A system and method for mixed c4 solvent deasphalting

Abstract

The application provides a mixed C4 solvent deasphalting system and method, and relates to the technical field of petroleum chemical industry.The system comprises a C4 separation unit, a two-component flow regulating unit, an extraction unit, a deoiling fractional separation unit and a purification unit, and the C4 separation unit, the two-component flow regulating unit, the extraction unit, the deoiling fractional separation unit and the purification unit are sequentially connected to form a circulation loop.The method forms a process flow of solvent separation, proportioning, extraction separation, fractional separation, purification recovery and circulation reuse by using the system, can continuously produce, improves production efficiency and meets the demand of large-scale production.Through the two-component flow regulating unit, different light / heavy deoiling requirements can be adjusted in real time, the flexibility of production is improved, the solvent is recycled in the whole process, the recycling rate is greater than or equal to 98%, the solvent cost is saved, energy is saved and reduced, and the environment is more protected.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and in particular to a system and method for deasphalting with a mixed C4 solvent. Background Technology

[0002] Heavy oil, as a crucial component in petroleum processing, faces the challenge of deep conversion and efficient utilization, which is a core issue for improving quality and efficiency, as well as energy conservation and emission reduction in the petrochemical industry. Solvent deasphalting technology, with its selective separation characteristics of asphaltenes, gums, and light components in heavy oil, has become a key process for heavy oil pretreatment and high-value component recovery. It is widely used in refining, heavy oil processing, and asphalt separation. The deasphalted asphalt, a product of this process, can be used to produce road asphalt, needle coke, and other products. Furthermore, the light and heavy deasphalting of the deasphalted oil serves as high-quality raw materials for deep processing technologies such as hydrorefining and catalytic cracking.

[0003] The core of solvent deasphalting technology lies in the solvent's selectivity in dissolving different components in heavy oil. Currently, the deasphalting solvents used in industry mainly include single solvents or simple compound solvents such as n-butane, isobutane, propane, and pentane. Although these solvents can achieve basic separation requirements under specific process conditions, with the increasingly complex properties of heavy oil feedstocks, such as increased density, viscosity, and asphaltene content, as well as the dynamic changes in market demand for light and heavy deasphalting products, traditional processes are gradually revealing many technical bottlenecks.

[0004] Existing technologies, such as CN117683558A, disclose a solvent and solvent deasphalting method for solvent deasphalting of catalytic cracking slurry. This method employs a compound solvent scheme to remove asphalt from the catalytic cracking slurry, significantly improving the yield of deasphalted oil. Simultaneously, the content of tricyclic and tetracyclic aromatics and gum content in the product is significantly increased, while the residual carbon content is significantly reduced. The resulting product is suitable for producing feedstocks such as oil-based needle coke. CN107001952A discloses a method for upgrading partially converted vacuum residue. First, the feedstock is stripped to obtain a first distillate and a first residue oil. Then, the first residue oil is solvent deasphalted to obtain deasphalted oil and asphalt fractions. The deasphalted oil is then fractionated under vacuum to obtain deasphalted gas oil distillate and heavy deasphalted residue oil. Subsequently, the two types of fractions react under the action of corresponding hydroconversion catalysts and hydrogen, respectively. Finally, the fractionated effluent recovers the atmospheric distillate and atmospheric residue oil from hydrocracking.

[0005] However, traditional processes often use a single solvent or a fixed ratio of compound solvents, resulting in fixed solvent selectivity. This makes it difficult to flexibly adjust product yield according to market demand, especially when processing feedstocks with different properties. It is impossible to optimize the product distribution of light and heavy deasphalting by adjusting the solvent composition, leading to poor operational flexibility. Furthermore, the preparation or procurement cost of dedicated deasphalting solvents is high, and the sources of some solvents, such as propane and pentane, depend on specific process byproducts, limiting supply stability. In addition, the solvent replacement process in traditional processes is complex, requiring production interruption and causing significant solvent loss and energy waste. Solvent emissions also bring certain environmental pressures. The selective dissolution capacity of a single solvent for light and heavy deasphalting components in heavy oil is limited, making it difficult to balance the yield and purity of deasphalted oil, thus affecting the processing effect of downstream deep processing technologies.

[0006] Therefore, there is an urgent need for a system and method for deasphalting using mixed C4 solvents to solve the above-mentioned technical problems. Summary of the Invention

[0007] The purpose of this invention is to provide a system and method for deasphalting with a mixed C4 solvent, which can flexibly adjust the solvent composition, improve deasphalting selectivity and product yield; by using a mixed solvent of n-butane and isobutane and adjusting their ratio in real time, precise control of the separation efficiency of light and heavy components during the deasphalting process can be achieved. The various technical effects of the preferred solutions among the many technical solutions provided by this invention are detailed below.

[0008] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a system for deasphalting with a mixed C4 solvent, comprising a C4 separation unit, a two-component flow rate regulating unit, an extraction unit, an oil removal and grading separation unit, and a purification unit, wherein the C4 separation unit, the two-component flow rate regulating unit, the extraction unit, the oil removal and grading separation unit, and the purification unit are sequentially connected to form a circulation loop.

[0009] Preferably, the C4 separation unit is used to separate high-purity n-butane and high-purity isobutane, and its outlet is connected to the two-component flow regulating unit, while its inlet is connected to the purification unit and the recovery end of the deoiling and fractionation separation unit. The two-component flow regulating unit is used to regulate the flow ratio of n-butane and isobutane, and its outlet is connected to the inlet of the extraction unit. The extraction unit is used to achieve contact separation of heavy oil and mixed C4 solvent, and its outlet is connected to the asphalt treatment end of the deoiling and grading separation unit and the purification unit, respectively. The deoiling and grading separation unit is used to separate light deoiling and heavy deoiling in stages. Its outlet is connected to the light deoiling treatment end of the purification unit and the heavy deoiling treatment end of the purification unit, respectively, and its recovery end is connected to the C4 separation unit. The purification unit is used to remove solvents from each product and output the finished product, and its recovery end is connected to the C4 separation unit.

[0010] Preferably, the C4 separation unit is a mixed C4 separation device, and the two-component flow regulating unit includes an isobutane regulating valve and a n-butane regulating valve, wherein: The two outlets of the mixed C4 separation device are respectively connected to the isobutane regulating valve and the n-butane regulating valve; The outlets of both the isobutane regulating valve and the n-butane regulating valve are connected to the extraction unit.

[0011] Preferably, the extraction unit is an extractor, which has a heavy oil inlet, an upper outlet connected to the deoiling and grading separation unit, and a lower outlet connected to the asphalt processing end of the purification unit.

[0012] Preferably, the oil removal and grading separation unit includes a heavy oil removal separator and a light oil removal separator, wherein: The upper outlet of the heavy oil separator is connected to the inlet of the light oil separator, and the lower outlet of the heavy oil separator is connected to the heavy oil removal processing end of the purification unit. The upper outlet of the light deoiling separator is the solvent recovery end, which is connected to the C4 separation unit. The lower outlet of the light deoiling separator is connected to the light deoiling treatment end of the purification unit.

[0013] Preferably, the asphalt treatment end of the purification unit adopts an asphalt stripping tower, the heavy deoiling treatment end of the purification unit adopts a heavy deoiling stripping tower, and the light deoiling treatment end of the purification unit adopts a light deoiling stripping tower, wherein: The inlet of the asphalt stripping tower is connected to the lower outlet of the extraction unit; The inlet of the heavy stripping tower is connected to the heavy stripping outlet of the oil removal and classification separation unit; The inlet of the light stripping tower is connected to the light stripping outlet of the oil removal and classification separation unit. The upper outlets of the asphalt stripping tower, the heavy deoiling stripping tower, and the light deoiling stripping tower are all solvent recovery ends, and the solvent recovery ends are all connected to the C4 separation unit.

[0014] Secondly, this embodiment provides a method for deasphalting with a mixed C4 solvent. The system for deasphalting with a mixed C4 solvent, as described above, includes the following steps: S1: The solvent is passed into the C4 separation unit to separate high-purity n-butane and high-purity isobutane; S2: The flow ratio of the high-purity isobutane and the high-purity n-butane is adjusted by the two-component flow adjustment unit to form a mixed C4 solvent; S3: The mixed C4 solvent is introduced into the extraction unit and comes into contact with the heavy oil feedstock in the extraction unit. The mixed C4 solvent selectively dissolves the light and heavy de-oiling components in the heavy oil and separates them to obtain preliminarily separated deasphalted oil and de-oiled asphalt solution. S4: The preliminarily separated deasphalted oil is passed into the heavy deasphalting separator of the deasphalting and grading separation unit, and the preliminarily separated light deasphalted oil and heavy deasphalted oil solutions are separated step by step; S5: The initial separation and light deoiling are passed into the light deoiling separator of the deoiling and grading separation unit to separate the mixed solvent and the light deoiling solution; S6: The deoiled asphalt solution, the heavy deoiled solution, and the light deoiled solution are respectively fed into the corresponding processing end of the purification unit for stripping to remove the solvent, thereby obtaining mixed solvent, deoiled asphalt, heavy deoiled and light deoiled finished products, and the mixed solvent is recovered at the same time. S7: The mixed solvent recovered in steps S5 and S6 is recycled back to the C4 separation unit for reuse.

[0015] Preferably, the temperature of the extraction unit in step S3 is 100-150℃ and the pressure is 2-6MPa.

[0016] Preferably, the temperature inside the heavy oil separator in step S4 is 100-150℃ and the pressure is 2-6MPa.

[0017] Preferably, the temperature inside the light oil separator 6 in step S5 is 220-270°C and the pressure is 3-8 MPa.

[0018] The mixed C4 solvent deasphalting system provided by this invention, by setting up a C4 separation unit, a two-component flow regulation unit, an extraction unit, an oil removal and classification separation unit, and a purification unit that are connected in sequence and can form a circulation loop, has no solvent leakage channels throughout the entire process of solvent separation, proportioning, use, and recovery, so that the solvent recycling rate is ≥98%. Moreover, the mixed C4 is mostly a by-product resource of refinery catalytic cracking and ethylene cracking units, which is widely available and inexpensive. Compared with traditional open or semi-open systems that use dedicated deasphalting solvents, it significantly reduces solvent procurement costs and environmental treatment costs, and lowers raw material costs. Furthermore, the mixed C4 solvent has a strong selective dissolution ability for light and heavy deasphalting components, and the deasphalting product has high purity, which meets the requirements of subsequent hydrorefining, catalytic cracking and other processing.

[0019] The method for deasphalting with mixed C4 solvents provided by this invention, through the aforementioned system, forms a process flow of solvent separation, proportioning, extraction separation, fractionation separation, purification and recovery, and recycling. This allows for continuous production, improves production efficiency, and meets the needs of large-scale production. The dual-component flow control unit allows for real-time adjustment of the ratio of n-butane to isobutane to adapt to different light / heavy deasphalting requirements, enhancing production flexibility. Furthermore, the solvent is recycled throughout the entire process, with a recycling rate of ≥98%, saving solvent costs while simultaneously reducing energy consumption and emissions, making it more environmentally friendly. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of an embodiment of the system for deasphalting with mixed C4 solvents according to the present invention; Figure 2 This is a flowchart of the method for deasphalting using a mixed C4 solvent according to the present invention.

[0022] In the diagram: 1. Mixed C4 separation unit; 2. Isobutane regulating valve; 3. n-Butane regulating valve; 4. Extractor; 5. Heavy oil stripper; 6. Light oil stripper; 7. Asphalt stripping tower; 8. Heavy oil stripping tower; 9. Light oil stripping tower. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] In the description of this invention, it should be understood that the terms "center," "side," "length," "width," "height," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and "side," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0026] Figure 1 This is a structural schematic diagram of this embodiment, as shown below. Figure 1 As shown, this embodiment provides a system for deasphalting with mixed C4 solvents, including a C4 separation unit, a two-component flow rate regulation unit, an extraction unit, an oil degreasing and grading separation unit, and a purification unit. The C4 separation unit, the two-component flow rate regulation unit, the extraction unit, the oil degreasing and grading separation unit, and the purification unit are sequentially connected to form a circulation loop.

[0027] This mixed C4 solvent deasphalting system, through the sequentially connected and loop-forming C4 separation unit, two-component flow regulation unit, extraction unit, deoiling and grading separation unit, and purification unit, achieves a solvent-free external leakage channel throughout the entire process of solvent separation, proportioning, use, and recovery, resulting in a solvent recycling rate of ≥98%. Furthermore, the mixed C4 solvent is primarily a byproduct of refinery catalytic cracking and ethylene cracking units, making it widely available and inexpensive. Compared to traditional open or semi-open systems using dedicated deasphalting solvents, this significantly reduces solvent procurement costs and environmental treatment expenses, lowering raw material costs. Moreover, the mixed C4 solvent exhibits strong selective dissolution of both light and heavy deoiling components, resulting in high-purity deasphalted products that meet the requirements of subsequent hydrorefining and catalytic cracking processes.

[0028] Specifically, in this embodiment, the C4 separation unit is used to separate high-purity n-butane and high-purity isobutane. Its outlet is connected to the two-component flow regulation unit, and its inlet is connected to the recovery end of the purification unit and the deoiling and fractionation separation unit. The two-component flow regulation unit is used to regulate the flow ratio of n-butane and isobutane, and its outlet is connected to the inlet of the extraction unit. The extraction unit is used to achieve contact separation of heavy oil and mixed C4 solvent, and its outlet is connected to the asphalt treatment end of the deoiling and fractionation separation unit and the purification unit, respectively. The deoiling and fractionation separation unit is used to separate light deoiling and heavy deoiling in stages, and its outlet is connected to the light deoiling treatment end and the heavy deoiling treatment end of the purification unit, respectively. Its recovery end is connected to the C4 separation unit. The purification unit is used to remove solvents from each product and output the finished product. Its recovery end is connected to the C4 separation unit.

[0029] In this embodiment, the C4 separation unit is a mixed C4 separation device 1, and the two-component flow regulation unit includes an isobutane regulating valve 2 and a n-butane regulating valve 3. The two outlets of the mixed C4 separation device 1 are respectively connected to the isobutane regulating valve 2 and the n-butane regulating valve 3; the outlets of both the isobutane regulating valve 2 and the n-butane regulating valve 3 are connected to the extraction unit.

[0030] The extraction unit is an extractor 4, which is equipped with a heavy oil inlet. The upper outlet of the extractor 4 is connected to the de-oiling and grading separation unit, and the lower outlet is connected to the asphalt processing end of the purification unit.

[0031] The oil removal and separation unit includes a heavy oil separator 5 and a light oil separator 6. The upper outlet of the heavy oil separator 5 is connected to the inlet of the light oil separator 6, and the lower outlet of the heavy oil separator 5 is connected to the heavy oil removal processing end of the purification unit. The upper outlet of the light oil separator 6 is a solvent recovery end, which is connected to the C4 separation unit, and the lower outlet of the light oil separator 6 is connected to the light oil removal processing end of the purification unit.

[0032] The purification unit employs an asphalt stripping tower 7 for the asphalt treatment end, a heavy deoiling stripping tower 8 for the heavy deoiling treatment end, and a light deoiling stripping tower 9 for the light deoiling treatment end. The inlet of the asphalt stripping tower 7 is connected to the lower outlet of the extraction unit; the inlet of the heavy deoiling stripping tower 8 is connected to the heavy deoiling outlet of the deoiling and grading separation unit; the inlet of the light deoiling stripping tower 9 is connected to the light deoiling outlet of the deoiling and grading separation unit; and the upper outlets of the asphalt stripping tower 7, heavy deoiling stripping tower 8, and light deoiling stripping tower 9 are all solvent recovery ends, each connected to the C4 separation unit.

[0033] In use, the solvent ratio can be adjusted simply by regulating the valves. The ratio of n-butane to isobutane can be precisely adjusted via isobutane regulating valve 2 and n-butane regulating valve 3. This allows for targeted increases in the yield of either heavy or light deoiling without changing the solvent, modifying process equipment, or interrupting production. The wide ratio adjustment range adapts to different light / heavy deoiling needs, enhancing production flexibility. The operation is simple, the equipment failure rate is low, and it is suitable for continuous industrial production. Furthermore, the high solvent recycling rate significantly reduces solvent loss and emissions, alleviating environmental pressure; it also avoids energy waste during solvent replacement, resulting in a reduction in overall process energy consumption.

[0034] This embodiment also provides a method for deasphalting with a mixed C4 solvent, using the above-mentioned system for deasphalting with a mixed C4 solvent, including the following steps: S1: The solvent is passed into the C4 separation unit to separate high-purity n-butane and high-purity isobutane; S2: The flow ratio of high-purity isobutane and high-purity n-butane is adjusted by a two-component flow adjustment unit to form a mixed C4 solvent. S3: A mixed C4 solvent is introduced into the extraction unit, where it contacts the heavy oil feedstock. The mixed C4 solvent selectively dissolves the light and heavy deoiled components in the heavy oil, separating them to obtain preliminarily separated deasphalted oil and deoiled asphalt solution. The temperature of the extraction unit is 100-150℃, and the pressure is 2-6MPa.

[0035] During the process, the solvent is introduced into the mixed C4 separation device 1 to separate high-purity n-butane and high-purity isobutane. The flow ratio of isobutane and n-butane is adjusted by the isobutane regulating valve 2 and the n-butane regulating valve 3, respectively, and mixed to form a mixed C4 solvent. The mixed C4 solvent is then introduced into the extractor 4, where it comes into countercurrent contact with the heavy oil feedstock. The mixed solvent selectively dissolves the light and heavy de-oiling components in the heavy oil. The upper part forms a preliminary separated deasphalted oil, and the lower part forms a de-oiled asphalt solution.

[0036] S4: The initially separated deasphalted oil is passed into the heavy deoil separator 5 of the deoiling and grading separation unit, and the initial light deoiled and heavy deoiled solutions are separated step by step; wherein, the temperature inside the heavy deoil separator 5 is 100-150℃ and the pressure is 2-6MPa.

[0037] In this embodiment, the preliminary deasphalted oil from step S3 enters the heavy deoiling separator 5. After separation, the upper part forms a preliminary light deoiling solution, and the lower part forms a heavy deoiling solution.

[0038] S5: The initially separated light deoiled solution is introduced into the light deoiling separator 6 of the deoiling and grading separation unit to separate the mixed solvent and the light deoiled solution; wherein, the temperature inside the light deoiling separator 6 is 220-270℃ and the pressure is 3-8MPa.

[0039] In this embodiment, the initial separation and light deoiling in step S4 enters the light deoiling separator 6. After separation, a mixed solvent is formed in the upper part and a light deoiling solution is formed in the lower part.

[0040] S6: The deoiled asphalt solution, heavy deoiled solution, and light deoiled solution are respectively fed into the corresponding processing end of the purification unit for stripping to remove the solvent, and the mixed solvent, deoiled asphalt, heavy deoiled and light deoiled finished products are obtained respectively, while the mixed solvent is recovered. During the process, the deoiled asphalt solution from step S3 is fed into the asphalt stripping tower 7 of the purification unit. After stripping, a mixed solvent is formed in the upper part and deoiled asphalt is formed in the lower part. The heavy deoiled solution from step S4 is fed into the heavy deoiled stripping tower 8 of the purification unit. After stripping, a mixed solvent is formed in the upper part and heavy deoiling is formed in the lower part. The light deoiled solution from step S5 is fed into the light deoiled stripping tower 9 of the purification unit. After stripping, a mixed solvent is formed in the upper part and light deoiling is formed in the lower part.

[0041] S7: The mixed solvent recovered in steps S5 and S6 is recycled back to the C4 separation unit for reuse.

[0042] The following is a detailed description with reference to specific embodiments.

[0043] Example 1 In the mixed C4 feedstock, the mass fraction of n-butane is 45%, and the mass fraction of isobutane is 55%; the density of the heavy oil feedstock (20℃) is... Viscosity (50℃) is The regulating valve adjusts the ratio of n-butane to isobutane to 3:7, with n-butane flow rate of 150 t / h and isobutane flow rate of 350 t / h. The extractor temperature is 109℃, the pressure is 3.4 MPa, and the solvent to heavy oil mass ratio is 4.2:1. The heavy oil de-oiling separator temperature is 121℃, the pressure is 3.3 MPa, and the light oil de-oiling separator temperature is 226℃, the pressure is 4.5 MPa. The heavy oil de-oiling yield is 41.3%, the light oil de-oiling yield is 24.7%, the de-oiled bitumen yield is 34.0%, and the solvent recycling rate is 98.4%.

[0044] Example 2 In the mixed C4 feedstock, the mass fraction of n-butane is 45%, and the mass fraction of isobutane is 55%; the density of the heavy oil feedstock (20℃) is... Viscosity (50℃) is The regulating valve adjusts the ratio of n-butane to isobutane to 6:4, with n-butane flow rate of 276 t / h and isobutane flow rate of 184 t / h. The extractor temperature is 114℃, the pressure is 3.5 MPa, and the solvent to heavy oil mass ratio is 4:1. The heavy deoiling separator temperature is 125℃, the pressure is 3.5 MPa, and the light deoiling separator temperature is 232℃, the pressure is 4.5 MPa. The heavy deoiling yield is 36.2%, the light deoiling yield is 28.5%, the deoiled bitumen yield is 35.3%, and the solvent recycling rate is 98.6%.

[0045] This mixed C4 solvent deasphalting method, employing the aforementioned mixed C4 solvent deasphalting system, forms a process flow encompassing solvent separation, proportioning, extraction separation, fractionation separation, purification and recovery, and recycling. It allows for continuous production, improving efficiency and meeting the demands of large-scale production. Through a two-component flow control unit, the ratio of n-butane to isobutane can be adjusted in real time to adapt to different light / heavy deoiling requirements, enhancing production flexibility. Furthermore, the solvent is recycled throughout the entire process, achieving a recycling rate of ≥98%, saving solvent costs while simultaneously conserving energy and reducing emissions, making it more environmentally friendly.

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A system for deasphalting using a mixed C4 solvent, characterized in that, It includes a C4 separation unit, a two-component flow rate regulation unit, an extraction unit, an oil removal and classification separation unit, and a purification unit, wherein the C4 separation unit, the two-component flow rate regulation unit, the extraction unit, the oil removal and classification separation unit, and the purification unit are sequentially connected to form a circulation loop.

2. The system for deasphalting with mixed C4 solvents according to claim 1, characterized in that: The C4 separation unit is used to separate high-purity n-butane and high-purity isobutane. Its outlet is connected to the two-component flow regulating unit, and its inlet is connected to the purification unit and the recovery end of the deoiling and fractionation separation unit. The two-component flow regulating unit is used to regulate the flow ratio of n-butane and isobutane, and its outlet is connected to the inlet of the extraction unit. The extraction unit is used to achieve contact separation of heavy oil and mixed C4 solvent, and its outlet is connected to the asphalt treatment end of the deoiling and grading separation unit and the purification unit, respectively. The deoiling and grading separation unit is used to separate light deoiling and heavy deoiling in stages. Its outlet is connected to the light deoiling treatment end of the purification unit and the heavy deoiling treatment end of the purification unit, respectively, and its recovery end is connected to the C4 separation unit. The purification unit is used to remove solvents from each product and output the finished product, and its recovery end is connected to the C4 separation unit.

3. The system for deasphalting with mixed C4 solvents according to claim 2, characterized in that: The C4 separation unit is a mixed C4 separation device (1), and the two-component flow regulating unit includes an isobutane regulating valve (2) and a n-butane regulating valve (3), wherein: The two outlets of the mixed C4 separation device (1) are respectively connected to the isobutane regulating valve (2) and the n-butane regulating valve (3). The outlets of the isobutane regulating valve (2) and the n-butane regulating valve (3) are both connected to the extraction unit.

4. The system for deasphalting with a mixed C4 solvent according to claim 3, characterized in that: The extraction unit is an extractor (4), which is provided with a heavy oil inlet. The upper outlet of the extractor (4) is connected to the deoiling and grading separation unit, and the lower outlet is connected to the asphalt processing end of the purification unit.

5. The system for deasphalting with mixed C4 solvents according to claim 1, characterized in that: The oil removal and grading separation unit includes a heavy oil removal separator (5) and a light oil removal separator (6), wherein: The upper outlet of the heavy oil separator (5) is connected to the inlet of the light oil separator (6), and the lower outlet of the heavy oil separator (5) is connected to the heavy oil removal end of the purification unit. The upper outlet of the light deoiling separator (6) is the solvent recovery end, which is connected to the C4 separation unit. The lower outlet of the light deoiling separator (6) is connected to the light deoiling treatment end of the purification unit.

6. The system for deasphalting with mixed C4 solvents according to claim 1, characterized in that: The asphalt treatment end of the purification unit adopts an asphalt stripping tower (7), the heavy deoiling treatment end of the purification unit adopts a heavy deoiling stripping tower (8), and the light deoiling treatment end of the purification unit adopts a light deoiling stripping tower (9), wherein: The inlet of the asphalt stripping tower (7) is connected to the lower outlet of the extraction unit; The inlet of the heavy stripping tower (8) is connected to the heavy stripping outlet of the oil removal and classification separation unit; The inlet of the light stripping tower (9) is connected to the light stripping outlet of the oil removal and classification separation unit; The upper outlets of the asphalt stripping tower (7), the heavy stripping tower (8), and the light stripping tower (9) are all solvent recovery ends, and the solvent recovery ends are all connected to the C4 separation unit.

7. A method for deasphalting using a mixed C4 solvent, characterized in that: The system for deasphalting using a mixed C4 solvent as described in any one of claims 1-6 includes the following steps: S1: The solvent is passed into the C4 separation unit to separate high-purity n-butane and high-purity isobutane; S2: The flow ratio of the high-purity isobutane and the high-purity n-butane is adjusted by the two-component flow adjustment unit to form a mixed C4 solvent; S3: The mixed C4 solvent is introduced into the extraction unit and comes into contact with the heavy oil feedstock in the extraction unit. The mixed C4 solvent selectively dissolves the light and heavy de-oiling components in the heavy oil and separates them to obtain preliminarily separated deasphalted oil and de-oiled asphalt solution. S4: The preliminarily separated deasphalted oil is passed into the heavy deasphalting separator of the deasphalting and grading separation unit, and the preliminarily separated light deasphalted oil and heavy deasphalted oil solutions are separated step by step; S5: The initial separation and light deoiling are passed into the light deoiling separator of the deoiling and grading separation unit to separate the mixed solvent and the light deoiling solution; S6: The deoiled asphalt solution, the heavy deoiled solution, and the light deoiled solution are respectively fed into the corresponding processing end of the purification unit for stripping to remove the solvent, thereby obtaining mixed solvent, deoiled asphalt, heavy deoiled and light deoiled finished products, and the mixed solvent is recovered at the same time. S7: The mixed solvent recovered in steps S5 and S6 is recycled back to the C4 separation unit for reuse.

8. The method for deasphalting with mixed C4 solvents according to claim 7, characterized in that: The temperature of the extraction unit in step S3 is 100-150℃, and the pressure is 2-6MPa.

9. The method for deasphalting with mixed C4 solvents according to claim 7, characterized in that: The temperature inside the heavy oil separator (5) in step S4 is 100-150℃ and the pressure is 2-6MPa.

10. The method for deasphalting with a mixed C4 solvent according to claim 7, characterized in that: The temperature inside the light oil separator (6) in step S5 is 220-270℃ and the pressure is 3-8MPa.

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