Continuous coking production system and process method for hydrogenated unconverted oil

Abstract

The invention belongs to the technical field of petrochemical engineering, and relates to a continuous coking production system and process method for hydrogenated unconverted oil, and the production system comprises a membrane filter, a raw material tank, a homogenizer, a tubular furnace, a coking machine, an oil cooler and a stock bin. According to the invention, the continuous production of the high-quality petroleum coke is realized by combining a synergistic process method of membrane filtration, modification, homogeneous emulsification and tubular furnace coking machine coupling with a graphite adding and hydraulic conveying technology without a noble metal catalyst. The sulfur content, the ash content and the volatile components of the petroleum coke prepared by the technological method all meet the industrial standards, the requirement of pre-culture low-emission anode coke of electrolytic aluminum can be met, and the cost is low.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology and relates to a continuous coking production system and process for hydrogenated unconverted oil. Background Technology

[0002] Petroleum coke is an important byproduct of crude oil refining and is widely used in steelmaking, aluminum smelting, and chemical industries. Petroleum coke is a solid carbonaceous residue formed during the high-temperature (typically 450–550℃) coking of crude oil or heavy residue oil, after thermal cracking and condensation reactions. Its main component is carbon (80–95%), with small amounts of sulfur, nitrogen, oxygen, heavy metals (such as vanadium and nickel), and ash. With increasingly stringent environmental regulations, the use of high-sulfur petroleum coke (sulfur content >3%) is severely restricted, leading to a significant increase in market demand for low-sulfur petroleum coke. High-quality petroleum coke is in high demand in electrolytic aluminum production, but its high price limits its overall use.

[0003] Traditional heavy oil coking processes primarily use oil slurry as raw material, which, after pretreatment, is directly fed into a tubular furnace for heating. Subsequently, cracking and condensation reactions occur in 2-4 coking towers, ultimately producing petroleum coke. While this process has been industrialized, it still suffers from the following problems: The heavy oil composition is complex; asphaltenes, gums, and solid impurities easily lead to coking in the tubular furnace, reducing heat transfer efficiency and requiring frequent shutdowns for cleaning, thus affecting continuous production. Product quality is low: petroleum coke obtained from direct coking has high sulfur content, a loose structure, and a small specific surface area, making it difficult to meet the requirements of high-value-added applications (such as electrode-grade coke). Traditional processes do not adequately upgrade heavy oil, resulting in poor selectivity in cracking reactions, low yields of light oil, and the high-temperature coking process easily generates harmful gases (such as SO₂). x NO x ).

[0004] To improve the quality of petroleum coke, Chinese patent CN113563921A discloses a method and system for producing low-sulfur petroleum coke, mainly through a combination of residue hydrotreating, catalytic cracking, and delayed coking processes. However, this method has the following drawbacks: the system is complex, involving multiple units of residue hydrotreating, catalytic cracking, and delayed coking, making operation difficult; it has high requirements for raw materials, requiring a sulfur content >3.0%; and it has high energy consumption, requiring a large amount of hydrogen (1.1%-1.5% feed rate) and high-pressure equipment for hydrodesulfurization. The overall process has poor economic efficiency and operational continuity, and limited adaptability to raw materials. Chinese patent CN115197748A discloses a method and system for producing both low-carbon olefins and low-sulfur coke. This system requires the coupling of multiple processes (hydrotreating + coking + cracking), making operation and maintenance difficult. It is only suitable for high-sulfur residue oil, has high hydrotreating pretreatment costs that are easily affected by raw material fluctuations, relies on high-pressure hydrotreating and large amounts of hydrogen, requires huge equipment investment, and necessitates precious metal catalysts. Increasing olefin yield requires sacrificing coking scale, making economic balance difficult. Multiple stages of pollutant emissions necessitate additional treatment facilities, and continuity needs to be improved.

[0005] Therefore, there is an urgent need to develop a continuous coking production system for high-quality petroleum coke that simplifies the process, has strong raw material adaptability, and is low-cost and low-energy-consumption, in order to overcome the limitations of existing technologies. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a continuous coking production system and process for hydrotreated unconverted oil. Through a synergistic process of membrane filtration-modification-homogenization emulsification-tubular coking machine coupling, combined with graphite addition and hydraulic conveying technology, high-quality petroleum coke can be produced continuously without the need for precious metal catalysts.

[0007] The technical solution adopted by this invention to solve the technical problem is: This invention provides a continuous coking production system for hydrotreated unconverted oil, comprising a membrane filter, a feed tank, a homogenizer, a tubular furnace, a coking machine, an oil cooler, and a silo. The membrane filter has a hydrotreated unconverted oil inlet, a filtered oil slurry outlet, and a filtered product outlet. The filtered oil slurry outlet pipeline passes sequentially through a feed preheater and a modifier and connects to the inlet of the feed tank. The homogenizer has a water inlet, a graphite inlet, a feed inlet, and a polyacrylamide inlet. The outlet of the feed tank is connected to the feed inlet of the homogenizer via a pipeline. The outlet pipeline of the homogenizer is connected to the inlet of the tubular furnace. The outlet of the tubular furnace is connected to the inlet of the coking machine via a pipeline. The outlet of the coking machine is connected to the inlet of the oil cooler via a pipeline. The outlet of the oil cooler is connected to the silo via a pipeline.

[0008] Furthermore, the water inlet pipeline of the homogenizer is connected to the outlet of the water tank via a first flow meter and a water pump.

[0009] Furthermore, a raw material pump and a second flow meter are installed sequentially on the outlet pipeline of the raw material tank.

[0010] Furthermore, the membrane filter is a sintered inorganic membrane filter. The pore size of the inorganic membrane ranges from 80 to 110 nm.

[0011] Furthermore, the coking machine is a plow-type coking machine, which has a rotating plow assembly inside, with 4-36 plow blades.

[0012] Furthermore, the oil cooler is a rake-type vacuum external tracing pipe cooler, and the refrigerant is heat transfer oil.

[0013] Another aspect of the present invention provides a process method for a continuous coking production system, comprising the following steps: (1) After the unconverted hydrogenated oil passes through the membrane filter, the filter slurry and the filtered oil slurry are obtained. The filtered oil slurry enters the raw material preheater and is heated to 340-360℃. It then enters the modifier and enters the raw material tank after modification. The modified raw material is pumped into the homogenizer by the raw material pump. During the homogenization process, graphite and polyacrylamide emulsifier are added. The graphite accounts for 0.03-0.05% of the oil slurry mass, and the polyacrylamide emulsifier accounts for 0.1-0.5% of the oil slurry mass. At the same time, 0.5-1% of the oil slurry mass of water is pumped in (the role of water is to increase the flow rate, prevent the oil slurry from coking in the tubular furnace, and further remove nitrogen oxides). The homogenization is carried out at 400-450℃ for 3-5 hours, the homogenization pressure is 0.1-0.6MPa, and the homogenizer speed is 3000rpm±50rpm. (2) The homogenized slurry enters the tubular furnace, is heated to 450-480℃, stays for 20-40 seconds, and then enters the coking machine. The coking machine temperature is 470-490℃ and the pressure is 0.1-0.6MPa. (3) After the oil slurry stays in the coking machine for 8-10 hours, it enters the oil cooler after coking to cool down to 140-160℃. After cooling, the petroleum coke particles enter the silo and are finally packaged.

[0014] Furthermore, the unconverted hydrogenated oil contains 62-70 wt% aromatics and 8-12 wt% saturated hydrocarbons.

[0015] Furthermore, the operating temperature of the membrane filtration is 280-300℃, preferably 290℃. The transmembrane pressure difference of the membrane filtration is 0.4-0.6MPa. The feed flow rate of the membrane filtration is 2-5 m / s; appropriate feed can prevent membrane fouling.

[0016] Furthermore, the operating temperature range of the oil cooler is 80-200℃.

[0017] Furthermore, the coking machine is heated with molten salt at 450-550℃.

[0018] The innovative aspects of this invention are as follows: (1) A modular pretreatment unit is formed by combining a membrane filter with a modifier. The membrane filter efficiently removes impurities such as gum and asphaltenes, while the modifier reduces the viscosity of the raw materials through gentle pyrolysis. The two work synergistically to significantly improve the efficiency of subsequent coking. Conductive graphite and polyacrylamide emulsifier are added to the homogenizer at the same time. Graphite can increase condensation nuclei and regulate the microstructure of coke, while the emulsifier prevents asphaltenes from agglomerating through charge stabilization. Quantitative water injection by a water pump not only improves the fluidity of the system (reducing the risk of coking in the tubular furnace) but also serves as a heat carrier to improve heat transfer efficiency.

[0019] (2) Tubular furnace-coking machine coupled reactor: The tubular furnace and the plow-type coking machine are continuously coupled to achieve constant temperature coking of materials for 8-10 hours, avoiding the energy consumption of switching in traditional coking towers.

[0020] (3) Molten salt heating system: The coking machine uses molten salt as the heating medium, which is more precise in temperature control and reduces energy consumption than steam heating.

[0021] The advantages and positive effects of this invention are: (1) The continuous coking production system of the present invention achieves continuous production of high-quality petroleum coke by using a synergistic process method of membrane filtration-modification-homogenization emulsification-tube furnace coking machine coupling, combined with graphite addition and hydraulic conveying technology, without the need for precious metal catalysts.

[0022] (2) The petroleum coke prepared by the process of the present invention has a low sulfur content (S≤2wt%), which can meet the requirements of pre-baked low-emission anode coke for electrolytic aluminum and has a low cost. Attached Figure Description

[0023] Figure 1 This is a flow chart of the continuous coking production system process of the present invention. Detailed Implementation

[0024] As a specific embodiment of the present invention, the present invention provides a continuous coking production system for hydrotreated unconverted oil, including a membrane filter, a feed tank, a homogenizer, a tubular furnace, a coking machine, an oil cooler, and a silo. The membrane filter has a hydrotreated unconverted oil inlet, a filtered oil slurry outlet, and a filtered material outlet. The filtered oil slurry outlet pipeline passes sequentially through a feed preheater and a modifier and connects to the inlet of the feed tank. The homogenizer has a water inlet, a graphite addition port, a feed inlet, and a polyacrylamide addition port. The outlet of the feed tank is connected to the feed inlet of the homogenizer via a pipeline. The outlet of the homogenizer is connected to the inlet of the tubular furnace via a pipeline. The outlet of the tubular furnace is connected to the inlet of the coking machine via a pipeline. The outlet of the coking machine is connected to the inlet of the oil cooler via a pipeline. The outlet of the oil cooler is connected to the silo via a pipeline.

[0025] Specifically, the water inlet pipeline of the homogenizer is connected to the outlet of the water tank via a first flow meter and a water pump.

[0026] Specifically, a raw material pump and a second flow meter are installed sequentially on the outlet pipeline of the raw material tank.

[0027] Specifically, the membrane filter is a sintered inorganic membrane filter. The pore size of the inorganic membrane ranges from 80 to 110 nm.

[0028] Specifically, the coking machine is a plow-type coking machine, which has a rotating plow assembly inside, with 4-36 plow blades.

[0029] Specifically, the oil cooler is a rake-type vacuum external tracing pipe cooler, and the refrigerant is heat transfer oil.

[0030] As another specific embodiment of the present invention, the present invention provides a process method for a continuous coking production system, the steps of which are as follows: (1) After the unconverted hydrogenated oil passes through the membrane filter, the crude slurry and the filtered slurry are obtained. The filtered slurry enters the raw material preheater and is heated to 340-360℃. It then enters the modifier and enters the raw material tank after modification. The modified raw material is pumped into the homogenizer by the raw material pump. During the homogenization process, graphite and polyacrylamide emulsifier are added. Graphite accounts for 0.03-0.05% of the slurry mass, and polyacrylamide emulsifier accounts for 0.1-0.5% of the slurry mass. (The role of graphite is to increase the polycondensation nuclei, and the role of polyacrylamide emulsifier is to emulsify the slurry with water.) At the same time, 0.5-1% of water by mass of the slurry is pumped in (the role of water is to increase the flow rate and prevent the slurry from coking in the tubular furnace). The homogenization is carried out at 400-450℃ for 3-5 hours, the homogenization pressure is 0.1-0.6MPa, and the homogenizer speed is 3000rpm±50rpm. (2) The homogenized slurry enters the tubular furnace, is heated to 450-480℃, stays for 20-40 seconds, and then enters the coking machine. The coking machine temperature is 470-490℃ and the pressure is 0.2-0.6MPa. (3) After the oil slurry stays in the coking machine for 8-10 hours, it enters the oil cooler after coking to cool down to 140-160℃. After cooling, the petroleum coke particles enter the silo and are finally packaged.

[0031] Specifically, the unconverted hydrotreated oil contains 62-70 wt% aromatics and 8-12 wt% saturated hydrocarbons.

[0032] Specifically, the operating temperature of the membrane filtration is 280-300℃, preferably 290℃. The transmembrane pressure difference of the membrane filtration is 0.4-0.6 MPa. The feed flow rate of the membrane filtration is 2-5 m / s; appropriate feed can prevent membrane fouling.

[0033] Specifically, the operating temperature range of the oil cooler is 80-200℃.

[0034] Specifically, the coking machine is heated with molten salt at 450-550℃.

[0035] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0036] Example 1 A continuous coking production system for hydrotreated unconverted oil includes a membrane filter, a feed tank, a homogenizer, a tubular furnace, a coking machine, an oil cooler, and a silo. The membrane filter is a sintered inorganic membrane filter with a pore size of 100 nm.

[0037] Membrane filters efficiently remove ≥0.1μm gum / asphalt particles from hydrotreated unconverted oil, providing high-quality feedstock for subsequent coking. The membrane filter has a hydrotreated unconverted oil inlet, a filtered slurry outlet, and a filter discharge outlet. The filtered slurry outlet is connected to the feedstock tank inlet via pipelines through a feedstock preheater and a modifier. The feedstock tank serves as a buffer container to store the filtered slurry, ensuring continuous feed and stable system pressure balance. The feedstock tank outlet is connected to the homogenizer feedstock inlet via a pipeline, and a feedstock pump and a second flow meter are installed sequentially on the feedstock tank outlet pipeline.

[0038] The homogenizer homogenizes the oil slurry components and regulates the electrical conductivity of the coke through high-shear dispersion. The homogenizer has a water inlet, a graphite inlet, a raw material inlet, and a polyacrylamide inlet. The water inlet pipeline of the homogenizer passes through a first flow meter and a water pump in sequence and connects to the outlet of the water tank.

[0039] The homogenizer outlet is connected to the inlet of the tubular furnace via pipeline. The tubular furnace rapidly heats the homogenized oil slurry, providing the activation energy required for coking. The outlet pipeline of the tubular furnace enters the inlet of the coking machine, and the outlet of the coking machine is connected to the inlet of the oil cooler via pipeline. The outlet of the oil cooler is connected to the silo via pipeline. The coking machine is a plow-type coking machine, equipped with a rotating plow assembly with 12 blades. The plow blades agitate the oil slurry to achieve continuous coking, producing dense coke. The oil cooler is a rake-type vacuum external pipe cooler, using heat transfer oil as the refrigerant. The heat transfer oil is used to gradient cool the coke, preventing thermal stress cracking and recovering waste heat.

[0040] The heat recovered by the oil cooler can be used for preheating of the raw material preheater, forming a heat recycling system.

[0041] Example 2 Table 1. Composition and content of unconverted hydrotreated oil

[0042] A process method for the continuous coking production system of Example 1 includes the following steps: (1) Hydrogenated unconverted oil (composition as shown in Table 1) was filtered through a sintered inorganic membrane filter to obtain slurry and coarse slurry (the coarse slurry was dried to recover precious metals). The filtration temperature was 290℃ and the transmembrane pressure difference was 0.6MPa. The slurry after membrane filtration was fed into the raw material preheater at a feed flow rate of 5m / s and heated to 350℃. It then entered the modifier and, after modification, entered the raw material tank. The modified raw material was pumped into the homogenizer by the raw material pump. During the homogenization process, graphite and polyacrylamide emulsifier were added. Graphite accounted for 0.05% of the slurry mass, and polyacrylamide emulsifier accounted for 0.5% of the slurry mass. At the same time, 0.5% of the slurry mass of water was pumped in. The homogenization was carried out at 450℃ for 4 hours, the homogenization pressure was 0.6MPa, and the homogenizer speed was 3000rpm. (2) The homogenized slurry enters the tubular furnace, is heated to 460°C, stays for 30 seconds, and then enters the coking machine. The coking machine temperature is 480°C and the pressure is 0.5MPa. (3) After the oil slurry stays in the coking machine for 9 hours, the coking machine is heated with molten salt at 500°C. After coking, it enters the oil cooler to cool down to 150°C. After cooling, petroleum coke particles are obtained, which enter the silo and are finally packaged.

[0043] Example 3 A process method for the continuous coking production system of Example 1 includes the following steps: (1) Hydrogenated unconverted oil (composition as shown in Table 1) was filtered through a sintered inorganic membrane filter to obtain slurry and coarse slurry. The filtration temperature was 290℃ and the transmembrane pressure difference was 0.4MPa. The slurry after membrane filtration was fed into the raw material preheater at a feed flow rate of 3m / s and heated to 350℃. It was then fed into the modifier and then into the raw material tank. The modified raw material was pumped into the homogenizer by the raw material pump. During the homogenization process, graphite and polyacrylamide emulsifier were added. Graphite accounted for 0.05% of the slurry mass and polyacrylamide emulsifier accounted for 0.1-0.5%. At the same time, 1% of the slurry mass of water was pumped in (the role of water is to increase the flow rate and prevent the slurry from coking in the tubular furnace). The homogenization was carried out at 430℃ for 5 hours. The homogenization pressure was 0.5MPa and the homogenizer speed was 3000rpm. (2) The homogenized slurry enters the tubular furnace, is heated to 450°C, stays for 40 seconds, and then enters the coking machine. The coking machine temperature is 470°C and the pressure is 0.6MPa. (3) After the oil slurry stays in the coking machine for 8 hours, the coking machine is heated with molten salt at 500°C. After coking, it enters the oil cooler to cool down to 140°C. After cooling, petroleum coke particles are obtained, which enter the silo and are finally packaged.

[0044] Comparative Example 1 The only difference from Example 2 is that graphite is replaced with micron-sized similar raw coke.

[0045] Comparative Example 2 The only difference from Example 2 is that no polyacrylamide emulsifier is added.

[0046] Comparative Example 3 The only difference from Example 2 is that the homogenization temperature is 460°C.

[0047] Comparative Example 4 The only difference from Example 2 is that the homogenization temperature is 390°C.

[0048] The petroleum coke prepared in Examples 2-3 and Comparative Examples 1-4 was subjected to component analysis. The quality indicators were in accordance with industry standard YBYJJ-1, with sulfur content ≤2wt%, volatile matter content ≤10wt%, ash content ≤0.3wt%, fixed carbon content ≥85wt%, and shot coke content 0.

[0049] Table 2 Component content and properties of petroleum coke products

[0050] In Comparative Example 1, when graphite was replaced with raw coke, the sulfur content increased significantly, exceeding the industry standard (≤2wt%). The ash and volatile matter content were inferior to those of the Example. Meanwhile, 0.8wt% of pellet coke appeared, indicating that the addition of conductive graphite can effectively reduce the sulfur content. The condensation nucleation effect of graphite can optimize the coke structure and reduce impurities. Raw coke cannot control microscopic homogeneity like graphite.

[0051] In Comparative Example 2, the lack of emulsifier led to a further increase in sulfur content, ash content, and volatile matter, with 0.6 wt% of pellet coke appearing. This demonstrates that the charge-stabilizing effect of polyacrylamide helps inhibit asphaltene agglomeration (reducing sulfide encapsulation). The lack of emulsifier resulted in uneven dispersion of impurities and an increase in side reactions during pyrolysis.

[0052] Comparative Example 3, with a homogenization temperature of 460℃, had the worst sulfur content (2.82wt%) and pellet coke (1wt%). This was due to excessively high temperature, which led to excessive cracking and the production of unstable intermediate products.

[0053] Comparative Example 4, with a homogenization temperature of 390℃, had a lower volatile matter content (3.9wt%) but a higher sulfur content (2.93wt%), indicating that insufficient temperature resulted in inadequate modification and reduced desulfurization efficiency of the gum.

[0054] Furthermore, the carbon content of all comparative examples was lower than that of the examples, highlighting the advantage of the process in improving carbon purity in the examples.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A continuous coking production system for hydrotreated unconverted oil, characterized in that, The system includes a membrane filter, a feed tank, a homogenizer, a tubular furnace, a coking machine, an oil cooler, and a silo. The membrane filter has an unconverted hydrotreated oil inlet, a filtered oil slurry outlet, and a filtered product outlet. The filtered oil slurry outlet pipeline passes sequentially through a feed preheater and a modifier before connecting to the inlet of the feed tank. The homogenizer has a water inlet, a graphite inlet, a feed inlet, and a polyacrylamide inlet. The outlet of the feed tank is connected to the feed inlet of the homogenizer via a pipeline. The outlet pipeline of the homogenizer is connected to the inlet of the tubular furnace. The outlet of the tubular furnace is connected to the inlet of the coking machine via a pipeline. The outlet of the coking machine is connected to the inlet of the oil cooler via a pipeline. The outlet of the oil cooler is connected to the silo via a pipeline.

2. The continuous coking production system according to claim 1, characterized in that, The water inlet pipeline of the homogenizer passes through the first flow meter and the water pump in sequence and is connected to the outlet of the water tank.

3. The continuous coking production system according to claim 1, characterized in that, A raw material pump and a second flow meter are installed sequentially on the outlet pipeline of the raw material tank.

4. The continuous coking production system according to claim 1, characterized in that, The membrane filter is a sintered inorganic membrane filter, and the pore size of the inorganic membrane is in the range of 80-110 nm.

5. The continuous coking production system according to claim 1, characterized in that, The coking machine is a plow-type coking machine.

6. The continuous coking production system according to claim 1, characterized in that, The oil cooler is a rake-type vacuum external pipe cooler, and the refrigerant is heat transfer oil.

7. A process method for a continuous coking production system according to any one of claims 1 to 6, characterized in that, The steps are as follows: (1) After the unconverted hydrogenated oil passes through the membrane filter, the filter slurry and the filtered oil slurry are obtained. The filtered oil slurry enters the raw material preheater and is heated to 340-360℃. It then enters the modifier and enters the raw material tank after modification. The modified raw material is pumped into the homogenizer by the raw material pump. During the homogenization process, graphite and polyacrylamide emulsifier are added. The graphite accounts for 0.03-0.05% of the oil slurry mass, and the polyacrylamide emulsifier accounts for 0.1-0.5% of the oil slurry mass. At the same time, 0.5-1% of the oil slurry mass of water is pumped in. The homogenization is carried out at 400-450℃ for 3-5 hours and the homogenization pressure is 0.1-0.6MPa. (2) The homogenized slurry enters the tubular furnace, is heated to 450-480℃, stays for 20-40 seconds, and then enters the coking machine. The coking machine temperature is 470-490℃ and the pressure is 0.1-0.6MPa. (3) After the oil slurry stays in the coking machine for 8-10 hours, it enters the oil cooler after coking to cool down to 140-160℃. After cooling, the petroleum coke particles enter the silo and are finally packaged.

8. The process method according to claim 7, characterized in that, The unconverted hydrotreated oil contains 62-70 wt% aromatics and 8-12 wt% saturated hydrocarbons.

9. The process method according to claim 7, characterized in that, The membrane filtration operates at a temperature of 280-300℃, has a transmembrane pressure difference of 0.4-0.6MPa, and a feed flow rate of 2-5m / s.

10. The process method according to claim 7, characterized in that, The operating temperature range of the oil cooler is 80-200℃.

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