Energy-saving sectional gradient low-temperature drying method for refractory materials and control system thereof

Abstract

The application relates to the technical field of refractory material preparation, and particularly discloses an energy-saving segmented gradient low-temperature drying method for refractory materials and a control system thereof. The drying method comprises five sequentially connected continuous steps of system initialization, surface free water pre-removal, internal moisture diffusion strengthening, moisture content gradient buffer balance and deep dehydration standard reaching, the whole process takes the water vapor partial pressure difference as the core dehydration driving force, and a control mode of reverse linkage of cavity temperature and environmental absolute humidity is adopted. The control system matched with the drying method comprises a sensing layer, an execution layer and a PLC control layer, and is provided with a built-in double-closed-loop linkage control module, so that automatic closed-loop management and control of the whole drying process can be accurately realized. The application can be used for drying treatment of various industrial shaped and unshaped refractory material blanks, efficient dehydration can be realized in a low-temperature environment, the comprehensive energy consumption of drying is significantly reduced, defects such as blank crust and cracking are effectively avoided, and the product quality and batch stability are ensured.

Description

Technical Field

[0001] This application relates to the field of refractory material preparation technology, and more specifically, to an energy-saving segmented gradient low-temperature drying method for refractory materials and its control system. Background Technology

[0002] Refractory materials are indispensable basic functional materials in high-temperature industries such as metallurgy, building materials, and chemicals. During the molding and preparation of various shaped refractory bricks and unshaped refractory castables, a drying process is required to remove free and chemically bound water from the green body. The effectiveness of the drying process directly affects the structural integrity, room-temperature mechanical properties, and high-temperature service stability of the refractory green body, making it one of the core processes in the industrial production of refractory materials. Currently, the most widely used drying technology in the refractory industry is the stepped heating hot air drying process, which uses a temperature gradient as the core dehydration driving force. By gradually increasing the drying environment temperature, the vaporization and removal of moisture inside the green body are achieved.

[0003] Existing refractory drying processes, driven primarily by temperature gradients, suffer from high overall energy consumption. These processes rely on temperatures above 100°C to achieve boiling and vaporization of moisture. To prevent cracking due to uneven heating between the inside and outside of the blank, multiple long-duration constant-temperature holding stages are often required. This not only further increases energy consumption but also results in lengthy drying cycles and low production efficiency, making it difficult to meet the energy-saving and cost-reduction needs of the refractory industry. This application addresses this issue by using the water vapor partial pressure difference as the core dehydration driving force, coupled with the inverse linkage adjustment of the chamber temperature and ambient absolute humidity throughout the drying process. This allows for stable mass transfer dynamics at temperatures far below the boiling point of water, achieving highly efficient low-temperature dehydration of refractory materials. This specifically solves the core problem of excessively high overall energy consumption in existing drying processes, while simultaneously ensuring both drying efficiency and blank drying quality. Summary of the Invention

[0004] To address the issue of high overall energy consumption in existing refractory drying processes driven primarily by temperature gradients, this application provides an energy-saving segmented gradient low-temperature drying method for refractory materials and its control system.

[0005] Firstly, this application provides an energy-saving segmented gradient low-temperature drying method for refractory materials, employing the following technical solution:

[0006] An energy-saving segmented gradient low-temperature drying method for refractory materials, comprising drying the refractory material blank to be dried, characterized by the following steps:

[0007] S1. System initialization: Moisture content and temperature sensors are pre-embedded inside the blank to be dried and connected to the control system. The full-process water vapor partial pressure difference locking range, inter-segment switching threshold and drying termination threshold are preset to complete the system self-check and cavity preheating. The water vapor partial pressure difference is the difference between the saturated water vapor partial pressure at the corresponding temperature inside the blank and the actual water vapor partial pressure in the drying cavity environment.

[0008] S2, Surface Free Water Pre-removal: Control the temperature and absolute humidity of the drying chamber, maintain the water vapor partial pressure difference within the preset range, complete this stage according to the surface moisture diffusion rate of the blank, and switch to the next stage.

[0009] S3. Internal moisture diffusion enhancement: As the internal temperature of the billet increases, the absolute humidity of the cavity environment is reduced simultaneously to maintain the water vapor partial pressure difference within the preset range. This stage is completed according to the internal moisture content gradient of the billet and then switched to the next stage.

[0010] S4. Moisture content gradient buffer balance: As the internal temperature of the billet decreases, the absolute humidity of the cavity environment is increased simultaneously to maintain the water vapor partial pressure difference within the preset range. This stage is completed according to the moisture content gradient inside the billet and then switched to the next stage.

[0011] S5. Deep dehydration meets standards: As the internal temperature of the billet increases, the absolute humidity of the cavity environment is reduced simultaneously to maintain the water vapor partial pressure difference within the preset range. The drying process is completed based on the overall moisture content of the billet and the moisture diffusion rate.

[0012] By adopting the above technical solution, the water vapor partial pressure difference is used as the core mass transfer driving force for moisture migration inside the green body, replacing the traditional drying mode based on temperature gradient. The water vapor partial pressure difference is the core original driving force for the diffusion of moisture from the inside of the material to the environment. When the saturated water vapor partial pressure inside the green body is higher than the water vapor partial pressure in the cavity environment, moisture will continuously migrate from the inside of the green body to the cavity environment. Stable dehydration can be achieved without reaching the boiling point of water. It is particularly suitable for the characteristics of refractory green bodies with high solid content, low porosity, and high internal moisture diffusion resistance. Even in low-temperature environments far below the boiling point of water, moisture migration can be continuously driven by a stable partial pressure difference. At the same time, the drying process is divided into five continuous functional stages, which accurately matches the moisture migration law of the entire process from the removal of surface free water to the deep removal of internal bound water in the refractory green body. This achieves efficient dehydration in low-temperature environments, which can significantly reduce the basic energy consumption of the drying process and avoid the risk of structural damage to the green body caused by high-temperature drying.

[0013] Preferably, in step S1, the sensor is pre-embedded in the surface, middle and deep layers of the billet, wherein the surface layer is located at a depth of 0 mm to 5 mm below the surface of the billet, the middle layer is located at 1 / 2 of the total thickness of the billet, and the deep layer is located at a distance of 5 mm from the non-heated surface of the billet; the preset water vapor partial pressure difference locking range is 1.2 kPa to 2.5 kPa.

[0014] By employing the above technical solution, monitoring elements are deployed at different depths of the billet. The three-point deployment—surface, middle, and deep—completely covers the entire path of moisture migration during the dehydration process. The surface layer corresponds to the core area of ​​free water removal, the middle layer to the transition area of ​​internal moisture diffusion, and the deep layer to the lag area of ​​moisture migration. This allows for precise capture of the moisture and temperature change patterns at different depths, providing comprehensive and accurate measurement data for subsequent drying stage switching and dynamic adjustment of process parameters. This effectively avoids control deviations caused by single-point data. The partial pressure difference locking range of 1.2 kPa to 2.5 kPa matches the reasonable dynamic range of moisture migration inside the refractory billet, ensuring a continuous and stable dehydration rate without causing structural cracking, delamination, or other defects due to excessively rapid moisture migration inside the billet caused by an excessively large partial pressure difference.

[0015] Preferably, in step S2, the temperature of the drying chamber is controlled at 45°C to 55°C, the absolute humidity of the environment is controlled at 35g / kg to 45g / kg of dry air, and the water vapor partial pressure difference is stabilized in the range of 1.2kPa to 1.8kPa; the switching condition for this stage is that the surface moisture diffusion rate reaches a decreasing inflection point that lasts for more than 30 minutes and the decrease is not less than 20%.

[0016] By adopting the above technical solution, the low temperature range of 45℃ to 55℃ combined with the corresponding high humidity environment can gently remove free water from the surface of the billet while maintaining a stable partial pressure difference. The high humidity environment can prevent the evaporation rate of surface moisture from being much greater than the internal moisture migration rate, thus preventing the rapid water loss and shrinkage of surface capillaries in the early stage of drying. This preserves a smooth diffusion channel for subsequent internal moisture migration and effectively solves the problem of surface crusting caused by excessively rapid temperature rise in the early stage of drying. The directional laminar flow parallel to the surface of the billet, combined with periodic static pressure fluctuations, can evenly sweep the surface of the billet, accelerate the water vapor diffusion efficiency of the surface boundary layer, and avoid inconsistent dehydration of the billet caused by uneven local humidity. Using the inflection point of the decreasing surface moisture diffusion rate as the basis for stage switching can accurately match the completion point of surface free water removal, avoiding problems of over-drying or insufficient drying.

[0017] Preferably, in step S3, the temperature of the drying chamber is controlled at 65°C to 75°C, the absolute humidity of the environment is controlled at 18g / kg to 28g / kg dry air, and the water vapor partial pressure difference is stable in the range of 1.8kPa to 2.5kPa. The switching condition for this stage is that the difference in the moisture diffusion rate between the middle layer and the surface layer of the blank appears to last for more than 30 minutes and the increase is not less than 30% at an inflection point.

[0018] By adopting the above technical solutions, the temperature range of 65℃ to 75℃, combined with the corresponding absolute humidity range, can gradually increase the partial pressure difference, continuously driving the internal moisture of the billet to migrate to the surface, thus avoiding the billet bulging and cracking problems caused by the violent vaporization of internal moisture due to sudden changes in the partial pressure difference. The directional air supply perpendicular to the thickness direction of the billet, combined with periodic static pressure fluctuations, can form an auxiliary pressure gradient in the thickness direction of the billet, enhance water vapor convection in the thickness direction of the billet, accelerate the migration rate of internal moisture, and form a mass transfer synergy with the partial pressure difference. Using the rising inflection point of the difference in the moisture diffusion rate between the middle layer and the surface of the billet as the basis for stage switching, the change node of the internal moisture migration rate can be accurately identified, and the process stage can be adjusted in a timely manner, which can effectively avoid the stress concentration problem in the billet caused by the lag in internal moisture migration.

[0019] Preferably, in step S4, the temperature of the drying chamber is controlled at 55°C to 60°C, the absolute humidity of the environment is controlled at 30g / kg to 38g / kg dry air, and the water vapor partial pressure difference is stabilized in the range of 1.2kPa to 1.5kPa; the switching condition in this stage is that the internal moisture content gradient is stabilized at no more than 1% / cm for 1 hour.

[0020] By adopting the above technical solution, the cooling range of 55℃ to 60℃, combined with the corresponding increase in absolute humidity, can slow down the evaporation rate of surface moisture while maintaining a stable partial pressure difference, reduce the difference in moisture evaporation rate between the inside and outside of the billet, and allow sufficient time for the internally lagging moisture to diffuse evenly to the surface, gradually balancing the moisture content gradient inside the billet. At the same time, it can fully release the thermal and wet stress generated in the billet during the heating and dehydration process. Using the stable threshold of the internal moisture content gradient as the basis for stage switching can ensure that the moisture distribution inside and outside the billet is uniform, which can effectively alleviate the problem of structural defects such as microcracks and delamination in the billet.

[0021] Preferably, in step S5, the temperature of the drying chamber is controlled at 75°C to 85°C, the absolute humidity of the environment is controlled at 8g / kg to 15g / kg dry air, and the water vapor partial pressure difference is stable in the range of 2.0kPa to 2.5kPa. The drying termination condition of this stage is that the overall average moisture content of the blank is stable at no more than 0.5% for 1 hour, and the moisture diffusion rate is stable at no more than 0.01% / h for 1 hour.

[0022] By adopting the above technical solutions, a temperature range of 75℃ to 85℃ combined with a corresponding low absolute humidity range can form a high and stable partial pressure difference, gently removing the physically bound water and weakly chemically bound water that is bound to the aggregate and binder inside the green body, ensuring the volume stability of the green body during the subsequent high-temperature firing process; high-speed turbulent circulation combined with periodic static pressure fluctuations can enhance the efficiency of water vapor discharge inside the cavity, avoiding the impact of the cavity's humidity rise on the dehydration effect; using the dual thresholds of the overall moisture content of the green body and the moisture diffusion rate as the drying termination conditions can ensure that the overall dehydration of the green body is uniform and meets the standards, while avoiding the problem of reduced structural strength of the green body caused by over-drying.

[0023] Preferably, in steps S2 to S5, the cavity temperature and the absolute humidity of the environment are always adjusted in opposite directions to maintain the water vapor partial pressure difference within a preset locking range.

[0024] By adopting the above technical solution, the entire process uses inverse linkage adjustment of temperature and absolute humidity. When the temperature rises, the saturated vapor pressure inside the blank increases simultaneously. At the same time, the ambient absolute humidity is reduced to offset the increase in internal saturated vapor pressure, maintain a stable pressure difference, and avoid excessive pressure difference caused by temperature rise. Conversely, when the temperature decreases, the ambient absolute humidity is increased simultaneously to offset the decrease in internal saturated vapor pressure, and avoid dehydration stagnation caused by excessive pressure difference. This linkage method breaks the problem that temperature rise in traditional drying is inevitably accompanied by drastic fluctuations in the pressure difference. It can maintain the vapor pressure difference within a preset locking range during the switching of drying stages and dynamic adjustment of process parameters, ensuring the continuous stability of dehydration mass transfer power. It can effectively avoid drastic fluctuations in mass transfer power caused by adjustment of a single parameter, thereby achieving stable and precise control of the drying process.

[0025] Secondly, this application provides a control system for an energy-saving segmented gradient low-temperature drying method for refractory materials, employing the following technical solution:

[0026] The control system for an energy-saving segmented gradient low-temperature drying method for refractory materials includes a sensing layer, an execution layer, and a PLC control layer.

[0027] The sensing layer includes a billet state monitoring unit and a cavity environment monitoring unit. The billet state monitoring unit includes a moisture content sensor and a temperature sensor for embedding the refractory billet at different depths. The cavity environment monitoring unit includes a temperature and humidity sensor, a static pressure sensor, and a wind speed sensor installed inside the drying cavity. All sensors communicate with the PLC control layer in real time.

[0028] The execution layer includes a temperature and humidity control component, a directional air supply component, and a sensible heat-latent heat separation and waste heat recovery component. All components are electrically connected to the PLC control layer and receive its linkage control commands.

[0029] The PLC control layer incorporates a parameter calculation module, a dual-closed-loop linkage control module, and a drying stage switching determination module. The dual-closed-loop linkage control module includes an inner-loop cavity temperature and humidity precision control unit and an outer-loop billet moisture characteristic adaptive control unit. The inner-loop cavity temperature and humidity precision control unit is used to adjust the temperature and humidity adjustment components in real time based on cavity environment monitoring data to maintain stable cavity temperature and humidity parameters. The outer-loop billet moisture characteristic adaptive control unit is used to dynamically adjust the control target of the inner loop based on the real-time state parameters inside the billet, and synchronously adjust the operating status of the directional air supply component and the sensible heat-latent heat separation waste heat recovery component. The drying stage switching determination module is used to automatically determine the drying process stage based on the billet state parameters and switch the corresponding control logic.

[0030] By adopting the above technical solution and employing a three-layer architecture consisting of a sensing layer, an execution layer, and a PLC control layer, a closed-loop management system for the entire drying process—including data acquisition, logical operation, and execution control—can be achieved. The dual-unit design of the sensing layer can simultaneously acquire environmental parameters of the controlled cavity and real-time status parameters of the controlled billet, providing complete input data for dual closed-loop control and avoiding material state deviations caused by relying solely on environmental parameter control. In the dual closed-loop linkage control architecture, the inner loop is a fast-response environmental parameter control loop, while the outer loop is a slow-response adaptive adjustment loop based on material state. The combination of fast and slow loops ensures parameter stability and adapts to the dynamic changes in the billet drying process. Through the synchronous linkage control of multiple components, the accurate execution of drying process parameters is ensured, achieving automated and intelligent management of the drying process. This effectively reduces parameter deviations caused by manual intervention and ensures batch stability of the drying process.

[0031] Preferably, the sensible heat-latent heat separation and waste heat recovery component is provided with an exhaust port and a return air port connected to the drying chamber, as well as a humidification branch connected to the temperature and humidity control component; the sensible heat-latent heat separation and waste heat recovery component is used to separate and recover the sensible heat and latent heat of the exhaust air from the drying chamber, wherein the sensible heat is used to preheat and supplement fresh air, and the latent heat is used to generate saturated water vapor and supply it to the drying chamber through the humidification branch, and the main intake air of the drying chamber preferentially adopts the return air treated by the sensible heat-latent heat separation and waste heat recovery component.

[0032] By adopting the above technical solution, the exhaust port corresponds to the exhaust end of the drying chamber, the return air port corresponds to the air inlet end of the drying chamber, and the humidification branch corresponds to the humidification input end of the temperature and humidity control component. The corresponding interface design allows the exhaust waste heat to be directly reused in the corresponding drying stage, reducing heat loss in intermediate links. Through the separation and recovery of sensible heat and latent heat, the different energy requirements of fresh air preheating and chamber humidification can be matched respectively, realizing the full-scale utilization of exhaust waste heat and reducing ineffective energy loss. Sensible heat is used to preheat and supplement fresh air, reducing energy consumption in the fresh air heating process, while latent heat is used to generate saturated water vapor to supply chamber humidity control, eliminating the need for additional independent steam generation equipment. At the same time, it realizes the closed-loop reuse of drying waste heat, which can further reduce the overall energy consumption of the drying process.

[0033] Preferably, the directional air supply component includes a multi-component zoned air supply nozzle, an airflow reversing valve, and a variable frequency fan; the PLC control layer regulates the air supply direction, wind speed, and cavity static pressure through the directional air supply component based on the internal moisture content gradient data of the billet, and dynamically adjusts the air supply parameters and airflow reversing cycle based on the real-time collected moisture diffusion rate of the billet.

[0034] By adopting the above technical solutions, the zoned air supply nozzles can be independently adjusted in opening, the airflow reversing valve can quickly switch between air supply and return directions, and the variable frequency fan can achieve stepless speed adjustment. The combination of these three can achieve seamless switching between multiple air supply modes, adapting to the mass transfer enhancement requirements of different drying stages. The zoned structural design can perform differentiated air supply control for the billets in different positions in the kiln, adapting to production scenarios where multiple specifications of billets are dried in the same kiln, thus improving the applicability of the equipment. At the same time, the air supply parameters can be dynamically adjusted according to the moisture diffusion rate of the billets, which can specifically enhance the moisture migration process inside the billets, helping to improve drying efficiency and the uniformity of billet dehydration.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. The method of this application, by using the water vapor partial pressure difference as the core dehydration driving force and coordinating the reverse linkage adjustment of the chamber temperature and the absolute humidity of the environment throughout the drying process, can form a stable and continuous mass transfer force in a low-temperature environment far below the boiling point of water, which helps to achieve efficient low-temperature dehydration of refractory materials and can significantly reduce the basic energy consumption of the drying process.

[0037] 2. The method of this application sets a moisture content gradient buffer balance stage between the core dehydration sections, and actively balances the internal moisture content gradient of the billet through cooling and humidification operations. This slows down the surface evaporation rate while ensuring the continuous diffusion of internal moisture, which can reduce the risk of stress concentration caused by the mismatch between internal and external dehydration rates and effectively alleviate the common problems of surface crusting and internal microcracks in the billet in the industry.

[0038] 3. The method of this application, through the inter-segment switching logic based on the internal moisture diffusion characteristics of the green body, uses the inflection point of moisture diffusion rate and the moisture content gradient threshold as the basis for stage switching. Unlike the traditional fixed-duration drying mode, it can adapt to the drying needs of green bodies of different materials and specifications, and helps to achieve adaptive and precise control of the drying process.

[0039] 4. The control system of this application, through a dual closed-loop architecture of precise temperature and humidity control of the inner ring cavity and adaptive control of the moisture characteristics of the outer ring blank, can synchronously link temperature and humidity adjustment, directional air supply and waste heat recovery components, and realize automated closed-loop management of the entire drying process, which helps to ensure the stability of process parameters and control accuracy.

[0040] 5. In this application, a sensible heat-latent heat separation waste heat recovery component is preferred. By separating and recovering the sensible heat and latent heat of the exhaust air from the drying chamber, the heat is used to supplement the fresh air preheating and the humidity regulation of the chamber, respectively. This helps to realize the cascade closed-loop recovery of waste heat in the drying process, which can further reduce the overall energy consumption of the entire drying process. Attached Figure Description

[0041] Figure 1 This is a flowchart of an energy-saving segmented gradient low-temperature drying method for refractory materials provided in this application. Detailed Implementation

[0042] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0043] Technical Concept: Currently, the industrial drying of refractory materials generally adopts a stepped heating hot air drying process driven by temperature gradients. This process suffers from high overall energy consumption, long drying cycles, and easy cracking of the green body. This type of process relies on high temperatures above 100℃ to vaporize moisture. To avoid structural defects caused by uneven heating inside and outside the green body, multiple long-term constant temperature holding stages are required, further aggravating energy consumption. At the same time, the existing process independently controls temperature and humidity, which cannot stably maintain the dehydration mass transfer dynamics, easily leading to problems such as surface crusting and internal micro-cracks. Moreover, it can only recover the sensible heat of the exhaust air, while a large amount of latent heat is directly discharged, resulting in ineffective energy loss.

[0044] This solution uses the water vapor partial pressure difference as the core driving force for dehydration and establishes a temperature and humidity reverse linkage adjustment mechanism to form a stable mass transfer force in a low-temperature environment far below the boiling point of water, thus achieving efficient low-temperature dehydration. It designs a five-stage segmented gradient drying process and has created a unique cooling and humidification moisture content gradient buffer balance section to balance the internal and external moisture distribution of the billet and release internal stress to avoid cracking. It is equipped with a dual closed-loop adaptive control system and a sensible heat-latent heat separation waste heat recovery system to realize full-process automated control and waste heat closed-loop utilization, simultaneously solving the core problems of high energy consumption, long cycle and unstable finished product quality.

[0045] The specific implementation method of the energy-saving segmented gradient low-temperature drying control system for refractory materials in this application is as follows:

[0046] This system is a dedicated industrial-grade control system for segmented gradient low-temperature drying of refractory materials. It is compatible with various mainstream industrial refractory drying equipment, such as intermittent chamber drying kilns, continuous tunnel drying kilns, and shuttle drying kilns. It can cover the drying needs of all types of refractory materials, including shaped refractory bricks, unshaped refractory castables, and precast components. It can achieve unmanned automatic closed-loop control of the entire drying process, while simultaneously completing the tiered closed-loop reuse of exhaust waste heat, taking into account drying efficiency, product yield, and energy saving and consumption reduction effects.

[0047] The system adopts a layered architecture design, including three parts: the sensing layer, the execution layer, and the PLC control layer. Real-time signal communication and command transmission between each layer are achieved via industrial Ethernet, with a communication latency of no more than 50ms, meeting the requirements for continuous and stable operation in industrial settings. The specific structure and working logic are as follows:

[0048] 1. Perception layer

[0049] The sensing layer includes a blank state monitoring unit and a cavity environment monitoring unit, which can realize real-time acquisition of the internal state of the blank and the state of the cavity environment in all dimensions throughout the drying cycle.

[0050] The billet condition monitoring unit includes a contact dielectric constant moisture content sensor that can be embedded at different depths in the refractory billet, and a Class A precision platinum resistance temperature sensor. The sensor housing adopts a high-temperature and high-humidity 95% ceramic encapsulation structure, which can work stably for a long time in an environment of 100℃ and 95%RH. The sensor is equipped with a high-temperature resistant polytetrafluoroethylene insulated lead wire, which is led out along the billet tooling frame to the wiring terminal outside the drying kiln. This avoids interference from the high temperature inside the kiln on the signal transmission throughout the process, and can accurately collect moisture content and temperature data at different depths of the billet.

[0051] The cavity environment monitoring unit includes temperature and humidity sensors, diffused silicon static pressure sensors, and hot-film wind speed sensors installed at multiple points inside the drying cavity. The sensors are arranged at the air inlet, air outlet, and the upper, middle, and lower layers of the blank placement area in the drying cavity. There are no fewer than 6 sets of environmental monitoring points in a single drying kiln, which can comprehensively collect environmental parameters inside the cavity and avoid control errors caused by single-point data deviations.

[0052] All sensors communicate with the PLC control layer in real time, with a data sampling frequency of no less than 1Hz. This allows for real-time feedback on the internal moisture distribution, temperature distribution, and cavity environment of the billet, providing accurate data support for subsequent closed-loop control.

[0053] 2. Execution layer

[0054] The execution layer includes temperature and humidity control components, directional air supply components, and sensible heat-latent heat separation and waste heat recovery components. All components are electrically connected to the PLC control layer and can receive and execute linkage control commands issued by the PLC control layer in real time. The command response time is no more than 10 seconds.

[0055] The temperature and humidity control components include a finned electric heating unit, a surface-cooled condensation dehumidification unit, and a low-pressure steam humidification unit. They can precisely control the temperature and absolute humidity inside the drying chamber, with a temperature control accuracy of ±1℃ and an absolute humidity control accuracy of ±0.5g / kg dry air. The components have built-in safety interlock functions such as over-temperature protection and water shortage protection to avoid equipment failure risks in industrial sites.

[0056] The directional air supply assembly includes multi-group zoned air supply nozzles, pneumatic airflow reversing valves, and variable frequency centrifugal fans. The air supply nozzles can adjust the air supply angle according to the placement position of the billet, enabling multi-mode air supply parallel to the billet surface and perpendicular to the billet thickness direction. The pneumatic airflow reversing valves can complete the air supply direction switching within 2 seconds, enabling bidirectional alternating air supply. The variable frequency fan can steplessly and precisely control the air supply speed within the range of 0.2m / s-2m / s, and can also be used in conjunction with the return air valve opening adjustment to achieve precise control of the cavity static pressure. For scenarios where multiple rows of billets are dried simultaneously, independent air supply control for each zone can be achieved, adapting to the synchronous drying needs of billets of different specifications.

[0057] The sensible heat-latent heat separation and waste heat recovery component is equipped with an exhaust air interface and a return air interface connected to the drying chamber, as well as a humidification branch connected to the temperature and humidity control component. The component integrates an air-to-air plate heat exchanger, a condenser heat exchange tank, and a steam generator, which can separate and recover the sensible heat and latent heat of the exhaust air from the drying chamber. The sensible heat is used to preheat the fresh air through the air-to-air plate heat exchanger, with a fresh air preheating efficiency of not less than 85%. The latent heat is recovered through the condenser heat exchange tank to heat pure water, and low-pressure saturated steam is generated in the steam generator and supplied to the drying chamber through the humidification branch, eliminating the need for an additional steam boiler. The main air intake of the drying chamber preferentially uses the return air treated by the sensible heat-latent heat separation and waste heat recovery component, achieving 100% closed-loop recovery of exhaust waste heat and significantly reducing energy consumption in the drying process.

[0058] 3. PLC control layer

[0059] The PLC control layer adopts an industrial-grade programmable logic controller, equipped with an industrial touch screen and human-machine interface. It has built-in parameter calculation module, dual closed-loop linkage control module, drying stage switching judgment module, and abnormal alarm and interlock module, which can realize the automated and intelligent management and control of the entire drying process.

[0060] The parameter calculation module can receive the collected data uploaded by the sensing layer in real time. Through the built-in calculation formula, it can output the core process parameters in real time, such as the saturated water vapor partial pressure at the corresponding temperature inside the billet, the actual water vapor partial pressure in the drying chamber, the water vapor partial pressure difference, the surface moisture diffusion rate of the billet, the moisture content gradient inside the billet, and the overall moisture diffusion rate of the billet, providing a data basis for subsequent control.

[0061] The dual closed-loop linkage control module includes an inner-loop cavity temperature and humidity precision control unit and an outer-loop billet moisture characteristic adaptive control unit. The inner-loop cavity temperature and humidity precision control unit can adjust the output power of the temperature and humidity control components in real time through a PID algorithm based on cavity environment monitoring data to maintain stable cavity temperature and absolute humidity parameters. The outer-loop billet moisture characteristic adaptive control unit can dynamically adjust the control target of the inner loop based on the real-time state parameters inside the billet, and synchronously adjust the air supply mode, wind speed, and static pressure parameters of the directional air supply component, as well as the return air ratio and humidification of the sensible heat-latent heat separation waste heat recovery component, to achieve adaptive control of the entire drying process without manual intervention to adjust process parameters.

[0062] The drying stage switching judgment module has built-in preset inter-stage switching thresholds and drying termination thresholds. It can automatically determine the current drying process stage based on the billet state parameters output in real time by the parameter calculation module, and automatically switch the control logic and parameter targets of the corresponding stage to realize automatic switching of drying stages and automatic termination of the drying process.

[0063] The abnormal alarm and interlock module can monitor the sensor communication status, actuator operation status, and cavity environment parameters in real time. When an abnormality occurs, it will immediately trigger an audible and visual alarm and an emergency stop interlock to avoid equipment failure and billet scrap risk.

[0064] Example 1: This example provides an energy-saving segmented gradient low-temperature drying method for refractory materials, including the following steps:

[0065] S1. System initialization: Moisture content and temperature sensors are pre-embedded inside the blank to be dried and connected to the control system. The full-process water vapor partial pressure difference locking range, inter-segment switching threshold and drying termination threshold are preset to complete the system self-check and cavity preheating. The water vapor partial pressure difference is the difference between the saturated water vapor partial pressure at the corresponding temperature inside the blank and the actual water vapor partial pressure in the drying cavity environment.

[0066] The sensors are embedded in the surface, middle, and deep layers of the billet. The surface layer is located at a depth of 0mm to 5mm below the surface of the billet, the middle layer is located at half the total thickness of the billet, and the deep layer is located 5mm away from the non-heated surface of the billet. Two sets of sensors are embedded at the same depth on the same billet, and the average value is taken as the valid data. The sampling frequency of the moisture content sensor and the temperature sensor is 1Hz. The preset water vapor partial pressure difference lock range is 1.85kPa. The system self-test includes sensor communication status detection, actuator action test, and safety interlock function test. The self-test is completed after all items pass. The cavity preheating adopts the no-load preheating method. The cavity is first preheated to 40℃, and then the kiln car loaded with the billet is pushed into the drying kiln to complete the preheating preparation.

[0067] S2, Surface Free Water Pre-removal: Control the temperature and absolute humidity of the drying chamber, maintain the water vapor partial pressure difference within the preset range, complete this stage according to the surface moisture diffusion rate of the blank, and switch to the next stage.

[0068] The drying chamber temperature is controlled at 50℃, the absolute humidity of the environment is controlled at 40g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 1.5kPa. The directional laminar flow air nozzles are evenly arranged along the length of the billet, with the nozzle angle forming a 15° angle with the surface of the billet, and the directional laminar flow velocity parallel to the surface of the billet is controlled at 0.75m / s. Periodic static pressure fluctuations are achieved by adjusting the variable frequency fan speed in conjunction with the opening of the return air valve, with a fluctuation period of 30s and a fluctuation amplitude of ±500Pa. The switching condition for this stage is that the surface moisture diffusion rate reaches a point of decline that lasts for more than 30 minutes and has a decrease of not less than 20%. The main air intake of the drying chamber comes entirely from the drying chamber exhaust air in step S4, and the chamber temperature is corrected only by a micro-sensible heat supplementation unit. The main heating device is in a low-power standby state with less than 5% of its rated power.

[0069] S3. Enhanced internal moisture diffusion: As the internal temperature of the billet increases, the absolute humidity of the cavity environment is reduced simultaneously to maintain the water vapor partial pressure difference within the preset range. This stage is completed according to the internal moisture content gradient of the billet and then switched to the next stage.

[0070] The drying chamber temperature is controlled at 70℃, the absolute humidity is controlled at 23 g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 2.15 kPa. The air nozzles are adjusted to be perpendicular to the thickness direction of the billet, and the directional air velocity is controlled at 1.25 m / s. The periodic static pressure fluctuation period is 20 s, and the fluctuation amplitude is ±800 Pa. The internal moisture content gradient is calculated by dividing the difference in moisture content between the middle layer and the surface layer by the vertical distance between the two layers of sensors. The switching condition for this stage is when the difference in moisture diffusion rate between the middle layer and the surface layer of the billet reaches an inflection point that lasts for more than 30 minutes and the increase is not less than 30%. The temperature and humidity are adjusted in steps, with adjustments made every 10 minutes. Each adjustment should not exceed 2℃ / 3g / kg dry air to avoid drastic parameter fluctuations. When the internal moisture content gradient is higher than 2% / cm, adjust the water vapor partial pressure difference to the 1.5kPa range, simultaneously reducing the cavity temperature by 2.5℃ and increasing the ambient absolute humidity by 4g / kg dry air. When the internal moisture content gradient is lower than 1% / cm, adjust the water vapor partial pressure difference to the 2.15kPa range, simultaneously increasing the cavity temperature by 2.5℃ and decreasing the ambient absolute humidity by 4g / kg dry air. When the internal moisture content gradient is greater than or equal to 1% / cm and less than or equal to 2% / cm, maintain the current water vapor partial pressure difference, cavity temperature, and ambient absolute humidity unchanged.

[0071] S4. Moisture Content Gradient Buffer Balance: As the internal temperature of the billet decreases, the absolute humidity of the cavity environment is increased synchronously to maintain the water vapor partial pressure difference within the preset range. This stage is completed according to the moisture content gradient inside the billet, and then the process switches to the next stage.

[0072] The drying chamber temperature is controlled at 57.5℃, the absolute humidity is controlled at 34 g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 1.35 kPa. The switching condition for this stage is that the internal moisture content gradient remains stable at no more than 1% / cm for 1 hour. When the moisture content of the deep layer of the billet is higher than that of the surface layer, the directional permeation airflow is controlled to deliver air from the air nozzles on the deep side of the bottom of the billet and return air from the return air inlet on the surface side of the top, forming a permeation airflow that runs through the thickness of the billet. The wind speed is controlled at 0.3 m / s, and the static pressure of the chamber is constant at 300 Pa. When the internal moisture content gradient drops to no more than 1% / cm, the directional airflow is switched to a bidirectional alternating directional airflow with a switching cycle of 10 min, a unidirectional air delivery duration of 5 min, and a static pressure fluctuation range of ±200 Pa. The internal pore channels of the billet are purged and repaired.

[0073] S5. Deep dehydration meets standards: As the internal temperature of the billet increases, the absolute humidity of the cavity environment is reduced simultaneously to maintain the water vapor partial pressure difference within the preset range. The drying process is completed based on the overall moisture content of the billet and the moisture diffusion rate.

[0074] The drying chamber temperature is controlled at 80℃, the absolute humidity is controlled at 11.5 g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 2.25 kPa. The high-speed turbulent circulation wind speed in the chamber is controlled at 1.75 m / s; the periodic static pressure fluctuation period is 15 s, and the fluctuation amplitude is ±1000 Pa. The drying termination condition for this stage is that the overall average moisture content of the blank remains stable at no more than 0.5% for 1 hour, and the moisture diffusion rate remains stable at no more than 0.01% / h for 1 hour. The main air intake ratio of the drying chamber is 70% from step S3. The dry and hot return air from the drying chamber exhaust after condensation and dehumidification consists of 30% fresh air that has been preheated by the sensible heat of the drying chamber exhaust in step S5, and is only supplemented by a small amount of main heating unit. All the drying chamber exhaust in step S5 enters the sensible heat-latent heat separation heat exchange unit. The sensible heat is used to preheat the fresh air, and the latent heat is used to generate saturated water vapor to supply the drying chamber in steps S4 and S2, realizing the closed-loop reuse of waste heat. After the drying process is terminated, all heating and humidification devices are stopped, and natural ventilation cooling is turned on. When the chamber temperature drops below 40°C, the kiln car is pushed out to complete the unloading of the billet.

[0075] In steps S2 to S5, the cavity temperature and the absolute humidity of the environment are always adjusted in opposite directions to maintain the water vapor partial pressure difference within the preset locking range.

[0076] Example 2: This example provides an energy-saving segmented gradient low-temperature drying method for refractory materials, including the following steps:

[0077] S1. System initialization: Moisture content and temperature sensors are pre-embedded inside the blank to be dried and connected to the control system. The full-process water vapor partial pressure difference locking range, inter-segment switching threshold and drying termination threshold are preset to complete the system self-check and cavity preheating. The water vapor partial pressure difference is the difference between the saturated water vapor partial pressure at the corresponding temperature inside the blank and the actual water vapor partial pressure in the drying cavity environment.

[0078] The sensors are embedded in the surface, middle, and deep layers of the billet. The surface layer is located at a depth of 0mm to 5mm below the surface of the billet, the middle layer is located at half the total thickness of the billet, and the deep layer is located 5mm away from the non-heated surface of the billet. Three standard sample billets are selected from each stack of billets for embedded sensors, and the average value is taken as the valid data. The sampling frequency of the moisture content sensor and the temperature sensor is 1Hz. The preset water vapor partial pressure difference lock range is 1.2kPa. The system self-test includes sensor communication status detection, actuator action test, and safety interlock function test. The self-test is completed after all items pass. The cavity preheating adopts the no-load preheating method. The cavity is first preheated to 35℃, and then the kiln car loaded with billets is pushed into the drying kiln to complete the preheating preparation.

[0079] S2, Surface Free Water Pre-removal: Control the temperature and absolute humidity of the drying chamber, maintain the water vapor partial pressure difference within the preset range, complete this stage according to the surface moisture diffusion rate of the blank, and switch to the next stage.

[0080] The drying chamber temperature is controlled at 45℃, the absolute humidity of the environment is controlled at 35g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 1.2kPa. The directional laminar flow air nozzles are evenly arranged along the length of the billet stack, with the nozzle angle forming a 15° angle with the billet surface, and the directional laminar flow velocity parallel to the billet surface is controlled at 0.5m / s. Periodic static pressure fluctuations are achieved by adjusting the variable frequency fan speed in conjunction with the opening of the return air valve, with a fluctuation period of 30s and a fluctuation amplitude of ±500Pa. The switching condition for this stage is that the surface moisture diffusion rate reaches a point of decline that lasts for more than 30 minutes and has a decrease of not less than 20%. The main air intake of the drying chamber comes entirely from the drying chamber exhaust air in step S3, and the chamber temperature is corrected only by a micro-sensible heat supplementation unit. The main heating device is in a low-power standby state with less than 5% of its rated power.

[0081] S3. Enhanced internal moisture diffusion: As the internal temperature of the billet increases, the absolute humidity of the cavity environment is reduced simultaneously to maintain the water vapor partial pressure difference within the preset range. This stage is completed according to the internal moisture content gradient of the billet and then switched to the next stage.

[0082] The drying chamber temperature is controlled at 65℃, the absolute humidity of the environment is controlled at 18 g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 1.8 kPa. The air nozzles are adjusted to be perpendicular to the thickness direction of the billet, and the directional air velocity is controlled at 1 m / s. The periodic static pressure fluctuation period is 20 s, and the fluctuation amplitude is ±800 Pa. The internal moisture content gradient is calculated by dividing the difference in moisture content between the middle layer and the surface layer by the vertical distance between the two layers of sensors. The switching condition for this stage is when the difference in moisture diffusion rate between the middle layer and the surface layer of the billet reaches an inflection point that lasts for more than 30 minutes and the increase is not less than 30%. The temperature and humidity are adjusted in steps, every 10 minutes. Each adjustment should not exceed 2℃ / 3g / kg dry air to avoid drastic parameter fluctuations. When the internal moisture content gradient is higher than 2% / cm, adjust the water vapor partial pressure difference to the 1.2kPa range, simultaneously reduce the cavity temperature by 2℃ and increase the ambient absolute humidity by 3g / kg dry air. When the internal moisture content gradient is lower than 1% / cm, adjust the water vapor partial pressure difference to the 1.8kPa range, simultaneously increase the cavity temperature by 2℃ and decrease the ambient absolute humidity by 3g / kg dry air. When the internal moisture content gradient is greater than or equal to 1% / cm and less than or equal to 2% / cm, maintain the current water vapor partial pressure difference, cavity temperature, and ambient absolute humidity unchanged.

[0083] S4. Moisture Content Gradient Buffer Balance: As the internal temperature of the billet decreases, the absolute humidity of the cavity environment is increased synchronously to maintain the water vapor partial pressure difference within the preset range. This stage is completed according to the moisture content gradient inside the billet, and then the process switches to the next stage.

[0084] The drying chamber temperature is controlled at 55℃, the absolute humidity of the environment is controlled at 30g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 1.2kPa. The switching condition for this stage is that the internal moisture content gradient is stable at no more than 1% / cm for 1 hour. When the moisture content of the deep layer of the billet is higher than that of the surface layer, the directional permeation airflow is controlled to send air from the air supply nozzle on the deep side of the bottom of the billet and return air from the return air inlet on the surface side of the top, forming a permeation airflow that runs through the thickness of the billet. The wind speed is controlled at 0.2m / s, and the static pressure of the chamber is constant at 300Pa. When the internal moisture content gradient drops to no more than 1% / cm, the directional airflow is switched to bidirectional alternating directional airflow with a switching cycle of 10min, a unidirectional air supply duration of 5min, and a static pressure fluctuation range of ±200Pa. The internal pore channels of the billet are purged and repaired.

[0085] S5. Deep dehydration meets standards: As the internal temperature of the billet increases, the absolute humidity of the cavity environment is reduced simultaneously to maintain the water vapor partial pressure difference within the preset range. The drying process is completed based on the overall moisture content of the billet and the moisture diffusion rate.

[0086] The drying chamber temperature is controlled at 75℃, the absolute humidity is controlled at 8 g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 2.0 kPa. The high-speed turbulent circulation wind speed in the chamber is controlled at 1.5 m / s. The periodic static pressure fluctuation period is 15 s, and the fluctuation amplitude is ±1000 Pa. The drying termination condition for this stage is that the overall average moisture content of the blank remains stable at no more than 0.5% for 1 hour, and the moisture diffusion rate remains stable at no more than 0.01% / h for 1 hour. The main air intake ratio of the drying chamber is 60% from the drying chamber in step S2. The dry, hot return air after condensation and dehumidification of the exhaust air is 40% fresh air that has been preheated by the sensible heat of the exhaust air from the drying chamber in step S5, and is only supplemented by a small amount of main heating unit; all the exhaust air from the drying chamber in step S5 enters the sensible heat-latent heat separation heat exchange unit, where the sensible heat is used to preheat the fresh air and the latent heat is used to generate saturated water vapor to supply the drying chambers in steps S4 and S2, realizing the closed-loop reuse of waste heat; after the drying process is terminated, all heating and humidification devices are stopped, natural ventilation cooling is turned on, and when the chamber temperature drops below 40°C, the kiln car is pushed out to complete the unloading of the billet.

[0087] In steps S2 to S5, the cavity temperature and the absolute humidity of the environment are always adjusted in opposite directions to maintain the water vapor partial pressure difference within the preset locking range.

[0088] Example 3: This example provides an energy-saving segmented gradient low-temperature drying method for refractory materials, including the following steps:

[0089] S1. System initialization: Moisture content and temperature sensors are pre-embedded inside the blank to be dried and connected to the control system. The full-process water vapor partial pressure difference locking range, inter-segment switching threshold and drying termination threshold are preset to complete the system self-check and cavity preheating. The water vapor partial pressure difference is the difference between the saturated water vapor partial pressure at the corresponding temperature inside the blank and the actual water vapor partial pressure in the drying cavity environment.

[0090] The sensors are pre-embedded in the surface, middle, and deep layers of the billet. The surface layer is located at a depth of 0mm to 5mm below the surface of the billet, the middle layer is located at half the total thickness of the billet, and the deep layer is located 5mm away from the non-heated surface of the billet. Three sets of pre-embedded points are set along the length of the same billet, and each set of points includes surface, middle, and deep sensors. The average value of multiple sets of data is taken as the valid data. The sampling frequency of the moisture content sensor and the temperature sensor is 2Hz. The preset water vapor partial pressure difference lock-in range is 2.5kPa. The system self-test includes sensor communication status detection, actuator action test, and safety interlock function test. The self-test is completed after all items pass. The cavity preheating adopts the no-load preheating method. The cavity is first preheated to 45℃, and then the kiln car loaded with the billet is pushed into the drying kiln to complete the preheating preparation.

[0091] S2, Surface Free Water Pre-removal: Control the temperature and absolute humidity of the drying chamber, maintain the water vapor partial pressure difference within the preset range, complete this stage according to the surface moisture diffusion rate of the blank, and switch to the next stage.

[0092] The drying chamber temperature is controlled at 55℃, the absolute humidity of the environment is controlled at 45g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 1.8kPa. The directional laminar flow air nozzles are evenly arranged along the length of the billet, with the nozzle angle forming a 15° angle with the surface of the billet, and the directional laminar flow velocity parallel to the surface of the billet is controlled at 1m / s. Periodic static pressure fluctuations are achieved by adjusting the speed of the variable frequency fan in conjunction with the opening of the return air valve, with a fluctuation period of 30s and a fluctuation amplitude of ±500Pa. The switching condition for this stage is that the surface moisture diffusion rate reaches a point of decline that lasts for more than 30 minutes and has a decrease of not less than 20%. The main air intake of the drying chamber comes entirely from the drying chamber exhaust air in step S4, and the chamber temperature is corrected only by a micro-sensible heat supplementation unit. The main heating device is in a low-power standby state with less than 5% of its rated power.

[0093] S3. Enhanced internal moisture diffusion: As the internal temperature of the billet increases, the absolute humidity of the cavity environment is reduced simultaneously to maintain the water vapor partial pressure difference within the preset range. This stage is completed according to the internal moisture content gradient of the billet and then switched to the next stage.

[0094] The drying chamber temperature is controlled at 75℃, the absolute humidity is controlled at 28g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 2.5kPa. The air nozzles are adjusted to be perpendicular to the thickness direction of the billet, and the directional air velocity is controlled at 1.5m / s. The periodic static pressure fluctuation period is 20s, and the fluctuation amplitude is ±800Pa. The internal moisture content gradient is calculated by dividing the difference in moisture content between the middle layer and the surface layer by the vertical distance between the two layers of sensors. The switching condition for this stage is when the difference in moisture diffusion rate between the middle layer and the surface layer of the billet reaches an inflection point that lasts for more than 30 minutes and the increase is not less than 30%. Temperature and humidity are adjusted in steps, every 10 minutes. Each adjustment should not exceed 2℃ / 3g / kg dry air to avoid drastic parameter fluctuations. When the internal moisture content gradient is higher than 2% / cm, adjust the water vapor partial pressure difference to the 1.8kPa range, simultaneously reduce the cavity temperature by 3℃ and increase the ambient absolute humidity by 5g / kg dry air. When the internal moisture content gradient is lower than 1% / cm, adjust the water vapor partial pressure difference to the 2.5kPa range, simultaneously increase the cavity temperature by 3℃ and decrease the ambient absolute humidity by 5g / kg dry air. When the internal moisture content gradient is greater than or equal to 1% / cm and less than or equal to 2% / cm, maintain the current water vapor partial pressure difference, cavity temperature, and ambient absolute humidity unchanged.

[0095] S4. Moisture Content Gradient Buffer Balance: As the internal temperature of the billet decreases, the absolute humidity of the cavity environment is increased synchronously to maintain the water vapor partial pressure difference within the preset range. This stage is completed according to the moisture content gradient inside the billet, and then the process switches to the next stage.

[0096] The drying chamber temperature is controlled at 60℃, the absolute humidity of the environment is controlled at 38g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 1.5kPa. The switching condition for this stage is that the internal moisture content gradient is stable at no more than 1% / cm for 1 hour. When the moisture content of the deep layer of the billet is higher than that of the surface layer, the directional permeation airflow is controlled to send air from the air supply nozzle on the deep side of the bottom of the billet and return air from the return air inlet on the surface side of the top, forming a permeation airflow that runs through the thickness of the billet. The wind speed is controlled at 0.4m / s, and the static pressure of the chamber is constant at 300Pa. When the internal moisture content gradient drops to no more than 1% / cm, the directional airflow is switched to bidirectional alternating directional airflow with a switching cycle of 10min, a unidirectional air supply duration of 5min, and a static pressure fluctuation range of ±200Pa. This is to purge and repair the pore channels inside the billet to avoid pore shrinkage and blockage.

[0097] S5. Deep dehydration meets standards: As the internal temperature of the billet increases, the absolute humidity of the cavity environment is reduced simultaneously to maintain the water vapor partial pressure difference within the preset range. The drying process is completed based on the overall moisture content of the billet and the moisture diffusion rate.

[0098] The drying chamber temperature is controlled at 85℃, the absolute humidity is controlled at 15g / kg dry air, and the water vapor partial pressure difference is stabilized within the range of 2.5kPa. The high-speed turbulent circulation wind speed in the chamber is controlled at 2m / s. The periodic static pressure fluctuation period is 15s, and the fluctuation amplitude is ±1000Pa. The drying termination condition for this stage is that the overall average moisture content of the blank remains stable at no more than 0.5% for 1 hour, and the moisture diffusion rate remains stable at no more than 0.01% / h for 1 hour. The main air intake ratio of the drying chamber is 80% from the drying chamber in step S3. The dry, hot return air after condensation and dehumidification of the exhaust air is 20% fresh air that has been preheated by the sensible heat of the exhaust air from the drying chamber in step S5, and is only supplemented by a small amount of main heating unit; all the exhaust air from the drying chamber in step S5 enters the sensible heat-latent heat separation heat exchange unit, where the sensible heat is used to preheat the fresh air and the latent heat is used to generate saturated water vapor to supply the drying chambers in steps S4 and S2, realizing the closed-loop reuse of waste heat; after the drying process is terminated, all heating and humidification devices are stopped, natural ventilation cooling is turned on, and when the chamber temperature drops below 40°C, the kiln car is pushed out to complete the unloading of the billet.

[0099] In steps S2 to S5, the cavity temperature and the absolute humidity of the environment are always adjusted in opposite directions to maintain the water vapor partial pressure difference within the preset locking range.

[0100] Comparative Example 1: The only difference between this comparative example and Example 1 is that the drying process does not use the water vapor partial pressure difference as the core control variable, but adopts the traditional temperature gradient control method. In stages S2 to S5, only the cavity temperature is controlled to adjust according to the preset curve, and the absolute humidity of the environment and the water vapor partial pressure difference are not controlled. The switching conditions of each stage are changed to reach the preset temperature target value. The other blank parameters, drying steps, air supply and static pressure parameters, and waste heat recovery methods are completely consistent with Example 1.

[0101] Comparative Example 2: The only difference between this comparative example and Example 1 is that the S4 moisture content gradient buffer equilibrium stage is not set. After the S3 internal moisture diffusion enhancement step is completed, it directly enters the S5 deep dehydration standard step. There is no cooling and humidification treatment between S3 and S5. The other green body parameters, process parameters of each step, air supply and static pressure parameters, waste heat recovery method, and inter-stage switching conditions are completely consistent with Example 1.

[0102] Comparative Example 3: The only difference between this comparative example and Example 1 is that: in stages S2 to S5, the cavity temperature and ambient absolute humidity adopt an independent control strategy. The temperature is adjusted according to a preset curve, and the humidity is adjusted according to an independent preset curve. The control method of simultaneous dehumidification during heating and simultaneous humidification during cooling is not implemented, and the water vapor partial pressure difference is not locked within a preset range. All other blank parameters, drying step division, air supply and static pressure parameters, waste heat recovery method, and inter-stage switching conditions are completely consistent with Example 1.

[0103] Comparative Example 4: The only difference between this comparative example and Example 1 is that the multi-stage waste heat closed-loop recycling system is cancelled. The air intake of each stage S2, S3, S4 and S5 is fresh air heated by the main heating device and then sent in. The exhaust air of each stage is directly discharged into the atmosphere. There is no energy coupling and waste heat recovery between stages. The other blank parameters, temperature and humidity parameters of each step, air supply and static pressure parameters, and inter-stage switching conditions are completely consistent with Example 1.

[0104] Comparative Example 5: The only difference between this comparative example and Example 1 is that it adopts the unidirectional stepped heating high-temperature hot air circulation drying process commonly used in the refractory materials industry. Specifically, the drying chamber is heated from room temperature to 80°C and kept at that temperature for 4 hours, then heated to 110°C and kept at that temperature for 12 hours, then heated to 150°C and kept at that temperature for 6 hours, and finally heated to 200°C and kept at that temperature for 6 hours. The entire process adopts continuous ventilation with a fixed air volume, without setting water vapor partial pressure difference control, without setting buffer balance section, without directional air supply and static pressure fluctuation, and without waste heat recovery. The other blank specifications and initial moisture content are completely consistent with Example 1.

[0105] Project 1: Comprehensive Energy Consumption and Drying Cycle Test for Refractory Material Drying. This experiment was strictly conducted in accordance with the provisions of GB / T30874-2014 "Test Method for Drying Performance of Refractory Materials". All tests were carried out in a constant temperature and humidity laboratory under standard atmospheric pressure, ambient temperature of 25℃, and relative humidity of 50%. The test objects included all blanks to be dried in Examples 1-3 and Comparative Examples 1-5. The material, dimensions, initial moisture content, and forming method of all blanks were kept completely consistent. During the experiment, the total time from the start of the drying process to the reaching of the drying termination standard for each group of samples was recorded as the drying cycle. At the same time, the total energy consumption of the entire drying process was recorded synchronously using a high-precision electricity meter and a gas flow meter. The comprehensive drying energy consumption per unit mass of dehydrated material was calculated by combining the total dehydration amount of each group of samples. All test data were repeated 3 times and the arithmetic mean was taken as the final result to compare the production efficiency and energy saving effect of different drying schemes.

[0106] Project 2: Inspection of Appearance Quality and Internal Defects of Dried Refractory Blanks. This experiment was conducted strictly in accordance with the provisions of GB / T10326-2017 "Inspection of Appearance, Dimensions, Cross-section and Internal Defects of Refractory Products". The test objects included all blank samples after drying in Examples 1-3 and Comparative Examples 1-5. First, a 100% appearance inspection was carried out on each group of samples. The presence of appearance defects such as crusting, cracks, missing corners, and edge chipping on the surface of each sample was recorded. The proportion of samples without appearance defects to the total number of samples was counted as the appearance yield. Subsequently, an industrial ultrasonic flaw detector was used to inspect the internal defects of each group of samples. The internal defects such as microcracks, delamination, and structural looseness caused by uneven moisture content were scanned on each sample. The number of internal defects detected and the maximum defect size of each group of samples were recorded. All inspection processes were completed by the same inspector under the same equipment parameters. The test data were verified twice to confirm the final results, which were used to compare the protection effect of different drying schemes on the structural integrity of the blanks.

[0107] Project 3: Testing of the Mechanical Properties and Volume Stability of Dried Refractory Green Body at Room Temperature. This experiment was conducted strictly in accordance with the provisions of GB / T3001-2017 "Test Method for Flexural Strength of Refractory Materials at Room Temperature", GB / T5072-2008 "Test Method for Compressive Strength of Refractory Materials at Room Temperature", and GB / T5988-2007 "Test Method for Linear Change Rate of Refractory Materials". The test objects included the standard samples of Examples 1-3 and Comparative Examples 1-5 after drying. First, each group of samples was processed into standard sizes according to the standard requirements. For each test block, the room temperature flexural strength and room temperature compressive strength were tested using a universal testing machine. Each group of test blocks consisted of no fewer than 6 blocks, and the arithmetic mean of the test results was taken. Subsequently, the permanent linear change rate of each group of samples after being kept at 110℃ for 24 hours was tested according to the standard requirements to characterize the volume stability of the green body. All environmental conditions, equipment parameters, and operating procedures were kept completely consistent throughout the testing process, and the test data were processed strictly according to the calculation methods specified in the standard. This was used to compare the impact of different drying schemes on the final performance of the refractory materials.

[0108] Table 1: Test Results of Comprehensive Energy Consumption and Drying Cycle for Drying Refractory Materials

[0109] Sample number Drying cycle (h) Comprehensive energy consumption per unit of dehydrated water (kcal / kg water) Example 1 28 398 Example 2 18 376 Example 3 40 421 Comparative Example 1 42 785 Comparative Example 2 26 405 Comparative Example 3 45 820 Comparative Example 4 28 862 Comparative Example 5 72 1260

[0110] Table 2: Results of Detection of Appearance Quality and Internal Defects of Dried Refractory Blanks

[0111] Sample number Appearance yield (%) Internal defect detection rate (%) Maximum internal defect size (mm) Example 1 99.5 0.5 No effective defects Example 2 100.0 0.0 No effective defects Example 3 99.0 1.0 ≤0.3 Comparative Example 1 82.0 28.0 ≤2.5 Comparative Example 2 65.0 45.0 ≤5.0 Comparative Example 3 78.0 32.0 ≤3.0 Comparative Example 4 99.0 1.0 ≤0.3 Comparative Example 5 84.0 35.0 ≤4.0

[0112] Table 3: Test results of mechanical properties and volume stability of dried refractory blanks at room temperature

[0113] Sample number Flexural strength at room temperature (MPa) room temperature compressive strength (MPa) Permanent linear change rate (%) after heat preservation at 110℃ for 24 hours Example 1 8.2 68.5 +0.08 Example 2 7.8 65.2 +0.06 Example 3 7.5 62.3 +0.10 Comparative Example 1 6.3 52.1 +0.22 Comparative Example 2 4.5 38.6 +0.35 Comparative Example 3 6.0 49.8 +0.25 Comparative Example 4 8.1 67.8 +0.09 Comparative Example 5 6.5 54.3 +0.20

[0114] As can be seen from Examples 1-3 and Comparative Example 1, and Tables 1-3, canceling the control logic based on the water vapor partial pressure difference and replacing it with the traditional temperature gradient control method will directly lead to unstable mass transfer dynamics in the drying process, significantly extended drying cycle, and a substantial increase in overall energy consumption. At the same time, the uniformity of dehydration of the green body will decrease, the appearance yield will decrease, and the probability of internal defects will significantly increase. Ultimately, it will also cause the room temperature mechanical properties and volume stability of refractory materials to deteriorate. This also verifies that the control logic based on the water vapor partial pressure difference is the core foundation for achieving low-temperature and high-efficiency drying in this scheme.

[0115] Based on Examples 1-3 and Comparative Example 2, and in conjunction with Tables 1-3, it can be seen that removing the moisture content gradient buffer balance stage and eliminating the cooling and humidification buffer treatment during the drying process, although it can slightly shorten the total drying time, will cause a serious imbalance in the moisture content gradient inside the billet. The internal stress cannot be effectively released during the drying process, the yield of the billet appearance will drop significantly, and the probability of defects such as internal microcracks and delamination will increase significantly. At the same time, it will seriously degrade the room temperature mechanical properties and volume stability of the refractory material during use. This also verifies that the moisture content gradient buffer balance stage is the core key link in this scheme to ensure the drying quality of the billet.

[0116] As can be seen from Examples 1-3 and Comparative Example 3, and Tables 1-3, canceling the temperature and humidity reverse linkage control mechanism and adopting a strategy of independent temperature and humidity control makes it impossible to maintain a stable water vapor partial pressure difference throughout the drying process. This will cause frequent fluctuations in the drying mass transfer dynamics, which will not only significantly prolong the drying cycle and greatly increase the overall energy consumption of drying, but also cause uneven dehydration of the green body, a decrease in appearance quality and internal structural integrity, and ultimately a significant deterioration in the performance of the refractory material. This also verifies that the temperature and humidity reverse linkage partial pressure difference locking mechanism is the core guarantee for achieving stable and precise control of the drying process in this solution.

[0117] Combining Examples 1-3 and Comparative Example 4 with Tables 1-3, it can be seen that eliminating the multi-stage waste heat closed-loop recovery system and using fresh air heating and direct exhaust in each drying stage will not significantly affect the drying quality, internal structural integrity, final mechanical properties, and volume stability of the billet. However, it will cause the overall energy consumption of the drying process to increase several times. This also verifies that the multi-stage waste heat closed-loop recovery system is the core support for achieving the ultimate energy-saving effect of this scheme, and also shows that the energy-saving design of this scheme will not have a negative impact on the drying quality of refractory materials.

[0118] As can be seen from Examples 1-3 and Comparative Example 5, and Tables 1-3, the unidirectional stepped heating high-temperature hot air circulation drying process commonly used in the refractory materials industry not only significantly extends the drying cycle and increases overall energy consumption, but also results in a low appearance yield and numerous internal defects due to the severe mismatch between the internal and external dehydration rates of the refractory material during high-temperature drying. Furthermore, high-temperature drying causes irreversible damage to the internal structure of the refractory material, deteriorating its room-temperature mechanical properties and volume stability. In contrast, this solution, through innovative design of the entire process, significantly shortens the drying cycle, reduces energy consumption, and significantly improves the drying quality and final performance of the refractory material, making it superior to conventional drying processes in the industry.

[0119] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An energy-saving segmented gradient low-temperature drying method for refractory materials, comprising drying a refractory material blank to be dried, characterized in that, Includes the following steps: S1. System initialization: Moisture content and temperature sensors are pre-embedded inside the blank to be dried and connected to the control system. The full-process water vapor partial pressure difference locking range, inter-segment switching threshold and drying termination threshold are preset to complete the system self-check and cavity preheating. The water vapor partial pressure difference is the difference between the saturated water vapor partial pressure at the corresponding temperature inside the blank and the actual water vapor partial pressure in the drying cavity environment. S2, Surface Free Water Pre-removal: Control the temperature and absolute humidity of the drying chamber, maintain the water vapor partial pressure difference within the preset range, complete this stage according to the surface moisture diffusion rate of the blank, and switch to the next stage. S3. Internal moisture diffusion enhancement: As the internal temperature of the billet increases, the absolute humidity of the cavity environment is reduced simultaneously to maintain the water vapor partial pressure difference within the preset range. This stage is completed according to the internal moisture content gradient of the billet and then switched to the next stage. S4. Moisture content gradient buffer balance: As the internal temperature of the billet decreases, the absolute humidity of the cavity environment is increased simultaneously to maintain the water vapor partial pressure difference within the preset range. This stage is completed according to the moisture content gradient inside the billet and then switched to the next stage. S5. Deep dehydration meets standards: As the internal temperature of the billet increases, the absolute humidity of the cavity environment is reduced simultaneously to maintain the water vapor partial pressure difference within the preset range. The drying process is completed based on the overall moisture content of the billet and the moisture diffusion rate.

2. The energy-saving segmented gradient low-temperature drying method for refractory materials according to claim 1, characterized in that: In step S1, the sensor is pre-embedded in the surface, middle and deep layers of the billet. The surface layer is located at a depth of 0 mm to 5 mm below the surface of the billet, the middle layer is located at 1 / 2 of the total thickness of the billet, and the deep layer is located at a distance of 5 mm from the non-heated surface of the billet. The preset water vapor partial pressure difference locking range is 1.2 kPa to 2.5 kPa.

3. The energy-saving segmented gradient low-temperature drying method for refractory materials according to claim 1, characterized in that: In step S2, the temperature of the drying chamber is controlled at 45°C to 55°C, the absolute humidity of the environment is controlled at 35g / kg to 45g / kg of dry air, and the water vapor partial pressure difference is stabilized in the range of 1.2kPa to 1.8kPa. The switching condition for this stage is that the surface moisture diffusion rate reaches a decreasing inflection point that lasts for more than 30 minutes and decreases by no less than 20%.

4. The energy-saving segmented gradient low-temperature drying method for refractory materials according to claim 1, characterized in that: In step S3, the temperature of the drying chamber is controlled at 65°C to 75°C, the absolute humidity of the environment is controlled at 18g / kg to 28g / kg dry air, and the water vapor partial pressure difference is stabilized in the range of 1.8kPa to 2.5kPa. The switching condition for this stage is that the difference in the moisture diffusion rate between the middle layer and the surface layer of the blank reaches an inflection point that lasts for more than 30 minutes and the increase is not less than 30%.

5. The energy-saving segmented gradient low-temperature drying method for refractory materials according to claim 1, characterized in that: In step S4, the temperature of the drying chamber is controlled at 55°C to 60°C, the absolute humidity of the environment is controlled at 30g / kg to 38g / kg dry air, and the water vapor partial pressure difference is stabilized in the range of 1.2kPa to 1.5kPa. The switching condition for this stage is that the internal moisture content gradient is stabilized at no more than 1% / cm for 1 hour.

6. The energy-saving segmented gradient low-temperature drying method for refractory materials according to claim 1, characterized in that: In step S5, the temperature of the drying chamber is controlled at 75°C to 85°C, the absolute humidity of the environment is controlled at 8g / kg to 15g / kg of dry air, and the water vapor partial pressure difference is stabilized in the range of 2.0kPa to 2.5kPa. The drying termination condition of this stage is that the overall average moisture content of the blank is stable at no more than 0.5% for 1 hour, and the moisture diffusion rate is stable at no more than 0.01% / h for 1 hour.

7. The energy-saving segmented gradient low-temperature drying method for refractory materials according to claim 1, characterized in that: In steps S2 to S5, the cavity temperature and the absolute humidity of the environment are always adjusted in opposite directions to maintain the water vapor partial pressure difference within the preset locking range.

8. A control system for an energy-saving segmented gradient low-temperature drying method for refractory materials, characterized in that, An energy-saving segmented gradient low-temperature drying method for a refractory material according to any one of claims 1-7, comprising a sensing layer, an execution layer and a PLC control layer; The sensing layer includes a billet state monitoring unit and a cavity environment monitoring unit. The billet state monitoring unit includes a moisture content sensor and a temperature sensor for embedding the refractory billet at different depths. The cavity environment monitoring unit includes a temperature and humidity sensor, a static pressure sensor, and a wind speed sensor installed inside the drying cavity. All sensors communicate with the PLC control layer in real time. The execution layer includes a temperature and humidity control component, a directional air supply component, and a sensible heat-latent heat separation and waste heat recovery component. All components are electrically connected to the PLC control layer and receive its linkage control commands. The PLC control layer incorporates a parameter calculation module, a dual-closed-loop linkage control module, and a drying stage switching determination module. The dual-closed-loop linkage control module includes an inner-loop cavity temperature and humidity precision control unit and an outer-loop billet moisture characteristic adaptive control unit. The inner-loop cavity temperature and humidity precision control unit is used to adjust the temperature and humidity adjustment components in real time based on cavity environment monitoring data to maintain stable cavity temperature and humidity parameters. The outer-loop billet moisture characteristic adaptive control unit is used to dynamically adjust the control target of the inner loop based on the real-time state parameters inside the billet, and synchronously adjust the operating status of the directional air supply component and the sensible heat-latent heat separation waste heat recovery component. The drying stage switching determination module is used to automatically determine the drying process stage based on the billet state parameters and switch the corresponding control logic.

9. The control system of the energy-saving segmented gradient low-temperature drying method for refractory materials according to claim 8, characterized in that: The sensible heat-latent heat separation and waste heat recovery component is equipped with an exhaust port and a return air port connected to the drying chamber, as well as a humidification branch connected to the temperature and humidity control component. The sensible heat-latent heat separation and waste heat recovery component is used to separate and recover the sensible heat and latent heat of the exhaust air from the drying chamber. The sensible heat is used to preheat and supplement fresh air, and the latent heat is used to generate saturated water vapor and supply it to the drying chamber through the humidification branch. The main intake air of the drying chamber preferentially adopts the return air treated by the sensible heat-latent heat separation and waste heat recovery component.

10. The control system of the energy-saving segmented gradient low-temperature drying method for refractory materials according to claim 8, characterized in that: The directional air supply component includes a multi-component zoned air supply nozzle, an airflow reversing valve, and a variable frequency fan. The PLC control layer regulates the air supply direction, wind speed, and cavity static pressure through the directional air supply component based on the internal moisture content gradient data of the billet. At the same time, it dynamically adjusts the air supply parameters and airflow reversing cycle based on the real-time collected moisture diffusion rate of the billet.

Images