Low-mesophase long-period continuous production process for electrode bonding asphalt

Abstract

The invention relates to the technical field of coal chemical industry and carbon material preparation, and discloses a low-mesophase long-period continuous production process of electrode-bonded pitch, which comprises the following steps: melting 100 parts by mass of medium-temperature coal pitch, and stripping solid-phase primary quinoline insoluble substances through a porous filtration system to obtain refined pitch; the refined asphalt enters an asphalt reactor, is pressurized by a reaction circulating pump, is mixed with the in-situ self-generated hydrogen supply flash oil fraction at a high-pressure pipe section, and is pumped into a tubular heating furnace; part of discharged fluid flows back, the rest fluid is injected into a negative-pressure asphalt gas stripping flash tower, and in-situ self-generated hydrogen supply flash oil fraction is condensed and intercepted at the top of the tower for circulation; the heavy-component asphalt in the tower kettle flows through negative-pressure series multi-stage blending kettles, high-temperature coal pitch is supplemented into the first kettle, and electrode bonding asphalt is obtained after cooling. According to the technical scheme, the hydrogen supply flash oil fraction is forcibly boosted and then injected into the high-pressure pipe section of the outlet of the reaction circulating pump, so that the technical effects of inhibiting generation of the anisotropic intermediate phase and maintaining stable conveying of the fluid are achieved.

Description

A process for long-cycle continuous production of electrode-bonded asphalt with low mesophase Technical Field

[0001] This invention relates to the field of coal chemical engineering and carbon material preparation technology, specifically a process for long-cycle continuous production of electrode bonding asphalt with low mesophase. Background Technology

[0002] High-power electric arc furnaces are widely used in the iron and steel smelting and aluminum electrolysis industries. The conductive core of the electric arc furnace is the graphite electrode. Manufacturing high-quality graphite electrodes relies on electrode bonding bitumen. The main function of the bonding bitumen is to tightly bind carbon aggregates such as petroleum coke together. After high-temperature calcination, it forms a dense carbon network structure between the aggregates, thereby giving the graphite electrode extremely high mechanical strength and excellent electrical conductivity.

[0003] Currently, industrial production primarily employs conventional thermopolymerization processes to prepare these types of asphalt materials. In production, light wash oil or anthracene oil is typically purchased externally and mixed into the raw materials as a hydrogen-donating solvent. The core reaction is mainly completed in a single-stage large stirred tank, after which the material flows through a tubular heat exchanger for water or air cooling. This process has a relatively short overall flow, and the initial investment in equipment and pipeline construction is relatively low. Directly purchasing readily available industrial solvents allows for rapid production startup. The control logic of the single-tank reaction is intuitive, making it relatively easy for frontline workers to operate the equipment for heating and cooling.

[0004] This process revealed serious operational bottlenecks during continuous long-term operation. The added hydrogen-supplying solvent is a low-boiling-point light component. When mixed into the high-temperature asphalt system at atmospheric pressure or before the feed pump, the fluid encounters extremely low local pressure when it reaches the impeller inlet of the high-temperature circulating pump. The light component undergoes violent vaporization instantaneously at this point. The accumulation of a large number of bubbles directly leads to cavitation cavitation in the pump. Simultaneously, the impeller is damaged, and the pipeline flow rate drops precipitously. Once the asphalt flow rate in the heating furnace tube slows down, the material is heated for a longer time, and the asphalt molecules are prone to excessive cross-linking, generating anisotropic mesophases, ultimately causing coking and shutdown of the furnace tubes. The cooling process after the material exits the furnace also presents problems. Asphalt itself is extremely viscous, and there is severe heat transfer lag when relying on external heat exchangers for cooling. The temperature of the material close to the tube wall drops, but the heat of the central fluid cannot dissipate. The high-temperature condensation reaction inside cannot be stopped at all, and the heavy components at the bottom of the equipment are prone to secondary coking. In addition, during the later removal of the remaining light components, the direct and intense heating of the single-stage reactor causes the residual small molecules to overflow rapidly. Violent boiling is highly likely to occur inside the reactor. Without the buffer of a temperature gradient, some macromolecules are heated too rapidly and directly undergo deep cross-linking and solidification, resulting in a highly unstable fixed carbon yield in the final product. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a process for long-cycle continuous production of electrode-bonded asphalt with low mesophase, solving the problems in existing continuous production processes for electrode-bonded asphalt where light hydrogen-supplying solvents easily cause cavitation cavitation in high-temperature circulating pumps, and where delayed material cooling leads to excessive cross-linking of asphalt macromolecules to form mesophase, ultimately resulting in secondary coking in pipelines and frequent system shutdowns.

[0006] To achieve the above objectives, the present invention provides a process for long-term continuous production of electrode bonding asphalt with low mesophase, comprising the following steps: 100 parts by mass of medium-temperature coal tar pitch is heated and melted, then pressurized and fed into a porous filtration system to remove solid-phase native quinoline insolubles, yielding refined asphalt; the refined asphalt is continuously fed into an asphalt reactor, extracted and pressurized by a reaction circulation pump; the in-situ self-generated hydrogen flash distillate fraction obtained in subsequent steps is pressurized and injected into the reaction circulation pump. The high-pressure section at the outlet is mixed with the mainstream material and then injected into a tubular heater for heating. The high-temperature fluid at the outlet of the tubular heater is diverted, with part of it circulating back to the asphalt reactor and the remainder being depressurized and injected into the asphalt stripping flash tower under negative pressure. The mixed oil and gas discharged from the top of the flash tower is condensed and retained to obtain the in-situ self-generated hydrogen flash oil fraction, which is then used as reflux for the previous cycle step. The heavy component asphalt extracted from the flash tower bottom is continuously and sequentially passed by gravity through a series of multi-stage blending kettles under negative pressure. High-temperature coal tar pitch is continuously added to the first blending kettle. The material is finally output after cooling to obtain electrode-bonded asphalt.

[0007] By adopting the above technical solution, the present invention combines fluid mechanics and reaction kinetics conditions in a continuous process flow, thereby achieving the effects of suppressing the formation of intermediate phases and extending the equipment operating cycle.

[0008] In this process, the solid-phase native quinoline insolubles entrained in the medium-temperature coal tar pitch will act as crystal nuclei in the subsequent high-temperature polycondensation reaction, easily inducing the attachment and growth of mesophase microspheres. Therefore, this scheme utilizes a porous filtration system at the front end of the reaction to physically remove these insoluble substances, eliminating heterogeneous nucleation centers at the source.

[0009] After initial purification, the core control aspect of this invention is how to avoid cavitation during high-temperature pump delivery and inhibit excessive cross-linking of macromolecules. In conventional processes, if a light hydrogen-donating solvent is added directly before the pump, the solvent is prone to instantaneous vaporization in the low-pressure zone at the pump impeller inlet under high-temperature conditions, leading to cavitation cavitation and abnormal flow. This process selects to set the injection point of the hydrogen-donating flash oil fraction within the high-pressure section at the outlet of the reaction circulation pump. Since this is the highest pressure zone of the system, the light fraction is forced to remain in a liquid phase, eliminating the risk of cavitation cavitation. The mixed material enters the tubular heater and undergoes a thermal condensation reaction. Under thermal stress, the aromatic side chains of the asphalt break and generate aromatic free radicals. At this time, the partially hydrogenated aromatic molecules abundant in the in-situ self-generated hydrogen-donating flash oil fraction act as hydrogen donors. The specific hydrogen transfer reaction formulas are as follows: R· + DH2 → RH + DH·; R· + DH· → RH + D; where R· is the asphalt macromolecular free radical, DH2 is the hydrogen donor molecule, and D is the dehydrogenated aromatic molecule.

[0010] The hydrogen donor transfers active hydrogen atoms to the macromolecular free radicals, saturating and capping them, thus blocking the free radical chain polymerization and cross-linking between free radicals. This restricts the reaction to the homogeneous condensation stage that generates soluble resin molecules, avoiding the formation of anisotropic intermediate phases.

[0011] The material heated by the tubular furnace carries a large amount of heat energy, which can easily lead to secondary coking if not handled promptly. The high-temperature fluid from the tubular furnace outlet is injected under reduced pressure into a flash distillation tower under negative pressure. Unreacted light oil fractions and dehydrogenated aromatic solvents after hydrogen atom transfer in the fluid vaporize under negative pressure. The vaporization process absorbs the latent heat of phase change, causing a sharp drop in the temperature of the heavy asphalt liquid phase remaining in the tower bottom. This in-situ quenching effect rapidly freezes the polymerization reaction, preventing coking of the material during its residence at the bottom of the tower. Simultaneously, the oil and gas discharged from the top of the tower condenses at a specific temperature in the fractionator, effectively trapping the polycyclic aromatic hydrocarbon intermediate fractions with hydrogen-donating activity, forming a closed-loop solvent circulation within the system.

[0012] Finally, the unreacted and lightly-removed heavy component pitch from the bottom of the flash distillation tower enters a multi-stage blending reactor connected in series. Under a negative pressure environment with progressively increasing temperature, the remaining low-boiling-point small molecules in the system are continuously extracted. According to the principle of chemical equilibrium shift, the removal of small molecule products drives the continued aromatic condensation reaction. During this process, the high-temperature coal tar pitch added is rich in heavy polycyclic aromatic hydrocarbons, which undergo solvation and miscibility with the refined materials, adjusting the rheological properties and coking value of the products.

[0013] Preferably, the medium-temperature coal tar pitch is heated to 160℃-190℃ to melt it; the pressure is increased to 0.4MPa-0.6MPa by a pump and sent into a porous filtration system; the porous filtration system is a sintered porous metal-ceramic filtration system with an absolute pore size of 5μm to 15μm, and the filtration pressure drop is controlled at 0.05MPa-0.15MPa.

[0014] By adopting the above technical solution, the aforementioned temperature range enables medium-temperature coal tar pitch to possess suitable dynamic viscosity, balancing fluid transport performance and filtration resistance. The micron-level solid pore size interception, combined with a specific filtration pressure drop range, prevents deep bridging and blockage of solid particles within the micropores while ensuring continuous liquid permeability, thus guaranteeing the stable operation of the filtration system.

[0015] Preferably, the refined asphalt is pressurized to 0.8MPa-1.5MPa by a reaction circulation pump; the injection rate of the in-situ self-generated hydrogen flash distillate is 3.0-10.0 parts by mass, which is pressurized to 1.0MPa-1.8MPa by a shielded pump and then injected into the high-pressure pipe section; the mixture is pumped into the radiant section of the tubular heater at a film flow rate of 2.0m / s-3.5m / s, and the bulk phase temperature of the material at the outlet of the tubular heater is controlled to be 380℃ to 395℃.

[0016] By employing the above technical solution, the flash oil injection pressure is set higher than the main pipeline fluid pressure to overcome system back pressure and achieve forced injection. A film velocity of 2.0 m / s–3.5 m / s keeps the fluid inside the pipe in a turbulent state, which thins the heat transfer boundary layer near the wall and reduces dead zone coking caused by local overheating. The bulk temperature range provides suitable thermodynamic conditions for the generation of free radicals and hydrogen transfer reactions.

[0017] Preferably, the high-temperature fluid from the tubular heater outlet is circulated back to the asphalt reactor at a volume ratio of 60% to 80%, and the remaining 20% ​​to 40% of the fluid is continuously injected into the asphalt stripping flash tower via a tangential injection distributor. The operating gauge pressure inside the flash tower is controlled at -0.06 MPa to -0.08 MPa, and the tower bottom operating temperature is reduced to 375℃-385℃. The mixed oil and gas discharged from the top of the flash tower enters the flash tower separator, and the vapor phase temperature at the condenser outlet of the separator is controlled at 310℃-330℃ to retain and obtain the in-situ self-generated hydrogen flash oil fraction.

[0018] By adopting the above technical solution, the control of the split ratio maintains the mass and heat balance within the heating system, while the tangential entry method accelerates the renewal rate of the gas-liquid separation interface. Furthermore, negative pressure flash evaporation combined with a condensation outlet gas phase temperature of 310℃-330℃ can retain fractions with moderate boiling points and rich in partially saturated aromatic structures as hydrogen-donating solvents, eliminating interference from excessively light or excessively heavy coking components on the circulation system.

[0019] Preferably, the multi-stage blending reactor in series includes a primary blending reactor, a secondary blending reactor, and a tertiary blending reactor connected in series. The operating gauge pressure of each blending reactor is maintained between -0.085 MPa and -0.095 MPa. The operating temperature of the primary blending reactor is 390℃-405℃, the operating temperature of the secondary blending reactor is 398℃-415℃, and the operating temperature of the tertiary blending reactor is 406℃-425℃.

[0020] By employing the above technical solution, the constructed progressively increasing temperature field and negative pressure environment allow the material to undergo stepwise heat treatment during gravity flow, avoiding material boiling and localized cross-linking caused by rapid heating in a single reactor. Simultaneously, the stepwise heating matches the higher activation energy required for the increase of asphalt molecular weight, contributing to the stable growth of the molecular structure.

[0021] Preferably, 5-15 parts by weight of high-temperature coal tar pitch are continuously added to the primary blending vessel using a metering pump; each blending vessel is equipped with a wall-scraping agitator with a stirring speed of 15-45 rpm; the average residence time of the material in a single blending vessel is controlled to be 40-90 minutes; the material at the bottom of the tertiary blending vessel is cooled to 280-300℃ by a heat exchanger before being output.

[0022] By adopting the above technical solution, high-temperature coal tar pitch is pre-mixed into the primary blending reactor, utilizing its heavy aromatic hydrocarbon skeleton as a plasticizer to improve the compatibility between macromolecules. The configured wall-scraping agitator is used to strip the boundary layer fluid from the inner wall surface, preventing excessive local residence time of materials and thus preventing coking and adhesion to the wall.

[0023] Preferably, the physicochemical properties of medium-temperature coal tar pitch are: softening point 80℃-90℃, toluene insoluble content 15wt%-25wt%, quinoline insoluble content 5wt%-10wt%, and coking value 45wt%-50wt%.

[0024] By adopting the above technical solution, the key physicochemical indicators of the basic raw materials are limited, ensuring that the materials entering the system have a relatively uniform initial polycyclic aromatic hydrocarbon molecular weight distribution, which provides a basis for the stability of process operating parameters.

[0025] Preferably, the physicochemical properties of high-temperature coal tar pitch are: softening point 110℃-120℃, toluene insoluble content 28wt%-34wt%, quinoline insoluble content 8wt%-14wt%, and coking value 55wt%-65wt%.

[0026] By adopting the above technical solution and introducing high-temperature coal tar pitch with high softening point and coking value as a modifier, the fixed carbon yield of electrode bonding pitch products can be improved to meet the performance requirements of downstream graphite electrode calcination conditions.

[0027] Preferably, a static mixer is installed in the high-pressure section of the reaction circulation pump outlet. After the in-situ self-generated hydrogen flash distillate is injected, it flows through the static mixer to complete the mixing.

[0028] By adopting the above technical solution, and with the help of the flow guiding element inside the static mixer, the light oil fraction and the high viscosity heavy component asphalt undergo fluid cutting and radial mixing, which improves the dispersion uniformity of hydrogen donor molecules in the asphalt matrix, thereby improving the subsequent hydrogen transfer mass transfer efficiency.

[0029] Preferably, the primary, secondary, and tertiary blending reactors all use ternary molten salt as the heat transfer medium, and the mass ratio of the ternary molten salt is 53% potassium nitrate, 40% sodium nitrite, and 7% sodium nitrate.

[0030] By adopting the above technical solution, the ternary molten salt with a specific ratio has a high specific heat capacity and thermal conductivity. Its chemical properties are relatively stable and it has no vapor pressure in the high-temperature operating range above 400℃. This avoids the problem of traditional heat transfer oil being prone to cracking and carbonization at high temperatures, and provides a stable external heat source for the blending kettle.

[0031] This invention provides a process for long-cycle continuous production of electrode-bonded asphalt with low mesophase. It offers the following advantages: 1. This invention employs a technical solution of forcibly pressurizing the hydrogen-supplying flash-evaporated oil fraction and injecting it into the high-pressure section of the reaction circulation pump outlet. The light fraction remains in a liquid phase in the high-pressure zone, releasing hydrogen atoms upon entering the heating furnace to saturate and seal the asphalt free radicals. This achieves the technical effect of suppressing the formation of anisotropic mesophase and maintaining stable fluid transport. Compared to the existing technology of directly adding light solvents to the front end of the pump, this solves the problem of instantaneous vaporization of the solvent at the pump inlet under high temperature and low pressure conditions, which can lead to cavitation and cavitation in the equipment, causing system shutdown.

[0032] 2. This invention employs a high-temperature fluid depressurization injection into a negative-pressure stripping flash distillation tower, combined with a top-of-tower condensation and retention of specific fractions for reflux. The gasification of oil fractions absorbs the latent heat of phase change, causing a rapid drop in the temperature of the bottom material. This achieves the technical effects of in-situ freezing and coking reaction, as well as realizing a self-closed-loop hydrogen supply solvent system. Compared with existing technologies that rely on conventional heat exchangers for cooling and continuously purchase additional hydrogen supply agents, this invention solves the shortcomings of the existing technology, such as delayed material cooling that easily leads to secondary coking at the bottom, and the difficulty in accurately matching the composition of external solvents to the process system.

[0033] 3. This invention employs a technical solution where heavy component asphalt is continuously gravity-fed through a series of multi-stage negative pressure blending reactors. Light components are removed in a stepped heating environment, and high-temperature coal tar pitch is added to the first reactor. This continuously extracts low-boiling-point products to drive the condensation reaction forward. Heavy polycyclic aromatic hydrocarbons are used to improve the system's compatibility, achieving the technical effect of steadily increasing the molecular structure of asphalt and improving the fixed carbon yield of the product. Compared with the existing technology that uses a single-stage reactor for rapid heating, this invention solves the problems of the material being prone to violent boiling during the process and the lack of deep cross-linking and solidification of macromolecules due to localized rapid heating. Attached Figure Description

[0034] Figure 1 is a schematic diagram of the process flow of an embodiment of the present invention; Figure 2 is a performance test diagram of the porous ceramic filtration system of the test examples of the present invention, wherein (a) shows the absolute change in the content of native quinoline insoluble matter in the material before and after passing through the ceramic filtration component in Examples 1-4, and (b) shows the initial pressure drop, the pressure drop at the set critical switching peak, and the recovery pressure drop trajectory when the system is put back into operation after online backwashing of the washing oil in each example during a single cycle; Figure 3 is a test diagram of the temperature drop and pump operating conditions of the test examples of the present invention, wherein (a) shows the bulk quenching temperature drop data of Examples 1-4 and Comparative Example 4 in the section from the tubular heater to the flash tower, and (b) shows the temperature drop data of each example and Comparative Example 3 during the operation of the circulating pump. The current and pressure fluctuation bandwidth; Figure 4 is a performance comparison diagram of the in-situ end-capping kinetics and homogeneous polycondensation degree test of the test examples of the present invention, where (a) is the difference in the content of newly generated secondary quinoline insoluble matter in the systems of Examples 1-4, Comparative Example 2 and Comparative Example 5, and (b) is the cumulative amount of β resin in the final product of each test object and the corresponding high temperature coking value level; Figure 5 is a comparison diagram of the comprehensive performance and operation cycle of the test examples of the present invention, where (a) is the limit of continuous operation hours and the proliferation range of secondary quinoline insoluble matter under full system load of Examples 1-4 and Comparative Example 1-5, and (b) is the macroscopic softening point limit and calcination coking value level of the product obtained before failure or during normal discharge. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0037] Coal tar pitch (CAS No.: 65996-93-2): Medium-temperature coal tar pitch is a polycyclic aromatic hydrocarbon mixture residue obtained after distilling light fractions from coal tar. Its physicochemical properties are defined as a softening point of 80℃ to 90℃, a toluene-insoluble content of 15wt% to 25wt%, a quinoline-insoluble content of 5wt% to 10wt%, and a coking value of 45wt% to 50wt%. High-temperature coal tar pitch is a polycyclic aromatic hydrocarbon mixture obtained by thermal polycondensation of medium-temperature coal tar pitch. Its physicochemical properties are defined as a softening point of 110℃ to 120℃, a toluene-insoluble content of 28wt% to 34wt%, a quinoline-insoluble content of 8wt% to 14wt%, and a coking value of 55wt% to 65wt%.

[0038] Wash oil is a mixture of aromatic hydrocarbon-rich fractions in the boiling point range of 230°C to 300°C, which are retained from coal tar after fractionation.

[0039] Example 1: This example provides a process for long-cycle continuous production of electrode-bonded asphalt with low mesophase, including the following steps: Step 1: 100 parts by mass of medium-temperature coal tar pitch are continuously fed into an atmospheric pressure asphalt melting kettle and heated to 180°C to melt it. The liquid asphalt is pressurized to 0.5 MPa by a bottom pump of the melting kettle and pumped into a parallel dual-channel sintered porous metal-ceramic filtration system. The absolute pore size of the ceramic micropores in the filtration system is 10 μm, and the filtration pressure drop is controlled at 0.1 MPa. After removing the solid-phase native quinoline insoluble matter, the refined liquid flows by gravity into the refined asphalt kettle.

[0040] Step Two: Refined asphalt continuously enters the asphalt reactor, is extracted by the reaction circulation pump, and pressurized to 1.2 MPa. The 6.5 parts by mass of the in-situ self-generated hydrogen flash distillate collected in Step Three is pressurized to 1.4 MPa using a shielded pump and directly injected into the high-pressure section of the asphalt reaction circulation pump outlet. After flowing through the static mixer in the pipeline, the mixture is forced into the radiant section of the tubular furnace tubes at a film flow velocity of 2.8 m / s, controlling the bulk phase temperature of the material at the tubular furnace outlet to 390℃.

[0041] Step 3: The high-temperature fluid from the tubular heater outlet is circulated back to the asphalt reactor at a volume ratio of 70%. The remaining 30% of the fluid is depressurized through a control valve and continuously injected into the asphalt stripping flash tower via a tangential distributor. The operating gauge pressure inside the flash tower is controlled at -0.075 MPa, and the latent heat of vaporization is used to lower the tower bottom operating temperature to 380℃. The mixed oil and gas discharged from the top of the flash tower enters the flash tower separator, where the vapor phase temperature at the condenser outlet is controlled at 320℃. The fraction obtained from liquefaction is the in-situ self-generated hydrogen flash oil fraction, which is used for reflux in Step 2. The remaining oil and gas below 320℃ enters the discharge zone of the subsequent condenser.

[0042] Step 4: The heavy component pitch extracted from the flash distillation tower continuously flows by gravity through a series of primary, secondary, and tertiary blending reactors. The operating gauge pressure of each blending reactor is maintained at -0.09 MPa. A ternary molten salt with a mass ratio of 53% potassium nitrate, 40% sodium nitrite, and 7% sodium nitrate is used as the heat transfer medium. The operating temperature of the primary blending reactor is controlled at 400℃, the secondary blending reactor at 410℃, and the tertiary blending reactor at 420℃. In the primary blending reactor, 10 parts by mass of high-temperature coal tar pitch are continuously added using a metering pump. A wall-scraping agitator is used inside the reactor at a stirring speed of 30 rpm. The average residence time of the material in a single blending reactor is controlled at 60 minutes. The shaped material at the bottom of the tertiary blending reactor is cooled to 300℃ by a heat exchanger before being output, yielding electrode-bonding pitch.

[0043] Example 2: This example provides a process for long-cycle continuous production of electrode-bonded asphalt with low mesophase, including the following steps: Step 1: 100 parts by mass of medium-temperature coal tar pitch are continuously fed into an atmospheric pressure asphalt melting kettle and heated to 190°C to melt it. The liquid asphalt is pressurized to 0.6 MPa by a bottom pump of the melting kettle and pumped into a parallel dual-channel sintered porous metal-ceramic filtration system. The absolute pore size of the ceramic micropores in the filtration system is 15 μm, and the filtration pressure drop is controlled at 0.15 MPa. After removing the solid-phase native quinoline insoluble matter, the refined liquid flows by gravity into the refined asphalt kettle.

[0044] Step Two: Refined asphalt continuously enters the asphalt reactor, is extracted by the reaction circulation pump, and pressurized to 1.5 MPa. The 10.0 parts by weight of the in-situ self-generated hydrogen flash distillate collected in Step Three is pressurized to 1.8 MPa using a shielded pump and directly injected into the high-pressure section of the asphalt reaction circulation pump outlet. After flowing through the static mixer in the pipeline, the mixture is forced into the radiant section of the tubular furnace tubes at a film flow velocity of 3.5 m / s, controlling the bulk phase temperature of the material at the furnace outlet to 395℃.

[0045] Step 3: The high-temperature fluid from the tubular heater outlet is circulated back to the asphalt reactor at a volume ratio of 80%. The remaining 20% ​​of the fluid is depressurized through a control valve and continuously injected into the asphalt stripping flash tower via a tangential distributor. The operating gauge pressure inside the flash tower is controlled at -0.06 MPa, and the latent heat of vaporization is used to lower the tower bottom operating temperature to 385℃. The mixed oil and gas discharged from the top of the flash tower enters the flash tower separator, where the vapor phase temperature at the condenser outlet is controlled at 330℃. The fraction obtained from liquefaction is the in-situ self-generated hydrogen flash oil fraction, which is used for reflux in Step 2. The remaining oil and gas below 330℃ enters the discharge zone of the subsequent condenser.

[0046] Step 4: The heavy component pitch extracted from the flash distillation tower continuously flows by gravity through a series of primary, secondary, and tertiary blending reactors. The operating gauge pressure of each blending reactor is maintained at -0.085 MPa. A ternary molten salt with a mass ratio of 53% potassium nitrate, 40% sodium nitrite, and 7% sodium nitrate is used as the heat transfer medium. The operating temperature of the primary blending reactor is controlled at 405℃, the secondary blending reactor at 415℃, and the tertiary blending reactor at 425℃. In the primary blending reactor, 15 parts by mass of high-temperature coal tar pitch are continuously added using a metering pump. A wall-scraping agitator is used inside the reactor at a stirring speed of 45 rpm. The average residence time of the material in a single blending reactor is controlled at 40 minutes. The shaped material at the bottom of the tertiary blending reactor is cooled to 280℃ by a heat exchanger before being output, yielding electrode-bonding pitch.

[0047] Example 3: This example provides a process for long-cycle continuous production of electrode-bonded asphalt with low mesophase, including the following steps: Step 1: 100 parts by mass of medium-temperature coal tar pitch are continuously fed into an atmospheric pressure asphalt melting kettle and heated to 160°C to melt it. The liquid asphalt is pressurized to 0.4 MPa by a bottom pump of the melting kettle and pumped into a parallel dual-channel sintered porous metal-ceramic filtration system. The absolute pore size of the ceramic micropores in the filtration system is 5 μm, and the filtration pressure drop is controlled at 0.05 MPa. After removing the solid-phase native quinoline insoluble matter, the refined liquid flows by gravity into the refined asphalt kettle.

[0048] Step Two: Refined asphalt continuously enters the asphalt reactor, is extracted by the reaction circulation pump, and pressurized to 0.8 MPa. The 3.0 parts by weight of the in-situ self-generated hydrogen flash distillate collected in Step Three is pressurized to 1.0 MPa using a shielded pump and directly injected into the high-pressure section of the asphalt reaction circulation pump outlet. After flowing through the static mixer in the pipeline, the mixture is forced into the radiant section of the tubular furnace tubes at a film flow velocity of 2.0 m / s, controlling the bulk phase temperature of the material at the tubular furnace outlet to 380℃.

[0049] Step 3: The high-temperature fluid from the tubular heater outlet is circulated back to the asphalt reactor at a volume ratio of 60%. The remaining 40% of the fluid is depressurized through a control valve and continuously injected into the asphalt stripping flash tower via a tangential distributor. The operating gauge pressure inside the flash tower is controlled at -0.08 MPa, and the latent heat of vaporization is used to lower the tower bottom operating temperature to 375℃. The mixed oil and gas discharged from the top of the flash tower enters the flash tower separator, where the vapor phase temperature at the condenser outlet is controlled at 310℃. The fraction obtained from liquefaction is the in-situ self-generated hydrogen flash oil fraction, which is used for reflux in Step 2. The remaining oil and gas below 310℃ enters the discharge zone of the subsequent condenser.

[0050] Step 4: The heavy component pitch extracted from the flash distillation tower continuously flows by gravity through a series of primary, secondary, and tertiary blending reactors. The operating gauge pressure of each blending reactor is maintained at -0.095 MPa. A ternary molten salt with a mass ratio of 53% potassium nitrate, 40% sodium nitrite, and 7% sodium nitrate is used as the heat transfer medium. The operating temperature of the primary blending reactor is controlled at 390℃, the secondary blending reactor at 398℃, and the tertiary blending reactor at 406℃. In the primary blending reactor, 5 parts by mass of high-temperature coal tar pitch are continuously added using a metering pump. A wall-scraping agitator is used inside the reactor at a stirring speed of 15 rpm. The average residence time of the material in a single blending reactor is controlled at 90 minutes. The shaped material at the bottom of the tertiary blending reactor is cooled to 290℃ by a heat exchanger before being output, yielding electrode-bonding pitch.

[0051] Example 4: This example provides a process for long-cycle continuous production of electrode-bonded asphalt with low mesophase, including the following steps: Step 1: 100 parts by mass of medium-temperature coal tar pitch are continuously fed into an atmospheric pressure asphalt melting kettle and heated to 170°C to melt it. The liquid asphalt is pressurized to 0.45 MPa by a bottom pump of the melting kettle and pumped into a parallel dual-channel sintered porous metal-ceramic filtration system. The absolute pore size of the ceramic micropores in the filtration system is 8 μm, and the filtration pressure drop is controlled at 0.08 MPa. After removing the solid-phase native quinoline insoluble matter, the refined liquid flows by gravity into the refined asphalt kettle.

[0052] Step Two: Refined asphalt continuously enters the asphalt reactor, is extracted by the reaction circulation pump, and pressurized to 1.0 MPa. The 8.0 parts by weight of the in-situ self-generated hydrogen flash distillate collected in Step Three is pressurized to 1.3 MPa using a shielded pump and directly injected into the high-pressure section of the asphalt reaction circulation pump outlet. After flowing through the static mixer in the pipeline, the mixture is forced into the radiant section of the tubular furnace tubes at a film flow velocity of 2.5 m / s, controlling the bulk phase temperature of the material at the tubular furnace outlet to 385℃.

[0053] Step 3: The high-temperature fluid from the tubular heater outlet is circulated back to the asphalt reactor at a volume ratio of 65%. The remaining 35% of the fluid is depressurized through a control valve and continuously injected into the asphalt stripping flash tower via a tangential distributor. The operating gauge pressure inside the flash tower is controlled at -0.07 MPa, and the latent heat of vaporization is used to lower the tower bottom operating temperature to 378°C. The mixed oil and gas discharged from the top of the flash tower enters the flash tower separator, where the vapor phase temperature at the condenser outlet is controlled at 315°C. The fraction obtained from liquefaction is the in-situ self-generated hydrogen flash oil fraction, which is used for reflux in Step 2. The remaining oil and gas below 315°C enters the discharge zone of the subsequent condenser.

[0054] Step 4: The heavy component pitch extracted from the flash distillation tower continuously flows by gravity through a series of primary, secondary, and tertiary blending reactors. The operating gauge pressure of each blending reactor is maintained at -0.088 MPa. A ternary molten salt with a mass ratio of 53% potassium nitrate, 40% sodium nitrite, and 7% sodium nitrate is used as the heat transfer medium. The operating temperature of the primary blending reactor is controlled at 395℃, the secondary blending reactor at 407℃, and the tertiary blending reactor at 419℃. In the primary blending reactor, 12 parts by mass of high-temperature coal tar pitch are continuously added using a metering pump. A wall-scraping agitator is used inside the reactor at a stirring speed of 25 rpm. The average residence time of the material in a single blending reactor is controlled at 75 minutes. The shaped material at the bottom of the tertiary blending reactor is cooled to 295℃ by a heat exchanger before being output, yielding electrode-bonding pitch.

[0055] Comparative Example 1: Compared with Example 1, the difference is that step one does not include the physical stripping and refining process of the sintered porous metal ceramic filter system, and the medium-temperature coal tar pitch melted at 180°C is directly fed into the refining pitch kettle, while the rest are the same.

[0056] Comparative Example 2: Compared with Example 1, the difference is that in step two, the in-situ self-generated hydrogen flash distillate was not refluxed into the high-pressure pipe section at the outlet of the asphalt reaction circulation pump, that is, the forced reflux of the hydrogen supply distillate was cut off, and all the 320°C condensate retained by the flash tower separator was directly discharged from the boundary area. The rest are the same.

[0057] Comparative Example 3: Compared with Example 1, the difference is that in step two, the injection point of the in-situ self-generated hydrogen flash distillate oil fraction, which was continuously fed into the asphalt reactor by refined asphalt and extracted by the reaction circulation pump and pressurized to 1.2 MPa, was changed to the suction port in front of the asphalt reaction circulation pump, which is at atmospheric pressure or low pressure. All other aspects are the same.

[0058] Comparative Example 4: Compared with Example 1, the difference is that the negative pressure operation of the flash tower is cancelled in step three and replaced with atmospheric pressure operation, so that the material entering the tower cannot undergo drastic phase change, gasification latent heat quenching and cooling. All other aspects are the same.

[0059] Comparative Example 5: Compared with Example 1, the difference is that in step four, the gradient temperature difference series design of the first, second and third stage blending kettles and the continuous replenishment of high-temperature coal tar pitch are cancelled. Instead, the heavy component pitch extracted from the flash tower kettle is directly sent into a single large-volume reactor and held at a constant temperature of 420℃ and -0.09MPa for a total of 180 minutes. All other aspects are the same.

[0060] Test Example 1: Test Objective: This test example aims to verify the physical stripping effect of the porous ceramic filtration system in Step 1 on the insoluble matter of native quinoline and the engineering feasibility of the dual-channel switching online backwashing process in long-term operation to prevent clogging.

[0061] Test steps: 1. Sampling and sample preparation: Under continuous and stable operating conditions, sealed samplers are set up at the outlet pipeline of the feeding melting kettle and the outlet pipeline of the porous ceramic filter system, respectively. Liquid medium-temperature coal tar pitch samples are collected at regular intervals, cooled and crushed for later use. For comparative example 1 without a filter system, samples are taken directly from the corresponding conveying pipeline.

[0062] 2. Determination of the removal rate of virgin quinoline insoluble matter: According to standard GB / T 2293 "Test method for quinoline insoluble matter in coking asphalt products", toluene was used to pre-extract the sample to remove low molecular weight components. Then, the residue was placed in quinoline solvent and centrifuged at 75°C for extraction. After filtration, drying and weighing, the mass percentage of quinoline insoluble matter before and after filtration was calculated. The desolvation efficiency was obtained by calculating the difference.

[0063] 3. Recording of Filtration Pressure Drop Fluctuations and Backwash Recovery Rate. Retrieve the continuous operation history trend curves from the distributed control system, extract the initial inlet and outlet pressure drop data of the filtration system during the initial stage of single-channel operation, extract the system pressure drop peak value before triggering automatic switching to the backup channel, and the pressure drop baseline value when the channel is put back into operation after online backwashing with high-temperature washing oil.

[0064] The corresponding test data are shown in Table 1.

[0065] Table 1: Desolidification Performance and Operating Pressure Drop Data of Filtration System

[0066] Conclusion: According to the data in Table 1 and Figure 2, after undergoing the sintered porous metal ceramic filtration system, the removal rate of native quinoline insoluble matter in Examples 1 to 4 remained stable at over 97.98%, and the amount of solid residue in the system after treatment was reduced to as low as 0.04 wt%, showing a fundamental difference in the system compared with Comparative Example 1, which did not undergo stripping treatment.

[0067] This thorough deconsolidation effect directly confirms the steric hindrance retention capacity within the low-viscosity thermodynamic stability region. At operating temperatures of 160℃ to 190℃, the asphalt fluid maintains Newtonian fluid characteristics with minimal viscous resistance. Micropores of 5μm to 15μm can precisely identify and intercept high-surface-energy coal powder and coke particles within the system. In the absence of these heterogeneous nucleation centers, the activation energy of the fusion phase transition of macromolecular aromatic rings in the subsequent tubular furnace and blending vessel is significantly increased. This locks in the initial path of spontaneous formation of mesophase microspheres at the material mesoscopic structural level, laying the foundation for a homogeneous glassy state in the final product.

[0068] The biggest obstacle to industrial scale-up of conventional asphalt filtration processes is the easy and permanent blockage of micropores by highly adhesive colloids and fine particles. Pressure drop trajectories recorded by the distributed control system show that when the pressure drop in the operating channels of each embodiment approaches the switching threshold of 0.15 MPa, the system automatically switches the flow path and introduces wash oil for high-pressure reverse purging. After backwashing, the pressure drop can return to near its initial level. The pressure drop recovery rate reaches a maximum of 96.74%, with only a very slight irreversible contamination loss, indicating that high-pressure online backwashing effectively removes the sticky filter cake layer deposited inside and on the surface of the ceramic micropores. This engineering test result eliminates the industrial drawback of requiring frequent shutdowns and disassembly for cleaning in continuous production of single micropore filtration, demonstrating that this physical stripping and refining process has the reliability to operate synchronously with the entire bulk thermal processing unit for long periods.

[0069] Test Example 2: Test Objective: This test example aims to verify the actual cooling range from the flash vaporization latent heat zone, and the inhibitory effect of injecting light components into the high-pressure section after the pump on the cavitation phenomenon of the high-temperature circulating pump.

[0070] Test Procedure: 1. Under continuous and stable system operation, Examples 1 to 4, as well as Comparative Examples 3 and 4, were selected as monitoring objects. Thermocouple temperature data from the outlet pipeline of the radiant section of the tubular heater was extracted in real time using the distributed control system, and the bulk phase temperature data at the bottom of the flash tower was extracted simultaneously. The difference between the two values ​​at the same time section was recorded to quantify the actual temperature drop of the material after it entered a negative or normal pressure environment.

[0071] 2. Continuously monitor and export the historical operating curve of the stator current of the asphalt reaction circulating pump drive motor, and calculate its current fluctuation range within a 24-hour observation period. Simultaneously, install a remote pressure transmitter at the high-pressure section of the circulating pump outlet to extract the gauge pressure fluctuation bandwidth at this measuring point, thereby assessing whether gas-liquid two-phase separation and cavitation phenomena exist within the centrifugal impeller.

[0072] The corresponding test data are shown in Table 2.

[0073] Table 2: Quenching Temperature Drop and Reaction Circulation Pump Operating Data

[0074] Conclusion: Based on the data in Table 2 and Figure 3, after being subjected to a negative pressure environment of -0.06 MPa to -0.08 MPa in Examples 1 to 4, the high-temperature asphalt phase experienced an instantaneous temperature drop of 5.1°C to 10.3°C. This confirms, on an engineering scale, the physical process of component vaporization absorbing a large amount of latent heat. In contrast, Comparative Example 4, which eliminated the negative pressure operation, lost the driving force to disrupt the original vapor-liquid phase equilibrium. The distillate could not undergo violent flash evaporation, resulting in a temperature drop of only 1.3°C inside the vessel. This thermal stagnation phenomenon makes it extremely easy for free macromolecules in the dead corners of the pipe walls and the bottom of the tower to break through the fusion activation energy barrier, thus evolving into an irreversible coking layer. Long-term observation of bulk heavy oil thermal processing shows that heat transfer on the equipment walls often has a significant response delay. This phase change endothermic mechanism relying on the light components of the process fluid within milliseconds provides a more fundamental thermodynamic defense against local overheating than external water cooling or heat transfer oil.

[0075] For this temperature control strategy, which relies on the phase change of low-boiling-point components within the system, to be implemented, the engineering layout of the fluid mixing section becomes a prerequisite for the continuous operation of the device. Monitoring data from Comparative Example 3 shows that when hydrogen-supplying flash oil with high saturated vapor pressure is incorporated into the high-temperature asphalt mainstream at atmospheric or low pressure, the mixture undergoes localized boiling in the low-pressure zone near the impeller leading edge of the centrifugal pump. The resulting bubbles collapse instantly upon entering the high-pressure zone, causing current fluctuations as high as 28.6A and a pressure bandwidth difference approaching 0.90MPa. This intense cavitation water hammer effect not only disrupts stable fluid transport but also causes fatigue damage to the mechanical seal and pump rotor within a short time, rendering them completely unsuitable for industrial application.

[0076] To address the aforementioned fluid transport bottleneck, this solution forcibly positions the injection point for the light components within the high-pressure section of the circulating pump outlet. This design ensures that the back pressure of the material system consistently exceeds the saturated vapor pressure of the retained fraction. Data from the embodiment confirms the reliability of this pipeline topology. The shifted injection point forces the hydrogen-supplying fraction into the static mixer and the radiant section of the heater in a pure liquid phase. The current differential of the circulating pump is reduced to below 1.5A, resulting in a highly stable laminar flow output characteristic at the outlet pressure. Stable feed conditions ensure uniform residence time within the tubular furnace, preventing localized dry burning of the furnace tubes due to flow pulsations, and establishing a reliable hydrodynamic channel for maintaining long-term dynamic equilibrium throughout the entire reaction system.

[0077] Test Example 3: Test Objective: This test example aims to demonstrate that, under the synergistic effect of in-situ hydrogen supply fraction reflux and gradient vacuum pulling, the system can achieve homogeneous condensation of macromolecules while suppressing the formation of mesophase coke (secondary quinoline insolubles), thereby obtaining electrode bonding asphalt with high coking value and high β resin content.

[0078] Test steps: 1. During the continuous and stable operation cycle of the system, the final shaped asphalt material was collected from the bottom discharge port of the three-stage blending vessel of Examples 1 to 4, and the discharge port of the reactor of Comparative Example 2 and Comparative Example 5. After the sample was naturally cooled to room temperature, it was mechanically crushed and sieved to the particle size that met the test standard as the experimental reference sample.

[0079] 2. Determination of quinoline insoluble matter (QI) and toluene insoluble matter (TI) in the finished product: A quantitatively prepared powder sample was taken, and the TI content was obtained using the solvothermal extraction method according to standard GB / T 2293 "Test Method for Quinoline Insoluble Matter in Coking Pitch Products". A parallel sample was placed in quinoline solvent and centrifuged at 75℃ for extraction. After filtration, drying, and weighing, the QI content of the finished product was obtained. The measured percentage of finished product QI mass was subtracted from the amount of primary QI residue recorded in Test Example 1 to obtain the content of newly generated secondary QI (intermediate phase coke) during the reaction. The β-resin content, representing the material's binding activity, was calculated using a formula, i.e., the difference between the TI content and the finished product QI content.

[0080] 3. Coking value determination: A portion of the pulverized sample is extracted and placed in a specially made quartz crucible with a lid. According to standard GB / T8727 "Determination of Coking Value of Coal Pitch Products", it is placed in a high-temperature muffle furnace and roasted for a specified time under constant high temperature and air isolation conditions. The percentage of residual coke mass after roasting relative to the initial sample mass is calculated.

[0081] The corresponding test data are shown in Table 3.

[0082] Table 3: Data on Physicochemical Properties and Intermediate Phase Suppression Efficiency of Finished Products

[0083] Conclusion: Based on the data in Table 3 and Figure 4, the example group strictly suppressed the increase in secondary QI to an extremely low range of 0.04wt% to 0.07wt% throughout the entire continuous thermal processing cycle. This indicates that the fluid system hardly underwent nucleation and development of anisotropic liquid crystal microspheres when crossing the high-temperature barrier of nearly 400℃. This microscopic stability is directly attributed to the forced reflux of the flash distillate rich in active α-hydrogen at high pressure from 310℃ to 330℃. Before finding coupling targets, the highly reactive aryl radicals generated by the thermal decomposition of bulk aromatics in the furnace tube are preemptively intervened by these small molecules acting as high-quality hydrogen donors. Because the dehydrogenation activation energy of the hydrogen donor is lower than the fusion barrier of the pitch macromolecules, free hydrogen atoms complete in-situ chain transfer and end-capping at a rate far exceeding that of molecular collision diffusion. This completely severs the runaway path of the evolution from a two-dimensional macromolecular plane to a three-dimensional mesophase fossil from the underlying logic of chemical kinetics. Comparative Example 2, which cut off the reflux of this fraction, showed a secondary QI surge of up to 18.45 wt%. Free radicals rapidly devoured and crosslinked each other in the high-temperature region without intervention, confirming the decisive role of this in-situ end-capping mechanism in the heavy oil anti-coking system.

[0084] The industrial-scale preparation of electrode bonding asphalt often faces the dilemma of suppressing coking while increasing residual carbon content. The example group, while suppressing mesophase formation, still achieved a high coking value exceeding 61 wt% and abundant β-resin accumulation, primarily due to the precise control of thermodynamic equilibrium in the multi-stage cascade reaction. Under a deep vacuum atmosphere of -0.085 MPa to -0.095 MPa, side-chain fragments and lightweight sterically hindered molecules detached due to thermal condensation were continuously stripped from the system. The reduction in microscopic steric hindrance, combined with the pulling effect of Le Chatelier equilibrium shift, forced the cross-coupling between macromolecules to continuously advance towards the formation of toluene-insoluble substances. This gentle and continuous process of increasing molecular weight precisely locks the degree of molecular condensation at the β-resin level, which possesses excellent rheological plasticity, endowing the product with superior skeletal bonding ability in the downstream carbon product calcination process.

[0085] Comparative Example 5, which eliminated the phase equilibrium pulling step and replaced it with a traditional single-volume reactor under constant temperature stagnation, saw a significant drop in the β-resin content of the final product to 21.93 wt%, and the coking value also failed to achieve a significant breakthrough. In a homogeneous temperature field lacking gradient degassing and high-temperature coal tar pitch solvation and harmonization, the pitch system is prone to mesoscale phase separation due to long-term deep thermal retention. The polarization of molecular weight distribution causes some heavy components to precipitate prematurely, forming hard carbon deposits, while the degree of polymerization of the remaining liquid phase consistently fails to meet the target. The example, through a temperature field distribution that gradually increases from 8°C to 12°C combined with the forced extraction of small molecules, not only avoids the excessive local reaction caused by the extreme high temperature of a single reactor, but also constructs a broad thermodynamic tolerance range for the homogeneous growth of large molecules, macroscopically breaking the technical constraint that "high adhesion inevitably comes with a high mesophase" in the traditional single-reactor process.

[0086] Test Example 4: Test Objective: This test example aims to comprehensively evaluate the overall performance of Examples 1 to 4 and Comparative Examples 1 to 5 in the continuous hot processing of the entire system using the controlled variable method. By comparing the core physicochemical indicators of the final product with the extreme continuous operation cycle of the device, the irreplaceable nature of the deep synergy of each link of this process is verified from the perspective of macro-engineering results.

[0087] Test Procedure: 1. Continuous Operation Cycle Monitoring and Fault Shutdown Recording: After the initial start-up of the unit stabilizes, the timer of the distributed control system is reset to zero, and the operating status of the core equipment is monitored throughout the process. For the example group that can operate stably for a long period, the total duration of maintaining the specified operating conditions is recorded; for the comparative group, once a coking blockage alarm is triggered, such as the pressure drop at the inlet and outlet of the tubular heating furnace exceeding 0.5MPa, or an irreversible and severe fluctuation in the current of the reaction circulation pump motor causes mechanical seizure, the system operation is immediately terminated and its actual continuous operation time is recorded.

[0088] 2. Macroscopic physicochemical index determination of the product: During the middle and late stages of operation of each group of units or before a shutdown due to a malfunction, samples of the final output electrode-bonded asphalt are collected. The softening point is determined using the ring and ball method according to standard GB / T 4507 "Determination of Softening Point of Asphalt - Ring and Ball Method" to assess the material's heat resistance and basic rheological characteristics in the downstream kneading and molding process. The coking value is determined using a specially made quartz crucible in a high-temperature muffle furnace according to standard GB / T 8727 "Determination of Coking Value of Coal Pitch Products" to quantitatively evaluate the carbon skeleton retention rate after roasting.

[0089] 3. The inverse deduction of the mesophase formation amount: Directly referencing the solvent extraction data from Test Examples 1 and 3, subtract the trace amounts of primary solid residue not removed in the initial filtration stage from the quinoline insoluble matter content in the final product to calculate the increase in free secondary quinoline insoluble matter generated during the reaction. This macroscopic value is used as the absolute boundary for evaluating the degree of uncontrolled free radical cross-linking and the proliferation of mesophase coke within the reaction system.

[0090] The corresponding test data are shown in Table 4.

[0091] Table 4: Comparison of Comprehensive Physicochemical Indicators of the Entire System and Continuous Operation Condition Tests

[0092] Conclusion: Based on the data in Table 4 and Figure 5, the example group, relying on the deep synergy of four dimensions, demonstrated overwhelming system engineering stability, with continuous operating time exceeding 2600 hours and all product indicators firmly locked within the excellent range of electrode binder. This long-term stability of the mesoscopic structure is a direct projection of the successful comprehensive intervention of primary nucleus physical stripping, in-situ free radical end-capping, phase change self-cooling, and vacuum gradient pulling. In heavy oil bulk thermal processing sites, the uncontrolled evolution of microscopic free radicals often ends in macroscopic pipeline crusting and blockage. The example maintained a pure liquid phase environment with secondary QI not exceeding 0.07wt% in a harsh radiative thermal field as high as 395℃, completely cutting off the evolution path of mesophase microspheres adhering to the inner wall of the equipment, verifying the closed-loop logic of this scheme in terms of chemical anti-coking and physical thermodynamic cooling.

[0093] The lack of this systematic coordination in each comparative example exposed fatal shortcomings in different dimensions. Comparative Example 1, which used a completely conventional straight-through process, and Comparative Example 2, which cut off the reflux of the hydrogen-supplying fraction, showed that the polycyclic aromatic hydrocarbon radicals in the system underwent unimpeded two-dimensional collisions and fusion at high temperatures. The secondary quinoline insolubles surged to 14.65 wt% and 18.45 wt%, respectively. A large amount of irreversible mesophase coke rapidly deposited in the slower-flowing stagnation zone, forcing the entire production line to shut down due to excessive pressure drop within a few hundred hours. Comparative Example 4, which eliminated the negative pressure quenching mechanism, thermodynamically confirmed the fragility of the anti-coking system. By depriving the light fraction of the path to break phase equilibrium and absorb latent heat of vaporization during the flash evaporation stage, the high-temperature fluid at the bottom of the tower adhered to the metal wall for a long time, forming localized hot spots. This led to the complete blockage of the feed distributor after only 245 hours. Comparative Example 3, which made erroneous changes to the engineering topology, provides the most extreme failure example. Due to the direct injection of the hydrogen-supplying fraction with high saturated vapor pressure into the low-pressure inlet in front of the circulating pump, the violent gas-liquid two-phase separation completely destroyed the hydraulic model of the centrifugal pump within 18 hours. The resulting severe cavitation water hammer caused the rotor to seize up. The material was scrapped with an extremely low coking value due to the forced shutdown before it could undergo deep modification. This reveals that the chemical mechanism at the laboratory level will be impossible to implement in the industrial field without a rigorous fluid dynamic back pressure design.

[0094] Compared to the groups that quickly shut down due to engineering failures, Comparative Example 5, which relied on the traditional large-volume single-reactor system, managed to maintain operation for a relatively long time, but its product's physicochemical properties were caught in an irreconcilable contradiction. Lacking a progressively increasing temperature gradient and the continuous extraction of small molecules from the deep vacuum, the cross-coupling of macromolecular systems within the reactor stagnated due to increased steric hindrance, resulting in a macroscopic coking value hovering around 55 wt%. Prolonged deep thermal retention further caused mesoscopic-scale phase separation in the liquid system, not only generating 8.53 wt% secondary coke but also causing severe polarization in the viscosity and softening point of the materials in the upper and lower layers of the reactor. The batch-to-batch inhomogeneity of the output product completely negated its industrial value as a high-end carbon skeleton binder.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for long-cycle continuous production of electrode bonding bitumen with low mesophase, characterized in that, Includes the following steps: S1. 100 parts by weight of medium-temperature coal tar pitch are heated and melted, and then pressurized and fed into a porous filtration system to remove solid-phase native quinoline insoluble matter to obtain refined pitch. S2. The refined asphalt is continuously fed into the asphalt reactor, extracted and pressurized by the reaction circulation pump; the in-situ self-generated hydrogen flash distillate obtained in S3 is pressurized and injected into the high-pressure section of the reaction circulation pump outlet to mix with the mainstream material, and then pumped into the tubular heater for heating; S3. The high-temperature fluid at the outlet of the tubular heater is diverted, part of which is circulated back to the asphalt reactor, and the remaining part is depressurized and injected into the asphalt stripping flash tower under negative pressure. The mixed oil and gas discharged from the top of the flash tower is condensed and retained to obtain the in-situ self-generated hydrogen flash oil fraction, which is then used for reflux in S2; in S4, the heavy component asphalt extracted from the flash tower bottom is continuously and sequentially passed by gravity through a series of multi-stage blending kettles under negative pressure. High-temperature coal tar pitch is continuously added to the first blending kettle, and the material is finally output after cooling to obtain electrode bonding asphalt.

2. The process for long-cycle continuous production of electrode bonding asphalt with low mesophase according to claim 1, characterized in that, In step S1, the medium-temperature coal tar pitch is heated to 160℃-190℃ to melt it; the pressure is increased to 0.4MPa-0.6MPa by a pump and sent into the porous filtration system; the porous filtration system is a sintered porous metal-ceramic filtration system with an absolute pore size of 5μm-15μm, and the filtration pressure drop is controlled at 0.05MPa-0.15MPa.

3. The process for long-cycle continuous production of electrode bonding asphalt with low mesophase according to claim 1, characterized in that, In step S2, the refined asphalt is pressurized to 0.8MPa-1.5MPa by the reaction circulation pump; the injection amount of the in-situ self-generated hydrogen flash distillate is 3.0-10.0 parts by mass, which is pressurized to 1.0MPa-1.8MPa by a shielded pump and then injected into the high-pressure pipe section; the mixture is pumped into the radiant section furnace tube of the tubular heater at a film flow rate of 2.0m / s-3.5m / s, and the bulk phase temperature of the material at the outlet of the tubular heater is controlled to be 380℃-395℃.

4. The process for long-cycle continuous production of electrode bonding asphalt with low mesophase according to claim 1, characterized in that, In step S3, the high-temperature fluid from the outlet of the tubular heater is circulated back to the asphalt reactor at a volume ratio of 60%-80%, and the remaining 20%-40% of the fluid is continuously injected into the asphalt stripping flash tower via a tangential injection distributor. The operating gauge pressure inside the flash tower is controlled at -0.06MPa to -0.08MPa, and the tower bottom operating temperature is reduced to 375℃-385℃. The mixed oil and gas discharged from the top of the flash tower enters the flash tower separator, and the vapor phase temperature at the condenser outlet of the separator is controlled at 310℃-330℃ to retain and obtain the in-situ self-generated hydrogen flash oil fraction.

5. The process for long-cycle continuous production of electrode bonding asphalt with low mesophase according to claim 1, characterized in that, In S4, the multi-stage blending reactor in series includes a primary blending reactor, a secondary blending reactor, and a tertiary blending reactor connected in series. The operating gauge pressure of each blending reactor is maintained between -0.085 MPa and -0.095 MPa. The operating temperature of the primary blending reactor is 390℃-405℃, the operating temperature of the secondary blending reactor is 398℃-415℃, and the operating temperature of the tertiary blending reactor is 406℃-425℃.

6. The process for long-cycle continuous production of electrode bonding asphalt with low mesophase according to claim 5, characterized in that, In S4, 5-15 parts by weight of the high-temperature coal tar pitch are continuously added to the primary blending vessel using a metering pump; each blending vessel is equipped with a wall-scraping agitator with a stirring speed of 15-45 rpm; the average residence time of the material in a single blending vessel is controlled to be 40-90 minutes; the material at the bottom of the tertiary blending vessel is cooled to 280-300℃ by a heat exchanger before being output.

7. The process for long-cycle continuous production of electrode bonding asphalt with low mesophase according to claim 1, characterized in that, The physicochemical properties of the medium-temperature coal tar pitch are as follows: softening point 80℃-90℃, toluene insoluble content 15wt%-25wt%, quinoline insoluble content 5wt%-10wt%, and coking value 45wt%-50wt%.

8. The process for long-cycle continuous production of electrode bonding asphalt with low mesophase according to claim 1, characterized in that, The physicochemical properties of the high-temperature coal tar pitch are as follows: softening point 110℃-120℃, toluene insoluble content 28wt%-34wt%, quinoline insoluble content 8wt%-14wt%, and coking value 55wt%-65wt%.

9. The process for long-cycle continuous production of electrode bonding asphalt with low mesophase according to claim 1, characterized in that, In step S2, a static mixer is installed in the high-pressure section of the outlet of the reaction circulation pump. After the in-situ self-generated hydrogen flash distillate is injected, it flows through the static mixer to complete the mixing.

10. The process for long-cycle continuous production of electrode bonding asphalt with low mesophase according to claim 5, characterized in that, The primary, secondary, and tertiary blending kettles all use ternary molten salt as the heat transfer medium, and the mass ratio of the ternary molten salt is 53% potassium nitrate, 40% sodium nitrite, and 7% sodium nitrate.

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