CN112745957B

CN112745957B - Method and system for preparing low-carbon olefin from crude oil

Info

Publication number: CN112745957B
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: 2024-02-13
Anticipated expiration: 2039-10-31
Also published as: CN112745957A

Abstract

The invention relates to a method and a system for preparing low-carbon olefin from crude oil, wherein the method is carried out as follows: the crude oil is sent into a first tube group of a convection section of a cracking furnace for preheating and then is gasified to form a first vapor phase and a first liquid phase; feeding the first liquid phase into a first tube set 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 circulating hydrogen, a hydrogenated light component and a hydrogenated heavy component; mixing the distilled top fraction with the middle fraction, mixing with the first vapor phase and the hydrogenated light component, sending 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 pyrolysis furnace, the vaporization treatment unit, the distillation unit, the catalytic pyrolysis unit and the hydroprocessing unit, and can effectively solve the problems that heavy pyrolysis raw materials can not be fully gasified in the convection section and are 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 generally refers to the general term of unsaturated hydrocarbon with four or less carbon atoms, and mainly comprises organic chemical raw materials with high economic value such as ethylene, propylene, isobutene, butadiene and the like. With the development of the economy in China, the demand of the organic chemical raw materials is increased year by year, and the increasing demand cannot be met even though the production scale of the low-carbon olefin is also increased year by year.

For a long time, naphtha is used for preparing low-carbon olefin products in China. But in recent years, with the mass exploitation of oil field associated gas in the middle east and shale gas in the united states, these inexpensive oil and gas resources are used in large quantities as ethylene raw materials, and the price of ethylene-related products is greatly reduced. 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 ethylene cracking device becomes an effective means for reducing the cost and enhancing the efficiency of the traditional ethylene enterprises. Therefore, special heavy hydrocarbons, particularly crude oil which is not processed, are used as raw materials of the cracking furnace to produce low-carbon olefins, which is beneficial to reducing the raw material cost and energy consumption of olefin production devices and rapidly adapting to the supply and demand change of cracking raw materials in the market.

Cracking furnaces are commonly used to steam crack various hydrocarbon feedstocks to produce olefins. Crude oil generally contains components such as saturated components, aromatic components, gum, and asphaltenes. Crude oil generally contains high molecular weight non-volatile components with boiling points exceeding 590 ℃, and the non-volatile components cannot be completely gasified when preheated in a convection section of a conventional cracking furnace, so that coking deposition is easy to form, even furnace tubes are blocked, and the production operation of the cracking furnace is influenced.

CN101583697a discloses a process for cracking a feedstock comprising synthetic oil, the process comprising: 1. hydroprocessing includes a broad boiling range aliquot of: a normally liquid hydrocarbon portion boiling in the range of 50°f to 800°f that is substantially free of resid, and b a thermally cracked hydrocarbon liquid boiling in the range of 600°f to 1050°f to provide a synthetic crude oil boiling in the range of 73°f to 1070°f that comprises greater than 25wt% aromatics, greater than 25wt% naphthenes, less than 0.3wt% S, less than 0.02wt% asphaltenes, and substantially free of resids other than asphaltenes; 2. adding to the synthetic crude a normally liquid hydrocarbon component boiling in the range of 100 DEG F to 1050 DEG 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 an optimal radiant coil outlet temperature for cracking the synthetic crude oil alone.

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

CN1957068A discloses the steam cracking of a hydrocarbon feedstock containing salt and/or particulate matter, which process comprises: a adding a non-desalted feedstock comprising salt and optionally particulate matter to the 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 of 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 the salts and any particulate matter in suspension; e removing from the flash/separation vessel in the vapor phase from 50 to 95% of the hydrocarbon feedstock of step a and cracking the vapor phase to produce an effluent comprising olefins; and f removing at least 5% of the hydrocarbon feedstock in the liquid phase from the flash/separation vessel together with the salt and any particulate matter in suspension. US3617493 also discloses a process similar to the above process using steam cracking crude oil.

CN1041967a discloses a method for decomposing a low-grade raw material, which comprises extracting the low-grade raw material from a preheater of a decomposing furnace during the thermal decomposition treatment of the low-grade raw material containing heavy fraction in the decomposing furnace, separating and removing the heavy fraction from the low-grade raw material by a gas-liquid separation method, and returning the low-grade raw material to the preheater for thermal decomposition reaction.

The raw materials are subjected to pyrolysis treatment by adopting the method, the crude oil passing through the convection section of the pyrolysis furnace is treated by adopting the flash tank, gas-liquid separation is realized, and gas phase enters the radiation section for pyrolysis. However, after the raw materials are subjected to flash evaporation, at least 5% of hydrocarbon raw materials remain in the liquid, so that the yield of the low-carbon olefin is affected, and the separated liquid phase is directly used as fuel oil, so that the raw materials are wasted.

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 the low-carbon olefin from the crude oil.

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

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

step 2, the first liquid phase is sent into a first tube group of a convection section of a cracking furnace to be preheated, and the preheated first liquid phase is distilled to form an overhead fraction, a middle fraction and a bottom fraction;

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

step 4, carrying out hydroprocessing treatment on the liquid fraction obtained in the step 3 to obtain circulating hydrogen, hydrogenated light components and hydrogenated heavy components;

and 5, mixing the 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 cracking gas, wherein the cracking gas and the catalytic cracking gas are separated to obtain the low-carbon olefin.

Wherein the pyrolysis furnace comprises a pyrolysis furnace of any structure disclosed in the prior art, preferably comprising a single hearth pyrolysis furnace and a dual hearth pyrolysis furnace.

In the invention, after the crude oil is gasified and distilled at 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 crude oil, improve the yield of 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 with a final boiling point above 600 ℃ and below 700 ℃ and dehydrated desalted crude oil.

In a further preferred embodiment, the crude oil comprises diesel oil, hydrogenated tail oil, light crude oil, dehydrated and desalted crude oil and crude oil with a final boiling point above 600 ℃ and below 700 ℃.

In a preferred embodiment, in step 1, the outflow temperature of the crude oil after preheating is 120-315 ℃, preferably 150-300 ℃.

In a preferred embodiment, in step 1, the liquid phase content in the first vapor phase is less than 10g/m ³ Preferably less than 200mg/m ³ 。

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

In a preferred embodiment, in step 1, the vaporization treatment is performed using a cyclone.

In a further preferred embodiment, the cyclone is selected from a volute cyclone, an axial flow vane cyclone, a straight cyclone, a cone combined cyclone or a straight cyclone.

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

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

In the present invention, the term "cyclone" refers to a cyclone in a broad sense, and includes both a narrow sense of "cyclone" and a separation device similar in principle thereto in the art, such as a cyclone. The cyclone separators mentioned in the present invention are all cyclone separators in a broad sense, unless otherwise specified. According to the invention, the working medium of the cyclone separator for vaporization treatment is mostly gas, and the cyclone separator conventionally used in the field can be selected, so long as the separation of preheated crude oil at the temperature of 120-315 ℃ can be realized, 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 cyclones is included, the cyclones 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 distillation treatment is carried out at a top temperature of 150 to 320 ℃, preferably 175 to 300 ℃, and a bottom temperature of 280 to 450 ℃, preferably 290 to 400 ℃.

Among them, distillation treatment is preferably performed under normal pressure.

In the invention, the vaporization treatment and distillation are combined to realize the vaporization treatment of the preheated crude oil mixture, so that the vaporization treatment is more sufficient, and the yield of the 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 performed after the vaporization treatment instead of two vaporization treatments (such as two cyclone separation), wherein the separation effect of the atmospheric distillation can separate corresponding products according to different temperature sections, so that compared with the cyclone separation effect, the atmospheric distillation has better effect, and the raw materials can be more fully utilized. The method carries out hydrotreatment on heavier components in the crude oil, and further utilizes the heavier components which are just used as fuel before, so that more low-carbon olefin products are obtained.

Specifically, in the invention, a mode of combining vaporization treatment and distillation is adopted to realize vaporization treatment of the preheated crude oil mixture, so that materials which cannot be reused originally (partial heavy components which are vaporized originally can be vaporized again, and the utilization rate of raw materials is improved) can be used for subsequent cracking, and the yield of vapor phase can be further improved. And the content of heavy components in the vapor phase can be effectively reduced, and the occurrence degree of coking during further pyrolysis of the vapor phase can be effectively reduced.

The invention does not adopt two vaporization treatments (such as cyclone separation), because the inventor finds that the improvement of the utilization rate of heavy components in the 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 after a plurality of tests, and corresponding products can be separated according to different temperature sections.

In a preferred embodiment, in step 3, the catalytic cracking treatment is performed using a catalytic cracking technique 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 at a reaction temperature of 500 to 650 ℃, a catalyst-to-oil ratio of 5 to 15, and a pressure of 0.1 to 0.2MPa.

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

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

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

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

In a still further preferred embodiment, in step 4, the hydrotreating is performed by catalytic hydrotreating, the catalyst used being Co-Ni-Mo/Al ₂ O ₃ The hydrogenation temperature is 260-280 ℃, 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 。

By adopting the method to carry out hydrotreatment on the liquid phase fraction, the liquid phase fraction can be fully hydrogenated, so that the hydrogenation rate of the mono-olefin is as high as 95%.

In the invention, the pyrolysis furnace is adopted for pyrolysis, and the catalytic cracking is adopted for retreating the heavy components subjected to vaporization treatment and distillation treatment to obtain catalytic pyrolysis gas, so that the components of crude oil are fully utilized. Specifically, the crude oil is subjected to vaporization treatment, distillation treatment and 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 also improved.

In the invention, the hydrogenation processing is carried out after the vaporization treatment, the distillation treatment and the catalytic cracking treatment, so that the raw material quantity required for the hydrogenation processing is small, the hydrogenation processing has strong pertinency and the cost is reduced. This is clearly different from the prior art solutions of hydroprocessing.

In a preferred embodiment, in step 5, at least one steam addition is performed before the second vapor phase is mixed with the first vapor phase and the hydrogenated light components are fed to the pyrolysis furnace.

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

In a still further preferred embodiment, the weight ratio of added steam 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 heavy component after hydrogenation to obtain a light component after steam stripping.

In a further preferred embodiment, the stripping treatment employs at least two strippers, one of which is in operation and the other is in standby, alternately switched.

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

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

stripping is carried out by high-temperature steam.

In a further preferred embodiment, the weight ratio of water vapor to heavy components after hydrogenation is (0.1-2): 1, preferably (0.4-1.5): 1, when the stripping treatment is carried out.

In a preferred embodiment, when a single hearth furnace is used, step 5 proceeds as follows: and (2) 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, then sending the mixture into a second tube group of a convection section of a cracking furnace, heating the mixture to a crossing temperature, and then carrying out cracking treatment to obtain cracking gas, wherein the cracking gas and the catalytic cracking gas are separated to obtain the low-carbon olefin.

In a preferred embodiment, when a single hearth furnace is used, the cross-over temperature in step 5 is 500-750deg.C, preferably 540-700deg.C.

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

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

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

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

In the invention, the cracking process comprises the following steps: mixing the distilled tower top fraction with 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 second tube group of a convection section of a cracking furnace, heating the mixture to a crossing temperature, cracking the mixture to obtain cracking gas containing low-carbon olefin, and separating the cracking gas to obtain the low-carbon olefin. The separation of the pyrolysis gas and the catalytic cracking gas to obtain the low-carbon olefin can be carried out by adopting a separation process in the prior art.

In a further preferred embodiment, the pyrolysis 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 of the pyrolysis gas during cooling and separation is reduced.

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

The hydrogen generated by cracking can be sent to a hydrotreating unit and the recycled hydrogen separated from the unit can be used as a raw material of hydrogenation reaction, so that the hydrogen consumption of the whole system is reduced, and the closed or approximate closed operation is realized.

In a preferred embodiment, when the pyrolysis furnace employed is a dual hearth pyrolysis furnace, step 5 comprises the sub-steps of:

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

Step 5.2, conveying the stripped light component into a second tube bank of a convection section of the cracking furnace, heating to a cross temperature, and then conveying into a second radiation section for second cracking treatment to obtain a second cracking gas;

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

In a further preferred embodiment, in step 5.1: the cross-over temperature in step 5.1 is 500-750deg.C, preferably 540-700deg.C; and/or the outlet temperature of the first radiation section of step 5.1 is 780-950 ℃, preferably 800-900 ℃; and/or the residence time of the first cleavage treatment in step 5.1 is from 0.05 to 1s, preferably from 0.1 to 0.7s; and/or the water-to-oil ratio of the first cracking treatment in step 5.1 is (0.1-2): 1, preferably (0.4-1.5): 1.

In a still further preferred embodiment, in step 5.2: the crossover temperature in step 5.2 is 520-760 ℃, preferably 550-710 ℃, more preferably higher than the crossover temperature in step 5.1; and/or the outlet temperature of the second radiant section of step 5.2 is 750-950 ℃, preferably 760-900 ℃, more preferably lower than the outlet temperature of the first radiant section of step 5.1; and/or the residence time of the second cleavage treatment in step 5.2 is from 0.05 to 1s, preferably from 0.1 to 0.7s; and/or the water-to-oil ratio of the second cracking treatment in step 5.2 is (0.1-2): 1, preferably (0.4-1.5): 1.

In general, because of the relatively high content of heavy components after hydrogenation, if the heavy components after hydrogenation and the overhead fraction are fed into the same radiation section of the cracking furnace together with the middle distillate, the first vapor phase and the light components after hydrogenation, serious coking phenomenon can occur due to high cracking temperature, so that a mode of discarding the heavy components after hydrogenation is adopted in order to ensure the operation period, but the yield of products is reduced. The inventors therefore propose a smart preferred solution, namely a double hearth pyrolysis furnace is preferred, such that the pyrolysis of different components of the feedstock is performed at different temperatures using two radiant sections, in particular the pyrolysis temperature of the overhead fraction with the middle distillate, the first vapor phase, the first radiant section of the hydrogenated light fraction may be higher, but the second radiant section of the stripped light fraction requires a relatively lower temperature. Thus, the lightest components can be cracked at a higher temperature (compared with the heavy components, the components are embodied with low crossing temperature and high cracking temperature), the cracking degree is improved to the greatest extent, and the product yield is improved; while the relatively heavier components are cracked at relatively lower temperatures, which can reduce the extent of coking.

It is another object of the present invention to provide a system for producing light olefins from crude oil, preferably for carrying out the method according to one of the objects of the present invention, the system comprising a pyrolysis furnace, a vaporization treatment unit, a distillation unit, a catalytic cracking unit and a hydroprocessing treatment unit, the pyrolysis furnace comprising a convection section first tube group, a convection section second tube group and a radiation section arranged in this order in a fluid direction. The vaporization treatment unit includes a first vapor phase outlet and a first liquid phase outlet.

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

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

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

In a still 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 phase 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 outside the separation unit, and the hydrogen refining unit sends out circulating hydrogen to circulate back 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 hydrotreated light ends outlet of the hydroprocessing unit are combined and connected to a second tube bank of the convection section.

In a preferred embodiment, the vaporization treatment unit is a cyclone, preferably the cyclone is selected from a rectangular inlet cyclone, a volute cyclone, an axial flow vane cyclone, a straight barrel cyclone, a cone barrel combined cyclone, a counter-current cyclone, a straight flow cyclone, or a straight flow multi-cyclone; preferably a spiral case type cyclone separator, an axial flow guide vane type cyclone separator, a straight cylinder type cyclone separator, a cone cylinder combined cyclone separator or a straight flow type cyclone separator. The cyclone separator is provided with an inner member comprising a skimming barrel at the top of the cyclone separator and/or a separator plate and vortex breaker 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, the feed inlet of which is connected to the post-hydrogenation heavy component outlet of the hydroprocessing unit.

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

In a preferred embodiment, the pyrolysis furnace is a dual hearth pyrolysis furnace, wherein the convection section second tube bank includes a convection section second tube bank first tube bank and a convection section second tube bank; the radiation section comprises a first radiation section and a second radiation 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.

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

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

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 after preheating, the crude oil is separated through a vaporization treatment unit to form a first vapor phase and a first liquid phase; the first liquid phase is sent into a first tube group of a convection section of a cracking furnace to be preheated, and enters a distillation unit after being preheated to form an overhead fraction, a middle fraction and a bottom fraction; feeding the bottom fraction into a catalytic cracking unit to obtain catalytic cracking gas and liquid phase fraction; feeding the liquid phase fraction into a hydroprocessing unit to obtain recycle hydrogen, a hydrogenated light component and a hydrogenated heavy component; mixing the tower top fraction with the middle fraction to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, then sending the mixture into a second tube group of a convection section of a cracking furnace, heating the mixture to a cross temperature, and then directly sending the mixture into a radiation section for cracking to obtain cracking gas, and separating the cracking gas from the catalytic cracking gas to obtain low-carbon olefins; contacting the hydrogenated heavy component with superheated steam of a convection section, and stripping to be used as fuel oil; and returning the hydrogen obtained by separating the circulating hydrogen and the pyrolysis gas to the hydrotreating unit, and taking the hydrogen and the 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 after preheating, the crude oil is separated through a vaporization treatment unit to form a first vapor phase and a first liquid phase; the first liquid phase is sent into a first tube group of a convection section of a cracking furnace to be preheated, and enters a distillation unit after being preheated to form an overhead fraction, a middle fraction and a bottom fraction; feeding the bottom fraction into a catalytic cracking unit to obtain catalytic cracking gas and liquid phase fraction; feeding 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 heavy component after hydrogenation to obtain a light component after steam stripping; mixing the tower top fraction with the middle fraction to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light components, feeding 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 crossing temperature, and feeding the mixture into a first radiation section for first cracking treatment to obtain first cracked gas; sending the stripped light component into a second tube bank of a convection section of the cracking furnace, heating to a crossing temperature, and sending into a second radiation section for second cracking treatment to obtain a second cracking gas; the first pyrolysis gas, the second pyrolysis gas and the catalytic pyrolysis gas are optionally mixed and then separated to obtain low-carbon olefin; and returning the hydrogen obtained by separating the circulating hydrogen and the pyrolysis gas to the hydrotreating unit, and taking the hydrogen and the 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 pyrolysis furnace (steam pyrolysis furnace) and is matched with the vaporization treatment unit, the distillation unit, the catalytic cracking unit and the hydroprocessing unit, so that the problems that heavy pyrolysis raw materials cannot be fully gasified in a convection section and are easy to coke in a radiation section and a quenching section can be effectively solved, and meanwhile, the higher yield of low-carbon olefin is obtained, and the running period is prolonged.

Drawings

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

FIG. 2 shows a schematic structural view of the system of the present invention when a dual hearth furnace is employed, the dual hearth furnace having two radiant sections, including a first radiant section and a second radiant section;

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

in FIGS. 1 to 3, a 1-convection section first tube group, a 2-convection section second tube group, a 3-first radiation section, a 4-cracking furnace, a 5-vaporization treatment unit, a 6-distillation unit, a 7-catalytic cracking unit, and an 8-hydroprocessing unit; 8.1-hydrotreating unit, 8.2-separation 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 to be preheated, and the preheated crude oil is separated by a vaporization treatment unit 5 to form a first vapor phase and a first liquid phase; the first liquid phase is sent into a first tube group 1 of a convection section of a cracking furnace to be preheated, and enters a distillation unit 6 after being preheated to form an overhead fraction, a middle fraction and a bottom fraction; feeding the bottom fraction into a catalytic cracking unit 7 to obtain catalytic cracked gas and a liquid fraction; the liquid phase fraction is sent to a hydroprocessing unit 8, is subjected to hydroprocessing before the hydroprocessing unit 8.1, and then passes through a separation unit 8.2 and a hydrogen refining unit 8.3 to obtain recycle hydrogen, a light component after hydrogenation and a heavy component after hydrogenation; mixing the tower top fraction with the middle fraction to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light component, then sending the mixture into a second tube group 2 of a convection section of a cracking furnace, heating the mixture to a crossing temperature, and then directly sending the mixture into a first radiation section 3 for cracking to obtain cracking gas, and separating the cracking 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 to be preheated, and after the preheating, the crude oil is separated by a vaporization treatment unit 5 to form a first vapor phase and a first liquid phase; the first liquid phase is sent into a first tube group 1 of a convection section of a cracking furnace to be preheated, and enters a distillation unit 6 after being preheated to form an overhead fraction, a middle fraction and a bottom fraction; feeding the bottom fraction into a catalytic cracking unit 7 to obtain catalytic cracked gas and a liquid fraction; feeding the liquid fraction into a hydroprocessing unit 8 to obtain recycle hydrogen, a hydrogenated light component and a hydrogenated heavy component; feeding the hydrogenated recombinant into a first stripping tower 9 (a second stripping tower 10 for standby) to obtain stripped light components; mixing the top fraction with the middle fraction to form a second vapor phase, mixing the second vapor phase with the first vapor phase and the hydrogenated light components, feeding the mixture into a first tube row of a second tube group 2 of a convection section of a cracking furnace 1, heating the mixture to a crossing temperature, and feeding the mixture into a first radiation section 3 for first cracking treatment to obtain first cracked gas; the stripped light components are sent to a second tube row of a second tube group 2 of the convection section of the cracking furnace 1, heated to cross temperature and then sent to a second radiation section 11 for second cracking treatment to obtain second cracking gas; the first pyrolysis gas, the second pyrolysis gas and the catalytic pyrolysis gas are optionally mixed and then separated to obtain low-carbon olefin; the hydrogen gas obtained by separating the recycle hydrogen and the pyrolysis gas is returned to the hydrotreating unit 8, and is used as a hydrogen feed for the hydrotreating unit together with fresh hydrogen.

Detailed Description

The present invention is described in detail below with reference to specific embodiments, and it should be noted that the following embodiments are only for further description of the present invention and should not be construed as limiting the scope of the present invention, and some insubstantial modifications and adjustments of the present invention by those skilled in the art from the present disclosure are still within the scope of the present invention.

In addition, the specific features described in the following embodiments may be combined in any suitable manner without contradiction. The various possible combinations of the invention are not described in detail in order to avoid unnecessary repetition.

The cracking furnaces of examples 1 to 3 and comparative examples of the present invention are single hearth cracking furnaces, specifically CBL-III type cracking furnaces (purchased from chinese petrochemical company). The cracking furnaces used in examples 4 to 6 of the present invention were double-radiation section cracking furnaces (double-hearth cracking furnaces), specifically CBL-VII cracking furnaces (purchased from chinese petrochemical company). The compositions of crude oils used in the following examples and comparative examples, which were measured according to the ASTM D5307 method, are shown in table 1.

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 fig. 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 the first tube group 1 of the convection section of the 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 (a vane type cyclone separator is selected in the embodiment) with an inner member for vaporization treatment to obtain a first vapor phase and a first liquid phase. The separation efficiency of the first cyclone separator 5 was 98%, and the liquid phase in the separated first vapor phase was 200mg/m ³ 。

(3) The first liquid phase is sent into a first tube group of a convection section of a cracking furnace to be preheated to 325 ℃, and the preheated first liquid phase enters a distillation unit 6 to form an overhead fraction (boiling point is lower than 255 ℃), a middle fraction (boiling point is 255-370 ℃) and a bottom fraction (boiling point is above 370 ℃);

(4) The bottom fraction of the distillation unit 6 is sent to a catalytic cracking unit 7, and is heated and then reacted and decomposed under the action of a high temperature catalyst, the catalytic cracking adopts a rare earth Y-type catalyst, the reaction temperature is 500 ℃, the catalyst-to-oil ratio is 5, and the pressure is 0.2MPa (gauge pressure), so that gas-phase catalytic cracking gas and liquid-phase fraction are respectively obtained. The liquid fraction enters a hydroprocessing unit 8. The catalyst adopted by the hydroprocessing unit is Co-Ni-Mo/Al ₂ O ₃ The hydrogenation temperature is 270 ℃, the hydrogenation pressure is 2.6MPa, the hydrogen-oil ratio is 3.0, and the crude oil volume space velocity is 2.0h ^-1 The hydrogenation rate of the mono-olefin is 95%. The catalytic hydrogenation product passes through a separation device and H ₂ Refining device for obtaining recycle hydrogen, light component (boiling point is less than 288 ℃) after hydrogenation and addingHeavy components (boiling point above 288 ℃) after hydrogen;

(5) Mixing the top fraction of the distillation unit 6 with 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 second tube group of a convection section of a cracking furnace, heating the mixture to a cross temperature (600 ℃) and then directly feeding the mixture into a radiation section for cracking to obtain cracking gas, wherein the operation parameters of the radiation section 3 are that the outlet temperature of a furnace tube is 840 ℃, and the residence time is 0.22s;

(6) Separating the pyrolysis gas and the catalytic pyrolysis gas products by a separation system (adopting a sequential separation flow) to obtain hydrogen, low-carbon olefin, pyrolysis gasoline, pyrolysis diesel oil and pyrolysis fuel oil;

(7) The heavy component after hydrogenation is contacted with superheated steam of a convection section, and is used as fuel oil after steam stripping.

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

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

Example 2

(1) The dehydrated and desalted crude oil is mixed with superheated steam in the first tube group 1 of the convection section of the 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 c and is fed to a first cyclone 5 with internals (in this example a vane-type cyclone is selected) for vaporisation to obtain a first vapour phase and a first liquid phase. The separation efficiency of the first cyclone separator 5 was 95%, and the liquid phase in the separated first vapor phase was 100mg/m ³ 。

(3) Preheating the first liquid phase in the first tube set of the convection section of the cracking furnace to 350 ℃, and feeding the preheated first liquid phase into a distillation unit 6 to form an overhead fraction (boiling point lower than 240 ℃), a middle fraction (boiling point between 240 and 380 ℃) and a bottom fraction (boiling point above 380 ℃);

(4) The bottom fraction of the distillation unit 6 is sent to a catalytic cracking unit 7, and is heated and then reacted and decomposed under the action of a high temperature catalyst, the catalytic cracking adopts a rare earth Y-type catalyst, the reaction temperature is 650 ℃, the catalyst-to-oil ratio is 15, and the pressure is 0.1MPa (gauge pressure), so that gas-phase catalytic cracking gas and liquid-phase fraction are respectively obtained. The liquid fraction enters a hydroprocessing unit 8. The catalyst adopted by the hydroprocessing unit is Co-Ni-Mo/Al ₂ O ₃ The 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 ^-1 The hydrogenation rate of the mono-olefin is 92%. The catalytic hydrogenation product passes through a separation device and H ₂ A refining device for obtaining recycle hydrogen, light components after hydrogenation (boiling point is less than 288 ℃) and heavy components after hydrogenation (boiling point is more than 288 ℃);

(5) Mixing the top fraction of the distillation unit 6 with 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 second tube group of a convection section of a cracking furnace, heating the mixture to a cross temperature (700 ℃) and then directly feeding the mixture into a radiation section for cracking to obtain cracking gas, wherein the operation parameters of the radiation section 3 are that the outlet temperature of a furnace tube is 900 ℃, and the residence time is 0.1s;

The lower olefins obtained by separation gave an ethylene yield of 25.60wt%, a propylene yield of 14.14wt%, a 1, 3-butadiene yield of 4.91wt% and a triene yield of 44.65wt%. The run period was 42 days.

Example 3

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

(2) The preheated crude oil is fed to a first cyclone 5 (in this example, a vane type cyclone) with internals at 220 c for vaporization to obtain a first vapor phase and a first liquid phase. The separation efficiency of the first cyclone separator 5 was 95%, and the liquid phase in the separated first vapor phase was 150mg/m ³ 。

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

(4) The bottom fraction of the distillation unit 6 is sent to a catalytic cracking unit 7, and is heated and then reacted and decomposed under the action of a high temperature catalyst, the catalytic cracking adopts a rare earth Y-type catalyst, the reaction temperature is 600 ℃, the catalyst-to-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 a hydroprocessing unit 8. The catalyst adopted by the hydroprocessing unit is Co-Ni-Mo/Al ₂ O ₃ The hydrogenation temperature is 280 ℃, the hydrogenation pressure is 2.8MPa, the hydrogen-oil ratio is 3.5, and the crude oil volume space velocity is 2.5h ^-1 The hydrogenation rate of the mono-olefin is 97%. The catalytic hydrogenation product passes through a separation device and H ₂ A refining device for obtaining recycle hydrogen, light components after hydrogenation (boiling point is less than 288 ℃) and heavy components after hydrogenation (boiling point is more than 288 ℃);

(5) Mixing the top fraction of the distillation unit 6 with 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 second tube group of a convection section of a cracking furnace, heating the mixture to a cross temperature (540 ℃) and then directly feeding the mixture into a radiation section for cracking to obtain cracking gas, wherein the operation parameters of the radiation section 3 are that the outlet temperature of a furnace tube is 800 ℃, and the residence time is 0.7s;

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

Example 4

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

The steps (1) to (4) in example 1 were repeated, except that:

(5) The hydrogenated heavy components are sent to a first stripping tower 9 and are subjected to stripping treatment by adopting 205 ℃ of water vapor, wherein the weight ratio of the water vapor to the hydrogenated heavy components is 1:1, obtaining a stripped light component;

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

(6) Mixing the top fraction of the distillation unit 6 with 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 row of a convection section second tube group of a cracking furnace, heating the mixture to a crossing temperature (560 ℃) and then directly feeding the mixture into a first radiation section for cracking to obtain 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 residence time is 0.22s;

The stripped light components are sent to a second tube row of a second tube group 2 of the convection section of the cracking furnace 1, and are sent to a second radiation section 11 for second cracking treatment after being heated to a crossing temperature (600 ℃) to obtain second cracking gas, and 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 residence time is 0.21s;

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

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

Example 5

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

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

(6) Mixing the top fraction of the distillation unit 6 with 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 row of a second tube group of a convection section of a cracking furnace, heating the mixture to a cross temperature (565 ℃) and then directly feeding the mixture into a first radiation section for cracking to obtain a first cracking gas, wherein the operation parameter of the first radiation section 3 is that the furnace tube outlet temperature is 820 ℃, and the residence time is 0.2s;

the stripped light components are sent into a second tube row of a convection section second tube group 2 of a cracking furnace 1, heated to a crossing temperature (580 ℃) and then sent into a second radiation section 11 for second cracking treatment to obtain second cracking gas, and the operation parameters of the second radiation section 11 are that the outlet temperature of a furnace tube is 800 ℃, and the residence time is 0.2s;

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

Example 6

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

(5) The hydrogenated heavy components are sent to a first stripping tower 9, steam at 245 ℃ is adopted for stripping treatment, wherein the weight ratio of the steam to the hydrogenated heavy components is 0.9:1, obtaining a stripped light component;

(6) Mixing the top fraction of the distillation unit 6 with 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 row of a convection section second tube group of a cracking furnace, heating the mixture to a crossing temperature (530 ℃) and then directly feeding the mixture into a first radiation section for cracking to obtain a first cracking gas, wherein the operation parameter of the first radiation section 3 is that the furnace tube outlet temperature is 950 ℃, and the residence time is 0.2s;

The stripped light components are sent into a second tube row of a convection section second tube group 2 of a cracking furnace 1, heated to a crossing temperature (600 ℃) and then sent into a second radiation section 11 for second cracking treatment to obtain second cracking gas, and the operation parameters of the second radiation section 11 are that the outlet temperature of a furnace tube is 800 ℃, and the residence time is 0.2s;

The lower olefins obtained by separation gave an ethylene yield of 25.77wt%, a propylene yield of 14.22wt%, a 1, 3-butadiene yield of 5.04wt% and a triene yield of 45.03wt%. The run period was 42 days.

Comparative example 1

This comparative example was subjected to pyrolysis in a Shan Lutang pyrolysis furnace using a conventional pyrolysis process.

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

From the results of the embodiment 1 and the comparative example 1, the traditional cracking device is adopted, the crude oil is put into operation for only 5 days, the normal operation of the crude oil in the cracking device can be ensured, and the crude oil is treated by adopting the cyclone separator, the atmospheric distillation device and the hydrogenation device, so that the coking can be effectively reduced, and the operation period reaches 42 days; moreover, example 1 effectively improved the yield of lower olefins under the same process conditions as compared to comparative example 1.

Comparative example 2

(1) The dehydrated and desalted crude oil is directly sent into a CBL-III cracking furnace (purchased from China stone chemical group Co.) to be preheated in a first tube group of a convection section, and the temperature of the preheated crude oil is 380 ℃ and the pressure is 0.15MPa. And feeding the preheated crude oil into a volute cyclone (first cyclone) provided with a separation plate and a vortex-proof device inner member for vaporization treatment. The separation efficiency of the spiral case type cyclone separator is 98%, and the liquid phase in the separated vapor phase is 200mg/m ³ 。

(2) Hydrotreating the separated liquid phase with Co-Ni-Mo/Al as catalyst ₂ O ₃ The 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 ^-1 The hydrogenation rate of the mono-olefin is 95%. The hydrotreated stream is mixed with naphtha to produce a mixture, wherein the mass ratio of the hydrotreated stream to naphtha is 90:10.

(3) The mixture was also fed into a CBL-III cracking furnace (purchased from chinese stone chemical group company) and preheated in the first tube group of the convection section at a temperature of 380 ℃ and a pressure of 0.15MPa. And feeding the preheated mixture into a guide vane type cyclone separator (a second cyclone separator) provided with a top skimming barrel, a separation plate and a vortex-preventing inner member 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/m ³ 。

(4) Feeding 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 temperature (510 ℃) crossing the convection section, and then feeding into a radiation section for cracking to generate cracking gas containing olefin; the operating parameter of the radiant section is water-oil ratio of 0.75, furnace tube outlet temperature of 840 ℃ and residence time of 0.21s. The ethylene yield of the product was 23.54wt%, the propylene yield was 12.27wt%, the 1, 3-butadiene yield was 4.42wt%, and the triene yield was 40.22wt%. And (3) contacting the liquid phase separated in the step (3) with superheated steam of a convection section, and performing steam stripping to obtain heavy fuel oil. The run period was 35 days.

In this comparative example, the vaporization treatment was replaced with the vaporization treatment and then the distillation treatment in example 1 with the adjustment of the order of the hydrotreatment, and the catalytic cracking treatment was not employed, and as a result, it was found that each of the produced products was lower in yield than example 1. The system of the invention is an integral body, and the high yield of the low-carbon olefin is obtained through mutual interaction, and meanwhile, the operation period is prolonged.

Claims

1. A method for preparing low-carbon olefin from crude oil, comprising the following steps:

step 1, feeding crude oil into a first tube group of a convection section of a cracking furnace for preheating, wherein the outflow temperature of the preheated crude oil is 220-315 ℃, and then adopting a cyclone separator for vaporization treatment to form a first vapor phase and a first liquid phase;

step 2, the first liquid phase is sent into a first tube group of a convection section of a cracking furnace to be preheated, and the preheated first liquid phase is distilled to form an overhead fraction, a middle fraction and a bottom fraction; the outflow temperature of the first liquid phase after preheating is 200-350 ℃, the top temperature of the distillation treatment is 150-320 ℃, and the bottom temperature of the distillation treatment is 280-450 ℃;

2. The method of claim 1, wherein the crude oil comprises one or more of a light crude oil, a crude oil having a final boiling point above 600 ℃ and below 700 ℃ and a dehydrated desalted crude oil.

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

the outflow temperature of the preheated crude oil is 220-300 ℃; and/or

The liquid phase content in the first vapor phase was 10g/m ³ The following is given.

4. A process according to claim 3, wherein in step 1 the liquid phase content in the first vapour phase is 200mg/m ³ The following is given.

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

the outflow temperature of the first liquid phase after preheating is 210-320 ℃; and/or

The temperature of the top of the distillation treatment is 175-300 ℃ and the temperature of the bottom of the distillation treatment is 290-400 ℃.

6. The method according to claim 1, wherein in step 4, the hydroprocessing treatment comprises hydrotreating, separation and hydrogen refining in this order, heavy components after hydrogenation are obtained by separation, and recycle hydrogen and light components after hydrogenation are obtained by hydrogen refining.

7. The method of claim 6, wherein the hydrotreating employs catalytic hydrotreating.

8. The method of claim 6, wherein the hydrotreating employs residuum hydrotreating.

9. The method of claim 6, wherein the hydrotreating employs a hydrocracking process.

10. The method according to one of claims 1 to 9, characterized in that step 4' is performed after step 4 and before step 5:

11. The method according to claim 10, wherein the stripping treatment adopts at least two strippers, one of which is in operation and the other is in standby state, and is alternately switched to use; when the pressure drop exceeds a set value in the steam stripping treatment process, the working state of the vaporizing device is cut out, and the standby state of the vaporizing device is cut in for vaporization treatment.

12. The method of claim 11, wherein the set value is 0.1-0.2 mpa g.

13. The method of claim 10, wherein the step of determining the position of the first electrode is performed,

when the single-hearth cracking furnace is adopted, the cracking furnace comprises a convection section first tube group, a convection section second tube group and a radiation section which are sequentially arranged along the fluid direction, and the step 5 is carried out as follows: mixing the 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, then sending the mixture into a second tube group of a convection section of a cracking furnace, heating the mixture to a crossing temperature, and then carrying out cracking treatment to obtain cracking gas, wherein the cracking gas and the catalytic cracking gas are separated to obtain low-carbon olefins; or (b)

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

14. The method of claim 13, wherein when the pyrolysis furnace used is a single hearth pyrolysis furnace,

the crossing temperature in the step 5 is 500-750 ℃; and/or

The outlet temperature of the radiation section in the step 5 is 780-950 ℃; and/or

The residence time of the pyrolysis in the step 5 is 0.05-1s; and/or

The water-oil ratio of the pyrolysis in the step 5 is (0.1-2): 1.

15. The method of claim 14, wherein when the pyrolysis furnace used is a single hearth pyrolysis furnace,

the crossing temperature in the step 5 is 540-700 ℃; and/or

The outlet temperature of the radiation section in the step 5 is 800-900 ℃; and/or

The residence time of the pyrolysis in the step 5 is 0.1 to 0.7s; and/or

The ratio of water to oil of the cracking in the step 5 is (0.4-1.5): 1.

16. The method of claim 13, wherein when the pyrolysis furnace is a dual hearth pyrolysis furnace,

the crossing temperature in the step 5.1 is 500-750 ℃; and/or

The outlet temperature of the first radiation section in the step 5.1 is 780-950 ℃; and/or

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

The water-oil ratio of the first cracking treatment in the step 5.1 is (0.1-2): 1.

17. The method of claim 16, wherein when the pyrolysis furnace is a dual hearth pyrolysis furnace,

the crossing temperature in the step 5.1 is 540-700 ℃; and/or

The outlet temperature of the first radiation section in the step 5.1 is 800-900 ℃; and/or

The residence time of the first cracking treatment in the step 5.1 is 0.1 to 0.7s; and/or

The water-oil ratio of the first cracking treatment in the step 5.1 is (0.4-1.5): 1.

18. The method of claim 13, wherein the step of determining the position of the probe is performed,

the crossing temperature in the step 5.2 is 520-760 ℃; and/or

The outlet temperature of the second radiation section in the step 5.2 is 750-950 ℃; and/or

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

The water-oil ratio of the second cracking treatment in the step 5.2 is (0.1-2): 1.

19. The method of claim 18, wherein the step of providing the first information comprises,

step 5.2, wherein the crossing temperature is 550-710 ℃; and/or

The outlet temperature of the second radiation section in the step 5.2 is 760-900 ℃; and/or

The residence time of the second cracking treatment in the step 5.2 is 0.1 to 0.7s; and/or

The water-oil ratio of the second cracking treatment in the step 5.2 is (0.4-1.5): 1.

20. A system for preparing low-carbon olefin from crude oil, which is used for carrying out the method of one of claims 1 to 19, the system 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 pipe group, a convection section second pipe group and a radiation section which are sequentially arranged along the fluid direction; the vaporization treatment unit comprises a first vapor phase outlet and a first liquid phase outlet, the vaporization treatment unit is a cyclone separator, and the distillation unit is a distillation tower;

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

the first pipe group of the convection section is connected with the material inlet of the distillation unit, and the bottom fraction outlet of the distillation unit is connected with the material inlet of the catalytic cracking unit and is used for conveying the bottom fraction of the distillation unit into the catalytic cracking unit;

the liquid phase outlet of the catalytic cracking unit is connected with the 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 light component after hydrogenation and a heavy component after hydrogenation;

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

21. The system of claim 20, further comprising a stripping treatment unit having a feed inlet coupled to the post-hydrogenation heavy ends outlet of the hydroprocessing unit.

22. The system of claim 21, wherein the stripping treatment unit comprises at least two stripping towers, wherein one of the stripping towers is in a working state, and the other is in a standby state, and the stripping towers are alternately switched to be used; when the pressure drop exceeds a set value in the vaporization process, the vaporization device in a working state is cut out, and the vaporization device in a standby state is cut in for vaporization treatment.

23. The system of claim 21, wherein when the pyrolysis furnace is a dual hearth pyrolysis furnace, the convection section second tube bank comprises a convection section second tube bank first tube bank and a convection section second tube bank; the radiation section comprises a first radiation section and a second radiation 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.

24. The system of claim 23, wherein the stripped lights outlet of the stripping treatment unit is connected to a second tube bank of the convection section second tube bank.