Multistage extraction separation system and method

Abstract

The present application relates to the field of petroleum chemical industry, and discloses a multi-stage extraction separation system and method. The system comprises an extraction unit, the extraction unit comprises N extraction towers in series, N>=2; a second extraction solvent spraying device is arranged inside the extraction tower, the second extraction solvent spraying device comprises a second extraction solvent feeding pipe and a second extraction solvent spraying port, the second solvent feeding pipe is provided with at least two second extraction solvent spraying ports in the axial direction of the extraction tower; in the material flow direction, the outlet of the raffinate of the former stage extraction tower is connected with the raw material inlet of the latter stage extraction tower through a raffinate outlet pipeline; the outlet of the raffinate of at least one extraction tower is connected with the raw material inlet of the preceding at least one stage extraction tower. The multi-stage extraction separation system greatly improves the extraction efficiency and the selectivity of the target product, and realizes the step-by-step enrichment of different ring number aromatics in the heavy oil rich in aromatics.

Description

Technical Field

[0001] This invention relates to the field of petrochemicals, and more specifically to a multi-stage extraction and separation system and method. Background Technology

[0002] As the oil refining industry shifts towards "component refining," the refined separation of aromatics with different ring numbers in heavy oils has become crucial for improving resource utilization. Heavy oils produced during petroleum processing (such as vacuum distillate, catalytic slurry oil, and furfural extract) are often rich in aromatic compounds. These unsaturated hydrocarbons with cyclic structures have wide applications in chemical raw materials, pharmaceuticals, fragrances, and fuels. Based on the number of rings, aromatics can be classified into monocyclic aromatics, bicyclic aromatics, and polycyclic aromatics. Aromatics with different ring numbers have different market demands and values ​​due to differences in their chemical properties and application areas. For example, monocyclic and bicyclic aromatics are suitable for preparing rubber filler oils, while tricyclic and tetracyclic aromatics are more suitable as raw materials for carbon materials.

[0003] In recent years, extraction technology has been applied in the field of aromatic hydrocarbon separation. By adding specific extractants, the selective separation of aromatic hydrocarbons can be achieved by utilizing the difference in interaction forces between the extractants and aromatic hydrocarbons. However, existing solvent extraction technology still has the following problems in the separation of aromatic hydrocarbons in heavy oil: (1) Low extraction efficiency: Heavy oil has a complex composition, and the strong interaction between aromatic hydrocarbons and non-aromatic hydrocarbons leads to low extraction efficiency; (2) Poor selectivity: Existing methods are difficult to separate and enrich aromatic hydrocarbons with different ring numbers, and often require multiple subsequent treatments; (3) High cost: The consumption of extractants is large and some extractants are expensive, which increases the cost of the entire separation process; (4) Product homogeneity: Traditional single-stage extraction can usually only produce two products, which fails to make full use of the potential value of multiple hydrocarbon components in the raw material.

[0004] CN109749773A discloses a multi-stage extraction desulfurization method for hydrotreated gasoline. This method uses an extractant to perform a second extraction desulfurization treatment on the hydrotreated gasoline, reducing the sulfur content in the gasoline through multiple extraction desulfurization processes. CN111089890A discloses a method for processing heavy diesel fractions. This method uses solvents of different polarities to perform multi-stage extraction separation of heavy diesel fractions, increasing the added value of the product. CN103589453A discloses a method for preparing aromatic rubber oil. The feedstock oil is premixed with light alkanes and fed into an extraction tower. The main solvent and antisolvent are premixed and then fed into the extraction tower as a binary composite solvent. CN105567301A discloses an extraction tower and solvent deasphalting method. This method sets 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.

[0005] However, the above content proposes optimization schemes for multi-stage separation of raw materials, compound utilization of extractants, and improvement of mass transfer efficiency, but does not propose innovative methods for improving product diversity, flexibly adjusting the polarity of compound solvents, or recycling products to enhance extraction effects. With the fluctuation of hydrocarbon composition in heavy feedstock oils and the iterative updates of target products, there is an urgent need to develop new extraction and separation systems and methods. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low extraction and separation efficiency of heavy oil, single extraction product, and inability to separate aromatic hydrocarbons of different ring numbers in stages in the existing technology, and to provide a multi-stage extraction and separation system and method. This multi-stage extraction and separation system greatly improves the extraction efficiency and target product selectivity, realizes the stepwise enrichment of aromatic hydrocarbons of different ring numbers in aromatic heavy oil, and significantly increases product diversity.

[0007] To achieve the above objectives, the first aspect of the present invention provides a multi-stage extraction and separation system, the system comprising an extraction unit, the extraction unit comprising N extraction towers connected in series, where N≥2; the extraction towers are provided with a raw material inlet, a first extraction solvent inlet, a second extraction solvent inlet, an extract outlet, and a raffinate outlet;

[0008] The extraction tower is equipped with a second extraction solvent injection device, which includes a second extraction solvent feed pipe and a second extraction solvent injection port. The second solvent feed pipe is provided with at least two second extraction solvent injection ports along the axial direction of the extraction tower.

[0009] Along the material flow direction, in two adjacent extraction towers, the raffinate outlet of the preceding extraction tower is connected to the feed inlet of the subsequent extraction tower via a raffinate discharge pipeline; the raffinate outlet of at least one extraction tower is connected to the feed inlet of the preceding at least one extraction tower.

[0010] A second aspect of the present invention provides a method for multi-stage extraction and separation, the method being carried out in the multi-stage extraction and separation system described in the first aspect above, the method comprising:

[0011] Fresh feedstock oil, a first extraction solvent, and a second extraction solvent are brought into countercurrent contact for N-stage extraction, where N ≥ 2. The raffinate from the first stage is used as fresh feedstock oil for the next stage. A portion of the raffinate from at least one subsequent stage extraction is recycled to at least one preceding stage extraction as supplementary feedstock oil.

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

[0013] (1) The multi-stage extraction and separation system provided by this invention achieves efficient and precise separation of aromatic hydrocarbons with different ring numbers in heavy oil through the synergistic effect of a multi-tower series structure, a second extraction solvent injection device, and raffinate circulation, increasing product diversity, enhancing separation selectivity, and improving separation efficiency. In this multi-stage extraction and separation system, the series design of the multi-stage extraction towers allows aromatic hydrocarbons with different ring numbers to be progressively enriched in the products of different tower sections, achieving precise separation of polycyclic aromatic hydrocarbons. The second extraction solvent injection device forms a gradient distribution of the second extraction solvent through multi-point injection, enhancing the solvent's selective dissolution ability for polycyclic aromatic hydrocarbons and achieving efficient separation of aromatic hydrocarbons with different ring numbers. The raffinate circulation system optimizes the extraction equilibrium state by dynamically adjusting the composition of the feedstock in the preceding towers, improving extraction separation selectivity and enhancing the system's adaptability to feedstock fluctuations. This system improves the yield and purity of the target product through the synergistic effect of each module, reduces operating costs through dynamic control and recycling of the solvent, and simultaneously meets the flexible processing needs of different oil product systems.

[0014] (2) The multi-stage extraction and separation method provided by the present invention achieves efficient and accurate separation and high-value utilization of aromatics with different ring numbers in heavy oil by innovatively combining multi-stage countercurrent extraction, gradient solvent injection and dynamic raffinate circulation process. While reducing solvent consumption, this method can produce multi-stage high-value-added aromatic products, significantly improve the separation purity of aromatics with different ring numbers, and has strong process flexibility. It is suitable for the efficient processing of complex raw material systems and provides an innovative path for the high-value utilization of aromatic resources. 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 This is a schematic diagram of the multi-stage extraction and separation device described in Preparation Example 1 of the present invention.

[0017] Explanation of reference numerals in the attached figures

[0018] 1 Extraction tower I 2 First extraction solvent inlet I

[0019] 3 Second extraction solvent inlet I 4 Second extraction jet device I

[0020] 5. Raw material inlet 6. Extract outlet I

[0021] 7. Raffinate outlet I 8. Extraction tower II

[0022] 9 First extraction solvent inlet II 10 Second extraction solvent inlet II

[0023] 11 Second extraction jet device II 12 Extraction liquid outlet II

[0024] 13 Raffinate Outlet II 14 Extraction Tower III

[0025] 15 First extraction solvent inlet III 16 Second extraction solvent inlet III

[0026] 17 Second extraction solvent injection device III 18 Extraction liquid outlet III

[0027] 19 Raffinate Discharge Line III 20 Raffinate Circulation Line III Detailed Implementation

[0028] 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.

[0029] The first aspect of the present invention provides a multi-stage extraction and separation system, the system comprising an extraction unit, the extraction unit comprising N extraction towers connected in series, where N≥2; the extraction towers are provided with a raw material inlet, a first extraction solvent inlet, a second extraction solvent inlet, an extract outlet, and a raffinate outlet;

[0030] The extraction tower is equipped with a second extraction solvent injection device, which includes a second extraction solvent feed pipe and a second extraction solvent injection port. The second solvent feed pipe is provided with at least two second extraction solvent injection ports along the axial direction of the extraction tower.

[0031] Along the material flow direction, in two adjacent extraction towers, the raffinate outlet of the preceding extraction tower is connected to the feed inlet of the subsequent extraction tower via a raffinate discharge pipeline; the raffinate outlet of at least one extraction tower is connected to the feed inlet of the preceding at least one extraction tower.

[0032] In this invention, the multi-stage extraction and separation system achieves efficient and precise separation of aromatic hydrocarbons with different ring numbers in heavy oil through the synergistic effect of a multi-tower series structure, a second extraction solvent injection device, and raffinate circulation, thereby enhancing separation selectivity and improving separation efficiency. In the system described in this invention, the series design of the multi-stage extraction towers allows aromatic hydrocarbons with different ring numbers to be progressively enriched in the products of different tower sections, achieving precise separation of polycyclic aromatic hydrocarbons; the second extraction solvent distribution device forms a gradient through multi-point injection, achieving efficient separation of aromatic hydrocarbons with different ring numbers; the raffinate circulation system optimizes the extraction equilibrium state by dynamically adjusting the composition of the feedstock in the preceding towers, improving extraction and separation selectivity, and enhancing the system's adaptability to feedstock fluctuations.

[0033] In this invention, unless otherwise specified, each extraction tower is equipped with a second extraction solvent injection device.

[0034] In this invention, preferably, the raffinate discharge pipeline is used to send the extract separated by the pre-extraction tower into the post-extraction tower as raw material.

[0035] In this invention, preferably, the system further includes a raffinate circulation pipeline, one end of which is connected to the raffinate outlet of the extraction tower, and the other end is connected to the feed inlet of at least one prior extraction tower, for conveying a portion of the raffinate to the prior at least one extraction tower.

[0036] In this invention, the other end of the raffinate circulation pipeline can be directly connected to the raw material inlet, or it can be connected to the raffinate discharge pipeline connected to the raw material inlet of the extraction tower. Preferably, the other end of the raffinate circulation pipeline is connected to the raffinate discharge pipeline connected to the raw material inlet of the extraction tower. It should be noted that, along the material flow direction, the feed pipeline of the first-stage extraction tower is equivalent to the raffinate discharge pipeline.

[0037] In this invention, the phrase "adjacent extraction towers, the raffinate outlet of the preceding extraction tower is connected to the feed inlet of the subsequent extraction tower via a raffinate discharge pipeline; the raffinate outlet of at least one extraction tower is connected to the feed inlet of at least one preceding extraction tower" can be understood as follows: for example, the extraction unit includes three extraction towers connected in series, the raffinate outlet of the first extraction tower is connected to the feed inlet of the second extraction tower via a raffinate discharge pipeline, the raffinate outlet of the second extraction tower is connected to the feed inlet of the third extraction tower via a raffinate discharge pipeline; the raffinate outlet of the second extraction tower is also optionally connected to the feed inlet of the first extraction tower via a raffinate circulation pipeline, and the raffinate outlet of the third extraction tower is also optionally connected to the feed inlet of the first extraction tower and / or the feed inlet of the second extraction tower via a raffinate circulation pipeline; however, at least one of the second and third extraction towers has its raffinate outlet connected to the feed inlet of at least one preceding extraction tower.

[0038] In some embodiments of the present invention, preferably, the raffinate outlet of the Nth stage extraction column is connected to the feed inlet of at least one preceding stage extraction column. In the present invention, by employing the above embodiments, the selectivity of the forestage extraction can be optimized through the recycling of light components, thereby improving the separation efficiency of the target aromatic hydrocarbons, while maintaining low energy consumption.

[0039] In some embodiments of the present invention, preferably, the extraction unit comprises 2-6 extraction towers connected in series, for example, 2, 3, 4, 5, or 6, preferably 3-5. In the present invention, controlling the number of extraction towers connected in series within the above-mentioned preferred range ensures the effective separation of aromatics of different ring numbers at each stage while avoiding excessive tower numbers that would lead to increased equipment complexity and energy consumption.

[0040] In some embodiments of the present invention, preferably, the second extraction solvent feed pipe is connected to the second extraction solvent inlet.

[0041] In some embodiments of the present invention, preferably, the system further includes a solvent recovery device for recovering the solvent in the extract separated by each stage of the extraction tower and the solvent in the raffinate flowing out of the raffinate discharge pipeline of the Nth stage extraction tower.

[0042] In this invention, to further improve extraction efficiency and selectivity, preferably, in each extraction tower, the second extraction solvent feed pipe is provided with at least three second extraction solvent injection ports along the axial direction of the extraction tower, more preferably with three to five second extraction solvent injection ports, for example, three, four, or five. Controlling the number of second extraction solvent injection ports within the above-mentioned preferred range in this invention helps to ensure a more uniform distribution of the second extraction solvent inside the extraction tower, further ensuring sufficient contact between the solvent and the raw material, preventing phase separation failure caused by excessively high local concentrations, and allowing the composition and properties of the composite solvent to undergo gradient changes within the extraction tower, thereby enhancing the selectivity of the solvent for aromatic hydrocarbons of different ring numbers.

[0043] 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.

[0044] In some embodiments of the present invention, preferably, the ratio of the distance between adjacent second extraction solvent injection nozzles 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, preferably 1:4-6. In the present invention, controlling the ratio of the distance between adjacent second extraction solvent injection nozzles to the height of the extraction tower within the above range maintains a stable concentration gradient, avoids premature mixing or insufficient dispersion of the solvent, improves the contact efficiency and extraction effect between the solvent and the feedstock oil, and facilitates precise control of the extraction selectivity, achieving efficient separation of aromatics with different ring numbers.

[0045] 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; 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.

[0046] 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 any range of two of the above values, preferably 2-4:1. 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 range is beneficial to improving the dispersibility of the solvent, forming moderate turbulence to promote mass transfer, and enhancing the mixing effect of the solvent.

[0047] In this invention, the length of the second extraction solvent injection port has a wide range of selectable values. Preferably, along the axial direction of the extraction tower, the ratio of the length of the second extraction solvent injection port 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, preferably 0.5-2:1. In this invention, controlling the ratio of the length of the second extraction solvent injection port to the diameter of the second extraction solvent feed pipe within the above range 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 stepped distribution within the extraction tower, improving solvent utilization efficiency, and enhancing the extraction effect.

[0048] 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, the second extraction solvent injection port has 2-20 injection holes, more 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 on each individual second extraction solvent injection port. In this invention, by setting a specific number of injection holes, it is beneficial to reduce local concentration peaks and improve the overall extraction equilibrium stability.

[0049] In this invention, the orifice diameter of the injection hole has a wide selection range. Preferably, the ratio of the orifice diameter to the diameter of the second extraction solvent feed pipe is 0.002-1:1, more preferably 0.01-0.05:1. Controlling the ratio of the orifice diameter to the diameter of the second extraction solvent feed pipe within the above range in this invention facilitates precise control of the distribution of the second extraction solvent within the extraction tower, improves extraction efficiency, and reduces solvent waste.

[0050] In this invention, the location of the raffinate outlet is not particularly limited. Preferably, the raffinate outlet is located at the top of the extraction tower. In this invention, the extract outlet is used to discharge the extracted extract from the extraction tower.

[0051] In this invention, the first extraction solvent inlet is preferably located at the upper part of the extraction tower. More preferably, the first extraction solvent inlet is located at a position at the upper part of the extraction tower below the raffinate outlet. In this invention, the first extractant inlet is connected to a feed distributor disposed inside the extraction tower. In this invention, the first extraction solvent inlet is used to feed the first extraction solvent into the extraction tower.

[0052] In this invention, the location of the feedstock oil inlet is not particularly limited, as long as it ensures that the first and second extraction solvents come into countercurrent contact with the upward-flowing feedstock oil for extraction. Preferably, the feedstock oil inlet is located at the bottom of the extraction tower. In this invention, the feedstock oil inlet is connected to a feed distributor located inside the extraction tower. In this invention, the feedstock oil inlet is used to feed the feedstock oil into the extraction tower.

[0053] In this invention, preferably, the second extraction solvent inlet is located between the raffinate outlet and the feed inlet, and more preferably, between the first extraction solvent inlet and the feed inlet. In this invention, the second extraction solvent inlet is used to feed the second extraction solvent into the extraction tower.

[0054] In this invention, the second extraction solvent feed pipe is disposed on the second extraction solvent feed pipe. Preferably, the second extraction solvent injection port is disposed between the first extraction solvent inlet and the feed oil inlet.

[0055] In this invention, the extract outlet is preferably located at the lower part of the extraction tower. More preferably, the extract outlet is located at a position below the feed oil inlet at the lower part of the extraction tower. In this invention, the extract outlet is used to discharge the extracted extract from the extraction tower.

[0056] In this invention, to improve the mixing and dispersion of the solvent and the feedstock oil, preferably, at least one of a sieve plate, a rotating disk, and a packing material is provided between the first extraction solvent inlet and the feedstock oil inlet. To further improve the interaction between the solvent and the feedstock oil, preferably, a packing material is provided between the first extraction solvent inlet and the feedstock oil inlet.

[0057] 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. This is beneficial for improving the mass transfer efficiency between the solvent and the feed oil, achieving more efficient and precise extraction and separation.

[0058] A second aspect of the present invention provides a method for multi-stage extraction and separation, the method being carried out in the multi-stage extraction and separation system described in the first aspect above, the method comprising:

[0059] Fresh feedstock oil, a first extraction solvent, and a second extraction solvent are brought into countercurrent contact for N-stage extraction, where N ≥ 2. The raffinate from the first stage is used as fresh feedstock oil for the next stage. A portion of the raffinate from at least one subsequent stage extraction is recycled to at least one preceding stage extraction as supplementary feedstock oil.

[0060] In this invention, the multi-stage extraction and separation method innovatively combines multi-stage countercurrent extraction, gradient solvent injection, and dynamic material circulation processes to achieve efficient and precise separation and high-value utilization of aromatics with different ring numbers in heavy oil. This method can produce multi-stage high-value-added aromatic products while reducing solvent consumption. The separation purity of monocyclic and dicyclic aromatics and polycyclic aromatics is significantly improved, and the process is highly flexible and suitable for the efficient processing of complex raw material systems, providing an innovative path for the high-value utilization of aromatic resources.

[0061] In some embodiments of the present invention, N is preferably 2-6, for example, it can be 2, 3, 4, 5, or 6, preferably 3-5. In the present invention, the number of extraction stages is controlled within the above-mentioned preferred range to ensure the effective separation of aromatics with different ring numbers step by step while avoiding an increase in equipment complexity and energy consumption.

[0062] In some embodiments of the present invention, preferably, the mass ratio of the raffinate used as supplementary feed oil in the raffinate of the subsequent extraction to the total mass of the raffinate of the subsequent extraction is 0.1-0.8:1. For example, it can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, or any value within the range of any two of the above values, preferably 0.1-0.5:1. In the present invention, controlling the mass of the raffinate used as supplementary feed oil in the raffinate of the subsequent extraction within the above range effectively improves the solvent's extraction and separation effect on the feedstock, while avoiding a significant increase in energy consumption and an increase in the design load of the equipment caused by excessive circulation of the extractant.

[0063] In some embodiments of the present invention, preferably, in each extraction stage within a unit time, 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, 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.

[0064] In this 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 each stage of the extraction tower per unit time.

[0065] In some embodiments of the present invention, preferably, within a unit time, the mass ratio of the mixed solvent of the first extraction solvent and the second extraction solvent to the total mass of the fresh feed oil and the replenished feed oil in each extraction stage is 1:0.5-6. For example, it can be 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, or any value within the range of any two of the above values, preferably 1:1-4. In the present invention, controlling the mass ratio of the mixed solvent to the total mass of the fresh feed oil and the replenished feed oil within the above range ensures the extraction and separation effect while avoiding the miscibility of the solvent and the solution and preventing stratification.

[0066] In some embodiments of the present invention, preferably, a portion of the raffinate from the Nth stage extraction is recycled to the prior at least one stage extraction as supplementary feedstock.

[0067] In some embodiments of the present invention, preferably, the method further includes: separating the extracts from each stage of extraction for solvent recovery to obtain a mixed solvent of a first extraction solvent and a second extraction solvent, as well as an extraction oil.

[0068] In some embodiments of the present invention, preferably, the remaining raffinate from the Nth stage extraction is separated for solvent recovery to obtain a mixed solvent of the first extraction solvent and the second extraction solvent, as well as raffinate oil.

[0069] In this invention, the method can retain the reuse value of solvents with different polarities, while directly obtaining aromatic products of various specifications.

[0070] 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 employed, and will not be elaborated upon here.

[0071] 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 1-2 g / mL, more preferably 1.1-1.6 g / mL. In this invention, the first extraction solvent is beneficial for dissolving and separating aromatics, including oligocyclic and polycyclic aromatic hydrocarbons, in heavy oils, achieving efficient separation and improving extraction efficiency.

[0072] 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 (NMP), N,N-dimethylformamide, phenol, dimethyl sulfoxide (DMSO), and sulfolane, and more preferably at least one selected from furfural, dimethyl sulfoxide, and N-methylpyrrolidone.

[0073] 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, or 2 g / mL, 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 effective separation of aromatic hydrocarbons with different ring numbers from saturated hydrocarbon components in the feed oil, and improving the extraction and separation efficiency and selectivity of polycyclic aromatic hydrocarbons.

[0074] 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.

[0075] In this invention, the first extraction solvent can be the same or different in each extraction stage, preferably the first extraction solvent is the same; the second extraction solvent can be the same or different in each extraction stage, preferably the second extraction solvent is the same.

[0076] 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℃.

[0077] 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%-90wt%.

[0078] In this invention, preferably, the content of tricyclic and above aromatic hydrocarbons in the feed oil is 10wt%-80wt%, more preferably 20wt%-60wt%.

[0079] 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.

[0080] 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 aforementioned range exhibit good solubility and dispersibility in the solvent of the extractant described herein, which is beneficial for the extraction process.

[0081] 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 bottom temperature of each N-stage extraction column is independently 30-80°C, more preferably 35-70°C.

[0082] In this invention, preferably, the top temperature of each of the N-stage extraction columns is 30-90°C, and more preferably 40-80°C.

[0083] The following combination Figure 1 The multi-stage extraction and separation system and method of the present invention will be described below, including preferred embodiments:

[0084] Fresh feed oil enters extraction tower I through feed inlet 5 connected to the feed pipeline. First extraction solvent I enters extraction tower I through first extraction solvent inlet I 2. Second extraction solvent I enters second extraction injection device I 4 through second extraction solvent inlet I 3. The mixture of first extraction solvent I and second extraction solvent I enters extraction tower I through second extraction solvent injection port via second extraction solvent I feed pipe. The mixture of first extraction solvent I and second extraction solvent I comes into countercurrent contact with the upward feed oil (fresh feed oil and supplementary feed oil from raffinate circulation pipeline III 20) for extraction, resulting in raffinate and extract. The extract is discharged from extraction tower I through extract outlet I 6 at the bottom of extraction tower I, and the raffinate is discharged from extraction tower I through raffinate outlet I 7 at the top of extraction tower I and enters extraction tower II via raffinate discharge pipeline I.

[0085] The first extraction solvent II enters the extraction tower II through the first extraction solvent inlet II 9, and the second extraction solvent II enters the second extraction injection device II 11 through the second extraction solvent inlet II 10. It then enters the extraction tower II through the second extraction solvent injection port via the second extraction solvent II feed pipe. The mixed solvent of the first extraction solvent II and the second extraction solvent II comes into countercurrent contact with the upward feed oil (raffinate from the extraction tower I and supplementary feed oil from the raffinate circulation pipeline III 20) to extract raffinate and extract. The extract is discharged from the extraction tower II through the extract outlet II 12 at the bottom of the extraction tower II, and the raffinate is discharged from the extraction tower II through the raffinate outlet II 13 at the top of the extraction tower II and enters the extraction tower III via the raffinate discharge pipeline II.

[0086] The first extraction solvent III enters the extraction tower III through the first extraction solvent inlet III 15, and the second extraction solvent III enters the second extraction injection device III 17 through the second extraction solvent inlet III 16. The mixture of the first and second extraction solvents III enters the extraction tower III through the second extraction solvent injection port via the second extraction solvent III feed pipe. The mixture of the first and second extraction solvents III comes into countercurrent contact with the upward-flowing feed oil (from the raffinate of extraction tower II) for extraction, yielding raffinate and extract. The extract is discharged from the extraction tower III through the extract outlet III 18 at the bottom, while the raffinate is discharged from the raffinate outlet at the top of the extraction tower III, entering the raffinate discharge line 19 and the raffinate circulation line III 20, respectively. 20 is connected to the feed line of extraction tower I and the raffinate discharge line I respectively, and is used to provide part of the raffinate as supplementary feed oil. The raffinate discharge line 19 is used to discharge part of the raffinate. The solvent is recovered from the extracts from extraction tower I, extraction tower II and extraction tower III, as well as part of the raffinate from extraction tower III, to obtain raffinate oil and extract oil.

[0087] The present invention will be described in detail below through embodiments.

[0088] 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);

[0089] Hydrocarbon composition: determined according to the standard "Determination of hydrocarbons in saturated hydrocarbon fractions of gas oil (mass spectrometry) SH / T100659".

[0090] The feedstock oils and their sources used in the following examples and comparative examples are as follows: furfural extract oil was obtained from a refinery of Sinopec, and the furfural extract oil was the 430℃-540℃ extract oil fraction; the properties and composition of the furfural extract oil used in this invention are shown in Table 1.

[0091] Preparation Example 1

[0092] The extraction tower is equipped with a second extraction solvent feed pipe with four second extraction solvent injection ports along the axial direction of the extraction tower. The spacing between two adjacent second extraction solvent injection ports is the same, and the ratio of the height of the extraction tower to the height of the extraction tower body is 1:6. The ratio of the diameter of the second extraction solvent injection port to the diameter of the second extraction solvent feed pipe is 2:1, and the ratio of the length of the second extraction solvent injection port to the diameter of the second extraction solvent feed pipe is 1:1. Each second extraction solvent injection port is equipped with nine injection holes, which are uniformly distributed in a ring. The ratio of the diameter of the injection holes to the diameter of the second extraction solvent pipe is 0.05:1, thus obtaining the extraction tower.

[0093] Example 1

[0094] Using the extraction tower of Preparation Example 1, furfural extract oil (its properties are shown in Table 1) was used as the fresh feed oil. The first extraction solvent, the second extraction solvent, and the fresh feed oil were introduced into extraction tower I through the first extraction solvent inlet, the second extraction solvent inlet, and the feed inlet, respectively, in a countercurrent contact for extraction, yielding extract and raffinate. The total flow rate of the first extraction solvent, the second extraction solvent, and the fresh feed oil entering extraction tower I was 2000 g / h. The raffinate obtained from extraction tower I was then introduced into extraction tower II, where it was countercurrently contacted with the first and second extractant solutions, respectively, introduced from the first and second extraction solvent inlets of extraction tower II, to obtain extract and raffinate. The raffinate obtained from extraction tower II was then introduced into extraction tower III, where it was countercurrently contacted with the first and second extractant solutions, respectively, introduced from the first and second extraction solvent inlets of extraction tower III, to obtain extract and raffinate. 20 wt% of the raffinate obtained from extraction tower III was used as supplementary feed oil, mixed with the fresh feed oil, and then introduced into extraction tower I.

[0095] The types and amounts of the first and second extraction solvents in extraction towers I, II, and III, as well as the extraction tower temperatures, are shown in Table 2.

[0096] (2) The extracts obtained from extraction tower I, extraction tower II and extraction tower III and the remaining 80 wt% raffinate obtained from extraction tower III are respectively fed into the solvent recovery system to recover the first extraction solvent and the second extraction solvent, and to obtain the extract oil and raffinate oil.

[0097] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 3.

[0098] Example 2

[0099] Using the extraction tower of Preparation Example 1, furfural extract oil (its properties are shown in Table 1) was used as the fresh feed oil. The first extraction solvent, the second extraction solvent, and the fresh feed oil were introduced into extraction tower I through the first extraction solvent inlet, the second extraction solvent inlet, and the feed inlet, respectively, in a countercurrent contact for extraction, yielding extract and raffinate. The total flow rate of the first extraction solvent, the second extraction solvent, and the fresh feed oil entering extraction tower I was 2000 g / h. The raffinate obtained from extraction tower I was then introduced into extraction tower II, where it was subjected to countercurrent contact with the first and second extractant solutions introduced into extraction tower II through the first and second extraction solvent inlets, respectively, for extraction. Extraction tower II yields extract and raffinate. The raffinate from extraction tower II is fed into extraction tower III, where it is countercurrently contacted with the first and second extractant solutions that enter extraction tower III from the first and second extractant inlets, respectively, to obtain extract and raffinate. 20 wt% of the raffinate from extraction tower III is used as supplementary feed oil for extraction tower I, and after being mixed with fresh feed oil, it is fed into extraction tower I. 20 wt% of the raffinate from extraction tower III is used as supplementary feed oil for extraction tower II, and after being mixed with fresh feed oil (raffinate from extraction tower I), it is fed into extraction tower II.

[0100] The types and amounts of the first and second extraction solvents in extraction towers I, II, and III, as well as the extraction tower temperatures, are shown in Table 2.

[0101] (2) The extracts obtained from extraction tower I, extraction tower II and extraction tower III and the remaining 60 wt% raffinate obtained from extraction tower III are respectively fed into the solvent recovery system to recover the first extraction solvent and the second extraction solvent, and to obtain the extract oil and raffinate oil.

[0102] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 3.

[0103] Examples 3-7

[0104] Examples 3-7 employed the same multi-stage extraction method as Example 1, except that the multi-stage extraction was performed under the conditions shown in Table 1.

[0105] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 3.

[0106] Comparative Example 1

[0107] The method described in Example 1 is different except that only extraction tower I is used; no second extraction solvent inlet is provided, and no second extraction solvent is added; raffinate oil and extract oil are obtained.

[0108] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 3.

[0109] Comparative Example 2

[0110] The method described in Example 1 is different in 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.

[0111] The hydrocarbon composition of the obtained raffinate and extract oil was analyzed, and the results are shown in Table 3.

[0112] Table 1 Properties of Crude Oil

[0113] project furfural extract oil Density at 20℃ (g / mL) 1.03 w(saturated hydrocarbons) / % 12.1 w(total aromatics) / % 87.9 w(monocyclic + bicyclic aromatic hydrocarbons) / % 35.6 w(tricyclic + tetracyclic aromatic hydrocarbons) / % 22.1 w(pentacyclic aromatic hydrocarbons) / % 30.2

[0114] Table 2

[0115]

[0116] Table 2 (continued)

[0117]

[0118]

[0119] Table 3

[0120]

[0121]

[0122] As can be seen from the results in Table 3, the extraction products obtained by the multi-stage extraction and separation system and method provided by the present invention have an aromatic hydrocarbon content of over 94 wt% in the extraction oil of tower I and a saturated hydrocarbon content of over 30 wt% in the raffinate oil of tower III, thus achieving effective separation of aromatic hydrocarbons with different ring numbers from saturated hydrocarbon components.

[0123] In particular, in Example 2, the extract oil from Tower I contained 54.wt% of aromatic hydrocarbons with five or more rings, meaning that the extract oil from Tower I contained 92.wt% of aromatic hydrocarbons with five or more rings in the feedstock (furfural extract oil); the raffinate oil from Tower III contained 41.6wt% of saturated hydrocarbons, meaning that the raffinate oil from Tower III contained 86.wt% of saturated hydrocarbons in the feedstock, of which only 12.8wt% contained aromatic hydrocarbons with five or more rings, accounting for 11wt% of the aromatic hydrocarbons with five or more rings in the feedstock.

[0124] In Comparative Example 1, the content of aromatic hydrocarbons with five or more rings in the extract oil was 32.8 wt%, meaning that the extract oil enriched 87 wt% of the aromatic hydrocarbons with five or more rings in the feedstock (furfural extract oil). However, the mass fraction of saturated hydrocarbons in the extract oil was 10.4 wt%, accounting for 70 wt% of the saturated hydrocarbons in the feedstock. Furthermore, the mass fraction of saturated hydrocarbons in the raffinate oil was 19.1 wt%, accounting for only 32 wt% of the saturated hydrocarbons in the feedstock, while the content of aromatic hydrocarbons with five or more rings was 19.4 wt%, accounting for 32 wt% of the aromatic hydrocarbons with five or more rings in the feedstock. It can be seen that the extraction process in the comparative example failed to effectively separate aromatic hydrocarbons and saturated hydrocarbons, resulting in a large amount of coexistence of the two in the extract oil and raffinate oil, and the separation effect was poor.

[0125] In Comparative Example 2, the content of each component in the four extracted products was not significantly different, but the content of tricyclic and higher aromatic hydrocarbons in the raffinate was as high as 43%, indicating poor extraction effect.

[0126] 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 combinations of 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 multi-stage extraction and separation system, characterized in that, The system includes an extraction unit, which comprises N extraction towers connected in series, where N≥2; each extraction tower is provided with a raw material inlet, a first extraction solvent inlet, a second extraction solvent inlet, an extract outlet, and a raffinate outlet; The extraction tower is equipped with a second extraction solvent injection device, which includes a second extraction solvent feed pipe and a second extraction solvent injection port. The second solvent feed pipe is provided with at least two second extraction solvent injection ports along the axial direction of the extraction tower. Along the material flow direction, in two adjacent extraction towers, the raffinate outlet of the preceding extraction tower is connected to the feed inlet of the subsequent extraction tower via a raffinate discharge pipeline; the raffinate outlet of at least one extraction tower is connected to the feed inlet of the preceding at least one extraction tower.

2. The system according to claim 1, wherein, The extraction unit comprises 2-6 extraction towers connected in series, preferably 3-5; Preferably, the raffinate outlet of the Nth stage extraction column is connected to the feed inlet of at least one prior stage extraction column; Preferably, the second extraction solvent feed pipe is connected to the second extraction solvent inlet; Preferably, the system further includes a solvent recovery device for recovering the solvent in the extract separated by each extraction tower and the solvent in the raffinate flowing out of the raffinate discharge pipeline of the Nth extraction tower.

3. The system according to claim 1 or 2, wherein, In each extraction tower, the second extraction solvent feed pipe is provided with at least three second extraction solvent injection ports along the axial direction of the extraction tower, preferably 3-5 second extraction solvent injection ports; Preferably, the ratio of the distance between adjacent second extraction solvent injection nozzles to the height of the extraction tower is 1:4-10, more preferably 1:4-6; 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, more 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 to the diameter of the second solvent feed pipe is 0.3-3:1, more preferably 0.5-2:1; Preferably, the second extraction solvent spray nozzle has 2-20 spray holes, more 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.

4. The system according to any one of claims 1-3, wherein, The raffinate outlet is located at the top of the extraction tower; Preferably, the first extraction solvent inlet is located at the upper part of the extraction tower, below the raffinate outlet; Preferably, the raw material inlet is located at the bottom of the extraction tower; Preferably, the second extraction solvent inlet is located between the raffinate outlet and the feed inlet, and more preferably between the first extraction solvent inlet and the feed inlet; Preferably, the second extraction solvent feed pipe is disposed between the first extraction solvent inlet and the raw material inlet; Preferably, the extract outlet is located at the bottom of the extraction tower, below the raw material inlet.

5. A method for multi-stage extraction and separation, characterized in that, This method is carried out in the multi-stage extraction and separation system according to any one of claims 1-4, and the method includes: Fresh feedstock oil, a first extraction solvent, and a second extraction solvent are brought into countercurrent contact for N-stage extraction, where N ≥ 2. The raffinate from the first stage is used as fresh feedstock oil for the next stage. A portion of the raffinate from at least one subsequent stage extraction is recycled to at least one preceding stage extraction as supplementary feedstock oil.

6. The method according to claim 5, wherein, The ratio of the mass of the raffinate used as supplementary feedstock to the total mass of the raffinate from the subsequent extraction is 0. . 1-0.8:1, preferably 0.1-0.5:1; Preferably, in each extraction stage within a unit time, the mass ratio of the first extraction solvent to the second extraction solvent is 1:0.001-0.5, more preferably 1:0.005-0.

1.

7. The method according to claim 5 or 6, wherein, Within a unit time, in each extraction stage, the mass ratio of the mixed solvent of the first extraction solvent and the second extraction solvent to the total mass of fresh feed oil and replenished feed oil is 1:0.5-6, preferably 1:1-4; Preferably, a portion of the raffinate from the Nth stage extraction is recycled to at least one prior stage extraction as supplementary feedstock. Preferably, the method further includes: separating the extracts from each extraction stage for solvent recovery to obtain a mixed solvent of the first extraction solvent and the second extraction solvent, as well as an extraction oil; Preferably, the remaining raffinate from the Nth stage extraction is separated for solvent recovery to obtain a mixture of the first and second extraction solvents and the raffinate oil.

8. The method according to any one of claims 5-7, wherein, The density of the first extraction solvent is 1-2 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, and more preferably at least one of furfural, dimethyl sulfoxide, and N-methylpyrrolidone; 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 5-8, wherein, The distillation range of the feedstock oil is ≥200℃, preferably 250℃-540℃; Preferably, the aromatic content in the feedstock oil is 20wt%-99wt%, more preferably 30wt%-90wt%; Preferably, the content of tricyclic and higher aromatic hydrocarbons 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.

10. The method according to any one of claims 5-9, wherein, The bottom temperature of each N-stage extraction column is independently 30-80℃, preferably 35-70℃; Preferably, the top temperature of each of the N-stage extraction columns is independently 30-90°C, and more preferably 40-80°C.

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