Load recovery system and method for a steam cracking furnace

Abstract

Provided are steam cracking processes including introducing a first hydrocarbon-containing feed to a convection section of a steam cracking furnace. The convection section can include (i) a first arrangement having a first economizer disposed downstream or upstream of a first heat exchanger and (ii) a second arrangement having a second heat exchanger in fluid communication with the first heat exchanger and a second economizer in fluid communication with the first economizer, the second arrangement disposed downstream of the first arrangement such that each of the first and second economizers alternate with each of the first and second heat exchangers. The processes can include (a) heating the first hydrocarbon-containing feed in the first heat exchanger at a hydrocarbon outlet temperature and (b) introducing water to the first economizer and removing the water from the convection section at an outlet temperature.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to U.S. Provisional Application No. 63 / 290,261, filed on December 16, 2021, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The embodiments of this disclosure generally relate to methods and systems for cracking hydrocarbons. Specifically, this disclosure relates to managing furnace temperature. Background Technology

[0004] Steam cracking is a commercial method for producing light olefins, such as ethylene and propylene. In a typical steam cracking process, the hydrocarbon feed is first preheated and mixed with dilution steam in the convection section of the furnace. After preheating in the convection section, the steam feed / dilution steam mixture is rapidly heated in the radiant section to achieve thermal cracking of the hydrocarbons. After a predetermined amount of thermal cracking has occurred, the furnace effluent is rapidly quenched either in an indirect heat exchanger or by direct injection of a quench feed stream.

[0005] Byproducts of cracking include carbon deposits, termed "coke," on the inner surfaces of the furnace's radiant tubes. Depending on the cracking feed, coke may also deposit in certain tubes in the convection section or in the furnace's quench system. Decoking operations affect cracking yield. Increasing the time between decoking operations by preventing coke accumulation and improving hydrocarbon conversion involves selective and controlled heating and cooling of portions of the steam cracker. Controlled heating typically utilizes a significant amount of energy from the furnace, at least partially released from it. Furthermore, steam crackers operate under different conditions depending on the type of feed, processing rate, scaling rate, and environmental factors. The furnace should be flexible enough to handle varying steam and flue gas rates for different convective loads.

[0006] There is a need for methods and systems that can provide temperature control for the furnace section, efficiently promote hydrocarbon conversion, and reduce furnace emissions from various feeds. Summary of the Invention

[0007] In at least one embodiment, a method, namely a steam cracking method, is provided. The method may include introducing a first hydrocarbon-containing feed into a convection section of a steam cracker. The convection section may include a first arrangement having a first heat exchanger and a first energy-saving device disposed downstream or upstream of the first heat exchanger. The convection section may include a second arrangement having a second heat exchanger in fluid communication with the first heat exchanger and a second energy-saving device in fluid communication with the first energy-saving device, the second arrangement being disposed downstream of the first arrangement such that each of the first and second energy-saving devices alternates with each of the first and second heat exchangers. The method may include heating the first hydrocarbon-containing feed in the first heat exchanger, the first hydrocarbon-containing feed exiting the convection section at a hydrocarbon outlet temperature. The method may include introducing water into the first energy-saving device. The method may include removing water from the convection section at a water outlet temperature. The method may include introducing hot flue gas from the radiant section of the steam cracker into the convection section.

[0008] In another embodiment, a method for designing a steam cracker is provided. The method may include simulating the processing of a hydrocarbon-containing feedstock in a convection section of the steam cracker. The convection section may include a plurality of heat exchangers and one or more heat recovery exchangers alternating with each of the heat exchangers, the heat exchangers including a first cooling fluid, and the heat recovery exchangers including a second cooling fluid. The method may include simulating heating of the convection section using hot flue gas from the radiant section of the steam cracker. The hot flue gas provides heat to the heat exchangers and one or more heat recovery exchangers. The method may include selecting the hydrocarbon outlet temperature of at least one of the plurality of heat exchangers and the outlet temperature of at least one of the one or more heat recovery exchangers. The method may include determining the arrangement of the plurality of heat exchangers and one or more heat recovery exchangers based on the hydrocarbon outlet temperature and the outlet temperature of one or more heat recovery exchangers.

[0009] In another embodiment, a steam cracking furnace is provided. The steam cracking furnace includes a convection section and a radiant section downstream of the convection section. The convection section may include a first heat exchanger in fluid communication with a first section of a pipeline. The convection (section) may include a second heat exchanger in fluid communication with both the first and second sections of the pipeline. The convection (section) may include a first energy-saving device disposed at a first location between the first and second heat exchangers, the first energy-saving device being in fluid communication with a water source. The convection section may include a second energy-saving device disposed at a second location downstream of the second heat exchanger, the second energy-saving device being in fluid communication with the first energy-saving device.

[0010] In another embodiment, a system for processing hydrocarbons is provided. The system includes a convection section and a radiative section downstream of the convection section. The system is configured to allow flue gas to flow from the radiative section through the convection section. The convection section includes a first energy-saving device in fluid communication with the boiler water feed. A second energy-saving device may be in fluid communication with the first energy-saving device and a steam drum. The system may include a first heat exchanger in fluid communication with a hydrocarbon source. The first heat exchanger may be disposed between the first and second energy-saving devices. The system may include a second heat exchanger in fluid communication with the first heat exchanger, and the second heat exchanger may be disposed downstream of the second energy-saving device.

[0011] Brief description of the attached figures

[0012] To gain a more detailed understanding of the above-described features of this disclosure, a more specific description of the disclosure, which has been briefly outlined above, can be obtained by referring to embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings are merely illustrative of exemplary embodiments and are therefore not intended to limit its scope; other equally effective embodiments may be recognized.

[0013] Figure 1 An apparatus that describes an implementation according to the present disclosure.

[0014] Figure 2 A flowchart depicting an example method for processing hydrocarbons according to an embodiment of this disclosure.

[0015] Figure 3 A flowchart depicting an example method for designing a steam cracker according to an embodiment of this disclosure.

[0016] Figure 4 Temperature load profiles of various effluents from a steam cracker for crude oil cracking feedstock, according to an embodiment of this disclosure, are depicted.

[0017] Figure 5 Plot the corresponding LMTD curves for the implementation scheme according to this disclosure.

[0018] To facilitate understanding, the same reference numerals are used where possible to indicate common elements in the figures. This covers elements and features of one embodiment that can be beneficially incorporated into other embodiments without further description.

[0019] Detailed description

[0020] This disclosure provides methods and systems for flexible, sustainable, and efficient cracking of hydrocarbons. Specifically, this disclosure provides methods and systems for managing temperature constraints in steam cracking furnaces. The hydrocarbon pyrolysis reactor (also referred to as a furnace) used in this disclosure includes a convection section and a radiant section. As used herein, a convection section can be described as a portion of the furnace in which the feed can be processed by convective heating. For example, as used herein, convective heating can be an indirect heat exchange of hot flue gas from the radiant section in a channel (e.g., a metal tube assembly) having a thermally conductive surface. The convection section may include one or more convection zones, each having an inlet into the convection section and an outlet out of the convection section. The convection section may include one or more heating zones, as well as a preheating zone, which preheats the feed using heated bottom material from a gas-liquid separator in a heat exchanger. Each convection zone may be connected in tube assemblies for heat exchange. As used herein, the terms “downstream” and “upstream” refer to relative positions along the furnace in the direction of hydrocarbon and / or water / steam flow through the pipes, but (e.g., as...) Figure 1 (As shown in the text) This term does not require that hydrocarbons and / or water / steam flow through a single continuous pipe.

[0021] Saturated steam from a steam drum can be superheated in a high-pressure steam superheater assembly. The term "superheating" refers to heating steam at a pressure above its condensation point to provide a temperature above saturation or condensation. For example, water can be heated to approximately 100°C at atmospheric pressure and then boiled to produce saturated steam, which can be further heated to approximately 200°C to produce superheated steam. Superheated steam has been found to be usable in the methods described herein because it does not condense immediately when it passes through cold pipes or equipment. In some embodiments, for high-pressure steam applications supplying electricity (e.g., ethylene plants or power plants), water can be heated from a supply of approximately 120°C (at pressures above 10 MPa) to approximately 300°C to boil, and then the saturated steam is passed through a superheater heat exchanger to provide additional superheat to the steam. To achieve the desired turbine inlet steam temperature under all furnace operating conditions, two or more fluid sources can be injected into the high-pressure steam superheater assembly. As used herein, the term "high-pressure steam" refers to steam having a pressure of about 3.5 MPa to about 5 MPa, and the term "ultra-high-pressure steam" refers to steam having a pressure higher than "high-pressure steam," for example, about 5 MPa to about 12.5 MPa, or about 9 MPa to about 11 MPa. A fluid source can be injected into high-pressure steam superheater groups arranged alternately between the pipes of multiple heat exchangers arranged in series. The superheater outlet temperature can be controlled at a substantially constant temperature, independent of changes in furnace load, degree of coking, excess oxygen level, and / or other variables. The superheater can maintain the temperature of the high-pressure steam at about 300°C or higher, for example, about 370°C to about 590°C, or about 425°C to about 590°C, and / or maintain the gauge pressure at about 4 MPa to about 12 MPa, for example, about 6 MPa to about 10 MPa, or about 7 MPa to about 9 MPa, to provide reliable superheat for steam exceeding about 50°C. A fluid source can inject water into parts of the system via flow control valves (one or more) and water atomizer nozzles (one or more). After heating, high-pressure steam can exit the convection section and a fine mist of water can be added to rapidly vaporize it, thus lowering the steam temperature in the convection section. High-temperature steam can be returned to the convection section for further heating and then exited for other uses in production facilities (e.g., ethylene production facilities). The amount of water added to the superheater controls the steam temperature.

[0022] To enhance coking control of the feedstock flow in the tube bundle and to capture waste heat, a high-pressure steam superheater can be located in the convection section. Because the superheater is situated within the flue / convection section, it serves to: superheat steam for operation of other processes and steam turbines, and quench flue gas as needed. In some embodiments, water added to the superheater can maintain the exhaust gas temperature below approximately 150°C. In some embodiments, water added to the superheater can extract waste heat from the flue gas flowing through the convection section to maintain the exhaust gas temperature below approximately 150°C.

[0023] The terms “conversion,” “transformed,” “cracking,” and “cracked” are broadly defined herein to include any suitable molecular decomposition, splitting, conversion, dehydrogenation, and / or reforming of hydrocarbons or other organic molecules by means of at least pyrolysis, and may optionally include one or more of the following methods: catalysis, hydrogenation, diluents, stripping agents, and / or related methods.

[0024] Hydrocarbon feedstocks that can be processed using the methods and systems described herein may include recirculated gases such as ethane, steam cracked oil / residue blends, gas oil, heating oil, jet fuel, diesel, kerosene, gasoline, coking naphtha, steam cracked naphtha, catalytic cracked naphtha, hydrocracking oil, reformate, residual liquid reformate, Fischer-Tropsch synthesis liquid, Fischer-Tropsch synthesis gas, natural gasoline, distillates, crude oil such as heavy crude oil, light straight-run naphtha (LVN), atmospheric tubular furnace bottoms, vacuum tubular furnace feed streams including bottoms, wide-boiling-range naphtha-gas oil condensate, heavy non-straight-run hydrocarbon feed streams from refineries, vacuum gas oil, heavy gas oil, crude oil-contaminated naphtha, atmospheric residue, heavy residue, hydrocarbon / residue blends, hydrogen / residue blends, liquefied petroleum gas (LPG), and mixtures thereof.

[0025] Unless otherwise stated, all percentages, parts, ratios, etc., are by weight. Unless otherwise stated, references to a compound or component include the compound or component itself and / or combinations with other compounds or components, such as mixtures of compounds. Furthermore, when quantities, concentrations, or other values ​​or parameters are given as a list of upper and lower limits, this should be understood as specifically disclosing all ranges formed by any pair of upper and lower limits, whether or not such ranges are disclosed individually.

[0026] Figure 1 The apparatus described herein includes some aspects. Heating of the hydrocarbon feedstock in line 131 can be achieved in any suitable manner, for example, by means of... Figure 1The furnace 100 shown is heated by indirect contact with the hydrocarbon-containing feed in the convection section 103. The convection section 103 may include a first preheating zone 105 having first and second sets of convection tubes 115, 117. The first set of convection tubes 115 may be located in a first preheating section 107 of the first preheating zone 105, and the second set of convection tubes 117 may be located in a second preheating section 109 of the first preheating zone 105, substantially adjacent to the first set of convection tubes 115. The hydrocarbon-containing feed disposed in line 131 may be fed into the first set of convection tubes 115 and heated by convection with hot flue gas from the radiation section 113 passing through the furnace 100 in direction 112, the hot flue gas passing through the convection section 103 and through each set of convection tubes (e.g., 115, 117). The hydrocarbon feed at the inlet of the convection pipe 115 of the first group can have a temperature of about 20°C to about 300°C, for example about 25°C to about 250°C, for example about 25°C to about 100°C, for example about 32°C to about 65°C, or 150°C to about 250°C (e.g. in some crude oil applications), and / or a pressure of about 790 kPa to about 1825 kPa, for example about 800 kPa to about 1800 kPa, for example about 800 kPa to about 1000 kPa, or alternatively about 1000 kPa to about 1800 kPa.

[0027] One or more (e.g., each) of a tube bank may have multiple parallel flow tube systems within the furnace, rather than just a single tube, as described, for example, in U.S. Patent No. 3,365,387, which is incorporated herein by reference. Thus, any one or more flow paths can be isolated by appropriate valve control, allowing a decoking cycle to run on one or more selected shut-off tube flow paths without interfering with the overall hydrocarbon pyrolysis process in the remaining operating tubes. Individual tube banks can be isolated, as disclosed in U.S. Patent No. 8,864,977, which is incorporated herein by reference.

[0028] The first set of convection tubes 115 includes one or more rows of tubes in fluid communication with each other. Each row of tubes can act as a heat exchanger, exchanging heat from flue gas traveling perpendicular to each row of tubes in direction 112 to the contents flowing through the tubes of that row. A first heat recovery exchanger 172 and a second heat recovery exchanger 174 (e.g., an energy-saving device or a steam superheater) can be arranged adjacent to one or more of the first heat exchanger 171 and the second heat exchanger 173, for example, in an alternating arrangement (relative to the vertical direction of the furnace 100). The heat recovery exchanger (also referred to as a "water supply device") can be a waste heat recovery exchanger that discharges loads to a utility steam supply. The energy-saving device can be a heat recovery exchanger that preheats the fluid flow within the energy-saving device at the outlet of the energy-saving device or downstream to increase steam production. The steam superheater can be a heat exchanger that superheats steam to convert existing generated steam into energy suitable for providing electricity to equipment (e.g., the main turbine). The first heat recovery exchanger 172 and the second heat recovery exchanger 174 may receive water from a water source 170, such as a boiler water source. While each of the first heat exchangers 171 and 173 and each of the first heat recovery exchangers 172 and 174 is depicted with two rows each, partially traversing the diameter of the furnace 100, other arrangements and numbers of rows are also covered and may be used depending on various factors such as feed flexibility, environmental conditions, and operating conditions. While the first preheating section 107 is depicted with alternating heat recovery exchangers and heat exchangers, other arrangements, such as alternating heat recovery heat exchangers and heat exchangers in the second preheating section 109, are also covered. In some embodiments, a selective catalytic reduction (SCR) bed 180 for nitrogen oxide reduction is disposed between the first preheating section 107 and the second preheating section 109. Nitrogen oxides may be NO, NO2, N2O, or combinations thereof. Energy-saving devices may be positioned above or below the SCR 180. The placement of the energy-saving device above or below the SCR 180 refers to its physical positioning, which directs the hot flue gas upwards, allowing the exhaust above the heat exchangers to use cooler flue gas compared to the exhaust below each heat exchanger. It has been found that placing the energy-saving device directly above the SCR 180 provides an increased temperature for the dry feed outlet and an increased temperature for the hydrocarbon feed in the first preheating section 107. This approach is highly effective because heat transfer to the hydrocarbon feed within the first preheating section 107 reduces the heat required to promote steam cracking of the hydrocarbon feed as it travels through the furnace. Energy-saving devices placed below the SCR 180 only increase the required dry feed outlet temperature for the already pinned dry hydrocarbon exhaust, which is already operating near the desired temperature. Energy-saving devices placed between dry hydrocarbon exhausts do not improve exhaust efficiency, and the increased mechanical complexity is not justified. All arrangements are covered depending on the type of hydrocarbon feed, operating conditions, and furnace conditions.For example, in the case of feed preheating load after steam generation via the furnace effluent (referred to as feed-preheating secondary TLE), some dry feed preheating load is removed from the convection section. Instead of the removed dry feed preheating load, a larger energy-saving unit consumes the same flue gas load that would have been consumed by dry feed preheating without removing the load from the convection section. Instead, this load is provided in an additional boiler feed water preheating unit. The additional boiler feed water preheating unit has the advantage of a low-cost flow scheme for ethane crackers. In this case, the dry feed preheating unit can be positioned above the larger BFW energy-saving unit. The SCR bed can be positioned below the BFW energy-saving unit, without additional dry feed preheating before steam injection.

[0029] Pinch point arrangement refers to the arrangement of heat exchangers to limit the load to a predetermined target or to confine it within that target. The pinch point is the section of the heat exchanger with the smallest temperature difference.

[0030] Furnace 100 is a steam cracking furnace and includes a radiant section 113 downstream of a convection section 103. The convection section 103 includes a first heat exchanger 171 in fluid communication with a first section of a pipeline. The convection section includes a second heat exchanger 173 in fluid communication with both the first and second sections of the pipeline. A first heat recovery exchanger 172 is a first energy-saving device and is located at a first position between the first heat exchanger 171 and the second heat exchanger 173, and is in fluid communication with a water source 170. A second heat recovery exchanger 174 is a second energy-saving device and is located at a second position downstream of the second heat exchanger 173, and is in fluid communication with the first heat recovery exchanger 172.

[0031] The first heat exchanger 171 includes a first surface area, and the second heat exchanger 173 includes a second surface area larger than the first surface area. The “surface area” of a heat exchanger refers to the inner surface of the tube exposed to flue gas (e.g., forming an interface with the flue gas). The ratio of the first surface area to the second surface area may be based on a predetermined heating rate of the hydrocarbon feed disposed within each heat exchanger. For example, the first surface area may have a larger surface area relative to the second surface area to achieve a higher temperature of the hydrocarbon feed within the first heat exchanger 171 relative to the second heat exchanger. Surface area refers to the area of ​​the tube within which the hydrocarbon feed can (indirectly) interact with the flue gas. The percentage of the first surface area to the total surface area (e.g., the first and second surface areas) may be from about 30% to about 100%, for example, from about 35% to about 50%. The percentage may depend on the relative temperature limitations of the furnace. In some implementations, preheating the warmer feed entering the convection section will require less initial preheating above the energy-saving unit compared to preheating the cooler feed, and potentially less initial preheating than the energy-saving unit at the furnace top, to minimize flue gas temperature. In some implementations, heavier feeds such as naphtha or crude oil will have a lower maximum temperature (e.g., a lower drying temperature limit) before water or steam injection compared to lighter feeds such as ethane. The lower maximum temperature may correspond to less preheating of the dry feed or may allow more of the dry feed preheating zone to be moved above the energy-saving unit.

[0032] The first heat exchanger 171 and the second heat exchanger 173 together comprise about 10 to about 20 rows of pipe, and the first heat recovery exchanger 172 and the second heat recovery exchanger 174 together comprise about 4 to about 10 rows of pipe. The number of rows of pipe may be determined based on the feed, furnace 101 temperature, predetermined heating rate of the hydrocarbon feed, and / or other considerations. In some embodiments, the first heat exchanger 171 comprises 2 to about 10 rows of pipe heated by flue gas flow in direction 112. In some embodiments, the second heat exchanger comprises about 5 to about 15 rows of pipe. In some embodiments, the pipe is about 5.5 meters to 25 meters long. In some embodiments, the pipe has a nominal pipe diameter (NPS) of about 3 inches to about 8 inches. In some embodiments, one or more energy-saving devices have the same or substantially the same diameter as another heat exchanger. In some embodiments, one or more energy-saving devices have a diameter equal to or greater than the diameter (NPS) of one or more heat exchangers by 2 inches.

[0033] The total external surface area of ​​the first heat recovery exchanger 172, the second heat recovery exchanger 174, the first heat exchanger 171, and the second heat exchanger 173 can be approximately 6,000 m². 2 To approximately 18,000 m 2 The total external surface area depends on the furnace size, the amount or rate of waste heat to be recovered, and / or other considerations.

[0034] A furnace 100 is provided for processing hydrocarbon-containing feedstock, including a convection section 103 and a radiant section 113 downstream of the convection section. The system is configured to allow flue gas to flow from the radiant section 113 through the convection section in direction 112. Specifically, the flue gas direction 112 is generally in an "upstream" direction.

[0035] The heated hydrocarbon feed from line 133 may be mixed with the main dilution steam from line 137 and / or the fluid, such as water, from line 135. The fluid may be steam, vapor, liquid, or a mixture thereof. The mixing of the heated hydrocarbon feed and the main dilution steam from line 137 and / or the fluid from line 135 may be carried out using any mixing device known in the art, such as a dual-sprayer assembly, either inside or outside the furnace 100, for example, outside the furnace 100. The fluid from line 135 may enter the first sprayer 102a of the dual-sprayer assembly, which may prevent or reduce hammering caused by sudden evaporation of the fluid when it is introduced into the heated hydrocarbon feed.

[0036] Secondary dilution steam from line 141 can be heated in the first superheater tube assembly 143 to produce the second separator feed 147. The secondary dilution steam can be sourced from preheated (e.g., in the convection section 103 of furnace 100) primary dilution steam. Either or both of the primary and secondary dilution steam can include acidic or process steam. Superheating the acidic or process dilution steam reduces or eliminates the risk of corrosion from condensation of the acidic or process steam. The primary dilution steam from line 137 can be injected into the second sprayer 102b of the dual sprayer assembly, and the resulting feed mixture from line 136 can enter the convection tubes 117 of the second assembly for additional heating with flue gas traveling in the direction 112 to produce the first separator feed 139. The first separator feed 139 can be mixed with the second separator feed 147 and introduced into the flash / liquid separator vessel 153 to produce two phases, including a gas phase from line 155 and a liquid phase from line 157. The gas phase of line 155 may include volatile hydrocarbons and vapor. The liquid phase of line 157 may include non-volatile hydrocarbons, including coke precursors. The gas phase may be fed into the lower convection section tube group 119 in the second preheating zone 111 of convection section 103. The second preheating zone 111 may be adjacent to the radiant section 113 of the furnace, and the gas phase may pass through the cross tube 160 to the radiant section of the pyrolysis furnace for cracking into the radiant section effluent of line 162. The radiant section effluent of line 162 may be rapidly cooled in a transfer line exchanger (“TLE”) 163 to generate saturated steam, which may be superheated in the superheater convection section 120. The steam from the TLE may be used to drive a large turbine or may be reintroduced into the furnace as dilution steam. In some embodiments, an ammonia injection grid system (AIG) 181 is disposed between the second preheating section 109 and the superheater convection section 120.

[0037] Figure 2A flowchart depicts a method 200 for processing hydrocarbons according to some aspects of this disclosure. Method 200 may include introducing a first hydrocarbon-containing feed into a convection section of a steam cracker 202. The convection section includes a first arrangement having a first heat exchanger and a first energy-saving device disposed downstream or upstream of the first heat exchanger. The convection section has a second arrangement having a second heat exchanger in fluid communication with the first heat exchanger and a second energy-saving device in fluid communication with the first energy-saving device. The second arrangement is disposed downstream of the first arrangement such that each of the first and second energy-saving devices is arranged alternately with each of the first and second heat exchangers.

[0038] Method 200 includes heating a first hydrocarbon-containing feed 202 in a first heat exchanger, the first hydrocarbon-containing feed exiting the convection section at a hydrocarbon outlet temperature. Method 200 includes introducing water into a first energy-saving device 206. Method 200 includes removing water from the convection section 208 at a water outlet temperature. Method 200 includes introducing hot flue gas from the radiant section of a steam cracker into the convection section 210. A second arrangement may be determined based on the hydrocarbon outlet temperature and water outlet temperature of the convection section. The hot flue gas alternately contacts the energy-saving device and the heat exchanger (due to the alternating configuration of the energy-saving device and the heat exchanger), such that heat is exchanged between the flue gas and the energy-saving device before and / or after heat exchange between the flue gas and the heat exchanger.

[0039] The first energy-saving device is located downstream of the first heat exchanger. The second arrangement is determined based on the operating parameters of the first hydrocarbon-containing feed being processed in the furnace and the second hydrocarbon-containing feed to be processed in the furnace, wherein the operating parameters include the operating mode. The operating mode may include cracking mode, decoking mode, or a combination thereof.

[0040] The first heat exchanger comprises a meandering continuous convection tube containing multiple substantially parallel rows. Determining the second arrangement of the 210 convection sections involves determining the number of parallel rows of the first heat exchanger based on the hydrocarbon outlet temperature to provide the surface area of ​​the first heat exchanger. Increasing the number of parallel rows of the first heat exchanger increases the surface area of ​​the first heat exchanger, and the increased surface area increases the hydrocarbon outlet temperature. Similarly, decreasing the number of parallel rows of the first heat exchanger decreases the surface area of ​​the first heat exchanger, and the decreased surface area decreases the hydrocarbon outlet temperature.

[0041] The water outlet temperature of the energy-saving device (e.g., the second energy-saving device) closest to the radiant section can be determined relative to the saturation temperature of water at a given pressure. The water outlet temperature can be approximately 170°C below the saturation temperature to approximately the saturation temperature, for example, approximately 60°C below the saturation temperature, or approximately 20°C below the saturation temperature. In some embodiments, the water outlet temperature can be approximately 160°C to approximately 328°C, for example, approximately 220°C to approximately 280°C. The hydrocarbon outlet temperature of the second heat exchanger 173 (e.g., the second hydrocarbon outlet of the second heat exchanger) is approximately 175°C to approximately 390°C, for example, approximately 200°C to approximately 300°C, or for example, approximately 240°C. The hydrocarbon outlet temperature is based on the flue gas temperature, the surface area of ​​one or more of the heat exchangers, the surface area of ​​one or more of the heat recovery exchangers, the arrangement of the heat exchangers relative to the heat recovery exchangers, or a combination thereof (one or more). In at least one operating mode, the hydrocarbon outlet temperature (e.g., at 133) is within approximately 5°C to approximately 30°C of the water outlet temperature of the second energy-saving device.

[0042] Figure 3 A flowchart depicts an example method 300 for designing a steam cracker according to some aspects of this disclosure. Method 300 may include (simulating) processing 302 hydrocarbon-containing feedstock in a convection section of the steam cracker. The convection section includes a plurality of heat exchangers and one or more heat recovery exchangers alternating with each of the heat exchangers. Each heat exchanger includes a first cold fluid. Each heat recovery exchanger includes a second cold fluid.

[0043] Method 300 includes (simulating) heating 304 convection section with hot flue gas from the radiant section of a steam cracker. The hot flue gas provides heat to a heat exchanger and one or more heat recovery exchangers.

[0044] Method 300 includes selecting the hydrocarbon outlet temperature of at least one of 306 heat exchangers and the outlet temperature of at least one of one or more heat recovery exchangers.

[0045] Method 300 includes determining the arrangement of 308 multiple heat exchangers and one or more heat recovery exchangers based on the hydrocarbon outlet temperature and the outlet temperature of one or more heat recovery exchangers.

[0046] The arrangement of multiple heat exchangers and one or more heat recovery exchangers can be determined based on the logarithmic mean temperature difference (LMTD) of each of the heat exchangers and heat recovery exchangers for countercurrent flow between hot flue gas and cold-side fluid, where the LMTD is determined by the following Equation 1:

[0047] …Equation 1, where:

[0048] It is the hot inlet temperature of the hot flue gas entering each heat exchanger or heat recovery exchanger. It is the hot outlet temperature of the hot fluid leaving the heat exchanger or heat recovery exchanger. It is the cold inlet temperature of the first or second cold fluid entering the heat exchanger or heat recovery exchanger. It is the cold outlet temperature of the first or second cold fluid leaving the heat exchanger or heat recovery exchanger. LMTD is a function of the temperature difference in the heat exchange, such that the heat transfer rate decreases as the temperature difference decreases with the cumulative heat transfer. Equation 1 represents the LMTD relationship for a countercurrent exchanger (such as the heat exchanger described herein).

[0049] In some embodiments, the arrangement of multiple heat exchangers and one or more heat recovery exchangers may be further based on regulating (e.g., minimizing) the total surface area of ​​the convection section. The total surface area may be substantially equal to the total interfacial area between the hot flue gas and the first and second cold fluids. In some embodiments, the surface area of ​​one or more heat exchangers or one or more heat recovery exchangers provides for regulating the load (Q) of one or more heat exchangers or one or more heat recovery exchangers. Each of the one or more heat recovery exchangers may be selected from energy-saving devices, steam superheaters, water exchangers, or combinations thereof. As used herein, “load (Q)” refers to the heat transfer rate measured in W or J / s.

[0050] The load (Q) of one or more of the heat exchangers and / or heat recovery exchangers can be simulated by calculating the LMTD of one or more of the heat exchangers and / or heat recovery exchangers using the LMTD equation shown in Equation 1.

[0051] Each load in each of the heat exchangers and heat recovery exchangers is related to the interfacial area (A) of each interface between the hot flue gas and the first and second cold fluids and the LMTD of each of the heat exchangers and heat recovery exchangers by the energy equation (Equation 2):

[0052] ...Equation 2,

[0053] Where Q is the load, U is the heat transfer coefficient, A is the interfacial area, and LMTD is the logarithmic mean temperature difference.

[0054] The heat transfer coefficient (U) is determined based on one or more parameters, such as flue gas slack film thickness, flue gas slack film conductivity, flue gas fouling resistance, heat exchanger or energy-saving device wall thickness, heat exchanger or energy-saving device wall conductivity, extended surface efficiency, cold fluid fouling resistance, cold fluid slack film thickness, cold fluid slack film conductivity, and combinations thereof (one or more). The heat transfer coefficient can have watts per meter (W / m). 2 The unit of Kelvin. The heat transfer area can be adjusted for cylindrical heat transfer components or extended surfaces.

[0055] The first heat recovery exchanger can be located upstream or downstream of the first heat exchanger. A second cold fluid can be introduced from the heat recovery exchanger to the steam generator heat exchanger to form steam. In some embodiments, the steam is introduced into a convection section to form superheated steam. The steam can be introduced into a convection section downstream of the first and second heat exchangers.

[0056] Method 300 can be performed by one or more computers or computer systems. Thus, it will be understood that method 300 can be executed by at least a portion of a computer, including using a processor, or by operating the processor via electrical signals representing data in a structured form. The method can be implemented in hardware, software, and / or firmware, and / or combinations thereof. The operation transforms the data into a computer model for simulating method design parameters such as furnace component arrangement and component dimensions. The data may include the properties and characteristics of the hydrocarbons to be fed into the furnace. The data transformation may include user-input principles such as mathematical relationships (e.g., Equations 1 and 2), scientific theories or laws, furnace limitations, environmental considerations, and other considerations. The computer model may access additional data from one or more libraries located on a server or in memory.

[0057] In some implementations, (simulating) processing 302 hydrocarbon feed in the convection section of a steam cracker involves using one or more computers or computer systems to simulate the processing of 302 hydrocarbon feed.

[0058] In some implementations, (simulating) heating the 304 convection section with hot flue gas from the radiant section of the steam cracker includes using one or more computers or computer systems to simulate heating the 304 convection section with hot flue gas.

[0059] Decoking and cracking operations

[0060] The systems and methods disclosed herein provide flexibility in the operation of a furnace (e.g., furnace 100) during normal cracking operations and during decoking operations. During cracking operations, “coke” can accumulate on various internal contact surfaces of the pyrolysis furnace, such as in the radiant section 161. Coke can be removed during decoking operations, which may include operating parameters of individual tube banks, such as the superheater convection section 200, to allow decoking of the radiant section 161. Decoking operations may include operating the furnace in decoking mode and allowing the generation of TLE steam in TLE 264 while simultaneously cooling the flue gas (in direction 112). In a split operation referred to herein as “decoking in operation,” a portion of the furnace, such as the thermal cracking tubes, may be isolated and decoked while other portions continue to operate in cracking mode.

[0061] The cracking mode may have a first set of operating conditions, including flue gas rate, TLE flow rate, and steam temperature. In some embodiments, the first set of operating conditions includes flue gas flow rates of approximately 150 tons per hour (“tph”) to approximately 350 tph, for example, approximately 200 tph to approximately 300 tph, for example, approximately 250 tph.

[0062] The decoking mode may have a second set of points, including flue gas velocity, TLE flow rate, and steam temperature. In some embodiments, the second set of operating conditions for the decoking mode includes flue gas flow rates of approximately 40 tph to approximately 60 tph, for example, approximately 45 tph to approximately 55 tph, for example, approximately 50 tph. In some embodiments, the second set of operating conditions may also be used for a steam standby mode. The steam standby mode refers to the transition to and from decoking and serves as a backup condition that can be maintained for several hours to several days and is easily changed to decoking or cracking modes. As the mode changes, the operating conditions change and are managed by regulating controls to maintain the temperature within the remaining furnace components within range. Specifically, the managed temperature is for one or more of the following: flue gas temperature, SCR 180 inlet temperature, AIG 181 inlet temperature, separator 153 inlet temperature, first separator feed 139 temperature, gas phase flow 160 temperature, superheater convection section 120, first preheating section 107, second preheating section 109, and / or the outlet of one or more of the heat recovery exchangers (e.g., first heat recovery exchanger 172, second heat recovery exchanger 174). In some embodiments, the SCR 180 is connected to the furnace inner wall and occupies a portion of the convection section volume, such that the flue gas passes through the SCR 180 without bypassing it.

[0063] The weight ratio of flue gas rates from cracking mode to decoking mode can be approximately 2:1 to approximately 7:1, for example, approximately 4:1 to approximately 6:1, or for example, approximately 5:1. In some embodiments, three different operating modes include: 1) a high superheated steam flow rate and low-load cracking mode with a saturated steam feed rate of approximately 66 tph (e.g., for cracking recirculated gas such as ethane); 2) a low superheated steam flow rate and high-load cracking mode with a saturated steam feed rate of approximately 20 to approximately 40 tph (e.g., for cracking crude oil); and 3) a very low saturated steam flow rate and high comparative flue gas flow rate decoking mode with a saturated steam feed rate of approximately 40 to approximately 50 tph, for example, approximately 48 tph. Operating mode 1 (e.g., cracking recirculated gas) can have an inlet flue gas temperature of approximately 700°C to approximately 1100°C, for example, approximately 800°C to approximately 1000°C, or for example, approximately 900°C. Operating mode 2 (e.g., cracked crude oil) may have an inlet flue gas temperature of about 675°C to about 1075°C, for example, about 775°C to about 975°C, or for example, about 877°C. Both operating modes 1 and 2 are cracking modes. In some embodiments, operating mode 1 may have an inlet flue gas temperature that is about 5°C to about 40°C, for example, about 10°C to about 30°C, or for example, about 23°C higher than the inlet flue gas temperature of operating mode 2. In some embodiments, operating mode 1 may have a flue gas flow rate that is about 1% to about 5%, for example, about 2% to about 4%, or for example, about 3% higher than that of operating mode 2, and operating mode 1 may have a saturated steam feed rate that is about 1.5 to about 2.5 times, for example, about 2.2 times that of operating mode 2. Increasing the flue gas temperature can improve the flexibility of decoking operations, wherein decoking operations (e.g., decoking operation 3) may have a flue gas temperature of about 150°C to about 200°C, different from that of cracking operations, and the ratio of flue gas flow rate to process flow rate may be substantially different from that of cracking operations. The ratio of flue gas flow rate to process flow rate (e.g., hydrocarbon feed flow) can affect heat transfer and cause the flue gas to cool more or less as it travels upwards in direction 112. The ratio of flue gas flow rate to process flow rate can also affect the temperature of upstream furnace components in the superheater convection section.

[0064] The disclosure also covers methods that can be performed by a programming system having algorithms stored in the system's memory. The algorithms may include a number of instructions that, when executed by a processor, cause the methods described herein to be performed.

[0065] Example

[0066] Figure 4 Describe the temperature load curves of various effluents from a steam cracker for crude oil cracking feedstock. Figure 5Plot the corresponding LMTD curves. Plot the flue gas curve 402 along the curves of each component in the convection section (e.g., 404, 406, 408, 410, 412, 414, 416, 418, 420, 422, 424). Based on the analysis of the curves, arrange components to improve heat transfer efficiency, for example, through convection heating from the flue gas to the heat exchanger and heat recovery exchanger. If a gap is shown, such as gap 432, then the service components, such as those depicted by 406, 408, 410, each may be shifted or rearranged in direction 430 to close the heat transfer gap 432. Components 406, 408, and 410 may be one or more superheaters shown in the superheater section. Furthermore, "pinch points" (e.g., 440) may be created to further improve heat transfer efficiency. As used herein, a "pinch" refers to a location within a heat exchange network (e.g., one or more heat exchangers) where the temperature difference between the hot and cold sides is minimized relative to the rest of the network. A pinch can be defined as a location where the temperature load curve of the hot side of the heat exchange region lies within approximately 10%, for example, approximately 5%, of the temperature load curve of the cold side of the heat exchange region. Specifically, a first drying hydrocarbon heat exchanger with six rows of pipes (e.g., indicated by curve 424) is positioned adjacent to a first energy-saving device with two rows of pipes (e.g., indicated by curve 422). The first hydrocarbon heat exchanger is in fluid communication with a second drying hydrocarbon heat exchanger with ten rows of pipes (e.g., indicated by curve 420). The second drying hydrocarbon heat exchanger 420 is positioned between the first energy-saving device and the second energy-saving device with four rows of pipes. The second energy-saving device 418 is in fluid communication with the first energy-saving device 422.

[0067] Figure 4 Each component curve corresponds to Figure 5 The LMTD curves depicted are 504, 506, 508, 510, 512, 514, 516, 518, 520, 522, and 524. The horizontal axis is the "geometry" or arrangement of the heat transfer elements, each geometry potentially having one or more rows of pipes arranged within the convection section, parallel to each other and each substantially perpendicular to the flue gas direction. LMTD curves can be arranged, for example, as shown in... Figure 5 The curve shown is essentially continuous.

[0068] The arrangement provides greater flexibility and furnace sustainability. Component arrangements can be made to achieve increasing or decreasing slopes in the load or LMTD curves while minimizing the amount of piping surface area. This is illustrated in Tables 1 and 2 below. Table 1 provides an example of an alternating dry hydrocarbon (HC) and boiler feed water (BFW) energy-saving unit arrangement. To achieve a second energy-saving unit outlet temperature of 483°F and a second dry hydrocarbon outlet temperature of 375°F, approximately 139,483 ft... 2The total heat exchange area is calculated using Equations 1 and 2 (above). Table 2 provides an illustration of a single energy-saving unit and a single dry feed preheating arrangement for processing the same crude oil feed as depicted in Table 1.

[0069] It can be seen that approximately 154,960 ft of energy is required to achieve the energy-saving unit outlet temperature of 483°F and the dry hydrocarbon outlet temperature of 375°F. 2 The total heat exchange area. Compared to the dual energy-saving device implementation scheme, this requires approximately 11% more external pipe surface area for the same amount of heat transfer.

[0070] Table 3 describes the processing of crude oil by a single energy-saving unit and a single dry feed preheating arrangement, with a heat exchange area of ​​139,483 ft as described in Table 1. 2 The same. However, with approximately the same heat exchange area, the dry hydrocarbon outlet temperature is 367 °F, which is about 2% lower than the embodiment in Table 1. Correspondingly, the flue gas outlet temperature is about 293 °F compared to about 282 °F, resulting in reduced waste heat recovery and lower efficiency, a reduction of 350 kW (1.3 MBTU / hr).

[0071]

[0072] Table 2 Arrangement of Individual Energy-Saving Devices and Individual Drying Feed Preheating Units

[0073]

[0074] Table 3 Arrangement of Individual Energy-Saving Devices and Individual Drying Feed Preheating Units

[0075]

[0076] Similar calculations for gas feed show that a single energy-saving device and a single dry feed preheating arrangement result in a 42% increase in the external surface area of ​​the heat transfer tubes to achieve the same surface area. Furthermore, with the same amount of surface area, the single energy-saving device and single dry feed preheating arrangement reduce both the energy-saving device and the dry hydrocarbon outlet temperature. The dry hydrocarbon outlet temperature decreases by 2.8%, and the energy-saving device outlet temperature decreases by 1.3%.

[0077] Energy-saving unit layouts, including positioning, number of rows, and diameter, can be selected to maximize steam production during cracking while minimizing recirculated gas steam production. Therefore, by setting pinch points to minimize steam production from one feed and maximize steam production from another, and bringing the two curves closer together, the range of steam temperature or desuperheater rate can be minimized. Specifically, energy-saving units can be configured such that the process conditions are the LMTD (Limited Area Tolerance) for recirculated gas and the area for crude oil feed, such that the two corresponding curves are within approximately 10% of each other.

[0078] The arrangement of energy-saving devices is determined based on the relative amounts of the drying feed rate, the water flow rate supplying the generated steam, and the available flue gas flow rate. In some embodiments, for crude oil crackers operating in naphtha cracking mode, operating conditions include high drying feed rates, high steam production, and low flue gas rates relative to other modes and / or feed types. In some embodiments, crude oil crackers in crude oil cracking mode have high drying feed rates, low steam production (e.g., due to TLE scaling), and low flue gas rates relative to other conditions. In some embodiments, crude oil crackers in decoking mode have very low drying feed rates (steam and air), very low steam production (due to TLE scaling and low drying feed rates), and very high flue gas rates relative to other conditions. The alternating arrangement of each embodiment reduces extreme operating conditions by clamping the flue gas temperature together with the preheating temperature of the drying feed or energy-saving device. In some implementations, if excessive flue gas is generated and insufficient steam production is not achieved, such as in decoking mode, the energy-saving unit with clamping reduces the imbalance by "disabling" some energy-saving unit areas. In some implementations, if a large dry feed, high steam production, and low flue gas rate are introduced (in the case of naphtha feed), then the dry feed chute reduces this imbalance by clamping the flue gas at the top of the convection section. This effectively disables some areas of the excessive dry feed chute in this operating mode. Arrangements and techniques for flexibility are particularly useful for crude oil crackers.

[0079] The energy-saving device arrangement described in this article can also be used to minimize the heat transfer area in an ethane cracker.

[0080] In general, methods are provided for arranging hot and cold service components, such as heat exchangers and heat recovery exchangers, to control the load on the convection section of a steam cracker. The steam cracker features alternating heat exchangers and heat recovery exchangers, which allow for the processing of various feed types and provide reduced flue gas temperatures released from the furnace. The reduced flue gas temperatures decrease the environmental impact of gases released into the atmosphere.

[0081] All documents mentioned herein are incorporated herein by reference, including any priority documents and / or test procedures, provided they do not contradict this document. As will be apparent from the foregoing general description and specific embodiments, while the form of this disclosure has been set forth and described, various changes may be made without departing from the spirit and scope of this disclosure. Therefore, it is not intended to limit the scope of this disclosure. Similarly, the term “comprising” is considered synonymous with the term “including.” Likewise, whenever a component, element, or group of elements is preceded by the conjunction “comprising,” it should be understood that we also consider a group of the same components or elements preceded by the conjunctions “substantially composed of,” “composed of,” “selected from,” or “is,” and vice versa.

[0082] For the sake of brevity, this document only explicitly discloses certain ranges. However, a range not explicitly stated can be described by combining any lower limit with any upper limit, and a range not explicitly stated can be described by combining any lower limit with any other lower limit; similarly, a range not explicitly stated can be described by combining any upper limit with any other upper limit. Furthermore, even if not explicitly stated, each point or individual value within a range is included between its endpoints. Thus, each point or individual value can serve as its own lower or upper limit, combined with any other point or individual value or any other lower or upper limit, to describe a range not explicitly stated.

Claims

1. Steam cracking methods, including: A first heat exchanger is introduced into the convection section of a steam cracker containing a first hydrocarbon feedstock. The convection section includes a first arrangement having a first heat exchanger and a first energy-saving device disposed downstream or upstream of the first heat exchanger. The convection section includes a second arrangement having a second heat exchanger in fluid communication with the first heat exchanger and a second energy-saving device in fluid communication with the first energy-saving device. The second arrangement is disposed downstream of the first arrangement such that each of the first and second energy-saving devices alternates with each of the first and second heat exchangers along the vertical direction of the steam cracker. The first hydrocarbon-containing feed is heated in a first heat exchanger, and then heated in a second heat exchanger. The first hydrocarbon-containing feed exits the outlet of the second heat exchanger at the hydrocarbon outlet temperature. Water is introduced into the first energy-saving device; Water is heated in a first energy-saving device, and then heated in a second energy-saving device, with the water exiting the outlet of the second energy-saving device at the water outlet temperature; and Hot flue gas from the radiant section of the steam cracker is introduced into the convection section.

2. The method according to claim 1, wherein the first energy-saving device is disposed downstream of the first heat exchanger, and wherein, As the hot flue gas flows from the radiant section through the convection section, it comes into contact with the second energy-saving device, then the second heat exchanger, then the first energy-saving device, and then the first heat exchanger.

3. The method of claim 1 or claim 2, wherein the first heat exchanger comprises a continuous convection tube in a meandering pattern, the continuous convection tube comprising a plurality of substantially parallel rows.

4. The method according to claim 1 or claim 2, wherein: The water outlet temperature is 160℃ to 328℃, and The hydrocarbon outlet temperature ranges from 175°C to 390°C.

5. The method according to claim 1 or claim 2, wherein in at least one operating mode, the hydrocarbon outlet temperature is within 5°C to 30°C of the water outlet temperature.

6. The method of claim 1, wherein each of the first and second energy-saving devices and each of the first and second heat exchangers alternately generate pinch points in the heat exchange network of the convection section along the vertical direction of the steam cracker, at which the temperature difference between the hot and cold sides is minimized relative to the rest of the heat exchange network.

7. The method according to claim 1, wherein the first energy-saving device is disposed upstream of the first heat exchanger, and wherein, As the hot flue gas flows from the radiant section through the convection section, it comes into contact with the second heat exchanger, then the second energy-saving device, then the first heat exchanger, and then the first energy-saving device.

8. Methods for designing steam cracking furnaces, including: The simulation describes the processing of hydrocarbon-containing feed in the convection section of a steam cracker, the convection section comprising a plurality of heat exchangers and one or more heat recovery exchangers alternating with each of the heat exchangers, one or more of the heat exchangers containing a first cooling fluid, and one or more of the heat recovery exchangers containing a second cooling fluid. The simulation uses hot flue gas from the radiant section of a steam cracker to heat the convection section, which in turn provides heat to a heat exchanger and one or more heat recovery exchangers. Select the hydrocarbon outlet temperature of at least one of a plurality of heat exchangers and the outlet temperature of at least one of a plurality of heat recovery exchangers; and The arrangement of multiple heat exchangers and one or more heat recovery exchangers is determined based on the hydrocarbon outlet temperature and the outlet temperature of one or more heat recovery exchangers.

9. The method of claim 8, wherein determining the arrangement is further based on minimizing the total surface area of ​​the convection section, wherein the total surface area is substantially equal to the total interfacial area between the hot flue gas and the first and second cold fluids.

10. The method of claim 9, further comprising adjusting the load of at least one of the heat exchanger and the heat recovery exchanger by adjusting the total surface area of ​​the convection section.

11. The method according to any one of claims 8 to 10, wherein one or more heat recovery exchangers are selected from energy-saving devices, steam superheaters, water exchangers, and one or more combinations thereof.

12. The method according to any one of claims 8 to 10, further comprising determining the logarithmic mean temperature difference (LMTD) of at least one of the heat exchangers and at least one of the heat recovery exchangers, wherein the LMTD is determined by the following equation: ， in It is the hot inlet temperature of the hot flue gas entering each heat exchanger or heat recovery exchanger. It is the hot outlet temperature of the hot fluid leaving the heat exchanger or heat recovery exchanger. It is the cold inlet temperature of the first or second cooling fluid entering the heat exchanger or heat recovery exchanger. It is the cold outlet temperature of the first or second cooling fluid leaving the heat exchanger or heat recovery exchanger.

13. The method of claim 12, further comprising adjusting the load of one or more heat exchangers and / or one or more heat recovery exchangers by adjusting the LMTD of one or more heat exchangers and / or one or more heat recovery exchangers.

14. The method of claim 12, wherein each load of each of the heat exchanger and the heat recovery exchanger is related by an energy equation to each interface area (A) of each interface between the hot flue gas and the first and second cold fluids and to each LMTD of each of the heat exchanger and the heat recovery exchanger: ， Where U is the heat transfer coefficient.

15. The method of claim 14, further comprising calculating the heat transfer coefficient (U) based on one or more parameters selected from: Flue gas stagnation film thickness; Flue gas stagnation membrane conductivity; Flue gas scaling resistance; Wall thickness of heat exchangers or energy-saving devices; The wall conductivity of heat exchangers or energy-saving devices; Extended surface efficiency; Cooling fluid scaling resistance; Cooling fluid stagnant film thickness; Cooling fluid stagnant film conductivity; and One or more combinations thereof.

16. The method of claim 15, wherein the convection section comprises two heat exchangers and two heat recovery exchangers.

17. The method of claim 15, further comprising: The second cooling fluid in the heat recovery exchanger is introduced into the steam generator heat exchanger to form steam; and Steam is introduced into the convection section to form superheated steam.

18. A steam cracking furnace, comprising a convection section and a downstream radiant section, wherein the convection section includes: A first dry hydrocarbon heat exchanger that is in fluid communication with the first section of the pipeline; A second drying hydrocarbon heat exchanger in fluid communication with the first and second sections of the pipeline; A first energy-saving device is disposed at a first position between a first drying hydrocarbon heat exchanger and a second drying hydrocarbon heat exchanger, and the first energy-saving device is in fluid communication with a water source; and A second energy-saving device is installed at a second location downstream of the second drying hydrocarbon heat exchanger, and the second energy-saving device is in fluid communication with the first energy-saving device.

19. The steam cracking furnace according to claim 18, wherein the first drying hydrocarbon heat exchanger has a first surface area and the second drying hydrocarbon heat exchanger has a second surface area, wherein the second surface area is greater than the first surface area.

20. The steam cracking furnace according to claim 18 or claim 19, wherein the first and second drying hydrocarbon heat exchangers together comprise 10 to 20 rows of pipes, and the first and second energy-saving devices together comprise 4 to 10 rows of pipes.

21. The steam cracker furnace of claim 18 or claim 19, wherein the total external surface area of the first economizer, the second economizer, the first dry hydrocarbon heat exchanger, and the second dry hydrocarbon heat exchanger is 6,000 m 2 to 18,000 m 2 .

22. The steam cracker of claim 18, wherein the convection section comprises a selective catalytic reduction (SCR) bed, and wherein the second energy-saving device is disposed directly above the SCR in the direction of flue gas flow through the convection section.

23. A system for processing hydrocarbons, comprising: Convection section; In the radiative section downstream of the convection section, the system is configured to allow flue gas to flow from the radiative section through the convection section, the convection section comprising: The first energy-saving device connected to the boiler water feed fluid; A second energy-saving device that is in fluid communication with the first energy-saving device and the steam drum; A first heat exchanger in communication with the hydrocarbon source fluid, the first heat exchanger being disposed between a first energy-saving device and a second energy-saving device; and A second heat exchanger is in fluid communication with the first heat exchanger and is located downstream of the second energy-saving device.

24. The system of claim 23, wherein the hydrocarbon source is a light hydrocarbon or a crude oil source.

25. The system according to claim 23 or claim 24, wherein the total external surface area of ​​the first energy-saving device, the second energy-saving device, the first heat exchanger, and the second heat exchanger is 6,000 m². 2 Up to 18,000 m 2 .

26. The system of claim 23 or claim 24, wherein the first heat exchanger comprises 2 to 10 rows of pipes, and the second heat exchanger comprises 5 to 15 rows of pipes.

27. The system according to claim 23 or claim 24, wherein the main pipeline has a length of 5.5 meters to 25 meters, said main pipeline being defined as the pipeline of each of the first energy-saving device, the second energy-saving device, the first heat exchanger, and the second heat exchanger.

28. Methods for designing steam cracking furnaces, including: The simulation describes the processing of hydrocarbon-containing feed in the convection section of a steam cracker, the convection section comprising a plurality of heat exchangers and one or more heat recovery exchangers alternating with each of the heat exchangers, one or more of the heat exchangers containing a first cooling fluid, and one or more of the heat recovery exchangers containing a second cooling fluid. The simulation uses hot flue gas from the radiant section of a steam cracker to heat the convection section, which in turn provides heat to a heat exchanger and one or more heat recovery exchangers. Select the hydrocarbon outlet temperature of at least one of a plurality of heat exchangers and the outlet temperature of at least one of a plurality of heat recovery exchangers; and The arrangement of multiple heat exchangers and one or more heat recovery exchangers is determined based on the following objectives: Furnace operation mode; Hydrocarbon-containing feed types; Furnace scaling conditions; Selective catalytic reduction (SCR) bed temperature; Ammonia injection grid temperature; Smoke exhaust temperature; The intermediate temperature of the steam superheater is at least 100°F higher than the saturation temperature of the steam; Steam superheater outlet temperature; Heat recovery exchanger outlet temperature; and Their combination.

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