Preparation method and system for high-efficiency circulating hydrogen supply solvent for direct coal liquefaction

Abstract

The present invention provides a method and system for preparing a high-efficiency circulating hydrogen supply solvent for direct coal liquefaction. The circulating solvent prepared by the method of the present invention has high hydrogen supply performance, can significantly improve the coal conversion rate and oil yield in the direct coal liquefaction process, and reduce hydrogen consumption and gas yield. The preparation method comprises the following steps: (1) fractionating the direct coal liquefaction oil in a first fractionation tower; (2) subjecting the mixture obtained by mixing heavy distillate oil and a 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) subjecting the mixture obtained by mixing the first heavy distillate oil and the middle distillate oil to a second hydrogenation reaction in a second hydrogenation reactor, and sending the resulting product to a second separation unit for separation to obtain a second heavy oil; (4) mixing the second heavy oil with the first middle distillate oil to obtain a circulating hydrogen supply solvent.

Description

Technical Field

[0001] The present 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] Direct coal liquefaction technology, proposed by German chemist Friedrich Bergius in 1913, involves mixing solid coal with a hydrogen-donating solvent and a catalyst to produce liquid fuel under high-temperature (400-500°C) and high-pressure (10.0-30.0 MPa) hydrogenation conditions. Over nearly a century of development, this technology has been continuously improved and innovated by researchers worldwide, resulting in numerous 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 Chinese patent CN200410070249 for a direct coal liquefaction method. In 2008, the world's first million-ton-scale direct coal liquefaction demonstration unit was built and successfully put into operation in Ordos.

[0003] Hydrogen-donating solvents play a key role in the direct coal liquefaction process. As a crucial medium in the reaction, they dissolve, swell, dilute, and disperse coal particles and coal radical fragments, maintaining a relatively uniform gas, liquid, and solid phase in the reactor. They also provide and transfer active hydrogen, supplying hydrogen to the radical fragments generated by coal pyrolysis, allowing them to quickly stabilize and convert into small-molecule oils.

[0004] In the long-term operation of the direct coal liquefaction (DCL) process, the DCL oil is hydrogenated to produce a stable hydrogen-donating solvent. This solvent is then recycled throughout the DCL process and is also known as the circulating hydrogen-donating solvent. The hydrogen-donating capacity of the circulating hydrogen-donating solvent affects the oil yield of the DCL process, and thus the profitability of the plant. Therefore, developing a method for preparing an efficient circulating hydrogen-donating solvent for DCL is crucial.

[0005] Chinese patent CN103468315B discloses a method for preparing a circulating solvent for direct coal liquefaction. Coal tar anthracene oil is mixed with direct coal liquefaction oil, and the mixed hydrogenation produces light distillate, middle distillate, and heavy distillate. A portion of the middle distillate and the heavy distillate are mixed to produce a direct coal liquefaction circulating solvent. The circulating solvent prepared by this method has a high hydrogen supply performance and improves the economic value of coal tar anthracene oil. However, anthracene oil has a high heteroatom nitrogen content, and nitrogen atoms can adversely affect the direct coal liquefaction reaction catalyst, 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. A heavy fraction oil with a temperature of >320°C, part of a medium fraction oil with a temperature of 200-320°C, and part of the direct coal liquefaction medium fraction oil with a temperature of 200-320°C in the preliminary fractionation stage are selected to prepare a direct coal liquefaction circulating solvent. This method selectively hydrogenates the heavy fraction of direct coal liquefaction oil with a temperature of >320°C, avoids excessive hydrogenation of the direct coal liquefaction medium fraction oil with a temperature of 200-320°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 by preparing the circulating solvent by a secondary hydrogenation method. First, the direct coal liquefaction oil is subjected to a first catalytic hydrogenation, and the resulting 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 middle distillate oil to form a direct coal liquefaction circulating solvent. This method increases the amount of active hydrogen and the saturation of unsaturated compounds in the heavy distillate oil through two hydrogenations, thereby improving the hydrogen supply performance and dissolving capacity of the circulating solvent. However, in this method, polycyclic aromatic hydrocarbons are still not fully partially saturated. Summary of the Invention

[0008] In response to at least one shortcoming of 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 direct coal liquefaction process, reduce hydrogen consumption and gas production rate, and increase the economic benefits of direct coal liquefaction.

[0009] To achieve its 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 fractionating tower to obtain light distillate oil, middle distillate oil and 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 first-stage 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 resulting product to a second separation unit for separation to obtain a second 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 of a mixed oil comprising wash oil in coal tar fraction and anthracene oil;

[0016] Preferably, the mass ratio of the wash oil to the 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 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.

[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, the hydrogenation catalyst used in the first hydrogenation reaction in step (2) and / or the second hydrogenation reaction in step (3) comprises an active component of a non-noble metal of Group VIB and / or Group VIII, and a support of 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 support 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-to-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: operating pressure of 8-30 MPa, operating temperature of 300-420°C, hydrogen-to-oil volume ratio of 100-1500, volume space velocity of 0.5-2.0h -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 0.7-1.5h -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 includes 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 part 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 fractionating tower for fractionating the coal direct liquefaction oil to obtain light distillate oil, middle distillate oil and heavy distillate oil;

[0035] a first hydrogenation reactor for receiving a mixture of the heavy distillate oil and the starting solvent and causing the mixture to undergo a first hydrogenation reaction with hydrogen to obtain a first hydrogenated product;

[0036] a first separation unit, configured 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 for receiving a mixture of the first-stage heavy distillate oil and at least a portion of the middle distillate oil, and subjecting the mixture to 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. 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 connected to the first hot high-pressure separator and the first cold high-pressure separator, respectively, 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-donating solvent obtained using the preparation method of the present invention has a high total content of monocyclic, bicyclic, and polycyclic aromatic hydrocarbons, a high hydrogen-to-carbon ratio, and a low heteroatom nitrogen content. The preparation method provided by the present invention is beneficial for increasing the partial saturation of polycyclic aromatic hydrocarbons in the hydrogen-donating solvent and increasing the amount of active hydrogen in the hydrogen-donating solvent. The preparation of a circulating hydrogen-donating solvent using the method of the present invention effectively addresses the problems of insufficient hydrogen supply capacity, low hydrogen supply efficiency, and high hydrogen consumption of existing hydrogen-donating solvents 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 high-efficiency 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 pertains. The term "and / or" as may be used herein includes any and all combinations of one or more of the related listed items. The terms "first", "second", "third", etc., are used for descriptive purposes only and are not to be understood 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 expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

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

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

[0050] (2) the mixture obtained by mixing the heavy distillate oil and the starting solvent is subjected to a first hydrogenation reaction (i.e., crude 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 resulting 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 is based on direct coal liquefaction oil and a starting solvent as raw materials, and a high-efficiency circulating hydrogen supply solvent is prepared by the method of direct coal liquefaction oil cutting and combining secondary hydrogenation. Specifically, the direct coal liquefaction oil is first fractionated, and the heavy distillate oil therein and the starting solvent (particularly the starting solvent obtained based on wash oil and anthracene oil) are mixed for crude hydrogenation, and then the first-level heavy distillate oil and the middle distillate oil obtained by 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 crude hydrogenation product and mixed as a circulating hydrogen supply solvent. The circulating solvent prepared by the process of the present invention has higher hydrogen supply performance, can significantly improve the coal conversion rate and oil yield in the direct coal liquefaction process, reduce hydrogen consumption and gas yield, and increase the economic benefit of direct coal liquefaction.

[0054] Furthermore, in step (2) of the present invention, the starting solvent is obtained by hydrogenating a mixed oil comprising wash oil and anthracene oil in coal tar fraction as a raw material. The starting solvent obtained by hydrogenating wash oil and anthracene oil contains a large amount of aromatic hydrocarbons and heteroatoms compared to 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 value-added clean utilization. The inventors have found that by adopting the method of the present invention, a circulating hydrogen supply solvent with better hydrogen supply performance can be prepared by using the starting solvent obtained based on wash oil and anthracene oil together with coal direct liquefaction oil as a raw material, thereby providing an effective way for the clean utilization of wash oil and anthracene oil. In addition, in the current 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 of insufficient utilization of wash oil and low utilization rate of wash oil in the existing technology, but also replace the gasoline and diesel fraction 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 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 may be, for example, a Mo-Ni / Al2O3 catalyst. 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. Specifically, for example, the HRK-658 catalyst produced by Axens may 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 to 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 ebullated bed reactor (referred to as "ebullated bed reactor"), preferably a forced internal circulation ebullated 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 ebullated 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 ebullated 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 subjected to crude hydrogenation. The crude hydrogenation process is more preferably carried out in a forced internal circulation ebullating bed reactor. During the crude hydrogenation process, the heavy oil product is cracked, and most of the polycyclic aromatic hydrocarbons in the structure are hydrocracking, 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). In addition, the distillation range of the heavy distillate oil in this step is relatively wide. In this hydrogenation process, particularly in the forced internal circulation ebullating bed reactor, carry out this rough hydrogenation process, starting solvent and heavy distillate are in hydrogenation process together, the starting solvent that obtains after the hydrogenation is rich in tetralin, and has removed heteroatoms, can not only replace the gasoline and diesel fraction of<350 ℃ in the direct coal liquefaction circulating solvent, improve gasoline and diesel yield, be conducive to finally obtain the circulation hydrogen supply solvent that hydrogen supply performance is excellent simultaneously. After rough hydrogenation, product separation is obtained one-level light distillate, one-level middle distillate and one-level heavy distillate, one-level heavy distillate (>350 ℃) wherein is mixed with part or all of middle distillate and carry out fine hydrogenation, and preferably carry out this fine hydrogenation process in fixed-bed reactor, be conducive to improving processing depth, make the further part saturation of aromatic ring structures such as one ring, two rings in the oil product structure. In the above process, the heavy distillate oil and the starting solvent are subjected to a crude hydrogenation and a fine hydrogenation process respectively, and the medium distillate oil is subjected to a fine hydrogenation process. On the one hand, this avoids the problem of insufficient hydrogenation of the aromatic structure and at the same time avoids the excessive hydrogenation of the aromatics in the medium distillate oil to cycloalkanes. On the other hand, it reduces the number of rings of the polycyclic aromatic hydrocarbons in the solvent structure, so that some polycyclic aromatic hydrocarbons are fully partially saturated, increases the number of active hydrogens in the heavy distillate oil and the starting solvent, and fully removes the heteroatom nitrogen in the solvent structure, 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 first medium distillate oil has a high hydrogen supply capacity, improves the solubility and dispersion ability 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 any hydrogenation catalyst commonly used by those skilled in the art in the hydrogenation process of direct 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, 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., a Mo-Ni / Al2O3 catalyst; wherein the content of Mo in the catalyst as MoO3 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 that can be obtained through commercial channels in the field, or can be prepared using the catalyst preparation technology disclosed in the prior art in the field; 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 Company, the RTC-2 catalyst of Sinopec Institute of Petroleum and Chemical Industry, etc.

[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-to-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 -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 0.7-1.5h -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 fractionating tower 120 in step (1) is 0.02 to 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 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 220 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 recycled as circulating hydrogen to enter the first hydrogenation reactor 150. In some examples, the operating temperature of the first hot high-pressure separator 160 is 250-400°C and the operating pressure is 10-21 MPa; the operating temperature of the first cold high-pressure separator 170 is 0-54°C and the operating pressure is 10-21 MPa; the operating temperature of the bottom of the second fractionation tower 220 is less than 300°C and the operating pressure is 0.02-0.2 MPa.

[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. The product obtained by the second hydrogenation reaction is separated into a third gas phase and a third liquid phase by the second hot high-pressure separator 260. The third gas phase enters the second cold high-pressure separator 270 for separation 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 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), while the secondary heavy oil is mixed with part or all of the first-stage middle distillate oil to obtain a circulating hydrogen supply solvent, the remaining middle distillate oil, the first-stage middle distillate oil, the light distillate oil, and the first-stage light distillate oil may 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 first-stage heavy distillate oil and part or all of the middle distillate oil for feeding into the second hydrogenation reactor is not particularly limited and is determined specifically 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 first-stage 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 first-level middle distillate oil in step (4), the mixing ratio of the first-level middle distillate oil is not particularly limited and is determined based on the amount of circulating hydrogen supply solvent required for the amount of coal slurry treated in 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 first-level middle distillate oil.

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

[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] a first fractionating tower 120 for fractionating the coal direct liquefaction oil to obtain light distillate oil, middle distillate oil and heavy distillate oil;

[0071] The first hydrogenation reactor 150 is configured 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;

[0072] a first separation unit, configured 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 configured to receive a mixture of the first-stage heavy distillate oil and at least a portion of the middle distillate oil, and to subject the mixture to 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 fractionating tower 120 for preheating the direct coal liquefaction oil to be input into the first fractionating 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 fractionating 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 port of the heating furnace 140 are connected by a pipeline; the feed port 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 the heavy distillate oil and the starting solvent obtained in the first fractionating 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 equipped 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 connected to the first hot high-pressure separator 160 and the first cold high-pressure separator 170, respectively, 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 to circulate at least a portion 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 a second gas phase output pipeline 171, which is provided with a compressor 107. The second gas phase output pipeline 171 is connected to the first hydrogen input pipeline 151, so that at least a portion 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. The first gas phase output from the first hot high-pressure separator 160 is cooled by the first heat exchanger 105 before entering 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 from the first hot high-pressure separator 160 and the second liquid phase output from 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 first heavy distillate oil and at least part of the middle distillate oil output from the second fractionating 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, enters the heating furnace 240 together with the hydrogen input from the second hydrogen input pipeline 251 to be heated and heated, 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 to circulate at least a portion 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 a fourth gas phase output pipeline 271, on which a compressor 108 is provided. The fourth gas phase output pipeline 271 is connected to the second hydrogen input pipeline 251, so that at least a portion 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. The third gas phase output from the second hot high-pressure separator 260 is cooled by the second heat exchanger before entering 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 with reference to 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 experiments can be carried out according to the corresponding conventional experimental steps or conditions in the art. Reagents used without specifying the manufacturer are all conventional reagents available in the art.

[0083] In the following examples, anthracene oil and wash oil from coal tar fractions were used to prepare the starting solvents, wherein the wash oil had a distillation range of 230°C (IBP) to 300°C (90%), as per national standard GB / T 24217-2009; and the anthracene oil had a distillation range of 280°C (IBP) to 360°C (50%), as per 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 above description, which will not be described in detail here.

[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, and 1.2 h. -1 Under the reaction conditions, hydrogenation was carried out using a Mo-Ni / Al2O3 catalyst (manufacturer: Axens, brand HRK-658 catalyst) to obtain a starting solvent.

[0088] The heavy distillate oil and the starting solvent were mixed in a 1:1 mass ratio and then fed into a first buffer tank 130. After being pressurized by a first high-pressure pump 101 and mixed with hydrogen, the mixture was then fed into a heating furnace 140 for heating to a temperature of 300°C at the furnace 140 outlet. The heated oil-gas mixture then entered a first hydrogenation reactor 150 (an ebullated-bed reactor) for a first hydrogenation reaction (crude hydrogenation). The reaction conditions are shown in Table 2. This reaction process includes hydrocracking to reduce the number of polycyclic aromatic hydrocarbons and heteroatom removal. 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 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 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 to form a crude hydrogenated material, which then enters the heating furnace 210. After being heated, the crude material enters the second fractionation tower 220, where it is fractionated into a first light distillate (distillation range <200°C), a first middle distillate (distillation range 200-350°C), and a first heavy distillate (distillation range >350°C).

[0090] The first-stage heavy distillate is mixed with some or all of the middle distillate and enters the second buffer tank 230. After being pressurized by the second high-pressure pump 102 and mixed with hydrogen, the mixture enters the heating furnace 240 for heating to a temperature of 300°C at the outlet of the heating furnace 240. The heated oil-gas mixture enters the second hydrogenation reactor 250 (a fixed-bed reactor) for a second hydrogenation reaction (fine hydrogenation). The reaction conditions are shown in Table 3. This further partially saturates the single-ring and double-ring aromatic ring structures in the oil product, increasing the amount of active hydrogen. 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, and 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 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 and second hydrogenation reactions are both amorphous alumina, and the active components are 20.6% MoO3 and 4.6% NiO relative to the total mass of the catalyst; specifically, the Sinopec Dalian Institute FFT-1B catalyst is used.

[0093] Example 2

[0094] The process was carried out in accordance with Example 1, except that the supports of the hydrogenation catalysts used in both the first and second hydrogenation reactions were amorphous alumina, and the active components were 21.0% MoO3 and 4.6% CoO relative to the total mass of the catalyst; specifically, Axens HR-1256 catalyst was used; and the reaction conditions for the first and second hydrogenation reactions in Example 2 were shown in Tables 2 and 3, respectively.

[0095] Example 3

[0096] The same method as in Example 1 was used except that the carrier of the hydrogenation catalyst used in both the first and second hydrogenation reactions was amorphous alumina, and the active components were 33.0% WO3 and 5.0% NiO relative to the total mass of the catalyst. Specifically, the RTC-2 catalyst of the Sinopec Institute of Petroleum and Chemical Industry was used. The reaction conditions of the first and second hydrogenation reactions in Example 3 are shown in Tables 2 and 3, respectively.

[0097] Example 4

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

[0099] Example 5

[0100] The process was carried out with reference to Example 1, except that the reactor used in the first hydrogenation reaction (crude hydrogenation) was a fixed bed reactor, and the reactor used in the second hydrogenation reaction (fine hydrogenation) was 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 by the second distillation tower 220 is directly mixed with part or all of the first-stage middle distillate oil to obtain a high-efficiency circulating hydrogen supply solvent for direct coal liquefaction.

[0103] Comparative Example 2

[0104] Compared with Example 1, other conditions remained unchanged, with the following differences: the coal direct liquefaction oil was not passed through the heating furnace 110 and the first fractionating tower 120, but was directly mixed with the starting solvent at a mass ratio of 1:1 before entering the first buffer tank 130 for subsequent reactions. The first-stage heavy distillate oil obtained in the second fractionating tower 220 was directly passed into the second buffer tank 230 for subsequent reactions; and the resulting second-stage heavy oil was mixed with part or all of the first-stage middle distillate oil to obtain a high-efficiency circulating hydrogen supply solvent for direct coal liquefaction.

[0105] Comparative Example 3

[0106] Compared to Example 1, all other conditions remained unchanged, with the exception that the heavy distillate oil obtained by direct coal liquefaction through the heating furnace 110 and the first fractionating tower 120 was directly fed into the first buffer tank 130 without introducing the starting solvent for subsequent reactions. Specifically, the weight ratio of the heavy distillate oil to the starting solvent was 1:0. All other procedures were carried out in the same manner as in 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 (crude 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 (crude 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] As can be seen from the data in Table 4, compared with Comparative Examples 1-2, Examples 1-5 of the present invention have a higher content of monocyclic and bicyclic aromatic hydrocarbons in the hydrogen-donating solvents obtained by the preparation method of the present invention, while taking into account a relatively high total content of polycyclic aromatic hydrocarbons, a higher hydrogen-carbon ratio, and a lower heteroatom N content. This indicates that the solvent prepared by the present invention is more suitable for use as a hydrogen-donating solvent for direct coal liquefaction. The preparation method provided by the present invention is beneficial to increasing the partial saturation of polycyclic aromatic hydrocarbons in the hydrogen-donating solvent and increasing the amount of active hydrogen in the hydrogen-donating solvent.

[0120] Comparison of Example 1 and Examples 2-5 shows that the total content of monocyclic, bicyclic, and polycyclic aromatic hydrocarbons in the hydrogen donor solvent prepared in Example 1 using the preferred first and second hydrogenation reactors is significantly higher than that in Examples 2-5, and the hydrogen-to-carbon ratio is also higher than that in Examples 2-5. Using an ebullating bed reactor for the first hydrogenation reaction and a fixed bed reactor for the second hydrogenation reaction facilitates obtaining a hydrogen donor solvent with superior 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 direct coal liquefaction test are shown in Table 5. The process conditions for the autoclave direct coal liquefaction test were as follows: a 0.5-liter stirred autoclave was used, 28 g of dry coal was loaded into the autoclave, a circulating solvent to coal mass ratio of 1.5:1, an initial hydrogen pressure of 10.0 MPa, an iron-based catalyst with an Fe addition of 1% of the dry coal mass fraction, and sulfur as a co-catalyst with an n(S) / n(Fe) ratio of 2. After heating to a reaction temperature of 455°C, the temperature was maintained constant for 60 minutes.

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

[0124] The n-hexane-soluble matter is defined as oil, the n-hexane-insoluble and THF-soluble matter is defined as asphaltenes and pre-asphaltenes (referred to as asphaltenes), 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 coal liquefaction test 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] The experimental results in Table 6 demonstrate that the circulating solvent prepared by the present method facilitates coal conversion during the direct coal liquefaction reaction, increasing the oil yield and reducing gas yield and hydrogen consumption. Its excellent direct coal liquefaction performance demonstrates that the circulating solvent prepared by the present method has a high hydrogen supply capacity and ability to disperse coal and coal pyrolysis free radicals.

[0131] Through the above-mentioned experiment, it can be seen that the scheme of the present invention has achieved the following technical effects: after cutting and combining secondary catalytic hydrogenation with coal direct liquefaction oil and starting solvent as raw materials, a high-efficiency circulating hydrogen-supply solvent for coal direct liquefaction is prepared, which can effectively solve the problems of insufficient hydrogen supply capacity, low hydrogen supply efficiency and high hydrogen consumption of existing hydrogen-supply solvents 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 circulating hydrogen-supply solvent for coal direct liquefaction without changing the existing coal direct liquefaction process flow, thereby achieving the purpose of improving the hydrogen supply capacity of the circulating solvent, and then improving the economic benefit of the overall direct coal liquefaction process. In the preferred embodiment, using coal direct liquefaction oil and starting solvent as raw materials, a boiling bed-fixed bed is adopted to carry out 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 will be readily understood that the above embodiments are merely examples for clarity of description and are not intended to limit the present invention to these examples. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to provide an exhaustive list of all possible implementations. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a high-efficiency circulating hydrogen supply solvent for direct coal liquefaction, characterized in that: The steps include: (1) fractionating the coal direct liquefaction oil in a first fractionating tower to obtain a light distillate oil, a middle distillate oil, and a heavy distillate oil; 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; (2) subjecting the heavy distillate oil and the starting solvent to a first hydrogenation reaction in a first hydrogenation reactor to a mixture obtained by mixing the heavy distillate oil and the starting solvent, 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; the starting solvent is obtained by hydrogenating a mixed oil comprising wash oil and anthracene oil in coal tar distillate oil; the distillation ranges of the first light distillate oil, the first middle distillate oil, and the first heavy distillate oil are respectively <200°C, 200-350°C, and >350°C; (3) mixing the first-stage 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 resulting product to a second separation unit for separation to obtain a second 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 mass ratio of the wash oil to the anthracene oil is 0.5-1.5:1; And / or, 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 ; And / or, the hydrogenation catalyst used to prepare the starting solvent includes a carrier and an active component, and the active component includes MoO3 and NiO.

3. The preparation method according to claim 2, characterized in that In step (2), the mass ratio of the wash oil to the anthracene oil is 1:1; and / or, in the hydrogenation catalyst used to prepare the starting solvent, 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; And / or, in the hydrogenation catalyst used to prepare the starting solvent, the carrier is Al2O3.

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

5.

5. 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; 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.

6. The preparation method according to any one of claims 1 to 3, 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 silicate.

7. The preparation method according to claim 6, characterized in that 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; And / or, in the hydrogenation catalyst used in the first hydrogenation reaction in step (2) and / or the second hydrogenation reaction in step (3), the carrier is selected from amorphous alumina and / or aluminum silicate.

8. The preparation method according to claim 6, 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 components are Mo and Ni, and the carrier is amorphous alumina.

9. The preparation method according to any one of claims 1 to 3, characterized in that In step (2), the reaction conditions of the first hydrogenation reaction include: operating pressure of 5-30 MPa, operating temperature of 290-390 °C, hydrogen-to-oil volume ratio of 100-1000, volume space velocity of 0.5-2.0 h -1 ; And / or, in step (3), the reaction conditions of the second hydrogenation reaction include: operating pressure of 8-30 MPa, operating temperature of 300-420 °C, hydrogen-to-oil volume ratio of 100-1500, volume space velocity of 0.5-2.0 h -1 .

10. The preparation method according to claim 9, characterized in that In step (2), the reaction conditions of the first hydrogenation reaction include: operating pressure of 10-21 MPa, operating temperature of 320-370 °C, hydrogen-to-oil volume ratio of 300-600, volume space velocity of 0.7-1.5 h -1 ; And / or, in step (3), the reaction conditions of the second hydrogenation reaction include: operating pressure of 15-21 MPa, operating temperature of 340-400 °C, hydrogen-to-oil volume ratio of 300-800, volume space velocity of 0.7-1.5 h -1 .

11. The preparation method according to any one of claims 1 to 3, characterized in that: In step (1), the coal direct liquefaction oil is coal direct liquefaction full distillate oil.

12. The preparation method according to any one of claims 1 to 3, characterized in that: In step (2), the first separation unit includes 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-level light distillate oil, the first-level middle distillate oil, and the first-level heavy distillate oil; 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.

13. The preparation method according to claim 12, characterized in that In step (2), at least a portion of the second gas phase is circulated into the first hydrogenation reactor; And / or, in step (3), at least a portion of the fourth gas phase is circulated into the second hydrogenation reactor.

14. 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 3, characterized in that: The system comprises: a first fractionating tower for fractionating the coal direct liquefaction oil to obtain light distillate oil, middle distillate oil and heavy distillate oil; a first hydrogenation reactor for receiving a mixture of the heavy distillate oil and the starting solvent and causing the mixture to undergo a first hydrogenation reaction with hydrogen to obtain a first hydrogenated product; a first separation unit, configured 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 for receiving a mixture of the first-stage heavy distillate oil and at least a portion of the middle distillate oil, and subjecting the mixture to 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. 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.

15. The preparation system according to claim 14, characterized in that: 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 connected to the first hot high-pressure separator and the first cold high-pressure separator, respectively, 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; 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.

16. The preparation system according to claim 15, characterized in that: The gas phase outlet of the first cold high-pressure separator is in communication with the first hydrogenation reactor so as to circulate at least a portion of the second gas phase into the first hydrogenation reactor; And / or, 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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