US2760495A - Reducing the nicotine content of tobacco smoke - Google Patents

Description

Aug. 28, 1956 sAMFlELD ET AL 2,760,495

REDUCING THE NICOTINE CONTENT OF TOBACCO SMOKE 2 Sheets-Sheet 2 Filed Dec. 16, 1954 REACTION CHAMBER a 4 3 K \v V) .V. m f\ J.) R mm W B 2 P T I S 2 CM l. OE MM V a RC V 8 3 5 1 E a f v AE VK 5 7 7 2 R V A" e 2 f m A u f. r IAIPII M 3 A 2 WA Vm \L V :17 VS Ma m L 5 E m fl v v A 1 8 1 HEAT EXCHANGE COOLING WATER I INVENTORS MAX MARCUS SAMFIELD EARL EVERETT LOCKLAIR BRANTLEY ARMSTEAD BROCK B7 1% KW ATTORNEYS United States Patent 9 REDUQING THE NICQTINE CONTENT OF TGBACCG SMOKE Application December 16, 1954, Serial No. 475,672

20 Claims. (Cl. 131-143) This invention relates to a method of treating tobacco which includes converting its normal content of nicotinic salts or nicotine, or both, into other substances which do not produce nicotine in the smoke of the tobacco.

It has been known since the Gross and Dixon Patent No. 1,962,145 issued on June 12, 1934, that ethylene or propylene oxide gas, when brought in contact with tobacco, combines the ewith in such a. way as to lessen the amount of nicotine present in the smoke therefrom, presumably by reaction with the nicotine or salts of nicotine to form products of different properties. The Gross and Dixon patent states that nicotine reduction by treatment with ethylene or propylene oxide gas is increased in response to increased initial moisture-content of the tobacco, increased concentration of the oxide, and increased length of exposure. The process disclosed in the Gross and Dixon patent has not, however, been commercially adopted because of the serious impairment of smoking taste and flavor which occurs when tobacco is exposed to either of these oxides for the times and under the conditions required, according to the teachings of that patent, to achieve a commercially significant nicotine reduction.

The object of the present invention is to bring about a usefully large reduction of nicotine in tobacco without detectably impairing its smoking taste or flavor.

Following the precedent established in the Gross and Dixon patent, the expressions nicotine reduction, reduction in nicotine content, denicotinization, and similar expressions, when used in the present specification and appended claims in reference to any particular tobacco, mean a reduction in the nicotine content of vapors distilled from that tobacco at temperatures near to the boiling point of water, as determined by the well-known silicotungstic acid test. These expressions donot mean or imply that matter has been extracted or physically removed from the tobacco leaf complex; they have reference to a change in the properties of the tobacco and more particularly a modification or reduction in its property of giving ofif nicotine-containing vapors when the tobacco is smoked.

We have discovered that changes in the smoking taste and flavor of tobacco treated with ethylene oxide are caused primarily by certain conditions prevailing in the process and not by the reduction in the amount of nicotine. Thus, we have found that treatment of identical tobaccos with ethylene om'de suflicient to bring about the same degrees of nicotine reduction may in one case result in a product of unchanged taste and flavor, and in another case one which is markedly altered in these respects. It appears that the interrelationship of the various factors involved in denicotinizati'on and in taste alteration is complicated, and that the prior art has given no guidance for the development or operation of a process of ethylene oxide denicotinizaticn that will predictably reduce the nicotine content of the tobacco to a commercially significant extent, and at the same time leave the taste of the tobacco not detectably impaired.

We have discovered that there is an average tempera- 2,160,495 Patented Aug. 28, 1956 lQQ ture above-which tobacco treated with ethylene oxide will suffer an impairment in smoking taste and flavor, and

below which no such impairment can be detected. Further, we have found that this temperature is not the same for all types of tobacco, but that it can be ascertained by a simple test for any given type or specimen of tobacco.

We have also found that exposure of tobacco to ethyleue oxide for an excessive period of time impairs the sucking taste and flavor. All other things being equal, an amount of denicotinization which can be effected in one hour without altering the flavor of the tobacco, seriously impairs the flavor if brought about by treatment wherein the eifective contact time extends over a period of five or six hours. Consequently, according to our invention, denicotinization is accomplished within specific time limits, either by using a higher partial pressure of ethylene oxide in the treating vapors, or by increasing the temperature of treatment within limits already indicated.

In addition to the effects of temperature and time, we have found that another factor affecting the denicotinization-flavor relationship is the continual replenishment of mixed treating vapors of the desired partial pressure of ethylene oxide in immediate contact with the tobacco. Thus, if a desired amount of denicotinization can be obtained by placing a mass of tobacco in a motionless body of gas consisting of a mixture of ethylene oxide and an inert gas at a predetermined starting partial pressure of ethylene oxide, and keeping the tobacco and the gas in motionless contact for a period of time long enough to achieve significant nicotine reduction, the flavor of the tobacco may be adversely affected. On the other hand, using the same partial pressure of ethylene oxide and the same temperature, but subjecting the tobacco to contact with fresh supplies of the ethylene oxide-containing mixture at frequent intervals during the process, the flavor can be maintained unimpaired while the same extent of denicotinization is achieved.

According to the present invention, a mixture of a reaction gas such as ethylene oxide or propylene oxide and an inert gas such as carbon dioxide, in which mixture the reaction gas does not exceed about 82% by volume, is brought into contact with a body of tobacco to be denicotinized during an effective contact time not exceeding about 2.5 hours; during such period the mixture is so pumped or handled as to be in a turbulent condition or in motion relative to the tobacco during part at least of the time it is in contact therewith; and during the period of contact the temperature of the tobacco is so controlled, as for example by extracting or dissipating heat therefrom during such period, that its average temperature does not rise materially above the temperature (herein called temperature t) at which the consumption by the particular tobacco of reaction gas, per pound of nicotine reduced, begins to increase with increasing temperature.

It is not necessary, though it may be beneficial, that the gaseous mixture shall be in a turbulent or moving state during all of the time that it is in contact with the tobacco. The preferred form of the invention, as described below, contemplates intermittent turbulence or motion whilethe gaseous mixture is being evacuated from and flowed into a chamber containing a mass of tobacco, with brief periods of dwell or rest between evacuations. However, the invention equally contemplates the use of other procedures, as mentioned below, in which the gaseous mixture and the tobacco are in continuous relative movement and the gaseous mixture in contact with the tobacco is continuously turbulent.

According to the invention in another of its aspects, reaction gas is added continuously or intermittently to the gaseous mixture during the period of contact. Preferably the amount added would be approximately equal to the amount consumed by the tobacco in the course of the reaction. The make-up quantities of'rea'ction gas may be added to the mixture during the period of turbulence, or the period of dwell, or both if both are used. Thus, the use of both turbulence and continuous or intermittent makeup provides a means by which the concentration of gaseous mixture in immediate contact with the tobacco is maintaineed, despite depletion by the reaction. Also, the use of turbulence created by alternate evacuation of the gaseous mixture and return thereof after make-up reactant has been added, provides a means of assuring a much more copious penetration of reactant into the interior of large tobacco masses than can be obtained by mere diffusion.

The temperature t of any particular type or kind of tobacco appears to be characteristic for that type or kind, varies considerably between different types and kinds of tobacco, and can be determined for any particular lot of tobacco by a simple laboratory test. Oneway of carrying out this test is as follows: A number of samples of the tobacco Whose temperature t is to be determined are placed in separate flasks and treated with pure ethylene oxide for equal periods of time under controlled and progressively higher temperatures in the respective flasks. For example, five temperatures may be selected such as 80, 100, 120, 140 and 160 F. The nicotine reduction and ethylene oxide consumption are then ascertained for each flask, and the ratio of lbs. of ethylene oxide consumed to lbs. of nicotine reduced in each flask is calculated. For example, in testing aged burley strips at the temperatures stated above the calculated ratios for the five temperatures were 1.95, 1.46, 1.02, 0.73 and 0.78 respectively. These figures are then plotted against the temperature of treatment in the respective flasks and the result is a curve having generally the appearance indicated in Fig. 1 annexed. For all tobaccos such curve is characterized by a rising trend A to the right of a low portion B. On the left the curve rises at C when pure ethylene oxide is used as in the above example. However, the test may also be performed using ethylene oxide mixed with an inert gas such as carbon dioxide. When the oxide is thus diluted the left-hand portion C of the curve does not rise so high as shown in Fig. 1 and, at low concentration of oxide, may even approach fiat- -ness. However, the portions A and B of the curve have about the same appearance whatever the concentration of the oxide. The portion B of the curve indicates approximately the temperature t at which the consumption by the particular tobacco of the particular oxide (in this case ethylene oxide), per pound of nicotine reduced,

begins to increase with increasing temperature. As an example, aged burley strips of good grades have a temperature 2 between about 150 and 155 F., and aged flue-cured strips a temperature 1 between about 120 and 125 F. It is not necessary for purposes of the present invention to ascertain temperature t with greater exactness than this. 7

According to a preferred example of the present invention (applied to well-humidified aged burleystrips having a temperature 1 between about 150 and 155 F.) a 'hogshead of the tobacco to be treated is submit-ted, in an enclosed chamber, and after removing substantially all the entrapped air therefrom by evacuation and flushmg with carbon dioxide, to the action of a mixture of ethylene oxide and carbon dioxide, the former being about 54% by volume, for one to three minutes, at an initial pressure of about 15.6 inches of mercury absolute. During this time, the partial pressure of ethylene oxide in the chamber, which initially was 8.4 inches of mercury absolute, tends to fall owing to combination of ethylene oxide with constituents of the of the tobacco. This, of course, tends to bring about a corresponding reduction in the total pressure and may be, but is not necessarily, compensated for in whole or in part by admitting addi- 'tional ethylene oxide gas, unmixed with carbon dioxide, into nated as the dwell period, the ethylene oxide-depleted vaporsa-re removed from the chamber by meansof a suction device until the total pressure within the chamber is reduced to about 7.0 inches of mercury absolute. When this point is reached, a fresh supply of the same oxide mixture is again admitted to the chamber till the pressure reaches about 15.6 pounds Hg abs. where it is held for one to three minutes with continual additions of pure ethylene oxide. These steps are then repeated through a large number of cycles, say 50, until the total effective contact time has reached about 1.2 hours and the average temperature of the tobacco in the hogshead, has reached a temperature of about 146 F This manner of treatment is herein called pulsing.

The total elapsed reaction time, measured from beginning to end of the pulsing treatment, is not an accurate indicator of the effective length of the exposure of the tobacco to ethylene oxide, because the time required for evacuation in each cycle may vary widely in different installations and with different pumps. The length of exposure is, however, accurately measured by effective contact time which we define as the length of time which would be required to obtain the same nicotine reduction without pulsing, if the treatment gas were kept in contact with the tobacco steadily under the conditions of temperature and partial pressure prevailing at dwell.

To bring the tobacco to the proper temperature and humidity for pulsing, preliminary steaming is employed in the manner now common in the ordering of tobacco, though one or two percent more of moisture is preferably left in the tobacco than is customary in the ordering of tobacco for blending and cigarette manufacture. We prefer to begin our treatment on tobacco with a moisture content of from about 9% to about 13%. Steam and air may then be effectively removed from the chamber and the tobacco by flushing the chamber with an inert gas such as carbon dioxide. When the pulsing treatment is over, the chamber is flushed once more with an inert gas such as carbon dioxide to remove all traces of ethylene oxide. Air is then admitted to the chamber and the hogsheads of tobacco removed.

While carbon dioxide is the preferred inert gas used in this process, other gases such as methane, propane,

butane, and nitrogen may be used in its place. However, carbon dioxide has the advantage over hydrocarbon diluents that it is non-flammable and tends to prevent explosions and fires which might result from the use of ethylene oxide or propylene oxide undiluted. In the case of the preferred mixture of ethylene oxide and carbon dioxide the ethylene oxide content may effectively range by volume from about 13% to about 75% and should preferably be from about 45% to about 55% of the mixed gas. However, both higher and lower concentrations of ethylene oxide in the mixture can be used, but if the ethylene oxide is present in less than about 10% the amount available for the reaction is so low that the process cannot practicably be carried out, and if the ethylene oxide concentration in the mixture is above about 82% it will explode in the absence of air if detonated by heat or spark. For most tobaccos the preferred mixture comprises approximately 50% ethylene oxide and the balance carbon dioxide. With a mixture containing 58% the explosive limit with air is not reached until air exceeds 12% of the total mixture. This provides a substantial safety factor. In all the mixtures above mentioned water vapor is often necessarily present.

Two beneficial features of the present invention, among others, are realized when the pulsing treatment is applied to a large bodyof tobacco such as a hogshead thereof. One is that a fresh supply of treatment gas is distributed throughout the mass of tobacco once in each pulsing cycle I as the pressure rises from valley to peak), and hence the process does not depend on diffusion for bringing ethylene oxide to the tobacco particles in the center of the mass.

the reaction vessel. At the end of one minute, desig-The other that the per odi evaPbIation of Water m,

the tobacco once in each cycle (as the pressure falls from peak to valley) serves to control or may otfset'entirely if desired, the rise in tempera-t 1re otherwise resulting from the exothermic reaction of ethylene oxide with tobacco.

Referring more especially to the second-mentioned of these features it is part of our invention, when applied in the form of a pulsing technique, to utilize the latent heat of evaporation of the water as a means of preventing the average temperature from rising above the temperature t of the particular tobacco. As above stated, the moisture content of the tobacco when first submitted to our process should be between about 9% and 13%. As an example when operating at the pressures (valley and peak) herein disclosed, and with a starting average tobacco temperature in the general region of 120 to 140 F. (for burley strips), the average temperature of the tobacco Will rise about 4 to 8 during treatment and 1% or more of the contained water will be evaporated. Since our tests indicate that the average temperature of the The duration of each pulse cycle depends largely on A the pumping equipment available. Since the maximum rate of reaction occurs at the peak of the cycle, when the partial pressure of the ethylene oxide is at its maximum, it is desirable to raise the pressure to its maximum as quickly as possible. We prefer to design the equipment so that seconds, or less, will suflice to raise the pressure from valley to peak. Similar considerations apply to the time required for evacuation, which should also be as rapid as possible. In most installations, one minute or hogshead would be likely to rise as much as 30 under less should sufiice to lower the pressure within the treatequivalent exposure to ethylene oxide without ofisetting ing vessel from peak to valley. evaporation, it appears that a useful feature of the present in subjecting tobacco to the pulse treatment accordinvention insofar as it may be embodied in a pulsing ing to our invention it is convenient to use apparatus of technique, is that heat is being intermittently and frethe type now used in ordering tobacco. The hogsheads quently removed from the tobacco during the time of of tobacco are introduced in the usual manner toan evacethylene oxide exposure, that is, after such exposure has uation chamber, and subjected to alternate steaming and begun "and before it has ended. By this means the temevacuation in order to raise the tobacco to the desired perature of the tobacco is prevented from rising to the levels of temperature and moisture content. After treatpoint where smoking taste and flavor will be impaired. ment with steam and evacuation, the tobacco is pref- Selection of the maximum and minimum pressures to erably then flushed with carbon dioxide in order to rebe used in the chamber during the pulsing technique demove residual steam and air from the tobacco. This flushpends upon a number of factors, according to the results ing step may also take the form of a sequence of flush: desired. Generally speaking, the lower the pressure at ing stages with intermediate stages of evacuation. The the valley of the pulsing cycle, the more rapidly Water tobacco is then ready for the pulsing treatment with a in the tobacco will be evaporated, heat willbe extracted mixture of ethylene oxide and carbon dioxide as above from the tobacco, and ethylene oxide mixture will be described, which is continued until the desired degree of pulled into the chamber on the next succeeding treatdenicotinization has been achieved. Finally the tobacco ment pulse. However, the pressurein the valley" shou d is flushed again with carbon dioxide, this time to rid not be less than the vapor Pressur f Water v r th parit of residual ethylene oxide. The tobacco is then disticular tobacco at the existing temperature. The pressure charged from the chamber. in the valley may be from about 4 to 8 inches Hg abs. By Way or" examples of the process carried out accordand a th pea a t 14 t 22 iIICheS- However, y y ing to our invention, using the pulsing technique in conof examples of preferred conditions, when the average tacting ethylene oxide with the tobacco, we set forth tobacco temperatureis a1'011nd145" the Pressures y data on several treatment runs under varying, and in 736 abmlt in Vallgy and at the Peak, and When some cases sharply contrasting, conditions. In each the t a co i ar un 10 h m Pr sur s m y bb case a hogshead of tobacco weighing from 900 to 1000 t ,Iespectively. lbs., was placed in a suitable chamber, subjected to the The ethylene oxide pulse is produced by admitting a thermovacuum process till the temperature thereof had mixture of ethylene oxide and inert diluent gas into the been raised to a starting temperature about 4 to 8 be- Cham in Whi h th t ac is C ntained at a tim Wh n low the temperature desired at the end of the run, and the valley pressure prevails therein. When the maxithe relative humidity had been brought to about 9% to mum pressure desired has been reached, further increase 13%, flushed with carbon dioxide to remove residual of gas pressure is checked and the gas is held momentarily steam and air, treated with ethylene oxide (mixed with or recirculated at constant pressure for a brief period of carbon dioxide) according to the pulsing technique above dwell at peak pressure. Due to th r a t on b tween described and under the conditions set forth in the table, ethylene oxide and tobacco the partial pressure of the flushed with carbon dioxide to remove residual treating ethylene oxide and correspondingly the total pressure of gas, discharged to the atmosphere, and tested. The rethe mixture tends to drop somewhat during dwell at the suits are summarized in the subjoined table.

Characteristics of Pulsing Treatment Nicotine Reduction Tobacco Approx. 1 23p. Cone. Length Eflective Pressures Ave. Nicotine Nic. Flavor tempt at end Ethy. No.0i Pulse- Contact Content Redue- Judged of Run Oxide, Pulse plus Time tion (as Percent Cycles Dwell (hrs) percent (1111111.) Valley Peak Start Finish of Start) Degrees Degrees 1 Burley 150-155 54 50 1 1.2 7.0 15.5 3.11 1.47 i 52.7 Good.

11 -155 144 48 20 a 1.5 5.0 21.0 2. 91 1.68 42.3 Very good. do 150-155 47 50 1 1.2 7.0 16.5 2.94 1.42 51.7 Poor. Cigarette Blend..- 150-155 143 50 150 1 3.3 6.5 15.5 1.65 0.17 89.8 Do. 5 Flue-cured"- 120-125 108 41 50 1 1.3 5.0 14.5 1. 94 1.01 48.0 Good. 6 d0 120-125 126 52 50 1 1.3 5.0 14.5 1.93 0.95 50.2 Faintly impaired. 7 Burley (11naged)-- 150-155 84 41 30 3 2.1 4.2 14.0 3.01 2.00 33.6 Good.

7 v The following explanations have reference to the numbered vertical columns in the above table.

COL J. In each example the tobacco was in the form of strips; in each case the tobacco was aged. except in Example 7. The tobacco of Example 4 was a cigarette blend.

Col. 2.The temperature I was determined for the particular lot or type of tobacco by the method above described. Temperature 2 is the temperature at which the consumption of ethylene oxide by the particular tobacco, per pound of nicotine reduced, begins to increase with increasing temperature as indicated at B in Fig. 1.

Col. 3.+Average temperature of all the tobacco in the hogshead at the end of the run is the arithmetical average of the readings of a large number of thermohms distributed throughout the hogshead at representative places near the center, the outside, top, bottom, etc.

Col. 4.'The treatment gas was a mixture of ethylene oxide and carbon dioxide, the concentration of the former being given in percent by volume of the mixture.

" Col. 5.-This states the number of times that treatment gas was pulsed into the chamber coincident with .the rise in pressure therein from valley to peak.

Col. 6.This states approximately the total elapsed time between the beginning of the inflow of treatment 'gas (pulse) and the end of the immediately following period of dwell at peak pressure, during each pulse cycle.

Col. 7.--The effective contact time is the length of time which would be required to obtain the same nicotine reduction without pulsing, if the same treatment gas were kept in contact with the same tobacco steadily under dwell conditions of temperature and pressure. Effective contact time is stated in this specification in hours and decimal parts of an hour.

Gals. 8 and 9.-The pressures during pulsing are given in inches of mercury absolute.

Cols. 10 and 1I.The average nicotine content of all the tobacco in the hogshead is the arithmetical average of the nicotine contents of each of a large number of samples systematically taken from representative positions within the hogshead, as determined by the silicotungstic acid test.

Col. 12.-The difference between the starting and finishing average nicotine content figures (cols. 10 and 11) is stated as a percent of the starting figure.

Col. 13.In all cases except Examples 3, 4, and 7 the treated tobacco was made up into cigarettes which were smoked by experienced judges or" tobacco and their judgment as to smoking taste and flavor is recorded. In Examples 3 and 4 persons experienced in cigarette manufacture judged the treated tobacco so poor in odor as to be unsuitable for cigarette manufacture. In Example 7 the tobacco, being unaged, was not yet ready for cigarette manufacture, but experienced judges of tobacco considered its flavor and aroma after ethylene oxide treata.

merit to be at least as good as it was before that treatment had been applied. I In order to illustrate more clearly the manner in which our invention may be carried out, we refer to the drawings hereto annexed wherein Fig. l is a chart on which has been drawn, in generalized form, a representative curve of the kind obtained when plotting the pounds of ethylene oxide consumed per pound of nicotine reduced for various temperatures of treatment of a particular tobacco. The nature of the tests, by which the temperature 1 for a particular type of tobacco may thus be determined, has been set forth above.

Fig. 2 shows diagrammatically one form of apparatus suitable for carrying out the process herein described.

Fig. 3 is a chart indicating diagrammatically the relationship of average tobacco temperature to pressure within the reaction chamber during the period of ethylene oxide pulsing treatment, showing the start and end of the 8 chart itself; these are as set forthin the text oi specification.

In operating our process it is preferred for reasons of economy to subject two batches of tobacco to concurrent treatment in two treating chambers manifolded together and to sources of gas and vapor supply as shown in the drawing. This is, however, not essential to the process.

Referring to Fig. 2, reaction chambers 1 and 2 and eachot such size as to hold several hogsheads of tobacco. The chambers can be sealed oii from the atmosphere, after the hogsheads have been wheeled in, by doors 1a and 2a known in the art. The two reaction chambers are connected by line 3 in which are interposed valves 4 and- 5 and which has a connection 6 for the admission of steam, and they are also connected by line 7 whichjis provided with valves 8 and 9. The reactionchambers are also provided with drain valves 10 and 11 respectively.

The source of ethylene oxide may be a vaporizer, comprising a drum 12 into which liquid ethylene oxide may be charged and a hot water coil 13 which serves to vaporize the ethylene oxide, which discharges vapors of ethylene oxide through line 14 controlled by valve 15 and thence through line 16 into line 17, which joins line 7 between valves 8 and 9. Carbon dioxide may be supplied to the system through line 18, whence it may flow either through line 19 controlled by valve 21 into line 16, where it is mixed with ethylene oxide, or through line controlled =by valve 22 into vapor separator 23.

Vapor separator 23 is equipped with drain valve 24. The vapor separator is connected by line 25 to the suctionend of pump 26, which discharges into lines 17 and 27, the latter being controlled by valve 28 and venting to-the atmosphere. Also conected to the vapor separator is line 29 from heat exchanger 30, the latter being interconnected by lines 31 and 32 controlled by valves 33 and 34 respectively to reaction chambers 1 and 2.

In carrying out the process, the above apparatus may, for example, be operated as follows: the reaction chambers are charged with the hogsheads of tobacco which it is desired to submit to the process. The moisture content and temperature of the tobacco is according to season, as well known in the art. At this stage the entire system is filled with air at atmospheric pressure, and all valves except 4, 5, 15, 21, and 22 are open. Doors 1a and 2a of the reaction chambers are then closed and sealed. After the reaction chambers are sealed, valves 8, 9, 10, 11, and 24 are closed, the pump is started, and both chambers are evacuated simultaneously through lines 31 and 32, air being expelled through line 27 to the atmospheric vent. After the pressure in the chambers reaches approximately 2 inches of mercury absolute, valves 33 and 34 are closed and then valves 4 and 5 are opened, admitting steam to chambers 1 and 2. Steam is admitted until the pressure of the steam in the chamber corresponds, as shown in standard saturated steam tables, approximately to the starting temperature desired in the hogsheads. When the desired steam pressure is reached, valves 4 and 5 are closed. Then valves 33 and 34 are opened, and the pump exhausts the mixture of steam and residual air to the atmosphere. This steaming and finishing is repeated several times until the tobacco treatment with intermediate parts omitted. No particular temperatures or pressures are to be inferred from the in thehogsheads reaches the desired average temperature as shown by thermometric devices inserted at various points in the tobacco masses. During the steaming and flushing most of the air will have been removed from the system. The exact number of fiushings will, of course, depend on the temperature desired in the hogsheads. When this temperature has been attained and the final flushing accomplished, valves 33 and 34 are closed,

In order to make sure that essentially all of the air has been removed from the system, it may optionally be flushed with carbon dioxide after the steaming and flushing cycles have been completed. This is accomplished by closing valve 28 and opening valves 8 and 33 and then admitting carbon dioxide by opening valve 22. Thus carbon dioxide is recirculated through chamber 1 while the pressure of carbon dioxide in the chamber is increasing. The maximum pressure of carbon dioxide in the chamber is determined by the desired degree of flushing. When that carbon dioxide pressure is reached in chamber 1 valve 22 is closed. Then valve 9 is opened and valve 8 is closed. This allows the pump to evacuate chamber 1 while filling chamber 2. After chamber 1 is pumped down to approximately 2 inches of mercury valve 33 is closed and 34 is opened. This recirculates caroon dioxide in chamber 2. After a sufiicient period of recirculation to substantially remove the residual air from chamber 2, chamber 2 is exhausted to the atmosphere by closing valve 9 and opening valve 28. After chamber 2 is pumped down to approximately 2 inches of mercury valve 28 and 34 are closed.

At this point vapor separator 23 is drained through valve 24 into air lock devices not shown. after the separator has been drained and valve 24 again closed, the system is ready for filling and pulsing which is accomplished as described below.

Valves 8 and 33 are opened and followed sequentially by valves 15 and 21. Valves 15 and 21 are metered proportioning valves and are opened to a sutiicient extent to achieve the desired proportions of ethylene oxide and carbon dioxide in the mixture in line 16. The pump recirculates the gas in chamber 1 until, at a predetermined pressure, which corresponds to the maximum pulse pressure desired, valves 15 and 21 are closed. Thereafter recirculation is continued for a predetermined time, depending on the pulse and pulse cycles desired. Since ethylene oxide is consumed by the reaction, valve 15 is partially opened during this recirculation to maintain thetotal pressure and ethylene oxide partial pressure in the system constant by adding additional ethylene oxide. As carbon dioxide is not consumed in the reaction, a constant ethylene oxide partial pressure is maintained by keeping the total pressure constant in this manner. At the end of the recirculation period valve 15 is closed. Then valve 9 is opened and valve 8 is closed. The result of this change in the valve settings is that the pump 26 now pumps gas from chamber 1 into chamber 2 until the maximum desired pulse pressure is achieved in chamber 2 or the desired minimum pressure is obtained in chamber 1, Whichever occurs first. If the minimum pressure is reached in chamber 1 before chamber is up to pressure, valve 33 is closed and the necessary additional gas mixture is supplied to chamber 2 by opening valves 15' and 21. Then valve 33 is closed and valve 34 opened, allowing gas to recirculate through chamber 2 at the maximum pressure for the desired length of time. During this recirculation period, valve 15 may be partially opened to maintain constant total pressure in chamber 2. At the end of the recirculation period valve 15 is closed, valve 8 is opened, and valve 9 is closed, thus pumping gas from chamber 2 into chamber 1. When chamber 1 has reached the desired pressure, valve 34 is closed and valve 33 is opened and recirculation in chamber 1 begins. Valve 15 is again opened to maintain constant pressure in chamber 1.

After the recirculation period valve 15 is closed and the pulsing process is repeated any desired number of times until the desired reduction of nicotine in the tobacco has been produced.

The change in tobacco temperature with time during pulsing is illustrated in Fig. 3. If it be assumed that the average temperature of the tobacco before pulsing is that indicated at 35, which might, for example, be 140 F., and the pressure is that indicated at 36, which might for example be 30 inches of mercury, the first step of pressure reduction 37 produces a corresponding drop in tempera ture 38. When ethylene oxide is admitted and the pressure rises as shown at 39 there is a corresponding rise in temperature 40, and during the period of dwell 41 at peak pressure the temperature continues to rise to a peak 42 owing to the exothermic reaction of ethylene oxide with elements of the tobacco. Constant pressure is maintained during the dwell 41 by admitting pure ethylene oxide sufiicient to offset the amount thereof absorbed by the tobacco. When the chamber is exhausted as shown at 43 the temperature falls as shown at 44- due to evaporation of water. According to the preferred method of carrying out the process, temperature peak- 42' is succeeded by a next following peak 46 which is permitted to be slightly higher, and so on till the pulsing treatment is concluded and the last pulse of ethylene oxide is exhausted as shown at 47. This final exhaustion drops the average temperature to the level indicated at 48 which is the temperature at the completion of treatment. As stated above, the process may be carried out so that temperature 48 is above, below or about equal to temperature 35, but for reasons of economy in operation it is preferred that temperature 48 be about 4 to 8 F. above temperature 35. The pulse cycle, minimum and maximum pressures and holding time can be adjusted to control the rise in temperature for any desired effective treating time in such manner as to prevent excessive temperature rise during the treatment.

Afer completing the last pulse in chamber 1 and at the end of the recirculation period valves 8 and 33 are closed and valves 9 and 34 are opened. Carbon dioxide is then admitted through valve 22, filling chamber 2 to a predetermined pressure which may for example be 15 inchesof mercury, whereupon valves 22, 9, and 34 are closed and 33 and 28 are opened thus exhausting reaction chamber 1 to the atmosphere. T hen valves 28 and 33 are closed and 8 and 34 are opened, allowing carbon dioxide to flow from chamber 2 to chamber 1 until the pressure in chamber 2 is for example about 8 inches of mercury, and in chamber 1 about 15 inches. Valve 34 is then closed and 33 opened, thus recirculating carbon dioxide in chamber 1. After a period of recirculation, valve 8 is closed and 28 is opened, carbon dioxide being thereby evacuated from chamber 1 to the atmosphere.

Thereafter valve 28 is closed and valves 8 and 22 are opened thus filling chamber 1 to a predetermined pressure of carbon dioxide, for example 15 inchesof mercury. When that pressure, which is preferably approximately the maximumpulsing pressure, is reachedvalve 22 is closed and gas is again recirculated through chamber 1. After a period of recirculation valve 8 is closed and 9 is opened, thus pumping carbon dioxide from chamber 1 into chamber 2. When the predetermined pressure is achieved in chamber 2 valve 33 is closed and valve 34 is opened, thus efiecting recirculation of the gas through chamber 2. lfrer sufiicient recirculation, valve9 is closedand valve 28 is opened, thus exhausting chamber 2 to the atmosphere. This flushing process is repeated several times until ethylene oxide is effectively removed from the system.

After the last flushing, the chamber under the higher pressure is exhausted to the atmosphere and air is admitted tothe vent valves (not shown) until both chambers are at atmospheric pressure. Then the doors are opened and the hogsheads are removed from the chambers inthe usual manner and the chambers refilled.

In the above description reference to exhausting to the atmosphere does not mean mere release ofpressure since usually the pressures within the system in the oper ation of the process will be below atmospheric. Consequently the step of exhausting a chamber to the atmosphere will ordinarily involve the use of pump 26. No control means for the several valves is herein specifically shown or claimed. it will, however, be obvious that, in lieu of manual actuation of these valves, mechanical and automatic devices may be employed to control them in response to pressure and temperature conditions in the reaction chambers and to a timer capable of being preset to the desired length of pulse, dwell at peak with or with 11 out recirculation, and pulse cycle, and the desired number of pulse cycles or total length of treatment.

The same general considerations apply to the use of propylene oxide as to the use of ethylene oxide in the above-described denicotinizing process and, as stated above, similar results are generally obtainable using other diluents than carbon dioxide.

While the pulsing technique above described is preferred, because it can be adapted to utilize in large. part existing tobacco-treating equipment, similar results can be obtained by other devices and operations which embody the same principles. Thus, we can obtain the necessary turbulence and intimate contact at the required temperatures and for the desired time by subjecting the tobacco to the treating gas in a fluidized-bed type of operation. We can also achieve the results by flowing a current of treating gas in contact with a relatively shallow layer of tobacco on a moving belt. In each case the partial pressure of ethylene oxide may be maintained as required by adding that component to the stream of mixed gases.

While one form of process carried out in accordance with our invention has been disclosed herein, the process may be carried out in other ways and in different kinds of apparatus as set forth in the appended claims.

What is claimed is:

1. In the process of treating tobacco with a gaseous reactant selected from the group consisting of ethylene and propylene oxides, the steps of contacting said tobacco with a mixture of said reactant and an inert gas during an efiective contact time long enough to produce substantial denicotinization but not longer than about 2.5 hours, and extracting heat from said tobacco after the said contact time has begun and before it has ended.

2. In the process of treating tobacco with a gaseous reactant selected fromthe group consisting of ethylene and propylene oxides, the steps of contacting said tobacco with a mixture of said reactant and an inert gas during an effective contact time sufiicient to produce substantial denicotinization but not longer than about 2.5 hours, and controlling the temperature of the tobacco during contact so that during the period of said contact the average temperature thereof does not rise materially above the temperature at which the consumption by said tobacco of said reaction gas, per pound of nicotine retluced,v begins to increase with increasing temperature.

3. In the process of treating tobacco with a gaseous reactant selected from the group consisting of ethylene and propylene oxides, the steps of contacting said tobacco with a mixture of said reactant and an inert gas during an effective contact time long enough to produce substantial denicotinization but not longer than about 2.5 hours, and dissipating heat from said tobacco during the period of said contact so that during the period of said contact the average temperature of the tobacco does not rise materially above the temperature at which the consumption by said tobacco of said reaction gas, per pound of nicotine reduced, begins to increase with increasin temperature.

4. In the process of treating tobacco with a gaseous reactant selected from the group consisting of ethylene and propylene oxides, the steps of contacting said'tobacco with a mixture of said reactant and an inert gas during an effective contact time long enough to'produce substantial denicotinization but not longer than about 2.5 hours, and evaporating water from said tobacco during the period of said contact time at such a rate that'during the period of said contact the average temperature of the tobacco does not rise materially above the temperature at which the consumption by said tobacco of said reaction gas, per pound of nicotine reduced, begins to increase With increasing temperature.

5. The process of treating tobacco with a mixture of an inert gas and a gaseous reactant selected from the group consisting of ethylene and propylene oxides which adding additional amounts of said gaseous reactant'to- 12 comprises exposing said tobacco to contact with said gas eous mixture, causing said mixture to be in a turbulent condition and in motion relative to the tobacco during part at least of the time it is in contact therewith, and extracting heat from the tobacco after the said contact has begun and before it has ended whereby to limit the rise in temperature of the tobacco during treatment.

6. The process of treating tobacco with a gaseous reactant selected from the group consisting of ethylene and propylene oxides, which comprises contacting said tobacco with a mixture of said reactant and an inert gas during an effective contact time sufficient to produce substantial denicotinization but not longer than about 2.5 hours, causing said mixture to be in motion relative to the tobacco being treated during part at least of said contact time, and extracting heat from the tobacco during said period of contact whereby to limit the rise in temperature of the tobacco during treatment.

7. The process of denicotinizing tobacco by means of a gaseous reactant selected from the group consisting oi ethylene and propylene oxides, which comprises contacting said tobacco with a mixture consisting of said reactant and an inert gas, and adding additional amounts of said gaseous reactant to the mixture and extracting heat from the tobacco during the time that the contact continues.

8. The process of treating tobacco with a mixture of an inert gas and a gaseous reactant selected from the group consisting of ethylene and propylene oxides which comprises exposing said tobacco to contact with said gaseous mixture, causing said mixture to be in motion relative to the tobacco during part at least of said contact, and supplying additional amounts of said gaseous reactant to the mixture during the time that the contact continues.

9. The process of treating tobacco with a mixture of an inert gasand a gaseous reactant selected from the group consisting of ethylene and propylene oxides which comprises exposing said tobacco to contact with said gaseous mixture while the mixture is in a turbulent condition, and supplying additional amounts of said gaseous reactant to the mixture and extracting heat from the tobacco during the time the mixture is in contact with the tobacco.

10. The process of denicotinizing tobacco by means of a gaseous reactant selected from the group consisting of ethylene and propylene oxides, which comprises contacting said tobacco with a mixture of predetermined concentration consisting of said reactant and an inert gas, and adding additional amounts of said gaseous reactant to said mixture during the period of contact whereby to maintain the average concentration of the mixture throughout the contact period approximately equalto the predetermined initial concentration thereof.

11. The process of denicotinizing tobacco by means of a gaseous reactant selected from the group consisting of ethylene and propylene oxides, which comprises contacting said tobacco with a mixture of predetermined concentration consisting of said reactant and an inert gas,

during the period of said contact.

12. The process of denicotinizing tobacco by means of a gaseous reactant selected from the group consisting of ethylene and propylene oxides, which comprises contacting said tobacco with a mixture of predetermined concentration consisting of said reactant and an inert gas,

causing said mixture to be in motion relative to. the

tobacco during part at least of the time it is in contact: therewith, adding additional amounts of said gaseous reactant to said mixture during the period of said contact,

l3 and extracting heat from said tobacco during said period whereby to limit the rise in temperature of the tobacco.

13. The process of denicotinizing tobacco by means of a gaseous reactant selected from the group consisting of ethylene and propylene oxides, which comprises contacting said tobacco with a turbulent and moving mixture of predetermined concentration consisting of said reactant and an inert gas, adding additional amounts of said gaseous reactant to said mixture during the period of contact and evaporating water from the tobacco during said period whereby to limit the rise in temperature of the tobacco.

14. in the process of denicotinizing tobacco, the steps of exposing said tobacco to contact with an atmosphere consisting of a mixture of an inert gas and a gaseous reactant selected from the group consisting of ethylene and propylene oxides, said mixture being at a concentration of reactant and said atmosphere being at a pressure such that the consumption of reactant by the tobacco appreciably raises the tobacco temperature during the time of exposure, reducing the pressure of said atmosphere upon the tobacco to a pressure at which water contained in the tobacco vaporizes and the tobacco is thereby lowered in temperature, and repeating said steps in alternation during an effective contact time long enough to produce the desired denicotinization of the tobacco not exceeding about 2.5 hours, and at an average temperature of the tobacco during the period of its exposure to said mixture not materially exceeding the temperature at which the consumption by said tobacco of said reaction gas, per pound of nicotine reduced, begins to increase with increasing temperature.

15. In the process of denicotinizing tobacco, the steps of exposing said tobacco to contact with a mixture of an inert gas and a gaseous reactant selected from the group consisting of ethylene and propylene oxides, said mixture being at a predetermined concentration of reactant and pressure, for a period of dwell long enough to produce an appreciable rise in the temperature of the tobacco, adding additional amounts of said gaseous reactant to the mixture during said period of dwell, reducing the pressure of the mixture upon the tobacco to a pressure at which water contained in the tobacco vaporizes and the tobacco is thereby lowered in temperature, and repeating said steps in alternation during an effective contact time long enough to produce the desired denicotinization of the tobacco not exceeding about 2.5 hours, the average temperature of the tobacco during the period of its exposure to said mixture not materially exceeding the temperature at which the consumption by said tobacco of said reaction gas, per pound of nicotine reduced, begins to increase with increasing temperature.

16. In the process of denicotinizing tobacco, the steps of exposing said tobacco to contact with an atmosphere consisting of a mixture of an inert gas and a gaseous reactant selected from the group consisting of ethylene and propylene oxides, said mixture being at a predetermined concentration of reactant and a pressure such that the consumption of reactant by the tobacco appreciably raises the tobacco temperature during the time of exposure, reducing the pressure of said atmosphere upon the tobacco to a pressure at which water contained in the tobacco vaporizes and the tobacco is thereby lowered in temperature, raising said pressure to approximately the pressure first mentioned by introducing additional quantities of said mixture of substantially the original predetermined concentration whereby the temperature of the tobacco is once more raised, and limiting the average temperature of the tobacco during the period of its exposure to said mixture so that it does not materially exceed the temperature at which the consumption by said tobacco of said reaction gas, per pound of nicotine reduced, begins to increase with increasing temperature.

17. In the process of denicotinizing tobacco, the steps of exposing said. tobacco to contact with a mixture of an inert gas and agaseous reactant selected from the group consisting of ethylene and propylene oxides, said mixture being at a predetermined concentration ofreactant and ate pressure between about 1,4and 22 inches of mercury absolute, for a time long enough to cause an appreciable rise in the temperature of the tobacco, re: ducing the pressure of the mixture upon the tobacco to a pressure between about 4 and 8 inches of mercury (abs) for a time long enough to cause an appreciable fall in the temperature of the tobacco, and repeating said steps in alternation during an effective contact time long enough to produce the desired denicotinization of the tobacco not exceeding about 2.5 hours, and at an average temperature of the tobacco during the period of its exposure to said mixture not materially exceeding the temperature at which the consumption by said tobacco of said reaction gas, per pound of nicotine reduced, begins to increase with increasing temperature.

18. In the process of denicotinizing tobacco, the steps of exposing said tobacco to contact with a mixture of an inert gas and a gaseous reactant selected from the group consisting of ethylene and propylene oxides, said mixture being at a predetermined concentration of reactant and a pressure between about 14 and 22 inches of mercury absolute, for a time sufficient to cause an appreciable rise in the temperature of the tobacco, reducing the pressure of the mixture upon the tobacco to a pressure between about 4 and 8 inches of mercury absolute for a time sufficient to cause an appreciable fall in the temperature of the tobacco, raising the pressure to between about 14 and 22 inches of mercury absolute by introducing additional quantities of said mixture of substantially the original predetermined concentration, and limiting the average temperature of the tobacco during the period of its exposure to said mixture to a temperature not materially exceeding the temperature at which the consumption by said tobacco of said reaction gas, per pound of nicotine reduced, begins to increase with increasing tempera-ture.

19. The method of denicotinizing burley tobacco which comprises subjecting the same to contact with an atmosphere initially at a pressure of approximately 14 to 22 inches of mercury absolute consisting of approximately equal parts by volume of ethylene oxide and carbon dioxide for a total effective contact time sufiicient to produce a substantial nicotine reduction in less than about 2.5 hours, repeatedly lowering the pressure of said atmosphere during the time of said contact to a pressure of about 4 to 8 inches of mercury absolute whereby to evaporate contained water and thus control the rise in temperature of the tobacco resulting from said contact, and after each such lowering of pressure restoring the pressure of the atmosphere to the first-mentioned pres sure by introducing quantities of said mixture containing additional amounts of ethylene oxide to replace that consumed by reaction with the tobacco, and controlling the alternating steps of lowering and raising the pressure so that the average temperature of the tobacco does not rise materially above about -155 F. at any time during the period of contact.

20. The method of denicotinizing flue-cured tobacco which comprises subjecting the same to contact with an atmosphere initially at a pressure of approximately 14 to 22 inches of mercury absolute consisting of approximately equal parts by volume of ethylene oxide and carbon dioxide for a total effective contact time sufficient to produce a substantial nicotine reduction in less than about 2.5 hours, repeatedly lowering the pressure of said atmosphere during the time of said contact to a pressure of about 4 to 8 inches of mercury absolute whereby to evaporate contained water and thus control the rise in temperature of the tobacco resulting from said contact, and after each such lowering of pressure restoring the pressure of the atmosphere to the first-mentioned pressure by introducing quantities of said mixture containing additional amounts of ethylene oxide to replace that consumed by reaction with the tobacco, and controlling the alternating steps of lowering and raising the pressure so that the average temperature of the tobacco does not rise materially above about i20-125 F. at any time during the period of contact.

UNITED STATES PATENTS Gross et a1. June 12, 1934 Hentrich et a1 June 2, 1936 Merriam et a1. May 11, 1937 Baer et a1. Sept. 27, 1938

Claims (1)

1. IN THE PROCESS OF TREATING TOBACCO WITH A GASEOUS REACTANT SELECTED FROM THE GROUP CONSISTING OF ETHYLENE

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