Wet material drying end point judgment method and wet material drying treatment system

Abstract

The invention belongs to the technical field of wet material treatment, and particularly relates to a wet material drying end point judgment method and a wet material drying treatment system. The drying end point judgment method comprises the following steps: acquiring a liquid level signal of a first liquid level detection device; according to the liquid level signal, liquid storage and liquid discharge operation of the metering tank is controlled, so that the metering tank circularly executes quantitative liquid storage and quantitative liquid discharge; obtaining a time interval between two adjacent times of quantitative liquid storage completion, and taking the time interval as a liquid storage period; comparing the currently obtained liquid storage period with a preset period threshold value; and judging whether the wet material drying process reaches an end point or not according to a comparison result. The change of the moisture content of the wet material during drying is indirectly reflected by monitoring the real-time rate of condensed water production, namely the change of the liquid storage period. The reduction of the evaporation rate, i.e. The prolonging of the liquid storage period, is a direct and synchronous result of the reduction of the water content. The problem of inaccurate determination of the drying end point of the wet material caused by inaccurate measurement is solved.

Description

Technical Field

[0001] This invention belongs to the technical field of wet material processing, and specifically relates to a method for determining the drying endpoint of wet materials and a wet material drying system. Background Technology

[0002] In the treatment of wet radioactive waste resin at nuclear power plants, vacuum drying is typically used to reduce the volume of waste resin with a moisture content of approximately 50%, ultimately drying it to below 4%. Accurate determination of the drying endpoint is crucial for ensuring treatment effectiveness and operational efficiency. However, in practice, the final moisture content of the material cannot be directly measured online. Currently, the commonly used method is to determine this by monitoring indirect parameters, primarily in two categories: first, monitoring the temperature of the material inside the dryer, determining the drying process as complete when it reaches a predetermined value; second, monitoring multiple parameters within the dryer, such as temperature, pressure, and humidity, and indirectly inferring the drying progress through the trends in these parameter changes.

[0003] Methods relying on material temperature for determination are problematic because conical dryers typically contain spiral agitators, making it difficult for temperature probes to accurately measure the material's center. Probes must be positioned close to the wall, leading to measurements heavily influenced by the temperature of the hot oil within the dryer jacket. These measurements fail to accurately reflect the material's average temperature. Furthermore, while the material temperature often stabilizes towards the end of the drying process, internal moisture continues to evaporate slowly, causing a sustained decrease in moisture content. Stopping drying solely because the temperature has reached a predetermined value may result in the material's moisture content remaining below the target level. Methods relying on multiple parameters such as temperature, pressure, and humidity within the dryer reflect the steam state and are only indirectly related to the material's moisture content. Throughout the drying process, temperature gradually increases while pressure and humidity gradually decrease. Even towards the end, these parameters do not reach a stable state, lacking a clear inflection point to indicate the drying endpoint. This makes judgments vague, heavily reliant on operational experience, and lacking accuracy and reliability. Summary of the Invention

[0004] This invention addresses the problem of inaccurate determination of the drying endpoint of wet materials.

[0005] On the one hand, the present invention provides a method for determining the drying endpoint of wet materials, based on a wet material drying system, the wet material drying system including a metering tank, the metering tank being used to receive condensate from the drying of wet materials, and the metering tank being provided with a first liquid level detection device; The method for determining the drying endpoint includes the following steps: Acquire the liquid level signal from the first liquid level detection device; Based on the liquid level signal, the liquid storage and drainage operations of the metering tank are controlled, so that the metering tank cyclically performs quantitative liquid storage and quantitative liquid drainage. The time interval between two consecutive completions of the quantitative liquid storage is obtained, and the time interval is taken as the liquid storage cycle; The currently obtained liquid storage period is compared with a preset period threshold. Based on the comparison results, determine whether the drying process of the wet material has reached its endpoint.

[0006] Preferably, when the liquid storage period is greater than or equal to the preset period threshold, the wet material drying process is determined to have reached its end.

[0007] Preferably, the period threshold is obtained by the following method: based on the wet material drying system, a drying test is conducted using a sample of wet material; During the experiment, the changes in the liquid storage cycle with drying time were recorded; At the end of the experiment, the final moisture content of the sample of the wet material was determined; Establish the correspondence between the liquid storage period and the final water content; Based on the target moisture content requirement, the corresponding liquid storage cycle value is determined from the correspondence, and this value is set as the cycle threshold of the wet material.

[0008] Preferably, the wet material is radioactive waste resin, and the target moisture content is less than 4%.

[0009] The present invention also provides a wet material drying system, comprising: a dryer, a condenser, a metering tank and a condensate tank connected in sequence by pipelines; The dryer is used to flash-evaporate wet materials into steam under negative pressure conditions; The metering tank is a vertical tank, and the upper inlet and lower outlet of the metering tank are respectively equipped with a first valve and a second valve, and the metering tank is equipped with a first liquid level detection device; It also includes a controller, which is connected to the first liquid level detection device, the first valve and the second valve respectively, and is used to: control the opening and closing of the first valve and the second valve according to the liquid level signal of the liquid level detection device, so that the metering tank performs quantitative liquid storage and quantitative liquid discharge in a cycle; and compare the liquid storage cycle with the set cycle threshold to determine whether the drying endpoint has been reached. The liquid storage cycle is the time interval between two consecutive quantitative liquid storage operations completed by the metering tank.

[0010] Preferably, the dryer is a conical container with an internal stirring device, and the outer wall of the dryer is provided with a heating jacket.

[0011] Preferably, the first liquid level detection device is an external liquid level gauge; the side wall of the metering tank is provided with a first interface and a second interface at intervals in the vertical direction, and the two ends of the liquid level gauge are respectively connected to the first interface and the second interface.

[0012] Preferably, the inlet of the condenser is connected to the steam outlet of the dryer via a first pipeline, and the first pipeline is equipped with a vacuum valve; the liquid outlet of the condenser is connected to the inlet of the metering tank via a second pipeline, and the second pipeline is equipped with the first valve.

[0013] Preferably, the system also includes a vacuum pump connected via a pipeline to the gas outlet side of the condenser to provide and maintain a negative pressure environment for the wet material drying system.

[0014] Preferably, the condensate tank is a horizontal tank, and a second liquid level detection device is provided on the condensate tank.

[0015] The beneficial effects of this invention are: This invention provides a method for determining the drying endpoint of wet materials. It indirectly reflects the change in moisture content during drying by monitoring the real-time rate of condensate production, i.e., the change in the liquid accumulation period. Moisture evaporation directly carries away heat, affecting the temperature of the wet material. A decrease in the evaporation rate, i.e., a longer liquid accumulation period, is a direct and simultaneous result of the decrease in moisture content. This method is not affected by heat sources and does not require deep penetration into the material, solving the problem of inaccurate endpoint determination due to inaccurate measurements. Furthermore, because the evaporation rate decreases significantly in the later stages of drying, the liquid accumulation period increases by orders of magnitude, forming a clear and objectively measurable inflection point. This completely overcomes the lag in temperature judgment, ensuring that drying only stops when the moisture content truly meets the target. The liquid accumulation period is a direct measure of the material's evaporation rate, with a clear physical meaning. Preliminary experiments can establish a definite correspondence between the liquid accumulation period and the final moisture content, thus transforming a vague, multi-factor comprehensive judgment into a clear and quantifiable numerical comparison. This makes the determination process objective and further improves the accuracy of endpoint determination.

[0016] This invention discloses a wet material drying system that transforms complex endpoint determination into a timing comparison logic that can be automatically executed by the controller. It can monitor the liquid accumulation cycle in real time and compare it with a preset cycle threshold. Once the condition is met, a stop command is automatically issued. This achieves precise closed-loop control of the process. By reasonably setting the cycle threshold, over-drying can be minimized while ensuring that the moisture content meets the standard, thereby improving overall processing efficiency. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for determining the drying endpoint of wet materials in one embodiment of the present invention; Figure 2 This is a system diagram of a wet material drying system according to one embodiment of the present invention; Figure 3 This is a schematic diagram of the metering tank in one embodiment of the present invention.

[0018] Explanation of reference numerals in the attached drawings: 1-Metering tank; 11-First valve; 12-Second valve; 13-First liquid level detection device; 2-Vacuum pump; 3-Dryer; 4-Condenser; 41-Vacuum valve; 5-Condensate tank; 51-Second liquid level detection device; 101-Upper end cap; 102-Lower end cap; 103-Upper flange; 104-Upper flange; 105-Side upper flange; 106-Side lower flange. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0020] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0021] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0022] In the related technology, the paper "Application Discussion of Hot Overpressure Treatment Technology for Low and Intermediate Radioactive Waste Resin in Nuclear Power Plants" describes an effective volume reduction treatment technology for low and intermediate radioactive waste resin, introduced from abroad and first applied in domestic nuclear power plants. It proposes the selection of the drying endpoint: the optimal drying endpoint is reflected by indicators such as temperature, pressure, and humidity within the conical dryer, and must be continuously corrected and ultimately determined through testing and operational debugging. However, the temperature, pressure, and humidity indicators within the conical dryer reflect the parameters of the steam within the dryer, and can only indirectly reflect the moisture content of the material during the drying process. Experimental data shows that throughout the drying process, the temperature within the conical dryer gradually increases, while the pressure and humidity gradually decrease. Even at the end of the drying process, the temperature, pressure, and humidity have not reached a stable state and continue to change slowly. There is no obvious inflection point to reflect the drying endpoint.

[0023] To address the problems existing in the aforementioned related technologies, the present invention provides a method for determining the drying endpoint of wet materials and a wet material drying system, which will be described in detail below with reference to specific embodiments.

[0024] See Figure 1 As shown, on one hand, the present invention provides a method for determining the drying endpoint of wet materials, based on a wet material drying system, the wet material drying system including a metering tank 1, the metering tank 1 being used to receive condensate from the drying of wet materials, and the metering tank 1 being provided with a first liquid level detection device 13; The method for determining the drying endpoint includes the following steps: S1: Obtain the liquid level signal from the first liquid level detection device 13.

[0025] Furthermore, the first liquid level detection device 13 can be a liquid level gauge, which is installed on the outer connecting pipe of the metering tank 1 to detect the liquid level height in the metering tank 1 in real time and convert the detected liquid level signal into a standard electrical signal and transmit it to the control system. This liquid level signal is not only used to determine the current liquid level status, but also provides a key input for the liquid storage and drainage control in subsequent steps.

[0026] S2: Based on the liquid level signal, control the liquid storage and drainage operations of metering tank 1, so that metering tank 1 cyclically performs quantitative liquid storage and quantitative liquid drainage; Furthermore, quantitative liquid storage and quantitative liquid discharge are controlled in a closed loop by setting upper and lower limits for the liquid level. Specifically, when the liquid level in metering tank 1 is lower than the lower limit, metering tank 1 is controlled to store liquid. When the liquid level reaches the upper limit, metering tank 1 stops storing liquid, completing one quantitative storage cycle. Similarly, during the liquid discharge process, when the liquid level is higher than the discharge start level (the upper limit), metering tank 1 is controlled to discharge liquid. When the liquid level drops to the discharge stop level (the lower limit), metering tank 1 stops discharging liquid, completing one quantitative discharge cycle. This ensures that the volume of liquid storage and discharge remains consistent each time, thereby improving the accuracy of subsequent cycle calculations.

[0027] By setting the upper and lower limits of the liquid level of metering tank 1, the volume of liquid stored and discharged in a single operation of metering tank 1 can be controlled to be quantitative, i.e., quantitative discharge and quantitative discharge.

[0028] S3: Obtain the time interval between two consecutive quantitative liquid storage completions, and use the time interval as the liquid storage cycle; Furthermore, the liquid storage cycle refers to the time elapsed from the completion of the previous liquid storage to the completion of the current liquid storage. The time point of each liquid storage completion is recorded, and the time interval between two adjacent liquid storage completions is calculated. This time interval reflects the change in the rate of moisture evaporation from the wet material during the drying process and is a key dynamic parameter for judging the drying progress.

[0029] S4: Compare the currently obtained liquid storage cycle with the preset cycle threshold; Furthermore, the preset cycle threshold is a time threshold pre-set based on material characteristics, drying process requirements, and historical data. For example, in the initial stage of drying, the material has a high moisture content, a fast evaporation rate, and a short liquid accumulation cycle; as drying progresses, moisture evaporation slows down, and the liquid accumulation cycle gradually lengthens. When the liquid accumulation cycle is detected to have lengthened to near or exceed the set threshold, it indicates that material evaporation has significantly slowed down, which can be used to determine whether the drying end point is approaching.

[0030] S5: Based on the comparison results, determine whether the drying process of the wet material has reached its endpoint.

[0031] Furthermore, if the current liquid storage cycle is greater than or equal to a preset threshold, the drying process of the wet material is determined to have reached its end, a drying completion signal is issued, and the next process is initiated. If the current liquid storage cycle is still less than the threshold, the drying process is determined to be incomplete, and the liquid storage-drainage cycle continues while monitoring the next cycle. This determination method is based on the changing trend of the evaporation rate during the drying process, and features sensitive response and accurate judgment. It can effectively avoid the problems of over-drying or under-drying that may be caused by traditional fixed-time or temperature-based judgment methods.

[0032] Therefore, the wet material drying endpoint determination method of this invention avoids the difficulties of direct temperature measurement, and indirectly reflects the change in material moisture content by monitoring the real-time rate of condensate production (reflected in the change of the liquid storage period). Water evaporation directly removes the latent heat of vaporization, affecting the material temperature; and the decrease in evaporation rate, i.e., the lengthening of the liquid storage period, is a direct and synchronous result of the decrease in moisture content. This method is not affected by heat sources and does not require deep penetration into the material, solving the problem of inaccurate measurement; moreover, because the evaporation rate decreases significantly in the later stages of drying, the liquid storage period increases by orders of magnitude, forming a clear and objectively measurable inflection point, completely overcoming the lag in temperature judgment, and ensuring that drying only stops after the moisture content truly meets the standard. The liquid storage period is a direct measure of the material's evaporation rate, and its physical meaning is clear. Through preliminary experimental calibration, a definite correspondence between the liquid storage period and the final moisture content can be established, thereby transforming the fuzzy, multi-factor comprehensive judgment into a clear, quantifiable comparison with the period threshold. This makes the determination process objective and consistent, completely eliminating human experience errors, and significantly improving the accuracy of endpoint determination and batch-to-batch consistency.

[0033] Preferably, when the liquid storage period is greater than or equal to a preset period threshold, the drying process of the wet material is determined to have reached its end.

[0034] Preferably, the period threshold is obtained by the following method: based on the wet material drying system, a drying test is conducted using a sample of wet material; S1: During the experiment, record the change in the liquid storage period with the drying time; S2: At the end of the test, determine the final moisture content of the wet material sample; S3: Establish the correspondence between the liquid storage period and the final water content; S4: Based on the target moisture content requirement, determine the corresponding liquid storage cycle value from the correspondence and set this value as the cycle threshold for wet materials.

[0035] Furthermore, a scatter plot is drawn with the liquid storage period as the abscissa and the measured final water content of the sample as the ordinate, and curve fitting is performed to obtain a calibration curve characterizing the relationship between the two. The corresponding liquid storage period value is determined from the corresponding relationship. Specifically, on the calibration curve, the abscissa value corresponding to the target water content (e.g., 4%) is found, and this abscissa value is the required period threshold.

[0036] Analysis of the calibration curves reveals that, at the end of the drying process, the liquid storage period increases rapidly and non-linearly as the moisture content decreases. Setting the period threshold within this rapid growth phase ensures that the judgment results meet the moisture content requirements while avoiding unnecessary over-drying, thus achieving a balance between energy saving and precise process control.

[0037] In one embodiment of the present invention, the wet material drying system processes waste resin material with a moisture content of approximately 50%, requiring drying to below 4% moisture content. The metering tank 1 has a diameter of 125 mm and a height of approximately 300 mm. The vertical distance between the upper side flange 105 and the lower side flange 106 is 300 mm, and a level gauge with a range of 300 mm is fitted and installed. During the waste resin drying process, the first valve 11 is open and the second valve 12 is closed. The moisture contained in the waste resin flashes into steam under negative pressure in the dryer 3, condenses into water through the condenser 4, and flows into the metering tank 1. When the liquid level in the metering tank 1 reaches the upper limit, the first valve 11 closes and the second valve 12 opens. The condensate accumulated in the metering tank 1 is discharged into the condensate tank 5; when the liquid level reaches the lower limit, the first valve 11 opens and the second valve 12 closes, and the water condensed in the condenser 4 continues to flow into the metering tank 1.

[0038] During the waste resin drying process, the liquid storage cycle of metering tank 1 is timed. In the early stages of drying, the waste resin drying rate is a relatively high and stable value, and the liquid storage cycle of metering tank 1 is approximately 2 minutes per tank. In the middle and later stages of drying, as the moisture content of the waste resin gradually decreases, the drying rate also gradually decreases, and the liquid storage cycle of metering tank 1 gradually increases. Based on the results of multiple experiments, as shown in Table 1 below, when the liquid storage cycle of metering tank 1 exceeds 30 minutes, the moisture content of the waste resin has decreased to below 4%, meeting the requirements for waste resin material drying, and the system can stop drying.

[0039] Table 1

[0040] It should be noted that the method for determining the aforementioned cycle threshold is not a simple empirical value or theoretical estimation, but rather based on experiments conducted on specific materials within the system. This method, through limited and controllable preliminary experiments, establishes a deterministic and quantifiable correspondence between the final moisture content of the material, which cannot be measured online in real time, and the liquid accumulation cycle (i.e., the dynamic parameter of the process), which can be continuously and accurately monitored online. This method of calibrating the threshold based on experimental data fundamentally overcomes the problems of large batch-to-batch variations and low reliability caused by subjective judgment. The system can automatically and objectively issue a shutdown command based on whether the real-time monitored liquid accumulation cycle exceeds the threshold. This not only significantly improves the accuracy and consistency of endpoint determination, ensuring that each batch of material consistently reaches the target moisture content and effectively preventing insufficient or excessive drying, but also improves processing efficiency by setting a timely shutdown after the moisture content reaches the target, avoiding ineffective over-drying time.

[0041] In one embodiment of the present invention, the wet material is radioactive waste resin with a target moisture content of less than 4%.

[0042] See Figure 2 As shown, the present invention also provides a wet material drying system, including a dryer 3, a condenser 4, a metering tank 1, and a condensate tank 5 connected in sequence by pipes; the dryer 3 is used to flash-evaporate the wet material into steam under negative pressure; the metering tank 1 is a vertical tank, with a first valve 11 and a second valve 12 respectively provided at the upper inlet and lower outlet, and the metering tank 1 is provided with a first liquid level detection device 13; it also includes a controller, which is connected to the first liquid level detection device 13, the first valve 11, and the second valve 12 by signal, and is used to control the opening and closing of the first valve 11 and the second valve 12 according to the liquid level signal of the liquid level detection device, so that the metering tank 1 performs quantitative liquid storage and quantitative liquid discharge in a cycle; the liquid storage cycle is compared with a set cycle threshold, and it is determined whether the drying endpoint has been reached; wherein, the liquid storage cycle is the time interval between two adjacent quantitative liquid storage operations completed by the metering tank 1.

[0043] Furthermore, the first valve 11 and the second valve 12 are drain valves.

[0044] In one embodiment of the present invention, the working process of the above-mentioned wet material drying system includes: S1: The wet material is dried under the negative pressure environment of dryer 3, so that the moisture in the wet material is converted into steam; S2: The steam is condensed in condenser 4 to obtain liquid condensate; S3: Condensate is introduced into metering tank 1. The controller controls the opening and closing of the first valve 11 and the second valve 12 according to the liquid level signal of the first liquid level detection device 13, so that metering tank 1 performs quantitative liquid storage and quantitative liquid discharge operations in a cycle. S4: The controller obtains the time interval between two consecutive quantitative liquid storage operations completed by metering tank 1, which is taken as a liquid storage cycle; S5: The controller compares the liquid storage cycle with the preset cycle threshold and determines whether the drying process has reached its end point based on the comparison result; if the end point is reached, the controller controls the dryer 3 to stop drying.

[0045] It should be noted that the wet material drying system of this invention transforms the complex endpoint determination into a timing comparison logic that can be automatically executed by the controller. The system can monitor the liquid accumulation cycle in real time and automatically, and compare it with a preset cycle threshold. Once the condition is met, a shutdown command is automatically issued. This not only reduces reliance on operator skills and the risk of human error, but also achieves precise closed-loop control of the process. By reasonably setting the cycle threshold, over-drying can be avoided to the greatest extent possible while ensuring that the moisture content meets the standard, thereby saving energy, shortening batch time, and improving overall processing efficiency. In addition, historical data on the liquid accumulation cycle is easy to record and analyze, providing a reliable data foundation for process optimization and traceability.

[0046] In one embodiment of the present invention, the dryer 3 is a conical container with an internal stirring device, and the outer wall of the dryer 3 is provided with a heating jacket.

[0047] See Figure 3 In one embodiment of the present invention, the first liquid level detection device 13 is an external liquid level gauge; the tank sidewall of the metering tank 1 is provided with a first interface and a second interface at intervals in the vertical direction, and the two ends of the liquid level gauge are respectively connected to the first interface and the second interface.

[0048] It should be noted that the metering tank 1 is a vertical cylindrical container used to receive and temporarily store the measured liquid. Its top and bottom are sealed by an upper end cap 101 and a lower end cap 102, forming a complete pressure vessel structure. An upper flange 103 is located at the top of the tank and serves as the liquid inlet. It is connected to the outlet of the condenser 4 via a first valve 11 to receive condensate. A lower flange 104 is located at the bottom of the tank and serves as the liquid outlet. It is connected to the condensate tank 5 via a second valve 12 to drain the accumulated metered liquid from the tank. The first and second ports of the metering tank 1 are connected to the first liquid level detection device 13 via upper side flange 105 and lower side flange 106, respectively, allowing communication between the inside of the tank and the inside of the first liquid level detection device 13. Specifically, the first liquid level detection device 13 is an external liquid level gauge with a clearly graduated transparent tube. Flanges are also provided at its upper and lower ends, which are bolted to the upper side flange 105 and the lower side flange 106, respectively.

[0049] In one embodiment of the present invention, the inlet of the condenser 4 is connected to the steam outlet of the dryer 3 through a first pipeline, and a vacuum valve 41 is provided on the first pipeline; the liquid outlet of the condenser 4 is connected to the inlet of the metering tank 1 through a second pipeline, and a first valve 11 is provided on the second pipeline.

[0050] It should be noted that the vacuum valve 41 is located between the dryer 3 and the condenser 4. Closing the vacuum valve 41 makes it easier to handle or maintain the dryer 3 separately.

[0051] In one embodiment of the present invention, a vacuum pump 2 is also included. The vacuum pump 2 is connected to the gas outlet side of the condenser 4 via a pipeline to provide and maintain a negative pressure environment for the wet material drying system.

[0052] It should be noted that vacuum pump 2 establishes and maintains the required negative pressure environment for the entire drying circuit (from dryer 3 to condenser 4) by continuously pumping non-condensable gases within the system. This negative pressure environment is a prerequisite for lowering the boiling point of water and achieving efficient flash dehydration of wet materials at relatively low temperatures, preventing material decomposition, performance degradation, or secondary pollution caused by high temperatures. Secondly, vacuum pump 2 provides the driving force for the directional flow of water vapor generated by the evaporation of wet materials from dryer 3 to condenser 4, improving the overall drying rate and efficiency. Simultaneously, the stable negative pressure environment ensures that the condensed liquid water reliably flows sequentially into metering tank 1 and condensate tank 5 under the influence of pressure difference and gravity. Therefore, vacuum pump 2 is not only a fundamental component for achieving vacuum drying but also a crucial prerequisite for ensuring stable material flow throughout the system, thereby enabling the accurate and reliable execution of the endpoint determination method based on the condensate generation rate.

[0053] In one embodiment of the present invention, the condensate tank 5 is a horizontal tank, and a second liquid level detection device 51 is provided on the condensate tank 5. The second liquid level detection device 51 can be configured as an external liquid level gauge, the same as the first liquid level detection device 13. The second liquid level detection device 51 monitors the accumulated liquid level in the condensate tank 5 in real time to prevent the tank from overflowing, and provides operators with clear instructions on the total amount of condensate and timely discharge, thereby ensuring the safe and orderly operation of the entire drying process.

[0054] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for determining the drying endpoint of wet materials, characterized in that, The wet material drying system includes a metering tank (1) for receiving condensate from the drying of wet materials, and a first liquid level detection device (13) is provided on the metering tank (1). The method for determining the drying endpoint includes the following steps: Obtain the liquid level signal from the first liquid level detection device (13); According to the liquid level signal, the liquid storage and discharge operations of the metering tank (1) are controlled so that the metering tank (1) performs quantitative liquid storage and quantitative liquid discharge in a cycle. The time interval between two consecutive completions of the quantitative liquid storage is obtained, and the time interval is taken as the liquid storage cycle; The currently obtained liquid storage period is compared with a preset period threshold. Based on the comparison results, determine whether the drying process of the wet material has reached its endpoint.

2. The method for determining the drying endpoint of wet materials according to claim 1, characterized in that, When the liquid storage period is greater than or equal to the preset period threshold, the drying process of the wet material is determined to have reached its end.

3. The method for determining the drying endpoint of wet materials according to claim 1, characterized in that, The period threshold is obtained by the following method: based on the wet material drying system, a drying test is conducted using a sample of wet material; During the experiment, the changes in the liquid storage cycle with drying time were recorded; At the end of the experiment, the final moisture content of the sample of the wet material was determined; Establish the correspondence between the liquid storage period and the final water content; Based on the target moisture content requirement, the corresponding liquid storage cycle value is determined from the correspondence, and this value is set as the cycle threshold of the wet material.

4. The method for determining the drying endpoint of wet materials according to any one of claims 1 to 3, characterized in that, The wet material is radioactive waste resin, and the target moisture content is less than 4%.

5. A wet material drying system, characterized in that, include: The dryer (3), condenser (4), metering tank (1) and condensate tank (5) are connected in sequence by pipes. The dryer (3) is used to flash steam wet materials into steam under negative pressure conditions; The metering tank (1) is a vertical tank. The upper inlet and lower outlet of the metering tank (1) are respectively provided with a first valve (11) and a second valve (12), and the metering tank (1) is provided with a first liquid level detection device (13). It also includes a controller, which is connected to the first liquid level detection device (13), the first valve (11) and the second valve (12) respectively, and is used to: control the opening and closing of the first valve (11) and the second valve (12) according to the liquid level signal of the liquid level detection device, so that the metering tank (1) performs quantitative liquid storage and quantitative liquid discharge in a cycle; compare the liquid storage cycle with the set cycle threshold to determine whether the drying endpoint has been reached; The liquid storage cycle is the time interval between two consecutive quantitative liquid storage operations completed by the metering tank (1).

6. The wet material drying system according to claim 5, characterized in that, The dryer (3) is a conical container with an internal stirring device, and the outer wall of the dryer (3) is provided with a heating jacket.

7. The wet material drying system according to claim 5, characterized in that, The first liquid level detection device (13) is an external liquid level gauge; the tank sidewall of the metering tank (1) is provided with a first interface and a second interface at intervals in the vertical direction, and the two ends of the liquid level gauge are respectively connected to the first interface and the second interface.

8. The wet material drying system according to claim 5, characterized in that, The inlet of the condenser (4) is connected to the steam outlet of the dryer (3) through a first pipeline, and a vacuum valve (41) is provided on the first pipeline; the liquid outlet of the condenser (4) is connected to the inlet of the metering tank (1) through a second pipeline, and the first valve (11) is provided on the second pipeline.

9. The wet material drying system according to claim 5, characterized in that, It also includes a vacuum pump (2), which is connected to the gas outlet side of the condenser (4) via a pipeline to provide and maintain a negative pressure environment for the wet material drying system.

10. The wet material drying system according to claim 5, characterized in that, The condensate tank (5) is a horizontal tank, and a second liquid level detection device (51) is provided on the condensate tank (5).

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