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Title:
TOBACCO EXTRACT SEPARATION
Document Type and Number:
WIPO Patent Application WO/2018/210774
Kind Code:
A1
Abstract:
Disclosed is a press (1) for separating a tobacco extract from a mixture (17) comprising the tobacco extract and tobacco solids (18), the press comprising: a variable volume separation chamber defined by a base (11), at least one side wall (12), and a compression surface (13), wherein the compression surface is arranged to move towards the base to decrease the volume of the separation chamber; and an actuator (14), to drive movement of the compression surface relative to the base; wherein the at least one side wall has a plurality of holes (15) therethrough, wherein at least one of the plurality of holes is covered by a mesh (16) having openings smaller than the hole.

Inventors:
SINTYUREVA MARINA (GB)
Application Number:
PCT/EP2018/062423
Publication Date:
November 22, 2018
Filing Date:
May 14, 2018
Export Citation:
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Assignee:
BRITISH AMERICAN TOBACCO INVESTMENTS LTD (GB)
International Classes:
A24B15/26; A24B15/24; B01D29/23; B01D29/82; B30B9/00
Domestic Patent References:
WO2014020337A12014-02-06
Foreign References:
US20160166956A12016-06-16
DE102008052720A12010-04-29
GB2103066A1983-02-16
EP0501185A11992-09-02
Other References:
ANONYMOUS: "Basket Presses Fratelli Baesso - fruit presses and apple shredders", 30 August 2018 (2018-08-30), XP055503453, Retrieved from the Internet [retrieved on 20180830]
ANONYMOUS: "Amazon.com: Mesh Bag for Fruit Press: Home & Kitchen", 30 August 2018 (2018-08-30), XP055503456, Retrieved from the Internet [retrieved on 20180830]
SOULFLOWER FARM: "Soul Flower Farm: DIY Cider Press", 28 August 2012 (2012-08-28), XP055503471, Retrieved from the Internet [retrieved on 20180830]
Attorney, Agent or Firm:
EIP (GB)
Download PDF:
Claims:
CLAIMS

1. A press for separating a tobacco extract from a mixture comprising the tobacco extract and tobacco solids, the press comprising:

a variable volume separation chamber defined by a base, at least one side wall, and a compression surface, wherein the compression surface is arranged to move towards the base to decrease the volume of the separation chamber; and

an actuator, to drive movement of the compression surface relative to the base; wherein the at least one side wall has a plurality of holes therethrough,

wherein at least one of the plurality of holes is covered by a mesh having openings smaller than the hole.

2. A press according to claim 1, wherein the at least one side wall comprises an inner surface which defines the separation chamber, and an outer surface opposite the inner surface, and wherein the outer surface is between the inner surface and the mesh.

3. A press according to claim 2, further comprising at least one outer wall, wherein the mesh is between the at least one outer wall and the at least one side wall.

4. A press according to claim 3, wherein the at least one outer wall has a plurality of holes therethrough, having a size greater than or equal to the size of the holes through the at least one side wall and positioned to correspond to the positions of the plurality of holes through the at least one side wall.

5. A press according to any one of claims 2 to 4, wherein the size of the plurality of holes through the at least one side wall is arranged to control a size of the tobacco solids able to pass through the plurality of holes through the at least one side wall.

6. A press according to any one of claims 1 to 5, wherein a spacing of the holes through the at least one side wall varies in dependence on distance from the base.

7. A press according to claim 6, wherein the spacing of the holes is relatively smaller in a first region of the at least one side wall relatively closer to the base and relatively greater in a second region of the side wall relatively further from the base than the first region.

8. A press according to claim 7, wherein the distance between the centres of adjacent holes along a particular direction is 10 mm in the first region and is 20 mm in the second region.

9. A press according to any one of claims 1 to 8, wherein the size of each of the mesh openings is in the range 0.1-0.3 mm.

10. A press according to any one of claims 1 to 9, wherein each of the holes is circular and has a diameter in the range 3-5 mm

11. A press according to any one of claims 1 to 10, wherein the compression surface is arranged to be stationary with respect to the base in a plane parallel to the base during movement of the compression surface towards the base, such that no shear force is experienced by a mixture being separated during operation of the press.

12. A method of separating a tobacco extract from a mixture comprising the tobacco extract and tobacco solids, the method comprising:

providing a mixture comprising a tobacco extract and tobacco solids; and compressing the mixture in a chamber to force the liquid tobacco extract out of the mixture;

wherein the chamber comprises at least one wall having a plurality of holes therethrough, such that the liquid tobacco extract is forced through the holes during the compressing.

13. A method according to claim 12, wherein at least one of the plurality of holes through the at least one wall is covered by a mesh having openings smaller than the at least one of the plurality of holes.

14. A method according to claim 12 or claim 13, wherein the mixture has a viscosity of at least 100 mPa-s.

15. A method according to any one of claims 12 to 14, wherein the mixture comprises one or more of: glycerol, propylene glycol and triacetin.

16. A method according to any one of claims 12 to 15, wherein the liquid tobacco extract comprises an aerosol generating agent.

17. Use of a press to separate a tobacco extract from a mixture comprising the tobacco extract and tobacco solids, the press comprising:

a variable volume separation chamber defined by a base, at least one side wall, and a compression surface, wherein the compression surface is arranged to move towards the base to decrease the volume of the chamber; and

an actuator, to drive movement of the compression surface relative to the base; wherein the at least one side wall has a plurality of holes therethrough.

18. A press for separating a tobacco extract from a mixture comprising the tobacco extract and tobacco solids, the press comprising: a variable volume separation chamber defined by a base, at least one side wall, and a compression surface, wherein the compression surface is arranged to move towards the base to decrease the volume of the chamber; and

an actuator, to drive movement of the compression surface relative to the base; wherein the at least one side wall has a plurality of holes therethrough, a spacing of the holes being relatively smaller in a first region of the side wall relatively closer to the base and relatively greater in a second region of the side wall relatively further from the base than the first region.

Description:
TOBACCO EXTRACT SEPARATION

Technical Field

The present invention relates to a press and method for separating a tobacco extract from a mixture comprising the tobacco extract and tobacco solids.

Background

There exist so-called e-cigarette devices, which typically vaporise a liquid to form an aerosol which can be inhaled, which may or may not contain nicotine. Some liquids for use in e-cigarette devices contain a tobacco extract in order to produce a sensory experience similar to that produced by a non-electronic cigarette.

Tobacco extracts are typically created from ground tobacco leaf, e.g. by mixing the ground tobacco leaf with a solvent to dissolve volatile components of the tobacco leaf, then removing the spent tobacco solids, and optionally removing excess solvent.

It is desirable for the amount of suspended solid material remaining in the final extract product to be as low as possible.

Summary

According to a first aspect of the present invention, there is provided a press for separating a tobacco extract from a mixture comprising the tobacco extract and tobacco solids. The press comprises a variable volume separation chamber and an actuator. The variable volume separation chamber is defined by a base, at least one side wall, and a compression surface, wherein the compression surface is arranged to move towards the base to decrease the volume of the separation chamber. The actuator is to drive movement of the compression surface relative to the base. The at least one side wall has a plurality of holes therethrough, wherein at least one of the plurality of holes is covered by a mesh having openings smaller than the hole.

The at least one side wall may comprise an inner surface which defines the separation chamber, and an outer surface opposite the inner surface. The outer surface may be between the inner surface and the mesh.

The press may further comprise at least one outer wall. The mesh may be between the at least one outer wall and the at least one side wall. The at least one outer wall may have a plurality of holes therethrough, having a size greater than or equal to the size of the holes through the at least one side wall and positioned to correspond to the positions of the plurality of holes through the at least one side wall.

The size of the plurality of holes through the at least one side wall may be arranged to control a size of the tobacco solids able to pass through the plurality of holes through the at least one side wall.

A spacing of the holes through the at least one side wall may vary in dependence on distance from the base. The spacing of the holes may be relatively smaller in a first region of the at least one side wall relatively closer to the base and relatively greater in a second region of the side wall relatively further from the base than the first region. The distance between the centres of adjacent holes along a particular direction may be 10 mm in the first region and 20 mm in the second region.

The size of each of the mesh openings may be in the range 0.1-0.3 mm. Each of the holes may be circular and have a diameter in the range 3-5 mm.

The compression surface may be arranged to be stationary with respect to the base in a plane parallel to the base during movement of the compression surface towards the base, such that no shear force is experienced by a mixture being separated during operation of the press.

According to a second aspect of the present invention, there is provided a method of separating a tobacco extract from a mixture comprising the tobacco extract and tobacco solids. The method comprises: providing a mixture comprising a tobacco extract and tobacco solids; and compressing the mixture in a chamber to force the liquid tobacco extract out of the mixture. The chamber comprises at least one wall having a plurality of holes therethrough, such that the liquid tobacco extract is forced through the holes during the compressing.

At least one of the plurality of holes through the at least one wall may be covered by a mesh having openings smaller than the at least one of the plurality of holes.

The mixture may have a viscosity of at least 100 mPa-s. The mixture may comprise one or more of: glycerol, propylene glycol and triacetin. The liquid tobacco extract may comprise an aerosol generating agent.

According to a third aspect of the present invention, there is provided use of a press to separate a tobacco extract from a mixture comprising the tobacco extract and tobacco solids. The press comprises a variable volume separation chamber and an actuator. The variable volume separation chamber is defined by a base, at least one side wall, and a compression surface, wherein the compression surface is arranged to move towards the base to decrease the volume of the chamber. The actuator is to drive movement of the compression surface relative to the base. The at least one side wall has a plurality of holes therethrough.

According to a fourth aspect of the present invention, there is provided a press for separating a tobacco extract from a mixture comprising the tobacco extract and tobacco solids. The press comprises a variable volume separation chamber and an actuator. The variable volume separation chamber is defined by a base, at least one side wall, and a compression surface, wherein the compression surface is arranged to move towards the base to decrease the volume of the chamber. The actuator is to drive movement of the compression surface relative to the base. The at least one side wall has a plurality of holes therethrough, a spacing of the holes being relatively smaller in a first region of the side wall relatively closer to the base and relatively greater in a second region of the side wall relatively further from the base than the first region.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 is a schematic view of a press according to an embodiment;

Figure 2 is a schematic view of part of a side wall of the press of Figure 1;

Figure 3 is a cross-section through part of a side wall of the press of Figure 1; Figure 4 is a cross-section through part of a side wall of a press according to an embodiment;

Figure 5 is a perspective view of a side wall and an outer wall of a press according to an embodiment;

Figure 6 is a schematic view of part of a side wall of a press according to an embodiment;

Figure 7 is a perspective view of a side wall of a press according to an embodiment; Figure 8 is a schematic view of a press according to an embodiment; and

Figure 9 is a flow diagram of a method of forming a tobacco extract according to an embodiment.

Detailed Description

A tobacco extract may be obtained by a method comprising the treatment of tobacco with a liquid solvent. For example, the treatment of tobacco with a liquid solvent may comprise adding the liquid solvent to tobacco, separating the resulting solvent-based liquid extract from the insoluble portion of tobacco feedstock, and optionally removing excess solvent to form a tobacco extract. It is known to separate the liquid extract from the tobacco solids by filtration. Known filtration methods include centrifugal solids filtration or vacuum fluidised bed filtration.

Liquids for use in e-cigarette devices typically comprise an aerosol generating agent. In this context, an "aerosol generating agent" is an agent that promotes the generation of an aerosol. An aerosol generating agent may promote the generation of an aerosol by promoting an initial vaporisation and/or the condensation of a gas to an inhalable solid and/or liquid aerosol. In some embodiments, an aerosol generating agent may improve the delivery of flavour from the aerosol generating material. Suitable aerosol generating agents include, but are not limited to: a polyol such as sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol; a non-polyol such as monohydric alcohols, high boiling point hydrocarbons, acids such as lactic acid, glycerol derivatives, esters such as diacetin, triacetin, triethylene glycol diacetate, triethyl citrate or myristates including ethyl myristate and isopropyl myristate and aliphatic carboxylic acid esters such as methyl stearate, dimethyl dodecanedioate and dimethyl tetradecanedioate.

Solvents suitable for use in the creation of a tobacco extract include water, a polyol or other suitable higher boiling liquid, glycerol, propylene glycol, triacetin, a myristate (e.g. isopropyl), and various combinations of these solvents. Including a solvent which is also an aerosol generating agent (e.g. glycerol, propylene glycol, triacetin, a myristate) in the extraction solvent may be advantageous because the resulting extract can be used directly in an e-cigarette device without requiring the addition of a separate aerosol generating agent. A challenge exists in creating a tobacco extract using solvents which have a relatively high viscosity. Most known separation methods have been developed for relatively low viscosity (e.g. aqueous-based) slurry systems having low solids content. As used herein, a slurry is a liquid, gel, solution, suspension or emulsion. The flow rate through a filter is inversely proportional to the liquid viscosity, meaning that filtration of highly viscous slurry systems, such as tobacco and glycerol mixtures, may be unpractically slow or even impossible.

For the purposes of this disclosure, water (at standard temperature and pressure (STP)) is considered to have a relatively low viscosity. Any substance having a viscosity less than or equal to 1 mPa-s is therefore considered to have a relatively low viscosity. A substance having a relatively high viscosity should be understood to have a viscosity greater than the viscosity of STP water (1 mPa-s), and may typically have a viscosity at least twice as high as the viscosity of STP water. A relatively high viscosity substance may, for example, have a viscosity of at least 5 mPa-s. Several relatively high viscosity substances envisaged for use in the embodiments may have a viscosity of at least 100 mPa-s.

The following disclosure proposes addressing the challenge of creating a tobacco extract using solvents which have a relatively high viscosity by applying an external stimulus to force liquid extract out of the solid matrix of a viscous slurry.

Figure 1 shows a press 1 for separating a tobacco extract from a mixture 17 comprising the tobacco extract and tobacco solids 18. The press 1 comprises a variable volume separation chamber defined by a base 11, at least one side wall 12, and a compression surface 13. The compression surface 13 is arranged to move towards the base 11 to decrease the volume of the chamber. The maximum volume of the separation chamber (i.e. the volume of the separation chamber when the distance between the compression surface 13 and the base 11 is at a maximum) may be selected based on the requirements of a particular intended application of the press 1. The at least one side wall 12 has a plurality of holes 15 therethrough, each of which is covered by a mesh 16 having openings smaller than the hole 15. Liquid tobacco extract is able to flow out of the separation chamber through the holes 15, during operation of the press 1 to separate the mixture 17, as indicated by the small block arrows in Figure 1. In the particular example, the separation chamber is defined by a single side wall and the compression surface 13 and the base 11 are circular, such that the separation chamber is cylindrical. However; other shapes of compression chamber (e.g. cubic, cuboidal, etc.) are also possible. In some examples the compression surface 13 is arranged to be stationary with respect to the base 11 in a plane parallel to the base 11 during movement of the compression surface 13 towards the base 11, such that no shear force is experienced by a mixture being separated during operation of the press 1 (i.e. all of the applied force is in a direction normal to the base 11). The mixture 17 contains particles of tobacco solids 18 having various sizes (e.g. in the range 355 um - 3.5 mm). A significant fraction of the particles are too large to pass through the holes 15 in the side wall 12 (e.g. because the size of the holes 15 has been selected based on the particle sizes expected to be present in the mixture 17, to create the effect of blocking a significant fraction of the particles 18). Avoiding applying a shear force to the mixture can advantageously prevent or reduce the break-up of particles of tobacco solids in the mixture into smaller particles, at least some of which may be able to pass through the holes.

The compression surface 13 seals against the side wall 12, so as to prevent fluid from passing between the compression surface 13 and the side wall 12. Both the mixture and a liquid tobacco extract separated from the mixture may thereby be prevented from passing between the compression surface 13 and the side wall 12. The seal may be formed in any suitable manner which permits maintenance of the sealing effect during movement of the compression surface 13 with respect to the side wall 12. The base 11 provides a surface against which contents of the separation chamber can be compressed. The base is fixed relative to the side wall, at least during application of a compressive force to contents of the separation chamber. In some examples the base includes one or more grooves or similar formations in the top surface, configured to allow liquid extract in a region of the separation chamber adjacent the base 11 to flow out of the separation chamber.

The press 1 further comprises an actuator 14, to drive movement of the compression surface 13 relative to the base 11 in the direction indicated by the larger block arrows. The actuator may be of any suitable type, e.g. a hydraulic actuator, a pneumatic actuator, a mechanical actuator, or suchlike. In the particular example, the compression surface 13 comprises a piston, and the actuator 14 comprises a hydraulic ram arranged to operate the piston to drive it towards and away from the base 11. The actuator 14 may be configured to apply a compressive force in the range 20-100kN. In some examples the actuator 14 is configured to apply a compressive force in the range 50- 80kN.

The press 1 may, in some examples, further comprise a container to receive liquid extract which flows out of the separation chamber through the holes 15. Such a container may be of any suitable design.

The at least one side wall 12 is rigid and comprised of a material that will not degrade as a result of exposure to the mixture that is to be separated using the press. The at least one side wall 12 has sufficient mechanical strength to maintain its shape against the outward force generated by the contents of the separation chamber as these contents are compressed by the compression surface. In the particular example the side wall 12 is formed from a sheet of stainless steel. Other suitable materials include aluminium, copper, and various plastics materials. In some examples the side wall may be coated, e.g. with a polymer material.

As mentioned above, the at least one side wall 12 has a plurality of holes 15 therethrough. In the particular example, each of the holes 15 is circular and has a diameter of 4 mm, although other shapes and/or sizes could alternatively be used. The holes 15 need not all have the same shape and/or size, although providing uniformly shaped and/or sized holes may simplify the manufacture of the press. The size and/or the shape of the holes may be selected in dependence on an expected particle size of the tobacco solids comprised in a mixture to be separated, such that tobacco solids of at least the expected size would be unable to pass through the holes.

Figures 2 and 3 shows an example of one of the plurality of holes 15 in more detail. As can be seen from Figures 2 and 3, the hole 15 is covered by a mesh 16 having openings smaller than the hole. At least one hole 15 of the plurality of holes is similarly covered by a mesh having openings smaller than the at least one hole. In some examples the mesh 16 comprises a plurality of mesh portions, each of which covers one or more of the holes 15. Alternatively, as is the case in the illustrated example, the mesh may comprise a single mesh portion which covers all of the holes 15. In the particular example the mesh comprises a stainless steel woven cloth having a mesh size in the range 0.1 - 0.3 mm.

The stainless steel cloth has low mechanical strength, and it is therefore fixed to the side wall 12 such that it is mechanically supported by the side wall 12. The mesh 16 may be fixed to the side wall 12 in any suitable manner which enables the mesh 16 to maintain a desired shape and position during compression of contents of the separation chamber. Examples of a suitable fixing technique are illustrated by Figures 4 and 5. In the particular examples of Figure 4, a portion of mesh 46 is clamped against a side wall 42 of a press by an outer wall 48. The outer wall 48 has a plurality of holes therethrough, having a size equal to or greater than the size of the holes in the side wall 42 and positioned to correspond to the positions of the holes in the side wall 42. Figure 5 shows a side wall 52 and an outer wall 58 for clamping a mesh therebetween according to an example, in which the outer wall 58 has a plurality of holes therethrough having a size greater than the size of the holes in the size wall 52 and positioned to correspond to the positions of the holes in the side wall 52. Making the holes in the outer wall larger than the holes in the side wall can advantageously reduce the cost of manufacturing a press comprising an outer wall. In the example of Figure 5 the clamping is effected by providing the outer wall 58 as a sheet configured to encircle the side wall 52, and fixing the vertical (as shown in Figure 5) edges of the sheet together (using any suitable fastening technique) such that the sheet is in tension and thereby exerts an inwards force against the side wall 52.

The distribution of the holes over the side wall can be uniform, e.g. such that the distance between the centres of adjacent holes (this quantity will hereinafter referred to as the "spacing" of the holes) is the same for each pair of adjacent holes in the side wall. This is the case with the side wall 12 of the press 1 shown in Figure 1. Alternatively, in some examples the distribution of the holes over the side wall is nonuniform, e.g. such that the spacing of the holes is not the same for each pair of adjacent holes. In some examples, such as the side wall 52 of Figure 5, the spacing of the holes varies in dependence on distance from the base. In some examples the horizontal spacing may be different to the vertical spacing. Figure 5 represents such an example, since the holes are arranged in circumferential rows which are relatively closer together in a vertical direction in a lower part of the side wall 52 and relatively further apart in the vertical direction in an upper part of the side wall 52. By contrast, the circumferential spacing of adjacent holes (i.e. the spacing between adjacent holes within a given row) is the same in the lower part as in the upper part. Figures 6 and 7 show two further examples of side walls where the spacing of the holes varies in dependence on distance from the base.

Figure 6 shows part of a side wall 62 for a press, e.g. the press 1. The side wall 62 may have any or all of the features of the side wall 12 discussed above, except that the spacing of the holes in the side wall 62 is non-uniform. The bottom (as shown in Figure 6) edge 65 of the side wall 62 is adjacent the base of a separation chamber when the side wall 62 is installed on a press. Thus, the side wall 62 has a first region 68 relatively closer to the base and a second region 69 relatively further from the base. The spacing of the holes is relatively smaller in the first region 68 and relatively greater in the second region 69. Similarly, Figure 7 shows a complete side wall 72 for a press, e.g. the press 1, having a first region 78 and a second region 79. The side wall 72 is the same as the side wall 62, except for the particular number and spacing of the holes. It will be appreciated that parameters relating to the exact arrangement of holes on a given side wall are selectable based on the particular application for which that side wall is intended to be used. The spacing of the holes may be selected based on a desired rate of separation. For example, a small spacing, such that more holes are present per unit area, can enable a higher rate of separation than a relatively larger spacing in which fewer holes are present per unit area. Varying the spacing in dependence on distance from the base can therefore vary the separation rate achievable at different stages of the separation process. In some examples the distance between the centres of adjacent holes along a particular direction is 10 mm in the first region and is 20 mm in the second region. The particular direction may be a direction perpendicular to a compression surface of a separation chamber. The particular direction may be a direction parallel to a compression surface of a separation chamber.

Figure 8 shows an alternative press 8 for separating a tobacco extract from a mixture 17 comprising the tobacco extract and tobacco solids. Similar to the press 1, the press 8 comprises a variable volume separation chamber defined by a base 81, at least one side wall 82, a compression surface 83 which is arranged to move towards the base 81 to decrease the volume of the chamber, and an actuator 84 to drive movement of the compression surface 83 relative to the base 81. The at least one side wall 82 has a plurality of holes 85 therethrough, the spacing of the holes 85 being relatively smaller in a first region 88 of the side wall 82 relatively closer to the base 81 and relatively greater in a second region 89 of the side wall 82 relatively further from the base.

The base 81, side wall 82, compression surface 83, actuator 84 and holes 85 may have any or all of the features described above in relation to the base 11, side wall 12, compression surface 13, actuator 14 and holes 15, respectively, of the press 1. However; unlike the holes 15, each hole 85 need not be covered by a mesh having openings smaller than the hole.

The operation of a press (e.g. the press 1 or the press 8) to separate a tobacco extract from a mixture comprising the tobacco extract and tobacco solids will now be described. Figure 9 is a flow diagram implementing an example of a method of forming a tobacco extract. In discussing Figure 9 reference is made to the diagrams of Figures 1-8 to provide contextual examples. Implementation, however, is not limited to those examples.

In block 910 of the example method 900 shown in Figure 9, a mixture is provided which comprises a liquid tobacco extract and tobacco solids. The tobacco solids may be in the form of suspended particles. The mixture may have any or all of the features of the mixture 17 described above in relation to Figure 1.

The mixture may comprise a solvent, which comprise glycerol, propylene glycol, triacetin, water, any other of the solvents listed above, or any other suitable solvent. The solvent may comprise any combination of suitable solvents. For example, the solvent may comprise a mixture of glycerol and water. The solvent may be an aerosol generating agent.

The mixture may have been made according to any suitable process. In a particular example, the mixture can be made using a "Simple Extraction" process, based on using glycerol as a solvent to leach volatile components from tobacco solids. In a specific example of the Simple Extraction process, ground and sieved tobacco, of which at least 90% by weight has a particle size in the range of about 355 μιη to about 3.5 mm, is mixed with glycerol heated to a predetermined temperature, at a 1 :9 ratio (tobacco: solvent (weight/weight)). Leaching is allowed to take place for a predetermined time period. The resulting extract is then filtered through percolation. In some examples the clarified extract is reheated, an appropriate amount of fresh tobacco leaf is added to ensure that the 1 :9 (tobacco: solvent) ratio is maintained, and the leaching process is repeated.

As discussed above, glycerol has a relatively high viscosity. This is also true of many other solvents which may be comprised in a tobacco extract, such as propylene glycol and triacetin. The mixture 17 may therefore have a relatively high viscosity. In particular examples, the mixture may have a viscosity of at least 100 mPa-s. The viscosity of the mixture may be high enough such that passive filtration of the mixture (i.e. without the application of an external force) would be impossible or impractically slow.

Providing the mixture comprises providing the mixture inside a separation chamber of a press, e.g. the press 1 of Figure 1 or the press 8 of Figure 8. For example, the mixture may be poured into the separation chamber through a suitable opening provided for this purpose. The mixture may be introduced into the chamber in any other suitable manner.

In block 920, the mixture is compressed in a chamber (e.g. the separation chamber of the press 1 or the press 8) to force the liquid extract out of the mixture. The chamber comprises at least one wall having a plurality of holes therethrough, such that the liquid tobacco extract is forced through the holes during the compressing. The chamber may have any or all of the features described above in relation to the press 1 and/or the press 8. The holes may have any or all of the features of the holes 15, 44, 55, 65, 75 or 85 described above. For example, a mixture which has been provided in the separation chamber of the press 1 or the press 8 can be compressed by driving the compression surface towards the base using the actuator. The tobacco extract comprised in the mixture will thereby be forced through the holes in the side wall during the compressing. Tobacco solids having a particle size larger than the size of the holes will remain within the separation chamber, and will become compressed into a relatively dry cake which can be removed from the separation chamber after completion of the separation operation.

In some examples each hole is covered by a mesh having openings smaller than the hole (e.g. examples performed using the press 1). In such examples the tobacco extract comprised in the mixture is forced through the mesh as it is forced through the holes in the side wall. In some examples in which the holes are covered by mesh, the mesh is provided on the outside of the holes, relative to the interior of the separation chamber, such that particles larger than the size of the holes are prevented or are substantially prevented from contacting the mesh. Such arrangements can advantageously prevent or reduce blockage of the mesh by tobacco solids particles.

The compression may be performed in accordance with preselected process parameters. For example, one or more of various parameters including (but not limited to) ambient temperature, mesh size (if a mesh is used), compression rate (i.e. speed of movement of the compression surface), and compressive force applied may be controlled to be equal or substantially equal to predetermined values. One or more parameters may be controlled to be within a predetermined range. An example set of process parameters for the press 1 used during a particular example separation operation are shown in Table 1.

Table 1: Example process parameters for a separation operation using the press 1 of Figure 1.

It will be appreciated that other values can be used, and that for any given separation operation, the particular value of each given parameter is expected to be selected in dependence on the particular requirements of that separation operation. In some examples the value of a particular parameter or combination of parameters is selected as a result of an expectation that it will result in a particular characteristic of the tobacco extract and/or of the separation process. Characteristics of the product tobacco extract which it may be desired to control include the amount of tobacco solids comprised in the extract, the amount of fine particles comprised in the extract, size of particles comprised in the extract, etc. Characteristics of the separation process which it may be desired to control include separation efficiency (i.e. percentage recovery of extract), process yield, process time, etc. An example set of process yield data, obtained using various different combinations of process parameters, is shown in Table 2.

Table 2: Example process yield data as a function of mesh size, temperature and solvent. "- " means no measurements were made.

The inventors have discovered the following relationships between process parameters and extract characteristics. Increasing the ambient temperature decreases the viscosity of the mixture, which can enable more extract to be forced out of the mixture using a given compressive force. Thus the process yield can be increased. A similar effect can be achieved by using a lower viscosity solvent. Increasing the compressive force applied causes more extract to be forced out of the mixture, all other parameters being equal, and therefore enables yield to be increased. However, it may also increase the amount of tobacco solids particles comprised in the extract. If a mesh is used, the size of the mesh openings affects the total amount of tobacco solids comprised in the extract, and also the size of tobacco solid particles comprised in the extract. A smaller mesh size can result in a lower amount of tobacco solids being comprised in the extract as compared to a larger mesh size. However; mesh size does not significantly affect process yield. Similarly, the amount and size of tobacco solids particles comprised in the extract is not significantly affected by temperature or solvent type.

It will therefore be appreciated that different combinations of process parameters will be more appropriate for achieving a given desired process characteristic and/or extract characteristic. For example, if it is desired that the amount of tobacco solids comprised in the product extract is minimized or maintained below a certain predetermined level, a relatively lower compressive force may be selected. By contrast, if a high yield is of greater concern, then a relatively higher compressive force may be selected.

The tobacco extract which is forced through the holes is collected in any suitable manner. For example, if a press such as the press 1 or the press 8 is used, the extract will flow down the outer surface of the side wall (or the outer surface of an outer wall, if present). It can therefore be collected by providing a tray or other suitable container around the base of the side wall.

Depending on the intended use for the product extract, further clarification to remove some or all of the remaining tobacco solids may be desired, and can be performed in any suitable manner. For example, clarification can be performed by centrifugation, and/or micro filtration with or without the use of filter aids.

The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and/or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.