Preparation method and preparation system of efficient circulating hydrogen-donor solvent for direct coal liquefaction

Abstract

According to the preparation method and the preparation system of the efficient circulating hydrogen-donating solvent for direct coal liquefaction, the circulating solvent prepared by the method has relatively high hydrogen-donating performance, the coal conversion rate and the oil yield in the direct coal liquefaction process can be remarkably improved, and the hydrogen consumption and the gas yield are reduced. The preparation method comprises the following steps: (1) fractionating the direct coal liquefaction oil in a first fractionating tower; (2) carrying out a first hydrogenation reaction on a mixed material obtained by mixing the heavy distillate oil and an initial solvent in a first hydrogenation reactor, and feeding the obtained product into a first separation unit for separation to obtain first-stage light distillate oil, first-stage medium distillate oil and first-stage heavy distillate oil; (3) performing a second hydrogenation reaction on a mixed material obtained by mixing the first-stage heavy distillate oil and the medium distillate oil in a second hydrogenation reactor, and feeding an obtained product into a second separation unit for separation to obtain second-stage heavy oil; and (4) mixing the second-stage heavy oil with the first-stage medium distillate oil to obtain the circulating hydrogen-donating solvent.

Description

Technical Field

[0001] The invention relates to a preparation technology of a circulating hydrogen supply solvent for direct coal liquefaction, and in particular to a preparation method and a preparation system of a high-efficiency circulating hydrogen supply solvent for direct coal liquefaction. Background Art

[0002] Coal direct liquefaction technology was proposed by German chemist Friedrich Bergius in 1913. It is a technology that mixes solid coal with hydrogen-supplying solvent and catalyst to produce liquid fuel under high temperature (400-500℃) and high pressure (10.0-30.0MPa) hydrogen reaction conditions. After nearly a hundred years of development, this technology has been continuously improved and innovated by researchers from various countries, forming many processes, such as the German IGOR process, the American EDS process, and the Japanese NEDOL process. In 2004, my country's Shenhua Group applied for a Chinese patent CN200410070249 for a coal direct liquefaction method, and in 2008 built the world's first million-ton coal direct liquefaction demonstration unit in Ordos and successfully put it into production.

[0003] Hydrogen supply solvent plays a key role in the direct coal liquefaction process. As an important medium in the reaction, it can dissolve, swell, dilute and disperse coal particles and coal free radical fragments, so that the gas, liquid and solid phases in the reactor are in a relatively uniform state; at the same time, it can provide and transfer active hydrogen, supply hydrogen to the free radical fragments generated by coal pyrolysis, so that they can quickly reach stability and convert into small molecule oil.

[0004] In the long-term operation of the coal direct liquefaction process, the coal direct liquefaction oil is hydrogenated to prepare a hydrogen supply solvent, which is circulated in the coal direct liquefaction process and is also called a circulating hydrogen supply solvent. The hydrogen supply capacity of the circulating hydrogen supply solvent affects the oil yield of the entire coal direct liquefaction process, and thus affects the profitability of the device. Therefore, it is particularly important to develop a method for preparing an efficient circulating hydrogen supply solvent for coal direct liquefaction.

[0005] Chinese patent CN103468315B discloses a method for preparing a circulating solvent for direct coal liquefaction. Coal tar anthracene oil is mixed with coal direct liquefaction oil, and mixed hydrogenation is performed to obtain light distillate oil, middle distillate oil and heavy distillate oil. Part of the middle distillate oil and the heavy distillate oil are mixed to obtain a circulating solvent for direct coal liquefaction. The circulating solvent prepared by this method has a high hydrogen supply performance and improves the economic value of coal tar anthracene oil. However, the heteroatom nitrogen content of anthracene oil is high, and nitrogen atoms can have an adverse effect on the catalyst for direct coal liquefaction reaction, thereby affecting the coal conversion rate.

[0006] Chinese patent CN105925304B discloses a method for preparing a circulating solvent for direct coal liquefaction, which performs preliminary fractionation on direct coal liquefaction oil. A heavy fraction of direct coal liquefaction oil with a temperature of >320°C is selected for hydrogenation, and the hydrogenated product is fractionated again, and a heavy fraction oil with a temperature of >320°C, part of a medium fraction oil with a temperature of 200 to 320°C, and part of a medium fraction oil of direct coal liquefaction with a temperature of 200 to 320°C in the preliminary fractionation stage are selected to prepare a circulating solvent for direct coal liquefaction. This method selectively hydrogenates the heavy fraction of direct coal liquefaction oil with a temperature of >320°C, avoids excessive hydrogenation of the medium fraction oil of direct coal liquefaction with a temperature of 200 to 320°C and competition with the heavy fraction oil, and significantly improves the hydrogen supply performance of the circulating solvent. However, this method has the problem of high hydrogen consumption.

[0007] Chinese patent CN104910961B discloses a method for preparing a circulating solvent for direct coal liquefaction, which is characterized in that the circulating solvent is prepared by a secondary hydrogenation method. First, the direct coal liquefaction oil is subjected to a first catalytic hydrogenation, and the obtained product is fractionated, wherein all or part of the heavy distillate oil is subjected to a second catalytic hydrogenation, and the liquid phase product of the secondary hydrogenation is mixed with all or part of the medium distillate oil to form a direct coal liquefaction circulating solvent. This method increases the number of active hydrogens and the saturation of unsaturated compounds in the heavy distillate oil by two hydrogenations, thereby improving the hydrogen supply performance and solubility of the circulating solvent. However, there are still polycyclic aromatic hydrocarbons in this method that are not fully partially saturated. Summary of the invention

[0008] In view of at least one shortcoming existing in the prior art, the present invention provides a method and system for preparing a high-efficiency circulating hydrogen supply solvent for direct coal liquefaction. The prepared circulating solvent has high hydrogen supply performance, can significantly improve the coal conversion rate and oil yield in the process of direct coal liquefaction, reduce hydrogen consumption and gas yield, and increase the economic benefits of direct coal liquefaction.

[0009] To achieve the purpose, the present invention provides the following technical solutions:

[0010] The present invention provides a method for preparing a high-efficiency circulating hydrogen supply solvent for direct coal liquefaction, comprising the following steps:

[0011] (1) fractionating the coal direct liquefaction oil in a first fractionation tower to obtain a light distillate oil, a middle distillate oil and a heavy distillate oil;

[0012] (2) subjecting the heavy distillate oil and the starting solvent to a first hydrogenation reaction in a first hydrogenation reactor, and sending the resulting product to a first separation unit for separation to obtain a first light distillate oil, a first middle distillate oil, and a first heavy distillate oil;

[0013] (3) mixing the primary heavy distillate oil with part or all of the middle distillate oil to obtain a mixture, subjecting it to a second hydrogenation reaction in a second hydrogenation reactor, and sending the obtained product to a second separation unit for separation to obtain a secondary heavy oil;

[0014] (4) Mixing the secondary heavy oil with part or all of the primary middle distillate oil to obtain the circulating hydrogen supply solvent.

[0015] Furthermore, in step (2), the starting solvent is obtained by hydrogenation reaction using a mixed oil comprising wash oil in coal tar fraction and anthracene oil as a raw material;

[0016] Preferably, the mass ratio of the wash oil to anthracene oil is 0.5 to 1.5:1, preferably 1:1;

[0017] Preferably, the hydrogenation reaction conditions for preparing the starting solvent include: temperature of 360-380°C, pressure of 17-19 MPa, volume space velocity of 1.0-1.2 h -1 ;

[0018] Preferably, the hydrogenation catalyst used to prepare the starting solvent comprises a carrier and an active component, wherein the active component comprises MoO 3 and NiO; more preferably, relative to the total mass of the catalyst, MoO 3 The content is 18.5-21.5%, and the NiO content is 4.3-4.6%; preferably, the carrier is Al 2 O 3 .

[0019] Preferably, in step (2), the mass ratio of the heavy distillate oil to the starting solvent is 1:0.5-1.5.

[0020] In some embodiments, in step (2), the first hydrogenation reactor is selected from a fixed bed reactor, an expanded bed reactor, a slurry bed reactor or a forced internal circulation ebullated bed reactor, preferably a forced internal circulation ebullated bed reactor;

[0021] In step (3), the second hydrogenation reactor is selected from a fixed bed reactor, an expanded bed reactor, a slurry bed reactor or a forced internal circulation ebullating bed reactor, preferably a fixed bed reactor.

[0022] In some embodiments, in the hydrogenation catalyst used in the first hydrogenation reaction in step (2) and / or the second hydrogenation reaction in step (3), the active component is a non-precious metal of group VIB and / or group VIII, and the carrier is an amorphous oxide and / or a silicate;

[0023] Preferably, the non-noble metal of group VIB is selected from Mo and / or W, and the non-noble metal of group VIII is selected from Co and / or Ni;

[0024] Preferably, the support is selected from amorphous alumina and / or aluminum silicate;

[0025] More preferably, the active components are Mo and Ni, and the carrier is amorphous alumina.

[0026] In some embodiments, in step (2), the reaction conditions of the first hydrogenation reaction include: an operating pressure of 5 to 30 MPa, an operating temperature of 290 to 390° C., a hydrogen-to-oil volume ratio of 100 to 1000, and a volume space velocity of 0.5 to 2.0 h -1 Preferably, the operating pressure is 10-21 MPa, the operating temperature is 320-370°C, the hydrogen-oil volume ratio is 300-600, and the volume space velocity is 0.7-1.5 h -1 ;

[0027] And / or, in step (3), the reaction conditions of the second hydrogenation reaction include: an operating pressure of 8 to 30 MPa, an operating temperature of 300 to 420°C, a hydrogen-to-oil volume ratio of 100 to 1500, and a volume space velocity of 0.5 to 2.0 h -1 Preferably, the operating pressure is 15-21 MPa, the operating temperature is 340-400°C, the hydrogen-oil volume ratio is 300-800, and the volume space velocity is 0.7-1.5 h -1 .

[0028] In some embodiments, in step (1), the coal direct liquefaction oil is coal direct liquefaction full distillate oil;

[0029] In step (1), the distillation ranges of the light distillate oil, the middle distillate oil and the heavy distillate oil are respectively <200° C., 200-310° C. and >310° C.;

[0030] In step (2), the distillation ranges of the first-level light distillate oil, the first-level middle distillate oil and the first-level heavy distillate oil are respectively <200°C, 200-350°C and >350°C.

[0031] In some embodiments, in step (2), the first separation unit comprises a first hot high-pressure separator, a first cold high-pressure separator and a second fractionation tower; the product obtained by the first hydrogenation reaction is separated into a first gas phase and a first liquid phase by the first hot high-pressure separator, the first gas phase enters the first cold high-pressure separator for separation to obtain a second gas phase and a second liquid phase, the first liquid phase and the second liquid phase enter the second fractionation tower for fractionation to obtain the first light distillate oil, the first middle distillate oil and the first heavy distillate oil; preferably, at least a portion of the second gas phase is circulated into the first hydrogenation reactor;

[0032] And / or, in step (3), the second separation unit includes a second hot high-pressure separator and a second cold high-pressure separator, the product obtained by the second hydrogenation reaction is separated by the second hot high-pressure separator to obtain a third gas phase and a third liquid phase, the third gas phase enters the second cold high-pressure separator and is separated to obtain a fourth gas phase and a fourth liquid phase; the third liquid phase and the fourth liquid phase are mixed to obtain the secondary heavy oil; preferably, at least a portion of the fourth gas phase is circulated into the second hydrogenation reactor.

[0033] The present invention also provides a coal direct liquefaction high-efficiency circulating hydrogen supply solvent preparation system for implementing the preparation method described above, the system comprising:

[0034] A first fractionation tower, used for fractionating the coal direct liquefaction oil to obtain light distillate oil, middle distillate oil and heavy distillate oil;

[0035] A first hydrogenation reactor is used to receive a mixture of the heavy distillate oil and the starting solvent, and to cause the mixture to undergo a first hydrogenation reaction with hydrogen to obtain a first hydrogenated product;

[0036] A first separation unit is used to separate the first hydrogenation product to obtain a first light distillate oil, a first middle distillate oil and a first heavy distillate oil;

[0037] A second hydrogenation reactor is used to receive a mixture of the primary heavy distillate oil and at least a portion of the middle distillate oil, and to cause the mixture to undergo a second hydrogenation reaction with hydrogen to obtain a second hydrogenated product;

[0038] a second separation unit, for separating the second hydrogenation product to obtain a secondary heavy oil;

[0039] The second separation unit is connected to a secondary heavy oil output pipeline, and the first separation unit is connected to a primary middle distillate oil output pipeline, and the primary middle distillate oil output pipeline is in communication with the secondary heavy oil output pipeline so that the secondary heavy oil is mixed with at least part of the primary middle distillate oil to obtain the circulating hydrogen supply solvent.

[0040] In some embodiments, the first separation unit includes a first hot high-pressure separator, a first cold high-pressure separator and a second fractionation tower; the first hot high-pressure separator is connected to the first hydrogenation reactor to separate the first hydrogenation reaction product and obtain a first gas phase and a first liquid phase; the first cold high-pressure separator is connected to the first hot high-pressure separator to separate the first gas phase and obtain a second gas phase and a second liquid phase; the second fractionation tower is respectively connected to the first hot high-pressure separator and the first cold high-pressure separator to receive the first liquid phase and the second liquid phase and fractionate them to obtain the first light distillate oil, the first middle distillate oil and the first heavy distillate oil; preferably, the gas phase outlet of the first cold high-pressure separator is connected to the first hydrogenation reactor to circulate at least part of the second gas phase into the first hydrogenation reactor;

[0041] And / or, the second separation unit includes a second hot high-pressure separator and a second cold high-pressure separator; the second hot high-pressure separator is connected to the second hydrogenation reactor to separate the second hydrogenation product and obtain a third gas phase and a third liquid phase; the second cold high-pressure separator is connected to the second hot high-pressure separator to separate the third gas phase to obtain a fourth gas phase and a fourth liquid phase; the liquid phase outlet of the second hot high-pressure separator and the liquid phase outlet of the second cold high-pressure separator are respectively connected to the secondary heavy oil output pipeline; preferably, the gas phase outlet of the second cold high-pressure separator is connected to the second hydrogenation reactor to circulate at least part of the fourth gas phase into the second hydrogenation reactor.

[0042] The technical solution provided by the present invention has the following beneficial effects:

[0043] The hydrogen supply solvent obtained by the preparation method of the present invention has a high total content of monocyclic, bicyclic and polycyclic aromatic hydrocarbons, a high hydrogen-carbon ratio and a low heteroatom N content. The preparation method provided by the present invention is conducive to improving the partial saturation of polycyclic aromatic hydrocarbons in the hydrogen supply solvent and increasing the amount of active hydrogen in the hydrogen supply solvent. The preparation of the circulating hydrogen supply solvent by the method of the present invention can effectively solve the problems of insufficient hydrogen supply capacity, low hydrogen supply efficiency and high hydrogen consumption of the existing hydrogen supply solvent in the direct coal liquefaction reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Shown is a schematic diagram of a system for preparing a highly efficient circulating hydrogen supply solvent for direct coal liquefaction in one embodiment. DETAILED DESCRIPTION

[0045] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention belongs. The term "and / or" as may be used herein includes any and all combinations of one or more related listed items. The terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the present invention, "primary light distillate oil, primary middle distillate oil and primary heavy distillate oil" are only names to distinguish them from the secondary heavy oil obtained by hydrogenation fractionation of the "primary heavy distillate oil" in the subsequent process, and "primary" and "secondary" have no special meanings.

[0047] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above-mentioned in this application can be understood according to the specific circumstances.

[0048] The present invention provides a method for preparing a high-efficiency circulating hydrogen supply solvent for direct coal liquefaction, see Figure 1 , including the following steps:

[0049] (1) fractionating the coal direct liquefaction oil in the first fractionation tower 120 to obtain light distillate oil, middle distillate oil and heavy distillate oil;

[0050] (2) subjecting the heavy distillate oil and the starting solvent to a mixed material to undergo a first hydrogenation reaction (i.e., rough hydrogenation) in a first hydrogenation reactor 150, and the resulting product is sent to a first separation unit for separation to obtain a first light distillate oil, a first middle distillate oil, and a first heavy distillate oil;

[0051] (3) the first-stage heavy distillate oil is mixed with part or all of the middle distillate oil to obtain a mixture, which is subjected to a second hydrogenation reaction (i.e., fine hydrogenation) in a second hydrogenation reactor 250, and the obtained product is sent to a second separation unit for separation to obtain a second heavy oil;

[0052] (4) Mixing the secondary heavy oil with part or all of the primary middle distillate oil to obtain the circulating hydrogen supply solvent.

[0053] The preparation method provided by the present invention uses coal direct liquefaction oil and a starting solvent as raw materials, and prepares an efficient circulating hydrogen supply solvent by a method of cutting and combining coal direct liquefaction oil with secondary hydrogenation. Specifically, the coal direct liquefaction oil is first fractionated, and the heavy distillate oil therein and the starting solvent (especially the starting solvent obtained based on wash oil and anthracene oil) are mixed for rough hydrogenation, and then the first-level heavy distillate oil and the middle distillate oil obtained by the fractionation are mixed for fine hydrogenation, and the second-level heavy oil obtained is separated from the first-level middle distillate oil obtained by the rough hydrogenation product and mixed as a circulating hydrogen supply solvent. The circulating solvent prepared by the process of the present invention has a high hydrogen supply performance, can significantly improve the coal conversion rate and oil yield in the coal direct liquefaction process, reduce hydrogen consumption and gas yield, and increase the economic benefits of coal direct liquefaction.

[0054] Furthermore, in step (2) of the present invention, the starting solvent is obtained by hydrogenation reaction using a mixed oil including wash oil and anthracene oil in coal tar fraction as raw materials. The starting solvent obtained by hydrogenation treatment based on wash oil and anthracene oil contains a large amount of aromatic hydrocarbons and heteroatoms compared with naphtha and diesel obtained from petroleum refining; whereas in the prior art, wash oil and anthracene oil are usually used directly as fuel, and a large amount of sulfur- and nitrogen-containing pollutant gases are generated during the combustion process, making it impossible to achieve high added value clean utilization. The inventors have found that by adopting the method of the present invention, the starting solvent obtained based on wash oil and anthracene oil can be used together with coal direct liquefaction oil as raw materials to prepare a circulating hydrogen supply solvent with better hydrogen supply performance, thereby providing an effective way for the clean utilization of wash oil and anthracene oil. In addition, in the existing technology for preparing circulating hydrogen supply solvents, there is no solution for simultaneously introducing wash oil and anthracene oil to prepare the starting solvent. The solution of the present invention can not only solve the problem that the wash oil cannot be fully utilized and the wash oil utilization rate is low in the existing technology, but also can replace the gasoline and diesel fractions with a temperature of less than 350°C in the coal direct liquefaction circulating solvent by introducing the starting solvent, thereby increasing the gasoline and diesel yield and improving the economic efficiency of coal liquefaction technology, while indirectly increasing the economic value of the wash oil and anthracene oil.

[0055] Preferably, when preparing the starting solvent, the mass ratio of the wash oil to the anthracene oil is 0.5-1.5:1, preferably 1:1; preferably, the hydrogenation reaction conditions for preparing the starting solvent include: temperature of 360-380°C, pressure of 17-19 MPa, volume space velocity of 1.0-1.2 h -1 The hydrogenation catalyst used to prepare the starting solvent can be, for example, Mo-Ni / Al 2 O 3 The catalyst is preferably MoO 3 The content is 18.5-21.5%, and the NiO content is 4.3-4.6%. For example, the HRK-658 catalyst of Axens Company can be used.

[0056] In a preferred embodiment, in step (2), the mass ratio of the heavy distillate oil to the starting solvent is 1:0.5-1.5, more preferably 1:1.

[0057] In some embodiments, in step (2), the first hydrogenation reactor 150 is selected from a fixed bed reactor, an expanded bed reactor, a slurry bed reactor or a forced internal circulation ebullating bed reactor (referred to as "ebullating bed reactor"), preferably a forced internal circulation ebullating bed reactor; in step (3), the second hydrogenation reactor 250 is selected from a fixed bed reactor, an expanded bed reactor, a slurry bed reactor or a forced internal circulation ebullating bed reactor, preferably a fixed bed reactor. The inventors have found that in the preparation process of the present invention, step (2) adopts a forced internal circulation ebullating bed reactor, and step (3) adopts a fixed bed reactor. The use of such a reactor combination is conducive to obtaining a circulating hydrogen supply solvent with better hydrogen supply performance.

[0058] In the present invention, the coal direct liquefaction oil is first fractionated to obtain light distillate oil, medium distillate oil and heavy distillate oil, and then the heavy distillate oil is mixed with a starting solvent (containing a large amount of aromatic hydrocarbons and heteroatoms) obtained by hydrogenating wash oil and anthracene oil, and then crude hydrogenation is performed. The crude hydrogenation process is more preferably performed in a forced internal circulation ebullating bed reactor. In the crude hydrogenation process, the heavy oil product is cracked, and most of the polycyclic aromatic hydrocarbons in the structure are hydrogenated and cracked, heteroatoms are removed, and the number of rings is reduced (four-ring or five-ring aromatic hydrocarbons are reduced to one-ring, two-ring or three-ring aromatic hydrocarbons), and the distillation range of the heavy distillate oil in this step is relatively wide. (>310 ℃), without introducing middle distillate oil, avoiding the middle distillate oil and heavy distillate oil robbing hydrogen in the hydrogenation process, thereby helping to reduce the hydrogen consumption and gas yield of the rough hydrogenation reaction; in the hydrogenation process, especially in the forced internal circulation ebullating bed reactor, the rough hydrogenation process is carried out, the starting solvent and the heavy distillate oil are in the hydrogenation process together, the starting solvent obtained after hydrogenation is rich in tetralin, and heteroatoms are removed, which can not only replace the gasoline and diesel fractions of <350 ℃ in the coal direct liquefaction circulating solvent, improve the gasoline and diesel yield, but also help to finally obtain a circulating hydrogen supply solvent with excellent hydrogen supply performance. After the rough hydrogenation, the product is separated to obtain a first-level light distillate oil, a first-level middle distillate oil and a first-level heavy distillate oil, and the first-level heavy distillate oil (>350 ℃) is mixed with part or all of the middle distillate oil for fine hydrogenation, and the fine hydrogenation process is preferably carried out in a fixed bed reactor, which is conducive to improving the processing depth, so that the aromatic ring structures such as one ring and two rings in the oil product structure are further partially saturated. In the above process, the heavy distillate oil and the starting solvent are subjected to the rough hydrogenation and fine hydrogenation processes successively, and the medium distillate oil is subjected to the fine hydrogenation process, which avoids the problem of insufficient hydrogenation of the aromatic structure on the one hand, and avoids the excessive hydrogenation of the aromatics in the medium distillate oil to cycloalkanes. On the other hand, the number of rings of polycyclic aromatic hydrocarbons in the solvent structure is reduced, so that some polycyclic aromatic hydrocarbons are fully partially saturated, the number of active hydrogens in the heavy distillate oil and the starting solvent is increased, and the heteroatom nitrogen in the solvent structure is fully removed, which can effectively prevent the heteroatom nitrogen from poisoning the catalyst in the coal liquefaction reaction. The circulating hydrogen supply solvent obtained by mixing the secondary heavy oil obtained by the second hydrogenation reaction with the primary medium distillate oil has a high hydrogen supply capacity, improves the solubility and dispersion capacity of the circulating solvent for coal and coal pyrolysis free radicals, and helps to improve the coal conversion rate and oil yield of direct coal liquefaction.

[0059] The hydrogenation catalyst used in the first hydrogenation reaction in step (2) and the second hydrogenation reaction in step (3) can be the hydrogenation catalyst commonly used by those skilled in the art in the direct hydrogenation process of coal liquefaction oil, and there is no particular limitation on this. In some preferred embodiments, in the hydrogenation catalyst used in the first hydrogenation reaction in step (2) and / or the second hydrogenation reaction in step (3), the active component is a non-precious metal of group VIB and / or group VIII, and the carrier is an amorphous oxide and / or silicate, and the mass content of the active component in the catalyst is, for example, 4-38%. Preferably, the non-precious metal of group VIB is selected from Mo and / or W, and the non-precious metal of group VIII is selected from Co and / or Ni. Preferably, the carrier is selected from amorphous alumina and / or aluminum silicate. More preferably, the active components are Mo and Ni, and the carrier is amorphous alumina, i.e., Mo-Ni / Al 2 O 3 Catalyst; wherein Mo is in the form of MoO 3 The content of Ni in the catalyst as NiO is, for example, 18.5-21.5wt%, and the content of Ni in the catalyst as NiO is, for example, 4.3-4.6wt%; in steps (2) and (3), a preferred hydrogenation catalyst is used to facilitate obtaining a circulating hydrogen supply solvent with better hydrogen supply performance. The first hydrogenation catalyst and the second hydrogenation catalyst of the above composition can be corresponding catalysts available through commercial channels in the art, or can be corresponding catalysts prepared by the catalyst preparation technology disclosed in the prior art in the art; for example, the corresponding hydrogenation catalyst used in CN104910961 B can be used, for example, a commercially available catalyst can be used, such as but not limited to the FFT-1B catalyst of Sinopec Dalian Institute, the HR-1256 catalyst of Axens, and the RTC-2 catalyst of Sinopec Institute of Petroleum and Chemical Corporation.

[0060] In some embodiments, in step (2), the reaction conditions of the first hydrogenation reaction include: an operating pressure of 5 to 30 MPa, an operating temperature of 290 to 390° C., a hydrogen-to-oil volume ratio of 100 to 1000, and a volume space velocity of 0.5 to 2.0 h -1 Preferably, the operating pressure is 10-21 MPa, the operating temperature is 320-370°C, the hydrogen-oil volume ratio is 300-600, and the volume space velocity is 0.7-1.5 h -1 ;

[0061] In some embodiments, in step (3), the reaction conditions of the second hydrogenation reaction include: an operating pressure of 8 to 30 MPa, an operating temperature of 300 to 420°C, a hydrogen-to-oil volume ratio of 100 to 1500, and a volume space velocity of 0.5 to 2.0 h -1Preferably, the operating pressure is 15-21 MPa, the operating temperature is 340-400°C, the hydrogen-oil volume ratio is 300-800, and the volume space velocity is 0.7-1.5 h -1 .

[0062] Furthermore, in step (1), the coal direct liquefaction oil is coal direct liquefaction full distillate oil. In some embodiments, the fractionation operating pressure of the first fractionation tower 120 in step (1) is 0.02-0.13 MPa.

[0063] In step (1), the distillation ranges of the light distillate oil, the middle distillate oil and the heavy distillate oil are respectively <200° C., 200-310° C. and >310° C.;

[0064] In step (2), the distillation ranges of the first-level light distillate oil, the first-level middle distillate oil and the first-level heavy distillate oil are respectively <200°C, 200-350°C and >350°C.

[0065] In some embodiments, in step (2), the first separation unit includes a first hot high-pressure separator 160, a first cold high-pressure separator 170 and a second fractionation tower 220; the product obtained by the first hydrogenation reaction is separated into a first gas phase and a first liquid phase by the first hot high-pressure separator 160, the first gas phase enters the first cold high-pressure separator 170 to separate into a second gas phase and a second liquid phase, the first liquid phase and the second liquid phase enter the second fractionation tower 220 and are fractionated to obtain the first light distillate oil, the first middle distillate oil and the first heavy distillate oil; preferably, at least part of the second gas phase is circulated into the first hydrogenation reactor 150 as circulating hydrogen. In some examples, the operating temperature of the first hot high-pressure separator 160 is 250-400°C and the operating pressure is 10-21MPa; the operating temperature of the first cold high-pressure separator 170 is 0-54°C and the operating pressure is 10-21MPa; the operating temperature of the bottom of the second fractionation tower 220 is less than 300°C and the operating pressure is 0.02-0.2MPa.

[0066] In some embodiments, in step (3), the second separation unit includes a second hot high-pressure separator 260 and a second cold high-pressure separator 270, and the product obtained by the second hydrogenation reaction is separated by the second hot high-pressure separator 260 to obtain a third gas phase and a third liquid phase, and the third gas phase enters the second cold high-pressure separator 270 to separate into a fourth gas phase and a fourth liquid phase; the third liquid phase and the fourth liquid phase are mixed to obtain the secondary heavy oil; preferably, at least part of the fourth gas phase is circulated as circulating hydrogen into the second hydrogenation reactor 250. In some examples, the operating temperature of the second hot high-pressure separator 260 is 250-400°C and the operating pressure is 10-21 MPa; the operating temperature of the second cold high-pressure separator 270 is 0-54°C and the operating pressure is 10-21 MPa.

[0067] In the present invention, in step (4), the secondary heavy oil is mixed with part or all of the primary middle distillate oil to obtain a circulating hydrogen supply solvent, and the remaining middle distillate oil, the primary middle distillate oil, the light distillate oil, and the primary light distillate oil can also be mixed to form a coal liquefaction product. In step (3), the specific mixing ratio of the middle distillate oil in the mixed material obtained by mixing the primary heavy distillate oil and part or all of the middle distillate oil for passing into the second hydrogenation reactor is not particularly limited, and is specifically determined according to the processing capacity of the downstream second hydrogenation reactor, that is, the difference between the processing capacity of the second hydrogenation reactor and the output of the primary heavy distillate oil is supplemented by the middle distillate oil. In the circulating hydrogen supply solvent obtained by mixing the secondary heavy oil with part or all of the primary middle distillate oil in step (4), there is no particular restriction on the mixing ratio of the primary middle distillate oil. It is determined based on the amount of circulating hydrogen supply solvent required for the amount of coal slurry treated by the upstream coal direct liquefaction reactor, that is, the difference between the amount of circulating hydrogen supply solvent required upstream and the output of the secondary heavy oil is supplemented by the primary middle distillate oil.

[0068] The circulating hydrogen supply solvent prepared by the present invention can be used for coal slurry configuration in the coal direct liquefaction process, has the ability to disperse coal and coal pyrolysis free radicals, and stabilize the free radicals in time, has high hydrogen supply capacity and low nitrogen atom content, promotes efficient conversion of coal, improves oil yield, increases hydrogen atom utilization, and reduces hydrogen consumption and gas yield.

[0069] The present invention also provides a coal direct liquefaction high-efficiency circulating hydrogen supply solvent preparation system for implementing the preparation method described above, see Figure 1 , the system comprising:

[0070] The first fractionation tower 120 is used to fractionate the coal direct liquefaction oil to obtain light distillate oil, middle distillate oil and heavy distillate oil;

[0071] The first hydrogenation reactor 150 is used to receive the mixture of the heavy distillate oil and the starting solvent, and to make the mixture undergo a first hydrogenation reaction with hydrogen to obtain a first hydrogenated product;

[0072] A first separation unit is used to separate the first hydrogenation product to obtain a first light distillate oil, a first middle distillate oil and a first heavy distillate oil;

[0073] The second hydrogenation reactor 250 is used to receive a mixture of the primary heavy distillate oil and at least a portion of the middle distillate oil, and to cause the mixture to undergo a second hydrogenation reaction with hydrogen to obtain a second hydrogenated product;

[0074] a second separation unit, for separating the second hydrogenation product to obtain a secondary heavy oil;

[0075] The second separation unit is connected to a secondary heavy oil output pipeline 280, and the first separation unit is connected to a primary middle distillate oil output pipeline 221. The primary middle distillate oil output pipeline 221 is in communication with the secondary heavy oil output pipeline 280 so that the secondary heavy oil is mixed with at least part of the primary middle distillate oil to obtain the circulating hydrogen supply solvent.

[0076] In some specific embodiments, a heating furnace 110 is further provided upstream of the first fractionation tower 120 for preheating the coal direct liquefied oil to be input into the first fractionation tower 120 to a desired temperature. A first buffer tank 130, a first high-pressure pump 101 and a heating furnace 140 are further provided between the first fractionation tower 120 and the first hydrogenation reactor 150. The first buffer tank 130 and the first high-pressure pump 101 are connected by a pipeline, and the first high-pressure pump 101 and the feed inlet of the heating furnace 140 are connected by a pipeline; the feed inlet of the heating furnace 140 is also connected to the first hydrogen input pipeline 151. The first buffer tank 130 is used to accommodate a mixture of heavy distillate oil and a starting solvent obtained in the first fractionation tower 120. The mixture in the first buffer tank 130 is pressurized by the first high-pressure pump 101 and the hydrogen input from the first hydrogen input pipeline 151 enters the heating furnace 140 for heating and temperature increase, and then enters the first hydrogenation reactor 150 for the first hydrogenation reaction. Specifically, the first hydrogenation reactor 150 is further provided with a first forced circulation pump 103 .

[0077] In some embodiments, the first separation unit includes a first hot high-pressure separator 160, a first cold high-pressure separator 170 and a second fractionation tower 220; the first hot high-pressure separator 160 is connected to the first hydrogenation reactor 150 to separate the first hydrogenation reaction product and obtain a first gas phase and a first liquid phase; the first cold high-pressure separator 170 is connected to the first hot high-pressure separator 160 to separate the first gas phase and obtain a second gas phase and a second liquid phase; the second fractionation tower 220 is respectively connected to the first hot high-pressure separator 160 and the first cold high-pressure separator 170 to receive the first liquid phase and the second liquid phase and fractionate them to obtain the first light distillate oil, the first middle distillate oil and the first heavy distillate oil. Preferably, the gas phase outlet of the first cold high-pressure separator 170 is connected to the first hydrogenation reactor 150, so as to circulate at least part of the second gas phase into the first hydrogenation reactor 150; specifically, the gas phase outlet of the first cold high-pressure separator 170 is connected to the second gas phase output pipeline 171, the second gas phase output pipeline 171 is provided with a compressor 107, and the second gas phase output pipeline 171 is connected to the first hydrogen input pipeline 151, so that at least part of the second gas phase output from the gas phase outlet of the first cold high-pressure separator 170 is pressurized by the compressor 107 and then merged into the first hydrogen input pipeline 151, and finally enters the first hydrogenation reactor 150. Specifically, a first heat exchanger 105 is provided between the first hot high-pressure separator 160 and the first cold high-pressure separator 170, and the first gas phase output from the first hot high-pressure separator 160 is cooled by the first heat exchanger 105 and then enters the first cold high-pressure separator 170. Specifically, a heating furnace 210 is provided between the second distillation tower 220 and the first hot high-pressure separator 160 and the first cold high-pressure separator 170. The first liquid phase output by the first hot high-pressure separator 160 and the second liquid phase output by the first cold high-pressure separator 170 are heated by the heating furnace 210 and then enter the second distillation tower 220.

[0078] In some specific embodiments, a second buffer tank 230, a second high-pressure pump 102, and a heating furnace 240 are further provided between the first separation unit and the second hydrogenation reactor 250. The feed port of the heating furnace 240 is connected to the second high-pressure pump 102, and the feed port of the heating furnace 240 is also connected to the second hydrogen input pipeline 251. The mixture of the primary heavy distillate oil and at least part of the middle distillate oil output from the second fractionation tower 220 of the first separation unit is first contained in the second buffer tank 230, and then after being pressurized by the second high-pressure pump 102, it enters the heating furnace 240 together with the hydrogen input from the second hydrogen input pipeline 251 to heat and raise the temperature, and then enters the second hydrogenation reactor 250 to carry out the second hydrogenation reaction. Specifically, the second hydrogenation reactor 250 is also equipped with a second forced circulation pump 104.

[0079] In some embodiments, the second separation unit includes a second hot high-pressure separator 260 and a second cold high-pressure separator 270; the second hot high-pressure separator 260 is connected to the second hydrogenation reactor 250 to separate the second hydrogenation product and obtain a third gas phase and a third liquid phase; the second cold high-pressure separator 270 is connected to the second hot high-pressure separator 260 to separate the third gas phase to obtain a fourth gas phase and a fourth liquid phase; the liquid phase outlet of the second hot high-pressure separator 260 and the liquid phase outlet of the second cold high-pressure separator 270 are respectively connected to the secondary heavy oil output pipeline 280. Preferably, the gas phase outlet of the second cold high-pressure separator 270 is connected to the second hydrogenation reactor 250, so as to circulate at least part of the fourth gas phase into the second hydrogenation reactor 250; specifically, the gas phase outlet of the second cold high-pressure separator 270 is connected to the fourth gas phase output pipeline 271, and the fourth gas phase output pipeline 271 is provided with a compressor 108, and the fourth gas phase output pipeline 271 is connected to the second hydrogen input pipeline 251, so that at least part of the fourth gas phase output from the gas phase outlet of the second cold high-pressure separator 270 is pressurized by the compressor 108 and then merged into the second hydrogen input pipeline 251, and finally enters the second hydrogenation reactor 250. Specifically, a second heat exchanger 106 is provided between the second hot high-pressure separator 260 and the second cold high-pressure separator 270, and the third gas phase output from the second hot high-pressure separator 260 is cooled by the second heat exchanger and then enters the second cold high-pressure separator 270.

[0080] The specific devices or elements involved in this article can all adopt devices or elements with corresponding functions known in the art. There is no special limitation on this and they will not be described one by one.

[0081] The present invention is further described below by means of specific examples, but it should not be understood that the present invention is limited thereto.

[0082] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. The reagents used without specifying the manufacturer are all conventional reagents available in the art.

[0083] In the following examples, anthracene oil and wash oil in coal tar fraction oil are used to prepare the starting solvent, wherein the wash oil distillation range is: 230°C (IBP)-300°C (90%), referring to the national standard GB / T 24217-2009; the anthracene oil distillation range is: 280°C (IBP)-360°C (50%), referring to the national standard GB / T 24211-2009.

[0084] Example 1

[0085] Use Figure 1The preparation system shown prepares a circulating hydrogen supply solvent. For a detailed description of the system, please refer to the previous description, which will not be described in detail again.

[0086] The coal direct liquefaction oil is a coal direct liquefaction full-fraction oil from a coal direct liquefaction unit. The coal direct liquefaction oil enters the heating furnace 110, and after being heated, enters the first distillation tower 120. In the first distillation tower 120, the coal direct liquefaction oil is fractionated into light distillate oil (distillation range <200°C), middle distillate oil (distillation range 200-310°C), and heavy distillate oil (distillation range >310°C).

[0087] The preparation method of the starting solvent is as follows: anthracene oil and washing oil are mixed in a mass ratio of 1:1, and heated at 380°C, 19 MPa, 1.2 h -1 Under the reaction conditions, Mo-Ni / Al 2 O 3 The catalyst (manufacturer is Axens, brand HRK-658 catalyst) is hydrogenated to obtain the starting solvent.

[0088] The heavy distillate oil and the starting solvent are mixed in a mass ratio of 1:1 and enter the first buffer tank 130. After being pressurized by the first high-pressure pump 101, they are mixed with hydrogen and enter the heating furnace 140 for heating. The outlet temperature of the heating furnace 140 is 300° C. The heated oil-gas mixture enters the first hydrogenation reactor 150 (an ebullating bed reactor) for the first hydrogenation reaction (rough hydrogenation). The reaction conditions are shown in Table 2. The reaction process includes hydrocracking to reduce the number of polycyclic aromatic hydrocarbons and heteroatom removal reaction. The material at the outlet of the first hydrogenation reactor 150 enters the first hot high-pressure separator 160, and the temperature of the first hot high-pressure separator 160 is controlled at 250°C. The first gas phase separated from the first hot high-pressure separator 160 is cooled by the first heat exchanger 105 and then enters the first cold high-pressure separator 170. The temperature of the first cold high-pressure separator 170 is controlled below 54°C. The second gas phase separated from the first cold high-pressure separator 170 is partially pressurized by the compressor 107 and circulated to the inlet of the heating furnace 140, and part of the gas is discharged as exhaust gas.

[0089] The first liquid phase separated from the first hot high-pressure separator 160 and the second liquid phase separated from the first cold high-pressure separator 170 are mixed into a crude hydrogenated material and enter the heating furnace 210. After being heated, the crude hydrogenated material enters the second fractionation tower 220, where the crude hydrogenated material is fractionated into a first light distillate oil (distillation range < 200°C), a first middle distillate oil (distillation range 200-350°C), and a first heavy distillate oil (distillation range > 350°C).

[0090] The first-level heavy distillate oil is mixed with part or all of the medium distillate oil and enters the second buffer tank 230. After being pressurized by the second high-pressure pump 102, it is mixed with hydrogen and enters the heating furnace 240 for heating. The outlet temperature of the heating furnace 240 is 300° C. The heated oil-gas mixture enters the second hydrogenation reactor 250 (a fixed bed reactor) for the second hydrogenation reaction (fine hydrogenation). The reaction conditions are shown in Table 3. The one-ring, two-ring and other aromatic ring structures in the oil product structure are further partially saturated to increase the amount of active hydrogen therein. The material at the outlet of the second hydrogenation reactor 250 enters the second hot high-pressure separator 260, and the temperature of the second hot high-pressure separator 260 is controlled at 250°C. The third gas phase separated from the second hot high-pressure separator 260 is cooled by the second heat exchanger 106 and enters the second cold high-pressure separator 270. The temperature of the second cold high-pressure separator 270 is controlled below 54°C. The fourth gas phase separated from the second cold high-pressure separator 270 is partially pressurized by the compressor 108 and circulated to the inlet of the heating furnace 240, and part of the gas is discharged as exhaust gas.

[0091] The third liquid phase separated from the second hot high-pressure separator 260 is mixed with the fourth liquid phase separated from the second cold high-pressure separator 270 to form a secondary heavy oil. The secondary heavy oil is mixed with part or all of the primary middle distillate oil to form a highly efficient circulating hydrogen supply solvent.

[0092] The carriers of the hydrogenation catalysts used in the first hydrogenation reaction and the second hydrogenation reaction are both amorphous alumina, and the active component is 20.6% MoO relative to the total mass of the catalyst. 3 , 4.6% NiO; specifically, the FFT-1B catalyst produced by Sinopec Dalian Institute was used.

[0093] Example 2

[0094] The method was carried out in accordance with Example 1, except that the carriers of the hydrogenation catalysts used in the first hydrogenation reaction and the second hydrogenation reaction were both amorphous alumina, and the active component was 21.0% MoO relative to the total mass of the catalyst. 3 , 4.6% CoO; specifically, Axens HR-1256 catalyst was used; the reaction conditions of the first hydrogenation reaction and the second hydrogenation reaction in Example 2 are shown in Tables 2 and 3, respectively.

[0095] Example 3

[0096] The method was carried out in accordance with Example 1, except that the carriers of the hydrogenation catalysts used in the first hydrogenation reaction and the second hydrogenation reaction were both amorphous alumina, and the active component was 33.0% WO relative to the total mass of the catalyst. 3 , 5.0% NiO; specifically, RTC-2 catalyst from Sinopec Petrochemical Research Institute was used; the reaction conditions of the first hydrogenation reaction and the second hydrogenation reaction in Example 3 are shown in Tables 2 and 3, respectively.

[0097] Example 4

[0098] The process is carried out with reference to Example 1, except that the reactor used in the first hydrogenation reaction (rough hydrogenation) is a fixed bed reactor, and the reactor used in the second hydrogenation reaction (fine hydrogenation) is an ebullating bed reactor.

[0099] Example 5

[0100] The process is carried out in accordance with Example 1, except that the reactor used in the first hydrogenation reaction (rough hydrogenation) is a fixed bed reactor, and the reactor used in the second hydrogenation reaction (fine hydrogenation) is a fixed bed reactor.

[0101] Comparative Example 1

[0102] Compared with Example 1, other conditions remain unchanged, except that the first-stage heavy distillate oil (>350°C) fractionated from the second distillation tower 220 is directly mixed with part or all of the first-stage middle distillate oil to obtain a coal direct liquefaction high-efficiency circulating hydrogen supply solvent.

[0103] Comparative Example 2

[0104] Compared with Example 1, other conditions remain unchanged, except that: the coal direct liquefaction oil does not pass through the heating furnace 110 and the first fractionation tower 120, but is directly mixed with the starting solvent in a mass ratio of 1:1 and then enters the first buffer tank 130 for subsequent reaction. The first-level heavy distillate oil obtained in the second fractionation tower 220 directly enters the second buffer tank 230 for subsequent reaction; the obtained second-level heavy oil is mixed with part or all of the first-level medium distillate oil to obtain a coal direct liquefaction high-efficiency circulating hydrogen supply solvent.

[0105] Comparative Example 3

[0106] Compared with Example 1, other conditions remain unchanged, except that the heavy distillate oil obtained by direct coal liquefaction oil passing through the heating furnace 110 and the first fractionation tower 120 directly enters the first buffer tank 130, and no starting solvent is introduced for subsequent reaction, that is, the heavy distillate oil and the starting solvent are in a mass ratio of 1:0. The rest are carried out with reference to Example 1.

[0107] The properties of the coal direct liquefaction whole distillate oil and the starting solvent used in the above examples and comparative examples are shown in Table 1. The reaction conditions of the first hydrogenation reaction (rough hydrogenation) are shown in Table 2, and the reaction conditions of the second hydrogenation reaction (fine hydrogenation) are shown in Table 3.

[0108] Table 1 Properties of coal direct liquefaction oil and starting solvent

[0109]

[0110]

[0111] Table 2 Reaction conditions of the first hydrogenation reaction (rough hydrogenation)

[0112] Example Reaction temperature / ℃ Reaction pressure / MPa Hydrogen to oil ratio / (v / v) <![CDATA[Space velocity per hour -1 > 1 370 18 450 1.5 2 380 30 600 2.0 3 350 5 500 0.7 4 370 18 300 2.0 5 290 19 450 0.7

[0113] Table 3 Reaction conditions of the second hydrogenation reaction (fine hydrogenation)

[0114] Example Reaction temperature / ℃ Reaction pressure / MPa Hydrogen to oil ratio / (v / v) <![CDATA[Space velocity per hour -1 > 1 390 15 480 1.5 2 400 30 800 2.0 3 370 8 550 0.7 4 390 15 350 2.0 5 300 19 480 0.7

[0115] The analysis data of the hydrogen supply solvent for the coal direct liquefaction cycle of Examples 1-5 and Comparative Examples 1-2 are shown in Table 4

[0116] Table 4 Analysis data of hydrogen supply solvent in coal direct liquefaction cycle

[0117]

[0118]

[0119] It can be seen from the data in Table 4 that, compared with Examples 1-5 of the present invention and Comparative Examples 1-2, the hydrogen supply solvents obtained by the embodiments of the preparation method of the present invention have higher contents of monocyclic and bicyclic aromatic hydrocarbons, while taking into account relatively high total content of polycyclic aromatic hydrocarbons, higher hydrogen-carbon ratio and lower heteroatom N content, indicating that the solvent prepared by the present invention is more suitable for use as a hydrogen supply solvent for direct coal liquefaction. The preparation method provided by the present invention is conducive to improving the partial saturation of polycyclic aromatic hydrocarbons in the hydrogen supply solvent and increasing the amount of active hydrogen in the hydrogen supply solvent.

[0120] By comparing Example 1 and Example 2-5, it can be seen that the total content of monocyclic, bicyclic and polycyclic aromatic hydrocarbons in the hydrogen supply solvent prepared in Example 1 using the preferred first and second hydrogenation reactors is significantly higher than that in Example 2-5, and the hydrogen-to-carbon ratio is also higher than that in Example 2-5. Using an ebullating bed reactor for the first hydrogenation reaction and a fixed bed reactor for the second hydrogenation reaction is conducive to obtaining a hydrogen supply solvent with better hydrogen supply performance.

[0121] Then, a high-pressure autoclave coal direct liquefaction test was carried out on the coal direct liquefaction circulating solvents in Examples 1-5 and Comparative Examples 1-3.

[0122] The properties of the coal samples used in the autoclave coal direct liquefaction test are shown in Table 5. The process conditions of the autoclave coal direct liquefaction test are as follows: a 0.5L stirred autoclave is used, the amount of coal entering the autoclave is 28g (dry coal), the mass ratio of the circulating solvent to the coal is 1.5:1, the initial pressure of hydrogen is 10.0MPa, the catalyst is an iron-based catalyst, the Fe addition amount is 1% of the dry coal mass fraction, the co-catalyst is sulfur, and n(S) / n(Fe) is 2. After heating to the reaction temperature of 455℃, the temperature is maintained for 60min.

[0123] The autoclave product is divided into two parts: a gas phase product and a liquid-solid mixture. The gas phase product is analyzed for composition using a gas chromatograph; the liquid-solid phase product is separated by Soxhlet extraction using n-hexane and tetrahydrofuran in turn.

[0124] The n-hexane soluble matter is defined as oil, the n-hexane insoluble and THF soluble matter is defined as asphaltene and pre-asphaltene (referred to as asphaltene components), and the THF insoluble matter is defined as unreacted coal. The results of the autoclave coal direct liquefaction test are shown in Table 6.

[0125] Table 5 Coal quality analysis data of coal direct liquefaction autoclave

[0126]

[0127]

[0128] Table 6 Results of direct liquefaction test of coal in autoclave

[0129] project Coal conversion rate / % Hydrogen consumption / wt% Oil yield wt% Gas yield wt% Water yield wt% Asphaltene yield wt% Example 1 87.57 3.95 59.36 13.02 10.91 8.47 Example 2 86.50 4.10 55.90 14.04 11.07 10.34 Example 3 86.33 4.09 55.23 13.92 11.89 9.92 Example 4 85.93 4.05 56.36 13.65 11.90 10.08 Example 5 86.41 4.11 56.90 14.03 11.23 10.61 Comparative Example 1 84.81 5.41 54.27 15.67 11.09 10.11 Comparative Example 2 84.16 5.09 54.38 15.53 11.27 9.98 Comparative Example 3 85.89 4.05 54.34 13.13 11.06 11.19

[0130] From the test results in Table 6, it can be seen that the circulating solvent prepared by the method of the present invention is beneficial to the conversion of coal during the direct coal liquefaction reaction, improves the oil yield of direct coal liquefaction, and reduces the gas yield and hydrogen consumption. Its excellent direct coal liquefaction effect shows that the circulating solvent prepared by the method of the present invention has a high hydrogen supply capacity and a dispersion capacity for coal and coal pyrolysis free radicals.

[0131] It can be seen from the above experiments that the scheme of the present invention achieves the following technical effects: using coal direct liquefaction oil and the starting solvent as raw materials to carry out cutting and combining secondary catalytic hydrogenation to prepare a coal direct liquefaction efficient circulating hydrogen supply solvent, which can effectively solve the problems of insufficient hydrogen supply capacity, low hydrogen supply efficiency and high hydrogen consumption of the existing hydrogen supply solvent in the coal direct liquefaction reaction process. In addition, the present invention adopts the existing more mature and reliable catalytic hydrogenation process, and can improve the hydrogenation depth of the coal direct liquefaction circulating hydrogen supply solvent without changing the existing coal direct process flow, thereby achieving the purpose of improving the hydrogen supply capacity of the circulating solvent, and then improving the overall economic benefits of the coal direct liquefaction process. In the preferred scheme, using coal direct liquefaction oil and the starting solvent as raw materials, a boiling bed-fixed bed is used for secondary catalytic hydrogenation, which can further significantly improve the hydrogen supply capacity of the prepared hydrogen supply solvent, further improve the hydrogen supply efficiency and reduce hydrogen consumption.

[0132] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A method for preparing a highly efficient circulating hydrogen supply solvent for direct coal liquefaction, characterized in that: The steps include: (1) fractionating the coal direct liquefaction oil in a first fractionation tower to obtain a light distillate oil, a middle distillate oil and a heavy distillate oil; (2) subjecting the heavy distillate oil and the starting solvent to a first hydrogenation reaction in a first hydrogenation reactor, and sending the resulting product to a first separation unit for separation to obtain a first light distillate oil, a first middle distillate oil, and a first heavy distillate oil; (3) mixing the primary heavy distillate oil with part or all of the middle distillate oil to obtain a mixture, subjecting it to a second hydrogenation reaction in a second hydrogenation reactor, and sending the obtained product to a second separation unit for separation to obtain a secondary heavy oil; (4) Mixing the secondary heavy oil with part or all of the primary middle distillate oil to obtain the circulating hydrogen supply solvent.

2. The preparation method according to claim 1, characterized in that: In step (2), the starting solvent is obtained by hydrogenation reaction using a mixed oil comprising wash oil in coal tar fraction and anthracene oil as a raw material; Preferably, the mass ratio of the wash oil to the anthracene oil is 0.5 to 1.5:1, preferably 1:1; Preferably, the hydrogenation reaction conditions for preparing the starting solvent include: temperature of 360-380°C, pressure of 17-19 MPa, volume space velocity of 1.0-1.2 h -1 ; Preferably, the hydrogenation catalyst used to prepare the starting solvent includes a carrier and an active component, and the active component includes MoO3 and NiO; more preferably, the MoO3 content is 18.5-21.5%, and the NiO content is 4.3-4.6% relative to the total mass of the catalyst; preferably, the carrier is Al2O3.

3. The preparation method according to claim 1 or 2, characterized in that: In step (2), the mass ratio of the heavy distillate oil to the starting solvent is 1:0.5-1.

5.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step (2), the first hydrogenation reactor is selected from a fixed bed reactor, an expanded bed reactor, a slurry bed reactor or a forced internal circulation ebullating bed reactor, preferably a forced internal circulation ebullating bed reactor; In step (3), the second hydrogenation reactor is selected from a fixed bed reactor, an expanded bed reactor, a slurry bed reactor or a forced internal circulation ebullating bed reactor, preferably a fixed bed reactor.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In the hydrogenation catalyst used in the first hydrogenation reaction in step (2) and / or the second hydrogenation reaction in step (3), the active component is a non-noble metal of group VIB and / or group VIII, and the carrier is an amorphous oxide and / or a silicate; Preferably, the non-noble metal of group VIB is selected from Mo and / or W, and the non-noble metal of group VIII is selected from Co and / or Ni; Preferably, the support is selected from amorphous alumina and / or aluminum silicate; More preferably, the active components are Mo and Ni, and the carrier is amorphous alumina.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In step (2), the reaction conditions of the first hydrogenation reaction include: an operating pressure of 5 to 30 MPa, an operating temperature of 290 to 390°C, a hydrogen-to-oil volume ratio of 100 to 1000, and a volume space velocity of 0.5 to 2.0 h -1 Preferably, the operating pressure is 10-21 MPa, the operating temperature is 320-370°C, the hydrogen-oil volume ratio is 300-600, and the volume space velocity is 0.7-1.5 h -1 ; And / or, in step (3), the reaction conditions of the second hydrogenation reaction include: an operating pressure of 8 to 30 MPa, an operating temperature of 300 to 420°C, a hydrogen-to-oil volume ratio of 100 to 1500, and a volume space velocity of 0.5 to 2.0 h -1 Preferably, the operating pressure is 15-21 MPa, the operating temperature is 340-400°C, the hydrogen-oil volume ratio is 300-800, and the volume space velocity is 0.7-1.5 h -1 .

7. The preparation method according to any one of claims 1 to 6, characterized in that: In step (1), the coal direct liquefaction oil is coal direct liquefaction full distillate oil; In step (1), the distillation ranges of the light distillate oil, the middle distillate oil and the heavy distillate oil are respectively <200° C., 200-310° C. and >310° C.; In step (2), the distillation ranges of the first-level light distillate oil, the first-level middle distillate oil and the first-level heavy distillate oil are respectively <200°C, 200-350°C and >350°C.

8. The preparation method according to any one of claims 1 to 7, characterized in that: In step (2), the first separation unit comprises a first hot high-pressure separator, a first cold high-pressure separator and a second fractionation tower; the product obtained by the first hydrogenation reaction is separated into a first gas phase and a first liquid phase by the first hot high-pressure separator, the first gas phase enters the first cold high-pressure separator for separation to obtain a second gas phase and a second liquid phase, the first liquid phase and the second liquid phase enter the second fractionation tower for fractionation to obtain the first light distillate oil, the first middle distillate oil and the first heavy distillate oil; preferably, at least a portion of the second gas phase is circulated into the first hydrogenation reactor; And / or, in step (3), the second separation unit includes a second hot high-pressure separator and a second cold high-pressure separator, the product obtained by the second hydrogenation reaction is separated by the second hot high-pressure separator to obtain a third gas phase and a third liquid phase, the third gas phase enters the second cold high-pressure separator and is separated to obtain a fourth gas phase and a fourth liquid phase; the third liquid phase and the fourth liquid phase are mixed to obtain the secondary heavy oil; preferably, at least a portion of the fourth gas phase is circulated into the second hydrogenation reactor.

9. A coal direct liquefaction high-efficiency circulating hydrogen supply solvent preparation system for implementing the preparation method according to any one of claims 1 to 8, characterized in that: The system comprises: A first fractionation tower, used for fractionating the coal direct liquefaction oil to obtain light distillate oil, middle distillate oil and heavy distillate oil; A first hydrogenation reactor is used to receive a mixture of the heavy distillate oil and the starting solvent, and to cause the mixture to undergo a first hydrogenation reaction with hydrogen to obtain a first hydrogenated product; A first separation unit is used to separate the first hydrogenation product to obtain a first light distillate oil, a first middle distillate oil and a first heavy distillate oil; A second hydrogenation reactor is used to receive a mixture of the primary heavy distillate oil and at least a portion of the middle distillate oil, and to cause the mixture to undergo a second hydrogenation reaction with hydrogen to obtain a second hydrogenated product; a second separation unit, for separating the second hydrogenation product to obtain a secondary heavy oil; The second separation unit is connected to a secondary heavy oil output pipeline, and the first separation unit is connected to a primary middle distillate oil output pipeline, and the primary middle distillate oil output pipeline is in communication with the secondary heavy oil output pipeline so that the secondary heavy oil is mixed with at least part of the primary middle distillate oil to obtain the circulating hydrogen supply solvent.

10. The preparation system according to claim 9, characterized in that: The first separation unit comprises a first hot high-pressure separator, a first cold high-pressure separator and a second fractionation tower; the first hot high-pressure separator is connected to the first hydrogenation reactor to separate the first hydrogenation reaction product and obtain a first gas phase and a first liquid phase; the first cold high-pressure separator is connected to the first hot high-pressure separator to separate the first gas phase and obtain a second gas phase and a second liquid phase; the second fractionation tower is respectively connected to the first hot high-pressure separator and the first cold high-pressure separator to receive the first liquid phase and the second liquid phase and fractionate them to obtain the first light distillate oil, the first middle distillate oil and the first heavy distillate oil; preferably, the gas phase outlet of the first cold high-pressure separator is connected to the first hydrogenation reactor to circulate at least part of the second gas phase into the first hydrogenation reactor; And / or, the second separation unit includes a second hot high-pressure separator and a second cold high-pressure separator; the second hot high-pressure separator is connected to the second hydrogenation reactor to separate the second hydrogenation product and obtain a third gas phase and a third liquid phase; the second cold high-pressure separator is connected to the second hot high-pressure separator to separate the third gas phase to obtain a fourth gas phase and a fourth liquid phase; the liquid phase outlet of the second hot high-pressure separator and the liquid phase outlet of the second cold high-pressure separator are respectively connected to the secondary heavy oil output pipeline; preferably, the gas phase outlet of the second cold high-pressure separator is connected to the second hydrogenation reactor to circulate at least part of the fourth gas phase into the second hydrogenation reactor.

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