System for oxygenated fuel combustion furnace with heat recovery and reduced flue gas recirculation

Abstract

The present disclosure includes oxygenated fuel furnaces for chemical production processes, as well as systems for steam cracking and other chemical production processes. Such a furnace uses an oxygenated fuel burner in the radiant section, and-not recirculating all flue gas from the outlet of the convection section back to the radiant section--recirculating flue gas entering a portion of the convection section from the convection section.

Description

Technical Field

[0001] The present disclosure generally relates to methods for producing chemicals and, more specifically but without limitation, to any oxy-fuel furnace for a chemical production process in which flue gas is either not recycled from the convection section to the radiation section or is recycled at a reduced rate relative to conventional systems, e.g., at a reduced rate that is insufficient to meet all of the energy requirements of the convection section functions and thus requires supplemental energy for feed preheating and / or steam generation. Background Art

[0002] Chemical synthesis equipment is used to provide a variety of chemicals. Typically, a dedicated fuel is burned or combusted to provide the heat of reaction for chemical synthesis, the energy to heat one or more process streams, the energy to evaporate a liquid (such as boiling water used as a diluent), the energy to do work (such as drive a compressor or pump), or the energy for other process operations throughout the chemical synthesis equipment. This burning or combustion of the fuel results in the generation of flue gas containing CO2, which can be environmentally harmful, and also results in a loss of the energy efficiency of the process. Similarly, steam is typically conventionally used within chemical synthesis equipment as a plant-wide heat and / or energy transfer fluid. Steam for heat and / or energy transfer is often generated via the combustion of fuel, resulting in the generation of additional flue gas and further loss of energy efficiency during chemical synthesis. In addition, due to the inefficiencies of transferring heat energy to and from steam, and particularly when using steam to power a turbine to generate electricity, using steam as a source of heat energy typically results in some losses.

[0003] Some efforts have been made to improve the efficiency of furnaces burning hydrocarbons. For example, oxy-fuel burner configurations have been proposed for the radiation section of furnaces used in chemical production processes. Summary of the Invention

[0004] As described above, oxygen-fuel burner configurations in the radiant section of furnaces for chemical production processes have been proposed. Combustion with a higher concentration of oxygen, as compared to combustion in air, results in a smaller amount of flue gas because air contains approximately 78% nitrogen (in addition to other minor components), which is not present in pure oxygen. As a result, no NOx combustion by-products are formed, and instead the main combustion by-products are CO2 and H2O. Given the absence of NOx (and other by-products and components resulting from air combustion), CO2 can be captured / purified from the flue gas much more readily. Further, when using pure oxygen instead of air to burn fuel in the furnace, the absence of nitrogen means that less mass of flue gas is heated by the thermal energy, such that relatively less fuel can be combusted to raise the temperature of the tubular reactor in the radiant section to a sufficient temperature (including reheating recycled flue gas). However, the smaller mass of flue gas typically results in less power being available from the flue gas in the convective section of the furnace.

[0005] The following disclosure includes additional improvements to the efficiency of such furnaces. For example, previously proposed configurations for oxygen-fuel furnaces in steam cracking systems typically recycle flue gas at a rate sufficient to meet the thermal energy requirements for preheating hydrocarbon feedstock and mixtures of steam and hydrocarbon feedstock in the convective section of the furnace, as well as for steam superheating, at levels similar to those in conventional air-fired furnaces. In addition to steam cracking applications, the methods and furnaces of the present invention can be used for steam methane reforming and various other applications using hydrocarbon-burning furnaces having a radiant section and heat recovery (e.g., convective section), such as those commonly used for chemical production.

[0006] Compared to existing oxygen-fuel furnace configurations, the furnaces and systems of the present invention either (a) do not recycle flue gas from the convective section to the radiant section, or (b) recycle a portion of the flue gas from the convective system to the radiant section at a rate insufficient to meet the full energy requirements of the convective section functions. In some such configurations, the recycling of flue gas is minimized (depending on whether and where the flue gas is recycled from the convective section) to: (a) reduce the amount of hydrocarbon that must be combusted to raise the temperature of the tubular reactor in the radiant section to a sufficient temperature (including reheating recycled flue gas), thereby reducing the energy consumption rate for a given process; (b) correspondingly reduce the CO2 produced by the combustion of the hydrocarbon; and reduce the capital costs associated with any required piping, blowers, and / or air separation units.

[0007] In some configurations of the furnace of the present invention for a chemical production process, the furnace comprises: a radiant shell that defines a radiant section having a gas inlet and a flue gas outlet; one or more oxy-fuel burners arranged in the radiant section; a tubular reactor arranged in the radiant section; a convection section having a convection inlet, a convection outlet, a convection channel extending from the convection inlet to the convection outlet, and a flue gas bypass arranged between the convection inlet and the convection outlet. In some such configurations, the convection inlet is coupled to the flue gas outlet of the radiant section to receive flue gas from the radiant section; and the flue gas bypass is configured to direct a portion of the received flue gas to one of the following: (i) the gas inlet of the radiant section; or (ii) the heater gas inlet of an oxy-fuel flue gas heater configured to reheat the recycled flue gas and deliver the reheated flue gas to the convection inlet; or (iii) both (i) and (ii). In some configurations, the convection section includes at least one heat exchanger arranged in the convection channel and configured to transfer thermal energy from the received flue gas to a mixture of steam and hydrocarbon feedstock; and the convection section is configured to: (a) receive thermal energy from a source other than the received flue gas; or (b) direct the mixture of steam and hydrocarbon through an additional heater that receives thermal energy from a source other than the received flue gas; or (c) both (a) and (b).

[0008] In some optional variations of the furnace of the present invention, at least one heat exchanger comprises a lower mix preheater (LMP).

[0009] In some optional variations of the furnace of the present invention, at least one heat exchanger comprises a steam superheater (SSH) configured to transfer thermal energy from the received flue gas to steam.

[0010] In some optional variations of the furnace of the present invention, at least one heat exchanger comprises an upper mix preheater (UMP) configured to transfer thermal energy from the received flue gas to a mixture of steam and hydrocarbon feedstock.

[0011] In some optional variations of the furnace of the present invention, at least one heat exchanger comprises a feed preheater (FPH) configured to transfer thermal energy from the received flue gas to the hydrocarbon feedstock. In such variations, the flue gas bypass can be arranged between the LMP and the UMP, between the UMP and the FPH, or between the FPH and the convection outlet.

[0012] Some configurations of the steam cracking system of the present invention include: one or more furnaces of the present invention; a transfer line exchanger (TLE); and a UMP steam heat exchanger coupled to the TLE. In some such systems, the radiant section is configured to heat a mixture of steam and hydrocarbon feedstock to a cracking reaction temperature; the TLE is coupled to the outlet of the tubular reactor and is configured to quench the heated mixture to a temperature below the cracking reaction temperature; and the UMP steam heat exchanger is configured to: receive TLE steam from the TLE; receive a mixture of steam and hydrocarbon feedstock from one of one or more heat exchangers in the convection section; transfer thermal energy from the TLE steam to the mixture; return the mixture to the furnace; and return the TLE steam to the TLE.

[0013] Some systems of the present invention optionally further include: an MPH steam heat exchanger coupled to the TLE and configured to receive TLE steam from the TLE, transfer thermal energy from the TLE steam to a mixture of steam and hydrocarbon feedstock, and return the TLE steam to the TLE; and a conduit coupled to the MPH steam heat exchanger and the UMP steam heat exchanger, the conduit being configured to receive steam and mix the received steam with the hydrocarbon feedstock.

[0014] Some systems of the present invention optionally further include: a carbon purification unit (CPU) configured to separate CO2 from flue gas.

[0015] Some configurations of the chemical production system of the present invention include: one or more furnaces; and a carbon purification unit (CPU) coupled to the convection outlet, the CPU being configured to separate CO2 from flue gas; wherein the system is configured to direct substantially all of the flue gas received by the convection section to the CPU. In some such systems, the furnace includes: a radiant housing defining a radiant section having a gas inlet and a flue gas outlet; one or more oxygen-containing fuel burners disposed in the radiant section; a tubular reactor disposed in the radiant section; and a convection section having a convection inlet, a convection outlet, and a convection channel extending from the convection inlet to the convection outlet, wherein the convection inlet is coupled to the flue gas outlet of the radiant section to receive flue gas from the radiant section. In some such systems, the convection section includes one or more heat exchangers disposed in the convection channel and configured to transfer thermal energy from the received flue gas to the hydrocarbon feedstock; the convection section is configured to direct the hydrocarbon feedstock through an additional heater that receives thermal energy from a source other than the received flue gas; and the radiant section is configured to heat the hydrocarbon feedstock to a reaction temperature.

[0016] In some configurations of the chemical production system of the present invention, the radiant section is configured to heat a mixture of steam and hydrocarbon feedstock to a reaction temperature, and the system further comprises: a transfer line exchanger (TLE) coupled to the outlet of the tubular reactor and configured to quench the heated mixture to a temperature below the cracking reaction temperature; a UMP steam heat exchanger coupled to the TLE and configured to: receive TLE steam from the TLE; receive a mixture of steam and hydrocarbon feedstock from one of one or more heat exchangers in the convection section; transfer thermal energy from the TLE steam to the mixture; return the mixture to the furnace; and return the TLE steam to the TLE.

[0017] Some configurations of the chemical production system of the present invention further comprise: an MPH steam heat exchanger coupled to the TLE; and a conduit coupled to the MPH steam heat exchanger and the UMP steam heat exchanger. In some such systems, the MPH steam heat exchanger is configured to: receive TLE steam from the TLE; receive hydrocarbon feedstock from one of one or more heat exchangers in the convection section; transfer thermal energy from the TLE steam to the mixture of steam and hydrocarbon feedstock; return the mixture of steam and hydrocarbon feedstock to the furnace; and return the TLE steam to the TLE. In some such systems, the conduit is coupled to the MPH steam heat exchanger and the UMP steam heat exchanger, and the conduit is configured to: receive hydrocarbon feedstock from the MPH; receive steam and mix the steam into the hydrocarbon feedstock; and direct the mixture of steam and hydrocarbon feedstock to the UMP steam heat exchanger.

[0018] Some chemical production systems of the present invention are configured to produce olefin products, and for each ton of olefin product produced, less than 12 gigajoules (GJ) of energy is consumed and less than 700 kilograms (kg) of carbon dioxide (CO2) is produced.

[0019] The term "coupled" is defined as connected, although not necessarily directly and not necessarily mechanically; two items that are "coupled" may be integral with each other. Unless the present disclosure specifically requires otherwise, the terms "a" and "an" are defined as one or more. As understood by those of ordinary skill in the art, the term "substantially" is defined as largely but not necessarily completely the specified content (and includes the specified content; for example, substantially 90 degrees includes 90 degrees, and substantially parallel includes parallel). In any embodiment of the apparatus, kit, and method of the present invention, the term "substantially" may be replaced with "[percentage] within" the specified content, where the percentage includes 0.1%, 1%, 5%, and / or 10%.

[0020] The terms "comprise" (and any form of comprise, such as "comprises" and "comprising"), "have" (and any form of have, such as "has" and "having"), "include" (and any form of include, such as "includes" and "including"), and "contain" (and any form of contain, such as "contains" and "containing") are open - ended linking verbs. Thus, an apparatus or kit that "comprises", "has", "includes", or "contains" one or more elements possesses those one or more elements, but is not limited to possessing only those elements. Similarly, a method that "comprises", "has", "includes", or "contains" one or more steps possesses those one or more steps, but is not limited to possessing only those one or more steps.

[0021] Further, an apparatus, device, or system configured in some way is at least configured in that way, but it may also be configured in other ways in addition to those specifically described.

[0022] Any embodiment of any of the inventive apparatus and methods may consist of or consist essentially of any of the described steps, elements, and / or features, rather than comprise / include / contain / have any of the described steps, elements, and / or features. Thus, in any claim, the terms "consisting of" or "consisting essentially of" may replace any of the above - recited open - ended linking verbs in order to change the scope of a given claim from what would otherwise be using an open - ended linking verb.

[0023] Details associated with the above - described embodiments and others are presented below.

[0024] Some details associated with aspects of the present disclosure have been described above, and others are described below. After reviewing the entire application (including the description of the drawings, the detailed description, and the claims), other implementations, advantages, and features of the present disclosure will become apparent. Description of the Drawings

[0025] The following figures are illustrative by way of example and not limitation. For the sake of brevity and clarity, every feature of a given structure is not always labeled in every figure in which that structure appears. The same label or reference numeral does not necessarily indicate the same structure. Instead, the same reference numeral may be used to indicate similar features or features having similar functions, and the same is true for different reference numerals. The dimensional drawings are drawn to scale (unless otherwise indicated), meaning that for at least the embodiments depicted in the figures, the sizes of the depicted elements are accurate relative to one another.

[0026] Figure 1 A flow block diagram depicting a general steam cracking apparatus or process is shown.

[0027] Figure 2 A schematic diagram depicting a prior art hydrocarbon steam cracking system is shown.

[0028] Figure 3 Depicts Figure 2 A schematic diagram of an example of the convection section of a prior art hydrocarbon steam cracking furnace of a system of

[0029] Figure 4 A block diagram depicting a second example of a prior art hydrocarbon steam cracking system having a furnace with a radiant section utilizing an oxygen-containing fuel burner is shown.

[0030] Figure 5 A block diagram depicting an example of a steam cracking furnace system of the present invention, showing three separate variants of the configuration of the present invention, is shown.

[0031] Figure 6 A block diagram depicting a second example of a steam cracking furnace of the present invention for use in a steam cracking system is shown.

[0032] Figure 7 A block diagram depicting a further example of a steam cracking furnace system of the present invention having a furnace with a radiant section utilizing an oxygen-containing fuel burner and a supplementary flue gas heater is shown. Detailed Description

[0033] Now referring to the drawings, and more particularly to Figure 1 , a flow block diagram showing an example of a general steam cracking apparatus or process is shown, which includes one or more of the following process sections for converting a feed stream 5 into a desired olefin product stream 50: a feed pretreatment section 10, a pyrolysis reaction section 20, a primary fractionation and compression section 30, a product fractionation (separation) and compression section 40, or a combination thereof. Such sections will be briefly described in the following several paragraphs and described in more detail hereinafter.

[0034] The feed pretreatment section 10 can be configured to condition the pressure of the feed 5, possibly remove undesirable components from the feed (such as carbon dioxide (CO2), mercury, water), combine the incoming feed with stored feed to minimize variations in the feed to the pyrolysis reaction section 20, and / or preheat the feed 5 to provide a pretreated feed stream 15.

[0035] The pyrolysis reaction section 20 can include at least one steam cracker or “pyrolysis” furnace and a transfer line exchanger (TLE) or other heat transfer equipment, the steam cracker or “pyrolysis” furnace being configured to crack hydrocarbons in the presence of steam to produce a cracked gas stream, the transfer line exchanger (TLE) or other heat transfer equipment being used to quench (and optionally harvest heat from the cracked gas stream) the cracked gas stream to provide a cooled cracked stream 25. Conventionally, the furnace of steam cracking equipment produces a high temperature environment by combustion of fuel (such as methane and hydrogen), which results in carbon dioxide emissions from conventional steam cracking equipment / processes. However, in the present embodiment, the furnace is instead a radiant electric furnace, where electric heating elements provide heat or thermal energy to tubes through which the feed stream flows in a heating chamber.

[0036] The primary fractionation and compression section 30 can be configured to provide further heat recovery from the cooled cracked gas stream 25 and quench the cooled cracked gas stream 25, remove one or more components (such as fuel oil, hydrogen sulfide, carbon dioxide, water, or combinations thereof) from the cracked gas stream 25, and / or compress the cracked gas stream 25, thus providing a compressed cracked gas stream 38.

[0037] The product fractionation or separation section 40 can be configured to fractionate the compressed cracked gas stream 38, selectively hydrogenate one or more streams produced during fractionation, and provide one or more olefin (such as ethylene, propylene) product streams 50. The product fractionation or separation section 40 can also provide one or more byproduct streams 60, such as but not limited to a C1 stream, a C2 saturated stream, a C3 saturated stream, a C4 saturated stream, an acetylene stream, a butadiene stream, a 1-butene stream, an isobutene stream, an aromatic stream, a hydrogen stream, a pyrolysis gasoline stream, and / or a fuel oil stream, or a stream containing a combination of these components. Some of these streams can be recycled to one or more sections of the steam cracking equipment. For example but not limited to, the C2, C3, and / or C4 saturated streams can be recycled to one or more pyrolysis furnaces of the pyrolysis reaction section 20, hydrogen can be purified (such as via a pressure swing adsorption unit (PSA) and a methanation reactor to remove CO) and recycled to a hydrogenation reactor (such as a C2, C3, acetylene, or diolefin hydrogenator) and / or used as a fuel source (such as via a fuel cell). The C1 stream can also be recycled to be used as fuel (such as for producing hydrogen from it).

[0038] Now refer to Figures 2 - 3 , Figure 2A more detailed example of a prior art steam cracking furnace system 100 (from Ullman, Encyclopedia of industrial chemistry, page 470, 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) is shown. System 100 includes a steam cracking furnace 104 having a radiant section 108 and a convection section 112. The radiant section has a burner 116 for heating a fired tubular reactor 120, in which the actual steam cracking of the hydrocarbon feedstock occurs. Flue gas 124 from burner 116 flows through the fired tubular reactor 120 to provide the necessary energy for the endothermic steam cracking process within the tubular reactor 120. The flue gas 124 then flows to the convection section 112 of the steam cracking furnace 104.

[0039] The hydrocarbon feedstock can be introduced into inlet stream 128, which is directed to convection tube bank 132 for superheating in the convection section 112 of the steam cracking furnace. The components and functions of the convection tube bank 132 are described in more detail below with reference to Figure 3 The components and functions of the convection tube bank 132 are described in more detail below with reference to

[0040] Boiler feed water is introduced into stream 136, which is also heated in the convection tube bank 132 and transferred to the steam drum 140.

[0041] Steam from the steam drum 140 is superheated in the convection tube bank 132 to form a stream 144 of superheated high-pressure (VHP) steam. The steam 148 is then injected into the hydrocarbon stream for mixing and the steam cracking process in the fired tubular reactor 120. The VHP steam typically has an absolute pressure in the range of 5.0 - 16.0 MPa.

[0042] The cracked hydrocarbon gas flows from the fired tubular reactor 120 to the transfer line heat exchanger 152, where it is cooled and discharged in stream 156 for further processing, i.e., distillation. The heat recovered from the cracked gas in the transfer line heat exchanger 152 is transferred to the steam drum 140.

[0043] Figure 3 An example of the convection section 112 of the steam cracking furnace is shown. In this example, the basic situation of the convection section 112 of a steam cracking furnace (104) processing 45 t / h of light hydrocarbon feedstock mixed with 18 t / h of dilution steam is presented. The hot flue gas enters the convection section at a temperature of 1173 °C, where heat is recovered by preheating the feedstock in the lower mixing preheater (LMP) of the convection tube bank, preheating the boiler feed water in the economizer (ECO) of the convection tube bank, and superheating the steam generated by the transfer line heat exchanger 152 in the upper superheater (USH) and lower superheater (LSH) of the convection tube bank 132.

[0044] The light hydrocarbon feedstock 128 of the naphtha is preheated and vaporized in a feed preheater (FPH), which is mixed with dilution steam 148 and further heated to 612 °C in an upper mixing preheater (UMP) and an LMP, and then the preheated mixed material stream 160 enters the combustion tube reactor 120 in the radiant section 108 of the furnace 104. Additional heat is recovered by preheating the boiler feed water 136 in the economizer (ECO) of the convective tube bank 132 and superheating the steam from the steam drum 140 in the USH, and then some boiler feed water is added at 164 to quench the temperature of the steam, and then it is further superheated in the LSH convective tube bank, where very high-pressure superheated steam (12.0 MPa, 470 °C) is generated.

[0045] Now referring to Figure 4 , shown herein and designated by reference numeral 100a is a block diagram of a second example of a steam cracking system having a furnace, the furnace having a radiant section utilizing an oxygen-containing fuel burner. The oxygen-containing fuel burner configuration means that oxygen (instead of air) is delivered to the radiant section with a hydrocarbon fuel (such as methane) to avoid nitrogen and argon. In this configuration, the convective section 112a is similar to a conventional air-fired furnace, except that it is configured as an oxygen-containing fuel burner and is fed pure oxygen instead of air, and a portion of the flue gas from the top of the convective section is recycled to the radiant section. In this configuration, the rate of recycle of a portion of the flue gas is sufficient to meet the energy requirements for the functions of feed preheating, economizer, mixing preheating, and steam superheating carried out in the convective section. More specifically, Figure 4 An example of an olefin 4 furnace of the prior art is illustrated (e.g., if a conventional furnace is retrofitted to utilize an oxygen-containing fuel burner in the radiant section).

[0046] In the example shown, the system 100a is similar to the system 100 in several respects. For example, the furnace 104a includes a radiant section 108a and a convective section 112a, and its convective section 112a receives the flue gas from the radiant section 108a. Some components of the convective tube bank 132a of the convective section 112a are different from those of the convective tube bank 132. For example, the convective tube bank 132a includes a single steam superheater (SSH) (instead of USH and LSH) to superheat the steam from the TLE, and includes a dilution steam superheater (DSSH) to superheat a portion of the dilution steam to be added to the hydrocarbon-steam mixture between the FPH and the UMP. Finally, in the furnace 104a, according to a particular embodiment, the temperature varies relative to those shown in Figure 3 . The heat exchangers in the convective section 112a extract thermal energy from the flue gas and thereby reduce the temperature of the flue gas to a temperature equal to or higher than 120 °C, and then the flue gas is recycled (hereinafter referred to as flue gas recycle (FGR)).

[0047] In addition to the oxygen-containing fuel burners and pure oxygen feed (instead of air) in the radiant section 108a, system 100a also includes a carbon purification unit (CPU) configured to isolate CO2 from the flue gas. An outlet conduit 204 extends from the outlet of the convective section 112a to the inlet of the CPU, and a bypass conduit 208 extends from conduit 204 at a point upstream of the CPU to redirect a portion of the flue gas back into the radiant section 108a. In this configuration, once a portion of the flue gas redirected from outlet conduit 204 is reheated in the radiant section 108a, it is sufficient to supply the energy requirements of the convective section 108a to preheat the feed and feed-steam mixture and superheat the steam from the TLE, and to increase the steam output through the TLE by preheating the boiler feed water (BFW) in the economizer.

[0048] Now referring Figure 5 , a block diagram of an example of a steam cracking furnace system of the present invention is shown herein and designated by reference numeral 100b, showing three separate variants of the system. System 100b is similar to system 100a in some respects. In this configuration, the convective section 112b includes a simplified convective tube bank 132b having LMP, SSH, UMP, and FPH; and does not have an ECO or DSSH, such that the convective section reduces the flue gas temperature by an amount approximately equal to Figure 4 that of the convective section 112a. In each of the three variants of this system, a portion of the flue gas is redirected from the radiant section 108b to the convective section, but this portion of the flue gas - even when reheated in the radiant section - is generally not sufficient to meet the energy requirements of the convective section. Thus, in this system, the convective section 112b is configured to (a) receive thermal energy from a source other than the flue gas; or (b) direct the feedstock (e.g., a mixture of feedstock and steam) through an additional heater that receives thermal energy from a source other than the flue gas; or (c) both (a) and (b). In Figure 5 each of the three variants (designated Option A, Option B, and Option C), the convective section 112b includes a flue gas bypass (212-1, 212-2, and 212-3, respectively) to direct a portion of the received flue gas to the gas inlet 216 of the radiant section 108b.

[0049] In Option A, a portion of the flue gas is directed from the convective section 112b to the gas inlet 216 of the radiant section 108b via the flue gas bypass 212-1 (not via 212-2 or 212-3) to be reheated in the radiant section 108b and supply thermal energy to the heat exchangers in the convective section 112b. In the configuration of Option A, the flue gas is removed from the convective section at a first temperature similar to the temperature of the recycled flue gas in Figure 4 ; however, more is removed thanFigure 4 A smaller portion of the available flue gas is used for recirculation such that in Figure 5 Option A, the system is configured to recirculate a portion of the flue gas that, even after reheating in the radiant section, is insufficient to meet the thermal energy requirements of the convective section (i.e., feed preheating and mixed preheating in the depicted configuration).

[0050] Specifically, for Figure 5 Option, the amount of flue gas recirculated is selected to provide sufficient thermal energy for the SSH and LMP functions (which require a temperature higher than that of the steam available from the TLE (which may be limited, for example, to providing steam at a maximum condensation temperature of 325 °C)). The bypass amount sufficient to meet the SSH and LMP requirements will depend on the temperature of the flue gas at the point of removal from the convective section (Option A, Option B, Option C) (which will necessarily affect the amount of energy required to reheat the recirculated flue gas in the radiant section 108b).

[0051] In Option B, a portion of the flue gas is directed from the convective section 112b via the flue gas bypass 212-2 (not via 212-1 or 212-3) to the gas inlet 216 of the radiant section 108b for reheating in the radiant section 108b and providing thermal energy to the heat exchanger in the convective section 112b. In the configuration of Option B, the flue gas is removed from the convective section at a second temperature that is higher than the first temperature at which the flue gas is removed in Option A - i.e., before removing thermal energy from the flue gas in the FPH heated by the flue gas ("FPH flue gas"). When the flue gas is removed from the convective section at this higher second temperature, even less hydrocarbon must be burned in the radiant section 108b to raise the tubular reactor in the radiant section to a sufficient temperature (including reheating the recirculated flue gas). However, as a compromise, the removal of a portion of the flue gas before it enters the "FPH flue gas" means that less thermal energy is available to preheat the feed in the FPH flue gas, such that additional thermal energy must be added separately to complete the feed preheating function. As in Option A, in Figure 5 Option B, the system is configured to recirculate a portion of the flue gas that, even after being reheated in the radiant section, is insufficient to meet the thermal energy requirements of the convective section (i.e., feed preheating and mixed preheating in the described configuration).

[0052] In Option C, a portion of the flue gas is directed from the convection section 112b to the gas inlet 216 of the radiant section 108b via the flue gas bypass 212-3 (not via 212-1 or 212-2) to be reheated in the radiant section 108b and supply heat energy to the heat exchangers in the convection section 112b. In the configuration of Option C, the flue gas is removed from the convection section at a third temperature that is higher than the second temperature at which the flue gas is removed in Option B - i.e., before removing the heat energy from the flue gas in the flue gas heated FPH (“FPH flue gas”) or the flue gas heated UMP (“UMP flue gas”). When the flue gas is removed from the convection section at the higher third temperature, less hydrocarbon must be burned than in Option A (slightly more than the hydrocarbon in Option B) to raise the tubular reactor in the radiant section 108b to a sufficient temperature (including reheating the recycled flue gas). However, as a compromise, the removal of a portion of the flue gas before it enters the “UMP” means that: (a) less heat energy is available to preheat the feedstock in the “FPH flue gas”, such that additional heat energy must be added separately to complete the feedstock preheating function, and (b) less heat energy is available to heat the feedstock-steam mixture in the “UMP flue gas”, such that additional heat energy must be added to heat the mixture. As in each of Option A and Option B, in Figure 5 Option C of the system is configured to recycle a portion of the flue gas - even after being reheated in the radiant section - that portion of the flue gas is not sufficient to meet the heat energy requirements of the convection section (i.e., feedstock preheating and mixing preheating in the described configuration).

[0053] In some configurations of each of Option A, Option B, and Option C, the gas bypasses 212-1, 212-2, or 212-3 may be adjustable to vary the amount of recycled flue gas, thereby allowing adjustment for different feedstock properties, furnace fouling, etc.

[0054] As explained above, the system 100b for each of Option A, Option B, and Option C requires additional thermal energy (beyond what is available from the flue gas) to preheat the feedstock, heat the feedstock-steam mixture, and superheat the steam. The additional energy can be supplied by or derived from any of a variety of sources, such as steam (e.g., from the TLE and / or from the feed-effluent exchanger), one or more additional heaters (e.g., electric heaters), or any of a variety of other sources of additional thermal energy. In the depicted configuration, the feed preheating function of the "FPH flue gas" heat exchanger is supplemented by an additional (e.g., external to the convection section 112b) heat exchanger ("FPH steam") configured to receive steam from the TLE and transfer thermal energy from the TLE steam to the feedstock from the "FPH flue gas" heat exchanger. Additionally, in the depicted configuration, the mixing preheating function of the "UMP flue gas" heat exchanger is supplemented by an additional (e.g., external to the convection section 112b) heat exchanger ("UMP steam") configured to receive steam from the TLE and transfer thermal energy from that TLE steam to the feedstock-steam mixture from the "UMP flue gas" heat exchanger. As shown, in this configuration, dilution steam is mixed into the feedstock between the "FPH steam" heat exchanger and the "UMP steam" heat exchanger such that the "UMP steam" heat exchanger begins preheating the mixture before the partially preheated mixture is directed to the "UMP flue gas" heat exchanger in the convection section 112b. As described above, in addition to Figure 5 the steam heat exchangers shown or instead of Figure 5 the steam heat exchangers shown, alternative sources of thermal energy can be used, and / or steam from alternative or additional sources (in addition to or other than the TLE and / or the feed-effluent exchanger) can be utilized.

[0055] Now referring to Figure 6, shown here and designated by reference numeral 100c, is a block diagram of a second example of the steam cracking furnace system of the present invention for use in a steam cracking system. System 100c is similar to system 100b in some respects, the main exception being that the convection section 112c is further simplified by omitting the SSH from the convection tube bank, and the radiant section 108c utilizes one or more flameless oxygen-containing fuel burners known in the art, with no flue gas being externally recycled from outside the convection section 112c to the radiant section 108c. In at least some configurations, such flameless oxygen-containing fuel burners can effectively recirculate or recycle a portion of the flue gas internally within the radiant section in order to stabilize the burner during the combustion of the fuel. The lack of external flue gas recirculation means that even less hydrocarbon fuel (e.g., methane) needs to be burned to raise the tubular reactor in the radiant section to a sufficient temperature, and thus even less flue gas is directed to the convection section 112c, and less thermal energy can be obtained from the flue gas in the convection section 112c. To compensate for the relative reduction in available thermal energy in the convection section 112c, system 100c also includes an LMP and an SSH, where the LMP provides thermal energy through an electric heater or electric heating element, and the SSH provides thermal energy through an electric heater or electric heating element. In other configurations, the thermal energy can be provided via any of a variety of known sources other than electric heaters or electric heating elements (e.g., additional local burners).

[0056] Now referring to Figure 7 , shown here is a block diagram of another example 100d of the steam cracking furnace system of the present invention, which has an oxygen-containing fuel radiant section and a supplementary oxygen-containing fuel flue gas heater. System 100d is similar to system 100b (including the option for arranging a flue gas bypass), the main exception being that system 100d includes a supplementary oxygen-containing fuel flue gas heater to add thermal energy to the flue gas recycled from the convection section (112b), and burns additional fuel to generate additional flue gas to supply thermal energy to the convection section (112b). More specifically, the flue gas heater receives the recycled portion of the flue gas from the flue gas bypass (212-1, 212-2, or 212-3) and burns fuel to reheat the flue gas and generate additional hot flue gas. More specifically, in the depicted configuration, the flue gas heater includes one or more oxygen-containing fuel burners to burn a hydrocarbon fuel (e.g., methane) with pure oxygen, reheating the recycled flue gas and generating additional hot flue gas to provide thermal energy to the convection section (112b).

[0057] In some variants, a portion of the recycled flue gas from the flue gas bypass (212-1, 212-2, or 212-3) is also directed to the gas inlet 216 of the radiant section 108b, as Figure 7As shown by the dashed arrow in [the figure], such that this portion of the recycled flue gas is reheated in the radiant section 108b.

[0058] In the depicted configuration, the flue gas heater is arranged between the radiant section 108b and the convective section 112b such that the flue gas generated in the radiant section 108b is conveyed to the convective section 112b through the flue gas heater. In other configurations, the flue gas heater can be separated from the inlet of the convective section, where the outlet of the flue gas heater is coupled to the inlet of the convective section (112b), such that the flue gas from the radiant section 108b does not pass through the flue gas heater until the flue gas has been recycled from the convective section. Alternatively, the reheated and additional flue gas from the flue gas heater is conveyed to the inlet of the convective section, either (a) directly such that the reheated and additional flue gas from the flue gas heater is mixed with the flue gas from the radiant section after both have entered the convective section, or (b) through a mixing chamber, where the reheated and additional flue gas from the flue gas heater is mixed (or begins to be mixed) with the flue gas from the radiant section in the mixing chamber before the mixture enters the convective section.

[0059] In the depicted configuration, the additional thermal energy added to the convective section through the flue gas heater does not provide all of the thermal energy requirements of the convective section, such that the "FPH steam" and "UMP steam" heat exchangers are still used to supplement the feed preheating and upper mixing preheating functions of the convective section (112b); however, considering a similar overall system throughput, the addition of the flue gas heater does reduce the amount of thermal energy input through the "FPH steam" and / or "UMP steam" heat exchangers relative to Figure 5 system 100b.

[0060] In other variations of any of the disclosed systems having a supplementary flue gas heater, the supplementary flue gas heater can be large enough to provide all of the thermal energy requirements of the convective section, such that the "FPH steam" and "UMP steam" heat exchangers can be completely omitted, for example, in a configuration similar to Figure 4 system 100a, but with a supplementary flue gas heater and recycled flue gas being directed to the supplementary flue gas heater, the radiant section (112a), or both. In system 100a, the supplementary flue gas heater can be added between the radiant section 108a and the lower mixing preheater (LMP) of the convective section 112a such that the flue gas from the radiant section 108a passes through the supplementary flue gas heater before entering the convective section 112a, or can be separated from the convective section 112a as described above, as a Figure 7 variant of system 100d.

[0061] Comparative modeling

[0062] Figure 4 、Figure 5 and Figure 6 The configurations of Figure 6 are modeled using commercial modeling software, where a conventional (non-oxygenated fuel) steam cracking system serves as the base case, Figure 4 The system of Figure 4 is designated as "warm FGR"; Figure 5 For the system of Figure 5 , Option A, where flue gas is removed from the flue gas bypass 212-1 at a temperature of 150 °C, is designated as "150 °C FGR"; Figure 5 For the system of Figure 5 , Option B, where flue gas is removed from the flue gas bypass 212-2 at a temperature of 330 °C, is designated as "330 °C FGR"; Figure 5 For the system of Figure 5 , Option C, where flue gas is removed from the flue gas bypass 212-3 at a temperature of 510 °C, is designated as "510 °C FGR"; and Figure 6 The system of Figure 6 is designated as "flameless OF". All options are modeled to produce 28 tons per hour of olefin product, a radiant section heating load of 18.3 MW, and a TLE load of 12 MW.

[0063] Some summary results of this modeling are shown in Tables 1, 2, and 3 (assuming 100% efficient use of steam for modeling purposes). In these tables, components with the suffix "–F" (e.g., FPH-F) designate thermal energy from flue gas, components with the suffix "–S" (e.g., FPH-S) designate thermal energy from steam, and components with the prefix "E–" (e.g., E-SSH) designate electrical heating.

[0064] Table 1: Energy and fuel consumption

[0065]

[0066] Table 2: Efficiency and relative consumption

[0067]

[0068] Table 3: Component loads

[0069]

[0070]

[0071] As shown in Tables 1 and 2, Figure 4 the warm FGR option of Figure 4 reduces the energy consumption of the conventional furnace, but Figure 5 and Figure 6 the energy consumption of the systems of Figure 6 is much lower than Figure 4 the energy consumption of Figure 4 . At Figure 5Among the options, Option A (150°C FGR) is the least optimized. Lower temperature recirculation reduces the thermal energy contributed by the steam heat exchangers (“FPH steam” and “UMP steam”), and reduces the temperature difference across the steam heat exchangers (“FPH steam” and “UMP steam”). However, it is noted that higher recirculation temperatures do result in a non - optimized use of the thermal energy in the flue gas, and thus require an increased flue gas recirculation rate (27 tons per hour for 510°C FGR vs. 20 tons per hour for 330°C vs. 23.9 tons per hour for 150°C FGR) to meet the energy input requirements of the LMP and the steam superheater. It was found that Figure 5 the highest efficiency among the three options is 330°C FGR.

[0072] An additional disadvantage of 150°C FGR is that the feedstock flexibility will be reduced due to the variables that must be balanced with the relatively more thermal energy available in the flue gas within the “FPH flue gas” heat exchanger. In particular, the rate of flue gas recirculation must be small enough such that the feed pre - heating does not completely evaporate before the mixing point (where steam is added to the feedstock), but large enough such that the desired cross - over temperature is obtained.

[0073] Figure 6 The flameless OF configuration requires much less methane usage and thus produces much less CO2. However, the total amount of energy used by the flameless OF configuration is similar to Figure 5 the total energy usage of the 330°C FGR configuration (Option B). From a cost perspective, the flameless OF configuration is expected to still be more favorable since the flameless OF configuration will not require external recirculation of the flue gas and thus will not require bypass / recirculation piping or blowers.

[0074] ***

[0075] Additional details regarding the various components of the steam cracking apparatus and method can be found in: (1) International Patent Application Publication No. WO 2020 / 150244 and (2) U.S. Patent No. 11,046,893; each of which is incorporated by reference in its entirety.

[0076] Additional details regarding the various components of the syngas synthesis apparatus and process can be found in International Patent Application Publication No. WO2020 / 150247, which is incorporated by reference in its entirety.

[0077] The foregoing specification and examples provide a complete description of the structure and use of exemplary embodiments. While some embodiments have been described above to a certain degree of particularity or with reference to one or more separate embodiments, many modifications may be made to the disclosed embodiments by those skilled in the art without departing from the scope of the invention. Accordingly, the different illustrative embodiments of the inventive device are not intended to be limited to the specific forms disclosed. Instead, they include all modifications and substitutions falling within the scope of the claims, and embodiments other than the illustrated embodiments may include some or all of the features of the depicted embodiments. For example, components may be combined into an integral structure, and / or connections may be substituted. Additionally, where appropriate, aspects of any of the above examples may be combined with aspects of any other example described to form additional examples having comparable or different characteristics and solving the same or different problems. Similarly, it will be understood that the above benefits and advantages may pertain to one embodiment or may pertain to several embodiments.

[0078] A claim is not intended to cover and should not be construed as covering a means-plus-function or step-plus-function limitation, unless such a limitation is expressly recited in a given claim using the phrase "means for" or "step for".

Claims

1. A furnace for a chemical production process, the furnace comprising: a radiant shell that defines a radiant section having a gas inlet and a flue gas outlet; one or more oxy-fuel burners arranged in the radiant section; a tubular reactor arranged in the radiant section; a convection section having a convection inlet, a convection outlet, a convection channel extending from the convection inlet to the convection outlet, and a flue gas bypass arranged between the convection inlet and the convection outlet, wherein: the convection inlet is coupled to the flue gas outlet of the radiant section to receive flue gas from the radiant section; and the flue gas bypass is configured to direct a portion of the received flue gas to one of the following: (i) the gas inlet of the radiant section; or (ii) the heater gas inlet of an oxy-fuel flue gas heater configured to reheat the recycled flue gas and deliver the reheated flue gas to the convection inlet; or (iii) both (i) and (ii); wherein the convection section includes at least one heat exchanger arranged in the convection channel and configured to transfer thermal energy from the received flue gas to a mixture of steam and hydrocarbon feedstock; and wherein the convection section is configured to: (a) receive thermal energy from a source other than the received flue gas; or (b) direct the mixture of steam and hydrocarbon through an additional heater that receives thermal energy from a source other than the received flue gas; or (c) both (a) and (b).

2. The furnace according to claim 1, wherein the at least one heat exchanger includes a lower mixing preheater (LMP).

3. The furnace according to any one of claims 1-2, wherein the at least one heat exchanger includes a steam superheater (SSH) configured to transfer thermal energy from the received flue gas to steam.

4. The furnace according to any one of claims 1-3, wherein the at least one heat exchanger includes an upper mixing preheater (UMP) configured to transfer thermal energy from the received flue gas to the mixture of steam and hydrocarbon feedstock.

5. The furnace according to any one of claims 1-4, wherein the at least one heat exchanger includes a feed preheater (FPH) configured to transfer thermal energy from the received flue gas to the hydrocarbon feedstock.

6. The furnace according to claim 4, wherein the flue gas bypass is arranged between the LMP and the UMP.

7. The furnace according to claim 5, wherein the flue gas bypass is arranged between the UMP and the FPH.

8. The furnace according to claim 5, wherein the flue gas bypass is arranged between the FPH and the convection outlet.

9. A steam cracking system, comprising: The furnace according to any one of claims 1-8, wherein the radiant section is configured to heat a mixture of steam and hydrocarbon feedstock to a cracking reaction temperature; A transfer line exchanger TLE, the transfer line exchanger TLE being coupled to an outlet of the tubular reactor and configured to quench the heated mixture to a temperature below the cracking reaction temperature; A UMP steam heat exchanger, the UMP steam heat exchanger being coupled to the TLE and configured to: Receive TLE steam from the TLE; Receive a mixture of steam and hydrocarbon feedstock from one of the one or more heat exchangers in the convection section; Transfer heat energy from the TLE steam to the mixture; Return the mixture to the furnace; And Return the TLE steam to the TLE.

10. The steam cracking system according to claim 9, further comprising: An MPH steam heat exchanger, the MPH steam heat exchanger being coupled to the TLE and configured to receive TLE steam from the TLE, transfer heat energy from the TLE steam to the mixture of steam and hydrocarbon feedstock, and return the TLE steam to the TLE; and A conduit, the conduit being coupled to the MPH steam heat exchanger and the UMP steam heat exchanger, the conduit being configured to receive steam and mix the received steam with the hydrocarbon feedstock.

11. The steam cracking system according to any one of claims 9-10, further comprising a carbon purification unit (CPU), the carbon purification unit being configured to separate CO2 from the flue gas.

12. A chemical production system, comprising: A furnace, the furnace comprising: A radiant housing, the radiant housing defining a radiant section having a gas inlet and a flue gas outlet; One or more oxygen-containing fuel burners, the one or more oxygen-containing fuel burners being arranged in the radiant section; A tubular reactor, the tubular reactor being arranged in the radiant section; A convection section, the convection section having a convection inlet, a convection outlet, and a convection channel extending from the convection inlet to the convection outlet, wherein the convection inlet is coupled to the flue gas outlet of the radiant section to receive flue gas from the radiant section; Wherein the convection section includes one or more heat exchangers, the one or more heat exchangers being arranged in the convection channel and configured to transfer heat energy from the received flue gas to the hydrocarbon feedstock; Wherein the convection section is configured to direct the hydrocarbon feedstock through an additional heater, the additional heater receiving heat energy from a source other than the received flue gas; and Wherein the radiant section is configured to heat the hydrocarbon feedstock to a reaction temperature; a carbon purification unit (CPU), the carbon purification unit being coupled to the convection outlet, the CPU being configured to separate CO2 from the flue gas; and Wherein the system is configured to direct substantially all of the flue gas received by the convection section to the CPU.

13. The system according to claim 12, wherein the radiant section is configured to heat a mixture of steam and the hydrocarbon feedstock to the reaction temperature, and the system further comprises: a transfer line exchanger TLE, the transfer line exchanger TLE being coupled to an outlet of the tubular reactor and configured to quench the heated mixture to a temperature below the cracking reaction temperature; a UMP steam heat exchanger, the UMP steam heat exchanger being coupled to the TLE and configured to: receive TLE steam from the TLE; receive a mixture of steam and hydrocarbon feedstock from one of the one or more heat exchangers in the convection section; transfer thermal energy from the TLE steam to the mixture; return the mixture to the furnace; and return the TLE steam to the TLE.

14. The system according to claim 13, further comprising: an MPH steam heat exchanger, the MPH steam heat exchanger being coupled to the TLE and configured to: receive TLE steam from the TLE; receive hydrocarbon feedstock from one of the one or more heat exchangers in the convection section; transfer thermal energy from the TLE steam to the mixture of steam and hydrocarbon feedstock; return the mixture of steam and hydrocarbon feedstock to the furnace; and return the TLE steam to the TLE; and a conduit, the conduit being coupled to the MPH steam heat exchanger and the UMP steam heat exchanger, the conduit being configured to: receive the hydrocarbon feedstock from the MPH; receive steam and mix the steam into the hydrocarbon feedstock; and direct the mixture of steam and hydrocarbon feedstock to the UMP steam heat exchanger.

15. The system according to any one of claims 13-14, wherein the system is configured to produce an olefin product and for each tonne of the olefin product produced, consumes less than 12 gigajoules (GJ) of energy and produces less than 700 kilograms (kg) of carbon dioxide (CO2).

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