MXPA97001391A - Method and apparatus for extending - Google Patents

Abstract

The present invention relates to an apparatus and method of tobacco expansion comprising a gas source of the tower, an obloid transport duct (20), in communication with the gas source, a tobacco feeder (18) in a location along the obloid transportation duct (20) and a separator (22) for recovery of tobacco from the expansion apparatus. The tobacco feeder (18) is adapted to introduce tobacco uniformly across the width of the obloid transportation duct (20). The apparatus improves the filling energy of the processed tobacco and can be operated at high production rates with less broken tobacco, which improves the performance of the tobacco

Description

METHOD AND APPARATUS FOR EXTENDING TOBACCO FIELD OF THE INVENTION The present invention relates to the spread of tobacco and, more particularly to the methods and apparatus for heating tobacco which has been impregnated with an extension agent.

BACKGROUND OF THE INVENTION Extension is a known way to improve the filling capacity per unit weight of tobacco (usually measured in units of volume per gram of tobacco). One of the best known methods for spreading tobacco includes the steps of impregnating a load of cut filler tobacco with an extension agent (or "impregnator") and then quickly heating the impregnated tobacco to volatilize the spreading agent, thereby causing an extension of the tobacco tissue. The heating can be effected conveniently by entering the tobacco into a stream of hot gas (or "tower gas") and directing the current through a pneumatic conveying column ("tower"). In many extension systems, a cyclone separator placed downstream of the tower separates the tobacco from the tower gas. U.S. Patent No. 3, 771, 533 describes a process in which the tobacco filler is impregnated with ammonia and carbon dioxide. The impregnated tobacco material is subjected to rapid heating, for example with a stream of air or air mixed with superheated stream, whereby the tobacco is blown as the impregnator is converted to a gas. US Patent No. 4, 336,814 (PM 745) describes methods for impregnating tobacco with liquid carbon dioxide, converting a portion of the impregnator to the solid form and then rapidly heating the impregnated tobacco to volatilize the impregnated carbon dioxide and blow tobacco The North American Patents Nos. 4, 235,250 and 4,258, 729 each describe the impregnation of the tobacco with gaseous carbon dioxide under pressure and then subjecting the bac to rapid heating after release of the pressure. U.S. Patent No. 4,366,825 discloses a tobacco extension method in a heated tower gas flow, with the separation of tobacco spread from the gas stream being obtained in a tangential separator. The patent discloses a typical construction prior to a tower construction, wherein the pneumatic conveyor column includes a cylindrical, vertically directed pipe. U.S. Patent No. 4,697,604 discloses another pneumatic conveyor column comprising an upwardly inclined duct of the rectangular cross section. The inclined ducts of the type described in the patent are generally unfavorable, since their inclination occupies extra floor space in the manufacturing facilities and because the inclined ducts allow gravity to drive the tobacco particles towards the lower wall of the duct . The rectangular shape also allows the present corners, where the localized countercurrents tend to trap the tobacco and toast (overheat) it. Corner regions exacerbate the risk of ignition (ignition) of tobacco within the tower. The pneumatic, cylindrical, traditional columns are not exempt from their own problems. The most problematic has been the tendency of the drawn tobacco to move along one side of a conventional tower, instead of dispersing more evenly between the tower gas. This flow phenomenon is adverse to the complete and efficient extension of tobacco and is referred to in the art as "binding". The limited region along the tower where the tobacco is concentrated or bound is also referred to as a dense phase region. When bonding occurs, a substantial portion of the pneumatic column remains as a gaseous region that contains very little tobacco and the concentrated tobacco directly interacts only with a limited portion of the gas stream passing through the tower, so that the Heating the bulk of the tobacco stream is not as fast or effective as might be expected. A more complete extension is achieved when the tobacco is heated uniformly as quickly as possible, starting immediately in the lower portions of the column.

The problem of concentration of tobacco along the wall of a conventional tower seems to become more and more problematic as the tower systems become even larger and / or as the speeds in conventional towers are reduced. There is otherwise a strong preference for lower gas velocities, since they minimize the pneumatic breaking of the tobacco filaments. Expansion towers of production scale may undergo binding effect over their entire lengths unless corrective action is taken. It is currently considered that bonding becomes especially problematic with larger towers due to an observed relationship between the diameter of a cylindrical tower and the strength of a dense phase flow regime. The pipe diameter seems to be proportional to the length of the pipe necessary for the dense phase flow to dissipate and for the mixing of the tower gas and tobacco to occur again. A cylindrical tower of a large diameter can therefore undergo bonding along the larger portion of its length than a thinner tower. In the past, operators of large conventional extension towers had tried to limit the linkage by using high gas velocities, the approach of which exacerbates the breaking of tobacco and reduces the time spent by tobacco in a given tower. The inclusion of the deviation within the expansion towers (known as "ski jumps") has also been attempted as a way to interrupt the linkage. However, such a deviation also exacerbates the break and it has been proven that its effectiveness in interrupting the bound flow is limited. A better solution has been sought and is described herein, which does not exacerbate the break and provides other advantages as will become apparent in the description that follows.

BRIEF DESCRIPTION OF THE INVENTION Accordingly, it is an object of the present invention to provide a tower unit and method for processing tobacco that minimize or completely avoid the occurrence of bonding within the tower to improve the extension and facilitate operation at low gas velocities with less tobacco breakage and higher cylinder volumes (CV's) in yield at production level. Yet another object of the present invention is to provide an extension tower unit wherein the tobacco is more completely dispersed within a gas flow through a larger portion of the tower column so that faster heating is effected and complete of the tobacco, particularly in the lower portion of the tower column.

It is another object of the present invention to prevent entrapment of the tobacco at the corners and the like as it passes through a tower unit. It is even another object of the present invention to provide an extension tower and tobacco processing method wherein the extended tobacco cylinder (CV) volume is improved upon leaving a commercial size tower unit. Even another object of the present invention is to provide an expansion tower and the tobacco process method where high cylinder volumes are obtained consistently.

(CV's) on a wider range of tobacco performance scales. Still another object of the present invention is to provide an extension tower and the method that can operate at a lower gas-to-mass flow rate of tobacco without suffering any detectable loss in the tobacco cylinder volume (CV).

BRIEF DESCRIPTION OF THE DRAWING A better understanding of the nature and objects of the present invention will be gained from the following detailed description taken in conjunction with the accompanying drawing, in which: Fig. 1 is a perspective view of a tower unit constructed in accordance with a preferred embodiment of the present invention; Fig. 2 is a cross-sectional view taken on line ll-ll in Fig. 1; Fig. 3 is a perspective view of the obloid transport duct constructed in accordance with the preferred embodiment shown in Fig. 1, together with the indication of stations along the obloid transport duct where the thermocouples were placed to provide the readings presented in graphic form in Figs. 7, 8 and 9; Figs. 4a and 4b are sectional views of the cylindrical transport ducts of the prior art, showing a diameter of 20.32 cm in diameter and a duct of 60.96 cm in diameter, respectively, which includes a representation of how the tobacco particles and the filaments flow through it; Fig. 5 is a graphical representation of the variations in the thermocouple readings at each of the different locations along the transport shown in Fig. 4a; Fig. 6 is a graphical representation of the variations in thermocouple readings at each of the different locations along the tower shown in Fig. 4b; Fig. 7 is a graphical representation of the variations in the thermocouple readings at each of the different locations along the obloid transport duct of the preferred embodiment in Fig. 3; FIG. 8 is a graphical representation of the variations in the thermocouple readings at each of the different locations along the transport duct of the prior art tower of FIG. 4a and those of the obloid transport duct of FIG. the present invention of Fig. 3, for different values of the mass flow rate of the tobacco; Fig. 9 is a graphic representation of the tobacco cylinder volume from the prior art tower of Fig. 4a compared to that of the present invention of Fig. 3, as a function of tobacco yield; and Fig. 6 is a geometric relationship and the formula useful in the practice of a preferred method which is an aspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The present invention describes a method and apparatus for rapid heating of the impregnated tobacco to thereby extend the same. The term "cylinder volume" (CV) is a measure of the relative filling capacity of tobacco to make smoking products. As used throughout this application, the values used in relation to CV are determined as follows: the tobacco filler weighing 10,000 grams is placed in a 3,358 cm diameter cylinder and compressed by a piston of 1875 grams and 3,335 cm in diameter for five minutes. The resulting volume of the filler is recorded as its cylinder volume. This test is performed conventionally under standard environmental conditions of 23.8 ° C and 60% relative humidity and, the sample is previously conditioned in that environment for 48 hours. The term "obloid" as used throughout this specification generally includes those forms shown in the drawing and which also includes other forms considered to be within the scope of the general understanding of any of the following terms: " oblong "(which deviates in a circular way through elongation); "flattened" (flattened or hollowed out at the poles); "ellipsoidal" (the cross section of the surface, all plane sections of which are ellipses); "oval" (a rectangular shape that has rounded corners or rounded ends) or "elliptical" (which refers to has a shape similar to an ellipse). Referring wings Figs. 4a and 4b and to U.S. Patent No. 4,366,825, the prior art included tower units having cylindrical transport ducts 34. Cylindrical ducts 34 and 341 shown in Figs. 4a and 4b are 20.32 and 60.96 cm in diameter, respectively. Referring now in particular to Fig. 4a, the analysis was carried out to attempt an understanding of what flow conditions arise at various locations from A to K within the cylindrical transport duct 34 of 20.32 cm in diameter.

Each labeled station was mapped to a cross-sectional plane through the duct 34. Although the AK locations may vary from one figure to another between the drawings, in the 20.32 cm transport duct of Figure 4a, location A was located along a horizontal portion of the duct 34 prior to the lower flexure 41a in the duct 34. The BJ locations were equidistanced and began over the term of the lower flexure 41a, with the last location J being located just below the beginning of the the upper flexure 41b in the duct 34 and the location K was located beyond the upper flexure 41b. The analysis included the placement of sets of four thermocouples 36, 37, 38 and 39, at each location A-K. In most locations, such as at location B, the thermocouples 36-39 were equidistanced around the cylindrical duct 34 so that the position of the thermocouple 36 is on the side 41c of the duct 34 remote from the inlet 35. This placement of thermocouples in Fig. 4a is repeated in a similar manner in all other locations. Similar arrangements were made for the prior art duct 34 'of Fig. 4b, as well as for the preferred embodiment of the present invention shown in Fig. 3. However, the transverse locations of the thermocouple groups for the The duct of Fig. 4a differs from those of duct 34, although they are correlated in the data presentations shown in Figs. 5-9. The positioning of the thermocouples in the preferred embodiment of the present invention also differed in some way as will be explained below in relation to the discussion of Fig. 3. Referring again to Fig. 4a, at each transverse location AK, each group of thermocouples would be used to deduce how uniformly the tobacco could be distributed through a defined plane at each location during the operation of the particular tower. Because the gas introduced into the tower is at an extreme temperature as compared to relatively cold tobacco, a well-mixed tobacco / gas system at a particular cross-sectional location would provide approximately equal readings between the thermocouples 36-39 at that location. If one or more thermocouples differed in the temperature readings of the others, then mis-mixing and bonding at or around the respective transverse location could be deduced. Referring specifically to Fig. 4a, the tobacco is fed through the inlet 35 into the cylindrical transport duct of 20.32 cm at a rate of tobacco yield ranging from about 67.14 to 261.1 kg per hour, a current velocity of gas approximately 25.84 meters per second and, a gas flow temperature of approximately 329.4 ° C to 385 ° C. After it flows through the lower bend 41a and tends generally towards the rear side 41c of the cylindrical pipe 34, the tobacco particles collected along the rear side 41c or around the location B to form what is referred to as a "dense phase flow" 42 or "bound" condition therein, which tends to continue along the back side 41c to approximately the location G. Just beyond the location G the tobacco particles 40 tended to disperse through the gas flow within the duct 34 to form what is referred to as a "dispersed phase flow" 44, which remains substantially established through the remainder of the duct 34 leading to the upper flexure 41b. The phase of dispersed flow 44 in or around the location G as shown in Fig. 4a is evidenced by the graphic display in Fig. 5. The thermocouple readings in the locations B-F provided substantial values for the standard deviation, indicating a condition linked along it. The readings at the G-J locations approached levels indicating a phase of dispersed gas flow. As previously described, the tobacco within the dense flow phase 42 is mixed only with an adjacent portion of the hot gas stream, inhibiting the rate of heat transfer to the tobacco. The presence of a dense flow phase 42 in the lower portions of the cylindrical duct 34 is adverse for a uniform, rapid heating of the tobacco as it enters the tower.

Referring now also to Figs. 4b and 6, in the conventional cylindrical duct, of commercial size 34 'in diameter of 60.96 cm pipe, the dense flush flow along the pipe wall 34' may extend, under certain circumstances, along the length of the pipe wall 34 '. the entire length of the 34 'duct, unless corrective measures are taken. The link 42 along the entire length of the duct 34 'is evidenced by the thermocouple readings plotted at the positions along the duct 34' in Fig. 6. As long as one does not wish to join theory, the Increased persistence of bonding in larger diameter towers may be related in principle to the recognized relationship in fluid mechanics where the length of pipe required to establish a given flow rate is proportional to the diameter of the pipe under consideration. Traditionally, attempts to control this extensive bonding in large conventional cylindrical extension towers have resorted to increasing the gas inlet velocities of the tower. Tower operators would prefer to operate extension towers sized for production at gas speeds of approximately 25.84 cm per second, but in order to combat the binding effect they have to raise gas speeds up to 45.6 cm per second or more. Those higher speeds are physically offensive to tobacco and exacerbate the breaking of the tobacco filaments. Even at high gas velocities, the production scale ducts 34 'still undergo potential bonding 42' even in the upper portions of the transport duct 34 '. Referring to Fig. 1 of the drawings, a preferred embodiment of the present invention provides a tower unit 10, which includes an inlet pipe section 12 for receiving a stream of hot gases, a Venturi pipe 16 downstream of the inlet 12 cooperating with a rotary inlet valve 18 and an obloid transport duct 20 downstream of the venturi 16. Preferably, the width of the venturi 16 remains the same as that of the obloid duct 20. The rotary valve 18 uniformly introduces a supply of tobacco in the Venturi tube 16 uniformly across the width of the tower as the gas stream passes through the Venturi tube 16 into the obloid transport duct 20. The rotary valve 18 is preferably fed with tobacco from a vibratory conveyor 19 to provide consistent feeding of tobacco uniformly through the Venturi tube 16. The discharge discharge of the feeder is rect angular, with the longer sides of the rectangle extending through a substantial portion of the width of the Venturi tube 16. The obloid transport duct 20 discharges the gas stream and the tobacco admitted into a separating unit 22 from which gas is discharged through a pipe 24. The tobacco in an extended condition is discharged through the outlet valve 26 of the separator unit 22. Preferably, the obloid transport duct 20 comprises a straight portion 28 placed vertically, which can range from 6.08 to 7.6 meters or more in height. At the entrance 12, the tower gases are introduced at a temperature of 260 ° to 398.8 ° C, preferably from 343.3 to 371.1 ° C and comprise steam of 75% to 85% quality with a lower air content and carbon dioxide, with the rest of the gas comprising nitrogen, approximately nitrogen, approximately 10% up to 15%. However, it will be readily apparent to those skilled in the art to the description that the present invention is operable with various types and variations of tower gases and at various gas temperatures. Referring now to Figs. 1 and 2, preferably the obloid transport duct 20 is constructed to have an obloid shape (as previously defined) throughout its entire length, although at least through a substantial portion of its vertical section 28. The transverse form of the obloid transport duct 20 at any location along it is preferably in the form of an oval configuration and, more preferably comprising, in cross section, a pair of opposing semicircular end pieces 30 and 30 ', which are interposed by spacer plates or flat portions 32 and 32'. The flat portions 32 and 32 'are preferably placed parallel to each other and separated by a distance D, which is to signify the "depth" of the duct. The width of the duct is characterized by the distance W in Fig. 2 measured from the lateral end of a circular end piece 30 towards the other. With reference to Figs. 2 and 3, the thermocouples were placed in each of the separate locations AH along the obloid transport duct 20 in a manner that provides the readings that can be interpreted in the same manner as those of the cylindrical transport ducts 34 and 3. 4'. Referring particularly to Fig. 2, in each of the AH locations of the preferred embodiment, a thermocouple was placed on one of the end portions 30, 30 'and at least two thermocouples were placed on each of the flat portions. 32 and 32 '. Referring particularly to FIG. 3, in the preferred embodiment, location A was upstream of the lower bend 41d of obloid transport duct 20 and location H was downstream of upper flexure 41e of obloid transport duct 20. Referring now to Figs. 2, 3 and 7, an obloid transport duct 20 was constructed in accordance with the preferred embodiment of the present invention and configured to handle the same tobacco performance scale as in the 20.32 cm cylindrical pilot duct 34 of Fig. 4a . Experimental information indicates that the obloid transport duct 20 initiates a fairly good flow phase as soon as the location A of the obloid duct in Fig. 3 before the lower flexion 41d. After the lower flexure 41d, a dispersed flow phase was restored and the tobacco remained in a dispersed phase 44 through the substantial length of the obloid duct 20, as evidenced by the thermocouple readings graphically set forth in Fig. 7. for the obloid duct 20. The data indicated that even in the lower vertical portions of the obloid duct and even in the lower horizontal portion 41 f of the obloid duct 20, the tobacco particles have been mixed with the gas flow of the tower to reach the initial and rapid heating of tobacco. Rapid heating ensures a more complete and efficient extension of tobacco. The ability of the present invention to establish a faster and more consistent dispersed flow phase is further evidenced in FIG. 8 where the thermocouple readings in a 20.32 cm diameter cylindrical pipeline are provided in comparison to those of a pipeline. of obloid 20 transport on a scale of tobacco yield speeds from 1.11 to 3.91 kilograms per minute. All of these performance scales, the present invention consistently achieved a flow phase dispersed in or around the location C thereof, considering that the 20.32 cm cylindrical duct 34 of Fig. 4a underwent bonding beyond its location C. The information illustrated in Fig. 8 also reveals that the obloid transport duct 20 of the present invention provides early initiation of a flow phase dispersed over a wide range of tobacco mass flow scales, considering that the duct Cylindrical transport 34 record readings indicating that as the yield of tobacco increased, the binding became more pronounced. For its significant advantage, the obloid transport duct 20 is effective on a larger scale of performance. In Fig. 9, the CV value of the tobacco treated in an obloid tower 20 constructed in accordance with the preferred embodiment shown in Figs. 1 and 2 was compared to the GV of the processed tobacco through a cylindrical tower 34, of pilot plant scale of a pipe diameter of 20.32 cm which was constructed in accordance with the prior art in Fig. 4a. The information set forth in Fig. 9 shows that as the yield of tobacco in kilograms per minute increases in a conventional cylindrical tower, the CV values of the discharged tobacco decrease significantly. In contrast, the obloid duct 20 of the preferred embodiment achieves a higher CV value at all performance values and the CV value remains uniformly constant across the performance scale. Without wishing to be bound by theory, it is considered that this advantage in CV consistency over a broader scale of performance is due to the ability of the obloid transfer duct 20 to produce the consistent initiation of dispersed phase flow in or around the location lower A of the obloid duct 20, just before the flexion 41d and recover the dispersed phase flow through location C, just after the lower flexion 41d. It is understood that these benefits of the present invention can be achieved with the imposition of relatively narrow plates between the semicircular halves of a cylindrical duct. Consequently, the improved CV and faster initiation of the dispersed flow phase can be achieved even with the size ducts for production of 60.96 cm in diameter or more by means of the rapidity of the change of its design to include flat plates between the semicircular portions as taught herein. Those flat plates could be as short as 7.62 cm in length up to 127 cm or more; however, the plates of more than 127 cm create practical problems with respect to how the tobacco is fed at the entrance of the tower. However, a preferred method for determining a depth D and a width W in retro-fitting an existing cylindrical tower or designing a new tower unit, to practice and enjoy the benefits of the present invention is now described. Assuming that a selected conventional cylindrical tower operates or is contemplated to operate at an inlet gas velocity V, and a designated, desirable (M,) tobacco yield scale, the first stage of the method preferably includes operating the selected tower. in successively lower scales of tobacco yield until an acceptable CV is obtained through it. In most conventional towers, the CV will be improved as performance is reduced. The performance scale at which an acceptable CV is obtained will be referred to as MCv- When doing these operations, the tower is operated preferably, experimentally and / or analytically, at moderate gas speeds of 18.24 to 30.4 meters per second, or more preferably at about 21.28 to 27.36 meters per second, whose speeds are preferred because they minimize the breaking of the tobacco filaments, while maintaining adequate transport characteristics.

Additionally, the temperature of the tobacco gas (tt) is adjusted so that the tobacco is discharged essentially at the same OV target outlet or moisture level for all those experimental operations. Once the reduced performance scale MCv is solved, its value, together with the length of the tower Lt, the residence time of the tobacco passing through the length of the tower Lt in the MCv yield and the determined density of Approximate or experimental way of tobacco in a linked condition is used to calculate the total volume that would occupy the tobacco if it were linked along the length Lt of the tower. This volume is referred to hereinafter as Volumeni. Upon undertaking this step, it is mathematically convenient and preferable to measure Lt as the distance between the lower flex 41d and the upper flex 41e, exclusively. From the value of the Volume! a calculation is attempted to solve the height h of a circle segment along the length of the tower Lt that provides a volume equal to the Volume !. Because the diameter and length of the selected tower are known, the calculation of the height h of such a circle segment is discernible by iterative calculations using the geometric relationships established in Fig. 10, where the ratio of Volume! to the total volume of the tower along the length Lt, a known value, equals the ratio of the cross-sectional area of the bond volume to the cross-sectional area of the pipe. (See also, Handbook of Mathematical Tables and Formulas, R. S. Burington, PhD, McGraw-Hill Book Company, 4a.De., Page 16). The value for the height h is therefore determined. The next step is to try another calculation to determine the value of a desired width W of the obloid transport duct 20. Fundamentally, the calculation determines which width value W is a rectangular duct having a height equal to the value of the height h, provides a Volume2, where Volume2 equals Volume! multiplied by the ratio of the desired design tobacco yield M i to the performance scale MCv- This step determines a value for the width W of the obloid transfer duct 20 in accordance with the following equations: (W) (h) (Lt ) = Volume! (MJMCV); and W = Volume? (M / MCv) / (h) (Lt). In effect, the previous stage extends the duct from the circular cross section to an obloid cross section by means of a factor of M / MC This relationship establishes a minimum value for W. It will be appreciated that the previous determination step W could be carried out by the determination of which hypothetical obloid duct (instead of a hypothetical rectangular duct), which has a height equal to the value of h, provides a volume2, where Volume2 equals Volumel multiplied by the factor of M / MCv. However, the resolution of the width W with reference to a rectangular duct is a mathematical convenience that does not seem to significantly change the final result. The last step is to solve the depth D of the obloid transport duct 20, preferably by setting D so that D, together with the W already determined, provided that a total area that approaches that of the total area of the original cylindrical duct or, some reduction in desired percentage or increase in the total area. Before fixing the design of the obloid duct for that value of D, it is preferable for the designer to be determined that the value contemplated for depth D provides sufficient capacity to admit a sufficiently large gas flow to reach the desired output OV or level of moisture in the tobacco for a selected tower gas temperature. However, it should be apparent that, the present invention will allow someone to operate at lower-to-mass gas ratios of tobacco without adversely affecting the tobacco output CV due to the more efficient, improved mixing and heating of the tobacco with the gas from the tobacco. tower.

Also, experience has indicated that if a value calculated for the depth D is approximately equal to a standard material size, the value for the depth D of conformity can be set so that the manufacture of the end portions 30 and 30 'can facilitated by the use of easily obtainable materials. In summary, for a selected cylindrical tower that has a design tobacco yield, the above method first determines a performance scale that produces an acceptable CV. Once it is determined, it is assumed conservatively that the linkage still exists along the entire length of the tower and the height of a circle segment that approximates the cross-sectional shape of such linkage is calculated. The method then determines how wide tobacco could be bound on a flat surface, no more than the same height, but the original, the largest tobacco yield scale. That width is then used to determine the width W of the obloid transport pipeline 20. The depth D is then determined by approaching the area of the original cylindrical pipe, with adjustment to ensure the admission of sufficient gas flow from the tower. The technique, in effect, determines a width that is sufficient for the tobacco to be laterally dispersed as it advances through the tower to such an extent that the binding of the tobacco becomes less dense and / or interrupted and the CV of the tobacco is improved. tobacco. Another way to determine the size and proportions of the cross-sectional shape of an obloid transport duct 20 according to the preferred embodiment is to analytically or experimentally determine the initial values for the depth D i and the width W i of a tower Obloid 20, and from this experimentally determine the CV values for the processed tobacco on a scale of tobacco yields at the same gas temperature of the tower and gas velocity, preferably at or about 21.28 to 27.36 meters per second. If the experimental data indicate that the CV values are too low on a tobacco yield scale Ri smaller than the specified yield scale R3, then the width W of the obloid duct increases, approximately in proportion proportional to the ratio of the R3 scales to Ri. The experiment is then repeated with the new values for the depth D and the width W to determine that the advantages of the present invention are obtained in the CV value.

Another approximation method for determining the dimensions of an obloid tower 20 according to the present invention is to establish a ratio of the width W of the obloid tower to the depth D of the obloid tower at a value on the scale of about 3 to 8, more preferably at a value between about 4.5 to 6.5, while satisfying the requirements to maintain the cross-sectional area suitable for the gas flow of the tower. This technique is particularly suitable for designing towers where the cross-sectional area is from approximately 322.58 to 1935.48 square centimeters. As noted previously, the benefits were obtained even with the inclusion of the flat portions 32, 32 'that are narrower than those provided by the above method and it may be preferred to construct an obloid transport duct outside the 3 to 8 scale. The production scale cylindrical towers tend towards diameters that approach or approach 60.96 cm in diameter to handle flow scales that vary from 1305.5 to 2051.5 kilograms per hour. The preferred embodiment of the present invention can be sized from a pilot plant size as described above to handle similar flow scales of a conventional 60.96 cm diameter tower by further increasing the width of the flat portion 32 and 32 'and increasing the radius of the semicircular portions 30 and 30 '. Preferably the depth D, defined by the present invention, would be maintained within a scale of 10.16 to 50.8 cm, or more preferably between 15.24 to 35.56 cm. In the cylindrical retrofit towers, any of the above design methods could be used to arrive at the appropriate values for the widths W and the depths D of an obloid transport duct 20 in accordance with the present invention, although more preferably, Equipment modifications would be avoided by applying the first method above. The preferred embodiments described above relate to the processes and apparatuses for the extension of tobacco which has been impregnated with an extension induction agent such as carbon dioxide, freon or other agent. The present invention is readily adaptable to other tobacco extension operations, such as instant drying or moisture laden tobacco to a predetermined final moisture level, such as described in US Patent No. 3, 357, 436 for Wright and EPO 528 227 A 1 of Kórber AG. In Wright, the tobacco is dried by introducing the tobacco at a location along a heated air path that transports the tobacco through a vertically oriented cylindrical pipeline to effect a moisture exchange between the tobacco and the air stream heated. The Kórber system brings the tobacco into the heated air stream and / or the superheated heated or hot stream, which is then directed through a cylindrical duct. These drying systems, like the extension towers, are prone to the effects of bonding within their ducts, whose problems can be alleviated with the application of the present invention, that is, to pass the tobacco that entered and the gaseous medium heated through an obloid duct built in accordance with and operated in view of previous teachings. The modalities described above are to be considered as illustrative rather than restrictive, and it should be appreciated that other persons may make variations, changes and equivalents without departing from the scope of the present invention as defined in the following claims. The practices in accordance with the present invention provide significant economic advantages in the operation of tobacco extension plants. In particular, the present invention provides higher CVs at higher tobacco yield scales with less tobacco disruption, resulting in higher filling capacity and higher tobacco yield.

Claims (19)

1. Apparatus for producing tobacco with gaseous medium comprising a transport duct to which the tobacco and the gaseous medium are fed, characterized in that the transport duct is obloid in cross section. The apparatus according to claim 1, wherein the obloid transfer duct is substantially oval in cross section. The apparatus according to claim 1, wherein the obloid transfer duct has a cross section defined by parallel spaced apart portions connected by opposing semicircular end potions. The apparatus according to claim 1, 2 or 3 further comprising: a first duct upstream of the obloid transport duct in communication with a source of the heated gaseous medium; a feeder for introducing the tobacco into the first duct, the obloid transport duct being positioned to receive the outlet of the feeder and the first duct; and a separator downstream of the transport duct. The apparatus according to claim 4, wherein the obloid transfer duct has a first bend at a location adjacent the feeder, a second bend at a location adjacent to the spacer and a straight vertical section between the first and second bends. The apparatus according to claim 4 or 5, wherein the first duct includes a Venturi tube and the feeder is adapted to introduce tobacco through the Venturi tube. The apparatus according to claim 6, wherein the venturi tube and the obloid transport duct are substantially the same width. The apparatus according to claim 4, 5 or 6, further comprising a vibrating conveyor positioned to supply tobacco to the feeder. The apparatus according to any preceding claim, wherein the transport duct has a width to depth ratio in the range of about 3 to 8. The apparatus according to claim 9, wherein the duct of Transport has a width to depth ratio in the range of approximately 4.5 to 6.5. A tobacco drying tower according to any preceding claim. 1

2. A tobacco extension tower according to any of claims 1 to 10. 1

3. An extension tower according to claim 12 having a transport duct, the transport duct in a cylindrical shape having a scale. of tobacco design yield that produces a first CV of tobacco, the transport pipeline in a cylindrical form that has a second smaller scale of tobacco yield that produces a second CV of larger tobacco, the improvement comprising the extension of the transport pipeline to an obloid cross-sectional shape approximately by a factor that includes a ratio of the tobacco design yield scale to the second lower scale of tobacco yield. An extension tower according to claim 13, wherein the enlargement results in a depth (D) of the obloid cross-sectional shape smaller than the diameter of the cylindrical shape. 15. A method for treating tobacco, comprising: establishing a flow of heated gaseous medium; feeding the tobacco into the flow of heated gaseous medium; dispersing the tobacco fed into the flow of heated gaseous medium by directing the flow of heated gaseous medium and tobacco fed through an obloid transport duct; and separating the tobacco from the gaseous medium downstream of the obloid transfer duct. 16. A method according to claim 15 wherein the feeding step includes supplying the tobacco at a location adjacent to the entrance of the transport duct uniformly across the width of the transport duct. 17. A method according to claim 15 or 16 for spreading tobacco, wherein the tobacco, before feeding into the heated gaseous medium, is treated with an extension agent. 18. A method according to claim 15 or 16 for altering the moisture content of the tobacco. 19. A method according to claim 18 for drying the tobacco.