阅读说明：本技术 油系针状焦原料深减压预处理系统 (Deep decompression pretreatment system for oil-based needle coke raw material ) 是由 牛永峰 任晶 徐�明 张可意 徐仁策 于 2021-11-12 设计创作，主要内容包括：本发明公开了一种油系针状焦原料深减压预处理系统,包括加热炉,减压塔,减压汽提塔,一线油出系统,二线油出系统,三线油出系统,顶污油出系统,沥青油出系统,油浆换热系统,所述减压塔从上到下依次与顶污油出系统、一线油出系统、减压汽提塔、沥青油出系统相连；所述减压汽提塔上半部与二线油出系统相连,下半部与三线油出系统相连；所述换热系统与各个换热器相连。本发明提供的油系针状焦原料深减压预处理系统将原料油浆深减压分离为一线油、二线油和三线油,实现了油浆的多级分离,组分更加简单,有利于进行后续的焦化处理,得到质量更高的针状焦产品。(The invention discloses an oil-based needle coke raw material deep decompression pretreatment system which comprises a heating furnace, a decompression tower, a decompression stripping tower, a first-line oil outlet system, a second-line oil outlet system, a third-line oil outlet system, a top dirty oil outlet system, an asphalt oil outlet system and an oil slurry heat exchange system, wherein the decompression tower is sequentially connected with the top dirty oil outlet system, the first-line oil outlet system, the decompression stripping tower and the asphalt oil outlet system from top to bottom; the upper half part of the reduced pressure stripping tower is connected with the second-line oil outlet system, and the lower half part of the reduced pressure stripping tower is connected with the third-line oil outlet system; the heat exchange system is connected with each heat exchanger. The deep decompression pretreatment system for the oil-based needle coke raw material provided by the invention separates the raw material oil slurry into the first-line oil, the second-line oil and the third-line oil through deep decompression, realizes multi-stage separation of the oil slurry, has simpler components, is beneficial to subsequent coking treatment, and obtains a needle coke product with higher quality.)

1. A deep decompression pretreatment system for oil-based needle coke raw materials is characterized by comprising a heating furnace, a decompression tower, a decompression stripping tower, a first-line oil outlet system, a second-line oil outlet system, a third-line oil outlet system, a top dirty oil outlet system, an asphalt oil outlet system and an oil slurry heat exchange system,

the heating furnace is connected with the decompression tower;

the vacuum tower comprises an intermediate oil pump and an intermediate oil heat exchanger, and is sequentially connected with a top sump oil outlet system, a first-line oil outlet system, a vacuum stripping tower and an asphalt oil outlet system from top to bottom;

the upper half part of the reduced pressure stripping tower is connected with the second-line oil outlet system, and the lower half part of the reduced pressure stripping tower is connected with the third-line oil outlet system;

the first-line oil outlet system comprises a first-line heat exchanger of a pressure reducing tower;

the second-line oil outlet system comprises a first heat exchanger on the second line of the vacuum tower, a second heat exchanger on the second line of the vacuum tower and a third heat exchanger on the second line of the vacuum tower;

the three-line oil outlet system comprises a first decompression tower three-line heat exchanger, a second decompression tower three-line heat exchanger and a third decompression tower three-line heat exchanger;

the asphalt oil outlet system comprises an asphalt oil first heat exchanger, an asphalt oil second heat exchanger and an asphalt oil third heat exchanger;

and the heat exchange system is connected with each heat exchanger and is used for exchanging heat between the oil slurry and each separated substance.

2. The deep decompression pretreatment system for oil-based needle coke raw material according to claim 1, wherein the one-line oil outlet system further comprises a vacuum tower one-line oil pump, a vacuum tower one-line reflux cooler, and the one-line oil is separated by the vacuum tower and then sequentially enters the one-line oil storage device through the vacuum tower one-line oil pump, the vacuum tower one-line heat exchanger and the vacuum tower one-line reflux cooler.

3. The deep decompression pretreatment system for oil-based needle coke raw material according to claim 1, wherein the two-line oil outlet system further comprises a two-line oil pump of the decompression tower, the two-line oil pump of the decompression tower is delivered to a cooler, and the two-line oil is separated by the decompression stripping tower and then sequentially passes through the two-line oil pump of the decompression tower, the two-line first heat exchanger of the decompression tower, the two-line second heat exchanger of the decompression tower, the two-line third heat exchanger of the decompression tower and the two-line delivery cooler of the decompression tower to enter the two-line oil storage device.

4. The deep decompression pretreatment system for oil-based needle coke raw material according to claim 1, wherein the three-wire oil outlet system further comprises a decompression tower three-wire oil pump, a decompression tower three-wire outward-feeding cooler, and the three-wire oil is separated by the decompression stripping tower and then sequentially passes through the decompression tower three-wire oil pump, the decompression tower three-wire first heat exchanger, the decompression tower three-wire second heat exchanger, the decompression tower three-wire third heat exchanger and the decompression tower three-wire outward-feeding cooler to enter the three-wire oil storage device.

5. The deep decompression pretreatment system for the oil-based needle coke raw material according to claim 1, wherein the top effluent oil discharge system comprises a first-stage condenser, a second-stage condenser, a third-stage condenser, an oil-water separation device, a decompression tower top vacuum pump, a decompression tower top oil pump, a decompression tower top water pump, wherein the top effluent oil is separated by a decompression tower, sequentially passes through the first-stage condenser and the second-stage condenser, enters the oil-water separation device through the third-stage condenser, is evacuated of non-condensable gas by the decompression tower top vacuum pump, is discharged into a top effluent oil storage device through the decompression tower top oil pump, and is discharged into the top effluent water storage device through the decompression tower top water pump.

6. The deep decompression pretreatment system for oil-based needle coke raw material according to claim 1, wherein the bitumen oil outlet system further comprises a decompression tower bottom pump, the bottom oil of the decompression tower is sent out to a cooler, and the bitumen oil is separated by the decompression tower and then sequentially passes through the decompression tower bottom pump, the first bitumen oil heat exchanger, the second bitumen oil heat exchanger, the third bitumen oil heat exchanger and the bottom oil of the decompression tower to be sent out to the cooler and then enters the bitumen oil storage device.

7. The deep decompression pretreatment system for oil-based needle coke raw material according to claim 1, wherein the connection sequence of each heat exchanger in the heat exchange system is as follows: the method comprises the following steps of slurry oil, a first-line heat exchanger of a decompression tower, a second-line third heat exchanger of the decompression tower, a third heat exchanger of a third-line of the decompression tower, an asphalt oil third heat exchanger, a second-line second heat exchanger of the decompression tower, an oil-in-oil heat exchanger, a third-line second heat exchanger of the decompression tower, an asphalt oil second heat exchanger, a first heat exchanger of the second-line first heat exchanger of the decompression tower, a first heat exchanger of the third-line of the decompression tower, an asphalt oil first heat exchanger and a heating furnace.

8. The deep decompression pretreatment method of the oil-based needle coke raw material is characterized by comprising the following steps of:

s1: the raw material slurry oil is subjected to heat exchange treatment and then enters a pretreatment heating furnace to be heated to 400 ℃;

s2: the heated raw material slurry oil enters a vacuum tower for vacuum fractionation, and overhead oil, first-line oil, middle-section oil and asphalt oil are obtained by fractionation from top to bottom in sequence;

s3: feeding the middle oil obtained in the step S2 into a pressure reduction stripping tower for secondary fractionation, obtaining two-line oil at the upper section and three-line oil at the lower section;

s4: and (3) taking the first-line oil obtained in the step (S2), the second-line oil obtained in the step (S3) and the third-line oil as needle coke raw materials, feeding the needle coke raw materials into a coking production line, feeding the asphalt oil obtained in the step (S2) into an asphalt oil storage device, and feeding the top dirty oil obtained in the step (S2) into a top dirty oil storage device and a top dirty water storage device after oil-water separation.

9. The deep decompression pretreatment system of oil-based needle coke feedstock as recited in claim 8, wherein in S2,

the distillation point range of the one-line oil is 180-220 ℃, and the pressure range is 0.9-1.0 MPa;

the distillation point range of the middle section oil is 290-340 ℃, and the pressure range is 1.0-1.1 MPa.

10. The deep decompression pretreatment system of oil-based needle coke feedstock as recited in claim 8, wherein in S3,

the distillation point range of the two-line oil is 290-320 ℃, and the pressure range is 0.9-1.05 MPa;

the distillation point range of the tri-line oil is 320-340 ℃, and the pressure range is 1.05-1.1 MPa.

Technical Field

The invention belongs to the field of needle coke production equipment, and particularly relates to a deep decompression pretreatment system for an oil-based needle coke raw material.

Background

The needle coke is a high-performance carbon material, has clear surface lines, is a rectangular strip sheet after being crushed, can observe a fiber structure under a microscope, has the excellent characteristics of small thermal expansion coefficient, high graphitization degree, heat resistance, corrosion resistance, high anisotropy degree and the like, and is widely applied to the fields of high-power (HP) and ultra-high-power (UHP) graphite electrodes, special functional materials, composite carbon materials thereof and the like.

The needle coke can be divided into two types of coal-based needle coke and petroleum needle coke according to different production raw materials, generally, the petroleum needle coke has better performance than the coal-based needle coke, the graphitization degree is higher, and the produced electrode material has stronger conductive capability. The raw material of the petroleum needle coke is required to be high in short-side chain polycyclic aromatic hydrocarbon content and low in colloidal asphalt content, and the catalytic oil slurry is rich in short-side chain polycyclic aromatic hydrocarbon and is one of excellent raw materials of the oil-system needle coke. However, the catalytic slurry oil has complex components and wide distillation range, and not only has lighter micromolecule substances, but also has heavy-molecular-weight fused aromatic hydrocarbons, in the carbonization process, the micromolecules or overflow systems or liquid phase mobile phases are generated, the alkane content in the micromolecule substances is high, the reaction intensity is accelerated, the expansion of intermediate phases is not facilitated, the fused ring macromolecules need to react at higher temperature and are easily aggregated into large coking particles, so that the catalytic slurry oil needs to be pretreated to reduce light components and macromolecular substances which are not conducive to coking reaction in the slurry oil, and the residual components of the slurry oil are more conducive to the generation of needle coke. At present, the commonly used pretreatment method is a reduced pressure distillation process, and after solid particles and oil residues of catalytic slurry oil are removed by a reduced pressure distillation device, aromatic hydrocarbon components are extracted to be used as raw materials for producing needle coke.

Chinese patent CN201711118959.5 discloses a method for preparing high-quality needle coke, wherein raw oil is subjected to a reduced pressure distillation device to obtain light distillate oil and heavy distillate oil, the light distillate oil is heated by a coking heating furnace and then enters a coke tower for coke charging, and then the feeding of the heating furnace is switched to the heavy distillate oil to continue the coke charging of the coke tower.

Chinese patent CN201510340928.9 discloses a method for producing needle coke raw material by oil slurry, which comprises the steps of feeding the raw material oil slurry into a reduced pressure distillation unit for reduced pressure distillation, separating out a light oil component, a middle oil component and a tail oil component, feeding the middle oil component into an electrostatic solid-liquid separation unit for electrostatic solid-liquid separation, removing residual solid particles to obtain refined middle oil, and feeding the refined middle oil component into an extraction unit for solvent extraction to obtain the needle coke raw material.

Chinese patent CN201310353779.0 discloses a pretreatment method for producing needle coke catalytic slurry oil, which is characterized in that a component for producing needle coke, which has the aromatic hydrocarbon content of more than 85 percent by mass and the initial boiling point of 350 ℃, is obtained by vacuum distillation and lateral line extraction and is used as a needle coke raw material.

The Chinese patent CN201810504927.7 discloses a processing technology and a system for producing needle coke raw oil by filtering catalytic slurry oil, wherein the catalytic slurry oil is pretreated by a filtering-reduced pressure distillation method, and is separated to obtain upper-stage oil mainly containing saturated hydrocarbon, middle-stage oil mainly containing polycyclic aromatic hydrocarbon and a small amount of polycyclic aromatic hydrocarbon, and lower-stage oil mainly containing colloid and asphaltene, and the middle-stage oil mainly containing polycyclic aromatic hydrocarbon and a small amount of polycyclic aromatic hydrocarbon is used as the needle coke raw material.

It can be seen that, in the center of the prior art, the middle-stage oil obtained by vacuum distillation is mostly used as a raw material for producing needle coke, however, the middle-stage oil is still a mixture of various fractions and needs to be further separated to obtain a needle coke product with higher quality, and meanwhile, the prior art has the defects of high energy consumption and high steam production cost.

Disclosure of Invention

The invention aims to solve the defects of the prior art and provide the deep decompression pretreatment system for the oil-based needle coke raw material, which can carry out multi-stage separation on oil slurry and has low steam production cost.

In order to achieve the purpose, the invention adopts the technical scheme that:

on one hand, the invention provides an oil-based needle coke raw material deep decompression pretreatment system, which comprises a heating furnace, a decompression tower, a decompression stripping tower, a first-line oil outlet system, a second-line oil outlet system, a third-line oil outlet system, a top dirty oil outlet system, an asphalt oil outlet system and an oil slurry heat exchange system,

the heating furnace is connected with the decompression tower and is used for heating the oil slurry after heat exchange;

the vacuum tower comprises a medium oil pump and a medium oil heat exchanger in the vacuum tower, and is sequentially connected with a top dirty oil outlet system, a first-line oil outlet system, a vacuum stripping tower and an asphalt oil outlet system from top to bottom, and is used for separating oil slurry into top dirty oil, first-line oil, middle-section oil and asphalt oil under reduced pressure;

the upper half part of the reduced-pressure stripping tower is connected with the second-line oil outlet system, and the lower half part of the reduced-pressure stripping tower is connected with the third-line oil outlet system and used for further reducing pressure and separating the middle-section oil into second-line oil and third-line oil;

the first-line oil outlet system comprises a first-line heat exchanger of the pressure reducing tower and is used for conveying separated first-line oil;

the second-line oil outlet system comprises a first heat exchanger on the second line of the vacuum tower, a second heat exchanger on the second line of the vacuum tower and a third heat exchanger on the second line of the vacuum tower, and is used for conveying the separated second-line oil;

the three-line oil outlet system comprises a first decompression tower three-line heat exchanger, a second decompression tower three-line heat exchanger and a third decompression tower three-line heat exchanger, and is used for conveying separated three-line oil;

the top dirty oil outlet system is used for conveying the separated top dirty oil;

the asphalt oil outlet system comprises an asphalt oil first heat exchanger, an asphalt oil second heat exchanger and an asphalt oil third heat exchanger, and is used for conveying separated asphalt oil;

and the heat exchange system is connected with each heat exchanger and is used for exchanging heat between the oil slurry and each separated substance.

Preferably, the first-line oil outlet system further comprises a first-line oil pump of the vacuum tower, a first-line reflux cooler of the vacuum tower, and the first-line oil is separated by the vacuum tower and then enters the first-line oil storage device through the first-line oil pump of the vacuum tower, the first-line heat exchanger of the vacuum tower and the first-line reflux cooler of the vacuum tower in sequence.

Preferably, the two-line oil outlet system further comprises a pressure reducing tower two-line oil pump, the pressure reducing tower two-line external cooler, and the two-line oil is separated by the pressure reducing tower two-line oil pump, the pressure reducing tower two-line first heat exchanger, the pressure reducing tower two-line second heat exchanger, the pressure reducing tower two-line third heat exchanger and the pressure reducing tower two-line external cooler to enter the two-line oil storage device.

Preferably, the three-line oil outlet system further comprises a vacuum tower three-line oil pump, the vacuum tower three-line delivery cooler, and the three-line oil is separated by the vacuum stripping tower and then sequentially enters the three-line oil storage device through the vacuum tower three-line oil pump, the vacuum tower three-line first heat exchanger, the vacuum tower three-line second heat exchanger, the vacuum tower three-line third heat exchanger and the vacuum tower three-line delivery cooler.

Preferably, the top dirty oil outlet system comprises a first-level condenser, a second-level condenser, a third-level condenser, an oil-water separation device, a vacuum pump at the top of the vacuum tower, an oil pump at the top of the vacuum tower, a water pump at the top of the vacuum tower, the top dirty oil after being separated by the vacuum tower sequentially passes through the first-level condenser and the second-level condenser, the third-level condenser enters the oil-water separation device, then the non-condensable gas is emptied by the vacuum pump at the top of the vacuum tower, the top dirty oil is discharged into a top dirty oil storage device by the oil pump at the top of the vacuum tower, and the top dirty water is discharged into a top dirty water storage device by the water pump at the top of the vacuum tower.

Preferably, the asphalt oil discharging system further comprises a vacuum tower bottom pump, the vacuum tower bottom oil is sent to a cooler, and the asphalt oil is separated by the vacuum tower and then enters the asphalt oil storage device through the vacuum tower bottom pump, the asphalt oil first heat exchanger, the asphalt oil second heat exchanger, the asphalt oil third heat exchanger and the vacuum tower bottom oil sending cooler in sequence.

Preferably, the connection order of each heat exchanger in the heat exchange system is as follows in sequence: the method comprises the steps of oil slurry, a first-line heat exchanger of a pressure reducing tower, a second-line third heat exchanger of the pressure reducing tower, a third heat exchanger of a third-line heat exchanger of the pressure reducing tower, an asphalt oil third heat exchanger, a second-line second heat exchanger of the pressure reducing tower, an oil heat exchanger in the pressure reducing tower, a third-line second heat exchanger of the pressure reducing tower, an asphalt oil second heat exchanger, a first heat exchanger of a second-line first heat exchanger of the pressure reducing tower, a first heat exchanger of the third-line heat exchanger of the pressure reducing tower, an asphalt oil first heat exchanger and a heating furnace, wherein the heat exchange temperature of the oil slurry is gradually increased, the heat recovery is realized to the maximum degree, and the energy consumption is reduced.

On the other hand, the invention also provides a deep decompression pretreatment method of the oil-based needle coke raw material, which comprises the following steps:

s1: the raw material slurry oil is subjected to heat exchange treatment and then enters a pretreatment heating furnace to be heated to 400 ℃;

s2: the heated raw material slurry oil enters a vacuum tower for vacuum fractionation, and overhead oil, first-line oil, middle-section oil and asphalt oil are obtained by fractionation from top to bottom in sequence;

s3: feeding the middle oil obtained in the step S2 into a pressure reduction stripping tower for secondary fractionation, obtaining two-line oil at the upper section and three-line oil at the lower section;

s4: and (3) taking the first-line oil obtained in the step (S2), the second-line oil obtained in the step (S3) and the third-line oil as needle coke raw materials, feeding the needle coke raw materials into a coking production line, feeding the asphalt oil obtained in the step (S2) into an asphalt oil storage device, and feeding the top dirty oil obtained in the step (S2) into a top dirty oil storage device and a top dirty water storage device after oil-water separation.

Preferably, in S2,

the distillation point range of the one-line oil is 180-220 ℃, and the pressure range is 0.9-1.0 MPa;

the distillation point range of the middle section oil is 290-340 ℃, and the pressure range is 1.0-1.1 MPa.

Preferably, in S3,

the distillation point range of the two-line oil is 290-320 ℃, and the pressure range is 0.9-1.05 MPa;

the distillation point range of the tri-line oil is 320-340 ℃, and the pressure range is 1.05-1.1 MPa.

Compared with the prior art, the deep decompression pretreatment system for the oil-based needle coke raw material, provided by the invention, separates the raw material oil slurry into the first-line oil, the second-line oil and the third-line oil through deep decompression by using the decompression tower and the decompression stripping tower, realizes multi-stage separation of the oil slurry, has simpler components, is beneficial to subsequent coking treatment and obtains a needle coke product with higher quality compared with the prior art in which the raw material oil slurry can only be separated into the middle-stage oil; the raw material oil slurry and each separated oil are subjected to heat exchange through the heat exchange system, so that the maximum recovery of heat is realized, and the energy consumption and the steam production cost are obviously reduced.

Drawings

FIG. 1 is a flow chart showing the design of the deep reduced pressure pretreatment system for oil-based needle coke raw material, and FIG. 2 is a schematic connection diagram showing the heat exchange system of the deep reduced pressure pretreatment system for oil-based needle coke raw material.

Wherein, 1, a heating furnace; 2-a vacuum tower; 21-medium oil pump; 22-medium oil heat exchanger; 3-decompression stripping tower; 41-a vacuum tower first-line oil pump; 42-a pressure reducing tower first-line heat exchanger; 43-a vacuum column first line reflux cooler; 51-a vacuum tower two-line oil pump; 52-a second-line first heat exchanger of the vacuum tower; 53-two-line second heat exchanger of the vacuum tower; 54-a second-line third heat exchanger of the decompression tower; 55-a second-line delivery cooler of the decompression tower; 61-a vacuum tower three-line oil pump; 62-a three-line first heat exchanger of the vacuum tower; 63-a three-line second heat exchanger of the pressure reduction tower; 64-a three-line third heat exchanger of the vacuum tower; 65-decompression tower three-line delivery cooler; 71-a primary condenser; 72-a secondary condenser; 73-a three-stage condenser; 74-oil-water separation device; 75-vacuum column top vacuum pump; 76-vacuum overhead oil pump; 77-vacuum tower top water pump; 81-vacuum tower bottom pump; 82-bitumen oil first heat exchanger; 83-bitumen oil second heat exchanger; 84-bitumen oil third heat exchanger; 85-sending the bottom oil of the vacuum tower to a cooler.

Detailed Description

For a better understanding of the present invention, specific embodiments thereof are described in further detail below with reference to the accompanying drawings.

As shown in the attached drawings 1 and 2, the deep decompression pretreatment system for the oil-based needle coke raw material, provided by the invention, comprises a heating furnace 1, a decompression tower 2, a decompression stripping tower 3, a first-line oil outlet system, a second-line oil outlet system, a three-line oil outlet system, a top dirty oil outlet system, an asphalt oil outlet system and an oil slurry heat exchange system, wherein the heating furnace 1 is connected with the decompression tower 2, the decompression tower 2 comprises a medium oil pump 21 and a medium oil heat exchanger 22, and the top dirty oil outlet system, the first-line oil outlet system, the decompression stripping tower and the asphalt oil outlet system are sequentially connected from top to bottom; the upper half part of the reduced-pressure stripping tower 3 is connected with the second-line oil outlet system, and the lower half part of the reduced-pressure stripping tower is connected with the third-line oil outlet system; the one-line oil outlet system comprises a pressure reducing tower one-line oil pump 41, a pressure reducing tower one-line heat exchanger 42 and a pressure reducing tower one-line reflux cooler 43; the two-line oil outlet system comprises a two-line oil pump 51 of the decompression tower, a two-line first heat exchanger 52 of the decompression tower, a two-line second heat exchanger 53 of the decompression tower, a two-line third heat exchanger 54 of the decompression tower and a two-line delivery cooler 55 of the decompression tower; the three-line oil outlet system comprises a decompression tower three-line oil pump 61, a decompression tower three-line first heat exchanger 62, a decompression tower three-line second heat exchanger 63, a decompression tower three-line third heat exchanger 64 and a decompression tower three-line delivery cooler 65; the top dirty oil outlet system comprises a first-stage condenser 71, a second-stage condenser 72, a third-stage condenser 73, an oil-water separation device 74, a vacuum pump 75 at the top of the vacuum tower, an oil pump 76 at the top of the vacuum tower and a water pump 77 at the top of the vacuum tower; the asphalt oil outlet system comprises a vacuum tower bottom pump 81, an asphalt oil first heat exchanger 82, an asphalt oil second heat exchanger 83, an asphalt oil third heat exchanger 84 and a vacuum tower bottom oil delivery cooler 85; the connection sequence of each heat exchanger in the heat exchange system is as follows: the method comprises the steps of oil slurry-a first-line heat exchanger 41 of a decompression tower, a second-line third heat exchanger 54 of the decompression tower, a third-line third heat exchanger 64 of the decompression tower, a third asphalt oil heat exchanger 83, a second-line second heat exchanger 53 of the decompression tower, an oil heat exchanger 22 of the decompression tower, a third-line second heat exchanger 63 of the decompression tower, a second asphalt oil heat exchanger 83, a first heat exchanger 52 of the decompression tower, a first heat exchanger 62 of the decompression tower, a first asphalt oil heat exchanger 82 and a heating furnace 1.

The deep decompression pretreatment system for the oil-based needle coke raw material can realize multi-stage separation of the raw oil slurry, and specifically comprises the following steps:

s1: the raw material slurry oil is subjected to heat exchange treatment and then enters a pretreatment heating furnace to be heated to 400 ℃;

s2: the heated raw material slurry oil enters a vacuum tower for vacuum fractionation, and overhead oil, first-line oil, middle-section oil and asphalt oil are obtained by fractionation from top to bottom in sequence; wherein, the first line oil is separated at the distillation point range of 180-220 ℃ and the pressure range of 0.9-1.0 MPa, and enters a first line oil storage device after passing through a first line oil pump 41 of the decompression tower, a first line heat exchanger 42 of the decompression tower and a first line reflux cooler 43 of the decompression tower in sequence; separating out middle oil at the distillation point range of 290-340 ℃ and the pressure range of 1.0-1.1 MPa;

s3: feeding the middle oil obtained in the step S2 into a pressure reduction stripping tower for secondary fractionation, obtaining two-line oil at the upper section and three-line oil at the lower section; wherein, the two-line oil is separated at the distillation point range of 290-320 ℃ and the pressure range of 0.9-1.05 MPa, and enters a two-line oil storage device after passing through a two-line oil pump 51 of a decompression tower, a two-line first heat exchanger 52 of the decompression tower, a two-line second heat exchanger 53 of the decompression tower, a two-line third heat exchanger 54 of the decompression tower and a two-line external cooler 55 of the decompression tower in sequence; separating three-line oil at the distillation point of 320-340 ℃ and the pressure of 1.05-1.1 MPa, sequentially passing through a vacuum tower three-line oil pump 61, a vacuum tower three-line first heat exchanger 62, a vacuum tower three-line second heat exchanger 63, a vacuum tower three-line third heat exchanger 64 and a vacuum tower three-line delivery cooler 65, and then entering a three-line oil storage device;

s4: the first-line oil obtained in S2, the second-line oil obtained in S3 and the third-line oil were fed as a needle coke raw material to a coking line. Separating out asphalt oil at the temperature of more than 340 ℃, and feeding the asphalt oil into an asphalt oil storage device after passing through a vacuum tower bottom pump 81, an asphalt oil first heat exchanger 82, an asphalt oil second heat exchanger 83, an asphalt oil third heat exchanger 84 and a vacuum tower bottom oil delivery cooler 85 in sequence; the top dirty oil is separated out from the top, and enters an oil-water separation device 74 through a first-stage condenser 71, a second-stage condenser 72 and a third-stage condenser 73 in sequence, then the non-condensable gas is evacuated through a vacuum pump 75 at the top of the vacuum tower, the top dirty oil is discharged into a top dirty oil storage device through an oil pump 76 at the top of the vacuum tower, and the top dirty water is discharged into the top dirty water storage device through a water pump 77 at the top of the vacuum tower.

In the embodiment, the raw material oil slurry is further separated into the first-line oil, the second-line oil and the third-line oil through the decompression tower 2 and the decompression stripping tower 3, so that the multistage separation of the oil slurry is realized, the subsequent coking treatment is facilitated, and the high-quality oil-based needle coke product is obtained.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.