Hot air circulation drying oven and control method thereof

Abstract

The invention discloses a hot air circulation drying oven and a control method thereof, and relates to the technical field of hot air circulation drying, the hot air circulation drying oven comprises an oven body, a heating circulation device and a stretching turn-back device, a drying cavity is formed in the oven body, and a wire inlet and a wire outlet are formed in the two ends of the drying cavity; the heating circulation device is arranged on the drying oven, the heating circulation device is communicated with the drying cavity, and the heating circulation device conducts heating circulation on the drying cavity; the hot air circulation drying oven comprises a drying cavity, at least two stretching and returning devices are arranged in the drying cavity, the two stretching and returning devices are arranged at the two ends of the drying cavity, the stretching and returning devices conduct stretching and returning on silk threads, the silk threads are located in the drying cavity, and the hot air circulation drying oven can achieve uniform distribution and efficient utilization of hot air; and meanwhile, the precise control of process parameters can be realized.

Description

Technical Field

[0001] This invention relates to the field of hot air circulating drying technology, and in particular to a hot air circulating drying oven and its control method. Background Technology

[0002] In the production of high-strength, high-modulus polyvinyl alcohol (PVA) fibers, the drying process is crucial, as its effectiveness directly impacts the quality, performance, and production efficiency of the final product. High-strength, high-modulus PVA fibers possess excellent properties such as high strength, high modulus, and corrosion resistance, and are widely used in numerous high-end fields including aerospace, building reinforcement, and protective materials. Therefore, the requirements for various process parameters in their production are extremely stringent, and the drying process is no exception.

[0003] Currently, common drying methods in the PVA fiber drying field have many limitations. Traditional drying equipment mostly uses quartz tube heating, which has significant drawbacks. Firstly, the temperature distribution is uneven, easily creating areas of excessively high or low temperature within the drying oven. Excessively high local temperatures cause PVA fibers to stick together, forming tangled fibers, affecting not only fiber dispersibility but also damaging physical properties, reducing strength and modulus. Conversely, excessively low local temperatures fail to effectively remove moisture from the fibers, resulting in incomplete drying and affecting the fiber's thermal stretchability. Secondly, traditional drying equipment has low thermal efficiency, with a large amount of heat lost to the surrounding environment during the drying process. This not only wastes energy and increases production costs but also contradicts the current development concepts of energy conservation, emission reduction, and green production.

[0004] Furthermore, existing drying equipment struggles to precisely control drying process parameters, leading to temperature fluctuations. The drying process of PVA fibers is a complex physicochemical process, influenced by various factors such as temperature, humidity, airflow, and drying time. Different production batches and specifications of PVA fibers may require different drying process parameters to ensure quality. However, traditional drying equipment often lacks advanced control systems, making it impossible to adjust drying parameters in real time according to actual conditions. This hinders the ability to meet diverse production needs, resulting in unstable product quality and significant batch-to-batch variations.

[0005] With the continuous expansion of applications and increasing market demand for high-strength, high-modulus PVA fibers, related industries have placed higher demands on the quality and production efficiency of PVA fibers. Therefore, developing a new type of drying equipment that can solve these problems, achieve uniform hot air distribution, improve thermal efficiency, and precisely control drying process parameters is of significant practical importance for enhancing the production level and market competitiveness of high-strength, high-modulus PVA fibers. Summary of the Invention

[0006] This invention provides a hot air circulating drying oven and its control method, which can achieve uniform distribution and efficient utilization of hot air, and at the same time achieve precise control of process parameters.

[0007] To solve the above problems, the present invention provides a hot air circulating drying oven, comprising: The drying oven as a whole has a drying cavity inside, and the drying cavity has a yarn inlet and a yarn outlet at both ends; A heating circulation device is installed on the oven and is connected to the drying cavity. The heating circulation device is used to heat and circulate the drying cavity. The stretching and folding device is provided in at least two sets, which are located at both ends of the drying cavity. The stretching and folding device stretches and folds the yarn so that the yarn is located inside the drying cavity.

[0008] The hot air circulating drying oven provided by this invention has, but is not limited to, the following beneficial effects compared to the prior art: This hot air circulating drying oven achieves uniform circulation of hot air within the drying chamber through a heating and circulation device, ensuring consistent heating and high drying efficiency for the yarn. At the same time, it utilizes at least two sets of stretching and reversing devices to make the yarn fold and turn multiple times within the drying chamber, significantly extending the drying path to ensure full contact with the hot air. Combined with the design of the yarn inlet and outlet, it meets the needs of continuous production, thereby improving drying quality and uniformity while achieving energy saving, consumption reduction, and optimized space utilization.

[0009] Preferably, the heating circulation device includes a high-temperature fan, an electric heating chamber, and electric heating tubes. The high-temperature fan is installed on the top of the oven as a whole. The electric heating chamber is connected to the air inlet of the high-temperature fan. Multiple electric heating tubes are provided, and all of the multiple electric heating tubes are installed in the electric heating chamber.

[0010] Preferably, the top and bottom of the drying cavity are respectively provided with air supply chambers, and the top, bottom and rear sides of the drying cavity are respectively provided with circulating air ducts. The circulating air ducts are connected to the air outlet of the high-temperature fan and the return air duct of the electric heating box to form a circulation loop.

[0011] Preferably, the oven is further provided with a temperature control component, which includes a main control temperature sensor and an over-temperature protection temperature sensor. The main control temperature sensor is installed inside the drying cavity, and the over-temperature protection temperature sensor is installed inside the electric heating chamber of the heating circulation device.

[0012] Preferably, this application also provides a control method, executed according to any one of the above-mentioned hot air circulating drying ovens, the control method comprising: Step 1: Set up two hot air circulating drying ovens, and connect the two hot air circulating drying ovens one in front of the other, so that one of the yarn inlets is aligned with the yarn outlet of the adjacent position; Step 2: The fiber bundle is introduced into the hot air circulating drying oven in the first section through the inlet. The temperature of the drying chamber, the power of the heater, and the frequency of the circulating fan are controlled. The fiber bundle is wound around multiple times in the drying chamber for preliminary drying. Step 3: The pre-dried fiber bundle is introduced into the hot air circulating drying oven described in Section 2. The temperature of the drying chamber, the power of the heater, and the frequency of the circulating fan are controlled. The fiber bundle is wound around multiple times in the drying chamber for secondary drying. Step 4: Control the relative humidity inside the drying chamber by adjusting the air volume regulating valve on the exhaust pipe of the hot air circulating drying oven described in Sections 1 and 2; Step 5: Monitor the surface temperature and moisture content of the filament bundles at the outlet of the two drying chambers in real time, and dynamically adjust the heater power, fan frequency, and exhaust valve opening to reduce the moisture content of the filament bundles at the outlet of the hot air circulating drying oven in the second section to 18%–22%, stabilize the surface temperature of the filament bundles at the outlet of the hot air circulating drying oven in the first section at 58℃–63℃, and stabilize the surface temperature of the filament bundles at the outlet of the second drying oven at 68℃–73℃.

[0013] The control method provided by this invention has, but is not limited to, the following beneficial effects compared to the prior art: By setting up two interconnected hot air circulating drying ovens and controlling different temperatures, heater power, and fan frequencies for each oven, the fiber bundles receive suitable drying conditions during the initial and secondary drying stages, avoiding fiber damage or uneven drying caused by one-time high-temperature drying. The humidity inside the oven is controlled by adjusting the airflow regulating valve on the exhaust duct, ensuring that moisture generated during the drying process is promptly discharged, maintaining a dynamic balance in the hot air circulation within the oven. By real-time monitoring of the surface temperature and moisture content of the fiber bundles at the outlet of both ovens, and dynamically adjusting the heater power, fan frequency, and exhaust valve opening, precise closed-loop control of the drying process is achieved, significantly improving product quality stability and production efficiency.

[0014] Preferably, in the hot air circulating drying oven described in the first section, the temperature of the drying cavity is 140℃~160℃, the heater power is 75%~100% of the rated power, and the frequency of the circulating fan is 40Hz~50Hz.

[0015] Preferably, in the hot air circulating drying oven described in Section 2, the temperature of the drying cavity is 150℃~170℃, the heater power is 70%~90% of the rated power, and the frequency of the circulating fan is 40Hz~50Hz.

[0016] Preferably, the fiber bundle is wound 4-5 times inside the hot air circulating drying oven.

[0017] Preferably, in step four, the humidity inside the oven described in the first and second sections is maintained within the relative humidity range of 10% to 25%. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of a hot air circulating drying oven according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the heating circulation device in the hot air circulating drying oven according to an embodiment of the present invention; Figure 3 This is a partial structural diagram of the oven according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the exhaust assembly according to an embodiment of the present invention; Figure 5 This is a flowchart illustrating the control method according to an embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures: 100. Oven assembly; 110. Drying cavity; 120. Yarn inlet; 130. Yarn outlet; 140. Air supply chamber; 150. Circulating air duct; 200. Heating and circulation device; 210. High-temperature fan; 220. Electric heating chamber; 230. Electric heating tube; 300. Stretching and folding device; 310. Roller; 400. Exhaust assembly; 410. Exhaust outlet; 420. Exhaust duct; 430. Air volume regulating valve. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings showing multiple embodiments according to this application. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort will fall within the scope of protection of this application.

[0022] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the specification of this application is for the purpose of describing specific embodiments only and is not intended to limit this application; the terms "comprising," "including," "having," "containing," etc., in the specification, claims, and accompanying drawings of this application are open-ended terms. Therefore, "comprising," "including," or "having" refers to, for example, a method or apparatus having one or more steps or elements, but is not limited to having only these one or more elements. The terms "first," "second," etc., in the specification, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0023] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0025] It should be emphasized that when the term "comprising / including" is used in this specification, it is used to explicitly indicate the presence of the stated feature, integer, step, or component, but does not exclude the presence or addition of one or more other features, integers, steps, components, or groups of features, integers, steps, or components.

[0026] like Figures 1 to 4As shown in the figure, an embodiment of the present invention provides a hot air circulating drying oven, including an oven body 100, a heating circulation device 200, and a stretching and folding device 300. The oven body 100 has a drying cavity 110, and the drying cavity 110 has a yarn inlet 120 and a yarn outlet 130 at both ends. The heating circulation device 200 is disposed on the oven and communicates with the drying cavity 110. The heating circulation device 200 is used to heat and circulate the drying cavity 110. At least two sets of stretching and folding devices 300 are provided, and the two sets of stretching and folding devices 300 are disposed at both ends of the drying cavity 110. The stretching and folding devices 300 stretch and fold the yarn so that the yarn is located inside the drying cavity 110.

[0027] The oven 100 is a closed box structure. The oven 100 has a drying chamber 110 for drying fiber bundles. The drying chamber 110 extends horizontally. The left and right ends of the drying chamber 110 are respectively opened with a fiber inlet 120 and a fiber outlet 130. After the fiber bundles enter the drying chamber 110 through the fiber inlet 120 and are dried, they are sent out through the fiber outlet 130.

[0028] The heating circulation device 200 is integrated on the oven body 100, and the air duct of the heating circulation device 200 is connected to the drying cavity 110. It can continuously deliver hot air into the drying cavity 110 and realize the circulation of hot air in the drying cavity 110, providing a stable drying temperature environment for the drying cavity 110.

[0029] At least two sets of stretching and folding devices 300 are provided. The two sets of stretching and folding devices 300 are respectively installed on the inner side of the inlet 120 end and the outlet 130 end of the drying cavity 110. After the fiber bundle passes through the inlet 120, it cooperates with the stretching and folding device 300. Through the traction and folding guidance of the stretching and folding device 300, the fiber bundle forms a folding travel path in the drying cavity 110, which prolongs the drying time of the fiber bundle in the drying cavity 110 and ensures the drying effect. At the same time, the stretching and folding device 300 also stretches and tensions the fiber bundle to avoid the fiber bundle sticking or twisting during the drying process.

[0030] The stretching and folding device 300 includes rollers 310, and there are two sets of rollers 310. The two sets of rollers 310 are respectively located at the two ends of the inlet 120 and outlet 130 of the drying cavity 110, and the rollers 310 can rotate around their own axis. The first set of rollers 310 is fixedly installed at the end of the inlet 120 side of the drying cavity 110, and the second set of rollers 310 is fixedly installed at the end of the outlet 130 side of the drying cavity 110. The installation heights of the two sets of rollers 310 are matched. After the fiber bundle enters the drying chamber 110 through the inlet 120, it is sequentially wound around the two sets of rollers 310. The rotation of the rollers 310 achieves the traction and conveying of the fiber bundle. At the same time, the span of the two sets of rollers 310 is used to make the fiber bundle form a return path in the drying chamber 110 area between the two sets of rollers 310, ensuring that the fiber bundle is always in the drying area of ​​the drying chamber 110 and completes the drying.

[0031] During the traction process of roller 310, the yarn is first pulled through roller 310 at inlet 120. After passing through roller 310 at inlet 120, the yarn moves to roller 310 at outlet 130 and is pulled by roller 310 at outlet 130. After traction, it turns back to the second roller 310 at inlet 120, and is then pulled by the second roller 310 at outlet 130. This process is repeated, so that the yarn forms multiple parallel drying paths in the drying cavity 110. This significantly increases the residence time and heating area of ​​the yarn in the drying cavity 110, ensuring that each section of yarn can be uniformly dried by hot air, effectively improving drying efficiency and drying uniformity.

[0032] In this embodiment of the application, the heating circulation device 200 includes a high-temperature fan 210, an electric heating chamber 220, and electric heating tubes 230. The high-temperature fan 210 is installed on the top of the oven assembly 100. The electric heating chamber 220 is connected to the air inlet of the high-temperature fan 210. Multiple electric heating tubes 230 are provided, and all of the multiple electric heating tubes 230 are installed inside the electric heating chamber 220.

[0033] In the above structure, the high-temperature fan 210 is fixedly installed at the top center of the oven 100 to provide power for hot air circulation. The electric heating chamber 220 is a closed cavity structure, fixedly installed at the top of the oven 100, and the air outlet of the electric heating chamber 220 and the air inlet of the high-temperature fan 210 are sealed and connected by a pipe. The electric heating tube 230 installed inside the electric heating chamber 220 is a finned U-shaped structure. Its fin design can increase the contact area with air and improve heating efficiency.

[0034] During operation, the electric heating tube 230 is powered on and heats up the air inside the electric heating chamber 220. The high-temperature fan 210 draws in the heated high-temperature air and delivers it into the drying cavity 110 to heat the drying cavity 110.

[0035] In this embodiment of the application, the top and bottom of the drying cavity 110 are respectively provided with air supply chambers 140, and the top, bottom and rear sides of the drying cavity 110 are respectively provided with circulating air ducts 150. The circulating air ducts 150 are connected to the air outlet of the high temperature fan 210 and the return air pipe of the electric heating box 220 to form a circulation loop.

[0036] In the above structure, the drying cavity 110 is provided with air supply chambers 140 at its upper top and lower bottom, respectively, for blowing hot air into the drying cavity 110 in both vertical and horizontal directions. Simultaneously, circulating air ducts 150 are provided at the upper top, lower bottom, and rear side of the drying cavity 110. These circulating air ducts 150 are connected to the air outlet of the high-temperature fan 210 and the return air duct of the electric heating chamber 220, forming a closed hot air circulation loop. During operation, high-temperature hot air is blown from the air supply chambers 140 onto the surface of the fiber bundle. After heat exchange, it flows back to the electric heating chamber 220 through the circulating air ducts 150 for reheating and reuse. This design, combining vertical and horizontal air supply with multi-channel return air, ensures uniform flow of hot air within the drying cavity 110, avoiding localized overheating or undercooling and significantly improving drying quality.

[0037] The drying cavity 110 has an air supply chamber 140 at its top and bottom, and a circulating air duct 150 at its top, bottom and rear sides. The circulating air duct 150 is connected to the air outlet of the high-temperature fan 210 and the return air duct of the electric heating box 220 to form a circulation loop.

[0038] Both the upper air supply chamber 140 and the lower air supply chamber 140 are sealed and connected to the air outlet of the high-temperature fan 210 through the main air duct. The upper top circulation duct 150 is connected to the upper air supply chamber 140, the lower bottom circulation duct 150 is connected to the lower air supply chamber 140, and the rear circulation duct 150 is a collection duct. The ends of all circulation ducts 150 are sealed and connected to the return air duct of the electric heating box 220, ultimately forming a closed hot air circulation loop with the air inlet of the high-temperature fan 210, the electric heating box 220, and the drying cavity 110.

[0039] During operation, high-temperature hot air is sent into the upper and lower air supply chambers 140 respectively, and blown from the air supply chambers 140 into the drying cavity 110. After heat exchange with the fiber bundles, the hot air flows back to the electric heating box 220 through the upper, lower and rear side circulation air ducts 150 of the drying cavity 110, is reheated and then enters the drying cavity 110 again, realizing the recycling of hot air and improving thermal efficiency.

[0040] In this embodiment of the application, the oven assembly 100 is further provided with an exhaust component 400. The exhaust component 400 includes an exhaust port 410, an exhaust pipe 420, and an air volume regulating valve 430. The exhaust port 410 is located on the rear side of the oven assembly 100 and is connected to the drying cavity 110. There are three exhaust ports 410. The exhaust pipe 420 is connected to each exhaust port 410 in a corresponding manner. The air volume regulating valve 430 is installed on the exhaust pipe 420.

[0041] In the above structure, the exhaust vent 410 is located on the rear wall of the oven body 100, and the inner side of the exhaust vent 410 is connected to the drying cavity 110. There are three exhaust vents 410 in total, and the three exhaust vents 410 are evenly distributed along the length of the oven body 100, which can realize the multi-point discharge of water vapor in the drying cavity 110.

[0042] There are three exhaust pipes 420, which correspond one-to-one with three exhaust ports 410. One end of the exhaust pipe 420 is sealed to the exhaust port 410, and the other end extends outward and can be connected to the external main exhaust pipe 420. The outer wall of the exhaust pipe 420 is insulated to prevent water vapor inside the pipe from condensing when it encounters cold.

[0043] Air volume regulating valve 430 is installed on each exhaust pipe 420. The air volume regulating valve 430 is a manual or electric regulating valve. It can adjust the exhaust air volume of each exhaust pipe 420 individually according to the humidity in the drying cavity 110, so as to achieve precise control of the amount of moisture discharged in the drying cavity 110.

[0044] In this embodiment of the application, the oven body 100 is further provided with a temperature control component, which includes a main control temperature sensor and an over-temperature protection temperature sensor. The main control temperature sensor is installed in the drying cavity 110, and the over-temperature protection temperature sensor is installed in the electric heating chamber 220 of the heating circulation device 200.

[0045] In the above structure, both the main control temperature sensor and the over-temperature protection temperature sensor are high-temperature resistant contact temperature sensors.

[0046] The main control temperature sensor is fixedly installed in the middle of the drying cavity 110. It can detect the actual drying temperature inside the drying cavity 110. The main control temperature sensor is electrically connected to the control system of the drying oven and transmits the temperature signal to the control system in real time.

[0047] The over-temperature protection temperature sensor is fixedly installed inside the electric heating chamber 220 of the heating circulation device 200 and is electrically connected to the control circuit of the electric heating tube 230. It is used to detect the air temperature inside the electric heating chamber 220. When the temperature inside the electric heating chamber 220 exceeds the preset safety threshold, the over-temperature protection temperature sensor will trigger the protection mechanism to cut off the power supply to the electric heating tube 230, prevent the equipment from being damaged due to over-temperature, and at the same time prevent high-temperature hot air from entering the drying chamber 110 and causing damage to the fiber bundles.

[0048] In this embodiment of the application, a control method is also provided, which is executed according to the above-described hot air circulating drying oven. The control method includes: Step 1: Setting up two sections of hot air circulating drying oven, with the two hot air circulating drying ovens connected one after the other, such that one of the fiber inlets 120 is aligned with the adjacent fiber outlet 130; Step 2: Introducing the fiber bundle into the first section of the hot air circulating drying oven through the fiber inlet 120, controlling the temperature of the drying chamber 110, the heater power, and the frequency of the circulating fan, and winding the fiber bundle multiple times in the drying chamber 110 for preliminary drying; Step 3: Introducing the preliminary dried fiber bundle into the second section of the hot air circulating drying oven, controlling the temperature of the drying chamber 110 and the heater power. The fiber bundles are wound multiple times in the drying chamber 110 for secondary drying, along with the frequency of the circulating fan. Step 4: The relative humidity inside the drying chamber 110 is controlled by adjusting the air volume regulating valve 430 on the exhaust pipe 420 of the first and second sections of the hot air circulating drying oven. Step 5: The surface temperature and moisture content of the fiber bundles at the fiber outlet 130 of the two drying chambers 110 are monitored in real time, and the heater power, fan frequency, and exhaust valve opening are dynamically adjusted to reduce the moisture content of the fiber bundles at the fiber outlet 130 of the second section of the hot air circulating drying oven to 18% to 22%, stabilize the surface temperature of the fiber bundles at the fiber outlet 130 of the first section of the hot air circulating drying oven at 58℃ to 63℃, and stabilize the surface temperature of the fiber bundles at the outlet of the second section of the oven at 68℃ to 73℃.

[0049] In the above control method, by connecting two sections of hot air circulating drying ovens one after the other, a continuous drying system is formed, effectively extending the drying path and total drying time of the fiber bundle. In the first oven, the fiber bundle is introduced through the inlet 120 and wound multiple times under the action of the stretching and folding device 300. It undergoes preliminary drying using the hot air environment within the drying chamber 110. This stage primarily removes surface and shallow moisture from the fiber bundle, laying the foundation for subsequent deep drying. The pre-dried fiber bundle then enters the second oven for secondary drying while remaining wound multiple times. The second oven can be set with different parameters such as temperature and airflow than the first oven to achieve more precise drying control. Throughout the drying process, by adjusting the airflow regulating valves 430 on the exhaust pipes 420 of both ovens, the relative humidity inside each drying chamber 110 can be controlled separately, preventing excessive humidity from affecting drying efficiency or causing the fiber bundle to become damp again. Meanwhile, the system monitors the surface temperature and moisture content of the filaments at the outlet 130 of the two drying chambers in real time. Based on the monitoring data, it dynamically adjusts the heater power, fan frequency, and exhaust valve opening to ensure that the moisture content of the filaments at the outlet 130 of the second drying chamber is strictly controlled within the target range of 18% to 22%, the surface temperature of the filaments at the outlet 130 of the first drying chamber is stable at 58℃ to 63℃, and the surface temperature of the filaments at the outlet of the second drying chamber is stable at 68℃ to 73℃. This achieves precise control over the drying quality of the fiber filaments and meets the specific requirements of subsequent processing technology for the moisture content and temperature of the filaments.

[0050] In this embodiment of the application, the temperature of the drying cavity 110 in the hot air circulating drying oven described in the first section is 140℃~160℃, the heater power is 75%~100% of the rated power, and the frequency of the circulating fan is 40Hz~50Hz.

[0051] Preferably, the temperature of the drying chamber 110 in the first drying oven is controlled at 140℃~160℃, the heater power is 75%~100% of the rated power, and the frequency of the circulating fan is 40Hz~50Hz. Under these parameters, the filament bundle is wound 4~5 times in the drying oven for preliminary drying, which can effectively remove most of the free moisture while avoiding fiber sticking due to excessive temperature. In actual operation, the temperature can be adjusted within this range according to the initial moisture content and variety of the filament bundle to obtain the best drying effect.

[0052] In this embodiment of the application, in the hot air circulating drying oven described in Section 2, the temperature of the drying cavity 110 is 150℃~170℃, the heater power is 70%~90% of the rated power, and the frequency of the circulating fan is 40Hz~50Hz.

[0053] Preferably, the temperature of the drying chamber 110 in the second drying oven is controlled between 150℃ and 170℃, the heater power is 70% to 90% of the rated power, and the frequency of the circulating fan is 40Hz to 50Hz. The fiber bundle is wound 5 to 6 times in the second drying oven to complete the final drying, further reducing the residual moisture to the target value, while simultaneously bringing the fiber surface temperature to the process requirements. This temperature range is conducive to the diffusion and evaporation of moisture inside the fiber and will not damage the fiber structure.

[0054] In this embodiment of the application, the fiber bundle is wound 4-5 times in the hot air circulating drying oven.

[0055] Preferably, the fiber bundle is wound 4 to 5 times in the hot air circulating drying oven. Guided by the roller 310 of the stretching and folding device 300, the fiber bundle forms multiple folding paths within the drying cavity 110, increasing the drying stroke. For example, it can be wound 4.5 times in the first drying section and 5.5 times in the second drying section, so that the total drying time meets the process requirements.

[0056] The actual number of turns can be adjusted appropriately according to the length of the drying oven, the linear speed of the filament bundle, and the drying requirements.

[0057] In this embodiment of the application, in step four, the humidity inside the oven described in the first and second sections is maintained within the relative humidity range of 10% to 25%.

[0058] In step four, the relative humidity inside the first and second drying ovens is maintained between 10% and 25% by adjusting the airflow regulating valve 430. This humidity range ensures effective moisture removal without causing excessive heat loss due to excessive dehumidification, thus maintaining a dynamic balance in the hot air circulation within the oven. Preferably, a humidity sensor can be installed for feedback control, automatically adjusting the air valve opening to achieve constant humidity drying.

[0059] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A hot air circulating drying oven, characterized in that, include: The oven assembly (100) has a drying cavity (110) inside, and the drying cavity (110) has a yarn inlet (120) and a yarn outlet (130) at both ends. A heating circulation device (200) is installed on the oven and is connected to the drying cavity (110). The heating circulation device (200) is used to heat and circulate the drying cavity (110). At least two sets of stretching and folding devices (300) are provided. The two sets of stretching and folding devices (300) are located at both ends of the drying cavity (110). The stretching and folding devices (300) stretch and fold the yarn so that the yarn is located inside the drying cavity (110).

2. The hot air circulating drying oven according to claim 1, characterized in that, The heating circulation device (200) includes a high-temperature fan (210), an electric heating chamber (220), and electric heating tubes (230). The high-temperature fan (210) is installed on the top of the oven assembly (100). The electric heating chamber (220) is connected to the air inlet of the high-temperature fan (210). There are multiple electric heating tubes (230), and all of the multiple electric heating tubes (230) are installed inside the electric heating chamber (220).

3. A hot air circulating drying oven according to claim 1, characterized in that, The drying cavity (110) is provided with air supply chambers (140) at the top and bottom respectively. The drying cavity (110) is also provided with circulating air ducts (150) at the top, bottom and rear respectively. The circulating air ducts (150) are connected to the air outlet of the high temperature fan (210) and the return air duct of the electric heating box (220) to form a circulation loop.

4. A hot air circulating drying oven according to claim 1, characterized in that, The oven assembly (100) is further provided with an exhaust system (400), which includes: An exhaust vent (410) is provided on the rear side of the oven assembly (100) and is connected to the drying cavity (110). Three exhaust vents (410) are provided. The exhaust pipe (420) is connected to the exhaust port (410) in a one-to-one correspondence; An air volume regulating valve (430) is installed on the exhaust pipe (420).

5. A hot air circulating drying oven according to claim 1, characterized in that, The oven assembly (100) is also equipped with a temperature control component, which includes a main control temperature sensor and an over-temperature protection temperature sensor. The main control temperature sensor is installed inside the drying cavity (110), and the over-temperature protection temperature sensor is installed inside the electric heating chamber (220) of the heating circulation device (200).

6. A control method, performed in a hot air circulating drying oven according to any one of claims 1-5, characterized in that, The control method includes: Step 1: Set up two hot air circulating drying ovens, and connect the two hot air circulating drying ovens one in front of the other, so that one of the yarn inlets is aligned with the yarn outlet of the adjacent position; Step 2: The fiber bundle is introduced into the hot air circulating drying oven in the first section through the inlet. The temperature of the drying chamber, the power of the heater, and the frequency of the circulating fan are controlled. The fiber bundle is wound around multiple times in the drying chamber for preliminary drying. Step 3: The pre-dried fiber bundle is introduced into the hot air circulating drying oven described in Section 2. The temperature of the drying chamber, the power of the heater, and the frequency of the circulating fan are controlled. The fiber bundle is wound around multiple times in the drying chamber for secondary drying. Step 4: Control the relative humidity inside the drying chamber by adjusting the air volume regulating valve on the exhaust pipe of the hot air circulating drying oven described in Sections 1 and 2; Step 5: Monitor the surface temperature and moisture content of the filament bundles at the outlet of the two drying chambers in real time, and dynamically adjust the heater power, fan frequency, and exhaust valve opening to reduce the moisture content of the filament bundles at the outlet of the hot air circulating drying oven in the second section to 18%–22%, stabilize the surface temperature of the filament bundles at the outlet of the hot air circulating drying oven in the first section at 58℃–63℃, and stabilize the surface temperature of the filament bundles at the outlet of the second drying oven at 68℃–73℃.

7. The control method according to claim 6, characterized in that, In the hot air circulating drying oven described in Section 1, the temperature of the drying chamber is 140℃~160℃, the heater power is 75%~100% of the rated power, and the frequency of the circulating fan is 40Hz~50Hz.

8. The control method according to claim 6, characterized in that, In the hot air circulating drying oven described in Section 2, the temperature of the drying cavity is 150℃~170℃, the heater power is 70%~90% of the rated power, and the frequency of the circulating fan is 40Hz~50Hz.

9. The control method according to claim 6, characterized in that, The fiber bundles are wound 4-5 times inside the hot air circulating drying oven.

10. The control method according to claim 6, characterized in that, In step four, the humidity inside the oven described in sections one and two is maintained within the relative humidity range of 10% to 25%.

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