Adiabatic olefin production

Abstract

Systems and methods for cracking hydrocarbons to produce olefins herein include heating a hydrocarbon feedstock or a mixture comprising steam and hydrocarbons to a first temperature to form a preheated feed, and further include heating steam in a turbine to a higher second temperature to form superheated reaction steam. The preheated feed is then mixed with the superheated reaction steam to form a reaction mixture at a cracking temperature, whereby the hydrocarbons are cracked to form olefins, producing a reaction effluent. The reaction effluent is then quenched and separated to recover the olefins.

Description

Technical Field

[0001] The embodiments disclosed herein involve the steam cracking of hydrocarbons to form olefins. Background Technology

[0002] To produce ethylene, hydrocarbons such as ethane, LPG, naphtha, and / or gas oil are typically heated in the convection section of a flame heater and mixed with dilution steam. The mixture (hydrocarbons plus dilution steam (HC+DS)) is further superheated in the convection section of the flame heater and then enters the radiative section of the flame heater. This mixture (HC+DS) is thermally cracked in a tubular reactor at high temperatures (e.g., 700°C to 900°C) and short residence times (e.g., 0.2 to 0.4 seconds). The effluent is rapidly cooled in a transfer line exchanger, generating steam, thereby rapidly freezing the reaction. The cooled effluent is then sent to a recovery section for product recovery.

[0003] When using a flame heater, the associated metal temperature also increases as the fluid is heated, and the achievable temperature is limited by metallurgical principles. Therefore, the maximum temperature of the tubes within the radiant section is typically restricted. Furthermore, flame heaters produce large amounts of carbon dioxide, which is another drawback of flame systems. Summary of the Invention

[0004] In one aspect, the embodiments disclosed herein relate to a method for cracking hydrocarbons to produce olefins. The method includes heating a hydrocarbon feedstock or a mixture comprising steam and hydrocarbons to a first temperature to form a preheated feed. The steam is then heated in a turbine to a higher second temperature to form superheated reaction steam. The preheated feed is mixed with the superheated reaction steam to form a reaction mixture at a cracking temperature, and the hydrocarbons are cracked to form olefins, thereby producing a reaction effluent, which is then quenched to stop the reaction. The reaction effluent is then separated to recover the olefins.

[0005] In another aspect, the embodiments disclosed herein relate to a system for cracking hydrocarbons to produce olefins. The system includes a heating system configured to heat a mixture comprising steam and hydrocarbons to a first temperature to form a preheated mixture. The system also includes a heating system comprising a turbine configured to heat the steam to a higher second temperature to form superheated reaction steam. A mixing system is provided for mixing the preheated mixture with the superheated reaction steam to form a reaction mixture at the cracking temperature. An adiabatic reaction zone is provided for adiabatic cracking of the hydrocarbons to form olefins, thereby producing a reaction effluent having a fourth temperature. Furthermore, a quenching system is provided for quenching the reaction effluent, and a separation system is provided for separating the reaction effluent to recover olefins.

[0006] In another aspect, the embodiments disclosed herein relate to a method for cracking hydrocarbons to produce olefins. The method includes heating a hydrocarbon feedstock or a mixture comprising steam and hydrocarbons to a first temperature to form a preheated feed. The method further includes heating steam in a turbine to form superheated steam. The preheated feedstock is mixed with the superheated steam to form a reaction mixture at a temperature below the cracking temperature, and the reaction mixture is then heated in a single-stage turbine to the cracking temperature to crack the hydrocarbons to form olefins, thereby producing a reaction effluent. The method then includes quenching and separating the reaction effluent to recover the olefins.

[0007] In another aspect, the embodiments disclosed herein relate to a system for cracking hydrocarbons to produce olefins. The system includes a first heating system configured to heat a mixture comprising steam and hydrocarbons to a first temperature to form a preheated mixture. The system also includes a second heating system comprising a turbine configured to heat the steam to form superheated steam at a temperature below the cracking temperature. A mixing system is provided for mixing the preheated mixture with the superheated steam to form a reaction mixture at a temperature below the cracking temperature. Furthermore, the system includes a single-stage turbine for heating the reaction mixture to the cracking temperature and cracking the hydrocarbons to form olefins, thereby producing a reaction effluent. A quenching system and a separation system are also provided for separating the reaction effluent to recover olefins.

[0008] Other aspects and advantages will become apparent from the following description and the appended claims. Attached Figure Description

[0009] Figure 1 The typical temperature rise of steam in a seven-stage axial compressor is illustrated.

[0010] Figure 2 Typical residence times for isothermal ethane cracking at 65 mol% conversion are illustrated.

[0011] Figure 3 This is a graph illustrating the steam temperature and total steam to oil weight ratio (S / O) at different mixing inlet temperatures of an adiabatic reactor used for ethane cracking.

[0012] Figure 4 A simplified process flow diagram of a system for steam cracking of hydrocarbons according to one or more embodiments disclosed herein is illustrated.

[0013] Figure 5 A simplified process flow diagram of a system for steam cracking of hydrocarbons according to one or more embodiments disclosed herein is illustrated.

[0014] Figure 6 and Figure 7An ethylene yield curve is illustrated, which illustrates the expected ethylene yield as a function of naphtha cracking temperature and residence time, achievable according to one or more embodiments disclosed herein.

[0015] Figure 8 A simplified process flow diagram of a system for steam cracking of hydrocarbons according to one or more embodiments disclosed herein is illustrated. Detailed Implementation

[0016] The embodiments described herein relate to the steam cracking of hydrocarbons to produce olefins. More specifically, the embodiments described herein relate to the steam cracking of hydrocarbons to produce olefins, wherein various heating loads are supplied by a turbine. Even more specifically, some embodiments described herein relate to systems and methods for producing olefins by cracking hydrocarbons in an adiabatic reactor using only electric heating via a turbine.

[0017] As used herein, a turbine is a device in which energy is transferred to a fluid through the dynamic action of one or more rotating turbines. Examples of machines that can be used to transfer energy between a rotor and a fluid include turbines and compressors. In some embodiments, an axial compressor is used to heat the fluid in the embodiments described herein. The turbines used in the embodiments herein may be electrically driven, and in certain embodiments, driven by green electricity.

[0018] Typically, in a compressor, energy transfer results in an increase in both temperature and pressure. Compressors generally increase the pressure from inlet to outlet. With many stages, the outlet pressure can increase many times over. However, in the embodiments described herein, the turbine is used for heating. When the compressor is used to heat the fluid rather than increase pressure, the additional energy supplied is converted into temperature. The pressure remains essentially constant from inlet to outlet. This is achieved by operating the compressor at supersonic speeds (e.g., measured at the blade tips). As the fluid exits the rotor, shock waves are generated and the pressure decreases. This, in turn, increases the fluid temperature. Therefore, in the embodiments described herein, the fluid is accelerated to high speeds (supersonic) at the tips of the rotor blades, generating shock waves that decrease the pressure at thin boundaries, thereby producing high temperatures.

[0019] Turbines operating in this manner can be used to increase the temperature of fluids to very high temperatures. In the embodiments described herein, a turbine is used to heat steam to very high temperatures, such as those in the range of 800°C to 1300°C. The high-temperature steam (referred to herein as “reaction steam”) is then mixed with hydrocarbons or a hydrocarbon-steam mixture, rapidly raising the temperature of the hydrocarbons from below or near the temperature at which thermal cracking occurs to a temperature sufficient for thermal cracking of the hydrocarbons to form ethylene, propylene, and other chemicals. For example, the temperature of the hydrocarbons or steam-hydrocarbon mixture can be in the range of 100°C to 750°C, such as 250°C or 350°C to 550°C or 650°C. The preheated hydrocarbons can then be rapidly heated with the reaction steam to the cracking temperature, such as 800°C to 1200°C, such as 850°C or 900°C to 1000°C or 1100°C. Mixing can occur rapidly outside the turbine in an adiabatic reactor. After the adiabatic cracking reaction, the reactor effluent can be quenched to stop the cracking reaction, and the reaction products, including the desired olefins, can be recovered.

[0020] In the reaction system according to the embodiments of this article, the hydrocarbon feedstock to be cracked can be any of a variety of feedstocks and can include a single hydrocarbon component (e.g., methane, ethane, propane, butane, etc.) or a mixture of two or more hydrocarbons (e.g., natural gas, butane, pentane, naphtha, gas oil, etc.). In some embodiments, the hydrocarbon feedstock can be derived from whole crude oil and can include one or more fractions of crude oil, including light fractions (naphtha, diesel, etc.) and heavy fractions (gas oil, heavy cycle oil, etc.) or residual fractions that have been adjusted for use as cracker feed.

[0021] The hydrocarbon feedstock or mixture of hydrocarbon feedstock and steam is preheated to a temperature below the initiation temperature of the cracking reaction, such as preheating to a temperature below 650°C. In some embodiments, the hydrocarbon feedstock or mixture of hydrocarbon feedstock and steam is preheated to a temperature where a low cracking rate is encountered, such as preheating to a temperature below 750°C. In some embodiments, the hydrocarbon feedstock is heated to a desired preheating temperature, such as a temperature in the range of 300°C to 650°C. In some embodiments, the hydrocarbon feedstock is heated to a first temperature, such as 150°C to 350°C, mixed with steam, and then further heated to a desired preheating temperature, such as 300°C to 750°C. In various implementations, the preheating temperature can be within the range of a lower limit of 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, or 500°C to an upper limit of 550°C, 600°C, 625°C, 650°C, 675°C, 700°C, 725°C, or 750°C, wherein any lower limit can be paired with any upper limit.

[0022] The preheated hydrocarbon feedstock is then rapidly heated to the cracking temperature and cracked to form olefins, such as ethylene, propylene, and butene. The cracking temperature is higher than the temperature at which cracking begins, which may depend on the hydrocarbon feedstock. The cracking temperatures used in the embodiments described herein can be in the range of approximately 750°C to 1300°C, such as, for example, 900°C to 1250°C, or 950°C to 1200°C. In various embodiments, the cracking temperature can be in the range of a lower limit of 750°C, 780°C, 800°C, 850°C, 900°C, 925°C, 950°C, 975°C, 1000°C, 1025°C, or 1050°C to an upper limit of 950°C, 975°C, 1000°C, 1025°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, or 1300°C, wherein any lower limit can be paired with any mathematically compatible upper limit.

[0023] To achieve the desired cracking temperature, embodiments of this invention use superheated steam to directly heat a preheated hydrocarbon feedstock or a mixture of preheated hydrocarbons and steam. The superheated steam used for the reaction according to embodiments of this invention is generated via a turbine, which may be electrically driven. The superheated steam used to heat the hydrocarbons to the cracking temperature can be in the range of, for example, 925°C to about 1400°C. The mixing of the superheated reaction steam with the preheated hydrocarbon feedstock will rapidly increase the temperature of the hydrocarbons to the cracking temperature, causing the hydrocarbons to crack to form ethylene and other cracked hydrocarbon products. In various embodiments, the temperature of the superheated reaction steam can be in the range of a lower limit of 925°C, 950°C, 975°C, 1000°C, 1025°C, 1050°C, or 1100°C to an upper limit of 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, or 1400°C, wherein any lower limit can be paired with any mathematically compatible upper limit. After the superheated reaction vapors are mixed with the hydrocarbon feedstock, the endothermic cracking reaction proceeds adiabatically, cooling the reaction mixture to a certain extent. In some embodiments, additional heat input can be provided to counteract the endothermic reaction if it is desired to maintain the reaction temperature. To maintain high selectivity for ethylene, reaction conditions (feed rate, feed temperature, etc.) can be selected to provide reaction effluents at temperatures greater than 750°C, such as greater than 800°C, greater than 825°C, greater than 850°C, greater than 875°C, or greater than 900°C.

[0024] The reaction effluent contains various components, the concentration of which depends on the feedstock and the severity of the reaction (reaction temperature and residence time at pyrolysis temperature). Typically, the residence time at pyrolysis temperature is less than 0.5 seconds (less than 500 milliseconds). Due to the very high temperature of the superheated steam that can be used according to the embodiments herein, and the minimal coking due to direct heating of the hydrocarbons (as opposed to radiant coils in a flame furnace), the residence time used in the embodiments herein can be in the range of 10 to 200 milliseconds, such as 20 to 180 milliseconds, 30 to 170 milliseconds, 50 to 160 milliseconds, or 60 to 150 milliseconds, where any lower limit can be combined with any upper limit.

[0025] As noted in US6685893, it is generally recognized in industry that for most feedstocks, and especially for heavier feedstocks such as naphtha, shorter residence times result in higher selectivity for ethylene and propylene because secondary degradation reactions are reduced. Furthermore, it is recognized that the lower the partial pressure of hydrocarbons in the reaction environment, the higher the selectivity. The reactor according to the embodiments described herein can provide higher temperatures and shorter residence times than those achievable in a flame furnace, thus providing favorable yields of ethylene and propylene.

[0026] After rapid heating and a short residence time at the pyrolysis temperature, the reaction effluent can be rapidly cooled or quenched to stop the pyrolysis reaction. For example, the reaction effluent can be cooled to temperatures below about 700°C, such as to temperatures in the range of about 300°C to about 600°C, using direct or indirect heat exchange. Indirect heat exchange quenching of the reaction mixture can be performed, for example, with preheated hot water or steam feed, hydrocarbon feedstock, or a hydrocarbon feedstock-steam mixture. In other embodiments, direct quenching of the reaction mixture can be carried out by mixing the reaction effluent with steam, circulating oil, gas oil, or other hydrocarbon media.

[0027] The resulting quenched reaction effluent can then be fed into a cooling and recovery section for further cooling and separation of the effluent to recover water / steam and one or more hydrocarbon fractions. The recovery section may include various separation units such as distillation columns, extractive distillations, flash tanks, stripping columns, and other unit operations typically used to separate mixtures to recover one or more chemical feed streams, such as higher-boiling pyrolysis oil fractions.

[0028] The hydrocarbon-steam mixture can have a steam-to-hydrocarbon ratio in the range of 0.05 to 1.2 w / w. Since the preferred steam-to-hydrocarbon ratio can depend on the hydrocarbon feedstock being processed and the desired preheating temperature, whether below the cracking start or with a small amount of cracking, the steam-to-hydrocarbon ratio of the hydrocarbon-steam mixture can range from a lower limit of 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5 w / w to an upper limit of 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, or 1.2 w / w, where any lower limit can be combined with any mathematically compatible upper limit.

[0029] The hydrocarbon feedstock or hydrocarbon-steam mixture can be mixed with superheated reaction steam at an appropriate rate to form a reaction mixture with a desired cracking temperature. The ratio used can depend on factors such as the desired steam-to-oil ratio, the reaction residence time, the initial temperature of the feed stream, and the heat capacity of the hydrocarbon feedstock. In some embodiments, the reaction mixture can have a steam-to-hydrocarbon ratio in the range of a lower limit of 0.25, 0.5, 0.75, 1.0, 1.5, or 2.0 w / w to an upper limit of 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, or higher, wherein any lower limit can be combined with any upper limit.

[0030] Heating of the hydrocarbon feedstock can be carried out in one or more heat exchangers or heaters. For example, heat recovery from various process streams can be used to heat the hydrocarbon feedstock via indirect heat exchange. Additionally or alternatively, an electric heater can be used to heat the hydrocarbon feedstock. The electric heater can be a radiant electric heater, a direct-heating electric heater, an induction electric heater, or an induction heater with a sensor. In some embodiments, the electricity supplied to the electric heater can be “green” electricity, thus making the entire process more environmentally friendly. If desired, a turbine operating at an outlet temperature well below the crack initiation temperature can also be used to preheat the hydrocarbon feedstock.

[0031] Heating of the dilution steam and the mixture of hydrocarbon feedstock and dilution steam can be carried out in a similar manner. For example, heat recovery from various process streams can be used to heat the dilution steam or the mixture of hydrocarbon feedstock and dilution steam via heat exchange. Additionally or alternatively, an electric heater or turbine can be used to heat or partially heat the dilution steam or the mixture of hydrocarbon feedstock and dilution steam. The electric heater can be a radiant electric heater, a direct heating electric heater, an induction electric heater, or an induction heater with a sensor.

[0032] Heating of superheated reaction steam can also be carried out in a similar manner. Initial heating of the steam can be achieved through heat exchange (heat recovery) with various process feed streams, such as reactor effluent. Heating the reaction steam to the desired reaction steam temperature can be carried out in stages. One or more stages may include the use of an electric heater, and in certain embodiments, induction heating with sensors is used. For example, sensor particles can be placed inside a tube receiving the steam feed, and the sensor particles are heated via an electric current applied to an electric coil disposed outside the tube, thereby heating the steam feed. Resistance heating (radiation), direct resistance heating (using a radiating coil as a resistor), and induction heating differ in their heating modes. Induction heating using sensors is another superior heating method because only the fluid is heated using this method. Therefore, all electrical energy is directed to heating the dilution or reaction steam, and heat is generated internally because there is no heating element for radiation.

[0033] The embodiments described herein use turbomachinery to heat or further heat the reaction steam to the highest possible reaction steam temperature. As previously noted, the reaction steam is heated to very high temperatures, such as greater than 950°C or greater than 1000°C. Such reaction steam temperatures can be achieved using electrically driven turbines, such as axial compressors. Furthermore, such turbines can provide reaction mixtures at temperatures much higher than those typically found in flame heaters.

[0034] In the embodiments described herein, instead of heating the mixture of hydrocarbons and dilution steam together in the turbine, only the dilution steam is heated to a high temperature, and the superheated dilution steam is mixed externally with the superheated hydrocarbon steam in separate containers. In the external containers, the hydrocarbons react, and the fluid is also adiabatically cooled by this method. After the reaction, a transmission line exchanger can be used to freeze the reaction and produce valuable ultra-high pressure steam.

[0035] In this method, the turbine only heats the dilution steam, thus eliminating the problem of coke formation and achieving stable operation. No coke forms within the turbine. Coke can form in an external container and can be cleaned using only steam or an optional steam / air method. A standby reactor vessel can be used in parallel operation, allowing for continuous reaction and chemical production while the reactor is being cleaned. In other words, the turbine can operate continuously to generate high-temperature steam. Olefins can also be continuously produced using the standby reactor vessel.

[0036] In the embodiments described herein, turbomachinery is used as a general term. It refers to single-stage and multi-stage axial and centrifugal compressors. However, in specific embodiments, axial compressors may be used.

[0037] A compressor increases the pressure from inlet to outlet. Through many stages, the outlet pressure can increase many times over. However, when a compressor is used to heat a fluid rather than increase its pressure, the additional energy supplied is converted into temperature. The pressure from inlet to outlet remains essentially constant. This is achieved by operating the compressor at supersonic speeds (at the blade tips). As the fluid leaves the rotor, shock waves are generated, reducing the pressure. This, in turn, increases the fluid temperature.

[0038] exist Figure 1 The diagram illustrates a typical temperature increase for steam as the working fluid in an axial compressor on a lossless basis. The actual temperature will be slightly lower due to fluid losses and non-ideals. However, a temperature difference exceeding 1300 K between the outlet and inlet of the axial compressor can be achieved through seven stages. The high temperature is limited to the fluid, and the surrounding material will be slightly cooler. Sufficient high temperatures for the desired cracking reaction can be achieved through improved metallurgy and appropriate design. Note that the steam does not coke and acts as an inert material. Typical operating temperatures for the pyrolysis reactor are 750–1000 °C. Selectivity for olefins can be significantly increased by reducing residence time. Steam can be generated in the plant at pressures in the range of, for example, 5–8 bara, and can be heated to, for example, 573 K using locally available hot fluids. Even if the steam is only available at low temperatures, it can be heated to above 1700 K using a turbine. Therefore, instead of heating the reaction mixture (HC+ dilution steam), only the reaction steam is heated to a very high temperature, well above the reaction temperature. This superheated reaction steam is then mixed with a preheated hydrocarbon mixture (and optionally a small amount of dilution steam). It is well known that hydrocarbons decompose at high temperatures and form coke. Therefore, the hydrocarbons are preheated to a sufficient level (800-1000 K), the temperature depending on the hydrocarbon feed, to a temperature at which coke formation is zero or essentially zero. To further suppress coking, the hydrocarbons can be heated with some dilution steam (e.g., steam to oil ratio (S / O) = 0.05 to 0.2 w / w). In the presence of steam, coke formation is suppressed. Therefore, for some steam, a higher preheating temperature can be used. This preheated hydrocarbon and steam mixture enters an adiabatic vessel. This can be a simple tank or cylindrical container or pipe or any shape of container or typical pyrolysis coil. An optional mixer can be used to mix the steam and hydrocarbon vapor. After mixing, the hydrocarbons in the entire mixture (hydrocarbons plus dilution steam plus reaction steam) are heated to a high temperature almost instantaneously. In the adiabatic vessel, the reaction proceeds adiabatically.

[0039] Figure 2The residence times required to achieve 65% conversion of ethane feed under isothermal conditions at different temperatures are shown. The residence time in an adiabatic reactor will be longer than this (isothermal) residence time and depends on the initial temperature. At very high inlet temperatures, the residence time is short. Currently, conventional flame heaters operate between 100 and 400 ms, and the coil outlet temperature varies from 800 to 950 °C. It should be noted that in flame heaters, the inlet temperature, known as the cross temperature, is always much lower than the coil outlet temperature. Typically, the coil outlet temperature is the hottest method fluid temperature in a conventional reactor. Inside the reactor (coil), the gas temperature increases non-linearly according to the heating rate determined by the heat release in the flame chamber. In an adiabatic reactor, the temperature profile is the opposite. It starts at a very high temperature and cools to a low temperature. Therefore, relatively short residence times (<100 ms) can be achieved because the average temperature in the reactor is always higher than the coil outlet temperature. Short residence times are always beneficial because they significantly improve olefin selectivity. Furthermore, the reaction proceeds adiabaticly, and therefore the temperature is not limited by the rate of heat transfer. Always achieving the highest possible inlet temperature is a challenge. In this configuration, the steam is heated to a high temperature and instantaneously mixed with hot hydrocarbons, thereby reaching a high temperature. Mixing alone controls the inlet temperature. Gas-gas mixing is very fast compared to convective or radiative heat transfer, and additional static mixers or packing can be installed to enhance mixing if needed. While ethane is shown as an example, this concept can be applied to any feedstock, from ethane to naphtha, diesel, and crude oil.

[0040] When a turbine (such as an axial compressor) is used solely for heating steam, for various mixtures (hydrocarbons plus reaction steam), the required temperature of the reaction steam entering the adiabatic section is as follows: Figure 3The diagram shows the ethane cracking process. Utilizing these effective mixing inlet temperatures, a 65% ethane conversion can be achieved. Another variable for maintaining heat balance is the steam-to-oil ratio. To reduce the temperature at the turbine outlet, a higher steam-to-oil ratio can be used. By manipulating the steam-to-oil ratio (or the steam flow rate to the turbine) and the steam outlet temperature at the turbine outlet, sufficient heat can be supplied as required by the method (i.e., meeting the endothermic load of the reaction). The reactor effluent temperature at the outlet of the adiabatic reaction section remains very high (>800°C), and a transfer line exchanger must be used to rapidly quench the effluent to freeze the reaction. This results in the generation of ultra-high pressure steam, which can be used to drive the turbine in the recovery section. A higher steam-to-oil (S / O) ratio significantly increases ethylene yield. For example, at S / O = 1 w / w, a 2.5% wt% higher single-pass C2H4 yield than with a conventional flame heater is achieved solely through a higher S / O ratio. Shorter residence times will increase additional ethylene yield. A higher steam-to-oil ratio also allows operation at very high ethane conversion rates. Ethane cracking is highly influenced by the equilibrium limit. At low temperatures and low hydrocarbon partial pressures, ethane equilibrium limits the conversion (C2H6). (C2H4 + H2). Because a high S / O ratio is required to supply the necessary heat, advantages can be gained by operating at high conversion rates. This reduces the need for a recovery section, thus saving capital expenditure. Although an example of ethane cracking is given, all feedstocks (ethane, propane, butane, LPG, naphtha, gas oil, hydrocracking vacuum gas oil, crude oil, condensate, residue, plastic pyrolysis oil, hydrogenated vegetable oil, etc.) can be cracked. The same reactor can be used for most, if not all, feedstocks. At high steam-to-oil ratios, coke formation is also significantly suppressed. Any coke formed can also be cleaned simply by steam decoking. For this purpose, the hydrocarbon stream is stopped, and high-temperature steam reacts with the coke in the adiabatic reactor and converts it to CO / CO2 via gasification.

[0041] A backup reactor could also be considered. Since it only heats steam, the compressor can run continuously.

[0042] As described further below Figure 4 and Figure 5The diagram shows a simplified schematic of the heating and reaction system according to an embodiment described herein. Diluent steam is compressed to the required high temperature in a turbine (such as a multi-stage (axial) compressor). Separately, the hydrocarbon feed is preheated in an exchanger using an available heat source. For gaseous feeds, such as ethane, this is another preheater. For liquid feeds, it is a vaporizer. More than one exchanger may be considered. Different heat sources can be used, including electric heaters. During vaporization, some steam may also be added to minimize coking in the exchanger. Optionally, an additional small amount of diluent steam sufficient to prevent coking in the turbine is added and then sent to another secondary compressor. This preheats the hydrocarbons and optionally the diluent steam to a moderate temperature. At this stage, there is no significant cracking reaction in the feed, and no coking occurs in the secondary compressor. This temperature is sufficient to achieve a high mixing temperature. Instead of a secondary compressor, an electric heater may be considered. Alternatively, a flame heater may be used. Using 100% H2 fuel in the flame preheater produces zero CO2. With fossil fuels, some CO2 will be present. Therefore, electric heaters or flame heaters can be considered as needed. In some cases, this heating may not be necessary. In such cases, the mixing temperature will be lower, and the main compressor must supply the load in the form of high S / O or higher steam temperatures. The superheated reaction steam from a separate turbine is then mixed with the preheated hydrocarbon feed at the inlet of the adiabatic reaction section. This can be a simple tank or a cracking coil placed in a box. The adiabatic reaction section may contain mixing devices, such as static mixers or other methods. The reaction takes place in the adiabatic reactor. The outlet is connected to a transfer line exchanger. Boiler feed water can be used to cool the effluent, and this produces ultra-high pressure steam. The cooled reactor effluent is then sent to the recovery section.

[0043] Two adiabatic reactors can be used, with one reactor used for pyrolysis and the other for decoking based on a previous cycle. Alternatively, a common spare unit can be used, allowing many reactors to share it. The unit capacity varies depending on the electrically driven compressor. Multiple such units will contribute to the total plant capacity.

[0044] In summary, the implementation described herein involves steam superheating using turbomachinery. The superheated steam is used to heat the hydrocarbon feed and supply heat for the reaction. Typically, a high S / O ratio is required to achieve sufficient feed conversion. Therefore, a significant amount of SHP will be generated. This can be used to preheat and / or superheat the feed and for use in the recovery section. Therefore, all utilities are electricity-based. Consequently, the plant produces zero CO2 and zero NOx. The reactor does not use any fossil fuels or hydrogen. Some preheating can be done with H2 flame heaters, and this will reduce electricity input because H2 is generated in the heaters and can be used for combustion. Therefore, some conventional heaters with H2 fuel can be considered, and the remaining heaters can be turbomachinery-type reactors to achieve the total plant capacity. This hybrid plant also has several advantages. In the event of a total power failure, some heaters, and therefore the recovery section, can be maintained using steam fueled with H2. This will improve uptime.

[0045] High temperatures are generated using electrical energy. In some implementations, there is no fuel flame heater, and therefore no carbon dioxide or NOx is emitted during chemical production. Existing plants can also achieve zero CO2 emissions by replacing the current flame heater with a turbomachinery heater. The turbomachinery heater also generates ultra-high-pressure steam, and therefore the turbine can also be used to drive turbines in the recovery section.

[0046] As a result of the electric heating according to the embodiments described herein, very high temperatures can be achieved. Sufficient reaction temperatures can be achieved by using high-temperature reaction steam and medium-temperature hydrocarbons, when the reaction steam is mixed with hydrocarbons or a hydrocarbon-dilution steam mixture. The reaction occurs adiabatically, and after the reaction, the reaction effluent is rapidly cooled in an exchanger and sent to the product recovery section.

[0047] When using a flame heater, the associated metal temperature is also heated when the fluid is heated, and the achievable temperature is limited by metallurgy. In contrast, the embodiment described herein utilizes a turbine to heat the reaction steam, indirectly providing heating to bring the entire reaction mixture to the reaction temperature.

[0048] The advantages of cracking hydrocarbons according to the embodiments described herein are a significant improvement in run length and higher selectivity for olefins. When the entire reaction mixture is heated by a flame heater or an electric heater, heat is typically transferred from the heat source (flame in the case of a flame heater, and heating element in the case of an electric heater) to the radiant tubes via radiation. Heat is then transferred from the radiant tubes to the reaction mixture by convection. During the process of thermally cracking the reaction mixture to produce olefins, byproduct reactions also occur to form coke. Therefore, coke deposits on the reactor walls, leading to limitations on olefin production via flame heaters or direct electric heating. After a period of time, the reaction is stopped, and the reactor is cleaned with steam / air. The reaction is typically carried out in a tubular reactor. Coke deposition depends on the tube temperature. When heated by a flame heater or an electric heater, the tube is hotter than the process (reaction) mixture. The higher the temperature, the higher the coking rate. Therefore, the metal or tube temperature is limited by the acceptable amount of coke deposition. When the reaction is carried out in an adiabatic mode, the fluid is hotter than the metal, and therefore the rate of coke deposition on the tube walls is reduced, resulting in a long run length. Thermal cracking is a homogeneous reaction (independent of surface area to volume ratio), while coke formation is inherently heterogeneous. Because the reaction is adiabatic in the embodiments described herein, a large tube diameter can be used by minimizing the residence time of the reaction, thereby minimizing the coke deposition rate. When convective heat transfer must be used (e.g., using flames or electrical elements to transfer heat), a small tube diameter is required to increase the heat transfer rate. In the adiabatic reactor according to the embodiments described herein, the inert material (diluent vapor) is heated to a very high temperature, and therefore coke deposition is absent. This very hot fluid is mixed with hydrocarbons to increase the temperature of the reaction feed mixture, and the tube temperature is equal to and typically lower than the fluid temperature.

[0049] The method of supplying heat to the reaction differs according to the embodiments described herein. Therefore, the tube metal temperature is relatively low. Using a turbine for heating, the fluid can be heated to very high temperatures. In the embodiments described herein, only the reaction vapors are heated to very high temperatures, and therefore there is no problem of severe coking in the reactor.

[0050] As described above, the embodiments described herein utilize electricity to heat the fluid via a turbine to supply energy to the superheated steam stream for the cracking reaction. In some embodiments, there is no flame heater, and all load is supplied by electricity or heat recovery. After preheating the hydrocarbon feed, it can be mixed with a small amount of dilution steam. Not all types of feed require dilution with a small amount of steam, and dilution with a small amount of steam is feed-specific. For illustrative purposes, a full range of naphtha will be considered. Similar concepts can be applied to ethane (gas feed) to gas oil (heavy feed) or other various hydrocarbon mixtures.

[0051] Typically, in a flame heater, naphtha is heated and mixed with dilution steam at a base weight ratio of 1:0.5 (steam to oil (S / O) = 0.5 w / w), and then superheated to 600-650°C in a convection section before entering the radiant section. The reaction occurs in the radiant section. The radiant section is heated to a temperature of 800-850°C (fluid temperature), and the reaction time in the tubular reactor is typically 200-400 milliseconds, where, in single-pass or multi-pass tubular reactors, the coil ID ranges from 1 inch to 7 inches, and the length is 20 ft to 400 ft. The reaction effluent is then cooled to 300-330°C by generating ultra-high pressure steam or high-pressure steam.

[0052] In the embodiments described herein, the hydrocarbon feedstock is vaporized, for example, naphtha is heated to 150–250 °C, then a small amount of steam is added (S / O = 0.05 to 0.2 w / w), and the mixture is further heated to a reasonable temperature in the range of about 400 to about 650 °C. These temperatures and S / O are chosen to eliminate coking during preheating. Coking is suppressed in the presence of steam, which is why a small amount of steam is added and heated above the specified temperature, depending on the nature of the hydrocarbon feedstock. The maximum temperature is kept slightly below the typical cross temperature, again minimizing coking during preheating or superheating of the feedstock. The remaining steam is superheated to very high temperatures (such as greater than 950 °C) separately. Additional steam may be used if necessary. Heating the steam to these very high temperatures is done via a turbine (which may be electrically powered). In the reaction zone, the preheated mixture of hydrocarbons and a small amount of steam is mixed with superheated reaction steam, and the reaction mixture is increased almost instantaneously to the cracking temperature. The reaction then proceeds adiabatic, producing olefins.

[0053] After a short reaction residence time (e.g., 30 to 160 milliseconds), the reaction effluent mixture is cooled (quenched) using a conventional heat exchanger and then sent to an additional heat recovery section and subsequently to a product recovery section. When the reaction occurs adiabatically, the reactor can be a tubular reactor with a large diameter or other type of vessel with an appropriate residence time. Therefore, coking is significantly reduced. During the reaction, there is almost no heat transfer to the external medium. If increased selectivity for olefins is desired, a small amount of heat (electric heating) can be added to maintain the reaction temperature at a slightly higher value. In this case, the added heat is very small, just enough to maintain the temperature. The benefit of adding heat versus slightly increasing the coking rate must be judged on a case-by-case basis. Either option will provide a longer run length and higher selectivity compared to a conventional flame heater. With additional heating, the selectivity will be higher than in a true adiabatic case. Furthermore, cheaper alloys can be used by breaking down the heating into two steps (dilution steam superheating and additional heating). When heat is added in the reaction section, it is no longer called an adiabatic reactor, but rather a non-isothermal, non-adiabatic reactor. Performance is unaffected except for the nomenclature used.

[0054] When using electricity to heat dilution steam or preheat reaction steam, this can be achieved, for example, by radiation. In this case, the heating element is heated by electricity and radiated onto the reaction tube, similar to a flame heater. In a direct resistance heater, the tube becomes the heating element. The resistance of the tube is used for heating. To avoid electric shock, low voltage (<100V) is typically used, and therefore this mode requires very high current, as the power requirement is almost the same in all cases. Alternatively, induction heating can be used, and the tube can be an alloy with induction capability. Furthermore, inductors can be used. Inductors are placed inside the tube, generating an induced current that heats the inductor. At this point, they function like a packed bed. A suitable inductor must be selected. One such material is SiC, and other high-temperature materials are also available. Any such material can be used as an inductor. Using a packed tube, the internal heat transfer coefficient is also very high compared to an empty tubular reactor. Furthermore, the metal or tube with the inductor can be inductive or non-inductive. Therefore, the tube temperature will not be high and will be much lower than with radiation methods.

[0055] With adiabatic operation, the outlet temperature can be controlled solely by adjusting the inlet temperature and flow rate. Higher inlet temperatures result in higher selectivity. However, limitations exist in any system. For greater efficiency, a low (or even low) conversion of the feed before the addition of steam is acceptable. At low conversions, selectivity for olefins is unaffected. The feed contains a small amount of steam, and therefore the coking rate is low. When it is necessary to maintain or adjust the conversion, induction heating of the tubes in the adiabatic section can be used again. This provides some heat and keeps the gas temperature relatively high. Of course, this increases the likelihood of coking. Therefore, optimal dilution steam and temperature should be used to obtain the best yield. Instead of supplying heat at the outlet, increasing the inlet temperature with a slightly higher inlet conversion is preferred. In this way, the reactor is always operated adiabatably, and therefore the run length is unaffected.

[0056] Now for reference Figure 4 This illustrates a simplified process flow diagram of a system for steam cracking of hydrocarbons according to one or more embodiments disclosed herein. Hydrocarbon feedstock 10, such as naphtha, is preheated to a moderate temperature in exchanger 12. Depending on the feed characteristics, an optional small amount of dilution steam 14 may be added. The amount of dilution steam is typically 0.05 to 0.1 w / w of the hydrocarbons, and for some heavy feeds, it can be up to 0.6 w / w to suppress coking during vaporization. The mixed feed 16, consisting of hydrocarbons plus dilution steam (HC+DS), is again heated to a moderate temperature in exchanger 18 to produce a heated mixed feed 20. Instead of an exchanger, an electric heater can be used to perform this heating of the mixed feed 16. By using an electric heater, ultra-high pressure steam production can be maximized, which can be used in the recovery section. Therefore, the optimal method for selecting the heat transfer medium can be chosen based on location, feed type, and operating conditions.

[0057] For simplicity, the implementation described herein is based on electric heating. Any type of electric heating can be used for this purpose. The hydrocarbon feed is typically heated from 200°C to 650°C in the exchanger or heater 18. By using an induction heater, heat transfer can be improved without coking because heat is generated in the inductor. Alternatively, a radiant heater (using electrical components) or a direct resistance heater (where electricity is applied directly to the heating coil or vessel) can be used to preheat the hydrocarbon feed instead of induction heating. At these outlet temperatures, the feed conversion rate is very low (<2%), so coking is generally not a problem. However, depending on the feed and coil design for this preheating to higher outlet temperatures, some additional conversion can be considered. For example, instead of limiting the naphtha feed temperature to 650°C, increasing the temperature to 700°C would result in some feed conversion. This results in a lower dilution vapor load that will be mixed later. The optimal effect depends on specific circumstances, such as the type of feed and the heating method.

[0058] The remaining steam, reaction steam 22, is superheated in turbine 24 to provide superheated reaction steam 26. Turbine 24 can be, for example, a linear compressor. Since only steam is heated in turbine 24, the steam can be heated to very high temperatures. Using a turbine, higher steam temperatures can be achieved than in other modes, such as radiant heating. Using a flame heater, it is difficult to achieve steam temperatures above 925°C due to metallurgical limitations. Using a turbine, steam can be heated very easily to temperatures above 1000°C.

[0059] The superheated reaction vapor 26 and the preheated hydrocarbon feedstock 20 are then mixed in a mixing device 28. In some embodiments, the mixing device 28 may be a simple mixing tee, or it may include a static mixer or other devices to facilitate close mixing of the reaction vapor and the preheated hydrocarbon feedstock.

[0060] After the high-temperature reaction vapor 26 is mixed with the preheated hydrocarbon plus vapor mixture 20 in mixer 28, a reaction mixture 30 is formed, and the reaction then proceeds adiabatically in reactor 32. The mixing zone 28 can be inside (e.g., integral) or outside (e.g., fluidly connected to the reactor) of the adiabatic reactor 32. The adiabatic reactor 32 can be internally or externally adiabatic. The mixing is a fluid-fluid type. Special mixing devices can be used to facilitate mixing. Simple T-type or Y-type mixing devices can also be used. Static mixers can also be used. Due to turbulence, the reaction mixture 30 rapidly reaches the adiabatic temperature. In the embodiments described herein, this reaction temperature is much higher than that typically encountered in typical flame pyrolysis heaters (>900°C). The pyrolysis reaction continues, and therefore the temperature drops because the reaction is endothermic. The temperature drop depends on the conversion level. Because the reaction proceeds adiabatically, it depends on volume rather than surface area. Surface area is only required if there is heat transfer from the outside to the inside or vice versa. Therefore, for reactor 32 according to the embodiment described herein, a large-diameter pipe or vessel with a low external surface area can be selected. Coking depends on surface area. Since the surface area is minimized, coke deposition is minimized, and therefore no additional pressure drop is caused by coking. The residence time is controlled by the volume of the adiabatic reaction section. High conversion rates can be achieved by appropriately selecting the flow rate for a given volume, as well as by appropriately selecting the dilution steam flow rate and hydrocarbon feed rate, and the preheated inlet temperature and superheated dilution steam temperature. Induction heating can also be used after mixing in reactor 32, and reactor 32 then operates as a non-isothermal, non-adiabatic reactor.

[0061] As with any pyrolysis reaction, the reaction must be quenched to retain the olefins. After the adiabatic reactor, the reaction effluent 34 is quenched using a transfer line exchanger 36. The transfer line exchanger 36 can be, for example, a shell-and-tube or two-tube exchanger. Alternatively, quenching the reaction effluent 34 directly with oil, steam, or water is also acceptable. Prior to quenching, a suitable outlet temperature (>750°C) is preferably obtained to maintain olefin selectivity.

[0062] Following quenching, the process resembles that of a conventional pyrolysis reactor system. The quenched reaction effluent 38 can be fed downstream to a cooling, heat recovery, and separation system 40. Secondary transfer line exchangers that generate steam or preheat the feed or other fluids, as well as tertiary exchangers that preheat the feed or generate low-pressure steam or preheat other fluids, are acceptable.

[0063] Similarly, any feedstock from ethane to vacuum gas oil can be used for olefin production. Any amount of steam with a steam-to-hydrocarbon ratio of 0.05 to 5 w / w can be used. Coking is highly likely without steam, and therefore steam-free conditions are not recommended. Very high steam-to-oil ratios may be uneconomical but are acceptable. The splitting of primary steam (mixed with naphtha for preheating) and secondary reaction steam (heated separately to high temperatures) can range from 0 to 1.0.

[0064] When significant coke deposits are present, the entire system can be cleaned online using a steam / air mixture or steam alone. If equipment downstream of the mixer must be cleaned, high-temperature steam can be used. This will convert the coke to CO / CO2 via a steam reforming reaction. Air (ambient or enriched air) can be used to burn the coke into CO / CO2. The same air can be used to clean the preheating section if needed. Air purification is only required in the low-temperature zone.

[0065] As described above for the embodiments described herein, the hydrocarbons are preheated with a dilution steam mixture. Typically, the preheated outlet temperature is maintained at a moderate level, resulting in low or near-zero feed conversion. To minimize steam dilution and the maximum superheated dilution temperature, a low (but small) conversion and a high cross-temperature are preferred. At low conversions (<30%), coking is low. At these low conversions, by-product concentrations are low. The final product distribution is independent of the cross-temperature at low initial conversions. Selectivity increases with reactor outlet temperature. Therefore, for each feed, the highest possible cross-temperature is preferred. In this context, the addition of a small amount of dilution steam helps suppress coke formation.

[0066] like Figure 4 The example illustrates a single feed stream. However, the embodiments described herein are not limited to single-feed reaction systems (one hydrocarbon feed, one reaction steam feed, one mixer, one adiabatic reactor, etc.). Now refer to... Figure 5 , Figure 5 The multi-feed flow / reactor concept is illustrated, and as many mixing / reaction units as needed can be used. For example... Figure 5 As illustrated, a preheated hydrocarbon feed or a preheated hydrocarbon feed plus a small amount of dilution steam can be provided to the hydrocarbon flow manifold 50. Reaction steam can be provided to the reaction steam manifold 52. The respective manifolds 50, 52 can then supply hydrocarbons and reaction steam to multiple mixing / reaction / quenching systems. Each mixing / reaction / quenching system may include an inlet pipe 56 for supplying hydrocarbons from manifold 50 and an inlet pipe 58 for supplying reaction steam from manifold 52 to mixer 60 and reaction coil 62, producing a cracked effluent 66, which can then be quenched and fed to a heat recovery and separation zone, as described above relative to... Figure 4 As described. Quenching can be performed by quenching the reaction effluent stream 66 either jointly or individually; in some embodiments, each of two or more reaction coils 62 is fluidly connected to a respective quenching system, and in other embodiments, each of two or more reaction coils 62 is fluidly connected to a common quenching system. The flow distribution to the multiple reaction coils and / or multiple inlet pipes can be controlled by a flow control device 64, which can be a valve, a flow venturi, or an equivalent orifice plate for uniformly distributing the flow to each mixer / reactor / quenching system. In this arrangement, a number of small reaction coils can be used if it is economically attractive or provides the desired operational flexibility.

[0067] In some implementation schemes, such as Figure 5 The illustrated reaction coils can be grouped together in a reaction tank, fluidly connected to a common steam tank and other utilities. For example, a reactor system comprising 2 to 20 reaction coils can be provided in a common shell, with each reaction coil fluidly connected to a hydrocarbon manifold and a steam manifold. This can be considered a single reactor system with multiple reaction coils. In other embodiments, such as in… Figure 4 In this context, an adiabatic reactor may consist of only one large tube used as the reactor.

[0068] In other embodiments, the shell may contain multiple mixing / reaction systems, but can provide hydrocarbons from multiple sources, such as a portion of a reaction coil fluidly connected to a gas oil supply unit, and other reaction coils fluidly connected to a naphtha supply unit. In this way, a common steam source can be used to crack multiple feedstocks. As with other embodiments, such a system may include separate or shared quenching systems.

[0069] like Figure 4As illustrated, the heating of the hydrocarbon or hydrocarbon plus dilution steam and the heating of the reaction steam are illustrated as spanning a single turbine, exchanger, or heater. Preheating of the hydrocarbon feed or superheating of the dilution steam can also be accomplished in a multi-pass coil arrangement according to the embodiments described herein. The adiabatic reactor can also be a multi-pass coil (tubular) reactor instead of a large vessel. When using a tubular reactor, if additional heating is required, it can be supplemented by electric heating when using induction heating of the sensor type. If no turbine or electric heater is used, the dilution steam superheating can also be of the exchanger type. Similarly, exchanger-type heating can also be applied to preheat the hydrocarbon feed.

[0070] Using this method, steam and the reaction mixture can be heated to very high temperatures (>1000°C). It should be noted that induction heating, with and without sensors, can also be used in the adiabatic section. Instead of sensors, simple inert or catalytic packing can be used. Inert packing only facilitates heat transfer. Heating can be accomplished through induction heating of the tubes or by utilizing electrical radiation or direct heating. Since the performance of the adiabatic section is volume-based, it can be a tubular reactor or a vessel.

[0071] According to the implementation scheme described herein, using steam as the heating medium has advantages. Steam is an inert material, and therefore there is no concern about coking; it can be heated to very high temperatures. Unlike air, it has a high specific heat and good thermal properties. It is readily available in pure form and can be recycled after condensation. It inhibits coke formation during thermal cracking. With the addition of more diluting steam, the partial pressure (and residence time) decreases, thereby improving olefin selectivity.

[0072] For naphtha feedstock, the increase in the steam to oil (hydrocarbon) ratio relative to ethylene yield at constant severity is shown to be... Figure 6 Increasing the steam-to-oil ratio lowers the maximum steam temperature required to achieve the desired conversion rate. Additionally, it produces less of the fuel component, such as methane or fuel oil. At a constant steam-to-oil ratio, increasing the steam temperature increases the volumetric flow rate of the reaction mixture. For a fixed adiabatic volume, this reduces the residence time. Reducing the residence time to achieve the same degree of severity also increases the ethylene yield. This is in... Figure 7 As shown in the image.

[0073] As described above for the embodiments described herein, turbine heating or a combination of turbine and electric heating can be used for the thermal cracking of hydrocarbon feedstocks to produce olefins. By heating steam and mixing superheated reaction steam with preheated hydrocarbons (or a mixture of hydrocarbons and dilution steam), the resulting thermal cracking produces a significant amount of olefins. Coke deposition is minimized, and long run lengths can be achieved. Reducing residence time with higher steam temperatures also increases ethylene yield. In all cases, as ethylene yield increases at a constant causticity, valuable byproducts such as propylene and butadiene also increase. At higher steam temperatures, the yields of aromatic compounds and fuel gas and fuel oil decrease accordingly. Causticity can also be varied by controlling flow rate and temperature. Therefore, the embodiments described herein are suitable for producing all types of hydrocarbons for olefin production and long run lengths are achievable in all cases. The reactor can be easily cleaned online with a steam / air mixture.

[0074] Furthermore, advantageously, the embodiment described herein eliminates the possibility of fouling in any turbine machinery used to provide heat. If a mixture of hydrocarbons and steam is processed in a turbine for heating and cracking within the turbine, the small gaps between the turbine blades and the vessel walls can be rapidly clogged by coke byproducts, and therefore long operating times are not conceivable. Moreover, coke can form on the turbine blades themselves, leading to imbalance and requiring shutdown and cleaning. While coatings and other means can be provided to delay turbine coking, these are expensive, may not provide complete or lasting coverage, and may only temporarily delay the inevitable shutdown required to remove small amounts of accumulated coke. The embodiment described herein (separating the heating and cracking reactions of the steam) avoids such problems and provides extremely long operating times in an adiabatic reactor with a much larger diameter compared to the gaps in the turbine, and can withstand a certain amount of coking.

[0075] All existing turbomachinery methods heat hydrocarbons and dilution steam together, and coke forms at any point when the hydrocarbon mixture is heated to high temperatures. This coke affects turbomachinery operation. In the embodiment described herein, only steam is heated, and no coke forms in the valuable turbine. Repair times are also long when the compressor fails. Therefore, uptime is improved by enhancing stability. The reaction takes place in a separate vessel, and thus coke deposits in the vessel. A backup vessel can be used for continuous operation while cleaning another vessel. Only steam is heated. Therefore, the conversion level can be controlled by controlling the amount of steam and by controlling the amount of hydrocarbons. Start-up and shutdown times are very fast.

[0076] While the embodiments described above envision heating steam only within the turbine machinery, other embodiments envision heating steam only to the pre-reaction temperature within a first turbine machinery heating stage, and then mixing the preheated steam with hydrocarbons for heating in a second turbine machinery heating stage, wherein the first and second stages take place in separate turbines. Thermal cracking produces coke as a byproduct, and therefore coking within the turbine machinery is unavoidable. The catalytic contribution of coking can be reduced by coating the machinery. When such a coating is available, both hydrocarbons and steam can be present within the turbine machinery, and the reaction can occur within the turbine machinery. Typically, several stages (5 to 10 stages) of axial compression are required to achieve suitable thermal conversion. With or without coating, the last stage or the last few stages of the turbine machinery will be used for the desired cracking. In this method, steam is preheated at a high temperature in a turbine as described above. The high-temperature steam is then mixed with hydrocarbons and reacted in the first stage of an axial compressor, where a thermal cracking reaction occurs to produce olefins. In this way, the reaction is not adiabatic, but some energy is also provided by the turbine machinery. Therefore, the temperature drop of the process is reduced, and the reaction is preferentially carried out in the first stage with a shorter residence time. More than one stage can be used if needed. Only the reaction section of the turbine machinery must be reserved, and the steam side does not require a reserve to address coking. This reduces the required capital and improves system reliability. Compared to a fully adiabatic temperature system, the hybrid system offers several process advantages, such as high olefin selectivity and relatively low hot steam temperatures. However, this results in a higher coking rate in the reaction zone. Depending on the situation, 100% adiabatic (one turbine machinery) or hybrid pyrolysis (two turbines, one for steam and one for pyrolysis) can be considered. Since the turbine machinery is nearly identical, the system can be designed for bidirectional operation via appropriate piping arrangements.

[0077] Refer again Figure 1 The steam temperature can be increased by 150°C to 300°C within a single turbine stage. This temperature increase can be used to heat the steam-hydrocarbon mixture in a single-stage turbine and cause it to react. According to the embodiments described herein, and as... Figure 8 As illustrated, where the same numbers represent the same components, steam 22 can be heated in a multi-stage turbine 24 to a temperature just below the temperature at which the cracking reaction occurs (cracking initiation temperature). For example, the multi-stage turbine can be used to increase the temperature of steam 22 from a range of 250°C to 500°C to produce superheated steam 26 at a temperature range of 600°C to 750°C. Other temperatures can be used and may depend on the heat recovery system and the hydrocarbons being processed. The superheated steam 26 can then be mixed with preheated hydrocarbons (10, 20) or a mixture of preheated hydrocarbon steam (10+14=20) (as described above relative to...). Figure 4The mixture (as described) is also mixed at a temperature below the temperature at which cracking occurs to any significant extent. The resulting reaction mixture 29 of preheated steam and preheated hydrocarbons can also be at a temperature below the cracking temperature. Then, in a single-stage turbine 80, the steam-hydrocarbon reaction mixture can be rapidly heated to the temperature at which the cracking reaction occurs. Alternatively, two-stage or other multi-stage turbines can also be used for this final heating and reaction step. In either case, keeping the smaller turbine on standby and separating the heating of the primary steam and hydrocarbons (or hydrocarbons plus dilution steam) up to the final reaction stage in the second turbine 80 provides a backup for the smaller turbine reactor, which reduces the required capital and improves system reliability, as noted above. The resulting reaction effluent can then be fed downstream for heat recovery and cracked hydrocarbon recovery, also as relative to Figure 4 As described.

[0078] As pointed out above, Figure 4 and Figure 8 The system can be used concurrently. Pyrolysis of cryogenic pyrolyzable feedstocks (e.g., pyrolysis temperatures of 750-900°C) can be performed in a manner similar to... Figure 8 Processed in systems where feedstock preferentially pyrolyzes at higher temperatures (e.g., >950°C) can be processed in similar ways. Figure 4 The system processes the effluent. The resulting effluent can then be processed for heat recovery and product recovery, with portions of each of these processes co-processing multiple reactor effluents.

[0079] Unless otherwise defined, all technical and scientific terms used shall have the same meaning as commonly understood by one of ordinary skill in the art to which these systems, devices, methods, processes and compositions pertain.

[0080] Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” include plural indicators.

[0081] As used herein and in the appended claims, the words “comprising,” “having,” and “including,” and all their grammatical variations, are each intended to have an open, non-limiting meaning and do not exclude additional elements or steps.

[0082] "Optional" means that the event or situation described below may or may not occur. The description includes both the scenarios in which the event or situation occurs and the scenarios in which it does not occur.

[0083] When the terms “approximately” or “about” are used, the term may indicate a value that varies by up to ±10%, up to 5%, up to 2%, up to 1%, up to 0.5%, up to 0.1%, or up to 0.01%.

[0084] A range can be expressed as from about one particular value to about another particular value, including end values. When expressing such a range, it should be understood that another implementation is from one particular value to another particular value, as well as all particular values ​​within that range and their combinations.

[0085] While this disclosure includes a limited number of embodiments, those skilled in the art who benefit from it will understand that other embodiments can be devised without departing from the scope of this disclosure. Therefore, the scope should be limited only by the appended claims.

Claims

1. A method for cracking hydrocarbons to produce olefins, the method comprising: The hydrocarbon feedstock or a mixture containing steam and hydrocarbons is heated to a first temperature to form a preheated feedstock; In the turbine, steam is heated to a higher second temperature to form superheated reaction steam; The preheated feed is mixed with the superheated reaction vapor to form a reaction mixture at the pyrolysis temperature, and the hydrocarbon is pyrolyzed to form olefins, thereby producing a reaction effluent; The reaction effluent was rapidly cooled; as well as The reaction effluent is separated to recover the olefin.

2. The method of claim 1, wherein heating the hydrocarbon feedstock or the mixture comprises heating via one or more of the following methods: The mixture is induction heated; The mixture is heated by electric radiation; The mixture is heated using a direct resistance type electric heating element; The mixture is heated via indirect heat exchange with an electrically heated heat exchange medium or the reaction effluent; or Combinations of two or more of these heating methods.

3. The method according to claim 1, wherein the first temperature is a temperature in the range of 150°C to 750°C.

4. The method according to claim 1, wherein the second temperature is a temperature in the range of 950°C to 1400°C.

5. The method according to claim 1, wherein the pyrolysis temperature is a temperature in the range of 900°C to 1300°C.

6. The method of claim 1, wherein the residence time of the pyrolysis is in the range of 10 to 500 milliseconds.

7. The method of claim 1, wherein the pyrolysis is adiabatic.

8. The method of claim 1, wherein the pyrolysis is non-isothermal and non-adiabatic.

9. The method of claim 1, wherein the mixture comprises steam and hydrocarbons in a steam-to-hydrocarbon ratio in the range of 0.05 to 0.6 (w / w).

10. The method of claim 1, wherein the reaction mixture comprises steam and hydrocarbons in a steam-to-hydrocarbon ratio in the range of 0.05 to 5 (w / w).

11. The method of claim 1, further comprising preheating the hydrocarbon stream and mixing the hydrocarbon stream with steam to form the mixture.

12. A system for cracking hydrocarbons to produce olefins, comprising: A heating system configured to heat a mixture containing steam and hydrocarbons to a first temperature to form a preheated mixture; A heating system, the heating system including a turbine configured to heat steam to a higher second temperature to form superheated reaction steam; A mixing system configured to mix the preheated mixture with the superheated reaction vapor to form a reaction mixture at a pyrolysis temperature; An adiabatic reaction zone is used for adiabatic cracking of the hydrocarbon to form an olefin, thereby producing a reaction effluent with a fourth temperature. A quenching system for rapidly cooling the reaction effluent; as well as A separation system for separating the reaction effluent to recover the olefin.

13. The system of claim 12, wherein the turbine comprises an axial compressor.

14. The system of claim 12, wherein the mixing system comprises a Y-type mixing device.

15. The system of claim 12, wherein the mixing system comprises a static mixer.

16. The system of claim 12, wherein the mixing system comprises a Venturi mixer.

17. The system of claim 12, wherein the mixing system comprises two or more mixers, and wherein the adiabatic reaction zone comprises two or more adiabatic reactors, the system further comprising a hydrocarbon feed manifold for supplying the preheated mixture to each of the two or more mixers, a reaction steam manifold for supplying the superheated reaction steam to the two or more mixers, and wherein each of the two or more mixers is fluidly connected to or integrated with a corresponding adiabatic reactor.

18. The system of claim 17, wherein the quenching system comprises a plurality of quenching zones, wherein the reaction effluent from each of the two or more adiabatic reactors is connected to a separate quenching zone.

19. The system of claim 17, wherein the reaction effluent from each of the two or more adiabatic reactors is connected to a common quenching system.

20. A method for cracking hydrocarbons to produce olefins, the method comprising: The hydrocarbon feedstock or a mixture containing steam and hydrocarbons is heated to a first temperature to form a preheated feedstock; Steam is heated in a turbine to form superheated steam; The preheated feed is mixed with the superheated steam to form a reaction mixture at a temperature lower than the pyrolysis temperature; The reaction mixture is heated to the cracking temperature in a single-stage turbine, and the hydrocarbons are cracked to form olefins, thereby producing a reaction effluent; The reaction effluent was rapidly cooled; as well as The reaction effluent is separated to recover the olefin.

21. A system for cracking hydrocarbons to produce olefins, comprising: A first heating system is configured to heat a mixture comprising steam and hydrocarbons to a first temperature to form a preheated mixture; A second heating system, comprising a turbine configured to heat steam to form superheated steam at a temperature below the pyrolysis temperature; A mixing system configured to mix the preheated mixture with the superheated steam to form a reaction mixture at a temperature below the pyrolysis temperature; A single-stage turbine is used to heat the reaction mixture to a cracking temperature and crack the hydrocarbon to form an olefin, thereby producing a reaction effluent; A quenching system for rapidly cooling the reaction effluent; as well as A separation system for separating the reaction effluent to recover the olefin.

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