CA1115164A - Tobacco product and improved process for the expansion of tobacco - Google Patents
Tobacco product and improved process for the expansion of tobaccoInfo
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- CA1115164A CA1115164A CA362,247A CA362247A CA1115164A CA 1115164 A CA1115164 A CA 1115164A CA 362247 A CA362247 A CA 362247A CA 1115164 A CA1115164 A CA 1115164A
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- tobacco
- carbon dioxide
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- expansion
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Abstract
NOVEL TOBACCO PRODUCT AND IMPROVED PROCESS
FOR THE EXPANSION OF TOBACCO
Abstract of the Disclosure A novel tobacco product comprising tobacco containing gaseous carbon dioxide in an amount of at least 1 part of gaseous carbon dioxide per 100 parts of tobacco. The product when heated rapidly is converted to expanded tobacco. An im-proved process for the expansion of tobacco is also provided, which employs carbon dioxide as the expansion agent in a sequence of steps comprising: (1) contacting tobacco with carbon dioxide gas at a pressure of at least 250 psig for a time sufficient to impregnate the tobacco with the carbon dioxide gas to form a gaseous carbon dioxide-tobacco system (2) releasing the pressure and (3) thereafter subjecting the carbon dioxide-treated tobacco to rapid heating conditions to remove the carbon dioxide and thereby expand the tobacco, The improvement in the above-described process comprising cooling the gaseous carbon dioxide and tobacco system in step (1) to a temperature close to the saturation temperature of carbon dioxide but not lower than -23°C.
FOR THE EXPANSION OF TOBACCO
Abstract of the Disclosure A novel tobacco product comprising tobacco containing gaseous carbon dioxide in an amount of at least 1 part of gaseous carbon dioxide per 100 parts of tobacco. The product when heated rapidly is converted to expanded tobacco. An im-proved process for the expansion of tobacco is also provided, which employs carbon dioxide as the expansion agent in a sequence of steps comprising: (1) contacting tobacco with carbon dioxide gas at a pressure of at least 250 psig for a time sufficient to impregnate the tobacco with the carbon dioxide gas to form a gaseous carbon dioxide-tobacco system (2) releasing the pressure and (3) thereafter subjecting the carbon dioxide-treated tobacco to rapid heating conditions to remove the carbon dioxide and thereby expand the tobacco, The improvement in the above-described process comprising cooling the gaseous carbon dioxide and tobacco system in step (1) to a temperature close to the saturation temperature of carbon dioxide but not lower than -23°C.
Description
Various processes have been proposed for expanding tobacco.
For example, to~acco has been contacted with a gas under scme-what greater than atmospherlc pressure, followed by a release of the pressure, whereby the tobacco cells are expanded to in-crease the volume of the treated tobacco. Other methods which have been employed or suggested have included the treat-ment of tobacco with various liquids, such as water or re-latively volatile organic liquids, to impregnate the tobacco with the same, after which the liquids are driven off to ex-pand the tobacco. Additional methods which have been suggestedhave included the treatment of tobacco with solid materials which, when heated, decompose to produce gases which serve to expand the tobacco. Other methods include the treatment of tobacco with gas-containing liquids, such as carbon dioxide-; containing water, under pressure to incorporate the gas in the tobacco and when the tobacco impregnated therewith is heated or the pressure thereon is reduced to thereby expand the tobacco. Additional techniques have been developed for expand-ing tobacco which involve the treatment of tobacco with gases which react to form solid chemical reaction products within the tobacco, which solid reaction products may then decompose by heat to produce gases within the tobacco which cause expan-sion of the tobacco upon their release. More specifically:
A patent to Wilford J. Hawkins, U.S. Patent 1,789,435, granted in 1931, describes a method and apparatus for expand-ing the volume of tobacco in order to make up the loss of weight caused in curing tobacco lea~. To accomplish this object, the cured and conditioned tobacco is contacted with a ` gas, which may be air, carbon dioxide or steam under about 20 pounds of pressure and the pressure is then relieved, whereby the tobacco tends to expand. The patent states that the volume of the tobacco may, by that process, be increased to the extent of about 5 - 15~.
An alien property custodian document No. 304,214 to Joachim Bohme, dated 1943, indicates that tobacco can be ex-panded using a high-frequency generator but that there are limitations to the degree of expansion which can be achieved without affecting the quality of the tobacco.
A patent to Frank J. Sowa, U.S. Patent 2,596,183, granted in 1952, sets forth a method for increasing the volume of shredded tobacco by adding additional water to the tobacco to cause the tobacco to swell and thereafter heating the moisture containing tobacco, whereby the moisture evaporates and the resulting moisture vapor causes expansion of the tobacco.
- A series of patents to Roger de la Burde, U.S. Patents 3,409,022, 3,409,023, 3,409,027 and 3,409,028, granted in 1968, relate to various processes for enhancing the utility of tobacco stems for use in smoking products by subjecting the stems to expansion operations utilizing various types of heat treatment or microwave energy.
A patent to John D. Hind, U.S. Patent 3,425,425, granted in 1969, which is assigned to the same assignee as the assignee of the present invention, relates to the use of t carbohydra.es co improve the puffing of tobacco stems. In that process, tobacco stems are soaked in an aqueous solution of carbohydrates and then heated to puff the stems. The car-bohydrate solution may also contain organic acids and/or certain salts which are used to improve the flavor and smoking qualities of the stems.
A publication in the "Tobacco Reporter" of November 1969 by P. S. Meyer describes and summarizes tobacco puffing or ex-pansion procedures or investigations for expanding and manipu-lating tobacco for purposes of reducing costs and also as the means for reducing the "tar" content by reduction in the de-livery of smoke. Mention is made in this publication of puffing tobacco by different procedures including the use of halogenated hydrocarbons, low pressure or vacuum operation, or high pressure steam treatment that causes leaf expansion from inside the cell when outside pressure is suddenly released.
Mention is also made in this publication of freeze-drying tobacco which can also be employed to obtain an increase in volume.
Since the above-mentioned "Tobacco Reporter" article was published, a number of tobacco expansion techniques, in-cluding some of the techniques described in the article, have been described in patents and/or published patent applications.
For example, U.S. Patent 3,524,452 to Glenn P. Moser et al and U.S. Patent 3,524,451 to 3ames D. Frederickson, both issued in 1970, relate to the expansion of tobacco using a volatile organic liquid, such as a halogenated hydrocarbon.
U.S. Patent 3,734,104 to William M. Buchanan et al.
which is assigned to the same assignee as the assignee of the present invention, issued in 1973, relates to a particular process for the expansion of tobacco stems.
U.S. Patent 3,710,802 to William H. Johnson, issued in 1273 and British Specification 1,293,735 to American Brands, Inc., published in 1972, both relate to freeze-drying methods f~or expanding tobacco.
South African applications 70/8291 and 70/8282 to R. J.
Reynolds Tobacco Company, both filed in 1970, relate to tobacco expansion employing chemical compounds which decompose to form a gas or with inert solutions of a gas under pressure to maintain the gas in solution until it impregnates the tobacco.
A patent to Robert G. Armstrong, U.S. Patent 3,771,533, issued in 1973, which is assigned to the same assignee as the assignee of the present invention, involves a treatment of tobacco with carbon dioxide and ammonia gases, whereby the tobacco is saturated with these gases and ammonium carbonate is formed in situ. The ammonium carbonate is thereafter de-composed by heat to release the gases w thin the tobacco cells and to cause expansion of the tobacco.
Despite all of the above-described advances in the art, no completely satisfactory process has been found. The dif-ficulty with the various earlier suggestions for expanding tohacco is that, in many cases, the volume is only slightly or at best only moderately increased. For example, freeze-~6 ;~
drying operations have the disad~antages of requiring elabor-ate and expensive equipment and ~ery substantial operating costs, With respect to the teaching of using heat energy, infrared or radiant microwave energy to expand tobacco stems, the difficulty is that while stems respond to these heating procedures, tobacco leaf has not generally been found to re-spond effectively to this type of process.
The use of special expanding agents, for example, halo-genated hydrocarbons, such as are mentioned in the Meyer pub-lication for expanding tobacco, is also not completely satis-factory, because some of the materials employed are not al-ways desired as additives. Furthermore, the introduction, in considerable concentration, of materials which are foreign to tobacco presents the problem of removing the expansion agent after the treatment has been completed in order to avoid affecting aroma and other properties of the smoke due to ex-traneous substances used or developed from the combustion of the treated tobacco.
The use of carbonated water has also not been found to ~ 20 be effecti~ve.
While the method employing ammonia and carbon dioxide .: gases is an improvement over the earlier described m~thods, it is not completely satisfactory under some circumstances in that undesired deposition of salts can result during the process.
Carbon dioxide has been used in the food industry as a coolant and, more recently, has been suggested as an extractant for food flavors. It has also been described in German Offen-legungsschrift 2,142,205 (Anmeldetag: 23 August 1971) for use, in either gaseous or liquid form, to extract aromatic materials from tobacco. However, there has been no suggestion, in con-nection with these uses, of the use of gaseous carbon dioxide ` for the expansion of these materials.
A process employing liquid carbon dioxide has been found to overcome many of the disadvantages of the above-mentioned prior art processes. The expansion of tobacco, using liquid carbon dioxide is described in Belgian Patent 821,568, which corresponds to Canadian Patent No. 1,013,640 to de la Burde and Aument (two of the present co-inventors) and assigned to the same assignee as the present application and ~n Belgian Patent 825,133 to Airco, Inc. This process may be described as a process for expanding tobacco comprising the steps of (1) contacting the tobacco with liquid carbon dioxide to impregnate the tobacco with the liquid carbon ` dioxide, (2) subjecting the liquid carbon dioxide-impregnated tobacco to conditions such that the liquid carbon dioxide is 20 converted to solid carbon dioxide and (3) thereafter subjecting the solid carbon dioxide-containing tobacco to conditions whereby the solid carbon dioxide is vaporized to cause ex-- pansion of the tobacco.
In our earlier work with gaseous CO2, at pressures of about 100 psia, we had found that only minute amounts of carbon dioxide gas could be incorporated in the tobacco and held there sufficiently long for the tobacco to be heated and expanded. Thus, we ~ound no substantial improvement over the prior art and gaseous CO2 was believed to be much less ; effective as an expanding agent than the liquid carbon dioxide employed in the expansion process of the above-mentioned Canadian Patent No. 1,013,640. We have now found that gaseous carbon dioxide can be introduced into tobacco in a manner whereby the gaseous carbon dioxide remains in the tobacco in an amount of one per cent or more to form a product which can then be expanded. Unexpectedly superior results and advantages can be achieved by employing gaseous C2 in the manner set forth in the present specification. The present process may be described as follows: A process for expanding tobacco to achieve at least about 50 per cent increase in cylinder volume, comprising the steps of (l) impregnating tobacco with gaseous carbon dioxide under a pressure of at least about 250 psig and at sufficient tempera-ture that substantially all of the carbon dioxide is maintain-ed in gaseous form, (2) decreasing the pressure on the carbon dioxide-impregnated tobacco and (3) heating the impregnated tobacco under conditions effective to liberate the carbon dioxide therein so as to cause expansion of the tobacco. The present invention also relates to an improvement in that process and have found that gaseous carbon dioxide can be in-troduced into tobacco in a manner whereby the gaseous carbon dioxide remains in the tobacco in an amount as high as three per cent or more to form a product which can then be expanded.
Unexpectedly superior results and advantages can be achieved ' ~
by employing gaseous CO2 in the manner set forth in the present specification.
This divisional application provides a process for expanding tobacco to achieve at least about 50 per cent increase in cylinder volume, comprising the steps (l) impregnating tobacco with gaseous carbon dioxide under a pressure of 400 to 800 psig for a period of l/4 to 30 minutes and at sufficient temperature that substantially all of the carbon dioxide is maintained in gaseous form, (2) decreasing the pressure on the carbon dioxide-impregnated tobacco and (3) heating the impregnated tobacco under conditions effective to liberate the carbon dioxide therein so as to cause expansion of the tobacco.
A novel tobacco product comprises tobacco containing gaseous carbon dioxide in an amount of at least 1 part of gaseous carbon dioxide per 100 parts of tobacco. The product, when rapidly heated is converted to expanded tobacco.
An improved process for the expansion of tobacco is also - provided which employs carbon dioxide as the expansion agent.
Tobacco, generally having a moisture content of from about 5 to about 35% by weight, is placed in a pressure vessel or similar confinable space. Carbon dioxide gas may be passed through to flush the vessel. Carbon dioxide pressure is then increased and brought to a value of from about 250 pounds per square inch gauge (psig) to about 1057 psig or even higher, and preferably to about 400 to 800 psig.
The tobacco is maintained under such a pressure under conditions A
whereby the carbon dioxide is substantially gaseous for form about 1/4 to about 30 minutes, to impregnate the tobacco with carbon dioxide. The pressure is then reduced in a period of from 1 to 800 seconds, preferably 10 to 120 seconds, preferably to atmospheric pressure, to produce a : product comprising tobacco containing at least 1% by weight of gaseous carbon dioxide, based on the weight of tobacco.
The resulting gaseous carbon dioxide-containing tobacco may then be heated in the same vessel but is preferably rapidly transferred, preferably within a few minutes, to a separate zone where it is subjected to conditions of temperature and i pressure, as by rapid heating in a gas at 100 to 370C and `: at or near atmospheric pressure for a period of from about 1 second to about 10 minutes, to expand the tobacco.
An improvement on the above-described invention wherein . the tobacco/CO2 system is cooled during or after pressurization, ', "
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. ~ .
as by circulation of a cooling agent through the jacket of the cha~her, to a te~perature close to the saturation temperature of carbon dioxide but not lower than -23C. As an alternative to using a cooling jacket in the improved process CO2 gas can be caused to flow through the system by venting a portion of the CO2 gas either during or following pressurization, pre-~erably while maintaining an infeed of CO2 gas such that there is not a loss in the system pressure due to the venting. With cooling, the resulting conditions are such that the carbon dioxide at the prevailing temperature and pressure remains sub-stantially in the gaseous state, but further such that the carbon dioxide, upon rapid reduction of pressure upon the sys-tem, is converted partially to a condensed state within the tobacco. Such conditions may be defined as such that the enthalpy of the carbon dioxide is kept at a value which is less than about 140 BTU per lbm. By this means a significantly greater residue of carbon dioxide remains in the tobacco at the beginning of the expansion step, than is the case without the cooling before pressure release, wherein the carbon dioxide, at higher enthalpy, remains primarily in the gas phase throughout. A further method of reducing the enthalpy of the system thereby causing an increased retention of carbon dioxide involves admission of additional quantities of CO2 gas during venting thereby causing additional sweeping of CO2 gas to flow through the system.
In connection with the present invention, if desired, the retention of carbon dioxide in the tobacco can be increased by pre-cooling or pre-freezing the tobacco prior to the impreg-nation cycle to cause a reduction in the system enthalpy. A
still further method of increasing the retention of carbon dioxide in the tobacco involves "pre-snowing" the tobacco with finely divided solid carbon dioxide (dry ice) prior to the im-_ ~ _ pregnation cycle wh~ch accomplishes both a pre-cooling of the tobacco and serves an an additional source for providing carbon dioxide to the tobacco; applied in proper amounts of ~rom about 5-50~ by weight of the tobacco, at least a portion of the dry ice will be incorporated into the tobacco during the pressurization cycle and by varying the amount of dry ice applied, a method of increasing and controlling the amount of carbon dioxide retained by the tobacco becomes possible. When such methods are involved, the tobacco/CO2 system may be main-tained for 1/4 to 30 minutes during the impregnation step,where the pressure is at least 250 psig, to impregnate the tobacco with carbon dioxide. The pressure is then reduced, in a period of 1 to 800 seconds, preferably 10 to 120 seconds and preferably but notnecessarily to atmospheric pressure. The tobacco is then rapidly transferred to a zone where it is subjected to conditions of temperature and pressure, as by rapid heating in a gas at 100 to 370C and at or near atmos-pheric pressure ~or one second to 10 minutes to expand the tobacco.
This invention relates broadly to an improved process for expanding tobacco employing a readily-available, relative-ly inexpensive, non-combustible, inoffensive, and non-toxic expansion agent and more particularly, to the production of an expanded tobacco product of substantially reduced density and increased filling power. The improved process employs carbon dioxide as the expansion agent. In general, the pro-cess comprises placing tobacco, preferably having a moisture content of from about 5 to about 35~, by weight, in a vessel or similar confinable space; the vessel or space may then be flushed with gaseous CO2 to remove most of the associated air, 3Q although this is not essential to the invention. The vessel is closed except ~or an inlet port, and carbon dioxide gas is introduced ar;d the pressure increased, by continued gas in-P _ ~
troduction or heating or both, under conditions whereby the CO2 in the ~essel remains primarily in the gas state to a final pressure of at least 250 psig, preferably 400 to 800 psig.
The required temperature to maintain the CO2 in a substantially gaseous state at a given pressure may be determined readily by one familiar with the use of phase diagrams or critical tables.
Wh~le pressures as high as 900 psig might be economically em-ployed, and a pressure of about 1057 would be acceptable, there is no known upper limit to the useful impregnation pres-lQ sure range other than that imposed by the capabilities of the equipment available. However, operation below the critical temperature is preferred for ease of control. The tobacco may fie maintained under these impregnating conditions from about 1/4 to 30 minutes, the longer times being in general applicable to lower pressure operation. Reference to the pressure~enthalpy diagram for CO2 as set forth in Figure 1 of the drawing will be of help in selecting desired conditions.
After the impregnation step, the gas pressure is reduced by venting. The final pressure may be atmospheric or some pres-sure near that to be employed in the expansion step, but pre-ferably the former. The time of pressure reduction is from 1 to about 800 seconds. The gaseous carbon dioxide-containing tobacco is then transferred to a zone where it is subjected to .
conditions whereby the carbon dioxide is removed to expand the tobacco. The transfer of the carbon dioxide-containing tofiacco to the heating or expansion zone should preferably be effected within as short a time as possible, preferably within about five minutes, and most preferably within about two minutes. As an alternative to rapid transfer, if desired, 3Q the carbon dioxide-containing tobacco may be stored in an insulated bulker or chilled or otherwise maintained in a re-latively cool condition. The heating or expansion step prefer-~~
ably involves exposing the carbon dioxide-containing tobacco to rapid heat;ng at a temperature of about 100 to 370C for a period o~ time of ~rom about 1 second to 10 minutes and sub-stantially atmospheric pressure.
In accordance with improvement in the present invention, the impregnation step is modified, as will be set forth in de-tail later in this specification. After the impregnation step, the gas pressure is reduced by venting. The final pressure may be atmospheric or some pressure near that to be employed lQ in the expansion step, but preferably the former. The time of pressure reduction is from 1 to about 800 seconds. The gaseous carbon dioxide-containing tobacco is then transferred to a zone where it is subjected to conditions whereby the carbon dioxide is removed to expand 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 possi~le, preferably within about five minutes, and most pre~erably within about two minutes. As an alternative to rapid transfer, if desired, the carbon dioxide-containing tobacco may fie stored in an insulated bulker or chilled or otherwise maintained in a relatively cool condition. The heat-ing or expansion step preferably involves exposing the carbon dioxide-containing tobacco to rapid heating at a temperature o~ ahout 100 to 370C for a period of time of from about 1 second to 10 minutes and substantia]ly atmospheric pressure.
To carry out the process of the invention, one may treat either whole cured tobacco leaf, tobacco in cut or chopped form, or selected parts of tobacco, such as tobacco stems or may be reconstituted tobacco. In comminuted form, the tobacco to be treated may have a particle size of from about 10 to about 100 mesh, but is preferably not smaller than about 30 mesh.
:,.
~ 12 -The tobacco may contain the natural moisture content of tobacco and may contain from about 5 to about 35% by weight ; moisture. It is preferred, however, for best results that the tobacco have at least about 8~ moisture (by weight) and no ~ore than about 22% (by weight) moisture. As used herein, % moisture may be considered equivalent to oven volatiles (OV~ since not more than about 0.9~ of the tobacco weight is volatiles other than water. The procedure for determining oven volatiles is set forth later in this specification.
10The tobacco will generally be placed in a pressure vessel which will be more fully described hereinafter. For example, it may be placed in a wire cage or on a platform positioned within the vessel.
The tobacco-containing pressure vessel may be then purged with carbon dioxide gas. The benefits of purging are the removal of gases that might interfere with a carbon dioxide recovery process and/or that might interfere with full penetration of the gaseous carbon dioxide. As an alternative to purging with carbon dioxide gas, the vessel may be evacuated prior to introduction of the carbon dioxide gas.
Either with or without a preliminary purging or evacuation of the vessel, carbon dioxide gas is fed to the vessel under conditions whereby the carbon dioxide gas pressure in the vessel is increased under conditions whereby the tobacco in the vessel is preferably at a temperature of from about -10 to about 60C, and the pressure in the vessel is above about 25Q psig, preferably about 400 to 800 psig. The tobacco is .' ' " ~
- - -~aintained unde~ cond~tions whe~ehy the carbon dioxide is at ~ p~essure afiove afiout 25Q psig and is under conditions afiove and to the right o$ the saturated vapor line of Figure 1 of the drawing ~rom a period of from about 15 seconds to a~out 30 ~inutes. The pressure is then reduced over a period of ~rom 1 to about 800 seconds, preferably 10 to 120 seconds, such that the temperature at no point drops below the satura-tion temperature for carbon dioxide at the simultaneous pres-sure, and the tobacco is brought to a temperature below about lQ lQC, and atmospheric pressure or the pressure at which the expansion step is to be carried out.
In the ~mprovement on this invention, the tobacco/C02 system during the impregnation step is cooled, as for example, by circulation of a refrigerant through the jacket of the Yessel containing the system, to reduce the enthalpy of the carbon dioxide fielow about 140 BTU/lbm, preferably while the pres-sure is maintained relatively constant by admission of additional carbon dioxide gas. The cooling is limited so that the carbon dioxide is not condensed to any significant degree 2Q and is not cooled to a temperature lower than -23C. The system is maintained under these impregnating conditions from about 1~4 to 30 minutes, the longer times being in general applicable to lower pressure operation. Reference to the afore-mentioned phase diagram or critical tables for carbon dioxide will be of help in selecting desired conditions. The pressure-temperature relationship is preferably maintained to keep the carbon dioxide gas at or near the saturation point. It is be-lieved that when the conditions are close to or at saturation, the absorption/adsorption characteristics of gaseous CO2 are greatly enhanced. This results in improved retention of gaseous CO2. The final pressure, when the pressure is reduced, may be atmospherlc or some pressure near that to be employed in the expansion step, but is preferably atmospheric. The time of pressure re~tion may be from about 1 to about 800 seconds.
It has been found that after the impregnation step, under conditions where the cooling of the improved process is not employed, a product will be formed having at least one part of carbon dioxide gas per one hundred parts of tobacco. By this is ~eant that at least one part of carbon dioxide gas, per one hundred parts of tobacco, will be associated with the tobacco in some manner, chemically and/or physically, for example by being absorbed by the tobacco. The product may have as high as three parts or more of gaseous carbon dioxide when the process ~s so conducted. This has been found to occur in the absence of added adsorbents or the like. Adsorbents, absorbents or the like may be present; however, it is preferred that they not be present since the process is effective without them and they might introduce undesired elements into the smoke or might not release the carbon dioxide in a totally effective manner. It has been found that after tne impregnation step, the tobacco may contain eyen greater amounts of carbon dioxide, as high as 3 parts (per hundred of tobacco~ or more. The pressure-temperature relation-shIp is preferably maintained to keep the gas at or near thesaturation point. It is believed that when the conditions are close to or at saturation, the absorption/adsorptlon character-istics of gaseous CO2 are greatly enhanced. This results in improved retention of gaseous CO2. The final pressure, when pressure is reduced, may be atmospheric or some pressure near that to be employed in the expansion step, but is preferably atmospheric. The time of pressure reduction may be from about 1 to about 800 seconds.
We have found that after the impregnation step, under 3Q conditions where the cooling of the improvement in the present invention is employed, a product will be formed which may have as high as three parts or more of gaseous carbon dioxide, per .
one hundred parts of tobacco. By this is meant that at least three parts of carbon dio~ide gas, per one hundred parts of tobacco, will be associated with the tobacco in some manner, chemically and/or physically, for example, by being absorbed by the tobacco. I have found this to occur in the absence of added adsorbents or the like. Adsorbents, absorbents or the like may be present; however, it is preferred that they not be present since the process is effective without them and they might introduce undesired elements into the smoke or might not release the carbon dioxide in a totally effective manner.
The tofiacco, after the impregnation step, may then be transported to a zone where it is subjected to conditions such that the carbon dioxide is removed and the tobacco is expanded, preferably by exposure to rapid heating at 100 to 370C for 1 second to 10 minutes and substantially atmospheric pressure.
~ description of the improvement on the presently claimed - process will be described below, said improvement relating specifically to the impregnation step.
To carry out the improvement on the present process, one may treat either whole cured tobacco leaf, tobacco in cut or chopped form, or selected parts of tobacco, such as tobacco stems : or ~ay be reconstituted tobacco. In comminuted form, the tohacco to fie treated may have a particle size of from ahout 10 to about 100 mesh but is preferably not smaller than about 30 mesh.
The tobacco may contain the natural moisture content of tobacco and may contain from about 5 to about 35~ by weight moisture. It is preferred, however, for best results that the tobacco have at least about 8% moisture (by weight) and no more ` 30 than about 22% (by weight) moisture. As used herein, % moisture may be considered equivalent to oven volatiles (OV) since not more than about 0.2% of tobacco weight is volatile other than water. Oven volatiles determination is a simple measurement ~ 16 -of weight loss on exposure in a circulating air oven for 3 hours at 100C.
The tobacco will generally be placed in a pressure vessel which will be more fully described hereinafter. For example, it may be placed in a wire cage or on a platform positioned within the ~essel.
The tobacco-containing pressure vessel may be then purged with carbon dioxide gas. The benefits of purging are the re-moval of gases that might interfere with a carbon dioxide re-lQ covery process and/or tha~ might interfere with full penetration of the gaseous carbon dioxide. As an alternative to purging with carbon dioxide gas, the vessel may be evacuated prior to introduction of the carbon dioxide gas.
The carbon dioxide which is employed in the process of this inyention will generally be obtained from a storage vessel where it is maintained at a pressure of from about 215 to 305 psig and temperatures o~ from -29 to-16C. The carbon dioxide may be introduced into the pressure vessel at 215 to 320 psig and -29 to -14C, but is preferably brought, by suitable means, to a tempera-20 ture above -23C, and a pressure above 250 psig before being introduced into the pressure vessel.
Either with or without a preliminary purging or evacuation of the vessel, carbon dioxide gas is fed to the vessel under conditions whereby the carbon dioxide gas pressure in the vessel is increased under conditions whereby the tobacco in the vessel is at a temperature of from about -10 to about 60C and the pressure in the vessel is above about 250 psig, preferably about 400 to 800 psig. The tobacco/CO2 system is cooled in such a way that the CO2 enthalpy is brought below about 140 BTU/lbm but the gas is preferably not condensed to any significant degree, while the pressure is, preferably, held substantially constant by admis-sion of additional gas, and the system is maintained at these :
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conditions from about 15 seconds to about 30 minutes. The pressure is then reduced over a period of from about 1 to about 800 seconds, ~hereby the tobacco is brought to a temperature below 10C, and atmospheric pressure or the pressure at which the expansion step is to be carried out.
The resulting carbon dioxide-treated tobacco may then be rapidly transported, as described earlier in this specification to a zone where it ls exposed to expansion conditions by sub-~ecting it to heat or the equivalent in order to remove the carhon dioxide from the tobacco. This may comprise the use of hot surfaces, or a stream of hot air, a mixture of gases and steam, or exposure to other energy sources, such as microwave energy or infrared radiation. It has been found that the use of a gas composition comprising at least 50%(by weight) f steam, and preferably above 80% (by weight) of steam, provides particularly satisfactory results. A convenient means of ex-; panding the carbon dioxide-containing tobacco is to place it or to entrain it in a stream of heated gas, such as superheated steam or to place it in a turbulent air stream maintained, for example, at a temperature of from about 150 to about 260C (as low as 100C and as high as 370C~ for a period of about 1 second to lQ minutes. The impregnated tobacco may also be heated by being placed on a moving belt and exposed to infrared heating fiy exposure in a cyclone dryer, by contact in a tower with superheated steam or a mixture of steam and air or the like. Any such contacting steps should not raise the tempera-ture o~ the atmosphere with which the tobacco is in contact to above about 370C and should preferably be from at about 100 to about 30ac r most preferably 150 to 260C when conducted 3Q at atmospheric pressure.
As is ~ell known in the processing of any organic matter, overheating can cause damage, first to colour, such as undue :.
darkening and, finally, .o the extent of charring. The necessary and sufficient temperature and exposure time for expansion without such da~age is a function of these two variables as well as the state of subdivlsion of the tobacco. Thus, to avoid undesirable da~age in the heating step, the impregnated tobacco should not be ~; exposed to the higher temperature levels, e.g. 370C, longer than 1 to 2 seconds.
One method for causing the expansion of the tobacco cells is to use the radiation methods described in either U.S.
Patents 3,40g,022 or 3,409,027. In this operation, the tobacco - never attains a temperature above about 140C, being cooled by the rapid evolution of gases. The presence of steam during heating assists in obtaining optimum results.
Another system, usually preferred, is to use a dispersion dryer, for example, one that is supplied either with steam alone or in combination with air. An example of such a dryer is a Proctor & Schwartz PB dispersion dryer, usually called hereafter a tower. The temperature in the dryer may range from about 120 to 370C with contact time in the dryer of about 1 to 10 seconds. In 2Q general, a 1 to 6 second contact time is utilized when the hot gas temperature is 260 to 315C or somewhat higher. As stated before, other known types of heating means may be used as long as they are capable of causing the impregnated tobacco to expand without excessive darkening. Th~ presence of a steam atmosphere of 20%
or more of the total hot gas composition aids in obtaining the best expansion; a high proportion (e.g., over 80% volume) of steam is preferred.
The present invention may be further understood by referring to the drawings. In the drawings:
Fig. 1 is a standard phase diagram plotting pressure of C2 (in p.s.i.a.) vs temperature (in F) of the tobacco bed for the carbon dioxide-tobacco system, with line I-II-III drawn thereon as an illustration of the system involved here.
Fig. 2 is a standard pressure enthalpy diagram, with line i I~I~ drawn thereon to further illustrate the present invention.
Fig. 3 is a standard pressure enthalpy diagram, with line - I-IV drawn thereon to illustrate the process of the present invention.
As a general illustration of the practice of this invention, reference may be made to Fig. 1. The conditions may, for example, - be such as are represented by line I-II-III on Fig. 1. For example, the tobacco, at about 12% OV in the form of cut bright filler, is placed in a pressure vessel capable of handling the desired pressure, for example, capable of handling a pressure of 1057 psig.
The vessel may be similar to the impregnation vessel described in Canadian Patent No. 1,013,640, but, in distinction to that appara-tus, need have no means for the handling of liquid CO2. The vessel may be f~ushed with gaseous CO2 or may be evacuated and is pressured with gaseous CO2 to bring the contents to a condition (at II~ where the pressure is greater than 250 psig and the temperature is not less than -23C. The pressure is then released (to III). The conditions of the entire sequence (as shown by line I-II-III) are such that the carbon dioxide is maintained below and to the right of the saturated vapor line on Fig. 1.
In one form of the invention, as may be seen from Fig. 2, the enthalpy of the CO2 is greater than about 140 BTU/lbm and the CO2 is present in gaseous form. The vessel may be maintained at these conditions for 1/4 to 30 minutes, as illustrated by line I-III. The pressure may then be reduced rapidly, preferably within 10 to 120 seconds, preferably to atmospheric pressure, as illustrated by line III-IV in Fig. 2.
The impregnated tobacco then is transferred (preferably but not necessarily directly) to a rapid heating zone or vessel such as the heating vessel described in Canadian Patent No. 1,013,640 mentioned above or as described earlier in this specification, for example, an expansion tower, microwave chamber, or the like.
The temperature at which the impregnated tobacco is main-tained prior to the expansion or rapid heating step will largely govern how long the CO2 remains in the tobacco in sufficient quantity to cause the desired expansion. If there is little insulation or means to keep the temperature down, the transfer should be rapid, preferably less than a few minutes. An insulated "bulking" container is preferred to accomplish the transfer.
Supplementary cooling may also be provided as, for example, by lQ applying crushed or powdered dry ice or by spraying liquid nitro-gen on the impregnated tobacco.
The rapid heating causes expansion of the tobacco at a temperature where the tobacco is pliable and elastic and the tobacco can be expanded without fracture to an approximation of its green leaf state. A significant and useful degree of expansion is realized.
Referring to the Fig. 3, an illustration of the present invention is shown. Tobacco at about 12% OV in the form of cut bright filler is placed in a pressure vessel. The vessel may be similar to the impregnation vessel described in Canadian Patent No. 1,013,640 but, in distinction to that apparatus, need have no means for the handling of liquid CO2. The vessel may be flushed with gaseous CO2 or may be evacuated and is pressured with CO2 to bring the contents to a condition wherein the pressure is greater than 250 psia and the temperature is not less than -23C, and the enthalpy is at or above 140 BTU/lbm as shown by line I-II
in the drawing. The enthalpy of the CO2 is then reduced by cooling below about 140 BTU/lbm (but at conditions of temperature and pressure such that the CO2 is present primarily as gas) as shown by line II-III. The vessel is maintained at these conditions for 1/4 to 30 minutes. The pressure is then reduced rapidly, preferably within 10 to 120 seconds, for example, to atmospheric pressure, as y illustrated by line III~
The impregnated tobacco then is transferred (preferably but not necessarily directly) to a rapid heating zone or vessel such as the heating vessel described in Canadian Patent No. 1,013,640, mentioned above, or as described earlier in this specification, for example, an expansion tower, microwave chamber, or the like.
The rapid heating causes expansion of the tobacco at a temperature where the tobacco is pliable and elastic and the tobacco can be expanded without fracture to an approximation of its green leaf state. A significant and useful degree of expansion is realized.
The temperature at which the impregnated tobacco is maintained prior to the expansion or rapid heating step will largely govern how long the CO2 remains in the tobacco in sufficient quantity to cause the desired expansion. If there is little insulation or means to keep the temperature down, the transfer should be rapid, preferably less than a few minutes. An insulated "bulking" con-tainer is preferred to accomplish the transfer. Supplementary `~ cooling may also be provided as, for example, by applying crushed or powdered dry ice or by spraying liquid nitrogen on the impregnated tobacco.
The following examples are illustrative:
A l-pound sample of commercial cased bright tobacco filler at 12.5% OV was placed in an autoclave-type pressure vessel and was pressurized to 800 psig with CO2 gas obtained from a CO2 supply tank which was maintained at a CO2 pressure at least ` slightly above the desired impregnation pressure. The impregnator system temperature was maintained above 30C during the pressure cycle by supplying extra heat to the system, when necessary, to prevent any formation of liquid or solid CO2 during the entire processing cycle. After a 15-minute contact time, the pressure and temperature conditions of the CO2 gas in the impregnator ~L ~, - r ' ~ r~
were found to correspond to an enthalpy ~alue of about 142 BTU/lb f C2 gas. The pressure was released by venting in about 30 seconds after which the tobacco temperature was found to be 2.2C.
The impregnated sample had a weight gain of 2.0~ which is attributable to the gaseous CO2 contained therein. The impreg-nated material was then, within about 5 minutes time, exposed to heating in a 3-inch diameter tobacco expansion tower by contact with superheated steam at 288C and a velocity of 140 ft/sec for about 4 seconds. The product exiting the expansion tower had an OV of 2.1%. The product was equilibrated at standard conditions of 23.9C and 60% RH for about 18 hours. The filling power of the equilibrated product was measured by the standardized cylinder volume (CV~ test described later in this specification as 74 cc/10 g at 11.2~ OV. This gave a corrected CV (CCV) value at 11% OV of 76 cc/10 g. An unexpanded control was found to have a cylinder volume of 36 cc/10 g. The sample after processing, therefore, had a 111% increase in filling power as measured by the CV method.
A series of bright tobacco samples were treated as in Example 1 under conditions where gaseous CO2 and substantially no liquid or solid CO2 would be formed. The tobacco feed OV
was varied from 9% to 14.6%. The conditions of each test and the test results are shown in Table I. Where no value is shown in the Table for a variable, the value is as in Example 1.
Table I
~ ller Expansion with Gaseous CO2 :
.: .
Test # 1 2 3 Tobacco Feed OV 9.0% 10.3% 14.6%
Impregnation Pressure, psig 800 800 800 C2 Temperature Prior to Vent, C 31.7 31.7 32.2 C2 Enthalpy Prior to Vent, BTU/lb. 143 143 143 Tobacco Temp. after Venting, C -20.0 -22.8 ~2.8 % C2 Retention on Tobacco 2.9 2.4 1.5 Product OV after Expansion 1.7% 1.8% 3.2%
Reordered Product CV 62 94 74 Reordered Product OV 11.6 10.3 11.3 Correct CV at 11% OV 66 88 76 % Increase in Filling Power 83 144 111 ; A series of bright tobacco samples were treated as in Example 1 under conditions where gaseous CO2 and substantially no liquid or solid CO2 would be formed. The hold time was varied.
The conditions and test results are shown in Table II. Where no value is shown in the Table for a variable, the value is as in Example 1.
Table II
Filler Expansion with Gaseous CO2 Test # 3 4 5 Tobacco Feed O~ 14.2%14.4%15.3%
: Impregnation Pressure, psig 800 800 800 Hold Time, Minutes 1 2 20 C2 Temperature prior to Vent, C 58.9 30.0 35.6 C2 Enthalpy prior to Vent, BTU/lb. 160 142 144 Tobacco Temp. after Venting, C 8.3 -5.6 4.4 % C2 Retention on Tobacco 2.0 2.6 1.5 Product OV after Expansion 2.2%2.0 3.8 Reordered Product CV 71.274.0 76.2 Reordered Product OV 11.111.6 11.6 Corrected CV at 11% OV 72 78 80 % Increase in Filling Power 100 117 122 Example 4 30A series of bright tobacco samples were treated as in Example 1 at conditions where no liquid or solid CO2 would be expected to be formed. The impregnation pressure was varied.
The test results are shown in Table III. Where no value is shown in the Table for a variable, the value ls as in Example 1.
Table III
Filler Expansion with Gaseous CO2 Test # 6 7 8 9 10 11 Tobacco Feed OV 14.5 13.6 lQ.3 16.1 13.2 13.3 Impregnation Pres-sure, psig 300 4Q0 500 600 700 800 Hold Time, Minutes 15 15 15 25 15 15 C2 Temperature prior to Vent, C -11.7 NA 20.6 20.6 19.4 53.9 10 C2 Enthalpy prior to Vent, BTU/lb. 143 NA 15Q 145 142 155 Tobacco Temp. after Venting, C -13.9 NA 3.3 -5.6 -16.7 20.6 Product OV after Expansion 2.2 1.9 2.1 2.1 3.4 2.7 Reordered Product CV 62 66 59 75 74 60 Reordered Product OV 10.7 11.5 11.7 11.4 11.5 11.6 Corrected CV at 11%
Increase in Filling Power 83 92 78 119 114 81 ~` .
A l-pound sample of commercial cased bright tobacco filler at 11.1% OV was placed in an FS-3 pressure vessel and '! pressurized to 800 psig with ~2 gas as in the procedure of Example 1. The impregnation system t~mperature was cooled by circulating a cooling solution through a jacket surrounding the impregnation vessel until the CO2 gas in the impregnator was cooled to near its saturation temperature. After a 15-minute contact time, the pressure and temperature conditions of ~he CO2 gas in the impregnator were found to correspond to an enthalpy ~alue of about 130 BTU/lb. of CO2 gas. Although some CO2 condensation probably occurred within the vessel, the C2 was present primarily as a gas. The pressure was released by venting in about 30 seconds after which the tobacco temperature was found to he -37.8C. The impregnated sample had a weight gain of about 3.5% attributable to CO2. This impregnated material was then heated as in Example 1. The product exiting the exp2n-sion tower had an OV of 1.9%. The equilibrated product had a CV
of 90.6 at an OV of 10.8%. This corresponds to a CCV of 89 or an increase in filling power of 147% over the unexpanded control ; (36 cc/10 g).
A series of bright tobacco samples were treated as in Example 5 at conditions where the CO2 gas would be coGled to near saturation prior to pressure release at three different pressures. The conditions and test results are shown in Table IV. Where no value is shown in the Table for a variable, the value is as in Example 1.
Table IV
:
Filler Expansion with Gaseous CO2 -Test # 12 13 14 ~- Tobacco Feed OV 9.5% 10.8 12.1 Impregnation Pressure, psig 800 600 500 Hold Time, Minutes 15 15 20 C2 Temperature prior to Vent, C 19.4 7.2 2.2 C2 Enthalpy prior to Vent, BTU/lb. 129 139 139 ` Tobacco Temp. after Venting, C -38.9 -27.8 -18.3 % C2 Retention on Tobacco 3.7 2.6 2.4 Product OV after Expansion 1.3% 1.4 1.9 Reordered Product CV 89 88 71 Reordered Product OV 10.5 10.9 11.9 Corrected CV at 11% OV 85 87 78 % Increase in Filling Power 136 142 117 The procedure of Example 5 was repeated using cased burley tobacco. The equilibrated expanded product was found to have a CV of 92.4 at 10.1% OV or an increase of about 100%
over the unexpanded control.
The procedure of Example 5 was repeated using a tobacco blend as normally used in cigarette manufacture. The product was found to have a CV of 78.1 at 11.1~ OV or an increase of about lQ5~ o~er the unexpanded control.
A l~pound sample of cased bright tobacco was processed as in Example 1 and found to have a CCV of 81. This product was blended at 25% with conventional tobacco blend. Cigarettes were smoked and found to have a desirable taste and aroma;
firmness of the tobacco rod was acceptable.
A 13-pound sample of cased bright tobacco was processed as in Example 5. The product was found to have a CCV of 78.
A 5-pound sample of cased bright tobacco was impregnated as in Example 5 but was then subjected to heating in a static bed using 149C steam for a 5-minute exposure. The equilibrated product was found to have a CV of 85.
A series of runs was conducted following the process of Example 5 and the runs were found to give cylinder volume results of 80, 80, 80, 79, 84, 78, 79, 78 and 79, respectively.
This gives an average CV of 80 for the 9 trials or an increase in filling power of 121% over the untreated control.
A series of 3 runs was conducted according to the pro-cess of Example 5, except that the feed tobacco was pre-chilled to a temperature just below -20C before the tobacco was con-tacted with the pressurized CO2 gas. The reordered product CV results under these circumstances were found to be 92, 92 and 87, respectively. This gave an average increase in filling power of 151% over the untreated control.
Two series of runs were conducted in a manner similar to Example 1. However, conditions were as indicated in Table V with a ten~minute hold period and the tower conditions were:
3-inch tower at 60,QF, with lQ0% steam. Series #2 was run under similar conditions to Series #1.
The results of both series of these runs are given in ' Table V together with the results for an unexpanded control sample and for a control sample which was expanded, without any C2 treatment:
Table V
S-eries #l Series #2 %Reordered % Reordered Press. (psig), OV CV/OV CCV OV CV/OV CCV
Control 11.836.8/12.6 - - - -Exp.control - - - 1.9 64.6/10.9 , 250 2.572.8/10.8 71.2 1.5 73.8/10.8 72.3 300 2.876.3/10.8 74.9 1.2 81.4/10.7 78.9 , 325 2.677.2/10.8 75.9 1.2 79.6/10.7 77.5 ~, 350 2.378.4/11.0 78.4 1.2 77.3/11.2 78.5 375 2.480.6/11.1 81.0 1.4 78.7/11.1 79.6 4Qo 2.678.5/11.2 79.9 1.4 82.0/11.1 85.6 800 2.892.0/11.2 93.3 1.5 97.6/11.1 98.0 It will be seen that pressures of 250 psig through 800 psig provided excellent expansion, compared with the controls.
The following experiments were also conducted:
Experiment 1 The impregnation procedure of Example 11 was repeated but the impregnated material was simply allowed to warm to room temperature and was not subjected to tower expansion. The re-sulting product showed no gain, and perhaps a slight loss, in CV compared to the untreated control.
Experiment 2 A comparison run of gaseous vs. liquid CO2 impregnation was conducted in the following manner.
1~ Liquid CO2~Three pounds of cased commercial bright tobacco filler (OV of 12.7%) was impregnated with liquid C2 at 800 psig, cooled to 19.6C, and held for 15 minutes.
Thereafter the excess liquid was drained and the pressure was re-leased. A 23% gain in weight was attributed to CO2 pickup.
The material was somewhat clumped together because of the large amount of retained CO2.
For example, to~acco has been contacted with a gas under scme-what greater than atmospherlc pressure, followed by a release of the pressure, whereby the tobacco cells are expanded to in-crease the volume of the treated tobacco. Other methods which have been employed or suggested have included the treat-ment of tobacco with various liquids, such as water or re-latively volatile organic liquids, to impregnate the tobacco with the same, after which the liquids are driven off to ex-pand the tobacco. Additional methods which have been suggestedhave included the treatment of tobacco with solid materials which, when heated, decompose to produce gases which serve to expand the tobacco. Other methods include the treatment of tobacco with gas-containing liquids, such as carbon dioxide-; containing water, under pressure to incorporate the gas in the tobacco and when the tobacco impregnated therewith is heated or the pressure thereon is reduced to thereby expand the tobacco. Additional techniques have been developed for expand-ing tobacco which involve the treatment of tobacco with gases which react to form solid chemical reaction products within the tobacco, which solid reaction products may then decompose by heat to produce gases within the tobacco which cause expan-sion of the tobacco upon their release. More specifically:
A patent to Wilford J. Hawkins, U.S. Patent 1,789,435, granted in 1931, describes a method and apparatus for expand-ing the volume of tobacco in order to make up the loss of weight caused in curing tobacco lea~. To accomplish this object, the cured and conditioned tobacco is contacted with a ` gas, which may be air, carbon dioxide or steam under about 20 pounds of pressure and the pressure is then relieved, whereby the tobacco tends to expand. The patent states that the volume of the tobacco may, by that process, be increased to the extent of about 5 - 15~.
An alien property custodian document No. 304,214 to Joachim Bohme, dated 1943, indicates that tobacco can be ex-panded using a high-frequency generator but that there are limitations to the degree of expansion which can be achieved without affecting the quality of the tobacco.
A patent to Frank J. Sowa, U.S. Patent 2,596,183, granted in 1952, sets forth a method for increasing the volume of shredded tobacco by adding additional water to the tobacco to cause the tobacco to swell and thereafter heating the moisture containing tobacco, whereby the moisture evaporates and the resulting moisture vapor causes expansion of the tobacco.
- A series of patents to Roger de la Burde, U.S. Patents 3,409,022, 3,409,023, 3,409,027 and 3,409,028, granted in 1968, relate to various processes for enhancing the utility of tobacco stems for use in smoking products by subjecting the stems to expansion operations utilizing various types of heat treatment or microwave energy.
A patent to John D. Hind, U.S. Patent 3,425,425, granted in 1969, which is assigned to the same assignee as the assignee of the present invention, relates to the use of t carbohydra.es co improve the puffing of tobacco stems. In that process, tobacco stems are soaked in an aqueous solution of carbohydrates and then heated to puff the stems. The car-bohydrate solution may also contain organic acids and/or certain salts which are used to improve the flavor and smoking qualities of the stems.
A publication in the "Tobacco Reporter" of November 1969 by P. S. Meyer describes and summarizes tobacco puffing or ex-pansion procedures or investigations for expanding and manipu-lating tobacco for purposes of reducing costs and also as the means for reducing the "tar" content by reduction in the de-livery of smoke. Mention is made in this publication of puffing tobacco by different procedures including the use of halogenated hydrocarbons, low pressure or vacuum operation, or high pressure steam treatment that causes leaf expansion from inside the cell when outside pressure is suddenly released.
Mention is also made in this publication of freeze-drying tobacco which can also be employed to obtain an increase in volume.
Since the above-mentioned "Tobacco Reporter" article was published, a number of tobacco expansion techniques, in-cluding some of the techniques described in the article, have been described in patents and/or published patent applications.
For example, U.S. Patent 3,524,452 to Glenn P. Moser et al and U.S. Patent 3,524,451 to 3ames D. Frederickson, both issued in 1970, relate to the expansion of tobacco using a volatile organic liquid, such as a halogenated hydrocarbon.
U.S. Patent 3,734,104 to William M. Buchanan et al.
which is assigned to the same assignee as the assignee of the present invention, issued in 1973, relates to a particular process for the expansion of tobacco stems.
U.S. Patent 3,710,802 to William H. Johnson, issued in 1273 and British Specification 1,293,735 to American Brands, Inc., published in 1972, both relate to freeze-drying methods f~or expanding tobacco.
South African applications 70/8291 and 70/8282 to R. J.
Reynolds Tobacco Company, both filed in 1970, relate to tobacco expansion employing chemical compounds which decompose to form a gas or with inert solutions of a gas under pressure to maintain the gas in solution until it impregnates the tobacco.
A patent to Robert G. Armstrong, U.S. Patent 3,771,533, issued in 1973, which is assigned to the same assignee as the assignee of the present invention, involves a treatment of tobacco with carbon dioxide and ammonia gases, whereby the tobacco is saturated with these gases and ammonium carbonate is formed in situ. The ammonium carbonate is thereafter de-composed by heat to release the gases w thin the tobacco cells and to cause expansion of the tobacco.
Despite all of the above-described advances in the art, no completely satisfactory process has been found. The dif-ficulty with the various earlier suggestions for expanding tohacco is that, in many cases, the volume is only slightly or at best only moderately increased. For example, freeze-~6 ;~
drying operations have the disad~antages of requiring elabor-ate and expensive equipment and ~ery substantial operating costs, With respect to the teaching of using heat energy, infrared or radiant microwave energy to expand tobacco stems, the difficulty is that while stems respond to these heating procedures, tobacco leaf has not generally been found to re-spond effectively to this type of process.
The use of special expanding agents, for example, halo-genated hydrocarbons, such as are mentioned in the Meyer pub-lication for expanding tobacco, is also not completely satis-factory, because some of the materials employed are not al-ways desired as additives. Furthermore, the introduction, in considerable concentration, of materials which are foreign to tobacco presents the problem of removing the expansion agent after the treatment has been completed in order to avoid affecting aroma and other properties of the smoke due to ex-traneous substances used or developed from the combustion of the treated tobacco.
The use of carbonated water has also not been found to ~ 20 be effecti~ve.
While the method employing ammonia and carbon dioxide .: gases is an improvement over the earlier described m~thods, it is not completely satisfactory under some circumstances in that undesired deposition of salts can result during the process.
Carbon dioxide has been used in the food industry as a coolant and, more recently, has been suggested as an extractant for food flavors. It has also been described in German Offen-legungsschrift 2,142,205 (Anmeldetag: 23 August 1971) for use, in either gaseous or liquid form, to extract aromatic materials from tobacco. However, there has been no suggestion, in con-nection with these uses, of the use of gaseous carbon dioxide ` for the expansion of these materials.
A process employing liquid carbon dioxide has been found to overcome many of the disadvantages of the above-mentioned prior art processes. The expansion of tobacco, using liquid carbon dioxide is described in Belgian Patent 821,568, which corresponds to Canadian Patent No. 1,013,640 to de la Burde and Aument (two of the present co-inventors) and assigned to the same assignee as the present application and ~n Belgian Patent 825,133 to Airco, Inc. This process may be described as a process for expanding tobacco comprising the steps of (1) contacting the tobacco with liquid carbon dioxide to impregnate the tobacco with the liquid carbon ` dioxide, (2) subjecting the liquid carbon dioxide-impregnated tobacco to conditions such that the liquid carbon dioxide is 20 converted to solid carbon dioxide and (3) thereafter subjecting the solid carbon dioxide-containing tobacco to conditions whereby the solid carbon dioxide is vaporized to cause ex-- pansion of the tobacco.
In our earlier work with gaseous CO2, at pressures of about 100 psia, we had found that only minute amounts of carbon dioxide gas could be incorporated in the tobacco and held there sufficiently long for the tobacco to be heated and expanded. Thus, we ~ound no substantial improvement over the prior art and gaseous CO2 was believed to be much less ; effective as an expanding agent than the liquid carbon dioxide employed in the expansion process of the above-mentioned Canadian Patent No. 1,013,640. We have now found that gaseous carbon dioxide can be introduced into tobacco in a manner whereby the gaseous carbon dioxide remains in the tobacco in an amount of one per cent or more to form a product which can then be expanded. Unexpectedly superior results and advantages can be achieved by employing gaseous C2 in the manner set forth in the present specification. The present process may be described as follows: A process for expanding tobacco to achieve at least about 50 per cent increase in cylinder volume, comprising the steps of (l) impregnating tobacco with gaseous carbon dioxide under a pressure of at least about 250 psig and at sufficient tempera-ture that substantially all of the carbon dioxide is maintain-ed in gaseous form, (2) decreasing the pressure on the carbon dioxide-impregnated tobacco and (3) heating the impregnated tobacco under conditions effective to liberate the carbon dioxide therein so as to cause expansion of the tobacco. The present invention also relates to an improvement in that process and have found that gaseous carbon dioxide can be in-troduced into tobacco in a manner whereby the gaseous carbon dioxide remains in the tobacco in an amount as high as three per cent or more to form a product which can then be expanded.
Unexpectedly superior results and advantages can be achieved ' ~
by employing gaseous CO2 in the manner set forth in the present specification.
This divisional application provides a process for expanding tobacco to achieve at least about 50 per cent increase in cylinder volume, comprising the steps (l) impregnating tobacco with gaseous carbon dioxide under a pressure of 400 to 800 psig for a period of l/4 to 30 minutes and at sufficient temperature that substantially all of the carbon dioxide is maintained in gaseous form, (2) decreasing the pressure on the carbon dioxide-impregnated tobacco and (3) heating the impregnated tobacco under conditions effective to liberate the carbon dioxide therein so as to cause expansion of the tobacco.
A novel tobacco product comprises tobacco containing gaseous carbon dioxide in an amount of at least 1 part of gaseous carbon dioxide per 100 parts of tobacco. The product, when rapidly heated is converted to expanded tobacco.
An improved process for the expansion of tobacco is also - provided which employs carbon dioxide as the expansion agent.
Tobacco, generally having a moisture content of from about 5 to about 35% by weight, is placed in a pressure vessel or similar confinable space. Carbon dioxide gas may be passed through to flush the vessel. Carbon dioxide pressure is then increased and brought to a value of from about 250 pounds per square inch gauge (psig) to about 1057 psig or even higher, and preferably to about 400 to 800 psig.
The tobacco is maintained under such a pressure under conditions A
whereby the carbon dioxide is substantially gaseous for form about 1/4 to about 30 minutes, to impregnate the tobacco with carbon dioxide. The pressure is then reduced in a period of from 1 to 800 seconds, preferably 10 to 120 seconds, preferably to atmospheric pressure, to produce a : product comprising tobacco containing at least 1% by weight of gaseous carbon dioxide, based on the weight of tobacco.
The resulting gaseous carbon dioxide-containing tobacco may then be heated in the same vessel but is preferably rapidly transferred, preferably within a few minutes, to a separate zone where it is subjected to conditions of temperature and i pressure, as by rapid heating in a gas at 100 to 370C and `: at or near atmospheric pressure for a period of from about 1 second to about 10 minutes, to expand the tobacco.
An improvement on the above-described invention wherein . the tobacco/CO2 system is cooled during or after pressurization, ', "
;'' `:
- 8(a) -. .
. ~ .
as by circulation of a cooling agent through the jacket of the cha~her, to a te~perature close to the saturation temperature of carbon dioxide but not lower than -23C. As an alternative to using a cooling jacket in the improved process CO2 gas can be caused to flow through the system by venting a portion of the CO2 gas either during or following pressurization, pre-~erably while maintaining an infeed of CO2 gas such that there is not a loss in the system pressure due to the venting. With cooling, the resulting conditions are such that the carbon dioxide at the prevailing temperature and pressure remains sub-stantially in the gaseous state, but further such that the carbon dioxide, upon rapid reduction of pressure upon the sys-tem, is converted partially to a condensed state within the tobacco. Such conditions may be defined as such that the enthalpy of the carbon dioxide is kept at a value which is less than about 140 BTU per lbm. By this means a significantly greater residue of carbon dioxide remains in the tobacco at the beginning of the expansion step, than is the case without the cooling before pressure release, wherein the carbon dioxide, at higher enthalpy, remains primarily in the gas phase throughout. A further method of reducing the enthalpy of the system thereby causing an increased retention of carbon dioxide involves admission of additional quantities of CO2 gas during venting thereby causing additional sweeping of CO2 gas to flow through the system.
In connection with the present invention, if desired, the retention of carbon dioxide in the tobacco can be increased by pre-cooling or pre-freezing the tobacco prior to the impreg-nation cycle to cause a reduction in the system enthalpy. A
still further method of increasing the retention of carbon dioxide in the tobacco involves "pre-snowing" the tobacco with finely divided solid carbon dioxide (dry ice) prior to the im-_ ~ _ pregnation cycle wh~ch accomplishes both a pre-cooling of the tobacco and serves an an additional source for providing carbon dioxide to the tobacco; applied in proper amounts of ~rom about 5-50~ by weight of the tobacco, at least a portion of the dry ice will be incorporated into the tobacco during the pressurization cycle and by varying the amount of dry ice applied, a method of increasing and controlling the amount of carbon dioxide retained by the tobacco becomes possible. When such methods are involved, the tobacco/CO2 system may be main-tained for 1/4 to 30 minutes during the impregnation step,where the pressure is at least 250 psig, to impregnate the tobacco with carbon dioxide. The pressure is then reduced, in a period of 1 to 800 seconds, preferably 10 to 120 seconds and preferably but notnecessarily to atmospheric pressure. The tobacco is then rapidly transferred to a zone where it is subjected to conditions of temperature and pressure, as by rapid heating in a gas at 100 to 370C and at or near atmos-pheric pressure ~or one second to 10 minutes to expand the tobacco.
This invention relates broadly to an improved process for expanding tobacco employing a readily-available, relative-ly inexpensive, non-combustible, inoffensive, and non-toxic expansion agent and more particularly, to the production of an expanded tobacco product of substantially reduced density and increased filling power. The improved process employs carbon dioxide as the expansion agent. In general, the pro-cess comprises placing tobacco, preferably having a moisture content of from about 5 to about 35~, by weight, in a vessel or similar confinable space; the vessel or space may then be flushed with gaseous CO2 to remove most of the associated air, 3Q although this is not essential to the invention. The vessel is closed except ~or an inlet port, and carbon dioxide gas is introduced ar;d the pressure increased, by continued gas in-P _ ~
troduction or heating or both, under conditions whereby the CO2 in the ~essel remains primarily in the gas state to a final pressure of at least 250 psig, preferably 400 to 800 psig.
The required temperature to maintain the CO2 in a substantially gaseous state at a given pressure may be determined readily by one familiar with the use of phase diagrams or critical tables.
Wh~le pressures as high as 900 psig might be economically em-ployed, and a pressure of about 1057 would be acceptable, there is no known upper limit to the useful impregnation pres-lQ sure range other than that imposed by the capabilities of the equipment available. However, operation below the critical temperature is preferred for ease of control. The tobacco may fie maintained under these impregnating conditions from about 1/4 to 30 minutes, the longer times being in general applicable to lower pressure operation. Reference to the pressure~enthalpy diagram for CO2 as set forth in Figure 1 of the drawing will be of help in selecting desired conditions.
After the impregnation step, the gas pressure is reduced by venting. The final pressure may be atmospheric or some pres-sure near that to be employed in the expansion step, but pre-ferably the former. The time of pressure reduction is from 1 to about 800 seconds. The gaseous carbon dioxide-containing tobacco is then transferred to a zone where it is subjected to .
conditions whereby the carbon dioxide is removed to expand the tobacco. The transfer of the carbon dioxide-containing tofiacco to the heating or expansion zone should preferably be effected within as short a time as possible, preferably within about five minutes, and most preferably within about two minutes. As an alternative to rapid transfer, if desired, 3Q the carbon dioxide-containing tobacco may be stored in an insulated bulker or chilled or otherwise maintained in a re-latively cool condition. The heating or expansion step prefer-~~
ably involves exposing the carbon dioxide-containing tobacco to rapid heat;ng at a temperature of about 100 to 370C for a period o~ time of ~rom about 1 second to 10 minutes and sub-stantially atmospheric pressure.
In accordance with improvement in the present invention, the impregnation step is modified, as will be set forth in de-tail later in this specification. After the impregnation step, the gas pressure is reduced by venting. The final pressure may be atmospheric or some pressure near that to be employed lQ in the expansion step, but preferably the former. The time of pressure reduction is from 1 to about 800 seconds. The gaseous carbon dioxide-containing tobacco is then transferred to a zone where it is subjected to conditions whereby the carbon dioxide is removed to expand 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 possi~le, preferably within about five minutes, and most pre~erably within about two minutes. As an alternative to rapid transfer, if desired, the carbon dioxide-containing tobacco may fie stored in an insulated bulker or chilled or otherwise maintained in a relatively cool condition. The heat-ing or expansion step preferably involves exposing the carbon dioxide-containing tobacco to rapid heating at a temperature o~ ahout 100 to 370C for a period of time of from about 1 second to 10 minutes and substantia]ly atmospheric pressure.
To carry out the process of the invention, one may treat either whole cured tobacco leaf, tobacco in cut or chopped form, or selected parts of tobacco, such as tobacco stems or may be reconstituted tobacco. In comminuted form, the tobacco to be treated may have a particle size of from about 10 to about 100 mesh, but is preferably not smaller than about 30 mesh.
:,.
~ 12 -The tobacco may contain the natural moisture content of tobacco and may contain from about 5 to about 35% by weight ; moisture. It is preferred, however, for best results that the tobacco have at least about 8~ moisture (by weight) and no ~ore than about 22% (by weight) moisture. As used herein, % moisture may be considered equivalent to oven volatiles (OV~ since not more than about 0.9~ of the tobacco weight is volatiles other than water. The procedure for determining oven volatiles is set forth later in this specification.
10The tobacco will generally be placed in a pressure vessel which will be more fully described hereinafter. For example, it may be placed in a wire cage or on a platform positioned within the vessel.
The tobacco-containing pressure vessel may be then purged with carbon dioxide gas. The benefits of purging are the removal of gases that might interfere with a carbon dioxide recovery process and/or that might interfere with full penetration of the gaseous carbon dioxide. As an alternative to purging with carbon dioxide gas, the vessel may be evacuated prior to introduction of the carbon dioxide gas.
Either with or without a preliminary purging or evacuation of the vessel, carbon dioxide gas is fed to the vessel under conditions whereby the carbon dioxide gas pressure in the vessel is increased under conditions whereby the tobacco in the vessel is preferably at a temperature of from about -10 to about 60C, and the pressure in the vessel is above about 25Q psig, preferably about 400 to 800 psig. The tobacco is .' ' " ~
- - -~aintained unde~ cond~tions whe~ehy the carbon dioxide is at ~ p~essure afiove afiout 25Q psig and is under conditions afiove and to the right o$ the saturated vapor line of Figure 1 of the drawing ~rom a period of from about 15 seconds to a~out 30 ~inutes. The pressure is then reduced over a period of ~rom 1 to about 800 seconds, preferably 10 to 120 seconds, such that the temperature at no point drops below the satura-tion temperature for carbon dioxide at the simultaneous pres-sure, and the tobacco is brought to a temperature below about lQ lQC, and atmospheric pressure or the pressure at which the expansion step is to be carried out.
In the ~mprovement on this invention, the tobacco/C02 system during the impregnation step is cooled, as for example, by circulation of a refrigerant through the jacket of the Yessel containing the system, to reduce the enthalpy of the carbon dioxide fielow about 140 BTU/lbm, preferably while the pres-sure is maintained relatively constant by admission of additional carbon dioxide gas. The cooling is limited so that the carbon dioxide is not condensed to any significant degree 2Q and is not cooled to a temperature lower than -23C. The system is maintained under these impregnating conditions from about 1~4 to 30 minutes, the longer times being in general applicable to lower pressure operation. Reference to the afore-mentioned phase diagram or critical tables for carbon dioxide will be of help in selecting desired conditions. The pressure-temperature relationship is preferably maintained to keep the carbon dioxide gas at or near the saturation point. It is be-lieved that when the conditions are close to or at saturation, the absorption/adsorption characteristics of gaseous CO2 are greatly enhanced. This results in improved retention of gaseous CO2. The final pressure, when the pressure is reduced, may be atmospherlc or some pressure near that to be employed in the expansion step, but is preferably atmospheric. The time of pressure re~tion may be from about 1 to about 800 seconds.
It has been found that after the impregnation step, under conditions where the cooling of the improved process is not employed, a product will be formed having at least one part of carbon dioxide gas per one hundred parts of tobacco. By this is ~eant that at least one part of carbon dioxide gas, per one hundred parts of tobacco, will be associated with the tobacco in some manner, chemically and/or physically, for example by being absorbed by the tobacco. The product may have as high as three parts or more of gaseous carbon dioxide when the process ~s so conducted. This has been found to occur in the absence of added adsorbents or the like. Adsorbents, absorbents or the like may be present; however, it is preferred that they not be present since the process is effective without them and they might introduce undesired elements into the smoke or might not release the carbon dioxide in a totally effective manner. It has been found that after tne impregnation step, the tobacco may contain eyen greater amounts of carbon dioxide, as high as 3 parts (per hundred of tobacco~ or more. The pressure-temperature relation-shIp is preferably maintained to keep the gas at or near thesaturation point. It is believed that when the conditions are close to or at saturation, the absorption/adsorptlon character-istics of gaseous CO2 are greatly enhanced. This results in improved retention of gaseous CO2. The final pressure, when pressure is reduced, may be atmospheric or some pressure near that to be employed in the expansion step, but is preferably atmospheric. The time of pressure reduction may be from about 1 to about 800 seconds.
We have found that after the impregnation step, under 3Q conditions where the cooling of the improvement in the present invention is employed, a product will be formed which may have as high as three parts or more of gaseous carbon dioxide, per .
one hundred parts of tobacco. By this is meant that at least three parts of carbon dio~ide gas, per one hundred parts of tobacco, will be associated with the tobacco in some manner, chemically and/or physically, for example, by being absorbed by the tobacco. I have found this to occur in the absence of added adsorbents or the like. Adsorbents, absorbents or the like may be present; however, it is preferred that they not be present since the process is effective without them and they might introduce undesired elements into the smoke or might not release the carbon dioxide in a totally effective manner.
The tofiacco, after the impregnation step, may then be transported to a zone where it is subjected to conditions such that the carbon dioxide is removed and the tobacco is expanded, preferably by exposure to rapid heating at 100 to 370C for 1 second to 10 minutes and substantially atmospheric pressure.
~ description of the improvement on the presently claimed - process will be described below, said improvement relating specifically to the impregnation step.
To carry out the improvement on the present process, one may treat either whole cured tobacco leaf, tobacco in cut or chopped form, or selected parts of tobacco, such as tobacco stems : or ~ay be reconstituted tobacco. In comminuted form, the tohacco to fie treated may have a particle size of from ahout 10 to about 100 mesh but is preferably not smaller than about 30 mesh.
The tobacco may contain the natural moisture content of tobacco and may contain from about 5 to about 35~ by weight moisture. It is preferred, however, for best results that the tobacco have at least about 8% moisture (by weight) and no more ` 30 than about 22% (by weight) moisture. As used herein, % moisture may be considered equivalent to oven volatiles (OV) since not more than about 0.2% of tobacco weight is volatile other than water. Oven volatiles determination is a simple measurement ~ 16 -of weight loss on exposure in a circulating air oven for 3 hours at 100C.
The tobacco will generally be placed in a pressure vessel which will be more fully described hereinafter. For example, it may be placed in a wire cage or on a platform positioned within the ~essel.
The tobacco-containing pressure vessel may be then purged with carbon dioxide gas. The benefits of purging are the re-moval of gases that might interfere with a carbon dioxide re-lQ covery process and/or tha~ might interfere with full penetration of the gaseous carbon dioxide. As an alternative to purging with carbon dioxide gas, the vessel may be evacuated prior to introduction of the carbon dioxide gas.
The carbon dioxide which is employed in the process of this inyention will generally be obtained from a storage vessel where it is maintained at a pressure of from about 215 to 305 psig and temperatures o~ from -29 to-16C. The carbon dioxide may be introduced into the pressure vessel at 215 to 320 psig and -29 to -14C, but is preferably brought, by suitable means, to a tempera-20 ture above -23C, and a pressure above 250 psig before being introduced into the pressure vessel.
Either with or without a preliminary purging or evacuation of the vessel, carbon dioxide gas is fed to the vessel under conditions whereby the carbon dioxide gas pressure in the vessel is increased under conditions whereby the tobacco in the vessel is at a temperature of from about -10 to about 60C and the pressure in the vessel is above about 250 psig, preferably about 400 to 800 psig. The tobacco/CO2 system is cooled in such a way that the CO2 enthalpy is brought below about 140 BTU/lbm but the gas is preferably not condensed to any significant degree, while the pressure is, preferably, held substantially constant by admis-sion of additional gas, and the system is maintained at these :
. .
P~
;`
conditions from about 15 seconds to about 30 minutes. The pressure is then reduced over a period of from about 1 to about 800 seconds, ~hereby the tobacco is brought to a temperature below 10C, and atmospheric pressure or the pressure at which the expansion step is to be carried out.
The resulting carbon dioxide-treated tobacco may then be rapidly transported, as described earlier in this specification to a zone where it ls exposed to expansion conditions by sub-~ecting it to heat or the equivalent in order to remove the carhon dioxide from the tobacco. This may comprise the use of hot surfaces, or a stream of hot air, a mixture of gases and steam, or exposure to other energy sources, such as microwave energy or infrared radiation. It has been found that the use of a gas composition comprising at least 50%(by weight) f steam, and preferably above 80% (by weight) of steam, provides particularly satisfactory results. A convenient means of ex-; panding the carbon dioxide-containing tobacco is to place it or to entrain it in a stream of heated gas, such as superheated steam or to place it in a turbulent air stream maintained, for example, at a temperature of from about 150 to about 260C (as low as 100C and as high as 370C~ for a period of about 1 second to lQ minutes. The impregnated tobacco may also be heated by being placed on a moving belt and exposed to infrared heating fiy exposure in a cyclone dryer, by contact in a tower with superheated steam or a mixture of steam and air or the like. Any such contacting steps should not raise the tempera-ture o~ the atmosphere with which the tobacco is in contact to above about 370C and should preferably be from at about 100 to about 30ac r most preferably 150 to 260C when conducted 3Q at atmospheric pressure.
As is ~ell known in the processing of any organic matter, overheating can cause damage, first to colour, such as undue :.
darkening and, finally, .o the extent of charring. The necessary and sufficient temperature and exposure time for expansion without such da~age is a function of these two variables as well as the state of subdivlsion of the tobacco. Thus, to avoid undesirable da~age in the heating step, the impregnated tobacco should not be ~; exposed to the higher temperature levels, e.g. 370C, longer than 1 to 2 seconds.
One method for causing the expansion of the tobacco cells is to use the radiation methods described in either U.S.
Patents 3,40g,022 or 3,409,027. In this operation, the tobacco - never attains a temperature above about 140C, being cooled by the rapid evolution of gases. The presence of steam during heating assists in obtaining optimum results.
Another system, usually preferred, is to use a dispersion dryer, for example, one that is supplied either with steam alone or in combination with air. An example of such a dryer is a Proctor & Schwartz PB dispersion dryer, usually called hereafter a tower. The temperature in the dryer may range from about 120 to 370C with contact time in the dryer of about 1 to 10 seconds. In 2Q general, a 1 to 6 second contact time is utilized when the hot gas temperature is 260 to 315C or somewhat higher. As stated before, other known types of heating means may be used as long as they are capable of causing the impregnated tobacco to expand without excessive darkening. Th~ presence of a steam atmosphere of 20%
or more of the total hot gas composition aids in obtaining the best expansion; a high proportion (e.g., over 80% volume) of steam is preferred.
The present invention may be further understood by referring to the drawings. In the drawings:
Fig. 1 is a standard phase diagram plotting pressure of C2 (in p.s.i.a.) vs temperature (in F) of the tobacco bed for the carbon dioxide-tobacco system, with line I-II-III drawn thereon as an illustration of the system involved here.
Fig. 2 is a standard pressure enthalpy diagram, with line i I~I~ drawn thereon to further illustrate the present invention.
Fig. 3 is a standard pressure enthalpy diagram, with line - I-IV drawn thereon to illustrate the process of the present invention.
As a general illustration of the practice of this invention, reference may be made to Fig. 1. The conditions may, for example, - be such as are represented by line I-II-III on Fig. 1. For example, the tobacco, at about 12% OV in the form of cut bright filler, is placed in a pressure vessel capable of handling the desired pressure, for example, capable of handling a pressure of 1057 psig.
The vessel may be similar to the impregnation vessel described in Canadian Patent No. 1,013,640, but, in distinction to that appara-tus, need have no means for the handling of liquid CO2. The vessel may be f~ushed with gaseous CO2 or may be evacuated and is pressured with gaseous CO2 to bring the contents to a condition (at II~ where the pressure is greater than 250 psig and the temperature is not less than -23C. The pressure is then released (to III). The conditions of the entire sequence (as shown by line I-II-III) are such that the carbon dioxide is maintained below and to the right of the saturated vapor line on Fig. 1.
In one form of the invention, as may be seen from Fig. 2, the enthalpy of the CO2 is greater than about 140 BTU/lbm and the CO2 is present in gaseous form. The vessel may be maintained at these conditions for 1/4 to 30 minutes, as illustrated by line I-III. The pressure may then be reduced rapidly, preferably within 10 to 120 seconds, preferably to atmospheric pressure, as illustrated by line III-IV in Fig. 2.
The impregnated tobacco then is transferred (preferably but not necessarily directly) to a rapid heating zone or vessel such as the heating vessel described in Canadian Patent No. 1,013,640 mentioned above or as described earlier in this specification, for example, an expansion tower, microwave chamber, or the like.
The temperature at which the impregnated tobacco is main-tained prior to the expansion or rapid heating step will largely govern how long the CO2 remains in the tobacco in sufficient quantity to cause the desired expansion. If there is little insulation or means to keep the temperature down, the transfer should be rapid, preferably less than a few minutes. An insulated "bulking" container is preferred to accomplish the transfer.
Supplementary cooling may also be provided as, for example, by lQ applying crushed or powdered dry ice or by spraying liquid nitro-gen on the impregnated tobacco.
The rapid heating causes expansion of the tobacco at a temperature where the tobacco is pliable and elastic and the tobacco can be expanded without fracture to an approximation of its green leaf state. A significant and useful degree of expansion is realized.
Referring to the Fig. 3, an illustration of the present invention is shown. Tobacco at about 12% OV in the form of cut bright filler is placed in a pressure vessel. The vessel may be similar to the impregnation vessel described in Canadian Patent No. 1,013,640 but, in distinction to that apparatus, need have no means for the handling of liquid CO2. The vessel may be flushed with gaseous CO2 or may be evacuated and is pressured with CO2 to bring the contents to a condition wherein the pressure is greater than 250 psia and the temperature is not less than -23C, and the enthalpy is at or above 140 BTU/lbm as shown by line I-II
in the drawing. The enthalpy of the CO2 is then reduced by cooling below about 140 BTU/lbm (but at conditions of temperature and pressure such that the CO2 is present primarily as gas) as shown by line II-III. The vessel is maintained at these conditions for 1/4 to 30 minutes. The pressure is then reduced rapidly, preferably within 10 to 120 seconds, for example, to atmospheric pressure, as y illustrated by line III~
The impregnated tobacco then is transferred (preferably but not necessarily directly) to a rapid heating zone or vessel such as the heating vessel described in Canadian Patent No. 1,013,640, mentioned above, or as described earlier in this specification, for example, an expansion tower, microwave chamber, or the like.
The rapid heating causes expansion of the tobacco at a temperature where the tobacco is pliable and elastic and the tobacco can be expanded without fracture to an approximation of its green leaf state. A significant and useful degree of expansion is realized.
The temperature at which the impregnated tobacco is maintained prior to the expansion or rapid heating step will largely govern how long the CO2 remains in the tobacco in sufficient quantity to cause the desired expansion. If there is little insulation or means to keep the temperature down, the transfer should be rapid, preferably less than a few minutes. An insulated "bulking" con-tainer is preferred to accomplish the transfer. Supplementary `~ cooling may also be provided as, for example, by applying crushed or powdered dry ice or by spraying liquid nitrogen on the impregnated tobacco.
The following examples are illustrative:
A l-pound sample of commercial cased bright tobacco filler at 12.5% OV was placed in an autoclave-type pressure vessel and was pressurized to 800 psig with CO2 gas obtained from a CO2 supply tank which was maintained at a CO2 pressure at least ` slightly above the desired impregnation pressure. The impregnator system temperature was maintained above 30C during the pressure cycle by supplying extra heat to the system, when necessary, to prevent any formation of liquid or solid CO2 during the entire processing cycle. After a 15-minute contact time, the pressure and temperature conditions of the CO2 gas in the impregnator ~L ~, - r ' ~ r~
were found to correspond to an enthalpy ~alue of about 142 BTU/lb f C2 gas. The pressure was released by venting in about 30 seconds after which the tobacco temperature was found to be 2.2C.
The impregnated sample had a weight gain of 2.0~ which is attributable to the gaseous CO2 contained therein. The impreg-nated material was then, within about 5 minutes time, exposed to heating in a 3-inch diameter tobacco expansion tower by contact with superheated steam at 288C and a velocity of 140 ft/sec for about 4 seconds. The product exiting the expansion tower had an OV of 2.1%. The product was equilibrated at standard conditions of 23.9C and 60% RH for about 18 hours. The filling power of the equilibrated product was measured by the standardized cylinder volume (CV~ test described later in this specification as 74 cc/10 g at 11.2~ OV. This gave a corrected CV (CCV) value at 11% OV of 76 cc/10 g. An unexpanded control was found to have a cylinder volume of 36 cc/10 g. The sample after processing, therefore, had a 111% increase in filling power as measured by the CV method.
A series of bright tobacco samples were treated as in Example 1 under conditions where gaseous CO2 and substantially no liquid or solid CO2 would be formed. The tobacco feed OV
was varied from 9% to 14.6%. The conditions of each test and the test results are shown in Table I. Where no value is shown in the Table for a variable, the value is as in Example 1.
Table I
~ ller Expansion with Gaseous CO2 :
.: .
Test # 1 2 3 Tobacco Feed OV 9.0% 10.3% 14.6%
Impregnation Pressure, psig 800 800 800 C2 Temperature Prior to Vent, C 31.7 31.7 32.2 C2 Enthalpy Prior to Vent, BTU/lb. 143 143 143 Tobacco Temp. after Venting, C -20.0 -22.8 ~2.8 % C2 Retention on Tobacco 2.9 2.4 1.5 Product OV after Expansion 1.7% 1.8% 3.2%
Reordered Product CV 62 94 74 Reordered Product OV 11.6 10.3 11.3 Correct CV at 11% OV 66 88 76 % Increase in Filling Power 83 144 111 ; A series of bright tobacco samples were treated as in Example 1 under conditions where gaseous CO2 and substantially no liquid or solid CO2 would be formed. The hold time was varied.
The conditions and test results are shown in Table II. Where no value is shown in the Table for a variable, the value is as in Example 1.
Table II
Filler Expansion with Gaseous CO2 Test # 3 4 5 Tobacco Feed O~ 14.2%14.4%15.3%
: Impregnation Pressure, psig 800 800 800 Hold Time, Minutes 1 2 20 C2 Temperature prior to Vent, C 58.9 30.0 35.6 C2 Enthalpy prior to Vent, BTU/lb. 160 142 144 Tobacco Temp. after Venting, C 8.3 -5.6 4.4 % C2 Retention on Tobacco 2.0 2.6 1.5 Product OV after Expansion 2.2%2.0 3.8 Reordered Product CV 71.274.0 76.2 Reordered Product OV 11.111.6 11.6 Corrected CV at 11% OV 72 78 80 % Increase in Filling Power 100 117 122 Example 4 30A series of bright tobacco samples were treated as in Example 1 at conditions where no liquid or solid CO2 would be expected to be formed. The impregnation pressure was varied.
The test results are shown in Table III. Where no value is shown in the Table for a variable, the value ls as in Example 1.
Table III
Filler Expansion with Gaseous CO2 Test # 6 7 8 9 10 11 Tobacco Feed OV 14.5 13.6 lQ.3 16.1 13.2 13.3 Impregnation Pres-sure, psig 300 4Q0 500 600 700 800 Hold Time, Minutes 15 15 15 25 15 15 C2 Temperature prior to Vent, C -11.7 NA 20.6 20.6 19.4 53.9 10 C2 Enthalpy prior to Vent, BTU/lb. 143 NA 15Q 145 142 155 Tobacco Temp. after Venting, C -13.9 NA 3.3 -5.6 -16.7 20.6 Product OV after Expansion 2.2 1.9 2.1 2.1 3.4 2.7 Reordered Product CV 62 66 59 75 74 60 Reordered Product OV 10.7 11.5 11.7 11.4 11.5 11.6 Corrected CV at 11%
Increase in Filling Power 83 92 78 119 114 81 ~` .
A l-pound sample of commercial cased bright tobacco filler at 11.1% OV was placed in an FS-3 pressure vessel and '! pressurized to 800 psig with ~2 gas as in the procedure of Example 1. The impregnation system t~mperature was cooled by circulating a cooling solution through a jacket surrounding the impregnation vessel until the CO2 gas in the impregnator was cooled to near its saturation temperature. After a 15-minute contact time, the pressure and temperature conditions of ~he CO2 gas in the impregnator were found to correspond to an enthalpy ~alue of about 130 BTU/lb. of CO2 gas. Although some CO2 condensation probably occurred within the vessel, the C2 was present primarily as a gas. The pressure was released by venting in about 30 seconds after which the tobacco temperature was found to he -37.8C. The impregnated sample had a weight gain of about 3.5% attributable to CO2. This impregnated material was then heated as in Example 1. The product exiting the exp2n-sion tower had an OV of 1.9%. The equilibrated product had a CV
of 90.6 at an OV of 10.8%. This corresponds to a CCV of 89 or an increase in filling power of 147% over the unexpanded control ; (36 cc/10 g).
A series of bright tobacco samples were treated as in Example 5 at conditions where the CO2 gas would be coGled to near saturation prior to pressure release at three different pressures. The conditions and test results are shown in Table IV. Where no value is shown in the Table for a variable, the value is as in Example 1.
Table IV
:
Filler Expansion with Gaseous CO2 -Test # 12 13 14 ~- Tobacco Feed OV 9.5% 10.8 12.1 Impregnation Pressure, psig 800 600 500 Hold Time, Minutes 15 15 20 C2 Temperature prior to Vent, C 19.4 7.2 2.2 C2 Enthalpy prior to Vent, BTU/lb. 129 139 139 ` Tobacco Temp. after Venting, C -38.9 -27.8 -18.3 % C2 Retention on Tobacco 3.7 2.6 2.4 Product OV after Expansion 1.3% 1.4 1.9 Reordered Product CV 89 88 71 Reordered Product OV 10.5 10.9 11.9 Corrected CV at 11% OV 85 87 78 % Increase in Filling Power 136 142 117 The procedure of Example 5 was repeated using cased burley tobacco. The equilibrated expanded product was found to have a CV of 92.4 at 10.1% OV or an increase of about 100%
over the unexpanded control.
The procedure of Example 5 was repeated using a tobacco blend as normally used in cigarette manufacture. The product was found to have a CV of 78.1 at 11.1~ OV or an increase of about lQ5~ o~er the unexpanded control.
A l~pound sample of cased bright tobacco was processed as in Example 1 and found to have a CCV of 81. This product was blended at 25% with conventional tobacco blend. Cigarettes were smoked and found to have a desirable taste and aroma;
firmness of the tobacco rod was acceptable.
A 13-pound sample of cased bright tobacco was processed as in Example 5. The product was found to have a CCV of 78.
A 5-pound sample of cased bright tobacco was impregnated as in Example 5 but was then subjected to heating in a static bed using 149C steam for a 5-minute exposure. The equilibrated product was found to have a CV of 85.
A series of runs was conducted following the process of Example 5 and the runs were found to give cylinder volume results of 80, 80, 80, 79, 84, 78, 79, 78 and 79, respectively.
This gives an average CV of 80 for the 9 trials or an increase in filling power of 121% over the untreated control.
A series of 3 runs was conducted according to the pro-cess of Example 5, except that the feed tobacco was pre-chilled to a temperature just below -20C before the tobacco was con-tacted with the pressurized CO2 gas. The reordered product CV results under these circumstances were found to be 92, 92 and 87, respectively. This gave an average increase in filling power of 151% over the untreated control.
Two series of runs were conducted in a manner similar to Example 1. However, conditions were as indicated in Table V with a ten~minute hold period and the tower conditions were:
3-inch tower at 60,QF, with lQ0% steam. Series #2 was run under similar conditions to Series #1.
The results of both series of these runs are given in ' Table V together with the results for an unexpanded control sample and for a control sample which was expanded, without any C2 treatment:
Table V
S-eries #l Series #2 %Reordered % Reordered Press. (psig), OV CV/OV CCV OV CV/OV CCV
Control 11.836.8/12.6 - - - -Exp.control - - - 1.9 64.6/10.9 , 250 2.572.8/10.8 71.2 1.5 73.8/10.8 72.3 300 2.876.3/10.8 74.9 1.2 81.4/10.7 78.9 , 325 2.677.2/10.8 75.9 1.2 79.6/10.7 77.5 ~, 350 2.378.4/11.0 78.4 1.2 77.3/11.2 78.5 375 2.480.6/11.1 81.0 1.4 78.7/11.1 79.6 4Qo 2.678.5/11.2 79.9 1.4 82.0/11.1 85.6 800 2.892.0/11.2 93.3 1.5 97.6/11.1 98.0 It will be seen that pressures of 250 psig through 800 psig provided excellent expansion, compared with the controls.
The following experiments were also conducted:
Experiment 1 The impregnation procedure of Example 11 was repeated but the impregnated material was simply allowed to warm to room temperature and was not subjected to tower expansion. The re-sulting product showed no gain, and perhaps a slight loss, in CV compared to the untreated control.
Experiment 2 A comparison run of gaseous vs. liquid CO2 impregnation was conducted in the following manner.
1~ Liquid CO2~Three pounds of cased commercial bright tobacco filler (OV of 12.7%) was impregnated with liquid C2 at 800 psig, cooled to 19.6C, and held for 15 minutes.
Thereafter the excess liquid was drained and the pressure was re-leased. A 23% gain in weight was attributed to CO2 pickup.
The material was somewhat clumped together because of the large amount of retained CO2.
2. Gaseous CO2--Three pounds of cased commercial ; 10 bright tobacco filler (OV of 13.3%~ was pressurized with gaseous CO2 at 800 psig and 19.6C for l5 minutes. Thereafter the pressure was released. A 3% gain in weight was attributed to CO2 pickup. The material was free-flowing and easy to handle.
Roth samples were processed in a 4-inch diameter tobacco expansion tower and the samples were equilibrated and measured for cylinder volume. The samples which utilized the liquid impregnation was found to have a CCV of 79 and the comparable sample impregnated with CO2 gas was found to have a CCV of 82.
Experiment 3 A series of trials was conducted over an impregnation pressure range of 20, 40, 60, 80, 100, 200, 300, 400, 600 and 800 psig, employing 10-minute contact time, following the pattern of Example 1, with expansion in the tower with a steam temperature of 316 C. These samples were run, together with an unexpanded control and with a control which was not contacted with CO2 with the conditions and the results set forth in Table VI:
Table VI
Reordered Pressure (psig) OV% CV OV CCV
Control 13.630.8 13.3 33.2 Exp. control 2.249.3 12.2 50.1 2.955.7 11.8 57.2 2.454.3 11.9 56.3 2.057.7 11.6 58.2 2.557.7 11.7 58.7 100 2.655.7 11.7 56.7 200 2.356.4 11.7 57.4 300 2.755.0 11.8 56.5 400 1,965.9 11.5 68.9 600 1.875.9 11.6 80.7 800 1.884.4 11.5 88.4 , 10 Table VI illustrates that some expansion may be obtain-ed at lower pressures, but pressures of about 400 psig may be necessary to achieve product objectives. It will be seen, how-ever, from Example 14, that a pressure of 250 psig can be effective to produce a satisfactory degree of expansion.
The terms "cylinder volume" and "corrected cylinder volume" are units for measuring the degree of expansion of - tobacco. The term "oven-volatiles content" or "oven volatiles"
is a unit for measuring moisture content (or percentage of moisture) in tobacco. As used throughout this application, the values employed, in connection with these terms, are determined as follows:
Cylinder Volume (CV) Tobacco filler weighing 10.000 g is placed in a 3.358-cm diameter cylinder and compressed by a 1875-g piston 3.335-cm in diameter for 5 minutes. The resulting volume of filler is reported as cylinder volume. This test is carried out at standard environmental conditions of 23.9C and 60% RH; con-ventionally unless otherwise stated, the sample is pre-condition-ed in this environment for 18 hours.
Corrected Cylinder Volume (CCV~
The CV value may be ad~usted to some specified oven-volatile cc,ntent in order to facilitate comparisons.
CV ~ CV + F (OV - OVs) where OVs is the specified OV
and F is a correction factor (Yolume per %) predetermined for the particular type of tobacco filler being dealt with.
Oven-Volatiles Content (OV) The sample of tobacco filler is weighed before and after exposure for 3 hours in a circulating air oven controlled at 100C. The weight loss as percentage of ir.itial weight is oven-volatiles content.
For bright tobacco employed in the present application, the value of F in the calculation of CCV is 7.6 on average for - gaseous CO2 expanded tobacco.
Unless otherwise indicated, all percentages used herein are by weight.
Roth samples were processed in a 4-inch diameter tobacco expansion tower and the samples were equilibrated and measured for cylinder volume. The samples which utilized the liquid impregnation was found to have a CCV of 79 and the comparable sample impregnated with CO2 gas was found to have a CCV of 82.
Experiment 3 A series of trials was conducted over an impregnation pressure range of 20, 40, 60, 80, 100, 200, 300, 400, 600 and 800 psig, employing 10-minute contact time, following the pattern of Example 1, with expansion in the tower with a steam temperature of 316 C. These samples were run, together with an unexpanded control and with a control which was not contacted with CO2 with the conditions and the results set forth in Table VI:
Table VI
Reordered Pressure (psig) OV% CV OV CCV
Control 13.630.8 13.3 33.2 Exp. control 2.249.3 12.2 50.1 2.955.7 11.8 57.2 2.454.3 11.9 56.3 2.057.7 11.6 58.2 2.557.7 11.7 58.7 100 2.655.7 11.7 56.7 200 2.356.4 11.7 57.4 300 2.755.0 11.8 56.5 400 1,965.9 11.5 68.9 600 1.875.9 11.6 80.7 800 1.884.4 11.5 88.4 , 10 Table VI illustrates that some expansion may be obtain-ed at lower pressures, but pressures of about 400 psig may be necessary to achieve product objectives. It will be seen, how-ever, from Example 14, that a pressure of 250 psig can be effective to produce a satisfactory degree of expansion.
The terms "cylinder volume" and "corrected cylinder volume" are units for measuring the degree of expansion of - tobacco. The term "oven-volatiles content" or "oven volatiles"
is a unit for measuring moisture content (or percentage of moisture) in tobacco. As used throughout this application, the values employed, in connection with these terms, are determined as follows:
Cylinder Volume (CV) Tobacco filler weighing 10.000 g is placed in a 3.358-cm diameter cylinder and compressed by a 1875-g piston 3.335-cm in diameter for 5 minutes. The resulting volume of filler is reported as cylinder volume. This test is carried out at standard environmental conditions of 23.9C and 60% RH; con-ventionally unless otherwise stated, the sample is pre-condition-ed in this environment for 18 hours.
Corrected Cylinder Volume (CCV~
The CV value may be ad~usted to some specified oven-volatile cc,ntent in order to facilitate comparisons.
CV ~ CV + F (OV - OVs) where OVs is the specified OV
and F is a correction factor (Yolume per %) predetermined for the particular type of tobacco filler being dealt with.
Oven-Volatiles Content (OV) The sample of tobacco filler is weighed before and after exposure for 3 hours in a circulating air oven controlled at 100C. The weight loss as percentage of ir.itial weight is oven-volatiles content.
For bright tobacco employed in the present application, the value of F in the calculation of CCV is 7.6 on average for - gaseous CO2 expanded tobacco.
Unless otherwise indicated, all percentages used herein are by weight.
Claims (5)
1. A process for expanding tobacco to achieve at least about 50 per cent increase in cylinder volume, comprising the steps of (1) impregnating tobacco with gaseous carbon dioxide under a pressure of 400 to 800 psig for a period of 1/4 to 30 minutes and at sufficient temperature that substantially all of the carbon dioxide is maintained in gaseous form, (2) decreasing the pressure on the carbon dioxide-impregnated tobacco and (3) heating the impregnated tobacco under conditions effective to liberate the carbon dioxide therein so as to cause expansion of the tobacco.
2. The process of Claim 1 wherein the pressure is reduced to substantially atmospheric pressure in step (2).
3. The process of Claim 2 wherein said temperature in step (1) is sufficient that substantially all of the carbon dioxide remains in gaseous form when the pressure is reduced to atmospheric pressure.
4. The process of Claim 2 wherein step (3) includes heating the tobacco to a temperature in the range of about 100 to 370°C.
5. A process as in Claim 1, 2 or 3 wherein the impregnation is carried out at a temperature of not lower than -23°C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA362,247A CA1115164A (en) | 1978-03-29 | 1980-10-10 | Tobacco product and improved process for the expansion of tobacco |
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/891,290 US4235250A (en) | 1978-03-29 | 1978-03-29 | Process for the expansion of tobacco |
| US891,468 | 1978-03-29 | ||
| US891,290 | 1978-03-29 | ||
| US05/891,468 US4258729A (en) | 1978-03-29 | 1978-03-29 | Novel tobacco product and improved process for the expansion of tobacco |
| CA323,817A CA1115163A (en) | 1978-03-29 | 1979-03-20 | Tobacco product and improved process for the expansion of tobacco |
| CA362,247A CA1115164A (en) | 1978-03-29 | 1980-10-10 | Tobacco product and improved process for the expansion of tobacco |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1115164A true CA1115164A (en) | 1981-12-29 |
Family
ID=27426137
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA362,247A Expired CA1115164A (en) | 1978-03-29 | 1980-10-10 | Tobacco product and improved process for the expansion of tobacco |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1115164A (en) |
-
1980
- 1980-10-10 CA CA362,247A patent/CA1115164A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |