Two-stage hydroprocessing process for coal and heavy oil

Abstract

The application discloses a two-stage hydrogenation co-treatment process of coal and heavy oil, which comprises the following steps: (a) mixing oil-coal slurry raw material containing catalyst and sulfurizing agent with hydrogen, preheating the mixture in a preheating furnace, and then feeding the mixture into a first hydrogenation reactor to perform hydrogenation co-treatment reaction; (b) performing gas-liquid separation on the product of the first hydrogenation reactor by using a hot high-pressure separator, feeding the liquid phase into an atmospheric and vacuum distillation device, and obtaining naphtha, diesel oil and atmospheric tail oil; (c) dividing the atmospheric tail oil into two paths, one of which is recycled to the preheating furnace to be mixed with the oil-coal slurry for reuse, and the other of which is mixed with heavy oil to be fed into a second hydrogenation reactor to perform blending reaction under hydrogen condition; and (d) performing gas-liquid separation on the product of the second hydrogenation reactor by using a hot high-pressure separator, feeding the liquid phase into the atmospheric and vacuum distillation device, and obtaining naphtha, diesel oil, wax oil and vacuum tail oil. Compared with the prior art, the method can improve the coal conversion rate and the light fuel oil yield, effectively utilize inferior tail oil, and prolong the service life of the catalyst.

Description

Technical Field

[0001] This invention belongs to the field of coal chemical technology, specifically relating to a two-stage hydrogenation co-processing technology for coal and heavy oil. Background Technology

[0002] Most coal is consumed through direct combustion for power generation, steelmaking, and heating. Direct combustion has low energy utilization and produces large amounts of dust and harmful gases, causing air pollution and severely impacting the environment. Chemical processing transforms coal into higher value-added products, which can not only reduce environmental pollution but also address crude oil shortages and decrease dependence on external oil resources. Coal / heavy oil hydrorefining technology is a third-generation direct coal liquefaction technology developed from direct coal liquefaction. This technology combines coal liquefaction with the conversion of heavy oil into lighter fuels, simultaneously converting both coal and heavy oil into lighter fuels, achieving the rational utilization of both.

[0003] The middle distillate or tail oil recycling process involves recycling part or all of the liquid products from a specific distillation fraction back to the unit for secondary reactions, which is an effective means to improve feedstock utilization and light fuel oil yield. Simultaneously, the heavy fraction of the hydrocracking products can also undergo secondary hydrocracking to increase its cracking depth. Current technology involves mixing low-quality catalytic diesel and heavy hydrocracking feedstock for hydrocracking, followed by two-stage hydrocracking of the resulting middle distillate to obtain high-aromatic-potential heavy naphtha and low-BMCI tail oil. The hydrocracking of the middle distillate can be carried out at lower temperatures and hydrogen partial pressures, offering good economic benefits. Lower temperatures reduce the cracking of heavy naphtha, further improving naphtha yield.

[0004] However, while existing technologies for coal / heavy oil co-refining can achieve high coal conversion rates, they result in low yields of light products and generate large quantities of hydrotreated tail oil. This tail oil contains unconverted coal, all coal ash, heavy metals and impurities from the residual oil, and coke generated from condensation, making it the heaviest component among the co-refining products. The tail oil has poor properties and is difficult to process further. Currently, the main methods for treating coal-oil co-refining or heavy oil hydrotreated tail oil include direct combustion, hydrocracking, tail oil recycling, and the preparation of lubricating oil base oils. Among these, tail oil recycling and hydrocracking can increase the conversion depth of the feedstock and improve the yield of light fuel oil, making them the simplest and most effective treatment methods. Summary of the Invention

[0005] The purpose of this invention is to provide a two-stage hydrotreating process for coal and heavy oil, which employs tail oil recycling and re-blending and hydrotreating. This process can significantly reduce tail oil yield and effectively extend the service life of the catalyst while improving coal conversion rate and light fuel oil yield.

[0006] This invention provides a two-stage hydrotreating process for coal and heavy oil, comprising the following steps: Coal and first heavy oil are mixed to form an oil-coal slurry. The oil-coal slurry is then mixed with an oil-soluble hydrogenation catalyst, a sulfiding agent, and hydrogen and preheated to convert the active metal component of the oil-soluble hydrogenation catalyst into a sulfidated state. The preheated material is then fed into a first hydrogenation reactor for first hydrogenation co-treatment to obtain the first hydrogenation reaction product. The first hydrogenation reaction product is subjected to gas-liquid separation, and the liquid phase product obtained from the gas-liquid separation is subjected to atmospheric pressure fractionation to obtain atmospheric pressure tail oil carrying the sulfidated catalyst and unconverted coal solids; The atmospheric pressure tail oil is divided into a first tail oil stream and a second tail oil stream. The first tail oil stream is returned to the upstream of the first hydrogenation reactor, so that the first tail oil stream and the oil-coal slurry enter the first hydrogenation reactor together. The second tail oil stream is mixed with the second heavy oil and fed into the second hydrotreating reactor in the presence of hydrogen for the second hydrotreating co-processing. The second hydrotreating co-processing uses the sulfidated catalyst carried by the second tail oil stream as the hydrotreating catalyst, and no external catalyst or sulfiding agent is added to the second hydrotreating reactor.

[0007] Furthermore, before preparing the oil-coal slurry, the coal is subjected to at least one pretreatment of screening, dewatering, and deashing.

[0008] Furthermore, the coal content in the oil-coal slurry is 20% to 60% by mass.

[0009] Furthermore, the first heavy oil and the second heavy oil are each independently selected from one or more of the following: atmospheric residue, vacuum residue, catalytic cracking slurry, medium-temperature coal tar, and low-temperature coal tar. The first heavy oil and the second heavy oil may be the same as or different.

[0010] Furthermore, the oil-soluble hydrogenation catalyst is selected from one or more of molybdenum naphthenate, molybdate, molybdenum isooctanoate, iron oleate, nickel naphthenate, and nickel oleate; based on the mass of coal in the oil-coal slurry, the total amount of active metal components added to the oil-soluble hydrogenation catalyst is 100–2000 μg / g.

[0011] Furthermore, the sulfiding agent is one or both of carbon disulfide and sulfur powder; based on the mass of coal in the oil-coal slurry, the amount of sulfiding agent added is 200-4000 μg / g, calculated by the mass of elemental sulfur.

[0012] Furthermore, the reaction temperature of the first hydrotreating process is 400–470°C, the reaction pressure is 10.0–16.0 MPa, the hydrogen-to-oil volume ratio is 1000:1–2000:1, and the volume hourly space velocity is 0.6–1.2 h⁻¹; the oil phase volume in the hydrogen-to-oil volume ratio is the total volume of the first heavy oil and the first tail oil stream entering the first hydrotreating reactor.

[0013] Furthermore, the mass of the first tail oil stream accounts for 30% to 70% of the total mass of the atmospheric pressure tail oil before diversion, and the mass of the second heavy oil accounts for 30% to 70% of the total mass of the second tail oil stream and the second heavy oil.

[0014] Furthermore, the reaction temperature of the second hydrotreating is 400–460°C, the reaction pressure is 10.0–16.0 MPa, the hydrogen-to-oil volume ratio is 600:1–1800:1, and the volume hourly space velocity is 0.6–1.2 h⁻¹, and the reaction temperature of the second hydrotreating is higher than that of the first hydrotreating; the oil phase volume in the hydrogen-to-oil volume ratio is the total volume of the second tail oil stream and the second heavy oil entering the second hydrotreating reactor.

[0015] Further, the gas phase obtained by gas-liquid separation of the first hydrogenation reaction product is fed into the second hydrogenation reactor after impurities are removed; the second hydrogenation reaction product generated by the second hydrogenation reactor is separated into a gas phase and a liquid phase by hot high-pressure separation, and the gas phase is separated into a circulating gas and an oil phase by cooling and cold high-pressure separation. The circulating gas is recycled to the first hydrogenation reactor, and the oil phase and the liquid phase obtained by hot high-pressure separation enter the atmospheric and vacuum distillation unit for distillation to obtain naphtha, diesel oil, wax oil and vacuum tail oil.

[0016] The beneficial effects of this invention are as follows: 1. In the coal / heavy oil co-processing reaction stage, on the one hand, heavy oil can act as a hydrogen-donating solvent and heat transfer medium for coal, stabilizing the large molecular free radicals generated by coal pyrolysis; on the other hand, coal particles can provide coke-carrying centers for heavy oil macromolecules, inhibiting their further condensation and aggregation, reducing coke yield. At the same time, the mineral components in coal have certain catalytic activity, resulting in a synergistic effect in the co-processing of the two.

[0017] 2. The coal / heavy oil co-processing hydrogenation tail oil is partially recycled and mixed with the coal-oil slurry before being reintroduced into the first hydrogenation reactor. This can increase the cracking depth of the feedstock, extend the service life of the catalyst, reduce the tail oil yield, and increase the yield of light fuel oil.

[0018] 3. The coal / heavy oil co-processing hydrogenation tail oil enters the second hydrogenation reactor for blending reaction with heavy oil. On the one hand, the unconverted coal in the tail oil can continue to react, improving the utilization rate of raw materials; on the other hand, the undeactivated catalyst in the tail oil does not need to be sulfided again, which can effectively promote the hydrogenation reaction of heavy oil. At the same time, the coal particles in the tail oil can play a good role in suppressing coke, thereby better promoting the conversion of heavy oil. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a schematic diagram of the process flow of the method of the present invention; Figure 2 These are schematic diagrams of the coal powder crushing equipment used in Examples 1 and 2; Figure 3 This is a schematic diagram of the pulverizing equipment for crushed coal powder in Examples 1 and 2. Figure 4 Schematic diagrams of the coal powder drying equipment used in Examples 1 and 2; Figure 5 Schematic diagrams of the oil-coal slurry preparation apparatus in Examples 1 and 2; Figure 6 This is a schematic diagram of the process flow of the continuous small-scale heavy oil slurry bed hydrogenation test apparatus used in Examples 1 and 2; Figure 7 The image shows the Raman spectrum of the sulfide-state Mo-Ni catalyst obtained in Example 1. Figure 8 The X-ray diffraction pattern of the sulfided Mo-Ni catalyst obtained in Example 1 is shown below. Figure 9 The X-ray diffraction pattern of the sulfidated Ni-Fe catalyst obtained in Example 2 is shown below. Figure 10 The images show scanning electron microscope (SEM) images, high-resolution transmission electron microscope (HRTEM) images, and elemental distribution diagrams of the sulfide-state Ni-Fe catalyst obtained in Example 2. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0023] The properties of the raw coal and raw oil used in the examples are shown in Table 1 and Table 2, respectively.

[0024] Table 1. Analysis Data of Raw Coal Industry Table 2 Properties of Crude Oil The properties of the raw coal and raw oil used in the examples are shown in Tables 1 and 2, respectively. The raw material analysis data in Tables 1 and 2 were determined according to the corresponding petroleum and coal analysis methods.

[0025] Xinjiang coal and Indonesian coal underwent dewatering and screening pretreatment before preparation of oil-coal slurry, respectively. The particle size of the pretreated coal was 180–200 mesh. The moisture content of the pretreated coal samples was 0.80 wt% and 0.93 wt%, respectively, as shown in Table 1.

[0026] The examples employ a continuously fed slurry-bed hydrogenation reactor. The term "residence time" as used herein refers to the average residence time of the liquid and solid materials within the corresponding hydrogenation reactor under steady-state feed conditions; reaction pressure refers to the total operating pressure within the corresponding hydrogenation reactor.

[0027] The hydrogen volume fraction in the supplied hydrogen gas is not less than 99.9%. Both the first and second hydrogenation reactors are continuously fed with hydrogen, and the specified reaction pressure is maintained by replenishing with new hydrogen. The hydrogen volume ratio is calculated under standard conditions; the first stage liquid oil is based on the liquid oil component of the oil-coal slurry entering the first hydrogenation reactor, and the second stage liquid oil is based on the liquid mixture of tail oil fraction and heavy oil entering the second hydrogenation reactor.

[0028] The hydrogen feed rates listed in Tables 6 and 10 are the net fresh hydrogen input rates calculated for the two-stage reaction process, excluding the amount of recycled hydrogen; the reactor hydrogen-to-oil ratio is calculated based on the total amount of hydrogen at the reactor inlet, including recycled hydrogen.

[0029] Except for the differences in raw material composition, catalyst composition, temperature and pressure as clearly described in the examples, Examples 1 and 2 use the same oil-coal slurry preparation method, reactor type, material separation method and analysis method.

[0030] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0031] Example 1 Xinjiang coal crusher ( Figure 2 After being crushed, it is then processed by a pulverizer. Figure 3 After pulverization, the coal powder is sieved using 180-mesh and 200-mesh standard sieves, collecting the coal powder that passes through the 180-mesh sieve but is retained on the 200-mesh sieve. The resulting coal powder is then dried in a drying device (…). Figure 4 The coal powder was dried at 105°C for 4 hours under nitrogen protection. After treatment, the moisture content of the coal powder was 0.80 wt% and the ash content was 6.77 wt%. No deashing treatment was performed in this example.

[0032] 25.2 kg of pretreated Xinjiang dry coal and 34.8 kg of Ma Ruichang slag were placed in a stirred tank. Figure 5 The mixtures were uniformly mixed to obtain an oil-coal slurry. The mass content of Xinjiang coal in the oil-coal slurry was 42%, and the basic properties of the oil-coal slurry are shown in Table 3.

[0033] Table 3 Properties of Xinjiang kerosene and coal slurry This embodiment uses a Mo-Ni bimetallic oil-soluble catalyst. The oil-soluble precursor of Mo is molybdenum naphthenate, and the mass content of Mo in the molybdenum naphthenate feedstock is 6.0%; the oil-soluble precursor of Ni is nickel naphthenate, and the mass content of Ni in the nickel naphthenate feedstock is 8.0%.

[0034] The molar ratio of Mo to Ni is 3:2 (i.e., the mass ratio of molybdenum to nickel is 2.45:1), and the total amount of active metals added, Mo and Ni, is 300 μg / g, based on the mass of dry coal in the oil-coal slurry. This corresponds to 213.1 mg of Mo and 86.9 mg of Ni per 1.000 kg of dry coal; correspondingly, 3.552 g of molybdenum naphthenate and 1.086 g of nickel naphthenate are added.

[0035] In this embodiment, sulfur powder with a purity of 99.9% is used as the sulfiding agent. The amount of sulfiding agent added, based on the mass of elemental sulfur, is 600 μg / g, with the mass of dry coal in the oil-coal slurry as the basis. This corresponds to 0.6 g of sulfur powder added for every 1.000 kg of dry coal.

[0036] The oil-coal slurry was heated to 100℃, and molybdenum naphthenate, nickel naphthenate, and sulfur powder were added under nitrogen protection. The mixture was stirred at 500 r / min for 30 min using a mechanical stirrer to obtain a homogeneous oil-coal slurry containing catalyst and sulfurizing agent. This homogeneous oil-coal slurry was used as the experimental raw material and tested in a 3L / h heavy oil slurry bed hydrogenation continuous pilot-scale test device. Figure 6 ) to conduct continuous experiments.

[0037] After the oil-coal slurry is prepared, it is kept at 100℃ and transported by a high-pressure feed pump under continuous stirring to prevent coal powder and sulfur powder from settling.

[0038] The oil-coal slurry is mixed with hydrogen and then fed into a preheater, with the preheater outlet temperature controlled at 360℃. During this preheating process, molybdenum naphthenate and nickel naphthenate undergo thermal decomposition and in-situ sulfidation with sulfur provided by sulfur powder, forming a sulfidated Mo-Ni catalyst dispersed in the oil-coal slurry. Figure 7 Raman spectra of catalysts Figure 8 XRD of the catalyst.

[0039] The preheated material enters the first slurry-bed hydrogenation empty tank reactor. The reaction temperature in the first hydrogenation reactor is 420℃, the reaction pressure is 14 MPa, the volume ratio of hydrogen to liquid oil is 1500:1 under standard conditions, and the liquid hourly space velocity (LISH) based on the volume of liquid oil is 1.0 h⁻¹. -1 The effective volume of the first hydrogenation reactor is 3.0 L, and the total volumetric flow rate of the liquid oil entering the first hydrogenation reactor is controlled at 3.0 L / h, with a nominal liquid phase residence time of 60 min.

[0040] The first hydrogenation reaction product enters a first hot high-pressure separator at an operating temperature of 350℃ and an operating pressure of 13.7 MPa for gas-liquid separation. The liquid phase obtained from the first hot high-pressure separator and the condensate obtained from the first cold high-pressure separator are combined and then subjected to atmospheric distillation to obtain naphtha fraction with an initial boiling point to 180℃, diesel fraction with a boiling point of 180–350℃, and atmospheric tail oil with a boiling point above 350℃. The property data of the atmospheric tail oil are shown in Table 4.

[0041] Table 4 Properties of Hydrogenated Atmospheric Pressure Tail Oil Products (Section 1) The atmospheric tail oil is divided into a first tail oil stream and a second tail oil stream by mass, each accounting for 50% of the total mass of the atmospheric tail oil before diversion. The first tail oil stream is returned upstream of the preheater, mixed with fresh oil-coal slurry, and then enters the first hydrogenation reactor together.

[0042] The second tail oil stream was mixed with Marie's ordinary residue, which served as the second heavy oil, at a mass ratio of 1:1, so that the Marie's ordinary residue accounted for 50% of the total mass of the mixed feed to the second hydrotreating reactor. The properties of the second stage mixed feed are shown in Table 5.

[0043] Table 5 Properties of Hydrogenation Feed and Discharge in Section 2 The second hydrotreating reactor is a slurry-bed hydrotreating empty tank reactor with an effective volume of 3.0 L. No additional catalyst or sulfiding agent is added during the mixing of the second tail oil stream with the Marie ordinary residue or before it enters the second hydrotreating reactor. The hydrotreating catalyst required for the second hydrotreating co-processing is derived from the sulfided Mo-Ni catalyst carried by the second tail oil stream (…). Figure 7 , Figure 8 ).

[0044] The reaction temperature in the second hydrogenation reactor is 440℃, the reaction pressure is 14 MPa, the volume ratio of hydrogen to liquid oil is 1200:1 under standard conditions, and the liquid hourly space velocity (LISH) is 1.0 h⁻¹ based on the total volume of the second tail oil stream and the Marie-Oxley ordinary residue. -1 The total volumetric flow rate of the liquid oil entering the second hydrogenation reactor is controlled at 3.0 L / h, and the nominal liquid phase residence time is 60 min.

[0045] The gas phase obtained from the first hot high-pressure separator is cooled to 45°C and then enters the first cold high-pressure separator. The resulting hydrogen-containing gas is washed sequentially with water and then with a 20% (w / w) methyldiethanolamine aqueous solution. After being compressed to 14.2 MPa, it is sent to the second hydrogenation reactor. The product of the second hydrogenation reaction enters the second hot high-pressure separator, which operates at 350°C and 13.7 MPa. The resulting gas phase is cooled to 45°C and then enters the second cold high-pressure separator. The recycle gas obtained from the second cold high-pressure separator is purified of impurities and compressed to 14.2 MPa before being returned to the first hydrogenation reactor.

[0046] The liquid phase obtained from the second hot high-pressure separator is combined with the condensate obtained from the second cold high-pressure separator, and then subjected to vacuum distillation to obtain naphtha fraction with an initial boiling point of up to 180°C, diesel fraction with a boiling point of 180–350°C, wax oil fraction with a boiling point of 350–500°C, and vacuum tail oil with a boiling point greater than 500°C.

[0047] After establishing the first tail oil flow cycle and the second stage feed, the system operated continuously and stably for 12 hours, followed by material balance calculations and sampling analysis over an additional 8 hours. The properties of the second-stage hydrogenation feed and effluent are shown in Table 5.

[0048] Based on the dry ash-free coal benchmark, the conversion rate of Xinjiang coal after the first and second stages of hydrogenation is 97.95 wt%. The total material balance data is shown in Table 6 after verification from the original experimental records.

[0049] Table 6. Overall Material Balance for Hydrogenation in Stages 1 and 2 *Note: This oil-coal slurry feedstock includes heavy oil supplemented by the second stage of hydrogenation.

[0050] Example 2 Indonesian coal crusher ( Figure 2 After being crushed, it is then processed by a pulverizer. Figure 3 After pulverization, the coal powder is sieved using 180-mesh and 200-mesh standard sieves, collecting the coal powder that passes through the 180-mesh sieve but is retained on the 200-mesh sieve. The resulting coal powder is then dried in a drying device (…). Figure 4 The coal powder was dried at 105°C for 4 hours under nitrogen protection. After treatment, the moisture content of the coal powder was 0.93 wt% and the ash content was 10.25 wt%. No deashing treatment was performed in this example.

[0051] 21 kg of pretreated Indonesian dry coal and 39 kg of Yumen slag were placed in a stirring tank. Figure 5 The mixture is uniformly mixed in the oil and coal to obtain an oil-coal slurry. The mass content of Indonesian coal in the oil-coal slurry is 35%, and the basic properties of the oil-coal slurry are shown in Table 7.

[0052] Table 7 Properties of Indonesian Kerosene and Coal Slurry This embodiment uses a Ni-Fe bimetallic oil-soluble catalyst. The oil-soluble precursor of Ni is nickel naphthenate, and the mass content of Ni in the nickel naphthenate feedstock is 8.0%; the oil-soluble precursor of Fe is iron oleate, and the mass content of Fe in the iron oleate feedstock is 6.0%.

[0053] The molar ratio of Ni to Fe is 1:1 (i.e., the mass ratio of Ni to Fe is approximately 1.05:1), and the total amount of active metals added, Ni and Fe, is 1000 μg / g, based on the mass of dry coal in the oil-coal slurry. This corresponds to 512.4 mg of Ni and 487.6 mg of Fe per 1.000 kg of dry coal; 6.405 g of nickel naphthenate and 8.127 g of iron oleate are also added accordingly.

[0054] In this embodiment, CS2 with a purity of 99.5% is used as the sulfiding agent. The amount of sulfiding agent added, based on the mass of elemental sulfur, is 1500 μg / g, with the mass of dry coal in the oil-coal slurry as the basis. According to the theoretical mass fraction of sulfur in CS2 of 84.23%, this corresponds to the addition of 1.790 g of CS2 with a purity of 99.5% per 1.000 kg of dry coal.

[0055] The oil-coal slurry was heated to 80°C, and nickel naphthenate and iron oleate were added under nitrogen protection. The mixture was stirred at 500 r / min for 30 min to ensure uniform dispersion of the coal powder and oil-soluble catalyst precursor. The mixture was then cooled to 30°C and transferred to a sealed, nitrogen-protected feed tank. CS2 was added, and the mixture was circulated and stirred for 20 min under sealed conditions. The feed tank and feed pipeline were kept sealed to prevent CS2 volatilization loss. The oil-coal slurry, uniformly mixed with the catalyst and sulfiding agent, was used as the experimental raw material and tested in a 3 L / h heavy oil slurry bed hydrogenation continuous pilot-scale test device. Figure 6 ) to conduct continuous experiments.

[0056] The oil-coal slurry containing the catalyst and CS2 is mixed with hydrogen and then fed into a preheater, with the preheater outlet temperature controlled at 370℃. During the preheating process, nickel naphthenate and iron oleate undergo thermal decomposition and in-situ sulfidation with the sulfur released from the decomposition of CS2, forming a sulfidated Ni-Fe catalyst dispersed in the oil-coal slurry. Figure 9 XRD of the catalyst Figure 10 SEM, HRTEM, and elemental mapping images of the catalyst.

[0057] The preheated material enters the first slurry-bed hydrogenation empty tank reactor. The reaction temperature in the first hydrogenation reactor is 430℃, the reaction pressure is 16 MPa, the volume ratio of hydrogen to liquid oil is 1800:1 under standard conditions, and the liquid hourly space velocity (LISH) based on the volume of liquid oil is 1.0 h⁻¹. -1The effective volume of the first hydrogenation reactor is 3.0 L, and the total volumetric flow rate of the liquid oil entering the first hydrogenation reactor is controlled at 3.0 L / h, with a nominal liquid phase residence time of 60 min.

[0058] The first hydrogenation reaction product enters a first hot high-pressure separator at an operating temperature of 350℃ and an operating pressure of 15.7 MPa for gas-liquid separation. The liquid phase obtained from the first hot high-pressure separator is combined with the condensate obtained from the first cold high-pressure separator and then subjected to atmospheric distillation to obtain naphtha fraction with an initial boiling point to 180℃, diesel fraction with a boiling point of 180–350℃, and atmospheric tail oil with a boiling point above 350℃. The property data of the atmospheric tail oil are shown in Table 8.

[0059] Table 8 Properties of Hydrogenated Atmospheric Pressure Tail Oil Products (Section 1) The atmospheric tail oil is divided into a first tail oil stream and a second tail oil stream by mass, each accounting for 50% of the total mass of the atmospheric tail oil before diversion. The first tail oil stream is returned upstream of the preheater, mixed with fresh oil-coal slurry, and then enters the first hydrogenation reactor together.

[0060] The second tail oil stream was mixed with the Yumen reduced residue, which serves as the second heavy oil, at a mass ratio of 1:1, so that the Yumen reduced residue accounted for 50% of the total mass of the mixed feed to the second hydrotreating reactor. The properties of the second stage mixed feed are shown in Table 9, verified from the original records.

[0061] Table 9 Properties of Hydrogenation Feed and Discharge in Section 2 The second hydrotreating reactor is a slurry-bed hydrotreating empty tank reactor with an effective volume of 3.0 L. No additional catalyst or sulfiding agent is added when the second tail oil stream is mixed with the Yumen slag or before entering the second hydrotreating reactor. The hydrotreating catalyst required for the second hydrotreating process is derived from the sulfidated Ni-Fe catalyst carried by the second tail oil stream. Figure 9 ).

[0062] The reaction temperature of the second hydrotreating reactor is 440℃, the reaction pressure is 16 MPa, the volume ratio of hydrogen to liquid oil under standard conditions is 1200:1, and the liquid hourly space velocity (LISH) based on the total volume of the second tail oil stream and the Yumen reduced slag is 1.0 h⁻¹. -1 The total volumetric flow rate of the liquid oil entering the second hydrogenation reactor is controlled at 1.0 L / h, and the nominal liquid phase residence time is 60 min.

[0063] The gas phase obtained from the first hot high-pressure separator is cooled to 45°C and then enters the first cold high-pressure separator. The resulting hydrogen-containing gas is washed sequentially with water and then with a 20% (w / w) methyldiethanolamine aqueous solution. After being compressed to 16.2 MPa, it is sent to the second hydrogenation reactor. The product of the second hydrogenation reaction enters the second hot high-pressure separator, which operates at 350°C and 15.7 MPa. The resulting gas phase is cooled to 45°C and then enters the second cold high-pressure separator. The recycle gas obtained from the second cold high-pressure separator is purified of impurities and compressed to 16.2 MPa before being returned to the first hydrogenation reactor.

[0064] The liquid phase obtained from the second hot high-pressure separator is combined with the condensate obtained from the second cold high-pressure separator, and then subjected to vacuum distillation to obtain naphtha fraction with an initial boiling point of up to 180°C, diesel fraction with a boiling point of 180–350°C, wax oil fraction with a boiling point of 350–500°C, and vacuum tail oil with a boiling point greater than 500°C.

[0065] After establishing the first tail oil flow cycle and the second stage feed, the system operated continuously and stably for 12 hours, followed by material balance calculations and sampling analysis over an additional 8 hours. The properties of the second-stage hydrogenation feed and effluent are shown in the verified Table 9.

[0066] Based on the dry ash-free coal benchmark, the conversion rate of Indonesian coal after the first and second stages of hydrogenation is 98.40 wt%. The total material balance data is shown in Table 10.

[0067] Table 10: Overall Material Balance for Hydrogenation in Stages 1 and 2 *Note: This oil-coal slurry feedstock includes heavy oil supplemented by the second stage of hydrogenation.

[0068] Blank Comparison Example 1 In this technology, the catalyst serves to liquefy coal and inhibit coking of heavy components during the liquefaction process, while the sulfiding agent helps the catalyst to form a sulfidized state, thereby enhancing its catalytic effect. The reaction without the addition of a catalyst and sulfiding agent is shown in Table 11.

[0069] Table 11 Blank Comparison *Note: Toluene-insoluble matter refers to the toluene-insoluble matter in the tail oil from the second stage of hydrotreating.

[0070] Based on the above research, the following three valid conclusions can be drawn: (1) Fe active metal is beneficial to coal liquefaction and improves the conversion rate of dry basis ashless coal; Mo active metal is beneficial to heavy oil cracking and reduces tail oil yield.

[0071] (2) The first stage of hydrogenation is carried out at a lower temperature, which is conducive to the liquefaction of coal; the second stage of hydrogenation is carried out at a higher temperature, which is conducive to the lightening of heavy oil.

[0072] (3) The addition of catalyst can effectively promote the hydrogenation and liquefaction reaction of coal and improve the conversion rate of dry ashless coal; the addition of sulfiding agent can convert the metal in the catalyst into sulfided metal, further improving the catalyst activity.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A two-stage hydrotreating process for coal and heavy oil, characterized in that, Includes the following steps: Coal and first heavy oil are mixed to form an oil-coal slurry. The oil-coal slurry is then mixed with an oil-soluble hydrogenation catalyst, a sulfiding agent, and hydrogen and preheated to convert the active metal component of the oil-soluble hydrogenation catalyst into a sulfidated state. The preheated material is then fed into a first hydrogenation reactor for first hydrogenation co-treatment to obtain the first hydrogenation reaction product. The first hydrogenation reaction product is subjected to gas-liquid separation, and the liquid phase product obtained from the gas-liquid separation is subjected to atmospheric pressure fractionation to obtain atmospheric pressure tail oil carrying the sulfidated catalyst and unconverted coal solids; The atmospheric pressure tail oil is divided into a first tail oil stream and a second tail oil stream. The first tail oil stream is returned to the upstream of the first hydrogenation reactor, so that the first tail oil stream and the oil-coal slurry enter the first hydrogenation reactor together. The second tail oil stream is mixed with the second heavy oil and fed into the second hydrotreating reactor in the presence of hydrogen for the second hydrotreating co-processing. The second hydrotreating co-processing uses the sulfidated catalyst carried by the second tail oil stream as the hydrotreating catalyst, and no external catalyst or sulfiding agent is added to the second hydrotreating reactor.

2. The two-stage hydrotreating process for coal and heavy oil according to claim 1, characterized in that, Before preparing the oil-coal slurry, the coal is subjected to at least one of the following pretreatments: screening, dewatering, and deashing.

3. The two-stage hydrotreating process for coal and heavy oil according to claim 1, characterized in that, The coal content in the oil-coal slurry is 20% to 60% by mass.

4. The two-stage hydrotreating process for coal and heavy oil according to claim 1, characterized in that, The first heavy oil and the second heavy oil are each independently selected from one or more of the following: atmospheric residue, vacuum residue, catalytic cracking slurry, medium-temperature coal tar, and low-temperature coal tar. The first heavy oil and the second heavy oil may be the same as or different.

5. The two-stage hydrotreating process for coal and heavy oil according to claim 1, characterized in that, The oil-soluble hydrogenation catalyst is selected from one or more of molybdenum naphthenate, molybdate, molybdenum isooctanoate, iron oleate, nickel naphthenate, and nickel oleate; based on the mass of coal in the oil-coal slurry, the total amount of active metal components added to the oil-soluble hydrogenation catalyst is 100-2000 μg / g.

6. The two-stage hydrotreating process for coal and heavy oil according to claim 1, characterized in that, The sulfiding agent is one or both of carbon disulfide and sulfur powder; based on the mass of coal in the oil-coal slurry, the amount of sulfiding agent added is 200-4000 μg / g, calculated by the mass of elemental sulfur.

7. The two-stage hydrotreating process for coal and heavy oil according to claim 1, characterized in that, The first hydrotreating reaction was carried out at a temperature of 400–470 °C, a reaction pressure of 10.0–16.0 MPa, a hydrogen-to-oil volume ratio of 1000:1–2000:1, and a volume hourly space velocity of 0.6–1.2 h⁻¹. -1 The oil phase volume in the hydrogen-oil volume ratio refers to the total volume of the first heavy oil and the first tail oil stream entering the first hydrogenation reactor.

8. The two-stage hydrotreating process for coal and heavy oil according to claim 1, characterized in that, The mass of the first tail oil stream accounts for 30% to 70% of the total mass of the atmospheric pressure tail oil before diversion, and the mass of the second heavy oil accounts for 30% to 70% of the total mass of the second tail oil stream and the second heavy oil.

9. The two-stage hydrotreating process for coal and heavy oil according to claim 7, characterized in that, The second hydrotreating reaction was carried out at a temperature of 400–460 °C, a reaction pressure of 10.0–16.0 MPa, a hydrogen-to-oil volume ratio of 600:1–1800:1, and a volume hourly space velocity of 0.6–1.2 h⁻¹. -1 Furthermore, the reaction temperature of the second hydrotreating process is higher than that of the first hydrotreating process; the oil phase volume in the hydrogen-oil volume ratio is the total volume of the second tail oil stream and the second heavy oil entering the second hydrotreating reactor.

10. The two-stage hydrotreating process for coal and heavy oil according to claim 1, characterized in that, The gas phase obtained by gas-liquid separation of the first hydrogenation reaction product is fed into the second hydrogenation reactor after impurities are removed. The second hydrogenation reaction product generated by the second hydrogenation reactor is separated into a gas phase and a liquid phase by hot high-pressure separation. The gas phase is separated into a circulating gas and an oil phase by cooling and cold high-pressure separation. The circulating gas is recycled to the first hydrogenation reactor. The oil phase and the liquid phase obtained by hot high-pressure separation enter the atmospheric and vacuum distillation unit for distillation to obtain naphtha, diesel oil, wax oil and vacuum tail oil.

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