Direct coal liquefaction system and direct coal liquefaction method

Abstract

The invention provides a direct coal liquefaction system and a direct coal liquefaction method. The direct coal liquefaction system comprises a coal-oil slurry preparation unit, a preheating mixing unit, a first direct coal liquefaction reactor, a second direct coal liquefaction reactor, a third direct coal liquefaction reactor, a first separation unit, a distillation tower, a hydrogenation unit, a second separation unit and a hydrogen supply unit, the technical problems of coal powder deposition, mineral substance deposition, low utilization rate, poor operation stability, solid particle powder entrainment and the like of the reactor in the existing direct coal liquefaction technology are solved, and the bottleneck problem restricting further amplification of the reactor is solved, so that long-period efficient operation of the direct coal liquefaction device is realized; the utilization rate and the single-series scale of the direct coal liquefaction reactor are improved, the energy utilization efficiency is improved, and energy conservation and carbon reduction are facilitated.

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] Since the German chemist Bergius invented the direct coal liquefaction technology in the 20th century, the direct coal liquefaction process has undergone technological progress in different periods. The technological upgrades are mainly reflected in catalysts, circulating solvents, solid-liquid separation, etc., and can be divided into several representative levels of technical stages.

[0003] The development of coal direct liquefaction technology in my country started in the 1950s. The Dalian Petroleum Research Institute of the Chinese Academy of Sciences and the China Coal Research Institute successively carried out research on coal direct liquefaction technology. In the 1990s, the former Shenhua Group developed a coal direct liquefaction high-efficiency catalyst and China Shenhua coal direct liquefaction process with independent intellectual property rights on the basis of fully digesting and absorbing the advantages of various foreign processes. Compared with foreign processes, China Shenhua's coal direct liquefaction process has the advantages of large single-series processing capacity, high oil yield, and good stability. In 2010, the world's first coal direct liquefaction million-ton demonstration unit independently developed and constructed by my country - Shenhua Ordos 1.08 million t / a coal direct liquefaction industrial unit successfully entered commercial operation, marking the entry of coal direct liquefaction into the industrial development stage, and also marking that my country has become the only country in the world that has mastered the core technology of coal direct liquefaction industrialization, and has accumulated rich and valuable experience in engineering construction, industrial operation, localization of large-scale equipment, and development of coal-based special fuels. At present, the million-ton demonstration unit has been successfully operated commercially for more than 10 years, achieving a maximum single operation time of 420 days, far exceeding the design value. However, compared with petrochemical units, there is still much room for improvement. At the same time, it also exposed some problems that need to be solved urgently, such as mineral deposition in the coal direct liquefaction reactor and coal powder deposition at the gas-liquid interface, short operation cycle, low oil yield, etc., which seriously affect the long-term efficient operation and economic benefits of industrial units.

[0004] Both the German IGOR+ process and the Japanese NEDOL process use bubbling bed reactors. After the 150t / d pilot plant built by Japan NEDOL was put into operation, it was found that large particles were deposited at the bottom of the reactor. For this reason, a discharge device was set at the bottom of the reactor to discharge raw coal, coal ash or solid particles that may remain in the reactor from time to time. German IG Company also found mineral deposition in the reactor through industrial tests.

[0005] CN1257252C discloses a method for direct coal liquefaction, which uses a suspended bed reactor with forced circulation at the bottom, which can effectively reduce the deposition of minerals, but the internal structure of the reactor is relatively complex, and a liquid collecting cup and a central tube are provided, and the reactor volume utilization efficiency is low; in order to ensure the normal operation of the circulating pump, there must be a space for gas-liquid separation at the top, so there is a gas-liquid interface, and at the same time, light materials can be separated in time, and secondary cracking of the target product can be avoided to a certain extent. However, the actual operation of the million-ton coal direct liquefaction demonstration device shows that the presence of a gas-liquid interface at the top of the reactor easily leads to coal powder deposition and agglomeration at the top of the reactor, which reduces the gas-liquid separation space, and at the same time, the deposited and agglomerated materials easily fall off and enter the liquid collecting cup, affecting the normal operation of the circulating pump at the bottom of the reactor, deteriorating the mass and heat transfer of materials in the reactor, deteriorating the operating stability, and increasing the risk of large-area coking in the reactor, resulting in the inability of the coal direct liquefaction reactor to achieve long-term operation, which is a key factor affecting the long-term operation of the device. In addition, the reactor used in this process also has an engineering scale-up bottleneck. The forced internal circulation reactor material needs to pass through 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 reactor diameter 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 operating stability and weak anti-interference ability, and is greatly affected by hydrogen flow, raw material feed rate, and circulation pump circulation. Therefore, achieving long-term efficient operation of direct coal liquefaction and improving the scale of a single series are key technical issues that need to be solved urgently.

[0006] China Coal Research Institute Co., Ltd. has disclosed a method and system for direct coal liquefaction (patent number: CN103074097B), in which part of the high-temperature material at the outlet of the second liquefaction reactor is directly returned to the first liquefaction reactor through a circulation pump without gas-liquid separation. In this process, since the material at the outlet of the reactor has not been separated from the gas and liquid, the gas content at the inlet of the circulating material pump is high, the circulating pump is easily evacuated, and the system stability is poor; the reactor used is a bubbling bed, slurry bed or loop reactor without internal components, which has the risk of reactor deposition and coking, thus seriously affecting the long-term stable operation of the system; at the same time, it will cause the light components in the liquefied product at the outlet of the second reactor to enter the reactor again, resulting in secondary cracking of the light products and reducing the yield of liquid products.

[0007] China Shenhua Coal-to-Liquid Chemical Co., Ltd. discloses a coal direct liquefaction method and coal direct liquefaction device (CN108048121B), in which an intermediate separation device and a second reactor feed pump are arranged between the first liquefaction reactor and the second liquefaction reactor, which can reduce secondary cracking, reduce hydrogen consumption and gas yield, and improve coal conversion rate and oil yield. In order to adapt to the above system, corresponding supporting devices must be set, such as a set of separation systems, wear-resistant high-pressure control valves at the bottom of the intermediate separator, etc., which will greatly increase equipment investment and operating costs. After the oil-coal slurry passes through the first reactor, the reaction is not sufficient, the solid content in the material is large, and the content of high-viscosity asphalt substances produced by pyrolysis is high, and deposition and coking are prone to occur during the intermediate separation process. Therefore, this process is not conducive to the long-term stable operation of the system.

[0008] 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 the gas-liquid interface at the top of the reactor can be eliminated and the coal powder deposition at the top of the reactor can be reduced, 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.

[0009] To sum up, 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 that 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, promote the large-scale and industrialized development of coal direct liquefaction, further consolidate my country's world leading position in coal direct liquefaction technology, and ensure national energy security. Summary of the invention

[0010] 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 scale-up of the coal direct liquefaction reactor, so as to realize long-term efficient operation of the coal direct liquefaction device, improve the utilization rate of the coal direct liquefaction reactor, break through the scale-up bottleneck of the coal direct liquefaction reactor, and further improve the single series scale of the coal direct liquefaction device.

[0011] To achieve one aspect of the above-mentioned invention object, the present invention provides a coal direct liquefaction system comprising:

[0012] An oil-coal slurry preparation unit, used for preparing oil-coal slurry for direct coal liquefaction by using the first solvent oil as solvent oil;

[0013] A preheating and mixing unit, used to mix the oil-coal slurry from the oil-coal slurry configuration unit with hydrogen and preheat the mixture to increase the temperature;

[0014] 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;

[0015] 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, and is used to perform 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;

[0016] 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, and is used to utilize 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, the third solvent oil and hydrogen; wherein the first, second and third coal direct liquefaction reactors are suspended bed reactors with material secondary distribution internal components;

[0017] a first separation unit connected to the third product outlet, used for separating the third reaction product to separate light oil and non-condensable gas therefrom, and sending part of the remaining heavy oil after separation as a circulating material to the circulating material inlet of the first coal direct liquefaction reactor, and sending the other part to the distillation tower;

[0018] A distillation tower, used for distilling and separating the light component oil from the first separation unit and another part of the heavy component oil to obtain coal direct liquefaction crude oil and remaining liquefied asphalt;

[0019] A hydrogenation unit, used for hydrogenating the CDL crude oil to obtain CDL oil;

[0020] a second separation unit, for separating the coal direct liquefaction oil from the hydrogenation unit to obtain non-condensable gas, 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, and sending the mixed oil of the heavy oil and the 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

[0021] The hydrogen supply unit is respectively connected to the preheating and 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.

[0022] In a preferred embodiment, the first separation unit comprises:

[0023] A first hot high-pressure separator is used to separate the third reaction product, and to feed a portion of the heavy oil fraction discharged from the bottom into the circulating material inlet of the first coal direct liquefaction reactor as a circulating material, and another portion into the distillation tower, and to feed a first portion of the separated light components from the top into the preheating and mixing unit for heat exchange and cooling, and a second portion into the first cold high-pressure separator;

[0024] 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.

[0025] In a preferred embodiment, the second separation unit comprises:

[0026] A second hot high-pressure separator, for performing gas-liquid separation on the coal direct liquefied oil from the hydrogenation unit, so as to obtain a processed gas phase at the top and a separated liquid phase at the bottom;

[0027] a second cold high-pressure separator, used to further perform gas-liquid separation on the gas phase from the second hot high-pressure separator to separate the non-condensable gas and obtain the separated liquid phase at the bottom; and

[0028] a fractionation 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 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.

[0029] In a preferred embodiment, the oil-coal slurry configuration unit comprises:

[0030] 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 by a kneading machine and then enter the oil-coal slurry preparation tank;

[0031] A low-pressure coal slurry circulation pump, the inlet of which is connected to the oil-coal slurry outlet of the coal slurry preparation tank, and the outlet of which 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;

[0032] 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.

[0033] In a preferred embodiment, the preheating mixing unit comprises:

[0034] An oil-coal slurry heat exchanger, used for exchanging heat and raising the temperature of 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 part of the light components from the first hot high-pressure separator;

[0035] an oil-coal slurry heating furnace for further heating the mixed material from the oil-coal slurry heat exchanger; and

[0036] A hydrogen heating furnace, used for heating the second part 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 coal direct liquefaction reactor after mixing the mixed material with the mixed material from the oil-coal slurry heating furnace;

[0037] In a preferred embodiment, the hydrogenation unit comprises:

[0038] a raw material buffer tank, used for receiving the crude oil of direct coal liquefaction from the distillation tower;

[0039] A hydrogenation raw material pump, used to deliver the crude coal direct liquefaction oil in the raw material buffer tank to the raw material heating furnace;

[0040] a raw material heating furnace, used for heating the CDL crude oil and the third part of hydrogen from the hydrogen supply unit; and

[0041] The hydrogenation reactor is used for carrying out hydrogenation treatment on the feed from the raw material heating furnace as raw material to obtain coal direct liquefaction oil.

[0042] In a preferred embodiment, the internal components of the first coal direct 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 coal direct 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.

[0043] Preferably, the fresh material distributor comprises 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 the horizontal direction and is a ring pipe structure, comprising 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 branch pipe is 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; downward distribution holes are provided on the distribution branch pipe and the distribution ring pipe, which are used to uniformly feed the gas-liquid mixed feed into the reactor; preferably, the pipe 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;

[0044] 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 connected to the larger diameter end of the conical structure; 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 pipe 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 pipe is higher than the air inlet at the lower end of the bubble dispenser.

[0045] Preferably, the bubble dispenser comprises 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 comprises 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;

[0046] The upper end of the central tube extends into the bubble cap and is spaced a preset distance from the bubble cap top plate to facilitate 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 cap side plate and the central tube, and a plurality of gas-liquid distribution slits for gas-liquid discharge are provided at the lower end of the bubble cap side plate;

[0047] A throat portion is provided in the central tube, and the throat portion includes a contraction port, a throat and an expansion port which are sequentially connected from bottom to top; the air supply pipe includes a horizontally arranged air inlet pipe and an air outlet pipe which is vertically arranged in the central tube and coaxially arranged with the throat, and the upper air outlet of the air outlet pipe is located 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; a plurality of air inlet pipes are provided, each of which is respectively connected to the air outlet pipe, and the plurality of air inlet pipes are evenly spaced along the circumferential direction of the air outlet pipe.

[0048] In a preferred embodiment, a feed inlet 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 also provided from top to bottom between the gas phase outlet and the feed inlet; a circulating material extraction port, a flushing oil inlet and a disturbed hydrogen inlet are also provided from top to bottom between the feed inlet and the slurry phase material outlet, wherein the flushing oil inlet is arranged at the center of the first hot high-pressure separator and the opening is arranged downward.

[0049] In order 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 coal direct liquefaction system, comprising the following steps:

[0050] S1, mixing coal powder, catalyst, sulfiding agent and first solvent oil to prepare oil-coal slurry that can be transported by pump;

[0051] S2, mixing the oil-coal slurry with hydrogen, preheating the mixture and sending 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;

[0052] S3, mixing the first reaction product, hydrogen and the second solvent oil and sending the mixture into a second coal direct liquefaction reactor to perform a second coal direct liquefaction reaction to obtain a second reaction product;

[0053] S4, mixing the second reaction product, hydrogen and the third solvent oil and sending the mixture into a third coal direct liquefaction reactor to perform a third coal direct liquefaction reaction to obtain a third reaction product;

[0054] S5, separating the third coal liquefaction product in the first separation unit to separate the light component oil and non-condensable gas therefrom, and sending part of the heavy component oil remaining after the separation into the first coal direct liquefaction reactor as a circulating material;

[0055] S6, sending another part of the heavy component oil and the light component oil into a distillation tower for distillation separation, so as to obtain coal direct liquefaction crude oil and remaining liquefied asphalt by distillation;

[0056] S7, mixing the coal direct liquefaction crude oil with hydrogen and then subjecting it to 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 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.

[0057] 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;

[0058] Wherein, T1, T2 and T3 are independently 390-470°C, preferably 410-460°C, 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 coal-oil slurry space velocity is 0.3-2.0t / (h·m 3 ) preferably 0.5 to 1.5 t / (h·m 3 ).

[0059] 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 to 1000 L / kg, preferably 400 to 600 L / kg, and N3≥N2≥N1.

[0060] In a preferred embodiment, the first solvent oil is used in an amount of 45-90 wt% of the oil-coal slurry; the second solvent oil is used in an amount of 2-20 wt% of the oil-coal slurry; and the third solvent oil is used in an amount of 1-10 wt% of the oil-coal slurry.

[0061] 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%;

[0062] Preferably, the mass ratio of the circulating material entering the first coal direct liquefaction reactor to the oil-coal slurry is (0.2-30):1, preferably (1-12):1.

[0063] In a preferred embodiment, in the first coal direct liquefaction reaction, the temperature rise is controlled between 60 and 80°C; in the second coal direct liquefaction reaction, the temperature rise is controlled between 20 and 30°C; in the third coal direct liquefaction reaction, the temperature rise is controlled between 5 and 10°C.

[0064] 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.

[0065] 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 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 mono- and bi-cyclic aromatic content is >50wt%.

[0066] 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.

[0067] Compared with the prior art, the present invention has the following advantages:

[0068] 1. The present invention adopts a suspended bed coal direct liquefaction reactor with gas secondary distribution. The internal components of the reactor are arranged at the bottom of the reactor, and there are no internal components above the feed distribution plate. Compared with the forced internal circulation suspended bed reactor currently used in industry, the internal circulation system of the reactor is cancelled, the internal components are simplified, the volume utilization rate of the reactor is significantly improved, the gas-liquid interface at the top of the reaction is eliminated, and coal powder deposition is avoided. The long-term operation of the coal direct liquefaction device can be realized, and the coal powder processing capacity of the device is also improved. In addition, compared with the bubbling bed reactor, the gas retention coefficient of the reactor is low and the reactor processing capacity is high. The bubbling bed reactor is prone to mineral and coal powder deposition and coking reaction.

[0069] 2. The coal direct liquefaction suspended bed reactor adopted in the present invention has a distribution plate with a special structure, which realizes the secondary distribution of gas, liquid and solid, and makes the gas-liquid-solid three-phase flow distribution more uniform while maintaining a high liquid velocity in the reactor, ensuring the stable unidirectional plug flow of the medium in the reactor. More importantly, it avoids mineral deposition and breaks through the bottleneck of reactor engineering amplification, so as to 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 in the reaction process and promotes the coal liquefaction reaction.

[0070] 3. By circulating the liquid materials in the hot high-pressure separator between the hot high-pressure separator and the coal direct liquefaction reactor, the one-way 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 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.

[0071] 4. 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 circulating 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, the system stability is improved, the reaction system is easy to control and operate, and it is conducive to the long-term stable operation of the device.

[0072] 5. By introducing hydrogen and solvent into the second and third coal direct liquefaction reactors, the partial pressure of hydrogen and the amount of active hydrogen in the reaction system are guaranteed, which is beneficial to the conversion of coal and asphaltene, and ultimately improves the coal liquefaction conversion rate and oil yield. At the same time, the supply of hydrogen and solvent is regulated to accurately control the temperature change of the coal liquefaction reaction unit, prevent temperature runaway, avoid coking inside the reaction unit, and ensure the long-term stable operation of the coal liquefaction reaction unit.

[0073] 6. Under the condition of the same coal slurry processing capacity and coal liquefaction reaction unit processing scale, two coal liquefaction reaction units are connected in series, and the liquefaction reaction temperature rises are about 70-90°C and 35-45°C respectively; three coal liquefaction reaction units are connected in series, and the liquefaction reaction temperature rises are about 60-70°C, 5-20°C and 1-10°C 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 is to avoid the generation of a large number of pyrolysis free radicals of coal powder in the first reactor, and prevent the free radical condensation reaction caused by insufficient hydrogen supply, which is beneficial to the coal liquefaction conversion and the 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 promote the coal liquefaction conversion.

[0074] 7. By optimizing the design of the hot high-pressure separator structure, setting 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 are 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 is controlled, the service life of the high-temperature solid-containing high-differential pressure reducing valve is extended, and the long-term stable operation of the coal direct liquefaction device is ensured.

[0075] 8. Through heat exchange 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, the 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.

[0076] 9. 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 the product plan, such as the composition requirements of special liquid fuels, thereby achieving flexible and adjustable product plans, improving the market adaptability of coal direct liquefaction technology and the adaptability of national energy security and national defense security to the demand for special liquid fuels.

[0077] In summary, by adopting the technical scheme of the present invention, in the above-mentioned coal direct liquefaction system, three series reactors are adopted, 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, 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 cooperating with the first hot high-pressure separator to separate light products and recycle heavy products, which can effectively solve the problem of secondary cracking of light products that is easily generated due to the use of three reactors and prolong the residence time of heavy products, and cooperate with the introduction of hydrogen and solvent 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 coal and heavy products, and improve the coal liquefaction conversion rate and oil yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 A schematic structural diagram of a coal direct liquefaction system provided for a typical embodiment of the present invention;

[0079] Among them, Figure 1 The following reference numerals are included:

[0080] 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 high-temperature and high-pressure separator; 190, first cold and high-pressure separator; 200, distillation tower; 210, raw material buffer tank; 220, raw oil heating furnace; 230, hydrogenation reactor; 240, second hot and high-pressure separator; 250, second cold and 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;

[0081] Figure 2 a is a schematic structural diagram of an embodiment of the first coal direct liquefaction reactor of the present invention;

[0082] Figure 2 b is a schematic structural diagram of an embodiment of the second and third coal direct liquefaction reactors of the present invention;

[0083] Among them, Figure 2 a and attached Figure 2 b includes the following reference numerals:

[0084] 112, fresh material feed port; 113, circulating 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;

[0085] Figure 3 It is a structural schematic diagram of an embodiment of a hot high-pressure separator of the present invention;

[0086] Among them, Figure 3 The following reference numerals are included:

[0087] 181, feed port; 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 tower tray; 189, circulating material extraction port;

[0088] Figure 4 for Figure 2 a is a schematic diagram of an embodiment of a fresh material distributor;

[0089] Figure 5 for Figure 4 A cross-sectional schematic diagram of a fresh material distributor;

[0090] Figure 6 is a schematic diagram of one embodiment of a dispensing tray with a blister dispenser;

[0091] Among them, the above-mentioned Figures 4 to 6 The following reference numerals are included:

[0092] 1. Feeding 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. Bubble dispenser;

[0093] 12. center tube; 121. throat tube; 122. air inlet tube; 123. air outlet tube; 124. contraction port; 125. throat tube; 126. expansion port;

[0094] 13. blister; 131. blister top plate; 132. blister side plate; 133. gas-liquid distribution slit. DETAILED DESCRIPTION

[0095] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments 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.

[0096] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme 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 described embodiments 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 creative work should fall within the scope of protection of the present invention.

[0097] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0098] like Figure 1 As shown, the coal direct liquefaction system of the present invention includes an oil-coal slurry configuration unit, a preheating mixing unit, a first coal direct liquefaction reactor 150, a second coal direct liquefaction reactor 160, a third coal direct liquefaction reactor 170, a first separation unit, a distillation tower 200, a hydrogenation unit, a second separation unit and a hydrogen supply unit; each of which will be further described below:

[0099] Coal-oil slurry configuration unit

[0100] The oil-coal slurry configuration unit is well known in the art, and is used to configure oil-coal slurry for direct coal liquefaction using the first solvent oil as the solvent oil. In one embodiment thereof, the oil-coal slurry configuration unit, for example, includes 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 configure the oil-coal slurry using the first solvent oil, coal powder, a catalyst, and a sulfiding agent, for example, wherein the first solvent oil and coal powder and the first solvent oil and the catalyst are premixed by a kneading machine and then enter 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.

[0101] In this embodiment, among the first solvent oil, coal powder, catalyst and vulcanizing agent as raw materials, coal powder and part of the first solvent oil are first premixed by a mixer before being added to the oil-coal slurry preparation tank, and the catalyst and part of the first solvent and the optional vulcanizing agent are also first premixed by 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, the operating temperature is 60 to 150 ° C, the residence time is 10 to 60 minutes, and the mass ratio of coal powder to circulating solvent is 5 to 7: 1. In the present invention, by premixing the raw materials separately by a mixer and then 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.

[0102] After the raw materials are configured into pumpable oil-coal slurry in the oil-coal slurry preparation tank 110, part of them are circulated by the low-pressure coal slurry pump 101 to maintain the stability of the oil-coal slurry, and part of them are sent to the high-pressure coal slurry pump 102 for pressurization and then sent to the preheating mixing unit.

[0103] In the present invention, the preparation temperature of the oil-coal slurry can generally be 50-250°C, such as 100 or 150°C, and the mass concentration of the oil-coal slurry can be 10-55%, such as 20%, 30% or 40%; the catalyst used in the direct coal liquefaction reaction process can be a catalyst commonly used by those skilled in the art in the direct coal liquefaction process, for example, the direct coal liquefaction catalyst is selected from one or more of nano-scale hydrated iron oxide, natural ore, pure iron compound, nano-scale ferrous sulfide, and precious metals; wherein the pure iron compound is selected from one or more of the group consisting of iron oxide, sulfide and hydroxide, and the precious metal catalyst can be an oil-soluble catalyst or a supported catalyst; a more preferred catalyst can be nano-scale hydrated iron oxide or nano-scale ferrous sulfide. The amount of the catalyst can account for 0.05-3wt% of the oil-coal slurry, such as 0.1-2wt% (active metal / oil-coal slurry).

[0104] Preheating mixing unit

[0105] 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; wherein 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, it is sent into the fresh material feed port of the first coal direct liquefaction reactor 150.

[0106] In this embodiment, the oil-coal slurry is premixed with the first part of hydrogen and then preheated by the oil-coal slurry heat exchanger 120, and then heated by the oil-coal slurry heater 130, and then mixed with the second part of hydrogen heated by the hydrogen heating furnace 140 to reach the temperature required for the reaction, and sent to 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.

[0107] Coal liquefaction reaction unit

[0108] 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.

[0109] like Figure 2 As shown in a and 2b, the first coal direct liquefaction reactor 150 is provided with a fresh material feed inlet 112 and a circulating material feed inlet 113 connected to the preheating mixing unit at the bottom, and a first product outlet 114 at the top, for performing the coal direct liquefaction reaction and delivering the obtained first reaction product from the first product outlet 114.

[0110] 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 hydrogen from the hydrogen supply unit.

[0111] 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, for using 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.

[0112] During operation, the mixture of the coal-oil slurry and hydrogen from the preheating mixing unit is used as fresh material and the circulating material to enter the first coal direct liquefaction reactor 150 through the fresh material feed port 112 and the circulating material feed port 113 for reaction, 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.

[0113] 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 gas phase products and liquid phase products; wherein, the temperature rise of the first coal direct liquefaction reactor can be controlled by the outlet temperature of the oil-coal slurry heating furnace 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, while the amount of solvent active hydrogen 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.

[0114] In a preferred embodiment, the temperature rise of the first coal direct liquefaction reactor is 60-80°C, such as 65, 70 or 75°C, the temperature rise of the second coal direct liquefaction reactor is 20-30°C, such as 22, 25 or 28°C, and the temperature rise of the third coal direct liquefaction reactor is 5-10°C, such as 6 or 8°C; 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%.

[0115] In the present invention, in order to better ensure that the coal has a higher 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 The temperature is 390-470°C, preferably 410-460°C, and T3≥T2≥T1, preferably, the difference between T3 and T2 is 5-15°C, and the difference between T2 and T1 is 5-15°C; 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 space velocity of the oil-coal slurry in each reactor (i.e., the space velocity calculated based on the amount of the oil-coal slurry) is 0.3-2.0t / (h·m 3 ), preferably 0.5 to 1.5 t / (h·m 3 ).

[0116] Further preferably, the ratio of the volume of hydrogen entering the first coal direct liquefaction reactor to the weight of the oil-coal slurry is recorded as N1, the ratio of the volume of hydrogen entering the second coal direct 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 coal direct liquefaction reactor to the weight of the oil-coal slurry is recorded as N3, N1, N2 and N3 are independently selected from 300 to 1000 L / kg, preferably 400 to 600 L / kg, and N3≥N2≥N1.

[0117] The study found that controlling the various process conditions of the liquefaction reaction within the above range can reduce construction investment costs and enable the coal liquefaction reaction to be more complete, ensuring a higher coal conversion rate and liquid fuel yield during the liquefaction reaction.

[0118] In the present invention, the first, second and third coal direct liquefaction reactors can be suspended bed reactors with gas secondary distribution; wherein, the internal components in the first coal direct 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 coal direct 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 the reactor volume utilization rate is high, which is conducive to maintaining a stable unidirectional plug flow in the reactor and extending the reactor operation cycle.

[0119] 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 tube structure, including a distribution ring pipe 5 arranged around the guide chamber 2 and a plurality of, for example, four distribution branch pipes 4 arranged between the guide chamber 2 and the distribution ring pipe 5, the distribution branch pipe 4 being arranged radially 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 arranged 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 directly above the top of the guide cavity 2, and is vertically connected to the guide cavity 2, and 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.

[0120] In the above Figure 4 and 5In the embodiment shown, the feed liquid fed tangentially from the feed pipe 1 generates cyclone diversion in the guide chamber 2, so that the gas phase with lower density is better separated from the liquid phase due to the cyclone 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.

[0121] In some other embodiments, the tube 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 facilitate the remaining gas-liquid mixture to enter the distribution pipe. For example, the tube diameter and / or aperture can be relatively increased 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.

[0122] In one embodiment, Figure 6 As 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 from the bubble top plate 131 by a preset distance 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 The lower end is provided with a plurality of gas-liquid distribution slits for gas-liquid discharge; a throat portion 121 is provided in the central tube 12, and the throat portion includes a contraction port, a throat and an expansion port which are sequentially connected from bottom to top; the air supply pipe includes a horizontally arranged air inlet pipe 122 and an air outlet pipe 123 which is vertically arranged in the central tube and coaxially arranged with the throat, and the upper air outlet of the air outlet pipe 123 is in the throat; 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 a plurality of, for example 4, air inlet pipes, each of which is respectively connected to the air outlet pipe, and the plurality of air inlet pipes are evenly spaced along the circumferential direction of the air outlet pipe.

[0123] 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 promote the coal direct liquefaction reaction.

[0124] 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 wall so that the material fed into the diffuser can be dispersed from the material outlet to the bottom of the reactor.

[0125] The first separation unit

[0126] 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 send a part of the heavy component oil remaining after the separation as a circulating material to the circulating material inlet 113 of the first coal direct liquefaction reactor 150, and the other part to the distillation tower 200.

[0127] 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.

[0128] The first cold high-pressure separator 190 is used to separate the first part of the light components and the second part of the light components after heat exchange and temperature reduction, so as to obtain 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 part of the second gas phase can be circulated to the coal direct liquefaction reactor as circulating hydrogen, and the other part can be discharged as tail gas to control the purity of hydrogen supplied by the hydrogen supply unit. The purity of the circulating hydrogen can be greater than 80%, such as greater than 85%.

[0129] In this embodiment, the third reaction product from the third coal direct liquefaction reactor 170 enters the first high temperature and high pressure separator 180 to achieve oil and gas separation, and a part of the heavy component oil separated by the first hot high pressure separator 180 is transported through the circulation pump 103 and enters the first coal direct liquefaction reactor 150, thereby realizing the circulation of the separated materials of the first hot high pressure separator 180 in the coal direct 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 part of the non-condensable gas obtained at the top is returned to the coal direct liquefaction reactor as circulating hydrogen, and a part is burned and discharged as tail gas, and light component oil is obtained at the bottom; the light component oil produced at the bottom of the first cold high pressure separator 190 is mixed with another part of the heavy component oil at the bottom of the first hot high pressure separator 180 and enters the distillation tower 200.

[0130] In the present invention, the circulation of the heavy component oil as the circulating material is conducive 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 at the bottom of the reactor is adopted 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 processing capacity of the device, and facilitating the realization of single-series scale amplification of coal direct liquefaction device; shortening the one-way residence time of the raw material is conducive 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 the coal and asphalt 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.

[0131] like Figure 3 As shown, in one embodiment, the middle of the first hot high-pressure separator is provided with a feed port 181 for introducing the third reaction product, a gas phase outlet 184 is provided at the top, and a slurry phase material outlet 183 is provided at the bottom; a washing oil spray port 185 and a washing tray 188 are also provided from top to bottom between the gas phase outlet 184 and the feed port 181; a circulating material extraction port 189, a flushing oil inlet 186 and a disturbance hydrogen inlet 187 are also provided from top to bottom between the feed port 181 and the slurry phase material outlet 183, wherein the flushing oil inlet 186 is provided at the center of the first hot high-pressure separator 180 (i.e., on the axis) and the opening is provided downward. Of course, a pressure gauge 182 can be further provided on the upper part of the first hot high-pressure separator 180 to monitor the pressure.

[0132] 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 solid powder of the rising gas phase in the first hot high-pressure separator from being entrained, and at the same time, an oil film is formed at the gas-liquid interface to prevent the coal powder from being deposited at the gas-liquid interface; in addition, the injection of flushing oil is beneficial to relatively reduce the solid content in the material drawn out from the slurry phase material outlet 183, and increase the solid content of the circulating material drawn out 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 the service life. Among them, both the washing oil and the flushing oil can be self-produced heavy oil in the system of the present invention.

[0133] In some embodiments, the solid content of the circulating material leaving the first hot high-pressure separator 180 is 10-20%; the solid content of the heavy component oil fed to the distillation tower is lower than that of the circulating material, for example, lower by more than 2%, such as a solid content of ≤10%, preferably ≤8%. By injecting flushing oil, the solid content of the circulating material is relatively increased, and the circulation amount of the circulating material can also be relatively increased, the residence time of the light component can be relatively reduced, and the liquefaction conversion rate and oil yield of the coal can be increased. In the present invention, the feed mass ratio of the circulating material to the oil-coal slurry entering the first coal direct liquefaction reactor can be (0.2-30):1, preferably (1-20):1, such as 2:1, 5:1 or 10:1.

[0134] Distillation tower

[0135] The distillation tower 200 is used to distill and separate the light component oil from the first separation unit and another part of the heavy component oil, so as to obtain coal direct liquefaction crude oil and the remaining coal liquefaction pitch by distillation.

[0136] The distillation tower 200 can be a distillation separation tower commonly used 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 part of the heavy component oil from the first hot high-pressure separator 180 are separated into solid and liquid in the distillation tower 200 to obtain coal direct liquefaction crude oil and coal liquefaction pitch. In some embodiments, in order to ensure that a higher coal direct liquefaction liquid product is obtained, and at the same time, the coal liquefaction pitch has good transportation performance and is easier to solidify and form, preferably, the solid content in the coal liquefaction pitch at the bottom of the vacuum distillation tower can be controlled to be 35-60%, such as 40%, 50% or 55%, and the softening point can be 170-190°C, such as 175, 180 or 185°C.

[0137] Hydrogenation Unit

[0138] The hydrogenation unit is used to hydrogenate the CDL crude oil to obtain CDL oil; in one embodiment, the hydrogenation unit includes a feedstock buffer tank 210, a hydrogenation feedstock pump 104, a feedstock heating furnace 220 and a hydrogenation reactor 230; wherein the feedstock buffer tank 210 is used to receive the CDL crude oil distilled from the distillation tower 200; the hydrogenation feedstock pump 104 is used to deliver the CDL crude oil in the feedstock buffer tank 210 to the feedstock heating furnace 220; the feedstock heating furnace 220 is used to heat the CDL 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 feedstock heating furnace 220 as a feedstock to obtain CDL oil.

[0139] 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 subjected to catalytic hydrogenation reaction in the hydrogenation reactor 230 to achieve partial hydrogenation saturation of aromatics, and at the same time, desulfurization, denitrogenation and deoxygenation reactions occur.

[0140] In the process of hydrogenation 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-to-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 0.8-1.5 h -1 , the hydrogen-oil ratio is 300-600:1. Controlling the process conditions in the coal direct liquid oil hydrogenation process within the above range is conducive to a more complete coal direct liquefaction oil hydrogenation reaction, achieving partial saturation of aromatics in coal liquefaction oil, increasing the amount of active hydrogen in the solvent, and improving the hydrogen supply capacity of the solvent, which is conducive to promoting coal liquefaction conversion and improving oil yield; at the same time, removing heteroatoms in coal liquefaction oil, providing qualified raw materials for downstream coal direct liquefaction product processing.

[0141] In a preferred embodiment, the hydrogenation reactor adopts an ebullated bed reactor or an ebullated bed-fixed bed combination reactor; wherein, the ebullated bed reactor has a wide adaptability to the hydrogenation raw materials 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 for the hydrogenation raw materials 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 in series with a fixed bed reactor has certain complementary advantages when conducting solvent hydrogenation, which is beneficial to the sufficient hydrogenation conversion of coal direct liquefaction crude oil under low reaction pressure.

[0142] In the process of hydrogenation of coal direct liquefaction oil, a hydrogenation catalyst is used to catalytically hydrogenate coal direct liquefaction oil obtained by distillation. The above-mentioned hydrogenation catalyst is well known in the art, for example, it can be a supported catalyst, the catalyst shape is strip-shaped or spherical, preferably the carrier is alumina, and the active metal component of the supported catalyst is any one or more of Group VIB or Group VIII, more preferably the metal components of Group VIB are Mo and W, and the metal components of Group VIII are Ni and Co.

[0143] Second separation unit

[0144] 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 the light oil and at least part of the medium oil are sent out as coal direct liquefaction product oil, the heavy oil or the mixed oil group of the heavy oil and part of the medium oil is used as a circulating solvent, and the circulating solvent is respectively sent to the oil-coal slurry configuration unit as the first solvent oil, sent to the second feed port as the second solvent oil, and sent to the third feed port as the third solvent oil. In some embodiments, the distillation range of the medium oil falls within 220 to 350°C. 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 to 350°C, which can be flexibly controlled according to the demand for circulating solvents and product solutions.

[0145] In one embodiment, the second separation unit includes a second hot high-pressure separator 240, a second cold high-pressure separator 250 and a fractionation 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 fractionation 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, fed into the second feed port as the second solvent oil, and fed into the third feed port as the third solvent oil.

[0146] 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 gas phase product produced by the second hot high-pressure separator 240 enters the second cold high-pressure separator 250 for further separation after cooling, and its temperature can be controlled below 50°C; part of the gas phase 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 purity of hydrogen; 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 fuel formed includes naphtha, jet fuel, diesel, etc.

[0147] 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 content is above 70%; the distillate oil has a relatively high content of some saturated aromatics 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 mono- and di-ring aromatics is >50wt%. Using it as a direct coal liquefaction solvent has a stronger hydrogen supply capacity and a higher yield of liquid fuel.

[0148] Hydrogen supply unit

[0149] 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, it is mixed with the oil-coal slurry from the high-pressure coal slurry feed pump and enters the oil-coal slurry heat exchanger, as the second part of hydrogen, it is mixed with the oil-coal slurry from the oil-coal slurry heating furnace and enters the first coal direct liquefaction reactor, as the third part of hydrogen, it is supplied to the second coal direct liquefaction reactor, as the fourth part of hydrogen, it is supplied to the third coal direct liquefaction reactor, and as the fifth part of hydrogen, it is supplied to the hydrogenation reactor. It is understood in the art that the hydrogen partial pressure of the first, second and third coal direct liquefaction reactors can be controlled by the first, second, third and fourth parts of hydrogen supply, so as to promote the liquefaction conversion of coal.

[0150] The present invention also provides a method for direct coal liquefaction, comprising the following steps: S1, mixing coal powder, a catalyst, a sulfiding agent and a first solvent to prepare an oil-coal slurry that can be transported by a pump;

[0151] S2, mixing the oil-coal slurry with hydrogen, preheating the mixture and sending 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;

[0152] S3, mixing the first reaction product, hydrogen and second solvent oil and sending the mixture into a second coal direct liquefaction reactor to perform a second coal direct liquefaction reaction to obtain a second reaction product;

[0153] S4, mixing the second reaction product, hydrogen and the third solvent oil and sending the mixture into a third coal direct liquefaction reactor to perform a third coal direct liquefaction reaction to obtain a third reaction product;

[0154] S5, separating the third coal liquefaction product in the first separation unit to separate light oil and non-condensable gas therefrom, and sending part of the heavy oil remaining after the separation into the first coal direct liquefaction reactor as a circulating material;

[0155] S6, sending another part 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 asphalt;

[0156] S7, mixing the CDL crude oil with hydrogen and conducting a hydrogenation reaction, and separating the obtained CDL oil to obtain a circulating solvent and a 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.

[0157] The present invention is further described in detail below in conjunction with specific examples / comparative examples. These examples should not be construed as limiting the scope of protection claimed by the present invention.

[0158] Example 1

[0159] This example uses a scale of 180 kg / day. Figure 1 The coal direct liquefaction system shown was used to carry out a coal direct liquefaction test.

[0160] Shendong coal from Shendong mining area of ​​State Energy Group was used as experimental raw coal. The raw coal was crushed and dried into coal powder with a moisture content of less than 4%. 80% of the coal powder particle size was controlled below 200 meshes. The coal powder was mixed with coal direct liquefaction catalyst, sulfur powder, and the first solvent oil in an oil-coal slurry preparation tank 110. After sufficient stirring, a pumpable coal slurry was obtained. The concentration of the oil-coal slurry 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:

[0161] 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 out from the first product outlet of the first coal direct liquefaction reactor 150 is mixed with the third part of hydrogen and the second solvent oil and then enters the second coal direct liquefaction reactor 160 for reaction, and the obtained second reaction product is mixed with the third part of hydrogen and the third solvent oil and then enters the third coal direct liquefaction reactor 170 for reaction;

[0162] 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 19.0Mpa, and the coal-oil slurry space velocity is 0.7t / (h·m 3); the ratio of hydrogen to oil-coal slurry entering the first coal direct liquefaction reactor is about 400L / kg, the ratio of hydrogen to oil-coal slurry entering the second coal direct liquefaction reactor is about 500L / kg, the ratio of hydrogen to oil-coal slurry entering the third coal direct liquefaction reactor is about 600L / kg, and the hydrogen partial pressure of the three reactors is about 12.5MPa; the amount of the second solvent oil entering the second coal direct liquefaction reactor is 10wt% of the oil-coal slurry feed amount, and the amount of the third solvent oil entering the third coal direct liquefaction reactor is 5wt% of the oil-coal slurry feed amount; the coal liquefaction catalyst is Fe(OOH) catalyst (preparation method see Example 1 of CN1274415C), the coal liquefaction catalyst addition amount is 1.0wt% (Fe / dry coal), the auxiliary agent is sulfur, and n(S) / n(Fe) is controlled to be 2;

[0163] 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 enters the first cold high-pressure separator 190 for oil and gas separation to obtain a second gas phase and a second liquid phase after heat exchange cooling; 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 asphalt at the bottom of the distillation tower is controlled to be 50wt%.

[0164] Then, the coal direct liquefaction crude oil produced from the distillation tower 200 enters the raw material buffer tank 210, and then after being pressurized by the hydrogenation raw material pump 104, it is mixed with hydrogen and heated by the raw material heating furnace 220 before entering the hydrogenation reactor 230. The hydrogenation reactor uses an ebullient bed hydrogenation reactor to perform catalytic hydrogenation reaction, so that two-ring and above aromatic hydrocarbons in the coal direct liquefaction oil are partially hydrogenated and saturated, and desulfurization, denitrification and deoxygenation reactions occur at the same time; the hydrogenation catalyst uses a NiMo / Al2O3 hydrogenation catalyst (the preparation method is shown in Example 1 in CN100497540C);

[0165] In the hydrogenation process of coal direct liquefaction crude oil, the reactor pressure is 19MPa, the reaction temperature is 380℃, and the volume space velocity is 1.0h -1, hydrogen to oil ratio 300. The outlet product 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, and the temperature is controlled at 250°C; the third gas phase product of the second hot high-pressure separator enters the second cold high-pressure separator 250 after cooling to obtain a fourth gas phase and a fourth liquid phase, and the temperature is 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, and the purity of the circulating hydrogen is controlled to be above 85%; the third liquid phase at the bottom of the second hot high-pressure separator and the fourth liquid phase of the second cold high-pressure separator are mixed and decompressed, and then the product is distilled and cut in the fractionation 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 mixed oil of the fractionated heavy oil and the medium oil with a distillation range of 220-350°C, and its aromatic content is greater than 50%.

[0166] Example 2

[0167] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0168] The ratio of the amount of the circulating material entering the first coal direct liquefaction reactor to the amount of the oil-coal slurry is 0.2, and the solid content of the circulating material is 10%.

[0169] Example 3

[0170] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0171] The ratio of the amount of the circulating material entering the first coal direct liquefaction reactor to the amount of the oil-coal slurry is 30, and the solid content of the circulating material is 19%.

[0172] Example 4

[0173] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0174] The ratio of the second solvent oil to the coal-oil slurry entering the second coal direct liquefaction reactor is 2wt%, and the ratio of the third solvent oil to the coal-oil slurry entering the third coal direct liquefaction reactor is 1wt%.

[0175] Example 5

[0176] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0177] The ratio of the second solvent oil entering the second coal direct liquefaction reactor to the amount of oil-coal slurry is 20wt%, and the ratio of the second solvent oil entering the second coal direct liquefaction reactor to the amount of oil-coal slurry is 10wt%.

[0178] Example 6

[0179] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0180] The ratio of hydrogen to oil-coal slurry entering the first coal direct liquefaction reactor is 300 L / kg, the ratio of hydrogen to oil-coal slurry entering the second coal direct liquefaction reactor is 600 L / kg, and the ratio of hydrogen to oil-coal slurry entering the third coal direct liquefaction reactor is 700 L / kg.

[0181] Example 7

[0182] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0183] 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.

[0184] Example 8

[0185] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0186] The concentration of the oil-coal slurry is 55wt%, and the reaction pressure of the three reactors is about 30MPa.

[0187] Example 9

[0188] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0189] Xinjiang Hami coal is used as raw coal (the properties of the raw coal are shown in Table 1). The average temperature of the first coal direct liquefaction reactor is about 390°C, the average temperature of the second coal direct liquefaction reactor is about 420°C, and the average temperature of the second coal direct liquefaction reactor is about 430°C. The reaction pressure of the three reactors is about 20.0MPa, and the ratio of hydrogen to oil-coal slurry entering the three reactors is 500L / Kg.

[0190] Example 10

[0191] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 9 in that:

[0192] 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, the average temperature of the third coal direct liquefaction reactor is about 440°C, and the reaction pressure of the three reactors is about 5MPa.

[0193] Embodiment 11

[0194] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0195] 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.

[0196] Example 12

[0197] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0198] The flushing oil inlet of the first hot high-pressure distributor stops inputting flushing oil. The rest is the same as in Example 1.

[0199] During operation, due to the significant increase in the solid content at the bottom, the bottom pressure reducing valve of the first hot high-pressure separator could not work normally for a long time.

[0200] Example 13

[0201] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0202] The circulating oil extraction outlet in the first hot high-pressure separator stops discharging material, and the circulating material and the heavy oil material to be sent to the distillation tower are both taken out from the slurry phase material outlet. The rest is the same as in Example 1.

[0203] Embodiment 14

[0204] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0205] The raw coal is Xinjiang Hami coal. 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.

[0206] Embodiment 15

[0207] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0208] The direct coal liquefaction oil hydrogenation adopts a combination of ebullated bed and fixed bed reactors. The reaction temperature of the ebullated bed reactor is 370℃, the reaction pressure is 13.7MPa, and the volume space velocity is 1.5h -1， The hydrogen-to-oil ratio is 300; the fixed bed reactor reaction temperature is 370°C, the reaction pressure is 13.7MPa, and the volumetric space velocity is 1.0h -1 , the hydrogen-to-oil ratio is 600.

[0209] Example 16

[0210] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0211] 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.

[0212] Comparative Example 1

[0213] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0214] 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.

[0215] During operation, the temperature rises of the second and third coal direct liquefaction reactors are approximately 19°C and 8°C respectively, and the temperature fluctuations of the second and third coal direct liquefaction reactors are large, making it difficult to operate the system stably.

[0216] Comparative Example 2

[0217] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0218] 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.

[0219] 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.

[0220] Embodiment 17

[0221] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0222] The circulating solvent is distillate oil with a temperature of >240°C.

[0223] Embodiment 18

[0224] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0225] Xinjiang Hami coal was used as the 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, and the coal-oil slurry space velocity was 2.0 t / (h·m 3 ), the ratio of hydrogen to oil-coal slurry in the first, second and third coal liquefaction reactions is 500L / kg.

[0226] Embodiment 19

[0227] The direct coal liquefaction method provided in this embodiment is different from that in Embodiment 1 in that:

[0228] The circulating solvent is a mixed oil of heavy oil and medium oil with a distillation range of 270-350° C., and the aromatic content is greater than 70%.

[0229] Embodiment 20

[0230] Compared with Example 1, the difference is that the fresh material distributor in the first coal direct liquefaction reactor is replaced by a conventional distributor, that is, the air guide pipe and the flow guide chamber are cancelled, and the distribution branch pipes are in a cross shape, and the feed pipe is connected to the cross of the distribution branch pipes so as to directly feed the feed into each distribution branch pipe. The rest is the same as Example 1.

[0231] Embodiment 21

[0232] Compared with Example 1, the difference is that the fresh material distributor in the first coal direct liquefaction reactor is replaced by the conventional distributor in Example 20, and the gas supply pipes provided in the bubble distributors in the first, second and third coal direct liquefaction reactors are cancelled. The rest is the same as Example 1.

[0233] Comparative Example 3

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

[0235] The coal liquefaction test was conducted using the China Shenhua process coal direct liquefaction continuous test device disclosed in CN1257252C. The device uses two series-connected forced circulation suspended bed reactors, high-fraction materials are not circulated, the second coal direct liquefaction reactor is not injected with solvent, and the ratio of hydrogen to oil-coal slurry is 800L / Kg. However, coking problems are easily generated when running for a long time.

[0236] Comparative Example 4

[0237] The difference between this comparative example and Example 1 is:

[0238] 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.

[0239] The results of the direct coal liquefaction reaction in the above Examples 1 to 21 and Comparative Examples 1 to 4 are shown in Table 2.

[0240] Table 1 Coal quality analysis results

[0241]

[0242]

[0243] Table 2 Coal direct liquefaction results

[0244]

[0245]

[0246] Referring to Table 2, by comparing Example 1 with Comparative Example 1, the liquefaction conversion rate was reduced from 91.51% to 90.21%, a decrease of 1.3 percentage points, and the distilled oil yield was reduced 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 was reduced to 89.10%, and the distilled oil yield was reduced to 53.15%, indicating that the introduction of hydrogen and solvent into the inlet of the second and third coal direct liquefaction reactors ensures the hydrogen partial pressure during the coal direct liquefaction reaction, increases the amount of active hydrogen in the reaction system, and promotes the liquefaction conversion of coal and the oil yield;

[0247] By comparing Example 1 with Example 20, it can be seen that under the same reaction conditions, compared with the conventional fresh material distributor, the first coal direct liquefaction reactor adopts an improved and innovative fresh material distributor, which can reduce the disturbance of the air cushion layer under the distribution plate and the liquid surface under it, which is beneficial to the stable operation of the bubble distributor on the distribution plate, and is beneficial to the hydrogenation conversion of asphalt substances, so that the asphalt yield is significantly reduced from 15.24% to 14.45%;

[0248] By comparing Example 20 with Example 21, it can be seen that under the same reaction conditions, compared with the conventional bubble cap distributor, the improved distributor of the present invention significantly increases the distilled oil yield and significantly reduces the asphalt yield because the setting of the gas supply pipe is conducive to a better mixing and distribution effect of gas and liquid; compared with Example 21, the distilled oil yield of Example 1 is further significantly increased and the asphalt yield is further significantly reduced;

[0249] By comparing Example 1 with Example 12 and Example 13, it can be seen that the use of the improved first hot high-pressure separator of the present invention promotes the liquefaction conversion of coal, is beneficial 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 the product quality is significantly improved;

[0250] Comparing Comparative Example 1 with Comparative Example 3, the coal direct liquefaction process (forced internal circulation suspended bed reactor) developed by China Shenhua in the early stage, it can be seen that under the same reaction conditions, no solvent is injected after the second reactor, and the conversion rate and oil yield of Shenhua coal are similar in the two, the former is 90.21% and 55.36%, respectively, and the latter is 90.15% and 55.32%, respectively. The gas yields of the two are also basically the same, 13.90% and 13.83% respectively; this is because the China Shenhua process adopts a forced internal circulation suspended bed reactor. In order to ensure the normal operation of the circulation pump, an internal circulation cup is set in the reactor, and there is a gas-liquid separation space at the top of the reactor. The reaction residence time of the heavy component is prolonged, and the light component is quickly separated, which also realizes the efficient synergistic conversion of different microscopic components in the coal. However, since there is a gas-liquid interface at the top of the internal circulation suspended bed reactor with a circulation pump at the bottom, coal powder deposition and coking are prone to occur, which in turn affects the circulation volume of the reactor, and the long-term operation of the device is restricted;

[0251] By comparing Example 1 with Comparative Example 4, it can be seen that compared with a coal liquefaction system having two liquefaction reactors but no secondary material distribution (e.g., 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, and cooperates with the first hot high-pressure separator to separate light products and circulate heavy products, which can effectively solve the problem of secondary cracking of light products easily generated by the use of three reactors and prolong the residence time of heavy products, cooperates with the introduction of hydrogen and solvent at the inlet of the second and third coal direct liquefaction reactors, ensures the hydrogen partial pressure of the coal direct liquefaction reaction and the amount of active hydrogen in the system, promotes the hydrogenation liquefaction reaction of coal and heavy products, and improves the liquefaction conversion rate and oil yield of coal;

[0252] In addition, in the present invention, by using a mixed oil 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 the product plan, such as the composition requirements of special liquid fuels, thereby achieving flexible and adjustable product plans, improving the market adaptability of the direct coal liquefaction technology and the adaptability of national energy security and national defense security to the demand for special liquid fuels;

[0253] In addition, referring to the above embodiments, the coal liquefaction system of the present invention can achieve good coal liquefaction reaction effect regardless of Shenhua coal or Hami coal, and has wide adaptability to coal types.

[0254] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A coal direct liquefaction system, characterized in that: The direct coal liquefaction system comprises: An oil-coal slurry preparation unit, used for preparing oil-coal slurry for direct coal liquefaction by using the first solvent oil as solvent oil; A preheating and mixing unit, used to mix the oil-coal slurry from the oil-coal slurry configuration unit with hydrogen and preheat the mixture to increase the 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, and is used to perform 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, and is used to utilize 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, the third solvent oil and hydrogen; wherein the first, second and third coal direct liquefaction reactors are suspended bed reactors with material secondary distribution internal components; a first separation unit connected to the third product outlet, used for separating the third reaction product to separate light oil and non-condensable gas therefrom, and sending part of the remaining heavy oil after separation as a circulating material to the circulating material inlet of the first coal direct liquefaction reactor, and sending the other part to the distillation tower; A distillation tower, used for distilling and separating the light component oil from the first separation unit and another part of the heavy component oil to obtain coal direct liquefaction crude oil and coal liquefaction asphalt; A hydrogenation unit, used for hydrogenating the CDL crude oil to obtain CDL oil; a second separation unit, for separating the coal direct liquefaction oil from the hydrogenation unit to obtain coal direct 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 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.

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

3. The direct coal liquefaction system according to claim 1 or 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 by a kneading machine and then enter the oil-coal slurry preparation tank; A low-pressure coal slurry circulation pump, the inlet of which is connected to the oil-coal slurry outlet of the coal slurry preparation tank, and the outlet of which 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; A high-pressure coal slurry feed pump, used for pressurizing part of the coal-oil slurry from the low-pressure coal slurry circulation pump and delivering it; The preheating mixing unit comprises: An oil-coal slurry heat exchanger, used for exchanging heat and raising the temperature of 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 part of the 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 it into the fresh material feed port of the first coal direct liquefaction reactor after mixing it with the mixed material from the oil-coal slurry heating furnace.

4. The direct coal liquefaction system according to claim 3, characterized in that: The hydrogenation unit comprises: a raw material buffer tank, used for receiving the crude oil of direct coal liquefaction from the distillation tower; A hydrogenation raw material pump, used to deliver the CDL crude oil in the raw material buffer tank to the raw material heating furnace; a raw material heating furnace, used for heating the CDL crude oil and the third part 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 as raw material 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 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.

6. The direct coal liquefaction system according to claim 5, characterized in that: The fresh material distributor comprises 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 the horizontal direction and is a ring pipe structure, comprising 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 branch pipe is 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; downward distribution holes are provided on the distribution branch pipe and the distribution ring pipe, which are used to uniformly feed the gas-liquid mixed feed into the reactor; preferably, the pipe 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; 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 connected to the larger diameter end of the conical structure; 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 pipe 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 pipe is higher than the air inlet at the lower end of the bubble dispenser.

7. The direct coal liquefaction system according to claim 5 or 6, characterized in that: The bubble dispenser comprises 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 comprises 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; The upper end of the central tube extends into the bubble cap and is spaced a preset distance from the bubble cap top plate to facilitate 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 cap side plate and the central tube, and a plurality of gas-liquid distribution slits for gas-liquid discharge are provided at the lower end of the bubble cap side plate; A throat portion is provided in the central tube, and the throat portion includes a contraction port, a throat and an expansion port which are sequentially connected from bottom to top; the air supply pipe includes a horizontally arranged air inlet pipe and an air outlet pipe which is vertically arranged in the central tube and coaxially arranged with the throat, and the upper air outlet of the air outlet pipe is located 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; a plurality of air inlet pipes are provided, each of which is respectively connected to the air outlet pipe, and the plurality of air inlet pipes are evenly spaced along the circumferential direction of the air outlet pipe.

8. The direct coal liquefaction system according to any one of claims 1 to 7, characterized in that: A feed inlet 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 inlet; a circulating material extraction port, a flushing oil inlet and a disturbed hydrogen inlet are provided from top to bottom between the feed inlet 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.

9. A method for direct coal liquefaction using the coal direct liquefaction system according to any one of claims 1 to 8, comprising the following steps: S1, mixing coal powder, catalyst, sulfiding agent and first solvent oil to prepare oil-coal slurry that can be transported by pump; S2, mixing the oil-coal slurry with hydrogen, preheating the mixture and sending 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 the second solvent oil and sending 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 sending 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 the light oil component and the non-condensable gas therefrom, and sending a portion of the heavy oil component remaining after the separation into the first coal direct liquefaction reactor as the circulating material; S6, sending another part 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 asphalt; S7, mixing the CDL crude oil with hydrogen and conducting a hydrogenation reaction, and separating the obtained CDL oil to obtain a circulating solvent and a 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.

10. The method according to claim 9, 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; Wherein, T1, T2 and T3 are independently 390-470°C, preferably 410-460°C, 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 coal-oil slurry space velocity is 0.3-2.0t / (h·m 3 ) preferably 0.5 to 1.5 t / (h·m 3 ).

11. The method according to claim 10, 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 to 1000 L / kg, preferably 400 to 600 L / kg, and N3≥N2≥N1.

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

13. The method according to any one of claims 9 to 12, characterized in that: 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%; Preferably, the mass ratio of the circulating material entering the first coal direct liquefaction reactor to the oil-coal slurry is (0.2-30):1, preferably (1-12):

1.

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

15. The method according to claim 14, characterized in that The solid content of the coal liquefaction asphalt at the bottom of the distillation tower is 35-60%, and the softening point is 170-190°C.

16. The method according to claim 15, characterized in that The circulating solvent is a distillate oil with a temperature of >220°C in the coal direct liquefaction oil, and its aromatic 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 mono- and bi-cyclic aromatic content is >50wt%.

Images