Method and system for preparing low-carbon olefin by cracking petroleum raw material and application thereof

Abstract

The invention relates to the technical field of low-carbon olefin preparation, and discloses a method and a system for preparing low-carbon olefin by cracking a petroleum raw material and application of the method and the system. According to the method provided by the invention, unrefined crude oil can be directly used as a raw material for preparing the low-carbon olefin, and the method has the characteristics of wide raw material source and low cost, and also has the advantages of high product yield, high production efficiency and the like, so that the method is very suitable for industrial popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of low-carbon olefin preparation, and in particular to a method and system for preparing low-carbon olefins by cracking petroleum raw materials and applications thereof. Background Art

[0002] Light olefins are one of the important organic raw materials in the chemical industry. Currently, one of the main methods for producing light olefins is to use naphtha and other petroleum refining products to produce them using a tubular cracking furnace steam cracking method. In order to reduce the raw material cost of light olefin production, in recent years, the process of directly cracking crude oil to produce light olefins has become one of the research hotspots in this field.

[0003] Researchers found that when crude oil is directly used as cracking raw material, some high molecular weight non-volatile components in crude oil accumulate in the cracking furnace, causing coking and even blockage in the radiation section, requiring frequent decoking of the cracking furnace, which seriously affects production efficiency and product yield. Although some low-carbon olefin preparation processes have been developed based on the characteristics of crude oil, the yield and selectivity of low-carbon olefins are still insufficient to meet the needs of industrial applications. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems that the product yield and selectivity of preparing light olefins by cracking petroleum raw materials in the prior art are insufficient, and when crude oil is used as a raw material and the existing method is directly used to prepare light olefins, coking and clogging of the reaction furnace tubes are easily generated, which has an adverse effect on the product yield and production efficiency, and the production cost is high by using refinery oil products such as naphtha, etc., and provide a method and system for preparing light olefins by cracking petroleum raw materials and their application. The method provided by the present invention has the advantages of high yield and high selectivity of light olefins, and solves the problems of fast coking of the cracking furnace, insufficient production efficiency and yield when crude oil is directly used as a production raw material, and can meet the needs of large-scale production.

[0005] In order to achieve the above object, the first aspect of the present invention provides a method for preparing light olefins by cracking petroleum raw materials, the method comprising the following steps:

[0006] (1) Vaporizing the petroleum raw material to obtain a vapor phase and a liquid phase;

[0007] (2) hydrogenating the liquid phase obtained in step (1) to obtain a hydrogenated light component and a hydrogenated heavy component;

[0008] (3) subjecting the mixture of the steam phase obtained in step (1) and the hydrogenated light component obtained in step (2) to microwave cracking to obtain microwave cracking gas.

[0009] A second aspect of the present invention provides a system for preparing light olefins, the system comprising a pretreatment unit and a microwave cracking unit, the pretreatment unit comprising a vaporization unit and a hydrogenation unit connected in sequence.

[0010] The third aspect of the present invention provides the use of the system described in the second aspect in the preparation of light olefins, especially in the preparation of light olefins directly using crude oil as raw material.

[0011] The fourth aspect of the present invention provides the use of the method described in the first aspect and / or the system described in the second aspect in improving the target product yield, selectivity and operation cycle of preparing light olefins by direct cracking of crude oil.

[0012] Through the above technical solution, the present invention can at least achieve the following beneficial effects:

[0013] (1) The method provided by the present invention can directly use crude oil as raw material. Compared with the traditional process using crude oil refining products such as naphtha as raw materials, the present invention greatly reduces the production cost. In addition, the method effectively solves the problem of easy coking of the reaction tube when preparing light olefins using crude oil as raw material, can be operated for a long time, improves production efficiency, reduces the production cost caused by stopping to clean and maintain the cracking furnace, and is easier to manage, suitable for industrial production and promotion.

[0014] (2) The present invention uses a combination of vaporization and hydroprocessing to efficiently obtain light components that can be used to prepare low-carbon olefins from petroleum raw materials, and then combines microwave treatment to crack the light components, which has higher production efficiency and reduces the emission of harmful substances such as waste gas and waste residue. The process is more environmentally friendly and meets the needs of green and sustainable development. In addition, the microwave treatment method has the advantages of high heating efficiency, low cracking temperature, and further improved product selectivity, which can further improve the yield of the target product. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the system used in Example 1.

[0016] Description of Reference Numerals

[0017] 1-preheating unit; 2-vaporization unit; 3-microwave cracking unit; 4-hydrogenation treatment device; 5-(hydrogenation product) separation device (ie, first separation device); 6-hydrogen refining device; 7-hydrogenation unit. DETAILED DESCRIPTION

[0018] 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.

[0019] In the present invention, unless otherwise specified, "petroleum raw materials" refers to raw materials for the preparation of light olefins based on petroleum, such as unrefined petroleum and various petroleum products obtained through refining. "Crude oil" refers to unrefined petroleum. The relative density of petroleum raw materials can usually be characterized by API value (also called API degree). As the API value increases, the relative density of crude oil decreases.

[0020] 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.

[0021] In the present invention, unless otherwise specified, when the temperature of 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.

[0022] In the present invention, the numbering of the operation methods (for example, "first", "second", etc. in the first separation and the second separation) is only used to facilitate the distinction between similar operations in different steps or processing processes in the description, and has no limiting effect on the specific operation methods and conditions and the operation sequence in the actual process.

[0023] The method of producing low-carbon olefins by direct cracking of crude oil can significantly reduce the cost of raw materials and has become a hot topic in this field. However, if crude oil is directly used to replace the existing cracking process for production of refining products such as naphtha, not only the yield and selectivity of low-carbon olefins are not ideal, but also the high molecular weight non-volatile components contained in the crude oil enter the cracking furnace radiation section, causing the cracking furnace to coke or even block, resulting in problems such as low production efficiency, and serious equipment damage may also occur, not only delaying production, but also causing additional equipment replacement and maintenance costs. In addition, the current cracking process mainly uses the mode of burning fuel in the furnace to provide heat for the reaction, resulting in waste gas emissions such as carbon dioxide, carbon monoxide, nitrogen oxides and sulfides, which makes the environmental protection pressure of the production enterprise greater.

[0024] The inventor of the present invention found in the research process that although crude oil is first subjected to certain pretreatment, after separating the light components for the production of light olefins, the light components are then subjected to heating and cracking treatment to achieve the purpose of preparing light olefins using crude oil as raw material, but the yield and selectivity are still to be improved. Moreover, the temperature of thermal cracking treatment is usually high, which makes the reaction energy consumption huge, and also causes a large amount of carbon emissions and harmful waste gas emissions, which cannot meet the needs of green sustainable development. After long-term research, the inventor cleverly found that after separating the light components that can be used for the production of light olefins in petroleum raw materials in a specific way, the light component cracking combined with the method of microwave treatment can effectively improve the target product yield and selectivity of preparing light olefins using crude oil as raw material, and the reaction tube coking speed is also relatively slow during the preparation process, and it can be operated for a long time. Moreover, by adopting the method of microwave treatment, microwave energy is used as a heat source on the one hand, and heating is carried out from the inside of the material, which can greatly reduce the cracking temperature, thereby reducing energy consumption, and on the other hand, the selective heating of microwaves also has a promoting effect on the selective improvement of cracking reaction products, which can improve the yield of light olefins such as ethylene and propylene. Moreover, the heating speed of heating by microwave radiation is fast and no exhaust gas is produced, which is more environmentally friendly than traditional processes. In addition, since the heating target of the microwave heating method directly becomes the heating body, there is no need to go through the process of heat conduction during the heating process, thereby increasing the heating speed and further improving production efficiency. The inventors also found that because the atoms and molecules of the substance will vibrate at high speed under the action of microwaves, a more favorable environment is established for chemical reactions, making the reaction conditions milder and improving production safety.

[0025] Based on the above findings, the first aspect of the present invention provides a method for preparing light olefins by cracking petroleum feedstock, the method comprising the following steps:

[0026] (1) Vaporizing the petroleum raw material to obtain a vapor phase and a liquid phase;

[0027] (2) hydrogenating the liquid phase obtained in step (1) to obtain a hydrogenated light component and a hydrogenated heavy component;

[0028] (3) subjecting the mixture of the steam phase obtained in step (1) and the hydrogenated light component obtained in step (2) to microwave cracking to obtain microwave cracking gas.

[0029] The present invention has no particular restrictions on the specific selection of the petroleum raw material used in step (1), and any petroleum raw material that can obtain light components for preparing light olefins by microwave cracking can be applicable to the present invention. In order to obtain a higher yield of light olefins, according to a preferred embodiment of the present invention, wherein, in step (1), the API value of the feedstock oil is not less than 18, preferably not less than 20, and more preferably not less than 22. For example, the API value of the feedstock oil can be 22-45 (for example, it can be 22, 25, 30, 35, 40, 45, or it can be any intermediate value of any two of the above values), preferably 25-35.

[0030] Any petroleum or petroleum product whose API value meets the above requirements can be used as a petroleum raw material and is applicable to the present invention. According to some preferred embodiments of the present invention, wherein, in step (1), the petroleum raw material is selected from at least one of (unrefined) crude oil, light naphtha, naphtha, diesel and hydrogenated tail oil.

[0031] Preferably, the crude oil is selected from at least one of 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.

[0032] In the present invention, there is no particular limitation on the specific methods and operating conditions of the vaporization treatment in step (1) and the hydrogenation treatment in step (2). Any vaporization and hydrogenation method in the art that can process the above-mentioned petroleum raw materials, especially crude oil, and obtain light components that can be used for microwave cracking to prepare low-carbon olefins can be applied to the present invention.

[0033] In the present invention, vaporization refers to a treatment method of heating a liquid material (under a certain pressure) to a vaporization point and converting it into a gaseous substance. Any method in the art that can achieve the above purpose can be applied to the present invention. According to a preferred embodiment of the present invention, the vaporization method includes: mixing the material to be treated with water vapor and then vaporizing it to obtain a vapor phase and a liquid phase.

[0034] Preferably, during the vaporization process, the weight ratio of the water vapor to the petroleum raw material is 0.5-1.5:1.

[0035] According to a preferred embodiment of the present invention, the petroleum raw material and / or water vapor can be preheated before the vaporization treatment. Preferably, the petroleum raw material can be preheated to 150-350°C. Preferably, it is 150-250°C. For example, it can be 150°C, 180°C, 200°C, 220°C, 250°C, or any intermediate value between any two of the above values. Preferably, the water vapor can be preheated to 150-350°C. Preferably, it is 150-250°C. For example, it can be 150°C, 180°C, 200°C, 220°C, 250°C, or any intermediate value between any two of the above values. Preferably, the preheating temperature of the water vapor and the petroleum raw material is the same.

[0036] According to a preferred embodiment of the present invention, the vaporization treatment is carried out in a manner selected from at least one of steam stripping, flash evaporation and cyclone separation.

[0037] The inventors of the present invention also found in their research that if the flash evaporation method is used to process petroleum raw materials, especially crude oil, at least 5% of the hydrocarbon raw materials that can be used to prepare light olefins usually remain in the liquid phase after vaporization, which affects the total yield of light olefins and also causes a waste of raw materials. After a large number of experiments, the inventors found that the cyclone separation method can incorporate more hydrocarbon raw materials into the vapor phase, thereby obtaining a higher overall yield of light olefins.

[0038] Based on the above findings, according to a preferred embodiment of the present invention, the vaporization treatment is carried out by cyclone separation.

[0039] Preferably, the conditions for the cyclone separation include: a temperature of 150-400°C and a separation efficiency of not less than 50%. The separation efficiency refers to the weight of the light components separated from the petroleum raw materials for subsequent treatment as a proportion of the weight of the feed petroleum raw materials. For example, a separation efficiency of 20% means: 100g of the feed petroleum raw materials, 20g of the light components are finally separated.

[0040] Preferably, the separation efficiency of the cyclone separation is 65-80%.

[0041] For example, the temperature of the cyclone separation can be 150°C, 180°C, 200°C, 220°C, 250°C, 280°C, 300°C, 320°C, 350°C, 380°C, 400°C, or any intermediate value between any two of the above values.

[0042] For example, the separation efficiency of the cyclone separation may be 65%, 68%, 70%, 72%, 75%, 78%, 80%, or any intermediate value between any two of the above values.

[0043] In the present invention, hydrogenation refers to a process of hydrotreating a petroleum raw material (especially a heavy component in which light olefins cannot be obtained by cracking) to obtain a hydrogenated light component that can be used for the preparation of light olefins. Any method that can achieve this purpose can be applied to the present invention. According to a preferred embodiment of the present invention, the hydrogenation method includes: mixing the material to be treated with hydrogen, and then hydrotreating it in the presence of a catalyst to obtain a light component after hydrogenation and a heavy component after hydrogenation.

[0044] Preferably, the hydroprocessing method is selected from at least one of catalytic hydrogenation, residue hydrogenation and hydrocracking.

[0045] Preferably, during the hydrotreatment, the volume ratio of hydrogen to liquid phase is 2-5:1, preferably 2.5-3.5:1.

[0046] According to some preferred embodiments of the present invention, the conditions of the hydrotreatment include: temperature 200-300°C, pressure 2-3MPa, liquid phase volume space velocity 1.5-3h -1 The conditions of the hydrogenation treatment are preferably such that the monoolefin hydrogenation rate is not less than 90%, for example, it may be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.2%, 99.5%, 99.8%, 99.9%, 100%, or any intermediate value between any two of the above values.

[0047] For example, the temperature of the hydrotreatment can be 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 285°C, 290°C, 295°C, 300°C, or any intermediate value between any two of the above values.

[0048] For example, the pressure of the hydrotreatment may be 2 MPa, 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, 2.9 MPa, or 3 MPa, or any intermediate value between any two of the above values.

[0049] For example, the liquid phase volumetric space velocity of the hydroprocessing process may be 1.5 h -1 , 1.8h -1 , 2h -1 , 2.2h -1 , 2.5h -1 , 2.8h -1 , 3h -1 , or it can be any intermediate value between any two of the above values.

[0050] Preferably, the method further comprises the operations of first separating the product obtained after the hydrotreatment to remove heavy components, and refining hydrogen to obtain light components and circulating hydrogen.

[0051] Any catalyst that can be used for petroleum hydrofining can be applied to the method provided by the present invention. For example, the present invention can use Co-Ni-Mo / Al2O3 catalyst (such as a self-prepared catalyst or a commercially available catalyst having such composition characteristics) to carry out the above-mentioned hydroprocessing.

[0052] According to some preferred embodiments of the present invention, the liquid phase is preheated before the hydrotreatment, preferably to 120-360° C., preferably 180-280° C., for example, 180° C., 200° C., 220° C., 250° C., 280° C., or any intermediate value between any two of the above values.

[0053] According to a preferred embodiment of the present invention, the method further comprises performing a first separation on the obtained hydroprocessed product after the hydroprocessing to remove the heavy components after the hydrogenation, and performing hydrogen refining on the obtained product to obtain light components and circulating hydrogen. The present invention has no particular restrictions on the separation method and the specific hydrogen refining method used in the first separation, and any method in the art that can achieve the above purpose can be applied to the present invention.

[0054] In the present invention, "microwave cracking" refers to the process of thermal cracking of the light components obtained by the above pretreatment under the action of microwaves. The present invention has no particular restrictions on the specific microwave cracking treatment method and conditions, as long as the light components obtained by the pretreatment can be converted into light olefins.

[0055] In order to obtain a higher yield of light olefins and improve the reaction efficiency, according to a preferred embodiment of the present invention, in step (3), the microwave cracking method includes: subjecting the vapor phase obtained in step (1) and the mixture of hydrogenated light components obtained in step (2) to microwave cracking reaction in the presence of an absorbing material and optional water vapor to obtain microwave cracking gas. "Optional" means that water vapor is not a necessary raw material for the microwave cracking process, and it can be added or not according to actual needs.

[0056] Preferably, the absorbing material is selected from at least one of silicon carbide, composite ferrite and organic high molecular polymer nanomaterial. More preferably, the particle size of the absorbing material is 2-20 mm, preferably 5-14 mm. "Composite ferrite" is a material with special structure and properties, usually composed of two or more oxides, which is mainly composed of two main parts: lattice and magnetic ions, wherein the lattice is composed of oxide ions, and the magnetic ions are mainly provided by transition metal ions. By selecting a composite ferrite composed of specific oxides, an absorbing material with better performance can be formed. "Organic high molecular polymer nanomaterial" can also be called "functional polymer nanomaterial", which usually refers to a polymer nanomaterial with certain functionality. In the present invention, a functional polymer nanomaterial with absorbing properties can be selected as an absorbing material in the microwave cracking process, for example, polystyrene absorbing materials, polypropylene absorbing materials, etc. can be selected.

[0057] Preferably, the conditions of the microwave cracking reaction include: cracking temperature 450-850°C, residence time 0.05-1s, preferably microwave power in the reactor is 2-12000kW, and preferably microwave frequency is 100-3500MHz.

[0058] For example, the cracking temperature can be 450°C, 480°C, 500°C, 520°C, 550°C, 580°C, 600°C, 620°C, 650°C, 680°C, 700°C, 720°C, 750°C, 780°C, 800°C, 820°C, 850°C, or any intermediate value between any two of the above values.

[0059] For example, the residence time can be 0.05s, 0.1s, 0.15s, 0.2s, 0.25s, 0.3s, 0.35s, 0.4s, 0.45s, 0.5s, 0.55s, 0.6s, 0.65s, 0.7s, 0.75s, 0.8s, 0.85s, 0.9s, 0.95s, 1s, or any intermediate value between any two of the above values.

[0060] For example, the microwave power in the reactor can be 2 kW, 10 kW, 50 kW, 100 kW, 300 kW, 500 kW, 800 kW, 1000 kW, 1500 kW, 2000 kW, 2500 kW, 3000 kW, 3500 kW, 4000 kW, 4500 kW, 5000 kW, 5500 kW, 6000 kW, 6500 kW, 7000 kW, 7500 kW, 8000 kW, 8500 kW, 9000 kW, 9500 kW, 10000 kW, 10500 kW, 11000 kW, 11500 kW, 12000 kW, or any intermediate value between any two of the above values.

[0061] For example, the microwave frequency can be 100 MHz, 300 MHz, 500 MHz, 800 MHz, 1000 MHz, 1200 MHz, 1500 MHz, 1800 MHz, 2000 MHz, 2200 MHz, 2500 MHz, 2800 MHz, 3000 MHz, 3200 MHz, 3500 MHz, or any intermediate value between any two of the above values.

[0062] Preferably, the microwave power is 1000-10000 kW, and the microwave frequency is 1000-2500 MHz.

[0063] According to a preferred embodiment of the present invention, the optional water vapor temperature is 100-650°C, preferably 180-520°C (for example, it can be 180°C, 200°C, 220°C, 250°C, 280°C, 300°C, 320°C, 350°C, 380°C, 400°C, 420°C, 450°C, 480°C, 500°C, 520°C, or any intermediate value between any two of the above values).

[0064] Preferably, the weight ratio of the optional water vapor to light components is 0.1-2:1, preferably 0.4-1.5:1.

[0065] The inventors of the present invention accidentally discovered during research that the yield of light olefins can be further improved by adjusting the treatment conditions of microwave cracking according to different pretreatment methods.

[0066] According to a particularly preferred embodiment of the present invention, the method comprises:

[0067] (1) Vaporization treatment: mixing the crude oil with water vapor and then vaporizing it to obtain a vapor phase and a liquid phase. The vaporization treatment includes: passing the mixture of the crude oil and water vapor into a cyclone separator and performing cyclone separation under the condition that the separation efficiency is not less than 65%;

[0068] (2) Hydrogenation treatment: The liquid phase obtained in step (1) is mixed with hydrogen and subjected to hydrogenation treatment in the presence of a catalyst to obtain a hydrogenated light component and a hydrogenated heavy component. The conditions of the hydrogenation treatment include: a hydrogen-to-oil ratio (i.e., a volume ratio of hydrogen to liquid phase) of 2.8-3.2:1, a temperature of 255-270°C, a pressure of 2.6-2.8 MPa, and a liquid phase volume space velocity of 1.8-2.2 h / min. -1 ;

[0069] (3) Microwave cracking: the vapor phase obtained in step (1) and the hydrogenated light component obtained in step (2) are mixed in a weight ratio of 0.5-1:1, and a microwave cracking reaction is carried out in the presence of a microwave absorbing material and optionally water vapor to obtain a microwave cracked gas, wherein the conditions of the microwave cracking reaction include: a temperature of 750-800° C., a residence time of 0.5-0.8 s, a microwave power of 3000-8000 kW, and a microwave frequency of 2000-3000 MHz; the API value of the mixture of the vapor phase and the hydrogenated light component is 3-30 higher than that of the petroleum feedstock (the API difference between the mixture and the petroleum feedstock may be 3, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, or any intermediate value between any two of the above values).

[0070] Preferably, in step (1), the feedstock oil is preheated to 200-250°C before mixing with the steam. For example, the feedstock oil can be preheated to 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, or any intermediate value between any two of the above values.

[0071] Preferably, in step (1), the temperature of the water vapor is 200-250° C. Preferably, the temperature of the water vapor is the same as the temperature of the preheated feedstock oil. For example, the temperature of the water vapor can be 200° C., 210° C., 220° C., 230° C., 240° C., 250° C., or any intermediate value between any two of the above values.

[0072] More preferably, the weight ratio of water vapor to feedstock oil is 0.5-1: 1. For example, it may be 0.5: 1, 0.6: 1, 0.7: 1, 0.8: 1, 0.9: 1, 1: 1, or any intermediate ratio between any two of the above ratios.

[0073] Preferably, in step (1), the temperature of the cyclone separation is 300-320°C.

[0074] Preferably, in step (2), the conditions of the hydrogenation treatment are such that the hydrogenation rate of monoolefins in the liquid phase reaches 92% or more, preferably 92-98%.

[0075] Preferably, in step (3), the absorbing material is silicon carbide (preferably with a particle size of 5-10 mm).

[0076] Preferably, in step (3), the weight ratio of the steam phase to the light components after hydrogenation is 0.7-0.9:1.

[0077] Preferably, in step (3), the microwave power of the microwave cracking reaction is 5000-8000 kW (for example, it can be 5000 kW, 5500 kW, 6000 kW, 6500 kW, 7000 kW, 7500 kW, 8000 kW, or any intermediate value between any two of the above values).

[0078] Preferably, in step (3), the microwave frequency of the microwave pyrolysis reaction is 2000-2500 MHz.

[0079] Preferably, in step (3), the optional amount of water vapor is such that the water-to-oil ratio of microwave cracking (i.e., the weight ratio of water vapor to the mixture of steam phase and light components after hydrogenation) is 0.5-2:1.

[0080] Preferably, in step (3), the temperature of the water vapor is 260-320°C.

[0081] According to a preferred embodiment of the present invention, the method further comprises:

[0082] (4) performing a second separation on the microwave cracking gas obtained in step (3) to obtain light olefins.

[0083] In order to further improve the yield of light olefins, preferably, the microwave cracking gas is subjected to heat exchange treatment before the second separation to reduce the temperature of the microwave cracking gas by 50-300°C, preferably by 100-200°C.

[0084] A second aspect of the present invention provides a system for cracking petroleum feedstock to prepare light olefins, the system comprising a pretreatment unit and a microwave cracking unit, the pretreatment unit comprising a vaporization unit and a hydrogenation unit connected in sequence.

[0085] According to a preferred embodiment of the present invention, the vaporization unit is selected from at least one of a stripping device, a flash device and a cyclone separation device.

[0086] Preferably, the cyclone separation device is selected from a cyclone separator, preferably selected from at least one of a volute cyclone separator, an axial flow guide vane cyclone separator, a straight cylinder cyclone separator, a cone cylinder combination cyclone separator and a direct current cyclone separator.

[0087] According to a preferred embodiment of the present invention, the hydrogenation unit at least comprises a hydroprocessing device.

[0088] Preferably, the hydrogenation unit comprises a hydroprocessing device, a first separation device and a hydrogen refining device which are connected in sequence.

[0089] According to a preferred embodiment of the present invention, the microwave cracking unit comprises a tubular reactor (arranged along the fluid direction) and a microwave generator fixed outside the tubular reactor, and preferably the microwave generator comprises a magnetron. The magnetron is used to control the microwave power, and the more magnetrons there are, the higher the microwave power that can be provided. The magnetrons should be evenly distributed outside the tubular reactor to minimize the mutual interference and cancellation of electromagnetic waves emitted by each magnetron.

[0090] According to a preferred embodiment of the present invention, the system further comprises a second separation unit connected to the microwave cracking unit (for separating light olefins from the microwave cracking products).

[0091] The method and system (using the method to prepare light olefins) provided by the present invention can effectively improve the yield and selectivity of the target product when preparing light olefins using petroleum raw materials, and can use crude oil as a raw material to prepare light olefins while ensuring a high yield and selectivity of the target product and a long operating cycle.

[0092] Based on this, the third aspect of the present invention provides the use of the system described in the second aspect in the preparation of light olefins, especially in the preparation of light olefins directly using crude oil as raw material.

[0093] The fourth aspect of the present invention provides the use of the method described in the first aspect and / or the system described in the second aspect in improving the target product yield, selectivity and operation cycle of preparing light olefins by direct cracking of crude oil.

[0094] The present invention will be described in detail below by way of examples. It should be understood that the following examples are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0095] In the following examples, unless otherwise specified, the crude oil used is dehydrated and desalted crude oil, and its API value is 32. Unless otherwise specified, the reagents used are commercial products purchased from regular chemical suppliers, and the purity is analytical grade.

[0096] In the following embodiments, unless otherwise specified, the microwave cracking unit uses a microwave cracking furnace including a tubular reactor and magnetrons evenly arranged and fixed outside the tubular reactor to perform microwave cracking on the material to be processed. The microwave power is adjusted by adjusting the number of magnetrons. During the adjustment process, the magnetrons should be evenly arranged outside the reactor to reduce the interference and cancellation of electromagnetic waves emitted by different magnetrons. The vaporization unit uses a guide vane cyclone separator with internal components, wherein the internal components are conventional internal components located at the bottom of the cyclone separator.

[0097] Example 1

[0098] use Figure 1 The system shown in FIG. 1 is used to prepare light olefins according to the following method:

[0099] (1) Vaporization treatment:

[0100] The dehydrated and desalted crude oil is passed into the preheating unit 1 and preheated to 220°C to obtain the preheated crude oil. The water vapor (220°C) is mixed with the preheated crude oil at a weight ratio of 0.75:1, and the obtained mixture is passed into the vaporization unit 2. The mixture is subjected to cyclone separation at 290°C, and the separation efficiency of the cyclone separator is 71%, into a vapor phase and a liquid phase.

[0101] (2) Hydrogenation treatment

[0102] The liquid phase obtained in step (1) (preheated to 190°C) is sent to the hydroprocessing unit 7, wherein the liquid phase first enters the hydroprocessing device 4, and the obtained products enter the separation device 5 and the hydrogen refining device 6 in turn to obtain circulating hydrogen, hydrogenated light components with a boiling point of 288°C or below, and hydrogenated heavy components with a boiling point greater than 288°C. The hydroprocessing unit treats the liquid phase by catalytic hydrogenation, and the catalyst used is Co-Ni-Mo / Al2O3. The hydrogenation temperature is controlled to be 268°C, the pressure is 2.68MPa, the hydrogen-to-oil ratio (the volume ratio of hydrogen to liquid phase) is 3:1, and the liquid phase volume space velocity is 2h -1 , the monoolefin hydrogenation rate is 94%.

[0103] (3) Microwave pyrolysis:

[0104] The steam phase obtained in step (1) and the hydrogenated light component obtained in step (2) are mixed at a weight ratio of 0.8:1 (the API value of the obtained mixture is about 44.1) and sent to the microwave cracking unit 3, where a microwave cracking reaction occurs in the presence of a microwave absorbing material (silicon carbide, with a particle size of 7 mm) to generate microwave cracking gas. The temperature of the microwave cracking reaction is set to 780°C, the residence time is 0.5s, the microwave power is 6500kW, and the frequency is 2300MHz.

[0105] (4) Product separation:

[0106] The microwave cracking gas is passed through a quencher and a cracking gas separation system (adopting the LUMMUS sequential separation process) to separate hydrogen, light olefins, cracking gasoline, cracking diesel and cracking fuel oil.

[0107] It was observed that the operation cycle of the above process was 55 days. The steam cracking reaction products were analyzed, among which the ethylene yield was 26.32wt%, the propylene yield was 15.97wt%, the 1,3-butadiene yield was 4.65wt%, and the total yield of the above trienes was 46.94wt%.

[0108] Example 2

[0109] use Figure 1 The system shown in FIG. 1 is used to prepare light olefins according to the following method:

[0110] (1) Vaporization treatment:

[0111] The dehydrated and desalted crude oil is passed into the preheating unit 1 and preheated to 220°C to obtain the preheated crude oil. The water vapor (220°C) is mixed with the preheated crude oil at a weight ratio of 0.85:1, and the obtained mixture is passed into the vaporization unit 2. The mixture is subjected to cyclone separation at 330°C, and the separation efficiency of the cyclone separator is 73%, into a vapor phase and a liquid phase.

[0112] (2) Hydrogenation treatment

[0113] The liquid phase obtained in step (1) (preheated to 205°C) is sent to the hydroprocessing unit 7, wherein the liquid phase first enters the hydroprocessing device 4, and the obtained products enter the separation device 5 and the hydrogen refining device 6 in turn to obtain circulating hydrogen, hydrogenated light components with a boiling point of 288°C or below, and hydrogenated heavy components with a boiling point greater than 288°C. The hydroprocessing unit treats the liquid phase by catalytic hydrogenation, and the catalyst used is Co-Ni-Mo / Al2O3. The hydrogenation temperature is controlled to be 275°C, the pressure is 2.75MPa, the hydrogen-to-oil ratio (the volume ratio of hydrogen to liquid phase) is 3.2:1, and the liquid phase volume space velocity is 2h -1 , the monoolefin hydrogenation rate is 95%.

[0114] (3) Microwave pyrolysis:

[0115] The steam phase obtained in step (1) and the hydrogenated light component obtained in step (2) are mixed at a weight ratio of 0.8:1 (the API value of the obtained mixture is about 44.8) and sent to the microwave cracking unit 3, where a microwave cracking reaction occurs in the presence of a microwave absorbing material (silicon carbide, with a particle size of 7 mm) to generate microwave cracking gas. The temperature of the microwave cracking reaction is set to 780°C, the residence time is 0.5s, the microwave power is 6500kW, and the frequency is 2300MHz.

[0116] (4) Product separation:

[0117] The microwave cracking gas is passed through a quencher and a cracking gas separation system (adopting the LUMMUS sequential separation process) to separate hydrogen, light olefins, cracking gasoline, cracking diesel and cracking fuel oil.

[0118] It was observed that the operation cycle of the above process was 58 days. The steam cracking reaction products were analyzed, among which the ethylene yield was 26.8wt%, the propylene yield was 16.2wt%, the 1,3-butadiene yield was 4.25wt%, and the total yield of the above trienes was 47.25wt%.

[0119] Comparative Example 1

[0120] In this comparative example 1, only a conventional cracking furnace was used for cracking.

[0121] The dehydrated and desalted crude oil and water vapor are directly fed into the cracking furnace in a ratio of 1:1. After passing through the convection section, they directly enter the radiation section. The operating parameters of the radiation section are a furnace tube outlet temperature of 760°C, a residence time of 0.1s, and a water-to-oil ratio of 1:1; steam cracking is performed. The cracking gas is separated using the LUMMUS sequential separation process to obtain light olefins.

[0122] It was observed that the operation cycle of the above process was 5 days. The steam cracking reaction products were analyzed, among which the ethylene yield was 21.49wt%, the propylene yield was 13.29wt%, the 1,3-butadiene yield was 4.03wt%, and the total yield of the above trienes was 38.81wt%.

[0123] Comparative Example 2

[0124] The dehydrated and desalted crude oil and water vapor are preheated to 220°C respectively, and then the crude oil and water vapor are mixed and preheated to 360°C, and the weight ratio of water vapor to preheated crude oil is 0.8:1. The preheated crude oil and water vapor are flashed to obtain a vapor phase (light component, API is about 49.5) and a liquid phase (heavy component), and the separation efficiency of the flash evaporation is 60%.

[0125] The light component is sent to a conventional cracking furnace for cracking to obtain cracking gas, and water vapor and steam phase are sent to the cracking furnace. The cracking temperature is 790°C, the residence time is 0.3s, and the amount of water vapor is such that the water-oil ratio in the mixture of water vapor and steam phase is 1.2:1.

[0126] The cracked gas is passed through a quencher and a cracked gas separation system (using the LUMMUS sequential separation process) to separate hydrogen, light olefins, cracked gasoline, cracked diesel and cracked fuel oil.

[0127] It was observed that the operation cycle of the above process was 45 days. The steam cracking reaction products were analyzed, among which the ethylene yield was 22.8wt%, the propylene yield was 13.9wt%, the 1,3-butadiene yield was 4.1wt%, and the total yield of the above trienes was 40.8wt%.

[0128] By comparing the results of Examples 1-2 with Comparative Example 1, it can be seen that the conventional cracking device and method (Comparative Example 1) uses crude oil as a raw material and only maintains a 5-day operation cycle, while the method provided by the present invention (Examples 1 and 2) can ensure that crude oil is normally used in the cracking device, greatly slowing down the coking rate and maintaining long-term operation. Moreover, compared with the conventional cracking method, the method of the present invention effectively improves the yield of light olefins and the selectivity of the target product.

[0129] By comparing the results of Example 1 and Comparative Example 2, it can be seen that when the crude oil is treated in the preferred manner of the present invention and the light components obtained are treated by microwave cracking, the yield of light olefins and the selectivity of target products can be further improved, and the operation time is also longer.

[0130] 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 by cracking petroleum raw materials, characterized in that: The method comprises the following steps: (1) Vaporizing the petroleum raw material to obtain a vapor phase and a liquid phase; (2) hydrogenating the liquid phase obtained in step (1) to obtain a hydrogenated light component and a hydrogenated heavy component; (3) subjecting the mixture of the steam phase obtained in step (1) and the hydrogenated light component obtained in step (2) to microwave cracking to obtain microwave cracking gas.

2. The method according to claim 1, wherein: In step (1), the API value of the petroleum feedstock is not less than 18, preferably not less than 20, and more preferably not less than 22; Preferably, the petroleum raw material is selected from at least one of crude oil, light naphtha, naphtha, diesel and hydrogenated tail oil, and preferably the crude oil is selected from at least one of 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; And / or, in step (1), the vaporization treatment method includes: mixing the petroleum raw material with water vapor and then vaporizing it to obtain a vapor phase and a liquid phase, and preferably the vaporization treatment method is selected from at least one of steam stripping, flash evaporation and cyclone separation; Preferably, during the vaporization process, the weight ratio of the water vapor to the petroleum raw material is 0.5-1.5:1; Preferably, the vaporization treatment is carried out by cyclone separation, and preferably the conditions for the cyclone separation include: a temperature of 150-400° C., a separation efficiency of not less than 50%, preferably 65-80%.

3. The method according to claim 1, wherein: In step (2), the hydrogenation method includes: mixing the liquid phase with hydrogen, and then performing hydrogenation treatment in the presence of a catalyst to obtain a hydrogenated light component and a hydrogenated heavy component. Preferably, the hydrogenation treatment method is selected from at least one of catalytic hydrogenation, residue hydrogenation and hydrocracking; Preferably, in the hydroprocessing, the volume ratio of hydrogen to liquid phase is 2-5:1, preferably 2.5-3.5:1; Preferably, the conditions of the hydrotreatment include: temperature 200-300°C, pressure 2-3MPa, liquid phase volume space velocity 1.5-3h -1 ; More preferably, the method further comprises performing a first separation on the obtained product after the hydrotreatment to remove the hydrogenated heavy components, and performing hydrogen refining on the obtained product to obtain light components and circulating hydrogen.

4. The method according to claim 1, wherein: In step (3), the microwave cracking method includes: subjecting the mixture of the vapor phase obtained in step (1) and the hydrogenated light component obtained in step (2) to a microwave cracking reaction in the presence of a microwave absorbing material and optionally water vapor to obtain a microwave cracking gas; Preferably, the absorbing material is selected from at least one of silicon carbide, composite ferrite, ultrafine metal particles and organic polymer nanomaterials; Preferably, the conditions of the microwave cracking reaction include: cracking temperature 450-850°C, residence time 0.05-1s, preferably microwave power in the reactor is 2-12000kW, more preferably 1000-10000kW, preferably microwave frequency is 100-3500MHz; Preferably, the optional water vapor has a temperature of 100-650°C, preferably 180-520°C; More preferably, the weight ratio of the optional water vapor to the mixture of the steam phase and the hydrogenated light components is 0.1-2:1, preferably 0.4-1.5:

1.

5. The method according to any one of claims 1 to 4, wherein: The method further comprises: (4) performing a second separation on the microwave cracking gas obtained in step (3) to obtain light olefins.

6. A system for cracking petroleum raw materials to prepare light olefins, characterized in that: The system comprises a pretreatment unit and a microwave cracking unit (3), wherein the pretreatment unit comprises a vaporization unit (2) and a hydrogenation unit (7) which are connected in sequence.

7. The system according to claim 6, wherein: The vaporization unit (2) comprises at least one of a stripping device, a flash device and a cyclone separation device; More preferably, the cyclone separation device is selected from a cyclone separator, preferably at least one selected from a volute cyclone separator, an axial flow guide vane cyclone separator, a straight cylinder cyclone separator, a cone cylinder combination cyclone separator and a direct current cyclone separator; and / or, the hydrogenation unit (7) comprises at least a hydroprocessing device, preferably the hydrogenation unit (7) comprises a hydroprocessing device (4), a first separation device (5) and a hydrogen refining device (6) connected in sequence; And / or, the microwave cracking unit (3) comprises a tubular reactor and a microwave generator fixed outside the tubular reactor, and preferably the microwave generator comprises a magnetron.

8. The system according to claim 6 or 7, wherein: The system further comprises a second separation unit connected to the microwave cracking unit.

9. Use of the system according to any one of claims 6 to 8 in the preparation of light olefins, especially in the preparation of light olefins directly using crude oil as raw material.

10. Use of the method according to any one of claims 1 to 5, and / or the system according to any one of claims 6 to 8 in improving the target product yield, selectivity and operation cycle of preparing light olefins by direct cracking of crude oil.

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