Method for producing homogeneous sheets of nicotine-free plant fibers

Abstract

1. A method for producing a homogeneous sheet made of nicotine-free plant fiber, characterized in that: solid components of a raw material comprising the nicotine-free plant fiber are ground to a particle size of about 20-220 μm, preferably about 80-180 μm; the ground material thus obtained is mixed with water, at least one binder, and at least one material for forming an aerosol until a mixture is obtained with a liquid content of about 30-50%, preferably about 35-40%; the mixture is subjected to a first layering to obtain continuous strips with a thickness of about 1-20 mm, preferably about 1-10 mm; the strips already subjected to the first layering are subjected to a series of further layering steps until strips with a fairly constant thickness of about 90-280 μm, preferably about 140-200 μm, are obtained; and the strips are dried until their liquid content is about 8-15%.

Description

[Technical field]

[0001] The present invention relates to a method for producing a homogenous sheet of nicotine-free vegetable fibres.

[0002] Methods are known for producing reconstituted tobacco, both traditional and new, the latter also called HNB (heat-not-burn). In general, reconstituted tobacco is obtained using tobacco by-products and waste products (veins, shredded leaves, flour, etc.), which are mostly powdered and suitably comminuted to be mixed with water, glycerin binder and other liquid additives, making it possible to obtain a very fluid mixture (slurry) with a liquid content of about 70% by weight, which is then poured onto a steel strip, thereby transferring it to drying. Here, evaporation of the liquid fraction of the mixture takes place, so that the solid residue forms a kind of continuous strip of tobacco with approximately the same width as the steel strip. The dried strip of mixture is then separated from the steel strip and cut according to requirements into strips of various sizes. These strips are then transformed into thin filaments, which are suitably mixed and fed into a conventional cigarette packing machine.

[0003] Depending on the raw materials used, and in particular whether shredded tobacco by-products with a particle size between 20 μm and 220 μm at most are used, or crushed tobacco leaves with dimensions between 5 and 10 mm, reconstituted tobacco is differentiated as conventional or non-conventional.

[0004] WO 2016 / 050469, WO 2016 / 050470, WO 2016 / 050471 and WO 2016 / 050472 describe known techniques for the production of reconstituted tobacco, but these require large equipment and involve high energy consumption in bringing the consistency of the slurry to that of a tobacco sheet when the product is rather fluid. It suffices to point out that drying ovens can reach lengths of up to 100 meters.

[0005] Another drawback of the known techniques for producing reconstituted tobacco using by-products is that the formation of the sheet resulting from the slurry film is rather irregular, since the starting product is not homogeneous and its distribution on the steel strip is not uniform. Said drawback results from the inability to regularly roll or cut the reconstituted tobacco sheet.

[0006] WO 2019 / 157576 describes a method for the preparation of reconstituted vegetable material pieces, in which between the pre-lamination and final lamination stages, remixing of the pre-laminated sheets is effected inside a mixer to obtain a homogenous mass which is then subjected to final lamination.

[0007] WO 2016 / 067226 describes a method for preparing reconstituted tobacco, said reconstituted tobacco comprising a first drying unit, a grinding unit, a mixing unit for a solid component (i.e. tobacco powder with a solid powder of a natural binder), a mixing unit for a liquid component (i.e. a liquid / nanogel containing propylene glycol and glycerin), a unit for mixing the solid mixed component with the liquid mixed component, one to three lamination units for obtaining a film of 0.15-0.3 mm, and a dryer for reducing the moisture content of the film.

[0008] The object of the present invention is to use known technology to produce reconstituted tobacco sheets and shreds in areas where it has not yet been used, while at the same time modifying the known technology in order to eliminate the drawbacks which it already highlights in the field of certain tobaccos and which will highlight even more in these new fields of use. In particular, the present invention aims to produce homogeneous sheets and shreds of nicotine-free plant fibers, in particular potato, hemp, tea, chamomile, mint, sage, rosemary, eucalyptus, etc.

[0009] Another object of the present invention is to produce homogenous sheets of vegetable fibers using equipment that is much smaller in size than known equipment for the production of reconstituted tobacco.

[0010] Another object of the present invention is to produce a homogenous sheet made of vegetable fibers with limited energy consumption.

[0011] Another object of the present invention is to produce homogeneous sheets made of vegetable fibres using equipment that is already partly available on the market, even if it has never been used in this particular technical field.

[0012] Another object of the present invention is to produce a homogenous sheet made of vegetable fibers having suitable properties to meet various market demands.

[0013] Another object of the present invention is to produce a homogenous sheet made of vegetable fibers by processing at low temperatures, thereby preserving all the aromas of the raw materials used.

[0014] According to the present invention, all these objects, as well as other objects resulting from the following description, are achieved jointly or separately by a method for producing a homogeneous sheet made of nicotine-free vegetable fibres according to claim 1.

[0015] In particular, the method according to the invention for producing a homogeneous sheet of nicotine-free plant fibres is characterised in that it comprises the following steps carried out in sequence: the solid components of the raw material are crushed until their particle size is about 20-220 μm, preferably about 80-180 μm, the crushed matter thus obtained is mixed with water, optionally powdered cellulose, at least one binder and at least one material for forming an aerosol until a mixture is obtained having a liquid content of about 30-50%, preferably about 35-40%, said mixture is subjected to a first layering in order to obtain continuous strips having a thickness of about 120 millimetres, preferably about 1-10 mm, said strips already subjected to said first layering are subjected to a series of further layering steps until strips having a remarkably constant thickness of about 90-280 μm, preferably about 140-200 μm, are obtained, and said strips are dried until their liquid content is about 8-15%.

[0016] The invention will be further defined hereinafter in some of its preferred embodiments, reported purely for illustrative and non-limiting purposes with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 shows a general schematic diagram of an installation for the production of homogeneous sheets made of plant fibers according to the invention.

[0018] [Diagram 2] FIG. 1 shows the feed section of the installation when the plant fibre sheets are obtained from plant leaves.

[0019] [Diagram 3] FIG. 1 shows the feed section of the installation, where the plant fibre sheets are obtained from the stems and branches of plants.

[0020] [Diagram 5] FIG. 2 shows a partial scheme of an installation with two separate lines for pre-processing of plant leaves, stems and branches.

[0021] [Diagram 5] FIG. 1 shows a section of a crushing, mixing and storage installation.

[0022] [Figure 6] FIG. 2 shows a schematic diagram of one of the cylinder refiners of the facility.

[0023] [Figure 7] FIG. 2 illustrates, in plan, a layered section of a facility in accordance with a particular embodiment.

[0024] [Figure 8] FIG. 2 is a schematic diagram of a hot air dryer of the facility.

[0025] [Figure 9] FIG. 2 shows a schematic diagram of a hot air dryer of the installation in a different embodiment.

[0026] As can be seen in these figures, the method according to the invention for producing homogeneous sheets of vegetable fibres free of nicotine uses an installation comprising several sections, the purpose of which is to take the input of raw materials and transform them into continuous strips of vegetable fibres which are then sent for further processing or packaging. The raw materials used can consist, for example, of potato, hemp, tea, chamomile, mint, sage, rosemary, eucalyptus, etc.

[0027] More specifically, the installation for carrying out the method according to the invention comprises a pre-processing section of the starting solid product (plant leaves, stems, branches) in preparation for subsequent comminution processing, a comminution and storage section abstaining from subsequent mixing with a suitable processing fluid, a mixing section of solid and liquid materials to obtain a homogeneous mixture having a rather high consistency, a section for converting the mixture and, in particular, portions of said mixture into continuous strips, a rolling line of continuous strips to reduce them to the desired final thickness, and a drying section of the laminated web.

[0028] Conveniently, the solid starting product preparation and pre-processing section can comprise a plant leaf pre-processing section for use in the preparation of plant fibre sheets (Figures 2, 4) and / or a plant stem and branch preparation and pre-processing section (Figures 3, 4).

[0029] In the case of the preparation and pre-processing of plant leaves (Figures 2, 4), the relevant section includes a feeding station with a bench 2 for unpacking the plant leaves, which generally contains the plant leaves and for transferring these to a grinder 4.

[0030] Conveniently, the output of the grinder 4 is connected via an air conveying line 6 to a cyclone 8, where the conveying air is separated from the solid product, which is transferred to a vibrating screen 10 for separation of the fine fraction resulting from the remainder of the product. The outlet of the fine fraction is connected directly to a mill 12, preferably a low-temperature mill, while the outlet of the remainder of the product feeds a conventional twist lever machine 14, which removes all the twist not previously removed from the package of plant leaves.

[0031] From the output of the twist lever machine 14, it is fed into a classification chamber 16 for the separation of all the heavy objects resulting from the plant leaves, which are transferred via a pneumatic conveying line 18, a cyclone 20, a belt conveyor 22 equipped with a metal detector 24 to remove all metal objects, a weighing system 26 (master scale) and a pneumatic conveying line 28 to storage and mixing silos 30, from which the heavy objects can then be transferred via another pneumatic conveying 32 to the cold mill 12. These silos 30 are sized to contain the amount of product required to form a batch according to a specific recipe.

[0032] On the other hand, when the preparation and pre-processing section is provided for processing plant stems and branches used to prepare sheets made of plant fibers (Figures 3, 4), the preparation and pre-processing section includes a tilter 34 for a container containing the plant stems and branches, a feeder 36 for feeding the plant stems and branches onto a vibrating conveyor 38 and separating all heavy bodies from the plant stems and branches, and a pneumatic conveying line 42 for moving the plant stems and branches to a hammer mill or chopper 42, where the plant stems and branches are chopped.

[0033] The hammer mill or chopper 42 has an outlet which is in turn connected by a pneumatic conveying line 44 equipped with a cyclone filter 46 to one or more storage silos 48 .

[0034] The outlet of the storage silo 48 is in turn connected by a screw conveyor 50 to a measuring system 52 (slave scale), which feeds the chopped stalks and branches in the proportions required and prepared by the specific recipe, which can then go via a pneumatic conveying 53 line to the storage and mixing silo 30, from which the chopped stalks and branches can then be transported via a pneumatic conveying line 32 to the cold mill 12, which grinds the various products received to make their average particle size about 20-220 μm, preferably about 80-180 μm.

[0035] There are various types of mills that can be used, but it is more advantageous to use a cold pin mill, which makes it possible to store the product at a low processing temperature, thereby preserving the aroma of the raw materials used.

[0036] The pin mill is conventional in itself and comprises, in a closed structure, a fixed disc and a rotating disc or two counter-rotating discs on which are provided facing and partially interpenetrating pins. Being a conventional installation in itself, the pin mill is generally indicated at 12 in Figures 4 and 5, but not in its internal structural features or mode of operation.

[0037] Preferably, the pin mill 12 is arranged for cryogenic grinding, i.e., grinding in the presence of liquid nitrogen.

[0038] As mentioned above, in an installation for the production of sheets made of vegetable fibres, the cold pin mill 12 has some advantages over conventional mills, especially due to the different way in which the comminuted product is treated. Indeed, grinding at room temperature can result in a poor quality product, while grinding in the presence of liquid nitrogen allows the physical properties and the chemical and organoleptic characteristics of the product to be preserved.

[0039] The amount of liquid nitrogen used in the cryogenic grinding process is an important factor to consider when investigating the advantages and disadvantages of the process and may vary depending on the material being processed. Liquid nitrogen at a temperature of -175°C is injected onto the product in the chamber of the screw conveyor 55 which feeds the mill 12, its residence time in contact with the nitrogen being approximately 2-5 seconds and the transport time of the product in the screw 55 is also approximately 2-5 seconds. The temperature of the product leaving the mill 12 is advantageously below 10°C, so that the nitrogen vapours released almost instantly on contact with the raw material to be cooled flow countercurrently through the entire feed system of the mill to perform the desired pre-cooling effect. The flow of liquid nitrogen in the pre-cooling system and in the mill is controlled by thermocouples which make the cryogenic grinding process completely automatic.

[0040] In summary, the positive aspects of cryogenic grinding are higher yields, better quality of the final product without breaking or disrupting the molecular structure, less energy required, better quality of the final product, less waste due to overheating and oxidation, a more homogenous and superior final product, and less material that is reprocessed in the grinding system.

[0041] Conveniently, the outlet of the cold pin mill 12 is connected to a fluidized bed screen 54 which serves to separate the comminuted material which emerges from the mill itself from the larger particle size, necessarily visible, material generally having an average particle size of about 20-220 μm, preferably about 80-180 μm.

[0042] Conveniently, the fluidized bed screen 54 thus serves to classify the product and separate product having fragments larger than 220 μm from product having fragments between 20 μm and 220 μm before reintroducing the product into the mill 12, which is passed via pneumatic conveyance 56 to one or more mixing and storage silos 58.

[0043] Advantageously, the outlet of the mixing and storage silo 58 is connected by a pneumatic transport line 60 to a cyclone filter 62 having the function of fractionating the dust-laden air, and more specifically separating said dust, from which it can then be recovered and reintroduced into the cycle before being discharged.

[0044] Conveniently, the outlet of the cyclone filter 62 is fed via a continuous dosing system 66 to a mixer 64, preferably using a screw, which may be of various types, for example, of the tilting or vertical spiral type.

[0045] The mixer 64 is fed with metered amounts of chopped raw materials, water, at least one binder, and at least one material for forming an aerosol, and is configured to obtain a mixture having a liquid content of about 30-50%, preferably about 35-40%.

[0046] More specifically, the liquid or moisture values ​​indicated herein are intended to be determined according to a measurement system based on the wetness standard. More specifically, said moisture values ​​are defined as the proportion of water contained in the total amount of the corresponding product, in other words the percentage between the amount of water and the total amount of the assembly. Conveniently, these values ​​are obtained using conventional methods for measuring the amount of water in products, as provided in relevant documents such as the status report of common moisture methods used within the tobacco industry in "Analytical and bioanalytical chemistry" by Nils Rose ET AL, "Tobacco Moisture, Water and Oven Volatiles" (July 1, 2014, pages 1-16).

[0047] Preferably, at least one duct for the injection of water, materials for the formation of an aerosol (e.g. glycerin) and at least one binder are connected to said mixer 64. Conveniently, one or more injection ducts can be provided for other additives that the specific formulation requires and are prepared.

[0048] More specifically, the facility includes one or more storage tanks 68 for aerosol-forming materials and one or more premixers 70, to which premixer 74 can be introduced materials for forming the aerosol, preferably multiple additives dosed in the correct ratio to form the liquid that is introduced to the mixer 64.

[0049] In order to increase the resistance of the final product sheet and at the same time the consistency of the product itself, the final product is preferably introduced into the mixer 64 together with the other components of the mixture and also with powdered cellulose. Conveniently, the cellulose powder used is not a compound derived from cellulose but is made of organic fibres obtained from natural cellulose. Powdered cellulose is thus added, preferably with a particle size comprised between 50 and 100 μm and preferably in a proportion comprised between 2 and 10% by weight relative to the crushed tobacco.

[0050] The powdered cellulose added is mainly or exclusively of natural origin, more particularly, said powdered cellulose thus added is not synthetic and is not obtained by chemical processing.

[0051] The powdered cellulose added in this way does not have a binding function, but does have the function of lowering the specific gravity of the final product and reducing the solid content of the tobacco, thereby reducing the cost of the final product, since cellulose is much less expensive than tobacco. Furthermore, the addition of cellulose makes the final product tougher by increasing the tensile strength, and therefore the final product can be processed more easily, which is particularly useful when pleated sheets of the final product are obtained.

[0052] The powdered cellulose can be contained in bags or big bags prior to its use and introduced directly into the mixer 64 (FIG. 1), in which case, after being poured into a conventional hopper, it is fed into a cyclone filter 72 which introduces the powdered cellulose in metered amounts into the mixer 64 via a continuous dosing system 73, preferably of the screw type.

[0053] Alternatively, the powdered cellulose can be introduced in the pneumatic conveying line 28, again via a cyclone filter 72 and a continuous dosing system 73, which feeds the mixing and storage silo 30, from which the powdered cellulose is then transferred, together with the other components of the mixture visible in the line itself, via the pneumatic conveying line 32 to the mill 12 (FIG. 4). From the mill 12, the contents of the mixing and storage silo 30 are then transferred via the pneumatic conveying line 56 to the silo 58, from where it is transferred in the mixer 64, via the pneumatic conveying line 60 to the cyclone filter 62 and the metering device 66.

[0054] Preferred materials for aerosol formation (and more specifically for the formation of visible aerosols) include, for example, polyhydric alcohols (e.g., glycerin, propylene glycol, triethylene glycol and tetraethylene glycol), aliphatic esters of monovalent, divalent or polycarboxylic acids (e.g., methyl stearate, dimethyldodecane and dimethyltetradecane), and the like, as well as mixtures thereof. Suitably, glycerin, propylene glycol, triethylene glycol and tetraethylene glycol can be mixed together to form an aerosol-forming material. Furthermore, the aerosol-forming material can be provided as part of the binding material (e.g., when the binding material is propylene glycol). Advantageously, a suitable combination of materials for aerosol formation can also be provided.

[0055] Preferably, the at least one binder comprises at least one of hydroxypropyl cellulose, hydroxypropyl and methyl cellulose, hydroxyethyl cellulose, microcrystalline cellulose, methyl cellulose, carboxymethyl cellulose (CMC), corn starch, potato starch, guar gum, locust bean gum, pectin, and alginates (e.g., ammonium alginate and sodium alginate).

[0056] Preferably, said binder and added powdered cellulose are defined by different materials.Conveniently, said powdered cellulose mainly serves to form a three-dimensional framework, which has high thickening effect, pseudoplasticity and excellent ability to hold liquid, while said binder exclusively or mainly serves to bind the various components that are mixed together.

[0057] Conveniently, the outlet of said pre-mixer 70 is connected to the inlet of a hydrator 74 , which has other inlets connected to a water supply line 76 and a compressed air supply line 78 .

[0058] Preferably, the outlet of the mixer 64 feeds a unit 80 for forming the mixture to obtain portions 82, the units 80 being preferably separated from one another in the form of loaves. Conveniently, the forming unit 80 comprises a pair of forming cylinders 84, which present grooves, preferably parallel to the axis of the cylinders themselves, intended to pick up the mixture at the inlet and to provide the portions 82 at the outlet. Conveniently, the unit 80 is further adapted to perform a roughening of the mixture, and for this purpose preferably comprises a hopper 86, which is provided with a lump breaker inside and with the pair of forming cylinders 84 at the bottom.

[0059] Conveniently, at the exit of the forming unit 80 a conveyor belt 88 is provided for transporting the portion 82 to a first rolling unit 90 .

[0060] Preferably, the first rolling unit 90 includes a lobe feeder 92 to homogenize the mixture formed by the portions 82 . Preferably, the mixture is subjected to a first rolling step after having undergone a homogenization and shaping stage in order to be transformed into a continuous strip having a substantially constant width between 100 and 2000 mm and a thickness between 1 and 10 mm.

[0061] Advantageously, a further metal detector 94 can be provided along the transport path from the forming unit 80 to the lobe feeder 92, the metal detector 94 having the function of removing any metal parts present in the mixture that may damage subsequent processing units, which are conveyed along a separate path and collected in a suitable container 96 before entering the lobe feeder 92.

[0062] The lobe feeder 92 includes a series of Roots-type feed rollers between which the portions 82 (exiting from the forming roller 84 of the forming unit 80) are passed, thereby mixing and homogenizing them together before being forced between a pair of rolling rolls 98, which are configured to form a continuous strip having a thickness of about 1-20 mm, preferably about 1-10 mm.

[0063] Advantageously, the lobe feeder 92 thus causes homogenization of the product exiting the forming unit 80 and which may have lumps. Advantageously, the lobe feeder 92 further feeds the product into the pair of feeders 92. rolling It is advanced forward to force it into the opening between the rolls 98 .

[0064] Therefore, the first rolling The unit 90 conveniently includes a homogenization module, preferably defined by the lobe feeder 92 described above, which homogenizes the premixed mixture. rolling This prerequisite is located immediately upstream of the module. rolling The module consists of at least one pair of Rolling Mill98, and at least one pair of Rolling Mill 98 is configured to form a continuous strip having a thickness of approximately 1-20 mm, preferably about 1-10 mm. Advantageously, the resulting strip has greater elasticity.

[0065] Conveniently, in a version of the installation not shown, the rolling line 100 can be provided directly downstream of the lobe feeder 92. More specifically, in this case, the rolling line receives a single layer of continuous strips having a thickness of about 1 to 20 mm, preferably about 1 to 10 mm, which strips are fed by the first rolling line 100 provided with the lobe feeder 92. rolling unit 90 Come out.

[0066] Advantageously, the first rolling Downstream of and above Unit 90 rolling Upstream of the line 100, a lamination unit 102 can be provided. Preferably, the lamination unit 102 is configured to lay down a continuous strip of a single layer having a thickness of about 1 to 10 mm on several layers, the strip being composed of the first rolling On leaving the unit 90 , the strip is thereby transformed into a multi-layer belt having a thickness of about 2-20 mm, which is then fed to the inlet of the rolling line 100 .

[0067] Preferably, the above Lamination Unit 102 consists of an upstream conveyor belt 104, which serves to lay the product belt on a lower downstream conveyor belt 106, preferably associated with the rolling line 100, and which arranges the product belt such that it is superimposed on the downstream conveyor belt 106, for example by multiple folding on itself. Preferably, the upstream conveyor belt 104 is elevated relative to the downstream conveyor belt 106, and is provided with a continuous forward movement relative to its support structure and at the same time with a continuous movement of alternating motion with its support structure parallel to its longitudinal axis.

[0068] Conveniently, a lamination unit 102 feeds the subsequent lower layer rolling line 100 and, depending on the type of installation, the upstream conveyor belt 104 of the lamination unit 102 can be arranged parallel or perpendicular to the downstream conveyor belt 106, which is advantageously the injection belt of the rolling line 100. More specifically, when the conveyor belt of the rolling line 100 has a width substantially equal to the width of the product belt leaving the lamination unit 102, the upstream conveyor belt 104 is arranged parallel to the downstream conveyor belt 106, which is advantageously the injection belt of the rolling line 100. rolling 1) while being arranged parallel to the infeed conveyor belt 106 of the line 100 (FIG. 1). rolling If the conveyor belt of line 100 is wider than the product belt exiting the lamination unit 102, the upstream conveyor belt 104 may be wider than the infeed conveyor belt 106. rolling Preferably, they are arranged perpendicular to the line 100 (FIG. 7). In this way, the alternating movement of the support structure of the upstream conveyor belt 104 of the stacking unit 102 allows the product belt to be spread over the entire useful width of the rolling line 100.

[0069] In either case, however, the alternating movement of the support structure of the upstream conveyor belt 104 of the stratifying unit 102 causes the stratification of the product belt, which is then conveyed from the first rolling unit 90 to the underlying rolling onto the first conveyor belt 106 of the line 100; rolling The resulting belt is formed having a width substantially equal to the useful width of the rolling line itself.

[0070] The rolling line 100 is formed by several rolling stations, each layer rolling station including a pair of cylinders 108 defining an increasingly narrow pass between them in order to progressively reduce the thickness of the strip of product being processed. rolling The line 100 is configured to gradually increase the thickness of the continuous strip to between 90 and 280 μm, preferably between about 140 and 200 μm.

[0071] Preferably, between each rolling station and the next, there is provided a conveyor belt 110, preferably having a length of about 1.5 to 2 m, i.e. a length sufficient to allow the product to rest before being subjected to the subsequent rolling step.

[0072] Advantageously, the rolling line 100 then comprises one or more calibration Each station is completed and calibration The station is a pair of calibration It is formed by roll 112.

[0073] Advantageously, said pair of cylinders 108 and possibly further said calibration The roll 112 may be heated, thereby rolling The drying stage can already start during the rolling process. Conveniently, downstream of the rolling line 100, there is a dryer 114, which preferably has air recirculation, to bring the liquid content of the rolled strip to about 8-15% (Fig. 8). Conveniently, the dryer 114 can be divided into two units 116, 118, which are placed in series with each other (Fig. 9). In this case, the upstream unit 116 is provided for performing a first drying stage and has a steel belt or net belt conveyor inside for transporting the product leaving the rolling line 100, and the unit 118 downstream is provided for performing a second drying stage and a subsequent cooling stage and has a network belt conveyor inside.

[0074] Additionally, the dryer 114 is conveniently equipped with sensors 120, preferably infrared, at the inlet and outlet, which monitor the product along its entire length.

[0075] For the preparation of plant fibre sheets from plant leaves, the cartons containing said leaves are placed on an opening bench 2 (Figure 2) where individual packets of plant leaves are removed from the cartons and sent to said grinder 4, which grinds the leaves themselves to a substantially uniform size between 5 and 10 mm.

[0076] Conveniently, the comminuted material is then transferred along the pneumatic conveying line 6 to the cyclone 8 which separates the comminuted material from the air and causes it to fall onto a vibrating screen 10 .

[0077] Here separation of the finer fraction from the remainder takes place, the finer fraction being sent directly to the cold mill 12, the remainder being sent via the twisting lever machine 14 to the sorting chamber 16 for separation of all heavy bodies from the shredded leaves, to remove all metal bodies via the metal detector 24 with the pneumatic conveying line 18, the cyclone 20, the conveyor belt 22, the weighing system 26 (master scale) and the pneumatic conveying line 28, to the storage and mixing silo 30, from where it is then transported via the pneumatic conveying line 32 to the cold mill 12.

[0078] When plant fibre sheets are produced from plant stalks and branches, the relevant container is placed on a tilter 34 (Figure 3) which feeds the plant fibre sheets onto the vibrating conveyor 38 to remove any weights. The stems and branches are then transferred via the air line 40 to the hammer mill 42 which chops them to a size of 5-8 mm.

[0079] From here, the chopped stems and branches, separated from the transport air in the cyclone 46, are sent to the storage silo 48, from where different types of chopped stems and branches resulting from different plant characteristics are picked up and transported via the screw conveyor 50 to the dispenser 52, which deposits the chopped stems and branches for preparation according to a specific recipe.

[0080] From here the chopped and precisely dosed stems and branches are transported via air lines to the cold mill 12 .

[0081] If the installation is to handle all the leaves, stems and branches of the plant, it further enters the pneumatic conveying line 28 which feeds the mixing and storage silo 30 and then into the pneumatic conveying line 53 which exits the storage silo 48 (Figure 4).

[0082] Regardless of the type of raw material produced, and therefore the nature of the solid portion of this raw material introduced from the fluidized bed screen 54 into the shredding unit fed by the upper cryogenic mill 12, the ground material leaves with an average particle size of about 20 to 220 μm, preferably about 80 to 180 μm. The ground material is sent to the mixing and storage silo 58, from where it is then removed and transferred to the mixer 64 as required.

[0083] In addition to the comminuted raw materials, any cellulose and generally any solid product leaving the mixing and storage silo 30, water, at least one binder and at least one aerosol-forming material are further introduced. Advantageously, compressed air and other additives can also be introduced.

[0084] Conveniently, the mass then has a liquid (moisture) percentage of about 30-50% by weight, preferably 35-40% by weight, based on wet weight, i.e. a rather high viscosity. mixture are mixed together to form

[0085] Preferably, the mixture thus obtained is transferred to the forming unit 80, from which the portions 82, preferably in the form of loaves, emerge continuously.

[0086] These portions 82 of the mixture exiting said forming unit 80 are suitably transferred to a first rolling unit 90 configured to homogenize the mixture and provide a continuous strip having a thickness at its outlet of about 1-20 mm, preferably approximately 1-10 mm.

[0087] The above No. 1 rolling The continuous strip exiting unit 90 is rolling directly to line 100 or, more conveniently, Lamination The unit 102 can be folded on itself, so that rolling It is deposited in layer form on the injection belt of line 100 .

[0088] Conveniently, as mentioned above, the stack is obtained by dropping the continuous belt onto the upstream conveyor belt 104 of the stacking unit 102, which is advanced relative to its structural support, which is moved by a reciprocating motion, thereby placing the product belt in several layers on the downstream conveyor belt 106 at the entrance to the rolling line 100. Depending on the installation and the direction of the reciprocating motion of the support structure of the conveyor belt 104 of the stacking unit 102, the product belt is placed in several layers parallel to the longitudinal direction of the rolling line 100 or perpendicular thereto.

[0089] Advantageously, with each passage from one station of the rolling line 100 to another, the product strip undergoes thinning until it reaches a desired thickness, corresponding to the output measuring cylinder 112, having a remarkably constant value of about 90-280 μm, preferably about 140-200 μm. Advantageously, furthermore, at the exit from the rolling line 100, the strip has a liquid content lower than 20% or even 15%, if the lamination cylinder 108 is heated and the removal of moisture has already started during lamination.

[0090] The product web exiting the rolling line 100 is then dried in the dryer 114 where its liquid content is reduced to about 8-15%.

[0091] Advantageously, said dryer 114 is of the air recirculation type and is somewhat more advantageous, both in terms of manufacturing complexity and overall size and in terms of energy consumption, compared to dryers conventionally used in reconstituted tobacco production equipment, since the conventional equipment deals with a very fluid and unstable product (slurry), unlike the much more viscous and stable product handled by said equipment. Advantageously, equipment dealing with slurries requires conventional irradiation and conduction dryers, whereas said equipment can advantageously use an air recirculation dryer 114 with a combined system of network belt conveyors, or steel belt conveyors for said first drying stage, and net belt conveyors for said second drying stage and said cooling stage. Thus, with the same performance, smaller dimensions (approximately 45 m compared to conventional dryer diameters of over 100 m) and less energy consumption due to the smaller amount of moisture removed (using approximately 1000 kg of steam per hour compared to over 5000 kg of steam per hour from conventional dryers) are obtained.

[0092] Conveniently, at the exit of the dryer 114, the product is ready to be wound onto reels or cut into sheets or into strips of predetermined size for use in its intended application.

[0093] Conveniently, in the method according to the invention, homogenization of the mixture is mainly or exclusively performed by the lobe feeder 92, and in any case always only upstream, preferably just upstream of the pre-rolling module, which transforms the homogenized mixture into continuous strips having a thickness of about 1-20 mm, preferably about 1-10 mm, and thereby passes to the inlet of the final rolling line 100.

[0094] More specifically, once the homogenized mixture has been transformed into continuous strips having a thickness of about 1-20 mm, preferably about 1-10 mm, the latter cannot be subsequently remixed but is sent in strip form to the rolling line 100, whereby it is brought to the desired thickness, which has a remarkably constant value of about 90-280 μm, preferably about 140-200 μm. Advantageously, the fact that the rolling line 116 receives strips at its inlet, rather than a misshapen mixture, makes it possible to guarantee a constant inlet flow, which increases the accuracy of the sheet thickness in the subsequent rolling process, and further makes it possible to reduce the number of stacking cylinders 108 of the line itself, which reduces the overall dimensions of the installation as well as its costs.

[0095] Advantageously, the installation can include, instead of or in addition to the forming unit 80, a cylinder refiner 112 upstream thereof, which has the task of making the solid components of the mixture obtain a particle size not exceeding 20 μm.

[0096] The refiner (FIG. 6) comprises a number of cylinders 124 arranged in succession close to each other inside a closed vessel, thereby delimiting corresponding grinding slots. The lower cylinder 124' is mounted on its axis outside a plane containing the axes of all the other cylinders 124 and acts as a feeder of the mixture, which is taken from the bottom of the vessel and made to stand upwards to transfer between the lower cylinder and the cylinder immediately above it and then follow between all the other cylinders. The various pairs of cylinders 124 between which the mixture is transferred rotate at different speeds, in the sense that the upper cylinder rotates at a faster speed than the lower cylinder, and the upper and lower cylinders cooperate, thereby subjecting the mixture to a stretching treatment during its passage between each pair of the cylinders 124, thereby reducing the particle size of the mixture itself. In fact, one of the fundamental elements for the success of the refining process is precisely the different speeds of the different cylinders 124, on which the passage of the total product of the mixture transporting through the comminution slot depends.

[0097] The pressure between the cylinders is hydraulically controlled.

[0098] All the cylinders 124 are cooled using cooling water circulating inside each cylinder, thus counteracting the heat generated by the mixture due to both the movement of the cylinders and friction with the product. In this way, the temperature of the entire product is reduced until it reaches 25°C.

[0099] The frictional action exerted on the mixture by the latter of the cylinders 124, by the aforementioned refiner 122, produces a considerable binding action of the cellulose fibers contained in the raw material, which entails the double benefit of improving the aromatic composition of the product and eliminating the need to introduce more fibers into the mixture to obtain the required binding effect.

[0100] The operation of the plant in this different embodiment provides that the chopped raw material leaving the preparation and pre-treatment station is fed to the cold pin mill 12 in proportionally dosed amounts obtained according to the recipe and is therefrom ground to a particle size of about 20-220 μm, preferably about 80-180 μm.

[0101] The product is then transferred, in the manner previously described, to the mixer 64 where the product mixture is formed as described above.

[0102] The mixture thus obtained is then fed to the cylinder refiner 122, which has the task of making the solid components of the mixture obtain a particle size not exceeding 20 μm. Thus, the frictional action exerted on the mixture by the cylinder 124 of the refiner 122 produces a considerable binding action of the raw materials, more particularly of the cellulose fibers contained in their stems, branches and veins, which entails a double benefit: on the one hand, improving the aroma composition of the product, and on the other hand, eliminating the need to introduce more fibers into the mixture to obtain the required binding effect.

[0103] Although FIG. 1 shows diagrammatically the location of the refiner 122 between the mixer 64 and the forming unit 80, the invention further provides that the refiner 112 can take the place of the forming unit 80, in which case the mixture leaving the refiner 122 is transferred directly to the first rolling unit 90 for continuing the processing cycle according to the method previously described.

Claims

1. 1. A method for producing a homogenous sheet of nicotine-free plant fibers, comprising: The solid component of the raw material containing nicotine-free plant fiber is ground to a particle size of about 20 to 220 μm, preferably about 80 to 180 μm; the grinding material thus obtained is mixed with water, at least one binder, and at least one material for forming an aerosol until a mixture is obtained with a liquid content of about 30-50% by weight on a wet basis, preferably about 35-40% by weight on a wet basis; said mixture being subjected to a first rolling step to obtain a continuous strip having a thickness of about 1 to 20 mm, preferably about 1 to 10 mm; the strip already subjected to the first rolling step is subjected to a series of further rolling steps until a strip having a very constant thickness of about 90 to 280 μm, preferably about 140 to 200 μm, is obtained; The method of claim 1, wherein the strips are dried until their liquid content is about 8-15% by weight on a wet basis.

2. 2. The method of claim 1, wherein the dried continuous strip is wound or cross-cut or chopped into yarns of predetermined dimensions.

3. 3. The method according to claim 1 or 2, characterized in that the solid components of the raw material are broken down by grinding.

4. 4. The method according to claim 1, wherein the solid components of the raw material are ground using a grinder.

5. 5. The method according to any one of claims 1 to 4, characterized in that the solid components of the raw material are ground using a cold pin mill (12).

6. 6. The method according to claim 1, wherein the powdered cellulose is further mixed with other substances to form the mixture.

7. The method of claim 6, wherein the powdered cellulose is made of organic fibers obtained from natural cellulose.

8. The method of claim 6 or 7, characterized in that the mixture is formed using powdered cellulose having a particle size between 50 and 100 μm.

9. 9. The method according to any one of the preceding claims, characterized in that the mixture is formed with powdered cellulose in a proportion comprised between 2% and 10% by weight of the raw materials.

10. 10. The method according to claim 1, wherein the ground components of the raw materials are mixed with powdered cellulose before forming the mixture with the ground components.

11. The mixture is A roughening step by passing it through at least a pair of grooved cylinders (84), and / or A method according to any one of claims 1 to 10, characterized in that said mixture is subjected to a purification step by passing it through at least a pair of refining cylinders (124, 124') until the particle size reaches 20 μm.

12. 12. The method according to any one of claims 1 to 11, characterized in that the mixture undergoes a homogenization and forming step before undergoing the first rolling step.

13. 13. The method according to any one of claims 1 to 12, characterized in that the binder is selected from the group consisting of hydroxypropyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, microcrystalline cellulose, methylcellulose, carboxymethylcellulose (CMC), corn starch, potato starch, guar gum, locust bean gum, pectin and alginates, in particular ammonium alginate and sodium alginate.

14. 14. A method according to any one of claims 1 to 13, characterized in that the mixture is subjected to a homogenization and shaping stage in order to be transformed into a continuous strip having a substantially constant width between 100 and 2000 mm and a thickness between 1 and 10 mm, followed by the first rolling step.

15. 15. The method according to any one of claims 1 to 14, characterized in that the mixture is subjected to homogenization and shaping steps in order to be transformed into a series of parts (82) before being subjected to the first rolling step.

16. 16. The method according to any one of claims 1 to 15, characterized in that the first rolling step of the mixture is carried out using a unit (90) comprising a lobe feeder (92) and at least a pair of rolling cylinders (98).

17. 17. The method according to any one of claims 1 to 16, characterized in that the first rolling step comprises a homogenization step carried out before obtaining the continuous strip having a thickness of about 1 to 20 mm, preferably about 1 to 10 mm.

18. 18. A method according to any one of claims 1 to 17, characterized in that the mixture first undergoes a forming step in order to be transformed into a series of portions (82), followed successively by a step of homogenizing said portions (82) before obtaining said continuous strips having a thickness of about 1 to 20 mm, preferably about 1 to 10 mm.

19. 19. The method according to any one of claims 1 to 18, characterized in that the mixture is homogenized mainly or exclusively by means of a lobe feeder (92) placed at the inlet of at least one pair of mill rolls (98).

20. 20. A method according to any one of the preceding claims, characterized in that at the exit of the first rolling step a monolayer tape is obtained having a thickness of approximately 1 to 10 mm.

21. 21. The method according to any one of claims 1 to 20, characterized in that the strip already subjected to the first rolling step is subjected to layering before being subjected to the series of further rolling steps until a multi-layer strip of about 2 to 20 mm thick is obtained.

22. The method of claim 21, wherein in the series of further rolling steps, the mixture is placed between one rolling station and the next rolling station.

23. 23. A method according to any one of claims 1 to 22, characterized in that the series of further rolling steps is carried out with at least partially heated mating cylinders (108).

24. The method according to claim 1, wherein the rolled strips are dried by passing them through an air recirculation dryer (114).

25. The method of claim 1, wherein the vegetable fiber comprises at least one of the following vegetable substances: potato, hemp, tea, chamomile, mint, sage, rosemary, and eucalyptus.

26. 26. The method according to any one of claims 1 to 25, characterized in that the first rolling step is carried out in a first rolling unit (90) comprising a homogenization module of the mixture and a pre-rolling module, the homogenization module being located immediately upstream with respect to the pre-rolling module, the pre-rolling module being defined by at least a pair of rolling rolls (98), the rolling rolls (98) being configured to form a continuous strip having a thickness of about 1 to 20 mm, preferably about 1 to 10 mm.

27. 27. The method of claim 26, wherein the homogenization module includes a lobe feeder (92).

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