[0001] This invention relates to processes for reordering, i.e., increasing the moisture
content, and drying tobacco or other hygroscopic organic materials, such as pharmaceutical
and agricultural products, including but not limited to fruits, vegetables, cereals,
coffee, and tea. More particularly, this invention relates to the use of controlled
humidity air to moisten or dry these materials.
[0002] The art has long recognized the desirability of controlling the moisture content
of various organic materials, including tobacco. For example, the moisture content
of tobacco that has been processed into a useful product has been altered numerous
times. Each processing step, e.g., stem removal, cutting, blending components, adding
flavors, expansion and fabricating into cigarettes, requires certain optimum moisture
levels, which must be controlled carefully, to ensure top quality tobacco and other
hygroscopic organic material products. Moreover, the manner in which the moisture
content of the tobacco is altered can have a lasting effect on the physical, chemical
and subjective characteristics of the final product. Accordingly, the methods used
for bringing about changes in the moisture content of tobacco or other organic materials
are important.
[0003] Reordering of expanded tobacco is a particularly demanding process. Typically, tobacco
obtained from the expansion process will have a moisture content below 6%, and often
less than 3%. At such low moisture contents the tobacco is very susceptible to breakage.
Additionally, the expanded tobacco structure is subject to collapse upon reordering,
i.e., a full or partial return of the tobacco to its unexpanded state. This collapse
results in a loss of filling power, thus decreasing the benefit derived from the expansion
process.
[0004] Various means for reordering expanded tobacco have been used. The most common method
is to subject the tobacco to a water spray, typically while tumbling the tobacco in
a rotating cylinder. Another method is to use saturated steam as the reordering medium.
Yet another method is to blow high humidity air through a moving bed of tobacco on
a conveyor, as shown in U.S. Patent No. 4,178,946.
[0005] None of the above methods has been found to be completely satisfactory for use on
expanded tobacco. Tumbling tobacco in a spray cylinder results in breakage of the
fragile expanded tobacco. Direct contact with liquid water tends to cause collapse
of the expanded tobacco structure. Steam reordering also results in expanded tobacco
structure collapse. While this may be partially attributed to the high temperatures
in a steam environment, exposing expanded tobacco to any gaseous environment in which
water condensation occurs, such as a steam or highly humidified air environment, results
in collapse.
[0006] One method, which has been employed to avoid these difficulties, is to place dry,
expanded tobacco in a chamber containing air at a desired humidity level and allow
the tobacco to equilibrate in the chamber over a period of from 24 hours to 48 hours.
Air velocity through the chamber is kept very low, typically not more than about 25
feet per minute. This procedure results in little or no collapse of the expanded tobacco
structure. However, the long times required, 24 hours to 48 hours, have limited its
application to laboratory purposes.
[0007] Attempts have been made to reduce the residence time required of such equilibration
processes by increasing air velocity. Such approaches have been unsuccessful due to
an inability to duplicate the maintenance of filling power observed in slow laboratory
equilibration, the size of conveyors required to carry the tobacco in order to accommodate
the long residence times required, the nonuniformity of the moisture content of the
tobacco product exiting such conveyors, and the incidence of fires in such units as
described in U.S. Patent No. 4,202,357.
[0008] The use of drying as a means for controlling moisture content during the processing
of tobacco is of equal importance as that of reordering. When tobacco is dried, both
physical and chemical changes can occur that affect the physical and subjective quality
of the product. Therefore, the method of drying tobacco is exceedingly important.
[0009] There are two types of drying equipment generally used by the tobacco industry: rotary
driers and belt or apron driers. Pneumatic-type driers are also used occasionally.
The particular dryer used is chosen for the drying operation required. Belt or apron
driers, for example, are normally used for strip tobacco, whereas rotary driers are
used for cut tobacco. Both rotary and belt driers are used for drying stems.
[0010] In a belt dryer, tobacco is spread on a perforated belt and air is directed either
upward or downward through the belt and tobacco bed. Nonuniform drying of the tobacco
often occurs due to channels being blown in the bed allowing the drying air to locally
bypass the tobacco.
[0011] Most rotary driers used in the tobacco industry are lined with steam coils and may
function as either indirect or direct heat driers depending on whether the heat is
applied outside or inside the drier shell containing the tobacco. Moreover, they may
be operated either co-currently where the tobacco and air flow in the same direction
or countercurrently where the tobacco and air flow in opposite directions. Rotary
drying must be controlled carefully to avoid overdrying, which causes both chemical
changes and unnecessary breakage by the rotary motion. In addition, if drying occurs
too quickly, an impervious layer may be formed on the outer surface of the tobacco
making it difficult for moisture on the inside of the tobacco to diffuse to the surface.
The formation of such a layer slows the drying rate and results in nonuniformity in
drying.
[0012] Use of a rotary or belt drier to dry tobacco can result in a thermal treatment that
may result in chemical and physical changes to the tobacco. While not always undesirable,
these changes are driven by the objective of removing water from the tobacco. In typical
tobacco applications, the need to dry the tobacco in a limited amount of time dictates
a thermal treatment result from the drying step, preventing optimization of thermal
treatment apart from the process constraints imposed by drying.
[0013] The present invention is defined by the independent claims, to which reference should
be made.
[0014] Embodiments of the invention have the advantage that tobacco or other suitable hygroscopic
and agricultural products, including but not limited to fruits, vegetables, cereals,
coffee and tea may be recordered or dried with little or no breakage, even of fragile
tobacco exiting the expansion process. It further has the advantage of reordering
expanded tobacco with little or no loss of expanded tobacco structure and enables
drying of tobacco or other suitable hygroscopic organic material at approximately
atmospheric pressure, for example, without the use of vacuum and at a selected temperature
wherein the thermal treatment imparted can be controlled during the process to an
extent unattainable in conventional tobacco drying processes.
[0015] In a preferred process embodying the invention, changes in the moisture content of
tobacco or other suitable organic materials are affected by contacting the tobacco
with air which has a relative humidity carefully controlled above or below the equilibrium
relative humidity of the organic material with which it is in contact. The relative
humidity of the air is continuously increased or decreased, as appropriate, during
processing to maintain a controlled differential between the relative humidity of
the air and the equilibrium relative humidity of the organic material with which it
is in contact. Careful, continuous control of relative humidity allows control of
the rate of moisture mass transfer between the organic material and its environment
so that structural changes to the tobacco are minimized. Utilization of relative humidity
as the primary driving force for moisture mass transfer allows independent control
of thermal treatment. This process can be carried out in either a batch or continuous
fashion. Furthermore, the process can be carried out without the use of rotating cylinders
and the consequent breakage that occurs with their use.
[0016] Examples of processes embodying the invention and of preferred embodiments thereof
will now be described with reference to the accompanying drawings, in which:
Figure 1 is a plot of air relative humidity (RH) percent versus tobacco moisture content
or OV;
Figure 2 is a schematic diagram of a laboratory apparatus for reordering hygroscopic
organic material according to this invention by ramping air RH over time;
Figure 3 is a cut-away view of an exemplary apparatus for carrying out this invention
on a continuous basis;
Figure 3a is a cross-sectional view of a portion of the spiral conveyor stack shown
in Figure 3, which shows the path of the air flow relative to the path of the hygroscopic
organic material;
Figure 4 is a schematic diagram of an alternate apparatus suitable for carrying out
this ivnention on a continuous basis;
Figure 5 is a block diagram illustrating the application of the present invention
to a reordering process; and
Figure 6 represents a typical RH profile of the air adjacent to the tobacco over time,
obtained during reordering in the apparatus of Figure 3.
[0017] The present invention relates to processes for adjusting the moisture content of
tobacco or other suitable hygroscopic organic material, such as pharmaceutical and
agricultural products, including but not limited to fruits, vegetables, cereals, coffee,
and tea while minimizing breakage, changes to the physical structure, or thermally
driven changes to the chemical composition of the tobacco to be treated. More particularly,
the present invention relates to the use of controlled humidity air for the purpose
of either reordering or drying tobacco or other suitable hygroscopic organic material.
The moisture content of tobacco or other suitable hygroscopic organic material is
either increased or decreased by gradually and continuously increasing or decreasing,
as appropriate, the relative humidity of the air contacting the tobaccor or other
suitable hygroscopic organic material. In this manner moisture transfer is controlled,
allowing other process variables such as temperature, air velocity, and air pressure
to be optimized separately.
[0018] Two commonly used methods for characterizing the physical structure of tobacco are
cylinder volume. (CV) and specific volume (SV). These measurements are particularly
valuable in assessing the benefits of this process in reordering tobacco.
Cylinder Volume (CV)
[0019] Tobacco filler weighing 20 grams, if unexpanded, or 10 grams, if expanded, is placed
in a 6-cm diameter Densimeter cylinder, Model No. DD-60, designed by the Heinr. Borgwaldt
Company, Heinr. Borgwaldt GmbH, Schnackenburgallee No. 15, Postfack 54 07 02, 2000
Hamburg 54 West Germany. A 2-kg piston, 5.6 cm in diameter, is placed on the tobacco
in the cylinder for 30 seconds. The resulting volume of the compressed tobacco is
read and divided by the tobacco sample weight to yield the cylinder volume as cc/gram.
The test determines the apparent volume of a given weight of tobacco filler. The resulting
volume of filler is reported as cylinder volume. This test is carried out at standard
environmental conditions of 75°F and 60% RH; conventionally, unless otherwise stated,
the sample is preconditioned in this environment for 24-48 hours.
Specific Volume (SV)
[0020] The term "specific volume" is a unit for measuring the volume occupied by solid objects,
e.g., tobacco, using Archimedes' principle of fluid displacement. The specific volume
of an object is determined by taking the inverse of its true density. Specific volume
is expressed in "cc/grams". Both mercury porosity and helium pycnometry are suitable
methods for making these measurements, and the results have been found to correlate
well. When helium pycnometry is used, a weighed sample of tobacco, either "as is",
dried at 100°C for 3 hours, or equilibrated, is placed in a cell in a Quantachrome
Penta-Pycnometer Model 2042-1 (manufactured by Quantachrome Corporation, 5 Aerial
Way, Syosset, New York). The cell is then purged and pressured with helium. The volume
of helium displaced by the tobacco is compared with volume of helium required to fill
an empty sample cell. The tobacco volume is determined based on the fundamental principles
of the ideal gas law. As used throughout this application, unless stated to the contrary,
specific volume was determined using the same tobacco sample used to determine OV,
i.e., tobacco dried after exposure for 3 hours in a circulating air oven controlled
at 100°C.
[0021] As used herein, moisture content may be considered equivalent to oven-volatiles content
(OV) since not more than about 0.9% of tobacco weight is volatiles other than water.
Oven-volatiles determination is a simple measurement of tobacco weight loss after
exposure for 3 hours in a circulating air oven controlled at 100°C. The weight loss
as percentage of initial weight is oven-volatiles content.
[0022] "Sieve test" refers to a method of measuring the shred-length distribution of a sample
of cut filler. This test is frequently used as an indicator of degradation of shred
length during processing. Tobacco filler weighing 150 ± 20 grams, if unexpanded, or
100 ± 10 grams, if expanded, is placed in a shaker apparatus. The shaker apparatus
utilizes a series of 12-inch diameter, round screen trays (manufactured by W.S. Tyler,
Inc., a subsidiary of Combustion Engineering Inc. Screening Division, Mentor, Ohio
44060) that meet ASTM (American Society of Testing Materials) standards. Normal screen
sizes for sieve trays are 6 mesh, 12 mesh, 20 mesh, and 35 mesh. The apparatus has
a shaking distance (stroke) of about 1-1/2 inches, and a shaking speed of 350 ± 5
rpm. The shaker agitates the tobacco for a period of 5 minutes in order to separate
the sample into different particle size ranges. Each of the particle size ranges is
weighed, thus yielding a particle size distribution of the sample.
[0023] Laboratory experiments have shown that attempts to reorder tobacco rapidly by exposing
the tobacco to high humidity air results in CV losses. It has also been shown that
CV losses occur when either condensation or overwetting occur within a bed of expanded
tobacco. Condensation occurs when humid air contacts tobacco which is at a temperature
below the dew point of the humid air. Overwetting can occur when moisture variations
are created within a tobacco bed due to non-uniform exposure to humid air. Therefore,
a successful humid-air reordering system must operate at a relatively slow rate with
good control of the air relative humidity, air temperature, air flow and pressure
through the bed of tobacco. This is best accomplished by gradually increasing the
moisture content of the humid air passing through the tobacco in such a manner that
the tobacco is exposed to a stream of air which is nearly at equilibrium with the
tobacco.
[0024] Referring to FIG. 1, line ABC is an isotherm for 75°F for a typical expanded bright
tobacco. This isotherm relates the tobacco's OV to the RH of the air surrounding it
at equilibrium for a given temperature. Thus point B indicates that at 75°F and 60%
RH, this sample of expanded tobacco will have an OV of about 11.7% upon equilibration.
Line DEF of FIG. 1 represents a typical RH profile for tobacco which is reordered,
according to this invention. Line GEF of FIG. 1 represents an alternative RH profile
which also has been found satisfactory. Line HF of FIG. 1 represents a path typical
of the prior art such as laboratory reordering in an equilibrium chamber at very low
air velocities. Line IJ of FIG. 1 represents the application of this invention to
the drying of the tobacco.
[0025] FIG. 1 shows that reordering tobacco from an OV of about 6.5%, where it would be
in equilibrium with air having about 30% RH, to an OV of about 11.7%, where it would
be in equilibrium with air having about 60% RH, could be accomplished by exposing
it to air which is increased in moisture from about 40% RH in small increments over
a period of time until it reaches about 60% RH, rather than being exposed to 60% RH
air directly. When carried out under these slowly changing conditions, mass transfer
between the air stream and the tobacco is relatively slow because the driving force
is small, and the expanded tobacco structure is maintained. Reordering of expanded
tobacco with no loss in CV may also be achieved by exposing the tobacco to air which
is increased in moisture content from about 40% RH in small increments over a period
of time of about 40 to about 60 minutes until it reaches an RH of about 62%. This
reduces the overall time required to complete the reordering process without significantly
changing the expanded tobacco structure. Thus, lines DEF and GEF of FIG. 1 each represent
effective embodiments of the present invention when reordering tobacco.
[0026] Referring to FIG. 1, near-equilibrium conditions between the air stream and the tobacco
are illustrated by line segment EF and line ABC. It will be appreciated that at tobacco
OV's below about 7% the difference between the relative humidity of the air in equilibrium
with the tobacco and the relative humidity of the humid-air stream used for reordering
can be quite large without adversely affecting the filling power of the tobacco. It
will also be appreciated that at tobacco OV's from about 7.5% to about 11.5% the relative
humidity of the humid air stream used for reordering can be from about 2% to about
8% above the relative humidity of the air in equilibrium with the tobacco, with the
greater deviation from equilibrium corresponding to the lower tobacco OV, without
adversely affecting the filling power of the tobacco.
[0027] When the present invention was used to dry tobacco, no measured loss in tobacco CV
was observed. This was found to be the case even when the relative humidity of the
drying air stream was significantly below the relative humidity of the air in equilibrium
with the tobacco, i.e., the relative humidity of the drying air stream was below the
equilibrium conditions of the tobacco. Therefore, it will be appreciated that line
IJ of FIG. 1 illustrates only one of many possible paths which may be used when drying
tobacco according to the present invention.
[0028] The present invention may be carried out as either a batch or a continuous process.
When carried out as a batch reordering process, the relative humidity of the air stream
contacting the tobacco is increased over time to provide a continuous increase in
moisture content of the tobacco. This may be accomplished in an environmental chamber
such as the one illustrated in FIG. 2. The tobacco to be reordered is placed at a
bed depth of about 2 inches, in trays having screen mesh bottoms, inside an environmental
chamber so that a stream of controlled humidity air may pass through the tobacco in
a downward direction. Chambers ranging in size from about 20 cubic feet to about 80
cubic feet (manufactured by Parameter Generation and Control, Inc., 1104 Old US 70,
West, Black Mountain, N.C. 28711) were used in a number of studies. The environmental
chambers were equipped with microprocessors which permitted controlled ramping of
humid-air conditions within the chamber. Tests were conducted in which dry, expanded
tobacco was reordered from initial OV levels of about 2% to final OV levels of about
11.5% by incrementally ramping the RH from initial levels as low as about 30% RH and
as high as about 52% RH over periods ranging from about 30 minutes to about 90 minutes
to final RH levels between about 59% and about 65%. Air velocities in the range of
about 50 feet/minute to about 200 feet/minute were used. RH and temperature measurements
were monitored with a Thunder model 4A-1 instrument (manufactured by Thunder Scientific
Corp., 623 Wyoming, S.E., Albuquerque, New Mexico 87123). Air velocities were measured
with an Alnor Thermo Anemometer model 8525 (manufactured by Alnor Instrument Co.,
7555 N. Linder Ave, Skokie, Illinois 60066). Tests in which relative humidities were
ramped from starting values as high as about 52% to final RH values as high as about
62% in time as short as about 40 minutes, resulted in a reordered tobacco with full
CV retention when compared to similar tobacco reordered in an environmentally controlled
room with air maintained at 60% RH and 75°F passing through the tobacco at low velocity
for 24 hours to 48 hours. Ramping in this manner was successful with humid-air velocities
as high as about 200 feet/minute and temperatures from about 75°F to about 90°F. Expanded
tobacco reordered in this manner showed minimal, if any, loss of CV compared to expanded
tobacco reordered in an environmentally controlled room.
[0029] The present invention may be carried out as a continuous process most effectively
in a Frigoscandia self-stacking spiral conveying machine, such as the one shown in
FIG. 3. This apparatus is a specially modified Model GCP 42 spiral freezer supplied
by Frigoscandia Food Process Systems AB of Helsingborg, Sweden. Dry tobacco to be
reordered enters the unit 10 on a conveyor 13, is conveyed through the unit 10 in
a spiral geometry from the bottom to the top of the spiral stack 14 as shown, and
exits at the tobacco exit 11 after reordering. Humidified air is blown down through
the tobacco from the humid air inlet 15 to the bottom of the spiral stack 14 where
it exits through the humid air exit 16, essentially flowing countercurrent to the
direction of tobacco flow, i.e., the majority of the humid-air flow is from the top
of the stack downward through the tiers of the tobacco bed, while the tobacco moves
upward following the spiral path of the conveyor. A small portion of the humid air
follows the spiral path of the conveyor stack from top to bottom in a true countercurrent
path. These types of air flows are shown in FIG. 3a. This arrangement has been found
to effectively duplicate the ramping of RH obtained in the apparatus of FIG. 2.
[0030] Referring to FIG. 3a, which is a cross-sectional view of a portion of the spiral
conveyor stack 14 shown in FIG. 3, the path of the air flow 20 and 22 relative to
the path of the tobacco bed 21 is illustrated. As shown in FIG. 3a, the air flow 20
and 22 is from the top of the stack downward. The tobacco flow is from the bottom
to the top of the unit and is illustrated as moving from the right to the left-hand
side of FIG. 3a as it progresses up the spiral conveyor stack 14. The major portion
of the air flow 20, which is essentially countercurrent to the path of the tobacco,
is directed through the tier of the tobacco bed 21 and contacts the tobacco bed on
the level immediately below, while a small portion of the air flow 22 passes over
the tobacco bed 21 in a direction countercurrent to the path of the tobacco bed 21.
This portion of the air flow 22 may later pass through the tobacco bed 21.
[0031] Key to the successful implementation of this invention, in the case of reordering,
is providing a means of steadily increasing the relative humidity of the air in contact
with the tobacco as the tobacco OV increases, The Frigoscandia self-stacking spiral
conveyor, by virtue of its self-stacking design, channels the majority of air flow
downward through the multiple tiers of conveyor (the conveyor stack), which are carrying
tobacco. By feeding tobacco into the bottom of the conveyor stack and humidified air
into the top of the stack, the overall flow of air and tobacco is essentially countercurrent.
This essentially countercurrent flow provides a natural continuous RH gradient in
the air contacting the tobacco because the air is progressively dehydrated as it moves
downward through the tiers of tobacco undergoing the reordering process. By judicious
selection of conveyor belt speed, air and tobacco flow rates, and control of entering
air temperature and RH, conditions like those used in batch laboratory ramped reordering
experiments can be approximated on a continuous basis. For reordering approximately
150 lb/hr of 3% OV expanded tobacco, belt speeds which provide from about 40 minutes
to about 80 minutes residence time and air conditions of from about 75°F to about
95°F with entrance relative humidities of from about 61% to about 64% at air flows
of from about 1000 cubic feet per minute (CFM) to about 2500 CFM have been found to
provide full reordering without significant CV loss or measurable breakage of the
tobacco using the modified Frigoscandia GCP 42 spiral unit.
[0032] Devices for recording relative humidity over time such as Model 29-03 RH/Temperature
recorder (manufactured by Rustrak Instruments Co. of E. Greenwich, RI), have been
run through the Frigoscandia unit while reordering tobacco. These devices have shown
a steady increase in air relative humidity as the device is conveyed up the spiral
stack, with initial RH recordings of from about 35% to about 45% at the bottom of
the stack, where tobacco is driest, to about 62% at the top of the stack, where the
tobacco is most fully reordered.
[0033] FIG. 6 is a typical curve of RH versus time obtained with the Rustrak unit. The percent
RH of the air adjacent to the tobacco bed versus time is shown in FIG. 6. Tobacco
with an initial OV of about 3% entered the spiral reordering unit and was contacted
with air having an RH of about 43% (Point A of FIG. 6). FIG. 6 shows that as the tobacco
progressed through the spiral reordering unit, the RH of the air adjacent to the tobacco
increased from about 43% to about 62% at the exit of the unit (Point B of FIG. 6).
The tobacco had an OV of about 11% upon exiting the spiral reordering unit. The RH
of the air entering the spiral reordering unit was controlled to yield reordered tobacco
with no significant loss of CV.
[0034] Other means of providing ramped RH air, such as the unit shown in FIG. 4, may also
be used to carry out this invention on a continuous basis. Referring to FIG. 4, tobacco
enters the unit at the tobacco inlet 40 on conveyor 43, and exits at the tobacco exit
41. Air with steadily increasing relative humidity is blown, either up flow or down
flow, through the tobacco bed 42 in a multiplicity of zones 44 to reproduce the effect
of ramping in the apparatus of FIG. 2. This ramping effect could be accomplished by
moving air from a single source in a serpentine fashion from the right to left in
FIG. 4, providing essentially countercurrent air flow to the direction of tobacco
movement. Thus, air exiting a given zone would become the inlet air to the adjacent
one on its left.
[0035] To carry out the process of the present invention, one may treat whole cured tobacco
leaf, tobacco in cut or chopped form, either expanded or non-expanded tobacco or selected
parts of tobacco such as stems or reconstituted tobacco. The process may be applied
to any or all of the above with or without flavorings added. For the specific case
of drying tobacco, it has been found that non-expanded cut filler can be dried continuously,
at essentially ambient temperature, by essentially countercurrent flow through the
modified Frigoscandia self-stacking spiral conveyor from a tobacco moisture content
of about 21% OV to about 15% OV in about one hour. In this case, air entered the top
of the unit at about 85°F and about 58% RH and exited at about 77°F and about 68%
RH. Drying was accomplished with little or no thermal treatment of the tobacco.
[0036] Alternatively, the process of the present invention may be used to dry tobacco having
a temperature significantly above ambient temperature, e.g., tobacco at about 200°F
to about 250°F. When tobacco in this temperature range is dried, the RH and temperature
of the drying air is adjusted to provide appropriate conditions for carrying out the
process of the present invention.
[0037] Analogous to reordering tobacco, it was found that drying was best accomplished in
a minimum amount of time by setting the final air moisture content lower than that
which would be required to bring the tobacco to its desired final air moisture level,
thereby increasing the air-tobacco moisture gradient, and accordingly, the driving
force to bring about the drying. Unlike the reordering process, the final moisture
content of the air stream can be maintained at a level much less than that which would
be in equilibrium with the tobacco at the desired OV level after drying.
Experiment No. 1
[0038] To demonstrate the advantage of reordering dry, expanded tobacco by metering water
to it slowly as compared to spray cylinder reordering, a 20-gram sample of tobacco
filler was placed in a sealed desiccator. This sample had been impregnated with liquid
carbon dioxide and expanded in an expansion tower at 550°F. The OV of this expanded
tobacco filler was 3.4%. It was calculated that approximately 1.89 grams of water
would be required to increase this sample's OV content to 11.5%. This amount of water
was put into a small glass bottle with a rubber stopper having a 1/8-inch inside diameter
glass tube extending through it. The bottle was also sealed in the desiccator. After
nine days, all of the water had been adsorbed by the tobacco. The tobacco was then
analyzed and found to have an as-is OV of about 11.5%. As used herein, as-is refers
to tobacco prior to being equilibrated in an environmental chamber with air maintained
at 60% RH and 75°F passing through it at a low velocity for a period of from 24 hours
to 48 hours. This process of equilibration is generally used as a means for bringing
tobacco to a standard condition prior to CV, SV and sieve measurements being made.
After this standard equilibration, the desiccator-reordered tobacco had a CV of about
9.5 cc/gram and an SV of about 2.9 cc/gram at an OV of about 11.6%. By comparison,
when a second sample of the same tobacco was placed directly inside the equilibration
chamber and reordered by equilibration under standard conditions, the equilibrated
OV was about 11.3% and the CV and SV values were about 9.4 cc/gram and about 2.7 cc/gram,
respectively. A third sample of the expanded tobacco filler was reordered in a spray
cylinder to an as-is OV of about 11.5%. After equilibration, this sample had a CV
of about 8.5 cc/gram and an SV of about 1.9 cc/gram at an equilibrium OV of about
11.6%.
[0039] As seen from the data in TABLE 1, the tobacco sample that was reordered in the desiccator
by a slow metering of water showed a significant improvement in equilibrium CV and
SV compared to the sample that had been spray reordered. This sample also showed a
slight improvement in CV and SV when compared with the sample equilibrated directly
in the equilibration chamber.
TABLE 1
Sample |
As Is |
Equilibrated |
|
OV(%) |
SV(cc/gm) |
OV(%) |
CV(cc/gm) |
SV(cc/gm) |
Tower Exit |
3.4 |
3.0 |
11.3 |
9.4 |
2.7 |
Cylinder Reordered |
11.5 |
1.8 |
11.6 |
8.5 |
1.9 |
Desiccator |
11.5 |
2.7 |
11.6 |
9.5 |
2.9 |
[0040] A second set of experiments was carried out using an environmental chamber to reorder
expanded tobacco filler. For this purpose, a Parameter Generation and Control (PGC)
chamber was used. This chamber was equipped with a Micro-pro 2000 microprocessor supplied
by Parameter Generation and Control Inc., which permitted controlled ramping of the
conditions inside the chamber.
Experiment No. 2
[0041] Approximately 3 pounds of bright tobacco impregnated with liquid carbon dioxide and
expanded under conditions similar to those described in Experiment No. 1, was placed
at a bed depth of about 2-inches inside a tray. The tray, which had solid sides and
a screen mesh bottom, was placed inside an environmental chamber. The sample was then
reordered over a 1-hour period using air at about 75°F with an initial RH of about
36% ramped to a final RH of about 60%. Air movement was in a downward direction through
the tobacco bed at a velocity of about 45 ft/min. This experiment was then repeated
over time intervals of 3 hours, 6 hours, and 12 hours. The results, presented in TABLE
2, indicate that for ramping periods up to about 6 hours the rate of reordering does
affect tobacco CV and SV, at these experimental conditions. The slower the rate of
reordering, the higher the CV and SV observed. Moreover, reordering according to the
present invention results in CVs at least about 1 cc/gram greater, and SVs at least
about 0.2 cc/gram greater than those observed for tobacco reordered in a spray cylinder.
However, it has been found that most of this benefit is achieved by ramping in as
little as one hour.
TABLE 2
|
As Is |
Equilibrated In An Environmental Chamber |
|
OV(%) |
SV(cc/gm) |
OV(%) |
CV(cc/gm) |
Tower Exit |
3.10 |
3.06 |
11.33 |
9.71 |
Spray Cylinder |
11.51 |
1.61 |
11.37 |
8.61 |
Ramped 1 hr. |
10.83 |
1.85 |
11.38 |
9.72 |
Ramped 3 hr. |
11.44 |
1.88 |
11.36 |
9.81 |
Ramped 6 hr. |
11.45 |
1.90 |
11.30 |
9.88 |
Ramped 12 hr. |
11.41 |
1.97 |
11.27 |
9.89 |
Experiment No. 3
[0042] A laboratory study was conducted on the affect of both reordering rate and temperature
on tobacco CV and SV. Seven sets of runs were carried out using tobacco impregnated
with carbon dioxide and expanded in an expansion tower at about 550°F. The expanded
tobacco was reordered by the following methods:
(1) By equilibrating for 24 hours in an environmental chamber at 60% RH and 75°F with
air movement through the tobacco at a rate of about 25 ft/min;
(2) By spraying with water to increase the OV to about 7.5%, then equilibrating at
60% RH and 75°F for 24 hours as in (1);
(3) By spraying with water to increase the OV to about 7.5%, then final reordering
in a spray cylinder;
(4) By spraying with water to about 7.5% OV, then using humid-air ramped from an initial
RH of about 46% to a final RH of about 60%; and
(5) By ramping with humid air from about 46% RH to about 60% RH.
[0043] Reordering with humid air was carried out inside a PGC environmental chamber equipped
with a microprocessor to control ramping over selected time intervals. The following
conditions were selected:
(1) Ramping times: 30, 60, and 90 minutes;
(2) Air temperatures: 75°F and 95°F;
(3) Air Velocities: upward through the tobacco bed at about 45 ft/min, and downward
through the tobacco bed at about 175 ft/min; and
(4) Tobacco bed thickness: 2 inches.
[0044] The tobacco used for all reordering except through the spray cylinder, was collected
at the tower exit after expansion and sealed in double plastic bags prior to reordering.
As a result, the tobacco cooled from about 200°F, the temperature of the tobacco at
the expansion tower exit, to ambient temperature before reordering. When reordering
by ramping at about 95°F, the tobacco, while still in the sealed bags, was pre-warmed
sufficiently to avoid condensation upon contact with the humid air before being exposed
to the ramped conditions. Data for these runs is presented in TABLES 3a through 3e.
TABLE 3a
Sample |
As Is |
Equilibrated |
|
OV(%) |
SV(cc/gm) |
OV(%) |
CV(cc/gm) |
X Exit Tower |
3.43 |
3.02 |
11.31 |
9.04 |
S Through Sprayers Only |
8.06 |
2.14 |
11.68 |
8.66 |
C Through Sprayers & Cylinder |
11.53 |
1.81 |
11.59 |
8.59 |
F Through Sprayers & Ramped 90 min (46% RH to 60% RH, 75°F) |
11.27 |
1.87 |
11.51 |
9.01 |
H Through Sprayers & Ramped 90 min (46% RH to 60% RH, 75°F) |
10.96 |
1.98 |
11.36 |
9.48 |
I Sample H Held 15 min at 60% RH, 75°F |
11.54 |
1.95 |
11.56 |
9.40 |
J Through Sprayers & Ramped 60 min (46% RH to 62% RH, 95°F) |
10.37 |
2.38 |
11.28 |
9.85 |
K Sample J Held 15 min at 62% RH, 95°F |
11.17 |
2.26 |
11.22 |
9.88 |
TABLE 3b
Sample |
As Is |
Equilibrated |
|
OV(%) |
SV(cc/gm) |
OV(%) |
CV(cc/gm) |
X Exit Tower |
3.01 |
2.58 |
11.34 |
9.23 |
S Through Sprayers Only |
7.51 |
2.13 |
11.39 |
8.87 |
C Through Sprayers & Cylinder |
11.86 |
1.59 |
11.64 |
8.07 |
F Through Sprayers & Ramped 60 min (46% RH to 60% RH, 75°F) |
10.55 |
1.64 |
11.45 |
8.86 |
G Sample F Held 15 min at 60% RH, 75°F |
11.56 |
1.64 |
11.42 |
8.61 |
H Through Sprayers & Ramped 30 Min (46% RH to 60% RH, 75°F) |
10.28 |
1.97 |
11.27 |
8.99 |
I Sample H Held 15 min at 60% RH, 75°F |
11.73 |
1.82 |
11.25 |
8.61 |
TABLE 3c
Sample |
As Is |
Equilibrated |
|
OV(%) |
SV(cc/gm) |
OV(%) |
CV(cc/gm) |
A Exit Tower |
1.81 |
2.78 |
11.37 |
9.23 |
B Ramped 60 min (46% RH to 60% RH, 95°F) |
10.91 |
1.86 |
11.47 |
8.86 |
C Ramped 60 min (46% RH to 60% RH, 75°F) |
10.53 |
2.02 |
11.28 |
9.20 |
D Ramped 90 min (46% RH to 60% RH, 95°F) |
10.84 |
1.99 |
11.45 |
8.90 |
E Through Sprayers |
5.39 |
2.37 |
11.25 |
8.71 |
F Through Sprayers & Put Directly at 60% RH, 95°F for 30 min |
10.80 |
1.81 |
11.27 |
8.39 |
G Through Sprayers & Ramped 60 min (46% RH to 60% RH, 95°F) |
10.66 |
1.85 |
11.23 |
8.65 |
H Through Sprayers & Ramped 90 min (46% RH to 60% RH, 95°F) |
10.76 |
1.82 |
11.24 |
8.62 |
I Through Sprayers & Ramped 60 min (46% RH to 60% RH, 75°F) |
10.65 |
1.90 |
11.23 |
8.75 |
J Through Sprayers & Ramped 90 min (46% RH to 60% RH, 75°F) |
10.57 |
1.87 |
11.38 |
8.74 |
K Through Sprayers & Put Directly at 60% RH, 75°F for 30 min |
10.73 |
1.87 |
11.22 |
8.64 |
L Through Sprayers and Cylinder |
10.98 |
1.60 |
11.39 |
8.28 |
TABLE 3d
Sample |
As Is |
Equilibrated |
|
OV(%) |
SV(cc/gm) |
OV(%) |
CV(cc/gm) |
T1 Exit Tower |
2.83 |
3.01 |
11.92 |
9.46 |
T2 Put Directly at 60% RH, 75°F, 30 min |
11.24 |
2.27 |
11.77 |
9.08 |
T3 Ramped 90 min (46% RH to 60% RH, 75°F) |
11.08 |
2.24 |
11.83 |
9.29 |
T4 Ramped 90 min (30% RH to 60% RH, 75°F) |
9.77 |
2.39 |
11.85 |
9.43 |
S1 Through Sprayers |
4.78 |
2.82 |
11.66 |
8.98 |
S2 Through Sprayers & Put Directly at 60% RH, 75°F for 30 min |
11.10 |
2.19 |
11.64 |
8.89 |
S3 Through Sprayers & Ramped 90 min (46% RH to 60% RH, 75°F) |
10.54 |
2.25 |
11.27 |
9.05 |
S4 Through Sprayers & Ramped 60 min (46% RH to 60% RH, 75°F) |
10.56 |
2.22 |
11.73 |
9.03 |
S5 Through Sprayers & Ramped 30 min (46% RH to 60% RH, 75°F) |
9.74 |
2.29 |
11.67 |
9.19 |
C Through Sprayers and Cylinder |
10.48 |
1.95 |
11.81 |
8.80 |

[0045] The data presented in TABLES 3a through 3e show that gains of from about 0.5 cc/gram
to about 1 cc/gram in CV and from about 0.3 cc/gram to about 0.4 cc/gram in SV may
be achieved by ramped reordering of cooled tobacco, i.e., tobacco at about 75°F up
to about 95°F, as compared to cylinder spray reordering of hot tobacco exiting the
expansion tower. Ramped reordering directly from the tower exit OV was found to be
preferable to first spraying the tobacco to increase its OV content to about 7% followed
by ramped reordering. No significant difference was seen in the CV or SV of tobacco
reordered by ramping using humid air with an initial RH of about 46% as compared to
tobacco reordered by ramping from an initial RH of about 30%, or in tobacco reordered
by ramping over a period of either about 60 minutes or about 90 minutes. It was also
observed that tobacco could be reordered either with the air movement directed downward
through the tobacco bed at velocities of from about 175 ft/min to about 235 ft/min
or with the air directed upward through the tobacco bed at up to about 45 ft/min with
no significant differences in CV or SV. Additionally, it was observed that ramped
reordering yielded equivalent or better CVs and SVs as compared to tobacco reordered
by placing it directly in an environmental chamber at 60% RH and 75°F after exiting
the expansion tower. Finally, it was observed that spraying with water to increase
the OV to about 7.5% followed by ramping with humid air resulted in better CVs and
SVs as compared to spraying followed by final reordering in a spray cylinder.
Experiment No. 4
[0046] Tests were conducted to determine the effect of air flow and air velocity on entrainment,
channeling, and compaction of the tobacco. These tests were carried out using two
PGC environmental chambers. In both chambers, actual air movement was approximately
500 CFM. Air movement was in an upward direction through the tobacco bed in one PGC
chamber, and in a downward direction through the tobacco bed in the other. Tobacco
samples, 2-inches in depth, were placed inside open-top trays 5" X 5 3/4" with screen
mesh bottoms and with 4-inch high solid sides. These trays were placed on shelves
inside the environmental chambers. Air was forced through the samples by covering
the non-occupied shelf area with cardboard and sealing any cracks with tape. Air velocity
was varied by changing the number of sample containers through which the air passed.
Tobacco used for these tests was impregnated with carbon dioxide and expanded at about
550°F. The tobacco had been reordered through a first stage by spraying with water
to about 8% OV immediately after expansion. Conditions inside the chambers during
the tests were controlled at about 75°F and about 60% RH. Both a vane anemometer (Airflow
Instrumentation, Model LCA 6000, Frederick, Maryland) and a hot-wire anemometer (Alnor
Instrument Company, Skokie, Illinois, Thermometer Model 8525) were used to measure
air velocities. These instruments were placed directly above or below the samples
for air movement in the upward and downward directions, respectively.
[0047] With air movement in an upward direction, some slight lifting of the tobacco was
observed immediately when the air was turned on at average velocities as low about
26 ft/min. Small air channels then formed, and the tobacco would settle. As a result
of these channels, air flow was found to be very non-uniform across the tobacco bed
(about 22 ft/min to about 45 ft/min for an average flow of about 26 ft/min). With
increasing average air flows, more channeling was apparent, and at above 45 ft/min
considerable entrainment and "blow up" of tobacco was observed, followed by significant
channeling of the bed.
[0048] With air movement in a downward direction some compaction and corresponding reduction
in air velocity through the beds was observed at all velocities studied. This is shown
in TABLE 4. At an initial velocity of about 192 ft/min, tobacco bed depth compacted
about 28%, and, as a result, the air velocity through the bed was reduced to about
141 ft/min. At initial air velocities of about 141 ft/min or less, tobacco bed compaction
was about half that observed at about 192 ft/min, and air flow through the tobacco
bed was reduced much less.
TABLE 4
Effect of Bed Compaction on Air Velocity Through Bed |
Air Velocity (ft/min) |
Bed Depth (in) |
Start |
End |
% Change |
Start |
End |
% Change |
192 |
141 |
27 |
2 |
1.45 |
28 |
161 |
144 |
11 |
2 |
1.65 |
18 |
141 |
133 |
6 |
2 |
1.70 |
15 |
104 |
98 |
6 |
2 |
1.80 |
10 |
43 |
41 |
5 |
2 |
1.90 |
5 |
[0049] Based on the above experiments it was determined that expanded tobacco can be reordered
preferably by ramping at the following conditions:
(a) Time: from about 60 minutes to about 90 minutes;
(b) RH: from an initial RH of from about 30% to about 45% to a final RH of from about
60% to about 64%;
(c) Temperature: from about 75°F to about 95°F;
(d) Air flow: upward at velocities up to about 45 ft/min or downward at velocities
up to about 235 ft/min.
Experiment No. 5
[0050] Approximately 150 lb/hr of a mixture of bright and burley tobacco, which had been
impregnated with carbon dioxide according to the process described in co-pending and
commonly assigned application Cho et al., S.N. 07/717,067, and expanded as described
in the above examples, was passed through a cooling conveyor to reduce its temperature
from about 200°F to about 85°F prior to being fed to a modified Frigoscandia Model
GCP 42 self-stacking spiral unit. Tobacco flow through the spiral unit was from the
bottom to the top. Air flow was from the top to the bottom of the unit, providing
an essentially countercurrent flow of tobacco to air. This arrangement provided ramped
reordering of the tobacco as a result of the continuous dehydration of the air by
the tobacco. Tobacco entered the process at about 3% OV and exited at about 11% OV.
Equilibrated CV of the feed material was about 10.53 cc/gm, while the equilibrated
CV of the reordered material was about 10.46 cc/gm, indicating no significant loss
of filling power of the tobacco across the reordering process, i.e., no statistically
significant loss of filing power as determined by standard analysis of variance procedure.
Additionally, there was no measurable reduction in tobacco particle size, as determined
by the sieve test, during the reordering process.
Experiment No. 6
[0051] A series of experiments was carried out using various types of tobacco expanded at
different tower temperatures in which the tobacco was reordered according to the process
of the present invention. In each run, approximately 150 lb/hr of tobacco, based on
reordered tobacco mass, was reordered in the modified Frigoscandia self-stacking spiral
unit described in Experiment No. 5. The inlet air to the reordering unit was set at
about 85°F with a relative humidity of about 62%. The air exiting the reordering unit
was typically about 90°F to about 95°F with a relative humidity of about 40% to about
45%. As shown in TABLE 5, tobacco reordered according to the process of the present
invention showed no significant loss of filling power.

Experiment No. 7
[0052] Approximately 200 lb/hr. of bright tobacco with an OV of about 21.6% was fed to the
modified Frigoscandia self-stacking unit described in Experiment No. 5 operating as
a drying unit. Tobacco flow through the spiral drying unit was from the bottom to
the top. Air flow was from the top to the bottom of the unit, providing an essentially
countercurrent flow of tobacco to air. The tobacco was successfully dried to about
12.2% OV in about 60 minutes residence time using air with an inlet temperature of
about 95°F and an inlet RH of about 35%. Air exiting the drying unit was at about
83°F and about 62% RH. The tobacco entering and exiting the drying unit was cool to
the touch, with an estimated temperature of about 75°F, indicating that substantially
no thermal treatment of the tobacco had taken place. No change in the equilibrated
tobacco CV occurred as a result of the drying process. This particular drying experiment
was designed to minimize thermal treatment. Similar drying results could be achieved
using higher temperatures to provide a controlled degree of thermal treatment.
[0053] While the invention has been particularly shown and described with reference to preferred
embodiments, it will be understood by those skilled in the art that various changes
in form and details may be made without departing from the spirit and scope of the
invention.
1. A process for increasing the moisture content of organic material which comprises
the steps of:
(a) contacting organic material with an air stream having a relative humidity near
the equilibrium conditions of the organic material, and
(b) increasing the relative humidity of the air stream contacting the organic material
to increase the moisture content of the organic material in such a manner that the
relative humidity of the air stream contacting the organic material is maintained
near the equilibrium conditions of the organic material until the desired moisture
content of the organic material is achieved.
2. A process according to claim 1, whereby the equilibrated CV of the organic material
after step (b) is not significantly less than the equilibrated CV of the organic material
prior to step (a).
3. A process for increasing the moisture content of organic material which comprises
the steps of:
(a) forming an organic material bed by depositing organic material on a conveyor,
(b) contacting the organic material with an air stream flowing in a path essentially
countercurrent to the path of the organic material bed, and
(c) causing a portion of the moisture content of the air stream to be transferred
to the organic material in such a manner that the relative humidity of the air stream
contacting the organic material is maintained near the equilibrium conditions of the
organic material, whereby the air stream is progressively dehydrated and the organic
material is progressively hydrated as the air stream flows essentially countercurrent
to the path of the organic material bed until the desired moisture content of the
organic material is achieved.
4. The process of claim 13, wherein the equilibrated CV of the organic material after
step (c) is not significantly less than the equilibrated CV of the organic material
prior to step (b).
5. A process according to any of claims 1 to 4, wherein the organic material temperature
is below about 38°C (100°F) prior to contacting it with the air stream.
6. A process according to any of claims 1 to 5, wherein prior to the step of contacting
organic material with an air stream the organic material has an initial moisture content
of from about 1.5% to about 13%.
7. A process according to claim 6, wherein prior to the step of contacting organic material
with an air stream the organic material has an initial moisture content of from about
1.5% to about 6%.
8. A process according to claim 3, wherein the desired moisture content of the organic
material after step (c) is from about 11% to about 13%.
9. A process according to any preceding claim, wherein the air stream contacting the
organic material has a relative humidity of from about 30% to about 64% at a temperature
of from about 21°C (70°F) to about 49°C (120°F).
10. A process according to any preceding claim, wherein the temperature of the air stream
is selected to provide a desired thermal treatment to the organic material, while
the relative humidity of the air stream is selected to provide reordering.
11. A process according to any preceding claim, wherein the organic material is tobacco.
12. A process according to claim 11, wherein the tobacco is expanded tobacco.
13. A process according to claim 11, wherein tobacco is selected from the group comprised
of expanded or non-expanded tobacco, whole leaf tobacco, cut or chopped tobacco, stems,
reconstituted tobacco or any combination of these.
14. A process for decreasing the moisture content of organic material which comprises
the steps of:
(a) contacting organic material stream having a relative humidity near or below the
equilibrium conditions of the organic material, and
(b) decreasing the relative humidity of the air stream contacting the organic material
as the moisture content of the organic material decreases in such a manner that the
relative humidity of the air stream contacting the organic material is maintained
near or below the equilibrium conditions of the organic material until the desired
moisture content of the organic material is achieved.
15. The process of claim 14, wherein the equilibrated CV of the organic material after
step (b) is not significantly lower than the equilibrated CV of the organic material
prior to step (a).
16. A process for decreasing the moisture content of organic material which comprises
the steps of:
(a) forming an organic material bed by depositing organic material on a conveyor,
(b) contacting the organic material with an air stream flowing in a path essentially
countercurrent to the path of the organic material bed, and
(c) causing a portion of the moisture content of the organic material to be transferred
to the air stream in such a manner that the relative humidity of the air stream contacting
the organic material is maintained near or below the equilibrium conditions of the
organic material, whereby the organic material is progressively dehydrated and the
air stream is progressively hydrated as the air stream travels in a path essentially
countercurrent to the path of the organic material bed until the desired moisture
content of the organic material is achieved.
17. The process of claim 16, wherein the equilibrated CV of the organic material after
step (c) is not significantly lower than the equilibrated CV of the organic material
prior to step (b).
18. A process according to any of claims 14 to 17, further comprising the step of preheating
the organic material temperature of from about 38°C (100°F) to about 121°C (250°F)
prior to step (a).
19. A process according to any of claims 14 to 18, wherein the organic material temperature
is below about 121°C (250°F) prior to the step of contacting it with the air stream.
20. A process according to claim 19, wherein the organic material temperature is below
about 38°C (100°F) prior to the step of contacting it with the air stream.
21. A process according to any of claims 14 to 20, wherein prior to the step of contacting
the organic material with an air stream the organic material has a moisture content
of from about 11% to about 40%.
22. The process according to any of claims 14 to 21, wherein the air stream which contacts
the organic material has a relative humidity of from about 20% to about 60% at a temperature
of from about 21°C (70°F) to about 49°C (120°F).
23. A process according to any of claims 14 to 22, wherein the temperature of the air
stream is selected to provide a desired thermal treatment.
24. A process according to any of claims 14 to 22, wherein the temperature of the air
stream is selected to provide substantially no thermal treatment.
25. A process according to any of claims 14 to 24, wherein the temperature of the air
stream is from about 24°C (75°F) to about 121°C (250°F).
26. A process according to any of claims 14 to 25, wherein the organic material is tobacco.
27. A process according to any of claim 26, wherein the tobacco is cut tobacco.
28. A process according to claim 26, wherein tobacco is selected from the group comprised
of expanded or non-expanded tobacco, whole leaf tobacco, cut or chopped tobacco, stems,
reconstituted tobacco or any combination of these.
29. A process according to any preceding claim, wherein the step of contacting organic
material with an air stream is carried out in a continuous manner using a spiral coveyor
in which the air stream flows in a path essentially counter current to the direction
of flow of organic material.
30. A process according to any preceding claim, wherein the step of contacting organic
material with an air stream is carried out in a continuous manner using a linear conveyor.
31. A process according to claim 30, wherein the linear conveyor is configured to provide
a multiplicity of zones of increasing relative humidity.
32. A process according to any preceding claim, wherein the step of contacting the organic
material with an air stream is carried out using an air stream having a velocity of
from about 0.23 m/s (45 feet/minute) to about 1.22 m/s (240 feet/minute).
33. A process according to any preceding claim, wherein the step of contacting the organic
material with an air stream is carried out by directing the air stream either downward
or upward through the organic material bed, or by directing the air stream both downward
and upward through the organic material bed.
34. A process according to any of claims 1 to 10 or 14 to 25, wherein the organic material
is a hygroscopic organic material.
35. A process according to claim 29, wherein the hygroscopic organic material is selected
from the group comprised of fruits, vegetables, cereals, coffee, pharmaceuticals,
tea, and any combination of these.
36. A process according to claim 29, wherein the spiral conveyor comprises a stack having
a plurality of tiers and the air stream essentially flows through the stack sequentially
through successive tiers.