A production process for improving the performance of needle coke

Abstract

The present application relates to the technical field of needle coke production, and particularly relates to a production process for improving the performance of needle coke. The process steps are as follows: step one: in the delayed coking process part of the needle coke production process, water vapor is introduced 3-5 hours before the end of the coke drum feeding process; step two: the ratio of the coke drum feeding amount to the water vapor feeding amount is the oil gas ratio, and the oil gas ratio gradually decreases in operation, that is, the water vapor amount gradually increases, and finally the oil gas ratio reaches 2-4:1; step three: after the end of the coke drum feeding process, water vapor is continuously introduced to coke drawing, and the duration is 6-36 hours. The present application realizes that in the delayed coking part of the needle coke production process, water vapor is introduced according to a specific range of oil gas ratio from a specific time point, and the coke drawing process is carried out for a specific length of time, so that the CTE value of the needle coke product is reduced and the strength is improved, and the process is simple and can be operated on the basis of existing equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of needle coke production, in particular to a production process for improving the performance of needle coke. BACKGROUND

[0002] Needle coke is a kind of high-quality petroleum coke, which has a series of advantages such as low thermal expansion coefficient, low porosity, low sulfur, low ash content, low metal content, high electrical conductivity and easy graphitization. In the production of needle coke, the delayed coking process is generally used as the basis, and appropriate raw materials need to be selected, because not all high-aromatic raw materials can be successfully converted into needle coke. The main sources of raw materials that can be used to produce needle coke in industry include: catalytic cracking clarified oil (FCCDO), naphtha, and ethylene tar (ET) obtained by steam cracking of naphtha and gas oil to produce ethylene, thermal cracking tar (TR), and coal tar (CR) produced by coal coking or gasification. Needle coke is the main raw material for producing high-power and ultra-high-power graphite electrodes. Whether it is oil-based needle coke or coal-based needle coke, the production process consists of three parts: raw material pretreatment, delayed coking, and calcination.

[0003] Among them, delayed coking is the main part of the device process. Delayed coking is a process that combines continuous and intermittent processes to produce gas, various finished oils, and coke. The raw material is heated in a heating furnace and then enters the coking tower (intermittent process), and vaporization and cracking occur while maintaining the temperature in the coking tower. Therefore, this process is a kind of thermal cracking process for heavy oil. The delayed coking process device for petroleum heavy oil includes a fractionating tower, a heating furnace, and a coking tower, etc. The process is a continuous process in the fractionating tower and the heating furnace, but it is an intermittent process in the coking tower. Therefore, two or more coking towers are necessary to correspond to one fractionating tower and one heating furnace. Generally, the raw material enters the bottom of the fractionating tower, is blended with the circulating oil, and the temperature at the bottom of the tower is stabilized. Then, the material at the bottom of the fractionating tower is pumped into the coking furnace, rapidly heated to coking conditions, cracked and vaporized in a short time, and then enters the coking tower. In the coking tower, cracking, vaporization, and condensation occur until coke is formed. The liquid is vaporized and returned to the fractionating tower from the top of the coking tower. Coke is continuously formed and accumulated in the tower until the required amount is reached, and then the second tower is switched to continue. After the coking tower stops feeding, it is cooled and treated with high-pressure water to cut the coke, and then prepared for the next cycle. The operation of the coking tower directly affects the performance indicators of the needle coke.

[0004] Density, coefficient of thermal expansion, strength, resistivity, ash content and sulfur content are generally taken as the main performance indicators of needle coke, which are used to measure the quality of needle coke. Coefficient of thermal expansion (CTE) is one of the important parameters of needle coke, and the size of CTE is directly related to the quality of needle coke product. The smaller the CTE, the better the thermal shock resistance of needle coke under rapid temperature change. Generally, customers hope that the CTE of the product is as low as possible. The strength of needle coke depends on the absolute porosity, and is closely related to CTE. The lower the CTE, the worse the anti-shock stability of needle coke, and the lower the anti-crushing or anti-wear resistance, that is, the lower the strength. Generally, customers hope that the strength of the product is as high as possible.

[0005] In the production of needle coke, there is a process called "pulverization" applied to the end of the delayed coking stage. Pulverization is mainly applied to the end of the coking process in the coke drum in the delayed coking process. A certain medium is introduced into the bottom of the coke drum, including water vapor, nitrogen, light oil, etc. Since the temperature in the coke drum is relatively high, it has reached more than 500°C at the end of the coking process. Therefore, the medium vaporizes rapidly and rises through the fine pores of the coking in the coke drum, forming a physical stretching effect, thereby promoting the formation of a streamlined microstructure of the coking before it is completely solidified. The more such microstructure, the more it is considered to be a characteristic of high-quality needle coke.

[0006] The prior art mainly uses light oil, nitrogen and water vapor for the pulverization process:

[0007] Chinese patent CN108130119A discloses a pulverization and drying method for industrial production of needle coke. The coking raw material produced by the pretreatment device is introduced into the bottom of the fractionating tower as raw material to exchange heat with the high-temperature oil gas from the coking tower, and is mixed with the circulating oil before being heated in the coking heating furnace and then entering the coking tower ABC for coking. When the raw material of a certain tower is loaded, the pulverization and drying oil from the pulverization and drying heating furnace is switched to perform pulverization and drying. The pulverization and drying oil comes from the light oil in the upper part of the fractionating tower. After the pulverization and drying is completed, the coking tower is cooled, decoked, pressurized and preheated for the next time of raw material feeding. The pulverization medium used in this method is coal tar fraction and petroleum fraction, which aims to allow part of the organic light components in the medium to participate in the coking process in the coke drum during the pulverization process, so as to simultaneously improve the quality of the coke from the physical and chemical levels.

[0008] Chinese patent CN111892941A discloses a coking device, which also contains a coking process: first, the intermediate phase raw material is heated by the intermediate phase raw material heating unit and then enters the front coke tower, after the formation of the intermediate phase process in the coke tower is completed, the intermediate phase raw material heated by the intermediate phase raw material heating unit is switched to the rear coke tower, and the coking raw material heated by the coking raw material heating unit is introduced into the front coke tower, after the coking process in the front coke tower is completed, the coking raw material heated by the coking raw material heating unit is switched to the rear coke tower, and the intermediate phase raw material heated by the intermediate phase raw material heating unit is switched from the rear coke tower to any empty coke tower, after the front coke tower is decoked, the intermediate phase raw material heated by the intermediate phase raw material heating unit is introduced again, and the operation process of each coke tower is repeated. The total time of the coking process is 16-72h; the time for forming the intermediate phase process is 30-70% of the total time. This method is also organic medium coking, and the medium used is the side line light wax oil produced by the coke tower during the coking process.

[0009] Chinese patent CN106883871A discloses a method for producing needle coke by a combined process. The raw oil is fractionated into light fraction oil and heavy fraction oil by a vacuum distillation device, the heavy fraction oil is discharged from the device, the light fraction oil enters a hydrotreating device, and the liquid phase product obtained after hydrotreating is separated into at least a hydrotreated light fraction oil and a hydrotreated heavy fraction oil by a fractionation device. The hydrotreated heavy fraction oil is heated by a heating furnace a and then enters a coke tower to form an intermediate phase material, the coking gas generated by the coke tower is obtained after a coking fractionation tower to obtain coking wax oil, the coking wax oil is mixed with the hydrotreated light fraction oil and then heated by a heating furnace b to enter the coke tower as a coking material, and the coke tower sequentially completes the intermediate phase formation stage and the coking stage to obtain needle coke. This method is also organic medium coking, and the medium used is the coking wax oil and the hydrotreated light fraction oil produced by the coke tower.

[0010] Chinese patent CN113583701A discloses a production process for improving the optical properties of needle coke, the coking medium uses diesel oil, a small amount of nitrogen gas is introduced to promote the flow of diesel oil in the furnace tube, the coking temperature is controlled at 420-600℃, and pressure reduction operation is adopted, the pressure of the coke tower is uniformly reduced from 5-15kg / cm2 to 4-12kg / cm2, and the coking period is 6-16h. The coking medium used in this method is diesel oil, and nitrogen gas is used to promote the flow.

[0011] Chinese patent CN113698956A discloses a production process for improving the pressure strength of needle coke, which includes: raw material pretreatment stage; large cycle temperature rising stage, pressure reduction and temperature rising coke drawing stage and cooling stage. Similar to the previous patent, diesel is used as the coke drawing medium, and the overall process adds a so-called "large cycle temperature rising stage".

[0012] Chinese patent CN212559472U discloses a production system for needle coke, which adopts "one furnace with three towers", one tower for reaction, one tower for coke removal and one tower for coke drawing, uses a tower coking furnace for heating, uses nitrogen circulating gas for coke drawing, and uses a nitrogen heater for heating. This method uses nitrogen for coke drawing, and nitrogen does not affect the reaction in the coke tower due to its inertness.

[0013] Disadvantages of the prior art:

[0014] (1) The existing light oil, including wax oil, diesel oil, hydrogenated light oil, etc., is used for coke drawing in order to allow organic components to participate in coking reaction and play a role in reinforcing green coke. In experiments, it is found that light oil medium coke drawing will crack to produce combustible gas above 510℃, which may cause safety problems, and the volatile matter of green coke product increases significantly.

[0015] (2) The existing nitrogen coke drawing method mainly aims to use the inertness of nitrogen to stretch the microstructure of green coke without affecting the reaction in the coke tower. This method needs to introduce pure nitrogen, which has the highest cost. In experiments, it is found that due to the different diameters of the fine pores of green coke products, nitrogen coke drawing will appear the phenomenon that most of the gas flow passes through the large pores and almost does not pass through the small pores, causing serious unevenness of coke drawing, and further affecting the overall quality of needle coke products.

[0016] (3) The existing steam coke drawing is usually carried out after the end of the feeding process in the coke tower, and a considerable part of the green coke has already solidified, so the stretching effect is limited, and most of the steam coke drawing processes do not set the best process conditions for the timing and duration. Invention content:

[0017] The technical problem to be solved by the present application is to provide a production process for improving the performance of needle coke, which realizes the introduction of water vapor at a specific time point and a specific range of oil-gas ratio in the delayed coking part of the needle coke production process, carries out a specific length of time of coke drawing process, reduces the CTE value of needle coke products and improves the strength, and the process is simple and can be operated on the basis of existing equipment. Overcomes the deficiency that the existing steam coke drawing is usually carried out after the end of the feeding process in the coke tower, and a considerable part of the green coke has already solidified, so the stretching effect is limited.

[0018] The technical solution adopted by the present application is: a production process for improving the performance of needle coke, which has the following process steps:

[0019] Step one: in the delayed coking process part of the production process of needle coke, water vapor is introduced 3-5 hours before the end of the coke drum feed process, and the water vapor is mixed with the raw oil and the circulating oil feed;

[0020] Step two: the ratio of coke drum feed quantity to water vapor feed quantity is oil gas ratio, and the oil gas ratio gradually decreases during operation, that is, the amount of water vapor gradually increases, and finally the oil gas ratio reaches 2-4:1;

[0021] Step three: after the end of the coke drum feed process, water vapor is continuously introduced to coke, and the duration is 6 to 36 hours, and the water vapor is condensed and discharged from the top of the coke drum;

[0022] Step four: after the water vapor coke is finished, stop the water vapor, and the coke drum is slowly cooled to prepare for hydraulic decoking.

[0023] Further, the water vapor introduced into the coke drum is heated by a heating furnace, and the outlet temperature is 490-510 DEG C.

[0024] Further, the water vapor is introduced into the coke drum 4 hours before the end of the feed process in step one.

[0025] Further, in step two, the final oil gas ratio is 3:1.

[0026] Further, in step three, the water vapor is continuously introduced to coke, and the duration is 24 hours.

[0027] Further, in step one, the needle coke coking reaction is set as follows: delayed coking is used, the coke drum inlet temperature is 450-500 DEG C, the feed rate is 100-200 kg / h, the pressure in the tower is controlled to 1-2.0 MPa, the coking temperature is controlled to 450-490 DEG C, the coking time is 24-48 hours, the coking reaction is carried out, and the generated needle coke is deposited in the coke drum.

[0028] Further, in the needle coke coking reaction in step one, the oil gas product at the top outlet of the coke drum is separated by a fractionating tower to obtain a mixture containing gas, oil, aromatic hydrocarbon and heavy fraction, which is circulated into the coke drum as circulating oil.

[0029] The beneficial effects of the present application are:

[0030] 1. Water vapor coke is safer and lower in cost than nitrogen and oil gas coke;

[0031] 2. The water vapor is introduced in advance before the end of the feed, and the coke is not completely solidified when the coke is started, which is more conducive to forming a streamline microstructure and reducing the CTE of the needle coke product;

[0032] 3. The water vapor coke is continuously introduced for a period of time after the end of the feed, which can enhance the strength of the needle coke product;

[0033] 4. The process of this invention can be implemented by only changing some operating conditions on the basis of existing equipment. It is simple to operate and has low cost. Detailed implementation method:

[0034] Example 1:

[0035] The needle coke feedstock was mixed oil slurry A. Pilot-scale experiments were conducted without using a coke pulling process. The product CTE value was 2.48 (10). -6 (°C), strength is 20.5%.

[0036] (1) Steam is introduced 3 hours before the end of the coke tower feeding.

[0037] (2) The oil-gas ratio of the coke tower feed and steam gradually decreases, eventually reaching 2:1.

[0038] (3) After the coke tower feeding process is completed, water vapor is continuously introduced to pull the coke for 6 hours.

[0039] (4) Analysis of the needle coke sample (3) showed a CTE of 2.37 (10). -6 / ℃), with a particle strength of 21.3%.

[0040] Example 2:

[0041] The needle coke feedstock was mixed oil slurry A. Pilot-scale experiments were conducted without using a coke pulling process. The product CTE value was 2.48 (10). -6 (°C), strength is 20.5%.

[0042] (1) Steam is introduced 4 hours before the end of the coke tower feeding.

[0043] (2) The oil-gas ratio of the coke tower feed and steam gradually decreases, eventually reaching 3:1.

[0044] (3) After the coke tower feeding process is completed, water vapor is continuously introduced to pull the coke for 12 hours.

[0045] (4) Analysis of the needle coke sample (3) showed a CTE of 2.25 (10). -6 / ℃), with a particle strength of 33.6%.

[0046] Example 3:

[0047] The needle coke feedstock was mixed oil slurry A. Pilot-scale experiments were conducted without using a coke pulling process. The product CTE value was 2.48 (10). -6 (°C), strength is 20.5%.

[0048] (1) Start to inject steam 5 hours before the end of the feeding of the coke drum.

[0049] (2) The oil-gas ratio of the feeding of the coke drum and the steam is gradually reduced, and finally reaches 3 to 1.

[0050] (3) After the end of the feeding of the coke drum, steam is continuously injected to coke, and the duration is 24 hours.

[0051] (4) The sample of the needle coke in (3) is analyzed, and the CTE is 2.10 (10 -6 / ℃), and the particle strength is 35.5%.

[0052] Example 4:

[0053] The needle coke raw material is mixed oil slurry A, and a pilot experiment is carried out without using the coke drawing process, and the product CTE value is 2.48 (10 -6 / ℃), and the strength is 20.5%.

[0054] (1) Start to inject steam 5 hours before the end of the feeding of the coke drum.

[0055] (2) The oil-gas ratio of the feeding of the coke drum and the steam is gradually reduced, and finally reaches 4 to 1.

[0056] (3) After the end of the feeding of the coke drum, steam is continuously injected to coke, and the duration is 36 hours.

[0057] (4) The sample of the needle coke in (3) is analyzed, and the CTE is 2.45 (10 -6 / ℃), and the particle strength is 30.2%.

[0058] Example 5:

[0059] The needle coke raw material is mixed oil slurry B, and a pilot experiment is carried out without using the coke drawing process, and the product CTE value is 2.51 (10 -6 / ℃), and the strength is 26.3%.

[0060] (1) Start to inject steam 5 hours before the end of the feeding of the coke drum.

[0061] (2) The oil-gas ratio of the feeding of the coke drum and the steam is gradually reduced, and finally reaches 2 to 1.

[0062] (3) After the end of the feeding of the coke drum, steam is continuously injected to coke, and the duration is 16 hours.

[0063] (4) The sample of the needle coke in (3) is analyzed, and the CTE is 2.38 (10 -6 / ℃), and the particle strength is 28.5%.

[0064] Example 6:

[0065] The needle coke raw material is mixed oil slurry B, and the pilot experiment is carried out without using the coke drawing process, and the product CTE value is 2.51 (10 -6 / ℃), and the strength is 26.3%.

[0066] (1), water vapor is introduced 4 hours before the end of the coke tower feeding.

[0067] (2), the oil-gas ratio of the coke tower feeding and water vapor is gradually reduced, and finally reaches 3 to 1.

[0068] (3), after the end of the coke tower feeding process, water vapor is continuously introduced to draw coke, and the duration is 32 hours.

[0069] (4), the sample of (3) needle coke is analyzed, and the CTE is 2.24 (10 -6 / ℃), and the particle strength is 31.8%.

[0070] It can be understood that the above specific description of the present application is only used to illustrate the present application and is not limited to the technical solutions described in the embodiments of the present application. Those skilled in the art should understand that the present application can still be modified or replaced equivalently to achieve the same technical effect; as long as the use needs are met, it is within the protection scope of the present application.

Claims

1. A production process for improving the properties of needle coke, characterized by: The process steps are as follows: Step one: in the delayed coking process part of the production process of needle coke, water vapor is introduced 3-5 hours before the end of the coke drum feed process, and the water vapor is mixed with the raw oil and the circulating oil feed; The process setting of the needle coke coking reaction is as follows: delayed coking is adopted, the coke drum inlet temperature is 450-500℃, the feed rate is 100-200 kg / h, the pressure in the tower is controlled to 1-2.0 MPa, the coking temperature is controlled to 450-490℃, the coking time is 24-48 hours, and the coking reaction is carried out, and the generated needle coke is deposited in the coke drum; Step two: the ratio of coke drum feed quantity to water vapor feed quantity is oil gas ratio, and the oil gas ratio gradually decreases during operation, that is, the amount of water vapor gradually increases, and finally the oil gas ratio reaches 2-4:1; Step three: after the end of the coke drum feed process, water vapor is continuously introduced to coke, and the duration is 6-36 hours, and the water vapor is condensed and discharged from the top of the coke drum; Step four: after the end of water vapor coke, stop water vapor, slowly cool the coke drum, and prepare for hydraulic decoking.

2. The production process for improving the performance of needle coke according to claim 1, characterized by: The water vapor introduced into the coke drum is heated by a heating furnace, and the outlet temperature is 490-510℃.

3. The production process for improving the performance of needle coke according to claim 1, characterized by: In step one, water vapor is introduced 4 hours before the end of the coke drum feed process.

4. The production process for improving the performance of needle coke according to claim 1, characterized by: In step two, the final oil gas ratio is 3:

1.

5. The production process for improving the performance of needle coke according to claim 1, characterized in that: In step three, water vapor is continuously introduced to coke, and the duration is 24 hours.

6. The production process for improving the performance of needle coke according to claim 1, characterized by: In step one, in the needle coke coking reaction, the oil gas product at the top outlet of the coke drum is separated by a fractionating tower to obtain a mixture containing gas, oil, aromatic hydrocarbon and heavy fraction, which is circulated into the coke drum as circulating oil.