CN107194113B - Roller drying experimental equipment and method for establishing tobacco roller drying REA model - Google Patents

Roller drying experimental equipment and method for establishing tobacco roller drying REA model Download PDF

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CN107194113B
CN107194113B CN201710452044.1A CN201710452044A CN107194113B CN 107194113 B CN107194113 B CN 107194113B CN 201710452044 A CN201710452044 A CN 201710452044A CN 107194113 B CN107194113 B CN 107194113B
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tobacco
drying
temperature
moisture content
time
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CN107194113A (en
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李巧灵
李跃锋
陈河祥
谢卫
刘泽春
黄惠贞
苏明亮
林志平
曾强
王锐亮
罗登炎
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China Tobacco Fujian Industrial Co Ltd
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    • A—HUMAN NECESSITIES
    • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
    • A24B—MANUFACTURE OR PREPARATION OF TOBACCO FOR SMOKING OR CHEWING; TOBACCO; SNUFF
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Abstract

The invention relates to roller drying experimental equipment and a method for establishing a tobacco roller drying REA model. Wherein, dry experimental apparatus of cylinder includes: the rotary drum is provided with a hole, and the hole is positioned on a rotating axis of the rotary drum; and the sampling device can enter and exit the cylinder cavity of the roller through the hole. The roller drying experimental equipment can be used for detecting physical property parameters in the tobacco drying process, further establishes a tobacco roller drying REA model, and provides a good tool for researching the tobacco drying behavior.

Description

Roller drying experimental equipment and method for establishing tobacco roller drying REA model
Technical Field
The invention belongs to the field of material drying treatment, and particularly relates to roller drying experimental equipment and a method for establishing a tobacco roller drying REA model.
Background
In modern large-scale cigarette production, drum drying equipment is widely applied to drying and dehydrating tobacco materials. The drying and dehydration are key hot and wet links in the tobacco material processing, and run through the whole processing flow from primary drying after picking, threshing and redrying to shredding of the tobacco raw materials. The primary purpose of drying tobacco is to remove a specific amount of moisture from the tobacco, allowing the tobacco to meet packing density requirements, while also improving the sensory quality of the tobacco. In the tobacco drying process, the change of the temperature and the humidity of the tobacco has more obvious influence on the physical quality and the sensory quality of the tobacco processing. Understanding the drying behaviour of tobacco in a drum is of great importance for accurately controlling the drying process, developing and improving drying systems.
With the development of numerical calculation techniques, various drying models are widely used to describe the drying characteristics of crops. Various semi-empirical or empirical models were developed by Newton, Page, Modified Page, Henderson and Pasis, Logarithmic, Two-term, Wang and Singh, and Midili et al. However, the equations for different models vary widely, and a particular model fits well to a particular experimental condition, and the results typically deviate when the range of experimental conditions is changed or expanded. How to select a suitable model to evaluate the drying process of tobacco in a large industrial drum is a difficult problem for those skilled in the art.
Industrial roll equipment is bulky, with a typical industrial roll having a diameter of about 1.9m and a length of about 9.6 m. In the drum drying process, only the tobacco temperature and moisture parameters of the inlet and outlet ports can be detected, and the specific change of the tobacco in the drum cannot be known by the skilled person. Knowing how the drying action of the tobacco takes place in the drum is also a problem for the person skilled in the art.
Disclosure of Invention
In one aspect, the present invention provides a drum drying experimental apparatus, including:
the rotary drum is provided with a hole, and the hole is positioned on a rotating axis of the rotary drum; and
and the sampling device can enter and exit the barrel cavity of the roller through the hole.
The roller drying experimental equipment has the advantages that: with which it is possible to collect the tobacco sample being dried during the rotary drying of the drum. Because the hole is positioned on the rotating axis of the roller, the sampling device can not influence the rotation of the roller when entering and exiting the roller cavity of the roller through the hole and can not be interfered by the rotation of the roller, thereby smoothly collecting the tobacco sample. The rotation of the roller is not required to be stopped during sampling, so that the normal drying process of the tobacco is hardly influenced, and the parameters of the collected sample are very considerable and accurate.
The roller drying experimental equipment can be used for collecting the physical and chemical parameters of the tobacco subjected to different drying times at different drying temperatures, and the parameters are of great significance for understanding the drying behavior of the tobacco and establishing a tobacco drying model.
In one embodiment, the drum drying experimental facility of the invention has a moving path of the sampling device when entering and exiting the drum cavity, which is coincident with the rotation axis of the drum.
In one embodiment, the drum drying experimental facility of any one of the present invention, the sampling device is provided with an open sample groove.
In one embodiment, the drum drying experimental facility of any one of the present inventions, the sampling device in one embodiment, the drum drying experimental facility of any one of the present inventions, further comprises:
a temperature sensor (e.g. an infrared temperature sensor) disposed outside the drum and in the vicinity of the aperture for measuring the temperature of the dried sample collected by the sampling device.
The temperature sensor can accurately and quickly measure the temperature of the tobacco sample.
In one embodiment, the roller drying experimental facility according to any one of the present invention, the roller has a length of 0.5 to 2m (e.g. 0.6m, 0.8m, 1m, 1.2m, 1.5m, 1.7m, 1.9m) and a diameter of 1 to 3m (e.g. 1.5m, 1.9m, 2m, 2.5 m).
The inventor finds that the parameters detected by using the roller with the sizes are used for establishing a cigarette drying model, and the accuracy of the model is high.
In one embodiment, the length of the portion of the sampling device extending into the roller is 0.5 to 1 times the length of the roller, for example 0.8 to 1 times the length of the roller.
In another aspect, the present invention provides a method for establishing a functional relationship between moisture content X of tobacco and drying time t when the tobacco is dried in a drum, comprising:
a) in the process of drying tobacco by using the roller drying experimental equipment of any one of the invention, different drying temperatures T are adoptedbThen, at different drying times t, the tobacco samples in the drum are collected by a sampling device, and the following parameters of each tobacco sample are respectively detected: dry basis weight m of tobaccotTobacco moisture content mwAnd tobacco temperature Tt；
b) Establishing an REA model for tobacco drying according to the parameters in the step a), and determining the functional relation between the moisture content X of the tobacco and the drying time t according to the REA model.
In one embodiment, the method of any of the present invention, the tobacco temperature is the tobacco surface temperature.
In one embodiment, the method of any of the present invention, further comprising: and (4) placing the detected tobacco sample back into the roller cavity by using a sampling device.
In one embodiment, the method of any one of the present invention, step b), further comprises:
-calculating the moisture content X of the tobacco,
Figure BDA0001322727050000031
-calculating the rate of change of moisture content of tobacco over time
Figure BDA0001322727050000032
-calculating the rate of change of tobacco temperature with time
Figure BDA0001322727050000033
In one embodiment, the method of any one of the present invention, step b), further comprises: calculating the following parameters according to the fact that the heat quantity transferred to the tobacco by the drying gas in the drying process is equal to the sum of the heat absorption quantity of tobacco temperature rise and the heat absorption quantity of tobacco moisture gasification: the heat transfer coefficient h of the tobacco-drying gas interface.
The inventor finds that the heat transfer coefficient h of the tobacco-dry gas interface is calculated by the method and used for building a tobacco drying model, and the prediction result of the model is very accurate.
In one embodiment, the method of any one of the present invention, step b) further comprises calculating the drying temperature T based on the following equationbHeat transfer coefficient h of tobacco-dry gas interface at dry time tT,t：
Figure BDA0001322727050000041
Wherein the content of the first and second substances,
a is the specific surface area of tobacco;
Cp,wis the specific heat capacity of water;
Cp,tis the specific heat capacity of tobacco;
ΔHwis the latent heat of water vaporization.
In one embodiment, the method of any of the present invention, calculating the heat transfer coefficient h of the tobacco-drying gas interface by:
at a drying temperature TbThen, for different drying times t ═ t1、t2、t3…tnSampling and detecting, and solving the tobacco heat transfer coefficients corresponding to different drying times
Figure BDA0001322727050000042
Averaging to obtain
Figure BDA0001322727050000043
At different drying temperatures Tb＝T1、T2、T3…TmSampling and detecting to obtain the product with different drying temperatures
Figure BDA0001322727050000044
Averaging to obtain
Figure BDA0001322727050000045
In one embodiment, the method of any of the present invention calculates the mass transfer coefficient h of the vapor at the tobacco-drying gas interface by the following equationm：
Figure BDA0001322727050000046
DvIs the diffusivity of the drying gas;
kbis the thermal conductivity of the drying gas;
ρbis the density of the dry gas.
In one embodiment, the REA model comprises
Figure BDA0001322727050000047
And (X-X)e) A functional relationship of (i), i.e.
Figure BDA0001322727050000048
Wherein the content of the first and second substances,
Figure BDA0001322727050000051
Figure BDA0001322727050000052
to a drying temperature TbLower saturated steam concentration;
Figure BDA0001322727050000053
for the tobacco temperature TtLower saturated steam concentration;
ρv,bto a drying temperature Tb(ii) the steam concentration;
a is the specific surface area of tobacco;
hmthe mass transfer coefficient of the vapor at the tobacco-dry gas interface;
Xeto balance the water content.
In one embodiment, the process of any of the present invention, g (X-X)e) Is an equation of degree n with respect to X, preferably n is greater than or equal to 3.
In one embodiment, the method of any of the present invention, the moisture content of tobacco X as a function of drying time t is as follows:
Figure BDA0001322727050000054
the above functional relationship is particularly suitable for upper tobacco leaves.
In one embodiment, the method of any of the present invention, the moisture content of tobacco X as a function of drying time t is as follows:
Figure BDA0001322727050000055
the above functional relationship is particularly suitable for lower tobacco leaves.
In one embodiment, the method of any of the present invention, the moisture content of tobacco X as a function of drying time t is as follows:
Figure BDA0001322727050000056
U＝165～170，V＝75～80，W＝11～13；
preferably, the functional relationship is as follows:
Figure BDA0001322727050000061
the above functional relationship is suitable for various tobacco leaves.
In one embodiment, the method of any of the present invention,
Figure BDA0001322727050000062
refers to the relative activation energy.
In one embodiment, the method of any of the present invention,
Figure BDA0001322727050000063
in one embodiment, the functional relationship of the tobacco moisture content X to the drying time t further comprises the following parameters: tobacco temperature Tt。
In one embodiment, the functional relationship of the tobacco moisture content X to the drying time t further comprises the following parameters: drying temperature Tb。
In one embodiment, the functional relationship of the tobacco moisture content X to the drying time t further comprises the following parameters: equilibrium moisture content Xe。
In one embodiment, establishing a functional relationship between the moisture content X of the tobacco and the drying time t is: establishing the moisture content X and the tobacco temperature T of the tobaccotAs a function of the drying time t.
In one embodiment, establishing a functional relationship between tobacco moisture content X and drying time T refers to establishing tobacco moisture content X and tobacco temperature TtDrying temperature TbAs a function of the drying time t.
In one embodiment, the heat transfer coefficient h is 1.8 to 2.2 W.m-2·K-1(e.g., 1.9, 2.0, 2.1 W.m)-2·K-1)。
In one embodiment, the mass transfer coefficient hm＝0.0020～0.0026m·s-1(e.g., 0.002, 0.0022, 0.0024, 0.0026 mS-1)。
In one embodiment, the equilibrium moisture content XeFor the moisture content of the tobacco in the drumThe value at which equilibrium is reached.
In one embodiment, the equilibrium moisture content XeObtained by calculation from the following equation:
Figure BDA0001322727050000064
equilibrium moisture content X measured according to different relative humidity RHeAnd fitting an equation to obtain the values of the parameters C and D.
In one embodiment, the tobacco comprises one or more of tobacco leaf, stem, cut tobacco, lamina.
In a further aspect, the present invention provides a method of predicting the correspondence between moisture content value X and drying time t of tobacco when it is dried in an industrial drum, comprising:
1) the following parameters of tobacco were measured: initial tobacco dry basis weight mt0Tobacco moisture content mw0Tobacco temperature Tt0Equilibrium water content XeAnd calculating the moisture content of tobacco
Figure BDA0001322727050000071
Setting drum drying temperature Tt；
2) M is to bet0、mw0、Tt0、X0、Tt、XeSubstituting the obtained value into a functional relation established by any one of the methods of the invention, and calculating to obtain the time-dependent change rate of the moisture content of the tobacco
Figure BDA0001322727050000072
3) Calculating the time-dependent change rate of the tobacco temperature according to the following formula
Figure BDA0001322727050000073
Figure BDA0001322727050000074
4) Calculate the smoke after a period of time Δ t according to the following equationGrass moisture content X1And tobacco temperature Tt1：
Figure BDA0001322727050000075
Figure BDA0001322727050000076
Preferably, Δ t ≦ 60 s;
5) substituting the tobacco moisture content and the tobacco temperature obtained by the calculation in the step 4) into the function relation in the step 2), and calculating the time change rate of the tobacco moisture content after delta t
Figure BDA0001322727050000077
6) And (5) repeating the steps 2) to 5) to obtain the corresponding relation between the moisture content value X and the drying time t.
In one embodiment, a method of predicting a moisture content value X versus drying time t of tobacco as it is dried in an industrial drum, comprises:
1) the following parameters of tobacco were measured: initial tobacco dry basis weight mt0Tobacco moisture content mw0Tobacco temperature Tt0Equilibrium water content XeAnd calculating the moisture content of tobacco
Figure BDA0001322727050000078
Setting drum drying temperature Tt；
2) M is to bet0、mw0、Tt0、X0、Tt、XeSubstituting into the function relation between tobacco moisture content X and drying time t when tobacco is dried in the roller, and calculating to obtain the time-dependent change rate of tobacco moisture content
Figure BDA0001322727050000081
3) Calculating the time-dependent change rate of the tobacco temperature according to the following formula
Figure BDA0001322727050000082
Figure BDA0001322727050000083
4) Calculating the moisture content X of the tobacco after a period of time delta t according to the following formula1And tobacco temperature Tt1：
Figure BDA0001322727050000084
Figure BDA0001322727050000085
Preferably, Δ t ≦ 60 s;
5) substituting the tobacco moisture content and the tobacco temperature obtained by the calculation in the step 4) into the function relation in the step 2), and calculating the time change rate of the tobacco moisture content after delta t
Figure BDA0001322727050000086
6) And (5) repeating the steps 2) to 5) to obtain the corresponding relation between the moisture content value X and the drying time t.
The functional relation between the moisture content X of the tobacco and the drying time t when the tobacco is dried in the roller is as follows:
Figure BDA0001322727050000087
U＝165～170，V＝75～80，W＝11～13；
Figure BDA0001322727050000088
Figure BDA0001322727050000089
to a drying temperature TbLower saturated steam concentration;
Figure BDA00013227270500000810
for tobacco dimension TtLower saturated steam concentration;
ρv,bto a drying temperature Tb(ii) the steam concentration;
a is the specific surface area of tobacco;
hmthe mass transfer coefficient of the vapor at the tobacco-dry gas interface;
Xeto balance the water content.
In one embodiment, the functional relationship between the moisture content X of the tobacco and the drying time t when the tobacco is dried in the drum is obtained by the method according to any of the invention.
The invention has the advantages of
One or more embodiments of the present invention may have one or more of the following benefits:
(1) by utilizing the roller drying experimental equipment originally created by the invention, various parameters in the tobacco drying process are accurately and reasonably detected, and the parameters are used for establishing the functional relation between the moisture content of the tobacco and the drying time when the tobacco is dried in the roller;
(2) the REA model is preferably selected from the models to be used for evaluating the functional relation between the moisture content of the tobacco and the drying time when the tobacco roller is dried, so that an accurate prediction result is obtained; the REA model introduces dry temperature and humidity conditions into the model as variables, and obtains REA characteristic fingerprint information of the tobacco lamina, namely relative activation energy (delta E/delta E) belonging to the tobacco laminae) With free water (X-X)e) The relationship is not influenced by drying conditions and only represents the drying characteristics of the material, so that the kinetic parameters of the same REA model can describe the drying kinetic behavior of the tobacco lamina under different drying conditions. The conventional semi-empirical and empirical thin-layer drying model cannot obtain the drying characteristics of the tobacco lamina, the parameters in the model are determined based on certain experimental conditions, and once the certain experimental conditions are changed, the parameters in the model need to be changed correspondingly, namely the model has no universality.
(3) In determining parameters h and hmWhen, the conventional classical equation is not used, because tobacco is not a sized substance, itWhen the calculation is carried out by using a classical equation, errors occur, and the patent calculates h and h according to experimental data in the drying process and an energy conservation equationmAccurately and reasonably determine h and hmThe value enables the model prediction result to be accurate;
(4) and predicting the moisture content of the tobacco after the specific drying time according to the functional relation between the moisture content of the tobacco and the drying time when the tobacco is dried in the roller, wherein the relative deviation between the experimental value and the predicted value is small and is respectively 2.5 percent and 1.7 percent.
(5) The REA model used in the embodiment is simple to construct, the required experimental data are few, the drying dynamic behavior of the tobacco lamina under the comprehensive drying condition can be predicted, and the prediction is accurate and quick. For tobacco enterprises, the obtained kinetic model of the tobacco flakes under the comprehensive drying condition is more applicable than the kinetic model of the tobacco flakes under the specific drying condition. Because the REA model focuses on obtaining the drying characteristics of the material, the relation between the relative activation energy and the free water is determined by the drying characteristics of the material and is not influenced by the conditions of drying temperature and humidity, and the REA model meets the requirements of tobacco enterprises better.
(6) The inventor creatively discovers that the drying time or the moisture content of the tobacco in the drum drying process can be predicted by determining the equilibrium moisture content of the tobacco and combining the functional relationship of the invention.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
FIG. 1 is a schematic view of a drum drying experimental facility according to one embodiment,
description of reference numerals: 1, a blower; 2 an air mass flow meter; 3, a steam generator; 4, a steam flow meter; 5, an electric control valve; 6 a mixing chamber; 7 a mixing chamber temperature controller; 8, a mixed gas mass flowmeter; 9 inlet gas temperature and humidity meter; 10 a drum temperature controller; 11 an infrared temperature sensor; 12 a sampling device; 13 a roller; 14 outlet gas temperature and humidity meter; 15 moisture removing device;
FIG. 2 is a schematic view of an industrial drum and drum of an embodiment;
FIG. 3 is a schematic view of a portion of a drum drying experimental apparatus;
description of reference numerals: a drum 13; a hole 131; a drum rotation axis 132; a sampling device 12; a sample cell 121;
FIG. 4 is a graph showing the change of the moisture content X of the upper smoke with the drying time t;
FIG. 5 is a graph showing the change in the moisture content X of the lower smoke with the drying time t;
FIG. 6 shows the tobacco temperature trend of the upper smoke with time at different drying temperatures;
FIG. 7 shows the tobacco temperature trend of the lower smoke with time at different drying temperatures;
FIG. 8 equilibrium moisture content XeTemperature and relative humidity;
FIG. 9 relative activation energy E of upper smokev/Ev,eWith free water X-XeThe correlation of (2);
relative activation energy E of lower smoke in FIG. 10v/Ev,eWith free water X-XeThe correlation of (2);
FIG. 11 is a graph showing the correlation between the normalized relative activation energy and free water;
FIG. 12 comparison of experimental and model predicted values for top smoke dried at 105 deg.C/RH 0.024;
FIG. 13 shows the comparison of experimental and model predicted values for lower smoke dried at 105 deg.C/RH 0.024;
FIG. 14 is a comparison of experimental values and model predicted values for the drying of the cigarette in the middle of Henan, at 105 deg.C/RH 0.024;
FIG. 15 the upper smoke is dried at 95 deg.C and115 deg.C, relative humidity RH and equilibrium moisture content XeThe predicted result of (2);
FIG. 16 shows the result of predicting the moisture content X of the upper smoke when the upper smoke is dried at 95 ℃/RH0.034/320s and115 ℃/RH0.017/250 s.
Detailed Description
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Example 1
1.1 preparation of samples
The tobacco leaf materials are cut into shreds, balanced in a constant temperature and humidity chamber for 48 hours, and adjusted to the moisture content of a humidity base of 23% for later use. These 2 tobacco samples have similar three-dimensional dimensions: average length 2cm, average width 0.1cm, average thickness 0.018 cm.
The surface area a of the tobacco sample can be calculated from the following formula:
Figure BDA0001322727050000111
wherein m (kg) is the initial mass of the tobacco thread, without considering the shrinkage effect of the tobacco thread during the drying process. The initial mass of the tobacco shred in the patent is 2kg, As(m2) Is the surface area of a single tobacco shred, Vs(m3) Is the volume of a single tobacco shred, pt(kg·m-3) Is the true density of the tobacco. The area and volume distribution of the single tobacco shred calculated according to the three-dimensional size of the tobacco sample is 0.4756cm2And 0.0036cm3. Assuming that the true density of the upper and lower smoke is 1.033g.cm-3The surface area A of the tobacco sample was calculated to be 25.6m2。
1.2 roller drying experimental equipment
The industrial roller drying equipment used in the cigarette industry is a roller dryer with the length of 9.6m and the diameter of 1.9m, and in the industrial drying process of tobacco, only the temperature and the moisture content of cut tobacco at the inlet and the outlet of a roller can be detected, and the physical and chemical changes of the cut tobacco in the roller cannot be sampled and measured.
In order to establish the function relationship between the moisture content of tobacco and the drying time when the tobacco is dried in the roller, the roller drying experimental equipment shown in FIG. 1 is adopted in the embodiment. The apparatus comprises: (1) a blower; (2) an air mass flow meter; (3) a steam generator; (4) a steam flow meter; (5) an electrically controlled valve; (6) a mixing chamber; (7) a mixing chamber temperature controller; (8) a mixed gas mass flow meter; (9) an inlet gas hygrothermograph; (10) a drum temperature controller; (11) an infrared temperature sensor; (12) a sampling device; (13) a drum; (14) an outlet gas hygrothermograph; (15) a moisture removal device; a drum motor for rotating the drum.
The blower 1 serves, inter alia, to feed air into the mixing chamber 6. The air mass flow meter 2 is used to detect the amount of air input into the mixing chamber 6. The steam generator 3 is used to feed steam into the mixing chamber 6. The steam flow meter 4 is used to detect the amount of steam input into the mixing chamber 6 by the steam generator 3. The electrically controlled valve 5 is used to control the amount of steam input into the mixing chamber 6 by the steam generator 3. The mixing chamber 6 provides a space for mixing the air and the steam. The mixing chamber temperature controller 7 is used to control the temperature of the mixing chamber 6. The mixing chamber 6 is able to feed dry gas to the drum 13. The mixture mass flow meter 8 is used to control the flow of gas input to the drum 13 from the mixing chamber 6. The drum 13 is provided with an air inlet and an air outlet. The inlet gas hygrothermograph 9 is used to measure the temperature and humidity of the gas at the drum inlet. The outlet gas temperature and humidity meter 14 is used for measuring the temperature and humidity of the drum outlet gas. The drum temperature controller 10 serves to control the temperature inside the drum. The moisture removing device 15 is used to remove moisture from the drum.
Fig. 3 shows a partial schematic view of the drum drying experimental apparatus of fig. 1. As shown in fig. 3, the drum 13 is provided with a hole 131, the hole 131 is located on the rotation axis 132 of the drum 13, and the sampling device 12 can enter and exit the drum cavity of the drum 13 through the hole 131. The path of movement of the sampling device 12 into and out of the chamber coincides with the axis of rotation 132 of the roller. The sampling device 12 is provided with an open sample well 121, and the sampling device 12 is arranged to be capable of being flipped about the axis of rotation 132 of the drum 13.
Fig. 2 is a schematic view of an industrial drum and an embodiment drum. As shown in fig. 2, the industrial drum has a length of about 9.6m and a diameter of about 1.9m, and can only detect the physicochemical parameters of the tobacco at the inlet and outlet, without knowing the specific drying behaviour of the tobacco in the drum. The roller used in the embodiment has a diameter of 1.9m and a length of 1m, so that the movement state of the cut tobacco in the roller is close to the actual state, and the sampling is convenient.
1.3 tobacco roller drying experiment
As shown in fig. 3, at the start of the experiment, the power supply is first turned on at various places of the apparatus, and the blower 1 and the drum motor are started. The drying temperature is set by the mixing chamber temperature controller 7 and the drum temperature controller 10. Example 1 only dry gas was introduced into the drum, and no steam was introduced. The person skilled in the art can inject steam into the roller according to the process requirement, adjust the proportion of the drying gas and the steam, and the invention also belongs to the technical scheme scope of the invention. Specific experimental parameters for example 1 are shown in table 1 below.
When the whole system reaches the set value and is stabilized for a period of time (30min), the tobacco shred samples are uniformly added into the roller 13 at one time by the sampling device 12. Specifically, the sample trough of sampling device 12 faces upwards, holds the tobacco shred sample, then stretches into the cylinder with sampling device 12 through hole 131 on cylinder 13, overturns sampling device 12, makes the tobacco fall into the cylinder, begins the timing simultaneously. At a predetermined point in time (30, 60, 90, 120, 150, 180, 210, 240, 300, 360, 420, 480, 600, 720, 840, 960, 1080, 1200, 1500, and 1800 seconds), the sampling device 12 is extended through an aperture in the drum into the drum with the sample well 121 facing upward for 5 seconds so that several tobacco samples fall into the sample well 121. The sampling device 12 and the tobacco sample collected thereby are then quickly removed from the drum and the temperature of the removed tobacco sample is measured using an infrared temperature sensor and taken as the tobacco temperature Tt. Then, 10g of the tobacco sample was taken from the sampling tank of the sampling device 12 to measure the moisture content X, and the remaining tobacco sample in the sampling device was returned to the drum. And (3) measuring the average water content X of the material by adopting an oven method. And then, measuring the average temperature and the water content of the materials at different preset time points. The experiment under each condition was repeated 3 times.
TABLE 1 parameters of the experimental conditions
Figure BDA0001322727050000131
Figure BDA0001322727050000141
1.4 tobacco drying kinetics model: REA model
The inventors have surprisingly found that the REA model is used to evaluate tobacco drying behaviour, with particularly accurate predictions.
The REA (reaction Engineering approach) model simulates the drying kinetics by using the principles of chemical reaction Engineering, which considers the drying process to be a process in which evaporation and condensation of water compete together, so that for the drying process of tobacco, the drying rate can be described by the following equation:
Figure BDA0001322727050000142
in the formula:
mw(kg) and mt(kg) masses of water and tobacco, respectively;
Ttis the tobacco temperature (the tobacco surface temperature detected by the infrared temperature sensor in this example);
X(kg·kg-1) Is the water content of the tobacco,
Figure BDA0001322727050000143
hm(m·s-1) Is the mass transfer coefficient;
A(m2) Is the surface area of the tobacco;
Figure BDA0001322727050000144
(kg·m-3) Is the saturated vapor concentration at the tobacco-drying gas interface;
ρv,b(kg·m-3) Is the drying temperature TbLower steam concentration
ΔEv(J·mol-1) Is the apparent activation energy.
The REA model assumes relative activation energies under different drying conditions
Figure BDA0001322727050000145
With free water (X-X)e) The relationship between the two is consistent, so that when the tobacco is dried under any conditions, the relative activation energy
Figure BDA0001322727050000146
And free water (X-X)e) The relationship of (a) to (b) is as follows:
Figure BDA0001322727050000147
Figure BDA0001322727050000151
equilibrium activation energy (. DELTA.E)v,e) Can be represented by relative humidity RH ═ ρv/ρv,sat(T)And drying temperature (T)b) And (4) calculating.
XeThe equilibrium moisture content can be calculated from the temperature and the relative humidity of the drying gas, and the Henderson equation is adopted for calculation:
Figure BDA0001322727050000152
RH and PsCalculated from the Antoine equation:
Figure BDA0001322727050000153
Figure BDA0001322727050000154
in the formula: h is absolute humidity, Ps (MPa) is saturated vapor pressure at the temperature, and C and D are equation parameters and can be obtained by nonlinear fitting according to experimental data.
From the temperature and relative humidity (28 ℃/0.77) of the compressed air of table 1, section 1.3, one can calculate Ps 0.003781 from equation (7), then absolute humidity H0.018342 from equation (6), then relative humidity at different temperatures, and then from equations (5) and (6).
From equations (1) and (4), equation (3) can be varied as:
Figure BDA0001322727050000155
wherein dX/dt can be obtained from tobacco drying experiments, pv,sat(Tt)And ρv,sat(Tb)Can be calculated from equation (9) and tobacco temperature (T)t) And drying gas temperature (T)b) And (4) calculating. The saturated water vapor concentration may be represented by the following formula:
Figure BDA0001322727050000156
Figure BDA0001322727050000161
Figure BDA0001322727050000162
Figure BDA0001322727050000163
the heat and mass transfer coefficients are estimated experimentally in this example, taking into account the heterotypic structural properties of the tobacco itself. And then according to dimensionless parameters: re, Nu, Pr and Sc, establish the correlation between heat and mass transfer coefficients. The heat transfer coefficient (h) of the present embodiment is calculated by the following heat balance equation:
Figure BDA0001322727050000164
in the formula: dTt/dt is obtained experimentally,. DELTA.Hw(J·kg-1) Latent heat of vaporization of water, Cp,wAnd Cp,t(J·kg-1·K-1) Is divided intoOther than the specific heat capacity of water and tobacco.
Figure BDA0001322727050000165
Figure BDA0001322727050000166
Cp,t＝1450+2724X (14)
Mass transfer system hmCan be calculated from the following equation:
Figure BDA0001322727050000167
Figure BDA0001322727050000168
Figure BDA0001322727050000169
Figure BDA00013227270500001610
water vapor diffusivity:
Figure BDA0001322727050000171
specific heat capacity of dry gas:
Figure BDA0001322727050000172
Figure BDA0001322727050000173
density of dry gas:
Figure BDA0001322727050000174
heat transfer of dry gasCoefficient:
Figure BDA0001322727050000175
Figure BDA0001322727050000176
viscosity of drying gas:
Figure BDA0001322727050000177
Figure BDA0001322727050000178
in the formula: cp,b(J·kg-1·K-1) Is the specific heat capacity of the dry gas, Pr is the Prandtl number, Sc is the Schmidt number, kb(W·m-1·K-1) Is the heat conductivity of the dry gas, Dv(m2·s-1) Is the diffusion coefficient of the dry gas, pb(kg·m-3)andμb(kg·s-1·m-1) Density and viscosity of the drying gas, respectively.
By the above equation, relative activation energy (. DELTA.E/. DELTA.E)e) Can be obtained by calculation through experimental data, and then the relative activation energy (delta E/delta E) is obtained by fitting a unitary cubic equatione) With free water (X-X)e) The relationship (2) of (c). Since the REA model emphasizes the dry nature of the materials, the relative activation energies (Δ E/Δ E) of different materialse) With free water (X-X)e) The relationship of (c) is different, so this relationship can be referred to as the REA characteristic fingerprint information of the material.
1.6 results of the practice
1.6.1 relationship between moisture content of tobacco and change of tobacco temperature with time
FIGS. 4-7 show the moisture content of tobacco and the temperature of tobacco as a function of drying time under different drying conditions. FIGS. 4and 5 show different drying temperatures TbThe moisture content X of the upper tobacco and the lower tobacco was changed with the drying time at the temperature of 65 ℃, 85 ℃, 105 ℃, 125 ℃ and 145 ℃. FIGS. 6 and 7 show different drying temperatures TbNext (65 ℃, 85 ℃, 105 ℃, 125 ℃, 145 ℃),tobacco temperature T of upper tobacco and lower tobaccotTrend over time. As can be seen from fig. 4and 5, the drying temperature has a significant influence on the drying rate of the cut tobacco, and the higher the drying temperature is, the faster the drying rate is, and finally, a steady state is reached. As can be seen from fig. 6 and 7, in the initial stage of drying, the temperature of the tobacco is lower than the wet bulb temperature of the tobacco under the same conditions, the heat quantity provided by the drying gas to the tobacco is larger than the energy required by the evaporation of the moisture in the tobacco, and the temperature of the tobacco gradually rises; when the temperature of the tobacco rises to the wet bulb temperature, the heat provided by the drying gas to the tobacco is equal to the energy required for the moisture in the tobacco to evaporate, and the temperature of the tobacco stays at the wet bulb temperature for a period of time: as drying progresses, the moisture in the tobacco evaporates more and more difficultly, the heat provided to the tobacco by the drying gas is greater than the energy required for the moisture in the tobacco to evaporate, the temperature of the tobacco begins to rise rapidly, and when the tobacco is dried to an equilibrium moisture content, the temperature of the tobacco rises to the temperature of the drying gas.
1.6.2 equilibrium moisture content of tobacco XeResult of calculation of (2)
As can be seen from FIGS. 4-7, the time for the tobacco to reach the equilibrium moisture content at different drying temperatures is all 1800s, which is due to the same soil type, fertilizing amount and environmental conditions of the same crop. But the upper and lower smoke exhibited different X's due to different light intensity and harvest timeeNumerical values. X of upper and lower smoke according to equations (5) - (7)eThe fitting correlation with the temperature and the humidity is shown in fig. 8, and the fitting degrees are 0.9988 and 0.9998 respectively. By fitting, the results of parameters C and D in equation (5) are shown in table 2 below. Since the parameter C is very sensitive to the exponential influence, the difference in the value of the parameter C between the upper smoke and the lower smoke is large.
TABLE 2 calculation of parameters C and D
Figure BDA0001322727050000181
1.6.3 determination of Heat and Mass transfer coefficients
Using experimental data, and according to equation (11), the time of each instant can be obtainedCoefficient of heat transfer hT,tThen averaging the heat transfer coefficients at all times to obtain an average h under different drying conditionsT,ave. Calculating the mass transfer coefficient h under the corresponding drying condition according to the equation (15.1)mT、The calculation results are shown in Table 3 below. As can be seen from the results of Table 3, the heat transfer coefficient and the mass transfer coefficient are little affected by the drying conditions, and therefore h for the upper fume and the lower fume furtherT,aveAnd hmTThe average values are respectively calculated. Further, the values of the upper fume and the lower fume are averaged to obtain the overall heat transfer coefficient h and mass transfer coefficient h under all drying conditionsm。
Figure BDA0001322727050000191
TABLE 3 calculation of Heat and Mass transfer coefficients
Figure BDA0001322727050000192
The inventors have found that the heat treatment conditions and the tobacco type have a heat transfer coefficient h and a mass transfer coefficient hmThe effect of (a) is not significant. The inventor creatively uses h as 2.0 W.m-2·K-1And hm＝0.0024m·s-1The method is used as the heat transfer coefficient and the mass transfer coefficient of tobacco and used for establishing an REA model, and the prediction result is very accurate.
1.6.4 establishing correlation between relative activation energy and moisture content (establishing function relationship between moisture content X and drying time t of tobacco when drying in roller)
The upper part below is at TbExamples of assignments were made for drum drying experiments at 105 ℃.
According to equation (8), the relative activation energies of tobacco under different drying conditions can be calculated from the drying curve, for example
(1) The tobacco shred temperature T at each moment can be obtained according to experimentstThe water content ratio X and the water content ratio change rate dX/dt are shown in Table 4 below. Drying temperature TbThe set temperature is 105 ℃, and the quality of cut tobaccomt is 1.55kg, mass transfer coefficient hmIs 0.0024 m.s-1The surface area A of the cut tobacco is 25.6m2Equilibrium water content Xe0.027. According to the equation (9.1), the saturated water vapor concentration rho at the temperature of the corresponding tobacco shred can be calculatedv,sat(Tt)The saturated water vapor concentration ρ at the corresponding drying temperature is calculated from the equation (9.2)v,sat(Tb)＝0.688kg.m-3The water vapor concentration ρ under the condition corresponding to the drying temperature is calculated according to equation (10)v,b＝0.0165kg.m-3. Substituting all the data into equation (8) can calculate the relative activation energy delta E at each momentv/ΔEv,eAs shown in table 4 below.
TABLE 4
Figure BDA0001322727050000201
Figure BDA0001322727050000211
FIGS. 9-11 show the relative activation energies (Δ E)v/ΔEv,e) With free water (X-X)e) The relationship of (1). FIG. 9 is a correlation of relative activation energy of upper smoke with free water; FIG. 10 is a graph of the relative activation energy of lower smoke in relation to free water; fig. 11 shows the correlation between the relative activation energy and free water of the upper smoke and the lower smoke after data unification.
In the initial stage of drying, the relative activation energy is lower, more free water is contained in the tobacco, the water is continuously evaporated along with the continuous drying, the water content in the tobacco is reduced to the equilibrium water content, and the relative activation energy is 1 at the moment, which indicates that the drying is balanced and the drying is not continued. As can be seen from FIGS. 9 to 11, the relative activation energies (. DELTA.E/. DELTA.E) under different drying conditionse) With free water (X-X)e) The relationship curves of (A) and (B) are substantially coincident, showing the relative activation energies (Δ E/Δ E)e) With free water (X-X)e) The relationship of (a) is negligible affected by the drying conditions. Fitting was performed using a one-dimensional cubic equation, with the following results:
upper smoke (R)2＝0.9599)：
Figure BDA0001322727050000212
Lower smoke (R)2＝0.9456)：
Figure BDA0001322727050000213
Because the tobacco shreds at different parts need to be mixed and dried under the same drying condition in the actual production of cigarettes, the patent tries to establish a uniform relative activation energy (delta E/delta E)e) With free water (X-X)e) The relationship (2) of (c). The data for the upper and lower smoke are fitted simultaneously, see fig. 11, and the fitted equation is shown in equation (25):
Figure BDA0001322727050000221
relative activation energy (Delta E/Delta E) after unification treatmente) With free water (X-X)e) Relationship (R)2＝0.9501)：
1.6.5 comparison of the results of the model with the experimental values
Introducing tobacco drying parameters into an REA model, and fitting a drying characteristic curve of tobacco by using the REA model:
(1) the initial mass and the moisture content of the tobacco and the temperature and humidity conditions of drying are consistent with the experimental conditions and assigned values;
(2) the relative activation energy and (delta E/delta E) are calculated according to experimental datae) With free water (X-X)e) A unitary cubic equation of (a);
(3) the drying rate dX/dT was calculated according to equation (1), and the temperature change rate dT was calculated according to equation (11)t/dt；
(4) The quality of the tobacco at the next moment is obtained according to the initial tobacco quality and the drying rate obtained by calculation;
(5) and (4) calculating the moisture content and the temperature of the tobacco at the next moment according to the step (4), and repeating the steps (2) to (5) to obtain the change values of the moisture content and the temperature of the tobacco in the whole drying process along with time.
Assignment examples, take top smoke 105 ℃ dry as an example:
(1) initial water content X of 0.29 and tobacco shred temperature TtAt 28 ℃ and a drying temperature TbAt 105 ℃, according to the equations (5) to (6), the corresponding relative humidity RH is 0.024, and the equilibrium moisture content X is obtainede0.027, then X — Xe 0.29-0.027 0.263;
(2) calculating the initial (Δ E) according to equation (25)v/ΔEv,e) When 0.06855, Δ E is calculated according to equation (4)e＝11726.0J.mol-1Then Δ E at this timev＝0.06855×11726.0＝803.8J.mol-1。
(3) According to the equations (9.1) and (9.2), p at the corresponding temperature can be respectively calculatedv,sat(Tt)And ρv,sat(Tb)The values are respectively 0.027kg.m-3And 0.688kg.m-3Then ρv,bρ can be calculated from equation (10)v,b＝0.688×0.024＝0.0165kg.m-3. Mass transfer coefficient hmIs 0.0024 m.s-1The surface area A of the cut tobacco is 25.6m2. All data are substituted into equation (1) and dX/dt ═ 0.00013s is calculated-1(ii) a The heat transfer coefficient h is 2.0 W.m-2·K-1Mass m of starting tobaccot1.55kg, mass m of initial moisturewIt was 0.45 kg. Latent heat of vaporization Δ H of waterwCalculated from equation (12) and has a value of-2365.27 KJ.kg-1. The specific heat capacities of water and tobacco were calculated from equations (13) and (14) and were Cp,w＝4190.58J·kg-1·K-1And Cp,t＝2240J·kg-1·K-1. All data are substituted into equation (11), and dT is calculatedt/dt＝0.648K.s-1。
(4) Taking 10s as a calculation cycle, the water content X at the next time 10s is 0.29+10 XdX/dt is 0.289, and the tobacco shred temperature T ist＝28+10×dTtAnd/dt is 34.48 ℃, and the moisture content and tobacco temperature at 10s are obtained according to the step (4).
(5) And (5) repeating the steps (2) to (4) to obtain the change values of the moisture content and the temperature of the tobacco along with time in the whole drying process, which are shown in the following table 5.
Figure BDA0001322727050000241
Figure BDA0001322727050000251
Figure BDA0001322727050000261
Figure BDA0001322727050000271
Figure BDA0001322727050000281
Figure BDA0001322727050000291
Figure BDA0001322727050000301
And comparing the drying rate and the tobacco shred temperature predicted by the REA model with the experimental value. Figures 12 and 13 show graphs comparing REA models and experimental measurements of upper smoke at 105 ℃/RH0.024 dry conditions and lower smoke at 85 ℃/RH0.050 dry conditions, respectively. As can be seen from the figure, for different tobaccos under different experimental conditions, the REA model can accurately predict the change trend of the dry-basis moisture content and the temperature of the tobaccos along with the drying time; the predicted values of the dry basis moisture content and temperature of the tobacco are very close to the experimentally measured values.
In REA modelIn (1), the relative activation energy (. DELTA.E/. DELTA.E)e) With free water (X-X)e) The relationship is considered as the fingerprint of different dry substances, and the relative activation energy (delta E/delta E) is expressed by the difference of the physicochemical structures of the different dry substancese) With free water (X-X)e) The relationship of (c) is also different. Although the upper and lower cigarettes can obtain respective relative activation energies (Δ E/Δ E)e) With free water (X-X)e) Relationship (D), but normalized relative activation energy (Δ E/Δ E)e) With free water (X-X)e) The relationship (2) can also simulate the drying behaviors of the upper smoke and the lower smoke, and the simulation effect is better, which indicates that the upper smoke and the lower smoke belong to tobacco, the overall drying characteristics of the upper smoke and the lower smoke are not greatly different, and the upper smoke and the lower smoke mainly determine the drying characteristics of the upper smoke and the lower smoke and are different in equilibrium moisture content. To verify this inference, the normalized relative activation energies (Δ E/Δ E) were usede) With free water (X-X)e) The relation of (1), equation (25), is to simulate the drying behavior of the central smoke of Henan at 105 deg.C/RH 0.024, at which the equilibrium moisture content XeIs 0.031, and fig. 14 is a graph showing the comparison result between the experimental value of drying and the predicted value of REA of the central smoke in Henan under the condition of 105 ℃/RH0.024, and it can be seen from the graph that the predicted result is basically consistent with the experimental result. Therefore, the inventor creatively finds that the drying behavior of the mixed cut tobacco can be predicted according to equation (25) as long as the equilibrium moisture content of the mixed cut tobacco under the temperature and humidity conditions is determined.
2.4.5 practical application of model
In one embodiment, the time required for the tobacco to dry to a particular moisture content is predicted.
During the drying process of the tobacco industry, the moisture of the tobacco needs to be removed from 22.5 +/-0.1 percent to 12.0 +/-1.0 percent. It can be seen that monitoring and controlling the stability of the moisture content at the outlet under different drying conditions is crucial. To this end, the REA model established above was used to predict the time required for top tobacco to dry to 12.0% at 95 ℃ and115 ℃. Calculating the relative humidity and X of tobacco at 95 ℃ and115 ℃ by equations (4) - (6)eThe results are shown in FIG. 15. FIG. 16 shows the upper smoke at 95 ℃/RH0.034/320s andand (4) predicting the water content under the drying condition of 115 ℃/RH0.017/250 s. FIG. 16 As can be seen from FIG. 16, the time required for the upper tobacco to dry to 12% moisture content under conditions of 95 ℃/RH0.034and 115 ℃/RH0.017 was 320 and 250 seconds, respectively.
And (3) experimental detection: the water content is respectively 12.3 percent and 11.8 percent in a drying experiment under the conditions of 95 ℃/RH0.034and 115 ℃/RH0.017, and the relative deviation from the predicted value is 2.5 percent and 1.7 percent in 320s and 250s sampling, thus meeting the requirements of process indexes. Therefore, the functional relation between the moisture content of the tobacco and the drying time established by the invention is very accurate.
The parameter calculation equation used in the above embodiment is as follows:
drying gas:
specific heat capacity C of dry gasp,b(J·kg-1·K-1)，
Figure BDA0001322727050000321
Density of dry gas ρb(kg·m-3)，
Figure BDA0001322727050000322
Viscosity of drying gas mub(kg·s-1·m-1)，
Figure BDA0001322727050000323
Dry gas thermal conductivity kb(W·m-1·K-1)，
Figure BDA0001322727050000324
Water vapor:
water vapor diffusivity of Dv(m2·s-1)，
Figure BDA0001322727050000325
Saturated vapor concentration at the tobacco-drying gas interface
Figure BDA0001322727050000326
(kg·m-3)，
Figure BDA0001322727050000327
Water:
latent heat of vaporization Δ H of waterw(J·kg-1)，
Figure BDA0001322727050000328
Specific heat capacity of water Cp,w(J·kg-1·K-1)，
Figure BDA0001322727050000331
Tobacco shred:
specific heat capacity C of tobacco shredp,t(J·kg-1·K-1),
Cp,t＝1450+2724X
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention and not to limit it; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will understand that: modifications to the specific embodiments of the invention or equivalent substitutions for parts of the technical features may be made; without departing from the spirit of the present invention, it is intended to cover all aspects of the invention as defined by the appended claims.

Claims (16)

1. A method of establishing a functional relationship between moisture content X of tobacco and drying time t as the tobacco is dried in a drum, comprising:
a) in the process of drying tobacco by using a roller drying experimental device, different drying temperatures T are adoptedbThen, at different drying times t, the tobacco samples in the drum are collected by a sampling device, and the following parameters of each tobacco sample are respectively detected: dry basis weight m of tobaccotTobacco moisture content mwAnd tobacco temperature Tt；
b) Establishing an REA model for tobacco drying according to the parameters in the step a), and determining the functional relation between the moisture content X of the tobacco and the drying time t according to the REA model;
in step a), the drum drying experimental facility includes:
the rotary drum is provided with a hole, and the hole is positioned on a rotating axis of the rotary drum; and
the sampling device can enter and exit the cylinder cavity of the roller through the hole;
in step b), the REA model refers to the drying process for tobacco, and the drying rate can be described by the following equation:
Figure FDA0002889285870000011
in the formula:
mw(kg) and mt(kg) masses of water and tobacco, respectively;
Ttthe tobacco temperature is the tobacco surface temperature detected by an infrared temperature sensor;
X(kg·kg-1) Is the water content of the tobacco,
Figure FDA0002889285870000012
hm(m·s-1) Is the mass transfer coefficient;
A(m2) Is the surface area of the tobacco;
Figure FDA0002889285870000013
at the tobacco-dry gas interfaceSaturated steam concentration;
ρv,b(kg·m-3) Is the drying temperature TbLower steam concentration
ΔEv(J·mol-1) Is the apparent activation energy;
in the step b), the functional relation between the moisture content X of the tobacco and the drying time t is as follows:
Figure FDA0002889285870000014
U＝165～170，V＝75～80，W＝11～13；
wherein, Delta Ev(J·mol-1) Is the apparent activation energy, Δ Ev,eTo balance the activation energy;
Figure FDA0002889285870000021
Figure FDA0002889285870000022
to a drying temperature TbLower saturated steam concentration;
Figure FDA0002889285870000023
for the tobacco temperature TtLower saturated steam concentration;
ρv,bto a drying temperature Tb(ii) the steam concentration;
a is the surface area of the tobacco;
hmthe mass transfer coefficient of the vapor at the tobacco-dry gas interface;
Xeto balance the water content.
2. The method of claim 1, further comprising: and (4) placing the detected tobacco sample back into the roller cavity by using a sampling device.
3. The method of claim 1, step b) further comprising:
-calculating the moisture content X of the tobacco,
Figure FDA0002889285870000024
-calculating the rate of change of moisture content of tobacco over time
Figure FDA0002889285870000025
-calculating the rate of change of tobacco temperature with time
Figure FDA0002889285870000026
4. The method of claim 1, step b) further comprising: calculating the following parameters according to the fact that the heat quantity transferred to the tobacco by the drying gas in the drying process is equal to the sum of the heat absorption quantity of tobacco temperature rise and the heat absorption quantity of tobacco moisture gasification: the heat transfer coefficient h of the tobacco-drying gas interface.
5. The method of claim 1, step b) further comprising calculating a drying temperature T based on the following equationbHeat transfer coefficient h of tobacco-dry gas interface at dry time tT,t：
Figure FDA0002889285870000027
Wherein the content of the first and second substances,
a is the surface area of the tobacco;
Cp,wis the specific heat capacity of water;
Cp,tis the specific heat capacity of tobacco;
ΔHwis the latent heat of water vaporization.
6. The method of claim 5, wherein the heat transfer coefficient h of the tobacco-drying gas interface is calculated by:
at a drying temperature TbThen, for different drying times t ═ t1、t2、t3…tnSampling and detecting, and solving the tobacco heat transfer coefficients corresponding to different drying times
Figure FDA0002889285870000031
Averaging to obtain
Figure FDA0002889285870000032
At different drying temperatures Tb＝T1、T2、T3…TmSampling and detecting to obtain the product with different drying temperatures
Figure FDA0002889285870000033
Averaging to obtain
Figure FDA0002889285870000034
7. The method of claim 6, wherein the mass transfer coefficient h of the vapor at the tobacco-drying gas interface is calculated by the following equationm：
Figure FDA0002889285870000035
Cp,b(J·kg-1·K-1) Is the specific heat capacity of the drying gas,
Dvis the diffusivity of the drying gas;
kbis the thermal conductivity of the drying gas;
ρbis the density of the dry gas.
8. The method of claim 1, wherein the path of movement of the sampling device into and out of the chamber coincides with the axis of rotation of the drum.
9. The method of claim 1, wherein the sampling device is provided with an open sample well.
10. The method of claim 9, wherein the sampling device is configured to be reversible about the axis of rotation of the drum.
11. The method of claim 1, further comprising:
and the temperature sensor is arranged outside the roller and near the hole and is used for measuring the temperature of the dry sample collected by the sampling device.
12. The method of claim 1, wherein the roller has a length of 0.5 to 2m and a diameter of 1 to 3 m.
13. A method of predicting the correspondence of moisture values X to drying times t of tobacco when it is dried in an industrial drum, comprising:
1) the following parameters of tobacco were measured: initial tobacco dry basis weight mt0Tobacco moisture content mw0Tobacco temperature Tt0And calculating the moisture content of tobacco
Figure FDA0002889285870000041
Setting drum drying temperature Tt；
2) M is to bet0、mw0、Tt0、X0、TtSubstituting into the functional relation established by the method according to any one of claims 1-7, and calculating to obtain the time-dependent change rate of the moisture content of the tobacco
Figure FDA0002889285870000042
3) Calculating the time-dependent change rate of the tobacco temperature according to the following formula
Figure FDA0002889285870000043
Figure FDA0002889285870000044
4) Calculating the moisture content X of the tobacco after a period of time delta t according to the following formula1And tobacco temperature Tt1：
Figure FDA0002889285870000045
Figure FDA0002889285870000046
5) Substituting the tobacco moisture content and the tobacco temperature obtained by the calculation in the step 4) into the function relation in the step 2), and calculating the time change rate of the tobacco moisture content after delta t
Figure FDA0002889285870000047
6) And (5) repeating the steps 2) to 5) to obtain the corresponding relation between the moisture content value X and the drying time t.
14. The method of claim 13, wherein Δ t ≦ 60 s.
15. A method of predicting the correspondence of moisture values X to drying times t of tobacco when it is dried in an industrial drum, comprising:
1) the following parameters of tobacco were measured: initial tobacco dry basis weight mt0Tobacco moisture content mw0Tobacco temperature Tt0Equilibrium water content XeAnd calculating the moisture content of tobacco
Figure FDA0002889285870000048
Setting drum drying temperature Tt；
2) M is to bet0、mw0、Tt0、X0、Tt、XeSubstituted into tobaccoCalculating the time change rate of the tobacco moisture content in the functional relation between the tobacco moisture content X and the drying time t during drying in the roller
Figure FDA0002889285870000049
3) Calculating the time-dependent change rate of the tobacco temperature according to the following formula
Figure FDA00028892858700000410
Figure FDA00028892858700000411
In the formula: dTt/dt is obtained experimentally,. DELTA.Hw(J·kg-1) Latent heat of vaporization of water, Cp,wAnd Cp,t(J·kg-1·K-1) The specific heat capacities of water and tobacco, respectively;
4) calculating the moisture content X of the tobacco after a period of time delta t according to the following formula1And tobacco temperature Tt1：
Figure FDA0002889285870000051
Figure FDA0002889285870000052
5) Substituting the tobacco moisture content and the tobacco temperature obtained by the calculation in the step 4) into the function relation in the step 2), and calculating the time change rate of the tobacco moisture content after delta t
Figure FDA0002889285870000053
6) Repeating the steps 2) to 5) to obtain a corresponding relation between the moisture content value X and the drying time t;
the functional relation between the moisture content X of the tobacco and the drying time t when the tobacco is dried in the roller is as follows:
Figure FDA0002889285870000054
U＝165～170，V＝75～80，W＝11～13；
Figure FDA0002889285870000055
Figure FDA0002889285870000056
to a drying temperature TbLower saturated steam concentration;
Figure FDA0002889285870000057
for the tobacco temperature TtLower saturated steam concentration;
ρv,bto a drying temperature Tb(ii) the steam concentration;
a is the surface area of the tobacco;
hmthe mass transfer coefficient of the vapor at the tobacco-dry gas interface;
Xeto balance the water content.
16. The method of claim 15, wherein Δ t ≦ 60 s.
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