Method and apparatus for heat recovery from decomposition gases

Abstract

A system for recovering heat from decomposition gas products includes a heat exchanger comprising one or more coiled tube bundles, each comprising a mandrel, tubes wound in concentric layers around the mandrel, and a tube sheet. The tubes and tube sheet define one or more tube circuits. Decomposition gas products are supplied to the heat exchanger and flow along the shell side of the exchanger around the outside of the tubes with virtually no change in the direction of the decomposition gas products. A supply stream and one or more process streams flow inside the tubes, more specifically, through separate tube circuits. The supply stream and process streams are heated by indirect heat transfer to the decomposition gas products, so that separate fluid streams can be heated simultaneously without a convection section. Related methods for heat recovery are also disclosed.

Description

Technical Field

[0001] The present disclosure generally relates to devices, systems, and methods for treating decomposition gases, and more particularly, but not exclusively, to recovering heat from a decomposition gas stream through indirect heat exchange.

Background Art

[0002] It is generally known to utilize the heat available from combustion products in a combustion furnace for further use in processing systems and methods. Examples include heating (or preheating) a feed stream or utility stream (e.g., preheating boiler feed water, superheating dilution steam, superheating high-pressure steam, preheating combustion air, and generating steam). Combustion of fuel generates high-temperature exhaust gas or combustion products. The high-temperature exhaust gas is utilized in a convection section to heat various streams, e.g., preheating a feed stream and / or generating steam and / or preheating boiler feed water or other process streams to recover heat from the residual energy in the fuel and make it available for use elsewhere in the system. For example, in a known ethylene furnace system, the convection section is used to heat (or preheat) the feed, boil water to generate steam or superheat steam, while cooling the reaction product (decomposition gas) against boiling water to generate steam. The arrangement of the convection section can vary depending on the feedstock to be heated. The amount of heat required for the thermal decomposition of a given feedstock includes the enthalpy required for vaporization (in the case of a liquid feed) and heating of the feedstock, the endothermic heat of reaction for the decomposition process, and the enthalpy required for heating the decomposition gas in the reaction coil. Lighter feedstocks (e.g., ethane, propane, mixtures thereof, etc.) require less heating than heavier feedstocks (e.g., vacuum gas oil, etc.).

[0003] In recent years, new regulations and policies have been introduced to limit carbon dioxide and other emissions in order to counter the effects of global warming and climate change. In response to these regulations, policies, and other factors, it has been proposed to modify certain decomposition gas treatment systems and methods to rely on electric heaters that do not burn fuel, or to modify the furnace to significantly reduce the amount of fuel burned (sometimes referred to as "low-emission furnaces"). Heat recovery from the convection section is not possible in systems with electric heaters because there is no convection section because there is no exhaust gas. Alternatively, heat recovery from the convection section of low-emission furnaces may not be practical because the amount of heat available for recovery is insufficient to heat the supply stream to the desired temperature or generate enough steam. As a result, alternative systems and methods for heat exchange have been proposed, but these systems and methods also have their own drawbacks and disadvantages.

[0004] For example, U.S. Patent No. 4,479,869 to Petterson et al. ("Petterson") utilizes a heat exchanger to preheat the feedstock outside the convection section. Petterson further appears to disclose a flexible feedstock pyrolysis process that exchanges heat with superheated steam to heat various feedstocks with different heat requirements. The steam is generated in a primary quenching exchanger and superheated in the convection section of the combustion heater. However, as with the general overview above, Petterson relies on burning fuel to superheat the steam, which not only inherently creates emissions, but such heat for superheating the steam cannot be utilized with an electric heater or low-emission furnace. Furthermore, Petterson appears to disclose generating steam as an intermediate fluid in the convection section, which reduces thermodynamic efficiency.

[0005] In a further example, Publication No. EP4056892A1 to Zellhuber et al. ("Zellhuber '892") appears to disclose a hybrid steam cracking system using multiple cracking furnaces, including both electric and fuel combustion units connected to a common heat recovery system. In some embodiments, the common heat recovery system may use steam resulting from the rapid cooling of reaction products as the heat recovery medium. Steam resulting from the rapid cooling of an electric heating reactor can be used to preheat air used to reduce the fuel consumption of the combustion reactor. A suitable apparatus for performing heat recovery does not appear to be disclosed in Zellhuber '892. The use of multiple cracking furnaces, as well as steam resulting from rapid cooling, has drawbacks such as increased capital costs and system complexity.

[0006] Publication No. EP4056894A1 to Zellhuber et al. ("Zellhuber '894") appears to disclose a steam cracking arrangement for a system comprising an electrolytic furnace and a quenching train having at least three cooling steps. Thereafter, the process gas stream (i.e., cracking gas) is cooled against vaporized water and a mixture of feed hydrocarbons and process (i.e., diluent) vapor. Each "cooling step" in Zellhuber '894 includes a separate heat exchange device. In some embodiments, it appears to disclose a step of further cooling the process gas stream against boiler feedwater, as well as a step of superheating saturated vapor in a convection zone. Suitable apparatus for performing the cooling steps is not described in detail. In the cooling train of Zellhuber '894, the use of multiple heat exchange devices downstream of the primary or first quenching step increases the number of pieces of equipment and significantly increases the capital cost and other costs of the system.

[0007] Publication WO2022069726A1 ("Jenne") to Jenne et al. appears to disclose a concept for thermal integration in an electrically heated reactor. A preheater is used to heat the feed before the electrically heated reactor. The preheater is thermally integrated in the sense that reactor byproducts from the decomposition reaction (mainly methane and hydrogen) are used as fuel. The apparatus described is a combustion heater separate from the electric heater, which substantially provides the same function as the convection section in a conventional combustion heater, namely, preheating the feed, boiler feedwater, and superheating the steam. The radiant load is provided by electrical means, mainly to heat the feed to the reaction temperature and to provide the heat of reaction for the steam decomposition process. In Jenne, if the byproducts contain carbon, including species such as methane or ethane, there are still carbon dioxide emissions from the combustion heater. Furthermore, the available heat in the decomposition gas is used to generate steam, a utility, rather than directly providing part of the heating load to the process stream.

[0008] Publication WO2022034013A1 to Oud et al. ("Oud'013") appears to describe a shell-and-tube heat exchanger for use as a transfer line exchanger in a hydrocarbon cracking reactor system. In the method disclosed in Oud'013, the cracking gas flows through a straight tube in the tube-side space, and the hydrocarbon feed flows in the shell-side space outside the straight tube. To minimize vortices caused by changes in the flow direction of the shell-side fluid, a spiral baffle is elaborately arranged around a central collector pipe. A bellows is required to compensate for the difference in thermal expansion of the tube relative to the shell. The spiral baffle and bellows increase the capital cost of the system, as well as maintenance costs in case of fouling of the baffle and bellows. The baffle and bellows can also result in a pressure drop due to changes in the flow direction of the shell-side fluid. Furthermore, when decomposition gases are flowed into the space on the side of the tube using Oud'013, the film heat transfer coefficient (W / m²K) decreases, resulting in the need for a relatively large heat transfer area. If a substantial amount of heat needs to be recovered from the decomposition gases, the straight tubes become very long, further increasing the mechanical complexity and cost of such systems.

[0009] US20200172814A1 ("Oud'814") to Oud et al. does not pertain to electrically heated systems. Rather, the amount of fuel required in the radiant section is reduced by various means (e.g., preheating the combustion air). Instead of heating the feedstock in the convection section as in conventional systems, increased firebox efficiency can be achieved by using the waste heat of the decomposition gases in the transfer line exchanger. For example, Oud'814 claims that increasing firebox efficiency using the concepts described therein can reduce fuel gas by up to approximately 20%, or even more. Reduced fuel combustion leads to insufficient energy for preheating the feedstream. To balance the heat input, the feedstock is preheated with a priority on generating steam using higher-grade heat (in other words, heat available at higher temperatures). The waste heat in the decomposition gases is first recovered in the transfer line exchanger by heating the feedstock or a mixture of feedstock and diluent before sending it to the radiant coil. Appropriate apparatus for performing the cooling step is not described. Initially quenching the reaction products using the supply stream results in longer residence times at high temperatures, which may prevent the products from cooling quickly enough or to a temperature low enough to freeze the decomposition gases, which is preferable for maximizing ethylene production and avoiding undesirable by-products.

[0010] In the above and other examples of known decomposition gas systems, devices, and methods, carbon dioxide and other harmful emissions may still be present. Furthermore, some solutions rely on intermediate processing fluids (e.g., steam), reducing thermodynamic efficiency. Many of the proposed solutions utilize multiple heat exchangers or heat one process stream at a time, increasing the number of equipment and overall cost. Known heat exchangers have straight tubes through which the decomposition gas flows (i.e., in the space on the side of the tubes), resulting in large, expensive, and mechanically complex designs. For example, such designs may require baffles and / or bellows, which have the aforementioned drawbacks. These and other factors of known decomposition gas systems, devices, and methods have harmful environmental impacts, reduce efficiency, and lead to a lower overall return on investment. [Overview of the project] [Problems that the invention aims to solve]

[0011] Therefore, it would be advantageous to have a decomposition gas device, system, and method that overcomes the shortcomings and disadvantages of known systems and methods. [Means for solving the problem]

[0012] This disclosure broadly concerns the recovery of heat from a decomposition gas stream via indirect heat exchange with a coiled tube bundle. More specifically, devices, systems, and methods are disclosed for recovering heat from a decomposition gas stream from a vapor decomposer, etc., by flowing the decomposition gas stream over the outer surface of a coiled tube bundle and indirectly exchanging heat with a hydrocarbon feed plus one or more of the following flowing inside the tubes of the coiled tube bundle: dilution steam, superheated steam, boiler feedwater ("BFW"), diathermal oil, or any other products. The concepts of this disclosure can also be described as devices, systems, and methods for heating one or more feed streams before they enter the reaction coil of a vapor decomposer, which are particularly advantageous for use in the absence (or absence of) a convection section. Non-limiting embodiments may include cases where there is no heating by combustion products, or where the heat input available from combustion products is limited (e.g., in the case of an electrovaporator or electroheated reactor, or a low-emission vapor decomposer). The concepts of this disclosure can also be used as part of a system that uses a combination of combustion heating and electroheating.

[0013] In some examples, the heat exchanger may include a pressure vessel containing one or more coil-wound bundles defining a transfer line exchanger ("TLE"). Each coil-wound bundle consists of tubes wound around a central mandrel and arranged in multiple tube layers separated by spacers. The tubes of each coil-wound bundle may provide one or more tube circuits, each tube circuit having an inlet end coupled to a first tube sheet and an outlet connected to a second tube sheet.

[0014] An exemplary system may include a primary TLE having an inlet (e.g., one or more nozzles) for receiving high-temperature decomposition gases. The primary TLE may include one or more coiled tube bundles, which receive high-temperature decomposition gases at temperatures in the range of 500 to 1400 degrees Celsius, more preferably 500 to 875 degrees Celsius. In non-limiting examples, the temperature is between 700 degrees Celsius and 875 degrees Celsius. The high-temperature decomposition gases are first quenched in the primary TLE and supplied to the outlet (e.g., one or more nozzles) of the primary TLE to output the cooled decomposition gases from the primary TLE after the initial quenching. Some examples of the system are intended to use other types of TLEs instead of coiled tube bundles as the primary TLE. The inlet(s) and outlet(s) nozzles are preferably oriented parallel to the flow direction of the decomposition gases, but may be arranged in a non-parallel configuration in some cases. The decomposition gas flows through the spaced layers of coiled tubes containing the bundles (i.e., around the outside of the coiled tubes), while boiling water or some other rapidly cooling fluid flows inside one or more tube circuits containing each coiled bundle.

[0015] The system may further include a secondary TLE. The decomposition gas received in the secondary TLE may already be quenched and have a lower temperature than described above. In such an example, the quenched decomposition gas heats the supply or utility stream via indirect heat transfer. More specifically, the secondary TLE may include one or more coiled tube bundles. The quenched decomposition gas flows through the spaced layers of coiled tubes containing the bundle (i.e., around the outside of the coiled tubes), while the supply or utility stream to be heated flows inside the coiled tubes.

[0016] An example of a method for recovering heat can be summarized as including: partially cooling decomposition gas products from multiple reactor coils at 700–875°C (or the aforementioned temperatures) to a temperature in the range of 550–700°C relative to boiling water in a primary TLE (which may also be referred to herein as the “primary heat exchanger”); supplying the decomposed waste to the inlet of a secondary TLE (which may also be referred to herein as the “secondary heat exchanger”), which has a coiled tube bundle having one or more tube circuits; preheating one or more hydrocarbon feed streams to a temperature in the range of 450–700°C, more preferably 500–650°C, in some of the tube circuits (which may also be referred to herein as the “process tube circuits”); and / or preheating process vapor (dilution vapor), BFW, or diathermal oil streams in other circuits of the tube circuits (which may also be referred to herein as the “service tube circuits”). The decomposition gases flow through spaced layers of coiled tubes, including the bundle, and through the interior of one or more tube circuits containing the fluid to be heated. In some examples, the primary transfer line exchange also includes a coiled tube bundle for the initial quenching operation.

[0017] The concepts of the present disclosure provide the flexibility to heat one or more fluids in parallel within a single coiled bundle containing multiple intertwined tube circuits using a single decomposition gas product stream. In other words, the concepts of the present disclosure provide flexibility in defining the number and arrangement of tube circuits within the coiled bundle, thereby enabling the simultaneous heating of multiple fluids with respect to a common decomposition gas flow within a single coiled bundle. The apparatus may also be configured to heat multiple fluids within two or more coiled bundles arranged in series within a single shell, or it may be configured to heat them within separate shells arranged in series. There are many possibilities for the arrangement of the tube circuits. For example, without limitation, (i) each process tube circuit is connected to a single reactor coil; (ii) several tube circuits containing balancing dilution vapors may be connected to multiple reactor coils; (iii) several tube circuits superheat vapors resulting from the quenching of reaction products; (iv) several tube circuits in a second coiled tube bundle in series with a first coiled tube bundle are used to heat BFW; (v) several tube circuits in a second coiled tube bundle in series with a first coiled tube bundle are used to heat diathermal oil for use in further downstream processes.

[0018] Further methods of using the apparatus include combinations of combustion heaters and electric heaters with a common heat recovery system. For example, decomposition gas products from both electric and combustion heaters are combined and supplied to the inlet(s) of a pressure vessel or secondary TLE. The supply stream to each combustion heater can be heated either in the convection section of the combustion heater (using the excess heat from the combustion products) or in the tubular circuit of a coil-wound heat exchanger bundle (or secondary TLE). Dilution vapors may be preheated and / or superheated to balance the heat load from all of the decomposition gases to a portion of the hydrocarbon feedstock.

[0019] Further features, advantages, and distinguishing aspects of the concepts of the present disclosure will be described in detail with reference to the accompanying drawings. Otherwise, they will be understood by those skilled in the art by considering the present disclosure.

[0020] The present disclosure will be more fully understood by referring to the following figures, which are for illustrative purposes only. These non-limiting and non-exhaustive embodiments are described with reference to the following drawings, and like labels refer to like parts throughout the various figures unless otherwise indicated. The particular shapes of the elements depicted may be selected to facilitate recognition in the drawings. The figures do not depict all aspects of the teachings disclosed herein and are not intended to limit the scope of the claims.

Brief Description of the Drawings

[0021] [Figure 1] It is a schematic diagram of a heat recovery system including a convection section and a primary transfer line exchanger. [Figure 2] It is a schematic diagram of an embodiment of a heat recovery system including an electric heater according to the present disclosure. [Figure 3A] It is a schematic diagram of the heat recovery system of FIG. 2 including a plurality of electric heaters and a common transfer line. [Figure 3B] It is a schematic plan view of the heat recovery system of FIG. 3A. [Figure 4A] It is a schematic diagram of the transfer line exchanger of the heat recovery system of FIG. 2 having a single coiled tube bundle. [Figure 4B] It is a schematic diagram of the transfer line exchanger of the heat recovery system of FIG. 2 having a plurality of coiled tube bundles. [Figure 4C] It is a schematic diagram of the tube circuit in the transfer line exchanger of FIG. 4B. [Figure 5] It is a schematic diagram of an embodiment of the heat recovery system of FIG. 2 including a primary transfer line exchanger and a secondary transfer line exchanger including a coiled tube bundle.

Modes for Carrying Out the Invention

[0022] As will be understood by those of ordinary skill in the relevant art, the present disclosure is merely exemplary and in no way limiting. Other embodiments of the systems and methods of the present disclosure will be readily apparent to those skilled in the art who receive the support of the present disclosure.

[0023] Each of the features and teachings disclosed herein can be used separately or in combination with other features and teachings to provide heat recovery devices, systems, and methods. Examples of the use of many of these additional features and teachings are described in more detail, separately and in combination, with reference to the accompanying drawings. This detailed description is merely intended to teach those skilled in the art further details for implementing aspects of the present teachings and is not intended to limit the scope of the claims. Accordingly, the combinations of features disclosed in the detailed description may not be necessary for implementing the teachings in the broadest sense and are instead taught merely for purposes of illustrating particularly typical examples of the present teachings.

[0024] Furthermore, the various features of the examples and dependent claims can be combined in ways that are not specifically and explicitly enumerated to provide further effective embodiments of the present teachings. Also, note particularly that all ranges or displays of values of a group of entities disclose all possible intermediate values or intermediate entities for the purposes of the original disclosure as well as for the purpose of limiting the subject matter. Also, note particularly that the dimensions and shapes of the components shown in the figures are designed to assist in understanding the manner of implementation of the present teachings, but in some embodiments, it is not intended to limit the dimensions and shapes shown in the examples. In some embodiments, the dimensions and shapes of the components shown in the figures are to scale exactly and are intended to limit the dimensions and shapes of the components.

[0025] In general, the concepts of the present disclosure are effective for heating feed or other processing streams in systems that do not include a convection section or an exhaust gas heat source (e.g., in a system with an electroheated steam decomposer), or in systems where the heat available in the convection section is limited (e.g., in a low-emission furnace), or in a combination of the two. One particular application of the present technology may be for feed heating and / or exhaust cooling sections (secondary TLEs) in an electroheated furnace designed and developed by the applicant. This is the subject of U.S. Provisional Patent Application No. 63 / 269,752 (filed March 22, 2022), the entirety of which is incorporated herein by reference. The concepts of the present disclosure are effective for recovering heat from a low-emission decomposition furnace that generates heat by burning a minimum amount of fuel, but is therefore limited by the amount of heat available to preheat the feed or other streams (e.g., BFW in a non-limiting example). The concept of this disclosure combines multiple heating services within a single vessel and reduces costs by utilizing a smaller surface area for heat transfer than necessary through the use of straight tubing, while simultaneously increasing reliability and reducing maintenance downtime by eliminating the need for bellows required in straight tubing designs. Furthermore, embodiments of this disclosure provide the flexibility to simultaneously heat different feeds and / or other streams, including BFW, steam, and dithermal oil, in separate tubing circuits. In some embodiments, the decomposition gas stream may be mixed before further cooling in the secondary TLE, which provides operational advantages compared to mixing the decomposition gas stream at a lower temperature downstream of the secondary TLE.

[0026] Unless the context clearly indicates a different meaning, the term “decomposition gas” refers to the material stream formed within a pyrolysis decomposition system under controlled residence time, temperature profile, and partial pressure. The hydrocarbons in the raw materials are decomposed into smaller molecules, primarily ethylene, but also including other olefins and diolefins. The resulting product mixture can vary considerably depending on the raw materials and the severity of the decomposition operation. By-products (or secondary products) include acetylene aromatic compounds, C4 and C5 fractions, and fuel oil, while hydrogen and methane can be used as fuel within the plant or refined (for example, hydrogen). Unless otherwise specified, the terms “reactor emissions,” “reaction products,” and “product stream” may be used interchangeably with “decomposition gas” and may have the same definitions as those given above for “decomposition gas,” unless otherwise noted.

[0027] The terms “heater,” “decomposition furnace,” and “vapor decomposition furnace” may refer to any device for supplying one or more of the following: (i) the heat input required to heat and / or vaporize the raw materials; (2) the heat input required to heat the feed from the inlet temperature to the outlet temperature; and (iii) the heat input required for the endothermic reaction.

[0028] Beginning with Figure 1, which illustrates a schematic diagram of a conventional steam cracking furnace and associated heat recovery system 20, provided to highlight the advantages and merits of the present disclosure. The heat recovery system 20 includes a convection section 22 that heats all of the supply stream 24 for combustion products (e.g., exhaust gas 26 from the radiant section firebox 28). More specifically, the convection section 22 may work in cooperation with the radiant section firebox 28 to define the furnace. The convection section 22 may include a plurality of separate heat exchangers 30 positioned within the exhaust gas stream 26 from the radiant section 28 and provided in the form of a bundle of straight tubes passing through the convection section 22 one or more times. The radiant section 28 may be heated by a plurality of burners 32. The supply stream 24 containing hydrocarbons is supplied to the convection section 22, and the supply stream 24 is preheated in one of the heat exchangers 30 in the convection section 22. The BFW 34 also passes through one of the heat exchangers 30 in the convection section 22 for preheating. Next, the preheated BFW 34 is supplied to the steam drum 36. Steam 38 (which may be dilution steam) from elsewhere in the system 20 may be further heated in one of the heat exchangers 30 in the convection section 22 and combined with the supply stream 24. The combined stream 40 of hydrocarbon feed and dilution steam passes through another heat exchanger 30 in the convection section 22 to be further heated, and then passes through the radiation section 28 to heat the combined stream 40 to the reaction temperature, forming a decomposition gas stream 42. The decomposition gas stream 42 may be immediately quenched, for example, in the primary transfer line exchanger 44. The decomposition gas stream 42 (or reaction product stream) exiting the radiation section 28 is quenched or cooled against water from the steam drum 36 and, together with the saturated steam supplied to the steam drum 36, generates saturated steam in the primary transfer line exchanger 44. A saturated steam stream 46 is drawn from the steam drum 36 and further heated (or superheated) in the heat exchanger 30 of the convection section 22 to produce superheated high-pressure steam 48, which can be used elsewhere in the system 20. The primary transfer line exchanger 44 outputs a rapidly cooled decomposition gas stream 50 as an exhaust for further processing.Although not shown in Figure 1, additional heat exchangers may be used downstream of the primary transfer line exchanger 44 to further cool the rapidly cooled decomposition gas stream 48.

[0029] Traditionally, heat recovery from reactor effluent or decomposition gases uses at least one set of single-pass shell-and-tube heat exchangers (TLEs) equipped with straight tubes. This is positioned as the first exchanger into which the decomposition gases enter after the radiating section and may be called the primary TLE. The primary TLE first cools the decomposition gases flowing through the straight tubes. This is usually done by vaporizing high-pressure water, which provides latent heat. Some systems also use a secondary TLE positioned downstream of the primary TLE. The secondary TLE may further cool the decomposition gases before a downstream water quenching tower. The amount of heat that can be recovered in the primary and secondary TLEs depends on the difference between the inlet and outlet temperatures for the decomposition gases. For the primary TLE, the inlet temperature matches the reactor outlet temperature, and for the secondary TLE, the inlet temperature matches the maximum acceptable outlet temperature from the primary TLE. This depends on the type of feed. The minimum acceptable outlet temperature from the TLE depends on fouling considerations regarding the initiation of condensation of heavy components. Condensation causes deposits to form, and the outlet temperature and pressure drop rise rapidly. The rise continues until the resulting operating time or the time between wash and / or decoking cycles is controlled by the TLE operation. For example, the minimum acceptable outlet temperature for a typical liquid feed is ~360°C due to condensation of heavy components in the decomposition gas, in which case the secondary TLE is usually not used to avoid further condensation in the secondary TLE. In the case of decomposition of light hydrocarbons, primary TLE fouling from condensation is less. In that case, multiple TLEs can be used in series (e.g., a primary TLE producing high-pressure steam and a secondary TLE producing low-pressure steam) to preheat the feed or other heat recovery loads.

[0030] In other words, with lighter feedstocks (e.g., ethane), the use of secondary TLEs is conceivable because reaction products can be cooled to lower temperatures. Conventional primary TLE designs are described in Ullmann's Encyclopaedia of Industrial Chemistry, April 15, 2009, article "Ethylene," section 5.2. Note that all primary TLE designs from this reference cool the reactor effluent (or decomposition gas) by essentially flowing the effluent inside a straight tube. Similarly, conventional secondary TLE designs have a straight tube, and the product gas flows inside the tube. Prior art designs avoided having the decomposition gas flow on the shell side outside the straight tube because multiple changes in direction could create stagnation zones, as well as concerns regarding cleaning, mechanical and metallurgical issues. As will be explained in more detail below, the concept of the present disclosure replaces the flow of the decomposition gas inside a straight tube with the flow of the decomposition gas outside a coiled tube, through spaced layers of coiled tubes in a channel formed between the concentric layers of the coiled tube and the shell (i.e., around the outside of the coiled tube), which has advantages such as a substantial change in direction and a reduced pressure drop.

[0031] To reduce emissions from a steam cracking reactor, various approaches have been proposed in the known technologies already mentioned above. Many of these approaches reduce the amount of fuel burned, which in turn reduces the amount of heat available in the convection section to preheat the hydrocarbon feed stream 24. In the case of an electric heating reactor, there is no exhaust gas stream 26 available for preheating the feed stream 24 and / or the BFW 34 and / or steam generation. In such cases, it is desirable to minimize or eliminate steam generation (by quenching of reaction products) and maximize heat recovery from reactor emissions to the product feed. Heat can be transferred between the feed stream 24 (or combined steam and feed stream 40) and the products in a heat exchanger, or between the products and an intermediate fluid (e.g., steam or dithermal oil), and from the intermediate fluid to the feed 24 or other streams to be heated. To achieve the best thermodynamic efficiency, the preferred heat recovery method is indirect heat exchange, because the intermediate fluid will inevitably have a lower temperature available to the process stream. In certain configurations, it may be desirable to have an intermediate treatment fluid, for example, to reduce or eliminate concerns about fouling or cleaning inside the tubes. Conventional heat exchange (or heat recovery) methods have only considered exchanging heat between two streams at a time. The concept of the present disclosure provides a method for heating multiple streams simultaneously (in parallel or in series) by a single common decomposition gas outflow stream. In one embodiment, the present disclosure also provides a method for directly cooling decomposition gas from a reaction coil or coil(s) to a BFW in order to generate high-pressure steam. In one embodiment, the present disclosure provides a method for directly cooling decomposition gas from at least one reaction coil to preheat a combination of hydrocarbon feed and dilution steam.

[0032] During the development of embodiments of this disclosure, research was conducted on electric heaters and / or electric reactors. In this research, conventional shell-and-tube heat exchangers with straight tubes were basically considered as an alternative to non-convection sections for electric reactors. Several important observations were made, including: (1) To achieve the desired inlet temperature or crossover temperature ("TXO") to the reactor coil, the required tube length for straight tubes is very long, and the metallurgy of the tubes must be upgraded to high-temperature alloys (e.g., stainless steel, e.g., SS347H), which significantly increases costs. (2) Long tubes expand proportionally to their length when heated, and the resulting stress in the tubes and tube sheets must be compensated for (e.g., by using bellows devices and / or shell metallurgy with similar thermal expansion properties), thus increasing the overall cost. (3) The aforementioned problems can be mitigated by using shorter heat exchangers arranged in series, with one exchanger per feed stream, and exchangers operating at lower temperatures may not require metallurgical upgrades, but this results in a number of separate heat exchangers with a complex piping layout as a result of preheating multiple feed streams separately, thus increasing costs, and coke particles carried over from the reactor may accumulate in the transitions between the series heat exchangers and / or in the piping and manifolds. Even with the above mitigation measures, it was clear that there are limits to the maximum achievable TXO when using heat exchangers with straight tubes, and therefore to the overall limits of feasible heat recovery.

[0033] As a result, somewhat unexpectedly, it was found that preheating the feed using multiple shell-and-tube heat exchangers with straight tubes is even more expensive than preheating the feed in a convection section according to conventional methods. As with conventional primary TLEs, by performing a first or initial rapid cooling using BFW to generate steam, the metal surface is kept at a sufficiently low temperature, and the heat exchanger tubes do not need to be made of expensive high-temperature alloys. This is because the metal temperature of the tubes is kept low by the very high heat transfer coefficient (latent heat at a constant temperature) of boiling water. However, when the reactor effluent is cooled by the feed gas, the metal surface becomes very hot, and as mentioned above, more expensive materials are required. Consequently, the high cost of conventional shell-and-tube heat exchangers in the prior art is at least in part due to: (A) a low heat transfer coefficient resulting from the decomposition gas flowing inside the tubes with a very low allowable pressure drop. As a result, the convection film heat transfer coefficient is low, and the surface area required for heating is large, so a large amount of shell (or heat exchanger) is required, and the metal temperature of the tubes is high. (B) Using multiple shells (or heat exchangers), with each heat exchanger heating only one stream, limits flexibility and increases the number of units and overall cost.

[0034] In contrast, and as will be further discussed later, the concept of the present disclosure addresses the high cost of recovering heat from decomposition gases and preheating the feed stream by relying on a higher overall heat transfer coefficient with the same pressure drop, thereby reducing the total surface area available for heating; alternatively, or in combination, the higher heat transfer coefficient allows for a higher TXO for the same exhaust inlet temperature. In some embodiments, the overall heat transfer coefficient is 2 to 3 times higher than that of a heat exchanger with straight tubes while maintaining the same (or comparable) pressure drop. Furthermore, the concept of the present disclosure offers further flexibility, including the ability to heat multiple feeds to multiple reactor coils for a single common decomposition gas outflow stream.

[0035] Figure 2 is a schematic diagram of one or more embodiments of the heat recovery system 100 according to the present disclosure. The system 100 includes an electric heating furnace 102 (sometimes referred to as the "electric heater 102"). In one or more embodiments, the system 100 is for naphtha feed to reaction coils 104 in the electric heating furnace 102, but the concepts of the system 100 and related methods can also be applied to other types of feed and multiple reaction coils 104 and heating electric furnace 102. The naphtha feed 106 is first vaporized in a vaporizer 108 and then mixed with dilution vapor 110. The naphtha dilution vapor mixture 112 is then heated against saturated vapor 114 in a superheater 116. The heated naphtha dilution vapor mixture 118 is fed into one (or more) tube circuits of a coil-wound heat exchanger 122 or secondary TLE 122, where it is further heated relative to the reaction products (as further described herein) to produce a further heated naphtha dilution vapor mixture 120. The temperature of the further heated naphtha and dilution vapor mixture 120 entering the reaction coil 104 from the secondary TLE 122 is the crossover temperature ("TXO"), preferably greater than 550°C, more preferably greater than 600°C. In one embodiment, the TXO range is 500°C to 650°C, encompassing all intervening and limiting values. TXO shares an inverse relationship with the amount of electrical energy used to heat the reaction mixture (i.e., the further heated naphtha vapor mixture 120) in the reaction coil 104. That is, the higher the TXO, the less electrical energy is used to heat the mixture 120 in the reaction coil 104 to the reaction temperature.

[0036] Further thermal decomposition of the heated mixture 120 takes place in the reaction coil 104 by adding heat from the electric heating furnace 102, producing decomposition gas reaction products 124. In one embodiment, the temperature of the decomposition gas reaction products 124 exiting the reactor coil 104 is in the range of 500 to 1400 degrees Celsius, more preferably 500 to 875 degrees Celsius. In non-limiting examples, the temperature is between 750 degrees Celsius and 875 degrees Celsius, including all intermediate and limiting values. To maintain the yield of the reaction, it is generally preferable to "freeze" or rapidly cool the reaction products 124. Thus, the decomposition gas reaction products 124 exiting the reaction coil 104 are supplied to the primary TLE 126, where they are cooled against pressurized boiler feedwater (BFW) 128 from the steam drum 130 to produce high-pressure saturated steam 114. Cooling the reaction product 124 in the primary TLE 126 is preferably done by freezing the reaction to the minimum amount necessary to maintain the reaction yield and conserve heat for use elsewhere in the system 100. In other words, the system 100 is intended to cool the reaction product 124 to a lower degree than in conventional systems, generating less vapor, thereby leaving more heat load available for recovery elsewhere in the system.

[0037] In one or more embodiments, the reaction product 124 is cooled in a primary TLE 126 to a temperature in the range of 550°C to 700°C (including all intervening and limiting values) to form a quenched reaction product 132 (which may also be referred to herein as “minimally quenched decomposition gas 132”). The quenched reaction product 132 is fed into a secondary TLE 122 and cooled to the reactor feed or naphtha dilution vapor mixture 118. The exhaust 134 is output from the secondary TLE 122 for further processing. The system 100 may also supply export steam 136 from a steam drum 130 for use elsewhere in the system 100, and output the product 138 (e.g., water and / or steam) from a superheater 116 to a condenser for reuse. In this way, the secondary TLE 122 preheats the reactor feed (or naphtha dilution vapor mixture 118) with respect to the residual heat in the decomposition gas products 124 via indirect heat transfer, without providing a convection section or burning a large amount of fuel.

[0038] In one or more embodiments, the system 100 of Figure 2 is suitable for use with an electric heater, which is the subject of U.S. Provisional Patent Application No. 63 / 269,752 (filed March 22, 2022). The entire contents of this document are incorporated herein by reference. The electric heater described in this reference uses a separate electric furnace for each reaction coil and, in some examples, uses a ceramic silicon carbide heating element for heating. In further embodiments, feeds to two or more electric furnaces can be heated in a secondary TLE 122 for the corresponding reaction products, as illustrated and described with reference to Figures 3A and 3B.

[0039] Figures 3A and 3B are schematic diagrams of one or more embodiments of the system 100 of Figure 2, having multiple electric heaters and a common transfer line. Starting from Figure 3A, two separate feed streams 103A, 103B (both of which may be naphtha feed stream 106, or naphtha dilution vapor mixture 112, or some other feed) are heated in separate tubular circuits of the secondary TLE 122. Separate preheated feed streams 105A, 105B are fed to separate reactor coils 104A, 104B associated with their respective electric heaters 102A, 102B, forming decomposition gas product streams 124A, 124B according to the processes described herein. The decomposition gas streams 124A, 124B, 104B from their respective reactions 104A are quenched minimally for their respective BFW streams 128A, 128B in the primary TLE 126A, 126B. The rapidly cooled decomposition gas products 132A and 132B are then mixed in a common transfer line 140 and supplied via the common transfer line 140 to a single common secondary TLE 122 for cooling to supply streams 103A and 103B. The electric heaters 102A and 102B may be a single unit or a common group of multiple units in various embodiments. Furthermore, the single common secondary TLE 122 may also provide a common waste 134 for further processing.

[0040] In summary, the concept of this disclosure allows separate supply streams (e.g., streams 103A, 103B, etc., as described herein) to remain isolated while being heated by a common decomposition gas flow. The isolation of the supply streams provides flexibility in the operation of the entire system 100. Furthermore, the secondary TLE 122 can be a single device (e.g., a coil-wound heat exchanger) replacing two or more shell-and-tube heat exchangers in conventional systems and methods, potentially reducing costs. In some embodiments, there may be any number of separate supply streams heated by a single device (e.g., three, four, five, six, seven, eight, nine, ten, or more separate supply streams). The flexibility of system 100 allows for any number of different configurations of supply streams, heaters, transfer lines, and other features. While it is not practical to illustrate all possible configurations, such configurations are intended in this disclosure and are not limited to the configuration shown in Figure 3A.

[0041] Figure 3B is a schematic plan view of system 100 of Figure 3A, providing further details regarding the electric heaters described herein. As previously stated, each electric heater 102A, 102B may have the arrangement highlighted by dashed boxes in Figure 3B. Each electric heater (including, but not limited to, electric heaters 102, 102A, 102B) includes a selected number of heating elements 142 (which may be ceramic silicon carbide or some other material) arranged around their respective reactor coils 104A, 104B. The heating elements 142 are electrically connected via electrical cables to a power controller 144, which is associated with a transformer 146. The power controller 144 is operable to control the amount of power (i.e., electrical energy) supplied to the heating elements 142, thereby controlling the heat output from the heating elements 142. The transformer 146 transmits electrical energy between the heater circuits without changing the frequency. The transformer 146 and power controller 144 are connected to bus 148 via electrical cables. Bus 148 may be common to multiple or all heaters and can operate to connect the heaters to a common high-voltage power supply. In one embodiment, each heater includes its own primary TLE 126 as part of the overall heater system. This is shown by the inclusion of each primary TLE 126 within the dashed box in Figure 3B. Alternatively, the primary TLE 126 may be omitted from each heater and instead considered a separate component. This is shown by the dashed line 150. Such an alternative arrangement may be applicable, for example, when electric heaters share a common primary TLE 126. While the features of only one heater (e.g., electric heater 102A) are illustrated and described, other heaters described herein may each have similar features in a similar arrangement.

[0042] Figure 4A is a schematic diagram providing further details of the secondary TLE 122 of system 100. In one embodiment, the secondary TLE 122 is a heat exchanger, and therefore Figure 4A provides further details of the heat exchanger intended in this disclosure. In summary, minimally quenched decomposition gas 132 flows into a pressure vessel 152 or shell 152 through an inlet 154 of the shell 152. The minimally quenched decomposition gas 132 flows around the outside of tubes 156 contained in a coiled bundle 158 or coiled tube bundle 158 inside the shell 152 (i.e., the "shell side" of the secondary TLE 122). The tubes 156 in the coiled tube bundle 158 contain a fluid 160 to be heated. The fluid 160 may be a process fluid, such as hydrocarbons plus dilution vapor (or, in a non-limiting example, a naphtha dilution vapor mixture 118). Tube 156 is wound in concentric layers around a central mandrel 162 and separated by spacer bars or rods 164. A shroud 166 surrounds and supports the tube bundle 158 and is provided to guide the decomposition gas flow across tube 156. Tube 156 is schematically shown in both side and cross-sectional views in the detailed image of Figure 4A, showing the winding angle of tube 156 around the mandrel 162 (which can be any angle between 0 degrees (i.e., greater than 0 degrees) and 20 degrees with respect to a horizontal reference plane passing through the vertical mandrel 162), as well as the axial and radial spacing of tube 156 within the coiled tube bundle 158. As a result, the minimally quenched decomposition gas 132 flowing around the outside of tube 156 transfers heat to the fluid 160 inside tube 156 via indirect heat transfer, obtaining the advantages described herein.

[0043] More specifically, the secondary TLE 122 includes a shell 152. The shell 152 may be an external shell 162 which can be generally oriented vertically as shown in Figure 4A, but other configurations are also possible. More specifically, the secondary TLE 122 is oriented vertically in a preferred embodiment. That is, the longest dimension (typically length) of the secondary TLE 122 is oriented perpendicular to the horizontal plane, or, according to the usual meanings of “top” and “bottom,” the top of the secondary TLE 122 is directly above the bottom. In some embodiments, the secondary TLE 122 may be oriented horizontally. That is, the longest dimension of the TLE 122 is oriented perpendicular to the vertical, or parallel to the plane of the horizontal line. The shell 152 includes an inlet 154 and an outlet 170, and generally defines a flow path through the shell 152, indicated by arrows 172. Furthermore, the shell 152 may have a longitudinal axis 174 which is a vertical centerline passing through the shell 152, with the inlet 154 and outlet 170 centered on axis 174. The coiled tube bundle 158 is positioned inside the shell 152, and as previously described, the tubes 156 are a concentric layer around the mandrel 162. The mandrel 162 may be aligned with the longitudinal axis 174, and the coiled tube bundle 158 and the tubes 156 are similarly centered on the longitudinal axis 174. The coiled tube bundle 158 is connected to tube sheets 176, 178 to realize the flow scheme described herein, and in particular to define tube circuits for heating different fluids. Although not shown, the tube sheets 176, 178 may define inlets and outlets for the flow of process fluid through the tubes 156 of the bundle 158, and the tube sheets 176, 178 may transport the fluid or process stream to, through, and away from the coiled tube bundle 158, thereby recovering heat from the minimally quenched decomposition gas 132 via indirect heat transfer along the flow path 172.

[0044] Figure 4A also provides a representation of the winding angle of the tubes 156 in the coiled tube bundle 158. The total length of the tubes 156 can be changed independently of the diameter of the shell 152 by adjusting the winding angle of the tubes 156 with respect to the horizontal plane passing through the shell 152. For example, reducing the winding angle with respect to the horizontal increases the tube density and tube length. The scale of Figure 4A shows the minimum spacing between the tubes 156, but there may be axial (i.e., vertical) spacing between the concentric layers, which can increase the contact area between the minimally quenched decomposition gas 132 and the tubes 156. More specifically, the tubes 156 may have a first spacing in the radial direction perpendicular to the longitudinal axis 184. The first spacing is greater than a second spacing in the axial direction Y, which is parallel to and aligned with the longitudinal axis 174.

[0045] In some embodiments, the first spacing is, on average, 10 or more times the average of the second spacing. Thus, the ratio of the first spacing to the second spacing can be expressed as >10:1. The average spacing between tubes 156 within each bundle of coiled tubes 148 is important because the reduction in pressure drop achievable by the secondary TLE 122 is at least partially due to the flow of the quenched reaction product 132 to the outside of the structure where the radial spacing between layers is relatively large. In other words, the specific spacings described herein allow for a further reduction in pressure drop, which is achieved by providing large radial spacings between the tubes 156 that do not obstruct the flow of the reaction product 132 through the secondary TLE 122, or otherwise substantially alter the direction of the flow of the reaction product 132 through the secondary TLE 122. The relatively smaller second spacing increases the surface area of ​​the tubes 156 in contact with the reaction products 132, thereby improving heat transfer, but at the same time, it is not large enough to change the direction of flow of the reaction products 132 substantially away from the longitudinal axis 174. As a result, the spacing between the tubes 156 provides further advantages and superiority compared to conventional transfer line exchangers and heat exchangers.

[0046] Figure 4A is a non-limiting example of a secondary TLE 122 having a single coiled tube bundle 158. A secondary TLE 122 may also have multiple coiled tube bundles 158 (for example, at least two coiled tube bundles 158A, 158B, as in Figure 4B). In one or more embodiments, a plane 180 passes through the shell 152 and the axis 174. In one embodiment, the plane 180 is a horizontal plane passing through the shell 152 and intersecting the longitudinal axis 174 passing through the shell 152, and the plane 180 is perpendicular to the axis 174. The plane 180 may be a conceptual dividing line of the shell 152 that separates the shell 152 into a first part 152A and a second part 152B, providing further context for the concepts of the present disclosure. In practice, the shell 152 is a single integrated single part having a continuum including the first and second parts 152A, 152B. In one embodiment, the first and second portions 152A and 152B are separate cylindrical sections of different diameters, which are separated and connected to each other by a transition piece having a tapering or changing diameter to connect the two sections. The first portion 152A of the shell 152 is the upper part of the shell 152 on the first side or upper side of the plane 152, and the second portion 152B of the shell 152 is the lower part of the shell 152 on the second side or lower side of the plane 180 opposite to the first side.

[0047] Furthermore, the inlet 154 enters the first portion 152A of the shell 152, and the second portion 152B leads to the outlet 170 of the shell 152. As a result, the flow path 172 through the shell 152 sequentially traverses the inlet 174, the first portion 152A of the shell 152, the second portion 152B of the shell 152, and the outlet 170. Thus, the flow path 172 follows the longitudinal axis 174 of the shell 152 with virtually no change in the direction of the fluid or discharge (e.g., minimally quenched decomposition gas 132, or otherwise) along the flow path 172. The secondary TLE 122 also includes a first heat transfer surface and a second heat transfer surface. These may be a first coiled tube bundle 158A and a second coiled tube bundle 158B, respectively. Furthermore, the plane 180 may be a reference plane through which all discharge flows with virtually no change in direction. The first coiled tube bundle 158A is located within the first portion 152A of the shell 152, and the second coiled tube bundle 158B is located within the second portion 152B of the shell 152. Although the first and second tube bundles 158A, 158B are schematically shown as cylinders in Figure 4B, in practice the first and second heat tube bundles 158A, 158B may include features illustrated and described with respect to the detailed view in Figure 4A. In one or more embodiments, the first and second coiled tube bundles 158A, 158B may be separate coiled tube bundles, each including a plurality of coiled tubes 156 arranged around a single mandrel 162, and the respective coiled tube bundles 158A, 158B are spaced apart from each other along the mandrel 162. The secondary TLE 122 may also include further tube sheets 182, 184 corresponding to further coiled tube bundles 158B. Similar to tube sheets 176 and 178, tube sheets 182 and 184 help define the flow path for process fluid to flow into, through, and away from tube 156 of the coiled tube bundle 158B. In other words, tube sheets 176, 178, 182 and 184 help define the tube circuits described herein.

[0048] In summary, Figure 4B shows the configuration of a secondary TLE 122 in which two coiled tube bundles 158A and 158B are arranged in series along the longitudinal axis 174, having a common decomposition gas flow, or a common flow of quenched reaction products 132. The configuration of Figure 4B provides greater flexibility to the system 100 by enabling, in some non-limiting examples, the following: (i) preheating the feed by different inlet temperatures; (ii) preheating the BFW in the lower bundle 158B to increase vapor generation; or (iii) preheating other service fluids (e.g., diathermal oil) for further downstream needs. Such configurations may be particularly advantageous for decomposer systems using gaseous feeds (e.g., propane or ethane) because cooling the decomposition gas to low temperatures is possible before the reaction products condense and cause fouling and blockage.

[0049] The configuration of the secondary TLE 122 (or heat exchanger 122) in Figures 4A and 4B offers several advantages compared to known transfer line exchangers and heat exchangers. In particular, the coiled tube bundle 158 (or tube bundles 158A, 158B) can cool the quenched reaction product 132 along the flow path 172 to the desired temperature without a separate downstream cooling unit and without causing the flow direction of the product 132 to deviate substantially away from the longitudinal axis 174. As a result, the pressure drop in the decomposition gas reaction product 132 through the secondary TLE 122 is significantly lower than when the reaction product 132 flows through the tube side (i.e., through tube 156). The reduction in pressure drop minimizes compression costs and also improves the reactor yield for selectivity of chemical reactions that favor low pressure. The reduction in pressure drop is at least partially due to the cooling of the reaction product 132 on the shell side (i.e., outside the tube 152), which eliminates the need for piping to pass the cooled reaction product 132 from the secondary TLE 122 to the exhaust cooler, and also eliminates the pressure drop associated with inlet losses, bends, and T-tubes for flow distribution.

[0050] Furthermore, the plot space and capital costs associated with the secondary TLE122 are significantly reduced compared to known transfer line exchangers and heat exchangers. These advantages are particularly evident for low-pressure decomposition gas emissions utilizing thicker piping (e.g., pipes) with a diameter of 20 inches or more. Finally, tube bundles 158, 158A, and 158B operate in series as separate heat recovery or cooling circuits in different sections of the secondary TLE122, with operating capacities that can be varied according to the operating load of the system incorporating the secondary TLE122. In other words, the coolant capacity through each bundle 158, 158A, and 158B can be adjusted in response to the operating characteristics of larger processing systems, thereby optimizing heat transfer and enabling more efficient processing applications that meet the changing demands in a wider range of systems.

[0051] The secondary TLE122 overcomes many of the shortcomings and disadvantages of the known heat exchangers described herein. For example, a single shell 152 can provide indirect heat transfer to preheat the feed or other processing fluid via coiled tube bundles 158, 158A, 158B when there is no convection section or when the heat load on the convection section is insufficient (e.g., as in low-emission furnaces). By using a single shell 152, a considerable amount of piping and support structure associated with connecting and supporting multiple heat exchangers in series and parallel, as in the known systems described herein, is eliminated. As previously stated, the tube length in the secondary TLE122 can be varied independently of the shell diameter by adjusting the coil angle. Thus, the secondary TLE122 is more compact and has a higher overall heat transfer coefficient than known heat exchangers. The surface area available for cooling is smaller than that of equivalent shell and tube exchangers, and in some embodiments, the surface area of ​​coiled tube bundles 158, 158A, 158B may be about one-third of the surface area in known heat exchangers. In addition, high capacity or heavy operating loads can be handled even by a single train.

[0052] When the rapidly cooled reaction product 132 flows around tube 156, the lowest pressure drop may occur on the shell side. Placing the cooler feed inside tube 156 reduces the tube sheet temperature at the hot end, thereby effectively reducing the maximum metal design temperature by the same amount, resulting in higher heat recovery than would be possible if the reaction product 132 were placed inside the tube, within the constraints of the maximum temperature (due to material limits or concerns about coking deposits). The layer of tube 156 also forms a “path” for the vapor flow, which is relatively large. The spacing of tube 158 described herein minimizes the risk of blockage and provides a relatively large opening area perpendicular to the flow, thereby allowing flow through the layer with virtually no change in the direction of the flow of the reaction product 132, as described herein.

[0053] Unless otherwise indicated by context, when describing the flow direction of the quenched reaction products 132, "no substantial change in direction" means that the bulk flow of the quenched reaction products 132 is primarily between the layers of the coiled tubes 152 and parallel to the axis 174, and that there may be slight deviations affecting 10% or less, or more preferably 5%, of the overall bulk fluid flow due to components that do not significantly affect the direction of the bulk flow (e.g., temperature devices or other protrusions). In addition, changes in the cross-sectional area of ​​the bulk flow are not considered a "substantial change in direction" or deviation from the direction of the bulk flow, as long as the change in cross-sectional area maintains a common longitudinal axis. Small-scale changes in flow direction (i.e., less than the diameter of a single tube 156) due to turbulence or turbulence of the flow do not affect the overall bulk direction of the flow and are therefore not considered a "substantial change in direction" or deviation from the longitudinal axis. In at least some examples, when describing the flow direction of the quenched reaction product 132, "without substantial change of direction" means that at least 90% of the bulk flow, or more preferably at least 95% of the bulk flow, is parallel to the longitudinal axis 174, or the deviation from parallel is within an acceptable range (i.e., within 3 degrees of parallel). In some embodiments, "without substantial deviation from the longitudinal axis" may have a similar meaning to "without substantial change of direction" as stated above.

[0054] Figure 4C is a schematic diagram of the tube circuit in the secondary TLE 122. Referring to Figures 4A-4C, the quenched reaction product 132 is supplied to the inlet 174 of the secondary TLE 122. The secondary TLE 122 may include two coiled tube bundles 158A and 158B in series, and tube sheets 176, 178, 182, and 184 may work with tube 156 to define one or more tube circuits in each of bundles 158A and 158B. For example, each of bundles 158A and 158B may include two tube circuits in one or more embodiments. A common flow of quenched reaction product 132 (or decomposition gas flow) is cooled to multiple streams in different tube circuits. In the first tube circuit 186A within the second coiled bundle 158B, a supply gas (FF) is heated (or preheated) to the reaction product flow 132. Next, dilution vapor (DS) is added to the heated feed gas (FF). In one embodiment, the dilution vapor (DS) is instead mixed with the feed gas (FF) outside or outside the shell 152, as indicated by the dashed arrow 187. In the second tube circuit 186B within the first coiled tube bundle 158A, the mixture MF of feed and dilution vapor is further heated and output for the reaction product 132 to be subjected to further processing (e.g., a heater or furnace). The first and second circuits 186A, 186B may be arranged such that the inlet tube sheet is on the first or left side of the secondary TLE 122, and the inlet tube sheet related to the second circuit 186B is perpendicularly above the inlet of the first circuit 186A with respect to the axis 174. Furthermore, the first and second circuits are arranged in series to define a single path for the fluid flow.

[0055] In one or more embodiments, boiler feedwater (BFW) is heated for the flow of reaction products 132 in a third tube circuit 186C within a second coiled tube bundle 158B and output as heated boiler feedwater (HBFW). In a fourth tube circuit 186D within a first coiled tube bundle 158A, saturated steam (SS) is superheated for the flow of reaction products 132 and output as superheated saturated steam (SH). Other configurations are possible. For example, heating the feed (FF) and / or a mixture of feed and dilution steam (MF) in only a single tube circuit rather than two circuits 186A, 186B in series, and heating other process fluids (e.g., at least diathermal oil in one of circuits 186A, 186B, 186C, 186D instead of the aforementioned fluids), or heating in a different fifth circuit. In addition, tube sheets 176, 178, 182, and 184 can, in some embodiments, define a total of more or fewer than four circuits, each bundle 158A, 158B having more or fewer than two circuits. In one embodiment, the outlet tube sheet is common to at least two of circuits 186A, 186B, 186C, and 186D, so that two separate feeds enter the circuits separately but exit from the same outlet tube sheet, providing further flexibility in the arrangement of circuits 186A, 186B, 186C, and 186D. In further embodiments, a common feed is split into two or potentially more separate tube sheets, so that a common feed stream is distributed to different circuits 186A, 186B, 186C, and 186D, providing further and other flexibility. Thus, the concepts of the present disclosure allow multiple process streams to be heated, including preheating one or more feed streams simultaneously in a single heat exchange device via indirect heat transfer that does not utilize convection sections as in the prior art.

[0056] Figure 5 is a schematic diagram of an embodiment of a heat recovery system 100 in which both the primary TLE 126 and the secondary TLE 122 include coiled tube bundles. While the concept of this disclosure may be particularly advantageous when used with a secondary heat exchanger after an initial quenching to freeze reaction products, this disclosure intends to use heat exchangers with one or more coiled tube bundles (e.g., the type described with reference to at least Figures 4A-4C) as the primary and second heat exchangers or as both the primary and secondary TLE 126, 122. Other configurations may also be possible, for example, with the primary TLE 126 being a heat exchanger with coiled tube bundles and the secondary TLE 122 being a conventional device.

[0057] Rapid cooling is a critical aspect for reaction yield and product quality and is typically performed separately for each individual coil of the reactor to minimize residence time. However, this disclosure is not limited to the use of conventional rapid coolers in this manner. It is intended herein that a heat exchanger having a coiled tube bundle be used as a primary TLE cooler for decomposition gas emissions in direct fluid communication with a decomposition heating furnace. In such an example, the inlet to the primary TLE 122 may be designed to minimize residence time and avoid vortices and backmixing. In Figure 5, the decomposition gas 124 exiting the reaction coil 104 is cooled against boiling water in the coiled tube bundle 158 of the primary TLE 126. The rapidly cooled decomposition gas 132 is then fed to the secondary TLE 122, where it is further cooled against the reaction feed (or heated naphtha dilution vapor mixture 118). By cooling the rapidly cooled decomposition gas 132 relative to the mixture 118, the mixture 118 is heated via indirect heat transfer, raising the crossover temperature TXO of the further heated mixture 120 supplied from the secondary TLE 122 to the reactor coil 104 and heater 102. Although the primary and secondary TLEs 126, 122 are illustrated as separate devices in Figure 5, in some embodiments the primary and secondary TLEs 126, 126 can be combined into a single vessel or shell (i.e., a single TLE). Similarly, the primary TLE 126 having one or more coiled tube bundles 158 flows the decomposition gas reaction product 124 not through the interior of a straight tube, but rather, as described above for the secondary TLE 122, the reaction product 124 flows into the surrounding shell-side space outside the tube. Such an arrangement avoids the need to cool the tube sheet or other structure at the point where the decomposition gas 124 transitions from the inlet region to the cooling region of the primary TLE 126. This is the case for conventional primary TLE, as described in detail in the following reference: Ullmann's Encyclopaedia - "Ullmann's Encyclopaedia of Industrial Chemistry", April 15, 2009, article "Ethylene", section 5.2.Thus, the concept of the present disclosure is not limited to secondary heat exchangers after the initial quenching, but rather also includes heat exchanger devices for the initial cooling or quenching step as primary heat exchangers. Furthermore, the present disclosure is not limited to using separate containers for primary and secondary heat exchange modes, given that both primary and secondary TLEs can be combined into a single container.

[0058] System 100 offers design flexibility that allows for many other configurations and variations beyond those described herein. For example, (a) heating a portion of the dilution vapor separately in a dedicated tubular circuit in parallel with the hydrocarbon feed; (b) including diathermal oil tubing bundles in parallel or series, allowing preheated diathermal oil to be used downstream for further process requirements; (c) in the case of turndown or when only some heaters are operating, unused feed coils can be used for other purposes; and / or (d) the concepts of the present disclosure can be adapted to other reactions in which the combustion heating load is replaced by electric heating, or in other words, to other applications in which the convection section is not utilized or does not provide a sufficient heat load to heat the reactor feed, and many others.

[0059] In summary, the concepts of the present disclosure do not utilize shell-and-tube heat exchangers with straight tubes and do not utilize steam as an intermediate fluid in the convection section. The concepts of the present disclosure do not necessarily preclude the use of steam produced by quenching (e.g., quenched steam used to preheat a vaporized liquid naphtha feed, as described herein) to partially provide heating for other areas of the system or method, but the present disclosure minimizes or eliminates steam produced by quenching by prioritizing indirect heat exchange with the reactor feed. In embodiments where the system is a hybrid system with both a fuel combustion furnace and an electric heating furnace, the amount of heat available from the decomposition gases may actually exceed the preferred heat load for preheating the feed, because there is additional heat available from the exhaust gases in the combustion section. In such embodiments, some tube circuits may be dedicated to: (1) superheating steam before it expands in a steam turbine to generate axial work; or (2) superheating diluted steam and mixing it with a hydrocarbon feed to provide an optimal steam-to-oil ratio. (3) Can be used to preheat air and then reduce fuel consumption in the combustion section, or (4) Can preheat any other service fluid (e.g., hot oil) for further downstream processing.

[0060] Furthermore, the concepts of this disclosure provide devices, systems, and methods for performing subsequent cooling steps in a single apparatus (shell) rather than in multiple steps (multiple shells). As described herein, system 100 can simultaneously heat multiple feeds against a combined decomposition gas stream within a single shell, thereby reducing the number of equipment and providing other advantages compared to known systems and methods. The concepts of this disclosure do not preheat the hydrocarbon feed stream using the heat of combustion from reactor byproducts. Instead, the feed stream is heated by indirect heat exchange with the reaction products, and the reactor byproducts may be available to heat other non-electrically heated furnaces. Neither the indirect heat exchange intended in this disclosure nor any inherent emissions are generated.

[0061] The decomposition gas flows along a substantially continuous path within the shell-side space surrounding the tube, and the tube defines a tube circuit connected to inlet and outlet tube sheets, so the coiled tube can expand and contract without placing a large load on the connecting tube sheets, and bellows are not utilized. The present disclosure intends to provide a continuous passage for the decomposition gas flow with substantially no change in direction by providing coiled tubes around a central mandrel, thereby eliminating baffles and other flow control devices in the prior art that can lead to undesirable pressure loss, vortices, backmixing, and potential fouling and / or blockage. Each tube circuit can be used for the same process fluid, or different process fluids to be heated, such as steam, or different feedstocks to separate reactor coils. Furthermore, the concept of the present disclosure can be used to quench the reaction products by indirect heat exchange with the feed stream, although it may be preferable to initially quench the reaction products by generating steam, as this provides a short residence time at high temperatures to improve reaction yield and product quality. According to this disclosure, the amount of rapid cooling is minimized so that the reaction products exit the rapid cooler at a high temperature in the range of 550-700°C (which, depending on the raw materials used, may be considered the temperature at which the reaction products are “frozen”), and subsequent cooling is carried out in a vessel including a bundle of wound coil heat exchangers.

[0062] The concept of this disclosure reduces the total surface area used for heat recovery from decomposition gases by more than 50% compared to conventional devices, systems, and methods in which the decomposition gases flow inside the tube (i.e., on the tube side), thereby reducing not only material costs but also piping, construction, and installation costs. Furthermore, the concept of this disclosure provides a more robust configuration with respect to the mechanical loads caused by the thermal expansion of the tubes relative to the tubes and / or shell, eliminating the need for bellows devices to compensate for the thermal loads resulting from the difference in thermal expansion between the tubes and the shell.

[0063] The improved performance is possible because the feed is heated to a higher temperature (higher crossover temperature TXO) than in conventional straight-tube shell-and-tube heat exchangers or other known heat exchangers, thus reducing the amount of external energy used to preheat the feed stream within the reactor coil. This advantage arises because the straight tubes used in conventional designs have inherent limitations in their heat transfer coefficient for a given pressure drop, which cannot be overcome by adding more tubes. This is because adding tubes reduces the average speed per tube and therefore the film heat transfer coefficient. Once the maximum tube length (based on fabrication or other mechanical limitations) is set, the maximum effective heat recovery is also set. The same limitations do not apply to the wound-coil heat exchangers intended in this disclosure. The tube length can be increased independently of the flow path length on the shell side by winding the tubes at a larger or smaller angle. In this way, heat transfer resistance can be minimized on both sides, leading to an overall reduction in the required surface area. It has been found that the area occupied by the type of coil-wound heat exchanger intended in this specification is 0.25 to 0.5 times the area occupied by a conventional shell-and-tube heat exchanger (i.e., one with straight tubes).

[0064] Furthermore, the concepts of this disclosure provide multiple tubular circuits so that different feedstocks and / or auxiliary fluids (e.g., steam, process (diluent) steam, boiler feedwater, or dithermal oil) can be heated in series or in parallel using a single combined outflow stream from multiple reactor coils. The heat exchanger intended herein may be divided into two bundles in series, but the continuous flow path to the decomposition gas or reactor exhaust is maintained with virtually no change in direction (this term is defined herein). Heating multiple separate feedstocks to a steam decomposer within a common shell offers many advantages when operating with mixed or variable feedstocks, among other advantages and benefits described herein, as well as reduced piping costs.

[0065] Considering the above, one or more embodiments of the system can be summarized as including: a heater; a reactor coil communicating with the heater (i.e., contained within or heated by the heater) and configured to output a reaction product stream; a primary heat exchanger communicating with the reactor coil and configured to cool the reaction product stream to form a quenched reaction product stream; and a secondary heat exchanger communicating with the primary heat exchanger, the secondary heat exchanger comprising at least one bundle of coiled tubes configured to heat a feed stream via indirect heat transfer to the quenched reaction product stream from the primary heat exchanger to form a heated feed stream.

[0066] In one embodiment, the heater is at least one of an electric heater and a low-emission furnace.

[0067] In one embodiment, at least one coiled tube bundle of the secondary heat exchanger further includes a mandrel, a plurality of coiled tubes arranged in concentric layers around the mandrel, and at least one tube sheet coupled to the plurality of tubes, wherein the quenched reaction product flows around the outside of the plurality of coiled tubes, and the feed stream flows inside the plurality of coiled tubes, heating the feed stream to the quenched reaction product stream via indirect heat transfer.

[0068] In one embodiment, the rapidly cooled reaction product flows around the outside of multiple coiled tubes with virtually no change in direction from the inlet to the outlet of the secondary heat exchanger.

[0069] In one embodiment, at least one coiled tube bundle of the secondary heat exchanger includes a plurality of tubes wound in a coil shape within a concentric layer, and the quenched reaction product flows around the outside of the plurality of coiled tubes.

[0070] In one embodiment, at least one coiled tube bundle includes a first coiled tube bundle and a second coiled tube bundle arranged in series within a secondary heat exchanger.

[0071] In one embodiment, a first coiled tube bundle and a second tube bundle are related to each tube sheet such that they define at least two tube circuits passing through the first coiled tube bundle and the second tube bundle, respectively.

[0072] In one embodiment, the first tube circuit of the second coiled tube bundle and the second tube circuit of the first coiled tube bundle are arranged in series and configured to heat the supply stream relative to the rapidly cooled reaction product stream.

[0073] In one embodiment, the third tube circuit of the first coiled tube bundle and the fourth tube circuit of the second coiled tube bundle are arranged in parallel and are configured to heat one of a plurality of process streams relative to a rapidly cooled reaction product stream.

[0074] In one embodiment, the process streams include boiler feedwater, saturated steam, and dithermal oil.

[0075] In one embodiment, the primary heat exchanger includes at least one coiled tube bundle.

[0076] In one embodiment, the temperature of the heated supply stream output from the secondary heat exchanger to the reactor coil is in the range of 500°C to 650°C, the temperature of the reaction product stream leaving the reactor coil is in the range of 750°C to 875°C, and the temperature of the rapidly cooled reaction product stream output from the primary heat exchanger to the secondary heat exchanger is in the range of 550°C to 700°C.

[0077] One or more embodiments of the system can be summarized as follows: A heater; a reactor coil communicating with the heater and configured to output a reaction product stream; a primary heat exchanger communicating with the reactor coil and configured to cool the reaction product stream to form a quenched reaction product stream; and a secondary heat exchanger communicating with the primary heat exchanger, the secondary heat exchanger comprising a shell; at least one coiled tube bundle inside the shell, the at least one coiled tube bundle comprising a mandrel and a plurality of coiled tubes arranged in concentric layers around the mandrel; and at least one tube sheet coupled to the plurality of tubes, wherein the quenched reaction product stream flows through the shell side of the secondary heat exchanger, and a feed stream flows through the tube side of the secondary heat exchanger, heating the feed stream with respect to the quenched reaction product stream via indirect heat transfer to form a heated feed stream.

[0078] In one embodiment, a plurality of coiled tubes in at least one coiled tube bundle and at least one tube sheet cooperate to define a plurality of tube circuits, the first of which is configured to heat a supply stream relative to a quenched reaction product stream, and the second of which is configured to heat a process stream relative to a quenched reaction product stream.

[0079] In one embodiment, the process stream is one of boiler feedwater, saturated steam, or dithermal oil.

[0080] In one embodiment, the heater is an electric heater or a low-emission furnace, or both, and the primary heat exchanger includes at least one coiled tube bundle.

[0081] In one embodiment, the heater comprises a plurality of heaters, the reactor coil is one of a plurality of reactor coils, each associated with one of the plurality of heaters, the primary heat exchanger is one of a plurality of primary heat exchangers, each associated with one of the plurality of reactor coils, and the secondary heat exchanger is configured to heat separate feed streams to the plurality of reactor coils via indirect heat transfer to a combined quenched reaction product stream from the plurality of primary heat exchangers in a single vessel.

[0082] In one embodiment, the rapidly cooled reaction product stream flows through the shell side with virtually no change in direction.

[0083] In one embodiment, the temperature of the heated supply stream output from the secondary heat exchanger to the reactor coil is in the range of 400°C to 700°C, preferably 500°C to 650°C.

[0084] In one embodiment, the temperature of the reaction product stream exiting the reactor coil is in the range of 750°C to 875°C.

[0085] In one embodiment, the temperature of the rapidly cooled reaction product stream output from the primary heat exchanger to the secondary heat exchanger is in the range of 550°C to 700°C.

[0086] In one embodiment, the reaction product stream is a decomposition gas stream, and the rapidly cooled reaction product stream is a rapidly cooled decomposition gas stream.

[0087] The embodiments also include methods according to any of the non-limiting embodiments described above.

[0088] One or more embodiments of the method may be summarized as including: partially cooling decomposition gas products from one or more reactor coils to boiling water using a primary heat exchanger from a first temperature of 700°C to 875°C to a second temperature of 550°C to 700°C to form quenched decomposition gas products having the second temperature; supplying the quenched decomposition gas products to the inlet of a second heat exchanger including at least one coiled tube bundle having a plurality of tube circuits; preheating a supply stream to one or more reactor coils to a third temperature of 500°C to 650°C relative to the quenched decomposition gas products in at least one of the plurality of tube circuits to form a preheated supply stream having the third temperature; heating one or more process streams in at least two of the plurality of tube circuits; and further heating the preheated supply stream by one or more reactor coils to form decomposition gas products in an open fluid loop.

[0089] In one embodiment, preheating the supply stream involves flowing the quenched decomposition gas products around the outside of at least one coiled tube bundle and flowing the supply stream inside at least one of a plurality of tube circuits.

[0090] In one embodiment, heating one or more process streams involves passing one or more process streams inside at least second of a plurality of tube circuits, and heating one or more process streams via indirect heat transfer with rapidly cooled decomposition gas products flowing around the outside of at least one coiled tube bundle.

[0091] In one embodiment, preheating the supply stream and heating one or more process steams are performed simultaneously within a single shell of a secondary heat exchanger.

[0092] In one embodiment, the primary heat exchanger includes at least one coiled tube bundle.

[0093] In one embodiment, one or more process streams include one or more of boiler feedwater, saturated steam, and dithermal oil.

[0094] In one embodiment, at least one coiled tube bundle of a secondary heat exchanger further includes a mandrel, a plurality of coiled tubes arranged in concentric layers around the mandrel, and at least one tube sheet coupled to the plurality of tubes, wherein the at least one tube sheet and corresponding ones of the plurality of tubes cooperate to define a plurality of tube circuits.

[0095] In one embodiment, further heating of a preheated supply stream includes heating by an electric heater, a low-emission furnace, or both.

[0096] One or more embodiments of the method can be summarized as involving the simultaneous heating of separate fluid streams to reactor effluent using at least one coiled tube bundle of a single heat exchanger.

[0097] One or more embodiments of the device can be summarized as including a single heat exchanger comprising at least one coiled tube bundle configured to heat one or more fluid streams toward a common reactor discharge, wherein the common reactor discharge flows around the outside of the at least one coiled tube bundle, and the one or more fluid streams flow through one or more tube circuits within the at least one coiled tube bundle.

[0098] The above description of the exemplary embodiments, including those described in the abstract, is not intended to be exhaustive or to limit the embodiments to the exact forms disclosed. While specific embodiments and examples are described herein for illustrative purposes, various equivalent modifications can be made without departing from the spirit and scope of the disclosure, as will be apparent to those skilled in the art. The teachings provided herein for various embodiments are applicable outside the context of heat exchangers and are not limited to the exemplary heat exchanger systems, methods, and devices described herein.

[0099] Many of the methods described herein can be carried out with modifications. For example, many of the methods may include further actions, omit some actions, and / or perform actions in a different order than those illustrated or described.

[0100] The above description provides specific details to give a complete understanding of the various embodiments of this disclosure. However, as those skilled in the art will see, this disclosure can be implemented without such specific details. In other cases, well-known structures related to heat recovery and heat exchanger devices, systems, and methods are not described in detail to avoid unnecessarily obscuring the description of the embodiments of this disclosure.

[0101] The following describes the specific terms and phrases used herein. Where used throughout this document, including in the claims, the singular forms “a,” “an,” and “the” include plural references unless otherwise specified. Any of the features and elements described herein may be singular; for example, “shell” may refer to a single shell. The terms “include” and “comprise,” and their derivatives, mean to include without limitation. The phrases “associated with” and “associated with,” and their derivatives, may mean to include, contain, be connected to, encompass, be contained within, connect or be connected to, combine or be combined with, be communicable with, cooperate with, be interconnected, juxtapose, be adjacent, be fixed to or be fixed with, have, possess, etc. Further definitions of specific words and phrases are provided throughout this disclosure.

[0102] The use of ordinal numbers such as 1st, 2nd, 3rd, etc., does not necessarily imply a ranking; rather, it may simply be distinguishing between multiple instances of a certain action or similar structure or material.

[0103] Throughout this specification, the claims, and the drawings, the following terms have the meanings expressly associated herein, unless the context clearly indicates otherwise. The term “in this specification” refers to the specification, claims, and drawings relating to this application. The phrases “in one embodiment,” “in another embodiment,” “in various embodiments,” “in some embodiments,” “in other embodiments,” and other derived terms refer to one or more features, structures, functions, limitations, or characteristics of the disclosure, and are not limited to identical or different embodiments, unless the context clearly indicates otherwise. As used herein, the term “or” is an inclusive “or” operator and is equivalent to the expression “A or B, or both” or “A or B or C, or any combination thereof,” and lists containing further elements are treated similarly. The term “based on” is not exclusive and, unless the context clearly indicates otherwise, allows for further features, functions, aspects, or limitations not described herein. Furthermore, throughout this specification, the meanings of “a,” “an,” and “the” include singular and plural references.

[0104] In general, unless otherwise specified, the materials for fabricating the present invention and / or its components may be selected from suitable materials such as composites, ceramics, plastics, metals, polymers, thermoplastics, elastomers, and plastic compounds, either alone or in any combination.

[0105] For illustrative purposes, the foregoing description uses specific scientific terms and formulas to provide a complete understanding of the disclosed embodiments. It will be apparent to those skilled in the art that specific details are not necessary to carry out the invention. The embodiments have been selected and described to best illustrate the principles of the disclosed embodiments and their practical applications, so that those skilled in the art can utilize the disclosed embodiments, as well as various embodiments with various modifications to suit specific intended uses. Thus, the foregoing disclosure is not intended to be exhaustive or to limit the invention to the detailed forms disclosed, and as will be apparent to those skilled in the art, many modifications and variations are possible considering the teachings above.

[0106] The terms “top,” “bottom,” “up,” “bottom,” “up,” “down,” “above,” “below,” “left,” “right,” and other similar derivatives have general meanings as indicators of direction or position, such as gravity pulling an object downwards, and left referring to the direction west when facing north on a basic azimuthal diagram. These terms are not limited to orientations that may be expressly, implicitly, or essentially disclosed in this disclosure, and any aspect of the embodiments of this disclosure may be arranged in any orientation unless the context clearly indicates a different meaning.

[0107] As used herein, the term “substantially” is to be interpreted as including normal tolerances or manufacturing errors due to minor differences and variations in manufacturing. Unless the context clearly indicates otherwise, relative terms such as “approximately” and “substantially,” and other derived terms, when used to describe a value, quantity, number, or dimension, generally refer to a value, quantity, number, or dimension that is within plus or minus 5% of the stated value, quantity, number, or dimension. Furthermore, any specific dimensions of components or features provided herein are for illustrative purposes only, relating to the various embodiments described herein, and it should be understood that, as such, unless the context clearly indicates otherwise, it is expressly intended in this disclosure that dimensions greater than or smaller than the stated dimensions may be included.

[0108] This application claims priority to U.S. Provisional Patent Application No. 63 / 498,725, filed on April 27, 2023. The entire contents of this document are incorporated herein by reference.

[0109] In consideration of the detailed description above, these and other modifications can be made to the embodiments. In general, the terms used in the following claims should not be interpreted as limiting the claims to specific embodiments disclosed in the specification and claims, but rather as encompassing all possible embodiments, along with the entire scope of equivalents to which such claims are entitled. Accordingly, the breadth and scope of the disclosed embodiments should not be limited by any of the above embodiments, but should be defined solely by the following claims and their equivalents.

Claims

1. It is a system, A heater and At least one reactor coil configured to receive heat from the heater and output a reaction product stream, A primary heat exchanger, which is in communication with the reactor coil and configured to cool the reaction product stream to form a rapidly cooled reaction product stream, A system comprising: a secondary heat exchanger communicating with the primary heat exchanger, the secondary heat exchanger comprising at least one bundle of coiled tubes configured to heat at least one supply stream to the rapidly cooled reaction product stream from the primary heat exchanger via indirect heat transfer to form at least one heated supply stream.

2. The system according to claim 1, wherein the heater is at least one of an electric heater and a low-emission furnace.

3. The at least one coiled tube bundle of the secondary heat exchanger is further, Mandrel and, Multiple coil-shaped tubes arranged in concentric layers around the mandrel, The plurality of tubes are joined together, and the set includes at least one tube sheet, The system according to claim 1, wherein the rapidly cooled reaction product flows around the outside of the plurality of coiled tubes, and the supply stream flows inside the plurality of coiled tubes, heating the supply stream to the rapidly cooled reaction product stream via indirect heat transfer.

4. The system according to claim 1, wherein the at least one coiled tube bundle of the secondary heat exchanger includes a plurality of tubes wound in a coil shape within a concentric layer, and the rapidly cooled reaction product flows around the outside of the plurality of coiled tubes.

5. The system according to claim 1, wherein the at least one coiled tube bundle includes a first coiled tube bundle and a second coiled tube bundle arranged in series within the secondary heat exchanger.

6. The system according to claim 5, wherein the first coiled tube bundle and the second coiled tube bundle are related to each tube sheet such that they define at least two tube circuits passing through the first coiled tube bundle and the second tube bundle, respectively.

7. The system according to claim 6, wherein the first tube circuit of the second coiled tube bundle and the second tube circuit of the first coiled tube bundle are arranged in series and configured to heat the supply stream relative to the rapidly cooled reaction product stream.

8. The system according to claim 7, wherein the third tube circuit of the first coiled tube bundle and the fourth tube circuit of the second coiled tube bundle are arranged in parallel and each is configured to heat one of a plurality of process streams relative to the rapidly cooled reaction product stream.

9. The system according to claim 8, wherein the plurality of process streams include boiler feedwater, saturated steam, and dithermal oil.

10. The system according to claim 1, wherein the primary heat exchanger includes at least one coiled tube bundle.

11. The system according to claim 1, wherein the temperature of the heated supply stream output from the secondary heat exchanger to the reactor coil is in the range of 400°C to 700°C, the temperature of the reaction product stream leaving the reactor coil is in the range of 500°C to 1400°C, and the temperature of the rapidly cooled reaction product stream output from the primary heat exchanger to the secondary heat exchanger is in the range of 550°C to 700°C.

12. It is a system, A heater and At least one reactor coil, which is in communication with the heater and configured to output a reaction product stream, A primary heat exchanger, which is in communication with at least one reactor coil and configured to cool the reaction product stream to form a rapidly cooled reaction product stream, The primary heat exchanger and the secondary heat exchanger which are in communication with each other are included, Shell and, The at least one coiled tube bundle inside the shell, the at least one coiled tube bundle comprising a mandrel and a plurality of coiled tubes arranged in concentric layers around the mandrel, The plurality of tubes are joined together, and the set includes at least one tube sheet, The rapidly cooled reaction product stream flows through the shell side of the secondary heat exchanger, and the supply stream flows through the tube side of the secondary heat exchanger, heating the supply stream with respect to the rapidly cooled reaction product stream via indirect heat transfer, thereby forming a heated supply stream.

13. The system according to claim 12, wherein the plurality of coiled tubes of the at least one coiled tube bundle and the at least one tube sheet cooperate to define a plurality of tube circuits, the first of which the plurality of tube circuits is configured to heat the supply stream relative to the quenched reaction product stream, and the second of which the plurality of tube circuits is configured to heat the process stream relative to the quenched reaction product stream.

14. The system according to claim 13, wherein the process stream is one of boiler feedwater, saturated steam, or dithermal oil.

15. The system according to claim 12, wherein the heater is an electric heater or a low-emission furnace or both, and the primary heat exchanger includes at least one coiled tube bundle.

16. The system according to claim 12, wherein the heater is one of a plurality of heaters, the at least one reactor coil is one of a plurality of reactor coils each associated with one of the plurality of heaters, the primary heat exchanger is one of a plurality of primary heat exchangers each associated with one of the plurality of reactor coils, and the secondary heat exchanger is configured to heat separate supply streams to the plurality of reactor coils via indirect heat transfer to a combined quenched reaction product stream from the plurality of primary heat exchangers in a single vessel.

17. The system according to claim 12, wherein the temperature of the heated supply stream output from the secondary heat exchanger to the at least one reactor coil is in the range of 450°C to 700°C.

18. The system according to claim 17, wherein the temperature of the reaction product stream exiting the at least one reactor coil is in the range of 500°C to 875°C.

19. The system according to claim 18, wherein the temperature of the rapidly cooled reaction product stream output from the primary heat exchanger to the secondary heat exchanger is in the range of 550°C to 700°C.

20. The system according to claim 18, wherein the reaction product stream is a decomposition gas stream, and the rapidly cooled reaction product stream is a rapidly cooled decomposition gas stream.

21. It is a method, The decomposition gas products from one or more reactor coils are partially cooled using a primary heat exchanger to boiling water from a first temperature of 500°C to 875°C to a second temperature of 550°C to 700°C, thereby forming rapidly cooled decomposition gas products having the second temperature. The rapidly cooled decomposition gas product is supplied to the inlet of a second heat exchanger which includes at least one coiled tube bundle having a plurality of tube circuits. The supply stream to one or more reactor coils is preheated to a third temperature of 450°C to 700°C relative to the rapidly cooled decomposition gas product in at least the first of the plurality of tube circuits, thereby forming a preheated supply stream having the third temperature. In at least a second of the plurality of tube circuits, one or more process streams are heated, A method comprising further heating the preheated supply stream with one or more reactor coils to form the decomposition gas products in an open fluid loop.

22. The method according to claim 21, wherein the preheating of the supply stream includes flowing the rapidly cooled decomposition gas products around the outside of the at least one coiled tube bundle and flowing the supply stream inside the at least first of the plurality of tube circuits.

23. The method according to claim 22, wherein heating the one or more process streams includes passing the one or more process streams inside at least the second of the plurality of tube circuits, and heating the one or more process streams via indirect heat transfer with the rapidly cooled decomposition gas products flowing around the outside of the at least one coiled tube bundle.

24. The method according to claim 21, wherein the preheating of the supply stream and the heating of the one or more process steams are performed simultaneously within a single shell of the secondary heat exchanger.

25. The method according to claim 21, wherein the primary heat exchanger includes at least one coiled tube bundle.

26. The method according to claim 21, wherein the one or more process streams include one or more of boiler feedwater, saturated steam, and dithermal oil.

27. The at least one coiled tube bundle of the secondary heat exchanger is further, Mandrel and, Multiple coil-shaped tubes arranged in concentric layers around the mandrel, The plurality of tubes are joined together, and the set includes at least one tube sheet, The method according to claim 21, wherein at least one tube sheet and corresponding tubes cooperate to define the plurality of tube circuits.

28. The method according to claim 21, wherein the further heating of the preheated supply stream includes heating by an electric heater or a low-emission furnace, or both.

29. The method according to claim 21, wherein preheating the supply stream to one or more reactor coils with respect to the rapidly cooled decomposition gas products includes heating an intermediate fluid with respect to the rapidly cooled decomposition gas products and preheating the supply stream with respect to the intermediate fluid.

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