A heat pump cold and hot double-end utilization strip tobacco redrying system based on a wet heat-induced coefficient and a control method

Abstract

The application provides a heat pump cold and hot double-end utilization strip tobacco redrying system and a control method based on a moisture-heat-induced coefficient, and the system comprises: a closed box body and a strip tobacco conveying system penetrating through the box body; the box body is sequentially provided with a drying area and a cooling area along a conveying direction, the drying area is further provided with a moisture removal system, and the system further comprises a heat pump host, a waste heat recovery module and a control system; the heat pump host comprises a compressor, a cold end heat exchanger and a hot end heat exchanger connected through a refrigerant pipeline; the waste heat recovery module is connected to an outlet of the moisture removal system, recycles the moisture and heat of the circulating gas, preheats fresh air and then sends the fresh air into an air inlet of the hot end heat exchanger; the control system comprises a controller and temperature and humidity sensors distributed in the drying area and the cooling area, the controller is pre-installed with temperature and humidity data collected by the temperature and humidity sensors and a moisture-heat-induced coefficient control algorithm, and the controller controls the cooperative action of the compressor, the hot end heat exchanger and the moisture removal system, so that closed-loop regulation of the moisture-heat-induced coefficient in the strip tobacco drying process is realized.

Description

Technical Field

[0001] This invention relates to the field of tobacco re-drying technology, specifically to a tobacco re-drying system and control method based on the heat pump dual-end utilization of heat and cold based on the hydrothermal variability coefficient. Background Technology

[0002] Re-drying of tobacco leaves is a crucial step in the tobacco leaf re-drying process. Through processes such as drying, cooling, and rehumidification, it adjusts the moisture content of the leaves after threshing to the requirements for packaging and storage (usually 11%~13%), while simultaneously improving the physical properties and sensory quality of the leaves. With the deepening implementation of the carbon peaking scheme in the domestic tobacco industry, tobacco leaf re-drying enterprises are increasingly demanding reductions in petrochemical energy consumption and improvements in the consistency of processing quality.

[0003] Current tobacco re-drying machines typically include a drying zone, a cooling zone, and a rehumidification zone. In the drying zone, steam is used to heat and dry the tobacco sheets, producing a large amount of high-temperature condensate. In the rehumidification zone, steam-water atomizing nozzles are used to humidify and rehydrate the tobacco sheets. This traditional process has the following technical problems:

[0004] (1) Low thermal energy utilization efficiency and serious energy waste. The high-temperature condensate (usually above 90°C) generated in the drying zone enters the recovery pipeline directly, and a large amount of waste heat is lost to the environment; at the same time, the steam required by the rehumidification zone still relies on fossil energy boilers, resulting in a contradictory situation of "heat being discharged on one side and energy being consumed on the other". Existing improvement schemes, such as using condensate preheating fresh air and solar steam supply, can reduce energy consumption to a certain extent, but still do not achieve direct coupling between waste heat in the drying zone and energy use in the rehumidification zone.

[0005] (2) Insufficient temperature and humidity control precision affects the consistency of tobacco processing quality. During the re-drying process, tobacco undergoes drastic temperature and humidity changes, and its internal moisture migration and heat and moisture transfer processes are complex. Studies have shown that the "heat and moisture accumulation effect" experienced by tobacco during thermal processing—that is, the influence of the combined effect of temperature and humidity on the internal structure of the material—directly relates to the final filling value, crush resistance, and sensory quality of the tobacco. However, existing processes lack quantitative evaluation indicators and control methods for this effect, and the drying and rehumidification processes are often controlled independently, making it difficult to achieve a precise match between processing intensity and material response characteristics.

[0006] (3) In recent years, heat pump technology has been introduced into the tobacco processing field due to its high efficiency and energy-saving characteristics. For example, Chinese patent CN202410182918.6 discloses a device for heating, drying and cooling tobacco sheets using a gas source heat pump. It uses two-stage gas source heat pumps connected in series to cool the ambient air and then use it for drying, thus realizing combined heating and cooling. Another internal circulation dehumidification heat pump curing barn uses a combined heating and cooling technology, so that the heat pump's heating and cooling energy is fully used in the entire curing process. However, the above technologies are mainly aimed at the initial curing stage of the curing barn. When applied to the re-curing of tobacco sheets, they have the following limitations: First, they mostly use air source heat pumps, which are greatly affected by ambient temperature and have insufficient stability; second, they focus on the single function of drying or cooling and do not connect the heat pump evaporator side (cooling end) and condenser side (heating end) to the re-curing process at the same time; third, they lack linkage control logic with the wet and hot characteristics of tobacco sheets.

[0007] (4) Lack of process parameter optimization methods based on the hygrothermal characteristics of materials. As a porous biomaterial, tobacco flakes exhibit significant nonlinearity and time-varying response to temperature and humidity. The "hygrothermal mutagenesis characteristics" of tobacco flakes from different origins, grades, and years vary. Existing re-drying processes mostly employ fixed parameters or simple feedback control, failing to dynamically adjust the energy configuration of the entire drying-cooling-rehydration process according to the characteristics of the incoming materials. This results in large deviations in the moisture content of the processed tobacco flakes and poor temperature consistency, especially when the ambient temperature is high, the cooling effect decreases more significantly.

[0008] In order to solve the above problems, people have been seeking an ideal technological solution. Summary of the Invention

[0009] Therefore, it is necessary to address the aforementioned technical problems by providing a heat pump-based dual-end utilization system and control method for tobacco re-drying, which utilizes both hot and cold ends. By introducing the thermodynamic coefficient as a quantitative indicator, the intensity response characteristics of tobacco under the combined action of heat and humidity are characterized. Based on this, an air-water source heat pump dual-end utilization system for tobacco re-drying is constructed. The waste heat from the high-temperature condensate in the drying zone is supplied to the drying zone after being raised by the water source heat pump. At the same time, the cooling capacity of the evaporator side of the air source heat pump is used to enhance the cooling of the tobacco, thereby achieving energy cascade utilization and synergistic optimization of processing quality, and solving the technical problems of high energy consumption and poor quality consistency in the existing technology.

[0010] To achieve the above objectives, the first aspect of the present invention provides a heat pump dual-end utilization tobacco re-drying system based on the coefficient of hygrothermal variation, comprising: a sealed box and a tobacco conveying system penetrating the box; the box is provided with a drying zone and a cooling zone in sequence along the conveying direction, and the drying zone is also provided with a dehumidification system; the heat pump dual-end utilization tobacco re-drying system further includes a heat pump host, a waste heat recovery module and a control system;

[0011] The heat pump unit includes a compressor, a cold-end heat exchanger, and a hot-end heat exchanger connected via refrigerant piping. The hot-end heat exchanger is located in the drying zone of the housing as the hot end and is used to heat the circulating air for drying the tobacco flakes. The cold-end heat exchanger is located in the cooling zone of the housing as the cold end and is used to cool the circulating air for cooling the dried tobacco flakes. The compressor is also connected to the outlet of the cold-end heat exchanger to change the circulating gas from a low-pressure, low-temperature state to a high-temperature, high-pressure state.

[0012] The waste heat recovery module is connected to the outlet of the dehumidification system to recover the humid and hot circulating gas, preheat the fresh air drawn in, and then send it into the air inlet of the hot end heat exchanger.

[0013] The control system includes a controller and temperature and humidity sensors distributed in the drying and cooling zones. The compressor, the hot-end heat exchanger, the cold-end heat exchanger, and the dehumidification system are electrically connected to the controller. The controller is pre-loaded with a humidity-induced thermal variability coefficient control algorithm based on enthalpy of moisture. This algorithm is used to control the coordinated operation of the compressor, the hot-end heat exchanger, and the dehumidification system based on the temperature and humidity data collected by the temperature and humidity sensors and the humidity-induced thermal variability coefficient control algorithm, so as to achieve closed-loop regulation of the humidity-induced thermal variability coefficient during the tobacco drying process.

[0014] In the above solution, a dual-end heat and cold utilization system for tobacco re-drying is constructed using an air-water source heat pump. The waste heat from the high-temperature condensate in the drying zone is raised by the water source heat pump and then re-supplied to the circulating air in the drying zone for heating, achieving cascade recovery and reuse of waste heat during the drying process. At the same time, the low-temperature cooling capacity of the evaporator side of the air source heat pump is used to cool the dried tobacco. This reduces energy consumption in the cooling process and avoids quality deterioration of the tobacco due to sudden cooling. From the two dimensions of energy supply and process control, energy saving and consumption reduction and processing quality are synergistically optimized, solving the technical problems of high energy consumption, serious waste of cooling capacity, and poor quality consistency in existing re-drying technologies.

[0015] Furthermore, the thermodynamic coefficient is introduced as a quantitative indicator. The enthalpy difference of the moist air at the inlet and outlet of the drying zone characterizes the moist heat energy absorbed by the tobacco. By normalizing the calculation with the theoretical total enthalpy change of the entire drying process, the thermo-humidity coupling state of the tobacco, which was originally difficult to quantify directly, is transformed into a numerical indicator that can be monitored in real time, accurately characterizing the state response characteristics of the tobacco in different drying sections. On this basis, based on the real-time data collected by temperature and humidity sensors in the drying and cooling zones, the controller uses a pre-set thermodynamic coefficient control algorithm based on enthalpy to coordinate the control of the compressor frequency, the speed of the circulating fan in the drying zone, and the operation of the dehumidification system. By linking the drying air supply temperature, hot air penetration intensity, and the ambient temperature and humidity of the drying zone, the target thermodynamic coefficient curve is dynamically tracked, achieving precise closed-loop regulation of the entire tobacco drying process. This ensures that the tobacco is in the optimal thermodynamic processing state in each drying section, ultimately achieving a high degree of consistency in the processing quality of tobacco with different batches and different initial moisture contents.

[0016] To achieve the above objectives, a second aspect of the present invention provides a method for controlling the hydrothermal enthalpy-based coefficient of variation, applied to the heat pump dual-end utilization tobacco re-drying system based on the hydrothermal enthalpy-based coefficient of variation described in the first aspect, comprising the following steps:

[0017] S1: Construct a calculation expression for the thermo-induced change coefficient by utilizing the enthalpy change of the humid heat gas during the drying process; wherein, the enthalpy of the humid heat gas is directly calculated from the real-time temperature and humidity data of the air inlet and outlet, the enthalpy difference between the inlet and outlet is used to characterize the humid heat energy absorbed by the tobacco, and then normalized with the total enthalpy change of the entire drying process to obtain the thermo-induced change coefficient.

[0018] S2: Set the target hydrothermal induced change coefficient curve for the drying process based on the grade of tobacco and process requirements;

[0019] S3: Real-time collection of temperature, relative humidity and tobacco moisture content at multiple monitoring points in the drying zone, and calculation of the actual damp-heat induced change coefficient;

[0020] S4: Compare the actual thermo-hygroscopic coefficient with the target thermo-hygroscopic coefficient curve. If the deviation exceeds the preset threshold, coordinate the adjustment of the compressor, the hot-end heat exchanger and the dehumidification system. Through comprehensive control of the hot-end output, convection intensity and ambient humidity and heat, the actual thermo-hygroscopic coefficient tracks the target thermo-hygroscopic coefficient curve.

[0021] It is understandable that this scheme is based on the principle of energy conservation: during the drying process, the decrease in enthalpy of the humid air flowing through the tobacco flakes is positively correlated with the amount of humid heat energy absorbed by the tobacco flakes. Therefore, by measuring the real-time temperature and humidity data at the inlet and outlet of the drying zone and calculating the enthalpy of the humid air, and then using the inlet and outlet enthalpy difference to characterize the humid heat energy absorbed by the tobacco flakes, and normalizing it in conjunction with the theoretical total enthalpy change throughout the drying process, a quantified humid-heat induced change coefficient can be obtained. This index directly correlates the change in the moisture content of the tobacco flakes with the temperature and humidity state of the drying environment, and can accurately reflect the state response characteristics of the tobacco flakes under the action of heat and humidity coupling.

[0022] Based on this, this solution pre-sets the target thermo-hygroscopic coefficient curve for the drying process and calculates the thermo-hygroscopic coefficient in real time using real-time temperature and humidity data from the air inlet and outlet. Based on real-time data collected by temperature and humidity sensors in the drying and cooling zones, the solution utilizes a pre-built thermo-hygroscopic coefficient control algorithm based on enthalpy in the controller to coordinate the control of compressor frequency, drying zone circulating fan speed, and dehumidification system operation. By dynamically tracking the target thermo-hygroscopic coefficient curve through the linkage adjustment of drying air supply temperature, hot air penetration intensity, and ambient temperature and humidity in the drying zone, the solution achieves precise closed-loop regulation of the entire tobacco drying process, ensuring that the tobacco is in the optimal thermo-hygroscopic processing state in each drying zone, and ultimately achieving a high degree of consistency in the processing quality of tobacco with different batches and different initial moisture contents.

[0023] Furthermore, the formula for calculating the hydrothermal causative coefficient is as follows:

[0024] H_act(L) = ΔH / Htotal

[0025] Wherein, H_act(L) is the thermo-hygroscopic coefficient, ΔH is the enthalpy absorbed by the tobacco and ΔH=H1-H2; H1 is the enthalpy of the hygroscopic gas calculated based on the temperature and humidity of the air inlet; H2 is the enthalpy of the hygroscopic gas calculated based on the temperature and humidity of the air outlet; Htotal is the total enthalpy change of the tobacco at the end of drying under a specific initial moisture content obtained from previous experiments.

[0026] It's understandable that enthalpy value combines the effects of temperature and humidity. Controlling the enthalpy value is equivalent to controlling the total level of energy input from the air to the material, thus avoiding quality defects caused by temperature and humidity mismatch. In practice, first determine Htotal through experiments, then calculate the enthalpy values ​​of the humid and hot gas at the inlet and outlet to obtain the enthalpy value absorbed by the tobacco. For materials such as tobacco, controlling the enthalpy value can effectively improve drying uniformity and product grade.

[0027] The beneficial effects of this invention are as follows:

[0028] This invention utilizes the hot end of a heat pump to provide a heat source for the drying section, achieving efficient utilization of the heat pump system's cooling capacity. The coefficient of performance (COP) can reach over 3.5, resulting in 30%-40% energy savings compared to traditional steam heating. Simultaneously, the cold end of the heat pump is used for the cooling section, enabling cascaded energy utilization. Furthermore, temperature and humidity coupling control precisely regulates the thermo-hygroscopic coefficient of variation during the drying process, eliminating the need for additional refrigeration units and reducing equipment investment and operating energy consumption. In addition, the drying and cooling zones are independently temperature and humidity controlled; the drying zone focuses on heat processing, while the cooling zone focuses on cooling and shaping, avoiding mutual interference. Through temperature and humidity coupling control, the tobacco flakes are dried under constant thermal stress, resulting in uniform color, intact aroma compounds, and significantly improved moisture content uniformity. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of the heat pump dual-end hot and cold tobacco re-drying system described in this invention;

[0030] Figure 2 This is a logic block diagram of the method for controlling the hydrothermal induced change coefficient based on wet enthalpy;

[0031] Figure 3 It is a curve of the coefficient of hygrothermal causation;

[0032] Figure 4 This is the control logic block diagram for the cooling section.

[0033] In the diagram, 1. Temperature and humidity sensor. Detailed Implementation

[0034] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0035] To facilitate understanding, the interactive parties and / or terms and / or custom terms involved in this invention will first be explained in conjunction with the technical solution of this invention:

[0036] The hygrothermal-dependent coefficient exponent (HTCE) is calculated by normalizing the enthalpy difference of moist air at the inlet and outlet of the drying zone with the theoretical total enthalpy change throughout the drying process. It is used to characterize the proportion of humid heat energy absorbed by the tobacco during the drying process and to quantitatively reflect the influence of the thermo-humidity coupling effect on the changes in the state of the tobacco.

[0037] Example 1

[0038] This embodiment provides a heat pump-based dual-end utilization system for tobacco re-drying based on the damp heat variability coefficient, such as... Figure 1 As shown, it includes: a sealed box and a tobacco conveying system that runs through the box; the box is provided with a drying zone and a cooling zone in sequence along the conveying direction, and the drying zone is also provided with a dehumidification system.

[0039] It is understood that the drying zone is used to dry tobacco flakes, and a large amount of high-temperature condensate is generated during the drying process, which needs to be discharged through the dehumidification system. In specific implementations, the dehumidification system includes a dehumidification fan.

[0040] The heat pump dual-end utilization tobacco re-drying system also includes a heat pump host, a waste heat recovery module, and a control system.

[0041] The heat pump unit includes a compressor, a cold-end heat exchanger, and a hot-end heat exchanger connected via refrigerant piping. The hot-end heat exchanger is located in the drying zone of the housing as the hot end and is used to heat the circulating air for drying the tobacco flakes. The cold-end heat exchanger is located in the cooling zone of the housing as the cold end and is used to cool the circulating air for cooling the dried tobacco flakes. The compressor is also connected to the outlet of the cold-end heat exchanger to change the circulating gas from a low-pressure, low-temperature state to a high-temperature, high-pressure state.

[0042] The waste heat recovery module is connected to the outlet of the dehumidification system to recover the humid and hot circulating gas, preheat the fresh air drawn in, and then send it into the air inlet of the hot end heat exchanger.

[0043] The control system includes a controller and temperature and humidity sensors 1 distributed in the drying and cooling zones. The compressor, the hot-end heat exchanger, the cold-end heat exchanger, and the dehumidification system are electrically connected to the controller. The controller is pre-loaded with a hydrothermal induced coefficient control algorithm based on enthalpy of moisture. Based on the temperature and humidity data collected by the temperature and humidity sensors 1 and the hydrothermal induced coefficient control algorithm, the controller controls the coordinated operation of the compressor, the hot-end heat exchanger, and the dehumidification system to achieve closed-loop regulation of the hydrothermal induced coefficient during the tobacco drying process.

[0044] In one possible embodiment, the waste heat recovery module includes a regenerative heat exchanger. The primary inlet of the regenerative heat exchanger is connected to the outlet of the exhaust system, and the primary outlet is connected to an vent pipe. The secondary inlet of the regenerative heat exchanger is connected to fresh air, and the secondary outlet is connected to the air inlet of the hot-end heat exchanger. It can be understood that the waste heat recovery module can further reduce the hot-end load of the heat pump.

[0045] It is understood that the circulating air in the drying zone is heated by the condenser and then penetrates the tobacco flakes on the conveyor belt to achieve tobacco flake drying. At the same time, the high-temperature exhaust gas generated during the tobacco flake drying process is connected to the primary side of the regenerating heat exchanger to preheat the incoming fresh air. After preheating, the fresh air is sent to the hot end heat exchanger to achieve secondary heating. The air in the cooling zone is cooled and dehumidified by the cold end heat exchanger to form low-temperature and low-humidity air, which forces the dried tobacco flakes to cool down.

[0046] In one possible embodiment, the hot-end heat exchanger includes multiple independently temperature-controlled first circulating air units arranged along the conveying direction within the drying zone. Each first circulating air unit includes a set of condenser coils and a circulating fan. The condenser coils are used to heat the drying circulating air, and the circulating fan is used to blow the heated and dried circulating air toward the smoke.

[0047] It is understood that in existing tobacco sheet re-drying processes and equipment, the drying zone typically comprises 3 to 6 sections for re-drying the tobacco sheets, with each drying section being 4-8 meters long. It is also understood that each drying section is equipped with at least one first circulating air unit. Initially, the initial frequency of the circulating fan in the first circulating air unit is set to 35Hz. Subsequently, the frequency of the circulating fan is controlled based on the temperature and humidity data collected by the temperature and humidity sensor and the humidity-induced variation coefficient control algorithm to adjust the convection intensity.

[0048] For example, increasing the operating frequency of the circulating fan can enhance the penetration of hot air, thereby increasing the temperature of the flue gas. Conversely, decreasing the operating frequency of the circulating fan can weaken the penetration of hot air, thereby decreasing the temperature of the flue gas.

[0049] Similarly, the initial frequency of the compressor is set to 35Hz, and the frequency of the compressor is subsequently controlled based on the temperature and humidity data collected by the temperature and humidity sensor and the thermo-hygroscopic coefficient control algorithm to adjust the output at the hot end.

[0050] For example, increasing the compressor's operating frequency can raise the air supply temperature in the drying zone, thereby increasing the smoke temperature. Conversely, decreasing the compressor's operating frequency can lower the air supply temperature, thus lowering the smoke temperature.

[0051] Similarly, the initial frequency of the dehumidification fan is set to 35Hz, and the frequency of the dehumidification fan is subsequently controlled based on the temperature and humidity data collected by the temperature and humidity sensor and the humidity-heat induced change coefficient control algorithm to regulate the humidity and heat of the environment.

[0052] For example, increasing the operating frequency of the exhaust fan can accelerate the removal of hot and humid air, thereby lowering the ambient temperature in the drying area. Conversely, decreasing the operating frequency of the exhaust fan can slow down the removal of hot and humid air, thereby increasing the ambient temperature in the drying area.

[0053] It is understandable that by working together through the above three regulation channels, comprehensive control of hot end output, convection intensity and ambient humidity and heat can be achieved, thereby realizing precise closed-loop regulation of the humidity and heat induced change coefficient in the tobacco drying process.

[0054] Furthermore, the cold-end heat exchanger includes an evaporator and a circulating fan. The evaporator is used to cool the circulating air, and the circulating fan is used to blow the cooled circulating air toward the smoke.

[0055] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple segments. These steps or segments are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or segments is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or segments in other steps.

[0056] Example 2

[0057] Based on the same inventive concept, this application also provides a method for controlling the hydrothermal enthalpy-based coefficient of variation, applied to the heat pump dual-end utilization tobacco re-drying system based on the hydrothermal enthalpy-based coefficient of variation described in Example 1, such as... Figure 2 As shown, the specific steps include:

[0058] S1: Construct a calculation expression for the thermo-induced coefficient by utilizing the enthalpy change of the humid heat gas during the drying process.

[0059] It is understandable that the formula for calculating the damp-heat induced change coefficient index H is composed of the normalized total enthalpy change of the entire drying process, obtained by directly calculating the inlet and outlet enthalpy difference from the real-time temperature and humidity data of the air inlet and outlet.

[0060] Specifically, the formula for calculating the hydrothermal causative coefficient is as follows:

[0061] H_act(L) = ΔH / Htotal

[0062] Wherein, H_act(L) is the thermo-hygroscopic coefficient, ΔH is the enthalpy absorbed by the tobacco and ΔH=H1-H2; H1 is the enthalpy of the hygroscopic gas calculated based on the temperature and humidity of the air inlet; H2 is the enthalpy of the hygroscopic gas calculated based on the temperature and humidity of the air outlet; Htotal is the total enthalpy change of the tobacco at the end of drying under a specific initial moisture content obtained from previous experiments.

[0063] It is understandable that the total enthalpy change of tobacco leaves at the end of drying is obtained through numerous prior experiments with different initial moisture contents. Subsequently, the corresponding total enthalpy change can be obtained simply by querying the collected tobacco leaf moisture content.

[0064] It is understandable that it is also possible to obtain the total enthalpy change of different types of tobacco at different initial moisture contents to achieve different target moisture contents, thereby adapting to different types of tobacco.

[0065] S2: A target moisture-heat variation coefficient curve for the drying process is set according to the strip tobacco grade and process requirements.

[0066] Specifically, in the existing strip tobacco redrying process and equipment, the drying zone usually includes 3 to 6 sub-zones for performing redrying and drying processing on the strip tobacco. Therefore, in this embodiment, the drying zone is divided into a plurality of sections along the length direction of the drying zone, a target moisture-heat variation coefficient is set for each section respectively, and the target moisture-heat variation coefficient increases section by section along the length direction of the drying zone, so as to finally form the target moisture-heat variation coefficient curve H_set(L), as specifically shown in Figure 3 the figure below.

[0067] Figure 3 in this embodiment, the length L of the drying zone is set to 30 m, and the drying zone is divided into three sections by length: the target moisture-heat variation coefficient H_set(L) in the first section (0<L≤10 m) is 4.5 °C / %, the target moisture-heat variation coefficient H_set(L) in the second section (10<L≤20 m) is 4.8 °C / %, and the target moisture-heat variation coefficient H_set(L) in the third section (20<L<30 m) is 5.1 °C / %.

[0068] S3: The temperature T, relative humidity RH and strip tobacco moisture content M at a plurality of monitoring points in the drying zone are collected in real time, Htotal is then determined based on the strip tobacco moisture content, and the actual moisture-heat variation coefficient H_act(L) is calculated based on the aforementioned calculation expression for the moisture-heat variation coefficient.

[0069] S4: The actual moisture-heat variation coefficient H_act(L) is compared with the target moisture-heat variation coefficient curve H_set(L). If the deviation exceeds a preset threshold, the compressor, the hot end heat exchanger and the moisture exhaust system are adjusted in a coordinated manner. Through the comprehensive control of the hot end output, convection intensity and ambient moisture and heat, the actual moisture-heat variation coefficient H_act(L) is made to track the target moisture-heat variation coefficient curve H_set(L).

[0070] Specifically, when the hot end heat exchanger comprises a plurality of first circulating air units with independent temperature control arranged in the drying zone along the conveying direction, each circulating air unit corresponds to one section, each of the first circulating air units comprises a set of condenser coils and a circulating fan, and the moisture exhaust system comprises a moisture exhaust fan, the control logic for coordinately adjusting the compressor, the hot end heat exchanger and the moisture exhaust system is as follows:

[0071] When the actual thermochromic coefficient is lower than the target thermochromic coefficient for that section, it means that the actual heat treatment intensity is less than the target heat treatment intensity. At this time, the compressor operating frequency and the corresponding section circulating fan frequency are increased simultaneously, and the exhaust fan frequency is decreased. By increasing the compressor frequency, the air supply temperature in the drying zone is increased, and by increasing the circulating fan frequency, the hot air penetration intensity is enhanced. At the same time, by decreasing the exhaust fan frequency, the rate of removal of hot and humid air is slowed down, and the ambient temperature and humidity in the drying zone are increased. The three factors work together to increase the thermochromic coefficient, so as to increase the actual heat treatment intensity.

[0072] When the actual thermo-hygroscopic coefficient is higher than the target thermo-hygroscopic coefficient for that section, it means that the actual heat treatment intensity is greater than the target heat treatment intensity. At this time, the compressor operating frequency and the corresponding section circulating fan frequency are reduced simultaneously, and the exhaust fan frequency is increased. By reducing the compressor frequency to lower the supply air temperature and reducing the circulating fan frequency to weaken the hot air intensity, and by increasing the exhaust fan frequency to accelerate the removal of hot and humid air and reduce the ambient humidity in the drying zone, the three factors work together to reduce the thermo-hygroscopic coefficient, thereby achieving the goal of reducing the actual heat treatment intensity.

[0073] Furthermore, when the cold-end heat exchanger includes an evaporator and a circulating fan, where the evaporator is used to cool the circulating air and the circulating fan is used to blow the cooled circulating air toward the flue gas, the flue gas temperature at the cooling zone outlet is also monitored in real time. The deviation between the actual flue gas temperature and the target temperature (30°C) is calculated, and the operating frequency of the circulating fan and the refrigerant flow rate of the evaporator are adjusted proportionally based on the deviation. See the detailed control process below. Figure 4 .

[0074] First, determine whether the difference between the drying terminal temperature and the target temperature is greater than a preset temperature threshold. For example, determine whether the difference between the drying terminal temperature and the target temperature is greater than 20℃. If so, the actual temperature is determined to be significantly higher than 30℃. In this case, calculate the difference between the actual temperature and the target temperature, and determine the frequency increase of the cooling zone circulating fan based on this temperature difference. Adjust the frequency of the cooling zone circulating fan based on this frequency increase to increase the amount of cold air blown through the smoke in the cooling zone and rapidly reduce the smoke temperature. Otherwise, determine that the actual temperature is slightly higher than 30℃. In this case, calculate the difference between the actual temperature and the target temperature, and determine the frequency decrease of the cooling zone circulating fan based on this temperature difference. Adjust the frequency of the cooling zone circulating fan based on this frequency decrease to reduce the amount of cold air blown through the smoke in the cooling zone, avoid over-cooling, and allow the temperature to steadily approach the target.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A heat pump dual-end utilization system for tobacco re-drying based on the hydrothermal variability coefficient, comprising: A sealed enclosure and a tobacco flake conveying system that runs through the enclosure; the enclosure is provided with a drying zone and a cooling zone in sequence along the conveying direction, and the drying zone is also provided with a dehumidification system; characterized in that it further includes a heat pump host, a waste heat recovery module and a control system; The heat pump unit includes a compressor, a cold-end heat exchanger, and a hot-end heat exchanger connected via refrigerant piping. The hot-end heat exchanger is located in the drying zone of the housing as the hot end and is used to heat the circulating air for drying the tobacco flakes. The cold-end heat exchanger is located in the cooling zone of the housing as the cold end and is used to cool the circulating air for cooling the dried tobacco flakes. The compressor is also connected to the outlet of the cold-end heat exchanger to change the circulating gas from a low-pressure, low-temperature state to a high-temperature, high-pressure state. The waste heat recovery module is connected to the outlet of the exhaust system to recover the humid and hot circulating gas, preheat the fresh air drawn in, and then send it into the air inlet of the hot end heat exchanger. The control system includes a controller and temperature and humidity sensors distributed in the drying and cooling zones. The compressor, the hot-end heat exchanger, the cold-end heat exchanger, and the dehumidification system are electrically connected to the controller. The controller is pre-loaded with a humidity-induced thermal variability coefficient control algorithm based on enthalpy of moisture. This algorithm is used to control the coordinated operation of the compressor, the hot-end heat exchanger, and the dehumidification system based on the temperature and humidity data collected by the temperature and humidity sensors and the humidity-induced thermal variability coefficient control algorithm, so as to achieve closed-loop regulation of the humidity-induced thermal variability coefficient during the tobacco drying process.

2. The heat pump dual-end utilization system for tobacco re-drying based on the hydrothermal variability coefficient according to claim 1, characterized in that, The hot-end heat exchanger includes multiple independently temperature-controlled first circulating air units arranged in the drying zone along the conveying direction. Each first circulating air unit includes a set of condenser coils and a circulating fan. The condenser coils are used to heat the drying circulating air, and the circulating fan is used to blow the heated and dried circulating air toward the smoke.

3. The heat pump dual-end utilization system for tobacco re-drying based on the hydrothermal variability coefficient according to claim 1 or 2, characterized in that, The cold-end heat exchanger includes an evaporator and a circulating fan. The evaporator is used to cool the circulating air, and the circulating fan is used to blow the cooled circulating air toward the smoke.

4. The heat pump dual-end utilization system for tobacco re-drying based on the hydrothermal variability coefficient according to claim 3, characterized in that, The waste heat recovery module includes a regenerative heat exchanger. The primary side inlet of the regenerative heat exchanger is connected to the outlet of the dehumidification system, and the primary side outlet is connected to the vent pipe. The secondary side inlet of the regenerative heat exchanger is connected to fresh air, and the secondary side outlet is connected to the air inlet of the hot end heat exchanger.

5. A method for controlling the hydrothermal enthalpy-based coefficient of variation, applied to the heat pump dual-end utilization tobacco re-drying system based on the hydrothermal enthalpy-based coefficient of variation as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: Construct a calculation expression for the thermo-induced change coefficient by utilizing the enthalpy change of the humid heat gas during the drying process; wherein, the enthalpy of the humid heat gas is directly calculated from the real-time temperature and humidity data of the air inlet and outlet, the enthalpy difference between the inlet and outlet is used to characterize the humid heat energy absorbed by the tobacco, and then normalized with the total enthalpy change of the entire drying process to obtain the thermo-induced change coefficient. S2: Set the target hydrothermal induced change coefficient curve for the drying process based on the grade of tobacco and process requirements; S3: Real-time collection of temperature, relative humidity and tobacco moisture content at multiple monitoring points in the drying zone, and calculation of the actual damp-heat induced change coefficient; S4: Compare the actual thermo-hygroscopic coefficient with the target thermo-hygroscopic coefficient curve. If the deviation exceeds the preset threshold, coordinate the adjustment of the compressor, the hot-end heat exchanger and the dehumidification system. Through comprehensive control of the hot-end output, convection intensity and ambient humidity and heat, the actual thermo-hygroscopic coefficient tracks the target thermo-hygroscopic coefficient curve.

6. The method for controlling the hydrothermal induced variation coefficient based on wet enthalpy according to claim 5, characterized in that, The target thermo-hygroscopic coefficient curve is divided into multiple segments along the length of the drying zone, and a target thermo-hygroscopic coefficient is set for each segment. The target thermo-hygroscopic coefficient increases segment by segment along the length of the drying zone.

7. The method for controlling the hydrothermal induced variation coefficient based on wet enthalpy according to claim 5, characterized in that, The expression for calculating the hydrothermal induced change coefficient is: H_act(L) = ΔH / Htotal Wherein, H_act(L) is the thermo-hygroscopic coefficient, ΔH is the enthalpy absorbed by the tobacco and ΔH=H1-H2; H1 is the enthalpy of the hygroscopic gas calculated based on the temperature and humidity of the air inlet; H2 is the enthalpy of the hygroscopic gas calculated based on the temperature and humidity of the air outlet; Htotal is the total enthalpy change of the tobacco at the end of drying under a specific initial moisture content obtained from previous experiments.

8. A method for controlling the hydrothermal induced change coefficient based on wet enthalpy according to claim 5, 6, or 7, characterized in that, When the hot-end heat exchanger includes multiple independently temperature-controlled first circulating air units arranged along the conveying direction within the drying zone, each circulating air unit corresponding to a section, each first circulating air unit including a set of condenser coils and a circulating fan, and the dehumidification system including a dehumidification fan, the control logic for coordinated adjustment of the compressor, the hot-end heat exchanger, and the dehumidification system is as follows: When the actual thermo-hygroscopic coefficient is lower than the target thermo-hygroscopic coefficient for that section, the operating frequency of the compressor and the frequency of the corresponding section's circulating fan are increased simultaneously, while the frequency of the exhaust fan is decreased, in order to synergistically improve the thermo-hygroscopic coefficient. Specifically, increasing the compressor frequency increases the supply air temperature in the drying zone, increasing the frequency of the circulating fan enhances the penetration intensity of hot air, and decreasing the frequency of the exhaust fan slows down the rate of removal of hot and humid air and increases the ambient temperature and humidity in the drying zone. When the actual thermo-hygroscopic coefficient is higher than the target thermo-hygroscopic coefficient for that section, the operating frequency of the compressor and the frequency of the corresponding section's circulating fan are reduced simultaneously, while the frequency of the exhaust fan is increased to synergistically reduce the thermo-hygroscopic coefficient. Specifically, reducing the compressor frequency lowers the supply air temperature, reducing the circulating fan frequency weakens the hot air intensity, and increasing the exhaust fan frequency accelerates the removal of hot and humid air and reduces the ambient humidity in the dry area.

9. The method for controlling the hydrothermal induced change coefficient based on wet enthalpy according to claim 5, characterized in that, When the cold-end heat exchanger includes an evaporator and a circulating fan, the evaporator is used to cool the circulating air, and the circulating fan is used to blow the cooled circulating air toward the flue gas. The flue gas temperature at the outlet of the cooling zone is also monitored in real time, the deviation between the actual flue gas temperature and the target temperature is calculated, and the operating frequency of the circulating fan and the refrigerant flow rate of the evaporator are adjusted proportionally according to the deviation.

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