JPS6033152B2 - Coal liquefaction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for liquefying coal.
When hydrogenating and liquefying a raw material slurry consisting of a hydrogenation catalyst and a hydrocarbon solvent, a high molecular weight component is separated from the heavy oil in the primary hydrogenation product, and the high molecular weight component is recycled to the primary hydrogenation product. The present invention relates to a method that streamlines hydrogenation by performing hydrogenation and secondary hydrogenation of only the remaining heavy oil.

Primary hydrogenation of the above-mentioned raw material slurry containing coal powder,
The technique of further secondary hydrogenating the heavy oil content in the primary hydrogenated product to lighten and liquefy it is well known, and typical examples include Tokkan Sho 53-145304 and Sho 53- 25606
There are numbers etc.

In these coal liquefaction methods, a raw material slurry is supplied to a primary hydrogenation reaction tower and hydrogenated under high temperature and pressure, and the obtained primary hydrogenated product is distilled to produce a gas component, a bonito oil fraction, It is separated into medium oil fraction, heavy oil containing solid content such as ash and catalyst, and the vertical oil fraction and medium oil fraction are respectively extracted as product oil or recycled as a solvent. This is a method in which the solid content is removed (deashed) or the solid content is directly sent to the secondary hydrogenation step without being removed, and the solid content is hydrogenated in the presence of a catalyst to make it lighter.
Separating various fractions before secondary hydrogenation and performing secondary hydrogenation of only heavy oil fractions reduces the amount of gas produced by hydrogenation of medium and light oil fractions and increases the yield of liquid products. This is to prevent an unnecessary increase in the amount of hydrogen used, but the heavy oil supplied to the secondary hydrogenation process is high molecular weight Nada water that could not be easily hydrogenated in the primary hydrogenation process. Since it contains a large amount of additive components, there were many problems in carrying out secondary hydrogenation of these components to lighten them to the desired fraction. These problems will be explained below with reference to FIG. 1, which shows the properties of hydrocarbon materials. In other words, the primary hydrogenation product contains many types of substances ranging from C ratio with a carbon number of 1 to preasphaltenes with a molecular weight of several thousand or more, char, ash, and inorganic substances such as catalysts. A gas component A having 1 to 4 carbon atoms is separated by gas-liquid separation, and then the liquid component is distilled to a boiling point of 180 to 20
Light oil crab fraction (naphtha) B up to about 0℃, boiling point 350~
The medium oil fraction (kerosene, light oil) C up to about 420°C is separated, and only the remaining heavy oil fraction D is supplied to the secondary hydrogenation process, but the vehicle oil fraction D contains ash and hydrogenation reaction. Char that does not pass through and benzene soluble (BS) and hexane insoluble (HI).
) asphaltene E and pyridine soluble (idi of P)
neSoluble: PS) and benzene insoluble (Beme
Contains preasphaltene F (neInsoluble: BI). If this heavy oil is fed as it is to the secondary hydrogenation step without being deashed, there is a problem that the secondary hydrogenation catalyst will be poisoned by the ash and the alkali metals contained therein. In addition, since it contains a large amount of asphaltene and pre-asphaltene, which have high molecular weight and are key to hydrogenation, strict hydrogenation conditions such as high temperature and pressure are required, and since these components have a high degree of unsaturation, the amount of hydrogen absorbed is low. Since there is a large amount of hydrogen and it takes a long time to add the required amount of hydrogen, a huge reaction vessel is required. Furthermore, asphaltene with a high degree of unsaturation is extremely susceptible to coking at high temperatures, which causes coking in the reaction vessel or piping, which impedes continuous operation, and also causes significant deterioration of the hydrogenation catalyst due to coking. On the other hand, even when young oil is deashed and subjected to secondary hydrogenation, only char and inorganic substances (ash and primary hydrogenation catalyst) are removed, and a large amount of asphaltenes and pre-asphaltenes mentioned above are still contained. Since they are the same in that they are supplied to the secondary hydrogen step, the above-mentioned problems cannot be avoided.

Furthermore, in the deashing process, a method is generally adopted in which heavy pre-asphaltenes such as char and inorganic substances are separated by sedimentation, so it takes a long time to sediment the fine particles, and the highest separation rate reported to date is Even if the car oil is supplied to the secondary hydrogenation process, it contains more than 130 ash.Therefore, the secondary water is caused by the amount of alkali metals contained in this ash. The presence of added catalysts is still a major problem.In view of the above problems, the present invention aims to improve the efficiency of the secondary hydrogenation process, and improves the efficiency of ash separation in the deashing process to improve the efficiency of catalyst addition. The purpose is to reduce the contamination of alkali metals, which are poisonous components.
In order to achieve this objective, the high molecular weight components of pre-asphaltene F and asphaltene B are removed together with char and inorganic substances in the deashing process of the car oil content in the primary hydrogenated product, and the remaining components are removed. In addition to supplying only relatively light components to the secondary hydrogenation process, the separated preasphaltene F and high molecular weight asphaltene E are mixed with the raw material slurry as a solvent and used again for primary water lacquering. . That is, the coal liquefaction method according to the present invention involves sequentially performing primary hydrogenation and secondary hydrogenation of a raw material slurry containing coal, and separating the primary hydrogenation product by distillation to obtain a light oil fraction and a medium oil fraction. A part of the above medium oil fraction is returned as a raw material slurrying solvent, and a heavy oil solvent is added to the car oil fraction to dissolve it. Q. A part of the medium oil crab is added to the non-falling component to separate it again into dissolved components and non-melting components including ash and hydrogenation catalyst, and the dissolved component is separated into At least a part of the components is returned as the slurrying solvent, the light oil solvent is distilled off from the dissolved components of the @ term to obtain car oil, and at least a part of the car oil is treated with a hydrogenation catalyst. The gist is that the crab is subjected to secondary hydrogenation at high temperature and high pressure in the presence of bonito to make it into bonito, and then separated into each crab component.

In the present invention, in the step of deashing the car oil obtained by distilling the primary hydrogenated product, a vert oil solvent is first added to reduce the HS content and the low molecular weight range of asphaltenes shown in Figure 1. The dissolved component G is separated from the insoluble component consisting of high molecular weight asphaltene, pre-asphaltene F, char, and inorganic substances that are insoluble in light oil solvents, and only the dissolved component G is supplied to the secondary hydrogenation step. .

On the other hand, on the day of the insoluble component, a medium oil solvent is added to form an insoluble component K consisting of char and inorganic substances, and a soluble component J consisting of asphaltenes and preasphaltenes F in the high molecular weight range.
The dissolved component J is returned as a slurrying solvent for the raw materials. Therefore, the component G supplied to the secondary hydrogenation step is:
Since it does not contain breasphaltene or high molecular weight asphaltene, which are difficult to hydrogenate, secondary hydrogenation can be carried out extremely efficiently. On the other hand, the Breasphaltenes and high molecular weight asphaltenes are fed together with the raw material slurry to the primary hydrogenation step again, where they are lightened into low molecular weight particles, and the G
The components that have not been lightened to the HS range will be repeatedly returned to the primary hydrogenation, and eventually these hydrogenated components will also be lightened to the target HS range, so the recovery rate of the product oil will increase. It also improves. The configuration and effects of the present invention will be described below based on drawings showing examples, but the following are representative examples and do not limit the present invention.

Figure 2 is a flow sheet showing an embodiment of the present invention, in which pulverized low-rank coal such as brown coal, lignite, lignite, and beet, hydrogenation catalysts such as iron oxide, iron sulfide, and red mud, and mainly recycled materials as described below are used. A raw material slurry is prepared by mixing a hydrocarbon-based slurry-forming solvent consisting of a solvent, and the slurry is pressurized to about 150 to 30 positive pressure, which is approximately equal to the primary hydrogenation reaction pressure, using a high-pressure pump P. Then, with the pipe 21, the hydrogen production device 1
The primary hydrogenation reaction column 2 is mixed with the primary hydrogenation day 2 supplied through the pipe 22 from 4, and is supplied to the heating furnace 1, and after being heated to 350 to 500 qo, which is approximately equal to the primary hydrogenation temperature, the primary hydrogenation reaction tower 2 supply to. The coal powder hydrogenated in the reaction tower 2 is supplied as a primary hydrogenated product from the top of the tower through a pipe 23 to a gas-liquid separator 3, where residual day 2 and C.I. ~ Volatile content of C4 is in pipe 24
It is then sent to the hydrogen production device 14 and reformed on day 2 for hydrogenation reaction, while the remaining slug IJ1 is fed to the distillation column 4 through the pipe 25. In the distillation column 4, the light oil fraction with a boiling point of up to about 200o0, the medium oil fraction with a boiling point of about 200 to 45,000, and the residual oil at the bottom of the column are separated, and the vertical oil fraction is extracted from the pipe 26 at the top of the column. Recovered as naphtha, medium oil fraction is pipe 27
A part of it is returned as a slurrying solvent via piping 28, and the military oil at the bottom of the tower is sent to mixing tank 9 through piping 29. The rest will be explained later. In addition, in the diagram, one
Although only the secondary hydrogenation reaction tower is shown, it is more common to have multiple reaction towers arranged in parallel or in series depending on the throughput, residence time, reaction method, etc., and the separator is a high-pressure separator, It is usually composed of an intermediate separator, a pressure reducing device, etc., and the distillation column 4 also includes a normal pressure distillation column that separates a light oil fraction and a medium oil fraction, and a medium pressure distillation column that separates a medium oil fraction and a young oil fraction. It is common to use a vacuum distillation column that separates the

The heavy oil component supplied to the mixing tank 9 is either a light oil solvent with a boiling point of up to about 180q○ supplied from the solvent recovery tower 6 via the pipe 30, or distilled and separated as naphtha from the secondary hydrogenation product. A light oil solvent of about the same level as the one supplied via the pump is mixed.

As a result, the low molecular weight components in the car oil are dissolved in the vertical oil solvent, and as shown in Figure 1, dissolved component G consisting of HS component and low molecular weight asphaltene, high molecular weight asphaltene, and pre-asphaltene are dissolved. The slurry is separated into alten F, char, and insoluble components consisting of inorganic substances, and this mixed slurry is sent to the settling tank 5 through the pipe 32. In this sedimentation tank 5, the unfallen components are sedimented and separated, the dissolved components G are sent to the solvent recovery tower 6 from the piping 33 at the top, and the insoluble components are discharged from the piping 34 at the bottom. In the present invention, the deashing of the heavy oil fraction is actually carried out in the sedimentation tank 5, and what is separated by sedimentation as non-falling components is the heavy distillate char and inorganic components in the pre-asphaltene, such as in the conventional method. It contains not only substances but also all pre-asphaltenes and high molecular weight asphaltenes, and these act as if they were flocculants, which accelerates the sedimentation rate of char and inorganic substances and significantly improves their separation efficiency. .

As a result, the content of inorganic substances in the car oil supplied to the secondary hydrogenation process can be reduced to a low level of 100 mm or less, which was considered extremely difficult with conventional methods. Next, the dissolved components sent from the settling tank 5 to the solvent recovery tower 6 are distilled here and separated into a light oil solvent at the top of the tower and a vehicle oil consisting of the HS component and low molecular weight asphaltene at the bottom of the tower. The vertical oil solvent is returned to the mixing tank 9 from the pipe 30 as described above. On the other hand, the pressure of the heavy oil is increased to around the secondary hydrogenation reaction pressure by the pressure booster pump P2, and in the pipe 35, it is passed from the hydrogen production device 14 to the pipe 36.
Receives the mixing of high-pressure hydrogen for secondary hydrogenation supplied via
After reaching the heating furnace 11 and being heated to near the reaction temperature, it is supplied from the pipe 37 to the secondary hydrogenation reaction tower 10'. This reaction column 1 is filled with a vehicle oil hydrogenation catalyst such as a Co-Mo-Ni system, and multiple units may be installed in series or parallel as necessary, but here, the primary hydrogenation reaction conditions are as follows. milder temperatures and pressures are applied. For example, when an iron-based catalyst is used for the primary hydrogenation and conditions of approximately 430 to 48,000 or 230 to 28 ppm are adopted, Co
-380 to 430q○, 150 using Mo-Nj catalyst
A condition of approximately 250 atmospheres is adopted. As described above, in the present invention, since the heavy oil supplied to the secondary hydrogenation process does not contain pre-asphaltenes and high molecular weight asphaltene, which are difficult to hydrogenate, the secondary hydrogenation process can be sufficiently performed under relatively mild conditions. Hydrogenation can be carried out, and inorganic substances (
Since the amount of ash is extremely low, the problem of catalyst poisoning due to alkaline components is drastically reduced. The secondary hydrogenation product is sent to the gas-liquid separator 12 through a pipe 38, where it is separated into unreacted hydrogen, a gas component having 1 to 4 carbon atoms, and an oil component having more than 4 carbon atoms.
The gas component is sent from the pipe 39 to the hydrogen production device 14 to be reformed into hydrogen for hydrogenation, while the oil component is sent to the distillation column 13 from the pipe 40 to light oil (naphtha) with a boiling point of about 180q○, boiling point 180 to 30,000. intermediate oil fraction, boiling point 300~
It is separated into a medium oil fraction of about 400 qo and a heavy oil fraction with a boiling point of 400 oC or more, and a part of the vertical oil fraction is extracted as a product naphtha, and the remainder is mixed as a light oil solvent from the pipe 31 as described above. It is returned to tank 9.

Further, the intermediate oil fraction extracted from the pipes 42 and 43 is mixed with heavy oil and taken out as fuel oil. On the other hand, the insoluble components including preasphaltenes and high molecular weight asphaltenes separated in the settling tank 5 are transferred from the pipe 34 to the mixing tank 7.
A part of the medium oil fraction of the primary hydrogenated product that is sent to the distillation column 4 and supplied via the pipe 44 is mixed into the mixing tank 7, so that the pre-asphaltenes mentioned above are mixed into the mixing tank 7. and high molecular weight range asphaltene are dissolved and supplied to the settling tank 8 in the form of a slurry containing char and inorganic substances (ash, primary hydrogenation catalyst, etc.) as insoluble components.

In the sedimentation tank 8, the dissolved component J in which the pre-asphaltene and the high molecular weight asphaltene are dissolved, and the unmelted component K
The unmelted component K is sent to the gasification furnace 15 through the pipe 45 to gasify residual hydrocarbons, and the generated gas is sent to the hydrogen production device 14 to be used for production of hydrogen for hydrogenation. On the other hand, the entire amount of the melted component J is returned as a slurrying solvent through the pipe 46, and the presphaltene and high molecular weight asphaltene contained therein are returned to the primary hydrogenation step and further lightened. However, as shown in the figure, a part of the dissolved components is transferred from pipe 47 to solvent refined charcoal (SRC).
It is advantageous to recover SRC for carbon material production as a created product by supplying it to the recovery column 16 and separating it by distillation. In this case, the top fraction, which is mainly composed of asphaltenes coming out from the top of the recovery column and the medium oil fraction in the primary hydrogenated product added in the mixing tank 7, is transferred from the pipe 48 to the slurry solvent. It will be returned as Next, FIG. 3 is a flow sheet showing another embodiment of the present invention, in which the recovery rate of light oil crab fraction from heavy oil can be further increased.

That is, in the example shown in Figure 2, the relatively high boiling point (
420 to 450 qo or more) is separated as heavy oil, and only relatively light components of the vehicle oil are supplied to a secondary hydrogenation process equipped with a fixed bed reactor 10. However, in the example shown in FIG. 3, the heavy oil components are further separated, including those with low boiling points, and a relatively vertical fraction is sent to a secondary hydrogenation step equipped with a moving bed reactor 17. The method is adopted. That is, the primary hydrogenated product is heated to a boiling point of 2 in the distillation column 4.
Light oil fraction (naphtha) up to about 0,000 and boiling point 200
Separate into a medium oil fraction with a boiling point of ~35,000 and a car oil fraction with a boiling point of 35,000 or more, and mix the heavy oil in a mixing tank 9 with a boiling point of 180.
After mixing with a light oil solvent of o0 or less to dissolve relatively low molecular weight components and separating them into dissolved and insoluble components in a sedimentation tank 5, the dissolved components are sent to a solvent recovery tower 6 to remove the bushy oil solvent. However, the remaining vehicle quality oil G is supplied to the catalyst mixing tank 18. Since this heavy oil contains primary hydrogenation products with a boiling point of 350oC or higher, the content of light fractions is relatively large compared to the example in Figure 2, and the secondary hydrogenation product The reaction can also be carried out under milder conditions. Therefore, the same catalyst as the primary hydrogenation catalyst, for example, an iron-based catalyst, is supplied from the pipe 49 to the catalyst mixing tank 18 to form a slurry, and the slurry is supplied to the suspended bed secondary hydrogenation reactor 17. ing. That is, the slurry is pressurized to around a predetermined secondary hydrogenation pressure by the pressure boost pump P2, mixed with hydrogen sent from the pipe 36, and then heated to the heater 11.
Here, the temperature is raised to around a predetermined hydrogenation temperature, and then supplied to the secondary hydrogenation reactor 17, where the secondary hydrogenation reaction is carried out under conditions comparable to or lower than the primary hydrogenation reaction conditions. The secondary hydrogenated product is first flashed to a gas-liquid separator 12 to separate gas and liquid, and the gas component is sent to the hydrogen production device 14 and the liquid component to the distillation column 13, respectively.

In the distillation column 13, it is separated into vertical oil (naphtha) with a boiling point of about 180 qo, medium oil with a boiling point of about 180 to 350 qo, and residual oil containing the hydrogenation catalyst at the bottom of the column, and the light oil is recovered as naphtha. Alternatively, the medium oil is returned to the mixing tank as the above-mentioned light oil solvent, and the medium oil is extracted from the pipe 53 and mixed with a portion of the heavy oil separated from the primary hydrogenated product sent from the pipe 50, to form fuel oil. Take it out as This is because the car oil contains a relatively large amount of light components compared to the case shown in Figure 2.
This is because it can be used as a fuel oil simply by mixing it with the medium oil in the secondary hydrogenation product. In addition, some of the medium oil is piped 5
It is also possible to return it as a solvent for heavy oil for secondary hydrogenation via 2. On the other hand, the column bottom rock oil is returned as a slurrying solvent for the raw material through the pipe 51 without removing the catalyst. That is, the catalyst used in the secondary hydrogenation process for producing the final product is supplied fresh from pipe 49, and the catalyst for primary hydrogenation is supplied mainly through pipe 5, which is mainly used in the secondary hydrogenation.
The catalyst supplied from No. 1 is used, and fresh catalyst for primary hydrogenation is sufficient to replenish the shortage. That is, the heavy oil supplied to the secondary hydrogenation step in the method of the present invention does not contain ash pre-asphaltenes or high molecular weight asphaltenes, and catalyst poisoning due to coking etc. hardly occurs. There is little deterioration or poisoning of the catalyst in the secondary hydrogenation step, and it can be fully reused as a catalyst for primary hydrogenation. However, the primary hydrogenation process is hydrogenation of raw coal, and contains a large amount of catalyst poisoning components such as ash and substances that easily cause coking, so the catalyst used in the primary hydrogenation may deteriorate or be damaged. Poison cannot be reused unless it is significantly recycled. Therefore, in both the examples shown in Figs. 2 and 3, the ash separated from the vehicle oil, which is the primary hydrogenation product, and the inorganic substances containing the primary hydrogenation catalyst are led to the gasifier 15, and the accompanying hydrocarbons are removed from the gas. It is collected and disposed of as ash. As explained above, in the present invention, the primary hydrogenated product is separated into a light oil fraction, a medium oil fraction, and a heavy oil fraction,
By first washing vehicle oil with a light oil solvent before supplying it to the secondary hydrogenation process, not only solids such as char and ash primary hydrogenation catalyst but also precipitates that inhibit the secondary hydrogenation reaction are removed. Asphaltenes and high molecular weight asphaltenes are also removed as insoluble materials, and only the remaining low molecular weight asphaltenes and HS components are supplied to the secondary hydrogenation process, so secondary water can be efficiently processed under extremely mild conditions. This also stabilizes the quality of the product.

In addition, in separating the dissolved components and insoluble components, pre-asphaltenes and high molecular weight asphaltenes, which are removed as unfallen components, act as flocculants for separating ash and other solids, so secondary hydrogenation The inorganic content in the heavy oil supplied to the process can be drastically reduced. Result 2
Deterioration and poisoning of the catalyst during the secondary hydrogenation reaction are suppressed, and the catalyst used for the secondary hydrogenation can be reused as a catalyst for the primary hydrogenation. The inorganic content in the oil is also reduced and the quality of the product oil is improved.
On the other hand, the plasphaltenes and high molecular weight asphaltenes that were separated together with char and inorganic substances as insoluble components are further separated and returned as a raw material slurrying solvent, and subjected to primary hydrogenation together with coking coal to form light This improves the product recovery rate.

In the present invention, when a light oil solvent is added to the car oil content in the primary hydrogenated product to separate it into soluble components and insoluble components,
Depending on the type of light oil solvent used, the boundary between the soluble component indicated by G in FIG. 1 and the insoluble component indicated by day varies.

Therefore, the type of light oil solvent (boiling point range) should be appropriately selected depending on the performance of the secondary hydrogenation catalyst, the secondary hydrogenation conditions (temperature, pressure, residence time), and the composition of the primary hydrogenation product. However, in order to ensure the above-mentioned effects, a vertical oil with a boiling point of at least 200 qo or less, more preferably 180 qo or less should be used. Furthermore, in the present invention, a part of the pre-asphaltenes and high-molecular-weight asphaltenes in the insoluble components can be recovered as solvent refined carbon (SRC), and not only liquid products but also solid products can be obtained, so that product diversification is possible. It becomes possible.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the relationship between the molecular weight, boiling point, and solvent solubility of hydrocarbons produced by coal liquefaction, Figures 2 and 3
The figure is a flow sheet showing an example of the present invention. 1, 11... Heating furnace, 2... Primary hydrogenation reaction tower, 3, 12... Gas-liquid separation tank, 4, 13...
... Distillation column, 5, 8 ... Sedimentation tank, 6 ...
Solvent recovery tower, 7, 9... Mixing tank, 10, 17.
...Secondary hydrogenation reaction tower, 14...Hydrogen production device, 15...Gasification furnace, 16...S
RC recovery tower, 18... Catalyst mixing tank. Figure 2 Figure 1 Figure 3

Claims (1)

[Claims] 1. A raw material slurry consisting of coal, a hydrogenation catalyst, and a hydrocarbon slurry solvent is treated at high temperature and high pressure to perform primary hydrogenation, and this primary hydrogenation product is further treated with a hydrogenation catalyst. 2 in the presence of
In a method for liquefying coal by subhydrogenating it to make it lighter, (a)
(b) separating the primary hydrogenated product by distillation into a light oil fraction, a medium oil fraction, and a heavy oil fraction containing insoluble components;
A part of the medium oil fraction is returned as the slurrying solvent, and a light oil solvent is added to the heavy oil to separate it into a soluble component and an insoluble component, and (c) the medium oil fraction is added to the insoluble component. Adding a part of the oil fraction and separating it again into dissolved components and insoluble components containing ash and hydrogenation catalyst, and returning at least a part of the dissolved components as the slurry-forming solvent; ) The light oil solvent fraction is separated by distillation from the dissolved components in item ) to obtain heavy oil, and at least a part of the heavy oil is subjected to secondary hydrogenation at high temperature and high pressure in the presence of a hydrogenation catalyst to make it lighter. A method for liquefying coal, which is characterized by separating it into its respective fractions. 2. A coal liquefaction method as set forth in claim 1, in which a portion of the dissolved components obtained in item (c) is distilled to recover solvent-refined coal at the bottom of the column, and the fraction is returned as a slurry solvent. 3. A coal liquefaction method according to claim 1 or 2, in which the insoluble components including the ash and hydrogenation catalyst obtained in item (c) are supplied to a gasifier, and hydrogen for hydrogenation is obtained from the produced gas. 4 In any one of claims 1 to 3, 2
A coal liquefaction method in which the secondary hydrogenation reaction is carried out under a fixed bed catalyst. 5 In any one of claims 1 to 4, (
A coal liquefaction method in which a hydrogenation catalyst is added to the heavy oil obtained in item d) to perform a secondary hydrogenation reaction. 6 In any one of claims 1 to 5, 1
Both the secondary hydrogenation catalyst and the secondary hydrogenation catalyst are the same iron-based catalyst, and the catalyst-containing column bottom residue obtained by distilling the secondary hydrogenation product is returned as it is as a slurry solvent.Coal liquefaction Method. 7 In any one of claims 1 to 4, (
The coal liquefaction method according to item (a), wherein the light oil fraction has a boiling point of 200°C or less, and the medium oil fraction has a boiling point of 200 to 420°C. 8. In any of claims 1 to 3, 5 and 6, the boiling point of the light oil fraction in item (a) is 200°C or less,
A method for liquefying coal in which a medium oil fraction has a boiling point of 200 to 350°C. 9 In claim 8, a medium oil fraction obtained by distilling and separating a secondary hydrogenation product is added to a part of the heavy oil fraction obtained by distilling and separating in item (d). A method of liquefying coal that is mixed and extracted as fuel oil. 10 In any one of claims 1 to 9,
A method for liquefying coal, in which a part of a light oil fraction having a boiling point of 180° C. or less among fractions obtained by distilling and separating a secondary hydrogenated product is supplied as the light oil solvent according to item (b) above. 11. A coal liquefaction method as set forth in claim 10, in which the light oil solvent fraction distilled and separated in item (d) is returned as the light oil solvent in item (b). 12 In any one of claims 1 to 11, a part of the medium oil fraction obtained by distilling the secondary hydrogenation product is used as a solvent for secondary hydrogenation before the secondary hydrogenation. A method of liquefying coal by adding it to heavy oil.