Method and system for preparing low-carbon olefin and application

Abstract

The invention relates to the technical field of crude oil cracking, and discloses a method and system for preparing low-carbon olefin and application, and the method comprises the following steps: (1) vaporizing raw oil to obtain a gas phase and a liquid phase; (2) carrying out supercritical extraction and sedimentation on the liquid phase to obtain extracted oil, settled oil and asphalt; (3) performing microwave cracking on the gas phase, the extract oil and water vapor in the presence of an electromagnetic wave absorber to obtain microwave cracking gas; (4) performing catalytic cracking on the settled oil to obtain catalyst cracking gas; and (5) separating the microwave cracking gas and / or the catalytic cracking gas to obtain the low-carbon olefin. According to the present invention, microwave cracking is adopted, and is matched with the supercritical extraction unit and the catalytic cracking unit, such that the problem of easy coking during the cracking reaction of the heavy cracking raw material can be effectively solved, the high low-carbon olefin yield can be obtained, and the operation period can be prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of crude oil cracking, and in particular to a method and system for preparing light olefins and applications thereof. Background Art

[0002] Low-carbon olefins generally refer to olefins with carbon atoms less than or equal to 4, such as ethylene, propylene and butene. Low-carbon olefins are the basic raw materials for petrochemical production and can be used to produce polyethylene, polypropylene, etc. There are two main methods for producing low-carbon olefins: petroleum route and non-petroleum route (such as methanol to produce low-carbon olefins). The petroleum route generally refers to the use of petroleum to crack and prepare low-carbon hydrocarbons, such as thermal cracking, catalytic cracking, etc.

[0003] Currently, most industrial methods for preparing light olefins are petroleum cracking. However, due to the high content of heavy components in crude oil or cracking feedstock, it is easy to cause coking or even blockage in the reactor, and the yield of light olefins is low.

[0004] CN104093821A discloses a method of treating the separated heavy components of crude oil by hydrogenation to increase the paraffin content of the components and reduce the BMCI value. However, the hydrogenation process requires a large amount of hydrogen to react under medium or high pressure, which requires large equipment investment, high energy consumption, and it is difficult to ensure the safety of the process.

[0005] CN103210061A discloses a method for cracking heavy hydrocarbon feed, wherein the liquid phase of crude oil after gas-liquid separation is coked to generate coking effluent and coke. The coking technology in the method requires a coke tower and decoking equipment, which requires a large investment, and regular decoking makes the technology in a semi-continuous state, which is not conducive to the continuous operation of the entire process. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of easy coking and low yield of light olefins in the prior art during crude oil cracking, and to provide a method and system for preparing light olefins and their application.

[0007] In order to achieve the above object, the first aspect of the present invention provides a method for preparing light olefins, the method comprising:

[0008] (1) vaporizing the crude oil to obtain a gas phase and a liquid phase;

[0009] (2) subjecting the liquid phase to supercritical extraction and sedimentation to obtain extracted oil, sedimentation oil and asphalt;

[0010] (3) subjecting the gas phase, the extracted oil and the water vapor to microwave cracking in the presence of an electromagnetic wave absorber to obtain microwave cracking gas;

[0011] (4) catalytically cracking the sedimentation oil to obtain catalyst cracking gas;

[0012] (5) Separating the microwave cracking gas and / or catalytic cracking gas to obtain light olefins.

[0013] The second aspect of the present invention provides a system for preparing low-carbon hydrocarbons from crude oil, the system comprising: a feedstock oil vaporization unit, a supercritical extraction unit, a microwave cracking unit, a catalytic cracking unit and a cracking gas separation unit;

[0014] The feedstock oil vaporization unit is used to vaporize the feedstock oil to obtain a gas phase and a liquid phase;

[0015] The supercritical extraction unit is used to perform supercritical extraction and sedimentation on the liquid phase to obtain extracted oil, sedimentation oil and asphalt;

[0016] The microwave cracking unit is used to perform microwave cracking on the gas phase, the extracted oil and the water vapor to obtain microwave cracking gas;

[0017] The catalytic cracking unit is used to catalytically crack the sedimentation oil to obtain catalyst cracking gas;

[0018] The cracking gas separation unit is used to separate microwave cracking gas and / or catalytic cracking gas to obtain light olefins.

[0019] The third aspect of the present invention provides the use of the above-mentioned system in the preparation of light olefins, especially in the preparation of light olefins by direct cracking of crude oil.

[0020] A fourth aspect of the present invention provides the above-described method and / or application of the above-described system in improving the target product yield, selectivity and operation cycle of preparing light olefins by direct cracking of crude oil.

[0021] The present invention has achieved the following beneficial effects:

[0022] (1) The present invention adopts microwave cracking, and cooperates with a supercritical extraction unit and a catalytic cracking unit, which can effectively solve the problem of easy coking during the cracking reaction of heavy cracking raw materials, and at the same time obtain a higher yield of light olefins and extend the operation cycle.

[0023] (2) The heat source of the present invention can be electrically heated, and the microwave reactor uses electrical energy, which can effectively save energy and reduce carbon emissions.

[0024] (3) Compared with conventional thermal cracking, the microwave cracking of the present invention can improve the selectivity of light hydrocarbons and reduce the cracking temperature; at the same time, it can also reduce carbon emissions and energy consumption. In a preferred case, the preferred electromagnetic wave absorber (such as silicon carbide) of the present invention can further reduce the cracking temperature, while promoting rapid cracking of light components, so that more light components are converted into light olefins.

[0025] (4) In a preferred embodiment, the present invention uses a specific extraction solvent to extract the liquid phase, and then performs sedimentation, so as to fully extract the light components in the liquid phase, fully separate the liquid phase, and obtain as much microwave cracking raw material as possible, thereby improving the olefin yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The invention provides an implementation of a system for preparing light olefins.

[0027] Description of Reference Numerals

[0028] 1-heater, 2-cyclone separator, 3-microwave cracking unit, 4-extraction tower, 5-sedimentation tower, 6-solvent recovery tower, 7-supercritical extraction unit, 8-fluidized reactor, 9-catalyst regenerator, 10-catalytic cracking unit. DETAILED DESCRIPTION

[0029] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0030] In the present invention, "crude oil" refers to unrefined petroleum unless otherwise specified. API value (also called API gravity) can usually be used to characterize the relative density of petroleum (crude oil) and petroleum products (such as refined petroleum, etc.). As the API value increases, the relative density of crude oil decreases.

[0031] In the present invention, unless otherwise specified, "low-carbon olefins" refer to olefins with carbon atoms of 4 or less, including ethylene, propylene, butene and butadiene.

[0032] The first aspect of the present invention provides a method for preparing light olefins, the method comprising:

[0033] (1) vaporizing the crude oil to obtain a gas phase and a liquid phase;

[0034] (2) subjecting the liquid phase to supercritical extraction and sedimentation to obtain extracted oil, sedimentation oil and asphalt;

[0035] (3) subjecting the gas phase, the extracted oil and the water vapor to microwave cracking in the presence of an electromagnetic wave absorber to obtain microwave cracking gas;

[0036] (4) catalytically cracking the sedimentation oil to obtain catalyst cracking gas;

[0037] (5) Separating the microwave cracking gas and / or catalytic cracking gas to obtain light olefins.

[0038] According to the present invention, preferably, the feedstock oil is crude oil; more preferably, the API of the feedstock oil is greater than 10 (for example, 10, 20, 23, 25, 29, 30, 35, 40, 50, 60, 70, 80, 90, 100, 150, 200, 300, 400, and a range formed by any two of the above points), preferably 15-80.

[0039] According to the present invention, preferably, the feedstock oil includes at least one of light naphtha, naphtha, diesel, hydrogenated tail oil, light crude oil, crude oil with a final distillation point higher than 600°C and lower than 700°C, and dehydrated crude oil. More preferably, the feedstock oil includes diesel, hydrogenated tail oil, light crude oil, dehydrated crude oil with a final distillation point higher than 600°C and lower than 700°C.

[0040] According to the present invention, preferably, the vaporization method includes: heating the feedstock oil to 240-500°C (for example, 240°C, 300°C, 330°C, 350°C, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, and the range formed by any two of the above points), and then performing gas-liquid separation. The heating method may be electric heating. The gas-liquid separation may be performed in a cyclone separator, and the cyclone separator is selected from a volute cyclone separator, an axial flow guide vane cyclone separator, a straight cyclone separator, a cone-tube combined cyclone separator or a direct-flow cyclone separator; preferably, the cyclone separator is provided with internal components, and the internal components include a skimmer located at the top of the cyclone separator and / or an isolation plate and a vortex preventer at the bottom of the cyclone separator.

[0041] According to the present invention, preferably, the separation conditions of the cyclone separator make the gas phase separation efficiency greater than 20% (for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 99%, and the range composed of any two of the above points), more preferably greater than 30%, and further preferably 40-80%. In the present invention, the separation efficiency refers to the proportion of the weight of the gas phase separated from the crude oil to the total weight of the crude oil. A separation efficiency of 20% means: 20g of gas phase is separated from 100g of crude oil. The separation conditions of the cyclone separator can be adjusted according to conventional methods in the art, as long as the light component separation efficiency can meet the requirements.

[0042] In the present invention, the "cyclone separator" refers to a cyclone separator in a broad sense, including both a "cyclone separator" in a narrow sense and a separation device with similar principles in the art, such as a cyclone separator. Unless otherwise specified, the cyclone separators mentioned in the present invention are all cyclone separators in a broad sense.

[0043] According to the present invention, the cyclone separator for cyclone separation can be any cyclone separator conventionally used in the art, as long as it can separate crude oil at a temperature of 120-500° C. and the separation efficiency is above 20%.

[0044] The number of cyclone separators can be selected as required, and one or more cyclone separators can be included. When multiple cyclone separators are included, the multiple cyclone separators can be connected in parallel or in series.

[0045] In the present invention, unless otherwise specified, the external heating heat source in each step adopts electrical energy.

[0046] According to the present invention, preferably, the extraction solvent used in the supercritical extraction is a C1-C5 alkane, and more preferably, the extraction solvent includes at least one of propane, n-butane, isobutane, n-pentane and isopentane. Further preferably, the extraction solvent is n-butane and isobutane, wherein the weight ratio of n-butane to isobutane is 0.5-2:1 (for example, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.5:1, 2:1, and the range of any two of the above points). Using a specific weight ratio of n-butane and isobutane as the extraction solvent can separate more light components in the liquid phase, thereby further improving the utilization rate of the crude oil.

[0047] According to the present invention, preferably, the conditions of the supercritical extraction include: a weight ratio of the extraction solvent to the liquid phase of 0.1-10:1 (for example, 0.1:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and a range consisting of any two of the above), preferably 2-6:1, the pressure of the extraction tower is 1-8MPa (1MPa, 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, and a range consisting of any two of the above), and the temperature of the extraction tower is 80-180°C (for example, 80°C, 100°C, 120°C, 140°C, 150°C, 160°C, 170°C, 180°C, and a range consisting of any two of the above).

[0048] According to the present invention, preferably, the sedimentation conditions include: heating the top component of the extraction tower to 150-200°C (for example, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, and a range formed by any two of the above points), and then sending it into a sedimentation tower for sedimentation, obtaining a mixture of solvent and extract oil at the top of the sedimentation tower, and obtaining sedimentation oil at the bottom of the sedimentation tower.

[0049] According to the present invention, preferably, the method further comprises recovering the solvent from the top component of the settling tower to obtain the extracted oil and the solvent, wherein the solvent is cooled and then recycled. The solvent recovery method can be the solvent recovery method commonly used in the art, for example, the top component of the settling tower is heated and then sent to the solvent recovery tower to recover the solvent. The solvent is obtained at the top of the solvent recovery tower, and the extracted oil is obtained at the bottom of the solvent recovery tower.

[0050] In a preferred embodiment, the present invention converts the crude oil into a gas phase (the boiling point of the gas phase is <280°C) and a liquid phase by vaporization, and the liquid phase is subjected to supercritical extraction and sedimentation to obtain extracted oil and sedimented oil, wherein the gas phase and the extracted oil are mixed with water vapor and then enter a microwave cracking device for microwave cracking. Vaporization obtains a lighter crude oil fraction and a heavier crude oil fraction, wherein the heavier crude oil fraction is subjected to supercritical extraction to remove components such as colloids that are not conducive to the generation of light olefins and are easy to coke, so that the properties of the crude oil fraction entering the microwave reactor can be effectively improved, which is beneficial to improving the yield of light olefins and extending the reactor operation cycle.

[0051] In the present invention, the electric energy used in each step is green electricity, which can achieve zero carbon emissions of the production device.

[0052] According to the present invention, preferably, the dielectric constant of the electromagnetic wave absorber is 1-20 Farads / meter, more preferably 5-15 Farads / meter. More preferably, the electromagnetic wave absorber is selected from at least one of silicon carbide, composite ferrite, ultrafine metal particles, and organic polymer nanomaterials. In the present invention, unless otherwise specified, the dielectric constant refers to the relative dielectric constant. The relative dielectric constant of silicon carbide used in the present invention is generally 9-11 Farads / meter.

[0053] According to the present invention, preferably, the average particle size of the absorbing material is 2-20 mm, more preferably 5-14 mm, and further preferably 5-10 mm.

[0054] According to the present invention, preferably, the temperature of the microwave cracking is 400-780° C. (e.g., 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., 700° C., 750° C., 780° C., and a range consisting of any two of the above, more preferably 600-750° C.), preferably 700-750° C. In the present invention, unless otherwise specified, the temperature of microwave cracking refers to the temperature at the outlet of the reactor.

[0055] According to the present invention, preferably, the residence time of the microwave pyrolysis is 0.05-1s (for example, 0.05s, 0.1s, 0.2s, 0.3s, 0.4s, 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, 10s, and a range consisting of any two of the above points), preferably 0.1-0.7s.

[0056] According to the present invention, preferably, the power of the microwave used in the microwave cracking is 6-6000KW (for example, 6KW, 100KW, 1000KW, 2000KW, 3000KW, 4000KW, 5000KW, 6000KW, and the range formed by any two of the above points), and more preferably 3000-5000KW. In the present invention, in order to achieve the above power, different magnetrons can be combined, and the greater the microwave power, the more magnetrons need to be combined. Microwave power refers to the total microwave power provided by the microwave cracking device to the reactor.

[0057] According to the present invention, preferably, the frequency of the microwaves used in the microwave lysis is 100-3500 MHz (e.g., 100 MHz, 500 MHz, 1000 MHz, 1500 MHz, 2000 MHz, 2500 MHz, 3000 MHz, and a range consisting of any two of the above), more preferably 1000-2500 MHz.

[0058] According to the present invention, in order to further improve the yield, water vapor can be supplemented during microwave cracking of the gas phase and the extracted oil. Preferably, the mixture of the gas phase and the extracted oil and the water vapor is subjected to microwave cracking. More preferably, the water-oil weight ratio of the microwave cracking is 0.05-2.5:1 (for example, 0.05:1, 0.2:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.5:1, 2:1, 2.5:1, and the range composed of any two of the above points), preferably 0.3-1.8:1. Wherein, the water-oil weight ratio refers to the weight ratio of water-oil in the mixture of the gas phase, the extracted oil and the water vapor.

[0059] According to the present invention, preferably, the weight ratio of the gas phase to the extracted oil is 1-5:1 (for example, 1:1, 2:1, 3:1, 4:1, 5:1, and a range consisting of any two of the above points).

[0060] According to the present invention, preferably, the temperature of the water vapor is 100-650° C. (for example, 100° C., 150° C., 180° C., 200° C., 220° C., 240° C., 250° C., 300° C., 350° C., 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., and a range formed by any two of the above), more preferably 180-520° C. In the present invention, unless otherwise specified, when the temperature of the water vapor is higher than 100° C., the water vapor is high-pressure water vapor, that is, the temperature of the water vapor is the saturation temperature of water vapor under high pressure.

[0061] The catalytic cracking gas produced in the catalytic cracking process and the cracking gas produced directly entering the cracking furnace enter the separation device for separation to obtain light olefins. Catalytic cracking is combined with vaporization treatment, supercritical extraction, sedimentation and steam cracking to effectively improve the yield of light olefins.

[0062] The present invention can further process the heavy components in the crude oil through catalytic cracking, so as to make full use of the heavy components and improve the yield of light olefins.

[0063] According to the present invention, preferably, the catalyst used in the catalytic cracking is a solid acid selective molecular sieve catalyst; preferably, the catalyst includes at least one of an MMC-1 catalyst, an MMC-2 catalyst, a CHP-1 catalyst, a CHP-2 catalyst, a CRP-1 catalyst, a CHP-S catalyst, a CIP-1 catalyst, a CIP-2 catalyst, a CIP-3 catalyst, a CIP-4 catalyst, a CIP-5 catalyst and a CIP-S catalyst. The different types of catalysts listed above are all industrialized catalysts and can be obtained commercially.

[0064] According to the present invention, preferably, the temperature of the catalytic cracking is 450-680°C.

[0065] According to the present invention, preferably, the amount of the catalyst used is such that the catalyst-oil ratio is 2-25:1 (for example, 2:1, 5:1, 7:1, 9:1, 11:1, 13:1, 15:1, 17:1, 19:1, 20:1, 25:1, and a range consisting of any two of the above), preferably 5-15:1.

[0066] According to the present invention, the fluidized reactor can adopt a conventional reactor in the prior art. Preferably, catalytic cracking is performed in a fluidized reactor, wherein the fluidized reactor comprises a riser and a bed reactor, and more preferably comprises a first riser, a second riser, a bed reactor and a stripper. The fluidized reactor in the present invention can refer to the reactor disclosed in CN201684585U. Wherein, the reactor heating heat source adopts electric heating.

[0067] According to the present invention, preferably, the outlet temperature of the first riser is 530-590°C (for example, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, and a range formed by any two of the above points), preferably 560-580°C.

[0068] According to the present invention, preferably, the outlet temperature of the second riser is 600-650°C (for example, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, and a range formed by any two of the above points), preferably 600-630°C.

[0069] According to the present invention, preferably, the product of the first riser, the product of the second riser and the steam generated by the stripper enter the bed reactor together; more preferably, the space velocity of the bed reactor is 2h -1 -10h -1 .

[0070] According to the present invention, microwave cracking gas and catalytic cracking gas can be mixed for separation, or separated separately. Preferably, the process of separating microwave cracking gas and / or catalytic cracking gas includes: sequentially introducing the cracking gas into a quencher and a cracking gas separation system to obtain products such as hydrogen, methane, ethylene, propylene, butadiene, gasoline, fuel oil and diesel. The cracking separation system can be a separation process commonly used in the art, such as a sequential separation process of LUMMUS.

[0071] According to the present invention, in order to further improve the yield of low-carbon hydrocarbons, preferably, the cracked gas is first heat exchanged, and then enters the quencher and the cracked gas separation system in sequence. Heat exchange of the cracked gas first can also reduce the coking phenomenon of the cracked gas during cooling and separation.

[0072] The second aspect of the present invention provides a system for preparing low-carbon hydrocarbons from crude oil, the system comprising: a feedstock oil vaporization unit, a supercritical extraction unit, a microwave cracking unit, a catalytic cracking unit and a cracking gas separation unit;

[0073] The feedstock oil vaporization unit is used to vaporize the feedstock oil to obtain a gas phase and a liquid phase;

[0074] The supercritical extraction unit is used to perform supercritical extraction and sedimentation on the liquid phase to obtain extracted oil, sedimentation oil and asphalt;

[0075] The microwave cracking unit is used to perform microwave cracking on the gas phase, the extracted oil and the water vapor to obtain microwave cracking gas;

[0076] The catalytic cracking unit is used to catalytically crack the sedimentation oil to obtain catalyst cracking gas;

[0077] The cracking gas separation unit is used to separate microwave cracking gas and / or catalytic cracking gas to obtain light olefins.

[0078] According to the present invention, preferably, the microwave cracking unit comprises a tubular reactor and a microwave generator fixed outside the tubular reactor, wherein the tubular reactor can be arranged along the fluid direction.

[0079] According to the present invention, preferably, the feedstock oil vaporization unit comprises a heating device and a cyclone separator. More preferably, the cyclone separator is selected from at least one of a volute cyclone separator, an axial flow guide vane cyclone separator, a straight cyclone separator, a cone-tube combined cyclone separator and a direct-flow cyclone separator. More preferably, the cyclone separator is provided with internal components, and the internal components include a skimmer located at the top of the cyclone separator and / or an isolation plate and a vortex preventer at the bottom of the cyclone separator.

[0080] According to the present invention, preferably, the catalytic cracking unit comprises a fluidized reactor, wherein the fluidized reactor comprises a riser and a bed reactor, preferably comprises a first riser, a second riser, a bed reactor and a stripper.

[0081] According to the present invention, preferably, the catalytic cracking unit further comprises a catalyst regenerator, and the catalyst regenerator is used to regenerate the catalyst.

[0082] The third aspect of the present invention provides the use of the above-mentioned system in the preparation of light olefins, especially in the preparation of light olefins by direct cracking of crude oil.

[0083] A fourth aspect of the present invention provides the above-described method and / or application of the above-described system in improving the target product yield, selectivity and operation cycle of preparing light olefins by direct cracking of crude oil.

[0084] According to a particularly preferred embodiment of the present invention, the method for preparing light olefins comprises:

[0085] (1) The dehydrated and desalted crude oil is preheated to 320-330°C by electric heating to become preheated crude oil. The preheated crude oil is sent to a vaporizer with internal components for gas-liquid separation to obtain a gas phase and a liquid phase, wherein the vaporizer is a guide vane cyclone separator, and the separation efficiency of the cyclone separator is 50-55%.

[0086] (2) The liquid phase is sent to a supercritical extraction unit for separation to obtain extracted oil, sedimentation oil and asphalt; wherein the supercritical extraction unit comprises an extraction tower, a sedimentation tower and a solvent recovery tower connected in sequence. The liquid phase enters the upper part of the extraction tower, and the extraction solvent enters the lower part of the extraction tower. The liquid phase and the extraction solvent are countercurrently contacted in the extraction tower. The extraction solvent extracts the non-asphalt part in the liquid phase and draws it out from the top of the extraction tower, and the asphalt phase is discharged from the bottom of the extraction tower; wherein the extraction solvent is n-butane and isobutane in a weight ratio of 1-1.5:1, the weight ratio of the extraction solvent to the liquid phase is 3-4:1, the extraction tower pressure is 4-5MPa, and the extraction tower temperature is 140-150°C. The extraction solvent and the non-asphalt part drawn out from the top of the tower are heated to 160-170°C and then enter the sedimentation tower, the extraction solvent and the extracted oil are drawn out from the top of the tower, and the sedimentation oil is drawn out from the bottom of the tower. The extraction solvent and extraction oil drawn out from the top of the sedimentation tower are heated to 180-190°C and enter the solvent recovery tower, where the extraction solvent and extraction oil are separated. After the solvent is drawn out from the top of the tower, the temperature is lowered to 140-150°C for recycling, and the extraction oil is drawn out from the bottom of the tower.

[0087] (3) The gas phase, the extracted oil and the water vapor are sent to a microwave cracking unit for microwave cracking to obtain microwave cracking gas. The microwave cracking unit includes a tubular reactor and a microwave generator. The tubular reactor is filled with an electromagnetic wave absorber. In the presence of the electromagnetic wave absorber, the mixture of the gas phase, the extracted oil and the water vapor is cracked. The temperature of the water vapor is 200-220°C, the water-oil weight ratio of the mixture of the gas phase, the extracted oil and the water vapor is 0.7-1, and the weight ratio of the gas phase to the extracted oil is 3-3.5:1. The temperature of the microwave cracking reaction is 730-750°C, the electromagnetic wave absorber is silicon carbide (particle size is 0.5-1cm), the residence time is 0.5-0.6s, the corresponding microwave power in the reactor is 4500-5000KW, and the microwave frequency is 2000-2500MHz.

[0088] (4) The sedimentation oil is sent to a catalytic cracking unit for steam catalytic cracking to obtain catalytic cracking gas. The catalyst used in the catalytic cracking unit is a solid acid molecular sieve catalyst CHP-1 catalyst, and the catalyst-to-oil ratio is 11-14. The catalytic cracking unit includes a first riser, a second riser, a steam stripper and a bed reactor. The liquid phase is divided into two parts and enters the first riser and the second riser respectively. The steam stripper produces water vapor, and the products of the first riser and the second riser enter the bed reactor together with the water vapor. Among them, the outlet temperature of the first riser is 560-570°C, the outlet temperature of the second riser is 600-610°C, and the air velocity of the bed reactor is 5-6.2h -1 .

[0089] (6) After the microwave cracking gas is mixed with the catalytic cracking gas, it passes through a quencher and a cracking gas separation system (using the LUMMUS sequential separation process) to separate hydrogen, light olefins, cracking gasoline, cracking diesel and cracking fuel oil.

[0090] The present invention will be described in detail below by way of examples. In the following examples,

[0091] The cracking furnace used in Comparative Example 1 is a CBL-III cracking furnace (purchased from China Petrochemical Corporation).

[0092] The composition of the crude oil (API of the crude oil is 33.5) used in the following examples and comparative examples is shown in Table 1, and the composition is measured according to the ASTM D5307 method.

[0093] Table 1

[0094]

[0095]

[0096] Example 1

[0097] use Figure 1 The system shown is used to crack crude oil to produce light olefins.

[0098] (1) The dehydrated and desalted crude oil is preheated to 330°C by electric heating to become preheated crude oil. The preheated crude oil is sent to a vaporizer with internal components for gas-liquid separation to obtain a gas phase (the boiling point of the gas phase is less than 280°C) and a liquid phase, wherein the vaporizer is a guide vane cyclone separator, and the separation efficiency of the cyclone separator is 55%.

[0099] (2) The liquid phase is sent to a supercritical extraction unit for separation to obtain extracted oil, sedimentation oil and asphalt; wherein the supercritical extraction unit includes an extraction tower, a sedimentation tower and a solvent recovery tower connected in sequence. The liquid phase enters the upper part of the extraction tower, and the extraction solvent enters the lower part of the extraction tower. The liquid phase and the extraction solvent are countercurrently contacted in the extraction tower. The extraction solvent extracts the non-asphalt part in the liquid phase and draws it out from the top of the extraction tower, and the asphalt phase is discharged from the bottom of the extraction tower; wherein the extraction solvent is n-butane and isobutane in a weight ratio of 1:1, the weight ratio of the extraction solvent to the liquid phase is 3:1, the extraction tower pressure is 4.0 MPa, and the extraction tower temperature is 150°C. The extraction solvent and the non-asphalt part drawn out from the top of the tower are heated to 162°C and then enter the sedimentation tower, the extraction solvent and the extracted oil are drawn out from the top of the tower, and the sedimentation oil is drawn out from the bottom of the tower. The extraction solvent and extraction oil drawn out from the top of the sedimentation tower are heated to 180°C and enter the solvent recovery tower, where the extraction solvent and extraction oil are separated. After the solvent is drawn out from the top of the tower, the temperature is lowered to 150°C for recycling, and the extraction oil is drawn out from the bottom of the tower.

[0100] (3) The gas phase, the extracted oil and the water vapor are sent to a microwave cracking unit for microwave cracking to obtain microwave cracking gas. The microwave cracking unit includes a tubular reactor and a microwave generator. The tubular reactor is filled with an electromagnetic wave absorber. In the presence of the electromagnetic wave absorber, the mixture of the gas phase, the extracted oil and the water vapor is cracked. The temperature of the water vapor is 220°C, the water-oil weight ratio of the mixture of the gas phase, the extracted oil and the water vapor is 0.7, and the weight ratio of the gas phase to the extracted oil is 3.5:1. The temperature of the microwave cracking reaction is 750°C, the electromagnetic wave absorber is silicon carbide (particle size is 1 cm), the residence time is 0.6s, the corresponding microwave power in the reactor is 5000kw, and the microwave frequency is 2000MHz.

[0101] (4) The sedimentation oil is sent to a catalytic cracking unit for steam catalytic cracking to obtain catalytic cracking gas. The catalyst used in the catalytic cracking unit is a solid acid molecular sieve catalyst CHP-1 catalyst, and the catalyst-to-oil ratio is 11.8. The catalytic cracking unit includes a first riser, a second riser, a steam stripper and a bed reactor. The liquid phase is divided into two parts and enters the first riser and the second riser respectively. The steam stripper produces water vapor, and the products of the first riser and the second riser enter the bed reactor together with the water vapor. Among them, the outlet temperature of the first riser is 568°C, the outlet temperature of the second riser is 606°C, and the air velocity of the bed reactor is 6.2h -1 .

[0102] (6) After the microwave cracking gas is mixed with the catalytic cracking gas, it passes through a quencher and a cracking gas separation system (using the sequential separation process of LUMMUS) to separate hydrogen, light olefins, cracking gasoline, cracking diesel and cracking fuel oil. Among them, the yield of ethylene is 26.9wt%, the yield of propylene is 15.8wt%, the yield of 1,3-butadiene is 4.8wt%, and the total yield of the above trienes is 47.5wt%.

[0103] The operation cycle of the microwave cracking unit (tubular reactor) is 56 days.

[0104] Comparative Example 1

[0105] In this comparative example 1, only a conventional cracking furnace was used for cracking.

[0106] The dehydrated and desalted crude oil is directly sent to the cracking furnace, and after passing through the convection section, it directly enters the radiation section. The operating parameters of the radiation section are the furnace tube outlet temperature of 760℃, the residence time of 0.1s, and the water-oil ratio of 1:1; cracking is carried out. The cracking gas adopts the LUMMUS sequential separation process.

[0107] Analysis of the steam cracking reaction products 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%.

[0108] The operating cycle is 5 days.

[0109] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing light olefins, characterized in that: The method includes: (1) vaporizing the crude oil to obtain a gas phase and a liquid phase; (2) subjecting the liquid phase to supercritical extraction and sedimentation to obtain extracted oil, sedimentation oil and asphalt; (3) subjecting the gas phase, the extracted oil and the water vapor to microwave cracking in the presence of an electromagnetic wave absorber to obtain microwave cracking gas; (4) catalytically cracking the sedimentation oil to obtain catalyst cracking gas; (5) Separating the microwave cracking gas and / or catalytic cracking gas to obtain light olefins.

2. The method according to claim 1, wherein: The feedstock oil is crude oil; and / or, the API of the feedstock oil is greater than 10, preferably 15-80; Preferably, the feedstock oil includes at least one of light naphtha, naphtha, diesel, hydrogenated tail oil, light crude oil, crude oil with a final distillation point higher than 600° C. and lower than 700° C., and dehydrated and desalted crude oil.

3. The method according to claim 1, wherein: The vaporization method includes: heating the crude oil to 240-500° C. and then performing gas-liquid separation.

4. The method according to claim 1, wherein: The extraction solvent used in the supercritical extraction is a C1-C5 alkane, preferably, the extraction solvent includes at least one of propane, n-butane, isobutane, n-pentane and isopentane; Preferably, the conditions of the supercritical extraction include: the weight ratio of the extraction solvent to the liquid phase is 0.1-10:1, preferably 2-6:1; the pressure of the extraction tower is 1-8 MPa, and the temperature of the extraction tower is 80-180°C; Preferably, the sedimentation conditions include: heating the top component of the extraction tower to 150-200° C. and then sending it to a sedimentation tower for sedimentation, obtaining a mixture of solvent and extraction oil at the top of the sedimentation tower and obtaining sedimentation oil at the bottom of the sedimentation tower.

5. The method according to claim 1, wherein: The electromagnetic wave absorber is selected from at least one of silicon carbide, composite ferrite, ultrafine metal particles and organic high molecular polymer nanomaterials.

6. The method according to claim 1, wherein: The temperature of the microwave pyrolysis is 400-780°C, preferably 700-750°C; And / or, the residence time of the microwave pyrolysis is 0.05-1s, preferably 0.1-0.7s; And / or, the power of the microwave used in the microwave pyrolysis is 6-6000KW, preferably 3000-5000KW; and / or, the water-to-oil weight ratio in the mixture of the gas phase, the extracted oil and the water vapor is 0.05-2.5:1, preferably 0.3-1.8:1; Preferably, the weight ratio of the gas phase to the extracted oil is 1-5:

1.

7. The method according to claim 1, wherein: The catalyst used in the catalytic cracking is a solid acid selective molecular sieve catalyst; the temperature of the catalytic cracking is 450-680°C; Preferably, the amount of the catalyst used is such that the catalyst-oil ratio is 2-25:1, preferably 5-15:

1.

8. The method according to claim 1, wherein: The catalytic cracking is carried out in a fluidized reactor, wherein the fluidized reactor comprises a riser and a bed reactor, preferably comprises a first riser, a second riser, a bed reactor and a stripper.

9. The method according to claim 8, wherein: The outlet temperature of the first riser is 530-590°C, preferably 560-580°C; and / or, the outlet temperature of the second riser is 600-650° C., preferably 600-630° C.; And / or, the product of the first riser, the product of the second riser and the steam generated by the stripper enter the bed reactor together; preferably, the space velocity of the bed reactor is 2h -1 -10h -1 .

10. A system for preparing light hydrocarbons from crude oil, characterized in that: The system includes: a crude oil vaporization unit, a supercritical extraction unit, a microwave cracking unit, a catalytic cracking unit and a cracking gas separation unit; The feedstock oil vaporization unit is used to vaporize the feedstock oil to obtain a gas phase and a liquid phase; The supercritical extraction unit is used to perform supercritical extraction and sedimentation on the liquid phase to obtain extracted oil, sedimentation oil and asphalt; The microwave cracking unit is used to perform microwave cracking on the gas phase, the extracted oil and the water vapor to obtain microwave cracking gas; The catalytic cracking unit is used to catalytically crack the sedimentation oil to obtain catalyst cracking gas; The cracking gas separation unit is used to separate microwave cracking gas and / or catalytic cracking gas to obtain light olefins.

11. Use of the system according to claim 10 in the preparation of light olefins, especially in the preparation of light olefins by direct cracking of crude oil.

12. Use of the method according to any one of claims 1 to 9, and / or the system according to claim 10, in improving the target product yield, selectivity and operation cycle of preparing light olefins by direct cracking of crude oil.

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