Gradient extraction separation device and extraction separation method

Abstract

The invention relates to the field of petrochemical industry, and discloses a cascade extraction separation device and an extraction separation method. The cascade extraction and separation device comprises an extraction tower, the extraction tower is provided with a first extraction solvent inlet 1, a second extraction solvent inlet 2, a raw oil inlet 3, an extraction liquid outlet 5 and a raffinate outlet 6, the second extraction solvent inlet 2 is connected with a second extraction solvent feeding pipe arranged in the extraction tower, and the raw oil inlet 3 is connected with a raw oil outlet 4. And the second extraction solvent feeding pipe is provided with at least two second extraction solvent jet orifices 4 along the axial direction of the extraction tower. According to the method, a specific cascade extraction and separation device is adopted, and second extraction solvents are injected from second extraction solvent injection orifices at different heights in the extraction and separation device respectively, so that efficient separation of saturated hydrocarbons, few-ring aromatic hydrocarbons and polyring aromatic hydrocarbons in the aromatic hydrocarbon-rich heavy oil is realized.

Description

Technical Field

[0001] This invention relates to the field of petrochemicals, specifically to a cascade extraction and separation device and extraction and separation method. Background Technology

[0002] Under the influence of multiple factors such as refining overcapacity, the impact of new energy sources, and the "dual carbon" target, competition in the refined oil market has intensified, and demand is gradually reaching its peak. Traditional fuel-type refineries urgently need to transform into integrated refining and chemical processing plants. Component refining allows for the selection of more suitable components as processing feedstocks based on the characteristics and requirements of the target product, while avoiding the "supporting role" of useless components (such as polycyclic aromatic hydrocarbons in catalytic cracking) in the processing, achieving optimal utilization of resources by selecting appropriate components for olefins and aromatics. ExxonMobil's molecular management project, which combines the different molecular compositions of crude oil, establishes corresponding separation processes and reaction models, and further integrates them with system optimization and production scheduling to customize chemical production solutions. Targeted component separation maximizes the production of high-value-added products.

[0003] Solvent extraction (also known as liquid-liquid extraction or solvent extraction) is a crucial unit operation in the petroleum refining industry. It is a physical process that separates different components based on differences in solvent solubility without altering the composition of the feedstock. In the petrochemical field, solvent extraction is commonly used to separate saturated hydrocarbons from aromatic components. For catalytic reforming feedstocks, solvent extraction and extractive distillation can be used to produce BTX and high-quality gasoline; for vacuum distillate, solvent extraction can separate polycyclic aromatic hydrocarbons, and the raffinate can be used to produce lubricating oil base oils and environmentally friendly aromatic rubber plasticizers. Solvent extraction technology not only improves oil quality but also yields significant economic benefits.

[0004] The ideal components in heavy oil feedstocks have different definitions depending on the specific requirements. For example, feedstocks may contain both aromatics and saturated hydrocarbons. When maximizing the production of aromatics as a subsequent product or feedstock is required, aromatics are the ideal component. Conversely, when maximizing the production of saturated hydrocarbons as a subsequent product or feedstock is required, aromatics are the ideal component. Furthermore, extraction processes require the separation of aromatics with different ring numbers (monocyclic, bicyclic, tricyclic, tetracyclic, pentacyclic, and higher). Monocyclic and bicyclic aromatics can be considered ideal components (e.g., as rubber filler oils), while tricyclic and tetracyclic aromatics can also be considered ideal components (e.g., as carbon material feedstocks). For the separation of saturated hydrocarbons and aromatics, such as in furfural refining, conventional organic solvent systems and extraction processes can achieve this. However, for heavy oils rich in aromatics, conventional single organic solvents often fail to achieve high extraction efficiency and selectivity, making it difficult to efficiently separate aromatics with different ring numbers. An effective solution is to use composite solvents, by adding co-solvents or anti-solvents, and by controlling the solubility and selectivity of the main solvent, to achieve the separation of saturated hydrocarbons and oligocyclic aromatic hydrocarbons from polycyclic aromatic hydrocarbons.

[0005] Extraction towers are key equipment in solvent extraction processes. Currently, the two most commonly used extraction devices are mixed-sedimentation extractors and countercurrent extraction towers. Compared to mixed-sedimentation extractors, countercurrent extraction towers offer a more efficient liquid-liquid mass transfer mechanism and greater mass transfer kinetics. In countercurrent extraction, the less dense solute / solvent flows from bottom to top, while the denser solvent / solvent flows from top to bottom. For heavy distillate oils, the extraction solvent is the continuous phase, flowing from top to bottom, while the feedstock is the dispersed phase, flowing from bottom to top. During solvent-solute contact, polycyclic aromatic hydrocarbons (PAHs) are more polar and therefore dissolve more readily in the organic solvent than saturated hydrocarbons and oligocyclic aromatic hydrocarbons, forming the extract phase (extract). Undissolved components and a small amount of solvent (containing more saturated hydrocarbons and oligocyclic aromatic hydrocarbons) accumulate at the top of the tower, forming the raffinate phase (raffinate).

[0006] CN109401780A discloses a method for preparing rubber-filled oil using countercurrent extraction of heavy oil products with composite solvents. Specifically, it provides a method for separating polycyclic aromatic hydrocarbons (PAHs) using a composite solvent containing alkanes or cycloalkanes to prepare environmentally friendly rubber-filled oil. This method includes solvent extraction of the feedstock oil using a first extraction solvent and a second extraction solvent. In this method, the first and second extraction solvents enter the extraction tower through separate feed inlets. CN103589453A discloses a method for preparing aromatic rubber oil, specifically a method for separating PAHs using a composite solvent containing three solvents. In this method, the feedstock oil is premixed with light alkanes before entering the extraction tower, and the main solvent and antisolvent are premixed and then used as a binary composite solvent before entering the extraction tower. CN104073291A discloses an apparatus and method for liquid-liquid extraction to separate aromatics from diesel fuel. This method includes adjusting the composition of the composite solvent and adjusting the diameter of the extraction tower to improve the aromatic separation efficiency and increase the cetane number of the catalytic diesel fuel. In this method, the two solvents enter the extraction tower through separate feed inlets. CN105567301A discloses an extraction tower and a method for solvent deasphalting. The method involves setting multiple annular baffles in the packing zone of the extraction tower to increase the contact area between the two phases and improve the extraction effect.

[0007] The aforementioned patents propose control schemes for the formulation ratio of the composite solvent, the feed location, and the structure of the extraction tower. However, they lack flexible control over the distribution of the second extraction solvent within the extraction tower. During countercurrent extraction in the extraction tower, with the mass transfer between the solvent and the feed oil, timely control of the solubility and selectivity of the extraction solvent will further improve separation efficiency and achieve efficient separation of different components. Summary of the Invention

[0008] The purpose of this invention is to overcome the problem that existing extraction devices and methods cannot accurately control the dispersion and content of the second extraction solvent at different positions within the extraction tower, resulting in low separation efficiency of polycyclic aromatic hydrocarbons (PAHs) in heavy oil. This invention provides a stepped extraction separation device and method. The method employs a specific stepped extraction separation device, injecting the second extraction solvent at different heights within the device through injection ports. This allows for flexible control of the distribution and content of the second extraction solvent, achieving highly efficient separation of saturated hydrocarbons and oligocyclic aromatic hydrocarbons from PAHs in aromatic-rich heavy oil.

[0009] To achieve the above objectives, the first aspect of the present invention provides a cascade extraction and separation device, including an extraction tower. The extraction tower is provided with a first extraction solvent inlet 1, a second extraction solvent inlet 2, a feed oil inlet 3, an extract outlet 5, and a raffinate outlet 6. The second extraction solvent inlet 2 is connected to a second extraction solvent feed pipe provided inside the extraction tower. The second extraction solvent feed pipe is provided with at least two second extraction solvent injection ports 4 in the axial direction along the extraction tower.

[0010] A second aspect of the present invention provides an extraction and separation method, which is carried out in the staged extraction and separation apparatus described in the first aspect above, the method comprising:

[0011] The feedstock oil, the first extraction solvent, and the second extraction solvent are fed into the extraction tower for countercurrent contact extraction to obtain extract and raffinate.

[0012] Through the above technical solution, the present invention has the following beneficial effects:

[0013] (1) The step-by-step extraction and separation device provided by the present invention achieves precise control of the content and distribution of the second extraction solvent in the extraction tower by setting a second extraction solvent injection port on the second extraction solvent feed pipe inside the extraction tower. The solvent is distributed in a step-by-step manner in the tower, so that the solvent and the raw oil have more sufficient and uniform contact in the tower, thereby achieving step-by-step separation of aromatics with different ring numbers in heavy oil and improving extraction and separation efficiency and selectivity.

[0014] (2) The step-by-step extraction and separation device provided by the present invention is suitable for the extraction and separation of heavy oil rich in aromatics, and is particularly suitable for the separation of saturated hydrocarbons and oligocyclic aromatics and polycyclic aromatics in heavy oil. Due to the high viscosity and high aromatic content of heavy oil, it is easy for miscibility to occur when using conventional organic solvents. Moreover, conventional extraction devices and extraction methods cannot accurately control the dispersion and content of the second extraction solvent in the composite solvent at different positions in the extraction tower. The extraction and separation device described in the present invention makes the solvent distributed in a step-by-step manner in the tower, thereby achieving highly selective separation of polycyclic aromatics. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0016] Figure 1 These are schematic diagrams and enlarged partial views of the extraction and separation apparatus described in Example 1 of this invention;

[0017] Figure 2 This is a schematic diagram of the extraction and separation device described in Preparation Example 2 of the present invention.

[0018] Explanation of reference numerals in the attached figures

[0019] 1 First extraction solvent inlet; 2 Second extraction solvent inlet; 3 Feed oil inlet.

[0020] 4 Second extraction solvent injection port; 5 Extract outlet; 6 Raffinate outlet. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The first aspect of the present invention provides a cascade extraction and separation device, including an extraction tower. The extraction tower is provided with a first extraction solvent inlet 1, a second extraction solvent inlet 2, a feed oil inlet 3, an extract outlet 5, and a raffinate outlet 6. The second extraction solvent inlet 2 is connected to a second extraction solvent feed pipe provided inside the extraction tower. The second extraction solvent feed pipe is provided with at least two second extraction solvent injection ports 4 in the axial direction along the extraction tower.

[0023] In this invention, by setting second extraction solvent injection ports at different heights inside the extraction tower, the content and distribution of the second extraction solvent inside the extraction tower are precisely controlled. The solvent is distributed in a stepped manner inside the tower, which makes the contact between the solvent and the feed oil in the tower more sufficient and uniform, thereby achieving the separation of saturated hydrocarbons and oligocyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons in heavy oil, and improving the extraction separation efficiency and selectivity.

[0024] In some embodiments of the present invention, preferably, the second extraction solvent feed pipe is provided with at least two second extraction solvent injection ports along the axial direction of the extraction tower. To further improve extraction efficiency and selectivity, preferably, the second extraction solvent feed pipe is provided with at least three second extraction solvent injection ports 4 along the axial direction of the extraction tower, more preferably three to five second extraction solvent injection ports 4, for example, three, four, or five.

[0025] In this invention, the provision of at least three second extraction solvent injection ports along the axial direction of the extraction tower facilitates a more uniform distribution of the second extraction solvent within the extraction tower, thereby enabling more effective contact with the feed oil and improving extraction efficiency. Furthermore, by injecting the second extraction solvent at multiple heights, the composition and properties of the composite solvent within the extraction tower undergo gradient changes, thereby enhancing the selectivity of the solvent for aromatic hydrocarbons with different ring numbers and achieving effective separation of saturated hydrocarbons and oligocyclic aromatic hydrocarbons from polycyclic aromatic hydrocarbons.

[0026] In this invention, the shape of the second extraction solvent injection port is not particularly limited, but preferably the second extraction solvent injection port is tubular.

[0027] In this invention, the spacing between the second extraction solvent nozzles has a wide range of options. Preferably, the ratio of the spacing between adjacent second extraction solvent nozzles 4 to the height of the extraction tower is 1:4-10, for example, it can be 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any value within the range of any two of the above values.

[0028] In this invention, controlling the ratio of the distance between adjacent second extraction solvent nozzles to the height of the extraction tower within the aforementioned range helps ensure that the second extraction solvent is evenly distributed within the extraction tower, avoids excessively high or low local solvent concentrations, improves the contact efficiency and extraction effect between the solvent and the raw material oil, and facilitates precise control of the extraction selectivity, thereby achieving efficient separation of different components.

[0029] Preferably, the ratio of the spacing between adjacent second extraction solvent injection ports 4 to the height of the extraction tower is 1:4-6.

[0030] In this invention, preferably, the spacing between adjacent second extraction solvent injection ports is the same or decreases sequentially from top to bottom along the axial direction of the extraction tower, and more preferably, the spacing between adjacent second extraction solvent injection ports is the same. This helps ensure that the second extraction solvent is distributed in a stepped manner on the feed pipe, improving extraction efficiency and mass transfer efficiency. In this invention, the diameter of the second extraction solvent injection port has a wide selection range. Preferably, the ratio of the diameter of the second extraction solvent injection port to the diameter of the second extraction solvent feed pipe is 1.5-5:1, for example, it can be 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, or any value within the range of any two of the above values.

[0031] In this invention, controlling the ratio of the diameter of the second extraction solvent injection port to the diameter of the second extraction solvent feed pipe within the above-mentioned range is beneficial to improving the dispersibility of the solvent, enhancing the mixing effect of the solvent, and improving the extraction efficiency.

[0032] Preferably, the ratio of the diameter of the second extraction solvent injection port 4 to the diameter of the second extraction solvent feed pipe is 2-4:1.

[0033] In this invention, the length of the second extraction solvent injection port has a wide range of possible selection. Preferably, along the axial direction of the extraction tower, the ratio of the length of the second extraction solvent injection port 4 to the diameter of the second extraction solvent feed pipe is 0.3-3:1. For example, it can be 0.3:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, or any value within the range of any two of the above values.

[0034] In this invention, the ratio of the length of the second extraction solvent injection port to the diameter of the second extraction solvent feed pipe is controlled within the above-mentioned range. This not only ensures that the solvent has sufficient kinetic energy and dispersion effect during the injection process, but also avoids excessive diffusion or aggregation of the solvent at the injection point, forming a stable distribution in the extraction tower, improving the utilization efficiency of the solvent, and enhancing the extraction effect.

[0035] Preferably, along the axial direction of the extraction tower, the ratio of the length of the second extraction solvent injection port 4 to the diameter of the second extraction solvent feed pipe is 0.5-2:1.

[0036] In this invention, the second extraction solvent injection port is provided with injection holes, through which the second extraction solvent enters the extraction tower. The number of injection holes on the second extraction solvent injection port is not particularly limited. Preferably, 2-20 injection holes are provided on the second extraction solvent injection port 4, for example, 2, 4, 6, 8, 10, 12, 14, 16, 18, or 20, preferably 4-10. In this invention, the number of injection holes on the second extraction solvent injection port refers to the number of injection holes provided on each second extraction solvent injection port. In this invention, by providing a specific number of injection holes, it is beneficial to better disperse the second extraction solvent and to more accurately control the distribution of the second solvent within the extraction tower.

[0037] In this invention, the aperture of the injection orifice has a wide range of selectable values. Preferably, the ratio of the aperture of the injection orifice to the diameter of the second extraction solvent feed pipe is 0.002-1:1, for example, it can be 0.002:1, 0.005:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.1:1, 0.5:1, 1:1, or any value within the range of any two of the above values.

[0038] In this invention, controlling the ratio of the nozzle diameter to the second extraction solvent feed pipe diameter within the above-mentioned range is beneficial for accurately controlling the distribution of the second extraction solvent in the extraction tower, improving extraction efficiency, and reducing solvent waste.

[0039] Preferably, the ratio of the diameter of the injection hole to the diameter of the second extraction solvent feed pipe is 0.01-0.05:1.

[0040] In this invention, the location of the feed oil inlet 3 is not particularly limited, as long as it ensures that the first and second extraction solvents come into countercurrent contact with the upward-flowing feed oil for extraction. Preferably, the feed oil inlet 3 is located at the bottom of the extraction tower. In this invention, the feed oil inlet 3 is connected to a feed distributor located inside the extraction tower. In this invention, the feed oil inlet 3 is used to feed the feed oil into the extraction tower.

[0041] In this invention, the extract outlet 5 is preferably located at the lower part of the extraction tower. More preferably, the extract outlet 5 is located at the lower part of the extraction tower below the feed oil inlet 3. In this invention, the extract outlet 5 is used to discharge the extracted extract from the extraction tower.

[0042] In this invention, the location of the raffinate outlet is not particularly limited. Preferably, the raffinate outlet 6 is located at the top of the extraction tower. In this invention, the extract outlet 6 is used to discharge the extracted extract from the extraction tower.

[0043] In this invention, the first extraction solvent inlet 1 is preferably located at the upper part of the extraction tower. More preferably, the first extraction solvent inlet 1 is located at the upper part of the extraction tower below the raffinate outlet 6. In this invention, the first extractant inlet 1 is connected to a feed distributor disposed inside the extraction tower. In this invention, the first extraction solvent inlet 1 is used to feed the first extraction solvent into the extraction tower.

[0044] In this invention, the second extraction solvent inlet 2 is preferably located at the upper part of the extraction tower. More preferably, the second extraction solvent inlet 2 is located below the raffinate outlet 6. Even more preferably, the second extraction solvent inlet 2 is located below the first extraction solvent inlet 1. In this invention, the second extraction solvent inlet 2 is used to feed a second extraction solvent into the extraction tower.

[0045] In this invention, the second extraction solvent injection port 4 is disposed on the second extraction solvent feed pipe. Preferably, the second extraction solvent injection port 4 is disposed between the first extraction solvent inlet 1 and the feed oil inlet 3.

[0046] In this invention, to improve the mixing and dispersion of the solvent and the feed oil, preferably, at least one of a sieve plate, a rotating disk, and a packing material is provided between the first extraction solvent inlet 1 and the feed oil inlet 3. To further improve the interaction between the solvent and the feed oil, preferably, a packing material is provided between the first extraction solvent inlet 1 and the feed oil inlet 3.

[0047] In this invention, to better control the distribution and flow state of the solvent within the extraction tower, preferably, at least one of a sieve plate, a rotating disk, and packing material is provided between the second extraction solvent injection ports 4. This is beneficial for improving the mass transfer efficiency between the solvent and the feed oil, achieving more efficient and precise extraction and separation.

[0048] A second aspect of the present invention provides an extraction and separation method, which is carried out in the staged extraction and separation apparatus described in the first aspect above, the method comprising:

[0049] The feedstock oil, the first extraction solvent, and the second extraction solvent are fed into the extraction tower for countercurrent contact extraction to obtain extract and raffinate.

[0050] In this invention, the extraction and separation method has all the technical effects of the stepped extraction and separation device, which will not be repeated here.

[0051] In this invention, the type of feedstock oil is not particularly limited and can be any type of heavy oil conventional in the art. Preferably, the feedstock oil has a distillation range of >200℃, more preferably 250℃-540℃.

[0052] In this invention, the feedstock oil is preferably a heavy oil rich in aromatics, and the content of aromatics and polycyclic aromatic hydrocarbons in the heavy oil has a wide range of selection. Preferably, the aromatic content in the feedstock oil is 20wt%-99wt%, more preferably 30wt%-85wt%; the polycyclic aromatic hydrocarbon content in the feedstock oil is 10wt%-80wt%, more preferably 20wt%-60wt%.

[0053] In this invention, the specific type of feedstock oil is not particularly limited, as long as the distillation range, aromatic content, and polycyclic aromatic hydrocarbon content meet the above-mentioned ranges. Preferably, the feedstock oil is selected from at least one of furfural extract oil, light deasphalted oil, catalytic cracking heavy diesel oil, catalytic cracking recycle oil, vacuum distillate oil, coking wax oil, and coal liquefaction oil, and more preferably at least one of furfural extract oil, catalytic cracking recycle oil, and vacuum distillate oil. In this invention, the source of the feedstock oil is not particularly limited; for example, it can be sourced from Sinopec refineries.

[0054] In this invention, the relative density of the feedstock oil is not particularly limited. Preferably, the relative density of the feedstock oil at 20°C is 0.8-1.2 g / mL, more preferably 0.85-1.05 g / mL. In this invention, feedstock oils with a relative density within the above range exhibit good solubility and dispersibility in the solvent of the extractant described herein, which is beneficial to the extraction process.

[0055] In this invention, the first extraction solvent can be any extractant conventionally used in the art for the extraction and separation of heavy oils, as long as its density is greater than that of the feed oil to ensure that the feed oil and solvent can achieve a countercurrent extraction process. Preferably, the density of the first extraction solvent is 0.8-2 g / mL, for example, it can be 0.8 g / mL, 0.9 g / mL, 1 g / mL, 1.1 g / mL, 1.2 g / mL, 1.4 g / mL, 1.6 g / mL, 1.8 g / mL, 2 g / mL, or any value within any range of two of the above values, preferably 1.1-1.6 g / mL. In this invention, the first extraction solvent is beneficial for dissolving and separating aromatics, including oligocyclic aromatics and polycyclic aromatics, in heavy oils, achieving efficient separation and improving extraction efficiency.

[0056] In this invention, preferably, the specific type of the first extraction solvent is not particularly limited, as long as the density meets the above-mentioned range. Preferably, the first extraction solvent is at least one selected from furfural, N-methylpyrrolidone, N,N-dimethylformamide, phenol, dimethyl sulfoxide, and sulfolane, and more preferably furfural and / or dimethyl sulfoxide.

[0057] In this invention, the second extraction solvent can be any extractant conventionally used in the art for the extraction and separation of heavy oils, as long as its density is greater than that of the feed oil to ensure that the feed oil and solvent can achieve a countercurrent extraction process. Preferably, the density of the second extraction solvent is 0.8-2 g / mL, for example, it can be 0.8 g / mL, 0.9 g / mL, 1 g / mL, 1.2 g / mL, 1.4 g / mL, 1.6 g / mL, 1.8 g / mL, 2 g / mL, or any value within any range of two of the above values, preferably 0.9-1.6 g / mL. In this invention, the second extraction solvent is beneficial in working together with the first extraction solvent to reduce the solubility of the first solvent in oligocyclic aromatic hydrocarbons, thereby achieving the separation of saturated hydrocarbons and oligocyclic aromatic hydrocarbons from polycyclic aromatic hydrocarbons in the feed oil, and improving the extraction and separation efficiency and selectivity of polycyclic aromatic hydrocarbons.

[0058] In some embodiments of the present invention, preferably, the second extraction solvent is different from the first extraction solvent. The second extraction solvent is selected from at least one of furfural, N-methylpyrrolidone, phenol, dimethyl sulfoxide, sulfolane, water, and fatty alcohols having 1-8 carbon atoms. More preferably, it is selected from at least one of furfural, N-methylpyrrolidone, phenol, dimethyl sulfoxide, sulfolane, water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, n-hexanol, isohexanol, n-heptanol, isoheptanol, n-octanol, isooctanol, and ethylene glycol. More preferably, it is selected from at least one of water, ethanol, and sulfolane. In the present invention, the second extraction solvent is beneficial for further improving the extraction separation efficiency and selectivity.

[0059] In some embodiments of the present invention, preferably, the mass ratio of the first extraction solvent to the second extraction solvent is 1:0.001-0.5, for example, it can be 1:0.001, 1:0.005, 1:0.01, 1:0.02, 1:0.04, 1:0.06, 1:0.08, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, or any value within the range of any two of the above values, preferably 1:0.005-0.1. In the present invention, the mass ratio of the first extraction solvent to the second extraction solvent refers to the mass ratio of the first extraction solvent to the second extraction solvent entering the stepped extraction and separation device per unit time. In the present invention, controlling the mass ratio of the first extraction solvent to the second extraction solvent within the above range is beneficial to improving extraction efficiency and increasing the purity and quality of the product.

[0060] In some embodiments of the present invention, preferably, the mass ratio of the total mass of the first extraction solvent and the second extraction solvent to the mass of the raw oil is 0.5-6:1. For example, it can be 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, or any value within the range of any two of the above values, preferably 1-4:1. In the present invention, controlling the mass ratio of the total mass of the first extraction solvent and the second extraction solvent to the mass of the raw oil within the above range is beneficial to ensuring sufficient contact between the solvent and the raw oil, thereby improving the extraction efficiency and the purity and quality of the product.

[0061] In this invention, the extraction conditions are not particularly limited, and the conditions conventionally used in the art for extracting polycyclic aromatic hydrocarbons from heavy oils can be adopted. Preferably, the extraction conditions include: a bottom temperature of 30-70°C, more preferably 35-60°C; and a top temperature of 30-80°C, more preferably 40-70°C.

[0062] In this invention, preferably, the extraction and separation method includes: feeding the feed oil, a first extraction solvent, and a second extraction solvent into an extraction tower for countercurrent contact extraction to obtain an extract rich in aromatics and a raffinate rich in saturated hydrocarbons. More preferably, the method further includes: recovering the solvent from the extract and the raffinate to obtain a mixed solvent of the first and second extraction solvents, the raffinate oil, and the extract oil. In this invention, the solvent recovery method is not particularly limited, but flash evaporation is preferred. The flash evaporation method and conditions are not particularly limited, and conventional flash evaporation methods and conditions used in the art can be adopted, and will not be elaborated here.

[0063] The following combination Figure 1 The preferred embodiments of the present invention will be described below, along with the step-by-step extraction and separation apparatus and method of the present invention:

[0064] The feedstock oil enters the extraction tower through feedstock oil inlet 3, the first extraction solvent enters the extraction tower through the first extraction solvent inlet 1, and the second extraction solvent enters through the second extraction solvent inlet 2 and then enters the extraction tower through the second extraction solvent injection port 4. The mixed solvent of the first and second extraction solvents is countercurrently contacted with the upward-flowing feedstock oil for extraction. The extracted product is a raffinate rich in saturated hydrocarbons and oligocyclic aromatic hydrocarbons and an extract rich in polycyclic aromatic hydrocarbons. The raffinate is discharged from the extraction tower through the raffinate outlet 6 at the top of the extraction tower, and the extract is discharged from the extraction tower through the extract outlet 5 at the bottom of the extraction tower. After solvent recovery from the raffinate and the extract, raffinate oil and extract oil are obtained.

[0065] The present invention will be described in detail below through embodiments.

[0066] In the following examples and comparative examples:

[0067] The density parameter was measured in accordance with GB / T 13377 (Determination of density or relative density of crude oil and liquid or solid petroleum products);

[0068] The kinematic viscosity parameters were measured using GB / T 265 (Determination of kinematic viscosity and calculation of dynamic viscosity of petroleum products);

[0069] Hydrocarbon composition: determined according to the standard "Determination of hydrocarbons in saturated hydrocarbon fractions of gas oil (mass spectrometry) SH / T100659".

[0070] The feedstocks and their sources used in the following examples and comparative examples are as follows: furfural extract oil, catalytic cracking recycle oil, and vacuum distillate oil were all taken from a refinery of Sinopec. The furfural extract oil was the 430℃-540℃ extract oil fraction, the catalytic cracking recycle oil was the 250℃-500℃ recycle oil fraction, and the vacuum distillate oil was the 350-540℃ vacuum distillate oil. The properties and composition of the furfural extract oil, catalytic cracking recycle oil, and vacuum distillate oil used in this invention are shown in Table 1.

[0071] Preparation Example 1

[0072] Four second extraction solvent injection ports are installed along the axial direction of the extraction tower via a second extraction solvent feed pipe. The spacing between adjacent second extraction solvent injection ports is the same, with a height ratio of 1:5 to the tower height. The ratio of the second extraction solvent injection port diameter (d) to the second extraction solvent feed pipe diameter is 3:1, and the ratio of the second extraction solvent injection port length (l) to the second extraction solvent feed pipe diameter is 1:1. Each second extraction solvent injection port has eight injection holes evenly distributed in a ring, with the hole diameter being 0.02:1 of the second extraction solvent pipe diameter. The resulting extraction tower is denoted as Extraction Tower I. Figure 1 As shown.

[0073] Preparation Example 2

[0074] The extraction tower has a second extraction solvent feed pipe with three second extraction solvent injection ports along its axial direction. The spacing between adjacent injection ports is equal, with a height-to-total ... Figure 2 As shown.

[0075] Example 1

[0076] Using furfural extract oil (its properties are shown in Table 1) as the feed oil, furfural as the first extraction solvent, and water as the second extraction solvent, the mixture of the first and second extraction solvents and the feed oil are introduced into the extraction tower I (Preparation Example 1) through the first extraction solvent inlet, the second extraction solvent inlet, and the feed oil inlet, respectively, for countercurrent extraction. The temperature at the top of the extraction tower is 50°C, and the temperature at the bottom of the tower is 40°C. The total feed flow rate of the first and second extraction solvents and the feed oil into the extraction tower is 2000 g / h. The mass ratio of the first and second extraction solvents is 1:0.04, and the mass ratio of the mixture of the first and second extraction solvents to the feed oil is 2:1. An extract rich in polycyclic aromatic hydrocarbons and a raffinate rich in saturated hydrocarbons and oligocyclic aromatic hydrocarbons are obtained. The raffinate and the extract are fed into a solvent recovery system to recover the first and second extraction solvents, yielding raffinate oil and extract oil.

[0077] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 2.

[0078] Example 2

[0079] Using furfural extract oil (its properties are shown in Table 1) as the feed oil, furfural as the first extraction solvent, and water as the second extraction solvent, the mixture of the first and second extraction solvents and the feed oil are introduced into the extraction tower I (Preparation Example 1) through the first extraction solvent inlet, the second extraction solvent inlet, and the feed oil inlet, respectively, for countercurrent extraction. The temperature at the top of the extraction tower is 40°C, and the temperature at the bottom of the tower is 35°C. The total feed flow rate of the first and second extraction solvents and the feed oil into the extraction tower is 2000 g / h. The mass ratio of the first and second extraction solvents is 1:0.01, and the mass ratio of the mixture of the first and second extraction solvents to the feed oil is 1:1. An extract rich in polycyclic aromatic hydrocarbons and a raffinate rich in saturated hydrocarbons and oligocyclic aromatic hydrocarbons are obtained. The raffinate and the extract are fed into a solvent recovery system to recover the first and second extraction solvents, yielding raffinate oil and extract oil.

[0080] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 2.

[0081] Example 3

[0082] Using furfural extract oil (its properties are shown in Table 1) as the feed oil, dimethyl sulfoxide as the first extraction solvent, and ethanol as the second extraction solvent, the mixture of the first and second extraction solvents and the feed oil were introduced into extraction tower II (Preparation Example 2) through the first extraction solvent inlet, the second extraction solvent inlet, and the feed oil inlet, respectively, for countercurrent extraction. The temperature at the top of the extraction tower was 70°C, and the temperature at the bottom of the tower was 60°C. The total feed flow rate of the first and second extraction solvents and the feed oil into the extraction tower was 2000 g / h. The mass ratio of the first and second extraction solvents was 1:0.1, and the mass ratio of the mixture of the first and second extraction solvents to the feed oil was 3:1. An extract rich in polycyclic aromatic hydrocarbons and a raffinate rich in saturated hydrocarbons and oligocyclic aromatic hydrocarbons were obtained. The raffinate and the extract were fed into a solvent recovery system to recover the first and second extraction solvents, yielding raffinate oil and extract oil.

[0083] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 2.

[0084] Example 4

[0085] Using catalytic cracking recycle oil (its properties are shown in Table 1) as feedstock, furfural as the first extraction solvent, and water as the second extraction solvent, the mixture of the first and second extraction solvents and the feedstock oil are introduced into extraction tower I (Preparation Example 1) through the first extraction solvent inlet, the second extraction solvent inlet, and the feedstock oil inlet, respectively, for countercurrent extraction. The temperature at the top of the extraction tower is 50°C, and the temperature at the bottom of the tower is 40°C. The total feed flow rate of the first and second extraction solvents and the feedstock oil entering the extraction tower is 2000 g / h. The mass ratio of the first and second extraction solvents is 1:0.05, and the mass ratio of the mixture of the first and second extraction solvents to the feedstock oil is 2:1. An extract rich in polycyclic aromatic hydrocarbons and a raffinate rich in saturated hydrocarbons and oligocyclic aromatic hydrocarbons are obtained. The raffinate and the extract are fed into a solvent recovery system to recover the first and second extraction solvents, yielding raffinate oil and extract oil.

[0086] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 2.

[0087] Example 5

[0088] Using vacuum distillate oil (its properties are shown in Table 1) as feedstock, furfural as the first extraction solvent, and sulfolane as the second extraction solvent, the mixed solvent of the first and second extraction solvents and the feedstock oil were introduced into extraction tower II (Preparation Example 2) through the first extraction solvent inlet, the second extraction solvent inlet, and the feedstock oil inlet, respectively, for countercurrent extraction. The temperature at the top of the extraction tower was 50°C, and the temperature at the bottom of the tower was 40°C. The total feed flow rate of the first and second extraction solvents and the feedstock oil into the extraction tower was 2000 g / h. The mass ratio of the first and second extraction solvents was 1:0.05, and the mass ratio of the mixed solvent of the first and second extraction solvents to the feedstock oil was 4:1. An extract rich in polycyclic aromatic hydrocarbons and a raffinate rich in saturated hydrocarbons and oligocyclic aromatic hydrocarbons were obtained. The raffinate and the extract were fed into a solvent recovery system to recover the first and second extraction solvents, yielding raffinate oil and extract oil.

[0089] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 2.

[0090] Example 6

[0091] Using furfural extract oil (its properties are shown in Table 1) as the feed oil, furfural as the first extraction solvent, and n-propanol as the second extraction solvent, the mixture of the first and second extraction solvents and the feed oil are introduced into the extraction tower I (Preparation Example 1) through the first extraction solvent inlet, the second extraction solvent inlet, and the feed oil inlet, respectively, for countercurrent extraction. The temperature at the top of the extraction tower is 50°C, and the temperature at the bottom of the tower is 40°C. The total feed flow rate of the first and second extraction solvents and the feed oil into the extraction tower is 2000 g / h. The mass ratio of the first and second extraction solvents is 1:0.2, and the mass ratio of the mixture of the first and second extraction solvents to the feed oil is 5:1. An extract rich in polycyclic aromatic hydrocarbons and a raffinate rich in saturated hydrocarbons and oligocyclic aromatic hydrocarbons are obtained. The raffinate and the extract are fed into a solvent recovery system to recover the first and second extraction solvents, yielding raffinate oil and extract oil.

[0092] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 2.

[0093] Comparative Example 1

[0094] The method is the same as in Example 1, except that a second extraction solvent inlet is not provided and no second extraction solvent is added; raffinate oil and extract oil are obtained.

[0095] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 2.

[0096] Comparative Example 2

[0097] The method is the same as in Example 1, except that a second extraction solvent inlet is not provided; the first extraction solvent and the second extraction solvent are mixed, and the resulting mixed solution enters the extraction tower from the first extraction solvent inlet; raffinate oil and extract oil are obtained.

[0098] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 2.

[0099] Table 1 Properties of Crude Oil

[0100] project furfural extract oil Catalytic cracking recycle oil Vacuum distillate oil Density at 20℃ (g / mL) 1.0244 1.0410 963.5 <![CDATA[Kinematic viscosity at 100℃ / (mm 2 / s)]]> 66.86 2.417 26.95 w(saturated hydrocarbons) / % 17.1 9.1 58.2 w(total aromatics) / % 82.9 90.9 41.8 w(monocyclic aromatic hydrocarbons) / % 18.2 5.4 11.2 w(bicyclic and higher aromatic hydrocarbons) / % 64.7 85.5 30.6

[0101] Table 2

[0102]

[0103]

[0104] As can be seen from the results in Table 2, by using the extraction separation device provided by this invention, and by injecting a second extraction solvent at different heights inside the extraction tower, the content and distribution of the second extraction solvent inside the extraction tower can be precisely controlled, thereby achieving efficient separation of saturated hydrocarbons and oligocyclic aromatic hydrocarbons from polycyclic aromatic hydrocarbons in heavy oil. The content of saturated hydrocarbons and monocyclic aromatic hydrocarbons in the raffinate oil is 70-90 wt%, and the content of polycyclic aromatic hydrocarbons in the extract oil is 50-90 wt%.

[0105] Based on the contents of Examples 1 and 6 of this invention and Table 2, it can be seen that, compared with Example 1, the mass ratio of the first extraction solvent to the second extraction solvent and the mass ratio of the mixed solvent of the first extraction solvent and the second extraction solvent to the feed oil in Example 6 are not within the preferred range, resulting in an increase in the aromatic content in the raffinate and a deterioration in the separation effect.

[0106] Based on the contents of Example 1, Comparative Examples 1-3 and Table 2 of this invention, it can be seen that, compared with Example 1, Comparative Example 1 only added the first extraction solvent and did not add the second extraction solvent, resulting in poor separation effect and extremely low raffinate oil yield of only 10.1%, failing to fully extract and separate saturated hydrocarbons and monocyclic aromatic hydrocarbons; Comparative Example 2 added the first and second extraction solvents together, resulting in poor separation effect and a raffinate oil yield of only 24.2%, and the extracted oil contained a large amount of aromatic hydrocarbons, failing to achieve effective separation of monocyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons.

[0107] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A stepped extraction and separation device, comprising an extraction tower, characterized in that, The extraction tower is provided with a first extraction solvent inlet (1), a second extraction solvent inlet (2), a feed oil inlet (3), an extract outlet (5), and a raffinate outlet (6). The second extraction solvent inlet (2) is connected to a second extraction solvent feed pipe provided inside the extraction tower. The second extraction solvent feed pipe is provided with at least two second extraction solvent injection ports (4) along the axial direction of the extraction tower.

2. The apparatus according to claim 1, wherein, The feed pipe is provided with at least three second extraction solvent injection ports (4) along the axial direction of the extraction tower, preferably 3-5 second extraction solvent injection ports (4); Preferably, the ratio of the distance between adjacent second extraction solvent injection ports (4) to the height of the extraction tower is 1:4-10, more preferably 1:4-6.

3. The apparatus according to claim 1 or 2, wherein, The ratio of the diameter of the second extraction solvent injection port (4) to the diameter of the second extraction solvent feed pipe is 1.5-5:1, preferably 2-4:1; Preferably, along the axial direction of the extraction tower, the ratio of the length of the second extraction solvent injection port (4) to the diameter of the second extraction solvent feed pipe is 0.3-3:1, and more preferably 0.5-2:

1.

4. The apparatus according to any one of claims 1-3, wherein, The second extraction solvent spray port (4) is provided with 2-20 spray holes, preferably 4-10; Preferably, the ratio of the diameter of the injection hole to the diameter of the second extraction solvent feed pipe is 0.002-1:1, and more preferably 0.01-0.05:

1.

5. The apparatus according to any one of claims 1-4, wherein, The feedstock inlet (3) is located at the bottom of the extraction tower; Preferably, the extract outlet (5) is located at the lower part of the extraction tower, below the feed oil inlet (3); Preferably, the raffinate outlet (6) is located at the top of the extraction tower; Preferably, the first extraction solvent inlet (1) is located at the upper part of the extraction tower, below the raffinate outlet (6); Preferably, the second extraction solvent inlet (2) is located below the raffinate outlet (6); Preferably, the second extraction solvent injection port (4) is disposed between the first extraction solvent inlet (1) and the raw material oil inlet (3); Preferably, at least one of a sieve plate, a rotating disk, and a packing material is provided between the first extraction solvent inlet (1) and the raw material oil inlet (3), preferably a packing material; Preferably, at least one of a sieve plate, a rotating disk, and a packing material is provided between the second extraction solvent injection ports (4).

6. An extraction and separation method, characterized in that, The method is carried out in the stepwise extraction and separation apparatus according to any one of claims 1-5, and the method includes: The feedstock oil, the first extraction solvent, and the second extraction solvent are fed into the extraction tower for countercurrent contact extraction to obtain extract and raffinate.

7. The method according to claim 6, wherein, The distillation range of the feedstock oil is >200℃, preferably 250℃-540℃; Preferably, the aromatic hydrocarbon content in the feedstock oil is 20wt%-99wt%, more preferably 30wt%-85wt%; the polycyclic aromatic hydrocarbon content in the feedstock oil is 10wt%-80wt%, more preferably 20wt%-60wt%. Preferably, the feedstock oil is selected from at least one of furfural extract oil, light deasphalted oil, catalytic cracking heavy diesel oil, catalytic cracking recycle oil, vacuum distillate oil, coking wax oil, and coal liquefaction oil, and more preferably from at least one of furfural extract oil, catalytic cracking recycle oil, and vacuum distillate oil. Preferably, the relative density of the raw oil at 20°C is 0.8-1.2 g / mL, more preferably 0.85-1.05 g / mL.

8. The method according to claim 6 or 7, wherein, The density of the first extraction solvent is 0.8-2 g / mL, preferably 1.1-1.6 g / mL; Preferably, the first extraction solvent is at least one of furfural, N-methylpyrrolidone, N,N-dimethylformamide, phenol, dimethyl sulfoxide and sulfolane, preferably furfural and / or dimethyl sulfoxide; Preferably, the density of the second extraction solvent is 0.8-2 g / mL, more preferably 0.9-1.6 g / mL; Preferably, the second extraction solvent is different from the first extraction solvent. The second extraction solvent is selected from at least one of furfural, N-methylpyrrolidone, phenol, dimethyl sulfoxide, sulfolane, water, and fatty alcohols having 1-8 carbon atoms. It is more preferably selected from at least one of furfural, N-methylpyrrolidone, phenol, dimethyl sulfoxide, sulfolane, water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, n-hexanol, isohexanol, n-heptanol, isoheptanol, n-octanol, isooctanol, and ethylene glycol. More preferably, it is selected from at least one of water, ethanol, and sulfolane.

9. The method according to any one of claims 6-8, wherein, The mass ratio of the first extraction solvent to the second extraction solvent is 1:0.001-0.5, preferably 1:0.005-0.1; Preferably, the mass ratio of the total mass of the first extraction solvent and the second extraction solvent to the mass of the raw oil is 0.5-6:1, more preferably 1-4:

1.

10. The method according to any one of claims 6-9, wherein, The extraction conditions include: a bottom temperature of 30-70℃, preferably 35-60℃; and a top temperature of 30-80℃, preferably 40-70℃. Preferably, the method further includes: solvent recovery of the extract and the raffinate to obtain a mixed solvent of the first extraction solvent and the second extraction solvent, raffinate oil and extract oil.

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