CN112745957A

CN112745957A - Method and system for preparing low-carbon olefin from crude oil

Info

Publication number: CN112745957A
Application number: CN201911048418.9A
Authority: CN
Inventors: 周丛; 王国清; 张利军; 彭晖; 石莹; 刘同举; 张兆斌; 蒋冰
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2019-10-31
Filing date: 2019-10-31
Publication date: 2021-05-04
Anticipated expiration: 2039-10-31
Also published as: CN112745957B

Abstract

The invention relates to a method and a system for preparing low-carbon olefin from crude oil, wherein the method comprises the following steps: sending crude oil into a first tube group of a convection section of a cracking furnace for preheating and then carrying out vaporization treatment to form a first vapor phase and a first liquid phase; feeding the first liquid phase to a first tube bank of a convection section and then distilling; catalytically cracking the distilled bottom fraction to obtain catalytically cracked gas and liquid fraction; carrying out hydroprocessing treatment on the liquid phase fraction to obtain recycle hydrogen, a hydrogenated light component and a hydrogenated heavy component; mixing the distilled overhead fraction and the middle fraction, mixing with the first vapor phase and the hydrogenated light component, feeding into a cracking furnace for cracking treatment to obtain cracking gas, and separating to obtain the low-carbon olefin. The invention adopts the matching of the cracking furnace, the vaporization treatment unit, the distillation unit, the catalytic cracking unit and the hydroprocessing unit, and can effectively solve the problems that the heavy cracking raw material can not be fully gasified in the convection section and is easy to coke in the radiation section and the quenching part.

Description

Method and system for preparing low-carbon olefin from crude oil

Technical Field

The invention relates to the field of low-carbon olefin preparation, in particular to a method and a system for preparing low-carbon olefin from crude oil.

Background

The low-carbon olefin is a general term for unsaturated hydrocarbons with four or less carbon atoms, and mainly includes organic chemical raw materials with high economic value, such as ethylene, propylene, isobutene, butadiene and the like. With the economic development of China, the demand of the organic chemical raw materials is increased year by year, and although the production scale of the low-carbon olefin is also increased year by year, the increased demand cannot be met.

For a long time, China always prepares low-carbon olefin products from naphtha. However, in recent years, along with the mass exploitation of middle east oilfield associated gas and U.S. shale gas, these cheap oil and gas resources are used in large quantities as ethylene raw materials, which causes a sharp drop in the price of ethylene-related products. In order to cope with the impact of market competition, the raw material source of the ethylene cracking device is expanded, the raw material cost is reduced, and the method becomes an effective means for cost reduction and efficiency improvement of the traditional ethylene enterprises. Therefore, special heavy hydrocarbons, especially unprocessed crude oil, are used as the raw materials of the cracking furnace to produce low-carbon olefin, which is beneficial to reducing the raw material cost and energy consumption of an olefin production device and is quickly adapted to the supply and demand change of the cracking raw materials in the market.

Olefins are typically produced by steam cracking various hydrocarbon feedstocks using a cracking furnace. Crude oil generally contains components such as saturates, aromatics, gums, and asphaltenes. The crude oil generally contains high molecular weight nonvolatile components with the boiling point of more than 590 ℃, and the nonvolatile components can not be completely gasified if being preheated in a convection section of a conventional cracking furnace, can easily form coking deposition, even block a furnace tube and influence the production operation of the cracking furnace.

CN101583697A discloses a process for cracking a feedstock comprising synthetic oil, the process comprising: 1. hydroprocessing includes the wide boiling range aliquot of: a normally liquid hydrocarbon fraction boiling in the range of 50 to 800 ° f that is substantially free of resid, and b thermally cracked hydrocarbon liquid boiling in the range of 600 to 1050 ° f to provide a synthetic crude oil boiling in the range of 73 to 1070 ° f that contains greater than 25 wt% aromatics, greater than 25 wt% naphthenes, less than 0.3 wt% S, less than 0.02 wt% asphaltenes and is substantially free of resid other than asphaltenes; 2. adding to the synthetic crude oil a normally liquid hydrocarbon component boiling in the range of 100 to 1050 degrees F; and 3, cracking the mixture produced by 2 in a cracking furnace to provide a cracked effluent, wherein the cracking furnace includes a radiant coil outlet, wherein the cracking is conducted under conditions sufficient to obtain a radiant coil outlet temperature greater than the optimum radiant coil outlet temperature for cracking the synthetic crude oil alone.

The method mixes the crude oil into the existing ethylene production raw material, dilutes the crude oil, improves the cracking performance of the crude oil, and improves the conversion rate of olefin. However, the method is limited by the source of the existing ethylene production raw material, and a large amount of crude oil cannot be effectively utilized to produce low-carbon olefins.

CN1957068A discloses steam cracking of a hydrocarbon feedstock containing salt and/or particulate matter, the process comprising: a feeding an undesalted feedstock comprising salt and optionally particulate matter to a convection section of a pyrolysis furnace; b heating the hydrocarbon feedstock; c feeding the hydrocarbon feedstock to a flash/separation vessel located upstream of the dry point; d separating the hydrocarbon feedstock into a vapor phase substantially depleted in non-volatile components and salts and a liquid phase enriched in non-volatile components and salts, said liquid phase containing 5% liquid phase at all points in the convection section upstream of the flash/separation vessel to maintain salts and any particulate matter in suspension; e removing from the flash/separation vessel 50-95% of the hydrocarbon feedstock of step a in the vapor phase and cracking the vapor phase to produce an effluent comprising olefins; and f removing at least 5% of the hydrocarbon feedstock from the flash/separation vessel in the liquid phase together with the salt and any particulate matter in suspension. US3617493 also discloses a process similar to the above process using steam cracking of crude oil.

CN1041967A discloses a method for decomposing a low-grade raw material, which comprises, when a low-grade raw material containing a heavy fraction is subjected to a thermal decomposition treatment in a decomposing furnace, extracting the low-grade raw material from a preheater of the decomposing furnace, separating and removing the heavy fraction from the low-grade raw material by a gas-liquid separation method, and then returning the low-grade raw material to the preheater to perform a thermal decomposition reaction.

The raw materials are cracked by adopting the method, the raw oil passing through the convection section of the cracking furnace is processed by adopting a flash tank, the gas-liquid separation is realized, and the gas phase enters the radiation section for cracking. However, at least 5% of the hydrocarbon raw material is still left in the liquid after the flash evaporation of the raw material, which affects the yield of the low-carbon olefin, and the separated liquid phase is directly used as fuel oil, thereby causing the waste of the raw material.

Disclosure of Invention

The invention aims to solve the problems of insufficient vaporization of crude oil, easy coking in the cracking process and low yield of low-carbon olefin in the prior art, and provides a method and a device for preparing low-carbon olefin from crude oil.

One of the purposes of the invention is to provide a method for preparing low-carbon olefin by crude oil, which comprises the following steps:

step 1, sending crude oil into a first tube group of a convection section of a cracking furnace for preheating, and then carrying out vaporization treatment to form a first vapor phase and a first liquid phase;

step 2, sending the first liquid phase into a first tube group of a convection section of a cracking furnace for preheating, and distilling the preheated first liquid phase to form a tower top fraction, a middle fraction and a tower bottom fraction;

step 3, carrying out catalytic cracking treatment on the tower bottom fraction obtained in the step 2 to obtain catalytic cracked gas and liquid phase fraction;

step 4, carrying out hydroprocessing treatment on the liquid phase fraction obtained in the step 3 to obtain recycle hydrogen, a hydrogenated light component and a hydrogenated heavy component;

and 5, mixing the tower top fraction and the middle fraction in the step 2 to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, and then sending the mixture into a cracking furnace for cracking treatment to obtain cracked gas, and separating the cracked gas and the catalytic cracked gas to obtain the low-carbon olefin.

Wherein the cracking furnace comprises any structure of cracking furnace disclosed in the prior art, and preferably comprises a single-hearth cracking furnace and a double-hearth cracking furnace.

In the invention, crude oil is vaporized and distilled under normal pressure, the obtained gas phase directly enters a cracking furnace, the obtained liquid phase is subjected to catalytic cracking, the obtained catalytic cracking gas and the cracking gas enter a separation system together, and the liquid phase enters a hydrogenation unit to optimize the cracking performance of the raw material and then enters the cracking furnace as the raw material. The method can effectively improve the cracking efficiency of the crude oil, improve the yield of the low-carbon olefin in the product, prolong the operation period and reduce the occurrence of coking.

In a preferred embodiment, the crude oil comprises light naphtha, diesel, hydrogenated tail oil, light crude oil, crude oil having an end point above 600 ℃ and below 700 ℃, and dehydrated and desalted crude oil.

In a further preferred embodiment, the crude oil comprises diesel oil, hydrogenated tail oil, light crude oil, dehydrated crude oil subjected to dehydration and desalination treatment, and crude oil having a final boiling point higher than 600 ℃ and lower than 700 ℃.

In a preferred embodiment, in step 1, the outflow temperature of the preheated crude oil is 120-.

In a preferred embodiment, in step 1, the content of liquid phase in the first vapor phase is less than 10g/m³Preferably less than 200mg/m³。

In a preferred embodiment, in step 1, the vaporization treatment is at least one of stripping, flashing and cyclonic separation, preferably cyclonic separation.

In a preferred embodiment, in step 1, a cyclone is used for the vaporization treatment.

In a further preferred embodiment, the cyclone separator is selected from the group consisting of a volute type cyclone separator, an axial flow guide vane type cyclone separator, a straight tube type cyclone separator, a cone and cylinder combination type cyclone separator, and a straight flow type cyclone separator.

In a further preferred embodiment the cyclone separator is provided with internals comprising a skimmer drum at the top of the cyclone separator and/or a separating plate, vortex breaker, at the lower part of the cyclone separator.

Wherein, the cyclone separator has the advantages of small volume and high separation efficiency.

In the present invention, the "cyclone" refers to a cyclone in a broad sense, including both a "cyclone" in a narrow sense and a separation device similar to its principle in the art, such as a cyclone. Unless otherwise specified, the cyclone separators mentioned in the present invention are all cyclone separators in a broad sense. According to the invention, most of the working medium of the cyclone separator for vaporization treatment is gas, and the cyclone separator which is conventionally used in the field can be selected as long as the separation and preheating of crude oil can be realized under the conditions of the temperature of 120-315 ℃, and the separation efficiency can reach more than 90%.

The number of the cyclone separators can be selected according to the requirement, and one or more cyclone separators can be included. When a plurality of cyclone separators are included, the plurality of cyclone separators may be connected in parallel or in series.

In a preferred embodiment, in step 2, the outflow temperature of the first liquid phase after preheating is 200-350 ℃; preferably 210-320 ℃.

In a preferred embodiment, in step 2, the temperature at the top of the distillation column is 150-.

Among them, the distillation treatment is preferably carried out under normal pressure.

In the invention, a mode of combining vaporization treatment and distillation is adopted for realizing the vaporization treatment of the preheated crude oil mixture, so that the vaporization treatment is more sufficient, and the yield of a vapor phase can be further improved. And effectively reduces the phenomenon of coking when the vapor phase is further cracked.

In the application, the atmospheric distillation is carried out after the vaporization treatment, instead of adopting two vaporization treatments (such as two times of cyclone separation), wherein the separation effect of the atmospheric distillation can separate corresponding products according to different temperature sections, and the atmospheric distillation has better separation effect than the cyclone separation and can more fully utilize raw materials. According to the method, the heavier components in the crude oil are subjected to hydrotreating, and the heavier components which are only used as fuel before are further utilized, so that more low-carbon olefin products are obtained.

Specifically, in the invention, a mode of combining vaporization treatment and distillation is adopted for realizing vaporization treatment of the preheated crude oil mixture, so that the material which cannot be reused originally can be used for subsequent cracking after further distillation treatment (the part of the heavy component after vaporization treatment originally can be vaporized again, and the utilization rate of the raw material is improved), and the yield of a vapor phase can be further improved. And the heavy component content in the vapor phase can be effectively reduced, and the occurrence degree of coking when the vapor phase is further cracked can be effectively reduced.

In the invention, two times of vaporization treatment (such as cyclone separation) is not adopted, because the inventor finds that the improvement of the utilization rate of heavy components is not particularly obvious by simply repeating the vaporization treatment after a plurality of tests, but also finds that the separation effect of atmospheric distillation is better than that of cyclone separation, and corresponding products can be separated according to different temperature sections.

In a preferred embodiment, in step 3, the catalytic cracking treatment is performed by using a catalytic cracking technology disclosed in the prior art, preferably using a rare earth Y-type catalyst (e.g. a rare earth Y-type zeolite catalytic cracking catalyst), preferably, the reaction temperature is 500-650 ℃, the catalyst-oil ratio is 5-15, and the pressure is 0.1-0.2 MPa.

The rare earth Y-type catalyst is adopted for catalytic cracking treatment, so that the aim of producing more light olefins can be met.

In a preferred embodiment, in step 4, the hydroprocessing treatment comprises in sequence hydrotreating, separation and hydrogen refining.

Wherein, heavy components after hydrogenation are obtained by separation, and recycle hydrogen and light components after hydrogenation are obtained by hydrogen refining.

In a further preferred embodiment, in step 4, the hydrotreating employs at least one of catalytic hydrotreating, residue hydrotreating, and hydrocracking treatment.

In a still further preferred embodiment, in step 4, the hydrotreating is carried out using catalytic hydrotreating using Co-Ni-Mo/Al as catalyst₂O₃The hydrogenation temperature is 260 ℃ and 280 ℃, the hydrogenation pressure is 2.4-2.8MPa, the hydrogen-oil ratio is 2.5-3.5, and the volume space velocity of the liquid phase is 1.8-2.5h^-1。

The method for hydrotreating the liquid phase fraction can realize full hydrogenation of the liquid phase fraction, so that the mono-olefin hydrogenation rate is as high as 95%.

In the invention, the cracking furnace is adopted for cracking, and simultaneously, the catalytic cracking is adopted for reprocessing the heavy components after vaporization treatment and distillation treatment to obtain catalytic cracking gas, so that the components of the crude oil are fully utilized. Specifically, the crude oil is subjected to vaporization treatment and distillation treatment, and then is matched with catalytic cracking treatment and hydroprocessing treatment, so that the cracking efficiency of the crude oil can be further improved, and the yield of low-carbon olefins in the product can be improved.

In the invention, the raw material quantity needing hydrotreating is less, the hydrotreating pertinence is strong and the cost is reduced. This is clearly different from the prior art schemes of hydroprocessing.

In a preferred embodiment, in step 5, at least one addition of steam is carried out before the second vapor phase is mixed with the first vapor phase and the hydrogenated light components and then sent to the cracking furnace.

In a further preferred embodiment, the steam is superheated in the convection section of the cracking furnace.

In a further preferred embodiment, the weight ratio of steam added to crude oil is (0.1-2):1, preferably (0.4-1.5): 1.

In a preferred embodiment, step 4' is performed after step 4 and before step 5:

and 4', carrying out steam stripping treatment on the hydrogenated heavy component to obtain a steam stripped light component.

In a further preferred embodiment, the stripping treatment adopts at least two stripping towers, wherein one stripping tower is in a working state, and the other stripping towers are in a standby state and are alternately switched for use.

In a further preferred embodiment, when the pressure drop during the stripping treatment exceeds a set value, the vaporizer in the working state is switched off, and the vaporizer in the standby state is switched on for vaporization treatment; more preferably, the set value is 0.1 to 0.2 MPaG.

In a preferred embodiment, steam at 110-250 ℃ is used for steam stripping treatment;

high temperature steam is used for steam stripping.

In a further preferred embodiment, the weight ratio of steam to hydrogenated heavies in the stripping treatment is (0.1-2):1, preferably (0.4-1.5): 1.

In a preferred embodiment, when a single-hearth furnace is used, step 5 is performed as follows: and (3) mixing the tower top fraction and the middle fraction in the step (2) to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture into a second tube group of a convection section of the cracking furnace, heating the mixture to a cross temperature, performing cracking treatment to obtain cracked gas, and separating the cracked gas and the catalytic cracked gas to obtain the low-carbon olefin.

In a preferred embodiment, when a single-furnace cracking furnace is used, the cross-over temperature of step 5 is 500-750 ℃, preferably 540-700 ℃.

In a preferred embodiment, when a single-hearth cracking furnace is used, the outlet temperature of the radiant section in step 5 is 780-950 ℃, preferably 800-900 ℃.

In a preferred embodiment, when a single-hearth furnace is used, the residence time for the cracking in step 5 is 0.05 to 1s, preferably 0.1 to 0.7 s.

In a preferred embodiment, when a single-hearth furnace is used, the water-to-oil ratio for the cracking in step 5 is (0.1-2):1, preferably (0.4-1.5): 1.

In the present invention, the water-oil ratio refers to a weight ratio.

In the present invention, the process of cracking comprises: mixing the top fraction and the middle fraction after distillation treatment to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture into a second tube group of a convection section of a cracking furnace, heating the mixture to a cross temperature, cracking the mixture to obtain cracking gas containing low-carbon olefin, and separating the cracking gas to obtain the low-carbon olefin. The cracking gas and the catalytic cracking gas are separated to obtain the low-carbon olefin, and the low-carbon olefin can be separated by adopting a separation process in the prior art.

In a further preferred embodiment, the cracked gas is subjected to a heat exchange treatment prior to separation.

Wherein, in order to further improve the yield of the low-carbon olefin in the product, the pyrolysis gas is subjected to heat exchange treatment before separation. The yield of the low-carbon olefin in the product can be further improved, and the coking phenomenon generated when the pyrolysis gas is cooled and separated can be reduced.

The hydrogen obtained by separating the recycle hydrogen and the pyrolysis gas obtained by the hydroprocessing unit can be returned to carry out hydroprocessing and can be used as a hydroprocessing hydrogen raw material together with fresh hydrogen.

Wherein, the hydrogen generated by cracking can be sent into a hydrotreating unit, and the hydrogen and the circulating hydrogen separated from the unit are jointly used as the raw material of hydrogenation reaction, thereby reducing the hydrogen consumption of the whole system and realizing closed or approximately closed operation.

In a preferred embodiment, when the cracking furnace used is a double-hearth cracking furnace, step 5 comprises the following substeps:

step 5.1, mixing the tower top fraction and the middle fraction to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture to a first tube bank of a second tube bank of a convection section of a cracking furnace, heating the mixture to a cross temperature, and sending the mixture to a first radiation section for first cracking treatment to obtain first cracking gas;

step 5.2, sending the stripped light components into a second tube bank of a second tube group of a convection section of the cracking furnace, heating to a cross temperature, and sending into a second radiation section for second cracking treatment to obtain second cracking gas;

and 5.3, optionally mixing the first cracked gas, the second cracked gas and the catalytic cracked gas, and separating to obtain the low-carbon olefin.

In a further preferred embodiment, in step 5.1: step 5.1 the crossover temperature is 500-; and/or, in step 5.1, the outlet temperature of the first radiation section is 780-; and/or the residence time of the first cleavage treatment in step 5.1 is 0.05 to 1s, preferably 0.1 to 0.7 s; and/or the water-oil ratio of the first cracking treatment in the step 5.1 is (0.1-2):1, preferably (0.4-1.5): 1.

In a still further preferred embodiment, in step 5.2: step 5.2 the crossover temperature is 520 ℃ and 760 ℃, preferably 550 ℃ and 710 ℃, more preferably higher than the crossover temperature of step 5.1; and/or the outlet temperature of the second radiant section in step 5.2 is 750-; and/or the residence time of the second cleavage treatment in step 5.2 is 0.05 to 1s, preferably 0.1 to 0.7 s; and/or the water-oil ratio of the second cracking treatment in the step 5.2 is (0.1-2):1, preferably (0.4-1.5): 1.

Generally, heavy components in the heavy components after hydrogenation are more, and if the heavy components are added into the same radiation section of the cracking furnace together with the overhead fraction, the middle fraction, the first vapor phase and the light components after hydrogenation, severe coking phenomenon can be generated due to high cracking temperature, so that the heavy components after hydrogenation are abandoned in order to ensure the operation period, but the product yield is reduced. Therefore, the inventor proposes a skillful preferred scheme, namely a double-hearth cracking furnace is preferably adopted, so that the raw materials with different components are cracked under different temperature conditions by adopting two radiation sections, specifically, the cracking temperature of the overhead fraction, the middle fraction, the first vapor phase and the first radiation section of the hydrogenated light components can be higher, but the temperature of the second radiation section of the stripped light components is lower. Thus, the lightest component can be cracked at higher temperature (compared with the heavy component, the low crossing temperature and the high cracking temperature are embodied), the cracking degree is improved to the maximum extent, and the product yield is improved; while relatively heavier components crack at relatively lower temperatures, which can reduce the extent of coking.

The second purpose of the invention is to provide a system for preparing low-carbon olefins by using crude oil, which is preferably used for carrying out the method in the first purpose of the invention, the system comprises a cracking furnace, a vaporization treatment unit, a distillation unit, a catalytic cracking unit and a hydroprocessing treatment unit, and the cracking furnace comprises a convection section first pipe group, a convection section second pipe group and a radiation section which are sequentially arranged along the fluid direction. The vaporization treatment unit includes a first vapor phase outlet and a first liquid phase outlet.

In a preferred embodiment, the convection section first tube bank forms a closed loop connection with the material inlet of the vaporization processing unit and the first liquid phase outlet of the vaporization processing unit.

In a preferred embodiment, the first tube bank of the convection section is connected to the feed inlet of the distillation unit.

In a further preferred embodiment, the bottoms outlet of the distillation unit is connected to the feed inlet of the catalytic cracking unit for feeding the bottoms of the distillation unit to the catalytic cracking unit.

In a further preferred embodiment, the liquid phase outlet of the catalytic cracking unit is connected to the feed inlet of the hydroprocessing unit for feeding the liquid phase fraction produced by the catalytic cracking unit to the hydroprocessing unit.

In a preferred embodiment, the hydroprocessing unit includes a hydrotreating unit, a separation unit, and a hydrogen refining unit.

In a further preferred embodiment, the liquid fraction produced by the catalytic cracking unit sequentially passes through a hydrotreating unit, a separation unit and a hydrogen refining unit in the hydrotreating unit, wherein heavy components after hydrogenation are discharged from the outside of the separation unit, and the hydrogen refining unit sends out recycle hydrogen to be recycled to the hydrotreating unit and further sends out light components after hydrogenation.

In a preferred embodiment, the first vapor phase outlet of the vaporization treatment unit, the overhead and middle distillate outlets of the distillation unit, and the hydrogenated light components outlet of the hydroprocessing unit are combined and connected to the second tube bank of the convection section.

In a preferred embodiment, the vaporization treatment unit is a cyclone separator, preferably, the cyclone separator is selected from a rectangular inlet cyclone separator, a spiral shell type cyclone separator, an axial flow guide vane type cyclone separator, a straight tube type cyclone separator, a cone and cylinder combination type cyclone separator, a counter flow type cyclone separator, a straight flow type cyclone separator or a straight flow type multi-cyclone separator; preferably a volute type cyclone separator, an axial flow guide vane type cyclone separator, a straight cylinder type cyclone separator, a cone-cylinder combined type cyclone separator or a straight-flow type cyclone separator. The cyclone separator is provided with an internal component which comprises a skimming cylinder positioned at the top of the cyclone separator and/or a separation plate and a vortex breaker positioned at the lower part of the cyclone separator.

In a preferred embodiment, the distillation unit is a distillation column.

In a preferred embodiment, the system further comprises a stripping treatment unit, wherein a material inlet of the stripping treatment unit is connected with a heavy component outlet after hydrogenation of the hydroprocessing unit.

In a further preferred embodiment, the stripping treatment unit comprises at least two stripping towers, wherein one of the vaporization towers is in a working state, and the other vaporization towers are in a standby state and are alternately switched for use; preferably, when the pressure drop in the vaporization process exceeds a set value, the vaporization device in the working state is switched off, and the vaporization device in the standby state is switched on for vaporization treatment; wherein the set value is preferably 0.1-0.2 MPaG.

In a preferred embodiment, the cracking furnace is a dual-hearth cracking furnace, wherein the convection section second tube bank comprises a convection section second tube bank first tube row and a convection section second tube bank second tube row; the radiating section comprises a first radiating section and a second radiating section; the first tube bank of convection section second nest of tubes links to each other with first radiation section, the second tube bank of convection section second nest of tubes links to each other with second radiation section.

In a further preferred embodiment, the first vapor phase outlet of the vaporization treatment unit, the overhead and middle distillate outlets of the distillation unit, and the hydrogenated light components outlet of the hydroprocessing unit are combined and connected to the first tube bank of the second tube bank of the convection section.

In a still further preferred embodiment, the stripped lights outlet of the stripping treatment unit is connected to the second tube bank of the convection section.

In the invention, when a single-hearth cracking furnace is adopted, crude oil is sent into a first tube group of a convection section of the cracking furnace for preheating, and is separated by a vaporization treatment unit after being preheated to form a first vapor phase and a first liquid phase; sending the first liquid phase into a first tube group of a convection section of a cracking furnace for preheating, and then sending the preheated first liquid phase into a distillation unit to form a tower top fraction, a middle fraction and a tower bottom fraction; sending the bottom fraction into a catalytic cracking unit to obtain catalytic cracked gas and liquid phase fraction; sending the liquid phase fraction into a hydroprocessing unit to obtain recycle hydrogen, a hydrogenated light component and a hydrogenated heavy component; mixing the overhead fraction and the middle fraction to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture into a second tube group of a convection section of a cracking furnace, heating the mixture to a cross temperature, directly sending the mixture into a radiation section for cracking to obtain cracked gas, and separating the cracked gas and the catalytic cracked gas to obtain low-carbon olefin; contacting the hydrogenated heavy components with superheated steam in a convection section, and using the heavy components as fuel oil after steam stripping; and returning the hydrogen obtained by separating the circulating hydrogen and the pyrolysis gas to a hydrotreating unit, and taking the hydrogen and fresh hydrogen as hydrogen raw materials of the hydrotreating unit.

In the invention, when a double-hearth cracking furnace is adopted, crude oil is sent into a first tube group of a convection section of the cracking furnace for preheating, and is separated by a vaporization processing unit after being preheated to form a first vapor phase and a first liquid phase; sending the first liquid phase into a first tube group of a convection section of a cracking furnace for preheating, and then sending the preheated first liquid phase into a distillation unit to form a tower top fraction, a middle fraction and a tower bottom fraction; sending the bottom fraction into a catalytic cracking unit to obtain catalytic cracked gas and liquid phase fraction; sending the liquid phase fraction into a hydroprocessing unit to obtain recycle hydrogen, a hydrogenated light component and a hydrogenated heavy component; carrying out steam stripping treatment on the hydrogenated heavy component to obtain a steam stripped light component; mixing the overhead fraction and the middle fraction to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, feeding the mixture into a first tube bank of a second tube group of a convection section of a cracking furnace, heating the mixture to a cross temperature, and feeding the mixture into a first radiation section to perform first cracking treatment to obtain first cracking gas; sending the stripped light component into a second tube bank of a second tube group of a convection section of the cracking furnace, heating to a cross temperature, and sending into a second radiation section for second cracking treatment to obtain second cracking gas; optionally mixing the first cracked gas, the second cracked gas and the catalytic cracked gas, and separating to obtain low-carbon olefin; and returning the hydrogen obtained by separating the circulating hydrogen and the pyrolysis gas to a hydrotreating unit, and taking the hydrogen and fresh hydrogen as hydrogen raw materials of the hydrotreating unit.

Compared with the prior art, the invention has the following beneficial effects: the invention adopts the cracking furnace (steam cracking furnace) which is simultaneously matched with the vaporization treatment unit, the distillation unit, the catalytic cracking unit and the hydroprocessing unit, can effectively solve the problems that heavy cracking raw materials can not be fully gasified in a convection section and are easy to coke in a radiation section and a quenching part, and simultaneously obtains higher yield of low-carbon olefin and prolongs the operation period.

Drawings

FIG. 1 shows a schematic diagram of the system of the present invention when a single-hearth furnace is used, which contains only one radiant section, the first radiant section;

FIG. 2 is a schematic diagram of the system of the present invention when a dual-hearth furnace is used, the dual-hearth furnace having two radiant sections, including a first radiant section and a second radiant section;

FIG. 3 shows a schematic diagram of the hydroprocessing process of FIGS. 1 and 2;

in FIGS. 1 to 3, 1-convection section first tube bank, 2-convection section second tube bank, 3-first radiation section, 4-cracking furnace, 5-vaporization treatment unit, 6-distillation unit, 7-catalytic cracking unit, 8-hydroprocessing unit; 8.1-hydrotreating unit, 8.2-separating unit, 8.3-hydrogen refining unit, 9-first stripping tower, 10-second stripping tower and 11-second radiation section.

In fig. 1, the cracking furnace is a single-hearth cracking furnace, crude oil is sent into a first tube group 1 of a convection section of a cracking furnace 4 for preheating, and after preheating, the crude oil is separated by a vaporization treatment unit 5 to form a first vapor phase and a first liquid phase; sending the first liquid phase into a convection section first tube group 1 of a cracking furnace for preheating, and then sending the preheated first liquid phase into a distillation unit 6 to form a tower top fraction, a middle fraction and a tower bottom fraction; feeding the bottom fraction to a catalytic cracking unit 7 to obtain a catalytic cracked gas and a liquid fraction; sending the liquid phase fraction into a hydroprocessing unit 8, carrying out hydroprocessing in a hydroprocessing unit 8.1, and then passing through a separation unit 8.2 and a hydrogen refining unit 8.3 to obtain recycle hydrogen, a hydrogenated light component and a hydrogenated heavy component; mixing the overhead fraction and the middle fraction to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture into a second tube group 2 of a convection section of a cracking furnace, heating the mixture to a cross temperature, directly sending the mixture into a first radiation section 3 for cracking to obtain cracked gas, and separating the cracked gas to obtain low-carbon olefin; and returning the hydrogen obtained by separating the circulating hydrogen and the pyrolysis gas to the hydroprocessing unit, and taking the hydrogen and the fresh hydrogen as hydrogen raw materials of the hydroprocessing unit.

In fig. 2, the cracking furnace is a double-hearth cracking furnace, crude oil is sent into a first tube group 1 of a convection section of a cracking furnace 4 for preheating, and after preheating, the crude oil is separated by a vaporization treatment unit 5 to form a first vapor phase and a first liquid phase; sending the first liquid phase into a convection section first tube group 1 of a cracking furnace for preheating, and then sending the preheated first liquid phase into a distillation unit 6 to form a tower top fraction, a middle fraction and a tower bottom fraction; feeding the bottom fraction to a catalytic cracking unit 7 to obtain a catalytic cracked gas and a liquid fraction; sending the liquid phase fraction into a hydroprocessing unit 8 to obtain recycle hydrogen, a hydrogenated light component and a hydrogenated heavy component; feeding the hydrogenated heavy component into a first stripping tower 9 (a second stripping tower 10 for later use) to obtain a stripped light component; mixing the overhead fraction and the middle fraction to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, feeding the mixture into a first tube bank of a second tube bank 2 of a convection section of a cracking furnace 1, heating the mixture to a cross temperature, and feeding the mixture into a first radiation section 3 to perform first cracking treatment to obtain first cracking gas; sending the stripped light components into a second tube bank of a second tube bank 2 of a convection section of a cracking furnace 1, heating to a cross temperature, and sending into a second radiation section 11 for second cracking treatment to obtain second cracked gas; optionally mixing the first cracked gas, the second cracked gas and the catalytic cracked gas, and separating to obtain low-carbon olefin; and returning the hydrogen obtained by separating the circulating hydrogen and the pyrolysis gas to the hydrotreating unit 8, and taking the hydrogen and the fresh hydrogen as the hydrogen raw material of the hydrotreating unit.

Detailed Description

While the present invention will be described in detail with reference to the following examples, it should be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the present invention.

It is to be further understood that the various features described in the following detailed description may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.

In the embodiments 1 to 3 and the comparative example, the cracking furnace is a single-hearth cracking furnace, specifically, a CBL-III type cracking furnace (purchased from the china petrochemical group corporation). The cracking furnace used in embodiments 4 to 6 of the present invention is a dual radiation section cracking furnace (dual hearth cracking furnace), specifically, a CBL-VII type cracking furnace (purchased from petrochemical group corporation, china). The compositions of the crude oils used in the following examples and comparative examples are shown in Table 1, and the compositions were measured according to the method of ASTM D5307.

TABLE 1

Analysis item	ASTM D5307
		IP，℃	69
10％，℃	192
		20％，℃	272
30％，℃	337
		40％，℃	393
50％，℃	446
		60％，℃	508
70％，℃	595
		75％，℃	653
80％，℃	-
		90％，℃	-
EP，℃	-

Example 1

The method is carried out by adopting the system shown in figure 1, wherein the vaporization treatment unit adopts a cyclone separator, and the cracking furnace is a single-hearth cracking furnace.

(1) The dehydrated and desalted crude oil is mixed with superheated steam in a first tube group 1 of a convection section of a cracking furnace 4 and then preheated to obtain preheated crude oil, wherein the weight ratio of the superheated steam to the crude oil is 0.75: 1. The crude oil is continuously heated to 280 ℃ to become preheated crude oil.

(2) The preheated crude oil has a temperature of 280 ℃ and is sent to a first cyclone separator 5 with an internal component (in the embodiment, a guide vane type cyclone separator is selected) for vaporization treatment to obtain a first vapor phase and a first liquid phase. The separation efficiency of the first cyclone 5 was 98%, and the liquid phase in the separated first vapor phase was 200mg/m³。

(3) Sending the first liquid phase into a first tube group of a convection section of a cracking furnace for preheating, preheating to 325 ℃, and sending the preheated first liquid phase into a distillation unit 6 to form a tower top fraction (the boiling point is lower than 255 ℃), a middle fraction (the boiling point is 255-;

(4) and (3) feeding the tower bottom fraction of the distillation unit 6 into a catalytic cracking unit 7, heating, and then reacting and decomposing under the action of high temperature and a catalyst, wherein the catalytic cracking adopts a rare earth Y-type catalyst, the reaction temperature is 500 ℃, the catalyst-oil ratio is 5, and the pressure is 0.2MPa (gauge pressure), so that a gas phase catalytic cracking gas and a liquid phase fraction are respectively obtained. The liquid fraction enters the hydroprocessing unit 8. The catalyst adopted by the hydroprocessing unit is Co-Ni-Mo/Al₂O₃The hydrogenation temperature is 270 ℃, the hydrogenation pressure is 2.6MPa, the hydrogen-oil ratio is 3.0, and the volume space velocity of crude oil is 2.0h^-1The hydrogenation rate of monoene is 95%. The catalytic hydrogenation product passes through a separation device and H₂A refining device for obtaining recycle hydrogen, light components (the boiling point is below 288 ℃) after hydrogenation and heavy components (the boiling point is above 288 ℃) after hydrogenation;

(5) mixing the top fraction and the middle fraction of the distillation unit 6 to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture into a second tube group of a convection section of the cracking furnace, heating the mixture to a crossing temperature (600 ℃), and directly sending the mixture into a radiation section for cracking to obtain cracked gas, wherein the operation parameters of the radiation section 3 are that the outlet temperature of a furnace tube is 840 ℃ and the retention time is 0.22 s;

(6) separating the cracked gas and the catalytic cracked gas product by a separation system (adopting a sequential separation process) to obtain hydrogen, low-carbon olefin, cracked gasoline, cracked diesel oil and cracked fuel oil;

(7) the hydrogenated heavy components are contacted with superheated steam in a convection section, and are used as fuel oil after being stripped.

(8) And returning the hydrogen obtained by separating the circulating hydrogen and the pyrolysis gas to the hydroprocessing unit to be used as a hydrogen raw material of the hydroprocessing unit.

The low-carbon olefin obtained by separation has the ethylene yield of 25.61 wt%, the propylene yield of 14.15 wt%, the 1, 3-butadiene yield of 4.86 wt% and the triene yield of 44.62 wt%. The operating cycle was 42 days.

Example 2

(1) The dehydrated and desalted crude oil is mixed with superheated steam in a first tube group 1 of a convection section of a cracking furnace 4 and then preheated to obtain preheated crude oil. The crude oil is continuously heated to 315 ℃ to become preheated crude oil.

(2) The preheated crude oil has a temperature of 315 ℃, and is sent to a first cyclone separator 5 with an internal component (in the embodiment, a guide vane type cyclone separator is selected) for vaporization treatment to obtain a first vapor phase and a first liquid phase. The separation efficiency of the first cyclone 5 was 95%, and the liquid phase in the separated first vapor phase was 100mg/m³。

(3) The first liquid phase is sent to a convection section first tube group of a cracking furnace to be preheated to 350 ℃, and the preheated first liquid phase enters a distillation unit 6 to form a tower top fraction (the boiling point is lower than 240 ℃), a middle fraction (the boiling point is 240-;

(4) and (3) feeding the tower bottom fraction of the distillation unit 6 into a catalytic cracking unit 7, heating, and then reacting and decomposing under the action of high temperature and a catalyst, wherein the catalytic cracking adopts a rare earth Y-type catalyst, the reaction temperature is 650 ℃, the catalyst-oil ratio is 15, and the pressure is 0.1MPa (gauge pressure), so that a gas phase catalytic cracking gas and a liquid phase fraction are respectively obtained. The liquid fraction enters the hydroprocessing unit 8. The catalyst adopted by the hydroprocessing unit is Co-Ni-Mo/Al₂O₃The hydrogenation temperature is 260 ℃, the hydrogenation pressure is 2.4MPa, the hydrogen-oil ratio is 2.5, and the volume space velocity of crude oil is 1.8h^-1The hydrogenation rate of monoene is 92%. The catalytic hydrogenation product passes through a separation device and H₂A refining device for obtaining recycle hydrogen, light components (the boiling point is below 288 ℃) after hydrogenation and heavy components (the boiling point is above 288 ℃) after hydrogenation;

(5) mixing the top fraction and the middle fraction of the distillation unit 6 to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture into a second tube group of a convection section of the cracking furnace, heating the mixture to a crossing temperature (700 ℃), and directly sending the mixture into a radiation section for cracking to obtain cracked gas, wherein the operation parameters of the radiation section 3 are that the outlet temperature of a furnace tube is 900 ℃, and the retention time is 0.1 s;

The low-carbon olefin obtained by separation has the ethylene yield of 25.60 wt%, the propylene yield of 14.14 wt%, the 1, 3-butadiene yield of 4.91 wt% and the triene yield of 44.65 wt%. The operating cycle was 42 days.

Example 3

(1) The dehydrated and desalted crude oil is mixed with superheated steam in a first tube group 1 of a convection section of a cracking furnace 4 and then preheated to obtain preheated crude oil. The crude oil continues to heat to 220 ℃ to become preheated crude oil).

(2) The preheated crude oil has a temperature of 220 ℃, and is sent to a first cyclone separator 5 with an internal component (in the embodiment, a guide vane type cyclone separator is selected) for vaporization treatment to obtain a first vapor phase and a first liquid phase. The separation efficiency of the first cyclone 5 was 95%, and the liquid phase in the separated first vapor phase was 150mg/m³。

(3) The first liquid phase is sent to a convection section first tube group of a cracking furnace to be preheated to 260 ℃, and the preheated first liquid phase enters a distillation unit 6 to form a tower top fraction (the boiling point is lower than 215 ℃), a middle fraction (the boiling point is 215-320 ℃) and a tower bottom fraction (the boiling point is above 320 ℃);

(4) the bottom fraction of the distillation unit 6 is fed to a catalytic cracking unit 7, heated and catalytically cracked at high temperatureThe reaction is decomposed under the action of a catalyst, the catalytic cracking adopts a rare earth Y-type catalyst, the reaction temperature is 600 ℃, the catalyst-oil ratio is 10, and the pressure is 0.15MPa (gauge pressure), so that gas phase catalytic cracking gas and liquid phase fraction are respectively obtained. The liquid fraction enters the hydroprocessing unit 8. The catalyst adopted by the hydroprocessing unit is Co-Ni-Mo/Al₂O₃The hydrogenation temperature is 280 ℃, the hydrogenation pressure is 2.8MPa, the hydrogen-oil ratio is 3.5, and the volume space velocity of crude oil is 2.5h^-1The hydrogenation rate of the monoene was 97%. The catalytic hydrogenation product passes through a separation device and H₂A refining device for obtaining recycle hydrogen, light components (the boiling point is below 288 ℃) after hydrogenation and heavy components (the boiling point is above 288 ℃) after hydrogenation;

(5) mixing the top fraction and the middle fraction of the distillation unit 6 to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture into a second tube group of a convection section of the cracking furnace, heating the mixture to a crossing temperature (540 ℃), and directly sending the mixture into a radiation section for cracking to obtain cracked gas, wherein the operation parameters of the radiation section 3 are that the outlet temperature of a furnace tube is 800 ℃ and the retention time is 0.7 s;

The low-carbon olefin obtained by separation has the ethylene yield of 25.63 wt%, the propylene yield of 14.14 wt%, the 1, 3-butadiene yield of 4.89 wt% and the triene yield of 44.66 wt%. The operating cycle was 42 days.

Example 4

The method is carried out by adopting the system shown in FIG. 2, wherein the vaporization treatment unit adopts a cyclone separator, and the cracking furnace is a double-hearth cracking furnace.

Steps (1) to (4) in example 1 were repeated except that:

(5) and (3) feeding the hydrogenated heavy component into a first stripping tower 9, and carrying out stripping treatment by adopting steam at 205 ℃, wherein the weight ratio of the steam to the hydrogenated heavy component is 1: 1, obtaining stripped light components;

the stripping tower is monitored by pressure, when the pressure drop in the gasification process exceeds a set value of 0.10MPa, the first stripping tower 9 is cut off, and the second stripping tower 10 is adopted for vaporization; the first stripping tower 9 after being cut out is purged and then is burnt by adopting steam/air, and burnt gas enters a coke cleaning tank of the cracking furnace for treatment and is discharged after meeting the environmental protection requirement;

(6) mixing the top fraction and the middle fraction of the distillation unit 6 to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture into a first tube bank of a second tube bank of a convection section of a cracking furnace, heating the mixture to a cross temperature (560 ℃) and then directly sending the mixture into a first radiation section for cracking to obtain a first cracking gas, wherein the operation parameters of the first radiation section 3 are as follows: the water-oil ratio is 0.75, the outlet temperature of the furnace tube is 840 ℃, and the retention time is 0.22 s;

sending the stripped light components into a second tube bank of a second tube bank 2 of a convection section second tube bank of a cracking furnace 1, heating to a crossing temperature (600 ℃), sending into a second radiation section 11, and carrying out second cracking treatment to obtain second cracked gas, wherein the operation parameters of the second radiation section 11 are as follows: the water-oil ratio is 0.75, the outlet temperature of the furnace tube is 800 ℃, and the retention time is 0.21 s;

(7) mixing the first cracked gas, the second cracked gas and the catalytic cracked gas, and separating by a separation system (adopting a sequential separation process) to obtain hydrogen, low-carbon olefin, cracked gasoline, cracked diesel and cracked fuel oil;

The low-carbon olefin obtained by separation has the ethylene yield of 25.75 wt%, the propylene yield of 14.25 wt%, the 1, 3-butadiene yield of 5.02 wt% and the triene yield of 45.02 wt%. The operating cycle was 42 days.

Example 5

Steps (1) to (4) in example 2 were repeated except that:

(5) and (3) feeding the hydrogenated heavy component into a first stripping tower 9, and carrying out stripping treatment by adopting water vapor at 235 ℃, wherein the weight ratio of the water vapor to the hydrogenated heavy component is 0.95: 1, obtaining stripped light components;

(6) mixing the top fraction and the middle fraction of the distillation unit 6 to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture into a first tube bank of a second tube group of a convection section of the cracking furnace, heating the mixture to a crossing temperature (565 ℃), directly sending the mixture into a first radiation section, and cracking the mixture to obtain first cracked gas, wherein the operation parameters of the first radiation section 3 are that the outlet temperature of a furnace tube is 820 ℃ and the retention time is 0.2 s;

feeding the stripped light components into a second tube bank of a second tube bank 2 of a convection section second tube bank of a cracking furnace 1, heating to a crossing temperature (580 ℃), feeding into a second radiation section 11, and performing second cracking treatment to obtain second cracking gas, wherein the operation parameters of the second radiation section 11 are that the outlet temperature of a furnace tube is 800 ℃ and the retention time is 0.2 s;

The low-carbon olefin obtained by separation has the ethylene yield of 25.76 wt%, the propylene yield of 14.24 wt%, the 1, 3-butadiene yield of 5.06 wt% and the triene yield of 45.06 wt%. The operating cycle was 42 days.

Example 6

Steps (1) to (4) in example 3 were repeated except that:

(5) and (3) feeding the hydrogenated heavy component into a first stripping tower 9, and carrying out stripping treatment by adopting water vapor at 245 ℃, wherein the weight ratio of the water vapor to the hydrogenated heavy component is 0.9: 1, obtaining stripped light components;

(6) mixing the top fraction and the middle fraction of the distillation unit 6 to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture into a first tube bank of a second tube group of a convection section of the cracking furnace, heating the mixture to a crossing temperature (530 ℃), and directly sending the mixture into a first radiation section for cracking to obtain a first cracking gas, wherein the operation parameters of the first radiation section 3 are that the outlet temperature of a furnace tube is 950 ℃ and the retention time is 0.2 s;

feeding the stripped light components into a second tube bank of a second tube bank 2 of a convection section second tube bank of a cracking furnace 1, heating to a crossing temperature (600 ℃), feeding into a second radiation section 11, and performing second cracking treatment to obtain second cracking gas, wherein the operation parameters of the second radiation section 11 are that the outlet temperature of a furnace tube is 800 ℃ and the retention time is 0.2 s;

The low-carbon olefin obtained by separation has the ethylene yield of 25.77 wt%, the propylene yield of 14.22 wt%, the 1, 3-butadiene yield of 5.04 wt% and the triene yield of 45.03 wt%. The operating cycle was 42 days.

Comparative example 1

The comparative example employed a conventional cracking process for cracking in a single-hearth cracking furnace.

The dehydrated and desalted crude oil is directly sent into a cracking furnace, and directly enters a radiation section for cracking after passing through a convection section. The cracking gas adopts a sequential separation process. Analysis of the steam cracking reaction product revealed that the yield of ethylene was 21.49 wt%, the yield of propylene was 13.29 wt%, the yield of 1, 3-butadiene was 4.03 wt%, and the yield of triene was 38.81 wt%. The running period was 5 days.

From the results of example 1 and comparative example 1, it can be seen that the conventional cracking apparatus is adopted, the operation period of the crude oil is only maintained for 5 days, while the normal operation of the crude oil in the cracking apparatus can be ensured by the invention, and the crude oil is treated by the cyclone separator, the atmospheric distillation apparatus and the hydrogenation apparatus, so that the occurrence of coking can be effectively reduced, and the operation period reaches 42 days; moreover, under the same process conditions, compared with the comparative example 1, the example 1 effectively improves the yield of the low-carbon olefin.

Comparative example 2

(1) The dehydrated and desalted crude oil is directly sent into a CBL-III type cracking furnace (purchased from China petrochemical industry group company), and is preheated in a first pipe group at a convection section, wherein the temperature of the preheated crude oil is 380 ℃, and the pressure is 0.15 MPa. Sending the preheated crude oil into a volute type cyclone separator (a first cyclone separator) provided with a separation plate and an internal component of a vortex breaker, and carrying out vaporization treatment. The separation efficiency of the volute type cyclone separator is 98 percent, and the liquid phase in the vapor phase after separation is 200mg/m³。

(2) The separated liquid phase is subjected to hydrogenation treatment by adopting Co-Ni-Mo/Al as a catalyst₂O₃The hydrogenation temperature is 270 ℃, the hydrogenation pressure is 2.6MPa, the hydrogen-oil ratio is 3.0, and the volume space velocity of crude oil is 2.0h^-1The hydrogenation rate of monoene is 95%. Mixing the hydroprocessed material flow with naphtha to obtain a mixture, wherein the mass ratio of the hydroprocessed material flow to the naphtha isIs 90: 10.

(3) The mixture was also fed into a CBL-III type cracking furnace (from China petrochemical industry group) and preheated in the first tube bank at a convection section at a temperature of 380 ℃ and a pressure of 0.15 MPa. Sending the preheated mixture into a guide vane type cyclone separator (a second cyclone separator) provided with a top skimming cylinder, a separation plate and a vortex breaker inner component for vaporization treatment. The separation efficiency of the guide vane type cyclone separator is 98%, and the liquid phase in the separated vapor phase is 200mg/m³。

(4) Sending the vapor phase separated in the step 3 and the vapor phase separated in the step 1 into a second tube group of a convection section of the CBL-III steam cracking furnace, heating to a cross temperature (510 ℃), then sending into a radiation section, and cracking to generate cracking gas containing olefin; the operation parameters of the radiation section are that the water-oil ratio is 0.75, the outlet temperature of the furnace tube is 840 ℃, and the retention time is 0.21 s. The product had an ethylene yield of 23.54 wt%, a propylene yield of 12.27 wt%, a 1, 3-butadiene yield of 4.42 wt%, and a triene yield of 40.22 wt%. And (3) contacting the liquid phase separated in the step (3) with superheated steam in a convection section, and performing steam stripping to obtain the heavy fuel oil. The running period was 35 days.

In this comparative example, two vaporization treatments were used instead of the vaporization treatment and then the distillation treatment in example 1 while adjusting the order of the hydrotreatment, and the catalytic cracking treatment was not used, and as a result, it was found that each product yield was lower than that of example 1. The system of the invention is integrated, and the system interacts with each other to obtain higher yield of the lower olefin and prolong the operation period.

Claims

1. A method for preparing low-carbon olefin by crude oil comprises the following steps:

2. The method according to claim 1, wherein the crude oil comprises light naphtha, diesel oil, hydrogenated tail oil, light crude oil, crude oil with an end point higher than 600 ℃ and lower than 700 ℃ and dehydrated and desalted crude oil, preferably the crude oil comprises diesel oil, hydrogenated tail oil, light crude oil, dehydrated and desalted crude oil with an end point higher than 600 ℃ and lower than 700 ℃.

3. The method according to claim 1, wherein, in step 1,

the outflow temperature of the preheated crude oil is 120-315 ℃, and preferably 150-300 ℃; and/or

The content of the liquid phase in the first vapor phase is 10g/m³Hereinafter, it is preferably 200mg/m³The following.

4. The method according to claim 1, wherein in step 1, the vaporization treatment is at least one of stripping, flashing and cyclonic separation, preferably a cyclone separator.

5. The method according to claim 1, wherein, in step 2,

the outflow temperature of the preheated first liquid phase is 200-350 ℃; preferably 210 ℃ and 320 ℃; and/or

The tower top temperature of the distillation treatment is 150-320 ℃, preferably 175-300 ℃, and the tower bottom temperature is 280-450 ℃, preferably 290-400 ℃.

6. The method of claim 1, wherein in step 4, the hydroprocessing treatment comprises hydrotreating, separation and hydrogen refining in sequence, preferably the hydrotreating employs at least one of catalytic hydrotreating, residue hydrotreating and hydrocracking treatment; more preferably, the heavy component after hydrogenation is obtained by separation, and the recycle hydrogen and the light component after hydrogenation are obtained by hydrogen refining.

7. The method according to any one of claims 1 to 6, wherein step 4' is performed after step 4 and before step 5:

step 4', steam stripping treatment is carried out on the hydrogenated heavy component to obtain a steam stripped light component;

preferably, at least two stripping towers are adopted in the stripping treatment, wherein one stripping tower is in a working state, and the other stripping towers are in a standby state and are switched to use in turn; preferably, when the pressure drop exceeds a set value in the stripping treatment process, the vaporizing device in the working state is switched off, and the vaporizing device in the standby state is switched on for vaporizing treatment; more preferably, the set value is 0.1 to 0.2 MPaG.

8. The method of claim 7,

when a single-hearth cracking furnace is used, step 5 is performed as follows: mixing the tower top fraction and the middle fraction in the step 2 to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, sending the mixture into a second tube group of a convection section of a cracking furnace, heating the mixture to a cross temperature, performing cracking treatment to obtain cracked gas, and separating the cracked gas and the catalytic cracked gas to obtain low-carbon olefin; or

When the adopted cracking furnace is a double-hearth cracking furnace, the step 5 comprises the following substeps:

9. The method according to any one of claims 1 to 6, wherein, when the cracking furnace used is a single-hearth cracking furnace,

step 5, the crossing temperature is 500-750 ℃, preferably 540-700 ℃; and/or

Step 5, the outlet temperature of the radiation section is 780-950 ℃, preferably 800-900 ℃; and/or

The residence time of the cracking in the step 5 is 0.05-1s, preferably 0.1-0.7 s; and/or

The water-oil ratio of the cracking in the step 5 is (0.1-2) to 1, preferably (0.4-1.5) to 1.

10. The method of claim 8, wherein, when the cracking furnace is a double-hearth cracking furnace,

step 5.1 the crossover temperature is 500-; and/or

Step 5.1, the outlet temperature of the first radiation section is 780-950 ℃, preferably 800-900 ℃; and/or

The residence time of the first cracking treatment in step 5.1 is 0.05-1s, preferably 0.1-0.7 s; and/or

In step 5.1, the water-oil ratio of the first cracking treatment is (0.1-2):1, preferably (0.4-1.5): 1.

11. The method of claim 8,

step 5.2 the crossover temperature is 520 ℃ minus 760 ℃, preferably 550 ℃ minus 710 ℃; and/or

Step 5.2, the outlet temperature of the second radiation section is 750-; and/or

The residence time of the second cracking treatment in step 5.2 is 0.05-1s, preferably 0.1-0.7 s; and/or

In step 5.2, the water-oil ratio of the second cracking treatment is (0.1-2):1, preferably (0.4-1.5): 1.

12. A system for preparing low carbon olefins from crude oil, which is used for carrying out the method of any one of claims 1 to 11, and comprises a cracking furnace, a vaporization treatment unit, a distillation unit, a catalytic cracking unit and a hydroprocessing treatment unit, wherein the cracking furnace comprises a convection section first tube bank, a convection section second tube bank and a radiation section which are sequentially arranged along a fluid direction; preferably, the vaporization treatment unit comprises a first vapor phase outlet and a first liquid phase outlet, preferably the vaporization treatment unit is a cyclone.

13. The system of claim 12,

the convection section first pipe group is connected with a material inlet of the vaporization processing unit and a first liquid phase outlet of the vaporization processing unit in a closed loop; and/or

The first tube group of the convection section is connected with a material inlet of the distillation unit, and a bottom fraction outlet of the distillation unit is connected with a material inlet of the catalytic cracking unit and used for sending the bottom fraction of the distillation unit into the catalytic cracking unit; and/or

And a liquid phase outlet of the catalytic cracking unit is connected with a material inlet of the hydroprocessing unit and is used for sending the liquid phase fraction generated by the catalytic cracking unit into the hydroprocessing unit to obtain circulating hydrogen, a hydrogenated light component and a hydrogenated heavy component.

14. The system of claim 12 or 13, further comprising a stripping treatment unit having a feed inlet connected to a hydrogenated heavy ends outlet of the hydroprocessing unit;

preferably, the stripping treatment unit comprises at least two stripping towers, wherein one of the vaporization towers is in a working state, and the other vaporization towers are in a standby state and are alternately switched for use; more preferably, when the pressure drop exceeds a set value in the vaporization process, the vaporization device in the working state is switched off, and the vaporization device in the standby state is switched on for vaporization treatment; wherein the set value is preferably 0.1-0.2 MPaG.

15. The system of claim 14, wherein when the furnace is a dual-hearth furnace, the convection section second tube bank comprises a convection section second tube bank first tube row and a convection section second tube bank second tube row; the radiating section comprises a first radiating section and a second radiating section; the first tube row of the second tube group of the convection section is connected with the first radiation section, and the second tube row of the second tube group of the convection section is connected with the second radiation section; preferably:

a first vapor phase outlet of the vaporization treatment unit, an overhead fraction outlet and a middle fraction outlet of the distillation unit and a hydrogenated light component outlet of the hydroprocessing unit are combined and connected with a first tube bank of a second tube bank of the convection section after combination;

and a stripping light component outlet of the stripping treatment unit is connected with a second tube row of the second tube bank of the convection section.