U.S. patent number 3,753,440 [Application Number 05/232,541] was granted by the patent office on 1973-08-21 for tobacco expansion process.
This patent grant is currently assigned to R. J. Reynolds Tobacco Company. Invention is credited to James Gilbert Ashburn.
United States Patent |
3,753,440 |
Ashburn |
August 21, 1973 |
TOBACCO EXPANSION PROCESS
Abstract
The filling capacity of tobacco is increased by establishing a
body of water-moistened tobacco in a bed in a hermetically sealed
chamber. A partial vacuum is applied to the bed to remove occluded
air and the tobacco is contacted with vapors of a compound having
an atmospheric pressure boiling point between about -10 and
+80.degree. C., the temperature of the tobacco during contact being
maintained at or below the boiling point of the compound at the
prevailing pressure, whereby the tobacco is impregnated with the
compound in the liquid state by condensation. The impregnated
tobacco is then equilibrated, and a drying gas at a temperature
between about 40.degree. and 80.degree. C. is passed through the
bed to remove a portion of the moisture and the impregnating
compound as vapors. A hot gas at a temperature above about
90.degree. C. and more than about 18.degree. C. above the boiling
point of the compound is then passed through the tobacco to expand
it.
Inventors: |
Ashburn; James Gilbert
(Winston-Salem, NC) |
Assignee: |
R. J. Reynolds Tobacco Company
(Winston-Salem, NC)
|
Family
ID: |
22873552 |
Appl.
No.: |
05/232,541 |
Filed: |
March 7, 1972 |
Current U.S.
Class: |
131/296; 131/901;
131/902 |
Current CPC
Class: |
A24B
3/182 (20130101); Y10S 131/901 (20130101); Y10S
131/902 (20130101) |
Current International
Class: |
A24B
3/18 (20060101); A24B 3/00 (20060101); A24b
003/18 () |
Field of
Search: |
;131/140-144 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3144871 |
August 1964 |
De Souza et al. |
3524451 |
April 1968 |
Fredrickson |
3683937 |
August 1972 |
Fredrickson et al. |
|
Primary Examiner: Rein; Melvin D.
Claims
What is claimed is:
1. A process for expanding the filling capacity of tobacco which
comprises establishing a body of tobacco having a water moisture
content of between about 8 and 30 percent by weight (dry basis) in
a stationary bed in a hermetically sealable chamber, sealing said
chamber and applying a partial vacuum thereto to remove a portion
of the occluded, non-condensable gases therefrom, passing vapors of
a compound having an atmospheric pressure boiling point between
about -10 and +80.degree. C. into said chamber having a temperature
at or below the boiling point of said compound at the prevailing
pressure whereby the tobacco in said bed is impregnated by said
compound at least partially in the form of a condensate,
equilibrating the body of impregnated tobacco body for a period
sufficient to insure penetration of said condensate into the
individual particles of the tobacco body, passing a drying gas
through said bed at a temperature between about 40.degree. and
80.degree. C. for a time sufficient to remove as vapor a portion of
the water moisture and the impregnating compound, and thereafter
rapidly passing a hot gas having a temperature above about
90.degree. C. and at least about 18.degree. C. above the boiling
point of said compound at the prevailing pressure into contact with
said tobacco whereby to vaporize and remove substantially all of
said compound within said bed and concomitantly expand the
tobacco.
2. The process of claim 1 in which the amount of compound
impregnating the tobacco when the hot gas passed into contact
therewith is between about 1 and 40 parts by weight of compound per
100 parts by weight of tobacco (dry basis).
3. The process of claim 2 wherein said amount is between about 2
and 10 parts by weight of compound per 100 parts by weight of
tobacco (dry basis).
4. The process of claim 1 wherein said compound is a hydrocarbon or
a halogenated hydrocarbon.
5. The process of claim 4 wherein said compound is
trichloromonofluoromethane.
6. The process of claim 1 wherein said tobacco is shredded tobacco.
Description
BACKGROUND OF THE INVENTION
This invention relates to a process of treating tobacco and has for
an object the provision of a process for increasing the filling
capacity of tobacco.
Tobacco leaves when harvested contain a considerable quantity of
water and during the normal tobacco curing process this water is
removed by drying, resulting in shrinkage of the leaf structure. In
the usual process of preparing tobacco for storage and subsequent
cigar or cigarette manufacture, the tobacco regains very little, if
any, of the shrinkage resulting from the drying step so that a
significant loss in the filling capacity of the tobacco is the
result. Thus, the cured tobacco has a bulk density which is in
excess of that required for making satisfactory cigarettes or
cigars. Also, during cutting of leaf or strips for making cut
filler for cigarettes, frequently the shreds are laminated together
to form hard, dense particles which occupy far less volume than the
original shreds occupied. This is wasteful since these hard
compacted shreds are not necessary in the tobacco to produce an
article which is satisfactory for smoking.
Several procedures have been suggested in the prior art for
increasing the normal filling capacity of tobacco. Certain of these
procedures have involved puffing operations in which the tobacco is
subjected to high pressure steam, followed by sudden release of
pressure. Such processes have not usually been satisfactory since
they result in the production of excessive amounts of fines. Also,
it has been suggested that the filling capacity of tobacco may be
increased (i.e., bulk density reduced) by exposing the tobacco to
the vapors of an organic liquid to condense the liquid in the
tobacco followed by air drying at ambient temperatures and
pressures. However, such procedures have not been wholly
satisfactory because they are not effective for increasing the
filling capacity to any great extent. Other methods that have been
proposed involve contacting the tobacco with a volatile organic
liquid and then heating the liquid-impregnated tobacco to a
temperature above the boiling point of the liquid whereby to
vaporize the liquid directly in the tobacco causing expansion.
Embodiments of these last-mentioned procedures are described in
U.S. Pat. Nos. 3,524,451 and 3,524,452 issued Aug. 18, 1970, and
No. 3,575,178 issued Apr. 20, 1971.
An object of this invention is to provide a batch process for
expanding tobacco.
Another object of this invention is the provision of a tobacco
expansion process which involves the use of vapors of a tobacco
impregnating compound and which may be carried out in equipment
readily available to tobacco processors.
A further object of this invention is the provision of a process
for increasing the filling capacity of tobacco under conditions
such that the process can be readily controlled to produce the
desired product.
An additional object of this invention is the provision of a
process for expanding tobacco using vapors of an impregnating
compound thereby eliminating the requirement of handling large
quantities of liquid in commercial operations.
A further and additional object of this invention is to provide a
process for increasing the filling capacity of tobacco which
eliminates the requirement of using excessive quantities of
impregnating liquid thereby avoiding substantial energy
requirements associated with the vaporization of excess
liquids.
A still further object of this invention is the provision of a
tobacco expansion process which facilitates recovery of the
impregnating liquid through the use of relatively simple and
inexpensive equipment.
Further and additional objects will appear from the following
description, the accompanying drawing and the appended claims.
GENERAL DESCRIPTION OF THE INVENTION
In accordance with one embodiment of this invention, a process is
provided in which a body of tobacco having a moisture content of
about 8 to 30 percent by weight (dry basis) is established in a bed
in a hermetically sealable chamber. The chamber is sealed and a
vacuum applied to remove a portion of the non-condensable gas
(e.g., air) occluded within the tobacco. The tobacco is then
contacted with vapors of a compound which has an atmospheric
pressure boiling point between about -10 and +80.degree. C. under
conditions such that a substantial portion of the vapors condense
on the moist tobacco. The tobacco body is then allowed to stand
(i.e., equilibrated) for a period of time to permit penetration of
the condensate into the tobacco particles. A drying gas at a
temperature between about 40.degree. and 80.degree. C. is then
passed through the bed to remove as vapor a portion of the water
and a portion of the compound. Thereafter the tobacco is subjected
to vapor-expanding conditions by passing a gas, preferably steam,
heated to a temperature above about 90.degree. C. and at least
18.degree. C. above the boiling point of said compound at the
prevailing pressure through the impregnated tobacco whereby to
vaporize the liquid impregnant and to expand the vapor and cause
simultaneous expansion of the tobacco. The resulting tobacco has a
lower bulk density (i.e., higher filling capacity) than the
untreated tobacco charged to the process and is suitable for use in
the manufacture of smoking tobacco articles such as cigarettes,
cigars, pipe tobacco and the like.
The tobacco to be treated in accordance with the process of this
invention is preferably a cured tobacco and may be in the form of
shreds, strips, leaves, stems or sheets of reconstituted tobacco.
However, the process is easier to control and the best results are
obtained if tobacco shreds are used. This is for the reason that
usually shreds are relatively easy to handle and the final product
of the process need not be subjected to shredding as may be
necessary for cigarette manufacture. Shredding of the final product
results in compressing the product which tends to destroy the
ultimate objective of the process of this invention, namely, to
expand the tobacco and eliminate compressed particles, as may have
resulted from prior treatment including shredding. Any type of
tobacco may be used in the practice of this invention, and it is
particularly useful for the processing of burley, flue-cured and
Oriental (e.g., Turkish) tobaccos.
Burley and flue-cured tobaccos used in the manufacture of
cigarettes ordinarily have a moisture content of about 11 to 14
percent by weight. In the practice of this invention, the moisture
content of the tobacco when contacted with the vapor of the
compound is usually in excess of about 8 percent by weight, and
preferably within the range of 10 to 20 percent by weight of the
tobacco. The desired moisture content may be achieved by drying the
tobacco or by the addition of water, as may be appropriate. This
latter may be effected by any suitable procedure such as
sprinkling, spraying, wet steam treatment, or the like, as is known
to those skilled in the art. The presence of the indicated
percentage of moisture is desired since the internal structure of
the tobacco is thereby rendered sufficiently pliable or flexible to
permit the ready penetration of the impregnating compound into the
individual tobacco particles and the expansion of puffing when the
impregnating compound vaporizes and expands within the tobacco upon
subsequent treatment with the steam or other hot gas. If the
moisture content is less than about 8 percent, the impregnation
step proceeds at a very slow rate. If the moisture content is
greater than about 20 percent, the partial drying step described
below would be unnecessarily prolonged.
In accordance with this invention, the moist tobacco, which usually
contains an occluded gas such as air, is introduced into a
hermetically sealable impregnating chamber, the chamber is sealed
and a vacuum applied to remove at least a portion of the occluded
gas. Preferably the vacuum is applied to the chamber to reduce the
absolute pressure from atmospheric to less than about 1/10
atmospheric. By removing occluded air, the tobacco can be most
effectively contacted by the vapor and the condensate in the
subsequent impregnating step. The vapors of the impregnating
compound are then introduced into the chamber so that the compound
rapidly comes into contact with the tobacco. During the vapor
treatment the tobacco in the chamber is maintained at a temperature
and pressure which will permit a substantial proportion of the
vapors to condense directly on the tobacco particles. Thus, the
temperature is preferably at or below the boiling point of the
impregnating compound at the pressure prevailing within the chamber
to insure that the desired vapor condensation occurs. Also, it is
preferred that the temperature of the tobacco during the
impregnating step be above about 0.degree. C. so that impregnation
with the vapors and the subsequent condensation will readily
occur.
The amount and concentration of vapors in the atmosphere used to
treat the tobacco are not critical except to the extent that
sufficient vapor should be present to provide an impregnated
tobacco which will contain sufficient condensed liquid and vapor to
permit the desired expansion when the impregnated tobacco is
subjected to the heating and expansion step. In accordance with the
present invention, the impregnating vapor is introduced into the
previously evacuated chamber containing the tobacco. This permits
the quantity of the impregnating material to be precisely
controlled. For example, if 20 percent by weight impregnant is
desired on the tobacco, the quantity to be admitted to the chamber
is readily calculated based on the weight of the tobacco plus the
additional quantity of vapor necessary to occupy the void space in
the chamber under the pressure conditions selected.
Super-atmospheric pressure may be employed during impregnation, if
desired, to introduce the calculated quantity of vapor into the
chamber. Alternatively, the impregnation step may be carried out by
forcing the impregnating vapor through the tobacco in the chamber
thereby causing significant amounts of the vapor to contact the
tobacco with resultant condensation. Other variations may also be
used to effect impregnation with equally satisfactory results.
Regardless of the details of the impregnation technique used, it is
desirable that the actual amount of impregnant introduced into the
tobacco be such that after the tobacco has been subjected to the
gas drying step and just before expanding with the hot gas, the
impregnant concentration will be at least one part but not more
than 40 parts by weight based on the weight of the tobacco (dry
basis) and preferably between 2 parts and 10 parts by weight of
impregnant per 100 parts of tobacco (dry basis). This will minimize
redistribution of tobacco constituents which are soluble in the
condensed impregnant.
The compounds or mixtures employed for impregnating the tobacco are
preferably ones which are organic in nature, are chemically inert
to the tobacco being treated and have boiling points at atmospheric
pressure between about -10.degree. and +80.degree. C. Compounds
having boiling points above 80.degree. C. do not provide good
expansion and are difficult to remove completely from the tobacco
without adversely affecting its flavor and aroma. Compounds having
boiling points below about -10.degree. C. at atmospheric pressure
require that the temperature of the tobacco be brought to an
abnormally low point or the pressure to be increased to an
undesired or unnecessarily high level in order to enable the
necessary condensation to occur on the tobacco. Preferably, the
atmospheric pressure boiling point of the impregnating compound or
mixtures is between about 15.degree. and 40.degree. C. Illustrative
organic compounds which may be used to carry out this invention
include acetone, methyl ethyl ketone, methyl ethyl ether, methyl
propyl ether, diethyl ether, dimethoxymethane, furan,
tetrahydrofuran, methanol, ethanol, ethyl formate, pentane,
isopentane, hexane, pentene, hexene, cyclobutane, cyclopentane
cyclohexane, cyclopentene, cyclohexene, benzene, ethyl chloride,
propyl chloride, t-butyl chloride, methylene chloride, methyl
bromide, ethyl bromide, chloroform, carbon tetrachloride,
ethylidene chloride, trichlorofluoromethane,
trichlorotrifluoroethane, octafluorocyclobutane,
1,1,1-chlorodifluoroethane, 1,2-dichlorotetrafluoroethane,
chlorodifluoromethane and azeotropic mixtures of the
above-mentioned compounds such as the
trichlorofluoro-methane-isopentane azeotrope. Compounds that are
preferred are the nonoxygenated organic compounds which are
relatively nonpolar in nature and are relatively or substantially
immiscible in water. These preferred compounds, as a group, have
relatively low specific heats and thus require only a low energy
input to cause them to vaporize and expand within the tobacco.
Preferred materials are the hydrocarbons and the halogenated
hydrocarbons within the group previously mentioned. Most preferred
are isopentane and trichlorofluoromethane because their boiling
points permit the impregnation step to be carried out without
excessive heating or cooling requirements. As previously noted,
mixtures of vapors of several compounds may also be used if the
boiling points of the mixtures are within the indicated temperature
range.
After vapor impregnation and condensation, the tobacco is allowed
to stand (i.e., equilibrate) for at least 10 minutes and up to
several hours in order to allow the condensate to penetrate into
the tobacco shreds or other pieces. This penetration is aided by
the moisture present in the tobacco (i.e., from 10 to 20 percent)
at this stage. Following equilibration the partial drying step is
carried out prior to steaming. The partial drying step is an
important feature of this invention and is effected by rapidly
passing dry air or other chemically inert gas, such as vapors of
the impregnating compound, through the tobacco bed to remove as
vapors, portions of the moisture and the impregnating compound. The
temperature of the drying vapors as they enter the bed of tobacco
is between about 40.degree. C. and about 80.degree. C. and time of
sweeping the vapors through the tobacco is preferably from about 5
to 30 minutes. The purpose of the partial drying step is to remove
sufficient water from the tobacco so that during the subsequent
steaming step, water condensing on the tobacco will not raise the
tobacco moisture so high that the expanded tobacco might collapse
again. It will be appreciated by those skilled in the art that the
temperature of the gas used in the partial drying step is
determined to some extent by the moisture content of the gas
source. Since removal of moisture from the tobacco is a primary
objective, it is preferred that the sweeping gas be as dry as
practicable in order to achieve good drying efficiency.
After the partial drying step, moisture that remains in the tobacco
is at least about 5 percent by weight and the amount of impregnant
is at least about one percent by weight. All impregnant is not
removed during the partial drying step because the final portions
of impregnant do not migrate very rapidly from the dried tobacco
even though the tobacco is warmed to a temperature above the
boiling point of the impregnant.
Following partial drying, the tobacco is then rapidly heated to
vaporize the impregnating liquid whereby the liberated vapors
expand and puff the tobacco particles to the desired extent. The
expanding step is preferably carried out directly in the chamber
used for impregnation but it may be carried out after removal to a
separate piece of equipment. In any event, the impregnated tobacco
is rapidly heated by a hot moist gas, preferably steam, to raise
the temperature at least 18.degree. C. without a corresponding
increase in pressure whereby the tobacco is puffed by vaporization
of the liquid and subsequent vapor expansion. Preferably the hot
gas temperature is at least about 90.degree. C. and the time of
exposure to the hot gas may vary from a few seconds to several
minutes.
After the puffing, it may be desirable, at least with certain
organic materials, to remove last traces of the vapors by passing
hot, moist air through the expanded tobacco. The expanded tobacco
is then adjusted, if necessary, to the moisture content desired for
the final product. This is usually carried out by wet steaming,
spraying, etc., and the final moisture content is preferably within
the range of 11 to 14 percent by weight. This tobacco product,
having decreased bulk density, is particularly useful for the
manufacture of smoking products such as cigarettes, cigars and pipe
tobacco. The bulk density having been decreased, considerable
savings in tobacco cost are obtained in the manufacture of these
smoking products without sacrificing quality.
In order to measure the filling capacity of a cut filler tobacco
product as described in the following examples, a compressometer is
used which is essentially composed of a cylinder 9.5 centimeters in
diameter with a graduated scale on the side. A piston 9.4
centimeters in diameter slides in the cylinder. Pressure is applied
to the piston and volume in milliliters of a given weight of
tobacco, 100 grams, is determined. Experiments have shown that this
apparatus will accurately determine the volume (filling capacity)
of a given amount of cut tobacco with good reproducibility. The
pressure on the tobacco applied the piston in all examples was 2.30
pounds per square inch applied for five seconds, at which time the
volume reading was taken. This pressure corresponds closely to the
pressure normally applied by the wrapping paper to tobacco in
cigarettes. The moisture content of the tobacco affects the filling
capacity values determined by this method, therefore, comparative
filling capacities were obtained at similar moisture contents.
DESCRIPTION OF THE DRAWING
For a more complete understanding of this invention, reference will
now be made to the accompanying drawing in which
FIG. 1 is a schematic showing of the apparatus used for carrying
out the process of Example I embodying this invention, and
FIG. 2 is a schematic showing of equipment that may be used for
carrying out this invention in commercial practice where it is
desirable to recover the impregnant used.
FIG. 1 shows a hermetically sealable pressure vessel or chamber 10
in which is 11 inches high by 41/4 inches in diameter. A cover 12
is removably fastened to the flanged top of the vessel by bolts and
nuts 14 and a gasket 16 is placed underneath the cover for
hermetically sealing the vessel 10. A vapor line 18 of 1/4-inch
pipe extends from the bottom of the vessel, and attached to line 18
are a valve 20 and pressure gauge 22. Mounted an inch above the
bottom of the vessel 10 is a wire screen disk 24 to support a bed
of tobacco 26. The inside of the vessel is lined with three layers
of wet strength cardboard (not shown), each 1/64 of an inch thick
(e.g., template paper) to serve as insulation.
FIG. 2 is a schematic of plant scale equipment for expanding
tobacco by the method of this invention. A tobacco tub 28 which may
be supported on wheels (not shown) is filled half full of tobacco
30 which rests on a screen 32 near the bottom of the tub. The tub
of tobacco is pushed into a vacuum chamber 34, and a flexible hose
36 is coupled to the bottom of the tub. Across the top of tub 28 is
a hold-down screen 38 to prevent expanding tobacco from overflowing
the tub. It is obvious that more than one tub of tobacco can be
treated simultaneously in vacuum chamber 34.
The chamber is evacuated through vacuum line 40, and this line is
then closed. Trichlorofluoromethane, or other suitable impregnating
material, is fed from tank 42 through valve 44 into heater 46. The
impregnant boils in heater 46 and vapor goes through valve 48 and
flexible line 36 into tub 28 and condenses on tobacco 30. Vapor is
fed in this manner until a rate pressure, e.g., 15 psig., is
reached. Valve 44 is then closed.
After an equilibration period (e.g., 1 hour) to allow impregnant to
penetrate into the tobacco, valve 50 is opened and fan 52 is turned
on. Vapor leaves the vacuum chamber through line 54 and goes into
cold water condenser 56. Vapor that condenses (moisture and also a
portion of impregnant) flows into tank 42 through conduit 58. Vapor
pressure exerted by the impregnant prevents all vapor from
condensing. Vapor that does not condense leaves the condenser 56
through line 60 and passes through fan 52, heater 46, and the tub
of tobacco 30. This operation consists of warm dry vapor sweeping
up through the tobacco for the purpose of evaporating a portion of
the impregnant and a portion of the moisture from the tobacco.
Fan 52 and heater 46 are then turned off, and valve 48 is closed.
Steam is introduced through line 62 for a short period of time,
e.g., 15 to 90 seconds. Steam condenses on tobacco 30, causing
impregnant deep in the tobacco to flash to vapor and expand the
tobacco. Expanding tobacco causes the top of the bed to rise and
the tobacco bed may reach hold-down screen 38.
Impregnant vapor driven out of the tobacco, and any excess steam,
condense in condenser 56 and the condensate flows into tank 42.
Water in tank 42 floats on the impregnant, trichlorofluoromethane,
and can be periodically drawn off through tap 64.
In order to facilitate removal and handling of the tub of tobacco,
it can be readily cooled by closing valve 50 and again evacuating
chamber 34.
SPECIFIC EXAMPLES
EXAMPLE I
Cut (i.e., shredded) flue-cured tobacco at 20 percent by weight
moisture (dry basis) was loaded into the vessel 10 shown in FIG. 1.
The bed of tobacco 26 was 10 inches deep, and rested on screen 24.
The quantity of tobacco used was 270 grams, equivalent to 216 grams
dry tobacco and 54 grams moisture. The washer 16 and cover 12 were
placed on the vessel and the vessel was sealed.
Air was removed from the vessel by connecting valve 20 to a vacuum
pump for 15 minutes. Valve 20 was then closed and connected to a
small flask (not shown) that contained 135 grams of liquid
trichlorofluoromethane. Valve 20 was again opened and the flask of
liquid was heated by means of a water bath. The liquid evaporated
and the vapor passed into the vessel in contact with the tobacco
26.
After all of the volatile liquid had entered the vessel, gauge 22
indicated 4 pounds pressure. Valve 20 was closed and the vessel 10
was placed in an oven at 50.degree. C. for 90 minutes. The pressure
rose to 17 psig.
The vessel was removed from the oven and connected at valve 20 to
an ince water condenser. Valve 20 was opened, causing excess
trichlorofluoromethane vapor to leave the vessel 10 and condense;
the quantity recovered was 88 grams.
Cover 12 was then removed from the vessel. The tobacco bed had
reached to 7.5 inches of depth. A source of dry air at 55.degree.
C. was connected to line 18 and the air was passed into the bottom
of the vessel and up through the tobacco rapidly. A hold-down
screen, weighted with 300 grams of weights, was placed over the
tobacco to hold the tobacco plug in the vessel against rising
air.
Air flow at 55.degree. C. through the tobacco was continued for 20
minutes. The warm dry air evaporated a large portion of volatile
impregnant from the tobacco, removed some moisture, and also warmed
the tobacco.
The side wall of the vessel was extended 6 inches by adding a
section of cardboard tube (not shown) to the top of the vessel. A
source of saturated steam was connected to valve 20, and steam was
passed up through the bed 26 of tobacco for 30 seconds. Steam
caused the tobacco to expand, and caused the bed thickness to
increase from 7.5 to 16 inches.
The filling capacity of the tobacco was measured by the
compressometer described above. Filling capacity prior to treatment
was 443 ml./100 grams, and filling capacity after expansion was 827
ml./100 grams, both measurements made on tobacco conditioned to
12.4 percent moisture.
EXAMPLE II
The general procedure of Example I was repeated except that 100
grams of tobacco having a moisture content of 12.4 percent was
treated with 110 grams of trichlorofluoromethane. The vessel was
heated at 45.degree. C. for 90 minutes during which time the gauge
pressure increased from 6 to 16 pounds. The vessel was then removed
from the oven and vented by opening valve 20. A source of
trichloromonofluoromethane vapor was connected to line 18 and vapor
heated to 80.degree. C. by means of a suitable heat exchanger (not
shown) was passed up through the tobacco for 15 minutes. A total of
1.5 liters of trichloromonofluoromethane was vaporized during this
15-minute period at the end of which time the temperature of the
vapor emerging from the top of the tobacco bed was 60.degree. C.
The tobacco was then contacted with saturated steam for 15 seconds
via line 18 to give expanded tobacco with a filling capacity of 634
ml./100 grams (measured after adjusting the moisture to 12.4
percent). Untreated tobacco had a filling capacity of 374 ml./100
grams.
EXAMPLE III
Cut flue-cured tobacco (4 pounds, moisture 13.9 percent) was put
into a metal tub 16 inches wide and 30 inches long. The tobacco
formed a bed 3.5 inches deep which rested on a perforated metal
plate two inches above the tub bottom. The tub of tobacco was put
into a jacketed autoclave equipped with special connections. These
included a line into the top of the autoclave chamber for
introducing or removing vapor, and a second line into the bottom
which was connected directly to the bottom of the tub below the
perforated metal plate.
A vacuum generated by steam jets and connected to the top of the
autoclave was employed to evacuate the autoclave for 15 minutes.
The evacuated autoclave was heated by circulating 65.degree. C.
water through the jacket and trichlorofluoromethane vapor at
65.degree. C. was introduced into the chamber until pressure in the
autoclave reached 30 psig. After the tobacco had equilibrated at 30
psig. for 45 minutes, pressure was released via the connection in
the bottom of the tub. The jacket temperature was then raised to
82.degree. C. and heated trichlorofluoromethane vapor was rapidly
passed through the autoclave from top to bottom. This sweeping
operation was continued for 10 minutes. Steam was then passed into
the bed of tobacco for 30 seconds causing the impregnated tobacco
to expand. The autoclave was evacuated once again for 15 minutes to
dry and cool the expanded tobacco.
The above sequence of operations caused filling capacity of the
tobacco to increase from 442 to 850 ml./100 grams, both
measurements at a 12.4 percent tobacco moisture basis.
EXAMPLE IV
Cut flue-cured tobacco (85 pounds, moisture 13.2 percent) was put
into a round wooden tub, 42 inches in diameter. The tobacco was
supported on wire mesh, 4 inches above the bottom of the tub. Depth
of the tobacco bed was 14 inches. The tub of tobacco was placed in
a vacuum chamber that is normally used for conditioning a hogshead
of tobacco. A pipe connection into the bottom of the tub served as
access for introducing vapor or steam into the tobacco at the
bottom of the bed.
The chamber was closed and was evacuated for 30 minutes by means of
steam jets. The vacuum line was closed, and warm
trichlorofluoromethane vapor was introduced into the evacuated
chamber via the tub connection until vapor filled the chamber at a
positive pressure of 5 psig. Tobacco was allowed to equilibrate at
this pressure for 1 hour before venting the chamber. Steam was
introduced to the bottom of the tobacco bed for 45 seconds causing
the impregnated tobacco to expand. The chamber was evacuated for 25
minutes in order to remove excess moisture and to cool the
tobacco.
The product contained 14.1 percent moisture. After conditioning to
12.4 percent moisture, the filling capacity was 651 ml./100 grams,
compared to an initial filling capacity of 433 ml./100 grams (12.4
percent moisture). In this example, the impregnated tobacco was not
warmed and dried by sweeping hot vapors through the tobacco (as in
Example III), and, consequently, the product was not as highly
expanded.
It will be appreciated from the foregoing that this invention
provides a means whereby the impregnating liquid may be rapidly and
efficiently introduced into the tobacco before the latter is
subjected to the heat expansion process. A method has been provided
whereby large quantities of impregnating fluid are rendered
unnecessary and, accordingly, it is not necessary to provide
expensive equipment for the recovery and recycling of impregnating
fluid although it will be appreciated that economic conditions may
dictate that the fluid be recovered for reuse in the process.
Equipment suitable for recovery of the impregnant can be readily
adapted for use with the apparatus and process described herein.
Also, by this procedure the processor can make use of equipment
that is normally found in plants for processing tobacco for the
manufacture of cigarettes, cigars and the like. One such piece of
equipment which can be readily modified is disclosed in U.S. Pat.
No. 3,262,458 issued July 26, 1966.
While particular embodiments of this invention have been described
in the foregoing, it will, of course, be apparent that other
modifications may be made without departing from the spirit and
scope of this invention.
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