Method and system for preparing low-carbon olefin from crude oil 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 from crude oil and application, and the method comprises the following steps: (1) pretreating the crude oil to obtain a light component and a heavy component; (2) in the presence of a wave-absorbing material, carrying out microwave cracking on the light component to obtain microwave cracking gas; (3) performing catalytic cracking on the heavy component to obtain catalytic cracking gas; and (4) separating the microwave cracking gas and / or the catalytic cracking gas to obtain the low-carbon olefin. According to the invention, the light component and the heavy component obtained by pretreating the crude oil are respectively subjected to microwave cracking and catalytic cracking, so that the cracking rate of the crude oil and the yield of low-carbon olefin are improved, the coking phenomenon during cracking is reduced, and the running time of the device is 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 from crude oil and applications thereof. Background Art

[0002] Low-carbon olefins are a general term for unsaturated hydrocarbons with carbon content of C4 or less, mainly including organic chemical raw materials with high economic value such as ethylene, propylene, isobutylene, butadiene, etc. The steam cracking method of tubular cracking furnace is currently the most important method for producing ethylene. At the same time, tubular cracking furnace is also the main production unit for ethylene, propylene, butadiene, and aromatics. my country's steam cracking units have always used naphtha as raw material to prepare low-carbon olefin products. In recent years, the utilization of crude oil has shifted from energy utilization to chemical industry. The use of special heavy hydrocarbons, especially crude oil directly entering the cracking unit to produce low-carbon olefins, can effectively improve the utilization rate of crude oil chemical products; skipping the refining step and not building a refining unit can greatly save investment, which is conducive to reducing the raw material cost and energy consumption of olefin production units, and better adapting to changes in the energy and chemical markets.

[0003] Crude oil contains some high molecular weight non-volatile components with a boiling point exceeding 590°C. If these non-volatile components enter the cracking reaction device, they are likely to generate coke, causing coking deposition in the reactor and even clogging the reactor, affecting the yield of the cracking product and shortening the operating cycle of the reactor.

[0004] Therefore, it is urgent to find a method that can increase the operating cycle of the reactor and improve the yield of the cracking product. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem of crude oil being easy to coke during the cracking process and the low yield of light olefins in the prior art. The present invention provides a method and system for preparing light olefins from crude oil and its application, which can improve the cracking efficiency of crude oil raw materials, extend the operation cycle, reduce the coking phenomenon during cracking, and improve the yield of light olefins in the product. At the same time, due to the use of clean energy, carbon emissions are effectively reduced.

[0006] The inventors of the present invention have found that microwave cracking of the light components obtained by separating crude oil and catalytic cracking of the heavy components can improve the yield of light olefins and the operation cycle of the device. Therefore, the first aspect of the present invention provides a method for preparing light olefins from crude oil, which comprises the following steps:

[0007] (1) Pre-treating crude oil to obtain light components and heavy components;

[0008] (2) in the presence of a microwave absorbing material, the light component is subjected to microwave cracking to obtain microwave cracking gas;

[0009] (3) catalytically cracking the heavy components to obtain catalytic cracking gas;

[0010] (4) Separating the microwave cracking gas and / or catalytic cracking gas to obtain light olefins.

[0011] The second aspect of the present invention provides a system for preparing light olefins from crude oil, the system comprising: a crude oil pretreatment unit, a microwave cracking unit, a catalytic cracking unit and a cracking gas separation unit; wherein:

[0012] The crude oil pretreatment unit is used to pretreat the crude oil to obtain light components and heavy components;

[0013] The microwave cracking unit is used to perform microwave cracking on the light component to obtain microwave cracking gas;

[0014] The catalytic cracking unit is used to catalytically crack the heavy components to obtain catalytic cracking gas;

[0015] The cracking gas separation unit is used to separate microwave cracking gas and / or catalytic cracking gas to obtain light olefins.

[0016] 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.

[0017] 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.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention subjects the light components and heavy components obtained by crude oil pretreatment to microwave cracking and catalytic cracking, respectively, thereby increasing the cracking rate of crude oil and the yield of light olefins, reducing the occurrence of coking during cracking, and extending the operating time of the device.

[0020] (2) The method of the present invention can effectively solve the problem that heavy cracking raw materials cannot be fully gasified in the convection section and are easily coked in the radiation section and the quenching part, while obtaining a higher yield of light olefins and extending the operation cycle of the device.

[0021] (3) Compared with conventional thermal cracking, the microwave cracking of the present invention can improve the selectivity of light olefins and reduce the cracking temperature; at the same time, it can also reduce carbon emissions and energy consumption. In a preferred case, the preferred microwave absorbing material (such as silicon carbide) of the present invention can further reduce the cracking temperature, while promoting the rapid cracking of light components, so that more light components are converted into light olefins.

[0022] (4) In a preferred embodiment, the present invention can further improve the yield and operation cycle of light olefins by adopting a specific pretreatment method to obtain light components for microwave cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an implementation method of a system for preparing light olefins from crude oil provided by the present invention.

[0024] Description of Reference Numerals

[0025] 1-heater, 2-cyclone separator, 3-microwave cracking unit, 4-fluidized reactor, 5-catalyst regenerator, 6-catalytic cracking unit. DETAILED DESCRIPTION

[0026] 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.

[0027] In the present invention, unless otherwise specified, "crude oil" refers to unrefined petroleum. 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.

[0028] 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.

[0029] The first aspect of the present invention provides a method for preparing light olefins from crude oil, the method comprising the following steps:

[0030] (1) Pre-treating crude oil to obtain light components and heavy components;

[0031] (2) in the presence of a microwave absorbing material, the light component is subjected to microwave cracking to obtain microwave cracking gas;

[0032] (3) catalytically cracking the heavy components to obtain catalytic cracking gas;

[0033] (4) Separating the microwave cracking gas and / or catalytic cracking gas to obtain light olefins.

[0034] According to the present invention, the temperature of the microwave cracking can be selected in a wide range. Preferably, the temperature of the microwave cracking is 350-850°C (for example, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 720°C, 740°C, 750°C, 760°C, 780°C, 800°C, 850°C, and a range consisting of any two of the above), more preferably 500-800°C, and further preferably 700-800°C. In the present invention, unless otherwise specified, the temperature of the microwave cracking refers to the temperature at the outlet of the reactor.

[0035] According to the present invention, the residence time of the microwave pyrolysis can be selected within a wide range. 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.

[0036] According to the present invention, preferably, the power of the microwave used in the microwave cracking is 2-120000KW (for example, 2KW, 100KW, 1000KW, 2000KW, 3000KW, 4000KW, 5000KW, 6000KW, 7000KW, 8000KW, 9000KW, 10000KW, 100000KW, 120000KW, and the range formed by any two of the above points), more preferably 6-6000KW, and further preferably 500-5000KW. 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.

[0037] According to the present invention, preferably, the frequency of the microwaves used in the microwave pyrolysis is 500-3000 MHz (e.g., 500 MHz, 1000 MHz, 1500 MHz, 2000 MHz, 2500 MHz, 3000 MHz, and a range consisting of any two of the above), more preferably 800-2000 MHz.

[0038] According to the present invention, preferably, the water-oil weight ratio in the light component of the microwave cracking is 0.1-2:1 (for example, 0.1:1, 0.2:1, 0.3:1, 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, and a range consisting of any two of the above points), and more preferably 0.4-1.5:1.

[0039] According to the present invention, preferably, the dielectric constant of the absorbing material is 1-20 Farads / meter, more preferably 5-15 Farads / meter. Further preferably, the absorbing material includes at least one of silicon carbide, carbon fiber and graphite. 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.

[0040] 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.

[0041] According to the present invention, preferably, the API of the crude oil is greater than 28 (for example, 29, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 300, 400, and a range formed by any two of the above points), more preferably 30-100, and further preferably 33-80.

[0042] According to the present invention, preferably, the crude 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 crude oil includes at least one of 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.

[0043] According to the present invention, preferably, in step (1), the pretreatment method is at least one of steam stripping, flash evaporation and cyclone separation. The inventors further found that cyclone separation can obtain light components that are more suitable for microwave cracking, which can further improve the yield of light olefins and extend the reactor operation cycle. Therefore, the pretreatment method is more preferably cyclone separation. When the crude oil is pretreated by flash evaporation, usually at least 5% of the hydrocarbon raw materials that can be used for the preparation of light olefins remain in the liquid phase after pretreatment, which affects the total yield of light olefins on the one hand, and also causes a waste of raw materials on the other hand.

[0044] According to the present invention, preferably, the cyclone separation process comprises: heating crude oil and water vapor, and then sending them into a cyclone separator for separation to obtain light components and heavy components.

[0045] According to the present invention, the weight ratio of water vapor to crude oil can be selected in a wide range; preferably, the weight ratio of water vapor to crude oil is 0.4-1.5:1 (for example, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.5:1, and the range formed by any two of the above points), preferably 0.5-1.2:1.

[0046] In the present invention, the heating may be performed by electric heating. Preferably, the heating temperature is 300-600°C (for example, 300°C, 320°C, 340°C, 350°C, 380°C, 400°C, 450°C, 500°C, 550°C, 600°C, and a range consisting of any two of the above), more preferably 350-550°C.

[0047] According to a preferred embodiment of the present invention, the cyclone separation process includes: preheating crude oil and water vapor respectively and then mixing them to obtain a mixed material, then heating the mixed material, and then sending it into a cyclone separator for separation to obtain a light component and a heavy component. More preferably, the crude oil preheating temperature is 60-100°C (for example, 60°C, 70°C, 80°C, 90°C, 100°C, and a range consisting of any two of the above points), and the water vapor preheating temperature is 200-400°C (for example, 200°C, 220°C, 240°C, 250°C, 280°C, 300°C, 350°C, 400°C, and a range consisting of any two of the above points).

[0048] 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.

[0049] According to the present invention, preferably, the separation conditions of the cyclone separator make the light component separation efficiency greater than 10% (for example, 11%, 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 light components separated from the crude oil to the total weight of the crude oil. A separation efficiency of 20% means: 20g of light components are 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.

[0050] According to the present invention, preferably, the API of the light component obtained after cyclone separation is not less than 40, for example, the API is 40, 45, 48, 50, 55, 60, 70, 80, 90, 100, and a range consisting of any two of the above points, and more preferably, the API of the light component is 40-70. Limiting the API within the above preferred range can not only obtain raw materials suitable for microwave cracking and improve the yield of light olefins, but also reduce the load of catalytic cracking, reduce the demand for catalysts, and thus reduce costs.

[0051] In the present invention, the cyclone separator is a cyclone separator commonly used in the art, and the cyclone separator can be selected from at least one of a volute cyclone separator, an axial flow guide vane cyclone separator, a straight cyclone separator, a cone combination cyclone separator, and a direct flow cyclone separator. The cyclone separator can be provided with internal components, and the internal components can 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. The type and structure of the cyclone separator are not particularly limited, as long as the separation efficiency can be met.

[0052] 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.

[0053] 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 120-400° C. and the separation efficiency is above 10%.

[0054] 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.

[0055] In the present invention, in order to make full use of crude oil, the heavy components separated from the crude oil are subjected to catalytic cracking to further improve the yield of light olefins.

[0056] According to the present invention, the catalyst used in the catalytic cracking is not particularly limited and can be selected in a wide range. The catalyst used in the catalytic cracking can be a solid acid selective molecular sieve catalyst. For example, the catalyst includes at least one of CHP-1 catalyst, CHP-2 catalyst, CRP-1 catalyst, CHP-S catalyst, CIP-1 catalyst, CIP-2 catalyst, CIP-3 catalyst, CIP-4 catalyst, CIP-5 catalyst and CIP-S catalyst. The catalysts of different types listed above are all industrialized catalysts and can be obtained commercially.

[0057] According to the present invention, the temperature of the catalytic cracking can be selected within a wide range. Preferably, the temperature of the catalytic cracking is 400-700°C, preferably 500-650°C.

[0058] According to the present invention, preferably, the amount of the catalyst used is such that the catalyst-oil ratio is 5-30:1 (for example, 5:1, 7:1, 9:1, 11:1, 13:1, 15:1, 17:1, 19:1, 21:1, 23:1, 25:1, 30:1, and a range consisting of any two of the above), preferably 10-25:1.

[0059] According to the present invention, the catalytic cracking reaction can be carried out in a conventional catalytic cracking reaction, preferably, 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. The fluidized reactor in the present invention can refer to the reactor disclosed in CN201684585U.

[0060] According to the present invention, preferably, the outlet temperature of the first riser is 500-550°C (for example, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, and a range formed by any two of the above points), preferably 520-540°C.

[0061] 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 620-640°C.

[0062] 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; preferably, the space velocity of the bed reactor is 2h -1 -10h -1 .

[0063] 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 allowing the cracking gas to enter a quencher (heat exchanger) 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.

[0064] According to the present invention, in order to further improve the yield of light olefins, preferably, the cracked gas is first heat exchanged, and then enters the quencher and the cracked gas separation system in sequence. The first heat exchange of the cracked gas can also reduce the coking phenomenon of the cracked gas during cooling and separation.

[0065] The second aspect of the present invention provides a system for preparing light olefins from crude oil, the system comprising: a crude oil pretreatment unit, a microwave cracking unit, a catalytic cracking unit and a cracking gas separation unit; wherein:

[0066] The crude oil pretreatment unit is used to pretreat the crude oil to obtain light components and heavy components;

[0067] The microwave cracking unit is used to perform microwave cracking on the light component to obtain microwave cracking gas;

[0068] The catalytic cracking unit is used to catalytically crack the heavy components to obtain catalytic cracking gas;

[0069] The cracking gas separation unit is used to separate microwave cracking gas and / or catalytic cracking gas to obtain light olefins.

[0070] 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.

[0071] According to the present invention, preferably, the crude oil pretreatment 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-type 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] According to a particularly preferred embodiment of the present invention, a method for preparing light olefins from crude oil comprises:

[0077] (1) The dehydrated and desalted crude oil (API of the crude oil is 30-35) is preheated to 75-85°C to obtain preheated crude oil, and water vapor is sent into a preheater to be preheated to 290-310°C. The preheated crude oil and water vapor are mixed and preheated to 350-370°C, and the weight ratio of water vapor to preheated crude oil is 0.5-0.6:1.

[0078] The preheated crude oil and water vapor mixture is sent to a cyclone separator with internal components for separation into a vapor phase (light component) and a liquid phase (heavy component). The separation efficiency of the cyclone separator is 60-65%.

[0079] (2) The vapor phase is sent into 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 absorbing materials, and the vapor phase is cracked in the presence of the absorbing materials. The temperature of the microwave cracking reaction is 740-780°C, the water-oil weight ratio is 0.7-0.8:1, the absorbing material is silicon carbide, the residence time is 0.3-0.35s, the microwave power is 4000-5000kW, the microwave frequency is 1800-2000MHz, and the microwave cracking furnace is a tubular reactor.

[0080] (3) The liquid phase is sent to a catalytic cracking unit for 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 10-15. The catalytic cracking unit includes a first riser, a second riser, a stripper and a bed reactor. The liquid phase is divided into two parts and enters the first riser and the second riser respectively. The stripper generates 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 530-538°C, the outlet temperature of the second riser is 630-636°C, and the air velocity of the bed reactor is 6-6.5h -1 .

[0081] The present invention will be described in detail below by way of examples. In the following examples,

[0082] The average particle size of silicon carbide is 12 mm.

[0083] The cracking furnace used in Comparative Example 1 is a CBL-III cracking furnace (purchased from China Petrochemical Corporation).

[0084] 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.

[0085] Table 1

[0086] Analyze Project ASTM D5307 IP,℃ 69 10％，℃ 192 20％，℃ 272 30％，℃ 337 40％，℃ 393 50％，℃ 446 60％，℃ 508 70％，℃ 595 75％，℃ 653 80％，℃ - 90％，℃ - EP,℃ -

[0087] Example 1

[0088] use Figure 1 The system shown is used to crack crude oil to produce light olefins.

[0089] (1) The dehydrated and desalted crude oil is preheated to 80°C to obtain preheated crude oil. At the same time, water vapor is sent into a preheater to be preheated to 300°C. The preheated crude oil and water vapor are mixed and preheated to 360°C. The weight ratio of water vapor to preheated crude oil is 0.5:1.

[0090] The preheated crude oil and water vapor mixture is sent to a cyclone separator with internal components for separation to obtain a vapor phase (light component) and a liquid phase (heavy component). The separation efficiency of the cyclone separator is 60%, and the API of the separated light component is 50.

[0091] (2) The vapor phase is 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 absorbing materials, and the vapor phase is cracked in the presence of the absorbing materials. The temperature of the microwave cracking reaction is 750°C, the water-oil weight ratio is 0.75:1, the absorbing material is silicon carbide, the residence time is 0.3s, the microwave power is 5000kW, the microwave frequency is 2000MHz, and the microwave cracking furnace is a tubular reactor.

[0092] (3) The liquid phase is sent to a catalytic cracking unit for 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 538°C, the outlet temperature of the second riser is 636°C, and the air velocity of the bed reactor is 6.2h -1 .

[0093] (4) 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 26.07wt%, the yield of propylene is 15.85wt%, the yield of 1,3-butadiene is 4.91wt%, and the total yield of the above trienes is 46.83wt%.

[0094] The operation cycle of the microwave cracking unit (tubular reactor) is 50 days.

[0095] Example 2

[0096] use Figure 1 The system shown is used to crack crude oil to produce light olefins.

[0097] (1) The dehydrated and desalted crude oil is preheated to 80°C to obtain preheated crude oil, and water vapor is sent into a preheater to be preheated to 240°C. The preheated crude oil and water vapor are mixed and preheated to 400°C. The weight ratio of water vapor to preheated crude oil is 0.6:1.

[0098] The preheated crude oil and water vapor mixture is sent to a cyclone separator with internal components for separation to obtain a vapor phase (light component) and a liquid phase (heavy component). The separation efficiency of the cyclone separator is 55%, and the API of the separated light component is 54.

[0099] (2) The vapor phase is 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 absorbing material, and the vapor phase is cracked in the presence of the absorbing material. The temperature of the microwave cracking reaction is 760°C, the water-oil weight ratio is 0.7:1, the absorbing material is silicon carbide, the residence time is 0.25s, the microwave power is 5000kW, and the microwave frequency is 2000MHz.

[0100] (3) The liquid phase is sent to a catalytic cracking unit for 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 with a catalyst-to-oil ratio of 15. 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 520°C, the outlet temperature of the second riser is 620°C, and the air velocity of the bed reactor is 7h -1 .

[0101] (4) 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 25.8wt%, the yield of propylene is 14.19wt%, the yield of 1,3-butadiene is 4.8wt%, and the total yield of the above trienes is 44.79wt%.

[0102] The operation cycle of the microwave cracking unit (tubular reactor) is 48 days.

[0103] Example 3

[0104] The method of Example 1 was followed, except that in step (2), the temperature of the microwave cracking reaction was 650° C., the water-oil weight ratio was 0.7:1, and the residence time was 0.25 s.

[0105] Among them, the yield of ethylene was 12.5wt%, the yield of propylene was 8.75wt%, the yield of 1,3-butadiene was 2.3wt%, and the total yield of the above trienes was 23.55wt%.

[0106] Example 4

[0107] The method of Example 1 was followed, except that the preheated crude oil was mixed with water vapor and then preheated to 600° C., and the weight ratio of water vapor to preheated crude oil was 0.6:1. The separation efficiency of the cyclone separator was 90%, and the API value of the light component after separation was 36.

[0108] Among them, the yield of ethylene was 21.5wt%, the yield of propylene was 11.83wt%, the yield of 1,3-butadiene was 4.5wt%, and the total yield of the above trienes was 37.83wt%.

[0109] The operation cycle of the microwave cracking unit (tubular reactor) is 40 days.

[0110] Comparative Example 1

[0111] In this comparative example 1, only a conventional cracking furnace was used for cracking.

[0112] 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.

[0113] 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%.

[0114] The operating cycle is 5 days.

[0115] Comparative Example 2

[0116] The method of Example 1 is followed, except that the vapor phase obtained after cyclone separation of the crude oil enters an industrial cracking furnace, which uses fuel gas as a heating source instead of microwave heating; the operating temperature of the radiation section of the cracking furnace is 800°C.

[0117] Among them, the yield of ethylene was 22.6wt%, the yield of propylene was 12.43wt%, the yield of 1,3-butadiene was 4.80wt%, and the total yield of the above trienes was 39.83wt%.

[0118] The operating cycle is 30 days.

[0119] It can be seen from the results of the embodiment and comparative example 1 that, with the conventional cracking device, the crude oil can only maintain a 5-day operation cycle, while the present invention can ensure the normal use of the crude oil cracking device, and can effectively reduce the occurrence of coking, and the operation cycle reaches more than 40 days. Compared with comparative examples 1-2, the operation cycle of embodiments 1-2 and embodiment 4 of the present invention is significantly improved. Preferably, embodiments 1-2 of the present invention can obtain a higher total yield of trienes. Moreover, it can be seen from the comparison of embodiment 1 with comparative example 2 that the operating temperature of the radiation section of the cracking furnace is significantly higher than the temperature of the microwave cracking reaction in embodiment 1, that is, the microwave cracking of the present invention can significantly reduce the reaction temperature of the cracking.

[0120] 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 from crude oil, characterized in that: The method comprises the following steps: (1) Pre-treating crude oil to obtain light components and heavy components; (2) in the presence of a microwave absorbing material, the light component is subjected to microwave cracking to obtain microwave cracking gas; (3) catalytically cracking the heavy components to obtain catalytic cracking gas; (4) Separating the microwave cracking gas and / or catalytic cracking gas to obtain light olefins.

2. The method according to claim 1, wherein: The temperature of the microwave pyrolysis is 350-850°C, preferably 500-800°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 2-120000 KW, preferably 6-6000 KW, more preferably 500-5000 KW; And / or, the frequency of the microwave used in the microwave pyrolysis is 500-3000 MHz, preferably 800-2000 MHz; And / or, the dielectric constant of the absorbing material is 1-20 Farad / m, preferably 5-15 Farad / m.

3. The method according to claim 1, wherein: The water-oil weight ratio in the light component of the microwave cracking is 0.1-2:1, preferably 0.4-1.5:1; And / or, the absorbing material includes at least one of silicon carbide, carbon fiber and graphite.

4. The method according to claim 1, wherein: The API of the crude oil is greater than 28, preferably 30-100, more preferably 33-80; Preferably, the crude 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.

5. The method according to claim 1, wherein: In step (1), the pretreatment method is at least one of steam stripping, flash evaporation and cyclone separation, preferably cyclone separation.

6. The method according to claim 5, wherein: The cyclone separation process includes: heating crude oil and water vapor, and then sending them into a cyclone separator for separation to obtain light components and heavy components; Preferably, the weight ratio of water vapor to crude oil is 0.4-1.5:1, preferably 0.5-1.2:1; Preferably, the heating temperature is 300-600°C, preferably 350-550°C; Preferably, the separation conditions of the cyclone separator are such that the light component separation efficiency is greater than 10%; Preferably, the API of the light component obtained after cyclone separation is not less than 40.

7. The method according to claim 1, wherein: The catalyst used in the catalytic cracking is a solid acid selective molecular sieve catalyst; And / or, the temperature of the catalytic cracking is 400-700°C, preferably 500-650°C; Preferably, the amount of the catalyst used is such that the catalyst-oil ratio is 5-30:1, preferably 10-25:

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 500-550°C, preferably 520-540°C; and / or, the outlet temperature of the second riser is 600-650° C., preferably 620-640° 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 olefins from crude oil, characterized in that: The system includes: a crude oil pretreatment unit, a microwave cracking unit, a catalytic cracking unit and a cracking gas separation unit; wherein, The crude oil pretreatment unit is used to pretreat the crude oil to obtain light components and heavy components; The microwave cracking unit is used to perform microwave cracking on the light component to obtain microwave cracking gas; The catalytic cracking unit is used to catalytically crack the heavy components to obtain catalytic cracking gas; The cracking gas separation unit is used to separate microwave cracking gas and / or catalytic cracking gas to obtain light olefins; Preferably, the crude oil pretreatment unit comprises a heating device and a cyclone separator; Preferably, the microwave cracking unit comprises a tubular reactor and a microwave generator fixed outside the tubular reactor; 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; Preferably, the catalytic cracking unit further comprises a catalyst regenerator, and the catalyst regenerator is used to regenerate the catalyst.

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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