A three-dimensional circulating tobacco leaf curing method

Abstract

This invention discloses a three-dimensional circulating tobacco curing method, relating to the field of agricultural product processing technology. The method includes the following steps: hanging the tobacco leaves to be cured onto a driving mechanism using tobacco leaf clamps; moving the tobacco leaf clamps along a three-dimensional circulating path within the drying chamber via the driving mechanism, while simultaneously regulating the temperature and humidity within the drying chamber using a heat source to achieve staged curing; wherein the three-dimensional circulating path includes multiple level path segments distributed at different heights, and vertical reversing segments connecting adjacent level path segments. The three-dimensional circulating tobacco curing method provided by this invention has the following beneficial effects: eliminating temperature and humidity dead zones, improving the quality of cured tobacco leaves; enabling single-point operation, reducing labor workload; and fully utilizing heat energy.

Description

Technical Field

[0001] This invention belongs to the field of agricultural product processing technology, specifically relating to a three-dimensional circulating tobacco curing method. Background Technology

[0002] Tobacco curing is a crucial step in the entire tobacco production process, determining the final commercial value and intrinsic quality of tobacco leaves. Traditional tobacco curing often uses fixed, multi-layered curing barns, where tobacco bundles with wet leaves are manually stacked layer by layer onto fixed racks inside the barn. Because traditional curing barns often have dead zones in their hot air circulation, the temperature and humidity distribution between layers and between the front and back sections is uneven, easily leading to inconsistent curing quality, with some areas showing greenness or others being covered in ash, and the entire process of loading and unloading relies on manual climbing and stacking, resulting in extremely high labor intensity. Summary of the Invention

[0003] To address the problems of uneven temperature and humidity in the drying room and the difficulty of manual stacking, this invention provides a three-dimensional circulating tobacco leaf drying method, the specific technical solution of which is as follows: A three-dimensional circulating tobacco curing method includes the following steps: S1. Loading: The tobacco leaves to be cured are hung on the drive mechanism using tobacco leaf clamps; S2. Circulating baking: The tobacco leaf clamp is driven by the drive mechanism to move along the three-dimensional circulating path in the drying room, and the temperature and humidity in the drying room are adjusted by the heat source to achieve staged baking; The three-dimensional loop path includes multiple hierarchical path segments distributed at different heights, as well as vertical reversal segments connecting two adjacent hierarchical path segments.

[0004] Preferably, at least a portion of the hierarchical path segments are projected in a serpentine shape in the vertical plane.

[0005] Preferably, the driving mechanism includes a drive chain assembly, the movement direction of which forms the three-dimensional loop path; the drive chain assembly includes a first drive chain and a second drive chain arranged side by side, the projection distance between two opposite mounting points on the first drive chain and the second drive chain in the horizontal plane remains constant, and the two ends of the tobacco leaf clip are respectively connected to the two opposite mounting points.

[0006] Preferably, on the drive chain assembly, the distance d between any two adjacent tobacco leaf clips is greater than the length L of the tobacco leaf to be cured.

[0007] Preferably, on the drive chain assembly, the distance d between any two adjacent tobacco leaf clips is less than the length L of the tobacco leaf to be cured; In the vertical reversing section, the two opposite mounting points drive the two ends of the tobacco clip to move along a spiral line, so that the horizontal projection trajectory of the tobacco clip rotates by (2n+1)×180°, where n is a natural number.

[0008] Preferably, both the first drive chain and the second drive chain are universal drive chains; on the vertical reversing section, a pair of helical guide rails are symmetrically fixed, and the first drive chain and the second drive chain are respectively limited and slidably connected to the helical guide rails on the corresponding sides.

[0009] Preferably, the distance d is 0.3 to 0.5 times the length L of the tobacco leaves to be cured.

[0010] Preferably, in step S2, the staged baking includes a yellowing stage, a color-fixing stage, and a drying stage, wherein the adjustment of the temperature and humidity in the drying chamber is achieved by controlling the dry-bulb temperature and the wet-bulb temperature, respectively. During the yellowing stage: control the dry bulb temperature to slowly rise to 38℃ and maintain the temperature for 30~40 hours, while controlling the wet bulb temperature to slowly rise to 35~37℃ and maintain the temperature for 30~40 hours. During the color fixation stage: control the dry bulb temperature to slowly rise to 54℃ and maintain the temperature for 15~25h, while controlling the wet bulb temperature to first rise to 37~39℃ and maintain the temperature for 15~25h, and then control the wet bulb temperature to rise again to 39~41℃ and maintain the temperature for 15~25h. During the dry bulb stage: control the dry bulb temperature to slowly rise to 68℃ and maintain the temperature for more than 7 hours, while controlling the wet bulb temperature to rise to 40~43℃ and maintain the temperature for more than 17 hours.

[0011] Preferably: During the yellowing stage, the slow heating includes heating at a rate of 1°C / h; During the color-fixing stage, the slow heating includes: heating to 42°C at a heating rate of 1°C / 4h, then heating to 46°C at a heating rate of 1°C / 3h, then heating to 50°C at a heating rate of 1°C / 2h, and then heating to 54°C at a heating rate of 1°C / 1h. During the drying stage, the slow heating includes heating at a rate of 1℃ / h.

[0012] Preferably: In step S1, the tobacco leaf clip adopts a long strip hanging structure with a span that matches the width of the drying room; and the loading and unloading of the tobacco leaf clip on the three-dimensional circulation path, as well as the unloading after drying, are all completed at the same operation position at the door of the drying room on the three-dimensional circulation path. In step S2, the heat source is a variable frequency dual-temperature air source heat pump, and the cyclic baking step includes: dynamically adjusting the output frequency of the variable frequency dual-temperature air source heat pump by frequency conversion control in accordance with the cycle of the tobacco leaves being moved in a three-dimensional circulation within the drying room.

[0013] The three-dimensional circulating tobacco curing method provided by this invention has the following beneficial effects: 1. Eliminating temperature and humidity dead zones and improving the quality of cured tobacco leaves: A drive mechanism continuously moves the tobacco leaves within a three-dimensional circulating path composed of multi-level path segments and vertical reversing segments. This ensures that all tobacco leaves in the curing chamber are in a dynamic, alternating position throughout the curing process, overcoming the temperature and humidity dead zones caused by uneven local wind speeds and heat source segregation in traditional static curing chambers. The entire batch of tobacco leaves receives uniform heating and dehumidification, reducing the proportion of raw and ash-covered tobacco, and improving the yield of high-quality tobacco, color uniformity, and intrinsic aroma quality after curing.

[0014] 2. Enables single-point operation and reduces workload: Based on the conveyor belt properties of this closed-loop three-dimensional circulation path, the loading and unloading of tobacco leaves after drying can be completed at the same fixed operating position near the entrance of the drying room. Operators no longer need to manually climb and set up tobacco clamps inside the narrow, high-temperature drying room, which greatly improves the working environment and reduces the loading and unloading time and labor intensity of single-room drying.

[0015] 3. Full utilization of thermal energy: Because the tobacco leaves are in motion inside the drying chamber, their surface convective heat transfer coefficient is significantly higher than that of static stacking, greatly improving the efficiency of moisture evaporation and heat and moisture exchange with the air. Combined with staged drying process control, thermal energy utilization efficiency is maximized. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art are briefly introduced below.

[0017] Figure 1 This is a simplified side view diagram of the three-dimensional circulation path trajectory structure in Example 1 of the three-dimensional circulating tobacco curing method of the present invention; Figure 2 This is a side view of the mechanical interference and jamming state of adjacent tobacco leaves in a three-dimensional circulating tobacco curing method when they are tightly loaded with a narrow spacing and without using a spiral spatial reversal path. Figure 3 This is a simplified side view diagram of the three-dimensional spatial torsion path trajectory structure in Example 2 of the three-dimensional circulating tobacco curing method of the present invention; Figure 4 This is a hyperbola graph showing the staged baking process control used in step S2 of the three-dimensional circulating tobacco baking method of the present invention.

[0018] Figure Labels 10 - Tobacco leaves to be cured; 20 - Tobacco leaf clamp; 30 - Drive mechanism. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0020] It should be noted that similar labels in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0021] Please see Figures 1 to 4 This embodiment provides a three-dimensional circulating tobacco curing method, including the following steps: S1. Loading: The tobacco leaves 10 to be cured are mounted on the drive mechanism 30 via the tobacco leaf clamp 20.

[0022] S2. Circulating baking: The tobacco leaf clamp 20 is driven by the drive mechanism 30 to move along the three-dimensional circulating path in the drying room. At the same time, the temperature and humidity in the drying room are regulated by the heat source to achieve staged baking.

[0023] The three-dimensional loop path includes multiple hierarchical path segments distributed at different heights, as well as vertical reversal segments connecting two adjacent hierarchical path segments.

[0024] Specifically, in step S1, the drive mechanism 30 constructs a closed-loop motion frame within the drying chamber. The wet tobacco leaves 10 to be dried are clamped and fixed in rows using rigid, elongated tobacco leaf clips 20. The two ends of the tobacco leaf clips 20 serve as the main force-bearing points, rotating or flexibly hanging on designated mounting points of the drive mechanism 30, allowing each tobacco leaf clip 20 to have independent gravity-dependent downward freedom during the movement. This loading method changes the traditional fixed drying chamber operation mode that requires manual climbing and stacking. It transforms the complex spatial stacking action into static operation point mounting, laying the foundation hardware architecture for subsequent fully automated three-dimensional circulating drying.

[0025] In step S2, the drive mechanism 30 outputs stable power, pulling all the attached tobacco leaf clips 20 to move continuously or intermittently along a specific closed-loop trajectory in the three-dimensional space inside the drying chamber. At this time, heat is continuously transferred inside the drying chamber through a heat source (such as an air source heat pump) and circulated by a fan. Because the spatial position of the tobacco leaves 10 within the drying chamber is dynamically changing, they not only traverse different vertical airflow layers horizontally but also experience different thermal energy gradients vertically. This continuous dynamic displacement offsets the static temperature and humidity dead zones caused by duct design defects and uneven thermodynamic insulation within the drying chamber, ensuring that the windward surface and heating probability of all tobacco leaves in the entire drying chamber are almost completely equal. Simultaneously with the dynamic cyclical movement of the tobacco leaf clips 20, the overall temperature and humidity field inside the drying chamber is adjusted in stages according to the biochemical evolution laws within the tobacco leaves. The heat source precisely controls the dry-bulb and wet-bulb temperatures inside the drying chamber based on the process requirements of the three core biochemical stages of tobacco leaf development: yellowing, color fixation, and drier leaves. During the entire life cycle of tobacco curing, the rate of moisture evaporation, the progress of pigment degradation, and the cycle of the drive mechanism 30 form an organic process coupling, thereby achieving highly quantified stage curing.

[0026] Furthermore, the "three-dimensional circulation path" has undergone a scientific spatial gradation: 1. Multi-level path segments: This three-dimensional circulation path breaks away from the traditional single-layer configuration in terms of vertical height, dividing into multiple level path segments distributed at different heights. These level path segments are stacked from top to bottom or bottom to top within the drying chamber, serving as the main heating and curing areas where tobacco leaves spend the longest time inside the drying chamber, greatly expanding the space utilization rate of the drying chamber in terms of vertical height.

[0027] 2. Vertical Reversing Section: At the end of each hierarchical path segment, a "vertical reversing section" connects it to an adjacent hierarchical path segment at a different height. Physically, the vertical reversing section enables the drive mechanism 30 to change its primary motion direction (e.g., from horizontal to left, reversing downwards or upwards via the vertical section, and then transitioning to horizontal to right). Furthermore, since the tobacco leaves 10 to be cured are always vertically downwards on adjacent hierarchical path segments, after passing through the "vertical reversing section," the tobacco leaves 10 to be cured change direction along the circulation path from one side of the three-dimensional circulation path to the other.

[0028] The skeleton design of "hierarchical path segment + vertical reversing segment" folds and compresses an extremely long single-line circulation path into a drying room with a limited volume. This ensures that the tobacco leaves have a sufficiently long heating movement and achieves modular high-density arrangement in the height and width directions. The vertical reversing segment ensures that the entire system does not experience physical interference or jamming in the high-density folded state.

[0029] The three-dimensional circulating tobacco curing method provided in this embodiment has the following beneficial effects: 1. Eliminating temperature and humidity dead zones and improving the quality of cured tobacco leaves: A drive mechanism continuously moves the tobacco leaves within a three-dimensional circulating path composed of multi-level path segments and vertical reversing segments. This ensures that all tobacco leaves in the curing chamber are in a dynamic, alternating position throughout the curing process, overcoming the temperature and humidity dead zones caused by uneven local wind speeds and heat source segregation in traditional static curing chambers. The entire batch of tobacco leaves receives uniform heating and dehumidification, reducing the proportion of raw and ash-covered tobacco, and improving the yield of high-quality tobacco, color uniformity, and intrinsic aroma quality after curing.

[0030] 2. Enables single-point operation and reduces workload: Based on the conveyor belt properties of this closed-loop three-dimensional circulation path, the loading and unloading of tobacco leaves after drying can be completed at the same fixed operating position near the entrance of the drying room. Operators no longer need to manually climb and set up tobacco clamps inside the narrow, high-temperature drying room, which greatly improves the working environment and reduces the loading and unloading time and labor intensity of single-room drying.

[0031] 3. Full utilization of thermal energy: Because the tobacco leaves are in motion inside the drying chamber, their surface convective heat transfer coefficient is significantly higher than that of static stacking, greatly improving the efficiency of moisture evaporation and heat and moisture exchange with the air. Combined with staged drying process control, thermal energy utilization efficiency is maximized.

[0032] Furthermore, at least some hierarchical path segments project in a serpentine shape in the vertical plane.

[0033] Furthermore, the drive mechanism 30 includes a drive chain assembly, the movement direction of which forms a three-dimensional loop path. The drive chain assembly includes a first drive chain and a second drive chain arranged side by side. The projection distance between two opposite mounting points on the first and second drive chains in the horizontal plane remains constant, and the two ends of the tobacco leaf clip 20 are respectively connected to the two opposite mounting points.

[0034] Furthermore, on the drive chain assembly, the distance d between any two adjacent tobacco leaf clips 20 is greater than the length L of the tobacco leaf 10 to be cured.

[0035] Specifically, the three-dimensional circulating tobacco curing method provided in this embodiment includes a set of closed-loop drive chain groups in its drive mechanism 30. The overall movement trajectory of the drive chain group outlines and forms the three-dimensional circulating path inside the curing chamber.

[0036] To achieve stable double-end support and synchronous traction of the tobacco leaf clamp 20, the drive chain assembly has two symmetrically arranged side by side: a first drive chain located on the left side of the drying chamber and a second drive chain located on the right side of the drying chamber (as per the instruction manual). Figure 1(From a side view perspective, the first and second drive chains overlap in their vertical projections). The first and second drive chains are mechanically installed in a parallel configuration of equal length and operate synchronously under the drive of a power source (such as a drive motor). Throughout the entire movement, the projected distance between any mounting point on the first drive chain and its corresponding mounting point on the second drive chain remains constant in the horizontal plane (this projection distance matches the length of the tobacco clip 20). By rotating or flexibly attaching the left and right ends of the rigid, elongated tobacco clip 20 to these two opposing mounting points, the tobacco clip 20 is horizontally spanned between the two drive chains like a stretcher. As the chains move, the tobacco clip 20 not only receives stable, balanced support in both directions but also moves long distances up and down and laterally within the drying chamber, following the chains.

[0037] As per the instruction manual Figure 1 As shown, in a specific embodiment of this implementation, in order to extend the single cycle of the tobacco leaf 10 in the drying chamber as much as possible and make full use of the heated space, the projection of one of the hierarchical path segments in the three-dimensional circulation path in the vertical plane (i.e., in the side view plane) presents a continuous, reciprocating, wavy, serpentine structure. In this implementation, the center distance d between any two adjacent tobacco leaf clips 20 on the drive chain assembly is specifically set to be greater than the length L of the tobacco leaf 10 to be dried (i.e., satisfying the geometric boundary condition d > L). The vertical reversing segment connecting two adjacent hierarchical path segments adopts a conventional straight-up or straight-down vertical path layout in terms of physical configuration. See Appendix Figure 1When the drive mechanism 30 pulls the tobacco leaf clip 20 to move counterclockwise in a cyclical manner, within the straight horizontal or vertical section, the entire tobacco leaf 10 hangs naturally vertically downwards under the action of a constant gravitational torque. When the tobacco leaf clip 20 travels with the chain to the critical point of the vertical reversal section (e.g., the upper right corner where it is about to switch from a straight upward section to a horizontal leftward movement), the tobacco leaf clip 20 undergoes a 90° change of direction of movement along the chain trajectory. At this time, due to the downward direction of gravity, the tobacco leaf clip 20 attached to the attachment point will rotate relative to the chain trajectory, thereby causing the lateral orientation of the tobacco leaf 10 relative to the three-dimensional cyclic path to undergo an adaptive gravitational deflection swing (e.g., from the right side of the chain's forward direction to the left side of the chain's forward direction). During this dynamic reversal process, since the center distance d between the front and rear is pre-defined to be greater than the tobacco leaf length L, when the tobacco leaf 10 behind swings along the corner in a gravity-driven arc with the tobacco leaf clip, the previous tobacco leaf clip 20 and its attached tobacco leaf 10 have already moved out of the arc area within the semi-circular swing envelope it sweeps forward. The leaf tip and leaf body have sufficient and ample physical buffer space during the swing, thus, in a purely two-dimensional straight path layout, a smooth reversal without mechanical collision or blade friction damage can be adaptively completed simply by relying on the large spacing. This implementation method has a simple structure and does not require special deformation of the chain and guide rail.

[0038] Furthermore, on the drive chain assembly, the distance d between any two adjacent tobacco leaf clips 20 is less than the length L of the tobacco leaf 10 to be cured; in the vertical reversing section, the two opposite mounting points drive the two ends of the tobacco leaf clips 20 to move along a spiral line, so that the horizontal projection motion trajectory of the tobacco leaf clips 20 rotates by (2n+1)×180°, where n is a natural number.

[0039] Specifically, because the large spacing constraint of d > L must be met in Embodiment 1, a considerable proportion of the space in the drive chain assembly is occupied by "air," limiting the total capacity of tobacco leaves for a single drying chamber. To achieve high-density three-dimensional circulating loading within the limited volume of the drying chamber, Embodiment 2 is also provided in this implementation.

[0040] In Example 2, the center distance d between any two adjacent tobacco leaf clips 20 on the drive chain group is greatly compressed, making it significantly smaller than the length L of the tobacco leaf 10 to be cured (i.e., satisfying the high-density constraint that d < L).

[0041] Before detailing the effective mechanism of this embodiment, we will first refer to the appendix to the specification. Figure 2 Mechanistic defects analysis of the opposing state (conventional planar path) that does not adopt this implementation method: such as Figure 2As shown, if the spacing between adjacent tobacco leaf clips is d < L, and the vertical reversing sections on both sides still follow the conventional straight-up-down two-dimensional path, then when the dense tobacco leaf clips 20 move with the chain to the upper right corner (ascent-to-lateral reversing point) or the lower left corner (descendance-to-lateral reversing point), the tobacco leaves behind attempt to swing left or right and turn around under the downward force of gravity. Due to the narrow front-to-back spacing, the envelope swept by the tobacco leaves behind, the rigid components of the tobacco leaf clips 20 in front, and the leaf body of the tobacco leaves in front geometrically overlap in the same two-dimensional vertical plane. As a result, the ends of the tobacco leaves will be stuck or squeezed by the mechanical structure in front (e.g., Figure 2 The jammed state shown in the upper right and lower left corners can not only easily cause tobacco leaf tearing, but may even cause the drive chain assembly to jam due to increased mechanical resistance.

[0042] To overcome the "physical bottleneck" caused by the narrow two-dimensional spacing, this embodiment performs three-dimensional spatial topology reconstruction on the vertical commutation segment. (Refer to the appendix of the specification.) Figure 3 As shown, in this embodiment, the vertical reversal segments on both sides are specially designed as three-dimensional spatial spiral path segments.

[0043] When the drive chain pulls the tobacco clip 20 from the straight hierarchical path section into the vertical reversing section, the two opposite mounting points no longer move side by side in two dimensions, but instead twist and shift outward or backward in three-dimensional space. This causes the two ends of the tobacco clip 20 to move along two intersecting spiral trajectories with specific curvatures. Guided by these spiral trajectories, as the tobacco clip 20 rises or falls with the chain as a whole, its projected motion trajectory in the horizontal plane will precisely rotate (2n+1)×180° (where n is a natural number greater than or equal to 0, preferably 0).

[0044] The core mechanical engineering essence of this horizontal projection motion trajectory with an odd multiple of 180° rotation lies in the fact that, throughout the entire stroke of the tobacco leaf clip 20 as it passes through the vertical reversing section, the relative spatial positions of the first and second drive chains in the horizontal plane are alternately reversed (i.e., the first drive chain, originally located on the left, gradually twists and moves to the right, while the second drive chain, originally located on the right, gradually twists and moves to the left). This alternation of left and right tracks forces the tobacco leaf clip 20, which spans between the two chains, to rotate 180° synchronously in the horizontal plane around the center line connecting its two ends while moving along the path.

[0045] Through this three-dimensional "horizontal rotation and turning," the gravity-induced turning, which originally required a large-span swing in a two-dimensional plane, is cleverly transformed into a "horizontal rotation and turning" performed in place in space. When adjacent layers of tobacco change direction, as dynamic components misaligned in space, they utilize the third-dimensional spatial misalignment and time difference to avoid each other's two-dimensional envelope circles. This eliminates collision interference between adjacent tobacco leaves in the turning area, allowing for smooth and unimpeded turning, and enabling the spacing d on the chain to be safely compressed to a state much smaller than the tobacco leaf length L, resolving the physical conflict between high-density loading and dynamic cyclic turning.

[0046] Furthermore, both the first drive chain and the second drive chain adopt universal transmission chains; on the vertical reversing section, a pair of helical guide rails are symmetrically fixed, and the first drive chain and the second drive chain are respectively limited and slidably connected to the helical guide rails on the corresponding sides.

[0047] Furthermore, the distance d is 0.3 to 0.5 times the length L of the tobacco leaf to be cured 10.

[0048] Specifically, in the aforementioned established three-dimensional spiral path segment, to ensure the smooth and stable movement of the parallel symmetrical first and second drive chains even under high loads, torsion, and spatial left-right reversal, both the first and second drive chains utilize universal transmission chains (or universal articulated chains) in their hardware. Each link of this universal transmission chain possesses spatial articulated degrees of freedom for rotation in both horizontal and vertical directions.

[0049] In conjunction with the universal drive chain, a pair of spatially staggered spiral guide rails are symmetrically and fixedly installed in the vertical reversing sections on both sides of the drying chamber. These spiral guide rails undergo three-dimensional bending and torsional shaping according to the preset spatial motion envelope trajectories at both ends of the tobacco leaf clamps. During the follow-up process, the links or slider components of the first and second drive chains are respectively limited and slidably connected within the corresponding spiral guide rails. By gradually changing the tangent and normal directions of the two guide rails in three-dimensional space, the rigid rails apply three-dimensional spatial limiting and torsional torque to the universal drive chain, thereby enabling the first and second drive chains to not only smoothly climb or descend slopes but also smoothly complete bending and spatial reversal movements under external forces.

[0050] Under the rigid support and trajectory constraint of this driving medium, as per the attached instruction manual... Figure 3 As shown, on the entire moving line of the three-dimensional loop path, the center distance d between any two adjacent tobacco leaf clips 20 can be further optimized and limited to 0.3 to 0.5 times the length L of the tobacco leaf 10 to be cured (i.e., satisfying 0.3L≤d≤0.5L).

[0051] The significance of setting this parameter range in the tobacco processing field is as follows: If the spacing d is too extremely compressed (e.g., below 0.3), although theoretically the number of loads can be further increased, at the instantaneous starting point when the tobacco leaf clip 20 cuts into the vertical reversing section with the chain (at which point the left and right interleaving of space has not yet fully unfolded, and the vertical height difference and horizontal projection angle difference between the two chains have not yet widened), the leaf edges of adjacent tobacco leaves are easily squeezed, abraded, or locally rotten due to the extremely narrow spatial distance, and may even cause chain links to jam when cutting into the corner. On the other hand, if the spacing d exceeds 0.5L, although the turning is extremely smooth and frictionless, the filling coefficient of the vertical three-dimensional space inside the drying chamber will decrease significantly, failing to maximize the technical support role of the spiral design for large loading volumes. Therefore, precisely limiting the ratio to between 0.3 and 0.5 times allows the horizontal rotation of dense tobacco leaves to obtain excellent "safety margin" within the three-dimensional dynamic misalignment gap created by the spatial spiral trajectory, thereby increasing the unit three-dimensional filling density of the drying chamber to an optimal value while isolating mechanical collisions and friction damage.

[0052] Furthermore, in step S2, the staged baking includes a yellowing stage, a color-fixing stage, and a drying stage. The temperature and humidity inside the drying oven are adjusted by controlling the dry-bulb temperature and the wet-bulb temperature, respectively. During the yellowing stage: control the dry bulb temperature to slowly rise to 38℃ and maintain the temperature for 30~40 hours, while controlling the wet bulb temperature to slowly rise to 35~37℃ and maintain the temperature for 30~40 hours.

[0053] During the color fixation stage: control the dry bulb temperature to slowly rise to 54℃ and maintain the temperature for 15~25h, while controlling the wet bulb temperature to first rise to 37~39℃ and maintain the temperature for 15~25h, and then control the wet bulb temperature to rise again to 39~41℃ and maintain the temperature for 15~25h.

[0054] During the dry bulb stage: control the dry bulb temperature to slowly rise to 68℃ and maintain the temperature for more than 7 hours, while controlling the wet bulb temperature to rise to 40~43℃ and maintain the temperature for more than 17 hours.

[0055] Specifically, while the drive mechanism 30 drives the tobacco leaf clamp 20 to continuously and dynamically circulate through the multi-level path sections and vertical reversing sections inside the drying chamber, the overall heat and humidity environment inside the drying chamber is not constant. Instead, it needs to be scientifically and quantitatively regulated in accordance with the evolution of moisture and the physiological and biochemical degradation patterns within the tobacco leaves. In step S2, this stage of drying includes the interconnected yellowing stage, color-fixing stage, and drying stage. The temperature and humidity regulation inside the drying chamber is achieved through the coordinated operation of the heat pump main unit's heating output and the dehumidification / humidification system, ultimately mapping and accurately reflecting the joint dynamic control of the dry-bulb temperature curve and wet-bulb temperature curve inside the drying chamber.

[0056] Please refer to the instruction manual for details. Figure 4 As shown (where the thin solid line represents the dry-bulb temperature control curve and the thicker solid line represents the wet-bulb temperature control curve), the specific temperature and humidity control benchmarks for the three stages are as follows: 1. Yellowing Stage (Stable Dry Bulb, Adjusted Humidity Bulb): The core of the process lies in promoting the degradation of chlorophyll in the tobacco leaves and the full conversion of starch into soluble sugars, achieving a harmonious balance between yellowing and dryness. The control system dynamically adjusts the heat source and circulating fan to slowly raise the dry bulb temperature in the drying chamber from approximately 23°C (initial ambient temperature) to 38°C and stabilize it at this temperature for 30 to 40 hours (preferably 35 hours) for stable yellowing. Simultaneously, the dehumidification window or dehumidification system is controlled to slowly raise the wet bulb temperature from 20°C to 35-37°C (preferably 36°C) and maintain a stable temperature and humidity within this range for 30 to 40 hours (preferably 35 hours). Under the slow temperature rise and stable temperature control in this stage, the circulating tobacco leaves begin to soften and wilt, ensuring that the leaves visually reach 80% yellowing and one-third of the main stem softens before entering the next stage—the golden transition physical indicators.

[0057] 2. In the color-fixing stage (stabilizing wet-bulb and increasing dry-bulb): The core of the process lies in locking in the quality and pigments of the tobacco leaves after they turn yellow by continuously removing the moisture evaporated from the tobacco leaves, preventing non-enzymatic browning or tarnishing. The control system slowly and gradually increases the dry-bulb temperature in the drying chamber from 42℃ to 54℃, and then maintains this peak temperature for 15 to 25 hours (preferably 20 hours) to achieve color fixation and aroma enhancement in the dry leaves. During this period, the wet-bulb temperature is controlled in a step-by-step manner, first stabilizing at 37~39℃ (preferably 38℃), and then gradually increasing to 39~41℃ (preferably 40℃) and stabilizing the temperature. Through this step-by-step wet-bulb temperature control, ensuring that the tobacco leaves are fully yellowed and ready for drying, the process is completed.

[0058] 3. During the drying stage (limited dry bulbs, controlled wet bulbs): The core of the process lies in the intensive dehydration of the thick main ribs until they are completely dry. The control system controls the dry bulb temperature to slowly rise again to the limit dryness red line temperature of 68℃, and maintains it at this temperature for more than 7 hours. At the same time, the wet bulb temperature is raised and precisely controlled within a narrow range of 40~43℃ (preferably 42℃), and maintained at a stable temperature for more than 17 hours, until all the main ribs of the tobacco leaves in the entire kiln that are in a state of circulation are completely dry.

[0059] Furthermore: During the yellowing stage, slow heating includes heating at a rate of 1℃ / h.

[0060] During the color-fixing stage, the slow heating process includes: heating to 42°C at a rate of 1°C / 4h, then heating to 46°C at a rate of 1°C / 3h, then heating to 50°C at a rate of 1°C / 2h, and finally heating to 54°C at a rate of 1°C / 1h.

[0061] During the drying stage, slow heating includes heating at a rate of 1℃ / h.

[0062] Specifically, based on the three-stage control benchmark constructed above, in order to ensure that the temperature and humidity field experienced by the tobacco leaf clip 20 during movement has extremely high smoothness and to avoid excessive wear and stiffness caused by rapid burning of tobacco or low temperature, this embodiment also makes specific process limitations on the slow heating and temperature change rate of the whole process and the final control after shutdown.

[0063] Refer to the instruction manual. Figure 4 The overall rate control and shutdown / cooling logic is as follows: 1. Slow temperature rise during the yellowing stage: In the initial stage of yellowing, the initial slow temperature rise process of dry bulb temperature (23℃→38℃) and wet bulb temperature (20℃→36℃) is restricted to a constant, small-amplitude rate of 1℃ / h to prevent cell necrosis caused by local overheating.

[0064] 2. Slow Heating During the Color Fixing Stage: The dry-bulb temperature rise during the color fixing stage adopts a stepped process of "variable slope and slow acceleration": First, the dry-bulb temperature is controlled to rise at an extremely slow rate of 1℃ / 4h to 42℃, giving the tobacco leaves a stable transition period for moisture evaporation; then the rate is increased to 1℃ / 3h to 46℃ (at which point the tobacco veins begin to turn completely yellow); next, the temperature is increased at 1℃ / 2h to 50℃ (achieving 2 / 3 dryness); finally, the temperature is rapidly increased to 54℃ at a rate of 1℃ / 1h, and then maintained at 54℃ for more than 18 hours. The control of the wet-bulb temperature is precisely linked to the time interval on the horizontal axis: during the period of 55~70h on the horizontal axis, the wet-bulb temperature rises from 36℃ to 38℃; during the period of 70~90h, it is maintained at a stable temperature of 38℃; during the period of 90~95h, it rises from 38℃ to 40℃, and during the period of 95~115h, it is maintained at a stable temperature of 40℃. This intricate interweaving of hyperbolas and the time axis allows the drying chamber's dehumidification capacity to perfectly match the tobacco leaves' water loss pattern.

[0065] 3. Slow Heating and Finishing of the Dry Bulb Stage: During the dry bulb stage, the dry bulb temperature starts at 54℃ and steadily increases to 68℃ at a standard slow heating rate of 1℃ / h. The wet bulb temperature rises from 40℃ to 42℃ between 115 and 120 hours, and then stabilizes at 42℃ after 120 hours. After all baking processes in the dry bulb stage are completed, the control system shuts down the heat pump promptly. At this time, due to the large amount of high-temperature heat energy accumulated in the drying chamber, to prevent localized high-temperature airflow stagnation and scorching of the tobacco leaves, the motors of the entire system are not immediately shut off. The control system keeps the drive mechanism 30 running, and the circulating fan continues to operate until the dry bulb temperature in the drying chamber drops below 50℃ due to natural cooling or forced exchange, at which point the circulating fan stops running. This cooling protection action ensures that both the equipment and the product are in a safe and stable state.

[0066] Furthermore: In step S1, the tobacco leaf clip 20 adopts a long strip hanging structure with a span matching the width of the drying chamber. Furthermore, the loading and unloading of the tobacco leaf clip 20 on the three-dimensional circulation path, as well as the unloading after drying, are all completed at the same single operation point at the entrance of the drying chamber along the three-dimensional circulation path.

[0067] In step S2, the heat source is a variable frequency dual-temperature air source heat pump. The cyclic baking step includes: coordinating with the cycle of the tobacco leaf clip 20 moving in a three-dimensional circulation within the drying room, and dynamically adjusting the output frequency of the variable frequency dual-temperature air source heat pump through variable frequency control.

[0068] Specifically, the three-dimensional circulating tobacco curing method provided in this embodiment has the following causal relationship between its process steps, high-density loading capacity, and the specifications of the underlying physical equipment: 1. Long strip hanging structure matching the span: In step S1, in order to maximize the use of the width space of the drying room and reduce the ineffective side gaps, the tobacco clip 20 is geometrically designed as a rigid long strip hanging structure with a span matching the width of the drying room (in a preferred embodiment, its physical length is set to 2.3 meters).

[0069] 2. Optimization of Labor Intensity for Single-Point Loading: Based on the complete closed-loop rotation attribute of this three-dimensional circulating path, the long strip-shaped tobacco leaf clamp 20 performs single-point operations in the loading and unloading processes of step S1 and after drying, all at the same fixed operating position (i.e., a single standing point) that extends along the three-dimensional circulating path and is exposed to the door of the drying chamber. Workers do not need to enter the hot, humid, and stuffy interior of the drying chamber; they only need to stand at the door, and the drive mechanism 30 will deliver empty loading points or dried tobacco leaves to the worker sequentially, much like a rotating conveyor belt. This greatly improves the working environment, shortens the loading time, and reduces labor intensity.

[0070] 3. Frequency Conversion Heat Pump Energy Efficiency Coupling Control: In step S2, the core heat source of the system adopts a high-efficiency variable frequency dual-temperature air source heat pump. During the baking process, this variable frequency heat pump efficiently converts and transports hot air from the environment into heat energy within the drying chamber through a low-power variable frequency compressor (energy efficiency ratio can reach 1:4 or 1:5). To achieve extreme energy saving, the control system can establish a "dynamic control mechanism": in conjunction with the cycle of the tobacco leaf clamp 20's vertical and horizontal three-dimensional cyclic movement within the drying chamber (i.e., the air resistance caused by the movement of the tobacco leaves along the chain, and the cycle of airflow segregation inside the drying chamber), the output frequency of the variable frequency dual-temperature air source heat pump is synchronously and dynamically adjusted. Through this process coupling of the mechanical displacement cycle and the heat pump frequency conversion cycle, it achieves significantly more energy savings than conventional air source heat pump drying chambers, realizing a unified approach of high-capacity mechanical automation and low energy consumption.

[0071] The specific execution mechanism for dynamically adjusting the output frequency of the variable frequency dual-temperature air source heat pump through frequency conversion control, in conjunction with the three-dimensional circulation movement cycle of the tobacco leaf clip 20 within the drying chamber, is as follows: 1. Real-time frequency modulation logic (dynamic fine-tuning) based on microscopic three-dimensional cyclic movement cycle The drive chain assembly drives 165 tobacco leaf clips 20 to move continuously in a closed loop within the drying chamber along a preset hierarchical path and a vertical reversing section. The process of the tobacco leaf clips 20 moving from the front end to the rear end of the drying chamber, then climbing from the bottom to the top and returning to the origin constitutes one single equipment cycle displacement cycle. (In this embodiment, the single-cycle displacement period) The preferred time is 20 to 40 minutes. Because the drying chamber is equipped with a main heating air duct and a return air vent, there is a fixed static thermal field gradient in the vertical height and front-to-back direction inside the drying chamber (for example, the area near the main air supply vent has extremely fast heat exchange, while the area near the bottom return air vent has relatively slow heat exchange).

[0072] As the tobacco leaf clip 20 moves with the chain, the control system monitors the actual dry-bulb temperature inside the drying chamber in real time through temperature sensors fixed at different levels within the chamber. The target dry bulb temperature preset in the process curve Deviation value between In conjunction with the current spatial position of the tobacco leaf clip 20, the output frequency of the heat pump is dynamically adjusted in real time according to the following rules: 1) When the frequency is increased: When a large quantity of wet tobacco leaves (clamped in 20) enters the main heating duct area along with the chain, or when they climb from a low-temperature level to a high-temperature level, the rapid evaporation of moisture on the surface of the wet tobacco leaves will instantly absorb a large amount of heat, causing the actual temperature of that area to rise. A sharp drop occurred, and the deviation value... Increase. At this time, within a specific time node of the aforementioned single-cycle displacement cycle (for example, the first 1 / 3 of the cycle when the tobacco leaf clamp enters the intense heat exchange phase), the control system automatically controls the output frequency of the air source heat pump to be increased to a high-frequency, high-power operating state of 50Hz~70Hz to generate high-intensity heat output, effectively compensating for the heat loss caused by the high-density movement and heat exchange of the tobacco leaves, and ensuring that the temperature inside the drying room does not drop below the process limit.

[0073] 2) Lowering the frequency: When the batch of tobacco leaves (clamp 20) moves away from the main heating duct and into the insulation layer path section, or moves towards the bottom return air vent, the heat exchange rate in this space area decreases, and the tobacco leaves in the preceding section have already absorbed sufficient heat, resulting in a lower actual temperature inside the drying chamber. Extremely close to or slightly exceeding the target temperature Deviation value The frequency approaches zero. In the latter half of this cyclic displacement cycle, the control system automatically lowers the output frequency of the air source heat pump to a low-frequency energy-saving operating state of 15Hz~30Hz (or enters the variable frequency heat preservation mode). This utilizes the residual heat from the airflow disturbance caused by the movement of tobacco leaves for heat preservation, preventing local overheating in the drying room from scorching the tobacco leaves, and achieving ultimate temperature control smoothness and energy-saving effect.

[0074] 2. Variable frequency reference adjustment based on the macroscopic baking stage cycle (macroscopic coarse adjustment) In addition to the dynamic fine-tuning mentioned above that aligns with the micro-movement cycle, the reference operating frequency range of the variable frequency heat pump is also deeply coupled with the time cycles of the three macroscopic process stages: "yellowing, color stabilization, and brittle drying." 1) During the yellowing stage (30~40h): At this time, the process requires "stable temperature and slow yellowing", and the tobacco leaves lose water slowly. The reference output frequency of the heat pump is generally controlled in the low-to-medium frequency range of 25Hz~35Hz, and is adjusted slightly with the aforementioned micro-displacement cycle to maintain a mild thermal environment of 38℃.

[0075] 2) During the color-fixing stage (15~25h): The dry-bulb temperature needs to be continuously increased from 42℃ to 54℃, and a large amount of moisture is removed from the tobacco leaves, resulting in the highest heat consumption of the entire process. The reference output frequency of the heat pump is increased and locked in the high-frequency, high-power range of 55Hz~75Hz. At this time, in conjunction with the micro-displacement cycle, when the dense tobacco clips are detected passing through the vertical reversing section, the frequency is further pushed to the peak to ensure the accurate execution of the stepped heating rate (1℃ / 4h, etc.) with high output.

[0076] 3) During the dry core stage (over 7 hours): At this point, the blades are dry, and only the thick main core contains water. Although a high temperature of 68℃ is still required, the total amount of moisture evaporated throughout the building has been significantly reduced, resulting in less heat loss. Therefore, after the initial temperature rise, the heat pump's base output frequency will be actively lowered and maintained in the mid-frequency range of 35Hz~45Hz during the 68℃ stable temperature period to prevent ineffective power consumption and achieve adaptive energy efficiency control throughout the entire process.

[0077] Furthermore, the following section explains how the control system measures the displacement speed of the tobacco leaf clamp. "Temperature deviation value" The heat pump output frequency is decoupled from "spatial location" and dynamically adjusted. The specific control algorithm and internal logic will be explained below: 1. Algorithm architecture selection for the control system The control system described in this embodiment employs a feedforward-feedback cascade composite control algorithm (or, in actual industrial PLCs, an improved dual-closed-loop PID control algorithm with feedforward compensation). Wherein: 1) Main loop (feedback loop): based on the actual dry-bulb temperature inside the drying oven. With process target temperature deviation value As the feedback input, the basic frequency regulation is calculated by the main PID controller. .

[0078] 2) Secondary circuit (feedforward compensation circuit): The displacement speed of the tobacco leaf clamp 20 driven by the drive chain assembly. The current spatial position of the tobacco leaf clips (i.e., whether they have entered the main heating duct or the vertical reversing section) is used as the feedforward disturbance input, and the dynamic prediction frequency compensation is calculated by the feedforward compensator. .

[0079] 3) Final control output: The final execution frequency of the heat pump compressor. (in (This is the baseline operating frequency for the current baking stage).

[0080] 2. Displacement velocity "and frequency change" The qualitative and quantitative decoupling logic of " chain displacement speed This directly determines the flux of wet tobacco leaves passing through the main heating duct per unit time (i.e., the rate of change of heat absorption load). The control system internally establishes a velocity-heat load feedforward decoupling mathematical matrix, and the qualitative and quantitative relationships of its decoupling and control are specifically implemented as follows: 1) When displacement velocity Improved decoupling compensation: When process requirements necessitate (e.g., during the color fixing stage to accelerate large-area dehumidification of tobacco leaves throughout the chamber), the control system drives the chain assembly to change its displacement speed from the initial speed. Increase to high speed At that time, the number of wet tobacco leaves entering the high-temperature zone per unit time increases exponentially, which is thermodynamically equivalent to applying a downward step temperature disturbance.

[0081] The feedforward compensator adjusts according to the speed change. In actual temperature Before a significant drop occurs, the impending heat deficit in the drying chamber is predicted using the decoupling coefficient, triggering feedforward positive compensation. At this point, the feedforward frequency compensation amount... With change in velocity The correlation exhibits a positive linear or exponentially increasing relationship, and the calculation formula is as follows: (in the formula, The velocity disturbance compensation coefficient is set to 1.5~3.5 Hz / (m / min) based on the drying chamber filling coefficient.

[0082] Through this decoupling logic, when speed When the frequency is increased, the output frequency of the heat pump increases rapidly. (Directly boosting the frequency by 5Hz~15Hz) advances the power of the heat pump, offsetting the "cold wind effect" caused by the accelerated movement of tobacco leaves, thus achieving active predictive control of temperature.

[0083] 2) When the displacement velocity Decoupling protection during reduction or pause: Conversely, when the tobacco leaves are sandwiched in the yellowing section and undergo slow circulation, the displacement speed changes from... Reduce to (Or, after feeding is completed, the machine enters a temporary stop state.) When the high-density heat exchange load per unit time drops sharply, excess heat is easily generated and accumulated in the drying room.

[0084] Feedforward compensator senses If the value is negative, quickly output the negative frequency compensation amount. At this point, the feedforward adjustment is executed before the temperature sensor feedback, actively reducing the frequency of the heat pump compressor. (Directly lowering the frequency by 8Hz~20Hz) forcibly suppresses the heat pump's output power. Subsequently, the main feedback loop adjusts the frequency based on the slight residual temperature deviation. Fine-tuning of the PID tail trajectory ensures that the execution frequency smoothly returns to the low-frequency heat preservation range of 15Hz~30Hz, avoiding localized overheating and scorching of tobacco leaves inside the drying chamber caused by slowing down or stopping the machine.

[0085] 3. Three-dimensional composite decoupling based on spatial location The aforementioned decoupling control is further combined with the three-dimensional spatial coordinates of the tobacco leaves clamped in the drying chamber (obtained via limit switches or encoders set on the chain track): The control system has a pre-set "spatial thermal resistance mapping table" for the inside of the drying chamber. When the spatial position sensor indicates that a large number of tobacco leaf clips 20 are in the "vertical reversal segment" (i.e., the left and right double chains are spatially spirally interleaved and horizontally projected and rotated), the system will detect the change in temperature. When the airflow resistance in a region is greater than that in a straight tiered path segment, the local thermal convection efficiency undergoes a sudden change.

[0086] At this point, the control system will automatically adjust the speed compensation coefficient in the feedforward loop. The correction increases the value by 15% to 25%, so that even at the same displacement speed... When the tobacco leaf clamp runs to the vertical reversing spiral section, the frequency conversion sensitivity of the heat pump will be actively increased (the output frequency will be increased by 3Hz~6Hz on the original basis) to provide stronger airflow penetration and ensure that the temperature and humidity fields of the reversing zone and the main baking zone always remain dynamically equipotential and balanced.

[0087] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be within the scope of protection of the present invention.

Claims

1. A stereoscopic circulating tobacco leaf curing method, characterized by, Includes the following steps: S1. Loading: The tobacco leaves (10) to be cured are hung on the drive mechanism (30) by the tobacco leaf clamp (20); S2. Circulating baking: The tobacco leaf clamp (20) is driven by the driving mechanism (30) to move along the three-dimensional circulating path in the drying room, and the temperature and humidity in the drying room are adjusted by the heat source to achieve staged baking; The three-dimensional loop path includes multiple hierarchical path segments distributed at different heights, as well as vertical reversal segments connecting two adjacent hierarchical path segments.

2. The stereoscopic circulation tobacco leaf curing method according to claim 1, wherein, At least some of the hierarchical path segments project in a serpentine shape in the vertical plane.

3. The stereoscopic circulating tobacco leaf curing method according to claim 1, wherein, The drive mechanism (30) includes a drive chain group, the movement direction of the drive chain group forms the three-dimensional loop path; the drive chain group includes a first drive chain and a second drive chain arranged side by side, the projection distance between two opposite mounting points on the first drive chain and the second drive chain in the horizontal plane remains constant, and the two ends of the tobacco leaf clip (20) are respectively connected to the two opposite mounting points.

4. The three-dimensional circulating tobacco curing method according to claim 3, characterized in that, On the drive chain assembly, the distance d between any two adjacent tobacco leaf clips (20) is greater than the length L of the tobacco leaf (10) to be cured.

5. The three-dimensional circulating tobacco curing method according to claim 3, characterized in that, On the drive chain assembly, the distance d between any two adjacent tobacco leaf clips (20) is less than the length L of the tobacco leaf (10) to be cured; In the vertical reversing section, the two opposite mounting points drive the two ends of the tobacco clip (20) to move along a spiral line, so that the horizontal projection motion trajectory of the tobacco clip (20) rotates by (2n+1)×180°, where n is a natural number.

6. The three-dimensional circulating tobacco curing method according to claim 5, characterized in that, Both the first drive chain and the second drive chain are universal drive chains; on the vertical reversing section, a pair of helical guide rails are symmetrically fixed, and the first drive chain and the second drive chain are respectively limited and slidably connected to the helical guide rails on the corresponding sides.

7. The three-dimensional circulating tobacco curing method according to claim 5, characterized in that, The distance d is 0.3 to 0.5 times the length L of the tobacco leaf (10) to be cured.

8. The three-dimensional circulating tobacco curing method according to any one of claims 1 to 7, characterized in that, In step S2, the staged baking includes a yellowing stage, a color-fixing stage, and a drying stage. The adjustment of temperature and humidity within the drying chamber is achieved by controlling the dry-bulb temperature and wet-bulb temperature, respectively. During the yellowing stage: control the dry bulb temperature to slowly rise to 38℃ and maintain the temperature for 30~40h, while controlling the wet bulb temperature to slowly rise to 35~37℃ and maintain the temperature for 30~40h. During the color fixation stage: control the dry bulb temperature to slowly rise to 54℃ and maintain the temperature for 15~25h, while controlling the wet bulb temperature to first rise to 37~39℃ and maintain the temperature for 15~25h, and then control the wet bulb temperature to rise again to 39~41℃ and maintain the temperature for 15~25h. During the dry bulb stage: control the dry bulb temperature to slowly rise to 68℃ and maintain the temperature for more than 7 hours, while controlling the wet bulb temperature to rise to 40~43℃ and maintain the temperature for more than 17 hours.

9. The three-dimensional circulating tobacco curing method according to claim 8, characterized in that: During the yellowing stage, the slow heating includes heating at a rate of 1°C / h; During the color-fixing stage, the slow heating includes: heating to 42°C at a heating rate of 1°C / 4h, then heating to 46°C at a heating rate of 1°C / 3h, then heating to 50°C at a heating rate of 1°C / 2h, and then heating to 54°C at a heating rate of 1°C / 1h. During the drying stage, the slow heating includes heating at a rate of 1℃ / h.

10. The three-dimensional circulating tobacco curing method according to any one of claims 1 to 7, characterized in that: In step S1, the tobacco leaf clip (20) adopts a long strip hanging structure with a span that matches the width of the drying room; and the loading and unloading of the tobacco leaf clip (20) on the three-dimensional circulation path and the unloading after drying are all completed at the same operation position at the door of the drying room on the three-dimensional circulation path. In step S2, the heat source is a variable frequency dual-temperature air source heat pump, and the cyclic baking step includes: coordinating the cycle of the tobacco leaf clip (20) moving in a three-dimensional cycle in the drying room, and dynamically adjusting the output frequency of the variable frequency dual-temperature air source heat pump through frequency conversion control.

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