Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR IMPROVING THE FILLABILITY OF TOBACCO
The invention relates to a method for increasing the
fillability of tobacco materials, such as for example cut
tobacco leaves, ribs or plant-based tobacco additives with
cellular structure, by treatment of the tobacco material,
which has 8 to 16 wt.% initial moisture, with a treatment gas
consisting of nitrogen and/or argon at pressures of 50 to
1,000 bar in either one autoclave or with cascade-type
switching in several autoclaves followed by thermal after-
treatment of the tobacco material discharged after
decompression has occurred.
The expansion of tobacco with inert gases under high
pressures, which is also known as the INCOM expanding method,
has shown its advantages over the pressure treatment of
tobacco with carbon dioxide, ammonia or volatile organic gases
and is known, for example, from US 4 289 148, according to
which tobacco material with moisture of more than 20 wt.% is
treated in the autoclave at operating temperatures between 0
and 50°C. The pressure reduction takes place within 0.5 to 10
minutes, and in the examples referred to, 1.3 minutes, after
which the tobacco discharged is subjected to thermal after-
treatment e.g. with saturated steam, during which it is
expanded.
According to DE 31 19 330 A1 a tobacco material with reduced
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moisture of 10 to 15 wt.% is additionally used at an operating
temperature below 50°C, to achieve greater cooling of the
tobacco material to be discharged when the tension is
released. The pressure reduction times in this case are 1.3 to
2 minutes.
DE 34 14 625 C2 discloses a cascade method, according to which
after cooling of the treatment gas before admitting it into
the reactor, cooling of the autoclave or use of an undercooled
and liquefied treatment gas, a lower impregnation temperature
of the tobacco is [achieved]. The pressure reduction times
amount to 0.5 to 10, especially 1 to 2 minutes. The minimum
temperatures of the tobacco discharged should be below 0°C.
Analogously, also according to DE 39 35 774 C2 with a cascade-
type expansion method, the necessary low impregnation
temperatures of 25/45°C were achieved by circulating the
treatment gas via a cooler.
Although with this known expanding method good values are
obtained as regards the increase in the fillability of tobacco
and/or of the degree of expansion, these are relatively
expensive due to the necessary cooling of the autoclave or
autoclaves and because of the additional cooling of the
treatment gas.
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The aim of the invention is to improve the existing INCOM
methods and to achieve equally good or better degrees of
expansion independently of expensive cooling measures.
According to the invention a method is therefore proposed of
the type initially mentioned in accordance with the patent
claim preamble, characterised in that the decompression is
carried out with at least one holding stage, whose pressure
corresponds to 3 to 60%, preferably 3 to 30% of the original
maximum pressure and in that the heating of the system whilst
under residual pressure is carried out in such a way that the
tobacco discharge temperature following full pressure
reduction lies within the range 10 to 80°C.
Surprisingly it has transpired that with lower tobacco
moistures in the range 8 to 16 wt.% the existing theory, of
providing a low treatment temperature and/or a low discharge
temperature, does not lead to optimal expansion results. On
the contrary, only by heating the system whilst it is under
residual pressure was it possible to achieve surprisingly good
values with regard to the expansion effect and/or the
fillability, with the heat of compression being used to
advantage and not eliminated, according to the method, and
additional cooling of the autoclave or autoclaves being
unnecessary.
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The pressure reduction from the maximum pressure in question
to the pressure of the holding stage is preferably carried out
within an interval of 20 seconds to 5 minutes, whilst the
reduction of the residual pressure is carried out within an
interval of 3 seconds to 3 minutes.
Furthermore, to achieve the tobacco discharge temperature
according to the invention, it is appropriate to effect the
temperature increase by means of a holding time, by
circulation of the gas under residual pressure via a heat-
exchanger and/or by transferring heated gas from a further
autoclave.
In a further preferred variant of the method, the high
pressure treatment or the sequence of high pressure treatment
and thermal treatment is carried out several times with the
same tobacco material.
Especially good results are achieved, if the initial moisture
of the tobacco material is within the range 10 to 14 wt.% and,
furthermore, if the thermal after-treatment of the tobacco
material is carried out with saturated steam.
The method according to the invention is explained below With
reference to examples.
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Example 1
To carry out the method according to the invention, and also
for the comparative tests, the high pressure treatment was
carried out with a treatment gas consisting of nitrogen in a
laboratory autoclave with a used content of 2 1, wherein to
adjust the desired operating temperatures, a casing was used
for circulation of the liquid media. The pressure build-up/
gas supply to the autoclave took place from below, the
pressure reduction/gas discharge from the autoclave took place
upwards. To adjust the final pressure a compressor was used,
whilst the tobacco temperature was measured in the upper
section or upper half of the tobacco filling unit with a
thermocouple element.
The laboratory device for thermal after-treatment of the
tobacco consisted of a permeable conveyor belt/wire gauze,
which was driven at a speed of approx. 5 cm/s. The tobacco
mat guided between baffles was after-treated under a steam
nozzle approx. 160 mm wide with a slit-type outlet of approx.
8 mm with approx. 10 kg/h saturated steam. A steam suction
device was situated below the conveyor belt opposite the steam
nozzle.
The tobacco samples treated in this way were spread out in
flat trays and conditioned at 21°C and 60% relative humidity.
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The fillabilities were determined by means of a Borgwaldt
density meter and the specific volume converted into ml/g with
a nominal moisture of 12 wt.% and a nominal temperature of
22°C. From the data of the untreated comparison sample and the
expanded sample, the relative improvement in fillability
and/or the degree of expansion is calculated as follows:
d% _ (FE-FH) * 100% / Fg
(FH = fillability untreated, FE= fillability expanded)
A PVC pipe with a perforated bottom inserted was used to
receive the tobacco in the autoclave. The gas supply during
the pressure build-up took place up to a final pressure of 700
bar. 300 g Virginia blend with 12% moisture was used as
tobacco. The test results are shown in the following tables,
where TA means the discharge temperature of the tobacco
subjected to high-pressure treatment. In test 1, during the
pressure reduction, two holding stages each lasting 2 minutes
at 40o bar and 100 bar were applied, and in tests 2 and 3 only
one holding stage lasting 2 minJ4 min at 50 bar was applied.
In comparison test no. 4 the pressure reduction took place
directly, i.e. without a holding stage in a pressure reduction
time of < 1 min.
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Table 1: Test results
Operating temperature °C
60 80
No. Operation pressure TAC A% T"C 0%
reduction
1 Holding stage at 400 16 83 - -
and 100 bar, each 2
min
2 Holding stage at 50 15 93 20 90
bar, 2 min
3 Holding stage at 50 33 93 41 90
bar, 4 min
4 None (comparison) -25 80 -3 81
The above tests nos. 1 to 3 with various pressure and time
values for the holding stage and two operating temperatures of
the autoclave show, in comparison with test 4 with direct
pressure reduction, that the holding times with a pre-selected
holding stage (pressure) produced a clear increase in the
discharge temperature from -25°C or -3°C up to +33°C or
+41°C
and, in contrast to the existing technical theory, an
increased improvement in fillability in spite of high
discharge temperatures.
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$xample 2
Analogously to example 1, the high-pressure treatment was
carried out with 150 g tobacco at an operating temperature of
the autoclave of 40°C. During the pressure reduction in test
no. 5 a holding stage of 2 min was applied at 50 bar and
during the holding time the gas is circulated by means of a
circulation pump via a heat exchanger with a temperature of
80°C. This time the gas supply during the pressure reduction
and during the circulation took place from above, the gas
discharge with holding stage and pressure reduction downwards.
A sealing ring between the upper limit of the tobacco
insertion container and the autoclave lid guaranteed the
direct entry of the gas into the tobacco insertion container.
Table 2: Test results
Operating temperature 40°C
No. Operation during T"°C D%
pressure reduction
Holding stage 2 min at 10 79
50 bar, circulation via
heat exchanger (80°C)
6 None (Comparison) -105 69
Example 3
A procedure similar to that of Example 2 was followed, wherein
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during pressure reduction, the pressure was kept constant at
50 bar for a holding stage of 1 min and heated gas from a
second autoclave, designated the "donor" was introduced into
the treatment container. The donor, before the transfer, had a
pressure of 100 bar and an operating temperature of 80°C with
a content of 4 1. The gas supply during pressure reduction and
during transfer now took place from below, the gas outlet with
holding stage and pressure reduction upwards.
Table 3: Test results
Operating temperature 40°C
No. Operation during T"°C d%
pressure reduction
7 Holding stage 1 min at 16 89
50 bar, transfer from
donor, pressure 100 bar
Operating temperature
60°C
In contrast to example 1, in which the heating, by means of a
holding time with a pre-selected holding stage/pre-selected
pressure presupposes a raised operation temperature, examples
2 and 3 above show that the circulation according to example 2
via a heat exchanger or the transfer of gas from the donor
according to example 3 with a constant holding stage/constant
pressure also lead to a raised operating temperature when the
operating temperature of the gas-containing treatment
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container, designated the "acceptor" is 40°C. The variant
involving a transfer from the donor container according to
example 3 in particular leads to a clear increase in the
fillability improvement over the comparative test no. 6 in
example 2.
For interpretation of these surprising results it can be
assumed that the heating of the high-pressure-treated tobacco
under residual pressure leads to a preliminary expansion in
the autoclave, producing additional improvements in
fillability, which cannot be achieved with the known method.
To confirm this assumption in the following example 4, the
pressure treatment was carried out without thermal after-
treatment with saturated steam, to test a possible effect of a
preliminary expansion, with direct conditioning of the samples
treated. It is true that the improvements in fillability
without thermal after-treatment are small, but in the
following example 4, an additional effect apgears during
heating under residual pressure.
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Example 4
150 g tobacco were subjected to high--pressure treatment at an
operating temperature of the autoclave of 60°C, and the
tobacco was not subjected to thermal after-treatment after
complete pressure reduction. During pressure reduction there
was a holding stage of 1 min at 50 bar with a transfer of
heated gas from a second autoclave analogous to example 3, the
donor having a pressure of 200 bar and an operating
temperature of 80°C before the transfer. In the comparative
test no. 9 the pressure reduction took place directly and
without a holding stage.
Table 4: Test results
Operating temperature 60°C
No. Operation during pressure T,°C D%
reduction
8 Holding stage 1 min at 50 19 21
bar,
transfer from donor, pressure
200 bar
Operating temperature 80°C
9 None (Comparison) -69 8
The above results confirm the assumption of an albeit slight
preliminary expansion before the thermal after-treatment with
saturated steam during heating of the high-pressure-treated
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tobacco whilst it is under residual pressure.
The following examples 5 and 6 show a further embodiment of
the method according to the invention, in which the high-
pressure treatment/high-pressure treatment and thermal after-
treatment are carried out several times with the same tobacco
material.
Example 5
In a first stage, 150 g tobacco were subjected to high-
pressure treatment at an operating temperature of the
autoclave of 60°C, analogously to example 3 by transfer of
heated treatment gas from the donor with a holding stage with
constant pressure. Before the transfer the donor had a
pressure of 300 bar and an operating temperature of 80°C; the
holding stage was adjusted to 1 min at 200 bar.
The tobacco material from the first stage, expanded and
conditioned according to test no. 10, was used as base
material for a further cycle of treatment consisting of high-
pressure treatment and thermal after-treatment. The high-
pressure treatment was carried out with 100 g tobacco and at
an operating temperature of the autoclave of 60°C, and a
holding stage of 1 min at 100 bar was provided during pressure
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reduction. The donor container before the transfer, possessed
a pressure of 200 bar at an operating temperature of 80°C, the
results of this test and test no. 10 are shown by Table 5.
Table 5: Test results
Operating temperature 60°C
No. Operation during pressure T"C 0%
reduction
Holding stage 1 min at 200 26 86
bar,
transfer from donor, pressure
300 bar
Operating temperature 80C
11 Holding stage 1 min at 100 24 116
bar,
(Treatment
transfer from donor, pressure of expanded
200 bar tobacco from
Operating temperature 80C test 10)
$xample 6
A procedure analogous to that of example 5 was followed,
wherein however in this case two identical pressure treatment
cycles were carried out one after the other, followed by
thermal after-treatment. The results are as follows.
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Operating temperature 60°C
No. Operation during pressure T"°C d%
reduction
12 Holding stage 1 min at 100 30 103
(double
bar,
transfer from donor, pressure pressure
200 bar treatment
Operating temperature 80°C followed by
thermal
treatment)
Whereas the expanded tobacco material of stage 1 from example
was used for renewed treatment in stage 2, in this example 6
the pressure treatment cycle was carried out twice in
succession and only then was the pressure-treated tobacco
material subjected to the thermal after-treatment. Both
methods are based on the principle of a multiple expansion by
repetition of the sequence of high-pressure treatment and
thermal after-treatment or one repeated high-pressure
treatment only followed by thermal after-treatment.
Example 5 shows that the effect of the first expansion stage
can be further increased by the renewed treatment in stage 2
and a tobacco material with extremely high fillability is
obtained. Example 6 is simpler, due to the omission of an
after-treatment stage, but does not reach the maximum value of
example 5.
