CH649198A5 - METHOD FOR EXPANDING TOBACCO. - Google Patents

Description

The invention relates to an improved method for expanding tobacco, in which an easily available, relatively cheap, non-combustible, non-disturbing and non-toxic expansion agent is used. The invention particularly relates to the manufacture of an extensive tobacco product with a significantly reduced density and increased filling power. In the method according to the invention, carbon dioxide is used as an expansion agent. The procedure is generally as follows

that tobacco, preferably with a moisture content of 5 to 35% by weight, is introduced into a vessel or a similar delimitable space, the vessel or the space then being flushed with gaseous CO 2 to remove most of the air present , although this is not essential to the invention. The vessel is closed except for an inlet opening and carbon dioxide gas is introduced. The pressure is increased to a final pressure of at least 1.7 MPa, preferably 2.7-5.5 MPa, by further gas introduction and / or by io heating under conditions in which the CO 2 remains in the vessel mainly in the gas state . The temperature required to maintain the CO 2 in a substantially gaseous state at a given pressure can easily be determined using phase diagrams or critical tables. Although pressures as high as 6.3 MPa can be used economically and an overpressure of around 7.4 MPa would be acceptable, there is no other known upper limit for an applicable range of impregnation pressures than is given by the conditions of the available plant . However, operation below the critical temperature is preferred for ease of control. The tobacco can be kept under these impregnation conditions Va for up to 30 minutes, longer times generally being applicable for operation at lower pressure. The pressure enthalpy diagram for C02 according to Figure 1 of the drawings is useful for selecting the desired conditions. After the impregnation stage, the gas pressure is reduced by venting. The ultimate pressure may be atmospheric pressure or a pressure close to that used in the expansion stage, but is preferably the former. The time for the pressure reduction is expediently 1 to 800 s. The tobacco containing gaseous carbon dioxide is then transferred to a zone where it is exposed to conditions that remove the carbon dioxide, thereby expanding the tobacco. The transfer of the carbon dioxide containing tobacco to the heating or expansion zone should preferably be effected within as short a time as possible, preferably within about 5 minutes, most preferably within about 2 minutes. As an alternative to rapid transfer, the carbon dioxide-containing tobacco can, if desired, be stored in an insulated container or cooled, or otherwise kept in a relatively cold condition. The heating or expansion step preferably provides for exposure of the tobacco containing carbon dioxide to rapid heating to a temperature of 100 to 370 ° C over a period of 1 second to 10 minutes substantially at atmospheric pressure.

According to an improvement, the impregnation step is modified in the manner specified below. After the impregnation step, the gas pressure is reduced by venting 55. The ultimate pressure can be atmospheric pressure or a pressure close to that used in the expansion stage. However, it is preferably the former. The pressure reduction period is generally 1 to 800 s. The gaseous carbon-60 containing tobacco is then transferred to a zone where it is exposed to conditions that remove the carbon dioxide, thereby expanding the tobacco. The transfer of the carbon dioxide-containing tobacco to the heating or expansion zone should preferably be accomplished within as short a time as possible, preferably within about 5 minutes, more preferably within about 2 minutes. As an alternative to rapid transmission, the

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Tobacco containing carbon dioxide is stored in an insulated container or cooled or otherwise kept in a relatively cool condition. In the heating or expansion step, the tobacco containing carbon dioxide is preferably subjected to rapid heating to a temperature of 100 to 370 ° C over a period of 1 s to 10 min at substantially atmospheric pressure.

To carry out the process according to the invention, one can treat either whole smoked tobacco leaves, cut or shredded tobacco or selected parts of tobacco, for example tobacco stalks or reconstituted tobacco. In crushed form, the tobacco to be treated can have a particle size of 2 mm to 150 µm, but is preferably not less than about 0.600 mm.

The tobacco can contain the natural moisture content of the tobacco and it can contain 5 to 35% by weight of moisture. For best results, however, it is preferred that the tobacco contain at least 8 wt% and at most 22 wt% moisture. The percent moisture given herein can be considered equivalent to oven volatiles (OV) because no more than about 0.9% of the tobacco weight is volatiles other than water. The procedure for determining the volatiles in the furnace is given below.

The tobacco is generally placed in a pressure vessel, which is explained in more detail below. For example, it can be placed in a wire cage or on a platform that is arranged inside the vessel.

The pressure vessel containing the tobacco can then be flushed with carbon dioxide. The advantages of purging are the removal of gases that could interfere with the carbon dioxide recovery process and / or that could interfere with full penetration of the gaseous carbon dioxide. As an alternative to purging with carbon dioxide gas, the vessel can be evacuated before the introduction of the carbon dioxide gas.

Either with or without purging or evacuating the vessel, carbon dioxide gas is introduced into the vessel under conditions where the carbon dioxide gas pressure in the vessel is increased under conditions where the tobacco in the vessel is preferably at a temperature of -10 to 60 ° C and the pressure in the vessel is above 1.7 MPa and is preferably 2.7-5.5 MPa. The tobacco is kept under conditions in which the carbon dioxide has an overpressure above 1.7 MPa, and is in conditions above and to the right of the saturation steam line in FIG. 1. The treatment duration is 15 s to 30 min. The pressure is then reduced over a period of 1 to 800 seconds, preferably 10 to 120 seconds, so that the temperature does not drop below the carbon dioxide saturation temperature at the same time as the pressure is applied, and the tobacco is brought to a temperature below about 10 ° C and brought to atmospheric pressure or the pressure at which the expansion stage is carried out.

According to an improvement of the invention, the Ta-bak / CO 2 system is cooled during the impregnation stage, for example by circulating a coolant through the jacket of the vessel containing the system, thereby reducing the enthalpy of the carbon dioxide to below about 325.640 kJ / kg. This is preferably done while the pressure is kept relatively constant by adding more carbon dioxide gas. Cooling is limited so that the carbon dioxide is not condensed to any appreciable extent and is not cooled to a temperature below -23 ° C. The system is maintained under these impregnation conditions for up to 30 minutes, with longer times generally being used when operating at a lower pressure. The aforementioned phase diagram or critical tables about carbon dioxide are useful to select the desired conditions. The pressure / temperature relationship is preferably maintained so that the carbon dioxide gas is maintained at or near the saturation point. It is believed that when the conditions are near or near saturation, the absorption / adsorption properties of gaseous CO 2 are greatly increased. This results in an improved retention of gaseous C02. The ultimate pressure, if the pressure is reduced, may be atmospheric pressure or a pressure close to that used in the expansion step. However, it is preferably atmospheric pressure. The time period for the pressure reduction can be 1 to 800 s.

It has been found that after the impregnation step, under conditions where cooling is not used in the improved process, a product is formed which contains at least 1 part by weight of carbon dioxide gas per 100 parts by weight of tobacco. This is to be understood to mean that at least 1 part by weight of carbon dioxide gas per 100 parts by weight of tobacco is present with the tobacco in a certain way either chemically and / or physically, for example in an absorbed manner in the tobacco. The product can have as much as 3 parts by weight or more of gaseous carbon dioxide if the process is carried out in this way. It has been shown that this takes place in the absence of added absorbents or the like. Adsorbents, absorbents or the like may be present, but it is preferred that such substances are not present, since the process is also effective without these substances and because this could introduce undesirable elements into the smoke or because the carbon dioxide would not be completely in this way could be released effectively. It has been shown that after the tobacco impregnation stage, even higher amounts of carbon dioxide, for example as high as 3 parts by weight (per 100 parts by weight of tobacco),

or more. The pressure / temperature relationship is preferably maintained so that the gas is maintained at or near the saturation point. It is believed that when the conditions are near or at saturation, the absorption / adsorption properties of gaseous CO 2 are greatly increased. This leads to an improved retention of gaseous C02. The ultimate pressure, if the pressure is reduced, can be atmospheric pressure or a pressure close to that used in the expansion stage. However, it is preferably atmospheric pressure. The time for the pressure reduction can be 1 to 800 s.

It has been found that, after the impregnation step, under conditions where cooling takes place according to the invention, a product is formed which can contain as much as 3 parts by weight or more of gaseous carbon dioxide per 100 parts by weight of tobacco. This is to be understood to mean that at least 3 parts by weight of carbon dioxide gas per 100 parts by weight of tobacco are present in the tobacco in a certain manner, for example chemically and / or physically, in the tobacco. It has been found that this is the case in the absence of added adsorbents or the like. Adsorbents, absorbents, or the like may be present, but it is preferred that such materials not be present because the process is effective without them and because they could introduce undesirable elements into the smoke

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or could result in the carbon dioxide not being released in a fully effective manner.

After the impregnation step, the tobacco can then be transferred to a zone where it is subjected to conditions such that the carbon dioxide is removed and the tobacco is expanded. This is preferably done by rapid heating to 100 to 370 ° C over a period of 1 s to 10 min at essentially atmospheric pressure.

In particular, the improvement in the impregnation level will be described below.

When carrying out the method according to the invention, either whole smoked tobacco leaves, cut or shredded tobacco or selected parts of tobacco, e.g. B. tobacco stalk or reconstituted tobacco can be used. In crushed form, the tobacco to be treated can have a particle size of 2.0 mm to 150 µm, but is preferably not less than 0.600 mm.

The tobacco can contain the natural moisture content of the tobacco and it can contain 5 to 35% by weight of moisture. However, for best results, it is preferred that the tobacco have at least 8% by weight and no more than 22% by weight moisture. The percent moisture reported herein can be considered equivalent to oven volatiles (OV) since no more than about 0.9% of the weight of tobacco is volatiles other than water. The volatile substances in the furnace are determined by simply measuring the weight loss when the material is exposed for 3 hours in a convection oven at 100 ° C.

The tobacco is generally placed in a pressure vessel, which is described in more detail below. For example, it can be placed in a wire cage or on a platform that is arranged inside the vessel.

The pressure vessel containing the tobacco can then be flushed with carbon dioxide gas. The advantages of purging are the removal of gases that could interfere with the carbon dioxide recovery process and / or that could interfere with the full penetration of the gaseous carbon dioxide. As an alternative to purging with the carbon dioxide gas, the vessel can be evacuated prior to the introduction of the carbon dioxide gas.

The carbon dioxide used in the process according to the invention is generally obtained from a storage vessel, where it is kept at an overpressure of 1.5-2.1 MPa and temperatures of -29 to -16 ° C. The carbon dioxide can be introduced into the pressure vessel at 1.5-2.2 MPa gauge pressure and -29 to -14 ° C, but is preferably brought to a temperature above -23 ° C and a gauge pressure above 1.7 MPa by suitable means before it is inserted into the pressure vessel.

Either with or without prior purging or evacuation of the vessel, carbon dioxide gas is introduced into the vessel under conditions where the carbon dioxide gas pressure in the vessel is increased under conditions where the tobacco in the vessel is at a temperature of -10 to 60 ° C and the overpressure in the vessel is above approximately 1.7 MPa and is preferably 2.7-5.5 MPa. The tobacco / CO 2 system is cooled in such a way that the CO 2 enthalpy is brought below about 325.640 kJ / kg, but the gas is preferably not condensed to a significant extent. The pressure is preferably maintained substantially constant by the addition of additional gas and the system is maintained under these conditions for 15 seconds to 30 minutes. The pressure is then reduced over a period of 1 to 800 seconds, bringing the tabaic to a temperature below 10 ° C and to atmospheric pressure or a pressure at which the expansion step is carried out.

The resulting carbon dioxide-treated tobacco 5 can then be rapidly transported, as described above, to a zone where it is subjected to expansion conditions by being heated or treated in an equivalent manner to remove the carbon dioxide from the tobacco. Hot surfaces or a stream of hot air, a mixture of gases and air can be used here, or exposure to other energy sources, for example microwave energy or infrared radiation, can take place. It has been found that the use of a gas composition with at least 50% by weight of water vapor and preferably more than 80% by weight of water vapor gives particularly good results. A suitable measure for the expansion of the tobacco containing carbon dioxide is to introduce it into a stream of heated gas or to carry it away, for example from superheated steam, or into a turbulent air stream, for example at a temperature of 150 to 260 ° C. (as low as 100 ° C and as high as 370 ° C) over a period of 1 s to 10 min. The impregnated tobacco can also be heated by placing it on a moving belt and subjecting it to infrared heating. The heating can also be done in a cyclone dryer, by contact in a tower with superheated steam or a mixture of steam and air or the like. Such contact stages should not raise the temperature of the atmosphere with which the tobacco is in contact to above about 370 ° C. The temperature should preferably be 100 to 300 ° C, most preferably 150 to 260 ° C when operating at atmospheric pressure.

35 As is well known in the processing of organic substances, overheating can cause damage, first discoloration, for example darkening, and finally charring. The necessary and sufficient temperature and exposure time for expansion without such damage is a function of these two variables and the state of the tobacco subdivision. In order to avoid undesirable damage in the heating stage, the impregnated tobacco should therefore not be exposed to temperatures of, for example, 370 ° C. for longer than 1 to 2 s.

Another method of expanding the tobacco cells is to use radiation methods such as those described in US Pat. Nos. 3,409,022 and 3,409,027. The tobacco never reaches a temperature above about 140 ° C and is cooled by the rapid release of gases. The presence of water vapor during heating helps to obtain optimal results.

Another system that is usually preferred is the use of a dispersion dryer, such as one that is supplied with air either with water vapor alone or with a combination of water vapor. An example of such a dryer is a Praetor & Schwarzt-PB dispersion dryer, which is commonly referred to below as a tower. The temperature in the dryer can be 120 to 370 ° C, the contact time in the dryer being about 1 to 10 s. Generally, a contact time of 1 to 6 seconds is used when the temperature of the hot gas is 260 to 315 ° C or slightly higher than 65. As indicated herein, other known types of heaters can be used as long as they are able to cause the impregnated tobacco to expand without excessive darkening.

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The presence of a water vapor atmosphere of 20% or more of the total hot gas composition helps to obtain the best expansion, with a high proportion (e.g. more than 80% by volume) of water vapor being preferred.

The invention is explained in more detail with reference to the accompanying drawings. Show it:

Figure 1 is a standard phase diagram plotting the pressure of CO 2 (in psia) against the temperature (in ° F) of the tobacco bed for the carbon dioxide / tobacco system, line I-II-III taking this into account drawn system illustrates;

Figure 2 is a standard pressure enthalpy diagram wherein line I-IV further illustrates the invention; and

Fig. 3 is a standard pressure enthalpy diagram, in which the line I-IV illustrates the inventive method.

For a general explanation of the method according to the invention, reference is made to FIG. 1. For example, the conditions may be as indicated by line I-II-III in Figure 1. For example, the tobacco is placed with about 12% by weight OV in the form of a cut glossy filler in a pressure vessel capable of withstanding the desired pressure, for example 7.4 MPa (1057 psig) overpressure. The vessel can be similar to the impregnation vessel according to US application SN 441 767. In contrast to this device, however, there is no need to have a device for handling liquid CO 2. The vessel can be flushed with gaseous C02 or it can be evacuated. It is pressurized with gaseous CO 2 to bring the contents to a state (at II) where the gauge pressure is greater than 1.7 MPa (250 psig) and the temperature is not less than -23 ° C. The pressure is then released (to III). The overall order conditions (indicated by line I-II-III) are such that the carbon dioxide is held below and to the right of the saturation steam line of FIG.

According to one embodiment of the invention, as can be seen from FIG. 2, the enthalpy of the CO 2 is greater than approximately 325.640 kJ / kg (140 BTU / lbm) and the CO 2 is in gaseous form. The vessel can be held for up to 30 minutes under these conditions, as indicated by line I-III. The pressure can then be reduced rapidly, preferably within 10 to 120 s, preferably to atmospheric pressure, as shown by line III-IV of FIG. 2.

The impregnated tobacco is then (preferably, but not necessarily directly) transferred to a rapid heating zone or a vessel such as the heating vessel according to US application SN 441 767, for example an expansion tower, a microwave chamber or the like.

The temperature at which the impregnated tobacco is held prior to expansion or the rapid heating step is largely determined by how long the CO 2 remains in the tobacco in sufficient quantity to effect the desired expansion. If there is little insulation or means to keep the temperature down, the transfer should be rapid, preferably within less than a few minutes. An insulated container is preferred for the transfer. Additional cooling can also be provided, for example by applying crushed or powdered dry ice to the impregnated tobacco or by spraying liquid nitrogen on it.

The rapid heating causes the tobacco to expand at a temperature where the tobacco is foldable and elastic. The tobacco can be expanded to about its state of green leaves without breaking. A significant and useful amount of expansion is obtained.

An illustration of the method according to the invention is given in FIG. Tobacco with about 12 wt .-% OV in the form of cut glossy filler is placed in a pressure vessel. The vessel can be similar to the impregnation vessel according to US application SN 441 767, but, unlike this device, does not need to have a device for handling liquid CO 2. The vessel can be flushed with gaseous C02 or evacuated. It is pressurized with CO 2 to bring the contents to a state where the pressure is greater than 1.7 MPa (250 psia) and the temperature is not less than -23 ° C. The enthalpy is at or above 325,640 kJ / kg (140 BTU / lbm), as indicated by line I-II of the drawing. The enthalpy of the CO 2 is then reduced by cooling to below about 325,640 kJ / kg (140 BTU / lbm) (but under conditions of temperature and pressure that the CO 2 is mainly present as a gas), as indicated by line II-III becomes. The vessel is held for up to 30 minutes under these conditions. The pressure is then rapidly reduced, preferably within 10 to 120 seconds, for example to atmospheric pressure, as indicated by line III-IV.

The impregnated tobacco is then (preferably, but not necessarily directly) transferred to a rapid heating zone or a vessel, such as a heating vessel according to US application SN 441 767, for example an expansion tower, a microwave chamber or the like. The rapid heating causes the tobacco to expand at a temperature at which the tobacco is foldable and elastic. The tobacco can be expanded to about the state of its green leaf without breaking. A significant and useful amount of expansion is obtained.

The temperature at which the impregnated tobacco is kept prior to expansion or rapid heating is largely determined by how long the CO 2 remains in the tobacco in sufficient quantity to cause the desired expansion. If there is little insulation or means to hold the temperature down, the transfer should be quick, in less than a few minutes. An insulated container is preferred for the transfer. Additional cooling can also be provided, for example by applying crushed or powdered dry ice to the impregnated tobacco or by spraying liquid nitrogen on it.

The invention is illustrated in the examples.

example 1

A 0.45 kg sample of commercial, wrapped light tobacco filler with 12.5% by weight OV was placed in an autoclave type pressure vessel and brought to 5.5 MPa gauge pressure with CO 2 gas obtained from a CO 2 feed tank which was kept at a CO 2 pressure of at least slightly above the desired impregnation pressure. The impregnation system temperature was maintained above 30 ° C during the pressure cycle by adding additional heat to the system if necessary to prevent the formation of liquid or solid CO 2 throughout the treatment cycle. After a contact time of 15 minutes, it was found that the pressure and temperature conditions of the CO 2 gas in the impregnation

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Device corresponded to an enthalpy value of about 330.292 kJ / kg of CO 2 gas. The pressure was released by releasing about 30 seconds after the tobacco temperature was 2.2 ° C. The impregnated sample had a weight gain of 2.0% due to the gaseous CO 2 contained therein. The impregnated material was then heated in a tobacco expansion tower with a diameter of 7.5 cm over a period of about 5 minutes by contact with the heated water vapor of 288 ° C and a speed of 42 m / s for a period of about 4 s. The product which left the expansion tower had an OV value of 2.1% by weight. The product was equilibrated under standard conditions of 23.9 ° C and a relative humidity of 60% for about 18 hours. The filling power of the balanced product was measured by the standardized test of the cylinder volume (CV) described later. A value of 74 cm3 / 10 g at 11.2% by weight

Obtained OV. This gave a correct CV (CCV) value at 11 wt.% OV of 76 cm3 / 10 g. An unexpanded control sample was found to have a cylinder volume of 36 cm3 / 10 g. The sample therefore had a 111% increase in filling power after the treatment, measured by the CV method.

Example 2

A number of light tobacco samples were treated as in Example 1 under conditions where gaseous CO 2 and essentially no liquid or solid CO 2 were formed. The OV value of the tobacco feed was varied from 9 to 14.6% by weight. Table I summarizes the conditions of the individual tests and the test results obtained. If no value is specified for a variable in the table, the value is the same as in example 1.

Table I

Filler expansion with gaseous C02

Test No.

1

2nd

3rd

OV value of the tobacco feed

9.0%

10.3%

14.6%

Impregnation pressure, MPa

5.62

5.62

5.62

C02 temperature before draining, ° C

31.7

31.7

32.2

C02 enthalpy before draining, joule / kg

332 618

332 618

332 618

Tobacco temperature after draining, ° C

-20.0

-22.8

+2.8

% C02 retention of tobacco

2.9

2.4

1.5

OV value of the product after expansion,% by weight

1.7

1.8

3.2

CV value of the reordered product

62

94

74

OV value of the reordered product,% by weight

11.6

10.3

11.3

corrected CV value at 11 wt% OV

66

88

76

% Increase in filling power

83

144

111

Example 3

A series of light tobacco samples were prepared as in Example 1 under conditions where gaseous CO 2 and essentially no liquid or solid CO 2 were formed

treated. The hold time was varied. Conditions 40 and the test results obtained are summarized in Table II. If no value is specified for a variable in the table, the value is as in example 1.

Tables

Filler expansion with gaseous C02

Test No.

3rd

4th

5

OV value of the tobacco feed

14.2%

14.4%

15.3%

Impregnation pressure, at MPa

5.62

5.62

5.62

Holding time, min

1

2nd

20th

C02 temperature before draining, ° C

58.9

30.0

35.6

C02 enthalpy before draining, joule / kg

372 160

330 292

334 944

Tobacco temperature after draining, ° C

8.3

-5.6

4.4

% C02 retention of tobacco

2.0

2.6

1.5

OV value of the product after expansion,% by weight

2.2

2.0

3.8

CV value of the reordered product

71.2

74.0

76.2

OV value of the reordered product,% by weight

11.1

11.6

11.6

corrected CV value at 11 wt% OV

72

78

80

% Increase in filling power

100

117

122

Example 4

A series of light tobacco samples were treated as in Example 1 under conditions where it was expected that no liquid or solid CO 2 would be formed.

65 The impregnation pressure was varied. The test results are summarized in Table III. If no value is specified for a variable in the table, the value is as in example 1.

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Table III Filler expansion with gaseous C02

Test No.

6

7

8th

9

10th

11

OV value of the tobacco feed

14.5

13.6

10.3

16.1

13.2

13.3

Impregnation pressure, MPa

2.11

2.81

3.52

4.22

4.92

5.62

Holding time, min

15

15

15

25th

15

15

COz temperature before draining, ° C

-11.7

N / A

20.6

20.6

19.4

53.9

C02 enthalpy before draining,

Joules / kg

332 618

N / A

348,900

337 270

330 292

360 530

Tobacco temperature after draining, ° C

-13.9

N / A

3.3

-5.6

-16.7

20.6

OV value of the product after

Stretch, wt%

2.2

1.9

2.1

2.1

3.4

2.7

CV value of the reordered product

69

66

59

75

74

60

OV value of the reordered product,

% By weight

10.7

11.5

11.7

11.4

11.5

11.6

corrected CV value at OV 11 wt%

66

69

64

79

77

65

% Increase in filling power

83

92

78

119

114

81

Example 5

A 0.45 kg sample of commercial coated light tobacco filler with an OV value of 11.1% by weight was placed in an FS-3 pressure vessel and adjusted to 5.5 MPa with CO 2 gas according to the procedure of Example 1 Overpressure. The temperature of the impregnation system was lowered by circulating a cooling solution through a jacket surrounding the impregnation vessel until the CO 2 gas in the impregnation device was cooled to near saturation. After a contact time of 15 minutes, it was found that the pressure and temperature conditions of the CO 2 gas in the impregnation device corresponded to an enthalpy value of approximately 302 380 kJ / kg of CO 2 gas. Although some condensation of C02 may have taken place within the vessel, the C02 was primarily present as a gas. The pressure was released by releasing 30 seconds after the tobacco temperature was determined to be -37.8 ° C. The impregnated sample had a weight gain of about 3.5% due to CO 2. This impregnated material was then heated as in Example 1. The product emerging from the expansion tower had an OV value of 1.9% by weight. The equilibrated product had a CV value of 90.6 with an OV value of 10.8% by weight. This corresponds to a CCV value of 89 or an increase in filling power of 147% 30 compared to the non-extended control sample (36 cm3 / 10 g).

Example 6

A series of light tobacco samples were treated at three different pressures as in Example 5, under conditions where the CO 2 gas was cooled to near 35 saturation. The conditions and test results are summarized in Table IV. If no value is specified for a variable in the table, the value is as in example 1.

Table IV Filler Expansion with Gaseous C02

Test No.

12

13

14

OV value of the tobacco feed

9.5%

10.8

12.1

Impregnation pressure, MPa

5.62

4.22

3.52

Holding time, min

15

15

20th

C02 temperature before draining, ° C

19.4

7.2

2.2

C02 enthalpy before draining, joule / kg

300 054

323 314

323 314

Tobacco temperature after draining, ° C

-38.9

-27.8

-18.3

% C02 retention of tobacco

3.7

2.6

2.4

OV value of the product after expansion,% by weight

1.3

1.4

1.9

CV value of the reordered product

89

88

71

OV value of the reordered product,% by weight

10.5

10.9

11.9

corrected CV value at 11 wt% OV

85

87

78

% Increase in filling power

136

142

117

Example 7

The procedure of Example 5 was repeated using wrapped Burley tobacco. The equilibrated expanded product was found to have a CV of 92.4 at 10.1 wt% OV or an increase of approximately 100% over the unexpanded control.

Example 8

The procedure of Example 5 was repeated using a tobacco blend as is normally used in cigarette manufacture. The product was found to have a CV of 78.1 at 11.1 wt% OV or an increase of approximately 105% over the unexpanded control.

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Example 9

A 0.45 kg sample of wrapped light tobacco was treated as in Example 1. It was found to have a CCV of 81. This product was mixed with 25% by weight conventional tobacco blend. The cigarettes were smoked. They were found to have a desired taste and aroma. The strength of the tobacco rod was acceptable.

Example 10

A 5.90 kg sample of wrapped light tobacco was treated as in Example 5. The product was found to have a CCV of 78.

Example 11

A 2.27 kg sample of wrapped light tobacco was impregnated as in Example 5. However, it was then heated in a static bed for 5 minutes with steam at 149 ° C. The equilibrated product was found to have a CV of 85.

Example 12

A series of tests was carried out according to the procedure of Example 5. Cylinder volume values of 80, 80, 80, 79, 84, 78, 79, 78 and 79 were obtained.

This results in an average CV value for the 9 examinations of 80 or an increase in the filling power of 121% compared to the untreated control sample.

5 Example 13

A series of three experiments were carried out in accordance with Example 5, with the exception that the tobacco feed was precooled to a temperature just below -20 ° C. before the tobacco was contacted with pressurized CO 2 gas. The CV values of the rearranged product were found to be 92.92 and 87, respectively. This results in an average increase in fill power of 151% compared to the untreated control sample.

15 Example 14

Two series of tests were carried out similarly to Example 1. However, as indicated in Table V, the conditions were with a 10 minute hold period. The tower conditions were as follows: 7.5 cm tower with 316 ° C and 20 100% water vapor. Row # 2 was run under conditions similar to Row # 1.

The results of both series of experiments are summarized in Table V together with the results for a non-extended control sample and a control sample which had been expanded without C02-25 treatment.

Table V

Overpressure, MPa

Row number 1

Row number 2

% By weight

rearranged

CCV

% By weight

rearranged

CCV

OV

CV / OV

OV

CV / OV

control

11.8

36.8 / 12.6

_

_

-

_

Expansion control

-

-

-

1.9

64.6 / 10.9

-

1.76

2.5

72.8 / 10.8

71.2

1.5

73.8 / 10.8

72.3

2.11

2.8

76.3 / 10.8

74.9

1.2

81.4 / 10.7

78.9

2.29

2.6

77.2 / 10.8

75.9

1.2

79.6 / 10.7

77.5

2.46

2.3

78.4 / 11.0

78.4

1.2

77.3 / 11.2

78.5

2.64

2.4

80.6 / 11.1

81.0

1.4

78.7 / 11.1

79.6

2.81

2.6

78.5 / 11.2

79.9

1.4

82.0 / 11.1

85.6

5.62

2.8

92.0 / 11.2

93.3

1.5

97.6 / 11.1

98.0

It can be seen that an excellent expansion was obtained at overpressures of 1.7-5.6 MPa compared to the control samples.

The following comparison tests were also carried out.

Trial 1

The impregnation procedure of Example 11 was repeated, but the impregnated material was only allowed to warm to room temperature and was not subjected to tower expansion. The resulting product showed no increase and possibly even a slight loss in CV compared to the untreated control.

Trial 2

A comparison test with an impregnation with gaseous and liquid CO 2 was carried out in the following way.

1. Liquid C02: 1.36 kg of coated, commercially available light tobacco filler (OV value 12.7% by weight) was impregnated with liquid C02 at 5.62 MPa gauge pressure, cooled to 19.6 ° C. and held for 15 minutes. After that, the excess liquid was drained and the pressure was released. A 23% weight gain was attributed to the COz intake. The material was about 45 clumped together due to the large amount of C02 retained.

2. Gaseous C02: 1.36 kg of coated, commercially available light tobacco filler (OV value 13.3% by weight) were pressurized with gaseous C02 at 5.62 MPa overpressure and 19.6nC for 15 minutes. The pressure was then removed. A 3% weight gain was attributed to the C02 intake. The material was free flowing and easy to handle.

Both samples were treated in a 10.16 cm diameter tobacco expansion tower 55 and the samples were equilibrated. The cylinder volume was measured. The samples using liquid impregnation were found to have a CCV of 79. The comparative sample, which had been impregnated with 60 CO 2 gas, had a CCV value of 82.

Trial 3

A series of experiments was carried out in the impregnation pressure range of 0.141.0.281.0.422, 0.562.0.703.1.41, 2.11.28.1.4.22 and 5.62 MPa, using a contact time of 10 minutes has been. The procedure was as in Example 1, with the expansion in a tower

11

649 198

at a steam temperature of 316 ° C. These samples were treated with an unexpanded control sample and a control sample that had not been contacted with CO 2 under the conditions shown in Table VI. The results obtained are summarized in Table VI.

Table VI

Overpressure, MPa

OV

rearranged

% By weight

CV

OV

CCV

control

13.6

30.8

13.3

33.2

Expansion control

2.9

49.3

12.2

50.1

0.141

2.9

55.7

11.8

57.2

0.281

2.4

54.3

11.9

56.3

0.422

2.0

57.7

11.6

58.2

0.562

2.5

57.7

11.7

58.7

0.703

2.6

55.7

11.7

56.7

1.41

2.3

56.4

11.7

57.4

2.11

2.7

55.0

11.8

56.5

2.81

1.9

65.9

11.5

68.9

4.22

1.8

75.9

11.6

80.7

5.62

1.8

84.4

11.5

88.4

Table VI shows that some expansion is available at lower pressures, but pressures of around 2.81 MPa may be required to obtain the target products. However, it can be seen from Example 14 that an excess pressure of 1.76 MPa can be effective in order to obtain a satisfactory extent of expansion.

The terms "cylinder volume" and "corrected cylinder volume" are units for measuring the degree of expansion of the tobacco. The term «content of im

Oven Volatiles »or« Oven Volatiles »is a unit for measuring the moisture content (or percentage moisture) in tobacco. The specified values are determined as follows.

5

Cylinder volume (CV)

Tobacco fillers with a weight of 10,000 g are placed in a cylinder with a diameter of 3.358 cm and pressed together with a pestle with 1875 g and a diameter of 3.335 cm for 5 minutes. The resulting volume of the filler is given as the cylinder volume. This test is carried out in the standard ambient conditions of 23.9 ° C and a relative humidity of 60%. Unless otherwise stated, the procedure is conventional. The sample is preconditioned in this environment for 18 hours.

Corrected Cylinder Volume (CCV) The CV value can be set to a specific specified content of volatile substances in the furnace to facilitate comparisons.

CV = CV + F (OV — OVs), where OVs is the specified OV value. F is a correction factor (volume%) which is predetermined for the respective type of tobacco filler.

25th

Oven volatile matter content (OV) The tobacco filler sample is weighed before and after 3 hours exposure in a forced air oven at a controlled temperature of 100 ° C. The weight loss as a percentage of the initial weight is the content of volatile substances in the oven.

For the light tobacco used herein, the value of F when calculating CCV averages 7.6 for tobacco expanded with gaseous C02.

35 Unless otherwise stated, all percentages are by weight.

s

3 sheets of drawings

Claims (4)

649198 1. A method of expanding tobacco, in which tobacco is treated under pressure with gaseous CO 2 and then the pressure is reduced, characterized in that the tobacco is exposed to the gas under an excess pressure of at least 1.7 MPa, and the treated tobacco pressure reduction to release the CO 2 contained in the treated tobacco. 2. The method according to claim 1, characterized in that one cools the carbon dioxide gas / tobacco system before the pressure reduction to a temperature which is close to the condensation temperature of the carbon dioxide. 2nd PATENT CLAIMS 3rd 649198 are released and cause the tobacco to expand. Despite the advances described above, no fully satisfactory process has yet been found. In many cases, the proposed expansion treatments for tobacco had the difficulty that the volume was increased only slightly and at best only moderately. Freeze-drying processes, for example, have the disadvantage that they require complex and expensive equipment and are associated with considerable operating costs. The problem with using thermal energy, infrared or radiation microwave energy to expand the tobacco stems is that although the stems respond to these heating processes, the tobacco leaf generally does not respond effectively to this type of process. The use of special expansion agents, for example halogenated hydrocarbons, as mentioned in the Meyer publication on the expansion of tobacco, is also not completely satisfactory, since some of the materials used are not always desired as additives. In addition, the introduction of foreign materials for tobacco in considerable concentration brings with it the problem of removing the expansion agent after the end of treatment, so as to avoid impairment of the aroma properties and other properties of the smoke, which is attributable to external substances that are present in the Incineration of the treated tobacco used or developed. The use of carbonated water has also not proven to be effective. Although the use of ammonia and carbon dioxide gas is an improvement over the methods previously described, it is not entirely satisfactory in certain circumstances because undesirable salt deposition can occur during the process. Carbon dioxide has been used as a coolant in the food industry. More recently, it has also been proposed as an extractant for food flavors. DE-OS 2 142 205 describes its use in gaseous or liquid form for the extraction of aromatic materials from tobacco. In connection with these uses, however, there is no indication of using gaseous carbon dioxide to expand these materials. A process using liquid carbon dioxide has been found to overcome many of the disadvantages of the above known processes. The expansion of tobacco using liquid carbon dioxide is described in BE-PS 821 568, which corresponds to US application SN 441 767. This process can be described as a tobacco expansion process in which (1) the tobacco is contacted with liquid carbon dioxide to impregnate the tobacco with the liquid carbon dioxide, (2) the tobacco impregnated with liquid carbon dioxide is subjected to such conditions, that the liquid carbon dioxide is converted to solid carbon dioxide, and (3) thereafter the tobacco containing solid carbon dioxide is subjected to conditions by which the solid carbon dioxide is vaporized, causing the tobacco to expand. Previous work with gaseous CO 2 at pressures of approximately 689 kPa found that only small amounts of carbon dioxide gas were incorporated into the tobacco and held for a sufficient time that the tobacco could be heated and expanded. Thus, no significant improvement over the prior art was found. It has been assumed that gaseous CO 2 is less effective as an expansion agent than liquid carbon dioxide, which is used in the expansion process according to US application SN 441 767. It has now been found that gaseous carbon dioxide can be introduced into the tobacco in such a way that the gaseous carbon dioxide remains in the tobacco in an amount of 1% by weight or more, thereby forming a product that can be expanded thereon. Unexpectedly good results and benefits can be obtained using gaseous CO 2 in the manner set forth herein. The method of the invention can be described as a method of expanding tobacco to obtain a cylinder volume increase of at least 50%, in which (1) tobacco with gaseous carbon dioxide under an overpressure of at least 1.7 MPa and at a sufficiently high temperature is impregnated so that substantially all of the carbon dioxide is retained in gaseous form, (2) the pressure on the carbon dioxide-impregnated tobacco is reduced, and (3) the impregnated tobacco is heated under conditions effective to release the carbon dioxide therein to cause the tobacco to expand. The invention also relates to an improvement of this method and it has been found that gaseous carbon dioxide can be incorporated into tobacco in such a way that the gaseous carbon dioxide remains in the tobacco in an amount as high as 3% by weight or more, thereby creating a product is formed, which can be extended to this. Surprisingly good results and advantages can be obtained using gaseous CO 2 in the manner given herein. The method according to the invention enables the production of a new tobacco product which contains gaseous carbon dioxide in an amount of at least 1 part by weight per 100 parts by weight of tobacco. The product is converted into extensive tobacco when heated rapidly. The invention further provides an improved method for expanding tobacco, in which carbon dioxide is used as an expansion agent. Tobacco generally with a moisture content of 5 to 35% by weight is placed in a pressure vessel or in a similar delimitable space. Carbon dioxide gas can be passed through the purging vessel. The carbon dioxide pressure is then increased and brought to a value of at least 1.7 MPa, for example up to 7.4 MPa or even higher, preferably 2.7-5.5 MPa overpressure. The tobacco is held under such pressure under conditions where the carbon dioxide is substantially gaseous, for example, Va for 30 minutes to impregnate the tobacco with the carbon dioxide. The pressure is then reduced to, preferably, atmospheric pressure, for example in a period of 1 to 800 s, preferably 10 to 120 s, whereby a product is obtained which comprises tobacco, for example comprising at least 1% by weight of gaseous carbon dioxide, based on the Weight of tobacco. The resulting gaseous carbon dioxide-containing tobacco can then be heated in the same vessel, but is preferably rapidly, preferably within a few minutes, transferred to a separate zone where it is subjected to temperature and pressure conditions, e.g., by rapid heating in a gas to 100 to 370 'C at or near atmospheric pressure for a period of 1 s to 10 min that the tobacco is expanded. According to an improvement, the tobacco / C02 system is used during or after pressurization, for example 5 10th 15 20th 25th 30th 35 40 45 50 55 60 65 649198 3. The method according to claim 1 or 2, characterized in that the pressure is reduced to substantially atmospheric pressure. 4. The method according to any one of the preceding claims, characterized in that the overpressure is 2.7 to 5.5 MPa. 5. The method according to any one of the preceding claims, characterized in that the tobacco is heated to a temperature in the range of 100 to 370 ° C after the pressure reduction. Various methods have been proposed for expanding tobacco. For example, tobacco has already been contacted with a gas of slightly more than atmospheric pressure, and the pressure has subsequently been removed. In this way, the tobacco cells are expanded, increasing the volume of the tobacco being treated. In other methods that have been used or suggested, for example, the tobacco has been treated with various liquids, such as water or a relatively volatile organic liquid, to impregnate the tobacco. The liquid was then stripped off to expand the tobacco. In other methods that have been proposed, for example, the tobacco has been treated with solid materials that decompose when heated to form gases that expand the tobacco. In other methods, for example, the tobacco is treated with liquids containing gas, such as water containing carbon dioxide, under pressure to incorporate the gas into the tobacco. When the tobacco impregnated therewith is heated or the pressure thereon is reduced, the tobacco is expanded. For the expansion of tobacco, further techniques have also been developed in which the tobacco is treated with gases which react with the formation of solid chemical reaction products in the tobacco. These solid reaction products can then be decomposed by heating, thereby producing gases in the tobacco which, when released, cause the tobacco to expand. For example, U.S. Patent 1,789,435 describes a method and apparatus for expanding the volume of tobacco to compensate for the weight loss caused by smoking the tobacco leaf. For this purpose, the smoked and conditioned tobacco is contacted with a gas, which can be air, carbon dioxide or water vapor, under a pressure of approximately 98 kPa. The pressure is then reduced, causing the tobacco to expand. This patent states that this method can increase the volume of the tobacco by about 5 to 15%. A trustee document no. 304 214 by Joachim Böhme from 1943 states that tobacco can be expanded using a high frequency generator. However, there are limits to the degree of expansion that can be obtained without affecting the quality of the tobacco. US Pat. No. 2,596,183 describes a method for increasing the volume of shredded tobacco in which additional water is added to the tobacco in order to cause the tobacco to swell. The moist tobacco is then heated, causing the moisture to evaporate and the resulting moisture vapor to expand the tobacco. U.S. Patent Nos. 3,409,022, 3,409,023, 3,409,027 and 3,409,028 describe various methods of increasing the usefulness of tobacco stems for smoking products, in which the stems are subjected to expansion processes using different types of heat treatment or microwave energy. U.S. Patent 3,425,425 relates to the use of carbohydrates to improve the tensile properties of tobacco stems. In this process, the tobacco stems are soaked in an aqueous solution of carbohydrates and then heated to fizzle out the stems. The carbohydrate solution can also contain organic acids and / or certain salts which are used to improve the aroma and smoking properties of the stems. In a publication in “Tobacco Reporter” from November 1969 by P.S. Meyer describes tobacco traction or expansion properties or studies on the expansion and manipulation of tobacco to reduce costs. Furthermore, the tar content should be reduced by reducing the smoke supply. This publication also describes the puffing of tobacco by various methods, for example using halogenated hydrocarbons, low pressure or vacuum operation or a high pressure water vapor treatment which causes the leaf to expand from the inside of the cell if the external pressure is suddenly removed. This publication also mentions the freeze-drying of tobacco, which can also be used to obtain an increase in volume. Since the appearance of this article in "Tobacco Reporter", a number of tobacco expansion techniques, including some of the above techniques, have been described in the patent literature. For example, U.S. Patents 3,524,452 and 3,524,451 relate to the expansion of tobacco using an organic volatile liquid, such as a halogenated hydrocarbon. U.S. Patent No. 3,734,104 relates to a particular method of expanding tobacco stems. US Pat. No. 3,710,802 and GB Pat. No. 1,293,735 both relate to freeze-drying methods for expanding tobacco. ZA-PS 70/8291 and 70/8292 relate to tobacco expansion, in which chemical compounds that decompose to form a gas or inert solutions of a gas under pressure are used to keep the gas in solution until it impregnated the tobacco. U.S. Patent 3,771,533 relates to the treatment of tobacco with carbon dioxide and ammonia gas. The tobacco is saturated with these gases and ammonium carbonate is formed in situ. The ammonium carbonate is then decomposed by heat, causing the gases in the tobacco cells 5 10th 15 20th 25th 30th 35 40 45 50 55 60 65 4th cooled by circulating a coolant through the jacket of the chamber to a temperature close to the saturation temperature of the carbon dioxide, but not lower than - 23 ° C. As an alternative to using a cooling jacket in the improved process, CO 2 gas can be flowed through the system by venting a portion of the CO 2 gas either during or after pressurization, preferably while maintaining the COa gas feed, that there is no loss in system pressure due to deflation. When cooling, the resulting conditions are such that the carbon dioxide remains essentially in the gaseous state at the prevailing temperature and pressure. However, they are still sized so that after a rapid decrease in pressure on the system, the carbon dioxide is partially converted to a condensed state within the tobacco. Such conditions can be defined such that the enthalpy of carbon dioxide is maintained at a value that is less than about 325.640 kJ / kg. This leaves a significantly larger residue of carbon dioxide in the tobacco at the beginning of the expansion stage than is the case without cooling before the pressure is removed, the carbon dioxide with a higher enthalpy remaining primarily in the gas phase. Another method of reducing the enthalpy of the system, which results in increased retention of carbon dioxide, involves the addition of additional amounts of CO 2 gas during the purge, which results in an additional purge of CO 2 gas that flows through the system , is effected. If desired, the retention of carbon dioxide in the tobacco can be increased by pre-cooling or pre-freezing the tobacco prior to the impregnation cycle to effect a reduction in system enthalpy. Another method for increasing the retention of carbon dioxide in the tobacco is to "pre-snow" the tobacco with finely divided solid carbon dioxide (dry ice) before the impregnation cycle, which both pre-cools the tobacco and provides a further source for the supply of carbon dioxide to the tobacco is obtained. If the correct amounts of 5 to 50% by weight based on the tobacco are used, then at least part of the dry ice is incorporated into the tobacco during the pressurization cycle. By varying the amount of dry ice supplied, the amount of carbon dioxide retained in the tobacco can be increased and controlled. When using such methods, the tobacco / CO 2 system Va can be held for up to 30 minutes during the impregnation stage, where the excess pressure is at least 1.7 MPa, in order to impregnate the tobacco with carbon dioxide. The pressure is then reduced to atmospheric pressure over a period of 1 to 800 s, preferably 10 to 120 s, and preferably, but not necessarily. The tobacco is then rapidly transferred to a zone where it can cope with such temperature and pressure conditions, for example by rapid heating in a gas to 100 to 370 ° C. and at atmospheric pressure or close to it, over a period of 1 s to 10 min. is suspended that the tobacco is expanded.