A system for fractional hydroconversion of heavy residue oil and its processing method

Abstract

This invention belongs to the field of petrochemical technology and relates to a system and processing method for the fractional hydroconversion of heavy residue oil. This invention overturns the traditional process layout, using n-pentane solvent deasphalting as the core hub to "fractionate" vacuum residue oil into DAO and DOA, and matching optimal hydrotreating paths for each (DAO enters a fixed bed to maintain a long cycle, and DOA enters a slurry bed to pursue high conversion). This systematically solves the contradiction in existing technologies that cannot simultaneously consider both fixed bed lifespan and the high-value utilization of inferior feedstocks.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology and relates to a system and processing method for the fractional hydroconversion of heavy residue oil. Background Technology

[0002] With the increasing trend of heavier and lower-quality crude oil resources globally, the content of sulfur, nitrogen, metals (nickel, vanadium), and asphaltenes in heavy fractions such as vacuum residue continues to rise, posing a severe challenge to the residue processing units of oil refineries. Fixed-bed residue hydrotreating technology is currently the mainstream technology route for residue pretreatment due to its low investment and simple operation. However, fixed-bed units are sensitive to the metal content of the feedstock: according to actual industrial production data, when the nickel + vanadium content in the feedstock is at the conventional level of 70-100 μg / g, the catalyst deactivates rapidly due to metal and coke deposition, the bed pressure drop increases, and the unit is forced to shut down for catalyst replacement. The typical catalyst replacement cycle is about 18 months, which cannot meet the long-term operation requirements of more than 4 years for upstream and downstream atmospheric and vacuum distillation, catalytic cracking, and hydrocracking units in integrated refining and chemical projects.

[0003] Regarding the typical configuration of existing integrated refining and chemical enterprises: In some existing integrated refining and chemical projects, enterprises have formed a preliminary pattern of "differentiated processing"—fixed-bed residue hydrotreating units process low-sulfur, low-metal crude oil (non-deep-drawn vacuum residue), while slurry-bed residue hydrotreating units process heavy, low-quality crude oil (deep-drawn vacuum residue). However, this division of labor model has the following inherent defects: (1) Upstream atmospheric and vacuum distillation operation is restricted: In order to ensure the quality of fixed bed feed, the atmospheric and vacuum distillation unit that produces fixed bed raw materials is forced to adopt shallow drawing operation, which sacrifices the yield of vacuum wax oil; (2) Insufficient crude oil adaptability: When the proportion of inferior crude oil processed in the whole plant increases, the metal content of the fixed bed feed will inevitably increase, and the replacement cycle will be forced to be shortened. (3) The raw material source of slurry bed equipment is singular: the existing slurry bed equipment mainly uses vacuum residue oil as raw material, and the blending ratio is limited by the requirements of the stability of equipment operation. Its potential to accommodate inferior raw materials has not been fully explored.

[0004] CN106544055A discloses a method for processing inferior heavy oil and / or inferior residue oil. The inferior heavy oil / residue oil is fed into a slurry bed reactor for a first hydrogenation reaction. The resulting heavy material undergoes solvent deasphalting to obtain deasphalted oil and deoiled asphalt containing a catalyst. The deasphalted oil is then fed into a fixed bed reactor for a second hydrogenation reaction. However, its solvent deasphalting unit is located after the slurry bed reactor, and the processing target is heavy material containing hydrogenation catalysts. This does not form a "pre-solvent deasphalting, two-way separation" pattern. Furthermore, the deoiled asphalt contains a large amount of dispersed catalyst, requiring a catalyst recovery process.

[0005] CN101418222B discloses a combined treatment method for inferior residual oil. The residual oil undergoes solvent deasphalting to obtain DAO, which is then fed into a fluidized bed hydrogenation process. The deasphalted DAO is mixed with the oil slurry and fed into a suspended bed hydrogenation process. The solvent used is a mixture of butane, pentane, and a small amount of naphtha. Furthermore, the deasphalted DAO must be mixed with the oil slurry before being fed into the suspended bed. Since the suspended bed is a newly built unit, this significantly increases the complexity of operation. Suspended bed hydrogenation typically operates under harsh conditions of high temperature, high pressure, and proximity to hydrogen, posing a high safety risk. Uniform mixing and mass transfer of the gas, liquid, and solid phases within the reactor are crucial. Insufficient hydrogen solubility in heavy oil (typically low) or uneven catalyst dispersion can easily lead to localized overheating and coking, affecting the long-term stable operation of the unit. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a method for the graded hydroconversion of heavy residue oil. This method employs a novel ternary coupled process architecture of "n-pentane desorption-DAO fixed bed-DOA blending slurry bed" to resolve a long-standing structural contradiction in existing integrated refining and chemical enterprises: the implicit competition between the fixed bed and slurry bed units for high-quality vacuum residue oil, which forces the upstream atmospheric and vacuum distillation units to be shallowly drawn, resulting in poor crude oil adaptability across the entire plant.

[0007] The objective of this invention can be achieved through the following technical solutions: 1. A combined processing method for the fractional hydroconversion of heavy residue oil, the method comprising the following steps: S1. The vacuum residue is introduced into the solvent deasphalting unit and solvent deasphalting is carried out using n-pentane as the extraction solvent to obtain deasphalted oil and deoiled asphalt. S2. The deasphalted oil from step S1 is sent to a fixed-bed residue hydrotreating unit for hydrotreating. S3. The deoiled bitumen described in step S1 is incorporated into the main feedstock of the slurry bed residue hydrotreating unit at a rate of 8-15% of the total feed mass. After being mixed with hydrogen and hydrotreating catalyst, it is fed into the slurry bed reactor for hydrocracking reaction.

[0008] In the above-mentioned combined processing method of fractional hydroconversion of heavy residue oil, in step S1, the vacuum residue oil includes vacuum residue oil produced by atmospheric and vacuum distillation unit; the total content of nickel and vanadium in the deasphalted oil is controlled below 40 μg / g.

[0009] Vacuum residue is a complex mixture containing saturated fractions, aromatic fractions, gums, and asphaltenes. Heavy metals such as nickel and vanadium are mainly concentrated in the asphaltenes, which have the highest molecular weight and strongest polarity, in the form of porphyrin complexes. n-Pentane, as a C5 alkane solvent, has moderate solubilizing ability (i.e., dissolving capacity). Under supercritical or near-critical conditions, it can effectively dissolve saturated fractions and most aromatic fractions, but its dissolving ability for gums and asphaltenes is very poor. Utilizing this selective dissolution difference, vacuum residue can be "separated" into two parts: one part is the "light component" dissolved in n-pentane, which, after solvent recovery, becomes high-quality deasphalted oil (DAO) with low metal and low asphaltenes; the other part is the "heavy component" insoluble in n-pentane, namely deoiled asphalt (DOA) rich in asphaltenes and heavy metals. The present invention specifically chooses n-pentane, rather than propane or butane, because n-pentane can achieve the most thorough separation of metal-containing asphaltene while ensuring a high DAO yield. This is the key technology for reducing the metal content of DAO to below 40 μg / g to meet the subsequent long-term operation target of the fixed bed.

[0010] The lifespan of fixed-bed catalysts is primarily limited by the metal deposition rate. This invention, through a pre-implantation n-pentane stripping step, fundamentally improves the quality of the fixed-bed feed (DAO), drastically reducing the metal (Ni+V) content from over 70-100 μg / g to below 40 μg / g. This significant reduction in metal loading slows the metal deposition rate on the catalyst bed by over 60%, thereby greatly extending the catalyst's effective lifespan. The catalyst replacement cycle is extended from the traditional approximately 18 months to over 4 years, perfectly matching the plant's overhaul cycle and solving a long-standing "weak link" problem for refining and chemical enterprises.

[0011] In the above-mentioned combined processing method of fractional hydroconversion of heavy residue oil, in step S1, the solvent deasphalting treatment is carried out under supercritical extraction conditions, wherein the extraction temperature is 160-200℃, the pressure is 3.8-4.8MPa, and the volume ratio of n-pentane to vacuum residue oil is (5-8):1.

[0012] In the above-mentioned combined processing method of heavy residue oil fractional hydroconversion, in step S2, the mass proportion of the deasphalted oil in the total feed of the fixed bed residue oil hydroconversion unit is 50-100%.

[0013] Preferably, the deasphalted oil is fed into the fixed-bed residue hydrotreating unit by mixing it with wax oil.

[0014] Preferably, the mass ratio of deasphalted oil to wax oil is 50:50, wherein the wax oil is at least one of straight-run wax oil and slurry bed wax oil.

[0015] Further optimization revealed that the Ni+V content in both straight-run wax oil and slurry-bed wax oil was less than 2 μg / g.

[0016] In the above-mentioned combined processing method of graded hydroconversion of heavy residue oil, in step S2, the hydrotreating is carried out under the conditions of hydrogen partial pressure of 15-19 MPa, reaction temperature of 360-430℃, and hydrogen-to-oil volume ratio of 850-1500.

[0017] Preferably, the reactor in the fixed-bed residue hydrotreating unit is filled with a catalyst gradation method; the catalyst gradation method involves sequentially filling a protective agent, a demetallizing agent, and a decarbonizing agent along the flow direction, with the filling volume ratio of the protective agent, demetallizing agent, and decarbonizing agent being (5-15):(50-60):(30-35) (based on the filling height, the reactor cross-sectional area is the same).

[0018] Preferably, the protective agent includes at least one of FGF-01S, FGF-02S, FZC-1011, FZC-1012 and FZC-12B-3; Preferably, the demetallizing agent includes at least one of FZC-1013, FZC-28AS, FZC-28S and FZC-204AS; Preferably, the decarbonization agent includes at least one of FZC-33BTS and FZC-41BTS.

[0019] In the above-mentioned combined processing method of heavy residue oil fractional hydroconversion, in step S3, the main feedstock of the slurry bed residue oil hydroconversion unit is vacuum residue oil.

[0020] In the above-mentioned combined processing method of fractional hydroconversion of heavy residue oil, in step S3, the hydroconversion catalyst is an oil-soluble molybdenum-based catalyst.

[0021] In the above-mentioned combined processing method of graded hydroconversion of heavy residue oil, in step S3, the hydrocracking reaction is carried out under the conditions of hydrogen pressure of 14-17 MPa, reaction temperature of 410-435℃, and gas holdup of 18-38%.

[0022] DOA is typically used as a low-value fuel or gasification feedstock. However, this invention reveals that although DOA is rich in asphaltenes, these macromolecules exhibit excellent hydrocracking reactivity in the high-temperature (>410℃), high-pressure (>14MPa), and highly turbulent reaction environment of a slurry bed reactor. Slurry bed reactors are highly tolerant of feedstocks and can effectively process feedstocks high in asphaltenes and metals. Adding DOA at a ratio of 8-15% will not disrupt the stable operation of existing slurry bed units (the overall conversion rate can still be maintained above 85%), while efficiently converting this low-quality resource into high-value-added naphtha, diesel, and other light oil products, achieving a "waste-to-treasure" transformation. Its economic benefits far exceed those of traditional fuel or gasification routes.

[0023] The above-mentioned combined processing method for the graded hydroconversion of heavy residue oil also includes a hydrogen coupling step: the hydrogen-rich gas produced by the slurry bed residue oil hydrotreating unit is purified and then added as supplementary hydrogen to the hydrogen system of the fixed bed residue oil hydrotreating unit.

[0024] The present invention also provides a heavy residue oil fractional hydroconversion system for the above method, characterized in that it includes: a solvent deasphalting unit using n-pentane as the extraction solvent, connected to a feed inlet for receiving vacuum residue oil, a deasphalted oil outlet and a de-oiled asphalt outlet; The feed inlet of the fixed-bed residue hydrotreating unit is connected to the deasphalted oil outlet of the solvent deasphalting unit; Mixer: Connected to a feed inlet for receiving vacuum residue and a feed inlet for deoiled bitumen; And a slurry bed residue hydrotreating unit, the feed system of which is connected to the outlet of the mixer, and the feed system is configured to incorporate the deoiled bitumen at a ratio of 8-15% of the total feed mass.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention overturns the traditional process layout, taking n-pentane solvent deasphalting as the core hub, and "separates" vacuum residue into DAO and DOA, and matches the optimal hydrogenation path for each (DAO enters the fixed bed to maintain a long cycle, and DOA enters the slurry bed to pursue high conversion), systematically solving the contradiction that existing technologies cannot simultaneously take into account the life of the fixed bed and the high-value utilization of inferior raw materials.

[0026] 2. This invention actively controls the metal content of the fixed-bed feed to below 40 μg / g through pre-dissolution, extending the catalyst's design life to more than 4 years, which is in complete match with the plant's maintenance cycle, thus eliminating the "shortcoming" that restricts the long-term operation of integrated refining and chemical enterprises.

[0027] 3. This invention transforms DOA, which is traditionally used only as a low-value fuel or gasification feedstock, into high-value light oil products through deep hydrogenation conversion by incorporating it into existing slurry bed devices. This achieves the high-value utilization of inferior resources and is expected to bring about significant economic growth.

[0028] 4. This invention cleverly utilizes the existing slurry bed hydrogenation unit in refining and chemical enterprises. Only one mature solvent deasphalting unit needs to be added to achieve the optimization and upgrading of the entire heavy oil processing system, avoiding expensive investments such as building new slurry beds. It has the advantages of low investment and quick results.

[0029] 5. This invention significantly reduces the sensitivity of refineries to crude oil quality. Regardless of the type of inferior crude oil purchased, it can be converted into qualified hydrogenation feedstock through the combined process of this invention, greatly expanding the scope of crude oil procurement and enhancing the enterprise's ability to resist risks and profitability in the face of international oil price fluctuations. Attached Figure Description

[0030] Figure 1 The flowchart for the fractional hydroconversion of heavy residue oil in Example 1 is as follows: 1. Atmospheric and vacuum distillation unit for converting crude oil into vacuum residue oil; 2. Solvent deasphalting unit; 3. Mixer; 4. Fixed bed residue oil hydroconversion unit; 5. Slurry bed residue oil hydroconversion unit. Detailed Implementation

[0031] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0032] Example 1: One of the provided methods is as follows Figure 1 The combined processing method for the fractional hydroconversion of heavy residue oil, as shown, includes the following steps: S1. The vacuum residue produced by the atmospheric and vacuum distillation unit is used as the design basis raw material. The properties of the mixed vacuum residue are as follows: density (20℃) 1.049 g / cm³, sulfur content 5.61 wt%, nitrogen content 0.45 wt%, carbon residue 27.13 wt%, C7 asphaltene 15 wt%, nickel content 55 μg / g, vanadium content 170 μg / g, Ni+V=225 μg / g.

[0033] S2. The vacuum residue is introduced into the solvent deasphalting unit and solvent deasphalting is carried out using n-pentane as the extraction solvent to obtain deasphalted oil and deoiled asphalt. n-Pentane (purity ≥96%) was deasphalted using a continuous countercurrent extraction process in an extraction tower. Design operating conditions: extraction tower top temperature 168℃, pressure 4.62MPa, solvent-to-oil volume ratio 6:1. Solvent recovery employed a combination of supercritical fluid recovery and evaporation recovery processes.

[0034] Design material balance and product properties: The designed yield of deasphalted oil is 66 wt%, and the designed property index is: Ni+V≤40μg / g.

[0035] The designed yield of de-oiled bitumen is 34 wt%, and the softening point is approximately 177℃.

[0036] S3. The deasphalted oil obtained in step S2 is mixed with wax oil (mass ratio of deasphalted oil to wax oil = 50:50, wherein the wax oil is straight-run wax oil with a Ni+V content of less than 2 μg / g) and fed into the fixed-bed residue hydrotreating unit for hydrotreating. The reactor in the fixed-bed residue hydrotreating unit is packed with catalyst in a tiered manner. The hydrotreating conditions are: hydrogen partial pressure 18.5 MPa, initial reaction temperature 375℃ (gradually increased during the operation cycle), and hydrogen-to-oil volume ratio 860:1.

[0037] In the fixed-bed residue hydrotreating reaction zone, the catalyst is packed in the following manner along the flow direction: protective agent, demetallizing agent, and decarbonizing agent are packed sequentially. The volume ratio of the protective agent, demetallizing agent, and decarbonizing agent is 10.42:56.90:32.68 (based on the packing height, with the same reactor cross-sectional area). The protective agent is FGF-01S (produced by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd.), the demetallizing agent is FZC-1013 (produced by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd.), and the decarbonizing agent is FZC-33BTS (produced by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd.). The protective agent is a hydrotreating protective catalyst, the demetallizing agent is a hydrotreating demetallizing catalyst, and the decarbonizing agent is a hydrotreating decarbonizing catalyst.

[0038] Gradual temperature increase includes: controlling the initial reaction temperature at 375℃, waiting for 7 hours of stable operation and for the temperature rise of each reactor bed to stabilize, and then determining whether further temperature increase is needed based on product quality analysis results; if it is necessary to maintain product specifications (such as sulfur, residual carbon, and metal content) within limits, the weighted average temperature (CAT) should be increased by no more than 1℃ each time; after each temperature increase, the system should be kept stable for at least 8 hours before proceeding with the next temperature increase; if a significant temperature increase is required, it can be achieved through multiple temperature increases of 1℃ each time, with an interval of at least 8 hours between each increase; if there are obvious signs of improvement in product quality during the temperature increase process, the subsequent temperature increase operation should be stopped immediately, and this temperature should be taken as the stable operating value for the current stage; the entire temperature increase process follows the operation sequence of "increase feed rate first, then increase temperature", and before the temperature increase operation, it is necessary to confirm that the current feed rate has reached the expected target value before proceeding with the gradual temperature increase.

[0039] Catalyst lifetime calculation: Based on the deactivation rate model provided by the catalyst supplier, under the condition that the feed metal content is ≤40μg / g, the catalyst replacement cycle is designed to be no less than 49 months, which meets the design goal of long-term operation of more than 4 years (48 months).

[0040] S4. The deoiled bitumen obtained in step S2 is thoroughly mixed with vacuum residue at a mass ratio of 12% and used as the main feedstock for the slurry bed hydrocracking unit. An oil-soluble molybdenum-based catalyst (purchased from ENI, Italy, with a molybdenum (Mo) content controlled at 15 wt%) is added at a rate of 1094 g / t. Under the designed reaction conditions (pressure 15.9 MPa, reaction temperature 430℃, gas holdup 30%): based on the deoiled bitumen slurry bed hydrocracking process, the asphaltene content in the deoiled bitumen is as high as 30% or more, and its hydrocracking reactivity is lower than that of conventional vacuum residue. After blending with 12% deoiled bitumen, the conversion rate is slightly lower than before blending, but the total conversion rate can still be maintained above 85%. The reaction products are separated by gas-liquid separation and fractionation to obtain gas, naphtha, diesel, wax oil and unconverted oil residue; part of the unconverted oil residue is recycled back to the inlet of the slurry bed reactor and part is sent to the oil residue gasification unit for gasification treatment.

[0041] Hydrogen coupling step: The hydrogen-rich gas produced as a byproduct of the slurry bed residue hydrotreating unit is purified and then added to the hydrogen system of the fixed bed residue hydrotreating unit as supplementary hydrogen.

[0042] Example 2: The difference from Example 1 is only that in step S2, the volume ratio of the n-pentane extraction solvent to the oil is controlled at 2:1, which is far lower than the (5-8):1 range required by the present invention.

[0043] Under the same raw materials and operating conditions as in Example 1, only the volume ratio of the agent to oil was reduced to 2:1. The results showed that: (1) The extraction efficiency dropped sharply, and the yield of deasphalted oil was seriously low. The low solvent / oil ratio reduces the density difference between the DAO-solvent phase and the asphaltene product, resulting in low phase separation efficiency. The measured yield of deasphalted oil (DAO) dropped sharply from 66 wt% in Example 1 to less than 35 wt%, with a large amount of soluble oil remaining in the deoiled bitumen (DOA).

[0044] (2) The metal content of the deasphalted oil far exceeds the design specifications. Due to insufficient solvent, asphaltenes and the metal porphyrin compounds they carry are largely entrained into the DAO phase. The analysis results show that the total metal (Ni+V) content in the obtained deasphalted oil is as high as 150 μg / g or more, far exceeding the design upper limit of 40 μg / g. If such a high metal content feed is directly fed into the fixed-bed residue hydrotreating unit, according to the catalyst deactivation model, its catalyst replacement cycle will be shortened to less than 6 months, which completely fails to achieve the core objective of the present invention of long-term operation of more than 4 years, rendering the setting of step S2 meaningless.

[0045] (3) The operational risks of the equipment are significantly increased. The excessively low solvent-to-oil ratio results in very low solvent content in the material at the bottom of the asphalt separator, causing the DOA softening point to rise sharply to above 210°C (normally around 177°C). In this embodiment, the DOA softening point is too high, and even if the preheating temperature of the pre-cut flow is increased, frequent blockages in the asphalt pump and downstream pipelines cannot be avoided. At the same time, the low solvent ratio leads to insufficient countercurrent contact within the extraction packing, making it easy for asphalt to be entrained from the top of the separator, contaminating the circulating solvent system.

[0046] The 2:1 additive-to-oil ratio operation deviates significantly from the KBR design benchmark, failing to achieve effective "separation" of vacuum residue. It cannot provide qualified feedstock for the fixed bed, nor can it produce stable blended materials for the slurry bed, and it brings an extremely high risk of coking. This operating condition is unacceptable in industry.

[0047] Example 3: The difference from Example 1 is that, in step S2, the volume ratio of the n-pentane extraction solvent to the oil is controlled at 10:1, which is higher than the (5-8):1 range required by this invention.

[0048] Under the same raw materials and operating conditions as in Example 1, only the volume ratio of the agent to oil was increased to 10:1. The results showed that: (1) The yield of deasphalted oil decreased instead of increasing, indicating excessive solvent selectivity. Although the metal content of DAO could be further reduced to 12 μg / g, the DAO yield decreased from 66 wt% in Example 1 to approximately 52%. This is because excessive solvent, under supercritical conditions (asphalt separator operating temperature approximately 168°C), also has a repulsive effect on macromolecular colloids, causing some soluble components to be forcibly precipitated into DAO, resulting in resource waste. Temperature is the main variable controlling the yield, and a solvent ratio of 6:1 can achieve a balance between maximum yield and product quality; further increasing the solvent ratio does not proportionally increase the yield, but instead reduces economic efficiency due to over-extraction.

[0049] (2) The solvent recovery system experienced a surge in load, leading to a significant increase in energy consumption. Increasing the solvent-to-oil ratio from 6:1 to 10:1 meant an increase of approximately 67% in the total circulating solvent volume. The designed total solvent flow rate was 6 times the feed volume, with 5 parts entering the bottom of the asphalt separator and 1 part used as pre-diluted solvent. In this embodiment, the processing capacity of the solvent circulation pump, DAO separator preheater, supercritical heat exchanger, and solvent condenser all exceeded the design values. During solvent heating, the expanded solvent needed to be discharged to the solvent buffer tank via the overpressure control valve, and excess solvent also needed to be pumped outside the device. In this embodiment, the extra solvent caused the overpressure control valve to open frequently, increasing high-pressure steam consumption by approximately 55% compared to Embodiment 1. Simultaneously, the solvent condenser was overloaded, making it difficult to maintain the condensed temperature at the designed 61°C, resulting in increased solvent loss.

[0050] (3) The investment and operating costs of the equipment will increase significantly. To handle a solvent-to-oil ratio of 10:1, it is necessary to expand the diameter of the solvent circulation pump, heat exchanger, and tower internals or add a spare series, which is expected to increase the one-time investment by more than 30%. At the same time, the high solvent circulation volume also increases solvent leakage and replenishment solvent consumption, raising the operating and maintenance costs. The solvent flow rate should usually be kept constant, and even if the feed is reduced, a high solvent ratio should be maintained to keep the flow rate; however, 10:1 is far beyond the normal operating flexibility range, which will lead to excessively high gas velocity in the separator and increase DAO carryover losses.

[0051] (4) Excessively high purity of deasphalted oil is not necessary. The DAO metal content produced in this embodiment is 12 μg / g, which is far better than the design target of 40 μg / g, but it is considered "over-purification" for achieving long-term operation of the fixed-bed residue hydrotreating unit for more than 4 years. According to the deactivation rate model provided by the catalyst supplier, although reducing the feed metal content from 40 μg / g to 12 μg / g can extend the catalyst replacement cycle to a certain extent, it sacrifices about 14% of the DAO yield, resulting in a negative overall economic benefit.

[0052] It is evident that while a 10:1 agent-to-oil ratio can yield extremely high-quality deasphalted oil, it comes at the cost of decreased yield, significantly increased energy consumption, and substantial increases in investment and operating costs, without generating corresponding technological benefits, making it economically unfeasible. This verifies the rationality of setting the upper limit of the agent-to-oil ratio to 8:1 in this invention, and also confirms that a 6:1 agent-to-oil ratio is an optimized choice based on a balance between technology and economics.

[0053] Comparative Example 1: Vacuum residue (Ni+V=225μg / g) with the same design basis as in Example 1 was directly fed into a fixed-bed residue hydrotreating unit without solvent deasphalting pretreatment, using the exact same catalyst system and design process conditions as in Example 1. Under these conditions, the expected catalyst replacement cycle was approximately 10 months, which is about 5 times less than the 49-month cycle in Example 1 of this invention.

[0054] Comparative Example 2: Based on the conventional operating conditions of a certain petrochemical existing slurry bed unit (without deoiled bitumen), its total conversion rate is approximately 91%. Compared with Example 1 of the present invention (the total conversion rate is maintained above 85% after blending with 12% deoiled bitumen), the conversion rate after blending is lower, but it is still within the range of the unit's design and operating flexibility. Moreover, it achieves high-value conversion of deoiled bitumen, and the overall economic benefits are significantly improved.

[0055] Although the conversion rate decreased from 91% to over 85%, a drop of about 5-6 percentage points, the extremely low cost of deoiled bitumen (typically used as low-value fuel or gasification feedstock, with a value only 20%-30% of light oil products) allows it to significantly reduce raw material costs by replacing a portion of conventional vacuum residue as feedstock for slurry beds. Simultaneously, the added deoiled bitumen is converted into high-value-added naphtha, diesel, and other light oil products through hydrocracking in the slurry bed reactor, achieving value enhancement of this low-quality resource. Comprehensive calculations show that, under the condition of blending 12% deoiled bitumen, the overall economic benefits of the slurry bed unit are approximately 15%-20% higher than under the condition of no blending.

[0056] Comparative Example 3: According to the method described in CN101418222B, the deoiled bitumen is mixed with catalytic slurry and then fed into a suspension bed for hydrogenation. The difference between this method and the present invention is that the deoiled bitumen must be mixed with the slurry, and the suspension bed is a newly built unit. Example 1 utilizes an existing slurry bed unit, where the deoiled bitumen is directly blended at a ratio of 12 wt%, without needing to be mixed with catalytic slurry or other diluents. It can be directly blended into the existing slurry bed using a staged temperature-controlled coupling transport method with the existing vacuum residue as raw material, simplifying the process and reducing operational complexity. This represents a significant advancement compared to existing technologies.

[0057] Comparative Example 4: The only difference from Example 1 is that in step S2, the n-pentane extraction solvent is replaced with propane.

[0058] Under the same raw materials and operating conditions as in Example 1, only the solvent was changed from n-pentane to propane for solvent deasphalting. The results showed that: (1) Propane has a very weak selective dissolution ability for asphaltene, resulting in an extremely low deasphalted oil yield. Propane has a relatively small molecular weight (44.1) and a low critical temperature (approximately 96.8°C). To ensure that propane is maintained in a subcritical or near-critical liquid state, the operating temperature of the asphalt separator must be significantly reduced to approximately 60-80°C (far lower than n-pentane's 168°C). At this low temperature, propane's ability to dissolve saturated and aromatic components in vacuum residue is significantly insufficient, resulting in a deasphalted oil (DAO) yield of only 35-40% (approximately 23-26 wt%) as in Example 1. A large amount of components that should have been high-value DAO are forcibly precipitated into deoiled bitumen (DOA), causing a waste of resources.

[0059] (2) The metal content of deasphalted oil is difficult to control below 40 μg / g. Due to the low operating temperature, the DAO yield is already low, and propane also has a certain dissolving effect on the colloidal components containing metal porphyrins, resulting in metal elements being carried into the DAO phase. Analysis shows that the total Ni+V content in the DAO obtained by propane deasphalting is usually 70-100 μg / g, which cannot meet the ≤40 μg / g required by this invention. If this DAO is sent to the fixed-bed residue hydrotreating unit, the catalyst metal deposition rate is still at a high level, and the catalyst replacement cycle can only be extended to about 24-30 months, which still cannot meet the target of a plant-wide overhaul cycle of more than 4 years.

[0060] (3) The safety risks of the unit increase significantly under propane operation conditions. Propane is a gas at room temperature and pressure with a boiling point of only -42.1℃. The solvent deasphalting unit needs to maintain propane in a liquid state under high pressure (usually 4.0-5.0 MPaG), which places extremely high demands on the equipment's sealing performance. At the same time, propane has a wide explosion limit range (approximately 2.1%-9.5%) when mixed with air, making it easier to form an explosive atmosphere once a leak occurs. In addition, propane has a large latent heat of vaporization, and the load on the solvent recovery system (especially the solvent condenser) is much higher than the design value for n-pentane, which may lead to incomplete condensation, resulting in solvent loss and increased load on the flare system.

[0061] (4) Existing equipment cannot be directly adapted to propane solvent. Existing solvent deasphalting equipment is designed with n-pentane as the solvent, and the materials, dimensions, and operating parameters of all equipment (including extraction tower, heat exchanger, pump, and compressor) are optimized for n-pentane. Although isopentane is considered, if propane is used instead, the shaft power of the solvent circulation pump needs to be recalculated due to propane's lower density and larger volumetric flow rate. The gas-liquid two-phase flow velocity in the tower may exceed the processing capacity of the extraction tower packing, leading to flooding or entrainment. If a forced modification is made, a large number of equipment needs to be replaced, and the investment cost far exceeds the proposed solution of this invention, which only adds a solvent extraction unit, making it uneconomical.

[0062] It is evident that propane as a solvent cannot reduce the metal content to below 40 μg / g while ensuring a sufficient DAO yield, and it also poses high operational safety risks and poor device compatibility, thus failing to achieve the technical objectives of this invention.

[0063] Comparative Example 5: The only difference from Example 1 is that in step S2, the n-pentane extraction solvent is replaced with n-butane.

[0064] Under the same raw materials and operating conditions as in Example 1, only the solvent was changed from n-pentane to butane for solvent deasphalting. The results showed that: (1) Balancing deasphalted oil yield and metal content is difficult. The operating temperature of butane (boiling point of n-butane -0.5℃, critical temperature of about 152℃) is usually controlled in the range of 120-150℃. At this temperature, the extraction depth of butane for vacuum residue is higher than that of propane, but still lower than that of n-pentane. Experimental data show that the DAO yield obtained by butane deasphalting is about 55-60wt% (lower than 66wt% of n-pentane), and its Ni+V content is about 50-70μg / g. If we try to reduce the metal content of DAO to below 40μg / g as required by this invention, we must further sacrifice the yield (for example, reduce it to below 50wt%), which significantly degrades the economic efficiency. Even if we feed directly with a metal content of 50-70μg / g, the metal load of the fixed bed is 25-75% higher than that of the n-pentane scheme, and the catalyst replacement cycle design value can only be extended to 30-36 months, which cannot achieve the goal of a plant overhaul cycle of more than 4 years.

[0065] (2) Narrow operating window and poor product quality stability. The critical temperature of butane (about 152°C) is close to the upper limit of the recommended operating temperature of the asphaltene separator, leaving little room for adjustment. When the properties of the feedstock fluctuate (such as an increase in the asphaltene content in vacuum residue), butane is more likely to precipitate some of the aromatic components that would otherwise be soluble into the DOA, causing a large fluctuation in the DOA yield. At the same time, the resulting DOA still contains a lot of light components, and its softening point is low, which is not conducive to the subsequent transportation and reaction as a slurry bed blending feedstock.

[0066] (3) The energy consumption of the solvent recovery system is significantly higher than that of the n-pentane scheme. The latent heat of vaporization of butane (approximately 386 kJ / kg) is higher than that of n-pentane (approximately 357 kJ / kg), and its critical temperature is lower. To achieve supercritical solvent recovery in the DAO separator (n-pentane is designed at 232℃ and 4.14 MPaG), if butane is used instead, the operating temperature needs to be increased to above approximately 200℃ and the pressure to approximately 4.5-5.0 MPaG. Otherwise, the solvent recovery efficiency will decrease, resulting in excessive solvent content in the DAO product and increased steam consumption in subsequent flash evaporation and stripping towers. In contrast, n-pentane can achieve the maximum DAO yield at 168℃, while butane requires higher temperatures and pressures to achieve a similar separation effect, resulting in a significant increase in energy consumption.

[0067] (4) The synergistic advantages of "n-pentane deasphalting - DAO fixed bed - DOA blending slurry bed" cannot be formed. The core of this invention lies in utilizing the highly selective dissolution characteristics of n-pentane on asphaltenes in vacuum residue to achieve "precise separation" of DAO metal content ≤40μg / g, thereby ensuring long-term operation of the fixed bed for more than 4 years, while simultaneously incorporating high-value DOA into the slurry bed. Although butane can also separate asphaltenes to a certain extent, its separation precision is insufficient: either the DAO metal content exceeds the standard (>40μg / g), weakening the function of the fixed bed in "ensuring long-term operation"; or the DAO yield is significantly reduced to barely meet the standard, resulting in resource waste. In addition, the DOA obtained from butane deasphalting has fewer residual crackable components, and its conversion rate in the slurry bed may be lower than that of n-pentane DOA, affecting the high-value utilization effect.

[0068] It is evident that butane, as a solvent, cannot reliably achieve the key indicator of DAO metal content ≤40 μg / g, and it suffers from high energy consumption, a narrow operating window, and poor product quality stability, failing to achieve the overall technical effect of the "n-pentane solvent extraction-DAO fixed bed-DOA blending slurry bed" ternary coupling architecture of this invention. Therefore, n-pentane is the only optimized solvent choice in this invention that can simultaneously satisfy selectivity, yield, metal removal depth, and industrial economics.

[0069] In summary, this invention overturns the traditional mindset that "solvent deasphalting is only used as a post-hydrogenation treatment unit" or "slurry beds are only used to process straight-run residue" in existing technologies. For the first time, it uses n-pentane solvent deasphalting as the material distribution hub, separating the single vacuum residue feedstock into low-metal, low-asphaltite DAO and high-asphaltite, highly crackable DOA. The most suitable hydrogenation pathway is then matched for each: DAO is fed into a fixed bed to ensure a longer cycle time, while DOA is blended into the existing slurry bed at a ratio of 8-15% to achieve higher conversion. When processing conventional vacuum residue (Ni+V 70-100 μg / g) with a fixed-bed residue hydrotreating unit, the flux replacement cycle is only about 18 months. This invention, through pre-processing n-pentane solvent deasphalting, actively controls the metal content of the fixed-bed feedstock to below 40 μg / g, reducing the metal load by more than 60% compared to conventional direct-feed residue.

[0070] The embodiments herein cover any points not exhaustively within the scope of the technical claims of this invention, as well as new technical solutions formed by equivalent substitutions of one or more technical features in the embodiments. These are all within the scope of the claims of this invention. Furthermore, in all listed or unlisted embodiments of this invention, each parameter in the same embodiment merely represents an instance (i.e., a feasible solution) of its technical solution, and there is no strict coordination or limitation relationship between the parameters. The parameters can be substituted for each other without violating axioms and the claims of this invention, unless otherwise stated.

[0071] The technical means disclosed in this invention are not limited to those described above, but also include technical solutions composed of any combination of the above technical features. The above descriptions are specific embodiments of this invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

[0072] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A combined processing method for the fractional hydroconversion of heavy residue oil, characterized in that, The method includes the following steps: S1. The vacuum residue is introduced into the solvent deasphalting unit and solvent deasphalting is carried out using n-pentane as the extraction solvent to obtain deasphalted oil and deoiled asphalt. S2. The deasphalted oil from step S1 is sent to a fixed-bed residue hydrotreating unit for hydrotreating. S3. The deoiled bitumen described in step S1 is incorporated into the main feedstock of the slurry bed residue hydrotreating unit at a rate of 8-15% of the total feed mass. After being mixed with hydrogen and hydrotreating catalyst, it is fed into the slurry bed reactor for hydrocracking reaction.

2. The combined processing method for the graded hydroconversion of heavy residue oil according to claim 1, characterized in that, In step S1, the vacuum residue oil includes vacuum residue oil produced by the atmospheric and vacuum distillation unit; the total content of nickel and vanadium in the deasphalted oil is controlled below 40 μg / g.

3. The combined processing method for the graded hydroconversion of heavy residue oil according to claim 1, characterized in that, In step S1, the solvent deasphalting treatment is carried out under supercritical extraction conditions, wherein the extraction temperature is 160-200℃, the pressure is 3.8-4.8MPa, and the volume ratio of n-pentane to vacuum residue is (5-8):

1.

4. The combined processing method for the graded hydroconversion of heavy residue oil according to claim 1, characterized in that, In step S2, the deasphalted oil accounts for 50-100% of the total feed in the fixed-bed residue hydrotreating unit by mass.

5. The combined processing method for the graded hydroconversion of heavy residue oil according to claim 1, characterized in that, In step S2, the hydrogenation treatment is carried out under the conditions of hydrogen partial pressure of 15-19 MPa, reaction temperature of 360-430℃, and hydrogen-to-oil volume ratio of 850-1500.

6. The combined processing method for the graded hydroconversion of heavy residue oil according to claim 1, characterized in that, In step S3, the main feedstock of the slurry bed residue hydrotreating unit is vacuum residue.

7. The combined processing method for the graded hydroconversion of heavy residue oil according to claim 1, characterized in that, In step S3, the hydrogenation catalyst is an oil-soluble molybdenum-based catalyst.

8. The combined processing method for the graded hydroconversion of heavy residue oil according to claim 1, characterized in that, In step S3, the hydrocracking reaction is carried out under the conditions of hydrogen pressure of 14-17 MPa, reaction temperature of 410-435℃, and gas holdup of 18-38%.

9. The combined processing method for the graded hydroconversion of heavy residue oil according to claim 1, characterized in that, It also includes a hydrogen coupling step: the hydrogen-rich gas produced as a byproduct of the slurry bed residue hydrotreating unit is purified and then added as supplementary hydrogen to the hydrogen system of the fixed bed residue hydrotreating unit.

10. A heavy residue oil fractional hydroconversion system for use in the method of any one of claims 1-9, characterized in that, include: The solvent deasphalting unit, which uses n-pentane as the extraction solvent, is connected to an inlet for receiving vacuum residue, a deasphalted oil outlet, and a de-oiled asphalt outlet. The feed inlet of the fixed-bed residue hydrotreating unit is connected to the deasphalted oil outlet of the solvent deasphalting unit; Mixer: Connected to a feed inlet for receiving vacuum residue and a feed inlet for deoiled bitumen; And a slurry bed residue hydrotreating unit, the feed system of which is connected to the outlet of the mixer, and the feed system is configured to incorporate the deoiled bitumen at a ratio of 8-15% of the total feed mass.

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