Method and system for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization

Abstract

This invention belongs to the field of needle coke preparation technology, and relates to a method and system for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization. The method includes: 1) extraction distillation, in which a mixed solvent and medium- and low-temperature coal tar are distilled and extracted to obtain circulating oil, circulating solvent, and refined pitch; 2) pitch carbonization, using a non-isothermal method and a combination of steam and circulating oil for coking, to carbonize the refined pitch to obtain semi-coke; 3) calcination of the semi-coke to obtain needle coke. This invention can obtain refined pitch with low heteroatom content and low quinoline insoluble content; the semi-coke obtained through non-isothermal static settling results in a uniform component distribution in the reaction system, good needle coke fiber structure, stable product quality, and high yield; the combined coking process effectively controls the molecular reactivity in the system, obtaining high-quality needle coke.

Description

Technical Field

[0001] This invention belongs to the field of needle coke preparation technology, and relates to a method and system for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization. Background Technology

[0002] Needle coke, due to its excellent characteristics such as low coefficient of thermal expansion, good electrical conductivity, high mechanical strength, and strong oxidation resistance, is widely used as a raw material for graphite electrodes and battery anodes. Medium- and low-temperature coal tar pitch has a high aromatic content, is abundant, and inexpensive, making it an important high-quality raw material for producing coal-based needle coke. However, its low content of heteroatoms and quinoline insolubles (QI) leads to high reactivity and viscosity in the reaction system during carbonization, resulting in low content of the semi-coke mesophase and poor optical texture, leading to high resistivity and poor quality of the resulting needle coke. Therefore, the preparation of needle coke using medium- and low-temperature coal tar pitch requires optimization of the raw material composition and thermal polymerization process.

[0003] In the existing patent CN114806620A, two different solvents are first mixed, and two extraction and sedimentation separations are performed. Then, the heavy phase and light phase are separated and distilled for recovery to pretreat the coal-based needle coke raw material. Although the yield of refined pitch is high and the content of quinoline insoluble matter is low, the extraction process is complicated and the yield is low.

[0004] In the existing patent CN110791315A, the catalyst powder in the oil slurry is first removed by chemical precipitation, then the oil slurry is purified by conventional compression reduction and polymerization, and finally needle coke powder is obtained by delayed coking and calcination. The needle coke has a low resistivity, but this process is not suitable for preparing needle coke from medium and low temperature coal tar with high oxygen content.

[0005] Patent CN109777458A uses a raw material distillation tower, a delayed coking tower, and a coking fractionation tower to prepare needle coke. Although this device has high coking efficiency, it also produces a variety of light oils as byproducts, resulting in high ash content in the prepared coke, which has a significant impact on the microcrystalline structure of the product.

[0006] The existing thermal polymerization process uses isothermal polymerization, which results in uneven distribution of components in the internal reaction system during carbonization, with a large number of needle coke embedded structures; low yield, unstable product quality, and large fluctuations in key quality indicators such as volatile matter and ash content of needle coke.

[0007] In existing carbonization processes, a single coking method is used in the nucleation and solidification stages. In the later stages of carbonization, the loss of light components in the system leads to poor orderliness of the mesophase fiber structure.

[0008] As can be seen from the existing technologies for preparing needle coke, although needle coke can be obtained, there are still problems such as a large number of embedded structures, poor order of intermediate phase fiber structure, low yield, uneven component distribution, and unstable quality of needle coke products. Summary of the Invention

[0009] To address the technical problems of uneven component distribution, numerous embedded structures, and low yield in existing needle coke preparation methods, this invention provides a method for preparing needle coke from medium- and low-temperature coal tar through extraction distillation and carbonization. The method employs an extraction-distillation composite process to pretreat medium- and low-temperature coal tar, obtaining refined pitch and recycled oil with low heteroatom content and low quinoline insoluble content. Semi-coke is obtained through a non-isothermal static polymerization process, resulting in a uniform component distribution in the reaction system within the carbonization tower, good needle coke fiber structure, stable product quality, and high yield. During carbonization, a combination of water vapor and recycled oil is used for coke pulling, effectively controlling the molecular reactivity in the system, thereby obtaining high-quality needle coke.

[0010] This application also provides a system for preparing needle coke, which has a simple structure and produces refined pitch with low heteroatom content and low quinoline insoluble content, while also obtaining the circulating oil required for combined coke pulling.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] A method for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization includes the following steps:

[0013] 1) Extractive distillation

[0014] Medium- and low-temperature coal tar and mixed solvent are fed into the integrated distillation and extraction unit at a mass ratio of 1:2. Distillation and extraction yields circulating oil, solvent oil, and refined asphalt. The solvent oil is returned to the integrated distillation and extraction unit as a mixed solvent.

[0015] 2) Asphalt carbonization

[0016] 2.1) The refined asphalt obtained in step 1) is pressurized and mixed with water vapor to obtain a mixed oil-gas mixture;

[0017] 2.2) After preheating, the mixed oil and gas enter the reactor and carbonize using an intermittent non-isothermal polymerization method. In the nucleation stage, water vapor is used for coking, and in the solidification stage, the circulating oil from step 1) is used for coking to obtain semi-coke.

[0018] 3) Calcination

[0019] Under a nitrogen atmosphere, the semi-coke from step 2) is calcined and cooled to obtain powdered needle coke.

[0020] Furthermore, in step 1), the distillation extraction temperature is 320°C, the reflux ratio of the distillation extraction device is 3:1, and the mixed solvent includes a main agent and a composite additive, wherein the composite additive accounts for 3wt% to 5wt%; the main agent is composed of toluene and n-heptane in a mass ratio of 2 to 4:1, and the composite additive is composed of tertiary amine oxide and polyacrylic acid microgel in a mass ratio of 1:1.

[0021] Furthermore, in step 1), the refined asphalt has the following specifications: aromaticity 0.75–0.83, quinoline insoluble content ≤0.3%, C content 85–87%, H content 7–9%, O content 3–5%, S content 0.21–0.32%, and N content 0.17–0.29%; the circulating oil is a 240℃–320℃ fraction, the circulating oil contains 40–60% 2–3 ring aromatics, and the circulating oil has a branching degree of 0.4–0.6.

[0022] Furthermore, in step 2), the steam temperature is 300℃, the preheating temperature of the mixed oil and gas is 340℃~380℃, the carbonization temperature is 380℃~440℃, the temperature interval is 10℃~40℃, the heating rate is 1.5℃ / min, the reaction pressure is 0.5MPa, the carbonization reaction time is 12h, and the first 8h uses steam to pull the coke, and the last 4h uses circulating oil to pull the coke.

[0023] Furthermore, the semi-coke obtained in step 2) has a mesophase content of 80% to 97% and a mesophase optical texture index of 79 to 89.

[0024] Furthermore, in step 3), the calcination conditions are: pressure 0.01 MPa, temperature increased to 800℃ at a rate of 3℃ / min, and constant temperature reaction for 2 hours; then, with the pressure unchanged, the temperature is increased to 1400℃ at a rate of 1℃ / min, and constant temperature reaction for 2 hours.

[0025] Needle coke prepared by a medium-low temperature coal tar extraction distillation-carbonization method has an average resistivity of at least 185 μΩ·m and a coefficient of thermal expansion of 1.20 × 10⁻⁶. -6 / ℃~1.48×10 -6 / ℃.

[0026] A preparation system for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization includes an integrated distillation and extraction device, a refined asphalt tank, a circulating oil tank, a water storage tank, a second preheater, a third preheater, and a carbonization tower. The integrated distillation and extraction tower is connected to the refined asphalt tank and the circulating oil tank respectively. The water storage tank is connected to the carbonization tower in sequence via the second preheater and the third preheater. The third preheater is also connected to the refined asphalt tank and the circulating oil tank.

[0027] Furthermore, the integrated distillation and extraction device includes a distillation and extraction column, a first preheater, a first condenser, a second condenser, and a first gas-liquid separator. The distillation and extraction column is respectively provided with a raw material inlet, a top outlet, an upper side outlet, a lower side inlet, and a lower side outlet. The first preheater is connected to the top outlet, the upper side outlet, and the lower side outlet via the raw material inlet. The top outlet is connected to a circulating oil tank via the second condenser and the first gas-liquid separator. The lower side outlet is connected to a refined asphalt tank. The upper side outlet is connected to the interior of the distillation and extraction column via the first condenser and the lower side inlet.

[0028] Furthermore, the integrated distillation and extraction device also includes a third condenser, a second gas-liquid separator V, and a first tail gas treatment tank connected in sequence; the third condenser is also connected to the first gas-liquid separator.

[0029] The beneficial effects of this invention are:

[0030] 1. The integrated distillation and extraction device of the present invention can not only achieve medium- and low-temperature coal tar fractionation but also solvent extraction. The refined pitch after extraction and distillation has a QI content of ≤0.3 and an aromaticity of 0.75-0.83, providing high-quality raw materials for further carbonization. After secondary condensation, the light components at the top of the tower are separated to obtain circulating oil with suitable aromatic content for coking, providing sufficient precipitated gas for semi-coke solidification. The process is simple and easy to operate, saving solvent. After the pilot test, it can also be used for distillation of coking oil produced in the carbonization process to obtain a variety of light products such as naphtha and anthracene oil, thereby realizing the fractional utilization of coal tar.

[0031] 2. The composite additive in the mixed solvent of this invention includes tertiary amine oxide and polyacrylic acid microgel. The tertiary amine oxide is a surface-active component, which increases the surface activity of the system during the extraction process, which is beneficial to reduce the viscosity of the system and improve the mass transfer efficiency. The polyacrylic acid microgel is an adsorbent, which can capture the insoluble components in the extraction system in a timely manner, so that the insoluble components can quickly settle to the bottom of the extraction tower, thereby further improving the separation efficiency. The refined asphalt obtained thereby has a QI content of ≤0.1 and an ash content of ≤50ppm.

[0032] 3. In the carbonization process of this invention, water and steam are used for coking during the nucleation stage. On the one hand, this can increase the linear velocity of oil and gas in the furnace tube, thereby inhibiting coking and blockage of the furnace tube. On the other hand, the appropriate amount of water injection can control the reaction time in the coking tower, improve the mass and heat transfer in the tower, and thus improve the optical structure of the semi-coke. In the solidification stage, circulating oil is used for coking, which can replenish the loss of light components in the later stage of carbonization in a timely manner, increase the amount of product gas released, and the external force brought about by the evolution of product gas is more conducive to orienting the carbonaceous mesophase into a preferred needle-like structure.

[0033] 4. The non-isothermal polymerization method of this invention utilizes the component migration principle of asphalt components. Based on the component separation phenomenon, a corresponding gradient non-isothermal thermal field is provided. A high-temperature zone is set in the upper part to promote the first apparent reaction of component transformation and increase the reaction rate of the upper asphalt molecules. A low-temperature environment is provided in the lower part to inhibit the second apparent reaction of component transformation and reduce the reaction rate of asphalt molecules. At the same time, it alleviates the excessive reaction of the lower high molecular weight components caused by gravity deposition and effectively suppresses the self-acceleration effect. This results in a uniform component distribution and a narrow molecular weight distribution in the reaction system within the carbonization tower. The resulting needle-like coke fibers have a good structure, low coefficient of thermal expansion, good electrical conductivity, and stable product quality with a high yield. Attached Figure Description

[0034] Figure 1 This is a polarized light microstructure of the needle-shaped coke prepared in Example 7;

[0035] Figure 2 This is a scanning electron microscope (SEM) image of the needle-shaped coke prepared in Example 7;

[0036] Figure 3 The image shows the polarized light microstructure of the needle-shaped coke prepared in Comparative Example 7.

[0037] Figure 4 The image shows the scanning electron microscope structure of the needle-shaped fossil prepared in Comparative Example 7.

[0038] Figure 5 This is a schematic diagram of the needle coke preparation system provided by the present invention;

[0039] in:

[0040] V101—Raw material tank; V102—Insoluble heavy component tank; V103—Solvent tank; V104—First gas-liquid separator tank; V105—Second gas-liquid separator tank; V106—First tail gas treatment tank; V201—Refined asphalt tank; V202—Circulating oil tank; V203—Water storage tank; V204—Third gas-liquid separator tank; V205—Circulating oil collection tank; V206—Fourth gas-liquid separator tank; V207—Second tail gas treatment tank;

[0041] E101—First condenser; E102—Second condenser; E103—Third condenser; E201—Fourth condenser; E202—Fifth condenser; F101—First preheater; F201—Second preheater; F202—Third preheater;

[0042] T101—Distillation and extraction tower; T201—Carbonization tower; P101—Raw material pump; P201—Refined asphalt pump; P202—Circulating oil pump; P203—Water pump. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0044] This invention uses medium- and low-temperature coal tar as raw material. After heating with a mixed solvent, it undergoes distillation extraction to obtain heavy components (refined pitch), light components, solvent oil, and insoluble matter. The heavy components (refined pitch) are then carbonized to prepare semi-coke, while the light components are fractionated to obtain light component oil (recycled oil), and the solvent oil is recycled. By setting different temperatures for each stage of the carbonization reaction, a non-isothermal static polymerization process is used to obtain semi-coke. Simultaneously, water vapor is used for coke pulling during the nucleation stage, and the distilled light component oil (recycled oil) is used for coke pulling during the solidification stage to obtain semi-coke. The semi-coke is then calcined at high temperature to obtain needle coke. During the carbonization stage, an oil and gas recovery system is used to recover coking heavy distillate oil and water-containing light distillate oil.

[0045] The method for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization provided by the present invention includes the following steps:

[0046] 1) Extractive distillation

[0047] A mixed solvent and low-temperature coal tar are fed into an integrated distillation and extraction unit. Distillation and extraction yields circulating oil, solvent oil, and refined asphalt. The solvent oil is returned to the integrated distillation and extraction unit as a mixed solvent. Specifically, this includes:

[0048] 1.1) The medium-low temperature coal tar and the mixed solvent are fed into the distillation and extraction integrated device in a mass ratio of 1:2.

[0049] 1.2) By adjusting the temperature of the distilled circulating oil and gas, the reflux ratio, and the temperature of the integrated distillation and extraction tower, circulating oil and gas, solvent oil and gas, and refined pitch are extracted from medium- and low-temperature coal tar through distillation and extraction.

[0050] 1.3) After the circulating oil and gas are condensed, the circulating oil is obtained. After the solvent oil and gas tower is condensed, the solvent oil is returned to the integrated distillation and extraction tower for recycling. The refined asphalt tower collects and keeps it warm.

[0051] In step 1), the temperature inside the distillation extraction apparatus is 320℃, and the reflux ratio is 3:1.

[0052] The mixed solvent comprises a main agent and a composite additive, with the composite additive accounting for 3 wt% to 5 wt% of the mixed solvent and the main agent accounting for 95 wt% to 97 wt%. The main agent is composed of toluene and n-heptane in a mass ratio of 2 to 4:1, and the composite additive is composed of tertiary amine oxide and polyacrylic acid microgel in a mass ratio of 1:1.

[0053] In this step, the refined asphalt has the following specifications: aromaticity 0.75–0.83, quinoline insoluble matter (QI) content ≤0.1, ash content ≤50 ppm, C content 85–87%, H content 7–9%, O content 3–5%, S content 0.21–0.32%, and N content 0.17–0.29%.

[0054] The circulating oil is a 240℃~320℃ fraction, with 40~60% of 2~3 ring aromatics and a branching degree of 0.4~0.6.

[0055] 2) Asphalt carbonization

[0056] 2.1) The refined asphalt obtained in step 1) is pressurized and mixed with water vapor to obtain a mixed oil-gas mixture.

[0057] 2.2) After the mixed oil and gas are preheated, they enter the reactor and are carbonized by intermittent non-isothermal polymerization. In the nucleation stage, water vapor is used for coking, and in the solidification stage, the circulating oil from step 1) is used for coking to obtain semi-coke.

[0058] In this step, steam is used to preheat the refined asphalt at a temperature of 300℃. The preheating temperature of the mixed oil and gas is 340℃~380℃, the carbonization temperature is 380℃~440℃, the temperature interval is 10℃~40℃, the heating rate is 1.5℃ / min, the reaction pressure is 0.5MPa, and the carbonization reaction time is 12h. For the first 8h, steam is used for coking, and for the last 4h, circulating oil is used for coking.

[0059] In step 2), the carbonization temperature decreases from top to bottom within the reactor, with a heating rate of 1.5℃ / min in different regions, and a reaction pressure of 0.5MPa within the reactor. The temperature in different regions remains constant during the reaction.

[0060] In the process, the feed rate of refined asphalt is 5 kg / h, the feed rate of water vapor in the nucleation stage is 0.8 to 1.2 kg / h, and the feed rate of circulating oil in the coking stage is 1.0 to 1.5 kg / h.

[0061] 3) Calcination

[0062] Under a nitrogen atmosphere, the semi-coke from step 2) is calcined and cooled to obtain powdered needle coke.

[0063] In this step, the calcination conditions are: pressure 0.01 MPa, temperature increased to 800℃ at a rate of 3℃ / min, and constant temperature reaction for 2 hours; then, with the pressure unchanged, the temperature is increased to 1400℃ at a rate of 1℃ / min, and constant temperature reaction for 2 hours.

[0064] The present invention also provides a preparation system for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization.

[0065] See Figure 5 The preparation system includes an integrated distillation and extraction device, a refined asphalt tank V201, a circulating oil tank V202, a water storage tank V203, a second preheater F201, a third preheater F202, and a carbonization tower T201. The integrated distillation and extraction device is connected to the refined asphalt tank V201 and the circulating oil tank V202 respectively. The water storage tank V203 is connected to the carbonization tower T201 in sequence via the second preheater F201 and the third preheater F202. The third preheater F202 is also connected to the refined asphalt tank V201 and the circulating oil tank V202.

[0066] The integrated distillation and extraction unit includes a distillation and extraction column T101, a first preheater F101, a first condenser E101, a second condenser E102, and a first gas-liquid separator V104. The distillation and extraction column T101 is equipped with a raw material inlet, a top outlet, an upper side outlet, a bottom inlet, and a bottom outlet. The first preheater F101 is connected to the top outlet, upper side outlet, and bottom outlet via the raw material inlet. The top outlet is connected to a circulating oil tank V202 via the second condenser E102 and the first gas-liquid separator V104. The bottom outlet is connected to a refined asphalt tank V201, and the upper side outlet is connected to the interior of the distillation and extraction column T101 via the first condenser E101 and the bottom inlet. The integrated distillation and extraction unit also includes a third condenser E103, a second gas-liquid separator V105, and a first tail gas treatment tank V106, connected in sequence. The third condenser E103 is also connected to the first gas-liquid separator V104.

[0067] The preparation system also includes an oil and gas recovery unit, which includes a third gas-liquid separator V204, a circulating oil collection tank V205, a fourth gas-liquid separator V206, a second tail gas treatment tank V207, a fourth condenser E201, and a fifth condenser E202. The carbonization tower T201 is connected in sequence to the fourth condenser E201, the third gas-liquid separator V204, the fifth condenser E202, the fourth gas-liquid separator V206, and the second tail gas treatment tank V207. The third gas-liquid separator V204 is also connected to the circulating oil collection tank V205.

[0068] Specifically, the distillation extraction column T101 is equipped with a raw material inlet (section A), a top outlet (section C), an upper side outlet (section E), a lower side inlet (section D), a lower side outlet (section B), and a bottom outlet (section F). The raw material tank V101 is connected to the raw material inlet (section A) via the raw material pump P101 and the first preheater F101. The upper side outlet (section E) is connected to the lower side inlet (section D) via the first condenser E101 and the solvent tank V103. The top outlet (section C) is connected to the bottom outlet (section F). Section C is connected sequentially to the middle of the side of the second condenser E102 and the first gas-liquid separator V104. The top of the first gas-liquid separator V104 is connected sequentially to the third condenser E103, the second gas-liquid separator V105 and the first tail gas treatment tank V106. The bottom of the first gas-liquid separator V104 is connected to the circulating oil tank V202. The bottom outlet of the tower (Section B) is connected to the refined asphalt tank V201, and the bottom outlet of the tower (Section F) is connected to the insoluble heavy component tank V102.

[0069] During implementation, the mixed solvent enters the distillation and extraction tower T101 from the lower side inlet (section D). The medium- and low-temperature coal tar, after being preheated sequentially by the feed pump P101 and the first preheater F101, enters the distillation and extraction tower T101 from the feed inlet (section A). The medium- and low-temperature coal tar is distilled to separate light fractions (circulating oil and gas), solvent oil and gas, heavy fractions (refined asphalt), and insoluble matter. The heavy fractions (refined asphalt) enter the refined asphalt tank V201 from the lower side outlet (section B) for heat preservation and later use. The insoluble matter is collected in the insoluble heavy fraction tank V102. The solvent oil and gas exit from the upper side outlet. (Section E) After being cooled by the first condenser E101, it enters the solvent tank V103 and enters the distillation extraction tower T101 for recycling from the bottom inlet (Section D). The light component fraction (circulating oil and gas) is condensed from the top outlet (Section C) by the second condenser E102 and then enters the first gas-liquid separator V104 for flash evaporation to separate the circulating oil and non-condensable gas. The circulating oil enters the circulating oil tank V202 for later use. The non-condensable gas is condensed again by the third condenser E103 and then enters the second gas-liquid separator V105 for secondary separation. The separated light component tail gas enters the first tail gas treatment tank V106 for discharge.

[0070] During medium- and low-temperature coal tar distillation and extraction, the temperature of the oil and gas exiting the top of the tower is adjusted by regulating the temperature of the oil and gas entering the distillation and extraction tower T101, the reflux ratio at the top of the tower, and the insulation of the tower body (i.e., controlling the cutting point) to obtain various products.

[0071] In this invention, refined asphalt from the refined asphalt tank V201 is pressurized by the refined asphalt pump P201 and then enters the third preheater F202. Water vapor from the water storage tank V203 is preheated in the second preheater F201 via the water pump P203 and mixed with the refined asphalt pumped in by the refined asphalt pump P201. Both mixtures then enter the third preheater F202 for further preheating before entering from the bottom of the carbonization tower T201. The carbonization tower T201 employs a non-isothermal polymerization method, with the temperature increasing sequentially from top to bottom to ensure uniform product composition. During the refined asphalt nucleation stage, steam coking is used; during the refined asphalt solidification stage, circulating oil collected in the circulating oil tank V202 is used for coking. The circulating oil is pumped into the third preheater F202 via the circulating oil pump P202. After preheating, the coke enters the bottom of carbonization tower T201 and is solidified and coked with refined asphalt to obtain semi-coke. At the same time, other products are generated in carbonization tower T201. After exiting the top of carbonization tower T201 and being condensed in the fourth condenser E201, the coke enters the third gas-liquid separator V204 from the top and is flash-separated to separate coking heavy distillate oil and water-containing light distillate oil. The coking heavy distillate oil enters the circulating oil collection tank V205 from the bottom of the third gas-liquid separator V204 for collection. The water-containing light distillate oil enters the fifth condenser E202 from the side of the third gas-liquid separator V204 for secondary condensation and then enters the fourth gas-liquid separator V206 to separate low-carbon hydrocarbon non-condensable gas. After H2S gas is removed by the second tail gas treatment tank V207, the gas is discharged.

[0072] During implementation, refined asphalt in refined asphalt tank V201 is extracted and pressurized by refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas then passes through the third preheater F202 and the heated oil line before being sent into the preheated carbonization tower T201. Different temperatures are set at different heights of the carbonization tower T201 according to the process conditions. A non-isothermal static polymerization process is used to obtain semi-coke, and each temperature control point is operated using a programmed temperature change mode to synchronize with the operation of the third preheater F202. During the nucleation stage of polymerization, water vapor is used for coke pulling, and the solidification stage uses distilled light component oil for coke pulling.

[0073] The high-temperature oil and gas generated at the top of the carbonization tower T201 is cooled to 150-200°C by the fourth condenser E201 and then enters the third gas-liquid separator V204 for separation. The non-condensable gas separated by flash evaporation is cooled by the fifth condenser E202 and then separated again by the fourth gas-liquid separator V206. The separated non-condensable gas (low-carbon hydrocarbons) is discharged after H2S gas is removed by the second tail gas treatment tank V207.

[0074] The following are several specific examples illustrating the method for preparing needle coke according to the present invention, but the preparation method of the present invention is not limited thereto.

[0075] Example 1

[0076] The method for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization provided in this embodiment specifically includes the following steps.

[0077] 1) Extractive distillation

[0078] 1.1) The mixed solvent is fed into the distillation and extraction tower T101 from section D. The medium-low temperature coal tar is preheated and fed into the distillation and extraction tower T101 from section A. The feed rate of the medium-low temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h.

[0079] At the same time, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2-4 L / min.

[0080] In the mixed solvent, the main agent accounts for 97 wt% and the composite additive accounts for 3 wt%. The main agent is composed of toluene and n-heptane mixed in a 2:1 ratio, and the composite additive is composed of tertiary amine oxide and polyacrylic acid microgel mixed in a 1:1 ratio.

[0081] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0082] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 120℃, and the reflux ratio is 3:1.

[0083] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0084] 2) Asphalt carbonization

[0085] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0086] Based on the process conditions, different temperatures are set at different heights of the carbonization tower T201. A non-isothermal static polymerization process is used to obtain semi-coke. Each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202. During the polymerization process, water vapor is used to pull coke in the nucleation stage, and light component oil obtained by distillation is used to pull coke in the solidification stage.

[0087] Specifically, in step 2), the water vapor feed rate is 0.8 kg / h, and the circulating oil feed rate is 1.0 kg / h.

[0088] The upper, middle, and lower parts (from top to bottom) of the carbonization tower T201 were sequentially heated to 480℃, 440℃, and 400℃, respectively, at a heating rate of 1.5℃ / min. The reaction pressure inside the carbonization tower T201 was 0.5MPa, and the carbonization reaction time was 12h. For the first 8h, water vapor was used for coking, and for the last 4h, circulating oil was used for coking to obtain semi-coke.

[0089] 3) Oil and gas recovery

[0090] The high-temperature generated oil and gas from the top of the carbonization tower T201 is cooled to 150-200°C by the fourth condenser E201 and then enters the third gas-liquid separator V204 for separation. The non-condensable gas separated by flash evaporation is cooled by the fifth condenser E202 and then separated again by the fourth gas-liquid separator V206. The separated non-condensable gas (low-carbon hydrocarbons) is discharged after H2S gas is removed by the second tail gas treatment tank V207.

[0091] 4) Calcination

[0092] Under a nitrogen atmosphere, the semi-coke from step 2) is calcined and cooled to obtain needle coke.

[0093] Specifically, in step 4), the calcination conditions are: pressure 0.01 MPa, temperature increased to 800℃ at a rate of 3℃ / min, and constant temperature reaction for 2 hours; then, pressure unchanged, temperature increased to 1400℃ at a rate of 1℃ / min, and constant temperature reaction for 2 hours.

[0094] Example 2

[0095] 1) Distillation extraction

[0096] 1.1) The mixed solvent is fed into the distillation and extraction tower T101 from section D on the distillation and extraction tower T101. The medium- and low-temperature coal tar is preheated and fed into the distillation and extraction tower T101 from section A on the distillation and extraction tower T101. The feed rate of the medium- and low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h.

[0097] At the same time, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2-4 L / min.

[0098] In the mixed solvent, the main agent accounts for 97 wt% of the mixed solvent; the composite additive accounts for 3 wt% of the mixed solvent. The main agent is composed of toluene and n-heptane mixed in a 2:1 ratio, and the composite additive is composed of tertiary amine oxide (TAO) and polyacrylic acid microgel (ATP) mixed in a 1:1 ratio.

[0099] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0100] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 120℃, and the reflux ratio is 3:1.

[0101] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0102] 2) Asphalt carbonization

[0103] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0104] Based on the process conditions, different temperatures are set at different heights of the carbonization tower T201. A non-isothermal static polymerization process is used to obtain semi-coke. Each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202. During the polymerization process, water vapor is used to pull coke in the nucleation stage, and light component oil obtained by distillation is used to pull coke in the solidification stage.

[0105] Specifically, in step 2), the water vapor feed rate is 0.8 kg / h, and the circulating oil feed rate is 1.0 kg / h.

[0106] The upper, middle, and lower parts of carbonization tower T201 were sequentially heated to 470℃, 440℃, and 410℃ respectively, at a heating rate of 1.5℃ / min. The reaction pressure inside carbonization tower T201 was 0.5MPa. Semi-coke was obtained after 12 hours of carbonization. Specifically, water vapor was used for coke pulling in the initial stage of carbonization for 8 hours, followed by circulating oil for coke pulling for 4 hours.

[0107] 3) Oil and gas recovery

[0108] The high-temperature generated oil and gas from the top of the carbonization tower T201 is cooled to 150-200°C by the fourth condenser E201 and then enters the third gas-liquid separator V204 for separation. The non-condensable gas separated by flash evaporation is cooled by the fifth condenser E202 and then separated again by the fourth gas-liquid separator V206. The separated non-condensable gas (low-carbon hydrocarbons) is discharged after H2S gas is removed by the second tail gas treatment tank V207.

[0109] 4) Calcination

[0110] Under a nitrogen atmosphere, the semi-coke from step 2) is calcined and cooled to obtain needle coke.

[0111] Specifically, in step 4), the calcination conditions are: pressure 0.01 MPa, temperature increased to 800℃ at a rate of 3℃ / min, and constant temperature reaction for 2 hours; then, pressure unchanged, temperature increased to 1400℃ at a rate of 1℃ / min, and constant temperature reaction for 2 hours.

[0112] Example 3

[0113] 1) Extractive distillation

[0114] 1.1) The mixed solvent is fed into the distillation and extraction tower T101 from section D on the distillation and extraction tower T101. The medium- and low-temperature coal tar is preheated and fed into the distillation and extraction tower T101 from section A on the distillation and extraction tower T101. The feed rate of the medium- and low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h.

[0115] At the same time, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2-4 L / min.

[0116] In the mixed solvent, the main agent accounts for 97 wt% of the mixed solvent; the composite additive accounts for 3 wt% of the mixed solvent. The main agent is composed of toluene and n-heptane mixed in a 3:1 ratio, and the composite additive is composed of benzyl chloride quaternary ammonium salt and polyacrylic acid microgel mixed in a 1:1 ratio.

[0117] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0118] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 120℃, and the reflux ratio is 3:1.

[0119] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0120] 2) Asphalt carbonization

[0121] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0122] Based on the process conditions, different temperatures are set at different heights of the carbonization tower T201. A non-isothermal static polymerization process is used to obtain semi-coke. Each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202. During the polymerization process, water vapor is used to pull coke in the nucleation stage, and light component oil obtained by distillation is used to pull coke in the solidification stage.

[0123] Specifically, in step 2), the water vapor feed rate is 0.9 kg / h, and the circulating oil feed rate is 1.2 kg / h.

[0124] The upper, middle, and lower parts of carbonization tower T201 were sequentially heated to 460℃, 440℃, and 420℃, respectively, at a heating rate of 1.5℃ / min and a reaction pressure of 0.5MPa. Semi-coke was obtained after 12 hours of carbonization. Specifically, water vapor was used for coke pulling in the initial stage of carbonization for 8 hours, followed by circulating oil for coke pulling for 4 hours.

[0125] 3) Oil and gas recovery

[0126] The high-temperature generated oil and gas from the top of the carbonization tower T201 is cooled to 150-200°C by the fourth condenser E201 and then enters the third gas-liquid separator V204 for separation. The non-condensable gas separated by flash evaporation is cooled by the fifth condenser E202 and then separated again by the fourth gas-liquid separator V206. The separated non-condensable gas (low-carbon hydrocarbons) is discharged after H2S gas is removed by the second tail gas treatment tank V207.

[0127] 4) Calcination

[0128] Under a nitrogen atmosphere, the semi-coke from step 2) is calcined and cooled to obtain needle coke.

[0129] Specifically, in step 4), the calcination conditions are: pressure 0.01 MPa, temperature increased to 800℃ at a rate of 3℃ / min, and constant temperature reaction for 2 hours; then, pressure unchanged, temperature increased to 1400℃ at a rate of 1℃ / min, and constant temperature reaction for 2 hours.

[0130] Example 4

[0131] 1) Extractive distillation

[0132] 1.1) The mixed solvent is fed into the distillation and extraction tower T101 from section D on the distillation and extraction tower T101. The medium- and low-temperature coal tar is preheated and fed into the distillation and extraction tower T101 from section A on the distillation and extraction tower T101. The feed rate of the medium- and low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h.

[0133] At the same time, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2-4 L / min.

[0134] In the mixed solvent, the main agent accounts for 96 wt% of the mixed solvent; the composite additive accounts for 4 wt% of the mixed solvent. The main agent is composed of toluene and n-heptane in a 3:1 ratio, and the composite additive is composed of iodomethyl quaternary ammonium salt and tannin in a 1:1 ratio.

[0135] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0136] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 180℃, and the reflux ratio is 3:1.

[0137] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0138] 2) Asphalt carbonization

[0139] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0140] Based on the process conditions, different temperatures are set at different heights of the carbonization tower T201. A non-isothermal static polymerization process is used to obtain semi-coke. Each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202. During the polymerization process, water vapor is used to pull coke in the nucleation stage, and light component oil obtained by distillation is used to pull coke in the solidification stage.

[0141] Specifically, in step 2), the water vapor feed rate is 1.1 kg / h and the circulating oil feed rate is 1.3 kg / h.

[0142] The upper, middle, and lower parts of carbonization tower T201 were sequentially heated to 460℃, 440℃, and 420℃, respectively, at a heating rate of 1.5℃ / min and a reaction pressure of 0.5MPa. Semi-coke was obtained after 12 hours of carbonization. Specifically, water vapor was used for coke pulling in the initial stage of carbonization for 8 hours, followed by circulating oil for coke pulling for 4 hours.

[0143] 3) Oil and gas recovery

[0144] The high-temperature generated oil and gas from the top of the carbonization tower T201 is cooled to 150-200°C by the fourth condenser E201 and then enters the third gas-liquid separator V204 for separation. The non-condensable gas separated by flash evaporation is cooled by the fifth condenser E202 and then separated again by the fourth gas-liquid separator V206. The separated non-condensable gas (low-carbon hydrocarbons) is discharged after H2S gas is removed by the second tail gas treatment tank V207.

[0145] 4) Calcination

[0146] Under a nitrogen atmosphere, the semi-coke from step 2) is calcined and cooled to obtain needle coke.

[0147] Specifically, in step 4), the calcination conditions are: pressure 0.01 MPa, temperature increased to 800℃ at a rate of 3℃ / min, and constant temperature reaction for 2 hours; then, pressure unchanged, temperature increased to 1400℃ at a rate of 1℃ / min, and constant temperature reaction for 2 hours.

[0148] Example 5

[0149] 1) Extractive distillation

[0150] 1.1) The mixed solvent is fed into the distillation and extraction tower T101 from section D on the distillation and extraction tower T101. The medium- and low-temperature coal tar is preheated and fed into the distillation and extraction tower T101 from section A on the distillation and extraction tower T101. The feed rate of the medium- and low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h.

[0151] At the same time, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2-4 L / min.

[0152] In the mixed solvent, the main agent accounts for 96 wt% of the mixed solvent; the composite additive accounts for 4 wt% of the mixed solvent. The main agent is composed of toluene and n-heptane mixed in a 4:1 ratio, and the composite additive is composed of iodomethyl quaternary ammonium salt and tannin mixed in a 1:1 ratio.

[0153] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0154] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 180℃, and the reflux ratio is 3:1.

[0155] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0156] 2) Asphalt carbonization

[0157] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0158] Based on the process conditions, different temperatures are set at different heights of the carbonization tower T201. A non-isothermal static polymerization process is used to obtain semi-coke. Each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202. During the polymerization process, water vapor is used to pull coke in the nucleation stage, and light component oil obtained by distillation is used to pull coke in the solidification stage.

[0159] Specifically, in step 2), the water vapor feed rate is 1.1 kg / h and the circulating oil feed rate is 1.4 kg / h.

[0160] The upper, middle, and lower parts of carbonization tower T201 were sequentially heated to 450℃, 440℃, and 430℃, respectively, at a heating rate of 1.5℃ / min and a reaction pressure of 0.5MPa. Semi-coke was obtained after 12 hours of carbonization. Specifically, water vapor was used for coke pulling in the initial stage of carbonization for 8 hours, followed by circulating oil for coke pulling for 4 hours.

[0161] 3) Oil and gas recovery

[0162] The high-temperature generated oil and gas from the top of the carbonization tower T201 is cooled to 150-200°C by the fourth condenser E201 and then enters the third gas-liquid separator V204 for separation. The non-condensable gas separated by flash evaporation is cooled by the fifth condenser E202 and then separated again by the fourth gas-liquid separator V206. The separated non-condensable gas (low-carbon hydrocarbons) is discharged after H2S gas is removed by the second tail gas treatment tank V207.

[0163] 4) Calcination

[0164] Under a nitrogen atmosphere, the semi-coke from step 2) is calcined and cooled to obtain needle coke.

[0165] Specifically, in step 4), the calcination conditions are: pressure 0.01 MPa, temperature increased to 800℃ at a rate of 3℃ / min, and constant temperature reaction for 2 hours; then, pressure unchanged, temperature increased to 1400℃ at a rate of 1℃ / min, and constant temperature reaction for 2 hours.

[0166] Example 6

[0167] 1) Extractive distillation

[0168] 1.1) The mixed solvent is fed into the distillation and extraction tower T101 from section D on the distillation and extraction tower T101. The medium- and low-temperature coal tar is preheated and fed into the distillation and extraction tower T101 from section A on the distillation and extraction tower T101. The feed rate of the medium- and low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h.

[0169] At the same time, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2-4 L / min.

[0170] In the mixed solvent, the main agent accounts for 95 wt% of the mixed solvent; the composite additive accounts for 5 wt% of the mixed solvent. The main agent is composed of toluene and n-heptane in a 4:1 ratio, and the composite additive is composed of iodomethyl quaternary ammonium salt and tannin in a 1:1 ratio.

[0171] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0172] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 180℃, and the reflux ratio is 3:1.

[0173] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0174] 2) Asphalt carbonization

[0175] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0176] Based on the process conditions, different temperatures are set at different heights of the carbonization tower T201. A non-isothermal static polymerization process is used to obtain semi-coke. Each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202. During the polymerization process, water vapor is used to pull coke in the nucleation stage, and light component oil obtained by distillation is used to pull coke in the solidification stage.

[0177] Specifically, in step 2), the water vapor feed rate is 1.2 kg / h, and the circulating oil feed rate is 1.5 kg / h.

[0178] The upper, middle, and lower parts of carbonization tower T201 were sequentially heated to 450℃, 440℃, and 430℃, respectively, at a heating rate of 1.5℃ / min and a reaction pressure of 0.5MPa. Semi-coke was obtained after 12 hours of carbonization. Specifically, water vapor was used for coke pulling in the initial stage of carbonization for 8 hours, followed by circulating oil for coke pulling for 4 hours.

[0179] 3) Oil and gas recovery

[0180] The high-temperature generated oil and gas from the top of the carbonization tower T201 is cooled to 150-200°C by the fourth condenser E201 and then enters the third gas-liquid separator V204 for separation. The non-condensable gas separated by flash evaporation is cooled by the fifth condenser E202 and then separated again by the fourth gas-liquid separator V206. The separated non-condensable gas (low-carbon hydrocarbons) is discharged after H2S gas is removed by the second tail gas treatment tank V207.

[0181] 4) Calcination

[0182] Under a nitrogen atmosphere, the semi-coke from step 2) is calcined and cooled to obtain needle coke.

[0183] Specifically, in step 4), the calcination conditions are: pressure 0.01 MPa, temperature increased to 800℃ at a rate of 3℃ / min, and constant temperature reaction for 2 hours; then, pressure unchanged, temperature increased to 1400℃ at a rate of 1℃ / min, and constant temperature reaction for 2 hours.

[0184] Example 7

[0185] 1) Extractive distillation

[0186] 1.1) The mixed solvent is fed into the distillation and extraction tower T101 from section D on the distillation and extraction tower T101. The medium- and low-temperature coal tar is preheated and fed into the distillation and extraction tower T101 from section A on the distillation and extraction tower T101. The feed rate of the medium- and low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h.

[0187] At the same time, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2-4 L / min.

[0188] In the mixed solvent, the main agent accounts for 96 wt% and the composite additive accounts for 4 wt%. The main agent is composed of toluene and n-heptane in a 3:1 ratio, and the composite additive is composed of iodomethyl quaternary ammonium salt and tannin in a 1:1 ratio.

[0189] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0190] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 180℃, and the reflux ratio is 3:1.

[0191] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0192] 2) Asphalt carbonization

[0193] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0194] Based on the process conditions, different temperatures are set at different heights of the carbonization tower T201. A non-isothermal static polymerization process is used to obtain semi-coke. Each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202. During the polymerization process, water vapor is used to pull coke in the nucleation stage, and light component oil obtained by distillation is used to pull coke in the solidification stage.

[0195] Specifically, in step 2), the water vapor feed rate is 1.0 kg / h, and the circulating oil feed rate is 1.2 kg / h.

[0196] The upper, middle, and lower parts of carbonization tower T201 were sequentially heated to 460℃, 440℃, and 420℃ respectively, at a heating rate of 1.5℃ / min and a reaction pressure of 0.5MPa. Semi-coke was obtained after 12 hours of carbonization. Specifically, water vapor was used for coke pulling in the initial stage of carbonization for 8 hours, followed by circulating oil for coke pulling for 4 hours.

[0197] 3) Oil and gas recovery

[0198] The high-temperature generated oil and gas from the top of the carbonization tower T201 is cooled to 150-200°C by the fourth condenser E201 and then enters the third gas-liquid separator V204 for separation. The non-condensable gas separated by flash evaporation is cooled by the fifth condenser E202 and then separated again by the fourth gas-liquid separator V206. The separated non-condensable gas (low-carbon hydrocarbons) is discharged after H2S gas is removed by the second tail gas treatment tank V207.

[0199] 4) Calcination

[0200] Under a nitrogen atmosphere, the semi-coke from step 2) is calcined and cooled to obtain needle coke.

[0201] Specifically, in step 4), the calcination conditions are: pressure 0.01 MPa, temperature increased to 800℃ at a rate of 3℃ / min, and constant temperature reaction for 2 hours; then, pressure unchanged, temperature increased to 1400℃ at a rate of 1℃ / min, and constant temperature reaction for 2 hours.

[0202] Comparative Example 1

[0203] In this comparative example, a mixed solvent (main agent and composite additive) was used for extraction and distillation of medium- and low-temperature coal tar. Isothermal carbonization was used in the carbonization stage, water vapor coking was used in the nucleation stage, and circulating oil coking was used in the solidification stage.

[0204] 1) Extractive distillation

[0205] 1.1) The mixed solvent is fed into the distillation and extraction tower T101 from section D on the distillation and extraction tower T101. The medium- and low-temperature coal tar is preheated and fed into the distillation and extraction tower T101 from section A on the distillation and extraction tower T101. The feed rate of the medium- and low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h.

[0206] At the same time, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2-4 L / min.

[0207] In the mixed solvent, the main agent accounts for 97 wt% of the mixed solvent; the composite additive accounts for 3 wt% of the mixed solvent. The main agent is composed of toluene and n-heptane in a 2:1 ratio, and the composite additive is composed of iodomethyl quaternary ammonium salt and tannin in a 1:1 ratio.

[0208] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0209] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 180℃, and the reflux ratio is 3:1.

[0210] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0211] 2) Asphalt carbonization

[0212] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0213] Based on the process conditions, the carbonization tower T201 is set to an isothermal static polymerization process to obtain semi-coke, and each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202; during the polymerization process, water vapor is used to pull coke in the nucleation stage, and light component oil obtained by distillation is used to pull coke in the solidification stage.

[0214] Specifically, in step 2), the water vapor feed rate is 0.8 kg / h, and the circulating oil feed rate is 1.0 kg / h.

[0215] The upper, middle, and lower parts of carbonization tower T201 were all heated to 440℃ at a rate of 1.5℃ / min, and the reaction pressure was 0.5MPa. Semi-coke was obtained after 12 hours of carbonization. Specifically, water vapor was used for coke pulling in the initial stage of carbonization for 8 hours, followed by circulating oil for coke pulling for 4 hours.

[0216] 3) Oil and gas recovery. Same as in Example 1.

[0217] 4) Calcination. Under a nitrogen atmosphere, the semi-coke from step 2) was calcined and cooled to obtain needle coke. The calcination conditions were the same as in Example 1.

[0218] Comparative Example 2

[0219] In this comparative example, a mixed solvent (main agent and composite additive) was used for extraction and distillation of medium- and low-temperature coal tar. Non-isothermal carbonization was used in the carbonization stage, and steam coking was used in the nucleation stage.

[0220] 1) Extractive distillation

[0221] 1.1) The mixed solvent is fed into the distillation and extraction tower T101 from section D on the distillation and extraction tower T101. The medium- and low-temperature coal tar is preheated and fed into the distillation and extraction tower T101 from section A on the distillation and extraction tower T101. The feed rate of the medium- and low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h.

[0222] At the same time, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2-4 L / min.

[0223] In the mixed solvent, the main agent accounts for 97 wt% and the composite additive accounts for 3 wt%. The main agent is composed of toluene and n-heptane in a 2:1 ratio, and the composite additive is composed of iodomethyl quaternary ammonium salt and tannin in a 1:1 ratio.

[0224] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0225] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 180℃, and the reflux ratio is 3:1.

[0226] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0227] 2) Asphalt carbonization

[0228] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0229] Based on the process conditions, a non-isothermal static polymerization process is set for carbonization tower T201 to obtain semi-coke, and the operation of each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202; water vapor coke pulling is used in the nucleation stage during the polymerization process.

[0230] Specifically, in step 2), the water vapor feed rate is 0.8 kg / h.

[0231] The upper, middle, and lower parts of carbonization tower T201 were heated to 470℃, 440℃, and 410℃ respectively, at a heating rate of 1.5℃ / min, and the reaction pressure was 0.5MPa. Semi-coke was obtained after carbonization for 12 hours. Specifically, water vapor was used for coke pulling in the initial stage of carbonization for 8 hours.

[0232] 3) Oil and gas recovery. Same as in Example 1.

[0233] 4) Calcination. Under a nitrogen atmosphere, the semi-coke from step 2) was calcined and cooled to obtain needle coke. The calcination conditions were the same as in Example 1.

[0234] Comparative Example 3

[0235] In this comparative example, a mixed solvent (main agent and composite additive) was used for extraction and distillation of medium- and low-temperature coal tar. Non-isothermal carbonization was used in the carbonization stage, and circulating oil coke pulling was used in the solidification stage.

[0236] 1) Extractive distillation

[0237] 1.1) The mixed solvent is fed into the distillation and extraction tower T101 from section D on the distillation and extraction tower T101. The medium- and low-temperature coal tar is preheated and fed into the distillation and extraction tower T101 from section A on the distillation and extraction tower T101. The feed rate of the medium- and low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h.

[0238] At the same time, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2-4 L / min.

[0239] In the mixed solvent, the main agent accounts for 97 wt% and the composite additive accounts for 3 wt%. The main agent is composed of toluene and n-heptane in a 3:1 ratio, and the composite additive is composed of iodomethyl quaternary ammonium salt and tannin in a 1:1 ratio.

[0240] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0241] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 180℃, and the reflux ratio is 3:1.

[0242] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0243] 2) Asphalt carbonization

[0244] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0245] Based on the process conditions, a non-isothermal static polymerization process is set for carbonization tower T201 to obtain semi-coke, and the operation of each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202; during the solidification stage of the polymerization process, circulating oil is used to pull coke.

[0246] Specifically, in step 2), the circulating oil feed rate is 1.2 kg / h.

[0247] The upper, middle, and lower sections of carbonization tower T201 were heated to 460, 440, and 420℃ respectively, at a heating rate of 1.5℃ / min, and the reaction pressure was 0.5MPa. Semi-coke was obtained after carbonization for 12 hours. Specifically, after the initial 8-hour carbonization reaction, coke was pulled out using circulating oil for 4 hours.

[0248] 3) Oil and gas recovery. Same as in Example 1.

[0249] 4) Calcination. Under a nitrogen atmosphere, the semi-coke from step 2) was calcined and cooled to obtain needle coke. The calcination conditions were the same as in Example 1.

[0250] Comparative Example 4

[0251] The difference between this comparative example and Example 7 is that the rate of coke pulling during the carbonization process is different.

[0252] 1) Extractive distillation

[0253] 1.1) The mixed solvent is fed into the distillation extraction tower T101 from section D. The preheated low-temperature coal tar is fed into the distillation extraction tower T101 from section A. The feed rate of the low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h. Simultaneously, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2–4 L / min.

[0254] In the mixed solvent, the main agent accounts for 96 wt% and the composite additive accounts for 4 wt%. The main agent is composed of toluene and n-heptane in a 3:1 ratio, and the composite additive is composed of iodomethyl quaternary ammonium salt and tannin in a 1:1 ratio.

[0255] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0256] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 180℃, and the reflux ratio is 3:1.

[0257] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0258] 2) Asphalt carbonization

[0259] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0260] Based on the process conditions, a non-isothermal static polymerization process is set for carbonization tower T201 to obtain semi-coke, and the operation of each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202; during the polymerization process, water vapor is used for coke pulling in the nucleation stage, and circulating oil is used for coke pulling in the solidification stage.

[0261] Specifically, in step 2), the water vapor feed rate is 0.4 kg / h, and the circulating oil feed rate is 0.8 kg / h.

[0262] The upper, middle, and lower sections of carbonization tower T201 were heated to 460, 440, and 420℃ respectively, at a heating rate of 1.5℃ / min, and the reaction pressure was 0.5MPa. Semi-coke was obtained after 12 hours of carbonization. Specifically, steam coking was used for the initial stage of carbonization for 8 hours, followed by circulating oil coking for 4 hours.

[0263] 3) Oil and gas recovery. Same as in Example 1.

[0264] 4) Calcination. Under a nitrogen atmosphere, the semi-coke from step 2) was calcined and cooled to obtain needle coke. The calcination conditions were the same as in Example 1.

[0265] Comparative Example 5

[0266] In this comparative example, a mixed solvent (without composite additives) was used for extraction and distillation of medium- and low-temperature coal tar. Non-isothermal carbonization was used in the carbonization stage, water vapor coking was used in the nucleation stage, and circulating oil coking was used in the solidification stage.

[0267] 1) Extractive distillation

[0268] 1.1) The mixed solvent is fed into the distillation extraction tower T101 from section D. The preheated low-temperature coal tar is fed into the distillation extraction tower T101 from section A. The feed rate of the low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h. Simultaneously, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2–4 L / min. The mixed solvent is a mixture of toluene and n-heptane in a 4:1 ratio.

[0269] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0270] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 180℃, and the reflux ratio is 3:1.

[0271] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0272] 2) Asphalt carbonization

[0273] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0274] Based on the process conditions, the carbonization tower T201 is set to a non-temperature static polymerization process to obtain semi-coke, and each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202; during the polymerization process, water vapor is used for coke pulling in the nucleation stage and circulating oil is used for coke pulling in the solidification stage.

[0275] Specifically, in step 2), the water vapor feed rate is 1.1 kg / h and the circulating oil feed rate is 1.2 kg / h.

[0276] The upper, middle, and lower sections of carbonization tower T201 were heated to 450, 440, and 440℃ respectively, at a heating rate of 1.5℃ / min, and the reaction pressure was 0.5MPa. Semi-coke was obtained after carbonization for 12 hours. Specifically, water vapor was used for coke pulling in the initial stage of carbonization for 8 hours, followed by circulating oil for coke pulling for 4 hours.

[0277] 3) Oil and gas recovery. Same as in Example 1.

[0278] 4) Calcination. Under a nitrogen atmosphere, the semi-coke from step 2) was calcined and cooled to obtain needle coke. The calcination conditions were the same as in Example 1.

[0279] Comparative Example 6

[0280] In this comparative example, the mixed solvent (main agent and composite additive) and medium-low temperature coal tar extraction distillation were used. Non-isothermal carbonization was used in the carbonization stage, water vapor coking was used in the nucleation stage, and circulating oil coking was used in the solidification stage.

[0281] 1) Extractive distillation

[0282] 1.1) The mixed solvent is fed into the distillation extraction tower T101 from section D. The preheated low-temperature coal tar is fed into the distillation extraction tower T101 from section A. The feed rate of the low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h. Simultaneously, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2–4 L / min.

[0283] In the mixed solvent, the main agent accounts for 98 wt% and the composite additive accounts for 2 wt%. The main agent is composed of toluene and n-heptane in a 4:1 ratio, and the composite additive is composed of iodomethyl quaternary ammonium salt and tannin in a 1:1 ratio.

[0284] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0285] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 180℃, and the reflux ratio is 3:1.

[0286] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0287] 2) Asphalt carbonization

[0288] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0289] Based on the process conditions, a non-isothermal static polymerization process is set for carbonization tower T201 to obtain semi-coke, and the operation of each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202; during the polymerization process, water vapor is used for coke pulling in the nucleation stage, and circulating oil is used for coke pulling in the solidification stage.

[0290] Specifically, in step 2), the water vapor feed rate is 0.5 kg / h, and the circulating oil feed rate is 0.2 kg / h.

[0291] The upper, middle, and lower sections of carbonization tower T201 were heated to 450, 440, and 430℃ respectively, at a heating rate of 1.5℃ / min, and the reaction pressure was 0.5MPa. Semi-coke was obtained after 12 hours of carbonization. Specifically, water vapor was used for coke pulling in the initial stage of carbonization for 8 hours, followed by circulating oil for coke pulling for 4 hours.

[0292] 3) Oil and gas recovery. Same as in Example 1.

[0293] 4) Calcination. Under a nitrogen atmosphere, the semi-coke from step 2) was calcined and cooled to obtain needle coke. The calcination conditions were the same as in Example 1.

[0294] Comparative Example 7

[0295] In this comparative example, the mixed solvent includes the main agent, and the mixed solvent is extracted and distilled with medium and low temperature coal tar. Isothermal carbonization is used in the carbonization stage, and no water vapor or circulating oil is added.

[0296] 1) Extractive distillation

[0297] 1.1) The mixed solvent is fed into the distillation extraction tower T101 from section D. The preheated low-temperature coal tar is fed into the distillation extraction tower T101 from section A. The feed rate of the low-temperature coal tar is 5 kg / h, and the feed rate of the mixed solvent is 10 kg / h. Simultaneously, nitrogen gas is introduced into the distillation extraction tower T101 at a flow rate of 2–4 L / min. The mixed solvent is a mixture of toluene and n-heptane in a 2:1 ratio.

[0298] 1.2) The temperature of the oil and gas exiting the tower top is adjusted by regulating the temperature of the oil and gas entering the tower, the reflux ratio at the tower head, and the insulation of the tower body (i.e., controlling the cutting point).

[0299] The preheating temperature of the medium-low temperature coal tar is 100℃, the temperature set inside the distillation extraction tower T101 is 300℃~320℃, the outlet temperature of the middle and upper part of the distillation extraction tower T101 is 180℃, and the reflux ratio is 3:1.

[0300] 1.3) The circulating oil obtained by condensing the circulating oil and gas generated in section C of the distillation extraction tower T101 is collected in the circulating oil tank V202 for later use. The solvent oil obtained by condensing the solvent oil and gas generated in section E of the distillation extraction tower T101 is collected in the solvent tank V103 and sent from section D into the distillation extraction tower T101 for recycling. The soluble heavy components (refined asphalt) generated in section B of the distillation extraction tower T101 are collected in the refined asphalt tank V201 for heat preservation. The insoluble matter generated in section F of the distillation extraction tower T101 is collected in the insoluble heavy component tank V102.

[0301] 2) Asphalt carbonization

[0302] The refined asphalt in the refined asphalt tank V201 is extracted and pressurized by the refined asphalt pump P201, and mixed with high-temperature water vapor from the second preheater F201 to obtain high-temperature oil gas. The high-temperature oil gas passes through the third preheater F202 and the heating oil line in sequence before being sent into the preheated carbonization tower T201.

[0303] Based on the process conditions, the carbonization tower T201 is set to an isothermal static polymerization process to obtain semi-coke, and each temperature control point adopts a programmed temperature change operation mode to synchronize with the operation of the third preheater F202.

[0304] The upper, middle, and lower parts of the carbonization tower T201 were heated to 440℃ at a rate of 1.5℃ / min, and the reaction pressure was 0.5MPa. Semi-coke was obtained after 12 hours of carbonization.

[0305] 3) Oil and gas recovery. Same as in Example 1.

[0306] 4) Calcination. Under a nitrogen atmosphere, the semi-coke from step 2) was calcined and cooled to obtain needle coke. The calcination conditions were the same as in Example 1.

[0307] To demonstrate the superiority of the method for preparing needle coke of the present invention, the physical properties of the needle coke prepared in Examples 1-7 are compared with those of the needle coke prepared in Comparative Examples 1-7.

[0308] The specific testing methods for physical characteristics are as follows.

[0309] The intermediate phase content and optical texture index were determined according to YB / T077-2017 "Determination of Optical Structure of Coke".

[0310] The coefficient of thermal expansion was determined according to GB / T3074.4-2016 "Determination of Coefficient of Thermal Expansion (CTE) of Graphite Electrode".

[0311] Resistivity was determined according to GB / T24525-2009 "Method for Determination of Resistivity of Carbon Materials".

[0312] The measurement results of the above physical properties are shown in Table 1.

[0313] Table 1. Physical properties of needle coke prepared in Examples 1-7 and Comparative Examples 1-7

[0314]

[0315]

[0316] As can be seen from Table 1, the needle coke prepared by the method of this application has a resistivity of less than 600 μΩ·m, with a minimum of 185 μΩ·m, indicating low resistivity; and a coefficient of thermal expansion of less than 1.5 × 10⁻⁶. -6 / ℃, minimum is 1.20×10 -6 / ℃, with a small coefficient of thermal expansion.

[0317] This is because the distillation extraction device of this invention can simultaneously cut medium- and low-temperature coal tar fractions and extract heavy components to obtain refined asphalt. Furthermore, the composite additives introduced during the extraction process effectively increase the surface activity of the system, promptly capturing insoluble components in the extraction system, allowing them to quickly settle to the bottom of the extraction tower, achieving high separation efficiency. The resulting refined asphalt has a QI content ≤0.1, an ash content ≤50ppm, and an aroma content of 0.75–0.83. During the carbonization process, a non-isothermal thermal field is provided to the carbonization system. A high-temperature zone is set in the upper part to promote the first apparent reaction of component transformation, increasing the reaction rate of the upper asphalt molecules, while a low-temperature environment is provided in the lower part to inhibit the second apparent reaction of component transformation. By observing the reaction, the reaction rate of asphalt molecules is reduced, while the excessive reaction of the lower high molecular weight components caused by gravity deposition is alleviated, effectively suppressing the self-acceleration effect, resulting in a uniform distribution of components and a narrow molecular weight distribution in the reaction system within the carbonization tower. During the mesophase formation stage, water-gas coking is used. On the one hand, this increases the linear velocity of oil and gas in the furnace tubes, thus inhibiting coking and blockage. On the other hand, appropriate water injection can regulate the reaction time within the coking tower, improving mass and heat transfer. During the solidification stage, circulating oil coking is used to promptly replenish the loss of light components in the later stages of carbonization, increasing the amount of product gas released. The external force resulting from the evolution of the product gas is more conducive to orienting the carbonaceous mesophase into a preferred needle-like structure.

[0318] In Comparative Example 7, on the one hand, because the mixed solvent used in the distillation extraction unit did not contain composite additives, the extraction and separation efficiency was poor, and the content of quinoline insoluble matter was high. This mainly included asphaltenes, gums, and other large molecular polycyclic aromatic hydrocarbons, with a large number of oxygen-containing functional groups and heteroatoms. During carbonization, oxygen-containing crosslinking affected the planarity, leading to internal defects in the planar aromatic sheets, increasing steric hindrance and structural strain. The oxygen-containing crosslinked and catalytically condensed carbons were replaced by heteroatoms and cycloalkyl groups, resulting in poor planar aggregation of the mesophase and a widening of the needle-like spacing of the mesophase. On the other hand, a significant component migration effect occurred inside the carbonization tower during the carbonization process. Heavy components deposited, while light components spontaneously moved upwards. The reaction rate at the bottom of the tower was greater than that at the top, meaning that the molecular activity, molecular weight, softening point, viscosity, and aromaticity of the asphalt products were all higher than those at the top. Ultimately, this led to excessively rapid coking at the bottom of the tower, resulting in the formation of a large number of mosaic structures, while a large amount of light components were lost at the top of the tower, resulting in a low semi-coke yield. In addition, during the later stages of carbonization and the solidification of the intermediate phase, the system lacks light components and the amount of gas released is small, resulting in poor orientation of the formed intermediate phase. Ultimately, the needle-like coke lattice has poor order, which reduces the thermal shock resistance and toughness at high temperatures, resulting in a low coefficient of thermal expansion of the product.

[0319] The needle-shaped foci prepared in Example 7 and Comparative Example 7 of this invention were subjected to polarized light microscopy and scanning electron microscopy to obtain polarized light microstructure images and scanning electron microscopy images, respectively. See [link to relevant documentation]. Figures 1-4 .

[0320] from Figure 1 and Figure 2 It can be seen that the needle coke obtained in Example 7 is mainly composed of fine fibers, with high microstructural order, high total fiber content, and very obvious lamellar structure. The lamellar structure is relatively regular and uniform in thickness, exhibiting a structure similar to graphite lamellars. This is because in Example 7, after solvent extraction and distillation, the content of quinoline insolubles is reduced, the ash content is ≤50ppm, and the overall oxygen content in the raw material is reduced. During the thermal polymerization process, the active sites generated by aromatic carbon in the system are more easily connected to aliphatic carbon, resulting in fewer internal defects and better planarity of the aromatic flakes, thus generating larger lamellar molecules. During the carbonization process, a gradient non-isothermal thermal field corresponding to the system is provided to avoid excessive polymerization reaction caused by increased molecular reactivity, thereby achieving a uniformly distributed asphalt system, effectively inhibiting the reaction rate of asphalt molecules deposited at the bottom, promoting the mutual fusion of intermediate phases, and mitigating the self-accelerating effect of the reaction. The use of circulating oil for coke pulling during the curing stage can timely replenish the loss of light components in the later stage of carbonization, increase the amount of product gas released, and make the axial arrangement of lamellar molecules more orderly, the lamellar thickness more uniform, and the fiber orientation better.

[0321] from Figure 3 and Figure 4It can be seen that the needle coke obtained in Comparative Example 7 is mainly composed of short fibers, with low microstructural order and low total fiber content. It contains some lamellar structures, but these lamellar structures are not regular, and the thickness of the lamellar structures varies significantly. This further demonstrates that compared to Example 7, the refined asphalt obtained from the distillation extraction unit in Comparative Example 7 has poor separation efficiency, higher quinoline insoluble content, and more oxygen-containing functional groups and heteroatoms. During carbonization, oxygen-containing crosslinking affects the planarity, resulting in poor planar aggregation of the mesophase and a wider needle-like spacing in the mesophase. In the early stage of carbonization, the isothermal polymerization process leads to uneven distribution of asphalt system components, which ultimately results in excessively rapid coking at the bottom of the tower, generating a large number of mosaic structures. In the later stage of carbonization and the mesophase solidification stage, the lack of light components in the system and the low amount of gas evolution lead to poor orientation of the formed mesophase and disordered stacking of planar macromolecules in the mesophase, resulting in more mosaic structures. Ultimately, the lamellar structures have poor order and poor uniformity in thickness.

[0322] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent modifications or substitutions made by those skilled in the art within the scope of the technology described in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization, characterized in that, Includes the following steps: 1) Extractive distillation Medium- and low-temperature coal tar and mixed solvent are fed into the integrated distillation and extraction unit at a mass ratio of 1:

2. After distillation and extraction, circulating oil, solvent oil and refined asphalt are obtained. The solvent oil is returned to the integrated distillation and extraction unit as a mixed solvent. The mixed solvent includes a main agent and a composite additive, wherein the composite additive accounts for 3wt% to 5wt% of the mixed solvent; the main agent is composed of toluene and n-heptane in a mass ratio of 2 to 4:1, and the composite additive is composed of tertiary amine oxide and polyacrylic acid microgel in a mass ratio of 1:

1. 2) Asphalt carbonization 2.1) The refined asphalt obtained in step 1) is pressurized and mixed with water vapor to obtain a mixed oil-gas mixture; 2.2) After preheating, the mixed oil and gas enter the reactor and carbonize using an intermittent non-isothermal polymerization method. In the nucleation stage, water vapor is used for coking, and in the solidification stage, the circulating oil from step 1) is used for coking to obtain semi-coke. 3) Calcination Under a N2 atmosphere, the semi-coke from step 2) is calcined and cooled to obtain powdered needle coke.

2. The method for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization according to claim 1, characterized in that, In step 1), the distillation extraction temperature is 320℃ and the reflux ratio is 3:

1.

3. The method for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization according to claim 2, characterized in that, In step 1), the refined asphalt has the following specifications: aromaticity 0.75~0.83, quinoline insoluble content ≤0.3%, C content 85~87%, H content 7~9%, O content 3~5%, S content 0.21~0.32%, and N content 0.17~0.29%; the circulating oil is a 240℃~320℃ fraction, the circulating oil contains 40~60% 2~3 ring aromatics, and the degree of branching of the circulating oil is 0.4~0.

6.

4. The method for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization according to claim 3, characterized in that, In step 2), the steam temperature is 300℃, the mixed oil and gas preheating temperature is 340℃~380℃, the carbonization temperature is 380℃~440℃, and the temperature interval is 10℃~40℃. The heating rate is 1.5℃ / min, the reaction pressure is 0.5MPa, the carbonization reaction time is 12h, and the first 8h uses steam to pull the coke, and the last 4h uses circulating oil to pull the coke.

5. The method for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization according to claim 4, characterized in that, The semi-coke obtained in step 2) has a mesophase content of 80% to 97% and a mesophase optical texture index of 79 to 89.

6. The method for preparing needle coke by medium- and low-temperature coal tar extraction distillation-carbonization according to claim 5, characterized in that, In step 3), the calcination conditions are: pressure 0.01 MPa, temperature increased to 800℃ at a rate of 3℃ / min, and constant temperature reaction for 2 hours; then, pressure unchanged, temperature increased to 1400℃ at a rate of 1℃ / min, and constant temperature reaction for 2 hours.

7. The needle coke prepared by the method for preparing needle coke by medium-low temperature coal tar extraction distillation-carbonization as described in any one of claims 1-6, characterized in that, The needle coke has a minimum average resistivity of 185 μΩ•m and a coefficient of thermal expansion of 1.20 × 10⁻⁶. -6 / ℃~1.48×10 -6 / ℃.

8. A preparation system for implementing the method for preparing needle coke by medium-low temperature coal tar extraction distillation-carbonization according to any one of claims 1-6, characterized in that, The preparation system includes an integrated distillation and extraction device, a refined asphalt tank (V201), a circulating oil tank (V202), a water storage tank (V203), a second preheater (F201), a third preheater (F202), and a carbonization tower (T201). The integrated distillation and extraction device is connected to the refined asphalt tank (V201) and the circulating oil tank (V202) respectively. The water storage tank (V203) is connected to the carbonization tower (T201) in sequence via the second preheater (F201) and the third preheater (F202). The third preheater (F202) is also connected to the refined asphalt tank (V201) and the circulating oil tank (V202).

9. The preparation system according to claim 8, characterized in that, The integrated distillation and extraction device includes a distillation and extraction column (T101), a first preheater (F101), a first condenser (E101), a second condenser (E102), and a first gas-liquid separator (V104). The distillation and extraction column (T101) is provided with a raw material inlet, a top outlet, an upper side outlet, a bottom inlet, and a bottom outlet. The first preheater (F101) is connected to the top outlet, the upper side outlet, and the bottom outlet via the raw material inlet. The top outlet is connected to the circulating oil tank (V202) via the second condenser (E102) and the first gas-liquid separator (V104). The bottom outlet is connected to the refined asphalt tank (V201). The upper side outlet is connected to the interior of the distillation and extraction column (T101) via the first condenser (E101) and the bottom inlet.

10. The preparation system according to claim 9, characterized in that, The integrated distillation and extraction device also includes a third condenser (E103), a second gas-liquid separator (V105), and a first tail gas treatment tank (V106) connected in sequence; the third condenser (E103) is also connected to the first gas-liquid separator (V104).

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