CN112888322A

CN112888322A - Method and apparatus for producing reconstituted tobacco

Info

Publication number: CN112888322A
Application number: CN201980069126.5A
Authority: CN
Inventors: G·格兰佐托
Original assignee: Comas SpA
Current assignee: Comas SpA
Priority date: 2018-09-17
Filing date: 2019-09-12
Publication date: 2021-06-01
Anticipated expiration: 2039-09-12
Also published as: EP3852554A1; EP4316271A2; WO2020058814A1; US20220030927A1; BR112021004940A2; JP2022500043A; CN112888322B; EP4316271A3; KR20210075095A

Abstract

The present application relates to a method for producing reconstituted tobacco, characterized in that: -comminuting the solid constituents of the tobacco so as to bring their particle size to about 20-220 μm, preferably about 80-180 μm; -mixing the comminuted product thus obtained with water, 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 lamination so as to obtain a continuous strip with a thickness of about 1-20mm, preferably about 1-10 mm; -said strip having undergone said first lamination is subjected to a series of further rolling passes so as to obtain a strip having a substantially constant thickness of about 90-280 μm, preferably about 140-200 μm; -the strip is dried so that its liquid content reaches about 8-15%.

Description

Method and apparatus for producing reconstituted tobacco

The present invention relates to a method and apparatus for producing reconstituted tobacco, both conventional and unconventional, also known as HNBs (heat not burned).

Conventionally, reconstituted tobacco is obtained by using tobacco by-products and processing waste (veins (rib), small pieces of leaves, dust, etc.) suitably shredded until they are actually reduced to powder and mixed with water, glycerol binder and other liquid additives, so as to be able to obtain a very flowable mixture (slurry) with a liquid content of about 70% by weight, which is then poured into a covering on a steel band and conveyed with it into a drying oven. Here, the liquid part of the mixture evaporates so that the solid residue forms a continuous tobacco rod having approximately the same width as the steel band. The strips of dry mixture are then separated from the steel strip and cut into pieces of various sizes as required. These fragments are then transformed into filaments, which are suitably mixed and fed into a conventional packaging machine for cigarettes.

Reconstituted tobaccos are distinguished as conventional or unconventional types, depending on the raw material used, and in particular on whether the tobacco product used is cut into cut tobacco leaves of a particle size between 50 μm and 120 μm or a size between 5 and 10 mm.

WO2016/050469, WO2016/050470, WO2016/050471, WO2016/050472 describe known techniques for producing reconstituted tobacco, which require considerable equipment and involve high energy consumption in order to bring the mixture (which has considerable flowability during production) to the consistency of the tobacco sheet. It is noted that the length of the drying oven can be up to 100 m.

Another drawback of the known technique for producing reconstituted tobacco using by-products consists in that the formation of the sheet starting from the layer of mixture is rather irregular, since the initial products are not uniform and their distribution on the steel belt is not uniform; therefore, the reconstituted tobacco sheet cannot be rolled up and cannot be cut regularly.

The object of the present invention is to eliminate these drawbacks and to produce reconstituted tobacco of conventional and unconventional type, with a much smaller size of the equipment.

It is another object of the present invention to produce reconstituted tobacco with limited energy consumption.

It is another object of the present invention to produce reconstituted tobacco using equipment that is partially commercially available, even though the equipment has never been used in this particular technical field.

It is another object of the present invention to replace conventional methods for producing reconstituted tobacco.

It is another object of the present invention to produce reconstituted tobacco having characteristics suitable to meet different market needs.

It is another object of the present invention to operate at low temperatures to produce reconstituted tobacco and thereby retain all of the aroma of the tobacco.

All these objects, as well as others that will become clear from the following description, are achieved according to the present invention by a reconstituted tobacco production method according to claim 1 and an apparatus according to claim 16.

In particular, the method for producing reconstituted tobacco according to the invention is characterized in that it comprises the sequential execution of the following steps:

-comminuting the solid constituents of the tobacco until their particle size reaches about 20-220 μm, preferably about 80-180 μm;

-mixing the comminuted product thus obtained with water, 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 lamination so as to obtain a continuous strip with a thickness of about 1-20mm, preferably about 1-10mm,

-said strip, having undergone said first rolling, is subjected to a series of further rolling passes until a strip having a substantially constant thickness of about 90-280 μm, preferably about 140-200 μm, is obtained;

-the strip is dried so that its liquid content reaches about 8-15%.

The invention will be further clarified by the following description of some preferred embodiments, which are given by way of non-limiting example only, with reference to the accompanying drawings, in which:

FIG. 1 shows in a schematic general view an apparatus for producing reconstituted tobacco according to the invention,

FIG. 2 shows the energy supply portion thereof, in the case of a plant for producing reconstituted tobacco of conventional type;

FIG. 3 shows the energy supply section thereof in the case of an apparatus for producing reconstituted tobacco of the non-conventional (HNB) type;

FIG. 4 shows the supply portion of the veins;

FIG. 5 shows a grinding, mixing and storage portion thereof;

figure 6 shows its refiner displacement in a schematic view;

FIG. 7 shows a plan view of a layered portion thereof in a different embodiment;

FIG. 8 shows its hot air dryer in a schematic representation; and

fig. 9 shows in a schematic view a hot air dryer thereof in a different embodiment.

As can be seen from the figures, the plant for producing reconstituted tobacco according to the invention comprises a plurality of sections arranged in series, the purpose of which is to operate on the input raw materials until they are transformed into a continuous strip of reconstituted tobacco, to be sent for the subsequent cigarette wrapping operation.

In particular, the apparatus for producing reconstituted tobacco according to the invention comprises:

-a comminution unit of the solid constituents of tobacco, so as to bring their particle size to a value of about 20-220 μm, preferably about 80-180 μm; advantageously, the comminution unit comprises a grinder 20 (preferably cryogenic) and/or a grinder 24 and/or a hammer mill 54;

a kneader 80, which kneader 80 is supplied with metered amounts of comminuted material, water, at least one binder and at least one material for forming an aerosol; the kneader is arranged to obtain a mixture with a liquid content of about 30-50%, preferably about 35-40%;

a first lamination unit 100 for obtaining from said mixture a continuous strip with a thickness of about 1-20mm, preferably about 1-10 mm;

a roll line 116, the roll line 116 being located downstream of the first lamination unit 100 for bringing the continuous strip to a thickness of about 90-280 μm, preferably about 140-200 μm;

a dryer 122, which dryer 122 is arranged downstream of the roller line 116, so that the liquid content of the strip laminated and coming out of the roller line 116 amounts to about 8-15%.

Advantageously, the apparatus 1 further comprises: a mixture forming unit 92 for forming a plurality of portions 97 of the mixture; suitably, therefore, the first lamination unit 100 is arranged to obtain a continuous strip with a thickness of about 1-20mm, preferably about 1-10mm, from the portion 97 of the mixture.

Preferably, the apparatus according to the invention comprises:

a pre-treatment portion of the initial solid products (tobacco leaves, veins, pieces of leaves, powders, etc.) for preparing them for a subsequent grinding treatment,

-a grinding and storage section waiting for subsequent mixing with a suitable treatment liquid; suitably, the grinding section comprises the comminution unit;

-kneading sections of solid and liquid materials in order to obtain a homogeneous mixture of considerable consistency;

-a portion for transforming the mixture into a continuous strip, in particular for a plurality of portions of the mixture;

a continuous strip-rolling line for reducing it to a suitable final thickness,

-a section for drying the laminate strip.

Preferably, the portions used for preparing and pre-treating the initial solid product will vary depending on whether the plant is used for producing reconstituted conventional type tobacco (fig. 2) or non-conventional type tobacco (fig. 3). In addition, advantageously, a preparation and pre-treatment section of the tobacco veins (figure 4) can also be provided, in order to be used for the production of reconstituted tobacco, both of the conventional type and of the unconventional type.

Advantageously, in the case where the preparation and pre-treatment section is to be fed to a plant for the production of reconstituted tobacco of conventional type (figure 2), it comprises a tipping device 2 of cartons containing tobacco products, so as to pour their contents on a feeder 4 of a vibrating conveyor 6, which vibrating conveyor 6 separates any weights from the products to be treated. The heavy objects are collected in a suitable container 8 and the product to be treated is conveyed by means of a pneumatic conveying line 10 to a cyclone 12, a conveyor 14 provided with a metal detector 16 for removing any metal bodies and a pneumatic conveying line 18, and to a grinding mill 20, preferably of the cryogenic type.

Advantageously, in the case where the preparation and pre-treatment section is arranged for preparing reconstituted tobacco of the unconventional type (figure 3), it comprises a feeding station with a counter 22 for unloading the tobacco bales, which usually contain these, from a carton of about 200 kg, which is then conveyed to a grinder 24.

Suitably, the output of the mill 24 is connected by a pneumatic conveying line 26 to a cyclone separator 28, in which cyclone separator 28 the conveying air is separated from the solid product, which is conveyed to a vibrating screen 30 for separating the fines fraction from the rest of the product. The output of the fines fraction is connected directly to the cryogenic grinder 20, while the output of the remainder of the product is fed to a conventional string remover 32, which string remover 32 serves to remove any string that has not previously been removed from the tobacco bale.

The outlet of the fine wire removal machine 32 feeds a separation chamber 34 for separating any heavier foreign matter from the ground tobacco leaves which are conveyed to the cryogenic grinding mill 20 by means of a pneumatic conveying line 36, a cyclone 38, a belt conveyor 40 (the belt conveyor 40 being provided with a metal detector 42 for removing any metal bodies) and a pneumatic conveying line 44.

Advantageously, in the case where the preparation and pretreatment portion is provided for preparing tobacco veins for the production of reconstituted tobacco of conventional type and of unconventional type (figure 4), it comprises: a tipping device 46 for cartons containing tobacco veins; a feeder 48 for feeding the veins to a vibrating conveyor 50, the vibrating conveyor 50 being used to separate any weights from them; and pneumatic conveying lines 52 for their movement to a hammer mill 54 where they are crushed.

The output of the hammer mill 54 is connected to one or more storage silos 60 by means of pneumatic conveying lines 56 provided with cyclone filters 58.

The output of the storage silo 60 is in turn connected by a screw conveyor 62 to a metering device 64, the metering device 64 being arranged to meter the shredded veins before they are fed to the grinding mill 20 (preferably cryogenic) by a pneumatic conveyor line 66.

As mentioned above, the apparatus according to the invention also comprises an attrition mill 20 (figure 5) which grinds the various products received so as to bring their average particle size to about 20-220 μm, preferably about 80-180 μm.

Various types of mills can be used, although it is more advantageous to use a low temperature cascade mill, which allows the product to be kept at a lower process temperature, thereby retaining the aroma of the tobacco.

Pin disc mills are conventional per se and comprise a closed structure inside which there are fixed and rotating discs or two counter-rotating discs provided with steps facing each other and partially penetrating each other. It is generally indicated at 20 in fig. 5 as a device conventional per se, but without its internal structural features or its mode of operation.

Preferably, the cascade mill 20 is intended to be cryogenically ground, i.e. ground in the presence of liquid nitrogen.

As mentioned above, in plants for the production of reconstituted tobacco, cryogenic pin mills are slightly more advantageous than conventional mills, mainly due to the different ways in which the product to be ground is handled. In fact, grinding at room temperature may result in obtaining a product of inferior quality, whereas grinding in the presence of liquid nitrogen will preserve the physical properties and the chemical and organoleptic characteristics of the product.

In studying the advantages and disadvantages of the process, the amount of liquid nitrogen used in the cryogenic grinding process is an essential part to consider and may vary depending on the material being processed. Liquid nitrogen at a temperature of-175 ℃ is injected on the product inside the chamber of the screw conveyor 68, which is fed to the grinder 20, and its residence time in contact with nitrogen is about 2 to 5 seconds, which is also the time for the product fed to the pin grinder to pass inside the worm (cochlea). Advantageously, the temperature of the product coming out of the grinder 20 is lower than 10 ℃, so that the nitrogen vapours released almost immediately upon contact with the tobacco to be cooled flow all the upstream of the grinder feed system, thus achieving the desired pre-cooling effect. The flow of liquid nitrogen in the pre-cooling system and the grinder is controlled by thermocouples, which fully automates the cryogenic grinding process.

In summary, the positive factors of cryogrinding are:

-a higher yield of the product,

better final product quality without breaking or tearing the molecular structure,

a reduction in the energy required for the operation,

the quality of the final product is better,

a reduction in the amount of scrap due to overheating and oxidation,

a more uniform and finer final product,

lower amount of material to be reprocessed in the grinding system.

Preferably, the output of the cascade cryogrinding mill 20 is connected to a fluidized sieve bed 70, which fluidized sieve bed 70 has the function of separating the ground product, which comes out of the mill itself, usually with an average particle size of about 20-220 μm, preferably about 80-180 μm, from the larger size particles which are inevitably present.

It is therefore preferred that the sieve with fluidized bed has the function of sorting the products and of recycling (after separating them from the products between 20 μm and 120 μm) the products with a size fraction greater than 120 μm back into the grinding mill 20, which are sent through pneumatic conveying lines 72 to one or more mixing and storage silos 74.

Advantageously, the output of the mixing and storage silo 74 is fed by means of a pneumatic conveying line 76 to a cyclone filter 78, which cyclone filter 78 has the function of breaking down the air containing dust, more specifically of separating the dust from the air, which dust is recovered and sent back into the circulation, which air can then be discharged.

Conveniently, the output of the cyclone filter 78 is fed by means of a continuous metering system (preferably by means of a spiral structure) to a kneader 80, which kneader 80 can be of various types, for example of the horizontal type with an inversion or of the vertical spiral type.

The kneader 80 is supplied with a quantity of shredded tobacco, water, at least one binder and at least one material for forming an aerosol and is arranged to obtain a mixture with a liquid content of about 30-50%, preferably about 35-40%.

In particular, the values of liquid or humidity described in this specification will be used to determine on a wet basis from a measurement system. In particular, the value of humidity is defined as the percentage of water contained in the total mass of the corresponding product, in other words it is the percentage between the amount of water and the total mass of the mixture. Suitably, these values are obtained using conventional methods provided in the literature for measuring the amount of water in products, such as those described by Nils Rose ET AL in "analytical and bioanalytical chemistry" (7 months, 1 day 2014, pages 1-16) in "status reports on tobacco moisture, water and oven volatiles-moisture methods commonly used in the tobacco industry".

Preferably, at least one pipe or water inlet leads the material for forming the aerosol (e.g. glycerol) and at least one binder (binding agent) to the kneader 80. Conveniently, one or more inlet ducts can be provided for other additives required for the particular formulation to be prepared.

More particularly, the system comprises one or more tanks 82 for storing the material forming the aerosol and one or more pre-mixers 84 into which said material for forming the aerosol and preferably a plurality of additives (which are metered in the correct proportions) can enter in order to form the liquid to be introduced into the mixer 80.

Examples of preferred materials for forming aerosols, particularly for forming visible aerosols, include polyols (e.g., glycerol, propylene glycol, triethylene glycol, and tetraethylene glycol), aliphatic esters of mono-, di-, or polycarboxylic acids (e.g., methyl stearate, dimethyl dodecanedicarboxylate, and dimethyl tetradecanedicarboxylate), and mixtures thereof. Suitably, glycerol, propylene glycol, triethylene glycol and tetraethylene glycol can be mixed together to form the aerosol-forming material. The aerosol-forming material can also be supplied as part of the binder (e.g. when the binder is alginate propylene glycol). Advantageously, suitable combinations of materials for forming the aerosol can also be provided.

Preferably, the at least one agent and binder comprises at least one of hydroxypropyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, microcrystalline cellulose, methyl cellulose, carboxymethyl cellulose (CMC), corn starch, potato starch, pectin, carob seed powder, pectin, and alginates (e.g., ammonium alginate and sodium alginate).

Advantageously, the output of the premixer 84 is connected to the input of a hydrator 86, the hydrator 86 having a line 88 for water and a further input connected to a supply line 90 for compressed air.

The output of the mixer 80 feeds the mixture to the forming unit 92, preferably so as to obtain a plurality of portions 97, these portions 97 preferably being similar to the bread/cake and separate from each other. Suitably, the forming unit 92 comprises a pair of forming rollers 96, the pair of forming rollers 96 having a groove, preferably parallel to the axis of the cylinder, arranged to pick up the incoming mixture and the output section 97. Advantageously, the forming unit 92 is also arranged to perform a coarse mixing, for which purpose it preferably comprises a hopper 94, which hopper 94 is provided with the broken pieces inside it and at the bottom with said pair of forming rollers 96.

Advantageously, at the outlet of the forming unit 92, a conveyor belt 98 is provided for conveying the portions 97 to a first lamination unit 100.

Preferably, the first lamination unit 100 includes a leaf feeder 102.

Advantageously, a further metal detector 104 may be provided along the transport path from the forming unit 92 to the leaf feeder 102, the function of this further metal detector 104 being to remove any metal parts that may still be present in the mixture and that may damage the subsequent processing units. These metal portions are conveyed along special paths to the inlet of the leaf feeder 102 and collected in a suitable container 106.

The leaf feeder 102 comprises a series of feeding leaf rollers between which the portions 97 (from the forming rollers 96 of the forming unit 92) are conveyed so as to push them between a pair of moving rolling cylinders 108, the rolling cylinders 108 being arranged to form a continuous strip having a thickness of about 1-20mm, preferably about 1-10 mm.

Preferably, in a not shown variant of the apparatus, the roller line 116 may be arranged just downstream of the leaf feeder 102. In particular, in this case, the roller line receives a continuous strip input of thickness of about 1-20mm, preferably about 1-10mm, exiting from a first lamination unit 100 provided in a leaf feeder 102.

Advantageously, the lamination unit 110 may be arranged downstream of the first lamination unit 100 and upstream of the roll line 116. Preferably, it is provided to arrange the continuous single-layer strip, coming out from the first lamination unit 100, having a thickness of about 1-10mm on a plurality of layers, so as to transform it into a multi-layer strip having a thickness of about 2-20mm, which is then sent to the rolling line 116.

Preferably, said stacking unit 110 comprises an upstream conveyor belt 112, the function of which upstream conveyor belt 112 is to deposit the product strip on a lower downstream conveyor belt 114, which downstream conveyor belt 114 preferably belongs to a roll line 116, the product strip being arranged so that it is stacked on said downstream conveyor belt 114, for example so that it is folded on itself several times. Preferably, the upstream conveyor belt 112 is elevated above the downstream conveyor belt 114 and is provided with a continuous forward movement relative to its support structure, while there is a reciprocating movement with its support structure, parallel to its longitudinal axis.

Suitably, the laminating unit 110 feeds the lower continuous roll line 116, and the upstream conveyor belt 112 laminating unit 110 may be arranged parallel or perpendicular to the roll line 116, depending on the type of equipment. In particular, when the width of the downstream conveyor 114 of the rollers 116 is substantially equal to the width of the strip of products leaving the lamination unit 110, the upstream conveyor 112 is arranged parallel to the downstream conveyor 114, which downstream conveyor 114 is disposed on the rollers 116 (fig. 1), whereas when the downstream conveyor 114 of the rollers 116 is wider than the products leaving the lamination unit 110, it is preferable that the upstream conveyor 112 is arranged orthogonally to the downstream conveyor 114 on which the rollers 116 are disposed (fig. 8), so that by its movement, the strip of products can be distributed over the entire useful width of the rollers 116.

Conveniently, in both cases, the reciprocating movement of the structure supporting the lamination unit 110 of the upstream conveyor belt 112 causes the lamination of the strip of product leaving the first lamination unit 100 on the underlying first downstream conveyor belt 114 of the rolling line 116 and forming a laminated strip having a width substantially equal to the useful width of the rolling line itself.

The nip line 116 is formed by a plurality of laminating stations, each of which includes a pair of cylinders 118 defining an increasingly narrower passageway therebetween for progressively reducing the strip thickness of the product being processed. In particular, the roller line 116 is arranged such that the annular strip gradually reaches a thickness of 90-280 μm, preferably about 140-200 μm.

Preferably, a downstream conveyor 114 is arranged between one lamination station and the next, the length of the downstream conveyor 114 preferably being about 1.5-2m, the downstream conveyor 114 having the function of resting the product before it is subjected to the next lamination step.

Advantageously, the roller line 116 is in turn completed by one or more calibration stations, each of which is formed by a pair of calibration cylinders 120.

Advantageously, the lamination cylinder 118 and possibly also the calibration cylinder 120 can be heated in order to be able to start the drying step already during rolling.

Conveniently, a dryer 122 is provided downstream of the roller line 116, preferably with air recirculation (fig. 7), to bring the liquid content of the roller bar to about 8-15%. Advantageously, the dryer 122 can be divided into two

units

124, 126 arranged in series with respect to each other. More particularly, the upstream unit 124 is arranged to perform a first drying step and has, inside it, a carrier made of steel plate or a mesh conveyor belt for conveying the products coming out of the roller line 16; the downstream unit 126 is arranged to perform a second drying step and a subsequent cooling step and is internally provided with a mesh conveyor belt.

Also, advantageously, the dryers 122 are arranged at the inlet and outlet of the sensor 128, preferably with infrared light, which sensor 128 controls the product along the entire length.

The operation of the apparatus for producing conventional reconstituted tobacco (FIG. 2) is described below.

Preferably, the container of tobacco scraps is arranged on a tipping bucket 2, which tipping bucket 2 is turned over so that the products are taken to a feeder 4, which feeder 4 delivers them to a vibrating conveyor 6. Here, the heavy objects are separated from the tobacco by-products, which are collected in the container 8, while the tobacco by-products are conveyed by the air flow along the pneumatic conveying line 10 to the cyclone 12, which cyclone 12 separates the air from the solid products and makes them fall on the conveyor 14, which conveyor 14 is used to convey them to the cryogenic grinder 20 through the pneumatic line 18.

Preferably, instead, in order to produce unconventional reconstituted tobacco (fig. 3), the cartons containing the tobacco leaves are arranged in an unpacking table 22, in which unpacking table 22 the individual bales of tobacco leaves are taken out of the cartons and sent to a grinder 24, which grinder 24 reduces the blades themselves to a substantially uniform size of between 5 and 10 mm.

Conveniently, the product thus comminuted is then conveyed along a pneumatic conveying line 26 to a cyclone separator 28, which cyclone separator 28 separates it from the air and drops it onto a vibrating screen 30.

Here, the finer fraction (which is sent directly to the cryogenic grinding mill 20) is separated from the rest, which reaches the separation chamber 34 after passing through the fine wire remover 32. Here, any heavy objects are separated from the shredding blade which is sent to the cryogenic grinding mill 20 after control of the metal detector 42.

Conveniently, when the formulation requires, the shredded tobacco veins can also be conveyed to the same cryogenic grinder 20, which can be used to produce both conventional and unconventional types of reconstituted tobacco.

In this case (fig. 4), the lobed container is arranged on a tipper 46, which tipper 46 feeds the veins themselves to a vibrating conveyor 50 for removing any heavy objects. The veins are then conveyed through pneumatic line 52 to a hammer mill 54 which chops them so that their size is reduced to between 5 and 8 mm.

From here, the shredded veins separated by conveying air in the cyclone 58 are conveyed to a storage silo 60, from which storage silo 60 different types of veins from different qualities of tobacco can be taken and conveyed by a screw conveyor 62 to a metering device 64 of the veins, which metering device 64 meters them according to the particular formulation to be prepared.

The fine cut and metered correct amount of veins are conveyed to the cryogenic grinder 20 by pneumatic conveying lines 66.

Advantageously, the average particle size of the ground product exiting the comminution unit is about 20 to 220 μm, preferably about 80 to 180 μm, independently of the type of reconstituted tobacco to be produced and the type of solid tobacco fraction introduced into the comminution unit. Preferably, the ground product (supplied by cryogenic grinder 20) coming out of the sieve with the fluidized bed has an average particle size of about 20-220 μm, preferably about 80-180 μm.

Advantageously, the product thus ground is sent to a mixing and storage silo 60, from which the product can then be taken out and transferred to a kneader 80 as required.

Preferably, in the mixer 80, in addition to the ground tobacco (and preferably the solid product from the mixing and storage silo 60), water, at least one binder and at least one aerosol-forming material are introduced. Preferably, compressed air and other additives are also added.

Preferably, they are all remixed together to form a mixture having a liquid percentage (moisture) of about 30-50 wt% (on a wet basis), preferably about 35-40 wt%, i.e., a relatively dense consistency.

The mixture thus obtained is preferably conveyed to a forming unit 92, from which forming unit 92 a plurality of portions 97 emerge, preferably shaped like bread.

Thus, it is preferred that the portion 97 of the mixture coming out of the forming unit 92 is conveyed to a first lamination unit 100, which first lamination unit 100 is arranged to output a continuous strip having a thickness of about 1-20mm, preferably about 1-10 mm.

This continuous strip from the first laminating unit 100 is conveyed directly to the nip 116 or is folded on itself by the laminating unit 110 to be placed in a laminated form on the input belt 114 of the nip 116.

Preferably, as mentioned above, the lamination is obtained by letting the continuous strip fall on a conveyor belt 112 which advances with respect to its supporting structure which is reciprocated so as to have more than one layer of product strips on said downstream conveyor belt 114. Depending on the alternating direction of movement of the apparatus and the support structure of the conveyor belt 112 just downstream of the laminating unit 110, the product strips can be arranged in layers parallel to the longitudinal direction of the roller line 116 or orthogonal thereto.

Preferably, during each passage from one station to another of the roll lines 116, the strip undergoes a thickness reduction until a suitable thickness corresponding to the moving output calibration cylinder 120 is reached, which has a substantially constant value of about 90-280 μm, preferably about 140-200 μm. Moreover, advantageously, in the case where the moving cylinder 118 is heated and the water has been removed during the rolling treatment, the strip has a liquid content as low as 20%, or even as low as 15%, at the outlet of the rolling line 116.

The product strip exiting the roll line 116 is then dried in a dryer 122 where it has a liquid content of about 8-15%.

Preferably, the dryer 122 is in an air recirculation, which dryer 122 is more advantageous in terms of complexity, as well as burden and energy consumption, than dryers conventionally used in production systems for reconstituted tobacco. This is because conventional systems handle products (mixtures) which are very fluid and poorly stable, which are much denser and more stable than the treated products of the apparatus according to the invention. Thus, although the system for treating the slurry requires a conventional radiant and conductive dryer, the apparatus according to the invention may advantageously use an air recirculating dryer 122 having a screen conveyor or a combined system of a steel belt conveyor for the first drying step and a mesh belt conveyor for the second drying step and the cooling step. Thus, with the same performance, we obtain a reduction in size (by about 45m compared to more than 100m for a conventional dryer) and lower energy consumption (lower amounts of water are known to be removed) (using about 1000 kg/h of steam compared to more than 5000 kg/h for a conventional dryer).

Preferably, at the outlet of the dryer 122, the product is ready to be wound on reels or cut into strands of a given size for packaging of cigarettes.

Conveniently, in the case where the plant is set up for producing reconstituted tobacco of the unconventional type, it uses, in addition to the different preparation and treatment sections already described, a cylinder refiner 130 (as an alternative to the forming unit 92 or in addition upstream of the forming unit 92), the task of this cylinder refiner 130 being to bring the particle size of the solid components of the mixture to a value not exceeding 20 μm.

The refiner (fig. 6) comprises a plurality of cylinders 132 in a closed container, which cylinders 132 are arranged in series in narrow proximity between them so as to define respective grinding gaps. The lower cylinder 132 is mounted with the axis outside the plane containing the axes of all the other cylinders 132 and serves as a feeder of the mixture which is taken from the bottom of the container and rises upwards so as to pass between the lower cylinder and the cylinder immediately above, then following all the other cylinders. The pairs of cylinders 132 between which the mixture passes rotate at different speeds, so that the upper cylinder rotates at a greater speed than the lower cylinder with which it cooperates, so as to stretch the mixture as it passes between each pair of cylinders 132, thus reducing the particle size of the mixture itself. One of the essential parameters for the success of the refining process is the different speeds of the different cylinders 132, on which the passage of the entire mass of the mixture through the grinding gap will depend. The pressure between the cylinders is hydraulically controlled.

All the cylinders 132 are cooled by cold water circulating inside each cylinder, thus counteracting the heat generated by mixing due to the friction (by the motion for the cylinders themselves and friction with the product). Thus, the temperature of the product was reduced to 25 ℃.

Due to the cylinder refiner 130 described now, the friction exerted on the mixture by the cylinders 132 of the cylinder refiner 130 produces a considerable binding action of the cellulose fibres contained in the tobacco (in particular in its veins), and this produces a double advantage: the aromatic component of the product is formed and no additional fibers need to be introduced into the mixture to achieve the desired bonding effect.

The operation of the apparatus in this different embodiment requires that the chopped leaves and the broken veins from the preparation and pretreatment station are fed to the cascade cryogenic grinder 20 in metered amounts in proportion to the formulation and thus reach a particle size of about 20-220 μm, preferably about 80-180 μm.

The product is then transferred to the mixer 80 in the manner already described, forming a product mixture in the mixer 80, as described above.

The mixture thus obtained is fed to a cylinder refiner 130, the task of which cylinder refiner 130 is to bring the solid constituents of the mixture to a particle size of not more than 20 μm. In this way, the friction exerted on the mixture by the cylinders 132 of the cylinder refiner 130 produces a considerable binding action of the cellulose fibres contained in the tobacco (in particular in its veins), which results in the double advantage of producing, on the one hand, the aromatic component of the product and, on the other hand, the absence of the need to introduce other fibres into the mixture in order to obtain the desired binding effect.

Fig. 1 schematically shows the position of the cylinder refiner 130 between the kneader 80 and the forming unit 92, but it is also provided according to the invention that the cylinder refiner 130 can replace the forming unit 92, in which case the mixture leaving the cylinder refiner 130 is conveyed directly to the first laminating unit 100 for continuing the treatment cycle according to the method already described.

Claims

1. A method for producing reconstituted tobacco, characterized in that:

-comminuting the solid constituents of the tobacco so as to achieve a particle size of the fixed constituents of the tobacco of about 20-220 μm, preferably about 80-180 μm;

-said mixture is subjected to a first lamination so as to obtain a continuous strip with a thickness of about 1-20mm, preferably about 1-10 mm;

-said strip having undergone said first lamination is subjected to a series of further rolling passes so as to obtain a strip having a substantially constant thickness of about 90-280 μm, preferably about 140-200 μm;

-the strip is dried so that its liquid content reaches about 8-15%.

2. The method of claim 1, wherein: the continuous strip of dry material is wound or cut into predetermined size threads.

3. The method according to one or more of the preceding claims, characterized in that: the solid components of tobacco are comminuted by grinding.

4. The method according to one or more of the preceding claims, characterized in that: the solid components of the tobacco are comminuted by means of a attrition mill.

5. The method according to one or more of the preceding claims, characterized in that: the solid components of the tobacco are crushed by a cryogenic cascade mill (20).

6. The method according to one or more of the preceding claims, characterized in that: the mixture of comminuted product, water, at least one binder and at least one material arranged to form an aerosol is subjected to:

-a roughing step for passing at least one pair of cylinders (92) having grooves; and/or

-a refining step by passing the mixture through at least one pair of refining cylinders (132, 132') until its particle size reaches not more than 20 μm.

7. The method according to one or more of the preceding claims, characterized in that: before the first rolling step, the mixture is subjected to a homogenization and formation step.

8. The method of claim 7, wherein: the mixture is subjected to a homogenization and formation step for transforming it into a continuous strip having a substantially constant width comprised between 100mm and 2000mm and a thickness comprised between 1mm and 10mm, in order to be subjected to the first rolling stage again.

9. The method of claim 7, wherein: the mixture is subjected to a homogenization and formation step for transforming it into a series of portions (97) for further carrying out the first lamination step.

10. The method according to one or more of the preceding claims, characterized in that: the first rolling of the mixture is carried out by means of a unit (100), said unit (100) comprising a leaf feeder (102) and at least one pair of rolling cylinders (108).

11. The method according to one or more of the preceding claims, characterized in that: a single-layer strip with a thickness of about 1-10mm was obtained at the output of the first laminate.

12. The method according to one or more of the preceding claims, characterized in that: the strips, having undergone the first lamination, are laminated until a multilayer strip with a thickness of about 2-20mm is obtained, before the series of further rolling passes.

13. The method according to one or more of the preceding claims, characterized in that: in the series of further roll passes, the mixture rests between one lamination station and the next.

14. The method according to one or more of the preceding claims, characterized in that: the lamination is performed by pairs of cylinders (118) which are at least locally heated.

15. The method according to one or more of the preceding claims, characterized in that: the laminate strips are dried by passing through a circulating air dryer (122).

16. Apparatus for producing reconstituted tobacco, characterized in that it comprises:

-a comminution unit (20, 24, 54) of the solid constituents of the tobacco for bringing the fixed constituents of the tobacco to a particle size of about 20-220 μm, preferably about 80-180 μm;

-a kneader (80) fed with metered amounts of comminuted material, water, at least one binder and at least one material for forming an aerosol and arranged to obtain a mixture having a liquid content of about 30-50%, preferably a liquid content of about 35-40%;

-a first lamination unit (100) for obtaining a continuous strip with a thickness of about 1-20mm, preferably about 1-10mm, from said mixture;

-a roller (116) located downstream of said first lamination unit (100) to bring said continuous strip to a thickness of 90-280 μm, preferably about 140-200 μm;

-a dryer (122) for bringing the liquid content of the laminate strip to about 8-15%.

17. The apparatus according to the preceding claim, characterized in that: the dryer has air recirculation.

18. The device according to one or more of the preceding claims, characterized in that: the shredding unit includes an attrition mill.

19. The device according to one or more of the preceding claims, characterized in that: the chopping unit comprises a cryogenic cascade mill (20).

20. The device according to one or more of the preceding claims, characterized in that: the apparatus comprises a formation unit (92) of the mixture downstream of the kneader (80) and upstream of the first lamination unit (100).

21. The device according to one or more of the preceding claims, characterized in that: the forming unit (92) is also arranged to perform homogenization of the mixture.

22. The device according to one or more of the preceding claims, characterized in that: the forming unit (92) is arranged to transform the mixture into a continuous strip having a substantially constant width between 100 and 2000mm and a thickness between 1-4 mm.

23. The device according to one or more of the preceding claims, characterized in that: the forming unit (92) is arranged to subdivide the mixture into a plurality of portions (97) starting at the first lamination unit (100).

24. The device according to one or more of the preceding claims, characterized in that: the forming unit (92) comprises a roughing machine having at least one pair of forming rollers (96) and/or a cylinder refiner (130).

25. The device according to one or more of the preceding claims, characterized in that: the first lamination unit (100) comprises a leaf feeder (102) and at least one pair of rolling cylinders (108).

26. The device according to one or more of the preceding claims, characterized in that: the apparatus comprises a lamination unit (110) downstream of the first lamination unit (100).

27. The apparatus according to the preceding claim, characterized in that: the laminating unit (110) comprises an upstream conveyor belt (112) fed by the first laminating unit (100) and provided with a continuous movement with respect to a support structure of the upstream conveyor belt, which support structure is provided with a reciprocating movement with respect to an underlying downstream conveyor belt (114), the downstream conveyor belt (114) preferably being the roller line (116).

28. The device according to one or more of the preceding claims, characterized in that: the roll line (116) includes a plurality of roll stations that are separated from each other by a length of the conveyor belt (114) sufficient to lay the product strip between the roll station and a subsequent roll station.

29. The device according to one or more of the preceding claims, characterized in that: at least a portion of the cylinders (118, 120) of the nip line (116) are heated.

30. The device according to one or more of the preceding claims, characterized in that: the hot air dryer (122) comprises: a first unit (124) in which a first step of drying the product strip coming out of the rolling line (116) is carried out; and a second unit (126) arranged in series with the first unit, in which a second drying step is carried out and in which a subsequent cooling step of the product strip, which has been partially dried, leaving the first unit (124) is carried out.

31. The apparatus of claim 30, wherein: at least one mesh conveyor is used inside the hot air dryer (122).

32. The apparatus according to claim 30 and/or 31, characterized in that: the dryer (122) with hot air is arranged inside the first unit (124) of a steel belt or mesh belt conveyor and inside the second unit (126) of a mesh belt conveyor.