Coal direct liquefaction residue solvent extraction deashing method, refined pitch and application

Abstract

The application discloses a coal direct liquefaction residue solvent extraction deashing method, refined pitch and application, and relates to the technical field of solid waste resource treatment. The method improves the hot dissolution effect of the extractant and the liquefaction residue by reasonably controlling the process conditions and process parameters, mixes the scale inhibitor composed of multi-hydrocarbon-based organic matter, an additive and coking wash oil with the extractant, adds the ground liquefaction residue into the obtained mixture, and prepares a slurry by controlling the stirring speed, the reaction temperature and the like. The addition of the scale inhibitor improves the concentration of the residue extraction liquid, and enhances the treatment capacity and efficiency. The filter used for precision filtration is a stainless steel sintered filter element, which can resist high temperature and pressure, is helpful to prolong the service life, and is more conducive to the stripping of the pitch and other viscous substances in the liquefaction residue. The prepared ultra-low-ash refined pitch can be used as a high-quality raw material of high-end carbon materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste resource processing, in particular to a coal direct liquefaction residue solvent extraction deashing method, refined pitch and application. BACKGROUND

[0002] The energy endowment state and economic development determine that China is the world's largest coal producer and consumer, and coal currently accounts for a high proportion in China's energy consumption structure, while the country still has a high dependence on foreign oil. Based on the coal endowment advantage, great efforts are made to develop modern coal chemical industry and to strive for efficient conversion of coal to oil and gas. Coal direct liquefaction technology is extremely prominent in the field of coal-to-oil and has extremely important energy strategic significance.

[0003] China is the only country in the world that masters the key technology of million-ton coal direct liquefaction, but there has been no major breakthrough in the efficient resource utilization technology of coal liquefaction residue. Coal direct liquefaction technology produces gasoline and diesel, by-product gas, water and coal liquefaction residue, and the yield of coal liquefaction residue is generally 30% of the raw coal. It has the characteristics of high carbon, high ash and high sulfur, and is composed of heavy oil, liquefaction intermediates, unconverted coal and minerals. Traditional gasification, coking and combustion do not reflect the high value-added utilization potential of liquefaction residue. The preparation of high-end carbon materials from coal liquefaction residue is currently a hot topic in the field of coal direct liquefaction technology, and the key to this process is efficient deep deashing of the residue. Due to the characteristics of the residue, such as small particle size of solid matter, very high viscosity, and small density difference between liquid phase and particulate solid matter, the difficulty of removing inorganic ash from liquefied pitch is increased.

[0004] Therefore, developing efficient deep deashing technology for the fluid characteristics and physical properties of liquefied pitch in the extraction system, breaking through the technical bottleneck of preparing high-end carbon materials from liquefied pitch, and completing the development of the entire process chain are also important components of coal liquefaction process technology development and industry chain extension. The breakthrough of the technology will promote the rapid development of direct liquefaction technology, help the transformation and upgrading of the industry, and have a significant support and leading role. SUMMARY

[0005] One of the purposes of the present application is to provide a coal direct liquefaction residue solvent extraction deashing method, which improves the processing capacity, stability and continuity of the liquefaction residue extraction deashing refining process.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0007] A coal direct liquefaction residue solvent extraction deashing method, comprising the following steps in sequence:

[0008] (1) the extractant and the scale inhibitor are added into a preparation tank in sequence for stirring and heating, when the temperature of the materials in the preparation tank reaches 60℃, the ground liquefaction residue is added into the preparation tank to start pulping; after the addition of the liquefaction residue is completed, N2 is introduced into the preparation tank, the pressure is adjusted to 0.1-0.3MPa and the stirring is kept, when the temperature of the preparation tank reaches 80-160℃, the temperature is kept for a period of time; the scale inhibitor accounts for 0.05-0.2% of the mass percentage of the extractant; the mass ratio of the extractant to the ground residue is 1-3:1;

[0009] The scale inhibitor consists of the following components in mass percentage:

[0010] 20-30% of polyhydric hydrocarbon-based organic matter, 10-20% of an additive, and the balance of coking wash oil;

[0011] (2) after the temperature is kept for a period of time, the obtained slurry is pumped into a metering tank at one time, the slurry is pumped into a centrifuge for centrifugal separation after being stabilized in the metering tank;

[0012] (3) the extractant obtained by centrifugal separation is introduced into a storage tank connected with the centrifuge, and the extractant is sent into a filter for precision filtration from the storage tank; the filter core of the filter used for precision filtration is made of sintered stainless steel mesh material, and the pore size of the filter hole is 0.5-5μm;

[0013] (4) the filtrate obtained after precision filtration in step (3) is introduced into a flash tower, the extractant at the top of the flash tower is recycled, and the deashed refined pitch is at the bottom of the flash tower;

[0014] (5) the filter residue obtained by centrifugal separation in step (3) and the filter residue obtained after precision filtration in step (4) are introduced into a drying machine for drying treatment and recycling.

[0015] The above-mentioned coal direct liquefaction residue solvent extraction and deashing method, in step (1), the extractant is coking wash oil; the polyhydric hydrocarbon-based organic matter is alkyl phenol, alkyl phenol polyoxyethylene ether, polyether polyol or polyol fatty acid ester, the polyhydric hydrocarbon-based organic matter forms a hydrocarbon derivative protective layer on the surface of the medium to inhibit the deposition of asphaltene; the additive is a surfactant.

[0016] The above-mentioned coal direct liquefaction residue solvent extraction and deashing method, the surfactant is selected from one or more of sodium dodecyl sulfonate, dodecyl benzene sulfonic acid, benzoic acid and dodecyl phenol.

[0017] The coal direct liquefaction residue solvent extraction and deashing method, in step (1), the particle size of the ground liquefaction residue is <2 mm; the heating mode of the configuration tank is oil bath heating, steam heating or electric heating; the stirring rate of the extractant and the scale inhibitor in the configuration tank is 80-200 rpm, and the stirring time is 10-45 min; after the pressure is adjusted to 0.1-0.3 MPa, the stirring rate is adjusted to 100-250 rpm; and the constant temperature time is 30-90 min.

[0018] The coal direct liquefaction residue solvent extraction and deashing method, in step (2), a horizontal screw centrifuge is used for centrifugal separation, the separation linear velocity of the horizontal screw centrifuge is 60-120 m / s, and the temperature in the centrifuge is 70-120 ℃.

[0019] The coal direct liquefaction residue solvent extraction and deashing method, in step (3), the solid content in the centrifugal separation obtained extract liquid is <1-2%; the filter has a highest pressure resistance of 2.0 MPa and a highest temperature resistance of 260 ℃.

[0020] The coal direct liquefaction residue solvent extraction and deashing method, in step (3), the precise filtration specific steps are as follows:

[0021] Step one, feeding-filtration-positive blowing: the filter is preheated to 80-120 ℃ and kept constant, the extract liquid in the centrifuge is continuously pumped through the filter inlet, when the filter outlet pressure difference is greater than 2.5 kgf / cm 2 , the feeding is stopped; at this time, the N2 positive blowing mode is started, the positive blowing pressure is ≤3 kgf / cm 2 , when the outlet pressure difference is less than 0.5 kgf / cm 2 , the N2 blowing is stopped, the extract liquid in the centrifuge is continuously pumped into the filter again, when the filter inlet and outlet pressure difference is greater than 2.5 kgf / cm 2 , the feeding is stopped, the positive blowing mode is started again, and the feeding-filtration-filter outlet pressure difference is greater than 2.5 kgf / cm 2 -positive blowing-outlet pressure difference is less than 0.5 kgf / cm 2 , the operation cycle is repeated, until the filter inlet and outlet pressure difference is still greater than 2.5 kgf / cm 2 after the positive blowing, the step two reverse blowing mode is started;

[0022] Step two, reverse blowing: the N2 reverse blowing is started, the reverse blowing gas pressure is ≤5 kgf / cm 2 , after a period of time, the N2 reverse blowing is stopped, the filter residue on the filter surface is blown to the filter bottom by nitrogen, the filter core restores the filtrate flux, the step one operation is started, and the filter bottom filter residue is discharged regularly.

[0023] The coal direct liquefaction residue solvent extraction and deashing method has the characteristics that in step (5), the drying temperature of the drying machine is 200-300 DEG C, and the drying time is 0.5-3 h.

[0024] Another object of the present application is to provide a refined pitch obtained by the coal direct liquefaction residue solvent extraction and deashing method, the ash content of the deashed refined pitch is less than 200 ppm, and the quinoline insoluble content is less than 0.05%.

[0025] Still another object of the present application is to provide the application of the refined pitch, the refined pitch is used as a raw material of high-performance pitch-based carbon fiber, foam carbon lithium ion battery negative electrode material or acicular coke and other high-end carbon materials.

[0026] Compared with the prior art, the present application has the following beneficial technical effects:

[0027] (1) The present application is aimed at the unique structure composition of the liquefaction residue, the physical characteristics and the dissolution performance of the mixed system of the extractant, the scale inhibitor composed of multi-hydrocarbon-based organic matter, additive and coking wash oil is mixed with the extractant, the scale inhibitor and the extractant are heated to 60 DEG C, then the ground liquefaction residue is added, and the slurry is prepared by controlling the stirring speed, reaction temperature and the like; the addition of the scale inhibitor improves the concentration of the residue extraction liquid, enhances the treatment capacity and efficiency; in addition, the filter element of the filter used for precision filtration is made of sintered stainless steel mesh material, the use of the sintered stainless steel filter element can improve the physical and chemical properties of the filter element surface, greatly improve the continuous operation period and stability of the liquefaction residue preparation ultra-low ash (<200 ppm) refined pitch process.

[0028] (2) The present application method is beneficial to improve the hot dissolution efficiency of the liquefaction residue, reduce the viscosity of the extraction system, improve the traditional filtration separation efficiency, reduce the loss of the extractant, improve the recovery efficiency of the extractant, and prolong the continuous and stable operation period of the liquefaction residue extraction and deashing refining process.

[0029] (3) Based on the high viscosity characteristics of the asphaltene in the liquefaction residue extraction suspension system, the scale inhibitor is introduced into the extraction system composed of the liquefaction residue and the coking wash oil, which can improve the concentration of the liquefaction residue extraction liquid, reduce the viscosity of the residue slurry system, improve the flow performance of the residue slurry system, help to remove the viscous asphaltene on the pipe wall, facilitate the smoothness of the pipeline for transporting the residue slurry system, prolong the cleaning period of the residue conveying pipeline, improve the treatment capacity, stability and continuity of the liquefaction residue extraction and deashing refining process.

[0030] (4) The use of stainless steel sintered metal filter element is conducive to the stripping of high-viscosity substances such as asphaltene in the liquefaction residue, and in addition, the stainless steel sintered metal filter element enhances the multiple functions of wear resistance, corrosion resistance and thermal stability of the filter element, and significantly improves the efficiency and economic performance of the liquefaction residue extraction and deashing refining process technology.

[0031] In summary, the coal direct liquefaction residue solvent extraction and deashing method, refined asphalt and application provided by the present application introduce a dispersing scale inhibitor into a high-viscosity extraction system composed of liquefaction residue and wash oil, use a stainless steel sintered filter element, and select a centrifugal separation-precision filtration coupled process for the deashing and refining of liquefaction residue, which has the advantages of high degree of automation, large processing capacity, safe and closed stable long-term operation, and is suitable for special working conditions such as high ash content of coal liquefaction residue, high-viscosity system of coal liquefaction residue extraction, ultra-high filtration precision and high-temperature process environment. The ultra-low ash refined asphalt prepared can be used as high-quality raw material for high-end carbon materials (high-performance asphalt-based carbon fiber, foam carbon, lithium ion battery negative electrode material and needle coke, etc.). BRIEF DESCRIPTION OF DRAWINGS

[0032] The present application will be further described below in conjunction with the drawings:

[0033] Figure 1 A high-definition photo of the liquefaction residue of the present application;

[0034] Figure 2 A high-definition photo of the refined asphalt obtained by the method of the present application; DETAILED DESCRIPTION

[0035] The present application provides a coal direct liquefaction residue solvent extraction and deashing method, refined asphalt and application. In order to make the advantages and technical solutions of the present application clearer and more explicit, the present application will be further described below in conjunction with specific examples.

[0036] The raw materials described in the present application can be obtained through commercial channels. As shown in Figure 1 The liquefaction residue of the present application has an appearance similar to asphalt, which is a flaky solid with black luster, brittle and easy to break. The sulfur content in the residue is high, which is caused by the use of sulfur additives in the liquefaction process. The sulfur in the residue exists mainly in the form of inorganic sulfur. The nitrogen content of the residue is 0.82%, and the ash content is 15.52%, which is mainly composed of minerals in coal and residual liquefaction catalyst. As shown in Figure 2 The ash content of the deashing and refining product of the liquefaction residue is less than 200 ppm, the QI is less than 500 ppm, the sulfur content is less than 100 ppm, the recovery rate of the extractant can reach 96%, and the yield of the refined asphalt can reach 96%.

[0037] The main technical idea of the present application is that the use of scale inhibitor is beneficial to viscosity reduction of the extraction system, improvement of the agent residue ratio, and extension of the pipeline cleaning cycle; the use of the stainless steel sintered filter element effectively reduces the adhesion of the extract on the surface of the filter element, and is beneficial to the rapid recovery of the filtering efficiency by back flushing; and the suitable hot dissolution-filtering process parameters are beneficial to the dissolution of the liquefied residue and the improvement of the separation efficiency. The scale inhibitor, the stainless steel sintered filter element, and the suitable process parameters, combined with the horizontal screw centrifugation-precision filtration coupling technology, can realize the deep deashing of the liquefied residue by extraction, and realize the stable long-period operation of the continuous process.

[0038] The raw materials required for the present application, the liquefied residue, the extractant, and the scale inhibitor are prepared, wherein the liquefied residue is ground to a particle size of <2mm for standby, the dissolution time is shortened, and the dissolution efficiency is improved; the extractant is selected as the cheap and easily available coking wash oil; and the scale inhibitor is composed of the following components in mass percentage: 20-30% of the multi-hydrocarbon-based organic matter, 10-20% of the additive, and the balance of the coking wash oil.

[0039] The multi-hydrocarbon-based organic matter is preferably selected from alkyl phenol, alkyl phenol polyoxyethylene ether, polyether polyol, or polyol fatty acid ester, etc. These multi-hydrocarbon-based organic matters contain multiple hydroxyl groups, have strong positive electricity, and have strong adsorption capacity, and are preferentially adsorbed on the medium surface to form a hydroxyl derivative protective layer, thereby inhibiting the deposition of asphaltene.

[0040] The additive is preferably selected from one or more of sodium dodecyl sulfonate, dodecyl benzene sulfonic acid, benzoic acid, and dodecyl phenol. The organic acid provides lipophilic groups to ensure better dissolution and dispersion of asphaltene in the liquefied residue wash oil extraction system, and the presence of the lipophilic groups and chains in the molecular structure can be adsorbed on the lipophilic surface of asphaltene to hinder the aggregation, bonding, and adhesion of the lipophilic solid phase, thereby reducing the space friction and space structure force, and further reducing the viscosity and shear force. In addition, the additive is actually a surfactant, which can reduce the interfacial surface tension, form a stable dispersion system of the liquefied residue and the wash oil, and effectively improve the dispersion performance and stability.

[0041] The present application is a coal direct liquefaction residue solvent extraction deashing method, and the required system mainly includes a configuration tank, a metering tank, a centrifuge, a storage tank, a filter, a flash tower, and a dryer. The configuration tank, the metering pump, and the centrifuge are connected in sequence, the extract outlet of the centrifuge is connected with the storage tank, the residue outlet of the centrifuge is connected with the dryer, the filter has a highest pressure resistance of 2.0MPa and a highest temperature resistance of 260℃, the filter element is made of sintered stainless steel mesh material, and the filter pore size is 0.5-5μm. The residue outlet of the filter is connected with the dryer, and the filtrate outlet of the filter is connected with the flash tower.

[0042] The method of the present application specifically includes the following steps:

[0043] Step one, hot dissolution

[0044] The extractant is added to a preparation tank. The outer shell of the preparation tank is heated by oil bath, steam, or electricity. The preparation tank is equipped with a stirrer, which is turned on simultaneously during the addition of the extractant. The stirring speed is 80-200 rpm, and the scale inhibitor accounts for 0.05-0.2% of the extractant mass. The stirring time is 10-45 min. The tank body is heated to 80-160℃. When the solvent temperature in the preparation tank reaches 60℃, the residue powder (extractant mass / residue mass = 1-3:1) is added to start slurry preparation. After the residue powder is added, N2 is introduced and the pressure is adjusted to 0.1-0.3 MPa. The stirring speed is adjusted to 100-250 rpm. When the temperature of the preparation tank reaches 80-160℃, it is kept at a constant temperature for 30-90 min. The slurry is then pumped into the metering tank in one go. The pump at the bottom of the metering tank continuously and stably pumps the slurry into the centrifuge.

[0045] Step 2: Centrifugation

[0046] This invention preferably uses a horizontal screw centrifuge for centrifugal separation. The horizontal screw centrifuge is a continuous feeding and discharging device, highly suitable for large-scale, long-term continuous operation. Increasing the linear velocity and separation temperature of the horizontal screw centrifuge can improve the separation efficiency of the extract and raffinate, which is beneficial for reducing the solid content in the extract. However, excessively high linear velocity and separation temperature both lead to increased energy consumption. This invention preferably uses a horizontal screw centrifuge with a separation linear velocity of 60–120 m / s, an internal temperature of 70–120°C, and a solid content in the extract of <1–2%.

[0047] Step 3: Precision Filtration

[0048] (1) Feed-Filtration-Forward Blow: The filter is preheated to 80~120℃ and kept constant. The extract from the centrifugal separation is continuously pumped into the filter. When the pressure difference between the inlet and outlet of the filter is greater than 2.5 kgf / cm³, the filter is prepared. 2 Stop feeding and start the N2 forward purging mode (nitrogen flow direction is the same as the filtration direction), with the forward purging pressure not exceeding 3 kgf / cm². 2 After 5 minutes, the outlet pressure difference is less than 0.5 kgf / cm. 2 When the N2 purging is stopped, the extract from the centrifuge is continuously pumped back into the filter, and the pressure difference between the inlet and outlet of the filter is again greater than 2.5 kgf / cm². 2 Stop feeding at the designated time, then restart the forward blowing mode, ensuring the pressure difference between the feed, filter, and filter outlet is greater than 2.5 kgf / cm². 2 - Forward blowing - outlet pressure difference less than 0.5 kgf / cm 2 The operation is repeated in this cycle until the pressure difference between the filter inlet and outlet remains greater than 2.5 kgf / cm² after forward blowing. 2 This mode will then terminate and enter the backflush mode.

[0049] (2) Backflush: open N2 backflush (nitrogen flow direction opposite to the direction of filtration, aimed at blowing off the filter cake attached to the surface of the filter core to restore the filtration flux), the backflush gas pressure is not more than 5 kgf / cm 2 , stop N2 backflush after 10 min, the filter residue on the surface of the filter core is blown to the bottom of the filter by nitrogen, the filter core restores the filtrate flux, enters step (1) operation, and the filter residue at the bottom is discharged regularly.

[0050] Fourth step, recovery of the extractant in the extract by vacuum flash distillation

[0051] The filtrate in the filter enters the flash distillation column, the extractant at the top is reused for hot dissolution with the residue, and the bottom is the deashed refined pitch with ash content lower than 200 ppm and QI (quinoline insoluble) content lower than 0.05%, as shown in the formula (I). It is mainly used as a raw material for high-performance pitch-based carbon fibers, foam carbon, lithium ion battery negative electrode materials, and needle coke and other high-end carbon materials. Figure 2

[0052] Fifth step, recovery of the extractant in the extract residue by drying the filter residue

[0053] The centrifugal filter residue and the filter residue discharged regularly contain 20-30% of the extractant, and the extractant remaining in the filter residue is recovered by heating drying (such as thin film drying or vacuum drying or stripping, etc.), the drying temperature is 200-300 DEG C, the drying time is 0.5-3 h, and the recovered extractant can be mixed with the extractant recovered by vacuum distillation and reused for pulping with the residue. The dry filter residue can be used as fuel or gasification raw material.

[0054] The application will be described in detail below through specific examples, and the property analysis of the raw material liquefied residue in the examples is shown in Table 1.

[0055] Table 1 Property analysis of liquefied residue

[0056]

[0057] The application is further illustrated in combination with Examples 1-4 and Comparative Examples 1-4, and the influence of different process parameters and ratios on the properties of refined pitch can be known from the product property analysis of Examples 1-4 shown in Table 2 and the product property analysis of Comparative Examples 1-4 shown in Table 3.

[0058] Table 2 Product property analysis of refined pitch in Examples 1-4

[0059]

[0060] Table 3 Product property analysis of pitch in Comparative Examples 1-4

[0061] ​

[0062] The parts not described in the present application can be realized by those skilled in the art with reference to the prior art.

[0063] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application, and are not used as a limitation to the present application, and as long as the above embodiments are within the spirit and scope of the present application, appropriate changes and variations made to the above embodiments should fall within the scope of the claims of the present application.

Claims

1. A method for descaling of coal direct liquefaction residue by solvent extraction, characterized by, Comprise the following steps in sequence: (1) the extractant and scale inhibitor are added into the configuration tank in sequence for stirring and heating, when the temperature of the materials in the configuration tank reaches 60℃, the ground liquefied residue is added into the configuration tank to start pulping; after the addition of the liquefied residue is completed, N2 is introduced into the configuration tank, the pressure is adjusted to 0.1~0.3MPa and the stirring is kept, when the temperature of the configuration tank reaches 80~160℃, the temperature is kept for a period of time; the mass percentage of the scale inhibitor in the extractant is 0.05~0.2%; the mass ratio of the extractant to the ground residue is 1~3:1; The scale inhibitor is composed of the following components in mass percentage: 20~30% of polybasic hydrocarbon-based organic matter, 10~20% of auxiliary agent, and the balance of coking wash oil; (2) after the temperature is kept for a period of time, the obtained slurry is pumped into the metering tank at one time, the slurry is pumped into the centrifuge for centrifugal separation after being stabilized in the metering tank; (3) the obtained extractive liquid is introduced into the storage tank connected with the centrifuge, and the extractive liquid is sent into the filter for precision filtration from the storage tank, the filter core of the filter used for precision filtration is made of sintered stainless steel mesh material, and the pore size of the filter hole is 0.5~5μm; (4) the obtained filtrate after precision filtration in step (3) is introduced into the flash tower, the extractant at the top of the flash tower is recycled, and the deashed refined asphalt is at the bottom of the flash tower; (5) the filter residue obtained in step (3) and the filter residue obtained after precision filtration in step (4) are introduced into the drying machine for drying treatment and recycling; in step (1), the extractant is coking wash oil; the polybasic hydrocarbon-based organic matter is alkyl phenol, alkyl phenol polyoxyethylene ether, polyether polyol or polyol fatty acid ester, the polybasic hydrocarbon-based organic matter forms a hydrocarbon derivative protective layer on the medium surface by adsorption to inhibit the deposition of asphaltene; the auxiliary agent is a surfactant.

2. The method according to claim 1, wherein the coal direct liquefaction residue is subjected to the solvent extraction and deashing process. The surfactant is selected from one or more of sodium dodecyl sulfonate, dodecyl benzene sulfonic acid, benzoic acid and dodecyl phenol.

3. The method according to claim 1, wherein the coal direct liquefaction residue is subjected to the solvent extraction and deashing process. In step (1), the particle size of the ground liquefied residue is <2mm; the heating mode of the configuration tank is oil bath heating, steam heating or electric heating; the stirring rate of the extractant and scale inhibitor in the configuration tank is 80~200rpm, and the stirring time is 10~45min; after the pressure is adjusted to 0.1~0.3MPa, the stirring rate is adjusted to 100~250rpm; the temperature keeping time is 30~90min.

4. The method according to claim 1, wherein the coal direct liquefaction residue is subjected to the solvent extraction and deashing process. In step (2), a horizontal screw centrifuge is used for centrifugal separation, the separation linear velocity of the horizontal screw centrifuge is 60~120m / s, and the temperature in the centrifuge is 70~120℃.

5. The method according to claim 1, wherein the coal direct liquefaction residue is subjected to the solvent extraction and deashing process. In step (3), the solid content in the obtained extractive liquid is <1~2%; the filter can withstand a pressure of up to 2.0MPa and a temperature of up to 260℃.

6. The method according to claim 1, wherein the coal direct liquefaction residue is subjected to the solvent extraction and deashing process. In step (3), the specific steps of precision filtration are: Step 1, feed-filtration-positively blowing: the filter is preheated to 80-120℃ and kept constant, the extraction liquid in the centrifuge is continuously pumped through the inlet of the filter into, when the pressure difference of the filter outlet is greater than 2.5kgf / cm 2 , the feeding is stopped; at this time, the N2 positively blowing mode is started, the positively blowing pressure is ≤3kgf / cm 2 , when the pressure difference of the outlet is less than 0.5kgf / cm 2 , the N2 blowing is stopped, the extraction liquid in the centrifuge is continuously pumped into the filter again, when the pressure difference of the filter inlet and outlet is greater than 2.5kgf / cm 2 , the feeding is stopped, the positively blowing mode is started again, when the pressure difference of the feed-filtration-filter outlet is greater than 2.5kgf / cm 2 -positively blowing-outlet pressure difference less than 0.5kgf / cm 2 , the operation cycle is repeated, until the pressure difference of the filter inlet and outlet after positively blowing is still greater than 2.5kgf / cm 2 , the termination is entered into the back blowing mode of step 2; Step two, back flushing: open N2 back flushing, back flushing gas pressure ≤ 5kgf / cm 2 After a period of time, stop N2 back flushing, filter residue on the surface of the filter is blown to the bottom of the filter by nitrogen, the filter core restores the filtrate flux, enters step one operation, the filter residue at the bottom of the filter is discharged regularly.

7. The method according to claim 1, wherein the method is characterized by: In step (5), the drying temperature of the drying machine is 200~300℃, and the drying time is 0.5~3h.

8. A refined bitumen, characterized in that, The application discloses a refined pitch obtained by a coal direct liquefaction residue solvent extraction and deashing method according to any one of claims 1-7, wherein the ash content of the refined pitch is less than 200 ppm, and the quinoline insoluble content is less than 0.05%.

9. Use of a refined bitumen according to claim 8, characterized in that, The application is to use the refined pitch as raw material of high-end carbon materials such as high-performance pitch-based carbon fiber, foam carbon lithium ion battery negative electrode material or needle coke.

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