A method for preparing negative electrode coke raw material based on ethylene tar of delayed coking process

Abstract

The application discloses a method for preparing negative electrode coke raw materials from ethylene tar based on a delayed coking process and belongs to the technical field of petroleum chemical industry. The method divides ethylene tar into two paths: the first path is injected into the top of a coke tower, flows down along the tower wall and exchanges heat with upgoing high-temperature oil gas to condense; the second path is tangent to a heating furnace tube, and the gum of conventional raw materials is used to wrap asphaltene in ethylene tar to inhibit coking of the furnace tube. By adjusting the steam injection amount in sections to maintain a high flow rate, the deep condensation reaction is delayed to the coke tower. The two paths of materials are combined in the tower and subjected to multiphase synergistic reaction to generate fibrous coke with optical anisotropy. The application avoids the coking risk of mixed raw materials through path optimization and multi-point injection design, ensures long-period stable operation of the system and realizes energy saving and consumption reduction; meanwhile, the microstructure required by the negative electrode coke can be directionally constructed, and the electrochemical performance of the negative electrode coke is improved.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically relating to a method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process. Background Technology

[0002] With the explosive growth of the lithium-ion battery market, the demand for high-performance artificial graphite anode materials and their precursors—high-quality anode coke—is becoming increasingly urgent. Currently, anode coke is mainly produced by delayed coking of specific petroleum fractions such as vacuum residue and catalytic slurry, but this route faces bottlenecks such as large fluctuations in raw material costs and limited control over the anisotropic structure of the products.

[0003] Ethylene tar, a major byproduct of the ethylene industry, is rich in polycyclic aromatic hydrocarbons and is widely recognized as an ideal low-cost raw material for preparing high-value-added carbon materials. However, the direct utilization of ethylene tar in existing delayed coking processes faces multiple technical barriers: 1. Poor thermal compatibility and coking of furnace tubes: When ethylene tar is mixed with conventional petroleum-based feedstocks, asphaltenes are easily precipitated and components are separated during high-temperature heating, which leads to rapid coking of the inner wall of the heating furnace tubes and severely shortens the operating cycle of the unit. 2. Difficulty in microstructure control: Ethylene tar has excessively high thermal reactivity and extremely fast polycondensation rate. Under the traditional coking control logic, it is very easy to generate amorphous sponge coke, making it difficult to form the anisotropic fibrous structure required for the preparation of high-quality anode materials. 3. Process mismatch: The thermal balance and separation system of the existing equipment has not been optimized for the physical properties of ethylene tar, resulting in poor operational stability and difficulty in controlling the content of impurities in the product.

[0004] To address the aforementioned problems, existing technologies typically employ the addition of chemical additives or the establishment of complex pretreatment units such as hydrogenation and distillation. However, this significantly increases equipment investment costs and operating energy consumption, thereby reducing the economic efficiency and resource utilization of the process.

[0005] Therefore, how to utilize existing delayed coking units to convert ethylene tar into high-quality negative electrode coke through simple and efficient control methods has become a key issue that urgently needs to be addressed in the industry. Summary of the Invention

[0006] This invention addresses the aforementioned problems in the existing technology by proposing a method for preparing negative electrode coke feedstock from ethylene tar based on a delayed coking process, which can successfully convert ethylene tar into high-quality negative electrode coke.

[0007] This invention can be achieved through the following technical solutions: A method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process includes the following steps: S1. Provide conventional feedstock and ethylene tar feedstock. The conventional feedstock includes vacuum residue and catalytic slurry and is introduced into the heater. The ethylene tar feedstock is divided into a first path and a second path. The first path bypasses the heater and is directly connected to the top of the coke tower. The second path is connected to the furnace tube feeding system of the heater. S2. The ethylene tar in the first path is injected from the top of the coke tower. The injection point is located in the slow-flowing gas phase area inside the coke tower and is arranged towards the tower wall. The liquid ethylene tar is used to exchange heat with the high-temperature oil and gas rising inside the coke tower, which induces the heavy components of ethylene tar to undergo a condensation reaction and cause them to settle downward along the tower wall. S3. The ethylene tar in the second path enters the furnace tube of the heating furnace through tangential injection and merges with the conventional raw materials flowing in the tube to form a vortex. The gum components in the conventional raw materials physically encapsulate the asphaltenes in the ethylene tar to inhibit the precipitation of asphaltenes and coking of the ethylene tar during the heating process in the furnace tube. S4. By adjusting the steam injection rate of different pipe sections inside the heating furnace, the high flow rate of the mixing material inside the furnace tube is maintained, so as to delay the deep polycondensation reaction window of conventional raw materials and second-path ethylene tar into the coke tower. S5. The condensation products falling from the wall of the coking tower and the mixed stream entering from the bottom of the coking tower converge in the tower. Driven by the sensible heat of oil and gas and the heat supply of furnace tubes, a multiphase synergistic reaction is carried out. After the coking cycle is completed, a fibrous coke structure with optical anisotropy is generated, which can be used as a raw material for lithium battery anode.

[0008] As a further improvement of the present invention, in step S1, the proportion of ethylene tar feedstock is controlled to be no less than 20%, and the proportion of catalytic oil slurry feedstock is controlled to be no less than 15%.

[0009] As a further improvement of the present invention, in step S2, the output end of the feed nozzle set at the top of the coke tower is inclined toward the tower wall of the coke tower, so that the injection point of ethylene tar is located at the edge of the spherical top of the coke tower, and the horizontal distance from the gas phase outlet at the top of the tower is not less than 1 / 2 of the tower diameter.

[0010] As a further improvement of the present invention, in step S2, low-temperature ethylene tar below 100°C is introduced through the first path as a conditioning cold source to replace the conventional top quench oil injection into the top of the coke tower.

[0011] As a further improvement of the present invention, in step S4, the heating furnace has a first gas injection point and a second gas injection point, wherein, The first gas injection point is located in the convection section of the furnace tube area of ​​the heating furnace, which is upstream of the injection port of the ethylene tar in the second path. The second gas injection point is located in the radiant section of the furnace tube area of ​​the heating furnace, downstream of the first gas injection point.

[0012] As a further improvement of the present invention, in step S4, by adjusting the fluid flow rate at the first steam injection point, the linear velocity of the material flow in the convection section furnace tube area is controlled between 2.0 m / s and 3.5 m / s, and the outlet temperature of the convection section is maintained below 360°C, so as to suppress early coking after ethylene tar is mixed with conventional raw materials.

[0013] As a further improvement of the present invention, in step S4, by adjusting the fluid flow rate at the second steam injection point, the flow velocity of the material in the radiant section furnace tube area is maintained between 3.0 m / s and 5.0 m / s. By utilizing the shear force generated by the high flow velocity and the residence time control, the occurrence point of the deep polycondensation reaction is guided into the coke tower.

[0014] As a further improvement of the present invention, in step S5, the operating pressure at the top of the coke tower is controlled to be in a slightly positive pressure state, and the reaction temperature is controlled at 480-520℃.

[0015] As a further improvement of the present invention, in step S5, when the coking tower is in the late stage of the coking cycle and a tower switching operation is performed, the ethylene tar in the first path and the conventional raw material flow at the outlet of the heating furnace are controlled to perform a tower switching action simultaneously, so that the ethylene tar is switched from the currently full coking tower to another coking tower that has completed preheating and is ready to be fed, so as to maintain the consistency of the reaction time and blending ratio of the ethylene tar components and the conventional raw material components in each coking tower.

[0016] As a further improvement of the present invention, step S6 is also included, in which the reaction products at the top of the coke tower are introduced into the fractionation tower for staged cooling and component cutting. By using the physical components and temperature gradient control inside the fractionation tower, the rich gas, diesel oil, light wax oil and heavy wax oil at the top of the tower are extracted sequentially from top to bottom.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. Completely solve the coking problem: Some ethylene tar bypasses the heating furnace and is directly injected into the coking tower, fundamentally eliminating the root cause of coking caused by incompatibility of raw materials in high-temperature areas, and ensuring the long-term safe and stable operation of the unit.

[0018] 2. Excellent product quality: By precisely controlling the temperature and residence time in the reaction zone (the upper gas phase space and the lower coke layer of the coke tower), ethylene tar undergoes two stages: "rapid heating and cracking" and "deep polycondensation," which is conducive to generating high-quality coke with a well-developed fibrous structure, good graphitization performance, and high specific capacity of the resulting anode material.

[0019] 3. Simple process and extremely low investment: No need to add complex pretreatment equipment or use expensive chemical additives. It only uses existing equipment and adjusts the operation mode to achieve "zero modification" integration, which greatly reduces the technical application threshold and cost.

[0020] 4. Energy saving and comprehensive utilization of resources: Fully utilize the waste heat of high-temperature oil and gas that originally needed to be removed by cooling in the coking tower as a heat source for reaction, reducing the overall energy consumption of the system, while realizing the efficient conversion of all components of ethylene tar and high carbon yield.

[0021] 5. High operational flexibility: Ethylene tar feed can be adjusted as an independent variable, making it easy to adjust the output according to market demand and plant conditions without affecting the normal processing of petroleum-based feedstocks by the main plant. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process of the present invention. Figure 2 This is a schematic diagram showing the position of the feed nozzle of the coke tower according to the present invention.

[0023] In the diagram, 100 is the first feed buffer tank; 101 is the heat exchanger; 110 is the radiant buffer tank of the heating furnace; 120 is the second feed buffer tank; 130 is the heating furnace; 140 is the coke tower; 141 is the feed nozzle; 150 is the fractionation tower; 151 is the gas-liquid separator; and 160 is the pump. Detailed Implementation

[0024] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings to further illustrate the technical methods of the present invention. However, the present invention is not limited to these embodiments.

[0025] like Figures 1-2 As shown, this invention provides a method for preparing negative electrode coke feedstock from ethylene tar based on a delayed coking process, comprising the following steps: S1. Provide conventional feedstock and ethylene tar feedstock. The conventional feedstock includes vacuum residue and catalytic slurry and is introduced into the heater 130. The ethylene tar feedstock is divided into a first path and a second path. The first path bypasses the heater 130 and is directly connected to the top of the coke tower 140. The second path is connected to the furnace tube feeding system of the heater 130. S2. The ethylene tar in the first path is injected from the top of the coking tower 140. The injection point is located in the slow-flowing gas phase area inside the coking tower 140 and is arranged towards the tower wall. The liquid ethylene tar is used to exchange heat with the high-temperature oil and gas rising inside the coking tower 140, which induces the heavy components of ethylene tar to undergo a condensation reaction and causes them to settle downward along the tower wall. S3. The ethylene tar in the second path enters the furnace tube of the heating furnace 130 through tangential injection and merges with the conventional raw materials flowing in the tube to form a vortex. The gum components in the conventional raw materials physically encapsulate the asphaltenes in the ethylene tar to inhibit the precipitation of asphaltenes and coking of the ethylene tar during the heating process in the furnace tube. S4. By adjusting the steam injection rate of different pipe sections inside the heating furnace 130, the high flow rate of the mixing material inside the furnace tube is maintained, so as to delay the deep polycondensation reaction window of conventional raw materials and second-path ethylene tar into the coke tower 140. S5. The condensation products falling from the wall of coke tower 140 and the mixed stream entering from the bottom of coke tower 140 converge in the tower. Driven by the sensible heat of oil and gas and the heat supply of furnace tubes, a multiphase synergistic reaction is carried out. After the coking cycle is completed, a fibrous coke structure with optical anisotropy is generated, which can be used as a raw material for lithium battery anode.

[0026] This invention, through the synergistic design of the above S1-S5 steps, cleverly solves the technical problems in the prior art where ethylene tar is difficult to utilize directly, easily leads to coking in furnace tubes, and the products cannot meet the requirements of anode materials. The specific principle and beneficial effects are as follows: 1. Fundamentally solve the problem of "coking in furnace tubes" (for S1, S2, and S3) Existing problem: Ethylene tar is rich in asphaltenes, and when mixed with conventional residual oil, it is very easy to separate into layers at high temperatures, causing rapid coking and blockage of the 130 tube in the heating furnace.

[0027] The solution proposed in this application is as follows: (1) Physical isolation and low temperature transportation: Ethylene tar is divided into "first path" through S1 and S2, so that it completely bypasses the heating furnace 130 and is directly injected into the coking tower 140 at low temperature (less than 100°C). This fundamentally eliminates the conditions for thermal polycondensation reaction of ethylene tar in the high temperature furnace tube and physically cuts off the source of coking.

[0028] (2) Swirl coating and flow rate control: For the "second path" ethylene tar (S3) that must enter the heating furnace 130, tangential injection technology is used to make it form a swirling mixture with conventional raw materials (residue oil / oil slurry). The gum and asphaltenes in the conventional raw materials act as a "coating layer" to physically isolate the highly active ethylene tar components. At the same time, the gas injection rate in S4 is adjusted to maintain a high flow rate in the furnace tube, and the fluid shear force is used to suppress the aggregation and sedimentation of asphaltenes.

[0029] This enables the safe and stable co-coking of ethylene tar with conventional feedstocks without the addition of expensive chemical dispersants, ensuring the long-term operation of the unit.

[0030] 2. Targeted control of "optical anisotropy" structures (for S2 and S5) Existing problem: Ethylene tar has excessively high reactivity, and under traditional processes, it is easy to generate amorphous sponge coke, which lacks the fibrous structure required for negative electrode materials.

[0031] The solution proposed in this application is as follows: (1) Mild condensation in the tower: In S2, ethylene tar is injected into the slow-flow gas phase zone of coke tower 140, and the sensible heat of the high-temperature oil and gas (410-420℃) in the tower is used for "mild heat exchange". This environment avoids the drastic heating rate in the heating furnace 130, so that the heavy components of ethylene tar undergo a "slow dehydrogenation-ordered arrangement" process, inducing the formation of a well-developed fibrous mesophase.

[0032] (2) Multiphase synergistic coking: In S5, the condensation products settling at the top of the tower and the mixed stream rising from the bottom of the tower converge in the high-temperature zone (480-520℃). This "countercurrent contact" design allows the highly active ethylene tar components to undergo gas-phase deposition and liquid-phase adhesion growth on the surface of the formed coke layer. Driven by the combined heat of oil and gas and the heat supplied by the furnace tubes, a dense coke structure with optical anisotropy is forcibly constructed.

[0033] Under this design, the resulting coke has a well-developed pore structure and an ordered crystal arrangement, with good graphitization performance, which fully meets the performance requirements of lithium-ion battery anode materials for high specific capacity and long cycle life.

[0034] 3. Achieve "energy saving and consumption reduction" and "process adaptation" (for S2 and S4) Existing problem: The thermal balance of existing equipment is difficult to adapt to high aromatic feedstocks, and additional cooling or heating is usually required.

[0035] The solution proposed in this application is as follows: (1) Waste heat utilization and cold source replacement: In S2, low-temperature ethylene tar is used to replace the traditional top quench oil. This not only provides the cold source required for the reaction to balance the heat field inside the tower, but also absorbs the heat of high-temperature oil and gas to complete its own preheating and cracking, thus realizing the cascade utilization of energy.

[0036] (2) Guided coking: S4 delays the deep polycondensation reaction window to within the coke tower 140 by precisely adjusting the gas injection rate (controlling the flow rate in the convection and radiation sections). This not only protects the heating furnace 130 but also reduces the heat load on the heating furnace 130 and reduces fuel consumption.

[0037] The entire process does not require large-scale hardware modifications to the existing delayed coking unit (such as adding a new hydrogen unit or a complex heat exchanger 101). It significantly improves economic efficiency by simply refactoring the process and fine-tuning the parameters.

[0038] Overall, this embodiment achieves uniform dispersion and stable flow of raw materials in the system through innovative feeding paths and multi-point injection design, fundamentally avoiding the risk of mixed coking and ensuring long-term stable operation of the unit. At the same time, it cleverly utilizes the waste heat of high-temperature oil and gas in the coke tower 140 to provide a heat source for the reaction, achieving energy saving and consumption reduction. By precisely controlling process parameters and raw material ratios, it directionally constructs the well-developed pore structure required for the negative electrode coke, thereby improving its electrochemical performance.

[0039] The entire method relies entirely on existing industrial equipment, requiring no complex modifications or expensive pretreatment. It involves low investment, is easy to implement, and is highly adaptable. Compared to existing technologies, it has at least the following advantages: 1. Completely solve the coking problem: Some ethylene tar bypasses the heating furnace 130 and is directly injected into the coking tower 140, which fundamentally eliminates the root cause of coking caused by incompatibility of raw materials in high-temperature parts, and ensures the long-term safe and stable operation of the unit.

[0040] 2. Excellent product quality: By precisely controlling the temperature and residence time in the reaction zone (the upper gas phase space and the lower coke layer of the coke tower 140), ethylene tar undergoes two stages: "rapid heating and cracking" and "deep polycondensation," which is conducive to generating high-quality coke with a well-developed fibrous structure, good graphitization performance, and high specific capacity of the resulting anode material.

[0041] 3. Simple process and extremely low investment: No need to add complex pretreatment equipment or use expensive chemical additives. It only uses existing equipment and adjusts the operation mode to achieve "zero modification" integration, which greatly reduces the technical application threshold and cost.

[0042] 4. Energy saving and comprehensive utilization of resources: The waste heat of high-temperature oil and gas that originally needed to be removed by cooling is fully utilized in the coke tower 140 as a reaction heat source, which reduces the overall energy consumption of the system and realizes the efficient conversion of all components of ethylene tar with high carbon yield.

[0043] 5. High operational flexibility: Ethylene tar feed can be adjusted as an independent variable, making it easy to adjust the output according to market demand and plant conditions without affecting the normal processing of petroleum-based feedstocks by the main plant.

[0044] Preferably, in step S1, the proportion of ethylene tar feedstock is controlled to be no less than 20%, mainly controlling the content of coke impurities (sulfur and metals), and the proportion of catalytic oil slurry feedstock is controlled to be no less than 15%, mainly controlling the structure of raw coke, improving specific capacity, and enhancing cycle life.

[0045] This formulation scheme achieves synergistic effects between raw material purity and microstructure: on the one hand, the introduction of a high proportion of ethylene tar significantly reduces the interference of harmful impurities on electrochemical reactions, improving the chemical stability and safety of the material; on the other hand, the anisotropic fiber structure generated by the precise control of the catalytic slurry effectively constructs a rapid lithium-ion diffusion channel and alleviates lattice expansion during charging and discharging, thereby endowing the final anode material with higher specific capacity, excellent first-efficiency performance, and extremely long cycle life.

[0046] Preferably, in step S2, the output end of the feed nozzle 141 at the top of the coke tower 140 is inclined toward the tower wall of the coke tower 140, so that the injection point of ethylene tar is located at the edge of the spherical top of the coke tower 140, and the horizontal distance from the gas phase outlet at the top of the tower is not less than 1 / 2 of the tower diameter. This position is a relatively slow flow area of ​​oil and gas, which can effectively prevent the high-speed upward oil and gas from carrying the unreacted ethylene tar droplets to the fractionation system, prevent coking in the fractionation tower 150, and ensure that the ethylene tar sprayed out falls along the tower wall to the coke bed. The sensible heat of the upward high-temperature oil and gas in the tower is used as the heat source for the reaction. The coke produced by condensation falls to the coke bed, and the oil and gas produced by cracking rise with the high-temperature oil and gas.

[0047] This design not only ensures the long-term safe operation of the subsequent fractionation system by completely eliminating the "droplet entrainment" phenomenon, but more importantly, it realizes in-situ heat recovery and graded coking: the waste heat of the system replaces part of the external heating load, significantly reducing energy consumption; at the same time, through the pre-condensation reaction in the gas phase space, the material falling into the bottom coke layer has a good coking precursor structure, effectively avoiding the disturbance of the bottom coke layer flow field by secondary feeding, thereby ensuring the orientation consistency and compactness of the raw coke product at the microscale.

[0048] Preferably, in step S2, low-temperature ethylene tar (below 100°C) is introduced via the first path as a regulating cold source to replace the conventional overhead quench oil injected into the top of the coke tower 140. It should be noted that after the ethylene tar enters the delayed coking furnace 130, its high aromatic content, high carbon residue, and difficulty in vaporization cause a delayed reaction within the furnace, resulting in a large amount of condensation heat being released concentratedly within the coke tower 140, causing a surge in tower temperature. To control the tower top temperature and suppress excessive cracking, low-temperature ethylene tar (below 100°C) is introduced to replace the overhead quench oil (175°C), effectively balancing the large amount of condensation heat released within the coke tower 140, thus saving energy and reducing consumption.

[0049] Preferably, in step S3, multiple heating furnaces 130 are set, and the flow rate of ethylene tar in each branch is controlled at 3-6 t / h, and the flow rate deviation of each ethylene tar is controlled to be no more than 5%. The ethylene tar is evenly fed to each radiating branch of the heating furnace 130. Through a gradual process of "dispersion-mixing-homogenization", coking in the furnace tube is suppressed from the source. The injection port adopts tangential injection of ethylene tar and mixed raw materials, which reduces drag by swirling flow and reduces pressure drop by 10-20%. Swirling mixing is generated at the injection point, and the mixing is more thorough. The gum components in the residue oil and catalytic slurry uniformly "encapsulate" the asphaltenes in the ethylene tar, avoiding the rapid coking of asphaltenes in the ethylene tar.

[0050] Preferably, in step S4, the heating furnace 130 has a first gas injection point and a second gas injection point, wherein, The first gas injection point is located in the convection section of the furnace tube area of ​​the heating furnace 130, which is upstream of the injection port of the second path ethylene tar. By introducing the gas injection medium in advance, the initial turbulence and flow rate of the material after entering the convection section are increased, preventing the high viscosity ethylene tar from depositing and coking during the preheating stage, and enhancing the convective heat transfer efficiency. The second gas injection point is located in the radiant section of the furnace tube area of ​​the heating furnace 130, downstream of the first gas injection point. It further increases the flow rate inside the tube before the material reaches the highest reaction temperature. By shortening the residence time of the material in the high-temperature radiant zone, it effectively prevents the excessive cracking of ethylene tar. This not only ensures the long-term safe operation of the heating furnace 130 under high heat load, but also provides stable raw material support with precise superheat for the subsequent generation of high-quality, high-crystallinity anisotropic coke in the coke tower 140.

[0051] Furthermore, in step S4, by adjusting the fluid flow rate at the first steam injection point, the linear velocity of the material flow in the convection section furnace tube area is controlled between 2.0 m / s and 3.5 m / s, and the outlet temperature of the convection section is maintained below 360°C, that is, below the asphalt coking temperature, so as to suppress early coking after the ethylene tar is mixed with conventional raw materials. By adjusting the fluid flow rate at the second steam injection point, the flow velocity of the material in the radiant section furnace tube area is maintained between 3.0 m / s and 5.0 m / s. The shear force and residence time generated by the high flow velocity are used to control the flow rate, which avoids excessive flow velocity in the radiant section, increased heat load of the heating furnace 130, and increased energy consumption of the device. At the same time, the design flow velocity of the radiant section furnace tube is met, so that coking is delayed until it occurs in the coke tower 140, thus achieving guided coking.

[0052] This solution eliminates the early coking tendency of ethylene tar-rich feedstocks by locking the temperature threshold of the convection section, enabling the heating furnace 130 to achieve an industry-leading operating cycle. At the same time, the flow velocity in the radiation section is controlled within the scientific range of 3.0-5.0 m / s. This not only uses high flow velocity to suppress deposited coking and achieves "coking shift" to the coke tower 140, but also successfully avoids the heat load waste and increased power costs caused by excessive gas injection due to blindly pursuing flow velocity. It achieves a balance between low energy consumption operation and high-quality guided coking, providing process assurance for the final production of high-quality negative electrode coke with an oriented microstructure.

[0053] Preferably, in step S5, the operating pressure at the top of the coke tower 140 is controlled to be in a slightly positive pressure state. This slightly positive pressure environment effectively avoids the tendency of "secondary cracking" and "bulking" caused by component retention. At the same time, the reaction temperature is controlled at 480-520℃. The precise control of the medium temperature range endows the coke with high graphitization potential and well-developed graphene sheet orientation, ensuring that the obtained negative electrode material precursor has extremely high anisotropic characteristics.

[0054] Preferably, in step S5, when the coke tower 140 is in the late stage of the coking cycle and is undergoing a tower switching operation, the ethylene tar in the first path and the conventional raw material flow at the outlet of the heating furnace 130 are controlled to perform a tower switching action simultaneously, so that the ethylene tar is switched from the currently full coke tower 140 to another coke tower 140 that has completed preheating and is ready for feeding, so as to maintain the consistency of the reaction time and blending ratio of the ethylene tar components and the conventional raw material components in each coke tower 140.

[0055] This synchronous switching strategy significantly improves the overall quality uniformity and production continuity of raw coke products: it completely solves the problem of "layered structure heterogeneity" caused by component imbalance during tower switching, ensuring that each batch of coke has a highly uniform component ratio and microstructure from the bottom sweep coke to the top coke; from a materials science perspective, this component constancy directly locks the graphitization level and pore distribution characteristics of the anode material precursor, greatly reducing the performance index deviation between different production batches, and providing key process guarantees for the large-scale and standardized production of high-quality anode materials.

[0056] Preferably, the method further includes step S6, in which the reaction products at the top of the coke tower 140 are introduced into the fractionation tower 150 for staged cooling and component cutting. Using the physical components and temperature gradient control inside the fractionation tower 150, the rich gas, diesel oil, light wax oil and heavy wax oil at the top of the tower are extracted sequentially from top to bottom.

[0057] This design employs a "multi-stage phase equilibrium stepped separation" technology. The high-temperature cracked gas escaping from the top of the coke tower 140 enters the fractionation tower 150. Utilizing multi-stage mass transfer components (such as high-efficiency trays and structured packing) and precisely proportioned cold reflux, a continuously distributed temperature and concentration field is constructed along the tower's height. By precisely adjusting the tower top pressure and the temperatures of each side stream, the kinetic diameter and boiling point gradient of the complex carbon chain components are cut: light components are enriched and separated in the top reflux, while the condensate of heavy components is collected from top to bottom through oil collection tanks at different locations. This precisely separates the originally continuously distributed cracking products into a gas phase, light fractions, and heavy fractions.

[0058] This invention also provides a system for preparing negative electrode coke feedstock from ethylene tar based on a delayed coking process, comprising: a heating furnace 130, a coke tower 140, and a fractionation tower 150, wherein the bottom of the heating furnace 130 is connected to the bottom of the coke tower 140, and the top of the coke tower 140 is connected to the bottom of the fractionation tower 150, wherein... The mixed feedstock of vacuum residue and catalytic slurry is first fed into the first feed buffer tank 100, then fed into the heater radiant buffer tank 110 after heat exchange through the heat exchanger 101, and finally transported to the top of the heater 130 by the pump 160. The first feed buffer tank 100 is used for this purpose. Ethylene tar is first fed into the second feed buffer tank 120, and then divided into the first path and the second path to be transported to the top of the coke tower 140 and the top of the heating furnace 130, respectively.

[0059] The top of the fractionation tower 150 is separated into gasoline, top gas, and sulfur-containing wastewater by the gas-liquid separator 151 and transported out separately. Diesel fuel is output from the upper and middle sections of the 150 fractionation tower; The lower and middle sections of the fractionation tower 150 output light wax oil; Heavy wax oil is output from the bottom of the 150 fractionation tower.

[0060] Specifically, for better illustration, the following is a detailed comparison between this embodiment and Comparative Example 1 and Comparative Example 2: The present invention was implemented on a delayed coking industrial unit with a capacity of 3.2 million tons / year. The unit is equipped with four coking towers 140 (towers A to D), which are switched every 28 hours. The conventional feedstock is a mixture of vacuum residue and catalytic oil slurry. In this industrial trial, one furnace and two towers were put into operation.

[0061] 1. This embodiment (1) Implementation steps A new ethylene tar pipeline is added along the first path, along with one ethylene tar buffer tank and two centrifugal pumps (160, outlet pressure 2.6 MPa), connected from the plant's ethylene tar storage tank to the buffer tank. After one hour of coking in coke tower 140A, ethylene tar is injected through feed nozzle 141 from the edge of the top of the spherical tower of coke tower 140. This position effectively prevents unreacted ethylene tar droplets from being carried into the fractionation system by the high-speed upward oil and gas, preventing coking on the oil and gas line and in fractionation tower 150. At the same time, feed nozzle 141 is angled downwards towards the tower wall of coke tower 140, ensuring that the ethylene tar enters the slow-flow zone of oil and gas in coke tower 140 after being sprayed out, and falls down the tower wall towards the coke bed. The sensible heat of the upward high-temperature oil and gas in the tower is used as the heat source for the reaction. The coke produced by condensation falls to the coke bed, while the oil and gas produced by cracking rise with the high-temperature oil and gas.

[0062] One hour after coking tower 140A entered the coking stage, the top pressure was controlled at 0.11 MPa (g), and the top temperature was monitored at 415℃. After 28 hours, the process was switched to coking tower 140B (which had just entered the coking stage one hour prior), and ethylene tar was injected under the same conditions. After coking tower 140A stopped feeding, it continued to complete the coking cycle and then decoke removal. This cyclical operation has been running continuously for 155 days without any abnormalities.

[0063] Adjust the first gas injection rate of the radiant branch of heater 1306 to 150-250 kg / h, and reduce the second gas injection rate to 150-250 kg / h. Open the process of ethylene tar to branch A1, control the injection of ethylene tar into branch A1, and then sequentially inject ethylene tar into branches A2, A3, A4, A5, and A6. Control the flow rate of ethylene tar in each branch and distribute it evenly to each branch of heater 130 according to the ethylene tar ratio.

[0064] (2) Effect Unit operation: The outlet temperature and pressure drop of the radiant section of the heater 130 remained stable. The wall temperature of each radiant branch pipe of the heater 130 did not rise significantly, and there was no abnormal temperature rise or pressure drop increase due to coking. The temperature of each section of the fractionation tower 150 was stable, with no signs of salt formation, coking, or tray blockage. The overall pressure drop of the fractionation tower 150 was normal, proving that ethylene tar did not cause entrainment or secondary coking.

[0065] Product Analysis: Samples of the generated mixed coke (containing conventional feedstock coke and ethylene tar coke) were analyzed. Pure processing feedstock ratio: coke sulfur content 1.04%, iron content 120 ug / g, nickel content 52 ug / g, vanadium content 38 ug / g; ethylene tar feedstock ratio: catalytic slurry 26 t / h, residue oil 76 t / h, ethylene tar 39 t / h, coke sulfur content reduced to 0.76%, iron content 60 ug / g, nickel content 41 ug / g, vanadium content 20 ug / g, coke improved from 3A coke to 2A coke. Utilizing ethylene tar to reduce impurity content (sulfur and metals), and catalytic slurry to improve the structure of the green coke, increases specific capacity, and extends cycle life, the produced coke meets the requirements for producing negative electrode carbon materials.

[0066] Economic efficiency: During operation, the overall energy consumption of the unit is reduced by about 2% due to the utilization of waste heat. The ethylene tar blending ratio of the unit reaches 32.17%, and the maximum blending capacity of ethylene tar is 47.20 t / h. Compared with selling ethylene tar as fuel oil, the efficiency is increased by 792 yuan per ton. No chemical additives are required, and no pretreatment of ethylene tar is required, resulting in low processing costs.

[0067] 2. Comparative Example 1 On the same equipment, an experiment was conducted to mix ethylene tar with conventional feedstock at a ratio of 10% in the feedstock tank, and add 850 ppm / t (relative to the total feed) of commercial asphaltene dispersant and stabilizer. After heat exchange in the feedstock heat exchange system, the mixture was heated in heater 130 and then entered coke tower 140. After 90 days of operation, the pressure drop of feedstock heat exchanger 101, where the heat source exceeds 250°C, began to increase, requiring the operation of a bypass line. After 360 days of operation, the final heat exchange temperature dropped by 70°C, causing an increase in the heat load of heater 130. Thermocouples on the surface of the radiant section furnace tubes of heater 130 showed an abnormal local temperature rise exceeding 650°C, and the pressure drop of the furnace tubes increased from 1.2 MPa to 1.5 MPa, an increase of approximately 25%, indicating that scaling had begun on the inner wall of the furnace tubes. To avoid risks, the equipment was shut down for maintenance, and coking and blockage of the feedstock side of heat exchanger 101, which had a temperature above 250°C, was found.

[0068] This comparison shows that the simple additive mixing method cannot effectively solve the fundamental problem of coking in furnace tubes and increases the cost of additives.

[0069] 3. Comparative Example 3 On the same equipment, an experiment was conducted to mix ethylene tar with conventional feedstock at a ratio of 5% in the feedstock tank. After heat exchange in the feedstock heat exchange system, the mixture was heated in heater 130 and then entered coke tower 140. After 172 days of operation, thermocouples on the surface of the radiant section furnace tubes in heater 130 showed an abnormal local temperature rise exceeding 650°C, with a pressure drop increase of approximately 25%, indicating coking on the inner wall of the furnace tubes. To avoid risks, the experiment was stopped. Upon disassembly and inspection of the equipment, it was found that the heat source temperature of feedstock heat exchanger 101 exceeded 150°C, indicating coking and blockage on the feedstock side.

[0070] This comparison shows that the simple mixing method cannot effectively solve the fundamental problem of coking in furnace tubes.

[0071] The technical means disclosed in this invention are not limited to those described above, but also include technical solutions composed of any combination of the above technical features. The above are specific embodiments of this invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

[0072] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0073] Furthermore, in this invention, the use of terms such as "first," "second," and "a" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. The terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly specified. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0074] The technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0075] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process, characterized in that, Includes the following steps: S1. Provide conventional feedstock and ethylene tar feedstock. The conventional feedstock includes vacuum residue and catalytic slurry and is introduced into the heater. The ethylene tar feedstock is divided into a first path and a second path. The first path bypasses the heater and is directly connected to the top of the coke tower. The second path is connected to the furnace tube feeding system of the heater. S2. The ethylene tar in the first path is injected from the top of the coke tower. The injection point is located in the slow-flowing gas phase area inside the coke tower and is arranged towards the tower wall. The liquid ethylene tar is used to exchange heat with the high-temperature oil and gas rising inside the coke tower, which induces the heavy components of ethylene tar to undergo a condensation reaction and cause them to settle downward along the tower wall. S3. The ethylene tar in the second path enters the furnace tube of the heating furnace through tangential injection and merges with the conventional raw materials flowing in the tube to form a vortex. The gum components in the conventional raw materials physically encapsulate the asphaltenes in the ethylene tar to inhibit the precipitation of asphaltenes and coking of the ethylene tar during the heating process in the furnace tube. S4. By adjusting the steam injection rate of different pipe sections inside the heating furnace, the high flow rate of the mixing material inside the furnace tube is maintained, so as to delay the deep polycondensation reaction window of conventional raw materials and second-path ethylene tar into the coke tower. S5. The condensation products falling from the wall of the coking tower and the mixed stream entering from the bottom of the coking tower converge in the tower. Driven by the sensible heat of oil and gas and the heat supply of furnace tubes, a multiphase synergistic reaction is carried out. After the coking cycle is completed, a fibrous coke structure with optical anisotropy is generated, which can be used as a raw material for lithium battery anode.

2. The method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process according to claim 1, characterized in that, In step S1, the proportion of ethylene tar feedstock is controlled to be no less than 20%, and the proportion of catalytic oil slurry feedstock is controlled to be no less than 15%.

3. The method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process according to claim 1, characterized in that, In step S2, the output end of the feed nozzle at the top of the coke tower is inclined toward the tower wall so that the injection point of ethylene tar is located at the edge of the spherical top of the coke tower and the horizontal distance from the gas phase outlet at the top of the tower is not less than 1 / 2 of the tower diameter.

4. The method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process according to claim 1, characterized in that, In step S2, low-temperature ethylene tar below 100°C is introduced via the first path as a conditioning cold source, replacing the conventional top quench oil injection into the top of the coke tower.

5. The method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process according to claim 1, characterized in that, In step S4, the heating furnace has a first gas injection point and a second gas injection point, wherein, The first gas injection point is located in the convection section of the furnace tube area of ​​the heating furnace, which is upstream of the injection port of the ethylene tar in the second path. The second gas injection point is located in the radiant section of the furnace tube area of ​​the heating furnace, downstream of the first gas injection point.

6. The method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process according to claim 5, characterized in that, In step S4, by adjusting the fluid flow rate at the first steam injection point, the linear velocity of the material flow in the convection section furnace tube area is controlled between 2.0 m / s and 3.5 m / s, and the outlet temperature of the convection section is maintained below 360°C, so as to suppress early coking after ethylene tar is mixed with conventional raw materials.

7. The method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process according to claim 5, characterized in that, In step S4, by adjusting the fluid flow rate at the second steam injection point, the flow velocity of the material in the radiant section furnace tube area is maintained between 3.0 m / s and 5.0 m / s. By utilizing the shear force generated by the high flow velocity and the residence time control, the occurrence point of the deep polycondensation reaction is guided into the coke tower.

8. The method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process according to claim 1, characterized in that, In step S5, the operating pressure at the top of the coke tower is controlled to be in a slightly positive pressure state, and the reaction temperature is controlled at 480-520℃.

9. The method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process according to claim 1, characterized in that, In step S5, when the coke tower is in the late stage of the coking cycle and a tower switching operation is performed, the ethylene tar in the first path and the conventional raw material flow at the outlet of the heating furnace are controlled to perform a tower switching action simultaneously, so that the ethylene tar is switched from the currently full coke tower to another coke tower that has completed preheating and is ready to be fed, so as to maintain the consistency of the reaction time and blending ratio of the ethylene tar components and the conventional raw material components in each coke tower.

10. A method for preparing negative electrode coke feedstock from ethylene tar based on delayed coking process according to claim 1, characterized in that, It also includes step S6, which introduces the reaction products at the top of the coke tower into the fractionation tower for staged cooling and component cutting. Using the physical components and temperature gradient control inside the fractionation tower, the rich gas, diesel, light wax oil and heavy wax oil at the top of the tower are extracted sequentially from top to bottom.

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