A coal direct liquefaction system and a coal direct liquefaction method

Abstract

The present invention provides a coal direct liquefaction system and a coal direct liquefaction method. The coal direct liquefaction system includes an oil-coal slurry configuration unit, a preheating mixing unit, a first coal direct liquefaction reactor, a second coal direct liquefaction reactor, a third coal direct liquefaction reactor, a first separation unit, a distillation tower, a hydrogenation unit, a second separation unit and a hydrogen supply unit. The present invention solves the technical difficulties of reactor coal powder deposition, mineral deposition, low utilization rate, poor operating stability and solid particle powder entrainment in the existing coal direct liquefaction technology, as well as the bottleneck problem that restricts the further expansion of the reactor, thereby realizing long-term and efficient operation of the coal direct liquefaction device, improving the utilization rate and single-series scale of the coal direct liquefaction reactor, improving energy utilization efficiency, and contributing to energy conservation and carbon reduction.

Description

Technical Field

[0001] The present invention relates to the field of direct coal liquefaction, and in particular to a direct coal liquefaction system and a direct coal liquefaction method. Background Art

[0002] CN1257252C discloses a method for direct coal liquefaction, which uses a suspended bed reactor with forced circulation at the bottom. This method effectively reduces mineral deposition, but the reactor's internal structure is relatively complex, with a liquid collection cup and a central tube, resulting in low reactor volume utilization efficiency. To ensure the normal operation of the circulating pump, a gas-liquid separation space must be provided at the top, resulting in a gas-liquid interface. This allows for the timely separation of lightweight materials and, to a certain extent, avoids secondary cracking of the target product. However, actual operation of a million-ton-scale direct coal liquefaction demonstration unit has shown that the presence of a gas-liquid interface at the top of the reactor can easily lead to coal dust deposition and agglomeration at the top of the reactor, reducing the gas-liquid separation space. Furthermore, deposited and agglomerated materials easily fall into the liquid collection cup, affecting the normal operation of the circulating pump at the bottom of the reactor, deteriorating material mass and heat transfer within the reactor, reducing operational stability, and increasing the risk of large-scale coking in the reactor. This makes it impossible for the direct coal liquefaction reactor to achieve long-term operation, a key factor affecting the long-term operation of the unit. In addition, the reactor used in this process also has an engineering scale-up bottleneck. The forced internal circulation reactor material needs to pass around the liquid collecting cup to enter the top space of the reactor. At this time, the material needs to migrate from the near-wall side to the central discharge port. When the diameter of the reactor increases and the lateral migration distance becomes longer, the minerals are more likely to separate, resulting in inconsistent mineral content and particle size distribution between the central tube and the reactor discharge port. Mineral deposition is prone to occur, making the reactor unable to operate for a long period of time and restricting the scale-up of a single series. At the same time, the reactor used in this process has poor operational stability and weak anti-interference ability. It is greatly affected by the hydrogen flow rate, raw material feed rate, and circulation volume of the circulating pump. Therefore, achieving long-term and efficient operation of direct coal liquefaction and improving the scale of a single series are key technical issues that need to be solved urgently.

[0003] China Coal Research Institute Co., Ltd. has disclosed a direct coal liquefaction method and system (Patent No. CN103074097B). This method returns a portion of the high-temperature material at the outlet of the second liquefaction reactor directly to the first liquefaction reactor through a circulation pump without gas-liquid separation. Because this process does not separate the gas-liquid material at the reactor outlet, the gas holdup at the inlet of the circulating material pump is high, making the circulating pump prone to evacuation and poor system stability. The reactors used are bubbling beds, slurry beds, or loop reactors without internals, which pose the risk of reactor deposition and coking, seriously affecting the long-term stable operation of the system. Furthermore, light components in the liquefied product at the outlet of the second reactor can re-enter the reactor, causing secondary cracking of the light products and reducing the liquid product yield.

[0004] China Shenhua Coal-to-Liquid Chemical Co., Ltd. has disclosed a direct coal liquefaction method and apparatus (CN108048121B). An intermediate separation device and a second reactor feed pump are installed between the first and second liquefaction reactors. This reduces secondary cracking, lowers hydrogen consumption and gas yield, and improves coal conversion and oil yield. To adapt to this system, corresponding supporting equipment, such as a separation system and a wear-resistant high-pressure control valve at the bottom of the intermediate separator, must be installed, significantly increasing equipment investment and operating costs. After the oil-coal slurry passes through the first reactor, the reaction is incomplete, resulting in a high solids content and a high content of highly viscous asphalt-like substances produced by pyrolysis. This makes deposition and coking more likely during the intermediate separation process. Therefore, this process is detrimental to the long-term stable operation of the system.

[0005] On the basis of the above, China Shenhua Coal to Oil Chemical Co., Ltd. further disclosed a coal direct liquefaction system and a coal direct liquefaction method in CN108998068A. Its coal liquefaction reactor is only a shell without any components inside. Although it can eliminate the gas-liquid interface at the top of the reactor and reduce the coal powder deposition at the top of the reactor, the more critical thing is that the distribution plate and other internal components are not considered in the reactor. The three-phase material is unevenly distributed, and a dead zone is easily formed at the bottom, which can easily lead to mineral deposition in the reactor and increase the risk of coal powder agglomeration or coking. The reactor cannot operate normally for a long time.

[0006] In summary, the engineering practice results of the world's first million-ton coal direct liquefaction unit show that there is an urgent need to solve the technical problems of coal powder deposition and mineral deposition in the reactor during the coal direct liquefaction process, which affect the long-term operation of the unit and the reactor and further engineering expansion of the reactor. At the same time, it is necessary to prevent the secondary cracking of light components in the reaction process, improve the yield of target products, realize the long-term operation of the coal direct liquefaction unit and the scale expansion of a single series, and promote the large-scale and industrial development of coal direct liquefaction. Summary of the Invention

[0007] The purpose of the present invention is to provide a coal direct liquefaction system and a coal direct liquefaction method to solve the technical problems of coal powder deposition, mineral deposition, low utilization rate, poor operating stability and solid particle powder entrainment in the coal direct liquefaction reactor in the existing coal direct liquefaction technology, as well as the bottleneck problem of further expansion of the scale of the coal direct liquefaction reactor, so as to achieve long-term and efficient operation of the coal direct liquefaction device, improve the utilization rate of the coal direct liquefaction reactor, break through the expansion bottleneck of the coal direct liquefaction reactor, and further increase the single series scale of the coal direct liquefaction device.

[0008] To achieve one aspect of the above-mentioned object of the invention, the present invention provides a direct coal liquefaction system comprising:

[0009] an oil-coal slurry preparation unit, configured to prepare an oil-coal slurry for direct coal liquefaction using the first solvent oil as solvent oil;

[0010] A preheating and mixing unit, used for mixing the oil-coal slurry from the oil-coal slurry configuration unit with hydrogen and preheating the mixture to increase its temperature;

[0011] a first coal direct liquefaction reactor, wherein the first coal direct liquefaction reactor is provided with a fresh material feed port and a circulating material feed port connected to the preheating and mixing unit at the bottom, and a first product outlet at the top, for performing a coal direct liquefaction reaction and delivering the obtained first reaction product from the first product outlet;

[0012] a second coal direct liquefaction reactor, wherein the second coal direct liquefaction reactor is provided with a second feed inlet at the bottom and a second product outlet at the top, for performing a coal direct liquefaction reaction using the material from the second feed inlet to obtain a second reaction product; wherein the second feed inlet is used to receive the first reaction product, the second solvent oil and hydrogen;

[0013] a third coal direct liquefaction reactor, wherein the third coal direct liquefaction reactor is provided with a third feed inlet at the bottom and a third product outlet at the top, for utilizing the material from the third feed inlet to carry out a coal direct liquefaction reaction to obtain a third reaction product; wherein the third feed inlet is used to receive the second reaction product, a third solvent oil and hydrogen; wherein the first, second and third coal direct liquefaction reactors are suspended bed reactors with internal components for secondary material distribution;

[0014] a first separation unit connected to the third product outlet, for separating the third reaction product to separate light oil and non-condensable gas therefrom, and feeding a portion of the remaining heavy oil as a circulating material to the circulating material inlet of the first coal direct liquefaction reactor, and feeding the other portion to the distillation column;

[0015] a distillation tower for distilling and separating the light component oil and another portion of the heavy component oil from the first separation unit to obtain coal direct liquefaction crude oil and the remaining liquefied asphalt;

[0016] a hydrogenation unit for hydrogenating the CDL crude oil to obtain CDL oil;

[0017] a second separation unit for separating the direct coal liquefaction oil from the hydrogenation unit to obtain non-condensable gas, light oil, medium oil and heavy oil, and delivering the light oil and at least part of the medium oil as direct coal liquefaction product oil, and delivering a mixture of the heavy oil and optional medium oil as the first solvent oil to the oil-coal slurry configuration unit, as the second solvent oil to the second feed port, and as the third solvent oil to the third feed port; and

[0018] The hydrogen supply unit is respectively connected to the preheating mixing unit, the second feed port, the third feed port and the hydrogenation unit to supply hydrogen, wherein the hydrogen is fresh hydrogen and / or non-condensable gas used as circulating hydrogen.

[0019] In a preferred embodiment, the first separation unit comprises:

[0020] a first hot high-pressure separator for separating the third reaction product, feeding a portion of the heavy oil component discharged from the bottom as a circulating material into the circulating material inlet of the first coal direct liquefaction reactor, feeding another portion into a distillation column, and feeding a first portion of the separated light component from the top into the preheating and mixing unit for heat exchange and cooling, and feeding a second portion into a first cold high-pressure separator;

[0021] The first cold high-pressure separator is used to separate the first part of light components and the second part of light components after heat exchange and temperature reduction to obtain the non-condensable gas and light component oil.

[0022] In a preferred embodiment, the second separation unit includes:

[0023] a second hot high-pressure separator for performing gas-liquid separation on the coal direct liquefaction oil from the hydrogenation unit to obtain a processed gas phase at the top and a separated liquid phase at the bottom;

[0024] a second cold high-pressure separator, for further performing gas-liquid separation on the gas phase from the second hot high-pressure separator to separate the non-condensable gas and obtain a separated liquid phase at the bottom; and

[0025] a fractionating tower for fractionating the liquid phase from the second hot high-pressure separator and the liquid phase from the second cold high-pressure separator to obtain light oil, medium oil and heavy oil, and sending the light oil and at least part of the medium oil as coal direct liquefaction product oil, using the heavy oil or a mixture of the heavy oil and the medium oil as the circulating solvent, and sending the circulating solvent as the first solvent oil to the oil-coal slurry configuration unit, as the second solvent oil to the second feed port, and as the third solvent oil to the third feed port.

[0026] In a preferred embodiment, the oil-coal slurry configuration unit comprises:

[0027] An oil-coal slurry preparation tank is used to prepare the oil-coal slurry using the first solvent oil, coal powder, catalyst and sulfiding agent, wherein the first solvent oil and coal powder, as well as the first solvent oil and catalyst are premixed in a kneader and then enter the oil-coal slurry preparation tank;

[0028] a low-pressure coal slurry circulation pump, wherein the inlet of the low-pressure coal slurry pump is connected to the oil-coal slurry outlet of the coal slurry preparation tank, and the outlet is respectively connected to the oil-coal slurry preparation tank and the high-pressure coal slurry feed pump, for circulating part of the oil-coal slurry back to the oil-coal slurry preparation tank and sending part of the oil-coal slurry out;

[0029] The high-pressure coal slurry feed pump is used to pressurize part of the oil-coal slurry from the low-pressure coal slurry circulation pump and then send it out.

[0030] In a preferred embodiment, the preheating mixing unit comprises:

[0031] an oil-coal slurry heat exchanger, configured to heat and heat up a mixture of the oil-coal slurry from the high-pressure coal slurry pump and the hydrogen from the hydrogen supply unit with the first portion of light components from the first hot high-pressure separator;

[0032] an oil-coal slurry heating furnace for further heating the mixed material from the oil-coal slurry heat exchanger; and

[0033] a hydrogen heating furnace, for heating the second portion of hydrogen from the hydrogen supply unit and feeding the mixed material from the oil-coal slurry heating furnace into the fresh material feed port of the first direct coal liquefaction reactor after mixing the mixed material with the mixed material;

[0034] In a preferred embodiment, the hydrogenation unit comprises:

[0035] a raw material buffer tank for receiving crude coal direct liquefaction oil from the distillation tower;

[0036] A hydrogenation raw material pump, used to deliver the crude CDL oil in the raw material buffer tank to the raw material heating furnace;

[0037] a raw material heating furnace for heating the CDL crude oil and the third portion of hydrogen from the hydrogen supply unit; and

[0038] The hydrogenation reactor is used for carrying out hydrogenation treatment on the feed from the raw material heating furnace to obtain coal direct liquefaction oil.

[0039] In a preferred embodiment, the internal components of the first direct coal liquefaction reactor are arranged at the bottom of the reactor, including a fresh material distributor, a material diffuser and a distribution plate with a bubble distributor; the internal components of the second and third direct coal liquefaction reactors are arranged at the bottom of the reactor, including the material diffuser and the distribution plate with the bubble distributor; the material diffuser is arranged at the bottom of the reactor, and the fresh material distributor is arranged between the material diffuser and the distribution plate; preferably, there are no internal components above the distribution plate.

[0040] Preferably, the fresh material distributor includes a feed pipe, a distribution pipe, an air guide pipe and a guide chamber; the feed pipe is connected to the fresh material feed port; the distribution pipe is arranged in a horizontal direction and is a ring-tube structure, including a distribution ring pipe arranged around the guide chamber and a plurality of distribution branches arranged between the guide chamber and the distribution ring pipe, the distribution branches are arranged radially along the distribution ring pipe, one end of which is connected to the guide chamber and the other end is connected to the distribution ring pipe; downward distribution holes are provided on the distribution branches and the distribution ring pipe for uniformly feeding the gas-liquid mixture into the reactor; preferably, the diameter of the distribution pipe and / or the aperture of the distribution hole are configured so that the total pressure drop of the distribution pipe is less than the pressure drop of the air guide pipe;

[0041] The guide cavity is a guide cavity with a hollow chamber, the lower and upper parts of which are conical structures, and the middle part is a cylindrical section connecting the ends with larger diameters of the conical structures; the feed pipe outlet is connected to the side of the lower part of the guide cavity along the tangential direction, the distribution pipe inlet is connected to the middle part of the guide cavity, the air inlet of the air guide tube is located directly above the guide cavity and is vertically connected to the guide cavity, and the air outlet at the upper end of the air guide tube is higher than the air inlet at the lower end of the bubble dispenser.

[0042] Preferably, the bubble dispenser includes a vertically arranged central tube, a bubble located at the upper end of the central tube, and an air supply pipe connected to the air inlet of the central tube for supplying air into the central tube; the bubble includes a bubble top plate and a bubble side plate, and the bubble side plate is connected to the edges of the bubble top plate and extends downward;

[0043] The upper end of the central tube extends into the bubble and is spaced a preset distance from the bubble top plate to facilitate passage of material; a liquid inlet is provided at the lower end of the central tube; an annular flow channel is formed between the bubble side plate and the central tube, and a plurality of gas-liquid distribution slits are provided at the lower end of the bubble side plate for gas and liquid discharge;

[0044] A throat portion is provided in the central tube, and the throat portion includes a contraction port, a throat pipe and an expansion port connected in sequence from bottom to top; the air supply pipe includes a horizontally arranged air inlet pipe and an air outlet pipe vertically arranged in the central tube and coaxially arranged with the throat pipe, and the upper air outlet of the air outlet pipe is in the throat pipe; the air inlet pipe passes through the air inlet of the central tube and is connected to the air outlet pipe; there are multiple air inlet pipes, each of which is connected to the air outlet pipe respectively, and the multiple air inlet pipes are evenly spaced along the circumferential direction of the air outlet pipe.

[0045] In a preferred embodiment, a feed port for introducing the third reaction product is provided in the middle of the first hot high-pressure separator, a gas phase outlet is provided at the top, and a slurry phase material outlet is provided at the bottom; a washing oil spray port and a washing tower plate are provided from top to bottom between the gas phase outlet and the feed port; a circulating material extraction port, a flushing oil inlet and a disturbed hydrogen inlet are provided from top to bottom between the feed port and the slurry phase material outlet, wherein the flushing oil inlet is provided at the center of the first hot high-pressure separator and the opening is provided downward.

[0046] To achieve another aspect of the above-mentioned object of the invention, the present invention provides a method for direct coal liquefaction using the above-mentioned direct coal liquefaction system, comprising the following steps:

[0047] S1, mixing coal powder, catalyst, sulfiding agent and first solvent oil to prepare a pumpable coal-oil slurry;

[0048] S2, mixing the oil-coal slurry with hydrogen, preheating the mixture, and then feeding it into a first coal direct liquefaction reactor with the circulating material to perform a first coal direct liquefaction reaction to obtain a first reaction product;

[0049] S3, mixing the first reaction product, hydrogen, and second solvent oil, and then feeding the mixture into a second coal direct liquefaction reactor to perform a second coal direct liquefaction reaction to obtain a second reaction product;

[0050] S4, mixing the second reaction product, hydrogen and the third solvent oil and feeding the mixture into a third coal direct liquefaction reactor to perform a third coal direct liquefaction reaction to obtain a third reaction product;

[0051] S5, separating the third coal liquefaction product in the first separation unit to separate light oil and non-condensable gas, and sending a portion of the heavy oil remaining after the separation into the first coal direct liquefaction reactor as a circulating material;

[0052] S6, sending another portion of the heavy component oil and the light component oil into a distillation tower for distillation separation to obtain direct coal liquefaction crude oil and remaining liquefied asphalt;

[0053] S7, mixing the coal direct liquefaction crude oil with hydrogen and then performing a hydrogenation reaction, and separating the obtained coal direct liquefaction oil to obtain a circulating solvent and a coal direct liquefaction liquid product oil, and respectively sending the circulating solvent as the first solvent oil to the oil-coal slurry configuration unit, as the second solvent oil to the second coal direct liquefaction reactor, and as the third solvent oil to the third coal direct liquefaction reactor.

[0054] In a preferred embodiment, the average reaction temperature in the first coal direct liquefaction reaction process is recorded as T1, the reaction pressure is recorded as P1, and the hydrogen partial pressure is recorded as PH1; the average reaction temperature in the second coal direct liquefaction reaction process is recorded as T2, the reaction pressure is recorded as P2, and the hydrogen partial pressure is recorded as PH2; the average reaction temperature in the third coal direct liquefaction reaction process is recorded as T3, the reaction pressure is recorded as P3, and the hydrogen partial pressure is recorded as PH3;

[0055] Among them, T1, T2 and T3 are independently 390~470℃, preferably 410~460℃, and T3≥T2≥T1; P1, P2 and P3 are independently 5~35MPa, preferably 10~20MPa, and P1≥P2≥P3; PH1, PH2 and PH3 are independently 4.5~28MPa, preferably 8~13MPa; the oil-coal slurry space velocity is 0.3~2.0t / (h·m3), preferably 0.5~1.5t / (h·m3).

[0056] In a preferred embodiment, the ratio of the volume of hydrogen to the weight of the oil-coal slurry in the first coal liquefaction reaction is recorded as N1, the ratio of the volume of hydrogen to the weight of the oil-coal slurry in the second coal liquefaction reaction is recorded as N2, and the ratio of the volume of hydrogen to the weight of the oil-coal slurry in the third coal liquefaction reaction is recorded as N3. N1, N2 and N3 are independently selected from 300~1000L / kg, preferably 400~600L / kg, and N3≥N2≥N1.

[0057] In a preferred embodiment, the amount of the first solvent oil is 45-90 wt% of the oil-coal slurry; the amount of the second solvent oil is 2-20 wt% of the oil-coal slurry; and the amount of the third solvent oil is 1-10 wt% of the oil-coal slurry.

[0058] In a preferred embodiment, the solid content of the circulating material leaving the first hot high-pressure separator is 10-20%; the solid content of the heavy oil feed fed to the distillation column is ≤10%, preferably ≤8%;

[0059] Preferably, the mass ratio of the circulating material entering the first direct coal liquefaction reactor to the oil-coal slurry is (0.2-30):1, preferably (1-12):1.

[0060] In a preferred embodiment, in the first direct coal liquefaction reaction, the temperature rise is controlled between 60 and 80°C; in the second direct coal liquefaction reaction, the temperature rise is controlled between 20 and 30°C; in the third direct coal liquefaction reaction, the temperature rise is controlled between 5 and 10°C.

[0061] In a preferred embodiment, the solid content of the coal liquefaction pitch at the bottom of the distillation tower is 35-60%, and the softening point is 170-190°C.

[0062] In a preferred embodiment, the circulating solvent is a distillate oil with a temperature of >220°C in the coal direct liquefaction oil, and its aromatic hydrocarbon content is above 70%; preferably, the circulating solvent is a distillate oil with a temperature of >240°C in the coal direct liquefaction oil, and its monocyclic and bicyclic aromatic hydrocarbon content is >50wt%.

[0063] In the present invention, unless otherwise specified, the ratios involved are mass ratios, and the percentages or percentage contents involved are mass percentages or mass percentage contents.

[0064] Compared with the prior art, the present invention has the following advantages:

[0065] 1. The present invention utilizes a suspended bed direct coal liquefaction reactor with secondary gas distribution. The reactor internals are located at the bottom of the reactor, with no internals above the feed distribution plate. Compared with currently used forced internal circulation suspended bed reactors, this eliminates the reactor internal circulation system, simplifies the internals, significantly improves reactor volume utilization, eliminates the gas-liquid interface at the reactor top, and prevents coal dust deposition. This enables long-term operation of the direct coal liquefaction unit and improves the unit's coal dust processing capacity. Furthermore, compared with bubbling bed reactors, which are prone to mineral and coal dust deposition and coking reactions, the reactor has a lower gas retention coefficient and higher processing capacity.

[0066] 2. The coal direct liquefaction suspended bed reactor used in the present invention has a special structure distribution plate, which realizes the secondary distribution of gas, liquid and solid. While maintaining a high liquid velocity in the reactor, the gas-liquid-solid three-phase flow is more evenly distributed, ensuring a stable unidirectional plug flow of the medium in the reactor. More importantly, it avoids mineral deposition, breaks through the bottleneck of reactor engineering scale-up, and thus can further expand the scale of the device and improve the core competitiveness of direct coal liquefaction. At the same time, the feed distribution plate can generate evenly distributed micron-sized bubbles, which is beneficial to mass transfer and heat transfer during the reaction process, and promotes the coal liquefaction reaction.

[0067] 3. By circulating the liquid phase material of the hot high-pressure separator between the hot high-pressure separator and the coal direct liquefaction reactor, the single-pass reaction time of the raw materials is shortened, the light components are quickly separated in the reaction system, secondary cracking is avoided, the gas yield is low, and the hydrogen utilization efficiency is high. At the same time, the residence time of the heavy components that are more difficult to convert is extended, and the efficient synergistic conversion of different microscopic components of coal is achieved, the yield of liquid products is improved, and the economic benefits of direct coal liquefaction are enhanced.

[0068] The outlet product of the coal direct liquefaction reactor is fully separated into gas and liquid in the hot high-pressure separator, which improves the working condition of the circulation pump of the circulating material. The circulation volume is relatively stable, the flow state of the medium in the reactor is less affected by the fluctuation of the raw material and hydrogen flow rate, the system has strong anti-interference ability, and the system stability is improved. The reaction system is easy to control and operate, which is conducive to the long-term stable operation of the device.

[0069] By introducing hydrogen and solvent into the second and third direct coal liquefaction reactors, the liquefaction hydrogen partial pressure and active hydrogen content in the reaction system are maintained, which is beneficial for the conversion of coal and asphaltene, ultimately increasing the coal liquefaction conversion rate and oil yield. Simultaneously, regulating the supply of hydrogen and solvent allows for precise temperature control of the coal liquefaction reactor, preventing temperature fluctuations and coking within the reactor, thereby ensuring long-term stable operation of the coal liquefaction reactor.

[0070] Under the conditions of the same coal slurry processing capacity and coal liquefaction reaction unit processing scale, when two coal liquefaction reaction units are connected in series, their liquefaction reaction temperature rises are approximately 70~90℃ and 35~45℃ respectively; when three coal liquefaction reaction units are connected in series, their liquefaction reaction temperature rises are approximately 60~70℃, 5~20℃ and 1~10℃ respectively. It can be obviously seen that the three coal direct liquefaction reactors connected in series can effectively reduce the temperature gradient of a single coal direct liquefaction reactor, optimize the reaction load of each reactor, and make it easier to achieve stable control and operation of the coal liquefaction reaction unit. More importantly, it avoids the generation of a large number of pyrolysis free radicals of coal powder in the first reactor, prevents free radical condensation reactions caused by insufficient hydrogen supply, and is beneficial to the coal liquefaction conversion and long-term operation of the reactor; at the same time, the smaller the reactor temperature gradient, the higher the average reaction temperature of the reactor, which is beneficial to promoting the coal liquefaction conversion.

[0071] By optimizing the design of the hot high-pressure separator structure, installing a washing tower plate and spray on the top, and introducing flushing oil and disturbed hydrogen at the bottom, the technical problems of coking, coal powder deposition and entrainment of solid powder in the gas phase in the hot high-pressure separator were solved, avoiding adverse effects on downstream equipment and pipelines, hydrogenation catalysts, and product quality. At the same time, the solid content of the hot high-pressure separator was controlled, extending the service life of the high-temperature solid-containing high-differential pressure reducing valve, and ensuring the long-term stable operation of the coal direct liquefaction unit.

[0072] By exchanging heat between the oil-coal slurry and the gaseous product at the top of the hot high-pressure separator of the coal direct liquefaction device, the heat load of the oil-coal slurry heating furnace can be reduced, coking of the oil-coal slurry heating furnace tubes can be avoided, and the operation cycle of the heating furnace can be extended; at the same time, the thermal efficiency of the coal direct liquefaction device can also be greatly improved.

[0073] By using a mixture of heavy oil and medium oil with a flexibly adjustable distillation range as the circulating solvent, the distillation range of the medium oil in the circulating solvent can be adjusted according to product solutions, such as the composition requirements of special liquid fuels, thereby achieving flexible and adjustable product solutions, improving the market adaptability of direct coal liquefaction technology and the adaptability of national energy security and national defense security to the demand for special liquid fuels.

[0074] In summary, the technical solution of the present invention is adopted. In the above-mentioned coal direct liquefaction system, by adopting three reactors in series, and the reactor adopts a suspended bed reactor with secondary material distribution, it is beneficial to make the gas-liquid-solid three-phase flow distribution more uniform while maintaining a high liquid velocity in the reactor, ensuring a stable unidirectional plug flow of the medium in the reactor, and more importantly, avoiding mineral deposition, breaking through the bottleneck of reactor engineering amplification, and at the same time cooperating with the first hot high-pressure separator to separate light products and recycle heavy products, it can effectively solve the problem of secondary cracking of light products that is easily generated due to the use of three reactors and extend the residence time of heavy products. In conjunction with the introduction of hydrogen and solvent at the inlet of the second and third coal direct liquefaction reactors, the hydrogen partial pressure of the coal direct liquefaction reaction and the amount of active hydrogen in the system are guaranteed, the hydrogenation liquefaction reaction of coal and heavy products is promoted, and the coal liquefaction conversion rate and oil yield are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 A schematic structural diagram of a direct coal liquefaction system provided in accordance with a typical embodiment of the present invention;

[0076] Among them, Figure 1 The following reference numerals are included:

[0077] 110, oil-coal slurry preparation tank; 120, oil-coal slurry heat exchanger; 130, oil-coal slurry heating furnace; 140, hydrogen heating furnace; 150, first coal direct liquefaction reactor; 160, second coal direct liquefaction reactor; 170, third coal direct liquefaction reactor; 180, first hot high-pressure separator; 190, first cold high-pressure separator; 200, distillation tower; 210, raw material buffer tank; 220, raw oil heating furnace; 230, hydrogenation reactor; 240, second hot high-pressure separator; 250, second cold high-pressure separator; 260, fractionation tower; 101, low-pressure coal slurry circulation pump; 102, high-pressure coal slurry feed pump; 103, circulating material delivery pump; 104, hydrogenation raw material pump;

[0078] Figure 2 a is a schematic structural diagram of an embodiment of the first coal direct liquefaction reactor of the present invention;

[0079] Figure 2 b is a schematic structural diagram of an embodiment of the second and third coal direct liquefaction reactors of the present invention;

[0080] Among them, Figure 2 a and attached Figure 2 The following reference numerals are included in b:

[0081] 112, fresh material feed port; 113, recycled material feed port; 113', second feed port; 113'', third feed port; 114, first product outlet; 114', second product outlet; 114'', third product outlet; 115, fresh material distributor; 116, material diffuser; 10, distribution plate; 11, bubble cap distributor; 119, air cushion layer;

[0082] Figure 3 This is a schematic structural diagram of an embodiment of a hot high-pressure separator of the present invention;

[0083] Among them, Figure 3 The following reference numerals are included:

[0084] 181. Feed inlet; 182. Pressure gauge; 183. Slurry phase material outlet; 184. Gas phase product outlet; 185. Washing oil spray port; 186. Flushing oil inlet; 187. Disturbance hydrogen inlet; 188. Washing tray; 189. Circulating material extraction port;

[0085] Figure 4 for Figure 2 A schematic diagram of an embodiment of the fresh material distributor in a;

[0086] Figure 5 for Figure 4 A cross-sectional schematic diagram of a fresh material distributor;

[0087] Figure 6 is a schematic diagram of one embodiment of a dispensing tray with a blister dispenser;

[0088] Among them, the above-mentioned Figures 4-6 The following reference numerals are included:

[0089] 1. Feed pipe; 2. Diversion chamber; 3. Distribution pipe; 4. Distribution branch pipe; 5. Distribution ring pipe; 7. Distribution hole; 8. Air guide pipe; 10. Distribution plate; 11. Blister dispenser;

[0090] 12. Center tube; 121. Throat tube; 122. Inlet tube; 123. Outlet tube; 124. Constriction port; 125. Throat tube; 126. Expansion port;

[0091] 13. Bubble cap; 131. Bubble cap top plate; 132. Bubble cap side plate; 133. Gas-liquid distribution slit. DETAILED DESCRIPTION

[0092] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0093] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0094] It should be noted that the terms "first," "second," and the like in the specification and claims of the present invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate for the embodiments of the present invention described herein. In addition, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products, or apparatuses.

[0095] like Figure 1 As shown, the direct coal liquefaction system of the present invention includes an oil-coal slurry configuration unit, a preheating and mixing unit, a first direct coal liquefaction reactor 150, a second direct coal liquefaction reactor 160, a third direct coal liquefaction reactor 170, a first separation unit, a distillation column 200, a hydrogenation unit, a second separation unit, and a hydrogen supply unit; each of these will be further described below:

[0096] Coal-oil slurry configuration unit

[0097] The oil-coal slurry preparation unit is well known in the art and is used to prepare an oil-coal slurry for direct coal liquefaction using a first solvent oil as the solvent oil. In one embodiment, the oil-coal slurry preparation unit includes, for example, an oil-coal slurry preparation tank 110, a low-pressure coal slurry circulation pump 101, and a high-pressure coal slurry feed pump 102; wherein the oil-coal slurry preparation tank 110 is used to prepare the oil-coal slurry using the first solvent oil, coal powder, a catalyst, and a sulfiding agent, for example, the first solvent oil and coal powder, and the first solvent oil and catalyst are premixed in a kneader before entering the oil-coal slurry preparation tank; the inlet of the low-pressure coal slurry pump 101 is connected to the oil-coal slurry outlet of the oil-coal slurry preparation tank 110, and the outlet is connected to the oil-coal slurry preparation tank 110 and the high-pressure coal slurry feed pump 102, respectively, for circulating part of the oil-coal slurry back to the oil-coal slurry preparation tank 110 and sending part of the oil-coal slurry out; the high-pressure coal slurry feed pump 102 is used to pressurize part of the oil-coal slurry from the low-pressure coal slurry circulation pump 101 and send it out.

[0098] In this embodiment, among the first solvent oil, coal powder, catalyst and sulfiding agent as raw materials, the coal powder and part of the first solvent oil are first premixed in a mixer before being added to the oil-coal slurry preparation tank, and the catalyst, part of the first solvent and the optional sulfiding agent are also first premixed in a mixer before being added to the oil-coal slurry preparation tank, and then sent to the oil-coal slurry preparation tank to prepare the oil-coal slurry. Wherein, the mixer can be a centrifugal mixer with an operating temperature of 60~150℃, a residence time of 10~60min, and a mass ratio of coal powder to circulating solvent of 5~7:1. In the present invention, by premixing the raw materials separately in a mixer before preparing the oil-coal slurry, it is beneficial to achieve rapid and uniform mixing of the oil-coal slurry and reduce the preparation time of the oil-coal slurry.

[0099] After the raw materials are configured into pumpable oil-coal slurry in the oil-coal slurry preparation tank 110, part of the raw materials are circulated by the low-pressure coal slurry pump 101 to maintain the stability of the oil-coal slurry, and part of the raw materials are sent to the high-pressure coal slurry pump 102 for pressurization and then sent to the preheating mixing unit.

[0100] In the present invention, the oil-coal slurry preparation temperature can generally be 50-250°C, such as 100 or 150°C, and the oil-coal slurry mass concentration can be 10-55%, such as 20%, 30%, or 40%. The catalyst used in the direct coal liquefaction reaction can be a catalyst commonly used by those skilled in the art in direct coal liquefaction processes. For example, the direct coal liquefaction catalyst can be selected from one or more of nano-hydrated iron oxide, natural ores, pure iron compounds, nano-sized ferrous sulfide, and precious metals. The pure iron compounds can be selected from one or more of the group consisting of iron oxides, sulfides, and hydroxides. The precious metal catalyst can be an oil-soluble catalyst or a supported catalyst. More preferably, the catalyst can be nano-hydrated iron oxide or nano-sized ferrous sulfide. The catalyst can be used in an amount of 0.05-3 wt% of the oil-coal slurry, such as 0.1-2 wt% (active metal / oil-coal slurry).

[0101] Preheating mixing unit

[0102] The preheating mixing unit is used to mix the oil-coal slurry from the oil-coal slurry configuration unit with hydrogen and preheat the temperature. In one embodiment, the preheating mixing unit includes an oil-coal slurry heat exchanger 120, an oil-coal slurry heating furnace 130 and a hydrogen heating furnace 140. The oil-coal slurry heat exchanger 120 is used to heat and heat the mixture of the oil-coal slurry from the high-pressure coal slurry pump 102 and the first part of the hydrogen from the hydrogen supply unit with the first part of the light components from the first hot high-pressure separator 180. The oil-coal slurry heating furnace 130 is used to further heat the mixture from the oil-coal slurry heat exchanger 120. The hydrogen heating furnace 140 is used to heat the second part of the hydrogen from the hydrogen supply unit and, after further mixing with the mixture from the oil-coal slurry heating furnace 130, feed it into the fresh material feed port of the first coal direct liquefaction reactor 150.

[0103] In this embodiment, the oil-coal slurry is premixed with the first portion of hydrogen and then preheated by the oil-coal slurry heat exchanger 120, then heated by the oil-coal slurry heater 130, and then mixed with the second portion of hydrogen heated by the hydrogen heating furnace 140 to reach the temperature required for the reaction, and then fed into the first coal direct liquefaction reactor 150 as fresh material; due to the staged heating, the heating load of the oil-coal slurry heating device is effectively reduced, and the waste heat of the system is recovered. At the same time, the step-by-step heating is also conducive to the stability of the oil-coal slurry. In some embodiments, the outlet temperature of the oil-coal slurry heating furnace 130 can be controlled at above 350°C, and the fresh material inlet temperature of the first coal direct liquefaction reactor 150 can be controlled at above 360°C.

[0104] Coal liquefaction reaction unit

[0105] In the present invention, the coal liquefaction reaction unit for performing the direct coal liquefaction reaction comprises a first, a second and a third direct coal liquefaction reactor arranged in series.

[0106] like Figure 2 a and Figure 2 As shown in b, the bottom of the first coal direct liquefaction reactor 150 is respectively provided with a fresh material feed inlet 112 and a circulating material feed inlet 113 connected to the preheating mixing unit, and the top is provided with a first product outlet 114, which is used to carry out the coal direct liquefaction reaction and send the obtained first reaction product out from the first product outlet 114.

[0107] The second coal direct liquefaction reactor 160 is provided with a second feed inlet 113' at the bottom and a second product outlet 114' at the top, for using the material from the second feed inlet 113' to carry out a coal direct liquefaction reaction to obtain a second reaction product; wherein, the second feed inlet 113' is used to receive the first reaction product, the second solvent oil and the hydrogen from the hydrogen supply unit.

[0108] The third coal direct liquefaction reactor is provided with a third feed port 113'' at the bottom and a third product outlet 114'' at the top, which are used to use the material from the third feed port 113'' to carry out a coal direct liquefaction reaction to obtain a third reaction product; wherein, the third feed port 113'' is used to receive the second reaction product, the third solvent oil and hydrogen from the hydrogen supply unit.

[0109] During operation, the mixture of the oil-coal slurry and hydrogen from the preheating mixing unit is reacted with the recycled material through the fresh material feed port 112 and the recycled material feed port 113 respectively into the first coal direct liquefaction reactor 150, and the obtained first reaction product is then reacted with the second solvent oil and hydrogen through the second feed port 113' into the second coal direct liquefaction reactor 160, and the obtained second reaction product is then reacted with the third solvent oil and hydrogen through the third feed port 113'' into the third coal direct liquefaction reactor 170 to obtain a third reaction product.

[0110] In the present invention, under the action of a coal direct liquefaction catalyst, under high temperature and high pressure hydrogen conditions, coal powder undergoes a liquefaction reaction to generate a mixture of gaseous products and liquid products; wherein, the temperature rise of the first coal direct liquefaction reactor can be controlled by the outlet temperature of the oil-coal slurry heater 130, and the temperature rise range of the second and third coal direct liquefaction reactors can be controlled by the supply amount of the second and third solvent oils. At the same time, the amount of active hydrogen in the solvent in the reactor is supplemented to promote the liquefaction conversion of the coal, and the hydrogen partial pressure of the coal direct liquefaction reactor can also be controlled by the amount of hydrogen at the inlet of each coal direct liquefaction reactor, thereby ensuring the liquefaction conversion of the coal and improving the oil yield.

[0111] In a preferred embodiment, the temperature rise of the first coal direct liquefaction reactor is 60~80℃, such as 65, 70 or 75℃, the temperature rise of the second coal direct liquefaction reactor is 20~30℃, such as 22, 25 or 28℃, and the temperature rise of the third coal direct liquefaction reactor is 5~10℃, such as 6 or 8℃; the amount of the first solvent oil is 45~60wt% of the oil-coal slurry, such as 50wt%, 55wt% or 58wt%; the amount of the second solvent oil is 2~15wt% of the first reaction product, such as 5wt%, 10wt% or 12wt%; the amount of the third solvent is 1~5wt% of the second reaction product, such as 2 or 4wt%.

[0112] In the present invention, in order to better ensure that the coal has a high conversion rate and liquid fuel yield during the liquefaction reaction, in a preferred embodiment, the average reaction temperature of the first coal direct liquefaction reactor is recorded as T1, the reaction pressure is recorded as P1, and the hydrogen partial pressure is recorded as PH1; the average reaction temperature of the second coal direct liquefaction reactor is recorded as T2, the reaction pressure is recorded as P2, and the hydrogen partial pressure is recorded as PH2; the average reaction temperature of the third coal direct liquefaction reactor is recorded as T3, the reaction pressure is recorded as P3, and the hydrogen partial pressure is recorded as PH3; wherein T1, T2 and T3 are independently selected from 390~470℃, preferably 410~460℃, and T3≥T2≥T1, preferably, the difference between T3 and T2 is 5~15℃, and the difference between T2 and T1 is 5~15℃; P1, P2 and P3 are independently selected from 5~35MPa, preferably 10~20MPa, and P1≥P2≥P3; HP1, HP2 and HP3 are independently selected from 4.5~28MPa, preferably 8~13MPa; the oil-coal slurry space velocity in each reactor (i.e., the space velocity calculated based on the amount of the oil-coal slurry) is 0.3~2.0t / (h·m3), preferably 0.5~1.5t / (h·m3).

[0113] Further preferably, the ratio of the volume of hydrogen entering the first direct coal liquefaction reactor to the weight of the oil-coal slurry is recorded as N1, the ratio of the volume of hydrogen entering the second direct coal liquefaction reactor to the weight of the oil-coal slurry is recorded as N2, and the ratio of the volume of hydrogen entering the third direct coal liquefaction reactor to the weight of the oil-coal slurry is recorded as N3, N1, N2 and N3 are independently selected from 300~1000L / kg, preferably 400~600L / kg, and N3≥N2≥N1.

[0114] The study found that controlling the various process conditions of the liquefaction reaction within the above range can reduce construction investment costs, and can make the coal liquefaction reaction more complete, ensuring a higher coal conversion rate and liquid fuel yield during the liquefaction reaction.

[0115] In the present invention, the first, second and third direct coal liquefaction reactors can be suspended bed reactors with gas secondary distribution; wherein, the internal components in the first direct coal liquefaction reactor 150 are arranged at the bottom of the reactor, including a fresh material distributor 115, a material diffuser 116 and a distribution plate 10 with a bubble distributor 11; the internal components in the second and third direct coal liquefaction reactors are arranged at the bottom of the reactor, including a material diffuser 116 and a distribution plate 10 with a bubble distributor 11; wherein, the material diffuser 116 is arranged at the bottom of the reactor, and the fresh material distributor 115 is arranged between the material diffuser 116 and the distribution plate 10; preferably, there are no internal components above the distribution plate 10, which is conducive to eliminating the gas-liquid interface at the top of the reactor, avoiding coal powder deposition, and having a high volume utilization rate of the reactor, which is conducive to maintaining a stable unidirectional plug flow in the reactor and extending the reactor operation cycle.

[0116] In one embodiment, Figure 4 and 5 As shown, the fresh material distributor 115 includes a feed pipe 1, a distribution pipe 3, an air guide pipe 8 and a guide chamber 2; the feed pipe 1 is connected to the fresh material feed port 12; the distribution pipe 3 is arranged in the horizontal direction and is a ring pipe structure, including a distribution ring pipe 5 arranged around the guide chamber 2 and a plurality of, for example, four distribution branches 4 arranged between the guide chamber 2 and the distribution ring pipe 5, the distribution branch pipe 4 being radially arranged along the distribution ring pipe 5, one end of which is connected to the guide chamber 2 and the other end of which is connected to the distribution ring pipe 5; the distribution branch pipe 4 and the distribution ring pipe 5 are both provided with downward distribution holes for feeding the gas-liquid mixture For distribution, of course, a micro-bubble nozzle can be further provided on the distribution hole; the guide cavity 2 is a guide cavity with a hollow chamber, the lower and upper parts of which are truncated cone or conical structures, and the middle part is a cylindrical section connected to the larger diameter end of the truncated cone or conical structure; the outlet of the feed pipe is connected to the side of the lower part of the guide cavity 2 along the tangential direction, the inlet of the distribution pipe 3 is connected to the middle part of the guide cavity, the air inlet of the air guide pipe 8 is located just above the top of the guide cavity 2, and is vertically connected to the guide cavity 2, the air outlet at the upper end of the air guide pipe is higher than the air inlet at the lower end of the bubble dispenser, that is, it is in the air cushion layer 119. Among them, the micro-bubble nozzle is well known in the art, for example, it can include a feed section, a throat section and a discharge section connected in sequence, wherein the feed section and the discharge section are respectively connected to the two ends of the throat section with a smaller diameter through a reducing section.

[0117] In the above Figure 4 and 5 In the embodiment shown, the feed liquid fed tangentially from the feed pipe 1 generates a cyclonic diversion in the guide chamber 2, so that the gas phase with a lower density is better separated from the liquid phase due to the cyclonic separation effect and rises and finally enters the air cushion layer under the distribution plate 10 through the air guide pipe 8, while the remaining gas-liquid mixture enters the distribution pipe 3 under the action of centrifugal force and is ejected from the microbubble nozzle.

[0118] In some other embodiments, the diameter of the distribution pipe and / or the aperture of the distribution hole can be further configured to make the total pressure drop of the distribution pipe smaller than the pressure drop of the air duct, so as to be more conducive to the remaining gas-liquid mixture entering the distribution pipe, for example, relatively increasing the pipe diameter and / or aperture to reduce the pressure drop, which is well known in the art; of course, it can be understood in the art that the air duct 8 can also be configured to make its pressure drop greater than the total pressure drop of the distribution pipe 3, such as reducing the diameter of the air duct.

[0119] In one embodiment, Figure 6As shown, the bubble dispenser 11 includes a vertically arranged central tube 12, a bubble 13 at the upper end of the central tube and an air supply pipe connected to the air inlet of the central tube for supplying air to the central tube; the bubble 13 includes a bubble top plate 131 and a bubble side plate 132, and the bubble side plate 132 is connected to the edges of the bubble top plate 131 and extends downward; the upper end of the central tube extends into the bubble 13 and is spaced a preset distance from the bubble top plate 131 to facilitate the passage of materials; a liquid inlet is provided at the lower end of the central tube; an annular flow channel is formed between the bubble side plate 132 and the central tube 12, and the bubble side plate 132 is The lower end is provided with multiple gas-liquid distribution slits for gas-liquid discharge; the central tube 12 is provided with a throat portion 121, and the throat portion includes a contraction port, a throat pipe and an expansion port connected in sequence from bottom to top; the air supply pipe includes a horizontally arranged air inlet pipe 122 and an air outlet pipe 123 vertically arranged in the central tube and coaxially arranged with the throat pipe, and the upper end air outlet of the air outlet pipe 123 is in the throat pipe; the air inlet pipe passes through the air inlet of the central tube and is connected to the air outlet pipe; the air inlet pipe is provided with multiple, for example 4, and each of the air inlet pipes is connected to the air outlet pipe respectively, and the multiple air inlet pipes are evenly spaced along the circumferential direction of the air outlet pipe.

[0120] In the present invention, the coal direct liquefaction reactor adopts a distribution plate with a bubble distributor of special structure. Since the gas supply pipe is arranged in the throat part, it is beneficial to maintain a better gas-liquid mixing and distribution effect at high liquid velocity in the reactor, which is beneficial to promoting the coal direct liquefaction reaction.

[0121] In the present invention, the material diffuser 116 at the bottom of each reactor can be a liquid distributor commonly used in the art. For example, its shape can be pagoda-shaped, cylindrical, or polygonal barrel-shaped, and material outlets are evenly distributed on the side walls so that the material fed into the diffuser is dispersed from the material outlet to the bottom of the reactor.

[0122] First separation unit

[0123] The first separation unit is connected to the third product outlet 114'' and is used to separate the third reaction product to separate the light component oil and non-condensable gas therefrom, and to feed a portion of the remaining heavy component oil as a circulating material into the circulating material inlet 113 of the first coal direct liquefaction reactor 150, and the other portion into the distillation tower 200.

[0124] In one embodiment, the first separation unit includes a first hot high-pressure separator 180 and a first cold high-pressure separator 190; wherein the first hot high-pressure separator 180 is connected to the third product outlet 114'' to receive the third reaction product and separate it, and obtain the light component as the first gas phase from the top, and obtain the heavy component oil as the first liquid phase from the bottom, and then a part of the heavy component oil discharged from the bottom is sent to the circulating material inlet 113 of the first coal direct liquefaction reactor 150 as a circulating material, and the other part is sent to the distillation tower 200, and the first part of the separated light component is sent from the top to the oil-coal slurry heat exchanger 120 of the preheating mixing unit for heat exchange and cooling with the oil-coal slurry, and the second part is sent to the first cold high-pressure separator 190.

[0125] The first cold high-pressure separator 190 is used to separate the first light component and the second light component after heat exchange and temperature reduction, thereby obtaining the non-condensable gas as the second gas phase at the top and the light component oil as the second liquid phase at the bottom. A portion of the second gas phase can be circulated as circulating hydrogen to the direct coal liquefaction reactor, and the remaining portion can be discharged as tail gas to control the purity of the hydrogen supplied by the hydrogen supply unit. The circulating hydrogen purity can be greater than 80%, such as greater than 85%.

[0126] In this embodiment, the third reaction product from the third direct coal liquefaction reactor 170 enters the first high-temperature, high-pressure separator 180 for oil and gas separation. A portion of the heavy component oil separated by the first hot, high-pressure separator 180 is transported via a circulation pump 103 to the first direct coal liquefaction reactor 150, thereby achieving the circulation of the separated material of the first hot, high-pressure separator 180 in the direct coal liquefaction process. The light component produced at the top of the first hot, high-pressure separator 180 enters the first cold, high-pressure separator 190 after heat exchange and cooling. The temperature of the first cold, high-pressure separator 190 can be controlled below 50°C, and a portion of the non-condensable gas obtained at the top is returned to the direct coal liquefaction reactor as circulating hydrogen, and a portion is burned and discharged as tail gas, resulting in light component oil at the bottom. The light component oil produced at the bottom of the first cold, high-pressure separator 190 is mixed with another portion of the heavy component oil at the bottom of the first hot, high-pressure separator 180 and then enters the distillation tower 200.

[0127] In the present invention, the circulation of heavy component oil as a circulating material is beneficial to reducing the gas retention coefficient in the liquefaction reactor, and the reactor processing capacity is large; a high liquid velocity can be maintained in the reactor, and a distribution plate is used at the bottom of the reactor to ensure that the radial three-phase material flow state of the reactor is completely consistent, and the reactor axial stable unidirectional plug flow is avoided, thereby avoiding mineral deposition, breaking through the bottleneck of coal direct liquefaction reactor amplification, improving the device processing capacity, and facilitating the realization of single-series scale amplification of coal direct liquefaction device; shortening the single-pass residence time of the raw material is beneficial to reducing the residence time of the light component, avoiding secondary cracking, reducing the gas yield, increasing the catalyst content in the liquefaction reaction and the reaction residence time of coal and asphalt-like substances that are more difficult to convert, realizing efficient synergistic conversion of different microscopic components of coal, promoting coal liquefaction conversion, and improving oil yield.

[0128] like Figure 3 As shown, in one embodiment, the first hot high-pressure separator is provided with a feed inlet 181 for introducing the third reaction product in the middle, a gas phase outlet 184 at the top, and a slurry phase material outlet 183 at the bottom; a wash oil spray port 185 and a wash tray 188 are provided from top to bottom between the gas phase outlet 184 and the feed inlet 181; and a circulating material extraction port 189, a flushing oil inlet 186, and a disturbance hydrogen inlet 187 are provided from top to bottom between the feed inlet 181 and the slurry phase material outlet 183. The flushing oil inlet 186 is provided at the center (i.e., on the axis) of the first hot high-pressure separator 180 and opens downward. Of course, a pressure gauge 182 can also be provided on the top of the first hot high-pressure separator 180 to monitor the pressure.

[0129] In the present invention, by arranging a washing tray and a washing oil spray port in the first hot high-pressure separator, it is possible to prevent the entrainment of solid powder in the rising gas phase in the first hot high-pressure separator, and at the same time form an oil film at the gas-liquid interface to prevent coal powder from being deposited at the gas-liquid interface; in addition, the injection of flushing oil is conducive to relatively reducing the solid content in the material drawn out from the slurry phase material outlet 183, and increasing the solid content of the circulating material extracted from the circulating material extraction port 189, thereby relatively increasing the catalyst content in the liquefaction reaction and the residence time of the coal and asphalt materials that are more difficult to convert, thereby increasing the coal liquefaction conversion rate and oil yield; at the same time, by injecting disturbed hydrogen and flushing oil, it is also possible to prevent deposition and coking at the bottom of the hot high-pressure separator, thereby extending its service life. Wherein, both the washing oil and the flushing oil can be heavy oil produced by the system of the present invention.

[0130] In some embodiments, the solids content of the recycled material leaving the first hot high-pressure separator 180 is 10-20%. The solids content of the heavy oil fraction fed to the distillation column is lower than that of the recycled material, for example, at least 2% lower, such as ≤10%, preferably ≤8%. The injection of flushing oil can relatively increase the solids content of the recycled material, while also relatively increasing the amount of recycled material circulated, reducing the residence time of the light components, and improving the coal liquefaction conversion rate and oil yield. In the present invention, the feed mass ratio of the recycled material to the oil-coal slurry entering the first direct coal liquefaction reactor can be (0.2-30):1, preferably (1-20):1, such as 2:1, 5:1, or 10:1.

[0131] distillation tower

[0132] The distillation tower 200 is used to distill and separate the light component oil from the first separation unit and another portion of the heavy component oil to obtain coal direct liquefaction crude oil and the remaining coal liquefaction pitch.

[0133] The distillation tower 200 can be a commonly used distillation separation tower in the art, such as a vacuum tower. The light component oil from the bottom of the first cold high-pressure separator 190 and another portion of the heavy component oil from the first hot high-pressure separator 180 undergo solid-liquid separation in the distillation tower 200 to produce direct coal liquefaction crude oil and coal liquefaction pitch. In some embodiments, to ensure a higher direct coal liquefaction liquid product while also ensuring that the coal liquefaction pitch has good transportability and is easier to solidify and form, the solids content of the coal liquefaction pitch at the bottom of the vacuum distillation tower can preferably be controlled to 35-60%, such as 40%, 50%, or 55%, and the softening point can be controlled to 170-190°C, such as 175, 180, or 185°C.

[0134] Hydrogenation unit

[0135] The hydrogenation unit is used to hydrogenate the direct coal liquefaction crude oil to obtain direct coal liquefaction oil; in one embodiment, the hydrogenation unit includes a raw material buffer tank 210, a hydrogenation raw material pump 104, a raw material heating furnace 220 and a hydrogenation reactor 230; wherein, the raw material buffer tank 210 is used to receive the direct coal liquefaction crude oil distilled from the distillation tower 200; the hydrogenation raw material pump 104 is used to send the direct coal liquefaction crude oil in the raw material buffer tank 210 into the raw material heating furnace 220; the raw material heating furnace 220 is used to heat the direct coal liquefaction crude oil and the third part of hydrogen from the hydrogen supply unit; the hydrogenation reactor 230 is used to hydrogenate the feed from the raw material heating furnace 220 as raw material to obtain direct coal liquefaction oil.

[0136] During operation, the coal direct liquefaction crude oil produced by the distillation tower 200 enters the raw oil buffer tank 210, is pressurized by the hydrogenation raw material pump 104 and mixed with hydrogen, and enters the hydrogenation reactor 230 after being heated by the raw material heating furnace 220. The outlet temperature of the raw material heating furnace 220 can be controlled at above 300°C. The coal direct liquefaction oil is catalytically hydrogenated in the hydrogenation reactor 230 to achieve partial hydrogenation and saturation of aromatics, while desulfurization, denitrogenation and deoxygenation reactions occur.

[0137] In the process of hydrogenation reaction of crude oil from direct coal liquefaction, the hydrogenation reaction pressure can be controlled to be 3~30MPa, the reaction temperature to be 290~410℃, and the volume space velocity to be 0.5~3.0h -1 The volume ratio of hydrogen to coal direct liquefaction oil (hydrogen-oil ratio) is 200-2000:1; preferably, the hydrogenation reaction pressure is 15-19 MPa, the reaction temperature is 320-380 ° C, and the volume space velocity is 0.8-1.5h -1 , with a hydrogen-to-oil ratio of 300-600:1. Controlling the various process conditions during the direct coal liquefaction (CTL) hydrogenation process within the aforementioned range facilitates a more complete CTL hydrogenation reaction, achieving partial saturation of aromatics in the CTL, increasing the amount of active hydrogen in the solvent, and improving the solvent's hydrogen supply capacity, thereby promoting coal liquefaction and increasing oil yield. Simultaneously, it removes heteroatoms from the CTL, providing qualified raw materials for downstream CTL product processing.

[0138] In a preferred embodiment, the hydrogenation reactor adopts an ebullated bed reactor or an ebullated bed-solid bed combination reactor; wherein, the ebullated bed reactor has a wide adaptability to the hydrogenation feedstock during the reaction process, has no bed clogging problem, the catalyst can be replaced online, and the hydrogenation depth and solvent properties are stable; the fixed bed reactor has a high hydrogenation depth of the hydrogenation feedstock during the reaction process, a low catalyst wear rate, a high product yield and good quality, a desulfurization rate of more than 90%, a simple process and equipment structure, low investment cost, and stable operation; research has found that the ebullated bed-fixed bed combination reactor obtained by connecting an ebullated bed reactor and a fixed bed reactor in series has certain complementary advantages when performing solvent hydrogenation, which is conducive to sufficient hydrogenation conversion of crude oil from direct coal liquefaction under low reaction pressure.

[0139] During the CDL hydrogenation reaction, a hydrogenation catalyst is used to catalytically hydrogenate the CDL obtained by distillation. Such hydrogenation catalysts are well known in the art and can be, for example, supported catalysts in the form of bars or spheres, preferably supported on an alumina support. The active metal components of the supported catalyst are one or more of Group VIB or Group VIII, more preferably Mo and W from Group VIB and Ni and Co from Group VIII.

[0140] Second separation unit

[0141] The second separation unit is used to separate the coal direct liquefaction oil from the hydrogenation unit to obtain non-condensable gas, light oil, medium oil and heavy oil, and send the light oil and at least part of the medium oil as coal direct liquefaction product oil, and use the heavy oil or a mixed oil group of the heavy oil and part of the medium oil as a circulating solvent, and send the circulating solvent as the first solvent oil to the oil-coal slurry configuration unit, as the second solvent oil to the second feed port, and as the third solvent oil to the third feed port. In some embodiments, the distillation range of the medium oil falls within 220~350℃. For example, the medium oil can be a fraction or a mixture of multiple fractions with a distillation range falling within the temperature range of 220~350℃. The specific amount can be flexibly controlled according to the demand for circulating solvent and product plan.

[0142] In one embodiment, the second separation unit includes a second hot high-pressure separator 240, a second cold high-pressure separator 250 and a distillation tower 260; wherein the second hot high-pressure separator 240 is used to perform gas-liquid separation on the coal direct liquefaction oil from the hydrogenation unit, and obtain a third gas phase at the top and a third liquid phase at the bottom; the second cold high-pressure separator 250 is used to further perform gas-liquid separation on the third gas phase from the second hot high-pressure separator 240, so as to separate the non-condensable gas as the fourth gas phase at the top and obtain the fourth liquid phase at the bottom; the distillation tower 260 is used to fractionate the third liquid phase from the second hot high-pressure separator 240 and the fourth liquid phase from the second cold high-pressure separator 250 to obtain coal direct liquefaction product oil and a circulating solvent, and the circulating solvent is respectively fed into the oil-coal slurry configuration unit as the first solvent oil, into the second feed port as the second solvent oil, and into the third feed port as the third solvent oil.

[0143] During operation, the coal direct liquefaction oil from the hydrogenation reactor 230 enters the second hot high-pressure separator 240 for separation, and its separation temperature can be controlled between 150 and 300°C; the third gaseous product produced by the second hot high-pressure separator 240 is cooled and enters the second cold high-pressure separator 250 for further separation, and its temperature can be controlled below 50°C; part of the gaseous product at the top of the second cold high-pressure separator 250 is returned to the hydrogenation reaction system as circulating hydrogen, and the other part is discharged to control the hydrogen purity; the third liquid phase material at the bottom of the second hot high-pressure separator 240 and the fourth liquid phase material at the bottom of the second cold high-pressure separator 250 are respectively depressurized and flow into the fractionation tower 260 for distillation separation to obtain coal direct liquefaction product oil and solvent oil, and the solvent oil is circulated back to the coal direct liquefaction coal slurry preparation tank 110, the second and third coal direct liquid reactors as a circulating solvent. It can be understood in the art that the coal direct liquefaction product oil can be distilled and cut into different fractions after hydrogenation, for example, the liquid fuels formed include naphtha, jet fuel, diesel, etc.

[0144] In one embodiment, the first solvent oil, the second solvent oil and the third solvent oil are distillate oils with a distillation range of >220°C in the above-mentioned catalytic hydrogenation liquid phase product, and the aromatic hydrocarbon content is above 70%; the distillate oil has a high content of some saturated aromatic hydrocarbons and a strong hydrogen supply capacity. Using it as a solvent can further improve the effect of the liquefaction reaction, thereby increasing the yield of liquid fuel; preferably, the first solvent oil, the second solvent oil and the third solvent oil are distillate oils with a distillation range of >240°C, and the content of monocyclic and bicyclic aromatic hydrocarbons is >50wt%. Using it as a direct coal liquefaction solvent has a stronger hydrogen supply capacity and a higher yield of liquid fuel.

[0145] Hydrogen supply unit

[0146] The hydrogen supply unit is connected to the preheating mixing unit, the second feed port, the third feed port and the hydrogenation unit respectively to supply hydrogen, and the hydrogen is fresh hydrogen and / or non-condensable gas as circulating hydrogen. Specifically, for example, as the first part of hydrogen, the oil-coal slurry from the high-pressure coal slurry feed pump is mixed into the oil-coal slurry heat exchanger, as the second part of hydrogen, the oil-coal slurry from the oil-coal slurry heating furnace is mixed into the first coal direct liquefaction reactor, as the third part of hydrogen, the second coal direct liquefaction reactor is supplied, as the fourth part of hydrogen, the third coal direct liquefaction reactor is supplied, and as the fifth part of hydrogen, the hydrogenation reactor is supplied. It is understood in this art that the first, second, third and fourth part of hydrogen supply can control the hydrogen partial pressure of the first, second and third coal direct liquefaction reactors to promote the liquefaction conversion of coal.

[0147] The present invention also provides a direct coal liquefaction method, comprising the following steps: S1, mixing coal powder, a catalyst, a sulfiding agent and a first solvent to form a pumpable oil-coal slurry;

[0148] S2, mixing the oil-coal slurry with hydrogen, preheating the mixture, and then feeding it into a first coal direct liquefaction reactor with the circulating material to perform a first coal direct liquefaction reaction to obtain a first reaction product;

[0149] S3, mixing the first reaction product, hydrogen, and a second solvent oil, and then feeding the mixture into a second coal direct liquefaction reactor to perform a second coal direct liquefaction reaction to obtain a second reaction product;

[0150] S4, mixing the second reaction product, hydrogen and a third solvent oil and feeding the mixture into a third coal direct liquefaction reactor to perform a third coal direct liquefaction reaction to obtain a third reaction product;

[0151] S5, separating the third coal liquefaction product in a first separation unit to separate light oil and non-condensable gas, and feeding a portion of the remaining heavy oil after separation into the first coal direct liquefaction reactor as a circulating material;

[0152] S6, sending another portion of the heavy component oil and the light component oil into a distillation tower for distillation separation to obtain coal direct liquefaction crude oil and coal liquefaction pitch;

[0153] S7, mixing the CDL crude oil with hydrogen and performing a hydrogenation reaction, and separating the obtained CDL oil to obtain a circulating solvent and CDL liquid product oil, and sending the circulating solvent as the first solvent oil to the oil-coal slurry configuration unit, as the second solvent oil to the second CDL reactor, and as the third solvent oil to the third CDL reactor.

[0154] The present invention is further described in detail below with reference to specific examples / comparative examples. These examples should not be construed as limiting the scope of protection claimed in the present invention.

[0155] Example 1

[0156] This example uses a scale of 180 kg / day. Figure 1 The coal direct liquefaction system shown is used to conduct coal direct liquefaction tests.

[0157] Shendong coal from the Shendong mining area of ​​the State Energy Group was used as the experimental raw coal. The raw coal was crushed and dried into coal powder with a moisture content of less than 4%. The particle size of 80% of the coal powder was controlled to be below 200 mesh. The coal powder was mixed with a coal direct liquefaction catalyst, sulfur powder, and a first solvent oil in an oil-coal slurry preparation tank 110. After sufficient stirring, a pumpable coal slurry was obtained. The oil-coal slurry concentration was controlled to be 45%. The basic properties of the raw coal are shown in Table 1. The above-mentioned coal direct liquefaction method includes the following steps:

[0158] First, the oil-coal slurry is sequentially transported by the low-pressure coal slurry pump 101 and the high-pressure coal slurry pump 102, mixed with the first part of hydrogen, and then enters the oil-coal slurry heat exchanger 120 and the oil-coal slurry heating furnace 130 for heating, and then mixed with the second part of hydrogen heated by the hydrogen heating furnace 140 and enters the first coal direct liquefaction reactor 150 (its internal components are as follows Figure 4 and 5 The first reaction product drawn from the first product outlet of the first coal direct liquefaction reactor 150 is mixed with the third portion of hydrogen and the second solvent oil and then enters the second coal direct liquefaction reactor 160 for reaction. The obtained second reaction product is mixed with the third portion of hydrogen and the third solvent oil and then enters the third coal direct liquefaction reactor 170 for reaction.

[0159] The average temperature of the first coal direct liquefaction reactor is 450°C (reactor temperature rise is 63°C), the average temperature of the second coal direct liquefaction reactor is 455°C (reactor temperature rise is 11°C), and the average temperature of the third coal direct liquefaction reactor is 460°C (reactor temperature rise is 3°C). The reaction pressure of the three reactors is about 19.0 MPa, and the oil-coal slurry space velocity is 0.7 t / (h·m3); the ratio of hydrogen to oil-coal slurry entering the first coal direct liquefaction reactor is about 400 L / kg, the ratio of hydrogen to oil-coal slurry entering the second coal direct liquefaction reactor is about 500 L / kg, and the ratio of hydrogen to oil-coal slurry entering the third coal direct liquefaction reactor is about 200 L / kg. The ratio of hydrogen to coal-oil slurry in the direct liquefaction reactor was approximately 600 L / kg, and the hydrogen partial pressure of the three reactors was approximately 12.5 MPa. The amount of the second solvent oil entering the second coal direct liquefaction reactor was 10 wt % of the coal-oil slurry feed, and the amount of the third solvent oil entering the third coal direct liquefaction reactor was 5 wt % of the coal-oil slurry feed. The coal liquefaction catalyst was an Fe(OOH) catalyst (preparation method, see Example 1 of CN1274415C), the coal liquefaction catalyst addition amount was 1.0 wt % (Fe / dry coal), and the additive was sulfur, controlling n(S) / n(Fe)=2.

[0160] The third reaction product drawn from the third product outlet of the third coal direct liquefaction reactor 170 enters the first hot high-pressure separator 180 (see Figure 3) is used for oil and gas separation to obtain a first gas phase and a first liquid phase, and the separation temperature is controlled at 455°C. The first gas phase produced at the top of the first hot high-pressure separator 180 is cooled by heat exchange and then enters the first cold high-pressure separator 190 for oil and gas separation to obtain a second gas phase and a second liquid phase; the temperature of the first cold high-pressure separator 190 is controlled below 50°C, and part of the second gas phase at the top is discharged as circulating hydrogen and returned to the reactor inlet, and part is discharged, and the purity of the circulating hydrogen is controlled to be above 85%; the circulating material (solid content 15wt%) extracted from the circulating material extraction outlet 189 of the first hot high-pressure separator 180 is recycled back to the first coal direct liquefaction reactor, and the ratio of the circulating material amount to the oil-coal slurry amount is 3:1; the first liquid phase (solid content 6wt%) taken out from the slurry phase material outlet 183 of the first hot high-pressure separator 180 is mixed with the second liquid phase and then enters the distillation tower 200 for distillation separation, and the solid content in the coal liquefaction pitch at the bottom of the distillation tower is controlled to be 50wt%.

[0161] Then, the crude CDL oil produced from the distillation tower 200 enters the raw material buffer tank 210, is pressurized by the hydrogenation raw material pump 104, mixed with hydrogen, heated in the raw material heating furnace 220, and then enters the hydrogenation reactor 230. The hydrogenation reactor uses an ebullated bed hydrogenation reactor to perform a catalytic hydrogenation reaction, thereby partially hydrogenating and saturating the two-ring and higher aromatic hydrocarbons in the CDL oil, and simultaneously undergoing desulfurization, denitrification, and deoxygenation reactions. The hydrogenation catalyst uses a NiMo / Al2O3 hydrogenation catalyst (see Example 1 in CN100497540C for its preparation method).

[0162] In the hydrogenation process of coal direct liquefaction crude oil, the reactor pressure is 19 MPa, the reaction temperature is 380 ° C, and the volume space velocity is 1.0 h -1 , hydrogen-to-oil ratio 300. The product at the outlet of the hydrogenation reactor enters the second hot high-pressure separator 240 for oil-gas separation to obtain a third gas phase and a third liquid phase, with the temperature controlled at 250°C; the third gas phase product of the second hot high-pressure separator is cooled and enters the second cold high-pressure separator 250 for oil-gas separation to obtain a fourth gas phase and a fourth liquid phase, with the temperature controlled below 50°C; part of the fourth gas phase product at the top of the second cold high-pressure separator is returned to the hydrogenation catalytic reactor as circulating hydrogen, and the other part is discharged to control the purity of the circulating hydrogen to be above 85%; the product at the bottom of the second hot high-pressure separator is The third liquid phase and the fourth liquid phase of the second cold high-pressure separator are mixed and decompressed before product distillation and cutting in the fractionating tower 260 to obtain coal direct liquefaction product oil and circulating solvent, and the circulating solvent is respectively fed into the oil-coal slurry configuration unit as the first solvent oil, fed into the second feed port 113' as the second solvent oil, and fed into the third feed port 113'' as the third solvent oil, wherein the circulating solvent is a mixture of the distilled heavy oil and the medium oil with a distillation range of 220~350℃, and its aromatic hydrocarbon content is greater than 50%.

[0163] Example 2

[0164] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0165] The ratio of the amount of the circulating material to the amount of the oil-coal slurry entering the first direct coal liquefaction reactor is 0.2, and the solid content of the circulating material is 10%.

[0166] Example 3

[0167] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0168] The ratio of the amount of the circulating material entering the first direct coal liquefaction reactor to the amount of the oil-coal slurry is 30, and the solid content of the circulating material is 19%.

[0169] Example 4

[0170] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0171] The ratio of the second solvent oil to the oil-coal slurry entering the second coal direct liquefaction reactor is 2wt%, and the ratio of the third solvent oil to the oil-coal slurry entering the third coal direct liquefaction reactor is 1wt%.

[0172] Example 5

[0173] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0174] The ratio of the second solvent oil to the oil-coal slurry entering the second coal direct liquefaction reactor is 20wt%, and the ratio of the second solvent oil to the oil-coal slurry entering the second coal direct liquefaction reactor is 10wt%.

[0175] Example 6

[0176] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0177] The ratio of hydrogen to oil-coal slurry entering the first direct coal liquefaction reactor is 300 L / kg, the ratio of hydrogen to oil-coal slurry entering the second direct coal liquefaction reactor is 600 L / kg, and the ratio of hydrogen to oil-coal slurry entering the third direct coal liquefaction reactor is 700 L / kg.

[0178] Example 7

[0179] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0180] The ratio of hydrogen to oil-coal slurry entering the inlet of the second direct coal liquefaction reactor is 500 L / Kg, and the ratio of hydrogen to oil-coal slurry entering the inlet of the third direct coal liquefaction reactor is 1000 L / Kg.

[0181] Example 8

[0182] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0183] The concentration of the oil-coal slurry is 55 wt %, and the reaction pressure of the three reactors is about 30 MPa.

[0184] Example 9

[0185] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0186] Hami coal from Xinjiang Uygur Autonomous Region was used as the raw coal (properties of the raw coal are shown in Table 1). The average temperature of the first coal direct liquefaction reactor was about 390°C, the average temperature of the second coal direct liquefaction reactor was about 420°C, and the average temperature of the second coal direct liquefaction reactor was about 430°C. The reaction pressure of the three reactors was about 20.0 MPa, and the ratio of hydrogen to oil-coal slurry entering the three reactors was 500 L / Kg.

[0187] Example 10

[0188] The direct coal liquefaction method provided in this embodiment differs from that in Example 9 in that:

[0189] The average temperature of the first coal direct liquefaction reactor is about 420°C, the average temperature of the second coal direct liquefaction reactor is about 430°C, and the average temperature of the third coal direct liquefaction reactor is about 440°C. The reaction pressure of the three reactors is about 5MPa.

[0190] Example 11

[0191] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0192] The average temperature of the first coal direct liquefaction reactor is 455°C, the average temperature of the second coal direct liquefaction reactor is 460°C, the average temperature of the third coal direct liquefaction reactor is 465°C, and the reaction pressure is 30.0MPa.

[0193] Example 12

[0194] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0195] The flushing oil inlet of the first hot high-pressure distributor stops inputting flushing oil.

[0196] During operation, due to the significant increase in the solid content at the bottom, the pressure reducing valve at the bottom of the first hot high-pressure separator cannot work normally for a long time.

[0197] Example 13

[0198] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0199] The circulating oil extraction outlet in the first hot high-pressure separator stops discharging material, and the circulating material and the heavy oil to be fed into the distillation column are both taken out from the slurry phase material outlet.

[0200] Example 14

[0201] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0202] The raw coal is Hami coal from Xinjiang Uygur Autonomous Region. The coal direct liquefaction oil hydrogenation adopts a fixed bed reactor with a reaction pressure of 3MPa, a reaction temperature of 380℃, and a volume space velocity of 0.5h -1 , the hydrogen-to-oil ratio is 600.

[0203] Example 15

[0204] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0205] Coal direct liquefaction oil hydrogenation uses a combination of ebullated bed and fixed bed reactors. The reaction temperature of the ebullated bed reactor is 370°C, the reaction pressure is 13.7 MPa, and the volume space velocity is 1.5 h -1 , hydrogen-to-oil ratio is 300; fixed bed reactor reaction temperature is 370℃, reaction pressure is 13.7MPa, volume space velocity is 1.0h -1 , the hydrogen-to-oil ratio is 600.

[0206] Example 16

[0207] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0208] The reaction pressure of coal direct liquefaction oil hydrogenation is 30MPa, the reaction temperature is 370℃, and the volume space velocity is 3.0h -1 , the hydrogen-to-oil ratio is 800.

[0209] Comparative Example 1

[0210] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0211] The second and third coal direct liquefaction reactors are not injected with solvent oil, and the ratio of hydrogen to oil-coal slurry in the first coal direct liquefaction reactor is 600L / kg.

[0212] During operation, the temperature rise of the second and third coal direct liquefaction reactors is approximately 19°C and 8°C respectively, and the temperature fluctuations of the second and third coal direct liquefaction reactors are large, making stable operation of the system difficult.

[0213] Comparative Example 2

[0214] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0215] The second and third coal direct liquefaction reactors are not injected with solvent oil and hydrogen, and the ratio of hydrogen to oil-coal slurry entering the first coal direct liquefaction reactor is 500L / kg.

[0216] During operation, the temperature rise of the second and third coal direct liquefaction reactors is approximately 25°C and 16°C respectively, and the temperature fluctuation of the second and third coal direct liquefaction reactors is large, and the system cannot operate for a long time.

[0217] Example 17

[0218] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0219] The circulating solvent is distillate oil with a temperature of >240°C.

[0220] Example 18

[0221] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0222] Hami coal from Xinjiang Uygur Autonomous Region was used as raw coal. The average temperature of the first coal direct liquefaction reactor was 430°C, the average temperature of the second coal direct liquefaction reactor was 440°C, and the average temperature of the third coal direct liquefaction reactor was 450°C. The reaction pressure was 25.0 MPa, the oil-coal slurry space velocity was 2.0 t / (h·m3), and the ratio of hydrogen to oil-coal slurry in the first, second and third coal liquefaction reactions was 500 L / kg.

[0223] Example 19

[0224] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0225] The circulating solvent is a mixture of heavy oil and medium oil with a distillation range of 270-350° C., and the aromatics content is greater than 70%.

[0226] Example 20

[0227] Compared with Example 1, the difference is that the fresh material distributor in the first direct coal liquefaction reactor is replaced with a conventional distributor. That is, the gas guide pipe and the flow guide chamber are eliminated, and the distribution branches are in a cross shape. The feed pipe is connected to the cross of the distribution branches to directly feed the feed into each distribution branch. The rest of the process is the same as in Example 1.

[0228] Example 21

[0229] Compared with Example 1, the difference is that the fresh material distributor in the first direct coal liquefaction reactor is replaced with the conventional distributor of Example 20, and the gas supply pipes provided in the bubble cap distributors in the first, second, and third direct coal liquefaction reactors are removed. The rest is the same as Example 1.

[0230] Comparative Example 3

[0231] The difference between this comparative example and Example 1 is:

[0232] Coal liquefaction tests were conducted using the China Shenhua process for direct coal liquefaction continuous test equipment disclosed in CN1257252C. This equipment utilizes two suspended bed reactors in series with forced circulation. High-residue material is not circulated, and the second direct coal liquefaction reactor is not solvent-injected. The hydrogen to oil-coal slurry ratio is 800 L / kg. However, long-term operation can easily lead to coking problems.

[0233] Comparative Example 4

[0234] The difference between this comparative example and Example 1 is:

[0235] No third coal direct liquefaction reactor is provided (ie the second reaction product directly enters the first hot high-pressure separator), and no internal components are provided in the first and second coal direct liquefaction reactors.

[0236] The results of the direct coal liquefaction reactions in Examples 1 to 21 and Comparative Examples 1 to 4 are shown in Table 2.

[0237] Table 1 Coal quality analysis results

[0238]

[0239] Table 2 Coal direct liquefaction results

[0240]

[0241] Referring to Table 2, by comparing Example 1 with Comparative Example 1, the liquefaction conversion rate decreased from 91.51% to 90.21%, a decrease of 1.3 percentage points, and the distillate oil yield decreased from 58.20% to 55.36%, a decrease of about 2.84 percentage points; by comparing Example 1 with Comparative Example 2, the liquefaction conversion rate decreased to 89.10%, and the distillate oil yield decreased to 53.15%, indicating that the introduction of hydrogen and solvent into the inlets of the second and third coal direct liquefaction reactors ensured the hydrogen partial pressure during the coal direct liquefaction reaction, increased the amount of active hydrogen in the reaction system, and promoted the coal liquefaction conversion and oil yield;

[0242] Comparison between Example 1 and Example 20 shows that, under the same reaction conditions, the first coal direct liquefaction reactor employs an improved and innovative fresh material distributor, compared with a conventional fresh material distributor. This reduces disturbances to the air cushion layer below the distribution plate and the liquid level below it, facilitates stable operation of the bubble cap distributor on the distribution plate, and facilitates hydrogenation conversion of asphalt-like substances, resulting in a significant reduction in asphalt yield from 15.24% to 14.45%.

[0243] Comparison between Example 20 and Example 21 shows that, under the same reaction conditions, the improved distributor of the present invention significantly increases the distilled oil yield and significantly reduces the asphalt yield compared to the conventional bubble cap distributor, as the provision of the gas supply pipe facilitates better mixing and distribution of gas and liquid. Compared with Example 21, the distilled oil yield is further significantly increased and the asphalt yield is further significantly reduced in Example 1.

[0244] Comparison of Example 1 with Example 12 and Example 13 shows that the use of the improved first hot high-pressure separator of the present invention promotes the liquefaction conversion of coal, is conducive to improving the conversion rate and oil yield, and improves the economic benefits of direct coal liquefaction. It is also found that the use of the high-temperature and high-pressure separator described in the present invention significantly reduces the solid content in the product of the direct coal liquefaction device, and significantly improves the product quality.

[0245] Comparing Comparative Example 1 with Comparative Example 3, which are both early-developed coal direct liquefaction processes (forced internal circulation suspended bed reactors) by China Shenhua, we can see that under the same reaction conditions, without injecting solvent after the second reactor, the conversion rate and oil yield of Shenhua coal are similar in both cases, 90.21% and 55.36% in the former and 90.15% and 55.32% in the latter. The gas yields are also essentially the same, 13.90% and 13.83% respectively. This is because the China Shenhua process uses a forced internal circulation suspended bed reactor. To ensure the normal operation of the circulation pump, an internal circulation cup is provided in the reactor, and a gas-liquid separation space exists at the top of the reactor. This prolongs the reaction residence time of heavy components and allows for rapid separation of light components, similarly achieving efficient synergistic conversion of different microscopic components in the coal. However, since the internal circulation suspended bed reactor with a circulation pump at the bottom has a gas-liquid interface at the top, coal powder deposition and coking are prone to occur, which in turn affects the circulation volume of the reactor and restricts the long-term operation of the device.

[0246] By comparing Example 1 with Comparative Example 4, it can be seen that compared with a coal liquefaction system with two liquefaction reactors but no secondary material distribution (such as the coal liquefaction system of CN108998068A), the present invention adopts three reactors in series, and the reactor adopts a suspended bed reactor with secondary material distribution, which is beneficial to maintaining a high liquid velocity in the reactor while making the gas-liquid-solid three-phase flow distribution more uniform. At the same time, the first hot high-pressure separator is used to separate the light product and circulate the heavy product, which can effectively solve the problem of secondary cracking of the light product easily generated by the use of three reactors and prolong the residence time of the heavy product. The hydrogen and solvent are introduced at the inlet of the second and third coal direct liquefaction reactors to ensure the hydrogen partial pressure of the coal direct liquefaction reaction and the amount of active hydrogen in the system, promote the hydrogenation liquefaction reaction of the coal and the heavy product, and improve the coal liquefaction conversion rate and oil yield;

[0247] In addition, in the present invention, by using a mixture of heavy oil and medium oil with a flexibly adjustable distillation range as the circulating solvent, the distillation range of the medium oil of the circulating solvent can be adjusted according to product solutions, such as special liquid fuel composition requirements, thereby achieving flexible and adjustable product solutions.

[0248] In addition, referring to the above embodiments, the coal liquefaction system of the present invention can achieve good coal liquefaction reaction effect regardless of whether it is Shendong coal or Hami coal, and has a wide adaptability to coal types.

[0249] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A direct coal liquefaction system, characterized in that: The direct coal liquefaction system comprises: an oil-coal slurry preparation unit, configured to prepare an oil-coal slurry for direct coal liquefaction using the first solvent oil as solvent oil; A preheating and mixing unit, used for mixing the oil-coal slurry from the oil-coal slurry configuration unit with hydrogen and preheating the mixture to increase its temperature; a first coal direct liquefaction reactor, wherein the first coal direct liquefaction reactor is provided with a fresh material feed port and a circulating material feed port connected to the preheating and mixing unit at the bottom, and a first product outlet at the top, for performing a coal direct liquefaction reaction and delivering the obtained first reaction product from the first product outlet; a second coal direct liquefaction reactor, wherein the second coal direct liquefaction reactor is provided with a second feed inlet at the bottom and a second product outlet at the top, for performing a coal direct liquefaction reaction using the material from the second feed inlet to obtain a second reaction product; wherein the second feed inlet is used to receive the first reaction product, the second solvent oil and hydrogen; a third coal direct liquefaction reactor, wherein the third coal direct liquefaction reactor is provided with a third feed inlet at the bottom and a third product outlet at the top, for utilizing the material from the third feed inlet to carry out a coal direct liquefaction reaction to obtain a third reaction product; wherein the third feed inlet is used to receive the second reaction product, a third solvent oil and hydrogen; wherein the first, second and third coal direct liquefaction reactors are suspended bed reactors with internal components for secondary material distribution; a first separation unit connected to the third product outlet, for separating the third reaction product to separate light oil and non-condensable gas therefrom, and feeding a portion of the remaining heavy oil as a circulating material to the circulating material inlet of the first coal direct liquefaction reactor, and feeding the other portion to the distillation column; a distillation tower for distilling and separating the light component oil from the first separation unit and another portion of the heavy component oil to obtain coal direct liquefaction crude oil and coal liquefaction pitch; a hydrogenation unit for hydrogenating the CDL crude oil to obtain CDL oil; a second separation unit for separating the direct coal liquefaction oil from the hydrogenation unit to obtain direct coal liquefaction product oil and a circulating solvent, and feeding the circulating solvent into the oil-coal slurry configuration unit as the first solvent oil, into the second feed port as the second solvent oil, and into the third feed port as the third solvent oil; and A hydrogen supply unit is connected to the preheating and mixing unit, the second feed port, the third feed port and the hydrogenation unit respectively to supply hydrogen, wherein the hydrogen is fresh hydrogen and / or non-condensable gas; The internal components of the first direct coal liquefaction reactor are arranged at the bottom of the reactor, including a fresh material distributor, a material diffuser, and a distribution plate with a bubble distributor; the internal components of the second and third direct coal liquefaction reactors are arranged at the bottom of the reactor, including the material diffuser and the distribution plate with the bubble distributor; the material diffuser is arranged at the bottom of the reactor, and the fresh material distributor is arranged between the material diffuser and the distribution plate; The fresh material distributor includes a feed pipe, a distribution pipe, an air guide pipe, and a guide cavity; the feed pipe is connected to the fresh material feed port; the distribution pipe is arranged in a horizontal direction and is a ring-shaped structure, including a distribution ring pipe arranged around the guide cavity and a plurality of distribution branches arranged between the guide cavity and the distribution ring pipe, the distribution branches are arranged radially along the distribution ring pipe, one end of which is connected to the guide cavity and the other end is connected to the distribution ring pipe; the distribution branches and the distribution ring pipe are both provided with downward distribution holes for uniformly entering the reactor; The guide cavity is a guide cavity with a hollow chamber, the lower and upper parts of which are conical structures, and the middle part is a cylindrical section connecting the ends with larger diameters of the conical structures; the feed pipe outlet is connected to the side of the lower part of the guide cavity along the tangential direction, the distribution pipe inlet is connected to the middle part of the guide cavity, the air inlet of the air guide tube is located directly above the guide cavity and is vertically connected to the guide cavity, and the air outlet at the upper end of the air guide tube is higher than the air inlet at the lower end of the bubble dispenser.

2. The direct coal liquefaction system according to claim 1, characterized in that: The first separation unit comprises: a first hot high-pressure separator for separating the third reaction product, feeding a portion of the heavy oil component discharged from the bottom as a circulating material into the circulating material inlet of the first coal direct liquefaction reactor, feeding another portion into a distillation column, and feeding a first portion of the separated light component from the top into the preheating and mixing unit for heat exchange and cooling, and feeding a second portion into a first cold high-pressure separator; A first cold high-pressure separator is used to separate the first part of the light component and the second part of the light component after heat exchange and temperature reduction to obtain the non-condensable gas and light component oil; The second separation unit comprises: a second hot high-pressure separator for performing gas-liquid separation on the coal direct liquefaction oil from the hydrogenation unit to obtain a processed gas phase at the top and a separated liquid phase at the bottom; a second cold high-pressure separator, for further performing gas-liquid separation on the gas phase from the second hot high-pressure separator to separate the non-condensable gas and obtain a separated liquid phase at the bottom; and a fractionating tower for fractionating the liquid phase from the second hot high-pressure separator and the liquid phase from the second cold high-pressure separator to obtain light oil, medium oil and heavy oil, and sending the light oil and at least part of the medium oil as coal direct liquefaction product oil, using the heavy oil or a mixture of the heavy oil and the medium oil as the circulating solvent, and sending the circulating solvent as the first solvent oil to the oil-coal slurry configuration unit, as the second solvent oil to the second feed port, and as the third solvent oil to the third feed port.

3. The direct coal liquefaction system according to claim 2, characterized in that: The oil-coal slurry configuration unit comprises: An oil-coal slurry preparation tank is used to prepare the oil-coal slurry using the first solvent oil, coal powder, catalyst and sulfiding agent, wherein the first solvent oil and coal powder, as well as the first solvent oil and catalyst are premixed in a kneader and then enter the oil-coal slurry preparation tank; a low-pressure coal slurry circulation pump, wherein the inlet of the low-pressure coal slurry circulation pump is connected to the oil-coal slurry outlet of the coal slurry preparation tank, and the outlet is respectively connected to the oil-coal slurry preparation tank and a high-pressure coal slurry feed pump, for circulating part of the oil-coal slurry back to the oil-coal slurry preparation tank and sending part of the oil-coal slurry out; a high-pressure coal slurry feed pump, used for pressurizing and delivering part of the oil-coal slurry from the low-pressure coal slurry circulation pump; The preheating mixing unit comprises: an oil-coal slurry heat exchanger, configured to heat and heat a mixture of the oil-coal slurry from the high-pressure coal slurry feed pump and the hydrogen from the hydrogen supply unit with the first portion of light components from the first hot high-pressure separator; an oil-coal slurry heating furnace for further heating the mixed material from the oil-coal slurry heat exchanger; and The hydrogen heating furnace is used to heat the second part of hydrogen from the hydrogen supply unit and feed the mixed material from the oil-coal slurry heating furnace into the fresh material feed port of the first coal direct liquefaction reactor after mixing it.

4. The direct coal liquefaction system according to claim 3, characterized in that: The hydrogenation unit comprises: a raw material buffer tank for receiving crude coal direct liquefaction oil from the distillation tower; A hydrogenation raw material pump, used to deliver the crude CDL oil in the raw material buffer tank to the raw material heating furnace; a raw material heating furnace for heating the CDL crude oil and the third portion of hydrogen from the hydrogen supply unit; and The hydrogenation reactor is used for carrying out hydrogenation treatment on the feed from the raw material heating furnace to obtain coal direct liquefaction oil.

5. The direct coal liquefaction system according to any one of claims 1 to 4, characterized in that: The bubble dispenser includes a vertically arranged central tube, a bubble located at the upper end of the central tube, and an air supply pipe connected to the air inlet of the central tube for supplying air into the central tube; the bubble includes a bubble top plate and a bubble side plate, the bubble side plate being connected to the edges of the bubble top plate and extending downward; The upper end of the central tube extends into the bubble and is spaced a preset distance from the bubble top plate to facilitate passage of material; a liquid inlet is provided at the lower end of the central tube; an annular flow channel is formed between the bubble side plate and the central tube, and a plurality of gas-liquid distribution slits are provided at the lower end of the bubble side plate for gas and liquid discharge; A throat portion is provided in the central tube, and the throat portion includes a contraction port, a throat pipe and an expansion port connected in sequence from bottom to top; the air supply pipe includes a horizontally arranged air inlet pipe and an air outlet pipe vertically arranged in the central tube and coaxially arranged with the throat pipe, and the upper air outlet of the air outlet pipe is in the throat pipe; the air inlet pipe passes through the air inlet of the central tube and is connected to the air outlet pipe; there are multiple air inlet pipes, each of which is connected to the air outlet pipe respectively, and the multiple air inlet pipes are evenly spaced along the circumferential direction of the air outlet pipe.

6. The direct coal liquefaction system according to any one of claims 2 to 4, characterized in that: A feed port for introducing the third reaction product is provided in the middle of the first hot high-pressure separator, a gas phase outlet is provided at the top, and a slurry phase material outlet is provided at the bottom; a washing oil spray port and a washing tower plate are provided from top to bottom between the gas phase outlet and the feed port; a circulating material extraction port, a flushing oil inlet and a disturbed hydrogen inlet are provided from top to bottom between the feed port and the slurry phase material outlet, wherein the flushing oil inlet is provided at the center of the first hot high-pressure separator and the opening is provided downward.

7. A method for direct coal liquefaction using the direct coal liquefaction system according to any one of claims 1 to 6, comprising the following steps: S1, mixing coal powder, catalyst, sulfiding agent and first solvent oil to prepare a pumpable coal-oil slurry; S2, mixing the oil-coal slurry with hydrogen, preheating the mixture, and then feeding it into a first coal direct liquefaction reactor with the circulating material to perform a first coal direct liquefaction reaction to obtain a first reaction product; S3, mixing the first reaction product, hydrogen, and second solvent oil, and then feeding the mixture into a second coal direct liquefaction reactor to perform a second coal direct liquefaction reaction to obtain a second reaction product; S4, mixing the second reaction product, hydrogen and the third solvent oil and feeding the mixture into a third coal direct liquefaction reactor to perform a third coal direct liquefaction reaction to obtain a third reaction product; S5, separating the third coal liquefaction product in the first separation unit to separate light oil and non-condensable gas, and feeding a portion of the heavy oil remaining after the separation into the first coal direct liquefaction reactor as the circulating material; S6, sending another portion of the heavy component oil and the light component oil into a distillation tower for distillation separation to obtain coal direct liquefaction crude oil and coal liquefaction pitch; S7, mixing the CDL crude oil with hydrogen and performing a hydrogenation reaction, and separating the obtained CDL oil to obtain a circulating solvent and CDL product oil, and sending the circulating solvent as the first solvent oil to the oil-coal slurry configuration unit, as the second solvent oil to the second CDL reactor, and as the third solvent oil to the third CDL reactor.

8. The method according to claim 7, characterized in that The average reaction temperature in the first coal direct liquefaction reaction process is recorded as T1, the reaction pressure is recorded as P1, and the hydrogen partial pressure is recorded as PH1; the average reaction temperature in the second coal direct liquefaction reaction process is recorded as T2, the reaction pressure is recorded as P2, and the hydrogen partial pressure is recorded as PH2; the average reaction temperature in the third coal direct liquefaction reaction process is recorded as T3, the reaction pressure is recorded as P3, and the hydrogen partial pressure is recorded as PH3; Among them, T1, T2 and T3 are independently 390~470℃, and T3≥T2≥T1; P1, P2 and P3 are independently 5~35MPa, and P1≥P2≥P3; PH1, PH2 and PH3 are independently 4.5~28MPa; the oil-coal slurry space velocity is 0.3~2.0t / (h·m 3 ).

9. The method according to claim 8, characterized in that T1, T2 and T3 are independently 410~460℃; P1, P2 and P3 are independently 10~20MPa; PH1, PH2 and PH3 are independently 8~13MPa; the oil-coal slurry space velocity is 0.5~1.5t / (h·m 3 ).

10. The method according to claim 8 or 9, characterized in that The ratio of the volume of hydrogen to the weight of the oil-coal slurry in the first coal liquefaction reaction is recorded as N1, the ratio of the volume of hydrogen to the weight of the oil-coal slurry in the second coal liquefaction reaction is recorded as N2, and the ratio of the volume of hydrogen to the weight of the oil-coal slurry in the third coal liquefaction reaction is recorded as N3. N1, N2 and N3 are independently selected from 300~1000L / kg, and N3≥N2≥N1.

11. The method according to claim 10, characterized in that N1, N2 and N3 are each independently selected from 400 to 600 L / kg.

12. The method according to any one of claims 7 to 9 and 11, characterized in that The amount of the first solvent oil is 45-90 wt% of the oil-coal slurry; the amount of the second solvent oil is 2-20 wt% of the oil-coal slurry; and the amount of the third solvent oil is 1-10 wt% of the oil-coal slurry.

13. The method according to claim 12, characterized in that The first separation unit comprises: a first hot high-pressure separator for separating the third reaction product, feeding a portion of the heavy oil component discharged from the bottom as a circulating material into the circulating material inlet of the first coal direct liquefaction reactor, feeding another portion into a distillation column, and feeding a first portion of the separated light component from the top into the preheating and mixing unit for heat exchange and cooling, and feeding a second portion into a first cold high-pressure separator; A first cold high-pressure separator is used to separate the first part of the light component and the second part of the light component after heat exchange and temperature reduction to obtain the non-condensable gas and light component oil; The solid content of the circulating material leaving the first hot high-pressure separator is 10-20%; the solid content of the heavy oil feed fed to the distillation column is ≤10%; The mass ratio of the circulating material to the oil-coal slurry entering the first coal direct liquefaction reactor is (0.2~30):

1.

14. The method according to claim 13, characterized in that The solid content of the heavy oil fed to the distillation column is ≤8%; The mass ratio of the circulating material to the oil-coal slurry entering the first coal direct liquefaction reactor is (1~12):

1.

15. The method according to claim 13 or 14, characterized in that In the first coal direct liquefaction reaction, the temperature rise is controlled between 60~80℃; in the second coal direct liquefaction reaction, the temperature rise is controlled between 20~30℃; in the third coal direct liquefaction reaction, the temperature rise is controlled between 5~10℃.

16. The method according to claim 15, characterized in that The solid content of the coal liquefaction pitch at the bottom of the distillation tower is 35-60%, and the softening point is 170-190°C.

17. The method according to claim 16, characterized in that The circulating solvent is the distillate oil with a temperature greater than 220° C. in the coal direct liquefaction oil, and its aromatic hydrocarbon content is greater than 70%.

18. The method according to claim 17, characterized in that The circulating solvent is a distillate oil with a temperature greater than 240° C. in the coal direct liquefaction oil, and the content of monocyclic and bicyclic aromatic hydrocarbons therein is greater than 50 wt %.

Images