DE3441649A1 - IMPROVED METHOD FOR DRYING TOBACCO - Google Patents

Description

Improved Process for Drying Tobacco

Description

The invention relates to tobacco drying processes and, in particular, to a process for reducing the moisture content of expanded tobacco at high dry thermometer temperatures with controlled wet thermometer temperatures .

It is known in the manufacture of smoking articles such as cigarettes and the like, the

Moisture content of tobacco including leaves 15

and / or stems prior to size reduction for the subject Increase smoking articles to minimize breakage and have a more uniform particle size to achieve. It is then required that the

Moisture content of the tobacco material to one for the next 20

Reduce processing appropriate level.

Generally, cut tobacco with an original moisture content of about 16% to 35% is suitable for

the leaves and about 20% to 60% for the stems 25

except for a humidity range of approximately 12%

to 15% has been dried by means of hot air for a period and at temperature conditions that are sufficient to achieve the desired moisture reduction. The prior art discloses 30th

a number of methods and various devices for performing the drying of moistened tobacco, most of the prior art drying by means of gases in the temperature range of

teaches about 82 ⁰ C (180 ° F) to about 182 ⁰ C (36O ⁰ F) .. 35

The more recent state of the art discloses wet tobacco drying processes using humidified gases at temperatures as high as 3M3 ° C (650 ⁰ F) -Example-

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teaches example US Pat. No. 40 40 431, the drying of conditioned tobacco with hot gases in the temperature range of about 149 ° C (300 ⁰ F) to 316 ° C (6QO ⁰ F). The US Pat. No. 41 67 191 teaches the drying tobacco by means of gases within the range of about 121 ° C (250 ⁰ F) to about 343 ° C (650 ⁰ F) with wet bulb temperatures in the range of at least about 66 ° C (150 °) up to a maximum of 100 ⁰ C (212 ° F). Furthermore, the German patent application No. 31 30 778 teaches the shock treatment of tobacco by means of hot gases with a temperature as high as 1000 C, but does not specify any specific humidity thermometer temperatures. The gas treatment according to this German patent extends over a period of less than a second.

The methods known from the prior art, including those described above, are recognized the benefits of expanding or "puffing" the tobacco prior to its incorporation into the smoking article. Such an expansion of the tobacco reduces the tobacco density or increases its filling capacity, whereby the tobacco quality as well as the profitability of its production increases and at the same time the Tar and nicotine intake to smokers is reduced.

The prior art methods also have the importance of avoiding one Recognized shrinkage during the drying process and the resulting loss of filling capacity.

According to the present invention there is provided an improved, simple and economical drying method for Created tobacco that increases the filling capacity of the tobacco beyond what was previously known in the prior art, whereby the moisture content of the tobacco is at a preselected target minimum level with optimal energy consumption and minimal equipment with no associated

Shrinkage or charring of the tobacco is reduced. Various other features of the present invention will be apparent to those skilled in the art upon reading the disclosure given herein. 5

In particular, the present invention provides a method for reducing the moisture content of expanded tobacco, characterized by drying the expanded tobacco with hot gas at a wet bulb temperature within the range of about 66 ⁰ C (15O ⁰ F) to 100 ⁰ C (212 ⁰ F ) and a dry thermometer temperature in the range of about 343 ⁰ C (650 ⁰ F) to about 51O ⁰ C (95O ⁰ F) with a residence time sufficient to produce a tobacco product with a moisture content at the dryer exit of about 3% to about Receive 16%.

The present invention also provides a method of drying tobacco with hot gas at one temperature within the physical limits of the process apparatus, the temperature being calculated by that for the desired percentage improvement in the tobacco product fill value, the absolute term of an empirically determined linear equation of about 47.8 is added and the result by the linear term of an empirical The calculated linear equation is divided by approximately 0.094, while the absolute humidity of the hot Gas is maintained at a level above that one to prevent charring of the product adequate wet bulb temperature and that is within a range sufficient to to obtain a product with a moisture content at the dryer outlet of about 3% to about 16%.

It goes without saying that those skilled in the art could make various modifications in the various steps of the present disclosure disclosed method according to the invention can perform without the scope of protection and the inventive concept of the

differing invention. It is also understood that the term "expanded tobacco" used herein Green and recycled, including recycled tobacco means treated for volume increase became. The maximum level of expansion for tobacco results when it is in the green, freshly harvested (turgor) state is. During the smoking process, the moisture content and volume decrease. Expanded Tobacco is therefore also tobacco that has been subjected to the "re-expansion" of volume.

Furthermore, the term "absolute humidity" as used herein means the absolute water content in the air or the gas surrounding the tobacco subjected to the process of the invention.

The "wet bulb temperature", a term known in the art, is the temperature at which the Amount of heat that is applied to one surrounding the thermometer sphere moist cotton wick is equal to the heat loss due to evaporation of the water of the wick arises and which it with the reading of a dry thermometer and a psychrometric Diagram allows to determine the relative humidity of drying air. In most Dryers dry solids at or near the wet bulb temperature.

The invention is described in more detail below with reference to the accompanying drawings.

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Figure 1 is a schematic representation of the device for performing the method according to the invention ,

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FIG. 2 is a graph showing the increase in the fill value at various temperatures in the range from about 316 ⁰ C (600 ° F) to about 51O ⁰ C (95O ⁰ F) during the entire inventive method,

Figure 3 is a graphical representation (950 ⁰ F) shows the improvement of the fill value at different temperatures also in the range of about 316 ° C (600 ⁰ F) to about 51O ⁰ C during the drying step in the present process.

As shown in FIG. 1, gas is in a pipeline system, generally designated by the reference numeral 2 circulated with a closed circuit by means of a primary fan 3. The gas described below, which Can be air or a mixture of air and steam, flows through a preheater 4, in which his Temperature is raised to a level sufficient to achieve the desired humidity at the dryer outlet. A bypass line 6 is used to control the temperature of the drying gas by having a part of the recirculated hot gas bypassed around the heating section 4 and with that passed through the heater core Gas is mixed again. It should be noted that immediately in front of the heating device 4 a Steam inlet line 7 is located, which is used to To blow steam into the circulating gas stream to set the wet bulb temperature of the dryer on a to maintain a certain operating level. This steam replaces that lost through normal dryer leakage Steam.

The heated gas / steam / mixture flows along the Pipeline system 2, in which there is with the tobacco entering the system through the gas lock 8 comes into contact. This undried tobacco will

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from the feed hopper 9, which feeds the conveyor 11, supplied. After entering the pipeline system 2, the tobacco is pneumatically transported to the drying chamber 12 by the hot gas flow. At the top of the Tobacco emerging from the drying chamber 12 is pneumatically transported to the gas tobacco classifier 13. Dried Tobacco is separated from the gas flow and falls into the gas lock 14, from which it is transferred to the discharge conveyor 10 falls and is transported further downstream for further treatment.

The separated gas flow is through the pipeline system 2 circulates back with a closed circuit and flows through the one used as a protective device Sieve 17 to a separator 10 and to the primary fan 3-Das Sieve 17 prevents large tobacco particles from entering the separator 10 and damaging it. After this Leaving the sieve 17, the gas flows through the separator 18, in which small tobacco particles by means of a system

fine jets of water are removed from the recirculated gas flow. In addition, the separator 18 acts as a Booster blower and supports air circulation back to the primary fan 3- A pressure relief tube 19 is used to maintain a balanced pressure within the Circulation system 2 with a closed circuit by periodic Maintaining escape of some of the recirculated gas into the atmosphere. The remaining Gas is returned to the primary fan 3 where its pressure is increased and the cycle begins again.

Although only one drying chamber 12 is disclosed to advantageously allow a shorter residence time, the chamber size being chosen so that the capacity is sufficient to accommodate the drying up to the To enable the desired level of moisture, it goes without saying that the number, size and design of chambers can be varied to achieve any desired residence time for any desired degree of dryness.

A dwell time in the range of 1-4 seconds can advantageously be used in the one drying chamber will.

As is known in the art, the drying feature 12 in relation to the flow rate of the Gases be proportioned to allow a downward deposition of the denser tobacco parts. This The process results in a circular flow path within the chamber up to reducing the density during of lingering in this circular flow path and until the particles left behind are light enough to to be transported through the system, loosening of the denser particles taking place to thereby to improve the fill value.

In accordance with the invention that it is advantageous to optimize the filling value of the tobacco was observed, by maintaining the wet bulb temperatures within a range of about 66 ° C (15O ⁰ F) to about 100 ⁰ C (212 ° F) - preferably about 100 ⁰ to provide C (212 ° F) to provide a tobacco product with a moisture content by weight bezogen.auf when leaving the air lock 14 within a range of about 3% to about 16%, and preferably within the range of 13% to 14% . If tobacco were to be dried to a moisture content of below 3%, it would probably char - especially with the high gas temperatures aimed at according to the invention. On the other hand, if the moisture content of the tobacco at the exit of the drying chamber 16 were above 16%, many of the desired properties of the smoking article made with the tobacco would be lost.

As is known in the art, the moisture content of cut tobacco before drying can be approximately 18% to 90% for leaves to about 30% to 90% for the stem. To get the tobacco within the

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Drying chamber 12 to the desired range of 3% to 16% moisture content according to the present invention to dry, such critical factors as dwell time in the drying chamber, gas / solids ratio, Temperature increase and moisture content of the gas are taken into account. With the present invention is recognized that the filling value increased with a constant humidity at the exit of the drying chamber Dry thermometer temperatures and high humidity thermometer temperatures improved. With this realization according to the present invention, taking into account such parameters as stress on the device as well as time and energy consumption, an optimal selection of the above factors must be made.

The present invention will be further described with reference to the following test data used for the purpose the explanation of the improved filling values achieved with higher dry thermometer temperatures are.

As can be seen in Figure 1, a single Minicon drying chamber is used to conduct the tests in accordance with the high humidity drying method of the present invention. Like processes data presented in Table 1 show dry bulb temperatures of 316 ⁰ C (600 ⁰ F), 371 ° C (700 ⁰ F), 427 ° C (800 ⁰ F) and 482 ° C (900 ⁰ F) were applied to dry a mixture of leaf and stem tobacco with a humidity of approximately 43% at the dryer entrance. With this high input humidity, all four process operations were carried out with a low output of the dryer in order to achieve humidity levels of the tobacco close to 14% at the dryer output. The average production output was 77.4 absolutely dry (BD) N / h. (17.4 lbs / hr). This resulted in an average gas-to-solids ratio (G / S) of

118.8 N wet gas / N absolutely dry tobacco (BDT) (26.7 lbs wet gas / lbs. Absolutely dry tobacco). In detail the process data of Table 1 are as follows.

Tabel Temperature of 1 1 2 3 4th Dry thermometer C
(° F) 316
(600) 371
(700) 427
(800) 482
(900) Moisture thermometer ⁰ C
( ⁰ F) 100
(212) 100
(212) 100
(212) 100
(212) Production output in
absolutely dry N / h
(lbs / hr) 75.6
(17.0) 60.1
(13.5) 85.9
(19.3) 88.6
(19.9) Moisture content based on
the weight before soaking (%) 21.2 21.2 21.2. 21.2 at the dryer inlet (%) 42.8 42.4 42.8 42.9

Tobacco expansion was as in the drying chamber 12 and through the process including humidifying and The improvement in fill value achieved during drying was measured. Accordingly, fill values for tobacco samples were presented the soaking, at the dryer inlet and at the dryer outlet. Although more than one method of determining the Fill value was applied to analyze each sample, the results of these methods being essentially identical and support each other, is the method of filling value determination according to Borgwaldt (BWFV) shown here. It is believed that this method

3Q the most accurate for determining the fill value of a finished Cigarette product. As is well known, the Borgwaldt test is carried out on tobacco material in such a way that that tobacco sample material of a certain weight in a cylinder with a 3 kg (free fall) load for the duration of 30 seconds is squeezed. The sample weight and the height of the compressed column of tobacco are used to calculate the filling capacity of the sample in cm ^ / g. The results are balanced

approximately 14% moisture content and shown in Table 2 as follows

Table 2
5

Borgwaldt fill value (BWFV) and fill value improvement (FVI)

Dry thermometer temperature

316 ⁰ C 371 ° C 427 ° C 482 ° C (600 ⁰ F) (700 ⁰ F) (800 ⁰ F) (900 ⁰ F)

BWFV before soaking (cm ³ / g) 4.26 4.26 4.26 4.26

4.80 4.76 4th .83 4.74 4.91 5.30 5 .78 6.14 2.30 11.30 19th , 70 29.50 15.20 24.40 35 .70 44.10

BWFV at the dryer entrance after soaking (cnr / g)

BWFV at the dryer outlet (cm ~ 7g)
FVI from drying (%)
FVI through the process (%)

Based on these results, the fill value is 20 improvements (FVI) represented by the process and by drying in Figures 2 and 3, respectively. The data and the graphs clearly reveal that an increase in dryer temperature is a linear increase the filling value improvement (FVI) results. 25th

Tables 3 and 4 below show that the fill value improvement (FVI), represented as the tangential calculations of the slope of the straight lines in the graphs Representations of Figures 2 and 3 are similar. This means that dryer temperature is as important as that in the entire process (Figure 2 and Table 4) the drying stage alone (Figure 3 and Table 3). Tables 3 and 4 are detailed as follows:

Table 3

FVI by drying

m (slope) b (intersection point R (Correder Y-axis) lation)

BWFV at 14% humidity 0.090 -51.8 0.999

Table 4

FVI through the procedure

ra (slope) b (intersection IT (correditor Y-axis) lation)

BWFV at 14% humidity 0.089 -43.7 0.998 20

The calculation of the average value of these filling value improvements through the drying and through the process allows the establishment of a further table 5 as a basis for the establishment of an empirical linear equation in order to calculate the filling value improvement (FVI) starting from a given high temperature. The temperature is limited only by the desired percentage of moisture to be dried tobacco product, with a maximum wet bulb temperature of 100 ⁰ C (212 ⁰ F), by the residence time in the drying chamber, and by the temperature capacity of the apparatus used for the drying process. In detail, Table 5 is as follows:

Table 5

FVI average

m (slope) b (intersection IT (Cor

the y-axis) lation)

BWFV at 14% humidity 0.094 -43.7 0.998

Proceeding from this, one arrives at the general linear one Equation y = mT + b, where y equals the fill value improvement and T equals the dry thermometer temperature of the drying gas. On the basis of the average fill value improvement (FVI) according to Table 5, The general linear equation can be expressed empirically as follows: FVI = 0.04T - 47.8.

Accordingly, one can, for example, for a temperature of 593 ° C (1100 ⁰ F) - all other conditions as shown in Tables 2 and 3 - a FVI of 55.6 (that is 0.094 X 1100 to 47.8) expected. It goes without saying that the

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Correlation R was obtained by a linear regression equation known in statistics to reflect the percent accuracy of the data in Tables 3 and 4 and the resulting Table 5 which resulted in the aforementioned empirical linear equation for determining the FVI for a given temperature , are shown.

From the foregoing it can be seen that the present invention is a new combination from steps for the treatment of tobacco to the optimization of the fill value for smoking purposes to the physical ones Limits of the process device and the tobacco to be dried and up to the desired moisture content such a product is created.

Claims (10)

BROWN & WILLIAMSON TOBACCO CORPORATION 1500 Brown & Williamson Tower Louisville Galleria Louisville, Kentucky U0202 USA DR H MEYER-PLATH. oipi. ing DR M. BOTT-BODENHAUSEN. ' DR U KINKELDEY DiPL Biou BOOO MÜNCHEN 22 MAXIM1UANSTRAS5E 5B P 19 165-006 / Ms Improved process for drying tobacco Patent pending 1. A method for reducing the moisture content of expanded tobacco, characterized by drying the expanded tobacco with hot gas at a temperature within a range of about 66 ⁰ C (150 ⁰ F) to 10O ⁰ C (212 ⁰ F) as measured by the wet thermometer , and a range of about 343 ° C (650 ⁰ F) to about 510 ⁰ C (950 ⁰ F), as measured on the dry thermometer, with a dwell time sufficient to produce a tobacco product with a moisture content of about 3% to about 16 % based on the weight at the dryer outlet. 2. A method for reducing the moisture content of expanded tobacco, characterized by drying the expanded tobacco with hot gas at a temperature within the physical 34A1649 Limits of the process apparatus, the temperature being calculated by adding to the desired percentage Tobacco Product Fill Improvement the absolute term of approximately 47.8 of an empirically determined linear The equation is added and the result by the linear term of approximately 0.094 of an empirically determined linear equation is divided while the absolute humidity of the hot gas is at a level above that is maintained at a sufficient wet bulb temperature to prevent charring of the tobacco product and that is within a range sufficient to qualify as a tobacco product with a moisture content of about 3% to about 16% based on the weight at the dryer outlet to obtain. 3- A method according to claim 1 or 2, characterized geke η nzeichnet that the wet bulb temperature to about 100 ⁰ C (212 ° F) is maintained. 4. The method according to at least one of claims 1 to 3, characterized in that the hot gas is a mixture of air and steam. 5. The method according to at least one of claims 1-3, characterized in that the hot Gases consist of heated air. 6. The method according to at least one of claims 1-5, characterized in that the dry thermometer Te
is held. thermometer temperature to approximately 510 ⁰ C (950 ⁰ F) 7- The method according to at least one of claims 1-6, characterized in that the dry thermometer temperature to approximately 510 ° C (950 ⁰ F) and the wet thermometer temperature to approximately 100 ⁰ C (212 ° F) being held 8. The method according to at least one of claims 1-7, characterized in that the moisture content of the tobacco product at the dryer exit is approximately 14% by weight. 9. The method according to at least one of claims 1-8, characterized in that the dry thermometer temperature are maintained at approximately 510 ⁰ C (950 ⁰ F) and the wet thermometer temperature at approximately 100 ⁰ C (212 ° F), and that the moisture content of the tobacco product at the dryer exit is approximately 14% by weight. 10. The method according to at least one of claims 1-9, characterized in that the residence time for drying is in the range of 1 to 4 seconds.