Olefin preparation system

Abstract

The invention relates to the technical field of chemical engineering, and discloses an olefin preparation system. In the olefin preparation system, the raw material fluid and the hot carrier fluid are mixed in the cracking device and are subjected to cracking reaction to obtain the cracking fluid to prepare the product olefin, so that the heating rate and the heating temperature of the raw material fluid can be increased, the olefin yield can be increased, and the cracking pressure can be increased; the processing capacity of the equipment is improved and the energy consumption of the system is reduced while the high olefin yield is ensured. The raw material fluid is preheated by the preheating flow path before being mixed with the hot carrier fluid, so that the heating efficiency of the raw material fluid can be improved, heat energy generated by the fractionation device can be fully utilized, and the energy consumption of the system is further reduced. And moreover, the preheated raw material fluid is relatively low in temperature, so that the problem of coking in advance is avoided.

Description

Technical Field

[0001] The present application relates to the field of chemical technology, and in particular to an olefin preparation system. Background Art

[0002] At present, the production technology of ethylene and propylene usually adopts steam tube cracking technology. During the process of raw materials flowing in the tube, they are heated by the radiation heating of the high-temperature flue gas in the furnace, causing the temperature to rise and crack. However, there are many problems with the current cracking furnace.

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

[0004] At present, the radiation tubes of cracking furnaces are mostly made of nickel-based alloy steel tubes. Due to the limitation of the metal material itself, the maximum temperature that the outer wall of the furnace tube can withstand is about 1100℃. Therefore, if you want to further increase the cracking temperature to above 1000℃, it is difficult to achieve for the existing cracking furnace. Although new technologies such as heat-resistant coatings and ceramic furnace tubes have been introduced, due to the limitation of the structure itself, the cracking temperature has become the limit at about 1000℃ and cannot be further increased.

[0005] (2) It is difficult to shorten the stay time

[0006] The current cracking furnace reaction section adopts indirect heating, that is, the cracking raw materials flow in the tube, and the high-temperature heated flue gas heats the raw materials in the tube through convection and radiation heat transfer outside the tube. Since the outer wall of the tube cannot withstand higher temperatures, the time required for the heating process from the crossover temperature to the cracking temperature is also limited and cannot be further increased.

[0007] (3) It is difficult to further increase the processing capacity of a single cracking furnace

[0008] The pressure in the existing cracking furnace tube is about 0.05-0.1MPaG, and the density of the raw material in the furnace tube is about 0.75-0.8kg / m3. The low density makes the device bulky. At present, the maximum ethylene output of a single furnace is about 200kt / a. In order to obtain a higher output, the device is large and the investment is huge. At the same time, the increase in the complexity of the device also increases the failure rate and operation risk points. Summary of the invention

[0009] The present application provides an olefin preparation system, which can improve the olefin yield, and can also improve the equipment processing capacity and reduce the system energy consumption.

[0010] The present application provides an olefin preparation system. The olefin preparation system includes: a combustion device for outputting a heat carrier fluid; a cracking device connected to the combustion device, the cracking device is used to receive the heat carrier fluid and the raw material fluid, so that the raw material fluid and the heat carrier fluid are mixed in the cracking device and undergo a cracking reaction to obtain a cracked fluid to prepare product olefins; and a fractionation device, including a fractionation tower, a preheating flow path and a first heat exchanger, the fractionation tower is connected to the cracking device, the fractionation tower 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 tower and are used to pass the first fraction, the first heat exchanger is arranged in the preheating flow path, and the first fraction preheats the cracked raw material through the first heat exchanger to obtain the raw material fluid.

[0011] In one embodiment of the present application, the olefin preparation system also includes: a separation device, connected to the distillation tower, the distillation tower is also used to transmit the distillation product to the separation device, the separation device is used to separate the distillation product to obtain at least product olefins and circulating light hydrocarbon feedstock; the preheating flow path is also provided with a second heat exchanger, the second heat exchanger is used to preheat the circulating light hydrocarbon feedstock to obtain a circulating light hydrocarbon fluid; a mixing device, connected to the cracking device, the mixing device is used to mix the feedstock fluid, the circulating 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 the present application, the combustion device includes: a combustion furnace for generating a heat carrier fluid; and a distributor, the combustion furnace is connected to the cracking device through the distributor, and the heat carrier fluid is input into the cracking device through the distributor; the olefin preparation system also includes: a steam drum, connected to the cracking device, the steam drum is used to circulate and output a first cooling fluid to the cracking device to cool the cracking fluid; and a first superheater, which is arranged on the distributor and the first superheater is connected to the steam drum, the steam drum separates steam from the first cooling fluid flowing through the cracking 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 carrier fluid to form a first superheated steam.

[0013] In one embodiment of the present application, the olefin preparation system also includes: a compressor, which is respectively connected to the distillation tower, the separation device and the first superheater. The distillation product of the distillation tower is compressed by the compressor and then transmitted to the separation device. The first superheater is also used to transmit the first superheated steam to the compressor.

[0014] In one embodiment of the present 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 a cracking device, respectively, and the mixed fluid is input into the cracking device through the first distribution pipe and the nozzle in sequence; wherein the cracking fluid flows along a first direction in the cracking device, and the extension direction of the nozzle is inclined relative to the first direction.

[0015] In one embodiment of the present application, the cracking device includes multiple crackers, in which the raw material fluid and the heat carrier fluid are mixed and a cracking reaction occurs; the mixing device includes: a mixer, used to mix the raw material fluid, the circulating light hydrocarbon fluid and the first superheated steam to obtain a mixed fluid; a first distribution pipe, connected to the mixer, and the first distribution pipe is also connected to each cracker, and the mixed fluid is transmitted to each cracker through the first distribution pipe.

[0016] In one embodiment of the present application, the cracking device includes a plurality of crackers, in which the raw material fluid and the heat carrier fluid are mixed and a cracking reaction occurs; the olefin preparation system also includes: a separation device connected to the distillation tower, the distillation tower is also used to transmit the distillation product to the separation device, the separation device is used to perform product separation on the distillation product to obtain at least product olefins and circulating light hydrocarbon feedstock; the preheating flow path is also provided with a second heat exchanger, the second heat exchanger is used to preheat the circulating light hydrocarbon feedstock to obtain a circulating light hydrocarbon fluid; a first mixer, connected to some of the crackers, the first mixer is used to mix the raw material fluid and the first superheated steam and input them into the cracker; and a second mixer, connected to the remaining crackers, the second mixer is used to mix the circulating light hydrocarbon fluid and the first superheated steam and input them into the cracker.

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

[0018] In one embodiment of the present application, the olefin preparation system also includes: a separation device, which is connected to the distillation tower, the distillation tower is also used to transmit the distillation product to the separation device, the separation device is used to perform product separation on the distillation product to obtain at least product olefins and circulating hydrogen, and the burner is also used to receive the circulating hydrogen, and the fuel hydrogen, oxygen, second superheated steam and circulating hydrogen are burned to form a heat carrier fluid.

[0019] In one embodiment of the present application, the cracking device includes a plurality of crackers arranged along a second direction; the combustion device also includes: a distributor, in which a distribution chamber is arranged, and the combustion furnace is connected to each cracker 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 the present application, the olefin preparation system also includes: a steam-water separator, the preheating flow path is also provided with a third heat exchanger, the steam-water separator and the third heat exchanger are connected, the steam-water separator is used to circulate and output the second cooling fluid to the third heat exchanger for heat exchange with the quench oil in the preheating flow path; and a second superheater, which is arranged in the combustion device, the steam-water separator separates steam from the second cooling fluid flowing through the third heat exchanger and transmits it to the second superheater to exchange heat with the heat carrier fluid to form second superheated steam.

[0021] In one embodiment of the present application, the olefin preparation system also includes: a quenching water tower, which is connected to the distillation tower, the distillation tower distills to obtain a second fraction and transmits it to the quenching water tower for cooling; an oil-water separation tank, which is connected to the distillation tower and the quenching water tower, respectively, the quenching water tower cools the second fraction to obtain an oil-water mixture, which is transmitted to the oil-water separation tank, and the oil-water separation tank separates the light component oil from the oil-water mixture and transmits it to the distillation tower.

[0022] In one embodiment of the present application, the oil-water separation tank is also connected to the quenching water tower through a reflux flow path, and the condensed water separated from the oil-water mixture by the oil-water separation tank is returned to the quenching water tower through the reflux flow path, and the reflux flow path is provided with a fourth heat exchanger; the preheating flow path is provided with a fifth heat exchanger; the olefin preparation system also includes: a steam drum, connected to the cracking device, the steam drum is used to circulate and output the first cooling fluid to the cracking device to cool the cracking fluid; the new water is successively input into the steam drum after heat exchange through the fourth heat exchanger and the fifth heat exchanger.

[0023] In one embodiment of the present application, the olefin preparation system also includes: a stripping tower, which is respectively connected to the quenching water tower and the oil-water separation tank, the oil-water separation tank separates condensed water from the oil-water mixture and transmits it to the stripping tower for stripping, the stripping tower separates light hydrocarbons from the condensed water separated by the oil-water separation tank and transmits it to the quenching water tower; and a steam-water separator, the stripping tower is also connected to the 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 the present application, the olefin preparation system also includes: a compressor connected to the distillation tower; a separation device connected to the compressor, the distillation product of the distillation tower is compressed by the compressor and transmitted to the separation device, the separation device is used to separate the distillation product to at least obtain product olefins; wherein the compressor is also used to output steam to the stripping tower.

[0025] The beneficial effect of the present application is as follows: Different from the prior art, the present application provides an olefin preparation system. In the olefin preparation system, the raw material fluid and the heat carrier fluid are mixed in the cracking device and undergo cracking reaction to obtain the cracking fluid to prepare the product olefins. The raw material fluid and the heat carrier fluid of the present application are directly mixed in the cracking device, and the raw material fluid is directly heated by the heat carrier fluid, which can increase the heating rate and heating temperature of the raw material fluid, which is beneficial to increase the olefin yield. In addition, the heating method of directly mixing the raw material fluid and the heat carrier fluid of the present application can increase the cracking pressure, improve the equipment processing capacity and reduce the system energy consumption while ensuring a high olefin yield.

[0026] The fractionation device of the present application includes a fractionation tower, a preheating flow path and a first heat exchanger. The fractionation tower fractionates the cracking fluid to obtain at least a first fraction, and the first fraction preheats the cracking raw material through the first heat exchanger on the preheating flow path to obtain a raw material fluid. In other words, the raw material fluid of the present application is preheated by the preheating flow path before mixing with the heat carrier fluid, which can improve the heating efficiency of the raw material fluid, and can also make full use of the heat energy generated by the fractionation device, further reducing the energy consumption of the system. In addition, the temperature of the preheated raw material fluid is relatively low, and the problem of premature coking will not occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

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

[0029] Figure 2 It is a structural schematic diagram of the first embodiment of the venturi tube of the present application;

[0030] Figure 3 It is a structural schematic diagram of the second embodiment of the venturi tube of the present application;

[0031] Figure 4 This is a bottom-up structural schematic diagram of the third embodiment of the venturi tube of the present application;

[0032] Figure 5 is a bottom view structural schematic diagram of the fourth embodiment of the venturi tube of the present application;

[0033] Figure 6 It is a structural schematic diagram of an embodiment of the burner of the present application being arranged at the bottom of a combustion furnace;

[0034] Figure 7It is a structural schematic diagram of another embodiment of the present application in which the burner is arranged at the bottom of the combustion furnace;

[0035] Figure 8 It is a schematic diagram of another embodiment of the olefin preparation system of the present application. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application and are not used to limit the present application. In the present application, unless otherwise stated, the directional words used, such as "up", "down", "left", and "right", generally refer to the up, down, left, and right of the device in actual use or working state, specifically the drawing direction in the accompanying drawings.

[0037] In this application, unless otherwise clearly specified and limited, the terms "connected", "connected", "stacked" and the like should be understood in a broad sense, for example, it can be fixedly connected, detachably connected, or integrated; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0038] The present application provides an olefin preparation system, which is described in detail below. It should be noted that the description order of the following embodiments does not limit the preferred order of the embodiments of the present application. In the following embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0039] See also Figure 1 , Figure 1 It is a schematic diagram of an embodiment of an olefin preparation system of the present application.

[0040] In one embodiment, the olefin production system includes a combustion device 10, which is used to output a heat carrier fluid. The olefin production system also includes a cracking device 20, which is connected to the combustion device 10. The cracking device 20 is used to receive the heat carrier fluid and the raw material fluid, so that the raw material fluid and the heat carrier fluid are mixed in the cracking device 20 and undergo a cracking reaction to obtain a cracked fluid to produce product olefins.

[0041] In the above manner, in the olefin preparation system of the present embodiment, the raw material fluid and the heat carrier fluid are mixed in the cracking device 20 and undergo cracking reaction to obtain cracking fluid to prepare product olefins. The raw material fluid and the heat carrier fluid of the present embodiment are directly mixed in the cracking device 20, and the raw material fluid is directly heated by the heat carrier fluid, which can increase the heating rate and heating temperature of the raw material fluid, which is conducive to increasing the olefin yield. In addition, the heating method of directly mixing the raw material fluid and the heat carrier fluid of the present embodiment can increase the cracking pressure, improve the equipment processing capacity and reduce the system energy consumption while ensuring a high olefin yield.

[0042] In one embodiment, the olefin preparation system further includes a fractionation device 30, which is used to receive the cracking fluid and fractionate the cracking fluid to prepare product olefins. Specifically, the fractionation device 30 includes a fractionation tower 31, a preheating flow path 32 and a first heat exchanger 33. The fractionation tower 31 is connected to the cracking device 20, and the fractionation tower 31 is used to receive the cracking fluid and fractionate the cracking fluid to obtain at least a first fraction. The inlet and outlet of the preheating flow path 32 are both connected to the fractionation tower 31, and the preheating flow path 32 is used to pass the first fraction. The first heat exchanger 33 is arranged in the preheating flow path 32, and the first fraction preheats the cracking raw material through the first heat exchanger 33 to obtain a raw material fluid.

[0043] In the above manner, the raw material fluid of this embodiment is preheated by the preheating flow path 32 before mixing with the heat carrier fluid, which can improve the heating efficiency of the raw material fluid, and can also make full use of the heat energy generated by the fractionation device 30, further reducing the energy consumption of the system. In addition, the temperature of the preheated raw material fluid is low, and there will be no problem of premature coking. The pressure of the fractionation tower 31 can be 0.05MPaG~0.8MPaG, and the optimal pressure can be 0.15MPaG~0.6MPaG. The design temperature of the bottom of the fractionation tower 31 can be 195℃~220℃, and the design temperature of the top of the tower can be 105℃~170℃.

[0044] It should be noted that the cracking feedstock of this embodiment has a wide adaptability. The cracking feedstock can be light hydrocarbons (such as ethane, propane, butane, etc.), naphtha, light diesel fraction, diesel fraction, hydrogenated tail oil or heavy oil, etc. The light component feedstock and the heavy component feedstock can be separated or mixed together to enter the cracking device 20, which will be described in detail below.

[0045] In one embodiment, the cracking device 20 includes a cracker 21. The cracker 21 includes a venturi tube 22, a cracking section 23 and a quenching boiler 24. The venturi tube 22 is connected to the quenching boiler 24 through the cracking section 23. The raw material fluid and the heat carrier fluid are mixed in the venturi tube 22, and the raw material fluid is rapidly heated in the venturi tube 22 and enters the cracking section 23 to undergo a cracking reaction to obtain a cracking fluid. After the cracking fluid exits the cracking section 23, it enters the quenching boiler 24 to be rapidly quenched. The raw material fluid and the heat carrier fluid are mixed in the venturi tube 22, and a cracking reaction occurs in the cracking section 23 to obtain a cracking fluid to prepare product olefins. The raw material fluid and the heat carrier fluid are directly mixed in the venturi tube 22, and the raw material fluid is directly heated by the heat carrier fluid, which can increase the heating rate and heating temperature of the raw material fluid, which is conducive to increasing the olefin yield. In addition, the heating method of directly mixing the raw material fluid and the heat carrier fluid in this embodiment can increase the cracking pressure, while ensuring a high olefin yield, improving the equipment processing capacity and reducing the system energy consumption.

[0046] For further information, please also refer to Figure 2 and Figure 3 The venturi tube 22 includes a tapered section 221, a throat straight section 222 and a gradually expanding section 223. The tapered section 221, the throat straight section 222 and the gradually expanding section 223 are connected in sequence, and the gradually expanding section 223 is connected to the cracking section 23. For example, the average flow velocity in the venturi tube 22 is 100m / s to 200m / s, the flow velocity at the throat straight section 222 is 200m / s to 300m / s, and the entire mixing time is less than 30ms. The design flow velocity in the cracking section 23 is 150m / s to 250m / s, the cracking residence time is less than 50ms, and the outlet temperature of the cracking section 23 is 850℃ to 1150℃.

[0047] In one embodiment, the olefin preparation system further includes a mixing device 50, which is connected to the cracking device 20. The mixing device 50 is used to mix the raw material fluid, the circulating light hydrocarbon fluid and the first superheated steam to obtain a mixed fluid, and input the mixed fluid into the cracking device 20. In this embodiment, the raw material 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 mixed fluid can be 300°C to 400°C. In addition, the molar ratio of methane in the circulating light hydrocarbon fluid to hydrogen in the heat carrier fluid in this embodiment 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 carrier fluid, the production efficiency of olefins can be guaranteed and coking can be suppressed.

[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 raw material 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 the first distribution pipe 52 and the cracking device 20 respectively, and the mixed fluid is sequentially input into the cracking device 20 through the first distribution pipe 52 and the nozzle 53.

[0049] Please also read Figure 4 and Figure 5 , the nozzle 53 is connected to the tapered section 221 or the throat straight 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 connected in sequence along the first direction X, that is, the cracking fluid flows in the cracking device 20 along the first direction X. The tapered section 221, the throat straight section 222 and the gradually expanding section 223 of the venturi tube 22 are connected in sequence 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 is inclined relative to the first direction X and the outlet of the nozzle 53 faces the cracking section 23.

[0050] For example, the included angle between the extension direction of the nozzle 53 and the first direction X may be 45° to 90°. Figure 2 The nozzle 53 is exemplarily shown to be 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 The nozzle 53 is exemplarily shown to be connected to the tapered section 221 of the venturi tube 22, and the extending direction of the nozzle 53 is inclined relative to the first direction X, and the outlet of the nozzle 53 faces the gradually expanding section 223. The number of the nozzles 53 can be one or two or more. When the number of the nozzles 53 is two or more, the nozzles 53 are evenly spaced and distributed along the circumference of the venturi tube 22. Figure 4 It is exemplarily shown that the number of nozzles 53 is even and they are evenly spaced along the circumference of the venturi tube 22; Figure 5 The nozzles 53 are exemplarily shown to be odd in number and evenly spaced along the circumference of the venturi tube 22. In addition, the mixer 51 and the cracking section 23 are internally cast, and the innermost layer is a high-aluminum corundum tube or a corundum brick.

[0051] In one embodiment, the cracking device 20 includes a plurality of crackers 21. The mixer 51 is connected to each cracker 21 through a first distribution pipe 52, and the mixed fluid obtained by mixing in the mixer 51 is transmitted to each cracker 21 through the first distribution pipe 52. The cracking raw materials in this embodiment can be light component raw materials (such as ethane, methane, etc.) and heavy component raw materials (such as naphtha, light diesel fraction, etc.). The light component raw materials and the heavy component raw materials enter the mixer 51 together for mixing, and then are distributed to each cracker 21 through the first distribution pipe 52 for cracking reaction.

[0052] In one embodiment, the olefin preparation system further includes a steam drum 60, which is connected to the cracking device 20, and is used to circulate and output the first cooling fluid to the cracking device 20 to cool the cracking fluid. Specifically, the steam drum 60 is connected to the quenching boiler 24 through the second distribution pipe 61, and the steam drum 60 circulates and outputs the first cooling fluid to the quenching boiler 24 to cool the cracking fluid, so that the cracking fluid is rapidly quenched.

[0053] It should be noted that the quenching boiler 24 of this embodiment adopts forced circulation, the circulation ratio is 2.5-4, the pressure of the drum 60 is 8.5MPa-12.0MPa, the temperature of the cracking fluid after quenching is 300°C-450°C, 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 cracking device 20. The burner 15 is arranged at the bottom of the combustion furnace 11. The burner 15 is used to receive fuel hydrogen, oxygen and second superheated steam, and the fuel hydrogen, oxygen and second superheated steam are burned in the burner 15 and the combustion furnace 11 to form a heat carrier fluid. The temperature of the heat carrier fluid at the outlet of the combustion furnace 11 is adjusted by controlling the amount of the second superheated steam.

[0055] In this embodiment, the fuel hydrogen can be produced by electrolyzing water with green electricity generated by clean energy (photovoltaic, wind energy). In addition, the burner 15 of this embodiment can also be fed with circulating hydrogen to circulate and supplement when the fuel hydrogen supply is insufficient. The circulating hydrogen can be obtained by product separation of the cracking fluid, that is, the cracking fluid is separated to obtain at least product olefins and circulating hydrogen. In this embodiment, oxygen can be produced by electrolyzing water with green electricity generated by clean energy (photovoltaic, wind energy), and oxygen can also be separated by air separation. It can be seen that this embodiment uses green electricity generated by clean energy (photovoltaic, wind energy) to electrolyze water to produce hydrogen and oxygen, and uses high-temperature water vapor as a heat carrier fluid. After direct contact and cracking with the cracking raw material, it enters the subsequent links of the system with the cracking fluid and is directly condensed and separated into circulating water, saving energy while being pollution-free. The furnace combustion of the traditional tubular heating furnace uses the circulating hydrogen and methane separated from the cracking gas to burn with air, producing a large amount of CO2 and NO x The high temperature flue gas is directly discharged into the atmosphere.

[0056] This embodiment uses fuel hydrogen combustion to form a heat carrier fluid. Since the density of hydrogen is relatively small, the burner 15 of this embodiment is arranged at the bottom of the combustion furnace 11, that is, this embodiment adopts a bottom-burning furnace form, which is conducive to the full combustion of fuel hydrogen. The inner wall of the furnace of the combustion furnace 11 can be designed in the form of a water-cooled wall or a refractory insulation lining. The furnace pressure range of the combustion furnace 11 can be 0.1MPaG~1.0MPaG. The temperature of the heat carrier fluid at the outlet of the combustion furnace 11 is 1200℃~1800℃. The outer wall design temperature of the shell of the combustion furnace 11 and the cracker 21 is >95℃ to prevent low-temperature corrosion of acidic gases.

[0057] The burner 15 of this embodiment is an oxygen-deficient burner, and the equivalent ratio of hydrogen to oxygen can be 0.25 to 0.98. The burner 15 of this embodiment is an oxygen-deficient burner 15 of fuel hydrogen, oxygen and superheated steam (i.e., second superheated steam), and the excess coefficient is less than 1.0. In order to prevent unreacted oxygen from entering the cracking device 20 and reacting with the cracking raw material, the equivalent ratio of hydrogen to oxygen is controlled to be less than 1 in this embodiment, so that the amount of oxygen is less than the required theoretical amount of oxygen, thereby avoiding the cracking raw material from being consumed. The head of the burner 15 can be designed with a cooling water jacket for protection. The burner 15 on the traditional tubular cracking furnace adopts excess combustion of conventional fuel gas (H2, CO, CH4) and air, and the excess coefficient is generally 1.25.

[0058] In this embodiment, the second superheated steam input into the burner 15 is temperature-adjusting 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, a single or multiple 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 multiple burners 15 may be arranged in a circular and uniformly distributed manner, such as Figure 6 or the arrangement of the plurality of burners 15 may be linearly distributed, such as Figure 7 shown.

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

[0061] For example, for the example in which the above-mentioned cracking device 20 includes a plurality of crackers 21, the plurality of crackers 21 are arranged along the second direction Y. A distribution chamber 121 is provided inside the distributor 12, and the combustion furnace 11 is connected to each cracker 21 through the distribution chamber 121. The distribution chamber 121 is located on one side of the combustion furnace 11 in the second direction Y, and the distribution chamber 121 extends along the second direction Y. The cross-sectional area of ​​the distribution chamber 121 at each position in the second direction Y gradually decreases in the direction away from the combustion furnace 11. The cross-sectional area of ​​the distribution chamber 121 should be understood as the cross-sectional area of ​​the distribution chamber 121 perpendicular to the second direction Y. In other words, the distribution chamber 121 of the distributor 12 of this embodiment adopts a tapered flow channel design, so that the flow rate of the heat carrier fluid at the location of each cracker 21 is relatively consistent, which is conducive to ensuring that the heat carrier fluid is evenly distributed to each cracker 21.

[0062] In one embodiment, the combustion device 10 further includes a first superheater 13. The first superheater 13 is disposed in the distributor 12, and the first superheater 13 is connected to the steam drum 60. The first superheater 13 may be disposed upstream of the distribution chamber 121. The steam drum 60 separates steam from the first cooling fluid flowing through the cracking device 20 and transmits it to the first superheater 13. The steam transmitted from the steam drum 60 to the first superheater 13 exchanges heat with the heat carrier fluid to form first superheated steam.

[0063] The first superheater 13 is a high-pressure superheater, which can generate high-pressure superheated steam with a pressure of 8.5MPa to 12MPa and a temperature of 510°C to 560°C. After the cracking fluid is rapidly quenched by the quenching boiler 24, the high-pressure steam-water mixture in the quenching boiler 24 enters the steam drum 60 for steam-water separation, and the obtained high-pressure saturated steam enters the first superheater 13 to exchange heat with the heat carrier fluid in the distributor 12 to generate the first superheated steam.

[0064] In one embodiment, the olefin production system further comprises a separation device 40. The separation device 40 is connected to the fractionation tower 31 of the fractionation device 30. The fractionation tower 31 is also used to transmit the fractionation product to the separation device 40. The separation device 40 is used to perform product separation on the fractionation product to obtain at least product olefins.

[0065] It should be noted that the separation device 40 performs product separation on the distillation products and obtains at least the above-mentioned circulating hydrogen. The burner 15 is also used to receive the circulating hydrogen. The fuel hydrogen, oxygen, second superheated steam and circulating hydrogen are burned 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 the fractionation tower 31, the separation device 40 and the first superheater 13 respectively. The fractionation product of the fractionation tower 31 is compressed by the compressor 70 and then transmitted to the separation device 40. The first superheater 13 is also used to transmit the first superheated steam to the compressor 70.

[0067] The heating method of directly mixing the raw material fluid and the heat carrier fluid in this embodiment can increase the cracking pressure, and the cracking pressure can be increased to 0.5MPa-1.0MPa, so that the olefin yield is high and the equipment processing capacity is greatly improved. In addition, the investment in the compressor 70 of the compression process section can be saved, and the compressor 70 equipment of sections 1 to 3 can be omitted, which greatly reduces the energy consumption of the compressor 70.

[0068] In one embodiment, the separation device 40 performs product separation on the fractionation product and obtains at least a circulating light hydrocarbon feedstock. The preheating flow path 32 is further provided with a second heat exchanger 34, which is used to preheat the circulating light hydrocarbon feedstock to obtain a circulating light hydrocarbon fluid, and the circulating light hydrocarbon fluid is mixed with the above-mentioned feedstock fluid and the first superheated steam in the mixing device 50. In this embodiment, the circulating light hydrocarbon feedstock is preheated by the preheating flow path 32 to form a circulating light hydrocarbon fluid before being input into the mixing device 50, which can improve the heating efficiency, and can also make full use of the heat energy generated by the fractionation device 30, further reducing the energy consumption of the system.

[0069] In one embodiment, the cracked fluid output from the quench boiler 24 enters the bottom of the fractionation tower 31 for further cooling. The quench oil circulates through the preheating flow path 32, and the quench oil enters from the top of the fractionation tower 31 to directly contact and exchange heat with the cracked fluid. The heavy components in the cracked fluid are condensed and flow out from the bottom of the fractionation tower 31. Part of the heavy components enter the preheating flow path 32 as quench oil, and part is output as product fuel oil. The preheating flow path 32 of the side line of the fractionation tower 31 extracts the first fraction, preheats the cracked raw material and then cools it, part of which is circulated 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 further provided with a third heat exchanger 35, and the steam-water separator 81 is connected to the third heat exchanger 35. The steam-water separator 81 is used to circulate and output the second cooling fluid to the third heat exchanger 35 to exchange heat with the quench oil in the preheating flow path 32. The second superheater 14 is provided in the combustion device 10, and the steam-water separator 81 separates steam from the second cooling fluid flowing through the third heat exchanger 35 and transmits it to the second superheater 14 to exchange heat with the heat carrier fluid to form second superheated steam.

[0071] Specifically, the second superheater 14 is arranged at the distributor 12, and specifically, the second superheater 14 can be located between the first superheater 13 and the distribution chamber 121. The second superheater 14 can be a low-pressure superheater, and the second superheater 14 can generate a second superheated steam with a pressure of 0.5 MPa and a temperature of 160°C to 200°C. The process water in the steam-water separator 81 is heat-exchanged with the quench oil in the third heat exchanger 35 to generate a saturated steam-water mixture, and the steam-water mixture returns 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), part of which enters the burner 15 as temperature-adjusting steam, and the rest of the second superheated steam is used in other process links.

[0072] In one embodiment, the olefin preparation system further includes a quenching water tower 82. The quenching water tower 82 is connected to the fractionation tower 31, and the fractionation tower 31 is fractionated to obtain a second fraction and is transferred to the quenching water tower 82 for cooling. The second fraction is the light component in the cracked fluid, and the light component in the cracked fluid is cooled in the fractionation tower 31 and then output from the top of the fractionation tower 31 to the quenching water tower 82 for further condensation.

[0073] Optionally, the pressure of the quenching water tower 82 may be 0.05 MPaG to 0.8 MPaG, the top temperature of the quenching water tower 82 may be 35° C. to 65° C., and the bottom temperature of the quenching water tower 82 may be 80° C. to 160° C.

[0074] The olefin preparation system further includes an air intake tank 85 and an alkali washing tank 86. The quenching water tower 82 is connected to the compressor 70 via the air intake tank 85, and the compressor 70 is connected to the separation device 40 via the alkali washing tank 86. The second fraction input from the fractionation tower 31 to the quenching water tower 82 is condensed by the quenching water tower 82, and the cooled second fraction is output from the top of the quenching water tower 82 to the air intake tank 85 and then compressed by the compressor 70, and then enters the alkali washing tank 86 to remove acidic gas, and finally enters the separation device 40 for product separation.

[0075] In one embodiment, the olefin preparation system further includes an oil-water separation tank 83. The oil-water separation tank 83 is connected to the fractionation tower 31 and the quenching water tower 82 respectively. The quenching water tower 82 cools the second fraction to obtain an oil-water mixture which is transmitted to the oil-water separation tank 83. The oil-water separation tank 83 separates light component oil from the oil-water mixture and transmits it to the fractionation tower 31. Specifically, part of the light component oil separated from the oil-water mixture by the oil-water separation tank 83 is returned to the fractionation tower 31, and part of it is output as product gasoline.

[0076] The oil-water separation tank 83 is also connected to the quenching water tower 82 through the reflux flow path 821, and the condensed water separated from the oil-water mixture by the oil-water separation tank 83 is returned to the quenching water tower 82 through the reflux flow path 821. The reflux flow path 821 is provided with a fourth heat exchanger 822, and the preheating flow path 32 is provided with a fifth heat exchanger 36. The new water is sequentially heat-exchanged through the fourth heat exchanger 822 and the fifth heat exchanger 36 and then input into the steam drum 60. In this embodiment, the new water uses the heat energy of the reflux flow path 821 and the preheating flow path 32 to obtain preheated water, which is used as the supply of the steam drum 60. The preheated water after preheating is conducive to improving the efficiency of generating high-pressure saturated steam in the steam drum 60, and can also improve the energy utilization rate of the system and reduce the energy consumption of the system.

[0077] For example, the condensed water separated from the oil-water mixture by the oil-water separation tank 83 is returned to the middle and top of the quenching water tower 82 through the reflux flow path 821. The condensed water in the reflux flow path 821 exchanges heat with the new water in the fourth heat exchanger 822, that is, the new water is preheated to obtain transition water, and the transition water is heat exchanged with the quenching oil in the fifth heat exchanger 36 on the preheating flow path 32 to obtain preheated water. The reflux flow path 821 is also provided with a sixth heat exchanger 823, and the sixth heat exchanger 823 is located on the reflux flow path 821 connected to the top of the quenching water tower 82. The new water is also heat exchanged with the condensed water in the reflux flow path 821 in the sixth heat exchanger 823 to obtain process water, thereby improving the energy utilization rate of the system and reducing the energy consumption of the system. The process water can be used in other process links.

[0078] In one embodiment, the olefin preparation system further includes a stripping tower 84. The stripping tower 84 is connected to the quenching water tower 82 and the oil-water separator 83 respectively. The oil-water separator 83 separates condensed water from the oil-water mixture and transmits it to the stripping tower 84 for stripping. The stripping tower 84 separates light hydrocarbons from the condensed water separated by the oil-water separator 83 and transmits it to the quenching water tower 82. The stripping tower 84 is also connected to the preheating flow path 32 through the steam-water separator 81. The stripping tower 84 outputs process water to the steam-water separator 81 to exchange heat with the preheating flow path 32. The bottom of the stripping tower 84 outputs process water to the steam-water separator 81, and the steam-water separator 81 circulates and outputs the second cooling fluid to the third heat exchanger 35 to exchange heat with the quenching oil in the preheating flow path 32 to produce the above-mentioned 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 through some heat exchange links or by doing external work. The medium-pressure steam is input to the stripping tower 84 as steam supply for the stripping tower 84.

[0080] Please also read Figure 8 , Figure 8 It is a schematic diagram of another embodiment of the olefin preparation system of the present application.

[0081] In an alternative embodiment, the present embodiment is different 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 respectively heated in different mixers 51 and then enter different crackers 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 crackers 21, and the first mixer 51a is used to mix the feed fluid and the first superheated steam and input them into the crackers 21. The second mixer 51b is connected to the remaining crackers 21, and the second mixer 51b is used to mix the circulating light hydrocarbon fluid and the first superheated steam and input them into the crackers 21.

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

[0083] The fuel hydrogen 001 and the circulating hydrogen 002 are mixed with oxygen 004 and burned in the burner 15 and the combustion furnace 11 under oxygen. The second superheated steam 003 is introduced and the temperature of the heat carrier fluid at the outlet of the combustion furnace 11 is adjusted by controlling the amount of the second superheated steam 003. The heat carrier fluid is cooled after heat exchange with the first superheater 13 and the second superheater 14, and then evenly distributed through the distributor 12 to enter multiple crackers 21. The cracking feedstock 000 at room temperature is preheated by the first heat exchanger 33 on the preheating flow path 32 to obtain the feedstock fluid 010. The feedstock fluid 010 is mixed with the first superheated steam 011 and the circulating light hydrocarbon fluid 009 in the mixer 51, and the mixed fluid then enters the venturi tube 22 to mix with the upstream heat carrier fluid. The cracking raw material is rapidly heated in the venturi tube 22, and then enters the cracking section 23 to undergo cracking reaction after being rapidly heated to 950°C to 1200°C. The cracking raw material undergoes cracking reaction in the cracking section 23. As the reaction absorbs heat, the cracking fluid temperature drops to 850°C to 1150°C and then exits the cracking section 23. After exiting the cracking section 23, the cracking fluid enters the quenching boiler 24 to be rapidly quenched, specifically, it can be rapidly cooled to 300°C to 450°C within 0.5 seconds to terminate the occurrence of secondary reaction of the cracking fluid. The high-pressure steam-water mixture in the quenching boiler 24 enters the steam drum 60 for steam-water separation, and the high-pressure saturated steam 005 enters the first superheater 13 to generate the first superheated steam 011. A portion of the first superheated steam 011 enters the compressor 70, and the other portion enters the mixer 51 to heat the raw material fluid 010. The cracking fluid 007 exiting the quenching boiler 24 enters the fractionation tower 31 for further cooling. The circulating quench oil 016 enters from the upper part of the fractionation tower 31 and directly contacts with the cracking fluid 007 for heat exchange. The heavy components in the cracking fluid 007 are condensed and flow out from the bottom of the fractionation tower 31. Part of the heavy components enter the circulating quench oil 016, and part is output as product fuel oil 015. The preheating flow path 32 of the side line of the fractionation tower 31 extracts part of the diesel fraction 017 (i.e., the first fraction mentioned above) to preheat the cracking feedstock 000 and the new water 019, and then cools it. Part of it is recycled back to the fractionation tower 31, and the other part enters the circulating quench oil 016 for viscosity adjustment. The light component in the cracking fluid (i.e., the second fraction mentioned above) is cooled and flows out from the top of the fractionation tower 31, enters the quenching water tower 82 for further condensation, and the condensed oil-water mixture enters the oil-water separation tank 83 for separation. The cooled cracking fluid enters the suction tank 85 from the top of the quenching water tower 82, and then enters the compressor 70 for multi-stage compression, and then enters the alkali washing tank 86 to remove acidic gases, and finally enters the separation device 40 for product separation. The separated circulating light hydrocarbon raw material 021 (methane, ethane and propane) is partially returned to the mixer 51 as the circulating light hydrocarbon fluid 009, and the separated hydrogen is partially returned to the burner 15 as the circulating hydrogen 002. A part of the light component oil separated by the oil-water separation tank 83 is returned to the top of the fractionation tower 31, and a part is output as the product gasoline 020.Part of the condensed water separated from the oil-water separation tank 83 is returned to the middle and top of the quenching water tower 82 after heat exchange with the new water 019 through the circulating water pump. Another part of the condensed water enters the stripping tower 84 for stripping, and the light hydrocarbons in the condensed water are separated and returned to the top of the quenching water tower 82. The process water at the bottom of the stripping tower 84 enters the steam-water separator 81, and after heat exchange with the hot circulating quenching oil 016, a saturated steam-water mixture is generated. The steam-water 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 generate the second superheated steam 013. Part of the second superheated steam 013 enters the burner 15 for temperature adjustment, and part of the second superheated steam 013 is used in other process links. The new water 019 exchanges heat with the condensed water separated from the oil-water separation tank 83 to obtain transition water 018. The transition water 018 is heated by the quenching oil 016 to form preheated water 008 and input into the steam drum 60.

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

[0085] (1) The olefin preparation system of the embodiment of the present application uses a heat carrier fluid to directly heat the cracking feedstock to a high temperature, which can reach up to 1100°C to 1200°C, while the traditional steam tube cracking technology uses an indirect heating method, and the heating rate and maximum temperature are limited. Compared with the traditional steam tube cracking technology, the olefin preparation system of the embodiment of the present application has a higher cracking temperature and a higher olefin yield.

[0086] (2) The cracking pressure in the traditional steam tube cracking technology is 0.05MPaG~0.1MPaG. Due to the cracking efficiency and the strength of the pipe at high temperature, the cracking pressure cannot be further increased. The cracking device of the olefin preparation system of the embodiment of the present application adopts the method of direct mixing and heating of the raw material fluid and the heat carrier fluid for cracking. While increasing the cracking temperature, the cracking pressure can be increased. The cracking pressure can be increased to 0.5MPa~1.0MPa, so that the equipment processing capacity is greatly improved while ensuring a high olefin yield, especially the compressor investment in the compression process section can be saved, for example, the compressors of level 1 to level 3 can be omitted, which greatly reduces the energy consumption of the compressor.

[0087] (3) In the traditional steam tube cracking technology, the furnace combustion of the heating furnace uses the recycled hydrogen and methane separated from the cracking gas to burn with air, producing a large amount of CO2 and NO x The high-temperature flue gas is directly discharged into the atmosphere. The olefin preparation system of the embodiment of the present application uses green electricity generated by clean energy (photovoltaic, wind energy) to electrolyze water to produce hydrogen and pure oxygen, and uses the high-temperature water vapor generated by the combustion of process gas as a heat carrier fluid to directly mix with the cracking raw material for heating and cracking. After the cracking fluid enters the system, it is directly condensed and separated into circulating water, saving energy while being pollution-free.

[0088] (4) In the conventional steam tube cracking technology, the burner adopts the excess combustion of conventional fuel gas (H2, CO, CH4) and air, and the excess coefficient is generally 1.25. However, the burner of the olefin preparation system of the embodiment of the present application is an oxygen-deficient burner of fuel gas (H2) and 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, the partial pressure of raw hydrocarbon is limited, tar and coke are easily produced in the cracking tube, and the cracking furnace must be shut down for coking, and the coking cycle is generally 40-60 days. However, the heat carrier fluid of the olefin preparation system of the embodiment of the present application itself is used as dilution steam, and the mass ratio of the heat carrier fluid to the cracking raw material reaches 2.0-4.0, the partial pressure of raw hydrocarbon is lower, and the heat carrier fluid can carry part of the hydrogen, which can effectively inhibit the dehydrogenation reaction of hydrocarbons, the coking problem can be significantly improved, and the equipment operation cycle is greatly improved.

[0090] (6) In the olefin preparation system of 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 to 560°C (called the crossover temperature) in the furnace convection tube section and then enter the radiation tube for cracking. This process will cause the raw material to coke in the convection tube section in advance. However, the cracking raw material of the olefin preparation system of the embodiment of the present application is directly mixed with superheated steam and preheated to 300°C to 400°C, and then directly enters the mixer to mix with the high-temperature heat carrier fluid. The mixing preheating temperature is low, and the coking problem will not occur.

[0092] (8) The combustion furnace of the olefin preparation system of 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 as a water-cooled wall or a refractory insulation lining. The venturi tube and the cracking section are both designed as insulation linings. Considering the presence of coke in the cracking fluid and the problem of scouring the insulation material by the high-speed cracking fluid, the lining of the innermost side of the mixer in the embodiment of the present application that contacts the cracking fluid is preferably a high-aluminum corundum ceramic tube.

[0093] (9) The cracking pressure of the conventional steam tube cracking technology is low (0.05 MPaG to 0.1 MPaG). The cracked gas is generally quenched to 200°C to 250°C by a quench boiler and an oil quencher before entering an oil and gas fractionation tower for fractionation. The top temperature of the fractionation tower is generally controlled at 90°C to 105°C. The cracking pressure of the olefin preparation system of the embodiment of the present application is relatively high (0.5 MPa to 1.0 MPa), and the hydrocarbon partial pressure is relatively low. The cracked fluid is quenched to 300°C to 450°C within 0.5 seconds before entering the fractionation tower to terminate the occurrence of the secondary reaction of the cracked fluid. The top temperature of the fractionation tower is generally controlled at 105°C to 170°C.

[0094] The olefin preparation system provided by the present application is introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. An olefin production system, characterized in that: The olefin preparation system comprises: A combustion device for outputting a heat carrier fluid; A cracking device connected to the combustion device, the cracking device is used to receive the heat carrier fluid and the raw material fluid, so that the raw material fluid and the heat carrier fluid are mixed in the cracking device and undergo a cracking reaction to obtain a cracked fluid to prepare a product olefin; and The fractionation device comprises a fractionation tower, a preheating flow path and a first heat exchanger, wherein the fractionation tower is connected to the cracking device, and is used to receive the cracking fluid and fractionate the cracking fluid to obtain at least a first fraction, an inlet and an outlet of the preheating flow path are both connected to the fractionation tower and are used to pass the first fraction, and the first heat exchanger is arranged in the preheating flow path, and the first fraction preheats the cracking raw material through the first heat exchanger to obtain the raw material fluid.

2. The olefin production system according to claim 1, characterized in that: The olefin preparation system also includes: A separation device connected to the fractionation tower, the fractionation tower is also used to transmit the fractionation product to the separation device, the separation device is used to separate the fractionation product to obtain at least product olefins and circulating light hydrocarbon feedstock; the preheating flow path is also provided with a second heat exchanger, the second heat exchanger is used to preheat the circulating light hydrocarbon feedstock to obtain a circulating light hydrocarbon fluid; A mixing device is connected to the cracking device, and is used to mix the raw material fluid, the circulating light hydrocarbon fluid and the first superheated steam to obtain a mixed fluid, and input the mixed fluid into the cracking device.

3. The olefin preparation system according to claim 2, characterized in that: The combustion device comprises: a combustion furnace for generating the heat carrier fluid; and a distributor, the combustion furnace is connected to the cracking device through the distributor, and the heat carrier fluid is input into the cracking device through the distributor; The olefin preparation system also includes: a steam drum connected to the cracking device, the steam drum being used to circulate and output a first cooling fluid to the cracking device to cool the cracking fluid; and A first superheater is arranged on the distributor and connected to the steam drum. The steam drum separates steam from the first cooling fluid flowing through the cracking device and transmits the steam to the first superheater. The steam transmitted from the steam drum to the first superheater exchanges heat with the heat carrier fluid to form the first superheated steam.

4. The olefin production system according to claim 3, characterized in that: The olefin preparation system also includes: A compressor is connected to the distillation tower, the separation device and the first superheater respectively. The distillation product of the distillation tower is compressed by the compressor and then transmitted to the separation device. The first superheater is also used to transmit the first superheated steam to the compressor.

5. The olefin preparation system according to claim 2, characterized in that: The mixing device comprises: A mixer, used for mixing the raw material fluid, the circulating light hydrocarbon fluid and the first superheated steam to obtain the mixed fluid; A first distribution pipe connected to the mixer; and a nozzle connected to the first distribution pipe and the cracking device respectively, and the mixed fluid is sequentially input into the cracking device through the first distribution pipe and the nozzle; The cracking fluid flows in the cracking device along a first direction, 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 cracking device comprises a plurality of crackers, wherein the feed fluid and the heat carrier fluid are mixed and cracking reactions occur in the crackers; The mixing device comprises: A mixer, used for mixing the raw material fluid, the circulating light hydrocarbon fluid and the first superheated steam to obtain the mixed fluid; The first distribution pipe is connected to the mixer, and the first distribution pipe is also connected to each of the crackers. The mixed fluid is transmitted to each of the crackers through the first distribution pipe.

7. The olefin production system according to claim 1, characterized in that: The cracking device comprises a plurality of crackers, wherein the feed fluid and the heat carrier fluid are mixed and cracking reactions occur in the crackers; The olefin preparation system also includes: A separation device connected to the fractionation tower, the fractionation tower is also used to transmit the fractionation product to the separation device, the separation device is used to separate the fractionation product to obtain at least product olefins and circulating light hydrocarbon feedstock; the preheating flow path is also provided with a second heat exchanger, the second heat exchanger is used to preheat the circulating light hydrocarbon feedstock to obtain a circulating light hydrocarbon fluid; A first mixer connected to a part of the cracker, wherein the first mixer is used to mix the raw material fluid and the first superheated steam and input the mixture into the cracker; and The second mixer is connected to the remaining crackers, and is used to mix the circulating light hydrocarbon fluid and the first superheated steam and input them into the crackers.

8. The olefin production system according to claim 1, characterized in that: The combustion device comprises: a combustion furnace connected to the cracking device; and A burner is arranged at the bottom of the combustion furnace, and the burner is used to receive fuel hydrogen, oxygen and second superheated steam. The fuel hydrogen, oxygen and second superheated steam are burned in the burner and the combustion furnace to form the heat carrier fluid.

9. The olefin production system according to claim 8, characterized in that: The olefin preparation system also includes: A separation device is connected to the fractionation tower, the fractionation tower is also used to transmit the fractionation product to the separation device, the separation device is used to perform product separation on the fractionation product to obtain at least 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 burned to form the heat carrier fluid.

10. The olefin production system according to claim 8, characterized in that: The cracking device includes a plurality of crackers arranged along a second direction; The combustion device also includes: A distributor, wherein a distribution chamber is provided inside, and the combustion furnace is connected with each of the crackers 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 production system according to claim 8, characterized in that: The olefin preparation system also includes: A steam-water separator, the preheating flow path is further provided with a third heat exchanger, the steam-water separator is connected to the third heat exchanger, and the steam-water separator is used to circulate and output a second cooling fluid to the third heat exchanger to exchange heat with the quenching oil in the preheating flow path; and The second superheater is arranged in the combustion device. The steam-water separator separates steam from the second cooling fluid flowing through the third heat exchanger and transmits it to the second superheater to exchange heat with the heat carrier fluid to form the second superheated steam.

12. The olefin production system according to claim 1, characterized in that: The olefin preparation system also includes: A quenching water tower connected to the fractionation tower, the fractionation tower is used to obtain a second fraction through fractionation and the fraction is transferred to the quenching water tower for cooling; The oil-water separation tank is connected to the distillation tower and the quenching water tower respectively. The quenching water tower cools the second fraction to obtain an oil-water mixture which is transferred to the oil-water separation tank. The oil-water separation tank separates light component oil from the oil-water mixture and transfers it to the distillation tower.

13. The olefin production system according to claim 12, characterized in that: The oil-water separation tank is also connected to the quenching water tower through a reflux flow path, and the condensed water separated from the oil-water mixture by the oil-water separation tank is returned to the quenching water tower through the reflux flow path, and the reflux flow path is provided with a fourth heat exchanger; the preheating flow path is provided with a fifth heat exchanger; The olefin preparation system also includes: A steam drum connected to the cracking device, the steam drum being used to circulate and output a first cooling fluid to the cracking device to cool the cracking fluid; The new water is input into the steam drum after heat exchange through the fourth heat exchanger and the fifth heat exchanger in sequence.

14. The olefin production system according to claim 12, characterized in that: The olefin preparation system also includes: a stripping tower, connected to the quenching water tower and the oil-water separator, respectively, the oil-water separator separates condensed water from the oil-water mixture and transmits it to the stripping tower for stripping, and the stripping tower separates light hydrocarbons from the condensed water separated by the oil-water separator and transmits it to the quenching water tower; and The stripping tower is also connected to the preheating flow path through the steam-water separator, and the stripping tower outputs process water to the steam-water separator to exchange heat with the preheating flow path.

15. The olefin production system according to claim 14, characterized in that: The olefin preparation system also includes: A compressor connected to the fractionation tower; A separation device connected to the compressor, wherein the fractionation product of the fractionation tower is compressed by the compressor and then transmitted to the separation device, wherein the separation device is used to perform product separation on the fractionation product to obtain at least product olefins; Wherein, the compressor is also used to output steam to the stripping tower.

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