A four-stage tobacco baking process in the middle of a full-closed hot air circulation baking house

Abstract

The application discloses a four-section curing process for middle tobacco in a full-closed hot air circulation curing barn, which comprises the following steps: S1, a yellowing stage, S2, a color fixing stage, S3, a dry stem stage and S4, a moisture recovery stage; the dry ball temperature of the S1 yellowing stage is 36-42 DEG C, and the wet ball temperature is 36-37 DEG C; the dry ball temperature of the S2 color fixing stage is 45-54 DEG C, and the wet ball temperature is 37-39 DEG C; the dry ball temperature of the S3 dry stem stage is 60-68 DEG C, and the wet ball temperature is 40-41 DEG C; and the temperature of the S4 moisture recovery stage is 39-42 DEG C, and the moisture recovery time is 2-3 h. The S4 moisture recovery stage is added, the moisture recovery is carried out by using the residual heat of the curing barn, the moisture recovery quality is higher, the problems that the tobacco leaves are difficult to recover moisture and easy to be broken after being cured in the northern tobacco area are effectively solved, the effective yield of the tobacco leaves is improved, and the income of the tobacco growers is increased.

Description

TECHNICAL FIELD

[0001] The application relates to a four-stage baking process for middle tobacco leaves in a full-closed hot air circulation baking room and belongs to the tobacco baking technical field. BACKGROUND

[0002] As far as flue-cured tobacco is concerned, the tobacco baking process is a key technology for stimulating the inner quality of tobacco leaves, which determines the quality and industrial usability of tobacco products, so the quality research on the baking of flue-cured tobacco is of great significance. At present, the baking processes of existing intensive baking rooms and full-closed hot air circulation baking rooms are all conventional baking processes, and the three-stage baking method is implemented at the present stage. The method rapidly increases the temperature to fix the color after the tobacco leaves turn yellow, and the baking time is shortened compared with that of ordinary baking rooms, so that the high molecular compounds which are not fully decomposed are fixed in the tobacco leaf cells, and the baked tobacco leaves are often light in color, rigid, smooth, even green, and lack aroma, and the baking quality of tobacco leaves is reduced. In addition, due to climate factors, it is difficult for tobacco leaves in northern tobacco-growing areas in China to be rehydrated in the middle and late baking stages, and some farmers take measures such as water spraying to hard rehydrate, which leads to excessive rehydration of tobacco leaves, unqualified moisture of sold tobacco leaves, and serious influence on the quality and industrial usability of tobacco output. SUMMARY

[0003] In order to solve the above problems, a four-stage baking process for middle tobacco leaves in a full-closed hot air circulation baking room is provided, which is divided into four baking stages of S1 yellowing stage, S2 color fixing stage, S3 dry muscle stage and S4 rehydration stage according to dry ball temperature, wet ball temperature, baking time, heating speed, variable speed ventilation, tobacco change target and other factors, promotes the full decomposition and transformation of macromolecular substances such as starch and protein in tobacco leaves and the formation of aroma substances, makes the tobacco leaves slowly turn yellow, the internal macromolecular substances and aroma substances are more fully transformed, and higher quality tobacco leaves are obtained by baking, and the S4 rehydration stage is added, rehydration is carried out by using the waste heat of the baking room, the rehydration quality is higher, the problems of difficult rehydration and easy crushing of tobacco leaves in the late baking stage in northern tobacco-growing areas are effectively solved, the effective yield of tobacco leaves is improved, and the income of tobacco farmers is increased.

[0004] One aspect of the application provides a four-stage baking process for middle tobacco leaves in a full-closed hot air circulation baking room, comprising the following steps: S1 yellowing stage, S2 color fixing stage, S3 dry muscle stage and S4 rehydration stage.

[0005] The dry ball temperature of the S1 yellowing stage is 36-42 DEG C, and the wet ball temperature is 36-37 DEG C.

[0006] The dry ball temperature of the S2 color fixing stage is 45-54 DEG C, and the wet ball temperature is 37-39 DEG C.

[0007] The dry ball temperature of the S3 dry muscle stage is 60-68 DEG C, and the wet ball temperature is 40-41 DEG C.

[0008] The S4 moisture regaining stage temperature is 39-42℃, and the moisture regaining time is 2-3h.

[0009] Optionally, the S1 yellowing stage comprises the following steps:

[0010] S11. After starting the baking, the temperature is raised to 36-36.5℃ of dry bulb temperature and 36-36.5℃ of wet bulb temperature at a temperature raising speed of 1℃ per hour, and the temperature is kept stable for 1.5-2.5h, and the fan is operated at low speed to buffer the smooth temperature rising in the next step;

[0011] S12. The temperature is raised to 37.5-38℃ of dry bulb temperature and 37-37.5℃ of wet bulb temperature at a temperature raising speed of 1℃ per hour, and the temperature is kept stable for 8-10h, and the moisture removal device starts to work, and the baking is performed until the leaf tips of the middle temperature layer tobacco leaves are warm and soft;

[0012] S13. The temperature is raised to 40-40.5℃ of dry bulb temperature and 36-37℃ of wet bulb temperature at a temperature raising speed of 0.5℃ per hour, and the fan starts to operate at high speed, and the temperature is kept stable for 18-24h until the middle temperature layer tobacco leaves are wilted and collapsed, and the yellowing degree is 8-9;

[0013] S14. The temperature is raised to 41-42℃ of dry bulb temperature and 36.5-37℃ of wet bulb temperature at a temperature raising speed of 0.5℃ per hour, and the temperature is kept stable for 22-26h until the main veins of the middle temperature layer tobacco leaves are soft, and the tobacco leaves are in a state of yellow leaf and green veins, and the upper layer tobacco leaves start to be dry;

[0014] Specifically, in S14, the wet bulb temperature is 37℃ in the early stage, and if the tobacco leaves do not meet the moisture removal requirement, the wet bulb temperature can be adjusted to 36.5℃ in the later stage.

[0015] Optionally, the S2 color fixing stage comprises the following steps:

[0016] S21. The temperature is raised to 45-45.5℃ of dry bulb temperature and 37-37.5℃ of wet bulb temperature at a temperature raising speed of 0.5℃ per hour, and the temperature is kept stable for 12-16h until the middle temperature layer tobacco leaves are in a state of yellow leaf and yellow vein;

[0017] S22. The temperature is raised to 47-47.5℃ of dry bulb temperature and 37-37.5℃ of wet bulb temperature at a temperature raising speed of 0.5℃ per hour, and the temperature is kept stable for 12-14h until the middle temperature layer tobacco leaves are in a state of 1 / 2 dry leaf and small roll cylinder, and no green color appears in the whole furnace;

[0018] S23. The temperature is raised to 50-50.5℃ of dry bulb temperature and 38-38.5℃ of wet bulb temperature at a temperature raising speed of 1℃ per hour, and the temperature is kept stable for 10-10.5h until the low temperature layer tobacco leaves are in a state of small roll cylinder;

[0019] S24 is raised to dry bulb temperature 53.5-54℃ and wet bulb temperature 38.5-39℃ at a temperature rising speed of 1℃ per hour, and is kept stable for 15-16 hours until the leaves in the low-temperature layer are fully dried and in the form of large rolls.

[0020] Optionally, the S3 drying stage comprises the following steps:

[0021] S31 is raised to dry bulb temperature 60-60.5℃ and wet bulb temperature 40-40.5℃ at a temperature rising speed of 1℃ per hour, and is kept stable for 8-8.5 hours;

[0022] S32 is raised to dry bulb temperature 67.5-68℃ and wet bulb temperature 40.5-41℃ at a temperature rising speed of 1℃ per hour, and is kept stable for 14-20 hours until the tobacco stems in the whole furnace are fully dried, and the heat pump, fan and moisture removal device are stopped.

[0023] Optionally, the fan is started at low power during the S4 moisture recovery stage, and the moisture recovery device is operated according to a working cycle of 5 minutes of starting and 3 minutes of stopping.

[0024] Optionally, the temperature during the S4 moisture recovery stage is 40℃.

[0025] Optionally, the moisture recovery device during the S4 moisture recovery stage is the condensate water of the drying process.

[0026] Optionally, the S4 moisture recovery stage comprises blowing the condensate water after atomization into the tobacco chamber through the fan to recover the moisture of the tobacco leaves.

[0027] Optionally, in the S12 step of the S1 yellowing stage, when condensate water droplets appear in the observation window, the fan is indirectly started to run at high speed.

[0028] Another aspect of the present application provides an application of the above-mentioned four-stage drying process for the middle tobacco leaves in a full-closed hot air circulation drying barn in the field of tobacco leaf drying.

[0029] The beneficial effects of the present application include but are not limited to:

[0030] 1. The present application is divided into four drying stages, i.e. S1 yellowing stage, S2 color fixing stage, S3 drying stage and S4 moisture recovery stage, according to dry bulb temperature, wet bulb temperature, drying time, temperature rising speed, variable ventilation and changes in tobacco leaves, which promotes the sufficient decomposition and transformation of macromolecular substances such as starch and protein in tobacco leaves and the formation of aroma substances, makes the tobacco leaves slowly yellow, the internal macromolecular substances and aroma substances are more fully transformed, and higher quality tobacco leaves are obtained after drying, and the S4 moisture recovery stage is added, which uses the residual heat of the drying barn for moisture recovery, and the moisture recovery quality is higher, effectively solving the problems of difficult moisture recovery and easy crushing of tobacco leaves in the later stage of drying in northern tobacco-growing areas, improving the effective yield of tobacco leaves, and helping to increase the income of tobacco farmers.

[0031] 2. The present application prolongs the baking time of S13 and S14 of S1 yellowing stage, and the baking time of S24 step of S2 color fixing stage, promotes the sufficient decomposition and conversion of a series of high molecular compounds such as pigments, starches and proteins in the tobacco leaves, is beneficial to the synthesis of aroma substances, promotes the formation and accumulation of aroma substances in the tobacco leaves, and is beneficial to improving the quality of the tobacco leaves.

[0032] 3. The present application adopts the dehumidification condensate water of the baking process in the S4 moisture recovery stage, that is, the dehumidification condensate water is atomized and blown into the tobacco chamber by a fan to realize the recycling of the condensate water, effectively preserves the aroma substances lost with water vapor in the dehumidification process of the tobacco leaves, and improves the aroma quality and aroma amount through condensate water recovery, effectively improving the quality and characteristic level of the tobacco leaves.

[0033] 4. The present application creatively incorporates the moisture recovery stage into the baking process, supervises the implementation of the tobacco moisture recovery through technical means, and uses the residual heat of the curing barn and the dehumidification condensate water for moisture recovery, so that the moisture recovery quality is higher, the problems of difficult moisture recovery and easy crushing of the tobacco leaves in the later baking stage in the northern tobacco-growing areas are effectively solved, the effective yield of the tobacco leaves is improved, and the income of the tobacco growers is increased.

[0034] 5. In the S1 yellowing stage, the S11 step does not need to consider the change of the tobacco leaves and the dehumidification, in the S12 step, the dehumidification device starts to work, the dehumidification amount is small, if a large amount of condensed water droplets appear in the observation window, the fan is intermittently started at high speed, which is beneficial to reducing the longitudinal temperature difference in the chamber and facilitating the dehumidification; in the S13 step, the fan is operated at high speed to strengthen the ventilation and dehumidification, avoid the occurrence of brown reaction, and avoid the tobacco leaves from being baked black, while the baking time of S13 is prolonged to leave sufficient time to discharge the moisture of the tobacco leaves. DETAILED DESCRIPTION

[0035] The present application will be described in detail below in combination with examples, but the present application is not limited to these examples.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The reagents or raw materials used in the present application can be purchased through conventional routes, and unless otherwise specified, the reagents or raw materials used in the present application are used according to conventional methods in the art or according to the product instructions. In addition, any method and material similar or equivalent to that described can be applied to the method of the present application. The preferred implementation methods and materials described in the present patent are only for demonstration.

[0037] Example 1 Four-stage baking process for middle tobacco leaves in a full-closed hot air circulation curing barn

[0038] (1) The S1 yellowing stage includes the following steps:

[0039] S11. After starting the baking, increase the temperature to 36℃ of dry bulb temperature and 36℃ of wet bulb temperature at a rate of 1℃ per hour, stabilize for 2 hours, and run the fan at low speed to buffer the next step of stable temperature increase;

[0040] S12. Increase the temperature to 38℃ of dry bulb temperature and 37℃ of wet bulb temperature at a rate of 1℃ per hour, stabilize for 8 hours, and start the exhaust device, and bake until the leaf tips of the middle temperature layer are warm and soft;

[0041] S13. Increase the temperature to 40℃ of dry bulb temperature and 37℃ of wet bulb temperature at a rate of 0.5℃ per hour, stabilize for 18 hours, and run the fan at high speed, until the middle temperature layer of tobacco leaves wilts, collapses, and turns yellow by 8-9;

[0042] S14. Increase the temperature to 42℃ of dry bulb temperature and 37℃ of wet bulb temperature at a rate of 0.5℃ per hour, stabilize for 22 hours, until the main veins of the middle temperature layer of tobacco leaves become soft, and the upper layer of tobacco leaves starts to dry.

[0043] (2) The S2 color fixing stage includes the following steps:

[0044] S21. Increase the temperature to 45℃ of dry bulb temperature and 37℃ of wet bulb temperature at a rate of 0.5℃ per hour, stabilize for 12 hours, until the middle temperature layer of tobacco leaves turns yellow and the veins become yellow;

[0045] S22. Increase the temperature to 47℃ of dry bulb temperature and 37℃ of wet bulb temperature at a rate of 0.5℃ per hour, stabilize for 12 hours, until the middle temperature layer of tobacco leaves is 1 / 2 dry and presents small rolls, and there is no green color in the whole furnace;

[0046] S23. Increase the temperature to 50℃ of dry bulb temperature and 38℃ of wet bulb temperature at a rate of 1℃ per hour, stabilize for 10 hours, until the low temperature layer of tobacco leaves presents small rolls;

[0047] S24. Increase the temperature to 54℃ of dry bulb temperature and 39℃ of wet bulb temperature at a rate of 1℃ per hour, stabilize for 15 hours, until the low temperature layer of tobacco leaves is completely dry and presents large rolls.

[0048] (3) The S3 dry vein stage includes the following steps:

[0049] S31. Increase the temperature to 60℃ of dry bulb temperature and 40℃ of wet bulb temperature at a rate of 1℃ per hour, stabilize for 8 hours;

[0050] S32. Increase the temperature to 68℃ of dry bulb temperature and 41℃ of wet bulb temperature at a rate of 1℃ per hour, stabilize for 14 hours, until the whole furnace of tobacco leaves is completely dry, and the heat pump, fan, and exhaust device stop working.

[0051] (4) S4 conditioning stage; when the temperature in the curing barn naturally decreases to 40°C, the conditioning stage is started. At this time, the fan is started at low power, and the conditioning device is operated according to the working cycle of being started for 5 minutes and being stopped for 3 minutes, and the conditioning is performed for 2 hours, until the conditioning standard is reached, the tobacco conditioning is stopped, the problem of over-conditioning is prevented, and the 1# sample is obtained.

[0052] Example 2 Four-stage curing process for middle tobacco in a full-closed hot air circulation curing barn 2# sample

[0053] (1) S1 yellowing stage includes the following steps:

[0054] S11. After the start of curing, the temperature is increased to 36.5°C of dry bulb temperature and 36°C of wet bulb temperature at a rate of 1°C per hour, and is stabilized for 2.5 hours, and the fan is operated at low speed, so as to buffer the smooth temperature increase in the next step;

[0055] S12. The temperature is increased to 37.5°C of dry bulb temperature and 37.5°C of wet bulb temperature at a rate of 1°C per hour, and is stabilized for 10 hours, and the dehumidifying device is started to work, and the curing is performed until the tips of the middle temperature layer tobacco are warm and soft;

[0056] S13. The temperature is increased to 40.5°C of dry bulb temperature and 37°C of wet bulb temperature at a rate of 0.5°C per hour, and the fan is started to operate at high speed, and is stabilized for 24 hours, until the middle temperature layer tobacco is wilted and collapsed, and is 8-9% yellowed;

[0057] S14. The temperature is increased to 41°C of dry bulb temperature and 37°C of wet bulb temperature at a rate of 0.5°C per hour, and is stabilized for 26 hours, until the main veins of the middle temperature layer tobacco are soft, and the tobacco is in the state of yellow sheet and green veins, and the upper layer tobacco starts to be dry-tipped.

[0058] (2) S2 color fixing stage includes the following steps:

[0059] S21. The temperature is increased to 45.5°C of dry bulb temperature and 37.5°C of wet bulb temperature at a rate of 0.5°C per hour, and is stabilized for 16 hours, until the middle temperature layer tobacco is in the state of yellow sheet and yellow veins;

[0060] S22. The temperature is increased to 47.5°C of dry bulb temperature and 37.5°C of wet bulb temperature at a rate of 0.5°C per hour, and is stabilized for 14 hours, until the middle temperature layer tobacco is 1 / 2 dry sheet, and is in the state of small roll cylinder, and there is no green color in the whole furnace;

[0061] S23. The temperature is increased to 50.5°C of dry bulb temperature and 38.5°C of wet bulb temperature at a rate of 1°C per hour, and is stabilized for 10.5 hours, until the low temperature layer tobacco is in the state of small roll cylinder;

[0062] S24. The temperature is increased to 54°C of dry bulb temperature and 39°C of wet bulb temperature at a rate of 1°C per hour, and is stabilized for 16 hours, until the low temperature layer tobacco is fully dry, and is in the state of large roll cylinder.

[0063] (3) S3 drying stage includes the following steps:

[0064] S31. rise to dry bulb temperature 60.5℃ and wet bulb temperature 40.5℃ at a temperature rising rate of 1℃ per hour, and stabilize for 8.5h;

[0065] S32. rise to dry bulb temperature 67.5℃ and wet bulb temperature 40.5℃ at a temperature rising rate of 1℃ per hour, and stabilize for 20h until the tobacco in the whole furnace is fully dried, and the heat pump, fan and moisture removal device are stopped.

[0066] (4) S4 moisture recovery stage; when the temperature in the curing barn naturally decreases to 42℃, the moisture recovery stage is started. At this time, the fan is started at low power, and the moisture recovery device is operated according to a working cycle of 5 minutes on and 3 minutes off, for 3h until the moisture recovery standard is reached, and the moisture recovery of the tobacco is stopped to prevent over-moisture recovery, and the 2# sample is obtained.

[0067] Example 3: 3# sample of four-stage tobacco curing process in the middle part of a fully-closed hot air circulation curing barn

[0068] (1) S1 yellowing stage includes the following steps:

[0069] S11. after starting the curing, rise to dry bulb temperature 36℃ and wet bulb temperature 36℃ at a temperature rising rate of 1℃ per hour, and stabilize for 2h with the fan running at low speed to buffer the temperature for the next step;

[0070] S12. rise to dry bulb temperature 38℃ and wet bulb temperature 37℃ at a temperature rising rate of 1℃ per hour, and stabilize for 10h with the moisture removal device started, and the curing is continued until the tips of the tobacco in the middle temperature layer are warm and soft;

[0071] S13. rise to dry bulb temperature 40℃ and wet bulb temperature 37℃ in the early stage and 36℃ in the later stage at a temperature rising rate of 0.5℃ per hour, and stabilize for 24h with the fan started to run at high speed, until the tobacco in the middle temperature layer is wilted and collapsed, and 8-9% of the tobacco is yellowed;

[0072] S14. rise to dry bulb temperature 42℃ and wet bulb temperature 37℃ at a temperature rising rate of 0.5℃ per hour, and stabilize for 26h until the main veins of the tobacco in the middle temperature layer are soft and unbroken, and the upper layer of tobacco is dry-tipped.

[0073] (2) S2 color fixing stage includes the following steps:

[0074] S21. rise to dry bulb temperature 45℃ and wet bulb temperature 37℃ at a temperature rising rate of 0.5℃ per hour, and stabilize for 16h until the tobacco in the middle temperature layer is curled and hooked, and is in a yellow sheet and yellow vein state;

[0075] S22 is raised to dry bulb temperature 47℃ and wet bulb temperature 37℃ at a temperature raising speed of 0.5℃ per hour, and is kept stable for 14 hours until the tobacco leaves in the medium temperature layer are 1 / 2 dried and present small roll cylinders, and the whole furnace shows no green color;

[0076] S23 is raised to dry bulb temperature 50℃ and wet bulb temperature 38℃ at a temperature raising speed of 1℃ per hour, and is kept stable for 10 hours until the tobacco leaves in the low temperature layer are in small roll cylinder state;

[0077] S24 is raised to dry bulb temperature 54℃ and wet bulb temperature 39℃ at a temperature raising speed of 1℃ per hour, and is kept stable for 15 hours until the tobacco leaves in the low temperature layer are fully dried and present large roll cylinder state.

[0078] (3) S3 dry muscle stage includes the following steps:

[0079] S31 is raised to dry bulb temperature 60℃ and wet bulb temperature 40℃ at a temperature raising speed of 1℃ per hour, and is kept stable for 8 hours;

[0080] S32 is raised to dry bulb temperature 68℃ and wet bulb temperature 41℃ at a temperature raising speed of 1℃ per hour, and is kept stable for 20 hours until the tobacco leaves in the whole furnace are fully dried, and the heat pump, fan and moisture removal device stop working.

[0081] (4) S4 moisture recovery stage; when the temperature in the curing room naturally decreases to 40℃, the moisture recovery stage starts. At this time, the fan is started at low power in reverse, and the moisture recovery device is operated according to the working cycle of starting for 5 minutes and stopping for 3 minutes. The moisture recovery is 2 hours, and the moisture recovery standard is reached to stop the tobacco leaf moisture recovery to prevent over-moisture recovery problem from occurring, and obtain 3# sample.

[0082] Comparative Example 1 uses the conventional curing process of the intensive curing room to cure the tobacco leaves, and obtains D1# sample.

[0083] Comparative Example 2 uses the conventional curing process of the closed cycle to cure the tobacco leaves, and obtains D2# sample.

[0084] Experimental Example 1: Sensory quality evaluation of tobacco leaves

[0085] The 1#-3# samples obtained in Example 1-Example 3 and the D1#-D2# samples obtained in Comparative Example 1-Comparative Example 2 are subjected to sensory quality evaluation of tobacco leaves, and the full score of each evaluation is 9 points. The results are shown in Table 1.

[0086] Table 1: Sensory quality evaluation results of tobacco leaves

[0087]

[0088]

[0089] From the above table, the samples obtained in Examples 1-3 have improved aroma quality and aroma amount compared with the comparative examples, and the sensory quality and smoking quality of the tobacco leaves are effectively improved.

[0090] Appearance quality evaluation comparison of experimental example 2

[0091] The 1#-3# samples obtained in Examples 1-3 and the D1#-D2# samples obtained in Comparative Examples 1-2 were compared in terms of appearance quality evaluation, and the results are shown in Table 2.

[0092] Table 2: Results of tobacco appearance quality evaluation

[0093] Item 1# sample 2# sample 3# sample D1 sample D2# sample Maturity Mature Mature Mature Mature Mature Leaf structure Loose Loose Loose Loose Loose Identity Medium Medium Medium Medium Medium Oil content Yes Yes Yes Yes Yes Color Medium Medium Medium Medium Medium

[0094] As shown in Table 2, there is no significant difference between the samples obtained in the examples and the samples obtained in the comparative examples in terms of appearance quality evaluation.

[0095] Yield comparison of experimental example 3

[0096] The 1#-3# samples obtained in Examples 1-3 and the D1#-D2# samples obtained in Comparative Examples 1-2 were compared in terms of yield, and the results are shown in Table 3.

[0097] Table 3: Results of yield comparison

[0098]

[0099] As shown in Table 3, the proportion of superior tobacco in the samples obtained in the examples is higher than that in the samples obtained in the comparative examples, and the average price of the sample obtained in Example 1 is 0.4 yuan / kg higher than that of the D1# sample and 0.3 yuan / kg higher than that of the D2# sample.

[0100] Expected benefit analysis:

[0101] Using the four-stage middle tobacco drying process in the full-closed hot air circulation drying room provided in the present application, the energy consumption is reduced by 0.4 yuan / kg, the average purchase price is increased by 0.4 yuan / kg, and the total income per kilogram of middle dry tobacco is increased by 1.28 yuan. According to the conventional annual yield of 50 million kilograms of middle tobacco in the tobacco-growing area, it is expected to increase the income by 6.4 million yuan.

[0102] The above description is only for the embodiments of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the technical idea and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A four-stage curing process for tobacco leaves in the middle of a fully enclosed hot air circulating curing barn, characterized in that, Includes the following steps: S1 yellowing stage, S2 color fixing stage, S3 drying stage, and S4 re-moistening stage; The dry bulb temperature during the yellowing stage of S1 is 36~42℃, and the wet bulb temperature is 36~37℃. The S1 yellowing stage includes the following steps: until... S11. After starting baking, raise the temperature at a rate of 1°C per hour to a dry bulb temperature of 36~36.5°C and a wet bulb temperature of 36~36.5°C, stabilize the temperature for 1.5~2.5 hours, and run the fan at low speed to buffer the next step of stable temperature increase. S12. Increase the temperature at a rate of 1°C per hour to a dry bulb temperature of 37.5~38°C and a wet bulb temperature of 37~37.5°C, stabilize the temperature for 8~10 hours, start the dehumidification device, and bake until the tips of the tobacco leaves in the middle temperature layer are warm and soft. S13. Increase the temperature at a rate of 0.5℃ per hour until the dry bulb temperature reaches 40~40.5℃ and the wet bulb temperature reaches 36~37℃. Start the fan to run at high speed and maintain the temperature for 18~24 hours until the tobacco leaves in the mesophilic layer wither and collapse, turning 80~90% yellow. S14. Increase the temperature at a rate of 0.5℃ per hour to a dry bulb temperature of 41~42℃ and a wet bulb temperature of 36.5~37℃ and maintain the temperature for 22~26 hours until the main vein of the tobacco leaves in the mesophilic layer softens, becomes unbroken when wrapped around a finger, and appears as yellow leaves with green veins, and the tips of the upper tobacco leaves begin to dry. The dry-bulb temperature of the S2 color-fixing stage is 45~54℃, and the wet-bulb temperature is 37~39℃. The S2 color fixing stage includes the following steps: S21 is heated at a rate of 0.5℃ per hour to a dry bulb temperature of 45~45.5℃ and a wet bulb temperature of 37~37.5℃, and the temperature is maintained for 12~16 hours until the tobacco leaves in the mesophilic layer have hooked tips and curled edges, and are in a state of yellow leaves and yellow veins. S22 heats up to a dry bulb temperature of 47~47.5℃ and a wet bulb temperature of 37~37.5℃ at a rate of 0.5℃ per hour, and maintains the temperature for 12~14 hours until half of the tobacco leaves in the mid-temperature layer are dry and form small rolls, with no green color appearing in the entire furnace. S23 is heated at a rate of 1°C per hour to a dry bulb temperature of 50~50.5°C and a wet bulb temperature of 38~38.5°C, and then kept stable for 10~10.5 hours until the tobacco leaves in the low-temperature layer are in a small rolled-up state. S24 heats the tobacco leaves at a rate of 1°C per hour to a dry bulb temperature of 53.5-54°C and a wet bulb temperature of 38.5-39°C, and maintains the temperature for 15-16 hours until the tobacco leaves in the low-temperature layer are completely dry and in a large rolled state. The dry bulb temperature of the S3 dry rib stage is 60~68℃, and the wet bulb temperature is 40~41℃. The S3 dry reinforcement stage includes the following steps: S31 is heated to a dry bulb temperature of 60~60.5℃ and a wet bulb temperature of 40~40.5℃ at a rate of 1℃ per hour, and then kept at that temperature for 8~8.5 hours. S32 heats up to a dry bulb temperature of 67.5~68℃ and a wet bulb temperature of 40.5~41℃ at a rate of 1℃ per hour, and maintains the temperature for 14~20 hours until all tobacco leaves and tobacco fibers in the furnace are completely dry, at which point the heat pump, fan, and dehumidification device stop working. The temperature during the S4 rehydration stage is 39~42℃, and the rehydration time is 2~3 hours. During the S4 rehumidification stage, the fan starts at low power, and the rehumidification device operates in a work cycle of 5 minutes on and 3 minutes off.

2. The four-section curing process for tobacco leaves in the middle of a fully enclosed hot air circulating curing barn according to claim 1, characterized in that, The temperature during the S4 rehydration stage is 40°C.

3. The four-section curing process for tobacco leaves in the middle of a fully enclosed hot air circulating curing barn according to claim 2, characterized in that, The S4 rehumidification stage uses the dehumidifying condensate from the baking process.

4. The four-section curing process for tobacco leaves in the middle of a fully enclosed hot air circulating curing barn according to claim 3, characterized in that, The S4 rehumidification stage includes atomizing the dehumidifying condensate and then blowing it into the tobacco loading chamber by a fan to rehumidify the tobacco leaves.

5. The four-section curing process for tobacco leaves in the middle of a fully enclosed hot air circulating curing barn according to claim 1, characterized in that, In step S12 of the yellowing stage of S1, when condensation appears on the observation window, the fan is indirectly turned on and runs at high speed.

6. The application of the four-stage tobacco curing process in the middle of a fully enclosed hot air circulating curing barn as described in any one of claims 1 to 5 in the field of tobacco curing.

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