Preparation method and system of coal-based heat conduction oil

Abstract

The invention relates to the field of coal liquefaction, in particular to a preparation method and system of coal-based heat-conducting oil, coal-oil slurry is prepared by mixing pulverized coal and a hydrogen-donating solvent, and the coal-based heat-conducting oil is finally prepared by the steps of direct coal liquefaction, hydrotreating, two-time oil-gas separation, light and heavy component separation, steam stripping rectification, reduced pressure distillation and the like in sequence. The invention also provides a corresponding preparation system which integrates core equipment such as a mixing tank, a coal liquefaction reactor, a hydrogenation reactor, a fractionating tower, an oil-gas separator, a light-heavy separator, a stripping tower and a vacuum tower. A new process route for preparing the heat conduction oil is developed, a traditional preparation method for generating the heat conduction oil by extracting aromatic hydrocarbon from petroleum-based light oil through catalytic cracking is broken through, and the obtained heat conduction oil has high initial boiling point and flash point and stable heat conduction capability at high temperature.

Description

Technical Field

[0001] The invention relates to the field of coal liquefaction, and in particular to a method and system for preparing coal-based heat transfer oil. Background Art

[0002] Traditional heat transfer oil is usually petroleum-based heat transfer oil, which is mainly made from petroleum-based raw materials through catalytic cracking. Its main components are diaryl alkanes and have specific physical and chemical properties (density is about 1026-1030kg / m 3 , flash point is about 170-175℃, kinematic viscosity is about 27.5-33.7mm 2 / s, distillation range is about 320-370℃). However, there are two major problems in the application of the heat transfer oil: one is that the heat transfer oil brand is scarce and the output is limited; the other is that the petroleum-based heat transfer oil prepared by the traditional process is easy to lighten at high temperature, resulting in the pump being evacuated, the outlet flow of the pump fluctuates greatly, affecting the uniformity of the heat transfer of the heat transfer oil, and the heat transfer oil system needs to frequently remove light hydrocarbons, which poses a risk of scalding and heat transfer oil loss.

[0003] In view of the abundance of my country's coal resources and the increasing maturity of coal-to-liquids technology, especially the remarkable achievements in the development of coal-based special oils, the preparation of coal-based heat transfer oil has become a new way to solve the above problems.

[0004] However, the development of coal-based thermal oil is still in its infancy, and an efficient and economical preparation method and system are urgently needed to broaden the application scope of coal-to-oil products, enhance the utilization value of coal, and alleviate dependence on imported thermal oil. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of insufficient high-temperature stability of heat transfer oil prepared by traditional processes, and to provide a method and system for preparing coal-based heat transfer oil.

[0006] In order to achieve the above object, the first aspect of the present invention provides a method for preparing coal-based thermal oil, comprising the following steps:

[0007] (S1) mixing coal powder and hydrogen supply solvent to prepare oil-coal slurry;

[0008] (S2) subjecting the oil-coal slurry to a direct coal liquefaction reaction to obtain a coal liquefaction product;

[0009] (S3) separating the coal liquefaction product into gas, liquid and solid three phases, and performing atmospheric and vacuum distillation on the obtained liquid phase components to obtain a coal-based crude oil product;

[0010] (S4) subjecting the coal-based crude oil product to hydrogenation treatment to obtain a hydrogenation product;

[0011] (S5) performing a first oil-gas separation on the hydrogenation product to obtain a first gas phase component and a first liquid phase component;

[0012] (S6) performing a second oil-gas separation on the first gas phase component to obtain a second liquid phase component;

[0013] (S7) performing a third light-heavy separation on the first liquid phase component to obtain a third light component and a third heavy component;

[0014] (S8) performing a fourth oil-gas separation on the third light component and the second liquid phase component to obtain a fourth liquid phase component;

[0015] (S9) subjecting the third heavy component and the fourth liquid phase component to a fifth stripping distillation to obtain a fifth heavy component;

[0016] (S10) The fifth heavy component is subjected to a sixth reduced pressure distillation to obtain coal-based heat transfer oil.

[0017] A second aspect of the present invention provides a system for the preparation method, the system comprising:

[0018] A mixing tank, used to mix coal powder with hydrogen supply solvent to prepare oil-coal slurry;

[0019] A coal liquefaction reactor, used for subjecting the oil-coal slurry to a direct coal liquefaction reaction to obtain a coal liquefaction product;

[0020] A constant pressure reduction tower, used for performing constant pressure reduction fractionation on the coal liquefaction product to obtain a coal-based crude oil product;

[0021] Buffer tank for storing and stabilizing the coal-based crude oil product

[0022] A hydrogenation reactor, used for hydrogenating the coal-based crude oil product to obtain a hydrogenated product;

[0023] A thermal high fractionator is used to perform a first oil-gas separation on the hydrogenation product to obtain a first gas phase component and a first liquid phase component;

[0024] Cold high separation, used for performing a second oil-gas separation on the first gas phase component to obtain a second gas phase component and a second liquid phase component;

[0025] A hot low fraction is used to perform a third light-heavy separation on the first liquid phase component to obtain a third light component and a third heavy component;

[0026] Cold low fractionation, used for performing a fourth oil-gas separation on the third light component and the second liquid phase component to obtain a fourth liquid phase component;

[0027] a stripping tower, used for performing a fifth stripping distillation on the third heavy component and the fourth liquid phase component to obtain a fifth heavy component;

[0028] The vacuum tower is used to perform a sixth vacuum distillation on the fifth heavy component to obtain coal-based heat transfer oil.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention uses crude oil generated by direct liquefaction of coal as raw material to prepare coal-based heat transfer oil. Coal is directly liquefied under high temperature and high pressure, primary hydrogenation and iron-based catalyst to generate coal-based crude oil. After high temperature and high pressure, secondary hydrogenation, desulfurization, denitrification and partial aromatic saturation under the action of nickel-molybdenum catalyst, it is fractionated and decompressed to obtain 325-420°C fraction. The prepared coal-based heat transfer oil has the characteristics of high thermal stability, high density, high reliability, non-corrosiveness, strong anti-coking and the like, and is suitable for conducting heat under high temperature conditions.

[0031] Second, the present invention develops a new process route for the preparation of heat transfer oil, breaking the traditional preparation method of generating heat transfer oil by extracting aromatics from petroleum-based light oil through catalytic cracking, reducing the main reliance on foreign imports of heat transfer oil, and solving the problems of high price and long supply cycle of heat transfer oil.

[0032] 3. The method and system of the present invention are stable and easy to operate in production. They are also applicable to the production of other special oils (such as sealing oil and solvent oil) with high utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A process flow chart for preparing coal-based thermal oil provided by the present invention; wherein:

[0034] 1-hot high fractionator, 2-cold high fractionator, 3-hot low fractionator, 4-cold low fractionator, 5-stripping tower, 6-pressure reducing tower, 7-mixing tank, 8-coal liquefaction reactor, 9-normal and low pressure tower, 10-buffer tank, 11-hydrogenation reactor, 12-first heat exchanger, 13-reaction heating furnace, 14-fractionation heating furnace, 15-second heat exchanger, 16-third heat exchanger, 17-reduction pump, 18-fourth heat exchanger, 19-hydrogen circulation machine. DETAILED DESCRIPTION

[0035] The present invention is further described below, but is not limited to the following embodiments. Changes made by ordinary technicians in this field based on the embodiments are still within the scope of protection of this patent.

[0036] The first aspect of the present invention provides a method for preparing coal-based thermal oil, comprising the following steps:

[0037] (S1) mixing coal powder and hydrogen supply solvent to prepare oil-coal slurry;

[0038] (S2) subjecting the oil-coal slurry to a direct coal liquefaction reaction to obtain a coal liquefaction product;

[0039] (S3) separating the coal liquefaction product into gas, liquid and solid three phases, and performing atmospheric and vacuum distillation on the obtained liquid phase components to obtain a coal-based crude oil product;

[0040] (S4) subjecting the coal-based crude oil product to hydrogenation treatment to obtain a hydrogenation product;

[0041] (S5) subjecting the hydrogenation product to a first oil-gas separation at high temperature and high pressure to obtain a first gas phase component and a first liquid phase component;

[0042] (S6) subjecting the first gas phase component to a second oil-gas separation at low temperature and high pressure to obtain a second liquid phase component;

[0043] (S7) subjecting the first liquid phase component to a third light-heavy separation at high temperature and low pressure to obtain a third light component and a third heavy component;

[0044] (S8) performing a fourth oil-gas separation at low temperature and low pressure on the third light component and the second liquid phase component to obtain a fourth liquid phase component;

[0045] (S9) subjecting the third heavy component and the fourth liquid phase component to a fifth stripping distillation to obtain a fifth heavy component;

[0046] (S10) The fifth heavy component is subjected to a sixth reduced pressure distillation to obtain coal-based heat transfer oil.

[0047] In the present invention, the steps (S5) to (S8) are a step-by-step separation process, wherein the high temperature can be 370-375°C, the low temperature can be 50-60°C, the high pressure can be 13.1-13.3MPa, and the low pressure can be 2.5-2.7MPa. This separation process ensures that the liquid and gas components of different distillation ranges are completely separated by multiple temperature and pressure reduction treatments, thereby obtaining the desired recombinant oil product, namely the coal-based heat transfer oil.

[0048] In step (S1), the coal powder and the hydrogen supply solvent are uniformly mixed under the action of a stirrer to form a liquid with high fluidity, namely the oil-coal slurry.

[0049] Furthermore, the coal powder can be selected from at least one of lignite, sub-bituminous coal, bituminous coal and anthracite, and its particle size distribution is as follows: particles smaller than 74 μm account for ≥80%, particles smaller than 5 μm account for ≤5%, and the moisture content of the coal powder is ≤4wt%, and the ash content is ≤6wt%;

[0050] Further, the hydrogen supply solvent may be selected from at least one of coal tar, anthracene oil, and coal liquefaction aromatic oil, and its amount is 0.8-1.2 times the weight of the coal powder to form an oil-coal slurry containing 45-55wt% coal;

[0051] Furthermore, the mixing temperature may be 185-190° C., and the pressure may be slightly negative pressure, for example, less than -0.2 kPa.

[0052] In step (S2), the oil-coal slurry is mixed with liquid sulfur, hydrogen, and a catalyst to form a mixture, and then the mixture is subjected to a coal direct liquefaction reaction to obtain a coal liquefaction product. That is, coal is cracked and hydrogenated under high temperature and high pressure to obtain a product containing three phases of gas, liquid, and solid. In some embodiments, the conditions of the coal direct liquefaction reaction include:

[0053] Liquid sulfur is liquid sulfur, which can react with iron oxyhydroxide to produce Fe7S8, play the role of forming a catalyst, and also have the function of regulating the hydrogen sulfide content in the reaction system.

[0054] The iron-based catalyst may be iron oxide, ferroferric oxide, or iron oxyhydroxide, and the amount used may be 1 wt% of the coal powder;

[0055] The amount of liquid sulfur used is such that the hydrogen sulfide content in the reaction system is 1000-2500 ppm;

[0056] The amount of hydrogen used is such that the hydrogen content in the reaction system is above 86%;

[0057] The reaction temperature is 450-458°C;

[0058] The reaction pressure is 18.6-18.8MPa;

[0059] The reaction time is 1.5-2h.

[0060] In some embodiments, in step (S2), the temperature of the mixture before the direct coal liquefaction reaction is 365-375°C, that is, it can be preheated to 365-375°C in advance.

[0061] In some embodiments, in step (S3), the coal liquefaction product is subjected to multiple cooling and decompression to obtain a liquid phase component and a gas phase component. In addition, the atmospheric and vacuum fractionation can be to gradually reduce the pressure of the liquid phase component from 0.1-2MPa to 0.3-0.5kPa to obtain a liquid coal-based crude oil product with a distillation range of 270-420°C and a density greater than 995kg / m 3 , the total aromatic content is greater than 85%.

[0062] In step (S4), the hydroprocessing refers to mixing the coal-based crude oil with hydrogen to form a hydrogenated oil. In a fluidized bed or suspended bed reactor in the present field, the hydrogenated oil is hydroprocessed in a reaction system containing a nickel-based and / or molybdenum-based catalyst.

[0063] In some embodiments, in step (S4), the temperature of the mixed hydrogen oil before the hydrogenation treatment is 310-320° C. and the pressure is 14.1-14.3 MPa.

[0064] In some embodiments, in step (S4), the hydroprocessing can obtain a gas-liquid two-phase product having a cycloalkane content of ≥80% and a sulfur and nitrogen content of ≤0.5 ppm, namely, the hydrogenated product.

[0065] Furthermore, the conditions of the hydrotreatment include:

[0066] The amount of hydrogen used is such that the hydrogen content in the reaction system is above 91% (full load is 75,000 Nm 3 / h);

[0067] The reaction temperature is 378-385°C;

[0068] The reaction pressure is 13.1-13.5MPa;

[0069] The reaction time is 1.2-1.5h.

[0070] The inventors have found that the hydroprocessing can remove heteroatoms such as sulfur, nitrogen, oxygen and metal impurities in the coal-based crude oil. In addition, the hydroprocessing also includes the saturation reaction of some olefins and diolefins in the coal-based crude oil, and the dealkylation of monocyclic cycloalkanes, followed by isomerization into light isoparaffins and cycloalkanes with lower molecular weights, and then the oil in the reactor is circulated by a circulating pump at the bottom of the reactor to ensure that the catalyst bed forms a boiling state.

[0071] In step (S5), the hydrogenation product is subjected to a first oil-gas separation in a hot high-pressure separator in the art, and a first gas phase component is discharged from the top of the hot high-pressure separator, whose main components are light oil and hydrogen, and a first liquid phase component flows out from the bottom of the hot high-pressure separator, whose main components are aromatics (or polycyclic aromatics) and cycloalkanes.

[0072] In some embodiments, in step (S5), the conditions for the first oil-gas separation include: a temperature of 370-375°C and a pressure of 13.2-13.5 MPa. That is, the first gas phase component is collected at a temperature of 370-375°C and a pressure of 13.1-13.3 MPa, and the first liquid phase component is collected at a temperature of 370-375°C and a pressure of 2.5-2.7 MPa.

[0073] In step (S6), in the cold high-pressure separator of the present invention, the first gas phase component is subjected to a second oil-gas separation to separate and recover hydrogen in the first gas phase component, i.e., the second gas phase component; and liquid light oil, i.e., the second liquid phase component, is obtained at the same time. In some embodiments, the conditions for the second oil-gas separation include: a temperature of 50-60°C and a pressure of 13.3MPa.

[0074] In some embodiments, in step (S6), the hydrogen content in the second gas phase component is greater than 91%, the total content of carbon monoxide and carbon dioxide is less than 30 ppm, and the hydrogen sulfide content is 100-500 ppm, which can be recovered as circulating hydrogen, and can also be used for the above-mentioned hydrogen supply solvent or the second hydrogenation treatment.

[0075] In step (S7), in the hot low-pressure separator of the art, the first liquid phase component is subjected to a third light-heavy separation, and light oil, i.e., the third light component, is obtained from the top of the hot low-pressure separator; and heavy oil, i.e., the third heavy component, is discharged from the bottom of the hot low-pressure separator. The third light-heavy separation can ensure that the third heavy component is heavier, thereby ensuring that there is no light component in the heat transfer oil.

[0076] In some embodiments, in step (S7), the conditions for the third light-heavy separation include: a temperature of 370-375° C. and a pressure of 2.5-2.7 MPa.

[0077] It is worth noting that step (S6) and step (S7) are respectively used to separate the gas phase component and the liquid phase component obtained in step (S5), so their order can be selected according to the actual process conditions.

[0078] In step (S8), in the cold low-pressure separator of the present invention, the third light component and the second liquid phase component are subjected to a fourth oil-gas separation (i.e., deep oil-gas separation) to obtain a fourth liquid phase component. In addition, a fourth gas phase component can also be obtained at the same time, the main component of which is C 1-3 and sulfur-containing gases can be sent to the downstream desulfurization treatment device to recover C 1-3 .

[0079] Furthermore, the third light component and the second liquid phase component may be mixed in advance before the fourth oil-gas separation and enter the cold low-pressure separator in the form of a mixture; or may not be mixed in advance and enter the cold low-pressure separator separately.

[0080] In some embodiments, in step (S8), the conditions for the fourth oil-gas separation include: a temperature of 50-60°C and a pressure of 2.5-2.7 MPa.

[0081] In step (S9), in a fractionation tower in the field, the third heavy component and the fourth liquid phase component are subjected to a fifth stripping distillation to remove light components (i.e., to further ensure that there are no light components in the heat transfer oil), to obtain a fifth heavy component, the main component of which is aromatic oil. In some embodiments, the initial boiling point of the fifth heavy component is greater than 260°C and the density is greater than 995kg / m 3 .

[0082] In some embodiments, in step (S9), the conditions of the fifth stripping distillation include:

[0083] The working temperature is 350-360℃,

[0084] Working pressure is 0.11-0.15MPa,

[0085] The pressure of the stripping steam used is 1.1-1.3 MPa.

[0086] In some embodiments, in step (S9), the third heavy component is heated to 340-360° C. before the fifth stripping distillation, and the fourth liquid component is heat exchanged to 120-170° C. before the fifth stripping distillation;

[0087] Furthermore, the third heavy component and the fourth liquid phase component may be mixed in advance before the fifth stripping and rectification and enter the fractionation tower in the form of a mixture; or they may not be mixed in advance and enter the fractionation tower separately;

[0088] In some embodiments, in step (S9), the third heavy component and the fourth liquid phase component enter the lower part and the middle part of the fractionation tower respectively, and then steam is introduced into the bottom of the fractionation tower to perform a fifth stripping distillation.

[0089] In some embodiments, in step (S9), in addition to the fifth heavy component, the fifth stripping distillation can also obtain a fifth light component and a fifth medium component, wherein:

[0090] The fifth light component is mainly composed of C 1-6 and water vapor, which can be sent to the light hydrocarbon recovery unit after cooling and separation;

[0091] The fifth component mainly consists of diesel and naphtha, and can be sent to a downstream hydro-reforming unit.

[0092] In step (S10), in the vacuum tower of the present invention, the fifth heavy component is subjected to a sixth vacuum distillation to obtain a sixth heavy component collected at the bottom of the tower; at the same time, a sixth light component (mainly a small amount of light oil and hydrogen) can be obtained at the top of the tower and sent to a downstream light hydrocarbon recovery device after cooling.

[0093] In some embodiments, in step (S10), the conditions of the sixth reduced pressure distillation include: a temperature of 380-390°C and a pressure of 0.5-0.8 kPa.

[0094] In some embodiments, in step (S10), the fifth heavy component may be heat-exchanged to 370-390° C. before being subjected to the sixth reduced-pressure distillation.

[0095] In some embodiments, a portion of the sixth heavy component is used as the coal-based heat transfer oil of the present invention, and the other portion is mixed with the fifth heavy component after heat exchange, and the sixth vacuum distillation in step (S10) is repeated.

[0096] Furthermore, the temperature of the sixth heavy component after heat exchange may be 370-390°C.

[0097] In some embodiments, the coal-based heat transfer oil has high initial boiling point stability, and its initial boiling point reaches 322-328°C, ensuring that it does not vaporize at low temperatures, avoiding gas blockage, and ensuring stable operation of the delivery pump and uniform heat conduction. The coal-based heat transfer oil also has strong thermal stability, with an aromatic content of 74-77% and a total content of aromatics and cycloalkanes of 85-90%, which makes the oil stable for a long time at high temperatures and not easy to deteriorate. The coal-based heat transfer oil also has high density and compressibility, with a density of 1038-1043kg / m 3 This indicates that the oil has large molecules and a high expansion coefficient at high temperatures, meeting the requirements for efficient heat conduction. The coal-based heat transfer oil also has excellent fluidity, with a kinematic viscosity of 31-33 mm 2 / s, which indicates that the oil has good fluidity after heating, ensuring smooth operation of the system. The coal-based heat transfer oil is also highly safe, with a flash point of 194-197°C. Compared with petroleum-based heat transfer oil, it can significantly improve the safety of use and ensure worry-free operation.

[0098] As attached Figure 1 As shown, the second aspect of the present invention provides a system for the preparation method, the system comprising:

[0099] A mixing tank (7) is used to mix the coal powder and the hydrogen supply solvent to prepare an oil-coal slurry;

[0100] A coal liquefaction reactor (8) is used to subject the oil-coal slurry to a direct coal liquefaction reaction to obtain a coal liquefaction product;

[0101] A constant pressure reduction tower (9) is used to perform constant pressure reduction fractionation on the coal liquefaction product to obtain a coal-based crude oil product;

[0102] A buffer tank (10) for storing and stabilizing the coal-based crude oil product;

[0103] A hydrogenation reactor (11) is used to perform hydrogenation treatment on the coal-based crude oil product to obtain a hydrogenation product;

[0104] A thermal high fractionator (1) is used to perform a first oil-gas separation on the hydrogenation product to obtain a first gas phase component at the top of the tower and a first liquid phase component at the bottom of the tower;

[0105] A cold high fraction (2) is used to perform a second oil-gas separation on the first gas phase component to obtain a second gas phase component at the top of the tower and a second liquid phase component at the bottom of the tower;

[0106] A hot low fraction (3) is used to perform a third light-heavy separation on the first liquid phase component to obtain a third light component at the top of the tower and a third heavy component at the bottom of the tower;

[0107] Cold low fraction (4), used for performing a fourth oil-gas separation on the third light component and the second liquid phase component to obtain a fourth liquid phase component;

[0108] A stripping tower (5), used for performing a fifth stripping distillation on the third heavy component and the fourth liquid phase component to obtain a fifth heavy component located at the bottom of the tower;

[0109] The vacuum tower (6) is used to perform a sixth vacuum distillation on the fifth heavy component to obtain coal-based heat transfer oil at the bottom of the tower.

[0110] In some embodiments, the oil-coal slurry obtained in the mixing tank (7) is subjected to heat exchange in the first heat exchanger (12) and then enters the coal liquefaction reactor (8).

[0111] In some embodiments, the coal-based crude oil stored in the buffer tank (10) is mixed with hydrogen to form a hydrogenated oil, which is heated by a reaction heating furnace (13) and then enters a hydrogenation reactor (11) for a hydrogenation reaction;

[0112] The hydrogen can be new hydrogen introduced from outside, or can be hydrogen from a hydrogen circulation machine (19), that is, the second gas phase component obtained from the cold high fraction (2).

[0113] In some embodiments, the third heavy component obtained from the bottom of the hot low fraction (3) is heated by a fractionation heating furnace (14) and then enters the stripping tower (5) from the bottom of the stripping tower (5); and the fourth liquid phase component obtained from the cold low fraction (4) is heat exchanged in a second heat exchanger (15) and then enters the stripping tower (5) from the middle of the stripping tower (5).

[0114] Furthermore, the fourth gas phase component obtained from the cold low fraction (4) has C 1-3 and sulfur-containing gases can be sent to the downstream desulfurization treatment device to recover C 1-3 (Not shown in the attached figure).

[0115] In some embodiments, the fifth light component obtained from the top of the stripping tower (5) is sent to a light hydrocarbon recovery unit for recovery after cooling and separation; the fifth middle component obtained from the side line of the stripping tower (5) is sent to a downstream hydrogenation reforming unit for recovery; the fifth heavy component obtained from the bottom of the stripping tower (5) is heat exchanged using a third heat exchanger (16) and then enters a pressure reducing tower (6).

[0116] In some embodiments, the sixth light component obtained from the top of the vacuum tower (6) is sent to a downstream light hydrocarbon recovery device for recovery after cooling; and the sixth heavy component is obtained from the bottom of the vacuum tower (6).

[0117] Furthermore, a portion of the sixth heavy component is sent to a downstream storage device through a reducing pump (17) for storage as the coal-based heat transfer oil of the present invention; the remaining portion is heat exchanged using a fourth heat exchanger (18), and then returned to the vacuum tower (6) to participate in the sixth vacuum distillation again.

[0118] In this article, the initial distillation point refers to the temperature recorded at the moment when the first drop of condensate of the coal-based heat transfer oil falls from the end of the condenser when measuring the distillation range of the coal-based heat transfer oil, and the same applies to the distillation temperatures of 10%, 70% and 90%;

[0119] The aromatic hydrocarbon content and cycloalkane content are measured by an element analyzer;

[0120] The density is measured by an automatic density meter;

[0121] The kinematic viscosity is measured by GB / T265-1998 method;

[0122] The flash point is measured by GB / T 261 method.

[0123] The present invention will be further described in detail below through specific examples.

[0124] The coal powder is bituminous coal with a moisture content of 4% and 80% of the particles having a diameter less than 74 μm.

[0125] The hydrogen-donating solvent is obtained by mixing coal tar and anthracene oil in a weight ratio of 3:1.

[0126] Example 1

[0127] (S1) In a mixing tank (7), at a temperature of 185°C and a pressure of -0.2 kPa, coal powder (in an amount of 256 t / h) and a hydrogen supply solvent (in an amount of 300 t / h, i.e., 1.2 times the weight of the coal powder) are mixed to prepare an oil-coal slurry with a coal content of 50%; wherein:

[0128] (S2) In a mixing tank (7), the oil-coal slurry is mixed with liquid sulfur (2 t / h) and hydrogen (330,000 Nm 3 / h), ferric hydroxide (dosage is 2.5t / h) are mixed to form a mixture, the mixture is heat exchanged to 370°C using a first heat exchanger (12) and then sent to a coal liquefaction reactor (8), where a direct coal liquefaction reaction is carried out under the reaction conditions of a temperature of 455°C, a pressure of 18.6MPa and a time of 1.5h to obtain a coal liquefaction product.

[0129] (S3) separating the gas, liquid and solid three-phases of the coal liquefaction product to obtain a liquid product (temperature of 371°C and pressure of 2.6MPa); in a constant pressure reduction tower (9), reducing the pressure of the liquid product from 0.15MPa to 0.5kPa to obtain a liquid coal-based crude oil product with a distillation range of 270-420°C.

[0130] (S4) mixing the coal-based crude oil with hydrogen to obtain a hydrogenated oil, and heating the hydrogenated oil to a temperature of 315° C. and a pressure of 14.2 MPa using a reaction heating furnace (13), and hydrogenating the coal-based crude oil in a hydrogenation reactor (11) at a temperature of 380° C., a pressure of 13.2 MPa, a time of 1.3 h, and a catalyst of nickel oxide and molybdenum trioxide to obtain a hydrogenated product; wherein:

[0131] The hydrogen required for the hydrogenation reaction (temperature 176°C, pressure 14.7 MPa, amount 140,000 Nm 3 / h) is a mixture of the second gas phase component from the hydrogen circulation machine (19) and new hydrogen.

[0132] (S5) in the hot high fraction (1), at a temperature of 373° C. and a pressure of 13.1 MPa, the hydrogenation product is subjected to a first oil-gas separation, and a first gas phase component and a first liquid phase component are obtained at the bottom and the bottom of the hot high fraction (1), respectively; wherein,

[0133] The first gas phase component enters the cold high fraction (2),

[0134] The first liquid phase component enters the hot low fraction (3).

[0135] (S6) in the cold high fraction (2), at a temperature of 60° C. and a pressure of 13.1 MPa, subjecting the first gas phase component to a second oil-gas separation, and obtaining a second gas phase component and a second liquid phase component at the top and bottom of the cold high fraction (2), respectively;

[0136] The second gas phase component is used in step (S4) through a hydrogen circulation machine (19),

[0137] The second liquid phase component enters the cold low fraction (4).

[0138] (S7) In the hot low fraction (3), the first liquid phase component is subjected to a third light-heavy separation at a temperature of 375° C. and a pressure of 2.7 MPa, and a third light component and a third heavy component are obtained at the top and bottom of the hot low fraction (3), respectively; wherein:

[0139] The third light component enters the cold low fraction (4),

[0140] The third heavy component is heated to 350° C. in the fractionation heating furnace (14) and then enters the bottom of the stripping tower (5).

[0141] (S8) In the cold low fraction (4), the third light component and the second liquid phase component are subjected to a fourth oil-gas separation under the conditions of a temperature of 50° C. and a pressure of 2.7 MPa, and a fourth gas phase component and a fourth liquid phase component are obtained at the top and the bottom of the cold low fraction (4), respectively; wherein,

[0142] The fourth gas phase component is sent to the downstream desulfurization treatment device to recover C 1-3 ,

[0143] The fourth liquid phase component is heated to 120° C. in the second heat exchanger ( 15 ) and then enters the side line of the stripping tower ( 5 ).

[0144] (S9) After the third heavy component and the fourth liquid component enter the stripping tower (5), stripping steam is injected into the bottom of the stripping tower (5), and the third heavy component and the fourth liquid component are subjected to a fifth stripping distillation under the conditions of a bottom temperature of 350° C., a working pressure of 0.12 MPa, and a stripping steam pressure of 1.1 MPa, to obtain a fifth light component, a fifth medium component, and a fifth heavy component at the top, the side line, and the bottom of the stripping tower (5), respectively; wherein,

[0145] The fifth light component is sent to a light hydrocarbon recovery unit,

[0146] The fifth component is used as a raw material for producing diesel, naphtha, etc. and enters the hydrogenation reforming device.

[0147] The fifth heavy component is heat exchanged to 380° C. in the third heat exchanger (16) and then enters the vacuum tower (6).

[0148] (S10) in a vacuum tower (6), the fifth heavy component is subjected to a sixth vacuum distillation at a temperature of 385° C. and a pressure of 0.7 kPa, to obtain a sixth light component and a sixth heavy component at the top and bottom of the vacuum tower (6), respectively; wherein:

[0149] The sixth light component is sent to a light hydrocarbon recovery unit,

[0150] 80% of the sixth heavy component is sent to a storage tank as coal-based heat transfer oil through a reduction pump (17), and the remaining 20% ​​is transported by the reduction pump (17), heat-exchanged to 380° C. using a fourth heat exchanger (16), and then enters a vacuum tower (6);

[0151] The coal-based heat transfer oil has an initial distillation point of 328°C, a 10% distillation temperature of 355°C, a 70% distillation temperature of 395°C, a 90% distillation temperature of 422°C, an aromatic content of 75.4%, a total amount of aromatics and cycloalkanes of 87.0%, and a density of 1043 kg / m 3 , kinematic viscosity is 32.5mm 2 / s, flash point is 197℃.

[0152] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing coal-based thermal oil, characterized in that: The following steps are involved: (S1) mixing coal powder and hydrogen supply solvent to prepare oil-coal slurry; (S2) subjecting the oil-coal slurry to a direct coal liquefaction reaction to obtain a coal liquefaction product; (S3) separating the coal liquefaction product into gas, liquid and solid three phases, and performing atmospheric and vacuum distillation on the obtained liquid phase components to obtain a coal-based crude oil product; (S4) subjecting the coal-based crude oil product to hydrogenation treatment to obtain a hydrogenation product; (S5) performing a first oil-gas separation on the hydrogenation product to obtain a first gas phase component and a first liquid phase component; (S6) performing a second oil-gas separation on the first gas phase component to obtain a second liquid phase component; (S7) performing a third light-heavy separation on the first liquid phase component to obtain a third light component and a third heavy component; (S8) performing a fourth oil-gas separation on the third light component and the second liquid phase component to obtain a fourth liquid phase component; (S9) subjecting the third heavy component and the fourth liquid phase component to a fifth stripping distillation to obtain a fifth heavy component; (S10) The fifth heavy component is subjected to a sixth reduced pressure distillation to obtain coal-based heat transfer oil.

2. The preparation method according to claim 1, characterized in that: In step (S1), the coal powder is selected from at least one of lignite, sub-bituminous coal, bituminous coal and anthracite, and its particle size distribution is as follows: particles smaller than 74 μm account for ≥80%, particles smaller than 5 μm account for ≤5%, and the moisture content of the coal powder is ≤4wt%, and the ash content is ≤6wt%; The hydrogen supply solvent is selected from at least one of coal tar, anthracene oil and coal liquefied aromatic oil, and its amount is 0.8-1.2 times the weight of coal powder to form an oil-coal slurry with a coal content of 45-55wt%; The mixing temperature is 185-190°C and the pressure is less than -0.2 kPa.

3. The preparation method according to claim 1 or 2, characterized in that: In step (S2), the direct coal liquefaction includes mixing the oil-coal slurry with liquid sulfur, hydrogen, and a catalyst to form a mixture, and then subjecting the mixture to a direct coal liquefaction reaction to obtain a coal liquefaction product; Preferably, the temperature of the mixture before the direct coal liquefaction reaction is 365-375°C; Preferably, the conditions for the direct coal liquefaction reaction include: The catalyst is an iron-based catalyst of at least one of iron oxide, ferrosoferric oxide and iron oxyhydroxide, The amount of liquid sulfur used is such that the hydrogen sulfide content in the reaction system is 1000-2500ppm. The amount of hydrogen used is such that the hydrogen content in the reaction system is above 86%. The amount of catalyst used is 1% of the weight of coal powder. The reaction temperature is 450-458°C. The reaction pressure is 18.6-18.8MPa, The reaction time is 1.5-2h.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step (S3), the atmospheric and vacuum fractionation refers to gradually reducing the pressure of the liquid phase component from 0.1-2 MPa to 0.3-0.5 kPa to obtain a coal-based crude oil product with a distillation range of 270-420°C.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In step (S4), the hydroprocessing refers to mixing the coal-based crude oil product with hydrogen to form a hydrogenated oil, and then the hydrogenated oil is hydroprocessed in a reaction system containing a nickel-based and / or molybdenum-based catalyst; Preferably, the temperature of the hydrogenated oil before the hydrogenation treatment is 310-320° C. and the pressure is 14.1-14.3 MPa; Preferably, the conditions of the hydrotreatment include: The amount of hydrogen used is such that the hydrogen content in the reaction system is above 91%; The reaction temperature is 378-385°C. The reaction pressure is 13.1-13.5MPa, The reaction time is 1.2-1.5h, The nickel-based and / or molybdenum-based catalyst is nickel oxide and / or molybdenum trioxide.

6. The preparation method according to any one of claims 1 to 5, characterized in that In step (S5), the conditions for the first oil-gas separation include: a temperature of 370-375°C and a pressure of 13.2-13.5 MPa.

7. The preparation method according to any one of claims 1 to 6, characterized in that In step (S6), the conditions for the second oil-gas separation include: a temperature of 50-60°C and a pressure of 13.1-13.3 MPa.

8. The preparation method according to any one of claims 1 to 7, characterized in that In step (S7), the conditions for the third light-heavy separation include: a temperature of 370-375°C and a pressure of 2.5-2.7 MPa.

9. The preparation method according to any one of claims 1 to 8, characterized in that: In step (S8), the fourth oil-gas separation conditions include: a temperature of 50-60°C and a pressure of 2.5-2.7 MPa.

10. The preparation method according to any one of claims 1 to 9, characterized in that: In step (S9), the conditions of the fifth stripping distillation include: an operating temperature of 350-360°C, an operating pressure of 0.11-0.15 MPa, and an input stripping steam pressure of 1.1-1.3 MPa; Preferably, before the fifth stripping distillation, the third heavy component is heat exchanged to 340-360°C, and the fourth liquid component is heat exchanged to 120-170°C.

11. The preparation method according to any one of claims 1 to 10, characterized in that: In step (S10), the conditions of the sixth reduced pressure distillation include: temperature of 380-390°C and pressure of 0.5-0.8 kPa; Preferably, before the sixth vacuum distillation, the fifth heavy component is heat exchanged to 370-390° C.; Preferably, after the sixth vacuum distillation, the fraction at 325-420° C. is collected, a portion of which is used as heat transfer oil, and the remaining portion is heat-exchanged to 370-390° C. before repeating the sixth vacuum distillation.

12. A system for the preparation method according to any one of claims 1 to 11, characterized in that: The system comprises: A mixing tank, used to mix coal powder with hydrogen supply solvent to prepare oil-coal slurry; A coal liquefaction reactor, used for subjecting the oil-coal slurry to a direct coal liquefaction reaction to obtain a coal liquefaction product; A constant pressure reduction tower, used for performing constant pressure reduction fractionation on the coal liquefaction product to obtain a coal-based crude oil product; A buffer tank for storing and stabilizing the coal-based crude oil product; A hydrogenation reactor, used for hydrogenating the coal-based crude oil product to obtain a hydrogenated product; A thermal high fractionator is used to perform a first oil-gas separation on the hydrogenation product to obtain a first gas phase component and a first liquid phase component; Cold high separation, used for performing a second oil-gas separation on the first gas phase component to obtain a second gas phase component and a second liquid phase component; A hot low fraction is used to perform a third light-heavy separation on the first liquid phase component to obtain a third light component and a third heavy component; Cold low fractionation, used for performing a fourth oil-gas separation on the third light component and the second liquid phase component to obtain a fourth liquid phase component; a stripping tower, used for performing a fifth stripping distillation on the third heavy component and the fourth liquid phase component to obtain a fifth heavy component; The vacuum tower is used to perform a sixth vacuum distillation on the fifth heavy component to obtain coal-based heat transfer oil.

Images