Method for the production of homogenized tobacco material

Abstract

The invention relates to a method for producing homogenized tobacco material, comprising the steps of: selecting a first target value for a first tobacco characteristic; separately grinding (102) different tobacco types so as to obtain a plurality of different ground tobacco powders; blending (104) at least two of the plurality of different ground tobacco powders so as to form a first tobacco powder blend; blending (104) at least two of the plurality of different ground tobacco powders so as to form a second tobacco powder blend; checking (1123) a value of the first tobacco characteristic in the first tobacco powder blend; if the value of the first characteristic of the first tobacco powder blend is different from the first target value, adding the second tobacco powder blend to the first tobacco powder blend in order to obtain a value of the first tobacco characteristic in a mixture of the first and the second tobacco powder blends different from the value of the first tobacco characteristic in the first tobacco powder blend; and adding (1129) the second tobacco powder blend while mixing the first tobacco powder blend.

Claims

1. A method for producing homogenized tobacco material, comprising the steps of: selecting a first target value for a first tobacco characteristic; separately grinding different tobacco types so as to obtain a plurality of different ground tobacco powders; blending at least two of the plurality of different ground tobacco powders so as to form a first tobacco powder blend; blending at least two of the plurality of different ground tobacco powders so as to form a second tobacco powder blend; checking a value of the first tobacco characteristic in the first tobacco powder blend; if the value of the first characteristic of the first tobacco powder blend is different from the first target value, adding the second tobacco powder blend to the first tobacco powder blend in order to obtain a value of the first tobacco characteristic in a mixture of the first and the second tobacco powder blends different from the value of the first tobacco characteristic in the first tobacco powder blend; and adding the second tobacco powder blend while mixing the first tobacco powder blend.

2. The method according to claim 1, wherein the step of modifying a value of the first tobacco characteristic in the mixture includes bringing the value of the first tobacco characteristic in the mixture of the first and the second tobacco powder blends near the first target value.

3. The method according to claim 1, wherein the second tobacco powder blend has a value of the first characteristic different from the value of the first characteristic in the first powder tobacco blend.

4. The method according to claim 3, wherein, if the value of the first characteristic of the first tobacco powder blend is higher than the first target value, the method comprises the step of adding a second tobacco blend having a first characteristic value lower than said first target value; or if the value of the first characteristic of the first tobacco powder blend is lower than the first target value, the method comprises the step of adding a second tobacco blend having a first characteristic value higher than said first target value.

5. The method according to claim 1, wherein said first tobacco characteristic is the amount of reducing sugars, total alkaloids or total ammonia in dry weight basis of the total amount of tobacco present within the homogenized tobacco material.

6. The method according to claim 1, comprising: checking a value of the first tobacco characteristic after the addition of said second tobacco powder blend, and, if the value of the first tobacco characteristic of the mixture of the first and the second tobacco powder blends is within a tolerance range around the first target value: i. forming a slurry comprising the mixture; and ii. forming a sheet of homogenous tobacco material from the slurry.

7. The method according to claim 1, wherein adding the second tobacco powder blend comprises adding a second tobacco powder blend including the same tobacco types in substantially the same proportions as in the first tobacco powder blend.

8. The method according to claim 1, wherein said step of grinding different tobacco types so as to obtain a plurality of different ground tobacco powders includes: coarse grinding different tobacco types so as to obtain a plurality of different coarse ground tobacco powders having a first mean powder size; and fine grinding the mixture of the first tobacco powder blend and the second tobacco powder blend so as to obtain the mixture of the first and the second tobacco powder blends having a second mean powder size smaller than the first mean powder size.

9. The method according to claim 1, wherein, before the step of separately grinding different tobacco types, it includes: separately shredding the different tobacco types so as to obtain a plurality of different tobacco strips having a third mean strip size.

10. The method according to claim 8, wherein said first mean powder size is smaller than said third mean strip size.

11. The method according to claim 8, wherein the first mean powder size is comprised between about 300 microns and about 1200 microns.

12. The method according to claim 8, wherein the second mean powder size is comprised between about 50 microns and about 150 microns.

13. The method according to claim 1, wherein an amount of the mixture of the first and second tobacco powder blends is comprised between about 20 percent and about 93 percent in dry weight basis of the homogenized tobacco material.

14. The method according to claim 1, wherein the steps of: blending the different ground tobacco powders so as to form a first tobacco powder blend; mixing the first tobacco powder blend; include: inserting the different ground tobacco powders of different tobacco types into a mixer to form the first tobacco powder blend; checking a level reached by the first tobacco powder blend in the mixer; and if the level of the first tobacco powder blend in the mixer is above a threshold level, removing part of the first powder tobacco blend from the mixer before adding the second tobacco powder blend.

15. The method according to claim 4, including the step of drying the sheet of homogenous tobacco material.

16. The method according to claim 1, comprising: detecting the presence of possible metal objects.

17. The method according to claim 1, wherein the step of mixing the first and the second powder tobacco blends includes mixing the first and the second powder tobacco blend for a time interval comprised between about 5 minutes and about 480 minutes.

18. The method according to claim 1, including the step of: storing the first tobacco powder blend if a second tobacco powder blend having proper characteristics to modify a value of the first tobacco characteristic in a mixture of the first and the second tobacco powder blends with respect to the value of the first characteristic in the first tobacco powder blend is not available.

Description

(1) Specific embodiments will be further described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 shows a flow diagram of a method to produce slurry for homogenized tobacco material according to the invention;

(3) FIG. 2 shows a block diagram of a variant of the method of FIG. 1;

(4) FIG. 3 shows a block diagram of a method for production of a homogenized tobacco material according to the invention;

(5) FIG. 4 shows an enlarged view of one of the steps of the method of FIG. 1, 2 or 3;

(6) FIG. 5 shows an enlarged view of one of the steps of the method of FIG. 1, 2 or 3;

(7) FIG. 6 shows a schematic view of an apparatus for performing the method of FIGS. 1 and 2; and

(8) FIG. 7 shows a schematic view of an apparatus for performing the method of FIG. 3.

(9) FIG. 8 shows a schematic view of a casting system.

(10) With initial reference to FIGS. 1 and 2, a method for the production of a tobacco mixture according to the present invention is represented. The first step of the method of the invention is the selection 100 of the tobacco types to be used in the tobacco blend for producing the homogenized tobacco material. Tobacco types used in the present method are for example bright tobacco, dark tobacco, aromatic tobacco and filler tobacco.

(11) Only the selected tobacco types intended to be production of the used for the homogenized tobacco material undergo the processing according to following steps of the method of the invention.

(12) The method includes a further step 101 in which the selected tobacco is laid down. This step may comprise checking the tobacco integrity, such as grade and quantity, which can be for example verified by a bar code reader for product tracking and traceability. After harvesting and curing, the leaf of tobacco is given a grade, which describes the stalk position, quality, and colour.

(13) Further, the lay down step 101 might also include, in case the tobacco is shipped to the manufacturing premises for the production of the homogenized tobacco material, de-boxing or case opening of the tobacco boxes. The de-boxed tobacco is then preferably fed to a weighing station in order to weight the same.

(14) Moreover, the tobacco lay down step 101 may include bale slicing, if needed, as the tobacco leaves are normally transported in bales when boxed and shipped.

(15) The tobacco bales are separated depending on the tobacco type. For example there may be a processing line for each tobacco type. Therefore, the following steps are performed for each tobacco type, as detailed below. These steps may be performed subsequently per type such that only one production line is required. Alternatively, the different tobacco types may be processed in separate lines. This may be advantageous where the processing steps for some of the tobacco types are different. For example, in conventional primary tobacco processes bright tobaccos and dark tobaccos are processed at least partially in separate processes, as the dark tobacco often receives an additional casing.

(16) However, according to the present invention, preferably, no casing is added to the blended tobacco powder before formation of the homogenized tobacco web.

(17) Further, the method of the invention includes a step 102 of coarse grinding of the tobacco leaves.

(18) According to a variant of the method of the invention, after the tobacco lay down step 101 and before the tobacco coarse grinding step 102, a shredding step 103 is performed, as depicted in FIG. 2. In the shredding step 103 the tobacco is shredded into strips having a mean size comprised between about 1 millimetre and about 100 millimetres.

(19) Preferably, after the shredding step 103, a step of removal of non-tobacco material from the strips is performed (not depicted in FIGS. 1 and 2), for example a metal removal step.

(20) Subsequently, the shredded tobacco is transported towards the coarse grinding step 102. The flow rate of tobacco into a mill to coarse grind the strips of tobacco leaf is preferably controlled and measured.

(21) In the coarse grinding step 102, the tobacco strips are reduced to a first mean particle size of between about 0.3 millimetres and about 1.2 millimetres. At this stage, the tobacco particles are still with their cells substantially intact and the resulting particles do not pose relevant transport issues.

(22) Preferably, after the coarse grinding step 102, the tobacco particles are transported, for example by pneumatic transfer, to a blending step 104. In the blending step 104, some of the coarse ground tobacco particles of the different tobacco types selected for the tobacco blend are blended in order to form the desired first tobacco powder blend. The blending step 104 therefore is a single step for all the selected tobacco types. This means that after the step of blending there is only need for a single process line for all of the different tobacco types which are included in the first tobacco blend.

(23) In the blending step 104, preferably mixing of the various tobacco types in particles is performed. Preferably a step 112 of measuring and controlling one or more of the properties of the first tobacco powder blend is performed. This control is detailed below.

(24) In FIG. 4, the introduction of the various tobacco types, in this specific example four different tobacco types named 1, 2, 3 and 4, during the blending step 104 is shown. In this way a first tobacco powder blend is formed. It is to be understood that each tobacco type could be itself a sub-blend, in other words, the bright tobacco type could be for example a blend of Virginia tobacco and Brazil flue-cured tobacco of different grades.

(25) In the blending step 104, a target value is set for a first characteristic of the resulting first tobacco powder blend. This first characteristic is for example the amount of nicotine or of ammonia present in the first tobacco powder blend before the realization of a slurry for the homogenized tobacco material, so that the target value is the desired level of nicotine or ammonia present in the homogenized tobacco material.

(26) After the blending step 104 and the measuring and controlling step 112, a fine grinding step 105, to a tobacco powder mean size of between about 0.05 millimetres and about 0.15 millimetres is performed. This fine grinding step 105 reduces the size of the tobacco down to a powder size suitable for the slurry preparation. After this fine grinding step 105, the cells of the tobacco are at least partially destroyed and the tobacco powder may become sticky.

(27) The so obtained tobacco powder can be immediately used to form a tobacco slurry. Alternatively, a further step of storage of the tobacco powder, for example in suitable containers may be inserted (not shown).

(28) In FIG. 3, the measuring and controlling step 112 is detailed. In the coarse grinding step 102, preferably each grinded tobacco type arrives into a mixer.

(29) The grinded tobacco powders of the different types remain in the mixer while other bales of tobacco leaves of other types of tobacco which are included in the composition of the wished first tobacco powder blend are also grinded and arrive into the mixer.

(30) This process is carried out up to the point where all the types of tobacco needed to compose the first tobacco powder blend, in the correct relative quantities, are in the mixer. It is indeed checked (step 1121) whether all tobacco types which form the first tobacco powder blend have been introduced into the mixer.

(31) If not, then the introduction continues. If yes, the mixer proceeds to mix its content. Preferably, the mixer works up to the point when there is a homogeneous material in the mixer.

(32) Further, a check is made of the value of the first characteristic, for example of nicotine level or of ammonia level, of the first tobacco powder blend present in the mixer in step 1122. For example, a sample of the mixer content is taken and its levels in specified components (nicotine, ammonia . . . ) are checked.

(33) A comparison in step 1123 with the first target value is thus made. If the value of the first characteristic is equal to the first target value or it is within the desired values interval around the target value, then the production continues with the fine grinding step 105, detailed above.

(34) In case the value of the first characteristic is not equal to the first target value or it is not the desired values interval around the target value, for example the value of the first characteristic is too high or too low, the following takes place.

(35) It is optionally checked whether the mixer is full in step 1124. In case the mixer becomes full, then part of the mixer content is extracted and stored in step 1125, and the following steps are performed on the remaining part, that is, the part of the first tobacco powder blend which remains in the mixer.

(36) If the mixer is not full, or if part of the content of the mixer has been removed in part 1124, then it is checked (step 1126) whether there is a stored tobacco powder of the same blend with an opposite excess of the value of the first characteristic. If this powder exists in the storage (step 1127), this stored tobacco powder is added to the mixer (step 1129).

(37) The selection of the stored tobacco powder used, as well as the quantity of stored tobacco powder added in the mixer, is done by calculating the evaluated value of the first characteristic (1C) in the resulting mix, using standard mean calculation.

(38) For instance:
Final estimated resulting value of the first characteristic=((value of 1C in the mixer)(quantity of first blend in the mixer in kg)+(value of 1C in the tobacco stored)(quantity of tobacco stored added in kg))/(quantity of first blend in the mixer+quantity of tobacco stored added)

(39) If such a stored tobacco powder does not exists, the first tobacco powder blend present in the mixer is stored and removed from the mixer (step 1128).

(40) After the stored tobacco powder is added, a mixing step takes place (step 1130). The process then return to step 1122, where a new sample is taken from the content of the mixer, where now a mixture of the first tobacco powder blend and the stored added tobacco powder is present, and the value of the first characteristic is again tested.

(41) If the result is still not substantially equal to the first target value or within a tolerance range around it, the steps 1123-1130 are repeated, till the desired target value for the first characteristic is obtained.

(42) When the desired first characteristic value is obtained, the mixture of tobaccos in the mixer undergoes the fine grinding step 105 and then preferably a slurry is prepared with the finely ground tobacco powder mixture.

(43) With now reference to FIG. 5, a method of the invention for a manufacture of a homogenized tobacco web is shown. From step 112, step 105 of fine grinding is realized, and then the tobacco powder blend in the mixer is used in a subsequent slurry preparation step 106. Prior to or during the slurry preparation step 106, the method of the invention includes two further steps: a pulp preparation step 107 where cellulose fibres 5 and water 6 are pulped to uniformly disperse and refine the fibres in water, and a suspension preparation step 108, where an aerosol-former 7 and a binder 8 are premixed. Preferably the aerosol-former 7 includes glycerol and the binder 8 includes guar. Advantageously, the suspension preparation step 108 includes premixing guar and glycerol without the introduction of water.

(44) The slurry preparation step 106 preferably comprises transferring the premix solution of the aerosol-former and the binder to a slurry mixing tank and transferring the pulp to the slurry mixing tank. Further, the slurry preparation step comprises dosing the tobacco powder blend into the slurry mixing tank with pulp, and the guarglycerol suspension. More preferably, this step also includes processing the slurry with a high shear mixer to ensure uniformity and homogeneity of the slurry.

(45) Preferably, the slurry preparation step 106 also includes a step of water addition, where water is added to the slurry to obtain the desired viscosity and moisture.

(46) In order to form the homogenized tobacco web, preferably the slurry formed according to step 106 is cast in a casting step 109. Preferably, this casting step 109 includes transporting the slurry to a casting station and casting the slurry into web having a homogenous and uniform film thickness on a support.

(47) Preferably, during casting, the cast web thickness, moisture and density are controlled immediately after casting and more preferably are also continuously monitored and feedback-controlled using slurry measuring devices during the whole process.

(48) The homogenized cast web is then dried in a drying step 110 comprising a uniform and gentle drying of the cast web, for example in an endless, stainless steel belt dryer. The endless, stainless steel belt dryer may comprise individually controllable zones. Preferably the drying step comprises monitoring the cast leaf temperature at each drying zone to ensure a gentle drying profile at each drying zone and heating the support where the homogenized cast web is formed.

(49) Preferably, the drying profile is a so called TLC drying profile.

(50) At the conclusion of the web drying step 110, a monitoring step (not shown) is executed to measure the moisture content and number of defects present in the dried web.

(51) The homogenized tobacco web that has been dried to a target moisture content is then preferably wound up in a winding step 111, for example to form a single master bobbin. This master bobbin may be then used to perform the production of smaller bobbins by slitting and small bobbin forming process. The smaller bobbin may then be used for the production of an aerosol-generating article (not shown).

(52) The method of production of a slurry for the homogenized tobacco material according to FIG. 1 or 2 is performed using an apparatus for the production of a slurry 200 depicted schematically in FIG. 7. The apparatus 200 includes a tobacco receiving station 201, where accumulating, de-stacking, weighing and inspecting the different tobacco types takes place. Optionally, in case the tobacco has been shipped into cartons, in the receiving station 201 removal of cartons containing the tobacco is performed. The tobacco receiving station 201 also optionally comprises a tobacco bale splitting unit.

(53) In FIG. 7 only a production line for one type of tobacco is shown, but the same equipment may be present for each tobacco type used in the homogenised tobacco material web according to the invention. Further the tobacco is introduced in a shredder 202 for the shredding step 103. Shredder 202 can be for example a pin shredder. The shredder 202 is preferably adapted to handle all sizes of bales, to loosen tobacco strips and shred strips into smaller pieces.

(54) The shreds of tobacco in each production line are transported, for example by means of pneumatic transport 203, to a mill 204 for the coarse grinding step 102. Preferably a control is made during the transport so as to reject foreign material in the tobacco shreds. For example, along the pneumatic transport of shredded tobacco, a string removal conveyor system, heavy particle separator and metal detector may be present, all indicated with 205 in the appended drawing.

(55) Mill 204 is adapted to coarse grind the tobacco strips up to a size of between about 0.3 millimetres and about 1.2 millimetres. The rotor speed of the mill can be controlled and changed on the basis of the tobacco shreds flow rate.

(56) Preferably, a buffer silo 206 for uniform mass flow control, is located after the coarse grinder mill 204. Furthermore, preferably mill 204 is equipped with spark detectors and safety shut down system 207 for safety reasons.

(57) From the mill 204, the tobacco particles are transported, for example by means of a pneumatic transport 208, to a blender 210. Blender 210 preferably includes a silo in which an appropriate valve control system is present. In the blender, all tobacco particles of all the different types of tobacco which have been selected for the predetermined blend are introduced. In the blender 210, the tobacco particles are mixed to a uniform blend. From the blender 210, the blend of tobacco particles is transported to a fine grinding station 211.

(58) Blender 210 is depicted in an enlarged view in FIG. 6. The blender 210 receives the tobacco powder of different types from the mill 204. Further, the blender 210 is connected to several storage tobacco powder unit, in the drawings only two are depicted 216, 217. The two depicted tobacco powder units include one a tobacco powder having a value of the first characteristic below the target value, and the other one a tobacco powder having a value of the first characteristic above the target value. The tobacco powder contained in units 216, 217 can be used to adjust the value of the first tobacco characteristic of the tobacco powder inside the blender 210 as detailed in step 112.

(59) Fine grinding station 211 is for example an impact classifying mill with suitable designed ancillary equipment to produce fine tobacco powder to the right specifications, that is, to a tobacco powder between about 0.05 millimetres and about 0.15 millimetres. After the fine grinding station 211, a pneumatic transfer line 212 is adapted to transporting the fine tobacco powder to a buffer powder silo 213 for continuous feed to a downstream slurry batch mixing tank where the slurry preparation process takes place.

(60) The slurry which has been prepared using the tobacco powder above described in steps 100-109 and 112 of the method of the invention is preferably also cast in a casting station 300 as depicted in FIG. 8.

(61) Slurry from a buffer tank (not shown), is transferred by means of suitable pump with precision flow rate control measurement to the casting station 300. Casting station 300 comprises preferably the following sections. A precision slurry casting box and knife assembly 301 where slurry is cast onto a support 303, such as a stainless steel belt with the required uniformity and thickness for proper web formation, receives the slurry from the pump. A main dryer 302, having drying zones or sections is provided to dry the cast tobacco web.

(62) Preferably, the individual drying zones have steam heating on the bottom side of the support with heated air above the support and adjustable exhaust air control. Within the main dryer 302 the homogenized tobacco web is dried to desired final moisture on the support 303.