CN114437767B

CN114437767B - Method for removing mechanical impurities and ash in coal tar

Info

Publication number: CN114437767B
Application number: CN202011193507.5A
Authority: CN
Inventors: 严张艳; 李猛; 吴昊; 梁家林; 任亮; 赵广乐; 张璠玢; 胡志海
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2020-10-30
Filing date: 2020-10-30
Publication date: 2023-08-08
Anticipated expiration: 2040-10-30
Also published as: CN114437767A

Abstract

The invention relates to the field of coal tar processing, and discloses a method for removing mechanical impurities and ash in coal tar, which comprises the steps of (1) mixing coal tar to be treated with a first diluting medium to obtain a mixture flow, and then carrying out solid-liquid separation on the mixture flow to remove large-particle mechanical impurities and ash with the diameter of more than 20 mu m to obtain a first liquid-phase flow; (2) Carrying out solid-liquid separation on the first liquid-phase material flow to remove small-particle mechanical impurities and ash with the diameter not more than 20 mu m, so as to obtain a second liquid-phase material flow; the first dilution medium is at least one selected from hydrogenated diesel oil, hydrogenated tail oil, catalytic diesel oil, wash oil, anthracene oil and light aromatic hydrocarbon. According to the method, the coal tar to be treated is mixed with the diluting medium, and then the solid-liquid separation is carried out twice, so that mechanical impurities and ash in the coal tar can be effectively removed, long-period operation of separation equipment is ensured, and meanwhile, the yield of the coal tar can be effectively improved.

Description

Method for removing mechanical impurities and ash in coal tar

Technical Field

The invention relates to the field of coal tar processing, in particular to a method for removing mechanical impurities and ash in coal tar.

Background

Coal tar is used as an accessory product of coal processing, and the development and utilization value of the coal tar is continuously enhanced. The coal resources of China are rich compared with petroleum and natural gas resources, and the coal resources always belong to the large country of coal production. With the importance of the country on the classified utilization of coal, the country has larger coal tar productivity, so the clean processing of the coal tar has a profound effect on the economic development of the country. The existing coal tar industry has the problems of insufficient enterprise scale, single product type, relatively lagged processing technology, easy environmental pollution and the like. How to reasonably and cleanly utilize coal tar resources and improve the economic benefits of enterprises becomes more and more urgent.

In recent years, the number of fixed bed coal tar hydrogenation devices in China is increased, wherein the fixed bed hydrogenation devices have the characteristics of simple flow, small investment, simple operation, high technical maturity and the like. However, the coal tar has higher mechanical impurities and ash content, the mechanical impurity content is about 1wt%, the ash content is also up to 0.1-0.5wt%, the bed is easy to be blocked, the pressure drop rises fast, and the like, the device is forced to stop, the device start-up time is shortened, and the economic benefit of enterprises is seriously influenced. Therefore, in order to prolong the operation period of the coal tar hydrogenation device, mechanical impurities and ash in the coal tar are required to be removed, and then the coal tar is subjected to fixed bed hydrogenation to produce clean fuel and the like, which can greatly prolong the operation period of the device.

CN104673368A discloses a method and system for removing mechanical impurities and ash in coal tar full distillate, the removing method comprises: step A: filtering and removing impurities with the diameter of 20-50 mu m in the coal tar full fraction by using a filter press to obtain a first effluent; and (B) step (B): mixing the first effluent with diesel oil fraction in the volume ratio of 1:0.1-5 to obtain mixed oil; step C: and filtering and removing particles which are wrapped with impurities with the diameter of 1-20 mu m from the mixed oil by using a filter press, wherein the effluent is the coal tar full fraction for removing mechanical impurities and ash. However, the removal effect of the method is not obvious, and long-period operation of the separation equipment cannot be ensured. The removal system comprises a first filter press, first mixing equipment and a second filter press which are sequentially connected, wherein the slag unloading process of the filter press needs manual operation, and the increasingly strict requirements on cleaning and environmental protection are difficult to meet.

Disclosure of Invention

The invention aims to solve the problems of unobvious removal effect, short operation period of separation equipment and lower yield of coal tar in the existing process for removing mechanical impurities and ash in coal tar, and provides a method for removing mechanical impurities and ash in coal tar.

In the prior art, coal tar to be treated is usually filtered once to remove solid large particles with the diameter of more than 20 mu m, then is mixed with diesel oil fraction with the aromatic hydrocarbon content of less than 5wt percent and the paraffin content of more than 40wt percent to separate out asphaltene, and then is filtered once to remove solid small particles with the diameter of less than 20 mu m, which are wrapped by the asphaltene, so that the purpose of removing mechanical impurities and ash in the coal tar is achieved, but the removal effect of the method is poor, long-period operation of separation equipment cannot be guaranteed, and the liquid yield of the coal tar is lower. In order to solve the problems, the inventor of the present invention found in the research that mechanical impurities and ash in coal tar can be effectively removed by mixing the coal tar to be treated with a diluting medium (one or more selected from hydrogenated diesel oil, hydrogenated tail oil, catalytic diesel oil, wash oil, anthracene oil and light aromatic hydrocarbon), and then sequentially performing solid-liquid separation to remove solid large particles with a diameter of > 20 μm and solid small particles with a diameter of < 20 μm, i.e., mixing the coal tar to be treated with the diluting medium, and then performing a removal process of two solid-liquid separations, thereby guaranteeing long-period operation of separation equipment and effectively improving the yield of the coal tar. The reason for this is probably because the dilution medium can reduce the viscosity of the coal tar, effectively dissolve the heavy colloid wrapped outside the fine powder in the coal tar and separate out the fine powder, thereby effectively removing mechanical impurities and ash in the coal tar. Further, the inventors of the present invention have found in the study that mechanical impurities and ash in coal tar can be further removed and the yield of coal tar can be improved by mixing coal tar to be treated with a diluting medium having a total aromatic hydrocarbon content of 45wt% or more and a paraffin content of less than 30wt%. Presumably, the reason is that the aromatic hydrocarbon in the diluted medium and the colloid asphalt in the coal tar can be fused to a certain extent, so that the colloid asphalt in the system reaches a new dynamic balance again, ash partially wrapped in the heavy asphalt can be separated out in the process, and the phenomenon that the asphalt excessively separates out and adheres to a centrifuge or the yield of the coal tar is reduced is avoided.

In order to achieve the above object, the present invention provides a method for removing mechanical impurities and ash from coal tar, the method comprising:

(1) Mixing coal tar to be treated with a first diluting medium to obtain a mixture flow, and then carrying out solid-liquid separation on the mixture flow to remove large-particle mechanical impurities and ash with the diameter of more than 20 mu m to obtain a first liquid-phase flow;

(2) Carrying out solid-liquid separation on the first liquid-phase material flow to remove small-particle mechanical impurities and ash with the diameter not more than 20 mu m, so as to obtain a second liquid-phase material flow;

the first dilution medium is at least one selected from hydrogenated diesel oil, hydrogenated tail oil, catalytic diesel oil, wash oil, anthracene oil and light aromatic hydrocarbon.

According to the technical scheme, the coal tar to be treated is mixed with the diluting medium, and then the two solid-liquid separations are carried out, so that mechanical impurities and ash in the coal tar can be effectively removed, the long-period operation of the separation equipment is ensured, and the yield of the coal tar can be effectively improved. Further, mechanical impurities and ash in the coal tar can be further removed and the yield of the coal tar can be further improved by mixing the coal tar to be treated with a diluting medium with the total aromatic hydrocarbon content of more than 45wt% and the paraffin content of less than 30wt%. For example, by adopting the removal method provided in the embodiment 1 of the invention, the content of mechanical impurities in the obtained coal tar is 0.005 wt%, the content of ash is less than 0.002 wt%, and the yield of the obtained coal tar is 95.3%; by adopting the removal method provided in comparative example 2, the content of mechanical impurities in the obtained coal tar was 0.013 wt%, the content of ash was 0.008 wt%, and the yield of the obtained coal tar was 86.9%. The removal method provided by the invention has the characteristics of low energy consumption, simplicity in operation and low cost.

Drawings

FIG. 1 is a flow chart of a process for removing mechanical impurities and ash from coal tar in accordance with a preferred embodiment of the present invention.

Description of the reference numerals

1. Coal tar 2 first diluting medium to be treated

3. Coal tar intermediate tank 4 mixture stream

5. First centrifugal separation device 6 a first liquid phase stream

7. First solid particle 8-film filtering and separating equipment

9. Second liquid phase stream 10 oil residue

11. Second diluting medium 12 slag liquid tank

13. Second solid particles of washing liquid 14

15. Third liquid phase stream of second centrifugal separation device 16

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

As described above, the present invention provides a method for removing mechanical impurities and ash from coal tar, the method comprising:

The method for removing mechanical impurities and ash in coal tar can be summarized as mixing coal tar to be treated with a diluting medium, then sequentially carrying out solid-liquid separation to remove large-particle mechanical impurities and ash with the diameter of more than 20 mu m and small-particle mechanical impurities and ash with the diameter of not more than 20 mu m, namely, a removing process of firstly mixing and then carrying out separation twice, wherein the prior art generally carries out primary separation on the coal tar to be treated to remove the large-particle mechanical impurities and ash, then mixing with the diluting medium, then carrying out primary separation to remove the small-particle mechanical impurities and ash, namely, carrying out primary separation, then mixing and then carrying out a removing process of primary separation. As described above, the viscosity of the coal tar can be reduced by the dilution medium, and the heavy colloid wrapped outside the fine powder in the coal tar can be effectively dissolved to separate out the fine powder, so that the method disclosed by the invention can be used for effectively removing mechanical impurities and ash in the coal tar and improving the yield of the coal tar.

The method is not particularly limited in the source of the coal tar to be treated in the step (1), and can be used for coal tar generated by any process. The coal tar has a wide selection range, and preferably, the coal tar is low-temperature coal tar and/or medium-low-temperature coal tar.

In the invention, the distillation range of the coal tar is selected to be wider, and preferably, the distillation range of the low-temperature coal tar is 50-450 ℃; the distillation range of the medium-low temperature coal tar is 50-550 ℃.

According to the present invention, preferably, in step (1), the mixing conditions include: the temperature is 70-100deg.C, more preferably 80-100deg.C; the time is 1 to 10 hours, more preferably 1 to 3 hours.

According to the invention, the viscosity of the coal tar can be reduced by mixing the coal tar to be treated with the first diluting medium in a proper proportion, so that mechanical impurities and ash in the coal tar can be effectively removed, and preferably, the volume ratio of the coal tar to be treated to the first diluting medium in the step (1) is 1:0.1 to 3, more preferably 1:0.1-1.

According to the invention, preferably, the first diluent medium of step (1) has a total aromatic content above 45wt% and a paraffin content of less than 30wt%. It is further preferred that the total aromatic content of the first diluent medium of step (1) is above 50wt%, preferably 50-80wt%, and the paraffinic content is less than 25wt%. Under the preferable condition, heavy colloid coated outside the fine powder in the coal tar can be further dissolved to separate out the fine powder, so that the efficiency of removing mechanical impurities and ash is further improved, and the yield of the coal tar is further improved.

According to the present invention, the solid-liquid separation in step (1) is preferably performed using a centrifugal separation apparatus.

In the present invention, in order to better remove large-particle mechanical impurities and ash from coal tar, preferably, the operation conditions of the centrifugal separation device include: the temperature is 50-120 ℃, the pressure is 0.05-0.5MPa, and the rotating speed is 1000-6000r/min.

The invention has wider selection range for the centrifugal separation equipment, so long as the effect of removing large-particle mechanical impurities and ash in coal tar can be achieved, and the centrifugal separation equipment is preferably a horizontal decanter centrifuge or a disk centrifuge.

According to the present invention, the solid-liquid separation in step (2) is preferably performed using a membrane filtration separation apparatus.

In the present invention, in order to better remove small-particle mechanical impurities and ash in coal tar, preferably, the operating conditions of the membrane filtration separation device include: the temperature is 80-100 ℃; the pressure is 0.1-0.5MPa, more preferably 0.2-0.4MPa; the rotating speed is 2000-5000r/min.

The selection range of the membrane filtration separation equipment is wider as long as the effect of removing small-particle mechanical impurities and ash in coal tar can be achieved, and the membrane filtration separation equipment is preferably an inorganic membrane filtration pipe.

According to the present invention, the pore diameter of the inorganic membrane filtration tube is preferably 0.1 to 20. Mu.m, more preferably 0.5 to 15. Mu.m. In the preferred case, the removal of small-particle mechanical impurities and ash is facilitated, so that coal tar with lower mechanical impurities and ash content and higher yield is obtained.

According to the present invention, in order to achieve efficient use of the oil, preferably, the method further comprises: washing the oil residue obtained in the step (2) with a second diluting medium, and recycling washing liquid obtained by washing back to the step (1) for use; or alternatively

And (3) carrying out solid-liquid separation on the washing liquid obtained by washing to remove mechanical impurities and ash, obtaining a third liquid-phase stream, and recycling the third liquid-phase stream to the step (2).

According to the invention, preferably, the weight ratio of the oil sludge to the second diluting medium is 1:0.1 to 3, more preferably 1:0.2-2. The second diluent medium is at least one selected from hydrogenated diesel oil, hydrogenated tail oil, catalytic diesel oil, wash oil, anthracene oil and light aromatic hydrocarbon. In the present invention, the second diluting medium may be the same as the first diluting medium or different from the first diluting medium, and those skilled in the art may choose the second diluting medium according to the actual situation.

In the present invention, the washing liquid is preferably subjected to solid-liquid separation using a centrifugal separation apparatus. The operating conditions and the selection of the kind of the centrifugal separation device according to the invention are as described above and will not be described in detail here.

In order to clearly describe the method for removing mechanical impurities and ash from coal tar according to the present invention, a preferred embodiment is provided below in conjunction with fig. 1, which specifically includes:

(1) Introducing coal tar 1 to be treated and a first diluting medium 2 into a coal tar intermediate tank 3 for mixing to obtain a mixed stream 4, and then introducing the mixed stream 4 into a first centrifugal separation device 5 for solid-liquid separation to obtain first solid particles 7 and a first liquid-phase stream 6;

(2) Introducing the first liquid-phase material flow 6 into membrane separation filtering equipment 8 for solid-liquid separation to obtain oil residue 10 and a second liquid-phase material flow 9;

(3) The oil residue 10 is introduced into the oil residue tank 12 to be contacted with a second diluting medium 11 which is simultaneously introduced into the oil residue tank 12, the oil residue 10 is washed by the second diluting medium 11, and then washing liquid 13 obtained by washing is recycled to the step (1) to be mixed with the coal tar 1 to be treated.

Another preferred embodiment is provided below in conjunction with fig. 1, specifically including:

(3) The oil residue 10 is introduced into the oil residue tank 12 to be contacted with a second diluting medium 11 which is simultaneously introduced into the oil residue tank 12, the second diluting medium 11 washes the oil residue 10, then a washing liquid 13 obtained by washing is introduced into a second centrifugal separation device 15 for solid-liquid separation, so as to obtain second solid particles 14 and a third liquid-phase stream 16, and then the third liquid-phase stream 16 is recycled to be mixed with the first liquid-phase stream 6 in the step (2).

Unless otherwise indicated, the pressures described herein are all indicated as gauge pressures.

The present invention will be described in detail by examples. In the following examples, various raw materials used were obtained from commercial sources without particular explanation. Wherein, the specific physicochemical properties of coal tar, hydrogenated diesel oil I and hydrogenated diesel oil II are listed in Table 1;

the content of mechanical impurities is determined with reference to the method for determining mechanical impurities of petroleum and petroleum products and additives (GB 511);

the ash content is determined with reference to the petroleum product ash determination method (GB 508);

the yield of coal tar was calculated by the formula (mass of coal tar after treatment/mass of coal tar to be treated) ×100%.

TABLE 1

Note that: "-" indicates no measurement.

Example 1

The process shown in fig. 1 is adopted to remove mechanical impurities and ash in coal tar, and specifically comprises the following steps:

(1) Coal tar 1 to be treated in table 1 was mixed with a first diluent medium 2 (hydrogenated diesel oil II) according to 1: introducing the mixture into a coal tar intermediate tank 3 according to the volume ratio of 0.2, mixing for 2 hours at 80 ℃ to obtain a mixture flow 4, and introducing the mixture flow 4 into a first centrifugal separation device 5 (a horizontal decanter centrifuge, the operation conditions comprise that the temperature is 80 ℃, the pressure is 0.25MPa, and the rotating speed is 2500 r/min) for solid-liquid separation to obtain first solid particles 7 and a first liquid phase flow 6;

(2) Introducing the first liquid-phase material flow 6 into a membrane filtration separation device 8 (an inorganic membrane filtration pipe with the aperture of 10 mu m, and operating conditions comprise that the temperature is 90 ℃, the pressure is 0.3MPa, and the rotating speed is 3500 r/min.) for solid-liquid separation to obtain oil residue 10 and a second liquid-phase material flow 9;

(3) Introducing the oil sludge 10 into the slag tank 12 to be in contact with a second diluting medium 11 (hydrogenated diesel oil II) simultaneously introduced into the slag tank 12, wherein the weight ratio of the oil sludge 10 to the second diluting medium 11 (hydrogenated diesel oil II) is 1:1.5, the second diluting medium 11 (hydrogenated diesel oil II) washes the oil residue 10, and then the washing liquid 13 obtained by washing is recycled to the step (1) to be mixed with the coal tar 1 to be treated for use;

the resulting second liquid stream 9, the content of mechanical impurities and ash in the coal tar, and the yield of the coal tar are shown in table 2.

Example 2

(1) Coal tar 1 to be treated in table 1 was mixed with a first diluent medium 2 (hydrogenated diesel oil II) according to 1: introducing the mixture into a coal tar intermediate tank 3 according to the volume ratio of 0.3, mixing for 1h at 90 ℃ to obtain a mixture flow 4, and introducing the mixture flow 4 into a first centrifugal separation device 5 (a disc centrifuge, the operation conditions comprise that the temperature is 100 ℃, the pressure is 0.4MPa, and the rotating speed is 5000 r/min) for solid-liquid separation to obtain first solid particles 7 and a first liquid phase flow 6;

(2) Introducing the first liquid-phase material flow 6 into a membrane filtration separation device 8 (an inorganic membrane filtration pipe with the aperture of 8 mu m, wherein the operating conditions comprise the temperature of 100 ℃, the pressure of 0.4MPa and the rotating speed of 4500 r/min) for solid-liquid separation to obtain oil residue 10 and a second liquid-phase material flow 9;

(3) Introducing the oil sludge 10 into the slag tank 12 to be in contact with a second diluting medium 11 (hydrogenated diesel oil II) simultaneously introduced into the slag tank 12, wherein the weight ratio of the oil sludge 10 to the second diluting medium 11 (hydrogenated diesel oil II) is 1:1.5, washing the oil residue 10 by the second diluting medium 11 (hydrogenated diesel oil II), introducing washing liquid 13 obtained by washing into a second centrifugal separation device 15 (disc centrifuge, wherein the operation conditions comprise that the temperature is 100 ℃, the pressure is 0.4MPa, the rotating speed is 5000 r/min) for solid-liquid separation to obtain second solid particles 14 and a third liquid-phase stream 16, and recycling the third liquid-phase stream 16 to the step (2) for mixing with the first liquid-phase stream 6;

Example 3

The procedure of example 1 was followed except that the hydrogenated diesel oil II in step (1) was replaced with a commercially available hydrogenated diesel oil having a total aromatic hydrocarbon content of 48% by weight and a paraffin content of 28% by weight;

steps (2) and (3) are the same as in example 1, and the obtained second liquid stream 9, i.e. the content of mechanical impurities and ash in the coal tar, and the yield of the coal tar are shown in table 2.

Example 4

The procedure of example 1 was followed except that the hydrogenated diesel oil II in step (1) was replaced with hydrogenated diesel oil I;

Example 5

The procedure of example 1 was followed, except that the volume ratio of coal tar 1 to be treated in step (1) to the first dilution medium 2 (hydrogenated diesel oil II) was changed to 1:3, a step of;

Comparative example 1

The procedure of example 1 was followed except that the step of mixing with the first diluent medium in step (1) followed by solid-liquid separation was replaced with solid-liquid separation followed by mixing with the first diluent medium, specifically:

introducing the coal tar to be treated in table 1 into a first centrifugal separation device (horizontal decanter centrifuge, operating conditions comprise that the temperature is 80 ℃, the pressure is 0.25MPa, and the rotating speed is 2500 r/min) for solid-liquid separation to obtain first solid particles and a first liquid-phase stream, and introducing the first liquid-phase stream into a coal tar intermediate tank for mixing with a first diluting medium (hydrogenated diesel oil II) which is simultaneously introduced into the coal tar intermediate tank, wherein the volume ratio of the first liquid-phase stream to the first diluting medium (hydrogenated diesel oil II) is 1:0.2;

steps (2) and (3) are the same as in example 1, and the contents of mechanical impurities and ash in the obtained second liquid stream, i.e., coal tar, and the yields of the coal tar are shown in table 2.

Comparative example 2

The procedure of example 1 was followed except that in step (1), no hydrogenated diesel oil II was added;

TABLE 2

Example numbering	Mechanical impurity content/wt%	Ash content/wt%	Yield/%of coal tar
				Example 1	0.005	＜0.002	95.3
Example 2	0.003	＜0.002	96.1
				Example 3	0.008	0.002	90.1
Example 4	0.01	0.004	88.6
				Example 5	0.006	＜0.002	90.4
Comparative example 1	0.01	0.005	87.7
				Comparative example 2	0.013	0.008	86.9

As can be seen from the results of Table 2, compared with the removal method provided by the prior art, the method provided by the invention adopts the specific removal process of firstly mixing the coal tar to be treated with the diluting medium and then sequentially carrying out solid-liquid separation to remove large-particle mechanical impurities and ash and small-particle mechanical impurities and ash, so that the mechanical impurities and ash in the coal tar can be effectively removed, the long-period operation of the separation equipment is ensured, and meanwhile, the yield of the coal tar can be effectively improved.

In addition, as can be seen from the results of comparative examples 1, 3 and 4, the coal tar with lower mechanical impurities and ash content and higher yield can be obtained by adopting the diluting medium with the total aromatic hydrocarbon content of more than 50wt% and the paraffin content of less than 25wt%, thereby further ensuring the long-period operation of the separation equipment.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. A method for removing mechanical impurities and ash from coal tar, the method comprising:

the first dilution medium is selected from at least one of hydrogenated diesel oil, hydrogenated tail oil, catalytic diesel oil, wash oil, anthracene oil and light aromatic hydrocarbon;

the total aromatic hydrocarbon content of the first dilution medium in the step (1) is more than 50wt% and the paraffin content is less than 25wt%.

2. The method of claim 1, wherein in step (1), the mixing conditions comprise: the temperature is 70-100 ℃; the time is 1-10h.

3. The method of claim 2, wherein in step (1), the mixing conditions include: the temperature is 80-100 ℃; the time is 1-3h.

4. The method of claim 1, wherein the volume ratio of coal tar to be treated to the first diluent medium of step (1) is 1:0.1-3.

5. The method of claim 4, wherein the volume ratio of coal tar to be treated to the first diluent medium of step (1) is 1:0.1-1.

6. The method according to any one of claims 1 to 5, wherein the solid-liquid separation of step (1) is performed using a centrifugal separation apparatus;

the operating conditions of the centrifugal separation device include: the temperature is 50-120 ℃, the pressure is 0.05-0.5MPa, and the rotating speed is 1000-6000r/min.

7. The method of claim 6, wherein,

the centrifugal separation equipment is a horizontal decanter centrifuge or a disk centrifuge.

8. The method according to any one of claims 1 to 5, wherein the solid-liquid separation of step (2) is performed using a membrane filtration separation device;

the operating conditions of the membrane filtration separation device include: the temperature is 80-100 ℃; the pressure is 0.1-0.5MPa; the rotating speed is 2000-5000r/min.

9. The method of claim 8, wherein,

the operating conditions of the membrane filtration separation device include: the temperature is 80-100 ℃; the pressure is 0.2-0.4MPa; the rotating speed is 2000-5000r/min.

10. The method of claim 8, wherein the membrane filtration separation device is an inorganic membrane filtration tube;

the aperture of the inorganic membrane filter tube is 0.1-20 mu m.

11. The method of claim 10, wherein the membrane filtration separation device is an inorganic membrane filtration tube;

the aperture of the inorganic membrane filter tube is 0.5-15 mu m.

12. The method of any one of claims 1-5, wherein the coal tar to be treated in step (1) is low temperature coal tar and/or medium low temperature coal tar.

13. The method of claim 12, wherein,

the distillation range of the low-temperature coal tar is 50-450 ℃; the distillation range of the medium-low temperature coal tar is 50-550 ℃.

14. The method according to any one of claims 1 to 5, further comprising washing the oil residue obtained in step (2) with a second dilution medium, and recycling the washing liquid obtained by the washing back to step (1); or alternatively

15. The method of claim 14, wherein the weight ratio of oil sludge to second diluent medium is 1:0.1-3.

16. The method of claim 15, wherein the weight ratio of oil sludge to second diluent medium is 1:0.2-2.