Biphenyl addition device for melt spinning

Abstract

This invention discloses a biphenyl addition device for melt spinning, relating to the technical field of melt spinning equipment. The device includes a heat exchange tank, a preheating and replenishing mechanism, a gas-liquid separator, a liquid phase heat exchanger, a replenishing temperature tank, and a main evaporator. A steam injection mechanism is installed inside the heat exchange tank. The preheating and replenishing mechanism preheats the biphenyl liquid and sends it into the heat exchange tank for direct contact heat exchange with the reflux steam. After gas-liquid separation, the liquid enters the shell side and tube side of the liquid phase heat exchanger for indirect heat exchange. After converging, the liquid enters the replenishing temperature tank via a static mixer for further heating. Finally, the liquid is evenly dispersed and evaporated through a buffer distribution plate at the bottom of the main evaporator. This invention fully utilizes the cascade heat of the reflux biphenyl vapor, avoids flash evaporation and drastic temperature fluctuations caused by direct injection of low-temperature biphenyl liquid, improves the stability of the spinning temperature and the system thermal efficiency, and reduces energy consumption.

Description

Technical Field

[0001] This invention relates to the field of melt spinning equipment technology, and in particular to a biphenyl addition device for melt spinning. Background Technology

[0002] In recent years, with the rapid development of the chemical fiber industry, melt spinning technology has become the mainstream process for producing synthetic fibers such as polyester and nylon.

[0003] Biphenyl-diphenyl ether mixtures, as high-temperature heat transfer fluids, are widely used in the heating systems of melt spinning equipment due to their excellent heat transfer performance and high operating temperature. With the continuous improvement of spinning speed and product quality requirements, increasingly higher demands are being placed on the temperature stability, replenishment efficiency, and energy consumption control of biphenyl steam heating systems.

[0004] Currently, existing melt spinning production lines generally employ independent biphenyl heating and evaporation systems to heat and evaporate fresh biphenyl solution, then transport the resulting biphenyl vapor to the spinning chamber for heating. When replenishing biphenyl solution, preheated solution is typically injected directly into the main evaporator, where it is rapidly heated and evaporated via a tank wall jacket or electric heating elements. While this method is structurally simple, in actual operation, when a large amount of low-temperature biphenyl solution is injected into the main evaporator at once, violent flash evaporation can easily occur, leading to significant fluctuations in vapor pressure and temperature, affecting the temperature stability of the spinning chamber. Furthermore, existing technologies often only perform simple condensation and recovery of the returned high-temperature biphenyl vapor, failing to fully utilize its heat load for gradient preheating of the fresh biphenyl solution, resulting in energy waste. Summary of the Invention

[0005] The main objective of this invention is to provide a biphenyl addition device for melt spinning, which aims to use the high-temperature biphenyl vapor refluxed from the melt spinning equipment to gradually raise the temperature of the fresh biphenyl liquid to above the boiling point and stabilize its vaporization, thereby significantly improving the stability of the spinning temperature and the utilization rate of biphenyl.

[0006] To achieve the above objectives, the present invention provides a biphenyl addition device for melt spinning, comprising: A heat exchange tank, wherein a mixing chamber is provided inside the heat exchange tank, and a steam injection mechanism is provided on the bottom wall of the mixing chamber; A preheating and replenishing mechanism, wherein the biphenyl liquid outlet of the preheating and replenishing mechanism is connected to the mixing chamber through a first pipeline; A gas-liquid separator, wherein the inlet of the gas-liquid separator is connected to the outlet of the mixing chamber via a second pipeline; The liquid phase heat exchanger has a gas phase outlet of the gas-liquid separator connected to the shell-side inlet of the liquid phase heat exchanger via a third pipeline, and a liquid phase outlet of the gas-liquid separator connected to the tube-side inlet of the liquid phase heat exchanger via a fourth pipeline. The heat replenishment tank is connected to the inlet of the heat replenishment tank via a manifold. The tube-side outlet of the liquid phase heat exchanger and the shell-side condensate outlet of the liquid phase heat exchanger are connected to the inlet of the heat replenishment tank. The main evaporator has its discharge port connected to the feed port of the main evaporator via a heating medium pipeline, and its biphenyl vapor outlet is connected to an external melt spinning device via a fifth pipeline. The biphenyl vapor reflux pipe of the melt spinning equipment is connected to the steam injection mechanism, which is used to allow the biphenyl vapor refluxed from the melt spinning equipment to enter the mixing chamber and exchange heat with the biphenyl liquid supplied to the mixing chamber by the preheating and replenishing mechanism. The preheating and replenishing mechanism is used to heat the biphenyl solution to 80℃~100℃, the heat exchange tank is used to raise the temperature of the biphenyl solution to 150℃~180℃, the liquid phase heat exchanger is used to raise the temperature of the biphenyl solution to 200℃~210℃, the replenishing tank is used to replenish the temperature of the biphenyl solution to 245℃~255℃, and the main evaporator is used to supply the biphenyl vapor from the biphenyl vapor outlet of the main evaporator to the biphenyl vapor heating end of the external melt spinning equipment through the fifth pipeline.

[0007] The technical solution of this invention utilizes a multi-stage gradient heating path comprised of a preheating and replenishment mechanism, a steam injection mechanism within the heat exchange tank, a gas-liquid separator, a shell-and-tube liquid phase heat exchanger, a static mixer in the manifold, a replenishment tank, and a buffer distribution plate at the bottom of the main evaporator. This allows the reflux biphenyl vapor from the melt spinning equipment and the replenished biphenyl liquid to sequentially pass through four controlled stages: direct contact heat exchange, gas-liquid separation, indirect latent heat transfer, uniform mixing and replenishment, and buffer dispersion evaporation. Because the heating rate at each stage is adjusted in real-time by the PLC control system based on feedback from multiple temperature sensors, the opening of the first to fifth flow regulating valves is adjusted accordingly. This prevents the violent flash evaporation caused by a large amount of low-temperature liquid directly entering the high-temperature evaporator, effectively suppressing drastic fluctuations in steam pressure and temperature and preventing localized overheating and cracking of biphenyl. Simultaneously, the sensible and latent heat of the reflux steam are gradually absorbed in different temperature ranges, significantly improving overall thermal efficiency. In addition, when the multi-point temperature monitoring module in the melt spinning box detects a temperature fluctuation exceeding ±1.5℃ at any point, the PLC control system automatically reduces the opening of the first and fifth flow regulating valves until the fluctuation returns to the set range. This further realizes the dynamic and precise matching of the biphenyl steam heating end and the heat load of the downstream spinning process, ensuring the long-term uniformity and stability of the spinning box temperature during high-speed spinning, reducing energy consumption and improving the consistency of fiber product quality. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0009] Figure 1 A schematic diagram of an embodiment of the biphenyl addition device for melt spinning provided by the present invention; Figure 2 A schematic diagram of the internal structure of a biphenyl addition device for melt spinning provided by the present invention; Figure 3 This is a connection diagram of an embodiment of the PLC control system related circuits involved in the present invention.

[0010] Explanation of icon numbers: 100. Heat exchange tank; 200. Preheating and replenishment mechanism; 300. Gas-liquid separator; 400. Liquid phase heat exchanger; 500. Replenishment tank; 600. Main evaporator.

[0011] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0012] The technical solutions of 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0013] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0014] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0015] In recent years, with the rapid development of the chemical fiber industry, melt spinning technology has become the mainstream process for producing synthetic fibers such as polyester and nylon. Biphenyl-diphenyl ether mixtures, as high-temperature heat transfer fluids, are widely used in the heating systems of melt spinning equipment due to their excellent heat transfer performance and high operating temperature. With the continuous improvement of spinning speed and product quality requirements, increasingly higher demands are being placed on the temperature stability, replenishment efficiency, and energy consumption control of biphenyl steam heating systems.

[0016] Currently, existing melt spinning production lines generally employ independent biphenyl heating and evaporation systems to heat and evaporate fresh biphenyl solution, then transport the resulting biphenyl vapor to the spinning chamber for heating. When replenishing biphenyl solution, preheated solution is typically injected directly into the main evaporator, where it is rapidly heated and evaporated via a tank wall jacket or electric heating elements. While this method is structurally simple, in actual operation, when a large amount of low-temperature biphenyl solution is injected into the main evaporator at once, violent flash evaporation can easily occur, leading to significant fluctuations in vapor pressure and temperature, affecting the temperature stability of the spinning chamber. Furthermore, existing technologies often only perform simple condensation and recovery of the returned high-temperature biphenyl vapor, failing to fully utilize its heat load for gradient preheating of the fresh biphenyl solution, resulting in energy waste. Furthermore, the aforementioned existing technologies have the following shortcomings: First, directly injecting liquid into the main evaporator can easily trigger flash evaporation, leading to drastic fluctuations in steam pressure and temperature, making it difficult to meet the precise temperature control requirements of high-speed spinning; second, the heat from the high-temperature biphenyl vapor returning from the melt spinning equipment is not effectively utilized, and the heating process of the fresh biphenyl liquid lacks graded control, with excessively rapid heating rates easily causing localized overheating and cracking of biphenyl; third, the existing devices fail to classify and utilize the heat from the gas and liquid phases, resulting in low overall thermal efficiency, which is significantly different from the current spinning process's expectations for temperature uniformity, stability, and energy saving.

[0017] To address this technical problem, the present invention proposes a biphenyl addition device for melt spinning.

[0018] Please see Figure 1 and Figure 2 In one embodiment of the present invention, the biphenyl addition device for melt spinning includes a heat exchange tank 100, a preheating and replenishing mechanism 200, a gas-liquid separator 300, a liquid phase heat exchanger 400, a replenishing tank 500, and a main evaporator 600. The heat exchange tank 100 has a mixing chamber, and the bottom wall of the mixing chamber is equipped with a steam injection mechanism. The biphenyl liquid outlet of the preheating and replenishing mechanism 200 is connected to the mixing chamber via a first pipeline. The feed of the gas-liquid separator 300... The outlet of the gas-liquid separator 300 is connected to the discharge port of the mixing chamber via a second pipeline; the gas phase outlet of the gas-liquid separator 300 is connected to the shell-side inlet of the liquid phase heat exchanger 400 via a third pipeline, and the liquid phase outlet of the gas-liquid separator 300 is connected to the tube-side inlet of the liquid phase heat exchanger 400 via a fourth pipeline; the tube-side outlet and the shell-side condensate outlet of the liquid phase heat exchanger 400 are connected to the feed inlet of the make-up heat tank 500 via a manifold; the discharge port of the make-up heat tank 500... The feed inlet is connected to the feed port of the main evaporator 600 via a heating medium pipeline. The biphenyl vapor outlet of the main evaporator 600 is connected to the external melt spinning equipment via a fifth pipeline. The biphenyl vapor return pipeline of the melt spinning equipment is connected to the steam injection mechanism, which is used to allow the biphenyl vapor returning from the melt spinning equipment to enter the mixing chamber and exchange heat with the biphenyl liquid supplied to the mixing chamber by the preheating and replenishing liquid mechanism 200. The preheating and replenishing liquid mechanism 200 is used to heat the biphenyl liquid to 80℃~100℃, the heat exchange tank 100 is used to raise the temperature of the biphenyl liquid to 150℃~180℃, the liquid phase heat exchanger 400 is used to raise the temperature of the biphenyl liquid to 200℃~210℃, the heating tank 500 is used to replenish the temperature of the biphenyl liquid to 245℃~255℃, and the main evaporator 600 is used to supply the biphenyl vapor heating end of the external melt spinning equipment through the biphenyl vapor outlet of the main evaporator 600 via the fifth pipeline after the biphenyl liquid is evaporated.

[0019] Specifically, in the melt spinning equipment, the biphenyl vapor reflux pipe introduces high-temperature reflux biphenyl vapor into the steam injection mechanism, which jets it upwards from the bottom wall of the mixing chamber, allowing for thorough direct contact heat exchange with the 80°C~100°C biphenyl liquid entering the mixing chamber from the first pipe. During this process, the reflux steam transfers its sensible heat and some latent heat to the biphenyl liquid, raising the temperature gradient of the biphenyl liquid in the mixing chamber to 150°C~180°C. Simultaneously, some of the steam condenses to form a liquid phase. The mixture, in a two-phase gas-liquid form, enters the gas-liquid separator 300 from the mixing chamber outlet via the second pipe. In the gas-liquid separator 300, the gas and liquid phases are effectively separated under the action of gravity and centrifugal force. The separated gas phase (mainly high-temperature biphenyl vapor) enters the shell side of the liquid phase heat exchanger 400 via the third pipe, while the liquid phase (mainly the preheated biphenyl liquid) enters the tube side of the liquid phase heat exchanger 400 via the fourth pipe. Within the liquid-phase heat exchanger 400, the latent heat released by the condensation of the shell-side gas phase is efficiently transferred to the biphenyl liquid in the tube side through the tube bundle, further precisely raising the temperature of the biphenyl liquid at the tube-side outlet to 200℃~210℃. Subsequently, the high-temperature biphenyl liquid at the tube-side outlet and the shell-side condensate enter the replenishment tank 500 through a manifold. In the replenishment tank 500, the temperature of the biphenyl liquid is stabilized to 245℃~255℃ by an external replenishment medium or internal heating elements. The replenished biphenyl liquid then flows from the discharge port of the replenishment tank 500 into the main evaporator 600 at a controlled flow rate through the replenishment medium pipeline. Final evaporation is completed in the main evaporator 600, and the resulting stable biphenyl vapor is continuously supplied to the biphenyl vapor heating end of the melt spinning equipment through a fifth pipeline. This embodiment effectively solves the problem of severe flash evaporation caused by the direct injection of large amounts of low-temperature biphenyl liquid into the main evaporator 600 in the prior art through the above-described staged gradient heating process.

[0020] More specifically, during implementation, the preheating and replenishment mechanism 200 first stably heats the fresh biphenyl liquid to 80℃~100℃, avoiding direct and intense contact between the low-temperature liquid and the high-temperature steam. Subsequently, the biphenyl vapor returned from the melt spinning equipment undergoes the first stage of direct contact heat exchange in the mixing chamber of the heat exchange tank 100 through a steam jet mechanism, raising the temperature to 150℃~180℃ in a controlled manner. During this stage, most of the heat from the returned steam is directly absorbed. After the condensate and biphenyl liquid are fully mixed, they enter the gas-liquid separator 300. The separated gas and liquid phases enter the shell side and tube side of the liquid phase heat exchanger 400, respectively, to achieve the second stage of indirect heat exchange, precisely raising the liquid phase temperature to 200℃~210℃. At this point, the latent heat of the returned steam is fully recovered. Finally, the material entering the replenishment tank 500 already has a relatively high temperature base, requiring only a small amount of replenishment to reach 245℃~255℃, before entering the main evaporator 600 for stable evaporation. Because the entire heating process adopts a multi-stage, gradual approach, the temperature rise at each stage is strictly controlled, avoiding drastic fluctuations in temperature and pressure. This ensures the temperature stability of the biphenyl vapor supplied to the melt spinning equipment and meets the requirements of high-speed spinning processes for precise temperature control of the spinning box.

[0021] Meanwhile, this application significantly improves the system's thermal efficiency by utilizing the heat from the reflux biphenyl vapor in a tiered manner. In existing technologies, reflux vapor typically undergoes only simple condensation and recovery, resulting in low heat utilization. In this application, however, the reflux vapor first directly contacts the preheated biphenyl liquid in the heat exchange tank 100 for heat exchange, prioritizing the utilization of high-temperature heat. The uncondensed vapor phase enters the shell side of the liquid phase heat exchanger 400, further transferring its latent heat to the liquid phase, achieving secondary utilization of medium-temperature heat. Finally, the condensate and the heated liquid phase enter the make-up tank 500 together, effectively recovering low-grade heat as well. This process not only avoids localized overheating and cracking of biphenyl caused by excessively rapid heating rates but also significantly reduces overall energy consumption compared to existing technologies.

[0022] In one embodiment, the preheating and replenishing mechanism 200 heats the biphenyl solution to 85°C, the outlet temperature of the mixing chamber of the heat exchange tank 100 is controlled at 162°C, the tube-side outlet temperature of the liquid phase heat exchanger 400 reaches 204°C, and the outlet temperature of the replenishing tank 500 stabilizes at 250°C. After 72 hours of system operation, the temperature fluctuation of the spinning box is less than ±0.8°C. In another embodiment, the preheating and replenishing mechanism 200 heats the biphenyl solution to 96°C, the outlet temperature of the mixing chamber of the heat exchange tank 100 is controlled at 172°C, the tube-side outlet temperature of the liquid phase heat exchanger 400 reaches 207°C, and the outlet temperature of the replenishing tank 500 stabilizes at 248°C. Under higher spinning speed conditions, the biphenyl vapor outlet pressure fluctuation is less than ±0.015 MPa, verifying the stability and adaptability of the device within different temperature parameter ranges.

[0023] As can be seen from the above embodiments, the combined structure of heat exchange tank 100 (steam jet mixing), gas-liquid separator 300 (phase separation), liquid phase heat exchanger 400 (shell-tube staged heat exchange), and replenishment tank 500 (buffer replenishment) adopted in this application realizes full-process gradient control of biphenyl liquid from low-temperature replenishment to high-temperature steam supply. It makes full use of the waste heat of the return steam and avoids flash evaporation and local overheating. Thus, while ensuring the stability of melt spinning temperature, it significantly reduces energy consumption and solves the technical problems of large temperature fluctuations and serious energy waste that have long existed in the prior art.

[0024] In an embodiment of the present invention, the preheating and replenishing mechanism 200 includes a preheating and replenishing tank, an electric heating jacket, a stirrer, and a replenishing pump. The electric heating jacket covers the outer wall of the preheating and replenishing tank, the stirrer is disposed inside the preheating and replenishing tank, and the replenishing pump is disposed at the bottom of the preheating and replenishing tank, and the outlet of the replenishing pump forms a biphenyl liquid discharge outlet.

[0025] Specifically, fresh biphenyl solution first enters the preheating replenishment tank. An electric heating jacket tightly covers the outer wall of the preheating replenishment tank, and heat transfer oil or electric heating elements circulate within the jacket to uniformly heat the tank wall. A stirrer is vertically installed at the central axis of the preheating replenishment tank, with its blades extending to the lower part of the tank. During heating, it rotates continuously at a constant speed, creating a stable convective circulation of the biphenyl solution within the tank. The replenishment pump, a high-temperature resistant centrifugal pump or gear pump, is installed at the bottom outlet of the preheating replenishment tank. Its suction inlet is directly connected to the bottom of the tank, and its outlet serves as the biphenyl solution discharge outlet. The heated biphenyl solution is delivered at a controlled flow rate to the mixing chamber of the heat exchange tank 100 through the first pipeline.

[0026] More specifically, in actual operation, the preheating and replenishing mechanism 200 first delivers fresh biphenyl solution to the preheating and replenishing tank. The electric heating jacket continuously applies heat to the tank wall, causing the temperature of the biphenyl solution to gradually rise. Under the action of the stirrer, the biphenyl solution at different heights in the tank undergoes continuous forced convection mixing, avoiding thermal decomposition caused by excessively high local temperatures or uneven heating caused by temperature stratification. When the temperature of the biphenyl solution reaches the set range, the replenishing pump located at the bottom of the tank starts, sending the biphenyl solution into the mixing chamber through the first pipeline at a flow rate matching the heating load of the melt spinning equipment. At this time, high-temperature biphenyl vapor returning from the melt spinning equipment is sprayed upward from the bottom wall of the mixing chamber through the steam injection mechanism, directly contacting and exchanging heat with the biphenyl solution whose temperature has been controlled. Since the biphenyl solution entering the mixing chamber has been preheated uniformly to 80℃~100℃, the temperature gradient between the two is greatly reduced, thus avoiding the violent flash evaporation phenomenon that occurs when a large amount of low-temperature liquid suddenly comes into contact with high-temperature steam, and the pressure and temperature fluctuations in the mixing chamber are effectively suppressed.

[0027] This embodiment, through the specific structure of the preheating and replenishment mechanism 200, solves the technical problem of significant fluctuations in steam pressure and temperature caused by the direct injection of low-temperature biphenyl liquid into the main evaporator 600 in the prior art. During implementation, the uniform wall heating provided by the electric heating jacket, combined with the forced convection of the stirrer, ensures the consistency of the temperature field of the biphenyl liquid before entering the subsequent staged heating units. The arrangement of the replenishment pump at the bottom of the tank facilitates the extraction of the most temperature-stable lower layer liquid and allows for complete evacuation of the system during shutdown, reducing residue. Actual operation verification shows that this structure makes the staged heating process of the subsequent heat exchange tank 100, gas-liquid separator 300, and liquid phase heat exchanger 400 more stable, and the heat of the return steam is utilized efficiently in stages, resulting in an overall thermal efficiency increase of approximately 18% to 22% compared to the existing direct injection method.

[0028] In one specific embodiment, the preheating and replenishing mechanism 200 heats and stably controls the biphenyl liquid at 82℃~88℃, the stirrer speed is maintained at 210r / min, and the replenishing pump flow rate is set to 1.15 times the heating load of the spinning equipment per hour. After the system runs continuously for 96 hours, the temperature fluctuation of the steam at the outlet of the main evaporator 600 is less than ±1.2℃, and the content of biphenyl cracking byproducts is reduced by 47% compared with the prior art.

[0029] In another specific embodiment, the preheating and replenishing mechanism 200 heats and stably controls the biphenyl solution at 93℃~98℃, the stirrer speed is maintained at 245r / min, and the replenishing pump adopts frequency conversion control to adapt to the flow requirements under different spinning speeds. Under higher production conditions, the gas-liquid two-phase temperature gradient at the outlet of the mixing chamber is maintained at 165℃~175℃, and the system pressure fluctuation is less than ±0.012MPa, further verifying the effectiveness of the preheating and replenishing mechanism 200 in temperature stability and preventing local overheating in different temperature ranges.

[0030] This embodiment further achieves precise preheating and uniform delivery of the replenishing biphenyl solution through a combination structure of a preheating replenishment tank, an electric heating jacket, a stirrer, and a tank bottom replenishment pump. This controls the liquid temperature entering the mixing chamber from the source, avoids flash evaporation and local overheating, significantly improves the temperature uniformity of biphenyl vapor heating and the system's operational stability during melt spinning, and reduces energy consumption.

[0031] In an embodiment of the present invention, the steam injection mechanism includes a plurality of steam diffusion nozzles, and the nozzles of the plurality of steam diffusion nozzles are all arranged vertically upward.

[0032] Specifically, the replenishment pump in the preheating replenishment mechanism 200 connects its outlet biphenyl liquid discharge port to the mixing chamber through a first pipeline, allowing the biphenyl liquid, whose temperature has been controlled at 80℃~100℃, to be fed into the mixing chamber through the first pipeline to form a certain liquid level. High-temperature biphenyl vapor returning from the melt spinning equipment enters the steam diffusion nozzle and is uniformly sprayed out in the form of fine bubbles from the vertically upward nozzles of each nozzle. It slowly rises from the bottom of the mixing chamber, passing through the liquid phase, and undergoes sufficient direct contact and heat exchange with the liquid phase during its ascent. Afterwards, the gas-liquid mixture is sent from the outlet of the mixing chamber to the gas-liquid separator 300 through a second pipeline.

[0033] More specifically, in actual operation, the preheating and replenishing mechanism 200 first heats the biphenyl solution to a set temperature and then steadily delivers it into the mixing chamber by a replenishing pump, maintaining the liquid level at a certain height above the nozzle of the vapor diffusion nozzle. Subsequently, the recirculated high-temperature biphenyl vapor enters multiple vapor diffusion nozzles, each with its nozzle vertically upward-facing, dispersing the vapor into a large number of fine bubbles with controllable diameters, which are then uniformly released from the bottom of the mixing chamber. These fine bubbles rise slowly and vertically under buoyancy, passing through the entire liquid phase layer. During this process, a large interfacial area is formed between the bubbles and the surrounding biphenyl solution, and heat is efficiently transferred through the gas-liquid interface via convection and condensation, causing the biphenyl solution temperature to rise steadily to 150℃~180℃. Because the bubbles are evenly dispersed and rise along a stable path, violent boiling in local high-temperature areas is avoided. The pressure and temperature fields in the mixing chamber remain highly uniform. The gas-liquid mixture then enters the gas-liquid separator 300 to achieve phase separation. The gas phase enters the shell side of the liquid phase heat exchanger 400 to continue releasing latent heat, while the liquid phase enters the tube side and is further heated to 200℃~210℃. Finally, after being buffered to 245℃~255℃ by the heat replenishment tank 500, it enters the main evaporator 600 for stable evaporation.

[0034] This embodiment, through the specific structure of the aforementioned steam injection mechanism, solves the technical problem in the prior art where the direct injection of a large amount of low-temperature biphenyl liquid into the main evaporator 600 leads to severe flashing, significant fluctuations in steam pressure and temperature. During implementation, multiple steam diffusion nozzles disperse the return steam into fine bubbles that pass through the liquid phase from the bottom upwards, transforming the heat transfer process from a violent, one-time contact to a gradual, multi-interface contact. This significantly reduces the instantaneous temperature difference and avoids pressure disturbances caused by flashing. Simultaneously, this structure fully utilizes the sensible and latent heat of the return steam to perform a first-stage gradient temperature increase on the preheated biphenyl liquid. Together with the second-stage indirect heat exchange in the subsequent liquid phase heat exchanger 400 and the third-stage buffer in the make-up heat tank 500, it forms a complete temperature gradient control system. This significantly improves the temperature stability of the biphenyl steam supplied to the melt spinning equipment, increasing the overall system thermal efficiency by approximately 20% compared to the prior art.

[0035] In one specific embodiment, the steam injection mechanism employs 12 steam diffusion nozzles evenly distributed on the bottom wall of the mixing chamber, each nozzle having a nozzle diameter of 1.2 mm. The outlet temperature of the preheating and replenishing liquid mechanism 200 is controlled at 83°C to 87°C. After the reflux steam passes through the liquid phase in the form of fine bubbles, the outlet temperature of the mixing chamber stabilizes at 158°C to 163°C. The system operates continuously for 120 hours, and the outlet steam temperature fluctuation of the main evaporator 600 is less than ±0.9°C. The content of biphenyl pyrolysis products is reduced by 52% compared to the prior art.

[0036] In another specific embodiment, the steam jetting mechanism uses 18 steam diffusion nozzles with a nozzle diameter of 0.9 mm. The outlet temperature of the preheating and replenishing liquid mechanism 200 is controlled at 94℃~98℃. The outlet temperature of the mixing chamber after the bubbles pass through the liquid phase is stable at 169℃~174℃. Under higher spinning speed conditions, the system pressure fluctuation is less than ±0.011 MPa, further verifying the device's adaptability to temperature uniformity and prevention of local overheating under different nozzle numbers and orifice parameters.

[0037] As can be seen from the above embodiments, this embodiment further employs a steam diffusion nozzle with multiple vertically upward spray holes, which allows the recirculated biphenyl vapor to systematically pass through the liquid phase from the bottom of the mixing chamber in the form of fine bubbles. This achieves the dispersion and gradual evolution of the heat transfer process, fundamentally eliminating the problems of flash evaporation and drastic temperature fluctuations in the prior art. At the same time, it improves the cascade utilization efficiency of the recirculated steam heat, providing a stable temperature and low energy consumption biphenyl vapor supply for the melt spinning process.

[0038] In an embodiment of the present invention, the liquid phase heat exchanger 400 is a shell-and-tube heat exchanger, and a non-condensable gas discharge pipeline is provided at the top of the shell side of the shell-and-tube heat exchanger.

[0039] Specifically, the replenishment pump in the preheating replenishment mechanism 200 delivers biphenyl liquid, with its temperature controlled at 80℃~100℃, into the mixing chamber of the heat exchange tank 100 via the first pipeline. Multiple steam diffusion nozzles on the bottom wall of the mixing chamber, with vertically upward-facing nozzles, cause the return steam to form fine bubbles that rise upward through the liquid phase. The heat-exchanged gas-liquid mixture enters the gas-liquid separator 300 via the second pipeline to achieve phase separation. The separated gas phase enters the shell side of the shell-and-tube heat exchanger, while the liquid phase enters the tube side. Inside the shell-and-tube heat exchanger, the shell-side gas phase condenses on the outer surface of the tube bundle, releasing latent heat. This heat is transferred through the tube wall to the biphenyl liquid flowing inside the tube side, raising the temperature of the biphenyl liquid at the tube side outlet to 200℃~210℃. The non-condensable gas discharge pipeline at the top of the shell side continuously discharges the non-condensable gas accumulated at the highest point of the shell side, preventing it from forming a covering layer on the heat exchange surface.

[0040] More specifically, during operation, gaseous biphenyl vapor from the gas-liquid separator 300 enters the shell side of the shell-and-tube heat exchanger through the shell-side inlet, flows downwards along the outer side of the tube bundle and gradually condenses. The condensate collects along the tube wall and is discharged from the shell-side condensate outlet. Simultaneously, the biphenyl liquid in the tube side enters through the tube-side inlet, flows turbulently within the tubes, fully absorbs the heat transferred from the tube wall, and then flows out from the tube-side outlet. During this period, if trace amounts of non-condensable gases carried in the return steam or residual air from the system enter the shell side, these gases, due to their lower density, will gradually rise and accumulate in the top space of the shell side. They are discharged at a controlled flow rate through the non-condensable gas discharge pipe located at the top of the shell side, preventing the formation of a thermally resistive boundary layer on the surface of the condensing tube bundle. The non-condensable gas discharge pipe is typically connected to a regulating valve and a condensate recovery unit to ensure that the discharge process does not affect the shell-side pressure balance. Simultaneously, a small amount of accompanying steam is condensed and recovered again and returned to the make-up heat tank 500. This process maintains the overall heat transfer coefficient of the shell-and-tube heat exchanger at a high level, and the tube outlet temperature can be precisely stabilized at 200℃~210℃, providing uniform inlet conditions for the subsequent heating tank 500 to heat the biphenyl solution to 245℃~255℃ and for it to enter the main evaporator 600 for stable evaporation.

[0041] This embodiment, through the aforementioned shell-and-tube heat exchanger and its shell-side top non-condensable gas discharge pipe structure, solves the technical problems in the prior art, such as energy waste due to ineffective utilization of reflux steam heat and low heat transfer efficiency, local overheating and cracking caused by excessively rapid heating rates, and steam temperature fluctuations. In implementation, the shell-and-tube heat exchanger indirectly exchanges the latent heat of vapor phase condensation with the liquid phase heating process in separate chambers. Combined with the aforementioned preheating and replenishment mechanism 200 and the steam injection mechanism forming a stepped heating path, the temperature rise of the biphenyl liquid is controllable in stages. The non-condensable gas discharge pipe at the top of the shell side maintains a high heat transfer coefficient on the condensation side by timely removing accumulated gas, avoiding a decrease in heat exchange efficiency and temperature instability caused by increased thermal resistance. This allows for more thorough classification and utilization of reflux steam heat, significantly improving overall thermal efficiency compared to the prior art, while ensuring the stability of the biphenyl steam pressure and temperature supplied to the melt spinning equipment.

[0042] In one specific embodiment, the liquid phase heat exchanger 400 adopts a shell-and-tube structure. The diameter of the non-condensable gas discharge pipe at the top of the shell side is DN15, and the discharge flow rate is controlled at 0.8 to 1.2 kg per hour. The outlet temperature of the preheating and replenishing liquid mechanism 200 is 82°C to 87°C. The outlet temperature of the mixing chamber after the bubbles of the steam injection mechanism pass through the liquid phase is 157°C to 163°C. The tube-side outlet temperature of the shell-and-tube heat exchanger is stable at 203°C to 206°C. After the system has been running continuously for 110 hours, the fluctuation range of the steam temperature at the outlet of the main evaporator 600 is less than ±0.7°C, and the content of biphenyl cracking by-products is reduced by 54% compared with the prior art.

[0043] In another specific embodiment, the liquid phase heat exchanger 400 is still a shell-and-tube heat exchanger. The diameter of the non-condensable gas discharge pipe at the top of the shell side is DN20, and the discharge flow rate is controlled at 1.1 to 1.5 kg per hour. The outlet temperature of the preheating and replenishing liquid mechanism 200 is 94℃ to 98℃, the outlet temperature of the mixing chamber is 170℃ to 175℃, and the outlet temperature of the tube side is stable at 206℃ to 209℃. Under higher spinning speed conditions, the system pressure fluctuation is less than ±0.009MPa, which further verifies the stability and thermal efficiency improvement effect of this structure within different discharge pipe parameters and temperature ranges.

[0044] As can be seen from the above embodiments, this embodiment further adopts a shell-and-tube heat exchanger and sets a non-condensable gas discharge pipeline at the top of its shell side. By timely discharge of non-condensable gas, a highly efficient phase change heat transfer process is maintained, and the heat of the reflux biphenyl vapor is fully utilized in stages. Temperature fluctuations and local overheating are suppressed from the source, and the uniformity, stability and overall energy efficiency of biphenyl vapor heating during melt spinning are significantly improved.

[0045] In an embodiment of the present invention, the manifold includes a manifold tee and a static mixer. The static mixer is located downstream of the manifold tee. The tube-side outlet liquid flow and the shell-side condensate flow of the liquid phase heat exchanger 400 are combined in the manifold tee and then enter the make-up tank 500 through the static mixer.

[0046] Specifically, the preheating and replenishment mechanism 200 heats the biphenyl solution to 80℃~100℃ and then sends it into the mixing chamber of the heat exchange tank 100 through the first pipeline. Multiple steam diffusion nozzles on the bottom wall of the mixing chamber use vertically upward spray holes to cause the return steam to form fine bubbles that pass upward through the liquid phase and exchange heat to 150℃~180℃. The gas-liquid mixture enters the gas-liquid separator 300 through the second pipeline. The gas phase enters the shell side of the shell-and-tube liquid phase heat exchanger 400, and the liquid phase enters the tube side. The heat exchanged tube side outlet flow is... The temperature is 200℃~210℃, and the shell-side condensate temperature is slightly lower. The two streams enter the manifold tee of the manifold pipeline to achieve initial merging. Then, they flow through the downstream static mixer. In the static mixer, after multiple splitting, merging and radial mixing by the multi-unit internal components, they enter the feed inlet of the heating tank 500 with a uniform temperature field. The heating tank 500 then heats the mixture to 245℃~255℃ and then sends it to the main evaporator 600 for evaporation through the heating medium pipeline.

[0047] More specifically, during operation, the tube-side outlet stream and shell-side condensate stream of the shell-and-tube liquid heat exchanger 400 enter the manifold tee from their respective outlet pipes. After initial convergence within the tee, they immediately enter the downstream static mixer connected in series. The static mixer is equipped with multiple stages of fixed blades or spiral components, causing the two streams with temperature differences to be repeatedly cut, rotated, and recombine during flow, achieving molecular-level uniform mixing and avoiding temperature stratification or localized high-temperature zones. The homogeneous mixed stream enters the replenishment tank 500 in a stable state. The heating elements in the replenishment tank 500 only need to provide a small amount of heat to precisely raise the overall temperature to 245℃~255℃, and then enter the main evaporator 600 for stable phase change evaporation. The generated biphenyl vapor is supplied to the biphenyl vapor heating end of the melt spinning equipment through the fifth pipeline. Due to the combined use of the manifold tee and the static mixer, the two streams have achieved complete temperature and composition homogenization before entering the replenishment tank 500, thus eliminating pressure disturbances in the subsequent evaporation process caused by temperature inhomogeneity.

[0048] This embodiment solves the technical problems of severe flashing, large fluctuations in steam pressure and temperature, and low overall thermal efficiency caused by the direct injection of biphenyl liquid into the main evaporator 600, resulting from the specific structure of the manifold tee and static mixer in the above-mentioned manifold. During implementation, after the manifold tee completes the initial merging, the static mixer uses its internal components to fully mix the higher-temperature stream from the tube side outlet and the lower-temperature stream from the shell side condensate in a radial and axial manner, ensuring that the temperature field of the material entering the make-up tank 500 is uniform. This forms a complete coordination with the aforementioned preheating and make-up liquid mechanism 200, steam injection mechanism, and shell-and-tube liquid phase heat exchanger 400 in a stepped heating process, making the entire heating path controllable in stages, avoiding local overheating and cracking, and significantly improving the utilization rate of reflux steam heat. The overall energy consumption of the system is reduced by about 19% to 23% compared with the prior art, and the temperature stability of the biphenyl steam supplied to the melt spinning equipment is reliably guaranteed.

[0049] In one specific embodiment, the manifold uses a DN50 manifold tee connected in series with an SV-type static mixer downstream. The outlet temperature of the pipe-side liquid is controlled at 202℃~205℃, and the shell-side condensate temperature is 198℃~201℃. The temperature uniformity deviation of the liquid entering the replenishment tank 500 after mixing is less than 1.2℃. The outlet temperature of the preheating replenishment mechanism 200 is 83℃~88℃. After the system has been running continuously for 130 hours, the outlet steam temperature fluctuation of the main evaporator 600 is less than ±0.6℃, and the content of biphenyl cracking byproducts is reduced by 56% compared with the prior art.

[0050] In another specific embodiment, the manifold uses a DN65 manifold tee connected in series with an HX-type static mixer downstream. The outlet temperature of the liquid stream is controlled at 205℃~208℃, and the shell-side condensate temperature is 201℃~204℃. The temperature uniformity deviation of the liquid stream entering the replenishment tank 500 after mixing is less than 0.9℃. The outlet temperature of the preheating replenishment mechanism 200 is 95℃~99℃. Under higher spinning speed conditions, the system pressure fluctuation is less than ±0.008MPa, further verifying the temperature homogenization effect and operational stability of the manifold structure under different pipe diameters and mixer types.

[0051] As can be seen from the above embodiments, this embodiment further adopts a manifold pipeline including a manifold tee and a downstream static mixer. By fully and uniformly mixing the two streams after they merge, the temperature field consistency of the material at the 500 inlet of the reheat tank is ensured, which fundamentally suppresses flash evaporation and temperature fluctuations. At the same time, it improves the system's efficiency in utilizing the heat of the reflux steam in stages, providing a biphenyl steam supply with uniform temperature, stable operation and low energy consumption for the melt spinning process.

[0052] In an embodiment of the present invention, the heating tank 500 includes a tank body, an electric heating and heat tracing layer, a spray device, an upper temperature sensor, a middle temperature sensor, and a lower temperature sensor. The electric heating and heat tracing layer covers the outer wall of the tank body, the spray device is disposed inside the tank body, and the upper temperature sensor, the middle temperature sensor, and the lower temperature sensor are arranged sequentially from top to bottom along the height direction of the tank body.

[0053] In one embodiment, the heat replenishment tank 500 includes a tank body, an electric heating and heat tracing layer, a spray device, an upper temperature sensor, a middle temperature sensor, and a lower temperature sensor. The electric heating and heat tracing layer covers the outer wall of the tank body, and the spray device is disposed inside the tank body. The upper temperature sensor, the middle temperature sensor, and the lower temperature sensor are arranged sequentially from top to bottom along the height direction of the tank body to monitor the temperature at different height positions during the heat replenishment stage.

[0054] Specifically, the heating tank 500 has a vertical cylindrical structure, with an electric heating and heat tracing layer tightly covering the entire height of the outer wall of the tank. Controllable wall heat is provided through a heat-conducting medium or electric heating elements. The spray device is installed below the feed inlet at the top of the tank, with its spray heads arranged in a ring, so that the uniform material from the static mixer is sprayed downward in an atomized or curtain-like form. The upper temperature sensor, middle temperature sensor, and lower temperature sensor are installed sequentially from top to bottom along the height of the tank at different elevations on the inner wall of the tank. The measuring points correspond to the upper, middle, and lower spaces of the tank, respectively, and are used to collect temperature data at each height position during the heating stage in real time and feed it back to the control system.

[0055] More specifically, in actual operation, the biphenyl liquid, heated to 80℃~100℃ by the preheating and replenishment mechanism 200, undergoes the first stage of direct contact heat exchange in the mixing chamber of the heat exchange tank 100 with the high-temperature steam returning from the melt spinning equipment through the vertically upward steam diffusion nozzles to form fine bubbles. After being heated to 150℃~180℃, it enters the gas-liquid separator 300. The separated gas and liquid phases enter the shell-and-tube liquid phase heat exchanger 400 respectively to complete the second stage of indirect heat exchange. The tube-side outlet stream and the shell-side condensate are fully homogenized in the manifold through the manifold tee and static mixer, and then enter the replenishment tank 500 in a uniform state of about 200℃~210℃. The material is first evenly dispersed into fine droplets or films by a spraying device, flowing downwards along the tank's height. During its descent, it mixes thoroughly with the existing high-temperature biphenyl solution inside the tank. Simultaneously, an electrically heated heat tracing layer precisely replenishes heat to the tank walls, gradually raising the overall temperature to 245℃~255℃. During this period, an upper temperature sensor monitors the temperature of the initial spraying area, a middle temperature sensor monitors the temperature of the main mixing area, and a lower temperature sensor monitors the temperature of the outlet area. Together, these three sensors form a temperature profile monitoring system along the height. If any temperature deviation occurs at any location, the control system promptly adjusts the power of the electrically heated heat tracing layer or the feed flow rate to ensure that the temperature field inside the tank remains consistent in both the axial and radial directions, preventing localized overheating or temperature stratification. Subsequently, the biphenyl solution, having reached the required temperature, enters the main evaporator 600 at a stable flow rate through the heat replenishment medium pipeline from the lower discharge port of the replenishment tank 500. Final evaporation is completed in the main evaporator 600, and the resulting biphenyl vapor is continuously supplied to the melt spinning equipment through a fifth pipeline.

[0056] This embodiment solves the technical problems in the prior art caused by the direct injection of a large amount of low-temperature biphenyl liquid into the main evaporator 600, such as violent flash evaporation, large fluctuations in steam pressure and temperature, and local overheating and decomposition due to excessively rapid heating rate, through the specific structure of the above-mentioned heating tank 500. During implementation, the spraying device introduces the uniformly flowing material after confluence into the tank in a dispersed form, increasing the contact area between the liquid phase and the high-temperature medium inside the tank, and promoting rapid and stable mixing. The uniform wall heating provided by the electric heating tracing layer, combined with real-time monitoring by multi-point temperature sensors, achieves precise closed-loop control of the axial temperature gradient during the replenishment stage, keeping the temperature rise process in a controlled and gradual state, avoiding pressure disturbances and biphenyl cracking caused by sudden temperature changes in existing technologies. This structure, together with the aforementioned stepped heat exchange unit (preheating replenishment mechanism 200, steam injection mechanism, shell-and-tube liquid phase heat exchanger 400, and manifold), forms a complete temperature graded control system. It not only makes full use of the waste heat of the return steam, but also minimizes the heat input in the final replenishment stage. The overall thermal efficiency of the system is about 21% to 25% higher than that of existing technologies, while significantly reducing the temperature fluctuation of the biphenyl vapor supplied to the melt spinning equipment, meeting the requirements of high-speed spinning for precise temperature control. Furthermore, by using a replenishment tank 500, which includes a tank body, an electrically heated heat tracing layer, a spray device, and three temperature sensors arranged along the height direction, precise temperature field control and uniform mixing are achieved in the final replenishment stage of biphenyl solution. This eliminates flash evaporation, drastic temperature fluctuations, and local overheating from the source, significantly improving the cascade utilization efficiency of reflux steam heat and the stability and overall energy efficiency of biphenyl steam heating during melt spinning.

[0057] In an embodiment of the present invention, the main evaporator 600 includes a tank body and an electric heating jacket, the electric heating jacket covering the outer wall of the tank body; a buffer distribution plate is provided at the bottom of the main evaporator 600 corresponding to the outlet of the supplementary heating medium pipeline.

[0058] Specifically, the main evaporator 600 is a vertical cylindrical pressure vessel. The electric heating jacket completely covers the lower part of the outer wall of the tank. A buffer distribution plate is horizontally installed at the center of the tank bottom, directly above the outlet of the supplementary heating medium pipeline. Multiple evenly distributed overflow holes and guide grooves are formed on the plate. A biphenyl vapor outlet is located at the top of the tank, connected to the biphenyl vapor heating end of the melt spinning equipment via a fifth pipeline. During operation, the biphenyl liquid, heated to 245℃~255℃ by the supplementary heating tank 500, enters the bottom of the main evaporator 600 at a controlled flow rate through the supplementary heating medium pipeline. It first impacts the buffer distribution plate and then spreads evenly to the liquid phase zone through its overflow holes and guide grooves. The electric heating jacket provides a stable heat flow to the tank wall, maintaining the liquid phase in a saturated evaporation state. The generated steam is output through the top outlet.

[0059] More specifically, in the implementation process, the 245℃~255℃ biphenyl solution from the replenishment tank 500 flows downward along the replenishment medium pipeline, exits from the central pipe at the bottom of the main evaporator 600, and directly enters the central groove of the buffer distribution plate. The buffer distribution plate divides the liquid flow into multiple fine radial liquid films and liquid columns, which slowly overflow to the periphery of the liquid phase zone at the bottom of the tank, allowing the high-temperature liquid phase to fully integrate with the original liquid phase in a large-area, low-impact manner, avoiding sudden changes in local concentration and temperature. Simultaneously, the electric heating jacket operates at a low power to uniformly heat the tank wall, maintaining the temperature of the liquid phase zone stable near the evaporation point. The liquid phase continuously vaporizes to form stable steam that flows upward to the top space of the tank, and is then transported to the melt spinning equipment through the fifth pipeline. Throughout the process, the liquid phase has been preheated through a four-stage gradient heating process involving the preheating and replenishment mechanism 200, the heat exchange tank 100, the liquid phase heat exchanger 400, and the replenishment tank 500. Furthermore, it is uniformly dispersed within the main evaporator 600 via a buffer distribution plate. As a result, the vaporization process is characterized by stable surface evaporation rather than volume flash evaporation, and the pressure and temperature gradient within the tank remain within a very small range.

[0060] This embodiment solves the technical problems of violent flash evaporation, large fluctuations in steam pressure and temperature, local overheating and cracking, and low overall thermal efficiency caused by the direct injection of a large amount of low-temperature biphenyl liquid into the main evaporator 600, through the structure of the electric heating jacket and buffer distribution plate in the main evaporator 600. During implementation, the buffer distribution plate evenly disperses the biphenyl liquid, close to its evaporation temperature, into the liquid phase zone, allowing the newly introduced high-temperature liquid phase to quickly mix with the existing liquid phase in the tank and gradually vaporize, eliminating instantaneous disturbances in temperature and pressure. The gentle wall heating provided by the electric heating jacket further ensures the stability of the evaporation process. This structure, in conjunction with the aforementioned multi-stage gradient heating unit, fully utilizes the heat of the reflux steam, improving the overall thermal efficiency of the system by approximately 21% to 25% compared to existing technologies. Simultaneously, it ensures that the temperature uniformity and pressure stability of the biphenyl steam supplied to the melt spinning equipment meet the precise requirements of high-speed spinning processes.

[0061] In one specific embodiment, the main evaporator 600 uses an electric heating jacket with a power density of 2.8 kW / m², and the buffer distribution plate has 24 overflow holes with a diameter of 4 mm and 8 radial guide grooves. The outlet temperature of the supplementary heating tank 500 is stabilized at 248°C~252°C. After the system has been running continuously for 150 hours, the outlet steam temperature of the main evaporator 600 fluctuates by less than ±0.5°C, the pressure fluctuates by less than ±0.007 MPa, and the content of biphenyl cracking byproducts is reduced by 58% compared with the prior art.

[0062] In another specific embodiment, the electric heating jacket of the main evaporator 600 has a power density of 3.1 kW / m2, and the buffer distribution plate has 32 overflow holes with a diameter of 3 mm and 12 radial guide grooves. The outlet temperature of the supplementary heating tank 500 is stable at 246℃~251℃. Under higher spinning speed conditions, the outlet steam temperature fluctuation is less than ±0.6℃ and the pressure fluctuation is less than ±0.009 MPa, further verifying the supporting effect of this combination on evaporation stability under different heating power and distribution plate structural parameters.

[0063] As can be seen from the above embodiments, this embodiment further sets up a buffer distribution plate at the bottom of the main evaporator 600 and cooperates with an electric heating jacket. By uniformly dispersing the biphenyl liquid, which has been gradually heated to 245℃~255℃, into the liquid phase zone, the final evaporation process is made stable and controllable. This fundamentally eliminates the drastic temperature and pressure fluctuations caused by flash evaporation, while improving the comprehensive utilization rate of the heat of the reflux steam. This provides a biphenyl steam supply with uniform temperature, reliable operation, and low energy consumption for the melt spinning process.

[0064] In an embodiment of the present invention, a first flow regulating valve, a steam filter, and a check valve are sequentially arranged in the fluid passage of the biphenyl vapor reflux pipeline of the melt spinning equipment; a second flow regulating valve is arranged in the fluid passage of the first pipeline, a third flow regulating valve is arranged in the fluid passage of the second pipeline, a fourth flow regulating valve is arranged in the fluid passage of the third pipeline, and a fifth flow regulating valve is arranged in the fluid passage of the heat supply medium pipeline.

[0065] Specifically, the biphenyl vapor reflux pipeline of the melt spinning equipment is connected in series with a first flow regulating valve, a steam filter, and a check valve, and then connects to the steam injection mechanism on the bottom wall of the mixing chamber of heat exchange tank 100. A second flow regulating valve is installed on the first pipeline between the outlet of the preheating replenishment pump of the preheating replenishment mechanism 200 and the inlet of the mixing chamber. A third flow regulating valve is installed on the second pipeline between the outlet of the mixing chamber and the inlet of the gas-liquid separator 300. A fourth flow regulating valve is installed on the third pipeline between the gas phase outlet of the gas-liquid separator 300 and the shell-side inlet of the shell-and-tube liquid phase heat exchanger 400. A fifth flow regulating valve is installed on the replenishment medium pipeline between the discharge port of the replenishment tank 500 and the inlet of the buffer distribution plate of the main evaporator 600. All valves adopt a high-temperature corrosion-resistant structure and are interlocked with temperature and pressure sensors through actuators to achieve independent and precise control of the fluid flow rate in each section.

[0066] More specifically, in the implementation process, the biphenyl vapor returning from the melt spinning equipment first passes through the first flow regulating valve, and the amount of vapor entering the system is adjusted in real time according to the spinning load. It then passes through a steam filter to capture trace solid particles and droplets, and then through a check valve to prevent backflow when the pressure in the mixing chamber exceeds that of the return pipeline. Simultaneously, the second flow regulating valve adjusts the flow rate of the biphenyl liquid supplied to the mixing chamber by the preheating and replenishing mechanism 200 according to the opening of the first flow regulating valve, maintaining the gas-liquid ratio of the liquid phase to the vapor within a set range. This ensures that the fine bubbles ejected from the steam diffusion nozzle can fully penetrate the liquid phase layer to complete the first stage of heat exchange. When the mixed gas and liquid phases pass through the second pipeline, the third flow regulating valve stably controls the flow rate entering the gas-liquid separator 300, preventing drastic changes in the liquid level within the separator. When the separated gas phase passes through the third pipeline, the fourth flow regulating valve precisely matches the shell-side inlet flow rate, ensuring thermal balance between the condensation process and the tube-side heating process within the shell-and-tube heat exchanger. After being uniformly mixed through the manifold, the material enters the make-up heat tank 500 and is heated to 245℃~255℃. The fifth flow control valve then adjusts the flow rate into the buffer distribution plate based on the liquid level signal from the main evaporator 600, ensuring that the high-temperature liquid phase is dispersed into the liquid phase zone at a stable rate. This ultimately achieves evaporation on the inner surface of the main evaporator 600 rather than volume flash evaporation. The interlocking control of each control valve ensures flow matching throughout the entire process, from preheating of the make-up liquid to final steam output, maintaining a smooth temperature and pressure curve.

[0067] This embodiment solves the technical problems in the prior art caused by uncontrollable flow rates, such as direct liquid injection flash evaporation, drastic fluctuations in steam pressure and temperature, insufficient utilization of reflux steam heat, and local overheating and cracking. During implementation, the linkage between the first and second flow control valves stabilizes the heat exchange ratio between the reflux steam and the preheated liquid phase. The steam filter and check valve ensure the purity of the system medium and unidirectional flow, avoiding disturbances caused by impurity accumulation or backflow. The subsequent third, fourth, and fifth flow control valves further refine the flow rate in segments during the separation, heat exchange, and reheating stages. Working in conjunction with the aforementioned stepped heating structure, this transforms a single large temperature difference contact into a multi-stage, gradual process with smaller temperature differences. This keeps the phase change behavior in the mixing chamber, liquid phase heat exchanger 400, and main evaporator 600 stable. The overall system thermal efficiency is increased by approximately 22%–26% compared to the prior art, and the temperature uniformity of the spinning box is significantly improved.

[0068] In one embodiment, the opening of the first flow regulating valve in the reflux pipeline is maintained at 65%–72%, the corresponding flow rate of the second flow regulating valve is 1.8–2.2 tons per hour, and the steam filter has a filtration accuracy of 5 μm. After the system has been running for 120 hours, the temperature fluctuation of the steam at the outlet of the main evaporator (600) is less than ±0.5℃, the pressure fluctuation is less than ±0.006 MPa, and the content of biphenyl cracking byproducts is reduced by 61% compared to the prior art. In another embodiment, the opening of the first flow regulating valve is maintained at 78%–85%, the corresponding flow rate of the second flow regulating valve is 2.5–3.0 tons per hour, the fourth and fifth flow regulating valves are controlled by PID interlocking, and the steam filter has a filtration accuracy of 3 μm. Under higher spinning speed conditions, the outlet steam temperature fluctuation is less than ±0.6℃, and the pressure fluctuation is less than ±0.008 MPa, further verifying the supporting effect of this flow regulation combination on system stability within different flow parameter ranges.

[0069] As can be seen from the above embodiments, this embodiment further sets up multi-point flow regulating valves, steam filters and check valves in key pipelines. Through precise matching of flow rate and purification of the medium throughout the process, the stable and controllable process of biphenyl liquid step heating and evaporation is achieved, fundamentally eliminating the phenomenon of drastic temperature and pressure fluctuations and energy waste. It provides a high-quality biphenyl steam supply with uniform temperature, reliable operation and low energy consumption for melt spinning process.

[0070] Please continue reading. Figure 1 and Figure 2 And see Figure 3 In an embodiment of the present invention, the biphenyl addition device for melt spinning further includes a PLC control system. The PLC control system is electrically connected to the first flow regulating valve, the second flow regulating valve, the third flow regulating valve, the fourth flow regulating valve, the fifth flow regulating valve, and the upper, middle, and lower temperature sensors of the heating tank 500, respectively. The PLC control system is used to execute the following control logic: Based on the temperature feedback from the first temperature sensor installed in the heat exchange tank 100, the opening of the third flow regulating valve installed in the fluid passage of the second pipeline is adjusted to control the heating rate of the first gradient heating stage, so that the biphenyl liquid in the heat exchange tank 100 is heated to 150℃~180℃. Based on the temperature feedback from the second temperature sensor located at the tube outlet of the liquid phase heat exchanger 400, the opening of the fifth flow regulating valve located in the fluid passage of the fourth pipeline and the fourth flow regulating valve located in the fluid passage of the third pipeline are adjusted to control the heating rate of the second gradient heating stage, so that the biphenyl liquid at the tube outlet of the liquid phase heat exchanger 400 is heated to 200℃~210℃. Based on the temperature feedback from the upper, middle and lower temperature sensors of the heating tank 500, the opening of the fifth flow regulating valve installed on the fluid passage of the heating medium pipeline is adjusted to control the heating rate of the third gradient heating stage and maintain the outlet temperature of the heating tank 500 at 245℃~255℃. Based on the temperature feedback from the third temperature sensor installed in the main evaporator 600, the opening of the first flow regulating valve on the fluid passage of the biphenyl vapor reflux pipeline installed in the melt spinning equipment is adjusted to control the heating rate of the fourth gradient heating stage, so that the biphenyl liquid in the main evaporator 600 evaporates and is maintained at 245℃~255℃. The heating rates of the first, second, third, and fourth gradient heating stages are controlled within their respective preset ranges.

[0071] Specifically, the first temperature sensor is installed in the liquid phase zone of the mixing chamber in heat exchanger 100, the second temperature sensor is installed on the outlet pipe of the tube side of liquid phase heat exchanger 400, and the third temperature sensor is installed in the middle of the liquid phase zone of main evaporator 600. All three sensors transmit real-time temperature signals to the PLC control system. After receiving the signals, the PLC control system outputs 4mA to 20mA analog signals to the actuators of the corresponding flow regulating valves according to the preset PID algorithm, thereby changing the valve opening and precisely controlling the flow rate of each pipeline.

[0072] More specifically, in actual operation, the preheating and replenishing mechanism 200 first heats the biphenyl solution to 80℃~100℃ and sends it into the mixing chamber through the first pipeline. At this time, the PLC control system continuously adjusts the opening of the third flow regulating valve on the second pipeline based on the temperature value fed back by the first temperature sensor in the heat exchange tank 100, strictly limiting the heating rate of the first gradient heating stage to a preset range of 1.2~1.8℃ per minute. This ensures that the return steam from the steam injection mechanism fully contacts and exchanges heat with the liquid phase, and the material temperature in the mixing chamber steadily reaches 150℃~180℃ before entering the gas-liquid separator 300. Subsequently, based on the temperature data collected by the second temperature sensor at the tube outlet of the liquid phase heat exchanger 400, the PLC control system simultaneously adjusts the opening of the fifth flow regulating valve on the fourth pipeline and the fourth flow regulating valve on the third pipeline, controlling the heating rate of the second gradient heating stage within the range of 0.8~1.3℃ per minute, ensuring that the material at the tube outlet accurately reaches 200℃~210℃ before entering the manifold. After the homogeneous material flows into the supplementary heating tank 500, the PLC control system collects the differential signals from the temperature sensors at the top, middle, and bottom of the supplementary heating tank 500 in real time. By adjusting the opening of the fifth flow regulating valve on the supplementary heating medium pipeline, the heating rate of the third gradient heating stage is maintained within the range of 0.5~0.9℃ per minute, while ensuring that the axial temperature gradient inside the tank is less than 2.5℃, and the outlet temperature is stably maintained at 245℃~255℃. Finally, the material entering the main evaporator 600 is uniformly dispersed under the action of the buffer distribution plate. Based on the feedback value from the third temperature sensor in the main evaporator 600, the PLC control system fine-tunes the opening of the first flow regulating valve on the return pipeline to control the evaporation rate of the fourth gradient heating stage within the preset range, achieving stable vaporization of the liquid phase in the main evaporator 600 at 245℃~255℃. The steam is then stably supplied to the melt spinning equipment through the fifth pipeline.

[0073] This embodiment solves the technical problems in the prior art caused by direct injection of low-temperature biphenyl liquid leading to violent flash evaporation, large fluctuations in steam pressure and temperature, excessively rapid heating rate causing local overheating and cracking, and low thermal efficiency caused by the lack of classified utilization of reflux steam heat through the precise rate control of the four gradient heating stages of the above-mentioned PLC control system. In the implementation process, in the first gradient stage, the outlet flow of heat exchange tank 100 is regulated by the third flow regulating valve to maintain a gentle temperature rise curve in the contact heat exchange process between reflux steam and preheated liquid phase, avoiding instantaneous large-scale vaporization; in the second gradient stage, the coordinated regulation of the fourth and fifth flow regulating valves ensures the stability of latent heat transfer in liquid phase heat exchanger 400 and maintains a high heat transfer coefficient on the tube bundle surface; in the third gradient stage, the closed-loop action of the three-point temperature sensor and the fifth flow regulating valve eliminates temperature stratification in the make-up heat tank 500, ensuring that the material enters the main evaporator 600 in a uniform state; in the fourth gradient stage, the dynamic adjustment of the return flow by the first flow regulating valve ensures that the evaporation load of the main evaporator 600 is precisely matched with the spinning requirements. The aforementioned phased rate control makes the overall heating process of the system present a continuous and predictable gradient change, and the sensible heat and latent heat of the reflux steam are fully absorbed step by step. The system thermal efficiency is improved by about 22% to 26% compared with the existing technology, and the temperature fluctuation of the spinning box is kept within ±0.5℃ for a long time.

[0074] In one specific embodiment, the PLC control system sets the first gradient heating rate to 1.5℃ / min, the second gradient heating rate to 1.0℃ / min, the third gradient heating rate to 0.7℃ / min, and the fourth gradient evaporation rate to a steam flow rate of 450kg / h. The first temperature sensor in heat exchange tank 100 displays 162℃, the second temperature sensor at the tube outlet of liquid phase heat exchanger 400 displays 205℃, the maximum deviation of the three-point temperature sensor in make-up heat tank 500 is 1.8℃, and the third temperature sensor in main evaporator 600 displays 249℃. After the system runs continuously for 168 hours, the biphenyl vapor outlet temperature fluctuation is less than ±0.4℃, the pressure fluctuation is less than ±0.006MPa, and the content of cracking byproducts is reduced by 61% compared with the prior art.

[0075] In another specific embodiment, the PLC control system sets the first gradient heating rate to 1.3℃ / min, the second gradient heating rate to 0.9℃ / min, the third gradient heating rate to 0.6℃ / min, and the fourth gradient evaporation rate to a steam flow rate of 620kg / h. The outlet temperature of heat exchanger 100 is stable at 173℃, the tube-side outlet temperature of liquid phase heat exchanger 400 is stable at 207℃, and the maximum deviation of the three-point temperature sensor of the supplementary heating tank 500 is 1.2℃. Under higher spinning speed conditions, the outlet steam temperature fluctuation of the main evaporator 600 is less than ±0.5℃, and the pressure fluctuation is less than ±0.008MPa, further verifying the stability and adaptability of the control logic under different preset rate values ​​and load conditions.

[0076] As can be seen from the above embodiments, this embodiment further introduces a PLC control system to perform closed-loop precise control of the heating rate of the four gradient heating stages. Through multi-sensor feedback and multi-valve linkage, it suppresses drastic fluctuations in temperature and pressure from the source of the process, realizes the graded and efficient utilization of the heat of the reflux steam, significantly improves the temperature uniformity, stability and overall energy efficiency of the biphenyl steam heating in the melt spinning process, and meets the requirements of high-speed spinning for precise temperature control.

[0077] Please continue reading. Figure 1 and Figure 2 And see Figure 3 In an embodiment of the present invention, the PLC control system is also electrically connected to a multi-point temperature monitoring module disposed within the melt spinning chamber of the melt spinning equipment, and is used to execute the following control logic: When a temperature fluctuation at any point in the melt spinning box is detected to exceed ±1.5℃, the opening of the first flow regulating valve and the fifth flow regulating valve is reduced until the temperature fluctuation at that point returns to within ±1.5℃.

[0078] Specifically, the PLC control system is hardwired to a multi-point temperature monitoring module inside the melt spinning box via an additional communication module. This monitoring module consists of at least eight thermocouples or platinum resistance sensors, arranged at different heights and radial positions within the spinning box. It collects temperature field data within the box in real time and transmits it to the PLC control system input port in the form of 4mA to 20mA signals. Based on the original four-gradient heating stage control logic, the PLC control system adds an independent monitoring loop program, scanning the multi-point temperature data every 0.5 seconds. When the temperature fluctuation at any monitoring point exceeds ±1.5℃, it immediately outputs a control command to simultaneously reduce the opening of the first and fifth flow regulating valves until the temperature fluctuation at all monitoring points returns to within ±1.5℃.

[0079] More specifically, during actual operation, the multi-point temperature monitoring module inside the melt spinning box continuously collects temperature values ​​at various key locations within the box and sends them to the PLC control system. When a temperature fluctuation at a certain location exceeds ±1.5℃ due to instantaneous heat load changes or slight disturbances in upstream steam parameters, the PLC control system first determines that the fluctuation duration exceeds a preset threshold. Subsequently, it proportionally and synchronously reduces the opening of the first flow regulating valve on the return pipeline to reduce the amount of return steam entering the steam injection mechanism. At the same time, it reduces the opening of the fifth flow regulating valve on the make-up heating medium pipeline to reduce the flow rate of make-up biphenyl liquid entering the main evaporator 600. This adjustment directly affects the evaporation load in the fourth gradient heating stage, causing the biphenyl steam flow rate and temperature output from the main evaporator 600 to tend to be more gradual, thereby ensuring a stable supply to the heating end of the spinning box through the fifth pipeline. As the temperature fluctuations in the chamber gradually subside to within ±1.5℃, the PLC control system then gradually restores the opening of the two valves according to the set step size. It cross-verifies the feedback values ​​with the first temperature sensor of the heat exchange tank 100, the second temperature sensor at the tube outlet of the liquid phase heat exchanger 400, and the temperature sensor of the replenishment tank 500 to ensure that the heating rate of the four gradient heating stages remains within their respective preset ranges. The entire adjustment process achieves overshoot-free transition through PID parameter optimization, avoiding disturbances to the operating status of the upstream preheating replenishment mechanism 200 and the liquid phase heat exchanger 400.

[0080] This embodiment, through the connection and additional control logic between the aforementioned PLC control system and the multi-point temperature monitoring module of the melt spinning chamber, solves the technical problems in the prior art such as insufficient temperature stability of the melt spinning chamber, susceptibility to biphenyl vapor fluctuations leading to a decline in spun product quality, and slow response of the overall system to downstream load changes. During implementation, the real-time multi-location feedback provided by the multi-point temperature monitoring module allows the PLC control system to detect minute fluctuations at any point in the chamber early on. By reducing the opening of the first and fifth flow regulating valves in a coordinated manner, the input rate of the heat carrier entering the main evaporator 600 is directly reduced, making the evaporation process more stable and quickly pulling the chamber temperature fluctuations back to the target range. This logic, together with the rate control of the four gradient heating stages mentioned above, forms a double-layer closed-loop protection, suppressing the transmission of pressure disturbances caused by flash evaporation downstream from the source. It also improves the system's adaptability to varying operating conditions in the spinning process, ensuring that the overall temperature of the spinning chamber remains stable within ±0.8℃ of the process setpoint over a long period, significantly reducing fiber breakage rate and product quality dispersion caused by temperature fluctuations.

[0081] In one specific implementation, the PLC control system sets the scanning cycle of the multi-point temperature monitoring module to 0.5 seconds and the fluctuation threshold to ±1.5℃. When the temperature fluctuation at a certain point in the spinning chamber reaches ±1.7℃, the opening of the first flow regulating valve decreases from 65% to 52%, and the opening of the fifth flow regulating valve decreases from 58% to 47%. After 45 seconds, the fluctuation recovers to within ±1.2℃. After the system runs continuously for 200 hours, the temperature fluctuation of all monitoring points in the spinning chamber is less than ±0.7℃, and the fiber quality qualification rate is 17% higher than that of the prior art.

[0082] In another specific implementation, the PLC control system optimizes the fluctuation recovery target to ±1.0℃. When the temperature fluctuation at a certain point in the chamber reaches ±1.6℃, the opening of the first flow regulating valve decreases from 72% to 55%, and the opening of the fifth flow regulating valve decreases from 61% to 46%. After 38 seconds, the fluctuation recovers to within ±0.9℃. Under higher spinning speed conditions, the temperature fluctuation of the chamber is less than ±0.6℃, further verifying the support effect of this control logic on the temperature stability of the spinning process under different initial valve openings and load conditions.

[0083] As can be seen from the above embodiments, this embodiment further achieves active and rapid suppression of temperature fluctuations in the downstream spinning box by electrically connecting the PLC control system with the multi-point temperature monitoring module of the melt spinning box and by adding valve linkage control logic. By precisely adjusting the opening of the first flow regulating valve and the fifth flow regulating valve, the entire biphenyl steam supply system is dynamically matched with the actual spinning heat load, fundamentally eliminating the problems of drastic temperature fluctuations, energy waste and unstable product quality in the prior art, and providing a high-precision heat carrier supply with uniform temperature, rapid response and reliable operation for the melt spinning process.

[0084] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A biphenyl addition device for melt spinning, characterized in that, include: A heat exchange tank, wherein a mixing chamber is provided inside the heat exchange tank, and a steam injection mechanism is provided on the bottom wall of the mixing chamber; A preheating and replenishing mechanism, wherein the biphenyl liquid outlet of the preheating and replenishing mechanism is connected to the mixing chamber through a first pipeline; A gas-liquid separator, wherein the inlet of the gas-liquid separator is connected to the outlet of the mixing chamber via a second pipeline; The liquid phase heat exchanger has a gas phase outlet of the gas-liquid separator connected to the shell-side inlet of the liquid phase heat exchanger via a third pipeline, and a liquid phase outlet of the gas-liquid separator connected to the tube-side inlet of the liquid phase heat exchanger via a fourth pipeline. The heat replenishment tank is connected to the inlet of the heat replenishment tank via a manifold. The tube-side outlet of the liquid phase heat exchanger and the shell-side condensate outlet of the liquid phase heat exchanger are connected to the inlet of the heat replenishment tank. The main evaporator has its discharge port connected to the feed port of the main evaporator via a heating medium pipeline, and its biphenyl vapor outlet is connected to an external melt spinning device via a fifth pipeline. The biphenyl vapor reflux pipe of the melt spinning equipment is connected to the steam injection mechanism, which is used to allow the biphenyl vapor refluxed from the melt spinning equipment to enter the mixing chamber and exchange heat with the biphenyl liquid supplied to the mixing chamber by the preheating and replenishing mechanism. The preheating and replenishing mechanism is used to heat the biphenyl solution to 80℃~100℃, the heat exchange tank is used to raise the temperature of the biphenyl solution to 150℃~180℃, the liquid phase heat exchanger is used to raise the temperature of the biphenyl solution to 200℃~210℃, the replenishing tank is used to replenish the temperature of the biphenyl solution to 245℃~255℃, and the main evaporator is used to supply the biphenyl vapor from the biphenyl vapor outlet of the main evaporator to the biphenyl vapor heating end of the external melt spinning equipment through the fifth pipeline.

2. The biphenyl addition device for melt spinning as described in claim 1, characterized in that, The preheating and replenishing mechanism includes a preheating and replenishing tank, an electric heating jacket, a stirrer, and a replenishing pump. The electric heating jacket covers the outer wall of the preheating and replenishing tank, the stirrer is located inside the preheating and replenishing tank, the replenishing pump is located at the bottom of the preheating and replenishing tank, and the outlet of the replenishing pump forms the outlet of the biphenyl solution.

3. The biphenyl addition device for melt spinning as described in claim 1, characterized in that, The steam injection mechanism includes multiple steam diffusion nozzles, and the nozzle holes of the multiple steam diffusion nozzles are all arranged vertically upwards.

4. The biphenyl addition device for melt spinning as described in claim 1, characterized in that, The liquid phase heat exchanger is a shell-and-tube heat exchanger, and a non-condensable gas discharge pipeline is provided at the top of the shell side of the shell-and-tube heat exchanger.

5. The biphenyl addition device for melt spinning as described in claim 1, characterized in that, The manifold includes a manifold tee and a static mixer. The static mixer is located downstream of the manifold tee. The tube-side outlet liquid flow and the shell-side condensate flow of the liquid phase heat exchanger are combined in the manifold tee and then enter the make-up tank through the static mixer.

6. The biphenyl addition device for melt spinning as described in claim 1, characterized in that, The heating tank includes a tank body, an electric heating and heat tracing layer, a spray device, an upper temperature sensor, a middle temperature sensor, and a lower temperature sensor. The electric heating and heat tracing layer covers the outer wall of the tank body, and the spray device is disposed inside the tank body. The upper temperature sensor, the middle temperature sensor, and the lower temperature sensor are arranged sequentially from top to bottom along the height direction of the tank body.

7. The biphenyl addition device for melt spinning as described in claim 1, characterized in that, The main evaporator includes a tank body and an electric heating jacket, the electric heating jacket covering the outer wall of the tank body; a buffer distribution plate is provided at the bottom of the main evaporator corresponding to the outlet of the heating medium pipeline.

8. The biphenyl addition device for melt spinning as described in any one of claims 1 to 7, characterized in that, The fluid passage of the biphenyl vapor reflux pipeline of the melt spinning equipment is sequentially equipped with a first flow regulating valve, a steam filter, and a check valve; the fluid passage of the first pipeline is equipped with a second flow regulating valve, the fluid passage of the second pipeline is equipped with a third flow regulating valve, the fluid passage of the third pipeline is equipped with a fourth flow regulating valve, and the fluid passage of the heating medium pipeline is equipped with a fifth flow regulating valve.

9. The biphenyl addition device for melt spinning as described in claim 8, characterized in that, The biphenyl addition device for melt spinning also includes a PLC control system. The PLC control system is electrically connected to the first flow regulating valve, the second flow regulating valve, the third flow regulating valve, the fourth flow regulating valve, the fifth flow regulating valve, and the upper, middle, and lower temperature sensors of the replenishment tank. The PLC control system is used to execute the following control logic: Based on the temperature feedback from the first temperature sensor installed in the heat exchange tank, the opening of the third flow regulating valve installed in the fluid passage of the second pipeline is adjusted to control the heating rate of the first gradient heating stage, so that the biphenyl liquid in the heat exchange tank is heated to 150℃~180℃. Based on the temperature feedback from the second temperature sensor located at the tube outlet of the liquid phase heat exchanger, the opening of the fifth flow regulating valve located in the fluid passage of the fourth pipeline and the fourth flow regulating valve located in the fluid passage of the third pipeline are adjusted to control the heating rate of the second gradient heating stage, so that the biphenyl liquid at the tube outlet of the liquid phase heat exchanger is heated to 200℃~210℃. Based on the temperatures fed back by the upper, middle, and lower temperature sensors of the heating tank, the opening of the fifth flow regulating valve installed on the fluid passage of the heating medium pipeline is adjusted to control the heating rate of the third gradient heating stage and maintain the outlet temperature of the heating tank at 245℃~255℃. Based on the temperature feedback from the third temperature sensor installed in the main evaporator, the opening of the first flow regulating valve on the fluid passage of the biphenyl vapor reflux pipeline installed in the melt spinning equipment is adjusted to control the heating rate of the fourth gradient heating stage, so that the biphenyl liquid in the main evaporator evaporates and is maintained at 245℃~255℃. The heating rates of the first, second, third, and fourth gradient heating stages are controlled within their respective preset ranges.

10. The biphenyl addition device for melt spinning as described in claim 9, characterized in that, The PLC control system is also electrically connected to a multi-point temperature monitoring module located inside the melt spinning chamber of the melt spinning equipment, and is used to execute the following control logic: When the temperature fluctuation at any point in the melt spinning box exceeds ±1.5℃, the opening of the first flow regulating valve and the fifth flow regulating valve is reduced until the temperature fluctuation at that point returns to within ±1.5℃.

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