FI64046C - FOERFARANDE FOER EXPANDERING AV TOBAK - Google Patents

Description

f fH /.1 Γη! ,,,, ANNOUNCEMENT c A Γ \ λ £ ^ 11 ^ UTLÄGG NI NGSSKRI FT 6404 6? | §S cm 13 10 13: 3 ^ v ^ (51) Kv.ik. ^ int.ci. ^ A 24 B 3 / 18 FINLAND - FINLAND (21) p * tenttlh * kemu * - P * enttn * «knlng 782U17 (22) Htktmlspllvi - Ansöknlngsdag 07-08. 78 (FI) (23) Initial cloud - GiltlghcUdag 07-08.78 (41) Became public - Blivlt offentllg 09-02. 79

National Board of Patents and Registration (44) Date of issue and date of issue. - 30.06.83

Patents and Registration of Ancient Utilities and Utilities Published (32) (33) (31) Claim Requested — Begird prlorltet 08. 08.77 USA (US) 822793 (71) Philip Morris Incorporated, 100 Park Avenue, New York, New York 10017, USA (US) (72) Larry M. Sykes, Richmond, Virginia, Ray G. Snow, Richmond, Virginia,

Patrick Earle Aument, Richmond, Virginia, Roger Zygmunt de la Burde,

The present invention relates to a method for expanding tobacco. Various methods have been proposed for expanding tobacco. For example, tobacco has been contacted with a gas in a somewhat atmospheric atmosphere. Powhatan, Virginia, USA (US) (7 * 0 Method for expanding tobacco Other methods that have been used or proposed have involved treating the tobacco with various liquids, such as water or relatively volatile organic liquids, to saturate the tobacco, followed by removal of the liquids. Other proposed methods have involved treating the tobacco with solids which, when heated, decompose to produce gases that swell the tobacco.Other methods include treating the tobacco with gaseous esters such as carbon dioxide. with oxide-containing water, under pressure to introduce gas into the tobacco, and when the tobacco impregnated therein is removed or the pressure on the tobacco is reduced, the tobacco expands. Further methods for expanding tobacco have been developed in which tobacco is treated with gases that react to form solid chemical reaction products within the tobacco. The solid reaction products decompose under the influence of heat, forming gases in the tobacco which, when released, cause the tobacco to swell.

U.S. Patent No. 1,789,435 describes a method and apparatus for increasing the volume of tobacco to compensate for the loss of volume caused by drying a tobacco leaf. To achieve this goal, the dried and air-conditioned tobacco is contacted with a gas, which may be air, carbon dioxide, or steam, at a pressure of about 1.4 atm, and then the pressure is reduced, whereby the tobacco tends to swell. The publication states that the volume of tobacco can be increased by about 5-15% by this method.

It is also known that tobacco can be expanded using a high frequency generator, but that the degree of expansion that can be achieved without affecting the quality of the tobacco has limitations.

U.S. Patent No. 2,596,183 discloses a method of increasing the volume of cut tobacco by adding water to the tobacco to make it swell and then heating the tobacco containing moisture, whereby the moisture evaporates and the moist steam generated causes the tobacco to swell.

U.S. Patent Nos. 3,409,022, 3,409,023, 3,409,027 and 3,409,028 disclose various methods for improving the utilization of tobacco stalks for use in tobacco products by subjecting the stalks to expansion processes using various types of heat treatments or microwave energy.

U.S. Patent 3,425,425 describes the use of carbohydrates to improve the fluffing of tobacco stems. In this method, tobacco stems are dissolved in an aqueous solution of carbohydrates and then heated to fluff the stems. The carbohydrate solution may also contain organic acids and / or certain salts which are used to improve the taste and burning properties of the stalks.

The "Tobacco Reporter", November 1969, (P.S.Meyer) describes and outlines methods for expanding or expanding tobacco and studies related to expanding and handling tobacco to reduce costs and 3,64046 to find ways to reduce the "tar" content of smoke. The publication mentions various methods for fluffing tobacco, e.g. using halogenated hydrocarbons, low pressure or working under vacuum, or treatment with high pressure steam, which causes the leaf to swell from inside the cell when the external pressure suddenly decreases. This publication also mentions freeze-drying of tobacco, which can also be used to increase volume.

Numerous methods of expanding tobacco, including a few e.m. described in the publication, disclosed in the patent publication and patent applications. For example, U.S. Patent Nos. 3,524,452 and 3,524,451 describe the expansion of tobacco using a volatile organic liquid such as a halogenated hydrocarbon.

U.S. Patent No. 3,734,104 relates to a special method for expanding tobacco stems.

U.S. Patent 3,710,802 and GB Patent 1,293,735 describe freeze-drying methods for expanding tobacco.

South African Patents ZA 70/8291 and ZA 70/8292 deal with the expansion of tobacco by using chemical compounds which, when decomposed, form gases, or by using inert solutions of the gas under pressure to keep the gas in solution until it saturates the tobacco.

U.S. Patent No. 3,771,533 relates to the treatment of tobacco with carbon dioxide and ammonia gas, whereby the tobacco is saturated with these gases and ammonium carbonate is formed in situ. The ammonium carbonate is then decomposed by heating, releasing gases inside the tobacco cells which cause the tobacco to swell.

Despite all the advances described in the art above, a completely satisfactory method has not been invented. The difficulty with various previous proposals to inflate tobacco is that in many cases, the volume has increased only slightly or, at best, only moderately. The disadvantage of freeze-drying processes, for example, is that they require particularly fine and expensive equipment and considerable operating costs. With respect to the use of thermal energy, infrared, or radiation microwave energy to expand tobacco stalks, the difficulty is that while the stalks react to these heating processes, the tobacco leaf has generally not been found to respond effectively to this type of process.

4,64046

The use of special blowing agents, for example halogenated hydrocarbons, to expand the tobacco is also not entirely satisfactory, since the substances generally have to be evaporated or otherwise removed after the tobacco has been expanded. In addition, the introduction of a significant amount of foreign substances into the tobacco introduces a problem of removing the blowing agent after the treatment is completed. These foreign substances that are released when the tobacco burns must be removed so that they do not affect the a-rum or other properties of the smoke.

The use of carbonated water has also not been found to be effective.

The process using ammonia and carbon dioxide gases is an improvement over previous processes, but is not entirely satisfactory under all conditions, as undesired precipitation of salts can occur during the process.

Carbon dioxide has been used in the food industry as a refrigerant and has recently been proposed as an extractant for food flavors. DE-A-2 142 205 discloses it for use in either gaseous or liquid form for the extraction of aromatic substances from tobacco. However, in the context of these uses, the use of liquid carbon dioxide to swell these substances has not been proposed.

It has been found that by using liquid carbon dioxide, many of the disadvantages of the prior art mentioned above can be avoided. The expansion of tobacco using liquid carbon dioxide is described in FI patent publication 58048 and BE patent publication 825 133 Airco. Said method of expanding tobacco comprises the steps of (1) contacting the tobacco with liquid carbon dioxide to impregnate the tobacco with liquid carbon dioxide, (2) subjecting the tobacco impregnated with liquid carbon dioxide to conditions in which the liquid carbon dioxide is converted to solid carbon dioxide and (3) conditions in which solid carbon dioxide evaporates, causing the tobacco to swell.

The present invention represents significant improvements to this basic process.

The present invention relates to a method of expanding tobacco, wherein the tobacco is impregnated with liquid carbon dioxide under conditions in which substantially all of the carbon dioxide remains in liquid form, (2) the liquid carbon impregnated conditions in which solid carbon dioxide evaporates, causing the tobacco to swell and the resulting expanded tobacco to have a moisture content of no more than about 6%. The process according to the invention is characterized in that in step (1) tobacco is used which has an initial OV content (content of volatile substances in the oven) of about 17 to 25% and that the first step is carried out at a pressure of about 18 to 37 atm.

In the method according to the invention, it is possible to process either whole dried tobacco leaves, tobacco in cut or shredded form or selected parts of tobacco such as tobacco stalks or optionally reconstituted tobacco. The particle size of the tobacco to be impregnated in the comminuted form may correspond to a screen number of about 20-100 "mesh" (0.84-0.15 mm) but preferably not less than about 30 "mesh" (0.55 mm).

The tobacco used in the first stage should have a moisture content of about 17-25%, depending on the pressure used. The moisture content of tobacco can be referred to as "input moisture" or "input OV" and is approximately equal to the amount of volatiles (OV) in the oven, since generally no more than 0.9% by weight of tobacco contains volatiles other than water. It has now been found that by using said input OV concentration, the first step of the process can advantageously be carried out at pressures lower than what has hitherto been considered optimal. It has been found that the following input OV values are preferred for the following pressures: at 21 atm the input OV is between about 18-25%, at 28 atm the input OV is between about 17-25%, at 32 atm the input OV between about 17 and 25%, at 35 atm the input OV is between about 16 and 23%,

In order to increase the moisture content of the tobacco to the desired inlet moisture value, the tobacco can, for example, be sprayed with water or brought into contact with steam until the desired concentration is reached. Preferably this is done by spraying water. To reduce the moisture content of the tobacco to a desired value, the tobacco may be heated, preferably by indirect steam heating, until the desired concentration is reached.

By using the method according to the invention, the desired expansion can be achieved at lower pressures than previously found necessary to achieve the corresponding expansion. For example, it was previously considered that the process should be performed at a pressure of at least about 35 atm to obtain a product with a cylinder volume (CV) approaching about 70, which is clearly a commercially desirable expansion value. It has now surprisingly been found that a cylinder volume 68 can be obtained at a pressure of 21 atm, with an inlet OV of about 20% and an outlet OV of less than about 6%.

The terms "cylinder capacity" and "corrected cylinder volume" are units for measuring the degree of expansion of tobacco. The term "oven volatiles" (OV) is a unit for measuring the moisture content (or percentage of moisture) of tobacco. The terms are defined as follows:

Cylinder capacity (CV)

A tobacco filler weighing 10,000 g is placed in a 3.358 cm diameter cylinder and compressed with a piston weighing 1875 g and a diameter of 3,335 cm for 5 minutes. The volume of filler obtained is expressed as cylinder volume. This test is performed under normal ambient conditions at a temperature of 24 ° C and a relative humidity of 60%. Unless otherwise indicated, the sample is usually preconditioned in this environment for 18 hours.

Corrected Cylinder Volume (CCV) The CV value can be determined for a given furnace volatile matter concentration to facilitate comparisons.

CCV = CV + F (OV - OV), where OV is the determined OV and F is the S s correction factor (v / v) predetermined for the type of tobacco filler in question.

Volatile matter content (OV) in the oven

A sample of the tobacco filler is weighed before being placed in a convection oven set at 100 ° C and for 3 hours thereafter. Weight loss as a percentage of the initial weight is the concentration of volatile substances.

The expanded light tobacco used in the present invention has an F value for calculating the CCV of 7.4.

Tobacco having the desired inlet moisture is generally placed in a pressure vessel in such a way that it can be suitably immersed in or contacted with liquid carbon dioxide. For example, a metal mesh cage or a pallet can be used.

7 64046

The pressure vessel containing the tobacco can be cleaned with carbon dioxide gas, vacuum or other inert gas, the cleaning delivery usually taking about 1 to 4 minutes. The cleaning step can be omitted without damaging the final product. The advantage of purification is that in this way the gases that could interfere with the carbon capture process and the removal of all foreign gases from the tobacco that could interfere with the complete penetration of the liquid carbon dioxide are removed.

The liquid carbon dioxide used in the process of this invention can be obtained from a storage tank in which it is generally stored at a pressure of about 18 to 22 atm. Liquid carbon dioxide can be introduced into the pressure vessel at a pressure of 18 to 28 atm or 18 to 37 atm. At the time the liquid carbon dioxide is introduced into the pressure vessel, the interior of the vessel, including the tobacco to be treated, should preferably be at a pressure at least sufficient to keep the carbon dioxide in the liquid state.

The liquid carbon dioxide is introduced into the container in such a way as to allow complete contact with the tobacco, and the liquid carbon dioxide should preferably be used sufficiently to completely saturate the tobacco. In general, this means using about 1 to 10 parts by weight of liquid carbon dioxide per 1 part by weight of tobacco. The use of excess liquid carbon dioxide is uneconomical, but it will work. The temperature of the liquid carbon dioxide should preferably not exceed about 31 ° C during this impregnation step.

If necessary, the vessel can be heated, for example, with heating coils.

Tobacco and liquid carbon dioxide can be kept in contact with each other under these conditions for about 0.1 to 30 minutes.

After impregnating the tobacco with liquid carbon dioxide, generally after a total of about 0.1 to 30 minutes, and preferably after about 0.2 to 1 minute, any excess liquid carbon dioxide that may be present is drained from the container, preferably maintaining temperature and weight. conditions the same as during the contacting phase.

In the drain, the liquid is removed from the tobacco mass, for example through an outlet at the bottom of the chamber, while maintaining the pressure in the container. It has been found that unexpected benefits are achieved by using a post-flow period of at least 2 minutes after the continuous flow of liquid carbon dioxide drainage from the vessel has ceased 8,64046. Previously, the process was adjusted at this stage so that the amount of liquid carbon dioxide was monitored through a control glass connected to the impregnation vessel. After liquid CC> 2 was removed, the runoff was stopped at a stage where no more liquid was detected, i. when there was no longer a continuous flow of liquid CO2. A short check for additional fluid, immediately after stopping the flow, was sometimes used. According to the present invention, a post-drainage period is used, comprising waiting for at least two minutes and preferably waiting for at least about 3 minutes and then draining the liquid repeatedly until the continuous flow of liquid ceases a second time. The second flow of liquid usually takes less than a minute. The purpose of such a post-drainage period is to ensure that excess liquid is removed from the surface of the tobacco. To facilitate the post-drainage step, CO2 or other gas may be passed down through the pulp. It has been found that the after-effect period results in substantially complete removal of the liquid and results in: (1) more complete recovery of CO2 mainly as a liquid and not as a gas requiring condensation during the recovery step; on the surfaces of variable tobacco to a solid that binds the tobacco to clumps, which make it difficult to process and which must be broken down to form a "fine fraction" of tobacco, and (3) a reduction in heat load in the expansion equipment because inefficient solid CO2 does not have to evaporate from the surface.

The post-drainage period should be at least about 2 minutes, but is preferably about 2.5-6 minutes, with longer times providing some additional benefit. The time depends to a considerable extent on the shape and size of the containers.

After impregnation, draining and post-draining, the gas pressure is reduced quickly enough so that at least part of the carbon dioxide in the tobacco is converted to a solid.

The pressure in the vessel is reduced by releasing the gases to bring the contents of the vessel to atmospheric pressure. This emptying usually takes about 0.75 to 15 minutes, depending on the size of the container, but preferably it should not take longer than 3 minutes; after which the temperature in the container is generally about -85 to 95 ° C and the liquid carbon dioxide in the tobacco is partially converted to solid carbon dioxide. Reducing the pressure at atmospheric pressure is not necessary but reducing it to a pressure below about 5 atm is sufficient. Apparently, this is not as economically advantageous as lowering to atmospheric pressure.

The drainage and post-drainage should preferably be such that the tobacco contains about 6-25% by weight of solid CCl 2 and most preferably about 10-20% by weight of solid CCl 2.

After the carbon dioxide in the tobacco has been converted to its solid form, the tobacco containing the solid carbon dioxide is subjected to expansion conditions, whereby a heating or similar treatment is performed to vaporize and remove the solid carbon dioxide from the tobacco. Heating surfaces or hot air flow, a mixture of gas and steam or exposure to other energy sources, such as radiation microwave energy or infrared radiation, can be used for this. A suitable way to inflate solid carbon dioxide tobacco is to place it in a heated gas stream, such as superheated steam, or to carry it in a turbulent air stream maintained, for example, at a temperature as low as about 100 ° C and as high as 370 ° C and preferably about 150 to 260 ° C for about 0.2 to 10 seconds. Impregnated tobacco can also be heated by placing it on a moving belt and subjecting it to infrared heating, contacting it in a cyclone dryer, contacting the dispersion in the dryer with superheated steam or a mixture of steam and air, etc. None of these contacting steps should C and preferably the temperature should be about 100 to 300 ° C, most preferably 150 to 260 ° C when the contacting takes place at atmospheric pressure.

As is well known in the handling of organic material, overheating may cause damage, first to color, such as excessive darkening, and finally to charring. The temperature and exposure time required for swelling and sufficient without such damage is a function of these two variables as well as the condition of the tobacco comminution. Thus, to avoid unwanted damage during the heating step, impregnated tobacco should not be exposed to higher temperatures, e.g., 370 ° C, for more than a few tenths of a second.

Irradiation methods described in U.S. Patent Nos. 3,409,022 and 3,409,027 can be used to effect expansion of tobacco cells. A heat pump such as a Dayton heat pump or the like with an exhaust air temperature of 190-344 ° C can also be used. The pump is operated for about 0.2 s to 4 min. In this process, the tobacco never reaches a temperature above about 140 ° C because it cools under the influence of rapidly evolving gases. The presence of steam during heating promotes optimal results.

Another system involves the use of a dispersion dryer, for example one to which either steam alone or steam is fed together with air. An example of such a dryer is the Proctor & Schwartz PB dispersion dryer. The temperature in the dryer may be about 121 to 371 ° C, with the contact time in the dryer being about 4 minutes at the lowest temperature and about 0.1 to 0.2 seconds at the highest temperature. Generally, a contact sheet of 0.1 to 0.2 seconds is used when the hot gas temperature is 260 to 315 ° C or somewhat higher. As noted above, other types of heating devices can be used as long as they are capable of causing the impregnated tobacco to swell without excessive darkening. It should be noted that when a high percentage of oxygen is present in the hot gases, it promotes darkening, so that if a hot steam mixture is used, a large amount of steam (e.g. more than 80% by volume) is preferred. A vapor atmosphere that makes up at least 20% of the total hot gas combination helps to get the best expansion.

The flow or removal moisture of the product obtained from the heating step should be at most 6% and most preferably at most 3.0%, determined as OV.

It is important that the flow-OV content of the product leaving the heating / expansion step does not exceed 6%. The result of this relatively dry state is a permanent optimum expansion after equilibration to standard humidity conditions. Such a flow OV can be achieved by a suitable balance between the impregnated tobacco feed rate dryer and the drying gas temperature, which requires a constant gas flow. Flow rate is another variable to consider. The flow OV can also be reduced as desired by further processing the product, for example in a dryer.

After the tobacco is recovered from the heating / swelling step by the desired flow OV, it is generally equilibrated (rearranged) under conditions that are well known. The equilibration is preferably performed under standard conditions, which generally involve keeping the tobacco at 24 ° C and 60% RH (relative humidity) for at least 18 hours.

11,64046 This can be done in different types of devices, such as those described in BE patents 821,568 and 825,133.

It is important that a device in which liquid carbon dioxide-containing tobacco is converted to solid carbon dioxide-containing tobacco be able to contain the gases at the elevated pressures available. There can be numerous arrangements in the pressure vessel.

It should preferably have a valve inlet connected to a source of liquid carbon dioxide and a valve outlet at the bottom of the vessel from which the liquid can be drained. A second outlet with a valve can be added near the top for degassing and an o-Saxon inlet line, if desired, placed between the vessel and the inlet valve can be installed. A device for heating the vessel and / or the feed vessel, such as external heating coils, can be used. Placing the vessel on a load measuring platform simplifies the measurement of the carbon dioxide supply. An additional vessel, similarly equipped with a weighing device and heating coils, is preferred, although not necessary, because it allows the liquid carbon dioxide feed to be preheated from its usual low storage temperature of -20 ° C (at about 16 atm). In operation, the filler can be placed in a suitable holder for the main pressure vessel, such as a metal wire basket suspended above the bottom of the vessel. The sealed container can then be cleaned with carbon dioxide gas and the outlets closed, the liquid carbon dioxide being then discharged from storage, for example at 18 atm, in an amount sufficient to cover all the tobacco in the container. The temperature is raised by a heating device, e.g. heating coils, to bring the tobacco to the desired temperature, which should be below 31 ° C (critical temperature of carbon dioxide) and this state is preferably maintained for 1-20 minutes when saturation occurs. Excess liquid carbon dioxide is then drained off by opening the lower outlet of the vessel to a suitable container or similar discharge system, and when all excess liquid has been removed from the vessel, the vessel is brought to atmospheric pressure by venting the gases. The tobacco is then subjected to a solid carbon dioxide evaporation process, preferably by removing the solid carbon dioxide-containing tobacco from the container and passing it through a rapid heating system to effect expansion. The best systems for the expansion process are those that provide rapid, turbulent contact with hot gas or steam. With appropriate control of temperature and processing time, the product can be recovered in an expanded state at the desired moisture content.

12 64046

The following examples illustrate the invention.

Example 1 45.4 kg of light cigarette particles of cigarette filling size and OV content of 20% were placed in a metal wire basket in a pressure vessel. The vessel was closed except for the opening for the introduction of CX 2 gas. The gas was introduced to a pressure of 28 atm and the orifice was closed. The vessel was then filled with liquid CO 2 at 28 atm and -7 ° C enough to cover the tobacco mass. The system was held under these conditions for 30 seconds, then the bottom port was opened to allow liquid to be pumped out. The orifice was closed and after 3 minutes it was reopened to allow the accumulated liquid to escape. This opening was closed and the vessel was opened to the atmosphere through a valve at the upper end so that the pressure escaped within 180 seconds. When the top end was removed from the container and weighed, it was found that 8.2 kg of CCl 2 remained in the tobacco. The product was not difficult to separate and could be fed at a controlled rate to the next step. A similar batch without the drainage period retained 14.3 kg of CC> 2 and was a bad lump.

For expansion, a 20.3 cm diameter vertical dryer was used, fed at a speed of 38.1 m / s from 85% superheated steam in air at 249 ° C. The product from the CCl 4 treatment was fed at a rate of 1.68 kg / min to a dryer where the contact time with steam was estimated to be 3 seconds. The OV content of the product collected in the cyclone separator when cooled was 1.8%. Its equilibrium cylinder volume, corrected to 11% OV, was 74.0 cm / 10 g compared to 3 initial CVs of 34.0 cm / 10 g for the untreated light filler at its standard moisture content of 12.5% OV.

Example 2 45.4 kg batches of light tobacco similar to that used in the previous example and having the same yield moisture content were treated as above with a vessel emptying time of 177-190 seconds, except that a 3 minute drain period was omitted and except for variations in the expansion process and conditions. The result was a variable flow OV content and product filling capacity, as measured by CCV. The results and conditions of these experiments, in duplicate, are compared in Table 1. The expansion occurred by exposing the tower to 81-88% of the steam for about 3 seconds. It is found that the optimum filling capacity is achieved at a low 0V for the product leaving the expansion step, and that an OV of less than 6.0% is desirable and less than 2.5% is most desirable.

i3 64046

Table 1 3

Feed to the tower Temperature tor- Flow-OV,% CCV, cm / 10 g

kg / min at n ° ° C

2.50 149 12.0.12.2 59.4, 65.6 2.27 177 8.5, 7.8 65.0, 67.8 1.93 204 4.5, 4.8 67.8 , 69.2 1.42 249 1.8, 2.5 69.5, 75.4

Example 3

Light tobacco weighing 45.4 kg and having 20% OV was prepared for immersion as in Example 1. Liquid carbon dioxide was introduced into a chamber previously pressurized to 21 atm under the same pressure until the tobacco was covered and held for 30 seconds. ; the temperature was about -16.7 ° C. The liquid was pumped out through the bottom valve and a five minute sweep of CCl 2 gas from the top of the vessel to the bottom helped to remove the non-draining CC 2 liquid. The vessel was degassed to atmosphere in 152 seconds and the cooled product was removed.

This product was not lumpy and was introduced into an expansion tower flowing with an 85% steam flow at 38.1 m / s at 249 ° C with a total mass flow of 1.95 kg / min. The exposure time was estimated to be 3 seconds. The product contained 2.1% OV and, after equilibration to 12.0% OV, its cylinder volume, corrected to 11.0% OV, was 68.0 cm -1 / 10 g. The CCV of the starting filler was 37.3 cm -1 / 10 g with 12.5% OV.

Example 4 45.4 kg batches of light tobacco with varying OV content were treated by the method described in Example 1 (impregnation, dewatering, drainage, depressurization and expansion in the tower), changing only the temperature of the tower gas from 232 ° C to 254 ° C. ° C to compensate for increasing OV concentrations in the feed. The flow OV of all samples was between 1.3% and 2.8% OV. After re-conditioning, the CV of all samples was checked and corrected to 11.0% OV. The results shown in Table 2 show that the moisture (OV) required to achieve the best expansion, in this series at least 68 cm / 10 g CCV, is at least 17%.

14 64046

Table 2

Cylinder volume as a function of inlet humidity at 28 atm saturation

Product filling capacity

Input OV% Balanced CCV, 11% 0V

___ CV, cin / 10 g_cm3 / 10 g_ 10.1 44.5 50.6 10.6 52.5 · 55.0 10.9, 10.9 47.9, 48.5 53.1, 52.6 11.7 59.6 62.3 15.5 60.7 66.5 16.0, 16.0 59.6, 60.4 64.6, 67.0 17.1, 17.0 61.0, 62.2 69.1, 69.0 17.4, 17.5 62.2, 58.6 68.7, 67.9 17.7, 17.9 68.7, 64.6 72.9, 68.2 18.0, 18.4 62.0, 67.1 70.9, 72.5 19.0, 19.1 60.9, 63.2 68.3, 70.1 18.0, 18.3 69.2, 60.8 74.4, 68.1 19.4, 19.5 60.9, , 56.9 72.6, 69.4 19.7, 20.6 63.0, 68.9 73.8, 73.4 21.9, 21.9 68.2, 71.4 73.0, 76.5 23.0 59.1 68.6 23.5, 23.5 63.9, 66.3 70.7, 71.0 23.9, 24.2 58.6, 58.9 68.4, 68.6 25.7 '58.6 68.4

Example 5

Batches of light filler tobacco were then impregnated and then expanded in exactly the same manner as described in Example 1, except that the draining time (from opening to reopening) was varied as shown in the tables. The number of the first batches (Table 3) was 45.4 kg and their depth in the impregnator was 91 cm; the second group (Table 4) weighed 8 4 kq and had a depth of 1.52 m. The OV at the outlet of the expansion tower was about 2% in each experiment. The cylinder volume of the products was measured and also screened to compare size reduction. The three-minute purge was the same as the 3-minute runoff time, except that CC> 2 gas was blown downward as a purge gas through the impregnated tobacco.

15 64046

The results are summarized in Tables 3 and 4. As a size distribution that approximates the distribution of the comparison is desirable and generally aims at a sum of "small particles" and "fine fraction" (S + F) of no more than 2%, it is observed that two minutes or longer drain times gave the best results. There was little or no effect on the corrected CV.

Table 3

Effect of draining time on sieve fractions 45, U kg. items

Screen fractions,%

Drain time Long Medium Short Small Fine L + M S + F OCV minutes long cm / 10 g

(L) (M) (S) (F) 11% 0V

unexpanded 55.5 35.9 .7.0 0.9 0.6 91.4 1.5 comparison 0 38.2 50.0 9.2 1.2 1.2 88.2 2.4 74.6 1 41.9 47.7 8.1 1.2 1.2 89.6 2.4 73.7 2 43.7 47.0 7.3 1.0 0.9 90.7 1.9 76.3 3 42.2 49.2 6.8 0.7 1.0 91.4 1.7 74.2 .. 42.7 48.5 6.9 1.0 1.0 91.2 2.0 75.0 3 minutes ηδ. / Cleaning 64046] 6

Table 4 Effect of residence time on sieve fractions in 84 kg batches

Screen fractions,%

Central CCV

Exposure time Long long Short Small Fine L + -M S + F 3 .. minutes (L) (M) _ (S) (F) __ 001 / 1Q 9

Comparison 52.0 38.9 7.5. 1.1 0.5 90.9 1.6

V

o 38.3 48.5 10.0 2.0 1.3 86.8 3.3 74.4 3 44.5 45.7 7.7 1.2 0.9 90.2 2.1 76.6 6 44.1 46.1 7.7 1.2 0.9 90.2 2.1 76.8

The different sieve fractions used in the previous example are defined as follows: long = +10 (i.e., the particles remain on the 10 "mesh" sieve); medium = -10- + 20; short = -20 to +30; low = -30 to +50; and fine = -50.

Claims (3)

17,64046 Claim A method of expanding tobacco, comprising (1) impregnating the tobacco with liquid carbon dioxide under conditions in which substantially all of the carbon dioxide remains in liquid form, (2) subjecting the tobacco impregnated with liquid carbon dioxide to conditions in which liquid carbon dioxide is converted to solid carbon dioxide and (3) solid carbon dioxide , in which solid carbon dioxide evaporates, causing the tobacco to swell and the resulting expanded tobacco to have a moisture content of not more than about 6%, characterized in that tobacco with an initial OV content (oven volatiles content) of about 17-25% is used in step (1), and that the first step is performed at a pressure of about 18 to 37 atm. A method according to claim 1, characterized in that the excess liquid carbon dioxide is drained from the impregnated tobacco obtained in step (1), keeping the carbon dioxide in liquid form, the liquid carbon dioxide is drained from the tobacco until the continuous liquid flow ceases and waits at least 2 minutes before step (2). to remove more liquid carbon dioxide from tobacco · Method according to claim 1 or 2, characterized in that the first step is carried out at a pressure of about 25 to 32 atm.