Method and system for inhibiting coking of ethylene cracking furnace

Abstract

The invention relates to the technical field of petrochemical industry ethylene cracking, and discloses a method and a system for inhibiting coking of an ethylene cracking furnace. The method comprises the following steps: naphtha and diluted steam I are introduced into a mesoporous emulsifier from a first feeding hole in the bottom of the mesoporous emulsifier containing a nano-emulsification part and a second feeding hole in the side wall of the mesoporous emulsifier for emulsification treatment, and an oil-water emulsified mixture is obtained; the oil-water emulsified mixture is introduced into a first preheating section of a convection chamber of an ethylene cracking furnace for first preheating treatment, and a material I is obtained; introducing diluted steam II and the material I into a mesoporous disperser, and mixing to obtain a material II; and sequentially introducing the material II into a second preheating section of the convection chamber of the ethylene cracking furnace and a radiation chamber of the ethylene cracking furnace, and respectively carrying out heating treatment and cracking treatment. The method provided by the invention can prolong the operation cycle of the furnace tube and reduce the coking rate of the furnace tube of the ethylene cracking furnace in the normal operation cycle of an ethylene device.

Description

Technical Field

[0001] This invention relates to the field of petrochemical ethylene cracking technology, specifically to a method and system for suppressing coking in ethylene cracking furnaces. Background Technology

[0002] Ethylene cracking furnace tubes are highly susceptible to coking due to high temperatures. Their operating cycle is typically around 60 days, with coking taking 3-4 days. Frequent switching between ethylene cracking furnaces not only affects the stable operation and safe production of the ethylene plant but also consumes a significant amount of energy for coking. Coking in furnace tubes can be broadly categorized into three types: catalytic coking, free radical coking, and polycondensation coking. Based on existing coking principles, catalytic coking is the primary factor influencing the rapid coking rate in ethylene cracking furnaces. To reduce the coking rate of furnace tubes, it is essential to first inhibit catalytic coking.

[0003] There are many techniques for inhibiting catalytic coking. The main method involves preparing an oxide film with no catalytic dehydrogenation activity on the inner surface of the furnace tube. This film covers nickel and iron atoms, which have high dehydrogenation activity, preventing them from contacting hydrocarbon molecules and disrupting the initial conditions for catalytic coking. This inhibits catalytic coking in the furnace tube and significantly reduces the coking rate. However, forming an oxide film with no dehydrogenation activity on the inner surface of the furnace tube is costly and difficult to implement.

[0004] In addition, methods to reduce the coking rate of ethylene cracking furnace tubes also include improving the properties of feedstock oil, optimizing process parameters, using coking inhibitors, using new furnace tube materials, using new coking-inhibiting coatings on the inner surface of furnace tubes, strengthening furnace tube heat transfer, and in-situ coatings on the inner surface of furnace tubes. However, these methods have some drawbacks. For example: (1) Setting up heat transfer-enhancing furnace tubes only in the radiant section of the ethylene cracking furnace achieves the purpose of enhancing heat transfer through physical action, which prolongs the operation cycle of the cracking furnace, but the cost is high and the construction period is long. (2) Injecting liquid coking inhibitors into the cracking furnace inhibits coke formation or changes the coke structure through chemical reactions. It can make the coke soft and leave the cracking furnace with the reaction stream, but the operating cost is high and the operation is complicated.

[0005] Therefore, there is an urgent need to provide a new method that can effectively suppress coking in ethylene cracking furnaces. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of short furnace tube operating cycles caused by easy coking in ethylene cracking furnaces in the existing technology.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for suppressing coking in an ethylene cracking furnace, the method comprising: (1) Naphtha and dilution vapor I are introduced into the mesoporous emulsifier containing nano-emulsification components from the first feed port at the bottom and the second feed port on the side wall for emulsification treatment to obtain an oil-water emulsion mixture; The mass ratio of naphtha to dilution vapor I is 100:2~20; The emulsification conditions include: a jet diameter of dilution vapor I of 20–500 nm, a median jet diameter of dilution vapor I of 50–100 nm, a jet velocity of dilution vapor I of 10–343 m / s, a naphtha flow rate of 0.3–10 m / s, and a naphtha acceleration of 4900–49000 m / s². 2 ; (2) The oil-water emulsion mixture is introduced from the top of the mesoporous emulsifier into the first preheating section of the convection chamber of the ethylene cracking furnace for first preheating treatment to obtain material I; (3) The dilution steam II and the material I are introduced into a mesoporous disperser for dispersion to obtain material II; the temperature of the dilution steam II is ≥500℃; (4) The material II is sequentially introduced into the second preheating section of the convection chamber of the ethylene cracking furnace and the radiation chamber of the ethylene cracking furnace for heating and cracking treatment respectively; The mass ratio of dilution steam I to dilution steam II is 1:(1~599).

[0008] A second aspect of the present invention provides a system for suppressing coking in an ethylene cracking furnace, the system being used to implement the method described in the first aspect, the system comprising a mesoporous emulsifier containing nanoemulsifying components, a cracking furnace, and a mesoporous disperser; The cracking furnace includes an ethylene cracking furnace convection chamber and an ethylene cracking furnace radiation chamber; the ethylene cracking furnace convection chamber is provided with a first preheating section and a second preheating section. The outlet of the mesoporous emulsifier is connected to the inlet of the first preheating section of the convection chamber of the ethylene cracking furnace; the outlet of the first preheating section of the convection chamber of the ethylene cracking furnace is connected to the first inlet of the mesoporous disperser; the outlet of the mesoporous disperser is connected to the inlet of the second preheating section of the convection chamber of the ethylene cracking furnace; and the outlet of the second preheating section of the convection chamber of the ethylene cracking furnace is connected to the inlet of the radiation chamber of the ethylene cracking furnace.

[0009] The method for suppressing coking in ethylene cracking furnaces provided by this invention significantly improves the operating conditions of the ethylene cracking furnace within the radiant furnace tubes, extends the operating cycle of the furnace tubes, and reduces the coking rate of the ethylene cracking furnace during the normal operating cycle of the ethylene plant. Furthermore, the method provided by this invention is simple to implement, has low equipment investment costs, and does not increase operating costs. Attached Figure Description

[0010] Figure 1 This is a process flow diagram of an embodiment of the present invention for suppressing coking in an ethylene cracking furnace. Detailed Implementation

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0012] As previously stated, the first aspect of the present invention provides a method for suppressing coking in an ethylene cracking furnace, the method comprising: (1) Naphtha and dilution vapor I are introduced into the mesoporous emulsifier containing nano-emulsification components from the first feed port at the bottom and the second feed port on the side wall for emulsification treatment to obtain an oil-water emulsion mixture; The mass ratio of naphtha to dilution vapor I is 100:2~20; The emulsification conditions include: a jet diameter of dilution vapor I of 20–500 nm, a median jet diameter of dilution vapor I of 50–100 nm, a jet velocity of dilution vapor I of 10–343 m / s, a naphtha flow rate of 0.3–10 m / s, and a naphtha acceleration of 4900–49000 m / s². 2 ; (2) The oil-water emulsion mixture is introduced from the top of the mesoporous emulsifier into the first preheating section of the convection chamber of the ethylene cracking furnace for first preheating treatment to obtain material I; (3) The dilution steam II and the material I are introduced into a mesoporous disperser for dispersion to obtain material II; the temperature of the dilution steam II is ≥500℃; (4) The material II is sequentially introduced into the second preheating section of the convection chamber of the ethylene cracking furnace and the radiation chamber of the ethylene cracking furnace for heating and cracking treatment respectively; The mass ratio of dilution steam I to dilution steam II is 1:(1~599).

[0013] The method provided by this invention controls the emulsification conditions under the action of the nanoporous internals inside the mesoporous emulsifier. The dilution steam is dispersed into nanobubbles and uniformly mixed with naphtha to form a vapor-liquid emulsion fluid with a specific composition. The microbubbles formed by the steam condense into liquid water after heat exchange with the naphtha. The nano-diameter liquid water droplets are uniformly dispersed in the naphtha. During the oil-water emulsification and condensation process, water molecules form "CH...OH" hydrogen bonds with alkyl hydrogens and generate electron transfer from water molecules to oil molecules. The oil-water emulsion mixture is preheated and introduced into the mesoporous disperser. It is mixed according to the mass ratio of dilution steam I to high-temperature dilution steam II of 1: (1~599) to form a uniform flow field of positively charged water molecules. After entering the radiant tube, due to the free electron enrichment effect on the inner surface of the furnace tube under high temperature, a negative potential is formed. The positively charged water vapor molecules will be adsorbed by the inner surface of the furnace tube, forming a water molecule boundary layer on the inner surface of the furnace tube. This isolates the oil molecules from the contact with the dehydrogenating active metals nickel and iron, thereby reducing the coking rate of the radiant furnace tube.

[0014] In this invention, in step (1), the naphtha is introduced from the first feed port at the bottom of the mesoporous emulsifier, and the dilution steam I is introduced from the second feed port on the side wall of the mesoporous emulsifier; the oil-water emulsion mixture is introduced from the top of the mesoporous emulsifier into the first preheating section of the convection chamber of the ethylene cracking furnace.

[0015] More preferably, the second feed inlet is located vertically above the first feed inlet. The inventors have found that in this preferred configuration, sufficient mixing of steam and naphtha can be ensured, resulting in uniform emulsification and thus improving the suppression of coking in the ethylene cracking furnace.

[0016] Preferably, in step (1), the mass ratio of naphtha to dilution steam I is 100:5~16. The inventors have found that under these preferred conditions, the coking rate of the radiant furnace tubes can be further reduced.

[0017] Preferably, in step (1), the mass ratio of dilution steam I to dilution steam II is 1:(2~10). The inventors have found that under this preferred condition, the coking rate of the radiant furnace tube can be further reduced.

[0018] According to a preferred embodiment, in step (1), the average particle size of the oil-water emulsion mixture is 10~200nm.

[0019] Preferably, in step (1), the flow rate of the naphtha is 2160-3280 kg / h; the flow rate of the dilution steam I is 200-350 kg / h.

[0020] In a preferred embodiment, in step (2), the conditions for the first preheating treatment include a temperature of 180-280°C.

[0021] According to a preferred embodiment, in step (3), the dilution steam II is introduced from the side wall of the mesoporous disperser, and the material I is introduced from the bottom of the mesoporous disperser. The inventors have found that under these preferred conditions, the dilution steam II and naphtha can be better dispersed and mixed uniformly to achieve a molecular-level mixing effect, and further generate more electron transfer between water molecules and naphtha molecules, better forming a uniform flow field of positively charged water molecules, which is more conducive to reducing the coking rate of the radiant furnace tubes in the subsequent process.

[0022] In a preferred embodiment, material II flows out from the top of the mesoporous disperser and is introduced into the second preheating section of the convection chamber of the ethylene cracking furnace.

[0023] According to another specific embodiment, in step (3), the dispersion conditions include: the jet diameter of dilution steam II is 200~500 nm, the median jet diameter of dilution steam II is 340-360 nm, the jet velocity of dilution steam II is 20~50 m / s, the flow velocity of material I is 1~3 m / s, and the acceleration of material I is 5880~11760 m / s. 2 .

[0024] Preferably, in step (3), the flow rate of the dilution steam II is 1300-1600 kg / h.

[0025] Preferably, in step (3), the temperature of the dilution steam II is ≥600°C. The inventors have found that under these preferred conditions, the electron transfer effect between water molecules and naphtha molecules can be further improved, which is beneficial for reducing the coking rate of the radiant furnace tubes in the subsequent process.

[0026] According to a preferred embodiment, the method further includes: in step (3), before introducing the dilution steam II into the mesoporous disperser, the dilution steam II is first introduced into the third preheating section of the convection chamber of the ethylene cracking furnace for a second preheating treatment, so that the temperature of the dilution steam II is ≥500℃; preferably ≥600℃. The inventors have found that under these preferred conditions, the electron transfer effect between water molecules and naphtha molecules can be further improved, which is more conducive to reducing the coking rate of the radiant furnace tubes.

[0027] The present invention does not have any special requirements for the conditions of the second preheating treatment, as long as the temperature of the dilution steam II after the second preheating treatment can reach the required temperature (≥500°C). Those skilled in the art can carry out the work according to the technical means known in the art.

[0028] Preferably, in step (4), the conditions for the heat treatment include a temperature of 380-410°C.

[0029] In a preferred embodiment, in step (4), the conditions for the pyrolysis treatment include: the outlet temperature of the radiant chamber furnace tube is 830-850°C, and the outlet pressure of the radiant chamber furnace tube is 0.2-0.3 MPa.

[0030] In a preferred embodiment, both dilution steam I and dilution steam II are water vapor.

[0031] Preferably, the organic matter content in the dilution steam I and the dilution steam II is ≤30ppm, and the solid impurity content is ≤5ppm.

[0032] In this invention, the solid impurities refer to inorganic particles such as coke powder and iron oxide.

[0033] As previously stated, a second aspect of the present invention provides a system for suppressing coking in an ethylene cracking furnace, the system being used to implement the method described in the first aspect, the system comprising a mesoporous emulsifier containing nanoemulsifying components, a cracking furnace, and a mesoporous disperser; The cracking furnace includes an ethylene cracking furnace convection chamber and an ethylene cracking furnace radiation chamber; the ethylene cracking furnace convection chamber is provided with a first preheating section and a second preheating section. The outlet of the mesoporous emulsifier is connected to the inlet of the first preheating section of the convection chamber of the ethylene cracking furnace; the outlet of the first preheating section of the convection chamber of the ethylene cracking furnace is connected to the first inlet of the mesoporous disperser; the outlet of the mesoporous disperser is connected to the inlet of the second preheating section of the convection chamber of the ethylene cracking furnace; and the outlet of the second preheating section of the convection chamber of the ethylene cracking furnace is connected to the inlet of the radiation chamber of the ethylene cracking furnace.

[0034] Preferably, the bottom and sidewall of the mesoporous emulsifier are respectively provided with a first feed port and a second feed port; the first feed port is used to introduce naphtha; the second feed port is used to introduce dilution vapor I.

[0035] Preferably, the sidewall of the mesoporous disperser is further provided with a second inlet; the second inlet is used to introduce dilution vapor II.

[0036] Preferably, the first inlet of the mesoporous disperser is located at the bottom of the mesoporous disperser.

[0037] Preferably, the convection chamber of the ethylene cracking furnace further includes a third preheating section; the third preheating section is located between the second preheating section and the radiation chamber of the ethylene cracking furnace; the third preheating section is used to perform a second preheating treatment on the dilution steam II.

[0038] This invention is in Figure 1 The document provides a process flow diagram for suppressing coking in an ethylene cracking furnace according to a specific embodiment. The method includes: (1) Naphtha is introduced from the first feed port at the bottom of the mesoporous emulsifier, and dilution steam I is introduced from the second feed port on the side wall of the mesoporous emulsifier. The emulsification process is carried out in the mesoporous emulsifier containing nano-emulsification components to obtain an oil-water emulsion mixture. The mass ratio of naphtha to dilution vapor I is 100:2~20; The emulsification conditions include: a jet diameter of dilution vapor I of 20–500 nm, a median jet diameter of dilution vapor I of 50–100 nm, a jet velocity of dilution vapor I of 10–343 m / s, a naphtha flow rate of 0.3–10 m / s, and a naphtha acceleration of 4900–49000 m / s². 2 ; (2) The oil-water emulsion mixture is introduced from the top of the mesoporous emulsifier into the first preheating section of the convection chamber of the ethylene cracking furnace for first preheating treatment to obtain material I; (3) The dilution steam II is introduced into the third preheating section of the convection chamber of the ethylene cracking furnace for the second preheating treatment. The dilution steam II after the second preheating treatment is introduced from the side wall of the mesoporous disperser, and the material I is introduced from the bottom of the mesoporous disperser and dispersed in the mesoporous dispersion gas to obtain material II; the temperature of the dilution steam II is ≥500℃. (4) The material II is introduced from the top of the mesoporous disperser into the second preheating section of the convection chamber of the ethylene cracking furnace and the radiation chamber of the ethylene cracking furnace for heating and cracking treatment respectively; The mass ratio of dilution steam I to dilution steam II is 1:(1~599).

[0039] The present invention will be described in detail below through examples. Unless specific experimental steps or conditions are specified in the following examples, the procedures or conditions of known experimental steps described in the literature in this field can be followed. Unless the manufacturer is specified, all raw materials or instruments used are commercially available.

[0040] Mesoporous emulsifier: Specification DN200mm, manufactured by Hunan Changke Chengxiang Petrochemical Technology Co., Ltd., model CKCX08-200.

[0041] Mesoporous disperser: Specification DN400mm, manufactured by Hunan Changke Chengxiang Petrochemical Technology Co., Ltd., model CKCX08-400.

[0042] Dilution vapor I: Water vapor molecules, organic matter content of 8.9 ppm, solid impurity content of 0.8 ppm.

[0043] Dilution Steam II: Water vapor molecules, organic matter content of 8.9 ppm, solid impurity content of 0.8 ppm.

[0044] Example 1 A method for suppressing coking in an ethylene cracking furnace, the method comprising: (1) Naphtha is introduced from the first feed port at the bottom of the mesoporous emulsifier containing nano-emulsifying components, and dilution vapor I is introduced from the second feed port on the side wall of the mesoporous emulsifier containing nano-emulsifying components. The emulsification process is carried out in the mesoporous emulsifier containing nano-emulsifying components to obtain an oil-water emulsion mixture. The flow rate of the naphtha is 3120 kg / h, the flow rate of the dilution steam I is 320 kg / h, and the mass ratio of the naphtha to the dilution steam I is 100:10.26. The emulsification conditions were as follows: the jet diameter of dilution vapor I was 200 nm, the median jet diameter of dilution vapor I was 75 nm, the jet velocity of dilution vapor I was 300 m / s, the flow rate of naphtha was 5 m / s, and the acceleration of naphtha was 20000 m / s². 2 ; (2) The oil-water emulsion mixture is introduced from the top of the mesoporous emulsifier into the first preheating section of the convection chamber of the ethylene cracking furnace for first preheating treatment to obtain material I; The conditions for the first preheating treatment are: temperature 230℃; (3) Diluting steam II is introduced into the third preheating section of the convection chamber of the ethylene cracking furnace for a second preheating treatment so that the temperature of the diluting steam II reaches 610°C; then the diluting steam II after the second preheating treatment is introduced from the side wall of the mesoporous disperser, and the material I is introduced from the bottom of the mesoporous disperser to disperse with the diluting steam II to obtain material II; The flow rate of dilution steam II is 1450 kg / h, and the mass ratio of dilution steam I to dilution steam II is 1:4.53; Dispersion conditions: The jet diameter of dilution steam II is 400 nm, the median diameter of the jet of dilution steam II is 350 nm, the jet velocity of dilution steam II is 20 m / s, the flow velocity of material I is 2 m / s, and the acceleration of material I is 10000 m / s². 2 ; (4) The material II is introduced from the top of the mesoporous disperser into the second preheating section of the convection chamber of the ethylene cracking furnace and the radiation chamber of the ethylene cracking furnace for heating and cracking treatment respectively; Heat treatment conditions: temperature 390℃; The conditions for pyrolysis treatment were: the outlet temperature of the radiant chamber furnace tubes was 840℃ and the outlet pressure of the radiant chamber furnace tubes was 0.25MPa.

[0045] Example 2 A method for suppressing coking in an ethylene cracking furnace, the method comprising: (1) Naphtha is introduced from the first feed port at the bottom of the mesoporous emulsifier containing nano-emulsifying components, and dilution vapor I is introduced from the second feed port on the side wall of the mesoporous emulsifier containing nano-emulsifying components. The emulsification process is carried out in the mesoporous emulsifier containing nano-emulsifying components to obtain an oil-water emulsion mixture. The flow rate of the naphtha is 2530 kg / h, the flow rate of the dilution steam I is 205 kg / h, and the mass ratio of the naphtha to the dilution steam I is 100:8.1. The emulsification conditions were as follows: the jet diameter of dilution vapor I was 300 nm, the median jet diameter of dilution vapor I was 85 nm, the jet velocity of dilution vapor I was 250 m / s, the flow rate of naphtha was 3 m / s, and the acceleration of naphtha was 30,000 m / s². 2 ; (2) The oil-water emulsion mixture is introduced from the top of the mesoporous emulsifier into the first preheating section of the convection chamber of the ethylene cracking furnace for first preheating treatment to obtain material I; The conditions for the first preheating treatment are: temperature 241℃; (3) Diluting steam II is introduced into the third preheating section of the convection chamber of the ethylene cracking furnace for a second preheating treatment; so that the temperature of the diluting steam II is 607°C; then the diluting steam II after the second preheating treatment is introduced from the side wall of the mesoporous disperser, and the material I is introduced from the bottom of the mesoporous disperser to mix with the diluting steam II to obtain material II; The flow rate of dilution steam II is 1300 kg / h, and the mass ratio of dilution steam I to dilution steam II is 1:6.34; Dispersion conditions: The jet diameter of dilution steam II is 400 nm, the median diameter of the jet of dilution steam II is 350 nm, the jet velocity of dilution steam II is 30 m / s, the flow velocity of material I is 3 m / s, and the acceleration of material I is 11000 m / s². 2 ; (4) The material II is introduced from the top of the mesoporous disperser into the second preheating section of the convection chamber of the ethylene cracking furnace and the radiation chamber of the ethylene cracking furnace for heating and cracking treatment respectively; Heat treatment conditions: temperature 400℃; The conditions for pyrolysis treatment were: the outlet temperature of the radiant chamber furnace tubes was 845℃, and the outlet pressure of the radiant chamber furnace tubes was 0.2MPa.

[0046] Example 3 A method for suppressing coking in an ethylene cracking furnace, the method comprising: (1) Naphtha is introduced from the first feed port at the bottom of the mesoporous emulsifier containing nano-emulsifying components, and dilution vapor I is introduced from the second feed port on the side wall of the mesoporous emulsifier containing nano-emulsifying components. The emulsification process is carried out in the mesoporous emulsifier containing nano-emulsifying components to obtain an oil-water emulsion mixture. The flow rate of the naphtha is 2270 kg / h, the flow rate of the dilution steam I is 346 kg / h, and the mass ratio of the naphtha to the dilution steam I is 100:15.24. The emulsification conditions were as follows: the jet diameter of dilution vapor I was 100 nm, the median jet diameter of dilution vapor I was 55 nm, the jet velocity of dilution vapor I was 100 m / s, the flow rate of naphtha was 8 m / s, and the acceleration of naphtha was 45000 m / s². 2 ; (2) The oil-water emulsion mixture is introduced from the top of the mesoporous emulsifier into the first preheating section of the convection chamber of the ethylene cracking furnace for first preheating treatment to obtain material I; The conditions for the first preheating treatment are: temperature 258℃; (3) Diluting steam II is introduced into the third preheating section of the convection chamber of the ethylene cracking furnace for a second preheating treatment, so that the temperature of the diluting steam II is 605°C; then the diluting steam II after the second preheating treatment is introduced from the side wall of the mesoporous disperser, and the material I is introduced from the bottom of the mesoporous disperser to mix with the diluting steam II to obtain material II; The flow rate of dilution steam II is 1365 kg / h, and the mass ratio of dilution steam I to dilution steam II is 1:3.95; Dispersion conditions: The jet diameter of dilution steam II is 400 nm, the median diameter of the jet of dilution steam II is 350 nm, the jet velocity of dilution steam II is 40 m / s, the flow velocity of material I is 1 m / s, and the acceleration of material I is 8000 m / s². 2 ; (4) The material II is introduced from the top of the mesoporous disperser into the second preheating section of the convection chamber of the ethylene cracking furnace and the radiation chamber of the ethylene cracking furnace for heating and cracking treatment respectively; Heat treatment conditions: temperature 400℃; The conditions for pyrolysis treatment were: the outlet temperature of the radiant chamber furnace tubes was 840℃ and the outlet pressure of the radiant chamber furnace tubes was 0.25MPa.

[0047] Comparative Example 1 The method is similar to that in Example 1, except that in step (1), the flow rate of the naphtha is kept constant, and the flow rate of the dilution steam I is adjusted to 50 kg / h, so that the mass ratio of the naphtha to the dilution steam I is 100:1.6. The remaining steps are the same as in Example 1.

[0048] Comparative Example 2 The method is similar to that in Example 1, except that the dispersion is not performed in step (3); specifically: The diluted steam II after the second preheating treatment and the material I are directly introduced into the second preheating section of the convection chamber of the ethylene cracking furnace and the radiation chamber of the ethylene cracking furnace for heating and cracking treatment, respectively. The remaining steps are the same as in Example 1.

[0049] Test case The operating cycle in the above example was tested by using the method of reaching the limit value of the surface temperature of the radiant furnace tube. The test results are shown in Table 1.

[0050] Table 1

[0051] As can be seen from the results in Table 1, the method for suppressing coking in ethylene cracking furnaces provided by this invention has a better effect on suppressing coking in cracking furnace tubes than the comparative example.

[0052] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for suppressing coking in an ethylene cracking furnace, characterized in that, The method includes: (1) Naphtha and dilution vapor I are introduced into the mesoporous emulsifier containing nano-emulsification components from the first feed port at the bottom and the second feed port on the side wall for emulsification treatment to obtain an oil-water emulsion mixture; The mass ratio of naphtha to dilution vapor I is 100:2~20; The emulsification conditions include: a jet diameter of dilution vapor I of 20–500 nm, a median jet diameter of dilution vapor I of 50–100 nm, a jet velocity of dilution vapor I of 10–343 m / s, a naphtha flow rate of 0.3–10 m / s, and a naphtha acceleration of 4900–49000 m / s². 2 ; (2) The oil-water emulsion mixture is introduced from the top of the mesoporous emulsifier into the first preheating section of the convection chamber of the ethylene cracking furnace for first preheating treatment to obtain material I; (3) The dilution steam II and the material I are introduced into a mesoporous disperser for dispersion to obtain material II; the temperature of the dilution steam II is ≥500℃; (4) The material II is sequentially introduced into the second preheating section of the convection chamber of the ethylene cracking furnace and the radiation chamber of the ethylene cracking furnace for heating and cracking treatment respectively; The mass ratio of dilution steam I to dilution steam II is 1:(1~599).

2. The method according to claim 1, characterized in that, The mass ratio of dilution steam I to dilution steam II is 1:(2~10). And / or, in step (1), the flow rate of the naphtha is 2160-3280 kg / h; the flow rate of the dilution steam I is 200-350 kg / h.

3. The method according to claim 1, characterized in that, The second feed inlet is located above the first feed inlet in the vertical direction.

4. The method according to any one of claims 1-3, characterized in that, In step (2), the conditions for the first preheating treatment include a temperature of 180~280℃.

5. The method according to any one of claims 1-3, characterized in that, In step (3), the dilution vapor II is introduced from the side wall of the mesoporous disperser, and the material I is introduced from the bottom of the mesoporous disperser; And / or, in step (3), the flow rate of the dilution steam II is 1300-1600 kg / h.

6. The method according to any one of claims 1-3, characterized in that, In step (3), the temperature of the dilution vapor II is ≥600°C.

7. The method according to any one of claims 1-3, characterized in that, In step (3), the dispersion conditions include: the jet diameter of dilution steam II is 200-500 nm, the median jet diameter of dilution steam II is 340-360 nm, the jet velocity of dilution steam II is 20-50 m / s, the flow velocity of material I is 1-3 m / s, and the acceleration of material I is 5880-11760 m / s. 2 .

8. The method according to any one of claims 1-3, characterized in that, The method further includes: in step (3), before introducing the dilution steam II into the mesoporous disperser, the dilution steam II is first introduced into the third preheating section of the convection chamber of the ethylene cracking furnace for a second preheating treatment, so that the temperature of the dilution steam II is ≥500℃.

9. The method according to any one of claims 1-3, characterized in that, The organic matter content of the dilution steam I and the dilution steam II is ≤30ppm, and the solid impurity content is ≤5ppm.

10. A system for suppressing coking in an ethylene cracking furnace, characterized in that, The system is used to implement the method according to any one of claims 1-9, the system comprising a mesoporous emulsifier containing nanoemulsifying components, a pyrolysis furnace, and a mesoporous disperser; The cracking furnace includes an ethylene cracking furnace convection chamber and an ethylene cracking furnace radiation chamber; the ethylene cracking furnace convection chamber is provided with a first preheating section and a second preheating section. The outlet of the mesoporous emulsifier is connected to the inlet of the first preheating section of the convection chamber of the ethylene cracking furnace; the outlet of the first preheating section of the convection chamber of the ethylene cracking furnace is connected to the first inlet of the mesoporous disperser; the outlet of the mesoporous disperser is connected to the inlet of the second preheating section of the convection chamber of the ethylene cracking furnace; and the outlet of the second preheating section of the convection chamber of the ethylene cracking furnace is connected to the inlet of the radiation chamber of the ethylene cracking furnace.

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