An olefin production system

Abstract

The application relates to the chemical technology field and discloses an olefin preparation system. In the olefin preparation system, raw material fluid and heat carrier fluid are mixed in a cracking device and a cracking reaction is carried out to obtain cracking fluid so as to prepare product olefin, the heating rate and the heating temperature of the raw material fluid can be improved, the olefin yield is improved, the cracking pressure is improved, the equipment processing capacity is improved, the system energy consumption is reduced, and the high olefin yield is ensured. The raw material fluid is preheated by a preheating flow path before being mixed with the heat carrier fluid, the heating efficiency of the raw material fluid is improved, the heat energy generated by a fractionating device can be fully utilized, and the system energy consumption is further reduced. Moreover, the temperature of the preheated raw material fluid is low, and the problem of early coking does not occur.

Description

Technical Field

[0001] This application relates to the field of chemical technology, specifically to an olefin preparation system. Background Technology

[0002] Currently, ethylene and propylene production typically employs steam-tube pyrolysis technology. During the flow of feedstock within the tubes, it is heated by the radiation of high-temperature flue gas in the furnace, causing pyrolysis. However, current pyrolysis furnaces suffer from numerous problems.

[0003] (1) The increase in pyrolysis temperature is limited.

[0004] Currently, most radiant furnace tubes for pyrolysis furnaces are made of nickel-based alloy steel. Due to the limitations of the metal material itself, the highest temperature that the outer wall of the furnace tube can withstand is approximately 1100℃. Therefore, it is difficult to further increase the pyrolysis temperature to above 1000℃ for existing pyrolysis furnaces. Although new technologies such as heat-resistant coatings and ceramic furnace tubes have been introduced, the pyrolysis temperature has reached its limit at around 1000℃ due to the inherent limitations of this structural form, and cannot be further increased.

[0005] (2) The length of stay is difficult to shorten further.

[0006] The current pyrolysis furnace reaction section uses indirect heating, where the pyrolysis feedstock flows inside the tube, while high-temperature heating flue gas heats the feedstock inside the tube through convection and radiation outside the tube. Because the outer wall of the tube cannot withstand higher temperatures, the time required for the heating process from the cross temperature to the pyrolysis temperature is also limited and cannot be further increased.

[0007] (3) The single furnace throughput of the pyrolysis furnace is difficult to increase further.

[0008] The pressure in the existing cracking furnace tubes is approximately 0.05–0.1 MPaG, and the density of the feedstock in the tubes is approximately 0.75–0.8 kg / m³. This low density results in a large unit size. Currently, the maximum ethylene output per furnace is approximately 200 kt / a. Achieving higher output leads to large units and substantial investment. Furthermore, the increased complexity of the unit also increases the failure rate and operational risks. Summary of the Invention

[0009] This application provides an olefin preparation system that can improve olefin yield, increase equipment processing capacity, and reduce system energy consumption.

[0010] This application provides an olefin preparation system. The olefin preparation system includes: a combustion device for outputting a heat transfer fluid; a pyrolysis device connected to the combustion device, the pyrolysis device receiving the heat transfer fluid and a feedstock fluid, such that the feedstock fluid and the heat transfer fluid are mixed in the pyrolysis device and undergo a pyrolysis reaction to obtain a pyrolysis fluid to prepare the product olefin; and a fractionation device including a fractionation column, a preheating flow path, and a first heat exchanger. The fractionation column is connected to the pyrolysis device and is used to receive the pyrolysis fluid and fractionate it to obtain at least a first fraction. The inlet and outlet of the preheating flow path are both connected to the fractionation column and are used to pass the first fraction. The first heat exchanger is disposed in the preheating flow path, and the first fraction preheats the pyrolysis feedstock through the first heat exchanger to obtain a feedstock fluid.

[0011] In one embodiment of this application, the olefin preparation system further includes: a separation device connected to a fractionation tower, the fractionation tower being used to transfer fractionation products to the separation device, the separation device being used to separate the fractionation products to obtain at least product olefins and recycled light hydrocarbon feedstock; a preheating flow path further provided with a second heat exchanger, the second heat exchanger being used to preheat the recycled light hydrocarbon feedstock to obtain recycled light hydrocarbon fluid; and a mixing device connected to a cracking device, the mixing device being used to mix the feedstock fluid, the recycled light hydrocarbon fluid, and the first superheated steam to obtain a mixed fluid, and input the mixed fluid into the cracking device.

[0012] In one embodiment of this application, the combustion device includes: a combustion furnace for generating a heat transfer fluid; and a distributor, wherein the combustion furnace is connected to the pyrolysis device via the distributor, and the heat transfer fluid is input into the pyrolysis device via the distributor; the olefin preparation system further includes: a steam drum connected to the pyrolysis device, wherein the steam drum is used to circulate a first cooling fluid to the pyrolysis device to cool the pyrolysis fluid; and a first superheater disposed on the distributor and connected to the steam drum, wherein the steam drum separates steam from the first cooling fluid flowing through the pyrolysis device and transmits it to the first superheater, and the steam transmitted from the steam drum to the first superheater exchanges heat with the heat transfer fluid to form first superheated steam.

[0013] In one embodiment of this application, the olefin preparation system further includes a compressor connected to a fractionation tower, a separation device, and a first superheater, respectively. The fractionation products of the fractionation tower are compressed by the compressor and then transferred to the separation device. The first superheater is also used to transfer first superheated steam to the compressor.

[0014] In one embodiment of this application, the mixing device includes: a mixer for mixing a raw material fluid, a circulating light hydrocarbon fluid, and a first superheated steam to obtain a mixed fluid; a first distribution pipe connected to the mixer; and a nozzle connected to the first distribution pipe and the pyrolysis device, respectively, wherein the mixed fluid is sequentially input into the pyrolysis device through the first distribution pipe and the nozzle; wherein the pyrolysis fluid flows in the pyrolysis device along a first direction, and the extension direction of the nozzle is inclined relative to the first direction.

[0015] In one embodiment of this application, the pyrolysis apparatus includes multiple pyrolyzers, in which feed fluid and heat transfer fluid are mixed and undergo a pyrolysis reaction; the mixing apparatus includes: a mixer for mixing feed fluid, circulating light hydrocarbon fluid and first superheated steam to obtain a mixed fluid; and a first distribution pipe connected to the mixer and also connected to each pyrolyzer, through which the mixed fluid is transmitted to each pyrolyzer.

[0016] In one embodiment of this application, the pyrolysis apparatus includes multiple pyrolyzers, in which feedstock fluid and heat transfer fluid are mixed and undergo a pyrolysis reaction; the olefin preparation system further includes: a separation device connected to a fractionation tower, the fractionation tower also being used to transfer fractionation products to the separation device, the separation device being used to separate the fractionation products to obtain at least product olefins and recycled light hydrocarbon feedstock; a preheating flow path further includes a second heat exchanger, the second heat exchanger being used to preheat the recycled light hydrocarbon feedstock to obtain recycled light hydrocarbon fluid; a first mixer connected to some of the pyrolyzers, the first mixer being used to mix the feedstock fluid and a first superheated steam and input it into the pyrolyzers; and a second mixer connected to the remaining pyrolyzers, the second mixer being used to mix the recycled light hydrocarbon fluid and the first superheated steam and input it into the pyrolyzers.

[0017] In one embodiment of this application, the combustion device includes: a combustion furnace connected to a pyrolysis device; and a burner disposed at the bottom of the combustion furnace, the burner being used to receive fuel hydrogen, oxygen and second superheated steam, the fuel hydrogen, oxygen and second superheated steam being burned in the burner and the combustion furnace to form a heat carrier fluid.

[0018] In one embodiment of this application, the olefin preparation system further includes: a separation device connected to a fractionation tower, the fractionation tower being used to transfer fractionation products to the separation device, the separation device being used to separate the fractionation products to obtain at least product olefins and circulating hydrogen, and a burner being used to receive circulating hydrogen, fuel hydrogen, oxygen, second superheated steam, and circulating hydrogen combustion to form a heat carrier fluid.

[0019] In one embodiment of this application, the pyrolysis device includes a plurality of pyrolyzers arranged along a second direction; the combustion device further includes: a distributor, which has a distribution chamber inside, and the combustion furnace is connected to each pyrolyzer through the distribution chamber; wherein, the distribution chamber is located on one side of the combustion furnace in the second direction, and the distribution chamber extends along the second direction, and the cross-sectional area of ​​the distribution chamber at each position in the second direction gradually decreases in the direction away from the combustion furnace.

[0020] In one embodiment of this application, the olefin preparation system further includes: a steam-water separator, a third heat exchanger is provided in the preheating flow path, the steam-water separator and the third heat exchanger are connected, the steam-water separator is used to circulate and output a second cooling fluid to the third heat exchanger to exchange heat with the quench oil in the preheating flow path; and a second superheater, provided in the combustion device, the steam-water separator separates steam from the second cooling fluid flowing through the third heat exchanger and transfers it to the second superheater to exchange heat with the heat transfer fluid to form second superheated steam.

[0021] In one embodiment of this application, the olefin preparation system further includes: a quench tower connected to a fractionating tower, wherein the fractionating tower fractionates a second fraction and transfers it to the quench tower for cooling; and an oil-water separator connected to both the fractionating tower and the quench tower, wherein the oil-water mixture obtained by cooling the second fraction in the quench tower is transferred to the oil-water separator, and the oil-water separator separates a light component oil from the oil-water mixture and transfers it to the fractionating tower.

[0022] In one embodiment of this application, the oil-water separator is also connected to the quench tower via a reflux path. The condensate separated from the oil-water mixture by the oil-water separator is returned to the quench tower via the reflux path, which is equipped with a fourth heat exchanger. The preheating path is equipped with a fifth heat exchanger. The olefin preparation system also includes a steam drum connected to the cracking unit. The steam drum is used to circulate and output a first cooling fluid to the cracking unit to cool the cracking fluid. Fresh water is fed into the steam drum after passing through the fourth and fifth heat exchangers in sequence.

[0023] In one embodiment of this application, the olefin preparation system further includes: a stripping tower connected to a quench tower and an oil-water separator, wherein the oil-water separator separates condensate from the oil-water mixture and transmits it to the stripping tower for stripping; the stripping tower separates light hydrocarbons from the condensate separated from the oil-water separator and transmits it to the quench tower; and a steam-water separator, wherein the stripping tower is also connected to a preheating flow path through the steam-water separator; and the stripping tower outputs process water to the steam-water separator for heat exchange with the preheating flow path.

[0024] In one embodiment of this application, the olefin preparation system further includes: a compressor connected to a fractionation tower; and a separation device connected to the compressor, wherein the fractionation products of the fractionation tower are compressed by the compressor and then transferred to the separation device, and the separation device is used to separate the fractionation products to obtain at least the product olefin; wherein the compressor is also used to output steam to the stripping tower.

[0025] The beneficial effects of this application are as follows: Unlike existing technologies, this application provides an olefin preparation system. In this olefin preparation system, the feed fluid and the heat transfer fluid are mixed in a cracking unit and undergo a cracking reaction to obtain a cracked fluid to prepare the product olefins. In this application, the feed fluid and the heat transfer fluid are directly mixed in the cracking unit. Direct heating of the feed fluid by the heat transfer fluid increases the heating rate and temperature of the feed fluid, which is beneficial for increasing the olefin yield. Furthermore, the heating method of directly mixing the feed fluid and the heat transfer fluid in this application can increase the cracking pressure, thereby increasing equipment processing capacity and reducing system energy consumption while ensuring a high olefin yield.

[0026] The fractionation apparatus of this application includes a fractionation column, a preheating flow path, and a first heat exchanger. The fractionation column fractionates the pyrolysis fluid to obtain at least a first fraction. The first fraction is then used to preheat the pyrolysis feedstock through the first heat exchanger in the preheating flow path to obtain a feedstock fluid. In other words, the feedstock fluid of this application is preheated by the preheating flow path before mixing with the heat transfer fluid, which improves the heating efficiency of the feedstock fluid and fully utilizes the heat energy generated by the fractionation apparatus, further reducing system energy consumption. Furthermore, the preheated feedstock fluid has a lower temperature, preventing premature coking. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of an embodiment of the olefin preparation system of this application;

[0029] Figure 2 This is a schematic diagram of the structure of the first embodiment of the Venturi tube of this application;

[0030] Figure 3 This is a schematic diagram of the structure of the second embodiment of the Venturi tube in this application;

[0031] Figure 4 This is a bottom view of the structure of the third embodiment of the venturi tube in this application;

[0032] Figure 5 This is a bottom view of the fourth embodiment of the venturi tube in this application;

[0033] Figure 6 This is a schematic diagram of an embodiment in which the burner of this application is disposed at the bottom of the combustion furnace;

[0034] Figure 7This is a schematic diagram of another embodiment of the present application where the burner is disposed at the bottom of the combustion furnace;

[0035] Figure 8 This is a schematic diagram of another embodiment of the olefin preparation system of this application. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application. In this application, unless otherwise stated, directional terms such as "up," "down," "left," and "right" generally refer to up, down, left, and right in the actual use or working state of the device, specifically the drawing directions in the accompanying drawings.

[0037] In this application, unless otherwise expressly specified and limited, the terms "connected," "linked," "stacked," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0038] This application provides an olefin preparation system, which will be described in detail below. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments of this application. Furthermore, the descriptions of each embodiment have their own emphasis; parts not described in detail in a certain embodiment can be referred to in the relevant descriptions of other embodiments.

[0039] Please see Figure 1 , Figure 1 This is a schematic diagram of an embodiment of the olefin preparation system of this application.

[0040] In one embodiment, the olefin preparation system includes a combustion device 10 for discharging a heat transfer fluid. The olefin preparation system also includes a pyrolysis device 20 connected to the combustion device 10. The pyrolysis device 20 receives the heat transfer fluid and a feedstock fluid, such that the feedstock fluid and the heat transfer fluid are mixed in the pyrolysis device 20 and undergo a pyrolysis reaction to obtain a pyrolysis fluid for preparing the product olefin.

[0041] In the olefin preparation system of this embodiment, the feedstock fluid and the heat transfer fluid are mixed and undergo a pyrolysis reaction in the pyrolysis unit 20 to obtain a pyrolysis fluid for the production of olefins. In this embodiment, the feedstock fluid and the heat transfer fluid are directly mixed in the pyrolysis unit 20. Direct heating of the feedstock fluid by the heat transfer fluid increases the heating rate and temperature, which is beneficial for improving the olefin yield. Furthermore, this heating method of directly mixing the feedstock fluid and the heat transfer fluid increases the pyrolysis pressure, thereby improving equipment processing capacity and reducing system energy consumption while ensuring a high olefin yield.

[0042] In one embodiment, the olefin preparation system further includes a fractionation unit 30, which receives and fractionates the pyrolysis fluid to prepare the product olefin. Specifically, the fractionation unit 30 includes a fractionation column 31, a preheating flow path 32, and a first heat exchanger 33. The fractionation column 31 is connected to the pyrolysis unit 20 and receives and fractionates the pyrolysis fluid to obtain at least a first fraction. The inlet and outlet of the preheating flow path 32 are both connected to the fractionation column 31, and the preheating flow path 32 is used to pass the first fraction. The first heat exchanger 33 is disposed in the preheating flow path 32, and the first fraction preheats the pyrolysis feedstock through the first heat exchanger 33 to obtain a feedstock fluid.

[0043] In this embodiment, the raw material fluid is preheated by the preheating flow path 32 before mixing with the heat transfer fluid, which improves the heating efficiency of the raw material fluid and fully utilizes the heat energy generated by the fractionation device 30, further reducing system energy consumption. Furthermore, the preheated raw material fluid has a lower temperature, preventing premature coking. The pressure of the fractionation column 31 can be 0.05 MPaG to 0.8 MPaG, with an optimal pressure of 0.15 MPaG to 0.6 MPaG. The design temperature of the bottom of the fractionation column 31 can be 195℃ to 220℃, and the design temperature of the top can be 105℃ to 170℃.

[0044] It should be noted that the cracking feedstock in this embodiment is quite adaptable. The cracking feedstock can be light hydrocarbons (e.g., ethane, propane, butane), naphtha, light diesel fractions, diesel fractions, hydrotreated tail oil, or heavy oil, etc. The light and heavy components can be fed into the cracking unit 20 separately or mixed together, as will be described in detail below.

[0045] In one embodiment, the cracking unit 20 includes a cracker 21. The cracker 21 includes a Venturi tube 22, a cracking section 23, and a quench boiler 24. The Venturi tube 22 is connected to the quench boiler 24 via the cracking section 23. The feed fluid and the heat transfer fluid are mixed in the Venturi tube 22. The feed fluid is rapidly heated in the Venturi tube 22 and enters the cracking section 23 to undergo a cracking reaction, yielding a cracked fluid. The cracked fluid exits the cracking section 23 and enters the quench boiler 24 for rapid quenching. The feed fluid and the heat transfer fluid are mixed in the Venturi tube 22 and undergo a cracking reaction in the cracking section 23 to obtain the cracked fluid, thus preparing the product olefins. Direct mixing of the feed fluid and the heat transfer fluid in the Venturi tube 22, and direct heating of the feed fluid by the heat transfer fluid, can increase the heating rate and temperature of the feed fluid, which is beneficial for increasing the olefin yield. Furthermore, the heating method of direct mixing of the feed fluid and the heat transfer fluid in this embodiment can increase the cracking pressure, thereby increasing the equipment processing capacity and reducing system energy consumption while ensuring a high olefin yield.

[0046] Furthermore, please refer to the following: Figure 2 and Figure 3 The venturi tube 22 includes a converging section 221, a straight throat section 222, and a diverging section 223. The converging section 221, the straight throat section 222, and the diverging section 223 are connected sequentially, and the diverging section 223 is connected to the pyrolysis section 23. For example, the average flow velocity inside the venturi tube 22 is 100 m / s to 200 m / s, the flow velocity at the straight throat section 222 is 200 m / s to 300 m / s, and the entire mixing time is less than 30 ms. The designed flow velocity inside the pyrolysis section 23 is 150 m / s to 250 m / s, the pyrolysis residence time is less than 50 ms, and the outlet temperature of the pyrolysis section 23 is 850℃ to 1150℃.

[0047] In one embodiment, the olefin preparation system further includes a mixing device 50 connected to the cracking unit 20. The mixing device 50 is used to mix the feedstock fluid, the circulating light hydrocarbon fluid, and the first superheated steam to obtain a mixed fluid, which is then input into the cracking unit 20. In this embodiment, the feedstock fluid is indirectly preheated by the first heat exchanger 33 on the preheating flow path 32, and then directly mixed and heated with the circulating light hydrocarbon fluid and the first superheated steam in the mixing device 50. The temperature of the mixed fluid can be 300°C to 400°C. Furthermore, in this embodiment, the molar ratio of methane in the circulating light hydrocarbon fluid to hydrogen in the heat transfer fluid can be 0.5 to 2.0. By reasonably controlling the molar ratio of methane in the circulating light hydrocarbon fluid to hydrogen in the heat transfer fluid, both the olefin production efficiency and coking can be guaranteed.

[0048] Specifically, the mixing device 50 includes a mixer 51, a first distribution pipe 52, and a nozzle 53. The mixer 51 is used to mix the feed fluid, the circulating light hydrocarbon fluid, and the first superheated steam to obtain a mixed fluid. The first distribution pipe 52 is connected to the mixer 51. The nozzle 53 is connected to both the first distribution pipe 52 and the cracking device 20, and the mixed fluid is sequentially fed into the cracking device 20 through the first distribution pipe 52 and the nozzle 53.

[0049] Please refer to the following: Figure 4 and Figure 5 The nozzle 53 is connected to either the tapered section 221 or the straight throat section 222 of the venturi tube 22. The olefin preparation system has a first direction X, and the venturi tube 22, the cracking section 23, and the quench boiler 24 are sequentially connected along this first direction X, meaning the cracking fluid flows along the first direction X within the cracking unit 20. The tapered section 221, the straight throat section 222, and the diffusing section 223 of the venturi tube 22 are sequentially connected along the first direction X. The extension direction of the nozzle 53 can be perpendicular to the first direction X, or the extension direction of the nozzle 53 can be inclined relative to the first direction X, with the nozzle 53's outlet facing the cracking section 23.

[0050] For example, the angle between the extension direction of the nozzle 53 and the first direction X can be 45° to 90°. Figure 2 An example is shown where the nozzle 53 is connected to the throat straight section 222 of the venturi tube 22, and the extension direction of the nozzle 53 is perpendicular to the first direction X. Figure 3 An exemplary illustration shows a nozzle 53 connected to the tapered section 221 of a venturi tube 22, with the extension direction of the nozzle 53 inclined relative to the first direction X, and the outlet of the nozzle 53 facing the diverging section 223. The number of nozzles 53 can be one, two, or more. When the number of nozzles 53 is two or more, each nozzle 53 is evenly spaced along the circumference of the venturi tube 22. Figure 4 An example is shown where the number of nozzles 53 is even and they are evenly spaced along the circumference of the venturi tube 22; Figure 5 An example is shown where the number of nozzles 53 is odd and they are evenly spaced along the circumference of the venturi tube 22. Furthermore, the interior of the mixer 51 and the pyrolysis section 23 is made of castable material, with the innermost layer being a high-alumina corundum tube or corundum brick, etc.

[0051] In one embodiment, the pyrolysis apparatus 20 includes multiple pyrolyzers 21. A mixer 51 is connected to each pyrolyzer 21 via a first distribution pipe 52, and the mixed fluid obtained by mixing in the mixer 51 is transmitted to each pyrolyzer 21 via the first distribution pipe 52. In this embodiment, the pyrolysis feedstock can be a light component feedstock (e.g., ethane, methane, etc.) and a heavy component feedstock (e.g., naphtha, light diesel fraction, etc.). The light component feedstock and the heavy component feedstock enter the mixer 51 together for mixing, and then are distributed to each pyrolyzer 21 via the first distribution pipe 52 for pyrolysis reaction.

[0052] In one embodiment, the olefin preparation system further includes a steam drum 60 connected to the cracking unit 20. The steam drum 60 is used to circulate a first cooling fluid to the cracking unit 20 to cool the cracked fluid. Specifically, the steam drum 60 is connected to a quench boiler 24 via a second distribution pipe 61, and the steam drum 60 circulates the first cooling fluid to the quench boiler 24 to cool the cracked fluid, thereby rapidly cooling the cracked fluid.

[0053] It should be noted that in this embodiment, the quench boiler 24 adopts forced circulation with a circulation ratio of 2.5 to 4, the pressure of the steam drum 60 is 8.5 MPa to 12.0 MPa, the temperature of the pyrolysis fluid after quenching is 300℃ to 450℃, and the quenching time is less than 0.5s.

[0054] In one embodiment, the combustion device 10 includes a combustion furnace 11 and a burner 15. The combustion furnace 11 is connected to the pyrolysis device 20. The burner 15 is disposed at the bottom of the combustion furnace 11. The burner 15 is used to receive fuel hydrogen, oxygen, and second superheated steam, which are combusted in the burner 15 and the combustion furnace 11 to form a heat transfer fluid. The temperature of the heat transfer fluid at the outlet of the combustion furnace 11 is adjusted by controlling the amount of second superheated steam.

[0055] In this embodiment, fuel hydrogen can be produced by electrolyzing water using green electricity generated from clean energy (photovoltaic, wind power). Furthermore, the burner 15 in this embodiment can also introduce circulating hydrogen to supplement the fuel hydrogen supply when it is insufficient. Circulating hydrogen can be obtained by separating the products of the cracked fluid, specifically by separating the products of the cracked fluid to obtain at least olefins and circulating hydrogen. In this embodiment, oxygen can be produced by electrolyzing water using green electricity generated from clean energy (photovoltaic, wind power), or by separating oxygen through air separation. Therefore, this embodiment utilizes green electricity generated from clean energy (photovoltaic, wind power) to electrolyze water to produce hydrogen and oxygen, using high-temperature steam as the heat transfer fluid. After direct contact with the cracked feedstock for cracking, the steam enters the subsequent stages of the system and is directly condensed and separated into circulating water, saving energy and eliminating pollution. Traditional tubular furnaces use circulating hydrogen and fuel gases such as methane separated from cracked gas for combustion with air, producing large amounts of CO2 and NO. x The high-temperature flue gas is directly discharged into the atmosphere.

[0056] This embodiment uses hydrogen fuel combustion to form the heat transfer fluid. Due to the low density of hydrogen, the burner 15 is located at the bottom of the combustion furnace 11, i.e., a bottom-fired furnace, which facilitates complete combustion of the hydrogen fuel. The inner wall of the furnace 11 can be designed as a water-cooled wall or a refractory insulation lining. The internal pressure range of the combustion furnace 11 can be 0.1 MPaG to 1.0 MPaG. The outlet temperature of the heat transfer fluid from the combustion furnace 11 is 1200℃ to 1800℃. The outer wall temperature of both the combustion furnace 11 and the pyrolysis unit 21 is designed to be >95℃ to prevent low-temperature corrosion from acidic gases.

[0057] In this embodiment, burner 15 employs anaerobic combustion, with a hydrogen-to-oxygen equivalence ratio of 0.25 to 0.98. Burner 15 in this embodiment uses fuel hydrogen, oxygen, and superheated steam (i.e., second superheated steam) in an anaerobic combustion configuration, with an excess coefficient less than 1.0. To prevent unreacted oxygen from entering the pyrolysis unit 20 and reacting with the pyrolysis feedstock, the hydrogen-to-oxygen equivalence ratio is controlled to be less than 1, ensuring the oxygen content is less than the theoretically required amount, thereby preventing the consumption of the pyrolysis feedstock. The burner 15 head can be protected with a cooling water jacket. In conventional tubular pyrolysis furnaces, burner 15 uses excess combustion of conventional fuel gas (H2, CO, CH4) and air, with an excess coefficient typically of 1.25.

[0058] In this embodiment, the second superheated steam input to burner 15 is temperature-regulating steam. The superheat of the second superheated steam can be 10°C to 20°C. The feed mass ratio of hydrogen to the second superheated steam can be 0.05 to 1.35.

[0059] Optionally, one or more burners 15 may be arranged at the bottom of the combustion furnace 11. When multiple burners 15 are arranged at the bottom of the combustion furnace 11, the arrangement of these multiple burners 15 can be a uniform ring distribution, such as... Figure 6 As shown; or the arrangement of the multiple burners 15 can be linear, such as... Figure 7 As shown.

[0060] In one embodiment, the combustion device 10 further includes a distributor 12, through which the combustion furnace 11 is connected to the pyrolysis device 20, and the heat transfer fluid is input into the pyrolysis device 20 through the distributor 12.

[0061] For example, in the above-described pyrolysis apparatus 20, which includes a plurality of pyrolysis units 21 arranged along the second direction Y, a distribution chamber 121 is provided inside the distributor 12, through which the combustion furnace 11 is connected to each pyrolysis unit 21. The distribution chamber 121 is located on one side of the combustion furnace 11 in the second direction Y and extends along the second direction Y. The cross-sectional area of ​​the distribution chamber 121 at various positions in the second direction Y gradually decreases in the direction away from the combustion furnace 11. The cross-section of the distribution chamber 121 should be understood as the cross-section of the distribution chamber 121 perpendicular to the second direction Y. In other words, in this embodiment, the distribution chamber 121 of the distributor 12 adopts a tapered flow channel design, which makes the flow rate of the heat transfer fluid at the location of each pyrolysis unit 21 relatively consistent, which is beneficial to ensure that the heat transfer fluid is uniformly distributed to each pyrolysis unit 21.

[0062] In one embodiment, the combustion device 10 further includes a first superheater 13. The first superheater 13 is disposed on the distributor 12 and connected to the steam drum 60. The first superheater 13 may be disposed upstream of the aforementioned distribution chamber 121. Steam is separated from the first cooling fluid flowing through the pyrolysis device 20 in the steam drum 60 and transferred to the first superheater 13. The steam transferred from the steam drum 60 to the first superheater 13 exchanges heat with the heat transfer fluid to form first superheated steam.

[0063] The first superheater 13 is a high-pressure superheater, capable of generating high-pressure superheated steam with a pressure of 8.5 MPa to 12 MPa and a temperature of 510°C to 560°C. After the pyrolysis fluid is rapidly cooled by the quench boiler 24, the high-pressure steam-water mixture in the quench boiler 24 enters the steam drum 60 for steam-water separation. The resulting high-pressure saturated steam enters the first superheater 13 and exchanges heat with the heat transfer fluid in the distributor 12 to generate the first superheated steam.

[0064] In one embodiment, the olefin preparation system further includes a separation device 40. The separation device 40 is connected to the fractionation column 31 of the fractionation device 30, the fractionation column 31 is also used to transfer the fractionation product to the separation device 40, and the separation device 40 is used to separate the fractionation product to obtain at least the product olefin.

[0065] It should be noted that the separation device 40 separates the fractionation products and also obtains at least the above-mentioned circulating hydrogen. The burner 15 is also used to receive the circulating hydrogen, fuel hydrogen, oxygen, second superheated steam and the circulating hydrogen to form a heat carrier fluid.

[0066] In one embodiment, the olefin preparation system further includes a compressor 70. The compressor 70 is connected to a fractionating column 31, a separation device 40, and a first superheater 13. The fractionation products of the fractionating column 31 are compressed by the compressor 70 and then transferred to the separation device 40. The first superheater 13 is also used to transfer first superheated steam to the compressor 70.

[0067] The heating method in this embodiment, which directly mixes the feed fluid and the heat transfer fluid, can increase the cracking pressure to 0.5 MPa to 1.0 MPa, thereby ensuring a high olefin yield while significantly increasing the equipment's processing capacity. Furthermore, the investment in the compressor 70 in the compression process section can be saved, eliminating the need for one to three stages of compressor 70 equipment and substantially reducing compressor 70 energy consumption.

[0068] In one embodiment, the separation device 40 separates the fractionation products to obtain at least a recycled light hydrocarbon feedstock. The preheating flow path 32 is further equipped with a second heat exchanger 34, which preheats the recycled light hydrocarbon feedstock to obtain a recycled light hydrocarbon fluid. The recycled light hydrocarbon fluid is mixed with the aforementioned feedstock fluid and the first superheated steam in the mixing device 50. In this embodiment, the recycled light hydrocarbon feedstock is preheated by the preheating flow path 32 before entering the mixing device 50 to form a recycled light hydrocarbon fluid, which improves heating efficiency and fully utilizes the heat energy generated by the fractionation device 30, further reducing system energy consumption.

[0069] In one embodiment, the pyrolysis fluid output from the quench boiler 24 enters the bottom of the fractionation tower 31 for further cooling. Quenching oil circulates through the preheating path 32, entering the fractionation tower 31 from the top and directly contacting the pyrolysis fluid for heat exchange. Heavy components in the pyrolysis fluid are condensed and flow out from the bottom of the fractionation tower 31; part of the heavy components enters the preheating path 32 as quench oil, and part is output as product fuel oil. The preheating path 32 on the side stream of the fractionation tower 31 collects the first fraction, which is cooled after preheating the pyrolysis feedstock; part of it is recycled back to the fractionation tower 31, and the other part enters the quench oil for viscosity adjustment.

[0070] In one embodiment, the olefin preparation system further includes a steam-water separator 81. The preheating flow path 32 is also provided with a third heat exchanger 35, connected to the steam-water separator 81. The steam-water separator 81 circulates a second cooling fluid to the third heat exchanger 35 to exchange heat with the quench oil in the preheating flow path 32. A second superheater 14 is provided in the combustion device 10. The steam-water separator 81 separates steam from the second cooling fluid flowing through the third heat exchanger 35 and transfers it to the second superheater 14 to exchange heat with the heat transfer fluid to form second superheated steam.

[0071] Specifically, the second superheater 14 is located in the distributor 12, specifically between the first superheater 13 and the distribution chamber 121. The second superheater 14 can be a low-pressure superheater, capable of generating second superheated steam at a pressure of 0.5 MPa and a temperature of 160℃~200℃. The process water in the steam-water separator 81 exchanges heat with the quench oil in the third heat exchanger 35 to produce a saturated steam-water mixture, which is returned to the steam-water separator 81 for steam-liquid separation. The separated low-pressure saturated steam enters the second superheater 14 to generate low-pressure superheated steam (i.e., second superheated steam). A portion of the second superheated steam enters the burner 15 as temperature-regulating steam, while the remainder is used in other process stages.

[0072] In one embodiment, the olefin preparation system further includes a quench tower 82. The quench tower 82 is connected to a fractionating tower 31, which fractionates to obtain a second fraction and transfers it to the quench tower 82 for cooling. The second fraction is the light component of the cracked fluid. After being cooled in the fractionating tower 31, the light component in the cracked fluid is output from the top of the fractionating tower 31 to the quench tower 82 for further condensation.

[0073] Optionally, the pressure of the quench tower 82 can be 0.05 MPaG to 0.8 MPaG, the top temperature of the quench tower 82 can be 35℃ to 65℃, and the bottom temperature of the quench tower 82 can be 80℃ to 160℃.

[0074] The olefin preparation system also includes a suction tank 85 and an alkaline washing tank 86. A quench tower 82 is connected to a compressor 70 via the suction tank 85, and the compressor 70 is connected to a separation unit 40 via the alkaline washing tank 86. The second fraction fed into the quench tower 82 from the fractionation tower 31 is condensed in the quench tower 82. The cooled second fraction is output from the top of the quench tower 82 to the suction tank 85, then compressed by the compressor 70, and subsequently enters the alkaline washing tank 86 to remove acidic gases. Finally, it enters the separation unit 40 for product separation.

[0075] In one embodiment, the olefin preparation system further includes an oil-water separator 83. The oil-water separator 83 is connected to both the fractionation tower 31 and the quench tower 82. The oil-water mixture obtained by cooling the second fraction in the quench tower 82 is transferred to the oil-water separator 83. The oil-water separator 83 separates light component oil from the oil-water mixture and transfers it to the fractionation tower 31. Specifically, a portion of the light component oil separated from the oil-water mixture by the oil-water separator 83 is returned to the fractionation tower 31, and a portion is output as product gasoline.

[0076] The oil-water separator 83 is also connected to the quench tower 82 via a return flow path 821. The condensate separated from the oil-water mixture by the oil-water separator 83 returns to the quench tower 82 via the return flow path 821. A fourth heat exchanger 822 is installed in the return flow path 821, and a fifth heat exchanger 36 is installed in the preheating flow path 32. Fresh water is fed into the steam drum 60 after passing through the fourth heat exchanger 822 and the fifth heat exchanger 36 in sequence. In this embodiment, preheated water is obtained by utilizing the heat energy of the return flow path 821 and the preheating flow path 32. This preheated water serves as a feed for the steam drum 60. The preheated water helps improve the generation efficiency of high-pressure saturated steam in the steam drum 60, and also improves the system's energy utilization rate and reduces system energy consumption.

[0077] For example, the condensate separated from the oil-water mixture by the oil-water separator 83 returns to the middle and top of the quench tower 82 via the return flow path 821. The condensate in the return flow path 821 exchanges heat with fresh water in the fourth heat exchanger 822, preheating the fresh water to obtain transition water. This transition water then exchanges heat with quench oil in the fifth heat exchanger 36 on the preheating flow path 32 to obtain preheated water. The return flow path 821 is also equipped with a sixth heat exchanger 823, located on the return flow path 821 connected to the top of the quench tower 82. Fresh water also exchanges heat with the condensate in the return flow path 821 in the sixth heat exchanger 823 to obtain process water, improving the system's energy utilization rate and reducing system energy consumption. This process water can be used in other process stages.

[0078] In one embodiment, the olefin preparation system further includes a stripping tower 84. The stripping tower 84 is connected to a quench tower 82 and an oil-water separator 83. The oil-water separator 83 separates condensate from the oil-water mixture and transfers it to the stripping tower 84 for stripping. The stripping tower 84 separates light hydrocarbons from the condensate separated from the oil-water separator 83 and transfers it to the quench tower 82. The stripping tower 84 is also connected to a preheating flow path 32 via a steam-water separator 81. The stripping tower 84 outputs process water to the steam-water separator 81 for heat exchange with the preheating flow path 32. The bottom of the stripping tower 84 outputs process water to the steam-water separator 81. The steam-water separator 81 circulates a second cooling fluid to a third heat exchanger 35 for heat exchange with the quench oil in the preheating flow path 32, producing the aforementioned saturated steam-water mixture.

[0079] The compressor 70 is also used to output steam to the stripping tower 84. Specifically, the compressor 70 outputs medium-pressure superheated steam, which can be cooled to medium-pressure steam by passing through some heat exchange links or doing work. This medium-pressure steam is input into the stripping tower 84 as steam replenishment for the stripping tower 84.

[0080] Please refer to the following: Figure 8 , Figure 8 This is a schematic diagram of another embodiment of the olefin preparation system of this application.

[0081] In an alternative embodiment, this embodiment differs from the above embodiment in that the light component feedstock and the heavy component feedstock are fed separately, and the light component feedstock and the heavy component feedstock are heated in different mixers 51 and then fed into different pyrolyzers 21. Specifically, the mixing device 50 includes a first mixer 51a and a second mixer 51b. The first mixer 51a is connected to part of the pyrolyzer 21 and is used to mix the feedstock fluid and the first superheated steam before feeding it into the pyrolyzer 21. The second mixer 51b is connected to the remaining pyrolyzers 21 and is used to mix the circulating light hydrocarbon fluid and the first superheated steam before feeding it into the pyrolyzer 21.

[0082] The working process of the olefin preparation system of the present application is described below.

[0083] Fuel hydrogen 001 and circulating hydrogen 002 are mixed and then subjected to oxygen 004 in burner 15 and furnace 11 for oxygen-deficient combustion. Second superheated steam 003 is introduced, and the temperature of the heat carrier fluid at the outlet of furnace 11 is adjusted by controlling the amount of second superheated steam 003. The heat carrier fluid is cooled after heat exchange with first superheater 13 and second superheater 14, and then evenly distributed into multiple crackers 21 by distributor 12. The ambient temperature cracking feedstock 000 is preheated by first heat exchanger 33 on preheating flow path 32 to obtain feedstock fluid 010. Feedstock fluid 010 is mixed with first superheated steam 011 and circulating light hydrocarbon fluid 009 in mixer 51. The mixed fluid then enters venturi tube 22 to mix with the upstream heat carrier fluid. The pyrolysis feedstock is rapidly heated in the Venturi tube 22 to 950℃~1200℃ before entering the pyrolysis section 23 for pyrolysis. During the pyrolysis reaction in the pyrolysis section 23, as the reaction itself absorbs heat, the temperature of the pyrolysis fluid decreases to 850℃~1150℃ before exiting the pyrolysis section 23. The pyrolysis fluid then enters the quench boiler 24 for rapid cooling, specifically to 300℃~450℃ within 0.5 seconds, to terminate the secondary reaction. The high-pressure steam-water mixture in the quench boiler 24 enters the steam drum 60 for steam-water separation. The high-pressure saturated steam 005 enters the first superheater 13 to generate first superheated steam 011. Part of the first superheated steam 011 enters the compressor 70, and the other part enters the mixer 51 to heat the feedstock fluid 010. The pyrolysis fluid 007 exiting the quench boiler 24 enters the fractionation tower 31 for further cooling. The circulating quench oil 016 enters from the top of the fractionation tower 31 and directly contacts the cracked fluid 007 for heat exchange. Heavy components in the cracked fluid 007 are condensed and flow out from the bottom of the fractionation tower 31. Part of the heavy components enters the circulating quench oil 016, and part is output as product fuel oil 015. The preheating flow path 32 on the side stream of the fractionation tower 31 collects a portion of the diesel fraction 017 (i.e., the first fraction mentioned above) to preheat the cracked feedstock 000 and fresh water 019 before cooling. Part of this is recycled back to the fractionation tower 31, and the other part enters the circulating quench oil 016 for viscosity adjustment. The light components (i.e., the second fraction mentioned above) in the cracked fluid are cooled and flow out from the top of the fractionation tower 31, entering the quench tower 82 for further condensation. The condensed oil-water mixture enters the oil-water separator 83 for separation. The cooled cracked fluid enters the suction tank 85 from the top of the quench tower 82, then enters the compressor 70 for multi-stage compression, and then enters the alkaline washing tank 86 to remove acidic gases. Finally, it enters the separation unit 40 for product separation. A portion of the separated recycled light hydrocarbon feedstock 021 (methane, ethane, and propane) is returned to the mixer 51 as recycled light hydrocarbon fluid 009, and a portion of the separated hydrogen is returned to the burner 15 as recycled hydrogen 002. A portion of the light component oil separated by the oil-water separator 83 is returned to the top of the fractionation tower 31, and a portion is output as product gasoline 020.Part of the condensate separated from the oil-water separator 83 is returned to the middle and top of the quench tower 82 after heat exchange with fresh water 019 via a circulating water pump. Another portion of the condensate enters the stripping tower 84 for stripping, separating light hydrocarbons and returning them to the top of the quench tower 82. The process water at the bottom of the stripping tower 84 enters the steam-water separator 81, where it exchanges heat with hot circulating quench oil 016 to produce a saturated steam-water mixture. This mixture returns to the steam-water separator 81 for steam-liquid separation. The separated low-pressure saturated steam 006 enters the second superheater 14 to produce second superheated steam 013. Part of the second superheated steam 013 enters the burner 15 for temperature control, and the rest is used in other process stages. Fresh water 019 exchanges heat with the condensate separated from the oil-water separator 83 to obtain transition water 018. The transition water 018 is heated by the quench oil 016 to form preheated water 008, which is then fed into the steam drum 60.

[0084] The olefin preparation system of this application embodiment has the following characteristics:

[0085] (1) The olefin preparation system of this application uses a heat transfer fluid to directly heat the cracking feedstock to a high temperature, up to 1100℃~1200℃, while the traditional steam tube cracking technology uses an indirect heating method, which has a limited heating rate and maximum temperature. Compared with the traditional steam tube cracking technology, the olefin preparation system of this application has a higher cracking temperature and a higher olefin yield.

[0086] (2) In traditional steam pipe pyrolysis technology, the pyrolysis pressure is 0.05 MPaG to 0.1 MPaG. Due to the limitations of pyrolysis efficiency and the strength of the pipe material at high temperatures, the pyrolysis pressure cannot be further increased. In the olefin preparation system of this application, the pyrolysis device adopts a direct mixing and heating method of feed fluid and heat transfer fluid for pyrolysis. While increasing the pyrolysis temperature, the pyrolysis pressure can also be increased, reaching 0.5 MPa to 1.0 MPa. This ensures a high olefin yield while greatly improving the equipment's processing capacity. In particular, the investment in the compressor in the compression process section can be saved. For example, the first to third stage compressors can be eliminated, significantly reducing compressor energy consumption.

[0087] (3) In traditional steam tube pyrolysis technology, the furnace combustion of the heating furnace uses recycled hydrogen and methane fuel gases separated from the pyrolysis gas to be burned with air, producing a large amount of CO2 and NO. x The high-temperature flue gas is directly discharged into the atmosphere. However, the olefin preparation system of this application uses green electricity generated by clean energy (photovoltaic and wind power) to electrolyze water to produce hydrogen and pure oxygen. The high-temperature water vapor generated by the combustion of process gas is used as a heat carrier fluid to directly mix with the cracking raw materials and heat them for cracking. After cracking, the water vapor enters the downstream system with the cracking fluid and is directly condensed and separated into circulating water, which saves energy and is pollution-free.

[0088] (4) In the traditional steam tube cracking technology, the burner uses the excess combustion of conventional fuel gas (H2, CO, CH4) and air, and the excess coefficient is generally 1.25. However, the burner supporting the olefin preparation system in the embodiment of the present application is an oxygen-deficient burner of fuel gas (H2), pure oxygen and superheated steam, and the excess coefficient is less than 1.0.

[0089] (5) In the traditional steam tube cracking technology, the mass ratio of dilution steam to cracking raw material is 0.3 - 0.8, and the reduction of the partial pressure of the raw material hydrocarbon is limited. Tar and coke are likely to be generated in the cracking tube, and the cracking furnace must be shut down for coke cleaning. The coke cleaning period is generally 40 - 60 days. However, the heat carrier fluid in the olefin preparation system in the embodiment of the present application itself serves as dilution steam, and the mass ratio to the cracking raw material reaches 2.0 - 4.0. The partial pressure of the raw material hydrocarbon is lower, and the heat carrier fluid can carry some hydrogen by itself, which can effectively inhibit the dehydrogenation reaction of hydrocarbons, and the coking problem can be significantly improved, and the operation period of the equipment is greatly increased.

[0090] (6) In the olefin preparation system in the embodiment of the present application, the heat carrier fluid generated by the combustion furnace can be scientifically and evenly distributed into the corresponding cracker through the distributor.

[0091] (7) In the traditional steam tube cracking technology, the cracking raw material and the dilution steam need to be heated to a temperature of 500°C - 560°C (referred to as: cross temperature) in the convection tube section of the furnace and then enter the radiation tube for cracking. There will be a problem that the raw material cokes in the convection tube section in advance. However, the cracking raw material in the olefin preparation system in the embodiment of the present application is directly mixed with superheated steam and preheated to 300°C - 400°C, and then directly enters the mixer to be mixed with the high-temperature heat carrier fluid. The preheating temperature of the mixture is relatively low, and no coking problem will occur.

[0092] (8) The combustion furnace of the olefin preparation system in the embodiment of the present application is a bottom-fired furnace, that is, the burner is arranged at the bottom of the combustion furnace. The inner wall of the furnace of the combustion furnace can be designed in the form of a water-cooled wall or a refractory adiabatic lining. The venturi tube and the cracking section are both designed with heat-insulating linings. Considering that there is coke in the cracking fluid and there is a problem of erosion of the heat-insulating material by the high-speed cracking fluid, the lining of the mixer in the embodiment of the present application that is in contact with the cracking fluid on the innermost side is preferably made of high-aluminum corundum ceramic tube.

[0093] (9) Traditional steam pipe pyrolysis technology has low pyrolysis pressure (0.05 MPaG to 0.1 MPaG). The pyrolysis gas is usually quenched to 200°C to 250°C by a quench boiler and an oil quencher before entering the oil-gas fractionation tower for fractionation. The top temperature of the fractionation tower is generally controlled at 90°C to 105°C. In the olefin preparation system of this application, the pyrolysis pressure is higher (0.5 MPa to 1.0 MPa) and the hydrocarbon partial pressure is lower. The pyrolysis fluid is quenched to 300°C to 450°C within 0.5 seconds before entering the fractionation tower to terminate the secondary reaction of the pyrolysis fluid. The top temperature of the fractionation tower is generally controlled at 105°C to 170°C.

[0094] The olefin preparation system provided in this application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An olefin preparation system, characterized in that, The olefin preparation system includes: A combustion device for outputting a heat transfer fluid; the combustion device includes a combustion furnace and a burner, the burner being used to receive fuel hydrogen, oxygen and second superheated steam, the fuel hydrogen, the oxygen and the second superheated steam being burned in the burner and the combustion furnace to form the heat transfer fluid; A pyrolysis unit, connected to the combustion unit, is configured to receive the heat transfer fluid and the feed fluid, such that the feed fluid and the heat transfer fluid are mixed and undergo a pyrolysis reaction in the pyrolysis unit to obtain a pyrolysis fluid for the preparation of the product olefins; and The fractionation apparatus includes a fractionation column, a preheating flow path, and a first heat exchanger. The fractionation column is connected to the cracking apparatus and is used to receive the cracked fluid and fractionate the cracked fluid to obtain at least a first fraction. The inlet and outlet of the preheating flow path are both connected to the fractionation column and are used to pass the first fraction. The first heat exchanger is disposed in the preheating flow path, and the first fraction preheats the cracked feedstock through the first heat exchanger to obtain the feedstock fluid. The olefin preparation system further includes: A separation device is connected to the fractionation tower, which is used to separate the fractionation products to obtain at least olefins and recycled light hydrocarbon feedstock; the preheating flow path is also provided with a second heat exchanger, which is used to preheat the recycled light hydrocarbon feedstock to obtain recycled light hydrocarbon fluid. A mixing device is connected to the pyrolysis unit. The mixing device is used to mix the feed fluid, the circulating light hydrocarbon fluid, and the first superheated steam to obtain a mixed fluid, and to input the mixed fluid into the pyrolysis unit. The molar ratio of methane in the circulating light hydrocarbon fluid to hydrogen in the heat transfer fluid is 0.5 to 2.

0.

2. The olefin preparation system according to claim 1, characterized in that, The fractionation tower is also used to transfer the fractionated products to the separation unit.

3. The olefin preparation system according to claim 2, characterized in that, The combustion device also includes: A distributor is provided, through which the combustion furnace is connected to the pyrolysis unit, and the heat transfer fluid is input into the pyrolysis unit through the distributor. The olefin preparation system further includes: A steam drum, connected to the pyrolysis unit, is used to circulate a first cooling fluid to the pyrolysis unit to cool the pyrolysis fluid; and A first superheater is disposed on the distributor and connected to the steam drum. The steam drum separates steam from the first cooling fluid flowing through the pyrolysis unit and transmits it to the first superheater. The steam transmitted from the steam drum to the first superheater exchanges heat with the heat transfer fluid to form the first superheated steam.

4. The olefin preparation system according to claim 3, characterized in that, The olefin preparation system further includes: The compressor is connected to the fractionation tower, the separation device and the first superheater respectively. The fractionation products of the fractionation tower are compressed by the compressor and then transferred to the separation device. The first superheater is also used to transfer the first superheated steam to the compressor.

5. The olefin preparation system according to claim 2, characterized in that, The mixing device includes: A mixer for mixing the feed fluid, the circulating light hydrocarbon fluid, and the first superheated steam to obtain the mixed fluid; A first dispensing pipe is connected to the mixer; and The nozzle is connected to the first distribution pipe and the pyrolysis device respectively, and the mixed fluid is sequentially input into the pyrolysis device through the first distribution pipe and the nozzle; The pyrolysis fluid flows along a first direction in the pyrolysis device, and the extension direction of the nozzle is inclined relative to the first direction.

6. The olefin preparation system according to claim 2, characterized in that, The pyrolysis device includes multiple pyrolyzers, in which the feed fluid and the heat transfer fluid are mixed and undergo a pyrolysis reaction. The mixing device includes: A mixer for mixing the feed fluid, the circulating light hydrocarbon fluid, and the first superheated steam to obtain the mixed fluid; A first distribution pipe is connected to the mixer and also to each of the pyrolyzers, through which the mixed fluid is transmitted to each of the pyrolyzers.

7. The olefin preparation system according to claim 1, characterized in that, The pyrolysis unit includes multiple pyrolyzers, in which the feed fluid and the heat transfer fluid are mixed and undergo a pyrolysis reaction; the fractionation column is also used to transfer the fractionated products to the separation unit. The olefin preparation system further includes: A first mixer, connected to a portion of the pyrolysis unit, is used to mix the feed fluid and the first superheated steam and input them into the pyrolysis unit. as well as A second mixer, connected to the remaining pyrolyzers, is used to mix the circulating light hydrocarbon fluid and the first superheated steam and feed them into the pyrolyzers.

8. The olefin preparation system according to claim 1, characterized in that, The combustion furnace is connected to the pyrolysis device; The burner is located at the bottom of the combustion furnace.

9. The olefin preparation system according to claim 8, characterized in that, The fractionation tower is also used to transfer the fractionation products to the separation device, which is used to separate the fractionation products to obtain at least the product olefins and circulating hydrogen. The burner is also used to receive the circulating hydrogen. The fuel hydrogen, the oxygen, the second superheated steam, and the circulating hydrogen are combusted to form the heat carrier fluid.

10. The olefin preparation system according to claim 8, characterized in that, The pyrolysis device includes a plurality of pyrolyzers arranged along a second direction; The combustion device also includes: The distributor has a distribution chamber inside, and the combustion furnace is connected to each of the pyrolyzers through the distribution chamber. The distribution chamber is located on one side of the combustion furnace in the second direction, and the distribution chamber extends along the second direction. The cross-sectional area of ​​the distribution chamber at each position in the second direction gradually decreases in the direction away from the combustion furnace.

11. The olefin preparation system according to claim 8, characterized in that, The olefin preparation system further includes: A steam-water separator is provided in the preheating flow path, and a third heat exchanger is also provided therein. The steam-water separator is connected to the third heat exchanger, and the steam-water separator is used to circulate a second cooling fluid to the third heat exchanger for heat exchange with the quench oil in the preheating flow path; and The second superheater is disposed in the combustion device. The steam-water separator separates steam from the second cooling fluid flowing through the third heat exchanger and transfers it to the second superheater to exchange heat with the heat carrier fluid to form the second superheated steam.

12. The olefin preparation system according to claim 1, characterized in that, The olefin preparation system further includes: A quench tower is connected to the fractionation tower, where the fractionation tower divides the distillate to obtain a second fraction, which is then transferred to the quench tower for cooling. An oil-water separator is connected to both the fractionation tower and the quench tower. The oil-water mixture obtained by cooling the second fraction in the quench tower is transferred to the oil-water separator. The oil-water separator separates the light component oil from the oil-water mixture and transfers it to the fractionation tower.

13. The olefin preparation system according to claim 12, characterized in that, The oil-water separator is also connected to the quench tower via a return flow path. The condensate separated from the oil-water mixture by the oil-water separator is returned to the quench tower via the return flow path. The return flow path is equipped with a fourth heat exchanger. The preheating flow path is equipped with a fifth heat exchanger. The olefin preparation system further includes: A steam drum is connected to the pyrolysis unit, and the steam drum is used to circulate a first cooling fluid to the pyrolysis unit to cool the pyrolysis fluid. Fresh water is fed into the steam drum after passing through the fourth and fifth heat exchangers in sequence.

14. The olefin preparation system according to claim 12, characterized in that, The olefin preparation system further includes: A stripping tower is connected to both the quench tower and the oil-water separator. The oil-water separator separates condensate from the oil-water mixture and transfers it to the stripping tower for stripping. The stripping tower separates light hydrocarbons from the condensate separated from the oil-water separator and transfers them to the quench tower. The stripping tower is also connected to the preheating flow path via the steam-water separator, and the stripping tower outputs process water to the steam-water separator for heat exchange with the preheating flow path.

15. The olefin preparation system according to claim 14, characterized in that, The olefin preparation system further includes: The compressor is connected to the fractionation tower; The separation device is connected to the compressor, and the fractionation products of the fractionation tower are compressed by the compressor and then transferred to the separation device. The compressor is also used to output steam to the stripping tower.

Images