A method for producing needle coke

Abstract

The application discloses a method for preparing needle coke. Raw oil is heated by a heating furnace and then enters a coking tower to be charged. After the charging is completed, raw material for drawing coke is introduced into the coking tower to draw coke. After the drawing is completed, needle coke products are obtained through coke removal. The charging process controls the pressure of the coking tower in at least two stages. The pressure of the coking tower in different stages is in a decreasing trend, and the charging time is in a decreasing trend. The method is easy to operate, and the prepared needle coke has a low CTE value.

Description

Technical Field

[0001] This invention relates to a method for preparing needle coke, and more specifically to a method for preparing needle coke using petroleum-based or coal-based raw materials. Background Technology

[0002] Needle coke is an excellent carbon product, exhibiting a distinct streamlined texture. Due to its good electrical conductivity, orientation, and thermal conductivity, it has become a primary raw material for manufacturing ultra-high power graphite electrodes for steelmaking. Using ultra-high power electrodes in steelmaking can shorten smelting time by about two-thirds and reduce power consumption by about 50%, resulting in significant economic benefits.

[0003] CN202011305509.9 discloses a method and process system for producing needle coke from heavy oil, comprising: a fractional cutting process, using heavy oil as raw material to cut it into light distillate oil, heavy distillate oil and tailings; a hydrogenation process, wherein the heavy distillate oil is hydrogenated to obtain hydrogenated heavy distillate; a mixing process, wherein the hydrogenated heavy distillate is mixed with the light distillate oil to obtain a mixed oil; and a delayed coking process, wherein the mixed oil is subjected to delayed coking to obtain needle coke.

[0004] US4894144 discloses a method for simultaneously preparing needle coke and high-sulfur petroleum coke. It employs a hydrotreating process to pretreat straight-run heavy oil, and the hydrotreated residue is divided into two parts, which are then coked separately and subsequently calcined to obtain needle coke and high-sulfur petroleum coke.

[0005] US5286371 also discloses a hydrotreating process for straight-run residue, with a hydrotreating reaction temperature of 379-480℃ and a reaction pressure of 6.8MPa-34.4MPa. The treated heavy residue is mixed with catalytic cracking clarified oil and fed into a solvent deasphalting unit. The stream after deasphalting is used as feedstock for needle coke.

[0006] US4178229 discloses a method for producing high-quality petroleum coke from straight-run vacuum residue, which first converts vacuum residue into distillate oil and bitumen, and then further cracks the bitumen and hydrogen donor to produce feedstock for high-quality coke.

[0007] CN202010439340.X discloses a method for preparing needle coke for ultra-high power electrodes from heavy oil. The method uses heavy oil as raw material and employs a size exclusion separation method with polystyrene as the separation column packing to separate components with a relative molecular mass distribution of 400-1000. Acidic and basic components are removed by ion exchange chromatography to obtain a neutral raw material. The treated raw material undergoes a two-stage continuous carbonization process to prepare needle coke.

[0008] Needle coke is used as aggregate in the production of HP and UHP graphite electrodes. The main goal is to achieve a lower coefficient of thermal expansion (CTE). The CTE of needle coke prepared in the existing technology still needs to be further reduced. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a method for preparing needle coke, which is not only easy to operate but also produces needle coke with low CTE values.

[0010] A method for preparing needle coke involves heating the feed oil in a furnace and then feeding it into a coking tower for coking. After coking, a coking feedstock is introduced into the coke tower for coking. After coking, the needle coke product is obtained by removing the coke. The coking process is controlled by different pressures in the coke tower and is divided into at least two stages. The pressure in the coke tower decreases and the coking time decreases in different stages according to the order of the stages.

[0011] In the method of the present invention, the pressure difference between any two adjacent stages of the coking process is 0.2-0.9 MPa, preferably 0.2-0.7 MPa, and the coking time difference is 1-20 h, preferably 2-10 h.

[0012] In the method of this invention, taking the coking process as two stages as an example, the first stage is the early stage of coking and the second stage is the late stage of coking. Let the early stage of coking and the late stage of coking be the total coking time T1. The early stage of coking accounts for 60-95% of the total coking time T, preferably 80-95%. The pressure of the coke tower is controlled at 0.45-2.0 MPa during the early stage of coking, preferably 0.5-1.0 MPa. The pressure of the coke tower is controlled at 0.1-0.4 MPa during the late stage of coking, preferably 0.15-0.3 MPa.

[0013] In the method of the present invention, the coking process is controlled by different pressures in the coke tower in at least two stages, and the pressure of the coke tower decreases in different stages according to the order of the stages.

[0014] In the method of this invention, the pressure difference between any two adjacent stages of the coking process in the coke tower is 0.2-1.8 MPa, preferably 0.5-1.0 MPa.

[0015] In the method of this invention, taking the control of the coking process as two stages as an example, the first stage is the pre-coking stage and the second stage is the post-coking stage. Let the pre-coking stage and the post-coking stage be the total coking time T2. The pre-coking stage accounts for 20-70% of the total coking time T2, preferably 30-60%. The pressure of the coke tower is controlled at 0.45-2.0 MPa during the pre-coking stage, preferably 0.5-1.0 MPa. The pressure of the coke tower is controlled at 0.1-0.4 MPa during the post-coking stage, preferably 0.15-0.35 MPa.

[0016] In the method of the present invention, the feedstock oil and coking feedstock are selected from at least one of coal-based feedstock and petroleum-based feedstock, preferably selected from at least one of coal tar, coal tar pitch, heavy petroleum oil, ethylene tar, catalytic cracking slurry oil or thermal cracking residue oil.

[0017] In the method of the present invention, the solid content of the raw material oil is 0-500 μg / g, preferably 0-200 μg / g, more preferably 0-100 μg / g; the sulfur content is 0-1.0%, preferably 0-0.5%, more preferably 0-0.3%.

[0018] In the method of the present invention, the 5% distillation point temperature of the raw oil is 350℃-450℃, preferably 370℃-410℃; the 95% distillation point temperature is 450℃-550℃, preferably 480℃-520℃.

[0019] In the method of the present invention, the outlet temperature of the heating furnace during the coking process of the raw oil is controlled by a variable temperature, with a variable temperature range of 420℃-550℃, preferably 450℃-500℃; the variable temperature rate is 1-150℃ / h, preferably 5-50℃ / h.

[0020] In the method of the present invention, the circulation ratio of circulating oil to fresh raw material in the coking process of the feed oil is 0-2.0, preferably 0.1-0.5.

[0021] In the method of the present invention, the 5% distillation point temperature of the circulating oil in the coking process is 300℃-430℃, preferably 350℃-400℃.

[0022] In the method of the present invention, the coking time T1 is 12h-36h, preferably 20h-30h.

[0023] In the method of the present invention, the solid content of the coking feedstock is 0-500 μg / g, preferably 0-200 μg / g, more preferably 0-100 μg / g; the sulfur content is 0-1.5%, preferably 0-0.8%, more preferably 0-0.5%.

[0024] In the method of the present invention, the 5% distillation point temperature of the coking feedstock is 250℃-400℃, preferably 320℃-370℃; the 95% distillation point temperature is 420℃-520℃, preferably 440℃-500℃.

[0025] In the method of the present invention, the outlet temperature of the heating furnace in the coking process is controlled by temperature variation, with a temperature variation range of 450℃-550℃, preferably 470℃-530℃, and a temperature variation rate of 1-150℃ / h, preferably 5-50℃ / h.

[0026] In the method of the present invention, the circulation ratio of circulating oil to fresh raw material in the coking process is 0-2.0, preferably 0.5-1.5.

[0027] In the method of the present invention, the 5% distillation point temperature of the coking process circulating oil is 250℃-400℃, preferably 320℃-370℃.

[0028] In the method of the present invention, the focusing time T2 is 12h-36h, preferably 20h-30h.

[0029] In the method of the present invention, the mass ratio of the feed oil to the coking feed is 1:0.5-3.0, preferably 1:0.5-1.5.

[0030] The formation of needle coke follows the liquid-phase carbonization mechanism, which refers to the transformation of materials into a broad mesophase under sufficient temperature and time. However, coking feedstocks do not enter the coke tower at the same time. Feedstocks entering earlier have sufficient reaction time to complete the liquid-phase carbonization reaction, while feedstocks entering later do not have enough reaction time and enter the coke pulling stage. Due to the high reaction temperature in the coke pulling stage, feedstocks entering later are forced to coke at high temperatures. This portion of coke does not follow the liquid-phase carbonization mechanism, which seriously affects the quality of needle coke products. Therefore, this invention implements a pressure reduction process in the coking and coke pulling stages to allow the light components remaining in the system to be discharged from the reaction system as soon as possible, reducing the forced high-temperature coking reaction and significantly improving the application performance of needle coke products. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in detail below. However, it should be noted that the scope of protection of the present invention is not limited to these specific embodiments, but is determined by the claims in the appendix.

[0032] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0033] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0034] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight, unless being based on weight would not be in accordance with the common understanding of those skilled in the art.

[0035] In the context of this specification, any two or more embodiments of the present invention can be arbitrarily combined, and the resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0036] In the context of this invention, including in the embodiments and comparative examples, the coefficient of thermal expansion was determined according to the international standard GB / T3074.4 "Method for Determination of Coefficient of Thermal Expansion (CTE) of Graphite Electrodes", the volatile matter was determined according to the petrochemical standard SH / T0313 "Test Method for Petroleum Coke", the true density was determined according to the international standard GB / T6155 "Method for Determination of True Density of Carbon Materials", the resistivity was determined according to GB24525-2009 "Method for Determination of Resistivity of Carbon Materials", and the streamlined texture of the needle coke appearance was directly evaluated by visual inspection.

[0037] The present invention will be further described in detail below through embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0038] Example 1

[0039] Using catalytic slurry oil provided by a refinery as raw material, the properties are analyzed as shown in Table 1. The outlet temperature of the heating furnace during the coking stage of the raw material is 450℃-485℃, the heating rate is 10℃ / h, and the coking time T1 is 20h. Among them, the early stage of coking accounts for 80% of the total coking time T1. The coking tower pressure is 0.5MPa in the early stage of coking and 0.2MPa in the later stage of coking. The circulating mass ratio of coking circulating oil to fresh raw material during the coking stage is 0.3, and the 5% distillation point temperature of the circulating oil is 352℃. The sulfur content of the coking feedstock was 0.36%, the solid content was 43 μg / g, the 5% distillation point temperature was 325℃, and the 95% distillation point temperature was 452℃. The outlet temperature of the heating furnace during the coking stage was 470℃-495℃, the heating rate was 8℃ / h, and the coking time T2 was 21h. The early stage of coking accounted for 35% of the total coking time T2. The coke tower pressure was 0.8MPa in the early stage of coking and 0.2MPa in the later stage of coking. The circulating mass ratio of coking circulating oil to fresh feedstock during the coking stage was 1.0, and the 5% distillation point temperature of the circulating oil was 332℃. Within one coking reaction cycle, the mass ratio of coking feedstock to coking feedstock was 1:0.6. The properties of the obtained needle coke product are shown in Table 2.

[0040] Example 1-1

[0041] Using the same coking feedstock as in Example 1, the pressure of the coking tower in the later stage of coking was the same as that in the early stage of coking, which was 0.8 MPa. Other operating conditions were exactly the same as in Example 1. The properties of the obtained needle coke product are shown in Table 2.

[0042] Comparative Example 1

[0043] Using the same coking feedstock as in Example 1, the pressure of the coking tower in the later stage of coking was the same as that in the early stage of coking, which was 0.5 MPa. Other operating conditions were exactly the same as in Example 1. The properties of the obtained needle coke product are shown in Table 2.

[0044] Table 1 Properties of Catalytic Slurry

[0045] <![CDATA[Density g / cm 3 > 1.0425 Distillation range, °C 5％ 374 95％ 513 Solid content, μg / g 50 C%(w) 91.37 H%(w) 8.26 S%(w) 0.25 N%(w) 0.12 Four components % (w) Saturated portion 14.27 Aromatic components 82.65 gelatin 2.56 Asphalt 0.52

[0046] Table 2 Properties of needle coke produced in the examples and comparative examples

[0047] <![CDATA[CTE,10 -6 / ℃]]> 0.92 0.99 1.12 Volatile matter, w% 5.98 6.52 7.56 Ash content, w% 0.01 0.02 0.02 Sulfur content, w% 0.32 0.34 0.35 <![CDATA[True density, g / cm 3 > 1.44 1.39 1.38

[0048] Example 2

[0049] Using catalytic slurry oil provided by a refinery as raw material, the property analysis is shown in Table 3. The outlet temperature of the heating furnace during the coking stage of the raw material is 465℃-495℃, the heating rate is 20℃ / h, and the coking time T1 is 25h. Among them, the early stage of coking accounts for 85% of the total coking time T1. The coking tower pressure is 0.8MPa in the early stage of coking and 0.3MPa in the later stage of coking. The circulating mass ratio of coking circulating oil to fresh raw material during the coking stage is 0.4, and the 5% distillation point temperature of the circulating oil is 365℃. The sulfur content of the coking feedstock was 0.44%, the solid content was 92 μg / g, the 5% distillation point temperature was 345℃, and the 95% distillation point temperature was 468℃. The outlet temperature of the heating furnace during the coking stage was 480℃-505℃, the heating rate was 10℃ / h, and the coking time T2 was 26h. The early stage of coking accounted for 45% of the total coking time T2. The coke tower pressure was 0.65MPa in the early stage of coking and 0.25MPa in the later stage of coking. The circulating mass ratio of coking circulating oil to fresh feedstock during the coking stage was 1.3, and the 5% distillation point temperature of the circulating oil was 356℃. Within one coking reaction cycle, the mass ratio of coking feedstock to coking feedstock was 1:0.9. The properties of the obtained needle coke product are shown in Table 5.

[0050] Table 3 Properties of Catalytic Slurry

[0051] <![CDATA[Density g / cm 3 > 1.0312 Distillation range, °C 5％ 389 95％ 486 Solid content, μg / g 100 C%(w) 90.87 H%(w) 8.65 S%(w) 0.40 N%(w) 0.08 Four components % (w) Saturated portion 18.56 Aromatic components 80.07 gelatin 1.25 Asphalt 0.42

[0052] Example 3

[0053] Using catalytic slurry oil provided by a refinery as raw material, the properties are analyzed as shown in Table 4. The outlet temperature of the heating furnace during the coking stage of the raw material is 455℃-500℃, the heating rate is 3℃ / h, and the coking time T1 is 28h. Among them, the early stage of coking accounts for 90% of the total coking time T1. The coking tower pressure is 0.9MPa in the early stage of coking and 0.3MPa in the later stage of coking. The circulating mass ratio of coking circulating oil to fresh raw material during the coking stage is 0.2, and the 5% distillation point temperature of the circulating oil is 389℃. The sulfur content of the coking feedstock was 0.23%, the solid content was 85 μg / g, the 5% distillation point temperature was 358℃, and the 95% distillation point temperature was 495℃. The outlet temperature of the heating furnace during the coking stage was 470℃-505℃, the heating rate was 25℃ / h, and the coking time T2 was 30h. The early stage of coking accounted for 50% of the total coking time T2. The coke tower pressure was 0.85MPa in the early stage of coking and 0.30MPa in the later stage of coking. The circulating mass ratio of coking circulating oil to fresh feedstock during the coking stage was 0.8, and the 5% distillation point temperature of the circulating oil was 362℃. Within one coking reaction cycle, the mass ratio of coking feedstock to coking feedstock was 1:1.2. The properties of the obtained needle coke product are shown in Table 4.

[0054] Table 4 Properties of Catalytic Slurry

[0055] <![CDATA[Density g / cm 3 > 1.0652 Distillation range, °C 5％ 403 95％ 506 Solid content, μg / g 50 C%(w) 91.81 H%(w) 7.89 S%(w) 0.16 N% (w) 0.14 Four components % (w) Saturated portion 5.69 Aromatic components 92.10 gelatin 1.89 Asphalt 0.32

[0056] Table 5 Properties of needle coke in the examples

[0057] <![CDATA[CTE,10 -6 / ℃]]> 0.95 0.90 Volatile matter, w% 5.58 5.26 Ash content, w% 0.01 0.01 Sulfur content, w% 0.46 0.26 <![CDATA[True density, g / cm 3 > 1.43 1.44

Claims

1. A method for preparing needle coke, characterized in that: After being heated in a heater, the feedstock oil enters the coking tower for coking. After coking, the feedstock is introduced into the coke tower for coking. After coking, the product is decoked to obtain needle coke. The coking process is divided into two stages, with different pressures in the coke tower: the first stage is called the early coking stage, and the second stage is called the late coking stage. Let the total coking time T1 be the early and late coking stages. The early coking stage accounts for 60-95% of the total coking time T1. The pressure of the coke tower is controlled at 0.45-2.0 MPa during the early coking stage and 0.1-0.4 MPa during the late coking stage. The pressure difference in the coke tower between the two stages is 0.2-0.9 MPa, and the coking time difference is 1-20 hours. In the aforementioned feedstock coking process, the recycling ratio of recycled oil to fresh feedstock is 0-0.5; The coking process is divided into two stages, namely the early stage of coking and the late stage of coking. Let the total coking time T2 be the early stage and the late stage of coking. The early stage of coking accounts for 20-70% of the total coking time T2. The pressure of the coking tower is controlled at 0.45-2.0 MPa in the early stage of coking and 0.1-0.4 MPa in the late stage of coking. The pressure difference between the two stages of the coking process is 0.2-1.8 MPa.

2. The method according to claim 1, characterized in that: The coking process involves two stages, with a pressure difference of 0.2-0.7 MPa in the coke tower and a coking time difference of 2-10 hours.

3. The method according to claim 1, characterized in that: The early stage of coking accounts for 80-95% of the total coking time T1, and the pressure of the coking tower is controlled at 0.5-1.0 MPa during the early stage of coking; the pressure of the coking tower is controlled at 0.15-0.3 MPa during the later stage of coking.

4. The method according to claim 1, characterized in that: The pressure difference in the coke tower between the two stages of the coking process is 0.5-1.0 MPa.

5. The method according to claim 1, characterized in that: The early stage of coking accounts for 30-60% of the total coking time T2. During the early stage of coking, the pressure of the coking tower is controlled at 0.5-1.0 MPa; during the later stage of coking, the pressure of the coking tower is controlled at 0.15-0.35 MPa.

6. The method according to claim 1, characterized in that: The feedstock oil and coking feedstock are selected from at least one of coal-based feedstock and petroleum-based feedstock.

7. The method according to claim 6, characterized in that: The feedstock oil and coking feedstock are at least one of coal tar, coal tar pitch, heavy petroleum oil, ethylene tar, catalytic cracking slurry oil, or thermal cracking residue oil.

8. The method according to claim 1, characterized in that: The raw material oil has a solid content of 0-500 µg / g and a sulfur content of 0-1.0%.

9. The method according to claim 1, characterized in that: The raw material oil has a solid content of 0-200 µg / g and a sulfur content of 0-0.5%.

10. The method according to claim 1, characterized in that: The raw material oil has a solid content of 0-100 µg / g and a sulfur content of 0-0.3%.

11. The method according to claim 1, characterized in that: The 5% distillation point temperature of the feedstock oil is 350℃-450℃; the 95% distillation point temperature is 450℃-550℃.

12. The method according to claim 11, characterized in that: The 5% distillation point temperature of the feedstock oil is 370℃-410℃; the 95% distillation point temperature is 480℃-520℃.

13. The method according to claim 1, characterized in that: The outlet temperature of the heating furnace in the coking process of the raw oil is controlled by a variable temperature, with a temperature range of 420℃-550℃ and a temperature change rate of 1-150℃ / h.

14. The method according to claim 13, characterized in that: The outlet temperature of the heating furnace in the coking process of the raw oil is controlled by a variable temperature, with a temperature range of 450℃-500℃ and a temperature change rate of 5-50℃ / h.

15. The method according to claim 1, characterized in that: The recycling ratio of circulating oil to fresh feedstock in the coking process is 0.1-0.

5.

16. The method according to claim 1, characterized in that: The 5% distillation point temperature of the circulating oil in the coking process is 300℃-430℃.

17. The method according to claim 16, characterized in that: The 5% distillation point temperature of the circulating oil in the coking process is 350℃-400℃.

18. The method according to claim 1, characterized in that: The total coking time T1 is 12h-36h.

19. The method according to claim 18, characterized in that: The total coking time T1 is 20h-30h.

20. The method according to claim 1, characterized in that: The coking feedstock has a solid content of 0-500 µg / g and a sulfur content of 0-1.5%.

21. The method according to claim 1, characterized in that: The coking feedstock has a solid content of 0-200 µg / g and a sulfur content of 0-0.8%.

22. The method according to claim 1, characterized in that: The coking feedstock has a solid content of 0-100 µg / g and a sulfur content of 0-0.5%.

23. The method according to claim 1, characterized in that: The 5% distillation point temperature of the coking feedstock is 250℃-400℃; the 95% distillation point temperature is 420℃-520℃.

24. The method according to claim 23, characterized in that: The 5% distillation point temperature of the coking feedstock is 320℃-370℃; the 95% distillation point temperature is 440℃-500℃.

25. The method according to claim 1, characterized in that: The outlet temperature of the coking furnace in the coking process is controlled by a variable temperature system, with a temperature range of 450℃-550℃ and a temperature change rate of 1-150℃ / h.

26. The method according to claim 25, characterized in that: The outlet temperature of the coking furnace in the coking process is controlled by a variable temperature system, with a temperature range of 470℃-530℃ and a temperature change rate of 5-50℃ / h.

27. The method according to claim 1, characterized in that: The circulating ratio of circulating oil to fresh feedstock in the coking process is 0-2.

0.

28. The method according to claim 27, characterized in that: The circulating ratio of circulating oil to fresh feedstock in the coking process is 0.5-1.

5.

29. The method according to claim 1, characterized in that: The 5% distillation point temperature of the circulating oil in the coking process is 250℃-400℃.

30. The method according to claim 29, characterized in that: The 5% distillation point temperature of the circulating oil in the coking process is 320℃-370℃.

31. The method according to claim 1, characterized in that: The total time for focusing, T2, is 12h-36h.

32. The method according to claim 31, characterized in that: The total time for focusing, T2, is 20-30 hours.

33. The method according to claim 1, characterized in that: The mass ratio of the feedstock oil to the coking feedstock is 1:0.5-3.

0.

34. The method according to claim 33, characterized in that: The mass ratio of the feedstock oil to the coking feedstock is 1:0.5-1.5.