Coal liquefaction reaction system and coal liquefaction method

Abstract

The present invention provides a coal liquefaction reaction system and a coal liquefaction method. The coal liquefaction reaction system includes a coal slurry configuration unit, a coal liquefaction reaction unit, a first separation unit, a hydrogenation unit, a second separation unit and a hydrogen supply unit. The present invention solves the problems of insufficient hydrogen supply capacity in the second half of the liquefaction reaction and secondary cracking of light oil in the circulating material, thereby improving the oil yield.

Description

Technical Field

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

[0002] Direct coal liquefaction technology is an important coal conversion technology that converts coal directly into liquid hydrocarbon products under high temperature, high pressure, hydrogen supply solvent and catalyst conditions.

[0003] In 2003, the China Coal Research Institute developed a direct coal liquefaction method that combines countercurrent, loop, and online hydrogenation reactors in series, known as the China Coal Direct Liquefaction Process (CDCL process, CN1243813C). This process utilizes a countercurrent reactor and a loop reactor in series for coal hydroliquefaction, while simultaneously integrating solvent hydrogenation and stable hydrogenation of liquefied oil into the coal hydroliquefaction process. A separation device is added between the countercurrent and loop reactors. The oil separated by a high-temperature separator from the reacted material enters the online hydrogenation reactor directly, while difficult-to-liquefy coal and heavy liquefied oil enter the loop reactor. The gas, liquid, and solid phases are in full contact within the loop reactor, improving heat and mass transfer efficiency, boosting the efficiency of the coal liquefaction reaction, and increasing the yield of the liquefied coal. After hydrogenation in the online hydrogenation reactor, the circulating solvent is hydrogenated to produce a circulating solvent with excellent hydrogen supply capacity and stable liquefied oil properties. However, the hot, high-fraction gas phase used as circulating hydrogen contains a portion of light liquefied oil, which may undergo secondary cracking upon entering the liquefaction reactor.

[0004] In 2004, Shenhua Group developed the Shenhua Coal Direct Liquefaction Process (CN1257252C), a process with independent intellectual property rights. The catalyst is highly active γ-hydrated iron oxide. Two series-connected forced-circulation suspended-bed reactors serve as liquefaction reactors. These reactors offer easy temperature control, a low gas retention coefficient, high liquid phase utilization, and a high liquid phase flow rate, effectively preventing mineral deposition. Solid-liquid separation is achieved by vacuum distillation, resulting in a residue solids content of 50-55 wt%. The circulating solvent and primary liquefied product are hydrogenated using an offline forced-circulation suspended-bed hydrogenation reactor. The resulting solvent is stable and has a strong hydrogen supply capacity, enabling the production of high-concentration oil-coal slurries with solids contents of 45-55 wt%. This process also effectively prevents coking of the slurry during heating in the preheater. This process operates under mild liquefaction reaction conditions, typically with a reaction pressure of 19 MPa and a reaction temperature of 455°C. However, the solid residue contains substances that are difficult to react with during the liquefaction reaction, hindering raw material cost savings.

[0005] In 2006, Shenhua developed an improved direct coal liquefaction process (CN1869159A). The coal slurry is liquefied in two hollow cylindrical reactors connected in series. The reacted material is separated in a high-pressure separator, partially discharged through a pressure reducing valve, and the remainder is returned to the first reactor's reaction feed inlet, with a recycle ratio of 2-20. This process offers a short single-pass reaction time and allows for the timely separation of the generated oil, avoiding secondary decomposition of the target product and solid material deposition within the reactor. This improves oil yield and reduces hydrogen consumption. However, the temperature of the circulating material is lower than that of the reactor material, necessitating reheating, resulting in low thermal efficiency.

[0006] In 2013, the China Coal Research Institute proposed a method and system for direct coal liquefaction (CN103074097A). The liquefaction reaction occurs in two bubbling bed reactors, slurry bed reactors, or loop reactors with draft tubes connected in series. The liquefied product at the outlet of the second liquefaction reactor undergoes gas-liquid separation, and the remaining part enters the inlet of the first liquefaction reactor through a circulation pump with a circulation ratio of 0.5-8. This method can effectively utilize thermal energy, effectively balance the reaction loads of the two reactors, prevent solid particle deposition, and improve device stability. However, there is light oil in some of the liquefied products entering the first liquefaction reactor, which increases the residence time of the light oil and poses the problem of secondary cracking.

[0007] In 2017, Shenhua Group proposed a direct coal liquefaction method and apparatus (CN108048121A), which divides the direct coal liquefaction reaction process into two relatively independent reaction systems. By adding an oil-gas separation step for the first liquefaction product between the first and second liquefaction reactions, this not only effectively reduces the residence time of light oil, avoids secondary cracking, reduces gas yield and hydrogen consumption, but also helps reduce gas retention in the second liquefaction reaction, thereby increasing the residence time of difficult-to-convert substances in the reaction and increasing the hydrogen partial pressure during the reaction. However, the second liquid phase product enters the vacuum distillation unit together with the third liquid phase product, increasing the load of the vacuum distillation unit and reducing the processing capacity.

[0008] During the direct coal liquefaction reaction, when the temperature rises above 300°C, the weaker bridge bonds in the macromolecular structure of the coal begin to break, thereby generating a large number of free radical fragments based on structural unit molecules. Due to excessively high temperatures or untimely hydrogen supply, the free radical fragments produced by coal pyrolysis will undergo condensation reactions to form semi-coke or coke, reducing the oil yield of the direct coal liquefaction reaction. Currently, most direct coal liquefaction reaction processes use a series reaction system. In the second reactor or the latter stage of the liquefaction reaction, the hydrogen supply capacity of the circulating solvent decreases, and the hydrogen partial pressure also decreases, resulting in the formation of semi-coke or coke, which is not conducive to the liquefaction reaction. When the primary liquefaction product participates in the reaction as a circulating material, the light oil component suffers from the problem of secondary cracking, which reduces the coal liquefaction oil yield.

[0009] Therefore, there is still a need to improve the existing coal liquefaction reaction system and method, so as to achieve the purpose of increasing the coal liquefaction conversion rate and oil yield. Summary of the Invention

[0010] The main purpose of the present invention is to provide a coal direct liquefaction reaction system and a coal liquefaction method to solve the problems of insufficient hydrogen supply capacity in the second half of the liquefaction reaction and secondary cracking of light oil in the circulating material, so as to improve the oil yield.

[0011] To achieve one aspect of the above-mentioned purpose, the present invention adopts the following technical solutions:

[0012] A coal liquefaction reaction system, comprising:

[0013] Coal slurry preparation unit, used for preparing oil-coal slurry for direct coal liquefaction;

[0014] The coal liquefaction reaction unit includes a coal slurry preheater, a first coal liquefaction reactor, a first hot high-pressure separator, a booster feed pump, a second coal liquefaction reactor and a third coal liquefaction reactor; wherein,

[0015] The inlet of the coal slurry preheater is connected to the coal slurry configuration unit and the hydrogen supply unit respectively, so as to mix the oil-coal slurry with the hydrogen from the hydrogen supply unit and preheat the mixture to increase the temperature;

[0016] The first coal liquefaction reactor is provided with a fresh material inlet connected to the coal slurry preheater at the bottom and a first liquefied product outlet at the top, for performing a direct coal liquefaction reaction and delivering the obtained first liquefied product from the first liquefied product outlet;

[0017] The first hot high-pressure separator is connected to the first liquefied product outlet, and is used to perform gas-liquid separation on the first reaction product, and discharge the gas phase as the first gas phase product from the top and the liquid phase as the first liquid phase product from the bottom;

[0018] The booster feed pump is used to boost the pressure of the first liquid phase product and then feed it into the second coal liquefaction reactor;

[0019] The second coal liquefaction reactor is provided with a second feed inlet at the bottom and a second liquefied product outlet at the top, for performing a direct coal liquefaction reaction using the material from the second feed inlet to obtain a second liquefied product; wherein the second feed inlet is used to receive the first liquid phase product, the second circulating material and hydrogen;

[0020] The third coal liquefaction reactor is provided with a third feed inlet at the bottom and a third liquefied product outlet at the top, for utilizing the material from the third feed inlet to perform a direct coal liquefaction reaction to obtain a third liquefied product; wherein the third feed inlet is used to receive the second liquefied product and the third circulating material;

[0021] The first separation unit includes a second hot high-pressure separator, a first cold high-pressure separator, an atmospheric distillation tower and a vacuum distillation tower; wherein,

[0022] The second hot high-pressure separator is connected to the third liquefied product outlet, and is used to perform gas-liquid separation on the third liquefied product, and discharge the gas phase as the second gas phase product from the top and the liquid phase as the second liquid phase product from the bottom;

[0023] The first cold high-pressure separator is used to perform gas-liquid separation on the first gas phase product and the second gas phase product after cooling, and discharge the non-condensable gas as the third gas phase product from the top and the liquid phase as the third liquid phase product from the bottom;

[0024] The atmospheric distillation tower is used to distill and separate the second liquid phase product to obtain light component oil and heavy component oil, and a portion of the heavy component oil is fed into the fresh material inlet as a first circulating material, fed into the second feed port as a second circulating material, and fed into the third feed port as a third circulating material;

[0025] The vacuum distillation tower is used to perform vacuum distillation separation on the remaining heavy component oil from the atmospheric distillation tower to obtain distilled oil and liquefied residue at the bottom;

[0026] a hydrogenation unit for hydrogenating the third liquid phase product from the first cold high-pressure separator, the light component oil from the atmospheric distillation column, and the distillate oil from the vacuum distillation column to obtain coal direct liquefaction oil;

[0027] a second separation unit for separating the coal direct liquefaction oil from the hydrogenation unit to obtain non-condensable gas, coal liquefaction product oil and circulating solvent, and sending the circulating solvent to the coal slurry configuration unit; and

[0028] A hydrogen supply unit is connected to the coal slurry preheater, the second feed port and the hydrogenation unit respectively to supply hydrogen, wherein the hydrogen is fresh hydrogen and / or at least part of the non-condensable gas used as circulating hydrogen.

[0029] In a preferred embodiment, the second separation unit includes:

[0030] a third hot high-pressure separator for performing gas-liquid separation on the coal direct liquefaction oil from the hydrogenation unit, and discharging the gas phase as a fourth gas phase product from the top and the liquid phase as a fourth liquid phase product from the bottom;

[0031] a second cold high-pressure separator for performing gas-liquid separation on the cooled fourth gas phase product, and discharging non-condensable gas as the fifth gas phase product from the top and discharging the liquid phase as the fifth liquid phase product from the bottom; and

[0032] a fractionating tower for fractionating the fourth liquid phase product and the fifth liquid phase product to obtain light oil, medium oil, heavy oil, and tower bottom oil, and delivering the light oil, medium oil, and at least a portion of the heavy oil as coal direct liquefaction product oil, and delivering a mixture of the tower bottom oil and a portion of the heavy oil as the circulating solvent to the coal slurry configuration unit to prepare oil-coal slurry;

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

[0034] a mixing tank for receiving the third liquid phase product from the first cold high-pressure separator, the light component oil from the atmospheric distillation column, and the distilled oil from the vacuum distillation column;

[0035] a hydrogenation feed pump, used to deliver the oil product from the mixing tank into the hydrogenation reactor; and

[0036] The hydrogenation reactor is used for performing hydrogenation treatment using the oil product from the hydrogenation feed pump and the hydrogen from the hydrogen supply unit as raw materials to obtain coal direct liquefaction oil.

[0037] In a preferred embodiment, the first coal liquefaction reactor is a suspended bed reactor with gas secondary distribution; wherein,

[0038] The internal components of the first coal liquefaction reactor are arranged at the bottom of the reactor, including a fresh material distributor and a distribution plate with a bubble cap distributor, wherein the fresh material distributor is arranged below the distribution plate; preferably, there are no internal components above the distribution plate.

[0039] In a preferred embodiment, in the first coal liquefaction reactor, the fresh material distributor comprises:

[0040] a feed pipe connected to the fresh material feed port;

[0041] A distribution pipe, the distribution pipe is arranged in a horizontal direction, and the distribution pipe inlet is connected to the feed pipe outlet; the distribution pipe is provided with a plurality of downward distribution holes, and the distribution holes are provided with micro-bubble nozzles for distributing the gas-liquid mixed feed; and

[0042] An air guide tube is arranged vertically upward, with an air inlet at its lower end connected to the distribution pipe and an air outlet at its upper end extending to below the distribution plate, for guiding part of the gas phase in the gas-liquid mixed feed upward to form an air cushion layer below the distribution plate; the upper outlet of the air guide tube is higher than the air inlet at the lower end of the bubble distributor.

[0043] In a preferred embodiment, the fresh material distributor also includes a guide chamber with a hollow chamber, the lower and upper parts of the guide chamber are variable diameter frustum section structures or conical structures, and the middle part is a cylindrical section connected to the larger diameter end of the frustum section or conical structure; the feed pipe outlet is connected to the side of the lower part of the guide chamber along the tangential direction, the distribution pipe inlet is connected to the middle part of the guide chamber, and the air inlet of the air guide pipe is located directly above the guide chamber and is vertically connected to the guide chamber.

[0044] In a preferred embodiment, the bubble dispenser includes a vertically arranged central tube, a bubble 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 lower end of the central tube is a liquid inlet.

[0045] The blister comprises a blister top plate and a blister side plate, wherein the blister side plate is connected to the edges of the blister top plate and extends downward;

[0046] The upper end of the central tube extends into the bubble cap and is spaced apart from the bubble cap top plate by a preset distance;

[0047] 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 formed at the lower end of the bubble cap side plate;

[0048] The central tube is provided with a throat portion, which includes a contraction port, a throat pipe and an expansion port connected in sequence from bottom to top;

[0049] The air supply pipe includes an air outlet pipe vertically arranged in the central pipe and coaxially arranged with the throat pipe, and an upper air outlet of the air outlet pipe is located in the throat pipe.

[0050] In a preferred embodiment, the air supply pipe includes a horizontally arranged air inlet pipe, which passes through the air inlet of the central pipe and is connected to the air outlet pipe in an L shape;

[0051] A conical flow guide is provided at the bottom of the bubble top plate, which is coaxially arranged with the central tube, and the tip of the conical flow guide extends toward the central tube; the conical flow guide is pivotally connected to the bubble top plate, and under the action of fluid, the conical flow guide can rotate relative to the bubble top plate.

[0052] In order to achieve another aspect of the above-mentioned object, the present invention adopts the following technical solutions:

[0053] The method for direct coal liquefaction using the above-mentioned coal liquefaction reaction system comprises the following steps:

[0054] S1, preparing coal powder, catalyst and circulating solvent into oil-coal slurry;

[0055] S2, mixing the oil-coal slurry with hydrogen, preheating and reacting in a first coal liquefaction reactor to obtain a first liquefied product; separating the first liquefied product in a first hot high-pressure separator to obtain a first liquid phase product and a first gas phase product; mixing the first liquid phase product with hydrogen and reacting in a second coal liquefaction reactor to obtain a second liquefied product; and reacting the second liquefied product in a third coal liquefaction reactor to obtain a third liquefied product;

[0056] S3, the third liquefied product is separated by a second hot high-pressure separator to obtain a second gas phase product and a second liquid phase product; the first gas phase product is separated by a first cold high-pressure separator to obtain a third gas phase product and a third liquid phase product; the second liquid phase product is distilled by an atmospheric distillation unit to obtain a light component oil and a heavy component oil; part of the heavy component oil is fed to the first coal liquefaction reactor as a first circulating material to participate in the reaction, fed to the second coal liquefaction reactor as a second circulating material to participate in the reaction, and fed to the third coal liquefaction reactor as a third circulating material to participate in the reaction;

[0057] S4, separating the remaining heavy component oil into solid and liquid by vacuum distillation to obtain distilled oil and liquefied residue;

[0058] S5, mixing the distillate oil, light component oil and the third liquid phase product, heating them, and then feeding them into a hydrogenation reactor together with fresh hydrogen for hydrogenation treatment to obtain direct coal liquefaction oil;

[0059] S6, separating the direct coal liquefaction oil through a second separation unit to obtain non-condensable gas, light oil, medium oil, heavy oil and bottom oil, and sending the light oil, medium oil and at least part of the heavy oil as direct coal liquefaction product oil, and sending the mixed oil of the bottom oil and part of the heavy oil as the circulating solvent to the coal slurry configuration unit.

[0060] In one embodiment, step S6 is to separate the direct coal liquefaction oil through a third hot high-pressure separator to obtain a fourth gas phase product and a fourth liquid phase product; the fourth gas phase product is separated through a second cold high-pressure separator to obtain a fifth gas phase product and a fifth liquid phase product; then the fourth liquid phase product and the fifth liquid phase product are mixed, and then fractionated through a distillation tower 260 to obtain light oil, medium oil, heavy oil and bottom oil, and the light oil, medium oil and at least part of the heavy oil are sent out as direct coal liquefaction product oil, and the mixed oil of the bottom oil and part of the heavy oil is sent to the coal slurry configuration unit as the circulating solvent.

[0061] In a preferred embodiment, the reaction pressure in the first, second and third coal liquefaction reactors is 15-20 MPa, the reaction temperature is 390-460°C, and the weight ratio of hydrogen volume to coal slurry is 900-1000 L / kg; wherein, the reaction pressure of the second coal liquefaction reactor is 0.5-1.0 MPa higher than the pressure of the first coal liquefaction reactor, and the difference between the reaction temperature of the second and third coal liquefaction reactors and the reaction temperature of the first coal liquefaction reactor is 0-10°C, such as 2, 5 or 10°C.

[0062] In a preferred embodiment, the feed ratio of the first circulating material inlet to the fresh material inlet is 0.2-15:1, such as 0.3:1, 0.5:1, 1:1, 2:1 or 10:1; the ratio of the first circulating material, the second circulating material and the third circulating material is (1-2): (2-3): (5-7), such as 1:2:5 or 2:3:7.

[0063] Compared with the prior art, the present invention has the following advantages:

[0064] The present invention adds a hot high-pressure separator and a high-pressure hydrogen pipeline between the first liquefaction reactor and the second liquefaction reactor, separating the two reactors into two independent systems. The circulating hydrogen is mixed with the fresh hydrogen and then pressurized by the hydrogen compressor before entering the second liquefaction reactor together with the first liquid phase product, thereby increasing the hydrogen partial pressure in the second liquefaction reactor, effectively slowing down the condensation reaction occurring in the latter stage of the reaction, and thereby achieving the purpose of improving the direct coal liquefaction conversion rate and oil yield.

[0065] Secondly, the second liquid phase product is initially separated by an atmospheric distillation device to obtain liquefied heavy oil and liquefied light oil. Part of the liquefied heavy oil is re-entered into the coal liquefaction reactor as a circulating material for reaction, which increases the residence time of substances that are difficult to react in the liquefaction reaction in the reactor, allows the reaction materials to react fully, and saves raw material costs. The circulating material enters the first, second, and third coal liquefaction reactors respectively in proportion, which increases the effective utilization rate of the reactor, reduces the gas retention coefficient in the coal liquefaction reactor, is beneficial to increase the hydrogen partial pressure in the reactor, and shortens the single-pass reaction time. The liquefied light oil does not participate in the circulation reaction, which reduces the residence time of the light oil in the liquefaction reactor, effectively avoids secondary cracking of the coal liquefaction product, effectively reduces the load of the vacuum distillation tower, and increases the processing capacity.

[0066] Only fresh hydrogen is used during the hydrogenation reaction, reducing the content of possible impurities or impure substances, thereby reducing the content of impurities in the product and reducing the cost and process of subsequent treatment; extending the service life of the catalyst and reducing the frequency and cost of replacing the hydrogenation stabilized catalyst; and improving the efficiency and rate of the hydrogenation reaction, thereby shortening the production cycle and improving the purity of the product.

[0067] In order to improve the reaction efficiency, the present invention sets up three reactors in series, and by increasing the pressure of the second and third reactors and increasing the circulating feed amount of the second and third reactors, the reactor utilization rate is improved, the decomposition of difficult-to-decompose substances is promoted, and the direct coal liquefaction conversion rate and oil yield are improved.

[0068] In addition, the present invention adopts a suspended bed coal liquefaction reactor with secondary gas 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 reactor, the internal circulation system of the reactor is eliminated, 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, which can realize long-term operation of the direct coal liquefaction device and also improve the coal powder processing capacity of the device; in addition, due to the use of a special structure of fresh material distributor and distribution plate, a high liquid velocity can be maintained in the reactor, ensuring a stable unidirectional plug flow of the medium in the reactor, avoiding mineral deposition, breaking through the bottleneck of reactor engineering amplification, thereby further expanding the scale of the device, improving the core competitiveness of direct coal liquefaction, and improving the direct coal liquefaction conversion rate and oil yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 A schematic diagram of a coal liquefaction reaction system provided by a typical embodiment of the present invention is shown;

[0070] The description of the accompanying drawings is as follows:

[0071] 110, oil-coal slurry preparation tank; 120, coal slurry preheater; 130, first coal liquefaction reactor; 140, first hot high-pressure separator; 150, second coal liquefaction reactor; 160, third coal liquefaction reactor; 170, second hot high-pressure separator; 180, first cold high-pressure separator; 190, atmospheric distillation unit; 210, vacuum distillation column; 220, mixing tank; 230, hydrogenation reactor; 240, third hot high-pressure separator; 250, second cold high-pressure separator; 260, atmospheric distillation column; 101, high-pressure coal slurry feed pump; 102, hydrogen compressor; 103, booster feed pump; 104, circulating material delivery pump; 105, hydrogenation feed pump;

[0072] Figure 2 A schematic diagram of an embodiment of a fresh material distributor;

[0073] The description of the accompanying drawings is as follows:

[0074] 1. Feeding pipe; 2. Diversion chamber; 3. Distribution pipe; 8. Air guide pipe; 10. Distribution plate; 11. Blister dispenser;

[0075] Figure 3 for Figure 2 A cross-sectional schematic diagram of a fresh material distributor;

[0076] The description of the accompanying drawings is as follows:

[0077] 2. Diversion cavity; 4. Distribution branch pipe; 5. Distribution ring pipe; 7. Distribution hole; 8. Air guide pipe;

[0078] Figure 4 is a schematic diagram of one embodiment of a dispensing tray with a blister dispenser;

[0079] The description of the accompanying drawings is as follows:

[0080] 10. Distribution plate; 12. Center tube; 13. Bubble cap; 14. Conical flow guide; 121. Throat portion; 122. Air inlet pipe; 123. Air outlet pipe; 124. Contraction port; 125. Throat pipe; 126. Expansion port; 131. Bubble cap top plate; 132. Bubble cap side plate; 133. Gas-liquid distribution slit. DETAILED DESCRIPTION

[0081] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0082] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0083] It should be noted that the terms "first," "second," and the like in the specification and claims of the present invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate for the embodiments of the present invention described herein. In addition, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products, or apparatuses.

[0084] like Figure 1 As shown, the coal liquefaction reaction system of the present invention includes a coal slurry configuration unit, a coal slurry reaction unit, a first separation unit, a hydrogenation unit, a second separation unit and a hydrogen supply unit; each of these will be further described below:

[0085] The coal slurry configuration unit is well known in the art and is used to configure oil-coal slurry for direct coal liquefaction. Specifically, the required materials such as coal powder, catalyst and solvent can be mixed into oil-coal slurry in the oil-coal slurry preparation tank 110 in the coal slurry configuration unit, and then transported to the coal liquefaction reaction unit via the high-pressure coal slurry feed pump 101; wherein, part or all of the solvent used can be the recycled solvent from the second separation unit.

[0086] The coal liquefaction reaction unit includes a coal slurry preheater 120, a first coal liquefaction reactor 130, a first hot high-pressure separator 140, a second coal liquefaction reactor 150, and a third coal liquefaction reactor 160. The inlet of the coal slurry preheater is connected to a coal slurry configuration unit and a hydrogen supply unit, respectively, for mixing the oil-coal slurry with hydrogen from the hydrogen supply unit and preheating the mixture. The mixed hydrogen and oil-coal slurry are preheated in the coal slurry preheater 120 and then enter the first coal liquefaction reactor 130 together with the first circulating material for reaction.

[0087] The first coal liquefaction reactor 130 is provided with a fresh material inlet and a first circulating material inlet connected to the coal slurry preheater at the bottom, and a first liquefied product outlet at the top, for performing a direct coal liquefaction reaction and sending the obtained first liquefied product from the first liquefied product outlet to enter the first hot high-pressure separator 140.

[0088] The first hot high-pressure separator 140 is connected to the first liquefied product outlet and is used to separate the first liquefied product into a gas-liquid state, discharging the gas phase as the first gas phase product from the top and the liquid phase as the first liquid phase product from the bottom. The booster feed pump 103 is used to pressurize the first liquid phase product and feed it into the second coal liquefaction reactor 150, thereby ensuring that the system pressure in the second coal liquefaction reactor 150 is higher than that in the first coal liquefaction reactor 130.

[0089] The second coal liquefaction reactor 150 is provided with a second feed inlet at the bottom and a second liquefied product outlet at the top, for using the material from the second feed inlet to carry out a direct coal liquefaction reaction to obtain a second liquefied product; wherein, the second feed inlet is used to receive the first liquid phase product, the second circulating material and hydrogen.

[0090] The third coal liquefaction reactor 160 is provided with a third feed inlet at the bottom and a third liquefied product outlet at the top, for utilizing the material from the third feed inlet to carry out a direct coal liquefaction reaction to obtain a third liquefied product; wherein the third feed inlet is used to receive the second liquefied product and the third circulating material.

[0091] In the coal liquefaction reaction unit, a first hot high-pressure separator 140 is arranged after the first coal liquefaction reactor 130, so that the reactor forms two independent systems. The material enters the second coal liquefaction reactor 150 through the booster feed pump 103, and the hydrogen enters the second coal liquefaction reactor 150 through the hydrogen compressor 102 with booster pressure, thereby increasing the hydrogen partial pressure in the second coal liquefaction reactor.

[0092] The first separation unit includes a second hot high-pressure separator 170, a first cold high-pressure separator 180, an atmospheric distillation column 190, and a vacuum distillation column 210. The second hot high-pressure separator 170 is connected to the third liquefied product outlet and is used to perform gas-liquid separation on the third liquefied product, discharging the gas phase as the second gas phase product from the top and the liquid phase as the second liquid phase product from the bottom.

[0093] The first cold high-pressure separator 180 is used to separate the cooled first and second gaseous products into liquid form, discharging the non-condensable gas as the third gaseous product from the top and the liquid phase as the third liquid product from the bottom. A portion of the third gaseous product is used as recycled hydrogen, and the remainder is discharged.

[0094] The atmospheric distillation tower 190 is used to distill and separate the second liquid phase product to obtain light component oil and heavy component oil, wherein the obtained light component oil is directly fed to the hydrogenation unit; at the same time, a portion of the heavy component oil is fed to the first circulating material inlet as the first circulating material, to the second feed inlet as the second circulating material, and to the third feed inlet as the third circulating material; the remaining heavy component oil is fed to the vacuum distillation tower 210 for further separation.

[0095] The vacuum distillation tower 210 is used to perform vacuum distillation separation on the remaining heavy component oil from the atmospheric distillation tower to obtain distilled oil and liquefied residue at the bottom; wherein the liquefied residue can be further sent out to recover the asphalt resources therein.

[0096] In the first separation unit, a portion of the separated heavy component oil is transported in varying proportions via a circulating material delivery pump 104 to the first, second, and third coal liquefaction reactors 130, 150, and 160 for coal liquefaction reactions. This portion of the heavy component oil participates in the reactions as a circulating material, increasing the residence time of difficult-to-react substances in the reactors, ensuring full reaction of the reactants and saving raw material costs. It also reduces the gas retention coefficient in the first coal liquefaction reactor, which helps increase the hydrogen partial pressure within the reactors and shortens the single-pass reaction time.

[0097] The hydrogenation unit is used to hydrogenate the third liquid phase product from the first cold high-pressure separator 180, the light component oil from the atmospheric distillation tower 190, and the distillate oil from the vacuum distillation tower 210 to obtain coal direct liquefaction oil.

[0098] The hydrogenation stabilization treatment of coal direct liquefaction crude oil is well known in the art. In one embodiment, the hydrogenation unit includes a mixing tank 220, a hydrogenation feed pump 105 and a hydrogenation reactor 230; wherein the mixing tank 220 is used to receive the third liquid phase product from the first cold high-pressure separator 180, the light component oil from the atmospheric distillation tower 190 and the distilled oil from the vacuum distillation tower 210; the hydrogenation feed pump 105 is used to send the oil product from the mixing tank to the hydrogenation reactor 230; the hydrogenation reactor 230 is used to use the oil product from the hydrogenation feed pump and the hydrogen from the hydrogen supply unit as raw materials for hydrogenation treatment to obtain coal direct liquefaction oil.

[0099] In the hydrogenation unit, the third liquid phase product, light component oil, and distillate oil are mixed in a mixing tank 220 and then, along with hydrogen, enter a hydrogenation reactor 230 for reaction to produce a hydrogenated product. The liquefied light component oil does not participate in the circulation reaction but enters the hydrogenation unit directly, reducing the residence time of the light oil in the liquefaction reactor and effectively preventing secondary cracking of the coal liquefaction product. The third liquid phase material enters the hydrogenation reactor directly without undergoing vacuum distillation, effectively reducing the load on the vacuum distillation column and increasing processing capacity.

[0100] 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, heavy oil and bottom oil, and send the light oil, medium oil and at least part of the heavy oil as coal direct liquefaction product oil, and send the mixed oil of the bottom oil and part of the heavy oil as the circulating solvent to the coal slurry configuration unit.

[0101] In one embodiment, the second separation unit includes a third hot high-pressure separator 240, a second cold high-pressure separator 250 and a fractionation tower 260; the third hot high-pressure separator 240 is used to perform gas-liquid separation on the coal direct liquefaction oil from the hydrogenation unit, and discharge the gas phase as the fourth gas phase product from the top and the liquid phase as the fourth liquid phase product from the bottom; the second cold high-pressure separator 250 is used to perform gas-liquid separation on the fourth gas phase product after cooling, and discharge the non-condensable gas as the fifth gas phase product from the top and the liquid phase as the fifth liquid phase product from the bottom; the fractionation tower 260 is used to fractionate the fourth liquid phase product and the fifth liquid phase product to obtain light oil, medium oil, heavy oil and bottom oil, and send the light oil, heavy oil and at least part of the heavy oil as coal direct liquefaction product oil, and send the mixed oil of the bottom oil and part of the heavy oil as the circulating solvent to the coal slurry configuration unit to configure the oil-coal slurry.

[0102] The hydrogen supply unit is respectively connected to the coal slurry preheater 120, the second feed port and the hydrogenation unit to supply hydrogen, which is fresh hydrogen and / or at least part of the non-condensable gas used as circulating hydrogen.

[0103] In one embodiment, fresh hydrogen is mixed with circulating hydrogen and then enters the coal liquefaction reaction unit together with the configured oil-coal slurry to participate in the first coal liquefaction reaction. A portion of the third gaseous product of the first cold high-pressure separator 180 and the fifth gaseous product of the second cold high-pressure separator 250 is used as circulating hydrogen, and the remaining portion is discharged. Hydrogen is transported to the second coal liquefaction reactor 150 via the hydrogen compressor 102 to achieve the purpose of increasing the hydrogen partial pressure in the second coal liquefaction reactor 150, effectively slowing down the condensation reaction occurring in the latter part of the reaction, and thereby improving the direct coal liquefaction conversion rate and oil yield. Fresh hydrogen is directly transported to the hydrogenation reactor 230. Only fresh hydrogen is used during the hydrogenation reaction process, which can reduce the content of possible impurities or impure substances, thereby reducing the content of impurities in the product, reducing the cost and process of subsequent treatment, extending the service life of the catalyst, reducing the frequency and cost of replacing the catalyst, and improving the efficiency and rate of the hydrogenation reaction, thereby reducing the production cycle and improving the purity of the product.

[0104] In one embodiment, the first coal liquefaction reactor utilizes a suspended bed reactor with secondary gas distribution. The first coal liquefaction reactor internals are located at the bottom of the reactor, including a fresh feed distributor and a distribution tray with a bubble cap distributor. The fresh feed distributor is located below the distribution tray, and no internals are located above the distribution tray. During operation, fresh feed and first circulating feed enter the first coal liquefaction reactor through the fresh feed distributor and then undergo secondary distribution via the distribution tray with the bubble cap distributor, thereby achieving better mixing and distribution of the gas-liquid slurry. The second and third coal liquefaction reactors preferably do not have internals.

[0105] In one embodiment, Figure 2 As shown, in the first coal liquefaction reactor, the fresh material distributor includes:

[0106] A feed pipe 1 connected to the fresh material feed port;

[0107] A distribution pipe 3, the distribution pipe is arranged in a horizontal direction, and the distribution pipe inlet is connected to the feed pipe outlet; the distribution pipe is provided with a plurality of downward distribution holes 7 for distributing the gas-liquid mixed feed; and

[0108] Air duct 8 is vertically arranged upward, with its lower air inlet communicating with the distribution pipe and its upper air outlet extending below the distribution plate 10. This air duct is used to guide a portion of the gas phase in the gas-liquid mixed feed upward to form an air cushion below the distribution plate. The upper outlet of air duct 8 is higher than the lower air inlet of bubble distributor 11. Through the provision of air duct 8, a portion of the gas in the gas-liquid mixed feed delivered via feed pipe 1 is transported by air duct 8 to the air cushion below the distribution plate 10, thereby reducing the gas-liquid ratio of the gas-liquid mixed feed distributed via distribution pipe 3. This solves the problem of excessive gas-liquid ratio in the material distributed by the primary gas-liquid distributor, resulting in large fluctuations in the air cushion and the liquid level below it, thereby affecting the distribution effect of the secondary gas-liquid distributor. This facilitates uniform gas-liquid distribution. Furthermore, it solves the problem of the primary gas-liquid distributor, which, due to the large size of the bubbles produced, cannot meet the intense mass transfer requirements of the tower bottom area, thus easily generating coking and reducing oil yield.

[0109] In one embodiment, the fresh material distributor also includes a guide chamber having a hollow chamber, the lower and upper parts of the guide chamber are variable diameter frustum section structures or conical structures, and the middle part is a cylindrical section connected to the larger diameter end of the frustum section or conical structure; the feed pipe outlet is connected to the side of the lower part of the guide chamber along the tangential direction, the distribution pipe inlet is connected to the middle part of the guide chamber, and the air inlet of the air guide pipe is located directly above the guide chamber and is vertically connected to the guide chamber.

[0110] In this embodiment, the liquid material fed from the feed pipe 1 generates a vortex in the guide chamber 2. The gas phase with lower density is better separated from the liquid phase due to the cyclonic separation effect and rises, and finally enters the air cushion layer under the distribution plate 10 through the air guide pipe 8, while the remaining gas-liquid mixture enters the distribution pipe 3.

[0111] The distribution pipe 3 can be a gas-liquid distribution pipe commonly used in the art. In one embodiment, Figure 3As shown, the distribution pipe 3 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 and the distribution ring pipe. The distribution branch pipe 4 is radially arranged along the distribution ring pipe 5, one end of which is connected to the guide chamber 2 and the other end is connected to the distribution ring pipe 5, and is used to evenly feed the gas-liquid mixed feed from the guide chamber into the distribution ring pipe 5.

[0112] In one embodiment, Figure 4 As shown, the bubble cap dispenser 11 includes a vertically arranged central tube 12, a bubble cap 13 at the upper end of the central tube, and an air supply pipe connected to an air inlet of the central tube for supplying air into the central tube;

[0113] The bubble 13 includes a bubble top plate 131 and a bubble side plate 132, wherein the bubble side plate 132 is connected to the edges of the bubble top plate 131 and extends downward;

[0114] The upper end of the central tube extends into the bubble cap 13 and is spaced apart from the bubble cap top plate 131 by a preset distance to facilitate passage of materials; a liquid inlet is provided at the lower end of the central tube;

[0115] An annular flow channel is formed between the bubble cap side plate 132 and the central tube 12, and a plurality of gas-liquid distribution slits 133 for gas-liquid discharge are provided at the lower end of the bubble cap side plate 132;

[0116] The central tube 12 is provided with a throat portion 121, which includes a contraction port 124, a throat 125 and an expansion port 126 connected sequentially from bottom to top;

[0117] The air supply pipe includes a horizontally arranged air inlet pipe 122 and an air outlet pipe 123 vertically arranged in the central pipe and coaxially arranged with the throat pipe, and the upper air outlet of the air outlet pipe 123 is in the throat pipe; the air inlet pipe passes through the air inlet of the central pipe and is connected to the air outlet pipe; preferably, there are multiple air inlet pipes 122, each of which is respectively connected to the air outlet pipe 123, and the multiple air inlet pipes are evenly spaced along the circumferential direction of the air outlet pipe, which can supply more gas to the air outlet pipe and prevent large fluctuations in the gas-liquid interface.

[0118] During normal operation, the liquid phase enters through the liquid inlet at the lower end of the central tube. As the radius from the constriction to the throat gradually decreases, the liquid flow path gradually narrows, causing the liquid phase to flow at high speed in the throat, creating a negative pressure zone. This creates a certain suction effect on the gas phase in the air cushion layer surrounding the central tube. Gas is ejected upward from the outlet tube through the center of the throat. The liquid phase flows upward through the annular gap between the inner wall of the constriction and the outlet tube, completely surrounding the gas phase. Due to the boundary layer effect, the velocity of the liquid phase gradually increases from the inner wall of the central tube to the center, resulting in a high turbulence intensity in the liquid phase in contact with the gas phase, thus breaking bubbles down to micron levels. Furthermore, the outlet of the outlet tube is upward, and the exhaust direction is parallel to the liquid flow direction, which causes the bubble growth direction to be the same as the liquid flow direction. When the liquid flow velocity exceeds the bubble growth rate, the drag force of the liquid phase on the bubble acts as a force that helps the bubble escape from the outlet, shortening the bubble generation time. After the bubble is ejected from the outlet of the outlet tube, it is repeatedly broken by the strong turbulence, resulting in a smaller bubble diameter and more effective bubble breaking. The gas-liquid mixture flows out into the upper expansion port. As the fluid channel gradually widens, the fluid flow rate slows and the pressure increases. The pressure gradient within the fluid here easily generates vortices, which shear and break the bubbles a second time, facilitating the production of smaller bubbles. Finally, the gas-liquid mixture or two-phase mixture flows evenly out of the multiple gas-liquid distribution slits 133, ensuring uniform distribution throughout the reactor.

[0119] In one embodiment, a conical guide 14 is provided at the bottom of the bubble cap top plate 131, which is coaxially arranged with the central tube, with the tip of the conical guide 14 extending toward the central tube. The conical guide 14 is pivotally connected to the bubble cap top plate 13 and can rotate relative to the bubble cap top plate under the action of the fluid. Providing the conical guide 14 above the liquid outlet of the central tube can disperse bubbles, so that small bubbles generated in the central tube are immediately dispersed to the surrounding areas by the conical guide 14 when flowing out of the outlet, thereby reducing bubble aggregation to a certain extent. In addition, after flowing out of the central tube outlet, the gas-liquid mixture first collides with the wall of the conical guide 14. The fluid velocity gradient near the wall is large, and the bubbles are sheared again, which is conducive to generating smaller bubbles and improving the coal liquefaction effect.

[0120] The direct coal liquefaction method of the present invention comprises:

[0121] S1, preparing coal powder, catalyst and circulating solvent into oil-coal slurry;

[0122] S2, mixing the oil-coal slurry with hydrogen, preheating and reacting in a first coal liquefaction reactor 130 to obtain a first liquefied product; the first liquefied product is separated in a first hot high-pressure separator 140 to obtain a first liquid phase product and a first gas phase product; the first liquid phase product is mixed with hydrogen and reacted in a second coal liquefaction reactor 150 to obtain a second liquefied product; the second liquefied product is reacted in a third coal liquefaction reactor 160 to obtain a third liquefied product;

[0123] S3, the third liquefied product is separated by the second hot high-pressure separator 170 to obtain a second gas phase product and a second liquid phase product; the first gas phase product is separated by the first cold high-pressure separator 180 to obtain a third gas phase product and a third liquid phase product; the second liquid phase product is distilled by the atmospheric distillation unit 190 to obtain light component oil and heavy component oil; part of the liquefied heavy oil is fed into the first coal liquefaction reactor 130 as a circulating material to participate in the reaction; it is fed into the first coal liquefaction reactor 130 as a first circulating material to participate in the reaction, fed into the second coal liquefaction reactor 150 as a second circulating material to participate in the reaction, and fed into the third coal liquefaction reactor 160 as a third circulating material to participate in the reaction;

[0124] S4, separating the remaining heavy component oil into solid and liquid by vacuum distillation tower 190 to obtain distilled oil and liquefied residue;

[0125] S5, mixing the distillate oil, light component oil and the third liquid phase product, heating them, and then feeding them into the hydrogenation reactor 230 together with hydrogen for hydrogenation treatment to obtain direct coal liquefaction oil;

[0126] S6, separating the direct coal liquefaction oil through a second separation unit to obtain non-condensable gas, light oil, medium oil, heavy oil, and bottom oil, and sending the light oil, medium oil, and at least a portion of the heavy oil as direct coal liquefaction product oil, and sending a mixture of the bottom oil and a portion of the heavy oil as the circulating solvent to the coal slurry configuration unit;

[0127] Specifically, the coal direct liquefaction oil is separated by a third hot high-pressure separator 240 to obtain a fourth gas phase product and a fourth liquid phase product; the fourth gas phase product is separated by a second cold high-pressure separator 250 to obtain a fifth gas phase product and a fifth liquid phase product;

[0128] The fourth liquid phase product and the fifth liquid phase product are then mixed and fractionated in a fractionating tower 260 to obtain light oil, medium oil, heavy oil and bottom oil, and the light oil, medium oil and at least part of the heavy oil are sent out as coal direct liquefaction product oil, and the mixed oil of the bottom oil and part of the heavy oil is sent to the coal slurry configuration unit as the circulating solvent.

[0129] In the present invention, the first hot high-pressure separator 140 divides the first coal liquefaction reactor 130 and the second coal liquefaction reactor 150 connected in series into two independent reaction systems, thereby independently controlling the reaction pressure. Furthermore, after the circulating hydrogen is mixed with the fresh hydrogen, part of it enters the first coal liquefaction reactor 130 together with the oil-coal slurry, and part of it enters the second coal liquefaction reactor 150 after being pressurized by the hydrogen compressor 102. The reaction pressure of the first, second, and third coal liquefaction reactors can be 15-20 MPa, such as 16 or 18 MPa, and the reaction temperature is independently 350-480°C, preferably 390-460°C, such as 400, 420, or 440°C. The ratio of the volume of hydrogen to the weight of the coal slurry is independently 600-1300 L / kg, preferably 900-1000 L / kg.

[0130] In one preferred embodiment, the pressure of the second coal liquefaction reactor 150 is 0.5-1.0 MPa higher than the pressure of the first coal liquefaction reactor 130, such as 0.6 or 0.8 MPa; the difference between the reaction temperature of the second and third coal liquefaction reactors and the reaction temperature of the first coal liquefaction reactor is 0-10°C, such as 2, 5 or 10°C.

[0131] In this embodiment, by injecting high-pressure hydrogen into the second coal liquefaction reactor 150, the hydrogen partial pressure during the reaction process is increased, which is beneficial to the conversion of difficult-to-convert substances such as coal and asphaltene in the reaction materials, thereby improving the coal liquefaction conversion rate and oil yield, and is beneficial to alleviating the problem of untimely hydrogen supply in the latter stage of the liquefaction reaction, which causes coal pyrolysis to produce free radical fragments that undergo condensation reactions to produce semi-coke or coke, thereby reducing the oil yield of the direct coal liquefaction reaction.

[0132] In the direct coal liquefaction method provided by the present invention, the temperature of the first hot high-pressure separator 140 needs to be as close as possible to the temperature of the first coal liquefaction reactor 130. In a preferred embodiment, the temperature of the first hot high-pressure separator 140 is 350-480°C, and the residence time of the liquid phase is less than 5 minutes. At the same time, measures such as injection of disturbing hydrogen or cooling oil (circulating solvent) can be adopted; the adoption of the above measures is conducive to further suppressing the coking of materials during the oil-gas separation process. More preferably, in the above-mentioned first oil-gas separation process, the temperature of the first hot high-pressure separator 140 is 420-460°C, and the residence time of the liquid phase (separation time) is less than 3 minutes.

[0133] In one embodiment, the atmospheric distillation unit 180 has a cutoff point set at 320-350°C, producing a light component oil fraction with a temperature below the cutoff point and a heavy component oil fraction with a temperature above the cutoff point. The liquefied light component oil is completely fed into the hydrogenation reaction unit for reaction, reducing its residence time in the liquefaction reactor and effectively preventing secondary cracking of the coal liquefaction product.

[0134] In a preferred embodiment, the feed ratio of the first circulating material inlet to the fresh material inlet is (0.2-15):1, such as 0.3:1, 0.5:1 or 10:1, preferably (0.2-1:1); the ratio of the first circulating material, the second circulating material and the third circulating material is (1-2):(2-3):(5-7), such as 1:2:5, 2:3:7, 2:3:5 or 1:2:7. Part of the liquefied heavy component oil enters the coal liquefaction reaction unit as a circulating material, which increases the residence time of the difficult-to-react substances in the liquefaction reaction in the reactor, allows the reaction materials to react fully, and saves raw material costs; the circulating materials enter the first, second and third coal liquefaction reactors respectively in proportion, which increases the effective utilization rate of the reactors, reduces the gas retention coefficient in the first coal liquefaction reactor, and is conducive to improving the conversion rate and oil yield.

[0135] In a preferred embodiment, a portion of the second and fourth gaseous products are used as recycled hydrogen, along with fresh hydrogen, to participate in the coal liquefaction reaction, while the remainder is exhausted. The ratio of recycled hydrogen to fresh hydrogen is 0.6 to 1.5:1; more preferably, the ratio is 0.8 to 1.1:1.

[0136] In a preferred embodiment, the reaction pressure of the hydrogenation reactor 220 is 10-20 MPa, the reaction temperature is 320-400°C, and the volume space velocity is 0.5-2.0 h -1 The volume ratio of hydrogen to distilled oil is 200-1500:1, and the ratio of hydrogen partial pressure to total pressure of hydrogenation reactor is 0.80-0.90:1; preferably, the reaction pressure is 15-19 MPa, the reaction temperature is 350-390°C, and the volume space velocity is 0.5-1.5h -1 The volume ratio of hydrogen to distillate oil is 300 to 1200:1, and the ratio of hydrogen partial pressure to total pressure of the hydrogenation reactor is 0.83 to 0.87:1. The hydrogenation reaction unit is designed to remove heteroatoms from the primary coal liquefaction product, achieving partial saturation of aromatics in the coal liquefaction oil. Using fresh hydrogen for the reaction reduces the content of possible impurities or impurities, thereby lowering the impurity content in the product, reducing the cost and process of subsequent processing, extending the service life of the catalyst, reducing the frequency and cost of catalyst replacement, and improving the efficiency and rate of the hydrogenation reaction, thereby shortening the production cycle and improving product purity.

[0137] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0138] Example 1

[0139] This embodiment adopts Figure 1The coal liquefaction reaction system shown in the figure is used for coal liquefaction experiments, and three liquefaction reactors are connected in series. Among them, the internal components of the first coal liquefaction reactor are arranged at the bottom of the reactor, including a fresh material distributor and a distribution plate with a bubble distributor, wherein the fresh material distributor is arranged below the distribution plate; there are no internal components above the distribution plate; the second and third coal liquefaction reactors are empty cylindrical reactors without internal components.

[0140] like Figure 2-4 As shown, in the first coal liquefaction reactor, the fresh material distributor includes a feed pipe, a distribution pipe, an air guide pipe and a guide chamber; the feed pipe is connected to the fresh material feed port; the distribution pipe is arranged in the horizontal direction and is a ring pipe structure, including a distribution ring pipe 5 arranged around the guide chamber 2 and a plurality of, for example, four, distribution branch pipes 4 arranged between the guide chamber and the distribution ring pipe, 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 A downward distribution hole is provided on the top for distributing the gas-liquid mixed feed; the guide cavity is a guide cavity with a hollow chamber, the lower part of which is a truncated cone structure, the upper part is a conical structure, and the middle part is a cylindrical section connecting the lower and upper ends with larger diameters; the feed pipe outlet is connected to the side of the lower part of the guide cavity along the tangential direction, the distribution pipe inlet is connected to the middle part of the guide cavity, the air inlet of the air guide tube is located directly above the guide cavity, and is vertically connected to the guide cavity, and the air outlet at the upper end of the air guide tube is higher than the air inlet at the lower end of the bubble dispenser.

[0141] 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, the bubble side plate 132 is connected to the four edges of the bubble top plate 131 and extends downward; the upper end of the central tube extends into the bubble 13 and is spaced a preset distance from the bubble top plate 131 to facilitate the passage of material; a liquid inlet is provided at the lower end of the central tube; an annular flow channel is formed between the bubble side plate 132 and the central tube 12, and a plurality of gas-liquid distribution slits for gas-liquid discharge are provided at the lower end of the bubble side plate 132; a throat portion 121 is provided in the central tube 12, and the throat portion includes a plurality of gas-liquid distribution slits connected in sequence from bottom to top A contraction port, a throat and an expansion port; the air supply pipe includes a horizontally arranged air inlet pipe 122 and an air outlet pipe 123 vertically arranged in the central pipe and coaxially arranged with the throat pipe, and the upper air outlet of the air outlet pipe 123 is in the throat pipe; the air inlet pipe passes through the air inlet of the central pipe and is connected to the air outlet pipe; there are multiple air inlet pipes, each of which is connected to the air outlet pipe respectively, and multiple air inlet pipes are evenly spaced along the circumferential direction of the air outlet pipe; the bottom of the bubble top plate 131 is provided with a conical guide member 14 coaxially arranged with the central pipe, and the tip of the conical guide member 14 extends toward the central pipe; the conical guide member 14 is pivotally connected to the bubble top plate 13, and under the action of fluid, the conical guide member can rotate relative to the bubble top plate.

[0142] Shendong coal was used as the experimental raw material coal. The raw material coal, catalyst, and coal liquefaction circulating solvent were placed in a coal slurry tank and mixed to obtain oil-coal slurry. The basic properties of the raw material coal are shown in Table 1. The above-mentioned coal direct liquefaction method includes the following steps:

[0143] First, the above-mentioned oil-coal slurry, the first circulating material and hydrogen enter the first coal liquefaction reactor, the first liquefied product obtained by the reaction enters the first hot high-pressure separator, the temperature is controlled at 430°C, the residence time is 5 minutes, the first liquid phase product obtained by separation is transported by a booster feed pump, and mixed with hydrogen and the second circulating material before entering the second coal liquefaction reactor, and then the second liquefied product obtained and the third circulating material enter the third coal liquefaction reactor together with the reaction. In the three liquefaction reactors, the reaction temperature is controlled to be about 455°C, the reaction pressure of the first coal liquefaction reactor is 19.0MPa, the reaction pressure of the second coal liquefaction reactor is 19.5MPa, and the reaction pressure of the third coal liquefaction reactor is 19.0MPa. The ratio of hydrogen to oil-coal slurry is 1000L / Kg, the coal liquefaction catalyst is artificially synthesized 863 catalyst, the coal liquefaction catalyst addition amount is 1.0wt%, the auxiliary agent is sulfur, and n(S) / n(Fe) is controlled to be 2.0.

[0144] The third liquefied product from the third coal liquefaction reactor enters the second hot high-pressure separator for oil and gas separation, and the separation temperature is controlled at 450°C; the second gaseous product produced at the top of the second hot high-pressure separator is mixed with the first gaseous product separated by the first hot high-pressure separator and then cooled to enter the first cold high-pressure separator; the first cold high-pressure separator is controlled below 54°C, and the non-condensable gas part at the top is used as circulating hydrogen to mix with fresh hydrogen to form a coal slurry preheater, and the remaining part is discharged; the second liquid product separated at the bottom of the second hot high-pressure separator enters the atmospheric distillation unit for distillation; the atmospheric distillation unit has a cutting fraction temperature of 320°C, and part of the heavy component oil is fed into the fresh material inlet as the first circulating material, the second feed port as the second circulating material, and the third feed port as the third circulating material, and the feed ratio of the first circulating material to the fresh material is 0.3:1, and the ratio of the amount of the first circulating material, the second circulating material and the third circulating material is 1:2:7.

[0145] The remaining liquefied heavy component oil enters the vacuum distillation tower for solid-liquid separation, and the solid phase content in the bottom residue of the vacuum distillation tower is controlled to 50% to obtain distilled oil; the liquefied light component oil obtained by atmospheric distillation enters the hydrogenation unit.

[0146] Then, the distillate oil obtained from the vacuum distillation tower is mixed with the liquefied light component oil and the third liquid phase material in a mixing tank. After being pressurized by the hydrogenation feed pump, it is mixed with hydrogen and preheated before entering the catalytic hydrogenation reactor for catalytic hydrogenation reaction to achieve partial hydrogenation saturation of aromatics, and desulfurization, denitrogenation and deoxygenation reactions occur simultaneously. During the catalytic hydrogenation reaction, the pressure is controlled at 18.0 MPa, the reaction temperature is 375°C, and the volume space velocity is 1.0 h -1 , hydrogen-to-oil ratio is 400L / Kg, and the material at the outlet of the catalytic hydrogenation reactor enters the third hot high-pressure separator; the fourth gaseous product produced by the third hot high-pressure separator enters the second cold high-pressure separator after cooling, and its temperature is controlled below 54°C; part of the non-condensable gas at the top of the second cold high-pressure separator is used as circulating hydrogen, and part is discharged; the fourth liquid product obtained at the bottom of the third hot high-pressure separator is decompressed and flows into the distillation tower for product separation to obtain coal direct liquefaction product oil and circulating solvent, and the circulating solvent is distillate oil with a distillation temperature of not less than 220°C.

[0147] Example 2

[0148] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0149] The feed ratio of the partially liquefied heavy component oil of the first circulating material to the fresh material is 1:1, and the usage ratio of the first circulating material, the second circulating material and the third circulating material is 2:3:5.

[0150] Example 3

[0151] The direct coal liquefaction method provided in this embodiment differs from that in Example 2 in that:

[0152] The usage ratio of the first recycling material, the second recycling material and the third recycling material is 1:1:1.

[0153] Example 4

[0154] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0155] The reaction pressure of the second coal liquefaction reactor is 19.0 MPa.

[0156] Example 5

[0157] The direct coal liquefaction method provided in this embodiment differs from that in Example 1 in that:

[0158] The cut-off temperature of the atmospheric distillation unit is 350°C.

[0159] Example 6

[0160] Compared with Example 1, the difference is that the fresh material distributor in the first coal liquefaction reactor is replaced by a conventional distributor, that is, the air guide pipe and the flow guide chamber are cancelled, and the distribution branches are in a cross shape, and the feed pipe is connected to the cross of the distribution branches so as to directly deliver the feed into each distribution branch.

[0161] Example 7

[0162] Compared with Example 1, the differences are: the fresh material distributor in the first coal liquefaction reactor is replaced by the conventional distributor of Example 6, and the gas supply pipe provided in the bubble distributor in the first coal liquefaction reactor is cancelled.

[0163] Comparative Example 1

[0164] The difference between this comparative example and Example 1 is:

[0165] A coal liquefaction test was conducted using a coal direct liquefaction continuous test device without an atmospheric distillation device. Part of the second liquid phase material entered the first coal liquefaction reactor as a circulating material, with a feed ratio of 0.3:1 to the oil-coal slurry, and the remaining second liquid phase material entered the vacuum distillation tower.

[0166] Table 1

[0167]

[0168] Table 2 Coal direct liquefaction reaction results of Examples 1-7 and Comparative Example 1

[0169]

[0170] Comparison of Example 3 with Example 1 or 2 shows that, with the three-reactor arrangement of the present invention, controlling the ratio of the amounts of the first circulating material, the second circulating material, and the third circulating material is beneficial to improving the conversion rate and oil yield;

[0171] Comparison of Example 1 with Example 4 shows that increasing the pressure of the second coal liquefaction reactor is beneficial to slowing down the condensation reaction occurring in the latter stage of the reaction, thereby achieving the purpose of increasing the direct coal liquefaction conversion rate and oil yield;

[0172] Comparison between Example 1 and Example 6 shows that, under the same reaction conditions, the first coal liquefaction reactor using the improved and innovative fresh material distributor can reduce disturbances to the air cushion layer below the distribution plate and the liquid level below it, thereby facilitating stable operation of the bubble cap distributor on the distribution plate and improving oil yield.

[0173] By comparing Example 6 with Example 7, it can be seen that under the same reaction conditions, compared with the conventional bubble dispenser, the improved bubble dispenser 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 1 and Example 21, the distilled oil yield is further significantly increased and the asphalt yield is further significantly reduced.

[0174] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A coal liquefaction reaction system, characterized in that: The coal liquefaction reaction system comprises: Coal slurry preparation unit, used for preparing oil-coal slurry for direct coal liquefaction; The coal liquefaction reaction unit includes a coal slurry preheater, a first coal liquefaction reactor, a first hot high-pressure separator, a booster feed pump, a second coal liquefaction reactor and a third coal liquefaction reactor; wherein, The inlet of the coal slurry preheater is connected to the coal slurry configuration unit and the hydrogen supply unit respectively, so as to mix the oil-coal slurry with the hydrogen from the hydrogen supply unit and preheat the mixture to increase the temperature; The first coal liquefaction reactor is provided with a fresh material inlet connected to the coal slurry preheater at the bottom and a first liquefied product outlet at the top, for performing a direct coal liquefaction reaction and delivering the obtained first liquefied product from the first liquefied product outlet; The first hot high-pressure separator is connected to the first liquefied product outlet, and is used to perform gas-liquid separation on the first liquefied product, and discharge the gas phase as the first gas phase product from the top and the liquid phase as the first liquid phase product from the bottom; The booster feed pump is used to boost the pressure of the first liquid phase product and then feed it into the second coal liquefaction reactor; The second coal liquefaction reactor is provided with a second feed inlet at the bottom and a second liquefied product outlet at the top, for performing a direct coal liquefaction reaction using the material from the second feed inlet to obtain a second liquefied product; wherein the second feed inlet is used to receive the first liquid phase product, the second circulating material and hydrogen; The third coal liquefaction reactor is provided with a third feed inlet at the bottom and a third liquefied product outlet at the top, for utilizing the material from the third feed inlet to perform a direct coal liquefaction reaction to obtain a third liquefied product; wherein the third feed inlet is used to receive the second liquefied product and the third circulating material; The first separation unit includes a second hot high-pressure separator, a first cold high-pressure separator, an atmospheric distillation tower and a vacuum distillation tower; wherein, The second hot high-pressure separator is connected to the third liquefied product outlet, and is used to perform gas-liquid separation on the third liquefied product, and discharge the gas phase as the second gas phase product from the top and the liquid phase as the second liquid phase product from the bottom; The first cold high-pressure separator is used to perform gas-liquid separation on the first gas phase product and the second gas phase product after cooling, and discharge the non-condensable gas as the third gas phase product from the top and the liquid phase as the third liquid phase product from the bottom; The atmospheric distillation tower is used to distill and separate the second liquid phase product to obtain light component oil and heavy component oil, and a portion of the heavy component oil is fed into the fresh material inlet as a first circulating material, fed into the second feed port as a second circulating material, and fed into the third feed port as a third circulating material; The vacuum distillation tower is used to perform vacuum distillation separation on the remaining heavy component oil from the atmospheric distillation tower to obtain distilled oil and liquefied residue at the bottom; a hydrogenation unit for hydrogenating the third liquid phase product from the first cold high-pressure separator, the light component oil from the atmospheric distillation column, and the distillate oil from the vacuum distillation column to obtain coal direct liquefaction oil; a second separation unit for separating the coal direct liquefaction oil from the hydrogenation unit to obtain non-condensable gas, coal liquefaction product oil and circulating solvent, and sending the circulating solvent to the coal slurry configuration unit; and a hydrogen supply unit, connected to the coal slurry preheater, the second feed port and the hydrogenation unit, respectively, to supply hydrogen, wherein the hydrogen is fresh hydrogen and / or at least part of non-condensable gas; Wherein, the first coal liquefaction reactor adopts a suspended bed reactor with gas secondary distribution; wherein, The internal components of the first coal liquefaction reactor are arranged at the bottom of the reactor, including a fresh material distributor and a distribution plate with a bubble cap distributor, wherein the fresh material distributor is arranged below the distribution plate; Wherein, in the first coal liquefaction reactor, the fresh material distributor comprises: a feed pipe connected to the fresh material inlet; A distribution pipe, the distribution pipe is arranged in a horizontal direction, and the distribution pipe inlet is connected to the feed pipe outlet; the distribution pipe is provided with a plurality of downward distribution holes, and the distribution holes are provided with micro-bubble nozzles for distributing the gas-liquid mixed feed; and An air guide tube is vertically arranged upward, with an air inlet at its lower end communicating with the distribution tube and an air outlet at its upper end extending below the distribution plate, for guiding part of the gas phase in the gas-liquid mixed feed upward to form an air cushion layer below the distribution plate; the upper end outlet of the air guide tube is higher than the air inlet at the lower end of the bubble dispenser; In which, the fresh material distributor also includes a guide chamber with a hollow chamber, the lower and upper parts of the guide chamber are variable diameter frustum section structures or conical structures, and the middle part is a cylindrical section connected to the larger diameter end of the frustum section structure or conical structure; the feed pipe outlet is connected to the side of the lower part of the guide chamber along the tangential direction, the distribution pipe inlet is connected to the middle part of the guide chamber, and the air inlet of the air guide pipe is located directly above the guide chamber and is vertically connected to the guide chamber.

2. The coal liquefaction reaction system according to claim 1, characterized in that: The second separation unit comprises: a third hot high-pressure separator for performing gas-liquid separation on the coal direct liquefaction oil from the hydrogenation unit, and discharging the gas phase as a fourth gas phase product from the top and the liquid phase as a fourth liquid phase product from the bottom; a second cold high-pressure separator for performing gas-liquid separation on the cooled fourth gas phase product, and discharging non-condensable gas as the fifth gas phase product from the top and discharging the liquid phase as the fifth liquid phase product from the bottom; and a fractionating tower for fractionating the fourth liquid phase product and the fifth liquid phase product to obtain light oil, medium oil, heavy oil and tower bottom oil, and sending the light oil, medium oil and at least a portion of the heavy oil as coal direct liquefaction product oil, and sending a mixture of the tower bottom oil and a portion of the heavy oil as the circulating solvent to the coal slurry configuration unit; The hydrogenation unit comprises: a mixing tank for receiving the third liquid phase product from the first cold high-pressure separator, the light component oil from the atmospheric distillation column, and the distilled oil from the vacuum distillation column; a hydrogenation feed pump, used to deliver the oil product from the mixing tank into the hydrogenation reactor; and The hydrogenation reactor is used for performing hydrogenation treatment using the oil product from the hydrogenation feed pump and the hydrogen from the hydrogen supply unit as raw materials to obtain coal direct liquefaction oil.

3. The coal liquefaction reaction system according to claim 1 or 2, characterized in that: The bubble cap dispenser comprises a vertically arranged central tube, a bubble cap at the upper end of the central tube, and an air supply pipe connected to an air inlet of the central tube for supplying air into the central tube; The blister comprises a blister top plate and a blister side plate, wherein the blister side plate is connected to the edges of the blister top plate and extends downward; The upper end of the central tube extends into the bubble cap and is spaced apart from the bubble cap top plate by a preset distance; 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; The central tube is provided with a throat portion, which includes a contraction port, a throat pipe and an expansion port connected in sequence from bottom to top; The air supply pipe includes an air outlet pipe vertically arranged in the central pipe and coaxially arranged with the throat pipe, and an upper air outlet of the air outlet pipe is located in the throat pipe.

4. The coal liquefaction reaction system according to claim 3, characterized in that: The air supply pipe includes a horizontally arranged air inlet pipe, which passes through the air inlet of the central pipe and is connected to the air outlet pipe in an L shape; A conical flow guide is provided at the bottom of the bubble top plate, which is coaxially arranged with the central tube, and the tip of the conical flow guide extends toward the central tube; the conical flow guide is pivotally connected to the bubble top plate, and under the action of fluid, the conical flow guide can rotate relative to the bubble top plate.

5. A method for direct coal liquefaction using the coal liquefaction reaction system according to any one of claims 1 to 4, comprising the following steps: S1, preparing coal powder, catalyst and circulating solvent into oil-coal slurry; S2, mixing the oil-coal slurry with hydrogen, preheating and reacting in a first coal liquefaction reactor to obtain a first liquefied product; The first liquefied product is separated into a first liquid phase product and a first gas phase product by a first hot high-pressure separator; The first liquid phase product is mixed with hydrogen and enters the second coal liquefaction reactor for reaction to obtain a second liquefied product; The second liquefied product enters the third coal liquefaction reactor for reaction to obtain a third liquefied product; S3, the third liquefied product is separated in a second hot high-pressure separator to obtain a second gas phase product and a second liquid phase product; The first gas phase product and the second gas phase product are separated by a first cold high pressure separator to obtain a third gas phase product and a third liquid phase product; The second liquid phase product is distilled in a normal pressure distillation tower to obtain a light component oil and a heavy component oil; part of the heavy component oil is fed into the first coal liquefaction reactor as a first circulating material to participate in the reaction, fed into the second coal liquefaction reactor as a second circulating material to participate in the reaction, and fed into the third coal liquefaction reactor as a third circulating material to participate in the reaction; S4, separating the remaining heavy component oil into solid and liquid by vacuum distillation to obtain distilled oil and liquefied residue; S5, mixing the distillate oil, light component oil and the third liquid phase product, heating them, and then feeding them into a hydrogenation unit together with fresh hydrogen for hydrogenation treatment to obtain direct coal liquefaction oil; S6, separating the direct coal liquefaction oil through a second separation unit to obtain non-condensable gas, light oil, medium oil, heavy oil and bottom oil, and sending the light oil, medium oil and at least part of the heavy oil as direct coal liquefaction product oil, and sending the mixed oil of the bottom oil and part of the heavy oil as the circulating solvent to the coal slurry configuration unit.

6. The method according to claim 5, wherein The reaction pressure in the first, second and third coal liquefaction reactors is 15~20 MPa, the reaction temperature is 390~460℃, and the weight ratio of hydrogen volume to coal slurry is 900~1000 L / kg; among them, the reaction pressure of the second coal liquefaction reactor is 0.5~1.0 MPa higher than the reaction pressure of the first coal liquefaction reactor, and the difference between the reaction temperature of the second coal liquefaction reactor and the third coal liquefaction reactor and the reaction temperature of the first coal liquefaction reactor is 0~10℃.

7. The method according to claim 6, characterized in that The ratio of the usage of the first cycle material, the second cycle material and the third cycle material is (1~2): (2~3): (5~7).

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