzing hydracarbons with an electrified cracking furnace

Info

Publication number: EP4599024A1
Application number: EP22843366.0A
Authority: EP
Inventors: Sean Graeme GAAL; Deepak Kumar; Govert Gerardus Pieter Van Der Ploeg; Georgios Bellos
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2022-12-29
Filing date: 2022-12-29
Publication date: 2025-08-13
Also published as: WO2024141766A1

Abstract

A process for pyrolyzing hydrocarbons includes removing oxidizing gases from an atmosphere of an enclosure environment and providing electrical current to resistance heating elements to heat the reaction tubes to a desired temperature. The electrical current is provided to the resistance heating elements after the oxidizing gases are removed from the atmosphere of the enclosure environment. A feed stream having the hydrocarbons is introduced into reaction tubes that are positioned in the enclosure environment. The feed stream within the reaction tubes is heated to a reaction temperature, thereby pyrolyzing the hydrocarbons in the feed stream, and pyrolyzed hydrocarbons are extracted from the enclosure environment in a product stream. The resistance heating elements are made from a high-temperature material.

Description

PROCESSES FOR PYROLYZING HYDROCARBONS WITH AN ELECTRIFIED CRACKING FURNACE

BACKGROUND

Field

[0001] The present specification generally relates to processes for pyrolyzing hydrocarbons and, more specifically, to processes for pyrolyzing hydrocarbons using an electrified steam cracking furnace.

Technical Background

[0002] Hydrocarbon processing, such as steam cracking, accounted for 200 Mt of emitted carbon dioxide in 2000, which represents a significant fraction of the global anthropogenic emissions of 33.4 Gt carbon dioxide per year in 2019. Accordingly, processes and systems that reduce the carbon dioxide emissions during hydrocarbon processing, such as steam cracking, could have a substantial impact on global carbon dioxide production.

[0003] Electrification is one technology that reduces direct carbon dioxide emissions to zero for hydrocarbon processing. One of the electrification technologies for ethylene furnaces can be described by the implementation of electrically heated elements mounted on the walls of the furnace radiant box. The heating elements are electrically conductive and radiate heat to the process coils.

[0004] There are many materials that can be pyrolyzed with this invention, such as syngas rearrangement, adsorbent regeneration or many other chemical processes.

SUMMARY

[0005] According to one embodiment, a process for pyrolyzing hydrocarbons, comprises: removing oxidizing gases from an atmosphere of an enclosure environment; providing electrical current to resistance heating elements to heat the reaction tubes predominantly by radiation to a desired temperature, wherein the electrical current is provided to the resistance heating elements after the oxidizing gases are removed from the atmosphere of the enclosure environment; introducing a feed stream comprising the hydrocarbons into reaction tubes, wherein the reaction tubes are positioned in the enclosure environment; heating the feed stream

I within the reaction tubes to a reaction temperature, thereby pyrolyzing the hydrocarbons in the feed stream; and extracting pyrolyzed hydrocarbons from the enclosure environment in a product stream, wherein the resistance heating elements are made from a high-temperature materials.

[0006] In embodiments, the least one resistance heating element is made from graphite, carbon fiber, carbon, tungsten, molybdenum, rhenium, tantalum, zirconia, molybdenum disilicide, molybdenum disilicide composites, and zirconium diboride-silicon carbide composite.

[0007] In embodiments, oxygen, carbon dioxide and water molecules are removed from the atmosphere of the enclosure environment by positioning an appropriate oxygen, carbon dioxide, or water getter within the enclosure environment. An oxygen, carbon dioxide, or water getter is a sacrificial material, such as graphite or another material that when heated reacts with oxygen to form an oxide that will no longer react with the heating element. The sacrificial material can be made from a variety of materials, including the same material used for the heating element. In embodiments, the oxygen, carbon dioxide, or water getter can be easily replaced and protects the main heating elements.

[0008] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0009] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a graph showing the partial pressure of oxygen versus temperature for SiC; [0011] FIG. 2 is a graph showing the ratio of the surface of resistance heating elements to the surface of reaction tubes (surface ratio) versus temperature of the resistance heating element; and

[0012] FIG. 3 schematically depicts an enclosure environment with an oxygen, carbon dioxide, or water getter positioned within the enclosure environment according to embodiments disclosed and described herein.

DETAILED DESCRIPTION

[0013] Reference will now be made in detail to embodiments of processes for pyrolyzing hydrocarbons with an electrified cracking furnace. In one embodiment, a process for pyrolyzing hydrocarbons comprises: removing oxidizing gases (oxygen, carbon dioxide, or water) from an atmosphere of an enclosure environment; providing an electrical current to resistance heating elements to heat the reaction tubes predominantly by radiation to a desired temperature, wherein the electrical current is provided to the resistance heating elements after the oxidizing gases (oxygen, carbon dioxide, and water) are removed from the atmosphere of the enclosure environment; introducing a feed stream comprising the hydrocarbons into the reaction tubes, wherein the reaction tubes are positioned in the enclosure environment; heating the feed stream within the reaction tubes to a reaction temperature, thereby pyrolyzing the hydrocarbons in the feed stream; and extracting pyrolyzed hydrocarbons from the enclosure environment in a product stream, wherein the resistance heating elements are made from a carbon-based material.

[0014] In electrified cracking furnaces proposed elsewhere, heating elements are made from silicon carbide (SiC). However, heating elements made from SiC are limited by the maximum surface temperature and, thus, the heat flux they can radiate. SiC cannot operate at temperatures higher than 1400 °C, and preferably operating at temperatures less than 1350 °C, because the SiC will degrade rapidly due to active corrosion (fast corrosion rate) where volatile SiO(g) is formed instead of a passive, protective silica SiCh external film. This thermodynamic equilibrium is presented in FIG. 1 , which illustrates 10 studies investigating the thermodynamic equilibrium of SiC. The temperature is provided along the x-axis and the partial pressure of oxygen is provided along the y-axis. As shown in FIG. 1 , SiO(g) is formed at high temperatures, such as above 1400 °C in air or at lower temperatures when the partial pressure of oxygen is reduced. [0015] According to the above, when using SiC heating elements, the temperature of the heating elements should be limited to 1400 °C or below. However, limiting the heating element temperature to 1400 °C, such as below 1350 °C would require using a large surface area of electrically heated elements — which requires a large number of heating elements — to radiate desired heat to the radiant coils of a cracking furnace. The conventional technology has an average (coil-length wise) heat flux of up to 85 kW/m² (OD) of coil surface while the outer surface of the tubes reach a maximum temperature of 1100 °C. Based on the Stefan-Boltzmann law, the surface area of the heating elements should be 47% of the radiant coils external area to transfer 85 kW/m² when the heating elements are heated to 1400 °C. Accordingly, electrical heating elements that can perform at higher temperatures are desired.

[0016] One material that could be used in place of SiC in electrical heating elements is graphite. Graphite can be heated to at least 2400 °C before significant degradation under nitrogen or hydrogen atmospheres, or under a vacuum. This increase in temperature (z. e. , approximately 1000 °C compared to SiC) significantly increases the available heat flux and maximum tube temperature. Graphite is used in high temperature systems, such as in the Czochralski furnace methods (which are used to produce single crystal solar cells, silicon wafers for electronics and sapphire for LED) and the Bridgeman furnace methods (which produce multi-crystalline solar cells). Based on the Stefan-Boltzmann law for radiation, the surface area of heating elements could be equal to 4% of the radiant coils external area to transfer 85 kW/m² at 2400 °C. A sensitivity analysis is illustrated in FIG. 2, where the heating element’s temperature is compared with the surface area ratio between the heating elements and the coils. The surface area ratio is a ratio of the surface area of the heating elements (facing the radiant coils) to the external surface area of the coils. As shown in FIG. 2, as the temperature of the heating elements increases the required surface area ratio decreases from nearly 100% to below 10%, which shows that at higher temperatures, less heating element surface area (and less heating elements) is required. This significantly reduces the number and complexity of heating elements required, while allowing for even larger heat fluxes if required.

[0017] Even though graphite heating elements may be used in some high-temperature processes, they have not been used in hydrocarbon pyrolyzing because of the nature of the hydrocarbon pyrolyzing process. For instance, furnaces with graphite heating elements need a controlled atmosphere and are conventionally run in a vacuum or inert atmosphere, whereas conventional hydrocarbon pyrolyzing is done in furnaces with a natural draught of air through the furnace. In addition, and in part because of the precise control mentioned above, furnaces heated with graphite heating elements are generally smaller and are capable of up to 500 kW, whereas hydrocarbon pyrolyzing may require from 10 to 200 MW and will require multiple heating elements. Thus, processes and systems that allow graphite and similar materials to be used as heating elements in processes for hydrocarbon pyrolyzing are desired.

[0018] As noted above, furnaces with graphite heating elements need a controlled atmosphere and, thus, are not used in hydrocarbon pyrolyzing processes. This is because graphite is very combustible at high temperatures in the presence of oxidizing gases (such as oxygen, carbon dioxide, and water). Accordingly, graphite heating elements will be quickly oxidized and destroyed in a furnace in the presence of oxidizing gases. Typical hydrocarbon pyrolyzing furnaces are run with natural draught and purposefully allow fresh air into the radiant box. For instance, ethylene furnaces typically run with 10% to 20% excess air, which introduces a significant amount of oxygen into the radiant box. Accordingly, if graphite heating elements were used in a typical ethylene pyrolyzing furnace and process, the continuous addition of air would combust the graphite and destroy the heating elements. Graphite is known to oxidize in air at temperatures above 500 °C, which are significantly below the operating temperatures of a hydrocarbon pyrolyzing furnace. Therefore, the implementation of graphite elements in hydrocarbon pyrolyzing furnaces is a challenge and not previously contemplated.

[0019] In view of the above, embodiments of processes for pyrolyzing hydrocarbons according to embodiments disclosed and described herein remove oxidizing gases (O2, carbon dioxide, and water) from the atmosphere of the enclosure environment that is to be heated with resistance heating elements before an electrical current is applied to the resistance heating elements. Providing an electrical current to the resistance heating elements heats the resistance heating elements and thereby heats the components within the enclosure environment to a desired temperature. However, heating the resistance heating elements in the presence of oxygen can cause combustion and/or oxidation of the resistance heating element.

[0020] Embodiments of processes for pyrolyzing hydrocarbons according to embodiments disclosed and described herein will now be described with reference to FIG. 3. FIG. 3 is a cross-section of an enclosure environment used in processes for pyrolyzing hydrocarbons according to embodiments disclosed and described herein. The enclosure environment 300 houses reaction tubes 310 and resistance heating elements 320. The resistance heating elements 320 are generally positioned adjacent to the reaction tubes 310 so that the reaction tubes can be heated without creating hot spots or cool spots within the reaction tubes 310. It should be understood that the geometry of the reaction tubes 310 and the resistance heating elements 320 shown in FIG. 3 are illustrative only and, in embodiments, the geometry of the reaction tubes 310 and the resistance heating elements 320 can be different from the geometry shown in FIG. 3.

[0021] The reaction tubes 310 may be made from any suitable material such as, for example, copper, Fe-Cr and Fe-Cr-Al family of steels, nickel alloys. It should also be understood that the inner and outer diameter of the reaction tubes 310 may vary according to operating conditions and the desired temperature uniformity and pressure within the reaction tubes 310. Flowever, the inner and outer diameters of the reaction tubes 310 are not particularly limited in embodiments disclosed and described herein.

[0022] As mentioned hereinabove, the resistance heating elements 320 are made from materials that can operate at temperatures greater than 1200 °C, such as greater than 1250 °C, greater than 1300 °C, greater than 1350 °C, greater than 1400 °C, greater than 1450 °C, greater than 1500 °C, greater than 1550 °C, greater than 1600 °C, greater than 1650 °C, greater than 1700 °C, greater than 1750 °C, greater than 1800 °C, greater than 1850 °C, greater than

1900 °C, greater than 1950 °C, greater than 2000 °C, greater than 2050 °C, greater than

2100 °C, greater than 2150 °C, greater than 2200 °C, greater than 2250 °C, greater than

2300 °C, greater than 2350 °C, or greater than 2400 °C. Such materials are referred to herein as “high-temperature materials.” High temperature materials have the property that they do not melt, decompose, or otherwise degrade at the temperatures mentioned. Graphite was discussed above as a resistance heating element material; however, other materials that are conductive and are thermally stable could be used to form resistance heating elements 320. Accordingly, in embodiments, the resistance heating elements may be made from graphite, carbon, carbon fiber, platinum, zirconium, chromium, vanadium, rhodium, iridium, niobium, molybdenum, tantalum, rhenium, tungsten, zirconia, molybdenum disilicide, molybdenum disilicide composites, and zirconium diboride-silicon carbide composite.

[0023] According to embodiments disclosed and described herein, a first step in the process for pyrolyzing hydrocarbons is to remove oxidizing gases (oxygen, carbon dioxide, and water) from the atmosphere of the enclosure environment 300. Although it is desirable to remove all the oxidizing gases (O2, carbon dioxide, and water) from the atmosphere of the enclosure environment 300, this can be difficult to achieve. Accordingly, in embodiments, oxidizing gases (O2, carbon dioxide, and water) are removed from the atmosphere of the enclosure environment 300 such that after removing oxidizing gases from the atmosphere of the enclosure environment 300, the atmosphere of the enclosure environment comprises less than 10 parts per million (ppm), such as less than 9 ppm, less than 8 ppm, less than 7 ppm, less than 5 ppm, less than 4 ppm, less than 3 ppm, less than 2 ppm, or less than 1 ppm.

[0024] In embodiments, oxidizing gases (O2, carbon dioxide, and water) may be removed from the enclosure environment 300 by purging the enclosure environment 300 with an inert gas before an electrical current is provided to the resistance heating elements 320. Purging the enclosure environment 300 with an inert gas can be conducted by methods known in the art. In embodiments, and with reference again to FIG. 3, the inert gases may be introduced into the enclosure environment 300 via an inert gas inlet 330. Inert gases used in embodiments include, but are not limited to, nitrogen, carbon monoxide, helium, neon, argon, xenon, and radon. By purging oxygen from the enclosure environment 300 before providing electrical current to the resistance heating elements 320, there is little to no oxidizing gases (O2, carbon dioxide, and water) within the enclosure environment when the resistance heating elements 320 are heated and, thus, the possibility of combustion and/or oxidation of the resistance heating elements 320 is reduced.

[0025] In addition to, or as an alternative of, removing oxygen from the enclosure environment 300 by purge gas , oxygen can be removed from the enclosure environment 300 using an oxygen, carbon dioxide, or water getter 340. As used herein, an “oxygen, carbon dioxide, or water getter” refers to a sacrificial material that oxidizes or reacts with these gases at temperatures and pressures suitable for the enclosure 300, reaction coils 310 and heating elements 320. In embodiments, a sacrificial piece of the material may be used as a getter 340 by placing the sacrificial piece of material into fluid contact with the atmospheric gas of the enclosure environment 300. The sacrificial piece of material is then heated to initiate combustion and/or oxidation of the sacrificial piece of material thereby removing oxygen, carbon dioxide or water from the atmospheric gas of the enclosure environment 300.

[0026] In embodiments, the oxygen, carbon dioxide, or water getter 340 may be made from the same material as the resistance heating elements. For instance, the getter 340 may be made from but is not limited to, one of magnesium, aluminum, titanium, copper, rare earth elements (Ce, La), carbon fiber composite, carbon or graphite. In embodiments, the getter 340 is made from graphite. The amount of getter material that should be used may be determined based on the volume of the enclosure environment 300, the amount of oxidizing gases in the atmospheric gas of the enclosure environment 300, and the amount of combustible or oxidizable material in the getter material. For instance, based on published dimensions of a conventional ethylene pyrolyzing furnace, the internal gas volume of an enclosure environment can be about 145 m³, of which 20.9 vol% will be oxygen. Meaning that the enclosure environment comprises about 30 m³ oxygen at 25 °C, which converts to 1237 kmol of oxygen. Assuming combustion of carbon with the oxygen, carbon dioxide, and water in the air to produce carbon monoxide and hydrogen, 14.8 kg of carbon would consume all of the oxygen containing gases in the enclosure environment 300 and then allow the enclosure environment 300 to be heated to the desired temperature by resistance heating elements 320 without significant risk of combustion and/or oxidation of the resistance heating elements 320. The oxygen content of the chamber can be calculated from the Gibb’s free energy, or more conveniently from an Ellingham Diagram from which it is readily determined that the equilibrium oxygen content in the furnace chamber will be less than 1 x 10'¹⁶ atmospheres. An example is available here; https://web.mit.edn/2.813/www/readings/Ellingham_diagrams.pdf

[0027] As noted above, in embodiments, the oxygen, carbon dioxide, or water getter is used to remove oxygen containing gas from the enclosure environment before the resistance heating elements are heated, thereby removing oxygen from the enclosure environment. In embodiments, and with reference still to FIG. 3, the oxygen, carbon dioxide, or water getter 340 may be positioned within the enclosure environment 300. In the embodiment depicted in FIG. 3, the oxygen, carbon dioxide, or water getter 340 is positioned at the bottom of the enclosure environment 300. However, in embodiments, the oxygen, carbon dioxide, or water getter 340 may be positioned anywhere within the enclosure environment 300. In embodiments, an oxygen, carbon dioxide, or water getter 341 may be positioned at an inlet 351 where atmospheric gases are introduced into the enclosure environment 300 in addition to the oxygen, carbon dioxide, or water getter 340 positioned within the enclosure environment 300. This will allow the oxygen, carbon dioxide, or water getter 341 to remove oxygen from gases introduced into the enclosure environment 300 through the inlet 351. The gas is then able to leave through the gas outlet 360, purging gas from the enclosure 300.

[0028] As mentioned above, the oxygen, carbon dioxide, or water getter 340 may combust and/or oxidize to remove oxygen containing gas from the atmosphere of the enclosure environment 300. To achieve this combustion and/or oxidation, the oxygen, carbon dioxide, or water getter 340 is heated to a temperature where the oxygen, carbon dioxide, or water getter will combust and/or oxidize. The oxygen, carbon dioxide, or water getter can be heated by any suitable mechanism; however, it is not desirable to heat the atmosphere in the rest of the enclosure environment 300 to a temperature where the oxygen, carbon dioxide, or water getter 340 will combust and/or oxidize because this could cause unintentional combustion and/or oxidation of the resistance heating elements 320. Accordingly, in embodiments, the oxygen, carbon dioxide, or water getter 340 or 341 is connected to a source of electrical current, and the electrical current is provided to the oxygen, carbon dioxide, or water getter 340 or 341 to heat the oxygen, carbon dioxide, or water getter 340 or 341 before electrical current is provided to the resistance heating elements 320. In this way, the oxygen, carbon dioxide, or water getter 340 or 341 may be heated locally and cause combustion and/or oxidation of the oxygen, carbon dioxide, or water getter 340 or 341 without heating the atmosphere of the enclosure environment 300 to temperatures where the resistance heating elements 320 will also combust and/or oxidize.

[0029] According to embodiments, electrical current is provided to the resistance heating elements 320 after oxygen is removed from the atmosphere of the enclosure environment 300. Providing electrical current to the resistance heating elements 320 causes the temperature of the resistance heating elements 320 to increase and thereby increases the temperature of the components in the enclosure environment 300. As mentioned above, the resistance heating elements 320 may, according to embodiments, be heated to temperatures of greater than 1200 °C, such as greater than 1250 °C, greater than 1300 °C, greater than 1350 °C, greater than 1400 °C, greater than 1450 °C, greater than 1500 °C, greater than 1550 °C, greater than 1600 °C, greater than 1650 °C, or greater than 1700 °C. In embodiments, the resistance heating elements may be heated to temperatures that are from 1200 °C to 3000 °C, such as from 1250 °C to 1750 °C, from 1300 °C to 1700 °C, from 1350 °C to 1650 °C, from 1400 °C to 2000 °C, or from 1400 °C to 2400 °C.

[0030] Because the resistance heating elements 320 are heated via electrical current, various resistance heating elements 320 may be heated to different temperatures by adjusting the amount of current provided to the various resistance heating elements 320. For instance, and with reference again to FIG. 3, resistance heating elements 320a near the inlet 311 of the reaction tubes 310 may be heated to a different temperature than resistance heating elements 320b near the outlet 312 of the reaction tubes 310 by providing a different amount of current to the resistance heating elements 320a than the current provided to resistance heating elements 320b. This can be repeated with any of the resistance heating elements 320 and allows precision heating of various portions of the reaction tubes 310. Moreover, the electrical current provided to any of the resistance heating elements 320 may be modified in-process to allow in-process, real-time adjustment of the temperatures of the resistance heating elements 320. This can provide more control over the heating of the reaction tubes 310 and be used to prevent hot spots or cold spots within the reaction tubes 310.

[0031] A feed stream may be introduced into the reaction tubes 310 via the reaction tube inlet 311. The feed stream may be introduced into the reaction tubes 310 at any time during; however, in embodiments, the feed stream is introduced into the reaction tubes 310 after the electrical current is provided to the resistance heating elements 320. In one or more embodiments, the feed stream may be introduced into the reaction tubes 310 after the electrical current has been provided to the resistance heating elements 320 and after the reaction tubes 310 have had enough time to be heated by the resistance heating elements 320. In embodiments, the feed stream comprises hydrocarbons that are to be pyrolyzed by processes according to embodiments disclosed and described herein. The feed stream is not particularly limited — provided that it comprises hydrocarbons to be pyro lyzed — and in embodiments, the feed stream comprises for example ethane, propane, butane, naphtha, natural gas condensates, shale gas derivatives, shale oil, renewable hydrocarbons, circular hydrocarbons, or syngas derivatives.

[0032] As the feed stream traverses the reaction tubes 310 from the inlet 311 of the reaction tubes 310 to the outlet 312 of the reaction tubes 310, the feed stream is heated to a reaction temperature and the hydrocarbons within the feed stream are pyro lyzed. The flow of the feed stream through the reaction tubes 310 may be modified based upon the diameter of the reaction tubes 310, the temperature within the enclosure environment, and the amount of pyrolyzing that is desired.

[0033] In embodiments, the reaction tubes 310 are heated by the resistance heating elements 320 to temperatures from 700 °C to 1150 °C, such as from 925 °C to 1100 °C, from 950 °C to 1100 °C, from 975 °C to 1100 °C, from 1000 °C to 1100 °C, from 1025 °C to 1100 °C, from 1050 °C to 1100 °C, from 1075 °C to 1100 °C, from 900 °C to 1075 °C, from 925 °C to 1075 °C, from 950 °C to 1075 °C, from 975 °C to 1075 °C, from 1000 °C to 1075 °C, from 1025 °C to 1075 °C, from 1050 °C to 1075 °C, from 900 °C to 1050 °C, from 925 °C to 1050 °C, from 950 °C to 1050 °C, from 975 °C to 1050 °C, from 1000 °C to 1050 °C, from 1025 °C to 1050 °C, from 900 °C to 1025 °C, from 925 °C to 1025 °C, from 950 °C to 1025 °C, from 975 °C to 1025 °C, from 1000 °C to 1025 °C, from 900 °C to 1000 °C, from 925 °C to 1000 °C, from 950 °C to 1000 °C, from 975 °C to 1000 °C, from 900 °C to 975 °C, from 925 °C to 975 °C, from 950 °C to 975 °C, from 900 °C to 950 °C, from 925 °C to 950 °C, or from 900 °C to 925 °C.

[0034] As mentioned above, the hydrocarbons in the feed stream to be pyrolyzed traverses along the reaction tubes 310. The pyrolyzed hydrocarbons are then extracted as a product stream from the enclosure environment at the outlet 312 of the reaction tubes 310. According to embodiments, the product stream comprises, but is not limited to, olefins, methane, hydrogen, benzene, toluene, and xylene. In embodiments, the olefins comprise C2 to C3 olefins. And, in one or more embodiments, the olefins comprise ethylene. In embodiments, the typical product stream comprises from 20 wt% to 60 wt% ethylene, such as from 15 wt% to 55 wt% ethylene, from 20 wt% to 50 wt% ethylene, or from 25 wt% to 45 wt% ethylene.

[0035] To maintain this atmosphere (z.e., an atmosphere with little to no oxygen) in the enclosure environment 300 after the oxygen, carbon dioxide, or water getter 340 has been used to remove oxygen containing gas from the enclosure environment 300, or after the enclosure environment 300 has been purged with inert gas, a small flowrate of an inert gas, such as nitrogen, etc., may be introduced into the enclosure environment 300 such as via inert gas inlet 330. Without limitation, for a typical ethylene pyrolyzing furnace, about 1 to 1000 liters/min of inert gas would be more than sufficient to maintain a slight positive pressure and exclude ingress of air to the enclosure environment. Thus, in embodiments, an inert gas is introduced into the enclosure environment after electrical current is provided to the resistance heating elements. This positive pressure can also be achieved with a device to maintain a positive pressure, such as a backflow regulator or a control valve. The positive pressure may, in embodiments, be from 0.1 psig to 14.7 psig, or from 0.1 psig to 5.0 psig.

[0036] Reaction tube rupture in hydrocarbon pyrolyzing furnaces can occur. In conventional hydrocarbon pyrolyzing furnaces, such a rupture will release hydrocarbons in an oxygen rich atmosphere. This is a major risk, especially for electrified furnaces where there is no open connection with the atmosphere. The low oxygen atmosphere of embodiments disclosed and described herein will reduce the chance of combustion of hydrocarbons released from the reaction tubes in the event of reaction gases escaping. Therefore, vent handling through outlet 360 is an important aspect to consider for all designs to direct any gas leakage from the coils safely away from the process. The design should take into account potential air ingress into the box and the rate of resistance heating element combustion, the level of engineering to protect the resistance heating elements should reflect the required lifetime of the resistance heating element. Resistance heating elements are able to operate at these temperatures and a high heat flux for many years in the absence of oxygen. Also, by activating the oxygen getter before introducing hydrocarbons into the reaction tubes, the process according to embodiments is intrinsically safer.

[0037] A first aspect includes a process for pyrolyzing hydrocarbons, comprising: removing oxidizing gases from an atmosphere of an enclosure environment; providing electrical current to resistance heating elements to heat the reaction tubes to a desired temperature, wherein the electrical current is provided to the resistance heating elements after the oxidizing gases are removed from the atmosphere of the enclosure environment; introducing a feed stream comprising the hydrocarbons into reaction tubes, wherein the reaction tubes are positioned in the enclosure environment heating the feed stream within the reaction tubes to a reaction temperature, thereby pyrolyzing the hydrocarbons in the feed stream; and extracting pyrolyzed hydrocarbons from the enclosure environment in a product stream, wherein the resistance heating elements are made from a high-temperature material or materials.

[0038] A second aspect includes the process for pyro lyzing hydrocarbons according to the first aspect, wherein at least one resistance heating element is made from graphite, carbon, carbon fiber, platinum, zirconium, chromium, vanadium, rhodium, iridium, niobium, molybdenum, tantalum, rhenium, tungsten, zirconia, molybdenum disilicide, molybdenum disilicide composites, and zirconium diboride-silicon carbide composite.

[0039] A third aspect includes the process for pyrolyzing hydrocarbons according to any one of the first or second aspects, wherein the oxidizing gases are removed from the atmosphere of the enclosure environment by purging oxidizing gases from the atmosphere in the enclosure environment with an inert gas.

[0040] A fourth aspect includes the process for pyrolyzing hydrocarbons according to any one of the first to third aspects, wherein oxygen is removed from the atmosphere of the enclosure environment by positioning an oxygen, carbon dioxide, or water getter within the enclosure environment. [0041] A fifth aspect includes the process for pyrolyzing hydrocarbons according to the fourth aspect, wherein oxygen is removed from the atmosphere of the enclosure environment by positioning an oxygen, carbon dioxide, or water getter at an inlet where atmospheric gasses are introduced into the enclosure environment.

[0042] A sixth aspect includes the process for pyrolyzing hydrocarbons according to any one of the fourth or fifth aspects, wherein the oxygen, carbon dioxide, or water getter is comprised of the same material as the resistance heating elements.

[0043] A seventh aspect includes the process for pyrolyzing hydrocarbons according to any one of the fourth to sixth aspects, wherein the oxygen, carbon dioxide, or water getter is comprised of graphite or carbon.

[0044] An eighth aspect includes the process for pyrolyzing hydrocarbons according to any one of the fourth to seventh aspects, wherein an electrical current is provided to the oxygen, carbon dioxide, or water getter to heat the oxygen, carbon dioxide, or water getter before the electrical current is provided to the resistance heating elements.

[0045] A ninth aspect includes the process for pyrolyzing hydrocarbons according to any one of the first to eighth aspects, wherein the process further comprises introducing an inert gas into the enclosure environment after the electrical current is provided to the resistance heating elements.

[0046] A tenth aspect includes the process for pyrolyzing hydrocarbons according to any one of the first to ninth aspects, wherein the product stream comprises at least one of olefins, methane, hydrogen, benzene, toluene, or xylene.

[0047] An eleventh aspect includes the process for pyrolyzing hydrocarbons according to the tenth aspect, wherein the olefins comprise C2 to C3 olefins.

[0048] A twelfth aspect includes the process for pyrolyzing hydrocarbons according to any one of the tenth or eleventh aspects, wherein the olefins comprise ethylene.

[0049] A thirteenth aspect includes the process for pyrolyzing hydrocarbons according to any one of the first to twelfth aspects, wherein the feed stream comprises at least one of ethane, propane, butane, naphtha, natural gas condensates, shale gas or shale oil. [0050] A fourteenth aspect includes the process for pyrolyzing hydrocarbons according to any one of the first to thirteenth aspects, wherein the reaction tubes are heated to a temperature that is from 700 °C to 1 150 °C.

[0051] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. 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

What is claimed is:

1. A process for pyrolyzing hydrocarbons, comprising: removing oxidizing gases from an atmosphere of an enclosure environment; providing electrical current to resistance heating elements to heat the reaction tubes to a desired temperature, wherein the electrical current is provided to the resistance heating elements after the oxidizing gases are removed from the atmosphere of the enclosure environment; introducing a feed stream comprising the hydrocarbons into reaction tubes, wherein the reaction tubes are positioned in the enclosure environment; heating the feed stream within the reaction tubes to a reaction temperature, thereby pyrolyzing the hydrocarbons in the feed stream; and extracting pyrolyzed hydrocarbons from the enclosure environment in a product stream, wherein the resistance heating elements are made from a high-temperature materials.

2. The process for pyrolyzing hydrocarbons according to claim 1, wherein at least one resistance heating element is made from graphite, carbon, carbon fiber, platinum, zirconium, chromium, vanadium, rhodium, iridium, niobium, molybdenum, tantalum, rhenium, tungsten, zirconia, molybdenum disilicide, molybdenum disilicide composites, and zirconium diboride-silicon carbide composite.

3. The process for pyrolyzing hydrocarbons according to any one of claims 1 or 2, wherein the oxidizing gases are removed from the atmosphere of the enclosure environment by purging oxidizing gases from the atmosphere in the enclosure environment with an inert gas.

4. The process for pyrolyzing hydrocarbons according to any one of claims 1 to 3, wherein oxygen is removed from the atmosphere of the enclosure environment by positioning an oxygen, carbon dioxide, or water getter within the enclosure environment.

5. The process for pyrolyzing hydrocarbons according claim 5, wherein oxygen is removed from the atmosphere of the enclosure environment by positioning an oxygen, carbon dioxide or water getter at an inlet where atmospheric gasses are introduced into the enclosure environment.

6. The process for pyrolyzing hydrocarbons according to any one of claims 4 or 5, wherein the oxygen, carbon dioxide, or water getter is comprised of the same material as the resistance heating elements.

7. The process for pyrolyzing hydrocarbons according to any one of claims 4 to 6, wherein the oxygen, carbon dioxide, or water getter is comprised of graphite or carbon.

8. The process for pyro lyzing hydrocarbons according to any one of claims 4 to 7, wherein an electrical current is provided to the oxygen, carbon dioxide, or water getter to heat the oxygen, carbon dioxide, or water getter before the electrical current is provided to the resistance heating elements.

9. The process for pyrolyzing hydrocarbons according to any one of claims 1 to 8, wherein the process further comprises introducing an inert gas into the enclosure environment.

10. The process for pyrolyzing hydrocarbons according to any one of claims 1 to 9, wherein the product stream comprises at least one of olefins, methane, hydrogen, benzene, toluene, and xylene.

11. The process for pyrolyzing hydrocarbons according to claim 10, wherein the olefins comprise C2 to C3 olefins.

12. The process for pyrolyzing hydrocarbons according to any one of claims 10 or

11, wherein theolefins comprise ethylene.

13. The process for pyrolyzing hydrocarbons according to any one of claims 1 to

12, wherein the feed stream comprises at least one of ethane, propane, butane, naphtha, natural gas condensates, shale gas, shale oil, renewable, or circular hydrocarbons.

14. The process for pyrolyzing hydrocarbons according to any one of claims 1 to

13, wherein the reaction tubes are heated to a temperature that is from 700 °C to 1150 °C.

15. The process for pyro lyzing hydrocarbons according to any one of claims 1 to

14, where in the desired temperature is above the autoignition temperature of thehydrocarbons.