Electric furnace for producing olefins

Abstract

A method for pyrolyzing a hydrocarbon feed (105) includes feeding the hydrocarbon feed (105) into at least one coil (130) in a reaction section (112) of an electric heater (110), using electrical energy to heat the hydrocarbon feed (105) in the electric heater (110) to a reaction temperature, and directing the reaction output from the electric heater (110) to at least one exchanger (150) to cool the reaction output.

Description

BACKGROUND ART

[0001] Furnaces used in pyrolysis are generally fired heaters that use high-temperature combustion gases (flue gases) or gaseous and liquid fuels to generate heat and provide reaction duty. Heat raises the temperature of fluid flowing through coils disposed inside the fired heater. Thermal cracking reactions occur in the radiant section of the fired heater. These are highly endothermic reactions, and heat is added to maintain the reactions. Generally, 30% to 50% of the combustion duty is used to carry out the reaction in the radiant section of the heater. The remaining duty in the flue gas is recovered in the convection section of the heater and can be used for preheating the feed and / or generating steam. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEMS

[0002] In one aspect, embodiments of the present disclosure relate to a reactor for cracking a hydrocarbon feed, comprising: a heater chamber defining a reaction section of an electric heater; a plurality of electric heating elements disposed around the heater chamber, the plurality of electric heating elements being operated by electric power; at least one coil extending from a feed inlet through the reaction section; and a primary exchanger having an inlet fluidly connected to the at least one coil and an effluent outlet.

[0003] In another aspect, embodiments of the present disclosure relate to a method for pyrolyzing a hydrocarbon feed, comprising: feeding the hydrocarbon feed into at least one coil in a reaction section of an electric heater; using electrical energy to heat the hydrocarbon feed in the electric heater to a reaction temperature; and directing the reaction output from the electric heater to at least one exchanger to cool the reaction output.

[0004] In another embodiment, embodiments of the present disclosure relate to designing a pyrolysis plant comprising an electric heater and a recovery section for pyrolysis of a feed; determining the amount of steam to be produced and the amount of steam consumed by the pyrolysis plant; determining the amount of electricity used by the pyrolysis plant to pyrolysis the feed; and adjusting at least one parameter of the pyrolysis plant to reduce the amount of electricity used by the pyrolysis plant.

[0005] The diagrams shown in the attached sketches may be slightly modified for specific crude oil, hydrocarbon raw materials, and product slates. Other embodiments and advantages will become apparent from the following description and the attached claims. [Brief explanation of the drawing]

[0006] [Figure 1] This is a diagram showing the configuration of an electric heater according to an embodiment of the disclosure. [Figure 2] This is a simplified process flow diagram of a system for decomposing hydrocarbon mixtures according to embodiments of this specification. [Figure 3] This graph shows the expected ethylene yield and coil outlet temperature (COT) as the residence time increases. [Figure 4] This figure shows a graph comparing the metal temperature of a coil when heated by a combustion heater and when heated by an electric heater. [Modes for carrying out the invention]

[0007] Embodiments disclosed herein generally relate to the decomposition of hydrocarbons to produce light olefins such as ethylene and propylene, using an electric heater to heat the hydrocarbon feed to a reaction temperature. The electric heater is sometimes called an electric furnace. Useful hydrocarbon feeds in the embodiments herein can range from light hydrocarbons (ethane, propane, butane) and naphtha-range hydrocarbons (C5-C12) to heavier hydrocarbon gases and mixtures thereof, including whole crude oil.

[0008] The thermal decomposition of hydrocarbons is commonly used to produce light olefins. For example, ethane, when decomposed, mainly produces ethylene. Naphtha, when decomposed, can produce ethylene, propylene, butene, butadiene, and benzene as beneficial products. Thermal decomposition reactions are highly endothermic, and heat is supplied to sustain the reaction. To obtain a substantial feed conversion, the reactor temperature can easily exceed 700°C, and may even exceed 800°C, for example.

[0009] In some decomposition processes, catalysts may be employed to lower the operating temperature, but this may result in a lower ethylene yield than thermal decomposition. The heat of reaction per unit weight of the olefin produced is approximately the same for thermal decomposition and catalytic cracking, but the combustion duty in the case of thermal decomposition is extremely high. To heat the feed sufficiently (e.g., to a high temperature above 800°C) for ethylene production, a higher proportion of sensible heat (energy required to change the temperature of a substance without phase change) relative to the reaction duty may be used. Sensible heat can be recovered by exchange with other process fluids, and therefore ethylene heaters may be designed to efficiently preheat the feed and generate additional vapor. When using electric heaters according to this disclosure, since there is no flue gas containing high thermal energy, the electric heaters may be designed to preheat the feed and carry out the reaction, or other more efficient methods of preheating the feed may be used.

[0010] The decomposition reaction may produce a small amount of coke as a byproduct, which can deposit and accumulate in the reactor. To minimize coke deposits and improve olefin production, steam can be added to the hydrocarbon feed for decomposition.

[0011] In a combustion heater, the feed mixture (hydrocarbons and diluent vapor (DS)) is typically preheated in the convection section of the heater before entering the radiant section where the reaction takes place. Since these are high-temperature reactions, high-temperature flue gas is produced from the reaction in the combustion heater. Generally, only 30-50% of the combustion duty from the heater goes to the reaction section, and the remaining portion of the combustion duty can exit through the radiant section as flue gas. Energy in the flue gas can be recovered in the convection section of the combustion heater, which may contain coils suitably configured within it to recover heat from the flue gas. In the convection section of the combustion heater, the feed and diluent vapor are preheated and may also be superheated to a desired temperature before entering the radiant section. Even after heating the feed mixture surplus, thermal energy remains in the flue gas. If this energy is not recovered, it is wasted, increasing the cost of olefin production. In contrast, when using an electric heater according to embodiments of the present disclosure, 90–98% of the electrical energy used by the electric heater can be directed to the reaction in the reaction section of the heater. Therefore, the electric heaters disclosed herein can generate enough energy for the reaction, with little or no excess heat being generated. Since no significant amount of excess heat is generated, the electric heaters disclosed herein may not have a convection section.

[0012] To preserve the olefins formed in the reactor, the reaction output (also called the effluent) can be rapidly quenched. Older quenching methods involved injecting oil or water at the reactor outlet. More recent quenching methods have come to use indirect cooling. In some methods, the effluent can be cooled by generating high-pressure (or ultra-high-pressure) steam before sending it to a recovery section. This high-pressure steam was traditionally superheated in a convection section of a combustion heater. However, if an electric heater according to embodiments of the present disclosure is used, which does not have a convection section, the steam can be generated in other parts of the process (e.g., in an exchanger, or in a recovery section where the effluent is cooled, such as by using a secondary electric heater).

[0013] According to embodiments of the present disclosure, a reactor for decomposing a hydrocarbon feed may include an electric heater and at least one exchanger which can be used to cool the reaction output from the electric heater and / or to preheat the feed entering the electric heater. The electric heater may include a heater chamber defining a reaction section of the heater, a plurality of electric heating elements arranged around the heater chamber, the electric heating elements being powered, and a plurality of coils extending from a feed inlet to an outlet of the reaction section. In some embodiments, a primary exchanger may be used to initially cool the reaction output from the electric heater, and the primary exchanger may have an inlet fluid-connected to the plurality of coils and an effluent outlet. In some embodiments, a secondary exchanger may be used to further cool the primary exchanger effluent, and the secondary exchanger may have an inlet fluid-connected to the effluent outlet of the primary exchanger. In some embodiments, a tertiary exchanger may be used to further cool the secondary exchanger effluent, and the tertiary exchanger may have an inlet fluid-connected to the effluent outlet of the secondary exchanger.

[0014] The exchanger may further include a steam outlet and / or a steam channel that can direct heated steam to one or more areas of the reactor and / or a preheating section. For example, heated steam from the exchanger may be directed towards the feed inlet of an electric heater to preheat the feed before entering the electric heater. The preheating section may be installed separately from the reaction section of the electric heater or as a single unit with the reaction section. For example, the preheating section of the reactor may be spaced apart from the reaction section and downstream of the feed inlet of the electric heater. In some embodiments, the preheating section may include one or more exchangers. The feed inlet to the electric heater may be fluidly connected to multiple feed sources.

[0015] According to embodiments of the present disclosure, the main reaction section of an electric heater may have different configurations of one or more coils extending through the reaction section of the electric heater. The coils may be heated by different heating elements in a single electric heater, or the coils in the reaction section may be heated using a single heating element in the electric heater. Both preheating and reaction heat may be supplied by a single electric heater.

[0016] Figure 1 shows an example of a reactor 100 using an electric heater 110 according to an embodiment of the present disclosure. The electric heater 110 comprises a main reaction section of the reactor where a hydrocarbon feed 105 may be heated to a reaction temperature to decompose the hydrocarbon feed. The hydrocarbon feed 105 may be heated by a secondary exchanger 160 and flowed through a channel 120 to one or more coils 130 extending through the reaction section 112 of the electric heater 110. The reactor 100 may not include a convection section (as found in a combustion heater), but instead may include a channel 120 fluidly connected to coils 130 disposed in the electric heater 110 (for supplying one or more feeds to the electric heater), and one or more electric heating elements 140 disposed around coils 130 in the electric heater 110. The reactor 100 may further include feed exchangers (e.g., primary exchanger 150 and secondary exchanger 160) and a common flow path (e.g., through a header) from the feed exchangers that supplies various coils in the reaction section 112 of the reactor 100. Thus, in contrast to a combustion heater, the electric heater 110 may not include a convection section. Instead, the feed exchangers and common flow path (e.g., a header) may lead the feed to the coil 130.

[0017] A reactor using an electric heater 110 according to embodiments of the present disclosure may utilize the coil concept to decompose the feed passing through a coil 130. In the embodiments shown, four radiant coils 131, 132, 133, and 134 (collectively referred to as 130) may be configured in the electric heater 110 to extend through the reaction section 112 of the electric heater 110. However, more or fewer than four coils may be configured to extend through the reaction section of the electric heater 110. The reaction section 112 of the electric heater 110 may have one or more electric heating elements 140 positioned around the walls forming the reaction chamber of the electric heater 110, and the heating elements 140 may be directed to heat the reaction section 112. When the feed flows through the coil 130, the electric heating elements 140 around the coil 130 may be used to heat the feed flowing through the coil 130 to the decomposition reaction temperature.

[0018] According to embodiments of the present disclosure, each coil 130 can be controlled independently, including the amount of feed flowing through the coil, if any, and the temperature of the coil. For example, if a radiating coil 130 is connected to different feed manifolds, the coil 130 can decompose the fluid-connected feeds as each feed flows through the coil 130. By providing a reaction section of a reactor 100 capable of accepting multiple feeds, the equipment for the decomposition process can be compressed (for example, multiple feeds may be directed to a single electric heater 110 rather than using multiple heaters for multiple feeds), which can save plot space in the overall plant design.

[0019] The amount of feed into coil 130 can be controlled via a control valve 122. In embodiments where two or more different feeds are fluidly connected to coil 130, a control valve 122 positioned along the flow path 120 from the feed source to coil 130 can be controlled to allow the amount of feed to flow through coil 130. Furthermore, a flow venturi 124 may be associated with each coil to provide flow rate control of the feed flowing into coil 130. As it flows through coil 130, the feed may be heated to reaction temperature to decompose the feed using heat electrically supplied from the electric heating element 140 in the electric heater 110. For example, the same coils provided in the electric heater 110 according to embodiments of this disclosure (e.g., 131, 132, 133, or 134) may be used to decompose ethane in one run and naphtha in another run, or in other cases, the coils may be in decoking mode. Therefore, by using the coil concept, in order to decompose the feed, the feed flows through coils located inside the reaction section 112 of reactor 100, and specific processing conditions for each coil can be controlled to decompose whichever feed is flowing through the coil.

[0020] One or more additional passages 121 and valves 123 (e.g., separation valves or gate valves) may be fluidly connected to passage 120 and used to guide steam, or a mixture of steam and air, through the coil 130 for decoking the radiant coil (periodically removing coke buildup on the inner surface of the radiating tube). For decoking purposes, components in the electric heater may be configured in the same way as similar components in a conventional combustion heater, with the exception that the electric heater may use one or more electric heating elements instead of flame heating. By configuring components such as coils in the electric heater in the same manner as similar components in a combustion heater, a transfer line valve may be installed to separate the decoking outflow from the decoking outflow. Furthermore, a high-temperature separation valve may be used for a simpler decoking procedure (e.g., a separation valve may be used to separate one or more coils for decoking). When a high-temperature separation valve is not used, the outflow may be cooled sufficiently so that the coil and exchanger can be decoked by steam alone. When steam or air is used for decoking, a high-temperature separation valve may be used to divert the effluent into the decoking drum. The decoking effluent may also be directed to the reactor's recovery section along with the decomposer effluent.

[0021] The electric heater 100 may include one or more heating elements 140 distributed around the coil 130 so that the electric heating can be evenly distributed around the coil 130 in the reaction section 112. In contrast to the electric heater 110, the burner in a combustion heater releases intense heat into a small volume (flame shape). Thus, in a combustion heater, the coil surface facing the burner can reach extremely high temperatures, while the coil surface perpendicular to the burner can reach relatively cryogenic temperatures over a given length of the heater. The temperature gradient formed by the directional radiation of heat from the flame in the combustion heater is sometimes called the shadow effect. Due to the shadow effect, the peak temperature in the combustion heater may differ from the average temperature. In such a manner, the combustion heater tube design may be defined by the peak temperature. For example, the refractory bricks used to form the combustion heater are designed to withstand higher peak temperatures in the heater. Furthermore, since heat from the flame is transferred by conduction, the conductivity is designed to be high in order to transfer heat more quickly.

[0022] In the electric heaters of the present disclosure, electric heating can be controlled at a constant heat flux and directed to all sides of the coil (e.g., around the entire circumference of the coil). Furthermore, while it is difficult to control the heat input to any section of the coil (e.g., the bottom 20% or the top 20% of the coil) in the case of combustion heaters, electric heating according to embodiments of the present disclosure may involve segmenting the heater so that the heating elements heat multiple different sections of the coil so that the entire tube can be heated evenly. In some embodiments, a control system may be used to control the temperature of individual coils and / or individual segments of individual coils to give a specific heating profile of the coil for a particular decomposition process. By using the electric heaters of embodiments of the present disclosure, a more controlled, evenly distributed heating profile can be given to the coils in the heater, thereby significantly improving heat transfer performance, lowering peak tube temperature, and improving selectivity to olefins.

[0023] Figure 4 shows a graphical comparison of heating performance with respect to coil metal temperature between heating by a combustion heater (from a burner) and heating at a constant heat flux from an electric heater. As shown in Figure 4, when electric heating is used, the radial temperature gradient can be minimized (since there is no difference between the peak temperature and the average temperature), and therefore a lower heating temperature can be used to reach the desired metal temperature.

[0024] Furthermore, since the amount of heat to a single coil or a group of coils can be supplied by individual heating elements 140, said amount of heat can be individually controlled within the electric heater 110. In a conventional combustion heater, the entire firebox is heated by burners. Adjusting one or more burners aimed at a single coil affects the heat distribution of adjacent coils unless each coil is housed in a separate cell. With electric heating, heating and heat insulation can be separated without affecting other coils. Therefore, when an electric heater has multiple coils, each coil can be controlled independently. Furthermore, the heat input along different sections of the coil can be controlled. For example, a high heat flux at the inlet section of the coil and a low heat flux towards the end of the coil can be achieved by adjusting the heater parameters of one or more electric heating elements. By varying the heat profile along the coil, the reaction in the coil and / or the coking rate can be controlled. Depending on the furnace design, temperature and / or flux distribution can be imposed. Based on the independently controlled performance of coils in the cracking process, individual coil temperature control can be optimized to improve coil performance.

[0025] With an electric heater, the heat load can be varied from 0 to 100%, so adjusting turndown or heat severity (or coil outlet temperature (COT)) can be rendered unproblematic. With a combustion heater, extremely low turndown is impossible due to the risk of flame extinction. Furthermore, at low loads in a combustion heater, carbon monoxide, nitrogen oxides and nitrogen dioxide increase.

[0026] Compared with combustion heaters, electric heaters can achieve extremely high fluid temperatures. However, coil metallurgy can still limit the design. Therefore, ceramic tube coils can be used with electric heaters to achieve higher temperatures. In addition, other types of coils can be used, including single-pass coils or multi-pass coils configured in one row or multiple rows. Since the severity of each coil can be controlled independently, split cracking of different feeds through different coils can be easily achieved. Furthermore, co-cracking of different feeds can be carried out by mixing different feed streams and feeding the combined feed to the radiant coils.

[0027] After the feed in the coil 130 is heated to the reaction temperature, the reactants can be directed from the reaction section 112 to a primary exchanger such as a transfer line exchanger (TLE) 150 for rapid cooling to the outlet temperature. When the reaction effluent is cooled in the primary TLE 150, high-pressure and high-temperature steam can be generated. In some embodiments, the high-pressure and high-temperature steam can be directed to a preheating section of the reactor 100 to preheat the feed before it enters the reaction section 112. In some embodiments, the high-temperature steam can be mixed with the feed and directed into the reaction section 112 to facilitate heating of the feed for cracking.

[0028] The effluent from the primary TLE 150 can be directed to a secondary exchanger, for example, a TLE 160. In the secondary TLE 160, the effluent can be further cooled and steam can be generated. The steam generated from the secondary TLE 160 can be directed to the preheating section of the reactor and used to preheat the feed 105. In some embodiments, the steam generated from the secondary TLE 160 can be directed into the reaction section 112 to facilitate heating of the reaction section 112. In some embodiments, in addition to the first and second exchangers (e.g., the primary TLE 150 and the secondary TLE 160), additional exchangers (e.g., tertiary or higher-order TLEs) can be used.

[0029] In some embodiments, separate electric heating elements may be used with the primary TLE 150 and / or secondary TLE 160 to superheat the steam generated by the TLE. By generating little steam in the TLE, the additional heat in the effluent can be directed to preheat the reaction mixture. Thus, the maximum heat input to the reaction system 112 may go to decomposition heat (e.g., more than 90% of the heat), and only a small amount may go to heating the steam (a minimum amount of heat may be lost through the walls of the reaction section 112). In contrast, 10–40% of the combustion heat in the combustion heater may go to heating the steam and boiler feedwater.

[0030] The preheating section of reactor 100 may be formed integrally with the main reaction section in a single reactor unit, or the preheating section of the reactor may be provided separately from the main reaction section. According to embodiments of the present disclosure, all preheating of the feed to the reactor may be performed electrically. In some embodiments, a common preheated and mixed feed with a dilution vapor header may be employed. The preheating section may include one or more exchangers. In some embodiments, different feed types may be preheated in separate individual exchangers. For example, if reactor 100 is for decomposing ethane, naphtha, and gaseous oil, separate exchangers in the preheating section may be used to preheat each feed.

[0031] Since a common feed exchanger (e.g., TLE150) may be used with reactor 100 (for example, it may receive different feeds through different coils in the reaction section), the crossover temperature (or inlet temperature to the reaction section) can be well controlled and remain nearly constant from run start (SOR) to run end (EOR). This is different from a combustion heater, where coking in the radiant coils increases the crossover temperature over time, affecting process performance. Therefore, a low crossover temperature is usually used at SOR so as not to exceed metallurgical limits at EOR. In conventional combustion heaters, a feed / flue exchanger and / or auxiliary electric heaters are used to preheat the feed so that a constant temperature can always be achieved. Using electric heaters allows for the use of a high crossover temperature from the start to reduce the electrical energy for the reaction section and the cost of the heater (fewer radiant coils relative to a given ethylene capacity).

[0032] When only the feed / flue exchanger is used and no additional preheater is installed for the feed, additional heat may also be supplied by the primary (reactor) electric heater 110. The heater 110 may be designed and configured to supply heat for preheating operations.

[0033] To provide a better understanding of the embodiments disclosed herein, examples of different possible parameters for the reactor according to embodiments of this disclosure, such as those shown in Figure 1, are given below. However, other parameters may be used within the scope of this disclosure.

[0034] A first example of reactor 100 may include a radiating coil having an inlet tube diameter (ID) ranging from about 1 to 3 inches, an outlet tube diameter ranging from about 2 to 4 inches, and a length between 20 to 50 ft, and containing between 100 and 200 tubes; and a linear TLE having an ID ranging from about 2 to 8 inches and a length between about 20 to 30 ft, and containing between 40 and 50 tubes. In the case of the multipass coil, the inlet and outlet tube diameters can be up to 8 inches or more, and the total length can be 500 ft or more.

[0035] The first exemplary reactor 100 may have the following operating conditions.

[0036] Naphtha feed: SG=0.703, P / N / A, COP (coil outlet pressure): 30 psia, S / O=0.5, feed rate=95026 lb / h at 8000 operating hours, C2H4=29.0 wt%, C3H6=13.5 wt%, COT (coil outlet temperature)=1596°F (869°C), and TLE outlet=1100°F (593°C).

[0037] Four radiant coil tubes can be combined into a linear TLE (for example, as shown in Figure 1) and quenched. To maintain the yield the reaction has, the reaction output may be rapidly quenched and steam generation may be used. Saturated ultra-high pressure (SHP) steam may be generated. By designing the TLE to give conventionally low TLE outlet temperatures, the amount of duty for preheating the feed can be reduced. Therefore, higher outlet temperatures (e.g., 1000–1200°F) may be preferred over extremely low TLE outlet temperatures. Even at higher outlet temperatures, the reaction can still be quenched intrinsically. The heat available in the effluent may still be high, but may not be sufficient to heat the feed to a crossover state, which may also be relatively high (1000–1200°F). For process optimization, the TLE effluent may not be used for this service unless the heater effluent is cooled to a higher temperature (e.g., above 1200°F) (which may affect the yield), or if the crossover temperature is set to a lower temperature (which may increase the radiant coil duty cycle). In some embodiments, additional electric heaters may be used to preheat the feed to the crossover temperature without process optimization.

[0038] The reactor configuration may include a radiant electric heater to supply reaction heat and a subsequent TLE that generates SHP saturated steam. The energy remaining in the effluent may be used to preheat the feed (e.g., naphtha feed) and / or dilution steam and / or mixed feed (e.g., naphtha + dilution steam) in a shell-and-tube exchanger. Additional electric heaters may be used to preheat the feed to the crossover temperature to maintain the temperature method. Other hydrocarbon (HC) + dilution steam (DS) mixed stream headers (high temperature) may be used instead of naphtha feed headers or hydrocarbon feed headers. High temperature valves may be used to control the flow rate to groups of coils (or electric heaters). The flow rate to individual tubes may be distributed via flow venturis (e.g., 124 shown in Figure 1). Exchangers may be used for different feeds. For example, one exchanger for naphtha and one for gas feed may be sufficient for the entire plant.

[0039] The spill from the exchanger (for example, the secondary TLE 160) can be further quenched to approximately 200°C using quenching oil before entering the gasoline separator 170.

[0040] Operation option -1 Low crossover temperature (approximately 1000°F) with high TLE outlet temperature (approximately 1100°F). When a secondary TLE 160 is used to heat the feed mixture (HC+DS), a difference of at least 100°F is possible, making a shell-and-tube exchanger design feasible. There may be nearly equal flow on the tube side and shell side in the secondary TLE 160, and therefore the temperature drop on the effluent side may be nearly equal to the temperature reached on the shell side. The effluent can be cooled to 350°C (662°F). Thus, the naphtha+DS feed mixture can be heated to 300°C (572°F) using only external means. A common feed preheater can be used instead of a separate electric preheater for each electric heater 110. By optimizing the primary TLE 150 outlet temperature, a separate electric preheater can be eliminated. Superheating dilution by other means can also be used to preheat the naphtha+DS mixture. The primary heat load on naphtha feed is the naphtha vaporization duty. Using other sources such as quenched oil or low-pressure or medium-pressure steam to vaporize the naphtha can avoid the need for another electric heater.

[0041] Operation option -2 Reactor 100 can operate at high crossover temperatures and low TLE outlet temperatures, resulting in the lowest radiant duty cycle compared to other operating options. Low TLE outlet temperatures can be achieved in one stage (e.g., using primary TLE 150) or in two stages (e.g., using primary and secondary TLEs 150 and 160). SHP vapor can be generated in both stages. In some embodiments, only primary TLE 150 may be used for vapor generation (in the case of fast quenching). In some embodiments, secondary TLE 160 may be used to preheat the HC+DS mixture (it may operate similarly to a lower mixed preheat (LMP) coil in the combustion heater convection section, heating with the effluent instead of flue gas).

[0042] Operation option -3 A combination of operation option 1 and operation option 2 may be used in conjunction with other additions. For example, diluted steam may be superheated in different electric heaters, and the superheated diluted steam may be used to preheat hydrocarbons (and partial steam) to the crossover temperature.

[0043] While it is possible to carry out the decomposition reaction in a single electric heater, heat balance may not be achieved for different feeds. When using a single electric heater for the decomposition process, a portion of that heater may be dedicated to preheating the feed. Flow control may be based on a high-temperature stream, for example, using valve 122 and flow venturi 124. Thus, the temperature may be selected to improve reliability and cost-effectiveness. Preheating is a slow process and may utilize a larger flow channel surface area to be heated. Instead of using a separate electric heater for preheating, a shell-and-tube exchanger may be used to recover energy in the effluent for use in preheating. For example, the feed may enter the electric heater at approximately 140°F, and the effluent may exit the reaction section at approximately 650°F (before oil quenching). At such temperatures, two or more electric heaters may be used together with a common feed preheater (when no energy from other sources is included).

[0044] [Table 1]

[0045] When electricity is generated from a natural source (e.g., sunlight or wind) and the efficiency of generation is not critical, electric heaters can be up to 50% more efficient than conventional combustion heaters. However, when electricity must be generated using natural gas / fuel oil as a heat source, electric heating can be uneconomical.

[0046] Power grid Since the decomposition process using electric heaters according to embodiments of this disclosure can consume large amounts of power, it may be advantageous to minimize electrical losses as much as possible. For example, even assuming that electricity is available at the site at high voltage with minimal loss from the power plant, there may still be limitations in manufacturing equipment that uses high voltage. Most countries use 66kV transmission lines for long distances (e.g., from substation to substation), but power of 3000V to 11000V may be available to consumers. In the ethylene industry, ID fans consume a great deal of electricity. Most countries use 6000 to 6600V (e.g., PTTPE in Thailand, Petronas in Malaysia). Above 11kV, corona discharge should be considered. The above calculations show that approximately 50MW of power may be the minimum amount of consumption, but for 100MW, the following calculations are shown. For higher capacity electric heaters or multiple electric heaters, higher amounts may be considered.

[0047] [Table 2]

[0048] Low voltages of approximately 250-440V may not be used without excessive power loss in the conductor (cable). Current requirements can be very high, and it is preferable to use 6000V or higher. Assuming the cable is 50m from the transformer and 20mm thick, the resistance can be extremely low, for example, less than 0.001 ohms.

[0049] control Compared to combustion heaters, electric heating can be precisely controlled by adjusting the power. A voltage regulator may be used to adjust the power. However, at high power levels, power loss can be significant and impractical. In such cases, individual coil control may be preferable to overall electric heater control; that is, the power to each coil (or group of tubes) can be controlled. Furthermore, temperature distribution can be maintained by segmenting the power. For example, a 45ft coil may be segmented into five sections. The power to each section can be controlled (on or off), which may allow for different intensities in different coils, simultaneous decoking and decoking in different coils of the same heater, etc.

[0050] Other embodiments Generally, conventional ethylene plants are equipped with liquid feed headers and gas headers where the liquid feed is vaporized. Several low-temperature heat sources are available in the recovery section, such as naphtha + DS (0.2 w / w) feed. In this scenario, if electric heaters are used, one electric heater may be used for the entire plant. Similarly, dilution vapors can be superheated and supplied to all electric heaters in the plant. A similar approach may reduce the total number of electric heaters required for decomposition.

[0051] While the above example considers a single-pass coil configuration, other types of coil configurations may be used. Other coil configurations may include multi-pass coils, such as SRT-1 (serpentine coil), SRT III (four-flow coil), SRT V, VI, or VII (two-flow coils with multiple inlets and multiple outlets), U-coil (one inlet with one outlet), Y-coil (two inlets with one outlet), and other configurations. In contrast to conventional combustion heaters, where different types of heater coil designs may not be installed or operated within a radiant box, electric heaters according to embodiments of the present disclosure may include multiple different heater coil designs, including SRT-1 and SRT VI heater coil designs.

[0052] The coils can be manufactured from ceramic materials or metallic materials, including carbon steel, austenitic stainless steel, Cr-Mo steel, other alloy steels, and nickel-based alloys. When using ceramic tubes, relatively short residence times can be used (for example, with metal tubes, gas temperatures higher than 950°C may be difficult). Figure 3 shows graphs of expected ethylene yield and COT as residence time increases.

[0053] Since high temperatures are possible with the electric heaters of this disclosure, steam-only decoking may be used. Individual coils may also be decoked. Periodic decoking using steam / air may also be used to improve reliability.

[0054] According to embodiments of the present disclosure, a single header may be used to supply different feeds to electric heaters. Liquid headers (e.g., naphtha headers), gas headers (e.g., ethane headers), and / or mixed-stream headers (e.g., high-temperature naphtha + dilution vapor headers or ethane + dilution vapor headers) may be used to supply feeds to one or more electric heaters. By using mixed-stream headers, the maximum amount of electrical energy may be used for feed preheating and the minimum amount of electrical energy may be used for vapor generation.

[0055] An electric heater may contain numerous coils, which may be grouped into different groups or configured together within a single reaction section of the electric heater. The coil outlet temperature may be controlled to optimize olefin formation and achieve a desired run length. Such control may be implemented, at least partially, by providing groups of coils with their own feed control valves. A single electric heater may have one or more groups of coils. Unlike combustion heaters, electric heaters may be divided into numerous subsections by arranging insulators and / or diverting electrical energy to specific coils in their physical configuration. Power consumption for electric heaters can be high (e.g., ranging from tens to hundreds of megawatts). Therefore, the power grid may be divided to power each individual group of coils or to power several groups of coils. To control the temperature within a group of coils, the power grid may be segmented to supply power to each group of coils. In some embodiments, heating coils may be intertwine.

[0056] For example, using a vertically configured three-group system (e.g., l-2-3, l-2-3, l-2-3), maximum heat release can be achieved when all three groups receive full power from the power grid. When any of groups 1, 2, or 3 is active, the power is 1 / 3 of the total power. When using a portion of the power, even heating throughout the coil can be maintained. The groups can be configured vertically, with the lower l / 3 or 1 / 2 having a different power than the remainder. In some embodiments, the groups of coils can be configured horizontally. The duty cycle for complete disassembly until complete decoking can be precisely controlled. Furthermore, partial disassembly can be achieved using an electric heater. Two adjacent groups of coils may have different powers supplied to each group.

[0057] Evaporates in a reactor with an electric heater can be rapidly cooled by generating steam. The effluent outlet temperature can be selected to reduce steam generation while still allowing for rapid cooling of the reaction. Excess energy in the effluent can be used to preheat high-temperature feed mixtures (e.g., mixed hydrocarbons and diluted steam feeds) so that additional heaters are not required to preheat the feed. In the case of low-temperature feeds, already generated steam can be used. In this way, a higher portion of the supplied electrical energy can be used for the decomposition process.

[0058] method In the decomposition process, the feed mixture may be heated to a certain temperature level (reaction temperature) so that the reaction can take place. In conventional combustion heaters, energy in the flue gas may be used, and additional energy may be used to generate high-pressure steam. However, in electric heaters, the feed may be preheated by exchanging thermal energy with the effluent from the reaction. (This may be used in the recovery section when all compressors are powered by electricity, or to regenerate electricity, or to preheat other process streams.) A minimal amount of energy may be used with an electric heater reactor to generate high-pressure steam. The effluent from the electric heater may be rapidly quenched to a level sufficient to slow the pyrolysis reaction. The quenching / outlet temperature may be determined depending on the type of feed. For example, when decomposing ethane, the outlet temperature may be approximately 700-750°C (e.g., by generating steam, the reactor effluent is cooled to about 700°C). Further cooling of the effluent may be achieved by exchanging heat with the feedstream (e.g., ethane and dilution steam) in a tubular exchanger. In the case of naphtha crackers, the outlet temperature can be between 600°C and 700°C, which is higher than the outlet temperature when using a combustion heater.

[0059] In some embodiments, the outlet temperature may be lowered to generate more steam, which may be used in other areas of the reactor. For example, in the case of ethane, an outlet temperature of 350°C to 450°C may be selected to generate high-pressure steam in the transfer line exchanger (TLE) section of the reactor. In the case of naphtha cracking, an outlet temperature of 350°C to 525°C may be selected to generate steam. In the case of an electric heater according to embodiments of this disclosure, a relatively small transfer line exchanger (high-pressure exchanger) may be used for high-pressure steam generation. When using a relatively small TLE, a linear exchanger may be used, and the effluent may be integrated for further cooling. A conventional exchanger may also be used instead of a linear exchanger.

[0060] Other exchangers (secondary and / or tertiary) may be used with the electric heater of this disclosure, and the feed may be exchanged with the effluent using a low-pressure exchanger. In combustion heaters, after steam is generated using a primary exchanger, a secondary exchanger may be used only for some feeds (such as ethane and propane, which have a low fouling tendency). However, with the electric heater according to embodiments of this disclosure, all feeds (gas feeds and liquid feeds) may use a secondary exchanger. These secondary exchangers may be installed with individual reactors in correspondence with the electric heater, or they may be installed according to the overall plant design in correspondence with each type of feed.

[0061] For example, a plant may have ethane feed and naphtha feed led to multiple conventional combustion heaters, where, for illustrative purposes, two of the combustion heaters may decompose ethane, five of the combustion heaters may decompose naphtha, and one spare combustion heater may decompose any one of them. In such an example, each ethane combustion heater may have one secondary TLE, while the naphtha (and spare) combustion heaters may not have a secondary TLE. In the case of a reactor in a comparative plant, when using electric heaters according to embodiments of the present disclosure, all ethane electric heaters may be grouped together, and the ethane (optionally together with dilution vapor) may be fed to one or more secondary exchangers that heat the ethane (+ dilution vapor) feed for the ethane electric heaters. All naphtha electric heaters may be grouped together and may exchange heat with the naphtha (optionally mixed dilution vapor) feed. Secondary exchangers may be configured for each individual heater (e.g., a number of small exchangers) or for each feed (e.g., a few large exchangers for each feed type). In some embodiments, when designed for each individual heater, spare secondary exchangers may not be provided due to cost, but when designed for each feed, spare secondary exchangers may be provided because a single spare secondary exchanger can service the entire plant.

[0062] Furthermore, the use of the electric heaters disclosed herein may achieve design simplification, allowing the mixed flotation to be used to preheat the feed mixture after integrating the flotation from all primary TLEs in the plant (e.g., high-temperature (over 600°C) TLEs for ethane or naphtha cracking heaters). In this case, the entire integrated flotation can be divided into one, two, or more streams. One flotation stream may go to preheat the ethane, and another flotation stream may go to preheat the naphtha feed. The secondary exchanger may also be designed to preheat both the ethane and naphtha feeds in a single exchanger. Under these conditions, providing a spare secondary exchanger may not significantly increase costs but may significantly increase on-stream time. Currently, only primary TLEs can be cleaned in operation with the radiant coils in the combustion heater, while the secondary exchanger is mechanically cleaned (for a longer time, and therefore incurs losses in production). Providing a backup secondary exchanger increases operating time (the spill stream can continue to be directed where needed, while other stream lines can be cleaned).

[0063] The electric heaters according to embodiments of this disclosure may be used for different types of hydrocarbon decomposition processes. For example, the electric heaters disclosed herein may be used for a pyrolysis process for olefin production. In addition to olefin production, electric heaters as described herein may be used for catalytic reactors, such as methane reformers or dehydrogenation reactors such as propane dehydrogenation.

[0064] For decomposition, different hydrocarbon feeds may be supplied into the electric heater of the present disclosure. For example, the hydrocarbon feed may include C2, C3, C4, C5, ..., up to residual oil, and whole crude oil and any part / fraction or mixture thereof, condensates, and hydrocarbons having a broad boiling curve and an endpoint above 500°C. Such hydrocarbon mixtures may include, among other things, whole crude oil, virgin crude oil, hydrogenated crude oil, diesel fuel, vacuum diesel fuel, kerosene, jet fuel, diesel, kerosene, gasoline, synthetic naphtha, raffinate reformed oil, Fischer-Tropsch liquids, Fischer-Tropsch gases, natural gasoline, distillates, virgin naphtha, natural gas condensates, atmospheric pipe still bottoms, vacuum pipe still streams including bottoms, naphtha in the wide boiling point range up to diesel fuel condensates, heavy non-virgin hydrocarbon streams from refineries, vacuum diesel fuel, heavy diesel fuel, atmospheric residues, hydrocracker waxes, and Fischer-Tropsch waxes. In some embodiments, the hydrocarbon mixture may include hydrocarbons that boil from the naphtha range or lighter to the vacuum diesel range or heavier. If necessary, these feeds may be pretreated upstream of the processes disclosed herein to remove sulfur, nitrogen, metals, and Conradson carbon portions.

[0065] Figure 2 shows a block flow diagram of a process 200 that may be used to pyrolyze a hydrocarbon feed using an electric heater according to embodiments disclosed herein. As shown, a dilution stream 214, such as steam, is added to the hydrocarbon feed 210 and may be preheated in an exchanger 220 with the effluent 212. This may be done in one or more exchangers. Additional preheating may be done in a separate heater or in combination with a main electric heater. Exchangers and preheaters may be designed in particular for a single heater or, in general, to operate throughout the entire plant. Furthermore, exchangers and heaters may be designed to operate together, which may be considered in terms of overall economics.

[0066] Once the feed mixture 216 is preheated to a desired inlet temperature, also known as the crossover temperature (TXO), the preheated feed mixture 216 can then enter the electric heater 230. The electric heater can superheat the feed mixture 216 to the reaction temperature, and the decomposition reaction can proceed in the coils of the electric heater 230 (e.g., short residence time (SRT) coils). The flow to each coil can be distributed by control valves (e.g., high-temperature valves) and venturis. The heat input into the electric heater 230 can be manipulated by adjusting the electrical input.

[0067] In the reaction section (in the coil) of an electric heater, the decomposition process performance may be the same as when the reaction occurs in a conventional combustion heater. In other words, no significant difference in process performance may be detected in the reaction section of a conventional combustion heater and an electric heater according to embodiments of the present disclosure. Therefore, the electric heater of the present disclosure may have a reaction section that gives the same or similar level of pyrolysis performance as a combustion heater. In some embodiments, such as embodiments that provide uniform circumferential heating of individual coils, performance and selectivity may be improved, partly by a reduction in the number or temperature of hot spots associated with combustion heating.

[0068] The coil design can be modified depending on the electric heater design. For example, a single-pass design or a multi-pass series-parallel configuration may be used. In some embodiments, the coil design in an electric heater may be the same as the coil design in a combustion heater (for example, the same coil design as in Lummus Technology's SRT® furnaces, including SRT-I, SRT-II, SRT-III, SRT-V, SRT-VI, and SRT-VII combustion heaters). In some embodiments, different coil configurations may be used in a single electric heater. For example, meandering coils and multi-pass split design coils may be configured and operated in the reaction section of a single electric heater.

[0069] The severity of pyrolysis can be controlled by monitoring the outlet temperature of the output 218 from the electric heater 230 and by adjusting the heat input to the electric heater 230. Furthermore, the skin temperature of the coil in the electric heater 230 can be measured and / or predicted using devices and methods used in combustion heaters. For example, to monitor the skin temperature of the electric heater coil, which can be used in determining the first stage of coking, corrosion, excessive and insufficient equilibrium heat load in the heater, and prediction of coil life, for example, scanning infrared cameras, high-resolution imaging with focal plane array detectors, thermocouples, and selection of temperature measurement points can be used.

[0070] The output 218 from the electric heater 230 may be led to a cooler (e.g., TLE) 240, where the output 218 may be rapidly cooled (quenched) after leaving the reaction section of the electric heater 230. Quenching the output 218 may be done to prevent secondary reactions and to stabilize the gas composition from the output. The same type of TLE used with conventional combustion heaters may be used with the electric heater 230 of this disclosure. For example, cooling of the decomposed gas output 218 in the TLE 240 may be performed by vaporizing high-pressure boiler feedwater (BFW) 242, which may be brought around the TLE tube to cool the decomposed gas output 218 and vaporize to generate high-pressure steam 244. When decomposing a liquid feed (e.g., when processing a heavy diesel feed), a direct injection quench point may be provided to suppress fast fouling that may occur in the TLE cooling tube when the decomposed gas is cooled below the dew point of the heavy end of the decomposed gas.

[0071] The spillage 212 from the TLE240 can be analyzed and guided to different routes for different applications depending on the type of spillage. For example, the spillage 212 can be heated and subjected to further decomposition. In some embodiments, the spillage can be hydrogenated to reduce at least one component of nitrogen, sulfur, metal, and Conradson carbon in a hydrocarbon mixture. The same types of equipment and processes used with conventional combustion heaters for combined spillage analysis can be used with the electric heater 230 according to embodiments of this disclosure.

[0072] In some embodiments, when using the electric heater of this disclosure, the effluent can be cooled to a relatively higher TLE outlet temperature compared to the TLE outlet temperature when using a conventional combustion heater. For example, when using a conventional combustion heater, the effluent is cooled to 350°C–400°C (at the start of the decomposition cycle), and high-pressure steam (e.g., 115 bar) can be generated by cooling from a coil outlet temperature of 800–850°C. When minimal steam is required, such as when using the electric heater of this disclosure, the TLE outlet temperature can be raised to 600–650°C. Lower TLE outlet temperatures may result in slower pyrolysis reaction rates, thereby reducing the energy used to preheat the feed. Thus, lower TLE outlet temperatures may reduce electricity consumption in the electric heater, but also reduce steam generation. Optimal outlet temperature / steam generation can be determined for different pyrolysis processes. Examples using different TLE outlet temperatures are considered below for illustrative purposes.

[0073] When considering minimal vapor, it is possible to eliminate feed preheating and heat the feed to reaction temperature in a separate heater. Generally, in gas combustion heaters, the heater crossover temperature for naphtha is 1100-1175°F (593-635°C), and for ethane it is 1250-1300°F (677-704°C). This level of feed preheating cannot be achieved by effluent heating alone. Lowering the crossover temperature to 900°F (482°C) for naphtha and 1000°F (538°C) for ethane may eliminate the need for a separate electric preheater. Unfortunately, lowering the crossover temperature may increase the skin temperature of the tubes in the radiant coil and shorten the run length. For a reasonable run length, more coils are required. For liquid feeds, eliminating the electric preheater is difficult. Naphtha effluent may not be cooled below 350°C or 300°C because it condenses and fouls the line. However, ethane effluent can be cooled to 200°C, and its enthalpy can be used to preheat an ethane feed or an ethane / diluted vapor mixture feed. This process can be carried out using a secondary TLE, which can be used in conjunction with a conventional combustion heater or an electric heater. Furthermore, conventional decoking and feed switching can be used in conjunction with an electric heater according to embodiments of the present disclosure. For example, vapor can be used to decoke the coil in an electric heater disclosed herein.

[0074] Unlike conventional combustion heaters, the electric heaters according to embodiments of this disclosure do not have a convection section. In the electric heater, for example, a group of 1 to 10 or 20 (or any number that is actually feasible) coils may form the electric heater. The size of the coils and the electric heater may be defined by the decoking capacity.

[0075] An ethylene production plant may use one or more electric heaters. An ethylene production plant may have an ethylene production capacity well over 1800 kTA, and an average ethylene production capacity greater than 1500 kTA of ethylene. To achieve such production, multiple electric heaters (e.g., six or seven operational electric heaters and spare electric heaters) may be used in the plant. Each electric heater in the plant may be designed to optimize ethylene production. For example, in a plant capable of producing 1000 kTA (kilotons per year) of ethylene, five groups of coils + one spare group each form an electric heater (each group of coils / electric heater may have a size of 200 kTA). As another example, a 2000 kTA plant may include five groups of coils + one spare group each forming an electric heater (each electric heater may have a size of 400 kTA). A single electric heater may produce 200 kTA or more of ethylene, for example, ethylene between 250 kTA and 300 kTA. In some embodiments, an electric heater producing 200 kTA of ethylene may have a power consumption ranging from 65 MW to 130 MW. In some embodiments, an electric heater producing 1800 kTA of ethylene may consume a total power of as much as 1170 MW.

[0076] Depending on the electric heating system (e.g., resistance, electrostatic induction, and / or capacitance), heating may be supplied to each coil or each group of coils, depending, for example, the electric heater manufacturer. For example, in some embodiments, an electric heater (e.g., an electric heater including coils configured as in the SRT-VI® heater) may have a common pipe for multiple feeds, such as feed-1, feed-2, etc. (e.g., feed-1 may be naphtha, feed-2 may be liquefied petroleum gas (LPG), feed-3 may be ethane, etc.). The feeds may be preheated outside the electric heater where the pyrolysis reaction takes place. The group of coils (generating steam) and the TLE may form an electric heater according to embodiments of the present disclosure and may be separated for decoking or repair.

[0077] In combustion heaters, high-capacity heaters may use a twin-cell radiant box design, which may include two radiant cells in a common convection section. Single-cell combustion heaters may be used to construct a 200 kTA capacity. Since electric heaters do not have a convection section like conventional combustion heaters, 200 kTA ethylene production may be used as a basis for comparison between electric and combustion heaters. However, ethylene production from electric heaters may be less or more than 200 kTA (e.g., from about 170 kTA to over 400 kTA). Examples of electric heater designs for naphtha and ethane cracking based on 200 kTA of ethylene are given herein. For simplicity, we consider naphtha in the whole range at high intensity and pure ethane in 65% conversion. Furthermore, different coil configurations may be used in the electric heater (e.g., the coil configurations used in Lummus Technology's SRT-I, SRT-II, SRT-III, SRT-V, SRT-VI, or SRT-VII, or a single-pass coil configuration), but an example of electric heater design is presented using a coil configuration that matches the coil configuration in Lummus Technology's SRT-VI combustion heater, which is a highly selective two-pass coil with a long run length. An electric heater with this coil configuration can be used for both naphtha cracking and ethane cracking to produce ethylene. A standard coil outlet pressure of 25 psia may be used. Vapor-to-oil ratios (S / O) of 0.1 to 1.5 w / w may be used for various feeds, for example, 0.5 w / w may be used for naphtha cracking and 0.3 w / w may be used for ethane cracking. The electric heater can operate for at least 45 days.

[0078] Naphtha properties include a specific gravity (SG) of 0.707, an initial boiling point (IBP) of 91°F (33°C), a final boiling point (FBP) of 348°F (176°C) with a 50v% concentration of 189, 74.6 wt% paraffin, 16.65 wt% naphthenes, 8.75 wt% aromatic compounds, and an interference-to-noise power ratio (I / N ratio of P) of 0.83. 100% pure ethane can be used for the thermal decomposition of ethane in an electric heater.

[0079] Table 3 below provides exemplary design and operating parameters for electric heaters capable of thermally decomposing naphtha and ethane to produce ethylene. Case 1 corresponds to a naphtha heater design, and Case 2 corresponds to an ethane heater design.

[0080] [Table 3]

[0081] Cases 1A and 2A correspond to conditions with high crossover temperatures and low TLE outlet temperatures (to maximize steam generation), where all duty cycles can be supplied by an electric heater. This generates the maximum amount of steam. Cases 1B and 2B generate lower amounts of steam. The available heat in the effluent can be used to preheat the feed to the maximum extent. For some feeds, maximum preheating up to the crossover temperature of the reaction mixture is possible without the use of a separate electric heater. In some embodiments, a separate electric heater can be used to superheat the steam (up to about 500°C).

[0082] Using a high crossover temperature (or preheating temperature) can reduce the surface area of ​​the radiating coil, which can allow the electric heater to operate for at least 45 days. For example, an electric heater with eight coils configured in an SRT-VI configuration, as shown in Cases 1A and 2A, can achieve a capacity of 200 kT. Using a lower crossover temperature may require more coils to achieve the same capacity. For example, to achieve the same capacity, eight coils are used in Cases 1A and 2A, and nine coils are used in Cases 1B and 2B. When more coils are added, even lower crossover temperatures can be used without using a separate electric heater for feeding.

[0083] In the case of ethane cracking, the heat transfer coefficient is low because the hydrocarbon supply is low (due to the high ethylene yield). To obtain the greatest benefit, a slightly different SRT-VI design may be considered for ethane cracking. However, in case A, any coil design is possible, and in case B, it may be designed similarly using one more coil than in case A.

[0084] Table 4 below provides another example of design and operating parameters for an electric heater capable of thermally decomposing naphtha and ethane.

[0085] [Table 4]

[0086] Naphtha heaters can utilize more power than ethane cracking heaters. For example, the reaction section in a naphtha heater alone may have a minimum power consumption of approximately 70 MW / heater, while the reaction section of an ethane heater may have a minimum power consumption of approximately 52 MW / heater. When preheating is performed before cracking, the total power used may be 10-20% more than the power consumption of the reaction section alone. This calculation may assume an efficiency of 90% for electric heaters, but efficiencies exceeding 95% may be possible. For example, with electric heating, 90-98% of the electrical energy may be used for the reaction. Therefore, there may be little or no recovery of heat not used for the reaction. Since only enough energy for the reaction can be supplied by the electric heater, there is virtually no excess or wasted energy use.

[0087] Furthermore, since the electric heater of this disclosure lacks a convection section and a burner, the electric heater of this disclosure can be configured differently from conventional combustion heater layouts. Accordingly, the plot space of a reactor using the electric heater of this disclosure can be reduced compared to a combustion heater.

[0088] Electric heaters can have power requirements ranging from 2600 kW to 5200 kW per ton of ethylene. When producing 1800 kT of ethylene, electric heaters may use approximately 580 MW for pyrolysis of ethane and 1170 MW when pyrolysis of naphtha. Additional energy may be used to superheat the steam used in the cracking process and for the recovery section. For example, for the entire plant (including electric heaters, preheating components, and recovery components), approximately 600 MW of power may be used for an ethane cracker and approximately 1300 MW for a naphtha cracker. The energy source used to power the electric heaters (and / or supporting components for preheating and recovery) may be, for example, nuclear, hydroelectric, solar, wind, or renewable methods. In some embodiments, fossil fuels may be used to generate electricity for the electric heater plant. However, the use of fossil fuels for power generation may negate the environmental benefits of using electric heaters. Furthermore, when surplus electricity is used in or elsewhere within an electric heater, the resulting surplus thermal energy can be converted back into electricity (for example, using a generator).

[0089] The specific energy of the electric heater when pyrolyzing naphtha to produce ethylene may be less than or equal to approximately 5700 kW / T (kilowatts / ton) of ethylene, and the specific energy of the electric heater when pyrolyzing ethane to produce ethylene may be less than or equal to approximately 4200 kW / T of ethylene. When no steam is generated in the heater, additional energy may be required to power the recovery section. Accordingly, according to embodiments of this disclosure, power usage throughout the entire plant, including preheating components, electric heaters, and recovery components, may be planned in advance to take into account different pyrolysis processes that may be used in the plant and / or different feeds that can be thermally decomposed.

[0090] According to embodiments of this disclosure, the plant design may also include consideration of the starting conditions. Furthermore, the plan may also include consideration of the generation and consumption of steam resulting from pyrolysis, for example, determining what steam level should be generated to reduce total energy consumption to below a certain amount, and the generation of dilution steam from heat exchange using process streams. For example, by fully electrifying the plant, external steam can be reduced to a minimum, and a starting boiler may be eliminated in some cases when the plant is properly configured. The perfect steam balance may be determined before determining the amount of power for the electric heaters. For example, dilution steam may be superheated so that the energy balance of the decomposition heater does not significantly affect the severity of decomposition. The dilution steam may be superheated in the same heater where the feed is decomposed, or the dilution steam may be superheated in a separate heater. The choice of integrated or separate dilution steam heaters may depend on the available energy.

[0091] A method for designing a pyrolysis plant (including an electric heater for pyrolysis of feed, a recovery section, and optionally a preheating section) may include determining the amount of steam to be generated and the amount of steam consumed by the pyrolysis plant, determining the amount of electricity used by the pyrolysis plant to pyrolysis the feed, and adjusting at least one parameter of the pyrolysis plant to reduce the amount of electricity used by the pyrolysis plant. Parameters that can be adjusted to change the amount of energy used by the pyrolysis plant may be selected from at least one of the following: lowering the feed crossover temperature to the electric heater, designing the electric heater to have at least one additional coil to lower the feed crossover temperature, raising the outlet temperature from the recovery section, reducing the amount of steam consumed by the recovery section, increasing the amount of steam consumed by the preheating section, and others described above.

[0092] Using electric heaters for pyrolysis may require more power for pyrolysis than when electric heaters are used in other industries (e.g., for melting iron ore). For example, electric heaters in other industries may have a maximum power consumption of several kilowatts, while the power consumption of electric heaters disclosed herein, used for pyrolysis of hydrocarbon feeds, may be several megawatts. Therefore, the methods of this disclosure may involve designing a pyrolysis plant that uses a minimum amount of power while still being able to pyrolyze the selected feed. In some embodiments, electric heaters may be modularized, thereby allowing for design adjustments according to the pyrolysis process and feed. Other separation techniques such as adsorption / absorption may be considered when designing the plant. When alternatives to cryogenic separation are available, small-scale chemical olefins may be very attractive through this route.

[0093] In contrast to combustion heaters, electric heaters can maintain a constant crossover temperature throughout the entire pyrolysis process run. Furthermore, unlike combustion heaters, electric heaters can maintain a constant crossover temperature for low to high intensities and low to high throughputs.

[0094] Furthermore, the electric heaters of this disclosure do not generate flue gas and therefore may consist only of a radiant section and an effluent cooling section. Thus, the efficiency of electric heating can far exceed that of combustion heating, where generally 35-45% of the radiant duty is absorbed during gaseous fuel heating. By controlling heat loss (when the electric heater does not have the radiant duty absorbed during gaseous fuel heating), more than 95% of the electrical energy used to generate heat can be absorbed in the process. Thus, the reaction section duty in an electric heater can be relatively small compared to that of a combustion heater. However, while the flue gas generated in a combustion heater can be used to preheat the reaction mixture to the required reaction inlet temperature (crossover temperature, TXO), electric heaters do not have flue gas for preheating. The overall fuel efficiency (thermal efficiency) including preheating flue gas can be approximately 94%. When using a combustion heater, heating the reaction mixture from a battery provides additional energy available in the flue gas, even if the conditions are limited to reaction conditions. Flue gas can be used to generate and superheat high-pressure steam, which can then be used in the recovery section to drive the compressor. Although the radiative efficiency is low, the thermodynamic utilization rate of fuel energy is much higher.

[0095] In electric heating, there is no flue gas, so most of the heat used in the process can go to the reaction. Therefore, the amount of steam generated during the process can be significantly reduced. Steam generation can be used in the decomposition process as a way to recycle heat (for example, to preheat the feed before it enters the reaction section of the heater), and therefore, when steam generation is reduced, other heating options can be used to compensate for the reduced amount of steam. For example, additional preheating of the feed can be performed using a second electric heater. When the entire pyrolysis plant (e.g., one or more main reaction heaters, one or more recovery sections (e.g., exchangers), one or more preheating sections (e.g., preheating heaters), and / or post-treatment equipment) uses electric energy, preheating and reaction heating can be optimized in a more efficient way. For example, heat generated from one plant equipment unit (e.g., from a main reaction electric heater) can be recycled to another plant equipment unit (e.g., to a preheating section). Preheating optimization can also be done for a single electric heater, where thermal energy (high temperature) from the reactor effluent can be used to preheat the feed and / or generate steam.

[0096] Currently, ethane decomposers can produce a considerable amount of steam relative to the feed rate (approximately 2 kg SHP superheated steam / kg of ethane feed). Ethane heaters also utilize some form of preheating (secondary TLE). In the case of gas decomposition using electric heaters, electricity demand can be reduced by preheating the feed as much as possible using the effluent. Some level of external reaction mixture preheating may be performed when using electric heaters, and this can be done by additional electric heating. Under some circumstances, this may be contained in the main reaction heater or a separate preheater. The size and / or cost of the electric heater may be considered in accordance with electricity demand to optimize the design for sourcing preheater energy (e.g., from the main reaction heater or a separate preheater).

[0097] Using electric heating allows for a more uniform heating rate, and the input heat flux can be adjusted by manipulating the electrical input. The maximum metal temperature can occur near the ends of the coil. In some heater designs, there is no shadow factor. Therefore, the expected maximum tube metal temperature (TMT) can be considerably lower in electric heaters than that observed in combustion heaters. This can reduce the cost of electric heaters. Other advantages of using electric heaters may include, for example, control principles, plot space, and modularization.

[0098] As described herein, electric heaters can offer advantages over conventional combustion heaters. For example, electric heaters can supply only the duty cycle required for the reaction, while accounting for only minor losses (in combustion heaters, a large portion of the combustion duty cycle can be lost in the flue gas). Furthermore, reactor effluent from the electric heater can be used to preheat the feed, thereby reducing the total duty cycle supplied to the reactor. Electric heaters can also be more compact than combustion heaters (including both radiant and convection sections).

[0099] Furthermore, electric heaters can provide more controlled heating than combustion heaters. For example, electric heating can be more uniform than heating by combustion heaters, and the heating rate can be better controlled with electric heaters compared to combustion heaters. In addition, selected coils in an electric heater can be selectively controlled (e.g., controlled heating of a single coil or a group of coils) so that olefins can be produced much more selectively.

[0100] The use of electric heaters can also improve safety. Most heater accidents occur during starting and stopping, often due to improper handling of fuel safety standards. Since electric heaters do not use fuel, accidents related to fuel-type safety can be eliminated or reduced. Furthermore, compared to conventional heaters, the structure of electric heaters according to the embodiments disclosed herein can be simplified, so safety may be less of a concern in earthquake-prone areas and under strong wind loads (for example, due to lower structural height and the absence of fuel).

[0101] Although this disclosure has described a limited number of embodiments, those skilled in the art who would benefit from this disclosure will recognize that other embodiments can be devised without departing from the scope of this disclosure as described herein. Therefore, the scope of this disclosure should be limited only by the appended claims.

Claims

1. A reactor for decomposing hydrocarbon feed, A heater chamber defining the reaction section of the heater, Multiple independently controlled coils extending from the feed inlet through the reaction section, A plurality of electric heating elements are arranged within the heating chamber, wherein the plurality of electric heating elements are operated by electricity and arranged around the plurality of independently controlled coils, A control system configured to selectively heat different sections of at least one of the plurality of individually controlled coils to a selected temperature using the plurality of electrically heated elements, A primary exchanger comprising a fluid-connected inlet and outlet for the plurality of independently controlled coils, A reactor equipped with a hydrocarbon feed for decomposing hydrocarbon feed.

2. The reactor according to claim 1, further comprising a secondary exchange having an inlet fluid-connected to the outlet of the primary exchange.

3. The reactor according to claim 1 or 2, wherein the primary exchanger further comprises a steam outlet and a steam flow path directed toward the feed inlet.

4. The reactor according to claim 1 or 2, further comprising a preheating section spaced apart from the reaction section and downstream of the feed inlet, wherein the preheating section comprises at least one exchanger.

5. A method for thermally decomposing hydrocarbon feed, Supplying multiple hydrocarbon feeds into multiple individually controlled coils in the reaction section of an electric heater, Using electrical energy to heat the plurality of hydrocarbon feeds in the electric heater to the reaction temperature, To cool the reaction output from the electric heater, the reaction output is directed to at least one exchanger. Using a plurality of electric heating elements arranged around the plurality of individually controlled coils within the electric heater, selectively heats a different section of at least one of the plurality of individually controlled coils to a selected temperature. A method for pyrolysis of hydrocarbon feed, including hydrocarbon feed.

6. The method according to claim 5, further comprising recovering heat from the reaction output using at least one of the exchangers, and using the recovered heat to preheat the hydrocarbon feed before supplying it to the electric heater.

7. The method according to claim 5 or 6, further comprising separating the reaction output from the plurality of feeds together.

8. The method according to claim 5 or 6, wherein the plurality of hydrocarbon feeds have different compositions.

9. Using a valve to isolate one of the plurality of independently controlled coils, Decoking the separated coil and The method according to claim 5 or 6, further comprising:

10. A method for decomposing hydrocarbon feed in the reactor described in claim 1, An electric heater for thermally decomposing a feed and generating an output stream, the electric heater consuming the amount of power necessary to thermally decompose the feed, Entering the recovery section, the high-pressure boiler feedwater is configured to rapidly cool the output stream. A pyrolysis plant equipped with, The diluted vapor stream preheats the feed to the crossover temperature. The rapid cooling of the output stream evaporates the high-pressure boiler feedwater, thereby generating high-pressure steam to be released from the recovery section. Designing a pyrolysis plant, To determine the amount of high-pressure steam generated and the amount of dilution steam consumed by the pyrolysis plant, To determine the amount of electricity used by the pyrolysis plant to pyrolyze the feed, To reduce the amount of electricity used by the pyrolysis plant, the at least one parameter of the pyrolysis plant is selected from lowering the crossover temperature of the feed to the electric heater, lowering the temperature of at least one of the plurality of electric heating elements, and raising the outlet temperature from the recovery section. Methods that include...

11. The method according to claim 10, wherein adjusting at least one of the parameters is to lower the crossover temperature of the feed to the electric heater.

12. The method according to claim 11, further comprising designing the pyrolysis plant to have at least one additional coil to reduce the crossover temperature of the feed.

13. The method according to any one of claims 10 to 12, wherein the pyrolysis plant further comprises a preheating section, in which the dilution vapor stream preheats the feed to the crossover temperature, and the adjustment of at least one parameter includes reducing the amount of high-pressure vapor leaving the recovery section and increasing the amount of dilution vapor consumed by the preheating section by raising the outlet temperature from the recovery section.

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